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In modern high-speed digital circuits, the space of the traditional single-layered or double-layered circuit board is not enough, therefore multi-layered circuit and stacked distribution technology are widely applied to many applications. The signal via is a vertical interconnection structure to communicate different signal layers, which will be seriously interfere with the simultaneous switching noise by via through the parallel plate cavity that consists of power and ground plane. It is an important issue to minimize the influence from noise. In multi-layered printed circuit boards, shorting vias are usually utilized to interconnect the planes with the same voltage level. The major theme of this thesis is the placement of shorting vias affecting plane cavity mode. And we propose a design rule of the shorting vias to significantly decrease the simultaneous switching noise and improve the power integrity of multi-layered circuit board.

The spherical inverted-F antenna (SIFA) is a relatively new conformal antenna design that consists of a microstrip patch resonator on a spherical ground. The SIFA resembles a planar inverted-F antenna (PIFA) that has been conformally recessed onto a sphere. The basic design, simulation, and fabrication of a SIFA were recently reported. The aim of this thesis is to provide a three-fold improvement to the study of the SIFA: the fabrication of a dielectric-coated SIFA, a new analytical model based on the cavity method, and the analysis of a randomly oriented SIFA’s operation in a remote networking scenario. A key improvement to the basic SIFA design is the addition of a lossy dielectric coating to the outside of the sphere for purposes of impedance stability, bandwidth control, and physical ruggedization. The first contribution of this thesis is the fabrication of such a dielectric-coated SIFA. Two antennas are fabricated: a coated SIFA operating at 400 MHz, and an uncoated SIFA operating at 1 GHz for comparison. Both SIFAs are constructed of foam and copper tape; the coating is comprised of silicone rubber and carbon fiber. The fabricated designs perform with reasonable agreement to corresponding simulations, providing a basic proof of concept for the coated SIFA. The SIFA was previously studied analytically using a transmission line model. The second task of this thesis is to present a new model using the cavity method, as employed in microstrip patches. The SIFA cavity model uses a curvilinear coordinate system appropriate to the antenna’s unique geometry and is able to predict the antenna’s performance more accurately than the transmission line model. The final portion of this thesis examines the performance of the SIFA in a remote network scenario. Specifically, a line-of-sight link between two SIFAs operating in the presence of a lossy dielectric ground is simulated assuming that each SIFA is randomly oriented above the ground. This analysis is performed for both uncoated and coated SIFAs. A statistical analysis of the impedance match, efficiency, and power transfer between these antennas for all possible orientations is presented that demonstrates a design tradeoff between efficiency and predictability.

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The chemistry of actinides in solution is a very important aspect of the nuclear fuel cycle, especially as the energy needs of the world continue to increase. However, the radio-active nature of the actinides makes experimentation very difficult and dedicated expensive instruments are required. In addition, the disposal of radio-active waste materials requires a proper understanding of their chemistry at a molecular level. To tackle the problem, and to underpin the experimental studies, in this thesis we have studied the redox chemistry and disproportionation mechanism of actinyl complexes in solution using state-of-the art computational methods. Reduction potentials of actinyl complexes in solution have been estimated in solution using density functional theory (DFT) approaches. Solvation effects were included in the quantum chemistry calculations with the conductor like polarisable continuum model (CPCM) solvation method. First of all, we have validated our computational method by studying a variety of solute cavity definitions within the CPCM solvation model and assessed the performance of a range of DFT functionals to suitable to accurately describe the actinide chemistry in solution. Penta-valent uranyl(V) ions are unstable and readily disproportionate; in this study we have explored outer-sphere electron transfer and disproportionation mechanisms to determine the stability of these ions in solution. We have found that the process of outer-sphere disproportionation is unlikely to occur in non-aqueous solutions, such as DMSO, DMF, DCM, acetonitrile and pyridine, when the uranyl(V) ion is bound with a multi-dentate organic ligand. However, our computational results hypothesise that the presence of a trace of water in the experimental conditions can promote a disproportionation reaction by protonating the uranyl(V) ‘yl’ oxygen atoms and then the electron transfer process would proceed through either inner or outer sphere mechanism. In addition, the effect of alkali metal cations on the outer-sphere disproportionation mechanisms was also studied. Overall it has been shown that DFT can be used to accurately predict the redox properties of actinyl complexes in solution and thus contributing for an effective and efficient design of nuclear material separations, proper as well as safer radioactive waste disposal.