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The R6 procedure is used for the prevention and prediction of crack behaviour and other defects in the reactor pressure vessel(RPV). The RPV material is an upper-bainitic, low alloy steel structure, which deforms inhomogeneously when yielding. The current codes that are used to design and calculate the fracture, within an RPV, assume that the material yields continuously as the size of the L¨uders strain is less than 2%. However, the work of Wenman et al[1] has shown that the inclusion of a L¨uders band during calculations can reduce the residual stress in a material, when compared to standard work-hardening models and, consequently, reduces the amount of conservatism. The objective of the research was to determine whether Wenman’s finding could be generalised and therefore initiate a re-evaluation of R6 procedure, when looking into materials that yield discontinuously. This required further investigation into L¨uders bands, such as using failure assessment diagrams (FADs). The findings from FADs showed that at the temperature range for an RPV steel at -155±C for different micro-structures (assuming that the material deforms homogeneously), this reduced the amount of conservatism. However, at fracture toughness values more representative of room temperature behaviour, the converse was true. That is, assuming a discontinuous yield point reduced the amount of conservatism. It was also shown that the tempered martensite structure could be used as an alternative to the current upper bainitic, low alloy steel that is used in RPVs. Further insight is gained into the nature of a L¨uders band, by developing a theoretical model that showed explicit relations between L¨uders strain and the mean free-path(ferrite path), dislocation density and the grain-size. It was also shown that an explicit relation between the L¨uders strain and carbon content was possible from known data, which a new parameter Á was derived, and is the derivative of the work-hardening exponent with respect to the lower yield stress. / © Crown Copyright

M.Sc. (Geology) / The purpose of this work was to attempt to understand the behaviour of the ground around a series of holes bored in gold bearing rock by a reef boring machine. Furthermore this ground behaviour is compared with existing theoretical concepts of rock behaviour. The experimental boring site and the sequence of events at that site are described. The state of the rock surrounding the excavations is observed to deteriorate with increase in mining. The fracturing observed is characterised by spalling on the sides of the bored holes. This spalling increases in severity with closeness to the bored out region. Calculations of the stress acting on the sides of the bored holes were made from elastic theory using two techniques. One of these was a quick graphical technique and the other was a more complex analytical one. The analytical technique was used as a check on the results of the graphical technique. Finally the extent of spalling on the sides of the holes is compared with the theoretical stresses. A close correlation is found, and spalling appears to start when the stress level reaches the strength of the rock. As the stress level increases spalling increases in severity until such time as the ground around the bored area is fractured by large through going fractures. At this stage holes bored in this ground no longer spall.

Background: the incidence of high blood pressure in South Africa has increased over the past few decades (Chopra et al., 2009; Seedat, 2012). Public health scientists have warned that this trend might be correlated to a multitude of unhealthy behaviors at the individual level, including heavy alcohol consumption (Chopra et al., 2009; Hillbom et al., 2011; Seedat, 2012; Strogatz et al., 1991). Previous studies have established a synergistic effect between alcohol consumption and high blood pressure leading to an increased risk of cardiovascular and renal disease within countries of the global north (Abe et al., 1994; Keil et al., 1993; Steyn et al., 1997). Not only is this trend under studied in South Africa, the severity of alcohol’s impact on blood pressure remains to be discerned in the country. Objectives: shedding light on the epidemiological and social factors impacting the association between alcohol consumption and blood pressure. Based on previous observations, it is hypothesized that certain epidemiological factors will be strongly associated with high blood pressure in the presence of alcohol consumption. Findings from this research would inform healthcare professionals on the diagnosis of high blood pressure cases in the South African population as this research aims to identify the factors associated with high blood pressure, thus, alleviating the problem of underdiagnosed cases that have been found to incur heavy costs on the healthcare system (Chopra et al., 2009; Seedat, 2012). Methods: in the present study, we have investigated social and epidemiological factors, as informed by previous research, which are associated with blood pressure in the presence of alcohol consumption within a South African context by using data collected from the South African Demographic and Health Survey (SADHS). Conclusion: Our findings indicate a correlation between ethnicity and blood pressure, as well as having a heart attack and high blood pressure measurements.

The aerodynamics of a set of two-dimensional elliptic cylinders with eccentricity of 0.8 and 0.6 is studied experimentally during the organised wake condition. The dynamic calibration of the transducer used for measurement of fluctuating pressures is described in detail. The data on Strouhal number, unsteady pressures and wake geometry are presented as a function of angle of attack during static condition of the models. The effect of Reynolds number on the fluctuating pressure is also examined. The results indicate dependence of the unsteady forces on Reynolds number at zero angle of attack. Basing the Strouhal number on projected width appears to reduce its dependence on the angle of attack of the models. The existence of a large phase angle between the fluctuating pressures is of interest. The wake geometry study indicates a gradual reduction in the ratio of the lateral to the longitudinal spacing with increase in angle of attack. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

