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IEE Proceedings A (Science, Measurement and Technology)

Volume 138, Issue 4, July 1991

Volumes & issues:

Volume 138, Issue 4

July 1991

Characterisation of high frequency focused ultrasonic transducers using modulation transfer function: concept and experimental approach
Sensors for narrow-gap welding
  • Author(s): B.J. Corlett ; J. Lucas ; J.S. Smith
  • Source: IEE Proceedings A (Science, Measurement and Technology), Volume 138, Issue 4, p. 213 –222
  • DOI:  10.1049/ip-a-3.1991.0030
  • Type: Article
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  • p. 213 –222 (10)
    Narrow-gap welding is an important technique for increasing productivity in the manufacture of thick-walled components. The nature of the process demands an automated approach and requires precise control to ensure consistently high weld quality. The work described in the paper gives the design, construction and development of appropriate sensors and sensing techniques for the control of the narrow-gap TIG welding (GTAW) process. Sensing systems based on arc-voltage sensing and direct vision sensing were developed and successfully tested on an experimental welding system. The arc-voltage sensing included the design of a digital technique for calculating the size of the voltage drop as the welding torch approaches a sidewall. The vision-based work involved the development of a very fast access framestore and highly optimised techniques for extracting the position of contrast features within a live image. The relative merits of arc-based and vision-based techniques are discussed.
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Wave packet with special relativity demonstrating quantum rules, Schrödinger's equation and propagator integral
  • Author(s): I.S. Reed
  • Source: IEE Proceedings A (Science, Measurement and Technology), Volume 138, Issue 4, p. 223 –236
  • DOI:  10.1049/ip-a-3.1991.0031
  • Type: Article
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  • p. 223 –236 (14)
    The physics of special relativity is applied to a wave-packet model of a particle without the usual de Broglie-like assumption of Planck's rule, E = hv. The velocity of the particle is equated to the group-velocity of the wave-packet to associate the particle with its wave-packet. With such an identification it is demonstrated using special relativity that the momentum four-vector, P = [p, E/c2] of the particle is parallel and proportional to a central wave-number four-vector, K0 = [k0. ω0/c2], of the particle's wave-packet. The constant of proportionality, relating these two four-vectors, has the dimension of action and by diffraction experiments it has the value h/2π where h is Planck's constant. This refinement of the de Broglie wave-like nature of a particle suggests that special relativity underlies quantum physics more deeply than heretofore believed. The above quantum rules are used to find the wave-packet function in the one-dimensional case of a non-relativistic free particle and a particle in a conservative force field of potential V (x). This wave-packet function is shown to satisfy an integral time-evolution equation which relates the wave function at time t0 to the function at a slightly later time t. The resulting integral equation is equivalent to the propagator equation or path-integral hypothesised by Feynman. This fact also demonstrates, using the method of Feynman, that the wave-packet function satisfies Schrödinger's partial differential equation. The wave-packet function of a particle in a force field is directly shown to satisfy a linear integral equation which relates the wave-packet at one instant of time to its values at all later times. The kernel or propagator of this integral equation is also equivalent to Feynman's path integral. A computation demonstrates that the position of a moving particle in a simple quadratic potential well does not become more uncertain with the passage of time. This contrasts with the behaviour of a moving free particle which as a function of time becomes more and more difficult to accurately locate.
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Microprocessor based automatic sun tracker
Thermal treatment of sewage sludge by ohmic heating
  • Author(s): A.B. Murphy ; K.J. Powell ; R. Morrow
  • Source: IEE Proceedings A (Science, Measurement and Technology), Volume 138, Issue 4, p. 242 –248
  • DOI:  10.1049/ip-a-3.1991.0033
  • Type: Article
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  • p. 242 –248 (7)
    Electrical conductivity measurements and heating trials have been performed on three representative samples of dewatered sewage sludge to assess the feasibility of heating sewage sludge ohmically to the temperatures required for pasteurisation or sterilisation. The very high viscosity of the sludge necessitated the use of a three-terminal cell, the properties of which are detailed, for conductivity measurements. The electrical conductivity of the sludge samples ranged from 0.2 to 0.6 S/m at room temperature, increasing approximately linearly to 0.8–2.3 S/m at 90°C. These values are well within the range of conductivities that are ideal for ohmic heating. It was demonstrated that sewage sludge could be ohmically heated from room temperature to boiling point rapidly, uniformly and at energy efficiencies greater than 98%. Impedance measurements showed that the efficiency of the process is a function of the applied voltage, improving as the voltage is increased. The ohmic heating process appears ideally suited to the thermal pasteurisation or sterilisation of sewage sludge.
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Response of horizontal axis eddy current coils to layered media: a theoretical and experimental study

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