Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Klein, Benjamin; Committee Member: Alavi, Kambiz; Committee Member: Allen, Janet K.; Committee Member: Buck, John; Committee Member: Gaylord, Tom; Committee Member: Yoder, Douglas.

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [80]-83).

Thesis (Ph.D.)--Washington State University, December 2005. / Includes bibliographical references (p. 158-170).

Thesis (M.S.)--University of Wisconsin--Madison, 1963. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 56-57).

Thesis (Ph.D.)--Brown University, 2005. / Vita. Thesis advisor: Gregory P. Crawford. Includes bibliographical references (leaves 179-199). Also available online.

Thesis (Ph.D.)--Brown University, 2005. / Vita. Thesis advisor: Gregory P. Crawford. Includes bibliographical references (leaves 144-160).

Thesis (M.A. Sc.)--Dept. of Electrical and Computer Engineering, Concordia University, 1995. / "August 1995." Includes bibliographical references (leaves 128-134). Available also on the Internet.

Copper whiskers were grown by the hydrogen reduction of the halide vapours. The substrate and the whiskers were examined for growth morphologies. Whiskers of (100), (110) and (111) orientations in the diameter range 30-400μ were tested in tension. Differences in the work hardening characteristics of (111) and (100) whiskers were discussed in terms of the different kinds of jogs formed in the two orientations. Analysis of the diameter dependence of the yield stress resulted in a 1/d relation based on the assumption of surface nucleation of dislocations. Temperature and strain rate change experiments were made on (110) whiskers. Activation distance and activation energies were used to determine a rate controlling mechanism. At low temperatures, cross slip and intersection processes were indistinguishable, while at higher temperatures, cross slip is rate controlling. From the calculated activation distance and for a given rate controlling dislocation mechanism, stacking fault energies were estimated for copper and other FCC metals. A twinning model was proposed based on the idea of failure by recombination of a Lomer-Cottrell barrier. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Intermolecular interactions are anisotropic since they depend on the orientations of the interacting molecules. They are responsible for the orientational phase transitions observed in molecular systems. The effects of nonseparable interactions, which depend on both the molecular and intermolecular vector orientations, are investigated using Monte-Carlo simulations. It is found that for systems with quenched positional disorder, the nonseparability of the pair potential leads to orientational frustration. Expanding the pair potential in terms of its rotational invariants allows one to isolate random field terms whose presence are shown to be at the origin of the non-frustrated patches observed in such disordered systems. For liquid crystals, where translational and rotational degrees of freedom are in thermal equilibrium, Monte-Carlo results show that an ordering of the molecular orientations induces an ordering of the nearest-neighbor bond orientations only when the pair potential is nonseparable. These results suggest that it is necessary to reinterpret the mean-field theory of nematic liquid crystals as an approximation which neglects the presence of bond ordering in these systems. As well, they unravel the microscopic origin of the phenomeno-logical coupling between bond and molecular orientations invoked in Ginzburg-Landau theories of liquid crystals. The nonseparability of the intermolecular pair potential leads to a coupling between the nearest-neighbor bond orientational field and the molecular orientational field. It is shown that such coupling introduces new and interesting effects in liquid crystalline systems where interactions between the molecular and nearest-neighbor bond orientations are usually ignored. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Slip line length measurements have been carried out on oriented single crystals of high purity aluminum to qualitatively check the predictions of a new theory of plastic flow in strain hardened metals. This theory states that the slip line length L will be a function of the stress, σ, the yield strength, Ty, and the magnitude of the variation in the obstacle spacing, Tv. To achieve this purpose, the specimens were prestrained at room temperature to the same stress level insuring that they had the same structure. They were then electropolished and given a small increment of strain at a temperature between 298°K and 4°K or a strain rate from ɛ = 1x10⁻⁴ /min to ɛ = 2x10⁻¹ /min. The slip line lengths for these increments were found to increase with increasing strain rate and to decrease with increasing temperature, in agreement with the theory. By applying the increment of strain in small, divisions, the slip line length was found to increase during the region of transient deformation following a quench. This increase in L was due to an increase in stress. Lowering the prestrain temperature showed that the slip line length depended on the structure parameter Tv. A low temperature prestrain resulted in a smaller Tv and therefore shorter slip lines. From the 4°K increment, the parameters characterizing the prestrained structure and the structure after the increment could be determined. Using equations of the theory, these values were related to the experimental slip line length data with good quantitative agreement. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate