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24. On the split structure of lifted groupsAleksander Malnič, Rok Požar, 2016, original scientific article Abstract: Let ▫$\wp \colon \tilde{X} \to X$▫ be a regular covering projection of connected graphs with the group of covering transformations ▫$\rm{CT}_\wp$▫ being abelian. Assuming that a group of automorphisms ▫$G \le \rm{Aut} X$▫ lifts along $\wp$ to a group ▫$\tilde{G} \le \rm{Aut} \tilde{X}$▫, the problem whether the corresponding exact sequence ▫$\rm{id} \to \rm{CT}_\wp \to \tilde{G} \to G \to \rm{id}$▫ splits is analyzed in detail in terms of a Cayley voltage assignment that reconstructs the projection up to equivalence. In the above combinatorial setting the extension is given only implicitly: neither ▫$\tilde{G}$▫ nor the action ▫$G\to \rm{Aut} \rm{CT}_\wp$▫ nor a 2-cocycle ▫$G \times G \to \rm{CT}_\wp$▫, are given. Explicitly constructing the cover ▫$\tilde{X}$▫ together with ▫$\rm{CT}_\wp$▫ and ▫$\tilde{G}$▫ as permutation groups on ▫$\tilde{X}$▫ is time and space consuming whenever ▫$\rm{CT}_\wp$▫ is large; thus, using the implemented algorithms (for instance, HasComplement in Magma) is far from optimal. Instead, we show that the minimal required information about the action and the 2-cocycle can be effectively decoded directly from voltages (without explicitly constructing the cover and the lifted group); one could then use the standard method by reducing the problem to solving a linear system of equations over the integers. However, along these lines we here take a slightly different approach which even does not require any knowledge of cohomology. Time and space complexity are formally analyzed whenever ▫$\rm{CT}_\wp$▫ is elementary abelian. Keywords: algorithm, abelian cover, Cayley voltages, covering projection, graph, group extension, group presentation, lifting automorphisms, linear systems over the integers, semidirect product Published in RUP: 15.10.2015; Views: 2763; Downloads: 157 Full text (422,56 KB) |
25. Comparison of values among students of Faculty of Management at University of PrimorskaŠpela Jesenek, Ana Arzenšek, Katarina Košmrlj Muha, 2015, published scientific conference contribution abstract Keywords: vrednote, sistemi vrednot, Muskova lestvica vrednot, študenti, Fakulteta za management, etika, value systems, dominant values, Musek's value scale, university students, Faculty of Management Published in RUP: 14.10.2015; Views: 2683; Downloads: 69 Link to full text |
26. Fuzzy urban traffic signal control - an overviewAlenka Malej, Andrej Brodnik, 2007, original scientific article Abstract: Izboljšanje sistemov za upravljanje mestne prometne signalizacije je eden cenovno najučinkovitejših načinov za izboljšanje prometnega pretoka skozi mrežo semaforiziranih križišč. Pri razvoju novih sistemov se zadnja tri leta poleg tradicionalnih metod, ki temeljijo na uporabi modelov prometnega pretoka, čedalje več uporabljajo nove tehnologije, ki vključujejo uporabo umetne inteligence. Raziskave so pokazale učinkovitost metahevrističnih metod. Posebna mehka logika, tudi v kombinaciji z optimizacijskimi metodami, ponuja fleksibilnost, prilagodljivost, upravljanje pri netočnih ingormacijah in v konfliktnih situacijah. Naredili smo pregled raziskav s tega področja Keywords: prometna signalizacija, mehka logika, hibridni sistemi, porazdeljeno upravljanje, traffic signal control, hybrid systems, fuzzy logic, distributed control Published in RUP: 10.07.2015; Views: 4068; Downloads: 53 Link to full text |
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