This thesis is concerned with the development and study of a pattern recognition system for siphon and sewer condition/defect analysis based on acoustic characteristics. Pattern recognition has been studied and used widely in many fields including: identification and authentication; medical diagnosis and musical modelling. Audio based classification and research has been mainly focusing on speech recognition and music retrieval, but few applications have attempted to use acoustic characteristics for underground pipe condition classification. Traditional CCTV inspection methods are relatively expensive and subjective so remote techniques have been developed to overcome this concern and increase the inspection efficiency. The acoustic environment provides a rich source of information about the internal conditions of a pipe. This thesis reports on a classification system based on measuring the direct and reflected acoustic signals and describing the energy spectrum for each condition/pipe defect. A K-nearest neighbour classifier (KNN) and Support vector machines (SVMs) classifier have been adopted to train the classification system to identify sediment and pipe surface defects by comparing the measured acoustic signals with a database containing a range of typical conditions. Laboratory generated data and field collected data were used to train the proposed system and evaluate its ability. The overall accuracy of the system recognizing blockage and structural aspects in each of the series of experiments varies between 70% and 95%.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24612号 / 工博第5118号 / 新制||工||1979(附属図書館) / 京都大学大学院工学研究科航空宇宙工学専攻 / (主査)教授 江利口 浩二, 教授 嶋田 隆広, 教授 鈴木 基史 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

The purpose of these studies was to measure the drag coefficient of a small model submarine to add data to a Reynolds number study. First, a laser Doppler velocimeter (LDV) was used to measure the flow characteristics of the Mississippi State University water tunnel. The velocity and turbulence intensity profiles were measured for a range of freestream velocities of 8.6 m/s to 10.7 m/s. Several wake velocity profiles were taken for a model submarine at downstream distances of x/d = 10 to x/d = 28, with a freestream velocity of 8.6 m/s. A formula for the drag coefficient that uses only mean velocity measurements in the wake was derived for an axisymmetric body using the assumptions of a self-similar wake and a power law behavior of the wake scales. The experimental drag coefficient results are compared to computational fluid dynamic (CFD) solutions.

Superior properties of Silicon Carbide (SiC), such as wide bandgap, high breakdown field and high thermal conductivity, have made it the frontrunner to replace Silicon for applications requiring high breakdown strength, mechanical and radiation hardness. Commercial SiC devices are already available, although their expected performance has not yet been realized due to a few problems related to device fabrication technologies, such as selective doping. This work explores non-traditional techniques for SiC doping (and selective doping in particular) based on previously unknown types of defect reactions in SiC and novel epitaxial growth techniques, which offer advantages over currently available technologies. Recent developments in SiC epitaxial growth techniques at MSU have enabled the growth of high quality SiC epitaxial layers at record low temperatures of 1,300°C. Lower growth temperatures have enabled highly doped epilayers for device applications. Prototypes of SiC PiN diodes fabricated, demonstrated low values of the series resistance associated with anodes grown by the low temperature epitaxial growth technique. At room temperature, 100 ìm-diameter diodes with a forward voltage of 3.75 V and 3.23V at 1,000 A/cm2 before and after annealing were achieved. The reverse breakdown voltage was more than 680 V on average, even without surface passivation or edge termination. Reduced growth temperatures also enabled the possibility of selective epitaxial growth (SEG) of SiC with traditional masks used in the SEG in Si technology. Previously, SEG of SiC was impossible without high temperature masks. Good quality, defect free, selectively grown 4H-SiC epilayers were obtained using SiO2 mask. Nitrogen doped selectively grown epilayers were also obtained, which were almost completely ohmic, indicating doping exceeding 1x1019 cm-3. Moreover, conductivity modulation via defect reactions in SiC has been reported as a part of this work for the first time. The approach is based on a new phenomenon in SiC, named Recombination Induced Passivation (RIP), which was observed when hydrogenated SiC epilayers were subjected to above bandgap optical excitation. Additional acceptor passivation, and thereby modification of the conductivity of the epilayer, was observed. Results of investigations of the RIP process are presented, and conductivity modulation techniques based on the RIP process are proposed.

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