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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

Caching in iterative hill climbing /

Karhi, David, January 1900 (has links)
Thesis (M.S.)--Texas State University--San Marcos, 2008. / Vita. Includes bibliographical references (leaves 50-51). Also available on microfilm.
82

Formulações fortes para o problema integrado de dimensionamento e sequenciamento da produção

Carretero, Michelli Maldonado [UNESP] 01 July 2011 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:26:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-07-01Bitstream added on 2014-06-13T18:30:54Z : No. of bitstreams: 1 carretero_mm_me_sjrp.pdf: 795127 bytes, checksum: 64b07e80db6689945e91fc1c317deb3c (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Em alguns setores, o planejamento da produção envolve dois aspectos: o dimensionamento do tamanho dos lotes e a programação da produção (sequenciamento dos lotes). O primeiro problema consiste em determinar o tamanho dos lotes de produção de cada item a ser produzido em uma ou mais máquinas em cada período ao longo de um horizonte de planejamento finito. O segundo problema consiste em encontrar a ordem em que os lotes devem ser produzidos em um dado conjunto de máquinas. Estes dois aspectos do planejamento da produção podem ser tratados de forma independente: em um estágio é resolvido o problema de dimensionamento dos lotes e no outro, realizado antes ou depois, é resolvido o problema de seqüenciamento. No entanto, uma tendência recente na literatura são trabalhos que apresentam modelos matemáticos que capturam simultaneamente as relações entre os dois problemas. Na literatura pode-se encontrar modelos integrados que incluem restrições de eliminação de subrotas, propostas para o Problema do Caixeiro Viajante (PCV), para formular as restrições de sequenciamento. No entanto, alguns dos modelos propostos usam restrições de ordem polinomial que fornecem uma relaxação linear fraca. O objetivo desse trabalho é avaliar o uso de inequações válidas, propostas na literatura, para obtenção de formulações mais fortes para o problema integrado de dimensionamento e sequenciamento da produção. Resultados computacionais usando exemplares aleatórios e exemplares da literatura mostram que as reformulações propostas são eficientes para cenários em que o modelo original não é eficiente. / Often, the production planning involves the lot sizing and scheduling of items. The first problem is to determine the lot size of each item to be produced in one or more machines in each period over a finite planning horizon. The second problem is to find the order in which the items will be produced. These two aspects of the production planning can be treated independently: in one stage the lot sizing problem is solved, and in the other, that can be executed before or after, the scheduling problem is solved. A recent trend in the literature is to propose mathematical models that capture the relationships between these two problems. In the literature one can find integrated models that include subtour elimination constraints, proposed for the Traveling Salesman Problem, to formulate the scheduling decisions. However, in some of these models, constraints of polynomial order, that provides a weak linear relaxation, are used.The purpose of this study is to evaluate the use of valid inequalities proposed in the literature to obtain stronger formulations to the lot and scheduling problem. Computational results using random instances and instances from the literature show that the proposed formulations have a better performance in scenarios where the original model is not efficient.
83

Grupos de visitação na AMAN = um estudo de caso do problema do caixeiro viajante / Groups visiting the Military Academy of Agulhas Negras : a case study of the travelling salesman problem

