Thesis (M.Sc.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 134-139).

Thesis (M. Sc.)--York University, 1997. Graduate Programme in Physics and Astronomy. / Typescript. Includes bibliographical references (leaves 121-128). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL:http://wwwlib.umi.com/cr/yorku/fullcit?pMQ27361.

Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 57-58).

As the principal subsidized home ownership housing scheme in Beijing, the Economical and Suitable Housing Scheme (ESHS) has gone through several different stages in the past three decades. Following the newly developed housing policy framework in 2007, ESHS was endowed with the objective of providing affordable home ownership to low-income urban residents. Despite the rich literature on ESHS in China, relatively little is known about the performance of estates of ESHS in Beijing developed after 2007 under the new regulations. Largely missing from the existing literature is an analytical account of the development of ESHS in Beijing and an in-depth evaluation and explanation of its performance in recent years. This study thus aims to examine and analyze the effectiveness of ESHS since 2007 with the intention of helping to improve the effectiveness of ESHS and to provide useful lessons to other subsidized housing schemes in Beijing. Following the lead of scholars who have studied subsidized housing schemes in other countries and areas, this study built up its own analytical framework appropriate to the Chinese context. To achieve the study goal, the evaluation of the performance of ESHS was conducted in terms of four indicators: housing affordability, housing accessibility, housing availability and housing quality. The investigation of the causes were conducted from the public policy perspective focusing on policy design and policy implementation. To enhance the data base, open-ended interviews with officials at different levels from different government departments and structured questionnaire surveys with residents in ESHS in Beijing had been conducted. This study reveals that the performance of ESHS after 2007 was barely acceptable. Specifically, the housing affordability and housing accessibility and housing quality of ESHS were less than satisfactory. Even though the housing availability of ESHS in quantity terms did not have significant problems, the housing availability in terms of location was highly undesirable. As for housing affordability, it is found that the ESHS was more affordable to urban residents than to suburban residents, the major reason being the higher income enjoyed by the former. Regarding housing accessibility, this study found that the approach to determine the eligibility criteria of ESHS failed to include all the households who could not afford to purchase market housing. In the housing quality domain, it is found that ESHS housing estates in Beijing failed to meet the residents’ daily needs, and suffered from poor housing construction quality and inconvenient locations. In addition to the evaluation of performance, this study also found that besides the strong commitments from the government, policy design commensurate with policy goal and effective policy implementation determines the performance of a subsidized housing scheme. In particular, the formulation of eligibility criteria and the pricing mechanism at the policy design stage, and the conflicting interests of the three levels of government at the implementation stage were most critical. This study further argues that the four dimensions of performance which were inter-connected to each other were all commonly hinged upon the use of land as the main source of subsidy. This study adds to the existing literature on contemporary China by evaluating and explaining the most recent performance of a dominant housing subsidy policy tool in China. By constructing and employing a comprehensive conceptual framework for the analysis, this study offers to the contemporary China literature a sophisticated yet revealing conceptual tool to unveil the intricacies of housing subsidies in the rapidly changing China. / published_or_final_version / Urban Planning and Design / Doctoral / Doctor of Philosophy

