LiteMat - ett informationsblad från Matematiska institutionen vid LiU

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v.44, 2011

 

Seminars on Optimization

Monday 31 October 2011, Kompakta rummet 13:15, Nils-Hassan Quttineh (Linköping University, Department of Mathematics, Division of Optimization)

Title: Military Resource Planning

Abstract:
We present a resource planning and scheduling problem, where a number of aircraft need to be assigned to and routed between a given set of targets. There are many practical issues and limitations, that will be discussed, but in all we are able to present a mathematical model with similarities to the standard "Vehicle Routing Problem" model.

Welcome!

Nils-Hassan Quttineh

 

Friday 4 November 2011, Determinanten, 10:15
Fredrik Heintz (Linköping University, Dept. of Computer and Information Science)

Title: Complex Task Allocation for Collaborative Unmanned Aircraft Systems

Abstract:
Task Allocation is a well known problem studied in both mathematics and computer science. In its basic formulation each task is atomic and should be assigned to a single machine or agent. In our work with collaborative unmanned aircraft systems we have recognized the need for allocating complex tasks in the form of recursively defined, interdependent tasks. In this talk I will present an overview of the complex task allocation problem mainly from a multi-agent systems perspective. Most approaches are either based on distributed constraint satisfaction and optimization techniques or on defining a market for trading tasks. The purpose of the talk is to start a discussion about the potential for cross fertilization between optimization and multi-agent systems approaches to the interesting and challenging problem of complex task allocation.

Welcome!

Oleg Burdakov

 

Presentation av examensarbete i optimeringslära

Onsdagen den 2 november, Determinanten kl 10.15, Anna Borggren
Nivå: Kandidat
Opponent: Peter Mattsson och Johan Lind
Titel: Heuristiska sökmetoder för att finna den optimala ingrafen

Abstract:
I examensarbetet går jag igenom grunderna i lokalsökning, tabusökning och Simulated Annealing . Jag använder dem till att bilda metoder som får fram billigaste ingrafen till en graf. Därefter jämnför jag metoderna och analyser vilken som är bäst.

Välkomna!

 

Docentföreläsning i Matematisk statistik

Välkomna på docentföreläsning i Matematisk statistik

Dr. rer. nat. habil. Jörg-Uwe Löbus, MAI, föreläser torsdagen den 3 november, kl 10.15, över ämnet

Why is infinite dimensional calculus called stochastic calculus?

Lokal: BL32, B-huset, ingång 23

Abstract:
The lecture starts with the introduction of the basic Malliavin calculus and a comparison to its finite dimensional counterpart. It turns out that elementary infinite dimensional objects and operations yield the Wiener process, the Itô and Skorokhod stochastic integral, as well as solutions to certain stochastic differential equations.

The talk continues with a class of infinite dimensional diffusion processes with pointwise unbounded diffusion. The presentation turns to a probabilistic local chracterization of such a diffusion. Although there is a canonical finite dimensional counterpart, there are specific infinite dimensional phenomena.

All mathematical tools are analytical. However the mathematical objects of interest are of probabilistic nature.

Welcome!

Ingegerd Skoglund

 

Extra seminar in Computational Mathematics

Qaisar Abbas will present his work (a summary of his thesis) in computational mathematics on Thursday 3 November, 13.15-14.00 in Determinanten.

Title: Weak Boundary and Interface Procedures for Wave and Flow Problems

Abstract:
In this thesis, we have analyzed the accuracy and stability aspects of weak boundary and interface conditions (WBCs) for high order finite difference methods on Summations-By-Parts (SBP) form. The numerical technique has been applied to wave propagation and flow problems. The advantage of WBCs over strong boundary conditions is that stability of the numerical scheme can be proven. The boundary procedures in the advection-diffusion equation for a boundary layer problem is analyzed. By performing Navier-Stokes calculations, it is shown that most of the conclusions from the model problem carries over to the fully nonlinear case. The work was complemented to include the new idea of using WBCs on multiple grid points in a region, where the data is known, instead of at a single point. It was shown that we can achieve high accuracy, an increased rate of convergence to steady-state and non-reflecting boundary conditions by using this approach.

Using the SBP technique and WBCs, we have worked out how to construct conservative and energy stable hybrid schemes for shocks using two different approaches. In the first method, we combine a high order finite difference scheme with a second order MUSCL scheme. In the second method, a procedure to locally change the order of accuracy of the finite difference schemes is developed. The main purpose is to obtain a higher order accurate scheme in smooth regions and a low order non-oscillatory scheme in the vicinity of shocks. Furthermore, we have analyzed the energy stability of the MUSCL scheme, by reformulating the scheme in the framework of SBP and artificial dissipation operators. It was found that many of the standard slope limiters in the MUSCL scheme do not lead to a negative semi-definite dissipation matrix, as required to get pointwise stability. Finally, high order simulations of shock diffracting over a convex wall with two facets were performed. The numerical study is done for a range of Reynolds numbers. By monitoring the velocities at the solid wall, it was shown that the computations were resolved in the boundary layer. Schlieren images from the computational results were obtained which displayed new interesting flow features.

Welcome

Jan Nordström

 

Analysis Seminars

Friday 4 November 2011, Kompakta rummet 10.15-12:00, Mats Aigner, LiU

Title: A seminar series towards the Atiyah-Singer index theorem

Abstract:
The index theorem of M.F. Atiyah and I.M. Singer, first announced in 1963, is a deep result in mathematics, providing a fundamental link between analysis and topology. This series of seminars aims at giving a reasonably elementary and complete presentation of the mathematics involved in the statement and proof of the K-theoretical version of the index theorem.

Complete programme of the Analysis seminars

Welcome!

Bengt Ove Turesson

 

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Material skickas till litemat@mai.liu.se senast torsdagar kl. 12.