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Call number: LD2668 .T4 1986 P42 / Master of Science / Computing and Information Sciences

by Lee Yin-sum. / Thesis (M.B.A.)--Chinese University of Hong Kong, 1981. / Bibliography: leaves 55-56.

Ching Ngai-hung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 81-83). / Abstracts in English and Chinese. / Chapter CHAPTER 1 ´ؤ --- INTRODUCTION --- p.1 / Chapter 1.1 --- Background on Micro Power Supply --- p.1 / Chapter 1.2 --- Literature Survey --- p.3 / Chapter 1.2.1 --- Comparison Among Different Power Sources & Transduction Mechanisms --- p.3 / Chapter 1.2.2 --- Previous Works in Vibration Based Generator --- p.6 / Chapter CHAPTER 2 一 --- DESIGN OF THE MICRO-POWER GENERATOR --- p.8 / Chapter 2.1 --- Concept of Power Generation --- p.8 / Chapter 2.2 --- Design Objectives of the Micro Power Generation --- p.9 / Chapter 2.3 --- System Modelling and Configuration of the Generator --- p.10 / Chapter 2.4 --- RESONATING STRUCTURE --- p.13 / Chapter 2.4.1 --- Material Selection --- p.13 / Chapter 2.4.2 --- Fabrication Method --- p.14 / Chapter CHAPTER 3 一 --- INDUCTING STRUCTURE --- p.17 / Chapter 3.1 --- Selection of Winding Method --- p.17 / Chapter 3.2 --- Solenoid Windings --- p.19 / Chapter 3.2.1 --- Fabrication Process --- p.19 / Chapter 3.3 --- PCB Windings --- p.20 / Chapter 3.3.1 --- Fabrication Process of the Prototype of Six-layer PCB --- p.21 / Chapter CHAPTER 4 一 --- EXPERIMENTAL RESULTS --- p.27 / Chapter 4.1 --- Experimental Setup --- p.27 / Chapter 4.1.1 --- Generator Systems --- p.27 / Chapter 4.1.2 --- Measurement of Vibration and Output from the Generator --- p.28 / Chapter 4.1.3 --- Observations of Vibration Motions --- p.31 / Chapter 4.2 --- SPRING FOR THE MICRO GENERATOR --- p.32 / Chapter 4.2.1 --- Spring Micromachining Optimization --- p.32 / Chapter 4.2.2 --- Mode Shapes and Spiral-spring Structures --- p.35 / Chapter 4.3 --- MAGNET FOR THE MICRO GENEARTOR --- p.37 / Chapter 4.3.1 --- Generator Output and Magnetic Dipole Orientation --- p.37 / Chapter 4.4 --- HAND-WIRED COIL GENEARTOR --- p.45 / Chapter 4.4.1 --- Performance of Different Design of Housings --- p.45 / Chapter 4.5 --- PCB COIL GENERATOR --- p.48 / Chapter 4.5.1 --- Size of PCB Coils vs. Generator Output --- p.48 / Chapter 4.5.2 --- Effect of Number of PCB Layers --- p.54 / Chapter 4.5.3 --- Array of Generators --- p.61 / Chapter CHAPTER 5 一 --- MODELLING AND COMPUTER SIMULATION --- p.63 / Chapter 5.1 --- Modelling the Second-Order System --- p.63 / Chapter CHAPTER 6 一 --- APPLICATION DEMONSTRATIONS --- p.69 / Chapter 6.1 --- INFRARED SIGNAL TRANSMISSION --- p.69 / Chapter 6.2 --- RF WIRELESS TEMPERATURE SENSING SYSTEM --- p.70 / Chapter CHAPTER 7 ´ؤ --- CONCLUSION --- p.75 / Chapter CHAPTER 8 一 --- FUTURE WORK --- p.77 / BIBLIOGRAPHY --- p.81 / APPENDIX --- p.84

