Magister Educationis - MEd / In this mini-thesis, I explored the factors that affect grade 8 learners’ performance in reading in English.The study focused on reading as it was revealed by National Education Department and Western Cape Education Department that literacy and numeracy levels in schools in the Western Cape were poor. In addition, in March 1997, OBE was initiated in South Africa to develop a better educational system for all learners in schools and was perceived as a major step from the previous system (Botha, 2002). The system of OBE introduced the continuous assessment policies, which was a challenge for teachers already in the educational system. The study highlighted the theories of reading with particular emphasis on the evaluation of teaching of reading and assessment in the English classroom, learners’ home reading background and the influence of social practices and multiliteracies on learners’ reading proficiency. According to Alderson (2000) reading is perceived as a process of meaning- making with identification of different levels of meaning and understanding in and from text including reading skills. To elicit the factors that affect reading four variables were focused on during the study. The variables included reader, task, text and Social Practices and Multiliteracies variables, which interplayed in reading during tasks.In order to gather data the following data capturing methods were employed, firstly I highlighted the classroom observations to unpack the realities in classrooms for both the teacher and the learners. Then secondly I focused on the learners’ questionnaire to determine what happened during reading lessons and learners’ home reading practices. And thirdly I presented the teacher’s interview to highlight the reading strategies that she employed in class. Lastly I discussed the document analysis of grade 8 examination papers and classroom activities with a checklist. I discovered that the system of OBE put demands on teachers that they are not properly trained to do.Despite the fact that training was provided, it was too short and not clearly focused on interactive reading skills. When we consider the importance of multiliteracies, the teacher clearly draws on the learner’s home background by doing activities that make them feel that they are important. This teacher has the ability to successfully incorporate multimodal teaching methods in her class. The teacher also set time aside everyday to assess and mark the learners books, she then clarified issues that learners’ might encounter in the course of the reading lesson.However, there are some factors that could be addressed to improve reading abilities. The overcrowding and ghettoized condition of the class, did not promote morale within this environment. With the inception of OBE in-service training was provided, it was too short and not clearly focused on interactive reading skills. A further factor is learners’ use of Afrikaans during interactions with the teacher and each other,except for one learner who spoke English during the lesson.In conclusion, the evidence showed that the factors hat affect reading and therefore outcomes in education.

The perovskite family of materials is extremely large and provides a template for designing materials for different purposes. Among them, hybrid organic-inorganic perovskites (HOIPs) are very interesting and have been recently identified as possible next generation light harvesting materials because they combine low manufacturing cost and relatively high power conversion efficiencies (PCEs). In addition, some other applications like light emitting devices are also highly studied. This thesis starts with an introduction to the solar cell technologies that could use HOIPs. In Chapter 2, previously published results on the structural, electronic, optical and mechanical properties of HOIPs are reviewed in order to understand the background and latest developments in this field. Chapter 3 discusses the computational and experimental methods used in the following chapters. Then Chapter 4 describes the discovery of several hybrid double perovskites, with the formula (MA)$_2$M$^I$M$^{III}$X$_6$ (MA = methylammonium, CH$_3$NH$_3$, M$^I$ = K, Ag and Tl, M$^{III}$ = Bi, Y and Gd, X = Cl and Br). Chapter 5 presents studies on the variable presure and temperature response of formamidinium lead halides FAPbBr$_3$ (FA = formamidinium, CH(NH$_2$)$_2$) as well as the mechanical properties of FAPbBr$_3$ and FAPbI$_3$, followed by a computational study connecting the mechanical properties of halide perovskites ABX$_3$ (A = K, Rb, Cs, Fr and MA, X = Cl, Br and I) to their electronic transport properties. Chapter 6 describes a study on the phase stability, transformation and electronic properties of low-dimensional hybrid perovskites containing the guanidinium cation Gua$_x$PbI$_{x+2}$ (x = 1, 2 and 3, Gua = guanidinium, C(NH$_2$)$_3$). The conclusions and possible future work are summarized in Chapter 7. These results provide theoreticians and experimentalists with insight into the design and synthesis of novel, highly efficient, stable and environmentally friendly materials for solar cell applications as well as for other purposes in the future.

