This work explores the physics of micro and nano-scale systems immersed in a fluid. Previous literature has established an understanding of the fluid-solid interaction for systems including cantilevers and doubly clamped beams. Building on these advances, this work extends the theory of doubly clamped beams with an arbitrary amount of tension. Both the driven and stochastic dynamics of a doubly clamped beam are explored. The driven dynamics are investigated for a spatially applied harmonic driving force, and demonstrates quantitative agreement with an experimental beam that is driven electrothermally, in both air and in water. For the stochastic dynamics, the noise spectrum describes the thermal fluctuations at a given frequency. The theoretical model provides an analytical expression for the noise spectrum from an arbitrary number of modes. The noise spectrum of the first eleven modes are computed, and show excellent agreement with the noise spectrum from finite element simulations, which is computed from the deterministic ring down. This agreement is shown across different fluids (air and water), and for multiple measuring points including at the beam midpoint and the quarter point. In addition to exploring the linear dynamics of these systems, the case of large perturbations, resulting in nonlinear dynamics, is explored. This regime is motivated by exploring the theoretical dynamics of a uniformly shrinking doubly clamped beam. The challenges of modeling such a beam using finite element simulations are discussed. As a simpler and more direct alternative to access the nonlinear regime, a virtual beam is defined. The virtual beam controls the nonlinearity of the restoring force by modifying the Young's modulus. This work defines the Young's modulus such that the restoring force is like a Duffing oscillator. Then, the dynamics of this virtual beam are explored in air and water, and it is demonstrated that the Duffing oscillator serves as an appropriate reduced order model for this virtual beam. To understand the stochastic dynamics of the virtual beam, the stochastic Duffing oscillator is solved numerically. The ensemble autocorrelation of the beam dynamics are investigated for nonlinearities varying from linear to strongly nonlinear. The numeric autocorrelation is used to quantify the range of nonlinear strength where a deterministic approach, the ring down, can yield a good approximation. In the strongly nonlinear regime, the stochastic numerical approach is used to determine the autocorrelation. This research was supported by the National Science Foundation, grant number CMMI-2001559, and portions of the computations were conducted using the resources of Virginia Tech's Advanced Research Computing center. / Doctor of Philosophy / This work explores the physics of small systems immersed in a fluid, such as air or water. Previous literature has established an understanding of the force from a fluid acting on solids such as cantilevers and doubly clamped beams. Building on these advances, this work extends theory to doubly clamped beams with any amount of tension. Both the driven and stochastic, or randomly driven, dynamics of a doubly clamped beam are explored. The driven dynamics are developed for a driving force applied over part of the beam, and demonstrates quantitative agreement with an experimental beam, in both air and in water. For the stochastic dynamics, the noise spectrum describes the random thermal fluctuations of the beam at a given frequency. These thermal fluctuations are small, but measureable deviations of the system from equilibrium and are significant for these small scale systems. The noise spectrum can be estimated by computing the statistics from many randomly forced simulations. However, previous literature provides a direct computation of the noise spectrum with a single deterministic ring down. This work provides an analytical expression for the noise spectrum of a doubly clamped beam in tension in fluid for multiple modes. The theoretical noise spectrum shows excellent quantitative agreement with the ring down from finite element simulations. The agreement between theory and simulation is demonstrated in air and water, for a measurement of the noise spectrum at the beam midpoint and at the beam quarter point. In addition to exploring the linear dynamics of these systems, the case of large perturbations, resulting in nonlinear dynamics, is explored. This regime is motivated by exploring the theoretical dynamics of a uniformly shrinking doubly clamped beam. The challenges of modeling such a beam using finite element simulations are discussed. As a simpler and more direct alternative to access the nonlinear regime, a virtual beam is defined. The virtual beam controls the nonlinearity of the restoring force such that the system becomes increasingly stiff as the displacements become larger. This definition results in the restoring force following a Duffing oscillator. Then, the dynamics of this virtual beam are explored in air and water, and it is demonstrated that the Duffing oscillator serves as an appropriate reduced order model for this virtual beam. For varying nonlinear strengths, the stochastic numerical approach is used to quantify the dynamics, and the range of usefulness for the deterministic ring down is investigated. This research was supported by the National Science Foundation, grant number CMMI-2001559, and portions of the computations were conducted using the resources of Virginia Tech's Advanced Research Computing center.

付記する学位プログラム名: 京都大学卓越大学院プログラム「先端光・電子デバイス創成学」 / 京都大学 / 新制・課程博士 / 博士(工学) / 甲第23431号 / 工博第4886号 / 新制||工||1764(附属図書館) / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 白石 誠司, 教授 木本 恒暢, 教授 引原 隆士 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

<p> Some cumulative mass-yield ratios for thermal to epi-thermal neutron fissions of 239Pu have been measured by nondestructive Ge(Li) spectrometric and radiochemical methods. The mass-yield ratios of 85mKr, 91Sr- 91mY, 92Sr, 97Nb-97Zr, 99mTc, 103Ru, 105Ru, 131I, 132Te-132I, 133I, 135I-135Xe, 140Ba-140La, 143Ce and 147Nd for both thermal to epi-Cd and thermal to epi-Sm fissions did not show any significant fluctuations. The yields of 72Zn and 166Dy-166Ho in epi-Sm fission were found to be 30±2% lower than in the fission caused by thermal neutrons. Similarly the yields of 115Cd and 112Pd were found to be lower by 46±2% and 24±3% respectively. The 77 mass chain, measured as both 77Ge and 77As, showed only a very slight, if any, decrease for epi-Cd and epi-Sm fissions as compared with thermal neutron fissions.</p> <p> The results are consistent with the two-mode-of-fission hypothesis. An attempt has also been made to correlate the observations with the effect of the spin states of the fissioning nucleus at the saddle point.</p> / Thesis / Doctor of Philosophy (PhD)

