For over 30 years research has been done concerning the solidification and quenching of light metal alloys for the purpose of improving material properties. This thesis is concerned with an interesting new process for casting metals, by spraying water onto a sand mould, removing the sand and the directly quenching the part. This process is challenging since the component during solidification is extremely fragile, and the rate of cooling that is needed could seriously damage it. The water flow rate to the component needs to be quickly and precisely controlled. Additionally as this a new method there is very little prior art. The purpose of this thesis to develop a control system for the water sprayers flow rates. With this system the flow rate through the nozzles will be controlled indirectly using pressure feedback. The material properties and casting process, and how they influenced the design and construction of the spraying apparatus, are explained first. The hydraulic plant being controlled consists of three proportional valves connected to six spray nozzles. Based on experiments, the plant is extremely nonlinear making it difficult to control. Several controllers were developed and compared experimentally. The best performance was produced by extending a proportional plus integral plus derivative controller by adding an empirical nonlinear feedforward component; smoothing the setpoint; bounding the integration term; adding one bias at time zero and a 2nd bias for the remaining time (to mitigate valve stiction and to prime the hoses). This extended PID controller produced a 0.7% mean error and 1.9% mean absolute error for a multi-step setpoint covering a range of 0 to 80 PSI. Its performance was also highly repeatable. The standard deviations of the mean error, mean absolute error and maximum absolute error were less than 0.2 PSI over five runs. / Thesis / Master of Applied Science (MASc) / During the sand casting of aluminium and magnesium rapid cooling will greatly improve the material properties. By containing the liquid metal in a water soluble sand mould, and spraying it with water; the desired part shape and rapid cooling can be achieved. Removing the mould requires a powerful high flow rate jet. During the solidification of the metal, the flow rate must be reduced or the part would be demolished. This necessitated the development of a high speed, high flow rate controller to adjust the flow rate to remove the sand but not damage the part, and to maintain a smooth continuous cooling rate. The hydraulic system being controlled consists of three electronic valves connected to six spray nozzles. Several controllers are developed and compared experimentally. The best controller is shown to provide a quick and precise response.

<p> In this thesis, a high-speed inverse Walsh transform apparatus was designed and built which sums over the sixteen most dominant coefficients in the time base period. The transform includes a maximum of 64 terms. The Walsh function generator used works with a clock rate up to 10 MHz to produce 64 different sequency terms with accurate timing and hazard free operation. A synchronizing pulse is produced by the circuit to determine the beginning of the Walsh transform period. The final adder stage limits the speed of the apparatus to a 1 MHz square wave. An application of the instrument was made to reconstruct one line of an actual video signal.</p> / Thesis / Master of Engineering (MEngr)

В выпускной квалификационной работе магистранта рассматриваются основные направления развития высокоскоростного железнодорожного сообщения в Китае. Студент уделяет внимание общей характеристике железнодорожной инфраструктуры КНР, прослеживает историю строительства сети скоростных жд, анализирует текущее положение дел в индустрии. / In the student master thesis, the main directions of the development of high-speed rail communication in China are considered. The student pays attention to the general characteristics of the railway infrastructure of China, traces the history of the construction of high-speed rail network, analyzes the current state of affairs in the industry.

High-amplitude freestream turbulence and surface roughness elements can excite a laminar boundary-layer flow sufficiently enough to cause streamwise-oriented vortices to develop. These vortices resemble elongated streaks having alternate spanwise variations of the streamwise velocity. Following the transient growth phase, the fully developed vortex structures downstream undergo an inviscid secondary instability mechanism and, ultimately, transition to turbulence. This mechanism becomes much more complicated in high-speed boundary layer flows due to compressibility and thermal effects, which become more significant for higher Mach numbers. In this research, we formulate and test an optimal control algorithm to suppress the growth rate of the aforementioned streamwise vortex system. The derivation of the optimal control algorithm follows two stages. In the first stage, to optimize the computational cost of the analysis, the study develops an efficient numerical algorithm based on the nonlinear boundary region equations (NBREs), a reduced form of the compressible Navier-Stokes equations in a high-Reynolds-number asymptotic framework. The NBREs algorithm results agree well with direct numerical simulation (DNS) results. The numerical simulations are substantially less computationally costly than a full DNS and have a more rigorous theoretical foundation than parabolized stability equation (PSE) based models. The substantial reduction in computational time required to predict the full development of a G\"{o}rtler vortex system in high-speed flows allows investigation into feedback control in reasonable total computational time, which is the focus of the second part of the study. In the second stage, the method of Lagrange multipliers is utilized -- via an appropriate transformation of the original constrained optimization problem into an unconstrained form -- to obtain the adjoint compressible boundary-region equations (ACBREs) and corresponding optimality conditions, which constitute the basis of the optimal control approach. Numerical solutions for high-supersonic and hypersonic flows reveal a significant decrease in the kinetic energy and wall shear stress for all configurations considered. Streamwise velocity contour plots illustrate the qualitative effect of the optimal control iterations, demonstrating a significant decrease in the amplitude of the primary vortex instabilities.