Combinatorial techniques have changed the paradigm of materials research by allowing a faster data acquisition in complex problems with multidimensional parameter space. The focus of this thesis is to demonstrate biomaterials design and characterization via preparation of two dimensional combinatorial libraries with chemically-distinct structured patterns. These are prepared from blends of biodegradable polymers using thickness and temperature gradient techniques. The desired pattern in the library is chemically-distinct cell adhesive versus non-adhesive micro domains that improve library performance compared to previous implementations that had modest chemical differences. Improving adhesive contrast should minimize the competing effects of chemistry versus physical structure. To accomplish this, a method of blending and crosslinking cell adhesive poly(季aprolactone) (PCL) with cell non-adhesive poly(ethylene glycol) (PEG) was developed. We examine the interaction between MC3T3-E1 osteoblast cells and PCL-PEG libraries of thousands of distinct chemistries, microstructures, and roughnesses. These results show that cells grown on such patterned biomaterial are sensitive to the physical distribution and phases of the PCL and PEG domains. We conclude that the cells adhered and spread on PCL regions mixed with PEG-crosslinked non-crystalline phases. Tentatively, we attribute this behavior to enhanced physical, as well as chemical, contrast between crystalline PCL and non-crystalline PEG.

A novel combined piezoelectric-composite actuator configuration is proposed and analytically modeled in this work. The actuator is a low complexity, active compliant mechanism obtained by coupling a modified star cross sectional configuration composite beam with a helicoidal bimorph piezoelectric actuator coiled around it. This novel actuator is a good candidate as a hinge tension-torsion bar actuator for a helicopter rotor blade flap or blade tip and mirror rotational positioning. In the wing tip case, the tip deflection angle is different only according to the aerodynamic moment depending on the hinge position of the actuator along the chord and applied voltage because there is no centrifugal force. For an active blade tip subject to incompressible flow and 2D quasi steady airloads, its twist angle is related not only to aerodynamic moment and applied voltage but also to coupling terms, such as the trapeze effect and the tennis racquet effect. Results show the benefit of hinge position aft of the aerodynamic center, such that the blade tip response is amplified by airloads. Contrary to this effect, results also show that the centrifugal effects and inertial effect cause an amplitude reduction in the response. Summation of these effects determines the overall blade tip response. The results for a certain hinge position of Xh=1.5% chord aft of the quarter chord point proves that the tip deflection target design range[-2,+2] can be achieved for all pitch angle configurations chosen.

In this research, the homogenization relations for elastic properties in isotropic and anisotropic materials are studied by applying two-point statistical functions to composite and polycrystalline materials. The validity of the results is investigated by direct comparison with experimental results. In todays technology, where advanced processing methods can provide materials with a variety of morphologies and features in different scales, a methodology to link property to microstructure is necessary to develop a framework for material design. Statistical distribution functions are commonly used for the representation of microstructures and also for homogenization of materials properties. The use of two-point statistics allows the materials designer to consider morphology and distribution in addition to properties of individual phases and components in the design space. This work is focused on studying the effect of anisotropy on the homogenization technique based on two-point statistics. The contribution of one-point and two-point statistics in the calculation of elastic properties of isotropic and anisotropic composites and textured polycrystalline materials will be investigated. For this purpose, an isotropic and anisotropic composite is simulated and an empirical form of the two-point probability functions are used which allows the construction of a composite Hull. The homogenization technique is also applied to two samples of Al-SiC composite that were fabricated through extrusion with two different particle size ratios (PSR). To validate the applied methodology, the elastic properties of the composites are measured by Ultrasonic methods. This methodology is then extended to completely random and textured polycrystalline materials with hexagonal crystal symmetry and the effect of cold rolling on the annealing texture of near- Titanium alloy are presented.