Increasing costs associated with fossil fuel generation and a recognition and acceptance of the finite nature of this resource, have partially contributed to the growing popularity of alternative energy generation technology. International environmental treaties have also forced many states, primarily developing states, to deliberately review their fuels use. Jamaica having such a challenge requires accurate information regarding the impact of integrating generation from such technologies into its existing network. However, given a lack of resources, little work has been done to gather the relevant data that is required to evaluate the impact of embedded generation. Instead the findings from networks in other jurisdictions that have different operational and technical characteristics have been utilized. Anecdotal information regarding the availability of satisfactory renewable resources and the minimal impact that certain levels of integration will have on the existing network abounds among the engineering community on Jamaica. This research reviews the electricity and energy sectors of Jamaica. It further considers the efforts made by policy makers to fulfil the energy needs through a possible mix of fossil and renewable sources. Focus is then shifted to the analysis of available wind resource data which is then modelled to represent usable wind data for electricity generation. Actual system data is then used to produce an acceptable model of the current transmission network. The operation of the network is then considered on varying generation and loading conditions both with and without the inclusion of renewable sources. A final assessment of the impact of such sources is then made based on the magnitude and location in the network. The study concludes by highlighting the benefits to be derived from this work and reviews the challenges faced while conducting the study. It also recommends ways in which improvements to the system can be realized.

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The operating range and efficiency of a centrifugal compressor is limited by the development of rotating stall and surge at low mass flow rates. To extend the operating range of a compressor, flow control in the compressor can be used to suppress secondary flow structures that lead to rotating stall. The presented work seeks to use the novel idea of placing passive vortex generators (VG) upstream of the impeller to suppress rotating stall, while also developing new concepts and optimization of microvortex generators (MVG). To accomplish this goal, a new SIMPLE-type algorithm for compressible flows was written in Code_Saturne along with a 2nd-order MUSCL scheme for convective terms and an AUSM+-up scheme for mass flux computation. The new algorithm was successfully validated against several widely-used test cases. The new algorithm was used to model the flow of the NASA CC3, a high-speed centrifugal compressor, from choke to rotating stall with a vaneless and vaned diffuser. The new algorithm predicted the performance of the compressor with a vaneless diffuser very well; satisfactory results were obtained for the compressor with a vaned diffuser. The full compressor with a vaned diffuser was used to model rotating stall. A complex stall cycle between the inlet of the impeller and diffuser was observed and studied. The fundament behavior of MVG, i.e. micro (sub-boundary layer) vortex generator, in a turbulent boundary layer was investigated in a channel flow with RANS and LES. Complementary wind tunnel testing was conducted to validate the computational predictions. The configuration of the MVG was studied to determine an optimal configuration and several conclusions were reached on the design of MVG. Most importantly triangle MVG were found to be the most efficient shape followed by NACA0012 and e423-type MVG, and a MVG angle of 18˚ to 20˚ was found to be optimal. Rectangle MVG were observed to suffer flow separation on the vanes which reduced their performance. The circulation and drag of a MVG was found to have a logarithmic relationship with the device's Reynolds number. These findings were incorporated in a LES study to control separated flow on the e387 airfoil and achieved an improvement in lift-to-drag ratio of 11.27%. Additional recommendations for MVG implementation were given. Combining the work on the NASA CC3 with the work on MVG, vortex generators were implemented near the inlet of the impeller. A detailed optimization study was conducted for the implementation vortex generators in the compressor. It was found vortex generators equal to the boundary layer thickness were the most efficient on controlling the downstream flow. The best configuration was implemented into the full compressor with a vaned diffuser to assess the ability of vortex generators to suppress rotating stall. The vortex generators were found to suppress rotating stall and extend the operating range of the compressor.

Algae-derived biodiesel is currently under investigation as a suitable alternative to traditional fossil-fuels. Though it possesses many favorable characteristics, algae remains prohibitively expensive to mass produce and distribute. The most economical means of growing algae are large-scale open pond raceways. These, however, suffer from low culture densities; this fact impacts the cost directly through diminished productivity, as well as indirectly by raising costs due to the necessity of dewatering low culture density raceway effluent. Algae, as a photosynthetic organism, achieves higher culture densities when sufficient light is provided. In open ponds this can be accomplished by frequently cycling algae to the raceway surface. The current work examined delta wing vortex generators as a means of instigating this cycling motion. In particular the impact of spacing and angle of attack was analyzed. These vortex generators were found to significantly increase vertical mixing when placed in a series, developing precisely the motion desired. Their impact on power requirements was also examined. Specifically it was shown that increases in spacing and decreases in angle of attack result in lower power consumption. It was demonstrated that the most efficient mixing generation is achieved by larger spacings and smaller angles of attack. The impact that these devices had on raceway turbulence as measured by dissipation rate was also investigated and compared to published values for algae growth. Raceways were found to be significantly more turbulent than standard algae environments, and adding delta wings increased these levels further.

