The mathematical modelling of many scientific and technological problems leads to (initial) boundary value problems with systems of partial differential equations (PDEs).
These problems describe the interactions of temporal and spatial variations of the considered physical processes. The unknowns are functions of one or several spatial variables and, possibly, of time. In general, it is only possible to obtain approximations of the solution(s), which are based on discretizations in space and time. On the one hand, a high approximation quality should be ensured by an appropriately chosen discretization. And on the other hand, the transfer of important physical properties from the continuous model to the discrete problem, the socalled physical consistency of the discretization, is in many situations of utmost importance. The arising systems of algebraic equations have to be solved efficiently. The research groups are working at the modeling of processes from nature and industry and the derived models are analyzed. Further foci of the research are the development of appropriate discretizations, their analysis, their implementation, and their further development for the application on new classes of problems.
The application of these methods in collaboration with partners from science and industry leads to new insight into the structure of concrete problems. This insight results in new challenges for the further development, analysis, and the numerical simulation of the considered models.
Electrolytic diode with applied potential difference in reverse bias. Depletion of ion concentration in the vicinity of the sign change of the surface charge decreases the ionic current (http://dx.doi.org/10.1002/fuce.201500215)
Publications
Monographs

A.H. Erhardt, K. TsanevaAtanasova, G.T. Lines, E.A. Martens, eds., Dynamical Systems, PDEs and Networks for Biomedical Applications: Mathematical Modeling, Analysis and Simulations, Special Edition, articles published in Frontiers of Physics, Frontiers in Applied Mathematics and Statistics, and Frontiers in Physiology, Frontiers Media SA, Lausanne, Switzerland, 2023, 207 pages, (Collection Published), DOI 10.3389/9782832514580 .

E. Franck, J. Fuhrmann, V. MichelDansac, L. Navoret, eds., Finite Volumes for Complex Applications X  Volume 1, Elliptic and Parabolic Problems: FVCA10, Strasbourg, France, October 30, 2023  November 03, 2023, Invited Contributions, 432 of Springer Proceedings in Mathematics & Statistics, Springer International Publishing, Cham, 2023, 396 pages, (Collection Published), DOI 10.1007/9783031408649 .

E. Franck, J. Fuhrmann, V. MichelDansac, L. Navoret, eds., Finite Volumes for Complex Applications X  Volume 2, Hyperbolic and Related Problems: FVCA10, Strasbourg, France, October 30, 2023  November 03, 2023, 433 of Springer Proceedings in Mathematics & Statistics, Springer International Publishing, Cham, 2023, 308 pages, (Collection Published), DOI 10.1007/9783031408601 .

Z. Erkoç, A. Aman, U. Güdükbay, H. Si, Outofcore constrained Delaunay tetrahedralizations for large scenes, V.A. Garanzha, L. Kamenski, H. Si, eds., 143 of Lecture Notes in Computational Science and Engineering, Springer Nature Switzerland AG, Cham, 2021, pp. 113124, (Chapter Published), DOI 10.1007/9783030767983 .

H. Si, On decomposition of embedded prismatoids in $R^3$ without additional points, V.A. Garanzha, L. Kamenski, H. Si, eds., 143 of Lecture Notes in Computational Science and Engineering, Springer Nature Switzerland AG, Cham, 2021, pp. 95112, (Chapter Published), DOI 10.1007/9783030767983 .

V.A. Garanzha, L. Kamenski, H. Si, eds., Numerical Geometry, Grid Generation and Scientific Computing. Proceedings of the 10th International Conference, NUMGRID 2020 / Delaunay 130, Celebrating the 130th Anniversary of Boris Delaunay, Moscow, Russia, November 2020, 143 of Lecture Notes in Computational Science and Engineering, Springer Nature Switzerland AG, Cham, 2021, 417 pages, (Collection Published), DOI 10.1007/9783030767983 .

R. Ahrens, Z. Lakdawala, A. Voigt, V. Wiedmeyer, V. John, S. Le Borne, K. Sundmacher, Chapter 14: Numerical Methods for Coupled Population Balance Systems Applied to the Dynamical Simulation of Crystallization Processes, in: Dynamic Flowsheet Simulation of Solids Processes, S. Heinrich, ed., Springer, Cham, 2020, pp. 475518, (Chapter Published), DOI 10.1007/9783030451684_14 .

U.W. Pohl, A. Strittmatter, A. Schliwa, M. Lehmann, T. Niermann, T. Heindel, S. Reitzenstein, M. Kantner, U. Bandelow, Th. Koprucki, H.J. Wünsche, Chapter 3: StressorInduced Site Control of Quantum Dots for SinglePhoton Sources, in Semiconductor Nanophotonics, M. Kneissl, A. Knorr, S. Reitzenstein, A. Hoffmann, eds., 194 of Springer Series in SolidState Sciences, Springer, Heidelberg, 2020, pp. 5390, (Chapter Published), DOI 10.1007/9783030356569_3 .
Abstract
The strain field of selectively oxidized A10x current apertures in an A1GaAs/GaAs mesa is utilized to define the nucleation site of InGaAs/GaAs quantum dots. A design is developed that allows for the selfaligned growth of single quantum dots in the center of a circular mesa. Measurements of the strain tensor applying transmissionelectron holography yield excellent agreement with the calculated strain field. Singledot spectroscopy of sitecontrolled dots proves narrow excitonic linewidth virtually free of spectral diffusion due to quantumdot growth in a defectfree matrix. Implementation of such dots in an electrically driven pin structure yields singledot electroluminescence. Singlephoton emission with excellent purity is provided for this device using a Hanbury Brown and Twiss setup. The injection efficiency of the initian pin design is affected by a substantial lateral current spreading close to the oxide aperture. Allpying 3D cariertransport simulation a ppn doping profile is developed achieving a substantial improvement of the current injection. 
S. Rodt, P.I. Schneider, L. Zschiedrich, T. Heindel, S. Bounouar, M. Kantner, Th. Koprucki, U. Bandelow, S. Burger, S. Reitzenstein, Chapter 8: Deterministic Quantum Devices for Optical Quantum Communication, in: Semiconductor Nanophotonics, M. Kneissl, A. Knorr, S. Reitzenstein, A. Hoffmann, eds., 194 of Springer Series in SolidState Sciences, Springer, Heidelberg, 2020, pp. 285359, (Chapter Published), DOI 10.1007/9783030356569_8 .
Abstract
Photonic quantum technologies are based on the exchange of information via single photons. The information is typically encoded in the polarization of the photons and security is ensured intrinsically via principles of quantum mechanics such as the nocloning theorem. Thus, all optical quantum communication networks rely crucially on the availability of suitable quantumlight sources. Such light sources with close to ideal optical and quantum optical properties can be realized by selfassembled semiconductor quantum dots. These highquality nanocrystals are predestined singlephoton emitters due to their quasi zerodimensional carrier confinement. Still, the development of practical quantumdotbased sources of single photons and entangledphoton pairs for applications in photonic quantum technology and especially for the quantumrepeater scheme is very demanding and requires highly advanced device concepts and deterministic fabrication technologies. This is mainly explained by their random position and emission energy as well as by the low photonextraction efficiency in simple planar device configurations. 
V. John, P. Knobloch, U. Wilbrandt, Chapter 6: Finite Element Pressure Stabilizations for Incompressible Flow Problems, in: Fluids under Pressure, T. Bodnár, G. Galdi, Š. Nečasová, eds., Advances in Mathematical Fluid Mechanics, Birkhäuser, Cham, 2020, pp. 483573, (Chapter Published), DOI 10.1007/9783030396398_6 .
Abstract
Discretizations of incompressible flow problems with pairs of finite element spaces that do not satisfy a discrete infsup condition require a socalled pressure stabilization. This paper gives an overview and systematic assessment of stabilized methods, including the respective error analysis. 
M. Kantner, Th. Höhne, Th. Koprucki, S. Burger, H.J. Wünsche, F. Schmidt, A. Mielke, U. Bandelow, Chapter 7: MultiDimensional Modeling and Simulation of Semiconductor Nanophotonic Devices, in: Semiconductor Nanophotonics, M. Kneissl, A. Knorr, S. Reitzenstein, A. Hoffmann, eds., 194 of Springer Series in SolidState Sciences, Springer, Heidelberg, 2020, pp. 241283, (Chapter Published), DOI 10.1007/9783030356569_7 .
Abstract
Selfconsistent modeling and multidimensional simulation of semiconductor nanophotonicdevices is an important tool in the development of future integrated light sources and quantumdevices. Simulations can guide important technological decisions by revealing performance bottlenecks in new device concepts, contribute to their understanding and help to theoretically exploretheir optimization potential. The efficient implementation of multidimensional numerical simulationsfor computeraided design tasks requires sophisticated numerical methods and modeling techniques. We review recent advances in devicescale modeling of quantum dot based singlephotonsources and laser diodes by selfconsistently coupling the optical Maxwell equations with semiclassical carrier transport models using semiclassical and fully quantum mechanical descriptionsof the optically active region, respectively. For the simulation of realistic devices with complex,multidimensional geometries, we have developed a novel hpadaptive finite element approachfor the optical Maxwell equations, using mixed meshes adapted to the multiscale properties ofthe photonic structures. For electrically driven devices, we introduced novel discretization andparameterembedding techniques to solve the driftdiffusion system for strongly degenerate semiconductors at cryogenic temperature. Our methodical advances are demonstrated on variousapplications, including verticalcavity surfaceemitting lasers, grating couplers and singlephotonsources. 
M. Kantner, Electrically Driven Quantum Dot Based SinglePhoton Sources: Modeling and Simulation, Springer Theses, Springer, Cham, 2020, XVII, 180 pages, (Monograph Published), DOI 10.1007/9783030395438 .
Abstract
Semiconductor quantum optics is on the verge of moving from the lab to real world applications. When stepping from basic research to new technologies, device engineers will need new simulation tools for the design and optimization of quantum light sources, which combine classical device physics with cavity quantum electrodynamics. This thesis aims to provide a holistic description of singlephoton emitting diodes by bridging the gap between microscopic and macroscopic modeling approaches. The central result is a novel hybrid quantumclassical model system that selfconsistently couples semiclassical carrier transport theory with open quantum manybody systems. This allows for a comprehensive description of quantum light emitting diodes on multiple scales: It enables the calculation of the quantum optical figures of merit together with the simulation of the spatially resolved current flow in complex, multidimensional semiconductor device geometries out of one box. The hybrid system is shown to be consistent with fundamental laws of (non)equilibrium thermodynamics and is demonstrated by numerical simulations of realistic devices. 
R. Klöfkorn, E. Keilegavlen, F.A. Radu , J. Fuhrmann, eds., Finite Volumes for Complex Applications IX  Methods, Theoretical Aspects, Examples  FVCA 9, Bergen, June 2020, 323 of Springer Proceedings in Mathematics & Statistics, Springer International Publishing, Cham et al., 2020, 775 pages, (Collection Published), DOI 10.1007/9783030436513 .

V.A. Garanzha, L. Kamenski, H. Si, eds., Numerical Geometry, Grid Generation and Scientific Computing. Proceedings of the 9th International Conference, NUMGRID 2018 / Voronoi 150, Celebrating the 150th Anniversary of G.F. Voronoi, Moscow, Russia, December 2018, 131 of Lecture Notes in Computational Science and Engineering, Springer Nature Switzerland AG, Cham, 2019, 319 pages, (Collection Published), DOI 10.1007/9783030234362 .

M. Hintermüller, J.F. Rodrigues, eds., Topics in Applied Analysis and Optimisation  Partial Differential Equations, Stochastic and Numerical Analysis, CIM Series in Mathematical Sciences, Springer Nature Switzerland AG, Cham, 2019, 396 pages, (Collection Published).

P. Farrell, N. Rotundo, D.H. Doan, M. Kantner, J. Fuhrmann, Th. Koprucki, Chapter 50: DriftDiffusion Models, in: Vol. 2 of Handbook of Optoelectronic Device Modeling and Simulation: Lasers, Modulators, Photodetectors, Solar Cells, and Numerical Methods, J. Piprek, ed., Series in Optics and Optoelectronics, CRC Press, Taylor & Francis Group, Boca Raton, 2017, pp. 733771, (Chapter Published).

H.Chr. Kaiser, D. Knees, A. Mielke, J. Rehberg, E. Rocca, M. Thomas, E. Valdinoci, eds., PDE 2015: Theory and Applications of Partial Differential Equations, 10 of Discrete and Continuous Dynamical Systems  Series S, American Institute of Mathematical Science, Springfield, 2017, iv+933 pages, (Collection Published).

P. Exner, W. König, H. Neidhardt, eds., Mathematical Results in Quantum Mechanics. Proceedings of the QMath12 Conference, World Scientific Publishing, Singapore, 2015, xii+383 pages, (Collection Published).

A. Zisowsky, A. Arnold, M. Ehrhardt, Th. Koprucki, Chapter 7: Transient Simulation of k$cdot$pSchrödinger Systems Using Discrete Transparent Boundary Conditions, in: MultiBand Effective Mass Approximations  Advanced Mathematical Models and Numerical Techniques, M. Ehrhardt, Th. Koprucki, eds., 94 of Lecture Notes in Computational Science and Engineering, Springer, Cham et al., 2014, pp. 247272, (Chapter Published).

D. Klindworth, M. Ehrhardt, Th. Koprucki, Chapter 8: Discrete Transparent Boundary Conditions for Multiband Effective Mass Approximations, in: MultiBand Effective Mass Approximations  Advanced Mathematical Models and Numerical Techniques, M. Ehrhardt, Th. Koprucki, eds., 94 of Lecture Notes in Computational Science and Engineering, Springer, Cham et al., 2014, pp. 273318, (Chapter Published).

M. Ehrhardt, Th. Koprucki, eds., MultiBand Effective Mass Approximations  Advanced Mathematical Models and Numerical Techniques, 94 of Lecture Notes in Computational Science and Engineering, Springer, Cham et al., 2014, xvi+318 pages, (Monograph Published).

I. Laukaityte, R. Čiegis, M. Lichtner, M. Radziunas, Parallel Numerical Algorithm for the Traveling Wave Model, in: Parallel Scientific Computing and Optimization: Advances and Applications, R. Čiegis, D. Henty, B. Kågström, J. Žilinskas, eds., 27 of Springer Optimization and Its Applications, Springer, New York, 2008, pp. 237251, (Chapter Published).

M. Tlidi, R. Lefever, A.G. Vladimirov, On Vegetation Clustering, Localized Bare Soil Spots and Fairy Circles, in: Dissipative Solitons: From Optics to Biology and Medicine, N. Akhmediev, A. Ankiewicz, eds., 751 of Lecture Notes in Physics, Springer, Berlin, Heidelberg, 2008, pp. 381402, (Chapter Published).

U. Bandelow, H. Gajewski, R. Hünlich, Chapter 3: FabryPerot Lasers: Thermodynamicsbased Modeling, in: Optoelectronic Devices  Advanced Simulation and Analysis, J. Piprek, ed., Springer, New York, 2005, pp. 6385, (Chapter Published).
Articles in Refereed Journals

R. Araya, C. Cárcamo, A.H. Poza, E. Vino, An adaptive stabilized finite element method for the StokesDarcy coupled problem, Journal of Computational and Applied Mathematics, 443 (2024), pp. 115753/1115753/24, DOI 10.1016/j.cam.2024.115753 .
Abstract
For the StokesDarcy coupled problem, which models a fluid that flows from a free medium into a porous medium, we introduce and analyze an adaptive stabilized finite element method using Lagrange equal order element to approximate the velocity and pressure of the fluid. The interface conditions between the free medium and the porous medium are given by mass conservation, the balance of normal forces, and the BeaversJosephSaffman conditions. We prove the wellposedness of the discrete problem and present a convergence analysis with optimal error estimates in natural norms. Next, we introduce and analyze a residualbased a posteriori error estimator for the stabilized scheme. Finally, we present numerical examples to demonstrate the performance and effectiveness of our scheme. 
G.R. Barrenechea, V. John, P. Knobloch, Finite element methods respecting the discrete maximum principle for convectiondiffusion equations, SIAM Review, 66 (2024), pp. 186, DOI 10.1137/22M1488934 .
Abstract
Convectiondiffusionreaction equations model the conservation of scalar quantities. From the analytic point of view, solutions of these equations satisfy, under certain conditions, maximum principles, which represent physical bounds of the solution. That the same bounds are respected by numerical approximations of the solution is often of utmost importance in practice. The mathematical formulation of this property, which contributes to the physical consistency of a method, is called the discrete maximum principle (DMP). In many applications, convection dominates diffusion by several orders of magnitude. It is well known that standard discretizations typically do not satisfy the DMP in this convectiondominated regime. In fact, in this case it turns out to be a challenging problem to construct discretizations that, on the one hand, respect the DMP and, on the other hand, compute accurate solutions. This paper presents a survey on finite element methods, with the main focus on the convectiondominated regime, that satisfy a local or a global DMP. The concepts of the underlying numerical analysis are discussed. The survey reveals that for the steadystate problem there are only a few discretizations, all of them nonlinear, that at the same time both satisfy the DMP and compute reasonably accurate solutions, e.g., algebraically stabilized schemes. Moreover, most of these discretizations have been developed in recent years, showing the enormous progress that has been achieved lately. Similarly, methods based on algebraic stabilization, both nonlinear and linear, are currently the only finite element methods that combine the satisfaction of the global DMP and accurate numerical results for the evolutionary equations in the convectiondominated scenario. 
D. Abdel, N.E. Courtier, P. Farrell, Volume exclusion effects in perovskite charge transport modeling, Optical and Quantum Electronics, 55 (2023), pp. 884/1884/14, DOI 10.1007/s11082023051259 .
Abstract
Due to their flexible material properties, perovskite materials are a promising candidate for many semiconductor devices such as lasers, memristors, LEDs and solar cells. For example, perovskitebased solar cells have recently become one of the fastest growing photovoltaic technologies. Unfortunately, perovskite devices are far from commercialization due to challenges such as fast degradation. Mathematical models can be used as tools to explain the behavior of such devices, for example driftdiffusion equations portray the ionic and electric motion in perovskites. In this work, we take volume exclusion effects on ion migration within a perovskite crystal lattice into account. This results in the formulation of two different ionic current densities for such a driftdiffusion model  treating either the mobility or the diffusivity as densitydependent while the other quantity remains constant. The influence of incorporating each current density description into a model for a typical perovskite solar cell configuration is investigated numerically, through simulations performed using two different open source tools. 
D. Abdel, C. ChainaisHillairet, P. Farrell, M. Herda, Numerical analysis of a finite volume scheme for charge transport in perovskite solar cells, IMA Journal of Numerical Analysis, published online on 10.6.2023, DOI 10.1093/imanum/drad034 .
Abstract
In this paper, we consider a driftdiffusion charge transport model for perovskite solar cells, where electrons and holes may diffuse linearly (Boltzmann approximation) or nonlinearly (e.g. due to FermiDirac statistics). To incorporate volume exclusion effects, we rely on the FermiDirac integral of order −1 when modeling moving anionic vacancies within the perovskite layer which is sandwiched between electron and hole transport layers. After nondimensionalization, we first prove a continuous entropydissipation inequality for the model. Then, we formulate a corresponding twopoint flux finite volume scheme on Voronoi meshes and show an analogous discrete entropydissipation inequality. This inequality helps us to show the existence of a discrete solution of the nonlinear discrete system with the help of a corollary of Brouwer's fixed point theorem and the minimization of a convex functional. Finally, we verify our theoretically proven properties numerically, simulate a realistic device setup and show exponential decay in time with respect to the L^{2} error as well as a physically and analytically meaningful relative entropy. 
S. Katz, A. Caiazzo, V. John, Impact of viscosity modeling on the simulation of aortic blood flow, Journal of Computational and Applied Mathematics, 425 (2023), pp. 115036/1115036/18, DOI 10.1016/j.cam.2022.115036 .
Abstract
Modeling issues for the simulation of blood flow in an aortic coarctation are studied in this paper. From the physical point of view, several viscosity models for nonNewtonian fluids as well as a Newtonian fluid model will be considered. From the numerical point of view, two different turbulence models are utilized in the simulations. The impact of both, the physical and the numerical modeling, on clinically relevant biomarkers is investigated and compared. 
S. Katz, A. Caiazzo, B. Moreau, U. Wilbrandt, J. Brüning, L. Goubergrits, V. John, Impact of turbulence modeling on the simulation of blood flow in aortic coarctation, International Journal of Numerical Methods in Biomedical Engineering, 39 (2023), pp. e3695/1e3695/36, DOI 10.1002/cnm.3695 .
Abstract
Numerical simulations of pulsatile blood flow in an aortic coarctation require the use of turbulence modeling. This paper considers three models from the class of large eddy simulation (LES) models (Smagorinsky, Vreman, model) and one model from the class of variational multiscale models (residualbased) within a finite element framework. The influence of these models on the estimation of clinically relevant biomarkers used to assess the degree of severity of the pathological condition (pressure difference, secondary flow degree, normalized flow displacement, wall shear stress) is investigated in detail. The simulations show that most methods are consistent in terms of severity indicators such as pressure difference and stenotic velocity. Moreover, using secondorder velocity finite elements, different turbulence models might lead to considerably different results concerning other clinically relevant quantities such as wall shear stresses. These differences may be attributed to differences in numerical dissipation introduced by the turbulence models. 
L. Schmeller, D. Peschka, Gradient flows for coupling order parameters and mechanics, SIAM Journal on Applied Mathematics, 83 (2023), pp. 225253, DOI 10.1137/22M148478X .
Abstract
We construct a formal gradient flow structure for phasefield evolution coupled to mechanics in Lagrangian coordinates, present common ways to couple the evolution and provide an incremental minimization strategy. While the usual presentation of continuum mechanics is intentionally very brief, the focus of this paper is on an extensible functional analytical framework and a discretization approach that preserves an appropriate variational structure as much as possible. As examples, we first present phase separation and swelling of gels and then the approach of stationary states of multiphase systems with surface tension and show the robustness of the general approach. 
A. Alphonse, D. Caetano, A. Djurdjevac, Ch.M. Elliot, Function spaces, time derivatives and compactness for evolving families of Banach spaces with applications to PDEs, Journal of Differential Equations, 353 (2023), pp. 268338, DOI 10.1016/j.jde.2022.12.032 .
Abstract
We develop a functional framework suitable for the treatment of partial differential equations and variational problems on evolving families of Banach spaces. We propose a definition for the weak time derivative that does not rely on the availability of a Hilbertian structure and explore conditions under which spaces of weakly differentiable functions (with values in an evolving Banach space) relate to classical Sobolev?Bochner spaces. An Aubin?Lions compactness result is proved. We analyse concrete examples of function spaces over timeevolving spatial domains and hypersurfaces for which we explicitly provide the definition of the time derivative and verify isomorphism properties with the aforementioned Sobolev?Bochner spaces. We conclude with the proof of well posedness for a class of nonlinear monotone problems on an abstract evolving space (generalising the evolutionary pLaplace equation on a moving domain or surface) and identify some additional problems that can be formulated with the setting developed in this work. 
D. Peschka, Partial and complete wetting of thin films with dynamic contact angle, Physics of Fluids, 35 (2023), pp. 041705/1041705/6, DOI 10.1063/5.0146538 .
Abstract
The wetting of thin films depends critically on the sign of the spreading coefficient S. We discuss the cases S<0, S=0, and S>0 for transient models with contact line dissipation and find that the use of a dynamic contact angle solves problems for S>0 that models might otherwise have. For initial data with a nonzero slope and S>0, we show that there exists a finite time at which the contact angle of the thin film goes to zero. Then, a molecular precursor emerges from the thin film and moves outward at a constant velocity. 
A.K. Barua, R. Chew, L. Shuwang, J. Lowengrub, A. Münch, B. Wagner, Sharpinterface problem of the OhtaKawasaki model for symmetric diblock copolymers, Journal of Computational Physics, 481 (2023), pp. 112032/1112032/23, DOI 10.1016/j.jcp.2023.112032 .
Abstract
The OhtaKawasaki model for diblockcopolymers is well known to the scientific community of diffuseinterface methods. To accurately capture the longtime evolution of the moving interfaces, we present a derivation of the corresponding sharpinterface limit using matched asymptotic expansions, and show that the limiting process leads to a HeleShaw type moving interface problem. The numerical treatment of the sharpinterface limit is more complicated due to the stiffness of the equations. To address this problem, we present a boundary integral formulation corresponding to a sharp interface limit of the OhtaKawasaki model. Starting with the governing equations defined on separate phase domains, we develop boundary integral equations valid for multiconnected domains in a 2D plane. For numerical simplicity we assume our problem is driven by a uniform Dirichlet condition on a circular farfield boundary. The integral formulation of the problem involves both double and singlelayer potentials due to the modified boundary condition. In particular, our formulation allows one to compute the nonlinear dynamics of a nonequilibrium system and pattern formation of an equilibrating system. Numerical tests on an evolving slightly perturbed circular interface (separating the two phases) are in excellent agreement with the linear analysis, demonstrating that the method is stable, efficient and spectrally accurate in space. 
R. Shiri, L. Schmeller, R. Seemann, D. Peschka, B. Wagner, Impact of noise on spinodal dewetting of liquidliquid films, communications physics, 6 (2023), pp. 109/1109/11, DOI 10.1038/s4200502301208x .
Abstract
We investigate the spinodal dewetting of a thin liquid polystyrene (PS) film on a liquid polymethylmethacrylate (PMMA) subtrate. Following the evolution of the corrugations of the PS film via in situ measurements by atomic force microscopy (AFM) and those of the PSPMMA interface via ex situ imaging, we provide a direct and detailed comparison of the experimentally determined spinodal wavelengths with the predictions from linear stability analysis of a thinfilm continuum model for the bilayer system. The impact of rough interfaces and fluctuations is studied theoretically by investigating the impact of different choices of initial data on the unstable wavelength and on the rupture time. The key factor is the mode selection by initial data perturbed with correlated colored noise in the linearly unstable regime, which becomes relevant only for liquid bilayers to such an extent. By numerically solving the mathematical model, we further address the impact of nonlinear effects on rupture times and on the morphological evolution of the interfaces in comparison with experimental results. 
G.L. Celora, M.G. Hennessy, A. Münch, B. Wagner, S.L. Waters, The dynamics of a collapsing polyelectrolyte gel, SIAM Journal on Applied Mathematics, 83 (2023), pp. 11461171, DOI 10.1137/21M1419726 .

C. ChainaisHillairet, R. Eymard, J. Fuhrmann, A monotone numerical flux for quasilinear convection diffusion equations, Mathematics of Computation, 93 (2024), pp. 203231 (published online in June 2023), DOI 10.1090/mcom/3870 .

R. Araya, C. Cárcamo, A.H. Poza, A stabilized finite element method for the StokesTemperature coupled problem, Applied Numerical Mathematics. An IMACS Journal, 187 (2023), pp. 2449, DOI 10.1016/j.apnum.2023.02.002 .
Abstract
In this work, we introduce and analyze a new stabilized finite element scheme for the StokesTemperature coupled problem. This new scheme allows equal order of interpolation to approximate the quantities of interest, i.e. velocity, pressure, temperature, and stress. We analyze an equivalent variational formulation of the coupled problem inspired by the ideas proposed in [3]. The existence of the discrete solution is proved, decoupling the proposed stabilized scheme and using the help of continuous dependence results and Brouwer's theorem under the standard assumption of sufficiently small data. Optimal convergence is proved under classic regularity assumptions of the solution. Finally, we present some numerical examples to show the quality of our scheme, in particular, we compare our results with those coming from a standard reference in geosciences described in [38]. 
D. Budáč, V. Miloš, M. Carda, M. Paidar, J. Fuhrmann, K. Bouzek, Prediction of electrical conductivity of porous composites using a simplified Monte Carlo 3D equivalent electronic circuit network model: LSMYSZ case study, Electrochimica Acta, 457 (2023), pp. 142512/1142512/12, DOI 10.1016/j.electacta.2023.142512 .
Abstract
Multiphase electric charge conductors composed of materials with various properties are widely utilized in both research and industrial applications. The composite materials include porous electrodes and other components mainly applied in fuel cell and battery technologies. In this study, a simplified Monte Carlo equivalent electronic circuit (EEC) network model is presented. In comparison to similar models, the present EEC network model allows an accurate prediction of the electrical properties of such materials, thus saving timeconsuming experimental determination. The distinct feature of this EEC network model is that it requires only experimentally easily obtainable data as the input parameters: phase composition, porosity and bulk electrical conductivity of the individual constituents. During its run, the model generates a large number of artificial cubically shaped specimens based on random distribution of individual phases according to the input composition. Each of the specimens generated was modelled by a corresponding EEC network. The EEC networks were solved using Kirchhoff's laws, resulting in impedance response simulation for the prediction of composite conductivity values. The EEC network model was validated using lanthanum strontium manganite mixed with yttriastabilized zirconia. Excellent agreement was obtained between the experimentally determined and the calculated electrical conductivity for sample porosities of 0 to 60 %. Due to its variability, the EEC network model can be suitable for a wide range of practical applications. The presented approach has high potential to save an enormous amount of experimental effort, while maintaining sufficient accuracy, when designing corresponding multiphase electrode structures. 
K. Fellner, J. Fischer, M. Kniely, B.Q. Tang, Global renormalised solutions and equilibration of reactiondiffusion systems with nonlinear diffusion, Journal of Nonlinear Science, 33 (2023), pp. 66/166/49, DOI 10.1007/s0033202309926w .
Abstract
The global existence of renormalised solutions and convergence to equilibrium for reactiondiffusion systems with nonlinear diffusion are investigated. The system is assumed to have quasipositive nonlinearities and to satisfy an entropy inequality. The difficulties in establishing global renormalised solutions caused by possibly degenerate diffusion are overcome by introducing a new class of weighted truncation functions. By means of the obtained global renormalised solutions, we study the largetime behaviour of complex balanced systems arising from chemical reaction network theory with nonlinear diffusion. When the reaction network does not admit boundary equilibria, the complex balanced equilibrium is shown, by using the entropy method, to exponentially attract all renormalised solutions in the same compatibility class. This convergence extends even to a range of nonlinear diffusion, where global existence is an open problem, yet we are able to show that solutions to approximate systems converge exponentially to equilibrium uniformly in the regularisation parameter. 
R. Finn, M. O'Donovan, P. Farrell, J. Moatti, T. Streckenbach, Th. Koprucki, S. Schulz, Theoretical study of the impact of alloy disorder on carrier transport and recombination processes in deep UV (Al,Ga)N light emitters, Applied Physics Letters, 122 (2023), pp. 241104/1241104/7, DOI 10.1063/5.0148168 .
Abstract
Aluminum gallium nitride [(Al,Ga)N] has gained significant attention in recent years due to its potential for highly efficient light emitters operating in the deep ultraviolet (UV) range (<280 nm). However, given that current devices exhibit extremely low efficiencies, understand ing the fundamental properties of (Al,Ga)Nbased systems is of key importance. Here, using a multiscale simulation framework, we study the impact of alloy disorder on carrier transport, radiative and nonradiative recombination processes in a cplane Al 0.7 Ga0.3 N/Al0.8 Ga0.2 N quantum well embedded in a pn junction. Our calculations reveal that alloy fluctuations can open "percolative" pathways that promote transport for the electrons and holes into the quantum well region. Such an effect is neglected in conventional and widely used transport sim ulations. Moreover, we find that the resulting increased carrier density and alloy induced carrier localization effects significantly increase nonradiative AugerMeitner recombination in comparison to the radiative process. Thus, to suppress such nonradiative process and poten tially related material degradation, a careful design (wider well, multiquantum wells) of the active region is required to improve the effi ciency of deep UV light emitters. 
B. GarcíaArchilla, V. John, J. Novo, Second order error bounds for PODROM methods based on first order divided differences, Applied Mathematics Letters, 146 (2023), pp. 108836/1108836/7, DOI 10.1016/j.aml.2023.108836 .
Abstract
This note proves for the heat equation that using BDF2 as time stepping scheme in PODROM methods with snapshots based on difference quotients gives both the optimal second order error bound in time and pointwise estimates. 
B. GarcíaArchilla, V. John, J. Novo, PODROMs for incompressible flows including snapshots of the temporal derivative of the full order solution, SIAM Journal on Numerical Analysis, 61 (2023), pp. 13401368, DOI 10.1137/22M1503853 .
Abstract
In this paper we study the influence of including snapshots that approach the velocity time derivative in the numerical approximation of the incompressible NavierStokes equations by means of proper orthogonal decomposition (POD) methods. Our set of snapshots includes the velocity approximation at the initial time from a full order mixed finite element method (FOM) together with approximations to the time derivative at different times. The approximation at the initial velocity can be replaced by the mean value of the velocities at the different times so that when implementing the method to the fluctuations, as done mostly in practice, only approximations to the time derivatives are included in the set of snapshots. For the POD method we study the differences between projecting onto L2 and H1. In both cases pointwise in time error bounds can be proved. Including graddiv stabilization in both the FOM and the POD methods, error bounds with constants independent of inverse powers of the viscosity can be obtained. 
B. GarcíaArchilla , V. John, S. Katz, J. Novo, PODROMs for incompressible flows including snapshots of the temporal derivative of the full order solution: Error bounds for the pressure, Journal of Numerical Mathematics, published online on 26.08.2023, DOI 10.1515/jnma20230039 .
Abstract
Reduced order methods (ROMs) for the incompressible Navier?Stokes equations, based on proper orthogonal decomposition (POD), are studied that include snapshots which approach the temporal derivative of the velocity from a full order mixed finite element method (FOM). In addition, the set of snapshots contains the mean velocity of the FOM. Both the FOM and the PODROM are equipped with a graddiv stabilization. A velocity error analysis for this method can be found already in the literature. The present paper studies two different procedures to compute approximations to the pressure and proves error bounds for the pressure that are independent of inverse powers of the viscosity. Numerical studies support the analytic results and compare both methods. 
L. Giacomelli, M. Gnann, D. Peschka, Droplet motion with contactline friction: Longtime asymptotics in complete wetting, Proceedings of The Royal Society of London. Series A. Mathematical, Physical and Engineering Sciences, 479 (2023), pp. 20230090/120230090/23, DOI 10.1098/rspa.2023.0090 .
Abstract
We consider the thinfilm equation for a class of free boundary conditions modelling friction at the contact line, as introduced by E and Ren. Our analysis focuses on formal longtime asymptotics of solutions in the perfect wetting regime. In particular, through the analysis of quasiselfsimilar solutions, we characterize the profile and the spreading rate of solutions depending on the strength of friction at the contact line, as well as their (global or local) corrections, which are due to the dynamical nature of the free boundary conditions. These results are complemented with full transient numerical solutions of the free boundary problem. 
G. Gilardi, A. Signori, J. Sprekels, Nutrient control for a viscous CahnHilliardKellerSegel model with logistic source describing tumor growth, Discrete and Continuous Dynamical Systems  Series S, 16 (2023), pp. 35523572, DOI 10.3934/dcdss.2023123 .
Abstract
In this paper, we address a distributed control problem for a system of partial differential equations describing the evolution of a tumor that takes the biological mechanism of chemotaxis into account. The system describing the evolution is obtained as a nontrivial combination of a CahnHilliard type system accounting for the segregation between tumor cells and healthy cells, with a KellerSegel type equation accounting for the evolution of a nutrient species and modeling the chemotaxis phenomenon. First, we develop a robust mathematical background that allows us to analyze an associated optimal control problem. This analysis forced us to select a source term of logistic type in the nutrient equation and to restrict the analysis to the case of two space dimensions. Then, the existence of an optimal control and firstorder necessary conditions for optimality are established. 
A. Jha, V. John, P. Knobloch, Adaptive grids in the context of algebraic stabilizations for convectiondiffusionreaction equations, SIAM Journal on Scientific Computing, 45 (2023), pp. B564B589, DOI 10.1137/21M1466360 .
Abstract
Three algebraically stabilized finite element schemes for discretizing convectiondiffusionreaction equations are studied on adaptively refined grids. These schemes are the algebraicflux correction (AFC) scheme with the Kuzmin limiter, the AFC scheme with the BarrenecheaJohnKnobloch limiter, and the recently proposed monotone upwindtype algebraically stabilizedmethod. Both conforming closure of the refined grids and grids with hanging vertices are considered.A nonstandard algorithmic step becomes necessary before these schemes can be applied on gridswith hanging vertices. The assessment of the schemes is performed with respect to the satisfactionof the global discrete maximum principle, the accuracy, e.g., smearing of layers, and the efficiency insolving the corresponding nonlinear problems. 
A. Jha, O. Pártl, N. Ahmed, D. Kuzmin, An assessment of solvers for algebraically stabilized discretizations of convectiondiffusionreaction equations, Journal of Numerical Mathematics, 31 (2023), pp. 79103, DOI 10.1515/jnma20210123 .
Abstract
We consider fluxcorrected finite element discretizations of 3D convectiondominated transport problems and assess the computational efficiency of algorithms based on such approximations. The methods under investigation include fluxcorrected transport schemes and monolithic limiters. We discretize in space using a continuous Galerkin method and P_{1} or Q_{1} finite elements. Time integration is performed using the CrankNicolson method or an explicit strong stability preserving RungeKutta method. Nonlinear systems are solved using a fixedpoint iteration method, which requires solution of large linear systems at each iteration or time step. The great variety of options in the choice of discretization methods and solver components calls for a dedicated comparative study of existing approaches. To perform such a study, we define new 3D test problems for time dependent and stationary convectiondiffusionreaction equations. The results of our numerical experiments illustrate how the limiting technique, time discretization and solver impact on the overall performance. 
B. Spetzler, D. Abdel, F. Schwierz, M. Ziegler, P. Farrell, The role of vacancy dynamics in twodimensional memristive devices, Advanced Electronic Materials, published online on 08.11.2023, DOI 10.1002/aelm.202300635 .
Abstract
Twodimensional (2D) layered transition metal dichalcogenides (TMDCs) are promising memristive materials for neuromorphic computing systems as they could solve the problem of the excessively high energy consumption of conventional von Neumann computer architectures. Despite extensive experimental work, the underlying switching mechanisms are still not understood, impeding progress in material and device functionality. This study reveals the dominant role of mobile defects in the switching dynamics of 2D TMDC materials. The switching process is governed by the formation and annihilation dynamics of a local vacancy depletion zone. Moreover, minor changes in the interface potential barriers cause fundamentally different device behavior previously thought to originate from multiple mechanisms. The key mechanisms are identified with a charge transport model for electrons, holes, and ionic point defects, including imagechargeinduced Schottky barrier lowering (SBL). The model is validated by comparing simulations to measurements for various 2D MoS2based devices, strongly corroborating the relevance of vacancies in TMDC devices and offering a new perspective on the switching mechanisms. The insights gained from this study can be used to extend the functional behavior of 2D TMDC memristive devices in future neuromorphic computing applications. 
P. Farrell, J. Moatti, M. O'Donovan, S. Schulz, Th. Koprucki, Importance of satisfying thermodynamic consistency in optoelectronic device simulations for high carrier densities, Optical and Quantum Electronics, 55 (2023), pp. 978/1978/12, DOI 10.1007/s11082023052345 .
Abstract
We show the importance of using a thermodynamically consistent flux discretization when describing driftdiffusion processes within light emitting diode simulations. Using the classical ScharfetterGummel scheme with FermiDirac statistics is an example of such an inconsistent scheme. In this case, for an (In,Ga)N multi quantum well device, the Fermi levels show steep gradients on one side of the quantum wells which are not to be expected. This result originates from neglecting diffusion enhancement associated with FermiDirac statistics in the numerical flux approximation. For a thermodynamically consistent scheme, such as the SEDAN scheme, the spikes in the Fermi levels disappear. We will show that thermodynamic inconsistency has far reaching implications on the currentvoltage curves and recombination rates. 
D. FrerichsMihov, L. Henning, V. John, Using deep neural networks for detecting spurious oscillations in discontinuous Galerkin solutions of convectiondominated convectiondiffusion equations, Journal of Scientific Computing, 97 (2023), pp. 36/136/27, DOI 10.1007/s1091502302335x .
Abstract
Standard discontinuous Galerkin (DG) finite element solutions to convectiondominated convectiondiffusion equations usually possess sharp layers but also exhibit large spurious oscillations. Slope limiters are known as a postprocessing technique to reduce these unphysical values. This paper studies the application of deep neural networks for detecting mesh cells on which slope limiters should be applied. The networks are trained with data obtained from simulations of a standard benchmark problem with linear finite elements. It is investigated how they perform when applied to discrete solutions obtained with higher order finite elements and to solutions for a different benchmark problem. 
V. John, P. Knobloch, U. Wilbrandt, A posteriori optimization of parameters in stabilized methods for convectiondiffusion problems  Part II, Journal of Computational and Applied Mathematics, 428 (2023), pp. 115167/1115167/17, DOI 10.1016/j.cam.2023.115167 .
Abstract
Extensions of algorithms for computing optimal stabilization parameters in finite element methods for convectiondiffusion equations are presented. These extensions reduce the dimension of the control space, in comparison to available methods, and thus address the long computing times of these methods. One method is proposed that considers only relevant mesh cells, another method that uses groups of mesh cells, and the combination of both methods is also studied. The incorporation of these methods within a gradientbased optimization procedure, via solving an adjoint problem, is explained. Numerical studies provide impressions on the gain of efficiency as well as on the loss of accuracy if control spaces with reduced dimensions are utilized. 
CH. Merdon, W. Wollner, Pressurerobustness in the context of optimal control, SIAM Journal on Control and Optimization, 61 (2023), pp. 342360, DOI 10.1137/22M1482603 .
Abstract
This paper studies the benefits of pressurerobust discretizations in the scope of optimal control of incompressible flows. Gradient forces that may appear in the data can have a negative impact on the accuracy of state and control and can only be correctly balanced if their L^{2}orthogonality onto discretely divergencefree test functions is restored. Perfectly orthogonal divergencefree discretizations or divergencefree reconstructions of these test functions do the trick and lead to much better analytic a priori estimates that are also validated in numerical examples. 
A.H. Erhardt, S. Solem, Bifurcation analysis of a modified cardiac cell model, SIAM Journal on Applied Dynamical Systems, 21 (2022), pp. 231247, DOI 10.1137/21M1425359 .

F. Galarce Marín, D. Lombardi, O. Mula, State estimation with model reduction and shape variability: Application to biomedical problems, SIAM Journal on Scientific Computing, 44 (2022), pp. B805B833, DOI 10.1137/21M1430480 .
Abstract
We develop a mathematical and numerical framework to solve state estimation problems for applications that present variations in the shape of the spatial domain. This situation arises typically in a biomedical context where inverse problems are posed on certain organs or portions of the body which inevitably involve morphological variations. If one wants to provide fast reconstruction methods, the algorithms must take into account the geometric variability. We develop and analyze a method which allows to take this variability into account without needing any a priori knowledge on a parametrization of the geometrical variations. For this, we rely on morphometric techniques involving Multidimensional Scaling, and couple them with reconstruction algorithms that make use of reduced model spaces precomputed on a database of geometries. We prove the potential of the method on a synthetic test problem inspired from the reconstruction of blood flows and quantities of medical interest with Doppler ultrasound imaging. 
D. Peschka, L. Heltai, Model hierarchies and higherorder discretisation of timedependent thinfilm free boundary problems with dynamic contact angle, Journal of Computational Physics, 464 (2022), pp. 111325/1111325/22, DOI 10.1016/j.jcp.2022.111325 .
Abstract
We present a mathematical and numerical framework for the physical problem of thinfilm fluid flows over planar surfaces including dynamic contact angles. In particular, we provide algorithmic details and an implementation of higherorder spatial and temporal discretisation of the underlying free boundary problem using the finite element method. The corresponding partial differential equation is based on a thermodynamic consistent energetic variational formulation of the problem using the free energy and viscous dissipation in the bulk, on the surface, and at the moving contact line. Model hierarchies for limits of strong and weak contact line dissipation are established, implemented and studied. We analyze the performance of the numerical algorithm and investigate the impact of the dynamic contact angle on the evolution of two benchmark problems: gravitydriven sliding droplets and the instability of a ridge. 
P. Vágner, M. Pavelka, J. Fuhrmann, V. Klika, A multiscale thermodynamic generalization of MaxwellStefan diffusion equations and of the dusty gas model, International Journal of Heat and Mass Transfer, 199 (2022), pp. 123405/1123405/14, DOI 10.1016/j.ijheatmasstransfer.2022.123405 .
Abstract
Despite the fact that the theory of mixtures has been part of nonequilibrium thermodynamics and engineering for a long time, it is far from complete. While it is well formulated and tested in the case of mechanical equilibrium (where only diffusionlike processes take place), the question how to properly describe homogeneous mixtures that flow with multiple independent velocities that still possess some inertia (before mechanical equilibrium is reached) is still open. Moreover, the mixtures can have several temperatures before they relax to a common value. In this paper, we derive a theory of mixtures from Hamiltonian mechanics in interaction with electromagnetic fields. The resulting evolution equations are then reduced to the case with only one momentum (classical irreversible thermodynamics), providing a generalization of the MaxwellStefan diffusion equations. In a next step, we reduce that description to the mechanical equilibrium (no momentum) and derive a nonisothermal variant of the dusty gas model. These reduced equations are solved numerically, and we illustrate the results on effciency analysis, showing where in a concentration cell effciency is lost. Finally, the theory of mixtures identifies the temperature difference between constituents as a possible new source of the Soret coeffcient. For the sake of clarity, we restrict the presentation to the case of binary mixtures; the generalization is straightforward. 
A. Zafferi, D. Peschka, M. Thomas, GENERIC framework for reactive fluid flows, ZAMM. Zeitschrift für Angewandte Mathematik und Mechanik, 103 (2023), pp. e202100254/1e202100254/70 (published online on 09.05.2022), DOI 10.1002/zamm.202100254 .
Abstract
We describe reactive fluid flows in terms of the formalism General Equation for NonEquilibrium ReversibleIrreversible Coupling also known as GENERIC. Together with the formalism, we present the thermodynamical and mechanical foundations for the treatment of fluid flows using continuous fields and present a clear relation and transformation between a Lagrangian and an Eulerian formulation of the corresponding systems of partial differential equations. We bring the abstract framework to life by providing many physically relevant examples for reactive compressive fluid flows. 
G.L. Celora, M.G. Hennessy, A. Münch, B. Wagner, S.L. Waters, A kinetic model of a polyelectrolyte gel undergoing phase separation, Journal of the Mechanics and Physics of Solids, 160 (2022), pp. 104771/1104771/27, DOI 10.1016/j.jmps.2021.104771 .
Abstract
In this study we use nonequilibrium thermodynamics to systematically derive a phasefield model of a polyelectrolyte gel coupled to a thermodynamically consistent model for the salt solution surrounding the gel. The governing equations for the gel account for the free energy of the internal interfaces which form upon phase separation, as well as finite elasticity and multicomponent transport. The fully timedependent model describes the evolution of small changes in the mobile ion concentrations and follows their impact on the largescale solvent flux and the emergence of longtime pattern formation in the gel. We observe a strong acceleration of the evolution of the free surface when the volume phase transition sets in, as well as the triggering of spinodal decomposition that leads to strong inhomogeneities in the lateral stresses, potentially leading to experimentally visible patterns. 
D. Bothe, W. Dreyer, P.É. Druet, Multicomponent incompressible fluids  An asymptotic study, ZAMM. Zeitschrift für Angewandte Mathematik und Mechanik, published online on 14.01.2022, DOI 10.1002/zamm.202100174 .
Abstract
This paper investigates the asymptotic behavior of the Helmholtz free energy of mixtures at small compressibility. We start from a general representation for the local free energy that is valid in stable subregions of the phase diagram. On the basis of this representation we classify the admissible data to construct a thermodynamically consistent constitutive model. We then analyze the incompressible limit, where the molar volume becomes independent of pressure. Here we are confronted with two problems:(i) Our study shows that the physical system at hand cannot remain incompressible for arbitrary large deviations from a reference pressure unless its volume is linear in the composition. (ii) As a consequence of the 2nd law of thermodynamics, the incompressible limit implies that the molar volume becomes independent of temperature as well. Most applications, however, reveal the nonappropriateness of this property. According to our mathematical treatment, the free energy as a function of temperature and partial masses tends to a limit in the sense of epi or Gammaconvergence. In the context of the first problem, we study the mixing of two fluids to compare the linearity with experimental observations. The second problem will be treated by considering the asymptotic behavior of both a general inequality relating thermal expansion and compressibility and a PDEsystem relying on the equations of balance for partial masses, momentum and the internal energy.

J. Fischer, K. Hopf, M. Kniely, A. Mielke, Global existence analysis of energyreactiondiffusion systems, SIAM Journal on Mathematical Analysis, 54 (2022), pp. 220267, DOI 10.1137/20M1387237 .
Abstract
We establish globalintime existence results for thermodynamically consistent reaction(cross)diffusion systems coupled to an equation describing heat transfer. Our main interest is to model speciesdependent diffusivities, while at the same time ensuring thermodynamic consistency. A key difficulty of the nonisothermal case lies in the intrinsic presence of crossdiffusion type phenomena like the Soret and the Dufour effect: due to the temperature/energy dependence of the thermodynamic equilibria, a nonvanishing temperature gradient may drive a concentration flux even in a situation with constant concentrations; likewise, a nonvanishing concentration gradient may drive a heat flux even in a case of spatially constant temperature. We use time discretisation and regularisation techniques and derive a priori estimates based on a suitable entropy and the associated entropy production. Renormalised solutions are used in cases where nonintegrable diffusion fluxes or reaction terms appear. 
B. Gaudeul, J. Fuhrmann, Entropy and convergence analysis for two finite volume schemes for a NernstPlanckPoisson system with ion volume constraints, Numerische Mathematik, 151 (2022), pp. 99149, DOI 10.1007/s0021102201279y .
Abstract
In this paper, we consider a driftdiffusion system with crosscoupling through the chemical potentials comprising a model for the motion of finite size ions in liquid electrolytes. The drift term is due to the selfconsistent electric field maintained by the ions and described by a Poisson equation. We design two finite volume schemes based on different formulations of the fluxes. We also provide a stability analysis of these schemes and an existence result for the corresponding discrete solutions. A convergence proof is proposed for nondegenerate solutions. Numerical experiments show the behavior of these schemes. 
V. Miloš, P. Vágner, D. Budáč, M. Carda, M. Paidar, J. Fuhrmann, K. Bouzek, Generalized PoissonNernstPlanckbased physical model of the O$_2$ I LSM I YSZ electrode, Journal of The Electrochemical Society, 169 (2022), pp. 044505/1044505/17, DOI 10.1149/19457111/ac4a51 .
Abstract
The paper presents a generalized PoissonNernstPlanck model of an yttriastabilized zirconia electrolyte developed from first principles of nonequilibrium thermodynamics which allows for spatial resolution of the space charge layer. It takes into account limitations in oxide ion concentrations due to the limited availability of oxygen vacancies. The electrolyte model is coupled with a reaction kinetic model describing the triple phase boundary with electron conducting lanthanum strontium manganite and gaseous phase oxygen. By comparing the outcome of numerical simulations based on different formulations of the kinetic equations with results of EIS and CV measurements we attempt to discern the existence of separate surface lattice sites for oxygen adatoms and O^{2} from the assumption of shared ones. Furthermore, we discern massaction kinetics models from exponential kinetics models. 
M. O'Donovan, P. Farrell, T. Streckenbach, Th. Koprucki, S. Schulz, Multiscale simulations of unipolar hole transport in (In,Ga)N quantum well systems, Optical and Quantum Electronics, 54 (2022), pp. 405/1405/23, DOI 10.1007/s11082022037522 .
Abstract
Understanding the impact of the alloy microstructure on carrier transport becomes important when designing IIInitridebased LED structures. In this work, we study the impact of alloy fluctuations on the hole carrier transport in (In,Ga)N single and multiquantum well systems. To disentangle hole transport from electron transport and carrier recombination processes, we focus our attention on unipolar (pip) systems. The calculations employ our recently established multiscale simulation framework that connects atomistic tightbinding theory with a macroscale driftdiffusion model. In addition to alloy fluctuations, we pay special attention to the impact of quantum corrections on hole transport. Our calculations indicate that results from a virtual crystal approximation present an upper limit for the hole transport in a pip structure in terms of the currentvoltage characteristics. Thus we find that alloy fluctuations can have a detrimental effect on hole transport in (In,Ga)N quantum well systems, in contrast to unipolar electron transport. However, our studies also reveal that the magnitude by which the random alloy results deviate from virtual crystal approximation data depends on several factors, e.g. how quantum corrections are treated in the transport calculations. 
B. Takács, Y. Hadjimichael, High order discretization methods for spatialdependent epidemic models, Mathematics and Computers in Simulation, 198 (2022), pp. 211236, DOI 10.1016/j.matcom.2022.02.021 .
Abstract
In this paper, an SIR model with spatial dependence is studied and results regarding its stability and numerical approximation are presented. We consider a generalization of the original Kermack and McKendrick model in which the size of the populations differs in space. The use of local spatial dependence yields a system of integrodifferential equations. The uniqueness and qualitative properties of the continuous model are analyzed. Furthermore, different choices of spatial and temporal discretizations are employed, and stepsize restrictions for population conservation, positivity, and monotonicity preservation of the discrete model are investigated. We provide sufficient conditions under which high order numerical schemes preserve the discrete properties of the model. Computational experiments verify the convergence and accuracy of the numerical methods. 
A.F.M. TER Elst, A. Linke, J. Rehberg, On the numerical range of sectorial forms, Pure and Applied Functional Analysis, 7 (2022), pp. 19311940.
Abstract
We provide a sharp and optimal generic bound for the angle of the sectorial form associated to a nonsymmetric secondorder elliptic differential operator with various boundary conditions. Consequently this gives an, in general, sharper H^{∞}angle for the H^{∞}calculus on L_{p} for all p ∈ (1, ∞) if the coefficients are real valued. 
A. Glitzky, M. Liero, G. Nika, A coarsegrained electrothermal model for organic semiconductor devices, Mathematical Methods in the Applied Sciences, 45 (2022), pp. 48094833, DOI 10.1002/mma.8072 .
Abstract
We derive a coarsegrained model for the electrothermal interaction of organic semiconductors. The model combines stationary driftdiffusion based electrothermal models with thermistor type models on subregions of the device and suitable transmission conditions. Moreover, we prove existence of a solution using a regularization argument and Schauder's fixed point theorem. In doing so, we extend recent work by taking into account the statistical relation given by the GaussFermi integral and mobility functions depending on the temperature, chargecarrier density, and field strength, which is required for a proper description of organic devices. 
K. Hopf, Weakstrong uniqueness for energyreactiondiffusion systems, Mathematical Models & Methods in Applied Sciences, 21 (2022), pp. 10151069, DOI 10.1142/S0218202522500233 .
Abstract
We establish weakstrong uniqueness and stability properties of renormalised solutions to a class of energyreactiondiffusion systems, which genuinely feature crossdiffusion effects. The systems considered are motivated by thermodynamically consistent models, and their formal entropy structure allows us to use as a key tool a suitably adjusted relative entropy method. Weakstrong uniqueness is obtained for general entropydissipating reactions without growth restrictions, and certain models with a nonintegrable diffusive flux. The results also apply to a class of (isoenergetic) reactioncrossdiffusion systems. 
A. Alphonse, C.N. Rautenberg, J.F. Rodrigues, Analysis of a quasivariational contact problem arising in thermoelasticity, Nonlinear Analysis. An International Mathematical Journal, 217 (2022), pp. 112728/1112728/40, DOI 10.1016/j.na.2021.112728 .
Abstract
We formulate and study two mathematical models of a thermoforming process involving a membrane and a mould as implicit obstacle problems. In particular, the membranemould coupling is determined by the thermal displacement of the mould that depends in turn on the membrane through the contact region. The two models considered are a stationary (or elliptic) model and an evolutionary (or quasistatic) one. For the first model, we prove the existence of weak solutions by solving an elliptic quasivariational inequality coupled to elliptic equations. By exploring the fine properties of the variation of the contact set under nondegenerate data, we give sufficient conditions for the existence of regular solutions, and under certain contraction conditions, also a uniqueness result. We apply these results to a series of semidiscretised problems that arise as approximations of regular solutions for the evolutionary or quasistatic problem. Here, under certain conditions, we are able to prove existence for the evolutionary problem and for a special case, also the uniqueness of timedependent solutions. 
P.É. Druet, Maximal mixed parabolichyperbolic regularity for the full equations of multicomponent fluid dynamics, Nonlinearity, 35 (2022), pp. 38123882, DOI 10.1088/13616544/ac5679 .
Abstract
We consider a NavierStokesFickOnsagerFourier system of PDEs describing mass, energy and momentum balance in a Newtonian fluid with composite molecular structure. For the resulting parabolichyperbolic system, we introduce the notion of optimal regularity of mixed type, and we prove the shorttime existence of strong solutions for a typical initial boundaryvalueproblem. By means of a partial maximum principle, we moreover show that such a solution cannot degenerate in finite time due to blowup or vanishing of the temperature or the partial mass densities. This second result is however only valid under certain growth conditions on the phenomenological coefficients. In order to obtain some illustration of the theory, we set up a special constitutive model for volumeadditive mixtures. 
D. FrerichsMihov, V. John, On a technique for reducing spurious oscillations in DG solutions of convectiondiffusion equations, Applied Mathematics Letters, 129 (2022), pp. 107969/1107969/7, DOI 10.1016/j.aml.2022.107969 .
Abstract
This note studies a generalization of a postprocessing technique and a novel method inspired by the same technique which significantly reduce spurious oscillations in discontinuous Galerkin solutions of convectiondiffusion equations in the convectiondominated regime. 
V. John, P. Knobloch, O. Pártl, A numerical assessment of finite element discretizations for convectiondiffusionreaction equations satisfying discrete maximum principles, Computational Methods in Applied Mathematics, 23 (2023), pp. 969988 (published online on 30.09.2022), DOI 10.1515/cmam20220125 .
Abstract
Numerical studies are presented that investigate finite element methods satisfying discrete maximum principles for convectiondiffusionreaction equations. Two linear methods and several nonlinear schemes, some of them proposed only recently, are included in these studies, which consider a number of twodimensional examples. The evaluation of the results examines the accuracy of the numerical solutions with respect to quantities of interest, like layer widths, and the efficiency of the simulations. 
V. John, P. Knobloch, On algebraically stabilized schemes for convectiondiffusionreaction problems, Numerische Mathematik, 152 (2022), pp. 553585, DOI 10.1007/s00211022013259 .