Tavora, Rogerio Carvalho Mendes 01 July 2011 (has links)
Orientador: Luziane Ferreira de Mendonça / Dissertação ( mestrado profissional) - Universidade Estadual de Campionas, Instituto de Matemática, Estatística e Computação Científica / Made available in DSpace on 2018-08-17T15:32:08Z (GMT). No. of bitstreams: 1 Tavora_RogerioCarvalhoMendes_M.pdf: 4616708 bytes, checksum: 3a393a830c9e1127f5694b0a56d9fcd9 (MD5) Previous issue date: 2011 / Resumo: Comemorando os 200 anos de Academia Militar no Brasil a partir de março de 2011, estão previstas várias implementações e melhorias na estrutura de visitação da AMAN que, consequentemente, vão gerar um aumento substancial no número de grupos visitantes no ano de seu bicentenário. Diante dos fatos percebe-se a necessidade de um modelo matemático eficiente cuja finalidade seja permitir aos grupos visitantes percorrerem trajetos otimizados, ou seja, que passem pelos pontos principais de visitação no menor tempo e distância possíveis. O modelo matemático a ser adotado neste trabalho é o Problema do Caixeiro Viajante (Traveling Salesman Problem - TSP), um clássico da Otimização Combinatória pertencente 'a classe de problemas NP - difícil, que já possui eficientes algoritmos desenvolvidos. Serão utilizadas heurísticas próprias para a resolução do TSP com o intuito de se obter numericamente itinerários ótimos de visitação, considerando os diferentes grupos visitantes e suas dificuldades de acesso, dentre outras particularidades. / Abstract: Celebrating 200 years of the Military Academy in Brazil from March 2011, provides a lot of implementations and improvements in the structure of visitation of AMAN, consequently, will generate substantial growth in the number of visiting groups in the year of its bicentennial. Given the facts we see the need for an efficient mathematical model whose purpose is to allow visitors to wander paths optimized groups, ie passing through the main points of visitation in the shortest possible time and distance. The mathematical model to be adopted in this work is TSP (Traveling Salesman Problem - TSP), a classic combinatorial optimization class of problems NP - hard, that have already efficient algorithms. We will use own heuristics for solving the TSP in order to obtain numerically optimal routes for visitors, considering the various visiting groups and their difficulties of access, among other features. / Mestrado / Mestre em Matemática
84

Inteligencia computacional na sintese de meta-heuristicas para otimização combinatoria e multimodal / Computacional intelligence applied to the synthesis of metaheuristics for combinatorial and multimodal optimization

Gomes, Lalinka de Campos Teixeira 06 December 2006 (has links)
Orientadores: Fernando Jose Von Zuben, Leandro Nunes de Castro / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-15T01:42:44Z (GMT). No. of bitstreams: 1 Gomes_LalinkadeCamposTeixeira_D.pdf: 3303378 bytes, checksum: 65adc8d5ec20cd1f431eaca2fe3765cc (MD5) Previous issue date: 2006 / Resumo: Problemas de otimização combinatória apresentam grande relevância prática e surgem em uma ampla gama de aplicações. Em geral, a otimização combinatória está associada a uma explosão de candidatos à solução, inviabilizando a aplicação de métodos exatos. Frente à intratabilidade desta classe de problemas via métodos exatos, nos últimos anos tem havido um crescente interesse por métodos heurísticos capazes de encontrar soluções de alta qualidade, não necessariamente ótimas. Considerando o notório sucesso empírico de meta-heurísticas concebidas através da inspiração biológica e na natureza, essas abordagens vêm ganhando cada vez mais atenção por parte de pesquisadores. É fato conhecido que não existe uma única metodologia capaz de sempre produzir os melhores resultados para todas as classes de problemas, ou mesmo para todas as instâncias de uma mesma classe. Assim, a busca de solução para problemas de natureza combinatória constitui uma linha de pesquisa desafiadora. Nesta tese são considerados problemas de otimização combinatória multicritério e multimodal. Como principal contribuição, destaca-se a concepção de novas meta-heurísticas para a solução de problemas combinatórios de elevada complexidade, tendo sido propostas duas classes de ferramentas computacionais. A primeira envolve um método híbrido fundamentado em mapas auto-organizáveis de Kohonen e inferência nebulosa, em que um conjunto de regras guia o processo de treinamento do mapa de modo a permitir o tratamento de problemas com restrições e múltiplos objetivos. A segunda abordagem baseia-se em sistemas imunológicos artificiais. Em particular, a abordagem imunológica levou à proposição de meta-heurísticas capazes de encontrar e manter diversas soluções de alta qualidade, viabilizando o tratamento de problemas multimodais. Como casos de estudo, foram consideradas duas classes de problemas de otimização combinatória multimodal: o problema de roteamento de veículos capacitados e o problema do caixeiro viajante simétrico. As técnicas propostas foram também adaptadas para a solução de problemas de bioinformática, em particular ao problema de análise de dados de expressão gênica, produzindo resultados diferenciados e indicando um elevado potencial para aplicações práticas. / Abstract: Combinatorial optimization problems possess a high practical relevance and emerge on a wide range of applications. Usually, combinatorial optimization is associated with an explosion of candidates to the solution, making exact methods unfeasible. Before the unfeasibility of exact methods when dealing with this class of problems, lately there has been an increasing interest in heuristic methods capable of finding high-quality solutions, not necessarily the optimal one. Considering the widely known empirical success of metaheuristics conceived with inspiration on biological systems and on the nature itself, such approaches are receiving more and more attention from the scientific community. Evidently, there is no single methodology able to always produce the best results for all classes of problems, or even for all instances of one specific class. That is why the search for solutions to combinatorial problems remains a challenging task. This thesis considers multicriteria and multimodal combinatorial optimization problems. As the main contribution, one can emphasize the conception of new metaheuristics designed to the solution of high-complexity combinatorial optimization problems, and two classes of computational tools have been proposed. The first one involves hybrid method based on Kohonen self-organizing maps and fuzzy inference, in which a set of rules guides the training of the self-organizing maps in order to allow the handling of problems with constraints and multiple objectives. The second approach is based on artificial immune systems. Particularly, the immune-inspired approach leads to the proposal of metaheuristics capable of finding out and maintaining multiple high-quality solutions, making it possible to deal with multimodal problems. As case studies, the capacitated vehicle routing problem and the symmetric traveling salesman problem are considered, giving rise to combinatorial and multimodal problems. The proposed techniques were also adapted to the solution of problems in the field of bioinformatics, specifically the analysis of gene expression data, leading to distinguished results and indicating a high potential for practical applications. / Doutorado / Engenharia de Computação / Doutor em Engenharia Elétrica
85

Application of mixed-integer programming in chemical engineering

Pogiatzis, Thomas January 2013 (has links)
Mixed-Integer Programming has been a vital tool for the chemical engineer in the recent decades and is employed extensively in process design and control. This dissertation presents some new Mixed-Integer Programming formulations developed for two well-studied problems, one with a central role in the area of Optimisation, the other of great interest to the chemical industry. These are the Travelling Salesman Problem and the problem of scheduling cleaning actions for heat exchanger networks subject to fouling. The Travelling Salesman Problem finds a plethora of applications in many scientific disciplines, Chemical Engineering included. None of the mathematical programming formulations proposed for solving the problem considers fewer than O(n^2) binary degrees of freedom. The first part of this dissertation introduces a novel mathematical description of the Travelling Salesman Problem that succeeds in reducing the binary degrees of freedom to O(nlog2(n)). Three Mixed-Integer Linear Programming formulations are developed and the computational performance of these is tested through computational studies. Sophisticated methods are now available for scheduling the cleaning actions for networks of heat exchangers subject to fouling. In the majority of these, only one form of cleaning is used, which restores the performance of the exchanger back to its clean level. A recent study revised the scheduling problem for the case where there are several cleaning methods available. The second part of this dissertation extends their approach, developed for individual units, to heat exchanger networks and explores the concept of selection of cleaning techniques further. Mixed-Integer Programming formulations are proposed for the scheduling task, for two fouling scenarios: (i) chemical reaction fouling and (ii) biological fouling. A series of results are presented for the implementation of the scheduling formulations to networks of different sizes.
86

Application of Combinatorial Optimization Techniques in Genomic Median Problems

Haghighi, Maryam January 2012 (has links)
Constructing the genomic median of several given genomes is crucial in developing evolutionary trees, since the genomic median provides an estimate for the ordering of the genes in a common ancestor of the given genomes. This is due to the fact that the content of DNA molecules is often similar, but the difference is mainly in the order in which the genes appear in various genomes. The mutations that affect this ordering are called genome rearrangements, and many structural differences between genomes can be studied using genome rearrangements. In this thesis our main focus is on applying combinatorial optimization techniques to genomic median problems, with particular emphasis on the breakpoint distance as a measure of the difference between two genomes. We will study different variations of the breakpoint median problem from signed to unsigned, unichromosomal to multichromosomal, and linear to circular to mixed. We show how these median problems can be formulated in terms of problems in combinatorial optimization, and take advantage of well-known combinatorial optimization techniques and apply these powerful methods to study various median problems. Some of these median problems are polynomial and many are NP-hard. We find efficient algorithms and approximation methods for median problems based on well-known combinatorial optimization structures. The focus is on algorithmic and combinatorial aspects of genomic medians, and how they can be utilized to obtain optimal median solutions.
87

