Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-03-10T13:26:21Z No. of bitstreams: 1 jorgefelipebarbosamota.pdf: 2249566 bytes, checksum: 432c0da8b02f3dd942bb9fb9af4add75 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-03-13T18:36:13Z (GMT) No. of bitstreams: 1 jorgefelipebarbosamota.pdf: 2249566 bytes, checksum: 432c0da8b02f3dd942bb9fb9af4add75 (MD5) / Made available in DSpace on 2017-03-13T18:36:13Z (GMT). No. of bitstreams: 1 jorgefelipebarbosamota.pdf: 2249566 bytes, checksum: 432c0da8b02f3dd942bb9fb9af4add75 (MD5) Previous issue date: 2016-09-09 / As concessionárias de energia são obrigadas a aplicar parte de sua receita operacional líquida na execução de projetos de eficiência energética, de acordo com a Agência Nacional de Energia Elétrica (ANEEL). O projeto do tipo baixa renda é parte desse portfólio de projetos possíveis e capta a maior parte dessa aplicação. Dessa forma, torna-se de suma importância a criação de uma metodologia para dimensionar os projetos dessa tipologia e direcionar as tomadas de decisões das concessionárias de energia do Brasil. Métodos de otimização bioinspirados tratam de problemas combinatórios e não lineares, caso do equacionamento matemático do cálculo da relação custo benefício de projetos de eficiência energética de tipologia baixa renda. O presente trabalho propõe a aplicação de dois métodos de otimização reconhecidos, a otimização por colônia de formigas, ou Ant Colony Optimization (ACO), e a otimização por enxame de partículas, ou Particle Swarm Optimization (PSO), para calcular e otimizar a relação custo benefício de projetos de eficiência energética regulatórios do tipo baixa renda. Sendo assim, aplica métodos computacionais bioinspirados no dimensionamento dos projetos de eficiência energética, além de otimizar esses projetos, obtendo o melhor resultado operacional, do ponto de vista da eficiência energética, com o melhor custo para a sociedade. / The electricity utilities are required to invest part of its net operating income in the implementation of energy efficiency projects, according to the National Electric Energy Agency (ANEEL). The low-income type design is part of portfolio of possible projects and captures most of this application. Thus, it becomes very important to create a methodology to scale projects of this type and direct decision making of utilities in Brazil. Bioinspired optimization methods deal with combinatorial and nonlinear problems, if the mathematical equations for calculating the cost benefit rate of energy efficiency projects in low-income type. This paper proposes two recognized bioinspired optimization methods, the Ant Colony Optimization (ACO) and the Particle Swarm Optimization (PSO) to calculate and optimize the cost effectiveness of energy efficiency regulatory projects, the low-income type. Thus, propose a scientific methods of sizing of the energy efficiency projects, while optimizing these projects, obtaining the best operating result, from the point of view of energy efficiency with the best cost to society.

