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This thesis extends the study of the notion of termination equivalence of abstract structures first proposed by Kfoury. The connection with abstract data types (ADTs) is made by demonstrating that many kinds of equivalence between ADT implementations are in fact instances of termination equivalence between their underlying algebras. The results in the thesis extend the original work in two directions. The first is to consider how the termination equivalence of structures is dependent upon the choice of programming formalism. The termination equivalences for all of the common classes of programs and for some new classes of non-computable schemes are studied, and their relative strengths are established. The other direction is a study of a congruence property of equivalences relative to the join or addition datatype building operation. We decide which of the termination equivalences are congruences for all structures and for all computable structures, and for those equivalences which are not, we characterise those congruences closest to them (both stronger and weaker). These programmes of work involved the use of constructions and properties of structures relating to program termination which are of interest in themselves. These are examined and are used to prove some general results about the relative strengths of termination equivalences.

In order to investigate the unusual oxidation properties of a meso-substituted porphyrin, tetrakis(3,5-di-tert-butylhydroxyphenyl)-porphyrin (H[2]T[t]BHPP), X-ray crystallography and computer modelling have been used. The crystal structure of a number of complexes of TtBHPP (Pd(II), Zn(II), Ni(II), Fe(III)Cl and Ha[4][2+]), its oxidation product, H[2]PDM, and (H[2]O)ZnTPP have been determined. The Pd(II) and Zn(II) complexes have unusual structures, with approximately 28 cyclohexane solvent molecules per unit cell very loosely bound within the lattice. The Ni(II) complex has the most extensively ruffled core reported for a metalloporphyrin, with a short Ni-N bond distance 1.913(3)A. The crystal structures of H[2]PDM.6H[2]O and [H[4]T[t]BHPP][2+][Zn(CF[3]COO)[4]][2-]. 6H[2]O show interesting clathrate-like structures with extensive intermolecular hydrogen-bonding. The oxidised porphyrin, H[2]PDM, has a tetraquinone structure in the solid state which contrasts with the proposed diquinone/diphenol structure found in solution. Molecular Mechanics and Molecular Orbital calculations were used to investigate both geometric and electronic structures of the porphyrins and their oxidised counterparts. Due to the size and complexity of these calculations and the lack of experimental data these methods were not as useful as anticipated. The difference in behaviour of various metallo complexes of T[t]BHPP to oxidation is attributed to electronic effects rather than the geometric structures of the metalloporphyrins.

In this work an attempt has been made to derive a full finite element and boundary element theory for the analysis of thin and thick plates on elastic foundations. A new high order shear finite element capable of the analysis of thin thick plates has been derived using Hermitian and Lagrangian shape functions. Different new boundary element derivations for the analysis of thin plates on elastic foundations are introduced using 3 degrees-of-freedom per node. A full new derivation of boundary elements for thick plates on elastic foundations using complex Bessel functions is presented. Fourier and Hankel integral transforms have been employed for the derivation of different fundamental solutions required for boundary element analysis. Several techniques for dealing with singular and divergent integrals encountered with boundary integral equations were developed including the use of 'Modified Kelvin Functions' and fictitious boundary concept. some case studies with different loading and boundary conditions were tested and proved that the new derivations presented in this work are correct and reliable for the analysis of thin and thick plates on elastic foundations.

The modal characteristics of large skeletal structures (LSS) made from tubes of graphite reinforced Poly (Ether Sulphone) (PES), a high technology thermoplastic composite material, have been investigated. These large skeletal structures are intended for application in land-mobile communications networks and would be positioned at geosynchronous equatorial orbit (GEO). Experimental modal surveys of a number of skeletal configurations have been conducted under simulated unrestrained conditions, and have involved the prior commissioning of the modal survey apparatus used in their examination. The surveys have been performed in tandem with analogous natural frequency extractions from the structures' analytical models using the finite element (FE) method. The skeletal structures were fabricated using either the graphite reinforced PES material or perspex plastic, and formed representative sub-structures of candidate LSS configurations. The structures' geometries ranged in complexity from sparsely configured composite systems to a perspex platform-based bank of reflector arrays, and allowed the evolution of both local and global modal behaviour in these skeletal systems to be observed in detail. It has been found that the modal behaviour of predominantly uniaxially reinforced PES composite, in the state of uniaxial stress to which it will be subjected as a component of multi-bay LSS configurations, can be accurately described using an isotropic approximation for its material characteristics. Additionally, it has been found that the use of perspex plastic as a material for modelling representative multi-bay sub-structures of composite LSS is justified in consideration of the eventual stress environments to which the composite material will be subjected in LSS systems. Following this, a series of analytical parametric studies has been performed on a number of concept composite LSS suitable for use in a data-relay capacity at GEO. It has been found that the modal frequencies developed by these configurations are comparable to the published frequencies of similar skeletal structures intended for use at these orbits. It has also been established that the testing of a reduced modelling of the LSS can be highly instructive as to the general trends in modal behaviour developed by the large skeletal structures in orbit.

