abstract: This research work demonstrates the process feasibility of Ultrasonic Filament Modeling process as a metal additive manufacturing process. Additive manufacturing (or 3d printing) is the method to manufacture 3d objects layer by layer. Current direct or indirect metal additive manufacturing processes either require a high power heat source like a laser or an electron beam, or require some kind of a post processing operation to produce net-shape fully-dense 3D components. The novel process of Ultrasonic Filament Modeling uses ultrasonic energy to achieve voxel deformation and inter-layer and intra-layer mass transport between voxels causing metallurgical bonding between the voxels. This enables the process to build net-shape 3D components at room temperature and ambient conditions. Two parallel mechanisms, ultrasonic softening and enhanced mass transport due to ultrasonic irradiation enable the voxel shaping and bonding respectively. This work investigates ultrasonic softening and the mass transport across voxels. Microstructural changes in aluminium during the voxel shaping have also been investigated. The temperature evolution during the process has been analyzed and presented in this work. / Dissertation/Thesis / Masters Thesis Engineering 2016

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This research focuses on the theoretical analysis, development and experimental evaluation of a water cooled Electromagnetic Acoustic Transducer (EMAT) specifically designed for high-temperature Guided Wave Testing (GWT). Its novel design and detailed calculation of its optimum operating conditions resulted in its effectiveness at high temperatures for both short (500oC) and long-term inspection (250oC). All the steps followed for the theoretical and experimental investigation of the limitations of the existing technology and the development of a probe that can overcome these boundaries are presented. Finite Element Analysis (FEA) was performed for the optimization of the EMAT design and estimation of its ultrasonic and thermal properties at room and high temperatures over time. The wave mode purity profile of the Periodic Permanent Magnet (PPM) EMAT was theoretically studied as well as the effect of temperature rise on its ultrasonic performance. Thermal and Computational Fluid Dynamics (CFD) analysis was accomplished for the EMAT design optimization and calculation of its optimum operating conditions. The experimental validation of the theoretical study was also accomplished. The novel water cooled EMAT was developed and experimentally evaluated regarding its ultrasonic and thermal response at room and high temperatures. An empirical method for the enhancement of EMAT performance and its SNR was established. The wave mode purity characteristics of PPM EMAT were experimentally investigated via Laser vibrometry tests, which agreed with FEA results. The impedance analysis and ultrasonic evaluation of the EMAT at both room and high temperatures against various operating conditions were linked and compared to the results obtained from the ultrasonic, thermal and fluid FEA. In all cases, the experimental study is in good agreement with the theoretical results.

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M.Tech. / It is difficult to manage a pregnancy when fetal age, health status or potential pregnancy risks are not known. The aim of this study was to assess the impact of routine ultrasound screening as compared to selective use of ultrasound in the mid-trimester of pregnancy, on women using South African government health services. The three objectives investigated included assessment of the availability of reliable menstrual histories in the study population, the influence of ultrasound dating on obstetric management and the effect of ultrasound on pregnancy outcome due to the early detection of high risk pregnancies. A cluster randomised trial of 962 women was performed to test the hypothesis that midtrimester routine ultrasound screening in low risk pregnancies would result in improved antenatal care and perinatal outcome. Groups of eligible pregnant women were randomly selected to have either a routine scan followed by normal antenatal care or routine antenatal care which only allows for the selective use of ultrasound, in line with South African Antenatal Care Policy. Statistical analysis of the results confirmed that ultrasound dating is a more accurate predictor of the expected date of delivery when compared to other dating methods. Improved pregnancy dating resulted in a significant reduction in induction of labour for post-term pregnancy in the ultrasound screening group, suggesting a positive effect of ultrasound screening on obstetric management. No improvement was demonstrated in perinatal morbidity or mortality. The early detection of anomalous fetuses only led to one therapeutic abortion. The study did not possess the statistical power to demonstrate improved outcomes when multiple pregnancies were detected early in pregnancy. Currently there appears to be no urgent need to implement a routine antenatal screening programme in the Gauteng public health sector. In view of the fact that a third of the participants indicated that they were unsure of menstrual dates, and one third of the participants in the ultrasound screening group presented with an unreliable menstrual history, it is proposed that unsure dates be considered as a valid indication for the selective use of ultrasound in mid-trimester pregnancy.

M.Tech. (Chiropractic) / The aim of this study is to compare Chiropractic Manipulative Therapy of the lumbar spine combined with Therapeutic Ultrasound Therapy over the adjacent lumbar paraspinal muscles to ascertain the most effective protocol in the treatment of Chronic Mechanical Lower Back Pain. Thirty participants with Chronic Mechanical Lower Back Pain between the ages of 18 and 35 years were recruited. Successful participants were randomly placed in two groups, of fifteen participants each, which would receive different treatment protocols according to their group allocation. Group One received Chiropractic Manipulative Therapy to lumbar spine restrictions. Group Two received Chiropractic Manipulative Therapy to the lumbar spine restrictions as well as Therapeutic Ultrasound Therapy to the adjacent paraspinal muscles. The participants completed a total of seven visits, including 6 treatments over 3 weeks. Subjective and Objective readings were taken on the first, fourth and seventh visits. Subjective readings from each participant were recorded using the Oswestry Disability Iindex and Numerical Pain Rating Scale. Objective readings were taken and recorded three times consecutively using a Pressure Algometer over the adjacent lumbar paraspinal muscles and a Digital Inclinometer to measure lumbar spine range of motions. The statistical data was analysed using the Friedman test, Mann-Whitney test and the Bonferroni test. The results demonstrated overall that both groups responded favourably to their specific treatment protocols, however no significant differences between groups was noted, highlighting the positive effects of the manipulation alone.

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