Browsing Doctoral Dissertations by Title
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Marinković, Silvana (Kragujevac, Serbia , 2011)[more][less]
Abstract: In this dissertation functions and equations in some classes of lattices such as Post algebras, Stone algebras and multiple-valued logics, are studied. The dissertation, beside Preface and References with 46 items, consists of five chapters. In Introduction some basic notations which will be used in next chapters are given. Main results on Boolean functions and equations are exposed in Chapter 2. In Chapter 3, assuming that a general solution is known, the class of reproductive general solutions of the equation in Stone algebra is described. All general solutions of equations in one variable in multiple-valued logic are described in Chapter 4. A necessary and sufficient conditions that given sequence of recurrent inequalities represents solution of some consistent Post equation are given in Chapter 5. Also, it is proved that every Post transformation is the parametric solution of some consistent Post equation. URI: http://hdl.handle.net/123456789/1842 Files in this item: 1
SilvanaMarinkovicDoktorat.pdf ( 360.3Kb ) -
Drašković, Zoran (Beograd , 1990)[more][less]
Abstract: U radu to da bude upotrebljena Galerkinova procedura za dobijanje jednatina polja tanke ljuske neuniformne debljine iz jednatina polja trodimenzionog kontinuuma. Tako to (s obzirom na to da je u [54], odnosno u (57] vet bilo reti o konstitutivnim jednacinama tanke ljuske) da bude zaokruien rad na razvoju tzv. meAovitog modela u teoriji tanke ljuske - to je model tri polja, koji predstavlja neklasidan pristup u metodi konadnih elemenata i odlikuje se nezavisnim aproksimiranjem polja pomeranja, polja deformacije i polja napona, a u cilju uzimanja u obzir i granidnih uslova na licima ljuske (tto je inade nemogute u klasidnoj metodi konadnih elemenata). Osnovna odlika pristupa u radu bite koriiCenje invarijantnih (tj. nezavisnih od izbora koordinatnog sistema) aproksimacija (i to Leiandrovim polinomima) tih polja, Itode mann koji je nov u literaturi, a treba da omoguei, s jedne strane, geometrijski doslednije, a, sa druge strane, jednostavnije dobijanje jednadina polja tanke ljuske iz trodimenzione teorije URI: http://hdl.handle.net/123456789/4092 Files in this item: 1
Jerdnacine_polja.PDF ( 1.204Mb ) -
Draškovic, Zoran (Belgrade , 1990)[more][less]
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Stipanić, Ernest (Belgrade)[more][less]
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Dacić, Rade (Belgrade , 1965)[more][less]
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Mitrović, Slobodanka (Belgrade)[more][less]
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Komarčić, Lazar (Belgrade , 1902)[more][less]
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Lipkovski, Aleksandar (Belgrade , 1985)[more][less]
URI: http://hdl.handle.net/123456789/25 Files in this item: 1
phdAleksandarLipkovski.pdf ( 2.471Mb ) -
Miličić, Miloš (Belgrade , 1982)[more][less]
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Malinović, Todor (Novi Sad , 1986)[more][less]
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Obradović, Marko (Beograd , 2015)[more][less]
Abstract: First characterizations of probability distributions date to the thirties of last century. This area, which lies on the borderline of probability theory and mathematical statistics, attracts large number of researchers, and in recent times the number of papers on the subject is increasing. Goodness-of- t tests are among the most important nonparametric tests. Many of them are based on empirical distribution function. The application of characterization theorems for construction of goodness-of- t tests dates to the middle of last century, and recently has become one of the main directions in this eld. The advantage of such tests is that they are often free of distribution parametres and hence enable testing of composite hypotheses. The goals of this dissertation are the formulation of new characterizations of exponential and Pareto distribution, as well as the application of the theory of U-statistics, large deviations and Bahadur e ciency to construction and examination of asymptotics of goodness-of- t tests for aforementioned distributions. The dissertation consists of six chapters. In the rst chapter a review of di erent types of characterizations is presented, pointing out their abundance and variety. The special emphasis is given to the characterizations based on equidistribution of functions of the sample. Besides, two new characterizations of Pareto distribution are presented. The second chapter is devoted to some new characterizations of the exponential distributions presented in papers [65] and [53]. Six characterizations based on order statistics are presented. A special case of one of them (theorem 2.4.3) represents the solution of open problem stated by Arnold and Villasenor [9]. In the third chapter there are basic concepts on U-statistics, the class