Neste trabalho, foram investigadas as modificações na estrutura e a estabilidade de eletrocatalisadores Pt/C e Pt-RuOx/C, preparados pela decomposição térmica de precursores poliméricos. Experimentos de varredura de potencial e experimentos com potencial fixo foram realizados com o objetivo de acelerar os mecanismos de degradação dos catalisadores. Para identificar e compreender os fatores que levaram a degradação dos catalisadores, foram realizados experimentos para determinação da área superficial eletroquimicamente ativa dos catalisadores, através da adsorção/oxidação de CO, análises dos catalisadores por difração de raios X (DRX) e análises das soluções por espectrometria de massa com fonte de plasma indutivamente acoplado (ICP-MS).Foram avaliadas as modificações na estrutura e a estabilidade dos eletrocatalisadores Pt/C e Pt-RuOx/C quando submetidos a 2000 varreduras de potencial em diferentes intervalos (i) 0,05-0,5 V; (ii) 0,05-0,7 V e (iii) 0,05-0,9 V na presença e na ausência de metanol e também quando submetidos a um potencial fixo por várias horas. Foi observado, de maneira geral, um aumento no tamanho dos cristalitos, dissolução dos componentes metálicos e uma redução da área superficial eletroquimicamente ativa. Os resultados obtidos na primeira parte do trabalho também mostraram que a degradação dos catalisadores foi maior na presença de metanol e que condições de potencial cíclico aceleram os mecanismos de degradação quando comparadas a condições de potencial fixo. Após uma melhor compreensão dos mecanismos de degradação, a segunda parte do trabalho foi voltada para investigação da influência de modificações no método Pechini durante a síntese dos eletrocatalisadores Pt-RuOx/C na estrutura e estabilidade destes catalisadores. Para isto, os catalisadores foram submetidos a varreduras de potencial entre 0,05-0,6 V e experimentos com potencial fixo em 0,6 V na presença de metanol. Para avaliar a influência das modificações no método de preparo na eletroatividade dos catalisadores, foram realizados testes em uma DMFC utilizando uma MEA (Membrane Electrode Assemblies) formada por ânodo Pt-RuOx/C / membrana de Nafion® 117 / cátodo Pt/C comercial (E-TEK). O estudo da estabilidade mostrou que o catalisador cuja mistura composta pelas resinas e suporte de carbono foi submetida à rotação em um moinho de bolas antes do tratamento térmico se mostrou bem mais estável que os demais catalisadores (submetidos ao ultrassom). Já os catalisadores preparados com uma única resina contendo Pt e Ru e submetidos ao ultrassom antes do tratamento térmico, mostraram os melhores resultados nos experimentos em condições operacionais em célula a combustível unitária. A terceira e última parte deste trabalho teve por objetivo investigar os efeitos da utilização do carbono Black Pearls 2000 como suporte na estabilidade e eletroatividade de eletrocatalisadores Pt-RuOx/C. Testes em uma DMFC e varreduras de potencial na presença de metanol foram realizados e os resultados comparados com os obtidos para os catalisadores sintetizados com carbono Vulcan XC-72. Os catalisadores sintetizados com carbono Black Pearls 2000 apresentaram maior área superficial eletroquimicamente ativa que os catalisadores preparados com carbono Vulcan XC-72 pelo mesmo procedimento, indicando uma melhor dispersão das partículas metálicas sobre o suporte, uma vez que a quantidade de Pt nos catalisadores foi mantida constante. Esta melhor dispersão das nanopartículas metálicas sobre o suporte resultou em maiores valores de densidade de potência e densidade de corrente em célula a combustível unitária operando com metanol na fase líquida. Para dois dos três catalisadores, o desempenho foi superior ao catalisador comercial da E-TEK. A dissolução dos componentes metálicos e a redução da área superficial eletroquimicamente ativa foi menor para os catalisadores preparados com carbono Black Pearls 2000 e o tamanho de cristalito não variou