Die mathematische Beschreibung einer großen Zahl von Fragestellungen aus Wissenschaft und Technik führt auf Systeme partieller Differentialgleichungen (PDEs).
Partielle Differentialgleichungen beschreiben die Struktur der räumlichen und zeitlichen Variationen des Zustands des zugrundeliegenden physikalischen Systems. Die Unbekannten solcher Gleichungen sind Funktionen einer oder mehrerer räumlicher Variablen und ggf. der Zeit. Im Allgemeinen ist es lediglich möglich, partielle Differentialgleichungen approximativ, auf der Basis von Diskretisierungen in Raum und Zeit zu lösen. Eine hohe Approximationsgüte muss durch eine geeignete Wahl dieser Diskretisierungen gesichert werden. Weiterhin ist es notwendig, die resultierenden großen linearen oder nichtlinearen Systeme algebraischer Gleichungen effizient zu lösen. Innerhalb der Forschungsgruppen werden die zugrundeliegenden Diskretisierungsverfahren mathematisch analysiert, sie werden implementiert, verbessert und für die Anwendung auf neue Problemklassen weiterentwickelt. Diese Verfahren dienen als Basis für die Simulation der betrachteten Anwendungen.
Die Simulationen in Kooperation mit Partnern aus Wissenschaft und Industrie führen zu neuen Einsichten in die Struktur konkreter Fragestellungen. Damit entstehen neue Herausforderungen für die Weiterentwicklung, Analysis und numerische Behandlung der verwendeten Modelle.
Elektrolytische Diode mit angelegter Potentialdifferenz in Sperrichtung. Die Verarmung der Ionenkonzentration in der Nähe des Wechsels des Vorzeichens der Oberflächenladung verringert den ionischen Stromfluss (http://dx.doi.org/10.1002/fuce.201500215)
Publikationen
Monografien

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).
Artikel in Referierten Journalen

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, (2019), published online on 07.11.2019, 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. 
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. 
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), 1502310, DOI 10.1109/JSTQE.2019.2925926 .

F. Agnelli, A. Constantinescu, G. Nika, Design and testing of 3Dprinted microarchitectured polymer materials exhibiting a negative Poisson's ratio, Continuum Mechanics and Thermodynamics, (2019), pp. published online on 20.11.2019 (117), 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, 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), 1502310, 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, Challenges for driftdiffusion simulations of semiconductors: A comparative study of different discretization philosophies, Computers & Mathematics with Applications. An International Journal, published online on 18.06.2019, 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), e2918, 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. 
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, 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. 
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. 
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, Optics Letters, 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.
Beiträge zu Sammelwerken

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: Proceedings of ``SPIE Photonics West'', San Francisco, USA, B. Witzigmann, M. Osiński, Y. Arakawa, eds., 10912 of Physics and Simulation of Optoelectronic Devices XXVII, SPIE Digital Library, Bellingham, 2019, pp. published online on 26.02.2019, 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 
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 .

A. Linke, Nonlinear flux approximation scheme for burgers equation derived from a local BVP, in: Numerical Mathematics and Advanced Applications 2017, Proceedings of ENUMATH 2017, F.A. Radu, K. Kumar, I. Berre, J.M. Nordbotten, I.S. Pop, eds., Springer, Berlin et al., 2019.

