The induced potential difference across a standing shock front can be used to drive electric current through external loads. Such a "standing shock generator" presents an alternative scheme to the MHD generator for direct conversion of energy from high temperature supersonic flows. We make use of the supersonic flow behind a free running shock in a shock tube and let the flow impinge onto a conical obstacle mounted in the middle of the tube to create a standing shock. This cone has a conducting surface which acts as the anode. The cathode is mounted flush with the shock tube wall at a position upstream of the standing shock. By varying the load resistance, we have obtained current-voltage characteristics for the standing shock generator. These characteristics are families of parallel straight lines similar to the characteristics of a battery. The open-circuit voltage is found to depend on the standing shock potential and the work functions of the electrodes. The internal resistance (equivalent to the slope of the characteristic) is found to be dominated by the plasma-wall interaction at the surface boundary layers. The maximum current collected by the electrode is therefore limited to its ion saturation current. A typical result of the standing shock generator in our experiment gives 1 volt with 0.5.amp for the. 30X10⁻⁶ sec test time duration. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Cyclic electrodialysis is a novel separation process in which a modified membrane stack is operated in a periodic unsteady-state manner. Repeated reversals of polarity could avoid the main problems encountered in conventional electrodialysis; fouling and scale formation on the membranes. In cyclic electrodialysis the standard electrodialysis stack is converted into an adsorption-desorption stack with only one set of flow channels, the other set being replaced by storage compartments. Thesr compartments are in the form of three-layer membranes consisting of an anion and a cation selective membrane enclosing a core of non- selective material. The depleted and enriched products are produced successively in the single set of channels instead of simultaneously in adjacent channels. The process is potentially applicable for commercial desalination of brackish water to make it potable, to remove harmful ions from discharge waters, or to concentrate ionic solutions for recovery of valuable materials. Previously reported experiments with aqueous NaCl solutions in a closed (batch) system showed that a large separation factor could be obtained in cyclic electrodialysis. Batch operation is somewhat analogous to total reflux in distillation. The present work extends the earlier work to potentially more useful operating conditions in which feed is supplied and product removed. A constant-rate model has been developed for the process and used extensively throughout the work as a simple and efficient tool to compare various operating cycles and modes of operation. Scattered articles in the literature on the resistance of an electrodialysis stack have been compiled to develop a stack resistance model. Good agreement was obtained between the model predictions and measured values of resistance. Experimental apparatus is described and the effects of the following eight system parameters are reported: (i) Demineralizing path length (ii) Production rate (iii) Pause time (iv) Applied voltage (v) Initial concentration (vi) No-pause operation (vii) Pure-pause operation (vii) Semi-symmetric operation Large separations were achieved for asymmetrical paused operation with long demineralizing path, long pause time, high applied voltage, low feed concentration and small production rate. Despite the strong trade-off between production rate and separation, a separation factor as high as 50 was obtained at the highest production rate used. This value is higher than that obtained in commercial plants currently in use. The process looks promising and is worth further consideration. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

My thesis investigates automation and optimizations for occlusion filling, a problem resulting from the generation of new viewpoints in the 3D video conversion process. Image inpainting is a popular topic in image processing research. The ability to fill a region of an image in a manner that is visually pleasing is a difficult and computationally expensive task. Recently, the most successful methods have been exemplar-based, copying patches of the image from a specified source region into the region to be filled. These algorithms are designed to propagate both structure and texture into the fill region. They are brute force algorithms however, and are generally implemented as sequential algorithms to be run on the CPU. In this research, I have effectively mapped the costly portions of an exemplar-based image inpainting algorithm to the GPU. I produce equivalent inpainting results in less time by parallelizing the brute force patch searching portion of the algorithm. Furthermore, I compare the results with another recent, optimized inpainting algorithm, and apply both algorithms to the real world problem of occlusion filling in a 3D video conversion pipeline. / Graduate

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The dialogue between old and new architecture is a conversation brought to the forefront of the conservationist movement and city planning efforts as cities expand to their physical limits and eco-friendly reuse options become mainstream. As designers try and achieve a mutual respect between existing buildings and modern interventions, we are often faced with the dilemma of not only deciding which architectural artifacts should remain but also how to compose the different historic and modern layers in a way that formulates a new and more dynamic whole as a result of the interaction. The following thesis is an adaptive reuse project of a historically and architecturally significant, turn of the century firehouse located in northwest Washington, DC. This architectural endeavor seeks to find a mutually respectful balance between old and new architecture while highlighting the clear differences in building materials, design aesthetic, and construction methods. / Master of Architecture

