Browsing by Author "Pereira, Guilherme"
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- An automated warehouse design validation using discrete simulationPublication . Peixoto, Robson; Dias, Luís M.S.; Carvalho, Sameiro; Pereira, Guilherme; Geraldes, Carla A.S.In this paper we discuss the use of discrete simulation technique to support the redesign process of an automated warehouse system of the Brazilian Air Force unit. This unit is responsible for the supply of all uniform items and other military support material to their military forces. In particular, our work aims at analysing the inclusion of an automated sorting system to prepare uniforms individual kits in order to release downstream supply chain from this task. The main challenge was to investigate the impact on the existing storage system of a new sorting system and, simultaneously, to explore if additional management measures are required to satisfy both throughput levels and overall supply chain requirements. To accomplish a solution for such a complex problem simulation models were developed using ARENA software. Results have shown that the use of simulation allows not only the assessment of the impact of the new sorting equipment but also to test different warehouse management strategies that should be adopted concurrently to ensure that desired throughput levels can be achieved in the new scenario. In fact, this research illustrates the flexibility of the simulation tool to address several complex management issues simultaneously such as the introduction of picking sequencing rules, the use of a class-based storage policy, the addition of new picking stations, and an increase of the number of the available boxes used for transportation.
- An integrated approach for warehouse design and planningPublication . Geraldes, Carla A.S.; Carvalho, Sameiro; Pereira, GuilhermeWarehouse design and planning is a great challenge in the field of Supply Chain Management. Inventory level management, warehouse design and operations, and customers’ requirements are examples of important challenges in this context. Throughout this work we discuss a mathematical model aiming to support some warehouse management decisions and inventory decisions. Our aim is to show model’s potentialities and weaknesses when applied to real world problems and to identify challenging research opportunities for developing more global warehouse decision support models to fill the gap between researchers and warehouse practitioners.
- An integrated model for warehouse design and planningPublication . Geraldes, Carla A.S.; Carvalho, Sameiro; Pereira, GuilhermeWarehouse design is a field of interest for both practitioners and researchers that have attracted a lot of research attention in the last years. Nevertheless it remains a complex task with very few general models that capture the existing and often conflicting trade-offs of a warehouse system. Literature surveys show that most research efforts have been devoted to solve limited and well-defined problems rather than integrated ones. This is not surprising since developing an integrated model is more difficult to analyse and treat analytically. In this talk we present and discuss a high-level model that integrates some decisions involved in warehouse design and planning. Our aim is to analyse the value of integrating warehouse decisions showing that additional savings can be achieved.
- An optimisation model for the warehouse design and planning problemPublication . Geraldes, Carla A.S.; Carvalho, Sameiro; Pereira, GuilhermeIn spite of the importance of warehouses in the field of the supply chain management, there is not a single decision model that integrates all the decisions that concerns the warehouse design and planning problem. In this paper we discuss a mathematical programming model aiming to support some warehouse management and inventory decisions. Our aim is to address the complexity related to the modeling of the warehouse design and planning problem. In particular an optimisation model is presented to capture the trade-offs among both inventory and warehouse costs in order to achieve global optimal design satisfying throughput requirements.
- An optimisation model for the warehouse design and planning problemPublication . Geraldes, Carla A.S.; Carvalho, Sameiro; Pereira, GuilhermeIn spite of the importance of warehouses in the field of the supply chain management, there is not a single decision model that integrates all the decisions that concerns the warehouse design and planning problem. A number of warehouse decision support models have been proposed in the literature but considerable difficulties in applying these models still remain, due to the large amount of information to be processed and to the large number of possible alternatives. In this paper we discuss a mathematical programming model aiming to support some warehouse management and inventory decisions. Our aim is to address the complexity related to the modeling of the warehouse design and planning problem. In particular a large mixed-integer nonlinear programing model (MINLP) is presented to capture the trade-offs among both inventory and warehouse costs in order to achieve global optimal design satisfying throughput requirements.
- An optimisation model for the warehouse design and product assignment and allocation problemPublication . Geraldes, Carla A.S.; Carvalho, Sameiro; Pereira, GuilhermeWarehouse design and planning is a great challenge in the field of Supply Chain Management. In this paper we discuss an optimisation model aiming to support some warehouse management decisions. In particular a mixed-integer programming model (MILP) is presented to determine product assignment and allocation to the functional areas, as well as the size of each area. Our aim is to capture the trade-offs among the different warehouse costs in order to achieve global optimal design satisfying throughput requirements.
