Despite the benefits of fuel cell technology its advancement to being commercially functional is hindered by a number of crucial factors. These factors are often associated with the lack of appropriate materials or manufacturing routes that would enable the cost of electricity per kWh to compete with existing technology. Whilst most research efforts have been directed towards developing more active catalysts, the amount of catalyst required in the fuel cell can be further reduced by improving the platinum utilisation in the membrane electrode assembly. The platinum utilisation is a strong function of the catalyst layer preparation step and there remains significant scope for optimisation of this step. Whereas significant work has been conducted into the different components of the catalyst ink there is limited work and understanding on the influence of the mixing method of the catalyst ink. This study will focus on the influence of the mixing technique on the catalyst ink properties and on the final fuel cell performance. Specifically, the study will investigate the effect of the three different mixing techniques on (i) catalyst ink quality (ii) the physical properties of the resultant catalyst layer and (iii) the in-situ electrochemical performance of the membrane electrode assembly. A large set of characterisation techniques were chosen to effectively study the step wise processing of the catalyst layer, and fuel cell performance. The results presented here include a comparison of the various mixing techniques and a comprehensive 2 x 2 factorial design into the individual techniques. The results suggest that high energy mixing is required for effective distribution of catalyst layer components, an even catalyst layer topography and a highly functional ionomer network which consequently, enhances performance. The mixing energy referred to involves prolonged mixing time, enhanced mixing intensity or a combination of the two. During bead milling of catalyst inks, high intensity mixing seems to be beneficial however, prolonged mixing time appears to be detrimental to the ionomer film structure. During high shear stirring and ultrasonic homogenisation of catalyst inks, the ink mixture significantly heats up. It has been observed that at higher temperatures, Nafion elongates and the contact with catalyst agglomerates is enhanced. High shear stirring of catalyst inks seems to be most effective at high agitation rates. High mixing energies result in high shear forces and in addition, high mixing temperatures which appear to be beneficial to establishing an effective catalyst/Nafion interface, enhancing the three phase boundary observed during in-situ testing. Ultrasonic homogenisation seems to be more effective at prolonged sonication times. Due to the erosive nature of ultrasonic dispersion, sufficient time is required to establish a well dispersed and distributed catalyst ink. However, the nature of particle size distribution resulting from ultrasonication shows that inks are unstable and is not recommended for high throughput processing. Overall, fuel cell performance is not significantly affected by the mixing step however; mixing does have an observable impact on catalyst layer formulation. Generally, when optimizing membrane electrode assembly fabrication, mixing parameters should be carefully chosen. This goes without saying that parameters need to be effectively studied before foregoing catalyst ink processing.

There is a dearth of clear and consistent information on the effects of mix design parameters, and their corresponding interactions, on restrained shrinkage cracking in non-structural concrete patch repair mortars (PRMs). This dearth of information makes the design and development of PRMs with improved resistance to cracking challenging. The problem is further compounded by the fact that the existing code of practice for concrete repair - the EN 1504-3:2005 - specifies many material properties such as chloride ion content, compressive strength, bond strength, skid resistance and capillary absorption. Some of these material properties, such as skid resistance and chloride ion content, are not relevant to cracking. Also, empirical analytical models for predicting stresses and the age at cracking in PRMs need improvement to accommodate recent developments in materials such as admixtures and additives. Accurate prediction models help design engineers make informed choices during the selection of PRMs. The principal objective of this study was to generate new knowledge that would inform the design of non-structural PRMs and the development of performance requirements for these PRMs. This was accomplished through an investigation into the influence of multiple mix design parameters and crack-determining material properties on restrained shrinkage cracking, involving a critical review of literature and a comprehensive laboratory experimental programme. The experimental work was organised into two phases. Phase one entailed an investigation into the effect of water content, binder content, binder type, curing type, shrinkage reducing admixture (SRA) dosage, polymer type and polymer content on cracking. A 2⁵ full factorial experiment approach with three replicates was used in this phase. 32 mixes were studied. The sensitivity of cracking to the listed mix design parameters was determined with respect to the age at cracking in ring specimens made in accordance with ASTM C 1581. A trend analysis of the investigated mix design parameters and cracking was also done.

