Alexandre Xavier Martins

Universidade Federal de Ouro Preto · Department of Production Engineering (ICEA)

O problema da alocação de férias e força de trabalho tem sido um campo amplo para a realização de pesquisas em gestão e pesquisa operacional. No entanto, embora seja um problema comum e conhecido, encontrar boas soluções costuma ser uma tarefa difícil dada a sua característica combinatória, tornando ainda mais difícil encontrar a solução ótima para...

This work presents a computational study for two variants of a dynamic or multi-period two-level uncapacitated facility location problem. In this problem, first-level plants serve different demand patterns of scattered clients over a planning horizon via second-level facilities. In the first variant, second-level facilities can be supplied by only...

This paper addresses the Uncapacitated Single Allocation p-hub Maximal Covering Problem (USApHMCP), which aims to determine the best allocation for the p-hubs within a node network in order to maximize the network coverage. We proposed a search strategy-based heuristic Basic Variable Neighborhood Search (VNS) to solve the problem. Two different set...

The problem of vacation and workforce allocation has been a broad field for conducting research in management and operational research. However, even though it is a common and well-known problem, finding good solutions is usually a difficult task given its combinatorial feature, making it even more difficult to find the optimal solution in order to...

The inadequate infrastructure and the intensive people and vehicle flow lead to problems associated with urban roads in the world. The Strong Network Orientation Problem (SNOP) stands as an alternative to mitigate this scenario by the minimization of the sum of the distances traveled from each intersection point between roads, taking into account t...

This paper addresses the Uncapacitated Single Allocation p-hub Maximal Covering Problem (USApHMCP), which aims to determine the best allocation for p-hubs within a node network in order to maximize the network coverage. We proposed a search strategy-based heuristic VND (Variable Neighborhood Descent) to solve the problem. Two different sets of lite...

Este trabalho trata do problema de programação de horários em escolas. Dada sua natureza combinatória, ele é resolvido por meio de dois algoritmos metaeurísticos, um baseado em Simulated Annealing e outro em GRASP Ambos possuem parâmetros auto-adaptativos, dispensando, assim, a calibragem destes. Para testá-los são utilizados dados reais do departa...

This work addresses the multi-level capacitated minimum spanning tree (MLCMST) problem. It consists of finding a minimal cost spanning tree such that the flow to be transferred from a central node (root) to the other nodes is bounded by the edge capacities. In this paper, a hybrid algorithm, combining the Variable Neighborhood Search (VNS) metaheur...

This work presents a hybrid multi-start algorithm for solving generic binary linear programs. This algorithm, called HMS, is based on a Multi-Start Metaheuristic and combines exact and heuristic strategies to address the problem. The initial solutions are generated by a strategy that applies linear programming and constraint propagation for definin...

In this study, an aggregated flow formulation and a column generation strategy are proposed for the Strong Network Orientation Problem (SNOP) that consists in setting an orientation for each edge in a given graph, such that the resulting digraph is strongly connected and the total travel distance between all pairs of vertices is minimized. SNOP is...

This paper introduces a cooperative parallel heuristic for the uncapacitated single allocation hub location problem. The proposed heuristic consists in combining multiple parallel ILS-RVND local search and Path-Relinking, cooperating through asynchronously exchaging solutions in a shared pool. This method as devised to tackle large scale instances...

The routing and wavelength assignment (RWA) problem typically occurs in wavelength division multiplexing optical networks. Given a number of available wavelengths, we consider here the problem of maximising the number of accepted connections with respect to the clash and continuity constraints. We first propose a new strategy which combines two exi...

Este trabalho trata o Problema de Sequenciamento em Máquinas Paralelas Não-Relacionadas com Tempos de Preparação Dependentes da Sequência , objetivando minimizar o makespan. E proposto um algoritmo heurístico na qual a solução inicial e gerada por meio de um método construtivo guloso, e depois refinada pelo procedimento Iterated Local Search (ILS)....

