In this thesis, a resource allocation problem in OFDMA is studied for the energy efficiency of wireless network. The objective is to minimize the total energy consumption which includes transmission energy consumption, and circuit energy consumption at both transmitter and receiver with required per user’s rate constraint. For problem solution, a heuristic algorithm with low computational complexity and suboptimal solution is proposed, developed in two steps with an increasing order of complexity. Besides, a bounding scheme based on model linearization of formulated nonlinear system model is also proposed to give lower and upper bounds for both small- and large-scale OFDMA network for further algorithm performance evaluation, while the implemented exhaustive search is only capable to provide the optimal solution for small-scale instance for algorithm performance evaluation. Numerical results show that the proposal heuristic algorithm can achieve near-optimal performance with applicable computational complexity even for large-scale networks, and that the bounds from the bounding scheme are very tight for both small- and large-scale OFDMA networks.

In this research, a decision support model for coordinating sustainable product and supply chain design decisions is developed using a multi-stage hierarchical approach. The model evaluates alternate product designs and their corresponding supply chain configurations to identify the best product design and the corresponding supply chain configuration that maximizes the economic, environmental and societal benefits. The model considers a total life-cycle approach and incorporates closed-loop flow among multiple product lifecycles. In the first stage, a mixed integer linear programming model is developed to select for each product design an optimal supply chain configuration that maximizes the profit. In the subsequent stages, the economic, environmental and societal multiple life-cycle analysis models are developed which assess the economic, environment and the societal performance of each product design and its optimal supply chain configuration to identify the best product design with highest sustainability benefits. The decision support model is applied for an example problem to illustrate the procedure for identifying the best sustainable design. Later, the model is applied for a real-time refrigerator case to identify the best refrigerator design that maximizes economic, environmental and societal benefits. Further, sensitivity analysis is performed on the optimization model to study the closed-loop supply chain behavior under various situations. The results indicated that both product and supply chain design criteria significantly influence the performance of the supply chain. The results provided insights into closed-loop supply chain models and their behavior under various situations. Decision support models such as above can help a company identify the best designs that bring highest sustainability benefits, can provide a manager with holistic view and the impact of their design decisions on the supply chain performance and also provide areas for improvement.

Numerous studies have been done in the area of nurse scheduling, since this is a complex area with a lot of aspects that has to be taken into account. An interesting but little studied subject is how the requirements for the scheduling affect the possibility to construct a feasible schedule, or how the requirements affect the quality of the schedule. Of special interest is the effect of the composition of the workforce and of the change in scheduling rules. What is missing is results showing which composition and changes that are possible, and if so what is needed to be able to follow through with them. The changes tested in our simulation study are changes that is up for discussion at many wards in Sweden today, with topics such as split shifts and high part-time work percentages within the staff. In order to simulate various scheduling requirements and changes, an integer linear model for creating nurse schedules is developed. The results provide some insight into the dependence between scheduling requirements and the resulting schedules. In particular our simulation results indicate that there is an inherent conflict between high part-time work percentages and split or long work shifts. Our results can be used as a basis for future research on these topics in the area of nurse scheduling.

[pt] As despesas anuais em saúde para a maioria dos países são crescentes. Segundo a Organização Mundial de Saúde (OMS), em 2011 o Brasil gastou aproximadamente 10 porcento do produto interno bruto em saúde. Consequentemente, incrementar a eficiência na prestação de serviços médicos está se tornando cada vez mais importante. Em um hospital as salas de cirurgia representam um dos principais centros de custos e de rendimentos. As salas de cirurgia são um aspecto difícil de gerenciar devido à prioridade das partes envolvidas no processo, nomeadamente, pacientes, cirurgiões, staff, pessoal administrativo, e a escassez de recursos como leitos, salas de cirurgia, equipamentos especiais, etc. A presente dissertação aborda um problema real de programação de salas de cirurgia para pacientes eletivos de um hospital em Lisboa, onde é proposta uma reformulação do modelo de PLI proposto por Marques et al. (2012). Esta reformulação é baseada no problema da mochila, com o objetivo de encontrar soluções mais eficientes em termos computacionais. De acordo com os testes realizados, uma modificação no modelo que quebre sua simetria além de fornecer uma solução mais eficiente computacionalmente, melhora a solução original pois diminui o gap inicial de 782,59 porcento para 2,25 porcento. Também foi proposto um modelo de simulação no que foram criados vários cenários para avaliar a incerteza envolvida, nos quais a duração média das cirurgias foi submetida a valores majorados. Esta simulação pode servir como ferramenta de apoio na tomada de decisões, pois de acordo com o grau de conservadorismo de quem toma as decisões, podem ser estabelecidas políticas de programação das Salas de Cirurgia. / [en] For most countries annual health expenditures are increasing. According to the World Health Organization (WHO), in 2011, Brazil expends about 10 percent of its gross domestic product on health. Hence, improving health care efficiency is becoming increasingly important. Within a hospital, the Operating Rooms represent a major cost and incomes center. Operating Rooms are a difficult aspect to manage because many stakeholders involved in the process, namely, patients, surgeons, staff, hospital manager, and the scarcity of resources like beds, operating rooms, especial equipment, etc. This dissertation deals with a real problem of operating rooms programming for elective patients in a Lisbon hospital. For this problem, we propose a reformulation of the integer programming model proposed by Marques et al. (2012). This reformulation is based on the knapsack problem, in order to find a more efficient solution in terms of time. According to tests carried out, a reformulation in the model that breaks symmetry, computationally provides a more efficient solution and enhance the original solution because it reduces the initial gap from 782.59 percent to 2.25 percent. In addition, a simulation model was proposed to create various scenarios to assess the involved uncertainty, mainly due to surgery duration variation. This simulation can serve as a support tool in decision-making, according to the degree of conservatism of the decision maker, Operating Rooms scheduling policies can be established.

