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Science, Measurement and Technology, IEE Proceedings -

Issue 2 • Date Mar 2002

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Displaying Results 1 - 9 of 9
  • Method for RMS and power measurements based on the wavelet packet transform

    Page(s): 60 - 66
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (659 KB)  

    The study provides the theoretical basis for the use of the wavelet packet transform (WPT) method for RMS and power/energy measurements. The proposed method can simultaneously measure the distribution of RMS quantities and power with respect to individual frequency bands directly from the wavelet transform coefficients associated with the concurrent voltage-current pair. Their dependent quantities such as power factor and total harmonic band distortion can also be calculated. Uniform frequency bands result from the WPT decomposition of power system waveforms and can be used for identification of bands of harmonics. The frequency bands also retain both the time and frequency relationship of the original waveforms, which is one of the major benefits provided by this method. The method is evaluated by its application to both simulated and actual power system waveforms View full abstract»

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  • Evolution of near vertical incidence skywave communications and the Battle of Arnhem

    Page(s): 92 - 98
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1025 KB)  

    The use of near vertical incidence skywaves (NVIS) in battlefield communications is now commonplace. Though not referred to as such until recently, the propagation of HF radio waves over short distances without the intervention of the skip zone is a natural consequence of the use of appropriate frequencies plus transmitting and receiving antennas that favour high angles of radiation. It has occasionally been suggested that the first dedicated use of NVIS techniques took place during conflicts in the 1960s, whereas evidence exists of its use during the D-Day landings of June 1944. However, wartime documents have recently come to light which show that the British Army Operational Research Group carried out dedicated research into this method of short-range HF communication at least a year earlier and released its reports containing operational recommendations in 1943, prior to the Battle of Arnhem View full abstract»

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  • Characterisation of high-speed multiconductor interconnections

    Page(s): 85 - 91
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (665 KB)  

    The paper presents a method for the determination of the capacitance matrix needed in modelling and simulation of signal transmission in multiple coupled interconnecting lines. The method utilises capacitance measurements and thus one of its useful application areas is in the validation of numerous previously published algorithms based on various approximations to field equations, originally developed for the computation of capacitance matrices. The technique described is based on the active separation of the capacitance network, achieved through the use of a unity-gain amplifier. Thanks to the circuit configurations introduced with a unity-gain amplifier it is possible to make direct capacitance measurements in the multiconductor interconnecting structures. Measurement procedures are described and analysis of errors in measured quantities caused by the imperfections of measuring equipment is discussed. A sample of results obtained in measuring manufactured test structures is included for illustration of the method and measuring procedures View full abstract»

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  • Computation algorithms for efficient coupled electromagnetic-thermal device simulation

    Page(s): 67 - 72
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (661 KB)  

    Coupled electromagnetic thermal field problems using nonidentical finite-element meshes for the magnetic and thermal discretisation, as encountered for instance in the simulation of electromagnetic energy transducers such as motors and transformers, require the application of nonlinear iterative solution algorithms. The paper gives an overview of the commonly used weakly coupled block iterative Picard methods and relaxation techniques. Strongly coupled Newton methods, both with explicit and implicit Jacobian matrix computations are discussed. Local as well as global convergence issues are treated. In this respect, the use of an alternative continuation technique, the pseudotransient coupled algorithm, using transient calculations in the frequency domain by means of an envelope approach, is discussed. The performance of the algorithms is compared using representative benchmark problems with both moderate and strong interaction. This leads to indications and a choice table on how to select appropriate algorithms for these coupled problems View full abstract»

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  • High-frequency diffraction by a rectangular impedance cylinder on an impedance plane

    Page(s): 49 - 59
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (797 KB)  

    The scattering of a line source field by a rectangular impedance cylinder on an infinite impedance plane is studied. The diffraction problem is formulated into a modified Wiener-Hopf equation of the third kind and then solved approximately. The solution contains two infinite sets of constants, satisfying two infinite systems of linear algebraic equations. Numerical solutions of these systems are obtained for various values of the surface reactance, width and height of the rectangular cylinder, whereby the effects of these parameters on the diffraction phenomenon is studied. The results are compared with the corresponding physical optics solution and the agreement is very satisfactory View full abstract»

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  • Binocular-vision-based position sensor with PSDs and its application to mobile robot following

    Page(s): 79 - 84
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (644 KB)  

    A new binocular-vision-based position sensor with position sensitive devices (PSDs) is proposed. The features of the sensor are easy handling and fast processing, for detecting other travelling objects in a mobile robot system. The measurable range of angle in the lens-and-PSD sensor is restricted due to the image surface bulge of the lens. Thus, the proposed position sensor is controlled by stepping motors to face the light source in the prerunning car. The principle of the proposed position sensor is described and the characteristics of a trial sensor are discussed. Experimental results demonstrate the suitability of this position sensor for mobile robot systems View full abstract»

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  • Modelling partial discharge inception and extinction voltages of sheet samples of solid insulating materials using an artificial neural network

    Page(s): 73 - 78
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (657 KB)  

    This work attempts an estimation of partial discharge inception and extinction voltages (PDIV and PDEV) of sheet samples of solid dielectrics due to void inclusions of different sizes using an ANN. The effect of void dimensions and also the dielectric thickness of three common insulating materials, namely, Leatherite paper, polyethylene film and Perspex sheets on PDIVs and PDEVs are examined. Further, the effect of the permittivity of the insulating materials is also examined View full abstract»

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  • Organisational factors for success in new product development

    Page(s): 105 - 112
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (893 KB)  

    This paper describes an attempt to produce an evaluation taxonomy and framework to enable companies to assess their new product development (NPD) performance and the factors leading to success. This framework is based on a product's complexities (structural and functional) and related factors and commercial constraints. In particular, it looks at the management and organisational factors involved in NPD and how these may be enhanced to increase NPD success rates. An assessment tool and methodology (ATM) is described which evaluates a company's NPD activities and process performance. Significant findings relating to success in product development are shown from the initial results comparing successful product developments from a variety of companies. Also described are the results of a survey of company based NPD performance improvement approaches and the related NPD performance measurement systems and metrics being used. The results from the use of the ATM with Japanese companies within Japan are also included as a comparison View full abstract»

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  • Shaft encoder characterisation through analysis of the mean-squared errors in nonideal quantised systems

    Page(s): 99 - 104
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (669 KB)  

    Incremental shaft encoders with square outputs are characterised by quantisation of the sensed position and by additional errors caused by nonidealities in sensor construction that contribute to additional measurement error. Digital estimates of the velocity of a rotating mass are frequently calculated by the differentiation of successive quantised position estimates, derived from a digital sensor such as a shaft encoder. New formulae are presented for the associated mean-squared error. In particular, the combined influences of uniformly distributed noise, sinusoidal perturbations and quantisation error on a nominally constant rate system are treated in an analytical manner. Experimental data, obtained from encoder-based shaft velocity measurements, are utilised for sensor characterisation, using the theoretical models proposed. A 'figure-of-merit', defining the differential error caused by variations of transition locations from their nominal values over the circumference of the encoder, is obtained. It is shown that the influence of shaft velocity variation on the characterization process can be minimised by deriving the variation in the mean-squared velocity error due to the addition of a sinusoidal perturbation View full abstract»

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