Browsing Doctoral Dissertations by Title

Alshafah, Samira (Beograd , 2018)[more][less]
Abstract: Proteins with intrinsically disordered regions are involved in large number of key cell processes including signaling, transcription, and chromatin remodeling functions . On the other side, such proteins have been observed in people suffering from neurological and cardiovascular diseases, as well as various malignancies. Process of experimentally determining disordered regions in proteins is a very expensive and long  term process. As a consequence, a various computer programs for predicting position of disordered regions in proteins have been developed and constantly improved. In this thesis a new method for determining Amino acid sequences that characterize ordered/disordered regions is presented. Material used in research includes 4076 viruses wit h more than 190000 proteins. Proposed method is based on defining correspondence between n grams (including both repeats and palindromic sequence s) characteristics and their belonging to ordered/disordered protein regions. Positions of ordered/disordered regions are predicted using three different predictors. The features of the repetitive strings used in the research include mol e fractions, fract ional differences, and z values. Also, data mining techniques association rules and classification were applied on both repeats and palindromes. The results obtained by all techniques show a high level of agreement for a short length of less than 6, while the level of agreement grows up to the maximum with increasing the length of the sequences. The high reliability of the results obtained by the data mining techniques shows that there are n grams, both repeating sequences and palindromes, which uniquely ch aracterize the disordered/ ordered regions of the proteins . The obtained results were verified by comparing with the results based on n grams from the DisProt database which contain s the positions of experimentally verified disordered regions of the protein. Results can be used both for the fast localization of disordered/ordered regions in proteins as well as for further improving existing programs for their prediction. URI: http://hdl.handle.net/123456789/4746 Files in this item: 1
ThesisSamira_Alshafah.pdf ( 3.106Mb ) 
Ćirić, Miroslav (Beograd , 1991)[more][less]

Ranković, Slavko (Belgrade , 1972)[more][less]

Živaljević, Rade (Belgrade , 1983)[more][less]

Elfaghine, Halima (Beograd , 2016)[more][less]
Abstract: The subject of this thesis belongs the area of quality control, which represents the practical usage of statistics in following and improving the production process. In 1930 Walter Shewhart started studying quality control, based on control charts, and using statistical principles. Later on, after World War II, Edward Deming took this discipline to Japan, where it ourished. The design and the performance of control charts are the most important problems in this area. The purpose of studying the characteristics of control charts in this thesis is to compare the existing and the suggested control charts. The thesis is divided into four chapters. The rst chapter is introductory and contains motivation and basic de nitions related to this subject. In this study it is always assumed that the data are normally distributed, and that the incontrol process data are stationary and uncorrelated. Shewhart control charts and the corresponding limits are constructed in order to meet the given speci cations for the quality characteristic that we investigate. Quality control that is applied to a production process always has costs related to the control. The important parameters connected to the cost of quality control are: width of control limits k, the sample size n and the interval between the samples h. In Chapter 2 a new loss function is given, which is connected to the production process and to X−bar quality control chart. Using Matlab program for optimization, values of ^k; ^n and ^h are found, which minimize the loss function for given costs. For given values of cost, a nonlinear regression model is built using a package Sigma plot and the obtained values are compared to those obtained by numerical optimization. In Chapter 3, the time series model Yi = Xi + (1 − )Yi−1 is investigated, where 0 < B 1 is a constant, Xi are N( ; 2) distributed. Exponentially Weighted Moving Average (EWMA) control charts for this model are presented, and type I and type II errors are calculated in the case when i is large. For di erent sample sizes, the new comparison between the optimal design of the Xbar and EWMA control charts for Normally distributed quality characteristic is given, comparing the corresponding costloss functions, power functions and average run lengths. i The process of calibration is one of the methods in statistical process control, introduced for improving the quality of the products and for reducing the production costs. In Chapter 4, two new models of nonsymmetrical loss function are introduced. Here, the loss function is connected to one product under control (not to the whole sample). Using our program, written in statistical software R, the value which minimizes the expected loss for Shewhart X control chart is found. This value is used as the new central target value of the quality characteristic, that is, the production process is calibrated with this new value. The thesis ends with Conclusions, where the results of the thesis are summarized, and with some open problems to be investigated. URI: http://hdl.handle.net/123456789/4340 Files in this item: 1
Disertacija_Halima_Elfaghihe.pdf ( 1.104Mb ) 
Vukićević, Petar (Berlin , 1894)[more][less]

