By Topic

Science, Measurement and Technology, IEE Proceedings A

Issue 4 • Date Jul 1992

Filter Results

Displaying Results 1 - 10 of 10
  • Conditions for coalescence of multiple electric discharges

    Page(s): 210 - 212
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (156 KB)  

    Separate and coalesced electric discharges have been studied and the conditions for coalescence analysed. The discharges coalesce to operate at the minimum voltage, if this is not a minimum they will remain uncoalesced. The results are supportive evidence for Steenbeck's minimum potential principle. A model of a coalesced discharge is proposed and the principle conditions necessary for coalescence are given. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Criterion for the performance analysis of synchronous and asynchronous sampling instruments based on nonlinear processing

    Page(s): 141 - 152
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (756 KB)  

    The authors propose a criterion for the comparison of different sampling strategies (synchronous, asynchronous and random) and filtering algorithms used in digital instruments which provide the estimate of the time average of a signal processed with a nonlinear conversion of multiple inputs (e.g. wattmeters, RMS voltmeters, . . .). This criterion uses the Bayesian approach to incorporate, for every sampling strategy, any prior information on the influences of each incidental quantity which can vary the output of the instrument, transforming this output into a statistic. The asymptotic mean-squared error of the measurements has been assumed as an estimator of the error and its general expression, valid for the most common sampling strategies used in practice, has been deduced. This asymptotic error is a function of the frequency response of the digital filter used and, eventually, of the characteristic function of the probability distribution selected for the random variables generating the sampling instants. The particular formulae for different sampling strategies and filtering algorithms are discussed and compared. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Chronic disease management supported by informatics: example diabetes

    Page(s): 153 - 160
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    The management of chronic health care conditions already consumes more than half of all health care expenditure in developed countries. The author describes the investigations made by the Eurodiabeta Consortium with regard to diabetes, a life-long condition affecting more than 2% of the population. Partly funded by the European Community's Advanced Informatics in Medicine (AIM) framework programme, the Eurodiabeta Consortium comprised 16 complementary clinical, medical informatics and industrial partners, drawn from seven countries. Progress is reviewed and the opportunities and challenges ahead are explored. Other aspects covered are the Consortium's approach to the sensitive and crucial consideration of medical quality assurance, experience working with the European Commission, and the non-technological factors-social, economic and political-which must be addressed in the runup to bringing Eurodiabeta-type products into the market place. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electromagnetic field energy containment

    Page(s): 137 - 140
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    An electromagnetic virial relation in cylindrical geometry is derived which shows that limits on field energy containment imposed by the tensile strength of containment structures can be circumvented. The result is illustrated by two possible machines for which there is a much weakened theoretical virial constraint on the containment of field energy and which should be practically realisable with low dissipation. Not only do these machines represent potentially very useful high energy storage devices given development of appropriate technology, but also, one of them provides helpful insights into the dipolar rotating electric field model of ball lightning with confinement of electromagnetic field energy by atmospheric pressure. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Photoacoustic and photothermal deflection spectroscopy of semiconductors

    Page(s): 161 - 168
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    Photothermal techniques have been widely used for the determination of light absorption spectra of semiconductors, the main reason being the possibility of successfully measuring the weak absorption in the subgap region. The authors present and discuss the most relevant applications, particularly in the field of thin films of amorphous semiconductors. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Potential gradient measuring device based on a partial method

    Page(s): 174 - 178
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    The author presents a new method for measuring the potential above the remote-earth potential gradient of electric power plants. The advantage of the method is that there is no need for a galvanic connection between the measured item and the measuring device thereby avoiding any exposure to dangerous potentials that might otherwise be transferred from the measured item during the measurement. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Current shunts and resistors in use in NAMAS accredited laboratories

    Page(s): 179 - 181
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (188 KB)  

    Criteria are described for the design and construction of resistors and current shunts to be used in the measurement of direct and low frequency currents. Guidance is given on the methods of use, precautions necessary and sources of uncertainty. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electromagnetic theory without electric flux

    Page(s): 189 - 209
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1748 KB)  

    Whereas, to the physicist, the electric field in space is completely described by the field vector E, engineers commonly add the flux density, or displacement vector D as a separate quantity, and many regard the SI units as endorsing the need for two different vectors. The author examines the practical implications of a treatment which makes the concept of electric flux unnecessary, by concentrating attention of the charges. The electric field is defined as the potential, phi , and its gradient becomes an auxiliary function, thus reversing their customary roles. The distinction between what is meant by the terms 'electric' and 'magnetic' also changes. It is shown that this approach has advantages in electrostatic theory, clarifies the concept of potential datum, and gives an entirely different view of electromagnetic propagation. Energy radiation is described in terms of the behaviour of the charges instead of the fluxes and characterises most electromagnetic devices. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Influence of space charge on field emission of electrons from sharp edges

    Page(s): 169 - 173
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    A sharp-edged cathode and its adjacent anode are represented as a section of a pair of coaxial cylinders with an inner radius r0 and an outer radius r1. The field emission current density J is determined as a function of the anode voltage V1 and the cathode work function potential phi for degrees of space-charge that lead to a cathode field E in the range 0.9 E00, where E0 is the cathode field when there is no current flow. In the case where eV1<2 there is a particular value of J which is dependent on r0, r1, phi but independent of V1, for which space-charge effects have caused the current to be reduced to half of the emission current appropriate to the field E0. It is shown that this current is of particular significance to the experimenter when designing a field emission diode which uses a razor blade cathode. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Statistical process control in PCB manufacture: what are the lessons?

    Page(s): 182 - 188
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (588 KB)  

    A number of printed circuit board (PCB) manufacturers perceive that they face difficulties in the application of statistical process control (SPC). The difficulties include the product characteristics and process parameters to be measured and charted, the mix of different manufacturing technologies, the inherent variability of the chemistry used in the process, the interconnecting nature of the processes, small batch production runs, and the concept of performance-based charts. The authors report and examine the most common queries raised by representatives of the industry under the broad headings of: application, type of control chart and its design, interpretation and capability. View full abstract»

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