The development of a shape optimization solver using the existing Computational Fluid Dynamics (CFD) codes is taken up as topic of research in this thesis. A shape optimizer was initially developed based on Genetic Algorithm (GA) coupled with a CFD solver in an earlier work. The existing CFD solver is based on Kinetic Flux Vector Splitting and uses least squares discretization. This solver requires a cloud of points and their connectivity set, hence this CFD solver is a meshless solver. The advantage of a meshless solver is utilised in avoiding re-gridding (only connectivity regeneration is required) after each shape change by the shape optimizer. The CFD solver is within the optimization loop, hence evaluation of CFD solver after each shape change is mandatory. Although the earlier shape optimizer developed was found to be robust, but it was taking enoromous amount of time to converge to the optimum solution (details in Appendix). Hence a new evolving method, Ant Colony Optimization (ACO), is implemented to replace GA. A shape optimizer is developed coupling ACO and the meshless CFD solver. To the best of the knowledge of the present author, this is the first time when ACO is implemented for aerodynamic shape optimization problems. Hence, an exhaustive validation has become mandatory. Various test cases such as regeneration problems of (1) subsonic - supersonic nozzle with a shock in quasi - one dimensional flow (2) subsonic - supersonic nozzle in a 2-dimensional flow field (3) NACA 0012 airfoil in 2-dimensional flow and (4) NACA 4412 airfoil in 2-dimensional flow have been successfully demonstrated. A comparative study between GA and ACO at algorithm level is performed using the travelling salesman problem (TSP). A comparative study between the two shape optimizers developed, i.e., GA-CFD and ACO-CFD is carried out using regeneration test case of NACA 4412 airfoil in 2-dimensional flow. GA-CFD performs better in the initial phase of optimization and ACO-CFD performs better in the later stage. We have combined both the approaches to develop a hybrid GA-ACO-CFD solver such that the advantages of both GA-CFD and ACO-CFD are retained with the hybrid method. This hybrid approach has 2 stages, namely, (Stage 1) initial optimum search by GA-CFD (coarse search), the best members from the optimized solution from GA-CFD are segregated to form the input for the fine search by ACO-CFD and (Stage 2) final optimum search by ACO-CFD (fine search). It is observed that this hybrid method performs better than either GA-CFD or ACO- CFD, i.e., hybrid method attains better optimum in less number of CFD calls. This hybrid method is applied to the following test cases: (1) regeneration of subsonic-supersonic nozzle with shock in quasi 1-D flow and (2) regeneration of NACA 4412 airfoil in 2-dimensional flow. Two applications on shape optimization, namely, (1) shape optimization of a body in strongly rotating viscous flow and (2) shape optimization of a body in supersonic flow such that it enhances separation of binary species, have been successfully demonstrated using the hybrid GA-ACO-CFD method. A KFVS based binary diffusion solver was developed and validated for this purpose. This hybrid method is now in a state where industrial shape optimization applications can be handled confidently.

Dans ce mémoire, nous nous intéressons à l’optimisation des mouvements improductifs de chargement/déchargement, appelés shiftings, dans les problèmes de transport. Dans le premier contexte,nous introduisons le problème de shifting dans le cas du voyageur de commerce. Notre objectif est de chercher un circuit hamiltonien qui optimise à la fois le coût distance et le coût shifting. Nous proposons une modélisation mathématique du problème, puis, nous adaptons la métaheuristique d’optimisation par colonies de fourmis sous sa forme séquentielle et parallèle pour le résoudre. Dans le deuxième contexte, nous abordons le problème d’optimisation des plans de chargement et d’arrimage des conteneurs dans des barges. Ce problème consiste à chercher l’emplacement le plus convenable de chaque conteneur dans les barges de façon à faciliter son déchargement dans la chronologie des ports à visiter. D'abord, nous introduisons une modélisation mathématique du problème dans le cas d’une seule barge ou différents ports du trajet ont des coûts shiftings non-uniformes. L’objectif est d’optimiser le coût total de shiftings, la stabilitélongitudinale de la barge et celle transversale. Ensuite, nous généralisons le problème au cas d’un système de convoi de barges. Nous proposons, d’abord, un modèle mathématique en nombres entiers, dans lequel, nous considérons l’aspect multi-objectif en optimisant le nombre de shiftings, la stabilité du convoi et le nombre de barges utilisées dans le convoi. Puis, nous adaptons la méthode nsga-II en se basant sur les heuristiques du problème de bin-packing.L'ensemble des résultats obtenus est évalué en utilisant des mesures de performances adaptées au problème. / This work outlines the optimization of unproductive loading/unloading movements, called shiftings, in transport problems. in the first context, we introduce the shifting in the case of the traveling salesman problem. our goal is to find a hamiltonian circuit that optimizes both distance and shifting costs. we propose a mathematical modeling of the problem, and then we adapt the ant colony optimization metaheuristic in its sequential and parallel form to solve it. in the second context, we address the 3d container stowage planning problem of barges. this problem consists in finding the most suitable location of each container in the barge in order to facilitate its retrieval in the chronology of ports to be visited. firstly, we introduce a mathematical modeling of the problem in the case of a single barge where different ports are of non-uniform operational costs. the main objective is to optimize the total shiftings fees, the longitudinal stability of the barge and the transverse one. then, we generalize our problem to the case of barge convoy systems. we first propose a suitable mathematical modeling, in which, we consider the multi-objective aspect by optimizing the total number of shiftings, the convoy stability and the number of the real-used barges in the convoy. in order to solve this new variant, we propose a novel adaptation of the multi-objective evolutionary algorithm nsga-ii (non-dominated sorting genetic algorithm-ii) based on a set of heuristics introduced by the bin-packing problem resolution methods. the numerical results are evaluated using performance measures adapted to theproblem.

