西班牙D.A.S.大师LX-218超低反射式低音炮系统

西班牙D.A.S.大师专业音响推出了D.A.S. LX-218超低反射式低音炮系统.此系统中,2只45,72 cm(18 in)长冲程扬声器单元使用了来自美国麻省理工学院电子工程师们最新的专利S.O.T.A.电子技术,保证了在巨大低音输出功率下,低频下潜好、失真小.     

CES报道之三:T.H.E.Show给我的四大惊奇

<正>按照以往的经验,我空下一天的时间准备看T.H.E. Show。没想到,今年的T.H.E.Show竟然没几个展房,整个Alexis Park空荡荡,没见几个人影。这是有史以来T. H.E.Show参展厂商最少的一次,我想这个本来搭CES顺风车的音响展也该寿终正寝了。原本支持T.H.E.Show的厂商哪里去了?我猜,一些参加CES移师威尼斯人旅馆,     

更安全、易管理、高性能英特尔智能商用客户端打造全新商用计算环境

权威市场调查机构Gartner调查报告显示,从2010年开始,企业应当关注的最新10大战略技术排名如下:1.云计算;2.高级分析;3.客户端计算;4.绿色IT;5.新式数据中心;6.社交计算;7.安全-行为监控;8.闪存;9.虚拟化;10.移动应用。事实上,如果企业IT管理者希望成功地进行IT应用升级,了解处理     

严正声明

<正>近来,有人冒用本刊名义在网上公然征稿,收取各种费用,更有甚者建立网站,在各大论坛发布信息。对此,本刊编辑部特作如下声明:1.本刊网址:www.telecominfo.com.cn2.本刊投稿邮箱:dxkb@sh163.net;dxkb@public8.sta.net.cn;webmaster@telecominfo.com.cn3.本刊联系电话:021-64030202;     

Analytical form of EM fields radiated by circular aperture antennas of various current distributions

~~Analytical form of EM fields radiated by circular aperture antennas of various current distributions[1] Schelkunoff S. A., Advanced Antenna Theory, John Wiley &Sons, 1952. [2] E|liott R.S., Antenna Theory and Design, Prentice-Hall, Engie-wood Cliffs, N J, 1981. [3] R.W.P. King and G.S. Smith, Antennas in Matter: fundamen-tals, Theory and Applications, MIT Press, Cambirdge, MA,1981. [4] W.L. Stutzman and G.A. Thiele, Antenna Theory and Desigrn,John Wiley & S…     

JVC四款真高清多格式液晶监视器

.JVC在CC8N2008期间隆重推介四款真高清多格式液晶监视器--DT-V241D.DT-V20L1D.DT-V17L2D,DT-V9L1D.这些全新的高清专业监视器.能够提供专业人士所需要的特性,功能.可操作性.兼容性和系统的灵活性;且不管各款监视器规格如何.所有的控制面板都处于同一水平上,易于操作.     

数字递变异变赝衬底上2.6μm In0.83Ga0.17As/InP光电探测器的性能改进

研究了In_(0. 83)Al_(0. 17)As/In_(0. 52)Al_(0. 48)As数字递变异变缓冲层结构(DGMB)的总周期数对2. 6μm延伸波长In_(0. 83)Ga_(0. 17)As光电二极管性能的影响.实验表明,在保持总缓冲层厚度不变的情况下,通过将在InP衬底上生长的In_(0. 83)Al_(0. 17)As/In_(0. 52)Al_(0. 48)As DGMB结构的总周期数从19增加到38,其上所生长的In_(0. 83)Ga_(0. 17) As/In_(0. 83)Al_(0. 17)As光电二极管材料层的晶体质量得到了显著改善.对于在总周期数为38的DGMB上外延的In_(0. 83)Ga_(0. 17)As光电二极管,观察到其应变弛豫度增加到99. 8%,表面粗糙度降低,光致发光强度和光响应度均增强,同时暗电流水平被显著抑制.这些结果表明,随着总周期数目的增加,DGMB可以更有效地抑制穿透位错的传递并降低残余缺陷密度.     

