The Madden-Julian Oscillation (MJO), a tropical phenomenon that exists on the time scale of 30-90 days, commonly initiates over the Indian Ocean and slowly propagates into the western Pacific as a series of convective events, which have time scales on the order of hours or days. These events and the overall MJO convective envelope may interact with convectively coupled waves such as Kelvin waves that propagate more rapidly eastward with time scales of 3-5 days. Radar and sounding data collected during the DYNAMO/AMIE/CINDY2011 field campaign from October 2011 to February 2012 in the central Indian Ocean are used to study the interaction between Kelvin waves and the MJO in terms of atmospheric and cloud properties. The focus is on characterizing the precipitation characteristics, convective cloud spectrum, and atmospheric profiles of Kelvin waves during the active and suppressed phases of the MJO to gain insight on MJO initiation. Characteristics of waves identified using different satellite thresholds and filtering methods are compared. Composites of the radar and sounding observations are calculated for a total of ten Kelvin waves and three MJO events that occurred during the field campaign. Analyzed radar products include convective-stratiform classification of rain rate, rain area, and echo-top heights, as well as cloud boundaries. Sounding data includes profiles of wind speed and direction and relative humidity. Kelvin waves that occur during the suppressed MJO are convectively weaker than Kelvin waves during the active MJO, but display previously documented structure of low-level convergence and a moist atmosphere prior to the wave passage. During the active MJO, Kelvin waves have stronger convective and stratiform rain, and the entire event is longer, suggesting a slower moving wave. The Kelvin wave vertical structure is somewhat overwhelmed by the convective envelope associated with the MJO. When the MJO is developing, the Kelvin wave displays a moisture-rich environment after the passage, providing deep tropospheric moisture that is postulated to be important for the onset of the MJO. The convective cloud population prior to MJO initiation shows increased moisture and a population of low- to mid-level clouds. The moisture precedes shallow convection, which develops into the deep convection of the MJO, supporting the discharge-recharge theory of MJO initiation. Additionally, enhanced moisture after the passage of the pre-MJO Kelvin wave could also support the frictional Kelvin-Rossby wave-CISK theory of MJO initiation. With a better understanding of the interaction between the initiation of the MJO and Kelvin waves, the relationships between the environment and the onset of the convection of the MJO can be improved.

On s'intéresse dans ce mémoire aux équations de la magnétohydrodynamique (MHD) dans des milieux hétérogènes, i.e. dans des milieux pouvant présenter des variations (éventuellement brutales) de propriétés physiques. En particulier, on met ici l'accent sur la résolution des équations de Maxwell dans des milieux avec des propriétés magnétiques inhomogènes. On présentera une méthode non standard pour résoudre ce problème à l'aide d'éléments finis de Lagrange. On évoquera ensuite l'implémentation dans le code SFEMaNS, développé depuis 2002 par J.-L. Guermond, C. Nore, J. Léorat, R. Laguerre et A. Ribeiro, ainsi que les premiers résultats obtenus dans les simulations de dynamo. Nous nous intéresserons par exemple au cas de la dynamo dite de Von Kármán, afin de comprendre l'expérience VKS2. En outre, nous aborderons des cas de dynamo en précession, ou encore le problème de la dynamo au sein d'un écoulement de Taylor-Couette.

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The dynamics of the solar corona are dominated by the magnetic field which creates its structure. The magnetic field in most of the corona is ‘frozen’ to the plasma very effectively. The exception is in small localised regions of intense current concentrations where the magnetic field can slip through the plasma and a restructuring of the magnetic field can occur. This process is known as magnetic reconnection and is believed to be responsible for a wide variety of phenomena in the corona, from the rapid energy release of solar flares to the heating of the high-temperature corona. The coronal field itself is three-dimensional (3D), but much of our understanding of reconnection has been developed through two-dimensional (2D) models. This thesis describes several models for fully 3D reconnection, with both kinematic and fully dynamic models presented. The reconnective behaviour is shown to be fundamentally different in many respects from the 2D case. In addition a numerical experiment is described which examines the reconnection process in coronal magnetic flux tubes whose photospheric footpoints are spun, one type of motion observed to occur on the Sun. The large-scale coronal field itself is thought to be generated by a magnetohydrodynamic dynamo operating in the solar interior. Although the dynamo effect itself is not usually associated with reconnection, since the essential element of the problem is to account for the presence of large-scale fields, reconnection is essential for the restructuring of the amplified small-scale flux. Here we examine some simple models of the solar-dynamo process, taking advantage of their simplicity to make a full exploration of their behaviour in a variety of parameter regimes. A wide variety of dynamic behaviour is found in each of the models, including aperiodic modulation of cyclic solutions and intermittency that strongly resembles the historic record of solar magnetic activity.

The overarching goal of this thesis is to investigate and explore the barriers that a company would face while increasing the Levels of Automation (LoA), in the preassembly production unit. To achieve the primary goal of investigating the barriers this study takes a threefold approach. Firstly, the current LoA was measured for the preassembly workstations. This measurement was conducted by incorporating an existing methodology adapted from the literature review known as DYNAMO++ methodology. This method is incorporated such that, the current LoA of the preassembly workstations could be measured and analysed. The current LoA of the preassembly workstations are analysed to investigate the potential workstations where LoA could be increased, in line with the company’s triggers for implementing automation. For this, experiences of the personnel’s belonging to the operational level of preassembly workstations were incorporated, to find the scope of improvements for increasing the LoA. Additionally, the company’s triggers for implementing automation was investigated from the managerial level. The research questions were answered by adapting an explorative, single case study method. Additionally, four types of data collection techniques were used, such as – interviews, focus groups, observations, and document analysis. Subsequently, source triangulation was adapted to analyse the data collected; to develop a comprehensive understanding of the barriers identified., Finally, the barriers faced by the company to increase LoA are identified by considering the implications that the improvement opportunities would impose upon the production systems environment. The identified barriers were then categorised further based on factors that exist internal as well as external to the production systems environment. The barriers identified in this study highlights various factors that the management must consider beforehand while initiating automation decisions in future automation projects in the preassembly area. Regardless of the barriers faced by the company, there are more opportunities to improve manufacturing processes through automation technologies. This thesis contributes to the knowledge of the factors that restrain the implementation of automation technologies and how companies could deal with it.