após 2000 varreduras de potencial. Todos estes resultados mostram uma maior estabilidade dos catalisadores preparados com este suporte. / In this work, changes in the structure and stability of the Pt/C and Pt-RuOx/C catalysts, prepared by the thermal decomposition of polymeric precursors, were investigated. Potential scans and constant potential experiments were carried out, to accelerate catalyst degradation mechanisms. To comprehend the catalyst degradation, determination of the electrochemical active surface area by means of the method based on the CO-stripping voltammetry curve, catalysts analyses by X-ray diffraction (XRD), and solution analyses by inductively coupled plasma mass spectrometry (ICP-MS) were accomplished.The changes in the structure and stability of Pt/C and Pt-RuOx/C electrocatalysts subjected to 2000 potential scans at different potential ranges (0.05-0.5, 0.05-0.7, and 0.05-0.9 V) were monitored in sulfuric acid solution, in the absence and in the presence of methanol. The influence of application of a constant potential for a prolonged time period was also investigated. As a general behavior, there was increase in particle size, dissolution of catalyst components, and reduction in the electrochemically active surface area. Catalyst degradation was more pronounced in the presence of methanol, and the cyclic potential conditions revealed higher degradation rate compared to the rate observed in constant potential conditions. After a better comprehension of the degradation mechanisms, the second part of this work focused on monitoring the influence of modifications made to the Pechini method during the synthesis of Pt-RuOx/C electrocatalysts on the structure and stability of these catalysts after they were subjected to a large number of potential scans between 0.05 and 0.6 V and at constant potential of 0.6V vs. RHE for a prolonged time period in sulfuric acid 0.5 mol L-1 and in methanol 0.1 mol L-1 solution. DMFC tests were accomplished using membrane electrode assemblies (MEAs) prepared by hot-pressing a pretreated Nafion® 117 membrane together with the Pt-RuOx anode and an E-TEK cathode, in order to compare the catalytic activity of catalysts prepared by different methods. The stability study demonstrated that the catalyst whose resin/carbon support mixture was agitated in a balls mill before being subjected to heat-treatment was more stable than the other prepared catalysts (subjected to ultrasound). The catalysts prepared with the single resin consisting of Pt and Ru, subjected to ultrasound before heat-treatment, furnished the highest power density in the single fuel cell. The third and last part of this work aimed to investigate the effects of the use of Black Pearls 2000 carbon support on the stability and electroactivity of the Pt-RuOx/C catalysts. DMFC tests and potential scans in the presence of methanol were performed, and results were compared with those obtained for the catalysts synthesized with Vulcan XC-72 carbon. Catalysts synthesized with Black Pearls 2000 carbon presented larger electrochemically active surface area compared to catalysts prepared with Vulcan XC-72 carbon using the same procedure. This indicates better metallic particles dispersion on the support, since the amount of Pt was kept constant in the catalysts. This better dispersion of metallic particles on the carbon support resulted in higher power density and current density in the single fuel cell operating with methanol in the liquid phase. The performance of two of the three prepared catalysts was better than that of E-TEK commercial catalyst. The dissolution of the metallic components and the reduction in the electrochemically active surface area was smaller for catalysts prepared with Black Pearls 2000 carbon, and the crystallite size did not change after 2000 potential scans. All these results demonstrate the superior stability of the catalysts prepared with this support.

