Abstract The metal halide lamp is one of high-intensity discharge lamps. It has many advantages such as good color rendering, high efficacy and a variety of color presentations. However, the problems of acoustic resonance, a long transition period of cold starting, and an extremely high ignition voltage for hot restarting should be overcome. The investigation of the thesis is focused on the electrical characteristics of the metal halide lamp operating at high-frequency. Included are the acoustic resonance, starting transient and steady state operation. Various ballast circuits incorporating with ignitors are designed to drive several 70-W metal halide lamps. The operating frequency ranges with acoustic resonance, the ignition voltages for both cold starting and hot restarting, the transition period, the dimming performance, and the lamp equivalent resistance during the lamp life are measured and analyzed. Based on the investigated results, a useful guideline can be provided for the operation and design of the electronic ballast for metal halide lamps. Key words : Metal halide lamp, electronic ballast, acoustic resonance, hot restarting.

A high-frequency electronic ballast with auto-tracking control was proposed to operate the metal halide lamps at a specific frequency free from acoustic resonance. In case the acoustic resonance should happen, the operating frequency is changed step by step with the auto-tracking control, until the lamp is operated at a frequency with stable operation. The electrical characteristics of the lamps are first investigated. Based on the investigated results, a detection circuit is designed to identify the occurrence of acoustic resonance. With the auto-tracking control, the Class-D half-bridge series-resonant inverter can be adopted for the high-frequency electronic ballast to achieve high efficiency and high power density. The control strategy of auto-tracking is practically realized by a single-chip microprocessor. The proposed approach is implemented on a 70 W test lamp with an operating frequency range from 20 kHz to 30 kHz. To regulate the lamp power at its rated value, a buck-boost converter is used as a pre-regulator, which serves also as a power-factor-corrector to achieve a high power factor at the input line.

This thesis presents a single-stage high-power-factor electronic ballast for metal halide lamps. The proposed ballast integrates a buck-boost converter, a buck converter and a full-bridge inverter into a single power conversion circuit. The buck-boost converter is designed to be operated at the discontinuous conduction mode (DCM) with a constant duty ratio at a fixed switching frequency to provide a constant lamp power and to achieve a high power factor for a given ac input voltage. The full-bridge inverter supplies a square-wave current for the lamp at a low frequency the same as the line frequency to avoid acoustic resonance. For the universal input voltage ranged from 90 V to 264 V, the lamp remains at the rated power by controlling the duty-ratio of the buck converter. The circuit operation is analyzed in detail to derive the design equations. An electronic ballast for 70 W lamps is designed and tested. Computer simulations and experimental measurements are provided to verify that the proposed ballast has the merits of a nearly unity input power factor, a high efficiency greater than 82 % and can drive the lamp at a constant power.

Thesis (Ph. D.)--University of Chicago, Dept. of Comparative Literature, August 2001. / Includes bibliographical references. Also available on the Internet.

This thesis studies three novels of the Turkish writer Halide Edib (1884-1964) written between 1908 and 1912, and examines this historical period and her life during it. The thesis deals with the 1908 Constitutional Revolution, the '31 March Incident' and the Turkist movement, as reflected in her novels, as well as independently through secondary sources. The examination of Raik'in Annesi (1980) reveals Edib's ideas on 'ideal womanhood,' morality and divorce. Seviyye Talib (1990) includes her views on the Constitutional Revolution, women's modernisation and the '31 March Incident.' The study of Yeni Turan (1912) reveals much about Turkism, or Turanism, and its political opponent in the novel, Ottomanism. From these novels Edib's main ideas are brought out and examined. Among the recurrent themes analysed are her strong admiration for the Angle-Saxon culture, her understanding of Westernisation, her approach to Islam, and her views on women and family.

Thesis (M.S.)--Rochester Institute of Technology, 1987. / Typescript. Includes bibliographical references (leaves 45-47).

