四种桥函数的数学表达式

本文给出了四种桥函数的数学表达式及其证明，指出沃尔什函数系、方块脉冲函数系、哈尔函数系、赫尔函数系、特尔函数系都是桥函数系的一部分。     

新赏

众所周知．德系相机一直走高端路线，无论是相机性能还是制造工艺都堪称经典。与德系相机相对的日系相机，相对来说则较为大众一些，一般消费者都能接受。此次，德系哈苏与日系索尼合作，表现了德系相机预平民化的一种趋势。     

高职高专学校系部档案管理的现状和对策研究

系部档案是学校档案的重要组成部分，是学校档案的基本单元，它真实地记录了系部教学、科研和社会服务活动的过程和成果，记载着前一阶段教学与科研人员的思想、方法和经验，反映系部发展进程与规模，是高校档案管理信息的重要来源。我们有必要对高职高专学校系部档案管理工作的现状进行研究，并在此基础上尝试着对系部档案管理理念、档案管理制度、档案管理方法和档案管理载体等方面进行对策研究。     

1.8米望远镜钠信标自适应光学系统的高对比度成像性能研究

系外行星的直接成像是当今国际天文学研究的热点，而对潜在的系外行星候选体进行大面积普查将是未来十年天文学的迫切需要。国际上中小型2 m级望远镜上部署的ROBO-AO瑞利激光信标自适应光学系统（AO），可以灵敏而快速地删察系外行星候选体。但瑞利信标高度引起的聚焦非等晕效应是限制其行星探测能力的重要因素。基于1.8 m望远镜61单元钠信标自适应光学系统优化构建系外行星高对比度成像系统，它将在近红外波长范围内提供系外行星的高对比度成像。通过对钠信标AO高对比度成像过程的仿真，发现在理论上，钠信标AO系统的系外行星高对比度成像性能优于ROBO-AO，即在2 h曝光时间内，可以实现与母恒星光通量比为4×10?7的行星的直接成像，而相同环境下，ROBO-AO系外行星直接成像能力为1×10?6，其中行星与恒星的角间距为1'。     

钛酸铅系薄膜的热释电性能及其应用

叙述了钛酸铅系薄膜的热释电原理，介绍了国际上近几年钛酸铅系薄膜材料、制备工艺及热释电性能，并与块状陶瓷材料进行了比较，分析表明钛酸铅系薄膜具有优良的热释电性能及可观的应用前景。     

多层介质光学膜系的二阶膜厚误差因子分析

本文推导了多层介质光膜系的二阶膜相对误差因子表达式，以λ０／４高反射多层介质膜系为例对一阶和二阶误差因子进行了数值分析，比较了两者在不同波长区域对膜系光谱性能的影响，发现不应仅考虑一阶误差因子，而应同时考虑一阶和二阶误差因子的作用，才能较好地描述膜厚误差对膜系光谱性能的影响。     

三网融合的厂商机遇

三网融合的启动不仅推动广电系开始大规模网络改造，更使提前感受“山雨欲来风满楼”压力的电信系加快行动，抢夺竞争先机。     

贵州哲觉陆相二叠系一三叠系界线粘土岩的研究

黔西地区是一个海相、海陆交互相和陆相二叠系一三叠系剖面发育良好的地区，是研究海、陆相二叠系一三叠系界线及对比的理想地区。近几年来不少学者在该地区开展了陆相二叠系一三叠系界线综合地层学研究，在界线附近发现了多层粘土岩，并可与华南海相二叠系一三叠系界线粘土岩进行对     

卓京系也终于倒掉

继“德隆系”、“托普系”、“鸿仪系”、“飞天系”的丧生之后，近日，玩转传媒与通信产业的“卓京系”亦趋于崩溃。卓京系创始人、著名资本玩家覃辉的资本游戏随之中止。资本的脆弱与无常，在此文中一览无余     

性格宽厚的银衫绅士——Cambridge Audio（剑桥）Azur 640C/640A V2．0CD播放机／合并式放大器

系出英国名门 说起英国系的音响器材，发烧友们都会露出会心的一笑。没错，英国系的器材大多工艺质朴实在，用料简单，但校音却的确有一手，基本很难出现恶声，有着独特的音乐味，再加上大多数的品牌都继承了英系产品价格较为平易的特征，所以受到国内发烧友们青睐就一点不奇怪了。     

我校"信号与系统"课程的改革与建设

信号与系统是电气信息类专业重要的技术基础课程。近年来,课程组对“信号与系统”课程进行了全面的改革与建设,造就了一支高素质的教师队伍,提出了具有鲜明时代特征的教育教学思想,重构了课程体系,更新了教学内容,出版了高水平教材,改革了教学方法与手段,取得了丰硕成果,2003年被评为国家精品课程。     

Transfer Functions of Amplitude and Phase Fluctuations and Additive Noise in Varactor Doublers

In order to evaluate the spectral purity degradation produced by varactor doublers, the transfer properties of amplitude and phase fluctuations have been determined with reference to a theoretical analysis developed in a previous work. Quasi-stationary conditions have been assumed and the input and output tuning circuits have been approximated with a linear relation between frequency and reactance. The effect of the bias circuit has been taken into account both for fixed-bias and self-bias conditions. Then the additive-noise contribution of the doubler circuit elements have been obtained. Numerical examples and curves are given for all the evaluated quantities.     

Studies of the micro- and nanostructure of polycrystalline CdTe and CuInSe2 using atomic force and scanning tunneling microscopy

Atomic force microscopy (AFM) and scanning tunneling microscopy (STM) have been used to study the micro- and nanostructure of CdTe and CuInSe₂ thin films used for photovoltaic cells. Topographic images are comparable with those reported previously using conventional scanning electron microscopy (SEM)—to the limit of spatial resolution of the SEM technique. For higher magnifications, nanoscale structures and features have been observed for the first time with AFM and STM, and these observations have implications for the suitability and preparation of these semiconductors for high-efficiency solar cell realization.     

