By Topic

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

Popular Articles (October 2014)

Includes the top 50 most frequently downloaded documents for this publication according to the most recent monthly usage statistics.
  • 1. 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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 2. Chernobyl ¿ ethical and environmental considerations

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 3. Whitney forms: a class of finite elements for three-dimensional computations in electromagnetism

    Page(s): 493 - 500
    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 4. Tidal power

    Page(s): 392 - 398
    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 5. Large-scale electrical energy storage

    Page(s): 345 - 385
    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 6. Review of some recent advances in quantitative ultrasonic NDT

    Page(s): 265 - 274
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1472 KB)  

    Nondestructive testing is moving from being an art to a quantitative science. The paper first reviews the ultrasonic NDT literature; this is followed by consideration of the contribution which can be made to the understanding of analytically intractable wave-defect interaction problems by the use of numerical modelling based on explicit finite-difference schemes. Examples are presented of a developing family of ultrasonic NDT techniques which extract additional information from the wave field by combining time-of-flight and mode conversion information with ultrasonic spectroscopy. Immersion schemes, based on leaky Rayleigh waves for surface and near-surface defects are considered. These techniques are shown to extend the scope of ultrasonic NDT with improved reliability of detection and the potential to provide quantitative defect characterisations. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 7. Large-scale project management

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 8. Complementary variational formulation for eddy-current problems using the field variables E and H directly

    Page(s): 157 - 164
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1067 KB)  

    Complementary functionals, expressed in terms of either E and ¿¿ ¿¿ E or H and ¿¿ ¿¿ H, applying to linear eddy-current problems are given and are shown to be stationary subject to simple, and sometimes natural, boundary constraints. The analysis is carried through to a late stage before the pre-Maxwell zero-displacement current approximation is applied, in order not to obscure the principal results. The extension to a laminated media is considered. Representation of the quasistatic H-field in any current-free region of the problem by a scalar potential is allowable. The results are verified by perturbing the known `skin effect¿¿ quasi-static solution for parallel busbars. It is suggested how real eddy-current problems might be tackled by using the finite-element matrices for tetrahedral elements which have been derived by previous authors to apply to high-frequency problems and to the scalar Helmholtz equation. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 9. Calculation of self and mutual impedances for coils on ferromagnetic cores

    Page(s): 470 - 476
    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 10. The story of IFF (Identification Friend or Foe)

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 11. New considerations on the threshold of ventricular fibrillation for a.c.shocks at 50-60 Hz

    Page(s): 103 - 110
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (917 KB)  

    The most common cause of death in electric shock is thought to be ventricular fibrillation, a condition in which the circulation is arrested and death ensues very rapidly. A.C. shocks at 50-60 Hz are the most frequent cause of electrical accidents and therefore a careful analysis of available data must be the basis of protective measures. During the last few years valuable new results concerning the threshold of ventricular fibrillation have been obtained in experiments with animals, and progress in the field of physiology of the heart makes it possible to explain the influence of various parameters on the phenomena. For a given shock duration, the distribution of the threshold of current to produce ventricular fibrillation is log-normal. Probability limits for 05% and 50% for ventricular fibrillation are determined for shock durations from 8.3 ms to 5 s. When the 50% probabilities at different durations are examined a discontinuity is observed in the vicinity of the period of one heart cycle. This divides the threshold into two levels, a high level at durations shorter than one third of the period of the cardiac cycle and a level which is more than 20 times lower at shock durations longer than about six heart cycles. At the higher level, ventricular fibrillation only occurs if the shock falls within the vulnerable period of the cardiac cycle; at the lower level the initiation of ventricular fibrillation does not depend on the point of the cardiac cycle in which the shock starts. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 12. Electrical impedance imaging

    Page(s): 201 - 210
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1715 KB)  

    Electrical impedance imaging is introduced on a descriptive and historical basis. The physical situation to which it applies is identified, and its representation as mathematical equations is stated. Emphasis is made of the assumptions in the derivation and solution of the equations. Techniques for synthesising data are outlined and the practical problems of measuring data are covered. Methods of impedance imaging are reviewed and the quality of images they yield is discussed. Some medical applications for impedance imaging are given. Worthwhile approaches for further research are suggested. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 13. Wind energy conversion¿an introduction

