No description available.

No description available.

No description available.

This thesis investigates uniform mixing on Cayley graphs over Z_3^d. We apply Mullin's results on Hamming quotients, and characterize the 2(d+2)-regular connected Cayley graphs over Z_3^d that admit uniform mixing at time 2pi/9. We generalize Chan's construction on the Hamming scheme H(d,2) to the scheme H(d,3), and find some distance graphs of the Hamming graph H(d,3) that admit uniform mixing at time 2pi/3^k for any k≥2. To restrict the mixing time, we derive a sufficient and necessary condition for uniform mixing to occur on a Cayley graph over Z_3^d at a given time. Using this, we obtain three results. First, we give a lower bound of the valency of a Cayley graph over Z_3^d that could admit uniform mixing at some time. Next, we prove that no Hamming quotient H(d,3)/<1> admits uniform mixing at time earlier than 2pi/9. Finally, we explore the connected Cayley graphs over Z_3^3 with connected complements, and show that five complementary graphs admit uniform mixing with earliest mixing time 2pi/9.

No description available.

The work is divisible into three interconnected areas, the first of which is concerned with the empirical modelling of the rubber internal mixing process. Here, the mixing machine variables were changed in a statistical experimental design, and several resulting dispersion dependent material responses monitored. The values of these were next combined into a composite function which related to the goodness of mixing. A response equation in terms of this function and the process variables was obtained by regression analysis. Other response equations derived were for relating mixing time and dumped stock temperature to the input variables. These graduating functions were tested for adequacy of fit; graphical representations of the predictions of the models are shown in the form of contour graphs and isometric projections (both hard copy and colour graphics). These show visual evidence of the influence of each machine variable (and interaction) on the mixing process as a whole. Also by these means, it was possible to establish optimum conditions of mixing. Next nominally identical carbon blacks from different manufacturing locations were mixed into rubber at defined processing conditions. From tests on these mixes the blacks were noted to have different dispersibilities. This was possibly attributable to the varying fines fractions and moisture contents in the test carbon blacks. To check this hypothesis, these factors were varied systematically in two common black types. The compounds resulting from mixing these experimental blacks were subjected to a wide range of tests to establish whether fines or moisture significantly affected dispersibility of blacks in rubbers. Ouring the preceding work, and also in the course of a critical review included here, it became evident that the commonly used methods for establishing dispersion (and thus mixing efficiency) were lacking, from several points of view. Therefore lastly a technique based on the analysis of an image of a cut rubber surface viewed by dark field reflected light microscopy was developed. Specimen preparation is simple and analysis is accomplished using a standard television system and oscilloscope. This method yields results which discriminate between all levels of black dispersion and also correlate admirably with a variety of processing, mechanical and microscopical properties. In the final stages of the work the capabilities of the method were expanded (in cooperation with Dunlop Ltd, Technology Division) by interfacing a computer and peripherals with the original equipment; such that data acquisition, manipulation and parameter output was made easier, faster and thus more effective than in the initial concept.

Graduation date: 1999

Two-stroke outboard boat engines using total loss lubrication deposit a significant proportion of their lubricant and fuel directly into the water environment. Extensive atmospheric emission testing of outboard motors has taken place, however, emissions to the water are largely unaddressed in the literature and could be critical because the exhaust of most outboard engines is released below the water and mixed by the action of the propeller. The purpose of this work is to document the velocity and scalar field characteristics of a submerged swirling jet emanating from a propeller. The aim is to provide guidance on fundamental characteristics of such a jet, far enough downstream that it is relevant to the eventual modelling of this mixing problem (i.e. the mixing of engine emissions with water). Measurements of the velocity field (axial, tangential, and radial) and scalar field (concentration) were performed in a turbulent jet generated by a model boat propeller (0.02 m diameter) operating in a weak co-flow of 0.04 ms-1. The measurements were carried out up to 50 propeller diameters downstream of the source which was placed in a glass-walled flume, 0.4 m wide with a free surface depth of 0.15 m. The jet and scalar plume development were compared to that of a classical free round jet. Further, results with respect to velocity distribution, turbulence decay and integral flow properties plus scalar distribution, dilution and integral plume properties were all calculated and compared to existing literature. The velocity field results are the first published results to show the development of the flow fifty propeller diameters downstream. Up to ten propeller diameters downstream the results corroborate the earlier work of Petersson [1, 2]. Beyond ten propeller diameters downstream, the walls of the flume affected the flow. The concentration field results show that under these experimental conditions the propeller induced mixing exhibited a complete mixing length some 300 times shorter than for the wall-shear induced diffusion alone. Furthermore, a first principles relation was derived that illustrates the link between engine emission rate and propeller kinematics in generating the propeller-jet source concentration of pollutants. Using experimental results an estimate for benzene concentration fifty propeller diameters downstream of a 74 kW vessel was calculated to be around one third of the regulatory threshold for that chemical.

Thesis (Ph.D.)--University of Tulsa, 1974. / Bibliography: leaves 149-150.

Thesis (M. Phil.)--University of Hong Kong, 1997. / Includes bibliographical references (leaf 120-123).