P18-T200台式再流焊机研制成功

Ｐ１８—Ｔ２００台式再流焊机研制成功郝应征电子工业部第二研究所在广泛吸取国外再流焊机最新技术的基础上新近推出了新一代全新结构的红外再流焊机———Ｐ１８—Ｔ２００台式再流焊机。Ｐ１８—Ｔ２００台式再流焊机可焊接单面、双面各种密度的表面组装组件（ＳＭＡ）...     

再流区工艺参数对焊接可靠性的影响

影响表面组装焊接可靠性的因素很多，从钎焊机理入手，经过金相分析就再流区工艺参数对焊点微观结构的影响进行了研究，并结合焊点拉脱试验提出了再流区工艺控制的原则。     

P18—L25A型红外再流焊机设计与研制

本文主要介绍了Ｐ１８－Ｌ２５Ａ红外再流焊机适用技术范围，主要结构形式的设计，主要设计指标，该机工作原理及关键技术的设计与研制。     

再流焊接的一般要求及温度曲线测试方法

介绍了再流焊机的一般技术要求,并给出了典型焊接温度曲线以及温度曲线上主要控制点的工艺参数。     

电子组装无铅化过渡的问题及对策

4焊接设备的无铅化 面对无铅焊料的高熔点、低润湿,设备生产厂商应该对其主要焊接设备,即波峰焊机和再流焊机的结构和性能进行新的设计和改进,满足无铅化焊接的要求。     

P18—J200型红外再流焊机及其焊接工艺

主要介绍Ｂ１８－Ｊ２００型红外再流焊机的适用技术范围、主要结构、主要功能和技术指标、工作原理、关键技术的设计及其焊接工艺。     

P18一J200型红外再流焊机及其焊接工艺

主要介绍Ｐ１８一Ｊ２００型红外再流焊机的运用技术范围、主要结构、主要功能和技术指标、工作原理、关键技术的设计及其焊接工艺。     

霍尔传感器在高频逆变焊机中的应用

介绍了霍尔传感器的基本原理及其在高频逆变焊机中的应用.给出了采用霍尔传感器对焊机输出电压、电流以及直流母线电流进行精确测量,以解决焊机输出过流和逆变桥贯穿短路的保护问题,从而提高焊机可靠性的应用方案.     

泰克无铅波峰焊及液晶彩电、机顶盒生产线在推广应用中发展

常州市武进泰克电子设备有限公司从1992年成立以来，始终以“质量为本、科技先行”为企业方针，高起点研制无铅波峰焊、再流焊系列及物流输送生产线，为了适合国际环保的要求，开发生产了无铅波峰焊机、回流焊机。得到了苏州胜利科技、中国新科电子集团公司、中国飞利浦公司、上海竹井、常州星球、上海贝尔、南京厦普、十四所、四十九所等多家知名厂商的肯定，特别是无铅波峰焊接机已得到日本松下、飞利浦等设备专家，针对性能指标进行鉴定，取得了合格，并取得了专用认定证书。全方位性能指标已达到国内先进水平，得到了上百家独资、合资、国资企业的肯定，从而更加适应国际环保要求。     

SMT手工贴装技术工艺及其应用

以丝印机、贴片机、再流焊炉、波峰焊机为主体的大机器生产ＳＭＴ产品制造中无疑占据着主导的地位,然而配套手工贴装设备,开发手工贴装工艺对完成小批量产品生产、返修以及实验室试验板生产无颖有着实际价值。     

EHV transmission in the U.S.S.R. power grid

In 1965, 507 billion kWh of electricity was produced in the Soviet Union, and the total generating capacity of its power stations reached 114 000 MW. The total length of transmission lines, with voltages of 35 kV and higher, ran to 312 000 km. The capacity of the European power interconnections of the U.S.S.R. exceeded 68 000 MW in March 1966. The control of the power industry is centralized under the Ministry of Power and Electrificiation of the U.S.S.R. Ninety-four percent of its electric energy is generated at power stations that are part of interconnected systems. Thermal stations predominate; their generating capacity accounts for 77 percent of the total installed generation. Hydroelectric plants represent 22 percent of the total capacity and 18 percent of the total output. About one percent of the total power production is from nuclear plants. Thirty-six percent of the thermal plants are equipped to transmit heat energy as well as electric power.     