MSc (Mathematics) / Department of Mathematics and Applied Mathematics / The unsteady hydromagnetic chemically reacting mixed convection MHD ow over a permeable stretching sheet embedded in a porous medium with thermal radiation and heat source/sink is investigated numerically. The original partial di erential equations are converted into ordinary di erential equations by using similarity transformation. The governing non-linear partial di erential equations of Momentum, Energy, and Concentration are considered in this study. The e ects of various physical parameters on the velocity, temperature, and species concentration have been discussed. The parameters include the Prandtl number (Pr), Magnetic parameter (M), the Schmidt number (Sc), Unsteady parameter (A), buoyancy forces ratio parameter (N), Chemical reaction (K), Radiation parameter (Nr), Eckert number (Ec), local heat source/sink parameter (Q) and buoyancy parameter due to temperature ( ). The coe cient of Skin friction and Heat transfer are investigated. The coupled non-linear partial di erential equations governing the ow eld have been solved numerically using the Spectral Relaxation Method (SRM). The results that are obtained in this study are then presented in tabular forms and on graphs and the observations are discussed. / NRF

Im Rahmen des Projektes DRESDYN wird einem mit Fluid gefülltem rotierenden Behälter eine Präzession aufgezwungen. Durch Fertigungsungenauigkeiten und andere Einflusse weicht die Position des Masseschwerpunktes des Behälters von den Rotationsachsen ab, was zu harmonischen Kräften in der Behälterlagerung führt. Die Eigenfrequenzen der Unterkonstruktion liegen relativ niedrig, was eine zeitdiskrete quasistatische Betrachtung nicht mehr erlaubt. Eine transiente Analyse würde dagegen bei der Anzahl an Lastfällen einen viel zu großen Rechenaufwand verursachen. Da die Kräfte in einen statischen und harmonischen Anteil zerlegt werden können, kann die Frequenzganganalyse alternativ zur Lösung des Problems verwendet werden. Die Expansion der harmonischen Lösung liefert die diskreten Zeitschritte der Reaktionskraft- und Spannungsamplituden, welche für einen Ermüdungsfestigkeitsnachweis verwertet werden können.

The EU building sector is a main contributor to greenhouse gas emissions, which need to be cut as part of the global response to anthropogenic climate change. This cut can be realised through improvements in building energy performance, such as optimisation of facade design. The early stage of the architectural process has been identified as the ideal time to implement such sustainable design choices. There is need for simple guidelines and tools to provide quantitative data to support these architectural decisions. BIM and parametric design can provide this, by facilitating model-based analysis and simulation, as part of an unbroken flow of information through the design process. This study uses Dynamo (the visual programming add-in for Autodesk Revit) together with the Honeybee and Ladybug environmental plugins, to conduct daylight, solar heat gains and thermal losses analyses and simulations. The aim was to identify limitations and opportunities in using Dynamo-Revit, to establish an optimal range for glazing-to-wall ratio (GWR) and to provide some simple room-sizing guidelines for architects in the early stage of the design process. The Dynamo-Revit workflow was found to be effective for specific projects, but difficult to perfect for multiple different projects. An optimal range for GWR was found as 30-40% for east, south and west-facing rooms and around 50% for rooms facing only north. Results were tabulated, linking room orientation and depth with estimated daylight access, solar heat gains and thermal losses. The results were reasonable, but could be improved by the use of more sophisticated analysis and simulation techniques, which should be facilitated by forthcoming development of Honeybee and Ladybug in Dynamo.

This thesis entails the design and fabrication of a smartphone charger that is powered by a bicycle dynamo hub. In addition to the design and validation of the charger prototype, this thesis involves the testing and characterization of the dynamo hub power source, the design and construction of specialized test equipment, and the design and prototyping of a handlebar-mounted case for the smartphone and charging electronics. With the intention of making the device a commercial product, price, aesthetics, and marketability are of importance to the design. An appropriate description of the charger circuit is a microcontroller-based energy management system, tailored to meet strict power demands of current smartphones. The system incorporates a switched-mode power supply, lithium polymer battery, microcontroller, and specialized protection circuitry. Prototype testing confirms that the circuit meets the charging requirements of the smartphone at bicycle speeds ranging from 7 miles per hour to as high as 55 miles per hour.

Диссертационное исследование посвящено разработке рекомендаций для улучшения рабочего процесса проектирования инженерных сетей ОВ. В работе рассматриваются: этапы разработки цифровой модели здания, основы технологии проектирования, рекомендации по разработке систем отопления и вентиляции средствами программы Autodesk Revit и Linear, а также методика по разработке и реализация алгоритма, автоматизирующего процесс формирования документации. / The dissertation research is devoted to the development of recommendations for improving the workflow of designing engineering networks of the OB. The paper discusses: the stages of developing a digital building model, the basics of design technology, recommendations for the development of heating and ventilation systems using the Autodesk Revit and Linear programs, as well as a methodology for developing and implementing an algorithm that automates the process of generating documentation.