published_or_final_version / Physics / Doctoral / Doctor of Philosophy

No description available.

The development and validation of new technology for the accurate and traceable metering of high value fluids is presented here. The focus of this doctoral submission is on the determination of fluid density by the measurement of relative permittivity. A prototype cell, comprising a re-entrant cavity resonator, for the precise determination of the relative permittivity of gases and hydrocarbon liquids over a wide range of both pressures and temperatures has been developed for this work. Accuracies of measurement of relative permittivity with the re-entrant cavity resonator technique of better than 1 ppm may be achieved. Reference quality relative permittivity measurements were performed and expressions developed for ethylene which are specific to industrial metering applications ( 0 ≤ t ≤ 30°C and 5 ≤ p ≤ 10 MPa). The uncertainty in values of density calculated from the mapping relationship is approximately 0.03 % in density at a 95 % confidence level. The laboratory facility used to perform the fluid mapping or characterisation was based around a high-performance RF network analyser as the principle measuring instrument. However, an on-line instrument must be simple to operate, relatively compact, robust and considerably less expensive; particularly if it is to be widely deployed. The aimed accuracy in the measurement of relative permittivity of the on-line instrument was 5 ppm; a factor of five lower than the laboratory instrument. For the on-line instrument, the re-entrant cavity resonator was incorporated into a feedback oscillator circuit as the frequency determining element. The accuracy of measurement of relative permittivity of the on-line instrument was 2.5 ppm; a factor of two greater than the aimed accuracy. This accuracy of frequency measurement is only achievable over a relatively narrow range of operating conditions, which is ultimately a limiting factor in the applicability of the on-line instrument for high precision relative permittivity measurements in the field.

X-ray densitometry was used to investigate some environmental and genetic influences on wood formation in young Douglas-fir trees growing in the Pacific Northwest. Sampling methods were determined from sectional analyses of even-aged stems and eleven growth-ring width and density variables were measured in several trials to elucidate' some of the causes of variation. Breast height increment core samples were shown to giveve a good representation of stand properties and juvenile-mature correlations for a 40-year-old crop confirmed the validity of determining intra-ring density parameters on young material. Increment core samples from the Co-operative Douglas-fir Provenance Test (5 locations; 5 provenances/location) were used for both gravimetric and densi-tometric analyses. The major components of variation were found to be stand location and the individual tree effect. Provenances consistently accounted for less than 5% of the total variation. Genotype-environment interaction was shown to be small for all properties measured with the exception of the intra-ring density range. Between sites, earlywood widths were more variable than latewood widths, but latewood density properties (mean latewood and ring maximum densities) were more variable than those for earlywood (mean earlywood and ring minimum densities). Earlywood and latewood parameters varied independently of one another. It was suggested that genetic control was weak at the provenance level but strong for individual trees. Regression analyses using growth-ring components and monthly weather data for the outer five rings at each site uncovered some highly significant effects which helped to explain the observed year-to-year variation. Density variables were less affected by weather conditions than earlywood and latewood widths. An examination of eight ramets from each of ten 13-year-old clones revealed highly significant differences in all eleven intra-ring parameters. Heritability estimates for individual growth rings showed a regular increase with tree age, and latewood properties (width, density and ring maximum density) were found to be under strong genetic control. On a clone-mean basis, density was not related significantly to growth rate, so that vigour and density properties could be selected for independently. Crown phenology (flushing and shoot growth characteristics) was not strongly correlated with growth-ring parameters, although there was an indication that early flushing may be associated with higher latewood density. A study of four parent trees and their control-pollinated progeny proved unsatisfactory due to lack of adequate replication and atypical stand conditions, but nevertheless provided a vehicle for discussion of problems involved in assessing plus-tree wood quality and narrow-sense heritabilities. The combined results were discussed in terms of the genecology of Douglas fir and the implications for forest management and utilization. / Forestry, Faculty of / Graduate

