Magister Scientiae - MSc / Technological advancement has created a market for large area electronics such as solar cells and thin film transistors (TFT’s). Such devices now play an important role in modern society. Various types of conducting, semiconducting and insulating thin films of the order of hundreds, or even tens of nanometres are combined in strata to form stacks to create interactions and phenomena that can be exploited and employed in these devices for the benefit of mankind. One such is for the generation of energy via photovoltaic devices that use thin film technology; these are known as second and third generation solar cells. Silicon and its alloys such as silicon germanium (SiGex), silicon oxide (SiOx), silicon carbide (SiCx) and silicon nitride (SiNx) play an important role in these devices due to the fact that each material in its different structures, whether amorphous, micro or nano-crystalline or completely crystalline, has its own range of unique optical, mechanical and electrical properties. These structures and their material properties can thus exert a huge influence over the overall device performance. viii Chemical vapour deposition (CVD) techniques are most widely used in industry to obtain thin films of silicon and silicon alloys. Source gases are decomposed by the external provision of energy thereby allowing for the growth of a thin solid film on a substrate. In this study a variant of CVD, namely Hot Wire Chemical Vapour Deposition (HWCVD) will be used to deposit thin films of silicon nitride by the decomposition of silane (SiH4), hydrogen (H2) and ammonia (NH3) on a hot tantalum filament (~1600 C). Hydrogenated amorphous silicon nitride (a-SiNx:H) has great potential for application in optoelectronic devices. In commercial solar cell production its potential for use as anti-reflection coatings are due to its intermediate refractive index combined with low light absorption. An additional benefit is the passivation of interface and crystal defects due to the bonded hydrogen. This can lead to better photon conversion efficiency. Its optical properties including optical band gap, Urbach tail, and wavelength-dependent optical constants such as absorption coefficient and refractive index are crucial for the design and application in the relevant optoelectronic device. The final firing step in the production of micro-crystalline silicon solar cells, allows hydrogen to effuse into the solar cell from the a-SiNx:H, and drives bulk passivation of the grain boundaries. We therefore propose the exploration of annealing effects on the thin film structure. The study undertakes a comparison of optical and bonding structure of the as deposited thin film compared to that of the annealed thin film which would have undergone changes due to high temperature annealing under vacuum. However, it is difficult to simultaneously obtain all of these important ix optical parameters for a-SiNx:H thin films. Ultraviolet visible (UV-vis) spectroscopy will be the method of choice to investigate the optical properties. Infrared (IR) spectroscopy is a source of useful information on the microstructure of the material. In particular, the local atomic bonding configurations involving Si, N, and H atoms in a-SiNx:H films can be obtained by Fourier Transform Infrared Spectroscopy (FTIR). Therefore, this study will attempt to establish a relationship between film microstructure of a-SiNx:H thin films and their macroscopic optical properties.

Topology design of distributed local area networks (DLANs) can be classified as an NP-hard problem. Intelligent algorithms, such as evolutionary and swarm intelligence techniques, are candidate approaches to address this problem and to produce desirable solutions. DLAN topology design consists of several conflicting objectives such as minimization of cost, minimization of network delay, minimization of the number of hops between two nodes, and maximization of reliability. It is possible to combine these objectives in a single-objective function, provided that the trade-offs among these objectives are adhered to. This thesis proposes a strategy and a new aggregation operator based on fuzzy logic to combine the four objectives in a single-objective function. The thesis also investigates the use of a number of evolutionary algorithms such as stochastic evolution, simulated evolution, and simulated annealing. A number of hybrid variants of the above algorithms are also proposed. Furthermore, the applicability of swarm intelligence techniques such as ant colony optimization and particle swarm optimization to topology design has been investigated. All proposed techniques have been evaluated empirically with respect to their algorithm parameters. Results suggest that simulated annealing produced the best results among all proposed algorithms. In addition, the hybrid variants of simulated annealing, simulated evolution, and stochastic evolution generated better results than their respective basic algorithms. Moreover, a comparison of ant colony optimization and particle swarm optimization shows that the latter generated better results than the former. / Thesis (PhD)--University of Pretoria, 2009. / Computer Science / unrestricted

