Composites based on virgin and recycled polypropylene (PP and rPP) reinforced with 15 wt% sisal fibers, with and without alkali treatment, were prepared by compression molding in a mat composed of a three-layer sandwich structure. The sisal was characterized by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The composites were characterized according to physical and mechanical properties. Additionally, a factorial experimental design was used to statistically evaluate the mechanical properties of the composite. The FTIR and XRD indicated the partial removal of amorphous materials from the surface of the sisal after alkali treatment. The composites’ density results varied from 0.892 to 0.927 g·cm−3, which was in the desirable range for producing lightweight automotive components. A slight decrease in the hardness of the pure rPP and rPP composites in relation to the PP was observed. The water absorption was higher in rPP composites, regardless of the chemical treatment. Moreover, the impact resistance of PP and its composites was higher than the values for rPP. Statistical analysis showed that the alkali treatment was a significant factor for the hardness of the rPP and PP composites, and that the addition of the sisal layer was relevant to improve the impact resistance of the composites.

In this work we propose a multicriteria evaluation scheme for heuristic algorithms based on the classic Condorcet ranking technique. Weights are associated to the ranking of an algorithm among a set being object of comparison. We used five criteria and a function on the set of natural numbers to create a ranking. The discussed comparison involves three well-known problems of combinatorial optimization -Traveling Salesperson Problem (TSP), Capacitated Vehicle Routing Problem (CVRP) and Quadratic Assignment Problem (QAP). The tested instances came from public libraries. Each algorithm was used with essentially the same structure, the same local search was applied and the initial solutions were similarly built. It is important to note that the work does not make proposals involving algorithms: the results for the three problems are shown only to illustrate the operation of the evaluation technique. Four metaheuristics -GRASP, Tabu Search, ILS and VNS -are therefore only used for the comparisons.

ABSTRACT.To each instance of the Quadratic Assignment Problem (QAP) a relaxed instance can be associated. Both variances of their solution values can be calculated in polynomial time. The graph isomorphism problem (GIP) can be modeled as a QAP, associating its pair of data matrices with a pair of graphs of the same order and size. We look for invariant edge weight functions for the graphs composing the instances in order to try to find quantitative differences between variances that could be associated with the absence of isomorphism. This technique is sensitive enough to show the effect of a single edge exchange between two regular graphs of up to 3,000 vertices and 300,000 edges with degrees up to 200. Planar graph pairs from a dense family up to 300,000 vertices were also discriminated. We conjecture the existence of functions able to discriminate non-isomorphic pairs for every instance of the problem.

O objetivo do trabalho proposto é demostrar o ganho obtido com a implantação de métodos que buscam melhorar a competitividade de uma indústria metalomecânica através da redução no tempo de troca das ferramentas e nos ajustes necessários na execução de algumas atividades ocorridas na produção durante a mudança do diâmetro de tubos. Para alcançar tal objetivo, aplicou-se o método Troca Rápida de Ferramenta (TRF), também conhecido na literatura como Single Minute Exchange of Die (SMED), mapeamento de processos e o método PERT/CPM. Com o estudo de caso utilizado, foi possível verificar uma redução do tempo de troca do equipamento de formação de tubos de 12 horas para 4,52 horas. Uma redução significativa no tempo de setup, se comparado ao processo antes da sua aplicação.

Os resíduos sólidos domésticos são dejetos das atividades dos seres humanos em ambientes domésticos, cujo acúmulo representa um grande problema para a população. Dentre os tipos de resíduos sólidos domésticos existentes, as embalagens cartonadas assépticas, materiais compostos de polietileno, alumínio e papel-cartão, que são comumente utilizados para armazenar bebidas. A melhor maneira de destinar as embalagens cartonadas é a reciclagem, que pode ser realizada tanto de maneira artesanal, quanto separando seus componentes industrialmente. Este trabalho realizou uma pesquisa bibliográfica sobre os métodos de reciclagem de embalagens cartonadas assépticas mais empregados pelos autores de artigos científicos nos últimos dez anos. Para isso, foram realizadas buscas nos sites Science Direct, Scielo e Google Acadêmico. Em seguida, os artigos selecionados foram analisados