A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering, 2015 / Electrical utilities are tasked with managing large numbers of assets that have long useful lives and are fairly expensive to replace. With emphasis on medium voltage vacuum circuit breakers, a key challenge is determining when circuit breakers are close to their end-of-life and what the appropriate action at that point in time should be. Condition-based maintenance, intended to “do only what is required, when it is required,” has been reported as the most effective maintenance strategy for circuit breakers. This dissertation provides an overview, together with laboratory measurements, on non-intrusive technologies and analytics that could reduce maintenance costs, unplanned outages, catastrophic failures and even enhance the reliability and lifetime of circuit breakers by means of a real-time condition monitoring and effective failure prevention maintenance approach. The key areas of research are the condition assessment of the mechanical mechanism based on coil current signature diagnosis, degradation detection of the main interrupting contacts through thermal monitoring and interrupter vacuum integrity assessment based on magnetron atmospheric condition (MAC) testing. The information from test results allows both immediate onsite analysis and trending of key parameters which enables informed asset management decisions to be taken. / GS2016

by Han Dejun. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves [117]-[129]). / Abstract --- p.ii / Acknowledgment --- p.iv / Table of Contents --- p.v / Chapter 1. --- Introduction --- p.1-1 / Chapter 1.1 --- The Current Situation of Space-division Optical Switches --- p.1-1 / Chapter 1.1.1 --- Digital Optical switches (DOS) --- p.1-2 / Chapter 1.1.2 --- Twin-guide amplifier (TGA) --- p.1-3 / Chapter 1.1.3 --- Direction coupler with amplifiers --- p.1-4 / Chapter 1.1.4 --- Total internal reflection type switch with amplifier --- p.1-5 / Chapter 1.1.5 --- Semiconductor optical amplifier gate switches --- p.1-6 / Chapter 1.2 --- Existing Problems --- p.1-9 / Chapter 1.3 --- New Proposals --- p.1-10 / Chapter 1.3.1 --- New features --- p.1-11 / Chapter 1.3.2 --- New technology for OEIC --- p.1-13 / Chapter 1.3.3 --- Expected improvement in performance --- p.1-14 / Chapter 1.4 --- Organization of thesis --- p.1-17 / Chapter 2. --- Band Lineup And Optical Gain Calculation --- p.2-1 / Chapter 2.1 --- Introduction --- p.2-1 / Chapter 2.2 --- Band Lineup for InGaAsP MQW Structures --- p.2-3 / Chapter 2.2.1 --- Derivation According to Ishikawa et al.'s Scheme --- p.2-3 / Chapter 2.2.2 --- Derivation According to Krijn's scheme --- p.2-5 / Chapter 2.2.3 --- Improved band lineup calculation scheme --- p.2-7 / Chapter 2.3 --- Gain and Spontaneous Emission Rate Expressions --- p.2-13 / Chapter 2.3.1 --- Optical gain expressions --- p.2-13 / Chapter 2.3.2 --- Spontaneous Emission Rate Expressions --- p.2-16 / Chapter 2.3.3 --- Polarization characteristics --- p.2-17 / Chapter 2.4 --- Optical Absorption and Its Polarization Sensitivity --- p.2-18 / Chapter 2.4.1 --- Absorption in an intermixed QW Structure --- p.2-18 / Chapter 2.4.2 --- Electro-optical Absorption --- p.2-19 / Chapter 3. --- Design of the Optical Switches --- p.3-1 / Chapter 3.1 --- Design of Material Layer Structure --- p.3-2 / Chapter 3.2 --- Design of Device Geometrical Structure --- p.3-7 / Chapter 3.3 --- Optical Gain in Polarization Insensitive Gain Medium-- An Example --- p.3-8 / Chapter 3.4 --- Optical Absorption in Polarization Insensitive Gain Medium-- An Example --- p.3-15 / Chapter 4. --- Fabrication Technology --- p.4-1 / Chapter 4.1 --- Passive Waveguide Formation --- p.4-2 / Chapter 4.1.1 --- Impurity-free vacancies diffusion technology --- p.4-3 / Chapter 4.1.2 --- High energy ion implantation enhanced intermixing technology --- p.4-4 / Chapter 4.1.3 --- Elevated temperature O+ HE-IIEI of MQWs --- p.4-6 / Chapter 4.2 --- Oxygen Implant Isolation --- p.4-6 / Chapter 4.3 --- Self Aligned Ridged Waveguide Technology --- p.4-7 / Chapter 4.4 --- Reduction of Effective Facet Reflectivity --- p.4-11 / Chapter 4.5 --- Fabrication Process Flow --- p.4-12 / Chapter 4.5.1 --- Layer structure of the material --- p.4-12 / Chapter 4.5.2 --- Fabrication process flow for the Y-junction optical switches --- p.4-14 / Chapter 4.6 --- Schematic Structure of the Fabricated Switches --- p.4-19 / Chapter 5. --- Experimental Results --- p.5-1 / Chapter 5.1 --- High Energy Ion Implantation Enhanced Intermixing of Quantum Wells --- p.5-2 / Chapter 5.1.1 --- High energy ion implantation --- p.5-2 / Chapter 5.1.2 --- Rapid thermal annealing --- p.5-4 / Chapter 5.2 --- Photoluminescence --- p.5-6 / Chapter 5.3 --- Electroluminescence --- p.5-9 / Chapter 5.4 --- Current-Voltage characteristics --- p.5-12 / Chapter 5.5 --- Guided-Wave Optoelectronic Measurement --- p.5-14 / Chapter 5.5.1 --- Setup of the measurement --- p.5-14 / Chapter 5.5.2 --- Measurement of absorption loss for the blue-shifted QW structure --- p.5-16 / Chapter 5.5.3 --- Optical losses measurement by Fabry-Perot interference method --- p.5-18 / Chapter 5.5.4 --- Electroabsorption peak shift in IIEI wafer --- p.5-21 / Chapter 5.6 --- Oxygen Implant Isolation --- p.5-21 / Chapter 5.7 --- Characteristics of Optical Switches --- p.5-23 / Chapter 5.7.1 --- Current-voltage characteristics --- p.5-23 / Chapter 5.7.2 --- Optical mode and transmission characteristics --- p.5-24 / Chapter 5.7.3 --- Switch characteristics --- p.5-29 / Chapter 5.7.4 --- Discussion --- p.5-32 / Chapter 6. --- Conclusion and Future Studies --- p.6-1 / Chapter 6.1 --- Conclusion --- p.6-1 / Chapter 6.1.1 --- The major contributions to the Y-JOS --- p.6-1 / Chapter 6.1.2 --- The major contribution to the bandgap engineering for InGaAs(p)/InP heterostructure --- p.6-3 / Chapter 6.1.3 --- The major contributions to the HE-IIEI technology --- p.6-4 / Chapter 6.2 --- Topics for Future Studies --- p.6-5 / Chapter 6.2.1 --- Band lineup and optical gain calculation --- p.6-5 / Chapter 6.2.2 --- Optimization of HE-IIEI technology --- p.6-6 / Chapter 6.2.3 --- Optimization of the Fabrication of Y-JOS --- p.6-7 / Reference --- p.R1 / Appendix A Characteristics Of Strained Quantum Wells --- p.A1 / Appendix B Effective Index Change Induced by Quantum Well Intermixing --- p.A3 / Appendix C Abbreviation --- p.A13 / Appendix D List of Publications --- p.A14

