Student Number : 0110645G - MSc research report - School of Public Health - Faculty of Health Sciences / South Africa is one of the countries in sub-Saharan Africa that are severely affected by the HIV/AIDS pandemic. This epidemic has led to high mortality rates, decreased life expectancies, increasing poverty, and overburdened health systems. Objective: To quantify the disease burden related to HIV/AIDS in Leratong Hospital, a level 2 public sector hospital in Gauteng Province of South Africa. In the context of the recent introduction of anti-retroviral therapy programme in the hospital, it is hoped that this study will assist in defining a baseline to which future evaluation of the programme will be compared. Methods: This was a retrospective descriptive study on routinely collected hospital data. The records of all patients admitted into the four medical wards of the hospital in 2001 and 2004 (n=21,029) were analyzed. Data on their socio-demographic characteristics, discharge diagnoses, HIV status, clinical outcome and length of stay in the hospital were extracted and analyzed. Results: More than half (52%) of the patients were aged between 21 and 40 years. Between the two years, the annual total number of admissions to the medical wards decreased by 6.6%, and this was more pronounced in the female wards where the decline was more than 10%. HIV-related diseases accounted for four out of the top five diseases in all patients. The proportion of chronic diseases, such as hypertension, diabetes, congestive cardiac failure and cerebrovascular diseases, decreased from 15.3% in 2001 to 14.3% in 2004. The average length of stay (ALOS) increased from 3.7 days in 2001 to 4.1 days in 2004. Only 14% of all patients consented to HIV testing in the review period. Of these more than 90% were reactive to HIV. Although the proportion who had HIV tests decreased significantly from 16.9% in 2001 to 11% in 2004 (p<0.001), the HIV positive rate increased significantly from 89.1% in 2001 to 92.4% in 2004 (p<0.001). The proportion of patients admitted due to HIVrelated diseases increased significantly from 52% in 2001 to 58% in 2004 (p<0.001). The crude mortality rate for all patients during the two years studied was 13.6%. This increased significantly from 12% in 2001 to 15% in 2004 (p<0.001). Mortality was significantly higher in those patients with documented HIV results and those admitted with HIV-related diseases irrespective of their HIV status. While cause-specific mortality rate due to HIV-associated diseases either increased or remained very high, that due to diabetes mellitus decreased significantly between the two years studied (p=0.02). Patients’ length of stay in the hospital and mortality were both found to be associated with their age group, HIV status, diagnosis and year of admission. The study has demonstrated some changes in the clinical profile of the patients towards a preponderance of HIV-related diseases and crowding out of other chronic non-infectious diseases. Based on these results, it is therefore recommended that all patients should have access to voluntary counseling and testing (VCT) and emphasis should be placed on those diseases with high admission and mortality rates to improve patient care and outcome. Measures should be developed to ensure that patients with chronic noninfectious diseases are not crowded out.

When students are learning to read, the materials supplied typically will include extensive illustrations. The implicit assumption is that the inclusion of such illustrations will assist students in learning to read. Cognitive load theory suggests that this way of formatting learning materials may not be maximally effective as the inclusion of illustrations with written text constitutes redundant information that may interfere with learning. If working memory resources are devoted to the illustrations rather than the text, as is likely with young children, those resources will be unavailable to decipher the text. The elimination of redundant illustrations may thus enhance learning to read. Three experiments were conducted to investigate the effects of including illustrations in beginning reading materials. Experiment 1 compared reading materials consisting solely of simple prose passages with materials consisting of the same passages plus informative illustrations depicting the content of each passage. Reading proficiency improved more under the no illustrations condition. Experiment 2 compared the informative illustrations with uninformative illustrations. Reading proficiency improved more using uninformative illustrations. Experiment 3 compared uninformative illustrations with no illustrations and found no significant differences between these conditions. These results were interpreted within a cognitive load theory framework. It was concluded that informative illustrations are redundant and so impose an extraneous working memory load that interferes with learning to read.

