Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-03-19T18:02:26Z No. of bitstreams: 1 saulocustodiodeaquinoferreira.pdf: 1364913 bytes, checksum: efa844157e53551961fc063ecd615818 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-03-21T13:30:23Z (GMT) No. of bitstreams: 1 saulocustodiodeaquinoferreira.pdf: 1364913 bytes, checksum: efa844157e53551961fc063ecd615818 (MD5) / Made available in DSpace on 2018-03-21T13:30:23Z (GMT). No. of bitstreams: 1 saulocustodiodeaquinoferreira.pdf: 1364913 bytes, checksum: efa844157e53551961fc063ecd615818 (MD5) Previous issue date: 2017-12-04 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O presente trabalho apresenta uma nova metodologia para a reconfiguração de sistemas de distribuição de energia elétrica através da aplicação da técnica matemática de decomposição de Benders. Esta técnica possibilita dividir o problema global em dois subproblemas, mestre e escravo, que se comunicam através de restrições denominadas cortes, geradas a partir de informações do segundo subproblema e incluídas no primeiro de forma iterativa até que um critério de convergência seja alcançado. O objetivo do problema é a minimização de perdas técnicas na rede de distribuição através de redefinição de sua topologia, observando-se restrições operativas como níveis de tensão, conectividade e radialidade. A redução de perdas é atrativa por implicar em melhores níveis de tensão, menores esforços aos equipamentos do sistema e maior confiabilidade, proporcionando, portanto, benefícios para as concessionárias de distribuição e maior qualidade da energia aos consumidores. O problema de reconfiguração é de programação não linear inteira mista, de difícil tratamento. Na metodologia proposta, o primeiro subproblema determina as decisões de chaveamento considerando-se apenas restrições lineares associadas à topologia da rede, enquanto que o segundo avalia a operação mediante a decisão do primeiro considerando as não linearidades e as restrições de balanço de carga. A vantagem da aplicação da técnica de decomposição é que ela permite a inclusão de incertezas operativas no modelo, como a representação da aleatoriedade das cargas demandadas a rede conforme presente nesse trabalho. A representação destas incertezas é realizada no contexto de reconfiguração robusta, em que a tomada de decisões sobre topologia da rede deve otimizar a operação para o conjunto de cenários pré-definidos. Sistemas conhecidos da literatura especializada são utilizados para a avaliação da metodologia proposta. / This work shows a new methodology for the reconfiguration of electric energy distribution systems by the application of the mathematical technique named Benders decomposition. This technique makes it possible to divide the global problem into two subproblems, master and slave, which communicate with each other through constraints called slices, generated from information of the second subproblem and included in the first one iteratively until a convergence criterion is reached. The objective of the problem is to minimize technical losses in the distribution network by redefining its topology, observing operational constraints such as levels of voltage, connectivity and radiality. Loss reduction is attractive because it implies better voltage levels, less system equipment effort and greater reliability, thus providing benefits to distribution dealers and higher energy quality to consumers. The reconfiguration problem is non-linear mixed integer programming, difficult to process. In the proposed methodology, the first subproblem determines the switching decisions considering only linear constraints associated with the network topology, while the second one evaluates the operation by means of the decision of the first recital considering the nonlinearities and the load balance constraints. The advantage of the application of the proposed technique is that the decomposition model is potential for the representation of operational uncertainties, as well as the load demands according to the present work. The representation of these uncertainties is carried out in the context of robust reconfiguration, in which the decision making on network topology must optimize the operation under scenarios of a predefined set. Systems known in the literature are used for the evaluation of the proposed methodology.

Orientador: Antonio Carlos Moretti / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matemática, Estatística e Computação Científica / Made available in DSpace on 2018-08-26T14:54:10Z (GMT). No. of bitstreams: 1 Gambaro_Andre_M.pdf: 2586966 bytes, checksum: 3a18149e2d94fa07e52e9d0e184015d8 (MD5) Previous issue date: 2015 / Resumo: A gestão florestal é uma área de significativa importância para a indústria e sociedade e traz consigo desafios consideráveis de planejamento de curto e longo prazo onde modelos matemáticos têm sido propostos para apoio das decisões envolvidas. Neste contexto, o presente trabalho busca revisar a literatura em busca de apresentar os principais modelos e sistemas utilizados, em particular os modelos de simulação e de programação linear de tipo I e II para o problema de planejamento florestal de longo prazo. É proposta também para este problema uma abordagem que utiliza a técnica de decomposição de Dantzig-Wolfe e geração de colunas para integrar os aspectos de sistemas de simulação de intervenções florestais com a programação linear. A abordagem explora de perto as estruturas de rede dos subproblemas que são associados ao problema de caminho mínimo e resolvidos via programação dinâmica e programação linear. Por fim testes são realizados com a implementação da abordagem em instâncias do problema e os resultados apresentados / Abstract: The forest management has been of significative importance for industry and society along the years and brings with it considerable long and short term planning challenges where mathematical models have been proposed to support the decisions involved. In this context, this work aims to present a brief review of main models and systems of this area in the literature, particularly linear programming models of the type I and II. It is also proposed the use of Dantzig-Wolfe decomposition and column generation techniques for the long term forest planning problem in a way to approximate and integrate the simulation models with linear programming techniques. This method explores the network structure of the sub-problems which are close related to the shortest path problem and solved by dynamic programming and linear programming. Finally, tests with these techniques are performed for some instances of the problem and results are presented / Mestrado / Matematica Aplicada / Mestre em Matemática Aplicada

