Frequency response function of magnetic bearings using high-temperature superconductor

A high-temperature superconductor YBa₂Cu₃O_7-x with strong pinning force has allowed stable magnetic suspension with no control to be developed. Two types of superconducting magnetic bearings (SMB) using YBCO and permanent magnet were assembled. The two types are radial and axial. The dynamic stiffness of each SMB as it was cooled down under a magnetic field by liquid nitrogen was measured both radially and axially. As a result, it was found that the spring constants of these SMBs were almost as large as a practically desirable value; however, their damping coefficients were lower than the practical level. These findings are useful as one of the data bases for development of an optimum SMB design to support the weight of rotors in an axial direction.     

流体在环形狭缝中流动时园柱体的微振动

本文讨论了在两个园柱体的环形狭缝中不可压缩流体的流动．在一定的假设下，运用流体力学方程和流体对柱体的作用方程，导出了附加质量和转动惯量、振动频率和衰减系数．并对文（１）中的某些结果进行了必要的修正．     

Series resonant ZCS‐PFM DC‐DC power converter with high‐frequency high‐voltage transformer link for high‐power magnetron drive

This paper presents a single lossless inductive snubber‐assisted ZCS‐PFM series resonant DC‐DC power converter with a high‐frequency high‐voltage transformer link for industrial‐use high‐power magnetron drive. The current flowing through the active power switches rises gradually at a turned‐on transient state with the aid of a single lossless snubber inductor, and ZCS turn‐on commutation based on overlapping current can be achieved via the wide range pulse frequency modulation control scheme. The high‐frequency high‐voltage transformer primary side resonant current always becomes continuous operation mode, by electromagnetic loose coupling design of the high‐frequency high‐voltage transformer and the magnetizing inductance of the high‐frequency high‐voltage transformer. As a result, this high‐voltage power converter circuit for the magnetron can achieve a complete zero current soft switching under the condition of broad width gate voltage signals. Furthermore, this high‐voltage DC‐DC power converter circuit can regulate the output power from zero to full over audible frequency range via the two resonant frequency circuit design. Its operating performances are evaluated and discussed on the basis of the power loss analysis simulation and the experimental results from a practical point of view. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(3): 79–87, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20126     

智能同步广播激励器及其标频

使用智能同步广播激励器,并采用CCTV传输的1MHz标频信号,就有可能实现自适应相位跟踪同步广播。这将大大节省中波段的频率资源。     

用瞬态频率波动法诊断齿轮故障

利用瞬态频率波动法实现频率调制信号的解调，提取齿轮的局部裂纹信息，并通过黄河ＴＮ２５２型汽车变速器疲劳试验的信号分析来验证。     

裂纹梁动态响应有限元分析中的线弹簧模型

本文提出了一种以线弹簧模型为基础来分析裂纹梁动态响应的新数值方法．应用能量原理和断裂力学理论首次建立了线弹簧模型的刚度矩阵，从而确立了一种能使二维裂纹问题转化为一维分析的梁的有限元模型．使用这个模型，研究了不同裂纹长度和裂纹位置对悬臂梁固有频率和振型的影响，并把计算所得到的数值结果与现有的实验数据作了比较．结果表明，当无量纲裂纹长度小于０．６时，两者吻合得非常好；反之，两者之间存在较大的误差．对这种误差产生的原因，本文也作了解释．     

水轮机调速器与电网负荷频率控制

在现代电力系统中，水轮机调速器已成为水轮机控制系统的控制核心。文中叙述了水轮机调速器与电网负荷频率控制之间的关系，分析了调速器在电网一次调频、二次调频中的作用、静态特性和动态特性;通过建模、仿真及现场试验，提出了机组并联于大电网工况下的调速器PID参数整定范围和应有的机组功率控制模式。     

On stability of second-order quasi-polynomials with a single delay

In this note the stability of a second-order quasi-polynomial with a single delay is studied. Although there is a vast literature on this problem, most available solutions are limited to some particular cases. Moreover, some published results on this subject appear to contain imprecise, or even wrong, conditions. The purpose of this note is to show that by accurate application of known theories, a complete explicit characterization of stability regions can be derived in a most general case. As a byproduct of the proposed analysis, we show that in the high-order case the quasi-polynomial is delay-independent unstable whenever its delay-free version has an odd number of unstable roots (or, equivalently, a negative static gain).     

声表面波脉冲编码调制振荡器

论述了一种直接式声表面波脉冲编码调制振荡器的工作原理及设计方法。实际制作了工作频率为３９４ＭＨｚ、调制频偏大于２００ｋＨｚ、调制信号码速率大于４００ｋｂｉｔ／ｓ、输出功率大于５０ｍＷ、温度稳定性优于±５０×１０－６（－２０°Ｃ～＋６０°Ｃ）的性能优良的声表面波脉冲编码调制振荡器     

LD泵浦的声光调Q腔内倍频激光器

研制成用ＬＤ泵浦的声光调Ｑ的Ｎｄ：ＹＶＯ４－ＫＴＰ腔内倍频激光器，得到了ＴＥＭ００模、频率高达１００ｋＨｚ的稳定的５３２ｕｍ绿激光脉冲系列输出，阈值泵浦功率为２７ｍＷ；在连续５７０ｍＷ的泵浦功率下，绿激光脉冲的峰值功率达１１００Ｗ，脉宽为４．６ｕｓ；输出功率稳定，在±５℃的工作温度变化下，输出功率变化小于±２％。此种器件可望得到广泛的应用。