A first-order approximation is made of the frequency and magnitude of bedload transport downstream of the Pelton-Round Butte Dam Complex, lower Deschutes River, Oregon with implications for salmonid spawning habitat. Field measurements of channel hydraulics, geometry, and particle size were combined with one-dimensional hydraulic and bedload transport models to determine the streamflow needed to move the channel bed material and to predict how much material would move once bedload transport was initiated. Inflows and outflows from the Dam Complex, and the predicted bedload carried by each, were compared to evaluate the effect of the Dam Complex on downstream discharge and bedload transport. Predicted critical discharges were equaled or exceeded very infrequently during the 72-year streamflow record. In addition, discharges capable of transporting bed material exceeded threshold conditions by very little. This has resulted in low predicted rates and amounts of bedload transport over the period of record. The Pelton-Round Butte Dam Complex was found to slightly increase the magnitude of flood peaks and associated predicted bedload transport for post-dam transport events exceeding threshold transport conditions. An exception to this pattern was the effect of the Dam Complex on the flood of December 1964, the second largest flood on record. This large flood occurred under unique circumstances -- while the reservoir of Round Butte Dam was filling for the first time. Since none of the transport events that occurred after the reservoir finished filling were affected by the Dam Complex in the same way as the 1964 event, the influence of the Complex on the 1964 flood is considered unique. The two largest floods on record (1964 and 1996), despite their relatively large sizes with respect to all other recorded flood events, did not cause major morphological changes to the lower Deschutes River. This observation, along with other independently derived information, supports the conclusion that the lower Deschutes is a very stable river. / Graduation date: 1998

Vibration suppression of beams traversed by moving loads, using optimal Tuned-Mass-Damper (TMD) systems, is investigated. This study is performed on two different geometrical shapes of the beam, namely, uniform homogenous straight beam, and the uniform homogenous curved beam. Initially, three different models of the moving load on a straight beam were developed using the APDL coding in ANSYS©, a commercially available software. Results obtained from the numerical simulation of either a single moving load or a moving mass on the straight beam were compared and validated with those reported in literature. A comprehensive parameter sensitivity analysis was carried out on the beam traversed by moving load with and without the presence of random base excitation and the effects of different beam parameters on the dynamic response of the system were closely examined. Vehicles travelling on suspension bridges induce undesirable vibration, which must be suppressed to a great extent. A half-car planar model moving on a straight beam is considered to study the suppression of vibration and parameter optimization. Attempt is made to design an optimal TMD system to suppress the induced vibration of the bridge due to the moving vehicle, considerably. Furthermore, the effect of non-symmetrical and side-way motion of vehicles on bridges has been considered when both the torsional and flexural vibrations of the bridge-vehicle have been present. Optimum values of the double-acting TMDs parameters have been found to suppress the combined flexural and torsional vibrations of the supporting beam structure. Similar work has been carried out on a uniform homogenous curved beam traversed by either a moving load or a half-car planner model. The effects of the beam curvature angle and the type of loading are closely studied. Optimum values of the two TMDs were obtained to suppress the combined flexural and torsional vibrations of bridges traversed by traveling vehicles. / UOIT

This dissertation consists of two parts with two different topics. In the first part, we investigate ``Load-Share Model" for modeling dependency among components in a multi-component system. Systems, where the components share the total applied load, are often referred to as load sharing systems. Such systems can arise in software reliability models and in multivariate failure-time models in biostatistics, for example (see Kvam and Pena (2002)). When it comes to load-share model, the most interesting component is the underlying principle that dictates how failure rates of surviving components change after some components in the system fail. This kind of principle depends mostly on the reliability application and how the components within the system interact through the reliability structure function. Until now, research involving load-share models have emphasized the characterization of system reliability under a known load-share rule. Methods for reliability analysis based on unknown load-share rules have not been fully developed. So, in the first part of this dissertation, 1) we model the dependence between system components through a load-share framework, with the load-sharing rule containing unknown parameters and 2) we derive methods for statistical inference on unknown load-share parameters based on maximum likelihood estimation. In the second half of this thesis, we extend the existing uncertain supply literature to a case where the supply uncertainty dwells in the logistics operations. Of primary interest in this study is to determine the optimal order amount for the retailer given uncertainty in the supply-chain's logistics network due to unforeseeable disruption or various types of defects (e.g., shipping damage, missing parts and misplaced products). Mixture distribution models characterize problems from solitary failures and contingent events causing network to function ineffectively. The uncertainty in the number of good products successfully reaching the distribution center and retailer poses a challenge in deciding product-order amounts. Because the commonly used ordering plan developed for maximizing expected profits does not allow retailers to address concerns about contingencies, this research proposes two improved procedures with risk-averse characteristics towards low probability and high impact events.