of statistics important in the theory of unbiased estimation. Some of their asymptotic properties are given. U-empirical distribution functions, a generalization of standard empirical distribution functions, are also de ned. The fourth chapter is dedicated to the asymptotic e ciency of statistical tests, primarily to Bahadur asymptotic e ciency, i.e. asymptotic e ciency of the test when the level of signi cance approaches zero. Some theoretical results from the monograph by Nikitin [57], and papers [61], [59], etc. are shown. In the fth chapter new results in the eld of goodness-of- t tests for Pareto distribution are presented. Based on three characterizations of Pareto distribution given in section 1.1.2. six goodness-of- t tests, three of integral, and three of Kolmogorov type, are proposed. In each case the composite null hypothesis is tested since the test statistics are free of the parameter of Pareto distribution. For each test the asymptotic distribution under null hypothesis, as well as asymptotic behaviour of the tail (large deviations) under close alternatives is derived. For some standard alternatives, the local Bahadur asymptotic e ciency is calculated and the domains of local asymptotic optimality are obtained. The results from this chapter are published in [66] and [64]. The sixth chapter brings new goodness-of- t tests for exponential distribution. Based on the solved hypothesis of Arnold and Villasenor two classes of tests, integral and Kolmogorov type, are proposed, depending on the number of summands in the characterization. The study of asymptotic properties, analogous to the ones in the fth chapter is done in case of two and three summands, for which the tests have practical importance. The results of this chapter are presented in [39]. URI: http://hdl.handle.net/123456789/4288 Files in this item: 1
phdObradovicMarko.pdf ( 789.3Kb ) -
Aranđelović, Dragoljub (Belgrade)[more][less]
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Valjarević, Aleksandar (Niš , 2012)[more][less]
Abstract: The territory of Kosovo and Metohia has alwaus represented the hidrology interesting area of study, in which they compared the parameters of water drainage and their physical properties. Generalization is one of the methods for these porposes and may be used and the results can be applied to various forms of digital maps. URI: http://hdl.handle.net/123456789/3118 Files in this item: 1
ValjarevicAleksandarDD.pdf ( 39.32Mb ) -
Alagić, Mara (Belgrade , 1985)[more][less]
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Jokanović, Dušan (Podgorica)[more][less]
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Šandrih, Branislava (Beograd , 2020)[more][less]
Abstract: The main goal of this dissertation is to put different text classification tasks inthe same frame, by mapping the input data into the common vector space of linguisticattributes. Subsequently, several classification problems of great importance for naturallanguage processing are solved by applying the appropriate classification algorithms.The dissertation deals with the problem of validation of bilingual translation pairs, sothat the final goal is to construct a classifier which provides a substitute for human evalu-ation and which decides whether the pair is a proper translation between the appropriatelanguages by means of applying a variety of linguistic information and methods.In dictionaries it is useful to have a sentence that demonstrates use for a particular dictio-nary entry. This task is called the classification of good dictionary examples. In this thesis,a method is developed which automatically estimates whether an example is good or badfor a specific dictionary entry.Two cases of short message classification are also discussed in this dissertation. In thefirst case, classes are the authors of the messages, and the task is to assign each messageto its author from that fixed set. This task is called authorship identification. The otherobserved classification of short messages is called opinion mining, or sentiment analysis.Starting from the assumption that a short message carries a positive or negative attitudeabout a thing, or is purely informative, classes can be: positive, negative and neutral.These tasks are of great importance in the field of natural language processing and theproposed solutions are language-independent, based on machine learning methods: sup-port vector machines, decision trees and gradient boosting. For all of these tasks, ademonstration of the effectiveness of the proposed methods is shown on for the Serbianlanguage. URI: http://hdl.handle.net/123456789/5090 Files in this item: 1
BranislavaSandrihPhd_konacno.pdf ( 9.053Mb ) -
Ivanović, Jelena (Beograd , 2020)[more][less]
