Rozprawy doktorskie na temat „Shekel”

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 113-118).
Ductile fracture causing premature failure of parts during forming and crash has become an important factor limiting design of car bodies. The increasing usage of advanced high strength steels and other lightweight materials to meet ever-stringent standards on passenger safety and gas emissions makes related advances in experimental and computational mechanics a pressing issue. The industry has been using shell finite elements in design practice due to many practical advantages over solid elements. A constitutive assumption of the plane stress condition in shell elements, violated after the onset of localized necking, is responsible for an inaccurate numerical prediction of mechanical response with mesh-size sensitivity. This thesis proposes a new approach to predict ductile failure with shell elements. It is based on the concept of a Domain of Shell-to-Solid Equivalence (DSSE) in conjunction with the Hosford-Coulomb (HC) fracture initiation model. The latter is a micro-mechanically motivated phenomenological model for solid elements. DSSE is the domain in which shell element solutions are valid and comparable to solid elements. Consequently, it is appropriate to apply the HC model within DSSE. On the other hand, a shell element loses its reliability when exiting DSSE, thus being removed from the rest of a finite element model. A general shape of a localization locus that demarcates DSSE for proportional membrane loading is identified through a Marciniak-Kuczynski type localization analysis. The locus is successfully fitted by a mathematical form of the HC model, and a model parameter is simply determined by the Considére criterion. DSSE is then extended towards non-proportional and combined membrane and bending loading. The DSSE-HC model for shell elements covers three types of ductile failure observed in sheet metals: (1) in-plane shear localization, (2) biaxial fracture not preceded by localized necking, aka surface cracking, and (3) biaxial fracture in consequence of localized necking. Validation is made in two steps. First, the model accuracy is evaluated purely numerically, compared to solid elements. Secondly, a comprehensive experimental validation is performed at both specimen and structural levels. The former covers membrane stretching, stretch bending, pure bending, and in-plane shear. The latter is concerned with triangular cup-drawing.
by Keunhwan Pack.
Ph. D.

Dans le domaine de la mise en forme industrielle, des outils de simulation comme le logiciel Pam-stamp 2G permettent entre autres le prototypage et l’optimisation numérique des produits, réduisant ainsi les coûts expérimentaux de mise au point. Les éléments finis de type coques en hypothèse d’état plan de contrainte demeurent les plus utilisés car ils permettent une prise en compte réaliste des déformations majeures de membrane et de flexion. Cependant, de par leur définition, la contrainte normale pouvant apparaitre en cas de compression du flan dans la direction de l’épaisseur ou encore de flexion extrême sur petit rayon est systématiquement omise. De plus, Il existe de nouveaux procédés de mise en forme de tôle, comme le pliage/sertissage/emboutissage avec laminage et/ou écrasement ainsi que l’hydroformage, qui ne peuvent pas être traités avec ces formulations d’éléments coques classiques. L’utilisation de couches d’éléments volumiques est souvent considérée comme une alternative non convenable aux simulations de ces procédés. Outre le très haut coût CPU, s’ajoutent le rendu parfois non réaliste ainsi que la complexité liée à la découpe du maillage du flan. Récemment, des éléments de type “solid-shell” ont été mis à contribution mais requièrent des améliorations quant à leurs lois de comportements. L’objectif d’ESI group consiste en l’élaboration, l’évaluation, l’implémentation et la validation industrielle d’une nouvelle formulation d’élément fini. Cet élément devra permettre la gestion d’une éventuelle variation d’épaisseur avec prise en compte réaliste de la contrainte normale, tout en assurant des résultats dignes de ceux d’une coque conventionnelle en flexion. Une nouvelle formulation de type coque 3D est ainsi d’abord proposée. Des éléments coques triangulaires et quadrangulaire en théorie de Mindlin et de Kirchhoff sont utilisés. Cette approche est d’abord développée dans un solveur quasi-statique implicite de l’INSA de Lyon pour validation numérique sur cas académiques linéaires et non linéaires de référence. Une validation expérimentale sur opération de pliage dépliage est également réalisée. Aux vues des non linéarités dues au contact avec frottement, grandes déformations et grands déplacements posant des soucis de convergence en implicite au cours de la simulation d’opérations de mise en forme, la méthode est ensuite développée dans le solveur explicite de l’INSA de Lyon. Seuls les éléments en théorie de Mindlin sont considérés. Les particularités liées à cette méthode de résolution dynamique comme la matrice de masse, le pas de temps critique et l’optimisation du CPU sont traitées. Une nouvelle méthode de contact dédiée aux opérations de mise en forme impliquant du laminage et/ou de l’amincissement est également proposée. Elle permet une transition automatique d’éléments standards vers des éléments coque "3D", palliant ainsi le remaillage. Des essais de mise en forme en U avec ou sans laminage apportent une validation expérimentale concernant le retour élastique. Une fois validées, les techniques et formulations les plus abouties sont implémentées dans le code industriel dédié à la mise en forme Pam-stamp 2G v2011. Après une vérification sur tests de référence, des applications sont enfin menées sur cas critiques inspirés de procédés industriels complexes et nécessitant essentiellement une loi de comportement 3D
In the sheet metal forming industry, shell elements in plane-stress assumption are employed, as they perform quite well in simulating the major membrane and flexural large deformations involved. However, the normal stress, caused by compression along thickness direction of the blank or local high bending over very small radii, is hence systematically omitted. Besides, when it comes to unusual and challenging processes such as hydro-forming, thinning/thickening, forming with ironing, bottoming and so on, makeshift solutions such as layers of 3D solid hexahedrons or even recent “solid-shell” elements are no longer appropriate. An innovative 3D finite element formulation methodology overcoming the overcoming the plane-stress definition of classification shell elements, while keeping their very good bending assets is first proposed in this work. The method basically consists in adding a central node endowed with two degrees of freedom at the element center. These two extra translations normal to the element mid-plane give a new quadratic displacement field along the shell normal direction. A derivative normal strain can hence be expressed and a linear normal stress comes via a full 3D constructive law. A very pioneering contact technique, dedicated to forming processes with ironing, thinning/bottoming operations and allowing a usual-to-enhanced automatic element switch is developed as well. Once widely assessed, most interesting achievements are implemented in the dynamic explicit industrial code Pam-stamp 2 G v2011 and evaluated over critical industrial forming processes that require essentially a full 3D strain-stress behavior

