The overall aim of the presented work is the enhancement of the student experience through creating conditions where excellent learning can occur both individually and through working in communities of practice. There was a mixed method approach taken within the studies, with a bias towards a more qualitative slant. Each study had an action research focus through the use of small scale case studies of teaching and learning in practice. A criticism of qualitative research and particularly case studies, is in relation to generalisation of the findings. However, case studies in teaching and learning are context specific and explore the activity as it happens and therefore can contribute to the broader picture, through examples but they cannot provide incontrovertible best practice. The work presents two research objectives, the first being an exploration of the ways in which teaching and learning interventions can create conditions to support excellent learning. Within the studies presented in this thesis, the following are key headlines. PDP was found to be a positive addition to the curriculum in particular the activities of goal-setting and reflection. The intensive and bespoke transition programme delivered to the new students facilitated and enhanced student engagement. The module re-design which focused on authentic assessment, engagement, real-world learning and employability enhanced the student skill set. In addition to interventions to support students, the thesis also contains staff development activity. The two articles based on peer review found that, knowing and developing teacher immediacy plays a part in teacher development and can help create better connections with students. Although different each of the articles presents examples which others might find useful in enhancing practice. The second research objective considered how communities of practice for staff and students can support the conditions to enable excellent and purposeful teaching and learning. One of the articles focuses on an organisation set up to support teaching in higher education. It found that a support network can enhance knowledge and experiences and that a community of practice is one way of creating and maintaining groups of staff interested in teaching and learning. The articles on peer review show that this also has value at a more local level where teaching staff felt that by working together they had developed their individual approaches. This did not work for all staff and the study showed that this type of approach to staff development is very personal. Trust, honesty and commitment came out as important factors, which need to be fostered in a community of practice. For the students, working in peer learning groups (PLGs), connecting with each other very early on in their programme and sharing metaphors was found to have value. Learning in a university has been shown to be an isolating experience and working together has merits for both staff and students. This thesis has been based on small scale case studies and has evidenced developments at a local level, which I contend is the only way to change and develop practice. However, from a knowledge and generalisation perspective my research now needs to broaden, to determine cultural and subject differences, as this will make the evidence more compelling across the sector. Two specific areas from this study that would benefit from further research are, PLG groups in different subject contexts and staff working in communities of practice to support teaching and learning.

Made available in DSpace on 2014-06-11T19:29:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-07-01Bitstream added on 2014-06-13T18:07:38Z : No. of bitstreams: 1 bissoli_cf_me_sjc.pdf: 1658392 bytes, checksum: 87521fc116b48dbe7d8b1a4b112dee4e (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O propósito deste trabalho é analisar e verificar as medidas verticais de dentes humanos in vitro por meio de radiografias panorâmicas. O estudo foi baseado na montagem de uma boca com 28 dentes em um manequim de borracha, sendo utilizado para a realização das radiografias dois aparelhos ortopantomográficos (Rotograph plus e Panoura-10). O manequim, com o auxílio de suportes de madeira, foi radiografado com o plano oclusal paralelo ao horizontal, e também com seu plano oclusal à +5 graus e à -5 graus em relação ao plano horizontal. Os resultados obtidos indicaram que para a região de incisivos para o aparelho Rotograph plus a ampliação foi de 18,97% na maxila e 17,91% na mandíbula; para a região de pré-molares foi de 16,38% na maxila e 16,30% na mandíbula; e para a região de molares foi de 14,90% na maxila e 14,24% na mandíbula. Já para o aparelho Panoura-10 foi na região de incisivos 19,70% na maxila e 