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Under pressure small molecular systems exhibit a remarkable degree of polymorphism and unexpected behaviours. Two previously unexplored binary systems, those of niobium{hydrogen and water{oxygen, are explored and their phase diagrams mapped. In the case of water and oxygen, two hitherto unknown clathrate structures are found. A wide study of dense nitrogen at and above room temperature is also reported. The phase diagram of nitrogen is exceptionally complex for a single element and exhibits considerable metastability of phases. Current theoretical understanding of nitrogen has many disagreements with experimental observation. High quality structural data on various previously known phases are reported as well as a novel molecular phase. This new phase, λ-N2, has been studied using Raman spectroscopy and powder x-ray diffrraction. Combining experimental and theoretical results gives a layered structure with intermolecular interactions playing an important role and an apparently weakened intramolecular bond. The dissociation of the nitrogen triple bond is also examined. The amorphous η state is studied via Raman spectroscopy and optical and IR absorbance methods before laser heating at 255 GPa. After heating the sample becomes very much more transparent and shows signs that the nature of the bandgap has changed suggesting that the nitrogen may be in a crystalline atomic phase hitherto unknown. An effort to take nitrogen to considerably higher pressures is reported. A two stage diamond anvil cell was developed using focused ion beam micromachining. Although ultimately unsuccessful, to the author's knowledge this was the first ever attempt at designing such a system to be compatible with small molecular samples and Raman spectroscopy and various conclusions are as to how best to proceed with such developments.

Proton Exchange Membrane (PEM) fuel cells are becoming an increasingly important alternative to combustion engines as the fossil fuel reserves are depleted. Several papers have presented steady state analyses of the system, but few are known to present dynamic analysis of the flow and control of the hydrogen delivery process. This thesis presents the dynamic analysis of hydrogen delivery to a PEM fuel cell system. The hydrogen is delivered to the anode with use of an ejector for passive recirculation. The system to be studied consists of the manifolds, ejector, and pressure control valve. Models describing the elements of the anode delivery systems are formulated. The governing nonlinear equations are solved analytically and numerically, and the regimes of stable hydrogen delivery process are established. The linearized models are used for performance analysis and optimization of the hydrogen delivery process. The nonlinear model is used to improve the simulation of the dynamics of the PEM fuel cell system and validate the parameters at optimal linearized stability. Experiments are conducted to find the parameters used in the model, as well as validate the results. Both the linear and nonlinear models are implemented in Simulink and tested against the laboratory data from the PEM fuel cell system. The analysis showed that the models have the same time constant and dynamic behavior as the PEM system. The optimal parameters for stability and a faster response with no oscillations in the output are obtained. The redesigned valve and resulting dynamics of the PEM fuel cell system provides improved system performance.

Continued demands for better control of the operating conditions of structures and processes have led to the need for better means of measuring temperature (T), pressure (P), and relative humidity (RH). One way to satisfy this need is to use MEMS technology to develop a sensor that will contain, in a single package, capabilities to simultaneously measure T, P, and RH of its environment. Because of the advantages of MEMS technology, which include small size, low power, very high precision, and low cost, it was selected for use in this thesis. Although MEMS sensors that individually measure T, P, and RH exist, there are no sensors that combine all three measurements in a single package. In this thesis, a piezoresistive pressure sensor and capacitive humidity sensor were developed to operate in the range, of 0 to 2 atm and 0% to 100%, respectively. Finally, a polysilicon resistor temperature sensor, which can work in the range of -50ºC to 150ºC, was analyzed. Multimeasurement capability will make this sensor particularly applicable for point-wise mapping of environmental conditions for advanced process control. In this thesis, the development of sensors for such an integrated device is outlined. Selected results, based on the use of analytical, computational, and experimental solutions (ACES) methodology, particularly suited for the development of MEMS sensors, are presented for the pressure, relative humidity, and temperature sensors.

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Abstract Photovoltaic (PV) solar panels are solar energy collection systems with increasing terrestrial and roof applications reported worldwide. If the terrestrial mounting does not require specific wind resistance verifications, installing them on top of flat and gable roofs implies a drastic change of the roofing systems geometry, thus a re-evaluation of the wind-induced pressure is necessary. Among the roof top applications, provisions exist for the flat roofs mounted solar panels, however, design recommendations for wind-induced loadings on PV solar panels arrays flush-mounted on gable roofs are not fully developed in current wind loading standards (SEAOC PV2-2012) and building codes (ASCE 07, NBCC 2015), in spite of the numerous applications on residential and agricultural buildings, primarily due to the limited research investigating this topic. The current dissertation employs CFD k-ɛ and LE (Large Eddy) simulations for analyzing the effects of wind acting on solar panels flush-mounted on gable roofs, considering the influence of several parameters such as: the slope of the gable roof, the wind directions, the spaces between the adjacent solar panel arrays and the clearance between the roof surface and the solar panels. A comprehensive database of solar panels with different installation parameters subjected to wind speeds were developed under the current research project. The database includes detailed distribution of wind-induced pressure coefficients for the three parallel surfaces constituting the roof-solar panels systems: the top and bottom surfaces of the panels, and the roof surface under the panels, which represents a novel approach in investigating and clarifying the wind effects on solar panels. This approach also provides in detail the variation of the pressure coefficients on the three surfaces, due to the change of installation conditions (roof slope, arrays spacing, roof clearance) and wind parameters (wind speed and wind direction). As an original contribution to the existing knowledge, this thesis found that the installation of solar arrays on gable roofs, redistributes the wind-induced pressure on both sides of the roof windward and leeward, resulting in total horizontal wind-induced pressures on the entire roof lower than that registered on the corresponding roof without solar panels. In addition, dominant resultant pressure coefficients on solar panels concluded to be lower than for the roof without panels. When the roof clearance increases, total average pressure coefficients on the roof supporting the panels decreases on both, windward and leeward sides of the roof. Moreover, when the roof clearance increases, the pressures in the cavity decrease significantly on both windward and leeward sides of the roof, which could impact the requirements for installing and fixing such panels on gable roofs. For example, for 10” clearance the flush-mounted solar panels were subject to pressure instead of suction. Similarly, when panel array spacing increases, the magnitude of the net mean pressure coefficients on the roof surface under the solar panels further decreases for all wind directions investigated.

Under pressure is an expression of stress. It is about work becoming everything. It is about not being able to separate your self from your work. It is about carrying the office with you all the time.The result is a well kept together collection of garments ranging from commercial to experimental on the edge of not being wearable. / Program: Modedesignutbildningen

Graham Neil Thomas. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (p. 245-281). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

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