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Volume 136
Issue 4
IEE Proceedings A (Physical Science, Measurement and Instrumentation, Management and Education)
Volume 136, Issue 4, July 1989
Volume 136, Issue 4
July 1989
8-electrode capacitance system for two-component flow identification. Part 1: Tomographic flow imaging
- Author(s): C.G. Xie ; A. Plaskowski ; M.S. Beck
- Source: IEE Proceedings A (Physical Science, Measurement and Instrumentation, Management and Education), Volume 136, Issue 4, p. 173 –183
- DOI: 10.1049/ip-a-2.1989.0031
- Type: Article
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173
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An 8-electrode capacitance system for tomographic imaging of two-component flows has been designed based upon a 2-dimensional finite element model. Emphasis is made on the development of a linear back-projection image reconstruction algorithm. Some reconstructed images obtained using this algorithm are given. Limitations and possible future improvements of the system are discussed.
8-electrode capacitance system for two-component flow identification. Part 2: Flow regime identification
- Author(s): C.G. Xie ; A. Plaskowski ; M.S. Beck
- Source: IEE Proceedings A (Physical Science, Measurement and Instrumentation, Management and Education), Volume 136, Issue 4, p. 184 –190
- DOI: 10.1049/ip-a-2.1989.0032
- Type: Article
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p.
184
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Following the first paper on tomographic flow imaging, the authors describe a method for identifying the patterns of two-component flows using the same 8-electrode capacitance system, but using a simpler signal-processing system than that for tomographic reconstruction. The measured capacitance vector of an unknown flow is compared with the stored ‘fingerprint’ vectors of various known flow patterns, and, hence, the actual flow regime can be identified.
Several physical characteristics of impulse-corona discharge around conductors. Part 1: Streamer length and speed (discrete character of discharge)
- Author(s): C. Gary ; G. Drǎgan ; I. Lungu ; M. Colteanu
- Source: IEE Proceedings A (Physical Science, Measurement and Instrumentation, Management and Education), Volume 136, Issue 4, p. 191 –196
- DOI: 10.1049/ip-a-2.1989.0033
- Type: Article
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191
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Within the background of the technical and scientific co-operation between Electricité de France, the Polytechnical Institute of Bucharest and the Ministry of Electric Energy, Romania, the physical characteristics of impulse corona discharge around conductors have been investigated as well. A great number of experimental tests have been conducted to this purpose. The paper deals with several physical characteristics of corona discharge phenomena around conductors, such as streamer length, length dependence on time, streamer speed (i.e. speed variation with time) and the discharge discrete characteristic.
Several physical characteristics of impulse-corona discharge around conductors. Part 2: Onset voltage and delay time of corona discharge
- Author(s): C. Gary ; G. Drǎgan ; I. Lungu
- Source: IEE Proceedings A (Physical Science, Measurement and Instrumentation, Management and Education), Volume 136, Issue 4, p. 197 –201
- DOI: 10.1049/ip-a-2.1989.0034
- Type: Article
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197
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On the basis of the experimental tests conducted with the co-operation between Electricité de France and the Ministry of Electrical Energy, Polytechnical Institute of Bucharest, Rumania, the onset voltage and delay time of corona discharge around conductors was determined. The determination of these values has been investigated for single conductors (four types of conductors), as well as for bundled conductors (three types). The influence of the voltage impulse-wave type applied to conductors and of its polarity has also been dealt with. The paper outlines the onset impulse-corona voltage and the delay time as a function of the ratio between the applied voltage and its amplitude, or as a function of the square root of the slope. Computation relations have been also approached with regard to the onset voltage, and the delay time, respectively, of the impulse corona discharge around conductors.
Measurement of unipolar paced-evoked potentials
- Author(s): S. Gergely ; C. Walton ; A.P. Economides
- Source: IEE Proceedings A (Physical Science, Measurement and Instrumentation, Management and Education), Volume 136, Issue 4, p. 202 –206
- DOI: 10.1049/ip-a-2.1989.0035
- Type: Article
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202
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The development of intelligent and adaptive cardiac pacemakers is limited by the absence of a reliable measure of physiological state. Evidence exists to suggest that the required information may be obtained from the paced-evoked cardiac potentials. The most convenient way to measure these potentials, in clinical practice, is to use the existing single unipolar electrode for both stimulation and measurement. Owing to the electrochemistry of the electrode tissue system, an afterpotential exists across the electrodes following the stimulus. This is approximately two orders of magnitude larger than the potential to be measured. The system developed by the authors and described here cancels the after-potential in a novel, quasi-closed-loop, adaptive manner. The designs of the system and the electronic circuitry are described. Several sets of equipment have been constructed and used by the authors, and others, for the reliable measurement of the paced evoked cardiac potential.
Upper and lower bounds in eddy-current calculations
- Author(s): P. Hammond
- Source: IEE Proceedings A (Physical Science, Measurement and Instrumentation, Management and Education), Volume 136, Issue 4, p. 207 –216
- DOI: 10.1049/ip-a-2.1989.0036
- Type: Article
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207
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After reviewing the arguments for and against the existence of bounded solutions, the paper introduces a constrained variation which produces bounds for the electric and magnetic energies. It is shown that this principle has a geometrical foundation which can be used irrespective of the shape of the body in which the eddy-currents flow. The basis of the method encourages the expectation of economy in computation.
Hybrid finite-element method and boundary-element method using time-stepping for eddy-current calculation in axisymmetric problems
- Author(s): L. Pichon and A. Razek
- Source: IEE Proceedings A (Physical Science, Measurement and Instrumentation, Management and Education), Volume 136, Issue 4, p. 217 –222
- DOI: 10.1049/ip-a-2.1989.0037
- Type: Article
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217
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In the paper, the finite-element method and the boundary-element method are combined in cases of axisymmetric geometries. The basic equations are expressed in terms of the magnetic vector potential. The finite-element formulation is employed for the general diffusion equation in a bounded domain, while, in the exterior region, the boundary element method is developed for Laplace's equation from a single-layer potential formulation. The hybrid model is applied to eddy-current calculations for the case of an induction heating system. The method is compared with experimental results.
Approximate Fourier transform using square waves
- Author(s): R.D. Hughes and M.L. Heron
- Source: IEE Proceedings A (Physical Science, Measurement and Instrumentation, Management and Education), Volume 136, Issue 4, p. 223 –228
- DOI: 10.1049/ip-a-2.1989.0038
- Type: Article
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p.
223
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The technique of spectral analysis, by truncated approximations to the sine and cosine functions, is evaluated using a three-level approximation (−1, 0, +1), where the −1 and +1 sections are of equal length, and the length of the zero level is variable. An optimum ratio is found where the zero levels together cover 120° of the cycle length, to give the least amount of ringing, or leakage. The transform that converts the square-wave spectral estimates to the Fourier coefficients is evaluated. In applications where spectral estimates are required only for limited frequency bands, the technique is flexible and efficient. This analysis is also well suited to irregularly spaced samples, and for direct application to analogue signals.
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