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Surface-strip coal mine rehabilitation planning in South Africa and Australia is immature. Rehabilitation risk assessment, despite being advocated by leading practice guidelines and in some instances by legislation, is conducted with minimum requirements often met by rehabilitation professionals. Specialist data is gathered during mine approval and for the environmental impact assessment process. However, the focus of this is toward assessing mining impacts and not for rehabilitation risk assessment. Quantitative, integrated, multi-disciplinary rehabilitation risk assessment is seldom undertaken. This thesis provides a methodology towards the development of a quantitative, integrative, multi-disciplinary rehabilitation risk assessment model. Its purpose being to 'profile' surface-strip coal mine sites, in terms of their rehabilitation risk and potential for rehabilitation failure, from the outset of mine operations, with adjustments possible progressively during mine operations. The methodology was developed by first reviewing techniques suitable for the development of the model, as well as techniques developed by others. Bayesian networks (BN) were found to be the most suited. A R2AIN framework was then provided as a process towards developing several BN risk event models that can amalgamate to form a synthesis rehabilitation risk assessment model. A case study soil compaction BN model was used to demonstrate the framework in South Africa and Australia. The case study showed that it is possible to integrate and quantify rehabilitation risk, and most importantly to segregate risk into discrete contributing multidisciplines for analysis. Risk percentages can be calculated per multi-discipline, per mine phase, per site, to aid site risk ‘profiling’. It is recommended that further risk event BN models be prioritised for development and that a rehabilitation risk assessment model be developed to synthesise these into one model. This will require continuous improvements in the method, to build confidence, including extensive risk event and synthesis BN model evaluation and testing; improved BN input node states and values; and simplification of the conditional probability table construction method. Adaptation to other mining types, development activities and other regions should be investigated, as well as spatial linkages to geographic information systems. This research contribution improves upfront mine rehabilitation planning and decision making, providing improved tools and techniques than what currently exist. / Thesis (PhD)--University of Pretoria, 2020. / Geography, Geoinformatics and Meteorology / PhD / Unrestricted

In January this year, Region Västerbotten announced that the maternity ward in Lycksele would be closed until further notice. This paper is a case study of the closure of the maternity ward in Lycksele, located within the rural parts of northern Sweden. Previous research has focused on maternity ward closures in Canada and Australia whereas studies on maternity wards in northern Sweden is limited. Since large parts of northern Sweden consist of sparsely populated areas, the closure of Lycksele BB has resulted in women having to travel long distances to receive care. This paper seeks to provide a deeper understanding of the consequences of the closure of Lycksele BB by examining (1) what feelings women experience and how they manage these feelings, (2) the consequences of the maternity ward closure on women’s physical and mental health and (3) the consequences of the maternity ward closure in relation to the rural parts of northern Sweden. This study has been carried out by using a qualitative approach by conducting semi-structured interviews with two pregnant women, two mothers, and two midwives. The findings in this study show that women develop strategies to mitigate feelings of insecurity and anxiety. Both pregnant women and midwives create strategies to feel a stronger sense of control in an otherwise unpredictable situation. This contributes to major consequences for women’s mental and physical health as women are faced with new challenges, affecting their reproductive health and care. The findings also show that the closure of Lycksele BB is only a stepping stone for further welfare cuts which can result in people moving away from these sparsely populated areas. This study concludes that the issue goes beyond the closure of the maternity ward in Lycksele and raises bigger questions around the future of the rural parts of northern Sweden.

Fatigue-crack-growth-rate tests were conducted on compact tension specimens made of 7050-T7451 aluminum alloy and 9310 steel. Compact tension specimens were tested over a wide range of load ratios (0.1 less than, or equal to R less than, or equal to 0.9) to generate crack-growth-rate data from threshold to near fracture. Three methods were used to generate near threshold data. A crack-closure analysis was performed on both materials using the FASTRAN crack-closure model. The crack-growth-rate data for each material correlated very well and each collapsed onto a nearly unique curve in the low- and mid-rate regimes using the strip-yield model in the FASTRAN life-prediction code. For the 7050 alloy, a constraint factor of α = 1.8 was required, while for the 9310 steel α = 2.5 worked very well in correlating the test data over a very wide range in R values and rates from threshold to near fracture.