Call for Papers Journal of Electronic Science and Technology Special Section on Energy-Efficient Technologies

Guest Editors(Editorial Board of EET):Prof.Qi Huang Univ.of Electron.Sci.&Tech.of China huangqi@uestc.edu.cn Prof.Terrence Mak The Chinese Univ.of Hong Kong,stmak@cse.cuhk.edu.hk     

功耗决定未来

一年一度的Computex展会依旧热闹非凡.只是相比以往.今年的Computex更像一个通信展.WiMAX.3G.802.11n.Wireless USB及Bluetooth等最新产品纷纷登台,引人注目,就连一些新的移动终端设备.比如MID.都被深深烙印上通信的概念.     

外电场下氯甲烷的光谱和解离特性

为了研究外电场对氯甲烷分子光谱和解离特性的影响,采用密度泛函理论（density functional theory,DFT）B3LYP方法在6-311++G（d,p）基组水平上研究了不同外电场（-0.03 a.u.~0.03 a.u.）对氯甲烷分子结构以及解离特性的影响,包括键长、分子能隙、红外光谱以及解离势能面等. 计算结果表明,随着Z方向（C-Cl连线方向）外电场从-0.03 a.u.逐渐增加到0.03 a.u., C-Cl键的键长逐渐增大而C-H键的键长几乎不变, 分子能隙EG先增大后减小,当外加电场等于0.01 a.u.时达到峰值. C-Cl 伸缩（stretching, STR） 振动的频率是逐渐减小的, 而红外光谱（infrared,IR）振动强度是逐渐增加的. 通过进一步计算研究发现, 随着外电场（0~0.03 a.u.）继续增强, CH3Cl分子的势能曲线逐渐降低, 解离能逐渐减小. 当外电场大约是0.04 a.u.时解离能最小,发生解离. 因此,可以通过改变外电场来控制CH3Cl分子的降解.     

外差激光干涉测长非线性误差的消除

外差激光干涉仪能够通过光波细分达到亚纳米分辨率,因而在科学研究和精密机械制造中得到了广泛应用。然而,由于光学系统中不可避免的缺陷,导致被测信号中出现一个附加的相位误差,使测到的相位移和被测长度不呈线性关系,成为现有激光干涉仪难以逾越的精度极限。为此,通过光学相位补偿理论的研究得出一种消除激光干涉仪非线性误差的方法,它可以应用在大部分科学实验和工业制造中的纳米长度测量中,而且不论是一阶或二阶误差都可以通过这个方法被消除。     

Investigation of Properties of Motion of Superconductive Electrons in Superconductors by Nonlinear Quantum Mechanical Theory

The properties and rules of motion of superconductive electrons in steady and time-dependent non-equilibrium states of superconductors are studied by using the Ginzberg-Landau （GL） equations and nonlinear quantum theory. In the absence of external fields, the superconductive electrons move in the solitons with certain energy and velocity in a uniform system, The superconductive electron is still a soliton under action of an electromagnetic field, but its amplitude, phase and shape are changed. Thus we conclude that superconductivity is a result of motion of soliton of superconductive electrons. Since soliton has the feature of motion for retaining its energy and form, thus a permanent current occurs in superconductor. From these solutions of GL equations under action of an electromagnetic field, we gain the structure of vortex lines-magnetic flux lines observed experimentally in type-Ⅱ superconductors. In the time-dependent nonequilibrium states of superconductor, the motions of superconductive electrons exhibit still the soliton features, but the shape and amplitude have changed. In an invariant electric-field, it moves in a constant acceleration. In the medium with dissipation, the superconductive electron behaves still like a soliton, although its form, amplitude, and velocity are altered. Thus we have to convince that the superconductive electron is essentially a soliton in both non-equilibrium and equilibrium superconductors.     

浅谈配电网中无功补偿的应用

功率的补偿。无功功率对供电系统和负荷的运行都是十分重要的,电力系统网络元件的阻抗主要是电感性的。因此,为了输送有功功率,就要求送电端和受电端的电压有一相位差,这在相当宽的范围内可以实现;而为了输送无功功率,则要求两端电压有一幅值差,这只能在很窄的范围内实现。本文从如下几个方面对配电网中无功补偿的应用进行阐述。     

红外目标探测距离的估算

红外热成像系统探测距离的估算,对于提高红外系统设计水平,降低成本,缩短研制和生产周期都有非常重要的作用.但是探测距离受很多因素,如目标特性,大气传输、热成像系统参数等的影响,这使得红外热成像系统探测距离的估算难度大大增加.传统的红外作用距离估算一般是将大气透过率视为常数的,这会带来很大的误差.本文考虑了大气气溶胶模式下大气透过率随环境的改变,给出了更为具体的红外目标探测距离的表达式.通过编制程序和查找相关数据,计算了热成像系统对点源和扩展源的探测距离.     

