Dissertation (MA)--University of Pretoria, 2014. / lk2014 / Psychology / MA / Unrestricted

This thesis is divided in three main chapters devoted to the study of finite element approximations of fluid flows with special nonlinearities coming from boundary con- ditions. In Chapter 1, we consider the finite element approximations of steady Navier-Stokes and Stokes equations driven by threshold slip boundary conditions. After re-writing the problems in the form of variational inequalities, a fixed point strategy is used to show existence of solutions. Next we prove that the finite element approximations for the Stokes and Navier Stokes equations converge respectively to the solutions of each continuous problem. Finally, Uzawa’s algorithm is formulated and convergence of the procedure is shown, and numerical validation tests are achieved. Chapter 2 is concerned with the finite element approximation for the stationary power law Stokes equations driven by slip boundary conditions of “friction type”. It is shown that by applying a variant of Babuska-Brezzi’s theory for mixed problems, convergence of the finite element approximation formulated is achieved with classi- cal assumptions on the regularity of the weak solution. Solution algorithm for the mixed variational problem is presented and analyzed in details. Finally, numerical simulations that validate the theoretical findings are exhibited. In Chapter 3, we are dealing with the study of the stability for all positive time of Crank-Nicolson scheme for the two-dimensional Navier-Stokes equation driven by slip boundary conditions of “friction type”. We discretize these equations in time using the Crank-Nicolson scheme and in space using finite element approximation. We prove that the numerical scheme is stable in L2 and H1-norms with the aid of different versions of discrete Grownwall lemmas, under a CFL-type condition. / Thesis (PhD)--University of Pretoria, 2014. / lk2014 / Mathematics and Applied Mathematics / PhD / Unrestricted

Soils on the Eastern Highveld acidify naturally due to the high rainfall and the use of certain nitrogen fertilizers. Liming materials are used to ameliorate soil acidity. A large fraction of this liming material used is Basic oxygen furnace slag (BOF slag), a secondary by-product from the Iron and Steel industry, commercially known as Aglime. These slag contain various concentration of heavy metals, like vanadium. No vanadium guidelines exist in South Africa. This study was done to determine the V threshold values where maize experienced reduced growth and to determine the V loading rate through slag application. A pot trial was used to determine the concentrations where vanadium reduces plant growth, and to establish toxicity levels in maize. The pot trail was used to establish V threshold values with various indicators, like total V concentration in the soil, total V concentration in the plant, Bray 1 extractable V and ammonium acetate extractable V, where maize experienced reduced growth. The threshold value where maize showed reduced growth in sandstone derived soils was at a total V concentration in the soil of 73.3 mg kg-1. The Bray 1 extractable V at this threshold was 23.5 mg kg-1 and there was no V in the above ground plant material in the maize. The ammonium acetate extractability at this level was 1.68 mg kg-1. V toxicity occurred at a total V concentration of 150 mg kg-1, with Bray 1 extractable V at 77.6 mg kg-1 and total V in the maize plant 14.8 mg kg-1 For the dolerite derived soil the threshold value was determined to be 235 mg kg-1 for the total V concentration in the soil. The Total V concentration in the plant was 0.5 mg kg-1 and the Bray 1 extractable V was 30.3 mg kg-1. The ammonium acetate extractable V was 1.69 mg kg-1. A pot trail and field evaluation site was used to determine the V loading through slag application. Three slag where used containing different V concentrations, slag A containing the highest V (918 mg kg-1) and B (153 mg kg-1) and C (88.6 mg kg-1) had a lower V concentrations. Theoretical V loading values was determined for three different slags containing different V concentrations and by using the threshold V concentration generated in chapter 3, the period to reach the critical V threshold value for liming with slag A was determined. If all factors (V concentration and incorporation depth), were to be kept constant, it will take an estimated 186 years of liming with slag A for the sandstone derived soil to reach the threshold value of 100 mg kg-1 where V negatively affect the growth of maize plants. This period was calculated to be 472 years for the dolerite derived soil, due to the higher Fe content and finer textured soil, which increase the V sorption capacity of the soil. The safe period for the slag B and C in respect with V is much longer than slag A, but other heavy metal concentrations must be kept in mind for they too can accumulate in the soil and can influence the growth of maize negatively if certain threshold values are reached.The V concentration of all the parameters generated in the V toxicity pot trail was far below the threshold values of the slag pot trail and field evaluation site. This indicated that the slag use with high V concentration on the short term (10 years) is unlikely to negatively influence crop production. / Dissertation (MScAgric)--University of Pretoria, 2014. / lk2014 / Plant Production and Soil Science / MScAgric / Unrestricted

