Gravel bed braided rivers are distinctive natural environments that provide a wide range of key environmental, economic and recreational services. There is, however, a growing concern that over the twentieth century, an increasing number of braided rivers have metamorphosed into wandering or single thread channels, representing a loss of key habitats, geodiversity and amenity. While in some situations, shifts in channel pattern may be unambiguously linked to abrupt changes in flow or sediment supply, the lack of a theoretical basis underpinning the development and maintenance of braiding makes identification of the cause and effect of channel metamorphosis hazardous. A growing body of research has suggested that the transition between channel patterns may depend on the poorly understood interaction between the flow regime, sediment supply and vegetation colonisation. Such interactions are governed by critical thresholds, due to changes in flow resistance and bank strength associated with the distribution, form and intensity of vegetation colonisation. Subtle changes in flow or sediment supply that promote vegetation growth or indeed remove it through inundation or attrition. This can lead to complex non-linear shifts in the balance of forces that govern sediment transport and bedform morphodynamics, ultimately resulting in one-way changes in channel morphology. There is, therefore, a critical need to develop a quantitative understanding of these feedbacks in order to design sustainable river management programmes that seek to optimize the ecological and socio-economic benefits these rivers offer. During the last three decades, significant advances in the understanding of the morphodynamics of braided rivers have been made through a combination of field and physical experimentation. More recently, the emerging field of numerical modelling has created a new avenue to investigate the processes that govern channel dynamics. While this methodology offers significant promise through the construction of virtual experiments that examine the spectrum of drivers and responses of river systems, such models require careful and critical evaluation before they can be used to guide management practice. The wider goal of this research is to explore the application of a numerical modelling to investigate the feedbacks associated with the development and maintenance of braiding. Specifically, the state-of-the-art numerical model, BASEMENT, was used to examine channel responses to steady, and unsteady flow regimes, with and without the representation of vegetation. The research focuses on four main contributions: 1. The development of a systematic framework to quantify the evolving form and processes of braided rivers that can be used as part of a comprehensive approach to model validation. 2. Simulation of braiding development and maintenance using BASEMENT under steady flow conditions. Model simulations based on the natural prototype of the braided River Feshie were used to examine the sensitivity of emergent channel morphologies to the model parameterisation, focusing in particular on the representation of bank erosion and gravity-driven sediment transport. A novel multi6metric framework for model validation is presented and the results demonstrate the critical importance of lateral bank migration processes in order to maintain braided morphologies under steady flow. 3. A critical evaluation of the simulation of braiding under different form of steady and unsteady flow regimes is presented. These experiments investigate how the morphodynamics of braiding vary under energetically-normalised flow regimes characterized by differences in hydrograph form (peak discharge and duration). This experiment provides a novel insight into the role of flow variation in the maintenance of braiding. 4. Finally, the feedback between flow regimes, sediment transport and vegetation growth are examined using a novel model of vegetation colonisation and die- back. Four scenarios are presented, a no-vegetation model, one based on low growth rate, one based on an intermediate growth rate, and finally a high growth rate parameterisation. These simulations provide a clear insight into the non-linear processes driving channel evolution and demonstrate how subtle changes in the balance between flow frequency and vegetation growth can lead to divergent channel patterns. In summary, this thesis aims to advance our understanding of the morphodynamics of braided rivers and the role numerical models may have in helping to interrogate their behaviour and governing controls. It is hoped that this work may contribute, albeit in a small way, to advancing the science that promotes the sustainability of these fascinating and valuable environments.