Bibliography: pages 225-233. / SAP0-34 and mordenite, catalysts with quite different pore structures, are known to be suitable for methanol conversion to light olefins and propene oligomerization to a distillate type product, respectively. In this study, these catalysts were modified in various ways and the effect of these modifications on the activity and selectivity of the above two reactions investigated. SAP0-34, a small-pore silicoaluminophosphate molecular sieve, is highly selective in the formation of ethene and propene from methanol, but deactivates rapidly due to coke formation. This catalyst was synthesized and modified in various ways in an attempt to increase the catalyst lifetime and selectivity to ethene. Mild hydrothermal conditions encountered during deep-bed calcination of SAP0-34 were found to increase the catalyst lifetime. A number of further modifications were made to this deep-bed calcined material in an attempt to increase further the lifetime of this material. These modifications were : (i) Silanization - in order to neutralize the acidity on the external surface of the crystallites and hence reduce pore-mouth blockage by coke species on the crystallite external surface; (ii) Steaming - to investigate the effect of more severe hydrothermal conditions than those encountered under deep-bed-calcination conditions; (iii) Acid site poisoning by ammonia - in an attempt to reduce the rate of coke formation which takes place readily on strong acid sites; (iv) Boron impregnation - in order to reduce the intercrystalline void volume and thereby sterically hinder the formation of bulky coke molecules within the SAP0-34 pores; (v) Acid and caustic treatments - in order to reduce the catalyst acidity and thereby limit the rate of the coke formation reaction.

Includes bibliographical references (leaves 132-135). / Integrated resource planning aims to fulfil electricity requirements with supply and demand resources. Least cost resources are optimised as supply expansions compete with measures to modify the load in meeting energy services. A demand side study is conducted to determine representative load profiles for electricity use within South Africa. Analysis of electricity consumption us in g load profiles of each sector ' s end-use electrical loads is essential for determining the appropriate supply technologies as well as the impact of demand side management and energy efficiency measures . A supply side study considers all existing and future power generation options required for expected electricity growth and system load characteristics. Energy model, TIMES, provides time-slices for adequate load profile representation TIMES is a Partial Dynamic Equilibrium Model as constraints are placed on the investment, usage and availability of technologies. All optimisations are for the least cost to the system. Demand and supply options are integrated into a single plan using the TIMES model and the supply expansion plan is changed when demand reduction targets are achieved using DSM and EE. The base case us in g a business-as-usual approach is compared with a low and medium impact DSM and EE scenario. Demand resources are estimated from the industrial, commercial and residential economic sectors. The scope of the plan is 22 years and there is full utilisation of all existing supply capacity with small amounts of decommissioning. Mothballed power stations are recommissioned initially. Peak-load plants are needed from 2007 and OCGT are selected using natural gas or LNG. Intermediate-load capacity is needed by 2011 using CCGT. Base-load capacity demands are met using new coal PF power stations in 2014. FBC stations using discard coal begin operation in 2016. The capacity expansion plan anticipates 2. 93GW of OCGT, 2.5 GW of CCGT, 7. 2GW of coal PF, 2. 8 GW of FBC plants and 2 GW of pump storage stations to be in use by 2020. Imported hydroelectric capacity of0.9 G W and PBMR capacity of3 GW is expected to be commissioned by 2024. Approximately 4 % less installed capacity is needed when a medium impact DSM and EE strategy is implemented. The marginal cost of energy gradually increases from 0. 06 R/kWh in 2002 to 0. 175 R/kWh in 2016 and to 0.325 R/kWh in 2024 as supply capacity is added. Compound load profiles from all national electricity usage provide an effective means whereby appropriate supply technologies are selected whilst incorporating load modifications due to DSM and EE.

Includes bibliographical references (leaves 108-110). / The construct of approach to learning has proved to be powerful in explaining differences in students' experiences of learning in higher education. However this construct does not explain the impact that students' socio-economic background has on their experiences of higher education. For this reason, the construct of cultural capital that is widely used in the sociology of education literature was used in an attempt to explain the differences experienced by students from various social classes. Data of this study were collected through individual in-depth interviews with each of ten purposefully selected students. Students' approaches to learning were identified for both early and later in the course. A majority of students' approaches shifted from the use of a deep approach to a strategic approach. However, in terms of success in the course, the construct of approach to learning was limited in explaining why some students failed while others were successful in the course. Cultural capital better explained why these differences in performance occurred, and it further emphasized the importance of taking into account the different forms of cultural capital that students bring into higher education. This study has two main implications: firstly, it supports the promotion of deep approach to learning, however, a caution about the students workload should be taken as this might unintentionally promote the use of surface approach. Secondly, the results regarding cultural capital showed that students come from varying backgrounds. This implies that assessment should take this into account and should aim to be explicit in all demands.

