智能通信在楼宇自控系统中的应用

随着计算机技术、控制技术、通信技术及信息技术的飞速发展,人们对生活、办公环境安全性、舒适性的要求日渐增长,智能建筑应运而生。楼宇自动化控制系统是智能建筑的一个重要组成部分。通过结合具体的智能楼宇控制工程项目,在介绍系统概况的基础上,给出了系统的总体设计方案及子系统的监控方案,具有一定的实用价值。     

Advances in millimeter-wave subsystems in Japan

The authors describe the development trends and results of millimeter-wave systems in Japan in such fields as communication, radar, and measurement systems. The applications included are the W-40G waveguide transmission communication system, an automobile traffic control system using the 60-GHz band, a collision avoidance radar system for an automobile, a plasma electron density measuring system, and satellite communication. The authors describe the development of devices such as high-power FET amplifiers, traveling wave tube amplifiers (TWTAs), IMPATT amplifiers, low-noise amplifiers, and monolithic microwave integrated circuit (MMIC) devices used in constructing the millimeter-wave systems     

Progress in electrophotography in Western Europe

A review is given of the progress in electrophotographic science and technology in Western Europe during the years 1967 to early 1971. University research work is mainly directed towards two areas: 1) the electrical and physical properties of photoconductors, such as selenium, chalcogenides, oxides, and organic materials; and 2) the sensitization of these photoconductors. Industrial research teams report on the preparation of electrophotographic layers on development and on image evaluation. A bibliography including scientific papers and patents published on this subject during said period completes this review.     

Two-wave mixing in reflection holograms in photorefractivematerials

The intensity and phase of two counterpropagating optical beams in a photorefractive material are investigated both numerically and by using an approximate analytical theory. It is shown that in the reflection regime they are two situations where coupling between the beams may be spatially dependent; in the case of nearly degenerate two-wave mixing, and when a photocurrent is present. In these situations, previously obtained results may need significant correction     

Propagation in Broadside-Coupled Suspended-Substrate Stripline in E-Plane

The spectral-domain analysis is applied to the derivation of the propagation characteristics of the even and odd mode, for the broad-sidecoupled suspended-substrate stripline (BCSSS). The characteristic impedance, based on the current-power definition, as well as the effective permittivity are evaluated. Numerical results are presented illustrating the effects of several different dimensional parameters. Numerical results indicate a large spread between even- and odd-mode impedance for thin substrates (D/A < 0.045) and stripwidths ranging 0.046<= W/B<= 0.47, suggesting tight coupling. Negligible frequency dependence on odd-mode impedance is evident, as well as significant frequency effects on even-mode impedance. Considerable dispersion is shown to be present in the odd mode for wider strips. Measured results for a low-pass filter and cascaded transitions are presented.     

Autosolitons in InSb in a magnetic field

It is shown experimentally that a longitudinal magnetic field of comparatively small magnitude substantially changes the velocity of autosolitons in indium antimonide samples and produces an appreciable redistribution of the electric field of these autosolitons. In this case, the frequency and amplitude of the current oscillations in the external circuit of the sample increases or decreases, depending on the direction of the longitudinal magnetic field. Fiz. Tekh. Poluprovodn. 32, 697–700 (June 1998) An erratum to this article is available at .     

Errors in reprojection methods in computenzed tomography

Iterative tomographic reconstruction methods have been developed which can enforce various physical constraints on the reconstructed image. An integral part of most of these methods is the repro. jection of the reconstructed image. These estimated projections are compared to the original projection data and modified according to some criteria based on a priori constraints. In this paper, the errors generated by such reprojection schemes are investigated. Bounds for these errors are derived under simple signal energy assumptions and using probabilistic assumptions on the distribution of discontinuities. These bounds can be used in the enforcement of constraints, in the determination of convergence of the iterative methods, and in the detection of artifacts.     

中国数字电视的发展现状:前景明朗现状不乐观

在计算机和移动电话给人们带来全新的数字体验以后,数字电视开始引领传统家电的数字革命,在拥有最多的电视用户的中国,这场革命刚刚开始.我国计划分2005年、2008年、2010年和2015年四个步骤来实现由模拟电视向数字电视的过渡,到2015年在国内将全面停止播放模拟电视节目.目前在3.85亿个家庭里拥有4亿台彩电,因此在今后10年内这些彩电肯定要更换成数字电视或安装机顶盒,所以我国今后将从一个巨大的模拟电视机市场转变成海量的的数字电视市场.     

