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

Popular Articles (April 2015)

Includes the top 50 most frequently downloaded documents for this publication according to the most recent monthly usage statistics.
  • 1. Large-scale electrical energy storage

    Publication Year: 1980 , Page(s): 345 - 385
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (5801 KB)  

    The review has been prepared by staff of the CEGB who are actively studying different aspects of large-scale electrical energy storage. Some areas, such as pumped storage, have been studied in considerable depth, since this technique has been exploited commercially for many years in many parts of the world. Other topics, such as superconducting magnetic storage, are at a much less advanced stage of development and are still at the laboratory and paper study stage. The review starts by examining the role of storage on an electricity-supply system. At present, the major use is put to reducing the flexibility requirements on other plant, but in the future, load smoothing for use with those systems with a large nuclear component could be important. The benefits and limitations of storage in conjunction with renewable energy sources are also discussed. Turning to the technical possibilities, a description is given of the widely used pumped hydrostorage technique. Potential development such as the use of an underground lower reservoir are discussed. It is possible to store the compression energy of a gas turbine as compressed air in an underground cavern. A plant operating on this principle has been built at Huntorf in Germany, but it requires a premium fuel such as natural gas or distillate oil. The possibility of developments leading to a reduction or elimination of this fuel requirement are discussed. It is also possible to store hot water at a power station and re-use it in the steam cycle. This technique has had some practical use for many years and its advantages and disadvantages are discussed. Batteries have been used for storage for many years, but current types are generally too expensive for use for large scale electrical utility applications. The state of development is discussed of new types, which although primarily envisaged for use with electric vehicles, could be used in central stores. Flywheels are also being developed for use with electric vehicles an- their potential application to large-scale electrical energy storage is reviewed. Perhaps the most technically advanced storage technique would be to use a large superconducting magnet. The status of studies of this possibility is described. Finally, the relative advantages and disadvantages of the various technical possibilities are discussed. View full abstract»

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  • 2. Exchange-rate fluctuations and transaction exposure in the multinational corporation

    Publication Year: 1982 , Page(s): 261 - 264
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (526 KB)  

    Exchange-rate fluctuations can cause variations in the economic value of a firm conducting business in more than one currency. The paper examines the problem in a mean-variance framework. Strategies are derived for the preferred instrument of exchange-rate exposure management and the optimal degree of maintained exposure. View full abstract»

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  • 3. The story of IFF (Identification Friend or Foe)

    Publication Year: 1985 , Page(s): 435 - 437
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (333 KB)  

    At the beginning of the Second World War, the need for a system for identifying friendly aircraft became very apparent. The system which was developed was known as IFF: identification friend or foe. The development of IFF, from the beginning, and its various forms are described in the paper. The collaboration between the British and Americans later on in the war, to manufacture the Mark V sets, is also described. View full abstract»

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  • 4. Wind energy conversion¿an introduction

    Publication Year: 1983 , Page(s): 506 - 516
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2280 KB)  

    The global wind-energy resource is very large and widely distributed; and, within Europe, wind energy has the potential to provide an energy output equal to about three times the present electricity consumption. Although the wind is not very reliable as a source of power from day to day, it is a reliable source of energy year by year, and the main role for future wind-energy systems will be operating in parallel with electricity grid systems or, in remote locations, in parallel with diesel engines, so saving fuel. Systems integration studies indicate that existing utility grid systems could accept a contribution of about 20% from wind turbines, although, with changes to the future plant mix, the potential contribution is substantially greater: and similar percentage fuel savings are possible in remote locations with wind/diesel systems. Recent progress in the development of wind turbines is reviewed and the cost data now becoming available indicates that medium-sized machines, i.e. ? 20?40 m diameter and with power ratings in the range 50?500 kW, offer the most attractive economics for land-based applications in the near future, giving energy costs in the range 2.8?5.6 p/kWh, for a typical site where the annual average wind speed is 5.5 m/s (measured at the normal 10 m height); in windier locations energy costs will be lower. Corresponding capital costs for installed wind turbines are in the range ï¿¿750?1500/kW (with average outputs equal to about 30% of the rated). The UK, in common with some other countries, has a large offshore wind-energy potential, but, to be economically competitive, offshore systems will need to use multimegawatt wind turbines with diameters of 100 m and larger. Prototype machines in this size range already exist, but considerable further development is needed before the construction of large offshore wind turbine arrays can commence, although this is a realistic prospect for the 1990s. The economics of wind-energy conversion systems are alr- eady encouraging, and commercial applications already in evidence, most notably in the USA and Denmark where more than 2000 wind turbines with a total installed capacity in excess of 150 MW have been installed in the past two years. However, further operational experience is required to demonstrate that reliable operation can be sustained over periods of many years. As this experience is accumulated, and as the cost benefits associated with quantity production are achieved, the market for wind turbines can be expected to expand rapidly. View full abstract»

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  • 5. Solar cells

    Publication Year: 1980 , Page(s): 505 - 527
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3480 KB)  

    The history, state of the art and future prospects of the direct generation of electricity from sunlight are reviewed. Although expensive, photovoltaic solar cells have become progressively cheaper over the past five years and are already cost-effective for a wide range of low-power applications. The potential economic and social benefits of these devices are such that intensive and extensive efforts are being made to cut costs still further and encourage market growth. During the 1980s, silicon solar cell systems are expected to become cheaper to run than diesel generators. As a result, they are likely to be adopted for water pumping, irrigation and rural electrification, especially in developing countries. At a later stage, on-site photovoltaic generation may be used for houses, offices, hospitals, schools, shopping centres and factories. But a technological breakthrough to a highly-efficient thin-film cell is needed before photovoltaics can have any significant impact on the large-scale generation of electricity in industrialised countries. View full abstract»