Abstract: U teoriji kategorija, koherencija koja je vezana za odre eni tip kategori-ja, u najgrubljem smislu znaqi komutiranje dijagrama sastavljenih od kanonskihstrelica tih kategorija. Ovo komutiranje mo e biti bezuslovno ili uslovljenozadatim pretpostavkama. U savremenom smislu, koherencija, taqnije teoremekoherencije, podrazumevaju postojanje vernog funktora iz slobodno generisa-ne kategorije datog tipa u kategoriju koja omogu ava proveru jednakosti stre-lica. Takve su najqex e kategorije qije su strelice relacije ili dijagrami(mnogostrukosti, kobordizmi).Rezultati koherencije su od velikog znaqaja za opxtu teoriju dokaza. Naime,oni obezbe uju formiranje zadovoljavaju eg kriterijuma za jednakost izvo enjau odre enim deduktivnim sistemima i na taj naqin pru aju mogu nost defini-sanja osnovnog pojma kojim se teorija dokaza bavi.Predmet ove doktorske disertacije je prouqavanje topoloxkih dokaza ko-herencije i formiranje novih klasa politopa koje u takvim dokazima koheren-cije mogu poslu iti. Sadr aj disertacije je, dakle, u najve oj meri posve enspomenutim dokazima koherencije, odnosno raznovrsnim geometrijskim realiza-cijama specifiqnih apstraktnih politopa koji su zadati kombinatorno.Naime, ranih devedesetih godina, Mihail Kapranov je uveo familiju e-lijskih kompleksa pod nazivom permutoasociedri koja predstavlja ,,hibrid” dveznaqajne familije prostih politopa–familije asociedara i familije permuto-edara. Ovaj hibrid je predstavljao prvu geometrijsku interpretaciju udru i-vanja komutativnosti i asocijativnosti. Kapranov je pokazao da je datom elij-skom strukturom proizveoCW-loptu qime je dobio direktan topoloxki dokazkoherencije u simetriqnim monoidalnim kategorijama. Ubrzo nakon toga, Vik-tor Rajner i Ginter Cigler su ove elijske komplekse realizovali kao fami-liju konveksnih politopa. Me utim, dobijena familija nije familija prostihpolitopa. S druge strane, i svi asociedri i svi permutoedri jesu prosti. Onipripadaju nestoedarima–xiroko izuqavanoj familiji prostih politopa, kako sakombinatorne strane, tako i sa strane primena u torusnoj topologiji.Polazixte ove teze je da je prirodno prona i prost hibrid ove dve fami-lije, tj. prost permutoasociedar. Koriste i kombinatornu proceduru sliqnuonoj koja je proizvela i same asociedre i permutoedre, u ovoj disertaciji seuvodi apstraktni politop koji odgovara problemu koherencije, a koji se pritommo e realizovati kao prost politop. Preciznije, formirane su klasen-dimen-zionalnih prostih permutoasociedara koje daju topoloxki dokaz simetriqnemonoidalne koherencije, a zatim su te klase i geometrijski realizovane eks-plicitnim zadavanjem nejednaqina poluprostora uRn+1koji definixu politopexiii xivu klasama. Ovan-dimenzionalna realizacija je oznaqena saPAn. Pored toga,u tezi je ponu ena i alternativna realizacija iste familije uz pomo sumaMinkovskog. Naime, uvedena je familijan-dimenzionalnih politopa, oznaqe-na saPAn,c, koja je dobijena sumiranjem odre enih politopa. PolitopPAn,cjenormalno ekvivalentan politopuPAnza svakoc∈(0,1]. Req je o specifiqnojrealizaciji, po ugledu na realizaciju nestoedara Aleksandra Postnjikov, kojapodrazumeva da svaki sabirak, grubo reqeno, doprinosi nastajanju taqno jednepljosni rezultuju e sume Minkovskog. Drugim reqima, svaki sabirak dovodi dozarubljivanja teku e parcijalne sume odsecanjem jedne njene strane. Postnjikovje za sabirke koristio simplekse, dok ova disertacija pokazuje da je, u analog-noj realizaciji prostog permutoasociedra, za odre ene sabirke neophodno uzetipolitope koji ne samo da nisu simpleksi, ve nisu nu no ni prosti politopi. Usluqaju formiranja familijePAn,1, sabirci su definisani kao konveksni omo-taqi skupova taqaka uRn+1xto je znaqajna prednost sa stanovixta programi-ranja.Osim xto predstavlja direktan topoloxki dokaz teoreme koherencije u si-metriqnim monoidalnim kategorijama, poseban znaqaj ove alternativne reali-zacije je u uspostavljanju jasne veze izme u operacije sumiranja Minkovskogi operacije odsecanja strana permutoedra, tj. njegovog zarubljivanja. Iz oveveze implicitno sledi procedura za analognu realizaciju xire klase prostihpolitopa–familije prostih permutonestoedara.Na kraju, u tezi su date ocene hromatskih brojeva prostog permutoasociedrai nekih znaqajnih nestoedara, sa ciljem prouqavanja mogu e veze ovih klasapolitopa sa torusnim i kvazitorusnim mnogostrukostima.Tokom svih spomenutih istra ivanja, za potrebe ove disertacije je razvijenonekoliko softverskih rexenja (programa i aplikacija) uz pomo raznovrsnihprogramskih jezika i paketa (Java,polymake/Perl,Rhinoceros/ Grasshopper). Naj-znaqajnija me u njima opisana su u dodatku teze programskim kodom i odgo-varaju im ilustrativnim primerima. URI: http://hdl.handle.net/123456789/5104 Files in this item: 1
Ivanovic_Jelena_disertacija.pdf ( 2.983Mb ) -
Pešović, Marko (Beograd , 2021)[more][less]
