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After a year-long battle with cancer, Maurice Beck has died in his seventy-first year. Those of us who knew Maurice will realize that he did not give in to the threat of cancer but fought to the very end. Knowing how fit he was until recently, and the healthy lifestyle he lived, it comes as a shock to realize that he is no longer with us.

After graduating with a first class degree in Electrical Engineering from Leeds University in 1950, he pursued postgraduate studies at Imperial College in London. The research was concerned with servomechanisms and the then new work on time series analysis strongly influenced his future career.

In 1952, he joined ICI as an instrument and electrical engineer. The Billingham plants at that time employed 20 000 people and processed many kinds of raw materials. Maurice designed and maintained complex electronic systems for use in the extremely hostile on-site environment. In 1963 he moved to Bradford University to set up a new course: `Automation in Chemical Engineering', and researched the problems concerning measurement and control for processes handling difficult fluids, an endemic problem in his previous job. This progressed into an extensive programme of work on cross-correlation flowmeters, and he was awarded his PhD in 1969, on the basis of this research. The textbook he wrote on the subject (in collaboration with Andrzej Plaskowski) is well known to a generation of students.

In 1980, he became one of the founding professors of the new Department of Instrumentation and Analytical Science at UMIST, and later became Head of Department. Here the research proceeded on a wider front, and in the mid-1980s he became interested in using tomographic techniques to image process vessels and pipelines in order to obtain detailed information for design, measurement and control of multiphase processes. The differences from medical tomography soon became clear. Low-cost, safe, fast and highly sensitive tomographic sensors were required, capable of sensing through a thick wall.

By 1989, a major effort was needed to develop process tomography to meet industrial needs. In that year Maurice Beck was awarded one of the few SERC Senior Fellowships enabling him to work full-time on the subject. A Process Tomography Unit was set up in the Department of Electrical Engineering and Electronics at UMIST. This led to the establishment of a UK Process Tomography Group in 1990\endcolumn and the foundation of a European Concerted Action in Process Tomography (ECAPT) in 1992. The UMIST group of four people in 1990 soon expanded to a total of 30. ECAPT represented the output of 130 workers from over 40 groups (including 13 industrial groups) in 10 countries.

After its foundation in 1990, the UMIST group rapidly became a world leader in electrical tomography, using resistive, capacitive and inductive fields. The special features of high speed, low cost and safety attracted great interest, manifested in the form of research funding from many sources.

Maurice was a prodigious worker and this is reflected in his published output of papers, books and edited conference proceedings. As Guest Editor, he was responsible for the well-received special issue on process tomography, which was published in this journal in March 1996. Although single-minded in his enthusiasm for process tomography, he was never selfish. He was always ready to discuss ideas and exchange information in a way that, in the current climate, would not sit comfortably with the would-be exploiters of IPR. Nevertheless, he had an acute sense of the industrial need for technology transfer and was instrumental in setting up a commercial company to produce electrical tomographic systems. Undoubtedly, some other workers were able to capitalize on ideas gained through Maurice, but he felt that the excursions of the `swings and roundabouts' benefited him as well. His overriding concern was that the subject should go forward and progress be made.

Nor did his huge enthusiasm for process tomography mean that he neglected other aspects of his life: home construction projects with his children, holidays in the caravan with his grandchildren; no one was left out. In later life, he took up jogging and in his 60s took part in four London Marathons. More the tortoise than the hare, he always completed the course.

Maurice was held in the highest esteem by his peers and was awarded many honours and distinctions by professional and national institutions. In the technical world, he will be remembered as the father of process tomography. To those of us who knew him well, he will be remembered as a kind, generous and thoughtful gentleman, whose warm spirit and gifted leadership made us all feel proud to have known him.

Roger Waterfall UMIST October 1999

Sponsored by the Assembly of World Conferences on Experimental Heat Transfer, Fluid Mechanics, and Thermodynamics

The Nusselt-Reynolds Prize has been established by the Assembly of World Conferences to commemorate the outstanding contributions by Wilhelm Nusselt and Osborne Reynolds as experimentalists, researchers, educators, and authors. As many as three prizes may be bestowed at every World Conference: one in each of the areas of heat transfer, fluid mechanics, thermodynamics, or any combination of these.

The prize shall be bestowed for outstanding scientific and engineering contributions and eminent achievements in the fields of: heat transfer, fluid mechanics, and thermodynamics through (1) experimental studies and analytical/numerical extension of the measurements; (2) development of experimental techniques, visualization techniques, and/or instrumentation; and/or (3) development of design theory (that needs experimental data) and theory-based experimental correlations. These contributions should yield a deeper insight into physical phenomena involved or should yield significant technological advances. In addition to research, the awardee(s) should have made outstanding contributions to the field through teaching, design, or a combination of such activities. The prize is based on achievement through publications or through the application of the science or art. Nationality, age, sex, and society membership shall not be considered when evaluating qualifications of candidates. A candidate must be living at the time of designation as a recipient of the prize.

