975 resultados para |Cu x|[Si yAl]-MFI


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The quality assurance control program (QACP) in clinical radiology is very important to acquire, image quality, patient dose reduction and cost for the institution. The verification of the real tension on the x ray tube, it is one of many parameters that may be determined on a QACP. This act on image quality as absorbed dose in patient. Once proved the importance of this fact, this study come up with the determination of tension to any X ray tube used on medical routine, on quick, safe and low cost manner. To reach the aim of this study, the methodology consisted on measuring expose rates (ER) using different thicknesses of copper (Cu) plates like filters and relating these results with Half Layer Value (HLV). Afterwards, the HLV was associated to real tension that was acquired with kilo voltage of peak (kVp) measurers used on clinical routine. So walking in this path, when performed the ER, on any X ray tube, itâs possible acquire the HLV and consequently the real kVp, considering measures obtained before, on the methodology of kVp estimative development

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Este trabajo es parte de una investigación todavía en curso y objetiva observar cómo alumnos brasileños de la carrera de Letras - portugués y español - organizan y ponen en práctica la enseñanza del portugués a parejas hispanohablantes, en el contexto Teletandem. Buscamos comprender cómo/si son planificados los contenidos de LP que enseñan y el impacto de las prácticas de Teletandem a la formación de esos profesores de idiomas. Esta investigación es basada en la metodología cualitativa crítica, más específicamente en la visión de Carspecken. Los datos obtenidos hasta ahora muestran que, debido a la proximidad de las lenguas, este contexto de aprendizaje virtual requiere la presencia de un mediador que les señale a los aprendices aspectos lingüísticos y culturales que deben ser considerados.

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Pós-graduação em Ciência dos Materiais - FEIS

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Amorphous SiC(x)N(y) films have been deposited on (100) Si substrates by RF magnetron sputtering of a SiC target in a variable nitrogen-argon atmosphere. The as-deposited films were submitted to thermal anneling in a furnace under argon atmosphere at 1000 degrees C for 1 hour. Composition and structure of unannealed and annealed samples were investigated by RBS and FTIR. To study the electrical characteristics of SiC(x)N(y) films, Metal-insulator-semiconductor (MIS) structures were fabricated. Elastic modulus and hardness of the films were determined by nanoindentation. The results of these studies showed that nitrogen content and thermal annealing affect the electrical, mechanical and structural properties of SiC(x)N(y) films.

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The composite SmBa2Cu3O7-delta (Sm-123), obtained by the substitution of the ion Y for Sm in the very well known and studied YBa2Cu3O7-delta (Y-123), is potentially attractive for better understanding superconductivity mechanisms and for its applications as electronic devices. Sm-123 samples show higher critical temperatures than Y-123 ones do and a larger solubility of Sm in Ba-Cu-O solvent, which makes their growth process faster. When oxygen is present interstitially, it strongly affects the physical properties of the material. The dynamics of oxygen can be investigated by anelastic spectroscopy measurements, a powerful technique for the precise determination of the oscillation frequency and the internal friction when atomic jumps are possible. Anelastic spectroscopy allows determining the elasticity modulus (related to the oscillation frequency) and the elastic energy loss (related to the internal friction) as a function of the temperature. The sample was also investigated by X-ray diffraction (XRD), scanning electronic microscopy (SEM), and electric resistivity. The results obtained show a thermally activated relaxation structure composed by at least 3 relaxation processes. These processes may be attributed to the jumps of oxygen atoms present of the Cu-O plane in the orthorhombic phase.

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The identification, characterization and stability range of the phases present in a series of Cu-Al alloys, with Al content from 11.0 to 15.0 wt.%, were studied by Differential Thermal Analysis (DTA), Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction (SAED), Auger Electron Spectroscopy (AES), Energy Dispersive X-Ray Spectroscopy (EDX) and X-Ray Diffraction (XRD). In some alloys and in a temperature range from 790 degrees C to 850 degrees C the presence of black spots exhibiting regular shapes and an homogeneous distribution was noticed through metallographic microscopy. Data from TEM and AES indicate that these spots are made of two monocrystalline phases having different Al contents and a crystallographic orientation relationship. (C) 1998 Elsevier B.V. S.A. All rights reserved.