The control of particle emissions from an oil refinery is often difficult, due to changing operational conditions and the limited range of available treatment options. Excessive particle emissions have often been attributed start up problems with Fluidized Catalytic Cracker Units (FCCU) and little information is available regarding the exact composition and nature of these excessive emissions. Due to the complex nature of a FCCU, it has in the past been difficult to identify and control emissions, without the use of expensive end of pipe technologies. An Australian Oil Refinery, concerned with their catalyst emissions, sponsored this study of FCCU particle emissions. Due to the industrial nature of the project, a holistic approach to the management of emissions was taken, instead of a detailed investigation of a single issue. By looking at the broader range of issues, practical and useful outcomes can be achieved for the refinery. Initially, detailed emissions samplings were conducted to investigate the degree of particle emissions under start up conditions. Stack emissions were collected during a standard start up, and analysed to determine the particle size distribution and metal concentration of the emitted material. Three distinct stages of emissions were discovered, initially a high concentration of larger particles, followed by a peak in the very fine particles and finally a reduction of particle emissions to a more steady or normal operational state. The variation in particle emissions was caused by operational conditions, hardware design and catalyst characteristics. Fluctuations in the gas velocity through the system altered the ability of the cyclones to collect catalyst material. Also, the low bed level allowed air bypass to occur more readily, contributing to the increased emissions levels seen during the initial stage of the start up. Reduced fluidity characteristics of the circulating catalyst also affected the diplegs operations, altering the collection efficiency of the cyclone. During the loading of catalyst into the system, abraded material was quickly lost due to its particle size, contributing to fine particle emissions levels. More importantly, thermal fracturing of catalyst particles occurred when the cold catalyst was fed into the hot regenerator. Catalyst particles split causing the generation of large amounts of fine particle material, which is easily lost from the system. This loading of catalyst directly linked to the period of high concentration of fine particles in the emissions stream. It was found that metals, and in particular iron, calcium and silicon form a thick layer on the outside of the catalyst, with large irregular shaped metal ridges, forming along the surface of the particle. These ridges reduce the fluidity of the catalyst, leading to potential disruptions in the regenerator. In addition to this, the metal rich ridges are preferentially removed via attrition, causing metal rich material to be emitted into the atmosphere. To overcome these high particle emissions rates from the FCCU the refinery should only use calcinated catalyst to reduce the influence of thermal process and particle fracture and generation. Although the calcinated catalyst can fracture when added to the system, it is far less than that obtained with uncalicinated catalyst. To further reduce the risk of particle fracture due to thermal stresses the refinery should consider reducing the temperature gradients between the hot and cold catalyst. Due to the economics involved with the regenerator, possible pre-warming of catalyst before addition into system is the preferred option. This pre-heating of catalyst should also incorporate a controlled attrition stage to help remove the build up of metals on the surface of the particles whilst allowing this material to be collected before it can be released into the atmosphere. The remove of the metal crust will also improve the fluidity of the system and reduce the chance of catalyst blockages occurring. Finally, modelling of the system has shown that control of key parameters such as particle size and gas velocity are essential to the management of air emissions. The refinery should look at adjusting start up procedures to remove fluctuations in these key parameters. Also the refinery should be careful in using correlation found in the literature to predicted operational conditions in the system as these correlations are misleading when used under industrial situations.

L'utilisation des antennes MIMO est une technique qui permet d'exploiter de façon très efficace la diversité spatiale et temporelle présente dans certains systèmes de communication, dont le canal sans fil. Le principal avantage de cette technique est une très grande efficacité spectrale. De nos jours, où le canal radio-mobile est de plus en plus utilisé pour transmettre tout type d'information, les méthodes permettant une utilisation plus efficace du spectre électromagnétique ont une importance fondamentale. Les algorithmes de réception connus aujourd'hui sont très complexes, même en ce qui concerne les systèmes MIMO avec les codes espace-temps les plus simples. Cette complexité reste l'un des obstacles principaux à l'exploitation réelle. Cette thèse présente une étude très détaillée de la complexité, la performance et les aspects les plus intéressants du comportement des algorithmes de la réception pour le décodage MIMO, étude qui présente un moyen rapide pour une éventuelle conception des architectures adaptées à ce problème. Parmi les sujets présentés dans cette thèse, une étude approfondie de la performance et la complexité de ces algorithmes a été réalisée, ayant pour objectif d'avoir une connaissance suffisante pour pouvoir choisir, parmi le grand nombre d'algorithmes connus, le mieux adapté à chaque système particulier. Des améliorations aux algorithmes connus ont aussi été proposées et analysées.

