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Electrical Engineers, Proceedings of the Institution of

Issue 10 • Date October 1971

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Displaying Results 1 - 25 of 34
  • Application of incoherent-scatter data to communication

    Page(s): 1319 - 1322
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    The application of a very sensitive radar system to the observation of signals incoherently scattered in the ionosphere is briefly described. This technique can give more detailed information about height and time variations of bottom-side electron-density profiles than any other method, besides measuring several further parameters of the plasma. Electron-density profiles of the day-time lower Eregion, and of the whole of the night-time Eregion, allow much more reliable estimates than hitherto to be made of nondeviative h.f. absorption, and of the reflection heights of m.f. and l.f. waves. The morphology of the `valley¿ in the profile between the E and Fregions can be investigated; also the ability to measure details of profile changes during ionospheric disturbances should allow the accompanying deterioration in h.f. propagation conditions to be understood. Incoherent-scatter measurements give unique opportunities of making independent calibrations of statellite instruments in orbit, and of measuring plasma movements induced by neutral aid winds. An empirical law relating the temperature and density of the electrons has been discovered; this will help in predicting the changes in density which should occur when additonal heat energy is deposited in the ionosphere during disturbances. View full abstract»

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  • Use of flayer theory in ionospheric predictions

    Page(s): 1323 - 1326
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (690 KB)  

    Worldwide predictions of h.f. and m.f. radio propagation conditions require extensive data on the space and time variations of ionospheric parameters such as foF2 and hmF2. Theoretical values of these parameters can be obtained by solving equations that represent the effects of various physical processes governing Flayer behaviour. The effects of winds, which are driven by the daily heating of the upper atmosphere, on the midlatitude F2layer are briefly described. Consideration is also given to the polar and the low-altitude F2layer and to problems of Flayer storms. View full abstract»

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  • Theory of cylindrical antennas with arbitrary impedance loading

    Page(s): 1327 - 1332
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (661 KB)  

    A method of analysing cylindrical antennas with distributed impedance loading is presented. The loading is assumed to be an arbitrary but differentible function of position along the antenna. As an illustration, the most important class of such antennas in practice, the broadband cylindrical antennas with distributed resistive or capacitive loading, for which exprimental data are available, are analysed. The theoretica results are in satisfactory agreement with experiments. View full abstract»

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  • Analysis of multicomponent wavefields

    Page(s): 1333 - 1338
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (921 KB)  

    The problem considered is that of clculating the angles of arrival of a multimoded signal at an antena array from simultaneous measurements of the amplitude and the phase of the signal in each element of the array. A general solution with wide application is described. View full abstract»

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  • Factors influencing conversion efficiency in gaseous-plasma harmonic generators working at microwave frequencies

    Page(s): 1339 - 1344
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (800 KB)  

    This paper describes a novel application of the field-gradient theory of plasma microwave harmonic generation, proposed by Krenz and Kino, to the case of a positive column placed through a rectangular waveguide. The distribution of 2nd-harmonic power between the TE01 and TE11 waveguide modes has been examined experimentally and found to be in agreement with qualitative predictions made from the gradient model. An inverse-cubic depence between the 2nd-harmonic-conversion efficiency and electron-collision frequency, predicted by Krens, has also been observed. A metal probe plaved against the column, with the intention of introducing severe microwave-field gradients in the plasma resonace at the fundamental frequency, a best overall conversion of about 25% was produced for an input power of 500mW at 2.42 GHz. At higher power levels, the plasma electron density appropriate for fundamental resonance could not be sustained, and the conversion effiency fell. Experiments using 9.6 and 35GHz fundamental signals gave best conversion efficiencies to the second harmonic of only 2.5 % and about 0.01%, respectively. It is concluded that the gradient model provides a satisfactory description of 2nd-harmonic generation in gaseous plasmas, but that devices based on this model do not operate efficiently at high power levels or at high microwave frequencies. View full abstract»

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  • Relative-phase measurement at Q band

