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Vujičić Stanković, Staša (Beograd , 2016)[more][less]
Abstract: The basic goal of this doctoral thesis is a research into different techniques and models which are applied in information extraction, and providing an informatic support in processing of natural language texts from culinary and gastronomy domain. Information extraction is a subfield of computational linguistics which includes techniques for natural languages processing, in order to find relevant information, define their meaning and establish relations between them. A very special attention is given to ontology based information extraction. It consists of the following: recognition of instances of ontology concepts in non‐structured or semi‐ structured texts written in natural language, reasoning over the identified instances based on the rules defined in the ontology, as well as recognition of instances and their use for instantiating the proper ontology concepts. The main result of thesis reflects in the presentation of a new model for ontology based information extraction. Besides solving tasks of information extraction, the new model includes not only upgrade of existing lexical resources and ontologies, but also creation of the new ones. Its application resulted in development of a system for extraction of information related to the culinary domain, but this new model can be used in other fields as well. Beside this, the food ontology has been developed, Serbian WordNet is extended for another 1.404 synsets from the culinary domain, while electronic dictionary of Serbian is enlarged with 1.248 entries. The significance of the model application comes from the fact that the new and enriched linguistic resources can be used in other systems for natural language processing. The opening chapter of the thesis elaborates the need of providing an informatic model for processing a huge linguistic corpus related to culinary and gastronomy domain, through methodologically precise and solid approach integrating pieces of information on the domain. Also, the formalization of the basic research subject, text in electronic form, has been presented. Further on, the chapter contains a description of the natural languages approximations introduced in order to enable modern information technologies to process texts written in natural languages, and it emphasizes the need to make the characterisation of the text language with corresponding corpus and sublanguage. Further on in the first chapter, the task of information extraction, and the models for informatic processing of non‐structured or semi‐structured texts, used by the computer to interpret the meaning that the author (not necessarily a human) has intended to give while writing the text, are defined. Additionally, this chapter contains the description of the methods used in information extraction field – methods based on rules and methods based on machine learning. Their advantages and shortcomings are listed, so as the reasons why in this thesis are used techniques based on linguistic knowledge. As a conclusion to the introduction chapter, a special attention is given to ontologies, WordNet, and the significance of its usage as ontology. The second chapter contains the presentation of the linguistic resources and tools exploited in this thesis. It describes morphological dictionaries and local grammars used for solving the problem of information extraction from texts written in Serbian. A review of information extraction systems is given subsequently. At the end of the second chapter, the stages in processing of Serbian written texts during the information extraction in the software systems Unitex and GATE are described. The main result of the thesis is presented in the third chapter. It is the model for solving the problem of information extraction by integrating linguistic resources and tools, which includes creation of a text corpus, definition of tasks for information extraction, establishment of finite state models for information extraction, and their application accordingly, iterative enlarging of electronic morphological dictionaries, enrichment and enhancement of WordNet, and creation of new ontologies. Each of these steps is described thoroughly. Even though the model was at first considered as a solution for problems in processing Serbian, it can be equally applied for processing texts written in other languages, with the development of suitable language resources accordingly. The implementation of the above explained steps is described in the fourth chapter, through a system for information extraction from the culinary texts written in Serbian. Then follows the description of a bond in the development and mutual complement of lexical resources through steps in creating domain corpus, identifying culinary lexica, expanding and upgrading of WordNet and electronic morphological dictionaries, and developing of domain ontologies – the food ontology, the approximate measure ontology, and the ontology of ingredients that can be used as mutual replacements in the culinary domain. This system, developed for information extraction, has served for creating an advanced search system which, based on a corpus of culinary texts, generates all possible answers to inquiries made by users. In the frame of this system is implemented a specific method which serves for creation of links between different recipes. This is used in case when the user reviews a text of a recipe and notices that in preparing description features some part which already had appeared in other recipe, but with additional or different explanation. Another contribution of this thesis is application of developed ontologies in tasks that convert approximate measures into standard measures, and establishment of similarities among the recipes. The similarity of the recipes is defined as similarity of texts which describe process of course preparation in accordance with a specific recipe. The last chapter contains final conclusions and directions for future research. URI: http://hdl.handle.net/123456789/5836 Files in this item: 1
