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排序方式: 共有234条查询结果,搜索用时 15 毫秒
1.
2.
A finite difference simulation method for the time dependent viscous incompressible flow around a transversely and longitudinally oscillating circular cylinder at Reynolds numbers of Re=4×103 and 4×104 is presented. The Navier-Stokes equations in finite difference form are solved on a moving grid system, based on a time dependent coordinate transformation. Solution of the vortex street development behind the cylinder is obtained when the cylinder remains stationary and also when it is oscillating. Time eholution of the flow configuration is studied by means of stream lines, pressure contours and vorticity contours. The computer results predict the lock-in phenomenon which occurs when the oscillation frequency is close to the vortex shedding frequency in the transverse mode or around double the vortex shedding frequency in the longitudinal mode. The time dependent lift and drag coefficients are obtained by the integration of the pressure and shear forces around the body. The drag, lift and the displacement relations are also discussed. 相似文献
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4.
T. Sekiya A. Tzuzuki S. Kawakami Y. Torii N. Tsuboi T. Futakuchi 《Journal of Materials Science》1988,23(9):3300-3304
The rapidly quenched films in the Bi2O3-TiO2 system (0 to 60% TiO2) were prepared using a twin-roller type apparatus. The films precipitated Bi2O3 solid solutions of different types in the composition ranges, with TiO2 contents of 0 to 5, 7.5 to 10 and 12.5 to 40%, respectively. The first solid solution had a tetragonal structure of -form. The second, though also crystallized in the tetragonal structure, adopted a disordered modification of the -form. The third solid solution was -form (defect fluorite structure). The formation of amorphous phase commenced in the composition with 30% TiO2, and the films became completely amorphous beyond 50% TiO2. The quenched films showed a certain instability to decompose or transform into the different phase assemblage by annealing at higher temperatures (about 400 to 500° C, except 260° C for the pure Bi2O3 film). The quenched films were also characterized by a high photoconductivity. The photoconduction mechanism was suggested to be associated with a structural imperfection of Bi2O3 accompanied by a certain amount of pentavalent bismuth ion. 相似文献
5.
Changho Jung Hideyuki Tsuboi Michihisa Koyama Momoji Kubo Ewa Broclawik Akira Miyamoto 《Catalysis Today》2006,111(3-4):322-327
CO adsorption over Pd4 and Pt4 cluster supported by c-ZrO2(1 1 1) and CeO2(1 1 1) catalyst systems was investigated using periodic density functional method in order to clarify the support effect on CO activation. We found that the support increases the CO activation for bridge and three-fold sites but decreases for the atop site. Moreover, it was found that the support changes the site preference for the CO adsorption. Bridge site on both the Pt4/c-ZrO2 and Pt4/CeO2 show larger CO adsorption energies than those on the other sites while the atop site is energetically preferable on isolated Pt4 cluster. c-ZrO2 supported Pd shows the largest CO activation with large charge transfer from the catalyst to the CO molecule. This reveals that ZrO2 supported Pd can be a good catalyst for CO activation because of its higher probability to the three-fold site CO adsorption. We also found that positively charged M4 clusters on the support keep their strong electron-donating properties and have enough charge density to contribute to the activation of an adsorbed CO molecule by a charge transfer. 相似文献
6.
Fujiyoshi T. Shiratake S. Nomura S. Nishikawa T. Kitasho Y. Arakida H. Okuda Y. Tsuboi Y. Hamada M. Hara H. Fujita T. Hatori F. Shimazawa T. Yahagi K. Takeda H. Murakata M. Minami F. Kawabe N. Kitahara T. Seta K. Takahashi M. Oowaki Y. Furuyama T. 《Solid-State Circuits, IEEE Journal of》2006,41(1):54-62
A single-chip H.264 and MPEG-4 audio-visual LSI for mobile applications including terrestrial digital broadcasting system (ISDB-T / DVB-H) with a module-wise, dynamic voltage/frequency scaling architecture is presented for the first time. This LSI can keep operating even during the voltage/frequency transition, so there is no performance overhead. It is realized through a dynamic deskewing system and an on-chip voltage regulator with slew rate control. By the combination with traditional low power techniques such as embedded DRAM and clock gating, it consumes only 63 mW in decoding QVGA H.264 video at 15 frames/sec and MPEG-4 AAC LC audio simultaneously. 相似文献
7.