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  • 6. Unified approach to problems in electromagnetism

    Publication Year: 1984 , Page(s): 55 - 61
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (723 KB)  

    The development of a structure linking the various potentials and field vectors of the electric and magnetic fields is presented. The approach shows that it is usually possible to find alternative formulations, for a given problem, in a relatively simple manner. These alternative formulations, when correctly chosen, pose problems in dual or complementary form such that bounded solutions are possible. Such properties are particularly attractive when numerical solutions are being considered. The proposed structure is general, incorporating both electrostatic and magnetostatic systems as well as time varying field quantities. View full abstract»

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  • 7. Prediction of surge propagation influenced by corona and skin effect

    Publication Year: 1983 , Page(s): 264 - 272
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1078 KB)  

    The propagation equations with transient parameters are the only time-domain equations able to represent, without approximations, the skin effect in the line and in the earth. These equations were completed with a nonlinear term taking into account a simplified model of the impulsive corona effect, based on previous laboratory studies. A computer program for numerical integration of the new equations, for a unifilar line with earth return, was developed, and some applications were carried out, for various wave shapes and earth conductivities, involving lightning overvoltage propagation. The calculated results from tests on a high-voltage transmission line are in good agreement with the measured values. This shows that the attenuation, as well as the distortion, of the propagated lightning waveshape can be predicted by means of calculation for a unifilar line with earth return. View full abstract»

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  • 8. Road lighting

    Publication Year: 1983 , Page(s): 420 - 441
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3963 KB)  

    Historically, the lighting of roads and streets was introduced to combat the crime rate. Although this is still a major consideration in justifying the installations of road lighting, the chief criterion now is the reduction of the night-time accident rate. Visual performance is considerably poorer at night than by day, particularly with respect to contrast sensitivity. Road lighting is, therefore, designed to maximise the contrast of objects on and near the road by producing as high a luminance of the road surface and surroundings as possible. Objects then generally appear as silhouettes against a bright background. The performance of a road-lighting installation depends on the lantern light distribution, the light source, the road-surface reflection characteristics and the installation geometry. It is possible to calculate the performance of the lighting in terms of road-surface luminance and uniformity and of glare. Direct measures of visibility have also been proposed. Design methods and standards/codes of practice to ensure a reasonable quality of road lighting vary considerably from one country to another. The British Standard is in course of revision, and some radical changes in design method may be adopted. A certain variation in performance of the resulting installations, however, is inevitable, principally because of the differences that exist in the reflection characteristics of road surfaces. Economic considerations mean that only two light sources are serious contenders for modern traffic-route lighting in the UK: low- and high-pressure sodium. Capital cost, luminous efficacy and life are key factors in costing road lighting. Finally, one form of road lighting that poses quite different problems is that for tunnels. The determination of adequate lighting by day has prompted a considerable amount of research. View full abstract»

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  • 9. Ocean thermal-energy conversion

    Publication Year: 1983
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1284 KB)  

    Ocean thermal-energy conversion (OTEC) is a novel `alternative¿ energy technology that has created much interest in a number of countries; namely, the USA, Japan, France, Sweden, Holland, India and, most recently, the UK. In particular, the first three of these have had programmes to develop the required technology. However, most interest has been centred in the USA, where the current hiatus in Federal funding provides a timely opportunity to assess progress. This paper offers a survey of the prevailing position there; outlining the outstanding technical and associated problems, and likely future developments. Non-US programmes are only mentioned to contrast them with the American position. At present, it does not appear that OTEC plants will be commercially viable on a widespread basis even in the tropics. This is particularly true of the larger plants (400 MWe, MWe = megawatts of electrical energy, the final output of a power station) towards which the American programme is ultimately geared. There does seem to be a strong possibility that small OTEC plants, around 40 MWe or less, can be commercial in certain circumstances. This would be possible when one or, preferably, more of the following conditions are met: (i) where a land-based rather than `at sea¿ plant is possible, (ii) where alternative energy supplies are at a premium, i.e. islands or regions without indigenous energy supplies, and (iii) where conditions are such that an OTEC plant could operate in conjunction with either or both an aquaculture or desalination plant. View full abstract»

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  • 10. Chernobyl ¿ ethical and environmental considerations

    Publication Year: 1987 , Page(s): 834 - 840
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1027 KB)  

    The paper summarises briefly the main facts of the Chernobyl incident, the reactions to it, and the consequences in terms of global atmospheric pollution. Meteorological conditions determined the pattern of fallout, which over the UK for Cs137 varied in the ratio 10: 4000 Bq/m2 (on grass). There has been poor understanding by the media and the public of the quantitative aspects, aggravated by the differing characteristics of the several radionuclides (15 are listed), and the recent use of SI units in the west (becquerel, gray, sievert), while USSR still uses the old units (curie, rad, rem). Very complete information on fallout in the British Isles was obtained from Bracknell's meteorological data and the atmospheric dispersion models operated at Imperial College. Within two weeks, the cloud had spread widely across the northern hemisphere to North America and Hong Kong, but none in the southern hemisphere. Transfer through food chains depended on the variety of circumstances: the monitoring programmes and control measures were found to be in need of improvement, as no criteria existed for the amounts that justify intervention in the supply of foodstuffs to the public. Long-term effects in the UK of the measured radiation from this incident, in terms of deaths per year attributed to cancer are statistically 125, but must be compared with 1200 due to natural radiation out of a total of 150000 cancer-related deaths, which, in turn, are about one quarter of all deaths. The genetic consequences are insignificant, compared with the effects of smoking, or becoming parents at an advanced age. The disaster has underlined the responsibilities of top management and of professional engineers, the need to promote a ?safety culture?, and the value of effective organisation, the international exchange of experience, and the role of the media in improving public information. In any nuclear emergency, there are now older engineers and scientists who are willing to volunteer their s- ervices, as exposure is of less consequence to them than it would be to younger staff. View full abstract»

