In underwater wireless optical communications (UWOC), the obstruction of light propagation by air bubbles is one of the main factors which causes light power to fluctuate at the receiver. In this thesis, we construct a statistical model for the received power in the presence of air bubbles. First, we postulate some random variables based on some real experiments, such as the size of a bubble, the generation of each bubble, and the horizontal and vertical movements of a bubble. Second, we mathematically express the amount of obstructed power which the shade of each bubble causes over the beam area and sum them all up to get the total obstructed power. In order to use the method of moments, we find the expectation, the second and/or the third moments of the total obstructed power. Lastly, we use these two or three moments of it to find suitable distributions that match the simulation data, which are the Weibull distribution and Generalized gamma distribution respectively. With these distributions, we construct the statistical model of the received power. Furthermore, we show that those distributions fit well to the simulation data.

Nutrition of children is crucial for normal physical, mental, and social development especially in the 6 to 24 months age group, as they are in the fast growing phase. Literature has reported under-nourishment as one of the causes of child mortality, which implies that addressing under-nourishment in children is one way of reducing child mortality. Nutrition guidelines for infants and children have been formulated by the World Health Organisation and the National Department of Health in South Africa. In spite thereof, there is a concern about the children between the ages of 6 to 24 months from a particular township in Gauteng who suffer from under-nourishment. The aim of this study was to develop strategies to improve feeding practices among caregivers of children aged 6 to 24 months residing in the particular township. Method: The researcher followed a qualitative paradigm that was explorative and descriptive. The first phase was to collect and describe current caregivers feeding practices (including cultural practices) of children 6 to 24 months. Data collection was done by means of two focus groups with purposively selected caregivers of children aged 6 to 24 months admitted in paediatric ward and diagnosed with under-nourishment alone or under-nourishment accompanied by other diseases. Caregivers' suggestions on how they can nourish their children aged 6 to 24 months was explored and described. The collected data was transcribed and coded into themes and sub-themes, followed by literature control. Caregivers suggested the following measures to improve their children's nutritional status: discarding old habits and adding new habits; introducing feeding pattern; the need to be provided with knowledge regarding factors associated with nutritional status; having access to information regarding financial management. The strategies were then based on the following themes: (1) educating and training caregivers regarding (food groups, nutrition and malnutrition, preparation of food, hygienic maintenance of utensils and hands, Introducing and adhering to a certain feeding pattern and frequency, creation of small gardens, subsistence farming and the use of recyclable water and proper financial planning and budget (2) to motivate caregivers to enhance nutrition. The second phase was to refine the strategies with the inputs from purposively selected healthcare professionals based on their knowledge regarding nutrition of children. The completeness of the strategies were disconfirmed by healthcare professionals based on the fact that educating caregivers on food groups alone without simple meal plans and augmentation of available funds to buy those food groups was inadequate. Furthermore, drought, which leads to water restriction and lack of funds to buy seeds, hamper the sustainability of subsistence farming. The significance of the study was that the caregivers, being responsible for nutrition of the children and being co-contributors of these strategies, buy-in was expected to improve the nutrition of the children and to improve nutritional health status. It is further expected that the strategies will be relevant and useful to other caregivers in the township. / Dissertation (MCur)--University of Pretoria, 2016. / Nursing Science / MCur / Unrestricted

A vast literature has investigated the returns to investment in agriculture research and generally found extremely high rates of return. These results suggest policymakers would do well to maintain or increase resource allocation to public agricultural research. Remarkably little attention has been paid, however, to the issue of how best to allocate public agricultural research funding between competing research areas and organizations. This paper considers the relative returns to alternative uses of public agricultural research funds committed to the agricultural experiment stations of 10 western states of the United States over the years 1967-91. A model of expected utility maximization subject to risk is presented with comparative analysis. After establishing empirically that the mean variance analysis would be an inappropriate method to solving the problem, a stochastic dominance testing method is employed to identify dominated and undominated research categories and state agricultural experiment stations. The mean variance analysis also is used to evaluate whether research productivity has been increasing or decreasing over time, and to establish which among the western states hold absolute advantage in particular research areas.