Doutoramento em Engenharia Mecânica
A utilização dos métodos computacionais na Engenharia Mecânica tem assumido cada vez mais relevância, contribuindo para uma melhor compreensão dos processos de conformação plástica em chapa, especialmente aqueles que lidam com materiais anisotrópicos, como é o caso das ligas de alumínio. Dentre estes, o método dos elementos finitos (FEM) tem progredido substancialmente nas últimas duas décadas, em parte devido ao rápido desenvolvimento da arquitectura dos computadores. Para a correcta modelação dos processos de conformação plástica em chap: o desenvolvimento de um elemento finito preciso e eficiente, vocacionado para a modelação de estruturas com parede fina, como é o caso das chapas de metal; o estudo e implementação de modelos constitutivos, considerando a anisotropia material a três dimensões. Assim, é proposto um novo elemento finito sólido-casca, suportando um número arbitrário de pontos de integração numérica ao longo da sua espessura. Devido à sua topologia sólida com oito nós físicos, esta formulação avalia naturalmente variações de espessura, contacto simultâneo em duas faces e modelos constitutivos tridimensionais, aspectos cruciais neste tipo de aplicações. Do lado constitutivo, a caracterização de materiais anisotrópicos pode ser conseguida através de funções de cedência não quadráticas ou através de modelos policristalinos. A descrição matemática da anisotropia plástica é conveniente e computacionalmente eficiente devido ao facto de utilizar parâmetros mecânicos macroscópicos como dados de entrada. Por outro lado, a descrição policristalina é baseada em aspectos físicos micro-estruturais da deformação plástica, sendo a textura cristalográfica o principal dado de entrada para estes modelos. Assim, a rotação de cada um dos grãos é acompanhada individualmente e a anisotropia material é consequentemente evolucional. No entanto, quando comparado com os modelos fenomenológicos, os modelos policristalinos são computacionalmente intensivos e não passíveis de serem usados à escala industrial, em particular na análise de conformação em chapa. Neste trabalho, as duas alternativas são analisadas, mas devido ao seu carácter inovador, ênfase será dada a um modelo multi-escala optimizado, que utiliza o conceito da interacção dos sistemas de deslizamento ao nível do grão e uma transição micro-macro baseada na hipótese de que todos os grãos sofrem o mesmo nível de deformação macroscópico. No final, os dois tópicos referidos (elemento finito e lei constitutiva) são consolidados num código de elementos finitos, sendo então validados e comparados com resultados experimentais ou numéricos, previamente publicados por outros autores.
The use of computational methods in Mechanical Engineering has gained more relevance, contributing to a better understanding of sheet metal forming processes, especially when dealing with anisotropic materials, such as aluminum alloys. Among them, the finite element method (FEM) has made significant progress during the last two decades, partly because of the rapid progress of computational environment. For a proper modeling of anisotropic forming processes, it is necessary to use accurate and efficient finite elements. The class of solid-shell finite elements has been appearing in the last years as an excellent alternative to shell elements to model thin-walled structures, presenting at the same time a number of advantages, namely the use of full constitutive laws and automatic consideration of double-sided contact. At the same time, it is important to utilize constitutive laws that describe the material anisotropy properly. In this work, the main focus is given to the formulation of a new one point quadrature solid-shell finite element. As a distinctive feature, the formulation accounts for an arbitrary number of integration points through its thickness direction. Once it contains eight physical nodes, naturally evaluates thickness strain, double sided contact and full three-dimensional constitutive models, which are crucial aspects in this type of applications. Additionally, simulation of spring-back phenomena of a metal sheet can be made resorting only to a single layer of solid-shell finite elements containing several integration points through the thickness direction. On the constitutive side, anisotropic material modelling can be described utilizing non-quadratic mathematical yield functions or polycrystal models. Phenomenological description of plastic anisotropy is convenient and time-efficient since it is based on macroscopic mechanical properties of the material as input. On the other side, polycrystal description is based on the physical microstructural aspects of plastic deformation, being the crystallographic texture the main input to these models. However, compared to phenomenological approaches, despite having a more sounding theoretical basis, polycrystal models are computationally time-intensive and difficult to employ for large-scale industrial applications, particularly sheet forming analysis and design. Therefore, it is required to select an appropriate approach based on the problem characteristics. In this work, well-chosen anisotropic yield functions are reviewed. Additionally, the description of a time efficent grain-level single crystal model is carried out. In the numerical tests, finite element development and constitutive modelling topics are consolidated in an in-house FEM code, being validated and compared with experiments or numerical results previously reported in the literature.
FCT
POSI BD/12864/2003

Rural health settings face challenges in delivering and sustaining health services for their communities. Performance in rural health settings can be constrained by resources, staffing and the tyranny of distance from major centres. This research set out to determine how innovation might contribute to solutions and used a case study methodology to understand the organisational and contextual factors that support innovation in rural health settings. Further, the research examined how publicly available health data can be used to describe performance in rural health services through visualisation and the assembly of measures reflecting access, equity, quality, safety, sustainability and employee engagement.

La simulation numérique par la méthode des éléments finis (MEF) fournit de nos jours une grande aide pour les ingénieurs dans les processus de conception d’optimisation des produits. Malgré le développement croissant des ressources de calcul, la fiabilité et l’efficacité des simulations numériques par la MEF restent à améliorer. Ce travail de thèse consiste à développer une famille d’éléments solide-coque (SHB) pour la modélisation tridimensionnelle des structures minces. Cette famille d’éléments SHB est basée sur une formulation tridimensionnelle en grands déplacements et rotations. La technique dite “d’intégration réduite dans le plan”, en utilisant un nombre arbitraire de points d’intégration dans la direction de l’épaisseur, permet la modélisation des structures minces avec une seule couche d'éléments. Dans ce travail de thèse, deux éléments linéaires SHB prismatique et hexaédrique, ainsi que leurs contreparties quadratiques, ont été implantés dans le code par éléments finis ABAQUS pour l’analyse quasi-statique et dynamique des structures minces. La performance de ces éléments a été validée à travers une série de cas tests académiques, ainsi que sur des problèmes complexes de type impact/crash et des procédés de mise en forme de tôles minces. L'ensemble des résultats numériques obtenus révèle que les éléments SHB représentent une alternative intéressante aux éléments coques et solides traditionnels pour la modélisation tridimensionnelle des structures minces
Nowadays, the finite element (FE) simulation provides great assistance to engineers in the design of products and optimization of manufacturing processes. Despite the growing development of computational resources, reliability and efficiency of the FE simulations remain the most important features. The current work contributes to the development of a family of assumed strain based solid-shell elements (SHB), for the modeling of 3D thin structures. Based on reduced integration and special treatments to eliminate locking effects and to control spurious zero-energy modes, the SHB solid‒shell elements are capable of modeling most thin 3D structural problems with only a single element layer, while describing accurately the various through-thickness phenomena. In the current contribution, a family of prismatic and hexahedral SHB elements with their linear and quadratic versions have been implemented into ABAQUS using both standard/quasi-static and explicit/dynamic solvers. The performance of the SHB elements is evaluated via a series of popular benchmarks as well as with impact/crash and sheet metal forming processes. All numerical results reveal that the SHB elements represent an interesting alternative to traditional shell and solid elements for the 3D modeling of thin structural problems

