Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: Solid oxide fuel cell; SOFC; cost model; sputtering; tape casting; screen printing; performance model; process yield model. Includes bibliographical references (p. 93).

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 135-138). Also available in electronic version. Access restricted to campus users.

The main objectives of this study are:- 1 - to construct a wiring connecting system between the pulsed and direct current units to produce a pulsed submerged arc weld. 2 - to determine the boundary conditions for the welding parameters used to control weld profile and metal transfer during pulsed current submerged arc welding. 3 - to establish a relationship between the pulsed current frequency and the geometry of the deposited weld metal, and to apply the results to narrow gap welding. 4 - to design and construct a microprocessor interface system capable of handling, presenting and storing the data. The thesis has been divided into three parts as follows:- Part I The feasibility of pulsed current submerged arc welding process. Part II The use of pulsed current to control the geometry and properties of welding metal. Part III Computer aided monitoring of the welding parameters. In the first part, a review of relevant information is presented together with a description of the experimental technique used in connecting the pulsed and background current units. In the second part attention is focus sed on the procedure for identifying the usable zones within which a successful weld can be obtained. Critical boundary conditions of welding parameters were established using the combination of pulsed and direct currents. Having established these boundaries, the effects of pulsed current frequency on the weld profile and weld metal properties were investigated and the results used to establish a practical guide line on narrow gap applications. In the third part the design and construction of a microprocessor- based system was designed to monitor the welding parameters using binary counter, an analogue switch and voltage to frequency converters which enables real time values of welding variables to be determined over a period of between 1 - 100 seconds, depending on the memory size of the microprocessor.

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