Abstract Assembly lines are flow oriented production systems where parts of a product are assembl... more Abstract Assembly lines are flow oriented production systems where parts of a product are assembled in different workstations. Depending on the context, the planning and operation of these lines give rise to different combinatorial optimization problems.
Abstract: An interesting empirical result in the assembly line literature states that slightly un... more Abstract: An interesting empirical result in the assembly line literature states that slightly unbalanced assembly lines (in the format of a bowl-with central stations less loaded than the external ones) present higher throughputs than perfectly balanced ones. This effect is known as the bowl phenomenon. In this study, we analyze the presence of this phenomenon in assembly lines with heterogeneous workers (most of them, workers with disabilities).
Abstract An interesting empirical result in the assembly line literature states that slightly unb... more Abstract An interesting empirical result in the assembly line literature states that slightly unbalanced assembly lines (in the format of a bowl-with central stations less loaded than the external ones) present higher throughputs than perfectly balanced ones. This effect is known as the bowl phenomenon. In this study, we analyze the presence of this phenomenon in assembly lines with heterogeneous workers (most of them, workers with disabilities).
Resumo Este artigo estuda o problema de aloca����o de chaves em sistemas el��tricos de distribui�... more Resumo Este artigo estuda o problema de aloca����o de chaves em sistemas el��tricos de distribui����o, com o intuito de aumentar-se a confiabilidade da rede. O interesse deste trabalho decorre do fato de que falhas no sistemas de distribui����o respondem por 80% das interrup����es e do fato que a instala����o de chaves �� uma maneira eficaz de diminuir o n��mero de consumidores afetados por tais falhas.
Abstract We propose simple heuristics for the assembly line worker assignment and balancing probl... more Abstract We propose simple heuristics for the assembly line worker assignment and balancing problem. This problem typically occurs in assembly lines in sheltered work centers for the disabled. Different from the well-known simple assembly line balancing problem, the task execution times vary according to the assigned worker. We develop a constructive heuristic framework based on task and worker priority rules defining the order in which the tasks and workers should be assigned to the workstations.
Abstract: Assembly line balancing is a well-known problem in operations research. It consists in ... more Abstract: Assembly line balancing is a well-known problem in operations research. It consists in finding an assignment of tasks to some arrangement of stations where the tasks are executed. Typical objective functions require to minimize the cycle time for a given number of stations or the number of stations for a given cycle time.
Resumo: Apenas uma pequena parcela das pessoas portadoras de deficiência em idade ativa desenvolv... more Resumo: Apenas uma pequena parcela das pessoas portadoras de deficiência em idade ativa desenvolve algum tipo de atividade produtiva. As causas deste problema são complexas e envolvem preconceito e desinformação. Neste trabalho, mostramos como métodos de otimização podem ser usados para programar linhas de produção com esta classe de trabalhadores, de modo a tornar as deficiências tão invisíveis quanto possível.
Resumo. O problema de balanceamento de linhas de produção e designação de trabalhadores é uma ext... more Resumo. O problema de balanceamento de linhas de produção e designação de trabalhadores é uma extensão do problema simples de balanceamento de linhas onde os tempos de execução de tarefas são dependentes dos trabalhadores. Este problema tem sua motivação prática oriunda de linhas de produção com trabalhadores deficientes. Neste trabalho, estendemos uma formulação conhecida do problema para lidar com a possibilidade de layouts de linhas com máquinas em paralelo.
Abstract An electrical distribution system operates in a radial fashion, with substations as the ... more Abstract An electrical distribution system operates in a radial fashion, with substations as the sources and consumers areas as the destinations. Alternative paths or support feeders play an important and essential role for obtaining network reliability, in such a way that they are maintained disconnected from the system via sectionalizing switches. This scenario is only changed when a failure occurs, conducting to the activation of support feeders while maintaining the radial structure of the network.
Abstract The Steiner tree problem with revenues, budget and hop constraints is a variant of the S... more Abstract The Steiner tree problem with revenues, budget and hop constraints is a variant of the Steiner tree problem with two main modifications:(a) besides the costs associated with arcs, there are also revenues associated with the vertices, and (b) there are additional budget and hop constraints, which impose limits on the total cost of the network and on the number of edges between any vertex and the root, respectively.
Abstract In this research, we assess the impact of consumer purchasing behaviour on the productio... more Abstract In this research, we assess the impact of consumer purchasing behaviour on the production planning of perishable food products for companies operating in the fast moving consumer goods using direct store delivery. We build on previous marketing studies related to the effects of expiry dates, in order to derive mathematical formulae, which express the age dependent demand for different categories of perishable products. These demand expressions take into account both customer willingness to pay and product quality risk.