    Page(s): 1345 - 1350
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (759 KB)  

    A single-sideband suppressed-carrier ferrite modulator is used in a Qband serrodyne phase bridge. By suitably processing the bridge-detector output, relative phase in the unknown bridge arm may be measured to within 1% of its true value, despite nonlinearities in both the static insertion-loss and phase-shift characteristics of the modulator. The modulator drive is not critical. View full abstract»

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  • V.L.F. propagation parameters derived from observations of sunrise and sunset phenomena

    Page(s): 1351 - 1357
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (838 KB)  

    Received v.l.f. signals during sunrise and sunset times over the propagation path are used to deduce information about the attenuation coefficients and phase velocities of the day and night waveguide modes, as well as the conversion factors between these modes at the day/night transition. Unlike any previous method used to obtain modal propagation constants, the present method does not need a mobile receiver, since it directly makes use of the moving secondary source formed by the mode conversion that takes place at the shadow line, or transition. A two-night-modes/two-day-modes model is discussed in detail. It is seen that it has a wider range of validity, with regard to both the path length and the frequency, than both the two-night-modes/one-day-mode model suggested by Crombie in 1964, and the one-night-mode/two-daymodes model used for the early part of the sunrise period by Kaiser. View full abstract»

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  • Binary nonconsecutive one code for time-tag data compression

    Page(s): 1358 - 1360
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (329 KB)  

    A simple time-tag data-compression scheme which uses a binary nonconsecutive one code is introduced to provide higher data compression ratios than similar schemes which have been suggested. This data-compression scheme should be very easy to implement. In addition, it does not require a priori knowledge of the information source. View full abstract»

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  • Perception efficiency for radio and television displays

    Page(s): 1361 - 1362
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (261 KB)  

    Tests of the effect of time stress on human performance in the recognition situation were carried out using a standard television display with accompanying audio and noise sources, the student responding with a standard key punch. Reaction time and psychological moment measurements are reported and discussed. View full abstract»

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  • Parametric graphical computer display system using analogue storage

    Page(s): 1363 - 1372
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1296 KB)  

    A cathode-ray-tube graphical display system for use as a digital-computer output terminal has been developed The display employs analogue function-generation circuits to produce line drawings composed of straight-line and curved-line segments which are specified by parameters transferred from the computer in analogue form. To maintain a flicker-free image, while also imposing a minimal demand on the computer to which it is connected, the display incorporates an analogue memory composed of capacitors and field-effect-transistor switches. The displayed image may then be refreshed at the required rate by cyclically reading the line and curve control parameters from this memory. The computer need only access the memory to insert fresh data to be displayed or, infrequently, to refresh the stored information. The paper includes discussions of the specification of the overall display system, of the design of the analogue storage system and of two methods used to produce the required picture segments for display. Some results obtained with the display connected online to a small digital computer are shown. View full abstract»

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  • Computer-controlled queuing systems with feedback

    Page(s): 1373 - 1377
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (545 KB)  

    A generalised approach is presented for the study of a computer-controlled queuing system with general input, `first-come-first-served¿ queue discipline and multiple servers with feedback for either exponential servers or constant service times. Two generating functions for the state probabilities of the system corresponding to the two different types of service times are derived. Further, necessary and sufficient conditions for the existence of statistical equilibrium of the computer-controlled queuing system are obtained from the generating functions. The results obtained here generalise many results previously obtained by other workers. View full abstract»

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  • Waiting-time distribution in computer-controlled queuing system

    Page(s): 1378 - 1382
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (483 KB)  

    The paper presents two formulas for the determination of the waiting-time distribution in a computer-controlled queuing system with Poisson input, multiple-exponential servers and first-come-first-served queue discipline. The formulas obtained are expressed in terms of the stationary-state probabilities of the computer-controlled queuing system. One of the formulas is derived by means of the formula of total proability and the other is derived by the use of the theory of Markov chains. It is shown that, by virtue of a limiting process, the first formula obtained in the paper yields the waiting-time distribution in the conventional queuing system without computer control. Furthermore, application of the two formulas for the determination of waiting-time distribution is illustrated by an example. View full abstract»

