Uma nova heurística para o problema de minimização de trocas de ferramentas

O problema de minimização de troca de ferramentas (MTSP) busca uma sequência de processamento de um conjunto de tarefas, de modo a minimizar o número de trocas de ferramentas requeridas. Este trabalho apresenta uma nova heurística para o MTSP, capaz de produzir bons limitantes superiores para um algoritmo enumerativo. Esta heurística possui duas fases: uma fase construtiva que é baseada em um grafo em que os vértices correspondem a ferramentas e existe um arco k = (i, j) que liga os vértices i e j se e somente se as ferramentas i e j são necessárias para a execução de alguma tarefa k; e uma fase de refinamento baseada na meta-heurística Busca Local Iterativa. Resultados computacionais mostram que a heurística proposta tem um bom desempenho para os problemas testados, contribuindo para uma redução significativa no número de nós gerados de um algoritmo enumerativo.

A experiência do impossível: O problema da responsabilidade política em Jacques Derrida

This is intended to approach some aspects of the articulation between knowledge and social injunctions in order to understand the problems concerned with the determination of its finality by the very discourse. By analysing the controversy aroused by the work of Jacques Derrida, it can be noticed that the subordination of the discourse autonomy to the obligation of a response is based on the necessity of considering singular reasons; to actively recognize them would be one of the conditions for a rigorous reinterpretation of the discourse nature and role in the contemporary world.

O Agronegócio e o problema do trabalho infantil

This article attempts to identify and analyze the motives that led several sectors of agro-business to engage in the struggle for the eradication of child labor in Brazil, as launched by international organizations for the defense of children's and adolescents' rights. It is our hypothesis that economic globalization and the internationalization of children's rights have given visibility to the problem of child labor, thus demanding the mobilization of entrepreneurial sectors linked to agro-business productive chains in Brazil. The article is divided into four inter-related sections. In the first one, we attempt to provide evidence for the interference of social and labor problems within the ambit of the economic activities of the agro-business sector, within the current context of globalization. This is followed by a study of major UN, UNICEF and ILO investments to internalize children's rights and policies to combat child labor, giving salience to their repercussions in Brazil. In the third section, we analyze strategies adopted by firms linked to agro-business with the purpose of avoiding the use of child labor within their productive chains. Finally, we seek to understand the motivations that have led agro-businessmen to take part in the struggle against child labor. We conclude that firms linked to agro-business took up the project of combating child labor in virtue of the internationalization of children and adolescents' rights, the inclusion of social issues in international markets, the intensification of the fiscalization of public power, the growth of action around entrepreneurial social responsibility and increased consumer consciousness.

Flujo de potencia AC descentralizado para sistemas de potencia multi-área usando un método de descomposición basado en relajación Lagrangiana

A decentralized solution method to the AC power flow problem in power systems with interconnected areas is presented. The proposed methodology allows finding the operation point of a particular area without explicit knowledge of network data of adjacent areas, being only necessary to exchange border information related to the interconnection lines between areas. The methodology is based on the decomposition of the first-order optimality conditions of the AC power flow, which is formulated as a nonlinear programming problem. A 9-bus didactic system, the IEEE Three Area RTS-96 and the IEEE 118 bus test systems are used in order to show the operation and effectiveness of the distributed AC power flow.

Reformulação para um problema integrado de dimensionamento e sequenciamento de lotes

In this paper, some new constraints and an extended formulation are presented for a Lot Sizing and Scheduling Model proposed in the literature. In the production process considered a key material is prepared and is transformed into different final items. The sequencing decisions are related to the order in which the materials are processed and the lot sizing decisions are related to the final items production. The mathematical formulation considers sequence-dependent setup costs and times. Results of the computational tests executed using the software Cplex 10.0 showed that the performance of the branch-and-cut method can be improved by the proposed a priori reformulation.