This thesis presents the research work carried out in an experimental study on High Speed Milling and a predictive force model. The Oxley??s machining theory [36] that can be considered a purely theoretical approach, which has not yet been applied to the high speed milling process is used to model this process in order to predict the cutting forces. An experimental programme was carried out in order to study and understand the high speed milling process and to collect force data for machining of AISI 1020 plain carbon steel at speeds from 250 to 500m/min, feed rates 0.025 to 0.075mm/tooth and 0.5 and 0.8mm depths of cut, using three different tool configurations with different nose radii. The model developed by Young [5] using the Oxley??s machining theory, for conventional milling, was first applied to the high speed milling operation. The force predictions were satisfactory compared to the measured forces. Using this as the basis, a theoretical model was developed to predict the cutting forces in high speed milling. A smaller chip element was considered in applying the machining theory to satisfy the assumption of two dimensional deformation in the machining theory. Using the flow stress properties for plain carbon steels obtained by Oxley and his co-workers, the cutting force components: tangential, radial and vertical, were predicted with the new developed model for AISI 1020 steel for the same cutting conditions used in the experiment. The model was able to accurately predict the tangential force, while the other two components showed a good agreement with the experimental forces. Then the model was verified using two other materials namely, AISI 1045 plain carbon steel and AISI 4140 alloy steel. The alloy steel was used in both the states, virgin and hardened (heat treated) for the experiment. The comparison of predictions with experimental forces showed good results for these additional two materials. From the results obtained, it is concluded that the developed model can be used to predict the tangential cutting force accurately, while predicting the other force components with a favourable accuracy.

This thesis presents the research work carried out in an experimental study on High Speed Milling and a predictive force model. The Oxley??s machining theory [36] that can be considered a purely theoretical approach, which has not yet been applied to the high speed milling process is used to model this process in order to predict the cutting forces. An experimental programme was carried out in order to study and understand the high speed milling process and to collect force data for machining of AISI 1020 plain carbon steel at speeds from 250 to 500m/min, feed rates 0.025 to 0.075mm/tooth and 0.5 and 0.8mm depths of cut, using three different tool configurations with different nose radii. The model developed by Young [5] using the Oxley??s machining theory, for conventional milling, was first applied to the high speed milling operation. The force predictions were satisfactory compared to the measured forces. Using this as the basis, a theoretical model was developed to predict the cutting forces in high speed milling. A smaller chip element was considered in applying the machining theory to satisfy the assumption of two dimensional deformation in the machining theory. Using the flow stress properties for plain carbon steels obtained by Oxley and his co-workers, the cutting force components: tangential, radial and vertical, were predicted with the new developed model for AISI 1020 steel for the same cutting conditions used in the experiment. The model was able to accurately predict the tangential force, while the other two components showed a good agreement with the experimental forces. Then the model was verified using two other materials namely, AISI 1045 plain carbon steel and AISI 4140 alloy steel. The alloy steel was used in both the states, virgin and hardened (heat treated) for the experiment. The comparison of predictions with experimental forces showed good results for these additional two materials. From the results obtained, it is concluded that the developed model can be used to predict the tangential cutting force accurately, while predicting the other force components with a favourable accuracy.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (leaves 135-139). Also available in electronic version.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 70-73). Also available via the Internet.

Thesis (M.S.)--Rochester Institute of Technology, 1995. / Typescript. Bibliography: leaves 86-89.

Thesis (M.A.)--University of Hong Kong, 2001. / Includes bibliographical references. Also available in print.

abstract: The market for high speed camera chips, or image sensors, has experienced rapid growth over the past decades owing to its broad application space in security, biomedical equipment, and mobile devices. CMOS (complementary metal-oxide-semiconductor) technology has significantly improved the performance of the high speed camera chip by enabling the monolithic integration of pixel circuits and on-chip analog-to-digital conversion. However, for low light intensity applications, many CMOS image sensors have a sub-optimum dynamic range, particularly in high speed operation. Thus the requirements for a sensor to have a high frame rate and high fill factor is attracting more attention. Another drawback for the high speed camera chip is its high power demands due to its high operating frequency. Therefore, a CMOS image sensor with high frame rate, high fill factor, high voltage range and low power is difficult to realize. This thesis presents the design of pixel circuit, the pixel array and column readout chain for a high speed camera chip. An integrated PN (positive-negative) junction photodiode and an accompanying ten transistor pixel circuit are implemented using a 0.18 µm CMOS technology. Multiple methods are applied to minimize the subthreshold currents, which is critical for low light detection. A layout sharing technique is used to increase the fill factor to 64.63%. Four programmable gain amplifiers (PGAs) and 10-bit pipeline analog-to-digital converters (ADCs) are added to complete on-chip analog to digital conversion. The simulation results of extracted circuit indicate ENOB (effective number of bits) is greater than 8 bits with FoM (figures of merit) =0.789. The minimum detectable voltage level is determined to be 470μV based on noise analysis. The total power consumption of PGA and ADC is 8.2mW for each conversion. The whole camera chip reaches 10508 frames per second (fps) at full resolution with 3.1mm x 3.4mm area. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2017