Resumo. Neste artigo, estudamos a programação de rotação de culturas em um contexto de produção d... more Resumo. Neste artigo, estudamos a programação de rotação de culturas em um contexto de produção de hortaliças. O problema consiste, basicamente, em encontrar a ordem de plantio de cada cultura, de modo que sejam atendidas restrições de base ecológica tais como períodos de pousio, o cultivo de espécies para adubação verde ea proibição do plantio de duas culturas de mesma família botânica em sequência.
Resumo O aumento da confiabilidade em redes-sejam elas de telecomunicaç oes, logısticas ou de ene... more Resumo O aumento da confiabilidade em redes-sejam elas de telecomunicaç oes, logısticas ou de energia elétrica-passa pela criaçao de redundância nos caminhos ligando os nós fontes aos nós de demanda. No caso particular do sistema de distribuiçao de energia, que opera de forma radial, tais caminhos alternativos devem ser mantidos desconectados do sistema principal, o que é feito através de chaves seccionadoras.
Resumo Neste estudo aplicamos o método de decomposição de Benders para resolver o problema de emp... more Resumo Neste estudo aplicamos o método de decomposição de Benders para resolver o problema de empacotar o maior número possível de retângulos dentro de um retângulo maior. Este problema aparece em contextos logísticos de carregamento de caixas iguais em camadas verticais sobre a superfície de um palete. A abordagem baseada em decomposição de Benders particiona o problema original em dois outros problemas, mais simples de serem resolvidos.
ABSTRACT In this paper, a general scheme for generating extra cuts during the execution of a Bend... more ABSTRACT In this paper, a general scheme for generating extra cuts during the execution of a Benders decomposition algorithm is presented. These cuts are based on feasible and infeasible master problem solutions generated by means of a heuristic. This article includes general guidelines and a case study with a fixed charge network design problem. Computational tests with instances of this problem show the efficiency of the strategy.
Abstract We propose the Assembly Line Worker Integration and Balancing Problem (ALWIBP), a new as... more Abstract We propose the Assembly Line Worker Integration and Balancing Problem (ALWIBP), a new assembly line balancing problem arising in lines with conventional and disabled workers. The goal of this problem is to maintain high productivity levels by minimizing the number of workstations needed to reach a given output, while including in the assembly line a number of disabled workers.
In this article, we introduce two new variants of the Assembly Line Worker Assignment and Balanci... more In this article, we introduce two new variants of the Assembly Line Worker Assignment and Balancing Problem (ALWABP) that allow parallelization of and collaboration between heterogeneous workers. These new approaches suppose an additional level of complexity in the Line Design and Assignment process, but also higher flexibility; which may be particularly useful in practical situations where the aim is to progressively integrate slow or limited workers in conventional assembly lines.
Resumo. Neste trabalho, estudam-se heurısticas construtivas para o Problema de Balanceamento e De... more Resumo. Neste trabalho, estudam-se heurısticas construtivas para o Problema de Balanceamento e Designaçao de Trabalhadores em Linhas de Produçao, conhecido na literatura como ALWABP (do inglês: Assembly Line Worker Assignment and Balancing Problem). Este problema é tıpico de linhas de produç ao com trabalhadores deficientes, onde os tempos de execuçao de cada tarefa sao diferentes para cada trabalhador.
RESUMO O problema de minimizaçao do número máximo de pilhas abertas é um problema NP-difıcil ea r... more RESUMO O problema de minimizaçao do número máximo de pilhas abertas é um problema NP-difıcil ea resoluçao exata do problema pelos métodos sugeridos na literatura torna-se proibitivaa medida que o tamanho do problema aumenta pois o tempo de execuçao aumenta rapidamente. Neste trabalho, sao analisadas variaçoes de um modelo exato proposto na literatura, com o objetivo de tentar diminuir o tempo de execuçao necessário para se obter uma soluçao exata do modelo. PALAVRAS CHAVE.
We consider the two-level network design problem with intermediate facilities. This problem consi... more We consider the two-level network design problem with intermediate facilities. This problem consists of designing a minimum cost network respecting some requirements, usually described in terms of the network topology or in terms of a desired flow of commodities between source and destination vertices. Each selected link must receive one of two types of edge facilities and the connection of different edge facilities requires a costly and capacitated vertex facility. We propose a hybrid decomposition approach which heuristically obtains tentative solutions for the vertex facilities number and location and use these solutions to limit the computational burden of a branch-and-cut algorithm. We test our method on instances of the power system secondary distribution network design problem. The results show that the method is efficient both in terms of solution quality and computational times.
