No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

Interest in evaluating the performance and safety of offshore oil and gas platforms has been expanding due to the growing world energy supply and recent offshore catastrophes. In order to accurately assess the reliability of an offshore platform, all relevant uncertainties must be properly accounted for. This necessitates the development of a probabilistic demand model that accounts for the relevant uncertainties and model errors. In this study, a probabilistic demand model is developed to assess the deformation demand on asymmetric offshore jacket platforms subject to wave and current loadings. The probabilistic model is constructed by adding correction terms and a model error to an existing deterministic deformation demand model. The correction terms are developed to capture the bias inherent in the deterministic model. The model error is developed to capture the accuracy of the model. The correction terms and model errors are estimated through a Bayesian approach using simulation data obtained from detailed dynamic analyses of a set of representative asymmetric offshore platform configurations. The proposed demand model provides accurate and unbiased estimates of the deformation demand on offshore jacket platforms. The developed probabilistic demand model is then used to assess the reliability of a typical offshore platform considering serviceability and ultimate performance levels. In addition, a sensitivity analysis is conducted to assess the effect of key parameters on the results of the analyses. The proposed demand model can be used to assess the reliability of different design options and for the reliability-based optimal design of offshore jacket platforms.

Although different occupations/organisations have unique work characteristics, it seems possible to divide them into two categories, namely job demands and job resources. A valid, equivalent and reliable instrument is needed to measure job demands and resources and to compare them among different occupations/organisations. The aim of this study was to investigate the construct equivalence, validity and reliability of a measuring instrument of job demands and resources and to assess the differences between the job demands and job resources in various occupations/organisations in South Africa. A cross-sectional survey design was used. A stratified random sample (N = 2717) was taken from a population consisting of employees in various occupations and organisations. The occupations/organisations included academics (higher education institutions), staff at a university of technology, correctional officers. insurance staff and engineers. The Job Demands-Resources Scale (JDRS) was used to assess job demands and job resources in the different occupations/organisations. Descriptive statistics, exploratory factor analysis, reliability analysis and multivariate analysis of variance were used to analyse the data. Five reliable factors were extracted using principal component analysis, namely: overload, growth opportunities, organisational support, advancement and job insecurity. The results showed that the structure of job demands and job resources in the different occupations/organisations were equivalent. with the exception of one factor, namely organisational support. Engineers showed higher scores on overload and growth opportunities than Occupations/organisations. Academics in higher education institutions also experienced more growth opportunities than other groups. Engineers, academics in higher education institutions and employees in the insurance industry reported higher levels of organisational support than correctional officers and employees at a university of technology. Engineers obtained the highest score on advancement, while academics in higher education institutions obtained the lowest scores. Job insecurity was the highest for correctional officers and employees of a university of technology, and the lowest for engineers. Recommendations for future research were made. / Thesis (M.A. (Industrial Psychology))--North-West University, Potchefstroom Campus, 2006.

Coping strategies represent the efforts, both behavioural and cognitive, that people invest in order to deal with stressful encounters. Coping is a basic component for developing adaptation and plays a major role in the relationship between the individual and the environment, especially as a moderating element between stress and sickness. Against this backdrop of the impact that the well-being of employees has on organisations, it is of the essence that organisations need to understand how their members cope with the demands which the organisation places on them. This understanding can assist organisations to evaluate the resources they make available to help employees to cope more positively with the demands placed upon them. The general objective of this study was to investigate the psychometric properties of the Coping Orientations to the Problems Experienced Questionnaire (COPE) within different occupational groups in South Africa, to examine the construct equivalence and to assess reliability. A swey design was used. Random samples (N = 3178) were taken from electricity supply personnel, nurses and police officials, and the COPE was administered. Descriptive statistics, exploratory factor analysis and multivariate analysis of variance (MANOVA) were used to analyse the data. Exploratory factor analysis, using principal axis factoring with varimax rotation, was conducted on 53 items of the COPE and revealed four interpretable factors (Factor 1 = Approach Coping; Factor 2 = Avoidance; Factor 3 = Seeking Support; and Factor 4 = Turn to Religion). Highly acceptable Tucker's phi coefficients were found for all the comparisons, and therefore, sufficient evidence for the construct equivalence of the COPE was demonstrated. Alpha coefficients, ranging from 0,85 to 0,92, were obtained. Statistically significant differences were found between the coping strategies employed within the different organisational, gender and language groups. Recommendations for future research were made. / Thesis (M.A. (Industrial Psychology))--North-West University, Potchefstroom Campus, 2007.

The United States Navy is currently in a state of transition from mechanical to electric propulsion. Future warships, such as the new destroyer class, will contain an Integrated Power System (IPS) that provides power to all propulsion and ship service loads. These warships will likely have a dramatic increase in the number of power electronic loads, both AC and DC. For ship service loads, a DC Zonal Electric Distribution System (DCZEDS) will likely be used. DCZEDS requires a device that provides galvanic isolation between the feeder buses and the zones to prevent fault propagation between zones. For DCZEDS to be practical, DC-DC converters that provide galvanic isolation with an efficiency and reliability approaching that of existing low frequency AC isolation transformers must be placed between the feeder buses and the zones. This thesis examines the construction and operation of a prototype galvanically isolated DC-DC converter using commercial-off-the-shelf parts. The converter uses a single-phase high-frequency transformer link to provide galvanic isolation. This work shows that this converter topology is reliable enough to be used in an IPS. A three-phase solution using this topology can provide sufficient power density at the megawatt level, necessary for an interface converter in DCZEDS.