V. John, B. Moreau, J. Novo, Error analysis of a SUPGstabilized PODROM method for convectiondiffusionreaction equations, Computers & Mathematics with Applications. An International Journal, 122 (2022), pp. 4860, DOI 10.1016/j.camwa.2022.07.017 .
Abstract
A reduced order model (ROM) method based on proper orthogonal decomposition (POD) is analyzed for convectiondiffusionreaction equations. The streamlineupwind PetrovGalerkin (SUPG) stabilization is used in the practically interesting case of dominant convection, both for the full order method (FOM) and the ROM simulations. The asymptotic choice of the stabilization parameter for the SUPGROM is done as proposed in the literature. This paper presents a finite element convergence analysis of the SUPGROM method for errors in different norms. The constants in the error bounds are uniform with respect to small diffusion coefficients. Numerical studies illustrate the performance of the SUPGROM method. 
M. Landstorfer, R. Müller, Thermodynamic models for a concentration and electric field dependent susceptibility in liquid electrolytes, Electrochimica Acta, 428 (2022), pp. 140368/1140368/19, DOI 10.1016/j.electacta.2022.140368 .
Abstract
The dielectric susceptibility $chi$ is an elementary quantity of the electrochemical double layer and the associated Poisson equation. While most often $chi$ is treated as a material constant, its dependency on the salt concentration in liquid electrolytes is demonstrated by various bulk electrolyte experiments. This is usually referred to as dielectric decrement. Further, it is theoretically well accepted that the susceptibility declines for large electric fields. This effect is frequently termed dielectric saturation. We analyze the impact of a variable susceptibility in terms of species concentrations and electric fields based on nonequilibrium thermodynamics. This reveals some nonobvious generalizations compared to the case of a constant susceptibility. In particular the consistent coupling of the Poisson equation, the momentum balance and the chemical potentials functions are of ultimate importance. In a numerical study, we systematically analyze the effects of a concentration and field dependent susceptibility on the double layer of a planar electrode electrolyte interface. We compute the differential capacitance and the spatial structure of the electric potential, solvent concentration and ionic distribution for various nonconstant models of $chi$. 
M. Landstorfer, M. Ohlberger, S. Rave, M. Tacke, A modelling framework for efficient reduced order simulations of parametrised lithiumion battery cells, European Journal of Applied Mathematics, 34 (2023), pp. 554591 (published online on 29.11.2022), DOI 10.1017/S0956792522000353 .
Abstract
In this contribution we present a new modeling and simulation framework for parametrized Lithiumion battery cells. We first derive a new continuum model for a rather general intercalation battery cell on the basis of nonequilibrium thermodynamics. In order to efficiently evaluate the resulting parameterized nonlinear system of partial differential equations the reduced basis method is employed. The reduced basis method is a model order reduction technique on the basis of an incremental hierarchical approximate proper orthogonal decomposition approach and empirical operator interpolation. The modeling framework is particularly well suited to investigate and quantify degradation effects of battery cells. Several numerical experiments are given to demonstrate the scope and efficiency of the modeling framework. 
A. Mielke, J. Naumann, On the existence of globalintime weak solutions and scaling laws for Kolmogorov's twoequation model of turbulence, ZAMM. Zeitschrift für Angewandte Mathematik und Mechanik, 102 (2022), pp. e202000019/1e202000019/31, DOI 10.1002/zamm.202000019 .
Abstract
This paper is concerned with Kolmogorov's twoequation model for free turbulence in space dimension 3, involving the mean velocity u, the pressure p, an average frequency omega, and a mean turbulent kinetic energy k. We first discuss scaling laws for a slightly more general twoequation models to highlight the special role of the model devised by Kolmogorov in 1942. The main part of the paper consists in proving the existence of weak solutions of Kolmogorov's twoequation model under spaceperiodic boundary conditions in cubes with positive side length l. To this end, we provide new a priori estimates and invoke existence result for pseudomonotone operators. 
D. Abdel, P. Vágner, J. Fuhrmann, P. Farrell, Modelling charge transport in perovskite solar cells: Potentialbased and limiting ion depletion, Electrochimica Acta, 390 (2021), pp. 138696/1138696/12, DOI 10.1016/j.electacta.2021.138696 .
Abstract
From MaxwellStefan diffusion and general electrostatics, we derive a driftdiffusion model for charge transport in perovskite solar cells (PSCs) where any ion in the perovskite layer may flexibly be chosen to be mobile or immobile. Unlike other models in the literature, our model is based on quasi Fermi potentials instead of densities. This allows to easily include nonlinear diffusion (based on FermiDirac, GaussFermi or Blakemore statistics for example) as well as limit the ion depletion (via the FermiDirac integral of order1). The latter will be motivated by a grandcanonical formalism of ideal lattice gas. Furthermore, our model allows to use different statistics for different species. We discuss the thermodynamic equilibrium, electroneutrality as well as generation/recombination. Finally, we present numerical finite volume simulations to underline the importance of limiting ion depletion. 
D. Abdel, P. Farrell, J. Fuhrmann, Assessing the quality of the excess chemical potential flux scheme for degenerate semiconductor device simulation, Optical and Quantum Electronics, 53 (2021), pp. 163/1163/10, DOI 10.1007/s11082021028034 .
Abstract
The van Roosbroeck system models current flows in (non)degenerate semiconductor devices. Focusing on the stationary model, we compare the excess chemical potential discretization scheme, a flux approximation which is based on a modification of the drift term in the current densities, with another stateoftheart ScharfetterGummel scheme, namely the diffusionenhanced scheme. Physically, the diffusionenhanced scheme can be interpreted as a flux approximation which modifies the thermal voltage. As a reference solution we consider an implicitly defined integral flux, using Blakemore statistics. The integral flux refers to the exact solution of a local two point boundary value problem for the continuous current density and can be interpreted as a generalized ScharfetterGummel scheme. All numerical discretization schemes can be used within a Voronoi finite volume method to simulate charge transport in (non)degenerate semiconductor devices. The investigation includes the analysis of Taylor expansions, a derivation of error estimates and a visualization of errors in local flux approximations to extend previous discussions. Additionally, driftdiffusion simulations of a pin device are performed. 
P.É. Druet, Globalintime existence for liquid mixtures subject to a generalised incompressibility constraint, Journal of Mathematical Analysis and Applications, 499 (2021), pp. 125059/1125059/56, DOI 10.1016/j.jmaa.2021.125059 .
Abstract
We consider a system of partial differential equations describing diffusive and convective mass transport in a fluid mixture of N > 1 chemical species. A weighted sum of the partial mass densities of the chemical species is assumed to be constant, which expresses the incompressibility of the fluid, while accounting for different reference sizes of the involved molecules. This condition is different from the usual assumption of a constant total mass density, and it leads in particular to a nonsolenoidal velocity field in the NavierStokes equations. In turn, the pressure gradient occurs in the diffusion fluxes, so that the PDEsystem of mass transport equations and momentum balance is fully coupled. Another striking feature of such incompressible mixtures is the algebraic formula connecting the pressure and the densities, which can be exploited to prove a pressure bound in L^{1}. In this paper, we consider incompressible initial states with bounded energy and show the global existence of weak solutions with defect measure. 
M. Heida, M. Kantner, A. Stephan, Consistency and convergence for a family of finite volume discretizations of the FokkerPlanck operator, ESAIM: Mathematical Modelling and Numerical Analysis, 55 (2021), pp. 30173042, DOI 10.1051/m2an/2021078 .
Abstract
We introduce a family of various finite volume discretization schemes for the FokkerPlanck operator, which are characterized by different weight functions on the edges. This family particularly includes the wellestablished ScharfetterGummel discretization as well as the recently developed squareroot approximation (SQRA) scheme. We motivate this family of discretizations both from the numerical and the modeling point of view and provide a uniform consistency and error analysis. Our main results state that the convergence order primarily depends on the quality of the mesh and in second place on the quality of the weights. We show by numerical experiments that for small gradients the choice of the optimal representative of the discretization family is highly nontrivial while for large gradients the ScharfetterGummel scheme stands out compared to the others. 
S. Kayser, P. Farrell, N. Rotundo, Detecting striations via the lateral photovoltage scanning method without screening effect, Optical and Quantum Electronics, 53 (2021), pp. 288/1288/10, DOI 10.1007/s11082021029111 .
Abstract
The lateral photovoltage scanning method (LPS) detects doping inhomogeneities in semiconductors such as Si, Ge and Si(x)Ge(1x) in a cheap, fast and nondestructive manner. LPS relies on the bulk photovoltaic effect and thus can detect any physical quantity affecting the band profiles of the sample. LPS finite volume simulation using commercial software suffer from long simulation times and convergence instabilities. We present here an opensource finite volume simulation for a 2D Si sample using the ddfermi simulator. For low injection conditions we show that the LPS voltage is proportional to the doping gradient as previous theory suggested under certain conditions. For higher injection conditions we directly show how the LPS voltage and the doping gradient differ and link the physical effect of lower local resolution to the screening effect. Previously, the loss of local resolution was assumed to be only connected to the enlargement of the excess charge carrier distribution. 
O. Marquardt, Simulating the electronic properties of semiconductor nanostructures using multiband $kcdot p$ models, Computational Materials Science, 194 (2021), pp. 110318/1110318/11, DOI 10.1016/j.commatsci.2021.110318 .
Abstract
The eightband $kcdot p$ formalism been successfully applied to compute the electronic properties of a wide range of semiconductor nanostructures in the past and can be considered the backbone of modern semiconductor heterostructure modelling. However, emerging novel material systems and heterostructure fabrication techniques raise questions that cannot be answered using this wellestablished formalism, due to its intrinsic limitations. The present article reviews recent studies on the calculation of electronic properties of semiconductor nanostructures using a generalized multiband $kcdot p$ approach that allows both the application of the eightband model as well as more sophisticated approaches for novel material systems and heterostructures. 
G. Nika, Derivation of effective models from heterogenous Cosserat media via periodic unfolding, Ricerche di Matematica. A Journal of Pure and Applied Mathematics, published online on 01.07.2021, DOI 10.1007/s11587021006103 .
Abstract
We derive two different effective models from a heterogeneous Cosserat continuum taking into account the Cosserat intrinsic length of the constituents. We pass to the limit using homogenization via periodic unfolding and in doing so we provide rigorous proof to the results introduced by Forest, Pradel, and Sab (Int. J. Solids Structures 38 (2627): 45854608 '01). Depending on how different characteristic lengths of the domain scale with respect to the Cosserat intrinsic length, we obtain either an effective classical Cauchy continuum or an effective Cosserat continuum. Moreover, we provide some corrector type results for each case. 
A. Stephan, EDPconvergence for a linear reactiondiffusion system with fast reversible reaction, Calculus of Variations and Partial Differential Equations, 60 (2021), pp. 226/1226/35, DOI 10.1007/s00526021020890 .
Abstract
We perform a fastreaction limit for a linear reactiondiffusion system consisting of two diffusion equations coupled by a linear reaction. We understand the linear reactiondiffusion system as a gradient flow of the free energy in the space of probability measures equipped with a geometric structure, which contains the Wasserstein metric for the diffusion part and coshtype functions for the reaction part. The fastreaction limit is done on the level of the gradient structure by proving EDPconvergence with tilting. The limit gradient system induces a diffusion system with Lagrange multipliers on the linear slowmanifold. Moreover, the limit gradient system can be equivalently described by a coarsegrained gradient system, which induces a diffusion equation with a mixed diffusion constant for the coarsegrained slow variable. 
L. Lilaj, H. Harthum, T. Meyer, M. Shahrayari, G. Bertalan, A. Caiazzo, J. Braun, Th. Fischer, S. Hirsch, I. Sack, Inversionrecovery MR elastography of the human brain for improved stiffness quantification near fluidsolid boundaries, Magnetic Resonance in Medicine, (2021), published online on 28.06.2021, DOI 10.1002/mrm.28898 .

N. Ahmed, G.R. Barrenechea, E. Burman, J. Guzmán, A. Linke, Ch. Merdon, A pressurerobust discretization of Oseen's equation using stabilization in the vorticity equation, SIAM Journal on Numerical Analysis, 59 (2021), pp. 27462774, DOI 10.1137/20M1351230 .
Abstract
Discretization of NavierStokes' equations using pressurerobust finite element methods is considered for the high Reynolds number regime. To counter oscillations due to dominating convection we add a stabilization based on a bulk term in the form of a residualbased least squares stabilization of the vorticity equation supplemented by a penalty term on (certain components of) the gradient jump over the elements faces. Since the stabilization is based on the vorticity equation, it is independent of the pressure gradients, which makes it pressurerobust. Thus, we prove pressureindependent error estimates in the linearized case, known as Oseen's problem. In fact, we prove an O(h^{k}+^{1}/2) error estimate in the L^{2}norm that is known to be the best that can be expected for this type of problem. Numerical examples are provided that, in addition to confirming the theoretical results, show that the present method compares favorably to the classical residualbased SUPG stabilization. 
TH. Apel, V. Kempf, A. Linke, Ch. Merdon, A nonconforming pressurerobust finite element method for the Stokes equations on anisotropic meshes, IMA Journal of Numerical Analysis, 42 (2022), pp. 392416 (published online on 14.01.2021), DOI 10.1093/imanum/draa097 .
Abstract
Most classical finite element schemes for the (Navier)Stokes equations are neither pressurerobust, nor are they infsup stable on general anisotropic triangulations. A lack of pressurerobustness may lead to large velocity errors, whenever the Stokes momentum balance is dominated by a strong and complicated pressure gradient. It is a consequence of a method, which does not exactly satisfy the divergence constraint. However, infsup stable schemes can often be made pressurerobust just by a recent, modified discretization of the exterior forcing term, using H(div)conforming velocity reconstruction operators. This approach has so far only been analyzed on shaperegular triangulations. The novelty of the present contribution is that the reconstruction approach for the CrouzeixRaviart method, which has a stable Fortin operator on arbitrary meshes, is combined with results on the interpolation error on anisotropic elements for reconstruction operators of RaviartThomas and BrezziDouglasMarini type, generalizing the method to a large class of anisotropic triangulations. Numerical examples confirm the theoretical results in a 2D and a 3D test case. 
L. Baňas, R. Lasarzik, A. Prohl, Numerical analysis for nematic electrolytes, IMA Journal of Numerical Analysis, 41 (2021), pp. 21862254, DOI 10.1093/imanum/draa082 .
Abstract
We consider a system of nonlinear PDEs modeling nematic electrolytes, and construct a dissipative solution with the help of its implementable, structureinheriting spacetime discretization. Computational studies are performed to study the mutual effects of electric, elastic, and viscous effects onto the molecules in a nematic electrolyte. 
D. Bothe, P.É. Druet, Mass transport in multicomponent compressible fluids: Local and global wellposedness in classes of strong solutions for general classone models, Nonlinear Analysis. Theory, Methods & Applications. An International Multidisciplinary Journal. Series A: Theory and Methods, 210 (2021), pp. 112389/1112389/53, DOI 10.1016/j.na.2021.112389 .
Abstract
We consider a system of partial differential equations describing mass transport in a multicomponent isothermal compressible fluid. The diffusion fluxes obey the FickOnsager or Maxwell Stefan closure approach. Mechanical forces result into one single convective mixture velocity, the barycentric one, which obeys the NavierStokes equations. The thermodynamic pressure is defined by the GibbsDuhem equation. Chemical potentials and pressure are derived from a thermodynamic potential, the Helmholtz free energy, with a bulk density allowed to be a general convex function of the mass densities of the constituents. The resulting PDEs are of mixed parabolichyperbolic type. We prove two theoretical results concerning the wellposedness of the model in classes of strong solutions: 1. The solution always exists and is unique for shorttimes and 2. If the initial data are sufficiently near to an equilibrium solution, the wellposedness is valid on arbitrary large, but finite time intervals. Both results rely on a contraction principle valid for systems of mixed type that behave like the compressible Navier Stokes equations. The linearised parabolic part of the operator possesses the self map property with respect to some closed ball in the state space, while being contractive in a lower order norm only. In this paper, we implement these ideas by means of precise a priori estimates in spaces of exact regularity. 
D. Bothe, P.É. Druet, Wellposedness analysis of multicomponent incompressible flow models, Journal of Evolution Equations, 21 (2021), pp. 40394093, DOI 10.1007/s00028021007123 .
Abstract
In this paper, we extend our study of mass transport in multicomponent isothermal fluids to the incompressible case. For a mixture, incompressibility is defined as the independence of average volume on pressure, and a weighted sum of the partial mass densities of the species stays constant. In this type of models, non solenoidal effects affect the velocity field in the NavierStokes equations and, due to different specific volumes of the species, the pressure remains connected to the densities by algebraic formula. By means of a change of variables in the transport problem, we equivalently reformulate the PDE system as to eliminate positivity and incompressibility constraints affecting the density, and prove two type of results: the localintime wellposedness in classes of strong solutions, and the globalintime existence of solutions for initial data sufficiently close to a smooth equilibrium solution. 
D. Chaudhuri, M. O'Donovan, T. Streckenbach, O. Marquardt, P. Farrell, S.K. Patra, Th. Koprucki, S. Schulz, Multiscale simulations of the electronic structure of IIInitride quantum wells with varied indium content: Connecting atomistic and continuumbased models, Journal of Applied Physics, 129 (2021), pp. 073104/1073104/16, DOI 10.1063/5.0031514 .

O.C. Ernst, D. Uebel, S. Kayser, F. Lange, Th. Teubner, T. Boeck, Revealing all states of dewetting of a thin gold layer on a silicon surface by nanosecond laser conditioning, Applied Surface Science Advances, 3 (2021), pp. 100040/1100040/10, DOI 10.1016/j.apsadv.2020.100040 .
Abstract
Dewetting is a ubiquitous phenomenon which can be applied to the laser synthesis of nanoparticles. A classical spinodal dewetting process takes place in four successive states, which differ from each other in their morphology. In this study all states are revealed by interaction of pulsed nanosecond UV laser light with thin gold layers with thicknesses between 1 nm and 10 nm on (100) silicon wafers. The specific morphologies of the dewetting states are discussed with particular emphasis on the state boundaries. The main parameter determining which state is formed is not the duration for which the gold remains liquid, but rather the input energy provided by the laser. This shows that each state transition has a separate measurable activation energy. The temperature during the nanosecond pulses and the duration during which the gold remains liquid was determined by simulation using the COMSOL Multiphysics software package. Using these calculations, an accurate local temperature profile and its development over time was simulated. An analytical study of the morphologies and formed structures was performed using Minkowski measures. With aid of this tool, the laser induced structures were compared with thermally annealed samples, with perfectly ordered structures and with perfectly random structures. The results show that both, structures of the laser induced and the annealed samples, strongly resemble the perfectly ordered structures. This reveals a close relationship between these structures and suggests that the phenomenon under investigation is indeed a spinodal dewetting generated by an internal material wave function.
The purposeful generation of these structures and the elucidation of the underlying mechanism of dewetting by ultrashort pulse lasers may assist the realisation of various technical elements such as nanowires in science and industry. 
G. Fu, Ch. Lehrenfeld, A. Linke, T. Streckenbach, Locking free and gradient robust H(div)conforming HDG methods for linear elasticity, Journal of Scientific Computing, 86 (2021), DOI 10.1007/s10915020013966 .
Abstract
Robust discretization methods for (nearlyincompressible) linear elasticity are free of volumelocking and gradientrobust. While volumelocking is a wellknown problem that can be dealt with in many different discretization approaches, the concept of gradientrobustness for linear elasticity is new. We discuss both aspects and propose novel Hybrid Discontinuous Galerkin (HDG) methods for linear elasticity. The starting point for these methods is a divergenceconforming discretization. As a consequence of its wellbehaved Stokes limit the method is gradientrobust and free of volumelocking. To improve computational efficiency, we additionally consider discretizations with relaxed divergenceconformity and a modification which reenables gradientrobustness, yielding a robust and quasioptimal discretization also in the sense of HDG superconvergence. 
B. GarcíaArchilla, V. John, J. Novo, On the convergence order of the finite element error in the kinetic energy for high Reynolds number incompressible flows, Computer Methods in Applied Mechanics and Engineering, 385 (2021), pp. 114032/1114032/54, DOI 10.1016/j.cma.2021.114032 .

L. Heltai, A. Caiazzo, L.O. Müller, Multiscale coupling of onedimensional vascular models and elastic tissues, Annals of Biomedical Engineering (ABME), published online on 20.07.2021, DOI 10.1007/s10439021028040 .
Abstract
We present a computational multiscale model for the efficient simulation of vascularized tissues, composed of an elastic threedimensional matrix and a vascular network. The effect of blood vessel pressure on the elastic tissue is surrogated via hypersingular forcing terms in the elasticity equations, which depend on the fluid pressure. In turn, the blood flow in vessels is treated as a onedimensional network. The pressure and velocity of the blood in the vessels are simulated using a highorder finite volume scheme, while the elasticity equations for the tissue are solved using a finite element method. This work addresses the feasibility and the potential of the proposed coupled multiscale model. In particular, we assess whether the multiscale model is able to reproduce the tissue response at the effective scale (of the order of millimeters) while modeling the vasculature at the microscale. We validate the multiscale method against a full scale (threedimensional) model, where the fluid/tissue interface is fully discretized and treated as a Neumann boundary for the elasticity equation. Next, we present simulation results obtained with the proposed approach in a realistic scenario, demonstrating that the method can robustly and efficiently handle the oneway coupling between complex fluid microstructures and the elastic matrix. 
P.L. Lederer, Ch. Merdon, Guaranteed upper bounds for the velocity error of pressurerobust Stokes discretisations, Journal of Numerical Mathematics, published online on 6.11.2021, DOI https://doi.org/10.1515/jnma20210078 .
Abstract
This paper improves guaranteed error control for the Stokes problem with a focus on pressurerobustness, i.e. for discretisations that compute a discrete velocity that is independent of the exact pressure. A PragerSynge type result relates the errors of divergencefree primal and H(div)conforming dual mixed methods (for the velocity gradient) with an equilibration constraint that needs special care when discretised. To relax the constraints on the primal and dual method, a more general result is derived that enables the use of a recently developed mass conserving mixed stress discretisation to design equilibrated fluxes that yield pressureindependent guaranteed upper bounds for any pressurerobust (but not necessarily divergencefree) primal discretisation. Moreover, a provably efficient local design of the equilibrated fluxes is presented that reduces the numerical costs of the error estimator. All theoretical findings are verified by numerical examples which also show that the efficiency indices of our novel guaranteed upper bounds for the velocity error are close to 1. 
M. O'Donovan, D. Chaudhuri, T. Streckenbach, P. Farrell, S. Schulz, Th. Koprucki, From atomistic tightbinding theory to macroscale driftdiffusion: Multiscale modeling and numerical simulation of unipolar charge transport in (In,Ga)N devices with random fluctuations, Journal of Applied Physics, 130 (2021), pp. 065702/1065702/13, DOI 10.1063/5.0059014 .

M. Thomas, S. Tornquist, Discrete approximation of dynamic phasefield fracture in viscoelastic materials, Discrete and Continuous Dynamical Systems  Series S, 14 (2021), pp. 38653924, DOI 10.3934/dcdss.2021067 .
Abstract
This contribution deals with the analysis of models for phasefield fracture in viscoelastic materials with dynamic effects. The evolution of damage is handled in two different ways: As a viscous evolution with a quadratic dissipation potential and as a rateindependent law with a positively 1homogeneous dissipation potential. Both evolution laws encode a nonsmooth constraint that ensures the unidirectionality of damage, so that the material cannot heal. Suitable notions of solutions are introduced in both settings. Existence of solutions is obtained using a discrete approximation scheme both in space and time. Based on the convexity properties of the energy functional and on the regularity of the displacements thanks to their viscous evolution, also improved regularity results with respect to time are obtained for the internal variable: It is shown that the damage variable is continuous in time with values in the state space that guarantees finite values of the energy functional. 
A. Alphonse, C.N. Rautenberg, J.F. Rodrigues, Analysis of a quasivariational contact problem arising in thermoelasticity, Nonlinear Analysis. Theory, Methods & Applications. An International Multidisciplinary Journal. Series A: Theory and Methods, 217 (2022), pp. 112728/1112728/40 (published online on 13.12.2021), DOI 10.1016/j.na.2021.112728 .
Abstract
We formulate and study two mathematical models of a thermoforming process involving a membrane and a mould as implicit obstacle problems. In particular, the membranemould coupling is determined by the thermal displacement of the mould that depends in turn on the membrane through the contact region. The two models considered are a stationary (or elliptic) model and an evolutionary (or quasistatic) one. For the first model, we prove the existence of weak solutions by solving an elliptic quasivariational inequality coupled to elliptic equations. By exploring the fine properties of the variation of the contact set under nondegenerate data, we give sufficient conditions for the existence of regular solutions, and under certain contraction conditions, also a uniqueness result. We apply these results to a series of semidiscretised problems that arise as approximations of regular solutions for the evolutionary or quasistatic problem. Here, under certain conditions, we are able to prove existence for the evolutionary problem and for a special case, also the uniqueness of timedependent solutions. 
P. Farrell, S. Kayser, N. Rotundo, Modeling and simulation of the lateral photovoltage scanning method, Computers & Mathematics with Applications. An International Journal, 102 (2021), pp. 248260, DOI 10.1016/j.camwa.2021.10.017 .
Abstract
The fast, cheap and nondestructive lateral photovoltage scanning (LPS) method detects inhomogeneities in semiconductors crystals. The goal of this paper is to model and simulate this technique for a given doping profile. Our model is based on the semiconductor device equations combined with a nonlinear boundary condition, modelling a volt meter. To validate our 2D and 3D finite volume simulations, we use theory developed by Tauc [21] to derive three analytical predictions which our simulation results corroborate, even for anisotropic 2D and 3D meshes. Our code runs about two orders of magnitudes faster than earlier implementations based on commercial software [15]. It also performs well for small doping concentrations which previously could not be simulated at all due to numerical instabilities. Our simulations provide experimentalists with reference laser powers for which meaningful voltages can still be measured. For higher laser power the screening effect does not allow this anymore. 
D. Frerichs, V. John, On reducing spurious oscillations in discontinuous Galerkin (DG) methods for steadystate convectiondiffusion equations, Journal of Computational and Applied Mathematics, 393 (2021), pp. 113487/1113487/20, DOI 10.1016/j.cam.2021.113487 .

TH. Koprucki, A. Maltsi, A. Mielke, On the DarwinHowieWhelan equations for the scattering of fast electrons described by the Schrödinger equation, SIAM Journal on Applied Mathematics, 81 (2021), pp. 15521578, DOI 10.1137/21M139164X .
Abstract
The DarwinHowieWhelan equations are commonly used to describe and simulate the scattering of fast electrons in transmission electron microscopy. They are a system of infinitely many envelope functions, derived from the Schrödinger equation. However, for the simulation of images only a finite set of envelope functions is used, leading to a system of ordinary differential equations in thickness direction of the specimen. We study the mathematical structure of this system and provide error estimates to evaluate the accuracy of special approximations, like the twobeam and the systematicrow approximation. 
A. Maltsi, T. Niermann, T. Streckenbach, K. Tabelow, Th. Koprucki, Numerical simulation of TEM images for In(Ga)As/GaAs quantum dots with various shapes, Optical and Quantum Electronics, 52 (2020), pp. 257/1257/11, DOI 10.1007/s1108202002356y .
Abstract
We present a mathematical model and a tool chain for the numerical simulation of TEM images of semiconductor quantum dots (QDs). This includes elasticity theory to obtain the strain profile coupled with the DarwinHowieWhelan equations, describing the propagation of the electron wave through the sample. We perform a simulation study on indium gallium arsenide QDs with different shapes and compare the resulting TEM images to experimental ones. This tool chain can be applied to generate a database of simulated TEM images, which is a key element of a novel concept for modelbased geometry reconstruction of semiconductor QDs, involving machine learning techniques. 
W. Dreyer, P.É. Druet, P. Gajewski, C. Guhlke, Analysis of improved NernstPlanckPoisson models of compressible isothermal electrolytes, ZAMP Zeitschrift fur Angewandte Mathematik und Physik. ZAMP. Journal of Applied Mathematics and Physics. Journal de Mathematiques et de Physique Appliquees, 71 (2020), pp. 119/1119/68, DOI 10.1007/s00033020013415 .
Abstract
We consider an improved NernstPlanckPoisson model first proposed by Dreyer et al. in 2013 for compressible isothermal electrolytes in non equilibrium. The model takes into account the elastic deformation of the medium that induces an inherent coupling of mass and momentum transport. The model consists of convectiondiffusionreaction equations for the constituents of the mixture, of the NavierStokes equation for the barycentric velocity, and of the Poisson equation for the electrical potential. Due to the principle of mass conservation, crossdiffusion phenomena must occur and the mobility matrix (Onsager matrix) has a kernel. In this paper we establish the existence of a globalintime weak solution for the full model, allowing for a general structure of the mobility tensor and for chemical reactions with highly non linear rates in the bulk and on the active boundary. We characterise the singular states of the system, showing that the chemical species can vanish only globally in space, and that this phenomenon must be concentrated in a compact set of measure zero in time. With respect to our former study [DDGG16], we also essentially improve the a priori estimates, in particular concerning the relative chemical potentials. 
P.É. Druet, A. Jüngel, Analysis of crossdiffusion systems for fluid mixtures driven by a pressure gradient, SIAM Journal on Mathematical Analysis, 52 (2020), pp. 21792197, DOI 10.1137/19M1301473 .
Abstract
The convective transport in a multicomponent isothermal compressible fluid subject to the mass continuity equations is considered. The velocity is proportional to the negative pressure gradient, according to Darcy?s law, and the pressure is defined by a state equation imposed by the volume extension of the mixture. These model assumptions lead to a parabolichyperbolic system for the mass densities. The globalintime existence of classical and weak solutions is proved in a bounded domain with nopenetration boundary conditions. The idea is to decompose the system into a porousmediumtype equation for the volume extension and transport equations for the modified number fractions. The existence proof is based on parabolic regularity theory, the theory of renormalized solutions, and an approximation of the velocity field. 
M. Landstorfer, B. Prifling, V. Schmidt, Mesh generation for periodic 3D microstructure models and computation of effective properties, Journal of Computational Physics, 431 (2021), pp. 110071/1110071/20 (published online on 23.12.2020), DOI https://doi.org/10.1016/j.jcp.2020.110071 .
Abstract
Understanding and optimizing effective properties of porous functional materials, such as permeability or conductivity, is one of the main goals of materials science research with numerous applications. For this purpose, understanding the underlying 3D microstructure is crucial since it is well known that the materials? morphology has an significant impact on their effective properties. Because tomographic imaging is expensive in time and costs, stochastic microstructure modeling is a valuable tool for virtual materials testing, where a large number of realistic 3D microstructures can be generated and used as geometry input for spatiallyresolved numerical simulations. Since the vast majority of numerical simulations is based on solving differential equations, it is essential to have fast and robust methods for generating highquality volume meshes for the geometrically complex microstructure domains. The present paper introduces a novel method for generating volumemeshes with periodic boundary conditions based on an analytical representation of the 3D microstructure using spherical harmonics. Due to its generality, the present method is applicable to many scientific areas. In particular, we present some numerical examples with applications to battery research by making use of an already existing stochastic 3D microstructure model that has been calibrated to eight differently compacted cathodes. 
P. Vágner, M. Pavelka, O. Esen, Multiscale thermodynamics of charged mixtures, Continuum Mechanics and Thermodynamics, published online on 25.07.2020, DOI 10.1007/s00161020009005 .
Abstract
A multiscale theory of interacting continuum mechanics and thermodynamics of mixtures of fluids, electrodynamics, polarization and magnetization is proposed. The mechanical (reversible) part of the theory is constructed in a purely geometric way by means of semidirect products. This leads to a complex Hamiltonian system with a new Poisson bracket, which can be used in principle with any energy functional. The thermodynamic (irreversible) part is added as gradient dynamics, generated by derivatives of a dissipation potential, which makes the theory part of the GENERIC framework. Subsequently, Dynamic MaxEnt reductions are carried out, which lead to reduced GENERIC models for smaller sets of state variables. Eventually, standard engineering models are recovered as the lowlevel limits of the detailed theory. The theory is then compared to recent literature. 
M. Akbas, Th. Gallouët, A. Gassmann, A. Linke, Ch. Merdon, A gradientrobust wellbalanced scheme for the compressible isothermal Stokes problem, Computer Methods in Applied Mechanics and Engineering, 367 (2020), pp. 113069/1113069/25, DOI 10.1016/j.cma.2020.113069 .
Abstract
A novel notion for constructing a wellbalanced scheme  a gradientrobust scheme  is introduced and a showcase application for a steady compressible, isothermal Stokes equations is presented. Gradientrobustness means that arbitrary gradient fields in the momentum balance are wellbalanced by the discrete pressure gradient  if there is enough mass in the system to compensate the force. The scheme is asymptoticpreserving in the sense that it degenerates for low Mach numbers to a recent infsup stable and pressurerobust discretization for the incompressible Stokes equations. The convergence of the coupled FEMFVM scheme for the nonlinear, isothermal Stokes equations is proved by compactness arguments. Numerical examples illustrate the numerical analysis, and show that the novel approach can lead to a dramatically increased accuracy in nearlyhydrostatic low Mach number flows. Numerical examples also suggest that a straightforward extension to barotropic situations with nonlinear equations of state is feasible. 
I. Selmer, P. Farrell, I. Smirnova, P. Gurikov, Comparison of finite difference method and finite volume method simulations for a mass transport model describing the supercritical drying kinetic of gel particles in a packed bed, Gels, 6 (2020), pp. 45/145/26, DOI 10.3390/gels6040045 .

N. Ahmed, V. John, An assessment of two classes of variational multiscale methods for the simulation of incompressible turbulent flows, Computer Methods in Applied Mechanics and Engineering, 365 (2020), pp. 112997/1112997/20, DOI 10.1016/j.cma.2020.112997 .
Abstract
A numerical assessment of two classes of variational multiscale (VMS) methods for the simulation of incompressible flows is presented. Two types of residualbased VMS methods and two types of projectionbased VMS methods are included in this assessment. The numerical simulations are performed at turbulent channel flow problems with various friction Reynolds numbers. It turns out the the residualbased VMS methods, in particular when used with a pair of infsup stable finite elements, give usually the most accurate results for second order statistics. For this pair of finite element spaces, a flexible GMRES method with a Least Squares Commutator (LSC) preconditioner proved to be an efficient solver. 
C. Cancès, C. ChainaisHillairet, J. Fuhrmann, B. Gaudeul, A numerical analysis focused comparison of several finite volume schemes for an unipolar degenerated driftdiffusion model, IMA Journal of Numerical Analysis, 41 (2021), pp. 271314 (published online on 17.07.2020), DOI 10.1093/imanum/draa002 .
Abstract
In this paper, we consider an unipolar degenerated driftdiffusion system where the relation between the concentration of the charged species c and the chemical potential h is h(c) = log ^{c}/_{1c}. We design four different finite volume schemes based on four different formulations of the fluxes. We provide a stability analysis and existence results for the four schemes. The convergence proof with respect to the discretization parameters is established for two of them. Numerical experiments illustrate the behaviour of the different schemes. 
J.A. Carrillo, K. Hopf, M.Th. Wolfram, Numerical study of BoseEinstein condensation in the KaniadakisQuarati model for bosons, Kinetic and Related Models, 13 (2020), pp. 507529, DOI 10.3934/krm.2020017 .
Abstract
Kaniadakis and Quarati (1994) proposed a FokkerPlanck equation with quadratic drift as a PDE model for the dynamics of bosons in the spatially homogeneous setting. It is an open question whether this equation has solutions exhibiting condensates in finite time. The main analytical challenge lies in the continuation of exploding solutions beyond their first blowup time while having a linear diffusion term. We present a thoroughly validated timeimplicit numerical scheme capable of simulating solutions for arbitrarily large time, and thus enabling a numerical study of the condensation process in the KaniadakisQuarati model. We show strong numerical evidence that above the critical mass rotationally symmetric solutions of the KaniadakisQuarati model in 3D form a condensate in finite time and converge in entropy to the unique minimiser of the natural entropy functional at an exponential rate. Our simulations further indicate that the spatial blowup profile near the origin follows a universal power law and that transient condensates can occur for sufficiently concentrated initial data. 
R. Chill, H. Meinlschmidt, J. Rehberg, On the numerical range of second order elliptic operators with mixed boundary conditions in L$^p$, Journal of Evolution Equations, 21 (2021), pp. 32673288 (published online on 20.10.2020), DOI 10.1007/s00028020006426 .
Abstract
We consider second order elliptic operators with real, nonsymmetric coefficient functions which are subject to mixed boundary conditions. The aim of this paper is to provide uniform resolvent estimates for the realizations of these operators on L^{p} in a most direct way and under minimal regularity assumptions on the domain. This is analogous to the main result in [7]. Ultracontractivity of the associated semigroups is also considered. All results are for two different form domains realizing mixed boundary conditions. We further consider the case of Robin instead of classical Neumann boundary conditions and also allow for operators inducing dynamic boundary conditions. The results are complemented by an intrinsic characterization of elements of the form domains inducing mixed boundary conditions. 
D.H. Doan, A. Fischer, J. Fuhrmann, A. Glitzky, M. Liero, Driftdiffusion simulation of Sshaped currentvoltage relations for organic semiconductor devices, Journal of Computational Electronics, 19 (2020), pp. 11641174, DOI 10.1007/s10825020015056 .
Abstract
We present an electrothermal driftdiffusion model for organic semiconductor devices with GaussFermi statistics and positive temperature feedback for the charge carrier mobilities. We apply temperature dependent Ohmic contact boundary conditions for the electrostatic potential and discretize the system by a finite volume based generalized ScharfetterGummel scheme. Using pathfollowing techniques we demonstrate that the model exhibits Sshaped currentvoltage curves with regions of negative differential resistance, which were only recently observed experimentally. 
B. GarcíaArchilla, V. John, J. Novo, Symmetric pressure stabilization for equalorder finite element approximations to the timedependent NavierStokes equations, IMA Journal of Numerical Analysis, 41 (2021), pp. 10931129 (published online on 23.06.2020), DOI 10.1093/imanum/draa037 .

M.G. Hennessy, A. Münch, B. Wagner, Phase separation in swelling and deswelling hydrogels with a free boundary, Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, 101 (2020), pp. 032501/1032501/14, DOI 10.1103/PhysRevE.101.032501 .
Abstract
We present a full kinetic model of a hydrogel that undergoes phase separation during swelling and deswelling. The model accounts for the interfacial energy of coexisting phases, finite strain of the polymer network, andsolvent transport across free boundaries. For the geometry of an initially dry layer bonded to a rigid substrate,the model predicts that forcing solvent into the gel at a fixed rate can induce a volume phase transition, whichgives rise to coexisting phases with different degrees of swelling, in systems where this cannot occur in the freeswelling case. While a nonzero shear modulus assists in the propagation of the transition front separating thesephases in the drivenswelling case, increasing it beyond a critical threshold suppresses its formation. Quenchinga swollen hydrogel induces spinodal decomposition, which produces several highly localized, highly swollenphases which coarsen and are then ejected from free boundary. The wealth of dynamic scenarios of this systemis discussed using phaseplane analysis and numerical solutions in a onedimensional setting. 
D. Janke, A. Caiazzo, N. Ahmed, N. Alia, O. Knoth, B. Moreau, U. Wilbrandt, D. Willink, Th. Amon, V. John, On the feasibility of using open source solvers for the simulation of a turbulent air flow in a dairy barn, Computers and Electronics in Agriculture, 175 (2020), pp. 105546/1105546/16, DOI 10.1016/j.compag.2020.105546 .
Abstract
Two transient open source solvers, OpenFOAM and ParMooN, are assessed with respect to the simulation of the turbulent air flow inside and around a dairy barn. For this purpose, data were obtained in an experimental campaign at a 1:100 scaled wind tunnel model. Both solvers used different meshes, discretization schemes, and turbulence models. The experimental data and numerical results agree well for timeaveraged streamwise and verticalwise velocities. In particular, the air exchange was predicted with high accuracy by both solvers with relative errors less than 5 % compared to the experimental results. With respect to the turbulent quantities, good agreements at the second (downwind) half of the barn inside and especially outside the barn could be achieved, where both codes accurately predicted the flow separation and the rootmeansquare velocities. Deviations between simulations and experimental results regarding turbulent quantities could be observed in the first part of the barn, due to different inlet conditions between the experimental setup and the numerical simulations. Both solvers proved to be promising tools for the accurate prediction of timedependent phenomena in an agricultural context, e.g., like the transport of particulate matter or pathogenladen aerosols in and around agricultural buildings. 
C.K. Macnamara, A. Caiazzo, I. RamisConde, M.A.J. Chaplain, Computational modelling and simulation of cancer growth and migration within a 3D heterogeneous tissue: The effects of fibre and vascular structure, Journal of Computational Science, 40 (2020), pp. 101067/1101067/24, DOI 10.1016/j.jocs.2019.101067 .
Abstract
The term cancer covers a multitude of bodily diseases, broadly categorised by having cells which do not behave normally. Since cancer cells can arise from any type of cell in the body, cancers can grow in or around any tissue or organ making the disease highly complex. Our research is focused on understanding the specific mechanisms that occur in the tumour microenvironment via mathematical and computational modeling. We present a 3D individualbased model which allows one to simulate the behaviour of, and spatiotemporal interactions between, cells, extracellular matrix fibres and blood vessels. Each agent (a single cell, for example) is fully realised within the model and interactions are primarily governed by mechanical forces between elements. However, as well as the mechanical interactions we also consider chemical interactions, for example, by coupling the code to a finite element solver to model the diffusion of oxygen from blood vessels to cells. The current state of the art of the model allows us to simulate tumour growth around an arbitrary bloodvessel network or along the striations of fibrous tissue. 
L.G. Ramos, R. Kehl, R. Nabben, Projections, deflation and multigrid for nonsymmetric matrices, SIAM Journal on Matrix Analysis and Applications, 41 (2020), pp. 83105, DOI 10.1137/18M1180268 .

O. Souček, M. Heida, J. Málek, On a thermodynamic framework for developing boundary conditions for Kortewegtype fluids, International Journal of Engineering Science, 154 (2020), pp. 103316/1103316/28, DOI 10.1016/j.ijengsci.2020.103316 .
Abstract
We provide a derivation of several classes of boundary conditions for fluids of Kortewegtype using a simple and transparent thermodynamic approach that automatically guarentees that the derived boundary conditions are compatible with the second law of thermodynamics. The starting assumption of our approach is to describe the boundary of the domain as the membrane separating two different continua, one inside the domain, and the other outside the domain. With this viewpoint one may employ the framework of continuum thermodynamics involving singular surfaces. This approach allows us to identify, for various classes of surface Helmholtz free energies, the corresponding surface entropy production mechanisms. By establishing the constitutive relations that guarantee that the surface entropy production is nonnegative, we identify a new class of boundary conditions, which on one hand generalizes in a nontrivial manner the Navier's slip boundary conditions, and on the other hand describes dynamic and static contact angle conditions. We explore the general model in detail for a particular case of Korteweg fluid where the Helmholtz free energy in the bulk is that of a van der Waals fluid. We perform a series of numerical experiments to document the basic qualitative features of the novel boundary conditions and their practical applicability to model phenomena such as the contact angle hysteresis. 
M. Tlidi, E. BerríosCaro , D. PintoRamo, A.G. Vladimirov, M.G. Clerc, Interaction between vegetation patches and gaps: A selforganized response to water scarcity, Physica D. Nonlinear Phenomena, 414 (2020), pp. 132708/1132708/12, DOI 10.1016/j.physd.2020.132708 .
Abstract
The dynamics of ecological systems are often described by integrodifferential equations that incorporate nonlocal interactions associated with facilitative, competitive interactions between plants, and seed dispersion. In the weakgradient limit, these models can be reduced to a simple partialdifferential equation in the form of a nonvariational Swift?Hohenberg equation. In this contribution, we perform this reduction for any type of kernels provided that their Taylor series converge. Some parameters such as linear and nonlinear diffusion coefficients are affected by the spatial form of the kernel. In particular, Gaussian and exponential kernels are used to evaluate all coefficients of the reduced model. This weak gradient approximation is greatly useful for the investigation of periodic and localized vegetation patches, and gaps. Based on this simple model, we investigate the interaction between twowell separated patches and gaps. In the case of patches, the interaction is always repulsive. As a consequence, bounded states of patches are excluded. However, when two gaps are close to one another, they start to interact through their oscillatory tails. The interaction alternates between attractive and repulsive depending on the distance separating them. This allows for the stabilization of bounded gaps and clusters of them. The analytical formula of the interaction potential is derived for both patches and gaps interactions and checked by numerical investigation of the model equation. 
D. Uebel, S. Kayser, T. Markurt, O.C. Ernst, Th. Teubner, T. Boeck, Fast Raman mapping and in situ TEM observation of metal induced crystallization of amorphous silicon, CrystEngComm, 22 (2020), pp. 79837991, DOI 10.1039/D0CE00960A .
Abstract
Crystalline silicon is grown onto an amorphous silicon (aSi) seed layer from liquid tin solution (steady state liquid phase epitaxy, SSLPE). To investigate the crystallization of embedded aSi during our process, we adapted Raman measurements for fast mapping, with dwell times of just one second per single measurement. A purposely developed imaging algorithm which performs pointbypoint gauss fitting provides adequate visualization of the data. We produced scans of aSi layers showing crystalline structures formed in the aSi matrix during processing. Compared to scanning electron microscopy images which reveal merely the topography of the grown layer, new insights are gained into the role of the seed layer by Raman mapping. As part of a series of SSLPE experiments, which were interrupted at various stages of growth, we show that platelike crystallites grow laterally over the aSi layer while smaller, randomly orientated crystals arise from the aSi layer. Results are confirmed by an in situ TEM experiment of the metalinduced crystallization. Contrary to presumptions, initially formed surface crystallites do not originate from the seed layer and are irrelevant to the final growth morphology, since they dissolve within minutes due to Ostwald ripening. The aSi layer crystallizes within minutes as well, and crystallites of the final morphology originate from seeds of this layer. 
J.P. Köster, A. Putz, H. Wenzel, H.J. Wünsche, M. Radziunas, H. Stephan, M. Wilkens, A. Zeghuzi, A. Knigge, Mode competition in broadridgewaveguide lasers, Semiconductor Science and Technology, 36 (2020), pp. 015014/1015014/12, DOI 10.1088/13616641/abc6e7 .
Abstract
The lateral brightness achievable with highpower GaAsbased laser diodes having long and broad waveguides is commonly regarded to be limited by the onset of higherorder lateral modes. For the study of the lateralmode competition two complementary simulation tools are applied, representing different classes of approximations. The first tool bases on a completely incoherent superposition of mode intensities and disregards longitudinal effects like spatial hole burning, whereas the second tool relies on a simplified carrier transport and current flow. Both tools yield agreeing powercurrent characteristics that fit the data measured for 5 to 23 µm wide ridges. Also, a similarly good qualitative conformance of the near and far fields is found. However, the threshold of individual modes, the partition of power between them at a given current, and details of the near and far fields show differences. These differences are the consequence of a high sensitivity of the mode competition to details of the models and of the device structure. Nevertheless, it can be concluded concordantly that the brightness rises with increasing ridge width irrespective of the onset of more and more lateral modes. The lateral brightness 2W · mm¯¹ 1mrad¯¹ at 10MW · cm¯²2 power density on the front facet of the investigated laser with widest ridge (23 µm) is comparable with best values known from much wider broadarea lasers. In addition, we show that one of the simulation tools is able to predict beam steering and coherent beam 
M. Thomas, C. Bilgen, K. Weinberg, Analysis and simulations for a phasefield fracture model at finite strains based on modified invariants, ZAMM. Zeitschrift für Angewandte Mathematik und Mechanik, 100 (2020), pp. e201900288/1e201900288/51, DOI 10.1002/zamm.201900288 .
Abstract
Phasefield models have already been proven to predict complex fracture patterns in two and three dimensions for brittle fracture at small strains. In this paper we discuss a model for phasefield fracture at finite deformations in more detail. Among the identification of crack location and projection of crack growth the numerical stability is one of the main challenges in solid mechanics. We here present a phasefield model at finite strains, which takes into account the anisotropy of damage by applying an anisotropic split and the modified invariants of the right CauchyGreen strain tensor. We introduce a suitable weak notion of solution that also allows for a spatial and temporal discretization of the model. In this framework we study the existence of solutions and we show that the timediscrete solutions converge in a weak sense to a solution of the timecontinuous formulation of the model. Numerical examples in two and three space dimensions are carried out in the range of validity of the analytical results. 
A. Alphonse, M. Hintermüller, C.N. Rautenberg, Existence, iteration procedures and directional differentiability for parabolic QVIs, Calculus of Variations and Partial Differential Equations, 59 (2020), pp. 95/195/53, DOI 10.1007/s00526020017326 .
Abstract
We study parabolic quasivariational inequalities (QVIs) of obstacle type. Under appropriate assumptions on the obstacle mapping, we prove the existence of solutions of such QVIs by two methods: one by time discretisation through elliptic QVIs and the second by iteration through parabolic variational inequalities (VIs). Using these results, we show the directional differentiability (in a certain sense) of the solution map which takes the source term of a parabolic QVI into the set of solutions, and we relate this result to the contingent derivative of the aforementioned map. We finish with an example where the obstacle mapping is given by the inverse of a parabolic differential operator. 
A. Caiazzo, R. Maier, D. Peterseim, Reconstruction of quasilocal numerical effective models from lowresolution measurements, Journal of Scientific Computing, 85 (2020), pp. 10/110/23, DOI 10.1007/s1091502001304y .
Abstract
We consider the inverse problem of reconstructing an effective model for a prototypical diffusion process in strongly heterogeneous media based on lowresolution measurements. We rely on recent quasilocal numerical effective models that, in contrast to conventional homogenized models, are provably reliable beyond periodicity assumptions and scale separation. The goal of this work is to show that the identification of the matrix representation of these effective models is possible. Algorithmic aspects of the inversion procedure and its performance are illustrated in a series of numerical experiments. 
P.É. Druet, A theory of generalised solutions for ideal gas mixtures with MaxwellStefan diffusion, Discrete and Continuous Dynamical Systems  Series S, 14 (2021), pp. 40354067 (published online in Nov 2020), DOI 10.3934/dcdss.2020458 .
Abstract
After the pioneering work by Giovangigli on mathematics of multicomponent flows, several attempts were made to introduce global weak solutions for the PDEs describing the dynamics of fluid mixtures. While the incompressible case with constant density was enlighted well enough due to results by Chen and Jüngel (isothermal case), or Marion and Temam, some open questions remain for the weak solution theory of gas mixtures with their corresponding equations of mixed parabolichyperbolic type. For instance, Mucha, Pokorny and Zatorska showed the possibility to stabilise the hyperbolic component by means of the BreschDesjardins technique and a regularisation of pressure preventing vacuum. The result by Dreyer, Druet, Gajewski and Guhlke avoids emphex machina stabilisations, but the mathematical assumption that the Onsager matrix is uniformly positive on certain subspaces leads, in the dilute limit, to infinite diffusion velocities which are not compatible with the MaxwellStefan form of diffusion fluxes. In this paper, we prove the existence of global weak solutions for isothermal and ideal compressible mixtures with natural diffusion. The main new tool is an asymptotic condition imposed at low pressure on the binary MaxwellStefan diffusivities, which compensates possibly extreme behaviour of weak solutions in the rarefied regime. 
D. Frerichs, Ch. Merdon, Divergencepreserving reconstructions on polygons and a really pressurerobust virtual element method for the Stokes problem, IMA Journal of Numerical Analysis, 42 (2022), pp. 597619 (published online on 09.11.2020), DOI 10.1093/imanum/draa073 .
Abstract
Non divergencefree discretisations for the incompressible Stokes problem may suffer from a lack of pressurerobustness characterised by large discretisations errors due to irrotational forces in the momentum balance. This paper argues that also divergencefree virtual element methods (VEM) on polygonal meshes are not really pressurerobust as long as the righthand side is not discretised in a careful manner. To be able to evaluate the righthand side for the testfunctions, some explicit interpolation of the virtual testfunctions is needed that can be evaluated pointwise everywhere. The standard discretisation via an L^{2} bestapproximation does not preserve the divergence and so destroys the orthogonality between divergencefree testfunctions and possibly eminent gradient forces in the righthand side. To repair this orthogonality and restore pressurerobustness another divergencepreserving reconstruction is suggested based on RaviartThomas approximations on local subtriangulations of the polygons. All findings are proven theoretically and are demonstrated numerically in two dimensions. The construction is also interesting for hybrid highorder methods on polygonal or polyhedral meshes. 
J. Fuhrmann, M. Landstorfer, R. Müller, Modeling polycrystalline electrodeelectrolyte interfaces: The differential capacitance, Journal of The Electrochemical Society, 167 (2020), pp. 106512/1106512/15, DOI 10.1149/19457111/ab9cca .
Abstract
We present and analyze a model for polycrystalline electrode surfaces based on an improved continuum model that takes finite ion size and solvation into account. The numerical simulation of finite size facet patterns allows to study two limiting cases: While for facet size diameter $d^facet to 0$ we get the typical capacitance of a spatially homogeneous but possible amorphous or liquid surface, in the limit $L^Debye << d^facet$ , an ensemble of noninteracting single crystal surfaces is approached. Already for moderate size of the facet diameters, the capacitance is remarkably well approximated by the classical approach of adding the single crystal capacities of the contributing facets weighted by their respective surface fraction. As a consequence, the potential of zero charge is not necessarily attained at a local minimum of capacitance, but might be located at a local capacitance maximum instead. Moreover, the results show that surface roughness can be accurately taken into account by multiplication of the ideally flat polycrystalline surface capacitance with a single factor. In particular, we find that the influence of the actual geometry of the facet pattern in negligible and our theory opens the way to a stochastic description of complex real polycrystal surfaces. 
V. John, P. Knobloch, P. Korsmeier, On the solvability of the nonlinear problems in an algebraically stabilized finite element method for evolutionary transportdominated equations, Mathematics of Computation, 90 (2021), pp. 595611 (published online on 16.11.2020), DOI 10.1090/mcom/3576 .

