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Morphological development during crystallization of thin films of poly(ethylene oxide) (PEO) / poly(methyl methacrylate) (PMMA) blends has been reported. Studies have focused on the effects of the blend composition, PMMA molecular weight, film thickness, and crystallization temperature on the observed crystal morphology. As the blend composition was varied from 90 to 30 wt% PEO, the crystal morphology varied from spherulites to needles and dendrites. Variation of the crystallization temperature and PMMA molecular weight resulted in similar changes in morphology. A morphological map demonstrating the roles of the experimental controls on the observed crystal morphology has been developed. This map was used as a tool for more detailed studies of the observed morphologies and morphological transitions. The dendritic region of the map (~ 30 = 40 wt% PEO) was studied in detail. Changes in the diffusion length were achieved through variation of the PMMA molecular weight, and were shown to influence the secondary sidebranch spacing. Sidebranch spacing measurements revealed that coarsening of the dendritic microstructure occurred well after the competition between diffusion fields of neighboring dendrite arms vanished, indicating the existence of another coarsening mechanism. These studies of dendritic sidebranching indicate that polymer dendrites develop by mechanisms similar to those in small molecules and metals. A number of in-situ observations of morphological transitions have also been reported, including a dense-branched morphology (DBM)/dendrite transition, a DBM/stacked-needle/needle transition, and a transition from dendrites with 90o sidebranching to dendrites with 45o branching or a dense-branched morphology, both of which grow at 45o to the original dendrite trunk. The DBM/dendrite transition occurred over a range of crystallization temperatures, indicating that the transition is not sharp. Crystal growth rate measurements verified this result. The DBM/stacked-needle/needle transitions demonstrated distinct jumps in the crystal growth rate, indicating a change in the growth mechanism or direction. For the transition involving a change in the growth direction, the effective level of noise (fluctuation) was found to be important in morphological selection. The results of this work have helped to define new directions for the study of crystal morphologies, especially in the areas of spherulite formation and dendritic growth. / Ph. D.

Dans cette thèse de doctorat, nous étudions des algorithmes et des implémentations pour accélérer la résolution de systèmes linéaires denses en utilisant des architectures composées de processeurs multicœurs et d'accélérateurs. Nous nous concentrons sur des méthodes basées sur la factorisation LU. Le développement de notre code s'est fait dans le contexte de la bibliothèque MAGMA. Tout d'abord nous étudions différents solveurs CPU/GPU hybrides basés sur la factorisation LU. Ceux-ci visent à réduire le surcoût de communication dû au pivotage. Le premier est basé sur une stratégie de pivotage dite "communication avoiding" (CALU) alors que le deuxième utilise un préconditionnement aléatoire du système original pour éviter de pivoter (RBT). Nous montrons que ces deux méthodes surpassent le solveur utilisant la factorisation LU avec pivotage partiel quand elles sont utilisées sur des architectures hybrides multicœurs/GPUs. Ensuite nous développons des solveurs utilisant des techniques de randomisation appliquées sur des architectures hybrides utilisant des GPU Nvidia ou des coprocesseurs Intel Xeon Phi. Avec cette méthode, nous pouvons éviter l'important surcoût du pivotage tout en restant stable numériquement dans la plupart des cas. L'architecture hautement parallèle de ces accélérateurs nous permet d'effectuer la randomisation de notre système linéaire à un coût de calcul très faible par rapport à la durée de la factorisation. Finalement, nous étudions l'impact d'accès mémoire non uniformes (NUMA) sur la résolution de systèmes linéaires denses en utilisant un algorithme de factorisation LU. En particulier, nous illustrons comment un placement approprié des processus légers et des données sur une architecture NUMA peut améliorer les performances pour la factorisation du panel et accélérer de manière conséquente la factorisation LU globale. Nous montrons comment ces placements peuvent améliorer les performances quand ils sont appliqués à des solveurs hybrides multicœurs/GPU. / In this PhD thesis, we study algorithms and implementations to accelerate the solution of dense linear systems by using hybrid architectures with multicore processors and accelerators. We focus on methods based on the LU factorization and our code development takes place in the context of the MAGMA library. We study different hybrid CPU/GPU solvers based on the LU factorization which aim at reducing the communication overhead due to pivoting. The first one is based on a communication avoiding strategy of pivoting (CALU) while the second uses a random preconditioning of the original system to avoid pivoting (RBT). We show that both of these methods outperform the solver using LU factorization with partial pivoting when implemented on hybrid multicore/GPUs architectures. We also present new solvers based on randomization for hybrid architectures for Nvidia GPU or Intel Xeon Phi coprocessor. With this method, we can avoid the high cost of pivoting while remaining numerically stable in most cases. The highly parallel architecture of these accelerators allow us to perform the randomization of our linear system at a very low computational cost compared to the time of the factorization. Finally we investigate the impact of non-uniform memory accesses (NUMA) on the solution of dense general linear systems using an LU factorization algorithm. In particular we illustrate how an appropriate placement of the threads and data on a NUMA architecture can improve the performance of the panel factorization and consequently accelerate the global LU factorization. We show how these placements can improve the performance when applied to hybrid multicore/GPU solvers.

