Eccentricity and elliptic flow at fixed centrality in Au+Au collisions at √<SPAN style=

In this paper, elliptic flow is studied at fixed centrality in Au+Au collision at √s_NN=200 GeV in the AMPT model. It is observed that with the participant increasing, elliptic flow has an increase or a decrease at different fixed impact parameter, but it does not have a trivial fluctuation. It is analyzed that the initial space anisotropy dominates the participant dependence of elliptic flow in near-central collisions(b=5 fm) and mid-central collisions(b=8 fm), while the interaction between particles can mainly answer for the behavior of elliptic flow with participant in peripheral collisions (b=12 fm). To distinguish the pure geometrical effect, elliptic flow scaled by initial eccentricity is studied. It is found that the ratio v₂/ε increases with participant and reaches a saturation when the participant is large enough, indicating that the collision system may reach the local equilibrium.     

一类线性时变大系统的平稳振荡

令Ω是一个包含原点在内的有界集,如果对方程(1.1)存在正函数V(x,t),它在Ω和t≥0有定义,且极限关系在整个t的正半轴上一致成立;又假定在整个Ω~c和t≥0上都满足     

Trace initial interaction from final state observable in relativistic heavy ion collisions

In order to trace azimuthal angle dependence of the initial interaction in ultra-relativistic heavy ion collision, two azimuthal multiplicity-correlation patterns neighboring and fixed-to-arbitrary angularbin correlation patterns -- are suggested. From the simulation of Au ＋ Au collisions at √SNN = 200 GeV by using the Monte Carlo models RQMD with hadron re-scattering and AMPT with and without string melting, we observe that the correlation patterns change gradually from out-of-plane preferential one to inplane preferential one when the centrality of collision shifts from the central collision to peripheral collision, meanwhile the anisotropic collective flow v2 keeps positive in all cases. This regularity is found to be collision energy independent. The physics behind the two opposite trends of correlation patterns, in particular, the presence of out-of-plane correlation patterns at RHIC energy, are discussed.     

一类时变大系统的区间矩阵平稳振荡

一类时变大系统的区间矩阵平稳振荡王美娟（上海机械学院基础部，上海２０００９３）在文献［１］中，我们讨论了具有分解的大系统的区间矩阵平稳振荡问题．其中Ａｓｓ为ｎｓ×ｎｓ阶实常量矩阵．平均法是用来解决时变系统问题的很有成效的一种方法．它使我们有可能从常数...     

Global stability analysis of a ratio-dependent predator-prey system

A ratio dependent predator-prey system with Holling type Ⅲ functional response is considered. A sufficient condition of the global asymptotic stability for the positive equilibrium and existence of the limit cycle are given by studying locally asymp- totic stability of the positive equilibrium. The condition under which positive equilibrium is not a hyperbolic equilibrium is investigated using Hopf bifurcation.     

一类基于比率的捕食-食饵系统的全局稳定性分析

研究一类基于比率和具第Ⅲ类功能性反应的捕食-食饵系统．通过分析正平衡点的局部稳定性给出了系统正平衡点全局渐近稳定以及系统存在极限环的条件．运用Hopf分支理论讨论了当正平衡点是非双曲型时的情形．     

Eccentricity and elliptic flow at a fixed centrality in Au+Au collisions at （sNN）1/2=200 GeV in an AMPT model

In this paper, elliptic flow is studied at a fixed centrality in Au+Au collisions at （sNN）^1/2=200 GeV in the AMPT model. It is observed that as the participants increase, elliptic flow either increases or decreases at a different fixed impact parameter, but it does not have a trivial fluctuation. It is analyzed that the initial space anisotropy dominates the participant dependence of elliptic flow in near-central collisions（b=5 fm） and mid-central collisions（b=8 fm）, while the interaction between particles can mainly answer for the elliptic flow behavior with the participant in peripheral collisions （b=12 fm）. To distinguish the pure geometrical effect, elliptic flow scaled by initial eccentricity is studied. It is found that the ratio v₂ /∈increases with the participant and reaches a saturation when the participant is large enough, indicating that the collision system may reach a local equilibrium.     

Neighboring azimuthal bin-bin multiplicity correlation as a direct measure for the shear viscosity in relativistic heavy ion collisions

Neighboring azimuthal bin-bin multiplicity correlation is suggested to be a good measure for internal layer-to-layer interactions of the formed matter in relativistic heavy ion collisions. It is shown to be directly related to the shear viscosity of the formed matter. As an application of this method, the shear viscosity in the samples generated by a multi-phase transport model (AMPT) is estimated. The results are in qualitative agreement with the theoretical calculation from microscopic interactions, i.e., the larger the scattering cross section, the smaller the shear viscosity.     

Hopfield神经网络的稳定性及其在投资组合中的应用

在取消了神经元之间的连接权系数对称限制的基础上 ,讨论了 Hopfield神经网络的稳定性 ,得到了一些有益结论 .并将其应用于 Hopfield神经网络算法的改进上 .进而依据改进的算法以有价证券的选择为例进行了随机模拟 ,取得了令人满意的结果 .     

具有常数输入和饱和传染率食饵有病的生态-流行病模型

研究了一类疾病只在食饵中传播且具有饱和传染率的生态-流行病模型.通过理论分析得到了系统平衡点局部渐近稳定和全局渐近稳定的充分条件.