Table of contents

The main purpose of this paper is to introduce the five following papers on inverse problems, and to relate the field of inverse problems to measurements. Inverse techniques are an emerging suite of methods which, when fully embraced, promise to provide better experiments and improved understanding of physical processes. This paper provides an overview of the general procedure and concepts related to identification of parameters or functions by inverse techniques. A discussion of errors and their implication for an appropriate function for minimization in inverse procedures is presented, and two methods for achieving this minimization are discussed. Some sequential concepts for parameter estimation are presented, along with a discussion of residuals and confidence intervals. Experiment design and optimization are reviewed, and a discussion of residuals and their relation to model building is presented.

This paper deals with a rheological analysis strategy, developed in order to obtain an adequate characterization of the behaviour of material undergoing a large plastic deformation. Starting from physical and phenomenological considerations, a general rheological constitutive model is chosen and introduced into a finite element simulation of the experimental tests. The rheological analysis is then formulated as an inverse problem and the goal is to find the constitutive parameters which lead to the closest values to a set of experimental data measured under various operating conditions. The least square deviation between computed and measured variables is minimized with respect to the parameters of the constitutive equation for the material. The proposed method is illustrated by application to the torsion and tensile test of a general thermo-viscoplastic material. All rheological parameters defining the consistency and variation in strain rate sensitivity coefficient with the strain or temperature are simultaneously determined starting from a chosen constitutive law.

Optimal experiment design is the definition of the conditions under which an experiment is to be conducted in order to maximize the accuracy with which the results are obtained. This paper summarizes a number of methods by which the parameters of the mathematical model of the system are estimated and describes the application of the Fisher information matrix. Examples are given for thermal property estimation in which the estimation is affected both by measurement noise, which is present during any experiment, but also by uncertainties in the parameters of the model used to describe the system.

Experimental techniques to measure the thermal properties of solids are discussed. Experimental measurements and parameter estimation techniques are used to estimate the thermal properties. The importance of experimental design is emphasized, and criteria that give insight to the parameter estimation process and experiment are cited. A code-to-code communication technique is presented, which allows standard stand-alone direct solution programs to be linked with parameter estimation codes without modification. This method is called reusable interface technology (RIT). Aspects of this computational technique are discussed. The experimental/computational techniques are demonstrated with an experiment to estimate the thermal properties of an orthotropic carbon-carbon composite material. Two-dimensional, transient temperature and heat flux data are used to estimate two components of thermal conductivity (in the principal directions of the material) and the volumetric heat capacity.

Parameter estimation techniques have been utilized in the development of methodologies for the noninvasive determination of blood perfusion using measurements from a new thermal surface probe. The basic concept behind this work is that heat flux and temperature measurements from the probe are combined with results from a mathematical model of the probe and tissue in an estimation procedure for the determination of the blood perfusion. The key element of the probe is a thin sensor, which is placed in contact with the tissue and provides time-resolved signals representing heat flux and temperature while the probe is cooled by air jets. This probe has been newly modified to enhance performance. Parameter estimation techniques were developed which incorporate measured heat flux and/or temperature data and corresponding calculated data from the model to estimate blood perfusion and also the thermal contact resistance between the probe and the tissue. The sensitivity coefficients associated with heat flux were found to be much higher than those associated with temperature such that the heat flux measurements were the most influential in the estimation of the parameters. Simultaneous estimates of blood perfusion and contact resistance were successfully obtained using the Gauss minimization method. The resulting estimates of blood perfusion were consistent with the range of values found in the literature.

Properties important for describing the flow of multiple fluid phases through porous media are represented as functions of state variables (fluid saturations). A generalized procedure is presented to obtain the most accurate estimates of the multiphase flow functions from the available experimental data. The procedure is demonstrated for several different experimental designs, including a novel experiment in which fluid saturations are measured using nuclear magnetic resonance imaging. A method to evaluate the accuracy of the estimates is presented, and its use for assessing experimental design is demonstrated.

