新型模入通道保护模块在阀冷系统中的应用

针对目前换流阀冷却控制系统中,西门子模拟量输入通道易损坏的现状,介绍了一种新型的模拟量输入通道保护模块。该模块能有效避免高压直流输电工程中换流阀冷却系统模拟量输入通道易损坏的问题,提高了整个换流阀水冷控制系统模拟量采样的可靠性。     

电动汽车电机驱动系统效率优化控制

针对电动汽车专用PMSM控制系统的动态损耗问题,提出了一种改进的效率优化策略。分析了PMSM损耗模型,推导出系统损耗和定子磁链的关系,得到最优磁链与定子电阻相关。基于小波神经网络的动态定子电阻补偿方法,进而解决了由于最优磁链受动态定子电阻影响使得最优磁链难以准确计算的问题,以使电机驱动系统效率最佳。利用Matlab/Simulink仿真软件建立了系统模型,仿真结果证明,该策略能有效提高电动汽车驱动系统的效率。     

Interference Mitigation and Joint Decoding for Uplink LDPC-Coded Relay Cooperation

This paper proposes an efficient inter- ference mitigation and joint decoding scheme for uplink LDPC-coded relay cooperation over a Rayleigh fading channel, where a concatenation of Minimum-mean-squared error linear detectors （MMSE） and BP-based joint itera- tire decoding based on the introduced treble-layer Tanner graph are effectively designed to filter and decode the cor- rupted received sequence at a base station. It is demon- strated by theoretical analysis and numerical simulations that the proposed design can well combine the gains from coding and diversity, which consequently leads to a sig- nificant performance improvement over the conventional cooperation system under the same conditions.     

Second‐Order Statistics of System with Microdiversity and Macrodiversity Reception in Gamma‐Shadowed Rician Fading Channels

In this letter, a wireless communication system with microdiversity and macrodiversity reception in gamma‐shadowed Rician fading channels is considered. Exact and rapidly converging infinite‐series expressions for the average level crossing rate and average fade duration at the output of the system are provided. Numerical results are presented graphically to illustrate the proposed mathematical analysis and to examine the effects of the system's parameters on the quantities considered.     

Coexisting oblate and strongly triaxial structures in <Superscript>191</Superscript>Pt

Excited states in ¹⁹¹Pt have been populated using the reaction ¹⁸⁶W + ¹¹B at 85MeV beam energy. Gamma-ray coincidences were measured using the EUROGAM-II spectrometer array. The level scheme has been extended considerably. Evidence for favoured structures of highly triaxial shape with -90^° coexisting with oblate structures has been obtained by comparison with total Routhian surface and cranked shell model calculations. The presence of proton excitations in both positive- and negative-parity states has been confirmed.     

Phonetogram Changes for Trained Singers Over a Nine-Month Period of Vocal Training

Professional vocalists encounter demands requiring voluntary control of phonation, while utilizing a considerable range of frequency and intensity. These quantifiable acoustic events can be measured and represented in a phonetogram. Previous research has compared the phonetograms of trained and untrained voices and found significant differences between these groups. This study was designed to assess the effects of vocal training for singers over a period of nine months. Phonetogram contour changes were examined, with the primary focus on expansion of frequency range and/or intensity control. Twenty-one first-year, master's level, vocal music students, who were engaged in an intensive vocal performance curriculum, participated in this study. Following nine months of vocal training, significant differences were revealed in the subjects' mean frequency range and minimum vocal intensity across frequency levels. There was no significant difference for the mean maximum vocal intensity across frequency levels following vocal training.     

一种双极性三元数字信号发生器的设计

双极性三元数字信号发生器应用于某通信系统中,它采用5开关H桥电路结构,通过5个开关的有序导通实现将信号传输中的普通串行数字信号转换成双极性三元数字信号的功能。采用双极性三元数字信号作为调制信号,大大提高了某通信系统的抗干扰能力,确保该通讯系统在特殊情况下的正常使用。减小双极性三元数字信号的上升沿和下降沿时间,有利于提高通信系统的通信质量。文章详细介绍了该电路的设计方法,同时对其主要性能参数——输出码的高、低电平,上升与下降时间的实现方法进行了阐述。并简述了其混合集成产品的技术性能和使用情况。     

中间电平对CMOS数字电路的影响

很多情况都可以导致CMOS数字集成电路产生大的电源电流,但以CMOS的输入处于Vilmax与Vihmin之间的转折区而产生的大电流最为常见;而且其影响很重要,甚至会导致闩锁效应而对电路造成损坏。转折区的危险电平由管脚浮空、误操作、输入脉冲的上下沿和双向I／O这几种状态所产生。对每一种状态的影响及其原因进行了详细的分析,给出了解决的方法。对电路设计、试验、测试和分析具有一定的参考价值。     

Blind channel estimation for single‐input multiple‐output OFDM systems: zero padding based or cyclic prefix based?

Orthogonal frequency division multiplexing (OFDM) transmission equipped with multiple receive antennas constitutes a single‐input multiple‐output (SIMO) OFDM system. SIMO‐OFDM systems have been widely used in wireless communications. Compared to those approaches using training sequences, blind channel estimation methods for SIMO‐OFDM systems have the advantage of saving bandwidth and improving energy efficiency and system throughput. As far as blind channel identification is concerned, it is known that zero padding (ZP)‐based single‐input single‐output (SISO)‐OFDM systems have desirable features compared to conventional cyclic prefix (CP)‐based SISO‐OFDM systems. However, it is yet unknown whether ZP‐ or CP‐based SIMO‐OFDM systems are favourable for blind channel estimation. To investigate this problem, we first propose a short‐data effective method for blind channel estimation for ZP‐based SIMO‐OFDM systems. Then we analyse a number of issues surrounding blind channel estimation for ZP‐ and CP‐based SIMO‐OFDM systems. The issues brought up in the paper have not been discussed in the existing research. The significance of our investigation is that it provides a deep insight into blind channel estimation for ZP‐ and CP‐based SIMO‐OFDM systems. Copyright © 2011 John Wiley & Sons, Ltd.     

传声器阵列声压级在线校准*

在户外环境中对某一目标噪声源进行声压级测量时,由于单个传声器不能在多声源干扰情况下有效监测目标信号,为了有效抑制非目标信号的干扰,通常利用传声器阵列进行波束形成从而对目标信号进行增强。MEMS传声器阵列由于体积小,价格低等优点而得到广泛使用,为了解决在户外进行噪声监测时,MEMS然而MEMS传声器阵列器件的工艺误差和灵敏度退化问题会导致波束形成滤波器的性能下降存在由器件工艺误差和老化所导致的声压级测量不准确问题,从而影响声压级的测量结果。为了解决这一问题,本文介绍了一种通过比较补偿参考传声器与传声器阵列之间的测量声压级之偏差进行从而实时在线校准的方法。该方法利用TDOA多声源定位方法在时频点上对实时采集的信号对所采集的信号在时频点上挑选有效目标信号进行有效挑选,并利用参考传声器的标准频响特性去修正阵列的声压级测量误差值。为了验证方法的可行性,本文通过实验比较了不同环境噪声干扰下的测量声压级差与无干扰条件下的测量声压级差的一致性,结果证明该校准方法在具有较好高的精确性和鲁棒性,并且可推广于任意一种阵型的传声器阵列声源定位装置噪声监测装置。