The ionization of the most abundant elements in planetary nebulae has been determined for a number of models of nebulae at different epochs in their expansion. The values used for the temperatures and radii of the central stars and the sizes and densities of the shells have come from Seaton's evolutionary sequence. The ionizing radiation field has been taken from model atmosphere calculations of the central stars by Gebbie and Seaton, and Biihm and Deinzer. Emission -line fluxes have been calculated for the models and compared with observations of planetary nebulae by O'Dell, Osterbrock's group, and Aller and his collaborators. Results indicate that the central stars have strong He+ Lyman continuum excesses, similar to those predicted by Gebbie and Seaton. The mean abundance determinations for the nebulae made by Aller are confirmed, with the exception of nitrogen, which appears to be 3 or 4 times more abundant than his value. It is also seen that the electron temperatures of the nebulae are higher than previous theoretical determinations, providing better agreement with empirically derived values.

MSc., Faculty of Science, University of the Witwatersrand, 2011 / In this thesis, a novel type of electrostatic thruster is introduced. The Corona Ionization (CorIon) Space Propulsion system is an electrostatic propulsion system intended for use on satellites and for deep space probes. It makes use of the corona ionization mechanism to create the needed propellant ions. This same mechanism is also responsible for the thrust, thereby reducing its size and complexity. First, the effects of incomplete ionization of propellant molecules is discussed and conclusions drawn. Next, a mathematical model describing the electric field characteristics is derived. Considering the needle tip as a point charge and the exhaust plume to be cylindrically symmetric with a constant spread angle, the resultant electric field of both the needle tip and the produced ions obeys Poisson‘s equation. The charge density is obtained from the relationship between the drift velocity and the current. In order to solve the differential equation, we consider the electric field to only change in the radial direction so that Poisson‘s Equation is reduced to its radial part. This differential equation is solved to yield the electric field of the system. Some results are discussed. By integrating the electric field the relationship between the potential difference and the current of propellant ions is obtained. This relationship also yields insight into the ionization efficiency. Following this, an expression for the thrust is derived via two different methods: The first uses the energy conservation, and is termed ―Vector heating‖. The ions are viewed as a current heating the neutrals in the plume in the direction away from the needle. A temperature can be derived for the plume, and the resulting average gas velocity estimated from molecular theory. Finally, using the rocket thrust equation, an expression for the thrust is obtained. iv The second, more conventional method uses electrostatic repulsion to calculate the recoil on the needle: from the electric field computed for the system, an expression for the Coulomb forces on the ionized propellant can be derived. The recoil on the needle will experience the same force, resulting in thrust. Finally, the theoretical predictions for the various parameters are compared to experimental data. From this comparison, it is seen that there is a reasonable agreement between the experimental data and the model even though the electrostatic prediction underestimates the thrust of the system.