The present work aims to increase the diagnosis systems capabilities by choosing the location of sensors in the process. Therefore, appropriate sensor location will lead to better diagnosis performance and implementation easiness. The work is based on structural models ands some simplifications are considered in order to only focus on the sensor placement analysis. Several approaches are studied to solve the sensor placement problem. All of them find the optimal sensor configuration. The sensor placement techniques are applied to a fuel cell stack system. The model used to describe the behaviour of this system consists of non-linear equations. Furthermore, there are 30 candidate sensors to improve the diagnosis specifications. The results obtained from this case study are used to strength the applicability of the proposed approaches. / El present treball té per objectiu incrementar les prestacions dels diagnosticadors mitjançant la localització de sensors en el procés. D'aquesta manera, instal·lant els sensors apropiats s'obtenen millors diagnosticador i més facilitats d'implementació. El treball està basat en models estructurals i contempla una sèrie de simplificacions per tal de entrar-se només en la problemàtica de la localització de sensors. S'utilitzen diversos enfocs per tal de resoldre la localització de sensors, tot ells tenen com objectiu trobar la configuració òptima de sensors. Les tècniques de localització de sensors són aplicades a un sistema basat en una pila de combustible. El model d'aquest sistema està format per equacions no lineals. A més, hi ha la possibilitat d'instal·lar fins a 30 sensors per tal de millorar la diagnosis del sistema. Degut a aquestes característiques del sistema i del model, els resultats obtinguts mitjançant aquest cas d'estudi reafirmen l'aplicabilitat dels mètodes proposats.

Cette thèse propose une technique innovante de diagnostic non invasive pour les systèmes piles à combustible. Cette technique s'appuie sur la mesure de la signature magnétique générée par ces systèmes. A l'aide de ces champs magnétiques externes, il est possible d'obtenir une cartographie de la densité de courant interne par résolution d'un problème inverse. Ce problème est néanmoins mal posé : la solution est non unique et est extrêmement sensible au bruit. Des techniques de régularisation ont ainsi été mises en place pour filtrer les erreurs de mesures et obtenir une solution physiquement acceptable. Afin d'augmenter la qualité de reconstruction des courants, nous avons conçu notre outil de diagnostic de manière à ce qu'il soit uniquement sensible aux défaillances de la pile (capteur de défauts). De plus, cette reconstruction se base sur un nombre extrêmement faible de mesures. Une telle approche facilite l'instrumentation du système et augmente la précision et la rapidité de celui-ci. La sensibilité de notre outil à certaines défaillances (assèchements, appauvrissement en réactifs, dégradations) est démontrée.

Due to the rapid development of semiconductor technology, the number of transistors of integrated circuits in unit area increases by double in roughly every two years. We then can add more circuits and functionality into a single chip. The size of electronic products certainly is reduced. Besides, because of the blooming popularity of wireless network standards in recently year, sensors have been wireless connected to provide more functionality and intelligence. They are, namely, wireless sensor network (WSN). Before long, the integrated circuit design will not only be emphasized on front-end circuits and hardware design, but also integration and functionality, which is so-called the system-on-chip (SOC) design. The first topic of this thesis is the implementation of IEEE 802.15.4 network prototype and hardware design. The main purpose of prototyping is to realize the highly portable IEEE 802.15.4 protocol stack library which can be quickly transferred to different hardwares. Thus, it shortens the time to market. In ASIC hardware design, we use WISHBONE bus as the interconnection architecture which can be easily integrated into current SOC design for an embedded system. The second topic is an application of IEEE 802.15.4 in medical monitoring, including system prototyping and ASIC hardware design, which collects the bladder pressure readings by a wireless link and ECG signals from our ASIC sensors. Finally, we realize the medical monitoring in a prototypical system.

Fuel cells are electricity generators which convert chemical energy of hydrogen directly to electricity by means of electrochemical oxidation and reduction reactions. A single proton exchange membrane (PEM) fuel cell can only generate electricity with a potential between 0.5V and 1V. The useful potential can be achieved by stacking cells in series to form a PEM fuel cell stack. There is a potential to utilize 100W class fuel cells. Fuelling is the major problem of the portable fuel cells. The aim of this thesis is to design and manufacture a PEM fuel cell stack which can be used for portable applications. The PEM fuel cell stack is planned to be incorporated to a NaBH4 hydrolysis reactor for H2 supply. Within the scope of this thesis a new coating technique called &ldquo / ultrasonic spray coating technique&rdquo / is developed for membrane electrode assembly (MEA) manufacturing. New metal and graphite bipolar plates are designed and manufactured by CNC technique. A fuel cell controller hardware is developed for fuel supply and system control. The power densities reached with the new method are 0.53, 0.74, 0.77, and 0.88 W/cm2 for 20%, 40%, 50%, 70% Pt/C catalyst by keeping 0.4mg Pt/cm2 platinum loading constant, respectively. The power density increase is 267% compared to &ldquo / spraying of catalyst ink with air pressure atomizing spray gun&rdquo / . All parts of the PEM fuel cell stack designed were produced, assembled, and tested. The current density reached is 12.9A at 12 V stack potential and the corresponding electrical power of the stack is 155W.