Metal nanoparticles have a large surface area to volume ratio compared to their bulk counterparts, which makes them attractive to use as catalysts. Atoms on the surface of metal nanoparticles are very active due to their high surface energy resulting from their unsatisfied valency. First synthesis of gold nanoparticles with different shapes and bimetallic structure are explored in detail. Then an experimental method which could distinguish between the two mechanisms (homogeneous or heterogeneous) by using hollow plasmonic gold nanocatalyst is developed. Furthermore the catalytic activity of gold nanocages was changed by adding an inner platinum or palladium nanoshell. Results suggested that adding palladium inner shell increased the activity of gold nanocages towards the reduction nitro groups to amino groups. Controlling the selectivity of the catalyst is an important goal of catalysis research. Lastly selectivity of the plasmonic nanocatalyst (Gold sphere-Gold shell Nanorattles) with multiple plasmon modes was studied for photo-dimerization of nitro groups into azo dimers were studied on gold nanocatalyst surface. Results showed that selectivity can be controlled by changing the wavelength of the light exciting surface plasmon.

Though fundamental to our understanding of stellar, galactic, and cosmic evolution, the stellar explosions known as supernovae (SNe) remain mysterious. We know that mass loss and mass transfer are central processes in the evolution of a star to the supernova event, particularly for thermonuclear Type Ia supernovae (SNe Ia), which are in a close binary system. The circumstellar environment (CSE) contains a record of the mass lost from the progenitor system in the centuries prior to explosion and is therefore a key diagnostic of SN progenitors. Unfortunately, tools for studying the CSE are specialized to stellar winds rather than the more complicated and violent mass-loss processes hypothesized for SN Ia progenitors.

This thesis presents models for constraining the properties of a CSE detached from the stellar surface. In such cases, the circumstellar material (CSM) may not be observed until interaction occurs and dominates the SN light weeks or even months after maximum light. I suggest we call SNe with delayed interaction SNe X;n (i.e. SNe Ia;n, SNe Ib;n). I per- formed numerical hydrodynamic simulations and radiation transport calculations to study the evolution of shocks in these systems. I distilled these results into simple equations that translate radio luminosity into a physical description of the CSE. I applied my straightforward procedure to derive upper limits on the CSM for three SNe Ia: SN 2011fe, SN 2014J, and SN 2015cp. I modeled interaction to late times for the SN Ia;n PTF11kx; this led to my participation in the program that discovered interaction in SN 2015cp. Finally, I expanded my simulations to study the Type Ib;n SN 2014C, the first optically-confirmed SN X;n with a radio detection. My SN 2014C models represent the first time an SN X;n has been simultaneous modeled in the x-ray and radio wavelengths.

Thesis (Ph. D. of Philosophy)--University of Western Sydney, Hawkesbury, 1997.
"A thesis submitted to the School of Agriculture and Rural Development, Faculty of Agriculture and Horticulture, University of Western Sydney Hawkesbury, in part fulfilment of the requirements for the Degree of Doctor of Philosophy." Includes bibliographical references (p. 236-267).

The live export and feedlotting industries are the major intensive sheep industries in Australia. During live shipment, sheep are exposed to prolonged periods of high heat and humidity, with little relief for several days, while environmental conditions in a Western Australian sheep feedlot have not yet been assessed. The research described in this thesis was conducted to determine the physiological responses of sheep to conditions within the live export and feedlotting industries, with particular focus on that of heat stress. Merino wethers and Awassi rams developed significant change in physiological variables when exposed to prolonged periods of high heat and humidity, such as during long haul, live export voyages to the Northern Hemisphere. Physiological changes such as increased core temperature, respiratory rate, panting score and associated changes in blood gas variables were apparent in Merino wethers. However, Awassi rams showed exceptional ability to maintain homeostasis under the same environmental conditions, with no significant changes in core temperature and only slight alteration in blood gas variables. Results from this study indicated that electrolyte supplementation of sheep during live export would not be warranted because plasma electrolytes did not drastically change and blood gas variables quickly returned to normal following the heat. Further studies developed methods to determine the critical wet bulb temperature, otherwise known as the heat stress threshold (HST) of Merino rams, ram lambs and wethers exposed to live export conditions. These studies found that ram lambs had a lower HST than both adult rams and wethers. However, both adult rams and wethers had a similar HST. Heat stress thresholds determined from these studies have been used in a model to predict high risk shipments for particular classes of sheep (Stacey 2003). This thesis also details the environmental conditions within a Western Australian summer feedlot and the physiological responses of cross bred ewes and wethers to these conditions when fed feedlot rations. This study found that temperatures in a typical Western Australian feedlot in summer increased above 40 degrees C with low humidity; however, temperatures generally decreased to be within the sheep's thermoneutral zone at night. Both ewes and wethers had significantly increased core temperatures in response to these conditions, with sheep spending significantly more time in the shade than in the sun during the day. Both ewes and wethers had increased respiratory rates and panting scores during an intensive climate room experiment with similar environmental conditions. However, feed intake did not decrease even when climate room temperatures increased at night and humidity levels were higher than that found in typical feedlot conditions in Western Australia. Work completed within this thesis has led to a greater understanding of the physiological responses of sheep to prolonged and continuous high heat such as during live export and to conditions of a typical Western Australian summer feedlot. This research has set a foundation for further study of management of sheep during live export and feedlotting.