Made available in DSpace on 2014-06-11T19:30:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-08-14Bitstream added on 2014-06-13T20:20:28Z : No. of bitstreams: 1 rodriguez_lao_me_guara.pdf: 898092 bytes, checksum: 45f1b8e53bd80272f863dee05c614945 (MD5) / Para enfrentar os problemas do atual mundo globalizado e para se manter em atividade, as empresas vêm sendo obrigadas a empregar, em seu dia-a-dia, novos instrumentos de trabalho. A Teoria das Restrições, a Programação Linear Inteira e a Simulação de Sistemas surgem como potenciais ferramentas no auxílio à identificação e à solução dos problemas enfrentados pelas empresas nos dias de hoje. Este trabalho teve por objetivo principal desenvolver um método de planejamento e gerenciamento da produção, integrando essas três ferramentas. O método foi aplicado na linha de produção da Unidade de Cilindros para Laminação da empresa Aços Villares S/A com o intuito de melhorar o fluxo de produção e o cumprimento do prazo de liberação do produto entre as suas diversas áreas. Ao final do trabalho, concluiu-se que o referido método, além de facilitar e simplificar o processo de modelagem permite realizar análises mais aprofundadas do sistema real, em relação às que seriam conseguidas com a utilização das técnicas citadas, isoladamente. / In order to face the issues of the current globalized world and in order to keep working, companies have been pushed to put in practice new working tools. The Theory of Constraints, the Integer Linear Programming and the Systems Simulation appear as potential tools to support problem identification and solution which are faced by companies nowadays. This work aims to develop a planning and management method of production integrating these three tools. The method was applied to the production line at Aços Villares S/A Rolling Mill Roll Unit aiming at improving the production flow and the accomplishment of product liberation deadline among its many areas. At the end of this work, it has been concluded that the referred method, besides facilitating and simplifying the modeling process, it allows to achieve deeper analyses of the real system in relation to those which would be reached with the isolated mentioned techniques.

A localização de fábricas, fornecedores e/ou CDs é um problema de grande complexidade, principalmente em empresas com operações internacionais. Na literatura mundial são poucos os modelos desenvolvidos que tratam da localização de instalações em escala global. Este trabalho propõe um modelo de Programação Linear Inteira Mista que soluciona o problema minimizando os custos logísticos (custos fixos, custos de transferência, custos de distribuição, impostos não recuperáveis, estoques, take-or-pay, matéria-prima e custos de agregação de valor e transbordo) levando em consideração vários elos da cadeia de suprimentos. Como principais contribuições do modelo citam-se a inclusão de benefícios fiscais em transações internacionais, tais como o drawback, o cálculo pioneiro para custo no carregamento dos estoques e o tratamento dado aos custos tipo take-or-pay. São sugeridas adaptações do modelo para utilização em quaisquer segmentos de indústria. O modelo foi aplicado com sucesso em um caso real de uma indústria do segmento químico. / The location of factories, suppliers and distribution centers has always been a problem of great complexity, mainly for companies with global operations. In the literature, there are a few models developed for facilities location in a global scale. This work proposes a Mixed Integer Linear Programming model that solves the problem minimizing the total logistic cost (fixed, transfer and distribution costs, non recoverable duties, carrying, take-or-pay, raw material, added value and handling costs) taking into consideration several echelons in the supply chain network. The main contributions of the proposed model are the considerations regarding fiscal benefits in international trade such as drawback, the pioneer carrying cost calculation and the treatment given to the take-or-pay costs. Some adaptations of the model have been suggested for use in any type of industry. The model was successfully applied in a real case of a chemical industry.

