ὅδε οἶκος, ὦ ἑταῖρε, μνημεῖον ἐστιν ζῴων τῶν σοφῶν ἀνδρῶν, καὶ τῶν ἔργων αὐτῶν

Mechanics Colloquim

 

PROGRAM


MATEMATIČKI INSTITUT SANU
ODELJENJE ZA MEHANIKU

PROGRAM ZA OKTOBAR 2009.

Pozivamo Vas da učestvujete u radu sednica Odeljenja i to:

CETVRAK, 01. oktobar 2009. u 14 sati:(ZAJEDNICKI SASTANAK OBA ODELJENJA)


Andreas Griewank, Humboltd University Berlin

DERIVATIVE-BASED OPTIMIZATION Abstract: Since Cauchy's time standard optimization methods require the evaluation of first derivatives for objective and constraint functions. At least the existence of these gradients and Jacobians is typically needed to ensure convergence for any optimization method that does not simply cover the feasible domain with sample points. The latter shot-gun approach is clearly unsuitable for high-dimensional problems of current interest. To beat the 'curse of dimensionality' in nonlinear optimization one can exploit the fact that continuous and discrete adjoints alike yield first and second derivative vectors at costs proportional to the underlying function and constraint evaluations. We discuss the resulting 'selective derivative methods' in comparison to derivative-free-methods in terms of numerical efficiency, applicability, and user convenience. Finally we report numerical experiences from aerodynamics and oceanography as depicted on the graph.

SREDA, 07. oktobar 2009. u 18 sati:


Akademik Vladan D. Djordjevic, Masinski fakultet, Beograd
LUDVIG PRANTL I TEORIJA GRANIČNOG SLOJA - POVODOM 105 GODINA OD NASTANKA TEORIJE

Teorija granicnog sloja predstavlja jednu od najvaznijih grana mehanike fluida. Nepodeljeno je misljenje da je Ludvig Prantl (1875-1953) jedini autor ove teorije i da je svojim epohalnim radom iz 1904. god., u kome je teoriju promovisao, ucinio jedan od najvecih koraka u razvoju mehanike fluida. U ovom popularnom saopstenju autor ce govoriti o Ludvigu Prantlu i vremenu u kome je on stvarao, o teoriji granicnog sloja i ulozi koju je ta teorija odigrala ne samo u oblasti mehanike fluida kao nauke, nego i u primenama u tehnici, posebno u vazduhoplovstvu, itd. S obzirom da je teorija granicnog sloja u prilicnom obimu zastupljena i u radovima nasih autora, u okviru predavanja bice reci i o njihovim doprinosima.



SREDA, 14. oktobar 2009. u 18 sati:


Katica R. (Stevanovic) Hedrih, Masinski fakultet, Nis
VISIBILITY OF NONLINEARITY

Lecturer gave a few lectures dedicated to 90th plus 30th of the Theory of nonlinear dynamics in Mathematical Institute SANU as well as at Faculty of Mechanical Engineering in Nis. Aim of this lecture is to give a clearest approach to the property of nonlinearity in real mechanical system dynamics and in the different mathematical descriptions by nonlinear differential equations with respect to the formalisms of the coordinate transformations. A question of Visibility of Nonlinearity thought different coordinate system is present and was analyzed. By use a example of linear system dynamics and through formal transformation of the coordinates from Descartes to polar coordinate system we show that transformation of the coordinate from fixed coordinate system to moving coordinate system appear nonlinear member in the differential equation, which appear as results of the Corriolis’s inertia force introduced in the system visible through polar coordinate system. This example opened a formalisms of the coordinate transformation according visibility of nonlinearity or visibility of linearity in passing thought different coordinate systems by use formalisms of the mathematical coordinate transformation. A series of examples of mechanical system dynamics are presented by differential equations am in the light formal mathematical transformation of the coordinates and by “introducing” in the different coordinate space of the visibility or no visibility of the nonlinearity or linearity of the differential equations and some analysis of the inertia forces introduced by the properties of the new transformed coordinate system.



Sednice se održavaju u zgradi SANU, Knez Mihailova 35, u sali 2 na prvom spratu.

Sekretar Odeljenja
Bojan Međo
Upravnik Odeljenja
Akademik Teodor Atanacković, s.r.