Abstract Assembly lines are flow oriented production systems where parts of a product are assembl... more Abstract Assembly lines are flow oriented production systems where parts of a product are assembled in different workstations. Depending on the context, the planning and operation of these lines give rise to different combinatorial optimization problems.
Abstract: An interesting empirical result in the assembly line literature states that slightly un... more Abstract: An interesting empirical result in the assembly line literature states that slightly unbalanced assembly lines (in the format of a bowl-with central stations less loaded than the external ones) present higher throughputs than perfectly balanced ones. This effect is known as the bowl phenomenon. In this study, we analyze the presence of this phenomenon in assembly lines with heterogeneous workers (most of them, workers with disabilities).
Abstract An interesting empirical result in the assembly line literature states that slightly unb... more Abstract An interesting empirical result in the assembly line literature states that slightly unbalanced assembly lines (in the format of a bowl-with central stations less loaded than the external ones) present higher throughputs than perfectly balanced ones. This effect is known as the bowl phenomenon. In this study, we analyze the presence of this phenomenon in assembly lines with heterogeneous workers (most of them, workers with disabilities).
Resumo Este artigo estuda o problema de aloca����o de chaves em sistemas el��tricos de distribui�... more Resumo Este artigo estuda o problema de aloca����o de chaves em sistemas el��tricos de distribui����o, com o intuito de aumentar-se a confiabilidade da rede. O interesse deste trabalho decorre do fato de que falhas no sistemas de distribui����o respondem por 80% das interrup����es e do fato que a instala����o de chaves �� uma maneira eficaz de diminuir o n��mero de consumidores afetados por tais falhas.
Abstract We propose simple heuristics for the assembly line worker assignment and balancing probl... more Abstract We propose simple heuristics for the assembly line worker assignment and balancing problem. This problem typically occurs in assembly lines in sheltered work centers for the disabled. Different from the well-known simple assembly line balancing problem, the task execution times vary according to the assigned worker. We develop a constructive heuristic framework based on task and worker priority rules defining the order in which the tasks and workers should be assigned to the workstations.
Abstract: Assembly line balancing is a well-known problem in operations research. It consists in ... more Abstract: Assembly line balancing is a well-known problem in operations research. It consists in finding an assignment of tasks to some arrangement of stations where the tasks are executed. Typical objective functions require to minimize the cycle time for a given number of stations or the number of stations for a given cycle time.
Resumo: Apenas uma pequena parcela das pessoas portadoras de deficiência em idade ativa desenvolv... more Resumo: Apenas uma pequena parcela das pessoas portadoras de deficiência em idade ativa desenvolve algum tipo de atividade produtiva. As causas deste problema são complexas e envolvem preconceito e desinformação. Neste trabalho, mostramos como métodos de otimização podem ser usados para programar linhas de produção com esta classe de trabalhadores, de modo a tornar as deficiências tão invisíveis quanto possível.
Resumo. O problema de balanceamento de linhas de produção e designação de trabalhadores é uma ext... more Resumo. O problema de balanceamento de linhas de produção e designação de trabalhadores é uma extensão do problema simples de balanceamento de linhas onde os tempos de execução de tarefas são dependentes dos trabalhadores. Este problema tem sua motivação prática oriunda de linhas de produção com trabalhadores deficientes. Neste trabalho, estendemos uma formulação conhecida do problema para lidar com a possibilidade de layouts de linhas com máquinas em paralelo.
Abstract An electrical distribution system operates in a radial fashion, with substations as the ... more Abstract An electrical distribution system operates in a radial fashion, with substations as the sources and consumers areas as the destinations. Alternative paths or support feeders play an important and essential role for obtaining network reliability, in such a way that they are maintained disconnected from the system via sectionalizing switches. This scenario is only changed when a failure occurs, conducting to the activation of support feeders while maintaining the radial structure of the network.
Abstract The Steiner tree problem with revenues, budget and hop constraints is a variant of the S... more Abstract The Steiner tree problem with revenues, budget and hop constraints is a variant of the Steiner tree problem with two main modifications:(a) besides the costs associated with arcs, there are also revenues associated with the vertices, and (b) there are additional budget and hop constraints, which impose limits on the total cost of the network and on the number of edges between any vertex and the root, respectively.
Abstract In this research, we assess the impact of consumer purchasing behaviour on the productio... more Abstract In this research, we assess the impact of consumer purchasing behaviour on the production planning of perishable food products for companies operating in the fast moving consumer goods using direct store delivery. We build on previous marketing studies related to the effects of expiry dates, in order to derive mathematical formulae, which express the age dependent demand for different categories of perishable products. These demand expressions take into account both customer willingness to pay and product quality risk.