No description available.

Dans cette thèse de doctorat, nous menons des investigations théoriques et expérimentales relatives aux structures localisées dans des lasers à cavité verticale émettant par la surface (VCSELs), aussi appelées solitons de cavité. Elles consistent en des pics d'intensité lumineuse dans le plan transverse à la propagation du faisceau lumineux. Ils ont été notoirement proposés pour deux applications :stockage tout optique de l'information, et le traitement de l'information optique.Dans la première partie de cette thèse, nous investigons les aspects théoriques des structures localisées dans un VCSEL à grande surface d'émission soumis à une injection optique et à un retour retardé. Nous dérivons une équation de Swift-Hohenberg généralisée à retard, d'application lorsque le système est proche du régime de bistabilité optique. En premier lieu, nous caractérisons les structures localisées stationnaires, en construisant leur diagramme de bifurcation en serpentage, typique de leur regroupement dans la zone d'accrochage des paramètres. Ensuite, nous montrons que le retour retardé peut induire un mouvement spontané de structures localisées à deux dimensions dans une direction arbitraire du plan transverse. Nous caractérisons ces structures mobiles en estimant le seuil de ce mouvement, ainsi que sa vitesse.Dans la deuxième partie de cette thèse, nous rapportons la formation spontanée de structures localisées dans un VCSEL de 80 micromètres de diamètre, pompé au delà de son seuil d'émission laser, et soumis à une injection optique. Ces structures sont bistables en la puissance du faisceau d'injection, ainsi qu'en le courant électrique. Nous étudions expérimentalement leur formation pour différents décalages en fréquence avec le faisceau de pompe optique. Nous rapportons la première mesure expérimentale mettant en évidence le caractère vectoriel des structures localisées générées dans un laser à grande surface d'émission: la polarisation de la structure localisée n'est pas celle de l'injection optique, dans la mesure où cette dernière est elliptique. Nous apportons un éclairage théorique sur cette expérience, en prenant en compte la dynamique de retournement de spin propre aux VCSELs à puits quantique. Ces résultats laissent entrevoir la possibilité de multiplexer l'information transmise en utilisant les propriétés de polarisation des structures localisées, utilisées comme pixels à la surface du VCSEL. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

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The design and creation of a functional metalloanti body is presented. A survey of metalloprotein structures was carried out to determine the common structural features of metal binding sites. Metal ligands were then introduced into hypervariable loop 11 of the anti-lysozyme antibody HyHEL-5 and the site comprehensively modelled. The final model was used as a basis for site-directed mutagenesis and mutant antibodies were produced using a Xenopus laevis oocyte expression system. Antigen binding studies showed the mutants to have an affinity for lysozyme equivalent to the parent antibody, while subsequent metal binding experiments have shown the new site to be capable of binding the transition metals cobalt, nickel, copper, zinc and cadmium. A method for the rapid prediction and design of metal binding sites in proteins is described. A protein structure is screened for the location of putative metal sites by template matching. After the introduction of suitable liganding residues, the metal binding potential at each site is evaluated using hydrophobicity contrast. A point representing the metal ion within a new site may be optimised with-respect-to the ligands using multidimensional minimisation. The method has been tested on known metalloprotein structures. It was routinely able to identify the metal binding sites and position a metal point in the site to within 0.6A of the actual metal ion.

Helicopter blades are made of composite sandwich materials mainly loaded in fatigue. Normally, they have relatively thin skins. A through-the-thickness crack could appear in these coatings. The aim of this study is to characterize the through-the-thickness crack propagation in fatigue in thin woven glass fabric laminates. A specific fatigue test is developed so that these structures parts can undergo real stress conditions. A wide experimental campaign is undertaken which allows stating crack growth rates in several laminates. The propagation path is linked through microscopic investigations to specific damages of woven plies. Crack initiation duration influence on experimental results is also underlined. The finite element modelling is based on the architecture of the fabric and on the fatigue behaviours of the matrix and the fibre. The fatigue damage matrix is introduced with user spring elements that link the two fibres directions of the fabric. The glass fibre fatigue behaviour is based on S-N curves. Numerical results are compared to measured crack growth rates levels and observed damages in the crack tip.