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

M. Kantner, Th. Koprucki, Nonisothermal ScharfetterGummel scheme for electrothermal transport simulation in degenerate semiconductors, Preprint no. 2664, WIAS, Berlin, 2019, DOI 10.20347/WIAS.PREPRINT.2664 .
Abstract, PDF (1331 kByte)
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 Scharfetter? Gummel finite volume discretization for degenerate semiconductors obeying Fermi?Dirac 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. 
J. Fuhrmann, D.H. Doan, A. Glitzky, M. Liero, G. Nika, Unipolar driftdiffusion simulation of Sshaped currentvoltage relations for organic semiconductor devices, Preprint no. 2660, WIAS, Berlin, 2019, DOI 10.20347/WIAS.PREPRINT.2660 .
Abstract, PDF (1456 kByte)
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. Höhne, Th. Koprucki, S. Burger, H.J. Wünsche, F. Schmidt, A. Mielke, U. Bandelow, Multidimensional modeling and simulation of semiconductor nanophotonic devices, Preprint no. 2653, WIAS, Berlin, 2019, DOI 10.20347/WIAS.PREPRINT.2653 .
Abstract, PDF (9836 kByte)
Selfconsistent modeling and multidimensional simulation of semiconductor nanophotonic devices is an important tool in the development of future integrated light sources and quantum devices. Simulations can guide important technological decisions by revealing performance bottlenecks in new device concepts, contribute to their understanding and help to theoretically explore their optimization potential. The efficient implementation of multidimensional numerical simulations for computeraided design tasks requires sophisticated numerical methods and modeling techniques. We review recent advances in devicescale modeling of quantum dot based singlephoton sources and laser diodes by selfconsistently coupling the optical Maxwell equations with semiclassical carrier transport models using semiclassical and fully quantum mechanical descriptions of the optically active region, respectively. For the simulation of realistic devices with complex, multidimensional geometries, we have developed a novel hpadaptive finite element approach for the optical Maxwell equations, using mixed meshes adapted to the multiscale properties of the photonic structures. For electrically driven devices, we introduced novel discretization and parameterembedding techniques to solve the driftdiffusion system for strongly degenerate semiconductors at cryogenic temperature. Our methodical advances are demonstrated on various applications, including verticalcavity surfaceemitting lasers, grating couplers and singlephoton sources. 
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, Preprint no. 2644, WIAS, Berlin, 2019, DOI 10.20347/WIAS.PREPRINT.2644 .
Abstract, PDF (5234 kByte)
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. 
M. Akbas, Th. Gallouët, A. Gassmann, A. Linke, Ch. Merdon, A gradientrobust wellbalanced scheme for the compressible isothermal Stokes problem, Preprint no. 2641, WIAS, Berlin, 2019, DOI 10.20347/WIAS.PREPRINT.2641 .
Abstract, PDF (445 kByte)
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. 
J. Fuhrmann, M. Landstorfer, R. Müller, Modeling polycrystalline electrodeelectrolyte interfaces: The differential capacitance, Preprint no. 2640, WIAS, Berlin, 2019, DOI 10.20347/WIAS.PREPRINT.2640 .
Abstract, PDF (3691 kByte)
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. 
D.H. Doan, A. Fischer, J. Fuhrmann, A. Glitzky, M. Liero, Driftdiffusion simulation of Sshaped currentvoltage relations for organic semiconductor devices, Preprint no. 2630, WIAS, Berlin, 2019, DOI 10.20347/WIAS.PREPRINT.2630 .
Abstract, PDF (2299 kByte)
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. 
P.É. Druet, Globalintime existence for liquid mixtures subject to a generalised incompressibility constraint, Preprint no. 2622, WIAS, Berlin, 2019, DOI 10.20347/WIAS.PREPRINT.2622 .
Abstract, PDF (510 kByte)
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. Lübbering, J. Kunkel, P. Farrell, What company does my news article refer to? Tackling multiclass problems with topic modeling, Preprint no. 2621, WIAS, Berlin, 2019, DOI 10.20347/WIAS.PREPRINT.2621 .
Abstract, PDF (354 kByte)
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. 
C. Cancès, C. ChainaisHillairet, J. Fuhrmann, B. Gaudeul, A numerical analysis focused comparison of several finite volume schemes for an unipolar degenerated driftdiffusion model, Preprint no. 2620, WIAS, Berlin, 2019, DOI 10.20347/WIAS.PREPRINT.2620 .
Abstract, PDF (2725 kByte)
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. 
C. Grässle, M. Hintermüller, M. Hinze, T. Keil, Simulation and control of a nonsmooth CahnHilliard NavierStokes system with variable fluid densities, Preprint no. 2617, WIAS, Berlin, 2019, DOI 10.20347/WIAS.PREPRINT.2617 .
Abstract, PDF (11 MByte)
We are concerned with the simulation and control of a two phase flow model governed by a coupled CahnHilliard NavierStokes system involving a nonsmooth energy potential.We establish the existence of optimal solutions and present two distinct approaches to derive suitable stationarity conditions for the bilevel problem, namely C and strong stationarity. Moreover, we demonstrate the numerical realization of these concepts at the hands of two adaptive solution algorithms relying on a specifically developed goaloriented error estimator.In addition, we present a model order reduction approach using proper orthogonal decomposition (PODMOR) in order to replace highfidelity models by low order surrogates. In particular, we combine POD with spaceadapted snapshots and address the challenges which are the consideration of snapshots with different spatial resolutions and the conservation of a solenoidal property. 
O. Souček, M. Heida, J. Málek, On a thermodynamic framework for developing boundary conditions for Korteweg fluids, Preprint no. 2599, WIAS, Berlin, 2019, DOI 10.20347/WIAS.PREPRINT.2599 .
Abstract, PDF (2111 kByte)
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. 
G. Nika, B. Vernescu, Multiscale modeling of magnetorheological suspensions, Preprint no. 2598, WIAS, Berlin, 2019, DOI 10.20347/WIAS.PREPRINT.2598 .
Abstract, PDF (3159 kByte)
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. 
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, Preprint no. 2597, WIAS, Berlin, 2019, DOI 10.20347/WIAS.PREPRINT.2597 .
Abstract, PDF (1351 kByte)
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. 
A. Alphonse, M. Hintermüller, C.N. Rautenberg, Existence, iteration procedures and directional differentiability for parabolic QVIs, Preprint no. 2592, WIAS, Berlin, 2019, DOI 10.20347/WIAS.PREPRINT.2592 .
Abstract, PDF (408 kByte)
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. 
V. John, P. Knobloch, U. Wilbrandt, Finite element pressure stabilizations for incompressible flow problems, Preprint no. 2587, WIAS, Berlin, 2019, DOI 10.20347/WIAS.PREPRINT.2587 .
Abstract, PDF (2101 kByte)
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. 
A. Mielke, T. Roubíček, Thermoviscoelasticity in KelvinVoigt rheology at large strains, Preprint no. 2584, WIAS, Berlin, 2019, DOI 10.20347/WIAS.PREPRINT.2584 .
Abstract, PDF (472 kByte)
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. 
A. Caiazzo, R. Maier, D. Peterseim, Reconstruction of quasilocal numerical effective models from lowresolution measurements, Preprint no. 2577, WIAS, Berlin, 2019, DOI 10.20347/WIAS.PREPRINT.2577 .
Abstract, PDF (1550 kByte)
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. 
R. Schlundt, A multilevel Schur complement preconditioner with ILU factorization for complex symmetric matrices, Preprint no. 2556, WIAS, Berlin, 2018, DOI 10.20347/WIAS.PREPRINT.2556 .
Abstract, PDF (318 kByte)
This paper describes a multilevel preconditioning technique for solving complex symmetric sparse linear systems. The coefficient matrix is first decoupled by domain decomposition and then an approximate inverse of the original matrix is computed level by level. This approximate inverse is based on low rank approximations of the local Schur complements. For this, a symmetric singular value decomposition of a complex symmetric matix is used. The blockdiagonal matrices are decomposed by an incomplete LDL^{T} factorization with the BunchKaufman pivoting method. Using the example of Maxwell's equations the generality of the approach is demonstrated. 
A. Mielke, J. Naumann, On the existence of globalintime weak solutions and scaling laws for Kolmogorov's twoequation model of turbulence, Preprint no. 2545, WIAS, Berlin, 2018, DOI 10.20347/WIAS.PREPRINT.2545 .
Abstract, PDF (467 kByte)
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.
Vorträge, Poster