V. John, P. Knobloch, Existence of solutions of a finite element fluxcorrectedtransport scheme, Applied Mathematics Letters, 115 (2021), pp. 106932/1106932/6 (published online on 01.12.2020), DOI 10.1016/j.aml.2020.106932 .
Abstract
The existence of a solution is proved for a nonlinear finite element fluxcorrectedtransport (FEMFCT) scheme with arbitrary time steps for evolutionary convectiondiffusionreaction equations and transport equations. 
A. Linke, Ch. Merdon, M. Neilan, Pressurerobustness in quasioptimal a priori estimates for the Stokes problem, Electronic Transactions on Numerical Analysis, 52 (2020), pp. 281294, DOI 10.1553/etna_vol52s281 .

A. Mielke, T. Roubíček, Thermoviscoelasticity in KelvinVoigt rheology at large strains, Archive for Rational Mechanics and Analysis, 238 (2020), pp. 145, DOI 10.1007/s0020502001537z .
Abstract
The frameindifferent thermodynamicallyconsistent model of thermoviscoelasticity at large strain is formulated in the reference configuration with using the concept of the secondgrade nonsimple materials. We focus on physically correct viscous stresses that are frame indifferent under timedependent rotations. Also elastic stresses are frame indifferent under rotations and respect positivity of the determinant of the deformation gradient. The heat transfer is governed by the Fourier law in the actual deformed configuration, which leads to a nontrivial description when pulled back into the reference configuration. Existence of weak solutions in the quasistatic setting, i.e. inertial forces are ignored, is shown by time discretization. 
D.H. Doan, A. Glitzky, M. Liero, Analysis of a driftdiffusion model for organic semiconductor devices, Zeitschrift fur Angewandte Mathematik und Physik. ZAMP. Journal of Applied Mathematics and Physics. Journal de Mathematiques et de Physique Appliquees, 70 (2019), pp. 55/155/18, DOI 10.1007/s000330191089z .
Abstract
We discuss driftdiffusion models for chargecarrier transport in organic semiconductor devices. The crucial feature in organic materials is the energetic disorder due to random alignment of molecules and the hopping transport of carriers between adjacent energetic sites. The former leads to socalled GaussFermi statistics, which describe the occupation of energy levels by electrons and holes. The latter gives rise to complicated mobility models with a strongly nonlinear dependence on temperature, density of carriers, and electric field strength. We present the stateoftheart modeling of the transport processes and provide a first existence result for the stationary driftdiffusion model taking all of the peculiarities of organic materials into account. The existence proof is based on Schauder's fixedpoint theorem. 
M. Kantner, Generalized ScharfetterGummel schemes for electrothermal transport in degenerate semiconductors using the Kelvin formula for the Seebeck coefficient, Journal of Computational Physics, published online on 07.11.2019, urlhttps://doi.org/10.1016/j.jcp.2019.109091, DOI 10.1016/j.jcp.2019.109091 .
Abstract
Many challenges faced in today's semiconductor devices are related to selfheating phenomena. The optimization of device designs can be assisted by numerical simulations using the nonisothermal driftdiffusion system, where the magnitude of the thermoelectric cross effects is controlled by the Seebeck coefficient. We show that the model equations take a remarkably simple form when assuming the socalled Kelvin formula for the Seebeck coefficient. The corresponding heat generation rate involves exactly the three classically known selfheating effects, namely Joule, recombination and ThomsonPeltier heating, without any further (transient) contributions. Moreover, the thermal driving force in the electrical current density expressions can be entirely absorbed in the (nonlinear) diffusion coefficient via a generalized Einstein relation. The efficient numerical simulation relies on an accurate and robust discretization technique for the fluxes (finite volume ScharfetterGummel method), which allows to cope with the typically stiff solutions of the semiconductor device equations. We derive two nonisothermal generalizations of the ScharfetterGummel scheme for degenerate semiconductors (FermiDirac statistics) obeying the Kelvin formula. The approaches differ in the treatment of degeneration effects: The first is based on an approximation of the discrete generalized Einstein relation implying a specifically modified thermal voltage, whereas the second scheme follows the conventionally used approach employing a modified electric field. We present a detailed analysis and comparison of both schemes, indicating a superior performance of the modified thermal voltage scheme. 
R. Kehl, R. Nabben, D.B. Szyld, Adaptive multilevel Krylov methods, Electronic Transactions on Numerical Analysis, 51 (2019), pp. 512528, DOI 10.1553/etna_vol51s512 .

G. Nika, B. Vernescu, Multiscale modeling of magnetorheological suspensions, ZAMP Zeitschrift fur Angewandte Mathematik und Physik. ZAMP. Journal of Applied Mathematics and Physics. Journal de Mathematiques et de Physique Appliquees, 71 (2020), pp. 14/114/19 (published online on 23.12.2019), DOI 10.1007/s0003301912384 .
Abstract
We develop a multiscale approach to describe the behavior of a suspension of solid magnetizable particles in a viscous nonconducting fluid in the presence of an externally applied magnetic field. By upscaling the quasistatic Maxwell equations coupled with the Stokes' equations we are able to capture the magnetorheological effect. The model we obtain generalizes the one introduced by Neuringer & Rosensweig for quasistatic phenomena. We derive the macroscopic constitutive properties explicitly in terms of the solutions of local problems. The effective coefficients have a nonlinear dependence on the volume fraction when chain structures are present. The velocity profiles computed for some simple flows, exhibit an apparent yield stress and the flowprofile resembles a Bingham fluid flow. 
P. Vágner, C. Guhlke, V. Miloš, R. Müller, J. Fuhrmann, A continuum model for yttriastabilised zirconia incorporating triple phase boundary, lattice structure and immobile oxide ions, Journal of Solid State Electrochemistry, 23 (2019), pp. 29072926, DOI 10.1007/s10008019043569 .
Abstract
A continuum model for yttriastabilised zirconia (YSZ) in the framework of nonequilibrium thermodynamics is developed. Particular attention is given to i) modeling of the YSZmetalgas triple phase boundary, ii) incorporation of the lattice structure and immobile oxide ions within the free energy model and iii) surface reactions. A finite volume discretization method based on modified ScharfetterGummel fluxes is derived in order to perform numerical simulations.
The model is used to study the impact of yttria and immobile oxide ions on the structure of the charged boundary layer and the double layer capacitance. Cyclic voltammograms of an airhalf cell are simulated to study the effect of parameter variations on surface reactions, adsorption and anion diffusion. 
I. Selmer, A.S. Behnecke, P. Farrell, A. Bueno, P. Gurikov, I. Smirnova, Model development for scdrying kinetics of aerogels: Part 2. Packed bed of spherical particles, The Journal of Supercritical Fluids, 147 (2019), pp. 147/149147/161, DOI https://doi.org/10.1016/j.supflu.2018.07.006 .
Abstract
We apply here the previously developed mass transfer model (Part 1) for drying of aerogel monoliths to the supercritical drying of particles in a packed bed. We analyzed the influence of the operating conditions, flow rate, particle and autoclave size on the drying time and consumption of carbon dioxide. Although the model requires certain improvement to quantitatively predict the experimental drying kinetics, it captures all features of the supercritical drying: (i) transition of the limiting mass transfer step between diffusion in the gel and convection in the bulk fluid; (ii) role of CO2 density as natural variable for analysis of the CO2 consumption; (iii) influence of the autoclave dimensions on the drying process. We suggest a unified approach towards the analysis of drying process based on a dimensionless number. Practical recommendations on the rational selection of process parameters to achieve appropriate combinations of drying time and CO2 consumption are formulated. 
F. Agnelli, A. Constantinescu, G. Nika, Design and testing of 3Dprinted microarchitectured polymer materials exhibiting a negative Poisson's ratio, Continuum Mechanics and Thermodynamics, 32 (2020), pp. 433449 (published online on 20.11.2019), DOI 10.1007/s00161019008516 .
Abstract
This work proposes the complete design cycle for several auxetic materials where the cycle consists of three steps (i) the design of the microarchitecture, (ii) the manufacturing of the material and (iii) the testing of the material. We use topology optimization via a levelset method and asymptotic homogenization to obtain periodic microarchitectured materials with a prescribed effective elasticity tensor and Poisson's ratio. The space of admissible microarchitectural shapes that carries orthotropic material symmetry allows to attain shapes with an effective Poisson's ratio below 1. Moreover, the specimens were manufactured using a commercial stereolithography Ember printer and are mechanically tested. The observed displacement and strain fields during tensile testing obtained by digital image correlation match the predictions from the finite element simulations and demonstrate the efficiency of the design cycle. 
N.R. Gauger, A. Linke, P. Schroeder, On highorder pressurerobust space discretisations, their advantages for incompressible high Reynolds number generalised Beltrami flows and beyond, SMAI Journal of Computational Mathematics, 5 (2019), pp. 89129.
Abstract
Recently, highorder space discretisations were proposed for the numerical simulation of the incompressible NavierStokes equations at high Reynolds numbers, even for complicated domains from simulation practice. Although the overall spatial approximation order of the algorithms depends on the approximation quality of the boundary (often not better than third order), competitively accurate and efficient results were reported. In this contribution, first, a possible explanation for this somewhat surprising result is proposed: the velocity error of highorder space discretisations is more robust against quantitatively large and complicated pressure fields than loworder methods. Second, it is demonstrated that novel pressurerobust methods are significantly more accurate than comparable classical, nonpressurerobust space discretisations, whenever the quadratic, nonlinear convection term is a nontrivial gradient field like in certain generalised Beltrami flows at high Reynolds number. Then, pressurerobust methods even allow to halve the (formal) approximation order without compromising the accuracy. Third, classical highorder space discretisations are outperformed by pressurerobust methods whenever the boundary is not approximated with highorder accuracy. This improved accuracy of (loworder) pressurerobust mixed methods is explained in terms of a HelmholtzHodge projector, which cancels out the nonlinear convection term in any generalised Beltrami flow, since it is a gradient field. The numerical results are illustrated by a novel numerical analysis for pressurerobust and classical space discretisations. Further, the relevance of these results is discussed for flows that are not of Beltrami type. 
L. Heltai, A. Caiazzo, Multiscale modeling of vascularized tissues via nonmatching immersed methods, International Journal of Numerical Methods in Biomedical Engineering, 35 (2019), pp. 3264/13264/32, DOI 10.1002/cnm.3264 .
Abstract
We consider a multiscale approach based on immersed methods for the efficient computational modeling of tissues composed of an elastic matrix (in two or threedimensions) and a thin vascular structure (treated as a codimension two manifold) at a given pressure. We derive different variational formulations of the coupled problem, in which the effect of the vasculature can be surrogated in the elasticity equations via singular or hypersingular forcing terms. These terms only depends on information defined on codimension two manifolds (such as vessel center line, cross sectional area, and mean pressure over cross section), thus drastically reducing the complexity of the computational model. We perform several numerical tests, ranging from simple cases with known exact solutions to the modeling of materials with random distributions of vessels. In the latter case, we use our immersed method to perform an in silico characterization of the mechanical properties of the effective biphasic material tissue via statistical simulations. 
L. Heltai, N. Rotundo, Error estimates in weighted Sobolev norms for finite element immersed interface methods, Computers & Mathematics with Applications. An International Journal, 78 (2019), pp. 35863604, DOI 10.1016/j.camwa.2019.05.029 .
Abstract
When solving elliptic partial differential equations in a region containing immersed interfaces (possibly evolving in time), it is often desirable to approximate the problem using an independent background discretisation, not aligned with the interface itself. Optimal convergence rates are possible if the discretisation scheme is enriched by allowing the discrete solution to have jumps aligned with the surface, at the cost of a higher complexity in the implementation. A much simpler way to reformulate immersed interface problems consists in replacing the interface by a singular force field that produces the desired interface conditions, as done in immersed boundary methods. These methods are known to have inferior convergence properties, depending on the global regularity of the solution across the interface, when compared to enriched methods. In this work we prove that this detrimental effect on the convergence properties of the approximate solution is only a local phenomenon, restricted to a small neighbourhood of the interface. In particular we show that optimal approximations can be constructed in a natural and inexpensive way, simply by reformulating the problem in a distributionally consistent way, and by resorting to weighted norms when computing the global error of the approximation. 
V. Klika , M. Pavelka , P. Vágner, M. Grmela, Dynamic maximum entropy reduction, Entropy. An International and Interdisciplinary Journal of Entropy and Information Studies, 21 (2019), pp. 127.

P.L. Lederer, Ch. Merdon, J. Schöberl, Refined a posteriori error estimation for classical and pressurerobust Stokes finite element methods, Journal of Numerical Mathematics, 142 (2019), pp. 713748.
Abstract
Recent works showed that pressurerobust modifications of mixed finite element methods for the Stokes equations outperform their standard versions in many cases. This is achieved by divergencefree reconstruction operators and results in pressureindependent velocity error estimates which are robust with respect to small viscosities. In this paper we develop a posteriori error control which reflects this robustness. 
L.O. Müller, A. Caiazzo, P.J. Blanco, Reducedorder unscented Kalman filter with observations in the frequency domain: Application to computational hemodynamics, IEEE Transactions on Biomedical Engineering, 66 (2019), pp. 12691276, DOI 10.1109/TBME.2018.2872323 .
Abstract
Objective: The aim of this work is to assess the potential of the reduced order unscented Kalman filter (ROUKF) in the context of computational hemodynamics, in order to estimate cardiovascular model parameters when employing real patientspecific data. Methods: The approach combines an efficient blood flow solver for onedimensional networks (for the forward problem) with the parameter estimation problem cast in the frequency space. Namely, the ROUKF is used to correct model parameter after each cardiac cycle, depending on the discrepancies of model outputs with respect to available observations properly mapped into the frequency space. Results: First we validate the filter in frequency domain applying it in the context of a set of experimental measurements for an in vitro model. Second, we perform different numerical experiments aiming at parameter estimation using patientspecific data. Conclusion: Our results demonstrate that the filter in frequency domain allows a faster and more robust parameter estimation, when compared to its time domain counterpart. Moreover, the proposed approach allows to estimate parameters that are not directly related to the network but are crucial for targeting interindividual parameter variability (e.g., parameters that characterize the cardiac output). Significance: The ROUKF in frequency domain provides a robust and flexible tool for estimating parameters related to cardiovascular mathematical models using in vivo data. 
A. Zeghuzi, H.J. Wünsche, H. Wenzel, M. Radziunas, J. Fuhrmann, A. Klehr, U. Bandelow, A. Knigge, Timedependent simulation of thermal lensing in highpower broadarea semiconductor lasers, IEEE J. Select. Topics Quantum Electron., 25 (2019), pp. 1502310/11502310/10, DOI 10.1109/JSTQE.2019.2925926 .
Abstract
We propose a physically realistic and yet numerically applicable thermal model to account for short and long term selfheating within broadarea lasers. Although the temperature increase is small under pulsed operation, a waveguide that is formed within a fewnslong pulse can result in a transition from a gainguided to an indexguided structure, leading to near and far field narrowing. Under continuous wave operation the longitudinally varying temperature profile is obtained selfconsistently. The resulting unfavorable narrowing of the near field can be successfully counteracted by etching trenches. 
A. Glitzky, M. Liero, Instationary driftdiffusion problems with GaussFermi statistics and fielddependent mobility for organic semiconductor devices, Communications in Mathematical Sciences, 17 (2019), pp. 3359, DOI 10.4310/cms.2019.v17.n1.a2 .
Abstract
This paper deals with the analysis of an instationary driftdiffusion model for organic semiconductor devices including GaussFermi statistics and applicationspecific mobility functions. The charge transport in organic materials is realized by hopping of carriers between adjacent energetic sites and is described by complicated mobility laws with a strong nonlinear dependence on temperature, carrier densities and the electric field strength. To prove the existence of global weak solutions, we consider a problem with (for small densities) regularized state equations on any arbitrarily chosen finite time interval. We ensure its solvability by time discretization and passage to the timecontinuous limit. Positive lower a priori estimates for the densities of its solutions that are independent of the regularization level ensure the existence of solutions to the original problem. Furthermore, we derive for these solutions global positive lower and upper bounds strictly below the density of transport states for the densities. The estimates rely on Moser iteration techniques. 
W. Dreyer, C. Guhlke, R. Müller, The impact of solvation and dissociation on the transport parameters of liquid electrolytes: Continuum modeling and numerical study, European Physical Journal Special Topics, 227 (2019), pp. 25152538, DOI 10.1140/epjst/e20198001332 .
Abstract
Electrothermodynamics provides a consistent framework to derive continuum models for electrochemical systems. For the application to a specific experimental system, the general model must be equipped with two additional ingredients: a free energy model to calculate the chemical potentials and a kinetic model for the kinetic coefficients. Suitable free energy models for liquid electrolytes incorporating ionsolvent interaction, finite ion sizes and solvation already exist and have been validated against experimental measurements. In this work, we focus on the modeling of the mobility coefficients based on MaxwellStefan setting and incorporate them into the general electrothermodynamic framework. Moreover, we discuss the impact of model parameter on conductivity, transference numbers and salt diffusion coefficient. In particular, the focus is set on the solvation of ions and incomplete dissociation of a nondilute electrolyte. 
P. Farrell, D. Peschka, Nonlinear diffusion, boundary layers and nonsmoothness: Analysis of challenges in driftdiffusion semiconductor simulations, Computers & Mathematics with Applications. An International Journal, 78 (2019), pp. 37313747, DOI 10.1016/j.camwa.2019.06.007 .
Abstract
We analyze and benchmark the error and the convergence order of finite difference, finiteelement as well as Voronoi finitevolume discretization schemes for the driftdiffusion equations describing charge transport in bulk semiconductor devices. Three common challenges, that can corrupt the precision of numerical solutions, will be discussed: boundary layers at Ohmic contacts, discontinuties in the doping profile, and corner singularities in Lshaped domains. The influence on the order of convergence is assessed for each computational challenge and the different discretization schemes. Additionally, we provide an analysis of the inner boundary layer asymptotics near Ohmic contacts to support our observations. 
J. Fuhrmann, C. Guhlke, Ch. Merdon, A. Linke, R. Müller, Induced charge electroosmotic flow with finite ion size and solvation effects, Electrochimica Acta, 317 (2019), pp. 778785, DOI 10.1016/j.electacta.2019.05.051 .

A. Linke, L.G. Rebholz, Pressureinduced locking in mixed methods for timedependent (Navier)Stokes equations, Journal of Computational Physics, 388 (2019), pp. 350356, DOI 10.1016/j.jcp.2019.03.010 .
Abstract
We consider infsup stable mixed methods for the timedependent incompressible Stokes and NavierStokes equations, extending earlier work on the steady (Navier)Stokes Problem. A locking phenomenon is identified for classical infsup stable methods like the TaylorHood or the CrouzeixRaviart elements by a novel, elegant and simple numerical analysis and corresponding numerical experiments, whenever the momentum balance is dominated by forces of a gradient type. More precisely, a reduction of the L^{2} convergence order for high order methods, and even a complete stall of the L^{2} convergence order for lowestorder methods on preasymptotic meshes is predicted by the analysis and practically observed. On the other hand, it is also shown that (structurepreserving) pressurerobust mixed methods do not suffer from this locking phenomenon, even if they are of lowestorder. A connection to wellbalanced schemes for (vectorial) hyperbolic conservation laws like the shallow water or the compressible Euler equations is made. 
A. Alphonse, Ch.M. Elliott, J. Terra, A coupled ligandreceptor bulksurface system on a moving domain: Well posedness, regularity and convergence to equilibrium, SIAM Journal on Mathematical Analysis, 50 (2018), pp. 15441592, DOI 10.1137/16M110808X .
Abstract
We prove existence, uniqueness, and regularity for a reactiondiffusion system of coupled bulksurface equations on a moving domain modelling receptorligand dynamics in cells. The nonlinear coupling between the three unknowns is through the Robin boundary condition for the bulk quantity and the right hand sides of the two surface equations. Our results are new even in the nonmoving setting, and in this case we also show exponential convergence to a steady state. The primary complications in the analysis are indeed the nonlinear coupling and the Robin boundary condition. For the well posedness and essential boundedness of solutions we use several De Giorgitype arguments, and we also develop some useful estimates to allow us to apply a Steklov averaging technique for timedependent operators to prove that solutions are strong. Some of these auxiliary results presented in this paper are of independent interest by themselves. 
M. Heida, On convergences of the squareroot approximation scheme to the FokkerPlanck operator, Mathematical Models & Methods in Applied Sciences, 28 (2018), pp. 25992635, DOI 10.1142/S0218202518500562 .
Abstract
We study the qualitative convergence properties of a finite volume scheme that recently was proposed by Lie, Fackeldey and Weber [SIAM Journal on Matrix Analysis and Applications 2013 (34/2)] in the context of conformation dynamics. The scheme was derived from physical principles and is called the squareroot approximation (SQRA) scheme. We show that solutions to the SQRA equation converge to solutions of the FokkerPlanck equation using a discrete notion of Gconvergence. Hence the squareroot approximation turns out to be a usefull approximation scheme to the FokkerPlanck equation in high dimensional spaces. As an example, in the special case of stationary Voronoi tessellations we use stochastic twoscale convergence to prove that this setting satisfies the Gconvergence property. In particular, the class of tessellations for which the Gconvergence result holds is not trivial. 
L. Adam, M. Hintermüller, Th.M. Surowiec, A semismooth Newton method with analytical pathfollowing for the $H^1$projection onto the Gibbs simplex, IMA Journal of Numerical Analysis, 39 (2019), pp. 12761295 (published online on 07.06.2018), DOI 10.1093/imanum/dry034 .
Abstract
An efficient, functionspacebased secondorder method for the $H^1$projection onto the Gibbssimplex is presented. The method makes use of the theory of semismooth Newton methods in function spaces as well as MoreauYosida regularization and techniques from parametric optimization. A pathfollowing technique is considered for the regularization parameter updates. A rigorous first and secondorder sensitivity analysis of the value function for the regularized problem is provided to justify the update scheme. The viability of the algorithm is then demonstrated for two applications found in the literature: binary image inpainting and labeled data classification. In both cases, the algorithm exhibits meshindependent behavior. 
T. Ahnert, A. Münch, B. Niethammer, B. Wagner, Stability of concentrated suspensions under Couette and Poiseuille flow, Journal of Engineering Mathematics, 111 (2018), pp. 5177, DOI 10.1007/s106650189954x .
Abstract
The stability of twodimensional Poiseuille flow and plane Couette flow for concentrated suspensions is investigated. Linear stability analysis of the twophase flow model for both flow geometries shows the existence of a convectively driven instability with increasing growth rates of the unstable modes as the particle volume fraction of the suspension increases. In addition it is shown that there exists a bound for the particle phase viscosity below which the twophase flow model may become illposed as the particle phase approaches its maximum packing fraction. The case of twodimensional Poiseuille flow gives rise to base state solutions that exhibit a jammed and unyielded region, due to shearinduced migration, as the maximum packing fraction is approached. The stability characteristics of the resulting Binghamtype flow is investigated and connections to the stability problem for the related classical Binghamflow problem are discussed. 
C. Bertoglio, A. Caiazzo, Y. Bazilevs, M. Braack, M. EsmailyMoghadam, V. Gravemeier, A.L. Marsden, O. Pironneau, I.E. VignonClementel, W.A. Wall, Benchmark problems for numerical treatment of backflow at open boundaries, International Journal of Numerical Methods in Biomedical Engineering, 34 (2018), pp. e2918/1e2918/34, DOI 10.1002/cnm.2918 .
Abstract
In computational fluid dynamics, incoming velocity at open boundaries, or backflow, often yields to unphysical instabilities already for moderate Reynolds numbers. Several treatments to overcome these backflow instabilities have been proposed in the literature. However, these approaches have not yet been compared in detail in terms of accuracy in different physiological regimes, in particular due to the difficulty to generate stable reference solutions apart from analytical forms. In this work, we present a set of benchmark problems in order to compare different methods in different backflow regimes (with a full reversal flow and with propagating vortices after a stenosis). The examples are implemented in FreeFem++ and the source code is openly available, making them a solid basis for future method developments. 
A. Bradji, J. Fuhrmann, On the convergence and convergence order of finite volume gradient schemes for oblique derivative boundary value problems, Computational & Applied Mathematics, 37 (2018), pp. 25332565, DOI 10.1007/s4031401704638 .

A. Fischer, M. Pfalz, K. Vandewal, M. Liero, A. Glitzky, S. Lenk, S. Reineke, Full electrothermal OLED model including nonlinear selfheating effects, Physical Review Applied, 10 (2018), pp. 014023/1014023/12, DOI 10.1103/PhysRevApplied.10.014023 .
Abstract
Organic lightemitting diodes (OLEDs) are widely studied semiconductor devices for which a simple description by a diode equation typically fails. In particular, a full description of the currentvoltage relation, including temperature effects, has to take the low electrical conductivity of organic semiconductors into account. Here, we present a temperaturedependent resistive network, incorporating recombination as well as electron and hole conduction to describe the currentvoltage characteristics of an OLED over the entire operation range. The approach also reproduces the measured nonlinear electrothermal feedback upon Joule selfheating in a selfconsistent way. Our model further enables us to learn more about internal voltage losses caused by the charge transport from the contacts to the emission layer which is characterized by a strong temperatureactivated electrical conductivity, finally determining the strength of the electrothermal feedback. In general, our results provide a comprehensive picture to understand the electrothermal operation of an OLED which will be essential to ensure and predict especially longterm stability and reliability in superbright OLED applications. 
J. Haskovec, S. Hittmeir, P. Markowich, A. Mielke, Decay to equilibrium for energyreactiondiffusion systems, SIAM Journal on Mathematical Analysis, 50 (2018), pp. 10371075, DOI 10.1137/16M1062065 .
Abstract
We derive thermodynamically consistent models of reactiondiffusion equations coupled to a heat equation. While the total energy is conserved, the total entropy serves as a driving functional such that the full coupled system is a gradient flow. The novelty of the approach is the Onsager structure, which is the dual form of a gradient system, and the formulation in terms of the densities and the internal energy. In these variables it is possible to assume that the entropy density is strictly concave such that there is a unique maximizer (thermodynamical equilibrium) given linear constraints on the total energy and suitable density constraints. We consider two particular systems of this type, namely, a diffusionreaction bipolar energy transport system, and a driftdiffusionreaction energy transport system with confining potential. We prove corresponding entropyentropy production inequalities with explicitely calculable constants and establish the convergence to thermodynamical equilibrium, at first in entropy and further in L^{1} using CziszarKullbackPinsker type inequalities. 
G. Lazzaroni, R. Rossi, M. Thomas, R. Toader, Rateindependent damage in thermoviscoelastic materials with inertia, Journal of Dynamics and Differential Equations, 30 (2018), pp. 13111364, DOI 10.1007/s108840189666y .
Abstract
We present a model for rateindependent, unidirectional, partial damage in viscoelastic materials with inertia and thermal effects. The damage process is modeled by means of an internal variable, governed by a rateindependent flow rule. The heat equation and the momentum balance for the displacements are coupled in a highly nonlinear way. Our assumptions on the corresponding energy functional also comprise the case of the AmbrosioTortorelli phasefield model (without passage to the brittle limit). We discuss a suitable weak formulation and prove an existence theorem obtained with the aid of a (partially) decoupled timediscrete scheme and variational convergence methods. We also carry out the asymptotic analysis for vanishing viscosity and inertia and obtain a fully rateindependent limit model for displacements and damage, which is independent of temperature. 
P.W. Schroeder, Ch. Lehrenfeld, A. Linke, G. Lube, Towards computable flows and robust estimates for infsup stable FEM applied to the timedependent incompressible NavierStokes equations, SeMA Journal. Boletin de la Sociedad Espannola de Matematica Aplicada, 75 (2018), pp. 629653, DOI 10.1007/s4032401801571 .
Abstract
Infsup stable FEM applied to timedependent incompressible NavierStokes flows are considered. The focus lies on robust estimates for the kinetic and dissipation energies in a twofold sense. Firstly, pressurerobustness ensures the fulfilment of a fundamental invariance principle and velocity error estimates are not corrupted by the pressure approximability. Secondly, Resemirobustness means that constants appearing on the righthand side of kinetic and dissipation energy error estimates (including Gronwall constants) do not explicitly depend on the Reynolds number. Such estimates rely on an essential regularity assumption for the gradient of the velocity, which is discussed in detail. In the sense of best practice, we review and establish pressure and Resemirobust estimates for pointwise divergencefree H1conforming FEM (like ScottVogelius pairs or certain isogeometric based FEM) and pointwise divergencefree H(div)conforming discontinuous Galerkin FEM. For convectiondominated problems, the latter naturally includes an upwind stabilisation for the velocity which is not gradientbased. 
L. Blank, A. Caiazzo, F. Chouly, A. Lozinski, J. Mura, Analysis of a stabilized penaltyfree Nitsche method for the Brinkman, Stokes, and Darcy problems, ESAIM: Mathematical Modelling and Numerical Analysis, 52 (2018), pp. 21492185, DOI 10.1051/m2an/2018063 .

M. Thomas, C. Bilgen, K. Weinberg, Phasefield fracture at finite strains based on modified invariants: A note on its analysis and simulations, GAMMMitteilungen, 40 (2018), pp. 207237, DOI 10.1002/gamm.201730004 .
Abstract
Phasefield models have already been proven to predict complex fracture patterns in two and three dimensions for brittle fracture at small strains. In this paper we discuss a model for phasefield fracture at finite deformations in more detail. Among the identification of crack location and projection of crack growth the numerical stability is one of the main challenges in solid mechanics. We here present a phasefield model at finite strains, which takes into account the anisotropy of damage by applying an anisotropic split and the modified invariants of the right CauchyGreen strain tensor. We introduce a suitable weak notion of solution that also allows for a spatial and temporal discretization of the model. In this framework we study the existence of solutions %Second the mathematical background of the approach is examined and and we show that the timediscrete solutions converge in a weak sense to a solution of the timecontinuous formulation of the model. Numerical examples in two and three space dimensions are carried out in the range of validity of the analytical results. 
N. Ahmed, C. Bartsch, V. John, U. Wilbrandt, An assessment of solvers for some saddle point problems emerging from the incompressible NavierStokes equations, Computer Methods in Applied Mechanics and Engineering, 331 (2018), pp. 492513, DOI 10.1016/j.cma.2017.12.004 .
Abstract
Efficient incompressible flow simulations, using infsup stable pairs of finite element spaces, require the application of efficient solvers for the arising linear saddle point problems. This paper presents an assessment of different solvers: the sparse direct solver UMFPACK, the flexible GMRES (FGMRES) method with different coupled multigrid preconditioners, and FGMRES with Least Squares Commutator (LSC) preconditioners. The assessment is performed for steadystate and timedependent flows around cylinders in 2d and 3d. Several pairs of infsup stable finite element spaces with second order velocity and first order pressure are used. It turns out that for the steadystate problems often FGMRES with an appropriate multigrid preconditioner was the most efficient method on finer grids. For the timedependent problems, FGMRES with LSC preconditioners that use an inexact iterative solution of the velocity subproblem worked best for smaller time steps. 
N. Ahmed, A. Linke, Ch. Merdon, On really lockingfree mixed finite element methods for the transient incompressible Stokes equations, SIAM Journal on Numerical Analysis, 56 (2018), pp. 185209.
Abstract
Infsup stable mixed methods for the steady incompressible Stokes equations that relax the divergence constraint are often claimed to deliver lockingfree discretizations. However, this relaxation leads to a pressuredependent contribution in the velocity error, which is proportional to the inverse of the viscosity, thus giving rise to a (different) locking phenomenon. However, a recently proposed modification of the right hand side alone leads to a discretization that is really lockingfree, i.e., its velocity error converges with optimal order and is independent of the pressure and the smallness of the viscosity. In this contribution, we extend this approach to the transient incompressible Stokes equations, where besides the right hand side also the velocity time derivative requires an improved space discretization. Semidiscrete and fullydiscrete apriori velocity and pressure error estimates are derived, which show beautiful robustness properties. Two numerical examples illustrate the superior accuracy of pressurerobust space discretizations in the case of small viscosities. 
P. Farrell, M. Patriarca, J. Fuhrmann, Th. Koprucki, Comparison of thermodynamically consistent charge carrier flux discretizations for FermiDirac and GaussFermi statistics, Optical and Quantum Electronics, 50 (2018), pp. 101/1101/10, DOI 10.1007/s1108201813498 .
Abstract
We compare three thermodynamically consistent ScharfetterGummel schemes for different distribution functions for the carrier densities, including the FermiDirac integral of order 1/2 and the GaussFermi integral. The most accurate (but unfortunately also most costly) generalized ScharfetterGummel scheme requires the solution of an integral equation. We propose a new method to solve this integral equation numerically based on Gauss quadrature and Newton's method. We discuss the quality of this approximation and plot the resulting currents for FermiDirac and GaussFermi statistics. Finally, by comparing two modified (diffusionenhanced and inverse activity based) ScharfetterGummel schemes with the more accurate generalized scheme, we show that the diffusionenhanced ansatz leads to considerably lower flux errors, confirming previous results (J. Comp. Phys. 346:497513, 2017). 
M. Hintermüller, M. Hinze, Ch. Kahle, T. Keil, A goaloriented dualweighted adaptive finite element approach for the optimal control of a nonsmooth CahnHilliardNavierStokes system, Optimization and Engineering. International Multidisciplinary Journal to Promote Optimization Theory & Applications in Engineering Sciences, 19 (2018), pp. 629662, DOI 10.1007/s1108101893936 .
Abstract
This paper is concerned with the development and implementation of an adaptive solution algorithm for the optimal control of a timediscrete CahnHilliardNavierStokes system with variable densities. The free energy density associated to the CahnHilliard system incorporates the doubleobstacle potential which yields an optimal control problem for a family of coupled systems in each time instant of a variational inequality of fourth order and the NavierStokes equation. A dualweighed residual approach for goaloriented adaptive finite elements is presented which is based on the concept of Cstationarity. The overall error representation depends on primal residual weighted by approximate dual quantities and vice versa as well as various complementary mismatch errors. Details on the numerical realization of the adaptive concept and a report on numerical tests are given. 
V. John, P. Knobloch, J. Novo, Finite elements for scalar convectiondominated equations and incompressible flow problems  A never ending story?, Computing and Visualization in Science, 19 (2018), pp. 4763.
Abstract
The contents of this paper is twofold. First, important recent results concerning finite element methods for convectiondominated problems and incompressible flow problems are described that illustrate the activities in these topics. Second, a number of, in our opinion, important problems in these fields are discussed. 
A. Linke, Ch. Merdon, M. Neilan, F. Neumann, Quasioptimality of a pressurerobust nonconforming finite element method for the Stokes problem, Mathematics of Computation, 87 (2018), pp. 15431566, DOI 10.1090/mcom/3344 .
Abstract
Nearly all classical infsup stable mixed finite element methods for the incompressible Stokes equations are not pressurerobust, i.e., the velocity error is dependent on the pressure. However, recent results show that pressurerobustness can be recovered by a nonstandard discretization of the right hand side alone. This variational crime introduces a consistency error in the method which can be estimated in a straightforward manner provided that the exact velocity solution is sufficiently smooth. The purpose of this paper is to analyze the pressurerobust scheme with low regularity. The numerical analysis applies divergencefree H¹conforming Stokes finite element methods as a theoretical tool. As an example, pressurerobust velocity and pressure apriori error estimates will be presented for the (first order) nonconforming CrouzeixRaviart element. A key feature in the analysis is the dependence of the errors on the Helmholtz projector of the right hand side data, and not on the entire data term. Numerical examples illustrate the theoretical results. 
P. Farrell, A. Linke, Uniform second order convergence of a complete flux scheme on unstructured 1D grids for a singularly perturbed advectiondiffusion equation and some multidimensional extensions, Journal of Scientific Computing, 72 (2017), pp. 373395, DOI 10.1007/s1091501703617 .
Abstract
The accurate and efficient discretization of singularly perturbed advectiondiffusion equations on arbitrary 2D and 3D domains remains an open problem. An interesting approach to tackle this problem is the complete flux scheme (CFS) proposed by G. D. Thiart and further investigated by J. ten Thije Boonkkamp. For the CFS, uniform second order convergence has been proven on structured grids. We extend a version of the CFS to unstructured grids for a steady singularly perturbed advectiondiffusion equation. By construction, the novel finite volume scheme is nodally exact in 1D for piecewise constant source terms. This property allows to use elegant continuous arguments in order to prove uniform second order convergence on unstructured onedimensional grids. Numerical results verify the predicted bounds and suggest that by aligning the finite volume grid along the velocity field uniform second order convergence can be obtained in higher space dimensions as well. 
M. Kantner, M. Mittnenzweig, Th. Koprucki, Hybrid quantumclassical modeling of quantum dot devices, Phys. Rev. B., 96 (2017), pp. 205301/1205301/17, DOI 10.1103/PhysRevB.96.205301 .
Abstract
The design of electrically driven quantum dot devices for quantum optical applications asks for modeling approaches combining classical device physics with quantum mechanics. We connect the wellestablished fields of semiclassical semiconductor transport theory and the theory of open quantum systems to meet this requirement. By coupling the van Roosbroeck system with a quantum master equation in Lindblad form, we obtain a new hybrid quantumclassical modeling approach, which enables a comprehensive description of quantum dot devices on multiple scales: It allows the calculation of quantum optical figures of merit and the spatially resolved simulation of the current flow in realistic semiconductor device geometries in a unified way. We construct the interface between both theories in such a way, that the resulting hybrid system obeys the fundamental axioms of (non)equilibrium thermodynamics. We show that our approach guarantees the conservation of charge, consistency with the thermodynamic equilibrium and the second law of thermodynamics. The feasibility of the approach is demonstrated by numerical simulations of an electrically driven singlephoton source based on a single quantum dot in the stationary and transient operation regime. 
A. Linke, M. Neilan, L.G. Rebholz, N. Wilson, A connection between coupled and penalty projection timestepping schemes with FE spatial discretization for the NavierStokes equations, Journal of Numerical Mathematics, 25 (2017), pp. 229248, DOI 10.1515/jnma20161024 .
Abstract
We prove that in finite element settings where the divergencefree subspace of the velocity space has optimal approximation properties, the solution of Chorin/Temam projection methods for NavierStokes equations equipped with graddiv stabilization with parameter gamma, converge to the associated coupled method solution with rate 1/gamma as gamma goes to infinity. We prove this first for backward Euler schemes, and then extend the results to BDF2 schemes, and finally to schemes with outflow boundary conditions. Several numerical experiments are given which verify the convergence rate, and show how using projection methods in this setting with large graddiv stabilization parameters can dramatically improve accuracy. 
U. Wilbrandt, C. Bartsch, N. Ahmed, N. Alia, F. Anker, L. Blank, A. Caiazzo, S. Ganesan, S. Giere, G. Matthies, R. Meesala, A. Shamim, J. Venkatensan, V. John, ParMooN  A modernized program package based on mapped finite elements, Computers & Mathematics with Applications. An International Journal, 74 (2017), pp. 7488, DOI 10.1016/j.camwa.2016.12.020 .

R. Rossi, M. Thomas, Coupling rateindependent and ratedependent processes: Existence results, SIAM Journal on Mathematical Analysis, 49 (2017), pp. 14191494.
Abstract
We address the analysis of an abstract system coupling a rateindependet process with a second order (in time) nonlinear evolution equation. We propose suitable weak solution concepts and obtain existence results by passing to the limit in carefully devised timediscretization schemes. Our arguments combine techniques from the theory of gradient systems with the toolbox for rateindependent evolution, thus reflecting the mixed character of the problem. Finally, we discuss applications to a class of rateindependent processes in viscoelastic solids with inertia, and to a recently proposed model for damage with plasticity. 
G.R. Barrenechea, V. John, P. Knobloch, An algebraic flux correction scheme satisfying the discrete maximum principle and linearity preservation on general meshes, Mathematical Models & Methods in Applied Sciences, 27 (2017), pp. 525548, DOI 10.1142/S0218202517500087 .

