Beitrags-Archiv für die Kategory 'MATH'

Vortrag im Rahmen des DK-Seminars des Karl Popper Kollegs von Dr. Ralf Hielscher (TU Chemnitz)

Dienstag, 21. Februar 2017 14:23

Einladung zum Gastvortrag im Rahmen des DK-Seminars des Karl Popper Kollegs von

Dr. Ralf Hielscher

(TU Chemnitz)

zu dem Thema

Mathematical challenges in analysis of EBSD  images

Prof. Joaquim Júdice an der TeWi

Dr. Ralf Hielscher an der TEWI

Ort: I.2.01

Zeit: Mittwoch, 15.03.2017, 11:00 Uhr s. t.

Abstract:
Electron backscatter diffraction (EBSD) is an imaging modality in material science where an electron beam is used to locally resolve the crystalline structure in a polycrystalline material. In a first step for each spot on the specimen diffraction patterns, so called Kikuchy pattern, are measured. From these Kikuchy pattern information about the type of the local crystal structure as well as about their alignment are extracted. This process is called indexing. After indexing one ends up with an image with values being rotations representing the local orientation of the crystals at the surface of the material.
In this talk we cover several challenges associated with the analysis of EBSD data, including the indexing of the Kikuchy pattern, the colorization of rotations modulo crystal symmetry, the determination of the mean of rotations modulo symmetry, the segmentation of EBSD images into grains and the denoising of EBSD images.

Share

Thema: Institut, MATH, Veranstaltung | Kommentare (0) | Autor:

Einladung zum Vortrag von Tsiry Randrianasolo

Montag, 12. Dezember 2016 17:04

Einladung zum Gastvortrag im Rahmen des DK-Seminars des Karl Popper Kollegs von

Tsiry Randrianasolo

(Montanuniversität Leoben)

zu dem Thema

From Navier-Stokes Equations to Stochastic Navier-Stokes Equations

Prof. Joaquim Júdice an der TeWi

Tsiry Randrianasolo an der TEWI

Ort: I.2.01

Zeit: Mittwoch, 21.12.2016, 11:30 Uhr s. t.

Abstract:

In this talk we give a brief introduction into fluid dynamics by Euler and incompressible Navier-Stokes equations. Small scale perturbations are present in fluid motion, especially when the viscous forces are small compared to inertial forces. It is reasonable to introduce a random body force to capture this perturbation. From this, we will explain how the stochastic incompressible Navier-Stokes equations can be derived from its deterministic equivalent by using the central limit theorem and the large deviation principle. To conclude, we depict the main issue one can meet when a numerical approximation on these stochastic equations are performed.

Share

Thema: Institut, MATH, Veranstaltung | Kommentare (0) | Autor:

Einladung zum Vortrag von Prof. Helmut Prodinger

Dienstag, 6. Dezember 2016 16:02

Einladung zum Gastvortrag im Rahmen des DK-Seminars des Karl Popper Kollegs von

Prof. Helmut Prodinger

(Stellenbosch University, South Africa)

zu dem Thema

Rice’s Method and Combinatorial Identities

 

Prof. Helmut Prodinger an der TeWi

Ort: I.2.01

Zeit: Mittwoch, 14.12.2016, 10:00 Uhr s. t.

Abstract:

The method in question belongs to the analytic toolkit of the Analysis of Algorithms. It is based on replacing a certain alternating sum by a contour integral which is evaluated asymptotically via residues. It can also be used to proved exact formulas (identities), in which case the framework of contour integrals can be replaced by elementary partial fraction decomposition.

Share

Thema: Institut, MATH, Veranstaltung | Kommentare (0) | Autor:

Einladung zum Gastvortrag von Prof. Dr. Christian Clason

Montag, 14. November 2016 12:07

Einladung zum Gastvortrag im Rahmen des DK-Seminars von

Prof. Dr. Christian Clason

(Universität Duisburg-Essen)

zu dem Thema

Discrete regularization of parameter identification problems

 

Prof. Dr. Christian Clason an der TeWi

Ort: I.2.01

Zeit: Mittwoch, 16.11.2016, 10:00 Uhr s. t.

Abstract:

We consider linear and nonlinear parameter identification problems, where the unknown distributed parameter is known to take on values only from a discrete given set. This property can be promoted with the aid of a convex penalty. A regularized semismooth Newton method allows the numerical solution of the corresponding Tikhonov functional.
Numerical examples illustrate the effectiveness of the proposed approach.

Share

Thema: Institut, MATH, Veranstaltung | Kommentare (0) | Autor:

Einladung zum Gastvortrag von Dipl.-Ing. Dr. Roswitha Rissner

Dienstag, 8. November 2016 16:21

Einladung zum Gastvortrag im Rahmen des DK-Seminars von

Dipl.-Ing. Dr. Roswitha Rissner

(TU Graz)

zu dem Thema

Integer-valued polynomials on a square matrix

 

Dipl.-Ing. Dr. Roswitha Rissner an der TeWi

Ort: I.2.01

Zeit: Mittwoch, 23.11.2016, 11:00 Uhr s. t.