The perception of the expression of traditional handcrafts needs to be challenged. Therefore his bachelor degree work aims to develop new expressions in contemporary men`s wear through experimentations with tubular braiding. This works aims to utilize and express a progressive approach of the technique in terms of materials and method with the desire to create a contemporary expression when a handcraft method is utilized in fashion Starting to explore the handcraft technique braiding the tubular braiding technique was found. While the technique itself is similar in expression and properties to flat braiding the tubular braiding opens up for other possibilities for garment construction. Using the tubular braid as a starting point, the aim is to explore new ways of constructing contemporary menswear garments with the technique itself as well to construct new materials and find to a new expressions. The work also deals with the gap between the technique flat braiding, tubular braiding, construction and materials with different properties altering the initial expression of the technique. By experimenting with unconventional materials and scale for such an handcraft technique as braiding the expression and the traditional view of braiding and its construction and use will be altered and questioned - discovering that the tubular braid has possibilities to construct or sculpt garments on the body in a seamless manner. Hopefully machine-engineers of the future can invent new and progressive braiding processes to create fabrics for commercial application in fashion and also understand the potential of the tubular braiding method formed by the examples here. / <p>Program: Modedesignutbildningen</p>

Flexible risers that carry hydrocarbon fuels from the subsea facilities to the floatation units above the sea surface are composed of multiple metallic and polymeric layers (in their wall). Among these layers, the tensile armour layer consists of several helically wound metallic wires; these tensile armour layers carry the weight of the riser, provide tensile stiffness &amp; strength and maintain the structural integrity of the riser structure during harsh underwater currents. However, as the oil &amp; gas fields in shallow waters are receding, the oil &amp; gas industry is being forced to move towards deeper offshore waters, where the metallic tensile armour wires pose limitations (fatigue, corrosion, weight, etc.). In this thesis an alternative to metallic tensile armour wires will be presented in form of a flexible hybrid composite formed by stacking seven pultruded composite (carbon and vinyl-ester) circular rods in form of hexagonal pack, held together by an over-braid (Dyneema fibres) sleeve. The manufacturing process for hybrid composite tensile armour wires will be studied and their mechanical properties will be presented. A multi-scale finite element model developed for hybrid composite wires will be presented in this thesis to help further understand the mechanical properties of hybrid composite wires.

This research investigates composite tubes developed with hybrid preform manufacturing techniques of braiding and filament winding (FW). A quadriaxial braid-wound (QBW) preform [(±45°/0°/90°)2/(±45°/0°)] and a triaxial braided (TB60) preform [(±60°/0°)3] were developed. Quasi-isotropic (QI) fibre orientations were selected for both the lay-ups for comparison of mechanical properties. The large diameter of the tubes led to incomplete surface coverage with (±45°/0°)3 braided preforms (TB45). Circumferential distribution of multiple layers improved the coverage by reducing through the thickness resin pockets. Also addition of hoop winding improved the coverage and consolidated the braided preform. The use of braiding together with FW resulted in an improved fibre volume fraction. Also predicting surface coverage was a fundamental interest for a triaxial braided preform. An equation was proposed for cover factor estimation and was verified by using image analysis. Resin infusion of the preforms was carried out and composite tubes were fabricated. During resin infusion of braided preforms wrinkles were formed. A brief study on wrinkle formation was carried out and the reasons of wrinkle formation for braided tubes were identified based on existing literature. Longitudinal tensioning in conjunction with optimization of fibre amount in a layup and over-winding on braid was established to minimize wrinkle formation. This was primarily due to compaction of braided layers with hoop winding. Hence braid-winding has the additional advantage of manufacturing wrinkle free composite tubes. Finally composite tubes were tested under tension and torsion loads. One of the major findings was the effect of hoop winding on transverse deformation of the braid-wound tubes. As axial fibre percentage for QBW tube was less than that of TB45, the tensile strength was compromised. However presence of hoop winding resulted in lower transverse strain contributing to higher tensile modulus of QBW tubes along with lower Poisson's ratio. Although shear modulus of TB60 tube was exceptionally high for its fibre orientation, for QBW tubes, shear modulus was not significantly higher than that of other tubes. An aluminium tube was also tested for comparing the elastic properties of the QI tubes with those of an isotropic material. QBW tubes specific modulus was higher than that of the aluminium. The shear modulus of the QI and aluminium tubes was estimated by applying the theory for isotropic materials. In comparison to aluminium, for QBW tube the differences between estimated and actual shear modulus was higher. However QBW tube properties were in closer relation to those of the aluminium tube than TB60 tubes. Hence a QBW hybrid layup technique has the potential for manufacturing composite tubes without losing comparative composite material properties.

