Upcoming Events

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June 18 – 20, 2018 (WIAS-ESH)
Workshop/Konferenz: Nonlinear Dynamics in Semiconductor Lasers
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Host
WIAS Berlin
Monday, 18.06.2018, 15:00 (WIAS-406)
Joint Research Seminar on Nonsmooth Variational Problems and Operator Equations / Mathematical Optimization
Dr. J. Pfefferer, TU München:
hp-finite elements for fractional diffusion
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

Abstract
In this talk we introduce and analyze a numerical scheme based on hp-finite elements to solve boundary value problems involving the spectral fractional Laplacian. The approach is based on a reformulation of the problem posed on a semi-infinite cylinder in one more spatial dimension. After a suitable truncation of this cylinder, the resulting problem is discretized with linear finite elements in the original domain and with hp-finite elements in the extended direction. The proposed approach yields a reduction of the computational complexity in terms of degrees of freedom and even has slightly improved convergence properties compared to the state-of-the-art discretization using linear finite elements for both the original domain and the extended direction. The performance of the method is illustrated by numerical experiments.

Further Informations
Joint Research Seminar on Mathematical Optimization / Non-smooth Variational Problems and Operator Equations

Host
Humboldt-Universität zu Berlin
WIAS Berlin
Tuesday, 19.06.2018, 10:15 (WIAS-406)
Seminar Nichtlineare Optimierung und Inverse Probleme
Prof. Dr. G. Hu, Beijing Computational Science Research Center, China:
Outgoing radiation conditions for the Helmholtz equation in inhomogeneous periodic media
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

Host
WIAS Berlin
Tuesday, 19.06.2018, 15:00 (WIAS-406)
Seminar Modern Methods in Applied Stochastics and Nonparametric Statistics
Prof. Z. Shi, Tsinghua University, Beijing, China:
Low dimensional manifold model for image processing
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

Abstract
In this talk, I will introduce a novel low dimensional manifold model for image processing problem. This model is based on the observation that for many natural images, the patch manifold usually has low dimension structure. Then, we use the dimension of the patch manifold as a regularization to recover the original image. Using some formula in differential geometry, this problem is reduced to solve Laplace-Beltrami equation on manifold. The Laplace-Beltrami equation is solved by the point integral method. Numerical tests show that this method gives very good results in image inpainting, denoising and super-resolution problem. This is joint work with Stanley Osher and Wei Zhu.

Host
Humboldt-Universität zu Berlin
WIAS Berlin
Wednesday, 20.06.2018, 10:00 (WIAS-406)
Forschungsseminar Mathematische Statistik
Prof. Z. Shi, Tsinghua University, Beijing, China:
PDE-based methods for Interpolation on High Dimensional Point Cloud
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, 4. Etage, Weierstraß-Hörsaal (Raum: 406)

Abstract
Interpolation on high dimensional point cloud provides a fundamental model in many data analysis and machine learning problems. In this talk, we will present some PDE based methods to do interpolation on point cloud. Applications in image processing and data analysis are shown to demonstrate the performance of our methods.

Host
Humboldt-Universität zu Berlin
WIAS Berlin
Wednesday, 20.06.2018, 14:30 (WIAS-ESH)
INSTITUTSKOLLOQUIUM
Prof. Dr. M. C. Ferris, Computer Sciences Department and Wisconsin Institute for Discovery, University of Wisconsin-Madison, USA:
Modelling 100 percent renewable electricity
more ... Location
Weierstraß-Institut, Mohrenstr. 39, 10117 Berlin, Erdgeschoss, Erhard-Schmidt-Hörsaal

Abstract
In the past few decades, power grids across the world have become dependent on markets that aim to efficiently match supply with demand at all times via a variety of pricing and auction mechanisms. These markets are based on models that capture interactions between producers, transmission and consumers. Energy producers typically maximize profits by optimally allocating and scheduling resources over time. A dynamic equilibrium aims to determine prices and dispatches that can be transmitted over the electricity grid to satisfy evolving consumer requirements for energy at different locations and times. Computation allows large scale practical implementations of socially optimal models to be solved as part of the market operation, and regulations can be imposed that aim to ensure competitive behaviour of market participants. The recent explosion in the use of renewable supply such as wind, solar and hydro has led to increased volatility in this system. We develop models that aim to ensure enough generation capacity for the long term under various constraints related to environmental concerns, and consider the recovery of costs for this enhanced infrastructure. We demonstrate how risk can impose significant costs on the system that are not modeled in the context of socially optimal power system markets and highlight the use of contracts to reduce or recover these costs. We also outline how battery storage can be used as an effective hedging instrument.

Host
WIAS Berlin