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

Issue 9 • Date November 1987

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Displaying Results 1 - 9 of 9
  • Monte-Carlo calculation of electrically induced human-body currents

    Page(s): 705 - 711
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (814 KB)  

    A method is described for calculating the charges and currents induced in the human body by high-voltage alternating electric fields. This relates the surface charge induced on the body to the potential in a reciprocal Laplace problem, which is then calculated by a Monte-Carlo random-walk technique. The method is applied to an experimental geometry used to study the effect of electric fields on cardiac pacemakers. Induced charges and currents for several different body configurations are calculated. Calibration factors are also derived to correct the measured currents for the effect of the walls of the test area and the nonuniformity of the applied electric field. The solutions show good agreement with the magnitude of the total induced charge and its distribution over the body surface, as estimated in other experimental and computational work. View full abstract»

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  • Application of instrumental neutron activation analysis to the measurement of water tree growth in polymeric insulation

    Page(s): 712 - 716
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (554 KB)  

    The sensitive technique of instrumental neutron activation analysis (INAA) has been used to measure the penetration of ions into the water treed regions of polymeric materials. The technique has been used to study water trees grown in the laboratory, using a water electrode and to examine the concentration of trace elements in an XLPE cable which failed in service. The study shows that ions penetrate into and beyond the visible water-treed regions. This leads to a quantifiable difference in the distribution of trace elements in the treed and untreed regions of the polymer-insulated cable examined. The possibility of applying INAA techniques to cable testing is discussed View full abstract»

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  • Electromagnetic detection of metallic particles

    Page(s): 717 - 720
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (457 KB)  

    The effect of a conducting permeable spherical particle on the impedance of a solenoid is calculated, and consideration given to maximising the effect for detection purposes. For greatest sensitivity either the resistive change or the reactive change should be optimised, according to the method of detection; the frequency ranges needed to do so are indicated for both magnetic and non-magnetic particles View full abstract»

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  • Function representation of lightning impulse wave

    Page(s): 721 - 726
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (569 KB)  

    The paper presents mathematical descriptions which fit the front, the tail and the chopping of lightning impulses which correspond with real circuits. Values of the equation coefficients are calculated which depend on the wave shapes. The wavefront and the wave chopping are analysed, assuming an infinitely long tail and treating the tested device as a capacitance. The wavetail is analysed assuming the infinitely steep front. The tested device is then replaced by an inductance View full abstract»

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  • Charge transport in irradiated low-density polyethene

    Page(s): 727 - 730
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (518 KB)  

    A study has been made of the remanent effects of nuclear radiation on charge transport in additive-free low-density polyethene (LDPE) at 323 K. It was found that irradiation increased the conductivity of LDPE, with pure gamma radiation having a greater effect for a given absorbed dose than the mixed radiation of a thermal nuclear reactor. This increase in conductivity may be ascribed to an increase in trap density based on a trap-hopping conduction model. The measured current density also appears to be a function of Fn/n + 1, where F is the applied field and n a positive number. View full abstract»

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  • Charge storage on insulation surfaces in air under unidirectional impulse conditions

    Page(s): 731 - 740
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1369 KB)  

    In many insulation systems, overvoltages below the flashover level can give rise to discharges which produce free charge carriers. These charges may be deposited on insulation surfaces, resulting in a high surface field and consequent distortion of the normal field. This may result in increase, or decrease, in flashover voltage. Investigations were undertaken to examine the factors and mechanisms governing the production of surface. charge and the resulting field distortion. The experimental equipment consisted of a simple point-insulation-plane electrode assembly, mounted in a glass test cell filled with air, to which unidirectional impulse voltages were applied. Polycarbonate and polymethylmethacrylate samples were tested. Measurements of the discharge currents, residual surface field and resulting dust figure patterns were carried out. Under both positive and negative impulse voltages, discharge current pulses occurred resulting in high surface fields on the insulation sample. On the wavetail of the applied impulse discharge, currents occurred in a reverse direction to those originally produced by the applied impulse. With repeated impulses, the stored surface charge produced by one impulse significantly affected the discharge activity of the following impulse. Under flashover conditions, a substantial surface field remained following the flashover. View full abstract»

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  • Numerical calculation of transients in electrical circuits containing elements with nonlinear eddy-current skin effect

    Page(s): 741 - 746
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (692 KB)  

    The paper is concerned with the solution of transients in electrical circuits containing elements which exhibit nonlinear eddy-current skin effect. In the proposed method, the circuit and field equations are solved simultaneously, adjustments are made for eddy-current distribution after each time step. View full abstract»

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  • A snapshot of the profile of a quality circle programme at the eighteenth month stage

    Page(s): 747 - 751
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (744 KB)  

    The paper outlines the findings of a case study carried out in a printed-circuit board manufacturer, as part of a development project on quality circles funded by the Manpower Services Commission. At the time of study, the circle programme had been operational for around 18 months, which is recognised as a critical phase for circles. The strengths and weaknesses of the circle programme are discussed. Among the main findings are that circles were introduced to develop the communication and problem solving skills of employees, these objectives have been achieved, however, the trivial nature of many circle projects has caused some circle members, nonmembers and managers to question the benefits; most of the circles are facing problems due to the movement of people between departments, and the company has adopted a `classical¿¿ circle concept and is pursuing it in an almost evangelical fashion which is strangling the development of some circles. View full abstract»

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  • The Thames Barrier

    Page(s): 752 - 760
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1699 KB)  

    An area of over 100 km2 of industrial and residential property was at increasing risk from flooding, including some 700,000 residents and the central section of the underground railway. Attention was drawn to this risk in a 1966 report by Sir Herman Bondi, and the GLC was empowered by the Thames Barrier Act of 1972 to construct a barrier at Woolwich Reach, 13 km downstream from London Bridge. The alternatives of a barrier and a barrage were examined, and the final design employs rising sector gates, providing four main navigation opening each of 61 m, and a further six of 31 m. Rotation of the gates is by radius arms, driven from hydraulic cylinders, with three 140 kW pump power packs on each of the principal piers. The site is provided with three independent sources of electric power, connected to the piers via duplicated access tunnels. For the construction there were three main and 20 other contractors, and site work began in 1975, erection of the gates in 1980, and the barrier was first completely closed in 1982. The projects passed through three stages: feasibility, detailed design and contract letting, and construction and commissioning. The project was controlled through monthly site meetings. Total cost escalated from £110 × 106 at 1973 prices to £440 × 106 on completion in 1984, which has to be set against the estimate of £5000 × 106 as the cost of a major flood disaster. View full abstract»

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