京都大学 / 新制・課程博士 / 博士(理学) / 甲第22996号 / 理博第4673号 / 新制||理||1670(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 高柳 匡, 教授 杉本 茂樹, 教授 田中 貴浩 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Bio-based flax fiber polymer composites (FFPC) have the potential to replace metals and synthetic fibers in certain applications due to their unique mechanical properties. However, the long term reliability of FFPC needs to be better understood. In this study, the fatigue limit was evaluated using mathematical, thermographic, and energy-based approaches. Each approach determined fatigue limits around 45% load of ultimate tensile strength at a loading frequency of 5 Hz. Thermographic and energy-based approaches were also implemented at different loading frequencies (5, 7, 10, and 15 Hz) to define the effect of loading frequency on the fatigue life. Fatigue limit was found to decrease slowly with increasing loading frequency. Moreover, two forms of damage energy (thermal and micro-mechanical) during cyclic loading was separated using an experimental approach to pinpoint the main responsible damage energy for decreasing fatigue limit with increasing loading frequency.

Main goal of this thesis is improvement of an order book model so that it behaved more realistically, based on a model developed by J. Plačková in her diploma thesis in 2011. We consider this simple model for evolution of order book in which limit orders of unit size arrive according to independent Poisson processes. Frequency of buy limit orders below resp. sell limit orders above a given price level is described by demand and supply functions. Buy (resp. sell) limit orders that arrive with price above (resp. below) the current ask (resp. bid) price are converted into market orders and cancellation of orders is not allowed. We extend this model by introducing market makers who place at the same time one buy and one sell limit order with current bid and ask prices. We show how introducing market makers reduces the spread that in the original model was unrealistically large and also show a method of calculating the precise rate of market makers needed to reduce the spread to zero. 1

The following is an exploration into the composition and construction of a marine research laboratory situated on a remote sea cliff off the coast of Norway. The settlement is composed as a model of the world. Located at the chaotic boundary of earth, sea and sky, the <br />construction acts against these forces as threshold and counterpoint. It is the reconstitution of a world, a settlement, a center in a perceived infinity. / Master of Architecture

Background: Pulsed amperometric detection is a relatively new method for detection of ions and especially non-electrolytes such as carbohydrates in aqueous solutions. Pulsed amperometric detection relies on a redox reaction while electrochemical impedance simply measures the real and capacitive resistant of the solution. There is a correlation between the real impedance of a solution and the ionic strength of the solution. Method: This work explores measuring real impedance of pure water as a function of temperature from 25.0 to 60.0 °C to determine the relationship between impedance and temperature. Maintaining temperature at 25.0 °C, solutions of sodium chloride, potassium carbonate, sodium sulfate acetate and bicarbonate have been measured using impedance spectroscopy. Results: Regression analysis shows that measuring anions using impedance spectroscopy and simple stainless steel cylinders that detection limits at the parts per trillion (ppt) level are possible. There was no statistical difference when comparing impedance values of the same concentration of acetate and chloride in solution, showing real impedance is not dependent on ion size. However, ions with higher charge do result in lower impedance measurements. Conclusions: This work establishes the use of simple, small, robust stainless steel cylinders and impedance measurements following separation for the identification and quantification of ions in solution.

Using NASDAQ high frequency trading (HFT) and minute-by-minute Limit Order Book (LOB) data over 120 sample stocks in 10 weeks between 2008-2010, including the week of the Lehman Brothers crisis, we study how trading activities of HFTs, NHFTs (Non-HFTs) and their order placements interact, and affect overall market quality. We capture order placements via the depth (step) and the height (price) dimensions along the LOB. We first document that HFTs are active not only at the top of the LOB, but their orders are placed along the LOB with an average around the 5th step, slightly ahead of NHFTs who on average are close to the 6th step. Generally, both HFTs and NHFTs are more aggressive in order placement with large stocks and hidden orders and HFT orders are further ahead during the crisis week, though price-wise they all back off somewhat with more conservative placements by NHFTs. In market turmoil, whenever HFTs see NHFTs trade among themselves, they become less aggressive in order placement. However, when HFTs trade, other HFT orders become more aggressive by moving ahead. On the contrary, NHFTs generally become more aggressive when other NHFTs supply liquidity in trading, and more conservative when HFTs are the supplier. We find mixed results on the impact of HFTs order placements and trading activities on market quality by different measures, but aggressive orders by HFTs and NHFTs both are related with decreases in short-term market volatility. Our findings highlight the importance of not only studying HFTs and NHFTs activities along the LOB, but also in both depth and height dimensions, instead of only at the market inside quotes.

