UC3875在超声电源功率控制系统中的应用

根据超声波发生器的功率控制系统原理 ,阐述了移相控制策略对超声波发生器输出电压波形的影响 ,介绍了移相控制专用芯片UC3875的电路结构和使用设计方法。     

光折变三维信息存储器

分析光折变三维存储器的机理,探讨了光折变三维存储器的编码方式、光折变材料的选择及存储技术,阐述了其产业化进程.     

最新MDAC中的安全特征

本文描述数据访问组件MDAC(Microsoft Data Access Components)的结构与编程接口,分析了MDAC缓冲区溢出安全漏洞的原因,最后阐述了最新MDAC2.8的安全特征.     

水溶性油墨用富马酸改性松香树脂的研制

介绍了一种水溶性富马酸改性松香树脂的制备方法 ,选取了较佳的工艺条件 ,本产品经国内几家油墨厂使用 ,结果表明适合水溶性油墨的应用要求     

标识化语言的发展及在电子物流中的应用

重点阐述了XML技术的发展和对EDI技术的有效补充与改进，并展望基于XML技术的电子商务物流数据交换技术的发展前景。     

Optimal diagonal precoder for multiantenna communication systems

In this paper, we examine a multiantenna single-user wireless communication system fitted with a QR-based successive cancellation receiver (QR receiver). Initially, our consideration is confined to uncoded binary phase shift keying (BPSK) signals transmitted through independent and identically distributed (IID) Rayleigh fading channels and to the design of an optimum precoder for the transmitter. For minimum feeding back of the channel state information (CSI) to the transmitter from the receiver, we stipulate the precoder to be in the form of a power loading square diagonal matrix. We proceed to develop the theory for the design of this diagonal matrix based on the minimization of the lower bound of the average bit error rate (BER) of transmission. The design obtained provides substantially lower error rates than most of other existing schemes under the same environment. The corresponding gain in signal-to-noise ratio (SNR) can be several decibels. To further improve the performance, we extend the design to include an optimal detection order of the received bits using an iterative approach. This iterative process proves to have fast convergence and results in a design providing significant SNR gain. We also propose a subchannel dropping scheme for cases in which SNR is low, and when the minimum BER precoder is equipped with this scheme, its average performance can be substantially superior to the Vertical Bell Laboratories Layered Space-Time (V-BLAST) detection. We extend our design of the optimum precoder to quadrature amplitude modulation (QAM) modulation scheme and similar performance gain has been observed.     

Photoluminescence and X-ray Diffraction of Distributed Bragg Reflector

Spectral and structural characteristics of distributed Bragg reflector (DBR) in vertical-cavity surface-emitting lasers were studied with photoluminescence and double- crystal X- ray diffraction measurement. The expected high quality epitaxial DBR structure was verified. In the X- ray double- crystal rocking curves of DBR the zeroth- order peak, the first and second order satellite peaks were measured. Splitting of diffraction peak appeared in the rocking curves was analyzed. The effects of introduced deep energy levels on the structural perfection and optical properties were discussed.     

“菜鸟“小议

近年来,"菜鸟"作为一个新兴词语在网络上广为流传,甚至波及到社会生活的方方面面.通过语素分析和近义比较,可以来考察此词的读音和意义.     

基于PSR模型的水电工程生态效应评价指标体系构想

从水电工程生态效应评价指标体系研究的意义出发,通过分析水电工程生态效应评价的内涵,确立了评价指标的选取原则,基于压力(Pressure)-状态(State)-响应(Response)概念模型,构建了以科学、实用和可操作为目标的评价指标体系的框架。