参数扰动的RLC低通滤波器的随机共振

研究了RLC低通滤波器在电导受到非对称双值色噪声扰动时的随机共振现象．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．分析表明,在欠阻尼、临界阻尼和过阻尼RLC低通滤波器中,平均输出幅度增益对电导噪声的非对称性、相关时间、强度和信号频率都存在非单调依赖关系．适当的噪声和系统参数条件可以使有噪声时系统的平均输出幅度增益大于没有噪声时系统的平均输出幅度增益．噪声可以提高滤波器对高频信号的衰减率．恰当的条件可以获得平均输出幅度增益的最大值．     

双稳态施密特触发电路在OU噪声驱动下的逻辑随机共振

噪声能够帮助非线性系统产生反常的有序行为的现象吸引了人们的广泛关注.我们以一个双稳态的施密特触发电路作为模型系统,用OU(Ornstein-Uhlenbeck)噪声驱动,利用噪声进行逻辑计算,实现了逻辑门的模拟运算.同时研究了噪声强度、噪声相关时间下的逻辑随机共振,并且探讨了系统的弛豫性质对逻辑随机共振的影响.结果表明,色噪声驱动下的双稳态系统中的逻辑随机共振现象同样存在.     

参数扰动的RLC低通滤波器的随机共振

研究了RLC低通滤波器在电导受到非对称双值色噪声扰动时的随机共振现象.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.分析表明,在欠阻尼、临界阻尼和过阻尼RLC低通滤波器中,平均输出幅度增益对电导噪声的非对称性、相关时间、强度和信号频率都存在非单调依赖关系.适当的噪声和系统参数条件可以使有噪声时系统的平均输出幅度增益大于没有噪声时系统的平均输出幅度增益.噪声可以提高滤波器对高频信号的衰减率.恰当的条件可以获得平均输出幅度增益的最大值.     

信号调制白噪声作用下线性系统的随机共振

研究了信号调制白噪声作用下的二阶过阻尼线性系统中的随机共振现象.基于线性系统理论和相关删去法方法,得到了系统平均输出幅度增益的精确表达式.研究表明:输出幅度增益是噪声强度,系统阻尼系数和系统固有频率,以及激励信号频率的非单调函数,适当的噪声强度和系统参数可以使噪声情况下的输出幅度增益大于无噪声时的输出幅度增益.     

相关偏置信号调制噪声和加性噪声驱动线性系统随机共振

研究了偏置信号调制噪声和加性噪声驱动线性系统的随机共振现象。根据线性系统理论,得到了系统输出信噪比的精确表达式。研究结果表明：系统输出信噪比是系统衰减常数、调制信号偏置参数、信号调制噪声强度和加性噪声强度的非单调函数。同时,系统输出信噪比随两种噪声的相关强度成非单调关系。     

《二值噪声作用下线性系统的随机共振》

研究了二值噪声用下的二阶过阻尼线性系统的随机共振现象。基于线性系统理论和相关删去法方法,得到了系统平均输出幅度增益的精确表达式。研究表明：输出幅度增益是噪声的强度和相关时间、系统阻尼系数,以及激励信号的频率的非单调函数;另外,适当的噪声参数和系统参数可以使噪声情况下的输出幅度增益大于无噪声时的输出幅度增益。     

信号调制色噪声作用下线性系统的随机共振

研究系统的阻尼系数受二值噪声扰动时,信号调制二值噪声驱动的二阶过阻尼线性系统的随机共振现象.基于线性系统理论和相关删去法方法,得到了系统平均输出幅度增益的精确表达式.研究表明:系统的输出幅度增益是二值噪声的强度和相关率、系统固有频率、系统阻尼系数,以及激励信号的频率的非单调函数,适当的噪声参数可以使系统的输出幅度增益大于无噪声时的输出幅度增益.     

方波和非对称双值噪声作用下的熵随机共振研究

研究了在非对称双值噪声、白噪声和方波共同作用下受限系统中的熵随机共振现象。在绝热近似条件下,推导出了输出信噪比的表达式。分析表明,信噪比是非对称双值噪声的强度与非对称参数、白噪声强度,以及方波信号幅度的非单调函数。另外,信噪比随受限结构参数的变化而非单调变化。讨论了双值噪声的相关率对SNR的影响。     

双频信号作用下的单稳随机共振数值研究

在振动共振的基础上,研究了非线性单稳随机共振系统在高、低两种不同频率作用下的动力学特性,分析得出高频信号可以使系统产生分岔,而低频信号幅值及单稳系统非对称参数是系统跃迁阈值的影响因素,调节高、低频信号参数可改变势垒高度,诱发单稳随机共振效应。理论分析和数值仿真结果表明,在绝热近似条件下,单稳随机共振系统输出信号的信噪比及功率谱均呈非单调变化,同时通过级联后单稳系统输出的效果更佳,冲击信号仿真分析表明该类型随机共振系统有利于工程实际。     

乘性三值噪声作用下微分电路中的随机共振现象研究

基于线性系统理论,利用三值噪声的统计性质,推导出了系统输出幅度增益的解析表达式。研究表明,随着输入信号频率、三值噪声的定态概率、噪声状态间的跃迁速率、参数k(电容C的倒数)的增大,输出幅度增益出现一个最大值。当信号频率较低时,输出幅度增益随着k的增大而单调下降;当信号频率较高时,输出幅度增益随着k的增大而单调增大。当信号频率较低时,输出幅度增益随着定态概率的增大而单调增大;当信号频率较高时,输出幅度增益随着定态概率的增大而单调下降。随着G0(电阻的倒数)的增大,输出幅度增益单调减小。     

Numerical simulation of boundary-layer disturbance evolution

The use of numerical simulations to study the development of boundary-layer disturbances is illustrated for a number of different incompressible flow configurations. These include cases where the disturbances are generated by, or interact with, flow-control devices in the form of compliant panels, suction slots and microelectromechanical systems actuators. The velocity-vorticity system of governing equations used for the simulations is reviewed, along with the numerical discretization.     