    Page(s): 506 - 516
    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 14. Piezoelectric devices

    Page(s): 285 - 307
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3127 KB)  

    The history of the discovery of piezoelectricity and its application in practical devices is traced from the late 19th century. The origin of the piezoelectric effect is outlined in terms of the symmetry of the materials, and Tables are given in which the electroelastic properties are listed for single crystals, ferroelectric ceramics and polymers which show the phenomenon. The applications of both the direct and inverse piezoelectric effect are considered in devices operating at frequencies from DC to greater than 100 GHz. Particular attention is paid to signal processing using piezoelectric substrates for surface acoustic waves, and to the use of quartz in crystal-controlled oscillators, but the whole range of devices from low frequency transducers, through acoustic and ultrasonic devices to VHF filters is discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 15. 7Cs technique for project management

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 16. Microwave hyperthermia for cancer therapy

    Page(s): 493 - 522
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (4673 KB)  

    Owing to limitations of conventional therapeutic modalities (surgery, chemotherapy and radiotherapy) a renewed interest in cancer thermotherapy has resulted. Fundamental principles governing tissue absorption, guidelines for applicator selection and design and restrictions of each heating approach are discussed. The paper also focuses on recent innovative techniques utilising multiple applicators to achieve better heating uniformity within the safety and regulations guidelines. Current trends in the field of hyperthermia and future projections in equipment design are also presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 17. Electric field measurements in long gap discharge using pockels device

    Page(s): 139 - 146
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1572 KB)  

    The optical method using a Pockels device has been used to investigate an electric field distorted by space charges due to discharge development in air. A Pockels device placed in the discharge area has the advantage of directly measuring such a field. This method is successfully applied to the measurement of the electric field in and around the leader column propagating in a rod-plane gap of 1 m subjected to positive switching impulse voltage of 0.4 MV, and 1.03 MV in a rod-plane gap of 3 m. Moreover, in the 1 m gap system, the leader propagation is effectively controlled by using a conductive thread so that the leader column passes through the Pockels device and the exact electric field in the leader column is measured. The electric field at the device increases with the approach of the leader column and reaches its peak value on the arrival of the tip of the leader column. Finally, it falls to a low constant value during the leader propagation. From the results, it is found that the peak field at the tip of the leader column is 0.8 ~ 1.4 MV/m and that, subsequently, the low field in the leader column is 0.1 ~ 0.5 MV/m, notwithstanding the gap spacing of 1 ~ 3 m. Furthermore, the electric field calculated theoretically by using a space-charge model whose shape is a cylinder of 0.5 m in radius together with a hemisphere at the head of it agrees with the measured field. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 18. Solar cells

    Page(s): 505 - 527
    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 19. Motion of a conducting loop in a magnetic field

    Page(s): 217 - 222
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    The influence of Foucault losses on the motion of a conductor is investigated for the simple case of a small loop moving in the (primary) field of a magnetic dipole. Numerical data are given for the trajectory, the induced current and the magnetic force. Two types of motion are considered: a translation with assigned velocity ν0 and a translation governed by the sole action of the magnetic force View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 20. Electromagnetic suspension and levitation

    Page(s): 549 - 581
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (5289 KB)  

    The phenomenon of levitation has attracted attention from philosophers and scientists in the past. Recent advances, notably in power electronics and magnetic materials, have focused this attention within the last decade on the application of electromagnetic suspension and levitation techniques to advanced ground transportation. Regardless of the fact that there is, in effect, a separate technology involved for each electromagnetic method, the whole subject is given a blanket title of `maglev¿¿. There is also a very wide range of industrial applications to which magnetic suspension techniques could be profitably applied, particularly in the area of high-speed bearings to reduce noise and to eliminate friction, and yet it is only high-speed ground transportation that has caught the imagination of the media. The review deals with the physics and engineering aspects of the four principal contenders for advanced ground transportation and describes the most up to date developments in Germany, Japan, the USA and the UK in this field. The review also describes some of the very recent challenging developments in the application of electromagnetic suspension and levitation techniques to contactless hearings. A fairly comprehensive bibliography is given to enable the more interested reader to pursue the topic further in any one of the technologies dealt with in the paper. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 21. Practical experience of a 50 kWp photovoltaic system supplying power to a dairy farm on Fota Island, Cork, Ireland

