Transverse-integrated nodal di usion methods currently represent the standard in full core neutronic simulation. The primary shortcoming of this approach is the utilization of the quadratic transverse leakage approximation. This approach, although proven to work well for typical LWR problems, is not consistent with the formulation of nodal methods and can cause accuracy and convergence problems. In this work, an improved, consistent quadratic leakage approximation is formulated, which derives from the class of higher-order nodal methods developed some years ago. In this thesis a number of iteration schemes are developed around this consistent quadratic leakage approximation which yields accurate node average results in much improved calculational times. The most promising of these iteration schemes results from utilizing the consistent leakage approximation as a correction method to the standard quadratic leakage approximation. Numerical results are demonstrated on a set of benchmark problems and further applied to realistic reactor problems for particularly the SAFARI-1 reactor operating at Necsa, South Africa. The nal optimal solution strategy is packaged into a standalone module which may be simply coupled to existing nodal di usion codes, illustrated via coupling of the module to the OSCAR-4 code system developed at Necsa and utilized for the calculational support of a number of operating research reactors around the world. / Thesis(PhD (Reactor Science))--North-West University, Potchefstroom Campus, 2013

Given graphs G,H, is it possible to find a matching which, when deleted from G, destroys all copies of H? The answer is obvious for some inputs—notably, when G is a large complete graph the answer is “no”—but in general this can be a very difficult question. In this thesis, we study this decision problem when H is a fixed tree or cycle; our aim is to identify those H for which it can be solved efficiently. The H-transverse matching problem, TM(H) for short, asks whether an input graph admits a matching M such that no subgraph of G − M is isomorphic to H. The main goal of this thesis is the following dichotomy. When H is a triangle or one of a few small-diameter trees, there is a polynomial-time algorithm to find an H-transverse matching if one exists. However, TM(H) is NP-complete when H is any longer cycle or a tree of diameter ≥ 4. In addition, we study the restriction of these problems to structured graph classes. / Graduate

A search for diphoton events with large missing transverse energy is conducted using 3.1 pb^{-1} of integrated luminosity of proton-proton collisions at center of mass energy \sqrt{s}=7 TeV. The data were collected with the ATLAS detector at the CERN Large Hadron Collider during the period from March 30, 2010 until August 30, 2010. No excess of such events is observed above the Standard Model background prediction. This result is interpreted in the context of a gravity mediated One Universal Extra Dimension model with \Lambda R=20, N=6 and M_{D}=5 TeV, where \Lambda is the cutoff scale, N is the number of large extra dimensions and M_{D} is the Planck scale in the higher dimensional theory. The compactification radius of the Universal Extra Dimension, R, is excluded for values of 1/R < 728 GeV at 95\% CL, providing the most stringent limit on this model at the time of publication.

A search for diphoton events with large missing transverse energy is conducted using 3.1 pb^{-1} of integrated luminosity of proton-proton collisions at center of mass energy \sqrt{s}=7 TeV. The data were collected with the ATLAS detector at the CERN Large Hadron Collider during the period from March 30, 2010 until August 30, 2010. No excess of such events is observed above the Standard Model background prediction. This result is interpreted in the context of a gravity mediated One Universal Extra Dimension model with \Lambda R=20, N=6 and M_{D}=5 TeV, where \Lambda is the cutoff scale, N is the number of large extra dimensions and M_{D} is the Planck scale in the higher dimensional theory. The compactification radius of the Universal Extra Dimension, R, is excluded for values of 1/R < 728 GeV at 95\% CL, providing the most stringent limit on this model at the time of publication.

In this thesis, dual-frequency optoelectronic oscillators (OEOs) and their applications to transverse load sensing are studied. Two configurations of dual-frequency OEOs are proposed and investigated. In the first configuration, a polarization-maintaining phase-shifted fiber Bragg grating (PM-PSFBG) is employed in the OEO loop to the generation of two oscillating frequencies. The beat between the two oscillating frequencies is a function of the load applied to the PM-PSFBG, which is used in transverse load sensing. To avoid the frequency measurement ambiguity, a second configuration is proposed by coupling a dual-wavelength fiber laser to the dual-frequency OEO. A single tone microwave signal with the frequency determined by the birefringence of the grating is generated in the OEO and is fed into the fiber ring laser to injection lock the dual wavelengths. The sensitivity and the resolution are measured to be 9.73 GHz/(N/mm) and 2.06×10-4 N/mm, respectively. The high stability of the single-tone microwave signal permits accurate measurement, while the frequency interrogation allows an ultra-high speed demodulation.

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In safety-critical environments, it is crucial to have a backup strategy the system can turn to when facing a potentially unsafe situation. Run-time assurance provides a reliable methodology as a backup strategy. This work introduces a new framework for Run-time assurance, by generating trajectories in real-time using an optimal trajectory generation algorithm, then tracking the trajectory using transverse dynamics to design a feedback control law tailored for each trajectory generated. The generated trajectories are treated as safety backup trajectories that are only executed and followed by the plant if deemed necessary by the Run-time assurance logic. By using the Run-time assurance mechanism the system’s safety is ensured regardless of the behavior of the primary controller for the system with some constraints on the system. The framework assumes full knowledge of the environment and the system dynamics, while treating the trajectory generation part as a black box.

Post-tensioned segmental concrete box girders have been in use in the United States since the early 1970s. This unique bridge system uses post-tensioning to connect many smaller concrete bridge segments into very efficient long span bridges. However, because of the slender components, localized transverse bending becomes more critical when compared to more conventional bridge types. Bridge owners are finding that ratings for standard loads and permit trucks are often controlled by the transverse behavior of the girders near concentrated wheel loads. The popular analysis methods used today range from two dimensional frame models to three dimensional finite element models of the entire bridge. Currently, engineers must make sound engineering judgments on limited available information, while balancing safety and economy. To quantify and understand longitudinal and transverse behavior, the results from three live load tests of single cell segmental concrete box girder bridges are presented. Each bridge was instrumented with longitudinal and transverse strain sensors on at least two cross sections as well as rotation and deflection sensors, when possible. Two dimensional transverse frame models and three dimensional shell models were compared to the test results for each subject bridge. The two dimensional frame analyses using the common bottom web pin and roller boundary conditions provide mean absolute percent error in excess of 250%. Conversely, the newly introduced boundary conditions using pin supports at the top and bottom of each web was shown to reduce mean absolute percent error to 82%, which is on the same order of magnitude as longitudinal beamline analysis. The three dimensional shell models were insensitive to several changes including mesh fineness, number of spans modeled, and support conditions. Using uniform surface loading, the transverse modeling procedure was shown to provide significantly more accurate results than the common two dimensional frame models. A faster and more convenient analysis method using a program generated, structure specific, influence surface was also outlined. This method produced similar results when compared to the uniform surface loading method, while allowing additional automation for easier load application. / Ph. D.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18768号 / 理博第4026号 / 新制||理||1580(附属図書館) / 31719 / 京都大学大学院理学研究科数学・数理解析専攻 / (主査)教授 堤 誉志雄, 教授 上田 哲生, 教授 加藤 毅 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

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