The exchange rate is one of the most challenging macroeconomic policy issues in any economy. There is a general agreement that policymakers should aim at avoiding real exchange rate misalignment. To avoid real exchange rate misalignment, it is important to identify the equilibrium real exchange rate. To identify the equilibrium real exchange rate it is necessary to understand the drivers of the real exchange rate, and investigate the extent to which the real exchange rate is driven by various determinants. Despite the fact that the real exchange rate is a very important component of macroeconomic policy, empirical investigation of the real exchange rate in Namibia is very limited. It is against this background that the objective of this study is to estimate the equilibrium real exchange rate and the resulting real exchange rate misalignment for Namibia during period 1970 to 2004. It also investigates the impact of real exchange rate misalignment on economic performance and competitiveness. The equilibrium real exchange rate and resulting real exchange rate misalignments were estimated using theoretical models and the application of time series econometric techniques. The fundamental approach model and the model of real exchange rate and real prices of commodities exports were estimated using the Johansen full information maximum likelihood technique. According to the estimation based on the fundamental model the real exchange rate is determined by terms of trade, openness of the economy and ratio of investment to GDP. Equilibrium real exchange rate was estimated and the results showed that the real exchange rate was misaligned. Since Namibia is a commodity exporting country the relationship between the real exchange rate and prices of commodities was also investigated. The analysis revealed that there is a long-run co-movement between real exchange rate and prices of commodity exports. Increase in prices of commodities causes the real exchange rate to appreciate. There was some overvaluation and undervaluation. The VAR methodology was implemented to test the impact of real exchange rate misalignment on economic performance and competitiveness. The analysis revealed that real exchange rate misalignment hampers economic growth and competitiveness. It is important for policymakers to monitor the real exchange rate and ensure that it does not diverge significantly from its equilibrium value. Reduction in real exchange rate misalignment is also important to ensure that the country achieves a high level of export and remains competitive in order to have a sustainable level of growth. As a commodity exporting country, Namibia can have either a flexible nominal exchange rate regime which facilitates slow change of relative inflation rate, or price and wage flexibility to facilitate the maintenance of the nominal exchange rate peg. Alternatively, Namibia is a good candidate for pegging the currency to the prices of export commodities because its export is concentrated on few products. This option implies that Namibia leaves the CMA. However, it is important to note that Namibia is a proponent of regional integration and a move away from the CMA will not be consistent with the plans of SADC to establish a monetary union by 2016. / Thesis (PhD (Economics))--University of Pretoria, 2007. / Economics / PhD / unrestricted

Misalignment in turbomachinery has been commonly known to produce twotimes- running-speed (2N) response. This project aimed to investigate the source of the 2N vibration response seen in misaligned vibrating machinery by simulating misalignment through a coupling. Three flexible disc-pack couplings (4-bolt, 6-bolt, and 8-bolt coupling) were modeled, and parallel and angular misalignments were simulated using a finite element program. The stiffness terms obtained from the coupling simulations had 1N, 2N, and 3N harmonic components. The 4-bolt coupling had large 1N reaction components under angular and parallel misalignment. The 6-bolt coupling model only had a 1N reaction component under angular misalignment, and both cases of parallel misalignment showed a strong 2N reaction component, larger than both the 1N and 3N components. The 8-bolt coupling model under angular misalignment produced large 1N reaction components. Under parallel misalignment, it produced 1N, 2N, and 3N components that were similar in magnitude. All the couplings behaved linearly in the range studied. A simple model predicted that the 2N frequency seen in the response is caused by the harmonic (1N) term in the stiffness. The amplitude of the 2N component in the response depends on the amplitude of the 1N term in the stiffness compared to the average value of the stiffness and the frequency ratio. The rotordynamic response of a parallel and angular misaligned system was completed in XLTRC2. When the frequency ratio was 0.5, the system response with the 4-bolt and 6-bolt coupling had a synchronous 1N component that was much larger than the 2N component. The response did not have a 2N component when the 8-bolt coupling was used but the response did have a 1.6N component that was considerably larger than the 1N component. When the frequency ratio was 2, the system response with the 4-bolt and 6-bolt coupling had a synchronous 1N component and a relatively small ½ frequency component. The response with the 8-bolt coupling had a 0.4N component that was larger than the 1N component. A 5-tilting pad journal bearing was also tested to better understand its behavior under misalignment because some experts attribute the 2N response to the nonlinear forces produced by bearings with high unit loads. The response of the 5-tilting pad bearing did not produce any 2N components while the bearing was subjected to unit loads of up to 34.5 bars.

