278 resultados para Espinores puros


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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Engenharia Mecânica - FEG

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Ciências Biológicas (Biologia Celular e Molecular) - IBRC

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Ciência Florestal - FCA

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Over the past few years, the area of planted forests has expanded considerably in Brazil, reaching a level of 6.3 million hectares, which represents approximately 0.7% of the country, mainly with some species of the Eucalyptus genus. However, due to the global concern with biological invasions by exotic species, risk assessment is necessary to evaluate the potential of Eucalyptus species escaping cultivated stands and invading surrounding native ecosystems. Seedlings by natural regeneration from Eucalyptus grandis and E. urophylla, pure and hybrids between the two species were evaluated, by assessing natural regeneration of Eucalyptus in 18 sites located in Brazilian states with plantation forest tradition (Minas Gerais, São Paulo, Rio Grande do Sul and Espírito Santo). Sample plots were installed in the planted stands, along forest roads and in a nearby pasture or native vegetation.,at different distances from the Eucalyptus stands. Regeneration of Eucalyptus was not recorded in 90% of the plots installed outside the eucalipt stands. However, seedlings of eucalypts were observed in 29% of the plots within the commercial stands (mean density of 37 seedlings per hectare) and 40% of the plots located along forest roads (157 seedlings per hectare on average), but no adult plants by natural regeneration were found. The seedlings of eucalypt species studied rarely were found beyond the limits of the cultivated areas. In the planted stands or along forest roads, eucalypts can germinate, but the seedlings apparently do not establish. So the potential for invasion by seeds produced in commercial plantations of Eucalyptus is low.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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With advances in health care, has been na increase of demand for material that could replace the functions of the human body parts, thus evolved biomedic prosthesis which today are responsible for the constant improvement of the quality of life. The Titanium alloys are widely used as implants due to its properties, like high mechanical resistance, biocompatibility and corrosion resistance, and the addition alloying elements like Zirconium, may improve some of those properties. Such properties are related to the microstructure and consequently to the type of processing performed. The purpose of this dissertation was to characterize the experimental alloy Ti15Zr after route of processsing and heat treatment in order to extend the knowledge about this alloy. The latter has been abtained by fusion of pure metals in a arc melting furnace with an inert argon atmosphere. The material has been homogenized in a tube furnace at 950ºC for 24h and cold worked by swaging, after that, bars with 10 mm of diameter were obtained by the process of rotary forging. The samples were solubilized at 900º C for 2 hours and quenched in water. After that, 4 samples were submitted to the aging, at 400º C, 450º C, 500º C and 550º C. The microstructure and phase analysis was done by optical microscopy and X-rays diffraction (XRD), the mechanical characterization was carried out by microhardness test and finally, evaluation of corrosion resistance of the alloy by electrochemical tests. The XRD and the optical microscopy made it possible to analyze that the heat treatment influenced the phase shifting from α to α', and probably affected the alloy hardness, at the first aged sample at 500º Chas been a sudden increase in the value of hardness, probably by appearance of omega phase, unwanted phase to the medical application duo to great fragility, and finally ... (Complete abstract click electronic access below)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)