The bulge forming process is a method for shaping tubular components using an internal hydrostatic pressure combined with an axial compressive force. Initial investigations involved carrying out an extensive literature survey to determine the components which could be formed and the types of machines which have been used. Subsequent to this, initial tests were carried out using a previously designed die and tool block in conjunction with a compression testing machine. In these tests copper tubes were formed into expander/reducers and cross pieces by manual adjustment of the axial force and internal pressure. Having obtained experience of the difficulties associated with this die and toolblock, and the loading requirements necessary for theforming process, a new bulge forming machine was designed. The design of the machine was based on the following main criteria: (i) The machine should be free standing and self contained. (ii) The axial deformation of the ends of the tube blank should besynchronised to allow the bulge to form centrally on the tube. (iii) The internal bulge forming pressure should be externallycontrollable during the forming process. (iv) The design should incorporate facilities for subsequent automatic control using a micro-processor/computer. On the basis of these requirements, a machine was designed, built andcommissioned. After correcting a few problems encountered in the commissioning of the machine, a series of tests were carried out, forming tee and cross pieces from copper tube of two different wall thicknesses. These were found to be fairly easy to produce on this new machine. From the resulting components, formed at various combinations of internal pressure and axial compressive force, the limits for a successful forming operation were established. Further analysis of these components was then undertaken to evaluate the effects of the internal pressure and axial compressive force on the bulge height and the wall thickness in the deformation zone. From these results, which have been illustrated graphically, the greatest effect on the resulting bulge can seen to be the axial compressive force. An extension of a theoretical analysis has also been presented, which predicts the wall thickness distribution around the bulge zone. Comparison of these predictions with the experimental wall thickness distributions shows fairly good agreement, especially at the root and tip of the side branch.

In an effort to increase the available capacity of a lead-acid battery, the effects of pulsed discharge currents as opposed to the effects of continuous discharge currents on the battery were investigated, for a wide range of frequency, mark/space ratio and peak current of the discharge waveform. It was found that for certain conditions of pulsed discharge, the use of pulsed currents can provide a considerable increase in available capacity when compared to that obtained from using conventional continuous currents. In order to increase the efficiency and reduce the time of the lead-acid battery charge, the effects of using pulsed charging currents with ·and without depolarisation discharge pulses interspersed throughout the charging period as opposed to using conventional continuous current charging was investigated. For the tests performed, it was found that pulsed current charging without depolarisation pulses offers no advantages over conventional continuous current charging for three-stage and single-stage charging techniques. The use of pulsed currents with depolarisation pulses was found to be less effective than using conventional continuous current or straight pulsed current charging. A model for the cell terminal voltage and state-of-charge of the battery is derived from the results of an extensive series of tests performed by the author. In this writing for the first time a model accurately accounts for the dependence of recuperation, regeneration and wide variations in the discharge rate on the temperature of the electrolyte and the effects of these factors on the terminal voltage and state-of-charge. Additionally, for the first time a comprehensive model for use with pulsed discharge currents is derived. The models were tested under dynamic conditions of battery operation and were found to be able to predict battery state to a high degree of accuracy, and were also found to be more accurate than existing models.

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A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering, 2018 / Trans-radial amputees struggle daily when it comes to performing one or more of their activities of daily living (ADLs). Myoelectric prosthetic hands have recently been developed to a point where they can assist trans-radial amputees to perform their ADLs,making use of electromyographic (EMG) signals to drive the prosthetic hand. In order to function, a myoelectric prosthetic hand requires multiple electrodes to collect EMG data (denoted a channel) remaining forearm muscles, aswell as complex classification algorithms to process the data in real time. The focus of research in this field is directed at developing or improving the classification algorithms, often ignoring the optimisation of the EMG electrodes themselves. The electrodes can be optimised either by position or number, however in research where electrodes are optimised, classification accuracy is used as a measure of success for the optimisation, which requires optimisation of the classification algorithm itself. The focus of the current study was to develop a method that could optimise the EMG electrode placements and number, without needing a classification algorithm. A pre-existing 8-EMG channel dataset for seven subjects was used. The experimental method involved generating combinations of two, three and four channels from which optimal channel combinations were selected. The optimisation process made use of principal component analysis (PCA), which generated a reduced-quality model for each potential combination. The reduced-quality and original models were compared, and the optimal channel combinations identified from those comparisons with the least error. The success of the optimisation was defined as the impact that a reduced number of EMG channels would have on the percentage of variance retained (PVR) by the optimal channel combinations. The optimal channels for each subject were compared, and although each subject displayed variation, in general the important channels were identified as those that were located over the Extensor digitorum (ED), Flexor pollicis longus (FPL), Flexor digitorum superficialis (FDS), Flexor digitorum profundis (FDP), and iii Extensor carpi ulnaris (ECU) muscles. The optimal channel combinations for all subjects together had an average of 64.5% PVR for the 2-channel setup, 73.9% for the 3-channel setup, and 76.5% for the 4-channel setup. This shows that it is possible to reduce the number of channels and retain a large amount of variance in the data without the use of classification algorithms. / XL2019

