Asymmetric Effects on Escape Rates of Bistable System

The asymmetric effects on the escape rates from the stable states x_± in the bistable system are analyzed. The results indicate that the multiplicative noise and the additive noise always enhance the particle escape from stable states x_± of bistable. However, the asymmetric parameter r enhances the
particle escape from stable state x₊, and holds back the particle escape from stable state x_-.     

显微镜景深拓展技术研究

随着生命科学需求的日益迫切,显微镜的景深拓展成为显微领域的一个重要发展方向,为了更好地了解、研究显微景深问题,对景深拓展技术进行研究与总结。以显微景深的大幅提升为出发点,就光学切片扫描、空间光调制、波前编码及光场显微4个方面进行了全面的综合性论述。对这些技术的原理、方式及拓展水平进行了阐述,并就其技术缺陷、发展方向进行了归纳总结。随着技术水平的提高,显微景深较传统显微镜可提高1~2个数量级。     

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.     

基于改进中值滤波和提升小波变换的阈值去噪方法研究

对于实际拍摄的一些图像信噪比低,噪声密度大,且含有混合噪声,而现有算法大多只能去除单一噪声的问题。针对混合噪声中含有的脉冲噪声和高斯噪声,提出基于改进中值滤波和提升小波变换去噪相结合的方法。去噪过程中,使用中值滤波器提取脉冲噪声并采用中值滤波算法滤波后,构造提升小波,采用改进阈值函数提升小波阈值去噪方法去除高斯噪声。实验结果表明,当噪声值(,)=(0.4, 20)时,采用本文去噪方法,峰值信噪比（PSNR）为34.002 1,平均绝对误差（MAE）为2.365 3。     

一种远距离水下光电成像的方法

为了增大水下光电成像探测系统的探测距离,降低系统造价成本,对距离选通技术中存在问题进行分析研究,提出降低激光单脉冲能量,提升系统运行频率,增加CCD曝光时间的方法。利用噪声随机特性及目标回波的相关特性进行多脉冲累计提高探测距离。对距离选通系统进行适应性改进,并在室内水池进行实验。实验结果表明:此方法可有效增大系统探测距离,且目标图像质量与激光脉冲数量存在一定最优匹配关系,实验中10次脉冲累计获取到29 m距离处的目标图像质量最佳。     

机械系统摩擦动力学研究进展

摩擦环节对机械系统动力学行为有重要、甚至可能是关键的影响. 深入研究摩擦及摩擦动力学特点,对于解决机械系统中摩擦带来的不利影响, 发挥其有利作用, 是非常重要的. 本文介绍和评述了机械系统摩擦动力学的研究进展, 包括常用的摩擦模型及其特性, 摩擦系统自激振动、强迫振动和摩擦振动控制等. 除理论研究方法之外, 重点讨论了制动噪声振动、摩擦耗能和多领域摩擦振动控制等摩擦动力学的应用研究.     

Contributions of Computational Aeroacoustics to Jet Noise Research and Prediction

A brief review of recent progress in the field of computational aeroacoustics (CAA) is proposed. This paper is complementary to the previous reviews of Tam [(1995a) “Computational aeroacoustics: issues and methods”, AIAA J. 33(10), 1788–1796], Lele [(1997) “Computational Aeroacoustics: a review”, AIAA Paper 97–0018, 35th Aerospace Sciences Meeting and Exhibit, Reno, Nevada] and Glegg [(1999) “Recent advances aeroacoustics: the influence of computational fluid dynamics”, 6th International Congress on Sound and Vibration, Copenhagen, Danemark, 5–8 July, 43–58] on advances in CAA. After a short introduction concerning the current motivations of jet noise studies, connections between computational fluid dynamics (CFD) and CAA using hybrid approaches are discussed in the first part. The most spectacular advances are probably provided by the direct computation of jet noise, and some recent results are shown in the second part.     

三值噪声调制下电路中的随机共振现象

研究了在三值噪声和热噪声扰动下的RLC电路的平均输出幅度增益. 利用随机平均法和Shapiro-Loginov公式, 得到了平均输出幅度增益的精确表达式. 通过计算机模拟, 画出了平均输出幅度增益与平坦系数、有噪声和无噪声时, 输出信号振幅与输入信号频率之间的关系曲线. 从结果来看, 系统产生了双值噪声驱动的RLC电路中(文献[11])没有的随机共振现象, 甚至还出现了双共振峰.     

Effects of non-Gaussian noise on a calcium oscillation system

We investigate the effects of the non-Gaussian colored noise on a calcium oscillation system using stochastic simulation methods. It is found that the reciprocal coefficient of variance R has a maximum (R max ) with increasing noise intensity Q. The non-Gaussian noise parameter q has an important effect on the system. For some values of q (e.g., q = 0.9, q = 1.0), R has a maximum with increasing correlation time τ. Non-Gaussian noise induced spikes are more regular than Gaussian noise induced spikes when q is small and Q has large values. The R has a maximum with increasing q. Therefore, non-Gaussian noise could play more effective roles in the calcium oscillation system.     

Average consensus of multi-agent systems with communication time delays and noisy links

In this paper,we consider the average-consensus problem with communication time delays and noisy links.We analyze two different cases of coupling topologies:fixed and switching topologies.By utilizing the stability theory of the stochastic differential equations,we analytically show that the average consensus could be achieved almost surely with the perturbation of noise and the communication time delays even if the time delay is time-varying.The theoretical results show that multi-agent systems can tolerate relatively large time delays if the noise is weak,and they can tolerate relatively strong noise if the time delays are low.The simulation results show that systems with strong noise intensities yield slow convergence.