单相电动机变频调速研究

单相异步电动机广泛应用于家用电器,是家用电器的主要驱动部件,必须掌握单相电动机的基本特点、启动方法以及实现变频调速的方法,特别是单相异步电动机变频调速的关键技术。     

传热强化方法

该文简要介绍了国内外常见的在单相流体与相变流体对流传热方面的强化方法及机理。     

光场的位相特性及光学放大器中位相扩散分析(英文)

利用Pegg定义的位相研究相干态及弱压缩真空态的位相特性．利用位相态分析光学放大器（或衰减器）的位相演化，并将位相几率分布的扩散与传统的Fokker－Planck结果进行比较。     

巧用设计途径法求算不可逆相变过程的状态函数增量

等温等压不可逆相变过程和非等温等压不可逆相变过程状态函数增量可以通过设计途径法求算 ,所设途径中包含有与已知相变焓相应的可逆相变过程 .在标准压力下 ,通过改变温度设计途径 ;在一定温度下 ,通过改变压力设计途径     

DPLL implementation in carrier acquisition and tracking for burst DS-CDMA receivers

This paper presents the architectures, algorithms, and implementation considerations of the digital phase locked loop (DPLL) used for burst-mode packet DS-CDMA receivers. As we know, carrier offset is a rather challenging problem in CDMA system. According to different applications, different DPLL forms should be adopted to correct different maximum carrier offset in CDMA systems. One classical DPLL and two novel DPLL forms are discussed in the paper. The acquisition range of carrier offset can be widened by using the two novel DPLL forms without any performance degradation such as longer acquisition time or larger variance of the phase error. The maximum acquisition range is 1/(4T), where T is the symbol period. The design can be implemented by FPGA directly.     

Simulink在单相桥式半控整流电路中的仿真研究

通过仿真软件Matlab/Simulink,建立单相桥式半控整流电路的动态仿真模型,验证模型的正确性,并证明了该模型具有直观、快捷、灵活等优点,从而为《电力电子变流技术》教学中,引入一个有效的教学辅助手段。     

多晶VO_2材料的绝缘-金属转变研究

对用粉末冶金(烧结)法制得的多晶VO_2材料进行了X-射线结构分析和R-T曲线的实验研究.结果表明,纯的VO_2多晶材料升温时在338K发生数量级约为10~3倍的绝缘-金属转变,掺杂Cr的VO_2样品转变温度向低温方向偏移。当样品中含有5％以上的V_2O_5或样品淬油时,其R-T曲线将变得平坦.     

Al-Mn二十面体准晶的相变研究

分析了Al原子和Mn原子在二十面体准晶中的排列,计算并推导出了在急冷制备过程中,温度变化范围大约在1290.9℃,而熔炉的温度必须达到1810.9℃才能保证二十面体结构的生成,而且要控制温度变化速率,以减少Al晶体生成.而这种二十面体结构是亚稳定的,它在任何温度下存放一定时间都会发生相变.     

同步电动机晶闸管励磁系统扰动分析

应用自动控制原理对同步电动机晶闸管励磁系统进行扰动后的动态分析,提出了相应的性能指标。着重说明了各项性能指标满足系统运行的关键是反馈信号的采集、调试和锁定。     

Estimation of Shallow S-Wave Velocity Structure of Two Practical Sites from Microtremors Array Observation in Tangshan Area

Microtremors array observation for estimating S-wave velocity structure from phase velocities of Rayleigh and Love wave on two practical sites in Tangshan area by a China-US joint group are researched.The phase velocities of Rayleigh wave are estimated from vertical component records and those of Love wave are estimated from three-component records of microtremors array using modified spatial auto-correlation method.Haskell matrix method is used in calculating Rayleigh and Love wave phase velocities,and the shallow S-wave velocity structure of two practical sites are estimated by means of a hybrid approach of Genetic Algorithm and Simplex.The results are compared with the PS logging data of the two sites,showing it is feasible to estimate the shallow S-wave velocity structure of practical site from the observation of microtremor array.