L’artisanat verrier forestier moderne connaît un développement particulièrement important dans la région languedocienne qui bénéficie d’une tradition ancrée depuis le XIIIe s. Pour autant, les modes et structures de production sont encore peu documentés et l’historiographie en livre généralement l’image d’un modeste réseau d’officines isolées. Fondée sur la complémentarité des sources écrites, archéologiques et archéométriques, cette étude privilégie l’analyse de ces fabriques à partir de huit ateliers fouillés. Elle livre une approche des divers acteurs comme de l’environnement qui contribuent à la structuration formelle de cet art du feu. Une centaine de centres de production modernes a été recensée, le plus souvent rassemblés en foyers. Si leur développement demeure limité, ils font en revanche état d’une certaine autonomie dans la production. De la plus petite unité forestière aux grands établissements assimilés à des centres villageois, chaque site assure le cycle complet de la production du verre. Les ateliers bénéficient en général d’infrastructures relativement simples, rassemblées autour de deux à trois fours à vocation complémentaire : préparation des matières, fusion et recuit. Leur morphologie ainsi que les usages combinés qui en sont faits varient en fonction des époques et de l’importance de la fabrique. Terre propice à l’établissement de l’industrie verrière pour ses nombreuses ressources naturelles, le Languedoc moderne produit principalement du verre creux destiné à alimenter la province. Toutefois, à partir du premier tiers du XVIIIe s., cet artisanat forestier s’étiole progressivement au profit de grandes manufactures alimentées au charbon de terre. / The modern woodlands glassmaking enjoys a particularly siginifant development in the Lower Languedoc region which benefits from a deeply rooted tradition from the thirteenth century on. However, the ways and structures of production are as yet very poorly documented and the historiography generally gives a picture of a modest network of workshops producing objects for daily use.Based on the additionnal information of written archaeological and archeometrical sources, this study favours the analysis of these factories from eight excavated sites. At first place it gives an approach of the people as well as the surrounding area which shows the formal structuring of this ceramic skillset. About a hundred moderns production centres emerged, grouped together in a number of zones with several workshops near each other. Their extent is limited, on the other hand they indicate a certain autonomy in production. From the smallest unit in the woodlands to the big establishments which resembledl proper village settlements, each site ensured the complete cycle of the operational chain of glass production. Generally, the workshops were a relatively simple infrastructure assembled around two or three furnaces with complementary functions: frit, fusion and annealing furnaces.As a region favourable to the establishment of glassmaking due to the rich resources in raw materials, modern Languedoc produced mainly hollow, concave glass.. Basically their production supplied the province which was the biggest of the kingdom. It is only from the first third of the eighteenth century that this woodland craft industry declined progressively as big coal-fired factories took over.

