This research is comprised of two main parts. Firstly, burst pressures in vessel components are evaluated. Two types of failure mode are investigated, one due to excessive plastic deformation and the other due to plastic instability. Experimental tests, carried out on components made from mild steel, aluminium alloy 6061, and stainless steel 316/316L, provide good verification results. For burst pressure due to excessive plastic deformation, a numerical method for determination of its value in shallow spherical caps and torispheres subject to internal pressure is proposed. Burst pressure is defined as the maximum pressure at which a proposed plastic strain criterion is met. Plastic instability pressure is known as the maximum load at which a small load increment causes a very large deformation. For toroidal shells under internal pressure, a closed-form formula of plastic instability condition is derived. Then the corresponding pressure at instability is obtained by semi-analytical analysis. This pressure is also predicted by finite element analysis. Secondly, modern optimisation techniques including Simulated Annealing, Particle Swarm Optimization and Differential Evolution have been applied to the design of minimum weight toroidal vessels subject to internal pressure. Constraints are the first yield' pressure, plastic pressure, burst pressure and volume contained by the toroid. Optimality includes geometry and wall thickness. Shells are made from mild steel with constant or variable wall thickness. The optimisation process is performed by a rou!ine written in FORTRAN coupled with finite element analysis code ABAQUS. Depending on geometry parameters of the toroid, the material saving can be as high as 72%. The results show that Differential Evolution is the best method.

The wild grass Holcus lanatus is tolerant of a range of edaphic stresses. It possesses genetic adaptations to these conditions which can produce distinct ecotypes and utilises fungal associations to improve stress tolerance. This thesis explores the adaptations and processes employed by two distinct H. lanatus ecotypes from acid bog and limestone quarry soils in response to their soil of origin and the alternate soil type. A de novo RNA-Seq transcriptome was produced for this purpose. Given the role of fungal associations in H. lanatus edaphic adaptation, a novel RNA-Seq assembly, annotation and analysis pipeline was implemented to investigate the root-associated fungal community composition and gene expression response in both soils. Arbuscular mycorrhizal (AM) and non-AM infection was verified using root staining and PCR protocols. Both ecotypes displayed adaptation to their soils of origin with some soil type specific responses indicated. Additionally gene expression in both ecotypes was altered when transplanted to an alternate soil type, although the acid ecotype on lime soil displayed a degree of gene expression similarity to the lime ecotype on lime soil, thereby displaying plasticity in this population. Staining and RNA-Seq analyses detected differences in AM and non-AM infection between soil types, with an ecotype effect detected for non-AM infection on acid soil using root staining. Furthermore the novel RNA-Seq analysis was capable of detecting differences in fungal community composition based on best BLAST alignment, gene expression and gene function, displaying the multifunctional potential of this technique. This thesis identifies putative soil pH adaptations and emphasises the importance of incorporating root fungal community characterisation in studies of stress tolerance between environments whilst introducing a novel RNA-Seq analysis pipeline for studying natural multi-species fungal infections. This technique can incorporate plant-fungal relationships into analyses of stress tolerance adaptations, where the importance of these interactions is increasingly realised.

The laser heated pedestal growth technique has been successfully employed to grow pure and doped sapphire crystal fibres for characterisation as suitable sensor materials. Source materials used were polycrystalline and crystalline sapphire rods while fibres with typical diameters in the range 80 - 170 mm were grown. Pure sapphire fibres, both a- and c-axis, were found to grow easily with no complications such as melt instability. C-axis fibre growth was readily initiated while a-axis fibres required an appropriate a-axis oriented seed crystal. Dip-coating has been used to prepare suitably coated sapphire source rods for growth into doped fibres. Doped fibres grown included Cr3+:, Er3+:, Er3+:Yb3+: and Yb3+:Er3+:Al2O3. Er3+:Yb3+:Al2O3 fibres have been prepared with approximately equal concentration of both dopants while a 10:1 Yb3+ to Er3+ concentration ratio was used for preparing Yb3+:Er3+:Al2O3 fibres. Ruby fibres were also found to grow easily although brownish-green deposits have been observed on some of these fibres. Large transmission losses have been found in fibres with these deposits. Acid cleaning was not effective in removing these deposits, suggesting that they have diffused beneath the surface of the fibres. This was attributed to the condensation of chromium oxide on the fibre surface during growth. Growth of rare earth-doped fibres was initially problematic due to the constant breaking-off of the crystallising fibres from the melt. This was thought to be due to the flexibility of the small diameter source fibres used as well as the high concentration levels of doping. Replacing these small fibres with larger source rods thus permitted RE-doped fibres with relatively good optical quality to be grown. Fibres were grown with typical growth rates of 0.5 - 1 mm/min.

Le géoradar est une méthode électromagnétique haute fréquence (>10 MHz) utilisé pour caractériser les premiers mètres du sous-sol. Lors de la présence d'une topographie, les données géoradar sont déformées en conséquence. Afin de retrouver la vraie géométrie des réflecteurs, nous avons codés un algorithme de migration prenant en compte la topographie. La méthode est démontrée grâce à un modèle synthétique simple, puis testée avec succès sur des données réelles. Les algorithmes de migration apportent cependant du bruit dans les données. Pour pallier à ce problème, deux méthodes ont été mises en place : la première, inhérente à la migration, permet de réduire l'aliasing dit sur l'opérateur. La deuxième est un filtre ré-interpolant les traces en se basant sur un profil de pendage. Les deux méthodes suppriment un bruit incohérent des données mais dégradent les profils lorsqu'utilisées abusivement. Dans un deuxième chapitre, nous avons appliqués avec succès le géoradar dans un contexte de paléo-sismologie en Mongolie. L'utilisation conjointe de deux fréquences (50 et 500 MHz) ainsi que des comparaisons avec des tranchées a permis d'obtenir des informations complémentaires sur les géométries et les déplacements potentiels le long de deux failles. Dans un dernier chapitre, nous avons appliqués les mesures géoradar sur les dépôts pyroclastiques du volcan Tungurahua en Equateur. A nouveau, l'utilisation jointe de différentes fréquences (250, 500 et 800 MHz) nous permet d'imager efficacement les dépôts. Les unités principales sont mises en évidence avec l'antenne de 250 MHz et les architectures des dépôts sont observables avec les antennes de 500 et 800 MHz. / Georadar is a high frequency (>10MHz) electromagnetic method used to prospect near surface. When a topography is present, GPR images are distorted. To restore the true geometry of reflexions, we coded an migration algorithm which takes the topography into account. The method is first demonstrate on a simple synthetic model, and then succesfully applied on real data. However, migration algorithms bring noise to the data. Two methods have then been tested to avoid and remove it. The first one is inherent to the migration algorithm and reduce what is called operator's aliasing. The second one is a filter re-interpolating traces based on a profile containing the slope. Both methods remove inconsistent noise when used with caution, but decrease their quality when used with excess: reflexions presenting dip are the first to be deteriorated, as well as reflexions below strong topography. In a second chapter, we successfully used GPR in a paleo-sismology context in Mongolia. The use of two frequencies (50 and 500 MHz) as well as comparison with trenches bring complementaries informations on the geometry and possible offset along two faults. In the last chapter, GPR was tested over pyroclastic deposits from the Tungurahua volcano in Ecuador. Again, the combination of several frequencies (250, 500 and 800 MHz) has proven its efficiency. Main units were obvious with the 250 MHz antenna while the inner architecture of deposits was visible with the 500 and 800 MHz antenna.