The live export and feedlotting industries are the major intensive sheep industries in Australia. During live shipment, sheep are exposed to prolonged periods of high heat and humidity, with little relief for several days, while environmental conditions in a Western Australian sheep feedlot have not yet been assessed. The research described in this thesis was conducted to determine the physiological responses of sheep to conditions within the live export and feedlotting industries, with particular focus on that of heat stress. Merino wethers and Awassi rams developed significant change in physiological variables when exposed to prolonged periods of high heat and humidity, such as during long haul, live export voyages to the Northern Hemisphere. Physiological changes such as increased core temperature, respiratory rate, panting score and associated changes in blood gas variables were apparent in Merino wethers. However, Awassi rams showed exceptional ability to maintain homeostasis under the same environmental conditions, with no significant changes in core temperature and only slight alteration in blood gas variables. Results from this study indicated that electrolyte supplementation of sheep during live export would not be warranted because plasma electrolytes did not drastically change and blood gas variables quickly returned to normal following the heat. Further studies developed methods to determine the critical wet bulb temperature, otherwise known as the heat stress threshold (HST) of Merino rams, ram lambs and wethers exposed to live export conditions. These studies found that ram lambs had a lower HST than both adult rams and wethers. However, both adult rams and wethers had a similar HST. Heat stress thresholds determined from these studies have been used in a model to predict high risk shipments for particular classes of sheep (Stacey 2003). This thesis also details the environmental conditions within a Western Australian summer feedlot and the physiological responses of cross bred ewes and wethers to these conditions when fed feedlot rations. This study found that temperatures in a typical Western Australian feedlot in summer increased above 40 degrees C with low humidity; however, temperatures generally decreased to be within the sheep's thermoneutral zone at night. Both ewes and wethers had significantly increased core temperatures in response to these conditions, with sheep spending significantly more time in the shade than in the sun during the day. Both ewes and wethers had increased respiratory rates and panting scores during an intensive climate room experiment with similar environmental conditions. However, feed intake did not decrease even when climate room temperatures increased at night and humidity levels were higher than that found in typical feedlot conditions in Western Australia. Work completed within this thesis has led to a greater understanding of the physiological responses of sheep to prolonged and continuous high heat such as during live export and to conditions of a typical Western Australian summer feedlot. This research has set a foundation for further study of management of sheep during live export and feedlotting.

The effects of sheep scab, (Psoroptes ovis infestation) on the welfare of sheep were studied. Flocks of sheep naturally infested with sheep scab and flocks of uninfested sheep, were studied before and after treatment with acaricides. A group of sheep, experimentally infested with Psoroptes ovis mites, were studied throughout the infestation. Behaviour was studied using focal and scan sampling techniques. Sheep scab resulted in increases in rubbing, scratching and biting. Rubbing and scratching in infested sheep were sometimes accompanied by non-functional mouthing, considered to be a stereotypy. Times spent grazing, cudding and idling were not affected by sheep scab, but the bout lengths of grazing and idling were reduced. The experimental group showed an increasing neutrophilia through the infestation, with erratic increases in eosinophil count and fibrinogen, while haemoglobin concentration and haematocrit decreased. Naturally infested flocks showed lymphopenia after treatment. Serum globulin concentrations increased through the infestation, with a concurrent decline in serum albumin. The serum globulin started to decline within one month after treatment. Some lactate dehydrogenase isoenyzme fractions increased during the infestation. Prolactin decreased and β- endorphin increased throughout the experimental infestation, although seasonal factors may have influenced these results. There was no change in pressure nociceptor threshold due to sheep scab. A questionnaire survey of sheep farmers suggested that sheep scab in Britain had increased in incidence and distribution over the last decade. The welfare of sheep infected with sheep scab and the control of sheep scab are discussed in the context of the experimental findings.

The question posed in this work is how one would model and predict the rotational spectrum of open-shell open-shell van der Waals complexes. There are two secondary questions that arise: the nature of radical-radical interactions in such systems and the modelling of the large amplitude motion of the constituent molecules. Four different systems were studied in this work, each providing part of the answer to the main question. Starting with the large amplitude motion, there are two theoretical approaches that may be adopted: to either model the whole complex as a semi-rigid molecule, or to perform quantum dynamical calculations. We recorded and analysed the rotational spectrum (using Fourier transform microwave spectroscopy) of the molecule of tertiary butyl acetate (TBAc) which exhibits a high degree of internal rotation; and of the weakly-bound complex between a neon atom and a nitrogen dioxide molecule (Ne-NO2). We used the semi-rigid approach for TBAc and the quantum dynamical approach for Ne-NO2. We also explored the compatibility of these two approaches. Moreover, we were able to predict and analyse the fine and hyperfine structure of the Ne-NO2 spectrum using spherical tensor operator algebra and the results of our dynamics calculations. To explore the nature of the interactions in an radical-radical van der Waals complex we calculated the PESs of the possible states that the complex may be formed in, when an oxygen and a nitrogen monoxide molecule meet on a plane using a number of high level ab initio methods. Finally, our conclusions were tested and applied when we performed the angular quantum dynamics to predict the rotational spectrum of the complex between an oxygen and a nitrogen dioxide molecule, and account for the effect of nuclear spin statistics in that system.

The aim of this thesis is to describe how the company Royal Dutch Shell plc takes care of its brand and find out what image of the Shell brand has in the Czech Republic. The thesis is divided into theoretical and practical part. In the theoretical part I deal with the process of brand management. I describe here brand equity and its building, brand strategies, brand valuation. Onwards I describe brand research with an emphasis on the semantic differential. Semantic differential is a method of qualitative research used in the practical part of this thesis. In the practical part I deal with the activities and history of the company Royal Dutch Shell plc and the company Shell Czech Republic a.s. This part also contains research of the Shell brand, which forms the key part of this thesis. Based on this research, I find out image of the Shell brand and I compare it with a competitive brand OMV.

