基于软开关技术的氩弧焊逆变焊机

作为新型逆变弧焊电源核心技术的软开关技术,它较好解决了具有关断拖尾特性的IGBT开关转换,同时大大减少了变换器的环路损耗。电源的主要开关功率器件进行的是零开关,减少了功率器件的电压、电流应力。     

基于支持向量机的设备振动信号趋势预测

详细分析了支持向量机用于趋势预测的理论基础,通过Lorenz仿真信号的单步、多步预测证明,支持向量机由于采用了结构风险最小化准则表现出优秀的推广能力,预测区间较长且精度较高.工程应用实例也表明支持向量机在设备趋势预测中可以满足实际需要,具有很好的应用前景.     

Development of Cutting Condition Monitoring System for ID-blade Saw Slicing Machine

1 Introduction There are two ways ,the multi-wire sawslicing method and the inner-diameter blade slicing method,re-cently used for cutting wafers froma single crystal ingot . Multi-wire sawbecomes more popular iningot slicingprocesses ,because it has an advantage for slicinglarge diameter or long siliconingot and has efficiency for massproduction.However ,this method is difficult to control the wire cutting the ingot along its crystal orientationandit is less correspond to the request of some …     

多自由度系统结构动力计算的截断误差及其修正

多自由度系统结构强迫振动,一般按振型分解法计算.实际计算时,因为高阶振型影响很小,所以只取前Q阶振型.本文提出了一种新的求取Q值的方法,并提出了对由于计算时不能取全部振型而产生的计算误差进行弥补的办法,达到了取Q少、精度高、误差修正简便的目的.     

Analysis of digital spectral processing of laser Doppler vibration meter signals

A digital spectral method of the maximum harmonic for processing laser Doppler vibration meter signals from a surface vibrating according to a harmonic rule is analyzed. A digital model for this signal in the presence of additive and multiplicative noises is suggested. Examples are given for the effect of signal discretization frequency on the error of determining vibration amplitude. __________ Translated from Izmeritel’naya Tekhnika, No. 9, pp. 42–45, September, 2006.     

Vibrodiagnostic parameters of fatigue damage in rectangular plates. Part 3. Through-the-thickness and surface semi-elliptical cracks

The paper addresses the analytical determination of vibrodiagnostic parameters that describe the presence of normal-rupture flat through-the-thickness and surface semi-elliptical central cracks in a rectangular homogeneous plate of constant thickness for various plate fixing conditions and vibration modes. It is shown that the most sensitive vibrodiagnostic damage parameter of a plate is the variation of the logarithmic decrement in the case of a through-the thickness crack and the second-harmonic ratio of the vibration process in superharmonic resonance in the case of a surface crack. __________ Translated from Problemy Prochnosti, No. 5, pp. 27–47, September–October, 2006.     

Natural frequencies of a flat viaduct road part simply supported on two ends

Viaduct roads have wide application in big cities with high traffic loads, in order to decrease traffic density and to connect subways to highways. Viaduct roads are constructed using steel structures instead of concrete ones in areas of earthquake risks. The low weight of steel structures however causes problems such as vibration and noise. There is increasing demand especially in populated areas to suppress vibration and noise on highway roads for reducing noise-related environmental pollution. In this study, bending vibrations of rectangular plate viaduct roads, which are supported by six fixed elements of rectangular cross-sectional elements are considered. Natural frequencies are obtained using the Rayleigh-Ritz technique, finite elements analysis, experimentally and neural networks (NN).     

Molecular Dynamics Simulation for Ultrafine Machining

This article surveys the advances of molecular dynamics (MD) simulation in the research of ultrafine machining and related technologies. Modeling methods, including interatomic potentials and boundary conditions, are addressed. Algorithm strategies for MD simulations are discussed. By applying simulations with Tersoff potential, a case study of the material removal mechanism of the polishing based on coupling vibrations of liquid (PCVL) is presented.     

Leakage tests for Am solid sources used for liquid xenon detector monitoring

Experimental tests are described to check solid ²⁴¹Am radioactive sources used to monitor operation of liquid xenon detectors. In particular, radioactive leakage was tested in extreme temperature conditions following immersion in liquid nitrogen for different time periods. No radioactivity loss was detected from the sources considered. The paper describes the source characteristics, test methods and results obtained.     

高精度气压源的Fuzzy-PID控制研究

设计了Fuzzy—PID双模控制器并应用到高精度气源压力控制系统中．试验表明，单纯采用PID控制的高精度气源压力控制系统具有精度高的优点，但不适应系统参数的变化．Fuzzy—PID双模控制器具有响应速度快、稳态误差小、鲁棒性强的优点．通过试验比较了传统PID、Fuzzy控制和Fuzzy—PID双模控制3种控制策略，试验结果表明，Fuzzy—PID双模控制器综合了Fuzzy控制和PID控制的优点，适用于高精度气源压力控制系统．