Applications of Circulations and Removable Pairings to TSP and 2ECSS

Fu, Yao January 2014 (has links)
In this thesis we focus on two NP-hard and intensively studied problems: The travelling salesman problem (TSP), which aims to find a minimum cost tour that visits every node exactly once in a complete weighted graph, and the 2-edge-connected spanning subgraph problem (2ECSS), which aims to find a minimum size 2-edge-connected spanning subgraph in a given graph. TSP and 2ECSS have many real world applications. However, both problems are NP-hard which means it is unlikely that polynomial time algorithms exist to solve them, so methods that return close to optimal solutions are sought. In this thesis we mainly focus on k-approximation algorithms for the two problems, which efficiently return a solution within k times of the optimal solution. For a special case of TSP called graph TSP, using ideas from Momke and Svensson, we present a 25/18-approximation algorithm for a special class of graphs using circulations and T-joins, which improves the previous known best bound of 7/5 for such graphs. Moreover, if the graph does not contain special nodes, our algorithm ensures the ratio of 4/3. For 2ECSS, given any k-edge-connected graph G=(V,E), |V|=n, |E|=m, we present an approximation algorithm that gives a 2-edge-connected spanning subgraph with the number of edges at most n+(m-n)/(k-1)-(k-2)/(k-1) with a novel use of circulations, which improves both the approximation ratio and the simplicity of the proof compared to a result by Huh in 2004.
88

Využití matematických metod při plánování sítě obchodních zástupců / Application of mathematical methods for planning and managing network of sales representatives

Mitas, Lukáš January 2016 (has links)
Companies from multiple branches use as one way to offer their products and services network of sales representatives. This thesis study mainly designing process of such network and process of planning day to day routes of sales representatives with focus on minimizing cost caused by their work. For designing such network set covering problem model and matching problem model were used. For planning sales representatives routes travelling salesman problem, multiple salesperson travelling salesman problem, vehicle routing problem, nearest neighbor heuristic and authors own solution were used. Usage of multicriterial decision making is briefly mentioned as tool for managing such network on examples of equipment selection. As demonstration on real case, data from Tata Global Beverages (Jemča) company were used.
89

Optimalizace tras při odečtu plynoměrů / Route optimalisation for gas-meter reading

Šik, Petr January 2008 (has links)
This thesis aims to find an optimal route taken by workers reading gas-meters. The text consists of three parts: the collection of necessary data, the selection and subsequent modification of the heuristic method and the calculation itself. Two techniques of data collection are applied: purchase from a specialised company and calculation based on geographical coordinates. These techniques are compared in the end. The method of the nearest neighbour is used for calculation, after being modified for this particular case. The calculation itself is done by the program named Gas-meters, which was created for the purpose of this thesis. The route potentially used by the gas company workers is then the result of the thesis. Furthermore, the thesis presents specific corporate savings possibly brought by using the presented program.
90

Analýza a optimalizace efektivnosti zemědělsko-dřevozpracujícího podniku (reálná situace) / Analyses and optimization of efficiency in agriculture and wood-working company

Jágerová, Tereza January 2008 (has links)
This thesis aspires to optimize the processes in agriculture and wood-working company and to propose some changes if needed. At first, it is wood-working branch which is analyzed. The intent is to find an optimal route to distribute pallets and afterwards freight the vehicle by sawn wood and return back with. This is some modification of travelling salesman problem with more than one salesman and more centers including the condition that the travelling is dynamic in time and that only selected clients are visited. The agriculture problem is more complicated and complex because the model aims to find an optimal portfolio of diverse animal and vegetal production influenced by many factors and some of them are mentioned below. The agriculture model includes for example the stochastic character of weather and the condition that the herd of cattle should be stable.

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