The prize consists of a bronze plaque, an engrossed certificate, and an honorarium. The prize is administered by the Prize Board. The deadline for accepting nominations for the prize is 2 February 2000. The prize will be awarded at the Fifth World Conference held on 24-28 September 2001 in Thessaloniki, Greece, where the prize winners will also present plenary lectures on their subjects.

Nominators can obtain further information and download the nomination form from our webpage at www.thtlab.t.u-tokyo.ac.jp/N-Rprize.html

Professor Nobuhide Kasagi, Chairperson The Nusselt-Reynolds Prize Board Department of Mechanical Engineering, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan Tel: +81 3 5841 6417; Fax: +81 3 5800 6999

Television holography (TVH) can be defined as `the family of optical measurement techniques based on the electronic recording and processing of holograms'. Image-plane TVH was introduced in the early 1970s with the name `electronic speckle-pattern interferometry' (ESPI). Since then, TVH has undergone an impressive development and become one of the most promising optical techniques for non-destructive testing and industrial inspection. The aim of this review is to propose an original scheme for the systematic treatment of TVH and to review the existing techniques according to it. In this approach we split the measurement process into four highly independent stages (illumination and observation geometry, temporal treatment, secondary-correlogram generation and fringe-pattern analysis) and establish a common notation to formulate the corresponding techniques. Such a strategy allows the free combination of the techniques proposed for each stage as building blocks to obtain every particular variant of the whole TVH measurement process, whether it has already been reported or not, and also the incorporation of new techniques while retaining compatibility with the existing variants of the previous and following stages.

A plastic optical fibre reflectance sensor that makes full use of the critical angle of the fibres is implemented to monitor dew formation on a Peltier-cooled reflector surface. The optical configuration permits isolation of optoelectronic components from the sensing head and better light coupling between the reflector and the detecting fibre, giving a better signal of the onset of dew formation on the reflector. Continuous monitoring of the rate of change in reflectance as well as the absolute reflectance signals, the use of a novel polymethyl-methacrylate-coated hydrophobic film reflector on the Peltier element and the application of feedback around the point of dew formation, further reduces the possibility of contamination of the sensor head. Under closed-loop operation, the sensor is capable of cycling around the point of dew formation at a frequency of 2.5 Hz.

This paper describes a new method of evaluating the bubble/drop velocity using the signal from a hot-film probe placed in either a liquid-gas two-phase flow or a mixture flow of two immiscible liquids.

In previous works the dispersed phase velocity was measured by dual optical or resistance probes, while hot-film probes were used to measure the volume fraction and statistical velocity parameters of the continuous phase. This paper describes the extension of the hot-film technique to velocity measurements of both the continuous and dispersed phase with a single hot-film sensor. This technique was found to be beneficial in terms of direct slip velocity measurements.

Experimental tests were mainly carried out using kerosene-water flow and additional tests were performed for water-air flows. These were interface tests simulating the arrival of a bubble/drop front at the sensor location, and drop tests in still water and in a large-scale recirculating vertical kerosene-water pipe flow.

Three features of the `U'-shaped signal corresponding to the passage of a bubble/drop were investigated: (i) the voltage overshoot at the bubble/drop arrival, (ii) the corresponding maximum (negative) slope and (iii) the `kerosene' voltage value at the bottom of the `U'-shaped signal. This paper presents the applicability/limitations of these methods for bubble/drop velocity evaluations.

For the comparison of a measured quantity of a test object with that of a reference standard, various sequences of repeated measurements and various methods for the evaluation of measurement results are possible. A measurement cycle, consisting of a certain number of single measurements and leading to a value for the difference between a test object and a standard, may have common data with subsequent cycles. In this case, in which cycles are correlated to one another, the uncertainty calculation must take covariances into account. The paper presents the uncertainty calculation for the often-used correlated RTR cycle as well as for any cycle in general. Finally, the efficiencies of selected cycles are presented and discussed.

The development, analysis and experimental validation of a novel flow and cure sensor for use in the resin transfer moulding of composites are presented. A linear relationship is established between the flow front position in the mould and electrical admittance measurements gathered using the sensor setup, allowing accurate flow front location. The sensor performance as an indicator of flow front position is evaluated using visual verification. Its efficiency for monitoring of the curing stage is assessed by comparison of the measurements with data obtained from more conventional microdielectrometry. Experimental results demonstrate that the sensor can locate the flow front accurately. The measurement output is in the form of a complex number; this suggests a potential qualitative self-assessment method. The monitoring of the cure process using the new sensor shows performance similar to that of the established microdielectrometric techniques.

