Auflistung Doctoral Dissertations nach Titel
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Jovanović, Predrag (Belgrade , 2005)[more][less]
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Dimovski, Igor (Novi Sad , 2011)[more][less]
Zusammenfassung: A comprehensive pedagogical research regarding teaching mathematics at a tertiary, university level has been presented in the PhD dissertation. The educational resources tailored in an electronic form using the programme package Matlab are integrated in the learning process. The impact of ICT use to the essential knowledge that refers to multivariate calculus (functions of several variables, vector-valued functions and the three-dimensional analytical geometry) has been statistically explored by intensive use of 3D static and dynamic visual tools. Part of the students who have participated in the research have developed Matlab programmes all by their own. One part of the research has been focused on probable impact of the programming skills on learning mathematical concepts. URI: http://hdl.handle.net/123456789/3874 Dateien zu dieser Ressource: 1
PhD_I_Dimovski.pdf ( 5.423Mb ) -
Pavlović, Marina (Beograd , 2022)[more][less]
Zusammenfassung: The study of galaxies through high redshifts are key to understanding the evolution of galaxies through cosmic times. As such objects are very difficult to observe directly, they are mainly examined using empirically derived tools such as the numerous correlations between their different parametric characteristics, one of them being the linear relationship between far-infrared and radio emission in star-forming galaxies, named the Far Infrared-Radio (FIR) Correlation.Although the correlation was considered to be stable in terms of linearity, recent works, which include galaxies at high redshifts (0 < z < 6), showed a large deviation from the correlation in these systems. The goal of this doctoral dissertation is an examination of the physical processes that lead to this kind of behavior. As a possible cause of this evolution, we will assume for the first time, and examine interactions between galaxies (collisions and close approaches). Interactions be- tween galaxies lead to the formation of shock waves on large scales that can lead to changes in the relationship between infrared and radio emissions. Our hypoth- esis was tested in several stadiums and the main results are as follows: 1. We developed models of the evolution of the FIR correlation with redshift as functions of the galaxy interaction rate. We tested the models on a sample of galaxies with an already determined morphology separately for disc galaxies and for galaxies that have recently been or are currently interacting - irregular galaxies. 2. In a small sample of 34 galaxies that we took from paper Miettinen et al. (2017), it was shown that there is an indication that the interaction between galaxies can be responsible for the evolution of the correlation with the redshift. 3. The next analysis was performed on a much larger sample of star-forming galaxies taken from COSMOS field, where we did not find any evolution of corre- lation with the redshift. Also, it was shown that the mean value of the correlation parameter is lower in irregular galaxies than in disk galaxies. Although recent observations indicated an evolution of the FIR correlation with redshift, the results of this research failed to reproduce that evolution and showed that the FIR correlation is stable with redshift. However, it was also shown that due to the interaction of galaxies, the evolution of the FIR correlation is possible if the representation of interacting systems in the sample is higher. URI: http://hdl.handle.net/123456789/5460 Dateien zu dieser Ressource: 1
Disertacija_Marina_Pavlovic.pdf ( 8.624Mb ) -
Milanović-Lazarević, Smilja (Belgrade , 1987)[more][less]
URI: http://hdl.handle.net/123456789/248 Dateien zu dieser Ressource: 1
phdSmiljaMilanovicLazarevic.PDF ( 4.155Mb ) -
Dimitrijević, Milan (Belgrade)[more][less]
Zusammenfassung: A detailed analysis of the motion of a charged particle under the influence of Coulomb, polarization, and quadrupolar potential has been performed, and analytical expressions for particle path parameters have been obtained. Also, conditions for existence of a critical impact parameter, which separates paths ending in the atom from those going to infinity, have been examined, and methods for its determination have been elaborated. Results of this investigations have been applied to the theory of Stark broadening (broadening of spectral lines under the influence of collisions with charged particles), where a special attention has been paid to the adiabatic limit, and to quasistatic and impact approximations. Modification of Stark broadening functions has been performed and it has been demonstrated that the biggest influence of path curvature on them, is in the vicinity of the critical impact parameter, which separates paths ending in the atom from those going to infinity. The change in the values of the Stark broadening functions will have the largest influence on Stark broadening parameters for lines for which, at the most probable velocity, influence of the contribution of inelastic collisions is dominant and effective polarizability large. The application of semiempirical approximative approach for calculation of Stark broadening parameters for multiply charged emitters, has been analyzed as well, and the modification of semiclassical theory has been performed. The averaged ratio of experimental and theoretical results is 0.75 for semiempirical, 1.47 for semiclassical, and 1.04 for modified semiclassical approach.