Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (M.Sc.)--York University, 2007. Graduate Programme in Earth and Space Science. / Typescript. Includes bibliographical references (leaves 149-159). 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:MR38802

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Compositionally related glasses and ceramics of the Na$ sb2$O$ cdot$CaO$ cdot$Al$ sb2$O$ sb3 cdot$TiO$ sb2 cdot$SiO$ sb2$ system (sphene glass-ceramics) doped with Eu$ sp{3+}$ were examined using site-selective spectroscopic techniques (FLN). In sphene glass-ceramics, Eu$ sp{3+}$ preferentially partitions into the crystalline sphene phase. The partition ratio is concentration dependent, decreasing at higher concentrations, because of the limited solid solubility of Eu$ sp{3+}$ in sphene. The concentration occurs at the time of phase separation; Eu$ sp{3+}$ preferentially enters the more ionic (CaO, TiO$ sb2$)- rich droplet phase which eventually becomes sphene. In sphene, Eu$ sp{3+}$ substitutes for Ca$ sp{2+}$ appearing in three different sites caused by associated charge compensation defects. From an analysis of the FLN spectra of the different glasses, the framework for a model describing the coordination shell of Eu$ sp{3+}$ in oxide glasses is developed. The model suggests that Eu$ sp{3+}$ behaves as a network forming ion or quasi-molecular complex. The model is used to explain qualitative features of Eu$ sp{3+}$ FLN spectra including the dependence of the clustering of points of the major crystal field parameter ratios plot on the relative number of non-bridging oxygen ions and Eu$ sp{3+}$ ions in the glass.

In order to evaluate the safety of radioactive waste disposal underground it is important to understand the way in which radioactive material is transported through the rock to the surface. If the rock is fractured the usual models may not be applicable. In this work we look at three aspects of fracture networks: connectivity, flow and transport. These are studied numerically by generating fracture networks in a computer and modelling the processes which occur. Connectivity relates to percolation theory, and critical densities for fracture systems are found in two and three dimensions. The permeability of two-dimensional networks is studied. The way that permeability depends on fracture density, network size and spread of fracture length can be predicted using a cut lattice model. Transport through the fracture network by convection through the fractures and mixing at the intersections is studied. The Fickian dispersion equation does not describe the resulting hydrodynamic dispersion. Extensions to the techniques to three dimensions and to include other processes are discussed.

Thesis (Ph. D., Chemical Engineering)--University of Idaho, May 2006. / Major professor: Vivek Utgikar. Includes bibliographical references (leaves 99-107). Also available online (PDF file) by subscription or by purchasing the individual file.

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (M.S. in engineering)--Washington State University, August 2005. / Includes bibliographical references.