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Wednesday, 24.09.2014, 15.15 Uhr (WIAS-ESH)
BERLINER OBERSEMINAR Nichtlineare partielle Differentialgleichungen (Langenbach-Seminar)
J. Zinsl, TU München:
Transport distances and geodesic convexity for systems of degenerate diffusion equations
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
In my talk, I will introduce a Wasserstein-like transport distance between vector-valued measurable functions on the real line generalizing some aspects of the scalar theory by Dolbeault et al. (2009) and Lisini et al. (2010). Using this new distance, we are able to cast certain systems of nonlinear degenerate parabolic evolution equations into the variational framework of gradient ows. I will introduce a sufficient condition for the geodesic convexity of functionals with respect to this new distance. A possible application of this theory is proving existence of weak solutions to a class of systems of second- and fourth-order parabolic evolution equations. This is joint work with Daniel Matthes.

Further Informations
Berliner Oberseminar ``Nichtlineare Partielle Differentialgleichungen'' (Langenbach Seminar)

Host
WIAS Berlin
Humboldt-Universität zu Berlin
Thursday, 25.09.2014, 14.00 Uhr (WIAS-ESH)
Seminar Numerische Mathematik
Dr. J. Pellerin, WIAS Berlin:
Accounting for the geometrical complexity of geological structural models in Voronoi-based meshing methods
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
Depending on the specific method used to build a 3D structural model, and on the exact purpose of this model, its mesh must be adapted so that it enforces criteria on element types, maximum number of elements, and mesh quality. Meshing methods developed for applications others than geomodeling forbid any modification of the input model, that may be desirable in geomodeling to better control the number of elements in the final mesh and their quality.
The objective of this thesis is to develop meshing methods that fulfill this requirement to better manage the geometrical complexity of B-Rep geological structural models. An analysis of the sources of geometrical complexity in those models is first proposed. The introduced measures are a first step toward the definition of tools allowing objective comparisons of structural models and permit to characterize the model zones that are more complicated to mesh. We then introduce two original meshing methods based on Voronoi diagrams: the first for surface remeshing, the second for hybrid gridding. The key ideas of these methods are identical: (1) the use of a centroidal Voronoi optimization to have a globally controlled number of elements of good quality, and (2) combinatorial considerations to locally build the final mesh while sometimes modifying the initial model. The surface remeshing method is automatic and permits to simplify a model at a given resolution. The gridding method generates a hybrid volumetric mesh. Prisms and pyramids fill the very thin layers of the model while the remaining regions are filled with tetrahedra.

Host
WIAS Berlin
September 30 – October 2, 2014 (WIAS-ESH)
Workshop/Konferenz: Workshop Electrochemical Interfaces: Recent Topics and Open Questions
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Host
WIAS Berlin
Thursday, 02.10.2014, 14.00 Uhr (WIAS-406)
Seminar Numerische Mathematik
Prof. W. Huang, University of Kansas, USA:
Computation of eigenvalue problems with anisotropic diffusion operators
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

Abstract
Anisotropic eigenvalue problems can come from application of the Laplace-Beltrami operator to geometric shape analysis and imaging segmentation. They also arise from stability and sensitivity analysis and construction of special solutions for anisotropic diffusion partial differential equations. The latter appears in many areas of science and engineering including plasma physics, petroleum engineering, and image processing. This talk is concerned with finite element computation of those eigenvalue problems, with emphasis on anisotropic mesh adaptation and preservation of basic structures. Both analytical analysis and numerical results are presented.

Host
WIAS Berlin
Tuesday, 07.10.2014, 10.15 Uhr (WIAS-406)
Seminar Nichtlineare Optimierung und Inverse Probleme
Prof. Dr. N. Meyendorf, Institut für Keramische Technologien und Systeme IKTS, Berlin:
Heinrich Barkhausen in Berlin and Dresden -- New applications of his ideas for electromagnetic NDE
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

Abstract
After studying Physics Barkhausen graduated as Dr. phil. His Ph.D. thesis ``The problem of generation of vibrations under especial consideration of fast electric vibrations'' was published in 1907 and he immediately received an offer from Siemens Berlin where he worked as Engineer and habilitated in 1910 at the TH Berlin. In 1911 he accepted the world's first professorship in the communications branch of electrical engineering, at the Technical Academy in Dresden (1911) where he worked until his retirement in 1953 with short interruptions. His developments in modern amplifier techniques significantly impacted the electronics technology in Saxony (Germany) and Japan where some of his famous students came from and continued his work. The important effect that caries his name was discovered accidently by applying his new developed amplifiers (Physik. Zeitschrift., XX, 1919. Heinrich Barkhausen ``Zwei mit Hilfe der neuen Verstärker entdeckte Erscheinungen". - Two new phenomenos dicoverd by using the new amplifiers)

Today Barkhausen noise measurement is an efficient nondestructive technique for materials characterization. Usually the noise is detected by a coil while the magnetic hysteresis of the test material is cycled by an electromagnet. Due to magnetostrictive effects Barkhausen noise is highly sensitive to materials stresses and can be used for quantitative determination of residual stresses and external mechanical loads. The interaction of the magnetic structure (magnetic Bloch walls) with the microstructure of the material results in Barkhausen noise signals that are very sensitive to microstructure variations. Quantification of plastic deformation, of hardness, tensile strength, yield strength, and hardness depth are typical applications.

Other innovative techniques of creating Barkhausen noise by electric current magnetization (Eddy field technique) or using other related effects like Villary Effect, Matteucci Effect or Procopiu Effect open new areas of applications for ENDE. When an alternating electric current is used to excite a ferromagnetic wire an electric potential noise can be detected within the electric circuit. This noise can be related to the Barkhausen effect and is sensitive to remagnetization processes. The sensitivity of the effect to residual and applied stresses can be used to develop this technique as a principle for stress sensor technology.

Rotation of the Magnetic fields and autocalibration algorithm overcome the present limitation of the technique. A new auto-calibration method was developed to analyze two-dimensional stresses. A fixed calibration function based on defined parameters (determined experimentally) was applied. To adjust the auto-calibration function to the experimental reference values by varying functional parameters, a large number of measurement points were used. A method that can calculate, based on the multi-dimensional stress state at the measuring point, the stress components σxx and σyy for two perpendicular magnetization directions using the Barkhausen Noise effect has been presented.

Barkhausen noise reflects the fractal behavior of the mesoscopic materials behavior during fatigue. It has been shown that determing the fractal dimension of the Barkhausen noise opens essential new applications. The first instrument that applies this principle (FracDim) has been successfully applied for several industrial tasks like for instance evaluation of the remaining service life of large industrial plants and facilities.

Barkhausens major achievement was the development of new amplifier techniques. An established application of high end amplifier technology in NDE is eddy current testing and for instance eddy current testing at very high frequencies up to 100 MHz.

Applications for ultra-high frequency EC technology for low conducting and non-conduction Materials are under development at the Institute for packaging (IAVT) of the University of Dresden that continues Barkhausens legacy.

It has been shown, that eddy current measurement devices cannot only be used for characterizing conductivity and permeability and related properties of electrical conductive materials but also for permittivity characterization of insulating or poor conductive materials. Maxwell?s equations, FEM simulation and experimental research are used to proof this hypothesis. When applying eddy current technology on isotropic materials dielectric properties of the sample influence the measurement results.

That is not only an important finding regarding measurement accuracy in traditional eddy current measurement tasks. It is rather opening a completely new field of application for eddy current technology. Especially the High-frequency technology has the potential to serve for dielectric measurements with its easy applicability and inherent non-destructiveness. A lot of applications are conceivable: Permittivity change can be controlled over time, e.g. for cure monitoring of CFRPs, GFRPs, lacquers or other polymer materials. Local dielectric properties can be mapped with high resolution allowing for example to identify curing defects. And quantitative permittivity measurements are also feasible with a corresponding calibration, e.g. to identify the dielectric volume content within a composite material. Although the eddy current technology can be applied also on insulators like polymers, GFRP or ceramics the most probable application might be testing of poor conductive materials, like CFRP. There it is more suitable than capacitive setups, which struggle with electrode polarization and it has a higher penetration depth than the approaches relying on high-frequency wave propagation. However, independent from the sample characteristic, the HFECD might convince with contact-free measurement, the possibility of single-sided inspection , no need for special sample preparation and a very robust setup.

Host
WIAS Berlin

Wednesday, 08.10.2014, 15.15 Uhr (WIAS-ESH)
BERLINER OBERSEMINAR Nichtlineare partielle Differentialgleichungen (Langenbach-Seminar)
Prof. Dr. U. Stefanelli, University of Vienna, Austria:
Carbon geometries as optimal configurations
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
I would like to comment on the possibility of describing the geometry of some classes of three-dimensional carbon structures by minimizing suitable configurational potentials. The general aim is that of identifying regimes in which the specific 'objective structures' which can be experimentally observed are energetically favored. In particular, I will mention the case of fullerenes and concentrate on the discussion of nanotubes. This is joint work with E. Mainini, H. Murakawa, and P. Piovano.

