机械振动信号盲源分离的时域方法

介绍盲源信号分离基本原理,分析了瞬态混叠模型和卷积混叠模型的特征,给出两个源信号独立性的评判准则,研究了盲分离正确性的评价误差函数,进行数值仿真,并用时域卷积瞬态混叠模型对实际机械振动信号进行源信号的盲分离。数值仿真和实际信号的分离效果较好,说明所用方法在机械振动信号盲源分离中的适用性。文中还分析了多源信号分离中所用方法的收敛性。     

水面舰船尾流电导率信号分布规律的研究

在舰船尾流区与非尾流区之间存在显著的速度差和盐度(或密度)差,利用电导率探头可获得对应于这些差别的尾流电导率信号。在水槽中形成了与海洋环境类似的盐度分层流场,由双螺旋桨自航水面船模产生尾流,分别在盐度分层流场和非分层均匀流场中测量了尾流电导率信号的横向分布,并对盐度分层流场中水面舰船尾流的纵向速度分布进行了数值计算。结果表明:在盐度分层流场和非分层均匀流场中水面舰船尾流的电导率信号沿其横向近似呈高斯分布;尾流速度对其电导率信号的影响比盐度梯度的影响大得多;尾流的无量纲纵向速度亏损的数值计算结果与尾流的相对电导率信号横向分布的实测结果具有很好的一致性。     

畸变信号的反演修正在同步测压中的应用

本文说明了同步测压所包含的主要内容以及一套实用的同步测压系统的组成,分析了通过传压管道传递的压力信号产生畸变的原因,指出对畸变信号进行反演修正是同步测压过程中必不可少的关键环节。利用频域修正的方法可以对压力分布同步测量中的畸变信号进行反演,以消除输出信号的幅值误差和相位差,保证各个测压通道得到的信号在时间上具有良好的同步性。这样就可以通过对脉动压力分布进行面积加权积分,得到脉动气动力的时间历程。在对畸变信号进行反演修正时,得到测压系统的频率响应函数是关键,本文介绍了利用比较法来标定频响曲线的装置和方法。并通过实验演示了反演修正的效果,表明本文所采用的同步测压装置具有非常好的同步性能。     

Self-switching of a transverse plane wave propagating through a two-component elastic composite

The paper discusses the results of theoretical and numerical analysis of the interaction of nonlinear elastic plane harmonic waves in a composite material whose nonlinear properties are described by modeling it with a two-phase mixture. The interaction of two transverse vertically polarized harmonic waves is studied using the method of slowly varying amplitudes. The truncated and evolutionary equations as well as the Manley-Rowe relations are derived. The mechanism of energy pumping from a strong pumping wave with frequency ω to a weak signal wave with frequency 3ω is analyzed. The switching mechanism for hypersonic waves in a nonlinear elastic composite is similar to the switching mechanism observed in transistors __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 7, pp. 35–46, July 2007.     

一种基于小波变换的故障诊断改进算法

为提高多传感器组合导航系统对各导航传感器的在线故障检测能力，提出了一种基于调频高斯小波变换的导航传感器故障诊断改进算法。该算法在分析调频高斯小波特性的基础上，采用高斯小波变换计算出观测量的小波系数后，然后利用带遗忘因子的数据平滑算法对小波系数进行平滑，通过判断平滑值来诊断导航工作正常与否。其优点是仅利用传感器的观测量来直接检测导航传感器故障，适当选择小波变换的拉伸因子和数据的衰减因子可以对方差突变等软故障进行有效的在线检测，并解决了误检问题。仿真结果证明了该算法的有效性。     

摩擦信号分形维数与载荷和速度的关系研究

在立式万能摩擦磨损试验机上对GCr15/45#钢摩擦副进行不同接触载荷和滑动速度下的摩擦磨损试验,对初始滑动距离1 000 m内的摩擦系数信号进行数据采集,运用结构函数测度方法对摩擦系数信号进行分形表征,计算不同载荷和速度下的分形维数,研究摩擦信号的分形维数随载荷和速度的变化规律.结果表明,摩擦系数信号具有显著的分形特征,其分形维数随载荷和速度而变化.在相同载荷下,分形维数随滑动速度增加而增大;在相同速度下,分形维数随着接触载荷增加而增大.磨损率与摩擦系数信号的分形维数正相关.     

Nonlinear Electrodynamic Delay of Electromagnetic Signals in a Coulomb Field

We study the motion of electromagnetic signals in the Coulomb electric field of a compact gravitating center under the laws of the parameterized nonlinear electrodynamics of the vacuum. We evaluate the deflection angles of the rays along which the electromagnetic waves of two normal modes propagate in this field. We determine the nonlinear electrodynamic delay of the electromagnetic signal of one normal mode relative to the electromagnetic signal of another normal mode during their propagation from the same source to an observer.     

Neural network processing for adaptive line enhancement

This paper describes the inverstigation devoted to establish suitable weights in a feed-forward neural network realizing the narrow-band filtering map in the case of adaptive line enhancement(ALE) by the utility of the optimum common learning rate back propagation (OCLR BP) algorithm. It is found that a feed-forward network with 64 linear input and output neurons, and 8 odd sigmoid neurons in the hidden layer, i.e. an (64→8→64) architecture, could establish the specific input-output function in the case of relatively low signal-to-noise radio. Only is an input signal consisting of mixed periodic and broad-band components available to the network system. After learning, both the "fanning-in-connection patterns", each of which consists of weights fanning into a hidden-neuron From all the outputs of input-neurons, and the "fanning-out-connection patterns", each of which consists of weights fanning out from a hidden-neuron to all the inputs of output-neurons, are tuned to the periodic signals. The nonline     

Characterization and optimization of SOA-based UNI recirculating shift register switching window

The operation of an all-optical recirculating shift register implemented with the semiconductor optical amplifier (SOA)-based ultrafast nonlinear interferometer (UNI) in a counter-propagating, inverting configuration is methodically studied and analyzed. This is achieved by applying an appropriate model for a SOA deployed as the nonlinear element in an interferometric switch driven by ultrafast and strong feedback optical pulses. By means of numerical simulation the impact of the critical functional parameters on the formation of the switching window is thoroughly investigated and assessed enabling to provide useful design rules for their proper selection and combination so as to optimize the specific metric and ensure high performance. The undertaken theoretical treatment can be extended for characterizing other more complex all-optical circuits and subsystems of enhanced functionality that employ this type of shift register as the key building module.