Accurate flash point and flammability limit data are needed to design safe chemical processes. Unfortunately, improper data storage and reporting policies that disregard the temperature dependence of the flammability limit and the fundamental relationship between the flash point and the lower flammability limit have resulted in compilations filled with erroneous values. To establish a database of consistent flammability data, critical analysis of reported data, experimental investigation of the temperature dependence of the lower flammability limit, and theoretical and empirical exploration of the relationship between flash points and temperature limits are undertaken. Lower flammability limit measurements in a 12-L ASHRAE style apparatus were performed at temperatures between 300 K and 500 K. Analysis of these measurements showed that the adiabatic flame temperature at the lower flammability limit is not constant as previously thought, rather decreases with increasing temperature. Consequently the well-known modified Burgess-Wheeler law underestimates the effect of initial temperature on the lower flammability limit. Flash point and lower temperature limit measurements indicate that the flash point is greater than the lower temperature limit, the difference increasing with increasing lower temperature limit. Flash point values determined in a Pensky-Martens apparatus typically exceed values determined using a small-scale apparatus above 350 K. Data stored in the DIPPR® 801 database and more than 3600 points found in the literature were critically reviewed and the most probable value recommended, creating a database of consistent flammability data. This dataset was then used to develop a method of estimating the lower flammability limit, including dependence on initial temperature, and the upper flammability limit. Three methods of estimating the flash point, with one based entirely on structural contributions, were also developed. The proposed lower flammability limit and flash point methods appear to predict close to, if not within, experimental error.

Mathematics students and teachers are familiar with the difficulty of learning and teaching concepts of continuity and limits. Research has expanded our knowledge of how students think about these concepts, including different conceptions and metaphors students use to reason about continuity and limits at a point. From the literature I have identified four potentially problematic conceptions (PPCs) students may use when reasoning about limit and continuity at a point. Questionnaires were administered to 861 BYU students in various mathematics courses to determine how prevalent and persistent the PPCs are among the students in each course. Interviews were conducted with nine first semester calculus to get an idea of how students reason about continuity and limit at a point and how that influences whether they use the PPCs. Students showed evidence of holding the four PPCs with a decrease in these conceptions typically after they took a course in analysis. Participants also did not understand the Formal definition of a Limit until they took a course in Analysis. Students were able to reason appropriately using many different conceptions of continuity. Considering limit conceptions, students using a Dynamic conception of Limit tended to be better able to reason about continuity and limit at a point. Students who did not use a Dynamic conception of limit tended to use the PPCs in general and incorrectly more often.

Propulsion engine combustor design and analysis require experimentally verified data on the chemical kinetics of limiting fuel combustion rates. Among the important data is the combustion extinction limit as measured by the maximum global strain rate on a laminar, counterflow, non-premixed flame. The extinction limit relates to the ability to maintain combustor operation, and the extinction limit data for pure fuel versus air systems provide a relative reactivity scale for use in the design of flame holders. Extinction limit data were obtained for nine fuels by means of a laminar flame experiment using an opposed jet burner (OJB). The OJB consists of two axi-symmetric tubes (for fuel and oxidizer separately), which produce a flat, disk-like, counterflow diffusion flame. This paper presents results of experiments conducted in an OJB that measured extinction limits at one atmosphere for vaporized n-heptane, the Air Force-developed fuels JP-7, and JP-10, as well as methane, ethane, ethylene, propane, butane, and hydrogen. In hypersonic aircraft development it is desirable to design a Scramjet engine that is operated on hydrocarbon fuel, particularly JP-7 due to its distinct properties. This study provides key data for JP-7, for which very limited information previously existed. The interest in n-heptane is twofold. First, it has undergone a significant amount of previous flame structure and extinction limit study. Second, n-heptane (C7H16) is a pure substance, and therefore does not vary in composition, as does JP-7, which is a variable mixture of several different hydrocarbons. These two facts allow a baseline to be established by comparing the new OJB results to those previously taken. Additionally, the existing data for n-heptane, for mixtures up to 26 mole percent in nitrogen, is extended to 100% n-heptane, reaching an asymptotic limit. Extinction limit data for the two fuels are given with a comparison to hydrogen and several other gaseous hydrocarbon fuels. Complete experimental results are included. / Master of Science

As a result of growing concerns about the carbon emissions associated with the combustion of conventional hydrocarbon fuels, hydrogen is gaining more attention as a clean alternative. The combustion of hydrogen in air produces no carbon emissions. However, hydrogen-air combustion does have the potential to produce oxides of nitrogen (NOx), which are harmful pollutants. The production of NOx can be significantly curbed using lean premixed combustion, wherein hydrogen and air are mixed at an equivalence ratio (the ratio of stoichiometric to actual air in the combustion process) significantly less than 1.0 prior to combustion. Hydrogen is a good candidate for use in lean premixed systems due to its very wide flammability range. The potential for the stable combustion of hydrogen at a wide range of equivalence ratios makes it particularly well-suited to application in gas turbines, where the equivalence ratio is likely to vary significantly over the operating range of the machine. The strong lean combustion stability of hydrogen-air flames is due primarily to high reaction rates and the associated high turbulent burning velocities. While this is advantageous at low equivalence ratios, it presents a significant danger of flashback — the upstream propagation of the flame into the premixing device — at higher equivalence ratios. An investigation has been conducted into the operation of a specific hydrogen-air premixer design in a gas turbine engine. Laboratory tests were first conducted to determine the upper stability limits of a single premixer. Tests were then carried out in which eighteen premixers and a custom-fabricated combustor liner were installed in a modified Pratt and Whitney Canada PT6A-20 turboprop engine. The tests examined the premixer and engine operability as a result of the modifications. A computer cycle analysis model was created to help analyze and predict the behavior of the modified engine and premixers. The model, which uses scaled component maps to predict off-design engine performance, was integral in the analysis of premixer flashback which limited the operation of the modified engine. / Master of Science