Ho Chun Yan = 電離對單泡聲致發光的影響 / 何俊恩. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves [90]-93). / Text in English; abstracts in English and Chinese. / Ho Chun Yan = Dian li dui dan pao sheng zhi fa guang de ying xiang / He Junen. / Abstract --- p.i / Acknowledgements --- p.ii / Contents --- p.iii / List of Figures --- p.vii / List of Tables --- p.xii / Chapter Chapter 1. --- Introduction --- p.1 / Chapter Chapter 2. --- Hydro dynamical Framework --- p.7 / Chapter 2.1 --- Bubble wall motion --- p.8 / Chapter 2.2 --- Navier-Stokes equations --- p.10 / Chapter 2.3 --- Energy equation in water --- p.11 / Chapter 2.4 --- Boundary condition --- p.12 / Chapter 2.5 --- Equation of state of the gas in the bubble --- p.13 / Chapter 2.5.1 --- Hard-core van der Waals EOS --- p.13 / Chapter 2.5.2 --- Young's EOS --- p.14 / Chapter 2.6 --- Numerical method --- p.14 / Chapter 2.7 --- Numerical results and discussion --- p.15 / Chapter 2.8 --- Chapter summary --- p.19 / Chapter Chapter 3. --- Equilibrium Approach --- p.20 / Chapter 3.1 --- Saha equation --- p.21 / Chapter 3.2 --- Equation of state (EOS) --- p.22 / Chapter 3.3 --- Numerical method --- p.23 / Chapter 3.4 --- Numerical results --- p.23 / Chapter 3.5 --- Chapter summary --- p.28 / Chapter Chapter 4. --- Reaction Rates Approach --- p.29 / Chapter 4.1 --- Conservation equations --- p.30 / Chapter 4.2 --- Ionization and recombination processes --- p.32 / Chapter 4.2.1 --- Collisional ionization --- p.32 / Chapter 4.2.2 --- Radiative recombination --- p.33 / Chapter 4.2.3 --- Three-body recombination --- p.34 / Chapter 4.2.4 --- Consistency with Saha equation --- p.34 / Chapter 4.3 --- Equation of state --- p.35 / Chapter 4.3.1 --- Modified Van der Waals EOS --- p.35 / Chapter 4.3.2 --- Modified Young's EOS --- p.36 / Chapter 4.4 --- Numerical method --- p.37 / Chapter 4.5 --- Numerical results --- p.38 / Chapter 4.5.1 --- Effect of ionization on hydrodynamic variables --- p.38 / Chapter 4.5.2 --- Time variation of temperature --- p.40 / Chapter 4.5.3 --- Near the upper threshold of SBSL --- p.41 / Chapter 4.5.4 --- Onset of SBSL --- p.44 / Chapter 4.5.5 --- Effect of EOS --- p.46 / Chapter 4.5.6 --- Effect of physical parameters --- p.51 / Chapter 4.6 --- Chapter summary --- p.56 / Chapter Chapter 5. --- Emitted Radiation --- p.57 / Chapter 5.1 --- Bremsstrahlung emission --- p.59 / Chapter 5.1.1 --- Numerical results --- p.60 / Chapter 5.2 --- Simple blackbody radiation model --- p.63 / Chapter 5.2.1 --- Planck's law --- p.63 / Chapter 5.2.2 --- Calculated pulse width and spectrum --- p.64 / Chapter 5.3 --- Blackbody radiation with finite opacity --- p.68 / Chapter 5.3.1 --- Photon absorption --- p.68 / Chapter 5.3.2 --- Importance of photon absorption --- p.70 / Chapter 5.3.3 --- The refined model --- p.72 / Chapter 5.3.4 --- Pulse width and spectrum in the refined model --- p.73 / Chapter 5.4 --- Chapter summary --- p.80 / Chapter Chapter 6. --- Summary --- p.81 / Appendix A. Hydrodynamics of an SL Bubble --- p.83 / Chapter A.1 --- The normal viscous stress and heat conductivity --- p.83 / Chapter A.2 --- Transformation of Navier-Stoke equations --- p.83 / Chapter A.3 --- Transformation of the energy equation of liquid --- p.84 / Appendix B. Numerical Scheme for the gas dynamics with ionization --- p.85 / Chapter B.1 --- Finite difference equation --- p.85 / Chapter B.2 --- The TVD scheme --- p.86 / Bibliography --- p.90

Yeung, Hoi Sze. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 120-134). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese.

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Thesis (Ph.D.)--University of Nebraska-Lincoln, 2008. / Title from title screen (site viewed Sept. 16, 2008). PDF text: xvi, 196 p. : ill. (some col.) ; 9 Mb. UMI publication number: AAT 3297758. Includes bibliographical references. Also available in microfilm and microfiche formats.

Thesis (M.Sc.)--York University, 2007. Graduate Programme in Physics and Astronomy. / Typescript. Includes bibliographical references (leaves 77-79). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR38785

Thesis (Ph. D.)--California Institute of Technology, 1973. UM #73-07,291. / Advisor names found in the Acknowledgments pages of the thesis. Title from home page. Viewed 01/19/2010. Includes bibliographical references.

Thesis (Ph. D.)--University of Michigan, 1928. / "Reprinted from Physical review ... vol. 34, no. 1, July 1, 1929."

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references. Available also in a digital version from Dissertation Abstracts.