共查询到20条相似文献,搜索用时 31 毫秒
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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 相似文献
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《Electron Devices, IEEE Transactions on》1972,19(4):524-531
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. 相似文献
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Erbschloe D. Solymar L. Takacs J. Wilson T. 《Quantum Electronics, IEEE Journal of》1988,24(5):820-826
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 相似文献
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《Microwave Theory and Techniques》1985,33(10):946-950
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. 相似文献
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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 . 相似文献
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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. 相似文献
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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。 相似文献
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DingYaogen 《电子科学学刊(英文版)》2002,19(4):441-444
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. 相似文献
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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. 相似文献
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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 相似文献
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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 相似文献
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游小明 《信息安全与通信保密》2003,(5):16-17
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 相似文献
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中国带电清洗技术的突破 总被引:2,自引:0,他引:2
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 相似文献
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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 相似文献
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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.<> 相似文献