The first part of this dissertation employs a three-dimensional elastic-plastic finite element model of straight-through crack growth to correlate four well-known methodologies characterizing fatigue crack closure. The compliance offset and the adjusted compliance ratio (ACR) are experimental methods, whereas the node displacement and the contact stress methods are numerical approaches. Evolutions of crack closure from all four methodologies are compared for a numerical model of a single edge-cracked tension specimen subjected to different levels of constant amplitude cyclic loading. In the second part, a detailed two dimensional stress analysis is conducted for a single pin-joint under plane stress conditions. This study investigates the influence of material nonlinearity, friction, and pre-existing residual stresses from cold-working process on the local radial and hoop stress levels around the pin-loaded hole. Next, the beneficial influence of cold working process is quantified by computing the Mode I stress intensity factors style='mso-bidiont-style:normal'>KI for a single radial crack eanating from a side of a loaded hole. Two different loading configurations are considered: (a) an open hole in tension, (b) a pin-loaded hole. The stress intensity factors are computed using the J integral solutions and the weight functions specific to the crack configuration. The reductions in KI values due to different levels of cold-working process are presented for a range of crack lengths. The final part of the research involves a numerical investigation of an on-line crack compliance technique that is used for experimental measurements of residual stress fields along the crack growth path. A finite rectangular sheet is considered with a single crack emanating from a side of a central hole. The residual stress field is introduced around the hole by cold-working simulation. As part of validation, the normalized residual stress intensity factors computed using the on-line crack compliance technique are compared with those from the style='mso-bidiont-style:normal'>J-integral approach for the case of elastic crack growth. The influence of crack tip plasticity on the performance of the on-line crack compliance technique is studied by comparing the solutions of the elastic and elastic-plastic crack growth models.

Fatigue and crack-growth tests were conducted on 7050-T7451 aluminum alloy under a wide range of loading conditions. Crack-growth tests were conducted on compact, C(T), specimens under constant-amplitude loading, single-spike overloads, and a simulated aircraft spectrum loading. Fatigue tests were also conducted on single-edge-notch bend, SEN(B), specimens under constant-amplitude loading and three aircraft load spectra. The FASTRAN, life-prediction code, was used to make crack-growth predictions on the C(T) specimens; and to make fatigue-life calculations using a 12-micrometer initial flaw size at the center of the edge-notch on the SEN(B) specimens. The predictions agreed fairly well with most of the tests, except the model was unconservative on the single-spike overload tests and the severe spectrum Mini-TWIST+ Level 1 tests. The discrepancy was suspected to be caused by a low constraint factor and/or crack paths meandering around overload plastic zones. A roughness- and plasticity-induced crack-closure model would be needed to improve the model.

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Introduction: Transseptal puncture (TSP) is challenging in patients with prior percutaneous atrial septal defect (ASD) occluder. We aimed to perform a systematic review and meta-analysis of the safety and efficacy of catheter ablation for atrial fibrillation (AF) in patients with percutaneous ASD occluder. Methods: We searched PubMed, Medline, Embase, Ovid, and Cochrane for studies reporting results of AF ablation (freedom from AF, fluoroscopy/procedure time, and complications) in patients with percutaneous ASD occluders. Results: Three studies with a total of 64 patients met inclusion criteria. The success rate of TSP was 100%. All patients (but one) underwent TSP under fluoroscopic and intracardiac echocardiography guidance. Freedom from AF was achieved in 77.7% (95% confidence interval [CI]: 65.7–86.3) patients. In the subgroup analysis, comparing septal versus device puncture, no significant difference in recurrence of AF was observed (23.07% vs. 16.66%; risk ratio: 1.18; 95% CI: 0.35–4.00; p =.79, respectively). The total fluoroscopy time was not significantly different in patients with TSP via native septum or device (43.50 vs. 70.67 min; p =.44), total procedural time was significantly longer with TSP via the closure device (237.3 vs. 180 min; p =.004) compared with the native septum. There were no device dislodgement or residual interatrial shunt during the follow-up period. Conclusion: Catheter ablation for AF in patients with prior percutaneous ASD closure device is feasible and safe with favorable long-term outcomes.