The purpose of this thesis is to develop a high power, compact all solid-state blue laser, which is applicable in micro machining, LIDA, underwater ranging, biochemical techniques and so forth. The passive Q-switching technique, which is known to be a low-cost and simple method to raise the laser peak power was employed in this thesis. In the mean time, the intracavity-doubling technique was integrated to achieve the non-linear frequency conversion for generating blue laser at low cost. Based on our research finding, the reabsorption loss due to thermal effect and a paucity of suppression at wavelength of 1064 nm on laser mirrors could cause the four-level oscillation at 1064 nm instead of three-level oscillation at 914nm. Improvement in heat dissipating system, and suppression at wavelength of 1064 nm on mirror coating has led to a success in developing a quasi-three-level blue laser with peak power of 114W at wavelength 473 nm. A modified rate equation model of the quasi-three level passively Q-switched blue lasers was developed as well, in which the influence of the re-absorption loss in the gain medium and its intracavity frequency doubling were both considered. The influence of reabsorption loss upon the laser power deduction was studied by numerical simulation in order to optimize the laser performance.

Analysis of three-phase, three-level VSIs is done for high-power high-voltage applications. Complete Space Vector Modulation (SVM) algorithm is developed for a three-phase, three-level converter. Special attention is given to minimization of output ripple and voltage balance of the dc-link input capacitors. Verification of the proposed SVM algorithm is done by computer simulation. Comprehensive small-signal modeling of the three-level converter with a resistive load is developed the first time. Steady-state solutions reveal that the voltage across dc-link input capacitors is constant at the half of the dc-link voltage. / Master of Science

A quantized control means that the control force is restricted to takes only a finite number of prescribed levels. The well-known bang-bang control or relay control belongs to this category. This kind of control has the advantage of simple circuit realization using electronic switches or relays that feature low power consumption in their on-off operation. However, quantized control introduces noise and distortion, and even worse its high nonlinearity makes the stabilizing compensator design difficult. This thesis applies the concept of dynamic sliding mode to the synthesis of a multi-level quantized control, with the aim to stabilize the system, perform reference tracking and attenuate the switching noise. The applicability of the presented sliding-mode quantized control is demonstrated on a three-level buck converter. Compared with the conventional PWM (Pulse-Width Modulation) scheme, it eliminates the use of a complex three-level PWM generator and a current sensor. A 12V/8V three-level buck converter with sliding mode quantized control is designed and realized, which shows the output voltage with 0.4625% of average DC error, 2.8988% of the static output ripple and 2.3% of load regulation error in response to the load current steps from 0A/3A to 3A/0A, at a slew rate of 6.25A/£gsec.

Due to development of industries, power factor and harmonic pollution have become serious concerns in the power system. This thesis presents an adaptive linear neuron (ADALINE) - based static synchronous compensator (STATCOM) to cope with power quality issues in the industrial power system. The targeted compensating current of the STATCOM is generated based on the so-called LMS algorithm, thus the compensated system current becomes balanced and active even in reactive, unbalanced or distorted loads. In this thesis, the STATCOM is realized by using a three-level neutral point-clamped (NPC) inverter with the in-phase level-shifted sinusoidal pulse width modulation (IPLSPWM). Theoretical analysis of ADALINE method is detailed and hardware implementation of STATCOM is conducted to validate effectiveness of the proposed approach.

Though Nd:YAG has been widely used as the traditional high power solid-state laser gain medium, Yb:YAG has more advantages such as lower quantum defect, wider absorption and emission bandwidth, and longer fluorescence lifetime, which can be used in Q-switched lasers to storage more energy. In addition, a higher doping concentration Yb:YAG with thinner thickness reduces the shift of optical path, which reduces the ring cavity stability. Therefore Yb:YAG is an eminently suitable gain medium for the two-mirror ring laser. Due to the quasi-three-level characteristic of Yb:YAG, the thermal effect influences the re-absorption loss and deteriorates the laser performance, i.e. lower slope efficiency of laser. In this thesis, we improve the laser efficiency by using Yb:YAG crystal with proper thickness, and various round-trip transmittances with different output couplers were tried. The slope efficiency with 50.3 % has been achieved. We also tried to reduce the thermal loading of Yb:YAG by crystal fiber with Cu-Al alloy package. The fabrication process of Yb:YAG crystal fiber, including sample preparation, and coating design, and the experiment result of Yb:YAG crystal fiber ring laser will be presented in detail. Furthermore, we use numerical analysis to modify the passively Q-switched Yb:YAG ring laser rate equation with FDTD (finite difference time domain) method. The simulated repetition rate, pulse width and peak power were compared to the experimental results in order to optimaize laser performance.