We developed a technique for the high-sensitivity detection of the magnetically induced birefringence of gases. Elliptically polarized light from a GaAlAs diode laser was used to probe the change in ellipticity caused by the presence of oxygen gas in a transverse magnetic field. The change in ellipticity was analysed with a polarization analyser. By using high-quality optical elements with small optical anisotropies, we improved the light-extinction ratio of the polarization-analysis system to 1 × 10^-9so that the noise caused by intensity fluctuations of the light source was reduced to a level below that of shot noise. The minimum value that could be detected for the change in ellipticity was 6 × 10^-9rad, which was larger by a factor of 1.4 than the value expected at the shot-noise limit. The experimental value of the signal-to-noise ratio agreed with the theoretical prediction taking account both of the shot noise and of the residual noise caused by light-source-intensity fluctuations.

Both 1-port and 2-port measuring methods have been demonstrated and compared to determine the real part of the frequency-dependent effective relative permittivity, _re (f ), of microstrip lines fabricated on an alumina substrate. Signal flow diagram analysis has been used to derive equations from which _re (f ) was calculated at discrete frequencies for the substrate with a known dielectric constant, _r= 9.5. Both methods gave similar results for _re (f ) from 45 MHz to 50 GHz. In addition, the measured frequency dependence of _re (f ) was in agreement with the Kirschning-Jansen dispersion model within better than 2%. From the measured S -parameter data it was also possible to determine approximately the attenuation coefficient of the microstrips. Measured values obtained by the 2-port method were about 1.5-2 times the calculated values whereas the 1-port method suffered from radiation loss at the open end of the microstrips in the millimetre wave region. Both 1-port and 2-port methods can be used, for example, for quality checking purposes to verify how well the _rvalue of the substrate material employed is within the specified range in a broad frequency band. However, the 1-port method can be more easily used to determine _rof the substrate material at low microwave frequencies because it is faster than the 2-port method, the test structure is simpler and the calibration routine is easier to perform.

Four methods of range measurement for airborne ultrasonic systems - namely simple thresholding, curve-fitting, sliding-window, and correlation detection - are compared on the basis of bias error, standard deviation, total error, robustness to noise, and the difficulty/complexity of implementation. Whereas correlation detection is theoretically optimal, the other three methods can offer acceptable performance at much lower cost. Performances of all methods have been investigated as a function of target range, azimuth, and signal-to-noise ratio. Curve fitting, sliding window, and thresholding follow correlation detection in the order of decreasing complexity. Apart from correlation detection, minimum bias and total error is most consistently obtained with the curve-fitting method. On the other hand, the sliding-window method is always better than the thresholding and curve-fitting methods in terms of minimizing the standard deviation. The experimental results are in close agreement with the corresponding simulation results. Overall, the three simple and fast processing methods provide a variety of attractive compromises between measurement accuracy and system complexity. Although this paper concentrates on ultrasonic range measurement in air, the techniques described may also find application in underwater acoustics.

An acoustic driver system was developed to investigate unsteady combustion characteristics of solid propellants under pressure oscillations. Two model airplane engines driven by an electric motor were used to produce nearly sinusoidal pressure variations; a consistent peak-to-peak pressure variation of 10% of the mean pressure was obtained using the engines. A pressure insensitive, sub-miniature load cell was used to measure the thrust response of the solid propellants. The load cell was placed in a ceramic holder to protect it from the high temperature of gaseous products evolved during experiments, and the bottom of the holder was coated with several layers of a damping material to reduce the effect of vibrations produced by the engines. Measurements of the thrust response were successfully made over the frequency range 4-130 Hz near atmospheric pressure in air. A minimum signal-to-noise ratio of 3:1 was obtained using the system, and both amplitude and phase information could be simultaneously extracted from the thrust response data. The reliability of the present acoustic driver system was verified by comparing response data obtained from the present and radiation-driven facilities under radiation-driven conditions. For an AP/HTPB composite propellant under pressure-driven conditions with the present facility, maximum non-dimensional thrust responses at 35 W cm^-2were measured at 12 and 16 Hz, respectively, where the phase passed through approximately zero.

Electrostatic sensing technology in combination with cross-correlation signal processing techniques offers a promising and cost effective solution to the on-line continuous velocity measurement of particles in a stack. This paper presents the principle, design and evaluation of a novel instrumentation system, called `StackFlow 2000', which has recently been developed for the velocity measurement of particles in a stack. Experiments with aloxite, building plaster and icing sugar as test materials were conducted on a 300 mm bore stack-flow test facility over a velocity range of 2.5 to 22 m s^-1for particle-mass concentrations of between 0.1 and 10 mg m^-3 . The performance of the system was quantified in terms of repeatability, linearity, response time and the lower limit of mass concentration. The accuracy of the system was studied by comparing the measured particle velocity to the air velocity in the duct. Effects of sensor contamination on the measurement and the suitability of the system for a wider range of stack sizes are also included. Results obtained from the test facility have demonstrated that the system is capable of providing highly repeatable velocity readings with nonlinearity no greater than ±1%, and a response time of less than 1 s.