No description available.

Sand boil formation due to underseepage is a potential failure mechanism for levees in the Lower Mississippi River Valley. Sand boils were identified in the Buck Chute study area in the 1990s during high water events and during the 2009 Flood. The site is unique due to the presence of point bar and abandoned channel deposits. To understand the role of these alluvial deposits on sand boil formation at the site, a geologic investigation of the subsurface was conducted. Using shallow geophysics, cone penetrometer tests (CPT), borings, and a geographic information system (GIS), it was concluded that the thin blanket associated with point bar deposits, abandoned channel deposits causing a blocked seepage path, and head differential changes caused by the Muddy Bayou Control Structure were the controls of sand boil formation at Buck Chute.

No abstract is provided. / Thesis / Master of Engineering (MEngr)

<p>This dissertation examines the economic effects of alternative taxation policies on household consumption and investment decisions under uncertainty. A consideration of the alternative approaches to a theory of decision-making under uncertainty (Part 1) reveals that maximisation of expected utility is consistent with rational behaviour in a world of uncertainty. Howeve~, an alternative criterion of minimising the probability that the risky outcome will fall below some critical level (the "safety-:first" principle) may also appear as rational. Consequently, we consider both types of behavioural models.</p> <p>In a single-period framework (Part 2), the particular decision process we consider is that of an individual allocating his initial wealth between riskless assets with a secure rate of return and risky assets with a random rate of return. We then investigate the effects of taxation on risk-taking (both social and private).</p> <p>We observe that a chance-constrained portfolio choice model can be interpreted as a reasonable description of the investor's concern for safety, and that the qualitative results regarding portfolio separation (implying that optimal risky asset ratios are independent of initial wealth) and the effects of taxation (suggesting that a proportional or a lump-sum tax with full loss offsets encourages a movement towards the riskier assets) are the same both for a normal distribution of asset returns and the alternative assumption of a lognormal securities market.</p> <p>Part 2 also investigates the effects of a simple progressive tax schedule (a linear tax with a marginal tax rate which applies both above and below an exemption level) on risk~taking. Assuming only that the investor is a risk-avertor and that the risky asset is superior (or alternatively, assuming only decreasing absolute risk-aversion), we show that linearly progressive taxation of investment income (with full loss offsets) encourages the demand for the risky asset, and that exempting risky capital gains (losses) from taxation discourages (total) risktaking. We further show that a linearly progressive tax on investment income leads to greater risk-taking than a flat rate proportional tax where both of these taxes lead to equal losses of expected utility for the investor, or alternatively, where they yield the same expected revenue.</p> <p>Part 3 considers models of portfolio choice and consumption allocation in an intertemporal context. Apart from taxation of non-asset income and the case where the rate of return on riskless investment is zero, the kind of a priori restrictions we have placed on single-period preferences are no longer sufficient to determine the effects of taxation. However, given the relative nagnitudes of the income elasticities of consumption and of the risky asset demand, assumptions on the riskaversion measures allow us to determine these results. This analyssis, therefore, also indicates the kind of empirical knoftledge that is required in order to meaningfully discuss the implications of alternative taxation policies.</p> <p>We further pursue the framework of intertemporal consumption portfolio allocation to analyze the long debated issue of the differential incidence of a consumption (expenditure) tax rather than an (investment) income tax. We find that under some reasonably interpretable conditions, the differential incidence of a consumption tax is to encourage risktaking and discourage saving more effectively than an investment income tax. This result is in conflict with the general consensus in the literature that an income tax discourages saving as compared to a consumption tax. We, therefore, conclude in this context that with the introduction of uncertainty, the implications of fiscal policy are modified in an important way.</p> / Doctor of Philosophy (PhD)