Abstract:

siehe Beilage GV_Rissner_23112016

Share

Thema: Institut, MATH, Veranstaltung | Kommentare (0) | Autor:

Einladung zum Gastvortrag von PD Dr. Thorsten Hüls

Donnerstag, 4. Februar 2016 11:35

Einladung zum Gastvortrag von

PD Dr. Thorsten Hüls

(Universität Bielefeld, Deutschland)

zu dem Thema

A contour algorithm for computing stable fiber bundles of nonautonomous, noninvertible maps

PD Dr. Thorsten Hüls an der TeWi

 

Ort: Raum I.2.01

Zeit: Mittwoch, 17.02.2016, 10:00 Uhr c. t.

Abstract:

Stable fiber bundles are the nonautonomous analog of stable manifolds and these objects provide valuable information on the underlying dynamics. We propose an algorithm for their approximation that is based on computing zero contours of a particular operator. The resulting program applies to a wide class of models, including noninvertible and nonautonomous discrete time systems. Precise error estimates are provided and fiber bundles are computed for several examples. Finally, we apply the contour algorithm to (non)autonomous ODEs. For the famous three-dimensional Lorenz system, we calculate several approximations of the two-dimensional Lorenz manifold.

Share

Thema: Institut, MATH, Veranstaltung | Kommentare (0) | Autor:

Einladung zum Gastvortrag von Univ.-Prof. Dr. Mechthild Thalhammer

Freitag, 8. Januar 2016 11:30

Einladung zum Gastvortrag von

Univ.-Prof. Dr. Mechthild Thalhammer

(Universität Innsbruck)

zu dem Thema

Efficient time integrators for highly oscillatory Schrödinger equations

 

Univ.-Prof. Dr. Mechthild Thalhammer an der TeWi

 

Ort: Raum I.2.01

Zeit: Donnerstag, 14.01.2016, 10:00 Uhr s. t.

Abstract:

In this talk, I shall introduce multi-revolution composition methods (MRCM) for highly oscillatory evolution equations and analyse their error behaviour. The scope of applications in particular includes time-dependent linear Schrödinger equations, where the realisation of the composition approach relies on time-splitting pseudo-spectral methods. Numerical experiments illustrate and complement the theoretical investigations.

Share

Thema: Institut, MATH, Veranstaltung | Kommentare (0) | Autor:

Einladung zum Gastvortrag von Ass.-Prof. Dr Kamil Kazimierski

Mittwoch, 2. Dezember 2015 15:13

Einladung zum Gastvortrag von

Ass.-Prof. Dr Kamil Kazimierski

(Karl-Franzens-Universität Graz)

zu dem Thema

Removing compression artifacts from images

 

Ass.-Prof. Dr. Kamil Kazimierski an der TeWi

 

Ort: I.2.01

Zeit: Mittwoch, 09.12.2015, 11:00 Uhr s. t.

Abstract:

Compression is the quintessential tool for effcient storage of images. However, ugly artifacts go hand in hand with compression. In this talk I will discuss how the so called total generalized variation (TGV) can be employed to mitigate the artifacts caused by compression.

This is a joint work with Dr. Martin Holler, Graz University.

Share

Thema: Institut, MATH, Veranstaltung | Kommentare (0) | Autor:

Einladung zum Gastvortrag von Prof. Helmut Prodinger

Montag, 9. November 2015 15:42

Einladung zum Gastvortrag von

Prof. Helmut Prodinger

(Stellenbosch University, South Africa)

zu dem Thema

Ramanujan and his Impact on my Research

 

Prof. Helmut Prodinger an der TeWi

Ort: I.2.01

Zeit: Donnerstag, 19.11.2015, 15:00 Uhr s. t.

Abstract:

With the renewed interested in Ramanujan, which resulted in a recent movie, I would like to review, for the benefit of a younger generation of researchers, some results of Ramanujan that played a role in my own work.

Examples: Modular identities and digital search trees, asymptotic solution of a difference equation, Ramanujan’s Q(n)-function, Continued fractions and a new q-tangent function, one parameter extensions of Rogers-Ramanujan identities.

Share

Thema: Institut, MATH, Veranstaltung | Kommentare (0) | Autor:

Einladung zum Gastvortrag von Prof. Jon Lee

Dienstag, 6. Oktober 2015 14:45

Einladung zum Gastvortrag von

Prof. Jon Lee

(University of Michigan, USA)

zu dem Thema

Comparing polyhedral relaxations via volume

 

Ort: I.2.01

Prof. Jon Lee an der TeWi

Zeit: Mittwoch, 14.10.2015, 10:00 Uhr s. t.

Abstract:

With W. Morris in 1992, I introduced the idea of comparing polytopes relevant to combinatorial optimization via calculation of n-dimensional volumes. I will review some of that work (related to fixed-charge probelms) and describe some new work, with E. Speakman, relevant to the spatial branch-and-bound approach to global optimization. In this new work, we calculate exact expressions for 4-dimensional volumes of natural parametric families of polytopes relevant to different convex relaxations of trilinear monomials. As a consequence, we have practical guidance: (i) for tuning an aspect of spatial branch-and-bound implementations, (ii) at the modeling level.

Share

Thema: Institut, MATH, Veranstaltung | Kommentare (0) | Autor: