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" Because of the high volume and unpredictable arrival rates, stream processing systems may not always be able to keep up with the input data streams, resulting in buffer overflow and uncontrolled loss of data. To continuously supply online results, two alternate solutions to tackle this problem of unpredictable failures of such overloaded systems can be identified. One technique, called load shedding, drops some fractions of data from the input stream to reduce the memory and CPU requirements of the workload. However, dropping some portions of the input data means that the accuracy of the output is reduced since some data is lost. To produce eventually complete results, the second technique, called data spilling, pushes some fractions of data to persistent storage temporarily when the processing speed cannot keep up with the arrival rate. The processing of the disk resident data is then postponed until a later time when system resources become available. This dissertation explores these load reduction technologies in the context of XML stream systems. Load shedding in the specific context of XML streams poses several unique opportunities and challenges. Since XML data is hierarchical, subelements, extracted from different positions of the XML tree structure, may vary in their importance. Further, dropping different subelements may vary in their savings of storage and computation. Hence, unlike prior work in the literature that drops data completely or not at all, in this dissertation we introduce the notion of structure-oriented load shedding, meaning selectively some XML subelements are shed from the possibly complex XML objects in the XML stream. First we develop a preference model that enables users to specify the relative importance of preserving different subelements within the XML result structure. This transforms shedding into the problem of rewriting the user query into shed queries that return approximate answers with their utility as measured by the user preference model. Our optimizer finds the appropriate shed queries to maximize the output utility driven by our structure-based preference model under the limitation of available computation resources. The experimental results demonstrate that our proposed XML-specific shedding solution consistently achieves higher utility results compared to the existing relational shedding techniques. Second, we introduces structure-based spilling, a spilling technique customized for XML streams by considering the spilling of partial substructures of possibly complex XML elements. Several new challenges caused by structure-based spilling are addressed. When a path is spilled, multiple other paths may be affected. We categorize varying types of spilling side effects on the query caused by spilling. How to execute the reduced query to produce the correct runtime output is also studied. Three optimization strategies are developed to select the reduced query that maximizes the output quality. We also examine the clean-up stage to guarantee that an entire result set is eventually generated by producing supplementary results to complement the partial results output earlier. The experimental study demonstrates that our proposed solutions consistently achieve higher quality results compared to the state-of-the-art techniques. Third, we design an integrated framework that combines both shedding and spilling policies into one comprehensive methodology. Decisions on the choice of whether to shed or spill data may be affected by the application needs and data arrival patterns. For some input data, it may be worth to flush it to disk if a delayed output of its result will be important, while other data would best directly dropped from the system given that a delayed delivery of these results would no longer be meaningful to the application. Therefore we need sophisticated technologies capable of deploying both shedding and spilling techniques within one integrated strategy with the ability to deliver the most appropriate decision customers need for each specific circumstance. We propose a novel flexible framework for structure-based shed and spill approaches, applicable in any XML stream system. We propose a solution space that represents all the shed and spill candidates. An age-based quality model is proposed for evaluating the output quality for different reduced query and supplementary query pairs. We also propose a family of four optimization strategies, OptF, OptSmart, HiX and Fex. OptF and OptSmart are both guaranteed to identify an optimal solution of reduced and supplementary query pair, with OptSmart exhibiting significantly less overhead than OptF. HiX and Fex use heuristic-based approaches that are much more efficient than OptF and OptSmart. "

In the study, we confer with the effect of the circular cylinder for various flow fields, and investigate the phenomenon of the vortex shedding and fluid elastic instabilities. First, in the aspect of the vortex shedding, we observe the wake behind the cylinder after varying the locations of orifices on the cylinder and the forms of momentum addition, and the variation of the lift and drag coefficient can be obtained by using the commercial software STAR-CD. In the further study, we make the type of flow field to be a shear flow and build the database of the aerodynamic coefficients in different shear parameter and Reynolds numbers; furthermore, the database is an important basis for us to conjecture the surface force on the cylinder, and analyze the size of oscillations and the orbit that is caused by the shear parameter, mass ratio and damping factor respectively.

Syndecan-1 is a cell surface proteoglycan which participates in cell adhesion, differentiation, motility, morphogenesis and intracellular signaling. The two glycosaminoglycans heparan sulfate and chondroitin sulfate are covalently attached to the ectodomain of syndecan-1 via a tetra saccharide linkage sequence. However, the ectodomain can be modified having only one or neither of the glycosaminglycans attached. The glycosaminoglycans are capable of binding ligands such as fibroblast growth factors (FGFs) and support activation of receptors. The ectodomain is proteolytically cleaved from the cell surface by metalloproteinases in a process known as shedding. Shedding turns the ectodomain into a soluble effector which can stimulate other cells in the surroundings by delivering growth factors and also translocate into cells through endocytosis. In this study the aim was to find out if a modified ectodomain, which only contains chondroitin sulfate, could support intracellular signaling in the absence of heparan sulfate. The aim was also to find out whether a modified ectodomain could translocate into the cell. The methods used were cell culturing, isolation and purification of syndecan-1 ectodomain, cell signaling and immunohistochemistry. It was found that modified shed syndecan-1 ectodomain was able to support intracellular signaling almost to the same degree as wild type syndecan-1 ectodomain. This may suggest that heparan sulfate does not have to be present on the ectodomain to support intracellular signaling, although the signal is slightly higher when present. When trying to detect translocation of the ectodomain the results were too uncertain and further research is required.

Failures of high mast illumination poles (HMIPs) in recent years have raised concerns on the long-term fatigue performance of the poles by various transportation officials around the US. The thesis documents a study sponsored by the Texas Department of Transportation focused on the fatigue behavior of in-service HMIP systems. This study is an extension of previous investigations on the fatigue behavior of the poles that have demonstrated that many poles have poor performance and fail in fatigue before the AASHTO category E' limit. Galvanized specimens were also tested and some of them showed evidence of initial cracking, impacting the fatigue performance such that the galvanized poles behaved worse than the uncoated specimens. Ultrasonic Testing (UT) has shown several poles around the state of Texas contain cracks in the welds between the shaft and base plate. To further investigate the performance of the poles in-service, a field study was initiated to measure the wind speed and direction, as well as the corresponding stresses in the pole shaft. This thesis presents results from the field investigation. A data acquisition system was developed to gather wind data and induced stresses. The system was powered by a solar panel and can be remotely accessed via a wireless modem. Data collected throughout the year details the intensity and number of stress cycles experienced by the poles, and could be correlated with the measured wind velocity. Using the field data, more accurate estimates of expected fatigue life for the poles were made. The study provides TxDOT with valuable data on the performance of in-service poles so that the most critical fatigue cases can be identified and proper decisions can be made on the appropriate inspection or repair schedule. / text

Modern helicopters, civilian and military alike, are expected to operate in all weather conditions. Ice accretion adversely affects the availability, affordability, safety and survivability. Availability of the vehicle may be compromised if the ice formation requires excessive torque to overcome the drag needed to operate the rotor. Affordability is affected by the power requirements and cost of ownership of the deicing systems needed to safely operate the vehicle. Equipment of the rotor blades with built-in heaters greatly increases the cost of the helicopter and places further demands on the engine. The safety of the vehicle is also compromised due to ice shedding events, and the onset of abrupt, unexpected stall phenomena attributable to ice formation. Given the importance of understanding the effects of icing on aircraft performance and certification, considerable work has been done on the development of analytical and empirical tools, accompanied by high quality wind tunnel and flight test data. In this work, numerical studies to improve ice growth modeling have been done by reducing limitations and empiricism inherent in existing ice accretion models. In order to overcome the weakness of Lagrangian approach in unsteady problem such as rotating blades, a water droplet solver based on 3-D Eulerian method is developed and integrated into existing CFD solver. Also, the differences between the industry standard ice accretion analyses such as LEWICE and the ice accretion models based on the extended Messinger model are investigated through a number of 2-D airfoil and 3-D rotor blade ice accretion studies. The developed ice accretion module based on 3-D Eulerian water droplet method and the extended Messinger model is also coupled with an existing empirical ice shedding model. A series of progressively challenging simulations have been carried out. These include ability of the solvers to model airloads over an airfoil with a prescribed/simulated ice shape, collection efficiency modeling, ice growth, ice shedding, de-icing modeling, and assessment of the degradation of airfoil or rotor performance associated with the ice formation. While these numerical simulation results are encouraging, much additional work remains in modeling detailed physics important to rotorcraft icing phenomena. Despite these difficulties, progress in assessing helicopter ice accretion has been made and tools for initial analyses have been developed.Modern helicopters, civilian and military alike, are expected to operate in all weather conditions. Ice accretion adversely affects the availability, affordability, safety and survivability. Availability of the vehicle may be compromised if the ice formation requires excessive torque to overcome the drag needed to operate the rotor. Affordability is affected by the power requirements and cost of ownership of the deicing systems needed to safely operate the vehicle. Equipment of the rotor blades with built-in heaters greatly increases the cost of the helicopter and places further demands on the engine. The safety of the vehicle is also compromised due to ice shedding events, and the onset of abrupt, unexpected stall phenomena attributable to ice formation. Given the importance of understanding the effects of icing on aircraft performance and certification, considerable work has been done on the development of analytical and empirical tools, accompanied by high quality wind tunnel and flight test data. In this work, numerical studies to improve ice growth modeling have been done by reducing limitations and empiricism inherent in existing ice accretion models. In order to overcome the weakness of Lagrangian approach in unsteady problem such as rotating blades, a water droplet solver based on 3-D Eulerian method is developed and integrated into existing CFD solver. Also, the differences between the industry standard ice accretion analyses such as LEWICE and the ice accretion models based on the extended Messinger model are investigated through a number of 2-D airfoil and 3-D rotor blade ice accretion studies. The developed ice accretion module based on 3-D Eulerian water droplet method and the extended Messinger model is also coupled with an existing empirical ice shedding model. A series of progressively challenging simulations have been carried out. These include ability of the solvers to model airloads over an airfoil with a prescribed/simulated ice shape, collection efficiency modeling, ice growth, ice shedding, de-icing modeling, and assessment of the degradation of airfoil or rotor performance associated with the ice formation. While these numerical simulation results are encouraging, much additional work remains in modeling detailed physics important to rotorcraft icing phenomena. Despite these difficulties, progress in assessing helicopter ice accretion has been made and tools for initial analyses have been developed.

Maintaining water quality in distribution systems has become a prominent issue in the study of water networks. This thesis concentrates on disinfectant and particle counts as two important indicators of water quality. The models discussed in this work are based on data collected by the author. The experimental set-up and procedure are described and observations of particle counts, particle counter size distributions, monochloramine as disinfectant, temperature, heterotrophic plate counts and epifluorescence microscopy counts are reported. A model of the response of particle counts to an increase in flow is developed. This model is obtained from specification derived from the data and assumptions, and is validated by its interpretability and its fit to data. A local shear-off density and an initial biofilm shedding profile were introduced and thus a linear model for this part of the water quality dynamics could be obtained. A procedure for the identification of the parameters of the local shear-off function and for the determination of the biofilm shedding profile is presented. This profile can be used to provide information about the status of the distribution system in terms of shear-off from the biofilm on the pipe walls. Monochloramine decay dynamics are investigated. The chlorine meter data is preprocessed with the help of titration data to correct meter drift. The data is then used in calibrating two different possible chlorine models: a model with a single decay coefficient and a model with bulk decay coefficient and wall demand (as used in Epanet). Important difficulties in identifying these parameters that come about because of the structure of the models are highlighted. Identified decay coefficients are compared and tested for flow, inlet chlorine and temperature dependence. The merits and limits of the approach to modelling taken in this work and a possible generalisation are discussed. The water industry perspective and an outlook are provided.

Abstract Type XIII collagen is an integral membrane protein in type II orientation. In cells and tissues type XIII collagen has been located in various adhesive structures, like focal adhesions. Due to this, its biological role has been implicated in cell adhesion. This collagen also exists as a soluble protein due to the release of the ectodomain from the plasma membrane. In this thesis, ectodomain shedding, i.e. enzymatic release of the extracellular domain, was studied in detail, focusing on the phenomenon as it occurs in mammalian cells. It was found that the ectodomain is released by members of the mammalian proprotein convertase family, e.g. furin. Shedding was shown to take place at the cell surface, but based on additional observations, this cleavage may also take place intracellularly in the Golgi apparatus. Various intracellular mechanisms, depending on cell type, were found to be involved in the regulation of ectodomain shedding. Apparently, due to the liberation of the ectodomain, the level of type XIII collagen on the plasma membrane is maintained at a relatively even amount. The released ectodomain was shown to retain biological activity. It showed distinct matrix-specificity so that on vitronectin its influence on cell functions was anti-adhesive, anti-migratory, anti-proliferative and non-supportive of cell spreading. It was also demonstrated to affect the fibronectin matrix assembly in a manner that resulted in reduced amounts of the fibrillar fibronectin matrix. A large collection of human epithelial and mesenchymal cancer samples were screened for type XIII collagen mRNA expression and compared to the expression levels of pre-malignant and normal samples. It was discovered that malignant transformation upregulates the expression of type XIII collagen in mesenchymal cancers and particularly in the stroma of epithelial cancers, more so than in cancer epithelia. TGF-β1 was demonstrated as one factor contributing to the stimulation of expression. Based on cell culture experiments in this study, it was also deduced that the upregulated expression of type XIII collagen and the concomitant shedding of the ectodomain can remodel the tumour stroma, making it inauspicious for adhesion-dependent cell functions, particularly in vitronectin-rich milieu.

Should Eskom and municipalities be held liable for loss resulting from load shedding? In essence, this is the question this dissertation answers or at least sheds some light on. This dissertation looks at the possibility of holding Eskom and municipalities delictually or contractually liable for loss resulting from load shedding. It does this by first discussing the delictual elements and thereafter determining whether these elements are present in the current circumstances in which Eskom and municipalities find themselves. It also looks at the relevant forms of breach of contract which may be present under the circumstances. It discusses their applicability to Eskom’s Standard Conditions of Supply for Small Supplies with Conventional Metering. It also discusses the applicability of these forms of breach to the relevant electricity supply by-laws which, in essence, provide the terms and conditions relating to the agreement for the supply of electricity between municipalities and consumers. The nature of electricity supply contracts are discussed throughout the dissertation in brief. It is found that electricity in itself is a very unique thing where the supply and sale thereof cannot be separated. The dissertation also deals with some interesting legislation which has the effect of municipalities and Eskom having to prove that they were not negligent in causing loss to consumers. Furthermore, the dissertation looks at related topics, briefly discussing class actions, pure economic loss, the “once and for all” rule, mitigation of loss, prescription, concurrent actions and possible infringement of constitutional rights. It considers the types of loss which might be claimed for as well as alternatives to instituting claims for damages. In the end, the conclusion is reached that all claims must be assessed with due regard to the circumstances surrounding each claim. It also comes to the conclusion that, in general, Eskom can be held delictually and contractually liable for load shedding. The assessed contract contains provisions which are contrary to national legislation and thus inoperative. It is, however, doubtful if such liability would succeed since courts would in all probability deny such claims for fear of opening the flood gates. It might be harder and even impossible to hold municipalities delictually liable. However, municipalities might be contractually liable as it is clear that by-laws, which regulate the supply of electricity to the consumer by the municipality, are often inoperative since these are in conflict with national legislation. This dissertation does not proclaim to provide all the answers relating to claims resulting from load shedding. It is, however, hoped that it will provide some insight into the considerations that need to be taken into account whilst raising some thought provoking questions. / Dissertation (LLM)--University of Pretoria, 2011. / Private Law / unrestricted

Masters in Public Administration - MPA / Nigeria has been experiencing challenges in the distribution of power to the whole country in the past decades. As a result, more than half of Nigeria's population is affected by the ineffectiveness of the distribution of electricity which lowers their standard of living. As the country's power sector experienced a steady growth after its independence in 1960, it was anticipated at the time that, at that rate of growth and development, most of Nigeria should have been electrified by now. However, challenges in the distribution of electricity have persisted and this has negatively affected the economy and living standard of the country. From the management perspective, this research looks at the situation of the distribution of electricity in Nigeria from the year 2005 to 2015. Specifically, it will analyses management challenges affecting the distribution of electricity in the country. It is well documented how Nigeria is currently facing an electricity crisis despite all the government efforts to provide adequate power to the citizens. In the distribution of electricity in Nigeria, the research will look at how the planning of the organization is been done so as to ensure effective power delivery to the country. The research will further look at how the management manages the organization and how it is being controlled for effective power distribution. In this research, I shall use qualitative and quantitative research techniques. Secondary qualitative and quantitative data will be used in carrying out this research. Published books, journals, newspaper articles, and government policies shall be critically examined in order to produce a well-informed report. Before the research is conducted, the appropriate consent from the University of the Western Cape will be sought to ensure that all protocols are strictly adhered to.