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Volume 145
Issue 2
IEE Proceedings - Science, Measurement and Technology
Volume 145, Issue 2, March 1998
Volumes & issues:
Volume 145, Issue 2
March 1998
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- Author(s): R. Blue ; P. Conlin ; D. Uttamchandani ; O. Farish
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 145, Issue 2, p. 45 –48
- DOI: 10.1049/ip-smt:19981817
- Type: Article
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p.
45
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Furfuraldehyde (FFA) is produced in transformer oil by the thermal degradation of the paper insulation utilised in power transformers. Measuring the concentration of FFA gives a reliable indication as to the condition of the paper insulation. The authors report on an optoelectronic instrument constructed for the determination of FFA concentration in oil at the site of the transformer. The instrument can measure 0.1 ppm of FFA in transformer oil. - Author(s): G.A. Lester ; J. Watts ; D. Wilmington
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 145, Issue 2, p. 49 –51
- DOI: 10.1049/ip-smt:19981831
- Type: Article
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p.
49
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Imaging and display systems that allow the user to obtain distance information and evaluate changes in the relative positions of objects are finding increasing numbers of applications, one area that is of increasing importance is that of stereoscopic endoscopy. Perception of depth through stereoscopic imaging has been shown to give significant improvements in the efficiency with which surgeons carry out operations. Current stereoendoscope systems utilise a two camera system combined with either dual lenses or a single lens plus image splitter system for image capture. A camera and display system is described that allows stereoscopic pairs of images to be obtained through a standard single lens endoscope using a novel electro-optic shutter combined with a standard CCD camera. The use of this ferroelectric liquid crystal shutter allows the optical path to be switched at video frame rates and offers the advantages of being lightweight, simple to drive and having no moving parts. The present system uses field sequential display of the two images combined with FELC shutter glasses to present the left and right images to the user's eyes, although ‘glasses free’ systems could be implemented directly in combination with this camera arrangement. - Author(s): J. Bayard ; E. Dargent ; J. Grenet
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 145, Issue 2, p. 53 –57
- DOI: 10.1049/ip-smt:19981811
- Type: Article
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p.
53
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The use of different models to interpret results obtained from thermally stimulated depolarisation current experiments (TSDC) is discussed. It is shown that the compensation temperature Tc introduced in the TSDC model (compensation law) and the fictive equilibrium temperature Tfi used to characterise the thermal model are identical. The discussion is illustrated by different measurements carried out on a polyethylene terephthalate (PET). - Author(s): D. Sprevak ; R.S. Ferguson ; A.J. Walton ; M.I. Newsam
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 145, Issue 2, p. 58 –60
- DOI: 10.1049/ip-smt:19981810
- Type: Article
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p.
58
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A procedure for selecting alternative sets of optimal parameters for an NMOS semiconductor device manufacturing process is presented. An optimisation strategy is discussed which leads to the calculation of process parameters for devices that attain the designed characteristics while having the process parameters set at their most desirable values. - Author(s): P. Sewell ; J.D. Turner ; M.P. Robinson ; D.W.P. Thomas ; T.M. Benson ; C. Christopoulos ; J.F. Dawson ; M.D. Ganley ; A.C. Marvin ; S.J. Porter
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 145, Issue 2, p. 61 –66
- DOI: 10.1049/ip-smt:19981832
- Type: Article
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p.
61
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The authors present a comparison between different estimates of the shielding effectiveness (SE) of cavities containing apertures and predictions made using a rigorous variational solution. Although the rigorous solution is computationally intensive, the method can be used as a standard against which more practical approximations, numerical methods and laboratory measurements can be compared. SE predictions from three methods are compared to the rigorous solution. These are: electromagnetic time domain modelling using the transmission line modelling (TLM) method, experimental measurements in a screened room, and an approximate solution based on the interaction of the lowest order waveguide mode and the aperture field. These comparisons of shielding effectiveness evaluations were made for a rectangular cavity with a range of aperture sizes and for frequencies in the range 200 MHz to 1.0 GHz. The results show that the measurements compare well with the rigorous solution, time domain simulations have a relatively long computation time and may still have noticeable discrepancies while the approximate solutions are computationally very efficient but may be significantly in error in particular for observation points close to the aperture. - Author(s): K. Hameyer ; R. Mertens ; U. Pahner ; R. Belmans
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 145, Issue 2, p. 67 –75
- DOI: 10.1049/ip-smt:19981469
- Type: Article
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67
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Useful energy conversion in electromagnetic energy transducers takes place only in the air gap. Numerical field computation techniques which have a range of general applications are used for the design and optimisation of these electromagnetic devices. To predict their operational behaviour, particular attention has to be paid to the computation of the air gap values of the flux densities and the magnetic field strength. Ongoing research on force computations in electromagnetic devices using different approaches indicates the importance of this field. A new method for the accurate computation of the field quantities and, thus, the generated forces in two- and three-dimensional finite-element models, is presented. Solving a local Dirichlet problem analytically enhances the accuracy of the derived field quantities using a numerically computed potential solution. Derivatives required for the values of the flux density are calculated analytically, in order to improve their order of convergence towards the exact solution. A Fourier series is used to represent the local field solution of two- and three-dimensional problems. The paper is focused on the practical application of the static electromagnetic field solution of the Laplace equation in a local post-process. Finite-element test models using standard first-order elements are applied to demonstrate the proposed method. Advantages and drawbacks are discussed. - Author(s): L. Satish
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 145, Issue 2, p. 77 –84
- DOI: 10.1049/ip-smt:19981576
- Type: Article
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p.
77
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A novel approach using the short-time Fourier transform and wavelet transform (time–frequency analysis tools) for fault detection during impulse testing of power transformers is described. The neutral and/or capacitively transferred currents which are recorded during an impulse test can be directly analysed with this approach. These currents are considered to be evolving in time, i.e. as nonstationary signals, especially when there is a fault. Results from simulation studies are presented wherein the fault condition is modelled as a fast decaying transient superposed on the neutral current. A comparison of the two transforms is made to assess their ability to detect as small a fault as possible and other implemenational issues. Advantages of these methods over the conventional transfer-function method are demonstrated, and it appears that the wavelet transform is better suited for this task.
Portable optoelectronic instrument for measuring furfuraldehyde in transformer oil
Single camera three-dimensional endoscope system using a ferroelectric liquid crystal device
Comparison of DSC and TSDC investigations: α relaxation in polymers
Optimisation of empirical model for IC fabrication process using linear programming
Comparison of analytic, numerical and approximate models for shielding effectiveness with measurement
New technique to enhance the accuracy of 2-D/3-D field quantities and forces obtained by standard finite-element solutions
Short-time Fourier and wavelet transforms for fault detection in power transformers during impulse tests
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