移动产业2011年五大趋势:Google苹果双头垄断

新年伊始,移动产业的各种预测层出不穷,《今日美国报》专栏作家凯文·马尼(Kevin Maney)撰文,列举了2011年移动行业的五大趋势。以下为文章全文:2011年的移动行业有一些显而易见的趋势:Verizon可能会出售与其网络兼容的iPhone,苹果可能会发布新iPad,而用户则仍然有可能浪费大量时间玩《水果忍者》(Fruit Ninja)这样的游戏。     

RECENT PROGRESS IN MULTI—BEAM KLYSTRON IN IECAS

Recent research progresses in Multi-Beam Klystron(MBK)in IECAS are briefly introduced in the letter,The S-band MBKs of IECAs have peak power of 120-250kW,average power of 4-9kW,efficiency of 35-45%,gain of 41-46dB.beam voltage of 15-19kV,and weight of 40-45kg.Some key technical problem of MBK are also described and discussed.Among them,improving the design of MBK to botain the required bandwidth,raising beam transmission to increase average power,eliminating oscillation and spray spectrum,overcoming window breakdown caused by magic mode,reducing breakdown times of electron gun,are most important things for the practical MBK.Besides,further research owrk in MBK in IECAS is commented.     

FFT在时域紧缩场方向图测量中的应用

离散傅立叶变换(DFT)在信号的谱分析及系统的分析、设计和实现中起着非常重要的作用.其原因之一是计算DFT有很多高效快速的算法.快速傅立叶变换(FFT)算法就是其中之一.利用FFT算法,可以将微波测量中大量的计算简化,缩短了计算机的计算时间.在时域紧缩场测量方向图的过程中,利用FFT进行时域与频域间的转化,使一次仅能测量一个频率点的方向图,扩展到一次可以测量一个频段的方向图,从而大大缩减了测量时间.     

Switching conduction in ion-irradiated layers in GaAs

Experiments have been performed to investigate whether switching phenomena are observable in ion-irradiated GaAs. It is found that the V/I characteristics of H2+-and N+-irradiated layers show both negative resistance and switching from a high resistance to a low resistance state. Ion irradiation may thus be a useful method of fabricating switching devices.     

Electricity in China-generation in the People's Republic

Before the establishment of the People's Republic, China was a semi-colonial, semi-feudal society plagued by foreign interventions and internal power struggles. It was against this background that the electrical industry went through its infancy. Today, the People's Republic of China is facing an acute energy shortage, posing a problem which must be quickly overcome if the country's rapid industrialisation is to continue as planned. The author presents a brief history of power generation in China from 1949 to 1983 and examines possibilities for the future     

Telecommunications' role in national development in Ghana

Ghana has recognized the need for efficient and reliable telecommunication services. The widespread availability of these services will promote the nation's economic advancement and the decentralization of the government's activities. To achieve the objective of bringing telecommunications to all the people of Ghana, private sector participation is considered essential as a source of management skills, technology, and financing that will be required for the provision of services. In order to attract such participation, Ghana is putting in place the necessary policy, institutional, and regulatory frameworks to create an enabling environment for private sector investment in the telecommunication sector     

IT安全化安全IT化--信息安全产业发展问题与思考

信息安全在IT业中的角色演变 在当今信息时代,信息技术日新月异,信息产业已经成为拉动GDP增长的第一支柱产业,并以每年20%—30％的速度迅猛发展。其发展过程也经历了从传统IT向新型IT的转变,其中一个重要的转变因素便是信息安全。 1.传统IT与信息安全的关系。传统IT涵盖了五大类:通信、网络、计算机、软件、电子材料及元器件。这五类IT行业本身的发展一度呈现结构失衡:一方面过度投资到“信息高速公     

中国带电清洗技术的突破

一、电路故障的成因 通常,由于空气的污染和设备所处的环境及管理条件不同,空气中的灰尘、油污、酸碱及其气体、盐分、潮气、炭渍、金属尘埃、各种机械杂质等污染物质,不可避免地吸附在电路表面及其它部位,加之静电累积和在电场力的作用下,污秽的累积不断加重和变得牢固,各种污秽牢牢附着在线路表面,深层及各部位。灰尘、油污、酸碱及其气体、盐分、潮气、炭渍、金属尘埃、各种     

Telecommunications in Malaysia: diversity in adversity

The telecommunications industry in Malaysia has experienced a tremendous transformation in just over a decade. The government-owned Jabatan Talikom, which hitherto operated the network, was incorporated in 1987 and subsequently privatized a few years later, with a majority share holding by the government. The regulatory aspects were spun off under the slim looking JTM. This marked the beginning of liberalization, and many new players entered the fray. This article reviews the telecommunications infrastructure and services available in Malaysia and visits some of the telcos offering these services. Some pertinent issues affecting the industry are also discussed     

Losses in small-radius bends in single-mode fibres

Refractive index profiles and mode field radii determine small-radius bending losses in single-mode fibres. Losses in six different types of fibres were measured in bends with radii ranging from 1.25 to 8 mm. The results show that a refractive index depression in the core centre reduces the bending-loss sensitivity.<>