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  • 11. Calculation of self and mutual impedances for coils on ferromagnetic cores

    Publication Year: 1988 , Page(s): 470 - 476
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (715 KB)  

    By means of integral transform techniques, the paper establishes a new set of self- and mutual-impedance formulas relating to coils on ferromagnetic cores of circular cross-section. If the core is straight and infinitely long, the formulas are expressed in terms of convergent integrals that may be evaluated numerically. In the case of closed cores, e.g. toroidal cores, the formulas formally reduce to convergent series that may be truncated according to the degree of accuracy required. The formulas follow directly from the solution of Maxwell's equations and therefore offer the ultimate in accuracy. View full abstract»

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  • 12. Properties and failure modes of incandescent tungsten filaments

    Publication Year: 1980 , Page(s): 134 - 141
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1364 KB)  

    The behaviour of doped tungsten filaments is discussed with particular reference to the life-controlling processes in incandescent lamps. Since lamp failure is a complex phenomenon depending on many conditions, it appears that there is no single mechanism of universal validity by which the finite life of the tungsten filaments can be explained satisfactorily in all cases. It is suggested that, in addition to the nonuniform evaporation of the filament owing to local defects, other mechanisms, like migration and growth of the potassium-filled bubbles within the wire, and grain-boundary sliding promoted by unfavourable grain shape, may also contribute to the failure of incandescent lamps. Presumably, on the basis of a better understanding of the doping effect and failure mechanisms, further improvements can be achieved in lamp quality by optimisation of bubble dispersion, grain structure and other life-influencing parameters. View full abstract»

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  • 13. Solar photovoltaic and wind power in Greece

    Publication Year: 1987 , Page(s): 457 - 463
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (724 KB)  

    The high energy cost for power supply to the Greek islands, as well as the favourable solar and wind conditions, led to the utilisation of these local energy sources for power generation. On the island of Kythnos, the first wind park of a capacity of 100 kW was installed as well as a 100 kWp solar photovoltaic plant with storage facility. Both plants are grid-connected for parallel operation with the existing diesel power station. Also, a stand-alone 50 kWp solar photovoltaic plant was installed in Aghia Roumeli, Crete, to supply the community. The experience gained from the design, installation and operation of the above projects led to the implementation of some demonstration projects, and to a five-year programme in solar and wind energy for power generation. Existing data and results from the islands favour a large-scale wind usage for oil saving. Small stand-alone PV plants for small systems are cost-effective. Hybrid solar and wind power systems for small islands are realisable. View full abstract»

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  • 14. The importance of design

    Publication Year: 1983 , Page(s): 224 - 232
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1910 KB)  

    Based on a lecture delivered to the IEE, the paper considers the broad nature of product design, its relationship with associated disciplines, the profiles of competence required by present-day designers and the design brief. Some examples of successful product design are given. View full abstract»

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  • 15. Tidal power

    Publication Year: 1987 , Page(s): 392 - 398
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (979 KB)  

    The principal tidal power sites around the world are summarised, showing that the UK is fortunate in having three major potential sites. The first use of tidal power for generating electricity was a small scheme near Bristol built 56 years ago. Since then, the 240 MW Rance barrage and the recent 20 MW pilot `Straflo¿¿ turbine installed at Annapolis Royal in the Bay of Fundy are the main schemes built to date. These were built `in the dry¿¿. For an inlet off the White Sea, North Russia, a small tidal power plant was prefabricated complete and towed into position in the early 1960s. This method is favoured for the Severn barrage. An alternative method of in-situ construction has been proposed recently for the River Mersey estuary. Alternative methods of operation are discussed and the economics of tidal power compared with thermal stations. These show that, in the UK, forecasts of coal prices have dominated this aspect. Overall, the tides could be a highly predictable and substantial source of renewable energy whose development involves proven technology. View full abstract»

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  • 16. Industrial, scientific, medical and domestic applications of microwaves

    Publication Year: 1983 , Page(s): 467 - 503
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (5353 KB)  

    A comprehensive, critical review of applications of microwaves in industry, science, medicine and consumer services is given. A concise description of basic physical principles utilised in industrial, scientific, medical and domestic (ISM & D) applications of microwaves precedes an outline of characteristics of building blocks of circuitry employed. Numerous high-power and low-power applications are described. Potential health hazards, standards and safety considerations for these applications are also assessed. View full abstract»

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  • 17. The Thames Barrier

    Publication Year: 1987 , 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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  • 18. Dielectric heating in industry application of radio frequency and microwaves

    Publication Year: 1981 , Page(s): 583 - 588
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (867 KB)  

    Heat is generated in a variety of dielectric or electrical insulating materials when subjected to radio and microwave frequencies. This phenomenon has been successfully exploited for over 40 years by industry in a wide range of applications. Radio frequency (RF) is used for about 90% of all dielectric heating applications, but the more recent development of microwave heating is becoming well established. The place of RF and microwaves in the electromagnetic spectrum and the effects of different frequencies on materials is discussed. Brief details of the various techniques of applying the RF or microwave energy to materials are given. Finally, some typical applications such as welding, baking drying and preheating are discussed. View full abstract»

