Table of contents

The design, development and calibration of an impact force transducer or penetrometer, for use on the Huygens spacecraft scheduled to land on the surface of Saturn's satellite Titan, is described, The thumb-sized transducer employs a piezoelectric sensing element and is capable of working at cryogenic temperatures. Use of the sensor on a spacecraft imposes several reliability and safety constraints, as well as the desire to minimize mass (the sensor mass is 15 g). The impact force profile, measured at 10 kHz by the sensor, allows estimation of the density and cohesion of the surface material, and its particle size distribution. Sample profiles for terrestrial materials (sand, gravel and clay) are given.

An automatic system for measuring the three-dimensional form of turbine blades and relevant data processing principles are described. Automatic tracking between the measured blade and the measuring wheel, as well as the measuring procedure, are performed by means of rotation of the connecting arm, the measuring rod and the blade itself. The systematic errors created by installing the measured blade can be eliminated by using data processing. All parameters required by the designer can be assessed.

The roundness and sphericity of manufactured single crystal silicon spheres of nearly perfect geometry have been measured using a high-accuracy rotating probe instrument. Automated data collection, spindle error separation and fitting algorithms have been applied to generate 3D sphericity data. A two-dimensional roundness error profile of any great circle is determined with a standard uncertainty of 2.3 nm, and three dimensional sphericity error surface is determined with a standard uncertainty of 2.8 nm. When scaled with absolute diameter data, the sphericity error surface is transformed to a 3D data set of absolute radial dimensions. Two methods of computing the volume of an approximate sphere are presented. They are direct numerical integration and spherical harmonics. The algorithmic precision of the volume calculation is twelve significant digits for the direct numerical integration method and ten significant digits for the spherical harmonics method. These accuracies are several orders of magnitude better than the target uncertainty of 0.1 ppm or seven significant digits. Assuming a standard uncertainty in absolute diameter measurement of 2.8 nm, the volume is shown to be calculable with a standard uncertainty of 0.1 ppm.

Compound pendulum test mass suspensions for laser interferometer gravitational wave detectors offer a means of obtaining the maximum possible pendulum Q-factors and of avoiding violin string normal modes. Careful design can allow the transfer function to be equivalent to that of a simple pendulum. The suspension systems are also convenient for servo control of mirror orientation. We describe the design procedure and the expected performance of such systems. Preliminary experimental results on a compound pendulum are also presented.

Films that are semi-transparent in the infrared are extensively used in solar energy applications and agriculture. For analysing the performance of such systems, it is important to know the thermal radiation properties of these films. Whereas transmissivity can be determined easily, measurement of emissivity poses a problem. The intensity usually consists of radiation emitted from the film and transmitted background radiation. In this paper a method for determining the hemispherical total emittance, reflectance and transmittance of semi-transparent films simultaneously is presented. It has the distinctive features of simplicity and high precision. The results for some transparent films are presented.

A detailed account of the assembly of a thermopile heat-conduction isothermal titration calorimeter to be used in the study of biomolecular interactions is given. The instrument is built according to the twin-cell principle with a sensitivity of 5 mu J. Its reaction vessel volume is only 200 mu l. Stirring heats of the reaction vessel are below 5 mu J.

For part I see El Harrous et. al., ibid., vol.5, pp.1065-70 (1994). This paper continues the description of an isothermal titration calorimeter already outlined in the previous paper. We have determined its thermal parameters and report here on the performance of the calorimeter and the method of measuring via electrical compensation of the thermal effect. We have also calculated the effective volume of the reaction vessel and the heat of stirring of the reaction mixture in the vessel, and of injecting water into water. Finally, correct working of the calorimeter has been tested by a dilution experiment of a saccharose solution.