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This thesis investigates the impedance of acoustic liners, to attenuate noise originating from jet engines and enable compliance with international standards and regulations regarding noise from airplane jet engines. Experimental tests of two supplied liners were conducted in an impedance tube; one liner with known and predictable properties, and one liner with unknown properties. The tests included tonal excitations in the formats of stepped sine and random noise with frequencies within set boundaries. After post-processing of the captured data, the desired impedance could be analysed in terms of excitated frequencies and sound pressure levels. The conclusions from this project are that both of the liners deviated from their expected behavior, which was that liner 1 should have been unaffected by the alternated sound pressure levels, and liner 3 should have shown bigger affection due to the changed sound pressure level. Since the results were different than expected, there might have been minor sources of error during the measurements. It could be investigated if there is leakage from the mounting of the liners, or if the 3D printing resolution is sufficient. Because of limitations in time, there is more left in this project to investigate. Therefore, conducting similar studies where more frequencies, sound pressure levels, and multi-tonal measurements can be included, is suggested as future work.

"In this work an innovative wavelet packet based sifting process for signal decomposition has been developed and its application for health monitoring of time-varying structures is presented. With the proposed sifting process, a signal can be decomposed into its mono-frequency components by examining the energy content in the wavelet packet components of a signal, and imposing certain decomposition criteria. The method is illustrated for simulation data of a linear three degree-of-freedom spring-mass-damper system and the results are compared with those obtained using the empirical mode decomposition (EMD) method. Both methods provide good approximations, as compared with the exact solution for modal responses from a conventional modal analysis. Incorporated with the classical Hilbert transform, the proposed sifting process may be effectively used for structural health monitoring by monitoring instantaneous modal parameters of the structure for both, cases of abrupt structural stiffness loss and progressive stiffness degradation. The effectiveness of this method for practical application is evaluated by applying the methodology for experimental data and the results obtained matched with the field observations. The proposed methodology has shown better results in a comparison study which is done to evaluate performance of the proposed approach with other available SHM techniques, namely EMD technique and Continuous Wavelet Transform (CWT) method, for cases characterized by different damage scenarios and noise conditions."

Nesta contribuição apresentamos uma solução para a equação de transferência radiativa condutiva em geometria cilíndrica. Esta solução é aplicada para simular a radiação e campo de temperatura juntamente com o transporte de energia radiativa e condutiva proveniente do escape liberado em lançamentos de foguetes. Para este fim, discutimos uma abordagem semianalítica reduzindo a equação original, que é contínua nas variáveis angulares, numa equação semelhante ao problema SN da transferência radiativa condutiva. A solução é construída usando um método de composição por transformada de Laplace e o método da decomposição de Adomian. O esquema recursivo ´e apresentado para o sistema de equações de ordenadas duplamente discretas juntamente com as dependências dos parâmetros e suas influências sobre a convergência heurística da solução. A solução obtida, em seguida, permite construir o campo próximo relevante para caracterizar o termo fonte para problemas de dispersão ao ajustar os parâmetros do modelo, tais como, emissividade, refletividade, albedo e outros, em comparação com a observação, que são relevantes para os processos de dispersão de campo distante e podem ser manipulados de forma independente do presente problema. Além do método de solução, também relatamos sobre algumas soluções e simulações numéricas. / In this contribution we present a solution for the radiative conductive transfer equation in cylinder geometry. This solution is applied to simulate the radiation and temperature field together with conductive and radiative energy transport originated from the exhaust released in rocket launches. To this end we discuss a semi-analytical approach reducing the original equation, which is continuous in the angular variables, into an equation similar to the SN radiative conductive transfer problem. The solution is constructed using a composite method by Laplace transform and Adomian decomposition method. The recursive scheme is presented for the doubly discrete ordinate equations system together with parameter dependencies and their influence on heuristic convergence of the solution. The obtained solution allows then to construct the relevant near field to characterize the source term for dispersion problems when adjusting the model parameters such as emissivity, reflectivity, albedo and others in comparison to the observation, that are relevant for far field dispersion processes and may be handled independently from the present problem. In addition to the solution method we also report some solutions and numerical simulations.

<p>The Discontinuous Galerkin time domain (DGTD) method is promising in modeling of realistic multiscale electromagnetic systems. This method defines the basic concept for implementing the communication between multiple domains with different scales.</p><p>Constructing a DGTD system consists of several careful choices: (a) governing equations; (b) element shape and corresponding basis functions for the spatial discretization of each subdomain; (c) numerical fluxes onto interfaces to bond all subdomains together; and (d) time stepping scheme based on properties of a discretized</p><p>system. This work present the advances in each one of these steps.</p><p> </p><p>First, a unified framework based on the theory of differential forms and the finite element method is used to analyze the discretization of the Maxwell's equations. Based on this study, field intensities (<bold>E</bold> and <bold>H</bold>) are associated to 1-forms and curl-conforming basis functions; flux densities (<bold>D</bold> and <bold>B</bold>) are associated to 2-forms and divergence-conforming basis functions; and the constitutive relations are defined by Hodge operators.</p><p>A different approach is the study of numerical dispersion. Semidiscrete analysis is the traditional method, but for high order elements modal analysis is prefered. From these analyses, we conclude that a correct discretization of fields belonging to different p-form (e.g., <bold>E</bold> and <bold>B</bold>) uses basis functions with same order of interpolation; however, different order of interpolation must be used if two fields belong to the same p-form (e.g., <bold>E</bold> and <bold>H</bold>). An alternative method to evaluate numerical dispersion based on evaluation of dispersive Hodge operators is also presented. Both dispersion analyses are equivalent and reveal same fundamental results. Eigenvalues, eigenvector and transient results are studied to verify accuracy and computational costs of different schemes. </p><p>Two different approaches are used for implementing the DG Method. The first is based on <bold>E</bold> and <bold>H</bold> fields, which use curl-conforming basis functions with different order of interpolation. In this case, the Riemman solver shows the best performance to treat interfaces between subdomains. A new spectral prismatic element, useful for modeling of layer structures, is also implemented for this approach. Furthermore, a new efficient and very accurate time integration method for sequential subdomains is implemented.</p><p>The second approach for solving multidomain cases is based on <bold>E</bold> and <bold>B</bold> fields, which use curl- and divergence-conforming basis functions, respectively, with same order of interpolation. In this way, higher accuracy and lower memory consumption are obtained with respect to the first approach based on <bold>E</bold> and <bold>H</bold> fields. The centered flux is used to treat interfaces with non-conforming meshes, and both explicit Runge-Kutta method and implicit Crank-Nicholson method are implemented for time integration. </p><p>Numerical examples and realistic cases are presented to verify that the proposed methods are non-spurious and efficient DGTD schemes.</p> / Dissertation

The tree-width and branch-width of a graph are two well-studied examples of parameters that measure how well a given graph can be decomposed into a tree structure. In this thesis we give several results and applications concerning these concepts, in particular if the graph is embedded on a surface. In the first part of this thesis we develop a geometric description of tangles in graphs embedded on a fixed surface (tangles are the obstructions for low branch-width), generalizing a result of Robertson and Seymour. We use this result to establish a relationship between the branch-width of an embedded graph and the carving-width of an associated graph, generalizing a result for the plane of Seymour and Thomas. We also discuss how these results relate to the polynomial-time algorithm to determine the branch-width of planar graphs of Seymour and Thomas, and explain why their method does not generalize to surfaces other than the sphere. We also prove a result concerning the class C_2k of minor-minimal graphs of branch-width 2k in the plane, for an integer k at least 2. We show that applying a certain construction to a class of graphs in the projective plane yields a subclass of C_2k, but also show that not all members of C_2k arise in this way if k is at least 3. The last part of the thesis is concerned with applications of graphs of bounded tree-width to the Traveling Salesman Problem (TSP). We first show how one can solve the separation problem for comb inequalities (with an arbitrary number of teeth) in linear time if the tree-width is bounded. In the second part, we modify an algorithm of Letchford et al. using tree-decompositions to obtain a practical method for separating a different class of TSP inequalities, called simple DP constraints, and study their effectiveness for solving TSP instances.