The thesis contains two essays on the economic impacts of high-speed railway (HSR) in China. Utilizing a unique data set of towns in Dongguan, a city in South China, it provides empirical evidence on whether HSR affects economic growth and efficiency or not. The first essay uses the generalized method of moments (GMM) to estimate a dynamic panel data model of the town economies. The empirical results suggest that both HSR and expressway have a positive impact on the general economic development of the towns. However, HSR does not have a significant effect on the development of the manufacturing sector, while expressway does in this regard. These findings lend indirect support to the common argument that HSR can benefit the tertiary sector, but not necessarily other sectors. The second essay investigates the relationship between the advent of HSR and productive efficiency of the manufacturing sector. Using a stochastic frontier approach, it provides empirical evidence that proximity to expressway, rather than to HSR, enhances the efficiency of industrial enterprises.

Cavitation is the formation of vapour filled bubbles in a liquid. They can be generated either by the reduction of the ambient water pressure at constant temperature or by a temperature increase at constant pressure. In the results of the experiments presented in this work a range of different diameter cavitation bubbles were generated by focusing pulses of near IR radiation (le = 1064 nm) from a Q-switched Nd:YAG laser of varying energy in a small water tank. Single exposure high speed shadow photography and Schlieren techniques are used to visualise the oscillating motion of the cavitation bubbles with high temporal and spatial resolution. The optical analysis of the cavitation bubble in free water shows a smooth symmetrical oscillating motion during the first cycle. When the bubble is collapsing near a solid boundary the motion becomes asymmetrical. The Schlieren images in combination with matching plots of a thin film polyvinylidene fluoride (PVDF) pressure transducer confirm the formation of a liquid jet as well as different shock wave emissions for certain bubble to boundary parameters. They also indicate the importance of the resulting fluid flow to stresses induced in the solid boundary. In an attempt to visualise the fluid flow field around an oscillating cavitation bubble the IR laser radiation is focused in a solution of copper sulphate (CUS04) for contrast enhancement. High speed photography in combination with an accurately positioned Schlieren knife edge displays the heated path of the laser beam and the different shapes of the cavitation bubble. For the case of a bubble in free space the marked laser path indicates radial fluid flow only. For a bubble in front of a solid boundary the marked laser path clearly shows the motion of the fluid into the toroidal shaped bubble during the collapse process. For this case the marked paths are similar to numerically calculated streamline plots. In contrast to the solid boundary a flexible boundary was also used. The interaction of the cavitation bubble with the flexible boundary visualises partially the movement of the water but is found to still destroy some of the symmetry of the bubble.

M.Ing. / This dissertation documents the stages involved in determining the parameters that define surface integrity. Chapter one gives a basic introduction to the project; the problem statement; scope of work and project obstacles. This chapter laid down the requirements for the literature study in Chapters two and three. The literature study discusses machining, high-speed machining, titanium alloys and high speed machining of titanium alloys. Information from the literature study was used to determine the experimental program presented in Chapter 4. Two materials were investigated in this study: grade 2 titanium (commercially pure) and grade 5 titanium (an alloy containing 6% Aluminium and 4% Vanadium). A fixed feed rate of 0.25mm/rev was selected. Two depths of cut were used: 0.2mm and 1mm. Cuts were performed both lubricated and un-lubricated. Different cutting speeds were used both inside and outside recommended ranges. Surface roughness tests, optical microscopy, scanning-electron microscopy, microhardness tests and x-ray diffraction were used in the experimental program. Results obtained presented trends seen in previous work on surface integrity. Efforts were made to reduce errors in obtaining and examining data. Conclusions were drawn with regards to each surface integrity parameter tested for. It was found that different cutting speeds affect each surface integrity parameter differently.