19,31% na mandíbula, na região de pré-molares 18,49% na maxila e 17,88% na mandíbula e para molares 16,66% na maxila e 16,17% na mandíbula. Conclui-se que houve ampliações diferentes nas regiões anatômicas estudadas. Posteriormente foi feito o teste estatístico ANOVA, e não houve diferenças estatisticamente significantes entre as inclinações de +5 graus e -5 graus em relação ao plano oclusal paralelo ao horizontal nos dois aparelhos (p>0,05). Também foi concluído que o aparelho Panoura-10 obteve 18,03% de ampliação vertical geral média e que o Rotograph plus obteve 16,45% de ampliação vertical geral média. / The aim of this work is to analyze and to verify the vertical measurements of the human teeth in vitro by panoramic radiographs. The study was based in set up of 28 teeth in rubber manikin. The radiographs were made with two orthopantomographs (Rotograph plus and Panoura - 10). The manikin with wood supports was radiographic with oclusal plane parallel to horizontal plane and oclusal plane 5 degrees positive and 5 degrees negative to horizontal plane. The results has showed that in incisors region, in Rotograph plus, has enlarged 18,97 % for the maxilla and 17,91% for the mandible; in bicuspid region, 16,38% for the maxilla and 16,30%for the mandible; and molar region, 14,90% for the maxilla and 14,24% for the mandible. The Panoura - 10 has enlarged in incisor region, 19,70% for the maxilla and 19,31% for the mandible, mandible, in bicuspid region, 18,49 % for the maxilla and 17,88 % for the mandible and molar region 16,66 % for the maxilla and 16,17 % for the mandible. The conclusions were that different enlargements in anatomic regions studied occurred. The ANOVA test has known that significance statistical differences between the inclinations of +5 degrees and -5 degrees and oclusal plane parallel the horizontal plane in both (p>0,05) didn t happen. The Panoura - 10 has enlarged 18,03% in total vertical average and the Rotograph plus has enlarged, 16,45 % in total vertical average.

Speech signal processing for voice communications can be characterised in terms of silence compression, noise reduction, and speech compression. The limit in the channel bandwidth of voice communication systems requires efficient compression of speech and silence signals while retaining the voice quality. Silence compression by means of both voice activity detection (VAD) and comfort noise generation could present transparent speech-quality while substantially lowering the transmission bit-rate, since pause regions between talk spurts do not include any voice information. Thus, this thesis proposes smoothed likelihood ratio-based VAD, designed on the basis of a behavioural analysis and improvement of a statistical model-based voice activity detector. Input speech could exhibit noisy signals, which could make the voice communication fatiguing and less intelligible. This task can be alleviated by noise reduction as a preprocessor for speech coding. Noise characteristics in speech enhancement are adapted typically during the pause regions classified by a voice activity detector. However, VAD errors could lead to over- or under- estimation of the noise statistics. Thus, this thesis proposes mixed decision-based noise adaptation based on a integration of soft and hard decision-based methods, defined with the speech presence uncertainty and VAD result, respectively. At low bit-rate speech coding, the sinusoidal model has been widely applied because of its good nature exploiting the phase redundancy of speech signals. Its performance, however, can be severely smeared by mis-estimation of the pitch. Thus, this thesis proposes a robust pitch estimation technique based on the autocorrelation of spectral amplitudes. Another important parameter in sinusoidal speech coding is the spectral magnitude of the LP-residual signal. It is, however, not easy to directly quantise the magnitudes because the dimensions of the spectral vectors are variable from frame to frame depending on the pitch. To alleviate this problem, this thesis proposes mel-scale-based dimension conversion, which converts the spectral vectors to a fixed dimension based on mel-scale warping. A predictive coding scheme is also employed in order to exploit the inter-frame redundancy between the spectral vectors. Experimental results show that each proposed technique is suitable for enhancing speech quality for voice communications. Furthermore, an improved speech coder incorporating the proposed techniques is developed. The vocoder gives speech quality comparable to TIA/EIA IS-127 for noisy speech whilst operating at lower than half the bit-rate of the reference coder. Key words: voice activity detection, speech enhancement, pitch, spectral magnitude quantisation, low bit-rate coding.