prepared by Ling Hok Sun, Lawrence. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Abstract also in Chinese. / Chapter 1. --- Abstract --- p.2 / Chapter 2. --- Introduction --- p.3 / Chapter 3. --- Circuit Description --- p.8 / Chapter 4. --- Technology' --- p.10 / Chapter 5. --- Design --- p.13 / Chapter 5.1 --- TOP LEVEL --- p.13 / Chapter 5.2 --- Logic --- p.14 / Chapter 5.3 --- Tuner --- p.19 / Chapter 5.4 --- Gate Drive and Power Switch --- p.26 / Chapter 5.5 --- Full-Circuit Simulation --- p.43 / Chapter 6. --- Layout --- p.53 / Chapter 7. --- Characterization --- p.55 / Chapter 8. --- Conclusion --- p.65 / Chapter 9. --- Reference --- p.66 / Chapter 10. --- Appendix --- p.67

In this paper, an analysis of the clock-feedthrough effects in switched-current (SI)' circuits will be presented. The clock-feedthrough effects caused by the non-ideal characteristic of MOS switches when they are turned off limit the accuracy of the analog track-and-hold (T/H) circuits. A model to analyze and characterize this effect is established. A current-feedthrough cancellation technique is developed for analog/digital applications. This circuit allows SI filters to be implemented with small transistor sizes and still performs relatively well compared with the existing techniques. A SI lowpass biquadratic filter with a cutoff frequency of 5 KHz and a SI T/H circuit were implemented and fabricated using a two micron P-well CMOS process technology from MOSIS (MOS Integration Service). / Graduation date: 1992

No description available.