大视场宽谱段星敏感器光学系统设计

星敏感器是一种姿态测量系统,用于测量飞行器的实时姿态。该系统是一种基于CCD 探测器的适用于星敏感器的光学系统。通过相关参数的计算,利用ZEMAX 平台实现了具有良好成像质量的光学系统结构设计。该系统焦距为50 mm,F 数为1.8,具有较大的视场角:2=23,光谱范围较宽:500~850 nm,中心波长为680 nm。捕获三颗导航星的概率达100%。满足星敏感器对弥散斑、能量集中度和畸变等特殊要求。倍率色差得到了很好的校正,仅为0.087 m。系统仅使用6 片球面透镜,结构简单紧凑,易于加工制造。     

Calculations of systems unreliability by algebraic manipulation of failure event

Computations of reliability of a given system is an important field of research in reliability engineering. There are many techniques available in the literature. Some of these are based on Boolean algebra's relations. In these papers unions of events have been reduced to give the reliability of a system. Reduction of union of events involve a lot of work and give rise to a large number of terms.In this paper we have adopted a different approach. We first set up some simple algebraic lemmas on intersections and give their proofs. Next we represent the system failure event as the intersection of paths failure events. By applying our lemmas on this intersection of events step by step we are able to expand the system failure event in the form of unions of mutually exclusive events. Simple substitution of probabilities of success or failure, as the case may be, of the events involved in the union of expanded form gives the unreliability of the system.The algorithm is explained by an example.     

Statistical characteristics of chaoticity and incomplete chaoticity of irregular oscillations generated by a strongly nonlinear autonomous system with two degrees of freedom

The notion of the interval of nonergodicity as one of the statistical characteristics for time realizations of an irregular process is introduced. A method for determination of this factor based from the analysis of autocorrelation functions of truncated realizations is developed. The chaoticity of irregular oscillations in a strongly nonlinear autonomous system with two degrees of freedom is proved using the criterion of decomposition of time correlations. The statistical indication of the existence of incomplete chaoticity of oscillations in the case of incomplete decomposition of correlations is formulated. Conditions of weak distortions of the energy spectrum for truncated realizations are determined. Probability distribution functions for the characteristics of an irregular time process in the studied system are considered.     

基于Simulink的PD雷达地杂波的仿真

计算机技术的发展使雷达系统仿真得到广泛应用。环境杂波的仿真在雷达仿真中占有极其重要地位。介绍了PD（脉冲多普勒）雷达地杂波的频谱分布特性,讨论了网格叠加法计算地杂波的原理,给出了杂波散射系数模型,分析了杂波幅度起伏特性和频谱特性,给出了单元杂波信号的叠加方法。最后,建立了视频地杂波仿真模型,并绘出了三维功率谱。     

缝隙阵列天线DOA估计的互耦影响与修正

互耦的存在严重影响了DOA估计的精度，文中研究了存在互耦情况下的DOA估计问题，重点讨论了阵列单元互耦效应的有效计算和对MUSIC算法的修正问题；以缝隙阵列天线为例，通过对无限阵散射参量的修正得到有限阵的散射矩阵和阻抗矩阵，进而通过阻抗矩阵估计互耦的影响，并对MUSIC算法进行修正，最后给出了仿真结果。     

Excitation of luminescence in porous silicon with adsorbed ozone molecules

A new effect of the excitation of luminescence in porous silicon during adsorption of ozone from the gaseous phase was investigated. The signals of ozone-induced luminescence and photoluminescence decay with time of ozone exposure in a strictly correlated way; simultaneously, an oxide-phase growth is observed in porous silicon. A linear relationship was found between the luminescence intensity and the amount of oxide phase formed in the presence of ozone. Correlated shifts in the spectra of ozone-induced luminescence and photoluminescence are observed if the porosity of silicon varies. A mechanism for this effect is proposed. According to this mechanism, in the case of the dissociative adsorption of ozone, the exothermic reaction of oxidation of backbonds of a silicon atom takes place on the surface of nanocrystallites. Energy released is spent for the excitation of electron spectrum of silicon crystallites. The radiative relaxation in the case of ozone excitation proceeds similarly to that of the photon excitation of luminescence in porous silicon.     