Submitted by Marlene Santos (marlene.bc.ufg@gmail.com) on 2016-08-22T17:32:01Z No. of bitstreams: 2 Dissertação - Raina Ribeiro Marques - 2016.pdf: 13527010 bytes, checksum: 59c283fc484a08da24fa8c5c822eeeb3 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-08-23T11:54:05Z (GMT) No. of bitstreams: 2 Dissertação - Raina Ribeiro Marques - 2016.pdf: 13527010 bytes, checksum: 59c283fc484a08da24fa8c5c822eeeb3 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-08-23T11:54:05Z (GMT). No. of bitstreams: 2 Dissertação - Raina Ribeiro Marques - 2016.pdf: 13527010 bytes, checksum: 59c283fc484a08da24fa8c5c822eeeb3 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-07-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The robust optimization techniques can be used in problems subject to uncertainty in order to obtain robust solutions, that is, solutions that are less sensitive to the problem variations. Problems such as the facility location, specifically, the location of ambulances, have uncertainty in your data. Thus, an integer linear programming model for allocation of ambulances and stations is investigated considering that the service time is an uncertainty parameter, since this parameter is influenced by the nature of the call, traffic, or distance traveled, for example. It is proposed a model considering the application of a robust approach that controls the amount of uncertainty parameters related with the service time. A case study with real data provided by the fire department of the city of Catalão, Goiás, is performed on the models and the results show that the number of ambulances is greater than the current need, as pointed by the model without uncertainty. However, the results on the robust model show that the real number of ambulances in the city is able to serve a limited amount of demand, so for a maximum variation of the demand, the number of available ambulances are not able to support it. The model had worked well for the first two scenarios among the three ones tested, in which for the last scenario the model was quite sensitive to changes on the uncertainty parameters. / As técnicas de otimização robusta podem ser usadas em problemas sujeitos a incertezas com o intuito de obter soluções robustas, isto é, soluções menos sensíveis as variações do problema. Problemas como o de localização de instalações, especificamente, o de localização de ambulâncias possuem incertezas em seus dados. Assim, um modelo de programação linear inteira de localização de ambulâncias e bases é investigado considerando que o tempo de atendimento das chamadas é um parâmetro incerto, uma vez que este parâmetro é influenciado pela natureza da chamada, trânsito ou distância, por exemplo. Propõe-se um modelo a partir da aplicação de uma abordagem robusta que controla a quantidade de parâmetros incertos sobre o tempo de atendimento. A partir de um estudo de caso, com dados reais fornecidos pelo batalhão de corpo de bombeiros da cidade de Catalão, Goiás, considerado sobre os modelos, os resultados mostram que a quantidade de ambulâncias existente na corporação é maior que a necessidade atual, dado o modelo sem incertezas. Porém, os resultados sobre o modelo robusto apontaram que a quantidade de ambulâncias existentes na cidade é capaz de atender até certa variação do tempo de atendimento, sendo que para uma variação máxima, a quantidade de ambulâncias disponível não é capaz de suprir a demanda. O modelo se comportou bem para os dois primeiros cenários, dentre os três testados, sendo que para o último cenário o modelo se mostrou bastante sensível a variação dos parâmetros considerados incertos.

Le secteur des semi-conducteurs a connu un développement considérable ces dernières décennies, du fait des nouvelles applications de la microélectronique dans l'industrie. Le processus de fabrication est réputé pour sa complexité. L'un des ateliers les plus critiques de la production, l'atelier de photolithographie, est régi par un ensemble conséquent de contraintes de production. La multiplicité des ressources utilisées, le nombre important de produits traités, en font une zone importante à optimiser. Les objectifs de la thèse ont été de modéliser cet atelier sous la forme d'un problème d'ordonnancement sur machines parallèles et d'optimiser plusieurs critères jugés pertinents pour évaluer la qualité des solutions. Des résultats en termes de complexité, et d'algorithmes de résolution, ont permis une application industrielle, dans la mesure où un logiciel d'optimisation destiné à l'ordonnancement des lots en photolithographie a été développé. / Semiconductor manufacturing has grown considerably in recent decades, due to new industrial applications of microelectronic devices. The related manufacturing process is known to be complex. A bottleneck process step, the photolithography workshop, gathers various types of constraints, related to the number of auxiliary resources and the tools characteristics. The aims of the thesis were to model this workstation as a parallel machine scheduling problem and to optimize various criteria, determined by industrial needs. Some complexity results are provided and optimization algorithms led to an industrial application, i.e. a software providing optimized schedules in a specific fab.

Este trabalho trata de um problema de programação da produção em fundições de pequeno porte, que consiste em programar as ligas que devem ser produzidas em cada período do planejamento e como tais ligas devem ser usadas para a produção de itens sob encomenda, de modo que atrasos e custos operacionais sejam minimizados. Devido à certa incerteza nos dados do problema, a estratégia de horizonte rolante foi empregada. Este problema é representado por um modelo matemático de programação linear inteira mista. Neste trabalho foi desenvolvida uma heurística do tipo residual para obter uma boa solução inteira factível do problema, partindo da solução contínua encontrada pelos métodos relaxe-e-fixe e busca local / This work addresses a planning production problem that arises in small market-driven foundries, which consists of programming a number of alloys that have to be produced in each period of the planning horizon and how these alloys should be used to producing ordered items, in such way that delays and operational costs are minimized. Due to uncertainties in the problem data, the strategy of rolling horizon was used. This problem is modeled as a mixed integer linear programe. In this work we developed a residual typed heuristic in order to obtain a good feasible integer solution of the problem, which are built from the continuous solution found by relax-and-fix and local search methods. Keywords: Lot-sizing problems, mixed integer linear programming, production planning in foundries

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