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Physical Science, Measurement and Instrumentation, Management and Education - Reviews, IEE Proceedings A

Issue 9 • Date December 1986

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Displaying Results 1 - 9 of 9
  • Computation of the electric field at a solid/gas interface in the presence of surface and volume charges

    Page(s): 577 - 586
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (816 KB)  

    Enhancement of the electric field at a solid insulator/electrode/gas triple junction and on the surface of an insulator, due to imperfect contacts, surface irregularities and contamination, reduces the withstand voltage of the gas-only system. The charges deposited on the surface and in the bulk of the insulator, when stressed under high voltage, further modify the electric field. In the paper, the influence of accumulated static charges on the electric field distribution associated with a cylindrical insulator held between plane electrodes in atmospheric air is investigated. The electric field along the solid dielectric/air interface is calculated for different surface and volume charge distributions by using the finite-difference method based on Gauss's law. Derivation of the iteration equations are relatively easy, and, unlike most methods, there is no need for external imposition of solid dielectric/gas boundary conditions. The results indicate that, for some surface and volume charge distributions, field enhancement occurs at the triple junction, and this could initiate a surface flashover. View full abstract»

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  • A new UK national standard of electrical noise at 77 K in WG15

    Page(s): 587 - 595
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (766 KB)  

    A new UK national standard of electrical noise has been designed and manufactured. The device operates at liquid-nitrogen temperatures in WG15 at 7.3, 7.5 and 7.7 GHz and has an output noise temperature calculable to 0.2 K. The processes involved in the thermal and electrical evaluations of the standard are described, as are the operational details and the calculation of output noise power with its associated uncertainties. View full abstract»

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  • On the solution of open boundary field problems using the finite-element method

    Page(s): 596 - 600
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (385 KB)  

    This contribution examines the appropriateness of boundary conditions commonly used when open boundary electromagnetic field problems are approximated using the finite-element method. The use of infinite elements is also considered, and the effect of the choice of boundary model on the interior potential distribution examined. View full abstract»

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  • Force on a parallel circular loop moving above a conducting slab and the eddy-current distribution

    Page(s): 601 - 605
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (301 KB)  

    The purpose of this work is the determination of eddy-currents induced within a conducting slab, when a parallel circular current loop is moving above it. The field owing to the eddy-currents acts on the loop and produces forces on the loop. This geometrical configuration can approach problems of the electrical machines related to the magnetic suspension, when the geometry of these problems is compared with the above configuration. The rigorous analytical determination contributes either to the calculation of similar configurations or to the comparison of approximate solutions of more complicated configurations. View full abstract»

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  • Electrostatic discharges from the human body

    Page(s): 606 - 610
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (561 KB)  

    Many papers have been published on the subject of electrostatic discharge (ESD) and the effect of these discharges on electronic systems. Only two of these papers have attempted to measure the actual human discharge, the rest being concerned mainly with simulated ESD. A number of simulators are now commercially available to test the susceptibility of equipment to ESD. This paper reports the results of measurements of current peak magnitude and rise time of ESD derived from a charged human body under a variety of experimental conditions. Direct and induced ESD effects are measured using hand-held metal objects in addition to direct discharge from the finger. The influence of multiple earths is investigated and is found to decrease the severity of the ESD both in magnitude and rise time. The authors conclude, as a result of these measurements, that the currently available simulators grossly overestimate the magnitude of ESD, and, as a consequence, involve manufacturers in expensive overprotection of their equipment. View full abstract»

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  • Modelling gamma-source backscatter density gauges

    Page(s): 611 - 617
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (548 KB)  

    Gamma-source backscatter gauges are used to obtain a nonintrusive measurement of the density of rocks and soils from the surface. The static and moving-source versions of these instruments, which have been developed previously, allow an in situ investigation of a bulk sample of a material. Changes in gauge design and factors affecting the homogeneity of the material alter the backscatter characteristics. A model, which accurately represents the detector in its working environment, is developed for all gamma-source backscatter density gauges. Whereas previous models emulate the absorption and scattering processes, the presented model allows a direct comparison of the maxima and shape, or bandwidth, of the experimental and theoretically predicted results. The model makes this comparison possible through the formulation of characteristic differential equations together with accurate calculations of both the maxima and normalised bandwidth of the characteristics, for both versions of these back-scatter density gauges. This allows an accurate comparison of design parameters by different routes and could form a basis for new backscatter gauge designs. Fresh applications involving surface measurements of in situ bulk materials could also result from this model. View full abstract»

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  • The influence of vibration on the initiation of trees in dielectrics

    Page(s): 618 - 622
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (654 KB)  

    Polymeric insulation suffers from long-term degradation at low alternating stresses, through the development of tree-like structures of discharge channels emanating from protrusions and inhomogeneities. It can take a considerable time, following the application of voltage, before treeing begins. During this time microscopic voids and cracks form within the dielectric providing the necessary partial discharge activity for treeing to commence. The process leading to the formation of voids and cracks under the influence of low alternating fields has generally been thought to be electronic in nature. The work described in the paper demonstrates that this is not so, and that fatigue failure due to prolonged vibrational electrostatic forces is the cause. View full abstract»

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  • Identifying a product strategy

    Page(s): 623 - 629
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (778 KB)  

    The paper seeks to demonstrate how the increasingly rapid technological evolution requires the identification of a product strategy for survival. This cannot be implemented at a stroke; it requires short-term action leading to medium-and long-term solutions. Finance is a major factor and the paper sets out preferred arrangements for recovery of development costs and identifies potential sources of finance. It concludes by discussing the implementation of a product strategy, once identified and agreed. View full abstract»

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  • Engineering and industry¿the hidden hunger

    Page(s): 630 - 636
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (929 KB)  

    For many decades now, the performance of the UK as a manufacturing nation has been in steady decline in comparison with that of other major manufacturing nations, until, in 1984, for the first time in the history of the UK, more manufactured goods were imported than exported. Throughout this period, nothing that has been done in the country has made any difference to the trends, whether it be economic measures, higher education growth or political change. In the view of the author, there must be some very deep-seated reason for the obduracy of the trends, and it is his assertion that the country is in need of a fundamental re-direction of education so that the skills of designing and making become a major sector, indeed a spinal column, of the curriculum. The activities of designing and making are part and parcel of the very fabric of our culture, and are the roots of our manufacturing industry; however, for too long, education has been treating them as activities for the less able. Designing and making ought to be regarded as every bit as important as reading, writing and arithmetic. The author goes on to argue that an understanding of industry should be an essential part of the make-up of the education of a person, as significant as an understanding of literature, history or science. The lack of grounding in designing and making, and the lack of understanding of industry constitutes `the hidden hunger¿ from which the UK suffers, and which, in the author's view, is one of the fundamental reasons for our sluggish industrial performance. So long as the plant, i.e. our industrial culture, has its roots in unfriendly soil, then trimming and rearranging the upper branches will not make it into a healthy plant. It needs nourishment through its roots from the soil. We need to become an industrially educated nation. View full abstract»

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