971 resultados para Process patterns


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Grinding is a parts finishing process for advanced products and surfaces. However, continuous friction between the workpiece and the grinding wheel causes the latter to lose its sharpness, thus impairing the grinding results. This is when the dressing process is required, which consists of sharpening the worn grains of the grinding wheel. The dressing conditions strongly affect the performance of the grinding operation; hence, monitoring them throughout the process can increase its efficiency. The objective of this study was to estimate the wear of a single-point dresser using intelligent systems whose inputs were obtained by the digital processing of acoustic emission signals. Two intelligent systems, the multilayer perceptron and the Kohonen neural network, were compared in terms of their classifying ability. The harmonic content of the acoustic emission signal was found to be influenced by the condition of dresser, and when used to feed the neural networks it is possible to classify the condition of the tool under study.

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Grinding is a workpiece finishing process for advanced products and surfaces. However, the constant friction between workpiece and grinding wheel causes the latter to lose its sharpness, thereby impairing the result of the grinding process. When this occurs, the dressing process is essential to sharpen the worn grains of the grinding wheel. The dressing conditions strongly influence the performance of the grinding operation; hence, monitoring them throughout the process can increase its efficiency. The purpose of this study was to classify the wear condition of a single-point dresser using intelligent systems whose inputs were obtained by digitally processing acoustic emission signals. Two multilayer perceptron (MLP) neural networks were compared for their classification ability, one using the root mean square (RMS) statistics and another the ratio of power (ROP) statistics as input. In this study, it was found that the harmonic content of the acoustic emission signal is influenced by the condition of the dresser, and that the condition of the tool under study can be classified by using the aforementioned statistics to feed a neural network. © IFAC.

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In accordance with the mandate it received at the twenty-third session, in this document the secretariat has attempted to delve further into the links among technical progress, international competitiveness and social equity, although it does not, certainly, purport to have exhausted these subjects. Two qualifying remarks are called for here. First, the secretariat is deliberately abstaining from becoming embfoiled in the theoretical aspects of a controversy which has raged for centuries, and particularly since the French revolution, i.e., the debate surrounding the cause-and-effect relationships and possible areas of incompatibility among democratic governance, economic stability, growth and well-being. Rather than concerning itself with doctrine, the secretariat prefers to deal with the realities confronting virtually all the Governments of the region. These realities include the need to resume a sustained (and environmentally sustainable) growth process within the framework of the consolidation of pluralistic, democratic societies -societies that are faced with very real demands to address the many ways in which the majority of the population has been bypassed by development. Secondly, no attempt has been made in this document to provide a list of suitable policies for changing production patterns or for attaining greater social equity. Instead, the focus is on how certain pivotal analytical and policy aspects can be linked within an integrated approach so as to reinforce any existing areas of complementarity between efforts to achieve greater growth and efforts to seek greater social equity. This approach highlights the central tenet of the document: that growth, social equity and democracy can be compatible. What is more, there are significant but as yet largely unexplored areas in which social equity and changing production patterns complement and reinforce one another.

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Com base no clima de ondas para o sul da costa brasileira, a refração de ondas foi modelada para a obtenção de alturas e direção das ondas ao longo da costa sul de Santa Catarina. Essas informações permitem a estimativa da deriva litorânea potencial para a região. De acordo com a orientação da linha de costa, diferentes setores do litoral apresentam variados padrões de deriva. As estimativas foram realizadas com base nos dados médios anuais e para cada estação do ano, demonstrando assim a variabilidade dos padrões ao longo do ano. A configuração da linha de costa e os resultados das estimativas de intensidade e direção da deriva indicam o predomínio da deriva litorânea na porção sul da área e um equilíbrio entre processos de espraiamento e de deriva na porção norte. Padrões contrastantes de deriva entre a porção sul e norte da linha de costa indicam um balanço positivo de sedimentos na porção central, disponibilizando sedimentos para os processos de transporte através da costa. Considerando escalas temporais maiores, os padrões de deriva concordam com o processo de preenchimento costeiro que é controlado principalmente pelo aporte de sedimentos pela deriva litorânea.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Registration is a necessarily sophisticated evaluation process applied to vertebrate pesticide products. Although conducted to minimize any potential impacts upon public health, the environment and food production, the all-encompassing process of registration can stifle innovation. Vertebrate pesticides are rarely used to control pest animals in food crops. In contrast to agrochemicals, relatively small amounts of vertebrate pesticides are used (50.1%), usually in solid or paste baits, and generally by discrete application methods rather than by broad-scale spray applications. We present a hierarchy or sliding scale of typical data requirements relative to application techniques, to help clarify an evolving science-based approach which focuses on requiring data to address key scientific questions while allowing waivers where additional data have minor value. Such an approach will facilitate the development and delivery of increasingly humane, species-targeted, low residue pesticides in the New World, along with the phasing out of less desirable chemicals that continue to be used due to a lack of alternatives.

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Buteonine hawks represent one of the most diverse groups in the Accipitridae, with 58 species distributed in a variety of habitats on almost all continents. Variations in migratory behavior, remarkable dispersal capability, and unusual diversity in Central and South America make buteonine hawks an excellent model for studies in avian evolution. To evaluate the history of their global radiation, we used an integrative approach that coupled estimation of the phylogeny using a large sequence database (based on 6411 bp of mitochondrial markers and one nuclear intron from 54 species), divergence time estimates, and ancestral state reconstructions. Our findings suggest that Neotropical buteonines resulted from a long evolutionary process that began in the Miocene and extended to the Pleistocene. Colonization of the Nearctic, and eventually the Old World, occurred from South America, promoted by the evolution of seasonal movements and development of land bridges. Migratory behavior evolved several times and may have contributed not only to colonization of the Holarctic, but also derivation of insular species. In the Neotropics, diversification of the buteonines included four disjunction events across the Andes. Adaptation of monophyletic taxa to wet environments occurred more than once, and some relationships indicate an evolutionary connection among mangroves, coastal and varzea environments. On the other hand, groups occupying the same biome, forest, or open vegetation habitats are not monophyletic. Refuges or sea-level changes or a combination of both was responsible for recent speciation in Amazonian taxa. In view of the lack of concordance between phylogeny and classification, we propose numerous taxonomic changes. (C) 2009 Elsevier Inc. All rights reserved.