Fabrication and Electrical and Mechanical Properties of Carbon Nanotube Interconnections

Individual carbon nanotubes (CNTs) have been cut, manipulated, and soldered via electron‐beam‐induced deposition of amorphous carbon (a‐C) and using a scanning tunneling microscope inside a transmission electron microscope. All CNT structures, including simple tube–tube connections, crossed junctions, T‐junctions, zigzag structures, and even nanotube networks, have been successfully constructed with a high degree of control, and their electrical and mechanical properties have been measured in situ inside the transmission electron microscope. It is found that multiple CNTs may be readily soldered together with moderate junction resistance and excellent mechanical resilience and strength, and the junction resistance may be further reduced by current‐induced graphitization of the deposited a‐C on the junction.     

本体与AORBCO模型

讨论了哲学界和计算机科学界关于本体概念的异同，分析了本体研究中所存在的问题和原因，提出了本体的形式化描述模型AORBCO，论证了用AORBCO模型可把哲学和计算机科学界关于本体的概念很好地统一起来，使表达形式与表达内容有机结合，很好地解决了本体研究中所存在的一致性问题、完备性问题和结构性问题等。     

Operation and analysis of planar cryotrons and simple cryotron circuits

Simple cryogenic loops containing two drive cryotrons and a number of sensing cryotrons have been constructed. It is possible with such loops to study both the operating characteristics of the individual cryotrons as well as the static and dynamic switching characteristics of the loop. Some of the characteristics of the individual cryotrons and the reproducibility of cryotrons with these characteristics are discussed. The speed with which current can be transferred from one branch of the loop to another has been both measured experimentally and calculated theoretically from the dimensions and various measured parameters of the loop and its cryotrons. There is found to be good agreement between theory and experiment. The loops have been run dynamically in an effort to detect thermal effects associated with heat dissipation in the resistive cryotron elements. The upper limit to the dynamic operation is currently set by the viewing equipment and, to date, no adverse heating effects have been observed.     

小型化宽带蝶形微带天线的设计与仿真

传统形式上的微带贴片天线虽具有体积小、重量轻的特点,但窄带特性却制约了其工程应用的范围。在对曲边蝶形天线结构和特性理论分析的基础上,使用Ansoft公司的HFSS三维电磁场软件对其进行建模仿真,最终优化得出了在0.8～3.0GHz宽频带范围内都具有良好的辐射特性,且在工作带宽内VSWR<1.5的曲边蝶形微带天线,在小型化的基础上实现了微带天线的宽频带特性。     

Performance and reliability of an improved high-temperature GaAs Schottky junction and native-oxide passivation

We have developed a reliable, high-performance, batch-processed, GaAs tantalum Schottky diode (with a gold overlayer) and native-oxide passivated junction¹in a quasi-planar configuration, Varactors and mixers have been fabricated with near-ideal characteristics and state-of-the-art performance. Typically, they exhibit, at 0 V, a junction capacitance near 0.1 pF and a cutoff frequency in excess of 700 GHz when measured at 55 GHz. In a paramp application pumped at 101 GHz, and a signal frequency of 35 GHz, we have obtained a noise figure of 3.5 dB, a gain of 17 dB, and a bandwidth of 600 MHz. When used as frequency doublers (50-100 GHz) and triplers (35-105 GHz), we have realized better than 25-percent efficiency. As mixers, atXband, we achieved a single sideband noise figure of 6 dB and the diodes are typically able to sustain short pulse energy (1.5 × 10^-9s) of up to 4.5 ergs with no performance degradation. Reliability tests results to date indicate a MTBF of better than 10⁸h at 100°C and greater than 10⁵h at 200°C. In a commercial application of paramps (3.7-4.2 GHz), these diodes have successfully completed 2.5 million operational varactor hours with no performance degradation.     

幅相误差对修正MUSIC算法测向性能的影响与分析

首先阐述了阵列信号处理中广泛采用的修正MUSIC算法原理，并推导了天线阵元幅相误差条件下的修正MUSIC算法，重点分析了阵元幅相误差对修正MUSIC算法测向性能的影响。最后以均匀线阵为例进行了仿真，计算机仿真结果表明，阵元幅相误差严重影响着修正MUSIC算法的测向性能，因此在应用修正MUSIC算法进行来渡方向估计的时候，必须考虑阵元幅相误差的影响。     

Lasers and Photodetectors in Europe

This paper reviews the European activities on fiber optic semiconductor devices for optical communication. Progress in the development of lasers, LED's, and photodetectors and also first attempts of monolithic integration are reported. Emphasis is put on materials and devices for the wavelength range of 1200-1600 nm and for high-speed transmission. Results of recent work are highlighted. So, for example, extremely high reliability and high optical output power of LED's and Fabry-Perot lasers have been achieved. MOCVD growth techniques are increasingly applied for device fabrication; for lasers, highly reproducible characteristics have been demonstrated. Development of dynamic singlemode lasers (DSM) is under progress with low threshold currents and good optical characteristics reported. First electrically tunable single-mode lasers and DSM lasers with parallel coupled cavities have been realized. Long wavelength p-i-n photodetectors have reached maturity. InGaAsP and CdHgTe avalanche photodiodes show excellent properties for high-speed long-haul transmission. First steps of monolithic integration of several optical and electrical functions have been made and specifically for p-i-n-FET combinations good results have been achieved. The plans of European PTT authorities to implement fiber optics in trunk lines and subscriber loops will further push the activities on optoelectronic device technology.