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 22. Whitney forms: a class of finite elements for three-dimensional computations in electromagnetism

    Page(s): 493 - 500
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (911 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 cxpresses basic equations in terms of differential forms, instead of vector fields. The paper 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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 23. Advantage of incorporating geothermal energy into power-station cycles

    Page(s): 330 - 335
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (611 KB)  

    The generation of electricity from low-temperature geothermal sources has been hampered by the low conversion efficiencies of Rankine cycle operating below 150¿¿C. In the paper, the author shows how the electrical output derived from a geothermal borehole may be substantially improved on that expected from these cycles by incorporating the geothermal heat into a conventional steam-cycle power station to provide feedwater heating. This technique can yield thermal conversion efficiencies of 11% which, for a well-head temperature of 100¿¿C, is 50% greater than the output expected from a Rankine cycle. Coupled with the smaller capital costs involved, feedwater heating is thus a more attractive technique of converting heat into electricity. Although power stations above suitable geothermal resources would, ideally, have the geothermal heat incorporated from the design stage, experiments at Marchwood Power Station have shown that small existing sets can be modified to accept geothermal feedwater heating. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 24. Satellite-antenna measurement techniques

    Page(s): 417 - 434
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2995 KB)  

    Initially, the review takes a brief look at the various types of antenna systems that are used on satellites and shows that in terms of the measurement of their radiation characteristics, they can be categorised into two groups, i.e. low-gain (omnidirectional and quasi-omnidirectional) antennas, and medium- and high-gain antennas. With the first group, the main measurement difficulty lies with the suppression of multipath reflections, and the various range configurations that can be used to avoid or overcome this problem are described. Two of these are, for example, the ground reflection mode range and the use of baffles within an anechoic chamber. Following this, direct measurement ranges applicable to medium- and high-gain antennas are reviewed. These far-field approximation test range configurations include the elevated mode range, either in an outdoor environment or within an anechoic chamber, and the semi-open anechoic chamber. Subsequently, the review considers the various near-field and intermediate distance methods. Finally, some special techniques that have been devised to examine some particular satellite-antenna problems, such as the determination of the r.f. transparency of launch vehicle fairings and the effect of conductive thermal-control paint on satellite-reflector antennas, are presented. The review is principally from a European viewpoint. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 25. Road lighting

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 26. High-frequency losses in multiturn foil-wound air-cored inductors

    Page(s): 31 - 36
    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 27. Full-wave computed tomography. Part 4: Low-frequency electric current CT

    Page(s): 455 - 466
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1163 KB)  

    Imaging of 2-dimenslonal distributions of electric conductivity, from voltages measured on perlpheries of the distributions, is studied. It is understood that low-frequency electric currents are injected into the distributions. Optimum placement of electrodes, for maximising the value and sensitivity of voltage measurements, is studied theoretically and experimentally. The imaging theory developed suggests that arbitrary conductivity distributions cannot be unambiguosly reconstructed. Pieccwisc-constant distributions can be imaged successfully, however. Specimen images reconstructed from laboratory measurements, are presented of circularly symmetric conductivity distributions and of piecewise-constant disuibutions. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 28. Solar photovoltaic and wind power in Greece

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 29. Control and instrumentation of large nuclear power stations a review of future trends

    Page(s): 481 - 515
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (5899 KB)  

    The basic requirements of control and instrumentation (C & I) for large nuclear power stations are reviewed with special reference to the advanced gas-cooled reactor (AGR) and the pressurised water reactor (PWR), emphasising current developments and trends rather than established techniques. The extensive instrumentation, now provided for condition monitoring, particularly of the chemistry of both primary circuit coolant and the secondary steam and water circuits, is reviewed, and the way some of this instrumentation provides indication of failure of boiler tubes and fuel element cladding in AGRs is described. The power station is controlled automatically by a series of closed-loop controllers, and the current trend is discussed of employing direct digital control with redundancy, when it is justified to meet reliability requirements. However, the need for an effective operator interface is regarded as most important, and the current increased concern about ergonomics is identified, particularly in the design of the main control room, with a strong emphasis on formalised design procedures and reviews of existing designs. The increased use of computer-based techniques for control, protection, interlocks, alarm handling and display and data processing is discussed with special refer-ence to the use of colour visual-display units for data and alarm display. The special problems of high integrity applications, with the need for special design and validation of software, and the basic components of computer systems are described, and the current trend towards distributed systems and high-level user-orientated computer-programming languages is identified. Reliability aspects of C & I systems are discussed, including estimation, correlation with field experience and consideration of common mode effects. The need for evaluation and type testing and its cost are discussed and the results of such testing are reported. The overall structure of national and internati- nal C & I standards is described. The organisation and management of a C & I design group is discussed, and the requirements for a systems approach are identified with the use of a matrix structure in a multiproject environment. The rapid obsolescence of modern electronic equipment is discussed and the need for total life cycle support considerations to be incorporated in the design of both hardware and software is identified. An indication is given of current trends in instrumentation, computers and the improvement of operator interface systems. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 30. Ocean thermal-energy conversion