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  • 19. Vertical-axis wind turbine development in Canada

    Publication Year: 1983 , Page(s): 555 - 561
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (864 KB)  

    Recent Canadian progress in the development of the curved-blade Darrieus vertical-axis wind turbine (VAWT) is described. Co-operation between government, industry and power utilities in the conduct of field trials, over several years, has demonstrated inproved performance and reliability of grid-coupled turbines of this type. The rated power of the VAWTs currently under test ranges from 30kW, in a wind/diesel powerplant, to 230 kW, in an installation on an island in the Gulf of St. Lawrence. Progress has also been made in understaning the basic aerodynamic behaviour of the VAWT and theoretical methods for performance and load prediction have correspondingly improved. A brief description is given of `Project EOLE¿¿, a co-operative project between the federal government and the utility Hydro-Quebec to develop and test, during the next two to three years, a 4 MW VAWT prototype, which will be coupled to the power grid at a location on the south shore of the St. Lawrence River. View full abstract»

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  • 20. Communications security: a survey of cryptography

    Publication Year: 1982 , Page(s): 357 - 376
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2583 KB)  

    Our society has become highly dependent on its modern communications systems, e.g. the radio, television, telephone, telex, facsimile, high-speed datalinks etc. A high proportion of the information disseminated over these communications circuits is confidential in nature. In these situations the communicants should take steps to conceal the content of a message from not only the casual listener but also the determined interceptor. There is little doubt that this problem of protecting and securing communications will continue to grow at an increasing rate over the coming years, not only in its traditional military role but also in the public and commercial domains. The paper considers the type of cryptographic systems available today. As well as discussing the mathematical and statistical requirements of such systems, it explores how, with careful design, most of these needs can be met while the complexity of the hardware implementation is kept to a minimum. View full abstract»

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  • 21. Whitney forms: a class of finite elements for three-dimensional computations in electromagnetism

    Publication Year: 1988 , Page(s): 493 - 500
    Cited by:  Papers (50)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (620 KB)  

    It has been recognised that numerical computations of magnetic fields by the finite-element method may require new types of elements, whose degrees of freedom are not field values at mesh nodes, but other field-related quantities like, e.g. circulations along edges of the mesh. A rationale for the use of these special `mixed' elements can be obtained if one expresses basic equations in terms of differential forms, instead of vector fields. The authors gives an elementary introduction to this point of view, presents Whitney forms (the mixed finite elements alluded to), and sketches two numerical methods (dual, in some sense), for eddy-current studies, based on these elements View full abstract»

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  • 22. Ocean thermal energy conversion ¿ past progress and future prospects

    Publication Year: 1987 , Page(s): 381 - 391
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1465 KB)  

    An overview is provided of the current status of ocean thermal energy conversion, together with an historical perspective and the progress anticipated in the next ten years. The problems yet to be resolved are briefly described, and the importance of providing risk assessments is stressed so that funding agencies may be persuaded of the commercial prospects for this base-load generating system consisting predominantly of existing technology. It is concluded that a limited market exists for island developing nations, with prospects for substantial growth as OTEC plant efficiency improves or as oil prices increase. View full abstract»

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  • 23. Importance of concepts of project management

    Publication Year: 1981 , Page(s): 142 - 144
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    Management of capital projects can be recognised at the levels of techniques, functions and concepts, each of which are dependent on the others. Concepts are very important but all too frequently neglected. In particular, the view of a project as an instrument of change encourages a wider understanding of the environment of a project. From this follows an emphasis on both the objectives and the criteria for success. It also permits a reappraisal of the essential need of proper bases for control. Management of technically varied projects can have a great deal of common ground. View full abstract»

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  • 24. Active noise control systems

    Publication Year: 1987 , Page(s): 525 - 546
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3015 KB)  

    A retrospective review of the development of active noise control systems is presented, arguing that the design of active noise control (ANC) systems should be considered from a control systems point of view. This approach provides a design methodology that accounts for the design parameters of the system which determine its performance, thereby producing an ANC system that reduces the problems associated with, and the limited practical success of, previous techniques. Based on this argument, the fundamental conditions required for cancellation are derived in terms of the power spectral densities of the primary and secondary waves. These conditions are in turn related to the geometry-related (incorporating the acoustic response of the propagation medium) and source-related parameters of the system. From these conditions, the control structures employed in current ANC systems are examined and compared with the reported applications. A method for the design of controllers for use in ANC systems with broadband compact noise sources suitable for implementation on digital signal processing devices is presented. Using this method, experimental results using differing controllers are illustrated and discussed for both synthetic and practical sources. Finally, current developments in ANC systems are summarised and areas for further work are suggested. View full abstract»

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  • 25. Large-scale project management

    Publication Year: 1982 , Page(s): 625 - 633
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1337 KB)  

    A forum on the total management of large-scale projects was organised within the Management & Design Division of the IEE,* with the objective of providing an interchange of ideas among engineers actively engaged in this field, at superior levels of responsibility. Part 1 of this record of the forum is a summary of the introductory address by Vice Admiral Sir Lindsay Bryson, who traced the history of project management in the defence procurement sphere, leading to the recent trend towards placing management responsibility with a prime contractor in industry, taking as an example the Sting Ray torpedo project. The participants in the forum comprised some thirty invited members from the fields of industry, research and development, the public sector, and the armed services. They were invited to discuss a number of problem areas, and their views and experience have been collated and summarised in Part 2. This is intended to serve as a primer and checklist to assist those who are required to engage in such projects. It is proposed to initiate a further study of how project experience may be recorded, and to develop a recommended code of practice. View full abstract»

