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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The evolution of computer hardware as well as new applications of mathematical programming techniques, efficiently implemented in many commercial solvers, has given rise to new algorithms called hybrid metaheuristic, which have been applied to solve combinatorial problems. This work presents several approaches which try to deal with the hybridization of local search based metaheuristics with exact algorithms to solve two problems of combinatorial optimization. More specifically, the first problem, capacitated p-median problem, the proposed approach considers heuristic elimination of variable of the original mathematical model, that produce solutions of very good quality in a short amount of time, and a combination with an iterative procedure in which only a certain subset of points is considered. As regards the second problem, unrelated parallel machine scheduling with sequence and machine dependent setup time problem of minimizing makespan, is proposed a mathematical model to search the neighborhood of a solution and identify movement sequences to minimize the objective function. In both cases, mathematical models are solved using a commercial solver. Extensive computational experiments are carried out to demonstrate the good performance of the proposed approaches. / A recente evolução dos computadores como também dos métodos exatos oriundos da programação matemática, muitos destes eficientemente implementados em otimizadores comerciais, propiciou o surgimento de novos algoritmos, denominados metaheurísticas híbridas, que têm sido aplicados para resolução de problemas combinatoriais. Este trabalho apresenta abordagens que hibridizam metaheurísticas baseadas em busca local com algoritmos exatos de programação matemática para resolver dois problemas de otimização combinatória. Mais especificamente, para o primeiro problema, o problema das p-medianas capacitado, a proposta considera a eliminação heurística de variáveis do modelo matemático, que permite a obtenção de soluções de boa qualidade em um curto tempo computacional, e a combinação com um procedimento iterativo no qual apenas um determinado subconjunto de pontos é considerado. No que se refere ao segundo problema, programação de tarefas em máquinas paralelas não relacionadas com tempo de preparação dependente da sequência e da máquina com objetivo de minimizar o tempo de processamento total da máquina com maior carga entre todas (makespan), propõe-se um modelo matemático para varrer a vizinhança de uma solução e identificar sequências de movimentos de tarefas que podem ser aplicadas na respectiva solução de modo a minimizar a função objetivo. Nos dois casos os modelos matemáticos são resolvidos utilizando um otimizador comercial. Extensivos testes computacionais são realizados para demonstrar o bom desempenho das abordagens propostas.

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Indiana University-Purdue University Indianapolis (IUPUI) / Groundwater monitoring networks are subject to change by budgetary actions and stakeholder initiatives that result in wells being abandoned or added. A strategy for network design is presented that addresses the latter situation. It was developed in response to consensus in the state of Indiana that additional monitoring wells are needed to effectively characterize water availability in aquifer systems throughout the state. The strategic methodology has two primary objectives that guide decision making for new installations: (1) purposive sampling of a diversity of environmental variables having relevance to groundwater recharge, and (2) spatial optimization by means of maximizing geographic distances that separate monitoring wells. Design objectives are integrated in a discrete facility location model known as the p-median problem, and solved to optimality using a mathematical programming package.

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[pt] A administração pública possui responsabilidade orçamentária regida por legislações que estabelecem a transparência na adequação dos recursos públicos. Pautado por essas Leis, o orçamento público é composto pelo plano plurianual, diretrizes orçamentárias e orçamentos anuais, que garantem a estimativa de receita a ser aplicada em cada exercício financeiro. É imprescindível que o planejamento de aquisição e de estrutura dos sistemas considerem o momento de restrição orçamentária através dos regulamentos mencionados anteriormente, adicionados à Lei de Responsabilidade Fiscal, que estabelece o teto de gastos e a natureza a ser cumprida na aplicação dos valores. A ação 21A0 destinada ao Sistema de Fardamento Reembolsável, é classificada como investimento, portanto uma despesa discricionária, tendendo a diminuir o recebimento de recursos nos anos seguintes, fazendo-se de grande valor estudos cujo objetivo alcance a diminuição dos gastos para o acompanhamento do cenário nacional. Sendo assim, esta dissertação em uma primeira análise tem a intenção de apresentar uma metodologia através de um modelo matemático da p-Mediana, que indique qual melhor destino a ser enviada uma mercadoria do e-commerce, considerando a origem do usuário, aplicando para isto, a minimização do custo de frete e do custo fixo dos Postos de Venda de Fardamento Reembolsável (PRVF). Em uma segunda análise de sensibilidade, são realizadas rodagens no modelo para apresentar a variação do custo total dos postos a cada fechamento de funcionamento e, então, mostrar qual o número ideal de PRVF que deve ser mantido aberto, para que a Aeronáutica alcance o custo mínimo desta operação. / [en] Public administration has a budgetary responsibility ruled by a legislation which establishes transparency in the adequacy of public resources. Guided by these laws, the public budget is composed of the multi-year plan, budgetary guidelines and annual budgets, which guarantee the estimate of revenue to be applied in each financial year. It is essential that the acquisition planning and the system structure consider the moment of budget restriction through the regulations mentioned above and also the Fiscal Responsibility Law, which establishes the expenditure ceiling and the nature to be complied with in the application of the values. Action 21A0 for the Reimbursable Uniform System is considered an investment, therefore a discretionary expense, tending to reduce the receipt of funds in subsequent years, making studies of great value whose objective is to reduce expenses for monitoring the national scenario. In this regard, this dissertation in a first analysis intends to present a methodology through a p median mathematical model, which indicates the best destination to be sent the e-commerce merchandise, considering the user s origin, applying for this, the minimization of the freight cost and the fixed cost of the Reimbursable Uniform Sale Points. In a second sensitivity analysis, the model is run in order to present the operating cost of the stores based on their closure, and then show the ideal number of PRVF that must be kept open for the Air Force to reach the minimum cost of operation .

