摘要:

The increasing sophistication of modern technology and its widening areas of application have established the need for multidisciplinary activities, and biomedical engineering is a typical example of this trend. The evolution of the subject from the engineering approach of earlier biomedical workers is described, and some of the lessons learned before and during the transition are considered. An approach to this now rather extensive subject is made by separating the application to biomedical research from that to clinical medicine. The research section is stratified according to the level of biological organisation with which it is concerned, that is, from the molecular systems of biochemistry to the organ systems of physiology. At each level, sufficient background is given to show the relevance of biomedical engineering, and this approach is continued with the clinical applications, which are considered within conventional medical categories. The principal contribution to medicine is found to lie with the innovation of the new methods made possible by advancing technology. The more recent technological ideas of organ and function replacement are discussed followed by that of computer usage in various areas of biomedicine. In conclusion, a critical assessment of present achievements is attempted, and the possible future of biomedical engineering is discussed.

DOI:10.1049/piee.1971.0242

出版商:IEE    

年代:1971

数据来源: IET

摘要:

As the field of radar is very large, the treatment in the paper is necessarily brief, and is mainly confined to techniques and systems of current interest. All radar systems are subject to fundamental performance constraints stemming from the range, range rates and angle-measurement processes which are basic to radar. Most modern radar systems of interest are subject to further constraints arising from the environment in which they operate. The choice of the radiated carrier frequency affects many aspects of radar performance, including aerial directivity, the ability to distinguish target radial velocity, the target echoing area, attenuation in the atmosphere and clutter echoes. Highly directional aerials provide the basis for radar angle measurement and significant recent advances have been made in this field. Transmitters, including high-power transmiters and low-power solid-state microwave oscillators and amplifiers, are discussed. Radar receiving systems have been strongly influenced by recent advances in solid-state technology. Closely associated with the basic receiving function is the signal processing needed to achieve an acceptable approximation to matched filtering of the radar-echo signal. Radar-display technology continues to be dominated by the cathode-ray tube, however, the data presented for display are increasingly subject to preprocessing, often by digital computer, prior to display to the radar user. The use of computers in association with radar, initially to facilitate information display, has been broadened to more fully adaptive systems, in which the operating parameters of the radar are continuously adjusted to match the immediate requirements of the task in the light of information already obtained. By reradiating a pseudoecho on a frequency different from that of the radar, co-operative targets may be detected without any problems of clutter. Such radar operation is termed secondary radar. The paper concludes with brief description of air-surveillance radar, radar in guided weapons, radar in aircraft navigation, radar in airborne air defence, radar on the battlefield, miniature radars, radar meteorology and over-the-horizon radar.

DOI:10.1049/piee.1971.0243

出版商:IEE    

年代:1971

数据来源: IET

摘要:

The paper reviews the use, design and performance of the various forms of radio-isotope instrumentation, with some comment on the historical development of the subject, and possible developments, in the future. Earlier surveys published by the IEE have described nuclear measuring instruments for use in the laboratory and in nuclear-reactor experiments and other installations. Here it is proposed to review radio-isotope instrumentation, i.e. an instrument comprising a radio-isotope source and some measuring component, as used for investigational work in science and engineering, but more particularly in industry to improve both productivity and the quality of the product being manufactured. Emphasis is given throughout to the special techniques involved, and attention is also given, where possible, to applications in electrical engineering. An attempt is made to classify the various applications discussed and to give examples of each class.

DOI:10.1049/piee.1971.0244

出版商:IEE    

年代:1971

数据来源: IET

摘要:

High-voltage insulators may flashover at working voltage when polluted and wet. Pollution is deposited by various forces, of which aerodynamic ones are shown to be usually the most important. Theories to explain the pollution-flashover process are described. The performance of insulators in a polluted environment may be assessed by tests in natural conditions, or by the use of artificial methods, which are critically examined. The influence of a number of parameters, such as surface conductivity, overall length, leakage-path length and profile on insulator flashover is discussed. Studies of the effect of voltage waveshape show that direct voltage gives flashover at the lowest peak stress for a given pollution severity. Pollution flashover can be prevented by washing or greasing or by employing oil-bath or resistive-glazed insulators or special insulator assemblies. The advantages and disadvantages of these remedies are outlined. An analysis of the behaviour of polluted surge diverters and insulators with special functions introduces extra problems which are discussed. Organic insulating materials are degraded by tracking or erosion, but insulators using these materials have advantages, especially for ultra-high-voltage systems. An important aspect of the pollution problem which needs further study is the measurement of the site-pollution severity, so as to classify insulation requirements, and several methods of measurement are described.

DOI:10.1049/piee.1971.0245

出版商:IEE    

年代:1971

数据来源: IET

摘要:

The paper gives a survey of the most important aspect of arc-electrode processes (excluding externally heated cathodes) which concern engineers in a variety of applications. Although it is not possible to avoid discussion of the basic mechanisms and of the number of conflicting and still unresolved theories for them, the emphasis is, as far as possible, on those characteristics which affect the design and operation of devices or processes in which they occur. There is a brief general description of arc discharges and of important differences between them and glow discharges. After distinguishing between thermionic and nonthermionic cathodes (and commenting on the transitions of emission type which occur with some metals), the main body of the paper deals with nonthermionic cathodes. This begins with some of the chief observational data, such as current density, root splitting, electrode erosion, magnetic deflection, plasma jets and force on the cathode, and goes on to consider some of the important factors which affect cathode processes, including electrode material and surface state, current, gas and its pressure or vacuum. After commenting on zones within the cathode fall, there is a discussion of the many theories which have been put forward to explain the emission mechanism of cold-cathode arcs. It is suggested that no single process is responsible for all conditions, and that transitions in mode can occur, either abruptly or gradually, and the most significant principles and facts which must be taken into account are outlined. There is a short Section describing the main features of arc anodes, and the paper concludes with a discussion of electrode effects in mercury-arc convertors, gas-blast and oil circuit breakers, vacuum switches, arc heaters and plasma torches, arc welding, commutation and arc furnaces.

DOI:10.1049/piee.1971.0246

出版商:IEE    

年代:1971

数据来源: IET