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Biblioteca Digital do IPB (53.442 recursos)

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DGI - Resumos em Proceedings Não Indexados ao ISI

Mostrando recursos 1 - 20 de 26

  1. Operational research models in warehouse design and planning

    Geraldes, Carla A.S.; Carvalho, Sameiro; Pereira, Guilherme
    The design and operation of a warehouse involve many challenging decision problems. In this paper, a literature review on warehousing models is presented. Authors start with a hierarchy of decision problems encountered in setting up warehouse design and planning processes. Next, some operational research decision models and solution algorithms supporting decision making at each discussed level are presented. The aim is to link academic researchers and warehouse practitioners, explaining what planning models and methods are currently available for warehouse design and planning, and what are the future research opportunities.

  2. Avaliação de desempenho de lojas de retalho utilizando um modelo de data envelopment analysis multi-nível

    Vaz, Clara B.; Camanho, Ana; Guimarães, Rui

  3. Parallel machine scheduling using free software: an application

    Duarte, António J.S.T.; Carvalho, J.M. Valério de
    We will show how to implement large scale optimization by only using freely available software tools. We solve exactly a parallel machine scheduling problem with identical parallel machines and malleable tasks, subject to arbitrary release dates and due dates. The objective is to minimize a function of late work and setup costs. We use the COIN-OR BCP framework to implement column generation to solve a model that results from a Dantzig-Wolfe decomposition, and also CRIFOR MCFZIB to solve an equivalent network flow model. Computational results are presented.

  4. Heuristic approaches for a practical lot splitting and scheduling problem

    Pimentel, Carina; Alvelos, Filipe; Carvalho, J.M. Valério de; Duarte, António J.S.T.
    In this talk we present some heuristic approaches for a real world lot splitting and scheduling problem of a Textile factory. The problem consists of finding a weekly production plan for the knitting section of the company, establishing the quantities to produce of each component (organized in one or several lots), and where and when (starting/completion times) to produce them. Two important objectives to achieve are on time delivery of products and minimum levels of work-in-process inventory. We present some results for a set of randomly generated instances based on real world data.

  5. Uma abordagem metaheurística para um problema integrado de dimensionamento de lotes e de sequenciamento

    Pimentel, Carina; Alvelos, Filipe; Duarte, António J.S.T.; Carvalho, J.M. Valério de
    Nesta comunicação apresenta-se um problema integrado de dimensionamento de lotes e de sequenciamento desses lotes, baseado num problema real de uma indústria Têxtil. Numa solução para o problema as quantidades a produzir por artigo/componente/tamanho são divididas em vários lotes de dimensão variável, determinam-se as máquinas onde os lotes definidos serão produzidos, assim como a ordem segundo a qual esses lotes devem ser produzidos em cada máquina. Os objectivos a atingir são: (1) a minimização do atraso total e (2) a minimização do desvio entre os instantes de conclusão dos vários componentes que pertencem ao mesmo artigo final. Este segundo objectivo tem...

  6. Solution methods for an integrated lot sizing and scheduling problem

    Pimentel, Carina; Alvelos, Filipe; Carvalho, J.M. Valério de; Duarte, António J.S.T.
    In this talk we present results of an ongoing study, based on a problem of a textile factory. The core problem is an integrated lotsizing and scheduling one, characterized by sets of parallel machines, arbitrary demands and due dates for products, a compatibility matrix between machines and components and release dates of machines. In a solution, the quantities to produce by product/component/size are split among smaller lots, the machines in which those lots will be produced are determined, as well as the order in which they will be done. We present a MIP model and results of a VNS heuristic.

