Proefschrift-Utrecht. / Introduction, summary and vita in Dutch. Includes bibliographical references (p. 74-77).

Thesis (M.Phil.) - University of Queensland, 2004. / Includes bibliography.

Eddy current (EC) based testing and measurement methods are well known in non-destructive testing (NDT) world. EC sensors are extensively studied and used for material health monitoring and its property measurement. Target displacement measurement is one of the well-known applications of EC method. The main advantage of EC sensor is its working capability in harsh environment like humidity, contamination etc. It is non-contact, rugged and requires less maintenance. The range and sensitivity of target displacement is mainly determined by the probe geometry and its construction method. Also displacement measurement depends upon geometry and electromagnetic (EM) properties of the target plate. Any variation of ambient temperature alters the EM properties of the probe as well as EM properties of the target. Thus, many parameters like geometry, EM properties and temperature involved in target displacement measurement. Hence, while using EC sensor for displacement measurement, it demands careful design and measurement procedure to achieve high sensitivity and high precision with low temperature drift. To achieve these, we present the following. 1) A temperature compensation technique 2) Optimization of probe geometry and its construction method to increase the range and sensitivity 3) Selection of suitable probe measurement parameter (Z, R, X) based on target material properties 4) Making the displacement measurement less sensitive to tolerance in probe construction parameter. A temperature compensation technique for target displacement measurement, using a self-running LC oscillator has been presented. A sensing coil is energized by a Hartley oscillator. The oscillator voltage is maintained at a constant level by a closed loop feedback circuit and the average feedback current to the oscillator is measured for target displacement detection. The temperature drift of the feedback current is compensated by applying temperature compensation function (TCF) and this is verified experimentally. Cold rolled mild steel (carbon steel) is taken as a target material and the sensor is tested over a temperature range of 20 °C – 80 °C. It shows that the temperature drift is less than ±30 ppm/°C over 3 mm target displacement. To match all the sensor modules in mass production, components selection procedure is presented. To avoid mismatch across sensors in manufacturing process, the transistor based oscillator is modified with operational trans-conductance amplifier (OTA). The same temperature compensation formula (TCF) is applied to compensate the temperature drift of feedback current and achieved intended accuracy. Geometry and construction parameters of the eddy current sensing probe is optimized for target displacement measurement using Ansoft Maxwell, electromagnetic design software. EC probe with different geometry are analyzed in search of suitable geometry for target displacement measurement. Four shapes of commercially available core have been chosen for probe construction. For each shape of sensing probe, the radius and height of the probe is increased by 0 mm to 9 mm to find the effect of them on sensitivity and range of target displacement measurement. It has been observed that the probe with less height and maximum diameter has shown better performance. In addition to that, the probe geometry is optimized to achieve more sensitivity and range within the space available for probe mounting. It helps to utilize the available space effectively for probe design. Coil winding and mount-ing it inside the core window also important parameter in probe design. It has been observed that de-pressing the sensing coil inside the core window from sensing face by 3 mm decreases the sensitivity by 40 %. Hence, it is recommended to place the coil on the extreme end of the sensing face of the core. To know the effect of core permeability, it is varied from 1000 to 15000. It has been observed that it has no effect on sensitivity and measurement range. Only optimizing the probe geometry and its construction method is not adequate for target displacement measurement. We know that the EC based displacement measurement is also target material dependent. Generally probe impedance is measured and then the temperature drift of the sensing coil resistance is compensated to know the target displacement. Most of the temperature compensation techniques use this compensation technique and it is shown that those are suitable for high conductivity targets like copper. Choosing Z for displacement measurement may not be only best choice for all target materials. The displacement can be measured also through either R or X of the probe. Choosing the proper probe parameter for a given target material will provide a less temperature drift for target displacement measurement. To know about this, a simulation has been made for target displacement measurement with target metal of μr = 1, relative permittivity εr =1, and temperature coefficient of resistivity ∝ = 0.004 K-1. The conductivity (σ) of the target is varied from 1×106 S/m to 62×106 S/m in the temperature range of 20 ℃ – 80 ℃. Now the simulation has been repeated by fixing  as a constant and varying target μr. The metal plate with  = 1×106 S/m, εr=1 and ∝ = 0.004 K – 1 is taken as a target and μr is varied from 100 to 10000. For both conductivity and permeability sweep analysis, the target displacement is measured as a function of Z, R and X independently. The temperature drift in displacement measurement is also analysed for the above temperature range. An experiment has been conducted with copper, stainless steel and mild steel as target metal in the temperature range of 20 ℃ – 80 ℃. The temperature drift is calculated when the displacement is measured as function of Z, R and X. Based on the results, we have identified that the target material relative permeability determines the selection of probe measurement parameter for target displacement measurement. Hence, knowing tar-get r alone suffice to select the probe measurement parameter (Z or R or X) for displacement measurement. Optimizing the probe geometry, selecting the proper probe measurement parameter and temperature compensation technique suffice to provide a good sensitivity, range and low temperature drift for a single probe. But in general, one of the mass produced probes is selected as a reference probe and it is calibrated against the ambient temperature and target displacement. And the calibration curves are loaded to all the probes. Matching the probe construction parameters to each other across the production patches is not possible in mass production. This makes the temperature compensation function and displacement calibration are different for every individual probes for displacement measurement. This degrades the measurement accuracy. A simulation has been performed with pot core with commercial tolerance. Using this, we have obtained 24 probes due to variations in 1) Individual and few combinational variations in core and coil dimensions 2) Core permeability variation and 3) relative position of the coil with respect to core. Finally, we have quantified the displacement error for each probe. We have identified the important probe dimensional parameters that have to be controlled precisely in mass production to improve the measurement accuracy. It shows error of 0.86 % in the displacement measurement when the relative reactance and relative displacement is used for measurement. In practice, error in displacement measurement due to both the ambient temperature drift and the tolerance in probe construction parameter exist simultaneously. Hence, the combined error is computed for the target displacement range of 0 mm – 3 mm for the temperature range of 0 °C – 100 °C. The total error of less than 1 % is achieved for commercial standard probe tolerance. Finally, we have provided general factory production procedure and user calibration procedure of probe design to achieve cost effective displacement measurement with sensitivity and range with low temperature drift.

