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971.
LUO Kun FAN JianRen CEN KeFa 《科学通报(英文版)》2007,52(3):408-417
Without using any turbulent model, direct numerical simulation of a three-dimensional gas-solid two-phase turbulent jet was performed by finite volume method. The effects on dispersion of particles with different Stokes numbers by the transitional behavior of turbulent structures were investigated. To produce high-resolution results and reduce the computation and storage, the fractional-step projection algorithm was used to solve the governing equations of gas phase fluid. The low-storage, three-order Runge-Kutta scheme was used for time integration. The governing equations of particles were solved in the Lagrangian framework. These numerical schemes were validated by the good agreement be-tween the statistical results of flow field and the related experimental data. In the study of particle dis-persion, it was found that the effects on particle dispersion by the spanwise vortex structures were prominent. The new behaviors of particle dispersion were also observed during the evolution of the flow field, i.e. the transitional phenomenon of particle dispersion occurs for the particles with small and intermediate Stokes numbers. 相似文献
972.
WANG LiMin GE Wei CHEN FeiGuo 《科学通报(英文版)》2007,52(4):450-455
The velocity profiles and temperature distributions of gas flow in microchannels, for Knudsen numbers ranging from 0.01 to 0.20, are investigated with pseudo-particle modeling (PPM). It has been found that the velocity profiles are mainly affected by Knudsen number and the external force fields applied. When Knudsen number was increased, the slip velocities on the walls increased at the beginning, and then decreased. The temperature distributions were also significantly affected by the external force. The Darcy friction factor increased with increasing Knudsen number, and its variation with Mach number under increased Knudsen number was similar to the so-called premature laminar-turbulent transition observed in experiments. 相似文献
973.
XingLan Zhang 《科学通报(英文版)》2009,54(12):2018-2021
Based on public key, a quantum identity authenticated (QIA) system is proposed without quantum entanglement. The public key acts as the authentication key of a user. Following the idea of the classical public key infrastructure (PKI), a trusted center of authentication (CA) is involved. The user selects a public key randomly and CA generates a private key for the user according to his public key. When it is necessary to perform QIA, the user sends a sequence of single photons encoded with its private key and a message to CA. According to the corresponding secret key kept by CA, CA performs the unitary operations on the single photon sequence. At last, the receiver can judge whether the user is an impersonator. 相似文献
974.
975.
Three-dimensional crustal velocity structure of P-wave in East China from wide-angle reflection and refraction surveys 总被引:1,自引:0,他引:1
The 3-D crustal structure of P-wave velocity in East China is studied based on the data obtained by wide-angle seismic reflection and refraction surveys.The results suggest that a deep Moho disconti-nuity exists in the western zone of the study region,being 35―48 thick.High-velocity structure zones exist in the upper crust shallower than 20 km beneath the Sulu and Dabie regions.The cause of high-velocity zones is attributable to high-pressure metamorphic(HPM) and ultra-high-pressure metamorphic(UHPM) terran... 相似文献
976.
A kinetic model was presented for dilute solid-liquid two-phase flows with inelastic collisions by modeling the inelastic collisions with the revised BGK model (Santos and Astillero, 2005) and particle turbulence interactions with the Fokker-Planck operator. The formulated model kinetic equation was solved with the Chapman-Enskog method and the obtained approximate solution was further adopted to derive the constitutive relationships for the conservation equations of the particle phase. The new constitutive relationships would be suitable for the study on dilute solid-liquid two-phase flows such as sediment-laden flows in open channels or rivers. 相似文献
977.
In this work, we investigate the combustion of hydrogen fuel through the wind tunnel tests. Two kinds of fuel, the pure hydrogen
and the hydrogen-ethene mixture, have been chosen to heat the oxygen-enriched air. It is found that the stable pressure in
the engine combustor and the thrusts is almost the same in two cases. A valuable feature we revealed is that the heating pattern
of hydrogen and ethene mixture leads to a considerable delay of the establishment of the wall pressure in the combustor, compared
with the pure hydrogen case. This phenomenon implies a longer ignition delay time for the mixture case. The shorter ignition
delay resulting from the hydrogen heater is attributed to the continuity of chain propagation and the exclusion of the less
active C-containing radicals. 相似文献
978.
LiKui Fang YunFeng Li XiaoPing Gong XianChun Sang YingHua Ling XiaoWen Wang YunFei Cong GuangHua He 《科学通报(英文版)》2010,55(23):2517-2521
Leaf senescence as an active process is essential for plant survival and reproduction. However, premature senility is harmful to agricultural production. In this study, a rice mutant, named as psl3 (presescing leaf 3) isolated from EMS-treated Jinhui 10, displays obvious premature senility features both in morphological and physiological level. Genetic analysis showed that mutant trait was controlled by a single dominant gene (PSL3), which was located on rice chromosome 7 between SSR marker c7sr1 and InDel marker ID10 with an interval of 53.5 kb. The result may be useful for the isolation of the PSL3 gene. 相似文献
979.
We investigate the characteristics of emission current waves of antiferroelectric cathode material lanthanum-doped lead zirconate stannate titanate (PLZST) triggered by pulse field, and analyze the relationship of the emission current waveforms with the extraction voltage. The close correlation between the triggering pulse polarity and emission current waveform observed evidences the relevant physical process of electron emission. We speculate that the primary emission may result from local phase transition and field emission in the vicinity of triple junctions, and the plasma formation may enhance the electron emission. 相似文献
980.
Numerical simulation on the evolution of sediment waves caused by turbidity currents 总被引:2,自引:0,他引:2
JIANG mao XIE XiNong TANG SuLin ZHANG Cheng DU XueBin 《科学通报(英文版)》2007,52(17):2429-2434
Interest in the forming mechanism of sediment waves increases recently because of its significance on submarine engineering, sedimentary dynamics and hydrocarbon reservoir prediction in deep water. In this paper, the time-averaged continuity equations and Reynolds-averaged Navier-Stokes equations are applied in the numerical simulation of fluid dynamics. The modeling results are used to illuminate the effects of topography on turbidity current and explore the origin of submarine sediment waves. The research results show that (1) deposition occurs firstly at the lower ramp due to the deceleration of fluid, increase of density, loss of flow capacity and longer duration of flow passage; (2) density increase at the upslope due to the local jam results in velocity decrease and pressure increase; (3) sediment waves begin to be formed and migrated toward upstream in an area far away from the source with in- crease of the turbidity events; (4) deposition becomes more slowly with decrease of grain sizes, but the shape and sequences of these deposits are controlled by topography, not grain size. 相似文献