For pianists working within the western art music tradition, the ability to perform a large and complex repertoire from memory is almost a prerequisite for a successful career. Memorising and maintaining this repertoire requires considerable practice and can lead to physical overuse syndromes. Additionally, automated motor memory developed via physical practice is not always sufficient for secure recall, often leading to performance anxiety. It is important therefore for professionals to identify optimal practice strategies, and mental rehearsal has been widely advocated as a potential means of enhancing memorisation and performance fluency while at the same time avoiding physical overuse. The results of three studies that examined mental imagery rehearsal by expert pianists, adopting a mixed methods approach, are presented in this thesis. The first was a participant observation study of a course at which eleven advanced pianists learned to use a memorisation technique incorporating deliberate imagery; the study aimed to describe the teaching and learning of specific imagery techniques and to examine the potential advantages and drawbacks of this approach. The second study was an online questionnaire survey of thirty six piano students at UK conservatoires designed to investigate the teaching and implementation of mental rehearsal techniques at advanced training levels; the survey found that despite a widespread awareness of imagery rehearsal as a potentially effective strategy, training in specific techniques was not consistently available, and recommended mental practice strategies were adopted much less consistently than strategies involving physical practice. Finally, an fMRI study of fourteen expert pianists aimed to determine the neural correlates of imagery rehearsal and simulated piano playing. Differences observed in brain activation between tasks suggested increased involvement of working memory processes during mental imagery. The thesis concludes that mental imagery rehearsal techniques are acquired skills that can be taught and improved over time and which have specific advantages over motor learning, but that more pedagogical training is needed in order for these techniques to become fully effective and widely adopted.

The quality of an underwater image is degraded due to the effects of light scattering in water, which are resolution loss and contrast loss. Contrast loss is the main degradation problem in underwater images which is caused by the effect of optical back-scatter. A method is proposed to improve the contrast of an underwater image by mitigating the effect of optical back-scatter after image acquisition. The proposed method is based on the inverse model of an underwater image model, which is validated experimentally in this work. It suggests that the recovered image can be obtained by subtracting the intensity value due to the effect of optical back-scatter from the degraded image pixel and then scaling the remaining by a factor due to the effect of optical extinction. Three filters are proposed to estimate for optical back-scatter in a degraded image. Among these three filters, the performance of BS-CostFunc filter is the best. The physical model of the optical extinction indicates that the optical extinction can be calculated by knowing the level of optical back-scatter. Results from simulations with synthetic images and experiments with real constrained images in monochrome indicate that the maximum optical back-scatter estimation error is less than 5%. The proposed algorithm can significantly improve the contrast of a monochrome underwater image. Results of colour simulations with synthetic colour images and experiments with real constrained colour images indicate that the proposed method is applicable to colour images with colour fidelity. However, for colour images in wide spectral bands, such as RGB, the colour of the improved images is similar to the colour of that of the reference images. Yet, the improved images are darker than the reference images in terms of intensity. The darkness of the improved images is because of the effect of noise on the level of estimation errors.

Parabolic trough systems are one of the most commercially and technically developed technologies for concentrated solar power. With the current research and development efforts, the cost of electricity from these systems is approaching the cost of electricity from medium-sized coal-fired power plants. Some of the cost-cutting options for parabolic trough systems include: (i) increasing the sizes of the concentrators to improve the system’s concentration ratio and to reduce the number of drives and controls and (ii) improving the system’s optical efficiency. However, the increase in the concentration ratios of these systems requires improved performance of receiver tubes to minimise the absorber tube circumferential temperature difference, receiver thermal loss and entropy generation rates in the receiver. As such, the prediction of the absorber tube’s circumferential temperature difference, receiver thermal performance and entropy generation rates in parabolic trough receivers therefore, becomes very important as concentration ratios increase. In this study, the thermal and thermodynamic performance of parabolic trough receivers at different Reynolds numbers, inlet temperatures and rim angles as concentration ratios increase are investigated. The potential for improved receiver thermal and thermodynamic performance with heat transfer enhancement using wall-detached twisted tape inserts, perforated plate inserts and perforated conical inserts is also evaluated. In this work, the heat transfer, fluid flow and thermodynamic performance of a parabolic trough receiver were analysed numerically by solving the governing equations using a general purpose computational fluid dynamics code. SolTrace, an optical modelling tool that uses Monte-Carlo ray tracing techniques was used to obtain the heat flux profiles on the receiver’s absorber tube. These heat flux profiles were then coupled to the CFD code by means of user-defined functions for the subsequent analysis of the thermal and thermodynamic performance of the receiver. With this approach, actual non-uniform heat flux profiles and actual non-uniform temperature distribution in the receiver different from constant heat flux profiles and constant temperature distribution often used in other studies were obtained. Both thermodynamic and multi-objective optimisation approaches were used to obtain optimal configurations of the proposed heat transfer enhancement techniques. For thermodynamic optimisation, the entropy generation minimisation method was used. Whereas, the multi-objective optimisation approach was implemented in ANSYS DesignXplorer to obtain Pareto solutions for maximum heat transfer and minimum fluid friction for each of the heat transfer enhancement techniques. Results showed that rim angles lower than 60o gave high absorber tube circumferential temperature differences, higher receiver thermal loss and higher entropy generation rates, especially for flow rates lower than 43 m3/h. The entropy generation rates reduced as the inlet temperature increased, increased as the rim angles reduced and as concentration ratios increased. Existence of an optimal Reynolds number at which entropy generation is a minimum for any given inlet temperature, rim angle and concentration ratio is demonstrated. In addition, for the heat transfer enhancement techniques considered, correlations for the Nusselt number and fluid friction were obtained and presented. With heat transfer enhancement, the thermal efficiency of the receiver increased in the range 5% – 10%, 3% – 8% and 1.2% – 8% with twisted tape inserts, perforated conical inserts and perforated plate inserts respectively. Results also show that with heat transfer enhancement, the absorber tube’s circumferential temperature differences reduce in the range 4% – 68%, 3.4 – 56% and up to 67% with twisted tape inserts, perforated conical inserts and perforated plate inserts respectively. Furthermore, the entropy generation rates were reduced by up to 59%, 45% and 53% with twisted tape inserts, perforated conical inserts and perforated plate inserts respectively. Moreover, using multi-objective optimisation, Pareto optimal solutions were obtained and presented for each heat transfer enhancement technique. In summary, results from this study demonstrate that for a parabolic trough system, rim angles, concentration ratios, flow rates and inlet temperatures have a strong influence on the thermal and thermodynamic performance of the parabolic trough receiver. The potential for improved receiver thermal and thermodynamic performance with heat transfer enhancement has also been demonstrated. Overall, this study provides useful knowledge for improved design and efficient operation of parabolic trough systems. / Thesis (PhD)--University of Pretoria, 2015. / tm2015 / Mechanical and Aeronautical Engineering / PhD / Unrestricted

Modern data centers host hundreds of thousands of servers to achieve economies of scale. Such a huge number of servers create challenges for the data center network (DCN) to provide proportionally large bandwidth. In addition, the deployment of virtual machines (VMs) in data centers raises the requirements for efficient resource allocation and find-grained resource sharing. Further, the large number of servers and switches in the data center consume significant amounts of energy. Even though servers become more energy efficient with various energy saving techniques, DCN still accounts for 20% to 50% of the energy consumed by the entire data center. The objective of this dissertation is to enhance DCN performance as well as its energy efficiency by conducting optimizations on both host and network sides. First, as the DCN demands huge bisection bandwidth to interconnect all the servers, we propose a parallel packet switch (PPS) architecture that directly processes variable length packets without segmentation-and-reassembly (SAR). The proposed PPS achieves large bandwidth by combining switching capacities of multiple fabrics, and it further improves the switch throughput by avoiding padding bits in SAR. Second, since certain resource demands of the VM are bursty and demonstrate stochastic nature, to satisfy both deterministic and stochastic demands in VM placement, we propose the Max-Min Multidimensional Stochastic Bin Packing (M3SBP) algorithm. M3SBP calculates an equivalent deterministic value for the stochastic demands, and maximizes the minimum resource utilization ratio of each server. Third, to provide necessary traffic isolation for VMs that share the same physical network adapter, we propose the Flow-level Bandwidth Provisioning (FBP) algorithm. By reducing the flow scheduling problem to multiple stages of packet queuing problems, FBP guarantees the provisioned bandwidth and delay performance for each flow. Finally, while DCNs are typically provisioned with full bisection bandwidth, DCN traffic demonstrates fluctuating patterns, we propose a joint host-network optimization scheme to enhance the energy efficiency of DCNs during off-peak traffic hours. The proposed scheme utilizes a unified representation method that converts the VM placement problem to a routing problem and employs depth-first and best-fit search to find efficient paths for flows.

Heat exchangers are used in a wide variety of industrial applications. Augmentation of heat transfer can realize a reduction in heat transfer size and increase the effectiveness and efficiency of heat exchangers. Heat transfer can be enhanced with various methods where the turbulence of the fluid flow is enhanced: by adding ribs, grooves or steps to the channel wall, using helical inserts, or by adding bluff bodies in the channel flow. By using these methods, there is also an increase in pressure drop penalty and larger pumping power is required to achieve the same flow rate. Circular cylindrical bluff bodies have been found to have smaller drag coefficients than square, rectangular or triangular cylindrical bluff bodies in the channel flow. Heat transfer and pressure drop experimental tests were done for eight different circular cylindrical cross-bar arrays at 15 different Reynolds numbers, in the range of 640 to 12 500. Eight different cross-bar configurations were tested: the cylinder diameter to pitch ratios were, d/p = 0.025, d/p = 0.05, d/pi=i0.1 and d/p = 0.2, and the angle to the flow direction, was θ = 90° and θ = 45° for each of the four different diameter-to-pitch ratios. Transient CFD simulations were done using Ansys fluent for d/p = 0.05 and d/p = 0.2, for θ = 90°, at Reynolds numbers 920 and 9 700, to analyze the secondary flow structures in the wake of the cylinders, partly responsible for the heat transfer and pressure drop increase in the channel flow in comparison to the smooth channel. The k-Ω shear stress transport (SST) model was used for the simulations. A mesh dependence study was done for spatial discretization, temporal discretization and validated against the experimental setup. The pressure drop gradient was found from the test data for the hydraulically developed part of the test section to calculate the friction factors. With an increase in Reynolds number, the friction factors decreased until reaching an asymptotic value for all the cross-bar configurations. For θi=i90° the friction factors were larger than for θ = 45° for the same d/p ratio and Reynolds number. With an increase in d/p, the friction factors increased. The largest measured friction factor was f = 0.3, for configuration d/p = 0.2, θ = 90°, at Re = 640 and the smallest measured friction factor f = 0.02, for d/pi= 0.025, θ = 45°, at Re = 12 500. The friction factor ratio was then used to quantify the pressure penalty for using cylindrical cross-bars in the channel flow to enhance heat transfer. The maximum friction factor ratio, f/f0 = 16.7 occurred at Re = 9 700, for d/pi=i0.2, θ = 90° and the minimum friction factor ratio, f/f0 = 2.1, at Re = 640, for d/pi=i0.025, θ = 45°. The average Nusselt numbers were then calculated using the spatial integral average of the local Nusselt numbers. With an increase in Reynolds number, there was an increase in the average Nusselt number for all the cylindrical cross-bar configurations. For larger d/p ratios and θ = 90° cases, the average Nusselt numbers were larger than for smaller d/p ratios and θ = 45°. The largest average Nusselt number was Nuavg = 66.3, at Re = 9 700 for d/p = 0.2, θ = 90° and the smallest average Nusselt number, Nuavg = 8.7, at Re = 640 for d/p = 0.025, θ = 45°. The Nusselt number ratio could then be used to quantify the heat transfer enhancement of the cylindrical cross-bar channel to that of the smooth channel, where the largest Nusselt number ratio was, Nuavg /Nu0,avg = 3.3, for d/p = 0.2, θ = 90°, at Rei=i3 000 and the smallest Nuavg /Nu0,avg = 1.1, for d/p = 0.025, θ = 45°, at Re = 640. The CFD results concluded that the pressure drop increase and heat transfer enhancement were caused by the flow acceleration, flow separation, eddy formation, vorticity increase, and boundary layer deformation next to and behind the cylinders. The Strouhal number for the larger d/p ratios suggested that the unsteadiness in the flow is higher for the cylinder arrays with a larger diameter, increasing both the heat transfer enhancement and friction factor in comparison with the smaller diameter cylinder arrays. Finally, the thermal performance coefficients could be calculated by using the friction factor ratios and Nusselt number ratios. The thermal performance coefficient combines the effects of the heat transfer and pressure penalty increase. The thermal performance coefficients increased from Re = 640 until Rei=i3 000 after which it decreased with an increase in Reynolds number. This is because the pressure penalty starts to outweigh the heat transfer increase caused by the turbulators. The largest thermal performance coefficient was η = 1.6, for d/p = 0.025, θ = 45°, at Re = 3 000, and the lowest, η = 0.79, for d/p = 0.05, θ = 90°, at Re = 640. / Dissertation (MEng (Mechanical Engineering))--University of Pretoria, 2021. / Mechanical and Aeronautical Engineering / MEng (Mechanical Engineering) / Unrestricted

