Performance Analysis of Particle Swarm Optimization Approach for Location Area Planning in Cellular Network

Volume 2 Issue 4 (April 2014

A time-based pheromone approach for the ant system

The ant system (AS) is a metaheuristic approach originally developed for solving the traveling salesman problem. AS has been successfully applied to various hard combinatorial optimization problems and different variants have been proposed in the literature. In this paper, we introduce a time-based pheromone approach for AS (TbAS). Due to this nature TbAS is applicable to routing problems involving time-windows. The novelty in TbAS is the multi-layer pheromone network structure which implicitly utilizes the service time information associated with the customers as a heuristic information. To investigate the performance of TbAS, we use the well-known vehicle routing problem with time-windows as our testbed and we conduct an extensive computational study using the Solomon [29] instances. Our results reveal that the proposed time-based pheromone approach is effective in obtaining good quality solutions

Genotypes and population genetics of cryptococcus neoformans and cryptococcus gattii species complexes in Europe and the mediterranean area.

A total of 476 European isolates (310 Cryptococcus neoformans var. grubii, 150 C. neoformans var. neoformans, and 16 C. gattii species complex) from both clinical and environmental sources were analyzed by multi-locus sequence typing. Phylogenetic and population genetic analyses were performed. Sequence analysis identified 74 sequence types among C. neoformans var. neoformans (VNIV), 65 among C. neoformans var. grubii (56 VNI, 8 VNII, 1 VNB), and 5 among the C. gattii species complex (4 VGI and 1 VGIV) isolates. ST23 was the most frequent genotype (22%) among VNI isolates which were mostly grouped in a large clonal cluster including 50% of isolates. Among VNIV isolates, a predominant genotype was not identified. A high percentage of autochthonous STs were identified in both VNI (71%) and VNIV (96%) group of isolates. The 16 European C. gattii species complex isolates analyzed in the present study originated all from the environment and all belonged to a large cluster endemic in the Mediterranean area. Population genetic analysis confirmed that VNI group of isolates were characterized by low variability and clonal expansion while VNIV by a higher variability and a number of recombination events. However, when VNI and VNIV environmental isolates were compared, they showed a similar population structure with a high percentage of shared mutations and the absence of fixed mutations. Also linkage disequilibrium analysis reveals differences between clinical and environmental isolates showing a key role of PLB1 allele combinations in host infection as well as the key role of LAC1 allele combinations for survival of the fungus in the environment. The present study shows that genetic comparison of clinical and environmental isolates represents a first step to understand the genetic characteristics that cause the shift of some genotypes from a saprophytic to a parasitic life style

Proposta de um framework para prototipagem de sistemas heurísticos multiagentes baseados em algorítmos de colônia de formigas

O estudo de sistemas multiagentes muitas vezes se inicia com a implementação de um algoritmo-base, com variações conforme a necessidade do objeto de estudo. Porém, a comparação entre técnicas propostas se torna difícil, pois não existe uma metodologia de implementação de algoritmos. Deste modo, o presente artigo propõe um framework computacional que permita a prototipagem de um grande conjunto de variações de heurísticas baseadas em sistemas de formigas. Como exemplificação desta proposta de framework, escolheu-se quatro algoritmos considerados significativos na literatura. Então, realizou-se a implementação dos mesmos, analisando o esforço de implementação necessário. Os resultados mostraram uma redução significativa no tempo de implementação com o uso do framework proposto.<br>The study of multi-agent systems usually begins by implementing a base-algorithm, which is changed as required by the aim of the research. In this context, carrying out different algorithms, which have already been established, is not a trivial task as it requires implementing these algorithms.This article proposes a computer framework that enables one to prototype a large set of heuristics based on the Ant Colony System metaheuristic. As an example of the proposed framework, four important AS algorithms were implemented. The results show a significant reduction in the implementation time by using the proposed framework