In dieser Arbeit wird die Beschichtung von Substraten mit Hilfe einer Ultraschallsprühanlage beschrieben. Es wurden Dispersionen aus Siliziumnanopartikeln und Organosiliziumpräkursoren genutzt, um Beschichtungen mit verschiedenen Dicken im Bereich von einigen hundert Nanometern bis zu mehreren Mikrometern auf verschiedenen metallischen Substraten zu erzeugen. Anschließend wurden diese der Blitzlampentemperung (FLA) unterzogen. Bei dünnen Beschichtungen mit Dicken von ca. 19 µm wurden nach der Blitzlampentemperung Filme auf dem Substrat erzeugt. Es wurden unterschiedliche Objektgrößen nach der Blitzlampentemperung in Abhängigkeit von dem Umgebungsdruck und der Pulslänge beobachtet. Bei dickeren Beschichtungen mit Dicken von ca. 38 µm bzw. 57 µm wurden selbstablösende Folien aus Silizium bei moderaten Pulsenergien von 4 J/cm² und durch das Anlegen von 5∙10-3 mbar Unterdruck während der Blitzlampentemperung hergestellt. Durch die Verwendung von Pulslängen mit 17,5 ms und Energien von bis zu 60 J/cm² wurden aus den ca. 38 µm dicken Beschichtungen nach der Blitzlampentemperung durch Übertragung auf ein Molybdänsubstrat ultradünne Siliziumschichten mit 280 nm Schichtdicke erzeugt. Mit Hilfe von Siliziumpresslingen wurde die maximale Eindringtiefe der Energie bei der Blitzlampentemperung ermittelt. Diese wurden bei verschiedenen Pulslängen und Energien mit der Blitzlampe getempert. Durch das Brechungsvermögen der Presslinge wurde an diesen sowohl die Oberfläche als auch durch Querschnittsaufnahmen die Sinterung bzw. das Schmelzen in der Tiefe nach der Blitzlampentemperung untersucht. Der Einfluss der Blitzlampentemperung auf die Polymorphie und die Kristallinität von Bis-mut(III)oxiden wurde untersucht. Die Charakterisierung der Siliziumfolien, Siliziumschichten und Siliziumpresslinge als auch der Bismut(III)oxide erfolgte unter anderem mittels Röntgenpulverdiffraktometrie, Rasterelektronenmikroskopie sowie Röntgenphotoelektronenspektroskopie.

Dans le contexte du futur système de gestion du trafic aérien, un des objectifs consiste à réduire l’impact environnemental du trafic aérien. Pour respecter ce but, le concept de “free-route”, introduit dans les années 1990, semble bien adapté aujourd’hui. Les avions ne seraient plus contraints à voler le long de routes aériennes, mais pourraient suivre des trajectoires optimales en terme de consommation. L’objectif de cette thèse est d’introduire une nouvelle méthode de planification du trafic à l’horizon pré-tactique avec des objectifs quelques fois contradictoires, c’est-à-dire avec pour but de minimiser la consommation ou de façon équivalente la durée de trajet en tenant compte des conditions météorologiques et de minimiser l’encombrement de l’espace aérien.La méthode a été mise au point en deux étapes. La première étape a été consacrée au calcul d’une seule trajectoire optimale en terme de temps de vol en tenant compte du vent et de contraintes celles des zones interdites de survol. Cette optimisation est basée sur une adaptation de l’algorithme Ordered Upwind. La deuxième étape introduit un algorithme hybride développé, basé sur un algorithme de recuit simulé et sur l’algorithme déterministe développé dans la première étape, afin de minimiser un compromis entre la congestion et la consommation. L’algorithme combine ainsi la capacité d’atteindre la solution optimale globale via une recherche locale qui permet d’accélérer la convergence.Des simulations numériques avec des prévisions de vent sur du trafic européen donnent des résultats encourageants qui démontrent que la méthode globale est à la fois viable et bénéfique en terme du temps de vol total comme de la congestion globale donc de la diminution des conflits / In the context of the future Air Traffic Management system (ATM), one objective is to reduce the environmental impact of air traffic. With respect to this criterion, the “freeroute” concept, introduced in the mid 1990’s, is well suited to improve over nowadays airspace based ATM. Aircraft will no longer be restricted to fly along airways and may fly along fuel-optimal routes. The objective of this thesis is to introduce a novel pretactical trajectory planning methodology which aims at minimizing airspace congestion while taking into account weather conditions so as to minimize also fuel consumption.The development of the method was divided in two steps. The first step is dedicated to compute a time-optimal route for one aircraft taking into account wind conditions. This optimization is based on an adaptation of the Ordered Upwind Method on the sphere.The second step introduces a hybrid algorithm, based on simulated annealing and on the deterministic algorithm developed in the first step, in order to minimize congestion. Thus the algorithm combines the ability to reach a globally-optimal solution with a local-search procedure that speeds up the convergence.