On the north-western edge of the Witbank Coalfield, near the town of Delmas (Mpumalanga Province) a prominent and undulating sill is believed to affect quality of the coal in the seams mined in the area. The study area was separated into two subsections, Study Area A and Study Area B. In Study Area A the sill overlays the coal seams. The top of coal and the sill are separated by ~11 m thick sandstone with intermittent bands of shale, siltstone and carbonaceous shale. Study Area B, on the other hand, is located where the same sill underlies the coal seams. In this area, Dwyka tillites form the parting between the sill and the bottom coal seam. 51 composited samples were received from Study Area A and 26 uncomposited samples were received from Study Area B. In both areas, Seam 2 (bottom coal) was sampled due to its consistency and economic importance, as other seams were irregular over the complete area. Three parameters were assessed and compared to the thickness of the sill and the distance between the sill and the bottom coal; i.e. volatile matter, calorific value and ash. The volatile matter behaviour was further investigated using an empirical equation postulated by an industry specialist to determine whether the samples had been devolatilised by an external mechanism, i.e. contact metamorphism. The experimental calculation, based on a regression slope in relation to the South African baseline, indicated that two very different events had occurred on the coal seam. In Study Area A, the calculation indicated that the coal in the area was not devolatilised, thus implying that the sill had no influence on the coal. Conversely the results of the experimental equation in Study Area B indicated that the volatile matter of the lower coal seam had been greatly reduced by an external factor and the coal was devolatilised. Global studies of similar conditions point out that the content of volatile matter in the coal is the most affected variable during the intrusion of an igneous body into coal. This variability is governed by proximity to the sill, the shape of the intrusion, the thickness of the intrusion, orientation, location of the sill or lastly by the thermal conductivity of the country rock. In Study Area A the bottom coal seam was insulated from the heat conducted away from the sill by the presence of strata of different conductivities separating the sill intrusion from the bottom coal. On the other hand, in Study Area B heat was successfully transmitted to the bottom coal by highly conductive strata which separated the sill from the bottom coal. Therefore the study concluded that the sill had a significant influence on the bottom coal when it was underlying the coal (Study Area B) and a conductive layer separated the sill from the coal. In addition, the results indicate that neither the distance from the sill nor the thickness of the sill influence the effect which the sill had with the bottom coal seam in Study Area A. / Dissertation (MSc)--University of Pretoria, 2014. / lk2014 / Geology / MSc / Unrestricted

Dissertation (LLM)--University of Pretoria, 2014. / lk2014 / Mercantile Law / LLM / Unrestricted

The aim and objectives of this work is the development of a three dimensional graphene foam (GF) electrode for energy storage applications and study the electrochemical properties of the electrodes modified with different metal/metal oxides nanostructures. The GF was synthesised by chemical vapor deposition (CVD) and various metal/metal oxides were grafted on the surface of the GF by various method such as microwave irradiation (MW), aqueous chemical growth (ACG), successive ionic layer adsorption and reaction (SILAR) and reflux method. The interaction and formation mechanism between the GF and the metal/metal oxides nanostructures were all discussed. The obtained composite materials were characterized by Raman spectroscopy, X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM). The composite materials synthesised revealed different morphologies as seen by the different characterization techniques. The major interest in the GF for electrochemical capacitors is due to its unique structure, good conductivity and large surface area which offer the possibility for deposition/adsorption of metal/metal oxides for practical applications. The composite synthesised were all investigated as electrode for electrochemical capacitors in different electrolytes and tested with different operating voltages vs silver/silver chloride (Ag/AgCl). The electron kinetics of the composite materials was studied and all show excellent electrochemical performance. All the results have clearly shown and demonstrated the great potential of three dimensional composite based novel electrode materials for energy storage applications. I hereby declare that the matter embodied in this thesis entitled “Three dimensional graphene composites for energy storage applications” is the result of investigations carried out by me under the supervision of Prof. N. Manyala, in the Physics department at the University of Pretoria South Africa and that it has not been submitted elsewhere for the award of any degree or diploma. In keeping with the general practice in reporting scientific observations, due acknowledgement has been made whenever the work described is based on the findings of other investigators. / Thesis (PhD)--University of Pretoria, 2014. / lk2014 / Physics / PhD / Unrestricted