The objective of the first chapter of this thesis was to determine whether fungicide seed coatings constitute an effective strategy for increasing seedling recruitment in restoration scenarios in the Intermountain West. We tested a mixture of four fungicides that address potential fungal pathogens to bluebunch wheatgrass, a dominant bunchgrass that is commonly used in restoration. Across two sites and three years, we found that the fungicide seed coating increased emergence in five of the six sites and years, with an average increase of 59.1% over the control. There was a strong interaction (P < 0.001) between the effects of fungicide treatment, the year and the site on emergence. This interaction was likely related to the effects of the hydrothermal microsite environment on disease severity. Further research is necessary to fully understand the conditions under which fungicide seed coatings are most likely to be effective. The objectives the second chapter of this thesis were to 1) estimate the effects of golden eagle nest proximity to explosive disturbances on reproductive success given other relevant habitat variables (e.g. indices of topography and vegetation), and 2) determine the relative importance of nest proximity to explosive disturbances as a predictor of golden eagle reproductive success compared to other relevant habitat variables. Reproductive success data were collected from nesting territories within and surrounding land controlled and managed by the US Department of Defense. We fit the reproductive survey data using generalized linear mixed-effects models comprised of unique, hypothesis-based sets of habitat variables. We compared the models using AICc-based model selection processes. Given the best approximating model, we found no evidence that the likelihood of reproductive success was affected by nest proximity to explosive disturbances (P = 0.460). We further found nest proximity to explosive disturbances consistently ranked in the bottom 50% of relative variable importance. These results may indicate golden eagle tolerance or habituation to explosive military tests and trainings. Although the two chapters of this thesis are disjointed, they are loosely unified by the ecological importance of disturbance, invasive species, and restoration within the Great Basin ecoregion.

Surface reconstruction and 3D modeling is a challenging task, which has been explored for decades by the computer vision, computer graphics, and machine learning communities. It is fundamental to many applications such as robot navigation, animation and scene understanding, industrial control and medical diagnosis. In this dissertation, I take advantage of the consumer depth sensors for surface reconstruction. Considering its limited performance on capturing detailed surface geometry, a depth enhancement approach is proposed in the first place to recovery small and rich geometric details with captured depth and color sequence. In addition to enhancing its spatial resolution, I present a hybrid camera to improve the temporal resolution of consumer depth sensor and propose an optimization framework to capture high speed motion and generate high speed depth streams. Given the partial scans from the depth sensor, we also develop a novel fusion approach to build up complete and watertight human models with a template guided registration method. Finally, the problem of surface reconstruction for non-Lambertian objects, on which the current depth sensor fails, is addressed by exploiting multi-view images captured with a hand-held color camera and we propose a visual hull based approach to recovery the 3D model.