Numero 3

måndag 22 januari 1996, årgång 26

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).

Påminnelse: Olles lic.seminarium

...under rubriken Electronic mail from a user perspective idag måndag (22 jan.) kl. 10.00-12 i Kollegiesalen, administrationshuset (Valhallavägen 79).


IPLab-seminarium: WWW-teknik

Peter Svanberg och Anders Hillbo berättar om WWW-teknik - tips och regler för användare respektive informationsspridare - i form av ett IPLab-seminarium på fredag (26 jan.) kl. 9.15-10.15 i seminarierum 1537 (Lindstedtsv. 3, plan 5).


Konferens: Forskarinnovationsdagen 1996

Stiftelsen Innovationscentrum m.fl. inbjuder till Forskarinnovationsdagen måndagen den 11 mars i Svenska mässan, Göteborg. OBS: Sista anmälningsdag var igår (21 jan.)! Se Numeropärmen 96.010.


Mattekonferens i Quebec

...under rubriken Plates and shells: from matematical theory to engineering practice äger rum i sommar (22-27 juli). Se Numeropärmen 96.011.


IPLab-seminarier under våren

Följande tillfällen är inlagda för IPLab-seminarier.

26 jan.: WWW-teknik, Peter Svanberg & Anders Hillbo

16 febr.: Applications of three-dimensional interaction to collaborative work, Kai-Mikael Jää-Aro

1 mars: On the Usage of Communicative Theories in Workflow Management and CSCW, Peter Holm:

15 mars: Användbar IT, Cecilia Katzeff

Vi har för IPLabseminarierna bokat fredagar i udda veckor under resten av våren och återkommer senare när talare är klara.

Kerstin S. Eklundh, Lars Kjelldahl

Tidigarelagd ansökningstid för vissa stipendier

Vissa stipendier har i år tidigarelagt ansökningstiden jämfört med tidigare år - kolla!


C. F. Liljevalch j:ors resestipendier

...för studerande vid mat.-nat. fakulteten vid SU, ansökan senast 15 februari, blanketter i Numeropärmen 96.012 och hos Ann B.


Ragnar och Astrid Signeus fond

...ledigkungör rektor ett ellef flera stipendier eller bidrag ur, till forskarstuderande, lärare m.fl. för resa eller bidrag till vistelse vid annat universitet o.dyl. Ansökan senast 19 februari. Numeropärmen 96.013


PDC-seminarium: Growth of finite perturbations, a generalization of the concept of Lyapunov exponents

Erik Aurell håller PDC-seminarium under ovanstående rubrik imorgon tisdag (23 jan.) kl. 15.15 i seminarierum 1537 (Lindstedtsv. 3, plan 5).

Abstract

The predictability problem can be said to be this: Suppose the initial state of a system is known with an error \delta, and I accept a tolerance \Delta; for what time can the system typically be predicted with this tolerance?

If the system in question is a chaotic dynamical system with few degrees of freedom, and both \delta and \Delta are small, then the standard answer is that the predictability time depends only on the quotient \Delta/\delta, and is roughly inversely proportional to the largest Lyapunov exponent, i.e. T\sim \frac{1}{\lambda}\log \frac{\Delta}{\delta}.

If the system is a stochastic process, then the predictability time depends on the kind of process and usually also on \delta and \Delta separately.

In this talk I will present numerical simulations on a model example and explain heuristics that pertain to the case of a deterministic system with many degrees of freedom, and \delta and \Delta are not small. These systems then turn out to be, in a quantitative sense, more similar to stochastic processes than to deterministic systems with few degrees of freedom.

This is joint work with G. Boffetta, A. Crisanti, G. Paladin and A. Vulpiani, following earlier work by P. Gaspard and X.-J. Wang, Physics Reports, volume 235 (1993), pages 291-343.


PDC-seminarium: Entropy and atomic diffusion in condensed matter

Mikhail Dzugutov, PDC, håller PDC-seminarium under ovanstående rubrik tisdagen den 30 jan. kl. 15.15 i seminarierum 1537 (Lindstedtsv. 3, plan 5).

Abstract

In spite of its recent advances, kinetic theory has so far been unable to provide a unifying quantitative description of the equilibrium atomic diffusion in condensed phases. Detailed expressions have been derived for the transport coefficients in the dense fluid of hard spheres. To generalize these results to real systems, an adequate procedure of mapping the latter onto the reference model of hard spheres is required. However, the structural diversity observed in atomic systems at high densities, and the dependence of this diversity on the details of the interatomic interactions, poses a formidable problem in this approach.

I present here an observation, based on a Molecular Dynamics simulation of a diverse set of simple monatomic systems, explored in a range of thermodynamical conditions, which demonstrates that the diffusion coefficient, scaled by the frequency of atomic collisions, can be uniquely related to the excess entropy representing the measure of structural disorder. This result, besides its apparent conceptual consequencies, might be expected to find application in various fields of materials science and technology where a reliable a priory evaluation of atomic mobility in different phases is required.


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Senast ändrad 1996-01-21 <numero@nada.kth.se>