- Concepção e planeamento de armazénsPublication . Geraldes, Carla A.S.; Carvalho, Sameiro; Pereira, GuilhermeUma cadeia de abastecimento pode ser considerada como uma rede de entidades individuais que, colectivamente são responsáveis pela gestão de fluxos de materiais e de informação desde os fornecedores até ao consumidor final. Assim, a eficiência e eficácia destas redes é fortemente condicionada pelas operações em cada uma das entidades que a integram. Neste sentido, os armazéns proporcionam uma importante ligação entre fornecedores, distribuidores e consumidores pelo que podem ser considerados uma entidade essencial na gestão da cadeia de abastecimento. A concepção e planeamento de um armazém envolve decisões complexas para as quais são diminutas ferramentas de apoio às decisões envolvidas. A complexidade das decisões envolvidas inclui: enorme quantidade de informação a ser processada; elevado número de possíveis alternativas; a existência de vários objectivos que por vezes são conflituosos bem como a incerteza associada ao fluxo de materiais dentro e fora do armazém. São diminutos os modelos de apoio à decisão que integrem várias decisões envolvidas na concepção e planeamento de armazéns. Esta escassez de modelos integradores que traduzam a complexidade destes sistemas é devida à dificuldade de análise e ao complexo tratamento analítico que lhes é inerente. Nesta comunicação será discutido um modelo que integra algumas das decisões envolvidas na concepção e planeamento de armazéns tais como: gestão de inventários, a atribuição de produtos a diferentes zonas de armazenagem e a alocação dos produtos dentro das áreas de armazenamento. O objectivo é mostrar as potencialidades e as fraquezas do modelo quando aplicado a uma variedade de problemas bem como identificar novas oportunidades de investigação.
- A flexible decision supporttool for maintenance float systems - a simulation approachPublication . Peito, Francisco; Pereira, Guilherme; Leitão, Armando; Dias, Luís M.S.; Oliveira, José A.This paper is concerned with the use of simulation as a decision support tool in maintenance systems, specifically in MFS (Maintenance Float Systems). For this purpose and due to its high complexity, in this paper the authors explore and present a way to develop a flexible MFS model, for any number of machines in the workstation, spare machines and maintenance crews, using Arena simulation language. Also in this paper, some of the most common performance measures are identified, calculated and analysed. Nevertheless this paper would concentrate on the two most important performance measures in maintenance systems: system availability and maintenance total cost. As far as these two indicators are concerned, it was then quite clear that they assumed different behaviour patterns, especially when using extreme values for periodic overhauls rates. In this respect, system availability proved to be a more sensitive parameter.
- Gestão das operações logísticas num armazémPublication . Geraldes, Carla A.S.; Carvalho, Sameiro; Pereira, GuilhermeOs armazéns são elos importantes da cadeia logística, pelo que, no contexto de um mercado global, altamente competitivo e exigente, a sua gestão cumpre um papel muito relevante no que diz respeito quer à obtenção dos níveis de serviço prestados ao cliente quer à minimização dos custos logísticos totais. Neste trabalho é realizada a reestruturação de operações logísticas num armazém. A reestruturação realizada teve por base a implementação dos resultados obtidos por resolução de dois modelos de programação matemática que permitiram redimensionar as áreas funcionais no armazém e localizar os produtos dentro dessas áreas, segundo a política de localização adoptada. As soluções obtidas permitiram não só reestruturar o armazém como abriram lugar ao estudo e implementação de novas estratégias, para posterior optimização do processo de picking.
- Gestão de operações logísticas num armazém usando modelos de apoio à decisãoPublication . Geraldes, Carla A.S.; Carvalho, Sameiro; Pereira, GuilhermeOs armazéns são elos importantes da cadeia logística, pelo que, no contexto de um mercado global, altamente competitivo e exigente, a sua gestão cumpre um papel muito relevante no que diz respeito quer à obtenção dos níveis de serviço prestados ao cliente quer à minimização dos custos logísticos totais. Neste trabalho é realizada a reestruturação de operações logísticas num armazém. A reestruturação realizada teve por base a implementação dos resultados obtidos por resolução de dois modelos de programação matemática que permitiram redimensionar as áreas funcionais no armazém e localizar os produtos dentro dessas áreas, segundo a política de localização adoptada. As soluções obtidas permitiram não só reestruturar o armazém como abriram lugar ao estudo e implementação de novas estratégias, para posterior optimização do processo de picking.
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