Thesis (M.Sc.), Faculty of Engineering (Electrical Engineering), University of the Witwatersrand, 1994

Organic solvents in varnish can easily cause volatile organic compounds (VOCs) and odorous problems in manufacturing plants of enamel insulated wire. In general, the related process exhaust gases are treated by catalytic incinerators. However, the slight odors in the incinerated exhausts may induce uncomfortable feels to the inhabitants in the vicinity of the plants. Main components of odors are reported to be xylenes and to a lesser extent ketones. This study intended to oxidize the odorous compounds by chemical scrubbing method with either sodium hypochlorite or ozone as an oxidant and hydrogen peroxide as a reducing agent for the elimination of residual chlorine or ozone emitted from the oxidation scrubber. An additional study was the oxidation of aqueous mixed xylenes by sodium hypochlorite. The first part of the study was the chemical oxidation of aqueous xylenes by sodium hypochlorite. Results indicated that more than 95 % of 20 mg/L xylenes could be converted to some oxygenated hydrocarbons with an initial effective chlorine concentration of 180 mg/L at pH 6.5 over a prolonged reaction time of over 120 min. With pH < 3 and a reaction time of 120 min, xylenes could be oxidized to benzene carboxylic acid that precipitated as organic crystalline solids to the reactor bottom. The second part was chemical scrubbing of the odorous gases emitted from the catalytic incinerator. Operation conditions were an effective chlorine concentration of 1,500 mg/L and pH 6.5 for the oxidative scrubbing liquor, and a hydrogen peroxide concentration of 700 mg/L and pH > 12 for the reductive one. Results indicated that on an average, around 59 % of the influent xylenes could be removed, and the scrubbed gas was nearly odorless. 65.0 - 98.5 % of the influent non-aromatic compounds could be removed with trace amounts of chlorinated compounds in the gas were detected. The third one was the treatment of the odorous gases by using ozone as an oxidant and followed by activated carbon adsorption. 18 - 34 mg/m3 of ozone was added to the test gas with initial xylene concentrations of 25 - 55 mg/m3. Results indicated that only around 35 % of the added xylene was removed with ozone contact times of 0.15 - 0.6 min. Although 99.9 % of the residual ozone and odors were removed by the activated carbon, a longer operation time should be tested to verify the performance. Trace amounts of ring cleavage precursors of 2.4-dimethylphenol and ring cleavage products were found in the ozonized gas.

Die Arbeit beschreibt die Entwicklung und Evaluierung einer Technologieplattform für die Herstellung von oberflächennahen Mikrostrukturen mit hohen Aspektverhältnissen. Grundlage dieser Technologieplattform stellt ein neuartiges Konzept zur mechanischen und elektrischen Kontaktierung beweglicher Elemente mittels spezieller Träger dar, deren typische Breite unterhalb eines Mikrometers liegt. Basierend hierauf werden drei unterschiedliche Prozessabläufe zur Herstellung der Mikrostrukturen, auch als Air gap Insulated Microstructures (AIM) bezeichnet, vorgestellt. Der Schwerpunkt dieser Arbeit liegt dabei auf der mehrschichtigen Trägervariante mit Isolationsebene und Leitungsebene. Verschiedene Schichtkombinationen, bestehend aus Siliziumnitrid, Siliziumdioxid und Aluminium, sind in ihrem mechanischen, thermischen und Langzeitverhalten charakterisiert und im Hinblick auf ihre Anwendbarkeit für die Träger bewertet. Für die Strukturierung der Siliziumelemente wird ein Verfahren basierend auf einem CF-Polymer als Passivierungsschicht beschrieben. Neben verschiedenen Ausfallmechanismen für die Passivierung werden gezielte Optimierungen der Abscheide- und Ätzprozesse erläutert sowie deren Resultate dargestellt. Für die vollständige Trennung von Substrat und seismischer Masse ist eine isotrope, vom Aspektverhältnis nahezu unabhängige Siliziumstrukturierung nötig. Entsprechende Betrachtungen und Untersuchungen hierzu, unter Verwendung der Reaktionsgase SF6 und O2, stellen den Abschluss der Untersuchungen zur Prozessentwicklung dar. Um die Leistungsfähigkeit der Technologieplattform zu demonstrieren, erfolgt die Herstellung verschiedener Sensoren und Aktoren. Die Charakterisierung dieser Elemente in ihrem mechanischen, thermischen und Langzeitverhalten stellt den Abschluss dieser Arbeit dar.

Modern timber frame buildings are a unique combination of ancient carpentry techniques coupled with one of the newest enclosure systems found on construction sites around the world. Contemporary timber frame structures typically utilize structural-insulated panels (SIPs) attached to a timber frame skeleton to create functional, enclosed structures, such as houses, churches and a myriad of retail and industrial buildings. The skeleton contains large wooden members connected using wooden joints held together with wooden pegs or wedges. SIPs consist of a layer of rigid expanded polystyrene insulation covered on one side by oriented strand board and on the other side by oriented strand board, drywall, or some other interior finish. In timber frame buildings, SIPs also serve as diaphragm elements, which are flat structural assemblies loaded by shear forces in the plane of the panel. Current design methodologies for timber frame structures do not formally incorporate the structural benefits of SIPs as diaphragm elements, which contribute significantly to the ability of these buildings to resist lateral loads. The contribution of this research was to quantify necessary design parameters to enable timber frame designers to capitalize on the significant in-plane strength and stiffness of SIPs when designing timber frame structures to resist lateral loads. Strength and stiffness tests were conducted on three 8 ft (2.44 m) deep and 24 ft (7.32 m) long roof diaphragm assemblies, and two 20 ft (6.10 m) deep and 24 ft (7.32 m) long roof diaphragm assemblies. Data from these tests were collected, tabulated and analyzed according to existing methods typically utilized for post-frame diaphragm testing. Strength and stiffness of timber frame and SIP roof diaphragm assemblies were determined from monotonic test results and a value for Response Modification Coefficient, R, for use with seismic design procedures, was estimated utilizing cyclic test data. Procedures for calculating strength and stiffness of a roof diaphragm based on the strength and stiffness of test panels were presented and incorporated within post-frame diaphragm design methods. Diaphragm-frame interaction analyses were performed utilizing test data from roof diaphragm assemblies that demonstrated the code conformance of members within timber frames subjected to lateral loads. Using roof diaphragm test data and procedures developed for adjustments from the test panel to building roof length, example designs were conducted which confirmed the effectiveness of including SIPs as diaphragm elements for code conforming designs for wind and seismic load resistance of timber frame and SIP buildings. / Ph. D.

Thermal efficiency of Precast Concrete Sandwich Panel Walls has become a major topic when discussing the building envelope in academia. At Utah State University, research is being done to evaluate the structural and thermal efficiency of fiber reinforced polymer connectors being used today. In evaluating several different proprietary fiber reinforced polymer systems, researchers plan to develop design procedures to help engineers accurately determine minimum design requirements when using fiber reinforced polymer connectors. This largely requires a determination of the degree of composite action incurred by each system. Testing is performed by constructing small scale specimens (3 ft. by 4 ft., 0.91 m by 1.22 m). Each specimen contains one of the fiber reinforced polymer connecting systems. By constructing a five-wythe, two wall specimen, direct shear can be applied to the connectors using a push-off shear test method. By performing this test it can be determined to what degree the panel is acting compositely. Once the degree of composite action is determined, correlation can be made between design and degree of composite action. Economizing and simplifying this procedure is key to further implementation of precast concrete sandwich panel walls in all areas of our building infrastructure.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19734号 / 工博第4189号 / 新制||工||1646(附属図書館) / 32770 / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 辻 康之, 教授 村田 靖次郎, 教授 杉野目 道紀 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

With the development of fuel cell based power systems, the need for more advanced DC-DC power converters has become apparent. In such applications DC-DC converters provide an important link between low voltage fuel cell sources and inverter buses operating at significantly higher voltages. Advancements in converter efficiency, cost reduction, and size reduction are the most necessary. These challenges are formidable, even when considering the improvements made to conventional DC-DC topologies. However, it can be possible to achieve these criteria through the implementation of more advanced topologies. A recently developed efficient three-phase DC-DC topology offers benefits over standard designs. Passive component sizes and output ripple voltage were reduced as a result of an effective boost in switching frequency. Converter output voltage was reached more easily due to an increased transformer voltage boost ratio in addition to the turns ratio. For cost reduction, the converter was designed and built with discrete components instead of more expensive integrated modules. This thesis presents an overview of the three-phase converter, with a detailed focus on the design, implementation, and performance of the switching stage. The functionality of the three-phase topology is covered along with the selection of converter components. Simulation results are shown for both ideal and real converter models. Considerations for the switching device package with respect to circuit board and heat sinking configurations are discussed in support of the selection of an insulated metal substrate (IMS) circuit board. An effective circuit layout designed to minimize parasitic trace inductances as well as provide favorable component positioning is presented. Experimental converter test results are shown and the causes of undesired effects are identified. Switching stage modifications and their results are discussed along with the benefits of proposed future design enhancements. / Master of Science

In recent years, the lifetime of an insulated railroad joint in the field has decreased due to increasing wheel loads. The goal of this research is to investigate possible changes in insulated rail joint design in order to improve the performance of the insulated joint. The finite element program ABAQUS is used to model the supported butt joint. In this model, the rail, joint bars, epoxy, and ties surrounding the joint are modeled using solid elements. The remaining ties are modeled as an elastic foundation. The rail is subjected to a tensile load, as well as a vertical wheel load that is applied to the rail using Hertz contact theory. Parametric studies are performed by varying the tie width, joint bar length, and joint bar dimensions. Two different wheel load locations are also investigated: centered about the end post, and halfway between the tie under the end post and the tie just to the left of the end post. The vertical displacement of the rail and insulated joint is one measure used to determine the effect of the parameters on the insulated joint. However, since the most common cause of failure in insulated rail joints is the debonding of the epoxy, this research also focuses on the stresses present in the epoxy when the joint is subjected to a static wheel load. The two out-of-plane shear stresses as well as the normal peel stress are used to compare the various designs of the joint. / Master of Science

No description available.

This work is focused on the measurement of partial discharges in gas insulated conductors manufactured by ABB. The theoretical part contains the definition of partial discharges, their analysis and detection methods. It also deals with the general description of gas-insulated substations and then with the concrete components manufactured at ABB in the Brno-Slatina production plant. The practical part describes the course of measurement, definition of the main problems and their explanation. The output from the practical part is a measurement library with given characteristics, which show the location and character of the problem in detecting partial discharge in a given encapsulated assembly.