No description available.

[pt] Este trabalho tem como objetivo principal a aplicação do método híbrido dos elementos de contorno a problemas da mecânica da fratura linearmente elástica. São apresentados os desenvolvimentos de várias formulações e os principais aspectos das implementações computacionais referentes a cada uma delas. A consistência mecânica do método híbrido dos elementos de contorno facilita sobremaneira a compreensão dos diversos fatores envolvidos em sua aplicação à mecânica da fratura. Isto ocorre porque o apelo físico do método garante a interpretação adequada dos problemas presentes na análise dos mais diversos fenômenos da mecânica do contínuo. A contribuição mais relevante deste trabalho consiste na determinação de maneira rápida e direta do fator de intensidade de tensão em estruturas bidimensionais da elasticidade plana. Os efeitos de abertura e deslizamento das faces da trinca são considerados a partir da introdução de uma solução fundamental hipersingular, cujo entendimento físico é facilitado devido à consistência variacional do método híbrido. É proposta a utilização de uma função de Green, referente à série de Williams, nos nós do modelo estrutural correspondentes às pontas das trincas. Esta sistemática introduz os fatores de intensidade de tensão, modos I e II, como incógnitas do problema, sendo obtidos a partir da resolução do sistema de equações provenientes do método. Durante todo o desenvolvimento, são mostrados vários exemplos que validam e comprovam a aplicabilidade das formulações propostas, demonstrando a potencialidade do método quando aplicado à mecânica da fratura. / [en] Aim of this work is the application of the hybrid boundary element method to problems of the linear elastic fracture mechanics. Several formulations are introduced and the most relevant aspects of computational implementation are discussed. The mechanical consistency of the hybrid boundary element method enables the adequate mathematical description of the stress field related to a cracked continuum. The main attempt of this dissertation is to develop a computationally simples and fast procedure for the determination of stress intensity factors in two- dimensional elasticity. The effects of opening and sliding of the crack surfaces are considered by means of a hipersingular stress function, which are dealt with adequately in the frame of the variational formulation. It is shown that the stress series proposed by Williams for the local field around a crack tip may be considered as a Green´s function. As a consequence, the stress intensity factors corresponding to both Modes I and II are obtained as primary unknowns of the problem. Several numerical examples are presented in order top validate the formulations proposed. This shows the potentiality of the hybrid boundary element method for dealing with problems of the fracture mechanics. / [es] Este trabajo tiene como objetivo principal la aplicación del método híbrido de los elementos de contorno a problemas de mecánica de fracturas linealmente elásticas. Se describen varias formulaciones y los principales aspectos de su implementación computacional. La consistencia mecánica del método híbrido de los elementos de contorno facilita la comprensión de los diversos factores involucrados en su aplicación a la mecánica de fracturas. Esto ocurre porque el caracter físico del método garantiza la interpretación adecuada de los problemas que se presentan en el análisis de los más diversos fenómenos de la mecánica del contínuo. La contribuición más relevante de este trabajo consiste en la determinación de manera rápida y directa del factor de intensidad de tensión en extructuras bidimensionales de elasticidad plana. Son considerados los efectos de abertura y deslizamiento de las caras de la trinca a partir de la introducción de una solución fundamental hipersingular, cuya comprensión física se facilita debido a la consistencia variacional del método híbrido. Se propone la utilización de una función de Green, de la serie de Williams, en los nodos del modelo extructural correspondiente a las puntas de las trincas. Esta sistemática introduce los factores de intensidad de tensión, modos I y II, como incógnitas del problema, y se obtienen a partir de la resolución del sistema de ecuaciones provenientes del método. Durante todo el desarrollo, se muestran varios ejemplos que evalúan y comprueban la aplicabilidad de las formulaciones propuestas, demostrando la potencialidad del método cuando se aplica a la mecánica de fracturas.

