Naredni sastanak Seminara biće održan u sredu, 26. aprila 2017. u sali 301f Matematičkog instituta SANU sa početkom u 18 časova.
Predavač: Ivana Atanasovska, Matematički institut SANU
Naslov predavanja: UTICAJ FENOMENA KONTAKTA DEFORMABILNIH TELA NA DINAMIČKO PONAŠANjE SLOŽENIH MEHANIČKIH SISTEMA
Apstrakt: Fenomen kontakta deformabilnih tela predstavlja jednu od čestih nelinearnosti u mehanici složenih sistema. Posebno je važno rešavanje zadatka mehanike kontakta deformabilnih tela kada su kod mehaničkih sistema, čiji su tela u kontaktu deo, prisutni i drugi izvori nelinearnosti. U predavanju će biti opisan zadatak rešavanja promenljivih koje definišu mehaniku kontakta deformabilnih tela sa jednostavnom i sa složenom geometrijom kontaktnih površina. Posebno će biti prikazan pristup rešavanja kontaktnih problema deformabilnih tela diskretizacijom i primenom metode konačnih elemenata. Za rešavanje uticaja kontakta dva ili više deformabilna tela na dinamičko ponašanje složenog mehaničkog sistema, razvijen je novi pristup opisan odgovarajućim algoritmom. Primeri primene na konkretnim realnim složenim mehaničkim sistemima ilustrovaće prednosti razvijenog algoritma, pre svega kod postojanja geometrijskih i/ili materijalnih nelinearnosti u kontaktnim zonama, kao i pri pojavi udara.
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Naredni sastanak Seminara biće održan u utorak, 25. aprila 2017. u sali 301f Matematičkog instituta SANU sa početkom u 14:15 časova.
Predavač: Jasmina Perišić, Univerzitet Union Nikola Tesla
Naslov predavanja: AN ONTOLOGY BASED FRAMEWORK FOR PERSONALIZED E-LEARNING IN MOODLE
Apstrakt: In this work, we present a new approach to improve basic Moodle LMS (learning management system) by expanding it with two main functionalities: detection of learning style of the student and personalization of learning materials according to the student model. This approach is implemented through enriching Moodle with semantic technologies and ontology specially created to facilitate personalization. The result of applying these technologies is e-learning platform named MAL. In this paper, the functionality of the system and the way semantic technologies have been implemented into the MAL platform will be presented. We also conducted evaluation study to compare the effectiveness of both the non-adaptive approach and the adaptive approach based on semantics. The evaluation has been carried out at the Faculty of Entrepreneurial Business, the University Union "Nikola Tesla", Belgrade. The results are promising since they indicate that semantic adaptation of learning content implemented in MAL leads to significantly better learning outcome and improved efficiency of the learning process compared to the non-adaptive e-learning courses. They also indicate a positive attitude of students towards the developed learning environment.
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Počeo je sa radom Studentski seminar iz matematike!
Pozivaju se svi ljubitelji matematike da prisustvuju predavanjima.
Studenti će na predavanjima izlagati zanimljive teme u koje bi želeli da upute slušaoce.
Predloženi termin seminara je petkom u 12:15 na Matematičkom institutu SANU.
Sledeći sastanak Studentskog seminara biće u petak 21.04.2017. u 12:15 u učionici 301F (MI SANU).
Slušaćemo izlaganje Jelene Marković, studentkinje druge godine MATF-a, na temu Topologija - gde se matematika susreće sa magijom.
Više informacija o predavanju, kao i o samom seminaru, možete naći na trenutnoj internet stranici seminara:
http://www.mi.sanu.ac.rs/~borisa/seminar
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Naredni sastanak Seminara biće održan u petak, 21. aprila 2017. u sali 301f Matematičkog instituta SANU sa početkom u 14:15 časova.
Predavač: Vladimir Grujić, Matematički fakultet, Univerzitet u Beogradu
Naslov i sadržaj predavanja biće naknadno objavljeni.
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Naredni sastanak Seminara biće održan u sredu, 19. aprila 2017. u sali 301f Matematičkog instituta SANU sa početkom u 18 časova.
Predavač: Dr. Fotios Georgiades, Senior Lecturer, School of Engineering, College of Science, University of Lincoln, United Kingdom
Naslov predavanja: LINEAR AND NONLINEAR MODELLING/DYNAMICS OF L/SHAPEL BEAM – A SIMPLE ’COMPOSITE’ ELASTIC STRUCTURE
Apstrakt:
Since the 1960s, the dynamics of L-shaped coupled beams has been of interest because of their relative structural simplicity. It is among the simplest ‘composite’ elastic structures. It is derived all the equations of motion of an L-Shaped beam structure, and it is showed the importance of rotary inertia terms. The equations are decoupled in two motions, namely the in -plane bending and out-of-plane bending with torsion. A theoretical and numerical modal analysis has been performed and it is examined the effect of the orientation of the secondary beam (oriented in two ways) and also the shear effects. Parametric study of natural frequencies for various parameters of the L-Shaped beam showed stiffening and softening effects. Also in case that the length of secondary beam is less than 10% of the length of the primary beam, then the system behaves like cantilever beam with tip mass. Modelling of geometric nonlinearities indicates that the in-plane with out-of-plane motions are coupled together and has to be considered both planes even in examining up to 2nd order nonlinearities. Noted, so far in the literature of the L-Shaped beam structures with geometric nonlinearities the out-of-plane motions has been neglected. Although the two elastic beams are connected, the equations of motion form a self-adjoint system, therefore the projection of the dynamics in the infinite basis of the underlying linear system, lead to the modal equations with only nonlinear coupling and then well-known dimension reduction methods can be applied e.g. center manifolds. This work, paves the way for examination of dynamics in case of geometric nonlinearities of L-Shaped Beam structures, since it is almost impossible using commercial finite element software to perform nonlinear dynamic analysis e.g. the determination of Nonlinear Normal Modes as periodic orbits of millions of DOFs. Also, this work paves the way for analytical modelling and dynamic analysis of more complicated elastic structures e.g. a full airplane model.