Resumo. Neste artigo, estudamos a programação de rotação de culturas em um contexto de produção d... more Resumo. Neste artigo, estudamos a programação de rotação de culturas em um contexto de produção de hortaliças. O problema consiste, basicamente, em encontrar a ordem de plantio de cada cultura, de modo que sejam atendidas restrições de base ecológica tais como períodos de pousio, o cultivo de espécies para adubação verde ea proibição do plantio de duas culturas de mesma família botânica em sequência.
Resumo O aumento da confiabilidade em redes-sejam elas de telecomunicaç oes, logısticas ou de ene... more Resumo O aumento da confiabilidade em redes-sejam elas de telecomunicaç oes, logısticas ou de energia elétrica-passa pela criaçao de redundância nos caminhos ligando os nós fontes aos nós de demanda. No caso particular do sistema de distribuiçao de energia, que opera de forma radial, tais caminhos alternativos devem ser mantidos desconectados do sistema principal, o que é feito através de chaves seccionadoras.
Resumo Neste estudo aplicamos o método de decomposição de Benders para resolver o problema de emp... more Resumo Neste estudo aplicamos o método de decomposição de Benders para resolver o problema de empacotar o maior número possível de retângulos dentro de um retângulo maior. Este problema aparece em contextos logísticos de carregamento de caixas iguais em camadas verticais sobre a superfície de um palete. A abordagem baseada em decomposição de Benders particiona o problema original em dois outros problemas, mais simples de serem resolvidos.
ABSTRACT In this paper, a general scheme for generating extra cuts during the execution of a Bend... more ABSTRACT In this paper, a general scheme for generating extra cuts during the execution of a Benders decomposition algorithm is presented. These cuts are based on feasible and infeasible master problem solutions generated by means of a heuristic. This article includes general guidelines and a case study with a fixed charge network design problem. Computational tests with instances of this problem show the efficiency of the strategy.
Abstract We propose the Assembly Line Worker Integration and Balancing Problem (ALWIBP), a new as... more Abstract We propose the Assembly Line Worker Integration and Balancing Problem (ALWIBP), a new assembly line balancing problem arising in lines with conventional and disabled workers. The goal of this problem is to maintain high productivity levels by minimizing the number of workstations needed to reach a given output, while including in the assembly line a number of disabled workers.
In this article, we introduce two new variants of the Assembly Line Worker Assignment and Balanci... more In this article, we introduce two new variants of the Assembly Line Worker Assignment and Balancing Problem (ALWABP) that allow parallelization of and collaboration between heterogeneous workers. These new approaches suppose an additional level of complexity in the Line Design and Assignment process, but also higher flexibility; which may be particularly useful in practical situations where the aim is to progressively integrate slow or limited workers in conventional assembly lines.
Resumo. Neste trabalho, estudam-se heurısticas construtivas para o Problema de Balanceamento e De... more Resumo. Neste trabalho, estudam-se heurısticas construtivas para o Problema de Balanceamento e Designaçao de Trabalhadores em Linhas de Produçao, conhecido na literatura como ALWABP (do inglês: Assembly Line Worker Assignment and Balancing Problem). Este problema é tıpico de linhas de produç ao com trabalhadores deficientes, onde os tempos de execuçao de cada tarefa sao diferentes para cada trabalhador.
RESUMO O problema de minimizaçao do número máximo de pilhas abertas é um problema NP-difıcil ea r... more RESUMO O problema de minimizaçao do número máximo de pilhas abertas é um problema NP-difıcil ea resoluçao exata do problema pelos métodos sugeridos na literatura torna-se proibitivaa medida que o tamanho do problema aumenta pois o tempo de execuçao aumenta rapidamente. Neste trabalho, sao analisadas variaçoes de um modelo exato proposto na literatura, com o objetivo de tentar diminuir o tempo de execuçao necessário para se obter uma soluçao exata do modelo. PALAVRAS CHAVE.
We consider the two-level network design problem with intermediate facilities. This problem consi... more We consider the two-level network design problem with intermediate facilities. This problem consists of designing a minimum cost network respecting some requirements, usually described in terms of the network topology or in terms of a desired flow of commodities between source and destination vertices. Each selected link must receive one of two types of edge facilities and the connection of different edge facilities requires a costly and capacitated vertex facility. We propose a hybrid decomposition approach which heuristically obtains tentative solutions for the vertex facilities number and location and use these solutions to limit the computational burden of a branch-and-cut algorithm. We test our method on instances of the power system secondary distribution network design problem. The results show that the method is efficient both in terms of solution quality and computational times.
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Papers by Alysson M. Costa