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The study reported in this dissertation compares the learning effectiveness of two experimental methods that can be used in the teaching of kinematics to Grade 11 learners in Physical Science. The first method is the conventional ticker-timer experiment, while the second utilises high-technology microcomputer-based equipment. The purpose is to make recommendations for improved teaching of basic kinematics concepts and graphs, which learners have difficulties with (Halloun & Hestenes, 1985; McDermott et al., 1987). A group of 48 Grade 11 learners from Thuto-Boswa Secondary School, Ventersdorp, were used in the empirical research. They were divided into two groups of comparable abilities. Group A used the conventional apparatus and group B the microcomputerbased apparatus. The results of the pre- and post-tests were analysed statistically to compare the learning effectiveness of the two methods in terms of the outcomes reached, the gains obtained as well as d-values. Three months after the experiments were conducted the learners were tested again to determine the long-term effect of the methods. Both groups obtained a gain of approximately 0,2 in the pre- versus post-test analysis. The literature (e.g. Thornton, 1998) reveals larger gains with microcomputer-based experiments. Three possible reasons that could contribute to this discrepancy were investigated, namely the learners' acquaintance with the microcomputer, the educator's experience with the apparatus as well as the learners' cultural background and language. All three these factors were found to have a detrimental effect on the learning effectiveness, especially with the microcomputer-based method. Recommendations are made in connection with the teaching of basic kinematics concepts and graphs to Grade 11 learners in South African secondary schools. In addition, it is emphasised that educators should be adequately computer literate before expensive high-technology equipment is purchased for classroom use. It is also pointed out that the implementation of the computer as teaching aid can be a first step to improve computer literacy of disadvantaged learners in our schools. / Thesis (M.Ed.)--North-West University, Potchefstroom Campus, 2004.

The goal of this dissertation is to consolidate the theoretical foundation of variable-resolution (VR) methods in general and the partially-averaged Navier-Stokes (PANS) approach in particular. The accurate simulation of complex turbulent flows remains an outstanding challenge in modern computational fluid dynamics. High- fidelity approaches such as direct numerical simulations (DNS) and large-eddy simulation (LES) are not typically feasible for complex engineering simulations with cur- rent computational technologies. Low-fidelity approaches such as Reynolds-averaged Navier-Stokes (RANS), although widely used, are inherently inadequate for turbulent flows with complex flow features. VR bridging methods fill the gap between DNS and RANS by allowing a tunable degree of resolution ranging from RANS to DNS. While the utility of VR methods is well established, the mathematical foundations and physical characterization require further development. This dissertation focuses on the physical attributes of fluctuations in partially-resolved simulations of turbulence. The specific objectives are to: (i) establish a framework for assessing the physical fidelity of VR methods to examine PANS fluctuations; (ii) investigate PANS simulations subject to multiple resolution changes; (iii) examine turbulent transport closure modeling for partially-resolved fields; (iv) examine the effect of filter control parameters in the limit of spectral cut-off in the dissipative region; and (v) validate low-Reynolds number corrections with RANS for eventual implementation with PANS. While the validation methods are carried out in the context of PANS, they are considered appropriate for all VR bridging methods. The key findings of this dissertation are summarized as follows. The Kolmogorov hypotheses are suitably adapted to describe fluctuations of partially-resolved turbulence fields, and the PANS partially-resolved field is physically consistent with the adapted Kolmogorov hypotheses. PANS adequately recovers the correct energetics in instances of multiple resolution changes. Scaling arguments are used to determine the correct transport closure model for a partially-resolved field in a boundary layer. The need to modify the fε filter control parameter for cut-off in the dissipation range is highlighted. A low-Reynolds number near-wall correction was evaluated on a RANS model with the intent of adapting to it VR methods. Overall, PANS shows promise as a theoretically sound modeling approach, and this work lays the foundation for future PANS investigations.

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Since new product designs have little field data available a correlation between field and accelerated test life cannot be made. However, a step partially accelerated life test approach where samples are tested under normal conditions for a time and then run to failure on an accelerated test can be used to estimate the statistical model parameters. This thesis developed the maximum likelihood parameter estimates for a step partially accelerated life test based on a Weibull distribution model for a hypothetical automotive component. Using a Monte Carlo approach with type-II censoring, the effect of sample size and length of sampling period used on the variability of the estimated parameters was examined. A smaller sampling period and small sizes lead to significant variability, which decreased as the sampling period and sample size increased. Use of a partitioned sample did not lead to an improvement in the variability of the estimates. / Department of Mathematical Sciences

The defects and fault tolerance study is essential in the QCA devices in order to know its characteristics. Knowing the characteristics, one can understand the flow of information in a QCA system with and without manufacturing and operational defects. The manufacturing defects could be at device level or cell level. At the device level, the cell could be rotated, displaced vertically or horizontally, the cell could be missing or the size of the cell could be different. At the cell level, there could be a missing dot, dot could be displaced from its position or the size of the dots could be different. The operational defects are due to its surrounding, such as temperature or stray charge. Each of these defects and fault tolerances can be studies in detail in order to find the optimum working conditions where the information can be safely transmitted to the appropriate locations in the device.The theoretical studies have shown that at absolute temperature and without any defect, the QCA devices are operational. But it is almost impossible to manufacture a perfect or defect free device, and also it is impractical to think about operating a system at absolute zero temperature environment.Therefore, it is important to investigate the fault tolerant properties with defects and higher temperatures to see how far the QCA device can operate safely. Many studies have been done to investigate the fault tolerant properties in QCA devices. However, these studies have not completely exhausted the study of defects and temperature effects. In this study, the dot displacement and missing dots with temperature effects are investigated for the basic QCA devices and a Full Adder. In order to study fault tolerant properties, the existing theoretical model and computer simulation programs have been expanded and used. The defect characteristics have been simulated using normal distribution. / Department of Physics and Astronomy