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Volume 141
Issue 6
IEE Proceedings - Science, Measurement and Technology
Volume 141, Issue 6, November 1994
Volumes & issues:
Volume 141, Issue 6
November 1994
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- Author(s): P.N. Murgatroyd ; C.D. Pudney ; B.J. Donoghue
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 141, Issue 6, p. 429 –431
- DOI: 10.1049/ip-smt:19941375
- Type: Article
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p.
429
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Estimating the resistance of simple shapes provides an introduction to dual-bound variational methods. Imposition of equipotentials or current flow lines gives a physical understanding of the bounds. In developing a class of illustrative examples, some were found in which the bounds were reversed. This is due to approximation which in some cases is insufficiently precise; the range of validity has been explored. In two-dimensional current flow, new formulas for the bounds have been derived which do not reverse. - Author(s): B.W. Jervis ; M.R. Saatchi ; A. Lacey ; T. Roberts ; .M. Allen ; N.R. Hudson ; S. Oke ; M. Grimsley
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 141, Issue 6, p. 432 –440
- DOI: 10.1049/ip-smt:19941480
- Type: Article
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p.
432
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Two methods of identifying schizophrenia, Parkinson's disease (PD), and Huntington's disease (HD) are described. The methods are based on the analysis of the contingent negative variation (CNV), an event related potential (ERP) in the electroencephalogram. The first method involves spectrum analysis of the CNV and discriminant analysis of the Fourier harmonic frequency components. The other method involves the application of supervised learning artificial neural networks to the CNV features obtained in the time domain. Additionally, unsupervised artificial neural networks were used to presymptomatically assess the risk of HD. Sensitivities and specificities lie between 0.81 and 1.0 with low false positive rates (0 to 0.13) for differentiating between disease and normal data, and between disease data, dependent on disease and method. The preferred method for disease differentiation for accuracy and ease of application is the multilayer perceptron. Using Kohonen and ART networks for detecting abnormal CNVs in subjects at risk of HD (ARs) eight abnormals are identified in agreement with the prediction of risk derived from a published risk table. In addition, one of the abnormals has since developed symptomatic Huntington's disease. The recommended method is to combine the results of the Kohonen method with an ART2 and a modified ART1 network. - Author(s): D.A. Rickard ; H.S.B. Elayyan ; A. Haddad ; R.T. Waters
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 141, Issue 6, p. 441 –448
- DOI: 10.1049/ip-smt:19941341
- Type: Article
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p.
441
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Corona in a coaxial test cage is investigated by tests and simulation for combined alternating and direct voltage excitations. The results of a test program which varied the polarity, magnitude and ratio R of the peak alternating to peak total voltage are examined in detail. Data measured include current, power loss, charge transport and optical output from the corona. A quantitative treatment is given by implementing and adapting an existing alternating current corona model. The improved understanding allows inferences to be made relevant to the performance of full-scale hybrid systems in which alternating and direct voltage circuits are built in close proximity. - Author(s): M. Boutlendj and N.L. Allen
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 141, Issue 6, p. 449 –463
- DOI: 10.1049/ip-smt:19941313
- Type: Article
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449
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A survey is given of available data on the sparkover of air under various geometrical electrode arrangements. As positive switching impulses have been found to be the more severe stresses for external insulation, only the positive polarity is dealt with in detail; however, some data concerning the negative polarity in particular gap configurations have been included together with data for alternating voltages. Parameters affecting the dielectric strength of air insulation, such as gap geometry and spacing, radius of the conductor and the presence of surface protrusions, waveshape, voltage polarity and the effects of humidity and density, are surveyed. Finally, minimum clearances and gap factors for various electrode arrangements encountered in practice have been determined and compared with a recent IEC assessment method based upon data using the reference rod-plane airgap. - Author(s): T. Konefal and A.C. Marvin
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 141, Issue 6, p. 464 –470
- DOI: 10.1049/ip-smt:19941453
- Type: Article
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p.
464
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The coupling of radio frequency energy from a source of interference to a digital system via an interconnecting cable is described. The subsequent low level interaction of the threat energy with the digital system is explored using theoretical and numerical techniques. The analysis predicts the formation of intermodulation products within the system, using a quasilinear model. Verification of the analysis by measurement is presented. The techniques have application in ensuring electromagnetic compatibility of equipment at the design stage. - Author(s): C.M. Johnson and P.R. Palmer
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 141, Issue 6, p. 471 –480
- DOI: 10.1049/ip-smt:19941494
- Type: Article
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p.