The objective of this thesis is to study two Basins of the Gulf of Guinea (GoG), namely the Dahomey and the Liberian Basins. These Basins are located in the northern part of the GoG, where oil and gas exploration has significantly increased in the last 10 years or so. We proposed geological descriptions of these two Basins. The key characteristics of the two models are the presence of channels and pinch-outs for depths of between 1 km and 2 km (these values are rescaled for our numerical purposes to 600- m and 700-m depths) and normal faults below 3 km (for our numerical purposes we use 1 km instead of 3 km). We showed that these models are consistent with the plate tectonics of the region, and the types of rocks and ages of rocks in these areas. Furthermore, we numerically generated seismic data for these two models and depth-migrated them. We then interpreted the migrated images under the assumption that the geologies are unknown. The conclusions of our interpretations are that we can see clearly the fault systems in both models. However, our results suggest that seismic interpretations of the channels and pinch-outs associated with the geology of the Dahomey and Liberian Basins will generally be difficult to identify. In these particular cases, we missed a number of channels and pinch-outs in our interpretations. The limited resolution of seismic images is the key reason for this misinterpretation.

This paper presents a novel implementation of an embedded Java microarchitecture for secure, realtime, and multi-threaded applications. Together with the support of modern features of object-oriented languages, such as exception handling, automatic garbage collection and interface types, a general-purpose platform is established which also fits for the agent concept. Especially, considering real-time issues, new techniques have been implemented in our Java microarchitecture, such as an integrated stack and thread management for fast context switching, concurrent garbage collection for real-time threads and autonomous control flows through preemptive round-robin scheduling.

This thesis addresses the problems associated with security of the electricity supply in the UK. The British electricity supply industry has experienced a significant structural change. Competition has been brought into the electricity industry and a single wholesale electricity market of Great Britain has been established. The evolution of the British electricity market raises new challenges, such as improving the liquidity of wholesale markets and developing clean energy. The wholesale electricity prices are less transparent and trading arrangements are very complex in the British electricity market. In this thesis a fundamental model, called a stack model, has been developed in order to forecast wholesale electricity prices. The objective of the stack model is to identify the marginal cost of power output based on the fuel prices, carbon prices, and availability of power plants. The stack model provides a reasonable marginal cost curve for the industry which can be used as an indicator for the wholesale electricity price. In addition, the government's targets for climate change and renewable energy bring new opportunities for wind energy. Under the large wind energy penetration scenario the security of the energy supply will be essential. We have modelled the correlations between wind speed data for a set of wind farms. The correlation can be used to measure the portfolio risk of the wind farms. Electricity companies should build their portfolio of wind farms with low or negative correlations in order to hedge the risk from the intermittency of wind. We found that the VAR(1) model is superior to other statistic models for modelling correlations between wind speeds of a wind farm portfolio.

Network coding is a technique used to increase the capacity of a network by combining messages sent over the network. The combined messages could be separated by using sufficient original messages which were used to combine the messages. Network coding can be implemented in different layers of the 051 stack, but to date a complete comparison between different implementations of network coding has not been done. The goal of this dissertation is to implement a wireless node model with network coding in the MAC layer and evaluate the performance characteristics of reference networks that implement the new node model. This will serve as the first step of a greater goal, namely finding the most favourable position in the 051 stack to implement network coding. The characteristics of the different implementations of network coding are presented in this dissertation. Simulations were done in OPNET® to find further attributes concerning the implementation of network coding in the MAC layer. The simulation process used is presented and explained, and the results from the simulations are analysed. Network coding in the simulations was implemented opportunistically. The results show that the more often different nodes send frames to the coding node, the better network coding performs. The work contributes to finding the best layer for implementing network coding for its increased throughput. A benchmark network was created so that network coding could be implemented in all the layers of the 051 stack, and then be compared to each other. An implementation of network coding in the MAC layer was simulated and analyzed. We conclude that, because there are so many different purposes for which networks are used, a single instance of network coding is unlikely to be similarly beneficial to all purposes. There still remains work to find the most favourable position for network coding in the 051 stack for all the different types of network coding. / Thesis (M. Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2011