In the paper [HSS] Herrlich, Salicrup and Strecker were able to show that Kuratowski / Mrowka's Theorem concerning compactness for topological spaces could be applied to a wider setting. In this dissertation, which is based on the paper [F subscript 1], we interpret Kuratowski / Mrowka's result in the category R-Mod. Chapter One deals mainly with the preliminary definitions and results and we also show that there is a 1-1 correspondence between torsion theories and standard factorisation systems. In Chapter Two we, obtain for every torsion theory T, a theory of T-compactness which is an extension of the definition of compactness found in [HSS]. We then obtain a characterisation of T-compactness under certain conditions on the ring R and torsion theory T. In Chapter Three we examine the class of T-compact R-modules more closely when the ring R is T-hereditary and T-noetherian. We also obtain further characterisation of T-compactness under these additional conditions. In Chapter Four we show that many topological results have analogues in R-Mod. / Mathematical Sciences / M. Sc. (Mathematics)

Statistical data suggests that increased use of evidence-based medical therapies has largely contributed to the decrease in American death rate caused by heart disease. And my studies are about two applications of magnetic resonance imaging (MRI) as a non-invasive approach in evidence-based health care research. In my first study, the achievement of a pulmonary valve replacement surgery was assessed on a patient with tetralogy of Fallot (TOF). In order to evaluate the remodeling of right ventricle, two biventricular finite element models were built up for pre-surgical images and post-surgical images. In my second study, 3D Lagrangian strains and torsion in the left ventricle of ten rats were investigated using Displacement ENcoding with Stimulated Echoes (DENSE) cardiac magnetic resonance (CMR) images. Tools written in MATLAB were developed for 2D contouring, 3D modeling, strain and torsion computations, and statistical comparison across subjects.

In the past decades, wireless Machine-to-Machine (M2M) networks have been developed in various industrial and public service areas and envisioned to improve our daily life in next decades, e.g., energy, manufacturing, transportation, healthcare, and safety. With the advantage of low cost, flexible deployment, and wide coverage as compared to wired communications, wireless communications play an essential role in providing information exchange among the distributed devices in wireless M2M networks. However, an intrinsic problem with wireless communications is that the limited radio spectrum resources may result in unsatisfactory performance in the M2M networks. With the number of M2M devices projected to reach 20 to 50 billion by 2020, there is a critical need to solve the problems related to the design and applications in the wireless M2M networks. In this dissertation work, we study the wireless M2M networks design from three closely related aspects, the wireless M2M communication reliability, efficiency, and Demand Response (DR) control in smart grid, an important M2M application taking the advantage of reliable and efficient wireless communications. First, for the communication reliability issue, multiple factors that affect communication reliability are considered, including the shadowing and fading characteristics of wireless channels, and random network topology. A general framework has been proposed to evaluate the reliability for data exchange in both infrastructure-based single-hop networks and multi-hop mesh networks. Second, for the communication efficiency issue, we study two challenging scenarios in wireless M2M networks: one is a network with a large number of end devices, and the other is a network with long, heterogeneous, and/or varying propagation delays. Media Access Control (MAC) protocols are designed and performance analysis are conducted for both scenarios by considering their unique features. Finally, we study the DR control in smart grid. Using Lyapunov optimization as a tool, we design a novel demand response control strategy considering consumer’s comfort requirements and fluctuations in both the renewable energy supply and customers’ load demands. By considering those unique features of M2M networks in data collection and distribution, the analysis, design and optimize techniques proposed in this dissertation can enable the deployment of wireless M2M networks with a large number of end devices and be essential for future proliferation of wireless M2M networks. / Graduate / 0544 / flintlei@gmail.com

Fault localization is the process of realizing the true source of a failure from a set of collected failure notifications. Isolating failure recovery within the network optical domain is necessary to resolve alarm storm problems. The introduction of the monitoring trail (m-trail) has been proven to deliver better performance by employing monitoring resources in a form of optical trails - a monitoring framework that generalizes all the previously reported counterparts. In this dissertation, the m-trail design is explored and a focus is given to the analysis on using m-trails with established lightpaths to achieve fault localization. This process saves network resources by reducing the number of the m-trails required for fault localization and therefore the number of wavelengths used in the network. A novel approach based on Geographic Midpoint Technique, an adapted version of the Chinese Postman’s Problem (CPP) solution and an adapted version of the Traveling Salesman’s Problem (TSP) solution algorithms is introduced. The desirable features of network architectures and the enabling of innovative technologies for delivering future millimeter-waveband (mm-WB) Radio-over-Fiber (RoF) systems for wireless services integrated in a Dense Wavelength Division Multiplexing (DWDM) is proposed in this dissertation. For the conceptual illustration, a DWDM RoF system with channel spacing of 12.5 GHz is considered. The mm-WB Radio Frequency (RF) signal is obtained at each Optical Network Unit (ONU) by simultaneously using optical heterodyning photo detection between two optical carriers. The generated RF modulated signal has a frequency of 12.5 GHz. This RoF system is easy, cost-effective, resistant to laser phase noise and also reduces maintenance needs, in principle. A revision of related RoF network proposals and experiments is also included. A number of models for Passive Optical Networks (PON)/ RoF-PON that combine both innovative and existing ideas along with a number of solutions for m-trail design problem of these models are proposed. The comparison between these models uses the expected survivability function which proved that these models are liable to be implemented in the new and existing PON/ RoF-PON systems. This dissertation is followed by recommendation of possible directions for future research in this area.