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Cette thèse s’intéresse à l’histoire des allumettières de la E.B. Eddy Match de Hull des années 1850 jusqu’au déménagement de l’entreprise, en 1928. Pendant plus de sept décennies, des centaines de femmes s’affairent à la confection d’allumettes, ce bien nécessaire à tous quotidiennement. L’expérience des ouvrières employées par le plus grand producteur de cette industrie au Canada se définit par leurs conditions de vie et de travail difficiles. Bien que des améliorations s’observent au fil des ans, particulièrement à l’intérieur de la fabrique, la pauvreté de la classe ouvrière et les dangers de l’emploi restent une réalité bien présente. Pour mener à bien cette recherche, nous proposons dans un premier temps un examen de celles qui composent cette main-d’œuvre. En nous appuyant principalement sur les données du recensement canadien, nous examinons le portrait démographique et la situation socio-économique des allumettières, en plus de leur apport à la survie familiale. De ce fait, nous soulevons pourquoi le poids économique des jeunes filles et des femmes s’avère non négligeable pour de nombreux ménages dans un contexte de précarité qui touche l’ensemble de la classe populaire. Dans un deuxième temps, les conditions de travail sont observées. En utilisant l’exemple de l’emploi du phosphore blanc dans la confection d’allumettes, nous abordons les risques du métier présents au cours du 19e siècle jusqu’au début des années 1910. Alors que la substance est retirée du processus de production, d’autres dangers subsistent. Les conditions de travail dans les années 1920 subissent certaines avancées, mais restent généralement précaires. Les heures de travail sont réduites, mais les salaires n’augmentent pas nécessairement. La syndicalisation des travailleuses amène quelques progrès et laisse voir la volonté d’implication des allumettières dans le mouvement ouvrier catholique. Toutefois, l’expérience se termine par un échec et cause fort probablement le départ de la compagnie en 1928.