Art historians, archaeologists and also restorers of art works are called upon, within the scope of research and study of painted works of art, to determine and describe with accuracy the colours used by each artist. On the other hand, scientists who work on data banks of painted works of art are called upon to acquire very-high-resolution images combined with accurate colorimetric registration for archiving purposes. An extended study oriented towards colour measurement parameters determination is then necessary. From the current available relevant literature it is obvious that the research concerns primarily colorimetric fidelity without providing any details as far as mathematical processing of colour measurement data is concerned. In the present study there is suggested a non-destructive methodology for colour measurement that is much cheaper than the one that is applied if non-destructive spectrophotometry is used for this purpose. This is performed in a comparative manner with the help of a three-charge-coupled device or a mono-charge-coupled device colour detector five times less expensive than the first one, on two reference panels containing a total of 34 colour samples. Aiming at the uniquely and generally accepted determination of colour, the R, G and B values are first properly corrected and then transformed to x, y (chromaticity) and Y values in accordance with the CIE 1931 standard colorimetric XYZ system. This procedure is performed with a linear mathematical transformation followed by a least-squares method in order to determine the best values of the matrix elements and minimize the error between measured and computed values. The so-obtained values are then compared with the respective x, y and Y values provided by the spectrophotometer on the same reference panels. The mean relative difference between the chromaticity x and y values provided by the set of the two detectors and the values coming from the spectrophotometer is approximately 1.7%. The collected data expressed in tri-stimulus values are finally converted into CIELAB notation (L*a*b*) for data evaluation. An average colour accuracy of about three units in the CMC uniform colour space was achieved. These results offer a very promising attempt at elaborating a protocol of colour measurement in a reproducible way.

The charging of an insulator surface when irradiated with a stationary low-energy electron probe is simulated by Monte Carlo techniques. Results show that the irradiated core initially charges positively, causing a potential barrier to form, thereby attracting lower energy secondary electrons back towards the surface. However, as negative charge accumulates around the core periphery, more secondary electrons are returned to the core, which leads to a negative drift in the core potential. The core is expected to reach an equilibrium negative potential.

A phosphorescence anisotropy selective technique is proposed as a new method for real-time monitoring of immunological reactions and formation of antigen-antibody complexes. To assess the utility of the technique, a novel phosphorimeter has been developed. The phosphorimeter consists of a pulsed, frequency-doubled Nd:YAG laser, as a sample excitation source, a T-format dual-channel signal detection system, a digitizer and a microcomputer for data processing. Nonlinear regression software has also been developed, using a Marquardt curve-fitting procedure to extract time-resolved information on the resulting phosphorescence induced from the sample by the laser pulse. Two oppositely positioned photomultiplier tubes are used to collect the orthogonally polarized phosphorescence components, which are digitized by a digital storage adapter, and then transferred to an IBM microcomputer and the intensity or depolarization (anisotropy) of the emission is calculated. The range of emission lifetimes or rotational correlation times that can be routinely determined with this instrument extends from a few microseconds to milliseconds. The instrument has an 8 bit magnitude resolution and a signal sampling rate of 20 mega-samples per second. The averaging function of the instrument yields a single measurement with an average of over 2 to 255 excitation transients. To demonstrate the utility of the new instrument, bovine serum albumin has been employed as an antigen, which is added to a monoclonal IgG anti-bovine serum albumin antibody and the formation of the antigen-antibody complex is studied using the technique. Enhancement of the emission anisotropy signal by immobilization of the antibody on a large surface before addition of the antigen was also observed using this phosphorimeter.

The theoretical expression for the traction force in magnetic separation devices is re-examined. It is argued that the formula usually used is correct only to lowest order in chi . A more accurate expression is presented, and its structure and order of magnitude are discussed. With the help of this more precise force formulation, the reliability of future modelling should increase considerably. In addition, the anisotropic features of the traction force open up the possibility of new separation methods.

In this paper the theory, design and performance of an auto-integrating longitudinal coil used to measure fast pulsed currents flowing along sheets is presented. The sensitivity is given as a function of the sheet width, the coil-sheet distance and the coil load impedance. The coil has been used in N₂ laser investigations where current measurements are very difficult to achieve.

This Thomson-scattering diagnostic is used to measure the electron temperature and density of the plasma in the Madison Symmetric Torus reversed-field pinch, a magnetic confinement fusion research device. This diagnostic system is unique for its type in that it combines high performance with simple design and low-cost components. In the design of this instrument, careful attention was given to suppression of stray laser line light with simple and effective beam dumps, viewing dumps, apertures and a holographic edge filter. This allows use of a single-grating monochromator for dispersion of the Thomson scattered spectrum onto the microchannel plate detector. Alignment and calibration procedures for the laser beam delivery system, the scattered light collection system, and the spectrometer and detector are described. A sample Thomson-scattered spectrum illustrates typical data.

One of the most important parameters in characterization of integrated optical devices is precise determination of the effective cut-off wavelength of the fundamental and first-order modes, since this sets the exact region of single-mode operation. This paper describes an experimental set-up for determination of cut-off wavelengths of integrated optical waveguides, using the technique of spectral light transmission. Measurement results obtained with Ti:LiNbO₃ channel waveguides are presented for straight waveguides, bent waveguides and polarizers.