Abstract: The combinatorial objects can be joined in a natural way with the correspondingcombinatorial Hopf algebras. Many classical enumerative invariants of combinatorial objectsare obtained as a result of universal morphism from the corresponding combinatorial Hopfalgebras to the combinatorial Hopf algebra of quasisymmetric functions.On the other hand, to combinatorial objects we can assign some geometric objects such ashyperplane arrangement or convex polytope. For example, simple graph corresponds to graphicalzonotope and matroid corresponds to matroid base polytope. These classes of polytopes belongto the class of polytopes known as generalized permutohedra. For a generalized permutohedronthere is a weighted quasisymmetric enumerator which for different classes of generalizedpermutohedra represents generalizations of classical enumerative invariants such as Stanley’schromatic symmetric function for graph and Billera−Jia−Rainer quasisymmetric function formatroid.A weighted quasisymmetric enumerator associated with a generalized permutohedron is aquasisymmetric function. For certain classes of generalized permutohedra this enumeratorcoincides with the result of the universal morphism from corresponding combinatorial Hopfalgebra. URI: http://hdl.handle.net/123456789/5207 Files in this item: 1
Pesovic_Marko.pdf ( 1.804Mb ) -
Jelić Milutinović, Marija (Beograd , 2021)[more][less]
Abstract: In this dissertation we examine several important objects and concepts in combinatorialtopology, using both combinatorial and topological methods.The matching complexM(G) of a graphGis the complex whose vertex set is the setof all edges ofG, and whose faces are given by sets of pairwise disjoint edges. These com-plexes appear in many areas of mathematics. Our first approach to these complexes is newand structural - we give complete classification of all pairs (G,M(G)) for whichM(G) is ahomology manifold, with or without boundary. Our second approach focuses on determiningthe homotopy type or connectivity of matching complexes of several classes of graphs. Weuse a tool from discrete Morse theory called the Matching Tree Algorithm and inductiveconstructions of homotopy type.Two other complexes of interest are unavoidable complexes and threshold complexes.Simplicial complexK⊆2[n]is calledr-unavoidable if for each partitionA1t···tAr= [n] atleast one of the setsAiis inK. Inspired by the role of unavoidable complexes in the Tverbergtype theorems and Gromov-Blagojevi ́c-Frick-Ziegler reduction, we begin a systematic studyof their combinatorial properties. We investigate relations between unavoidable and thre-shold complexes. The main goal is to find unavoidable complexes which are unavoidable fordeeper reasons than containment of an unavoidable threshold complex. Our main examplesare constructed as joins of self-dual minimal triangulations ofRP2,CP2,HP2, and joins ofRamsey complex.The dissertation contains as well an application of the important “configuration space -test map” method. First, we prove a cohomological generalization of Dold’s theorem fromequivariant topology. Then we apply it to Yang’s case of Knaster’s problem, and obtain anew simpler proof. Also, we slightly improve few other cases of Knaster’s problem. URI: http://hdl.handle.net/123456789/5184 Files in this item: 1
Marija_Jelic_Milutinovic.pdf ( 5.212Mb ) -
Stojadinović, Tanja (Beograd , 2013)[more][less]
Abstract: Multiplication and comultiplication, which de ne the structure of a Hopf algebra, can naturally be introduced over many classes of combinatorial objects. Among such Hopf algebras are well-known examples of Hopf algebras of posets, permutations, trees, graphs. Many classical combinatorial invariants, such as M obius function of poset, the chromatic polynomial of graphs, the generalized Dehn-Sommerville relations and other, are derived from the corresponding Hopf algebra. Theory of combinatorial Hopf algebras is developed by Aguiar, Bergerone and Sottille in the paper from 2003. The terminal objects in the category of combinatorial Hopf algebras are algebras of quasisymmetric and symmetric functions. These functions appear as generating functions in combinatorics. The subject of study in this thesis is the combinatorial Hopf algebra of hypergraphs and its subalgebras of building sets and clutters. These algebras appear in di erent combinatorial problems, such as colorings of hypergraphs, partitions of simplicial complexes and combinatorics of simple polytopes. The structural connections among these algebras and among their odd subalgebras are derived. By applying the character theory, a method for obtaining interesting numerical identities is presented. The generalized Dehn-Sommerville relations for ag f-vectors of eulerian posets are proven by Bayer and Billera. These relations are de ned in an arbitrary combinatorial Hopf algebra and they determine its odd subalgebra. In this thesis, the generalized Dehn-Sommerville relations for the combinatorial Hopf algebra of hypergraphs are solved. By analogy with Rota's Hopf algebra of posets, the eulerian subalgebra of the Hopf algebra of hypergraphs is de ned. The combinatorial characterization of eulerian hypergraphs, which depends on the nerve of the underlying clutter, is obtained. In this way we obtain a class of solutions of the generalized Dehn-Sommerviller relations for hypergraphs. These results are applied on the Hopf algebra of simplicial complexes. URI: http://hdl.handle.net/123456789/4306 Files in this item: 1
phdTanjaStojadinovic.pdf ( 13.95Mb )