Nešović, Emilija (Kragujevac, Serbia , 2011)[more][less]
Abstract: The field of research in this dissertation is consideration of different types of curves in Minkowski spaces, as well as defining the notion of hyperbolic angle between spacelike and timelike vector. The research in this dissertation is connected with the following subjects: geometry of hyperquadrics in Minkowski space, finite type submanifolds and plane Minkowski geometry. This dissertation, beside Preface and References with 56 items, consists of four chapters: 1. Curves in hyperquadrics in Minkowski spaces; 2. Classification of 2 –type curves in Minkowski nspace ; 3. Wcurves in Minkowski spacetime; 4. Hyperbolic angle between vectors. In Chapter 1 the curves lying in hyperquadrics in Minkovski 3space and Minkowski 4space are studied. More precisely, the results related with the spacelike and timelike curves lying pseudosphere in Minkowski 3space are presented. Also, the necessary and sufficient conditions for spacelike curves lying in pseudohyperbolic space in Minkowski 4space are given. Curves of finite type 2 in Minkowski nspace are studied in details in Chapter 2. Also, there are given some known results related with finite type submanifolds. In Chapter 3, Wcurves (i.e. the curves having constant all curvature functions) in Minkowski spacetime are studied and some relations between Wcurves and finite type curves are given. Finally, in Chapter 4 one of the basic notions in Lorentzian geometry is considered, i.e. hyperbolic angle between two nonnull vectors. The notion of hyperbolic angle between two timelike vectors is wellknown, so in this chapter it is defined the notion between spacelike and timelike vectors. The measure of hyperbolic angle is also defined. By using the notion of hyperbolic angle between spacelike and timelike vectors, all spacelike curves of constant precession with nonnull principal normal and all timelike curves of constant precession in Minkowski 3space are classified and their explicit parameter equations are given. URI: http://hdl.handle.net/123456789/1916 Files in this item: 1
Dokt. disertacija dr E. NešovićR.pdf ( 3.472Mb ) 
Pantić, Živadin (Belgrade)[more][less]

