Comparing an Approximate Queuing Approach with Simulation for the Solution of a Cross-Docking Problem

Cross-docking is a logistics management concept in which products are temporarily unloaded at intermediate facilities and loaded onto output trucks to be sent to their final destination. In this paper, we propose an approximate nonstationary queuing model to size the number of docks to receive the trucks, so that their unloading will be as short as possible at the receiving dock, thus making the cross-docking process more efficient. It is observed that the stochastic queuing process may not reach the steady equilibrium state. A type of modeling that does not depend on the stationary characteristics of the process developed is applied. In order to measure the efficiency, performance, and possible adjustments of the parameters of the algorithm, an alternative simulation model is proposed using the Arena® software. The simulation uses analytic tools to make the problem more detailed, which is not allowed in the theoretical model. The computational analysis compares the results of the simulated model with the ones obtained with the theoretical algorithm, considering the queue length and the average waiting time of the trucks. Based on the results obtained, the simulation represented very well the proposed problem and possible changes can be easily detected with small adjustments in the simulated model

Gold nanowires and the effect of impurities

Metal nanowires and in particular gold nanowires have received a great deal of attention in the past few years. Experiments on gold nanowires have prompted theory and simulation to help answer questions posed by these studies. Here we present results of computer simulations for the formation, evolution and breaking of very thin Au nanowires. We also discuss the influence of contaminants, such as atoms and small molecules, and their effect on the structural and mechanical properties of these nanowires

Reciclagem de embalagens poliméricas contendo filme de alumínio metálico via processamento químico Recycling of aluminum metallic film polymeric packaging by chemical processing

Embalagens poliméricas contendo filme de alumínio, utilizadas para o acondicionamento de alimentos, foram recicladas via processamento químico com o auxílio de ácido sulfúrico e hidróxido de sódio. Os produtos provenientes desse processo de reciclagem foram os polímeros, com grau de impureza aceitável para reutilização em artigos plásticos com menores exigências e o sulfato de alumínio [(Al2SO4)3], utilizado como agente floculante em processos de tratamento de água e efluentes. Os testes de infravermelho (FTIR) e de chama realizados com os polímeros mostraram a presença de polietileno e poliéster, utilizados na fabricação deste tipo de embalagem.Polymer containing aluminum film used for packaging of foods was recycled by chemical processing with the aid of sulfuric acid and sodium hydroxide. The products obtained from the recycling process were polymer, free of impurities, and aluminum sulfate [(Al2SO4)3], which is used as flocculating agent in water treatment processes and effluent. Infrared (FTIR) and flame tests were performed to help characterizing the polymers. The tests showed the presence of polyethylene and polyester, which are products used in the manufacture of such packaging

Braquiterapia de alta taxa de dose associada a radioterapia externa no tratamento de angiossarcoma extenso do couro cabeludo: relato de caso Combination of high-dose rate brachytherapy and external beam radiotherapy for the treatment of advanced scalp angiosarcoma: case report

Os autores apresentam um caso de extenso angiossarcoma do couro cabeludo submetido a radioterapia exclusiva, pela associação de roentgenterapia de ortovoltagem e braquiterapia de alta taxa de dose utilizando um molde. Descrevem os aspectos clínicos, técnicos e a evolução terapêutica. Destacam as particularidades e a utilidade da braquiterapia de alta taxa de dose, nesta situação em particular, e fazem uma análise comparativa das dificuldades e limitações caso a braquiterapia de baixa taxa de dose fosse empregada. Concluem ser a braquiterapia de alta taxa de dose uma opção útil, prática e segura para as lesões neoplásicas superficiais do escalpe, podendo ser considerada uma alternativa ao tratamento com elétrons.<br>The authors report a case of a patient with an extensive angiosarcoma of the scalp that was submitted only to radiotherapy with a combination of orthovoltage roentgentherapy and high-dose rate brachytherapy, using a mould. The clinical and technical features as well as the therapeutic outcome are presented, and the usefulness and peculiarities of high-dose rate brachytherapy for this particular indication is discussed. A comparative analysis of the difficulties and limitations of employing low-dose rate brachytherapy is also presented. The authors concluded that high-dose rate brachytherapy might be an useful, practical and safe option to treat neoplastic lesions of the scalp, and an alternative treatment to electrontherapy