This thesis models and analyzes an in-situ method for measuring the density of the thermosphere at low Earth orbit (LEO) altitudes in real time. As satellites orbit in the thermosphere, the sparse yet present air perturbs their orbits via the drag force. The drag force is poorly characterized and has a significant effect at LEO altitudes relative to other forces, making this perturbation force one of the greatest uncertainties in LEO orbit propagation. A steadily increasing number of satellites orbit at LEO altitudes, so for safety, it is critical to accurately track these satellites to avoid collisions. Therefore, better knowledge of the drag force is required. The drag force depends directly on the air mass density in the thermosphere, and current knowledge of the thermospheric density is limited. Models exist to describe the variations in density over time, but due to the many unpredictable factors which affect the thermosphere, the best of these models are only accurate to within 10%. Also, currently available techniques to measure the thermospheric density can only return time-averaged measurements, which causes inaccuracies in orbit propagation due to local density variations. Some planned in-situ density measurement missions rely on measuring acceleration caused by the drag force, but this requires a highly accurate accelerometer to be able to separate the drag force from other stronger forces acting on a satellite. The Satellite Producing Aerodynamic Torque to Understand LEO Atmosphere (SPATULA) concept was introduced as an alternative method, which infers density based on measurements of the drag torque. In the rotational regime, drag produces the strongest torque at LEO altitudes by far, making it possible to acquire accurate density measurements with inexpensive, commercially available sensors and actuators on a SPATULA spacecraft. This thesis expands upon a preliminary study of the SPATULA concept. A SPATULA spacecraft's dynamics are modeled in three dimensions, and a novel method is introduced for modeling the dependence of external torques on the geometry and attitude of the spacecraft. In addition to the dynamics model, discrete-time algorithms for guidance, system state filtering, attitude control, and density estimation are developed for the six degrees of freedom case. The MathWorks tools MATLAB and Simulink are used to simulate the physics and system models. The simulations are used to evaluate the performance of the SPATULA system's density measurements and compare them to conventional methods. It is found that the accuracy and bandwidth of the SPATULA system have a significant dependence on the assumed accuracy of the torque models in the system's filter. When the bandwidth is set to avoid significant phase shift errors, the SPATULA system can produce real-time measurements of density accurate over a minimum time scale of about 60 seconds, and the density error has a standard deviation of about 2 x 10^-14 kg/m^3. This accuracy is about 6 times better than the best thermospheric models, and it is also better than reported accuracies of most other density measurement methods. If bandwidth is sacrificed, the density error standard deviation can be decreased by a factor of 4. This introduces additional error due to phase shift delays, but these can be corrected with signal processing techniques. With the higher accuracy, the SPATULA system loses its real-time ability, but the data it produces would still provide excellent insight for improving thermospheric models. With high accuracy and low cost, the SPATULA concept is a promising path to pursue toward improving thermospheric density knowledge. / Master of Science / This thesis models and analyzes a method for measuring the density of the upper atmosphere in real time directly onboard a satellite. As low Earth orbit (LEO) satellites orbit at low altitudes, the sparse yet present atmosphere changes their orbits via the drag force. The drag force is poorly characterized and has a significant effect at LEO altitudes relative to other forces, making this perturbation force one of the greatest uncertainties in LEO orbit prediction. A steadily increasing number of satellites orbit at LEO altitudes, so for safety, it is critical to accurately track and predict the orbits of these satellites to avoid collisions. Therefore, better knowledge of the drag force is required. The drag force depends directly on air density, and current knowledge of the upper atmospheric density is limited. Models exist to describe the variations in density over time, but due to the many unpredictable factors which affect the atmosphere, the best of these models are only accurate to within 10%. Also, currently available techniques to measure the upper atmospheric density can only return time-averaged measurements, which causes inaccuracies in orbit prediction due to local density variations. Some planned density measurement missions rely on measuring acceleration caused by the drag force, but this requires a highly accurate accelerometer to be able to separate the drag force from other stronger forces acting on a satellite. The Satellite Producing Aerodynamic Torque to Understand LEO Atmosphere (SPATULA) concept was introduced as an alternative method, which infers density based on measurements of the drag torque. Drag produces the strongest torque at LEO altitudes by far, making it possible to acquire accurate density measurements with inexpensive, commercially available parts on a SPATULA spacecraft. This thesis expands upon a preliminary study of the SPATULA concept. A SPATULA spacecraft's motion and rotation is modeled in three dimensions, and a novel method is introduced for modeling the dependence of external torques on the geometry and orientation of the spacecraft. In addition to the dynamics model, algorithms that could be implemented on a satellite's computer are developed for determining the best orientation, estimating the state of the system, controlling the orientation, and estimating density. The MathWorks tools MATLAB and Simulink are used to simulate the physics and system models. The simulations are used to evaluate the performance of the SPATULA system's density measurements and compare them to conventional methods. It is found that the accuracy and bandwidth of the SPATULA system have a significant dependence on the assumed accuracy of the torque models used by the system. When a high bandwidth is used to avoid problems associated with low bandwidth, the SPATULA system can produce real-time measurements of density accurate over a minimum time scale of about 60 seconds, and the density error has a standard deviation of about 2 x 10^-14 kg/m^2. This accuracy is about 6 times better than the best upper atmospheric models, and it is also better than reported accuracies of most other density measurement methods. If bandwidth is sacrificed, the density error standard deviation can be decreased by a factor of 4. This introduces additional error due to delayed measurements of quickly varying components of the density, but these can be corrected with signal processing techniques. With the higher accuracy, the SPATULA system loses its real-time ability, but the data it produces would still provide excellent insight for improving atmospheric density models. With high accuracy and low cost, the SPATULA concept is a promising path to pursue toward improving density knowledge.