Neste trabalho desenvolveu-se e implementou-se um modelo computacional paralelo multifísica para a simulação do transporte de substâncias e do escoamento hidrodinâmico, bidimensional (2D) e tridimensional (3D), em corpos de água. Sua motivação está centrada no fato de que as margens e zonas costeiras de rios, lagos, estuários, mares e oceanos são locais de aglomerações de seres humanos, dada a sua importância para as atividades econômica, de transporte e de lazer, causando desequilíbrios a esses ecossistemas. Esse fato impulsiona o desenvolvimento de pesquisas relativas a esta temática. Portanto, o objetivo deste trabalho é o de construir um modelo computacional com alta qualidade numérica, que possibilite simular os comportamentos da hidrodinâmica e do transporte escalar de substâncias em corpos de água com complexa configuração geométrica, visando a contribuir para seu manejo racional. Visto que a ênfase nessa tese são os aspectos numéricos e computacionais dos algoritmos, analisaram-se as características e propriedades numérico-computacionais que as soluções devem contemplar, tais como a estabilidade, a monotonicidade, a positividade e a conservação da massa. As estratégias de soluções enfocam os termos advectivos e difusivos, horizontais e verticais, da equação do transporte. Desse modo, a advecção horizontal é resolvida empregando o método da limitação dos fluxos de Sweby, e o transporte vertical (advecção e difusão) é resolvido com os métodos beta de Gross e de Crank-Nicolson. São empregadas malhas com distintas resoluções para a solução do problema multifísica. O esquema numérico resultante é semi-implícito, computacionalmente eficiente, estável e fornece acurácia espacial e temporal de segunda ordem. Os sistemas de equações resultantes da discretização, em diferenças finitas, das equações do escoamento e do transporte 3D, são de grande porte, lineares, esparsos e simétricos definidos-positivos (SDP). No caso 2D os sistemas são lineares, mas os sistemas de equações para a equação do transporte não são simétricos. Assim, para a solução de sistemas de equações SDP e dos sistemas não simétricos empregam-se, respectivamente, os métodos do subespaço de Krylov do gradiente conjugado e do resíduo mínimo generalizado. No caso da solução dos sistemas 3-diagonal, utiliza-se o algoritmo de Thomas e o algoritmo de Cholesky. A solução paralela foi obtida sob duas abordagens. A decomposição ou particionamento de dados, onde as operações e os dados são distribuídos entre os processos disponíveis e são resolvidos em paralelo. E, a decomposição de domínio, onde obtém-se a solução do problema global combinando as soluções de subproblemas locais. Em particular, emprega-se neste trabalho, o método de decomposição de domínio aditivo de Schwarz, como método de solução, e como pré-condicionador. Para maximizar a relação computação/comunicação, visto que a eficiência computacional da solução paralela depende diretamente do balanceamento de carga e da minimização da comunicação entre os processos, empregou-se algoritmos de particionamento de grafos para obter localmente os subproblemas, ou as partes dos dados. O modelo computacional paralelo resultante mostrou-se computacionalmente eficiente e com alta qualidade numérica. / A multi-physics parallel computational model was developed and implemented for the simulation of substance transport and for the two-dimensional (2D) and threedimensional (3D) hydrodynamic flow in water bodies. The motivation for this work is focused in the fact that the margins and coastal zones of rivers, lakes, estuaries, seas and oceans are places of human agglomeration, because of their importance for economic, transport, and leisure activities causing ecosystem disequilibrium. This fact stimulates the researches related to this topic. Therefore, the goal of this work is to build a computational model of high numerical quality, that allows the simulation of hydrodynamics and of scalar transport of substances behavior in water bodies of complex configuration, aiming at their rational management. Since the focuses of this thesis are the numerical and computational aspects of the algorithms, the main numerical-computational characteristics and properties that the solutions need to fulfill were analyzed. That is: stability, monotonicity, positivity and mass conservation. Solution strategies focus on advective and diffusive terms, horizontal and vertical terms of the transport equation. In this way, horizontal advection is solved using Sweby’s flow limiting method; and the vertical transport (advection and diffusion) is solved with Gross and Crank-Nicolson’s beta methods. Meshes of different resolutions are employed in the solution of the multi-physics problem. The resulting numerical scheme is semi-implicit, computationally efficient, stable and provides second order accuracy in space and in time. The equation systems resulting of the discretization, in finite differences, of the flow and 3D transport are of large scale, linear, sparse and symmetric positive definite (SPD). In the 2D case, the systems are linear, but the equation systems for the transport equation are not symmetric. Therefore, for the solution of SPD equation systems and of the non-symmetric systems we employ, respectively, the methods of Krylov’s sub-space of the conjugate gradient and of the generalized minimum residue. In the case of the solution of 3-diagonal systems, Thomas algorithm and Cholesky algorithm are used. The parallel solution was obtained through two approaches. In data decomposition or partitioning, operation and data are distributed among the processes available and are solved in parallel. In domain decomposition the solution of the global problem is obtained combining the solutions of the local sub-problems. In particular, in this work, Schwarz additive domain decomposition method is used as solution method and as preconditioner. In order to maximize the computation/communication relation, since the computational efficiency of the parallel solution depends directly of the load balancing and of the minimization of the communication between processes, graph-partitioning algorithms were used to obtain the sub-problems or part of the data locally. The resulting parallel computational model is computationally efficient and of high numerical quality.