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Publications

Publications by CESE

2000

Using metaheuristics in multiobjective resource constrained project scheduling

Authors
Viana, A; de Sousa, JP;

Publication
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH

Abstract
Although single objective metaheuristics are widely spread and applied in many combinatorial optimisation problems, only very recently have multiobjective metaheuristics (MOMH) been designed and used in practice. They aim at obtaining good approximations of the set of nondominated solutions of a problem, in an efficient way. In this work, we have applied multiobjective versions of simulated annealing and taboo search to the resource constrained project scheduling problem (RCPSP), in order to minimise the makespan, the "weighted" lateness of activities and the violation of resource constraints. Computational experience performed on randomly generated instances shows that this general approach is flexible, effective and able to deal with multiple objectives and with variations in the problem structure.

2000

A multi-agent framework for order negotiation in distributed manufacturing enterprises

Authors
Azevedo, AL; Sousa, JP; Oliveira, RT;

Publication
MULTI-AGENT-SYSTEMS IN PRODUCTION

Abstract
Current Production Planning and Control Systems do not in general satisfy the needs and challenges of production networks, as they lack the capacity to appropriately support a co-ordinated and effective communication between heterogeneous manufacturing sites. This paper presents a new approach, based on the multi-agent systems paradigm, for a planning (order negotiation) system suitable for distributed and virtual enterprises. The infrastructure and planning methodology (based on negotiations) proposed in this paper, have been designed for planning orders, involving a large number of scattered manufacturing plants, used in different production stages, connected through a complex logistic subsystem. A Decision Support System has been designed around an architecture based on several intelligent agents communicating through the Knowledge Query Manipulation Language (KQML). Copyright (C) 1999 IFAC.

2000

Reflections on the users involvement in the development of an information system for team centred quality management

Authors
Soares, A; Schmidt, C; Gaida, W;

Publication
AUTOMATED SYSTEMS BASED ON HUMAN SKILL 2000: JOINT DESIGN OF TECHNOLOGY AND ORGANISATION

Abstract
This paper gives an overview of a trans-european research and development project where a manufacturing team information system was developed. The focus is on the process of requirements analysis and specification, and on the prototype evaluation. Special emphasis is given to the effectiveness of the users involvement in the process. Copyright (C) 2000 IFAC.

1999

FAFNER-Accelerating Nesting Problems with FPGAs

Authors
Alves, JC; Ferreira, JC; Albuquerque, C; Oliveira, JF; Ferreira, JS; Matos, JS;

Publication
7th IEEE Symposium on Field-Programmable Custom Computing Machines (FCCM '99), 21-23 April 1999, Napa, CA, USA

Abstract
The nesting problem consists of defining the cutting plan of a piece of raw material in smaller irregular shapes, and has applications in the apparel and footwear industries. Due to its NP-hard nature, the optimal solution can only be guaranteed by exhaustively trying all possible solutions and choosing the best one. Because this is impractical in real-life industrial problems, automatic approaches are based on optimization meta-heuristics that search for sub-optimal but good enough solutions. These optimization techniques rely on the construction and evaluation of several solutions, thus requiring heavy geometric manipulation of the irregular polygons that constitute the problem data. Efficient processing of this geometric information is thus necessary to make effective fully automatic approaches to nesting problems in industrial environments. This paper describes Fafner, an FPGA-based custom computing machine that is used to accelerate the geometric operations, that are in the core of heuristic solutions to the nesting problem. The system is used as an auxiliary processor attached to a low cost personal computer, and combines a custom programmable processor with an array of custom circuits for the processing of irregular polygons.

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.

1998

Flexible hardware acceleration for nesting problems

Authors
Ferreira, JC; Alves, JC; Albuquerque, C; Oliveira, JF; Ferreira, JS; Matos, JS;

Publication
5th IEEE International Conference on Electronics, Circuits and Systems, ICECS 1998, Surfing the Waves of Science and Technology, Lisbon, Portugal, September 7-10, 1998

Abstract
The nesting (or placement) problem is an NP-hard combinatorial problem with important industrial applications, e.g. in apparel or footwear industry. This paper describes a hardware infrastructure to accelerate the processing of the underlying geometric information. The system consists of an FPGA-based reconfigurable platform enhanced by an ASIC for the processing of irregular polygons. The paper discusses the need for such a platform, establishes the main design guidelines and describes the architecture and modes of operation of both the reconfigurable infrastructure and the dedicated IC.

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