变频器技术介绍

本文综合阐述了变频器技术的应用背景、基本组成、基本原理和要求、常用方法及其发展趋势。     

透过CMIPPI-C-S2项目浅析灌溉项目中土方施工方法

该文通过一灌溉项目的执行,借助图片、图形,形象地论述了在土方施工过程中遇到的问题,以及如何有效地予以解决的方法。     

Railway wheel-flat and rail surface defect modelling and analysis by time–frequency techniques

Damage to the surface of railway wheels and rails commonly occurs in most railways. If not detected, it can result in the rapid deterioration and possible failure of rolling stock and infrastructure components causing higher maintenance costs. This paper presents an investigation into the modelling and simulation of wheel-flat and rail surface defects. A simplified mathematical model was developed and a series of experiments were carried out on a roller rig. The time–frequency analysis is a useful tool for identifying the content of a signal in the frequency domain without losing information about its time domain characteristics. Because of this, it is widely used for dynamic system analysis and condition monitoring and has been used in this paper for the detection of wheel flats and rail surface defects. Three commonly used time–frequency analysis techniques: Short-Time Fourier Transform, Wigner–Ville transform and wavelet transform were investigated in this work.     

Fast direction of arrival algorithm based on vector-sensor arrays using wideband sources

An acoustic vector sensor （AVS） can capture more information than a conventional acoustic pressure sensor （APS）. As a result, more output channels are required when multiple AVS are formed into arrays, making processing the data stream computationally intense. This paper proposes a new algorithm based on the propagator method for wideband coherent sources that eliminates eigen-decomposition in order to reduce the computational burden. Data from simulations and lake trials showed that the new algorithm is valid： it resolves coherent sources, breaks left/right ambiguity, and allows inter element spacing to exceed a half-wavelength.     

浅谈公路施工现场危险源辩识及控制管理

就公路施工现场如何对危险源进行辩识做了比较深入地分析与探讨,提出了控制管理的措施,以防止和减少施工生产安全事故的发生。     

蓄电池测试系统中SVPWM与SPWM的比较研究

针对高性能蓄电池测试系统主变流电路采用的SVPWM和SPWM调制方法，分析了二者间的内在联系，并进行了性能比较。在数字化控制系统中，较SPWM方案，SVPWM方案不仅提高了逆变器的直流电流利用率，且减小了输出电流的纹波系数，降低了谐波污染，使电路更接近单位功率因数运行。     

水声网络探测节点的一种运动目标参数估计算法

文章提出了一种水声网络探测节点的运动目标参数估计方法,即基于模型匹配原理的估计算法。给出了算法的原理和仿真分析。     

舞台车液压系统双动力源装置设计

介绍了一种舞台车液压系统双动力源结构，其在原液压系统动力源装置的基础上，通过加装一套油泵、电动机、电控箱及部分管路、电缆线等实现增加一套动力源结构，采用该装置可减少油耗，延长发动机及变速器使用寿命，减少维修保养费用，具有节能、环保等优点。     

目标和环境特性对被动声呐浮标探测范围的影响

被动声呐浮标的探测性能不仅和自身设备性能有关,还和目标运动特征及环境特性有着密切的关系。通过建立潜艇目标运动、海洋环境的数学模型,利用浅海平滑平均声场理论推导了潜艇深度变化后被动声呐浮标的探测范围,讨论了潜艇采用不同航速、航深以及海洋环境对被动声呐浮标探测范围的影响,并进行了仿真。结果表明,目标和环境特性对被动声呐浮标的探测范围有重要影响,这对航空反潜作战训练具有一定的指导意义。     

基于IWO算法的轴系—基座—壳体系统声辐射优化研究

针对轴系-基座-壳体结构复杂,对于激振力引起的结构表面声辐射尚未形成一套有效的计算和优化方法,文章尝试通过功率流有限元和声学边界元方法,对系统声优化问题进行了研究。在直线校中状态下,用相应单元模拟系统中减振器、隔振器和吸振器,建立轴系-基座-壳体系统有限元模型,利用有限元转子动力学,计算系统某特定工况下频率响应。在此基础上采用IWO算法,以各减振单元参数为设计变量,以传递路径的总功率流为目标函数进行优化,最后利用声学边界元方法对优化结果进行对比分析。结果表明,将流经路径总功率流替代场点声压为目标函数,不仅能将问题简化大大减少计算量,还能为系统减振降噪提供有效的优化计算方法,具有重要工程应用价值。