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 31. Automatic control of blood pressure by drug infusion

    Page(s): 639 - 645
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1231 KB)  

    Automatic control of arterial blood pressure by infusing the drug sodium nitroprusside is used for the treatment of elevated blood pressure after open-heart surgery at the Cardiac Surgical Intensive Care Unit of the University of Alabama Hospital. Controller design was based on investigations of the dynamics of the physiological responses of patients to nitroprusside infusion. A nonlinear PID digital controller has been used on over 1700 patients. Clinical experiences have shown that automatic control is safe and effective. The wide range of patient characteristics we have observed warranted the design of an improved controller.For analysis, design and evaluation, a model of the system related to arterial pressure and its response to nitro prusside was developed, and patient care practices were analysed. An adaptive multiple-mode multirate sampled-data controller was designed using model-based techniques, and was implemented with a microcomputer system. Simulation results were verified by experiments in the animal laboratory. Results from clinical evaluations with postsurgical patients were superior to the performance of previous automated infusion systems. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 32. Investigation into temperature variation of equivalent-circuit parameters of AT-cut quartz crystal resonators

    Page(s): 507 - 510
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    Despite the abundance of published information on the variation of resonant frequency with temperature of AT-cut quartz crystals, no work has been reported on the temperature variation of the equivalent-circuit elements. Measurements of the change in motional capacitance with temperature are reported in the paper. Results showed that motional capacitance increased linearly over the temperature range ¿¿ 10 to 70¿¿C. This increase was nearly three orders of magnitude greater than the change in crystal resonant frequency. Clearly, a corresponding decrease in motional inductance must occur to yield the observed frequency/temperature behaviour of AT-cut crystals. The apparent change in angle of cut which occurs with capacitive loading of a crystal was found to be a direct consequence of the large temperature coefficient of motional capacitance. Using this information it is now possible to calculate the apparent angle of cut for various load factors, and to predict the temperature behaviour of crystal oscillators more precisely. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 33. The sheffield respiration analysis system

    Page(s): 702 - 706
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (702 KB)  

    The paper describes a computerised system for analysing the respiration and the instantaneous heart rate from long-term recordings of respiration and ECG. The data are analysed as they are replayed at up to 64 times the real time. The respiratory signal is obtained using thoracic wall movement sensors or impendence pneumography. The factor used to quantitate the respiration is the breath-to-breath interval, which leads directly to the identification of respiratory pauses (or apnoea). The data are analysed in nonoverlapping time epochs of 1.7 min duration (real time). The system presents the results in two forms: firstly, a `trend plot¿¿ which is a summary of the results for the 1.7 minute epochs plotted against time, and, secondly, a numerical summary which allows comparisons to be made between subjects. The system is principally designed for use in investigations into the sudden infant death syndrome (cot death), but alteration of some of the `clinical¿¿ values contained in the system may make it a suitabl tool for other research. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 34. Analysis and design of protection systems for structures against direct lighting strokes. Part 1: Theory

    Page(s): 140 - 144
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (535 KB)  

    In the paper, a new method for the analysis and design of lightning protection systems for constructions and buildings against direct strokes is presented. while the theory of the method is discussed in the paper, its applications are presented in a companion paper with the same heading: `Part 2: Applications¿. The theory is based on the study of the critical field strength values in nonuniform fields, and its applications to an electromagnetics model of the lightning stroke. The main goal of the paper is to give the electrical engineer a tool for the determination of the parts of the structure and its vicinity, which are exposed to lightning strokes. The probability of strokes which may hit the structure is valuable information in the design of a reliable lightning protection system. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 35. Magnetoresistive transducers for the measurement of magnetic tape speed

