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Publications

Publications by SEM

1999

A simulation analysis of sequencing rules in a flexible flowline

Authors
Costa, MT; Ferreira, JS;

Publication
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH

Abstract
The paper concerns a flexible flowline scheduling problem, which arises in the footwear industry. Flexibility of the line allows for manufacturing simultaneously more products in lower quantities, but it also increases the complexity of the task of balancing the line, specially because the mix of products changes everyday. A simulation model to deal with the flexible line is developed and several job sequencing rules and different part input criteria are implemented. The impact of each rule on the quality of the schedules is measured, namely, according to makespan, productivity and average machine utilisation. Computational results concerning a real application are also presented. SIMPLE++ is the simulation language used.

1999

Efficiency, size, benchmarks and targets for bank branches: an application of data envelopment analysis

Authors
Camanho, AS; Dyson, RG;

Publication
Journal of the Operational Research Society

Abstract
This paper describes an application of data envelopment analysis (DEA) to the performance assessment of Portuguese bank branches. The analysis shows how DEA can complement the profitability measure currently used at the bank. The use of an efficiency-profitability matrix enabled the characterisation of the branches' performance profile. Consistent with the bank's development objectives, the analysis focused on the relation between branch size and performance. Two alternative target setting strategies were explored. One eliminates pure technical inefficiencies by focusing on the selection of appropriate benchmarks. The other attains the branches' most productive scale size through the elimination of scale inefficiencies, with minimal changes to branches' scale size.

1998

Capacity modelling for virtual enterprises

Authors
Bastos, JA; Sousa, JP;

Publication
GLOBALIZATION OF MANUFACTURING IN THE DIGITAL COMMUNICATIONS ERA OF THE 21ST CENTURY: INNOVATION, AGILITY, AND THE VIRTUAL ENTERPRISE

Abstract
The purpose of this paper is to present a new view on the problem of capacity planning in a distributed network of enterprises, i.e. in a Virtual Enterprise (VE). This view is based on a distributed planning architecture, that takes into account the requirements and characteristics of local capacity models. In order to cope with the new emerging problems that the VE are encountering, we have been designing and investigating two generic architectures of Decision Support Systems (DSS) for VE planning with capacity checking, applicable to different scenarios of distributed networks of enterprises. The first architecture is hierarchical and is based on the existence of a global decision-maker. The second one is fully distributed and is based in a multi-agent co-operative environment. This work is part of a broader project with a particular focus on the semiconductor industry.

1998

On the design of an order promise system for virtual enterprises

Authors
Azevedo, A; de Sousa, JP;

Publication
MANAGEMENT AND CONTROL OF PRODUCTION AND LOGISTICS, VOL 1 AND 2

Abstract
This paper describes an attempt to design an "Order Promise" system to support decision making in the so-called Virtual Enterprises. In this framework, planning and control activities are very complex, and have to take place both within the enterprise and across the whole supply network in order to achieve high levels of performance. This work is part of a broader project with a particular focus on the microelectronics industry which is a good example of Virtual Enterprise, and where a quick response to the customers needs and to unpredictable changes in production conditions is considered a major factor for success. Copyright (C) 1998 IFAC.

1998

A distributed order promise and planning system for the virtual enterprise

Authors
Azevedo, AL; Sousa, JP; Bastos, JA; Toscano, C;

Publication
GLOBALIZATION OF MANUFACTURING IN THE DIGITAL COMMUNICATIONS ERA OF THE 21ST CENTURY: INNOVATION, AGILITY, AND THE VIRTUAL ENTERPRISE

Abstract
This paper describes an <> system to support decision making in the planning processes of Virtual Enterprises, viewed as networks of different units, namely plants, logistic centres and storage facilities. The system aims at improving customer due date calculation, and is intended to be a multi-site planning tool to co-ordinate local activities across the Virtual Enterprise network. It is based on the use of aggregate information and on a set of local rough capacity models. This work is part of a broader project with a particular focus on the microelectronics industry. Companies of this industry are a good example of Virtual Enterprises, where a quick response to the customers needs and to unpredictable changes in production conditions is considered a major factor for success.

1997

Using an informal ontology in the development of a planning and control system - The case of the virtual enterprise

Authors
Soares, AL; deSousa, JP; Azevedo, AL; Bastos, JA;

Publication
RE-ENGINEERING FOR SUSTAINABLE INDUSTRIAL PRODUCTION

Abstract
This paper describes a preliminary experience in trying to improve the communication and to reach language agreements in the context of a large R&D trans-national project, comprising partners with different academic and industrial cultures. This kind of projects has difficulties in that, besides cultural and language problems, the project teams undertake work largely by themselves, with reduced interaction with each other. The use of ontologies has a great potential in reducing those problems. Within this research work our goal is to extend the communication role of an ontology towards the mediation of the development actors ''world views''. In doing so, we intend to improve the engineering of an intrinsically complex software system, particularly in the requirements identification, system specification and system design phases, overcoming some of the referred difficulties. It is presented an extract of the Virtual Enterprise ontology currently under construction, focusing in some core definitions relevant for the purpose of developing a distributed planning and control software system. An example concerning the development of such a system is described in older to demonstrate the usefulness of the ontology based systems development.

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