No description available.

No description available.

White dwarfs are particularly interesting due to their broad application to the field of astronomy (cosmochronology, SN Ia progenitors, asteroseismology). Examining distributions of white dwarf masses and temperatures, it is evident that there is some flaw in our ability to make physical atmosphere models. Tremblay and Bergeron (2009) used an {\it ad hoc} treatment of line broadening and derived significantly different surface gravity and temperatures for white dwarfs, demonstrating the importance of the line broadneing treatment in determining stellar parameters for high surface gravity stars. This thesis presents a new line broadening program, Xenomorph, based on simulation techniques. Xenomorph is used to examine various approximations used in line broadening calculations used in white dwarf atmospheres. Some approximations, like including fine structure and lower state perturbations, have small, if detectable effects. Ion motions during a transition can make features commonly seen in Stark profiles less pronounced and leads to an increase in the FWHM of the lines. Including a more complete basis set at higher densities will result in extra features, including asymmetries that has been observed in many experiments. / text

No description available.

A complete stochastic theory of relaxation is developed in terms of a homogeneous equation for the averaged density matrix of a system immersed in a thermal bath. This theory is then used as the basis of a new stochastic approach to the phenomenon of collisional broadening of spectral line shapes. Single photon and multiphoton processes are studied. The features of a line shape are linked by simple expressions to the statistical properties of a stochastic hermitian Hamiltonian. The ordinary line shape predicted by Kubo's approach is generalized. The present approach predicts broadening as well as asymmetry and shift. A representation of line shapes in multiphoton processes by diagrams is also developed.

Thesis (Ph. D.)-- University of Washington, 2004. / Vita. Includes bibliographical references (leaves 242-251).

No description available.

Clad alloys feature one or more different alloys bonded to the outside of a core alloy, with non-equilibrium, interalloy interfaces. There is limited understanding of the recovery and recrystallization behaviour of cold rolled clad aluminum alloys. In order to optimize the properties of such alloys, new heat treatment processes may be required that differ from what is used for the monolithic alloys. This study examines the recovery behaviour of a cold rolled Novelis FusionTM alloy containing an AA6XXX core with an AA3003 cladding on one side. The bond between alloys appears microscopically discrete and continuous, but has a 30 m wide chemical gradient. The as-deformed structure at the interalloy region consists of pancaked sub-grains with dislocations at the misorientation boundaries and a lower density organized within the more open interiors. X-ray line broadening was used to extract the dislocation density from the interalloy region and an equivalently deformed AA6XXX following static annealing using a modified Williamson-Hall analysis. This analysis assumed that Gaussian broadening contributions in a pseudo-Voigt function corresponded only to strain from dislocations. The kinetics of the dislocation density evolution to recrystallization were studied isothermally at 2 minute intervals, and isochronally at 175 and 205°C. The data fit the Nes model, in which the interalloy region recovered faster than AA6XXX at 175°C, but was slower at 205°C. This was most likely caused by change in texture and chemistry within this region such as over-aging of AA6XXX . Simulation of a continuous annealing and self homogenization process both with and without pre-recovery indicates a detectable, though small change in the texture and grain size in the interalloy region. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2013-10-02 10:19:10.279

The object of this thesis is to extend the current tables for two useful quantities when calculatingcollisional broadening, the cross-section of interaction and the velocity parameter.These quantities, which have hitherto been tabulated for lower states, have now been calculatedfor higher lying states and are used in the ABO - model for spectral line broadening.Having larger tables for these values enables broadening calculations for more spectral linesand this thesis shows examples of calculations which beneted from this. During the calculationsof the tables some unexpected behaviour in the distribution of values arose whichhas not been seen previously. This could point to an unknown underlying mechanism.

The threshold characteristics of multimode laser oscillators are considered in detail, and a new model is given for semiconductor diode lasers. Analytical expressions and numerical solutions are obtained for mode amplitudes, and over-all spectral characteristics of lasers operating above and below threshold. The theoretical results are i n agreement with experimental data. The band-ta-band absorption is included in the model and i t ' s effect is studied on the mixed broadening.