Composite materials are increasingly used in many industries due to the high strength and low weight properties that they exhibit. Since composites are becoming more popular, they are being used in applications such as aircraft, boats, wind turbine blades, and even sports equipment. Composite behavior is complicated since they are made up of two completely different materials such as strong thin fibers and a relatively weaker resin material that hold the fibers together. It is becoming more important to understand how composites behave in different situations so that equipment designers have reliable material information in order to design safe products that will not harm human life. Fabrication of composite material is not perfect and introduces defects such as the fibers being wavy and the matrix having voids. These defects decrease the strength of composites and if not accounted for in design, could be detrimental. To better understand the effects of these defects in composite materials, experimental tests can be performed to determine the material properties but it costs a lot of money and time. If the material properties of the composite do not match what is desired, different constituent materials are selected to create new composite specimens and the tests must be repeated which costs more time and more money. Computational approaches such as Finite Element Modeling (FEM) are gaining popularity as a way to predict composite behavior without the high cost of fabrication and equipment. Another advantage is the ability to test various materials and various defects by simply changing parameters in the computation. For this thesis, an FEM protocol is developed to model composites made from the material AS4/8552. First, the strength properties are extracted from a model without defects and then, defects such as waviness in the fiber and voids in the matrix are added to the model to see its effect. Knowing the effect of certain defects may help motivate composite fabricators to develop processes that eliminate detrimental defects.

This dissertation considers the general problem of controlling dynamic systems subject to large-scale sensor and actuator uncertainties. The assumption is made that the uncertainty is limited to either pure rotation (i.e. special orthogonal matrix) or that each axis is rotated independently. Although uncertainty can appear in more general forms, this representation describes a ``net-effect'' when the ideal axes have become misaligned that is of fundamental importance to the control of numerous systems. Adaptive observers and controllers are introduced that guarantee perfect reference trajectory tracking even with the appearance of these large-scale uncertainties. The specific contributions of this dissertation are as follows: (I) the problem of rigid-body attitude tracking with vector measurements, unknown gyro bias, and unknown body inertia matrix is addressed for the first time. In this problem, the body attitude acts as unknown special orthogonal matrix (i.e. sensor uncertainty). A set of adaptive observers and an adaptive controller is presented that guarantees perfect tracking as well as convergence of the attitude and bias estimates through a Lyapunov stability analysis. (II) An adaptive observer is developed for the scenario where the control is pre-multiplied by an unknown constant scaling and rotation matrix which gives a non-affine representation of the uncertainty. The observer is shown to be convergent given a certain persistence of excitation condition on the input signal and using a smooth projection scheme on the estimate of the unknown scaling. In addition, the observer is combined with a stabilizing control to guarantee perfect tracking which establishes a separation like property. (III) The class of uncertainties where each axis of the control is independently misaligned is examined. The problem is split into studies of in-plane and out-of-plane misalignment angles given that they exhibit fundamental technical differences in establishing convergence. Where possible, rigorous stability proofs are given for a series of adaptive observers. The structure of the observers assure that the estimates do not introduce any singularities into the control problem other than those inherent from the misalignment geometry. The inherent singularities are avoided through the use of projection schemes which allow for extension to the control problem. This work represents the first significant effort to develop adaptive observers and controllers for this class of misalignments. / text

Obesity, metabolic syndrome, and diabetes represent a major source of morbidity and mortality in the United States and worldwide. Chronic misalignment of an organism’s internal circadian clock with diurnal, cyclic changes in the external environment, prevalent in professions that require shift work, contributes significantly to Type 2 Diabetes development. Experimentally, only short-term models of circadian disruption have been explored. Therefore, the goal of this study was to establish an animal model of chronic circadian disruption, which would more closely mimic the harmful misalignment associated with metabolic syndrome in clinical studies. Moreover, since high fat diet consumption alters circadian behavior and rhythmic gene expression, contributing to the diet-induced phenotype, I hypothesized that chronic circadian disruption interacts with a high fat diet to worsen metabolic syndrome. To investigate circadian misalignment and diet-induced metabolic syndrome, I examined the contribution of the Aryl Hydrocarbon Receptor (AhR). AhR has similar PAS domain containing motifs as circadian clock proteins allowing for protein/protein interactions and crosstalk between AhR signaling and circadian rhythms. Furthermore, AhR activation is implicated in Type 2 Diabetes risk. To examine chronic circadian disruption, male wild-type (WT; C57Bl/6J) and AhR +/- mice were entrained to 12/12-hour light/dark cycles where lights were on from 10pm-10am and off from 10am-10pm. Misalignment was initiated by delaying the time of lights on by 8 hours on Monday. Mice were exposed to the misalignment schedule Monday-Friday then returned to the entrainment schedule Saturday and Sunday to mimic readjustment to society during the weekend. Circadian misaligned mice were exposed to the altered light schedule for 15 weeks and control animals remained on the12/12-hour light/dark cycle. Mice were fed a normal chow diet (10% fat) or a high fat diet (60% fat). Animals were sacrificed and samples were collected at 4-hour intervals on day 2 of the weekend. Exposure to chronic circadian misalignment by light disruption or high fat diet altered circadian rhythms of behavior, metabolic outputs, and expression of circadian clock, clock-controlled nuclear receptor, and lipid metabolism genes. A combination of light misalignment and high fat diet exacerbated the effects of either treatment alone further disrupting behavior, enhancing % body fat and fasting glucose, and dampening circadian clock gene expression. AhR +/- mice also were protected from the metabolic consequences of chronic misalignment and a high fat diet by resistance to altered behavioral and molecular circadian rhythms and disruption of metabolic outputs. With metabolic syndrome and Type 2 Diabetes occurrence on the rise, it is important to understand all contributing factors, including circadian disruption. Differences between chronic circadian misalignment and high fat diet-induced obesity in WT and AhR +/- mice furthers our understanding of the complex mechanisms that underlie Type 2 Diabetes development and advocates the discovery of potential therapeutic targets for the development of novel treatment options.

