The performance characteristics of pure hydrogen PEMFC (called HFC) stacks made with heterogeneous carbon fiber bipolar plates are studied in this thesis. In addition, the problem that the heterogeneous carbon fiber bipolar plate leaks in the high gas pressure is also solved in this studies so that the new plate can be used to the high current power sources. Because of the gas leakage of the first generation stack at high inlet gas pressure, the fuel supply is insufficient in the high current density. A 4-cell PEMFC stack made with this new bipolar plate is built with weight 370 g and volume 385 cm3 without a fan. The total power out of the 4-cell stack is about 30 W at room temperature. The specific power and volumetric power densities are 81 mW/g and 78 mW/cm3, respectively. The average power density is about 160 mW/cm2, but the power density of a single-cell can reach a value about 220 mW/cm2. The insufficient fuel supply cause that the power density of 4-cell PEMFC stack is lower than single cell, so it is necessary to solve the gas leakage at high pressure. Our experiment found that gas leakage occurs in heterogeneous bipolar plates can be relate to the insufficient or improper hot-pressing temperature, time and pressure while we are making the carbon fiber bunches. So the processes in making new carbon fiber bunches include water expansion, uniform glue adding, high hot-pressing pressure, and using proper temperature and enough solidification time. The airtight of the second generation of heterogeneous carbon fiber bipolar plates improves obviously with the new processes. No leakage occurs for gas pressure under 1atm. We expect that this design can be used to high inlet pressure. It is also quite suitable for various high-power electrical sources.

In this thesis, the design rule of the tag antenna and the properties of the high impedance surface structure are studied. We proceed to design the low profile and miniature high impedance surface structure. In order to be more competitive, we use PCB plates for fabrication to reduce the cost. The tags are intended to be placed inside two shorted metallic plates. In order to reduce the effect of the two parallel metallic plates, we use the slots to design the tag antenna. The EBG structure behaves as a high impedance surface and suppresses the surface wave. We add the EBG structure on the back of the antenna to reduce the back metallic effect. We use slot structure to design the non-planar RFID reader antenna that can be placed inside the three metallic plates to read the data. For the slot structure design, the electric field between the slots is perpendicular to the upper and lower metallic plates. According to the image theory, the induced image current will result in constructive effect to reduce the metallic effect. Finally, the hand-held RFID reader may not identify the RFID tag as the RFID tag placed at position deeper inside. The proposed non-planar reader can solve this problem to be used for more applications.

This paper presents the investigation of the nonlinear eigenvalue problem describing free vibrations of plates with elastically attached masses. We study properties of eigenvalues and eigenfunctions and prove the existence theorem. Theoretical results are illustrated by numerical experiments.

Thesis (M.Eng.)--Memorial University of Newfoundland, 2001. / Bibliography: leaves 106-113.

Thesis (Ph. D.)--University of Hong Kong, 1982. / Also availalbe in microfilm.

Thesis (Ph. D.)--University of Hong Kong, 1989.

Thesis (M. Phil.)--University of Hong Kong, 1988.

Thesis (Ph. D.)--University of Hong Kong, 1988.

A number of recent research studies have investigated the performance of panel zones in seismic-resistant steel Special Moment Resisting Frames (SMF). These recent studies investigated various options for attaching doubler plates to the column at beam-column joints in SMF for purpose of increasing the shear strength of the panel zone. This previous work was primarily focused on doubler plates that extend beyond the top and bottom of the attached beams, and considered cases both with and without continuity plates. As an extension to this previous research, this thesis explores the situation when a doubler plate is fitted between the continuity plates. The objective of this research was to evaluate various options for welding fitted doubler plates to the column and continuity plates through the use of finite element analysis, and to provide recommendations for design. The development and validation of the finite element model are described, along with the results of an extensive series of parametric studies on various panel zone configurations and attachment details for fitted doubler plates. Based on the results of these analyses, recommendations are provided for design of welds used for attaching fitted doubler plates in the panel zone of SMF systems. / text

The research work presented here deals with the problems of geometrically nonlinear analysis of thin shell structures. The specific objective was to develop geometrically nonlinear formulations, using Discrete-Kirchhoff Curved Triangular (DKCT) thin shell elements. The DKCT elements, formulated in the natural curvilinear coordinates, based on arbitrary deep shell theory and representing explicit rigid body modes, were successfully applied to linear elastic analysis of composite shells in an earlier research work. A detailed discussion on the developments of classical linear and nonlinear shell theories and the Finite Element applications to linear and nonlinear analysis of shells has been presented. The difficulties of developing converging shell elements due to Kirchhoff's hypothesis have been discussed. The importance of formulating shell elements based on deep shell theory has also been pointed out. The development of shell elements based on Discrete-Kirchhoff's theory has been discussed. The development of a simple 3-noded curved triangular thin shell element with 27 degrees-of-freedom in the tangent and normal displacements and their first-order derivatives, formulated in the natural curvilinear coordinates and based on arbitrary deep shell theory, has been described. This DKCT element has been used to develop geometrically nonlinear formulation for the nonlinear analysis of thin shells. A detailed derivation of the geometrically nonlinear (GNL) formulation, using the DKCT element based on the Total Lagrangian approach and the principles of virtual work has been presented. The techniques of solving the nonlinear equilibrium equations, using the incremental methods has been described. This includes the derivation of the Tangent Stiffness matrix. Various Newton-Raphson solution algorithms and the associated convergence criteria have been discussed in detail. Difficulties of tracing the post buckling behavior using these algorithms and hence the necessity of using alternative techniques have been mentioned. A detailed numerical evaluation of the GNL formulation has been carried out by solving a number of standard problems in the linear buckling and GNL analysis. The results compare well with the standard solutions in linear buckling cases and are in general satisfactory for the GNL analysis in the region of large displacements and small rotations. It is concluded that this simple and economical element will be an ideal choice for the expensive nonlinear analysis of shells. However, it is suggested that the element formulation should include large rotations for the element to perform accurately in the region of large rotations.