Browsing Doctoral Dissertations by Title
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Gajić, Ljiljana (Novi Sad , 1982)[more][less]
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Laković, Bosiljka (Titograd , 1979)[more][less]
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Laković, Bosiljka (Belgrade)[more][less]
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Jablan, Slavik (Belgrade , 1984)[more][less]
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Spasić, Slađana (Belgrade)[more][less]
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Cvetković, Ljiljana (Novi Sad)[more][less]
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Janikijevik, Ljiljana (Skopje , 1973)[more][less]
URI: http://hdl.handle.net/123456789/157 Files in this item: 1
phdLjiljanaJanikijevik.pdf ( 4.625Mb ) -
Teorija onfinitezimalnih transformacija i njihova primena na integraljenje diferencijalnih jednačinaOkiljević, Blažo (Belgrade , 1986)[more][less]
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Jarić, Jovo (Belgrade , 1973)[more][less]
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Đaja, Časlav (Belgrade , 1967)[more][less]
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Onić, Dušan (Beograd , 2013)[more][less]
Abstract: The evolution of supernova remnants is linked to the propagation of a collisionless shock wave, formed during the initial expansion of high-velocity supernova ejecta through the interstellar environment. Theoretical studies of shock waves are very important for the analysis of supernova remnants, as well as processes in the interstellar medium in general. In this doctoral dissertation, some theoretical results based on the magnetohydrodynamical theory of shock waves are presented, with special emphasis on ideal radiative magnetohydrodynamics for the optically thick case. Particularly, solutions for the case when jump in adiabatic index and/or ratio of gas to total pressure is allowed, are discussed. The main hypothesis of this dissertation is that thermal bremsstrahlung radiation at radio continuum frequencies can provide a signi cant contribution in the case of several Galactic supernova remnants. This hypothesis can give a natural explanation for nearly concave up radio continuum spectra of several Galactic supernova remnants that are expanding in the environment with higher than average density. In this context, it is important to identify the existence of the possible indicators of ensemble of thermal electrons at su ciently low temperatures and su ciently high densities so that the thermal bremsstrahlung radiation linked to a particular remnant could be observed at radio continuum frequencies (vicinity, interaction or expansion through the molecular cloud, presence of the cooled thermal X-ray electrons during the post Sedov-Taylor phases, detection of low-frequency turnovers associated with thermal absorption linked to the remnant, detection in H , identi cation of radio recombination lines linked to the remnant, etc). The signi cant presence of thermal component could theoretically explain radiospectral indices less than 0.5 measured for several evolutionary older supernova remnants, (mainly of mixed-morphology class) that expand in the high density region. Actually, these smaller radio-spectral indices, under the assumption of simple power law, would represent a natural manifestation of a signi cant fraction of thermal emission at radio continuum frequencies. However, present knowledge of the radio continuum spectra of Galactic supernova remnants is still not determined precisely enough for any de nite conclusions to be made about the inherent thermal radio-emission from supernova remnants. A thorough analysis is only possible in the case of three Galactic supernova remnants (3C396, IC443, 3C391) for which the thermal contribution is determined despite high associated uncertainties. New observations in the near future will lay the groundwork for making rmer conclusions about the existence of the so-called radio thermally active supernova remnants. This dissertation highlights the importance of observations of supernova remnants in X and -rays, and multiwavelength analysis is general. Besides, it suggests a possible detection of -rays from supernova remnant 3C434.1 based on the observations made by Fermi. URI: http://hdl.handle.net/123456789/3051 Files in this item: 1
Onic_Dusan_disertacija.pdf ( 10.67Mb ) -
Kuzmanović, Dragoslav (Beograd , 1986)[more][less]
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Golubović, Zoran (Belgrade , 1984)[more][less]
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Cuparić, Marija (Beograd , 2021)[more][less]
Abstract: The goal of this dissertation is the construction of new goodness-of-fit tests,analysis of their properties, as well as to obtain new theoretical findings regarding the limitingdistributions of weakly degeneratedV−statistics with estimated parameters. New goodness-of-fit tests are based on equidistributional type characterizations of two sample functions.Test statistics are formed asL2distances betweenV−empirical distribution functions ofstatistics from characterization, and also asL2andL∞distances betweenV−empiricalLaplace transformations of those statistics. In the latter case, resulting test statistics can beobserved asV−statistics with an estimated parameter or as functions of those statistics.Until now, limiting results were known for non-degenerateV−statistics with estimatedparameters, as well as for weakly degenerateV−statistics of degree two with estimatedparameters. Limiting results for the appropriate class of weakly degenerateV−statistics withan estimated parameter of degreem, wheremis even number, are derived in this dissertation.Owing to these results, asymptotic properties for presented tests are determined. To assessthe quality of these tests, empirical powers were determined using Monte Carlo simulations, aswell as approximate Bahadur efficiency. New results are presented regarding the approximateBahadur efficiency in case of close alternatives, which is applicable also when the limitingdistribution of statistics under the null hypothesis is not normal. In this sense, the comparisonbetween many tests is performed, both classical tests and recently developed tests.All previously mentioned results were obtained for complete samples. Additional, modifi-cation of previously introduced tests for randomly censored data was also proposed. In sucha case, the new theoretically justified bootstrap method is proposed for the approximation ofp−value. URI: http://hdl.handle.net/123456789/5212 Files in this item: 1
marijacuparicdr.pdf ( 1.771Mb ) -
Nešić, Slobodan (Belgrade , 1980)[more][less]
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Baralić, Đorđe (Beograd , 2013)[more][less]
Abstract: The main objects studied in this doctoral thesis are quasitoric manifolds and spaces arising as the images of polyhedral product functors. Quasitoric manifolds are particularly interesting as topological generalization of non-singular toric varieties. They are a research topic of many mathematical disciplines including toric geometry, symplectic geometry, toric topology, algebraic geometry, algebraic topology, theory of convex polytopes, and topological combinatorics. These objects have already found numerous applications in mathematics and sciences and they continue to be intensively studied. In this thesis we put some emphasis on combinatorial methods, focusing on the interaction of the geometry of toric actions and combinatorics of simple polytopes. This connection of geometry and combinatorics is based on the fundamental observation that convex polytopes naturally arise as orbit spaces of toric actions on quasitoric manifolds. Our main original contributions in this thesis are related to classical topological questions about degrees of maps between manifolds as well as their embeddings and immersions into Euclidean spaces. We follow the general scheme characteristic for Algebraic Topology where a topological problem is reduced, often by non-trivial reductions, to a question of arithmetical, algebraic, or combinatorial nature. We believe that the novel applications of this scheme developed in the thesis, especially the new techniques and calculations, have a potential to be applied on other problems about quasitoric manifods. Here is a summary of the content of the thesis. For the reader’s convenience and for completeness, in the first three chapters we give an elementary exposition of the basic theory of simplicial complexes, convex polytopes, toric varieties and quasitoric manifolds. The emphasis is on the fundamental constructions and central results, however the combinatorial approach, utilized in the thesis, allows us present the theory in a direct and concrete way, with a minimum of topological prerequisites. The mapping degrees of maps between quasitoric manifolds are studied in Chapter 4 with a particular emphasis on quasitoric 4-manifolds. Utilizing the technique pioneered by Haibao Duan and Shicheng Wang, which is based on the intersection form and the cohomology ring calculations, we demonstrate that a complete information about mapping degrees can be obtained in many concrete situations. The theorems and the corresponding criteria for the existence of mapping degrees are formulated in the language of elementary number theory. It is amusing that the question whether a number appears as a mapping degree between concrete 4-manifolds is directly linked with classical results from number theory such as whether a number can be expressed as a sum of two or three squares, etc. This approach allows us to analyze many concrete 4-manifolds, including CP2, CP2♯CP2, S2×S2, etc. In Chapter 5 we calculate the Stiefel-Whitney classes of some concrete quasitoric manifolds and their duals. This information is used to determine cohomological obstructions to embeddings and immersions of these manifolds in Euclidean spaces. As an initial observation we showed that the calculations are highly dependent on the action of torus. Indeed, there are examples of quasitoric manifolds over the same polytope which exhibit a very different behavior and different complexity of the associated characteristic classes. Focusing on the quasitoric manifolds over the n-dimensional cube, we are able to produce quasitoric manifolds which are very complex in the sense that they almost attain the theoretical minimum dimension for their embedding or (totally skew) immersion in Euclidean spaces. The thesis ends with an appendix with an outline of the theory of group actions and equivariant topology. URI: http://hdl.handle.net/123456789/4232 Files in this item: 1
phdDjordjeBaralic.pdf ( 8.102Mb ) -
Andrijević, Dimitrije (Belgrade)[more][less]
URI: http://hdl.handle.net/123456789/37 Files in this item: 1
phdDimitrijeAndrijevic.pdf ( 3.211Mb ) -
Dimitrijević, Radoslav (Belgrade)[more][less]
URI: http://hdl.handle.net/123456789/312 Files in this item: 1
phdRadoslavDimitrijevic.pdf ( 11.78Mb ) -
Cvetković, Dragoljub (Beograd , 1985)[more][less]
URI: http://hdl.handle.net/123456789/4101 Files in this item: 1
Trajektorije_pramenova.PDF ( 8.497Mb ) -
Cvetković, Dragoljub (Belgrade , 1985)[more][less]
URI: http://hdl.handle.net/123456789/249 Files in this item: 1
phdDragoljubCvetkovic.PDF ( 18.28Mb )