Energy use is the human activity responsible for the majority of its greenhouse gas emissions. In 2010 the global energy-related emissions of carbon dioxide - the principal greenhouse gas-jumped by 5.3% from the previous year, to a record 30.4 gigatonnes (IEA 2011a). The International Energy Agency (2011) has projected that the world's primary energy demand could increase by 33% and that energy related CO2 emissions will increase by 20% to 36.4 Gt between 2010 and 2035 (IEA 2011a). South Africa is one of the most energy intensive countries in the world, measured as GHG emissions per Gross Domestic Product produced. South Africa's energy intensiveness is a result of the energy intensive nature of a number of its key industries. The mineral industry is one such industry. It plays a crucial role in South Africa's economy and is the largest industry in its primary economic sector (Chamber of Mines 2010). Energy efficiency has been identified as one of the cheapest and most effective measures to reduce energy consumption and its associated greenhouse gas emissions. The Long Term Mitigation Scenarios coordinated by the University of Cape Town's Energy Research Centre identified that South Africa's industrial sector had cumulatively the greatest potential to reduce its GHG emissions through improved energy efficiency, ahead of the commercial, residential or transport sectors(Winkler 2007). South Africa's continued reliance on unsustainable energy production, particularly coal, increases the need for maximising energy efficiency to mitigate resource consumption and the GHG emissions associated with the production and use of fossil fuel generated energy. This project aims to identify and holistically evaluate the potential opportunities that exist for the reduction of energy and climate footprints of South Africa's gold industry sub-sector, with the aim of providing guidance to both government and industry for a path towards a more energy efficient industry with lower associated GHG emissions. To this end the thesis begins with a comprehensive review of the potential drivers, barriers and opportunities for increased EE and GHG emissions mitigation for the local minerals industry.

Gallium/H-ZSM-5 zeolite catalysts have been extensively researched for the aromatization of liquified petroleum gas (LPG). In 1989 BP and UOP collaborated to commission a pilot plant in Grangemouth, Scotland, for the aromatization of propane and butane. This plant, based on a technology called the Cyclar process, used continuous catalyst regeneration (CCR) and a gallium impregnated ZSM-5 zeolite catalyst to achieve yields of ca. 65% aromatics, mainly benzene, toluene and xylenes (BTX) [Guisnet and Gnep, 1992]. As a result of the Fischer-Tropsch process used by SASOL Ltd., South Africa is in an internationally unique position, in that it has a surplus of long chain linear alkenes with carbon numbers in the range C6-C8 . There could be large economic incentives to convert these alkenes into more valuable products, like alcohols or aromatics. Thus the purpose of this project was to determine if gallium/H-ZSM-5 catalysts, similar to those used in the Cyclar process, would be suitable for the aromatization of long chain alkenes. Three methods were investigated for the introduction of gallium into ZSM-5: (i) physical mixing with gallium oxide; (ii) impregnation by incipient wetness with gallium nitrate; (iii) ion-exchange with gallium nitrate. The catalysts were. tested with regard to their catalytic activity for the aromatization of 1-hexene and 1-octene.

A study was done to ascertain the presence of dreams and the quality of language in dreams in patients with aphasia. 24 aphasic subjects were interviewed using Kagan's (1998) Supported Conversation for Adults with Aphasia (SCA) technique of communication. The main hypothesis investigated was that aphasic patients would experience a better quality of language while dreaming than while awake. Severity being kept constant, aphasia in its acute stage displays greater discrepancy between pre- morbid and morbid language abilities than in its recovering, chronic stage. Therefore, a secondary hypothesis was formulated whereby the difference between language in waking life and language in dreams would be more significant in acute aphasics than in chronic aphasics. Thirdly, it was hypothesized that fluent aphasics would experience less dreaming, if any, since posterior lesions have been found to correlate with cessation or reduction in dreaming. Language in dreams was found to be significantly better than language in waking life amongst the 63% of subjects who reported dreaming. Differences in trends between the categories i) acute and chronic and ii) fluent and non- fluent aphasics, that is the second and third hypotheses, did not achieve statistical significance.

Due to the depletion of coarser grained ores, more mineralogically complex ores are being treated. These complex ores usually have finer grained valuable minerals. Liberation of these finer grained valuable minerals lies in grinding finer. Grinding to these fine sizes is energy intensive and using standard ball mills are energy inefficient at these sizes (P80 < 75μm). Therefore, stirred mills are becoming increasingly prevalent in the mineral processing industry. In order to optimize these mills, the effects and mechanisms of the significant variables need to be understood. This project investigated operating parameters against performance in a laboratory scale vertical stirred mill (Deswik mill), in an ultrafine grinding (UFG) application of MG2 reef in the bushveld igneous complex. The operating variables that were investigated are stirrer speed, solids concentration, media size and media filling. The Kwade stress energy model was tested on the grinding results. The grinding performance was quantified in two ways, i.e. grinding efficiency and grinding rate. The grinding performance for this study was also investigated through a statistical analysis. The experiments was designed using a face centred central composite design (FCCD) and the results was statistically analysed using a design of experiments (DOE) software.

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