471
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A novel approach to the construction and compensation of a coaxial resistive shunt is shown to produce significant improvements in performance when compared with equivalent shunts employing a conventional method of construction. A full theoretical treatment shows how the adopted measurement and compensation scheme provides a simple and realisable method for the elimination of skin effect errors in thin-walled shunts. These findings are employed in the design and construction of a current measurement system, rated at 5000 A with a 20 ns risetime, for use in a power semiconductor test rig. Experimental results concentrate on a comparison of the new shunt with an equivalent, conventional coaxial shunt and clearly demonstrate the improvements possible. The usable risetime and bandwidth are shown to be improved by an order of magnitude with excellent phase characteristics and a significant reduction in susceptibility to conducted and radiated interference. - Author(s): Y. Murooka ; T. Nakano ; Y. Takahashi ; T. Kawakami
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 141, Issue 6, p. 481 –485
- DOI: 10.1049/ip-smt:19941445
- Type: Article
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p.
481
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Both sensitivity and resolution of a Pockels field measuring system have been much improved by using a light-intensity-difference method with a modulated laser beam. Experimental results show an increase in sensitivity of over 200 times from that of the original field measuring system, and resolution, a ratio of signal to noise (S/N), is improved by more than 30 dB at an applied field strength of 200 V/cm. The minimum measurable field strength is 5.0 V/cm of AC field strength at the S/N ratio of 10.2 dB and 1.0 V/cm at the critical value of 0 dB, where the signal voltage equals the noise. Furthermore, it is found that by introducing a reflection-mirror technique, the field measuring system can be further simplified. - Author(s): S. Bouissou and F. Piriou
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 141, Issue 6, p. 486 –490
- DOI: 10.1049/ip-smt:19941177
- Type: Article
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p.
486
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The 3D numerical simulation of electromagnetic systems accounting for the electric circuit equation is studied for strand conductors. Two formulations in terms of potential (A and T0 Omega ) are compared and discussed. The finite element method is used to solve the magnetic equations with tetrahedral edge elements and tetrahedral nodal elements for, respectively, the A and T0 Omega formulation. As an example of application, an iron-core coil and a current transformer have been simulated. In the latter the numerical results are compared with the experimental results. - Author(s): R. Yacamini and H. Bronzeado
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 141, Issue 6, p. 491 –498
- DOI: 10.1049/ip-smt:19941450
- Type: Article
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p.
491
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The paper describes a method, using time domain analysis, in which the equations of mixed electrical and magnetic systems are solved not as separate but as a single system. The advantages of this method, from the viewpoint of a power system designer, are discussed and the inrush current is calculated for typical 5 kVA and 180 MVA transformers. From a transformer designer's viewpoint the distribution of fluxes within the transformer becomes more apparent so that the analysis of inrush and its implications can be carried out at the design stage. It is also shown how different parts of the transformer can be saturated to differing levels and how this can be incorporated into the analysis. - Author(s): D. O'Kelly
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 141, Issue 6, p. 499 –507
- DOI: 10.1049/ip-smt:19941077
- Type: Article
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p.
499
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The travelling wave excitation of semi-infinite and finite thickness steel plate is examined using a multilayer electrical circuit concentrated parameter analogue to represent the electromagnetic field equations. Normalised characteristics of surface impedance and power input for steel plate with finite resistivity and constant permeability show that the method gives reasonably accurate results. The method is their extended to represent magnetic material which includes both hysteresis and eddy current action using a digital simulation technique, previously described. Computed values of the fundamental surface impedance and power input are determined for magnetically semihard and hard materials. Field patterns inside the material are illustrated. Some experimental results on locked rotor machines validate the predicted values. - Author(s): S. Taylor ; G.R. Jones ; S.M. El Kholy
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 141, Issue 6, p. 508 –512
- DOI: 10.1049/ip-smt:19941339
- Type: Article
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p.
508
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Thermal reignition performance data for a two pressure SF6 model interrupter are presented with peak currents in the range 45-60 kA. Two different nozzle materials and two different test-circuit configurations have been used. The results show a strong correlation between a premature degradation in interrupter failure and the presence of tungsten particles produced from the upstream contact, and present in the contact gap during the current zero period. The relevance of these considerations to contact designs, commonly used in various high-voltage circuit. - Author(s): A. Bicknell ; J.S. Smith ; J. Lucas
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 141, Issue 6, p. 513 –520
- DOI: 10.1049/ip-smt:19941144
- Type: Article
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p.
513
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This paper describes the development of an arc voltage sensor for the measurement of the degree of penetration in tungsten-inert gas (TIG) welds. It is shown that the rate of change of the are voltage is directly related to the rate of movement of the weld pool surface. Weld penetration occurs when the surface of the weld pool falls. The sensor also detects the frequency of induced weld pool oscillations, which occur in one of two well defined modes according to the degree of penetration present. Spectral analysis of the voltage data, using the fast Fourier transform (FFT), provides a means of measuring weld bead size once full penetration has been detected. The sensor may be used to give closed loop computer control of bead size by varying the welding parameters. - Author(s): R.A. White ; J.S. Smith ; J. Lucas
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 141, Issue 6, p. 521 –526
- DOI: 10.1049/ip-smt:19941145
- Type: Article
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p.