During recent years it has become more and more obvious that we need to take care of products when they are worn out if we are to be more environmentally responsible. To make this possible much of the related work has to be performed in an automized way. When a disassembly process is automized a number of sensors is needed. These sensors gather a large amount of information which must be fused in an effective way. To this end we need a method that is fast, flexible, robust and easy to adapt to all kind of sensors. The first attribute (fastness) can be obtained by using a distributed sensor data processing architecture with local processors which pre-process data close to the sensors. The other attributes are obtained by using a fusion algorithm based on a novel fuzzy operator. In this article, this fuzzy operator is described and its properties investigated. A simulation is performed, applying the fuzzy operator to a sensor-based classification by size of electrical motors aimed for disassembly. The simulation clearly demonstrates the superiority of our fuzzy operator when compared to common AND and OR operators.

Determining the parametrization of the curve is a fundamental problem in approximation and interpolation. The goal of this paper is to develop an accurate and robust algorithm for the minimum zone problems. In this paper, we use an interval bias adaptive linear neural network structure together with an appropriate cost function and the least mean squares learning algorithm to carry out the interval regression analysis. Through appropriate choice of the output function of the input neuron, the interval polynomial regression use of a neural network (IPRNN) method developed in this paper is applicable to many problems (interval algebraic polynomial approximation, evaluation of straightness, roundness and ellipticity and so on). Generally, these problems have complicated constraints and the LSQ method cannot be used.

A new electron ion coincidence spectrometer for the study of single and double photoionization in the gas phase is described. The spectrometer employs a pulse scheme, which allows high mass and electron energy resolutions to be achieved simultaneously; the mass resolution is greater than 200 (, FWHM definition) and the electron energy resolutions are 55 meV and 300 meV for studying single and double photoionization respectively. A position-sensitive electron detector enables multiplex electron detection which significantly enhances the sensitivity of the instrument.

An electron-ion crossed beams experiment has been developed in which the energy loss of scattered electrons is used to determine cross sections for excitation in positive ions. Scattered electrons are confined by an axial magnetic field and are channelled into a detector using reflecting potentials and an (trochoidal) deflection. Complete collection of these electrons along with monitoring of the overlap and current of the beams enables absolute total cross sections to be determined. This technique has been used to study near threshold excitation of the D resonance transition in .

, CII, trochoidal spectrometer

This paper expands the applicability of holographic interferometry to measurements of unsteady temperature distributions for physical situations characterized by periodic pressure variations. For this purpose a new analytical model that accounts for pressure variations in the interpretation of the interferometric fringe pattern was elaborated. This model was then implemented into the newly developed evaluation procedure that is based on the measurement of the interference order as a continuous function of two spatial coordinates and time, by employing digital image processing algorithms. To validate the evaluation procedure, the oscillating temperature fields in a model of a thermoacoustic refrigerator were measured. These measurements proved the validity of the approach by indicating very good agreement with existing theory.

We demonstrate a novel -doped fibre laser operating in orthogonally polarized dual-frequency modes and its application to electric current sensing with frequency read-out. A Faraday rotating mirror and spatial hole burning effects in a gain medium and in a saturable absorber are utilized to control the lasing mode and polarization. The polarization mode beat frequency changes linearly in response to the non-reciprocal circular birefringence induced by an external magnetic field. When the laser was applied to sensing an alternating electric current with a simple phase-locked loop signal processing scheme, the slope coefficient of 8.0 kHz per turn and the noise equivalent current of 460 per turn were obtained. The new current sensor is immune to perturbations in the lead fibres.

It has been reported that textile defects can be found and classified by examining the optical diffraction pattern obtained by illuminating the defect-containing textile with a laser beam. Very little, however, can be found in the literature concerning the influence of the laser beam size on the performance of the method. We describe here a systematic method to determine an optimum beam size, and we demonstrate that the size of the illuminating beam must not be too small or too large, for the system to yield satisfactory results.

This work investigates the feasibility of an ultrasound scanner designed to reconstruct three-dimensional profiles of objects in air. There are many industrial applications in which it is important to obtain quickly and accurately the digital reconstruction of solid objects with contactless methods. The final aim of this project was the profile reconstruction of shoe lasts in order to eliminate the mechanical tracers from the reproduction process of shoe prototypes. The feasibility of an ultrasonic scanner was investigated in laboratory conditions on wooden test objects with axial symmetry. A bistatic system based on five airborne polyvinylidenedifluoride (PVDF) transducers was mechanically moved to emulate a cylindrical array transducer that can host objects of maximum width and height 20 cm and 40 cm respectively. The object reconstruction was based on a simplified version of the synthetic aperture focusing technique (SAFT): the time of flight (TOF) of the first in time echo for each receiving transducer was taken into account, a coarse spatial sampling of the ultrasonic field reflected on the array transducer was delivered and the reconstruction algorithm was based on the ellipsoidal backprojection. Measurements on a wooden cone section provided submillimetre accuracy in a controlled environment.