Master of Science / Department of Statistics / Dallas E. Johnson / Variability is inherent in most data and often it is useful to study the variability so scientists are able to make more accurate statements about their data. One of the most popular ways of analyzing variance in data is by making use of a one-way ANOVA which consists of partitioning the variability among observations into components of variability corresponding to between groups and within groups. One then has σ(subY)(superscript 2)=σ (sub A) (superscript)2+σ(sub e)(superscript 2). Thus there are two variance components. In certain situations, in addition to estimating these components of variance, it is important to estimate functions of the variance components. This report is devoted to methods for constructing confidence intervals for three particular functions of variance components in the unbalanced One- way random effects models. In order to compare the performance of the methods, simulations were conducted using SAS® and the results were compared across several scenarios based on the number of groups, the number of observations within each group, and the value of sigma (sub A)(superscript 2).

The study of anti-stall techniques for fans and compressors has never been more significant, since the potential applications were recognised in gas turbines, tunnel ventilation (jet fans) and industrial process where fans/compressors would benefit from the devices. This thesis will discuss the techniques achieving competitiveness by modifying the conventional casing design of the fan and compressor, which is referred to as casing treatments, taking into account the change of maximum efficiency and flow range. An experimental investigation to examine the influence of the vaned recess casing treatment on stall margin, operating efficiency and flow field of a low speed axial flow fan with aerospace type blade loading is presented. Different geometrical designs of the vaned passages were examined and more than 65% of stall margin improvements and over twice pressure rise with insignificant peak efficiency change were obtained. Experiments to examine the effect of casing treatments on the flow field were carried out using the same fan rig with a tip clearance of 1.2% of the blade height. A high frequency data acquisition system including both hardware and software was developed and the 3-D flow measurements with a slanted hot-wire were undertaken. The first detailed results of flow measurements associated with the vaned recess casing treatment are presented, including both time-averaged and ensemble-averaged measurement results. The flow features in both the solid casing and treated casing builds are captured and comparison between the builds presented. The results revealed that the stall margin improvement due to the casing treatment was not achieved by reducing the incidence nor by increasing the total pressure in the tip region. It appeared that the combined functions of elimination of the whirling flow, the removal of the randomness of the inlet flow and modification of the tip clearance flow are salient features associated with the mechanism of the treatment. The steady flow field of the test fan with various tip clearances has also been simulated in the rotating frame with computational fluid dynamics (CFD) to investigate the clearance effect on the end-wall flow development and to elucidate the behaviour of the tip leakage flow, and hopefully shed more light onto the flow phenomena involved.

Master of Science / Department of Agronomy / Ignacio Ciampitti / Sorghum [Sorghum bicolor (L.) Moench] has greater drought resilience than many other crops, producing food in the most stressful environments. Sorghum is a reasonable crop choice for farmers working with limited-water supply. The objective of this study was to compare sorghum hybrids differing in yield strategies under varying water supply environments. Yield, biomass, grain harvest index (HI), and yield components (seed number and seed weight) were compared in both rainfed and irrigated situations. Field experiments were established in 2014 and 2015 at Topeka, Scandia, Hutchinson, Garden City, and Tribune, KS. Three sorghum hybrids (Pioneer 85Y40, Pioneer 84G62, and Dekalb 53-67) with different yield potentials at varying water supply were studied. Hybrids 85Y40 and 84G62 tended to have greater yields than hybrid 53-67 when the environment's average yield level was greater than 8.5 Mg haˉ¹. The opposite scenario where hybrid 53-67 had greater yields than the other two hybrids tended to occur for environments yielding less than 8.5 Mg haˉ¹. Both biomass and HI were significantly correlated with grain yield (r values of 0.62 and 0.32 respectively), with biomass having an overall stronger correlation than HI in all environments. In yield group 3 (<8.5 Mg haˉ¹), biomass was much more strongly correlated (r=0.85) to yield than in the yield groups 1 and 2 (>9.5 Mg haˉ¹ and 8.5-9.5 Mg haˉ¹ with r values of 0.35 and 0.52 respectively) suggesting that biomass production is of utmost importance for yield production in drought prone environments. Harvest index on the other hand had a much stronger correlation with yield in group 1 (r=0.62) when compared to group 2 and 3 (r 0.13 and 0.36 respectively) showing the importance of not only biomass, but also of HI to maximize yield in high yielding environments. Hybrids 85Y40 and 84G62 had larger HI values relating to the yield trends in the highest yielding environments. Seed number had a stronger correlation with yield (r=0.77) than seed weight (r=0.37) supporting the importance of increasing seed number to improve yield in sorghum.

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