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41.
The origin of power-law distributions in self-organized criticality is investigated by treating the variation of the number of active sites in the system as a stochastic process. An avalanche is mapped to a first-return random-walk process in a one-dimensional lattice. In order to understand the reason of variant exponents for the power-law distributions in different self-organized critical systems, we introduce the correlations among evolution steps. Power-law distributions of the lifetime and spatial size are found when the random walk is unbiased with equal probability to move in opposite directions. It is found that the longer the correlation length, the smaller values of the exponents for the power-law distributions. 相似文献
42.
建立幂律流体环空内层流脉动流的数学模型,采用SIMPLE算法进行数值求解,得到幂律流体环空脉动层流的流动特性。结果表明:幂律流体环空脉动流的流动特性与稳态流动时差异较大;环空脉动流在距入口非常短的一段距离内就可达到充分发展,且不同时刻的入口段长度随时间而变化;低脉动频率下速度分布曲线类似于稳态时的抛物形分布,高频率下壁面附近的速度分布曲线发生扭曲,振荡速度的最大值出现在壁面附近;内、外壁面的摩擦系数和轴向压力梯度均近似满足正弦变化规律,脉动频率、振幅和流体流性指数的增加均会使壁面摩擦系数和轴向压力梯度及其变化幅度增大。 相似文献
43.
The shear-thinning/thickening effects on the plane Couette-Poiseuille flow with a uniform crossflow are studied. The detailed solution procedures for both theo- retical and numerical purposes are given. In order to clarify the difference between the Newtonian flow and the power-law flow, all cases of the plane Couette-Poiseuille flows with uniform crossflows for different power indexes are assigned to the phase diagram in the parameter plane corresponding to the Couette number and the crossflow Reynolds number. The effects of shear-thinning/thickening on the phase diagram are discussed. An important feature of the shear-thinning circumstance distinguished from the shear- thickening circumstance is discovered. 相似文献
44.
45.
Effects of vertex activity have been analyzed on a weighted
evolving network. The network is characterized by the probability
distribution of vertex strength, each edge weight and evolution of
the strength of vertices with different vertex activities. The model exhibits self-organized criticality behavior. The
probability distribution of avalanche size for different network sizes is also shown. In addition, there is a power law relation between the size and the duration of an avalanche and the average of avalanche size has been studied for different vertex activities. 相似文献
46.
In this paper, the acceleratingly growing network model with
intermittent processes is proposed. In the growing network, there
exist both accelerating and intermittent processes. The network is
grown from the number of nodes
m0 and the number of links added with each new node is a nonlinearly increasing function
m+aNβ(t)f(t), where N(t) is the number of nodes present at
time t. f(t) is the periodic and bistable function with
period T, whose values are 1 and 0 indicating accelerating
and intermittent processes, respectively. Here we denote the ratio
τ of acceleration time to whole one. We study the degree distribution p(k) of the model, focusing on the dependence of p(k) on the network parameters τ, T, m, a, N, and
β. It is found that there exists a phase transition point
kc such that if
k<>kc, then p(k) obeys a power-law distribution with exponent
-γ1, while if
k>kc, then
p(k) exhibits a power-law distribution with exponent -γ2.
Moreover, the exponents
γ1 and γ2 are independent of τ, T, m, a, and N, while they depend only on the
parameter β. More interesting, the phase transition point is
described by
kc=aNβ, which is equal to the value at which
p(k) is maximum in GM model. 相似文献
47.
We investigate a coupled quintessence scenario, which can provide a natural solution to the cosmic coincidence problem. We assume that the mass of dark matter particles depends on a power law function of the scalar field associated to dark energy and meanwhile the scalar field evolves in a power law potential. Since the dynamics of this system is dominated by an attractor solution, the mass of dark matter particles is forced to change with time as to ensure that the ratio between the energy densities of dark matter and dark energy becomes a constant at late times, and one thus solves the cosmic coincidence problem naturally. We then apply a statefinder diagnostic to this coupled quintessence scenario. It is shown that the evolving trajectory of this scenario in the s-r diagram is quite different from those of other dark energy models. 相似文献
48.
分形复合油藏非牛顿幂律流体不稳定渗流的数学模型 总被引:2,自引:0,他引:2
对不稳定渗流的数学模型进行了推导并建立了分形复合油藏不稳定渗流模型.在无限大地层、有界定压、有界封闭三种外边界条件下分别求出了它们在Laplace空间的解析解.对于两区的特殊情况,分析了井底压力动态特征和参数影响,制作了典型曲线.非牛顿幂律流体的幂律指数,分形参数均对典型曲线产生较大的影响,呈现出与牛顿流体和均质油藏明显不同的特征.这对于非均质油藏非牛顿流体的不稳定试井分析和研究非线性渗流特征都是十分重要的. 相似文献
49.
IntroductionThesqueezeflowofafluidbetweentwodisksorspheresisofrelevancetomanyapplications,includingtheformingofpolymermaterials ,squeezeflowrheometerandlubricationofbearings.Thesqueezeflowinteractionbetweensolidparticlesisalsofundamentaltothecomplexrhe… 相似文献
50.
以无权的高簇系数的Holme和Kim(HK)模型为基础,联系实际网络所应该具备的权重,引进了一种动态的赋权机制,提出了一种更大范围可路径长度和调簇系数的加权无标度网络模型.分析和仿真表明:大范围可调路径长度和簇系数的加权无标度网络模型不仅继承了HK模型的高聚类效应和无标度特性,且它的调节手段更丰富,调节范围更大,实现了... 相似文献