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This paper reports on the influence of sintering conditions on the flashover/pre-flashover characteristics of alumina insulators in vacuum under an impulse voltage. Four kinds of alumina insulator were studied, which were prepared using the same formula with different sintering conditions. The surface pre-flashover and flashover phenomena of different samples in vacuum have been observed under impulse voltage. Based on the experimental results, the characteristics of pre-flashover and flashover vary with different kinds of test samples. It was found that the insulators with a higher sintering temperature had a lower flashover voltage, and more active preflashover. From a scanning electron microscope (SEM) analysis of alumina insulators, we conclude that the methods of preparing alumina samples can affect their microstructure resulting in a change in the pre-flashover and flashover performance as alumina insulators.

CO2 concentrations and soil moisture conditions are important factors in photosynthesis of trees. This study investigated the photosynthetic CO2 responses in the leaves of Prunus sibirica L. and Pinus tabulaeformis Carr. under eight soil water conditions in a semiarid loess hilly region. CO2-response curves and physiological parameters were fitted using a rectangular hyperbola model, nonrectangular hyperbola model, exponential equation, and modified rectangular hyperbola model. Results revealed the relative soil water content (RWCs) for P. sibirica required to maintain higher photosynthetic rate ranging from 46.5 to 81.6%, and that for P. tabulaeformis ranging from 35.4 to 84.5%. When RWCs exceeded these ranges, the net photosynthetic rate of both species decreased. CO2-response curves and three parameters, carboxylation efficiency, CO2-compensation point, and photorespiration rate, were well fitted by the four models when RWCs was appropriate for P. sibirica and P. tabulaeformis. When RWCs exceeded the optimal ranges, only the modified rectangular hyperbola model could precisely simulate the CO2-response curves and photosynthetic parameters of both species. [ABSTRACT FROM AUTHOR]

The relaxation of the misfit strain by the formation of misfit dislocations in InxGa1-xN/GaN multiple quantum wells grown by metal-organic chemical-vapor deposition was investigated by the cross-sectional transmission electron microscopy, double crystal x-ray diffraction, and temperature-dependent photoluminescence. It is found that the misfit dislocations generated from strain relaxation are all pure-edge threading dislocations with burgers vectors of b=1/3(1120). The misfit dislocations arise from the strain relaxation due to the thickness of strained layer greater than the critical thickness. The relaxation of strained layer was mainly achieved by the formation of dislocations and localization of In, while the dislocations changed their slip planes from {0001} to {1010}. With the increasing temperature, the efficiency of photoluminescence decrease sharply. It indicates that the relaxation of the misfit strain has a strong effect on optical efficiency of film. [ABSTRACT FROM AUTHOR]

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Deals with a study which presented surface preflashover phenomena across alumina ceramics in vacuum. Experimental setup; Results and discussion.

Deals with a study which examined the surface roughness of indium phosphide wafers by X-ray reflexivity and crystal truncation rod (CTR) measurements. Determination of the root-mean-square roughness and the lateral correlation scale; Components of the scattering intensities in the scans transverse to the specular reflection rod; Discussion on the sensitivities of the methods to the surface structure and the role of the resolution functions in the CTR measurements.

Presents a study which investigated the Si[sub1-subx]Ge[subx]/Si strained-layer superlattices grown by molecular beam epitaxy on silicon substrates by x-ray double crystal diffraction and x-ray grazing incidence diffraction. Components of the superlattices; Discussion on lattice relaxation; Results of double-crystal diffraction.