W. Huang, L. Kamenski, On the mesh nonsingularity of the moving mesh PDE method, Mathematics of Computation, 87 (2018), pp. 18871911 (published online on 02.10.2017), DOI 10.1090/mcom/3271 .
Abstract
The moving mesh PDE (MMPDE) method for variational mesh generation and adaptation is studied theoretically at the discrete level, in particular the nonsingularity of the obtained meshes. Meshing functionals are discretized geometrically and the MMPDE is formulated as a modified gradient system of the corresponding discrete functionals for the location of mesh vertices. It is shown that if the meshing functional satisfies a coercivity condition, then the mesh of the semidiscrete MMPDE is nonsingular for all time if it is nonsingular initially. Moreover, the altitudes and volumes of its elements are bounded below by positive numbers depending only on the number of elements, the metric tensor, and the initial mesh. Furthermore, the value of the discrete meshing functional is convergent as time increases, which can be used as a stopping criterion in computation. Finally, the mesh trajectory has limiting meshes which are critical points of the discrete functional. The convergence of the mesh trajectory can be guaranteed when a stronger condition is placed on the meshing functional. Two meshing functionals based on alignment and equidistribution are known to satisfy the coercivity condition. The results also hold for fully discrete systems of the MMPDE provided that the time step is sufficiently small and a numerical scheme preserving the property of monotonically decreasing energy is used for the temporal discretization of the semidiscrete MMPDE. Numerical examples are presented 
P.L. Lederer, A. Linke, Ch. Merdon, J. Schöberl, Divergencefree reconstruction operators for pressurerobust Stokes discretizations with continuous pressure finite elements, SIAM Journal on Numerical Analysis, 55 (2017), pp. 12911314.
Abstract
Classical infsup stable mixed finite elements for the incompressible (Navier)Stokes equations are not pressurerobust, i.e., their velocity errors depend on the continuous pressure. However, a modification only in the right hand side of a Stokes discretization is able to reestablish pressurerobustness, as shown recently for several infsup stable Stokes elements with discontinuous discrete pressures. In this contribution, this idea is extended to low and high order TaylorHood and mini elements, which have continuous discrete pressures. For the modification of the right hand side a velocity reconstruction operator is constructed that maps discretely divergencefree test functions to exactly divergencefree ones. The reconstruction is based on local H(div)conforming flux equilibration on vertex patches, and fulfills certain orthogonality properties to provide consistency and optimal apriori error estimates. Numerical examples for the incompressible Stokes and NavierStokes equations confirm that the new pressurerobust TaylorHood and mini elements converge with optimal order and outperform signicantly the classical versions of those elements when the continuous pressure is comparably large. 
N. Ahmed, S. Becher, G. Matthies, Higherorder discontinuous Galerkin time stepping and local projection stabilization techniques for the transient Stokes problem, Computer Methods in Applied Mechanics and Engineering, 313 (2017), pp. 2852.
Abstract
We introduce and analyze discontinuous Galerkin time discretizations coupled with continuous finite element methods based on equalorder interpolation in space for velocity and pressure in transient Stokes problems. Spatial stability of the pressure is ensured by adding a stabilization term based on local projection. We present error estimates for the semidiscrete problem after discretization in space only and for the fully discrete problem. The fully discrete pressure shows an instability in the limit of small time step length. Numerical tests are presented which confirm our theoretical results including the pressure instability. 
N. Ahmed, T.Ch. Rebollo, V. John, S. Rubino, A review of variational multiscale methods for the simulation of turbulent incompressible flows, Archives of Computational Methods in Engineering. State of the Art Reviews, 24 (2017), pp. 115164.
Abstract
Various realizations of variational multiscale (VMS) methods for simulating turbulent incompressible flows have been proposed in the past fifteen years. All of these realizations obey the basic principles of VMS methods: They are based on the variational formulation of the incompressible NavierStokes equations and the scale separation is defined by projections. However, apart from these common basic features, the various VMS methods look quite different. In this review, the derivation of the different VMS methods is presented in some detail and their relation among each other and also to other discretizations is discussed. Another emphasis consists in giving an overview about known results from the numerical analysis of the VMS methods. A few results are presented in detail to highlight the used mathematical tools. Furthermore, the literature presenting numerical studies with the VMS methods is surveyed and the obtained results are summarized. 
N. Ahmed, T.Ch. Rebollo, V. John, S. Rubino, Analysis of a full spacetime discretization of the NavierStokes equations by a local projection stabilization method, IMA Journal of Numerical Analysis, 37 (2017), pp. 14371467, DOI 10.1093/imanum/drw048 .
Abstract
A finite element error analysis of a local projection stabilization (LPS) method for the timedependent NavierStokes equations is presented. The focus is on the highorder termbyterm stabilization method that has one level, in the sense that it is defined on a single mesh, and in which the projectionstabilized structure of standard LPS methods is replaced by an interpolationstabilized structure. The main contribution is on proving, theoretically and numerically, the optimal convergence order of the arising fully discrete scheme. In addition, the asymptotic energy balance is obtained for slightly smooth flows. Numerical studies support the analytical results and illustrate the potential of the method for the simulation of turbulent flows. Smooth unsteady flows are simulated with optimal order of accuracy. 
N. Ahmed, A. Linke, Ch. Merdon, Towards pressurerobust mixed methods for the incompressible NavierStokes equations, Computational Methods in Applied Mathematics, 18 (2018), pp. 353372 (published online on 18.11.2017), DOI 10.1515/cmam20170047 .
Abstract
In this contribution, classical mixed methods for the incompressible NavierStokes equations that relax the divergence constraint and are discretely infsup stable, are reviewed. Though the relaxation of the divergence constraint was claimed to be harmless since the beginning of the 1970ies, Poisson locking is just replaced by another more subtle kind of locking phenomenon, which is sometimes called poor mass conservation. Indeed, divergencefree mixed methods and classical mixed methods behave qualitatively in a different way: divergencefree mixed methods are pressurerobust, which means that, e.g., their velocity error is independent of the continuous pressure. The lack of pressurerobustness in classical mixed methods can be traced back to a consistency error of an appropriately defined discrete Helmholtz projector. Numerical analysis and numerical examples reveal that really lockingfree mixed methods must be discretely infsup stable and pressurerobust, simultaneously. Further, a recent discovery shows that lockingfree, pressurerobust mixed methods do not have to be divergencefree. Indeed, relaxing the divergence constraint in the velocity trial functions is harmless, if the relaxation of the divergence constraint in some velocity test functions is repaired, accordingly. 
N. Ahmed, On the graddiv stabilization for the steady Oseen and NavierStokes equations, Calcolo. A Quarterly on Numerical Analysis and Theory of Computation, 54 (2017), pp. 471501, DOI 10.1007/s100920160194z .
Abstract
This paper studies the parameter choice in the graddiv stabilization applied to the generalized problems of Oseen type. Stabilization parameters based on minimizing the H^{1}(Ω) error of the velocity are derived which do not depend on the viscosity parameter. For the proposed parameter choices, the H^{1}(Ω) error of the velocity is derived that shows a direct dependence on the viscosity parameter. Differences and common features to the situation for the Stokes equations are discussed. Numerical studies are presented which confirm the theoretical results. Moreover, for the Navier Stokes equations, numerical simulations were performed on a twodimensional ow past a circular cylinder. It turns out, for the MINI element, that the best results can be obtained without graddiv stabilization. 
W. Dreyer, C. Guhlke, M. Landstorfer, R. Müller, New insights on the interfacial tension of electrochemical interfaces and the Lippmann equation, European Journal of Applied Mathematics, 29 (2018), pp. 708753, DOI 10.1017/S0956792517000341 .
Abstract
The Lippmann equation is considered as universal relationship between interfacial tension, double layer charge, and cell potential. Based on the framework of continuum thermoelectrodynamics we provide some crucial new insights to this relation. In a previous work we have derived a general thermodynamic consistent model for electrochemical interfaces, which showed a remarkable agreement to single crystal experimental data. Here we apply the model to a curved liquid metal electrode. If the electrode radius is large compared to the Debye length, we apply asymptotic analysis methods and obtain the Lippmann equation. We give precise definitions of the involved quantities and show that the interfacial tension of the Lippmann equation is composed of the surface tension of our general model, and contributions arising from the adjacent space charge layers. This finding is confirmed by a comparison of our model to experimental data of several mercuryelectrolyte interfaces. We obtain qualitative and quantitative agreement in the 2V potential range for various salt concentrations. We also discuss the validity of our asymptotic model when the electrode curvature radius is comparable to the Debye length. 
P. Farrell, Th. Koprucki, J. Fuhrmann, Computational and analytical comparison of flux discretizations for the semiconductor device equations beyond Boltzmann statistics, Journal of Computational Physics, 346 (2017), pp. 497513, DOI 10.1016/j.jcp.2017.06.023 .
Abstract
For a Voronoï finite volume discretization of the van Roosbroeck system with general charge carrier statistics we compare three thermodynamically consistent numerical fluxes known in the literature. We discuss an extension of the ScharfetterGummel scheme to nonBoltzmann (e.g. FermiDirac) statistics. It is based on the analytical solution of a twopoint boundary value problem obtained by projecting the continuous differential equation onto the interval between neighboring collocation points. Hence, it serves as a reference flux. The exact solution of the boundary value problem can be approximated by computationally cheaper fluxes which modify certain physical quantities. One alternative scheme averages the nonlinear diffusion (caused by the nonBoltzmann nature of the problem), another one modifies the effective density of states. To study the differences between these three schemes, we analyze the Taylor expansions, derive an error estimate, visualize the flux error and show how the schemes perform for a carefully designed pin benchmark simulation. We present strong evidence that the flux discretization based on averaging the nonlinear diffusion has an edge over the scheme based on modifying the effective density of states. 
V. John, A. Linke, Ch. Merdon, M. Neilan, L.G. Rebholz, On the divergence constraint in mixed finite element methods for incompressible flows, SIAM Review, 59 (2017), pp. 492544, DOI 10.1137/15M1047696 .
Abstract
The divergence constraint of the incompressible NavierStokes equations is revisited in the mixed finite element framework. While many stable and convergent mixed elements have been developed throughout the past four decades, most classical methods relax the divergence constraint and only enforce the condition discretely. As a result, these methods introduce a pressuredependent consistency error which can potentially pollute the computed velocity. These methods are not robust in the sense that a contribution from the righthand side, which influences only the pressure in the continuous equations, impacts both velocity and pressure in the discrete equations. This paper reviews the theory and practical implications of relaxing the divergence constraint. Several approaches for improving the discrete mass balance or even for computing divergencefree solutions will be discussed: graddiv stabilization, higher order mixed methods derived on the basis of an exact de Rham complex, $bH(mathrmdiv)$conforming finite elements, and mixed methods with an appropriate reconstruction of the test functions. Numerical examples illustrate both the potential effects of using nonrobust discretizations and the improvements obtained by utilizing pressurerobust discretizations. 
M. Liero, J. Fuhrmann, A. Glitzky, Th. Koprucki, A. Fischer, S. Reineke, 3D electrothermal simulations of organic LEDs showing negative differential resistance, Optical and Quantum Electronics, 49 (2017), pp. 330/1330/8, DOI 10.1007/s1108201711674 .
Abstract
Organic semiconductor devices show a pronounced interplay between temperatureactivated conductivity and selfheating which in particular causes inhomogeneities in the brightness of largearea OLEDs at high power. We consider a 3D thermistor model based on partial differential equations for the electrothermal behavior of organic devices and introduce an extension to multiple layers with nonlinear conductivity laws, which also take the diodelike behavior in recombination zones into account. We present a numerical simulation study for a red OLED using a finitevolume approximation of this model. The appearance of Sshaped currentvoltage characteristics with regions of negative differential resistance in a measured device can be quantitatively reproduced. Furthermore, this simulation study reveals a propagation of spatial zones of negative differential resistance in the electron and hole transport layers toward the contact. 
A. Linke, Ch. Merdon, W. Wollner, Optimal L2 velocity error estimate for a modified pressurerobust CrouzeixRaviart Stokes element, IMA Journal of Numerical Analysis, 37 (2017), pp. 354374, DOI 10.1093/imanum/drw019 .
Abstract
Recently, a novel approach for the robust discretization of the incompressible Stokes equations was proposed that slightly modifies the nonconforming CrouzeixRaviart element such that its velocity error becomes pressureindependent. The modification results in an O(h) consistency error that allows straightforward proofs for the optimal convergence of the discrete energy norm of the velocity and of the L2 norm of the pressure. However, though the optimal convergence of the velocity in the L2 norm was observed numerically, it appeared to be nontrivial to prove. In this contribution, this gap is closed. Moreover, the dependence of the error estimates on the discrete infsup constant is traced in detail, which shows that classical error estimates are extremely pessimistic on domains with large aspect ratios. Numerical experiments in 2D and 3D illustrate the theoretical findings. 
E. Meca Álvarez, A. Münch, B. Wagner, Sharpinterface formation during lithium intercalation into silicon, European Journal of Applied Mathematics, 29 (2018), pp. 118145, DOI 10.1017/S0956792517000067 .
Abstract
In this study we present a phasefield model that describes the process of intercalation of Li ions into a layer of an amorphous solid such as aSi. The governing equations couple a viscous CahnHilliardReaction model with elasticity in the framework of the CahnLarché system. We discuss the parameter settings and flux conditions at the free boundary that lead to the formation of phase boundaries having a sharp gradient in ion concentration between the initial state of the solid layer and the intercalated region. We carry out a matched asymptotic analysis to derive the corresponding sharpinterface model that also takes into account the dynamics of triple points where the sharp interface in the bulk of the layer intersects the free boundary. We numerically compare the interface motion predicted by the sharpinterface model with the longtime dynamics of the phasefield model. 
A. Mielke, M. Mittnenzweig, Convergence to equilibrium in energyreactiondiffusion systems using vectorvalued functional inequalities, Journal of Nonlinear Science, 28 (2018), pp. 765806 (published online on 11.11.2017), DOI 10.1007/s0033201794279 .
Abstract
We discuss how the recently developed energydissipation methods for reactiondi usion systems can be generalized to the nonisothermal case. For this we use concave entropies in terms of the densities of the species and the internal energy, where the importance is that the equilibrium densities may depend on the internal energy. Using the logSobolev estimate and variants for lowerorder entropies as well as estimates for the entropy production of the nonlinear reactions we give two methods to estimate the relative entropy by the total entropy production, namely a somewhat restrictive convexity method, which provides explicit decay rates, and a very general, but weaker compactness method. 
K. Disser, G.P. Galdi, G. Mazzone, P. Zunino, Inertial motions of a rigid body with a cavity filled with a viscous liquid, Archive for Rational Mechanics and Analysis, 221 (2016), pp. 487526.
Abstract
We consider the system of equations modeling the free motion of a rigid body with a cavity filled by a viscous (NavierStokes) liquid. Zhukovskiy's Theorem states that in the limit of time going to infinity, the relative fluid velocity tends to 0 and the rigid velocity of the full structure tends to a steady rotation around one of the principle axes of inertia. We give a rigorous proof of this result.
In particular, we prove that every global weak solution in a suitable class is subject to Zhukovskiy's Theorem, and note that existence of these solutions has been established. Independently of the geometry and of parameters, this shows that the presence of fluid prevents precession of the body in the limit. In general, we cannot predict which axis will be attained, but we can show stability of the largest axis and provide criteria on the initial data which are decisive in special cases. 
M. Kantner, Th. Koprucki, Numerical simulation of carrier transport in semiconductor devices at cryogenic temperatures, Optical and Quantum Electronics, 48 (2016), pp. 543/1543/7, DOI 10.1007/s1108201608172 .
Abstract
At cryogenic temperatures the electron?hole plasma in semiconductors becomes strongly degenerate, leading to very sharp internal layers, extreme depletion in intrinsic domains and strong nonlinear diffusion. As a result, the numerical simulation of the drift?diffusion system suffers from serious convergence issues using standard methods. We consider a onedimensional pin diode to illustrate these problems and present a simple temperatureembedding scheme to enable the numerical simulation at cryogenic temperatures. The method is suitable for forwardbiased devices as they appear e.g. in optoelectronic applications. Moreover, the method can be applied to wide band gap semiconductors where similar numerical issues occur already at room temperature. 
M. Kantner, U. Bandelow, Th. Koprucki, J.H. Schulze, A. Strittmatter, H.J. Wünsche, Efficient current injection into single quantum dots through oxideconfined pndiodes, IEEE Transactions on Electron Devices, 63 (2016), pp. 20362042.
Abstract
Current injection into single quantum dots embedded in vertical pndiodes featuring oxide apertures is analyzed in the lowinjection regime suitable for singlephoton emitters. Experimental and theoretical evidence is found for a rapid lateral spreading of the carriers after passing the oxide aperture in the conventional pindesign. By an alternative design employing pdoping up to the oxide aperture the current spreading can be suppressed resulting in an enhanced current confinement and increased injection efficiencies, both, in the continuous wave and under pulsed excitation. 
A. Linke, G. Matthies, L. Tobiska, Robust arbitrary order mixed finite element methods for the incompressible Stokes equations with pressure independent velocity errors, ESAIM: Mathematical Modelling and Numerical Analysis, 50 (2016), pp. 289309.
Abstract
Standard mixed finite element methods for the incompressible NavierStokes equations that relax the divergence constraint are not robust against large irrotational forces in the momentum balance and the velocity error depends on the continuous pressure. This robustness issue can be completely cured by using divergencefree mixed finite elements which deliver pressureindependent velocity error estimates. However, the construction of H1conforming, divergencefree mixed finite element methods is rather difficult. Instead, we present a novel approach for the construction of arbitrary order mixed finite element methods which deliver pressureindependent velocity errors. The approach does not change the trial functions but replaces discretely divergencefree test functions in some operators of the weak formulation by divergencefree ones. This modification is applied to infsup stable conforming and nonconforming mixed finite element methods of arbitrary order in two and three dimensions. Optimal estimates for the incompressible Stokes equations are proved for the H1 and L2 errors of the velocity and the L2 error of the pressure. Moreover, both velocity errors are pressureindependent, demonstrating the improved robustness. Several numerical examples illustrate the results. 
D. Peschka, M. Thomas, A. Glitzky, R. Nürnberg, M. Virgilio, S. Guha, Th. Schröder, G. Cappellini, Th. Koprucki, Robustness analysis of a device concept for edgeemitting lasers based on strained germanium, Optical and Quantum Electronics, 48 (2016), pp. 156/1156/7, DOI 10.1007/s1108201603944 .
Abstract
We consider a device concept for edgeemitting lasers based on strained germanium microstrips. The device features an inhomogeneous tensile strain distribution generated by a SiN stressor deposited on top of the Ge microstrip. This geometry requires a lateral contact scheme and hence a full twodimensional description. The twodimensional simulations of the carrier transport and of the optical field, carried out in a cross section of the device orthogonal to the optical cavity, use microscopic calculations of the strained Ge material gain as an input. In this paper we study laser performance and robustness against ShockleyReadHall lifetime variations and device sensitivity to different strain distributions. 
D. Peschka, N. Rotundo, M. Thomas, Towards doping optimization of semiconductor lasers, Journal of Computational and Theoretical Transport, 45 (2016), pp. 410423.
Abstract
We discuss analytical and numerical methods for the optimization of optoelectronic devices by performing optimal control of the PDE governing the carrier transport with respect to the doping profile. First, we provide a cost functional that is a sum of a regularization and a contribution, which is motivated by the modal net gain that appears in optoelectronic models of bulk or quantumwell lasers. Then, we state a numerical discretization, for which we study optimized solutions for different regularizations and for vanishing weights. 
G.R. Barrenechea, V. John, P. Knobloch, Analysis of algebraic flux correction schemes, SIAM Journal on Numerical Analysis, 54 (2016), pp. 24272451.
Abstract
A family of algebraic flux correction schemes for linear boundary value problems in any space dimension is studied. These methods' main feature is that they limit the fluxes along each one of the edges of the triangulation, and we suppose that the limiters used are symmetric. For an abstract problem, the existence of a solution, existence and uniqueness of the solution of a linearized problem, and an a priori error estimate, are proved under rather general assumptions on the limiters. For a particular (but standard in practice) choice of the limiters, it is shown that a local discrete maximum principle holds. The theory developed for the abstract problem is applied to convectiondiffusionreaction equations, where in particular an error estimate is derived. Numerical studies show its sharpness. 
C. Bertoglio, A. Caiazzo, A Stokesresidual backflow stabilization method applied to physiological flows, Journal of Computational Physics, 313 (2016), pp. 260278.
Abstract
In computational fluid dynamics incoming flow at open boundaries, or emphbackflow, often yields to unphysical instabilities for high Reynolds numbers. It is widely accepted that this is due to the incoming energy arising from the convection term, which cannot be empha priori controlled when the velocity field is unknown at the boundary. In order to improve the robustness of the numerical simulations, we propose a stabilized formulation based on a penalization of the residual of a weak Stokes problem on the open boundary, whose viscous part controls the incoming convective energy, while the inertial term contributes to the kinetic energy. We also present different strategies for the approximation of the boundary pressure gradient, which is needed for defining the stabilization term. The method has the advantage that it does not require neither artificial modifications or extensions of the computational domain. Moreover, it is consistent with the Womersley solution. We illustrate our approach on numerical examples  both academic and reallife  relevant to blood and respiratory flows. The results also show that the stabilization parameter can be reduced with the mesh size. 
P. Bringmann, C. Carstensen, Ch. Merdon, Guaranteed error control for the pseudostress approximation of the Stokes equations, Numerical Methods for Partial Differential Equations. An International Journal, 32 (2016), pp. 14111432.
Abstract
The pseudostress approximation of the Stokes equations rewrites the stationary Stokes equations with pure (but possibly inhomogeneous) Dirichlet boundary conditions as another (equivalent) mixed scheme based on a stress in H(div) and the velocity in $L^2$. Any standard mixed finite element function space can be utilized for this mixed formulation, e.g. the RaviartThomas discretization which is related to the CrouzeixRaviart nonconforming finite element scheme in the lowestorder case. The effective and guaranteed a posteriori error control for this nonconforming velocityoriented discretization can be generalized to the error control of some piecewise quadratic velocity approximation that is related to the discrete pseudostress. The analysis allows for local infsup constants which can be chosen in a global partition to improve the estimation. Numerical examples provide strong evidence for an effective and guaranteed error control with very small overestimation factors even for domains with large anisotropy. 
A. Ern, D. Di Pietro, A. Linke, F. Schieweck, A discontinuous skeletal method for the viscositydependent Stokes problem, Computer Methods in Applied Mechanics and Engineering, 306 (2016), pp. 175195.
Abstract
We devise and analyze arbitraryorder nonconforming methods for the discretization of the viscositydependent Stokes equations on simplicial meshes. We keep track explicitly of the viscosity and aim at pressurerobust schemes that can deal with the practically relevant case of body forces with large curlfree part in a way that the discrete velocity error is not spoiled by large pressures. The method is inspired from the recent Hybrid HighOrder (HHO) methods for linear elasticity. After elimination of the auxiliary variables by static condensation, the linear system to be solved involves only discrete facebased velocities, which are polynomials of degree k >=0, and cellwise constant pressures. Our main result is a pressureindependent energyerror estimate on the velocity of order (k+1). The main ingredient to achieve pressureindependence is the use of a divergencepreserving velocity reconstruction operator in the discretization of the body forces. We also prove an L2pressure estimate of order (k+1) and an L2velocity estimate of order (k+2), the latter under elliptic regularity. The local mass and momentum conservation properties of the discretization are also established. Finally, two and threedimensional numerical results are presented to support the analysis. 
A. Fiebach, A. Glitzky, A. Linke, Convergence of an implicit Voronoi finite volume method for reactiondiffusion problems, Numerical Methods for Partial Differential Equations. An International Journal, 32 (2016), pp. 141174.
Abstract
We investigate the convergence of an implicit Voronoi finite volume method for reaction diffusion problems including nonlinear diffusion in two space dimensions. The model allows to handle heterogeneous materials and uses the chemical potentials of the involved species as primary variables. The numerical scheme uses boundary conforming Delaunay meshes and preserves positivity and the dissipative property of the continuous system. Starting from a result on the global stability of the scheme (uniform, meshindependent global upper and lower bounds), we prove strong convergence of the chemical activities and their gradients to a weak solution of the continuous problem. In order to illustrate the preservation of qualitative properties by the numerical scheme, we present a longterm simulation of the MichaelisMentenHenri system. Especially, we investigate the decay properties of the relative free energy and the evolution of the dissipation rate over several magnitudes of time, and obtain experimental orders of convergence for these quantities. 
R. HallerDintelmann, A. Jonsson, D. Knees, J. Rehberg, Elliptic and parabolic regularity for second order divergence operators with mixed boundary conditions, Mathematical Methods in the Applied Sciences, 39 (2016), pp. 50075026, DOI 10.1002/mma.3484/abstract .
Abstract
We study second order equations and systems on nonLipschitz domains including mixed boundary conditions. The key result is interpolation for suitable function spaces. 
W. Huang, L. Kamenski, J. Lang, Stability of explicit onestep methods for P1finite element approximation of linear diffusion equations on anisotropic meshes, SIAM Journal on Numerical Analysis, 54 (2016), pp. 16121634.
Abstract
We study the stability of explicit RungeKutta integration schemes for the linear finite element approximation of linear parabolic equations. The derived bound on the largest permissible time step is tight for any mesh and any diffusion matrix within a factor of 2 (d + 1), where d is the spatial dimension. Both full mass matrix and mass lumping are considered. The bound reveals that the stability condition is affected by two factors. The first one depends on the number of mesh elements and corresponds to the classic bound for the Laplace operator on a uniform mesh. The other factor reflects the effects of the interplay of the mesh geometry and the diffusion matrix. It is shown that it is not the mesh geometry itself but the mesh geometry in relation to the diffusion matrix that is crucial to the stability of explicit methods. When the mesh is uniform in the metric specified by the inverse of the diffusion matrix, the stability condition is comparable to the situation with the Laplace operator on a uniform mesh. Numerical results are presented to verify the theoretical findings. 
M. Khodayari, P. Reinsberg, A.A. AbdElLatif, Ch. Merdon, J. Fuhrmann, H. Baltruschat, Determining solubility and diffusivity by using a flow cell coupled to a mass spectrometer, ChemPhysChem, 17 (2016), pp. 16471655.

N. Ahmed, G. Matthies, Numerical study of SUPG and LPS methods combined with higher order variational time discretization schemes applied to timedependent convectiondiffusionreaction equations, Journal of Scientific Computing, 67 (2016), pp. 9881018.
Abstract
This paper considers the numerical solution of timedependent convectiondiffusionreaction equations. We shall employ combinations of streamlineupwind PetrovGalerkin (SUPG) and local projection stabilization (LPS) methods in space with the higher order variational time discretization schemes. In particular, we consider time discretizations by discontinuous Galerkin (dG) methods and continuous GalerkinPetrov (cGP) methods. Several numerical tests have been performed to assess the accuracy of combinations of spatial and temporal discretization schemes. Furthermore, the dependence of the results on the stabilization parameters of the spatial discretizations are discussed. Finally the longtime behavior of overshoots and undershoots is investigated. 
A. Caiazzo, R. Guibert, I.E. VignonClementel, A reducedorder modeling for efficient design study of artificial valve in enlarged ventricular outflow tracts, Computer Methods in Biomechanics and Biomedical Engineering, 19 (2016), pp. 13141318.
Abstract
A computational approach is proposed for efficient design study of a reducer stent to be percutaneously implanted in enlarged right ventricular outflow tracts (RVOT). The need for such a device is driven by the absence of bovine or artificial valves which could be implanted in these RVOT to replace the absent or incompetent native valve, as is often the case over time after Tetralogy of Fallot repair. Hemodynamics are simulated in the stented RVOT via a reduce order model based on proper orthogonal decomposition (POD), while the artificial valve is modeled as a thin resistive surface. The reduced order model is obtained from the numerical solution on a reference device configuration, then varying the geometrical parameters (diameter) for design purposes. To validate the approach, forces exerted on the valve and on the reducer are monitored, varying with geometrical parameters, and compared with the results of full CFD simulations. Such an approach could also be useful for uncertainty quantification. 
W. Dreyer, C. Guhlke, M. Landstorfer, Theory and structure of the metal/electrolyte interface incorporating adsorption and solvation effects, Electrochimica Acta, 201 (2016), pp. 187219.
Abstract
In this work we present a continuum theory for the metal/electrolyte interface which explicitly takes into account adsorption and partial solvation on the metal surface. It is based on a general theory of coupled thermoelectrodynamics for volumes and surfaces, utilized here in equilibrium and a 1D approximation. We provide explicit free energy models for the volumetric metal and electrolyte phases and derive a surface free energy for the species present on the metal surface. This surface mixture theory explicitly takes into account the very different amount of sites an adsorbate requires, originating from solvation effects on the surface. Additionally we account for electron transfer reactions on the surface and the associated stripping of the solvation shell. Based on our overall surface free energy we thus provide explicit expressions of the surface chemical potentials of all constituents. The equilibrium representations of the coverages and the overall charge are briefly summarized.
Our model is then used to describe two examples: (i) a silver single crystal electrode with (100) face in contact to a (0.01M NaF + 0.01M KPF6) aqueous solution, and (ii) a general metal surface in contact to some electrolytic solution AC for which an electron transfer reaction occurs in the potential range of interest. We reflect the actual modeling procedure for these examples and discuss the respective model parameters. Due to the representations of the coverages in terms of the applied potential we provide an adsorption map and introduce adsorption potentials. Finally we investigate the structure of the space charge layer at the metal/surface/electrolyte interface by means of numerical solutions of the coupled Poissonmomentum equation system for various applied potentials. It turns out that various layers selfconsistently form within the overall space charge region, which are compared to historic and recent pictures of the double layer. Based on this we present new interpretations of what is known as inner and outer Helmholtzplanes and finally provide a thermodynamic consistent picture of the metal/electrolyte interface structure. 
J. Fuhrmann, A numerical strategy for NernstPlanck systems with solvation effect, Fuel Cells, 16 (2016), pp. 704714.

J. Fuhrmann, A. Linke, Ch. Merdon, F. Neumann, T. Streckenbach, H. Baltruschat, M. Khodayari, Inverse modeling of thin layer flow cells for detection of solubility, transport and reaction coefficients from experimental data, Electrochimica Acta, 211 (2016), pp. 110.
Abstract
Thin layer flow cells are used in electrochemical research as experimental devices which allow to perform investigations of electrocatalytic surface reactions under controlled conditions using reasonably small electrolyte volumes. The paper introduces a general approach to simulate the complete cell using accurate numerical simulation of the coupled flow, transport and reaction processes in a flow cell. The approach is based on a mass conservative coupling of a divergencefree finite element method for fluid flow and a stable finite volume method for mass transport. It allows to perform stable and efficient forward simulations that comply with the physical bounds namely mass conservation and maximum principles for the involved species. In this context, several recent approaches to obtain divergencefree velocities from finite element simulations are discussed. In order to perform parameter identification, the forward simulation method is coupled to standard optimization tools. After an assessment of the inverse modeling approach using known realistic data, first results of the identification of solubility and transport data for O2 dissolved in organic electrolytes are presented. A plausibility study for a more complex situation with surface reactions concludes the paper and shows possible extensions of the scope of the presented numerical tools. 
CH. Heinemann, K. Sturm, Shape optimisation for a class of semilinear variational inequalities with applications to damage models, SIAM Journal on Mathematical Analysis, 48 (2016), pp. 35793617, DOI 10.1137/16M1057759 .
Abstract
The present contribution investigates shape optimisation problems for a class of semilinear elliptic variational inequalities with Neumann boundary conditions. Sensitivity estimates and material derivatives are firstly derived in an abstract operator setting where the operators are defined on polyhedral subsets of reflexive Banach spaces. The results are then refined for variational inequalities arising from minimisation problems for certain convex energy functionals considered over upper obstacle sets in $H^1$. One particularity is that we allow for dynamic obstacle functions which may arise from another optimisation problems. We prove a strong convergence property for the material derivative and establish stateshape derivatives under regularity assumptions. Finally, as a concrete application from continuum mechanics, we show how the dynamic obstacle case can be used to treat shape optimisation problems for timediscretised brittle damage models for elastic solids. We derive a necessary optimality system for optimal shapes whose state variables approximate desired damage patterns and/or displacement fields. 
A. Linke, Ch. Merdon, On velocity errors due to irrotational forces in the NavierStokes momentum balance, Journal of Computational Physics, 313 (2016), pp. 654661.
Abstract
This contribution studies the influence of the pressure on the velocity error in finite element discretisations of the NavierStokes equations. Three simple benchmark problems that are all close to realworld applications convey that the pressure can be comparably large and is not to be underestimated. For widely used finite element methods like the TaylorHood finite element method, such relatively large pressures can lead to spurious oscillations and arbitrarily large errors in the velocity, even if the exact velocity is in the ansatz space. Only mixed finite element methods, whose velocity error is pressureindependent, like the ScottVogelius finite element method can avoid this influence. 
A. Linke, Ch. Merdon, Pressurerobustness and discrete Helmholtz projectors in mixed finite element methods for the incompressible NavierStokes equations, Computer Methods in Applied Mechanics and Engineering, 311 (2016), pp. 304326.
Abstract
Recently, it was understood how to repair a certain L2orthogonality of discretelydivergencefree vector fields and gradient fields such that the velocity error of infsup stable discretizations for the incompressible Stokes equations becomes pressureindependent. These new 'pressurerobust' Stokes discretizations deliver a small velocity error, whenever the continuous velocity field can be well approximated on a given grid. On the contrary, classical infsup stable Stokes discretizations can guarantee a small velocity error only, when both the velocity and the pressure field can be approximated well, simultaneously.
In this contribution, 'pressurerobustness' is extended to the timedependent NavierStokes equations. In particular, steady and timedependent potential flows are shown to build an entire class of benchmarks, where pressurerobust discretizations can outperform classical approaches significantly. Speedups will be explained by a new theoretical concept, the 'discrete Helmholtz projector' of an infsup stable discretization. Moreover, different discrete nonlinear convection terms are discussed, and skewsymmetric pressurerobust discretizations are proposed. 
P.É. Druet, Some mathematical problems related to the second order optimal shape of a crystallization interface, Discrete and Continuous Dynamical Systems, 35 (2015), pp. 24432463.
Abstract
We consider the problem to optimize the stationary temperature distribution and the equilibrium shape of the solidliquid interface in a twophase system subject to a temperature gradient. The interface satisfies the minimization principle of the free energy, while the temperature is solving the heat equation with a radiation boundary conditions at the outer wall. Under the condition that the temperature gradient is uniformly negative in the direction of crystallization, the interface is expected to have a global graph representation. We reformulate this condition as a pointwise constraint on the gradient of the state, and we derive the first order optimality system for a class of objective functionals that account for the second surface derivatives, and for the surface temperature gradient. 
M. Liero, Th. Koprucki, A. Fischer, R. Scholz, A. Glitzky, pLaplace thermistor modeling of electrothermal feedback in organic semiconductors, ZAMP Zeitschrift fur Angewandte Mathematik und Physik. ZAMP. Journal of Applied Mathematics and Physics. Journal de Mathematiques et de Physique Appliquees, 66 (2015), pp. 29572977.
Abstract
In largearea Organic LightEmitting Diodes (OLEDs) spatially inhomogeneous luminance at high power due to inhomogeneous current flow and electrothermal feedback can be observed. To describe these selfheating effects in organic semiconductors we present a stationary thermistor model based on the heat equation for the temperature coupled to a pLaplacetype equation for the electrostatic potential with mixed boundary conditions. The pLaplacian describes the nonOhmic electrical behavior of the organic material. Moreover, an Arrheniuslike temperature dependency of the electrical conductivity is considered. We introduce a finitevolume scheme for the system and discuss its relation to recent network models for OLEDs. In two spatial dimensions we derive a priori estimates for the temperature and the electrostatic potential and prove the existence of a weak solution by Schauder's fixed point theorem. 
E. Meca Álvarez, I. Mercader, L. RamirezPiscina, Transitions between symmetric and nonsymmetric regimes in binarymixture convection, Physica D. Nonlinear Phenomena, 303 (2015), pp. 3949.

D. Peschka, M. Thomas, A. Glitzky, R. Nürnberg, K. Gärtner, M. Virgilio, S. Guha, G. Capellini, Th. Koprucki, Th. Schröder, Modeling of edgeemitting lasers based on tensile strained germanium microstrips, IEEE Photonics Journal, 7 (2015), pp. 1502115/11502115/15, DOI 10.1109/JPHOT.2015.2427093 .
Abstract
In this paper we present a thorough modeling of an edgeemitting laser based on strained germanium microstrips. The full band structure of the tensile strained germanium (Ge) layer enters the calculation of optical properties. Material gain for strained Ge is used in the twodimensional simulation of the carrier transport and of the optical field within a cross section of the microstrips orthogonal to the optical cavity. We study optoelectronic properties of the device for two different designs. The simulation results are very promising as they show feasible ways towards Ge emitter devices with lower threshold currents and higher efficiency as published insofar. 
M. Radszuweit, E. AlvarezLacalle, M. Bär, B. Echebarria, Cardiac contraction induces discordant alternans and localized block, Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, 91 (2015), pp. 022703/1022703/12.
Abstract
In this paper we use a simplified model of cardiac excitationcontraction coupling to study the effect of tissue deformation on the dynamics of alternans, i.e. alternations in the duration of the cardiac action potential, that occur at fast pacing rates and are known to be proarrhythmic. We show that small stretchactivated currents can produce large effects and cause a transition from inphase to offphase alternations (i.e. from concordant to discordant alternans) and to conduction blocks. We demonstrate numerically and analytically that this effect is the result of a generic change in the slope of the conduction velocity restitution curve due to electromechanical coupling. Thus, excitationcontraction coupling can potentially play a relevant role in the transition to reentry and fibrillation. 
CH. Brennecke, A. Linke, Ch. Merdon, J. Schöberl, Optimal and pressureindependent $L^2$ velocity error estimates for a modified CrouzeixRaviart Stokes element with BDM reconstructions, Journal of Computational Mathematics, 33 (2015), pp. 191208.
Abstract
Nearly all infsup stable mixed finite elements for the incompressible Stokes equations relax the divergence constraint. The price to pay is that a priori estimates for the velocity error become pressuredependent, while divergencefree mixed finite elements deliver pressureindependent estimates. A recently introduced new variational crime using lowestorder RaviartThomas velocity reconstructions delivers a much more robust modified CrouzeixRaviart element, obeying an optimal pressureindependent discrete H^{1} velocity estimate. Refining this approach, a more sophisticated variational crime employing the lowestorder BDM element is proposed, which also allows proving an optimal pressure independent L^{2 } velocity error. Numerical examples confirm the analysis and demonstrate the improved robustness in the NavierStokes case. 
W. Huang, L. Kamenski, R.D. Russell, A comparative numerical study of meshing functionals for variational mesh adaptation, Journal of Mathematical Study, 48 (2015), pp. 168186.
Abstract
We present a comparative numerical study for three functionals used for variational mesh adaptation. One of them is a generalization of Winslow's variable diffusion functional while the others are based on equidistribution and alignment. These functionals are known to have nice theoretical properties and work well for most mesh adaptation problems either as a standalone variational method or combined within the moving mesh framework. Their performance is investigated numerically in terms of equidistribution and alignment mesh quality measures. Numerical results in 2D and 3D are presented. 
W. Huang, L. Kamenski, A geometric discretization and a simple implementation for variational mesh generation and adaptation, Journal of Computational Physics, 301 (2015), pp. 322337.
Abstract
We present a simple direct discretization for functionals used in the variational mesh generation and adaptation. Meshing functionals are discretized on simplicial meshes and the Jacobian matrix of the continuous coordinate transformation is approximated by the Jacobian matrices of affine mappings between elements. The advantage of this direct geometric discretization is that it preserves the basic geometric structure of the continuous functional, which is useful in preventing strong decoupling or loss of integral constraints satisfied by the functional. Moreover, the discretized functional is a function of the coordinates of mesh vertices and its derivatives have a simple analytical form, which allows a simple implementation of variational mesh generation and adaptation on computer. Since the variational mesh adaptation is the base for a number of adaptive moving mesh and mesh smoothing methods, the result in this work can be used to develop simple implementations of those methods. Numerical examples are given. 
R. Huth, S. Jachalski, G. Kitavtsev, D. Peschka, Gradient flow perspective on thinfilm bilayer flows, Journal of Engineering Mathematics, 94 (2015), pp. 4361.
Abstract
We study gradient flow formulations of thinfilm bilayer flows with triplejunctions between liquid/liquid/air. First we highlight the gradient structure in the Stokes freeboundary flow and identify its solutions with the well known PDE with boundary conditions. Next we propose a similar gradient formulation for the corresponding thinfilm model and formally identify solutions with those of the corresponding freeboundary problem. A robust numerical algorithm for the thinfilm gradient flow structure is then provided. Using this algorithm we compare the sharp triplejunction model with precursor models. For their stationary solutions a rigorous connection is established using Gammaconvergence. For timedependent solutions the comparison of numerical solutions shows a good agreement for small and moderate times. Finally we study spreading in the zerocontact angle case, where we compare numerical solutions with asymptotically exact sourcetype solutions. 
T. Roubíček, M. Thomas, Ch. Panagiotopoulos, Stressdriven localsolution approach to quasistatic brittle delamination, Nonlinear Analysis. Real World Applications. An International Multidisciplinary Journal, 22 (2015), pp. 645663.
Abstract
A unilateral contact problem between elastic bodies at small strains glued by a brittle adhesive is addressed in the quasistatic rateindependent setting. The delamination process is modelled as governed by stresses rather than by energies. This results in a specific scaling of an approximating elastic adhesive contact problem, discretised by a semiimplicit scheme and regularized by a BVtype gradient term. An analytical zerodimensional example motivates the model and a specific localsolution concept. Twodimensional numerical simulations performed on an engineering benchmark problem of debonding a fiber in an elastic matrix further illustrate the validity of the model, convergence, and algorithmical efficiency even for very rigid adhesives with high elastic moduli. 
N. Ahmed, G. Matthies, Higher order continuous GalerkinPetrov time stepping schemes for transient convectiondiffusionreaction equations, ESAIM: Mathematical Modelling and Numerical Analysis, 49 (2015), pp. 14291450.
Abstract
We present the analysis for the higher order continuous GalerkinPetrov (cGP) time discretization schemes in combination with the onelevel local projection stabilization in space applied to timedependent convectiondiffusionreaction problems. Optimal apriori error estimates will be proved. Numerical studies support the theoretical results. Furthermore, a numerical comparison between continuous GalerkinPetrov and discontinuous Galerkin time discretization schemes will be given. 
N. Ahmed, V. John, Adaptive time step control for higher order variational time discretizations applied to convectiondiffusion equations, Computer Methods in Applied Mechanics and Engineering, 285 (2015), pp. 83101.
Abstract
Higher order variational time stepping schemes allow an efficient postprocessing for computing a higher order solution. This paper presents an adaptive algorithm whose time step control utilizes the postprocessed solution. The algorithm is applied to convectiondominated convectiondiffusion equations. It is shown that the length of the time step properly reflects the dynamics of the solution. The numerical costs of the adaptive algorithm are discussed. 
A. Caiazzo, G. Montecinos, L.O. Müller, E.M. Haacke, E.F. Toro, Computational haemodynamics in stenotic internal jugular veins, Journal of Mathematical Biology, 70 (2015), pp. 745772.
Abstract
Stenosis in internal jugular veins (IJVs) are frequently associated to pathological venous circulation and insufficient cerebral blood drainage. In this work, we set up a computational framework to assess the relevance of IJV stenoses through numerical simulation, combining medical imaging, patientspecific data and a mathematical model for venous occlusions. Coupling a threedimensional (3D) description of blood flow in IJVs with a reduced onedimesional model (1D) for major intracranial veins, we are able to model different anatomical configurations, an aspect of importance to understand the impact of IJV stenosis in intracranial venous haemodynamics. We investigate several stenotic configurations in a physiologic patientspecific regime, quantifying the effect of the stenosis in terms of venous pressure increase and wall shear stress patterns. Simulation results are in qualitative agreement with reported pressure anomalies in pathological cases. Moreover, they demonstrate the potential of the proposed multiscale framework for individualbased studies and computeraided diagnosis. 
J. Fuhrmann, Comparison and numerical treatment of generalized NernstPlanck models, Computer Physics Communications. An International Journal and Program Library for Computational Physics and Physical Chemistry, 196 (2015), pp. 166178.
Abstract
In its most widespread, classical formulation, the NernstPlanckPoisson system for ion transport in electrolytes fails to take into account finite ion sizes. As a consequence, it predicts unphysically high ion concentrations near electrode surfaces. Historical and recent approaches to an approriate modification of the model are able to fix this problem. Several appropriate formulations are compared in this paper. The resulting equations are reformulated using absolute activities as basic variables describing the species amounts. This reformulation allows to introduce a straightforward generalisation of the ScharfetterGummel finite volume discretization scheme for driftdiffusion equations. It is shown that it is thermodynamically consistent in the sense that the solution of the corresponding discretized generalized PoissonBoltzmann system describing the thermodynamic equilibrium is a stationary state of the discretized timedependent generalized NernstPlanck system. Numerical examples demonstrate the improved physical correctness of the generalised models and the feasibility of the numerical approach. 
CH. Heinemann, Ch. Kraus, Existence of weak solutions for a PDE system describing phase separation and damage processes including inertial effects, Discrete and Continuous Dynamical Systems, 35 (2015), pp. 25652590.
Abstract
In this paper, we consider a coupled PDE system describing phase separation and damage phenomena in elastically stressed alloys in the presence of inertial effects. The material is considered on a bounded Lipschitz domain with mixed boundary conditions for the displacement variable. The main aim of this work is to establish existence of weak solutions for the introduced hyperbolicparabolic system. To this end, we first generalize the notion of weak solution introduced in WIAS 1520. Then we prove existence of weak solutions by means of regularization, timediscretization and different variational techniques. 
CH. Heinemann, E. Rocca, Damage processes in thermoviscoelastic materials with damagedependent thermal expansion coefficients, Mathematical Methods in the Applied Sciences, 38 (2015), pp. 45874612.
Abstract
In this paper we prove existence of global in time weak solutions for a highly nonlinear PDE system arising in the context of damage phenomena in thermoviscoelastic materials. The main novelty of the present contribution with respect to the ones already present in the literature consists in the possibility of taking into account a damagedependent thermal expansion coefficient. This term implies the presence of nonlinear couplings in the PDE system, which make the analysis more challenging. 
A. Linke, Ch. Merdon, Guaranteed energy error estimators for a modified robust CrouzeixRaviart Stokes element, Journal of Scientific Computing, 64 (2015), pp. 541558.
Abstract
This paper provides guaranteed upper energy error bounds for a modified lowestorder nonconforming CrouzeixRaviart finite element method for the Stokes equations. The modification from [A. Linke 2014, On the role of the Helmholtzdecomposition in mixed methods for incompressible flows and a new variational crime] is based on the observation that only the divergencefree part of the righthand side should balance the vector Laplacian. The new method has optimal energy error estimates and can lead to errors that are smaller by several magnitudes, since the estimates are pressureindependent. An efficient a posteriori velocity error estimator for the modified method also should involve only the divergencefree part of the righthand side. Some designs to approximate the Helmholtz projector are compared and verified by numerical benchmark examples. They show that guaranteed error control for the modified method is possible and almost as sharp as for the unmodified method. 
A. Mielke, J. Naumann, Globalintime existence of weak solutions to Kolmogorov's twoequation model of turbulence, Comptes Rendus Mathematique. Academie des Sciences. Paris, 353 (2015), pp. 321326.
Abstract
We consider Kolmogorov's model for the turbulent motion of an incompressible fluid in ℝ^{3}. This model consists in a NavierStokes type system for the mean flow u and two further partial differential equations: an equation for the frequency ω and for the kinetic energy k each. We investigate this system of partial differential equations in a cylinder Ω x ]0,T[ (Ω ⊂ ℝ^{3} cube, 0 < T < +∞) under spatial periodic boundary conditions on ∂Ω x ]0,T[ and initial conditions in Ω x {0}. We present an existence result for a weak solution {u, ω, k} to the problem under consideration, with ω, k obeying the inequalities and . 
R.M. Arkhipov, I. Babushkin, M.K. Lebedev, Y.A. Tolmachev, M.V. Arkhipov, Transient Cherenkov radiation from an inhomogeneous string excited by an ultrashort laser pulse at superluminal velocity, Physical Review A, 89 (2014), pp. 043811/1043811/10.
Abstract
An optical response of onedimensional string made of dipoles with a periodically varying density excited by a spot of light moving along the string at the superluminal (subluminal) velocity is studied. We consider in details the spectral and temporal dynamics of the Cherenkov radiation, which occurs in such system in the transient regime. We point out the resonance character of radiation and the appearance of a new Dopplerlike frequency in the spectrum of the transient Cherenkov radiation. Possible applications of the effect as well as different string topologies are discussed 
A. Linke, On the role of the Helmholtz decomposition in mixed methods for incompressible flows and a new variational crime, Computer Methods in Applied Mechanics and Engineering, 268 (2014), pp. 782800.
Abstract
According to the Helmholtz decomposition, the irrotational parts of the momentum balance equations of the incompressible NavierStokes equations are balanced by the pressure gradient. Unfortunately, nearly all mixed methods for incompressible flows violate this fundamental property, resulting in the wellknown numerical instability of poor mass conservation. The origin of this problem is the lack of L2orthogonality between discretely divergencefree velocities and irrotational vector fields. In order to cure this, a new variational crime using divergencefree velocity reconstructions is proposed. Applying lowest order RaviartThomas velocity reconstructions to the nonconforming CrouzeixRaviart element allows to construct a cheap flow discretization for general 2d and 3d simplex meshes that possesses the same advantageous robustness properties like divergencefree flow solvers. In the Stokes case, optimal apriori error estimates for the velocity gradients and the pressure are derived. Moreover, the discrete velocity is independent of the continuous pressure. Several detailed linear and nonlinear numerical examples illustrate the theoretical findings. 
E. Jenkins, V. John, A. Linke, L.G. Rebholz, On the parameter choice in graddiv stabilization for the Stokes equations, Advances in Computational Mathematics, 40 (2014), pp. 491516.
Abstract
Graddiv stabilization has been proved to be a very useful tool in discretizations of incompressible flow problems. Standard error analysis for infsup stable conforming pairs of finite element spaces predicts that the stabilization parameter should be optimally chosen to be O(1). This paper revisits this choice for the Stokes equations on the basis of minimizing the $H^1$ error of the velocity and the $L^2$ error of the pressure. It turns out, by applying a refined error analysis, that the optimal parameter choice is more subtle than known so far in the literature. It depends on the used norm, the solution, the family of finite element spaces, and the type of mesh. Depending on the situation, the optimal stabilization parameter might range from being very small to very large. The analytic results are supported by numerical examples. 
R. Eymard, J. Fuhrmann, A. Linke, On MAC schemes on triangular Delaunay meshes, their convergence and application to coupled flow problems, Numerical Methods for Partial Differential Equations. An International Journal, 30 (2014), pp. 13971424.
Abstract
We study two classical generalized MAC schemes on unstructured triangular Delaunay meshes for the incompressible Stokes and NavierStokes equations and prove their convergence for the first time. These generalizations use the duality between Voronoi and triangles of Delaunay meshes, in order to construct two staggered discretization schemes. Both schemes are especially interesting, since compatible finite volume discretizations for coupled convectiondiffusion equations can be constructed which preserve discrete maximum principles. In the first scheme, called tangential velocity scheme, the pressures are defined at the vertices of the mesh, and the discrete velocities are tangential to the edges of the triangles. In the second scheme, called normal velocity scheme, the pressures are defined in the triangles, and the discrete velocities are normal to the edges of the triangles. For both schemes, we prove the convergence in $L^2$ for the velocities and the discrete rotations of the velocities for the Stokes and the NavierStokes problem. Further, for the normal velocity scheme, we also prove the strong convergence of the pressure in $L^2$. Linear and nonlinear numerical examples illustrate the theoretical predictions. 
A. Fiebach, A. Glitzky, A. Linke, Uniform global bounds for solutions of an implicit Voronoi finite volume method for reactiondiffusion problems, Numerische Mathematik, 128 (2014), pp. 3172.
Abstract
We consider discretizations for reactiondiffusion systems with nonlinear diffusion in two space dimensions. The applied model allows to handle heterogeneous materials and uses the chemical potentials of the involved species as primary variables. We propose an implicit Voronoi finite volume discretization on regular Delaunay meshes that allows to prove uniform, meshindependent global upper and lower $L^infty$ bounds for the chemical potentials. These bounds provide the main step for a convergence analysis for the full discretized nonlinear evolution problem. The fundamental ideas are energy estimates, a discrete Moser iteration and the use of discrete GagliardoNirenberg inequalities. For the proof of the GagliardoNirenberg inequalities we exploit that the discrete Voronoi finite volume gradient norm in $2d$ coincides with the gradient norm of continuous piecewise linear finite elements. 
A. Gloria, S. Neukamm, F. Otto, An optimal quantitative twoscale expansion in stochastic homogenization of discrete elliptic equations, ESAIM: Mathematical Modelling and Numerical Analysis, 48 (2014), pp. 325346.
Abstract
We establish an optimal, linear rate of convergence for the stochastic homogenization of discrete linear elliptic equations. We consider the model problem of independent and identically distributed coefficients on a discretized unit torus. We show that the difference between the solution to the random problem on the discretized torus and the first two terms of the twoscale asymptotic expansion has the same scaling as in the periodic case. In particular the L^{2}norm in probability of the H^{1}norm in space of this error scales like ε, where ε is the discretization parameter of the unit torus. The proof makes extensive use of previous results by the authors, and of recent annealed estimates on the Greens function by Marahrens and the third author. 
R. Guibert, K. Mcleod, A. Caiazzo, T. Mansi, Groupwise construction of reduced models for understanding and characterization of pulmonary blood flows from medical images, Medical Image Analysis, 18 (2014), pp. 6382.

A. Caiazzo, V. John, U. Wilbrandt, On classical iterative subdomain methods for the StokesDarcy problem, Computer & Geosciences, 18 (2014), pp. 711728.
Abstract
Iterative subdomain methods for the StokesDarcy problem that use Robin boundary conditions on the interface are reviewed. Their common underlying structure and their main differences are identified. In particular, it is clarified that there are different updating strategies for the interface conditions. For small values of fluid viscosity and hydraulic permeability, which are relevant in applications from geosciences, it is shown in numerical studies that only one of these updating strategies leads to an efficient numerical method, if this strategy is used in combination with appropriate parameters in the Robin boundary conditions. In particular, it is observed that the values of appropriate parameters are larger than those proposed so far. Not only the size but also the ratio of appropriate Robin parameters depends on the coefficients of the problem. 
A. Caiazzo, J. Mura, Multiscale modeling of weakly compressible elastic materials in harmonic regime and application to microscale structure estimation, Multiscale Modeling & Simulation. A SIAM Interdisciplinary Journal, 12 (2014), pp. 514537.
Abstract
This article is devoted to the modeling of elastic materials composed by an incompressible elastic matrix and small compressible gaseous inclusions, under a time harmonic excitation. In a biomedical context, this model describes the dynamics of a biological tissue (e.g. lung or liver) when wave analysis methods (such as Magnetic Resonance Elastography) are used to estimate tissue properties. Due to the multiscale nature of the problem, direct numerical simulations are prohibitive. We extend the homogenized model introduced in [Baffico, Grandmont, Maday, Osses, SIAM J. Mult. Mod. Sim., 7(1), 2008] to a time harmonic regime to describe the solidgas mixture from a macroscopic point of view in terms of an effective elasticity tensor. Furthermore, we derive and validate numerically analytical approximations for the effective elastic coefficients in terms of macroscopic parameters. This simplified description is used to to set up an efficient variational approach for the estimation of the tissue porosity, using the mechanical response to external harmonic excitations. 
L. Kamenski, W. Huang, A study on the conditioning of finite element equations with arbitrary anisotropic meshes via a density function approach, Journal of Mathematical Study, 47 (2014), pp. 151172.

L. Kamenski, W. Huang, How a nonconvergent recovered Hessian works in mesh adaptation, SIAM Journal on Numerical Analysis, 52 (2014), pp. 16921708.

L. Kamenski, W. Huang, H. Xu, Conditioning of finite element equations with arbitrary anisotropic meshes, Mathematics of Computation, 83 (2014), pp. 21872211.

A. PérezSerrano, J. Javaloyes, S. Balle, Directional reversals and multimode dynamics in semiconductor ring lasers, Physical Review A, 89 (2014), pp. 023818/1023818/14.
Abstract
We investigate the dynamics of longitudinal modes in quantumwell semiconductor ring lasers by means of a spatiotemporal travelling wave model. We report the existence of a novel multimode instability in such a system that provokes a periodic deterministic directional reversal involving jumps between consecutive longitudinal modes. The switching sequence follows the modal frequencies from blue to red, and every modal jump is accompanied by a reversal of the direction of emission. We characterize and analyze such instability via the bifurcation analysis of the full travelling wave model as well as by performing the linear stability analysis of the monochromatic solutions. 
K. Götze, Strong solutions for the interaction of a rigid body and a viscoelastic fluid, Journal of Mathematical Fluid Mechanics, 15 (2013), pp. 663688.
Abstract
We study a coupled system of equations describing the movement of a rigid body which is immersed in a viscoelastic fluid. It is shown that under natural assumptions on the data and for general goemetries of the rigid body, excluding contact scenarios, a unique localintime strong solution exists. 
M. Liero, A. Mielke, Gradient structures and geodesic convexity for reactiondiffusion systems, Philosophical Transactions of the Royal Society A : Mathematical, Physical & Engineering Sciences, 371 (2013), pp. 20120346/120120346/28.
Abstract
We consider systems of reactiondiffusion equations as gradient systems with respect to an entropy functional and a dissipation metric given in terms of a socalled Onsager operator, which is a sum of a diffusion part of Wasserstein type and a reaction part. We provide methods for establishing geodesic lambdaconvexity of the entropy functional by purely differential methods, thus circumventing arguments from mass transportation. Finally, several examples, including a driftdiffusion system, provide a survey on the applicability of the theory. We consider systems of reactiondiffusion equations as gradient systems with respect to an entropy functional and a dissipation metric given in terms of a socalled Onsager operator, which is a sum of a diffusion part of Wasserstein type and a reaction part. We provide methods for establishing geodesic lambdaconvexity of the entropy functional by purely differential methods, thus circumventing arguments from mass transportation. Finally, several examples, including a driftdiffusion system, provide a survey on the applicability of the theory. 
A. PérezSerrano, J. Javaloyes, S. Balle, Multichannel wavelength conversion using fourwave mixing in semiconductor ring lasers, IEEE Phot. Tech. Letter, 25 (2013), pp. 476479.
Abstract
We theoretically study alloptical simultaneous wavelength conversion of multiple channels by fourwave mixing in semiconductor ring lasers. Locking the semiconductor ring laser to a holding beam allows to achieve large conversion efficiencies with good signaltonoise ratio in several channels at multiGb/s bit rates. Crosstalk between signals, arising from the peculiar fourwave mixing cascade of modes in semiconductor ring lasers and their crossgain saturation, is studied in detail. We show that it can be controlled by adjusting the intensity of the holding beam, the bias current of the laser and the number, intensity and wavelength of signals that one wants to convert. 
A. PérezSerrano, J. Javaloyes, S. Balle, Spectral delay algebraic equation approach to broad area laser diodes, IEEE J. Select. Topics Quantum Electron., 19 (2013), pp. 1502808/11502808/8.

M.V. Arkhipov, R.M. Arkhipov, S.A. Pulkin, Effects of inversionless oscillation in twolevel media from the point of view of specificities of the spatiotemporal propagation dynamics of radiation, Optics and Spectroscopy, 114 (2013), pp. 831837.
Abstract
We report the results of computer simulation of the emission of radiation by an extended twolevel medium in a ring cavity. The cases of using strong external monochromatic, quasimonochromatic, and biharmonic radiation for pumping the twolevel medium are analyzed. It is shown that the emission of radiation with spectral content different from that of the pump radiation, which is interpreted as the inversionless oscillation, is the result of the spatiotemporal dynamics of light propagation in an extended twolevel medium imbedded in a cavity. The appearance of this radiation is not related to known resonances of amplification of a weak probe field in a thin layer of the twolevel system (the effect of inversionless oscillation) induced by strong resonance monochromatic or biharmonic field, as was thought before. 
C. Bertoglio, A. Caiazzo, M.A. Fernàndez, Fractionalstep schemes for the coupling of distributed and lumped models in hemodynamics, SIAM Journal on Scientific Computing, 35 (2013), pp. B551B575.

