With superior longevity, approximately 5 times that of compact fluorescents (CFLs), and high efficacy, around 1.5 times that of CFLs, LEDs are now attracting vast attention from both academic and industrial sectors. Unfortunately, current power supply drivers for LEDs have the following drawbacks: (1) for a two-stage configuration, the power factor correction (PFC) circuit can help LEDs achieve good operating performance but contain too many components and are large in size, have low efficiency and relatively high cost; (2) a single-stage configuration can perform well in PFC and efficiency, however reliability issues occur due to the use of the electrolytic capacitor. In this thesis, the theoretical analysis and implementation of two high power factor, soft-switched, electrolytic-capacitor-less LED drivers are presented. The two drivers solve the aforementioned issues while minimizing its size and cost. The detailed theoretical analysis illustrates the advantages of the presented circuits and provides insight into their design and operation. The simulated and experimental implementations verified the performance of both circuits, which achieve a high power factor, indicating that the drivers have good operating performance. Elimination of the electrolytic capacitors improves the LED drivers’ reliability. In addition, with the help of soft-switching capability, high efficiency is achieved. Simulation and experimental results are presented to support all merits of the two circuits. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2013-04-30 13:22:28.471

Electric weapons, such as the railgun, require a pulse power supply capable of providing reliable highcurrent, high-energy pulses of many megawatts. Pulsed alternators potentially have the same maintenance issues as other motor-generator sets, so a solid-state system would be desirable, but high voltage capacitor systems are not robust enough for the field. We propose here a Low Voltage Electrolytic Capacitor Pulse Forming Inductive Network (LVEC PFIN) which stores power in a relatively low voltage capacitor bank and provides weapon power pulses by first draining the capacitors into a power inductor and then interrupting the flow of current via a switch counterpulsing technique in order to achieve railgun-appropriate voltages. For this thesis, a 13 kJ LVEC PFIN was constructed, using solid-state semiconductor switches to redirect 25 kA of current into a 1 m. load, and the redirection of larger currents is clearly feasible. This technique may be a viable alternative once the energy densities and equivalent series resistances of low voltage capacitors and ultracapacitors reach the necessary levels.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1981. / Includes bibliographical references. / by Pablo G. Debenedetti. / Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1981.

Orientador: Nilson Cristino da Cruz / Banca: Francisco Trivinho Strixino / Banca: José Roberto Ribeiro Bortoleto / O Programa de Pós Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi / Resumo: Neste trabalho, a oxidação eletrolítica assistida por plasma (PEO) foi utilizada para produzir um revestimento cerâmico na superfície de substratos da liga (AA 5052) de alumínio. As propriedades elétricas deste revestimento foram analisadas através da espectroscopia de impedância elétrica (EIE). As espessuras dos revestimentos foram determinadas pelo método de correntes parasitas e microscopia eletrônica de varredura (MEV). O MEV foi empregado também na avaliação da topografia dos revestimentos. Para a determinação da estrutura e composição químicas foram empregadas as espectroscopias de absorção no infravermelho (IRS) e de energia dispersiva de raios x (EDS). As estruturas cristalinas foram determinadas pela técnica da difração de raios x. Os resultados revelaram que as superfícies foram recobertas por um revestimento complexo, contendo principalmente alumínio, oxigênio e silício, que aumento a resistividade elétrica 10-10 vezes em comparação com o alumínio como recebido / Abstract: In this work, plasma electrolytic oxidation (PEO) has been used to produce ceramic coating on AA 5052 aluminum alloy substrates. The electrical properties of coatings were analyzed using electrical impedance spectroscopy (EIS). The thickness of the coatings was determined by the eddy current method and scanning electron microscopy (SEM). SEM was also used to evaluate the topography of the coatings. Infrared absorption (IRS) and energy dispersive x-ray (EDS) spectroscopy have been employed to determine structural and the chemical composition and the crystalline structures were determined by X-ray diffraction. The results have revealed that the surfaces were covered by complex coatings, composed by aluminum, oxygen and silicon, which increased the electrical resistivity by 1010 times in comparison with the as-recebived aluminum / Mestre

Thesis. 1978. M.S.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. / Includes bibliographical references. / M.S.

No description available.

The object of this thesis is to discuss an experimental composite conservation process and its significance for the future of artifact conservation. Composite artifacts are artifacts comprised of multiple materials such as wood, iron, and brass. The experiment was designed around five Civil War Enfield rifles from the wreck of the Civil War blockade runner Modern Greece. The main conservation difficulty for both metal and wood from a saltwater site is the presence of chlorides. If not removed, the chlorides will cause the metals to further corrode. If the chlorides are left within the wood, once the wood dries the chlorides will crystallize and burst remaining cellular structure. The second major problem for wood is the cellular structure itself. Degraded waterlogged wood loses most of its cellular structure while submerged and this must be reinforced prior to drying or partial to total collapse of the wood will occur. Composite artifacts pose one more serious problem, their composite nature. In most instances treatments for one material type are damaging to the other materials present. Disassembly of an artifact often has detrimental effects on the whole artifact whether through initial damage or the inability to reassemble the artifact after stabilization. In 1979, four Enfield rifles from Modern Greece were compositely conserved using either tetraethyl orthosilicate, sucrose, or isopropyl rosin. All three treatments focused on the conservation of the wood, resulting in the current poor condition of the iron elements. The research of this thesis uses the combined treatments of silicone oil (to treat the wood) and electrolytic reduction [ER] (to stabilize the metals), with minimal disassembly. It was discovered that prolonged exposure of the wood elements during ER had deleterious effects, post the silicone oil treatment. This prompted a re-evaluation of the research strategy. It was determined to do a re-treatment of the wood components of four of the rifles with silicone oil after the ER process. It was apparent during the ER process that iron components had loosened and could be removed allowing the wood to be extracted from the ER process earlier than the iron. Even though the experiment did not go as planned and the initial results were undesirable, valuable information was ascertained for treatment strategies and positive results are expected for the final four rifles. The retreatment of the wood with silicone oil should allow the wood to retain its shape, making reassembly possible.

