The enormous competition in the telecommunications market results in the necessity of optimized and cost-efficient networks for the operators and service providers. Tracing users cost-efficiently is one of the major challenges in the study of location management of wireless cellular  networks. Tracking Area (TA) is a logical grouping of cells in Long Term Evolution (LTE) networks. TA manages and represents the location of User Equipments (UEs). One of the well-known performance consideration is the signaling overhead of tracking area update versus that for paging. This thesis deals with planning and optimization of tracking area configuration in LTE networks. TA design must be revised over time in order to adapt to changes and trends in UE location and mobility patterns. Re-optimization of the initial planning subject to different cost budgets is one of the problems considered in the thesis. By re-optimization, the design is successively improved by re-assigning some cells to TAs other than their original ones. To solve the resulting problem, an algorithm based on repeated local search is developed. By extending the line of research, the trade-off between the performance in terms of overall signaling overhead of the network and the reconfiguration cost is considered. This trade-off is modeled as a biobjective optimization problem to which the solutions are characterized by pareto-optimality. Solving the problem delivers a host of potential trade-offs among which the selection can be based on the preferences of a decision-maker. An integer programming model and a heuristic based on genetic algorithm are developed for solving the problem in large-scale networks. In comparison to earlier generations of cellular networks, LTE systems allow for a more flexible configuration of TA design by means of Tracking Area List (TAL). How to utilize this flexibility in applying TAL to large-scale networks remains unexplored. In this thesis, three approaches for allocating and assigning TA lists have been presented, and their performance is compared with each other, as well as with the standard location management scheme. Automatic reconfiguration is an important element in LTE. The network continuously collects UE statistics, and the management system adapts the network configuration to changes in UE distribution and demand. In this thesis an evaluation of dynamic configuration of TA design, including the use of TAL, has been performed and compared to the static configuration by using a case study.

In aircraft development, it is crucial to understand and evaluate behavior, performance, safety and other aspects of the systems before and after they are physically available for testing. Simulation models are used to gain knowledge in order to make decisions at all development stages. Modeling and simulation (M&S) in aircraft system development, for example of fuel, hydraulic and electrical power systems, is today an important part of the design process. Through M&S a problem in a function or system is found early on in the process. An increasing part of the end system verification relies on results from simulation models rather than expensive testing in flight tests. Consequently, the need for integrated models of complex systems, and their validation, is increasing. Not only one model is needed, but several interacting models with known accuracies and validity ranges are required. The development of computer performance and modeling and simulation tools has enabled large-scale simulation. This thesis includes four papers related to these topics. The first paper describes a modeling technique, hosted simulation, how to simulate a complete system with models from different tools, e.g. control software from one tool and the equipment model from another. The second paper describes the use of M&S in the development of an aircraft. The third and fourth papers describe how to increase knowledge of the model’s validity by sensitivity analysis and the uncertainty sources. In papers one and three an unmanned aerial vehicle is used as an example and in paper four a pressure regulator is the application.

Thermal barrier coating systems (TBCs) are used in gas turbines to prevent high-temperature degradation of metallic materials in the combustor and turbine. One of the main concerns regarding TBCs is poor reliability, and accurate life prediction models are necessary in order to fully utilise the beneficial effects of TBCs. This research project aims at developing deeper understanding of the degradation and failure mechanisms acting on TBCs during high temperature exposure, and to use this knowledge to improve life assessments of TBCs. The present work includes a study on the influence of coating interface morphology on the fatigue life of TBCs and a study on the influence of some different heat treatments on the adhesive properties of TBCs. The influence of coating interface morphology on fatigue life has been studied both experimentally and by modelling. Large interface roughness has been found experimentally to increase fatigue life of TBCs. The modelling work do, to some extent, capture this behaviour. It is evident, from the study, that interface morphology has a large impact on fatigue life of TBCs. Three thermal testing methods, that degrade TBCs, have been investigated: isothermal oxidation, furnace cycling and burner rig test. The degraded TBCs have been evaluated by adhesion tests and microscopy. The adhesion of TBCs has been found to depend on heat treatment type and length. Cyclic heat treatments, (furnace cycling and burner rig test), lower the adhesion of TBCs while isothermal oxidation increases adhesion. The fracture surfaces from the adhesion tests reveal that failure strongly depends on the pre-existing defects in the TBC.

In this thesis, we investigate two problems in robustness analysis of uncertain systems with structured uncertainty. The first problem concerns the robust finite frequency range H2 analysis of such systems. Classical robust H2 analysis methods are based on upper bounds for the robust H2 norm of a system which are computed over the whole frequency range. These bounds can be overly conservative, and therefore, classical robust H2 analysis methods can produce misleading results for finite frequency range analysis. In the first paper in the thesis, we address this issue by providing two methods for computing upper bounds for the robust finite-frequency H2 norm of the system. These methods utilize finitefrequency Gramians and frequency partitioning to calculate upper bounds for the robust finite-frequency H2 norm of uncertain systems with structured uncertainty. We show the effectiveness of these algorithms using both theoretical and practical experiments.