Abstract The interaction among the tooth wear, dynamic loads, and its corresponding frequency spectrum variation in a spur gear pair is investigated in the dissertation. A mathematical model for the dynamic responses of a profile shifting involute gear pair is derived. For simplicity, a two-step mesh stiffness model is proposed to approximate the load sharing and the time-varying stiffness effects in a mating gear pair. The analytic solutions for the dynamic responses of this simplified dynamic model are derived in both time and frequency domains. The effect of the tooth wear on the spectrum variation has been illustrated analytically. The amplitude and frequency modulations introduced from the periodic load fluctuation have also been discussed. In order to characterize the time-varying mesh stiffness, frictional coefficient, damping ratio, temperature rise and load sharing effects between engaged teeth, a computational algorithm with the quasi-linear iteration procedure is developed to include above instantaneous parameters in the teeth engagement process. The tooth wear equation proposed by Flodin and Andersson (1997) is employed to simulate the mild wear process for an engaging gear pairs. The interactions between the tooth wear and the dynamic loads for the Steel/Steel, POM/POM, Nylon/Nylon and Steel/Nylon gears pair have been studied numerically. Numerical examples indicate that the proposed models are valid for gear pairs with different materials.

Abstract The most common application of Distributed Generation (DG) is for reliability reasons. After experiencing an interruption, backup generators can be started to supply electricity to critical loads. The next most common application for DG is peak load shaving. During time periods of high energy demand or high energy prices, on-site generators are started up and used to serve part of the on-site loads. So DG can increase reliability of power supply, reduce loss of interruption and solve the problem of peak loads. Due to the high costs, only a few were installed. In order to investigate their economic values, in this thesis, several economic assessment methods are used to evaluate the cost-benefit of DG. Test results have revealed that, unless it is for environment protection reasons, the investment of DG is of little value if the fuel cost is high, and the electricity and the customer interruption costs are low. Keyword : Distributed Generation¡Mpeak load shaving.

<p>There are a huge number of customers using Ericsson’s prepaid telecom charging system. This means that even the smallest optimization done in its management of load results in a big win when considering time and CPU usage. Ericsson wishes therefore to learn about how the load management can be improved considering speed, i.e. faster response to load changes.</p><p>In this thesis work two subsystems of the prepaid telecom system are modeled. The first subsystem treats and prepares the telecom activity before it enters the second subsystem which checks if there is coverage for the action that the telecom activity asks for to be performed. A model which is an emulation of the subsystems is built using c++. It captures the timing of the real system not the logic or function. The c++ approach is compared to a Matlab approach which runs much slower in simulation. In addition, the model enables full view of the queue sizes and the rejects made by the regulator.</p><p>Verification has been performed with self generated data based on synthetic test cases. Verification and analysis show that the model captures the intended behavior of load management. Information about different software parameters and its influence on the output is obtained. Different scenarios are tested and the outcome discussed.</p>

The load distribution across the contact line(s) of spur gears is essential for the gear designer to be able to accurately stress gears for a given application. Existing gear standards (eg BS 436, AGMA 218 DIN 3990) use a thin slice (2D) model of the meshing gear teeth to estimate the contact line load distribution. This approach clearly fails to model properly teeth subjected to mal-distributed loads, since the buttressing effect of adjacent tooth sections tends to flatten the load distribution. Non-linear tooth modifications such as crowning and some forms of lead correction are also inadequately modelled. This thesis sets out the theory for a 3D elastic model of widefaced- spur gears that has been implemented on a micro-computer. The required 3D contact line influence coefficients for standard form zero modification spur gears with 18 to 100 teeth have been determined by Finite Element analysis. These theoretical values have been compared with results from experiments carried out on a complete large module (18. Omm) wide-faced spur gear. The effect of the various elemental gear errors (eg pitch, profile, lead) and profile modifications have been investigated using the 3D computer model; the results compared with results predicted by the existing gear design standards. The existing gear standards use 2D tooth compliance values up to 50% less than those obtained in this work, largely due to inadequate modelling of the gear body compliance, which is most significant in gear wheels. Comparison of 3D tooth compliance values shows a large discrepancy between author's results again due to inadequate modelling of the gear body.

The need to make more efficient use of energy resources by improved methods of control, the deferment of expensive pipework reinforcement or replacement and the requirement to accommodate different loading patterns on sections of the gas network have made the requirement for effective feedback control essential. Gas distribution systems are large and complex and a major problem in applying conventional feedback techniques is the cost and reliability of transmitting the data necessary for automatic control. In order to overcome these difficulties, state estimation techniques have been investigated as a means of providing information about a distribution system from a minimum number of measurement points. The theoretical background to the study is reviewed including the modelling technique and the results of experimental work which has been performed on a distribution network in order to verify the techniques developed are presented. The results show that state estimation techniques have considerable potential for this type of application.