An instrument which exploits the `tube-arrest' technique of subjecting a column of liquid to tension by dynamic stressing is described. In this apparatus two tension pulses are produced, one ab initio within the liquid, the other by free-surface reflection of a cavitation-generated shock wave. A method of deriving the tensile strength of a liquid from measurements of the velocity of these pulses is presented, and previous assumptions concerning the origin of tension in the `tube-arrest' technique are critically examined. The initial tension pulse is shown not to arise at the bottom of the liquid column as has been assumed hitherto, and the means by which cavitation is exploited to study the production of liquid jets by shock wave-bubble interaction are explained.

The process of ozone generating using `silent' or `barrier' discharges is described and analysed. Based upon conclusions from the analysis, a voltage control circuit is described which utilizes two IGBTs as switching devices with associated control circuitry. The circuit so developed has been used to control the output from a commercial ozone generator.

The magnetic induction field produced by non-homogeneously magnetized samples of arbitrary shape is expanded in terms of a complete set of functions, the vector spherical harmonics. The weighing coefficients of this expansion - the multipole moments - are computed and are given up to fifth order for the most common sample shapes and homogeneous magnetization. The magnetic flux threading a general detection coil is computed analytically and pick-up systems of rotational symmetry as well as transverse systems are discussed. The flux profiles of dipole and higher order multipole moments along the direction of the applied field are plotted for common coil geometries as functions of the sample position. Both the influence of position errors on the flux profiles and the crosstalk between mutually perpendicular components of the dipole vector are analysed.

Measurements of photoconductivity decay from the steady state for samples of amorphous silicon and silicon-carbon alloys were carried out using the experimental set-up with a Pockels cell as a light chopper. The developed electronic switching circuit allows measurements of decay times ranging down to microseconds. The advantage of the adopted method of light switching is that one can easily control the light intensity and photon energy. From knowledge of the photoconductivity decay time and the value of the steady state photoconductivity for a given sample, the carrier drift mobility can be calculated.

In some situations measurement results are stated without correcting for known systematic effects. It is shown here that this can be done as long as the uncertainty associated with the uncorrected result is properly evaluated. Since this procedure produces an enlarged uncertainty, it is strongly advised that corrected results always be stated.

1998 June 8-12 8th International Symposium on Measurement and Control in Robotics, Prague, Czech Republic Details: Associate Professor Jaromír Volf, ISMCR '98, Faculty of Mechanical Engineering, Czech Technical University, Technická 4, 166 07 Prague 6, Czech Republic. Telephone: +420 2 2435 2737, fax: +420 2 2431 0292, e-mail: volf@fsid.cvut.cz, WWW: http://www.fsid.cvut.cz/events/ismcr98 14-17 8th European Symposium on Semiconductor Detectors, Schloss Elmau, Germany Details: http://www.hll.mpe-garching.mpg.de/sds98, e-mail: pxh@mpe-garching.mpg.de 14-19 9th CIMTEC Forum on New Materials: Solid State Chemical and Biochemical Sensors, Florence, Italy Details: 9th CIMTEC Forum on New Materials, PO Box 165, 48018 Faenza, Italy. Telephone: +39 546 22461, fax: +39 546 664138 16-19 3rd International Conference on Vibration Measurements by Laser Techiques and Short Cource on Laser Vibrometry, Ancona, Italy Details: Professor E P Tomasini, Dipartimento di Meccanica, Università di Ancona, Via Brecce Bianche, I-60131 Ancona, Italy. Telephone: +39 (0)71 2204489, fax: +39 (0)71 2204813, e-mail: aivela@mehpl.cineca.it, WWW: http://www.unian.it/html/ 17-19 6th International Conference on New Actuators - ACTUATOR 98, Bremen, Germany Details: Dr Hubert Borgmann. Telephone: +49 421 3505 347, e-mail: borgmann@messe-bremen.de 24-26 Fifth International Conference on Structures Under Shock and Impact, Thessaloniki, Greece Details: Liz Kerr, Wessex Institute of Technology, Ashurst Lodge, Ashurst, Southampton SO40 7AA, UK. Telephone: +44 (0)1703 293223, fax: +44 (0)1703 292853, e-mail: wit@wessex.ac.uk, WWW: http://www.wessex.ac.uk 28-2 July Optical Spectrometry: Applications and Instrumentation into the 21st Century, Surrey, UK Details: Dr Mary Barnard, The Pines, Larch Avenue, Ascot SL5 0AW, UK. Telephone: +44 (0)1344 21485, fax: +44 (0)1344 21485. July 6-10 Conference on Precision Electromagnetic Measurements, Washington DC, USA Details: Norman Belecki, NIST, Building 220, Room B164, Gaithersburg, MD 20899-0001, USA. Telephone: +1 301 975 4223, fax: +1 301 926 3972, e-mail: norman.belecki@nist.gov, WWW: http://www.eeel.nist.gov/cpem98. 7-9 International Microscopy Conference and Exhibition, London, UK Details: Royal Microscopical Society, 37/38 St Clements, Oxford OX4 1AJ, UK. Telephone: +44 (0)1865 248768, Fax: +44 (0)1865 791237, e-mail: meetings@rms.org.uk (for conference), info@rms.org.uk (for exhibition), WWW: http://www.rms.org.uk 13-15 2nd European Conference on Magnetic Sensors and Actuators, Sheffield, UK Details: Conferences, The Institute of Physics, 76 Portland Place, London W1N 3DH. Telephone: +44 (0)171 470 4800, fax: +44 (0)171 470 4900, WWW: http://www.shef.ac.uk/ phys/emsa98.html and http://www.iop.org/Confs/EMSA 13-16 9th International Symposium on Applications of Laser Techniques to Fluid Mechanics, Lisbon, Portugal Details: Professor M V Heitor, Instituta Superior Técnico, Mechanical Engineering Department, 1096 Lisboa Codex, Portugal. Telephone: +351 1 841 73 79, fax: +351 1 849 61 56, e-mail: mheitor@termcomb.ist.utl.pt August 20-21 International Workshop on Optical Ferroelectric Materials, Breckenridge, CO, USA Details: Norman Sanford, NIST, Mailcode 815.04, 325 Broadway, Boulder, CO 80303-3328. Telephone:+1 303 497 5239, fax: +1 303 497 7671, e-mail sanford@boulder.nist.gov 24-27 NIWeek 98 Worldwide Conference on Measurement and Automation, Austin, TX, USA Details: WWW: http://www.natinst.com/uk 24-28 11th International Conference on Experimental Mechanics, Oxford, UK Details: BSSM, Surrey Technology Centre, Surrey Research Park, 40 Occam Road, Guildford GU2 5YG, UK. Telephone: +44 (0)1483 295 715, fax: +44 (0)1483 573 704 31-4 September 14th International Vacuum Congress, 10th International Conference on Solid Surfaces, 5th International Conference on Nanometer-scale Science and Technology and 10th International Conference on Quantitative Surface Analysis, International Convention Centre, Birmingham, UK September 29-1 October 4th Optical Fibre Measurement Conference, Teddington, UK Details: Mrs Jane Tsakalou, Conference Office, National Physical Laboratory, Teddington TW11 0LW, UK. Telephone: +44 (0)181 943 5400, WWW: http://www.npl.co.uk/npl/news/ October 11-16 October 6th International Conference on Nuclear Microprobe Technology and Applications, Cape Town, South Africa Details: Mrs G Stone, National Accelerator Centre, PO Box 72, Faure 7131, South Africa. Telephone: +27 21 843 3820, Fax: +27 21 843 3543, e-mail: icnmta98@nac.ac.za, WWW: http://www.nac.ac.za/icnmta98 19-23 Precision Thermometry Workshops, Gaithersburg, MD, USA Details: Andrea Swiger, National Institute of Standards and Technology, Bldg 221, Rm B1128, Gaithersburg, MD 20899-0001. Telephone: +1 301 975 4800, fax: +1 301 548 0206, e-mail: andrea.swiger@nist.gov December 8-11 2nd Asian Meeting on Ferroelectrics, International (AMF-2), Singapore Details: Weiguang Zhu, fax: +65 792 0415, e-mail: ewzhu@ntuvax.ntu.ac.sg 1999 May 17-21 3rd CCM Conference on Pressure Metrology from Ultra High Vacuum to Very High Pressures (10-7 Pa to 109 Pa), Torino, Italy Details: M Bergoglio, Istituto di Metrologia `G Colonnetti', Strada delle Cacce 73, 10135 Torino, Italy. E-mail: bergoglio@imc.to.cnr.it September 12-15 First International Symposium on Turbulence and Shear Flow Phenomena, Santa Barbara, CA, USA Details: N Kasagi, Department of Mechanical Engineering, University of Tokyo, Tokyo 113 8656, Japan. Telephone: +81 3 3812 2111 ext. 6417, fax: +81 3 5800 6999, e-mail: kasagi@thtlab.t.u-tokyo.ac.jp, WWW: http://tsfp.t.u-tokyo.ac.jp