Made available in DSpace on 2017-07-21T20:42:28Z (GMT). No. of bitstreams: 1 Selauco Vurobi Junior.pdf: 11393281 bytes, checksum: a1e8a368c73edec5e283ae8d58f5a808 (MD5) Previous issue date: 2007-12-13 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A Modified SAE 4118H steel was submitted to different isothermal treatments, between 700 and 400ºC for each 50ºC range, in order to evaluate the decomposition of austenite under constant temperature. The austenitization was conducted under vacuum air pressure of 10-2 atm during 15 minutes. Then, each sample was transferred to an isothermal bath stabilized in the temperature of interest. The time of each treatment was varied from 15 to 28800 seconds depending on the temperature of treatment. After each time of treatment specimens were quenched in stirred brine in order to stop transformation. After standard metallographic preparation, samples were etched with color etchants. With these reagents, the different microconstituintes of Modified SAE 4118H steel obtained after each isothermal treatment had excellent contrast. The volumetric fractions of microconstituintes were determined by systematic manual point count. For heat treated samples between 700 and 550ºC, the Modified SAE 4118H steel presented microstructure consisting of ferrite and pearlite. The bainitic microstructure formation was detected in 500 and 400ºC range. The rate of transformation of Modified SAE 4118H steel was compared with the DIN 25CrMo4 steel, because of the similarity of composition. The Modified SAE 4118H steel presented pearlite transformation faster than the DIN 25CrMo4 steel and bainitic reaction at lowest temperatures. Reducing the temperature of treatment more refined microstructures was provided, which raised the hardness levels of the Modified SAE 4118H steel. / Um aço SAE 4118H Modificado foi submetido a tratamentos isotérmicos entre 700 e 400ºC a cada 50ºC de intervalo, com a intenção de se avaliar a decomposição da austenita sob temperatura constante. Para tanto, o aço foi austenitizado sob vácuo de aproximadamente 10-2 atm durante 15 minutos. Na seqüência, transferiu-se cada amostra para um banho isotérmico estabilizado na temperatura de interesse. Variou-se o tempo de permanência sob tratamento isotérmico de 15 a 28800 segundos em função da temperatura de tratamento. Após o período de tratamento isotérmico cada amostra foi temperada em salmoura agitada para que fossem interrompidas as transformações. Após preparação metalográfica padrão, as amostras foram atacadas com reagentes de metalografia colorida. Com estes reagentes, conseguiu-se excelente contraste entre os diferentes microconstituintes do aço SAE 4118H Modificado, obtidos após cada tratamento isotérmico. As frações volumétricas dos microconstituintes formados foram determinadas por meio da contagem sistemática manual de pontos. Entre as Temperaturas de 700 e 550ºC o aço SAE 4118H Modificado apresentou microestrutura composta por ferrita e perlita. Entre 500 e 400ºC a microestrutura bainítica foi formada. As velocidades de transformação do aço SAE 4118H Modificado foram comparadas com aquelas apresentadas pelo aço DIN 25CrMo4, utilizado para a comparação devido à similaridade de composição. O aço SAE 4118H Modificado apresentou transformação perlítica mais rápida que o aço DIN 25CrMo4 e transformação bainítica a mais baixas temperaturas. A redução da temperatura de tratamento proporcionou microestruturas mais refinadas, o que elevou os níveis de dureza do aço SAE 4118H Modificado.

