Nada

Numero 40

fredag 21 november 1997, årgång 27

Veckoblad om forskning, undervisning och administration m.m.
NADA - Institutionen för numerisk analys och datalogi, KTH


Kalendarium

Aktuellt kalendarium (inte kalendariet som hör specifikt till denna Numeroutgåva).

Förbjudet att kopiera databaser

Som bilaga till pappersutgåvan av Numero (och i Numeropärmen 97.142) finns en artikel ur "Från Riksdag och departement" nummer 97:32, som beskriver de nya reglerna för kopiering av databaser.


Valberedningens förslag till vice rektor för grundutbildningen

Valberedningens kandidat till vice rektor för grundutbildningen är professor Christina Moberg.Numeropärmen 97.137


Ansökan om nya vidareutbildningskurser

Ansökan om nya vidareutbildningskurser sommaren -98, ht -98 och vt -99, ska vara "insänd" senast 1997-11-28. Ansökan skall göras på webben. Adressen är http://hymer.midgard.kth.se/fort/start.asp. Inge Frick är kontaktperson på NADA.Numeropärmen 97.139


NADAs Mac-arkiv tas ned för service

Tisdag 25/11 efter klockan 17 tas Nadas Mac-arkiv ned för uppgradering av system och utbyggnad av disk.

Arbetet beräknas pågå hela kvällen. Räkna inte med att kunna vara inloggad efter klockan 17.

Systemgruppen/Macstaff

Vetenskapsfestivalen 1998

Stockholms vetenskapfestival anordnas på Frescatiområdet den 18-26 april 1998. Ett flertal institutioner är redan engagerade men fler idéer är välkomna. Man vill ha besked före november månads slut. Mer information i Numeropärmen 97.141


I korthet

Konferens: PARA98, International Workshop on Applied Parallel Computing, Large Scale Scientific and Industrial Problems, 14-17 juni 1998, Umeå universitet (se http://www.hpc2n.umu.se/para98/)

Tjänster: Visiting Scientists/Scholars for the academic year 1998/1999. Sista ansökningsdag är den 15 december. STINT (Stiftelsen för internationalisering av högre utbildning och forskning). Numeropärmen 97.133

Stipendier: Postdoktorsstipendier 1998. Sista ansökningsdag är den 15 december. STINT (Stiftelsen för internationalisering av högre utbildning och forskning). Numeropärmen 97.134

Stipendier: Fellowships Programme. Sista ansökningsdag är den 15 december. STINT (Stiftelsen för internationalisering av högre utbildning och forskning). Numeropärmen 97.135

Pengar: Resebidrag ur Wallenbergsstiftelsens jubileumsfond. Sista ansökningsdag är den 11 december. Numeropärmen 97.136

Information: Informationsblad från matematisk-naturvetenskapliga fakultetskansliet vid Stockholms universitet. Numeropärmen 97.138

Kurs: Exploateringskunskap. Baskunskaper för att kunna starta eget företag. Teknikhöjden. Kursstart 27 januari. Hela programmet finns i Numeropärmen 97.140


Numerical libraries at Nada

The BLAS- and LAPACK-libraries for basic linear algebra operations can now be accessed from Nada's Sun Workstations. The compiled libraries can be found in the directory '/pkg/lapack/sunos5'. For further information on these libraries, see Netlib (www.netlib.org) or the PDC homepages (Computing resources, Software, Numerical libraries).

The libraries are written in Fortran. If you would like to use them with C programs, please contact me

Christer Andersson, <christe@nada.kth.se>

CID-seminarium: Supervisory control of a mobile teleoperator: interface metaphors and dialogue

Kristian Simsarian, SICS och CVAP, håller CID-seminarium under ovanstående rubrik idag fredag (21 nov.) kl. 9.00-10 i seminarierum 4523 (Lindstedtsv. 5, plan 5).

Abstract

This talk will describe aspects of a teleoperator system that enables a human operator to control a remote robot through the mediation of a distributed 3D spatial environment augmented by a language interface.

There are three main parts to the system, the robot semi-autonomy, the visualization of the remote environment and the human-machine interaction. Through semi-autonomy the robot takes the role of "assistant" under supervisory control. Visualization of the remote environment is done through an augmented 3D model of the remote environment with embedded video from the robot's working environment.

The HMI component comprises methods for specifying robot tasks via the shared model which is intended to provide a higher level of abstraction than manual direct control. This presentation will first provide background information on the three above mentioned areas and then will seek to introduce a new area for exploration that centers on "fault dialogue" between the assistant and supervisor or "what happens when things go wrong?"


Exjobbsseminarium i datalogi

Ett exjobbsseminarium i datalogi äger rum på tisdag (25 nov.) kl. 14.45-17.00 i seminarierum 4523 (Lindstedtsv. 5, plan 5).

Jörgen Björkner, F92, 20 poäng. Ansiktsdetektion och beräkning av ansiktsriktning. Arbetet är utfört vid Telia Research AB. Handledare: Stefan Carlsson. Examinator: Tony Lindeberg. Opponent: Hans Österlund.

