Fault degradation assessment of water hydraulic motor by impulse vibration signal with Wavelet Packet Analysis and Kolmogorov–Smirnov Test

The machinery fault diagnosis is important for improving reliability and performance of systems. Many methods such as Time Synchronous Average (TSA), Fast Fourier Transform (FFT)-based spectrum analysis and short-time Fourier transform (STFT) have been applied in fault diagnosis and condition monitoring of mechanical system. The above methods analyze the signal in frequency domain with low resolution, which is not suitable for non-stationary vibration signal. The Kolmogorov–Smirnov (KS) test is a simple and precise technique in vibration signal analysis for machinery fault diagnosis. It has limited use and advantage to analyze the vibration signal with higher noise directly.In this paper, a new method for the fault degradation assessment of the water hydraulic motor is proposed based on Wavelet Packet Analysis (WPA) and KS test to analyze the impulsive energy of the vibration signal, which is used to detect the piston condition of water hydraulic motor. WPA is used to analyze the impulsive vibration signal from the casing of the water hydraulic motor to obtain the impulsive energy. The impulsive energy of the vibration signal can be obtained by the multi-decomposition based on Wavelet Packet Transform (WPT) and used as feature values to assess the fault degradation of the pistons. The kurtosis of the impulsive energy in the reconstructed signal from the Wavelet Packet coefficients is used to extract the feature values of the impulse energy by calculating the coefficients of the WPT multi-decomposition. The KS test is used to compare the kurtosis of the impulse energy of the vibration signal statistically under the different piston conditions. The results show the applicability and effectiveness of the proposed method to assess the fault degradation of the pistons in the water hydraulic motor.     

Predicting the Impulse from the Curved Surface of Detonating Cylindrical Charges

TNT (Trinitrotoluene) equivalency depends on knowing the relative strength of different explosives compared to TNT. However, the current values for TNT equivalency mostly depend on work on spherical charges, whereas most military ammunition is cylindrical in shape. Cylindrical charges are known to give an enhanced blast close in when compared to that of spherical charges. A previous paper looked at predicting the peak pressure perpendicular to the curved side of a cylinder. This paper examines impulse data for the curved surface of cylindrical charges from the literature for Composition B and Pentolite and then describes experimental work carried out on cylindrical PE4 charges. Analysis of the free air experimental and literature data shows that it is possible to predict the impulse using a linear relationship, though it is not possible to decide on the best fit based on the current data. The fits for both I=K_IM^0.5/R and I= M^2/3/R give very similar correlation coefficients, where M is the charge mass and R the distance from the charge and K_I and are constants characteristic of the explosive. Values of K_I and have been fitted to literature and current experimental data for Composition B, Pentolite and PE4. Whichever of these two relationships is used, it should be possible to develop a method of determining TNT equivalency for the curved surface of cylindrical charges by using TNT equivalency=K_{I explosive}/K_{I TNT}, provided that data for TNT cylinders is obtained.     

Characteristic overpressure-impulse-distance curves for vapour cloud explosions using the TNO Multi-Energy model

A number of models have been proposed to calculate overpressure and impulse from accidental industrial explosions. When the blast is produced by ignition of a vapour cloud, the TNO Multi-Energy model is widely used. From the curves given by this model, data are fitted to obtain equations showing the relationship between overpressure, impulse and distance. These equations, referred herein as characteristic curves, can be fitted by means of power equations, which depend on explosion energy and charge strength. Characteristic curves allow the determination of overpressure and impulse at each distance.     

城市化与消费需求相互拉动的效应分析

从定量的角度,采用向量自回归模型,运用脉冲响应函数对我国城市化和全国平均消费水平进行了动态性研究,揭示了两者内在的相互促进方式.阐述了合理加快城市化建设对扩大消费水平起到决定性作用,平均消费需求的提高又反作用于城市化建设,两者相互拉动.通过脉冲响应函数分析,得出两者相互影响的过程.     

冲击性负荷的运行及计量方式分析

电弧炉属于一种典型的冲击性负荷,其主要特点是快速、随机的功率波动,由此带来的电压闪变及波形畸变使得传统的计量方式不适用冲击性负荷下的计量.本文分析了电弧炉的运行特点,通过模拟实验,得出了这种现象形成的原因,并提出了如何消除冲击性负荷对计量的影响见解.     

辽宁省城乡居民收入与GDP 增长的相关性分析

研究了辽宁省1 9 8 0-2 0 1 2年城镇居民人均收入增长指数数据、 农村居民人均收入增长指数数据与 辽宁省GDP 增长指数数据之间的关系, 从整体与局部的角度和相关系数得出了三者之间的关联特征, 并进一步建 立了变量间的向量自回归模型, 通过脉冲响应函数探讨了三者之间的动态联系。研究结果表明, 辽宁省GDP 增长 率与城镇居民人均收入增长率、 农村居民人均收入增长率之间具有密切的相关性, 但变化趋势存在不同步性; 从三 者之间的动态联系来看, 辽宁省GDP 增长率对城镇居民人均收入和农村居民人均收入的增长有明显的促进作用, 而城镇居民人均收入和农村居民人均收入的增长率对GDP 增长率的冲击不大。应采取有效措施, 缩小城乡居民人 均收入差距, 努力实现城乡居民人均收入与GDP 的同步增长。     

同轴全铰链双输出脉冲发生机构尺度综合与优化

以高效率、高平稳性、结构简化为主要目标,对全铰链同轴双输出函数发生机构进行尺度综合.将该六杆机构视作由一套基础四杆机构和一套等价四杆机构并联而成.采用分组综合的策略,即先建立按两个位置综合且瞬时传动比相等为目标的基础四杆机构综合模型进行求解.再以该四杆机构为基础,运用变杆长四杆机构的等价原则,求得与基础四杆机构具有相似运动规律的等价四杆机构的尺寸参数.这样较好地解决了这一特殊的高阶运动参数尺度综合问题.实例综合结果表明该机构脉动值仅为6%.     

基于神经网络的线性相位FIR滤波器设计

针对FIR滤波器的神经网络设计法,提出一种泛函连接人工神经网络的改进算法。通过设置不同的加权误差函数值来控制各个样本的学习率,改善了网络的学习效果;制定了神经网络训练集的选取规则,使用该规则选取样本对网络进行训练,可设计通带阻带截止频率指标精确可控的滤波器,克服了现有算法只能设计具有通带截止频率的滤波器和不能精确控制任意截止频率的不足。仿真结果表明所提出的方法能很好地满足设计要求。     

一种新的时变网络计算机辅助分析方法

本文根据电网络的基本性质，并结合单位样值函数的抽样作用，导出并实现了一种新的时变网络计算机辅助分析方法。该方法直接以节点电压和支路电流为解变量，对包含时变电阻、时变电感、时变电容、时变互感与四种时变受控源的一般电网络都可进行机助分析。