Disertacija_10_21.pdf ( 10.38Mb ) -
Banković, Milan (Beograd , 2016)[more][less]
Abstract: SMT solvers implement decision procedures that check for satisfiability of first-order logical formulae with respect to some decidable theory. They rely on the powerful techniques that are used for solving boolean satisfiability problem (SAT), combined with specific procedures that permit reasoning in a particular theory. Typical applications of SMT solvers are mostly found in software verification, and for this reason the theories frequently considered in SMT solvers are best suited for such kind of applications. Extending the applicability of SMT solvers to other areas may require defining new SMT theories, as well as developing the corresponding decision procedures for such theories. In that sense, in this thesis we consider improving of SMT solvers by extending their applicability to solving CSP problems. Such problems consider variables with finite domains, and the goal is to find the assignment of values to the variables of the problem satisfying all the imposed constraints. When CSP solving is considered, the main drawback of the existing SMT theories is that they are not adapted to the problems with finite domains, and are also incapable of reasoning about global constraints, which play the significant role in most CSP problems. For this reason, in this thesis a novel SMT theory is defined that enables natural representation of CSP problems, since it includes support for some frequently used global constraints. For such theory, we developed a decision procedure based on the existing techniques borrowed from the traditional CSP solvers, but these techniques are adapted in the way that permits their usage within SMT solvers. The decision procedure currently supports two types of global constraints: the alldifferent constraint and the linear constraint. In case of the alldifferent constraint, the main contribution is a novel algorithm for generating explanations of conflicts and propagations, which is required for the conflict analysis. In case of the linear constraint, a novel filtering algorithm is developed that takes into consideration the existence of the alldifferent constraints in the given problem, which can lead to a stronger propagation. Another direction of improving SMT solvers that is considered in the thesis is the usage of the parallelization techniques. We consider the parallelization of the simplex algorithm, which is used in SMT solvers as the decision procedure for the linear arithmetic. We also consider the parallel portfolio approach, as well as the hybridization of the two approaches. A comprehensive experimental evaluation is provided on a large number of instances, both industrial and randomly generated. For the purpose of all the mentioned research, during the work on the thesis a new open-source SMT solver called argosmt is developed, based on DPLL(T ) architecture. URI: http://hdl.handle.net/123456789/5835 Files in this item: 1
Disertacija_8.pdf ( 2.359Mb ) -
Boričić, Marija (Beograd , 2016)[more][less]
Abstract: After a brief introductory survey, this work is divided into two parts. The first part deals with presence of probability in logic (v. [16], [17], [18], [19], [22], [23] and [24]), and the second one is devoted to the application of entropy in classification of many–valued logics (v. [14], [15], [20], [21] and [25]). The basic idea, dominant in the first part of the work, is to enrich the Gentzen’s sequent calculus LK for propositional classical logic by a kind of probability operator defined over the sequents ¡ ` ¢ in order to express the fact that ”the truthfulness probability of ¡ ` ¢ belongs to the interval [a; b] µ [0; 1]”. We introduce the following four systems: LKprob, LKprob("), NKprob and LKfuzz. The basic form of sequents in LKprob is ¡ `b a ¢ with the above given intended meaning. The system LKprob(") is focused on the Suppes’ forms ¡ `n ¢ enabling to formalize the sentence ”the truthfulness probability of ¡ ` ¢ belongs to the interval [1 ¡ n"; 1] µ [0; 1]”, for some n 2 N. The system NKprob presents a natural deduction counterpart of the sequent calculus LKprob. The models founded on Carnap– Popper–Leblance probability semantics are defined for each of these calculi and accompanied by the corresponding soundness and completeness results. Finally, the calculus LKfuzz is introduced with a more general form of the sequents ¡ `x ¢, where x is an element of a finite lattice, with the aim to describe a fuzzification of LK. The meaning of ¡ `x ¢ is that ”x is the fuzziness measure of ¡ ` ¢”. Models for LKfuzz are given with soundness and completeness results, and a proof– theoretical treatment of LKfuzz includes the cut–elimination theorem. The second part of the work explores the fact that each logical system associated with the partition induced by the corresponding Lindenbaum–Tarski algebra makes it possible to define its entropy. We define the entropy of a logical system based on geometric distribution of measures over matching partition of set of formulae. This iv definition enables the classification of many–valued propositional logics according to their entropies. Asymptotic entropy approximations for some infinite–valued logics are proposed as well. The considered examples include Lukasiewicz’s, Kleene’s and Priest’s three–valued logics, Belnap’s four–valued logic, G¨odel’s and McKay’s m– valued logics, and Heyting’s and Dummett’s infinite–valued logics. URI: http://hdl.handle.net/123456789/5834 Files in this item: 1
