National Institute of the Republic of Serbia
ὅδε οἶκος, ὦ ἑταῖρε, μνημεῖον ἐστιν ζωῶν τῶν σοφῶν ἀνδρῶν, καὶ τῶν ἔργων αὐτῶν
PROGRAM
PROGRAM ZA SEPTEMBAR 2015.
Pozivamo Vas da učestvujete u radu sednica Odeljenja i to:
Sreda, 2. septembar 2015. u 18 casova, sala 301f:
Javier Urzay, Center for Turbulence Research, Stanford University (https://web.stanford.edu/~jurzay/)
RECENT ADVANCES AND OPEN CHALLENGES IN HIGH-SPEED COMBUSTION PHYSICS
Abstract: Great efforts have been dedicated over the last 50 years to the research and development of high-speed aerospace vehicles for terrestrial transportation, space exploration, and long-range global-strike weapons. However, superlative challenges related to mixing and combustion were identified very early in the history of development of high-speed propulsion. This lecture will review recent advances in the understanding of the fundamental physics and formulation of high-speed combustion, including autoigniting fuel sprays and supersonic flames. The presentation will emphasize the importance of interpreting dimensionless parameters in canonical problems for enabling understanding of more complex physical scenarios.
Petak, 4. septembar 2015. u 17 casova, Sala 301f MI SANU:
Kostas A.Lazopoulos, Mechanics Laboratory, School of Applied Maths & Physics, National Technical University of Athens, Greece
FRACTIONAL CONTINUUM MECHANICS Abstract: Since modern continuum mechanics is mainly characterized by the strong influence of microstructure, Fractional Continuum Mechanics has been a promising research field, satisfying both experimental and theoretical demands. The geometry of the fractional differential is corrected and the geometry of the tangent spaces of a manifold is clarified providing the bases of the missing Fractional Differential Geometry. The Fractional Vector Calculus is revisited along with the basic field theorems of Green, Stokes and Gauss. New concepts of the differential forms, such as fractional gradient, divergence and rotation are introduced. Application of the Fractional Vector Calculus to Continuum Mechanics is presented. The Fractional right and left Cauchy-Green deformation tensors and Green (Lagrange) and Euler-Almanssi strain tensors are exhibited. The change of volume and the surface due to deformation (configuration change) of a deformable body are also discussed. Fractional stress tensors are also introduced. Further the Fractional Continuum Mechanics principles yielding the fractional continuity and motion equations are also derived.
Sreda, 30. septembar 2015. u 18 casova, sala 301f, MI SANU
Srdjan Kostic, naucni saradnik, Institut za vodoprivredu ,,Jaroslav Cerni'', Beograd
srdjan.kostic@jcerni.co.rs, srdjanrgf@gmail.com
NELINEARNA DINAMIKA SEIZMOGENIH RASEDA
Rezime: Seizmogeni rasedi predstavljaju mehanicke diskontiuitete u Zemljinoj kori, po kojima kretanje u odredjenom velicinskom podrucju nije zanemarljivo i moze da uslovi nastanak zemljotresa. Sa stanovista teorijske mehanike, seizmicko kretanje duz raseda pokazuje svojstva stik-slip pomeranja, odnosno aperiodicnog smenjivanja ciklusa naglog, kratkotrajnog kretanja velike amplitude i dugotrajnog stacionarnog stanja (pomeranja vrlo male amplitude). Sa stanovista nelinearne dinamike, seizmicki rezim kretanja moze da se objasni ili postojanjem stranog atraktora (deterministicki haos), ili uticajem seizmickog suma. Na seminaru ce biti prikazani rezultati dosadasnjeg rada autora na izucavanju dinamike osnovnih mehanickih modela pomeranja duz seizmogenih raseda. Modeli su predstavljani nizom blokova koji su medjusobno povezani elasticnim oprugama i krecu se po hrapavoj povrsi. Dinamika ovih modela definisana je sistemima diferencijalnih jednacina sa kasnjenjem i sa sumom, pri cemu je kontakt blokova i hrapave povrsi odredjen specificnim zakonima trenja zavisnim samo od brzine pomeranja blokova ili i od brzine blokova i od stanja hrapavosti povrsi po joj se blokovi krecu. Resenja ovih sistema jednacina, za odredjene vrednosti kontrolnih parametara, ukazuju na pojavu bifurkacija u dinamickom sistemu, sa tipovima oscilacija koji mogu odgovarati razlicitim rezimima seizmickog i aseizmickog kretanja. Rezultati istrazivanja ukazuju na to da broj pokrenuti blokova u funkciji njihove amplitude pokazuje karakteristicnu Gutenberg-Rihter raspodelu, koja je utvrdjena da vazi za distribuciju realno osmatranih zemljotresa.
Predavanja su namenjena sirokom krugu slusalaca, ukljucujuci studente redovnih i doktorskih studija. Odrzavaju se sredom sa pocetkom u 18 casova u sali 301f na trecem spratu zgrade Matematickog instituta SANU, Knez Mihailova 36.