The design and analysis of a novel optical-to-microwave transducer based upon direct optical control of microwave gallium arsenide (GaAs) field-effect transistor (FET) switches is the subject of this thesis. The switch is activated by illuminating the gate depletion region of the FET device with laser light having a photon energy and wavelength appropriate to the generation of free carriers (electron-hole pairs) within GaAs. The effects of light on the DC and microwave properties of the GaAs FET are explored and analyzed to permit the characterization of the switching performance and transient response of a reflective microwave switch. The switch is novel in that it utilizes direct optical control, whereby the optically controlled GaAs FET is directly in the path of the microwave signal and therefore relies on optically-induced variations in the microwave characteristics of the switch. This contrasts with previous forms of optically controlled switches which rely on indirect methods with the optical stimulus inducing variations in the DC characteristics of the GaAs FET, such that there is no direct interaction between the optically illuminated GaAs FET and the microwave signal. Measured and simulated results relating to the switching performance and transient response of the direct optically controlled microwave switch have been obtained and published as a result of this work. For the first time, good agreement is achieved between the measured and simulated results for the rise and fall times associated with the transient response of the gate photovoltaic effect in optically controlled GaAs FET switches. This confirms that the GaAs FET, when used as an optically controlled microwave switch, has a transient response of the order of several micro-seconds. An enhanced model of the GaAs FET switch has been developed, which represents a more versatile approach and leads to improved accuracy in predicting switching performance. This approach has been shown to be valid for both optical and electrical control of the GaAs FET. This approach can be used to model GaAs FET switches in discrete or packaged forms and predicts accurately the occurrence of resonances which may degrade the switch performance in both switching states. A novel method for tuning these resonances out of the switch operating band has been developed and published. This allows the switch to be configured to operate over the frequency range 1 to 20 GRz. The agreement between the models and measured data has been shown to hold for two very different GaAs FET structures. The results of the direct optically controlled microwave GaAs FET switch have been used as the basis for the design of a novel direct optically controlled microwave phase shifter circuit; Measured and simulated results are in good agreement and verify that the performance of the optically controlled phase shifter is comparable with previously published results for electrically controlled versions of the phase shifter. The 10 GRz phase shifter was optically controlled over a 1 GRz frequency range and exhibited a mid-band insertion loss of 0.15 dB. The outcome of the work provides the basis for directly controlling the phase of a microwave signal using the output of an optical sensor, with the GaAs FET acting as an optical-to-microwave transducer through a monolithic interface.

This thesis examines the design, synthesis and biological applications of a series of inhibitors which incorporate an azobenzene photoswitch, a peptidyl backbone and a trifluoromethyl ketone warhead. The photoswitch can be isomerised by irradiation with UV or visible light and has been employed to modulate the reactivity of the enzyme. Chapter one gives a brief outline of some of the important areas related to this work. Examples of previously utilised photoswitches as well as some background on serine protease and the uses of fluorine in medicine has been covered. Chapter two outlines the synthesis of the key trifluoromethyl carbinol 2.6 by two different methods. The condensation of a fluorinated aldehyde with a nitroalkane affords an α-nitro trifluoromethyl carbinol which can be reduced to give the desired amine 2.6. Treatment of oxazolones with trifluoroacetic anhydride via a modified Dakin-West reaction gives trifluoromethyl ketones which can be reduced to give trifluoromethyl carbinols. Chapter three investigate the synthesis of substituted stilbenes and phenanthrenes as alternative molecular switches to azobenzenes. Molecular modelling of phenanthrenes suggests they may be suitable mimics of E-azobenzenes. Chapter four outlines the synthesis of a series of mono and disubstituted azobenzenes by direct sulfonation of azobenzene or by condensation of nitroso arenes with aryl amines. The switches incorporate one or two peptidyl residues designed to improve specificity towards the enzyme. Chapter five examines the photoisomerisation of eight potential inhibitors by irradiating with UV or visible light. Irradiation with UV light enriches the sample to give 78-93 % of the Z-isomer. Irradiation with visible light gave photostationary states with 14-21 % Z-isomer. Ambient photostationary states are ca. 22 % Z-isomer. Chapter six looks at the testing of five trifluoromethyl ketones as potential inhibitors ofα-chymotrypsin. The inhibitors vary in substituents, substitution patterns and chain length. The inhibitors were tested at both ambient and Z-enriched photostationary states and were found to exhibit slow binding kinetics. In all cases the Z-enriched inhibitor solution was at least 3-fold more potent than the ambient solution. Chapter seven is an experimental chapter and outlines the synthesis of the compounds prepared in this thesis.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 112-119). Also available via the Internet.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 74-78). Also available via the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 76-80). Also available on the Internet.