Stratgic alignment has been one of the top concerns for IT executives for decades. One of the great debates in literature regarding strategic alignment is what act ‘alignment’ means, why it is needed and how do enterprises stay aligned. Alignment has many definitions, but in this context, it is concerned with the integration of business and IT strategies. Research has proven that there are positive relations to enterprise performance when it is aligned.   This qualitative research investigates the causes of misalignment through the views and thoughts of IT professionals at a Scandinavian IT consultancy company. By using a model created by, Schlosser, Wagner, and Coltman, this thesis could establish the most common factors to achieve alignment in the given enterprise. The model allowed the field of business-IT alignment to be explored in IT projects, and allowed for a better understanding of what causes misalignment.   This thesis conducted six interviews to answers two research questions; (1) what factors cause misalignment in IT projects and (2) how do these factors differ in different methodologies. The results from the analysis found that the main factors of misalignment were ‘procedures / workflow alignment’, ‘managerial skills of business and IT employees’, ‘technical skills and knowledge of IT employees’, ‘mutual trust and respect between business and IT executives / employees’, ‘IT skills and knowledge of business executives/employees’ and ‘alignment of business and IT strategy/goals/plans’. The second research question could  concluded that more research is needed to understand how factors change using different methodologies, as the results were to similar to reach a definit conclusion. For future research the thesis recommends using a multiple case study using the same model to verify the data gathered in this thesis and to strengthen the use of the model.

This thesis presents a novel method of locating imbalance faults in rotating machinery through the study of bearing nonlinearities. Localisation in this work is presented as determining which discs/segments of a complex machine are affected with an imbalance fault. The novel method enables accurate localisation to be achieved using a single accelerometer, and is valid for both sub and super-critical machine operations in the presence of misalignment and rub faults. The development of the novel system for imbalance localisation has been driven by the desire for improved maintenance procedures, along with the increased requirement for Integrated Vehicle Health Management (IVHM) systems for rotating machinery in industry. Imbalance faults are of particular interest to aircraft engine manufacturers such as Rolls Royce plc, where such faults still result in undesired downtime of machinery. Existing methods of imbalance localisation have yet to see widespread implementation in IVHM and Engine Health Monitoring (EHM) systems, providing the motivation for undertaking this project. The imbalance localisation system described has been developed primarily for a lab-based Machine Fault Simulator (MFS), with validation and verification performed on two additional test rigs. Physics based simulations have been used in order to develop and validate the system. An Artificial Neural Network (ANN) has been applied for the purposes of reasoning, using nonlinear features in the frequency domain originating from bearing nonlinearities. The system has been widely tested in a range of situations, including in the presence of misalignment and rub faults and on a full scale aircraft engine model. The novel system for imbalance localisation has been used as the basis for a methodology aimed at localising common faults in future IVHM systems, with the aim of communicating the results and findings of this research for the benefit of future research. The works contained herein therefore contribute to scientific knowledge in the field of IVHM for rotating machinery.

The radial velocity anomaly which affects spectroscopic observations of stars undergoing transit by a companion body is known as the Rossiter-McLaughlin effect. This effect can be used to measure the obliquities of the orbits of transiting planets. In this thesis I present a tomographic method for analysing the effect, which manifests itself in stellar spectral line-profiles. I implement this method on seven systems known to host transiting planets, and some systems with early-type host stars, for which the transit events have not yet been shown to be the result of planetary companions. Despite being well-suited to examining systems with early-type, rapidly-rotating host stars which have a more pronounced Rossiter-McLaughlin effect, I find the tomographic method is able to produce reasonable results for the system parameters of planets orbiting relatively slowly-rotating stars. I show that the method provides a significant increase in the accuracy of determinations of the stellar rotation rate and is able to better constrain values for the transit impact parameter. Though I do not confirm the existence of any new planets around early-type stars, I do use the tomographic method to reject one candidate as a stellar eclipsing binary system, and also reveal that one of the candidate host stars is a non-radial pulsator. I show that the method is able to examine systems involving stars with a range of spectral types and rotation rates.