Until recently it was assumed that the healthy mammalian lung did not harbour a microbiota, unlike other body sites. However, through the use of sequencing based technologies this has been shown to not be the case. Low biomass communities of microbes can be identified in the healthy lung and the lung microbiota in various diseases states has been shown to differ form these 'healthy' communities. The sheep respiratory microbiota is of interest from both an animal health perspective and due to the potential use of the sheep as a large animal model for studying the lung microbiota. In this thesis I seek to characterise the composition and variability of the sheep lung microbiota; the differences between the sheep upper and lower respiratory tract bacterial communities and to assess whether exhaled breath condensate collection can be used as a non-invasive lung microbiota sampling method. To study the bacterial communities present in samples I have used 16S rRNA gene sequencing and analysis. In Chapter 3 I examine the inter-individual and spatial variability present within the sheep lung microbiota. Protected specimen brushings were collected from three lung segments in six animals at three time-points. In a separate sheep a greater number of brushings was taken (n=16) in order to examine the amount of variability over a smaller spatial scale. I find that there can be large differences between the bacterial communities isolated from different locations within the lung, even over short distances. Samples also cluster by the sheep from which they were taken, indicating a host specific influence on the lung microbiota. In Chapter 4 I compare whole lung washes and oropharyngeal swabs from 40 lambs in order to examine the differences between the upper and lower respiratory tract microbiotas. I find that oropharyngeal swabs separate into rumen-like or upper respiratory tract-like bacterial communities. Despite the fact that in humans the upper and lower respiratory microbiotas have been shown to have similar compositions, the sheep lung microbiota samples in this study do not resemble either oropharyngeal samples or reagent only controls. In my first two results chapters, lung sampling methods were used which involved either anaesthesia combined with a bronchoscopic procedure (Chapter 3) or samples being taken from dead animals (Chapter 4). In Chapter 5 I assess whether there is a less invasive way of taking lung microbiota samples from a living individual, both to minimise the procedural stress on animals used as models and to increase the pool of potential volunteers for human lung microbiota studies. I compared samples taken via protected specimen brushings to samples taken via exhaled breath condensate collection, a less invasive sampling technique. I find that condensate samples contain less bacterial DNA and different bacteria than brushing samples, indicating that it is unlikely they could be used as a replacement for invasive sampling methods. In my final results chapter I compare the results across Chapters 3, 4 and 5 to identify bacteria which occur consistently in the sheep lung and could therefore potentially be described as core lung microbiota members. In conclusion, while I have found that there are large differences between the sheep lung microbiota and that which has previously been described in humans, the sheep can still be of use as a model in studies where these differences would not have a significant impact, such as in Chapter 5 of this thesis. I have identified several bacterial members of the core sheep lung microbiota which in future it would be interesting to better characterise and to assess whether they play a role in sheep health.

Includes bibliographical references (leaves 290-309) Investigates aspects of the intake and utilization of barley grain and grain legume supplements by sheep fed low quality pasture hay and when grazing mature summer pastures.

Dichelobacter nodosus, an anaerobic bacterium, is the major transmissible agent of ovine footrot. The disease expresses as a virulent or benign lesion in the hoof. Virulence is related to the production of serine proteases, particularly a thermostable protease. Isolates of D. nodosus are characterised according to the type of protease produced (either heat-stable or heat-labile) and the electrophoretogram (zymogram) of the protease. This study reports on the use of the DNA-based typing techniques Pulsed-Field Gel Electrophoresis (PFGE) and Infrequent-Restriction-Site-PCR (IRS-PCR) to investigate the molecular epidemiology of D. nodosus, including a consideration of the relationship between genetic type, zymogram patterns and whole cell protein profiles. The aim of the project was to obtain a better understanding of D. nodosus strain diversity and dissemination in Australia and its relationship to virulence within the population. The overall intention was to use this information to assist in the long-term control of virulent footrot. Field isolates of D. nodosus from Western Australia (n = 735), New South Wales (n = 16), Victoria (n = 24) and South Australia (n = 21) were obtained and analysed. Both typing techniques that were used offered good differentiation between isolates for epidemiological purposes, and the results were in general agreement. PFGE provided slightly better discrimination between isolates, with 214 PFGE types (181 from Western Australia) compared to 94 IrsT types (77 from Western Australia). Within this diverse range of molecular types clonality was observed - with clones being defined as clusters of isolates having closely related PFGE types. The strains were categorised as genetically diverse, genetically similar or identified as the same strain. This diversity of genetic types was found overall, within flocks of sheep on a farm and within a single hoof where, on a number of occasions, multiple molecular types and zymogram types were found colonising a single hoof. One isolate that was experimentally inoculated into a flock of sheep produced six different genetic types when tested 12 months after the initial infection. This indicates that D. nodosus undergoes rapid genetic change, which means that follow-up epidemiological investigation of disease outbreaks and trace-backs need to be done as soon after infection as possible. The genetic differences appeared to be due to large insertions or deletions of DNA. Amongst sheep on some properties, isolates that had a different protease expression and virulence expression were found to have the same molecular type. Investigation of these isolates by SDS-PAGE showed that they also had the same whole cell protein profiles. Isolates from the same clonal groups also had the same protein profile, whereas genetically diverse isolates had different protein profiles. The lack of protein differences between isolates of the same molecular type, or within a clonal group, suggests that the differences in protease thermostability may be due to conformational changes in the protein, rather than to overall detectable genetic change and/or expression of different proteins. These results demonstrate that PFGE typing can be useful in predicting likely phenotypic expression of whole cell proteins. Further work is required to elucidate differences between virulent and benign strains of D. nodosus.

Dichelobacter nodosus, an anaerobic bacterium, is the major transmissible agent of ovine footrot. The disease expresses as a virulent or benign lesion in the hoof. Virulence is related to the production of serine proteases, particularly a thermostable protease. Isolates of D. nodosus are characterised according to the type of protease produced (either heat-stable or heat-labile) and the electrophoretogram (zymogram) of the protease. This study reports on the use of the DNA-based typing techniques Pulsed-Field Gel Electrophoresis (PFGE) and Infrequent-Restriction-Site-PCR (IRS-PCR) to investigate the molecular epidemiology of D. nodosus, including a consideration of the relationship between genetic type, zymogram patterns and whole cell protein profiles. The aim of the project was to obtain a better understanding of D. nodosus strain diversity and dissemination in Australia and its relationship to virulence within the population. The overall intention was to use this information to assist in the long-term control of virulent footrot. Field isolates of D. nodosus from Western Australia (n = 735), New South Wales (n = 16), Victoria (n = 24) and South Australia (n = 21) were obtained and analysed. Both typing techniques that were used offered good differentiation between isolates for epidemiological purposes, and the results were in general agreement. PFGE provided slightly better discrimination between isolates, with 214 PFGE types (181 from Western Australia) compared to 94 IrsT types (77 from Western Australia). Within this diverse range of molecular types clonality was observed - with clones being defined as clusters of isolates having closely related PFGE types. The strains were categorised as genetically diverse, genetically similar or identified as the same strain. This diversity of genetic types was found overall, within flocks of sheep on a farm and within a single hoof where, on a number of occasions, multiple molecular types and zymogram types were found colonising a single hoof. One isolate that was experimentally inoculated into a flock of sheep produced six different genetic types when tested 12 months after the initial infection. This indicates that D. nodosus undergoes rapid genetic change, which means that follow-up epidemiological investigation of disease outbreaks and trace-backs need to be done as soon after infection as possible. The genetic differences appeared to be due to large insertions or deletions of DNA. Amongst sheep on some properties, isolates that had a different protease expression and virulence expression were found to have the same molecular type. Investigation of these isolates by SDS-PAGE showed that they also had the same whole cell protein profiles. Isolates from the same clonal groups also had the same protein profile, whereas genetically diverse isolates had different protein profiles. The lack of protein differences between isolates of the same molecular type, or within a clonal group, suggests that the differences in protease thermostability may be due to conformational changes in the protein, rather than to overall detectable genetic change and/or expression of different proteins. These results demonstrate that PFGE typing can be useful in predicting likely phenotypic expression of whole cell proteins. Further work is required to elucidate differences between virulent and benign strains of D. nodosus.

