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Dissertação apresentada para obtenção do Grau de Doutor em Engenharia do Ambiente, ABSTRACT Genetic algorithms (GAs) have been used to solve difficult optimization problems in a number of fields. One of the advantages of these algorithms is that they operate well even in domains where little is known, thus giving the GA the flavor of a general purpose(More)
This report attempts to shed light to the fundamental concepts behind the stability of Multi-Agent Systems. We view the system as a discrete time Markov chain with a potentially unknown transitional probability distribution. The system will be considered to be stable when it has converged to an equilibrium distribution. Faced with the non-trivial task of(More)
Anecdotal evidence suggests that the dividend policy of German firms is more flexible than the one of their Anglo-American counterparts. This paper analyses the decision to change the dividend for a panel of 221 German firms from 1984 to 1994. The choice of the period of study is motivated by the fact that at the start of this period there was an economic(More)
This article presents a constraint-based behavioural architecture for low-level safe navigation, the Survival Kit. Instead of approaching the problem by customising a generic Behaviour-Based architecture, the Survival Kit embodies a dedicated semantics for safe navigation, which augments its expressiveness for the task. An instantiation of the architecture(More)
— This paper proposes a model for trail detection that builds upon the observation that trails are salient structures in the robot's visual field. Due to the complexity of natural environments, the straightforward application of bottom-up visual saliency models is not sufficiently robust to predict the location of trails. As for other detection tasks,(More)
A population of committees of agents that learn by using neural networks is implemented to simulate the stock market. Each committee of agents, which is regarded as a player in a game, is optimised by continually adapting the architecture of the agents using genetic algorithms. The committees of agents buy and sell stocks by following this procedure: (1)(More)
This paper describes a vehicle to perform a simple task using a decision control composed of a behavior hierarchy. First the model is presented. It is based on two fundamental components: the behavior module defining how each behavior element is implemented; and the blocker which is the basic component of the arbitration system, responsible for behavior(More)
This paper reports a study on modelling covert visual attention as a parallel process that unfolds in synergy with the embodied agent's action selection process. The parallel nature of the proposed model is according to the multiple covert attention hypothesis and thus suitable for the concurrent search for multiple objects in the embodied agent's visual(More)