A. Bradji, J. Fuhrmann, Some abstract error estimates of a finite volume scheme for a nonstationary heat equation on general nonconforming multidimensional spatial meshes, Applications of Mathematics, 58 (2013), pp. 138.
Abstract
A general class of nonconforming meshes has been recently studied for stationary anisotropic heterogeneous diffusion problems by R. Eymard and coworkers. Thanks to these basic ideas developed for stationary problems, we derive a new discretization scheme in order to approximate the nonstationary heat problem. The unknowns of this scheme are the values at the centre of the control volumes, at some internal interfaces, and at the mesh points of the time discretization. Although the numerical scheme stems from the finite volume method, its formulation is based on the discrete version for the weak formulation defined for the heat problem. We derive error estimates for the solution in discrete norm, and an error estimate for an approximation of the gradient, in a general framework in which the discrete bilinear form is satisfying ellipticity. We prove in particular, that, when the discrete flux is calculated using a stabilized discrete gradient, the convergence order is h+k , where h (resp. k) is the mesh size of the spatial (resp. time) discretization. This estimate is valid under the regularity assumption that the exact solution is twice continuously differentiable in time and space. These error estimates are useful because they allow us to get error estimates for the approximations of the exact solution and its first derivatives. 
B. Cousins, S. Le Borne, A. Linke, Z. Wang, Efficient linear solvers for incompressible flow simulations using ScottVogelius finite elements, Numerical Methods for Partial Differential Equations. An International Journal, 29 (2013), pp. 12171237.
Abstract
Recent research has shown that in some practically relevant situations like multiphysics flows (Galvin et al., Comput Methods Appl Mech Eng, 2012) divergencefree mixed finite elements may have a significantly smaller discretization error than standard nondivergencefree mixed finite elements. To judge the overall performance of divergencefree mixed finite elements, we investigate linear solvers for the saddle point linear systems arising in ScottVogelius finite element implementations of the incompressible NavierStokes equations. We investigate both direct and iterative solver methods. Due to discontinuous pressure elements in the case of ScottVogelius (SV) elements, considerably more solver strategies seem to deliver promising results than in the case of standard mixed finite elements such as TaylorHood elements. For direct methods, we extend recent preliminary work using sparse banded solvers on the penalty method formulation to finer meshes and discuss extensions. For iterative methods, we test augmented Lagrangian and H LU preconditioners with GMRES, on both full and statically condensed systems. Several numerical experiments are provided that show these classes of solvers are well suited for use with SV elements and could deliver an interesting overall performance in several applications. 
D. Knees, A. Schröder, Computational aspects of quasistatic crack propagation, Discrete and Continuous Dynamical Systems  Series S, 6 (2013), pp. 6399.
Abstract
The focus of this note lies on the numerical analysis of models describing the propagation of a single crack in a linearly elastic material. The evolution of the crack is modeled as a rateindependent process based on the Griffith criterion. We follow two different approaches for setting up mathematically well defined models: the global energetic approach and an approach based on a viscous regularization. We prove the convergence of solutions of fully discretized models (i.e. with respect to time and space) and derive relations between the discretization parameters (mesh size, time step size, viscosity parameter, crack increment) which guarantee the convergence of the schemes. Further, convergence rates are provided for the approximation of energy release rates by certain discrete energy release rates. Thereby we discuss both, models with selfcontact conditions on the crack faces as well as models with pure Neumann conditions on the crack faces. The convergence proofs rely on regularity estimates for the elastic fields close to the crack tip and local and global finite element error estimates. Finally the theoretical results are illustrated with some numerical calculations. 
W. Dreyer, C. Guhlke, R. Müller, Overcoming the shortcomings of the NernstPlanck model, Physical Chemistry Chemical Physics, 15 (2013), pp. 70757086, DOI 10.1039/C3CP44390F .
Abstract
This is a study on electrolytes that takes a thermodynamically consistent coupling between mechanics and diffusion into account. It removes some inherent deficiencies of the popular NernstPlanck model. A boundary problem for equilibrium processes is used to illustrate the new features of our model. 
A. Linke, L. Rebholz, On a reduced sparsity stabilization of graddiv type for incompressible flow problems, Computer Methods in Applied Mechanics and Engineering, 261262 (2013), pp. 142153.
Abstract
We introduce a new operator for stabilizing error that arises from the weak enforcement of mass conservation in finite element simulations of incompressible flow problems. We show this new operator has a similar positive effect on velocity error as the wellknown and very successful graddiv stabilization operator, but the new operator is more attractive from an implementation standpoint because it yields a sparser block structure matrix. That is, while graddiv produces fully coupled block matrices (i.e. blockfull), the matrices arising from the new operator are blockupper triangular in two dimensions, and in three dimensions the 2,1 and 3,1 blocks are empty. Moreover, the diagonal blocks of the new operator's matrices are identical to those of graddiv. We provide error estimates and numerical examples for finite element simulations with the new operator, which reveals the significant improvement in accuracy it can provide. Solutions found using the new operator are also compared to those using usual graddiv stabilization, and in all cases, solutions are found to be very similar. 
A. Mielke, R. Rossi, G. Savaré, Nonsmooth analysis of doubly nonlinear evolution equations, Calculus of Variations and Partial Differential Equations, 46 (2013), pp. 253310.
Abstract
In this paper we analyze a broad class of abstract doubly nonlinear evolution equations in Banach spaces, driven by nonsmooth and nonconvex energies. We provide some general sufficient conditions, on the dissipation potential and the energy functional, for existence of solutions to the related Cauchy problem. We prove our main existence result by passing to the limit in a timediscretization scheme with variational techniques. Finally, we discuss an application to a material model in finitestrain elasticity. 
A. Mielke, E. Rohan, Homogenization of elastic waves in fluidsaturated porous media using the Biot model, Mathematical Models & Methods in Applied Sciences, 23 (2013), pp. 873916.
Abstract
We consider periodically heterogeneous fluidsaturated poroelastic media described by the Biot model with inertia effects. The weak and semistrong formulations for displacement, seepage and pressure fields involve three equations expressing the momentum and mass balance and the Darcy law. Using the twoscale homogenization method we obtain the limit twoscale problem and prove the existence and uniqueness of its weak solutions. The Laplace transformation in time is used to decouple the macroscopic and microscopic scales. It is shown that the seepage velocity is eliminated form the macroscopic equations involving strain and pressure fields only. The plane harmonic wave propagation is studied using an example of layered medium. Illustrations show some influence of the orthotropy on the dispersion phenomena. 
P.N. Racec, S. Schade, H.Chr. Kaiser, Eigensolutions of the WignerEisenbud problem for a cylindrical nanowire within finite volume method, Journal of Computational Physics, 252 (2013), pp. 5264.
Abstract
We present a finite volume method for computing a representative range of eigenvalues and eigenvectors of the Schrödinger operator on a three dimensional cylindrically symmetric bounded domain with mixed boundary conditions. More specifically, we deal with a semiconductor nanowire which consists of a dominant host material and contains heterostructure features such as doublebarriers or quantum dots. The three dimensional Schrödinger operator is reduced to a family of two dimensional Schrödinger operators distinguished by a centrifugal potential. Ultimately, we numerically treat them by means of a finite volume method. We consider a uniform, boundary conforming Delaunay mesh, which additionally conforms to the material interfaces. The 1/r singularity is eliminated by approximating r at the vertexes of the Voronoi boxes. We study how the anisotropy of the effective mass tensor acts on the uniform approximation of the first K eigenvalues and eigenvectors and their sequential arrangement. There exists an optimal uniform Delaunay discretization with matching anisotropy. This anisotropic discretization yields best accuracy also in the presence of a mildly varying scattering potential, shown exemplarily for a nanowire resonant tunneling diode. For potentials with 1/r singularity one retrieves the theoretically established first order convergence, while the second order convergence is recovered only on uniform grids with an anisotropy correction. 
S. Amiranashvili, U. Bandelow, A. Mielke, Calculation of ultrashort pulse propagation based on rational approximations for medium dispersion, Optical and Quantum Electronics, 44 (2012), pp. 241246.
Abstract
Ultrashort optical pulses contain only a fewoptical cycles and exhibit broad spectra. Their carrier frequency is therefore not well defined and their description in terms of the standard slowly varying envelope approximation becomes questionable. Existing modeling approaches can be divided in two classes, namely generalized envelope equations, that stem from the nonlinear Schrödinger equation, and nonenvelope equations which treat the field directly. Based on fundamental physical rules we will present an approach that effectively interpolates between these classes and provides a suitable setting for accurate and highly efficient 
K. Galvin, A. Linke, L. Rebholz, N. Wilson, Stabilizing poor mass conservation in incompressible flow problems with large irrotational forcing and application to thermal convection, Computer Methods in Applied Mechanics and Engineering, 237240 (2012), pp. 166176.
Abstract
We consider the problem of poor mass conservation in mixed finite element algorithms for flow problems with large rotationfree forcing in the momentum equation. We provide analysis that suggests for such problems, obtaining accurate solutions necessitates either the use of pointwise divergencefree finite elements (such as ScottVogelius), or heavy graddiv stabilization of weakly divergencefree elements. The theory is demonstrated in numerical experiments for a benchmark natural convection problem, where large irrotational forcing occurs with high Rayleigh numbers. 
K. Hackl, S. Heinz, A. Mielke, A model for the evolution of laminates in finitestrain elastoplasticity, ZAMM. Zeitschrift für Angewandte Mathematik und Mechanik, 92 (2012), pp. 888909.
Abstract
We study the time evolution in elastoplasticity within the rateindependent framework of generalized standard materials. Our particular interest is the formation and the evolution of microstructure. Providing models where existence proofs are possible is a challenging task since the presence of microstructure comes along with a lack of convexity and, hence, compactness arguments cannot be applied to prove the existence of solutions. In order to overcome this problem, we will incorporate information on the microstructure into the internal variable, which is still compatible with generalized standard materials. More precisely, we shall allow for such microstructure that is given by simple or sequential laminates. We will consider a model for the evolution of these laminates and we will prove a theorem on the existence of solutions to any finite sequence of timeincremental minimization problems. In order to illustrate the mechanical consequences of the theory developed some numerical results, especially dealing with the rotation of laminates, are presented. 
A. Glitzky, An electronic model for solar cells including active interfaces and energy resolved defect densities, SIAM Journal on Mathematical Analysis, 44 (2012), pp. 38743900.
Abstract
We introduce an electronic model for solar cells taking into account heterostructures with active interfaces and energy resolved volume and interface trap densities. The model consists of continuity equations for electrons and holes with thermionic emission transfer conditions at the interface and of ODEs for the trap densities with energy level and spatial position as parameters, where the right hand sides contain generationrecombination as well as ionization reactions. This system is coupled with a Poisson equation for the electrostatic potential. We show the thermodynamic correctness of the model and prove a priori estimates for the solutions to the evolution system. Moreover, existence and uniqueness of weak solutions of the problem are proven. For this purpose we solve a regularized problem and verify bounds of the corresponding solution not depending on the regularization level. 
D. Knees, A. Schröder, Global spatial regularity for elasticity models with cracks, contact and other nonsmooth constraints, Mathematical Methods in the Applied Sciences, 35 (2012), pp. 18591884.
Abstract
A global higher differentiability result in Besov spaces is proved for the displacement fields of linear elastic models with self contact. Domains with cracks are studied, where nonpenetration conditions/Signorini conditions are imposed on the crack faces. It is shown that in a neighborhood of crack tips (in 2D) or crack fronts (3D) the displacement fields are B^{ 3/2 }_{ 2,∞} regular. The proof relies on a difference quotient argument for the directions tangential to the crack. In order to obtain the regularity estimates also in the normal direction, an argument due to Ebmeyer/Frehse/Kassmann is modified. The methods are then applied to further examples like contact problems with nonsmooth rigid foundations, to a model with Tresca friction and to minimization problems with nonsmooth energies and constraints as they occur for instance in the modeling of shape memory alloys. Based on Falk's approximation Theorem for variational inequalities, convergence rates for FEdiscretizations of contact problems are derived relying on the proven regularity properties. Several numerical examples illustrate the theoretical results. 
A. Linke, L.G. Rebholz, N.E. Wilson, On the convergence rate of graddiv stabilized TaylorHood to ScottVogelius solutions for incompressible flow problems, Journal of Mathematical Analysis and Applications, 381 (2011), pp. 612626.
Abstract
It was recently proven that, under mild restrictions, graddiv stabilized TaylorHood solutions of NavierStokes problems converge to the ScottVogelius solution of that same problem. However, even though the analytical rate was only shown to be $gamma^frac12$ (where $gamma$ is the stabilization parameter), the computational results suggest the rate may be improvable $gamma^1$. We prove herein the analytical rate is indeed $gamma^1$, and extend the result to other incompressible flow problems including Leray$alpha$ and MHD. Numerical results are given that verify the theory. 
A.G. Vladimirov, R. Lefever, M. Tlidi, Relative stability of multipeak localized patterns of cavity solitons, Physical Review A, 84 (2011), pp. 043848/1043848/4.
Abstract
We study the relative stability of different onedimensional (1D) and twodimensional (2D) clusters of closely packed localized peaks of the SwiftHohenberg equation. In the 1D case, we demonstrate numerically the existence of a spatial Maxwell transition point where all clusters involving up to 15 peaks are equally stable. Above (below) this point, clusters become more (less) stable when their number of peaks increases. In the 2D case, since clusters involving more than two peaks may exhibit distinct spatial arrangements, this point splits into a set of Maxwell transition pointsWe study the relative stability of different onedimensional (1D) and twodimensional (2D) clusters of closely packed localized peaks of the SwiftHohenberg equation. In the 1D case, we demonstrate numerically the existence of a spatial Maxwell transition point where all clusters involving up to 15 peaks are equally stable. Above (below) this point, clusters become more (less) stable when their number of peaks increases. In the 2D case, since clusters involving more than two peaks may exhibit distinct spatial arrangements, this point splits into a set of Maxwell transition points 
M. Augustin, A. Caiazzo, A. Fiebach, J. Fuhrmann, V. John, A. Linke, R. Umla, An assessment of discretizations for convectiondominated convectiondiffusion equations, Computer Methods in Applied Mechanics and Engineering, 200 (2011), pp. 33953409.
Abstract
The performance of several numerical schemes for discretizing convectiondominated convectiondiffusion equations will be investigated with respect to accuracy and efficiency. Accuracy is considered in measures which are of interest in applications. The study includes an exponentially fitted finite volume scheme, the StreamlineUpwind PetrovGalerkin (SUPG) finite element method, a spurious oscillations at layers diminishing (SOLD) finite element method, a finite element method with continuous interior penalty (CIP) stabilization, a discontinuous Galerkin (DG) finite element method, and a total variation diminishing finite element method (FEMTVD). A detailed assessment of the schemes based on the Hemker example will be presented. 
M. Case, V. Ervin, A. Linke, L. Rebholz, A connection between ScottVogelius and graddiv stabilized TaylorHood FE approximations of the NavierStokes equations, SIAM Journal on Numerical Analysis, 49 (2011), pp. 14611481.
Abstract
This article studies two methods for obtaining excellent mass conservation in finite element computations of the NavierStokes equations using continuous velocity fields. Under mild restrictions, the ScottVogelius element pair has recently been shown to be infsup stable and have optimal approximation properties, while also providing pointwise mass conservation. We present herein the first numerical tests of this element pair for the time dependent NavierStokes equations. We also prove that, again under these mild restrictions, the limit of the graddiv stabilized TaylorHood solutions to the NavierStokes problem converges to the ScottVogelius solution as the stabilization parameter tends to infinity. That is, in this setting, we provide theoretical justification that choosing the parameter large does not destroy the solution. A limiting result is also proven for the general case. Numerical tests are provided which verify the theory, and show how both ScottVogelius and graddiv stabilized TaylorHood (with large stabilization parameter) elements can provide accurate results with excellent mass conservation for NavierStokes approximations. 
A. Glitzky, Uniform exponential decay of the free energy for Voronoi finite volume discretized reactiondiffusion systems, Mathematische Nachrichten, 284 (2011), pp. 21592174.
Abstract
Our focus are energy estimates for discretized reactiondiffusion systems for a finite number of species. We introduce a discretization scheme (Voronoi finite volume in space and fully implicit in time) which has the special property that it preserves the main features of the continuous systems, namely positivity, dissipativity and flux conservation. For a class of Voronoi finite volume meshes we investigate thermodynamic equilibria and prove for solutions to the evolution system the monotone and exponential decay of the discrete free energy to its equilibrium value with a unified rate of decay for this class of discretizations. The essential idea is an estimate of the free energy by the dissipation rate which is proved indirectly by taking into account sequences of Voronoi finite volume meshes. Essential ingredient in that proof is a discrete SobolevPoincaré inequality. 
A. Caiazzo, M. Fernandez, J.F. Gerbeau, V. Martin, Projection schemes for fluid flows through a porous interface, SIAM Journal on Scientific Computing, 33 (2011), pp. 541564.

A. Caiazzo, M.A. Fernandez, V. Martin, Analysis of a stabilized finite element method for fluid flows through a porous interface, Applied Mathematics Letters, 24 (2011), pp. 21242127.

S. Amiranashvili, A.G. Vladimirov, U. Bandelow, A model equation for ultrashort optical pulses around the zero dispersion frequency, The European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics, 58 (2010), pp. 219226.
Abstract
The nonlinear Schrödinger equation based on the Taylor approximation of the material dispersion can become invalid for ultrashort and fewcycle optical pulses. Instead, we use a rational fit to the dispersion function such that the resonances are naturally accounted for. This approach allows us to derive a simple nonenvelope model for short pulses propagating in one spatial dimension. This model is further investigated numerically and analytically. 
S. Amiranashvili, U. Bandelow, A. Mielke, Padé approximant for refractive index and nonlocal envelope equations, Optics Communications, 283 (2010), pp. 480485.
Abstract
Padé approximant is superior to Taylor expansion when functions contain poles. This is especially important for response functions in complex frequency domain, where singularities are present and intimately related to resonances and absorption. Therefore we introduce a diagonal Padé approximant for the complex refractive index and apply it to the description of short optical pulses. This yields a new nonlocal envelope equation for pulse propagation. The model offers a global representation of arbitrary medium dispersion and absorption, e.g., the fulfillment of the KramersKronig relation can be established. In practice, the model yields an adequate description of spectrally broad pulses for which the polynomial dispersion operator diverges and can induce huge errors. 
J. Härdtlein, C. Pflaum, A. Linke, C.H. Wolters, Advanced expression templates programming, Computing and Visualization in Science, 13 (2010), pp. 5968.

H.G. Purwins, H. Bödeker, S. Amiranashvili, Dissipative solitons, Advances in Physics, 59 (2010), pp. 485701.

J. Fuhrmann, A. Fiebach, A. Erdmann, P. Trefonas, Acid diffusion effects between resists in freezing processes used for contact hole patterning, Microelectronic Engineering, 87 (2010), pp. 951954.
Abstract
Double patterning following an litho?lithoetch scheme is a possible option to create structure widths below the nominal resolution of optical light with current exposure technology. Interactions between the first and second resist layers may influence the final structure created. In this paper, we perform a model based investigation of the possible consequences of the diffusion of photogenerated acid from the second resist to the first one. As a consequence, less acid is available for the deprotection reaction, and we observe a tendency to an increase of the CD values of the primary structure. We attempt to explain observed footing effects in contact holes by this effect. 
A. Glitzky, J.A. Griepentrog, Discrete SobolevPoincaré inequalities for Voronoi finite volume approximations, SIAM Journal on Numerical Analysis, 48 (2010), pp. 372391.
Abstract
We prove a discrete SobolevPoincare inequality for functions with arbitrary boundary values on Voronoi finite volume meshes. We use Sobolev's integral representation and estimate weakly singular integrals in the context of finite volumes. We establish the result for star shaped polyhedral domains and generalize it to the finite union of overlapping star shaped domains. In the appendix we prove a discrete Poincare inequality for space dimensions greater or equal to two. 
A. Glitzky, K. Gärtner, Existence of bounded steady state solutions to spinpolarized driftdiffusion systems, SIAM Journal on Mathematical Analysis, 41 (2010), pp. 24892513.
Abstract
We study a stationary spinpolarized driftdiffusion model for semiconductor spintronic devices. This coupled system of continuity equations and a Poisson equation with mixed boundary conditions in all equations has to be considered in heterostructures. In 3D we prove the existence and boundedness of steady states. If the Dirichlet conditions are compatible or nearly compatible with thermodynamic equilibrium the solution is unique. The same properties are obtained for a space discretized version of the problem: Using a ScharfetterGummel scheme on 3D boundary conforming Delaunay grids we show existence, boundedness and, for small applied voltages, the uniqueness of the discrete solution. 
V. John, M. Roland, On the impact of the scheme for solving the higherdimensional equation in coupled population balance systems, International Journal for Numerical Methods in Engineering, 82 (2010), pp. 14501474.

A. Mielke, L. Paoli, A. Petrov, U. Stefanelli, Error estimates for spacetime discretizations of a rateindependent variational inequality, SIAM Journal on Numerical Analysis, 48 (2010), pp. 16251646.
Abstract
This paper deals with error estimates for spacetime discretizations in the context of evolutionary variational inequalities of rateindependent type. After introducing a general abstract evolution problem, we address a fullydiscrete approximation and provide a priori error estimates. The application of the abstract theory to a semilinear case is detailed. In particular, we provide explicit spacetime convergence rates for the isothermal SouzaAuricchio model for shapememory alloys. 
H. Si, J. Fuhrmann, K. Gärtner, Boundary conforming Delaunay mesh generation, Computational Mathematics and Mathematical Physics, 50 (2010), pp. 3853.

S. Amiranashvili, U. Bandelow, A. Mielke, Padé approximant for refractive index and nonlocal envelope equations, Optics Communications, 283 (2009), pp. 480485.
Abstract
Padé approximant is superior to Taylor expansion when functions contain poles. This is especially important for response functions in complex frequency domain, where singularities are present and intimately related to resonances and absorption. Therefore we introduce a diagonal Padé approximant for the complex refractive index and apply it to the description of short optical pulses. This yields a new nonlocal envelope equation for pulse propagation. The model offers a global representation of arbitrary medium dispersion and absorption, e.g., the fulfillment of the KramersKronig relation can be established. In practice, the model yields an adequate description of spectrally broad pulses for which the polynomial dispersion operator diverges and can induce huge errors. 
A.G. Vladimirov, A. Pimenov, D. Rachinskii, Numerical study of dynamical regimes in a monolithic passively mode locked semiconductor laser, IEEE J. Quantum Electron., 45 (2009), pp. 462468.

G. Kozyreff, M. Tlidi, A. Mussot, E. Louvergneaux, M. Taki, A.G. Vladimirov, Localized beating between dynamically generated frequencies, Physical Review Letters, 102 (2009), pp. 043905/1043905/4.

M. Tlidi, A.G. Vladimirov, D. Pieroux, D. Turaev, Spontaneous motion of cavity solitons induced by a delayed feedback, Physical Review Letters, 103 (2009), pp. 103904/1103904/4.

M. Ehrhardt, H. Han, Ch. Zheng, Numerical simulation of waves in periodic structures, Communications in Computational Physics, 5 (2009), pp. 849872.
Abstract
In this work we present a new numerical technique for solving periodic structure problems. This new approach possesses several advantages. First, it allows for a fast evaluation of the RobintoRobin operator for periodic array problems. Secondly, this computational method can also be used for biperiodic structure problems with local defects. Our strategy is an improvement of the recently developed recursive doubling process by Yuan and Lu.
In this paper we consider several problems, such as the exterior elliptic problems with strong coercivity, the timedependent Schrödinger equation and finally the Helmholtz equation with damping. 
J. Fuhrmann, A. Erdmann, Ch.R. Szmanda, A. Fiebach, M. Uhle, A model of selflimiting residual acid diffusion for pattern doubling, Microelectronic Engineering, 86 (2009), pp. 792795.

J. Fuhrmann, A. Linke, H. Langmach, H. Baltruschat, Numerical calculation of the limiting current for a cylindrical thin layer flow cell, Electrochimica Acta, 55 (2009), pp. 430438.

K. Gärtner, Existence of bounded discrete steady state solutions of the van Roosbroeck system on boundary conforming Delaunay grids, SIAM Journal on Scientific Computing, 31 (2009), pp. 13471362.
Abstract
The classic van Roosbroeck system describes the carrier transport in semiconductors in a drift diffusion approximation. Its analytic steady state solutions fulfill bounds for some mobility and recombination/generation models. The main goal of this paper is to establish the identical bounds for discrete in space, steady state solutions on 3d boundary conforming Delaunay grids and the classical ScharfetterGummelscheme. Together with a uniqueness proof for small applied voltages and the known dissipativity (continuous as well as space and time discrete) these discretization techniques carry over the essential analytic properties to the discrete case. The proofs are of interest for deriving averaging schemes for space or state dependent material parameters, which are preserving these qualitative properties, too. To illustrate the properties of the scheme 1, 4, 16 elementary cells of a modified CoolMOS like structure are depleted by increasing the applied voltage until steady state avalanche breakdown occurs. 
A. Glitzky, Energy estimates for electroreactiondiffusion systems with partly fast kinetics, Discrete and Continuous Dynamical Systems, 25 (2009), pp. 159174.
Abstract
We start from a basic model for the transport of charged species in heterostructures containing the mechanisms diffusion, drift and reactions in the domain and at its boundary. Considering limit cases of partly fast kinetics we derive reduced models. This reduction can be interpreted as some kind of projection scheme for the weak formulation of the basic electroreactiondiffusion system. We verify assertions concerning invariants and steady states and prove the monotone and exponential decay of the free energy along solutions to the reduced problem and to its fully implicit discretetime version by means of the results of the basic problem. Moreover we make a comparison of prolongated quantities with the solutions to the basic model. 
A. Glitzky, K. Gärtner, Energy estimates for continuous and discretized electroreactiondiffusion systems, Nonlinear Analysis. Theory, Methods & Applications. An International Multidisciplinary Journal. Series A: Theory and Methods, 70 (2009), pp. 788805.
Abstract
We consider electroreactiondiffusion systems consisting of continuity equations for a finite number of species coupled with a Poisson equation. We take into account heterostructures, anisotropic materials and rather general statistic relations.
We investigate thermodynamic equilibria and prove for solutions to the evolution system the monotone and exponential decay of the free energy to its equilibrium value. Here the essential idea is an estimate of the free energy by the dissipation rate which is proved indirectly.
The same properties are shown for an implicit time discretized version of the problem. Moreover, we provide a space discretized scheme for the electroreactiondiffusion system which is dissipative (the free energy decays monotonously). On a fixed grid we use for each species different Voronoi boxes which are defined with respect to the anisotropy matrix occurring in the flux term of this species. 
V. John, T. Mitkova, M. Roland, K. Sundmacher, L. Tobiska, A. Voigt, Simulations of population balance systems with one internal coordinate using finite element methods, Chemical Engineering Sciences, 64 (2009), pp. 733741.

A. Mielke, T. Roubíček, Numerical approaches to rateindependent processes and applications in inelasticity, ESAIM: Mathematical Modelling and Numerical Analysis, 43 (2009), pp. 399429.
Abstract
A general abstract approximation scheme for rateindependent processes in the energetic formulation is proposed and its convergence is proved under various rather mild data qualifications. The abstract theory is illustrated on several examples: plasticity with isotropic hardening, damage, debonding, magnetostriction, and two models of martensitic transformation in shapememory alloys. 
H. Stephan, Modeling of driftdiffusion systems, ZAMP Zeitschrift fur Angewandte Mathematik und Physik. ZAMP. Journal of Applied Mathematics and Physics. Journal de Mathematiques et de Physique Appliquees, 60 (2009), pp. 3353.
Abstract
We derive driftdiffusion systems describing transport processes starting from free energy and equilibrium solutions by a unique method. We include several statistics, heterostructures and cross diffusion. The resulting systems of nonlinear partial differential equations conserve mass and positivity, and have a Lyapunov function (free energy). Using the inverse Hessian as mobility, nondegenerate diffusivity matrices turn out to be diagonal, or  in the case of cross diffusion  even constant. 
S. Amiranashvili, A.G. Vladimirov, U. Bandelow, Solitarywave solutions for fewcycle optical pulses, Physical Review A, 77 (2008), pp. 063821/1063821/7.

M. Pietrzyk, I. Kanattšikow, U. Bandelow, On the propagation of vector ultrashort pulses, Journal of Nonlinear Mathematical Physics, 15 (2008), pp. 162170.

R. Čiegis, M. Radziunas, M. Lichtner, Numerical algorithms for simulation of multisection lasers by using traveling wave model, IEEE J. Select. Topics Quantum Electron., 13 (2008), pp. 327348.

D. Turaev, M. Radziunas, A.G. Vladimirov, Chaotic soliton walk in periodically modulated media, Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, 77 (2008), pp. 06520/106520/4.

A. Glitzky, Exponential decay of the free energy for discretized electroreactiondiffusion systems, Nonlinearity, 21 (2008), pp. 19892009.
Abstract
Our focus are electroreactiondiffusion systems consisting of continuity equations for a finite number of species coupled with a Poisson equation. We take into account heterostructures, anisotropic materials and rather general statistical relations. We introduce a discretization scheme (in space and fully implicit in time) using a fixed grid but for each species different Voronoi boxes which are defined with respect to the anisotropy matrix occurring in the flux term of this species. This scheme has the special property that it preserves the main features of the continuous systems, namely positivity, dissipativity and flux conservation. For the discretized electroreactiondiffusion system we investigate thermodynamic equilibria and prove for solutions to the evolution system the monotone and exponential decay of the free energy to its equilibrium value. The essential idea is an estimate of the free energy by the dissipation rate which is proved indirectly. 
O. Minet, H. Gajewski, J.A. Griepentrog, J. Beuthan, The analysis of laser light scattering during rheumatoid arthritis by image segmentation, Laser Physics Letters, 4 (2007), pp. 604610.

M. Tlidi, A. Mussot, E. Louvergneaux, G. Kozyreff, A.G. Vladimirov, M. Taki, Control and removing of modulational instabilities in low dispersion photonic crystal fiber cavities, , 32 (2007), pp. 662664.

D. Turaev, A.G. Vladimirov, S. Zelik, Chaotic bound state of localized structures in the complex GinzburgLandau equation, Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, 75 (2007), pp. 045601/1045601/4.

M. Lichtner, M. Radziunas, L. Recke, Wellposedness, smooth dependence and center manifold reduction for a semilinear hyperbolic system from laser dynamics, Mathematical Methods in the Applied Sciences, 30 (2007), pp. 931960.

A.G. Vladimirov, D.V. Skryabin, G. Kozyreff, P. Mandel, M. Tlidi, Bragg localized structures in a passive cavity with transverse modulation of the refractive index and the pump, Optics Express, 14 (2006), pp. 16.

H. Gajewski, J.A. Griepentrog, A descent method for the free energy of multicomponent systems, Discrete and Continuous Dynamical Systems, 15 (2006), pp. 505528.

M. Kočvara, A. Mielke, T. Roubíček, A rateindependent approach to the delamination problem, Mathematics and Mechanics of Solids, 11 (2006), pp. 423447.

U. Bandelow, M. Radziunas, A. Vladimirov, B. Hüttl, R. Kaiser, 40 GHz Modelocked semiconductor lasers: Theory, simulations and experiment, Optical and Quantum Electronics, 38 (2006), pp. 495512.

M. Radziunas, F. Ivanauskas, The convergence and stability of splitting finite difference schemes for nonlinear evolutionary type equations, Optical and Quantum Electronics, 45 (2005), pp. 334352.

P. Evans, A. Münch, Interaction of advancing fronts and meniscus profiles formed by surfacetensiongradientdriven liquid films, SIAM Journal on Applied Mathematics, 66 (2006), pp. 16101631.

A. Münch, Dewetting rates of thin liquid films, Physics of Fluids, 17 (2005), pp. S309S318.

N. Nefedov, M. Radziunas, K.R. Schneider, A. Vasil'eva, Change of the type of contrast structures in parabolic Neumann problems, Computational Mathematics and Mathematical Physics, 45 (2005), pp. 3751.

W. Dreyer, B. Wagner, Sharpinterface model for eutectic alloys. Part I: Concentration dependent surface tension, Interfaces and Free Boundaries. Mathematical Modelling, Analysis and Computation, 7 (2005), pp. 199227.

N. Nefedov, M. Radziunas, K.R. Schneider, Analyticnumerical investigation of delayed exchange of stabilities in singularly perturbed parabolic problems, Computational Mathematics and Mathematical Physics, 44 (2004), pp. 12131220.

A. Rathsfeld, R. Schneider, On a quadrature algorithm for the piecewise linear wavelet collocation applied to boundary integral equations, Mathematical Methods in the Applied Sciences, 26 (2003), pp. 937979.

A.M. Krasnosel'skii, D.I. Rachinskii, K.R. Schneider, Hopf bifurcations in resonance 2:1, Nonlinear Analysis. Theory, Methods & Applications. An International Multidisciplinary Journal. Series A: Theory and Methods, 52A (2003), pp. 943960.

G. Mastroianni, C. Frammartino, A. Rathsfeld, On polynomial collocation for second kind integral equations with fixed singularities of Mellin type, Numerische Mathematik, 94 (2003), pp. 333365.

N.N. Nefedov, K.R. Schneider, Delay of exchange of stabilities in singularly perturbed parabolic problems, Proceedings of the Steklov Institute of Mathematics, (2003), pp. S144S154.

M. Tlidi, A.G. Vladimirov, P. Mandel, Interaction and stability of periodic and localized structures in optical bistable systems, IEEE J. Quantum Electron., 39 (2003), pp. 197205.

H. Gajewski, K. Gärtner, Domain separation by means of sign changing eigenfunctions of $p$Laplacians, Applicable Analysis. An International Journal, 79 (2001), pp. 483501.

W. Dreyer, W.H. Müller, A study of the coarsening in tin/lead solders, International Journal of Solids and Structures, 37 (2000), pp. 38413871.
Contributions to Collected Editions

A.H. Erhardt, K. TsanevaAtanasova, G.T. Lines, E.A. Martens, Editorial: Dynamical systems, PDEs and networks for biomedical applications: Mathematical modeling, analysis and simulations, 10 of Front. Phys., Sec. Statistical and Computational Physics, Frontiers, Lausanne, Switzerland, 2023, pp. 0103, DOI 10.3389/fphy.2022.1101756 .

M. Heida, Finite volumes for simulation of large molecules, in: Finite Volumes for Complex Applications X  Volume 1, Elliptic and Parabolic Problems: FVCA10, Strasbourg, France, October 30, 2023  November 03, 2023, Invited Contributions, E. Franck, J. Fuhrmann, V. MichelDansac, L. Navoret, eds., 432 of Springer Proceedings in Mathematics & Statistics, Springer International Publishing, Cham, 2023, pp. 305313, DOI 10.1007/9783031408649_25 .
Abstract
We study a finite volume scheme for simulating the evolution of large molecules within their reduced state space. The finite volume scheme under consideration is the SQRA scheme developed by Lie, Weber and Fackeldey. We study convergence of a more general family of FV schemes in up to 3 dimensions and provide a convergence result for the SQRAscheme in arbitrary space dimensions. 
M. O'Donovan, R. Finn, S. Schulz, Th. Koprucki, Atomistic study of Urbach tail energies in (Al,Ga)N quantum well systems, in: 23nd International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD 2023), P. Bardella, A. Tibaldi, eds., IEEE, 2023, pp. 7980, DOI 10.1109/NUSOD59562.2023.10273479 .
Abstract
Aluminium gallium nitride is a system of interest for developing ultraviolet (UV) optoelectronic devices. Here Urbach tails induced by carrier localization effects play a key role in determining device behaviour. We study the electronic structure of Al x Ga 1x N/Al y Ga 1y N single quantum wells using an atomistic framework. Results show that the density of states exhibits a tail at low energies due to disorder in the alloy microstructure. Our analysis allows for insight into the orbital character of the states forming the Urbach tails, which can affect light polarization characteristics, and important quantity for deep UV light emitters. 
C. ChainaisHillairet, R. Eymard, J. Fuhrmann, An approximate twopoint Dirichlet flux for quasilinear convection diffusion equations, in: Finite Volumes for Complex Applications X  Volume 1, Elliptic and Parabolic Problems: FVCA10, Strasbourg, France, October 30, 2023  November 03, 2023, Invited Contributions, E. Franck, J. Fuhrmann, V. MichelDansac, L. Navoret, eds., 432 of Springer Proceedings in Mathematics & Statistics, Springer International Publishing, Cham, 2023, pp. 225233, DOI 10.1007/9783031408649_17 .

S. Matera, Ch. Merdon, D. Runge, Reduced basis approach for convectiondiffusion equations with nonlinear boundary reaction conditions, in: Finite Volumes for Complex Applications X  Volume 1, Elliptic and Parabolic Problems: FVCA10, Strasbourg, France, October 30, 2023  November 03, 2023, Invited Contributions, E. Franck, J. Fuhrmann, V. MichelDansac, L. Navoret, eds., 432 of Springer Proceedings in Mathematics & Statistics, Springer International Publishing, Cham, 2023, pp. 335343, DOI 10.1007/9783031408649_28 .
Abstract
This paper aims at an efficient strategy to solve driftdiffusion problems with nonlinear boundary conditions as they appear, e.g., in heterogeneous catalysis. Since the nonlinearity only involves the degrees of freedom along (a part of) the boundary, a reduced basis ansatz is suggested that computes discrete Green?slike functions for the present driftdiffusion operator such that the global nonlinear problem reduces to a smaller nonlinear problem for a boundary method. The computed basis functions are completely independent of the nonlinearities. Thus, they can be reused for problems with the same differential operator and geometry. Corresponding scenarios might be inverse problems in heterogeneous catalysis but also modeling the effect of different catalysts in the same reaction chamber. The strategy is explained for a massconservative finite volume method and demonstrated on a simple numerical example for catalytic CO oxidation. 
J. Fuhrmann, B. Gaudeul, Ch. Keller, Two entropic finite volume schemes for a NernstPlanckPoisson system with ion volume constraints, in: Finite Volumes for Complex Applications X  Volume 1, Elliptic and Parabolic Problems: FVCA10, Strasbourg, France, October 30, 2023  November 03, 2023, Invited Contributions, E. Franck , J. Fuhrmann, V. MichelDansac, L. Navoret, eds., Springer Proceedings in Mathematics & Statistics, Springer International Publishing, Cham, 2023, pp. 285294, DOI 10.1007/9783031408649_23 .

D. Abdel, N. Courtier, P. Farrell, Volume exclusion effects in perovskite charge transport modeling, in: 2022 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD 2022), Turin, Italy, 2022, J. Piprek, P. Bardella, eds., IEEE, 2022, pp. 107108, DOI 10.1109/NUSOD54938.2022.9894826 .

Y. Hadjimichael, O. Marquardt, Ch. Merdon, P. Farrell, Band structures in highly strained 3D nanowires, in: 2022 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD 2022), Turin, Italy, 2022, J. Piprek, Bardella Paolo, eds., IEEE, 2022, pp. 119120, DOI 10.1109/NUSOD54938.2022.9894837 .

O. Marquardt, M. O'Donovan, S. Schulz, O. Brandt, Th. Koprucki, Influence of random alloy fluctuations on the electronic properties of axial (In,Ga)N/GaN nanowire heterostructures, in: 2022 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD), Turin, Italy, 2022, J. Piprek, P. Bardella, eds., IEEE, 2022, pp. 117118, DOI 10.1109/NUSOD54938.2022.9894777 .
Abstract
Compound semiconductor heterostructures such as quantum dots, nanowires, or thin films, are commonly subject to randomly fluctuating alloy compositions if they contain ternary and quaternary alloys. These effects are obviously of an atomistic nature and thus rarely considered in heterostructure designs that require simulations on a continuum level for theoryguided design or interpretation of observations. In the following, we present a systematic approach to the treatment of alloy fluctuations in (In,Ga)N/GaN thin films and axial nanowire heterostructures. We demonstrate to what extent random alloy fluctuations can be treated in a continuum picture and discuss the impact of alloy fluctuations on the electronic properties of planar and nano wirebased (In,Ga)N/GaN heterostructures. 
S. Piani, W. Lei, L. Heltai, N. Rotundo, P. Farrell, Datadriven doping reconstruction, in: 2022 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD 2022), Turin, Italy, 2022, J. Piprek, P. Bardella, eds., IEEE, 2022, pp. 109110, DOI 10.1109/NUSOD54938.2022.9894774 .

J. Moatti, P. Farrell, Comparison of flux discretizations for varying bandedge energies, in: 2022 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD 2022), Turin, Italy, 2022, J. Piprek, P. Bardella, eds., IEEE, 2022, pp. 103104, DOI 10.1109/NUSOD54938.2022.9894742 .

M. O'Donovan, P. Farrell, T. Streckenbach, Th. Koprucki, S. Schulz, Carrier transport in (In,Ga)N quantum well systems: Connecting atomistic tightbinding electronic structure theory to driftdiffusion simulations, in: 2022 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD), Turin, Italy, 2022, J. Piprek, P. Bardella, eds., IEEE, 2022, pp. 9798, DOI 10.1109/NUSOD54938.2022.9894745 .

M. Thomas, M. Heida, GENERIC for dissipative solids with bulkinterface interaction, in: Research in the Mathematics of Materials Science, M.I. Espanõl, M. Lewicka, L. Scardia, A. Schlömkemper, eds., 31 of Association for Women in Mathematics Series, Springer, Cham, 2022, pp. 333364, DOI 10.1007/9783031044960_15 .
Abstract
The modeling framework of GENERIC was originally introduced by Grmela and Öttinger for thermodynamically closed systems. It is phrased with the aid of the energy and entropy as driving functionals for reversible and dissipative processes and suitable geometric structures. Based on the definition functional derivatives we propose a GENERIC framework for systems with bulkinterface interaction and apply it to discuss the GENERIC structure of models for delamination processes. 
K. Hopf, Global existence analysis of energyreactiondiffusion systems, in: Report 29: Variational Methods for Evolution (hybrid meeting), A. Mielke, M. Peletier, D. Slepcev, eds., 17 of Oberwolfach Reports, European Mathematical Society Publishing House, Zurich, 2021, pp. 14181421, DOI 10.4171/OWR/2020/29 .

D. Abdel, P. Farrell, J. Fuhrmann, Comparison of ScharfetterGummel schemes for (non)degenerate semiconductor device simulation, in: Proceedings of the 20th International Conference on Numerical Simulation of Optoelectronic Devices  NUSOD 2020, J. Piprek, K. Hinzer, eds., IEEE Conference Publications Management Group, Piscataway, 2020, pp. 107108.

S. Kayser, N. Rotundo, J. Fuhrmann, N. Dropka, P. Farrell, The lateral photovoltage scanning method (LPS): Understanding doping variations in silicon crystals, in: Proceedings of the 20th International Conference on Numerical Simulation of Optoelectronic Devices  NUSOD 2020, J. Piprek, K. Hinzer, eds., IEEE Conference Publications Management Group, Piscataway, 2020, pp. 4950.

A. Linke, Ch. Merdon, On the significance of pressurerobustness for the space discretization of incompressible high Reynolds number flows, in: Finite Volumes for Complex Applications IX  Methods, Theoretical Aspects, Examples  FVCA 9, Bergen, June 2020, R. Klöfkorn, E. Keilegavlen, A.F. Radu, J. Fuhrmann, eds., 323 of Springer Proceedings in Mathematics & Statistics, Springer International Publishing, Cham et al., 2020, pp. 103112.

A. Linke, Ch. Merdon, Wellbalanced discretisation for the compressible Stokes problem by gradientrobustness, in: Finite Volumes for Complex Applications IX  Methods, Theoretical Aspects, Examples  FVCA 9, Bergen, June 2020, R. Klöfkorn, E. Keilegavlen, A.F. Radu, J. Fuhrmann, eds., 323 of Springer Proceedings in Mathematics & Statistics, Springer International Publishing, Cham et al., 2020, pp. 113121.

C. Cancès, C. ChainaisHillairet, J. Fuhrmann, B. Gaudeul, On four numerical schemes for a unipolar degenerate driftdiffusion model, in: Finite Volumes for Complex Applications IX  Methods, Theoretical Aspects, Examples  FVCA 9, Bergen, June 2020, R. Klöfkorn, F. Radu, E. Keijgavlen, J. Fuhrmann, eds., Springer Proceedings in Mathematics & Statistics, Springer International Publishing, Cham et al., 2020, pp. 163171, DOI 10.1007/9783030436513_13 .

A. Jha, V. John, On basic iteration schemes for nonlinear AFC discretizations, in: Boundary and Interior Layers, Computational and Asymptotic Methods, BAIL 2018, G.N. Barrenechea, J. Mackenzie, eds., 135 of Lecture Notes in Computational Science and Engineering, Springer, Cham, 2020, pp. 113128, DOI https://doi.org/10.1007/9783030418007_7 .
Abstract
Algebraic flux correction (AFC) finite element discretizations of steadystate convectiondiffusionreaction equations lead to a nonlinear problem. This paper presents first steps of a systematic study of solvers for these problems. Two basic fixed point iterations and a formal Newton method are considered. It turns out that the fixed point iterations behave often quite differently. Using a sparse direct solver for the linear problems, one of them exploits the fact that only one matrix factorization is needed to become very efficient in the case of convergence. For the behavior of the formal Newton method, a clear picture is not yet obtained. 
S. Schulz, D. Chaudhuri, M. O'Donovan, S. Patra, T. Streckenbach, P. Farrell, O. Marquardt, Th. Koprucki, Multiscale modeling of electronic, optical, and transport properties of IIIN alloys and heterostructures, in: Physics and Simulation of Optoelectronic Devices XXVIII, B. Witzigmann, M. Osiński, Y. Arakawa, eds., 11274 of Proceedings of SPIE, San Francisco, 2020, pp. 1127416/11127416/10, DOI 10.1117/12.2551055 .

J. Fuhrmann, D.H. Doan, A. Glitzky, M. Liero, G. Nika, Unipolar driftdiffusion simulation of Sshaped currentvoltage relations for organic semiconductor devices, in: Finite Volumes for Complex Applications IX  Methods, Theoretical Aspects, Examples  FVCA 9, Bergen, June 2020, R. Klöfkorn, E. Keilegavlen, F.A. Radu, J. Fuhrmann, eds., 323 of Springer Proceedings in Mathematics & Statistics, Springer International Publishing, Cham et al., 2020, pp. 625633, DOI 10.1007/9783030436513_59 .
Abstract
We discretize a unipolar electrothermal driftdiffusion model for organic semiconductor devices with GaussFermi statistics and charge carrier mobilities having positive temperature feedback. We apply temperature dependent Ohmic contact boundary conditions for the electrostatic potential and use a finite volume based generalized ScharfetterGummel scheme. Applying pathfollowing techniques we demonstrate that the model exhibits Sshaped currentvoltage curves with regions of negative differential resistance, only recently observed experimentally. 
M. Kantner, Th. Koprucki, Nonisothermal ScharfetterGummel scheme for electrothermal transport simulation in degenerate semiconductors, in: Finite Volumes for Complex Applications IX  Methods, Theoretical Aspects, Examples  FVCA 9, Bergen, June 2020, R. Klöfkorn, E. Keilegavlen, F.A. Radu, J. Fuhrmann, eds., 323 of Springer Proceedings in Mathematics & Statistics, Springer International Publishing, Cham et al., 2020, pp. 173182, DOI 10.1007/9783030436513_14 .
Abstract
Electrothermal transport phenomena in semiconductors are described by the nonisothermal driftdiffusion system. The equations take a remarkably simple form when assuming the Kelvin formula for the thermopower. We present a novel, nonisothermal generalization of the ScharfetterGummel finite volume discretization for degenerate semiconductors obeying FermiDirac statistics, which preserves numerous structural properties of the continuous model on the discrete level. The approach is demonstrated by 2D simulations of a heterojunction bipolar transistor. 
M. Kantner, A. Mielke, M. Mittnenzweig, N. Rotundo, Mathematical modeling of semiconductors: From quantum mechanics to devices, in: Topics in Applied Analysis and Optimisation, M. Hintermüller, J.F. Rodrigues, eds., CIM Series in Mathematical Sciences, Springer Nature Switzerland AG, Cham, 2019, pp. 269293, DOI 10.1007/9783030331160 .
Abstract
We discuss recent progress in the mathematical modeling of semiconductor devices. The central result of this paper is a combined quantumclassical model that selfconsistently couples van Roosbroeck's driftdiffusion system for classical charge transport with a Lindbladtype quantum master equation. The coupling is shown to obey fundamental principles of nonequilibrium thermodynamics. The appealing thermodynamic properties are shown to arise from the underlying mathematical structure of a damped Hamitlonian system, which is an isothermal version of socalled GENERIC systems. The evolution is governed by a Hamiltonian part and a gradient part involving a Poisson operator and an Onsager operator as geoemtric structures, respectively. Both parts are driven by the conjugate forces given in terms of the derivatives of a suitable free energy. 
M. Kantner, Th. Koprucki, H.J. Wünsche, U. Bandelow, Simulation of quantum dot based singlephoton sources using the SchrödingerPoissonDriftDiffusionLindblad system, in: Proceedings of the 24th International Conference on Simulation of Semiconductor Processes and Devices (SISPAD 2019), F. Driussi, ed., 2019, pp. 355358, DOI 10.1007/9783030221160_11 .

M. Kantner, A generalized ScharfetterGummel scheme for degenerate and nonisothermal semiconductors, in: Proceedings of the 19th International Conference on Numerical Simulation of Optoelectronic Devices  NUSOD 2019, J. Piprek, K. Hinzer, eds., IEEE Conference Publications Management Group, Piscataway, 2019, pp. 78, DOI 10.1109/NUSOD.2019.8806839 .
Abstract
We present a highly accurate generalization of the ScharfetterGummel scheme for the discretization of the currentdensities in degenerate semiconductors under nonisothermalconditions. The underlying model relies on the Kelvin formula forthe Seebeck coefficient, which has the intriguing property that the?Tterm in the electrical current density expressions vanishesexactly when passing to the driftdiffusion form ? even thoughthe thermoelectric crosscoupling is fully taken into account. 
M. Kantner, Hybrid modeling of quantum light emitting diodes: Selfconsistent coupling of driftdiffusion, SchrödingerPoisson, and quantum master equations, in: Proc. SPIE 10912, B. Witzigmann, M. Osiński, Y. Arakawa, eds., Physics and Simulation of Optoelectronic Devices XXVII, SPIE Digital Library, Bellingham, 2019, pp. 10912OU/110912OU/8, DOI 10.1117/12.2515209 .
Abstract
The devicescale simulation of electrically driven solid state quantum light emitters, such as singlephoton sources and nanolasers based on semiconductor quantum dots, requires a comprehensive modeling approach, that combines classical device physics with cavity quantum electrodynamics. In a previous work, we have selfconsistently coupled the semiclassical driftdiffusion system with a Markovian quantum master equation in Lindblad form to describe (i) the spatially resolved current injection into a quantum dot embedded within a semiconductor device and (ii) the fully quantum mechanical lightmatter interaction in the coupled quantum dotphoton system out of one box. In this paper, we extend our hybrid quantumclassical modeling approach by including a Schroedinger?Poisson problem to account for energy shifts of the quantum dot carriers in response to modifications of its macroscopic environment (e.g., quantum confined Stark effect due to the diode's internal electric field and plasma screening). The approach is demonstrated by simulations of a singlephoton emitting diode. 
M. Kantner, Simulation of quantum light sources using the selfconsistently coupled SchrödingerPoissonDriftDiffusionLindblad system, in: Proceedings of the 19th International Conference on Numerical Simulation of Optoelectronic Devices  NUSOD 2019, J. Piprek, K. Hinzer, eds., IEEE Conference Publications Management Group, Piscataway, 2019, pp. 1516, DOI 10.1109/NUSOD.2019.8806839 .
Abstract
The devicescale simulation of electrically drivenquantum light sources based on semiconductor quantum dotsrequires a combination of the (classical) semiconductor deviceequations with cavity quantum electrodynamics. In this paper, weextend our previously developed hybrid quantumclassical modelsystem ? where we have coupled the driftdiffusion system witha Lindbladtype quantum master equation ? by including a selfconsistent Schrödinger?Poisson problem. The latter describes the(quasi)bound states of the quantum dot carriers. The extendedmodel allows to describe the biasdependency of the emissionspectrum due to the quantum confined Stark effect 
M. Lübbering, J. Kunkel, P. Farrell, What company does my news article refer to? Tackling multiclass problems with topic modeling, in: CEURWS.org/Vol2454/paper_41, CEURWS.org, Sun SITE Central Europe RWTH Aachen, Aachen, 2019, pp. 353364, DOI 10.20347/WIAS.PREPRINT.2621 .
Abstract
While it is technically trivial to search for the company name to predict the company a new article refers to, it often leads to incorrect results. In this article, we compare the two approaches bagofwords with knearest neighbors and Latent Dirichlet Allocation with knearest neighbor by assessing their applicability for predicting the S&P 500 company which is mentioned in a business news article or press release. Both approaches are evaluated on a corpus of 13k documents containing 84% news articles and 16% press releases. While the bagofwords approach yields accurate predictions, it is highly inefficient due to its gigantic feature space. The Latent Dirichlet Allocation approach, on the other hand, manages to achieve roughly the same prediction accuracy (0.58 instead of 0.62) but reduces the feature space by a factor of seven. 
J.H.M. Ten Thije Boonkkamp, N. Kumar, B. Koren, D.A.M. caps">caps">van der Woude, A. Linke, Nonlinear flux approximation scheme for Burgers equation derived from a local BVP, in: Numerical Mathematics and Advanced Applications 2017  ENUMATH 2017, F.A. Radu, K. Kumar, I. Berre, J.M. Nordbotten, I.S. Pop, eds., 126 of Lecture Notes Comput. Sci. Engrg., Springer Nature Switzerland AG, Cham, 2019, pp. 10151023, DOI 10.1007/9783319964157_96 .

J. Fuhrmann, C. Guhlke, A. Linke, Ch. Merdon, R. Müller, Models and numerical methods for electrolyte flows, in: Topics in Applied Analysis and Optimisation, M. Hintermüller, J.F. Rodrigues, eds., CIM Series in Mathematical Sciences, Springer Nature Switzerland AG, Cham, 2019, pp. 183209.

J. Fuhrmann, C. Guhlke, A. Linke, Ch. Merdon, R. Müller, Voronoi finite volumes and pressure robust finite elements for electrolyte models with finite ion sizes, in: Numerical Geometry, Grid Generation and Scientific Computing. Proceedings of the 9th International Conference, NUMGRID 2018 / Voronoi 150, V.A. Garanzha, L. Kamenski, H. Si, eds., 131 of Lecture Notes in Computational Science and Engineering, Springer Nature Switzerland AG, Cham, 2019, pp. 7383, DOI 10.1007/9783030234362 .

