A microscopic aggregation model of droplet dynamics in warm clouds

A microscopic model of warm clouds involving input of water droplets, dropletdroplet aggregation, droplet breakup, and precipitation is presented. Numerical simulations and analytical arguments indicate that after the stage of growth and just before precipitation sets in, a warm cloud is characterized by a droplet-size distribution which follows from an inverse power law as a function of the droplet size. When precipitation is taken into account, the above distribution is transformed into a distribution decaying exponentially with the droplet size, in agreement with field observations. It is suggested that the initiation of rainfall in a precipitating warm cloud can be viewed as an instability triggered by the presence of a power-law distribution.     

外势场中玻色--爱因斯坦凝聚性质的研究

(1)简要介绍BEC概念的一种含义及BEC形成的条件；(2)着重对外势场中的BEC作了研究，得出了低维情况下产生BEC的条件：当U(x)-2^η时，一维情况发生BEC满足η＜2；二维情况发生BEC满足η＞0。     

Power—Law in Depth—Dependence of Signal Speed in Vertical Granular Chain

The signal generated by an initial perturbation dispersively propagates in the vertical granular chain under gravity.For the power-law-type contact force,the signal speed follows power-law with the depth.When the perturbation is very weak,the exponent is 1/2(1-1/p).When the perturbation is very strong,the exponent approaches zero.The transition of the exponent from oscillatory regime with weak nonlinearity to quasi-solitary regime with strong nonlinearity is smooth.     

复杂计算机网络中的相变和整体关联行为

利用相变的概念解释复杂计算机网络中广泛存在的幂律现象,并未考虑到网络这一复杂系统中节点之间的相互关联作用.通过一种计算机网络模型,对网络中的相变和整体关联行为进行了分析和比较.研究表明,随着负载的增加,网络节点行为的空间和时间的长程相关性逐渐增强,整体关联行为逐渐显现;在临界状态,网络负载变化的功率谱呈现1/f²的特点,而节点排队长度变化的功率谱服从1/f^α分布,其中α≤2.网络节点行为在时间和空间上的关联进一步得到说明. 关键词： 计算机网络 相变 关联 幂律     

复杂网络幂律度分布和层次聚集函数标度指数的一种新的估计方法

提出一种估计复杂网络幂律度分布和层次聚集函数标度指数的新方法,并给出求解这些指数的数值算法．该方法可以克服目前网络研究中采用的图形线性拟合估计方法存在的偏差和不准确等不足之处．此外,通过对10个CNN网络进行KS检验统计量的比较,证实该方法比图形方法具有更好的拟合效果．     

Nonlinear Dynamical Behavior in BS Evolution Model Based on Small-World Network Added with Nonlinear Preference

We introduce a modified small-world network adding new links with nonlinearly preferential connection instead of adding randomly, then we apply Bak-Sneppen (BS) evolution model on this network. We study several important structural properties of our network such as the distribution of link-degree, the maximum link-degree, and the length of the shortest path. We further argue several dynamical characteristics of the model such as the important critical value f_c, the f₀ avalanche, and the mutating condition, and find that those characteristics show particular behaviors.     

Simplified lattice Boltzmann method for non-Newtonian power-law fluid flows

In this paper, we present a simplified lattice Boltzmann method for non-Newtonian power-law fluid flows. The new method adopts the predictor-corrector scheme and reconstructs solutions to the macroscopic equations recovered from the lattice Boltzmann equation through Chapman-Enskog expansion analysis. The truncated power-law model is incorporated into this method to locally adjust the physical viscosity and the associated relaxation parameter, which recovers the non-Newtonian behaviors. Compared with existing non-Newtonian lattice Boltzmann models, the proposed method directly evolves the macroscopic variables instead of the distribution functions, which eliminates the intrinsic drawbacks like high cost in virtual memory and inconvenient implementation of physical boundary conditions. The validity of the method is demonstrated by benchmark tests and comparisons with analytical solution or numerical results in the literature. Benchmark solutions to the three-dimensional lid-driven cavity flow of non-Newtonian power-law fluid are also provided for future reference.     

The collision frequency of electron-neutral-particle in the weakly ionized plasma with the power-law velocity distribution

We study the collision frequency of electron-neutral-particle in the weakly ionized plasma with the power-law velocity q-distribution and derive the formulation of the average collision frequency. We find that the average collision frequency in the q-distributed plasma also depends strongly on the q-parameter and thus is generally different from that in the Maxwell-distributed plasma, which therefore modifies the transport coefficients in the previous studies of the weakly ionized plasmas with the power-law velocity distributions.     

Flow pattern transition,pressure gradient,hold-up predictions in gas/non-Newtonian power-law fluid stratified flow

This work focuses on gas/non-Newtonian power-law fluid stratified pipe flow. Two different theoretical approaches to obtain pressure gradient and hold-up predictions are presented: the steady fully developed two-fluid model and the pre-integrated model. The theoretical predictions are compared with experimental data available for horizontal and for slightly downward inclined air/shear thinning fluid stratified flow taken from literature. The predictions of the pre-integrated model are validated showing a good agreement when compared with experimental data. The criteria for the transition from the stratified flow pattern are applied to gas/non-Newtonian stratified flow. The neutral stability analysis (smooth/wavy stratified flow) and the well-posedness (existence region of stratified flow) of governing equations are carry out. The predicted transition boundaries are obtained using the steady fully developed two-fluid model and the pre-integrated model, where the shape factors and their derivatives are accounted for. A comparison between the predicted boundaries and experimental flow pattern maps is presented and shows a good agreement. A comment on the shear stress modeling by the pre-integrated model is provided.