From its first appearance, wireless communications has changed thelife for many people worldwide. Currently, more than half of the world's population are using wireless devices for various purposes on a daily basis. While the early wireless systems could provide simple and specific low-rate services, today's systems can support a variety of more advanced services some of which require high data rate communications. This includes for example web-browsing and streaming multimedia applications. To meet the high demands on the current systems, many technical solutions have been proposed. Many of these solutions are powerful in the sense of boosting the system performance, but on the other hand, they impose a substantial control signaling overhead on the system. The control signaling refers to sending the control information that is necessary to establish and/or maintain the connection as opposed to the payload data that is transmitted during the connection. In this thesis, we are interested in evaluating the relations between the gain of deploying new techniques and the amount of control signaling overhead they incur. Moreover we are interested in finding efficient algorithms that can potentially reduce the control signaling overhead. More specifically, we first focus on the part of the control signaling overhead that concerns sending the scheduling assignments that describe how the channel resources are allocated among the users. We compare two ways for the signaling of scheduling assignments and we will study how different parameters such as scheduling granularity impact the control signaling overhead. We also provide two schemes that reduce the control signaling overhead substantially. We then provide an algorithm for fast blind identification of channel codes. This algorithm is very useful in improving the so-called blind decoding performance. This is essential since blind decoding is used to achieve adaptive modulation and coding in the control channel of some of the wireless communication systems such as 3GPP Long Term Evolution.

<p> This dissertation presents a qualitative case study of students enrolled in online courses and how they perceived the orientation program they completed before starting these courses. The study was based on the perspectives of students enrolled in a fully online program at a small community college in western Maine. They were interviewed individually to find out: (a) what are the perceptions of participants toward the materials presented in the orientation after completing their first semester; (b) what aspects of the orientation resonate most with participants when it comes to completing a course (nature of online learning, how to use course management system, technical requirements or learning skills and motivation). Besides the interviews, data was collected from the college&rsquo;s learning management system. </p><p> The results of the study show that participants were satisfied with the content of the orientation; however, more information pertaining to specific aspects of the learning management system should be included for additional satisfaction. Participants requested additional information concerning navigating courses, turning in assignments, and posting on discussion boards. The information provided in the interviews was consistent with the theory presented by Rovai&rsquo;s (2003) persistence model. Participants&rsquo; perceptions fell into tow categories, personal and technical. These results were consistent with the current literature pertaining to online courses, orientations, and persistence. </p><p> The results and findings of this study add to the body of knowledge concerning what materials in an orientation program are most effective in helping students complete online courses. The participants in this study perceived information about the use of the learning management system to be most important. Academic Deans and Student Services coordinators can learn more about what students&rsquo; perceive to be the important elements of an orientation program. The study also contributes to the existing literature on attrition, persistence, and retention.</p>

The ability to measure and quantify myocardial motion and deformation provides a useful tool to assist in the diagnosis, prognosis and management of heart disease. Myocardial motion can be measured by means of several different types of data acquisition. The earliest myocardial motion tracking technique was invasive, based on implanting radiopaque markers into the myocardium around the left ventricle, and recording the marker positions during the cardiac cycle by biplane cineradiography. Until recently, this was the only method with high enough spatial resolution of three-dimensional (3D) myocardial displacements to resolve transmural behaviors. However, the recent development of magnetic resonance imaging techniques, such as displacement encoding with stimulated echoes (DENSE), make detailed non-invasive 3D transmural kinematic analyses of human myocardium possible in the clinic and for research purposes. Diastolic left ventricular filling is a highly dynamic process with early and late transmitral inflows and it is determined by a complex sequence of many interrelated events and parameters. Extensive research has been performed to describe myocardial kinematics during the systolic phase of the cardiac cycle, but not by far the same amount of research has been accomplished during diastole. Measures of global and regional left ventricular kinematics during diastole are important when attempting to understand left ventricular filling characteristics in health and disease. This thesis presents methods for invasive and non-invasive quantification of cardiac kinematics, with focus on diastole. The project started by quantification of changes in global left ventricular kinematics during diastolic filling. The helical myocardial fiber architecture of the left ventricle produces both long- and short-axis motion as well as torsional deformation. The longitudinal excursion of the mitral annular plane is an important component of left ventricular filling and ejection. This was studied by analyzing the contribution of mitral annular dynamics to left ventricular filling volume in the ovine heart. In order to quantify strains for a specific body undergoing deformation, displacements for a set of internal points at a deformed configuration relative to a reference configuration are needed. A new method for strain quantification from measured myocardial displacements is presented in this thesis. The method is accurate and robust and delivers analytical expressions of the strain components. The developed strain quantification method is simple in nature which aids to bridge a possible gap in understanding between different disciplines and is well suited for sparse arrays of displacement data. Analyses of myocardial kinematics at the level of myocardial fibers require knowledge of cardiac tissue architecture. Temporal changes in myofiber directions during the cardiac cycle have been analyzed in the ovine heart by combining histological measurements of transmural myocardial architecture and local transmural strains. Rapid early diastolic filling is an essential component of the left ventricular function. Such filling requires a highly compliant chamber immediately after systole, allowing inflow at low driving pressures. Failure of this process can lead to exercise intolerance and ultimately to heart failure. A thorough analysis of the relation between global left ventricular kinematics and local myocardial strain at the level of myocardial fibers during early diastole in the ovine heart was performed by applying the method for strain quantification and the technique for computing temporal changes in myocardial architecture on measures of myocardial displacements and tissue architecture in the ovine heart. As data acquisition technologies develop, quantification methods for cardiac kinematics need to be adapted and validated on the new types of data. Recent improvements of DENSE magnetic resonance imaging enable non-invasive transmural strain analyses in the human heart. The strain quantification method was first tailored to displacement data from a surgically implanted bead array but has been extended to applications on non-invasive DENSE data measured in two and three dimensions. Validation against an analytical standard reveals accurate results and in vivo strains agree with values for normal human hearts from other studies. The method has in this thesis been used with displacement data from invasive marker technology and non-invasive DENSE magnetic resonance imaging, but can equally well be applied on any type of displacement data provided that the spatial resolution is high enough to resolve local strain variations.

