A bidisperse granular mixture in a slightly tilted compartmentalized chamber is experimentally found to show size segregation when vertically vibrated.A surface slope develops and large particles congregate to the low...A bidisperse granular mixture in a slightly tilted compartmentalized chamber is experimentally found to show size segregation when vertically vibrated.A surface slope develops and large particles congregate to the lower side.Particles right upon the upper tip of the dividing wall behave in a competitive way,i.e.,they can go to either compartment depending on the force exerted on them.展开更多
A new style of discharge process from a vertical open-top pipe with capillary outlet is reported. The outflux fluctuates greatly with time and the bulk condensed granular flow in the pipe shows stop-and-go motion when...A new style of discharge process from a vertical open-top pipe with capillary outlet is reported. The outflux fluctuates greatly with time and the bulk condensed granular flow in the pipe shows stop-and-go motion when the filling height is above a threshold. When the filling height falls to- wards the threshold, led by a transitional stage, the outflux and the bulk movement become much stable. The upper surface dropping velocity variation is measured. A heuristic theory is proposed to understand the stop-and-go motion and the transitional behavior.展开更多
Random walks are the most fundamental process among various dynamical processes, and most previous works focused on binary networks. This work studies random walks on deterministic weighted scale-free small-world netw...Random walks are the most fundamental process among various dynamical processes, and most previous works focused on binary networks. This work studies random walks on deterministic weighted scale-free small-world networks with a perfect trap. We derive an explicit expression of the mean first passage time on the network with a trap. Meanwhile, we present the evolutionary rule for the first passage time when the network grows. The study can be useful for understanding the random walks on weighted networks.展开更多
In this paper we focus on diamond film hot-filament chemical vapor deposition reactors where the only reactant is hydrogen so as to study the formation and transport of hydrogen atoms. Analysis of dimensionless number...In this paper we focus on diamond film hot-filament chemical vapor deposition reactors where the only reactant is hydrogen so as to study the formation and transport of hydrogen atoms. Analysis of dimensionless numbers for heat and mass transfer reveals that thermal conduction and diffusion are the dominant mechanisms for gas-phase heat and mass transfer, respectively. A simplified model has been established to simulate gas-phase temperature and H concentration distributions between the filament and the substrate. Examination of the relative importance of homogeneous and heterogeneous production of H atoms indicates that filament-surface decomposition of molecular hydrogen is the dominant source of H and gas-phase reaction plays a negligible role. The filament-surface dissociation rates of H2 for various filament temperatures were calculated to match H-atom concentrations observed in the literature or derived from power consumption by filaments. Arrhenius plots of the filament-surface hydrogen dissociation rates suggest that dissociation of H2 at refractory filament surface is a catalytic process, which has a rather lower effective activation energy than homogeneous thermal dissociation. Atomic hydrogen, acting as an important heat transfer medium to heat the substrate, can freely diffuse from the filament to the substrate without recombination.展开更多
文摘A bidisperse granular mixture in a slightly tilted compartmentalized chamber is experimentally found to show size segregation when vertically vibrated.A surface slope develops and large particles congregate to the lower side.Particles right upon the upper tip of the dividing wall behave in a competitive way,i.e.,they can go to either compartment depending on the force exerted on them.
基金the National Natural Science Foundation of China(Grant No.10274074) the Australian Research Council through a Discovery Project Grant
文摘A new style of discharge process from a vertical open-top pipe with capillary outlet is reported. The outflux fluctuates greatly with time and the bulk condensed granular flow in the pipe shows stop-and-go motion when the filling height is above a threshold. When the filling height falls to- wards the threshold, led by a transitional stage, the outflux and the bulk movement become much stable. The upper surface dropping velocity variation is measured. A heuristic theory is proposed to understand the stop-and-go motion and the transitional behavior.
基金Supported by the National Natural Science Foundation of China under Grant Nos 71301043, 71171185, and 71071044, and the 1000 Talent Plan for High-Level Foreign Experts under Grant No WQ20123400070.
文摘Random walks are the most fundamental process among various dynamical processes, and most previous works focused on binary networks. This work studies random walks on deterministic weighted scale-free small-world networks with a perfect trap. We derive an explicit expression of the mean first passage time on the network with a trap. Meanwhile, we present the evolutionary rule for the first passage time when the network grows. The study can be useful for understanding the random walks on weighted networks.
文摘In this paper we focus on diamond film hot-filament chemical vapor deposition reactors where the only reactant is hydrogen so as to study the formation and transport of hydrogen atoms. Analysis of dimensionless numbers for heat and mass transfer reveals that thermal conduction and diffusion are the dominant mechanisms for gas-phase heat and mass transfer, respectively. A simplified model has been established to simulate gas-phase temperature and H concentration distributions between the filament and the substrate. Examination of the relative importance of homogeneous and heterogeneous production of H atoms indicates that filament-surface decomposition of molecular hydrogen is the dominant source of H and gas-phase reaction plays a negligible role. The filament-surface dissociation rates of H2 for various filament temperatures were calculated to match H-atom concentrations observed in the literature or derived from power consumption by filaments. Arrhenius plots of the filament-surface hydrogen dissociation rates suggest that dissociation of H2 at refractory filament surface is a catalytic process, which has a rather lower effective activation energy than homogeneous thermal dissociation. Atomic hydrogen, acting as an important heat transfer medium to heat the substrate, can freely diffuse from the filament to the substrate without recombination.
