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

In a previous paper it was shown that the use of carry lookahead adders can reduce the delay it takes to compute the product with Wallace and Dadda multipliers. In this report, a more detailed analysis is provided on the use of carry lookahead adders to implement Dadda multipliers and Wallace multipliers. These two styles present different ways to use the arithmetic components and offer different benefits. Implementations of each style of multiplier are presented in this report. The performance delay and complexity of the implementations is compared and analyzed. / text

During the past decade, the high-speed rail (HSR) has got momentum in China, and a number of lines have been put into operation. However, it is noted that the HSR development in China is quite different from that in other regions. The discrepancies are mainly embodied in the duality of HSR types, the diversity of station locations, and the mixed-speed and cross-rail-type train running scheme. These characteristics have considerable impacts on the HSR stations in terms of the external accessibility in the HSR network as well as the internal accessibility in the cities. Based on the comparative study on the accessibility of main HSR stations in Yangtze River Delta, it is discovered that compared with the conventional rail (CR), the HSR has significantly improved the external accessibility of various cities. It is also found that the HSR has further enhanced the hub status of big cities in the rail network, while the differences among the other cities have been reduced, since the small cities have benefited much more from the HSR than the medium cities. Besides, introducing a new HSR line would improve the external accessibility of cities not only in the HSR network but also in the CR network, due to substantial increases in the efficiency of the whole rail system. In terms of the internal accessibility, it is found that the location choice of stations has significant impacts on the accessibility of HSR stations in cities, and the newly built stations have much lower accessibility due to their remote locations and the under-developed transport facilities and services connecting to them. Overall, for a complete journey by the HSR, the improvement in the external accessibility has made the internal accessibility of HSR stations more critical and sensitive. In this sense, more efforts should be paid to improve the urban transport system so as to fully utilize the positive effects brought about by the HSR. / published_or_final_version / Transport Policy and Planning / Master / Master of Arts in Transport Policy and Planning

Community engagement (CE) is an emerging concept with various definitions and acclaimed benefits. It became vital in the transport planning process because conventional approaches to transport planning no longer satisfy a diverse public and is required to improve the “quality of planning outcomes” (Booth and Richardson 2001, p. 148). Since Hong Kong will continue making railway the backbone for passenger transport, and very little (if any) community engagement has been explored for the city’s railway projects, this research aimed to appraise the role, adequacy, and effectiveness of CE in planning Hong Kong’s section of the high-speed Guangzhou-Shenzhen-Hong Kong Express Rail Link from years 2000 to 2010. Four objectives are pursued, which are to: (1) identify what community engagement (CE) means to the XRL project stakeholders, including their perceptions of CE strengths, weaknesses, and challenges during the XRL‘s planning process of Hong Kong‘s section; (2) identify major factors that shape the XRL project stakeholder understanding and perception of CE; (3) identify and evaluate the implications and the cause and effect that result from stakeholders’ understanding and perception of CE in planning Hong Kong‘s XRL section; and (4) identify scopes to improve the CE process for the city’s future transport infrastructure projects. The study first conducted a literature review. It then traced the development of CE in Hong Kong, particularly in the transport planning realm. News articles, MTR website on the XRL, and policy papers from the Legislative Council Policy Database were examined. A survey was distributed afterwards. 130 usable surveys were returned giving a 40.6% response rate. Results were then quantitatively analyzed with Spearman’s correlation and a two-tailed test. A member from each stakeholder group was lastly interviewed. Overall, CE improved since British rule, but its extent in planning the XRL fell short or according to Sheedy (2008), non-existent, thus making it ineffective in achieving CE benefits. By statute and the railway development process that professionals adhere to, genuine CE (or higher levels of it) are not encouraged nor guaranteed. Consequences include public resistance and protests after gazettal; respondents believing the government and MTR engagement efforts raised communities ‘buy-in’ of ‘pre-approved plans;’ “sometimes” disrespected and/or mistrusted their communities; “slightly” shared final decision-making with their communities; “sometimes” if not “always” used too much professional jargon; and only “slightly” to “sometimes” followed-up with communities after engaging them in the planning process. The CE concept in Hong Kong is not eminent either. Engaging people in the XRL planning process additionally showed no direct and comprehensive citizen involvement. This is probably due to the general public and government attitudes, which makes it challenging for genuine CE to occur on top of limited resources. On the bright side, many CE benefits were found true from descriptive analysis, and electronic media was deemed the most effective tool to engage citizens. From quantitative analysis, a stakeholder’s power and/or knowledge lacked a statistical significant relationship with how satisfied he or she was on how CE was conducted in XRL planning and his or her perceptions of it. A stakeholder’s exposure to CE, however, mostly had a negative statistically significant relationship with a few perceptions of community engagement. In the end, three major recommendations are offered to improve CE in Hong Kong’s transport planning framework. In no order of importance, the general community and XRL Sponsor (government and MTR) must change their attitude towards engagement. The XRL Sponsor must aggressively educate the general Hong Kong community about community engagement. Lastly, it should revise the Railways Ordinance to incorporate more CE characteristics. / published_or_final_version / Transport Policy and Planning / Master / Master of Arts in Transport Policy and Planning