Shiu Kwok Keung. / Bibliography: leaf 75 / Thesis (M.Ph.)--Chinese University of Hong Kong, 1984

by Chu Wing Fai. / Parallel title in Chinese characters. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1988. / Bibliography: leaves 89-92.

by Ng Yin Fun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 50-51). / Abstracts in English and Chinese. / Acknowledgments --- p.i / Abstract --- p.ii / Introduction --- p.3 / Chapter 1 --- Preliminaries --- p.4 / Chapter 1.1 --- Hilbert C*-modules --- p.4 / Chapter 2 --- Self-dual Hilbert C*-modules --- p.14 / Chapter 2.1 --- Self-duality --- p.14 / Chapter 2.2 --- Self-duality and some related concepts --- p.22 / Chapter 2.3 --- A criterion of self-duality of HA --- p.23 / Chapter 3 --- Hilbert W*-modules --- p.25 / Chapter 3.1 --- Extension of the inner product to --- p.25 / Chapter 3.2 --- Extension of operators to --- p.33 / Chapter 3.3 --- Self-dual Hilbert W*-modules --- p.36 / Chapter 3.4 --- Some equivalent conditions for a Hilbert W*-module to be self-dual --- p.43 / Bibliography --- p.50

鄧小虎. / "2000年6月" / 論文 (哲學碩士)--香港中文大學, 2000. / 參考文獻 (leaves 104-109) / 附中英文摘要. / "2000 nian 6 yue" / Deng Xiaohu. / Lun wen (zhe xue shuo shi)--Xianggang Zhong wen da xue, 2000. / Can kao wen xian (leaves 104-109) / Fu Zhong Ying wen zhai yao. / Chapter 一. --- 緒論 --- p.1 / Chapter 二. --- 第一章 --- p.3 / Chapter 1.1 --- 啓蒙運動的失敗 --- p.4 / Chapter 1.2 --- 啓蒙運動爲何註定失敗？ --- p.8 / Chapter 1.3 --- 情感主義及其源起 --- p.11 / Chapter 1.4 --- 現代文化就是情感主義式的文化 --- p.15 / Chapter 1.5 --- 提出德性倫理學以回應情感主義的挑戰 --- p.19 / Chapter 三´Ø --- 第二章重建德性倫理學（一） --- p.22 / Chapter 2.1 --- 如何建構有理據的德性倫理學？ --- p.23 / Chapter 2.2 --- 重建德性的第一階段：實踐體系 --- p.24 / Chapter 2.2.1 --- 內在價値 --- p.25 / Chapter 2.2.2 --- 共同設立的合作性活動 --- p.30 / Chapter 2.2.3 --- 傑出標準 --- p.32 / Chapter 2.3 --- 對於德性的初步瞭解及其不足 --- p.34 / Chapter 四´Ø --- 第三章重建德性倫理學（二） --- p.36 / Chapter 3.1 --- 第二階段：有整體性的人生 --- p.36 / Chapter 3.1.1 --- 可理解性與敘述 --- p.36 / Chapter 3.1.2 --- 兩類背景：社會性場景與個人歷史 --- p.37 / Chapter 3.1.3 --- 人生有敘述的整體性？ --- p.43 / Chapter 3.1.4 --- 統一的自我 --- p.46 / Chapter 3.1.5 --- 有敘述整體性的人生 --- p.49 / Chapter 3.2 --- 人生的目的（telos)與德性 --- p.51 / Chapter 3.3 --- 第三階段：傳統 --- p.55 / Chapter 3.4 --- 小結 --- p.59 / Chapter 五´Ø --- 第四章德性倫理學成功嗎？ --- p.63 / Chapter 4.1 --- 重建德性倫理學所必須克服的三項困難 --- p.63 / Chapter 4.2 --- 社會目的論 --- p.65 / Chapter 4.3 --- 價値衝突的悲劇處境 --- p.67 / Chapter 4.4 --- 共同目的和社群 --- p.78 / Chapter 4.5 --- 傳統和理性 --- p.86 / Chapter 六´Ø --- 總結啓蒙運動與德性倫理學 --- p.96 / 書目 --- p.103

by Lam Shek Ki. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 59-60). / Abstract also in Chinese. / Acknowledgment --- p.i / Abstract --- p.ii / Introduction --- p.2 / Chapter Chapter 1 --- Prelimnaries / Chapter §1.1 --- A Summary on C*-algebras and their representation theory --- p.4 / Chapter §1.2 --- Primitive ideals --- p.7 / Chapter §1.3 --- Canonical form of a matrix --- p.12 / Chapter Chapter 2 --- Uniqueness and basic properties of OA / Chapter §2.1 --- Uniqueness of Cuntz-Krieger Algebra --- p.13 / Chapter §2.2 --- Basic properties of OA --- p.25 / Chapter Chapter 3 --- A generalization of OA / Chapter §3.1 --- Universal Cuntz-Krieger Algebras --- p.33 / Chapter §3.2 --- Gauge action on AO A --- p.36 / Chapter Chapter 4 --- The ideal structure of OA and AO A / Chapter §4.1 --- Gauge-invariant ideals of AO A --- p.39 / Chapter §4.2 --- The primitive ideal space of AO A --- p.49 / Bibliography --- p.59

