Submitted in partial fulfilment of the requirements for the degree of Master of Education in the Department of Planning and Administration in the University of Zululand, 1990. / This study looks into the problem of failure in Matric in Black schools in KwaZulu. Some researchers have focused on causes for academic failure before. Some of these researchers are: Souper, (1976); Bryant, (1978); Havinghurst, (1979); Donald, (1980); Simons, (1980). Failure is rarely, if ever, attributable to one simple cause. There are likely to be a multiplicity of interrelated causes. Some' of these causes are : family disorganisation; family size and education; poor study facilities at home and teacher-pupil ratio. Failure at school may imply that one may fail in life. Society believes that school subjects are the means of i equipping pupils with the knowledge of understanding certain socio-economic and political demands. School subjects, it is believed, reveal the r, ealities that they should know in their society. It is through these school subjects that the child will know how to live comfortable with other people (Social Studies); how to look after his/her body, (Physiology and Hygiene); how other organisms are important in her/his life, (Biology/ Ecology; (Geography) .

This research focuses on finding the optimal maintenance policy for an item with varying failure behavior. We analyze several types of item failure rates and develop methods to solve for optimal maintenance schedules. We also illustrate nonparametric modeling techniques for failure rates, and utilize these models in the optimization methods. The general problem falls under the umbrella of stochastic optimization under uncertainty. / text

The study sought to establish the causes of high failure rate among matriculants in the Qumbu district in the Eastern Cape, South Africa. A qualitative research design was adopted. Interviews were used to collect data. The sample (N=21) was made up of 12 teachers, 3 learners from each of the selected 3 schools. Convenience sampling technique was used to select the participants. The data were thematically analyzed. The study concluded that parents were not involved in the teaching and learning of their children. There was a lack of learner-teacher support material and infrastructure in schools and this affected learner‟s performance. Disciplinary issues involving both teachers and learners negatively affected the performance of learners. The medium of instruction in schools also affected performance because in some schools learners were taught in Xhosa and that resulted in poor performance at school. The study recommended that parents need to be encouraged to be actively involved. Infrastructure needs to be improved in schools and more classrooms should be built. Learners need discipline and society at large should be involved in moulding learners and teachers‟ in this regard (Teachers should lead by example). In addition, teachers and learners need to be motivated to use English as a medium of instruction and teachers ought to use English when they communicate with learners.

Department of Public Health / MPH

Yes / Reliability is critical to the design, operation, maintenance, and performance assessment and improvement of wind turbines (WTs). This paper systematically reviews publicly available reliability data for both onshore and offshore WTs and investigates the impacts of reliability on the cost of energy. WT failure rates and downtimes, broken down by subassembly, are collated from 18 publicly available databases including over 18 000 WTs, corresponding to over 90 000 turbine‐years. The data are classified based on the types of data collected (failure rate and stop rate) and by onshore and offshore populations. A comprehensive analysis is performed to investigate WT subassembly reliability data variations, identify critical subassemblies, compare onshore and offshore WT reliability, and understand possible sources of uncertainty. Large variations in both failure rates and downtimes are observed, and the skew in failure rate distribution implies that large databases with low failure rates, despite their diverse populations, are less uncertain than more targeted surveys, which are easily skewed by WT type failures. A model is presented to evaluate the levelised cost of energy as a function of WT failure rates and downtimes. A numerical study proves a strong and nonlinear relationship between WT reliability and operation and maintenance expenditure as well as annual energy production. Together with the cost analysis model, the findings can help WT operators identify the optimal degree of reliability improvement to minimise the levelised cost of energy. / UK Engineering and Physical Sciences Research Council (EPSRC). Grant Number: EP/P009743/1

A class of lifetime distributions which has received considerable attention in modelling and analysis of lifetime data is the class of lifetime distributions with bath-tub shaped failure rate functions because of their extensive applications. The purpose of this thesis was to introduce a new class of bivariate lifetime distributions with bath-tub shaped failure rates (BTFRFs). In this research, first we reviewed univariate lifetime distributions with bath-tub shaped failure rates, and several multivariate extensions of a univariate failure rate function. Then we introduced a new class of bivariate distributions with bath-tub shaped failure rates (hazard gradients). Specifically, the new class of bivariate lifetime distributions were developed using the method of Morgenstern’s method of defining bivariate class of distributions with given marginals. The computer simulations and numerical computations were used to investigate the properties of these distributions.

Mελετάται η μίξη δύο συνεχών κατανομών με αύξοντα ρυθμό αποτυχίας και δίνονται συνθήκες για να έχει η μίξη φθίνοντα ρυθμό αποτυχίας. Όταν η μία από τις δύο κατανομές της μίξης είναι η εκθετική γίνεται αντιστροφή του ρυθμού αποτυχίας. Στην περίπτωση της μίξης δύο κανονικών κατανομών παρουσιάζεται ο τρόπος που συνδέεται το πλήθος των κορυφών της πυκνότητας με τον ρυθμό αποτυχίας της μίξης. Mελετάται επίσης, η μονοτονία του ρυθμού αποτυχίας διακριτών κατανομών χρησιμοποιώντας τον λόγο δύο διαδοχικών πιθανοτήτων και δίδεται μία συνθήκη για να έχει η μίξη δύο διακριτών κατανομών φθίνοντα ρυθμό αποτυχίας όταν η μία από τις δύο κατανομές της μίξης είναι η γεωμετρική. Τέλος, χρησιμοποιώντας τον λόγο διαδοχικών πιθανοτήτων, μελετούμε την μονοτονία του ρυθμού αποτυχίας για διδιάστατες διακριτές κατανομές. / The mixture of two continuous distributions, with increasing failure rates, is considered and the necessary conditions to have decreasing failure rate (DFR) are given. When one of these distributions is the Exponential, reversal of the failure rate is observed. In the case of two normal distributions the failure rate is associated with the number of modes. It is also considered the failure rate for discrete distributions in regard with the ratio of two consecutive probabilities. A condition to have DFR is given when one of the distributions of the mixture is the geometric. Finally, we make use of the ratio of two consecutive probabilities to study the failure rate for bivariate discrete distributions.

