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Volume 147
Issue 5
IEE Proceedings - Science, Measurement and Technology
Volume 147, Issue 5, September 2000
Volumes & issues:
Volume 147, Issue 5
September 2000
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- Author(s): W.T. Kuang and A.S. Morris
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 5, p. 213 –218
- DOI: 10.1049/ip-smt:20000477
- Type: Article
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p.
213
–218
(6)
An integrated ultrasonic robot tracking system that combines both a time-of-flight (TOF) and a Doppler tracking system is introduced. As TOF and Doppler tracking systems both have advantages and limitations, better accuracy and resolution can be achieved in three-dimensional dynamic robot tracking by combining the two systems. In the paper, the working principles, structure and experimental results for the TOF, Doppler and the combined tracking system are described in detail. - Author(s): L. Vigon ; M.R. Saatchi ; J.E.W. Mayhew ; R. Fernandes
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 5, p. 219 –228
- DOI: 10.1049/ip-smt:20000475
- Type: Article
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p.
219
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The electrical dipoles of eyes change by eye movements and blinks, producing a signal known as an electrooculogram (EOG). A fraction of EOGs contaminate the electrical activity of the brain (electroencephalogram, EEG). Ocular artefact (OA) is a collective term used to represent EEG contaminating potentials caused by eye movements and blinks. A procedure for quantifying the effectiveness of an algorithm for removing OA from the EEG was devised. This enabled the similarity between the EEG waveforms before contamination by OA and the contaminated EEG waveforms following their processing by an OA removal method to be measured. Four methods for OA removal were included in the study: extended independent component analysis (ICA), joint approximation diagonalisation of eigenmatrices (JADE), principal component analysis (PCA) and EOG subtraction. The operation of JADE and ICA is subject to amplitude scaling and channel permutation. Procedures were incorporated to estimate the amplitude of the recovered EEG waveforms and to allocate them to the correct channels. It was demonstrated that the signal separation techniques of JADE and extended ICA were more effective than EOG subtraction and PCA for removing OA from the EEG. EOG subtraction was shown to cause attenuation of the recovered EEG waveforms. The effect of additive Gaussian noise on the performance of the four OA removal methods was also investigated. This indicated that the performance of the methods was unaffected by an additive Gaussian noise source, as long as the signal-to-noise ratio remained above 50. - Author(s): T.-P. Tsao and C.-H. Lin
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 5, p. 229 –236
- DOI: 10.1049/ip-smt:20000423
- Type: Article
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p.
229
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Usually, the effect of power system unbalance is based on the limitation of generator thermo-rating. According to this limitation the protection scheme for system unbalance is designed. However, the authors find that the long- term effects of power system unbalance may become a cause of fatigue damage on low-pressure (LP) turbine blades even though the system unbalance is still within the limitation of generator thermal rating. As a result, turbine blades are possibly unprotected by traditional system unbalance protection schemes. In particular, for the last three stages of blades that are made of AISI-403 material and with vibration modes closing to the double-frequency avoidance zone, the long-term cumulative corrosion fatigue life expenditure of blades may be relatively large due to the inevitable corrosive operating environment with NaCl. Therefore, the influence of power system unbalance on turbine blades might be essential and would not always be neglected. - Author(s): J.E. Dolan and H.R. Bolton
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 5, p. 237 –242
- DOI: 10.1049/ip-smt:20000447
- Type: Article
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p.
237
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Application of an axial magnetic field to ferrite-loaded coaxial lines used as pulse sharpening elements is found experimentally to reduce leading edge shock front rise-times to 100–200 ps. The paper presents a novel physical model for axially biased lines. The 3-D gyromagnetic magnetisation equations for the ferrite are coupled with TEM-mode transmission-line equations in the time domain. The role of induced radial and axial magnetic field components in the magnetisation and shock front propagation process is outlined. Predicted and experimental results are compared for lines using both MgMn and NiZn ferrite types. General characteristics of axially biased ferrite lines are explored using the model. - Author(s): N.L. Allen and J.C. Evans
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 5, p. 243 –248
- DOI: 10.1049/ip-smt:20000577
- Type: Article
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p.
