Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Randy B. Machemehl. Vita. Includes bibliographical references. Also available from UMI.

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains viii, 95 p. : ill. Includes abstract. Includes bibliographical references (p. 79-91).

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references (p.137-141). Also available online,

Orientador: Fernando Iguti / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-26T15:45:20Z (GMT). No. of bitstreams: 1 Clapis_AntonioPedro_D.pdf: 6280663 bytes, checksum: d33f59de18e79beebaf4d0bb0cbdcd98 (MD5) Previous issue date: 1999 / Resumo: Nos últimos trinta anos pesquisadores tem procurado desenvolver métodos matemáticos e ou numéricos, na busca de se otimizar a configuração geométrica de uma dada estrutura. Como a análise estrutural é uma parte integrante do processo de otimização de forma, o progresso da otimização estrutural muitas vezes depende fundamentalmente do desenvolvimento de um bom modelo de elementos finitos. Partindo-se então do pressuposto que a discretização do modelo geometricamente e fisicamente tem sentido, pode-se implementar um algoritmo iterativo de busca da forma ótima de um elemento estrutural utilizando-se um principio heurístico de desenvolvimento. Extrapola-se um método de homogeneização do erro de discretização por elementos finitos no domínio para a homogeneização da densidade de energia de deformação por distorção (von Mises) dos elementos, onde o critério de convergência é a máxima densidade de energia de distorção permitida. Um código numérico em linguagem Fortran F32 é implementado. O programa tem como principal característica a utilização de dois modelos estruturais com graus de liberdade bem distintos (modelo físico e modelo geométrico). No modelo geométrico efetua-se a relocação dos nós da discretização por elementos finitos tendo como objetivo a melhor homogeneização possível da densidade de energia de deformação por distorção do elemento. A avaliação da potencialidade do método é feita através da otimização de algumas estruturas citadas na literatura e, com os resultados obtidos verifica-se a eficiência e a razão de convergência do método proposto / Abstract: In the past thirty years researchers have sought to develop mathematical methods and/or numerical methods to optimize the geometric configuration of a structure. Since structural analysis is part of the process of shape optimization, this success in our approach depends on the development of an adequate finite element model. Assuming that the geometrical and physical discretization of the model is established, it is possible to implement an iterative algorithm to seek the optimal shape of a structural component using a heuristic principIe. A method the balancing the error of each element in the plane stress state is extrapolated. This method is used to balance the energy of distortion deformation function (von Mises) of each element and the criterion to stop is the maximum distortion energy function in the uniaxial tension testoA numerical code using Fortran F32 language is implemented. The main characteristic of this code is the execution of two distinct structural modules (physical and geometric model). In the geometric model the nodes are relocated considering the homogenization the distortion deformation energy density per element. The potentiality of the proposed method is evaluated through some examples ftom the literature. With the results the efficiency and the convergence of the method are checked. / Doutorado / Mecanica dos Solidos / Doutor em Engenharia Mecânica

Orientador: Paulo Morelato França / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-14T08:51:37Z (GMT). No. of bitstreams: 1 Assis_LauraSilvade_M.pdf: 1632808 bytes, checksum: dfd28dc2bbd2bb5fe453a2fb1c2b7b6e (MD5) Previous issue date: 2009 / Resumo: O objetivo desta dissertação é desenvolver uma metodologia eficiente para solucionar o problema de agrupamento capacitado multicritério (PACM), no qual objetos com pesos associados são dados, os quais devem ser particionados em agrupamentos com capacidade limitada. Neste trabalho, o PACM está ambientado em um problema de reagrupamento de lotes urbanos, nos quais devem ser realizadas as leituras dos medidores de energia elétrica por concessionárias de distribuição de energia. A operação de leitura dos medidores é realizada sobre lotes geograficamente definidos e é desempenhada sobre rotas percorridas uma vez por mês pelos leituristas. A motivação deste trabalho é atribuída ao fato de que, com o passar do tempo, o tamanho e o formato dos lotes vão ficando obsoletos, devido a modificações introduzidas na conformação atual, desarranjando o equilíbrio entre os lotes e desatualizando as rotas. Por esse motivo é importante realizar um reagrupamento dos lotes buscando a diminuição dos custos operacionais de leitura, assim como a minimização dos custos e transtornos causados pelas modificações. O método proposto para resolver o problema abordado nesta dissertação é um algoritmo baseado na metaheurística GRASP (Greedy randomized adaptive search procedure). A eficiência do método proposto é testada sobre uma série de instâncias geradas e sobre uma rede real. Os experimentos computacionais demonstram a eficiência do método. / Abstract: The aim of this dissertation is to develop an eficient methodology to solve the multicriteria redistricting capacitated problem (PACM), in which objects with associated weights are given, which must be partitioned into groups with limited capacity. In this work, the PACM is inserted in to a reassignment problem of urban clusters of clients, in which the readings of the eletric energy measurement must be performed by the company of energy distribution. The reading operation is performed over lots geographically defined is performed once a month by the readers. The motivation of this work is due to the fact that the size and shape of the lots become obsolete after some time, due to modifications introduced in the current conformation, desarranging the balance between the lots and outdating the routes. For this reason it is important to achieve a reassignment of the lots trying to decrease the operational costs of reading, as well as minimizing the costs and inconvenience caused by the changes. The proposed method to solve the problem addressed in this dissertation is a algorithm based on GRASP (Greedy randomized adaptive search procedure) metaheuristic. The efectiveness of the proposed method is tested on a large number of generated instances and on a real network. Computational experiments demonstrate the efectiveness of the proposed approach. / Mestrado / Automação / Mestre em Engenharia Elétrica