In the United States, passenger rail has always been less competitive than in other parts of the world due to a number of factors. Many argue that in order for a passenger rail network to be successful major changes in service improvement have to be implemented to make it more desirable to the user. High-speed rail can offer such service improvement. With the current administration’s allocation of $8 billion in its stimulus package for the development of high-speed rail corridors and a number of regions being interested in venturing into such projects it is important that we understand the factors and regulatory structure that needs to exist in order for passenger railroad to be successful. This study aims to review how foreign countries have developed and their railroad systems to identify key factors that have contributed to its successful implementation. An evaluation of the factors, such as organization structure, operation, administration, development and type of funding, that are common to each of these projects will used as performance measures to identify potential locations and opportunities for high speed rail projects in the U.S. Southwest region. / text

Texas features a growing economy and population. The state boasts a large and well-developed network of roads, freight railroads, and air facilities, which make the state a vital link in the movement of people and goods. However, as the state continues to grow in population and economic significance, these systems are straining to meet state, national, and even global needs. It is increasingly obvious to residents and state officials that Texas should consider implementing alternative modes of transport, including development of passenger rail, for which Texas currently lags behind many of its peer states. Passenger rail provides quantifiable benefits in displacing less energy-efficient and higher pollutant-emitting air and automobile modes while generating potential positive economic impacts and enhancing consumer choice and multimodalism. Conveniently, renewed national interest in rail has invigorated research measuring the applicability of passenger rail services to many different regions of the United States, with the possibility that future national transportation visions will include passenger rail as an essential element. This thesis seeks to clarify the potential for passenger rail specifically in Texas through comparison and contrast with other regions and nations in the midst of new national-level knowledge and the changing transportation opportunities and challenges facing the state. Some of the ideal characteristics of successful international passenger systems exist in Texas, including optimal city spacing and a well-established rail network, which have fuelled ongoing interest demonstrated by various system proposals for high-speed intercity transportation in Texas over the last four decades. Despite these characteristics, the state presents a number of barriers to rail transport rooted in low transit use coupled with generally lower density and ambivalent support from politicians and residents when officials present realities of eminent domain and land use changes. However, with revitalized national rail interest and new federal rail planning requirements, the state may yet be able to work through these challenges to exploit the opportunities the state possesses. / text

This thesis explores the use of active inductors as a compact alternative to the bulky passive spiral structures in high-speed I/O circuits. A newly proposed PMOS-based topology is introduced and used in active-inductor terminations. The 1st prototype design fabricated in a 90-nm CMOS process consists of an output driver using active-inductor terminations to provide channel equalization and output impedance matching. From measurement results, the use of active inductors in the termination, as compared to when the active inductor is disabled, increases the vertical eye opening in the receiver side by a factor of two and reduces the jitterp-p by 30% of the transmitted 10 Gb/s (2³¹-1) pseudo-random binary sequence pattern, over a 6-inch FR4 channel. An output impedance matching with S₂₂ less than -10 dB over a bandwidth of 20 GHz is achieved. The pair of active-inductor terminations occupies 17×25 µm² and has a low overhead power consumption of 0.8 mW. In the 2nd prototype design, a 4-stage output buffer with active-inductor loads is designed and implemented in a 65-nm CMOS process. Simulation results verify that when operating at 31.25 Gb/s, the output eye of the active-inductor load buffer compares favorably with that of the passive-inductor load buffer. For a similar eye-height and 78% less timing jitter the active-inductor load design’s speed (31.25 Gb/s) is 25% faster than the passive-resistor load design (25 Gb/s). The active-inductor load output buffer achieves comparable performance in terms of speed, power, and output swing with other reported designs using passive inductors. Its total area is 135×30 µm² (including three differential active inductors) which is comparable to the size of a single passive spiral inductor having a 0.5~1 nH inductance.

High speed chemically reacting flows are important in a variety of aerospace applications, namely ramjets, scramjets, afterburners, and rocket exhausts. To study flame extinction under similar high Mach number conditions, we need access to thermochemistry measurements in supersonic environments. In the current work a two-stage miniaturized combustor has been designed that can produce open supersonic methane-air flames amenable to laser diagnostics. The first stage is a vitiation burner, and was inspired by well-known principles of jet combustors. We explored the salient parameters of operation experimentally, and verified flame holding computationally using a well-stirred reactor model. The second stage of the burner generates an external supersonic flame, operating in premixed and partially premixed modes. The very high Mach numbers present in the supersonic flames should provide a useful test bed for the examination of flame suppression and extinction using laser diagnostics. We also present the development of new line imaging diagnostics for thermochemistry measurements in high speed flows. A novel combination of vibrational and rotational Raman scattering is used to measure major species densities (O_2, N_2, CH_4, H_2O,CO_2, CO, & H_2) and temperature. Temperature is determined by the rotational Raman technique by comparing measured rotational spectra to simulated spectra based on the measured chemical composition. Pressure is calculated from density and temperature measurements through the ideal gas law. The independent assessment of density and temperature allows for measurements in environments where the pressure is not known a priori. In the present study we applied the diagnostics to laboratory scale supersonic air and vitiation jets, and examine the feasibility of such measurements in reacting supersonic flames. Results of full thermochemistry were obtained for the air and vitiation jets that reveal the expected structure of an under-expanded jet. Centerline traces of density, temperature, and pressure of the air jet agree well with computations, while measurements of chemical composition for the vitiation flow also agree well with predicted equilibrium values. Finally, we apply the new diagnostics to the exhaust of the developed burner, and show the first ever results for density, temperature, and pressure, as well as chemical composition in a supersonic flame.

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This thesis explores the use of active inductors as a compact alternative to the bulky passive spiral structures in high-speed I/O circuits. A newly proposed PMOS-based topology is introduced and used in active-inductor terminations. The 1st prototype design fabricated in a 90-nm CMOS process consists of an output driver using active-inductor terminations to provide channel equalization and output impedance matching. From measurement results, the use of active inductors in the termination, as compared to when the active inductor is disabled, increases the vertical eye opening in the receiver side by a factor of two and reduces the jitterp-p by 30% of the transmitted 10 Gb/s (2³¹-1) pseudo-random binary sequence pattern, over a 6-inch FR4 channel. An output impedance matching with S₂₂ less than -10 dB over a bandwidth of 20 GHz is achieved. The pair of active-inductor terminations occupies 17×25 µm² and has a low overhead power consumption of 0.8 mW. In the 2nd prototype design, a 4-stage output buffer with active-inductor loads is designed and implemented in a 65-nm CMOS process. Simulation results verify that when operating at 31.25 Gb/s, the output eye of the active-inductor load buffer compares favorably with that of the passive-inductor load buffer. For a similar eye-height and 78% less timing jitter the active-inductor load design’s speed (31.25 Gb/s) is 25% faster than the passive-resistor load design (25 Gb/s). The active-inductor load output buffer achieves comparable performance in terms of speed, power, and output swing with other reported designs using passive inductors. Its total area is 135×30 µm² (including three differential active inductors) which is comparable to the size of a single passive spiral inductor having a 0.5~1 nH inductance.