The circadian system controls 24-hour cycles of behavior and physiology, such as rest-activity and feeding rhythms. The human circadian system synchronizes with, or entrains to, the light/dark cycle (sunrise/sunset) to promote activity and food consumption during the day and rest at night. However, strict work schedules and nighttime light exposure impair proper entrainment of the circadian system, resulting in chronic circadian misalignment. Numerous studies have shown that chronic circadian misalignment results in poor health. Therefore, therapeutic interventions that could shift circadian rhythms and alleviate circadian misalignment could broadly impact public health. Although light is the most salient time cue for the circadian system, several laboratory studies have shown that exercise can also entrain the internal circadian rhythm. However, these studies were performed in controlled laboratory conditions with physically-active participants. The purpose of this study was to determine whether timed exercise can phase advance (shift earlier) the internal circadian rhythm in sedentary subjects in free-living conditions. Fifty-two young, sedentary adults (16 male, 24.3±0.76 yrs) participated in the study. As a marker of the phase of the internal circadian rhythm, we measured salivary melatonin levels (dim light melatonin onset: DLMO) before and after 5 days of timed exercise. Participants were randomized to perform either morning (10h after DLMO) or evening (20h after DLMO) supervised exercise training for 5 consecutive days. We found that morning exercisers had a significantly greater phase advance than evening exercisers. Importantly, the morning exercisers had a 0.6h phase advance, which could theoretically better align their internal circadian rhythms with the light-dark cycle and with early-morning social obligations. In addition, we also found that baseline DLMO, a proxy for chronotype, influenced the effect of timed exercise. We found that for later chronotypes, both morning and evening exercise advanced the internal circadian rhythm. In contrast, earlier chronotypes had phase advances when they exercised in the morning, but phase delays when they exercised in the evening. Thus, late chronotypes, who experience the most severe circadian misalignment, may benefit from exercise in the morning or evening, but evening exercise may exacerbate circadian misalignment in early chronotypes. Together these results suggest that personalized exercise timing prescriptions based on chronotype could alleviate circadian misalignment in young adults.

Dowel bars in jointed plain concrete pavement (JPCP) have the important function of transferring wheel loads from one slab to the other, hence ensuring that the deflections on each side of the joint are kept almost equal. As well, the dowels should not impede the concrete pavement movements due to environmental effects (temperature and moisture). Dowel bar misalignment, attributed to deficient construction practice, is a major cause of joint distress or faulting by inhibiting the free movement of the slab at the joint. To prevent these issues, tolerance guidelines on misalignment levels are implemented by transportation agencies. Review of previous studies indicate that many researchers analysed the effects of dowel bar misalignment on pavement behaviour using a pull-out test, that is a forcebased opening of the joint. These approaches neglect that joints movements in the field are strain-governed by non-linear temperature and shrinkage actions, leading to combined axial movements and curling of the slab. In this study, the fundamental dowel bar behaviour under shrinkage and thermal loading was determined through detailed 3D finite element modelling (3D-FEM). To that end, models of dowel jointed concrete slabs were developed and subjected to realistic non-linear profiles of shrinkage and thermal strains. Studies were carried out on a single-bar model, taking into account bar-concrete friction and plastic concrete behaviour. The parameters that were investigated included different configurations and levels of bar misalignment and different friction coefficients between the steel and the concrete, simulating the use of bond-breakers. To interpret the results from the numerical analysis, criteria for concrete damage were developed and used in parallel with measures of joint load transfer efficiency; these were obtained by examining the response of the slab under a Falling Weight Deflectometer (FWD) drop at the joint. The results were verified by comparing the outputs of a model consisting of one half of a slab to published data. The analysis of the models revealead that none of the models showed signs of significant damage after the application of shrinkage and two thermal cycles. Analyses with up to ten thermal cycles did not indicate progressive accumulation of damage, suggesting that for the chosen parameters there is no the concrete around the dowel bar will not fail. Models with bars placed higher in the slab and bars with angular misalignment exhibited more damage than the non-misaligned models without reaching the damage criteria used in this study. The models did not exhibit the amount of damage reported in the studies on dowel bar misalignment having used pull-out tests. It was found that no significant difference existed between uncoated and coated dowel bars models results with regards to concrete damage at the joint. However, a high coefficient of friction between the dowel and the concrete, simulating dowel bar corrosion, proved to be the most detrimental to joint integrity. All of the models performed very well with respect to joint load transfer efficiency, suggesting that the plastic strains in the concrete around the dowel did not have a significant impact on joint performance for the realistic range of parameters investigated.