Petroleum and Geosystems Engineering / Low salinity waterflooding is an emerging enhanced oil recovery (EOR) technique in which the salinity of the injected water is substantially reduced to improve oil recovery over conventional higher salinity waterflooding. Although there are many low salinity experimental results reported in the literature, publications on modeling this process are rare. While there remains some debate about the mechanisms of low salinity waterflooding, the geochemical reactions that control the wetting of crude oil on the rock are likely to be central to a detailed description of the process. Since no comprehensive geochemical-based modeling has been applied in this area, we decided to couple a state-of-the-art geochemical package, IPhreeqc, developed by the United States Geological Survey (USGS) with UTCOMP, the compositional reservoir simulator developed at the Center for Petroleum and Geosystems Engineering in The University of Texas at Austin. A step-by-step algorithm is presented for integrating IPhreeqc with UTCOMP. Through this coupling, we are able to simulate homogeneous and heterogeneous (mineral dissolution/precipitation), irreversible, and ion-exchange reactions under non-isothermal, non-isobaric and both local-equilibrium and kinetic conditions. Consistent with the literature, there are significant effects of water-soluble hydrocarbon components (e.g., CO2, CH4, and acidic/basic components of the crude) on buffering the aqueous pH and more generally, on the crude oil, brine, and rock reactions. Thermodynamic constrains are used to explicitly include the effect of these water-soluble hydrocarbon components. Hence, this combines the geochemical power of IPhreeqc with the important aspects of hydrocarbon flow and compositional effects to produce a robust, flexible, and accurate integrated tool capable of including the reactions needed to mechanistically model low salinity waterflooding. The geochemical module of UTCOMP-IPhreeqc is further parallelized to enable large scale reservoir simulation applications. We hypothesize that the total ionic strength of the solution is the controlling factor of the wettability alteration due to low salinity waterflooding in sandstone reservoirs. Hence, a model based on the interpolating relative permeability and capillary pressure as a function of total ionic strength is implemented in the UTCOMP-IPhreeqc simulator. We then use our integrated simulator to match and interpret a low salinity experiment published by Kozaki (2012) (conducted on the Berea sandstone core) and the field trial done by BP at the Endicott field (sandstone reservoir). On the other hand, we believe that during the modified salinity waterflooding in carbonate reservoirs, calcite is dissolved and it liberates the adsorbed oil from the surface; hence, fresh surface with the wettability towards more water-wet is created. Therefore, we model wettability to be dynamically altered as a function of calcite dissolution in UTCOMP-IPhreeqc. We then apply our integrated simulator to model not only the oil recovery but also the entire produced ion histories of a recently published coreflood by Chandrasekhar and Mohanty (2013) on a carbonate core. We also couple IPhreeqc with UTCHEM, an in-house research chemical flooding reservoir simulator developed at The University of Texas at Austin, for a mechanistic integrated simulator to model alkaline/surfactant/polymer (ASP) floods. UTCHEM has a comprehensive three phase (water, oil, microemulsion) flash calculation package for the mixture of surfactant and soap as a function of salinity, temperature, and co-solvent concentration. Similar to UTCOMP-IPhreeqc, we parallelize the geochemical module of UTCHEM-IPhreeqc. Finally, we show how apply the integrated tool, UTCHEM-IPhreeqc, to match three different reaction-related chemical flooding processes: ASP flooding in an acidic active crude oil, ASP flooding in a non-acidic crude oil, and alkaline/co-solvent/polymer (ACP) flooding. / text

Internet of Things (IoT) is a scenario that theorizes objects and people as potential nodes in an ever-growing wireless network. This idea pushes the development of low-cost wireless technologies that can run on portable power sources for months, or even years. One candidate technique that has shown promising results in this area thru the last years is BluetoothLow Energy (BLE). This thesis studies various techniques to enable and maintain large scale mesh networks over BLE communication. The initial study puts focus on an existing flooding based BLE mesh protocol. The thesis later presents an improved protocol that reduces power consumption with respect to the packet delivery ratio. Other enhancements which are added to the improved protocol are a self-adapting procedure and a packet routing algorithm. Simulations show that the improved protocol can save up to 50 % of the power consumption for a device, compared to the original protocol. / Sakernas Internet (IoT) är ett scenario som skisserar objekt och människor som potentiella noder i ett ständigt växande trådlöst nätverk. Denna vision driver utvecklingen av trådlösa lågkostnadsteknologier som kan köras på portabla strömkällor i flera månader. En kandiderande teknik som har visat goda resultat inom detta område är Bluetooth Low Energy (BLE). Detta uppsatsarbete studerar flera tekniker för att möjliggöra och upprätthålla storskaliga meshnätverk över BLE-kommunikation. Den inledande studien granskar ett existerande översvämningsbaserat meshprotokoll för BLE. Uppsatsarbetet presenterar därefter ett förbättrat protokoll som reducerar strömförbrukningen med avseende på kvoten mellan antalet mottagna paket genom antalet skickade paket. Ytterliggare upprustningar som tillkommer i det förbättrade protokollet är en procedur för självanpassning, samt en algorithm för dirigering av paket. Simuleringar visar att det förbättrade protokollet kan spara upp till 50 % av strömkonsumptionen för en enhet, jämfört med originalprotokollet.

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In his 1947 work "Theory of Braids" Emil Artin asked whether the braid group remained unchanged when one considered classes of braids under linkhomotopy, allowing each strand of a braid to pass through itself but not through other strands. We generalize Artin's question to string links over orientable surface M and show that under link-homotopy surface string links form a group PBn(M), which is isomorphic to a quotient of the surface pure braid group PBn(M). Surface braid groups and their properties are an area of active research by González-Meneses, Paris and Rolfsen, Goçalves and Guaschi, and our work explores the geometric and visual beauty of this subject. We compute a presentation of PBn(M) in terms of the generators and relations and discuss the orderability of the group in the case when the surface in question is a unit disk D.

Thermal Conductivity studies can provide fundamental information regarding the symmetry of the superconducting energy gap. To perform this kind of experiment, we need to use a very low temperature environment. Also a special mount has been to designed and constructed for the thermal conductivity measurements. This mount will allow holding the sample in different directions with respect to the applied magnetic field. The results are consistent with Wiedemann-Franz law to within 2.5\%. We also discuss a series of thermal conductivity experiments to shed additional light on the symmetry of the superconducting order parameter in the unconventional superconductor PrOs4Sb12.