Remarks on the adaptive control of linear plants with unknown high-frequency gain

Adaptive control of first-order linear systems of the form $\text{x}\text{?}\text{= ax + bu}$ with the sign of b unknown is considered. It is shown that stabilizing adaptive controllers exist that have globally bounded gain and prespecified terminal dynamics.     

Performance analysis and circuit design of high-frequency resonant inverter using a single reverse-conducting device

This paper is concerned mainly with a performance analysis and a design method of a newly developed zero-current switching quasi-resonant high-frequency inverter (ZCS-QRI) using a single reverse-blocking power device (high-frequency GATT). As a matter of fact, GATT is replaced by the latest MOS-gate power semiconductor devices, MOSFET, IGBT, MCT and Bi-MOS · GTO thyristor. The frequency-modulated single-ended inverter circuit, which incorporates an auxiliary diode and large reactor cascade branch in parallel with a resonant capacitor connected into the transformer-link series-resonant tuned tank load circuit can stably and efficiently operate in the frequency range from 20 kHz up to 50 kHz or so. It is proved that the ZCS-QRI is more suitable for several kilowatt induction-heating and melting power supplies and high-intensity ultrasonic generator, and switched-mode dc-dc converters. This simple high-frequency ZCS-QRI for induction-heating load model is analyzed introducing normalized resonant and load circuit parameters and control variable on the basis of computer-aided simulation. The load and frequency regulation characteristics of ZCS-QRI and ZCS operating range are illustrated with a normalized expression in addition to voltage and current peak values and stresses of the power semiconductor device. The practical computer-aided design procedure using the inverter characteristics in steady-state expressed in the normalized technique is demonstrated and discussed including a design example. The simulation results of ZCS-QRI are illustrated and compared with the experimental results in trial-produced breadboard.     

逆导型快速可控硅高频逆变CO2激光电源

采用逆导型快速可控硅ＲＣＡ Ｓ３９００ＭＦ研制的高频逆变ＣＯ２激光电源，逆变频率高达４０ｋＨｚ，具有效率高、成本低、启动快、稳流精度高等突出优点。     

无限深水域中浮体附加质量和阻尼系数的高频和低频渐近特性

本文讨论了无限深水域中浮体振荡频率当ω→0和ω→∞时附加质量和阻尼系数的渐近特性。给出了近似估算公式。     

适用于XRD的12kW高频高压电源系统研究

提出了一种适用于X射线衍射仪的大功率高频高压电源的设计方法;该电源系统采用高频技术,克服了传统工频电源设备笨重、体积大、效率低等缺陷;采用脉宽调制技术(PWM)对系统进行控制和保护,使信号稳定;采用功率因数校正(PFC)技术使系统的功率因数达到了0.9。     

基于新小波变换的图像边缘检测

介绍一种新的连续小波变换,其对于高频信号移动量小,对于低频信号移动量大,具有高分辨和自适应性的特点,数值积分的误差小,离散形式更具有灵活性,因此对于边缘检测其抗噪声能力强,能更好地检测出图像的边缘.     

高频雷达机动目标的时频图像处理方法研究

高频雷达机动目标检测实为复杂外部环境和强地海杂波下的非平稳弱信号处理,针对非平稳特征提出了基于时频分析和图像处理的方法.首先应用时频分析方法得到机动目标的时频谱,进而在时频谱上进行频率维的恒虚警检测并形成目标像、在时间维应用区域生长技术提取目标的速度时变脊线.时频图像处理方法经频率维和时间维的多级处理、在保证系统检测性能的情况下可精确提取机动目标的速度时变信息.实测数据的处理验证了其有效性.     

高频振捣对混凝土含气量和抗冻性的影响

采用4种水利水电工程常用的引气剂,配制水胶比为0.40,0.45,0.55(质量比)的二级配混凝土,检测高频振捣对混凝土含气量和抗冻性的影响.结果表明,水胶比相同时,含气量损失率基本上随着高频振捣时间的延长而增大;高频振捣时间相同时,含气量损失率随着水胶比的增大而增大;水胶比为0.40时,掺优质引气剂的混凝土其抗冻性对高频振捣并不敏感;水胶比为0.45时,高频振捣60,90 S后混凝土的抗冻性明显下降;水胶比增加至0.55时,混凝土的抗冻性随着高频振捣时间的延长迅速下降;引气剂的品质对高频振捣后混凝土的抗冻性能也有明显影响.根据试验结果,对混凝土的高频振捣时间提出了要求,可供施工参考.     

不锈钢与钛合金异径转接管的焊接

简要介绍了俄罗斯制造双金属异径转接管的两种焊接方法。举例说明了俄罗斯学者研究的不锈钢-钛合金转接管的结构及其真空扩散焊接工艺过程。通过大量的焊接试验与研究,制订了成熟的不锈钢与钛合金转接管扩散焊接工艺和相关的技术文件,扩大了真空扩散焊在异种金属连接中的应用。