Swallowing is an essential motor act that coordinates the movement of food or saliva from the mouth through the pharynx and into the esophagus while protecting the upper airways from aspiration of those materials. Disordered swallowing, or dysphagia, results when bolus movement from the oropharyngeal phase into the esophageal phase is uncoordinated. Dysphagia directly causes or increases the risk of aspiration during swallowing in many clinical pathologies including Parkinson’s disease, Alzheimer’s disease, cerebrovascular incidents (stroke) in addition to being prevalent among the elderly population. The coordination between breathing and swallowing is mediated through the interaction of the swallow and respiratory Central Pattern Generators (CPGs) located in the brainstem. In the pharyngeal phase of swallow respiratory airflow is temporarily interrupted, and then reset, when the bolus moves through the pharyngeal space. The lungs retain enough air during the swallow apnea to protect the lower airways from accidental aspiration of residual bolus material, modulate the latency to initiate the swallow, while providing sensory feedback for processing within the brainstem network. The timing of the pharyngeal phase of swallow with respiration occurs across a continuum of lung volumes. Following swallow, the latency to initiate inspiration of the subsequent respiratory cycle increases. The swallow-mediated increase in cycle duration on respiration may depend upon the central processing of pulmonary afferents that may also affect reconfiguration of the respiratory CPG to express the swallow CPG. The peripheral and central mechanisms of swallow-breathing coordination remain poorly understood. Here, the relationship between central inspiratory output and the resultant mechanical inflation of the lungs was manipulated and dissociated to test the hypothesis that a centrally- and peripherally-mediated “swallow gate” coordinates swallow initiation with central respiratory activity and vagally-mediated pulmonary feedback. We obtained data from decerebrate adult cats of either sex that fully recovered from isoflurane anesthesia prior to the decerebration procedure. Fictive swallows were elicited using electrical stimulation of the superior laryngeal nerves (SLN) or injection of water (Water) into the pharyngeal cavity. Both stimuli were presented at random during the central respiratory cycle and/or the mechanical ventilation cycle. Mechanical ventilation was either triggered in-phase with phrenic discharge activity or it was set independent of phrenic discharge activity. These two modes of mechanical ventilation facilitated our ability to analyze the collective and individual effect of lower airway feedback on swallow-breathing coordination. The efferent discharge activities were recorded from the right hypoglossal (XII), left phrenic (Phr), left lumbar iliohypogastric (Lum) and right vagus (X) or the right recurrent laryngeal (RLN) nerves using silver bipolar hooked electrodes. All nerve activity was full-wave rectified, amplified, RC integrated (τ=200-500 ms) and low-pass filtered prior to analysis for effects on swallow-breathing coordination across stimulation-ventilation conditions. We observed post-inspiratory type (Post-I) and expiratory type (Exp) swallows that produced discrete effects on central respiratory rhythm across all conditions. The Post-I type swallows disturbed the duration and amplitude of preceding central inspiratory activity, without affecting the duration of central expiratory activity. The Exp type swallows prolonged central expiration but produced no effect on central inspiratory activity. We observed that lung inflation negatively modulated swallow initiation during fixed mechanical ventilation in the absence of central respiratory output, i.e., during central apnea. Most swallow elicited during central apnea initiated during periods of low lower airway afferent feedback. Collectively, these findings extend the role for lower airway feedback beyond its role as a provider of lung afferent surveillance and identifies lower airway feedback as a modulator of swallow-breathing coordination.

This thesis presents a study on the design method to optimise the performance for producing green power from multiple renewable energy generators. The design method is presented through PLC (Programmable Logic Controller) theory. All the digital and analogue inputs are connected to the input cards. According to different operations conditions for each generator, the PLC will image all the inputs and outputs, from these images; a software program has been built to create a control method for multiple renewable energy generators to optimise production of green power. A control voltage will supply the output contractor from each generator via an interface relay. Three renewable generators (wind, solar, battery bank) have been used in the model system and the fourth generator is the back up diesel generator. The priority is for the wind generator due to availability of wind 24 hours a day, then solar, battery bank, and LPG or Diesel generators. Interlocking between the operations of the four contractors has been built to prevent interface between them. Change over between contractors, according to the generator's change over has also been built, so that it will delay supplying the main bus bar to prevent sudden supply to the load. Further study for controlling multiple renewable energy generators for different conditions such as controlling the multi-renewable energy generators from remote, or supplying weather forecast data from bureau of meteorology to the PLC directly as recommended. / Master of Electrical Engineering (Hons)