L'objectif de cette étude est de comprendre et de modéliser la phénoménologie du transport vertical dense descendant de particules de la classe A de la classification de Geldart. Dans un premier temps, une étude expérimentale est réalisée sur une maquette en statique (absence de circulation de solide) dans le but de déterminer expérimentalement l'effet des paramètres opératoires sur les grandeurs caractéristiques de la défluidisation des particules de FCC : vitesses de sédimentation, porosité de la phase dense, temps caractéristiques…. Ces données sont nécessaires pour l'étude de l'écoulement gaz/solide dense vertical descendant. La simulation numérique en 2D de la défluidisation est effectuée et les prédictions sont comparées aux données expérimentales. Dans un deuxième temps, des essais sur une maquette permettant de reproduire les phénomènes observés industriellement dans les écoulements denses verticaux descendants de particules sont entrepris. Les observations visuelles complètent les mesures de pressions locales obtenues le long de l'écoulement à différentes conditions avec et sans injection de gaz d'aération. L'étude expérimentale consiste à : - déterminer les limites des différents régimes en termes de débit surfacique de solide et de débit d'aération ; - établir les propriétés de l'écoulement dans les différents régimes. Dans un troisième temps, les propriétés des écoulements de différents régimes sont étudiées et modélisées par une approche monodirectionnelle du type bulle-émulsion. / The objective of this study is to understand and model the phenomenology of the vertical downward dense transport of class A particles of the Geldart classification. Initially, an experimental study is conducted on a static fluidized bed (no flow of solid) in order to determine experimentally the effect of operating parameters on the defluidization properties of FCC particles, such as, sedimentation rates, dense phase porosity, characteristic times ... These data are needed to study gas/solid dense downward flow. 2D numerical simulations of defluidization are performed and the predictions are compared with experimental data. In a second step, experiments are undertaken in a pilot unit able to reproduce the gas/solid dense downward flow phenomena observed in industrial units. Visual observations complement the local pressure measurements profile obtained for the different flow conditions with and without external injection of gas. The experimental study is conducted to: - determine the boundaries of different flow patterns in terms of solid mass flux and gas flowrate; - establish flow properties in different flow patterns. Finally, flow properties of the different patterns are studied and modelled by a monodimensional bubble/emulsion approach.

M. Tech., (Faculty of Applied and Computer Science), Vaal University of Technology / There is huge concern in the mining and industries to manage wastewater prior to discharge into the environment. It is generally cheaper and cost reducing for industries to treat its own wastewater before discharging to the local authority sewer. Dense Media Separation (DMS) Powders Company produces milled and atoms ferro-silicon by pyro-metallurgical process. DMS Powders uses municipal water for all processes taking place in the plants. The water used during the processes of milled and atom ferrosilicon powder is discharged into the environment without being treated. By treating this process wastewater before discharging will result in reducing the water consumption by recycling and the penalty costs for polluting the environment. The primary objective of this study is to find suitable method for treatment of DMS Powders’ process water using selected membrane processes. Membrane processes are better choice compared to traditional physical/chemical treatment processes, due to their advantages of approving water quality, no phase change, no chemical addition and simple operation. Two commercial membranes namely; NF-, and SW30HR are used in the treatment of DMS Powders process water. These membranes were purchased from (Dow/Filmtec) Manufacturing Company (Pty) situated in South Africa. Membranes were characterised by Scanning Electron Microscopy (SEM), Thermo Gravimetric Analysis (TGA), Differential Thermal Analysis (DTA) and Fourie Transform Infrared (FTIR) instruments. For synthetic water three membranes (NF- , NF90, and SW30HR) are investigated for the study. The fluxibility indicated that NF- membrane has higher flux compared to NF90 and SW30HR membranes. All the three membranes were very good in terms of rejection on single salts. Fouling was studied on DMS Powders process water. Concentration polarization was formed on NF- and SW30HR membranes investigations on selected membranes conclude that NF- membrane will be the suitable membrane for treatment of DMS Powders process water because of its high fluxibility and rejection. Discharged effluent of DMS Powders could comply with the legislature and environmental pollution could be minimised. The study revealed that fouling does occur during treatment of process water. SW30HR showed that M9 Plant had more fouling for M9 samples than other Plants (M8A and M8B). It was because of higher concentrations in suspended solids.or M8A, M8B and M9 process water.