Bojović, R. Dejan (Kragujevac, Serbia , 1999)[more][less]
Abstract: The field of research in this dissertation is consideration of convergence of finite differnce method for parabolic problems with generalized solutions. The research in this dissertation is connected with the following subjects: Numerical Analysis and Partial Differential Equations. This dissertation, beside Preface and References with 56 items, consists of five chapters: 1. Introductory Topics; 2. Parabolic Problems with Variable Operator: Convergence in W(2,1)norm; 3. Parabolic Problems with Variable Operator: Convergence in W(1,1/2)norm; 4. Convergence in L2 norm; 5. Application of Interpolatyion theory In Chapter 1 a brief review of the Sobolev spaces, anisotropic Sobolev spaces, multipliers in Sobolev spaces, interpolation theory of Banach spaces and existence of generalized solution of parabolic problems are presented. Initialboundaryvalue problems with variable (timedependent) operator are considered in Chapters 2 and 3. In Chapter 2 is proved convergence of finite difference scheme in discrete W(2,1) Sobolev norm. Convergence in W(1,1/2) norm is proved in Chapter 3. In Chapter 4, parabolic problem with variable coefficients is considered and convergence in L2 norm is proved. Finally, in Chapter 5 , interpolation theory is applied to the convergence analysis. URI: http://hdl.handle.net/123456789/1915 Files in this item: 1
doktorska disertacija Scan reduce.pdf ( 1.523Mb ) 
Hodžić, Sandra (Beograd , 2016)[more][less]
Abstract: In recent years there has been increasing interest in modeling the physical and chemical processes with equations involving fractional derivatives and integrals. One of such equations is the subdi usion equation which is obtained from the di usion equation by replacing the classical rst order time derivative by a fractional derivative of order with 0 < < 1: The subject of this dissertation is the initialboundary value problem for the subdi usion equation and its approximation by nite di erences. At the beginning, the onedimensional equation is observed. The existence and the uniqueness of weak solution is proved. The stability and the convergence rate estimates for implicite and the weighted scheme are obtained. The main focus is on twodimensional subdi usion problem with Laplace operator as well as problem with general secondorder partial di erential operator. It is assumed that the coe cients of the di erential operator satisfy standard ellipticity conditions that guarantees existence of solution in appropriate spaces of Sobolev type. In that case, apart from above mensoned, we constructed the additive and the factorized di erence schemes. We investigated their stability and convergence rate depending on the smoothness of the input data and of generalized solution. URI: http://hdl.handle.net/123456789/4455 Files in this item: 1
Disertacija_Sandra_Hodzic.pdf ( 913.2Kb ) 
Bejtullahu, Rasim (Pristina , 1976)[more][less]

Delić, Aleksandra (Beograd , 2016)[more][less]
Abstract: The time fractional di usionwave equation can be obtained from the classical diffusion or wave equation by replacing the rst or second order time derivative, respectively, by a fractional derivative of order 0 < 2. In particular, depending on the value of the parameter , we distinguish subdi usion (0 < < 1), normal di usion ( = 1), superdi usion (1 < < 2) and ballistic motion ( = 2). Fractional derivatives are nonlocal operators, which makes it di cult to construct e cient numerical method. The subject of this dissertation is the time fractional di usionwave equation with coe cient which contains a singular distribution, primarily Dirac distribution, and its approximation by nite di erences. Initialboundary value problems of this type are usually called interface problems. Solutions of such problems have discontinuities or nonsmoothness across the interface, i.e. on support of Dirac distribution, making it di cult to establish convergence of the nite di erence schemes using the classical Taylor's expansion. The existence of generalized solutions of this initialboundary value problem has been proved. Some nite di erence schemes approximating the problem are proposed and their stability and estimates for the rate of convergence compatible with the smoothness of the solution are obtained. The theoretical results are con rmed by numerical examples. URI: http://hdl.handle.net/123456789/4337 Files in this item: 1
ADelicDisertacija.pdf ( 1.356Mb ) 
Korać, Vanja (Beograd , 2014)[more][less]
Abstract: Digitalna forenzika je multidisciplinarna nauka koja podrazumeva spoj razlicitih nauĉnih disciplina (raĉunarske nauke, pravo, kriminologija) sa brojnim izazovima u uslovima masovnog generisanja digitalnih podataka (Big Data), virtuelizacije klijentske i serverske strane (Cloud Computng), neusaglašenosti standardizacionih tela i opšteg nedostatka brojnih standarda i eksperata u svim disciplinama. Kako se digitalna forenzika odnosi na sve digitalne uraĊaje, uţa nauĉna oblast uklјuĉuje brojne aplikacije digitalne forenzike, kao što su raĉunarska forenzika, forenzika mobilnih ureĊaja, forenzika na sistemima savremenih automobila, senzorskih mreţa itd. U ovom radu je analizirana i primenjena uţa nauĉna oblast raĉunarske forenzike. Opisana je digitalna forenzika raĉunarskih sistema baziranih na Windows i Linux platformi, sa fokusom na odreĊena mesta u implementiranom sistemu proaktivne digitalne forenzike koja mogu ukazati na forenziĉki relevantne dogaĊaje kritiĉne za bezbednost sistema. Opisane su brojne metodologije, tehnologije i tehnike istrage visokotehnološkog kriminala. Proces prikuplјanja podataka i digitalne forenziĉke analize „uţivo―, detalјno je razmatran. Izvršena je kratka revizija karakteristika i tipiĉno zahtevanih funkcionalnosti softverskih forenziĉkih alata, za inicijalni odgovor i oporavak podataka i particija magnetnih diskova. Opisani su i najvaţniji digitalni forenziĉki kompleti alata i njihove osnovne funkcionalnosti. U radu se istiĉu i najznaĉajniji elementi kojima treba posvetiti posebnu paţnju prilikom digitalne forenziĉke analize u virtuelnom okruţenju. TakoĊe su objašnjeni i najvaţniji segmenti samog virtuelnog okruţenja i naĉin na koji oni mogu biti znaĉajni alati, za postupak digitalne forenziĉke analize. U poslednjem delu ovog rada, fokus je usmeren na ranjivosti Windows i Linux platformi sa prikazanim naĉinima zlonamernog proboja sistema. Opisane su opšte ranjivosti i specifiĉne ranjivosti koje se odnose samo na Windows, odnosno samo na Linux platforme. TakoĊe, navedeni su i najĉešći naĉini zlonamernog iskorišćavanja sistema. Ranjivosti raĉunarskih sistema i mreţa mogu se odnositi na programe, hardver, konfiguraciju i lјude. Isklјuĉujući lјude kao najznaĉajniji i istovremeno najkritiĉniji faktor u zaštiti informacija, programske ranjivosti se tipiĉno koriste za online direktne napade, ili napade malicioznim programima. Otkrivanje i otklanjanje ranjivosti sistemskih programa je jedan od glavnih cilјeva digitalne forenzike. Pored skuplјanja forenziĉki relevantnih digitalnih podataka i izgradnje ĉvrstih digitalnih dokaza o kompjuterskom incidentu ili kriminalu za potrebe pravosudnog sistema, cilј digitalne forenziĉke analize je da se iskorišćene ranjivosti trajno otklone i da se incident/protivpravna aktivnost takve vrste više nikada ne ponovi. U tom smislu je doprinos ovog rada veoma znaĉajan. Praktiĉan primer ispitivanja ranjivosti servisa na Windows i Linux platformama obuhvatio je 80 operativnih sistema. Od tog broja, 51 se odnosi na Windows operativne sisteme, a 29 na Linux operativne sisteme. Dobijeni rezultati su rezultat dvogodišnjeg istraţivanja, jer je ispitivanje sistema vršeno u 2011. i 2013. godini. Kroz skeniranje i prikaz ranjivosti difoltno instaliranih Windows i Linux sistema preventivno se otkrivaju ranjivosti koje potencijalno mogu biti iskorišćene od strane bezbednosnih pretnji (maliciozni programi ili zlonamerni napadaĉi) i time ugroziti raĉunarske sisteme i informacije. Proaktivnim otklanjanjem ovih ranjivosti realizuje se preventivna zaštita. Uspostavlјanjem sistema proaktivne forenzike, obezbeĊuje se logovanje forenziĉki relevantnih dogaĊaja, tj. tragova pokušaja napada u realnom vremenu, ĉime se bitno olakšava forenziĉka istraga u sluĉaju incidenta ili protivpravne aktivnosti. URI: http://hdl.handle.net/123456789/3869 Files in this item: 1
doktorat_Vanja_Korac.pdf ( 9.093Mb ) 
Ilić, Dragana (Belgrade , 2008)[more][less]

Zougdani, Hassan (Belgrade , 1984)[more][less]
URI: http://hdl.handle.net/123456789/148 Files in this item: 1
phdHassanKhalifaZougdani.pdf ( 4.157Mb ) 
Đurić, Slavko (Kragujevac , 1968)[more][less]

Ćirić, Dušan (Belgrade , 1981)[more][less]

