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This thesis presents an experimental study both in the laboratory and field to develop and test a method for continuously measuring and monitoring scour using an automated identification technology known as Radio Frequency Identification (RFID). RFID systems consist of three main components, namely (a) the reader which controls the system, (b) the transponder (derived from transmitter/responder) that transmits data to the reader and (c) the excitation antenna that allows the communication between the reader and the transponder. The study provides an insight into the RFID technology and develops the framework for using this technology to eventually address two central themes in river mechanics and sediment transport; (a) the determination of the active layer thickness and (b) the scour/deposition depth around a hydraulic structure. In particular, this study develops the methodology for relating the signal strength of a radio frequency (RF) device with the distance between an excitation antenna and the RF device. The experiments presented herein are classified into two main groups, (1) the laboratory and (2) the RF signal vs. the detection distance experiments (field experiments). The laboratory experiments were designed to understand the effect of key RFID parameters (e.g., transponder orientation with respect to the excitation antenna plane, maximum antenna-transponder detection distance), measured in terms of the transponder return RF signal strength for various antenna-transponder distances, transponder orientations with respect to the excitation antenna plane and different mediums in between the excitation antenna and the transponder, on the overall performance of the RFID system. On the other hand, the RF signal vs. the detection distance experiments were based on the results obtained during the laboratory experiments and focused on developing calibration curves by relating the transponder return RF signal strength with the distance between the excitation antenna and a transponder. The laboratory results show that the dominant RFID parameters affecting the system performance are (a) the transponder orientation towards the excitation antenna plane and (b) the medium type in between the excitation antenna and the transponder. The differences in reading distances were attributed to the transponder inner antenna type, while the effect of the medium was related with the void ratio, where higher porosity materials have, less RF signal strength decay. The parameter that governs the RF signal strength decay was found to be the distance between the excitation antenna and the transponder (erosion process experiments). The RF signal strength decays almost linearly with distance, while the rate of the RF signal strength decay is controlled by the material type in between the excitation antenna and the transponder (deposition process experiments). The RF signal vs. the detection distance experiments demonstrate that the reading distance of the RFID system can be significantly increased by using a custom made excitation antenna. The custom made excitation antenna not only increases the reading distance between the antenna and the transponder to nearly 20 ft., but also allows the user to manipulate the excitation antenna's shape and size to meet the specific landscape requirements at the monitoring site.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19233号 / 工博第4068号 / 新制||工||1628(附属図書館) / 32232 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 中川 一, 教授 藤田 正治, 准教授 川池 健司 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Trois raisons poussent à caractériser et contrôler l´interaction plasma-surface dans les machines de fusion thermonucléaire : 1/ la limitation du temps de vie des éléments de première paroi du fait de leur érosion par le plasma, 2/ la pollution de celui-ci par les particules érodées et la diminution des performances qui en découle et 3/ la rétention du gaz de travail (D, T) dans les parois ou dans les couches redéposée constituées de produits d´érosion. Dans les machines à mur carbone, les points 1/ et 3/ sont étroitement couplés, jouant un rôle capital dans le bilan de matière du fait de la forte affinité chimique du carbone avec l´hydrogène ou ses isotopes. Si le bilan érosion/redéposition est souvent obtenu à partir d'analyses post-mortem d´echantillons prélevés dans la machine, deux méthodes sont utilisées pour établir le bilan de rétention en quantifiant la quantité d'hydrogène piégée dans la paroi : les analyses post-mortem, et le bilan de gaz décharge par décharge. Ces deux méthodes conduisent à des estimations en fort désaccord, la quantité d´hydrogène piégée obtenue à partir des analyses post-mortem étant inférieure d'un facteur quatre à celle obtenue à partir du bilan de gaz. La raison en est que la première est résolue dans l´espace et intégrée sur le temps, alors que la seconde st une valeur globale pour toute la machine mais résolue choc à choc. Résoudre le désaccord entre les eux estimations précitées implique alors d´étendre les mesures post-mortem à l´ensemble des éléments de première paroi et le bilan de gaz à toute la période pendant laquelle ces éléments ont été utilisés (périodes sans plasma, ou pendant lesquelles la machine était ouverte). / Three reasons can be invoked to characterize and control plasma-surface interaction in thermonuclear fusion devices : 1/ the plasma erosion limits the lifetime of the first wall components, 2/ the penetration of eroded particles in the plasma is the cause of fuel dilution and loss of performance and 3/ part of the fuel (D/T) is trapped in the wall or layers resulting from the redeposition of eroded particles. In carbon wall devices, points 1/ and 3/ are strongly coupled due to the chemical affinity of carbon with hydrogen or its isotopes. If the erosion/redeposition balance is often obtained from post-mortem analyses of samples extracted from the vacuum chamber, two methods are currently used to build the fuel balance, and particularly to quantify the amount of which trapped in the vessel : the post-mortem analyses cited above, and discharge per discharge gas balance. Estimations by these two methods exhibit a significant discrepancy, the amount of trapped hydrogen estimated by post-mortem being typically four times lower than that obtained from gas balance. The main reason is that the former value is resolved in space (it depends of the location of the sample in the vacuum vessel) but integrated in time (it concerns the whole period during which the sample was in the device), when the latter is a global value for the whole machine but is resolved discharge per discharge. For solving the discrepancy, one must perform post-mortemanalyses on a number of samples large enough for covering the whole vessel and extend gas balance measurements to the whole period during which the considered first wall elements were used, including the period in between plasmas and vents.