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Science, Measurement and Technology, IEE Proceedings -

Issue 3 • Date May 2001

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Displaying Results 1 - 8 of 8
  • Applications of describing functions to estimate the performance of nonlinear inductance

    Publication Year: 2001 , Page(s): 108 - 114
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    Passive filter design is traditionally considered to be very important for many power electronic circuits and power systems. It is is very critical in the design of these power electronic circuits and power systems to know how to obtain accurate corner frequencies. It is known that when the load is large, the inductance of an inductor is known to always change. This phenomenon is due to the fact that when the current load is high, the inductance always suffers from saturation or hysteresis. It is extremely difficult to estimate the actual value for the nonlinear inductance in large currents because the inductance is nonlinear. The paper investigates the saturation phenomenon for a nonlinear inductance. The describing function method can be used to linearise the nonlinear inductor and then estimate the inductance in large current situations. Hence, the corner frequency for the lowpass filter can also be calculated accurately. It is shown that, when the current is very large, the corner frequency drifts to a larger value in the low-pass filter. The drift value of the corner frequency can be easily calculated by the describing function. Simulation and experimental results verify this phenomenon. However, it should be stressed that the method used in the paper is restricted to low frequencies. The higher frequency effects are neglected throughout the paper View full abstract»

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  • Influence of polarisation on breakdown strength of polymeric composite dielectrics

    Publication Year: 2001 , Page(s): 125 - 128
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    The results of a study of electrical characteristics such as permittivity ε, loss factor tanδ and breakdown strength E b of new composite materials on the basis of polyvinylchloride filled with ferroelectric ceramic powder PZT are presented. It is shown that preliminary polarisation of composite materials by unipolar impulses of voltage enables the Eb of composites to be increased by a factor of 1.3-1.5 in comparison with nonpolarised composites. It is discovered that the value of the specific accumulated energy may be increased up to 105 J/m3. These composite materials can be used both for the electric field control in the insulation designs and for manufacture of capacitive stores of energy View full abstract»

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  • High voltage water treatment in recirculating systems

    Publication Year: 2001 , Page(s): 103 - 107
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    Water recirculation systems may require disinfection to reduce levels of bacteria that grow in the system. The levels often need to be maintained below maximum values specified by local or National government standards. Residual chemical disinfection methods are usually used to achieve this. An alternative method is to apply a high voltage to the water to reduce levels of bacteria in the recirculation stream. A theoretical model for the bacterial levels using this technique is presented. The model shows that a treatment device need not be highly effective in reducing bacteria levels in one pass. A lysing rate of 99% works as well as one of 100%. The most efficient system is one with a high recirculation flow rate rather than a high individual lysing rate. These ideas are validated by experimental testing on the bacteria E. coli using a point-of-use treatment device energised by a switch-mode power supply (SMPS). Levels of these bacteria in a closed-loop system were reduced by nearly 5 log within 15-20 min of operation. Also, the effectiveness of high voltage on the viability of Legionella was tested using a 50 Hz AC supply. In this case the high voltage exposure reduced the viability by 99.7%. Hence this high voltage treatment method may have applications in air conditioning systems View full abstract»

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  • Image-sequence motion estimation for the Dervish mine-clearance vehicle

    Publication Year: 2001 , Page(s): 89 - 94
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (864 KB)  

    The paper reports on the application of block matching with spatial transforms to image sequences of ground scenes taken from a moving camera. The motion is a general combination of rotation and translation. The use of spatial transforms with interpolation filtering to generate rotation reference templates and the hardware implementation, for use on a robot mine-clearance vehicle, are novel. It is shown that the emerging generation of single chip floating-point digital signal processors and CMOS image sensors are well suited to rapid prototyping of image sequence analysis, which has previously been the domain of expensive camera and custom VLSI hardware or cumbersome parallel machines View full abstract»

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  • Chaotic synchronisation in a four-coupled phase-locked loop system

    Publication Year: 2001 , Page(s): 115 - 120
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (764 KB)  

    The paper describes chaotic synchronisation, observed both experimentally and numerically, in a four-coupled phase-locked loop (PLL) system. The system consists of four PLLs and four couplers, constructed with four operational amplifiers. Each subsystem shows chaos and is described by a set of differential equations with seven degrees of freedom. When the synchronisation behaviour among these subsystems is observed, it is found that a subsystem easily synchronises with a subsystem positioned diagonally opposite, but hardly does so with adjacent subsystems. The on-off intermittency is observed for the difference between a couple of diagonally positioned subsystems. The chaotic transition of synchronised states in two diagonal pairs is investigated. From calculation of the local transverse Lyapunov exponent, it is considered that two hyperplanes exist in the phase space, and the phase point itinerates via the two planes View full abstract»

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  • Computational method in electrostatics based on Monte Carlo energy minimisation

    Publication Year: 2001 , Page(s): 121 - 124
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    A variational method is presented which uses the Monte Carlo technique to simulate the evolution of a distribution of discrete charges within a conductor towards an equilibrium configuration that is characterised by a minimum of electrostatic energy. Using this approach, the calculation of the capacitance of conductors of complex geometry is presented as a simple problem, as the proposed technique avoids the complex pre-calculations needed in other well known classical methods. The technique is also used to calculate other parameters of interest, such as the conductor polarisabilities and the calculation of the potential and field distributions from a discrete configuration of charge. The proposed method can be used to help students to develop a physical picture of how the charge distribution on a conductor surface is established. It represents a complement to the traditional numerical techniques in electrostatics for an approximate evaluation of fields and electrical parameters in problems that involve complex conducting shapes View full abstract»

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  • Analysis and modelling of structured wiring communication channels

    Publication Year: 2001 , Page(s): 129 - 136
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (724 KB)  

    The authors present equations for the calculation of the attenuation constant of both unshielded and shielded cables as a function of cable dimension, material parameters and frequency of operation. An analytical approach is given for calculating the return loss of a communication channel as a function of such parameters as impedance, length and propagation constant. A transmission-line matrix (TLM) method to assess the effects on attenuation and return loss of longitudinal variations along a structured wire cable is developed. Results are presented using both analytical and modelling approaches; these are validated against measurements View full abstract»

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  • Prediction of gaseous emissions from a chain grate stoker boiler using neural networks of ARX structure

    Publication Year: 2001 , Page(s): 95 - 102
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (800 KB)  

    The authors present the application of feedforward multi-layered perceptron networks as a simplistic means to model the gaseous emissions emanating from the combustion of lump coal on a chain-grate stoker-fired boiler. The resultant “black-box” models of the oxygen concentration, nitrogen oxides and carbon monoxide in the exhaust flue gas were able to represent the dynamics of the process and delivered accurate one-step-ahead predictions over a wide range of unseen data. This system identification approach is an alternative to the mathematical modelling of the physical process which, although lacking in model transparency and elegance, is able to produce accurate one-step-ahead predictions of the derivatives of combustion. This has been demonstrated not only with data sets that were obtained from the same series of experiments (which also demonstrated the repeatability of the model) but also for data with a temporal separation of almost eight months from the training data set View full abstract»

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