2010
Authors
Claro, J; de Sousa, JP;
Publication
JOURNAL OF HEURISTICS
Abstract
We propose a multiobjective local search metaheuristic for a mean-risk multistage capacity investment problem with irreversibility, lumpiness and economies of scale in capacity costs. Conditional value-at-risk is considered as a risk measure. Results of a computational study are presented and indicate that the approach is capable of producing high-quality approximations to the efficient sets with a modest computational effort. The best results are achieved with a new hybrid approach, combining Tabu Search and Variable Neighbourhood Search.
2010
Authors
Claro, J; de Sousa, JP;
Publication
COMPUTATIONAL OPTIMIZATION AND APPLICATIONS
Abstract
In this paper we address two major challenges presented by stochastic discrete optimisation problems: the multiobjective nature of the problems, once risk aversion is incorporated, and the frequent difficulties in computing exactly, or even approximately, the objective function. The latter has often been handled with methods involving sample average approximation, where a random sample is generated so that population parameters may be estimated from sample statistics-usually the expected value is estimated from the sample average. We propose the use of multiobjective metaheuristics to deal with these difficulties, and apply a multiobjective local search metaheuristic to both exact and sample approximation versions of a mean-risk static stochastic knapsack problem. Variance and conditional value-at-risk are considered as risk measures. Results of a computational study are presented, that indicate the approach is capable of producing high-quality approximations to the efficient sets, with a modest computational effort.
2010
Authors
Rocha, LF; Moreira, AP; Azevedo, A;
Publication
IFAC Proceedings Volumes (IFAC-PapersOnline)
Abstract
Automated Guided Vehicles (AGV) are self-driven vehicles used to transport material between workstations in the shop floor without the help of an operator, although they can also be applied in security and exploration. They are widely used in material handling systems and flexible manufacturing systems, where production orders are constantly changing. Today, and due to the constant development of technology, sophisticated machinery is increasingly available, thus enabling manufacturing firms to achieve significant process and setup time reductions. With this development, enterprises are encouraged to leave mass production approaches and start adopting small productions lot sizes, leading to constant changes in the production operation's sequences as well as changes in the factory layout. As a consequence of the development of technology, products started to spend a big percentage of time in the queue line or being transported from one workstation/storage to another. With the introduction of AGVs production process flexibility may increase, which, in many productions processes, is still below the expectations due to the used transportation system (ex: conveyors). At the same time, with the AGVs it is possible, to decrease transportations times and costs. In this article, we will study by means of simulation, the impact of the use of an AGV transportation based system in an industrial coating application. The AGV will be responsible for transporting the parts from the system's entrance to the workstations. With this, flexibility in the production process will increase, which will be reflected in system's productivity. © 2010 IFAC.
2010
Authors
Azevedo, A; Francisco, RP; Bastos, J; Almeida, A;
Publication
IFAC Proceedings Volumes (IFAC-PapersOnline)
Abstract
Industrial managers are in the expectation that the new generation factories bring more competitiveness to the manufacturing companies through innovative approaches, methods and tools that support the factory planning process. The concept of "factory as a product" perceives the factory as a complex long life product introducing design advantages for factory planning and optimization, seeking to improve quality, reduce ramp-up, product delivery and overall reduce time and costs. In order to attain these objectives, there is an urgent need for an innovative and suitable Virtual Factory Framework to structure the development of new generation factories. © 2010 IFAC.
2010
Authors
Francisco, RD; Azevedo, A; Bastos, J;
Publication
COLLABORATIVE NETWORKS FOR A SUSTAINABLE WORLD
Abstract
The paper underlines the interest of using a performance management system applied to monitor the strategy effectiveness and the interoperation's performance in the collaborative networks (CN). The aim with this study is to verify if a performance management system helps decision-makers reach the alignment among participants in a collaborative network. It is expected that this work provides an adequate tool for supporting quick decisions to meet the feasible and desirable improvements in inter-organisational processes. A framework (CNPMS) is also presented, having been developed to support the dynamic performance management, which was applied in case studies of two Brazilian collaborative networks.
2010
Authors
Francisco, RD; Bastos, J; Azevedo, A;
Publication
BALANCED AUTOMATION SYSTEMS FOR FUTURE MANUFACTURING NETWORKS
Abstract
In order to fulfill all challenges related to design, management, evaluation and reconfiguration of new or existing facilities, the development of a new, integrated and holistic factory framework is required. In this context, a new requirements model is proposed in the context of the innovative framework called Virtual Factory Framework. Using this approach in factory planning it is expected to improve the ability to generate better and more sustainable solutions over the entire factory life-cycle. This paper underlines the use of the life-cycle paradigm in order to enable the future factory planning approaches.
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