摘要:

A programme of research into the likelihood of damage to operators' eyes resulting from the increasing use of visual display units was recently commissioned by the Association of Optical Practitioners. In general the study by two members of the A.O.P. Occupational Visual Welfare Committee, S. Rosenthal and J. Grundy, showed that no evidence existed of damage or harmful effects on eye-sight as a result of visual display unit work or the radiation effects of visual display units. Their report, a shortened version of which follows, will be of interest to engineers concerned with the design or application of v.d.u.s.

DOI:10.1049/ree.1979.0033

出版商:IERE    

年代:1979

数据来源: IET

摘要:

The reserves of fossil fuels are analysed and some of the methods being developed to improve the energy yield from existing reserves are looked at, including enhanced oil recovery and magnetohydrodynamics. Other sources of energy not relying on fossil fuels are considered. Some could be tapped immediately or with some straightforward development, e.g. nuclear fission, solar, tidal and wave power. A proposed 2MW French prototype solar power station under construction in the Pyrenees is described. Future large-scale production of power by deep gasification of coal and by nuclear fusion are discussed and their role as potential replacements for coal, gas and oil are considered.Based on a lecture to the Beds and Herts Section on 11th May 1978.

DOI:10.1049/ree.1979.0035

出版商:IERE    

年代:1979

数据来源: IET

摘要:

Optical fibre cables are currently available having transmission losses of 3 dB/km and bandwidth x length products of 1 GHz km at an operating wavelength of 0.85μm. At the longer wavelength of 1.3μm attenuations as low as 0-5 dB/km, and repeater spacings of 50 km, have been demonstrated in the laboratory. The corresponding bandwidth of graded-index multimode fibres can be large, even with light-emitting diodes, while the combination of semiconductor lasers with single-mode fibres is capable of several hundred GHz km. Practical problems of cabling, jointing connectors, strength, sources and detectors are close to being solved.

DOI:10.1049/ree.1979.0036

出版商:IERE    

年代:1979

数据来源: IET

摘要:

This paper describes a simple method of measuring instabilities in communication systems such as satellite links. The technique is based on the use of a modified commercial phase meter and frequency synthesizer. This can linearly measure the magnitude of phase variation of a source, in a bandwidth of 1 kHz with a resolution down to 0.5 deg peak to peak, relative to a stable reference. Frequency instabilities of less than 0.1 Hz can also be measured.The paper includes typical measurements of noise introduced by high stability frequency sources, medium and high-power travelling-wave tubes and klystrons, and low-noise parametric amplifiers.

DOI:10.1049/ree.1979.0037

出版商:IERE    

年代:1979

数据来源: IET

摘要:

The use of scale modelling for assessment of helicopter homing systems is described, including appropriate measurement techniques for different frequency bands. The interaction of the antennas with the metal fuselage is of primary importance, and this is illustrated in three different homing applications.

DOI:10.1049/ree.1979.0038

出版商:IERE    

年代:1979

数据来源: IET

摘要:

The advent of the single-chip microprocessor has made possible the use of digital signal processing in low-cost communications circuitry. The all-digital approach has been used in a high-performance data modem for the transmission of burst messages through the voice channel of v.h.f. narrow band f.m. radio sets. The techniques used in this novel design of software modem are illustrated by reference to the version using coherent quadrature phase shift keying (q.p.s.k.) modulation and constraint length 48 convolutional encoding with sequential decoding.

DOI:10.1049/ree.1979.0039

出版商:IERE    

年代:1979

数据来源: IET