179 resultados para Estrela espectral. Rotação estelar. Dissertação. Estudo sistemático. Velocidade de rotação. Distribuição maxwelliana.


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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Física - FEG

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Pós-graduação em Geociências e Meio Ambiente - IGCE

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Pós-graduação em Engenharia Mecânica - FEIS

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

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

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The aim of this study was to compare temperature increases produced by a well-known equipment, the high-speed handpieces, with a relatively new instrument, the Er:YAG laser (350 mJ/10 Hz). Thirty-five bovine mandibular incisors, which were reduced to an enamel/dentin thickness of 2,5 mm, were used. Cavity preparation was done till a depth of 2, 5 mm. A thermocouple was placed to read the temperature inside of the pulp chamber. Analysis was performed in these groups: I - high-speed handpiece without water-cooling (n=10); II - high-speed handpiece with water-cooling (n=10); III - Er:YAG laser without water-cooling (n=5); IV- Er:YAG laser with water-cooling (n=10) Group III had only 5 teeth because it was impossible to properly make the cavity preparations by the laser equipment without water cooling. The temperature increases were recorded in a computer linked to the thermocouples and the data of the groups I, II and IV were submitted to Dunn's multiple comparison test (p<0,05). The medium temperature increases were: 11,64ºC for group I, 0,96ºC for group II, 40,86ºC for group III and 2,9°C for group IV. There were no statistical differences between groups lI and IV, and these were different from group I. The cavity preparations made by the high-speed and the laser equipment generated very similar heat increases under water-cooling. The water-cooling is essential to avoid aggressive temperature increases, both when using the high-speed and the laser equipment, and with laser it is especially necessary for ablation of enamel

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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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The dynamics of the rotation of a satellite is an old and classical problem, specially in the Euler formalism. However, with these variables, even in torque free motion problem, the integrability of the system is far from trivial, mainly when the three moments of the inertia are not equal. Another disadvantage occurs when the inclinations between some plans are null or close to zero, so the nodes become undetermined. In this work, we propose the use of modern Andoyer's variables. These are a set of canonical variables and therefore some significant advantages can be obtained when dealing with perturbation methods. On other the hand, the integrability of the torque free motion becomes very clear, as the system is reduced to a problem of one degree of freedom. The elimination of the singularities mentioned above, can be solved very easily, with Pincaré-type variables. In this work we give the background concepts of the Andoyer's variables and the disturbing potential is obtained for the rotational dynamics of a satellite perturbed by a planet. In the case when A = B (moments of inertia) and due to the current variables, the averaged system is trivially obtained through very simple integrations

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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In this work the main concepts to apply to dynamic signal analysis technique for rotating machines known as order analysis, discussing their characteristics and applying it on an experimental test rig. It aims to characterize the dynamic behavior of experimental test rig in run up and run down tests, it's operational speed range and the identification of the critical speed of shaft rotation. The results of the critical speed and stationary natural frequency of the shaft are discussed