An optical system has been developed to characterize transparent organic alloys during their directional solidification in situand in real time inside bulk samples with a high aspect ratio. Standard solidification experiments are performed within thin glass slides where solidification behaviour is modified compared with bulk solidification due to the space constraint. On the other hand, the interface can be easily observed via a microscope. For bulk samples, a more complex system had to be implemented. We designed a specific glass observation cell and an adapted solidification furnace. Optical elements were integrated inside the glass observation cell containing the solidifying alloy.

The resulting glass observation cell can be easily used as a tool for many optical characterization methods. Here we use the system to generate live images of the solid-liquid interface. These images, recorded on video, provided very interesting and fruitful information on the dynamic phenomena appearing at the interface. The whole interface as well as specific details of the interface could be observed. The images showed a resolution of a few micrometres, suitable to characterize interface features, as well as a high contrast and a constant magnification. As a consequence, further image processing to quantitatively characterize the solid-liquid interface could be easily performed. A method to determine the average radius of curvature of a cellular array was also implemented and is presented here.

A recently developed reflectometer was used for the determination of the wavelength-dependent refractive index of liquids. Reflectance from the prism-liquid interface was analysed using the formulae derived from the relation between Fresnel's amplitude reflection coefficients r_sand r_p . Two sets of test liquids were prepared and the real refractive indices of the solutions were determined at 590 nm. The consistency of the results was experimentally tested using a commercial Abbe refractometer

In this work, we use the diffraction properties of gratings (Talbot effect) to obtain a distance measurement through a Fourier transform method. The proposed technique is easy to use and requires low mechanical stability. Furthermore, it is suitable for out-of-laboratory applications and provides real-time (frame refresh) data acquisition capability.

This paper presents a study of the group velocity dispersion of some circumferential waves propagating around an elastic tube. The dispersive character of the circumferential waves is theoretically known, but the experimental measurement of the group velocity in a dispersive medium is still a complex operation. We have determined the characteristics of the circumferential wave dispersion for aluminium and steel tubes using a time-frequency representation. Among these time-frequency techniques, the Wigner-Ville distribution (WVD) is used here for its interesting properties in terms of acoustic applications. The WVD is applied to the analysis of the dispersion of S0 symmetric and A1 antisymmetric circumferential waves propagating around a tube with a radii ratio equal to 0.95 (internal radius:external radius). This allowed us to determine their group velocities and reduced cutoff frequencies. The results obtained are in good agreement with the calculated values using the proper modes theory.

A high-precision optical probe based on the principle of focusing-range detection is developed in this research. The probe adopted for use was directly taken from the pick-up head of a CD player. Because its principle is similar to that of the autofocusing probe, the characteristics of each component of the head were investigated and its conversion into a focusing probe was attempted. The S-curve within the focusing range can be analysed, revealing the linear relationship between the normalized focus-error signal (FES) and the measured distance. The system accuracy of the probe was found. Within the measurement range of 10 µm the linearity error was about 1%, the standard deviation was about 34 nm and the frequency response was about 8 kHz. Some practical applications were carried out, namely profile measurements of a step height, a CD surface and a silicon-wafer grating. All results were highly consistent with the nominal values.

A new technique for the measurement of input firing voltage in electrohydraulic discharges (EHD) is described in this note. EHD produces a spark channel and emits flash in the range of vacuum ultraviolet to visible light. We focused our attention on the relationship between the input firing voltage and flash feature of EHD. In order to detect flash features, a photodiode is used instead of a photomultiplier in this experiment. The amplitude and the pulse width of flash features for various input firing voltages have been investigated. It is found that the amplitude and pulse width increase linearly with input firing voltage between 5 and 80 kV.

In order to manufacture the UV-VUV Fourier transform spectrometer (FTS) beamsplitter, we present the experimental investigation of Al+MgF₂as a beamsplitter coating in the UV and VUV wavelength ranges, based on the technical requirements of the UV-VUV FTS beamsplitter during development. The effects of film layers, material selection and structure design have been analysed by means of some numerical calculations. We have developed a UV-VUV reflectometer employing a Seya-Namioka monochromator, mainly for measuring the spectral properties of beamsplitter coatings covered on the ultraviolet-fused silica base at an incident angle of 5°. The results of the measurements are discussed. This work extends the area of application of Al+MgF₂coatings.