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.

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'', Thematic Minisymposium MS ME13 1 ``Emerging Problems in the Homogenization of Partial Differential Equations'', ``9th International Congress on Industrial and Applied Mathematics (ICIAM 2019)'', July 15  19, 2019, Universitat de València, 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, May 24, 2019, 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, May 27  29, 2019, Delft University of Technology, Netherlands, May 28, 2019.

D. Peschka, Steering pattern formation of viscous flows, DMVJahrestagung 2019, 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, March 11  14, 2019, 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 of rateindependent gradientregularized damage models, ``Dynamics, Equations and Applications'' (DEA), 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.

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

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.

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

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

A. 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.
Preprints im Fremdverlag

M. Akbas, Th. Gallouët, A. Gassmann, A. Linke, Ch. Merdon, A gradientrobust wellbalanced scheme for the compressible isothermal Stokes problem, Preprint no. arXiv:1911.01295, Cornell University Library, arXiv.org, 2019.

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, 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.
Ansprechpartner
Beteiligte Gruppen des WIAS
Anwendungen
 Dynamik von Halbleiterlasern
 Modellierung dünner Filme und Nanostrukturen auf Substraten
 Modellierung und Simulation von Halbleiterstrukturen
 Modellierung von Phasenseparation und Schädigung in modernen Materialien
 Modellierung, Simulation und Optimierung für Anwendungen in der Biomedizin
 Nichtlineare Materialmodelle, multifunktionale Materialien und Hysterese im Zusammenhang mit elastoplastischen Prozessen
 Phasenübergänge und Hysterese im Zusammenhang mit Speicherproblemen
 Photovoltaik
 Pulse in optisch nichtlinearen Medien
 Quantenmechanische Modelle für Halbleiter
 Simulation, Optimierung und optimale Steuerung von Produktionsprozessen
 Thermodynamische Modelle elektrochemischer Systeme
Projekte/Drittmittel
 Mathematische Modellierung und Simulation der Wechselwirkung von Substraten mit Strömungen durch verallgemeinerte Gradientenflüsse
 Modelbased geometry reconstruction from TEM images
 Modellbasierte Abschätzung der Lebensdauer von gealterten LiBatterien für die 2ndLife Anwendung als stationärer Stromspeicher (MALLi2)
 MultiMaterial Electrocatalysis (MULTECAT)
 Musterbildung in mehrskaligen Systemen
 Numerische Lösungsverfahren für gekoppelte Populationsbilanzsysteme zur dynamischen Simulation multivariater Feststoffprozesse am Beispiel der formselektiven Kristallisation
 Understanding doping variations in silicon crystals
 Untersuchung elektrochemischer Doppelschichten in Feststoffoxidstellen
 Verbundprojekt “Wege zu sekundären Mg/Ca  LuftBatterien”
 Zuverlässigkeit effizienter Approximationen von Funktionen beschränkter Variation in der Beschreibung von Materialunstetigkeiten