  7. Modelos de planeamento de tricotagem - estudo de um caso

    Pimentel, Carina; Alvelos, Filipe; Carvalho, J.M. Valério de; Duarte, António J.S.T.
    Este trabalho é dedicado ao estudo e desenvolvimento de algoritmos para o planeamento da tricotagem de uma empresa multinacional do ramo têxtil, que se dedica à produção de artigos de malha fina. Esta empresa contém quatro secções produtivas, que se encontram divididas da seguinte forma: tricotagem, montagem, tinturaria e acabamento. O trabalho que aqui se apresenta está relacionado com a secção de tricotagem, a qual se encontra ainda dividida em três subsecções. Embora nesta secção sejam produzidos todos os componentes principais de um artigo final, nesta fase do trabalho apenas se considera a subsecção em>cotton, onde são produzidas as partes de corpos do...

  8. Integrated models for warehouse design and planning

    Geraldes, Carla A.S.; Carvalho, Sameiro; Pereira, Guilherme
    Market competition requires continuous improvement in the design and operation of supply chains. Warehouse management is a field of interest for both practitioners and researchers and involves material, information and financial flow management in a highly dynamic environment. Designing and planning a warehouse (distribution centre) involve different levels of decision-making, with high levels of interactions and interdependencies. So, to ensure an efficient performance of the warehouse, decisions having a significant impact on each other must be integrated. The aim of this work is to develop integrated models capable of capture the complex tradeoffs of a warehouse system.

  9. Concepção e planeamento de armazéns

    Geraldes, Carla A.S.; Carvalho, Sameiro; Pereira, Guilherme
    Uma 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....

  10. Evolution of portuguese regional unemployment patterns from 2004 to 2009.

    Nunes, Alcina; Barros, Elisa
    The data mining methodology, in particular the cluster analysis technique, is an important ally in the study of economic patterns in a multivariate framework. Aware of its analytical importance this paper adopts such method of study to identify groups of Portuguese administrative regions that share similar patterns regarding some characteristics of unemployed register individuals. The regional distribution of the unemployed individual characteristics is of core importance for the development of public policies directed to fight the unemployment phenomenon, especially in times of crisis. The research is based on annual cross-section data, from the Portuguese public employment service, for the period...

  11. Unemployment similarities among portuguese regions - a cluster analysis approach

    Barros, Elisa; Nunes, Alcina
    The regional distribution of the unemployed individual characteristics is of core importance for the development of public policies that can fight the unemployment phenomenon, especially in times of crises. The data mining cluster methodology allows finding groups of regional areas that share the same characteristics for the register unemployed and, therefore, helps in a better understanding of the problem and possible solutions. Preliminary results for the Portuguese regions show a clear division of the territory among four regions – north and south and urban and rural areas of the country – concerning individual characteristics such the gender, age, education or...

  12. Integrated approaches to warehouse planning and operations

    Geraldes, Carla A.S.; Carvalho, Sameiro; Pereira, Guilherme
    In this talk we discuss a tactical model recently available in warehouse literature. The model integrates the replenishment decision in inventory management, the allocation of products to warehousing systems and the assignment of products to storage locations in warehousing management. Our aim is to show the models’ potentialities and weaknesses when applied to a wide variety of problems and to identify challenging research opportunities for developing global warehouse decision support models that fill the gap between researchers and warehouse practitioners.

  13. Performance comparison between retailing stores using a Malmquist-type index

    Vaz, Clara B.; Camanho, Ana
    This study develops a framework that combines different methods to provide insights regarding the performance of retailing stores. Firstly, the framework enables to specify appropriate targets for stores using DEA. This involves comparing stores within homogeneous groups. Secondly, the framework compares the overall performance of these groups. This requires the combined use of Malmquist type index and statistical tests. This index is decomposed into components for comparing the efficiency spread between groups and the productivity differences between the best-practice frontiers of the groups.