Orientador: Flavio Keidi Miyazawa / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Computação / Made available in DSpace on 2018-08-07T21:41:01Z (GMT). No. of bitstreams: 1 Xavier_EduardoCandido_D.pdf: 20666026 bytes, checksum: 5e051653d938a813e227b1e2eebcd415 (MD5) Previous issue date: 2006 / Resumo: Neste trabalho estudamos diversos problemas de empacotamento considerados NP-difíceis. Assumindo a hipótese de que P ? NP, sabemos que não existem algoritmos eficientes (complexidade de tempo polinomial) exatos para resolver tais problemas. Uma das abordagens consideradas para tratar tais problemas é a de algoritmos de aproximação, que são algoritmos eficientes e que geram soluções com garantia de qualidade. Neste trabalho apresentamos alguns algoritmos aproximados para problemas de empacotamento com aplicações práticas. Outra maneira de se lidar com problemas NP-difíceis é o desenvolvimento de heurísticas. Neste trabalho também apresentamos heurísticas baseadas no método de geração de colunas para problemas de corte e empacotamento bidimensional. Resultados computacionais sugerem que tais heurísticas são eficientes e geram soluções de muito boa qualidade. / Abstract: In this work we study several packing problems that are NP-hard. If we consider that P ? NP, we know that there are no efficient (polynomial time complexity) exact algorithms to solve these problems. One way to deal with these kind of problems is to use approximation algorithms, that are efficient algorithms that produce solutions with quality guarantee. We present several approximation algorithms for some packing problems that have practical applications. Another way to deal with NP-hard problems is to develop heuristics. We also consider column generation based heuristics for packing problems. In this case, we present column generation algorithms for some two dimensional packing problems and also present computational tests with the proposed algorithms. The computational results shows that the heuristics are efficient and produce solutions of very good quality. / Doutorado / Doutor em Ciência da Computação

The representation of information in modern database systems is complicated by the need to represent relationships among pieces of information. A natural representation for such databases is the information graph that associates the pieces of information with vertices in the graph and the relationships with edges. Five characteristics of this representation are noteworthy. First, each vertex has a size (in bytes) sufficient to store its corresponding piece of information. Second, retrieval in an information graph may follow a number of patterns; in particular, retrieval of adjacent vertices via edge traversals must be efficient. Third, in many applications such as a dictionary or bibliographic archive, the information graph may be considered static. Fourth, the ultimate home for an information graph is likely to be a roughly linear medium such as a magnetic disk or CD-ROM. Finally, information graphs are quite large-hundreds of thousands of vertices and tens of megabytes in size. / Master of Science

This thesis is concerned with the development of heuristic algorithms for the popular Quadratic Assignment Problem (QAP) which finds a wide variety of applications in various fields. This discrete optimization problem, which seeks the placement of m facilities on m locations in order to minimize a quadratic interactive cost, is well known to be NP-hard and turns out to be computationally intractable for even moderately sized problems. Hence, problems involving more than 12-15 facilities usually need to be analysed by approximate solution procedures. The more successful heuristic procedures which exist for problem QAP are computationally intensive, some of these resulting from a premature termination of exact solution procedures. The motivation here is to develop a polynomial time heuristic which is effective with respect to the quality of solutions obtained, while at the same time not being computationally very expensive. The method proposed herein is flexible in that one can operate it to suitably trade solution quality against effort as desired, and is portable in that the modules used as building blocks can be employed in conjunction with other heuristics as well. Computational experience on test problems found in the literature is provided to evaluate the worth of this method. / M.S.

A dissertation submitted in partial ful lment of the degree of Master of Science in Engineering (Electrical) (50/50) in the Faculty of Engineering and the Built Environment Department of Electrical and Information Engineering May 2017 / Numerous applications in a wide variety of elds has resulted in a rich history of research into optimisation for scheduling. Although it is a fundamental form of the problem, the single machine scheduling problem with two or more objectives is known to be NP-hard. For this reason we consider the single machine problem a good test bed for solution algorithms. While there is a plethora of research into various aspects of scheduling problems, little has been done in evaluating the performance of the Simulated Annealing algorithm for the fundamental problem, or using it in combination with other techniques. Speci cally, this has not been done for minimising total weighted earliness and tardiness, which is the optimisation objective of this work. If we consider a mere ten jobs for scheduling, this results in over 3.6 million possible solution schedules. It is thus of de nite practical necessity to reduce the search space in order to nd an optimal or acceptable suboptimal solution in a shorter time, especially when scaling up the problem size. This is of particular importance in the application area of packet scheduling in wireless communications networks where the tolerance for computational delays is very low. The main contribution of this work is to investigate the hypothesis that inserting a step of pre-sampling by Markov Chain Monte Carlo methods before running the Simulated Annealing algorithm on the pruned search space can result in overall reduced running times. The search space is divided into a number of sections and Metropolis-Hastings Markov Chain Monte Carlo is performed over the sections in order to reduce the search space for Simulated Annealing by a factor of 20 to 100. Trade-o s are found between the run time and number of sections of the pre-sampling algorithm, and the run time of Simulated Annealing for minimising the percentage deviation of the nal result from the optimal solution cost. Algorithm performance is determined both by computational complexity and the quality of the solution (i.e. the percentage deviation from the optimal). We nd that the running time can be reduced by a factor of 4.5 to ensure a 2% deviation from the optimal, as compared to the basic Simulated Annealing algorithm on the full search space. More importantly, we are able to reduce the complexity of nding the optimal from O(n:n!) for a complete search to O(nNS) for Simulated Annealing to O(n(NMr +NS)+m) for the input variables n jobs, NS SA iterations, NM Metropolis- Hastings iterations, r inner samples and m sections. / MT 2017

by Ng Suk Fung. / "February 18, 2002." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (p. 215-222). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.