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  • Method of using redundancy in very large computer stores

    Page(s): 1383 - 1392
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1167 KB)  

    The organisation of a very large random-access computer store which uses redundancy in the form of error-correcting codes is described. The improvements in manufacturing yield which can be achieved by means of such redundancy are emphasised in the form of examples. However, with typical basic store sizes in the capacity range 107¿108 bits, some of the most significant improvements in manufacturing yield are achieved by programmed assembly which makes use of the ease of testability of such redundant systems. The conclusion is that widespread use of the proposed technique of design and manufacture can result in significant savings, both to designer and customer. View full abstract»

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  • Techniques for the measurement of source and drain series resistance in m.o.s. transistors

    Page(s): 1393 - 1398
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (701 KB)  

    Three methods for measuring the source and drain resistance of m.o.s. transistors operating in the unsaturated region are described. The results obtained on a number of simple m.o.s. transistors are presented to illustrate and compare each method and to indicate the significance of such measurements. View full abstract»

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  • Thermal insulation for energy storage

    Page(s): 1399 - 1407
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1163 KB)  

    Efficient thermal-energy storage requires effective thermal insulation. From a consideration of the possible heat-transfer modes, the requirements for a thermal barrier can be deduced. In a good conventional thermal insulation, most of the heat transfer takes place by conduction through the gas (air) in the insulation voids, the conductivity of the `still¿ gas representing the limiting performance of such a material. It follows that a better performance can be obtained only by reducing this gas-conducted heat by having voids smaller than the molecular mean-free path (`microporous¿), by replacing the air by a low-conductivity gas or by partially evacuating the insulation. View full abstract»

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  • Space harmonics in unified electrical-machine theory

    Page(s): 1408 - 1412
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (655 KB)  

    The paper deals with the applicability of unified machine theory to electrical machines where space harmonics can not be neglected. It is shown that there exists cases where a linear transformation can de determined to transform the set of time-depended linear differential equations for a machine at constant speed into a set of linear time-invariant differential equations, even if space harmonics are taken into considertation. A criterion for applicability is presented that involves the number of phases, the number of harmonics and the order of the harmonics that have to be considered. View full abstract»

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  • Performance of d.c. linear machines based on an assessment of flux distributions

    Page(s): 1413 - 1420
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (726 KB)  

    An analytical study is described of the magnetic-field system in a d.c. linear motor. The equations derived are solved by numerical techniques based on a finite-difference approximation. A modification of existing methods is adopted to deal with heterogeneous regions of permeability. The computed flux profiles are shown to compare favourably with experimental results obtained on a 2-pole machine, including the effects of armature reaction. The results are used in tahe derivation of the developed force and dynamic characteristics of a loaded machine, and the theoretical results are again shown to agree closely with experimental results. View full abstract»

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  • Design of microalternator for power-system-stability investigations

    Page(s): 1421 - 1441
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    The paper describes the design of a microalternator in which negative-resistance devices are employed to obtain representative constants of the model's rotor circuits. Dimensional scaling in assessing the parameters of model alternators is reviewed. Methods of calculating the model's principal constants from design data are outlined for a machine of salient-pole-rotor construction. Core and short-circuit losses are examined, and the choice of design criteria is discussed. Test results for a machine of salient-pole construction are given which compare very favourably with the constants derived from design considerations. Attention is also given to the special facilities which are provided by the time-constant regulator and other associated auxiliary equipment. View full abstract»

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  • Comparisons of synchronous-machine models in the study of the transient behaviour of electrical power systems

    Page(s): 1442 - 1458
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1886 KB)  

