摘要:

Standard electronic equipment such as radar and ship's logs are used in the fishing industry as in any seagoing trade. The more specialised equipment is the acoustic instrument used for finding fish. The development of commercial echo sounders owes much to their intelligent use by fishermen, and as a consequence they have diverged into specialist uses. It is likely that in the future the use of higher frequencies will become more widespread. Because acoustic instruments are used by navies to find submarines there is considerable fall out to the fishing industry, particularly in the use of research equipment. Some of this is used by fisheries scientists in the study of fish behaviour and in the assessment of fish stocks, but experience with advanced machines also leads to developments used directly by the fishermen. In the past large fishing vessels of the distant-water fleets have carried expensive equipment for locating fish. Since the establishing of national economic zones out to 200 miles, distant-water fleets have declined. They have been, or will be, replaced with more numerous smaller vessels, with smaller capacity to buy expensive equipment. The need to locate fish effectively remains, however, with cheaper machines scattered among more vessels.

DOI:10.1049/ip-a-1.1981.0080

出版商:IEE    

年代:1981

数据来源: IET

摘要:

Most studies of flux penetrating the end region of a machine, such as the stator core of a turbo-generator, have not taken into account the large core flux already present in the iron laminations. In the paper an experimental system is described in which the electric field within a stack of laminations is measured when flux penetrates from the surface in the presence of a large sinusoidal magnetic field at right-angles to the flux. The fundamental and third-harmonic components of electric field, computed using a two-dimensioanl model of the system, give good agreement with the experimental results. Analytical expressions for the electric field within the steel are obtained using a one-dimensional model assuming a stepB/Hcharacteristic, an assumption which is reasonable for the high field strengths present in a real machine. A comparison of the predictions of this theory are also made with the results from the experimental system.

DOI:10.1049/ip-a-1.1981.0081

出版商:IEE    

年代:1981

数据来源: IET

摘要:

The paper describes a simple lumped-circuit model of coupling between any two coaxial cables in a system ofncoaxial cables over a ground plane, orn+ 1 cables in free space. Theoretical predictions for various cable configurations are compared. Experimental results are presented and compared with the calculations (calculated using measured values ofZTthe surface transfer impedance of the braid). An experimental investigation of the effect of torsion in the cables on the coupling is also discussed.

DOI:10.1049/ip-a-1.1981.0082

出版商:IEE    

年代:1981

数据来源: IET

摘要:

A method is presented for solving for the electromagnetic field in a multilayer circular cylindrical structure, excited by a concentric coaxial helical winding. The method is based on a double transmission line technique and it uses the concept of E-mode and H-mode lines. The use of Bessel functions is completely obviated by employing micro-T circuits. Supporting experimental evidence is also presented.

DOI:10.1049/ip-a-1.1981.0083

出版商:IEE    

年代:1981

数据来源: IET

摘要:

The distribution of time lags to corona inception is examined theoretically and experimentally for the case where a double-exponential positive impulse voltage waveform is applied, at a fixed repetition rate, to a rod/plane gap. The influence of atmospheric humidity, temperature and pressure on the conditions for corona formation are discussed. Experimentally, the spread of the time-lag distribution is studied primarily as a function of humidity. The results are related to the variation, with humidity, of the negative-ion density prior to each impulse. Models for the conditions for detachment of electrons from negative ions, and for corona formation, which are derived from experiments using small air gaps, have been shown to agree with the results obtained in large air gaps.

DOI:10.1049/ip-a-1.1981.0084

出版商:IEE    

年代:1981

数据来源: IET

摘要:

Early diagnosis of intense foetal hypoxia, symtoms of which include changes in the foetal heart rate, may constitute a useful tool for the prevention of irreversible damage to the foetus. In the paper three automatic diagnostic methods are described, all based on analysis of the waveform of the autocorrelation function of the sum of signals representing the foetal heart rate and the uterine pressure. The three methods are compared and tested using records taken from a number of patients.

DOI:10.1049/ip-a-1.1981.0085

出版商:IEE    

年代:1981

数据来源: IET

摘要:

Drawing on his perspective of a long career in engineering and public affairs, the author traces the pattern of supply and demand for engineers during the last century. There is a divergence between British attitudes and those of other countries, leading up to the recent Finniston report, and the reactions to it.

DOI:10.1049/ip-a-1.1981.0086

出版商:IEE    

年代:1981

数据来源: IET