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排序方式: 共有484条查询结果,搜索用时 15 毫秒
481.
The aim of this study is to reveal the temporal and spatial heat transfer performance of an isothermally heated sphere placed in a uniform, downwardly directed flow using a micro-foil heat flow sensor (HFS). A HFS, whose response time is about 0.02 s, was pasted on the surface of a heated copper sphere. Experiments were carried out using air with a Grashof number of 3.3 × 105 and with several Reynolds numbers (Re) up to 1800. Three flow patterns appeared: a chaotic flow at Re<240; a two-dimensional steady separated flow at 240 Re<500, and a three-dimensional unsteady separated flow at Re 500. In addition, the instantaneous and time-averaged heat transfer performance around the sphere in each of the three regions was clarified. Next, enhancement of the latent heat storage rate of a solid phase change material (PCM) in a spherical capsule was performed. The flow around the spherical capsule, in which the solid PCM was filled and placed in a heated, upwardly directed flow, is the approximate adverse flow phenomenon around the heated sphere which was placed in a downwardly directed flow. In other words, the buoyant flow and the forced flow are in the opposite directions in these two cases. Tests of latent heat storage were run for two Reynolds numbers which represented different flow characteristics in the heat transfer experiments, Re=150 and 1800. Furthermore, copper plates were inserted into the solid PCM, of which thermal conductivity was considerably low, to enhance the latent heat storage rate for the two Reynolds number flows. 相似文献
482.
Hitoshi Kitaguchi Hanping Miao Hiroaki Kumakura Kazumasa Togano Takayo Hasegawa Tsutomu Koizumi 《Journal of Low Temperature Physics》1999,117(5-6):1525-1529
The high transport critical current density (J
c
) > 500 kA/cm
2
at 4.2 K, 10 T is obtained in the Bi-2212/Ag multilayer tapes fabricated by using PAIR (Pre-Annealing and Intermediate Rolling) and melt-solidification process. This J
c
value is twice higher than existing high-quality Bi-2212/Ag tapes (250 kA/cm
2
). By applying PAIR process to Bi-2212/Ag tapes, Bi-2212 grain alignment is much improved and a large J
c
enhancement is achieved. J
c
has been increased strongly by performing pre-annealing at 840°C in oxygen (1 atm) and intermediate rolling with 25% deformation. 相似文献
483.
Concentrations of synthetic antioxidants butylated hydroxyanisole, butylated hydroxytoluene, and tert-butyl hydroquinone were quantified using a high-performance liquid chromatograph with spectrofluorometric detector. The antioxidants
were separated and eluted on a reversed-phase column by gradient of a mixture of H2O/acetonitrile/acetic acid (66.5: 28.5∶5, by vol) and a mixture of acetonitrile/acetic acid (95∶5, vol/vol). The eluants were
monitored at emission and excitation wavelengths of 310 and 280 nm, respectively. Calibration curves obtained using peak areas
against concentration showed ligh coefficients of multiple determination (R
2>0.99) for all antioxidants. Known concentrations of added antioxidant standards were recoverable within 98–99% from oils
and over 93% from mouse blood. This method requires minimum sample extraction and purification before analysis and provides
a relatively high percentage recovery. The method has been applied successfully for the measurement of antioxidant concentrations
in oils, dried foods, and biological fluids. 相似文献
484.
Satoshi Hamakawa Masaki Koizumi Koichi Sato Junji Nakamura Toshio Uchijima Kazuhisa Murata Takashi Hayakawa Katsuomi Takehira 《Catalysis Letters》1998,52(3-4):191-197
The electrochemical membrane reactor of YSZ (yttria-stabilized zirconia) solid electrolyte coated with Pd and Ag as anode
and cathode, respectively, has been applied to the partial oxidation of methane to synthesis gas (CO + H2). The Pd|YSZ|Ag catalytic system has shown a remarkable activity for CO production at 773 K, and the selectivity to CO was
quite high (96.3%) under oxygen pumping condition at 5 mA. The H2 production strongly depended on the oxidation state of the Pd anode surface. Namely, the H2 treatment of the Pd anode at 773 K for 1 h drastically reduced the rate of H2 production, while air treatment enhanced the H2 production rate. From the results of the partial oxidation of CH4 with molecular oxygen, it is considered that the reaction site of the electrochemical oxidation of CH4 to synthesis gas was the Pd–YSZ–gas-phase boundary (triple-phase boundary). In addition, it is found that the oxygen species
pumped electrochemically over the Pd surface demonstrated similar activity to adsorbed oxygen over Pd, PdOad, for the selective oxidation of CH4 to CO, when the Pd supported on YSZ was used as a fixed-bed catalyst for CH4 oxidation with the adsorbed oxygen. The difference with respect to the H2 formation between the electrochemical membrane system and the fixed-bed catalyst reactor results from differences in the
average particle size of Pd and the way of the oxygen supply to the Pd surface.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献