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.     

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     

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     

General Trend in Electrical Communications in Japan

Systems are currently being designed for higher reliability and greater economy. Larger transmission capacity is required to meet a rapid increase in recent communication demands instigated by the introduction of video and information communications facilities. More flexibility, to deal with the variety of communication modes to come, and smaller hardware dimensions, to overcome situations caused by the high population density, seem to be particularly sought in the communication technology of Japan. Research and development concentrate on these objectives. The following is an explanation of the present state of the art and general trends in this country.     

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.     

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 .     

Rearrangements in cell populations in malignant growth

It is emphasized that one of signs of malignant growth is heterogeneity of cell population which arises at the earliest pretumour stages and determines the character of tumour progression. At the same time by means of selective influences on population of malignant cells it is possible to change their quantitative correlation and to obtain rearrangement of the normal cell interrelations. Initiation of the tumour, its progression and regression are considered on the basis of the population-cell rearrangement, typical of each of them separately. The concept of the unity of the carcinogenesis and anticarcinogenesis processes is also formulated.     

Noise in DMOS transistors in a BICMOS-technology

An experimental and theoretical study of the 1/f noise and the thermal noise in double-diffused MOS (DMOS) transistors in a BICMOS-technology has been carried out. By using an analytical model that consists of an enhancement MOS transistor in series with a depletion MOS transistor and a resistance, and by attributing noise sources to each device, the noise in DMOS devices is simulated accurately. Three distinct regions of operation are defined: enhancement transistor control, depletion transistor control and the linear region. In the first region, the noise is strictly determined by the enhancement transistor. It was found that the 1/f noise in this region is caused by mobility fluctuations and is very low. In the depletion transistor control region both transistors influence the total noise. Here the 1/f noise is dominated by the depletion transistor. The series resistance is only of importance in the linear region     

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     

Zeroing in on ethical issues in nanotechnology

Setting aside exaggerated notions of both the benefits and harms to be expected from nanotechnologies, we need to focus ethical investigation on specific initiatives at the nano scale that are already underway or planned. The aims are to anticipate ethical issues likely to arise in specific cases, to foster sensitivity to ethical issues and responsibility among nano specialists and policy makers, and to stimulate interchange between nano specialists and members of the public so that the public can become involved. After clarifying what the term "nanotechnology" embraces and looking at cautionary lessons from experience with the information technologies and biotechnology, the discussion turns to the importance of anticipating consequences, intended and unintended. Although specific nano options to consider are lacking, a brief survey indicates the issues to watch out for: preventable harms, conflicts about justice and fairness, respect for persons, and more specifically, safeguards for workers in new production processes, intellectual property concerns, preservation of university values in university/industry relationships, and conflicts of interest. Three main fronts of activity are needed to address ethical issues: 1) incorporating ethics research into nano research and development enterprises; 2) devising mechanisms to involve the public so that their perspectives and concerns feed back into research and development; and 3) initiating educational efforts at every level addressing both technical aspects and ethics and social implications aspects.     

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.     

Designing in reliability in advanced CMOS technologies

Assessment of design implications due to degradation of CMOS devices is increasingly required in the latest technologies. This paper presents selected topics relevant to realize an efficient design-in reliability methodology in the latest generation CMOS technologies. NBTI is discussed in terms of characterization using On-The-Fly (OTF) methodology. Extension of OTF method is discussed using bias patterns to gain insights into NBTI under analog operation. A reliability simulation methodology is discussed against requirements for optimization and integration within an existing design flow. The features of this methodology are illustrated using some simple design examples.     

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.     

Progress in display-device development in Western Europe

A review of the basic research and industrial development of display devices in Western Europe during the years 1968 to early 1973 will be given. The display types considered are: 1) active displays such as cathode ray tubes, light-emitting diodes, electroluminescence cells, and gas discharge devices, and 2) passive displays such as laser displays, light valves, and ferroelectric and liquid-crystal devices.     

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     

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     

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.     

Changes in optical properties of CdS nanoclusters in langmuir-blodgett films on passivation in ammonia

The optical properties of CdS nanoclusters are studied for samples in which the nanoclusters are embedded in the Langmuir-Blodgett film matrix or the matrix is removed by annealing in vacuum or ammonia atmosphere. After annealing the samples in vacuum or ammonia, the bands of emission from the nanoclusters and from the surface states appear in the photoluminescence spectrum, with the peaks at 2.9 or 2.7 eV and at 1.9 or 2.1 eV, respectively. It is found that, after treating the samples with ammonia, the photoluminescence of the nanoclusters becomes more intense, whereas the photoluminescence corresponding to recombination via the levels of the surface states becomes less intense. It is established that the increase in the photoluminescence intensity for the nanoclusters and the difference between the temperature dependence of the photoluminescence peak position and the temperature dependence of the band gap of bulk CdS are due to passivation of surface states in the nanoclusters. The experimental data are interpreted in the model of recombination of nonequilibrium charge carriers in the CdS nanoclusters, taking into account the exchange of charge carriers between the nanocrystals and trapping centers at their surface and the recombination of charge carriers via the levels of the surface states.     

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.<>     

DDN网在惠州市电信业务中的应用

本文介绍了ＤＤＮ的基本结构和作用，分析了ＤＤＮ设备的几个特点，指出了ＤＤＮ在惠州市电信业务中的几种主要的应用，最后还指出了ＤＤＮ设备使用中存在的问题。