Auflistung Doctoral Dissertations nach Titel
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Perović, Aleksandar (Belgrade)[more][less]
Zusammenfassung: The interpretation method is a characteristic common for all results from this thesis. The thesis consists of five chapters and two appendices. A brief overview of the contents of the thesis and the obtained results are presented in Chapter 1. Logical background and the well-known notions the basic notions, definitions and properties from forcing are given in the appendices of the thesis. An elementary proof of equivalence between Cohen forcing and forcing with propositional Lindenbaum algebras is presented in Chapter 2. Dense embedding and the interpretation method are used in that proof. A complete axiomatization of the notion of qualitative probability is presented in Chapter 3. Probabilistic logic LPP_2 LPP_2^FR(n) and LPP^S are extended with the qualitative probability operator π. Several formal techniques as infinite rules, elimination of quantifiers and interpretation method (implicitly), are used to prove the extended completeness theorem and decidability for these logics. In Chapter 4 of the thesis a complete axiomatization of the logic with polynomial weight formulas is presented and the extended completeness theorem is proved. Applications of the interpretation method are given. By using that method the compactness theorem for the non-archimedean valued probabilistic logics is proved in Chapter 5. URI: http://hdl.handle.net/123456789/100 Dateien zu dieser Ressource: 1
phdAleksandarPerovic.pdf ( 700.0Kb ) -
Laban, Miloš (Belgrade , 1980)[more][less]
URI: http://hdl.handle.net/123456789/61 Dateien zu dieser Ressource: 1
phdMilosLaban.pdf ( 3.780Mb ) -
Janković, Svetlana (Belgrade)[more][less]
URI: http://hdl.handle.net/123456789/91 Dateien zu dieser Ressource: 1
phdSvetlanaJankovic.pdf ( 2.277Mb ) -
Karadžić, Lazar (Belgrade)[more][less]
URI: http://hdl.handle.net/123456789/244 Dateien zu dieser Ressource: 1
phdLKaradzic.pdf ( 2.881Mb ) -
Petrović, Vojislav (Novi Sad)[more][less]
URI: http://hdl.handle.net/123456789/113 Dateien zu dieser Ressource: 1
phdVojislavPetrovic.pdf ( 32.11Mb ) -
Janković, Aleksandra (Belgrade , 1989)[more][less]
URI: http://hdl.handle.net/123456789/24 Dateien zu dieser Ressource: 1
phdAleksandraJankovic.pdf ( 3.292Mb ) -
Ušćumlić, Momčilo (Belgrade , 1965)[more][less]
URI: http://hdl.handle.net/123456789/222 Dateien zu dieser Ressource: 1
phdMomciloUscumlic.pdf ( 2.757Mb ) -
Radenović, Stojan (Belgrade)[more][less]
URI: http://hdl.handle.net/123456789/362 Dateien zu dieser Ressource: 1
phdStojanRadenovic.pdf ( 4.000Mb ) -
Janeva, Biljana (Skopje)[more][less]
URI: http://hdl.handle.net/123456789/102 Dateien zu dieser Ressource: 1
phdBiljanaJaneva.pdf ( 12.37Mb ) -
Stojanović, Miroslava (Belgrade)[more][less]
URI: http://hdl.handle.net/123456789/350 Dateien zu dieser Ressource: 1
phdMiroslavaStojanovic.pdf ( 2.145Mb ) -
Ćetković, Simon (Belgrade)[more][less]
URI: http://hdl.handle.net/123456789/169 Dateien zu dieser Ressource: 1
phdSimonCetkovic.pdf ( 5.595Mb ) -
Kostić, Aleksandra (Beograd , 2021)[more][less]
Zusammenfassung: This dissertation examines simplicial complexes associated with cyclotomic po-lynomials and irreducible characters of finite solvable groups. In the process of analysis ofthe associated objects special attention is paid to the noncommutativity of the examinedstructures.A collection of simplicial complexes can be associated to an algebraic object such as acyclotomic polynomial. In most cases, the homotopy type of associated simplicial complexesgives us complete information about the coefficients of the cyclotomic polynomial. The onlyexceptions are cyclotomic polynomials whose degree is a product of three different primenumbers and this case is the focus of research in this doctoral dissertation. When it ispossible, the homotopy type of a simplicial complex associated with the polynomialΦpqr(x),wherep,qandrare different prime numbers, is determined by using the discrete Morsetheory. However, in special cases, the simplicial complexes associated with the polynomialΦpqr(x)have a noncommutative fundamental group, thus providing a new noncommutativeinvariant of this type of polynomial. Complex presentations that appear as presentations ofthe fundamental groups of associated simplicial complexes are analyzed using Fox’s calculus.This thesis also focus on the study of simplicial complexes associated to a set of irreduciblecharacters of a finite solvable group. Two types of simplicial complexes are attached to aset of irreducible characters of a finite solvable group — character degree complex and primedivisor complex. The examination of the fundamental group of these types of simplicial com-plexes provides better understanding of the structure of the irreducible characters of finitesolvable groups. URI: http://hdl.handle.net/123456789/5096 Dateien zu dieser Ressource: 1
Teza-Aleksandra_Kostic.pdf ( 1.009Mb ) -
Peruničić, Predrag (Belgrade , 1984)[more][less]
URI: http://hdl.handle.net/123456789/76 Dateien zu dieser Ressource: 1
phdPredragPerunicic.pdf ( 1.623Mb ) -
