i Declaration I, Johann Richard Bredell, the undersigned, hereby declare that this thesis is my own original work. It is being submitted for the Degree of Master of Engineering (Mechanical) at the University of Stellenbosch. It has not been submitted, in its entirety or in part, for any degree or examination at any other University. …………………………… Signature of candidateThis ………. day of ………………….ii Abstract Forced draft air-cooled steam condensers (ACSCs) consisting of multiple fan units are used in direct cooled power plants to condense steam in a closed steam cycle. Axial flow fans located below an A-frame configuration of finned tube heat exchanger bundles, force ambient air through the system. In so doing, heat from the condensing steam is rejected to the environment via the finned tubes. The performance of an air-cooled system is proportional to the air mass flow rate and the temperature difference between the finned tubes and the ambient air. A variation in either will directly affect the efficiency of the steam turbines.Air flow distortions at the fan inlet caused by structures, wind and other fans may result in a significant reduction in flow rate as well as fan blade vibration. This phenomenon has an adverse affect on the cooling capacity of an ACSC, and consequently turbine performance, due to a decrease in air mass flow rate. In this study the effect of inlet flow distortions on fan performance (i.e. flow rate and fan shaft power) in an ACSC is numerically investigated by modelling a section (or sector) of such a system using the commercial computational fluid
Background. Injuries inflicted by gunshot wounds (GSWs) are an immense burden on the South African (SA) healthcare system. In 2005, Allard and Burch estimated SA state hospitals treated approximately 127 000 firearm victims annually and concluded that the cost of treating an abdominal GSW was approximately USD1 467 per patient. While the annual number of GSW injuries has decreased over the past decade, an estimated 54 870 firearm-related injuries occurred in SA in 2012. No study has estimated the burden of these GSWs from an orthopaedic perspective. Objective. To estimate the burden and average cost of treating GSW victims requiring orthopaedic interventions in an SA tertiary level hospital. Methods. This retrospective study surveyed more than 1 500 orthopaedic admissions over a 12-month period (2012) at Groote Schuur Hospital, Cape Town, SA. Chart review subsequently yielded data that allowed analysis of cost, theatre time, number and type of implants, duration of admission, diagnostic imaging studies performed, blood products used, laboratory studies ordered and medications administered. Results. A total of 111 patients with an average age of 28 years (range 13 -74) were identified. Each patient was hit by an average of 1.69 bullets (range 1 -7). These patients sustained a total of 147 fractures, the majority in the lower extremities. Ninety-five patients received surgical treatment for a total of 135 procedures, with a cumulative surgical theatre time of >306 hours. Theatre costs, excluding implants, were in excess of USD94 490. Eighty of the patients received a total of 99 implants during surgery, which raised theatre costs an additional USD53 381 cumulatively, or USD667 per patient. Patients remained hospitalised for an average of 9.75 days, and total ward costs exceeded USD130 400. Individual patient costs averaged about USD2 940 (ZAR24 945) per patient. Conclusion. This study assessed the burden of orthopaedic firearm injuries in SA. It was estimated that on average, treating an orthopaedic GSW patient cost USD2 940, used just over 3 hours of theatre time per operation, and necessitated a hospital bed for an average period of 9.75 days. Improved understanding of the high incidence of orthopaedic GSWs treated in an SA tertiary care trauma centre and the costs incurred will help the state healthcare system better prioritise orthopaedic trauma funding and training opportunities, while also supporting cost-saving measures, including redirection of financial resources to primary prevention initiatives.
Table grapes are commonly packed in multi‐layered packages consisting of cardboard carton, plastic liners and carry bag/pouch to maintain product quality along the cold chain. Each liner is characterized by the number and the size of perforations, which influence the environmental conditions around the produce inside the package. This study investigated the effects of different carton liners on the cooling rate and quality attributes of ‘Regal Seedless’ table grapes. Fruit quality attributes measured include weight loss, stem dehydration and browning, SO2 injury, decay, berry firmness and colour. Non‐perforated liners maintained relative humidity (RH) close to 100% during cold storage and during a 7 day shelf life period, which resulted in delaying the loss of stem quality but significantly (p ≤ 0.05) increasing the incidence of SO2 injury and berry drop during storage, as compared with perforated liners. Perforated liners improved fruit cooling rates but significantly (p ≤ 0.05) reduced RH. Low RH in perforated liners resulted in significant (p ≤ 0.05) increase in stem dehydration and browning as compared with non‐perforated liners. Berry firmness decreased by 78% after 42 days of storage at −0.5°C. Significant (p ≤ 0.05) differences in berry firmness between the different packages were observed only during the first 7 days of storage. Berry colour changed from greenish‐yellow to yellowish‐green in all types of plastic liner during the storage period. Fruit decay occurred in all packages after a 7 day shelf life, with the highest incidence of decay occurring in liners with less perforation. Copyright © 2011 John Wiley & Sons, Ltd.