Zejnullahu, Ramadan (Priština)[more][less]

Pevac, Irena (Belgrade)[more][less]

Ćiprijanović, Aleksandra (, 2016)[more][less]
Abstract: Studying cosmic rays is very important for better understanding of high energy physical processes, since particles accelerated in space can reach energies far above what we can produce in accelerators on Earth, at the moment. Processes that produce cosmic rays are still unexplained to some extent, and models that have been proposed are awaiting confirmation. Presence of cosmic rays can be measured by detecting different products of interactions of these high energy particles with the interstellar medium through which they propagate. This thesis deals with the accretion shock as sources of cosmic rays in clusters of galaxies, as well as cosmic rays accelerated in supernova remnants inside galaxies. No matter which of these mechanisms is being considered, cosmic rays will collide with atoms and ions in the interstellar medium, and produce, among other things, gamma rays, neutrinos, as well as light elements, of which we will discuss lithium. In the thesis we primarily develop models that describe gamma rays produced by cosmic rays accelerated in shocks that can appear in different processes. We first examine accretion of new gas onto already virialized structures (for example in galaxy clusters). For the first time, we include the change of gammaray pro duction with time, through the history of the universe, that reflects the evolution of accretion shocks which appear during large scale structure formation. Therefore, the models developed in this thesis describe the gamma rays from large scale struc tures more realistically, compared to models which have previously been developed and which use single redshift approximation for the gammaray origin. Models are used to derive the gammaray flux of all unresolved galaxy clusters. These mode led gamma rays are then compared to the isotropic diffuse gammaray background, measured by telescope FermiLAT. This leads to the conclusion that these cosmic rays have nonnegligible contribution to the isotropic diffuse gammaray background (depending on the normalization, they can even explain the whole isotropic diffuse gammaray background) and that this population of cosmic rays has to be taken into consideration in addition to other components that are thought to be major contributors, like for example, unresolved normal galaxies or blazars. In the thesis, models of gammaray production in accretion shocks are also com pared to observations of highenergy neutrinos detected by IceCube detector. Neu trinos are used to normalize gammaray models, from which we conclude that if the accretion shocks are predominantly strong, neutrino background is more limiting to the possible gammaray emissivity of these objects, compared to the gammaray background we first used. Study of neutrinos as products of cosmicray interactions is very important, since neutrinos interact weakly with other particles, and therefore keep all of the information about the time they were produced and about cosmic rays that produced them. One part of the thesis deals with the production of cosmic rays in supernova remnants, in particular, the case of the Small Magellanic Cloud, which was detected in gamma rays. In this galaxy we also have the first measurements of the lithium abundances in the interstellar gas outside of the Milky Way. Since gamma rays and lithium are produced through interactions of cosmic rays with the interstellar medium, their same origin can be used to estimate the production of lithium and gamma rays by any cosmicray population. We show that galactic cosmic rays, which are considered to be dominant population of cosmic rays in the Small Magellanic Cloud, can only explain a very small part of the observed abundance of lithium, if we assume that the entire present gammaray emissivity that we observe also originates from the interaction of galactic cosmic rays with gas within the galaxy. This conclusion is interesting, because it leads to the possible existence of other sources of lithium in the Small Magellanic Cloud. Also, using the fact that gamma rays and lithium share the same origin, we estimate how much can irregular dwarf galaxies contribute to the diffuse gammaray background. Study of several different products of cosmicray interactions with the interstellar medium (gamma rays, neutrinos and lithium) on smaller scales (within the galaxy), as well as on the largest scales (galaxy clusters), showed that in addition to the galactic cosmic rays accelerated in supernova remnants, other still hypothetical co smic rays (produced for example during accretion of gas on largest scales, or tidal interactions of galaxies) can have a nonnegligible contribution to the measurements. URI: http://hdl.handle.net/123456789/4758 Files in this item: 1
AleksandraCiprijanovic.pdf ( 29.40Mb )