Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xx, 217 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: Yunzhi Wang, Dept. of Materials Science and Engineering. Includes bibliographical references (p. 209-217).

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by Lau Chui-fong. / Title also in Chinese characters. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references. / Acknowledgements --- p.ii / Abstract --- p.iii / Table of Contents --- p.v / Chapter Chapter 1 : --- Nucleation --- p.1-1 / Chapter 1.1 --- Introduction --- p.1-1 / Chapter 1.1.1 --- Homogeneous Nucleation --- p.1-1 / Chapter 1.1.2 --- Heterogeneous Nucleation --- p.1-4 / Chapter 1.2 --- Experiments to Achieve High Undercooling --- p.1-6 / Chapter 1.2.1 --- General Reviews --- p.1-6 / Chapter 1.2.2 --- Experimental Details to Obtain Undercooled Ge --- p.1-8 / Chapter 1.2.2.1 --- Effects and Limitations of B2O3 --- p.1-8 / Chapter 1.2.2.2 --- Preparation of B2O3 --- p.1-9 / Chapter 1.2.2.3 --- Preparation of Highly Undercooled Ge --- p.1-10 / Table --- p.1-12 / Figures --- p.1-13 / References --- p.1-15 / Chapter Chapter 2 : --- Growth --- p.2-1 / Chapter 2.1 --- Introduction --- p.2-1 / Chapter 2.1.1 --- Morphologies of Solid´ؤliquid Interface --- p.2-1 / Chapter 2.1.2 --- Edgewise & Normal Growth Mechanism --- p.2-2 / Chapter 2.1.3 --- Formation of Dendrites --- p.2-4 / Chapter 2.2. --- Dendritic Growth of Ge --- p.2-5 / Chapter 2.2.1 --- Edgewise Dendritic Growth by Twin Planes --- p.2-5 / Chapter 2.2.2 --- Normal Growth of Ge at High Undercoolings --- p.2-7 / Figures --- p.2-8 / References --- p.2-15 / Chapter Chapter 3 : --- Polishing and Etching --- p.3-1 / Chapter 3.1. --- Introduction --- p.3-1 / Chapter 3.1.1 --- Surface Preparation --- p.3-1 / Chapter 3.1.2 --- Chemical Etching Experiments --- p.3-3 / Chapter 3.1.3 --- Morphology of Etch Pits --- p.3-5 / Chapter 3.2. --- Polishing and Etching of Ge <110> Dendrite --- p.3-7 / Chapter 3.2.1 --- Finding Twin Planes of <110> Dendrite --- p.3-7 / Chapter 3.2.2 --- Finding Twin Plane Orientation of <110> Dendrite --- p.3-9 / Figures --- p.3-11 / References --- p.3-15 / Chapter Chaptert 4 : --- Sound Emission During Crystallization of Undercooled Liquid Germanium --- p.4-1 / Abstract --- p.4-2 / Introduction --- p.4-3 / Experimental --- p.4-3 / Results --- p.4-4 / Discussion --- p.4-7 / Table --- p.4-10 / Figures --- p.4-11 / References --- p.4-14 / Chapter Chapter 5 : --- Microstructures of Undercooled Germanium --- p.5-1 / Abstract --- p.5-2 / Introduction --- p.5-3 / Experimental --- p.5-4 / Results --- p.5-5 / Discussion --- p.5-10 / Table --- p.5-14 / Figures --- p.5-15 / References --- p.5-25 / Chapter Chapter 6 : --- On the Dendrites and Dendritic Transitions in Undercooled Germanium --- p.6-1 / Abstract --- p.6-1 / Introduction --- p.6-2 / Experimental --- p.6-5 / Results --- p.6-9 / Discussion --- p.6-15 / Table --- p.6-17 / Figures --- p.6-18 / References --- p.6-32 / Chapter Chapter 7 : --- On the Growth of <110> Twin Dendritein / Undercooled Ge --- p.7-1 / Abstract --- p.7-1 / Introduction --- p.7-2 / Experimental --- p.7-3 / Results --- p.7-5 / Discussion --- p.7-8 / Figures --- p.7-13 / References --- p.7-24

Thesis (Ph. D.)--Oregon Graduate Center, 1980

Congestive Heart Failure (CHF) is a major fatal disease today in the United States. The heart's function is a mechanical one. To diagnose and treat CHF effectively there is a need to understand at the microstructural level, the differences in the response of the myocardium to a change in its mechanical environment. Hence to assess growth and remodeling processes in the myocardium, the fiber and myolaminar structure of two groups of Dahl salt-sensitive rats were compared: low salt (LS) normal controls and a high salt (HS) group with hearts in "transitional eutrophy" defined by normal size and shape but in transition from pressure overload hypertrophy to dilated hypertrophy. To create the HS group with transitional eutrophy, we fed Dahl salt-sensitive rats, a sustained high salt diet from age 6 wks till sacrifice at age 11-13 wks. Such rats have a heart that transitions from too thick (pressure overload hypertrophy at about age 9 wks) to too thin (dilated hypertrophy at about age 15 wks to death) with a transitional period (age 11-13 wks) having normal size and shape. Fiber angles, sheet angles, number and thickness of sheets were measured in the septum at four transmural quarters (TQ1 to TQ4 with TQ1 being closest to LV and TQ4 closest to RV). A uniformity index was defined to characterize sheet angle dispersion. Upon comparison to LS controls, the HS group had normal size hearts with normal shape. However, there was a significant increase in the number of sheets, which corresponded with a significant decrease in the thickness of sheets in all quarters in HS group. Differences in fiber angles were significant in TQ1, TQ2, and TQ4 with fiber angles more positive in HS group. Differences in sheet angles and uniformity index were not significant. Despite having a normal size and shape, we found that hearts in a state of transitional eutrophy have a significantly different fiber and sheet morphology. The experimental data was used to develop a model that represents the path to failure that may be taken by the myolaminae when the heart is subjected to excessive pressure overload.

published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

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The rapid thermal cycle involved in fiber laser welding (FLW) generates welds with narrow heat affected zones (HAZs) that contain large microstructural gradients, which make it very difficult to properly elucidate microstructural changes that occur during welding in the HAZ and fusion zone (FZ). Evaluation of the microstructural changes is, nonetheless, vital in order to understand and predict how FLW affects the mechanical properties of welded materials. Dual phase (DP) steels, which are designed to obtain soft ferrite and hard martensite, have gained increasing popularity in structural applications. In this research, the microstructural changes that occur in narrow HAZ and FZ are systematically studied by using a Gleeble thermo-mechanical simulation system and transmission electron microscopy (TEM). It is found that significant microstructural changes occur in the FZ and HAZ, which could result in dramatic changes in the mechanical properties of welded materials. An indication of this is the observation that the microhardness values in the FZ and adjacent HAZ are notably disparate from that in the base metal (BM). Further, cracks were observed in the zinc coating on the HAZs of both HSLA and DP980 steels, which may also have effect on mechanical performance of the welded materials.