Optimization and Performance Analysis of Zero Forcing Decision Feedback Detector for MIMO Block-Fading Channels with Per-Antenna Power Control

In multiple-input multiple-output (MIMO) antenna systems, the zero forcing decision feedback detector (ZF-DFD) is used to recover transmit signals. In this paper, we propose a per-antenna power control (PAPC) scheme based on ZF-DFD for MIMO block-fading channels. The optimal power controlled ZF-DFD can minimize the block error rate (BLER) and maximize the lower bound of the channel’s free distance at high signal-to-noise ratio (SNR) region subject to a power constraint. Additionally, the optimal power controlled ZF-DFD can achieve this BLER performance without any ordering operation at the receiver. The performance analysis among the conventional ZF-DFD without feedback, the optimal power controlled ZF-DFD with power feedback, and the ZF-DFD with full channel state information feedback shows that the optimal ZF-DFD achieves a tradeoff between performance and feedback overhead. We compare the bit error rate (BER) and BLER performance of the optimal ZF-DFD with other detectors without power feedback by simulation. In simulations, the execution times required by these detectors are also reported to compare their complexity. It comes straight that the optimal power controlled ZF-DFD proposed in this paper can achieve good performance with small feedback overhead and have low complexity. Kun Zhao was born in Hefei, China, on 9 October 1979. He received his BS and MS degrees from University of Science and Technology of China (USTC), in 2001 and 2003, all in Electrical Engineering. He is now a Ph.D. candidate at USTC.His research interests are in the area of spread spectrum and CDMA communications, radio resource management in mobile communications, space-time signal processing and multiuser MIMO. Ling Qiu received her BS degree from Southeast University, P. R. China, in 1990. She also received MS and Ph.D. degrees from University of Science and Technology of China (USTC), in 1997 and 1999, all in Electrical Engineering.From 1990 to 1994, she was an engineer in the Institute of Nanjing Electronic Technology. In 1999, she joined the Department of Electronic and Engineering and Information Science, USTC as a lecturer. Since 2002, she has been an Associate Professor. She is a coauthor of two books and over 40 conference/journal papers. Her research interests are in the area of wireless communications, spread spectrum and CDMA communications, wireless access networks and protocols, radio resource management in mobile communications, space-time signal processing and multiuser MIMO. Jinkang Zhu is a professor of Department of Electronic Engineering & Information Science of University of Science and Technology of China (USTC). Now he is director of Personal Communication Network and Spread Spectrum Lab. of USTC, Chair of the Academic Committee of School of Information Science & Technology of USTC, Vice-Chiar of the Academic Committee of USTC.He was Permanent V-President of School of Information Science & Technology of USTC, Chairman of PCN Experts Group of Communication Project of National R & D on High-Technology Programme of China, Member of Information Technology Expert Group of the Chinese Academy of Sciences, Member (Representation of China Mainland) of Technical Forum on Wireless Communications of Asia Pacific Region, Member of Technical Advisory Committee of IEEE VTC'99 Fall, Member of Technical Program Committee of IEEE VTC'2000, Member of Technical Program Committee of SCI'2001.His research area is Wireless and Mobile Communications, CDMA and Spread Spectrum Communications, Signal Process of Communications, and Wireless Networks. He got two awards of Ministry of Science & Technology of China, three awards of Chinese Academy of Science. He published five books and 100 papers, where synchronous CDMA method proposed is used in TD-SCDMA Standard of 3G as basic technology.     

Visx20/20B准分子激光治疗系统激光腔状态与治疗效果的关系分析

目的 分析Visx20/20B准分子激光系统激光腔状态与治疗效果的关系，探讨最佳激光腔状态，同时提出改进激光腔状态的方法，以获取手术最佳疗效。方法观察手术过程中激光腔的各种状态和术后病人的治疗效果，将激光腔各种状态与病人疗效进行对比，做出定性分析。在以后的工作中，随时根据激光腔状态来调整我们的治疗方案，从而力争达到病人的最佳治疗效果。结果 激光腔状态包括气体、激光腔本身清洁度、CV值、前后镜等几部分，对病人疗效影响较大。结论 准分子激光手术中，Visx20/20B型准分子激光系统激光腔各部分的状态与手术疗效有很大关系，必须随时关注激光腔状态，以保证手术最佳疗效。     

Further Notes and Anecdotes on Spread-Spectrum Origins

This sequel to R. A. Scholtz's monograph of May 1982, in this TRANSACTIONS, adds to the early history of spread-spectrum communications from circa 1900 until about 15 years ago. Relevant to the origins of this field of radio signaling, the following are included in a number of items of quite recent appreciation: the 1930 invention of secret communications featuring spectrum despreading via a locally generated reference at the receiver; a stratagem of electronic warfare during the Battle of the Bulge, in World War II, that cleverly made use of Armstrong's frequency modulation; and the role of a star actress from the motion picture field, in origination of frequency hopping for antijamming radio control of missiles. Some further, and first-hand, reminiscences are given of germinal M.I.T. spread-spectrum contributions, and of similar noise-correlation radar art. Extensive footnotes cast sidelights on the beginnings of information theory, and also, among other things, on the keeping of military high-technology secrets over decades, even between securitycleared family members. A variety of references is appended.