一种评估旋转式机械设备工况的方法

用数据采集系统采集旋转式机械设备旋转构件上所选测点的振动位移，并计算出该振动参数基本统计特性的数值，就可以应用本文提出的判断不等式对设备的工况进行初步评估。动力增益因子的引入使静态测量精度能用于对振动动态过程的分析。以集成电路制造专用设备硅片磨床为例，阐述了这种评估方法。     

Analysis of the essential factors for the adoption of mobile learning in higher education: A case study of students of the University of Technology

This paper analyzed the adoption of using mobile learning (m-learning) in higher education. Mobile Learning as a model of e-learning refers to the acquisition of knowledge, skills and attitudes by utilizing mobile technologies. With the increasing coverage of mobile networks, learning services can play the increasing and effective role in education at any time and place. Continuous access via mobile devices creates special facilities like sending and saving the learning content to learners etc, it is accompanied with continuous education. This paper, with a study of “what is the impact of the mobile phone usage in education?” provides approaches and theories of mobile learning in training. The paper aimed to evaluate the essential factors for the adoption and application of education information system that has been created by students. The survey was based on the history of technology adoption and covered students. Furthermore, a case study from students of K. N. Toosi University in Iran was presented to indicate the performance of this method in practice. The statistical society included 300 members from Information Technology students of Iran's K. N. Toosi University of Technology. The factors related to adoption of mobile learning in higher education was classified into seven main categories as: ease of use, trust, characters and personal qualities, context, perceived usefulness of using, behavioral intention, and culture of using a research model. From the results, mobile learning could be one of the promising educational technologies for development in educational environments and culture of using. The context of applications has a significant positive effect on the ease of use factor and usefulness and the ease of use has a positive effect on the usefulness factor. The trust factor has a positive and significant effect on the behavioral intention. The personal features and characters factor have a significant positive effect on the culture of using and the culture of using the application has a significant positive effect on the behavioral intention.     

黑体有效辐射面选取的讨论

黑体的有效辐射面是黑体检定工作中一个重要的概念,不同的检定装置有不同的黑体有效辐射面计算方法,但都存在着选取上的一些问题。由于检定装置入瞳的挡光,辐射面位置的选取有很大的淡确定性;黑体光阑因受辐射面选取的限制,检定时不能独立发挥作用。对于测量黑体亮度的光学零件平衡比对装置,可以使采样面和黑体有效辐射面合二为一,并提出了置于黑体不同位置上的可能性。     

虚拟人跑步运动的仿真

在计算机仿真中，跑步等运动的仿真是一个基本问题。本文首先简要介绍了通过求解雅可比矩阵解决逆运动学问题的方法。然后对人体的跑步模型进行了分析。最后应用逆运动学和动力学相结合的方法，以骨架模型和表面模型实现了逼真的虚拟人跑步运动。试验结果说明所用方法的可行性。     

协同伙伴选择的公平性研究

在协同网络中,协同伙伴的选择是一个非常关键的问题。以前关于这个问题的解决方案本质上是基于收发的性能而忽略了协同伙伴选择的公平性。该文提出通过下述机制来获得公平性的一种新策略。(1)通过用户各自的计数器建立帮助别人就是帮助自己的机制来抑制利己主义的用户;(2)在接收端设置阈值决定是否需要伙伴中继;(3)在最大吞吐量与网络节点寿命方差之间联立以建立动态平衡。仿真结果显示:这个策略能够在性能和公平性之间达到动态平衡,从而利于整个网络的公平,其公平性优于目前所知文献的方法。     

机电一体化设备的故障维修特点及可靠性分析

在我国科学技术的迅速发展背景下,机电一体化设备被广泛应用到各个行业领域,对提高我国社会生产力起到了较好的积极影响作用.但是在机电一体化设备的使用过程中,很容易出现各种各样的故障问题,进而影响到机电一体化设备的正常运行,对我国人民的生产活动造成较大影响.面对这种情况,必须要做好机电一体化设备的故障维修工作,不断提高机电一...