This thesis focuses on improving and extending the available toolset for Eulerian, i.e. grid based, free surface fluid animation and level set based surface tracking in the context of computer graphics and visual effects. More specifically three novel methods are presented each aimed towards reducing the amount of computer memory required for producing high resolution animations of incompressible free surface fluids. Each method is primarily developed for, but not limited to, the popular Stable Fluids method. Eulerian free surface fluid animation has historically required a large amount of computer memory, especially when high resolution results are desired. This problem has recently been addressed through the development of dynamic computational grids like the Dynamic Tubular Grid (DT-Grid) for level set computations. However, when animating free surface fluids a large amount of tracker particles are often added to the level set geometry in order to provide more accurate tracking of fluid surfaces. As a result the particle level set (PLS) method typically requires two orders of magnitude more memory than a DT-Grid level set. In order to reduce the gap in memory requirement between the level set and the particles this thesis introduces a fast and efficient compression method for such tracker particles. This compression is optionally combined with a specialized external memory algorithm that allows particle and level set data to be efficiently streamed back and forth between primary memory and secondary storage devices such as hard disk drives. The particle compression scheme is able to reduce the size of a DT-Grid particle level set by more than 65% while only inducing a 5% penalty to performance. If combined with the external memory algorithm particle level sets of virtually any size and resolution can be used in free surface fluid animations. The induced performance penalty of the combined scheme depends on the performance of the external storage device, however when using a traditional hard disk drive a 70% increase in simulation time was measured. This thesis also presents a purely Eulerian alternative to the PLS method through the introduction of a dual resolution level set representation. The method replaces the tracker particles with a level set of higher resolution, thus significantly increasing surface tracking accuracy compared to the unaided level set. The scheme is able to produce high quality results using up to 94% less memory than a PLS. The core component of the method is the Spatially Adaptive Morphology (SAM) filter which connects the high resolution representation of the level set with the lower resolution fluid, thus providing plausable animation also for small and/or thin surface features. A sheet preserving extension to the SAM filter is also presented that is able to preserve thin sheets of fluid indefinitely if so desired. Although this method adds mass to the simulation it is highly useful for animating phenomena like splashes, fountains and waterfalls. The final method presented in this thesis concerns the efficient local animation of oceans and other very large free surface fluids.For such scenarios large amounts of memory and computation time can be saved by only computing accurate fluid physics in a local fluid region immediately surrounding a point of interest. The fluid outside this region can then be animated using less accurate but significantly faster and less memory demanding models. However, for this approach to be accurate the local fluid must be contained in such a way that it behaves as if still part of a larger fluid. This thesis enables the local simulation of a larger body of fluid by introducing three different non-reflective boundary conditions for free surface fluid animation using a modified Stable Fluids method. Two simple wave dampening boundaries are presented as well as a significantly more advanced wave absorbing boundary based on the Perfectly Matched Layer (PML) approach. All three boundaries are shown to be effective in preventing wave reflection given large enough boundary regions. However the PML boundary is significantly more efficient, typically absorbing waves at a fraction of the distance required by the other two methods.

Published Article / In South Africa (SA) fire service employees train at accredited training centres to become qualified firefighters, but to progress to higher leadership positions, there is a perceived need to acquire advanced expertise in areas that could be addressed by Higher Education (HE). A study employing a survey and focus group discussion was conducted, in collaboration with the professional body for emergency services in SA, to ascertain this perceived need. It was found that a high percentage of qualified firefighters were interested in further academic offerings by HE institutions and that their aspirations are toward a structured Master's degree. This type of Higher Education offering would furthermore, have to be presented through a blended learning method.

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