吸油烟机气动噪声的数值模拟

基于混合CAA(Computational Aeroacoustics)方法,对某型号吸油烟机的气动噪声进行了数值模拟研究.首先,利用CFD软件Fluent对吸油烟机的非稳态流场进行计算,得到吸油烟机非稳态流场的压力和速度分布.然后,利用Lighthill声类比方法和Curle方程,采用声学软件Actran计算得到吸油烟机的声场.最后,分析了吸油烟机内声源频域结果和声场的声压级云图,得到了吸油烟机噪声传播指向特性.研究结果表明,吸油烟机噪声主要为中低频噪声,且以离散噪声为主.在叶片通过频率下,吸油烟机噪声具有明显的指向性特征,噪声主要由吸油烟机内离心风机主次进风口向外部传播.     

Importance sampling for stochastic systems under stationary noise having a specified power spectrum

We develop an importance sampling simulation scheme for estimating an extremely small probability of system failure with respect to a time-dependent stochastic system excited by stationary random noise having a specified power spectrum. First, we construct a system of random differential equations driven by a Wiener process, which can approximately give such a stationary random noise by the use of an extended version of the well-known Ornstein–Uhlenbeck process. Next, we suppose a stochastic response system driven by the constructed stationary random noise. Next, formulating the probability of system failure, we give an importance sampling scheme through the probability measure transformation based upon the Girsanov theorem, where multi design times are introduced to cope with stationary or almost stationary behavior of the system. Finally, we give numerical examples to demonstrate the efficiency of the proposed scheme.     

Numerical simulation of speckle noise in laser vibrometry

The fundamental mechanism by which speckle noise is generated in laser vibrometry before describing a new numerical simulation for prediction of speckle noise level in a real measurement is considered. Factors within the simulation include rate of change of phase within individual speckle transitions, low-pass filtering to match the frequency range of experimental data with which comparison is to be made, a track-and-hold facility for periods of low signal amplitude, and wavefront curvature effects. The simulation data provide real insight into the phase and amplitude modulation of the Doppler signal, and good agreement is found in the final comparison with experimental data from a measurement on a rotating target.     

On-chip stochastic resonance of ion channel systems with variable internal noise

We induced stochastic resonance in planar lipid bilayer systems with alamethicin ion channels, and varied alamethicin concentration, membrane area, and applied voltage. We found that membrane-induced microphonic noise significantly affects the signature of stochastic resonance, and that this noise can be used to optimize ion channel-based biosensors.     

Numerical simulation of the electro-acoustical response of a transducer excited by a time-varying electrical circuit

Existing methods for the modeling of piezoelectric transducer response are generally frequency domain-based. The major disadvantage of this type of model is that they cannot take into account the electrical elements present in the emitting or receiving circuit whose values vary with respect to time. The need for a method that accounts for time-varying elements arises, for example, when the circuit comprises active electrical elements, such as diodes, or when the transducer is excited by capacitive discharge via a switch. Indeed, in this last example, it is known that the output impedance of the generator depends on the state of the switch: if it is off, its value is high; if it is on, its value is low. A time-domain-based method is presented to compute the electro-acoustical response of a piezoelectric transducer and its electrical circuit, taking into account the presence of time-varying elements. An application to a current example makes it possible to show the influence of these elements on waveforms and the capacity of our model to account for them     

近爆作用下钢筋混凝土板动态破坏的数值模拟研究

当爆炸在结构构件表面发生时,产生的冲击波将会对结构构件造成损伤和破坏,而准确预测潜在的爆炸对结构构件造成的损伤是进行重要建筑物和防护结构抗爆设计的基础。为研究近爆作用下钢筋混凝土板的抗爆性能,采用AUTODYN软件建立了混凝土和钢筋的三维分离式实体模型,数值模型考虑了应变率对钢筋和混凝土材料动力本构特性的影响以及炸药-空气-结构之间的流固耦合相互作用,分析了不同炸药量作用下钢筋混凝土板的损伤机理和破坏特征,合理展现了钢筋混凝土板从混凝土开裂、碎片形成、部分钢筋屈服断裂到板局部震塌的动态演变过程。随着炸药量的增大,钢筋混凝土板的破坏模式逐渐由整体弯曲破坏转变为局部的冲切破坏     

不同雷诺数下圆柱绕流气动噪声数值模拟

基于大涡模拟和声类比相结合的混合方法对不同雷诺数下二维圆柱绕流的远场气动噪声进行预测.预测值与试验数据吻合良好.根据预测结果分析圆柱绕流气动噪声的声场特性,研究流场振荡规律对远场噪声的影响和圆柱绕流气动噪声的辐射特性,并寻找降低圆柱绕流气动噪声的途径.结果表明:随着雷诺数的增加,远场各测量点的总声压级增大;声场的最大声...     

A two-channel circuit for protecting a resonant gravitational antenna from correlated non-Gaussian interference

A modernized circuit with a noninertial nonlinear element, a whitening filter and a matched filter, connected in series-parallel, for suppressing correlated non-Gaussian interference at the output of a cryogenic resonant gravitational antenna is considered. The algorithm is based on the use of optimum processing of vector signals. __________ Translated from Metrologiya, No. 5, pp. 3–9, May, 2008.