The study aims to determine the contribution made by available ram growth- and breed standard parameters on the sale price of auctioned rams in Namibia. These findings serve as an indication of the importance ram buyers place on individual parameters in selecting rams for breeding purposes. It furthermore tries to establish whether scientific measurement for the estimation of ram breeding values takes precedence over subjective appraisal. The analysis of the 100 day and 270 day growth performance of the progeny of selected Veldram tested rams were used to evaluate the accuracy of the estimation of ram breeding values and may serve to validate the proper execution of these Veldram tests.

Toxoplasma gondii infects sheep horizontally (from cat faeces) or vertically (transplacentally). Vertically infected lambs sometimes die. Here, transmission and performance impacts were considered in one Charollais flock and one Swaledale flock. B1-PCR was performed on umbilical cord, heart and brain. MAT was performed on blood and pleural effusion. IgG-ELISA was performed on colostrum. B1-PCR was more sensitive than four other methods, producing a band in 50% of replicates when each replicate contained 0.02 parasite genome copies. 16/243 (6.6%) viable Charollais, 30/263 (11.4%) viable Swaledale, 3/54 non-viable Charollais and 0116 non-viable Swaledale were PCR-positive, showing no difference between flocks. At age four months 64/524 (12.2%) Charollais and 10/329 (3.0%) Swaledale were seropositive, showing relatively high seroprevalence in Charollais. 5/44 non-viable Charollais and 1114 non-viable Swaledale were seropositive. Colostrum ELISA was 75% sensitive and 100% specific relative to serum MAT. 15/408 (3.7%) Charollais and 31139 (2.2%) Swaledale were colostrum ELISA-positive, showing no difference between flocks. PCR positivity was not associated with seropositivity. PCR positivity was randomly dispersed between litters. In Charollais seropositivity was overdispersed between litters, seroprevalence was higher than PCR prevalence, young ewes' lambs were frequently PCR-positive and large litters frequently contained seropositive lambs. Those results might have been due to vertical transmission. In Swaledale, PCR positivity was not associated with ewe age and seropositivity was rare. Those results suggested little transmission. Lamb seroconversion, and colostrum ELISA positivity, were not associated with ewe age. Overall, it is suggested that ewes ingested oocysts but vertical transmission was sometimes interupted by lambing, especially in Swaledale. In eight cases clinical toxoplasmosis was suspected. No evidence was found suggesting subclinical effects of T. gondii leading to reduced lamb survival. Charollais born PCR-positive were relatively light at age two months but that association was not found in Swaledale. Serology did not confirm any stunting effect.

We study the motivation and groundwork for the construction of a Light-Shell Effective Theory, an effective field theory for describing the matter emerging from high-energy collisions and the accompanying radiation. We begin in chapter 2 with a simple electrodynamics calculation to motivate the picture of the ``light-shell," in which all electric and magnetic fields lie on a spherical shell that moves outward at the speed of light. The result turns out to do more than motivate, as it also hints at an important feature of the theory, namely the gauge in which we subsequently choose to do calculations, called Light-Shell Gauge.
Physics

Eva Shell is a contemporary version of the epistolary mode, with the inclusion of text messages, email and various other media. As the narrative unfolds, the reader gradually comes to realise which texts are attributed to each character. It is a novel positioned in the twenty-first century against a city backdrop. The novel itself is set largely in Cardiff, but also in Ghana and Normandy between 1989 and 2003. The narrative follows the lives of two sisters. Eva and Sally, as they begin to travel, embark upon careers and experience their first formative relationships. For Eva this is her first lesbian relationship of importance while for Sally it is prospective parenthood with a man whom we come to realise has sinister connections as an influential member of the Front National. Finally, through the erosion of their relationships and the death of their only surviving parent. Matthew Shell, Eva and Sally become closer than ever. This is when they realise that they have only just begun to mature into adulthood. 'The Morning Book', a poetry journal that Mr Shell kept for most of his adult life, is finally left to Eva upon his death. The events referred to in it pre-date much of the main action of the text and centre on the destructive relationship, silence and loss that Mr Shell experiences in his marriage. The 'Morning Book' exposes Eva to the realisation that her parents' relationship had been volatile and fraught. This in turn answers the questions she had while growing up about her father's silence around the topic of her mother. The novel is followed by a critical commentary that is divided into five sections. I start with a section entitled 'Narrative and Theme' in which I explain my plot and the reasoning behind my choice of themes. This is followed by a section called 'Form' in which I explain the approach behind my decision to use a variety of media to convey the narrative of the novel. In this section I also explore how my understanding and knowledge of the common ground shared between poetry and prose informs my own writing. 'The Writing Process' is a section in which I tackle some of the technicalities of writing Eva Shell, such as the difficulty I had in producing a text that is not displayed chronologically. 'Influences' is an area of the commentary that focuses on my critical influences through which I seek to demonstrate the importance of critical enquiry in relation to my creative process. In this section I also offer an understanding of how my writing can be read with reference to particular artistic movements and critical trends. I end with some 'Final Thoughts' on the writing process in relation to my critical ideas and original ambitions.

An urban community is a fusion of new and old that is constantly changing. We understand better the plight of a community through raising awareness of its unique history and visual character. Linking individual and community experiences offers an opportunity for dialogue, especially as long-time residents and their new neighbors learn about their different pasts and explore their common future. Community building happens from within, when many individuals sharing common values create positive change.