This thesis is focused on analyzing pitch as one of the key parameters in manufacturing hydraulic hoses. Data for this analysis was acquired directly on site at Semperflex Optimit s.r.o. In this paper, a description of processes will be provided, and the influence of these processes on the pitch will be investigated. During this analysis two processes were found to have the greatest influence on the pitch and improvements were suggested. Using the Gauge R&R method, the precision of the measuring system was assessed and the appropriate adjustments were made.

Composite IsoTruss™ structures incorporate intersecting longitudinal and helical members. At the intersections, the fiber tows can be interwoven to achieve mechanical interlocking for increased joint integrity. Interlocking introduces gaps and curvilinear fiber paths similar to the crossovers in filament-wound structures, potentially facilitating local delamination within the members, thus reducing the strength and/or damage tolerance of the structure. Optimizing the interlocking pattern at the joints along with efficient consolidation minimizes these effects. Joint specimens were fabricated using a specially designed machine. Specific tow intersection patterns at the joint were: 1) Completely encapsulating the longitudinal member with the tows of the helical member; and 2) Interweaving the tows of the helical member with the tows of the longitudinal member. Consolidation was accomplished using: 1) a braided sleeve; 2) a coiled sleeve; 3) a sparse spiral Kevlar® wrap; 4) a polyester shrink tape sleeve; 5) twisting the entire bundle of longitudinal fiber tows; and 6) cinching the joints using aramid fiber. Ultimate compression strength and stiffness is directly related to the straightness of the tows in the longitudinal members at the intersections. An encapsulated joint reduces member strength by only 4.6%; whereas, an interwoven joint reduces member strength by 30.5%. The fiber paths of the longitudinal member in encapsulated joints are straighter than in interwoven joints, resulting in an average strength difference of 26.2%. Physical properties, strength, and stiffness show that consolidation quality directly affects performance. Consolidation using sleeves provides high quality consolidation, high strength, and high stiffness. Encapsulated joints consolidated using sleeves have an average ultimate strength and Young's modulus 34% and 21% higher, respectively, than encapsulated joints consolidated using other methods. Interwoven joints consolidated using sleeves have an average ultimate strength and Young's modulus 28% and 19% higher, respectively, than interwoven joints consolidated using other methods. Consolidating specimens using a braided sleeve yields the highest quality based on consistency, strength, and stiffness. Consolidating specimens by twisting the longitudinal member yields the lowest strength and stiffness. These conclusions will be applied to IsoTrussâ„¢ grid structure design and manufacturing technology.

Topological order is a new field of research involving exotic physics. Among other things it has been suggested as a means for realising fault-tolerant quantum computation. Topological degeneracy, i.e. the ground state degeneracy of a topologically ordered state, is one of the quantities that have been used to characterize such states. Topological order has also been suggested as a possible quantum information storage. We study two-dimensional lattice models defined on a closed manifold, specifically on a torus, and find that these systems exhibit topological degeneracy proportional to the genus of the manifold on which they are defined. We also find that the addition of lattice dislocations increases the ground state degeneracy, a behaviour that can be interpreted as artificially increasing the genus of the manifold. We derive the fusion and braiding rules of the model, which are then used to calculate the braiding properties of the dislocations themselves. These turn out to resemble non-abelian anyons, a property that is important for the possibility to achieve universal quantum computation. One can also emulate lattice dislocations synthetically, by adding an external field. This makes them more realistic for potential experimental realisations. / Topologisk ordning är ett nytt område inom fysik som bland annat verkar lovande som verktyg för förverkligandet av kvantdatorer. En av storheterna som karakteriserar topologiska tillstånd är det totala antalet degenererade grundtillstånd, den topologiska degenerationen. Topologisk ordning har också föreslagits som ett möjligt sätt att lagra kvantdata. Vi undersöker tvådimensionella gittermodeller definierade på en sluten mångfald, specifikt en torus, och finner att dessa system påvisar topologisk degeneration som är proportionerlig mot mångfaldens topologiska genus. När dislokationer introduceras i gittret finner vi att grundtillståndets degeneration ökar, något som kan ses som en artificiell ökning av mångfaldens genus. Vi härleder sammanslagningsregler och flätningsregler för modellen och använder sedan dessa för att räkna ut flätegenskaperna hos själva dislokationerna. Dessa visar sig likna icke-abelska anyoner, en egenskap som är viktiga för möjligheten att kunna utföra universella kvantberäkningar. Det går också att emulera dislokationer i gittret genom att lägga på ett yttre fält. Detta gör dem mer realistiska för eventuella experimentella realisationer.

Ce travail de recherche est axé sur le développement de composites à liant phosphatique et fibres de renfort en verre E pour diverses applications structurales en Génie Civil. Dans une première partie, un bilan bibliographique nous permet d’identifier les principaux facteurs aux différentes échelles (nano, micro, méso et macro) ayant une influence sur le comportement global de composites à matrice minérale. Dans un second temps, les propriétés mécaniques et physico-chimiques des constituants sont présentées. Nous développons une méthodologie spécifique de caractérisation en traction, en compression et en cisaillement. Le développement de procédures expérimentales particulières en compression et en cisaillement permet l’identification des lois de comportement et l’évaluation des seuils d’endommagement et charges de rupture. La prévision des différents termes de rigidité élastique des systèmes composites est évaluée à partir d’expressions reprenant les principes de base de la micromécanique des composites. L’analyse du comportement à rupture est abordée au plan mésoscopique en considérant deux critères de résistance en plasticité, anisotropie (Tsai-Wu) et en contrainte normale, de cisaillement (Mohr-Coulomb). La deuxième partie de la recherche est consacrée à l’étude d’éléments structuraux mettant en oeuvre les formulations pultrudés de ces systèmes composites. L’expérimentation de poutres, présentant un rapport de la hauteur de la section à la portée de la poutre compris entre 1/15 et 1/50, met en évidence des modes de rupture spécifiques confirmant les faibles caractéristiques du matériau vis-à-vis de l’effort tranchant, du cisaillement interlaminaire et de la décohésion fibre/matrice. L’optimisation de la conception et du dimensionnement des poutres se poursuit en considérant des modifications d’ordre technologique : modification des sections par addition d’entretoises, confinement des sections par tressage circonférentiel, application d’un confinement par stratification directe. Pour chaque type de structures, nous cherchons à définir les limites de validité des méthodes de dimensionnement usuelles en examinant plus particulièrement la conformité des hypothèses de calcul (Navier-Bernoulli, Saint Venant), la cohérence des équations d’équilibre au regard de la cinématique dans chaque section. Dans un second temps, nous considérons des développements intégrant les non linéarités de comportement ou des modèles d’équilibre de type force adaptés à la redistribution interne des efforts tranchants. / This PhD thesis focuses on the development of E-glass reinforced Inorganic Phosphate Cement (IPC) matrix composites for structural applications in Civil Engineering. First, a bibliographical review highlights the main parameters occurring at different scales (nano, micro, meso and macro) influencing the global behaviour of the composite. Mechanical and physico-chemical properties of the different components are presented, followed by a characterization methodology in tension, in compression and in shear. The development of specific experimental procedures in compression and in shear leads to the identification of the constitutive equations and to the assessment of the damage and failure thresholds. The prediction of the different terms of elastic stiffness is assessed using micromechanical expressions. The failure is analysed at the macroscopic scale considering two failure criteria: Tsai-Wu and Mohr-Coulomb. The second part of the study is devoted to the analysis of loadbearing elements in glass reinforced mineral matrix. The realised beams show a height-to-span ratio between 1/15 and 1/50. The experimentation highlights specific failure modes confirming the weak shear performance of the composite in terms of shear force, interlaminar shear and fibre/matrix decohesion. Some technological modifications allow the optimisation of the design: the use of internal reinforcing struts, external confinement by fiber braiding and external wrapping. For each type of structure, we define the validity limits of the usual design methods examining the design hypotheses (Navier-Bernoulli, Saint Venant) and the equilibrium equations in function of the kinematics. In a second time, we consider the development of a force equilibrium model integrating a non-linear behaviour adapted to the internal redistribution of the shear forces.