Further Informations
Berliner Oberseminar ``Nichtlineare Partielle Differentialgleichungen'' (Langenbach Seminar)

Host
WIAS Berlin
Humboldt-Universität zu Berlin
Thursday, 16.10.2014, 16.00 Uhr (WIAS-ESH)
Forschungsseminar Mathematische Modelle der Photonik
Prof. U. Leonhardt, The Weizmann Institute of Science, Israel:
Transformation optics
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
Science Magazine listed transformation optics among the top 10 science insights of the decade 2000-2010. The lecture gives an introduction into this subject that may, literally, transform optics. Transformation optics grew out of ideas for invisibility cloaking devices and exploits connections between electromagnetism in media and in geometries. Within a short time it grew into a lively research area with applications ranging from invisibility and perfect imaging to the quantum physics of black holes. Invisibility has been a subject of fiction for millennia, from myths of the ancient Greeks and Germans to modern novels and films. In 2006 invisibility turned from fiction into science, primarily initiated by the publication of first ideas for cloaking devices and the subsequent demonstration of cloaking for microwaves. Perfect imaging is the ability to optically transfer images with a resolution not limited by the wave nature of light. Advances in imaging are of significant importance to modern electronics, because the structures of microchips are made by photolithography; in order to make smaller structures, light with increasingly smaller wavelength is used, which is increasingly difficult. Black holes are surrounded by horizons that create quantum particles from the virtual particles of the quantum vacuum, Hawking radiation. Understanding and testing this mysterious phenomenon will shed light on connections between quantum physics and general relativity.

Host
Humboldt-Universität zu Berlin
WIAS Berlin
Tuesday, 21.10.2014, 15.15 Uhr (WIAS-ESH)
Oberseminar Nonlinear Dynamics
Prof. E. Tobisch, Universität Linz, Institut für Analysis, Austria:
Nonlinear resonances in bounded domains
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Further Informations
Oberseminar Nonlinear Dynamics

Host
WIAS Berlin
Freie Universität Berlin
Thursday, 23.10.2014, 16.00 Uhr (WIAS-ESH)
Forschungsseminar Mathematische Modelle der Photonik
Prof. E. Tobisch, Universität Linz, Institut für Analysis, Austria:
Energy cascades in physical systems with small and moderate nonlinearity
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Host
Humboldt-Universität zu Berlin
WIAS Berlin
Wednesday, 12.11.2014, 15.15 Uhr (WIAS-ESH)
BERLINER OBERSEMINAR Nichtlineare partielle Differentialgleichungen (Langenbach-Seminar)
Prof. Dr. A. Mielke, WIAS Berlin:
On the microscopic origin of generalized gradient structures
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Further Informations
Berliner Oberseminar ``Nichtlineare Partielle Differentialgleichungen'' (Langenbach Seminar)

Host
WIAS Berlin
Humboldt-Universität zu Berlin
November 20 – 21, 2014 (WIAS-ESH)
Workshop/Konferenz: Workshop on Recent Advances in High-Frequency Statistics
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Host
WIAS Berlin
SFB 649: Ökonomisches Risiko
Xiamen University
DFG Research Unit 1735
Thursday, 27.11.2014, 16.00 Uhr (WIAS-ESH)
Forschungsseminar Mathematische Modelle der Photonik
Prof. Dr. R. Martin, Leibniz-Institut für Astrophysik Potsdam (AIP):
Highly stable mode-locked diode laser system for precision comparisons in microgravity
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
The contemporary term ?Astrophotonics? has already been in use since about a decade, but it is still a relatively new discipline to most physicists and astronomers. Adopting the definition of ?manipulation of light by materials? for photonics, quite analogous to the term ?electronics?, we understand astrophotonics as a subdiscipline of physics research and engineering, that utilizes optical effects of advanced materials for novel applications in observational astronomy and instrumentation. Historically, the field of photonics has emerged from optoelectronics with revolutionary innovations for the telecommunication sector. In a broader sense, there exist today a growing number of applications in other fields, such as industrial process technologies, sensor and illumination technologies, life science (biophotonics), etc. Astrophotonics seems to be a logical evolution in the area of astronomy, with promising applications for a future generation of instrumentation. I shall present a review of the evolution of astrophotonics with some remarks about the impact on the advance of astrophysics to date, and then focus on selected examples of current research like OH suppression fibre bragg gratings, miniaturized spectrographs ?on-the-chip?, and laser frequency combs for wavelength calibration in spectroscopy. I shall conclude with a somewhat speculative vision of future directions.

Host
Humboldt-Universität zu Berlin
WIAS Berlin
March 11 – 13, 2015 (WIAS-ESH)
Workshop/Konferenz: Applied Mathematics and Simulation for Semiconductors
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Host
WIAS Berlin