    Methods of modelling power systems in the study of the system transient behaviour are reviewed. Six machine models of varying complexity are developed from the fundamental machine equations. Factors in the form of the machine equations, which critically influence the economy of solution, are identified, The relationship between the machine and system equations is examined in relation to the digital solution of multimachine problems, and generalised methods of solution of the equations are outlined. Comparisons are made between results obtained from the range of machine models and those obtained from full-scale fault-throwing tests on the public supply system. In one case, a single machine connected to a system of high capacity is modelled, while, in the second example, two 60 MW machines connected to a large mulrimachine system is modelled. Both non-pole-slipping and pole-slipping tests for the case of the 2-machine system are examined, in which a machine marginally remained in synchronism and marginally lost synchronism, respectively. It is shown that models in which subtransient phenomena are simulated, but in which some transformer voltages in the stator equations, together with subtrasient saliency, are neglected, provide an adequate and economical model for system disturbances, including those in which the machine may fall from synchronism. View full abstract»

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  • Synchronous-machine sudden 3-phase short-circuit. Analysis by norton's, constant-flux-linkage and thévenin's theorems

    Page(s): 1459 - 1466
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (775 KB)  

    The paper presents a new technique of analysis. Equivalent circuits, which normally omit altogether the asymmetrical and 2nd-harmonic armature-current components, are made to give the complete solution including the said components by applying theorems which are well known for their simplifying effect. In the first alternative, Norton's theorem is used to replace the 3-phase armature-voltage source by equivalent current sources on the direct and quadrature axes. The appropriate axis loads presented by the rest of the machine are connected to the current sources. Thus, appropriately energised equivalent circuits are obtained which give the complete solution. In the second alternative, the `effective¿ 2-axis armature-voltage source, for short-circuit conditions, is determined by the constant-flux-linkage theorem. Then, by Thévenin's theorem, the appropriately energised equivalent circuits are obtained which again give the complete solution. View full abstract»

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  • Transient stability of power systems containing both synchronous and induction machines

    Page(s): 1467 - 1474
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (882 KB)  

    A method is described of calculating the effect of large induction motors on the transient performance of a multimachine power system under fault conditions. The representation of an induction motor is similar to that used for synchronous machines, and is therefore suitable for describing composite systems. The method is based on Park's equations and, unlike earlier methods, allows for the `deep-bar effect¿ usually present in large cage induction motors. The most accurate result is obtained by using the full set of equations, but more approximate methods using simplified equations are considered. The method is verified by tests on model machines connected by impedances representing transmission lines. Preliminary tests were made on a simple system comprising an induction motor connected to an infinite busbar through an impedance, and were followed by tests on a composite system containing a synchronous machine and an induction motor connected in parallel parts of the system. The results slow that good results are obtained with the accurate calculation which, however, requires a large amount of computer time, but that any approximation introduces considerable error. View full abstract»

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  • Design and parameters affecting the surface stress of overhead-power-line conductor systems

    Page(s): 1486 - 1492
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (893 KB)  

    To prevent undue radio interference and energy loss from overhead conductors, the permissible operating stress must be minimised. Therefore, the design of such conductors was investigated theoretically using a conformal transformation proposed by Timascheff. First, the effect of the design parameters, that is, the subconductor diameter, subconductor spacing, number of subconductors and phase spacing on the maximum surface stress, was considered. This showed that the surface stress decreases as the subconductor diameter, number of subconductors and phase spacing is increased. It also showed that there is an optimum subconductor spacing at which the surface stress is a minimum. Secondly, an equation defining the optimum subconductor spacing was determined. From this equation, it was found that the optimum spacing is affected by all the other parameters, and that subconductor spacings close to the optimum can be justified economically. Finally, the general design of conductor systems was discussed, and possible conductors for a 765kV system were computed using optimum spacings. This showed that the total conductor material is considerably reduced and that the overall diameter of the bundle remains unchanged with an increasing number of subconductors. A suggested computational method for determining possible conductor systems was also described. View full abstract»

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Aims & Scope

The Proceedings of the Institution of Electrical Engineers was published by the IET between 1963 and 1979.

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