Made available in DSpace on 2017-07-21T20:42:31Z (GMT). No. of bitstreams: 1 Denilson Aguiar.pdf: 7080788 bytes, checksum: 4859e2e6937c1b476dd432e9c7fb708b (MD5) Previous issue date: 2009-10-17 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The proposal of the present work is the processing of UNS S32520 commercial duplex stainless steel by high energy milling. First, using hardness by microindentation, optical and scanning electron microgaphies tests, was studied the influence of annealing between 400ºC and 1000ºC, with aim in α’- phase and σ-phase precipitation. For it, was taken some samples from commercial stainless steel sheet and comparing with and without annealing condition. Moreover, turning chips were machined from the sheet and then embbrietled isothermically at 475 ºC, for α’-phase precipitation and at 800 ºC, for σ-phase precipitation. Later, these turning chips were processing in Spex and Attritor types of high energy milling. Some powders were achieved which were conformed in green compacts by cold pressure. The green compacts were sintered at 1200ºC for several times. The characterizations by optical and scanning electron microscopy showed grains microstructure with morphologies less oriented than as-received material, where were influenced by type of milling machine and time of sintering. / A proposta do presente trabalho é o processamento de um aço inoxidável comercial superdúplex tipo UNS S32520 por meio de moagem de alta energia. Inicialmente, utilizando-se de análises de dureza pela microimpressão do penetrador e micrografias óptica e eletrônica de varredura, realizou-se o estudo da influência do envelhecimento entre temperaturas de 400ºC a 1000ºC, objetivando a precipitação das fases α’ e σ. Para isso, tomaram-se amostras de uma chapa comercial do referido aço e foram comparadas as condições de envelhecimento com a amostra sem evelhecimento. Em seguida, extraíram-se pequenos cavacos do aço, os quais foram fragilizados isotermicamente nas temperaturas de 475ºC, para precipitação da fase α’, e 800ºC, para precipitação da fase σ. Posteriormente, realizou-se processamento em moinhos de alta energia dos tipos Spex e Attritor. Os pós obtidos foram conformados a frio em pastilhas e posteriormente sinterizados em 1200ºC com tempos variados. As caracterizações por micrografias óptica e eletrônica de varredura do material obtido revelaram microestrutura dúplex com grãos refinados com morfologia menos orientada que o material como recebido, os quais se apresentaram dependentes do tipo de moinho usado e tempo de sinterização.

Combinatorial optimisation problems (COPs) pervade human society: scheduling, design, layout, distribution, timetabling, resource allocation and project management all feature problems where the solution is some combination of elements, the overall value of which needs to be either maximised or minimised (i.e., optimised), typically subject to a number of constraints. Thus, techniques to efficiently solve such problems are an important area of research. A popular group of optimisation algorithms are the metaheuristics, approaches that specify how to search the space of solutions in a problem independent way so that high quality solutions are likely to result in a reasonable amount of computational time. Although metaheuristic algorithms are specified in a problem independent manner, they must be tailored to suit each particular problem to which they are applied. This thesis investigates a number of aspects of the application of the relatively new Ant Colony Optimisation (ACO) metaheuristic to different COPs.The standard ACO metaheuristic is a constructive algorithm loosely based on the foraging behaviour of ant colonies, which are able to find the shortest path to a food source by indirect communication through pheromones. ACO’s artificial pheromone represents a model of the solution components that its artificial ants use to construct solutions. Developing an appropriate pheromone representation is a key aspect of the application of ACO to a problem. An examination of existing ACO applications and the constructive approach more generally reveals how the metaheuristic can be applied more systematically across a range of COPs. The two main issues addressed in this thesis are biases inherent in the constructive process and the systematic selection of pheromone representations.The systematisation of ACO should lead to more consistently high performance of the algorithm across different problems. Additionally, it supports the creation of a generalised ACO system, capable of adapting itself to suit many different combinatorial problems without the need for manual intervention.