The aim of this work is to improve the practice of multicomponent data processing in the time domain. I present a detailed study carried out on a 2D multicomponent dataset acquired over the Lomond Field, North Sea. I show that this area is seismically anisotropic and that failure to account for the anisotropy leads to poor converted wave imaging results. Anisotropy is included in a complex model-building scheme prior to Pre-Stack Time Migration (PSTM). The basic parameters required in converted wave processing are the converted-wave stacking velocity based on non-hyperbolic moveout and different P-wave to S-wave velocity ratios. These parameters are extracted from analysis on asymptotically binned gathers, that is, gathers binned with a constant value of the velocity ratio vp/vs. I present results of a sensitivity analysis and I show that in areas affected by dip the stacking velocity is sensitive to changes in the initial vp/vs ratio. These small velocity errors are propagated as the square in the re-calculation of the depth-variant velocity ratio and cannot be ignored. I show that using imaging criteria to define the binning velocity ratio provides a valid and velocity-independent estimate in zones of complex geology. The vertical velocity ratio is derived conventionally by event matching in the P-wave and converted wave stacks. I present an attempt to use well-log derived velocity ratios to avoid this interpretative step. The velocity ratio derived from 4C seismic data is about 30% higher than that derived from well logs. I analyse three possible causes for this discrepancy: the effects of gas, polar anisotropy and frequency-dependent dispersion. Gas has little effect in the Lomond Field logs, while polar anisotropy lowers the well-log derived vp/vs ratio by about 15%. Frequency-dependent dispersion also lowers the well-log derived velocity ratio, but it is difficult to quantify. Residual errors in the seismic interpretation have also to be considered. Importantly, I prove that the ratio leading to the best image is the one derived from seismic data, which suggests that the use of the raw well-log derived velocity ratio in multicomponent processing should be avoided. I quantify anisotropy using an effective parameter, representing converted-wave anisotropy, ceff, which is a combination of P- and S-wave anisotropy. This parameter can be estimated from converted wave seismic data alone and I illustrate two different ways of extracting it. I present imaging results from a full anisotropic PSTM processing sequence. This flow requires careful model building and allows updating in the time-migrated domain. Comparing the values of the anisotropic parameter and of the binning velocity ratio before and after PSTM highlights the difference between the initial model and the updated model. Both parameters are in fact sensitive to the presence of dip. I show that the values of the anisotropic parameter change after PSTM, suggesting that part of the residual moveout attributed to anisotropy prior to PSTM was caused by dip. This consideration confirms the importance of defining the model in the time-migrated domain. The PSTM image matches with a high degree of accuracy the geological interpretation carried out by BG Group. PSTM tests show that the inclusion of anisotropy allows the use of the full range of offsets, which is important to produce the correct image of the target area. I compare this result with the image obtained from a flow based on isotropic Dip Moveout (DMO) and post stack migration. Differences in the position of the steep-dipping events and geological misties are evident in the post-stack migrated image. This mis-positioning is due to the isotropic approximation and to the limitation of the DMO and post-stack migration flow. I also present results of an integrated analysis of local geology, well logs and seismic data to confirm the presence of polar anisotropy in the Lomond Field. The sediments forming the overburden are mainly composed of finely laminated shales. The image I obtained from the full Pre-Stack Depth Migration on P-P data reveals a depth mismatch with the well markers. Since the pre-stack gathers show that the correct velocities are applied, this depth mismatch has to be attributed to the presence of anisotropy. Other clear evidences of anisotropy come from well logs. P-velocity angular dependency is evident in sonic logs. I show that a similar angular dependency also exists when comparing interval velocities and average velocities from seismic data and from vertical well logs and check shots. These considerations leave little doubt that the Lomond Field is seismically anisotropic.

Yung, Yuk Lin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 65-73). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese.

Sou, Weng Hong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 96-106). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese.

"Microfluidic technologies are popular for biological research, enabling precise physical and chemical control of the microenvironment surrounding living cells and small organisms. Caenorhabditis elegans, a 1 mm long nematode, is capable of olfactory associative learning using the classical conditioning paradigm of pairing an unconditioned stimulus that elicits an innate response, such as food, with a second stimulus, such as an odor, which then elicits a learned behavioral response to this conditioned stimulus alone. Conventional chemotaxis assays on agar petri-plates have been widely used to observe behavioral changes indicative of associative learning; however, reproducibility of these behavioral assays is a major challenge. Here, we describe a microfluidic system that improves the reproducibility of chemotactic behavioral assays by providing better spatiotemporal control of stimuli, gentler worm handling, and more detailed behavioral quantification. Specifically, the microfluidic designs in this study present a uniform conditioning environment followed by a temporally stable linear odor gradient to assess changes to olfactory preference. Stimuli are presented in an enclosed environment to multiple worm populations whose locomotory patterns are analyzed using machine vision. Furthermore, we established an optimized protocol for a positive associative learning paradigm in which animals increase their preference for an odorant, butanone, when previously paired with bacterial food. We reproduced plate-based learning results in wild-type and learning-deficient genetic mutant animals, and demonstrated how developmental stages and chemicals alter the plasticity of olfactory preference. "