Sheep (Ovis aries) are widely used in experimental settings and breeding system, nevertheless pain treatment in this species seems to be overlooked. The first two studies described in this thesis were designed to evaluate administration of analgesics both in the experimental and clinical setting. The third study evaluated the pharmacokinetics and antinociceptive effects of tramadol and its metabolite O-desmethyltramadol (M1) in sheep in a preclinical model of pain. The first study consisted of a meta-analysis of the reported use of analgesics in sheep for experimental purposes. Studies involving experimental procedures in sheep carried out in selected years (2008-2011-2014) were identified using a search engine. A total of 75 papers were selected. The study showed that analgesic treatment was often not accurately reported. The second study consisted of an on-line questionnaire evaluating the current attitudes of Italian practitioners to assessment and treatment of pain in sheep. The questionnaire consisted of five sections regarding the demographic data, analgesic drugs and techniques used to treat pain, attitudes to pain relief and assessment of pain and the knowledge on the topic of sheep analgesia. Only a modest number of questionnaires were returned. The most commonly used drugs by sheep practitioners who replied to the questionnaire were non steroidal anti-inflammatory drugs and local anaesthetics. In the practitioners’ opinion the main reasons for analgesic drugs not to be administered to sheep was the lack of licensed drugs followed by costs, withholding times and regulations. The vast majority of practitioners were interested in improving their knowlwdge on sheep analgesia. The third study investigated the pharmacokinetic profile and antinociceptive effect of tramadol and M1 following intravenous administration in sheep. Six healthy adult sheep were administered 4 (T4) and 6 (T6) mg/kg of tramadol (T) and saline (SAL) over 2 minutes in a cross over design with a two weeks wash out period. At predetermined time points blood samples were collected, physiological parameters and mechanical nociceptive threshold (NMT) values were recorded. Tramadol and M1 fitted a two compartmental model and a non compartmental model respectively. Pharmacokinetic parameters were similar for T4 and T6. Tramadol and M1 plasma concentrations decreased rapidly. Physiological parameters were not statistically different between groups. No mechanical antinociceptive effects of tramadol were detected, as MNT values did not statistically differ between groups. In conclusion, these studies showed that there is great scope for improvement in pain assessment and treatment in sheep both in the research than clinical settings. Moreover more experimental and clinical studies regarding the pharmacokinetic and pharmacokinamic effects of analgesic drugs in sheep are advocated in order to improve their welfare.
La pecora domestica (Ovis aries) è una delle specie animali più comunemente allevate ed utilizzate nella ricerca biomedica; nonostante questo l’analgesia in questo animale è stata a lungo trascurata. I primi due studi presentati in questa tesi sono stati elaborati allo scopo di valutare la somministrazione di analgesici nell’ambito clinico e sperimentale. Il terzo studio valuta la farmacocinetica e gli effetti antinocicettivi del tramadolo e del suo metabolita O desmethyltramadol (M1). Il primo studio consiste in una meta-analisi sull’ uso di farmaci analgesici riportato nelle pecore utilizzate a fini sperimentali. Studi riguardanti procedure sperimentali in pecore effettuati in anni selezionati (2008-2011-2014) sono stati identificati utilizzando un motore di ricerca. In totale, sono stati selezionati 75 articoli scientifici. Lo studio evidenzia mostra che la terapia antalgica spesso non viene accuratamente riportata. Il secondo studio consiste in un questionario on line redatto allo scopo di valutare l’attuale approccio dei veterinari italiani, che si occupano della specie ovina, alla valutazione ed al trattamento del dolore in questa specie. Il questionario era diviso in cinque sezioni riguardanti i dati demografici, l’uso di farmaci analgesici a tecniche utilizzate per apportare analgesia, e l’approccio utilizzato dai veterinari nella valutazione e trattamento del dolore nella specie ovina, ed, infine, la loro conoscenza riguardo tale argomento. Un numero limitato di veterinari ha completato il questionario. I farmaci più comunemente utilizzati dai veterinari che hanno risposto al questionario sono i farmaci antiinfiammatori non steroidei e gli anestetici locali. Secondo l’opinione dei veterinari, le ragioni principali per cui la terapia analgesica non viene effettuata nella specie ovina erano la mancanza di farmaci registrati, il loro costo, i tempi di sospensione e la regolamentazione riguardante il loro utilizzo. La maggior parte dei veterinari si dimostrava interessata a migliorare le proprie conoscenze riguardo l’analgesia nella specie ovina. Il terzo studio investiga la farmacocinetica e gli effetti antinocicettivi del tramadolo ed M1 dopo somministrazione endovenosa nelle pecore. Due dosi di tramadolo, 4 mg/kg (T4) e 6 mg/kg (T6), e soluzione salina (SAL) sono state somministrate in due minuti a sei pecore adulte e sane in uno studio randomizzato “in cieco” con un periodo di sospensione di due settimane. A tempi predeterminati, sono stati effettuati i prelievi di sangue per l’analisi farmacocinetica, e sono stati registrati i parametri fisiologici e i valori dopo stimolazione nocicettiva meccanica (MNT). Tramadolo ed M1 presentano rispettivamente una cinetica bi-compartimentale e non-compartimentale. I parametri farmacocinetici sono simili per le due dosi T4 e T6. Le concentrazioni plasmatiche di tramadolo ed M1 sono rapidamente diminuite. I parametri fisiologici non sono risultati statisticamente diversi tra i gruppi. Non sono stati evidenziati effetti antinociettivi del tramadolo; infatti i valori di MNT non sono risultati statisticamente diversi tra i gruppi. Concludendo, questi studi hanno dimostrato che ci sono ampi margini di miglioramento nella valutazione e trattamento del dolore nella specie ovina sia in ambito sperimentale sia clinico. Inoltre, sono necessari studi sperimentali e clinici riguardanti la farmacocinetica e farmacodinamica di farmaci analgesici nella specie ovina al fine di migliorarne il benessere.

