***LITE MAT***

Ett informationsblad från matematiska institutionen vid Linköpings universitet

v49 1996

Föreläsningar

Matematiska kollokviet

Fredagen den 29 november kl 13.15 talar Jan-Olav Rönning om Generaliserade Perronträd med tillämpningar på maximalfunktioner.

Fredagen den 6 december kl 13.15 talar professor Iossif Ostrovskii, Charkov och Uppsala, om Zero distribution and growth of entire functions which are Fourier transforms of probability measures.

Summary: We consider the entire functions representable in the form where P is a probability measure on the real line and the integral converges absolutely in the whole complex plane. This class of functions plays an important role in problems related to decompositions of random variables into independent summands (see e.g. Linnik, Ju.V. & Ostrovskii, I.V. Decomposition of random variables and vectors. AMS, Providence, 1977).
The following problems are studied:
(1) Which can be zero-sets of these functions?
(2) Which can be Phragmén-Lindelöf indicators of these functions?
(3) Which is connection between the growth of these functions and the distribution of their zeros by arguments?
The complete solutions of (1) and (2) are obtained. Several phenomena related to (3) are discussed.

Fredagen den 13 december kl 13.15 talar docent Mats Andersson, Göteborg, om Taylors funktionalkalkyl med Cauchy-Fantappiè-Leray-formler.

Lokal: MAI:s seminarierum, ingång 23-25, 1 tr.

Lars Inge Hedberg

Licentiatseminarier

Fredagen den 13 december kl. 10.15 presenterar fil. mag. Hans B. Johansson, högskolan i Skövde, sin licentiatavhandling Uniform Approximation by Harmonic Functions. Opponent är docent Mats Andersson, Göteborg.

Lokal: MAI:s seminarierum, ingång 23-25, 1 tr.

Lars Inge Hedberg

Fredag den 13 december kl. 10.15 presenterar Stefan Engevall sin licenciatavhandling Cost Allocation in Distribution Planning.

Diskutant är Docent Kenth Lumsden, Institutionen för Transportteknik, Chalmers Tekniska Högskola.

Abstract: This thesis concerns cost allocation problems in distribution planning. The cost allocation problems we study are illustrated using the distribution planning situation at the Logistics department of Norsk Hydro Olje AB. The planning situation is modeled as a Traveling Salesman Problem and a Vehicle Routing Problem with an inhomogeneous fleet. The cost allocation problems are the problems of how to divide the transportation costs among the customers served in each problem. The cost allocation problems are formulated as cooperative games, in characteristic function form, where the customers are defined to be the players. The games contain five and 21 players respectively. Game theoretical solution concepts such as the core, the nucleolus, the Shapley value and the -value are discussed. From the empirical results we can, among other things, conclude that the core of the Traveling Salesman Game is large, and that the core of the Vehicle Routing Game is empty. In the accounting of Norsk Hydro the cost per can be found for each tour. We conclude that for a certain definition of the characteristic function, a cost allocation according to this principle will not be included in the core of the Traveling Salesman Game. The models and methods presented in this thesis can be applied to transportation problems similar to that of Norsk Hydro, independent of the type of products that are delivered.

Lokal: C3, hus C

Välkomna!
Peter Värbrand

Seminarium i numerisk analys

Torsdagen den 5 december kl 10.15 talar Bertil Gustafsson, TDB, Uppsala, om

High order difference methods for time-dependent partial differential equations.

Abstract:
High order difference methods for time-dependent PDEs are usually more efficient than lower order ones, when small errors in the solution are required. The efficiency is especially pronounced when the computation is carried out over long time-intervals. The construction of high order methods on structured grids is easy for the Cauchy problem, but more difficult when boundaries are present.

We will give a review of the theory for higher order methods, in particular for first order systems. We present the technique for constructing strictly stable approximations, that satisfy an energy estimate of the same type as the differential equation. The connection between compact implicit difference methods and finite-element methods will also be discussed, and numerical experiments will be presented.

Plats: nya seminarierummet (mellan ingång 23 och 25)

Välkomna!
Lars Eldén

Seminarium Optimeringslära

Tisdagen den 3 december kl 13.15 - 16.00, håller Professor David Boyce, Urban Transportation Center, University of Illinois at Chicago, ett seminarium

Advanced Route Choice Models: Extensions to More Realistic Cases

Abstract:
In the sequel to the first seminar, extensions of static and dynamic models to more realistic cases will be considered. The first case is to relax the assumption that travel times are known perfectly. If random perception errors exist, or link travel times are random variables, then stochastic route choice models can be formulated for both static and dynamic cases.

Moreover, origin-destination flows may be regarded as depending on route travel times, leading to variable or elastic demand models. Finally, the relationships between link travel times and link flows may be regarded as depending on several conflicting link flows, rather than the link's own flow only. As in the first seminar, formulations with optimization and variational inequality methods will be stressed.

Lokal: MAI:s seminarierum, ing 23, bv

Välkomna,
Jan Lundgren

Presentation av examensarbete

Fredagen den 6 december kl 10.00 presenterar Anders Movert (Y-tma) sitt examensarbete, inom området tillämpad matematik,

Cellular Automata, Lattice Gas Automata and Fluid Dynamics

Lokal: MAI:s seminarierum

Per Weinerfelt

Inför bokslutet

Kom ihåg att alla timförordnanden och övriga utbetalningar (reseräkningar)
skall vara löneförrättarna Birgitta,
Camilla och Theresia tillhanda senast den 1 december. Samtidigt vill jag påminna alla med externa forskningsprojekt att höstens resultat ej går att balansera om möjligheten till detta ej finns inskrivet i kontraktet eller i tilläggsbeslut.

Marie Johansson

Ansökningar om medel från forskningsråd och andra bidragsgivare

Alla beslut, positiva såväl som negativa måste lämnas till Birgitta Lumsden för diarieföring.

Ansökan om IVA:s resestipendier 1997 till Central- och Östeuropa samt forskarstipendier till Republiken Korea, ska vara IVA tillhanda senast den 20 december -96.

Övrigt

MAI:s gemensamma anslagstavla

Det har varit lite dåligt med anslagstavlor under en period men nu finns en gemensam anslagstavla i anslutning till huvudentrén, ing 23 vid det stora kopieringsrummet i optimeringsläras korridor. Tavlan är märkt "Matematiska institutionen".

Marie Johansson

Privata kopior

Nu finns en pärm i kopieringsrummen, ``PRIVATA KOPIOR'', där namn och antal tagna kopior ska antecknas.

Anna

Mer information om MAI finns på under MAIs hemsida
Material till Lite Mat lämnas till Maud Lindström senast torsdagar kl 12.00.
Tel 013-281405, Fax 013-100746, Email: litemat@mai.liu.se
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