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The development and application of an automated vision-based system for post weld inspection is discussed. The parameters of the weld bead profile have previously been measured manually using a variety of mechanical gauges. Such methods are slow, of dubious accuracy, and unsuited to online use. Here, structured light illumination, combined with fast, transputer based, image processing algorithms, provide weld profile metrology. A novel algorithm for analysing the laser stripe and finding the centre line of one pixel width is given. Speed is sufficient to provide online operation while accuracy is improved by a factor of ten. Results for butt and fillet welds are illustrated and an example of online operation provided. - Author(s): Z. Wu and L.E. Davis
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 141, Issue 6, p. 527 –530
- DOI: 10.1049/ip-smt:19941369
- Type: Article
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p.
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It is a common technique to use resonators to determine the surface resistance of high-temperature superconductors through the measurements of unloaded Q0 factor and resonant frequency. As the surface resistance may change very significantly between the normal and superconducting states, the quality factor may also have a large variation between the two states. It is thus desirable to develop measurement techniques to deal with the possible large variation in Q0 values. Six methods are proposed in the paper for both one- and two-port coupled resonators. These techniques are suitable for a network-analyser-based automated system used for the determination of surface resistance of superconductors. Example measurements using these techniques are also given. - Author(s): A. Hosseini-Sianaki ; W.A. Bullough ; R.C. Tozer ; M. Whittle ; J. Makin
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 141, Issue 6, p. 531 –537
- DOI: 10.1049/ip-smt:19941340
- Type: Article
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p.
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An understanding of the mechanical, thermal and electrical response characteristics of electrorheological (ER) fluids is vital to the design of any machine based on them. If the full potential of this original mechatronic medium is to be utilised, all will be included in steady and time domain-interactive optimisations of the particular application/process aim. The paper deals with the electrical modelling of ER fluids in the shear mode and presents the results of experimental tests conducted under true engineering conditions. In particular, the effects of the electrode separation and surface area are investigated for a range of shear rates and field magnitudes and a study of the effect of fluid temperature is reported. It is shown that controller capacitance typically does not vary significantly with the field strength, the shear rate or the temperature applied, but increases with increasing electrode surface area and reduces with increasing interelectrode spacing. The electrical resistance of a controller, however, although showing no reliable dependency on shear rate, reduces with increasing field strength, temperature and electrode surface area and increases with increasing interelectrode gap. - Author(s): F.C. Smith ; B. Chambers ; J.C. Bennett
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 141, Issue 6, p. 538 –546
- DOI: 10.1049/ip-smt:19941154
- Type: Article
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p.
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Although it is now some 50 years since the first practical application of radar absorbing materials (RAM), there does not seem to have been a comprehensive discussion in the literature of the optimum methodology for characterising such materials using free-space methods, the sources of error that arise in a typical laboratory measurement facility and, perhaps most important of all, an estimate of the measurement uncertainties. A previous paper started to address these problems by discussing calibration techniques for a vector network analyser system used for making complex reflectivity measurements on RAM. It is the aim of this paper to extend the discussion to include the use of a scalar measurement system (since these are still in common use), the factors affecting the design of a free-space reflectivity arch and the verification of measured reflectivity data. - Author(s): R.G. Kelly
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 141, Issue 6, p. 547 –556
- DOI: 10.1049/ip-smt:19941376
- Type: Article
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p.
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The careful specification of a structured design problem has promoted effective learning by facing students with the 'need to know' about subject matter that had failed to motivate them when taught by other methods. By partitioning the problem into subtasks and organising groups of students into design teams it has been possible for them to engage with a nontrivial system in the limited time available. Their understanding of concepts and techniques has thus been acquired in an applications context and general design skills have also been developed. The effectiveness of learning has been enhanced by the close integration of practical work with a variety of learning resources. There has been a marked improvement in students' interest and confidence, especially among those who were previously worried about the subject.
Reversal of bounds in some dual-bound resistance calculations
Artificial neural network and spectrum analysis methods for detecting brain diseases from the CNV response in the electroencephalogram
Corona space charge development for combined alternating and direct voltage excitation
Dielectric strength of air insulation for coordination of minimum clearances of overhead lines: a review
Prediction and measurement of EMC radiated immunity problems in interconnected digital electronic systems
Current measurement using compensated coaxial shunts
Modified Pockels sensor for electric-field measurements
Comparison between two formulations in terms of potential for the coupling of magnetic and electric circuit equations
Transformer inrush calculations using a coupled electromagnetic model
Travelling wave excitation of nonlinear magnetic materials of significant conductivity
Relationship between circuit-breaker performance and nozzle blocking, contact evaporation and particle production
Arc voltage sensor for monitoring of penetration in TIG welds
Vision-based gauge for online weld profile metrology
Automation-orientated techniques for quality-factor measurement: of high-Tc superconducting resonators
Experimental investigation into the electrical modeling of electrorheological fluids in the shear mode
Methodology for accurate free-space characterisation of radar absorbing materials
Microway: a structured design exercise for teaching microprocessor applications
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