Thesis (M.S.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaves 88-90). / xii, 90 leaves, bound ill. (some col.) 29 cm

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 92-96). / 111 leaves, bound ill. (some col.) 29 cm

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 78-82). / xiii, 82 leaves, bound ill. 29 cm

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M.Ing. / This dissertation covers a literature study of the reliability engineering, and this is then applied to the hospital oxygen supply system in order to determine the reliability of the system. The hospital oxygen supply system must comply with international and local legislation, which insists that the reliability of the system must be very high, since it supports life in the hospital. Since there were no previous studies conducted in terms of the oxygen supply system to the knowledge of the author, it definitely opens a new study field for the application of reliability engineering concepts. In the research it was found that no records were kept by the company on the failures occurring with the oxygen supply system. This increased the difficulty to calculate the actual reliability of the supply system. A reliability prediction was done, based on the failure rate data from a database. The reliability prediction of the .system was very low, and possibly not a very accurate prediction of the actual reliability of the system. The author therefore created a reliability calculation program, which calculates the reliability of the system and also keeps, an accurate failure data record on each component of the system. The main conclusion reached with this dissertation is that failure data feedback, and accurate records are a very important factor of reliability engineering. This may influence the company's ability to rectify design changes in their systems, as there is no idea where the failure occurred and how much money value is linked to the failures occurring.

M.Ing. / With an ever-increasing population and a decrease in availability of fresh water, the sustainable and secure supply of fresh water is a growing concern worldwide, and particularly so in South Africa. Plumbing systems have a significant impact on both the efficient use of water and water losses because high quality plumbing components can reduce wastage and leakage, while inferior components increase the risk of failures and leakage and can even have health impacts in case of leaching of toxic elements or contamination of drinking water. In recent years, South Africa has seen a plethora of imported and pirated plumbing components introduced onto the local market. While South African legislation requires that only plumbing components approved by the South African Bureau of Standards or Water Services Authorities (municipalities) shall be installed, it does not explicitly prohibit the importation and sale of non-compliant components. The availability of non-compliant components on the market combined with insufficient enforcement of legislation, have created a situation where many non-compliant components are installed, although the extent of this problem was not known at the start of the project. The study aimed to quantify the extent of non-compliant plumbing components installed in South Africa, as well as the impact this will have on future water demands and losses. Various research methods were used including literature reviews, surveys and interviews with role players, search of available plumbing components for sale in South Africa, on-site visits and analysis of some case studies. The study found that about 50% of plumbing components installed in South Africa do not comply with legal requirements. Because these components are of poor quality, they hurt the local industry whose components cost more in order to comply with SABS standards. Therefore, they suffer from reduced market share and lower profit margins, and South African job losses occur in the sector. In general, compliant Summary components are up to 135% more expensive than non-compliant components. This study also found that even plumbers who are IOPSA members, and therefore bound by a code of conduct to use only compliant components, install non-compliant components. The site visits to some government low-cost housing developments showed that less than 10% of the plumbing components installed were compliant, and a major problem with non-compliant components was leakage. Therefore if the situation does not change, on-site water leaks will remain a great concern in South Africa. In order to address this situation the main suggestions are better enforcement of legislation, better training and control of plumbers and restrictions on the importation of non-compliant components.

The most common management problem associated with irrigated agriculture is knowing when to apply irrigation and how much of it is required. This is termed irrigation scheduling. Despite numerous techniques and tools developed by the scientific community to aid and improve irrigation scheduling, surveys have shown that farmers growing the same crops in the same region use different amounts of water. This is because of low adoption rates of available irrigation scheduling aids and/or their poor application for various reasons ranging from cost, accessibility and simplicity of the methods. So, as part of a WRC funded project on using Wetting Front Detectors, we seek a simple approach that can be used to better manage irrigation using wetting front detectors (WFD). This prototype WFD was developed in Australia, and was designed to be simple so that it can be understood and used by farmers at any level of training. There are two versions; one is electronic called a FullStop and the other is mechanical, called the Machingilana, a sePedi word for a watchman. The mode of operation of this WFD is based on the physical properties of water movement in the soil or a porous media. The tool give a “Yes” or “No” answer to whether the water has penetrated to a specific depth, and that’s all the farmer needs to know to adjust his irrigation amount of interval according to a chosen algorithm. This experiment on wetting front detectors was undertaken at the University of Pretoria experimental station to: (1) Evaluate two different methods of using electronic wetting front detectors, (II) evaluating two different methods of using mechanical wetting front detectors, and (III) to compare the accuracy of the wetting front detector method against the neutron probe and a computer-based irrigation-scheduling model. Six treatments were evaluated. They were referred to as the Machingilana (MACH), crop factor (CF), FullStop 1 (FSI), FullStop 2 (FS2), neutron probe (NP) and Soil Water Balance model (SWB) treatment. The first four treatments used WFDs in different ways to manage irrigation. Lucerne (Medicago sativa, variety WL 525HQ) was chosen as experimental crop. The NP method was used as control treatment, given the acceptance and credibility this method has received from researchers. The aim was to use dry matter production per volume of water used as an indicator of treatment performance. However, it was later discovered that due to the extensive root system of Lucerne, the crop could compensate for either under- or over-irrigation and dry matter yield was not a good indicator of treatment performance. Statistical analysis of the dry matter yield data collected from three cycles revealed that the treatments were not significantly different at a 5% confidence level, although there was great variation in total amount of irrigation applied to each treatment per growth cycle. This is due to the fact that the crop was able to mine into deeper soil layers for water, although this strategy would not be sustainable in the long run without extra irrigation applied. In the light of this, the trend in soil water deficit obtained with the neutron water meter for each treatment was used to evaluate the six treatments. The four treatments based on WFDs (Machingilana, FS1, FS2 and CF) performed comparatively well to the control and SWB model treatments. However, this is not without discrepancies in all the WFD treatments or the control and SWB model treatment, but the problems associated with each treatment’s successes or failures have been outlined, and with follow-up research, those problems can be rectified. It is concluded that WFDs can be valuable, simple and affordable tools to better manage irrigation, provided appropriate guidelines for using them are applied. / Dissertation (MSc (Agriculture))--University of Pretoria, 2005. / Plant Production and Soil Science / unrestricted

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