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

(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.

Nous présentons l'auto-assemblage 2D de molécules Donneuses (D) et Acceptrices (A) d'électrons sur Au(111), ainsi que leur étude par un dispositif de Microscopie à Effet Tunnel couplé à une excitation lumineuse (LA-STM). Dans un premier temps, des systèmes 2D supramoléculaires robustes (liaisons hydrogène) D et/ou A ont été élaborés par un procédé en solution. Des liaisons hydrogène sont mises en évidence sur un assemblage d'un dérivé de porphyrine (D) pouvant en établir plusieurs, montrant le lien entre les liaisons établies et la géométrie obtenue. D'autre part, un réseau poreux "hôte" à base de molécules de PTCDI (A) et de mélamine est utilisé pour diriger la croissance de molécules "invitées" à l'intérieur des pores. Des systèmes hôte-invités sont alors élaborés en utilisant soit un dérivé thiolé de porphyrine (D), soit un polyoxométalate (POM). Une étude infrarouge de surface (PM-IRRAS) montre en plus que le réseau a une influence différente sur le processus d'organisation des deux molécules.Dans un deuxième temps, la mise en place d'un dispositif de LA-STM est décrite, avec une étude réalisée sur une bicouche moléculaire D/A constituée d'un polymère (PTB7) et d'un dérivé de fullerène (PC71BM). Premièrement, les effets photo-physiques, non spécifiques aux molécules et inhérents à la technique, ont été étudiés. Cela a permis de mesurer le courant à potentiels opposés DI=I(V+)-I(V-), attribué aux transferts de charge aux jonctions D/A. La localisation de ce courant permet d'identifier les jonctions D/A actives en surface avec une résolution nanométrique. / We present the 2D self-assembly of molecular electron Donors (D) and Acceptors (A) on Au(111) and their study by Light-Assisted Scanning Tunneling Microscopy (LA-STM). Firstly, hydrogen bonded supramolecular assemblies are elaborated from solutions. On one hand, a the self-assembly of a porphyrin derivative (D) show the relationship between the established hydrogen bonds and the obtained geometry. On the other hand, a PTCDI-melamine porous host network was used to template the growth of guest molecules within the pores. Host-guest systems are then elaborated using a thiolated porphyrin derivative and a polyoxometalate (POM) molecule. A surface infrared analysis (PM-IRRAS) shows that the network has different effects on the growth process and orientation angles of the two molecules.Secondly, we developed a LA-STM setup and we analysed a polymer/fullerene (PTB7/PC71BM) D/A molecular system. After the study of the photo-physical phenomena giving rise to the photo-current, we measured the current at opposite bias voltages DI=I(V+)-I(V-). We attribute this current to the photo-absorption of the molecules and to the electron transfer at the molecular D/A junctions which allows us to identify the active junctions on the surface with the nanometre resolution.

The IEEE 802.11a has become the mainstream protocol used in modern wireless communication system due to its high propagation rate of data (54 Mb/s). To meet high propagation rates, the communication devices used in IEEE 802.11a protocol usually present a high conversion gain and a high linearity (denoted as third order intercept point, IIP3). The IIP3 of conventional up- and down-conversion mixers are only about 0 dBm and -5 dBm, which fail to achieve a high propagation rate of data. This thesis utilizes the TSMC 0.18 µm CMOS technology to design and fabrication up- and down-conversion mixers with very high linearity for IEEE 802.11a application. The proposed high-linearity up-conversion mixer with 1.01 mm ¡Ñ 0.85 mm chip size and its wide bandwidth (5~6 GHz) is well suited for IEEE 802.11a application. To enhance the linearity and bandwidth, a transconductor stage with gm-boosted structure, a switch stgae with LO-body grounded structure and a load stage with shunt peaking structure are adopted in this research. Under 5.2/5.4/5.8 GHz operating frequencies, the implemented up-conversion mixer demonstrates a high conversion gain of 6.8/7.1/6.3 dB and a high linearity of 8.9/9/13.2 dBm, respectivly. In addition, a moderate consuming power (6.86 mW) of such mixer can be achieved at 1.2 V supply voltage. On the other hand, this thesis also designed and fabricated a high-linearity down-conversion mixer with chip size of 1.02 mm ¡Ñ 0.86 mm and 5.2 GHz center frequency. To improve the linearity and isolation and reduce the high-order noise, a transconductor stage with dual-gate structure and a load stage with RC-tank structure are adopted in this research. According to the EM-simulation resutls, the proposed down-conversion mixer presents a moderate conversion gain of 6 dB and a high linearity of 0.8 dBm. Additionly, a moderate consuming power (6.75 mW) of such mixer can be achieved at 1.8 V supply voltage.