We propose an efficient genetic algorithm (GA) for the design of hub-and-spoke networks with single allocation. The creation of the initial population is based on the greedy randomized search procedure, which provides high quality individuals. Furthermore, new crossover and mutation operators were implemented in order to improve the solution over t...

This work addresses the Vehicle Routing Problem with Simultaneous Pickup and Delivery (VRPSPD). Due to its complexity, we propose a heuristic algorithm for solving it, so-called GENVNS-TS-CL-PR. This algorithm combines the heuristic procedures Cheapest Insertion, Cheapest Insertion with multiple routes, GENIUS, Variable Neighborhood Search (VNS), V...

In 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...

This paper presents a multi-objective evolutionary 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 the design of optimal 3 to 10 elements Y...

We propose algorithms to compute tight lower bounds and high quality upper bounds (UBs) for the multilevel capacitated minimum spanning tree problem. We first develop a branch-and-cut algorithm, introducing some new features: (i) the exact separation of cuts corresponding to some master equality polyhedra found in the formulation; (ii) the separati...

This work deals with the routing and Wavelength assignment (RWA) in optical WDM networks independently on the underlying physical topology. We begin with a review of the literature presented some mathematical models formulated to solve theproblem, are also reviewed methods for setting lower bounds and heuristic methods. This problem has been shown...

The Routing and Wavelength Assignment problem occurs in optical networks where communication requests fulfilled without inducing wavelength conflicts. We propose a VND-ILS algorithm which is a hybridization of both the ILS metaheuristic and the VND local search. Three neighborhood structures are defined for the VND as well as a perturbation step in...

We propose a GRASP using an hybrid heuristic-subproblem optimization approach for the Multi-Level Capacitated Minimum Spanning Tree (MLCMST) problem. The motivation behind such approach is that to evaluate moves rearranging the configuration of a subset of nodes may require to solve a smaller-sized MLCMST instance. We thus use heuristic rules to de...

Esse trabalho tem seu enfoque no problema de blendagem de produtos de minério de ferro, estocados nos pátios da mina Cauê, da Companhia Vale do Rio Doce, em Itabira, Minas Gerais, para a composição de lotes. Propõe-se um modelo de programação linear por metas que visa a determinar os locais de retomada dos produtos estocados, de tal forma que a mis...

Resumo Este trabalho trata do problema de determinar a melhor maneira de conectar n terminais, de diferentes locais, a um computador central através de linhas de transmissão. Geralmente este problema é tratado considerando-se que todas as linhas de transmissão têm uma capacidade fixa Q. Isto corresponde a restringir o fluxo máximo de informação em...

Resumo Neste trabalho propomos um framework, denominado JFFO, para otimização através de metaheurísticas. Para sua validação, é construída uma aplicação para resolução do problema de roteamento de veículos com frota heterogênea e janelas de tempo. O framework torna possível a construção de aplicações para resolução de problemas em um curto período...

Resumo Este trabalho trata do problema de determinar a melhor maneira de conectar n terminais, de diferentes locais, a um computador central através de linhas de transmissão. Geralmente este problema é tratado considerando-se que todas as linhas de transmissão têm uma capacidade fixa Q. Isto equivale a impedir que o fluxo máximo de informação em qu...

Este trabalho apresenta um algoritmo eficiente, baseado na metaheurística Simulated Annealing (SA), para resolver o Problema de Roteamento de Veículos com Janela de Tempo. Esse problema tem como objetivo determinar as rotas de custo mínimo para uma frota de veículos de mesma capacidade, atendendo à demanda de um conjunto de clientes, para os quais...

We propose efficient algorithms to compute tight lower bounds and high quality upper bounds for the Multi-Level Capacitated Minimum Spanning Tree problem. We first develop a branch-and-cut algorithm for the problem. This algorithm is able to solve instances of medium size and to provide tight lower bounds for larger ones. We then use the branch-and...