The Fountains East and Fountains West groundwater compartments (by means of the Upper and Lower Fountain springs) have been supplying the City of Tshwane with water since the founding of Pretoria in 1855. These adjacent compartments, which are underlain by the Malmani dolomites of the Chuniespoort Group, are separated by the Pretoria syenite dyke and are bounded to the north by the rocks of the Pretoria Group (Timeball Hill Formation). The perennial, artesian springs that drain the compartments are situated within the Groenkloof Nature Reserve and currently supply the citizens of Pretoria with 46 ML/day of water. Inorganic chemistry data (2007-2012) as well as spring discharge volumes (2011-2012) for the Upper and Lower Fountain springs along with water levels obtained from DWA boreholes in the Fountains East and Fountains West compartments (1984-2013) and isotope data for both springs and numerous rainfall stations in the City of Tshwane (1979-2007) were used in order to aid in the characterization of the springs and the compartments to which they belong. This was done by means of statistical analysis, Piper diagrams, bar graphs and temporal plots. Interpretation of the water levels indicates that that the Fountains East compartment generally has more shallow water levels while the Fountains West compartment has average water levels that are approximately 8.5m deeper and irrespective of the compartment, groundwater flow is generally from the south to the north in the karst aquifer . From the chemistry data the hydrochemical characteristics of both springs are found to be similar with the groundwater signature for both springs being Ca(Mg)-HCO3 which is indicative of fresh, recently recharged groundwater. Isotopically both springs are found to be depleted (as a result of the rainout effect) and may indicated that recharge of the compartments did not occur in the Pretoria area. / Dissertation (MSc)--University of Pretoria, 2014. / lk2014 / Geology / MSc / Unrestricted

The broiler industry is considered an essential sub-sector of the agricultural industry for the stimulation of economic growth in South Africa. This subsector consists of a vibrant largescale component, and together with other participants, dominates the peripheral markets. However, smallholder broiler producers find it difficult to participate in formal markets. This is due to numerous constraints and barriers which impede entry of these resource-poor farmers. In addition, there is a general reluctance of buyers in formal markets to engage with the numerous smallholder farmers. The overall purposes of this study were to investigate the extent of smallholder farmer market access and establish reasons for the limited formal market access of smallholder farmers in the broiler industry in Gauteng Province. The study examined the broiler subsector in the province by using a holistic approach. It was, therefore, not restricted to smallholder farmers but also included other participants, such as retail supermarkets, various poultry associations, and government, all of which play a crucial role in broiler production and marketing. The specific objectives of this study were to: 1. Determine the size of the smallholder broiler sub-sector in Gauteng, with reference to the number of farmers involved and the quantities of broilers supplied; 2. Assess the economic viability of the smallholder broiler enterprise; 3. Determine the level of market participation of smallholder broiler farmers, with particular reference to the quantity of broilers sold in formal markets; 4. Identify farmer-related determinants of market participation - this included farming experience, level of education, economic status, and the gender of participants; and 5. Identify external determinants of smallholder broiler market participation, such as barriers to entry, actual market requirements, transaction costs and infrastructure required to start a broiler enterprise approved for formal markets. The results of the study indicated that smallholder broiler farmers in Gauteng dominated informal markets. These farmers lacked the land and financial capital essential for starting the extensive operations required to subcontract to the vertically integrated operators. Furthermore, access to information on business management and expansion, and broiler project management were restricted. The stringent sanitary requirements for broiler supply by supermarkets further prevented participation by smallholder farmers in these retail outlets. As such, smallholder farmers were inclined to congregate together and competed only in informal markets. It was recommended that the South African government should consider participating in a public private partnership (PPP) with established businesses in the broiler sub-sector to support the development of smallholder farmers. This could take the form of “soft loans” to enable the smallholder broiler farmers to have the capital and infrastructural requirements to be contract producers to the established broiler operators. To ensure success of this business enterprise, it is essential that there is thorough screening of prospective candidates. Additionally, support should ensure that smallholder farmers have increased access to training in business management, broiler management and business expansion. In addition to promoting formal market participation by smallholder broiler producers, government should also support the informal broiler market to ensure both its expansion and improved standards of service for the customers. This is a growing market with a loyal customer base for both live birds and fresh broiler meat. With more awareness and marketing, the turnover of this market could increase substantially in the future. / Dissertation (MInst(Agrar))--University of Pretoria, 2014. / lk2014 / Agricultural Economics, Extension and Rural Development / MInst(Agrar) / Unrestricted

Dissertation (LLM)--University of Pretoria, 2014. / lk2014 / Centre for Human Rights / LLM / Unrestricted

Dissertation (MScAgric)--University of Pretoria, 2014. / lk2014 / Agricultural Economics, Extension and Rural Development / MScAgric / Unrestricted