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  • 26. Low-pressure sodium discharge lamps

    Publication Year: 1981 , Page(s): 397 - 414
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (4431 KB)  

    The review article deals with the low-pressure sodium lamp, which, since its very introduction, has been the most efficient light source available. The principle of this lamp is that light is generated as the result of an electric discharge with sodium as emitting material and an inert gas as a ?buffer gas?. The spectrum emitted by this lamp consists of the yellow sodium resonance lines of 589.0 and 589.6 nm wavelength. Before it was first introduced commercially in 1932 several difficulties had to be overcome. A glass for the discharge tube that was resistant to the highly reactive sodium had to be developed, the composition of the rare-gas filling had to ensure easy ignition of the lamp and the heat insulation had to ensure the wall temperature reached 260¿¿¿C so as to give the correct sodium vapour pressure. One of the developments of the lamp that took place before the 1960s was that the detachable vacuum jacket, meant for heat insulation, was replaced by a sealed-on evacuated tube. The glass of the discharge tube has also undergone many improvements, resulting in a longer life for the lamp. The introduction of an indium-oxide coating as an infra-red reflecting layer has increased the luminous efficacy of the lamp up to 180 lm/W. The electrodes of the lamp also have an influence on the performance of the lamp. Other important phenomena, such as the imprisonment of resonance radiation, sodium migration and sodium depletion, greatly influence the life of the lamp and its luminous efficacy. Several experimental and theoretical studies give further insight into these discharge processes. Continuing research and development effort will probably lead to an increased luminous efficacy of the low-pressure sodium lamp in the future and the introduction of lower wattage lamps. Recently, hybrid ballast has been introduced with lower ballast losses than the conventional leakage-reactance transformer; also better insulation of the bend of the U-shaped tube has been applied in- order to reduce the increase in lamp voltage that occurs during its life. The low-pressure sodium lamp finds application in street lighting, safety and security lighting. View full abstract»

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  • 27. Discharge simulation

    Publication Year: 1986 , Page(s): 217 - 240
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2531 KB)  

    In recent years there has been great interest in simulating theoretically the growth of an electrical discharge in a gaseous dielectric. The review is a general introduction to the subject of discharge simulation and summarises the advances that have been made in modern computational techniques which enable the growth of a discharge to be traced from its initiation until instantaneous currents of perhaps many amperes are attained. In the first place the general continuity equations which govern the growth of a discharge are set up together with the appropriate boundary conditions. The formal solutions to these equations are summarised for the case of uniform applied electric fields and low ionisation densities when the space-charge distortion of the fields is negligible. Simulation models are then developed which take into account space-charge distortion of the field and enable the axial and radial development of a discharge between plane parallel electrodes to be traced from its initiation until the transient glow regime in reached. A summary is also given of preliminary investigations into the modelling of discharge growth in nonuniform-field electrode geometries. Most of the simulation methods described assume that all charged particles come into instantaneous equilibrium with ionisation and transport coefficients determined by the local values of the ratio electric field/gas pressure. In the later stages of discharge growth and near electrode surfaces this assumption is no longer valid, and possible models for following ionisation growth in nonequilibrium regions such as the cathode-fall are discussed and compared with corresponding Monte-Carlo and Boltzmann methods. View full abstract»

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  • 28. The economics of innovation

    Publication Year: 1985 , Page(s): 213 - 221
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1480 KB)  

    There are many different kinds of technical innovations, but one of the most important distinctions is between incremental improvements to an existing range of products and processes and the revolutionary transformations brought about by entirely new technologies and production systems. Such deep-going transformations justify the expression `change of paradigm¿¿ because they affect almost all branches of the economy to some extent. Examples of such paradigm changes are the introduction of electric power a century ago and the present revolution based on microelectronics. Each gave rise to a range of new products and changed the production system in many other industries. This paper makes some comparisons between these two technical revolutions and the social and economic changes which they engendered. On the basis of Schumpeter's theory of long cycles in economic development, it argues that a critical factor in each of these transformations was the adaptation of the institutional and educational framework in the leading industrial countries, to take advantage of the enormous productivity potential of the new technology. Today, as was also the case a century ago, there is some danger of Britain failing to make the necessary institutional changes in time to avoid further erosion of her position in world trade and economic performance. View full abstract»

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  • 29. Computation of the electric field at a solid/gas interface in the presence of surface and volume charges

    Publication Year: 1986 , Page(s): 577 - 586
    Cited by:  Papers (5)
    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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  • 30. DC conductivity of voltalit epoxy spacers in SF6

    Publication Year: 1985 , Page(s): 450 - 454
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (407 KB)  

    In order to determine the stremes in high voltage DC cable accessering containing a combination of Voltalit (a proprietary epoxy Insulation), SF4 and paper/oil inxulation, a knowledge of the surface and bulk conductivily of the Voltalit is required. It ii also necessary to determine the coefficient govering the dependence of both conductivities with temperature and stress, and the variation of conductivities with time after the application of a itep function of direct voltage. Although the bulk conductity of Voltalit has been determined previously, the surface conductlvity In an environment of SF6 it not available. The time dependence of both bulk and surface conductvities after the application of a direct voltage are also unknown. Measurements are made over the range of stress and temprature expected in cable accessories, and equations relating both bulk and surface conductivities with stress and temperature determined. The variation of conductiviiy with time after the application of a step voltage is also presented View full abstract»