Gopčević, Špiro (Beograd , 2007)[more][less]
Zusammenfassung: U radu je prikazana nelinearna analiza konstrukcija sa kablovima. Formulisan je odgovaraju´ci matematiˇcki model problema. Pretpostavljeno je da je materijal konstrukcije izotropan i linearno-elastiˇcan. Primenom korigovane Lagrange-ove formulacije i nelinearnog polja pomeranja popreˇcnog preseka, izvedene su linearizovane inkrementalne jednaˇcine ravnoteˇze elementa. Na osnovu analitiˇckog reˇsenja za lanˇcanicu, a za razliˇcite poˇcetne pretpostavke, izvedeni su konaˇcni elementi za plitku i duboku lanˇcanicu. Ovi konaˇcni elementi su koriˇs´ceni za aproksimaciju kablova u konstrukcijama. Kao ˇsto sledi iz samog naziva, kablovi u konstrukcijama sa kablovima obiˇcno su povezani sa drugim tipovima elemenata, te je osim modeliranja kablova, urad¯eno i modeliranje tankozidnih i grednih nosaˇca. Izvedeni konaˇcni elementi za gredne nosaˇce, takod¯e, mogu da se upotrebljavaju za aproksimaciju kablova u konstrukcijama sa kablovima. U sluˇcaju nelinearne statiˇcke analize usvojen je inkrementalno-iterativni postupak za reˇsavanje sistema nelinearnih jednaˇcina, u varijanti Newton-Raphson-ovog i/ili modifikovanog Newton-Raphsonovog postupka. U sluˇcaju nelinearne dinamiˇcke analize usvojena je direktna numeriˇcka integracija, u varijanti Newmark-ovog postupka, u kombinaciji sa inkrementalno-iterativnom analizom u vremenskim koracima. Urad¯ena je objektno orijentisana analiza matematiˇckog modela i dobijen je objektno-orijentisani model podataka zasnovan na objektno orijentisanoj paradigmi. Na osnovu matematiˇckog modela i objektno-orijentisanog modela podataka, urad¯en je raˇcunarski program u jeziku C++. Dobijeni program omogu´cava linearnu i nelinearnu analizu konstrukcija sa kablovima, usled dejstva statiˇckog i dinamiˇckog optere´cenja. Taˇcnost raˇcunarskog programa proverena je kroz test primere dostupne u literaturi. URI: http://hdl.handle.net/123456789/3811 Dateien zu dieser Ressource: 1
070Doktorat.pdf ( 3.216Mb ) -
Bjelica, Momčilo (Beograd , 1990)[more][less]
URI: http://hdl.handle.net/123456789/4139 Dateien zu dieser Ressource: 1
Nepokretna_tacka.PDF ( 4.361Mb ) -
Racković Babić, Kristina (Beograd , 2022)[more][less]
Zusammenfassung: Interplanetary dust grains contain important information about the Solar System. Analyzing these particles is an important aspect of the heliosphere study. Dust impacts have been observed using radio and wave instruments onboard the spacecraft since the 1980s. The interac- tion between the impact-generated plasma cloud and antenna – space- craft system elements generates the characteristic signal waveform. The present work focuses on the detection and interpretation of the dust generated signals from radio instruments onboard various space- craft orbiting at 1 AU. In the first part of the thesis, we aim to develop a model which links the observed electric signals to the dust impact properties. We propose a new model which takes into account the effect of impact - ionization - charge collection and electrostatic-influence. Our model provides an analytical expression for the pulse. It allows us to measure the amount of total ion charge, the fraction of escaping charge, the rise timescale, and the relaxation timescale. The proposed model is simple and conve- nient for large data fitting. To validate the model, we use the Time Do- main Sampler (TDS) subsystem of the STEREO/WAVES instrument, which generates high-cadence time series of voltage pulses for each monopole. Since the beginning of the STEREO mission in 2007, we have collected all the dust events detected by S/WAVES/TDS simul- taneously on all three monopoles at 1 AU. Our study confirms that the rise time vastly exceeds the spacecraft’s short timescale of elec- tron collection by the spacecraft. Aside from electron dynamics, we also obtained interesting results regarding the cloud’s electron tem- perature. The presented model provides an effective tool for analyzing vii dust waveforms, and is applicable for different space missions which investigate the distribution of dust particles, e.g., Solar Orbiter and Parker Solar Probe. In the second part of the thesis, we focus on the interstellar dust (ISD). Interplanetary and interstellar dust are the two main dust pop- ulations at 1 AU. Our objective is to search for interstellar dust by analyzing the data sets collected by STEREO and Wind, starting from the beginning of the missions. Between 2007 and 2012, while being at the solar minimum with a solar dipole pointing southward, all three spacecraft recorded ISD flux at 1 AU. However, before and after that period, the disappearance of the interstellar component was noticeable. The observed change of the impact rate suggests that the flux of inter- stellar dust at 1 AU varies with the solar cycle. Each time the magnetic dipole field changes its polarity during the solar cycle, small interstel- lar grains experience focusing or defocusing. Consequently, the dust grains are systematically deflected either towards, or away from the solar magnetic equator plane by the solar wind magnetic field which thus affects the dust dynamics and the total interstellar dust flux in the inner heliosphere. Our study provides the first quantitative de- scription of the time variation of ISD flux at 1 AU. URI: http://hdl.handle.net/123456789/5547 Dateien zu dieser Ressource: 1