Yes / Child undernutrition is a key public health issue that both causes and contributes to disease and death. Undernutrition accounts for 45% of under-five deaths globally most of which occur in Low- and Middle-income countries (LMIC). Malnutrition has a substantial and long-lasting effect on individuals, families, communities and the entire nation. This study aimed to assess the prevalence and determinants of undernutrition in under-five children in Nigeria. Methodology: This systematic review was done following the Cochrane library guidelines. A search of literature written in English language and published between 2000 and 2022 was done using PubMed, CINAHL, MEDLINE and ProQuest databases. The initial search resulted in 760 studies. These were exported to End note version 9 to remove duplicates. Titles and s were screened for studies that met the inclusion criteria. Finally, 11 studies that met the inclusion criteria were thoroughly assessed and data that were relevant to this systematic review were captured. The study findings were analyzed using descriptive statistics. Results: The prevalence of undernutrition was between 1.0% and 43.3%. The highest prevalence of underweight, wasting and stunting were 43.3%, 29.3% and 41%, respectively. Factors associated with undernutrition were age, sex, birth order, recent acute diarrhoea and acute respiratory infection, maternal literacy level, maternal income <$20 and socio-economic class among others. Conclusion: Under-five undernutrition is a huge public health issue in Nigeria. Prevalence of undernutrition varies widely across geo-political zone with a myriad of associated risk factors. Multi-level and multidisciplinary interventions are required to sustainably address the determinants of under-five undernutrition.

This study examined the potential significant differences in the distribution of adverse drug reactions (ADRs) by reporter (consumer versus physician) and patient outcome at case and event level. This study also contains exploratory questions to evaluate reporting of ADRs by consumers versus physician by system organ class (SOC) and reporter demographics within the United States Food & Drug Administration Adverse Event Reporting System (FAERS). The theoretical foundation applied in this quantitative study was the social amplification of risk framework. Data from the second quarter of 2016 were obtained from FAERS, and a total of 87,807 ADR reports corresponding to 143,399 ADRs were analyzed by utilizing the chi-square test, the odds ratio, and logistic regression. Cross-sectional design was employed to compare reporting of ADRs at the case and event level (case-based and event-based analyses, respectively) between reporters (consumer versus physician), specifically, for patient outcome, as well as SOC and reporter demographics. For both the case-based and event-based analyses, findings revealed that consumers reported more serious ADRs in comparison to physicians. Furthermore, findings confirmed a difference in ADR reporting between consumers and physicians depending on SOC groups. Additionally, consumers reported more nonserious ADRs in comparison to physicians. The results from this study may have implications for positive social change by augmenting pharmacovigilance systems at a national and international level to identify risks and risk factors spontaneously reported after drugs have been on the market.

Doctor of Philosophy / Department of Physics / Nobel S. Rebello / This research project investigates the difficulties students encounter when solving physics problems involving the integral and the area under the curve concepts and the strategies to facilitate students learning to solve those types of problems. The research contexts of this project are calculus-based physics courses covering mechanics and electromagnetism. In phase I of the project, individual teaching/learning interviews were conducted with 20 students in mechanics and 15 students from the same cohort in electromagnetism. The students were asked to solve problems on several topics of mechanics and electromagnetism. These problems involved calculating physical quantities (e.g. velocity, acceleration, work, electric field, electric resistance, electric current) by integrating or finding the area under the curve of functions of related quantities (e.g. position, velocity, force, charge density, resistivity, current density). Verbal hints were provided when students made an error or were unable to proceed. A total number of 140 one-hour interviews were conducted in this phase, which provided insights into students’ difficulties when solving the problems involving the integral and the area under the curve concepts and the hints to help students overcome those difficulties. In phase II of the project, tutorials were created to facilitate students’ learning to solve physics problems involving the integral and the area under the curve concepts. Each tutorial consisted of a set of exercises and a protocol that incorporated the helpful hints to target the difficulties that students expressed in phase I of the project. Focus group learning interviews were conducted to test the effectiveness of the tutorials in comparison with standard learning materials (i.e. textbook problems and solutions). Overall results indicated that students learning with our tutorials outperformed students learning with standard materials in applying the integral and the area under the curve concepts to physics problems. The results of this project provide broader and deeper insights into students’ problem solving with the integral and the area under the curve concepts and suggest strategies to facilitate students’ learning to apply these concepts to physics problems. This study also has significant implications for further research, curriculum development and instruction.