У раду је извршена детаљна анализа кретања наелектрисане честице под утицајем Кулоновог, поларизационог и квадруполног потенцијала и добијени су аналитички изрази за параметре путање честице. Такође су испитани услови за егзистенцију критичног сударног параметра, који раздваја путање које завршавају у атому од оних које одлазе у бесконачност, и разрађене методе за његово налажење. Резултати овог испитивања су примењени на теорију Штарковог ширења (ширења спектралних линија под утицајем судара са наелектрисаним честицама), при чему је посебна пажња посвећена адијабатској граници и квазистатичкој и сударној апроксимацији. Изведена је модификација функција Штарковог ширења и показано је да је највећи утицај закривљености путање на њих, у близини критичног сударног параметра, који раздваја путање које завршавају у атому од оних које одлазе у бесконачност. Промена у величини функција Штарковог ширења ће највише утицати на параметре Штарковог ширења код линија за које је, при највероватнијој брзини, утицај доприноса нееластичних судара доминантан а ефективна поларизабилност велика. Такође је анализирана примена семиемпиријског апроксимативног прилаза за израчунавање параметара Штарковог ширења за вишеструко наелектрисане емитере, при чему је извршена модификација семикласичне теорије. Усредњени однос експерименталних и теоријских резултата је 0.75 за семиемпиријски, 1.47 за семикласични а 1.04 за модификовани семикласични прилаз. URI: http://hdl.handle.net/123456789/77 Dateien zu dieser Ressource: 1
Dimitrijevic.pdf ( 6.262Mb ) -
Kovjanić, Milorad (Beograd , 2023)[more][less]
URI: http://hdl.handle.net/123456789/5598 Dateien zu dieser Ressource: 1
Milorad Kovjanić - Disertacija.pdf ( 2.190Mb ) -
Vince, Ištvan (Belgrade)[more][less]
URI: http://hdl.handle.net/123456789/125 Dateien zu dieser Ressource: 1
phdIstvanVince.pdf ( 48.21Mb ) -
Jovanović, Miljana (Beograd , 2024)[more][less]
Zusammenfassung: One of the main objectives of the Gaia mission of the European Space Agency is to construct a celestial reference frame at the wavelengths of the optical domain, Gaia CRF. This frame needs a link to the International Celestial Reference Frame – ICRF which is fixed with respect to distant objects (quasars). The objects serving for the purpose of linking are required to be visible in both domains (optical and radio). A set of 47 such objects has been proposed and included which in the radio domain have no detected extended emission. The mentioned objects are active galactic nuclei (AGN) the brightness of which varies over the whole electromagnetic spectrum. The brightness change may be due to activity in different AGN regions, but also to external factors. Such variations can lead to changes in the photocentre position and, consequently, to changes of the object coordinates. In order to establish which objects are suitable for linking these two frames we have examined the brightness variation in the optical domain. The objects have been observed from 2013 in the V and R bands. We have analysed the brightness, colour (V − R) and optical spectral index (α). It has been established that for the majority of objects the brightness is variable, or possibly variable. Almost 15% of all objects have significant changes in their brightness (more than 1 mag), only ∼10% are stable with minor brightness changes of ∼0.3 mag. The results concerning the change analysis of the colour and α are also presented. Based on these results 17 objects are chosen as suitable for linking ICRF to Gaia CRF. The results of the analysis, as well as the observed values, are essential for the examination of these objects because of their importance in astrometry, also in astrophysics. These data are relevant to a better understanding of formation and evolution of galaxies. URI: http://hdl.handle.net/123456789/5748 Dateien zu dieser Ressource: 1
MiljanaJovanovic-teza.pdf ( 6.418Mb ) -
Šćepanović, Radoje (Belgrade , 1978)[more][less]
URI: http://hdl.handle.net/123456789/204 Dateien zu dieser Ressource: 1
phdRadojeScepanovic.pdf ( 1.786Mb ) -
Lazović, Jovan (Belgrade , 1964)[more][less]
URI: http://hdl.handle.net/123456789/223 Dateien zu dieser Ressource: 1
phdJovanLazovic.pdf ( 3.356Mb ) -
Rašajski, Marija (Belgrade)[more][less]
URI: http://hdl.handle.net/123456789/177 Dateien zu dieser Ressource: 1
Phd-Marija.Rasajski.pdf ( 3.705Mb ) -
Trifunović, Milomir (Belgrade)[more][less]