Recently, there has been a surge in the research and application of "Green energy" in the United States. This has been driven by the following three objectives: (1) to reduce the nation's reliance on foreign oil, (2) to mitigate emission of greenhouse gas, and (3) to create an economic stimulus within the United States. Switchgrass is the biomass of choice for the Southeastern United States. In this dissertation, we address a feedstock logistics problem associated with the delivery of switchgrass for conversion into biofuel. In order to satisfy the continual demand of biomass at a bioenergy plant, production fields within a 48-km radius of its location are assumed to be attracted into production. The bioenergy plant is expected to receive as many as 50-400 loads of biomass per day. As a result, an industrialized transportation system must be introduced as early as possible in order to remove bottlenecks and reduce the total system cost. Additionally, we assume locating multiple bioenergy plants within a given region for the production of biofuel. We develop mixed integer programming formulations for the feedstock logistics problem that we address and for some related problems, and we solve them either through the use of decomposition-based methods or directly through the use of CPLEX 12.1.0. The feedstock logistics problem that we address spans the entire system-from the growing of switchgrass to the transporting of bio-crude oil, a high energy density intermediate product, to a refinery for conversion into a final product. To facilitate understanding, we present the reader with a case study that includes a preliminary cost analysis of a real-life-based instance in order to provide the reader appropriate insights of the logistics system before applying optimization techniques for its solution. First, we consider the benefits of active versus passive ownership of the production fields. This is followed by a discussion on the selection of baler type, and then, a discussion of contracts between various business entities. The advantages of storing biomass at a satellite storage location (SSL) and interactions between the operations performed at the production field with those performed at the storage locations are then established. We also provide a detailed description of the operations performed at a SSL. Three potential equipment options are presented for transporting biomass from the SSLs to a utilization point, defined in this study as a Bio-crude Plant (BcP). The details of the entire logistics chain are presented in order to highlight the need for making decisions in view of the entire chain rather than basing them on its segments. We model the feedstock logistics problem as a combination of a 2-level facility location-allocation problem and a multiple traveling salesmen problem (mATSP). The 2-level facility location-allocation problem pertains to the allocation of production fields to SSLs and SSLs to one of the multiple bioenergy plants. The mATSP arises because of the need for scheduling unloading operations at the SSLs. To this end, we provide a detailed study of 13 formulations of the mATSP and their reformulations as ATSPs. First, we assume that the SSLs are always full, regardless of when they are scheduled to be unloaded. We, then, relax this assumption by providing precedence constraints on the availability of the SSLs. This precedence is defined in two different ways and, is then, effectively modeled utilizing all the formulations for the mATSP and ATSP. Given the location of a BcP for the conversion of biomass to bio-crude oil, we develop a feedstock logistics system that relies on the use of SSLs for temporary storage and loading of round bales. Three equipment systems are considered for handling biomass at the SSLs, and they are either placed permanently or are mobile, and thereby, travel from one SSL to another. We use a mathematical programming-based approach to determine SSLs and equipment routes in order to minimize the total cost incurred. The mathematical program is applied to a real-life production region in South-central Virginia (Gretna, VA), and it clearly reveals the benefits of using SSLs as a part of the logistics system. Finally, we provide a sensitivity analysis on the input parameters that we used. This analysis highlights the key cost factors in the model, and it emphasizes areas where biggest gains can be achieved for further cost reduction. For a more general scenario, where multiple BcPs have to be located, we use a nested Benders' decomposition-based method. First, we prove the validity of using this method. We, then, employ this method for the solution of a potential real-life instance. Moreover, we successfully solve problems that are more than an order of magnitude larger than those solved directly by CPLEX 12.1.0. Finally, we develop a Benders' decomposition-based method for the solution of a problem that gives rise to a binary sub-problem. The difficulty arises because of the sub-problem being an integer program for which the dual solution is not readily available. Our approach consists of first solving the integer sub-problem, and then, generating the convex hull at the optimal integer point. We illustrate this approach for an instance for which such a convex hull is readily available, but otherwise, it is too expensive to generate for the entire problem. This special instance is the solution of the mATSP (using Benders' decomposition) for which each of the sub-problems is an ATSP. The convex hull for the ATSP is given by the Dantzig, Fulkerson, and Johnson constraints. These constraints at a given integer solution point are only polynomial in number. With the inclusion of these constraints, a linear programming solution and its corresponding dual solution can now be obtained at the optimal integer points. We have proven the validity of using this method. However, the success of our algorithm is limited because of a large number of integer problems that must be solved at every iteration. While the algorithm is theoretically promising, the advantages of the decomposition do not seem to outweigh the additional cost resulting from solving a larger number of decomposed problems. / Ph. D.