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京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18653号 / 工博第3962号 / 新制||工||1610(附属図書館) / 31567 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 杉浦 邦征, 教授 白土 博通, 教授 河野 広隆 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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This thesis presents a theoretical and numerical investigation of silicon-on-insulator trench based passive optical components, bend and splitter, respectively. Compact 90 degree and 105 degree bend and splitter are designed with high index-contrast rib waveguide at wavelength 1550nm and serve as building blocks of splitting network in micro-cantilever biosensing application. The main characteristic of trench based bend and splitter structures is their miniature size and their low radiation loss due to the strong light confinement in high index-contrast systems. Thus large scale, high density optical integrated splitting network becomes possible with the associated advantages of compactness. With FDTD simulation, we show that single-mode trench based bends and splitters exhibit around 16000nm X 16000nm overall size with low loss for different bending angle. Total efficiency is about 92.9% (90 degree bend), 89.3% (105 degree bend), 92% (90 degree splitter) and 84% (90 degree splitter) respectively.

Factors affecting the risk of ribcage injury in adult subjects during CPR were investigated using the torso region of the THUMS model, a full human body FE-model, representing an average adult male. The thoracic dynamic response of the model was compared to experimental PMHS hub loading impact data and live-subject CPR data found in the literature. The model was then used to study the risk of obtaining injuries in various simulated CPR conditions, also varying the stiffness of the costal cartilage. Parameters that are known to predict induced injuries were extracted from the model simulations, i.e. chest deflections, and maximum 1st principal strain and von-Mises stress in the ribs and sternum, as well as the pressure in the heart muscle. These were compared with values that have been reported to have the potential to cause injury. The predictions were compared to experimental findings of the probability of CPR resulting in fractures of the ribs and sternum. The previously mentioned parameters did not reach high enough values to predict fracture occurrences, but interesting trends were highlighted with regards to the different loading conditions investigated. It was demonstrated that human body FE-model simulation studies can be useful for investigating the influence of different CPR related loading conditions on the risk of occurrences of rib and sternal fractures.

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This dissertation presents the results of dynamic material tests and computational modeling exploring the effects of regional rib mechanical properties on thoracic fracture patterns. Test coupon modeling was used to verify the test setup. These material properties were incorporated into a human body computational model. The data from the material tests for all subjects indicate a statistically significant increase in the average stiffness and average ultimate stress for the cortical bone specimens located in the lateral (11.9 GPa modulus, 153.5 MPa ultimate stress) portion of the ribs versus the anterior (7.51 GPa, 116.7 MPa) and posterior (10.7 GPa, 127.7 MPa) rib locations. The results from computational modeling for both frontal and lateral impacts illustrate that the location and number of rib fractures are altered by the inclusion of rib material properties that vary by region. A sensitivity analysis of the effects of altering the failure strain criteria on the number of rib fractures predicted is performed revealing improved sensitivity of the modified THUMS model versus the original THUMS model for failure strains from 0.8 to 1.8%. The results from the small specimen tests are compared to results obtained for three-point bending of whole human rib sections. / Ph. D.

In the past few decades, the operating temperatures of gas turbine engines have increased significantly with a view towards increasing the overall thermal efficiency and specific power output. As a result of increased turbine inlet temperatures, the hot gas path components downstream of the combustor section are subjected to high heat loads. Though materials with improved temperature capabilities are used in the construction of the hot gas path components, in order to ensure safe and durable operation, the hot gas path components are additionally supplemented with thermal barrier coatings (TBCs) and sophisticated cooling techniques. The present study focusses on two aspects of gas turbine cooling, namely augmented internal cooling and external film cooling. One of the commonly used methods for cooling the vanes involves passing coolant air bled from the compressor through serpentine passages inside the airfoils. The walls of the internal cooling passages are usually roughened with turbulence promoters like ribs to enhance heat transfer. Though the ribs help in augmenting the heat transfer, they have an associated pressure penalty as well. Therefore, it is important to study the thermal-hydraulic performance of ribbed internal cooling passages. The first section of the thesis deals with the numerical investigation of flow and heat transfer characteristics in a ribbed two-pass channel. Four different rib shapes- 45° angled, V-shaped, W-shaped and M-shaped, were studied. This study further aims at exploring the performance of different rib-shapes at a large rib pitch-to-height ratio (p/e=16) which has potential applications in land-based gas turbines operating at high Reynolds numbers. Detailed flow and heat transfer analysis have been presented to illustrate how the innate flow physics associated with the bend region and the different rib shapes contribute to heat transfer enhancement in the two-pass channel. The bend-induced secondary flows were observed to significantly affect the flow and heat transfer distribution in the 2nd pass. The thermal-hydraulic performance of V-shaped and 45° angled ribs were better than W-shaped and M-shaped ribs. The second section of the study deals with the analysis of film cooling performance of different hole configurations on the endwall upstream of a first stage nozzle guide vane. The flow along the endwall of the airfoils is highly complex, dominated by 3-dimensional secondary flows. The presence of complex secondary flows makes the cooling of the airfoil endwalls challenging. These secondary flows strongly influence endwall film cooling and the associated heat transfer. In this study, three different cooling configurations- slot, cylindrical holes and tripod holes were studied. Steady-state experiments were conducted in a low speed, linear cascade wind tunnel. The adiabatic film cooling effectiveness on the endwall was computed based on the spatially resolved temperature data obtained from the infrared camera. The effect of mass flow ratio on the film cooling performance of the different configurations was also explored. For all the configurations, the coolant jets were unable to overcome the strong secondary flows inside the passage at low mass flow ratios. However, the coolant jets were observed to provide much better film coverage at higher mass flow ratios. In case of cylindrical ejection, the effectiveness values were observed to be very low which could be because of jet lift-off. The effectiveness of tripod ejection was comparable to slot ejection at mass flow ratios between 0.5-1.5, while at higher mass flow ratios, slot ejection was observed to outperform tripod ejection. / Master of Science