The electrical power grid is one of the most important infrastructures in the modernsociety. It supplies industrial and private customers with electricity and supportsother critical infrastructures such as the water supply. Thus, it is significant that the power grid is a reliable system. However, the power system experiences a hugetransition from classical production methods such as coal and nuclear power plantsto distributed renewable energy forms such as wind energy and photovoltaic. This change to a more distributed system challenges the existing power grid as well as the traditional business models of electric utilities. Thus, cost minimization to increase profitability and improvement of the power grid to increase customer satisfactionare in the focus. One approach to increase the reliability of the grid and decrease maintenance costs is a condition-based maintenance approach which requirescondition monitoring techniques. This thesis introduces into failure rate modelling for individual power system components and develops a method to calculate individual failure rates based onthe average failure rate, failure statistics, and condition monitoring data. This approach includes the analysis of failure statistics to identify failure causes and failure locations which are population characteristics but can be utilized to describe the heterogeneity within the population. Thus, the thesis first introduces into the topic of failure analysis and heterogeneity in populations. Different factors are identified and categorized which describe the condition development of a component overtime. Then, the literature within failure rate estimation is reviewed to present the factors which are used within failure rate modelling and to outline the existingmethods which consider the individual. However, limitations are discussed which emphasize the demand for a new approach. Consequently, this thesis introduce intoa new approach for estimating the failure rate for individual components. / <p>QC 20160526</p> / Energiforsk AB risk analysis program

Thesis (MPA.) -- University of Limpopo, 2016 / This study is an investigation of effective management of high failure rates in grade nine classes in selected schools of the Mamabolo circuit. The study was prompted by several factors such as repetition rate, overcrowding and over-aged learners experienced in grade nine classes. The problem statement provides the foundation within which the aim and objectives are described. The causal factors of grade nine failure rates and how the management of schools was affected were not overlooked. The main targets were the School Management Teams of selected schools in the Mamabolo circuit. A qualitative research method was used. Various methods of data collection were used such as face-to-face interview, observation and document analysis whereby the summary of learner performance, collected from the circuit office, was analysed. Key findings of this research suggest that the School Management Teams are faced with great challenges that emanate from high failure rates in grade nine classes. The majority of the schools in the Mamabolo circuit are characterised by very low school enrolment which affects the post establishment and results in management overload. Congestion in the classrooms is experienced in grade nine classes (see figure 4.5). Most of the School Management Teams consist of one principal and one HOD, while other members are post level one educators who are senior educators (see table 3.1). This situation, in some instances leads to reluctance in performing management duties as compared to the schools where the School Management Teams are constituted by appointed principal, deputy principal/s and HODs only. Grade nine classes are not effectively managed due to various challenges such as overcrowding, lack of furniture, shortage of Learner Teacher Support Material, over-aged learners, low morale, discipline problems, poor involvement of parents, teenage pregnancies and drop-outs. Furthermore, the study revealed that very few School Management Teams seem to acknowledge that they also contribute to the failure rate in grade nine. This was clearly indicated when the School Management Teams were responding to the question on the causes of poor academic performance in grade nine classes. Learners, parents, educators, some departmental policies and the Department of Education itself were mentioned as contributing factors to poor performance. The following conclusions were drawn from the study findings: There are serious challenges facing the School Management Teams in the Mamabolo circuit, which are emanating from high failure rates in grade nine classes. The School Management Teams find it difficult to effectively manage high failure rates. High failure rates have a negative impact on the management of schools and affect the functionality of the school as an institution of learning. Finally, although the School Management Teams in the Mamabolo circuit fail to effectively manage high failure rates in grade nine, this investigation indicates that they are very aware of their responsibilities as members of the School Management Teams. In order to improve the effective management of the School Management Teams, to eliminate the challenges experienced and to increase learner attainment in grade nine classes, the following recommendations should be considered: skills development workshops, planning, implementation and monitoring of curriculum activities, provision of human and physical resources and parental involvement.

The purpose with this study is to compare four different models to VaR in terms of accuracy, namely Historical Simulation (HS), Simple Moving Average (SMA), Exponentially Weighted Moving Average (EWMA) and Exponentially Weighted Historical Simulation (EWHS). These VaR models will be applied to one underlying asset which is the Brent Blend Oil using these confidence levels 95 %, 99 % and 99, 9 %. Concerning the return of the asset the models under two different assumptions namely student t-distribution and normal distribution will be studied