弱噪声极限下二维布朗运动的随机共振现象

在弱噪声极限下，应用多维Fokker-Planck方程的与时间有关问题方面的理论，推导了对称双稳势阱中二维布朗粒子的概率跃迁速率，并基于绝热近似理论研究了弱噪声极限下受小幅低频周期力驱动的二维布朗运动的随机共振现象.与以前的结果相比，所得到的信噪比与阻尼系数的大小无关.精确的数值模拟结果进一步说明了所得的信噪比的适用性. 关键词： 二维布朗运动 弱噪声极限 随机共振 信噪比     

Stochastic Resonance in a Simple Threshold Sensor System with Alpha Stable Noise

We investigate the effect of alpha stable noise on stochastic resonance in a single-threshold sensor system by analytic deduction and stochastic simulation. It is shown that stochastic resonance occurs in the threshold system in alpha stable noise environment, but the resonant effect becomes weakened as the alpha stable index decreases or the skewness parameter of alpha stable distribution increases. In particular, for Cauchy noise a nonlinear relation among the optimal noise deviation parameter, the signal amplitude and the threshold is analytically obtained and illustrated by using the extreme value condition for the output signal-to-noise ratio. The results presented in this communication should have application in signal detection and image restoration in the non-Gaussian noisy environment.     

Density functional study on the pressure profile of the inhomogeneous fluid mixture

By using the statistical mechanics, the pressure tensor for the multi component fluid mixture is derived. With the help of the classical density functional theory, profiles of the pressure components are calculated, and the influence of the total volume fraction, ratio of volume fraction, and size asymmetry on the pressure are studied. In addition, our results show that for the mixture confined in the hard cavity, the pressure shows a discontinuity near the cavity wall. However, in the soft cavity condition, the discontinuity disappears.     

单模非线性光学系统的弛豫速率与随机共振

应用变分法研究了一个单模非线性光学系统的弛豫速率对噪声强度的依赖性，并由线性响应理论考察了该系统的随机共振行为.研究结果表明当系统没有偏置时，单稳与多稳情形下的松弛速率对噪声强度的依赖性表现出很大的不同.揭示了对称的一维单稳系统中的随机共振现象，并针对一维单稳系统中随机共振存在的一般条件进行了分析. 关键词： 弛豫速率 随机共振 变分法 线性响应理论     

受迫薛罗格双匣化学反应模型的随机共振

为了在理论上揭示高斯白噪声激励的薛罗格双匣化学反应模型对弱周期扰动的线性与非线性响应 ,分四态近似和两态近似两种情形 ,基于绝热近似与速率方程方法 ,解析导出线性的和非线性的敏感性以及信噪比的表达式 ,并与数值模拟结果进行比较 ,在一次谐波的意义上得到了解析结果与数值模拟结果的定量一致性 .理论上讲 ,该模型只能表现出奇次谐波的随机共振 ,但数值模拟结果也出现了二次谐波的随机共振 ,其原因可能归结为在数值模拟中有限频率的截断引入了误差 ,也可能归结为信号的高次谐波与背景噪声难以区分所致 .     

Species separation of binary colloidal mixtures in the multi-Gauss potential: Effect of depletion

For the asymmetrical colloidal mixture subject to a confining potential and an external multi-Gauss potential, the separation of species is studied based on the classical density functional theory of simple fluids. The multi-Gauss potential consists of several Gauss barriers, which are distributed along the axial direction with uniform distance. The barrier width,barrier distance, and barrier height are individually adjusted to investigate their effects on the species separation. From the numerical results, it is concluded that in each condition, the competition between the external potential and the depletion potential determines the phase equilibrium and the separation. Species separation appears only in the region where the depletion is dominant. On the contrary, both species are absent in the regions where the external potential takes the absolute advantage.     

Density functional study of the pressure tensor for inhomogeneous Lennard—Jones fluids

Based on classical density functional theory,an expression of the pressure tensor for inhomogeneous fluids is presented.This takes into account greater correlation between particles,especially for systems that are geometrically confined or involve an interface.The density and pressure components of Lennard-Jones fluids confined in hard and softened nano-cavities are calculated.A comparison between the results of this work and IK expression suggests that the agreement depends on temperature.The interfacial tension for hard sphere fluids agrees well with the Monte Carlo result when the bulk density is not too large.The results of the solid-fluid interfacial tension for Lennard-Jones fluids demonstrate that different types of external potentials modulate the interfacial tension in different manners.     

可兴奋性细胞混沌放电区间的识别机理

在神经起步点记录到加周期分岔过程的生理实验数据，在对此分岔过程中位于周期n爆发 和周期(n+1)爆发之间的混沌的峰峰间期数据检测不稳定的周期轨道时，发现从靠近周期 n爆发的混沌的峰峰间期数据中，可以检测出不稳定的周期n轨道；而从靠近周期(n+1)爆 发的混沌的峰峰间期数据中，不仅可以检测出不稳定的周期(n+1)轨道，还可以检测出不稳 定的周期n轨道.针对该现象，借助于Sherman建议的胰腺β细胞模型，从非线性动力 学角度给出了理论解释.指明了由鞍结分岔和倍周期分岔分别产生第一类阵发和第三类阵发 为出现该 关键词： 峰峰间期 不稳定的周期轨道 鞍结分岔 倍周期分岔     

四川华蓥山地重力灾害类型及成因分析

从华蓥山所处的地理位置出发,全面的介绍了华蓥山地区近些年来的重力灾害发生的情况,可以看到重力灾害在本地区的影响之大,已经成为了本地区主要的灾害类型。通过各方面的调查研究,采用科学分析和经验指导相结合的方法,分析了引起重力灾害发生的各种因素,并重点从地质因素、水体因素、人为因素等3方面分析了华蓥山地重力灾害发生的成因,总结了可以引起重力灾害发生的外因和内因,可以看到重力灾害不单是某一个因素导致,而是由于众多的因素相互的影响所导致的。采取各种措施来预防灾害的发生,减少灾害给人类的生产和生活带来的危害。     

Characteristics of critical amplitude of a sinusoidal stimulus in a model neuron

The characteristics of the critical amplitude of a sinusoidal stimulus in a model neuron, Morris－Lecar model, are investigated numerically. It is important in the study of stochastic resonance to determine whether a periodic stimulus is subthreshold or not. The critical amplitude as a function of the stimulus frequency is not a constant, but a curve, which is the boundary between subthreshold and suprathreshold stimulation. It has been considered that this curve is U-shaped in the previous investigations, and this has been accepted as a universal phenomenon. Nevertheless, we think that it is only true for a type of neuron: namely, resonators. Actually, there exists another type of neuron, integrators, which can undergo a saddle-node on invariant circle bifurcation from the rest state to the firing state. For the latter we find that the critical amplitude increases monotonically as the frequency of sinusoidal stimulus is increased. This is shown by way of the Morris－Lecar model. As a consequence, the critical amplitude curve is studied further, and the dynamical mechanisms underlying the change in critical amplitude curve are uncovered. The results of this paper can provide a reference to choose the subthreshold periodic stimulus.