<p>The present work expose a technique of estimation of optimal direction for placing dental implant. A volumetric computed tomography (CT) scan is used as a help of the following searches. The work offers criteria of the optimal implant placement direction and methods of evaluation on direction’s significance. The technique utilizes structure tensor to find a normal to the jawbone surface. Direction of that normal is then used as initial direction for search of optimal direction.</p><p>The technique described in the present work aimed to support doctor’s decisions during dental implantation treatment.</p>

The present work expose a technique of estimation of optimal direction for placing dental implant. A volumetric computed tomography (CT) scan is used as a help of the following searches. The work offers criteria of the optimal implant placement direction and methods of evaluation on direction’s significance. The technique utilizes structure tensor to find a normal to the jawbone surface. Direction of that normal is then used as initial direction for search of optimal direction. The technique described in the present work aimed to support doctor’s decisions during dental implantation treatment.

No description available.

京都大学 / 新制・課程博士 / 博士(エネルギー科学) / 甲第24975号 / エネ博第471号 / 新制||エネ||88(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー変換科学専攻 / (主査)教授 長﨑 百伸, 教授 田中 仁, 教授 稲垣 滋 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

A spectroscopic diagnostic tool has been developed to determine the electron temperature and the neutral density in helium, hydrogen and argon plasmas from absolutely calibrated spectroscopic measurements. For each gas, a method of analysis which uses models specific to each species present in the plasma (neutral atom or singly ionized atom) has been defined. The experimental electron density is used as an input parameter to the models, and the absolutely calibrated spectroscopic data are processed beforehand to obtain the populations of the upper excited levels corresponding to the observed spectral lines. For helium plasmas, the electron temperature is inferred from the experimental helium ion excited level p = 4 population using a corona model, and then the neutral density is determined from the experimental helium neutral excited level populations using a collisional-radiative model for helium neutrals. For hydrogen plasmas, combinations of the electron temperature and the neutral density are determined from the experimental hydrogen neutral excited level populations using a collisional-radiative model specific to hydrogen atoms. For argon plasmas, the electron temperature is inferred from the experimental argon ion excited level populations using a collisional-radiative model for argon ions, and then the neutral density is determined from the experimental argon neutral excited level populations using a collisional-radiative model for argon neutrals. This diagnostic tool was applied to three experiments with different geometries and plasma conditions to test the validity of each data analysis method. The helium and hydrogen data analysis methods were tested and validated on helium and hydrogen plasmas produced in the VASIMR experiment, a plasma propulsion system concept. They gave electron temperatures and neutral densities that were consistent with other diagnostics and theory. The argon diagnostic tool was tested on argon plasmas produced in the VASIMR experiment, the Helimak experiment and the Helicon experiment. The electron temperature and neutral density obtained on both the Helimak and the Helicon experiments were consistent with other diagnostics and with theory, and validated the method of analysis. An impurity problem on the VASIMR experiment made it difficult for the data analysis to be validated.