Ultrasonic resonator cells for liquid attenuation and velocity measurements below 1 MHz with one planar and one concave piezoelectric transducer are described. Such cells with a limited sample volume are needed for broad band ultrasonic relaxation spectrometry and for studies in chemical reaction kinetics, particularly for frequencies below 200 kHz. Measurement and evaluation procedures are described and an example of a broad band spectrum is shown.

A multi-stage nitrogen laser was developed in an attempt to enhance the potential of the photochromic tracer technique for complex flow analysis. With this system, either single or multiple low-divergence ultraviolet beams can be produced. The resulting photochromic traces are of comparable length but are substantially finer than either the tracers produced by a commercial nitrogen laser or those produced by an excimer laser. A significant advantage of these finer traces is that they were not smeared by high shear rates, as is seen with the traces produced by the other types of laser, and this will lead to more accurate analysis of complex flows.

A novel theoretical method for optimization of a gamma densitometer was applied in measuring the area-averaged void fraction in gas-liquid flows. This theory provides design criteria that are comprehensive, mechanistic, quantitative and all are obtained from first principles. Also, a computer simulation was developed to test the design criteria and the predictions were compared with experimental data in the literature. Extensive experimental validation of the optimization theory was performed. Direct in situ measurement of void fraction using differential pressure, a double-sensor resistivity probe and lucite mock-ups were compared with the optimized gamma densitometer measurements. The results demonstrated good agreement between the reference measurements and the gamma densitometer in each case. The measured void fractions for the concurrent vertical forced flow ranged from 0.02 to 0.8, and spanned the bubbly, slug and churn turbulent flow regimes in a 25.4 mm tube. The mock-up studies used lucite tubes of 12.7 mm outer diameter as substitutes for the flow field over void fractions ranging from 0.03 to 0.8.

A simple but accurate hanging wire velocimeter for measuring flow velocities of fluids has been designed, based on the drag force detection method. It is found to be very sensitive for measuring velocities of liquids as low as 0.0002 m s^-1 for measuring streaming velocities in acoustically driven flows of liquids like water, propanol and silicone oil. The maximum streaming velocity measured with this velocimeter was about 0.035 m s^-1.

A thermal scanning camera has been used to measure the temperatures reached in a small tensile specimen of ductile Remco iron deformed at a strain rate of about 1600 s^-1 in a split Hopkinson bar apparatus. True strains as high as 3.3 were reached in times of about 200 mu s, leading to a significant rise in temperature of the specimen. To estimate this rise in temperature from the scanner's signal, account had to be taken of (i) movement of the specimen with respect to the camera during the scanning period, (ii) changing orientation of the specimen surface with respect to the infrared detector due to strain localization in the neck and (iii) changing emissivity of the specimen surface as deformation proceeds. Errors in the first two stages are small whereas those in the last stage impose tolerances of approximately +40 degrees C and -30 degrees C on the maximum temperatures. The possibility of scanning away from the axis of the specimen increases the upper tolerance by as much as 25 degrees C, Finally, the detector's rise time may have prevented the scanner resolving the steep temperature gradients present, Together these factors give an overall tolerance of between +100-150 degrees C to -30 degrees C on an estimated temperature of about 300 degrees C. It is clear, therefore, that despite this large margin of error there is a significant rise in temperature within the specimen, sufficient to affect the observed mechanical response.

We present results of innovative measurements of critical direct current transport currents at 4.2 K of the high-temperature superconductor, BiSrCaCuO(2212), in pulsed magnetic fields up to 31.5 T at an electric field criterion of 100 mu V m^-1. Up to 15 T the data agree within experimental error with those taken in continuous fields. The technique used is basically the classical four-terminal method on a sample consisting of a meander pattern cut into a 0.5 mm thick superconducting layer on an MgO substrate. The technique and results have significant technological relevance for superconducting magnets of greater than the present limit of about 20 T. The potential for measurements in 50 T or more is discussed as well as the extension of pulse lengths from approximately 20 to 100 ms.

A multi-interface level measurement system using a 64-segment capacitance sensor has been developed for use in oil separators. It can not only locate the multi-interfaces between different phases, such as gas/oil, oil/water and water/sludge, but also detect the foam layer between gas and oil. Experimental results show that the interfaces of gas/oil and oil/water can be easily identified by using a simple normalized difference algorithm and the foam signal has a unique spectrum that can be acquired by fast Fourier transform analysis.