The objective of this research is to advance the field of condition monitoring of electrolytic capacitors used in power electronics circuits. The construction process of an electrolytic capacitor is presented. Descriptions of various kinds of faults that can occur in an electrolytic capacitor are discussed. The methods available to detect electrolytic capacitor faults are discussed. The effects of the capacitor faults on the capacitor voltage and current waveforms are investigated through experiments. It is also experimentally demonstrated that faults in the capacitor can be detected by monitoring the capacitor voltage and current. Various ESR estimation based detection techniques available to detect capacitor failures in power electronics circuits are reviewed. Three algorithms are proposed to track and detect capacitor failures: an FFT based algorithm, a system modeling based detection scheme, and finally a parameter estimation based algorithm. The parameter estimation based algorithm is a low-cost real-time scheme, and it is inexpensive to implement. Finally, a detailed study is carried out to understand the failure mechanism of an electrolytic capacitor due to inrush current.

The object of this thesis is to discuss an experimental composite conservation process and its significance for the future of artifact conservation. Composite artifacts are artifacts comprised of multiple materials such as wood, iron, and brass. The experiment was designed around five Civil War Enfield rifles from the wreck of the Civil War blockade runner Modern Greece. The main conservation difficulty for both metal and wood from a saltwater site is the presence of chlorides. If not removed, the chlorides will cause the metals to further corrode. If the chlorides are left within the wood, once the wood dries the chlorides will crystallize and burst remaining cellular structure. The second major problem for wood is the cellular structure itself. Degraded waterlogged wood loses most of its cellular structure while submerged and this must be reinforced prior to drying or partial to total collapse of the wood will occur. Composite artifacts pose one more serious problem, their composite nature. In most instances treatments for one material type are damaging to the other materials present. Disassembly of an artifact often has detrimental effects on the whole artifact whether through initial damage or the inability to reassemble the artifact after stabilization. In 1979, four Enfield rifles from Modern Greece were compositely conserved using either tetraethyl orthosilicate, sucrose, or isopropyl rosin. All three treatments focused on the conservation of the wood, resulting in the current poor condition of the iron elements. The research of this thesis uses the combined treatments of silicone oil (to treat the wood) and electrolytic reduction [ER] (to stabilize the metals), with minimal disassembly. It was discovered that prolonged exposure of the wood elements during ER had deleterious effects, post the silicone oil treatment. This prompted a re-evaluation of the research strategy. It was determined to do a re-treatment of the wood components of four of the rifles with silicone oil after the ER process. It was apparent during the ER process that iron components had loosened and could be removed allowing the wood to be extracted from the ER process earlier than the iron. Even though the experiment did not go as planned and the initial results were undesirable, valuable information was ascertained for treatment strategies and positive results are expected for the final four rifles. The retreatment of the wood with silicone oil should allow the wood to retain its shape, making reassembly possible.

In this work, membrane set(s) had been incorporated into different crossflow electrofiltration (CEF) /electrodialysis (ED) treatment modules for treating various CMP wastewaters and simultaneously generating two streams of electrolytic ionized water (EIW). In general, CMP wastewaters have high alkalinity, turbidity, total solids content and silica content. In this investigation, CMP wastewaters were obtained from two wafer fabs in Taiwan and characterized by various standard methods. Then they were treated by the aforementioned treatment modules. Experiments were carried out based on the fractional factorial design and the L8 orthogonal arrays of the Taguchi method. Experimental factors such as electric field strength, transmembrane pressure for CEF, etc. were used to investigate their effects on the permeate qualities (i.e., oxidation-reduction potential, pH, etc.). According to the results of analysis of normal probability plots, analysis of variance (ANOVA) and regular analysis, the electric field strength was presumed to be a very significant parameter. Experimental results showed that filtrate flux increased with the increasing applied electric field strength. The permeate has a turbidity of below 1 NTU, TOC of below 3 mg/L, and TDS of below 250 mg/L under various operating conditions. Other permeate qualities were 15~22 mg/L of K, 53~68 mg/L of silica, 2~4 mg/L of NH4+ and 134~680 £gS/cm of electrical conductivity. But the values of electrical conductivity, pH, and oxidation-reduction potential (ORP) varied substantially for the anolyte EIW and catholyte EIW. Using these novel treatment modules, the optimal ORP and pH values of the anolyte EIW were 211.8 mV, 4.52 and 214.1 mV, 4.83, respectively, for single- and multi-membrane sets. The optimal ORP and pH values of the catholyte EIW were -165.0 mV, 11.21 and -172.0 mV, 10.81, respectively, for single- and multi-membrane sets. It is clear that permeate obtained in this study is suitable for high-level recycling. To further upgrade the water quality of permeate obtained above, a reverse osmosis (RO) unit was added to the treatment system. The water quality of silica for post-RO permeate were decreased from 53.7 to 0.98 mg/L for the anolyte EIW and from 68.05 to 1.32 mg/L for the catholyte EIW. The removal rates of Na and K by the RO unit were not significant. In addition, other unique properties of EIW (e.g., pH, ORP, and cluster size of water molecules) remained almost the same in post-RO permeate. The total recovery rate of the treated water could be above 85%. Therefore, the treated water at this stage could be reused as the cleaning media for the wafer surfaces or reused for the DI water production apparatus.