Dennis Tell, F93, 20 poäng. Automatisk måligenkänning i digitala bilder. Arbetet är utfört vid Ericsson Saab Avionics. Handledare: Stefan Carlsson. Examinator: Tony Lindeberg. Opponent: Jon Persson.

Martin Andersson, F92, 20 poäng. Performance of leveled commitment protocols for automated negotiation: An empirical study. Arbetet är utfört vid Washington University, St. Louis, USA. Handledare: Viggo Kann. Examinator: Stefan Arnborg. Opponent: Ola Ramström. Denna presentation kommer att genomföras på engelska i St Louis och med teknikens hjälp överföras till oss. Den börjar 16.00.

Erik Johansson, D88, 12 p. Effektiv och användarvänlig svensk rättstavning under Linux. Handledare: Viggo Kann. Examinator: Stefan Arnborg

Kerstin F.

PDC-seminarium: Structural Instablitity and Electronic Excitations in Nb3Sn

Babak Sadigh, Theoretical Physics, KTH, håller PDC-seminarium under ovanstående rubrik på tisdag (25 nov.) kl. 15.15 i seminarierum 1537 (Lindstedtsv. 3, plan 5).

Abstract

We have performed an extensive first principles study of the cubic-to-tetragonal structural phase transformation in the $A15$ compound $Nb3Sn$, using optimised norm-conserving pseudopotentials and the plane wave basis set. Our calculations confirm that cubic $Nb3Sn$ is unstable with respect to the sublattice distortions of $Gamma_{12}$ symmetry discovered by Shirane and Axe [Phys. Rev. B4, 2957 (1971)]. However, the cubic phase is stable with respect to the tetragonal strain if the atoms are frozen in their ideal positions. The structural instability with respect to the sublattice distortions is explained by an unusually strong electron-phonon coupling between the $Gamma_{12}$ phonons and the states at the Fermi level, while no such anomalous coupling has been found for the tetragonal strain. Finite temperature electronic structure effects are modelled using the exact Fermi-Dirac distribution function in self-consistent LDA calculations. Electronic excitations are found to stabilize the cubic phase above $T_M=450~K$. The model correctly reproduces several experimental findings, including the softening of the elastic constant $C'$ and zone-center optical $Gamma_{12}$ frequency $nu_{Gamma_{12}}$ as $T rightarrow T_M$, as well as their subsequent stiffening below $T_M$. Furthermore, $C'$ is found to approach zero at $T_M$, while $nu_{Gamma_{12}}$ does not, which is again consistent with the observed behavior of $Nb3Sn$.

Erik Aurell

Diskret matte-seminarium: Functions arising by coin flipping

Johan Wästlund håller seminarium i diskret matematik under ovanstående rubrik på torsdag (27 nov.) kl. 15.15-16.15 i seminarierum 3733, matematik, KTH (Lindstedtsvägen 25 - klocktornet, plan 7).

Abstract

Suppose that we repeatedly toss a coin which is unfair in the sense that the probability of observing "head" is some number $p$, and the probability of observing "tail" is $1-p$. Then the probability of a given event can be regarded as a function of $p$.

Some polynomials and rational functions occur as probabilities of events which are easy to describe. For example, the probability of observing two heads in the first two tosses is $p^2$, and the probability that the first tail occurs after an odd number of tosses is $frac{1}{1+p}$

László Lovász posed the problem of determining the class of functions arising in this way. In the talk I will state the problem in precise terms, and give a complete answer. I will also give some simple examples of events having probabilities given by transcendental functions like $e^{-p}$.

A. Björner och J. Håstad

Licentiatseminarium: One-dimensional Consolidation Models

Mariana Dorobantu håller licentiatseminarium under ovanstående rubrik fredagen den 5 dec. kl. 13.15 i sal D33 (Lindstedtsv. 5, plan 3).

Abstract

In a 1D case the state of flocculated suspension is described by the volume fraction and the pressure of the solids. Under the influence of gravity the flocs and liquid form an elasto-plastic structure at a certain stress. The sedimentation process is modeled by a parabolic conservation law with inter-phase velocity according to Darcy's law. In fact the equations are nearly hyperbolic and the solution develops near-shocks. These are important when e.g. simulating high centrifugal forces or filtering under pressure.

We present two approaches to the same model: A fixed grid two-phase problem and an inter-phase tracking scheme. Since the solution has different time scales an efficient numerical method must use implicit time stepping and allow for big variations in the time-step.

Using conservative discretization of space and the method of lines, a system of differential-algebraic equations (DAE) is built.

In the two-phase approach, a modified Gauss-Seidel iteration is implemented for solving a nonlinear two-phase problem at each time step.

For the inter-phase tracking method a modified BDF(3) solver is implemented. The initial singularity is removed by building an approximation to the solution at a time t_0>0.


^ Upp till Numeros hemsida.


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Senast ändrad 20 november 1997
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