The VT i-Ship Lab has been assigned the task of designing and building a Personal Hydrofoil Craft capable of carrying two people, featuring the distinctive capabilities of foiling and diving. This thesis examines the attributes of fully submerged hydrofoils and their prospective advancements. Diverse configurations of fully submerged hydrofoils are scrutinized, accompanied by an exploration of their respective stability characteristics. A comprehensive analysis is conducted on the design space trade-offs, incorporating potential flow-based methodologies such as the lifting line and vortex lattice methods, encompassing considerations for the free surface, structural computations, and propulsion optimization. In conjunction with the design study computational fluid dynamics is employed to verify the estimated values and to fine-tune the system allowing for a robust low-fidelity system that can quickly estimate the appropriate hydrofoil arrangement for the desired conditions. Various hydrofoil and craft configurations are explored discussing the trade-offs with a final design being chosen and a thorough mechanical design pursued. / Master of Science / The VT i-Ship Lab is conducting research on a watercraft known as a "Personal Hydrofoil Craft." This vehicle is designed to carry two people, glide on the water's surface, and dive underwater. Hydrofoil crafts use specialized underwater wings to reduce resistance and enhance efficiency. Our focus is on fully submerged hydrofoils, studying their stability and efficiency. We employ computer simulations and advanced methods to design and optimize these submerged hydrofoils. The goal is to enhance our understanding of their functionality and performance through real-life experiments. This research has the potential to improve watercraft technology, leading to more efficient and stable boats in the future. By exploring the science behind hydrofoil designs, we aim to contribute valuable insights to the field of water transportation.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第25017号 / 工博第5194号 / 新制||工||1991(附属図書館) / 京都大学大学院工学研究科化学工学専攻 / (主査)教授 外輪 健一郎, 教授 松坂 修二, 教授 佐野 紀彰 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

High-speed railways provide fast, comfortable and environmentally friendly transportation for passengers. However, they are fraught with high investment costs that decrease the willingness of governments to construct new lines. This thesis proposes a new way of building high-speed railways to decrease investment costs, where power from overhead wire is, for the majority of a journey, substituted with power from batteries located on the train sets. Not only can the construction and maintenance costs for the overhead wire itself be reduced; as tunnels can be narrowed when no overhead wire is needed, tunnelling costs decrease as well. An algorithm using dynamic programming is devised which calculates the optimal placement of overhead wire given a velocity and altitude profile of a journey, which is then applied on the planned Swedish high-speed line Ostlänken. The cost savings amount in total to approximately 5.689 billion SEK. It is a significant reduction in absolute terms, but is likely even higher, as the cost estimates for electrification are conservative. More studies on this aspect is needed to obtain more exact estimates. / Höghastighetståg erbjuder snabba, bekväma och miljövänliga passagerartransporter. Dock kräver dess banor höga investeringskostnader som kan avskräcka för nybyggnationer. För att minska dessa kostnader föreslår denna uppsats ett nytt sätt att bygga höghastighetsbanor på, där kontaktledning byggs på endast delar av sträckan. Där kontaktledning inte byggs drivs tågen av batterier placerade ombord. Utöver lägre kostnader för konstruktion och underhåll av själva kontaktledningen kan också kostnaden för tunneldrivning reduceras, då diametern på tunnlar kan minskas när ingen kontaktledning krävs. I rapporten presenteras en metod med dynamisk programmering för att beräkna den optimala placeringen av kontaktledningssträckor givet en hastighets- och höjdkurva för en bana. Metoden appliceras på den planerade höghastighetsbanan Ostlänken, där kostnadsbesparingarna beräknas uppgå till ungefär 5,689 miljarder SEK. Det är en signifikant besparing i absoluta mått som troligen är ännu större i verkligheten, eftersom de uppskattade kostnaderna för elektrifiering är konservativa. Det behövs fler studier kring dessa kostnader för att kunna erhålla mer exakta uppskattningar av kostnadsbesparingar.

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