Professional skepticism is a critical component of audit practice and current auditing standards direct auditors to remain skeptical throughout the duration of each audit engagement. Despite the importance and prevalence of an emphasis on professional skepticism throughout auditing standards, evidence indicates that auditors often fail to exercise an appropriate degree of professional skepticism. Prior accounting research suggests that auditors’ professionally skeptical behavior is affected by individual personality traits as well as situational (state) influences, whereby both factors contribute to auditor professional skepticism. Yet, prior research has primarily focused on trait skepticism; and little research to date has investigated the concept of state skepticism. The purpose if this research study is to experimentally investigate the impact of time pressure and trait skepticism on state skepticism, and to test a potential debiasing procedure on the impact of time pressure on state skepticism. In addition, this study examines the influence of both skepticism types on skeptical behavior.This research offers several contributions to accounting literature and practice. First, I contribute to the existing debate regarding the influences of professional skepticism by providing evidence that professional skepticism may be categorized as a temporary state, induced by situational aspects, in addition to being classified as an enduring trait. Second, I identify certain situational conditions which create differences in the level of state professional skepticism exhibited within an auditing context. Lastly, my findings may also be important to audit firms as they consider tools within their training arsenal equipped to promote an appropriate level of professional skepticism among employees. If auditor skepticism can be influenced by the frames they are provided, then audit firms may create an environment that promotes consistency in auditors’ application of professional skepticism, simply by engaging in goal framing.

Soot is a common byproduct of hydrocarbon based combustion systems. It poses a risk to human and environmental health, and can negatively or positively affect combustor performance. As a result, there is significant interest in understanding soot formation in order to better control it. More recently, the need to study soot formation in engine relevant conditions has become apparent. One engine relevant parameter that has had little focus is the ambient pressure. This body of work focuses on the formation of soot in elevated pressure environments, and a number of investigations are carried out with this purpose. Laminar coflow diffusion flames are used as steady, simple soot producers. First, a commonly studied flame configuration is further characterized. Coflow flames are frequently used for fundamental flame studies, particularly at elevated pressures. However, they are more susceptible to buoyancy induced instabilities at elevated pressures. The velocity of the coflow is known to have an effect on flame stability and soot formation, though these have not been characterized at elevated pressures. A series of flames are investigated covering a range of flowrates, pressures, and nozzle diameters. The stability limits of coflow flames in this range is investigated. Additionally, an alternative strategy for scaling these flames to elevated pressures is proposed. Finally, the effect of coflow rate on soot formation is evaluated. Identification of fundamental flames for coordinated research can facilitate our understanding of soot formation. The next study of this work focuses on adding soot concentration and particle size information to an existing fundamental flame dataset for the purpose of numerical model validation. Soot volume fraction and average particle diameters are successfully measured in nitrogen-diluted ethylene-air laminar coflow flames at pressures of 4, 8, 12, and 16 atm. An increase in particle size with pressure is found up to 12 atm, where particle sizes plateau. Particle size in the annulus is more sensitive to pressure. Next, the development of an alternative particle size measuring technique is studied. Time Resolved Laser Induced Incandescence (TiRe-LII) is a commonly used technique to measure soot concentrations and particle size at atmospheric pressure. However, Laser Induced Incandescence (LII) models suffer from an incomplete understanding of the effects of elevated pressures on the absorption, annealing, and cooling of soot. The present study focuses on what affect the laser temporal pulse shape and duration may have on particle sizing. TiRe-LII in flames at 1 and 15 bar is carried out, using laser pulses with tophat or Gaussian temporal profiles of varying duration. Mono-disperse equivalent primary particle diameters are calculated using the KAUST LII model. Little difference in particle sizing is found for different laser pulses. However, this data will be useful for validating the KAUST LII model when absorption and poly-dispersion are accounted for. In an effort to move one step closer to logistical fuel studies, the sooting tendencies of a number of liquid fuels are studied at pressures up to 10. Of parallel relevance, a sooting index for surrogate development is evaluated for elevated pressure applications. The Yield Sooting Index (YSI) methodology is applied to 11 normal, cyclic, and branched alkanes. When referencing to two n-alkane fuels, the YSI of n-alkanes determined at atmospheric pressures accurately reflects the relative sooting tendencies of these fuels at elevated pressures. The relative sooting tendencies of cyclo- and methyl-alkanes have a lower pressure sensitivity than n-alkanes.

