254 resultados para Transições


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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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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Matematica Aplicada e Computacional - FCT

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The main objective of this study was to analyze the reliability of blood lactate concentration ([La]), oxygen uptake (VO2) and heart rate (FC) in an intermittent protoco, performed at 95%VO2max with passive or active recovery in untrained subjects. Participated of this study, active healthy males with 20 to 25 years, which were doing aerobic exercises witha weekly frequency of 3 sessions at least. The individulas performed, in different days, the following protocols in a cyclergometer: 1) An incremental test until exhaustion to determine maximal oxygen uptake (VO2max) and the intensity at VO2max; b) Two transitions at 95%VO2max for the determination of the VO2 kinetics parameters and; c) Two intermittent tests until exhaustion, with repetitions at 95% IVO2max and with durantion defined as being half of the duration of the slow component. The duration of the recovery was half of the duration of the effort (effort:pause of 2:1). This test was performed with passive (GP) and active recovery (GA). The VO2 and FC were measured continulously in both tests. Blood collections were performed for the determination of the [La]. There was significant correlação in both groups for VO2 (ATIVA - 0.94, PASSIVA - 0.75), [La] (ATIVA - 0.83, PASSIVA - 0.90) and FC (0.93) only for the passive group. Thus, it can be concluded that the cardiorrespiratory and metabolic responses present good realiability in an intermittent exercise with active or passive recovery

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The aim of this work was the development a computer code for simulation and analysis of atomic spectra from databases constructed from the literature. There were created four routines that can be useful for spectroscopic studies in the atomic processes of laser isotope separation. In the first routine, Possible Transitions, the program checks the possible electron transitions from an energy level of the atom present in the database considering the selection rules for an electric dipole transition. The second routine, Locator Transitions, checks the possible electronic transitions within a user-specified spectral region. The routine Spectra Simulator creates simulated spectra using the graphical application gnuplot through lorentzian curve and finally, the routine Electronic Temperature determines the temperature of electronic excitation of the atom, thought the Boltzmann Plot Method. To test the reliability of the program there were obtained experimental emission spectra of a hollow cathode discharge of dysprosium and argon as a buffer gas. The hollow cathode discharge has been subjected to different values of operating currents and pressure of inert gas. The spectra obtained were treated with the assistance of program routines developed (Transition Locator and Spectra Simulator) and temperatures electronic excitation of the atoms of dysprosium in the different discharge conditions were calculated (routine Electronic Temperature). The results showed that the electronic excitation temperature of the neutral dysprosium atoms in the hollow cathode discharge increases with increasing current applied to the cathode and also by increasing the gas pressure buffer. The determination coefficients, R2, obtained by the Electronic Temperature routine using the linear adjust of the Boltzmann Plot Method were greater... (Complete abstract click electronic access below)

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Pós-graduação em Agronomia (Genética e Melhoramento de Plantas) - FCAV

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Pós-graduação em Geociências e Meio Ambiente - IGCE

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Pós-graduação em Química - IQ

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The main goal of this bachelor work is the study of the physical properties of solids by thermal expansion coefficient measurements, which allows the exploration of various aspects of phase transitions. In this study, some theoretical aspects were focused, for example the first and second order phase transitions, Landau theory for phase transition and the volumetric thermal expansion coefficient. Furthermore, on the origin of the thermal expansion from the Lennard-Jones potential, that contains the anharmonic terms, which give rise to the phononic thermal expansion in solids

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The Sol-gel process has facilitated the processing of Organic-Inorganic Hybrid Materials with several scientific applications and technologies. The hybrid combine the advantages of the Sol-gel process with specific characteristics of organic polymers, allowing processing of thin films without fractures or fissures. The incorporation of azo dyes in polymer matrices has been widely used in the investigation of optical properties. The azo dye Disperse Red (DR1) presents optical alterations when exposed to visible or ultraviolet light. The alterations occur due to transitions of their isomers, trans and cis, caused by photoisomerization, due to electronic transitions of azo group (-N=N-), presenting photochromic and/or photorefractive effects. The hybrid system used in this work is the precursor 3- Glycidoxypropyl-Trimethoxi-silane (GPTS), the Tetraethylorthosilicate (TEOS) and DR1 as a dopant. The characterizations were performed using absorption spectroscopy UV-Vis which allowed the identification of the absorption bands and its variations when the samples were treated thermally and/or illuminated by ultraviolet light

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Pós-graduação em Desenvolvimento Humano e Tecnologias - IBRC

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This paper presents the development and the main results for an interleaved boost rectifier operating as a special input power stage for a trolleybus type vehicle, allowing its feeding by alternate current (AC) or direct current (DC) distribution power systems. When feeding with two wires (single phase) alternate current distribution system, the converter accomplish active power factor correction, providing a relatively sinusoidal current with low total harmonic distortion (THD) and fully complying with IEC 61000-3-4 standards. In addition, a management control system promotes the required automatic operation changes for the proposed rectifier when the vehicle is changing from the DC distribution power system to the AC distribution power system and vice-versa, keeping its original electrical DC system characteristics for the adjustable speed driver sub-system. The main experimental results for a prototype rated at 150kW are presented, considering its application for a trolleybus with DC adjustable speed driver, demonstrating the proposed converter benefits and the possibility of AC feeding system for trolleybus type vehicle.