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Publicações

2000

Using metaheuristics in multiobjective resource constrained project scheduling

Autores
Viana, A; de Sousa, JP;

Publicação
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 Note on Two Simple Transformations for Improving the Efficiency of an ILP System

Autores
Costa, VS; Srinivasan, A; Camacho, R;

Publicação
Inductive Logic Programming, 10th International Conference, ILP 2000, London, UK, July 24-27, 2000, Proceedings

Abstract

2000

The impact of cache coherence protocols on parallel logic programming systems

Autores
De Castro Dutra, I; Costa, VS; Bianchini, R;

Publicação
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

Abstract
In this paper we use execution-driven simulation of a scalable multiprocessor to evaluate the performance of the Andorra-I parallel logic programming system under invalidate and update-based protocols. We use two versions of Andorra-I. One of them was originally designed for bus-based multiprocessors, while the other is optimised for scalable architectures. We study a well-known invalidate protocol and two different update-based protocols. Our results show that for our sample logic programs the update-based protocols outperform their invalidate-based counterpart for the original version of Andorra-I. In contrast, the optimised version of Andorra-I benefits the most from the invalidate-based protocol, but a hybrid update-based protocol performs as well as the invalidate protocol in most cases. We conclude that parallel logic programming systems can consistently benefit from hybrid update-based protocols. © Springer-Verlag Berlin Heidelberg 2000.

2000

Greenhouse adaptive climate control techniques to reduce energy demand

Autores
Cunha, JB; De Moura Oliveira, PB; Cordeiro, M;

Publicação
2000 ASAE Annual Intenational Meeting, Technical Papers: Engineering Solutions for a New Century

Abstract
An adaptive greenhouse climate controller was implemented to regulate the air temperature, humidity and carbon dioxide concentration, with the aim of achieving set-point accuracy and reduce energy consumption. An optimization algorithm, based on the minimization of a cost function, was used to tune a Proportional-Integral-Derivative controller. The cost function is computed over a future time horizon of one hour as a function of the errors between the predicted and desired outputs and the predicted energy demand. Since the controller must be able to predict the greenhouse climate, it was needed to employ recursive identification algorithms to estimate in real-time the parameters of the climate model. When compared with commercially available controllers, this adaptive controller proved to have better performance regarding set-point accuracy and energy consumption.

2000

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

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

Publicação
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

Measures to evaluate rankings of classification algorithms

Autores
Soares, C; Brazdil, P; Costa, J;

Publicação
DATA ANALYSIS, CLASSIFICATION, AND RELATED METHODS

Abstract
Due to the wide variety of algorithms for supervised classification originating from several research areas, selecting one of them to apply on a given problem is not a trivial task. Recently several methods have been developed to create rankings of classification algorithms based on their previous performance. Therefore, it is necessary to develop techniques to evaluate and compare those methods. We present three measures to evaluate rankings of classification algorithms, give examples of their use and discuss their characteristics.

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