The purpose of this study is to develop a solid-state blue laser which has advantages of high power, short wavelength, and compact. It can be applied in micromaching, LIDAR, underwater ranging, biochemical techniques, and so forth. We increased the peak power of the laser effectively by a low-cost, small, and easy-use passive Q-switching technique. In addition, intracavity frequency-doubling is an economic way to achieve non-linear frequency conversion for blue generation. By integrating of these two techniques, we develop a compact all solid-state high-power blue laser with 83 W peak power at 473 nm. Restricted to reabsorption loss, the optical to optical conversion efficiency of 4F3/2 ¡÷ 4I9/2 quasi-three-level laser is lower than 4F3/2 ¡÷ 4I11/2 four-level laser for Nd:YAG crystal. The reabsorption loss will change with the temperature variation of the gain medium, it enormously affects to the performance and stability of quasi-three-level lasers. Therefore, in addition to make systematic studies of the conversion efficiency of KNbO3, BBO, LBO as the intracavity SHG crystals for generation of high-power blue laser, we use the numerical analysis to investigate the influence of reabsorption loss to quasi-three-level passive Q-switching laser. At present, blue laser with peak power of 83 W and pulse width of 10.6 ns was generated as a result. To our knowledge, the compact all solid-state high-power pulsed blue laser is demonstrated for the first time by integrating of passive Q-switching and intracavity frequency-doubling simultaneously.

Reading skills are essential for all students for their successful advancement through school and on into adult life. With limited English, many Non English Speaking Background (NESB) students are under-achieving at school due to their lack of reading ability in English. This research investigates a skills-based program with an emphasis on decoding (often referred to as a bottom-up theoretical perspective) compared to a program emphasising the development of comprehension strategies, where higher level thinking is required (top-down perspective). Using a case study approach with one NESB student, it appeared that a skills-based approach was more successful and preferred by the student.

abstract: Currently, there is a clear gap in the missing data literature for three-level models. To date, the literature has only focused on the theoretical and algorithmic work required to implement three-level imputation using the joint model (JM) method of imputation, leaving relatively no work done on fully conditional specication (FCS) method. Moreover, the literature lacks any methodological evaluation of three-level imputation. Thus, this thesis serves two purposes: (1) to develop an algorithm in order to implement FCS in the context of a three-level model and (2) to evaluate both imputation methods. The simulation investigated a random intercept model under both 20% and 40% missing data rates. The ndings of this thesis suggest that the estimates for both JM and FCS were largely unbiased, gave good coverage, and produced similar results. The sole exception for both methods was the slope for the level-3 variable, which was modestly biased. The bias exhibited by the methods could be due to the small number of clusters used. This nding suggests that future research ought to investigate and establish clear recommendations for the number of clusters required by these imputation methods. To conclude, this thesis serves as a preliminary start in tackling a much larger issue and gap in the current missing data literature. / Dissertation/Thesis / Masters Thesis Psychology 2015

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Lithium-ion batteries are the most are widely used as electrical storage device in various applications such as portable electronics, electric vehicles, Photovoltaic application, telecommunication etc due to the characteristics of the batterie such as high-power density, long cycling and high-power efficiency. Extensive condition monitoring of the battery should be implemented due to the usage of the battery so that there will be an increase in all the overall performance and expectancy. This research is focused on implementing an online condition monitoring on the Li-ion battery using a signal injection through a power converter. The implemented technique in this research is known as the Electrochemical Impedance Spectroscopy (EIS). The EIS is a widely known technique used in determining the internal impedance of a battery cell. The estimated impedance can be used to determine the state of charge (Soc) and State of health (SoH) of a battery. The EIS is used to characterize the electrochemical behaviour thereby monitoring the change in the impedance of the cell of the battery. The EIS technique is accomplished by sinusoidally injecting current at different frequencies and measuring the voltage response. A standard Frequency Response Analyser (FRA) is used as an offline test while the battery is disconnected from the Load. The limitation of this standard FRA analyser is that it is bulky and Expensive. Attempts have been made to migrate the techniques to online operations, each having their own challenges. For an online Implementation, the interfacing power converter is used for Signal injection to measure the impedance of the battery. This work explores the low current ripple advantage of a threelevel boost converter to implement EIS on lithium ion battery.