A thesis submitted to the Faculty of Health Sciences, University of the Witwatersrand, for the degree of Doctor of Philosophy. Johannesburg, South Africa September 2017. / Although brachial blood pressure (BP) is a well-recognized risk factor for predicting cardiovascular events, aspects of aortic BP may enhance risk prediction. Pulse pressure (PP) is amplified from the aorta to peripheral arteries and variations in differences between brachial and aortic PP (PP amplification) are determined by factors that influence either the aortic forward (Pf) or backward (Pb)(reflected) pressure waves. Although aortic Pb may be more important than Pf in mediating cardiovascular risk, the best approach to assessing backward wave function (augmentation pressures [Pa] and index [AIx] or wave separation analysis); the relative impact of aortic Pb versus Pf on cardiovascular damage; and whether the ability of aortic-to-brachial PP amplification (PPamp) to add to risk prediction reflects backward or forward wave effects, is uncertain. In the present thesis I therefore first assessed in 808 community participants whether gender influences relations between Pa or AIx and left ventricular mass (LVM), a well-accepted end-organ measure. Aortic haemodynamics were determined using radial applanation tonometry and SphygmoCor software and LVM from echocardiography. In men, both AIx derived from Pa/central aortic PP (Pa/PPc) (p<0.01) and AIx derived from the second peak/first peak (P2/P1) of the aortic pulse wave (p<0.0005) were associated with LVM. In contrast, in women neither AIx derived from Pa/PPc (p=0.08) nor AIx derived from P2/P1 (p=0.17) were associated with LVM. Both the strength of the correlations (p<0.001 and p<0.0005) and the slope of the AIx-LVM relationships (p=0.001 and p<0.0005) were greater in men as compared to women. Therefore, in the present study I show that AIx is independently associated with LVMI in men, but not in women. I subsequently evaluated whether in women, measures of aortic systolic pressure augmentation (Pa or AIx) underestimate the effects of reflected waves on cardiovascular risk or whether Pb plays little role in cardiovascular risk prediction. In the same community sample I therefore evaluated sex-specific contributions of reflected (Pb and the reflection index [RI]) versus augmented (Pa and AIx) pressure wave indices to iii variations in PPc (n=1185, 65.0% women), and LVM (n=793, 64.9% women). Aortic Pb and Pf were determined using wave separation analysis. In both women and in men, independent of confounders, RI and Pb contributed more than Pf, whilst Pa and AIx contributed less than incident wave pressure (Pi) to variations in PPc (p<0.0001 for comparison of partial r values). In both men and in women Pb contributed more than Pf (p<0.05) to variations in LVM. Although in men Pa (partial r=0.33, p<0.0001) contributed to a similar extent as Pi ((partial r=0.34, p<0.0001) to variations in LVMI, in women Pa (partial r=0.05, p=0.36) failed to contribute to LVM, whilst Pi was significantly associated with LVM (partial r=0.30, p<0.0001). Similar results were obtained with AIx as opposed to Pa in the regression models. Therefore, in both women and in men, Pb is more closely associated with PPc and LVM than Pf, but indices of aortic pressure augmentation markedly underestimate these effects, particularly in women. As the relative impact of aortic Pb as compared to Pf on cardiovascular damage independent of brachial BP is uncertain, in 1174 participants from a community sample I subsequently assessed the relative impact of Pb and Pf on variations in LVM (n=786), aortic pulse wave velocity (PWV)(n=1019), carotid intima-media thickness (IMT)(n=578), transmitral early-to-late LV diastolic velocity (E/A)(n=779) and estimated glomerular filtration rate (eGFR)(n=1174). Independent of mean arterial pressure and confounders, PPc and both Pb and Pf were associated with end-organ measures or damage (p<0.05 to <0.0001). With adjustments for brachial PP and confounders, Pb remained directly associated with LVM (partial r=0.10, p<0.01), PWV (partial r=0.28, p<0.0001), and IMT (partial r=0.28, p<0.0001), and inversely associated with E/A (partial r=-0.31, p<0.0001) and eGFR (partial r=-0.14, p<0.0001). Similar relations were noted with the presence of end-organ damage (p<0.05 to <0.0001). In contrast, with adjustments for brachial PP and confounders, Pf no longer retained direct relations with LVM, PWV, and IMT or inverse relations with E/A and eGFR. Adjustments for Pb, but not Pf diminished brachial PP-independent relationships between PPc and end-organ measures. Thus, although both Pf and Pb contribute to end-organ measures and damage, independent of brachial iv BP, the impact of aortic BP is accounted for largely by Pb. PPamp is independently associated with cardiovascular outcomes. However, the aortic functional change most likely to account for this effect is uncertain. In 706 community participants I subsequently aimed to identify the aortic functional change that accounts for relations between PPamp and LVM. In multivariate models with the inclusion of brachial PP, 1/PPamp (partial r=0.12, p<0.005), Pb (partial r=0,09, p<0.05), and aortic PWV (partial r=0.09, p<0.05) were independently associated with LVMI. Similarly, in multivariate models with the inclusion of brachial PP, 1/PPamp (p<0.005), Pb (p<0.01), and aortic PWV (p<0.01) were independently associated with LV hypertrophy (LVH). With adjustments for Pb, the brachial PP-independent relationships between 1/PPamp and LVMI or LVH were abolished (p>0.08 for both). However, adjustments for PWV failed to modify brachial PP-independent relations between 1/PPamp and LVMI or LVH. Hence, independent relations between PPamp and LVM or LVH are largely accounted for by Pb. In conclusion, in the present thesis I show that the use of augmented pressures underestimates the impact of reflected pressure wave effects on end-organs, particularly in women; that brachial BP-independent relations between aortic BP and end organs is determined largely by Pb and that relations between PPamp and end organ measures is largely accounted for by Pb. These findings add to our understanding of the adverse effects of aortic functional changes on the cardiovascular system and suggest cost-effective approaches to add to risk prediction. / LG2018

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