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  • 31. Electronic aids for blind persons: an interdisciplinary subject

    Publication Year: 1984 , Page(s): 559 - 576
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3744 KB)  

    Aids for the handicapped is an emotive subject; ?electronic aids for the blind? is highly emotive because of the innovation the field has seen over the past 20 years and the controversy over what is best for the user and what is appropriate as a manufactured technology. The subject is reviewed against this background, showing the advances in reading aids to have had a smoother and more successful passage than has been experienced by the mobility aids. Many ideas which reached the stage of demonstration and even evaluation could not be covered because they were lost to posterity during the searching years of the 1970s, this following a productive period in the 1960s. Instead, emphasis has been placed on the history of those innovations which have survived to today and those which have yet to be fully tested by a critical field. It is seen that the very rapid advance in electronic and computer technology has been quickly adapted to the problem of nonvisual reading ink print and computer output data. There are some very fine, highly innovative aids now available to the field of blindness. By comparison, mobility, or more generally spatial perception which is a prerequisite to mobility, has seen less benefit from the new technologies. The reasons are discussed and the opportunities for innovation highlighted; but little seems to be on the horizon, which leads one to beleive that a new technology is likely to be forthcoming which will enable the realisation of artificial vision, a concept which demanded much attention during the past decade. The less obvious approach of acoustic spatial perception with its fundamental limitations may instead survive longer. Above all, the blind will not be served unless engineers find a way to make reliable aids of low cost, yet capable of powerful information transfer to the remaining senses of the blind person. This is a tough yet highly rewarding field in which to test one's technological stamina. View full abstract»

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  • 32. Monitoring the technological environment

    Publication Year: 1986 , Page(s): 361 - 364
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (473 KB)  

    For both defensive and aggressive reasons, knowledge of technological developments is essential to the long-term competitive success and survival of a firm. Such knowledge is necessary both at strategic and operational levels within the firm. It is insufficient, particularly at the strategic level, for a firm to limit itself to knowledge of the technologies with which it is experienced and the cultures with which it is familiar. Technological threats increasingly come from rival technologies and countries wish which we share neither language nor tradition. The paper, based on research at the Technical Change Centre, suggests that there is still a great deal that British firms can do at all levels to improve their ability to monitor technical change. View full abstract»

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  • 33. 7Cs technique for project management

    Publication Year: 1981 , Page(s): 73 - 77
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (635 KB)  

    There are many techniques that enable a project manager to control either the cost or the progress of a project, but these techniques do not usually combine these two aspects and therefore a measure is seldom available of the cost-effectiveness of a project. The author reviews some current techniques and then develops a new simple graphical one which is easy to apply and which reveals clearly both the overall costeffectiveness of the work done in a project, and also any increase or decrease in such cost-effectiveness. A comparison can be made at any time against the baseline originally agreed and defined at the start of the project and, moreover, any agreed change in the overall amount of work within the programme is automatically reflected both in the baseline and in the measure of work done so far. View full abstract»

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  • 34. Technology and the human factor

    Publication Year: 1988 , Page(s): 309 - 312
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    Technologies are conceived in science, gestated in engineering and applied in industry under the influence of economics and politics. Automation, the application in industry of information technology (IT) and other forms of new technology replace what were previously known as craft skills by other forms of activity. The controversial question is whether this replacement need constitute deskilling; and a difficulty is that repetitive and seemingly unskilled tasks may contain an element of inspection. IT can contribute to the retraining of workers, but a difficult question is what proportion of the population can be retrained for information-based instead of manual work. Automation is neither the sole cause of unemployment nor the remedy for it View full abstract»

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  • 35. Magnesium oxide as a high-temperature insulant

    Publication Year: 1981 , Page(s): 159 - 164
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (702 KB)  

    Magnesium oxide is widely used as a high-temperature insulant in the form of compacted powder. The reasons for its selection, and the nature of electrical conduction in refractory oxides at high temperatures, are discussed. The literature dealing with conduction in single crystals is reviewed, and results of resistivity measurements on compressed powders are reported. These show the effects on powder resistivity of impurities, specific surface, and of adsorbed or bound water. At 1000¿¿C the resistivity of commercially available fused magnesia powders approaches that of high-purity single crystals. View full abstract»

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  • 36. Practical experience of a 50 kWp photovoltaic system supplying power to a dairy farm on Fota Island, Cork, Ireland

    Publication Year: 1987 , Page(s): 407 - 412
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (663 KB)  

    The Fotavoltaic Project is a 50 kWp photovoltaic system used to supply electrical energy to a 250-head dairy farm on Fota Island in Cork Harbour, Ireland. It is one of the fifteen pilot projects, ranging from 30¿¿300 kWp, which have been built throughout Europe under the auspices of the Solar Energy Research and Development Programme of the EEC. The dairy farm was selected because its energy demand has the same seasonal variation as the output of a solar generator. The system consists of a 50 kW solar generator, a 600 Ah lead-acid battery, three 10 kVA self-commutated inverters which supply the dairy farm loads and a 50 kVA line-commutated inverter which delivers excess energy to the utility grid. The system operates automatically and is controlled by a microcomputer, which, in addition, monitors and records data for analysis. A VAX 11/780 computer at the National Microelectronics Research Centre continually displays the system's operation on a graphics terminal using data transmitted from Fota via a telephone link. The system began operating in June 1983 and data recording began in January 1984. During the peak milking period between March and August 1984, the PV array generated 20.52 MWh, 4.643 MWh was supplied to the dairy farm and 9.676 MWh was supplied to the utility grid. The paper describes the design of the system, the practical experiences gained and improvements which have been implemented since the system was installed. View full abstract»