URI: http://hdl.handle.net/123456789/343 Dateien zu dieser Ressource: 1
phdMilomirTrifunovic.pdf ( 2.571Mb ) -
Mišić, Miodrag (Belgrade)[more][less]
URI: http://hdl.handle.net/123456789/64 Dateien zu dieser Ressource: 1
phdMiodragMisic.pdf ( 2.242Mb ) -
Plavšić, Milan (Belgrade , 1966)[more][less]
URI: http://hdl.handle.net/123456789/214 Dateien zu dieser Ressource: 1
phdMilanPlavsic.pdf ( 1.692Mb ) -
Kastrati, Ruzhdi (Priština , 1989)[more][less]
URI: http://hdl.handle.net/123456789/4129 Dateien zu dieser Ressource: 1
Fourie_te_disa_klasa.PDF ( 1.942Mb ) -
Đorđević, Radmila (None)[more][less]
URI: http://hdl.handle.net/123456789/167 Dateien zu dieser Ressource: 1
phdRadmilaDjordjevic.pdf ( 1.940Mb ) -
Đorđević, Radmilo (Beograd , 1979)[more][less]
URI: http://hdl.handle.net/123456789/4104 Dateien zu dieser Ressource: 1
Vodjenje_po_potegu.PDF ( 812.6Kb ) -
Lučić, Blagota (Belgrade , 1985)[more][less]
URI: http://hdl.handle.net/123456789/52 Dateien zu dieser Ressource: 1
phdBlagotaLucic.pdf ( 1.076Mb ) -
Protić, Danijela (Beograd , 2023)[more][less]
Zusammenfassung: Anomaly detection is the recognition of suspicious computer network behavior by comparing unknown network traffic to a statistical model of normal network behavior. Binary classifiers based on supervised machine learning are good candidates for normality detection. This thesis presents five standard binary classifiers: the k-nearest neighbors, weighted k-nearest neighbors, decision trees, support vector machines and feedforward neural network. The main problem with supervised learning is that it takes a lot of data to train high-precision classifiers. To reduce the training time with minimal degradation of the accuracy of the models, a two-phase pre-processing step is performed. In the first phase, numeric attributes are selected to reduce the dataset. The second phase is a novel normalization method based on hyperbolic the tangent function and the damping strategy of the Levenberg-Marquardt algorithm. The Kyoto 2006+ dataset, the only publicly available data set of real-world network traffic intended solely for anomaly detection research in computer networks, was used to demonstrate the positive impact of such pre-processing on classifier training time and accuracy. Of all the selected classifiers, the feedforward neural network has the highest processing speed, while the weighted k-nearest neighbor model proved to be the most accurate. The assumption is that when the classifiers work concurrently, they should detect either an anomaly or normal network traffic, which occasionally is not the case, resulting in different decision about the anomaly, i.e. a conflict arises. The conflicting decision detector performs a logical exclusive OR (XOR) operation on the outputs of the classifiers. If both classifiers simultaneously detected an anomaly or recognized traffic as normal, their decision was no conflict had occurred. Otherwise a conflict is detected. The number of conflicts detected provides an opportunity for additional detection of changes in computer network behavior. URI: http://hdl.handle.net/123456789/5599 Dateien zu dieser Ressource: 1
Danijela Protic - Doktorska Disertacija.pdf ( 3.143Mb ) -
Bogdanović, Katarina (Beograd , 2025)[more][less]
Zusammenfassung: In the rst and the second chapter of dissertation we prove some new inequalities for the spectral radius, essential spectral radius, oper- ator norm, measure of non-compactness and numerical radius of Hadamard (Schur) weighted geometric means of positive kernel operators on Banach function and sequence spaces. The list of extensions and re nings of known inequalities has been expanded. Some new inequalities and equalities for the generalized and the joint spectral radius and their essential versions of Hadamard (Schur) geometric means of bounded sets of positive kernel op- erators on Banach function spaces have been proved. There are additional results in case of non-negative matrices that de ne operators on Banach sequence spaces. In the third part we present some inequalities for opera- tor monotone functions and (co)hyponormal operators and give relations of Schur multipliers to derivation like inequalities for operators. In particular, let Ψ, Φ be s.n. functions, p ⩾ 2 and φ be an operator monotone function on [0, ∞) such that φ(0) = 0. If A, B, X ∈ B(H) and A and B are strictly ac- cretive such that AX−XB ∈ CΨ(H), then also AXφ(B)−φ(A)XB ∈ CΨ(H) and ||AXφ(B) − φ(A)XB||Ψ ⩽ r φ A+A∗ 2 − A+A∗ 2 φ′ A+A∗ 2 A+A∗ 2 −1 A(AX − XB)B B+B∗ 2 −1 r φ B+B∗ 2 − B+B∗ 2 φ′ B+B∗ 2 Ψ . under any of the following conditions: (a) Both A and B are normal, (b) A is cohyponormal, B is hyponormal and at least one of them is normal, and Ψ := Φ(p)∗ , (c) A is cohyponormal, B is hyponormal and ||.||Ψ is the trace norm ||.||1. Alternative inequalities for ||.||Ψ(p) norms are also obtained. URI: http://hdl.handle.net/123456789/5780 Dateien zu dieser Ressource: 1
Katarina_Bogdanovic_disertacija.pdf ( 1.621Mb )
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