243
–248
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An ‘early streamer emission’ (ESE) terminal, for lightning protection, stimulates a burst of streamers from its tip before producing streamers induced by the field of a downward leader, approaching from a thundercloud. It has been claimed to enhance the probability of attachment of a lightning channel to a protection system. Experiments are described in which the performance of a simulated ‘early streamer emission’ terminal has been characterised. A negative slow-front impulse voltage has been applied to a plane suspended over a vertical rod to simulate the rise of electric field at the tip of the rod, which would be caused by an approaching leader discharge from a cloud. A positive auxiliary voltage impulse, of profile 1/30 µs, of sufficient amplitude to produce corona, has been applied independently at the rod at controlled, variable times during the rise of the slow-front field. The effects of this pulse on the corona produced at the rod by the negative impulse at the plane, on the breakdown voltage of the gap, and on the times to breakdown have been recorded. The general conclusions drawn are that the auxiliary corona has insignificant effects on breakdown when it is applied during the streamer phase of the slow-front corona, but that it influences growth when applied after the leader has been initiated by the ambient field. - Author(s): Z.D. Wang ; P.A. Crossley ; K.J. Cornick ; D.H. Zhu
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 5, p. 249 –255
- DOI: 10.1049/ip-smt:20000558
- Type: Article
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p.
249
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In a power transformer, high levels of partial discharge activity may lead to an insulation failure. If a partial discharge (PD) could be detected and located before the insulation fails, the transformer could be repaired or replaced before any consumers connected to the transformer lose supply. A technique is described in the paper that can be used to locate a PD in a power transformer with a continuous disc type winding. The technique requires knowledge about the physical geometry and design parameters of the transformer and also information about the characteristics of how the pulse or pulses caused by the PD propagate through the winding. The latter is difficult to obtain and consequently numerous simulation studies with slightly different assumptions were necessary before the technique could be considered validated. This involved analysing the data available at the terminals when a PD occurred in the winding and trying to extract the features related to the PD location. An algorithm using feature template matching has been used to locate the PD source in a 110 kV continuous disc type winding. Experimental tests carried out on this type of winding were extremely important in verifying the validity of the PD location algorithm. Results indicate that a location accuracy of better than 5% of the winding length is normally achieved. - Author(s): A.J. Shields and I.J. Kemp
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 5, p. 256 –260
- DOI: 10.1049/ip-smt:20000448
- Type: Article
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p.
256
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The paper reports further results from an investigation into partial discharge degradation of mica – an important component of many insulation systems. Further to work investigating axial stressing, transverse partial discharges have been applied across the surface of two forms of mica: ruby-muscovite and amber-phlogopite. The partial discharges were generated under AC, both polarities of DC, and both polarities of impulse electrical stressing. Three gaseous atmospheres (air, nitrogen (N2) and sulphur hexafluoride (SF6)) have been utilised to obtain degradation mechanisms for most practical environments. A discharge degradation mechanism, based on the effects of particle bombardment and chemical by-product formation, is hypothesised. This hypothesis is consistent with the experimental results. - Author(s): R.S. Dhariwal ; J.-M. Torres ; M.P.Y. Desmulliez
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 5, p. 261 –265
- DOI: 10.1049/ip-smt:20000506
- Type: Article
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p.
261
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For efficient operation, micromotors and microactuators, such as those employed in microsystems, are required to operate with high electric fields at electrode separations of the order of micrometres. An apparatus was built to accurately measure the breakdown voltage for electrode spacings as low as 0.5 µm. Breakdown voltage measurements in air and nitrogen are presented and discussed for the gap range 0.5 to 15 µm. Energy dispersive analysis of X-rays (EDAX) confirms the transfer of material from cathode to anode and vice versa during the breakdown mechanism. The Paschen law has been confirmed not to be applicable at gap settings of less than 4 µm. The shape of the curve and the breakdown voltage values are found to be the same for different gases and different high pressures up to 4 µm separation. Below this value, an analytical explanation of the breakdown voltage based on quantum tunnelling of electrons is obtained in terms of electrical field enhancement at microprotrusions and the work function of the electrode material. - Author(s): C.J. Carpenter
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 5, p. 266 –267
- DOI: 10.1049/ip-smt:20000602
- Type: Article
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p.
266
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- Author(s): P.N. Murgatroyd
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 147, Issue 5, p. 267 –268
- DOI: 10.1049/ip-smt:20000666
- Type: Article
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p.
267
–268
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Combined time-of-flight and Doppler ultrasonic tracking system for better performance in robot tracking
Quantitative evaluation of techniques for ocular artefact filtering of EEG waveforms
Long term effect of power system unbalance on the corrosion fatigue life expenditure of low pressure turbine blades
Shock front development in ferrite-loaded coaxial lines with axial bias
New investigations of the ‘early streamer emission’ principle
Partial discharge location in power transformers
Degradation and breakdown of mica under partial discharge stressing: transverse discharges
Electric field breakdown at micrometre separations in air and nitrogen at atmospheric pressure
Comment: Interaction of a moving charge and toroidal coil
Reply: Interaction of a moving charge and toroidal coil
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