Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2016. / This dissertation presents how material properties (solids densities, particle size distributions, particle shapes and concentration) of gold tailings slurries are related to their rheological parameters, which are yield stress and viscosity. In this particular case Bingham yield stresses and Bingham plastic viscosities. Predictive models were developed from analysing data in a slurry database to predict the Bingham yield stresses and Bingham plastic viscosities from their material properties. The overall goal of this study was to develop a validated set of mathematical models to predict Bingham yield stresses and Bingham plastic viscosities from their material properties. The interaction of the non-Newtonian material properties is very complex at varying mass solids concentrations. The evaluation of these interactions in terms of constitutive equations is almost impossible and the relationship between material properties, mass solids concentration and rheology can only be modelled in a statistical manner. The validity of each model is checked to ensure that predictions and interpretations are unbiased and efficient. This is done by comparing the resulting models to experimental data generated from test work. An in-depth analysis was conducted to see the interrelationship between the material properties and how they affect the yield stress and viscosity values.

Thesis (Ph.D.)--Boston University / This dissertation confronts contemporary physical cosmology with Karl Popper's standards of scientific method and theory construction. To the degree to which there are differences, an attempt is made to criticize the major cosmological models in the light of Popper's analysis and, in turn, to explore revisions necessitated in this analysis by the unique problems of cosmology. As background, the major facets of Popper's work are presented in detail: his falsifiability criterion for demarcating scientific theories from metaphysics, his hypothetico-deductive method, and his rejection of induction. Then the origins of general relativity and its competitors are analyzed both as explanatory background to modern cosmology and so as to reveal the history of certain problems pertinent to Popper's scheme: for instance, the use of arguments from simplicity, the ideas of the utility of analogy and models, and the relation of theory to reality. Finally, the great variety of evolutionary, fundamentalistic, and steady-state models available for study is explored in detail as to presupposition and methodology so that their distinctives are revealed and a basis for comparison with Popper's suggestions provided. [TRUNCATED]

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A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, South Africa, in ful lment of the requirements for the degree of Masters of Science. May 27, 2015. / Abstract The unsteady three-dimensional ow of a thin slender rivulet of incompressible Newtonian uid down an inclined porous plane is investigated. The leak-o velocity is not speci ed in the model but is determined in the process of deriving the invariant solution. A second order nonlinear partial di erential equation in two spatial variables and time and containing the leak-o velocity is derived for the height of the thin slender rivulet. Using Lie group analysis it is found that the partial di erential equation can be reduced in two steps to an ordinary di erential equation provided the leak-o velocity satis es a rst order linear partial di erential equation in three variables. An exact analytical solution with a dry patch in the central region is derived for a special leak-o velocity. Two models are considered, one with the leak-o velocity proportional to the height of the rivulet and the other with leak-o velocity proportional to the cube of the height. Numerical solutions are obtained for the height of the rivulet using a shooting method which also determines the two-dimensional boundary of the rivulet on the inclined plane. The e ect of uid leak-o on the height and width of the rivulet is investigated numerically and compared in the two models. The conservation laws for the partial di erential equation with no uid leak-o are investigated. Two conserved vectors are derived, the elementary conserved vector and a new conserved vector. The Lie point symmetry of the partial di erential equation associated with each conserved vector is obtained. Each associated Lie point symmetry is used to perform a double reduction of the partial di erential equation, but the solutions obtained are not physically signi cant.

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Abrasive finishing is a machining process which alters the surface of a workpiece to achieve a specific property. Typical abrasive finishing processes focus on geometric tolerances and surface topography. Abrasive finishing is primarily dependent on finishing forces, relative velocities, and abrasive size. The material removal rate in finishing is inversely related to the surface finish. Magnetic and electric fields have been used to control the force applied to abrasives which finish the workpiece. These processes show an increase in performance when the field is used to control the process. Field assisted finishing processes can be energy intensive and expensive. A novel finishing media is proposed which does not require a field to achieve a similar force response. This media has inherent thickening mechanisms driven by shear jamming. This shear jamming mechanism can deliver forces an order of magnitude higher than shear thickening mechanisms. This novel slurry is demonstrated as a viable finishing media with performance similar to magnetic abrasive finishing. / Thesis / Master of Applied Science (MASc)

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