The objectives of this study were (1) to evaluate the use of digital infrared thermal imaging as a diagnostic tool for early detection of mastitis, (2) to test the usefulness of thermography in the quantative evaluation of mammary function in high and low milk producing cows and (3) to establish base-line measurements of thermographic patterns of the bovine claw. To investigate these objectives, three experiments were conducted to determine the link between thermal temperature gradients of the bovine mammary gland to level of milk production (high milk producers vs. low milk producers), early diagnosis of mastitis and lameness evaluation in dairy cattle. The first study investigated the relationship between level of milk production to udder conformation and thermal signatures of the udder gradients. The second study (case study) involved the use of DITI for diagnosis of mastitis in dairy cows under a heatstressed environment. Lastly, the third study was to establish base-line measurements in temperature gradients of regions of the bovine claw.

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This work presents the modeling and analysis of EMI and thermal performance for switch power supply by using the CAD tools. The methodology and design guidelines are developed. By using a boost PFC circuit as an example, an equivalent circuit model is built for EMI noise prediction and analysis. The parasitic elements of circuit layout and components are extracted analytically or by using CAD tools. Based on the model, circuit layout and magnetic component design are modified to minimize circuit EMI. EMI filter can be designed at an early stage without prototype implementation. In the second part, thermal analyses are conducted for the circuit by using the software Flotherm, which includes the mechanism of conduction, convection and radiation. Thermal models are built for the components. Thermal performance of the circuit and the temperature profile of components are predicted. Improved thermal management and winding arrangement are investigated to reduce temperature. In the third part, several circuit layouts and inductor design examples are checked from both the EMI and thermal point of view. Insightful information is obtained. / Master of Science

Although suitable CAD tools for thermal and electrical analyses in power electronic systems are available, traditional stand-alone simulation method seldom takes into consideration of the inter-dependency of semiconductor device power loss and junction temperature in an iterative process. However these dependencies are important, especially for applications where both cooling and power losses are driven by complex mechanisms. For a power supply system, a dynamic design process is necessary to address both electrical and thermal issues. It is because the steady state temperatures of the system are obtained from loss-and-temperature iteration. Once a system solid body model is built, iterations between power loss and junction temperature calculations are performed to obtain the steady state temperature distribution. Since reliability and failure rate of components are directly related to temperatures, an accurate model is critical to provide proper thermal management, which achieves maximum power density. All cooling-related data such as placement of components, airflow rate, heat sink size, and device types are subjected to design changes in order to meet ultimately the temperature requirements. The goal of this thesis is to demonstrate the benefits of integrated analysis and design tools applied in distributed power supply systems designs. First, it will significantly speed up the design process and eliminate the errors resulting from repeated manual data entry and information exchange. Second, the integrated electrical-thermal design tools encompass electrical, thermal, layout, and packaging design to obtain the optimal system design. / Master of Science

Freeze concentration is a thermal separation process that is used to purify aqueous solutions. One application of recent interest is seawater desalination. For freeze concentration to be an effective desalination method, a high ice growth rate and product purity must be achieved with energy usage comparable to that of competing technologies. The purpose of this thesis is to develop a coupled heat and mass transfer model to predict the growth rate and purity of the solid phase for ice grown about a horizontal, immersed tube. By simultaneously solving the heat and mass transfer problems, this model improves upon previous attempts found in the literature. In addition, an experimental apparatus was constructed and a series of ten experiments was run, considering a range of cooling rates, process times, and saltwater concentrations. Average ice growth velocities ranged from 3.1-13.1 mm/h and the observed partition coefficient ranged from 0.42-0.71. The model was calibrated using experimental data, and the coefficients of variation for the fitted model's prediction of ice mass and capture concentration were 15.4% and 7.6% respectively. Based on insights from modeling and experimentation, a series of suggestions are made regarding future modeling and process design. / Master of Science / Freeze concentration is a thermal process that is used to purify a liquid containing dissolved solids. One application of recent interest is seawater desalination. For freeze concentration to effectively purify seawater, a high ice growth rate and product purity must be achieved with energy usage comparable to that of competing technologies. The purpose of this thesis is to develop a coupled heat and mass transfer model to predict the growth rate and purity of the solid phase for ice grown about a horizontal, immersed tube. By simultaneously solving the heat and mass transfer problems, this model improves upon previous attempts found in the literature. In addition, an experimental apparatus was constructed and a series of ten experiments was run, considering a range of cooling rates, process times, and saltwater concentrations. Average ice growth velocities ranged from 3.1-13.1 mm/h and the salinity of the ice ranged from 0.42-0.71% of the original concentration. Based on insights from modeling and experimentation, a series of suggestions are made regarding future modeling and process design.