Combinatorial optimisation problems (COPs) pervade human society: scheduling, design, layout, distribution, timetabling, resource allocation and project management all feature problems where the solution is some combination of elements, the overall value of which needs to be either maximised or minimised (i.e., optimised), typically subject to a number of constraints. Thus, techniques to efficiently solve such problems are an important area of research. A popular group of optimisation algorithms are the metaheuristics, approaches that specify how to search the space of solutions in a problem independent way so that high quality solutions are likely to result in a reasonable amount of computational time. Although metaheuristic algorithms are specified in a problem independent manner, they must be tailored to suit each particular problem to which they are applied. This thesis investigates a number of aspects of the application of the relatively new Ant Colony Optimisation (ACO) metaheuristic to different COPs.The standard ACO metaheuristic is a constructive algorithm loosely based on the foraging behaviour of ant colonies, which are able to find the shortest path to a food source by indirect communication through pheromones. ACO’s artificial pheromone represents a model of the solution components that its artificial ants use to construct solutions. Developing an appropriate pheromone representation is a key aspect of the application of ACO to a problem. An examination of existing ACO applications and the constructive approach more generally reveals how the metaheuristic can be applied more systematically across a range of COPs. The two main issues addressed in this thesis are biases inherent in the constructive process and the systematic selection of pheromone representations.The systematisation of ACO should lead to more consistently high performance of the algorithm across different problems. Additionally, it supports the creation of a generalised ACO system, capable of adapting itself to suit many different combinatorial problems without the need for manual intervention.

[pt] A seleção de materiais para o transporte de óleo e gás não é feita pela sua resistência à corrosão, mas sim pelas suas boas propriedades mecânicas, facilidade de fabricação e baixos custos. Devido às taxas de perda de material, causado pela corrosão interna, existe necessidade em se conhecer o comportamento dos aços de mais alta resistência, utilizados especialmente em gasodutos e oleodutos tais como API 5L X70 e API 5L X80. Um dos elementos responsáveis pela corrosão interna é o dióxido de carbono (CO2). O principal produto de corrosão da reação deste gás com o aço é um precipitado de carbonato de ferro que em determinada temperatura se acredita poder retardar o processo de corrosão, agindo como uma barreira à difusão das espécies. Neste trabalho foi estudado o comportamento destes aços numa solução de 1% NaCl contendo CO2, e a estabilidade do filme formado (FeCO3) à diferentes temperaturas. Técnicas de análise eletroquímicas como: curvas de polarização, resistência à polarização linear e de impedância eletroquímica foram usadas para estudar a formação do filme de carbonato de ferro sobre a superfície dos aços. O filme também foi observado e caracterizado por microscópio eletrônico de varredura (MEV) e difração de raios-X. / [en] The selection of materials for the transport of oil and gas, is not always made sufficiently emphasizing corrosion resistance, but rather good mechanical properties, ease of fabrication and low cost. Due to the material loss rates resulting from internal corrosion, it becomes necessary to thoroughly characterize the behaviour of the high strength steels which are used for oil and gas pipelines, such as API 5L X70 and API 5L X80. One the contributing factors responsible for internal corrosion is carbon dioxide (CO2). The main corrosion product resulting from the action of this gas, in solution, on the steel is an iron carbonate precipitate which is believed to retard further corrosion at some temperatures, acting as a diffusion barrier to the chemical species involved. The current work studies the behaviour of the above steels in a 1% NaCl solution containing CO2, and the stability of the FeCO3 film formed at different temperatures. Electrochemical analysis techniques, such as polarization curves, linear polarization resistance and impedance measurements were used to study the formation of the iron carbonate film on the surface of the steels. The film was also observed and characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD).