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971.
G. N. Kozhemyakin D. V. Lutskiy M. A. Rom P. V. Mateychenko 《Crystallography Reports》2008,53(7):1267-1271
The growth conditions and structural quality of Sb-Bi gradient single crystals with Bi content from 2 to 18 at %, grown by
the Czochralski method with solid phase feed, are investigated. Bi distribution in the crystals along their pulling direction
are studied by electron probe microanalysis and the change in the interplanar spacing is analyzed by double-crystal X-ray
diffraction. It is established that the pulling rate and feed mass affect the Bi distribution in Sb-Bi single crystals. 相似文献
972.
973.
974.
Three-dimensional laminar forced convection including steady-periodic transition is investigated up to periodic-chaotic transition
in the fully developed region of coolant passages with staggered arrays of pin fins. Comparative examples concern overall
pressure losses and heat transfer characteristics of circular, square and elliptical pins made of nickel and copper. In the
numerical model, transient conjugate heat transfer is assumed and space periodicities in pressure, velocity components and
temperatures are taken into account. In the range of operative conditions investigated, overall friction factors increase
almost linearly with the Reynolds number, while the increase of overall Nusselt numbers with the Reynolds number is characterized
by two slope changes connected with the onset of streamwise vortices, and the shedding of transverse vortices, respectively.
The use of copper, instead of nickel, increases the overall Nusselt number with all shapes, but is particularly beneficial
to the elliptical section. Square pins are characterized by the highest values of friction factors, but are also the best
performers as far as convection enhancing is concerned. The reverse is true for the elliptical pins which are characterized
by the lowest values of friction factors, but are the worst performers as far as convection enhancing is concerned. On the
basis of overall performances, the elliptical pins made of copper are the best choice, at least in the upper range of Reynolds
numbers investigated. 相似文献
975.
Adsorption of the copper ions from aqueous solutions, benzene, and water on the active carbon obtained by chemical activation
from walnut shells was studied. The active carbon was additionally oxidized with hydrogen peroxide and then impregnated with
nitrogen-containing compounds. As a result of impregnation with melamine, a secondary porosity is formed within the oxidized
active carbon, leading to an increase in the specific surface of the sorbent. A modified carbon surface is heterogeneous,
and the carbons themselves exhibit catalytic activity in the oxidation of luminol and decomposition of hydrogen peroxide. 相似文献
976.
977.
978.
979.
980.
S. V. Trukhanov V. V. Fedotova A. V. Trukhanov S. G. Stepin H. Szymczak 《Crystallography Reports》2008,53(7):1177-1180
Nanocrystalline manganite La0.50Ba0.50MnO3 was synthesized by the soft-chemical method. For this purpose, the sol-gel method was modified and improved. A trihydric saturated alcohol, e.g., glycerol, was suggested as a new organic matrix. The crystal structure of the composite was studied by X-ray powder diffraction at room temperature. A La0.50Ba0.50MnO3 powder annealed in air at T = 500°C is characterized by a perovskite-like cubic structure with the unit-cell parameter a = 3.869 Å. The chemical composition of the sample was studied by electron-probe X-ray microanalysis. The La: Ba: Mn cation ratio in the material was 1: 1: 2. The surface topography was examined with a scanning electron microscope. The crystallite size was ~30 nm. The dependence of the crystal structure and the surface topology on the annealing temperature was studied. The high-temperature treatment in air resulted in the growth of larger, micrometer-size, crystallites. 相似文献