Teza_KRB.pdf ( 10.95Mb ) -
Božović, Nataša (Belgrade)[more][less]
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Surla, Katarina (Novi Sad , 1980)[more][less]
URI: http://hdl.handle.net/123456789/47 Dateien zu dieser Ressource: 1
phdKatarinaSurla.pdf ( 3.177Mb ) -
Jevtić, Miroljub (Belgrade)[more][less]
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Vučković, Bojan (Beograd , 2017)[more][less]
Zusammenfassung: We present original results from the following fields of discrete mathematics: chromatic graph theory, extremal set theory and Boolean matrix theory. From the chromatic graph theory we investigate edge and total colorings satisfying the condition that neighboring vertices of a graph possess different values of multi-set, set or sum, induced by the giving coloring. Multi-set neighbor-distinguishing edge coloring of a graph is an assignment of colors to edges such that, for every edge uv of a graph, multi-set of the edges incident with the vertex u differs from the multi-set of the edges incident with the vertex v. The previous best result concerning the minimum number of colors required for such a coloring of an arbitrary graph states that four colors are sufficient. The author’s contribution is a proof that such a coloring is always possible with only three colors, which is in general case the optimal number of colors. We construct a graph for which we subsequently prove that a different number of colors is required to obtain a multi-set neighbor-distinguishing coloring and neighbor-distinguishing coloring by sum. As far as we know, this is the first example of such a graph. A few results concerning the neighbor expended sum distinguishing coloring are given. The main contribution is a proof that for an arbitrary graph there exists a total coloring from the set f1; 2; 3g, such that every two adjacent vertices have different sums of its adjacent vertices and incident edges. Also, for certain classes of graphs is proved that there exists such a coloring using only the colors from the set f1; 2g. Neighbor-distinguishing edge coloring of a graph G requires that every two adjacent edges receive different colors, while the sets of the edges incident with the vertices u and v differ for every edge uv of G. The author presents a procedure of edge coloring for an arbitrary graph without isolated edges, where we a smaller number of colors is used compared to all known results. For the adjacent vertex distinguishing total coloring of a graph G the condition is that every two adjacent and incident elements of V (G) [ E(G) receive different colors, while for every edge uv of G the set composed from the colors assigned to the edges incident with u together with the color of u, differs from such a set for v. The author improves the upper bound of the minimum number of colors needed for such a coloring, relative to the maximal degree of a graph. Frankl’s conjecture from the extremal set theory states that for every family closed under union there exists an element contained in at least half of the sets of the family. We give a proof that Frankl’s conjecture holds for every family contained from 12 elements, while it is known that this is true for families contained from 11 or less elements. Our proof is based on the efficient algorithm that exhausts all the possibilities, while using the results for subfamilies that eventual counter-example cannot contain, which we obtained in a number of consecutive steps. Family of sets G is an FC-family if for every family F containing G there exists an element from S G that appears in at least half of the sets of F. NonFC-family is every family that is not FC. The author’s contribution is the complete classification of all families consisting of 6 or less elements into FC and NonFC-families. From the Boolean matrices theory we present our results concerning the row space cardinality. Boolean matrices are the matrices whose all components are from the set f0; 1g, while the row space of a Boolean matrix is the set of vectors that can be obtained by disjunction from the rows of a matrix. We present the set consisted of all values a from the interval [2n2 + 2n3; 2n2] such that there exists a matrix of dimension n n having the row space cardinality equal to a. For the least positive integer an for which there exists no matrix of dimension n n having the row space cardinality equal to an, the author gives a lower bound that is an improvement over the previously known results. All proofs for the main results in the dissertation are constructive. Proofs of some of them require the use of computers where there is a calculation of a great number of possibilities. For other proofs this was not necessity, though algorithms following the steps of the proofs can be implemented to obtain a graph coloring or a matrix with the desired properties. URI: http://hdl.handle.net/123456789/4661 Dateien zu dieser Ressource: 1
Disertacija_-_Bojan_Vuckovic.pdf ( 1.143Mb )