M. Kantner, M. Mittnenzweig, Th. Koprucki, A hybrid quantumclassical modeling approach for electrically driven quantum dot devices, in: Proc. SPIE 10526, Physics and Simulation of Optoelectronic Devices XXVI, B. Witzigmann, M. Osiński, Y. Arakawa, eds., SPIE Digital Library, 2018, pp. 1052603/11052603/6, DOI 10.1117/12.2289185 .
Abstract
The design of electrically driven quantum light sources based on semiconductor quantum dots, such as singlephoton emitters and nanolasers, asks for modeling approaches combining classical device physics with cavity quantum electrodynamics. In particular, one has to connect the wellestablished fields of semiclassical semiconductor transport theory and the theory of open quantum systems. We present a first step in this direction by coupling the van Roosbroeck system with a Markovian quantum master equation in Lindblad form. The resulting hybrid quantumclassical system obeys the fundamental laws of nonequilibrium thermodynamics and provides a comprehensive description of quantum dot devices on multiple scales: It enables the calculation of quantum optical figures of merit (e.g. the second order intensity correlation function) together with the spatially resolved simulation of the current flow in realistic semiconductor device geometries in a unified way. 
M. Kantner, M. Mittnenzweig, Th. Koprucki, Modeling and simulation of electrically driven quantum light sources: From classical device physics to open quantum systems, in: 14th International Conference on Nonlinear Optics and Excitation Kinetics in Semiconductors, September 2327, 2018, Berlin, Germany (Conference Program), 2018, pp. 135.

S. Bartels, M. Milicevic, M. Thomas, Numerical approach to a model for quasistatic damage with spatial $BV$regularization, in: Proceedings of the INdAMISIMM Workshop on Trends on Applications of Mathematics to Mechanics, Rome, Italy, September 2016, E. Rocca, U. Stefanelli, L. Truskinovsky, A. Visintin, eds., 27 of Springer INdAM Series, Springer International Publishing, Cham, 2018, pp. 179203, DOI 10.1007/9783319759401_9 .
Abstract
We address a model for rateindependent, partial, isotropic damage in quasistatic small strain linear elasticity, featuring a damage variable with spatial BVregularization. Discrete solutions are obtained using an alternate timediscrete scheme and the VariableADMM algorithm to solve the constrained nonsmooth optimization problem that determines the damage variable at each time step. We prove convergence of the method and show that discrete solutions approximate a semistable energetic solution of the rateindependent system. Moreover, we present our numerical results for two benchmark problems. 
M. Patriarca, P. Farrell, J. Fuhrmann, Th. Koprucki, M. Auf DER Maur, Highly accurate discretizations for nonBoltzmann charge transport in semiconductors, in: Proceedings of the 18th International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD 2018), A. Djurišić, J. Piprek, eds., IEEE Conference Publications Management Group, Piscataway, NJ, 2018, pp. 5354.

M. Liero, J. Fuhrmann, A. Glitzky, Th. Koprucki, A. Fischer, S. Reineke, Modeling and simulation of electrothermal feedback in largearea organic LEDs, in: Proceedings of the 17th International Conference on Numerical Simulation of Optoelectronic Devices  NUSOD 2017, J. Piprek, M. Willatzen, eds., IEEE Conference Publications Management Group, Piscataway, 2017, pp. 105106, DOI 10.1109/NUSOD.2017.8010013 .

N. Ahmed, A. Linke, Ch. Merdon, Towards pressurerobust mixed methods for the incompressible NavierStokes equations, in: Finite Volumes for Complex Applications VIII  Methods and Theoretical Aspects, FVCA 8, Lille, France, June 2017, C. Cancès, P. Omnes, eds., 199 of Springer Proceedings in Mathematics & Statistics, Springer International Publishing AG, Cham, 2017, pp. 351359.

P. Farrell, Th. Koprucki, J. Fuhrmann, Comparison of consistent flux discretizations for drift diffusion beyond Boltzmann statistics, in: Proceedings of the 17th International Conference on Numerical Simulation of Optoelectronic Devices  NUSOD 2017, J. Piprek, M. Willatzen, eds., IEEE Conference Publications Management Group, Piscataway, 2017, pp. 219220, DOI 10.1109/NUSOD.2017.8010070 .

J. Fuhrmann, A. Glitzky, M. Liero, Hybrid finitevolume/finiteelement schemes for p(x)Laplace thermistor models, in: Finite Volumes for Complex Applications VIII  Hyperbolic, Elliptic and Parabolic Problems, FVCA 8, Lille, France, June 2017, C. Cancès, P. Omnes, eds., 200 of Springer Proceedings in Mathematics & Statistics, Springer International Publishing AG, Cham, 2017, pp. 397405, DOI 10.1007/9783319573946_42 .

J. Fuhrmann, C. Guhlke, A finite volume scheme for NernstPlanckPoisson systems with Ion size and solvation effects, in: Finite Volumes for Complex Applications VIII  Hyperbolic, Elliptic and Parabolic Problems, FVCA 8, Lille, France, June 2017, C. Cancès, P. Omnes, eds., 200 of Springer Proceedings in Mathematics & Statistics, Springer International Publishing AG, Cham, 2017, pp. 497505, DOI 10.1007/9783319573946_52 .

M. Kantner, U. Bandelow, Th. Koprucki, H.J. Wünsche, Multiscale modelling and simulation of singlephoton sources on a device level, in: EuroTMCS II  Theory, Modelling & Computational Methods for Semiconductors, 7th  9th December 2016, Tyndall National Institute, University College Cork, Ireland, E. O'Reilly, S. Schulz, S. Tomic, eds., Tyndall National Institute, 2016, pp. 65.

S. Ganesan, V. John, G. Matthies, R. Meesala, A. Shamim, U. Wilbrandt, An object oriented parallel finite element scheme for computations of PDEs: Design and implementation, in: 2016 IEEE 23rd International Conference on High Performance Computing Workshops (PDF only), pp. 106115, DOI 10.1109/HiPCW.2016.19 .

G. Lazzaroni, R. Rossi, M. Thomas, R. Toader, Some remarks on a model for rateindependent damage in thermoviscoelastodynamics, in: MURPHYSHSFS2014: 7th International Workshop on MUltiRate Processes and HYSteresis (MURPHYS) & 2nd International Workshop on Hysteresis and SlowFast Systems (HSFS), O. Klein, M. Dimian, P. Gurevich, D. Knees, D. Rachinskii, S. Tikhomirov, eds., 727 of Journal of Physics: Conference Series, IOP Publishing, 2016, pp. 012009/1012009/20.
Abstract
This note deals with the analysis of a model for partial damage, where the rateindependent, unidirectional flow rule for the damage variable is coupled with the ratedependent heat equation, and with the momentum balance featuring inertia and viscosity according to KelvinVoigt rheology. The results presented here combine the approach from [Roubíček M2AS'09, SIAM'10] with the methods from Lazzaroni/Rossi/Thomas/Toader [WIAS Preprint 2025]. The present analysis encompasses, differently from [Roubíček SIAM'10], the monotonicity in time of damage and the dependence of the viscous tensor on damage and temperature, and, unlike [WIAS Preprint 2025], a nonconstant heat capacity and a timedependent Dirichlet loading. 
A. Caiazzo, J. Mura, A twoscale homogenization approach for the estimation of porosity in elastic media subject area, in: Trends in Differential Equations and Applications, F.O. Gallego, M.V. Redondo Neble, J.R.R. Galván, eds., 8 of SEMA SIMAI Springer Series, Springer International Publishing Switzerland, Cham, 2016, pp. 89105.

A. Mielke, Free energy, free entropy, and a gradient structure for thermoplasticity, in: Innovative Numerical Approaches for MultiField and MultiScale Problems. In Honor of Michael Ortiz's 60th Birthday, K. Weinberg, A. Pandolfi, eds., 81 of Lecture Notes in Applied and Computational Mechanics, Springer International Publishing Switzerland, Cham, 2016, pp. 135160.
Abstract
In the modeling of solids the free energy, the energy, and the entropy play a central role. We show that the free entropy, which is defined as the negative of the free energy divided by the temperature, is similarly important. The derivatives of the free energy are suitable thermodynamical driving forces for reversible (i.e. Hamiltonian) parts of the dynamics, while for the dissipative parts the derivatives of the free entropy are the correct driving forces. This difference does not matter for isothermal cases nor for local materials, but it is relevant in the nonisothermal case if the densities also depend on gradients, as is the case in gradient thermoplasticity.
Using the total entropy as a driving functional, we develop gradient structures for quasistatic thermoplasticity, which again features the role of the free entropy. The big advantage of the gradient structure is the possibility of deriving timeincremental minimization procedures, where the entropyproduction potential minus the total entropy is minimized with respect to the internal variables and the temperature.
We also highlight that the usage of an auxiliary temperature as an integrating factor in Yang/Stainier/Ortiz "A variational formulation of the coupled thermomechanical boundaryvalue problem for general dissipative solids" (J. Mech. Physics Solids, 54, 401424, 2006) serves exactly the purpose to transform the reversible driving forces, obtained from the free energy, into the needed irreversible driving forces, which should have been derived from the free entropy. This reconfirms the fact that only the usage of the free entropy as driving functional for dissipative processes allows us to derive a proper variational formulation. 
D. Peschka, Numerics of contact line motion for thin films, in: 8th Vienna International Conference on Mathematical Modelling  MATHMOD 2015, 48 of IFACPapersOnLine, Elsevier, 2015, pp. 390393.

W. Huang, L. Kamenski, J. Lang, Stability of explicit RungeKutta methods for high order finite element approximation of linear parabolic equations, in: Numerical Mathematics and Advanced Applications  ENUMATH 2013, A. Abdulle, S. Deparis, D. Kressner, F. Nobile, M. Picasso, eds., 103 of Lecture Notes in Computational Science and Engineering, Springer International Publishing, Cham [et al.], 2015, pp. 165173.
Abstract
We study the stability of explicit RungeKutta methods for high order Lagrangian finite element approximation of linear parabolic equations and establish bounds on the largest eigenvalue of the system matrix which determines the largest permissible time step. A bound expressed in terms of the ratio of the diagonal entries of the stiffness and mass matrices is shown to be tight within a small factor which depends only on the dimension and the choice of the reference element and basis functions but is independent of the mesh or the coefficients of the initialboundary value problem under consideration. Another bound, which is less tight and expressed in terms of mesh geometry, depends only on the number of mesh elements and the alignment of the mesh with the diffusion matrix. The results provide an insight into how the interplay between the mesh geometry and the diffusion matrix affects the stability of explicit integration schemes when applied to a high order finite element approximation of linear parabolic equations on general nonuniform meshes. 
R.M. Arkhipov, M. Radziunas, A.G. Vladimirov, Theoretical analysis of the influence of external periodic forcing on nonlinear dynamics of passively modelocked semiconductor lasers, in: Proceedings of the XIV School Seminar Wave Phenomena in Inhomogeneous Media (Waves 2014), Section 9, Nonlinear dynamics and information systems (in electronic form and in Russian), 2014, pp. 36.

R.M. Arkhipov, M.V. Arkhipov, Modelocking in two section and single section lasers due to coherent interaction of light and matter in the gain and absorbing media, in: Proceedings of the XIV School Seminar Wave Phenomena in Inhomogeneous Media (Waves 2014), Section 3, Nonlinear and coherent optics (in electronic form and in Russian), 2014, pp. 4345.

TH. Koprucki, M. Kantner, J. Fuhrmann, K. Gärtner, On modifications of the ScharfetterGummel scheme for driftdiffusion equations with Fermilike statistical distribution functions, in: Proceedings of the 14th International Conference on Numerical Simulation of Optoelectronic Devices, NUSOD 2014, 14 September 2014, J. Piprek, J. Javaloyes, eds., IEEE Conference Publications Management Group, Piscataway, NJ, USA, 2014, pp. 155156.

A. Glitzky, A. Mielke, L. Recke, M. Wolfrum, S. Yanchuk, D2  Mathematics for optoelectronic devices, in: MATHEON  Mathematics for Key Technologies, M. Grötschel, D. Hömberg, J. Sprekels, V. Mehrmann ET AL., eds., 1 of EMS Series in Industrial and Applied Mathematics, European Mathematical Society Publishing House, Zurich, 2014, pp. 243256.

J. Fuhrmann, A. Linke, Ch. Merdon, Coupling of fluid flow and solute transport using a divergencefree reconstruction of the CrouzeixRaviart element, in: Finite Volumes for Complex Applications VII  Elliptic, Parabolic and Hyperbolic Problems  FVCA 7, Berlin, June 2014, J. Fuhrmann, M. Ohlberger, Ch. Rohde, eds., 78 of Springer Proceedings in Mathematics & Statistics, Springer International Publishing, Cham et al., 2014, pp. 587595.

K. Götze, Free fall of a rigid body in a viscoelastic fluid, in: Geophysical Fluid Dynamics, Workshop, February 1822, 2013, 10 of Oberwolfach Reports, Mathematisches Forschungsinstitut Oberwolfach, 2013, pp. 554556.

R.M. Arkhipov, M. Radziunas, A.G. Vladimirov, Numerical simulation of passively modelocked semiconductor lasers under dual mode optical injection regime, in: Proceedings of the Conference ICONO/LAT 2013 (Technical Digest on CD ROM), Section LAT01: SolidState Lasers, Materials and Applications, Russian Academy of Sciences, Moscow, 2013, pp. 111112.

R.M. Arkhipov, I. Babushkin, M.V. Arkhipov , Y.A. Tolmachev, Spectral and temporal characteristics of radiation from a periodic resonant medium excited at the superluminal velocity, in: Proceedings of the Conference ICONO/LAT 2013 (Technical Digest on CD ROM), Section LAT04: Diffractive Optics and Nanophotonics, Russian Academy of Sciences, Moscow, 2013, pp. 1415.

TH. Koprucki, K. Gärtner, Generalization of the ScharfetterGummel scheme, in: Proceedings of the 13th International Conference on Numerical Simulation of Optoelectronic Devices, NUSOD 2013, 1922 August 2013, J. Piprek, L. Chrostowski, eds., IEEE Conference Publications Management Group, Piscataway, NJ, USA, 2013, pp. 8586.

C. Carstensen, C. Merdon, J. Neumann, Aspects of guaranteed error control in CPDE, in: Numerical Solution of Partial Differential Equations: Theory, Algorithms, and Their Applications, O.P. Iliev, S.D. Margenov, P.D. Minev, P.S. Vassilevski, L.T. Zikatanov, eds., 45 of Springer Proceedings in Mathematics & Statistics, Springer, New York, 2013, pp. 103119.

A. Mielke, Gradient structures and dissipation distances for reactiondiffusion systems, in: Material Theory, Workshop, Dezember 1620, 2013, A. Desimone, S. Luckhaus, L. Truskinovsky, eds., 10 of Oberwolfach Reports, Mathematisches Forschungsinstitut Oberwolfach, 2013, pp. 34553458.

TH. Koprucki, K. Gärtner, Discretization scheme for driftdiffusion equations with strong diffusion enhancement, in: Proceedings of the 12th International Conference on Numerical Simulation of Optoelectronic Devices, NUSOD'12, J. Piprek, W. Lu, eds., IEEE Conference Publications Management Group, New Jersey, USA, 2012, pp. 103104.

A. Glitzky, J.A. Griepentrog, On discrete SobolevPoincaré inequalities for Voronoi finite volume approximations, in: Finite volumes for complex applications VI: Problems and perspectives, J. Fořt, J. Fürst, J. Halama, R. Herbin, F. Hubert, eds., Springer Proceedings in Mathematics 4, Springer, Heidelberg, 2011, pp. 533541.

S. Bartels, R. Müller, Die kalte Zunge, in: Besser als Mathe  Moderne angewandte Mathematik aus dem MATHEON zum Mitmachen, K. Biermann, M. Grötschel, B. LutzWestphal, eds., Reihe: Populär, Vieweg+Teubner, Wiesbaden, 2010, pp. 227235.

M. Jensen, R. Müller, Stable CrankNicolson discretisation for incompressible miscible displacement problems of low regularity, in: Numerical Mathematics and Advanced Applications 2009, Part 2, G. Kreiss, P. Lötstedt, A. Målqvist, M. Neytcheva, eds., Springer, Heidelberg et al., pp. 469477.
Abstract
In this article we study the numerical approximation of incompressible miscible displacement problems with a linearised CrankNicolson time discretisation, combined with a mixed finite element and discontinuous Galerkin method. At the heart of the analysis is the proof of convergence under low regularity requirements. Numerical experiments demonstrate that the proposed method exhibits secondorder convergence for smooth and robustness for rough problems. 
D. Turaev, A.G. Vladimirov, S. Zelik, Strong enhancement of interaction of optical pulses induced by oscillatory instability, in: CLEO/Europe and EQEC 2009 Conference Digest (Optical Society of America, 2009), poster EH.P.13 WED, 2009, pp. 11.

J. Fuhrmann, K. Gärtner, Modeling of twophase flow and catalytic reaction kinetics for DMFCs, in: Device and Materials Modeling in PEM Fuel Cells, S. Paddison, K. Promislow, eds., 113 of Topics in Applied Physics, Springer, Berlin/Heidelberg, 2009, pp. 297316.

H. Gajewski, J.A. Griepentrog, A. Mielke, J. Beuthan, U. Zabarylo, O. Minet, Image segmentation for the investigation of scatteredlight images when laseroptically diagnosing rheumatoid arthritis, in: Mathematics  Key Technology for the Future, W. Jäger, H.J. Krebs, eds., Springer, Heidelberg, 2008, pp. 149161.

M. Ehrhardt, J. Fuhrmann, A. Linke, E. Holzbecher, Mathematical modeling of channelporous layer interfaces in PEM fuel cells, in: Proceedings of FDFC2008  Fundamentals and Developments of Fuel Cell Conference 2008, Nancy, France, December 1012 (CD), 2008, pp. 8 pages.
Abstract
In proton exchange membrane (PEM) fuel cells, the transport of the fuel to the active zones, and the removal of the reaction products are realized using a combination of channels and porous diffusion layers. In order to improve existing mathematical and numerical models of PEM fuel cells, a deeper understanding of the coupling of the flow processes in the channels and diffusion layers is necessary.
After discussing different mathematical models for PEM fuel cells, the work will focus on the description of the coupling of the free flow in the channel region with the filtration velocity in the porous diffusion layer as well as interface conditions between them.
The difficulty in finding effective coupling conditions at the interface between the channel flow and the membrane lies in the fact that often the orders of the corresponding differential operators are different, e.g., when using stationary (Navier)Stokes and Darcy's equation. Alternatively, using the Brinkman model for the porous media this difficulty does not occur.
We will review different interface conditions, including the wellknown BeaversJosephSaffman boundary condition and its recent improvement by Le Bars and Worster. 
A. Mielke, Numerical approximation techniques for rateindependent inelasticity, in: Proceedings of the IUTAM Symposium on Theoretical, Computational and Modelling Aspects of Inelastic Media, B.D. Reddy, ed., 11 of IUTAM Bookseries, Springer, 2008, pp. 5363.

A. Mussot, M. Tlidi, E. Louvergneaux, G. Kozyref, A.G. Vladimirov, M. Taki, Removing modulational instabilities in low dispersion fiber cavities, in: 2007 European Conference on Lasers and ElectroOptics and the European Quantum Electronics Conference (CLEO® / EuropeIQEC) Conference Digest (oral presentation CD9WED), IEEE, 2007, pp. 11.

A.G. Vladimirov, D.V. Skryabin, M. Tlidi, Localized structures of light in nonlinear devices with intracavity photonic bandgap material, in: 2007 European Conference on Lasers and ElectroOptics and the European Quantum Electronics Conference (CLEO®/EuropeIQEC) Conference Digest (oral presentation IG4MON), IEEE, 2007, pp. 11.

U. Bandelow, H. Gajewski, R. Hünlich, Thermodynamic designed energy model, in: Proceedings of the IEEE/LEOS 3rd International Conference on Numerical Simulation of Semiconductor Optoelectronic Devices (NUSOD'03), J. Piprek, ed., 2003, pp. 3537.

H. Gajewski, H.Chr. Kaiser, H. Langmach, R. Nürnberg, R.H. Richter, Mathematical modelling and numerical simulation of semiconductor detectors, in: Mathematics  Key Technology for the Future. Joint Projects Between Universities and Industry, W. Jäger, H.J. Krebs, eds., Springer, Berlin [u.a.], 2003, pp. 355364.

R. Hünlich, G. Albinus, H. Gajewski, A. Glitzky, W. Röpke, J. Knopke, Modelling and simulation of power devices for highvoltage integrated circuits, in: Mathematics  Key Technology for the Future. Joint Projects Between Universities and Industry, W. Jäger, H.J. Krebs, eds., Springer, Berlin [u.a.], 2003, pp. 401412.

H. Gajewski, An application of eigenfunctions of $p$Laplacians to domain separation, in: Proceedings of Partial Differential Equations and Applications. A conference held in honor of the 70th birthday of Professor Jindřich Nečas, Olomouc, December 1317, 1999, Š. Nečasová, H. Petzeltová, N. Pokorný, A. Sequeira, eds., 126 of Math. Bohem., Academy of Sciences of the Czech Republic, Mathematical Institute, Prague, 2001, pp. 395401.
Preprints, Reports, Technical Reports

L. Ermoneit, B. Schmidt, Th. Koprucki, J. Fuhrmann, T. Breiten, A. Sala, N. Ciroth, R. Xue, L.R. Schreiber, M. Kantner, Optimal control of conveyormode spinqubit shuttling in a Si/SiGe quantum bus in the presence of charged defects, Preprint no. 3082, WIAS, Berlin, 2023, DOI 10.20347/WIAS.PREPRINT.3082 .
PDF (9473 kByte) 
A. Erhardt, D. Peschka, Ch. Dazzi, L. Schmeller, A. Petersen, S. Checa, A. Münch, B. Wagner, Modeling cellular selforganization in strainstiffening hydrogels, Preprint no. 3076, WIAS, Berlin, 2023, DOI 10.20347/WIAS.PREPRINT.3076 .
Abstract, PDF (14 MByte)
We develop a threedimensional mathematical model framework for the collective evolution of cell populations by an agentbased model (ABM) that mechanically interacts with the surrounding extracellular matrix (ECM) modeled as a hydrogel. We derive effective twodimensional models for the geometrical setup of a thin hydrogel sheet to study cellcell and cellhydrogel mechanical interactions for a range of external conditions and intrinsic material properties. We show that without any stretching of the hydrogel sheets, cells show the wellknown tendency to form long chains with varying orientations. Our results further show that external stretching of the sheet produces the expected nonlinear strainsoftening or stiffening response, with, however, little qualitative variation of the overall cell dynamics for all the materials considered. The behavior is remarkably different when solvent is entering or leaving from strain softening or stiffening hydrogels, respectively. 
D. Abdel, A. Glitzky, M. Liero, Analysis of a driftdiffusion model for perovskite solar cells, Preprint no. 3073, WIAS, Berlin, 2023, DOI 10.20347/WIAS.PREPRINT.3073 .
Abstract, PDF (541 kByte)
This paper deals with the analysis of an instationary driftdiffusion model for perovskite solar cells including FermiDirac statistics for electrons and holes and Blakemore statistics for the mobile ionic vacancies in the perovskite layer. The free energy functional is related to this choice of the statistical relations. Exemplary simulations varying the mobility of the ionic vacancy demonstrate the necessity to include the migration of ionic vacancies in the model frame. To prove the existence of weak solutions, first a problem with regularized state equations and reaction terms on any arbitrarily chosen finite time interval is considered. Its solvability follows from a time discretization argument and passage to the timecontinuous limit. Applying Moser iteration techniques, a priori estimates for densities, chemical potentials and the electrostatic potential of its solutions are derived that are independent of the regularization level, which in turn ensure the existence of solutions to the original problem. 
CH. Keller, J. Fuhrmann, M. Landstorfer, B. Wagner, A model framework for ion channels with selectivity filters based on continuum nonequilibrium thermodynamics, Preprint no. 3072, WIAS, Berlin, 2023, DOI 10.20347/WIAS.PREPRINT.3072 .
Abstract, PDF (7287 kByte)
A mathematical model framework to describe ion transport in nanopores is presented. The model is based on nonequilibrium thermodynamics and considers finite size effects, solvation phenomena as well as the electrical charges of membrane surfaces and channel proteins. Par ticular emphasis is placed on the consistent modelling of the selectivity filter in the pore. It is treated as an embedded domain in which the constituents can change their chemical properties. The diffusion process through the filter is governed by an independent diffusion coefficient and at the interfaces, de and resolvation reactions are introduced as Neumann interface conditions. The evolution of the molar densities is described by driftdiffusion equations, where the fluxes depend on the gradient of the chemical potentials and the electric force. The chemical potentials depend on the molar fractions and on the pressure in the electrolyte and accounts for solvation effects. The framework allows the calculation of currentvoltage relations for a variety of chan nel properties and ion concentrations. We compare our model framework to experimental results for calciumselective ion channels and show the general validity of our approach. Our parameter studies show that calcium and sodium currents are proportional to the surface charge in the se lectivity filter and to the diffusion coefficients of the ions. Moreover, they show that the negative charges inside the pore have a decisive influence on the selectivity of divalent over monovalent ions. 
L. Araujo, C. Lasser, B. Schmidt, FSSH2: Fewest Switches Surface Hopping with robust switching probability, Preprint no. 3071, WIAS, Berlin, 2023, DOI 10.20347/WIAS.PREPRINT.3071 .
Abstract, PDF (199 kByte)
This study introduces the FSSH2 scheme, a redefined and numerically stable adiabatic Fewest Switches Surface Hopping (FSSH) method. It reformulates the standard FSSH hopping probability without nonadiabatic coupling vectors and allows for numerical time integration with larger step sizes. The advantages of FSSH2 are demonstrated by numerical experiments for five different model systems in one and two spatial dimensions with up to three electronic states. 
Y. Hadjimichael, Ch. Merdon, M. Liero, P. Farrell, An energybased finitestrain model for 3D heterostructured materials and its validation by curvature analysis, Preprint no. 3064, WIAS, Berlin, 2023, DOI 10.20347/WIAS.PREPRINT.3064 .
Abstract, PDF (6517 kByte)
This paper presents a comprehensive study of the intrinsic strain response of 3D het erostructures arising from lattice mismatch. Combining materials with different lattice constants induces strain, leading to the bending of these heterostructures. We propose a model for nonlinear elastic heterostructures such as bimetallic beams or nanowires that takes into account local prestrain within each distinct material region. The resulting system of partial differential equations (PDEs) in Lagrangian coordinates incorporates a nonlinear strain and a linear stressstrain relationship governed by Hooke?s law. To validate our model, we apply it to bimetallic beams and hexagonal heteronanowires and perform numerical simulations using finite element methods (FEM). Our simulations ex amine how these structures undergo bending under varying material compositions and crosssectional geometries. In order to assess the fidelity of the model and the accuracy of simulations, we compare the calculated curvature with analytically derived formula tions. We derive these analytical expressions through an energybased approach as well as a kinetic framework, adeptly accounting for the lattice constant mismatch present at each compound material of the heterostructures. The outcomes of our study yield valuable insights into the behavior of strained bent heterostructures. This is particularly significant as the strain has the potential to influence the electronic band structure, piezoelectricity, and the dynamics of charge carriers. 
M. Demir, V. John, Pressurerobust approximation of the incompressible NavierStokes equations in a rotating frame of reference, Preprint no. 3058, WIAS, Berlin, 2023, DOI 10.20347/WIAS.PREPRINT.3058 .
Abstract, PDF (337 kByte)
A pressurerobust space discretization of the incompressible NavierStokes equations in a rotating frame of reference is considered. The discretization employs divergencefree, H1conforming mixed finite element methods like ScottVogelius pairs. An error estimate for the velocity is derived that tracks the dependency of the error bound on the coefficients of the problem, in particular on the angular velocity. Numerical examples illustrate the theoretical results. 
V. John, Ch. Merdon, M. Zainelabdeen, Augmenting the graddiv stabilization for TaylorHood finite elements with a vorticity stabilization, Preprint no. 3055, WIAS, Berlin, 2023, DOI 10.20347/WIAS.PREPRINT.3055 .
Abstract, PDF (2139 kByte)
The least squares vorticity stabilization (LSVS), proposed in Ahmed et al. for the ScottVogelius finite element discretization of the Oseen equations, is studied as an augmentation of the popular graddiv stabilized TaylorHood pair of spaces. An error analysis is presented which exploits the situation that the velocity spaces of ScottVogelius and TaylorHood are identical. Convectionrobust error bounds are derived under the assumption that the ScottVogelius discretization is well posed on the considered grid. Numerical studies support the analytic results and they show that the LSVSgraddiv method might lead to notable error reductions compared with the standard graddiv method. 
M. Heida, On the computation of high dimensional Voronoi diagrams, Preprint no. 3041, WIAS, Berlin, 2023, DOI 10.20347/WIAS.PREPRINT.3041 .
Abstract, PDF (553 kByte)
We investigate a recently implemented new algorithm for the computation of a Voronoi diagram in high dimensions and generalize it to N nodes in general or nongeneral position using a geometric characterization of edges merging in a given vertex. We provide a mathematical proof that the algorithm is exact, convergent and has computational costs of O(E*nn(N)), where E is the number of edges and nn(N) is the computational cost to calculate the nearest neighbor among N points. We also provide data from performance tests in the recently developed Julia package ,,HighVoronoi.jl”. 
K. Hopf, A. Jüngel, Convergence of a finite volume scheme and dissipative measurevaluedstrong stability for a hyperbolicparabolic crossdiffusion system, Preprint no. 3006, WIAS, Berlin, 2023, DOI 10.20347/WIAS.PREPRINT.3006 .
Abstract, PDF (444 kByte)
This article is concerned with the approximation of hyperbolicparabolic crossdiffusion systems modeling segregation phenomena for populations by a fully discrete finitevolume scheme. It is proved that the numerical scheme converges to a dissipative measurevalued solution of the PDE system and that, whenever the latter possesses a strong solution, the convergence holds in the strong sense. Furthermore, the “parabolic density part” of the limiting measurevalued solution is atomic and converges to its constant state for long times. The results are based on Young measure theory and a weakstrong stability estimate combining Shannon and Rao entropies. The convergence of the numerical scheme is achieved by means of discrete entropy dissipation inequalities and an artificial diffusion, which vanishes in the continuum limit. 
A. Alphonse, D. Caetano, A. Djurdjevac, Ch.M. Elliott, Function spaces, time derivatives and compactness for evolving families of Banach spaces with applications to PDEs, Preprint no. 2994, WIAS, Berlin, 2023, DOI 10.20347/WIAS.PREPRINT.2994 .
Abstract, PDF (527 kByte)
We develop a functional framework suitable for the treatment of partial differential equations and variational problems on evolving families of Banach spaces. We propose a definition for the weak time derivative that does not rely on the availability of a Hilbertian structure and explore conditions under which spaces of weakly differentiable functions (with values in an evolving Banach space) relate to classical SobolevBochner spaces. An AubinLions compactness result is proved. We analyse concrete examples of function spaces over timeevolving spatial domains and hypersurfaces for which we explicitly provide the definition of the time derivative and verify isomorphism properties with the aforementioned SobolevBochner spaces. We conclude with the proof of well posedness for a class of nonlinear monotone problems on an abstract evolving space (generalising the evolutionary pLaplace equation on a moving domain or surface) and identify some additional problems that can be formulated with the setting developed in this work. 
L. Schmeller, D. Peschka, Sharpinterface limits of CahnHilliard models and mechanics with moving contact lines, Preprint no. 2990, WIAS, Berlin, 2023, DOI 10.20347/WIAS.PREPRINT.2990 .
Abstract, PDF (5979 kByte)
We construct gradient structures for free boundary problems with moving capillary interfaces with nonlinear (hyper)elasticity and study the impact of moving contact lines. In this context, we numerically analyze how phasefield models converge to certain sharpinterface models when the interface thickness tends to zero. In particular, we study the scaling of the CahnHilliard mobility with certain powers of the interfacial thickness. In the presence of interfaces, it is known that the intended sharpinterface limit holds only for a particular range of powers However, in the presence of moving contact lines we show that some scalings that are valid for interfaces produce significant errors and the effective range of valid powers of the interfacial thickness in the mobility reduces. 
M. Heida, A. Sikorski, M. Weber, Consistency and order 1 convergence of cellcentered finite volume discretizations of degenerate elliptic problems in any space dimension, Preprint no. 2913, WIAS, Berlin, 2022, DOI 10.20347/WIAS.PREPRINT.2913 .
Abstract, PDF (601 kByte)
We study consistency of cellcentered finite difference methods for elliptic equations with degenerate coefficients in any space dimension $dgeq2$. This results in order of convergence estimates in the natural weighted energy norm and in the weighted discrete $L^2$norm on admissible meshes. The cells of meshes under consideration may be very irregular in size. We particularly allow the size of certain cells to remain bounded from below even in the asymptotic limit. For uniform meshes we show that the order of convergence is at least 1 in the energy seminorm, provided the discrete and continuous solutions exist and the continuous solution has $H^2$ regularity.
Talks, Poster

C. Cárcamo, Total pressurebased frequencydomain formulation and convergence analysis of Biot's poroelasticity equations with a new finite element stabilization, Minisymposium "Full and reducedorder modeling of multiphysics problems", WONAPDE 2024: Seventh Chilean Workshop on Numerical Analysis of Partial Differential Equations, Concepción, January 15  19, 2024, Universidad de Concepción, Barrio Universitario s/n, Region of BíoBío, Chile, January 16, 2024.

V. John, Finite element methods respecting the discrete maximum principle for convectiondiffusion equations, International Conference on 'Latest Advances in Computational and Applied Mathematics' (LACAM) 2024, February 21  24, 2024, Indian Institute of Science Education and Research Thiruvananthapuram, Kerala, India, February 21, 2024.

V. John, On using machine learning techniques for the numerical solution of convectiondiffusion problems, Seminartalk, Prof. Sashikumaar Ganesan, Indian Institute of Science Bangalore, Department of Computational and Data Sciences, Bangalore, India, February 13, 2024.

D. Abdel, N.E. Courtier, P. Farrell, Modelling and simulation of charge transport in Perovskite solar cells, SIAM Conference on Computational Science and Engineering (CSE23), Amsterdam, Netherlands, February 26  March 3, 2023.

CH. Keller, Continuumbased modeling of calciumselective ion channels, Conference on Mathematical Life Sciences, April 17  20, 2023, Universität Bonn, April 20, 2023.

CH. Keller, Mathematical modeling of biological ion channels, 93rd Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM), May 29  June 2, 2023, Technische Universität Dresden, May 31, 2023.

Y. Hadjimichael, Efficient implementation of implicit RungeKutta methods with downwindbiased operators., SIAM Conference on Computational Science and Engineering (CSE23), Minisymposium MS419 ``StructurePreserving TimeStepping Methods for Differential Equations", February 26  March 3, 2023, Society for Industrial and Applied Mathematic, Amsterdam, Netherlands, March 3, 2023.

Y. Hadjimichael, An energybased finitestrain constitutive model for bent heterostructured materials, GAMM 93rd Annual Meeting of the International Association of Applied Mathematics and Mechanics, May 30  June 2, 2023, Technische Universität Dresden, June 2, 2023.

M. Heida, Finite volumes for simulation of large molecules, Finite Volumes for Complex Applications (FVCA10), Strasbourg, France, October 30  November 3, 2023.

M. O'Donovan, Atomistic study of Urbach tail energies in (Al,Ga)N quantum well systems, 23rd International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD 2023), September 18  21, 2023, Politecnico di Torino, Italy, September 21, 2023.

M. O'Donovan, Impact of alloy disorder on carrier transport and recombination in (Al,Ga)Nbased UVC emitters, The 6th International Workshop on Ultraviolet Materials and Devices (IWUMD 2023), June 5  8, 2023, Metz Congrès Robert Schuman, France, June 7, 2023.

M. O'Donovan, Modeling random alloy fluctuations in carrier transport simulations of IIIN based light emitting diodes  Connecting atomistic tightbinding to driftdiffusion, 15th Annual Meeting Photonic Devices, March 29  31, 2023, ZuseInstitut Berlin, March 31, 2023.

D. Peschka, Multiscale limits of thinfilm models with moving support, In Search of Model Structures for Nonequilibrium Systems, April 24  28, 2023, Westfälische WilhelmsUniversität Münster, April 27, 2023.

D. Peschka, Multiscale limits of thinfilm models with moving support, Kolloquium des SFB 1114, Freie Universität Berlin, April 20, 2023.

D. Peschka, Sharpinterface limit of models with mechanics and contact lines, 10th International Congress on Industrial and Applied Mathematics (ICIAM 2023), Session 00247 ``Interfaces and Free Boundaries in Fluid Mechanics and Materials Science'', August 20  25, 2023, Waseda University, Tokyo, Japan, August 24, 2023.

D. Runge, Reduced basis approach for convectiondiffusion equations with nonlinear boundary reaction conditions, Finite Volumes for Complex Applications 10 (FVCA10), Université de Strasbourg, France, November 2, 2023.

D. Runge, Massconservative reduced basis approach for convectiondiffusion equations with nonlinear boundary reaction conditions, Leibniz MMS Days 2023, Leibniz Network "Mathematical Modeling and Simulation", Leibniz Institute for Agricultural Engineering and Bioeconomy Potsdam (ATB), Potsdam, April 18, 2023.

L. Schütz, M. Heida, M. Thomas, Materials with discontinuities on many scales, SCCS Days 2023 of the Collaborative Research Center  CRC 1114 ``Scaling Cascades in Complex Systems'', November 13  15, 2023.

M. Kniely, A thermodynamically correct framework for electroenergyreactiondiffusion systems, 22nd ECMI Conference on Industrial and Applied Mathematics, June 26  30, 2023, Wrocław University of Science and Technology, Poland, June 30, 2023.

M. Kniely, On a thermodynamically consistent electroenergyreactiondiffusion system, 93rd Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM 2023), Session 14 ``Applied Analysis'', May 30  June 2, 2023, Technische Universität Dresden, June 1, 2023.

M. Demir, Subgrid artificial viscosity modelling based defectdeferred correction method for fluidfluid interaction, 2023 International CMMSE conference and the Second conference on high performance computing (CHPC), July 3  8, 2023, Universidad de Cádiz, Spain, July 6, 2023.

M. Demir, Subgrid artificial viscosity modelling based defectdeferred correction method for fluidfluid interaction, European Conference on Numerical Mathematics and Advanced Applications (ENUMATH), September 4  8, 2023, Instituto Superior Técnico, Lisboa, Portugal, September 7, 2023.

K. Hopf, Normal form and the Cauchy problem for crossdiffusive mixtures, Workshop ``Variational Methods for Evolution'', December 3  8, 2023, Mathematisches Forschungsinstitut Oberwolfach, December 4, 2023.

K. Hopf, On crossdiffusive coupling of hyperbolicparabolic type, Variational and Geometric Structures for Evolution, October 9  13, 2023, Centro Internazionale per la Ricerca Matematica (CIRM), Levico Terme, Italy, October 13, 2023.

K. Hopf, Structure and approximation of crossdiffusive mixtures with incomplete diffusion, Universität Kassel, Fachbereich Mathematik und Naturwissenschaften, September 21, 2023.

K. Hopf, Structure, dynamics, and approximation of crossdiffusive mixtures with incomplete diffusion, Universität Hamburg, Fachbereich Mathematik, May 10, 2023.

K. Hopf, The Cauchy problem for multicomponent systems with strong crossdiffusion, Johannes GutenbergUniversität Mainz, Fachbereich Physik, Mathematik und Informatik, January 11, 2023.

M. Thomas, Damage in viscoelastic materials at finite strains, Workshop ``Variational Methods for Evolution'', December 3  8, 2023, Mathematisches Forschungsinstitut Oberwolfach, December 7, 2023.

M. Thomas, Some aspects of damage in nonlinearly elastic materials: From damage to delamination in nonlinearly elastic materials, Variational and Geometric Structures for Evolution, October 9  13, 2023, Università Commerciale Luigi Bocconi, Levico Terme, Italy, October 10, 2023.

M. Thomas, Approximating dynamic phasefield fracture with a firstorder formulation for velocity and stress, Nonlinear PDEs: Recent Trends in the Analysis of Continuum Mechanics, July 17  21, 2023, Universität Bonn, Hausdorff School for Advanced Studies in Mathematics, July 17, 2023.

M. Thomas, Approximating dynamic phasefield fracture with a firstorder formulation for velocity and stress, Seminar für Angewandte Mathematik, Technische Universität Dresden, June 5, 2023.

M. Thomas, Nonlinear fracture dynamics: Modeling, analysis, approximation, and applications, Presentation of project proposals in SPP 2256 ``Variational Methods for Predicting Complex Phenomena in Engineering Structures and Materials'', Bad Honnef, March 27, 2023.

A. Alphonse, Analysis of a quasivariational contact problem arising in thermoelasticity, European Conference on Computational Optimization (EUCCO), Session ``Nonsmooth Optimization'', September 25  27, 2023, Universität Heidelberg, September 25, 2023.

U. Bandelow, Laserdynamik  mathematische Modellierung, MBITechnikerschulung 2023, October 16, 2023, MaxBornInstitut, Wandlitz.

U. Bandelow, Modeling and simulation of semiconductor devices: From highpower lasers to quantum technologies, Winter School on IIISb Applications: NonVolatile Memories  A Modelling Perspective, February 27  March 3, 2023, Technische Universität Berlin, February 27, 2023.

U. Bandelow, Ultrashort solitons in the regime of event horizons in nonlinear optical media, Extreme Waves 2023, August 28  September 1, 2023, MaxPlanckInstitut für Physik komplexer Systeme, Dresden, August 29, 2023.

U. Bandelow, Unusual scenarios in the context of the modulation instability, Dissipative Solitons, Turbulence and Extreme Events in Nonlinear Photonics, September 6  8, 2023, International Solvay Institutes, Brussels, Belgium, September 7, 2023.

U. Bandelow, Unusual wavemixing processes in the context of the modulation instability, XIX International Workshop on Instabilities and Nonequilibrium Structures  INES 2023, December 4  8, 2023, Pontificia Universidad Catolica de Valparaiso, Chile, December 7, 2023.

A. Caiazzo, Multiscale and reducedorder modeling for poroelasticity, European Conference on Numerical Mathematics and Advanced Applications (ENUMATH), September 4  8, 2023, Instituto Superior Técnico, Lisboa, Portugal.

P. Farrell, Modeling and numerical simulation of twodimensional TMDC memristive devices, 10th International Congress on Industrial and Applied Mathematics (ICIAM 2023), Tokyo, Japan, August 20  25, 2023.

P. Farrell, Modeling and numerical simulation of twodimensional memristive devices, 22nd European Consortium for Mathematics in Industry (ECMI) Conference on Industrial and Applied Mathematics, June 26  30, 2023, Wrocław University of Science and Technology, Poland.

P. Farrell, Device physics characterization and interpretation in perovskite and organic materials (DEPERO), October 3  5, 2023, Eidgenössische Technische Hochshcule Zürich, nanoGe, Switzerland.

J. Fuhrmann, Thermodynamically consistent finite volume schemes for electrolyte simulations, 10th International Congress on Industrial and Applied Mathematics (ICIAM 2023), August 20  25, 2023, Waseda University, Tokyo, Japan, August 22, 2023.

J. Fuhrmann, Two entropic finite volume schemes for a NernstPlanckPoisson system with ion volume constraints, Finite Volumes for Complex Applications 10 (FVCA10), Université de Strasbourg, France, November 1, 2023.

J. Fuhrmann, Voronoi finite volume methods for complex applications in Julia, International Conference on Numerical Analysis of Partial Differential Equations (ANEDP 2023), October 16  18, 2023, Moulay Ismail University, Faculty of Sciences, Meknes, Morocco.

V. John, On slope limiters in discontinuous Galerkin discretizations of convectiondiffusion problems, European Conference on Numerical Mathematics and Advanced Applications (ENUMATH), Minisymposium MS06 ' 'Theoretical and computational aspects of the discontinuous Galerkin method' ', September 4  8, 2023, Instituto Superior Técnico, Lisboa, Portugal, September 5, 2023.

V. John, Finite element methods respecting the discrete maximum principle for convectiondiffusion equations I, 19th Workshop on Numerical Methods for Problems with Layer Phenomena, Charles University, Faculty of Mathematics and Physics, Department of Numerical Mathematics, Prague, Czech Republic, May 26, 2023.

V. John, On recent topics in the finite element analysis of convectiondiffusion problems (online talk), Numerical Analysis Seminar (Hybrid Event), University of Waterloo, Applied Mathematics, Canada, April 11, 2023.

M. Liero, Variational modeling of biomechanical systems, 10th International Conference on Computational Bioengineering (ICCB 2023), Minisymposium 223 ``Continuum Biomechanics of Active Biological Systems'', September 20  22, 2023, Technische Universität Wien, Austria, September 22, 2023.

CH. Merdon, Gradientrobust hybrid discontinuous Galerkin discretizations for the compressible Stokes equations, Forschungsseminar von Prof. Carsten Carstensen, HumboldtUniversität zu Berlin, Institut fuer Mathematik, October 17, 2023.

CH. Merdon, RaviartThomas enriched ScottVogelius finite element methods for the NavierStokes equations (online talk), City University of Hong Kong, Department of Mathematics, Hong Kong, January 18, 2023.

CH. Merdon, RaviartThomas enriched ScottVogelius FEM for the NavierStokes equations, Capita Selecta Seminar, SACS  Systems, Analysis and Computational Sciences, Department of Mathematics University of Twente (DAMUT), Enschede, Netherlands, May 10, 2023.

CH. Merdon, RaviartThomas enriched ScottVogelius finite element methods for the NavierStokes equations, GAMM 93rd Annual Meeting of the International Association of Applied Mathematics and Mechanics, May 30  June 2, 2023, Technische Universität Dresden, June 2, 2023.

CH. Merdon, RaviartThomasenriched ScottVogelius finite element methods for the Stokes equations on general meshes, The 29th Biennial Numerical Analysis Conference 2023, June 27  30, 2023, University of Strathclyde, Department of Mathematics and Statistics, Glasgow, UK, June 27, 2023.

O. Pártl, A computational framework for sustainable geothermal energy production in fracturecontrolled reservoir based on well placement optimization, Leibniz MMS Days 2023, Potsdam, April 17, 2023.

O. Pártl, Finite element methods respecting the discrete maximum principle for convectiondiffusion equations III, 19th Workshop on Numerical Methods for Problems with Layer Phenomena, Charles University, Faculty of Mathematics and Physics, Department of Numerical Mathematics, Prague, Czech Republic, May 26, 2023.

O. Pártl, Reconstruction of flow domain boundaries from velocity data via multistep optimization of distributed resistance, European Conference on Numerical Mathematics and Advanced Applications (ENUMATH), September 4  8, 2023, Instituto Superior Técnico, Lisboa, Portugal.

A. Stephan, On timesplitting methods for gradient flows with two dissipation mechanisms, In Search of Model Structures for Nonequilibrium Systems, April 24  28, 2023, Westfälische WilhelmsUniversität Münster, April 28, 2023.

CH. Keller, J. Fuhrmann, M. Landstorfer, B. Wagner, Development of an ionchannel modelframework for invitro assisted interpretation of current voltage relations, MATH+Day 2022, Technische Universität Berlin, November 18, 2022.

A. Maltsi, Symmetries in TEM images of strained crystals, ``European Women in Mathematics'' General Meeting 2022, Espoo, Finland, August 22  26, 2022.

A. Maltsi, Symmetries in TEM images of strained crystals, BMSBGSMath Junior Meeting, September 5  7, 2022, Universidad de Barcelona, Spain, September 6, 2022.

A. Alphonse, Directional differentiability and optimal control for quasivariational inequalities (online talk), ``Partial Differential Equations and their Applications'' Seminar, University of Warwick, Mathematics Institute, UK, January 25, 2022.

R. Müller, Nonequilibrium thermodynamics modeling of polycrystalline electrode liquid electrolyte interface, 31st Topical Meeting of the International Society of Electrochemistry, Meeting topic: ``Theory and Computation in Electrochemistry: Seeking Synergies in Methods, Materials and Systems'', Session 2: ``Theory and Computation of Interfacial and Nanoscale Phenomena'', May 15  19, 2022, RheinischWestfälische Technische Hochschule Aachen, May 17, 2022.

D. Peschka, Discretization of compressible Stokes flow using Hamiltonian and Onsager structures, Workshop on Numerical Methods and Analysis in CFD, July 5  8, 2022, WIAS Berlin, July 5, 2022.

D. Peschka, Gradient flows coupling order parameters and mechanics (online talk), Colloquium of the SPP 2171 (Online Event), Westfälische WilhelmsUniversität Münster, October 21, 2022.

D. Peschka, Steering the pattern formation of dewetting liquids (online talk), SFB 910 Symposium ``Pattern formation and coherent structure in dissipative systems'' (Online Event), Technische Universität Berlin, January 14, 2022.

A. Selahi, Homogenization in PDEbased battery models and recovery of ageing dynamics via Bayesian inference (online talk), Second Conference of Young Applied Mathematicians (Hybrid Event), September 18  22, 2022, Arenzano, Italy, September 21, 2022.

P. Vágner, Capacitance of the blocking YSZ I Au electrode, 18th Symposium on Modeling and Experimental Validation of Electrochemical Energy Technologies, March 14  16, 2022, DLR Institut für Technische Thermodynamik, Hohenkammer, March 16, 2022.

J. Sprekels, Deep quench approach and sparsity in the optimal control of a phase field model for tumor growth, PHAse field MEthods in applied sciences (PHAME 2022), May 23  27, 2022, Istituto Nazionale di Alta Matematica, Rome, Italy, May 27, 2022.

K. Hopf, Relative entropies and stability in strongly coupled parabolic systems (online talk), SIAM Conference on Analysis of Partial Differential Equations (PD22) (Online Event), Minisymposium ``Variational Evolution: Analysis and MultiScale Aspects'', March 14  18, 2022, March 16, 2022.

M. Thomas, Firstorder formulation for dynamic phasefield fracture in viscoelastic materials, PHAse field MEthods in applied sciences (PHAME 2022), May 23  27, 2022, Istituto Nazionale di Alta Matematica, Rome, Italy, May 25, 2022.

M. Thomas, Firstorder formulation for dynamic phasefield fracture in viscoelastic materials, Beyond Elasticity: Advances and Research Challenges, May 16  20, 2022, Centre International de Rencontres Mathématiques, Marseille, France, May 16, 2022.

TH. Eiter, Energyvariational solutions for a viscoelastoplastic fluid model (online talk), SIAM Conference on Analysis of Partial Differential Equations (PD22) (Online Event), Minisymposium ``Generalized Solvability Concepts for Evolutionary PDEs and their Properties'', March 14  18, 2022, March 16, 2022.

P. Farrell, Challenges for nonBoltzmann driftdiffusion charge transport simulations in semiconductors, International Conference on Boundary and Interior Layers, November 28  December 2, 2022, Universidad de Buenos Aires, Argentina, December 1, 2022.

P. Farrell, Datadriven solutions of illposed inverse problems arising from doping reconstruction in semiconductors, AI4Science 2022 : AI for Science, NASSMA Workshop, Rabat, Morocco, December 12  16, 2022.

M. Landstorfer, A. Selahi, M. Heida, M. Eigel, Recovery of battery ageing dynamics with multiple timescales, MATH+Day 2022, Technische Universität Berlin, November 18, 2022.

M. Liero, From diffusion to reactiondiffusion in thin structures via EDPconvergence (online talk), SIAM Conference on Analysis of Partial Differential Equations (PD22) (Online Event), Minisymposium ``Bridging Gradient Flows, Hypocoercivity and ReactionDiffusion Systems'', March 14  18, 2022, March 14, 2022.

M. Liero, Modeling, analysis, and simulation of electrothermal feedback in organic devices, Audit 2022, September 22  23, 2022, WeierstraßInstitut Berlin, September 22, 2022.

M. Liero, The impact of modeling, analysis, and simulation on organic semiconductor development (online talk), ERCOM Meeting 2022 (Hybrid Event), March 25  26, 2022, European Research Centers on Mathematics, Bilbao, Spain, March 26, 2022.

A. Mielke, On the existence and longtime behavior of solutions to a degenerate parabolic system (online talk), SIAM Conference on Analysis of Partial Differential Equations (PD22) (Online Event), Minisymposium MS43: ``Nonlinear Parabolic Equations and Systems'', March 14  18, 2022, March 16, 2022.

D. Abdel, P. Vágner, J. Fuhrmann, P. Farrell, Modeling and simulation of charge transport in perovskite solar cells, AMaSiS 2021: Applied Mathematics and Simulation for Semiconductors and Electrochemical Systems (Online Event), September 6  9, 2021.

D. Abdel, P. Vágner, J. Fuhrmann, P. Farrell, Modelling charge transport in perovskite solar cells: Potentialbased and limiting ion depletion, SIAM Conference on Computational Science and Engineering  CSE21 (Online Event), Texas, USA, March 1  5, 2021.

A. Maltsi, Modelbased geometry reconstruction of TEM images, MATH+ Day 2021 (Online Event), Technische Universität Berlin, November 5, 2021.

A. Maltsi, On the DarwinHowieWhelan equations in TEM imaging (online talk), Young Women in PDEs and Applications (Online Event), September 20  22, 2021, Universität Bonn, September 22, 2021.

A. Maltsi, Quantum dots and TEM images from a mathematician's perspective, Women in Mathematics Webinar (Online Event), UK, February 11  12, 2021.