Disertacija7.pdf ( 678.9Kb ) -
Mihić, Ljubica (Beograd , 2017)[more][less]
Abstract: Mathematical modeling of many phenomena which occur in the natural, technical sciences, economy requires signi cant knowledge of the theory of numerical integration. In the situations where the integral cannot be determined analytically, it is necessary to construct the for- mula which approximates its value with acceptable error. Besides the traditional formulae, the tendencies in the development of this area refer to increment of algebraic degree of precision of the quadrature formula and its error estimation. The subject of this dissertation is Gaussian quadrature formula with increased number of nodes which may have double multiplicity (sections 2 and 4) or arbitrary multiplicity (section 3). When we consider the addition of one node, one of the integration interval ends, the corresponding quadrature formula is called Gauss-Radau, and in the case of adding two new nodes, the appropriate formula is of Gauss-Lobatto type. Beside those formulae, in this dissertation we consider the Kronrod's extension of Gauss-Tur an quadrature formula, which includes the derivatives of the function at nodes. Here, the main aim is to deter- mine efficient error bounds of these formulae with respect to the different types of Chebyshev weight functions and Gori-Micchelli weight function which, in one special case, represents the generalization of the rst Chebyshev weight function. Introductory theorems and well-known statements that are used in the rest of the thesis are presented in the rst section. We described basic properties of orthogonal polynomials participating in the construction of Gaussian quadrature formula. Furthermore, the different types of remainder terms of quadrature formula are de ned, whereby in the following sections we analyze the integral representation of the remainder term. The recent results relating to the increasing number of the nodes of arbitrary multiplicity are exposed. The remaining three sections contain the chapters with original results. The second section is devoted to the estimation of the error of Gauss- Lobatto quadrature formulae with a double nodes at the endpoints. Af- ter detailed analysis of the kernel of the remainder term (see subsection 2.2.1), we proved the Theorems stating the behavior of the maximum modulus of the kernel. We computed xed values mentioned in the The- orems and established the real errors and the error bounds of quadrature formula. In third section we examine the Kronrod's extension of Gauss- Tur an quadrature formulae with respect to the special kind of Gori- Micchelli weight function. This extension, beside the nodes of Gauss- Tur an quadrature formula, also contains the zeros of Chebyshev polyno- mial of the second kind. In those new nodes, we consider just the values of the function (not the values of its derivatives). Previously mentioned Kronrod's extension is actually Chakalov-Popoviciu quadrature formu- la, so, by applying the methods for those formulae, we computed the coefficients and the error of Kronrod's formula. Gautschi-Li hypotheses are proven in the fourth section. Those hypotheses concern the Gauss-Radau quadrature formulae with respect to the Chebyshev weight functions of the second and the third kind. Subsection 4.4 consists of numerical examples and the tables with efficient error bounds. URI: http://hdl.handle.net/123456789/5833 Files in this item: 1
Disertacija-6.pdf ( 12.53Mb ) -
Vučetić, Milica (Beograd , 2017)[more][less]
Abstract: In this dissertation we discuss in uence of H emission from supernova remnants (SNRs) on H derived star formation rates (SFRs). We present the detection of 16 optical SNR candidates in a part of nearby spiral galaxy IC342, and two more poten- tial SNRs in NGC 185 galaxy. The candidates were detected by applying [S ii]/H ratio criterion on observations made with the 2 m telescope at Rozhen National Astronomical Observatory in Bulgaria. Also, in this dissertation we present the most up-to-date list of nearby galaxies with optically detected SNRs. When deri- ving H star formation rates, assumption is that the radiation is coming from the ionized gas surrounding hot and young stars { H ii regions. In this case, emission from SNRs contaminates H ux used to derive SFR. We found that the contribu- tion of SNRs' ux to the total H ux, for 18 galaxies in our sample of galaxies with optical SNRs, is 5 5%. Due to the observational selection effects, the SNR contamination of SFRs derived herein represents only a lower limit. M83 is the galaxy with the most detected optical SNRs and in this galaxy SNRs account for 9 per cent of the total H emission. We expect that fraction similar to this would be close to the real contribution of SNR emission to the total H emission in spiral galaxies. Using two dwarf galaxies as an example, Holmberg IX and NGC 185, we show that the contamination of H ux by SNRs, or other sources, can be much larger, up to ten times higher than total H ux coming from H ii regions of the observed galaxy. URI: http://hdl.handle.net/123456789/5832 Files in this item: 1
Disertacija-5.pdf ( 26.28Mb )