DECEA - Departamento de Ciências Exatas e Aplicadas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/551
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4 resultados
Resultados da Pesquisa
Item Geração de colunas para o problema de roteamento e atribuição de comprimentos de onda.(2012) Martins, Alexandre Xavier; Duhamel, Christophe; Mahey, Philippe; Souza, Maurício Cardoso de; Saldanha, Rodney RezendeNeste trabalho, apresenta-se um estudo sobre o Problema de Roteamento e Atribuição de Comprimentos de Onda em redes ópticas WDM independentemente da topologia física subjacente. Por se tratar de um problema NP difícil muitos métodos exatos e heurísticos vem sendo estudados para a sua resolução. Apresentamos o estudo da versão do problema onde o objetivo é maximizar o número de requisições atendidas. Inicialmente é feita uma revisão da literatura apresentando alguns modelos matemáticos formulados para a resolução do problema. Depois apresentamos uma estratégia baseada em geração de colunas que combina métodos já existentes. Os resultados computacionais sobre instâncias consagradas da literatura comprovam a eficiencia do métodoItem Heuristique VND-ILS pour le problème de routage et d’affectation de longueur d’onde.(2011) Martins, Alexandre Xavier; Duhamel, Christophe; Mahey, Philippe; Souza, Maurício Cardoso de; Saldanha, Rodney RezendeItem A multi-objective evolutionary algorithm based on decomposition for optimal design of Yagi-Uda antennas.(2012) Carvalho, Rodrigo de; Saldanha, Rodney Rezende; Gomes, B. N.; Lisboa, Adriano Chaves; Alexandre, Xavier MartinsThis paper presents a multi-objective evol utionary algorithm based on decomposition (MOEA/D) to design broadband optimal Yagi-Uda antennas. A multi-objective problem is formulated to achieve maximum directivity, minimum voltage standing wave ratio and maximum front-to-back ratio. The algorithm was applied to th e design of optimal 3 to 10 elements Yagi-Uda antennas, whose optimal Pareto fronts are provided in a single picture. The multi-o bjective problem is decomposed by Chebyshev decomposition, and it is solved by differential evolution (DE) and Gaussian mutation op erators in order to provide a better approximation of the Pareto front. The results show that the implemented MOEA/D is ef fi cient for designing Yagi-Uda antennas.Item Variable neighborhood descent with iterated local search for routing and wavelength assignment.(2012) Martins, Alexandre Xavier; Duhamel, Christophe; Mahey, Philippe; Saldanha, Rodney Rezende; Souza, Maurício Cardoso deIn this work we treat the Routing and Wavelength Assignment (RWA) with focus on minimizing the number of wavelengths to route demand requests. Lightpaths are used to carry the traffic optically between origin-destination pairs. The RWA is subjected to wavelength continuity constraints, and a particular wavelength cannot be assigned to two different lightpaths sharing a common physical link. We develop a Variable Neighborhood Descent (VND) with Iterated Local Search (ILS) for the problem. In a VND phase we try to rearrange requests between subgraphs associated to subsets of a partition of the set of lightpath requests. In a feasible solution, lightpaths belonging to a subset can be routed with the same wavelength. Thus, the purpose is to eliminate one subset of the partition. When VND fails, we perform a ILS phase to disturb the requests distribution among the subsets of the partition. An iteration of the algorithm alternates between a VND phase and a ILS phase. We report computational experiments that show VND-ILS was able to improve results upon powerful methods proposed in the literature.