Materials for extreme electrical contacts need to have high electrical conductivity coupled with good structural properties. Potential applications include motor contacts, high power switches, and the components of electromagnetic launch (EML) systems. In particular, the lack of durability of these materials in rail components limits practical EML implementation. These rails experience significant amounts of Joule heating, due to extreme current densities, and subsequent thermally-assisted wear. New more durable materials solutions are needed for these components. A systematic materials selection study was executed to identify and compare candidate materials solutions. Several possible candidate non-dominated materials as well as hybrid materials that could potential fill the "white spaces" on the Ashby charts were identified. A couple potential candidate materials were obtained and evaluated. These included copper-tungsten W-Cu, "self-lubricating" graphite-impregnated Cu, and Gr-W-Cu composites with different volume fractions of the constituents. The structure-property relations were determined through mechanical and electrical resistivity testing. A unique test protocol for exposing mechanical test specimens to extreme current densities up to 1.2 GA/m2 was developed and used to evaluate these candidate materials. The systematic design of multi-functional materials for these extreme electrical contacts requires more than an empirical approach. Without a good understanding of both the tribological and structural performance, the optimization of the microstructure will not be quickly realized. By using micromechanics modeling and other materials design modeling tools coupled with systematic mechanical and tribological experiments, the design of materials for these applications can potentially be accelerated. In addition, using these tools, more complex functionally-graded materials tailored to the application can be systematically designed. In this study, physics- and micromechanics-based models were used to correlate properties to the volume fraction of the constituents of the evaluated candidate materials. Properties correlated included density, elastic modulus, hardness, strength, and electrical resistivity of the W-Cu materials.

Silicon-based nanostructures are essential building blocks for nanoelectronic devices and nano-electromechanical systems (NEMS), and their mechanical and electrical properties play an important role in controlling the functionality and reliability of the nano-devices. The objective of this dissertation is twofold: The first is to investigate the mechanical properties of silicon nanolines (SiNLs) with feature size scaled into the tens of nanometer level. And the second is to study the electron transport in nickel silicide formed on the SiNLs. For the first study, a fabrication process was developed to form nanoscale Si lines using an anisotropic wet etching technique. The SiNLs possessed straight and nearly atomically flat sidewalls, almost perfectly rectangular cross sections and highly uniform linewidth at the nanometer scale. To characterize mechanical properties, an atomic force microscope (AFM) based nanoindentation system was employed to investigate three sets of silicon nanolines. The SiNLs had the linewidth ranging from 24 nm to 90 nm, and the aspect ratio (Height/linewidth) from 7 to 18. During indentation, a buckling instability was observed at a critical load, followed by a displacement burst without a load increase, then a fully recoverable deformation upon unloading. For experiments with larger indentation displacements, irrecoverable indentation displacements were observed due to fracture of Si nanolines, with the strain to failure estimated to be from 3.8% to 9.7%. These observations indicated that the buckling behavior of SiNLs depended on the combined effects of load, line geometry, and the friction at contact. This study demonstrated a valuable approach to fabrication of well-defined Si nanoline structures and the application of the nanoindentation method for investigation of their mechanical properties at the nanoscale. For the study of electron transport, a set of nickel monosilicde (NiSi) nanolines with feature size down to 15 nm was fabricated. The linewidth effect on nickel silicide formation has been studied using high-resolution transmission electron microscopy (HRTEM) for microstructural analysis. Four point probe electrical measurements showed that the residual resistivity of the NiSi lines at cryogenic temperature increased with decreasing line width, indicating effect of increased electron sidewall scattering with decreased line width. A mean free path for electron transport at room temperature of 5 nm was deduced, which suggests that nickel silicide can be used without degradation of device performance in nanoscale electronics.