Thesis (Ph. D.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains xxiv, 163 p. : ill. (some col.). + QuickTime and media files. Includes video files in the mpeg and wmv formats. Vita. Includes abstract. Includes bibliographical references (p. 126-136).

A theoretical approach to calculating impedance of metallicmagnetic/conductor layered structures is developed. Thefrequency range considered extends to the ferromagneticresonance region of soft magnetic films (of the order of 1GHz). The analysis includes the effects of screening of thehigh frequency fields by eddy currents as well as the dynamicsand relaxation of the magnetization of the ferromagneticsub-system. Analytical expressions for the impedance as afunction of frequency and material parameters and geometry ofmagnetic sandwich stripes are obtained. Two maincross-sectional layouts are considered: amagnetic/conductor/magnetic sandwich stripe with and withoutflux closure at the edges along the stripe length - with andwithout the magnetic film enclosing the conductor strip. Theimportance of good magnetic flux closure for achieving largespecific inductance gains and high efficiency at GHzfrequencies is emphasized. The theoretical results obtained were used to design andanalyze magneticfilm inductors produced using iron nitridealloy films. Patterned sandwiches, consisting of two Fe-N filmsenclosing a conductor film made of Cu, were fabricated onoxidized Si substrates using lift-off lithography. Theinductors exhibited a 2-fold specific inductance enhancement at1 GHz. The magnetic contribution to the total flux in thenarrow devices was less then predicted theoretically, which wasattributed to hardening of the magnetic material at the edgesof the strip leading to incomplete flux closure. Material anddesign issues important for further improving the performanceof the devices are discussed.

Modelling the energy exchange between the snowpack and the atmosphere is critical for many hydrological applications. Of the terms present in the snow energy balance, the turbulent fluxes of sensible and latent heat are the most challenging to estimate, particularly within mountain environments where the hydrological importance is great. Many of the flux estimation techniques, such as the bulk transfer method, are poorly adapted for use in complex terrain. In order to characterize the turbulence and to assess the suitability of flux estimation techniques, eddy covariance flux measurements and supporting meteorological data were collected from two mountain valley forest openings in Kananaskis Country, AB. These sites were generally calm, however wind gusts were frequently observed which markedly affected the turbulence characteristics and increased the rates of momentum and heat transfer. In order to successfully apply the bulk transfer technique at these sites, it was necessary to use environment-specific transfer coefficients to account for the effect of the surrounding complex terrain. These observations were compared with data collected on a treeless alpine ridge near Whitehorse, YT, where it was found that many of the turbulence characteristics were similar to flat sites. However, the boundary layer formed over the alpine ridge was very thin and the site was poorly suited for estimating surface fluxes. The mountain results were further contrasted with data collected over a homogeneous and flat prairie site located near Saskatoon, SK. This site included measurement of all of the snow energy terms, permitting an estimate of the energy balance closure obtainable over snow surfaces. The observed energy balance residual was very large, indicating that the eddy covariance technique was unable to capture all of the turbulent energy. It was concluded that an unmeasured transfer of sensible heat was occurring which was strongly correlated with the long-wave radiation balance. Mechanisms for this relationship were hypothesized. Two snow energy balance models were used to investigate the energy imbalance, where it was observed that the flux terms could be suitably simulated if effective parameters were used to augment the sensible heat transfer rate. The results from this thesis contribute to the understanding of heat transfer processes over snow surfaces during mid-winter conditions and improve the ability to model turbulent heat and mass fluxes from snow surfaces in complex environments.