With the soaring advancement of organolead halide perovskite solar cells rising from a power conversion efficiency of merely 3% to more than 22% shortly in five years, researchers’ interests on this big material family have been greatly spurred. So far, both in-depth studies on the fundamental properties of organolead halide perovskites and their extended applications such as photodetectors, light emitting diodes, and lasing have been intensively reported. The great successes have been ascribed to various superior properties of organolead halide hybrid perovskites such as long carrier lifetimes, high carrier mobility, and solution-processable high quality thin films, as will be discussed in Chapter 1. Notably, most of these studies have been limited to their polycrystalline thin films. Single crystals, as a counter form of polycrystals, have no grain boundaries and higher crystallinity, and thus less defects. These characteristics gift single crystals with superior optical, electrical, and mechanical properties, which will be discussed in Chapter 2. For example, organolead halide perovskite single crystals have been reported with much longer carrier lifetimes and higher carrier mobilities, which are especially intriguing for optoelectronic applications. Besides their superior optoelectronic properties, organolead halide perovskites have shown large composition versatility, especially their organic components, which can be controlled to effectively adjust their crystal structures and further fundamental properties. Single crystals are an ideal platform for such composition-structure-property study since a uniform structure with homogeneous compositions and without distraction from grain boundaries as well as excess defects can provide unambiguously information of material properties. As a major part of work of this dissertation, explorative work on the composition-structure-property study of organic-cation-alloyed organolead halide perovskites using their single crystals will be discussed in Chapter 3 and 4. Despite their outstanding charge transport characteristics, organolead halide perovskite single crystals grown by hitherto reported crystallization methods are not suitable for most optoelectronic devices due to their small aspect ratios and free standing growth. As the other major part of work of this dissertation, explorative work on growing organolead halide perovskite monocrystalline films and further their application in solar cells will be discussed in Chapter 5.

>Magister Scientiae - MSc / Perovskite solar cells have gained tremendous attention within the past decade, due to its rapid improvement in power conversion e ciency (PCE), with the current record cell at 25%. The aim of this study is to create a repeatable and scalable chemical vapour deposition technique that can be used to construct perovskite solar cells with a high PCE while maintaining long-term stability. The technique requires the formation of a uniform and compact lead halide layer, either PbI2 or PbCl2 that is sequentially converted into the perovskite structure with the exposure of Methylammonium iodide (MAI) vapour. The use of CVD with a 5 cm diameter quartz tube was successfully used to deposit uniform thin lms of both PbI2 and PbCl2 over an area of 6 cm2 with a thickness deviation of 5%. Thickness control was obtained by varying the amount of source material which allows for repeatable control within 5% error, without the need for a crystal thickness monitor.

Optical absorption spectra of alkali halide crystals containing H⁻ ions (U-centres) are calculated using a two-parameter model to describe the defect. It is shown that this model gives a satisfactory account of the observed anharmonic sideband of the main U-centre absorption band in the infrared, and also of the impurity-induced far infrared absorption for the two host crystals considered, potassium bromide and potassium iodide. The broadening of localized modes and resonances is also discussed. In particular, the anharmonic broadening is calculated for the main U-centre line in KI and KBr and for a localized gap mode in KI:KH. / Thesis / Doctor of Philosophy (PhD)

<p> The ultraviolet absorption spectrum of oxalyl chloride-fluoride has been recorded under high resolution, and has been attributed to a superposition of the spectra of the cis isomer (which appears weakly) and the trans isomer. The ultraviolet spectra of the cis isomers of oxalyl bromide, oxalyl chloride and oxalyl fluoride have also been identified. With the help of theoretical calculations, discrete absorption in the ultraviolet spectrum of trans oxalyl chloride-fluoride has been attributed to the superposition of four systems: (a) the singlet-singlet and singlet-triplet transitions which involve promotion of an electron from the highest energy non-bonding orbital (n₁) to the lowest energy antibonding orbital (π₁*) and (b) the singlet-singlet and singlet-triplet transitions which involve promotion from n₁ to the second lowest energy antibonding π orbital (π₂*). The S-S and S-T, n₁ → π₁* transitions have been analyzed in detail. </p> <p> Theoretical calculations have been carried out which indicate that α,β diketones, promotion of an electron to the lowest energy antibonding skeletal orbital (σ₁*) produces states which have a tendency towards dissociation along the C-C bond. It has been postulated that the diffuseness of the high energy absorption spectrum results from such a molecular dissociation, the Aᵤ(π₁,π₁*) state being strongly predissociated by the Aᵤ(n₁,σ₁*) state while the Aᵤ(n₁,π₁*) state is strongly predissociated by the Aᵤ(π₁,σ₁*) state. </p> <p> It has been postulated that the fluid phases of glyoxal and biacetyl consist of an equilibrium mixture of these molecules in various degrees of aggregation (e.g., monomeric, dimeric, trimeric,...). An ultraviolet band system previously assigned to a second n → π* transitions of these molecules has been reassigned to the first n → π* transition of a polymeric species. Some evidence has been assembled which supports this hypothesis. </p> / Thesis / Doctor of Philosophy (PhD)