M.H. Farshbaf Shaker, D. Peschka, M. Thomas, B. Wagner, Variational methods for viscoelastic flows and gelation, MATH+ Day 2021 (Online Event), Technische Universität Berlin, November 5, 2021.

M. Landstorfer, Modeling of concentration and electric field dependent susceptibilities in electrolytes (online talk), AA2  Materials, Light, Devices, Freie Universität Berlin, HumboldtUniversität zu Berlin, WIAS Berlin, February 26, 2021.

O. Marquardt, Modelling the electronic properties of semiconductor nanowire heterostructures (online talk), PDISeminar, PaulDrudeInstitut für Festkörperelektronik, August 23, 2021.

L. Mertenskötter, M. Kantner, H. Wenzel , U. Bandelow, Modeling and optimization of semiconductor lasers for quantum metrology applications, MATH+ Day 2021 (Online Event), Technische Universität Berlin, November 5, 2021.

R. Müller, Modeling polycrystalline electrodeelectrolyte interfaces: The differential capacitance (online talk), 14th Virtual Congress WCCM & ECCOMAS 2020, January 11  15, 2021, January 11, 2021.

D. Peschka, Mathematical modeling and simulation of substrateflow interaction using generalized gradient flows, Conference ``Dynamic Wetting of Flexible, Adaptive, and Switchable Substrates'' of the SPP 2171, Freiburg, November 8  10, 2021.

D. Peschka, Mathematical modeling and simulation of substrateflow interaction using generalized gradient flows, SPP 2171 Conference ``Dynamic Wetting of Flexible, Adaptive, and Switchable Substrates'', November 8  10, 2021, AlbertLudwigsUniversität Freiburg, November 10, 2021.

A. Zafferi, Coupling of thermoviscoelastic solids and reactive flows via GENERIC (online talk), CRC 1114 Conference 2021 (Online Event), MSDI4: ``Modeling and Analysis of Geological Fluid Flows'', March 1  3, 2021, Freie Universität Berlin, March 2, 2021.

A. Zafferi, Dynamics of rock dehydration on multiple scales, CRC 1114 Conference 2021 (Online Event), March 1  3, 2021.

A. Zafferi, Thermodynamics of reactiondiffusioninduced rock dehydration processes (online talk), 16thJoint European Thermodynamics Conference (Hybrid Event), June 14  18, 2021, Charles University Prague, Czech Republic, June 16, 2021.

B. Gaudeul, J. Fuhrmann, Two entropic finite volume schemes for a NernstPlanckPoisson system with ion volume constraints, AMaSiS 2021: Applied Mathematics and Simulation for Semiconductors and Electrochemical Systems (Online Event), September 6  9, 2021.

A. Glitzky, A coarsegrained electrothermal model for organic semiconductor devices (online talk), DMVÖMG Jahrestagung 2021 (Online Event), September 27  October 1, 2021, Universität Passau, September 29, 2021.

M. Thomas, Convergence analysis for fully discretized damage and phasefield fracture models (online talk), 15th International Conference on Free Boundary Problems: Theory and Applications 2021 (FBP 2021, Online Event), Minisymposium ``Phase Field Models'', September 13  17, 2021, WIAS, Berlin, September 14, 2021.

M. Thomas, GENERIC structures with bulkinterface interaction (online talk), 16th Joint European Thermodynamics Conference (Hybrid Event), June 14  18, 2021, Charles University Prague, Czech Republic, June 17, 2021.

U. Bandelow, Modeling and simulation of the dynamics in semiconductor lasers (online talk), 91st Annual Meeting of the International Association of Applied Mathematics and Mechanics, MS1: ``Computational Photonics''' (Online Event), March 15  19, 2021, Universität Kassel, March 16, 2021.

U. Bandelow , Ultrashort solitons in the regime of event horizons in nonlinear dispersive optical media, Solvay Workshop on Dissipative Solitons and Optical Frequency Comb Generation, September 15  16, 2021, International Solvay Institutes, Brussels, Belgium, September 16, 2021.

P.E. Druet, Modeling and analysis for multicomponent incompressible fluids (online talk), 8th European Congress of Mathematics (8ECM), Minisymposium ID 51 ``Partial Differential Equations describing FarfromEquilibrium Open Systems'' (Online Event), June 20  26, 2021, Portorož, Slovenia, June 23, 2021.

P.E. Druet, Wellposedness results for mixedtype systems modelling pressuredriven multicomponent fluid flows (online talk), 8th European Congress of Mathematics (8ECM), Minisymposium ID 42 ``Multicomponent Diffusion in Porous Media'' (Online Event), June 20  26, 2021, Portorož, Slovenia, June 22, 2021.

M. Hintermüller, Semismooth Newton methods: Theory, numerical algorithms and applications I (online talk), International Forum on Frontiers of Intelligent Medical Image Analysis and Computing 2021 (Online Forum), Xidian University, Southeastern University, and Hong Kong Baptist University, China, July 19, 2021.

M. Hintermüller, Semismooth Newton methods: Theory, numerical algorithms and applications II (online talk), International Forum on Frontiers of Intelligent Medical Image Analysis and Computing 2021 (Online Forum), Xidian University, Southeastern University, and Hong Kong Baptist University, China, July 26, 2021.

O. Marquardt, Datadriven electronic structure calculations for semiconductor nanostructures, Efficient Algorithms for Numerical Problems, January 17, 2020, WIAS Berlin, January 17, 2020.

G. Nika, An existence result for a class of electrothermal driftdiffusion models with FermiGauss statistics for organic semiconductors, Joint Mathematics Meeting, January 15  18, 2020, American Mathematical Society/ Mathematical Association of America, Denver, USA, January 15, 2020.

D. Peschka, Mathematical modeling and simulation of flows and the interaction with a substrate using energetic variational methods, CRC 1194 ``Interaction between Transport and Wetting Processes'', Technische Universität Darmstadt, January 22, 2020.

A. Zafferi, K. Huber, C09  Dynamics of rock dehydration (online talk), SCCS Days 2020 of the Collaborative Research Center  CRC 1114 ``Scaling Cascades in Complex Systems'', December 2  4, 2020, Freie Universität Berlin, December 3, 2020.

A. Zafferi, K. Huber, Dynamics of rock dehydration, CRC 1114: Scaling Cascades in Complex Systems (SCCS Days) (Online Event), December 2  4, 2020.

N. Dropka , P. Farrell, S. Kayser, N. Rotundo, Numerics for innovative semiconductor devices  An outlook, German Conference on Crystal Growth, Munich, March 11  13, 2020.

M.H. Farshbaf Shaker, D. Peschka, M. Thomas, Modeling and analysis of suspension flows, MATH+ Day 2020 (Online Event), Berlin, November 6, 2020.

C. Cancès, C. ChainaisHillairet, J. Fuhrmann, B. Gaudeul, On four numerical schemes for a unipolar degenerate driftdiffusion model, Finite Volumes for Complex Applications IX (Online Event), Bergen, Norway, June 15  19, 2020.

K. Hopf, Global existence analysis of energyreactiondiffusion systems, Workshop ``Variational Methods for Evolution'', September 13  19, 2020, Mathematisches Forschungsinstitut Oberwolfach, September 15, 2020.

M. Thomas, Nonlinear fracture dynamics: Modeling, analysis, approximation, and applications, Presentation of project proposals in SPP 2256 ``Variational Methods for Predicting Complex Phenomena in Engineering Structures and Materials'', Bad Honnef, January 30, 2020.

M. Thomas, Thermodynamical modelling via energy and entropy functionals (online talks), Thematic Einstein Semester on Energybased Mathematical Methods for Reactive Multiphase Flows: Student Compact Course ``Variational Methods for Fluids and Solids'' (Online Event), October 12  23, 2020, WIAS Berlin.

M. Thomas, WeierstraßGruppe "VolumenGrenzschichtProzesse", Sitzung des Wissenschaftlichen Beirats, WIAS Berlin, September 18, 2020.

B. Wagner, Pattern formation in dewetting films (online talk), Workshop ``Mathematical Modeling and Scientific Computing: Focus on Complex Processes and Systems'' (Online Event), November 19  20, 2020, Technische Universität München, November 19, 2020.

B. Wagner, Phasefield models of the lithiation/delithiation cycle of thinfilm electrodes (online talk), Oxford Battery Modelling Symposium (Online Event), March 16  17, 2020, University of Oxford, UK, March 16, 2020.

P. Farrell, D. Peschka, Challenges in driftdiffusion semiconductor simulations, Finite Volumes for Complex Applications IX (Online Event), Bergen, Norway, June 15  19, 2020.

J. Fuhrmann, D.H. Doan, A. Glitzky, M. Liero, G. Nika, Unipolar driftdiffusion simulation of Sshaped currentvoltage relations for organic semiconductor devices, Finite Volumes for Complex Applications IX (Online Event), Bergen, Norway, June 15  19, 2020.

J. Fuhrmann, C. Guhlke, M. Landstorfer, A. Linke, Ch. Merdon, R. Müller, Quality preserving numerical methods for electroosmotic flow, Einstein Semester on Energybased Mathematical Methods for Reactive Multiphase Flows: Kickoff Conference (Online Event), October 26  30, 2020.

M. Kantner, Nonisothermal ScharfetterGummel scheme for electrothermal transport simulation in degenerate semiconductors, Finite Volumes for Complex Applications IX (Online Event), June 15  19, 2020, University of Bergen, Bergen, Norway, June 16, 2020, DOI 10.1007/9783030436513_14 .

M. Kantner, Nonisothermal ScharfetterGummel scheme for electrothermal transport simulation in degenerate semiconductors (online talk), Finite Volumes for Complex Applications IX (Online Event), June 15  19, 2020, NORCE  Norwegian Research Centre, Bergen, Norway, June 16, 2020.

TH. Koprucki, K. Tabelow, T. Streckenbach, T. Niermann, A. Maltsi, Modelbased geometry reconstruction of TEM images, MATH+ Day 2020 (Online Event), Berlin, November 6, 2020.

R. Lasarzik, Dissipative solutions in the context of the numerical approximation of nematic electrolytes (online talk), Oberseminar Numerik, Universität Bielefeld, Fakultät für Mathematik, June 23, 2020.

M. Liero, Driftdiffusion simulation of Sshaped currentvoltage relations for organic semiconductor devices (online talk), SimOEP 2020: International Conference on Simulation of Organic Electronics and Photovoltaics (Online Event), August 31  September 2, 2020, Zürcher Hochschule für Angewandte Wissenschaften, Switzerland, September 1, 2020.

A. Linke, Ch. Merdon, On highorder pressurerobust space discretisations, their advantages for incompressible high Reynolds number generalised Beltrami flows and beyond, Einstein Semester on Energybased Mathematical Methods for Reactive Multiphase Flows: Kickoff Conference (Online Event), Berlin, October 26  30, 2020.

A. Linke, Ch. Merdon, On the significance of pressurerobustness for the space discretization of incompressible high Reynolds number flows, Finite Volumes for Complex Applications IX (Online Event), Bergen, Norway, June 15  19, 2020.

H. Si, Adaptive exponential time integration of the NavierStokes equations, 3rd AIAA Sonic Boom Prediction Workshop, January 5  10, 2020, American Institute of Aeronautics and Astronautics SciTech Forum, Orlando, Florida, USA, January 10, 2020.

A. Maltsi, Th. Koprucki, T. Streckenbach, K. Tabelow, J. Polzehl, Modelbased geometry reconstruction of quantum dots from TEM, Microscopy Conference 2019, Poster session IM 4, Berlin, September 1  5, 2019.

A. Maltsi, Th. Koprucki, T. Streckenbach, K. Tabelow, J. Polzehl, Modelbased geometry reconstruction of quantum dots from TEM, BMS Summer School 2019: Mathematics of Deep Learning, Berlin, August 19  30, 2019.

A. Alphonse, Directional differentiability for elliptic quasivariational inequalities, Workshop ``Surface, Bulk, and Geometric Partial Differential Equations: Interfacial, Stochastic, Nonlocal and Discrete Structures'', January 20  26, 2019, Mathematisches Forschungsinstitut Oberwolfach, January 25, 2019.

A. Alphonse, Directional differentiability for elliptic quasivariational inequalities, ICCOPT 2019  Sixth International Conference on Continuous Optimization, Best Paper Session, August 5  8, 2019, Berlin, August 5, 2019.

M. Heida, Convergences of the squareroot approximation scheme to the FokkerPlanck operator, ``9th International Congress on Industrial and Applied Mathematics" (ICIAM 2019), July 15  19, 2019, Universitat de València, Spain, July 17, 2019.

M. Kantner, A generalized ScharfetterGummel scheme for degenerate and nonisothermal semiconductors, 19th International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD), July 8  12, 2019, University of Ottawa, Canada, July 8, 2019.

M. Kantner, Devicescale simulation of quantum light emitting diodes, International Symposium ,,Semiconductor Nanophotonics'', November 4  5, 2019, Technische Universität Berlin, November 4, 2019.

M. Kantner, Hybrid modeling of quantum light emitting diodes: Selfconsistent coupling of driftdiffusion, SchrödingerPoisson, and quantum master equations, SPIE Photonics West, February 5  7, 2019, San Francisco, USA, February 6, 2019, DOI 10.1117/12.2515209 .

M. Kantner, Simulation of quantum dot based singlephoton sources using the SchrödingerPoissonDriftDiffusionLindblad system, International Conference on Simulation of Semiconductor Processes and Devices (SISPAD 2019), September 4  6, 2019, Università degli Studi di Udine, Italy, September 6, 2019.

M. Kantner, Simulation of quantum light sources using the selfconsistently coupled SchrödingerPoissonDriftDiffusionLindblad system, 19th International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD), July 8  12, 2019, University of Ottawa, Canada, July 8, 2019.

T. Keil, Optimal control of a coupled CahnHilliardNavierStokes system with variable fluid densities, ICCOPT 2019  Sixth International Conference on Continuous Optimization, Session ``Optimal Control of Phase Field Models'', August 5  8, 2019, Berlin, August 5, 2019.

R. Müller, Transport of solvated ions in nanopores: Modeling, asymptotics and simulation, Conference to celebrate the 80th jubilee of Miroslav Grmela, May 18  19, 2019, Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prag, Czech Republic, May 18, 2019.

R. Müller, Transport phenomena in electrolyte within a battery cell, Battery Colloquium, Technische Universität Berlin, April 18, 2019.

G. Nika, An existence result for a class of electrothermal driftdiffusion models with GaussFermi statistics for organic semiconductors, DMVJahrestagung 2019, September 23  26, 2019, KIT  Karlsruher Institut für Technologie.

G. Nika, Homogenization for a multiscale model of magnetorheological suspension, 9th International Congress on Industrial and Applied Mathematics (ICIAM 2019), Minisymposium MS ME13 1 ``Emerging Problems in the Homogenization of Partial Differential Equations'', July 15  19, 2019, Valencia, Spain, July 15, 2019.

D. Peschka, Dynamic contact angles via generalized gradient flows, Modelling of Thin Liquid Films  Asymptotic Approach vs. Gradient Dynamics, April 28  May 3, 2019, Banff International Research Station for Mathematical Information and Discovery, Canada, April 30, 2019.

D. Peschka, Dynamic contact angles via gradient flows, 694. WEHeraeusSeminar ``Wetting on Soft or Microstructured Surfaces'', Bad Honnef, April 10  13, 2019.

D. Peschka, Gradient formulations with flow maps  Mathematical and numerical approaches to free boundary problems, Kolloquium des Graduiertenkollegs 2339 ``Interfaces, Complex Structures, and Singular Limits'', Universität Regensburg, May 24, 2019.

D. Peschka, Gradient structures for flows of concentrated suspensions  jamming and free boundaries, 90th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM 2019), Section S11 ``Interfacial Flows", February 18  22, 2019, Technische Universität Wien, Austria, February 20, 2019.

D. Peschka, Mathematical modeling of fluid flows using gradient systems, Seminar in PDE and Applications, Delft University of Technology, Netherlands, May 28, 2019.

D. Peschka, Steering pattern formation of viscous flows, DMVJahrestagung 2019, Sektion ``Differentialgleichungen und Anwendungen'', September 23  26, 2019, KIT  Karlsruher Institut für Technologie, September 23, 2019.

D. Peschka, ``Numerical methods for charge transport in semiconductors: FEM vs FV", 9th International Congress on Industrial and Applied Mathematics (ICIAM 2019), July 15  19, 2019, Valencia, Spain, July 17, 2019.

A. Zafferi, An approach to multiphase flows in geosciences, MURPHYSHSFS 2019 Summer School on MultiRate Processes, SlowFast Systems and Hysteresis, Turin, Italy, June 17  21, 2019.

A. Glitzky, Driftdiffusion problems with GaussFermi statistics and fielddependent mobility for organic semiconductor devices, 90th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM 2019), Section S14 ``Applied Analysis'', February 18  22, 2019, Universität Wien, Technische Universität Wien, Austria, February 22, 2019.

K. Hopf, On the singularity formation and relaxation to equilibrium in 1D FokkerPlanck model with superlinear drift, Gradient Flows and Variational Methods in PDEs, November 25  29, 2019, Universität Ulm, November 25, 2019.

M. Thomas, Analysis for the discrete approximation of gradientregularized damage models, Mathematics Seminar Brescia, Università degli Studi di Brescia, Italy, March 13, 2019.

M. Thomas, Analysis for the discrete approximation of gradientregularized damage models, PDE Afternoon, Universität Wien, Austria, April 10, 2019.

M. Thomas, Analytical and numerical aspects for the approximation of gradientregularized damage models, 9th International Congress on Industrial and Applied Mathematics (ICIAM 2019), Thematic Minisymposium MS A3226 ``PhaseField Models in Simulation and Optimization'', July 15  19, 2019, Valencia, Spain, July 17, 2019.

M. Thomas, Analytical and numerical aspects of rateindependent gradientregularized damage models, Conference ``Dynamics, Equations and Applications (DEA 2019)'', Session D444 ``Topics in the Mathematical Modelling of Solids'', September 16  20, 2019, AGH University of Science and Technology, Kraków, Poland, September 19, 2019.

M. Thomas, Coupling of rateindependent and ratedependent systems, MURPHYSHSFS 2019 Summer School on MultiRate Processes, SlowFast Systems and Hysteresis, June 17  19, 2019, Politecnico di Torino, Turin, Italy.

M. Thomas, Dynamics of rock dehydration on multiple scales, SCCS Days 2019 of the Collaborative Research Center  CRC 1114, May 20  22, 2019, Freie Universität Berlin, Zeuthen, May 21, 2019.

M. Thomas, GENERIC structures with bulkinterface interaction, SFB 910 Symposium ``Energy Based Modeling, Simulation and Control'', October 25, 2019, Technische Universität Berlin, October 25, 2019.

A. Caiazzo, Data assimilation in onedimensional hemodynamics, European Conference on Numerical Mathematics and Advanced Applications (ENUMATH 2019), Minisymposium 36 ``DataDriven Computational Fluid Dynamics (Part 2)'', September 30  October 4, 2019, Eindhoven University of Technology, Netherlands, October 1, 2019.

A. Caiazzo, Geothermal reservoir: Modeling, simulation and optimization for district heating in hot sedimentary acquires, Leibniz MMS Days 2019, March 20  22, 2019, Universität Rostock , LeibnizInstitut für Atmosphärenphysik, Kühlungsborn, March 22, 2019.

A. Caiazzo, Multiscale hybrid modeling and simulation of cancer growth within a 3D heterogeneous tissue, CanadaGermany Workshop Mathematical Biology and Numerics, June 24  26, 2019, Universität Heidelberg, June 26, 2019.

J. Fuhrmann, A. Linke, Ch. Merdon, R. Müller, Induced charge electroosmotic flow including finite ion size effects, 13th International Symposium on Electrokinetics (ELKIN), Cambridge, USA, June 12  14, 2019.

A. Mielke, Thermodynamical modeling via GENERIC: From quantum mechanics to semiconductor devices, Institute of Thermomechanics's Seminar, Czech Academy of Sciences, Prague, March 21, 2019.

A. Maltsi, Th. Koprucki, T. Niermann, T. Streckenbach, K. Tabelow, J. Polzehl, Computing TEM images of semiconductor nanostructures, Applied Mathematics and Simulation for Semiconductors (AMaSiS 2018), WIAS Berlin, October 8  10, 2018.

N. Rotundo, On a thermodynamically consistent coupling of quantum system and device equations, The 20th European Conference on Mathematics for Industry (ECMI 2018), Minisymposium ``Mathematical Modeling of Charge Transport in Graphene and Low Dimensional Structures'', August 18  June 22, 2018, Budapest, Hungary, June 19, 2018.

A. Alphonse, Directional differentiability for elliptic QVIs of obstacle type, 89th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM 2018), Session PP07 ``DFG Priority Program 1962'', March 19  23, 2018, Technische Universität München, March 20, 2018.

A. Alphonse, Directional differentiability for elliptic quasivariational inequalities, Workshop ``Challenges in Optimal Control of Nonlinear PDESystems'', April 8  14, 2018, Mathematisches Forschungsinstitut Oberwolfach, April 12, 2018.

A. Alphonse, Optimal Control of Elliptic and Parabolic QuasiVariational Inequalities, Annual Meeting of the DFG Priority Programme 1962, October 1  3, 2018, Kremmen (Sommerfeld), October 3, 2018.

A. Alphonse, Parabolic quasivariational inequalities: Existence and sensitivity analysis, 4th Central European SetValued and Variational Analysis Meeting (CESVVAM 2018), November 24, 2018, PhilippsUniversität Marburg, November 24, 2018.

D.H. Doan, J. Fuhrmann, A. Glitzky, Th. Koprucki, M. Liero, On van Roosbroeck systems with GaussFermi statistics, Applied Mathematics and Simulation for Semiconductors (AMaSiS 2018), WIAS Berlin, October 8  10, 2018.

M. Heida, On Gconvergence and stochastic twoscale convergences of the square root approximation scheme to the FokkerPlanck operator, 89th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM 2018), Section S14 ``Applied Analysis'', March 19  23, 2018, Technische Universität München, March 21, 2018.

M. Heida, On convergence of the square root approximation scheme to the FokkerPlanck operator, Technische Universität Berlin, Institut für Mathematik, May 14, 2018.

M. Heida, On convergence of the square root approximation scheme to the FokkerPlanck operator, Oberseminar ``Optimierung'', HumboldtUniversität zu Berlin, Institut für Mathematik, May 29, 2018.

M. Kantner, M. Mittnenzweig, Th. Koprucki, A hybrid quantumclassical modeling approach for electrically driven quantum dot devices, SPIE Photonics West 2018: Physics and Simulation of Optoelectronic Devices XXVI, January 29  February 1, 2018, The Moscone Center, San Francisco, USA, January 29, 2018.

M. Kantner, Hybrid quantumclassical modeling of quantum dot based singlephoton emitting diodes, Workshop Applied Mathematics and Simulation for Semiconductors, WIAS Berlin, October 10, 2018.

M. Kantner, Modeling and simulation of electrically driven quantum light emitters, Leibniz MMS Days, Leibniz Institut für Oberflächenmodifizierung (IOM), Leipzig, March 2, 2018.

M. Kantner, Thermodynamically consistent modeling of electrically driven quantum dot based light emitters on a device scale, Workshop ,,Nonlinear Dynamics in Semiconductor Lasers (NDSL2018)'', June 18  20, 2018, WIAS, Berlin, June 18, 2018.

C. Cancès, C. ChainaisHillairet, J. Fuhrmann, B. Gaudeul, Numerical schemes for a reduced case of an improved NernstPlanckPoisson model, Applied Mathematics and Simulation for Semiconductors (AMaSiS 2018), WIAS Berlin, October 8  10, 2018.

P. Farrell, D. Peschka, Challenges for driftdiffusion simulations of semiconductors: A comparative study of different discretization philosophies, Applied Mathematics and Simulation for Semiconductors (AMaSiS 2018), WIAS Berlin, October 8  10, 2018.

L. Blank, A robust finite element method for the Brinkman problem, 13th International Workshop on Variational Multiscale and Stabilized Finite Elemements, WeierstraßInstitut, Berlin, December 5, 2018.

L. Blank, An unconditionally stable, low order, and robust finite element method for the numerical simulation of porous media flow, 39th Northern German Colloquium on Applied Analysis and Numerical Mathematics (NoKo 2018), June 1  2, 2018, Technische Universität Braunschweig, June 2, 2018.

A. Glitzky, Electrothermal feedback in organic LEDs, Workshop ``Numerical Optimization of the PEM Fuel Cell Bipolar Plate'', March 20, 2018, Zentrum für Solarenergie und WasserstoffForschung (ZSW), Ulm, March 20, 2018.

M. Thomas, D. Peschka, B. Wagner, V. Mehrmann, M. Rosenau, Modeling and analysis of suspension flows, MATH+ Center Days 2018, October 31  November 2, 2018, ZuseInstitut Berlin (ZIB), Berlin, October 31, 2018.

M. Thomas, Analysis and simulation for a phasefield fracture model at finite strains based on modified invariants, 89th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM 2018), Section DFG Priority Programmes PP1748 ``Reliable Simulation Techniques in Solid Mechanics. Development of Nonstandard Discretization Methods, Mechanical and Mathematical Analysis'', March 19  23, 2018, Technische Universität München, March 20, 2018.

M. Thomas, Analysis and simulation for a phasefield fracture model at finite strains based on modified invariants, Workshop ``Special Materials and Complex Systems'' (SMACS 2018), June 18  22, 2018, University of Milan/University of Pavia, Gargnano, Italy, June 18, 2018.

M. Thomas, Analysis and simulation for a phasefield fracture model at finite strains based on modified invariants, Analysis Seminar, University of Brescia, Department of Mathematics, Italy, May 10, 2018.

M. Thomas, Analysis for the discrete approximation of damage and fracture, Applied Analysis Day, June 28  29, 2018, Technische Universität Dresden, Chair of Partial Differential Equations, June 29, 2018.

M. Thomas, Analysis for the discrete approximation of gradientregularized damage models, Workshop ``Women in Mathematical Materials Science'', November 5  6, 2018, Universität Regensburg, Fakultät für Mathematik, November 6, 2018.

M. Thomas, Analytical and numerical approach to a class of damage models, The 12th AIMS Conference on Dynamical Systems, Differential Equations and Applications, Special Session 75 ``Mathematics and Materials: Models and Applications'', July 5  9, 2018, National Taiwan University, Taipeh, Taiwan, Province Of China, July 6, 2018.

M. Thomas, Analytical and numerical aspects of damage models, Berlin Dresden Prague Würzburg Workshop ``Mathematics of Continuum Mechanics'', November 29  30, 2018, Universität Würzburg, Institut für Mathematik, November 30, 2018.

M. Thomas, Gradient structures for flows of concentrated suspensions, The 12th AIMS Conference on Dynamical Systems, Differential Equations and Applications, Special Session 18 ``Emergence and Dynamics of Patterns in Nonlinear Partial Differential Equations and Related Fields'', July 5  9, 2018, National Taiwan University, Taipeh, Taiwan, Province Of China, July 7, 2018.

M. Thomas, Optimization of the radiative emission for mechanically strained optoelectronic semiconductor devices, 9th International Conference ``Inverse Problems: Modeling and Simulation'' (IPMS 2018), Minisymposium M16 ``Inverse and Control Problems in Mechanics'', May 21  25, 2018, The Eurasian Association on Inverse Problems, Malta, May 24, 2018.

M. Thomas, Rateindependent evolution of sets & applications to damage and delamination, PDEs Friends, June 21  22, 2018, Politecnico di Torino, Dipartimento di Scienze Matematiche ``Giuseppe Luigi Lagrange'', Italy, June 22, 2018.

W. Dreyer, NonNewtonian fluids and the 2nd law of thermodynamics, 3rd Leibniz MMS Days 2018, February 28  March 2, 2018, Wissenschaftszentrum Leipzig, March 1, 2018.

J. Fuhrmann, A. Linke, Ch. Merdon, C. Guhlke, R. Müller, Models and numerical methods for electroosmotic flow including finite ion size effects, Workshop on Ion Exchange Membranes for Energy Applications (EMEA2018), Bad Zwischenahn, June 26  28, 2018.

J. Fuhrmann, A. Linke, Ch. Merdon, C. Guhlke, R. Müller, Models and numerical methods for electroosmotic flow including finite ion size effects, Applied Mathematics and Simulation for Semiconductors (AMaSiS 2018), WIAS Berlin, October 8  10, 2018.

TH. Koprucki, Highly accurate discretizations for nonBoltzmann charge transport in semiconductors, 18th International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD 2018), Session ``Numerical Methods'', November 5  9, 2018, The University of Hong Kong, China, November 6, 2018.

TH. Koprucki, Numerical methods for driftdiffusion equations, sc Matheon 11th Annual Meeting ``Photonic Devices'', February 8  9, 2018, KonradZuseZentrum für Informationstechnik Berlin, February 8, 2018.

TH. Koprucki, Towards modelbased geometry reconstruction of quantum dots from TEM, 18th International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD 2018), Session ``Nanostructures'', November 5  9, 2018, The University of Hong Kong, China, November 8, 2018.

M. Liero, Feel the heatModeling of electrothermal feedback in organic devices, A Joint Meeting of the Society for Natural Philosophy and the International Society for the Interaction of Mathematics and Mechanics ``Mathematics & Mechanics: Natural Philosophy in the 21st Century'', June 24  27, 2018, University of Oxford, Mathematical Institute, UK, June 25, 2018.

O. Marquardt, Datadriven electronic structure calculations in semiconductor nanostructures  Beyond the eightband k&cdot&p formalism, 18th International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD 2018), Session ``Numerical Methods'', November 5  9, 2018, The University of Hong Kong, China, November 6, 2018.

U. Wilbrandt, Iterative subdomain methods for the StokesDarcy coupling, 6th European Conference on Computational Mechanics, 7th European Conference on Computational Fluid Dynamics (ECCMECFD 2018), June 11  15, 2018, University of Glasgow, UK, June 11, 2018.

A. Alphonse, A coupled bulksurface reactiondiffusion system on a moving domain, Workshop ``Emerging Developments in Interfaces and Free Boundaries'', January 23  28, 2017, Mathematisches Forschungszentrum Oberwolfach, January 25, 2017.

M. Heida, On Gconvergence and stochastic twoscale convergences of the squareroot approximation scheme to the FokkerPlanck operator, GAMMWorkshop on Analysis of Partial Differential Equations, September 27  29, 2017, Eindhoven University of Technology, Mathematics and Computer Science Department, Netherlands, September 28, 2017.

M. Kantner, Hybrid quantumclassical modeling of electrically driven quantum light sources, Meeting of the MATHEON Scientific Advisory Board 2017, TU Berlin, Institut für Mathematik, November 13, 2017.

M. Kantner, Simulations of quantum dot devices by coupling of quantum master equations and semiclassical transport theory, 17th International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD2017), July 24  28, 2017, Technical University of Denmark, Copenhagen, July 27, 2017.

M. Liero, Modeling and simulation of electrothermal feedback in largearea organic LEDs, Numerical Simulation of Optoelectronic Devices (NUSOD 2017), session ``LightEmitting Diodes'', July 24  28, 2017, Technical University of Denmark, Lyngby Campus, Kopenhagen, Denmark, July 25, 2017.

CH. Merdon, A novel concept for the discretisation of the coupled NernstPlanckPoissonNavierStokes system, 14th Symposium on Fuel Cell Modelling and Experimental Validation (MODVAL 14), March 2  3, 2017, Karlsruher Institut für Technologie, Institut für Angewandte Materialien, Karlsruhe, Germany, March 3, 2017.

CH. Merdon, Druckrobuste FiniteElementeMethoden für die NavierStokesGleichungen, Universität Paderborn, Institut für Mathematik, April 25, 2017.

CH. Merdon, Pressurerobustness in mixed finite element discretisations for the NavierStokes equations, Universität des Saarlandes, Fakultät für Mathematik und Informatik, July 12, 2017.

D. Peschka, Doping optimization for optoelectronic devices, Numerical Simulation of Optoelectronic Devices (NUSOD 2017), PostDeadline session, July 27  28, 2017, Technical University, Lyngby Campus, Kopenhagen, Denmark, July 28, 2017.

D. Peschka, Mathematical and numerical approaches to moving contact lines, Scuola Internazionale Superiore di Studi Avanzati (SISSA), Trieste, Italy, December 6, 2017.

D. Peschka, Motion of thin droplets over surfaces, Making a Splash  Driplets, Jets and Other Singularities, March 20  24, 2017, Brown University, Institute for Computational and Experimental Research in Mathematics (ICERM), Providence, USA, March 22, 2017.

D. Peschka, Variational structure of fluid motion with contact lines in thinfilm models, Kolloquium Angewandte Mathematik, Universität der Bundeswehr, München, May 31, 2017.

N. Ahmed, Higherorder discontinuous Galerkin time discretizations for the evolutionary NavierStokes equations, Technische Universität Dresden, Institut für Numerische Mathematik, March 9, 2017.

N. Ahmed, On really lockingfree mixed finite element methods for the transient incompressible Stokes equations, CASM International Conference on Applied Mathematics, May 22  24, 2017, Lahore University of Management Sciences, Centre for Advanced Studies in Mathematics, Pakistan, May 22, 2017.

C. Bartsch, ParMooN  A parallel finite element solver, Part I, Indian Institute of Science, Supercomputer Education and Research Centre, Bangalore, India, March 16, 2017.

A. Caiazzo, Estimation of cardiovascular system parameters from real data, 2nd Leibniz MMS Days 2017, February 22  23, 2017, Technische Informationsbibliothek, Hannover, February 22, 2017.

A. Caiazzo, Homogenization methods for weakly compressible elastic materials forward and inverse problem, Workshop on Numerical Inverse and Stochastic Homogenization, February 13  17, 2017, Universität Bonn, Hausdorff Research Institute for Mathematics, February 17, 2017.

P.É. Druet, Analysis of recent NernstPlanckPoissonNavierStokes systems of electrolytes, 88th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM 2017), Section S14 ``Applied Analysis'', March 6  10, 2017, Bauhaus Universität Weimar/Technische Universität Ilmenau, Weimar, March 7, 2017.

P.É. Druet, Existence of weak solutions for improved NernstPlanckPoisson models of compressible electrolytes, Seminar EDE, Czech Academy of Sciences, Institute of Mathematics, Department of Evolution Differential Equations (EDE), Prague, Czech Republic, January 10, 2017.

P. Friz, Geometric aspects in pathwise stochastic analysis, High Risk High Gain  Groundbreaking Research in Berlin, August 31  September 3, 2017, Technische Universität Berlin, Stabsstelle Presse, September 2, 2017.

J. Fuhrmann, A. Linke, Ch. Merdon, Models and numerical methods for ionic mixtures with volume constraints, 12th International Symposium on Electrokinetics, Dresden, September 10  12, 2017.

M. Hintermüller, Generalized Nash equilibrium problems in Banach spaces: Theory, NikaidoIsodabased pathfollowing methods, and applications, The Third International Conference on Engineering and Computational Mathematics (ECM2017), Stream 3 ``Computational Optimization'', May 31  June 2, 2017, The Hong Kong Polytechnic University, China, June 2, 2017.

M. Hintermüller, Nonsmooth structures in PDEconstrained optimization, Mathematisches Kolloquium, Universität DuisburgEssen, Fakultät für Mathematik, Essen, January 11, 2017.

M. Hintermüller, Recent trends in PDEconstrained optimization with nonsmooth structures, Fourth Conference on Numerical Analysis and Optimization (NAOIV2017), January 2  5, 2017, Sultan Qaboos University, Muscat, Oman, January 4, 2017.

TH. Koprucki, Comparison of consistent flux discretizations for drift diffusion beyond Boltzmann statistics, Numerical Simulation of Optoelectronic Devices (NUSOD 2017), session ``Numerical Methods'', July 24  28, 2017, Technical University of Denmark, Lyngby Campus, Kopenhagen, Denmark, July 27, 2017.

TH. Koprucki, Mathematical models as research data in numerical simulation of optoelectronic devices, Numerical Simulation of Optoelectronic Devices (NUSOD 2017), session ``Model Representation'', July 24  28, 2017, Technical University of Denmark, Lyngby Campus, Kopenhagen, Denmark, July 27, 2017.

CH. Merdon, Pressurerobust finite element methods for the NavierStokes equations, GAMM Workshop on Numerical Analysis, November 1  2, 2017, RheinischWestfälische Technische Hochschule Aachen, November 2, 2017.

CH. Merdon, Pressurerobust mixed finite element methods for the NavierStokes equations, scMatheon Workshop RMMM 8  Berlin 2017, Reliable Methods of Mathematical Modeling, July 31  August 3, 2017, HumboldtUniversität zu Berlin, August 2, 2017.

A. Mielke, Mathematical modeling of semiconductors: From quantum mechanics to devices, CIMWIAS Workshop ``Topics in Applied Analysis and Optimisation'', December 6  8, 2017, Centro de Matemática, Lisboa, Portugal, December 8, 2017.

U. Wilbrandt, ParMooN  A parallel finite element solver, Part II, Indian Institute of Science, Supercomputer Education and Research Centre, Bangalore, India, March 16, 2017.

K. Disser, Convergence for gradient systems of slow and fast chemical reactions, Joint Annual Meeting of DMV and GAMM, Session ``Applied Analysis'', March 7  11, 2016, Technische Universität Braunschweig, Braunschweig, March 11, 2016.

M. Kantner, Multiscale modeling and numerical simulation of singlephoton emitters, Matheon Workshop9th Annual Meeting ``Photonic Devices", Zuse Institut, Berlin, March 3, 2016.

M. Kantner, Multiscale modelling and simulation of singlephoton sources on a device level, EuroTMCS II Theory, Modelling & Computational Methods for Semiconductors, Tyndall National Institute and University College Cork, Cork, Ireland, December 9, 2016.

M. Liero, On $p(x)$Laplace thermistor models describing eletrothermal feedback in organic semiconductors, The 19th European Conference on Mathematics for Industry (ECMI 2016), Minisymposium 23 ``Charge Transport in Semiconductor Materials: Emerging and Established Mathematical Topics'', June 13  17, 2016, Universidade de Santiago de Compostela, Spain, June 15, 2016.

M. Liero, On electrothermal feedback in organic lightemitting diodes, Berlin Dresden Prague Würzburg Workshop ``Mathematics of Continuum Mechanics'', Technische Universität Dresden, Fachbereich Mathematik, December 5, 2016.

CH. Merdon, J. Fuhrmann, A. Linke, A.A. AbdElLatif, M. Khodayari, P. Reinsberg, H. Baltruschat, Inverse modelling of thin layer flow cells and RRDEs, The 67th Annual Meeting of the International Society of Electrochemistry, Den Haag, Netherlands, August 21  26, 2016.

R. Müller, W. Dreyer, J. Fuhrmann, C. Guhlke, New insights into ButlerVolmer kinetics from thermodynamic modeling, The 67th Annual Meeting of the International Society of Electrochemistry, Den Haag, Netherlands, August 21  26, 2016.

D. Peschka, Multiphase flows with contact lines: Solid vs liquid substrates, Industrial and Applied Mathematics Seminar, University of Oxford, Mathematical Institute, UK, October 27, 2016.

D. Peschka, Thin film free boundary problems  Modeling of contact line dynamics with gradient formulations, CeNoSKolloquium, Westfälische WilhelmsUniversität Münster, Center for Nonlinear Science, January 12, 2016.

M. Thomas, Analysis and optimization for edgeemitting semiconductor heterostructures, 7th European Congress of Mathematics (ECM), session CS8A, July 18  22, 2016, Technische Universität Berlin, Berlin, July 19, 2016.

M. Thomas, Analysis and optimization for edgeemitting semiconductor heterostructures, The 11th AIMS Conference on Dynamical Systems, Differential Equations and Applications, Special Session 2 ``Emergence and Dynamics of Patterns in Nonlinear Partial Differential Equation'', July 1  5, 2016, The American Institute of Mathematical Sciences, Orlando (Florida), USA, July 3, 2016.

M. Thomas, Nonsmooth PDEs in material failure: Towards dynamic fracture, Joint Annual Meeting of DMV and GAMM, Section 14 ``Applied Analysis'', March 7  11, 2016, Technische Universität Braunschweig, March 10, 2016.

N. Ahmed, A review of VMS methods for the simulation of turbulent incompressible flows, International Conference on Differential Equations and Applications, May 26  28, 2016, Lahore University of Management Sciences, Pakistan, May 27, 2016.

N. Ahmed, On the graddiv stabilization for the steady Oseen and NavierStokes evaluations, International Conference of Boundary and Interior Layers (BAIL 2016), August 15  19, 2016, Beijing Computational Science Research Center, Beijing, China, August 15, 2016.

A. Caiazzo, A comparative study of backflow stabilization methods, 7th European Congress of Mathematics (7ECM), July 18  22, 2016, Technische Universität Berlin, Berlin, July 19, 2016.

A. Caiazzo, Backflow stabilization methods for open boundaries, ChristianAlbrechtsUniversität zu Kiel, Angewandte Mathematik, Kiel, May 19, 2016.

D.H. Doan, Numerical methods in nonBoltzmann regimes, sc Matheon Workshop, 9th Annual Meeting ``Photonic Devices'', March 3  4, 2016, Zuse Institute Berlin, Berlin, March 4, 2016.

P.É. Druet, Existence of global weak solutions for generalized PoissonNernstPlanck systems, 7th European Congress of Mathematics (ECM), minisymposium ``Analysis of Thermodynamically Consistent Models of Electrolytes in the Context of Battery Research'', July 18  22, 2016, Technische Universität Berlin, Berlin, July 20, 2016.

P. Farrell, ScharfetterGummel schemes for NonBoltzmann statistics, Conference on Scientific Computing (ALGORITMY 2016), March 14  18, 2016, Slovak University of Technology, Department of Mathematics and Descriptive Geometry, Podbanské, Slovakia, March 17, 2016.

P. Farrell, ScharfetterGummel schemes for nonBoltzmann statistics, The 19th European Conference on Mathematics for Industry (ECMI2016), Minisymposium 23 ``Charge Transport in Semiconductor Materials: Emerging and Established Mathematical Topics'', June 13  17, 2016, Universidade de Santiago de Compostela, Spain, June 14, 2016.

J. Fuhrmann, Ch. Merdon, A thermodynamically consistent numerical approach to NernstPlanckPoisson systems with volume constraints, The 67th Annual Meeting of the International Society of Electrochemistry, Den Haag, Netherlands, August 21  26, 2016.

J. Fuhrmann, W. Dreyer, C. Guhlke, M. Landstorfer, R. Müller, A. Linke, Ch. Merdon, Modeling and numerics for electrochemical systems, Micro Battery and Capacitive Energy Harvesting Materials  Results of the MatFlexEnd Project, Universität Wien, Austria, September 19, 2016.

J. Fuhrmann, A. Linke, Ch. Merdon, M. Khodayari , H. Baltruschat, Detection of solubility, transport and reaction coefficients from experimental data by inverse modelling of thin layer flow cells, 1st Leibniz MMS Mini Workshop on CFD & GFD, WIAS Berlin, September 8  9, 2016.

J. Fuhrmann, A. Linke, Ch. Merdon, W. Dreyer, C. Guhle, M. Landstorfer, R. Müller, Numerical methods for electrochemical systems, 2nd Graz Battery Days, Graz, Austria, September 27  28, 2016.

C. Guhlke, J. Fuhrmann, W. Dreyer, R. Müller, M. Landstorfer, Modeling of batteries, Batterieforum Deutschland 2016, Berlin, April 6  8, 2016.

M. Hintermüller, Adaptive finite elements in total variation based image denoising, SIAM Conference on Imaging Science, Minisymposium ``Leveraging Ideas from Imaging Science in PDEconstrained Optimization'', May 23  26, 2016, Albuquerque, USA, May 24, 2016.

M. Hintermüller, Nonsmooth structures in PDE constrained optimization, 66th Workshop ``Advances in Convex Analysis and Optimization'', July 5  10, 2016, International Centre for Scientific Culture ``E. Majorana'', School of Mathematics ``G. Stampacchia'', Erice, Italy, July 9, 2016.

M. Hintermüller, Optimal control of multiphase fluids and droplets, WIASPGMO Workshop on Nonsmooth and Stochastic Optimization with Applications to Energy Management, May 10  12, 2016, WIAS Berlin, May 11, 2016.

M. Hintermüller, Optimal control of multiphase fluids and droplets, The Fifth International Conference on Continuous Optimization, Session: ``Recent Developments in PDEconstrained Optimization I'', August 6  11, 2016, Tokyo, Japan, August 10, 2016.

M. Hintermüller, Optimal control of multiphase fluids and droplets, Salzburg Mathematics Colloquium, Universität Salzburg, Fachbereich Mathematik, Austria, June 9, 2016.

M. Hintermüller, Optimal selection of the regularisation function in a localised TV model, SIAM Conference on Imaging Science, Minisymposium ``Analysis and Parameterisation of Derivative Based Regularisation'', May 23  26, 2016, Albuquerque, USA, May 24, 2016.

V. John, Analytical and numerical results for algebraic flux correction schemes, Conference on Recent Advances in Analysis and Numerics of Hyperbolic Conservation Laws, September 8  10, 2016, OttovonGuericke Universität Magdeburg, September 9, 2016.

A. Mielke, Entropyentropy production estimates for energyreaction diffusion systems, Workshop ``Forefront of PDEs: Modelling, Analysis and Numerics'', December 12  14, 2016, Technische Universität Wien, Institut für Analysis and Scientific Computing, Austria, December 13, 2016.

A. Mielke, Evolution driven by energy and entropy, SFB1114 Kolloquium, Freie Universität Berlin, Berlin, June 30, 2016.

A.G. Vladimirov, Interaction of temporal cavity solitons in driven fiber resonators and modelocked lasers, International Tandem Workshop on Pattern Dynamics in Nonlinear Optical Cavities, August 15  19, 2016, MaxPlanckInstitut für Physik komplexer Systeme, Dresden, August 15, 2016.

K. Disser, Asymptotic behavior of a rigid body with a cavity filled by a viscous liquid, Mathematical Thermodynamics of Complex Fluids, June 29  July 3, 2015, Centro Internazionale Matematico Estivo (CIME), Cetraro, Italy, June 30, 2015.

K. Disser, Asymptotic behavior of a rigid body with a cavity filled by a viscous liquid, Workshop ``Young Researchers in Fluid Dynamics'', June 18  19, 2015, Technische Universität Darmstadt, Fachbereich Mathematik, Darmstadt, June 18, 2015.

K. Disser, Asymptotic behavior of a rigid body with a cavity filled by a viscous liquid, Seminar ``Dynamische Systeme'', Technische Universität München, Zentrum Mathematik, München, February 2, 2015.

K. Disser, Asymptotic behavior of a rigid body with a cavity filled by a viscous liquid, Oberseminar ``Analysis'', Universität Kassel, Institut für Mathematik, Kassel, January 12, 2015.

K. Disser, Dynamik von Starrkörpern, die mit einer Flüssigkeit gefüllt sind, und das EiProblem, Mathematisches Kolloquium, HeinrichHeine Universität Düsseldorf, Institut für Mathematik, Düsseldorf, April 10, 2015.

N. Rotundo, Analytical methods for doping optimization for semiconductor devices, Minisymposium ``Numerical and Analytical Aspects in Semiconductor Theory'' of the 8th International Congress on Industrial and Applied Mathematics (ICIAM 2015), August 10  14, 2015, International Council for Industrial and Applied Mathematics, Beijing, China, August 10, 2015.

M. Heida, Modeling of fluid interfaces, Jahrestagung der Deutschen MathematikerVereinigung, Minisymposium ``Mathematics of Fluid Interfaces'', September 21  25, 2015, Universität Hamburg, Fakultät für Mathematik, Informatik und Naturwissenschaften, Hamburg, September 23, 2015.

CH. Heinemann, Damage processes in thermoviscoelastic materials with damagedependent thermal expansion coefficients, 3rd Workshop of the GAMM Activity Group Analysis of Partial differential Equations, September 30  October 2, 2015, Universität Kassel, Institut für Mathematik, October 1, 2015.

CH. Heinemann, On elastic CahnHilliard systems coupled with evolution inclusions for damage processes, 86th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM 2015), Young Researchers' Minisymposium 2, March 23  27, 2015, Lecce, Italy, March 23, 2015.

M. Landstorfer, Theory, structure and experimental justification of the metal/electrolyte interface, Minisymposium `` Recent Developments on Electrochemical Interface Modeling'' of the 8th International Congress on Industrial and Applied Mathematics (ICIAM 2015), August 10  14, 2015, International Council for Industrial and Applied Mathematics, Beijing, China, August 11, 2015.

M. Liero, Electrothermal modeling of largearea OLEDs, sc Matheon Center Days, April 20  21, 2015, Technische Universität Berlin, Institut für Mathematik, Berlin, April 20, 2015.

M. Liero, OLEDs  eine heiße Sache?, Organische Leuchtdioden, Workshop im Handlungsfeld Lichttechnik, OpTec Berlin Brandenburg e.V., Berlin, May 18, 2015.

M. Liero, On a PDE thermistor system for largearea OLEDs, Applied Mathematics and Simulation for Semiconductors (AMaSiS 2015), March 11  13, 2015, WIAS Berlin, Berlin, March 12, 2015.

CH. Merdon, Inverse modeling of thin layer flow cells for detection of solubility transport and reaction coefficients from experimental data, 17th Topical Meeting of the International Society of Electrochemistry Multiscale Analysis of Electrochemical Systems, May 31  June 3, 2015, Saint Malo Congress Center, France, June 1, 2015.

D. Peschka, Mathematical modeling, analysis, and optimization of strained germaniummicrobridges, sc Matheon Center Days, April 20  21, 2015, Technische Universität Berlin, Institut für Mathematik, Berlin, April 20, 2015.

D. Peschka, Numerics of contact line motion for thin films, MATHMOD 2015, Minisymposium ``Free Boundary Problems in Applications: Recent Advances in Modelling, Simulation and Optimization'', February 17  20, 2015, Technische Universität Wien, Institut für Analysis und Scientific Computing, Wien, Austria, February 19, 2015.

D. Puzyrev, Delay induced multistability and wiggling movement of laser cavity solitons, International Workshop ``Waves, Solitons and Turbulence in Optical Systems'' (WASTOS15), Berlin, October 12  14, 2015.

A. Glitzky, Finite volume discretized reactiondiffusion systems in heterostructures, Conference on Partial Differential Equations, March 25  29, 2015, Technische Universität München, Zentrum Mathematik, München, March 28, 2015.

M. Thomas, Analysis for edgeemitting semiconductor heterostructures, Minisymposium ``Numerical and Analytical Aspects in Semiconductor Theory'' of the 8th International Congress on Industrial and Applied Mathematics (ICIAM 2015), August 10  14, 2015, International Council for Industrial and Applied Mathematics, Beijing, China, August 10, 2015.

M. Thomas, Analysis of nonsmooth PDE systems with application to material failuretowards dynamic fracture, Minisymposium ``Analysis of Nonsmooth PDE Systems with Application to Material Failure'' of the 8th International Congress on Industrial and Applied Mathematics (ICIAM 2015), August 10  14, 2015, International Council for Industrial and Applied Mathematics, Beijing, China, August 12, 2015.

M. Thomas, Coupling rateindependent and ratedependent processes: Existence results, Applied Mathematics Seminar, Università di Pavia, Dipartimento di Matematica, Pavia, Italy, March 5, 2015.

M. Thomas, Coupling rateindependent and ratedependent processes: Evolutionary Gammaconvergence results, 86th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM 2015), Session on Applied Analysis, March 23  27, 2015, Università del Salento, Lecce, Italy, March 26, 2015.

M. Thomas, Coupling rateindependent and ratedependent processes: Existence and evolutionary Gamma convergence, INdAM Workshop ``Special Materials in Complex Systems  SMaCS 2015'', May 18  22, 2015, Rome, Italy, May 19, 2015.

M. Thomas, Coupling rateindependent and ratedependent processes: Existence results, 86th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM 2015), GAMM Juniors Poster Session, Lecce, Italy, March 23  27, 2015.

M. Thomas, Modeling of edgeemitting lasers based on tensile strained germanium microstripes, Applied Mathematics and Simulation for Semiconductors (AMaSiS 2015), March 11  13, 2015, WIAS Berlin, Berlin, March 11, 2015.

N. Ahmed, Adaptive time step control with variational time stepping schemes for convectiondiffusionreaction equations, 26th Biennial Numerical Analysis Conference, June 23  26, 2015, University of Strathclyde, Glasgow, UK, June 23, 2015.

N. Ahmed, Higher order time stepping schemes, 13th European Finite Element Fair, June 5  6, 2015, Charles University in Prague, Praha, Czech Republic, June 5, 2015.

A. Caiazzo, A Stokesresidual based backflow stabilization for incompressible flows, XXIV Congreso de Ecuaciones Diferenciales y Aplicaciones, June 8  12, 2015, Universidad de Cádiz, Cádiz, Spain, June 10, 2015.

A. Caiazzo, Modeling and simulation of fluid flows through a porous interface, Besançon Week on Numerical Analysis: XFEM, Nitsche FEM, Adaptive FEM, Artificial Boundary Conditions, June 15  21, 2015, Université de Franche Comté, Besançon, France, June 19, 2015.

A. Caiazzo, Multiscale modeling of weakly compressible elastic materials, Workshop on Aktive Drag Reduction, November 9  10, 2015, RheinischWestfälische Technische Hochschule Aachen, Institut für Geometrie und Praktische Mathematik, Aachen, November 10, 2015.

A. Caiazzo, Multiscale modeling of weakly compressible elastic materials in harmonic regime, Rheinische FriedrichWilhelmsUniversität Bonn, Institut für Numerische Simulation, Bonn, May 21, 2015.