    Page(s): 33 - 39
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (939 KB)  

    A method of employing space-periodic magnetoresistive transducers for the direct measurement of the speed of magnetic recording tape is described. The method is, in principle, similar to that devised for measuring strip speed in steel mills, using an inductive transducer. The wavelength-selective transducer is connected in a feedback configuration to an inductive write head placed upstream of the transducer, and the system records an ideally constant-wavelength pattern on the tape, so that the frequency of the transducer output is a direct measure of the tape speed. A digital variable delay line is used to compensate for slight variations in the recorded wavelength caused by variable phase delays encountered in the feedback loop. The error in the speed measurement is less than 0.1%. Three different experimental transducers are investigated, each of which is less than 2 mm long and utilises trackwidths of 100 ¿¿m or less. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 36. Design and operation perspective of a British UHV laboratory

    Page(s): 501 - 522
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (4017 KB)  

    The authors have, in the past, been directly involved in the design, planning and supervision of the construction, of a new ultra-high-voltage laboratory. The main purpose of the laboratory was to provide a major facility in the UK for the development of switchgear rated up to 765 kV and in the dielectric research required for such an undertaking. Following the opening of the laboratory in 1970, the author have in recent years been closely connected in the development of new ranges of open terminal and metalclad SF6 switchgear rated up to 525 kV and for fault currents up to 63 kA. These activities have been supported by extensive dielectric research studies, which have enabled the major factors influencing the insulation integrity of practical equipment to be determined. First, this paper outlines the criteria used in designing the laboratory and presents a critical appraisal of the facilities during the first 15 years of operation. Secondly, consideration is given to illustrating some significant laboratory activities. Examples are given of various switchgear and nonswitchgear components for systems ¿765 kV, which have been subjected to rigorous dielectric proving tests in the main test hall. The use of specific high-voltage test procedures (e.g. climatic, artificial rainfall, mixed voltage testing) are described, and important technical factors which have influenced the dielectric design of apparatus are considered. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 37. Relationship between various measurement techniques for void discharges

    Page(s): 593 - 606
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1303 KB)  

    The paper examines three insulation-measurement techniques, individual discharge measurements, conventional power frequency bridge techniques and the charge-transfer oscillogram; and shows the theoretical link between the results of each. The theoretical predictions are confirmed by experimental results on an artificial void model. This model demonstrates that, for a given voltage above discharge inception, two discharge states are possible. In practice, the void oscillates between the two states and noninteger values of average number of discharge per cycle are produced. A linear relationship between average number of discharges and voltage is observed. Consideration is given to the form of charge-transfer oscillograms, and the conductance and capacitance voltage curves, implied by an idealised trace growing in the specified manner, are given. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 38. Review of high-voltage gas breakdown and insulators in compressed gas

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 39. Misunderstanding nuclear power

    Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (907 KB)  

    Nuclear power has its proponents and opponents. The range of viewpoints of those opposing the increased use of nuclear power are examined, and comparisons are made with opposition to other industrial and technological innovations of the past. The advantages of nuclear fission as a source of power are discussed. Worldwide needs are for increased power, but fossil fuels and oil supplies are running down. The self interest and false assumptions of many objectors to the introduction of nuclear power are explained. The hazards associated with nuclear power stations are compared with other hazards already faced by the general public, and their possible effects are put into perspective. The problems of disposal of nuclear waste are also discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 40. Full-wave computed tomography. Part 2: Resolution limits

    Page(s): 616 - 622
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (851 KB)  

    Invoking our recently developed exact inverse theory, we derive limits on the resolution of individual spatial frequency components of a reconstructed image, set by imperfections of measurement. These are minimum limits, only achievable when one knows how to invert data without adulterating the underlying theory with strong assumptions (sweeping approximations are implicit in most practical inversion algorithms). Resolution limits on imaging with conservative fields are also derived, but (recognising the physical constraints on the formation of useful images) for situations simple enough that data inversion is easily effected without introducing approximations. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 41. Reliability prediction: a state-of-the-art review

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 42. A systems engineering approach to software development

