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Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(情報学) / 甲第19137号 / 情博第583号 / 新制||情||102 / 32088 / 京都大学大学院情報学研究科通信情報システム専攻 / (主査)教授 小野寺 秀俊, 教授 髙木 直史, 教授 佐藤 高史 / 学位規則第4条第1項該当

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Στην Πυρηνική Ιατρική, κατά τη διαδικασία ιατρικής απεικόνισης, η κίνηση των οργάνων λόγω της αναπνευστικής λειτουργίας και της σύσπασης του μυοκαρδίου αλλά και των υπόλοιπων κινούμενων οργάνων, δημιουργεί αλλοιώσεις στη διαγνωστική πληροφορία. Η σημαντικότερη αλλοίωση παρατηρείται στον καθορισμό των ορίων συγκεκριμένων οργάνων. Η μελέτη και η ποσοτικοποίηση του φαινομένου καθίσταται αναγκαία στα ευρέως χρησιμοποιούμενα κλινικά πρωτόκολλα πυρηνικής απεικόνισης (SPECT, PET). Το πακέτο προσομοιώσεων Gate είναι ένα πολύ δυνατό εργαλείο που παρέχει τη δυνατότητα ρεαλιστικής μοντελοποίησης συστημάτων πυρηνικής ιατρικής και χρήσης διακριτοποιημένων ομοιωμάτων. Με τη βοήθεια αυτού του εργαλείου και κάνοντας χρήση διακριτοποιημένων ομοιωμάτων XCAT και ITIS μπορούν να προσομοιωθούν ρεαλιστικά κλινικές εξετάσεις που επηρεάζονται από την κίνηση οργάνων. Τα XCAT και ITIS είναι ρεαλιστικά και ευέλικτα μοντέλα ανθρώπινης ανατομίας και φυσιολογίας. Τα XCAT παρέχουν την επιπλέον δυνατότητα της εισαγωγής κίνησης. Αυτή η μελέτη είναι σημαντική, καθώς πολλές ομάδες της επιστημονικής κοινότητας ασχολούνται με την παραγωγή αλγορίθμων διόρθωσης της κίνησης των πνευμόνων και της καρδιάς, κάνοντας χρήση προσομοιώσεων Monte Carlo, με σκοπό τη βελτίωση της απεικόνισης σημαντικών ιατρικών πληροφοριών που αλλοιώνονται λόγω της κίνησης. Οι προσομοιώσεις κλινικών εξετάσεων με το GATE, εισάγοντας ρεαλιστικά ανθρώπινα ομοιώματα, είναι μια μεθοδολογία αιχμής η οποία ανοίγει το δρόμο στη βελτιστοποίηση των διαγνωστικών και θεραπευτικών προσεγγίσεων, παρέχοντας ένα ισχυρό εργαλείο για το σχεδιασμό κλινικών πρωτοκόλλων, την ανάπτυξη διορθωτικών αλγορίθμων και τη μοντελοποίηση παραμέτρων όπως η κίνηση του σώματος εξαιτίας της λειτουργίας της καρδιάς καθώς και του αναπνευστικού συστήματος. / In nuclear medicine, during medical imaging procedures, organs' motion creates artifacts and loss in the diagnostic information, due to respiratory motion and myocardial contraction. The most significant challenge is to define the limits of specific organs and quantify the blurring caused by this motion. The study and quantification of this phenomenon is necessary for clinical protocols used in nuclear imaging (SPECT, PET), so as to achieve accurate diagnosis. GATE is a powerful Monte Carlo simulation toolkit, which enables the realistic modeling of a nuclear imaging system, using voxelized phantoms as input. Using this tool and computational anthropomorphic phantoms such as XCAT and ITIS phantom series can simulate realistically clinical tests. XCAT and ITIS are realistic and flexible models of human anatomy and physiology. XCAT provide the additional capability of importing motion. In the present thesis the XCAT and the ITIS anthropomorphic computational phantoms are used in a series of simulations modeling several clinical cases. Several groups in the scientific community are dealing with the development of motion correction algorithms in order to decrease the blurring in specific organs of interest and to increase the diagnostic value of nuclear imaging. Monte Carlo techniques combined with realistic human models can provide the ground truth for such applications. This is a cutting edge methodology that paves the way for optimization of diagnostic and therapeutic approaches, providing a powerful tool for the design of clinical protocols, developing algorithms and modeling parameters such as body movement due to pulmonary and heart motion.

FPGA clock frequencies are slow enough that only a fraction of the interconnect’s bandwidth is used. By exploiting this bandwidth, the transfer of large amounts of data can be greatly accelerated. Alternatively, it may also be possible to save area on fixed-bandwidth links by using on-chip serial signaling. For datapath-intensive designs which operate on words instead of bits, this can reduce wiring congestion as well. This thesis proposes relatively simple circuit-level modifications to FPGA interconnect to enable high-bandwidth communication. High-level area estimates indicate a potential interconnect area savings of 10 to 60% when serial links are used. Two interconnect pipelining techniques, wave pipelining and surfing, are adapted to FPGAs and compared against each other and against regular FPGA interconnect in terms of throughput, reliability, area, power, and latency. Source-synchronous signaling is used to achieve high data rates with simple receiver design. Statistical models for high-frequency power supply noise are developed and used to estimate the probability of error of wave pipelined and surfing links as a function of link length and operating speed. Surfing is generally found to be more reliable and less sensitive to noise than wave pipelining. Simulation results in a 65nm process demonstrate a throughput of 3Gbps per wire across a 50-stage, 25mm link.

La reducción de la tecnología MOSFET planar ha sido la opción tecnológica dominante en las últimas décadas. Sin embargo, hemos llegado a un punto en el que los materiales y problemas en los dispositivos surgen, abriendo la puerta para estructuras alternativas de los dispositivos. Entre estas estructuras se encuentran los dispositivos DG, SGT y Triple-Gate. Estas tres estructuras están estudiadas en esta tesis, en el contexto de rducir las dimensiones de los dispositivos a tamaños tales que los mecanismos cuánticos y efectos de calan coro deben tenerse n cuenta. Estos efectos vienen con una seria de desafíos desde el pun to de vista de modelación, unos de los más grandes siendo el tiempo y los recursos comprometidos para ejecutar las simulaciones. para resolver este problema, esta tesis propone modelos comlets analíticos y compactos para cada una de las geometrías, validos desde DC hasta el modo de operación en Rf para los nodos tecnológicos futuros. Dichos modelos se han extendido para analizar el ruido de alta frecuencia en estos diapositivos.

Improved transient performance and converter miniaturization are the major driving factors behind high frequency operation of switching power supplies. However, high speed operation is limited by topology, control, semiconductor, and packaging technologies. The inherent mitigation of switching loss in resonant converters makes them prime candidates for use when the limits of switching frequency are pushed. The goal of this thesis is to address two areas that practically limit the achievable switching frequency of resonant topologies. Traditional control methods based on single cycle response are impractical at high frequency; forcing the use of pulse density modulation (PDM) techniques. However, existing pulse density modulation strategies for resonant converters in dc/dc applications suffer from: • High semiconductor current stress. • Slow response and large filter size determined by the low modulating frequency. • Possibly operating at fractions of resonant cycles leading to switching loss; thereby limiting the modulating frequency. A series resonant converter with variable frequency PDM (VF-PDM) with integral resonant cycle control is presented to overcome the limitations of existing PDM techniques to enable efficient operation with high switching frequency and modulating frequency. The operation of the circuit is presented and analyzed, with a design procedure given to achieve fast transient performance, small filter size, and high efficiency across the load range with current stress comparable to conventional control techniques. It is shown that digital implementation of the controller can achieve favourable results with a clock frequency four times greater than the switching frequency. Driving the synchronous rectifiers is a considerable challenge in high current applications operating at high switching frequency. Resonant gate drivers with continuous inductor current experience excessive conduction loss, while discontinuous current drivers are subject to slow transitions and high peak current. Current source drivers suffer from high component count and increased conduction loss when applied to complementary switches. A dual-channel current source driver is presented as a means of driving two complementary switches. A single coupled inductor with discontinuous current facilitates low conduction loss by transferring charge between the MOSFET gates to reduce the number of semiconductors in the current path, and reducing the number of conduction intervals. The operation of the circuit is analyzed, and a design procedure based on minimization of the total synchronous rectifier loss is presented. Implementation of the digital logic to control the driver is discussed. Experimental results at megahertz operating frequencies are presented for both areas addressed to verify the theoretical results. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2012-09-09 20:43:56.997

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