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  • 37. High-frequency losses in multiturn foil-wound air-cored inductors

    Publication Year: 1987 , Page(s): 31 - 36
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (658 KB)  

    The paper discusses a coupled-circuit model which can be used to calculate the effective resistance of a multilayer foil-wound inductor and describes a formal method of solution for the large set of describing equations. Alternative methods of calculating the self and mutual inductances required in the model are compared, and it is shown that care is needed in calculating the mutual inductance between coaxial circular coils with slightly different diameters. Measured and computed results are presented for two examples of inductors for the frequency range of 20¿¿100 kHz which is normally encountered in switched-mode power supplies. It is shown that a simplified model, which assumes that the current distribution is the same in all layers, is inadequate, even for inductors where the winding buildup is small compared to the mean diameter. View full abstract»

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  • 38. The consultant's role in project management

    Publication Year: 1984 , Page(s): 420 - 422
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    One of the strengths of the consultancy industry is that it is project oriented, able to manage the growth and decay of project teams and the processing and dissemination of the large volume of information generated by all the participants. The paper describes the ways in which a project is distinct from an ongoing enterprise, the tasks of the project manager and the strains that a major project places on the resources within the owner's organisation. The paper identifies a number of parties to a project, both those directly and indirectly involved, and relates the capability of consultants to meet present-day circumstances. View full abstract»

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  • 39. Reliability prediction: a state-of-the-art review

    Publication Year: 1986 , Page(s): 202 - 216
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1882 KB)  

    The paper reviews the methods developed for predicting the reliability of systems, based upon design information, failure data on components, extrapolation from test data, and the use of mathematical models which relate predicted reliability to the various factors which can affect it, such as stress, application environments, quality and reliability programme activities. The fundamental limitations inherent in reliability prediction and modelling, related to logical, physical and human factors aspects, are described. The paper concludes with approaches that should be adopted to ensure that reliability predictions are realistic and credible, taking full account of physical and managerial factors involved in design, development and production. View full abstract»

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  • 40. Oboe: history and development

    Publication Year: 1985 , Page(s): 394 - 398
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (631 KB)  

    The paper describes the history and development of the Oboe bombing-guidance system, and its applications. Oboe is a ground-controlled system, and the ground based operators give instructions to the bomber crews. There are several different versions of the equipment, all operating on different wavebands. The paper gives the theory of the system, and the technique of its use in operation. The subsequent use of Oboe in Operation Trinity (a bombing raid on Brest Harbour in France) and the problems experienced (mainly due to interference from other navigational radar systems) are also described. View full abstract»

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  • 41. RF sampling gates: a brief review

    Publication Year: 1986 , Page(s): 45 - 49
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (714 KB)  

    The paper contains a brief review of the various techniques employed for the sampling of RF and microwave signals, and reference is made to subharmonic sampling as one of the possible applications. Particular attention is given to the two- and four-diode gate arrangements and the associated pulse strategies for fast switching time are discussed, as are the theoretical and practical aspects associated with the use of finite risetime sampling pulse trains. The design and operation of an experimental 10 GHz GaAs FET unit are given in detail, and recommendations are given in the concluding Section as regards development effort in sampling gates. View full abstract»

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  • 42. Xenon lamps

    Publication Year: 1980 , Page(s): 190 - 195
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (872 KB)  

    Xenon lamps are the most important discharge lamps, with a primarily continuous spectral energy distribution. It matches in the visible natural daylight very closely. The intense continuum of the xenon arc discharge is mainly generated by free electrons recombining to the densely packed excited energy levels of the xenon atom closely below the ionisation limit. Xenon lamp designs include aircooled short-arc, air and watercooled long-arc types for continuous operation as well as flashtubes and pulsed lamps, in a large variety of sizes, shapes and power ratings. Principal applications are for motion picture projection, amateur and professional photography, solar simulation for material testing, in the graphic arts industry, and for numerous technological and scientific purposes. View full abstract»

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  • 43. Contrasts in management styles-europe and the USA

    Publication Year: 1983 , Page(s): 288 - 291
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (572 KB)  

    The author of the paper, presented at a Savoy Place meeting of the Management and Design Division, received and presented on the 25th January 1983 at a joint divisional lecture with the Computing and Control Division, makes a detailed and discerning analysis of the factors implicit in `management style¿¿, with particular reference to his own experience in an international group of technological companies. Some 50 subsidiaries are each headed by a local national. The group applies world-wide ethical standards, and expects each manager at all levels to understand both his own culture in depth, and also the culture he may be moving into when joining a foreign affilicate. Rather than try to impose the management style of the parent company on foreign affiliates, it is far better to attempt to draw the greatest benefits from the unique style of each culture: some European examples of this are quoted. View full abstract»

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  • 44. Calculation of self and mutual impedances for coils on ferromagnetic cores

    Publication Year: 1988 , Page(s): 470 - 476
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    By means of integral transform techniques, the paper establishes a new set of self- and mutual-impedance formulas relating to coils on ferromagnetic cores of circular cross-section. If the core is straight and infinitely long, the formulas are expressed in terms of convergent integrals that may be evaluated numerically. In the case of closed cores, e.g. toroidal cores, the formulas formally reduce to convergent series that may be truncated according to the degree of accuracy required. The formulas follow directly from the solution of Maxwell's equations and therefore offer the ultimate in accuracy View full abstract»