    Page(s): 355 - 357
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    Sofware development benefits from an engineering approarh, because it has the same needs for keeping track of enhancements, modifications and standards. The progressive upgrading of software involves three factors: configuration control, host/satellite development, and development standards and methodologies. Configuration control is applied to developments that are useful additions to the kernel software, and permits variant projects to proceed in parallel with independence of bug fixing. Features of parallel development projects can also be merged into a single future system, which may yield a net saving of 50% in development activity. Formal review is a key control over quality in the enhancement of packages, and involves the whole project team. The engineering approach has been of benefit in relation to development costs, and also in the degree of customer support that can now be given. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 43. 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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 44. Importance of concepts of project management

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 45. Corona, breakdown and humidity in the rod-plane gap

    Page(s): 562 - 568
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (719 KB)  

    A survey is given of our knowledge of the effects of humidity on corona and breakdown when a positive impulse is applied to a rod-plane gap. It is shown that the minimum in the humidity correction factor Kh which exists, when the impulse wavefront is increased in the range 1 < Tcr < 1000 ¿s, is now substantiated by a number of experimental observations. The potential gradient for streamer propagation is discussed; its variation with humidity is similar to that of the breakdown condition with the lightning impulse (Tcr ~ 1 ¿S). The changes that occur for longer wavefronts are discussed in terms of the known facts relating to the increased probability of leader formation and propagation, as humidity increases. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 46. Dielectric heating in industry application of radio frequency and microwaves

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 47. Historical review of artificial light sources

    Page(s): 127 - 133
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1194 KB)  

    Simple oil lamps have been used for thousands of years, but the first major technical improvement was not made until the late eighteenth century. In the 1860s paraffin replaced the animal and vegetable oils used previously as lamp fuel. During the nineteenth century, gas and electric lighting developed together, the competition providing a stimulus to inventors in both fields. By about 1910 the tungsten filament lamp had become the preferred source of light for most applications, although discharge lighting was aheady available in primitive form. Since the 1930s filament lighting has been superseded by discharge or fluorescent lighting except in domestic use and a few specialised situations. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 48. Active noise control systems

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 49. Role of the consultant in offshore oil industry projects

    Page(s): 397 - 405
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1691 KB)  

    The complete process of evalution, planning, design, construction and installation of an offshore project is one of the most complex and demanding engineering tasks of modern times, utilising the combined skills of a wide range of engineering disciplines. With the growth of the offshore industry the consulting engineer has found himself increasingly involved in all aspects of offshore engineering, from the preparation of the initial feasibility studies to the provision of assistance in the operation of the completed facilities. The consulting engineer's primary role is to provide advice, based upon his knowledge of current and developing technology and the best available industrial practices, using an objective, unbiased approach. The expression of this advice frequently takes the form of a feasibility study for a complete new oilfield development scheme or for individual sections of the proposed production facility or offshore platform. When the project proceeds, the role of the consulting engineer may include preparation of the conceptual design, specification writing and detailed engineering design, tender preparation, evaluation and advice on selection of the contractor. The consultant may also be called upon to provide project management services, monitoring progress and costs and verifying performance against specification, during the detailed engineering and construction stages of the project, and to provide advice and assistance during commissioning. Other specialist services provided may include technical audits, hazard analysis and safety audits, environmental studies, survey and inspection services, quality assurance and certification and provision of training courses for the client's personnel. During the operating life of an offshore field, the consulting engineer may provide services to monitor the performance of production facilities, including equipment and structures, and provide advice on remedial work, expansion, repair and maintenance, and on - ny modifications which may be required as a result of changes in reservoir performance, changing economic conditions or new legislation. As the offshore oil industry finds it necessary to prospect for future oil and gas production in deeper waters and increasingly hostile environments, and as the larger offshore reservoirs are depleted and reserves become concentrated in smaller and commercially marginal fields, a high degree of technical innovation will be required to ensure the safe, reliable, environmentally acceptable and commercially viable offshore production of hydrocarbons. Participation in these highly complex and costly developments promises to expand the role of the consulting engineer, especially in such areas as research and development, including the preparation of studies and monitoring test programmes for industrial clients, and through joint industry and government-funded development studies. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 50. Vertical-axis wind turbine development in Canada

    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»

    Full text access may be available. Click article title to sign in or learn about subscription options.