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  • Using adiabatic logic for low-power VLSI
    (1998) Avery, Stephen
    Thesis
  • Low power digital VLSI design
    (1998) Choe, Swee Yew
    Thesis
  • Feed channel spacer characteristics and their optimisation
    (1998) Cao, Zhiyi
    Thesis
    The optimization of the spiral wound module design generally refers to the optimization of feed channel spacers, which is investigated in this thesis. The feed channel spacers serve to improve the mass transfer by promoting turbulence and provide passage for the fluid. However, the presence of spacers also significantly increases the channel pressure drop and consequently increases the energy costs of the process. The spacer design could therefore have a significant effect on process economics. The main aim of this work was to study spacer characteristics and test its major geometrical characteristics. To achieve this, custom designed spacers were developed in the laboratory and CFD simulations were used to visualize the flow management that spacer can achieve. Through experiments and CFD simulation, it was found that the transverse filament was one of the dominating factors in spacer design. Most of the pressure drop in the spacer filled channel was caused by the form drag introduced by the transverse filaments. The variation in transverse filament distance can greatly affect the number of transverse filaments in the channel and consequently affect the pressure drop and mass transfer in the channel. The experimental results showed that the diameter of the transverse filament also had a significant effect on channel pressure drop and mass transfer, especially at high flow rates. Increasing transverse filament diameter may result in a rapid increase in pressure drop and mass transfer caused by increased from drag and enhanced turbulence. Voidage alone was found not to be efficient for quantifying the geometrical properties of spacer filled channels. Two ratios, transverse filament diameter/channel height and transverse filament diameter/transverse distance, were established for quantifying the performance of the spacer filled channels. Novel spacers were developed as the result of this research. They provide similar mass transfer performance to the benchmark commercial spacer with lower pressure drop. Optimal novel spacer design was analysis based on economics analysis.
  • Low voltage CMOS analog integrated circuit design
    (1998) Wong, Louis S. Y.
    Thesis
    Designing analog circuits that can operate from low supply voltages has become of increasing importance in recent years. The rapid growth of battery operated portable devices and biomedical implant systems require low power dissipation to achieve long battery life and minimum battery size. The ever-increasing trend in the density of integrated circuits and smaller feature sizes has necessitated the supply voltage to be scaled down in order to reduce power dissipation and maintain reliability. Reducing supply voltage is one of the most effective ways to achieve low power dissipation. Within these low voltage integrated circuits, the analog circuits are always suffering from poor performance and become the bottleneck of the system. The objective of this thesis is to develop circuit techniques for the realisation of high performance low voltage CMOS operational amplifiers and digital-to-analog converters. In order to support the digital-to-analog converter and other mixed-signal systems, high speed and low voltage digital logic circuit technique was also developed for standard CMOS process. By studying both conventional and recent developments in analog circuit designs, reduction in supply voltage is always limited. Due to the fundamental limitation of transistor threshold voltage, alternative design techniques must be employed to further reduce the supply voltage. Several novel circuit techniques have been proposed in this thesis to regain circuit performance under low voltage condition. These include the reduction in transistor stacking to maximize the gate-source voltage, the use of floating-gate devices to perform dual functions in a single transistor, and by driving the back gate of a transistor to explore the extra current flow. Three operational amplifiers, three digital-to-analog converters and some high-speed digital circuits have been designed and fabricated to demonstrate the feasibility of the proposed techniques. All designed circuits are operated in genuinely low voltage as neither low threshold devices or charge pump circuitry is used. Experimental results are presented to show that supply voltage range from as low as 0.9V is sufficient.
  • Integrable Components for Silicon Microvalves
    (1998) Haji Babaei, Jafar
    Thesis