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  • 45. Short-time-series spectral analysis of biomedical data

    Publication Year: 1982 , Page(s): 663 - 672
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1126 KB)  

    In the paper a review is given of modern parametric spectral analysis methods based on difference-equation models, in contrast with classical spectral analysis based on Fourier transform approaches. The algorithms discussed are based on an autoregressive structure as this leads to simple, efficient estimators. To provide fast algorithms, recursion in model order is introduced, while a lattice-filter structure can also assist in improving the speed of certain algorithms. The problem of spectral leakage is considered, with emphasis being given to algorithms which produce fine frequency resolutions with small bias. Recursion in time, which produces a sequential estimation, is described, and gives rise to a range of algorithms ranging from Kalman-filter-type methods to simple LMS algorithms due to Widrow. A wide range of examples is given based on simulated data and biomedical cases.These illustrate the problems caused by initial phase shift in a short time series, but also the considerable improvement in frequency resolution over the FFT approach. The use of parametric spectral analysis in tracking fine frequency fluctuations is illustrated with gastrointestinal electrical activity data. View full abstract»

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  • 46. Comparison between insulating properties of transformer oil and a low-flammability ester Midel 7131

    Publication Year: 1982 , Page(s): 182 - 185
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (619 KB)  

    The paper presents alternating and impulse breakdown voltages for paper, Nomex 410 and Nomex 411, impregnated with naphthenic transformer oil or Midel 7131. The samples contained an oil gap between a pair of coplanar rings, and the breakdown voltages are discussed in terms of the matching of liquid and impregnated tape permittivities which were also measured. The alternating breakdown voltages appear to depend on the degree of stress raising in the liquid gap, whereas the impulse voltages apparently do not. The measurements indicate that Midel could replace transformer oil to impregnate either Kraft paper or Nomex without detriment to alternating or impulse withstand voltages. Midel appears inferior to transformer oil in a large gap between spheres. Nomex gives a better AC performance than paper. The performance at elevated temperatures, AC discharge levels and insulation life were not investigated in this study. View full abstract»

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  • 47. Finite-element analysis for nonlinear magnetic field problems with complex current sources

    Publication Year: 1982 , Page(s): 391 - 395
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (735 KB)  

    The paper shows how the Newton-Raphson algorithm can be applied to the solution of nonlinear field problems in which the current sources and potentials are complex. The use of the method is illustrated with reference to the steady-state operation of a single-phase induction motor. Convergence is shown to be rapid, even under conditions of excessive saturation. View full abstract»

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  • 48. Electrostatic precipitators

    Publication Year: 1988 , Page(s): 347 - 361
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1436 KB)  

    The author gives a survey of the significant developments in the science of electrostatic precipitation since 1970, with special reference to electrical characteristics. The review specifically identifies the main physical processes that take place and the relevant fundamental equations and relationships. Reference is made to electric and current fields, voltage-current relationships, collection theories, particle resistivity, back corona, energisation and modern technological developments. Also included are a select number of papers that give good reviews of specific areas, or that in their own right make an original contribution to the science of electrostatic precipitation View full abstract»

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  • 49. Review of high-voltage gas breakdown and insulators in compressed gas

    Publication Year: 1981 , Page(s): 303 - 312
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1771 KB)  

    In the past ten years there have been significant advances in the theoretical and experimental analysis of high-voltage gas breakdown and surface flashover of insulators in compressed gases. This has probably been fostered by the recent growth in the design and application of gas-insulated high-voltage equipment. The review describes the characteristics of compressed-gas breakdown, including the effects of failure of Paschen's law; conditioning; electrode area; material and surface; breakdown-voltage distribution; particle contamination; voltage waveform; temperature; and gas mixtures. The insulator-flashover characteristics are then described, including the effects of insulator-electrode interface; insulator material; insulator shape; voltage waveform; charge generation; particle contamination; surface contamination; conditioning; flashover distribution; and dependence on type of gas. The various mechanisms proposed for gas breakdown and insulator flashover are reviewed and discussed in relation to the experimental characteristics. Future theoretical and experimental work is suggested to clarify the gas-breakdown and insulator-flashover mechanisms, and which would also help bring about the design of improved high-voltage gas-insulated systems. View full abstract»

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  • 50. Model of the formation of a dry band on an NaCl-polluted insulation

    Publication Year: 1986 , Page(s): 285 - 290
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (696 KB)  

    A model of the apperarance of a dry band on a flat insulator subjected to saline fog pollution has been experimentally and theoretically investigated with the following simple hypotheses: (a) the surface temparature of the insulator is uniform, (b) the mass of evaporated water is proportional to the temparature difference between the conducting pollution layer and the ambient atmosphere, (c) the product of electrical resistance into the residual mass of pollution remains constant at constant temparature, (d) a dry stripe appears when, after evaporation, the residual mass of pollution is lower than a critical threshold. After a theoretical evaluation of the different terms of the energy-balance equation, the temporal evolution of the current, of the mass of pollution and of the surface temparature, was numarically computed together with the delay for appearance of a dry band, the energy required and the average dissipated power. Qualitative and quantitative agreemet was found between the theoretical model and experimental data with a 0.23 ¿¿ 0.035 m2 plane insulator. A sheet blotting paper wetted by a NaCl solution simulated the pollution. This theoretical model predicts the time of formation of a dry band under conditions where formation is known to occur, not whether or not formation will occur. View full abstract»

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