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One of the fundamental properties of an antenna is its ability to radiate or receive more energy in one given direction over all the others. This property is called the directivity. The optimization of the directivity usually requires a great deal of attention when an antenna is being designed. There are a number of iterative analytical and experimental procedures available for the optimization of the directivity, however they can be manually intensive, and very time consuming when computer simulation is employed. / Optimization of antenna parameters has been hindered by the need of techniques that prove to be reliable, robust and can search and find a global maximum. Past efforts have focused on techniques confined to small search volumes due to the time overheads of searching. With the increasing utility of the personal computer, techniques have emerged which can search large volumes efficiently and economically. Genetic Algorithms are one such technique. / Genetic Algorithms are an optimization technique based on the mechanics of natural selection, which combines the biological concepts of survival of the fittest among string structures. They operate on a population of candidate solutions and are able to change a number of parameters simultaneously while testing the solutions for goodness-of-fit. They also possess memory so that a good solution can be saved and tested from generation to generation. In this way they are able to quickly find and maintain the best solution to the problem. / A Genetic Algorithm is used to optimize the directivity of a linear array of dipole radiators. Mutual and self-coupling is taken into consideration through the use of the Method of Moments. The inter-element spacing as well as the radiator length are allowed to vary. This gives the optimization many degrees of freedom. The arrays so optimized are verified using a standard industrial antenna software simulation program. The optimized array achieves a directivity of approximately 1.5 dB better than published data for a uniform array of the same size. There is an overall reduction in the length of the array of one wavelength and the currents on the radiating elements are realisable. The final product is a basic computer aided design package capable of optimizing the directivity of a linear antenna array with the only inputs needed being the frequency of operation and the number of dipole elements. / Thesis (MEng(ElectronicsEngineering))--University of South Australia, 2005.

Thesis (Ph D.)--University of Nevada, Reno, 2007. / "May 2007." Includes bibliographical references (leaves 61-63). Online version available on the World Wide Web.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also in a digital version from UMI/Dissertation Abstracts International.

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This experiment was aimed at the determination of the dipole moment of the diatomic molecule HC1⁺ (in the ²π½ state). The method was to observe the Stark splitting optically by using a 3.4 meter Jarrell ash spectrograph. The charged diatomic molecule was obtained by passing HCl gas through a LoSurdo discharge tube in which a high electric field was applied; optical plates were obtained from the spectrograph and analysed. Dipole moment of HC1⁺ in the ²π½ state was found to be smaller than 0.8 debye. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Ultracold bialkali polar molecules present a wealth of opportunities in quantum science research and technology; including fields such as quantum simulation, quantum chemistry, quantum metrology, precision measurement and quantum computation. A great deal of interest lies in their rich internal rotational and vibrational state structure and their large electric dipole moment. However, the additional complexity also provides significant challenges. To date, only a limited number of molecular species are available at ultracold temperatures below 1 microkelvin. The assembly of heteronuclear ground state molecules from ultracold atoms has emerged as a promising approach for creating ultracold molecules. In this thesis, I will present the creation of the first ultracold gases of NaCs ground state molecules. First, we produce an ultracold mixture of Na and Cs. Second, we associate weakly bound molecular pairs from the Na-Cs mixture. Finally, we apply a two-photon stimulated Raman adiabatic passage (STIRAP) pulse to transfer the weakly bound NaCs molecules into the deeply bound rovibrational ground state. I report on the construction of a new apparatus that produces ultracold mixtures of Na and Cs. We use this apparatus to assemble weakly bound NaCs molecules and successfully transfer up to 20,000 ultracold dipolar NaCs molecules to their rovibrational ground state in each experimental run. On the way to these results, we demonstrated a pathway towards creating the first quantum degenerate mixtures of Na and Cs. We identified and characterized an interspecies Feshbach resonance at 864.12(5) G, adiabatically sweeping across it to form weakly bound NaCs Feshbach molecules. We characterized the Feshbach molecule formation in various parameter regimes. Next, we performed a study of accessible NaCs excited states and identified a pathway to the rovibrational ground state using one- and two-photon spectroscopy. Finally, we demonstrated STIRAP to the rovibrational ground state, and investigated basic properties of the ground state molecules.