The dynamics of a complex system can be understood by analyzing the phase space structure of that system. We apply geometric and statistical techniques to two Hamiltonian systems to find and exploit structure in the phase space that helps us get qualitative and quantitative results about the phase space transport. While the structure can be revealed by the study of invariant manifolds of fixed points and periodic orbits in the first system, there do not exist any fixed points (and hence invariant manifolds) in the second system. The use of statistical (or measure theoretic) and topological methods reveals the phase space structure even in the absence of fixed points or stable and unstable invariant manifolds. The first problem we study is the four-body problem in the context of a spacecraft in the presence of a planet and two of its moons, where we exploit the phase space structure of the problem to devise an intelligent control strategy to achieve mission objectives. We use a family of analytically derived controlled Keplerian Maps in the Patched-Three-Body framework to design fuel efficient trajectories with realistic flight times. These maps approximate the dynamics of the Planar Circular Restricted Three Body Problem (PCR3BP) and we patch solutions in two different PCR3BPs to form the desired trajectories in the four body system. The second problem we study concerns phase space mixing in a two-dimensional time dependent Stokes flow system. Topological analysis of the braiding of periodic points has been recently used to find lower bounds on the complexity of the flow via the Thurston-Nielsen classification theorem (TNCT). We extend this framework by demonstrating that in a perturbed system with no apparent periodic points, the almost-invariant sets computed using a transfer operator approach are the natural objects on which to pin the TNCT. / Ph. D.

Der Einsatz textiler Carbonbewehrungen im Betonbau etabliert sich, aufgrund ihrer hervorragenden zug- und korrosionsmechanischen Eigenschaften, zunehmend als technische und wirtschaftliche Alternative zur Stahlbewehrung. Sie ermöglichen je nach Anwendung, eine signifikante Reduzierung des Betonmaterialeinsatzes um bis zu 70 % sowie der damit verbundenen CO2-Emissionen. Um das Leistungspo- tenzial von textilbewehrtem Beton voll auszuschöpfen, ist eine effiziente Kraftüber- tragung zwischen Textilbewehrung und Betonmatrix entscheidend. Je nach Bean- spruchung sind bisher materialineffiziente, unverhältnismäßig große Verankerungs- längen erforderlich. Gefordert werden daher Bewehrungsstrukturen mit ausgepräg- ter Oberflächenprofilierung analog zu geripptem Betonstahl. Konventionelle, sub- traktive und additive Profilierungsverfahren erzeugen jedoch einen unterbrochenen Faserverlauf, wodurch das hohe zugmechanische Leistungspotenzial der anisotro- pen Carbonfasern nicht effizient ausgenutzt werden kann. Ziel dieser Arbeit ist da- her die Entwicklung neuartiger profilierter Textilbetonbewehrungen mit material- und verbundgerechter Profilierung auf Garnebene und entsprechender Fertigungstech- nologien, auf Basis der Flecht- und Tränkumformtechnik. Dies umfasst die Verfah- rens- und Maschinenentwicklung sowie die Modellierung profilierter Bewehrungs- strukturen zur anforderungsgerechten Auslegung und deren Technologienachweis.