The development of alternative binder systems for tungsten carbide (WC) based cemented carbides has again become of relevance due to possible changes in EU regulations regarding the use of Cobalt (Co). A framework for the ICME (Integrated Computational Materials Engineering) based Materials Design is presented to accelerate the development of alternative binder systems. Part one of this work deals with the design of the cemented carbide composite hardness. It has been shown that the intrinsic binder hardness is comparable to a bulk metal alloy and that based on the binder solubilities a solid solution strengthening model developed in this work can be employed. Using a method presented in this work the non-equilibrium, frozen-in binder solubilities can be obtained. Both the design of the binder phase and composite hardness is presented based on a general Materials Design approach. Part two deals with a multiscale approach to model the surface gradient formation. The experimentally missing data on liquid binder diffusion has been calculated using AIMD (Ab initio Molecular Dynamics). The diffusion through the liquid cemented carbide binder has to be reduced to an effective diffusion value due to the solid carbides acting as obstacles that increase the diffusion path. The geometrical reduction of the diffusion has been investigated experimentally using the SIMS (secondary ion mass spectroscopy) technique in WC-Nickel-58Nickel diffusion couples. The geometrical contribution of the so-called labyrinth factor has been proven by the combination of the experiments and in conjunction with DICTRA simulations using the precise liquid AIMD diffusivities. Unfortunately, despite the improved kinetic database and the geometrical diffusion reduction, the surface gradient formation cannot be explained satisfactory in complex cemented carbide grades. Additional, but so far unidentified, contributions have to be considered to predict the surface gradient thickness. / <p>QC 20170919</p>

The current movement towards multilingualism and multiculturalism in South Africa has placed language at the centre of all educational activity. With the implementation of the outcomes-based Curriculum 2005, the emphasis is on appropriate learning support material, and the learning programmes are seen as guides that allow teachers to be innovative and creative in designing instructional and learning material. The fact that Afrikaans was one of three compulsory language subjects at a school in the Soweto area motivated researchers of Technikon South Africa to embark upon an outreach project. The latter entailed a remedial programme to address the lack of Afrikaans language proficiency of the Grade 12 learners at this school. My role as the remedial teacher and my subsequent responsibility for the development of appropriate and relevant learning material for the intervention provided the impetus and motivation for this research. The aim of the study was to determine the criteria for developing materials, in order to develop the proficiency in Afrikaans of Grade 12 additional language learners. The intervention took the form of an ongoing action research cycle. The magnitude of the proficiency dilemma in this study was revealed by a pre-intervention assessment. Apart from the learners’ poor functional Afrikaans literacy, it also became apparent that the influence of affective variables in additional language learning should be considered. The literature survey undertaken to articulate the relevant information about Communicative Language teaching (CLT) emphasised the kind of teaching necessary to develop proficiency in an additional language. In addition, the exploration of the influence of affective factors on additional language teaching and learning allowed a better understanding of the learners’ needs and ensured a learning-centered approach. In the process of materials selection, adaptation and development, it was necessary to relate learning principles and procedure to theory, research methods and classroom practice. Reviewing the literature on issues such as designing and developing materials contributed to a pragmatic approach to materials development, and assisted in establishing the criteria for the development of appropriate materials. The study has attempted to show how to design appropriate and relevant teaching materials guided by a set of criteria. The implementation of the materials in the classroom integrated theory and practice. Thus in practice, through different action research cycles, the developed materials were shown to comply with the theoretical criteria to establish their effectiveness, and refined to suit the proficiency level of the particular learners. Finally, critical reflection resulted in a redesigned set of materials for Afrikaans as an additional language. The post-intervention assessment showed that there was indeed an improvement in the learners’ proficiency levels and that the average grade of their proficiency levels improved. Other findings suggested the probability of a positive attitude change in the learners. Thus, it can be concluded that the intervention may be judged as having been relatively successful. / Thesis (DPhil)--University of Pretoria, 2006. / Unit for Academic Literacy / DPhil / Unrestricted

The aim of this thesis is to describe the replacement of wire cutting laser cutting for cutting inserts made of hard material. Description of current situation in the company Vydona, tender and choice of laser and the need for post-laser workshop. The next section deals with the cutting of a particular sample. The last part of the technical economic assessment are calculated hourly rates of machines and the time and cost loads of different cutting inserts.