937 resultados para Armillary spheres.


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This paper presents a comparative analysis between the experimental characterization and the numerical simulation results for a three-dimensional FCC photonic crystal (PhC) based on a self-assembly synthesis of monodispersive latex spheres. Specifically, experimental optical characterization, by means of reflectance measurements under variable angles over the lattice plane family [1,1, 1], are compared to theoretical calculations based on the Finite Di®erence Time Domain (FDTD) method, in order to investigate the correlation between theoretical predictions and experimental data. The goal is to highlight the influence of crystal defects on the achieved performance.

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The production of pellets by Aspergillus niger and the FePO 4 (FeP) solubilization through the use of free or immobilized spores and pellets were studied. The media Sabouraud, MS-FeP, MS-K 2HPO 4, Czapek and Malt were used for pellets yield. Enhanced growth and pellets production were found in the Sabouraud and MS-FeP than those produced by the other media. Pellets produced in Sabouraud were larger in size and formed well-defined spheres than those produced in MS-FeP. Pellets amounts varying from 2 to 8 mg mL, -1 were inoculated in the MS-FeP medium. The greatest quantity of solubilized FeP was found when 6 mg of pellets mL, -1 were used. While the free spores were the worst form used for FeP solubilization in culture medium, free pellets allowed for the production of the greatest quantities of soluble phosphate, even after repeated use of the pellets. In the soil, pellets solubilized similar quantities of FeP compared to the immobilized A. niger spores and can be used with advantage since they are easily produced. © 2010 Academic Journals Inc.

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In this work, the effect of the milling time on the densification of the alumina ceramics with or without 5wt.%Y 2O 3, is evaluated, using high-energy ball milling. The milling was performed with different times of 0, 2, 5 or 10 hours. All powders, milled at different times, were characterized by X-Ray Diffraction presenting a reduction of the crystalline degree and crystallite size as function of the milling time increasing. The powders were compacted by cold uniaxial pressing and sintered at 1550°C-60min. Green density of the compacts presented an increasing as function of the milling time and sintered samples presented evolution on the densification as function of the reduction of the crystallite size of the milled powders. © (2010) Trans Tech Publications.

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The present study suggests the use of high energy ball milling to mix (to dope) the phase MgB2 with the AlB2 crystalline structure compound, ZrB2, with the same C32 hexagonal structure than MgB 2, in different concentrations, enabling the maintenance of the crystalline phase structures practically unaffected and the efficient mixture with the dopant. The high energy ball milling was performed with different ball-to-powder ratios. The analysis of the transformation and formation of phases was accomplished by X-ray diffractometry (XRD), using the Rietveld method, and scanning electron microscopy. As the high energy ball milling reduced the crystallinity of the milled compounds, also reducing the size of the particles, the XRD analysis were influenced, and they could be used as comparative and control method of the milling. Aiming the recovery of crystallinity, homogenization and final phase formation, heat treatments were performed, enabling that crystalline phases, changed during milling, could be obtained again in the final product. © (2010) Trans Tech Publications.

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