  14. Avaliação de desempenho no sector do retalho

    Vaz, Clara B.; Camanho, Ana
    O objectivo deste estudo é avaliar a eficiência das lojas de uma empresa de retalho de base alimentar, recorrendo à técnica de Data Envelopment Analysis. A eficiência é avaliada ao nível operacional e ao nível comercial, numa perspectiva de maximização de outputs. Os modelos foram definidos tendo em conta as características gerais do negócio de retalho, assim como a forma de funcionamento específica da empresa utilizada como caso de estudo. O modelo de eficiência operacional analisa a capacidade de cada loja em gerar vendas com o mínimo de recursos (i.e., área, stock, custos das vendas, encargos gerais e encargos com pessoal)...

  15. Avaliação de desempenho de lojas de retalho utilizando um modelo de Data Envelopment Analysis multinível

    Vaz, Clara B.; Camanho, Ana; Guimarães, Rui
    Este artigo descreve um método de avaliação de desempenho de lojas de retalho baseado na técnica de Data Envelopment Analysis (DEA). O método desenvolvido tem em conta que as lojas são organizações complexas que agregam várias secções, com alguma autonomia de gestão. Assim, desenvolveu-se um modelo de DEA multi-nível, que considera dois níveis de análise: a loja e as secções que a constituem. A análise do desempenho de cada secção comercial resulta da comparação com secções similares localizadas noutras lojas da cadeia e permite averiguar se existe disparidade no seu desempenho. A avaliação ao nível da loja permite definir objectivos...

  16. Assessing group performance with Malmquist indices: the evaluation of the brand effect in retailing

    Camanho, Ana; Vaz, Clara B.
    This study explores the differences in performance between two groups of grocery stores with different brands. The paper develops a Malmquist-type index to distinguish internal inefficiencies from those associated with the group (or brand) characteristics. A fundamental characteristic of the new index is to compare in a static setting.

  17. Analysis of the effect of environmental conditions on the performance of retailing stores

    Vaz, Clara B.; Camanho, Ana
    The assessment of performance in retailing services has gained considerable attention in recent years. The increased competition motivated the organisations to strive for efficiency in order to cut costs and deliver better customer services. This paper develops a method based on Data Envelopment Analysis (DEA) for the efficiency assessment of retailing stores. The method enables the quantification of inefficiencies taking into account the effect of exogenously factors (i.e., non-discretionary inputs and outputs). The method developed starts with the identification of the factors that affect the DMUs’ performance, including those outside the decision makers’ control. The statistical significance of the effect of...

  18. Assessing the brand effect on the efficiency of retailing stores

    Vaz, Clara B.; Camanho, Ana
    This paper explores the differences in performance between two groups of grocery stores that operate with different brands. The study develops a Malmquist-type index to distinguish internal inefficiencies from those associated with the group (or brand) characteristics. A fundamental characteristic of the new index is to compare groups in a static setting. The study described in this paper combines the use of a Malmquist-type index with statistical testes. The Malmquist-type index is decomposed into sub-indexes for comparing the efficiency spread between groups and the productivity differences between the best-practice frontiers of the groups. The hypothesis tests are used to verify...

  19. Comparison of two alternative store formats using a Malmquist-type index

    Vaz, Clara B.; Camanho, Ana
    This paper explores the differences in performance between two groups of retailing stores that operate with different formats. The study described in this paper combines the use of a Malmquist-type index (in a static setting) with statistical tests. This index is decomposed into sub-indexes for comparing the efficiency spread between groups and the productivity differences between the best-practice frontiers of the groups. The hypothesis tests are used to verify if the differences between groups captured by the Malmquist-type index and its components are statistically significant.

  20. Comparison of two alternative store formats using a Malmquist-type index

    Camanho, Ana; Vaz, Clara B.
    This paper explores the differences in performance between two groups of retailing stores that operate with different formats. The study uses a Malmquist-type index to distinguish internal inefficiencies from those associated with the group (or format) characteristics. A fundamental characteristic of the new index is to compare groups in a static setting. The study described in this paper combines the use of the Malmquist index with statistical tests. The Malmquist-type index is decomposed into sub-indexes for comparing the efficiency spread between groups and the productivity differences between the best-practice frontiers of the groups. The hypothesis tests are used to verify...

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