Summary Background Risk of mortality following surgery in patients across Africa is twice as high as the global average. Most of these deaths occur on hospital wards after the surgery itself. We aimed to assess whether enhanced postoperative surveillance of adult surgical patients at high risk of postoperative morbidity or mortality in Africa could reduce 30-day in-hospital mortality. Methods We did a two-arm, open-label, cluster-randomised trial of hospitals (clusters) across Africa. Hospitals were eligible if they provided surgery with an overnight postoperative admission. Hospitals were randomly assigned through minimisation in recruitment blocks (1:1) to provide patients with either a package of enhanced postoperative surveillance interventions (admitting the patient to higher care ward, increasing the frequency of postoperative nursing observations, assigning the patient to a bed in view of the nursing station, allowing family members to stay in the ward, and placing a postoperative surveillance guide at the bedside) for those at high risk (ie, with African Surgical Outcomes Study Surgical Risk Calculator scores ≥10) and usual care for those at low risk (intervention group), or for all patients to receive usual postoperative care (control group). Health-care providers and participants were not masked, but data assessors were. The primary outcome was 30-day in-hospital mortality of patients at low and high risk, measured at the participant level. All analyses were done as allocated (by cluster) in all patients with available data. This trial is registered with ClinicalTrials.gov , NCT03853824 . Findings Between May 3, 2019, and July 27, 2020, 594 eligible hospitals indicated a desire to participate across 33 African countries; 332 (56%) were able to recruit participants and were included in analyses. We allocated 160 hospitals (13 275 patients) to provide enhanced postoperative surveillance and 172 hospitals (15 617 patients) to provide standard care. The mean age of participants was 37·1 years (SD 15·5) and 20 039 (69·4%) of 28 892 patients were women. 30-day in-hospital mortality occurred in 169 (1·3%) of 12 970 patients with mortality data in the intervention group and in 193 (1·3%) of 15 242 patients with mortality data in the control group (relative risk 0·96, 95% CI 0·69–1·33; p=0·79). 45 (0·2%) of 22 031 patients at low risk and 309 (5·6%) of 5500 patients at high risk died. No harms associated with either intervention were reported. Interpretation This intervention package did not decrease 30-day in-hospital mortality among surgical patients in Africa at high risk of postoperative morbidity or mortality. Further research is needed to develop interventions that prevent death from surgical complications in resource-limited hospitals across Africa. Funding Bill & Melinda Gates Foundation and the World Federati...
A bstract Aim The Ilizarov external fixator (IEF) is frequently used in trauma and elective orthopaedics. Many of its biomechanical variables (ring size, wire diameter, wire number, half pins vs wires, etc.) and their influence on stability and stiffness have been investigated. There is, however, a paucity in the literature regarding the influence of the connecting rod numbers and configurations between the rings on IEF stability. The primary aim of this biomechanical study was to compare the stability between four- and three-rod IEF configurations. Secondarily to assess the difference in stability between symmetrical and asymmetrical spacing of the IEF rods. Materials and methods A custom jig was designed to facilitate mounting of a basic two-ring IEF in a hydraulic press. Controlled centre and off-centre (thus simulated bending) axial loading was then applied across the frame. The configurations were loaded up to 4,000 N. The frame deformation was plotted and the data were then analysed and interpreted. Results Negligible differences were observed between different four- and three-rod configurations as long as the applied force at the loading point (LP) was within the area of support (AOS) created by the rods. The different four-rod constructs were always more stable than the three-rod constructs during bending. Conclusion There is comparable stiffness between a four-rod and a three-rod IEF construct as long as the LP is within the AOS created by the rods. A four-rod IEF is stiffer than a three-rod IEF in bending. Clinical significance This study will possibly change some paradigms regarding the planning and application of IEFs by Orthopaedics Traumatologists and Reconstruction Surgeons. How to cite this article Thiart G, Herbert C, Sivarasu S, et al. Influence of Different Connecting Rod Configurations on the Stability of the Ilizarov/TSF Frame: A Biomechanical Study. Strategies Trauma Limb Reconstr 2020;15(1):23–27.
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