A.G. Vladimirov, Application of delay differential equations to the analysis of nonlinear dynamics in modelocked lasers, Colloquium Nonlinear Sciences, Universität Münster, Center for Nonlinear Sciences, May 19, 2015.

A.G. Vladimirov, Feedback induced instabilities of cavity solitons, International Symposium on Physics and Applications of Laser Dynamics 2015, November 4  6, 2015, CentraleSupélec, Metz, France, November 6, 2015.

K. Disser, Asymptotic behaviour of a rigid body with a cavity filled by a viscous liquid, Second Workshop of the GAMM Activity Group on "Analysis of Partial Differential Equations", September 29  October 1, 2014, Universität Stuttgart, Lehrstuhl für Analysis und Modellierung, October 1, 2014.

K. Disser, Asymptotic behaviour of a rigid body with a cavity filled by a viscous liquid, Autumn School and Workshop on Mathematical Fluid Dynamics, October 27  30, 2014, Universität Darmstadt, International Research Training Group 1529, Bad Boll, October 28, 2014.

S. Heinz, Analysis and numerics of a phasetransformation model, 13th GAMM Seminar on Microstructures, January 17  18, 2014, RuhrUniversität Bochum, Lehrstuhl für Mechanik  Materialtheorie, January 18, 2014.

TH. Koprucki, DeviceSimulation: Mathematische Fragestellungen und Numerik, BlockSeminar des SFB 787 ``Nanophotonik'', May 21  23, 2014, Technische Universität Berlin, GraalMüritz, May 23, 2014.

TH. Koprucki, On modifications of the ScharfetterGummel scheme for driftdiffusion equations with Fermilike statistical distribution functions, 14th International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD 2014), September 1  5, 2014, Palma de Mallorca, Spain, September 3, 2014.

M. Liero, Electrothermical modeling of largearea OLEDs, KickOff Meeting of the ECMI Special Interest Group ``Sustainable Energy'' on Nanostructures for Photovoltaics and Energy Storage, December 8  9, 2014, Technische Universität Berlin, Institut für Mathematik, December 8, 2014.

A. Linke, Ch. Merdon, Optimal and pressureindependent $L^2$ velocity error estimates for a modified CrouzeixRaviart element with BDM reconstructions, The International Symposium of Finite Volumes for Complex Applications VII (FVCA 7), BerlinBrandenburgische Akademie der Wissenschaften, June 15  20, 2014.

A. Linke, Ein neues Konstruktionsprinzip zur divergenzfreien Diskretisierung der inkompressiblen NavierStokesGleichungen, RuhrUniversität Bochum, Fakultät für Mathematik, July 17, 2014.

A. Linke, On the role of the Helmholtz decomposition in incompressible flows and a new variational crime, NonLinear PDE and Applications: Theoretical and Numerical Study, May 5  7, 2014, Abdelmalek Essadi University, Tanger, Morocco, May 6, 2014.

A. Linke, On the role of the Helmholtz decomposition in mixed methods for incompressible flows and a new variational crime, Technische Universität Wien, Institut für Analysis und Scientific Computing, Austria, April 2, 2014.

A. Linke, On the role of the Helmholtz decomposition in mixed methods for incompressible flows and a new variational crime, Technische Universität HamburgHarburg, Institut für Mathematik, January 7, 2014.

A. Linke, On the role of the Helmholtz decomposition in mixed methods for incompressible flows and a new variational crime, FriedrichAlexanderUniversität ErlangenNürnberg, Fachbereich Mathematik, November 20, 2014.

A. Linke, On the role of the Helmholtz decomposition in mixed methods for incompressible flows and a new variational crime, GeorgAugustUniversität Göttingen, Institut für Numerische und Angewandte Mathematik, December 9, 2014.

M. Radziunas, Effective numerical algorithm for simulations of broad area semiconductor lasers, "International Workshop on Application of Parallel Computation in Industry and Engeneering (APCIE) in conjunction with EUROPAR' 2014'', August 25  26, 2014, Porto, Portugal, August 25, 2014.

A. Glitzky, Driftdiffusion models for heterostructures in photovoltaics, 8th European Conference on Elliptic and Parabolic Problems, Minisymposium ``Qualitative Properties of Nonlinear Elliptic and Parabolic Equations'', May 26  30, 2014, Universität Zürich, Institut für Mathematik, organized in Gaeta, Italy, May 27, 2014.

M. Thomas, Existence & stability results for rateindependent processes in viscoelastic materials, Applied Mathematics Seminar, Università di Pavia, Dipartimento di Matematica, Italy, March 18, 2014.

M. Thomas, Existence and stability results for rateindependent processes in viscoelastic materials, Women in Partial Differential Equations & Calculus of Variations Workshop, March 6  8, 2014, University of Oxford, Mathematical Institute, UK, March 6, 2014.

M. Thomas, GENERIC for solids with dissipative interface processes, 85th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM 2014), GAMM Juniors' Poster Session, FriedrichAlexander Universität ErlangenNürnberg, March 10  14, 2014.

M. Thomas, Rateindependent systems with viscosity and inertia: Existence and evolutionary Gammaconvergence, Workshop ``Variational Methods for Evolution'', December 14  20, 2014, Mathematisches Forschungsinstitut Oberwolfach, December 18, 2014.

M. Thomas, Rateindependent, partial damage in thermoviscoelastic materials, 7th International Workshop on MultiRate Processes & Hysteresis, 2nd International Workshop on Hysteresis and SlowFast Systems (MURPHYSHSFS2014), April 7  11, 2014, WIAS Berlin, April 8, 2014.

M. Thomas, Rateindependent, partial damage in thermoviscoelastic materials with inertia, International Workshop ``Variational Modeling in Solid Mechanics'', September 22  24, 2014, University of Udine, Department of Mathematics and Informatics, Italy, September 23, 2014.

M. Thomas, Rateindependent, partial damage in thermoviscoelastic materials with inertia, Oberseminar ``Analysis und Angewandte Mathematik'', Universität Kassel, Institut für Mathematik, December 1, 2014.

M. Thomas, Stressdriven localsolution approach to quasistatic brittle delamination, 85th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM 2014), Session on Applied Analysis, March 10  14, 2014, FriedrichAlexander Universität ErlangenNürnberg, March 11, 2014.

M. Thomas, Thermomechanical modeling of dissipative processes in elastic media via energy and entropy, The 10th AIMS Conference on Dynamical Systems, Differential Equations and Applications, Special Session 8: Emergence and Dynamics of Patterns in Nonlinear Partial Differential Equations from Mathematical Science, July 7  11, 2014, Madrid, Spain, July 8, 2014.

A. Caiazzo, Effcient blood flow simulations for the design of stented valve size reducer in enlarged ventricular outflow tracts, 4th International Conference on Engineering Frontiers in Pediatric and Congenital Heart Disease, May 21  22, 2014, INRIA Research Centre Paris  Rocquencourt, France, May 22, 2014.

A. Caiazzo, Stabilization at backflow, European Finite Element Fair, May 30  31, 2014, Universität Wien, Austria, May 30, 2014.

J. Fuhrmann, A. Linke, Ch. Merdon, M. Khodayari, H. Baltruschat, Detection of solubility, transport and reaction coefficients from experimental data by inverse modeling of thin layer flow cells, 65th Annual Meeting of the International Society of Electrochemistry, Lausanne, Switzerland, August 31  September 5, 2014.

J. Fuhrmann, A. Linke, Ch. Merdon, Coupling of fluid flow and solute transport using a divergencefree reconstruction of the CrouzeixRaviart element, The International Symposium of Finite Volumes for Complex Applications VII (FVCA 7), BerlinBrandenburgische Akademie der Wissenschaften, June 15  20, 2014.

J. Fuhrmann, Ch. Merdon, Activity based finite volume methods for generalised NernstPlanckPoisson systems, 65th Annual Meeting of the International Society of Electrochemistry, Lausanne, Switzerland, August 31  September 5, 2014.

J. Fuhrmann, Activity based finite volume methods for generalised NernstPlanckPoisson systems, The International Symposium of Finite Volumes for Complex Applications VII (FVCA 7), BerlinBrandenburgische Akademie der Wissenschaften, June 15  20, 2014.

L. Kamenski, A study on the conditioning of finite element equations with general (anisotropic) meshes via a density function approach, 27th Chemnitz FEM Symposium, September 22  24, 2014, Technische Universität Chemnitz, September 24, 2014.

L. Kamenski, Hessian recovery and FE mesh adaptation, European Finite Element Fair, May 30  31, 2014, Universität Wien, Austria, May 31, 2014.

L. Kamenski, How a nonconvergent Hessian recovery works in mesh adaptation, 2014 AARMSCRM Workshop on Adaptive Methods for PDEs, August 17  22, 2014, Memorial University of Newfoundland, Canada, August 20, 2014.

A. Mielke, Gradient structures and dissipation distances for reactiondiffusion systems, Seminar ``Analysis of Fluids and Related Topics'', Princeton University, Department of Mechanical and Aerospace Engineering, Princeton, NJ, USA, March 6, 2014.

A. Mielke, How thermodynamics induces geometry structures for reactiondiffusion systems, Gemeinsames Mathematisches Kolloquium der Universitäten Gießen und Marburg, Universität Gießen, Mathematisches Institut, January 15, 2014.

A. Mielke, On gradient structures and dissipation distances for reactiondiffusion systems, Kolloquium ``Angewandte Mathematik'', FriedrichAlexanderUniversität ErlangenNürnberg, Department Mathematik, July 3, 2014.

A. Mielke, On gradient structures for reactiondiffusion systems, Joint Analysis Seminar, RheinischWestfälische Technische Hochschule Aachen (RWTH), Institut für Mathematik, February 4, 2014.

S. Neukamm, Homogenization of nonlinear bending plates, Workshop ``Relaxation, Homogenization, and Dimensional Reduction in Hyperelasticity'', March 25  27, 2014, Université ParisNord, France, March 26, 2014.

H. Stephan, Inequalities for Markov operators and applications to forward and backward PDEs, The 10th AIMS Conference on Dynamical Systems, Differential Equations and Applications, Special Session 88: Stochastic Processes and Spectral Theory for Partial Differential Equations and Boundary Value Problems, July 7  11, 2014, Madrid, Spain, July 8, 2014.

U. Wilbrandt, Iterative subdomain methods for StokesDarcy problems, Norddeutsches Kolloquium über Angewandte Analysis und Numerische Mathematik (NoKo), May 9  10, 2014, ChristianAlbrechtsUniversität zu Kiel, May 9, 2014.

TH. Koprucki, Generalization of the ScharfetterGummel scheme, Organic Photovoltaics Workshop 2013, December 10  11, 2013, University of Oxford, Mathematical Insitute, UK, December 10, 2013.

TH. Koprucki, Discretization scheme for driftdiffusion equations with a generalized Einstein relation, scshape Matheon Workshop ``6th Annual Meeting Photonic Devices'', February 21  22, 2013, KonradZuseZentrum für Informationstechnik Berlin, February 22, 2013.

S. Neukamm, Quantitative results in stochastic homogenization, sc Matheon Multiscale Seminar, Technische Universität Berlin, Institut für Mathematik, June 27, 2013.

S. Neukamm, Quantitative results in stochastic homogenization, Oberseminar Analysis, Technische Universität Dresden, Fakultät Mathematik und Naturwissenschaften, June 13, 2013.

P.N. Racec, WignerEisenbud problem within finite volume method: application to electronic transport in cylindrical nanowire heterostructures, QMATH12  Mathematical Results in Quantum Mechanics, September 10  13, 2013, HumboldtUniversität zu Berlin, Berlin, September 12, 2013.

A. Glitzky, Continuous and finite volume discretized reactiondiffusion systems in heterostructures, Asymptotic Behaviour of Systems of PDE Arising in Physics and Biology: Theoretical and Numerical Points of View, November 6  8, 2013, Lille 1 University  Science and Technology, France, November 6, 2013.

D. Knees, Crack evolution models based on the Griffith criterion, Workshop on Mathematical Aspects of Continuum Mechanics, October 12  14, 2013, The Japan Society for Industrial and Applied Mathematics, Kanazawa, Japan, October 13, 2013.

D. Knees, Global spatial regularity for elasticity models with cracks and contact, Journées Singulières Augmentées 2013, August 26  30, 2013, Université de Rennes 1, France, August 27, 2013.

D. Knees, Global spatial regularity results for crack with contact and application to a fracture evolution model, Oberseminar Nichtlineare Analysis, Universität Köln, Mathematisches Institut, October 28, 2013.

D. Knees, Modeling and analysis of crack evolution based on the Griffith criterion, Nonlinear Analysis Seminar, Keio University of Science, Yokohama, Japan, October 9, 2013.

D. Knees, On energy release rates for nonlinearly elastic materials, Workshop on Mathematical Aspects of Continuum Mechanics, October 12  14, 2013, The Japan Society for Industrial and Applied Mathematics, Kanazawa, Japan, October 12, 2013.

D. Knees, Weak solutions for rateindependent systems illustrated at an example for crack propagation, BMS Intensive Course on Evolution Equations and their Applications, November 27  29, 2013, Technische Universität Berlin, Berlin Mathematical School, November 28, 2013.

M. Thomas, A stressdriven local solution approach to quasistatic brittle delamination, BMS Intensive Course on Evolution Equations and their Applications, November 27  29, 2013, Technische Universität Berlin, Berlin Mathematical School, November 29, 2013.

M. Thomas, A stressdriven local solution approach to quasistatic brittle delamination, Seminar on Functional Analysis and Applications, International School of Advanced Studies (SISSA), Trieste, Italy, November 12, 2013.

M. Thomas, Mathematical modeling, analysis and optimization of strained germanium microbridges, sc Matheon Center Days, Technische Universität Berlin, November 5, 2013.

M. Thomas, Local versus energetic solutions in rateindependent brittle delamination, DIMO2013  Diffuse Interface Models, September 10  13, 2013, Levico Terme, Italy, September 13, 2013.

A. Fiebach, A. Glitzky, K. Gärtner, A. Linke, Voronoi finite volume methods for reactiondiffusion systems, MoMaS Multiphase Seminar Days  Journées MoMaS Multiphasiques, BuressurYvette, France, October 7  9, 2013.

A. Mielke, Gradient structures and dissipation distances for reactiondiffusion systems, Workshop ``Material Theory'', December 16  20, 2013, Mathematisches Forschungsinstitut Oberwolfach, December 17, 2013.

A. Mielke, Analysis, modeling, and simulation of semiconductor devices, Kolloquium Simulation Technology, Universität Stuttgart, SRC Simulation Technology, May 14, 2013.

A. Mielke, Coupling quantum mechanical systems with dissipative environments via GENERIC, Applied Analysis Seminar, University of Bath, Department of Mathematical Sciences, UK, May 23, 2013.

A. Mielke, Thermodynamic modeling of the MaxwellBloch and the semiconductor equations via GENERIC, Modeling, Analysis and Simulation of Optical Modes in Photonic Devices (MASOMO 13), April 10  12, 2013, WIAS Berlin, April 10, 2013.

A. Mielke, Using gradient structures for modeling semiconductors, Eindhoven University of Technology, Institute for Complex Molecular Systems, Netherlands, February 21, 2013.

TH. Koprucki, K. Gärtner, A. Wilms, U. Bandelow, A. Mielke, Multidimensional modeling and simulation of quantumdot lasers, Fachtagung LeibnizNano (1. NanotechnologieWorkshop der LeibnizGemeinschaft), Berlin, January 30  31, 2012.

TH. Koprucki, Discretization scheme for driftdiffusion equations with strong diffusion enhancement, 12th International Conference on Numerical Simulation of Optoelectronic Devices NUSOD'12, August 28  31, 2012, Chinese Academy of Science, Shanghai Institute for Technical Physics, August 29, 2012.

M. Liero, Interfaces in solar cells, 5th Annual Meeting Photonic Devices, February 23, 2012, KonradZuseZentrum für Informationstechnik, Berlin, February 24, 2012.

M. Liero, WIASTeSCA simulations in photovoltaics for a point contact concept of heterojunction thin film solar cells, International Workshop ``Mathematics for Semiconductur Heterostructures: Modeling, Analysis, and Numerics'', September 24  28, 2012, WIAS Berlin, September 25, 2012.

A. Linke, Coupled flows and poor mass conservation, Workshop ``Complex grids and fluid flows, conclusion of VFSitCom, National Research Project'', April 2  4, 2012, RhôneAlpes, Lyon, France, April 3, 2012.

A. PérezSerrano, J. Javaloyes, S. Balle, Multiple channel wavelength conversion using a semiconductor ring laser, European Semiconductor Laser Workshop 2012, September 20  23, 2012, Vrije Universiteit Brussel, Brussels, Belgium, September 21, 2012.

A. Glitzky, Mathematische Modellierung und Simulation organischer Halbleiterbauelemente, Senatsausschuss Wettbewerb (SAW), Sektion D der LeibnizGemeinschaft, LeibnizInstitut für Analytische Wissenschaften (ISAS), Dortmund, September 14, 2012.

M. Thomas, A model for rateindependent, brittle delamination in thermoviscoelasticity, International Workshop on Evolution Problems in Damage, Plasticity, and Fracture: Mathematical Models and Numerical Analysis, September 19  21, 2012, University of Udine, Department of Mathematics, Italy, September 21, 2012.

M. Thomas, A model for rateindependent, brittle delamination in thermoviscoelasticity, INDAM Workshop PDEs for Multiphase Advanced Materials (ADMAT2012), September 17  21, 2012, Cortona, Italy, September 17, 2012.

M. Thomas, Coupling of reactiondiffusion processes with thermomechanics using GENERIC, Winter School ``Calculus of Variations in Physics and Materials Science'', Würzburg, January 8  13, 2012.

M. Thomas, Thermomechanical modeling via energy and entropy, Seminar on Applied Mathematics, University of Pavia, Department of Mathematics, Italy, February 14, 2012.

M. Thomas, Thermomechanical modeling via energy and entropy using GENERIC, Workshop ``Mechanics of Materials'', March 19  23, 2012, Mathematisches Forschungsinstitut Oberwolfach, March 22, 2012.

K. Gärtner, A. Glitzky, Mathematics and simulation of the charge transport in semiconductor sensors, Fachtagung LeibnizNano (1. NanotechnologieWorkshop der LeibnizGemeinschaft), Berlin, January 30  31, 2012.

A. Mielke, Multidimensional modeling and simulation of optoelectronic devices, Challenge Workshop ``Modeling, Simulation and Optimisation Tools'', September 24  26, 2012, Technische Universität Berlin, September 24, 2012.

A. Mielke, On gradient flows and reactiondiffusion systems, Institutskolloquium, MaxPlanckInstitut für Mathematik in den Naturwissenschaften, Leipzig, December 3, 2012.

P.N. Racec, Finite volume discretization and Rmatrix formalism for cylindrical nanowire heterostructures, Seminar Laboratory 30 ``Nanoscale Condensed Matter Laboratory'', National Institute of Materials Physics, Bucharest, Romania, October 9, 2012.

P.N. Racec, Optimal finite volume discretization of Schrödinger equations for cylindrical symmetric nanowires, 76. Jahrestagung der DPG und DPG Frühjahrstagung 2012 of the Condensed Matter Section, Sektion ``Semiconductor Physics Division'', Sitzung ``Quanum Dots and Wires: Transport Properties I'', March 26  29, 2012, Technische Universität Berlin, March 28, 2012.

A. Fiebach, K. Gärtner, Finitevolumeapproximation of the MichaelisMenten kinetics, 3rd Spring School ``Analytical and Numerical Aspects of Evolution Equations'', Essen, March 28  April 1, 2011.

A. Glitzky, J.A. Griepentrog, Discrete SobolevPoincaré inequalities for Voronoi finite volume approximations, Finite Volumes for Complex Applications VI (FVCA 6), Prague, Czech Republic, June 6  10, 2011.

D. Knees, Numerical convergence analysis for a vanishing viscosity model in fracture mechanics, 7th International Congress on Industrial and Applied Mathematics, Session ``Materials Science II'', July 18  22, 2011, Society for Industrial and Applied Mathematics, Vancouver, Canada, July 19, 2011.

P.N. Racec, Rmatrix and finite volume method for cylindrical nanowire heterostructures, Mathematical Challenges of Quantum Transport in NanoOptoelectronic Systems, February 4  5, 2011, WIAS, February 4, 2011.

A. Caiazzo, Atlasbased reduced order modeling for fast patientspecifc simulations, 16th International Conference on Finite Elements in Flow Problems (FEF 2011), March 23  25, 2011, Arabellapark Hotel, München, March 24, 2011.

A. Caiazzo, Implicit coupling of dissipative boundary conditions models with projection schemes for NavierStokes equations, Workshop on Venous Hemodynamics, Medical Problems and Mathematical Modelling, October 25  26, 2011, Povo, Trento, Italy, October 26, 2011.

A.G. Vladimirov, Interaction of dissipative solitons and pulses in laser systems, Université Libre de Bruxelles, Optique Nonlinéaire Théorique, Belgium, April 21, 2010.

A.G. Vladimirov, Localized structures of light and their interaction, Imperial College London, Department of Applied Mathematics, UK, April 27, 2010.

A. Caiazzo, Blood flow through a porous interface: Numerical schemes and applications, IV International Symposium on Modeling of Physiological Flows 2010 (MPF2010), June 2  5, 2010, Cagliari, Italy, June 5, 2010.

A. Glitzky, Existence of bounded steady state solutions to spinpolarized driftdiffusion systems, Workshop on Drift Diffusion Systems and Related Problems: Analysis, Algorithms and Computations, WIAS, Research Group ``Numerical Mathematics and Scientific Computing'', March 25, 2010.

A. Glitzky, Uniform exponential decay of the free energy for Voronoi finite volume discretized reactiondiffusion systems, 8th AIMS International Conference on Dynamical Systems, Differential Equations and Applications, Special Session on Reaction Diffusion Systems, May 25  28, 2010, Technische Universität Dresden, May 26, 2010.

A. Mielke, The GENERIC formulation for dissipative temperaturedependent materials, International Symposium on Trends in Applications of Mathematics to Mechanics (STAMM 2010), August 30  September 2, 2010, Technische Universität Berlin, Institut für Mechanik, Berlin, September 1, 2010.

H. Stephan, Evolution equations conserving positivity, Colloquium of Centre for Analysis, Scientific Computing and Applications (CASA), Technische Universiteit Einhoven, Netherlands, April 21, 2010.

A. Fiebach, J. Fuhrmann, Numerical issues for reactiondiffusion processes in semiconductor photoresists, Workshop ``Evolution Equations, Related Topics and Applications'', München, September 7  11, 2009.

K. Hoke, Hartree solution of the KohnSham system for semiconductor devices, BerlinLeipzig Seminar on Numerics, MaxPlanckInstitut für Mathematik in den Naturwissenschaften, Leipzig, March 18, 2009.

K. Hoke, Iterative solution of the KohnSham system for semiconductor devices, International Conference ``Mathematics of Finite Elements and Applications 2009 (MAFELAP)'', Minisymposium ``Numerical Problems in Density Functional Theory'', June 9  12, 2009, The Brunel Institute of Computational Mathematics (BICOM), Uxbridge, UK, June 12, 2009.

A. Linke, Divergencefree mixed finite elements for the incompressible NavierStokes equations, Universität Stuttgart, Institut für Wasserbau, December 8, 2009.

A. Petrov, On the error estimates for spacetime discretizations of rateindependent processes, 8th GAMM Seminar on Microstructures, January 15  17, 2009, Universität Regensburg, NWFI Mathematik, January 17, 2009.

A. Petrov, On the existence and error bounds for spacetime discretizations of a 3D model for shapememory alloys, Lisbon University, Center for Mathematics and Fundamental Applications, Portugal, September 17, 2009.

A. Petrov, On the numerical approximation of a viscoelastic problem with unilateral constrains, 7th EUROMECH Solid Mechanics Conference (ESMC2009), Minisymposium on Contact Mechanics, September 7  11, 2009, Instituto Superior Técnico, Lisbon, Portugal, September 8, 2009.

A.G. Vladimirov, Enhancement of interaction of dissipative solitons above selfpulsing instability threshold, CPNLW09 Soliton 2009 ``Solitons in Their Roaring Forties: Coherence and Persistence in Nonlinear Waves'', January 6  9, 2009, Nice University, Nice, France, January 8, 2009.

A.G. Vladimirov, Spontaneous motion of dissipative solitons under the effect of delay, Australasian Conference on Optics, Lasers and Spectroscopy and Australian Conference on Optical Fibre Technology in association with the International Workshop on Dissipative Solitons (ACOLS ACOFT DS 2009), November 29  December 3, 2009, University of Adelaide, Australia, December 1, 2009.

A.G. Vladimirov, Strong enhancement of interaction of optical pulses induced by oscillatory instability, European Conference on Lasers and ElectroOptics and the XIth European Quantum Electronics Conference 2009 (CLEOtextsuperscript®/Europe  EQEC 2009, Munich, June 14  19, 2009.

U. Bandelow, Solitary wave solutions for fewcycle optical pulses, WIAS Workshop ``Nonlinear Optics in Guided Geometries'', May 18  20, 2009, WIAS, Berlin, May 19, 2009.

W. Dreyer, Stochastic evolution of many particle storage systems, 9th Hirschegg Workshop on Conservation Laws, September 6  12, 2009, Hirschegg, September 10, 2009.

M. Ehrhardt, J. Fuhrmann, A. Linke, Finite volume methods for the simulation of flow cell experiments, Workshop ``New Trends in Model Coupling  Theory, Numerics & Applications'' (NTMC'09), Paris, France, September 2  4, 2009.

M. Ehrhardt, The fluidporous interface problem: Analytic and numerical solutions to flow cell problems, 6th Symposium on Fuel Cell Modelling and Experimental Validation (MODVAL 6), March 25  26, 2009, Evangelische Akademie Baden, Bad Herrenalb, March 26, 2009.

M. Ehrhardt, The fluidporous interface problem: Analytic and numerical solutions to flow cell problems, Mathematical Models in Medicine, Business, Engineering (XI JORNADAS IMM), September 8  11, 2009, Technical University of Valencia, Institute of Multidisciplinary Mathematics, Spain, September 10, 2009.

J. Fuhrmann, A. Fiebach, A. Erdmann, P. Trefonas, Acid diffusion effects between resists in freezing processes used for contact hole patterning, 35th International Conference on Micro and Nano Engineering (MNE 2009), Ghent, Belgium, September 29  30, 2009.

J. Fuhrmann, Mathematical and numerical modeling of fuel cells and electrochemical flow cells, FraunhoferInstitut für Techno und Wirtschaftsmathematik, Kaiserslautern, December 1, 2009.

J. Fuhrmann, Mathematical and numerical models of electrochemical processes related to porous media, International Conference on Nonlinearities and Upscaling in Porous Media (NUPUS), October 5  7, 2009, Universität Stuttgart, October 6, 2009.

J. Fuhrmann, Model based numerical impedance calculation in electrochemical systems, 6th Symposium on Fuel Cell Modelling and Experimental Validation (MODVAL 6), March 25  26, 2009, Evangelische Akademie Baden, Bad Herrenalb, March 25, 2009.

J. Fuhrmann, Modeling and simulation of post exposure bake processes in double patterning, 7th Fraunhofer IISB Lithography Simulation Workshop, September 25  27, 2009, Hersbruck, September 26, 2009.

J. Fuhrmann, Modeling of reaction diffusion problems in semiconductor photoresists, Seventh Negev Applied Mathematical Workshop, July 6  8, 2009, Ben Gurion University of the Negev, Jacob Blaustein Institute for Desert Research, Sede Boqer Campus, Israel, July 8, 2009.

J. Fuhrmann, Numerical modeling in electrochemistry, Conference on Scientific Computing (ALGORITMY 2009), March 15  20, 2009, Slovak University of Technology, Department of Mathematics and Descriptive Geometry, Podbanské, March 17, 2005.

J. Fuhrmann, Reactiondiffusion processes in polymer resists, Workshop ``Evolution Equations, Related Topics and Applications'', September 7  11, 2009, HelmholzZentrum München, September 8, 2009.

K. Gärtner, J.A. Griepentrog, H. Langmach, The van Roosbroeck system, its mathematical properties, and detector simulation examples, 11th European Symposium on Semiconductor Detectors, Wildbad Kreuth, June 7  11, 2009.

K. Gärtner, Charge explosion studies, 5th Meeting of the Detector Advisory Committee for the European XFEL, April 28  29, 2009, European XDAC, Hamburg, April 28, 2009.

A. Glitzky, Discrete SobolevPoincaré inequalities for finite volume Voronoi approximations, Annual Meeting of the Deutsche MathematikerVereinigung and 17th Congress of the Österreichische Mathematische Gesellschaft, Section ``Partial Differential Equations'', September 20  25, 2009, Technische Universität Graz, Austria, September 21, 2009.

A. Glitzky, Discrete SobolevPoincaré inequalities using the $W^1,p$ seminorm in the setting of Voronoi finite volume approximations, International Conference on Elliptic and Parabolic Equations, November 30  December 4, 2009, WIAS, December 3, 2009.

V. John, On the numerical simulation of population balance systems, Karlsruher Institut für Technologie, Fakultät für Mathematik, December 9, 2009.

A. Linke, Mass conservative coupling of fluid flow and species transport in electrochemical flow cells, 13th Conference on Mathematics of Finite Elements and Applications (MAFELAP 2009), June 9  12, 2009, Brunel University, London, UK, June 10, 2009.

A. Linke, The discretization of coupled flows and the problem of mass conservation, Workshop on Discretization Methods for Viscous Flows, Part II: Compressible and Incompressible Flows, June 24  26, 2009, Porquerolles, Toulon, France, June 25, 2009.

A. Linke, The discretization of coupled flows and the problem of mass conservation, Seventh Negev Applied Mathematical Workshop, July 6  8, 2009, Ben Gurion University of the Negev, Jacob Blaustein Institute for Desert Research, Sede Boqer Campus, Israel, July 7, 2009.

H. Stephan, Inequalities for Markov operators, Positivity VI (Sixth Edition of the International Conference on Positivity and its Applications), July 20  24, 2009, El Escorial, Madrid, Spain, July 24, 2009.

H. Stephan, Modeling of diffusion prozesses with hidden degrees of freedom, Workshop on Numerical Methods for Applications, November 5  6, 2009, Lanke, November 6, 2009.

A. Fiebach, J. Fuhrmann, Some reaction diffusion problems in semiconductor device fabrication, Workshop on PDE Approximations in Fast Reaction  Slow Diffusion Scenarios, Leiden, Netherlands, November 10  14, 2008.

K. Hoke, Numerical treatment of the KohnSham system for semiconductor devices, Workshop on Mathematical Aspects of Transport in Mesoscopic Systems, Dublin, Ireland, December 4  7, 2008.

K. Hoke, On the numerics of the 3D KohnSham system, 4th Workshop on Mathematical Models for Transport in Macroscopic and Mesoscopic Systems, February 8  9, 2008, WIAS, February 9, 2008.

E. Holzbecher, H. Zhao, J. Fuhrmann, A. Linke, H. Langmach, Numerical investigation of thin layer flow cells, 4th Gerischer Symposium, Berlin, June 25  27, 2008.

A. Petrov, Error estimates for spacetime discretizations of a 3D model for shapememory materials, IUTAM Symposium ``Variational Concepts with Applications to the Mechanics of Materials'', September 22  26, 2008, RuhrUniversität Bochum, Lehrstuhl für allgemeine Mechanik, September 24, 2008.

A. Petrov, Existence and approximation for 3D model of thermally induced phase transformation in shapememory alloys, 79th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM 2008), Session ``Material models in solids'', March 31  April 4, 2008, Universität Bremen, April 1, 2008.

A. Petrov, Some mathematical results for a model of thermallyinduced phase transformations in shapememory materials, sc MatheonICM Workshop on Free Boundaries and Materials Modeling, March 17  18, 2008, WIAS, March 18, 2008.

A.G. Vladimirov, Nonlinear dynamics of pulse interactions in bistable optical systems, V International Conference ``Basic Problems of Optics'' BPO2008 in the framework of V International Congress ``Optics  XXI century'', October 20  24, 2008, St Petersburg, Russian Federation, October 23, 2008.

E. Bänsch, H. Berninger, U. Böhm, A. Bronstert, M. Ehrhardt, R. Forster, J. Fuhrmann, R. Klein, R. Kornhuber, A. Linke, A. Owinoh, J. Volkholz, Pakt für Forschung und Innovation: Das Forschungsnetzwerk ``Gekoppelte Strömungsprozesse in Energie und Umweltforschung'', Show of the Leibniz Association ``Exzellenz durch Vernetzung. Kooperationsprojekte der deutschen Wissenschaftsorganisationen mit Hochschulen im Pakt für Forschung und Innovation'', Berlin, November 12, 2008.

U. Bandelow, Solitary wave solutions for ultrashort optical pulses, Technical Conference ``Frontiers in Optics 2008, Laser Science XXIV'', October 19  23, 2008, Optical Society of America (OSA), Rochester, USA, October 21, 2008.

M. Ehrhardt, O. Gloger, Th. Dietrich, O. Hellwich, K. Graf, E. Nagel, Level Set Methoden zur Segmentierung von kardiologischen MRBildern, 22. Treffpunkt Medizintechnik: Fortschritte in der medizinischen Bildgebung, Charité, Campus Virchow Klinikum Berlin, May 22, 2008.

I. Kanattšikow, The short pulse equation: Integrability and generalizations, Gdańsk University of Technology, Institute of Theoretical Physics and Quantum Informatics, Gdańsk, Poland, June 30, 2008.

A. Linke, Mass conservative coupling of fluid flow and species transport in electrochemical flow cells, Annual Meeting of the Deutsche MathematikerVereinigung 2008, September 15  19, 2008, FriedrichAlexanderUniversität ErlangenNürnberg, September 16, 2008.

A. Linke, Mass conservative coupling of fluid flow and species transport in electrochemical flow cells, GeorgAugustUniversität Göttingen, November 11, 2008.

A. Linke, Lowestorder ScottVogelius elements for the incompressible NavierStokes equation, Universität Göttingen, Institut für Numerische und Angewandte Mathematik, January 10, 2007.

A. Linke, Nonnested multigrid solvers for mixed divergencefree ScottVogelius discretizations, 20th Chemnitz FEM Symposium, September 24  26, 2007, Technische Universität Chemnitz, Fakultät für Mathematik, September 26, 2007.

A. Linke, Stabilized finite element schemes for incompressible flow using ScottVogelius elements, Université de MarnelaVallée, Département de Mathématiques, ChampssurMarne, France, April 19, 2007.

A. Linke, Stabilized finite element schemes for incompressible flow using ScottVogelius elements, FriedrichAlexanderUniversität ErlangenNürnberg, Angewandte Mathematik III, July 3, 2007.

M. Pietrzyk, Multisymplectic analysis of the short pulse equation, 10th International Conference on Differential Geometry and Its Application, August 27  31, 2007, Olomouc, Czech Republic, August 28, 2007.

M. Lichtner, Invariant manifold theorem for semilinear hyperbolic systems, EQUADIFF 07, August 5  11, 2007, Technische Universität Wien, Austria, August 7, 2007.

A. Vladimirov, Autosolitons in optical devices with transverse refractive index modulation, International Conference on Coherent and Nonlinear Optics/International Conference on Lasers, Applications, and Technologies (ICONO/LAT 2007), May 28  June 1, 2007, Minsk, Belarus, May 29, 2007.

A. Vladimirov, Dissipative solitons in nonlinear optical devices with refractive index modulation, Workshop ``Nonlinear Effects in Photonic Materials'', March 12  14, 2007, WIAS, Berlin, March 14, 2007.

M. Lichtner, A spectral gap mapping theorem and smooth invariant center manifolds for semilinear hyperbolic systems, 6th AIMS International Conference on Dynamical Systems, Differential Equations & Applications, June 25  28, 2006, Université de Poitiers, France, June 28, 2006.

A. Linke, Computing generalized Oseen flows by stabilized lowestorder ScottVogelius elements, FriedrichAlexanderUniversität ErlangenNürnberg, Angewandte Mathematik III, July 21, 2006.

A. Vladimirov, Laser dissipative solitons and their interaction, Minisymposium on Dissipative Solitons, WIAS, Berlin, April 20, 2006.

A. Vladimirov, Localized structures of light in laser systems and their weak interactions, Technische Universität Berlin, June 14, 2006.

A. Vladimirov, Nonlinear dynamics and bifurcations in multimode and spatially distributed laser systems, June 20  23, 2006, St. Petersburg State University, Russian Federation, June 20, 2006.

A. Vladimirov, Nonlinear dynamics in multimode and spatially extended laser systems, Moscow State University, Physics Faculty, Russian Federation, November 10, 2006.

A. Vladimirov, Transverse Bragg dissipative solitons in a Kerr cavity with refractive index modulation, Laser Optics Conference, June 26  30, 2006, St. Petersburg, Russian Federation, June 28, 2006.

A. Vladimirov, G. Kozyreff, P. Mandel, M. Tlidi, Localized structures in a passive cavity with refractive index modulation, International Quantum Electronics Conference, June 12  17, 2005, München, June 15, 2005.

A. Vladimirov, Interaction of dissipative solitons in laser systems, Ben Gurion University of the Negev, Department of Mathematics, Beer Sheva, Israel, November 17, 2005.

D. Turaev, S. Zelik, A. Vladimirov, Chaotic bound state of localized structures in the complex GinzburgLandau equation, Conference Digest ``Nonlinear Guided Waves and their Applications'', Dresden, September 6  9, 2005.

J. Fuhrmann, H.Chr. Kaiser, Th. Koprucki, G. Schmidt, Electronic states in semiconductor nanostructures and upscaling to semiclassical models, Evaluation Colloquium of the DFG Priority Program ``Analysis, Modeling and Simulation of Multiscale Problems'', Bad Honnef, May 20  21, 2004.

H.Chr. Kaiser, On space discretization of reactiondiffusion systems with discontinuous coefficients and mixed boundary conditions, 2nd GAMM Seminar on Microstructures, January 10  11, 2003, RuhrUniversität Bochum, Institut für Mechanik, January 10, 2003.

A.G. Vladimirov, Moving discrete solitons in multicore fibers and waveguide arrays, European Quantum Electronics Conference, June 22  27, 2003, München, June 25, 2003.

A.G. Vladimirov, Moving discrete solitons in multicore fibers and waveguide arrays, Conference dedicated to the 60th birthday of Prof. Paul Mandel, April 11  12, 2003, Université Libre de Bruxelles, Optique Nonlinéaire Théorique, Belgium, April 11, 2003.
External Preprints

R. Araya, A. Caiazzo, F. Chouly, Stokes problem with slip boundary conditions using stabilized finite elements combined with Nitsche, Preprint no. hal04077986, Hyper Articles en Ligne (HAL), 2023.
Abstract
We discuss how slip conditions for the Stokes equation can be handled using Nitsche method, for a stabilized finite element discretization. Emphasis is made on the interplay between stabilization and Nitsche terms. Wellposedness of the discrete problem and optimal convergence rates are established, and illustrated with various numerical experiments. 
R. Finn, M. O'Donovan, P. Farrell, J. Moatti, T. Streckenbach, Th. Koprucki, S. Schulz, Theoretical study of the impact of alloy disorder on carrier transport and recombination processes in deep UV (Al, Ga)N light emitters, Preprint no. hal04037215, Hyper Articles en Ligne (HAL), 2023.
Abstract
Aluminium gallium nitride ((Al,Ga)N) has gained significant attention in recent years due to its potential for highly efficient light emitters operating in the deep ultraviolet (UV) range (< 280 nm). However, given that current devices exhibit extremely low efficiencies, understanding the fundamental properties of (Al,Ga)Nbased systems is of key importance. Here, using a multiscale simulation framework, we study the impact of alloy disorder on carrier transport, radiative and nonradiative recombination processes in a cplane Al0.7Ga0.3N/Al0.8Ga0.2N quantum well embedded in a pin junction. Our calculations reveal that alloy fluctuations can open "percolative" pathways that promote transport for the electrons and holes into the quantum well region. Such an effect is neglected in conventional, and widely used transport simulations. Moreover, we find also that the resulting increased carrier density and alloy induced carrier localization effects significantly increase nonradiative AugerMeitner recombination in comparison to the radiative process. Thus, to avoid such nonradiative process and potentially related material degradation, a careful design (wider well, multi quantum wells) of the active region is required to improve the efficiency of deep UV light emitters. 
F. Galarce, J. Mura, A. Caiazzo, Bias and multiscale correction methods for variational state estimation algorithms, Preprint no. arXiv:2311.14031, Cornell University, 2023, DOI 10.48550/arXiv.2311.14031 .
Abstract
The integration of experimental data into mathematical and computational models is crucial for enhancing their predictive power in realworld scenarios. However, the performance of data assimilation algorithms can be significantly degraded when measurements are corrupted by biased noise, altering the signal magnitude, or when the system dynamics lack smoothness, such as in the presence of fast oscillations or discontinuities. This paper focuses on variational state estimation using the socalled 'Parameterized Background Data Weak' method, which relies on a parameterized background by a set of constraints, enabling state estimation by solving a minimization problem on a reducedorder background model, subject to constraints imposed by the input measurements. To address biased noise in observations, a modified formulation is proposed, incorporating a correction mechanism to handle rapid oscillations by treating them as slowdecaying modes based on a twoscale splitting of the classical reconstruction algorithm. The effectiveness of the proposed algorithms is demonstrated through various examples, including discontinuous signals and simulated Doppler ultrasound data. 
P.L. Lederer, Ch. Merdon, Gradientrobust hybrid DG discretizations for the compressible Stokes equations, Preprint no. arXiv.2311.06098, Cornell University, 2023, DOI 10.48550/arXiv.2311.06098 .
Abstract
This paper studies two hybrid discontinuous Galerkin (HDG) discretizations for the velocitydensity formulation of the compressible Stokes equations with respect to several desired structural properties, namely provable convergence, the preservation of nonnegativity and mass constraints for the density, and gradientrobustness. The later property dramatically enhances the accuracy in wellbalanced situations, such as the hydrostatic balance where the pressure gradient balances the gravity force. One of the studied schemes employs an H(div)conforming velocity ansatz space which ensures all mentioned properties, while a fully discontinuous method is shown to satisfy all properties but the gradientrobustness. Also higherorder schemes for both variants are presented and compared in three numerical benchmark problems. The final example shows the importance also for nonhydrostatic wellbalanced states for the compressible NavierStokes equations. 
B. Spetzler, D. Abdel, F. Schwierz, M. Ziegler, P. Farrell, The role of mobile point defects in twodimensional memristive devices, Preprint no. arXiv:2304.06527, Cornell University, 2023, DOI 10.48550/arXiv.2304.06527 .
Abstract
Twodimensional (2D) layered transition metal dichalcogenides (TMDCs) are promising memristive materials for neuromorphic computing systems as they could solve the problem of the excessively high energy consumption of conventional von Neumann computer architectures. Despite extensive experimental work, the underlying switching mechanisms are still not understood, impeding progress in material and device functionality. This study reveals the dominant role of mobile defects in the switching dynamics of 2D TMDC materials. The switching process is governed by the formation and annihilation dynamics of a local vacancy depletion zone. Moreover, minor changes in the interface potential barriers cause fundamentally different device behavior previously thought to originate from multiple mechanisms. The key mechanisms are identified with a charge transport model for electrons, holes, and ionic point defects, including imagechargeinduced Schottky barrier lowering (SBL). The model is validated by comparing simulations to measurements for various 2D MoS2based devices, strongly corroborating the relevance of vacancies in TMDC devices and offering a new perspective on the switching mechanisms. The insights gained from this study can be used to extend the functional behavior of 2D TMDC memristive devices in future neuromorphic computing applications. 
P. Farrell, J. Moatti, M. O'Donovan, S. Schulz, Th. Koprucki, Importance of satisfying thermodynamic consistency in light emitting diode simulations, Preprint no. hal04012467, Hyper Articles en Ligne (HAL), 2023.
Abstract
We show the importance of using a thermodynamically consistent flux discretization when describing driftdiffusion processes within light emitting diode simulations. Using the classical ScharfetterGummel scheme with FermiDirac statistics is an example of such an inconsistent scheme. In this case, for an (In,Ga)N multi quantum well device, the Fermi levels show steep gradients on one side of the quantum wells which are not to be expected. This result originates from neglecting diffusion enhancement associated with FermiDirac statistics in the numerical flux approximation. For a thermodynamically consistent scheme, such as the SEDAN scheme, the spikes in the Fermi levels disappear. We will show that thermodynamic inconsistency has far reaching implications on the currentvoltage curves and recombination rates. 
B. GarcíaArchilla, V. John, J. Novo, PODROMs for incompressible flows including snapshots of the temporal derivative of the full order solution, Preprint no. arXiv:2206.09123, Cornell University, 2022, DOI 10.48550/arXiv.2206.09123 .

S. Piani, P. Farrell, W. Lei, N. Rotundo, L. Heltai, A weighted hybridizable discontinuous Galerkin method for driftdiffusion problems, Preprint no. arXiv:2211.02508, Cornell University, 2022, DOI 10.48550/arXiv.2211.02508 .

S. Piani, P. Farrell, W. Lei, N. Rotundo, L. Heltai, Datadriven solutions of illposed inverse problems arising from doping reconstruction in semiconductors, Preprint no. arXiv:2208.00742, Cornell University, 2022, DOI 10.48550/arXiv.2208.00742 .

M. Oliva, T. Flissikowsky, M. Góra, J. Lähnemann, J. Herranz, R. Lewis, O. Marquardt, M. Ramsteiner, L. Geelhaar, O. Brandt, Carrier recombination in highly uniform and phasepure GaAs/(Al,Ga)As core/shell nanowire arrays on Si(111): Mott transition and internal quantum efficiency, Preprint no. arXiv:2211.17167, Cornell University, 2022, DOI 10.48550/arXiv.2211.17167 .
Abstract
GaAsbased nanowires are among the most promising candidates for realizing a monolithical integration of IIIV optoelectronics on the Si platform. To realize their full potential for applications as light absorbers and emitters, it is crucial to understand their interaction with light governing the absorption and extraction efficiency, as well as the carrier recombination dynamics determining the radiative efficiency. Here, we study the spontaneous emission of zincblende GaAs/(Al,Ga)As core/shell nanowire arrays by μ photoluminescence spectroscopy. These ordered arrays are synthesized on patterned Si(111) substrates using molecular beam epitaxy, and exhibit an exceptionally low degree of polytypism for interwire separations exceeding a critical value. We record emission spectra over more than five orders of excitation density for both steadystate and pulsed excitation to identify the nature of the recombination channels. An abrupt Mott transition from excitonic to electronholeplasma recombination is observed, and the corresponding Mott density is derived. Combining these experiments with simulations and additional direct measurements of the external quantum efficiency using a perfect diffuse reflector as reference, we are able to extract the internal quantum efficiency as a function of carrier density and temperature as well as the extraction efficiency of the nanowire array. The results vividly document the high potential of GaAs/(Al,Ga)As core/shell nanowires for efficient light emitters integrated on the Si platform. Furthermore, the methodology established in this work can be applied to nanowires of any other materials system of interest for optoelectronic applications. 
N. Ahmed, V. John, X. Li, Ch. Merdon, Infsup stabilized ScottVogelius pairs on general simplicial grids for NavierStokes equations, Preprint no. arXiv:2212.10909, Cornell University, 2022, DOI 10.48550/arXiv.2212.10909 .

V. John, X. Li, Ch. Merdon, H. Rui, Infsup stabilized ScottVogelius pairs on general simplicial grids by RaviartThomas enrichment, Preprint no. arXiv:2206.01242, Cornell University, 2022, DOI 10.48550/arXiv.2206.01242 .

M. O'Donovan, P. Farrell, T. Streckenbach, Th. Koprucki, S. Schulz, Multiscale simulations of unipolar hole transport in (In,Ga)N quantum well systems, Preprint no. arXiv:2111.01644, Cornell University Library, arXiv.org, 2021.
Abstract
Understanding the impact of the alloy microstructure on carrier transport becomes important when designing IIInitridebased LED structures. In this work, we study the impact of alloy fluctuations on the hole carrier transport in (In,Ga)N single and multiquantum well systems. To disentangle hole transport from electron transport and carrier recombination processes, we focus our attention on unipolar (pip) systems. The calculations employ our recently established multiscale simulation framework that connects atomistic tightbinding theory with a macroscale driftdiffusion model. In addition to alloy fluctuations, we pay special attention to the impact of quantum corrections on hole transport. Our calculations indicate that results from a virtual crystal approximation present an upper limit for the hole transport in a pip structure in terms of the currentvoltage characteristics. Thus we find that alloy fluctuations can have a detrimental effect on hole transport in (In,Ga)N quantum well systems, in contrast to unipolar electron transport. However, our studies also reveal that the magnitude by which the random alloy results deviate from virtual crystal approximation data depends on several factors, e.g. how quantum corrections are treated in the transport calculations. 
J. Fuhrmann, C. Guhlke, Ch. Merdon, A. Linke, R. Müller, Induced charge electroosmotic flow with finite ion size and solvation effects, Preprint no. arXiv:1901.06941, Cornell University Library, 2019, DOI 10.1016/j.electacta.2019.05.051 .

A. Linke, Ch. Merdon, M. Neilan, Pressurerobustness in quasioptimal a priori estimates for the Stokes problem, Preprint no. arXiv:1906.03009, Cornell University Library, arXiv.org, 2019.

N.R. Gauger, A. Linke, P. Schroeder, On highorder pressurerobust space discretisations, their advantages for incompressible high Reynolds number generalised Beltrami flows and beyond, Preprint no. arXiv:1808.10711, Cornell University Library, arXiv.org, 2018.
Abstract
Recently, highorder space discretisations were proposed for the numerical simulation of the incompressible NavierStokes equations at high Reynolds numbers, even for complicated domains from simulation practice. Although the overall spatial approximation order of the algorithms depends on the approximation quality of the boundary (often not better than third order), competitively accurate and efficient results were reported. In this contribution, first, a possible explanation for this somewhat surprising result is proposed: the velocity error of highorder space discretisations is more robust against quantitatively large and complicated pressure fields than loworder methods. Second, it is demonstrated that novel pressurerobust methods are significantly more accurate than comparable classical, nonpressurerobust space discretisations, whenever the quadratic, nonlinear convection term is a nontrivial gradient field like in certain generalised Beltrami flows at high Reynolds number. Then, pressurerobust methods even allow to halve the (formal) approximation order without compromising the accuracy. Third, classical highorder space discretisations are outperformed by pressurerobust methods whenever the boundary is not approximated with highorder accuracy. This improved accuracy of (loworder) pressurerobust mixed methods is explained in terms of a HelmholtzHodge projector, which cancels out the nonlinear convection term in any generalised Beltrami flow, since it is a gradient field. The numerical results are illustrated by a novel numerical analysis for pressurerobust and classical space discretisations. Further, the relevance of these results is discussed for flows that are not of Beltrami type. 
G.R. Barrenechea, V. John, P. Knobloch, An algebraic flux correction scheme satisfying the discrete maximum principle and linearity preservation on general meshes, Preprint no. 201606, Nečas Center for Mathematical Modeling, 2016.

S. Neukamm, A. Gloria, F. Otto, An optimal quantitative twoscale expansion in stochastic homogenization of discrete elliptic equations, Preprint no. 41, MaxPlanckInstitut für Mathematik in den Naturwissenschaften, 2013.
Abstract
We establish an optimal, linear rate of convergence for the stochastic homogenization of discrete linear elliptic equations. We consider the model problem of independent and identically distributed coefficients on a discretized unit torus. We show that the difference between the solution to the random problem on the discretized torus and the first two terms of the twoscale asymptotic expansion has the same scaling as in the periodic case. In particular the L^{2}norm in probability of the H^{1}norm in space of this error scales like ε, where ε is the discretization parameter of the unit torus. The proof makes extensive use of previous results by the authors, and of recent annealed estimates on the Greens function by Marahrens and the third author. 
S. Amiranashvili, U. Bandelow, A.G. Vladimirov, Solitary wave solutions for fewcycle optical pulses, Preprint no. 500, DFG Research Center sc Matheon, 2008.
Contributing Groups of WIAS
Applications
 Electronic materials
 Mathematical Models and Methods for Lithiumion Batteries
 Modeling and simulation of semiconductor structures
 Modeling of thin films and nano structures on substrates
 Modeling, Simulation and Optimization for Biomedical Applications
 Nonlinear material models, multifunctional materials and hysteresis in continuum mechanics.
 Optical pulses in nonlinear media
 Phase field models for complex materials and interfaces
 Quantum models for semiconductors
 Simulation and optimization of industrial processes
 Thermodynamic models for electrochemical systems
Projects/Grants
 AI Based Simulation of Transient Physical Systems  From Benchmarks to Hybrid Solutions
 Coherent Transport of Semiconductor SpinQubits: Modeling, Simulation and Optimal Control
 Consortium Management
 DataDriven Stochastic Modeling of Semiconductor Laser
 Electronics of Nanotextured Perovskite Devices
 Interdisciplinary workflows, standardization of mathematical descriptions in the natural sciences and integration into the MaRDI platform
 Mathematical modeling and simulation of substrateflow interaction using generalized gradient flows
 Modeling Battery Electrodes with Mechanical Interactions and Multiple Phase Transitions upon Ion Insertion
 Nonlinear electrokinetics in anisotropic microfluids  analysis, simulation, and optimal control
 Recovery of Battery Ageing Dynamics with Multiple Timescales
 Volatile Electricity Markets and Battery Storage: A ModelBased Approach for Optimal Control
 Wasserstein Gradient Flows for Generalised Transport in Bayesian Inversion