Nous étudions la régression bayésienne sous contraintes de régularité et de forme. Pour cela,on considère une base de B-spline pour obtenir une courbe lisse et nous démontrons que la forme d'une spline engendrée par une base de B-spline est contrôlée par un ensemble de points de contrôle qui ne sont pas situés sur la courbe de la spline. On propose différents types de contraintes de forme (monotonie, unimodalité, convexité, etc). Ces contraintes sont prises en compte grâce à la loi a priori. L'inférence bayésienne a permis de dériver la distribution posteriori sous forme explicite à une constante près. En utilisant un algorithme hybride de type Metropolis-Hastings avec une étape de Gibbs, on propose des simulations suivant la distribution a posteriori tronquée. Nous estimons la fonction de régression par le mode a posteriori. Un algorithme de type recuit simulé a permis de calculer le mode a posteriori. La convergence des algorithmes de simulations et du calcul de l'estimateur est prouvée. En particulier, quand les noeuds des B-splines sont variables, l'analyse bayésienne de la régression sous contrainte devient complexe. On propose des schémas de simulations originaux permettant de générer suivant la loi a posteriori lorsque la densité tronquée des coefficients de régression prend des dimensions variables. / We investigate the Bayesian regression under shape and smoothness constraints. We first elicita Bayesian method for regression under shape restrictions and smoothness conditions. Theregression function is built from B-spline basis that controls its regularity. Then we show thatits shape can be controlled simply from its coefficients in the B-spline basis. This is achievedthrough the control polygon whose definition and some properties are given in this article.The regression function is estimated by the posterior mode. This mode is calculated by asimulated annealing algorithm which allows to take into account the constraints of form inthe proposal distribution. A credible interval is obtained from simulations using Metropolis-Hastings algorithm with the same proposal distribution as the simulated annealing algorithm.The convergence of algorithms for simulations and calculation of the estimator is proved. Inparticular, in the case of Bayesian regression under constraints and with free knots, Bayesiananalysis becomes complex. we propose original simulation schemes which allows to simulatefrom the truncated posterior distribution with free dimension.

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We report on a novel silicon nanowire-based field effect transistor with integrated ferroelectric gate oxide. The concept allows tuning the carrier transport in a non-volatile approach by switching the polarization in the ferroelectric layer close to the source Schottky-junction. We interpret the results in terms of tuning the transmissibility of the Schottky-junction for charge carriers. The experimental results provide a first step towards the integration of memory-in-logic concepts with reconfigurable nanowire transistors.

Placing recrystallization annealing in a manufacturing proces is often necessary in order to restore plasticity of worked blanks right before working products to its final shape. For better understanding of processes which are taking place in a material during annealing the use of in-situ techniques is favorable. Such observations enable us to watch changes in the materiál in real time at the original spot. Observations at grain-level are ideally made with scanning electron microscope – SEM by electron back-scattered diffraction – EBSD. The technique makes watching nucleation, growth and potential coarsening of recrystallized grains possible. Special construction of a tensile stage allows us to watch changes of a sample during tensile tests which can be used in observing influence of MnS inclusions on plasticity of free-cutting steels. Materials studied in this work are commonly used free-cutting steel 11SMnPb30 and its lead-free alternative 11SMnBi30.

In this thesis we study the interaction of helium, neon, argon and gallium ions with graphene. The graphene structure is contaminated with gallium ions during the graphene processing by focused gallium beam (FIB). The graphene properties are affected, e.g. reducing the electrical conductivity. The aim of this thesis is to verify the effect of selected ion beams on the graphene structure and select suitable ion beam for sputtering. Furthermore, the modification of standard heating stage used in LEIS instrument (Qtac 100) was designed and implemented. The LEIS instrument is connected to the complex UHV system for deposition and analysis of nanostructures – SPECS. This modification allows analysis of selected nanoparticles on suitable substrate at the elevated temperature.