The goal of this book is to provide engineers with a source of firm knowledge of the most frequently used non-destructive evaluation (NDE) techniques. The primary techniques (ultrasonics, acoustic emission, magnetics, eddy-current radiography, penetrants) are introduced from the fundamental laws of physics and described in depth in order to provide sufficient technical background. Typical examples are given which show usual NDE applications. At the end of each part of the book, a detailed bibliography is provided and problems are given which allow the reader to check his degree of understanding. Laboratory projects are suggested in the cases of magnetics and eddy currents. A list of names and addresses of the various organizations active in the area of NDE is supplied at the end of the book. This book is clear and very pedagogic and could be recommended for courses at undergraduate and graduate levels.

I did, however, notice a few unfortunate omissions. In the overview of the probabilistic nature of failure and inspection, some helpful words concerning neural networks and artificial intelligence were left out. A classification of the different NDE techniques from the point of view of their frequency and their cost would have been useful. This would have allowed minor techniques to be introduced. There were also no descriptions of real NDE testing situations (e.g. nuclear plant or aeroplane) explaining the time and cost constraints which engineers and technicians have to cope with.

Students in a science or engineering curriculum ought to be introduced early to the requirement that a meaningful measurement result should always be accompanied by a statement of its uncertainty. This book has been written specifically with this objective in mind. That the first edition has been successful in doing this is attested to by its popularity with both faculty and students, and its translation into six languages.

This book is not a statistics text - nor was it intended to be - but an introdution to the mathematics required for the analysis of measurements at the level of a first-year laboratory course. Part 1 begins with uncertainty as a qualitative concept and builds slowly, using many numerical examples and exercises for the student, to develop methods for quantifying uncertainty, and ultimately relating it to the standard deviation of a statistical distribution. Along the way, Taylor develops the rules for expressing and combining (`propagating') uncertainties, and introduces the student to the gaussian (normal) distribution and some of its properties. Part 2 covers, with somewhat more mathematical rigor, specific topics such as data rejection criteria, the binomial and Poisson distributions, covariance and correlation, least-squares fitting, and the chi-squared test.

I was not familiar with the first edition, and from a quick scan of the Preface I looked forward to reading this book and learning something about the state of statistical analysis in first-year university texts today. I was disappointed (in part with what the level of the book implies about the sad state of preparation of today's students). Although there are now two ISO publications ( International Vocabulary of Basic and General Terms in Metrology (VIM) and Guide to the Expression of Uncertainty in Measurement (GUM), Geneva, 1993), Taylor makes no mention of either, and never gives a formal definition of `uncertainty' (although he ultimately associates `random uncertainty' with the standard deviation of a gaussian distribution). The book also does not clearly define `error', or the distinction between error and uncertainty. The important point, that the `propagation of uncertainty' is additive in terms of variances is valid for any distributions with finite variance, is not emphasized; instead Taylor restricts the discussion solely to the normal distribution and or those that can be approximated by it.

I also find it unfortunate that the book does not clearly distinguish between the variance of a sample , the variance of a distribution , and the sample estimate of the variance of the distribution ( or ). Instead, he accepts the fact that formulas for the variance with either N or N - 1 dividing the sum of the squares of the deviations from the mean exist in the literature and concludes simply: `Nevertheless, you need to be aware of both definitions. In the physics laboratory, using the more conservative... def- inition... is almost always best.'

In spite of these shortcomings, the book is a significant contribution to a student laboratory reading list, and it is written at a level that facilitates a self-study program. It has an important message to deliver and it appears to be delivering it well.