In general all detonation waves have cellular structure formed by the trajectory of the triple points.This paperaims to investigate experimentally the propagation of detonation in narrow gaps for hydrogen-oxygen-argonmixtures in terms of various gap heights and gap widths.The gap of total length 1500 mm was constructed bythree pair of stainless plates,each of them was 500 mm in length,which were inserted in a detonation tube.Thegap heights were varied from 1.2 mm to 3.0 mm while the gap widths were varied from 10 mm to 40 mm.Variousargon dilution rates were tested in the present experiments to change the size of cellular structure.Attempts havebeen made by means of reaction front velocity,shock front velocity,and smoked foil to record variations of cel-lular structure inside the gaps.A combination probe composed of a pressure and an ion probe detected the arrivalof the shock and the reaction front individually at one measurement point.Experimental results show that thenumber of the triple points contained in detonation front decreases with decrease in the gap heights and gapwidths,which lead to larger cellular structures.For mixtures with low detonability,cell size is affected by a cer-tain gap width although conversely cell size is almost independent of gap width.From the present result it wasfound that detonation propagation inside the gaps is strongly governed by the gap height and effects of gap widthis dependent on detonability of mixtures. 相似文献
8.
Md Tasyrif Abdul Rahman Nobuyuki KawaharaKazuya Tsuboi Eiji Tomita 《International Journal of Hydrogen Energy》2014
In this work, spark-induced breakdown spectroscopy (SIBS) was employed to investigate the mixing process of a hydrogen jet in a constant-volume vessel. The local fuel concentration of the hydrogen jet was measured at several locations, using a SIBS sensor. A high-speed camera was used to visualize spark discharge fluctuations, and hydrogen jet concentration measurements were conducted simultaneously. Spectrally resolved atomic emissions from the plasma generated by the spark plug were examined to determine the local equivalence ratio. Direct visualization of the spark discharge provided useful information about the influence of spark discharge characteristics related to the spark timing. Using the developed SIBS sensor, atomic emission spectra were obtained from hydrogen Hα at 656 nm and nitrogen N (I) at 501 nm. Comparison of the intensity peaks of atomic emissions from hydrogen and nitrogen allows the local hydrogen concentration in a measured volume to be determined, and hence also the local equivalence ratio. The measurement results demonstrate the local variation in the equivalence ratio throughout the jet and along its axis. From the results, the spatial structure of the hydrogen jet affects the hydrogen/nitrogen mixing and could be clarified with SIBS technique when the spark is discharged. 相似文献
9.
10.
T. Katsumi H. Kodama T. Matsuo H. Ogawa N. Tsuboi K. Hori 《Combustion, Explosion, and Shock Waves》2009,45(4):442-453
A new composition of hydroxylammonium nitrate based solution containing ammonium nitrate, methanol, and water was developed
for monopropellant in a reaction control system (RCS) as an alternative to conventional hydrazine. In comparison with hydrazine,
this solution has a 20% higher specific impulse, 1.4 times higher density, and lower freezing point and toxicity. The linear
burning rate of the solution is moderate at the operating pressures of RCS thrusters. It was found that the linear burning
rate had some characteristics whose mechanisms had not been understood. The combustion mechanism of this solution was investigated.
The burning behavior was observed using a medium speed camera, and a temperature profile for the combustion wave was measured
with a 2.5 μm diameter thermocouple. From these results, the instability of the liquid-gas interface may trigger a sudden
increase in the burning rate, and methanol was found to be effective in reducing the bubble growth rate in the solution. The
reactivity of several catalysts was evaluated in an open-cup test, and the S405 catalyst for hydrazine showed the best performance
among them. Thruster tests were conducted using the S405 catalyst with variation in the propellant mass flow rate, catalyst
bed configuration, and length-to-diameter ratio of the combustor. As a result, parameters were determined that ensured long
operating time. The model thruster operated stably for up to 100 sec with a specific impulse I
sp = 240 sec, which corresponds to a 90% efficiency.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 4, pp. 109–120, July–August, 2009.
An erratum to this article can be found at 相似文献