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Naredni sastanak Seminara biće održan u utorak, 18. aprila 2017. u sali 809 Matematičkog fakulteta sa početkom u 18 časova.
Predavač: Luka C. Popović
Naslov predavanja: SPEKTROPOLARIZACIJA - NOVI POGLED U CENTAR AKTIVNIH GALAKSIJA
Apstrakt: U predavanju dajemo osvrt na značaj izučavanja aktivnih galaktičkih jezgara, njihovih karakteristika i veze njihovih spektralnih osobina sa centralnom supermasivnom crnom rupom.
Posebno dajemo osvrt na polarizaciju u spektru aktivnih galaktičkih jezgara koja može da obezbedi više informacija o njihovoj centralnoj strukturi. Predstavićemo jedan novi metod za određivanje masa supermasivnih crnih rupa iz polarizacije u širokim linijama.
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Prema kalendaru aktivnosti Matematičkog fakulteta, kao i prema Zakonu o državnim i drugim praznicima u Republici Srbiji neradni dani su 14, 15, 16. i 17. april, te se u petak 14.04. i u ponedeljak 17.04. neće raditi.
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Univerzitet u Mariboru organizuje letnju školu "Summer School on Solution Design" u periodu od 25.6. do 08.07.2017. Letnja škola je namenjena studentima master i doktorskih studija iz više oblasti.
Informacije o programu letnje škole mogu se naći i na sledećoj strani http://summer.outofthebox.um.si
Pet studenata Univerziteta u Beogradu će biti oslobođeno plaćanja kotizacije, koja pokriva troškove smeštaja, ishrane, materijala za učenje i jednodnevne izlete.
Studenti koji žele da konkurišu za oslobađanje kotizacije treba da dostave biografiju sa slikom i motivaciono pismo na engleskom jeziku najkasnije do petka, 28. aprila 2017. godine u Rektorat Univerziteta u Beogradu, Studentski trg 1, Beograd. Dokumentaciju dostaviti Sektoru za međunarodnu saradnju (prvi sprat, kancelarija br. 23), koleginici Marini Kostrici ili Branki Jandi Marković.
Kontakt osoba na Univerzitetu u Beogradu:
Marina Kostrica
Univerzitet u Beogradu/University of Belgrade
Studentski trg 1, 11000 Beograd/Studentski trg 1, 11000 Belgrade
Republika Srbija/Republic of Serbia
Tel. +381 11 3207453
Fax +381 11 3281 149
kostrm@rect.bg.ac.rs
http://www.bg.ac.rs
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Naredni sastanak Seminara biće održan u utorak, 11. aprila 2017. u sali 301f Matematičkog instituta SANU sa početkom u 14:15 časova.
Predavač: Zoran Maksimović, Univerzitet odbrane, Vojna akademija
Naslov predavanja: TWO METAHEURISTICS FOR SOLVING THE CONNECTED MULTIDIMENSIONAL MAXIMUM BISECTION PROBLEM
Apstrakt: In this paper, a connected multidimensional maximum bisection problem is considered. This problem is a generalization of a standard NP-hard maximum bisection problem, where each graph edge has a vector of weights and induced subgraphs must be connected. We propose two metaheuristic approaches, a genetic algorithm (GA) and an electromagnetism-like metaheuristic (EM). The GA uses modified integer encoding of individuals, which enhances the search process and enables usage of standard genetic operators. The EM, besides standard attraction repulsion mechanism, is extended with a scaling procedure, which additionally moves EM points closer to local optima. A specially constructed penalty function, used for both approaches, is performed as a practical technique for temporarily including infeasible solutions into the search process. Both GA and EM use the same local search procedure based on 1-swap improvements. Computational results were obtained on instances from literature with up to 500 vertices and 60000 edges. EM reaches all known optimal solutions on small-size instances, while GA reaches all known optimal solutions except for one case. Both proposed methods give results on medium-size and large-scale instances, which are out of reach for exact methods.
This is joint work with J. Kratica, A. Savić
Keywords: Genetic algorithms, Electromagnetism-like approach, Evolutionary computation, Graph bisection, Combinatorial optimization.
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Naredni sastanak KGTA seminara biće održan u utorak, 11. aprila 2017. u sali 844 Matematičkog fakulteta sa početkom u 14 časova.
Predavač: Vladimir Grujić, Matematički fakultet
Naslov predavanja: GKM TEORIJA (II DEO)
Apstrakt: GKM teorija je razvijena za računanje (ekvivarijantnih) kohomoloških prstenova mnogostrukosti sa torusnim dejstvom. Biće predstavljene osnove ove metode, uz razne primere.
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