Depuis la révolution tranquille, le Québec vit un mouvement de marginalisation de la foi. Notre recherche explore les raisons qui contribuent à la conversion de jeunes adultes urbains dans ce contexte où la foi n'est pas l'option la plus évidente. Dans un premier temps, nous abordons l'importance de la communauté tant pour la conversion que pour le cheminement spirituel en amont et en aval de celle-ci. Dans un second temps, nous appréhendons la contextualisation de l'Évangile, qui rend l'Église accessible. Dans un troisième temps, nous explorons le rôle des crises dans la recherche spirituelle. Finalement nous évoquons la dimension surnaturelle de la conversion. L'ekklesia idéale décrite dans Actes 2 nous donne un modèle de communauté ecclésiale inspirante. L'étude de cas menée dans une Église à Montréal montre un modèle d'assemblée qui cherche à appliquer ces principes aujourd'hui, dans un milieu marqué par la diversité, l'ouverture, la rencontre des cultures et l'esprit de communauté. / Since the Quiet Revolution, Quebec has undergone profound societal changes. Our research explores the reasons that contribute to the conversion of young urban adults in the midst of these shifts - when faith does not seem the most obvious option. First, we discuss the importance of community for conversion as well as for the spiritual journey before and after it. Secondly, we look at the contextualization of the Gospel, which makes the Church accessible. In a third step, we explore the role of crises in the spiritual search. Finally, we discuss the supernatural dimension of conversion. The ideal ekklesia described in Acts 2 gives us a model of an inspiring church community. The case study of a church in Montreal shows a model of an ekklesia that seeks to apply these principles today, in an environment marked by diversity, openness, cultural encounter and community spirit.

(1) A new model for the mass transfer in Direct Contact Membrane Distillation (DCMD) process is developed. The model is based on Direct Simulation Monte Carlo (DSMC) method. It avoids the over simplification of the resistance mechanisms and hence, give more accurate prediction. The model is validated by means of experiments. The influences of the main parameters in DCMD are also studied, including temperature difference between the feed side and the permeate side, the membrane's thickness and the pore size. Moreover, it is proposed to use aerogel as the membrane material. It is shown that the aerogel's hydrophobic property, low thermal conductivity and high porosity offer a much improved performance over the commonly used membrane material PTFE. The fresh water productivity can reach 10.0 kg/m2 per day. / (2) A new energy harvesting method for converting thermal energy to kinetic energy is proposed. This method is based on the rarefied gas phenomenon called Knudsen effect. By Knudsen effect, a gas flow can be generated from temperature difference. In order to generate Knudsen effect, a special material, aerogel, is used. It is a porous material full of holes of dozens of nanometers. Using Direct Simulation Monte Carlo (DSMC) simulation, it is shown that Knudsen effect still works under atmosphere pressure with aerogel material. Accordingly, a device is designed. Based on the numerical simulation, the device can generate about 70 W kinetic energy when driven by a solar panel with intensity of 1 kW/m2. / (3) A solar desalination system is designed. This system is based on a combination of Knudsen compressor and simple solar still. The Knudsen effect is generated from the aerogel driven by solar radiation. As a result, the system operates at lower pressure resulting in enhanced water evaporation process. Based on the simulation, the evaporation rate is significantly increased. It is found that in a typical summer day in tropic region like Hong Kong, such a system can generate about 5 kg fresh water per 1 m2 solar still per day. This number is about 30% higher than the simple direct solar still. Moreover, the proposed technology can be readily combined with other technologies such as condensation heat recovery to further improve the fresh water productivity. The optimal working condition is also studied. / Energy and water are two of the most important issues in the world today. The social and economic health of the world depends on sustainable supply of both energy and water. Especially, these two critical resources are always inextricably linked. To solve the emerging crisis of energy and water, renewable energy technologies is the key. On the other hand, recent advances in Micro-Electro-Mechanical Systems (MEMS) technology have opened new ways for us to use micro/nano scale physical and chemical effects. It is no doubted that the combination of the renewable energy technologies and micro/nano technologies will have great potential and there are plenty of room to explore. / The research presented in this thesis focuses on extending the micro scale effect to the macroscopic applications. Based on this idea, a new energy harvesting method and two new water desalination technologies are proposed, with computer simulations and experiment validations. These include: / Zhang, Peng. / Adviser: Ruxu Du. / Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 123-135). / 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. / Abstract also in Chinese.