A new thin shell finite element is presented. This new element doesn’ t have rotational degrees of freedom. Instead, in order to overcome the C1 continuity requirement across elements, the author resorts to enhance the geometric description of the flat triangles of a mesh made out of linear triangles, by means of Bernstein polynomials and triangular Bernstein-Bézier patches. The author estimates the surface normals at the nodes of a mesh of triangles, in order to use them to define the Bernstein-Bézier patches. Ubach, Estruch and García-Espinosa performed a comprehensive statistical comparison of different weighting factors. The conclusion of that work is that the inverse of the area of the circumscribed circle to the triangle and the internal angle of the triangle at the node considered, should be used as weighting factor. Using this new weighting factor, we reduce by about 10% the root mean square error in the estimation of normals of randomly generated surfaces with respect to the previous best weighting factor found in the literature. The author uses the information of the normal vectors at the nodes and the triangular Bernstein-Bézier patches to build cubic Bézier triangles. These cubic Bézier triangles are surface interpolants; C1 continuous at the nodes and C0 continuous across the edges. Owing to this approach, the new element is called Bézier-enhanced shell triangle (BEST). The BEST element takes advantage of all the nodes’ connectivities in each triangle of the mesh. The computation of the normal vectors at the nodes doesn’ t depend on the number of triangles surrounding each node of the mesh. The BEST element is independent from the mesh topology. A new paradigm is presented consisting on the reconstruction of the geometry of a cubic triangular element. This geometric reconstruction exploits the properties of cubic B-spline functions (cubic Bézier triangle). This way, the author builds a conforming continuum-based shell finite element. A cubic Bézier triangle has 30 parameters (3 coordinates for each of the 10 control points). Therefore it needs to apply 30 independent conditions. 15 of these conditions are given directly by the positions of the 3 vertices of the triangle and the orientations of the normal vectors at the 3 vertices. 8 of the remaining conditions are imposed introducing energy minimization considerations. These energy minimization considerations serve also to define a well-posed element. The author defines 3 different reduced problems for the 3 different shell deformation modes: bending deformation, membrane (in-plane extension) deformation and in-plane shear (drilling rotation) deformation. The only degrees of freedom of the BEST element are the vertices’ coordinates (9 variables). The remaining 21 parameters are solved internally. In order to fix the values of these 21 internal parameters, each BEST element solves 9 systems of linear equations of rank 3. The BEST element is successfully applied to the analysis of thin shells in linear and geometrically non-linear regimes using an implicit method. The non-linearity is solved using a Total Lagrangian formulation. The author succeeds at pre-integrating through-the-thickness efficiently and accurately. The through-the-thickness integrals are evaluated just once: at the reference configuration. There are just 14 through-the-thickness scalar integrals to perform for each Gauss point. The numerical examples results show that the BEST element has the potential to achieve cubic convergence. Although they also cast doubts on the possibility of reproducing this result for a wide range of problems. For in-plane shear dominated problems, the formulation used in this thesis only achieves linear convergence. For membrane oriented tests with curvature, the convergence is quadratic. The BEST element exhibits membrane locking behavior. The author suggests exploiting further the drilling rotations kinematics in order to solve membrane locking.
Se presenta un nuevo elemento finito de lámina delgada. Este nuevo elemento no usa rotaciones como grados de libertad. En su lugar, para sortear el requisito de mantener continuidad C1 entre elementos, el autor mejora la descripción geométrica de los triángulos planos de una malla de triángulos lineales, por medio de polinomios de Bernstein y particiones triangulares de Bernstein-Bézier. Para definir las particiones de Bernstein-Bézier, el autor estima las normales a la superficie en los nodos de una malla de triángulos. Ubach, Estruch y García-Espinosa hicieron una comparación estadística exhaustiva entre distintos factores de ponderación. La conclusión de dicho trabajo conduce a usar como factor de ponderación: el inverso del área de la circunferencia circunscrita al triángulo y el ángulo interno del triángulo en el nodo considerado. Con este nuevo factor de ponderación, se reduce en aproximadamente un 10% el error medio cuadrático cometido en la estimación de las normales de superficies generadas aleatoriamente, respecto del mejor factor usado previamente en la literatura. Con la información de los vectores normales en los nodos, el autor construye triángulos cúbicos de Bézier. Estos triángulos cúbicos de Bézier interpolan la superficie; con continuidad C1 en los nodos y C0 en las aristas. En virtud a este planteamiento, el nuevo elemento recibe el nombre de BEST. El elemento BEST aprovecha todas las conectividades nodales de cada triángulo de la malla. El número de triángulos que rodean cada nodo de la malla no afecta al cálculo de los vectores normales. El elemento BEST es independiente de la topología de la malla. Se propone un nuevo paradigma que consiste en reconstruir la geometría de un elemento triangular cúbico. Esta reconstrucción geométrica aprovecha las propiedades de las funciones cúbicas B-spline (triángulo cúbico de Bézier). Así, el autor crea un elemento de lámina conforme basado en el continuo. Un triángulo cúbico de Bézier tiene 30 parámetros (3 coordenadas para cada uno de los 10 puntos de control). Es necesario aplicar 30 condiciones independientes. 15 de estas condiciones se deducen de la posición de los 3 vértices del triángulo y de los vectores normales en los 3 vértices. De las otras 15 condiciones, 8 se obtienen a partir de criterios de minimización de la energía. Estos criterios de minimización de la energía sirven para definir un elemento bien planteado. El autor desarrolla 3 problemas reducidos para los 3 modos de deformación de la lámina: deformación de flexión, de membrana (extensión en el plano) y de cortante en el plano (rotación de taladro). Los únicos grados de libertad del elemento BEST son las posiciones de los vértices (9 variables). Los otros 21 parámetros se resuelven internamente. Para obtener estos 21 parámetros internos, hay que resolver 9 sistemas de ecuaciones lineales de rango 3 para cada elemento BEST. Se ha aplicado el elemento BEST con éxito al cálculo de láminas delgadas en régimen lineal y geométricamente no-lineal con un método implícito. La no-linealidad se plantea con una formulación Lagrangiana total. Se demuestra cómo pre-integrar en el espesor de manera eficiente y precisa. Solo es preciso evaluar las integrales en el espesor una vez: en la configuración de referencia. Solo hay 14 integrales escalares en el espesor para cada punto de Gauss. Los ejemplos numéricos muestran que el elemento BEST tiene potencial para converger cúbicamente. Pero también existen dudas sobre la capacidad de reproducir de manera consistente este resultado en un amplio rango de problemas. En problemas dominados por la deformación de cortante en el plano, la formulación utilizada en esta tesis solo alcanza convergencia lineal. En ejemplos orientados a la deformación de membrana que incluyen curvatura, la convergencia es cuadrática. El elemento BEST sufre de bloqueo por membrana. El autor sugiere desarrollar más profundamente la cinemática de las rotaciones de taladro para resolver el bloqueo por membrana.
Es presenta un nou element finit de làmina prima. Aquest nou element no fa servir rotacions com a graus de llibertat. Enlloc d'això, per esquivar el requisit de mantenir continuïtat C1 entre els elements, l'autor millora la descripció geomètrica dels triangles plans d'una malla de triangles lineals, mitjançant polinomis de Bernstein i particions triangulars de Bernstein-Bézier.Per definir les particions de Bernstein-Bézier, l'autor estima les normals a la superfície en els nodes d'una malla de triangles. Ubach, Estruch i García-Espinosa varen fer una comparació estadística exhaustiva entre diferents factors de ponderació. La conclusió d'aquest treball condueix a fer servir com a factor de ponderació: l'invers de l'àrea de la circumferència circumscrita al triangle i l'angle intern del triangle en el node considerat. Amb aquest nou factor de ponderació, es redueix aproximadament en un 10% l'error quadràtic mig comès en l'estimació de les normals de superfícies generades aleatòriament, respecte del millor factor usat prèviament a la literatura.Amb la informació dels vectors normals en els nodes, l'autor construeix triangles cúbics de Bézier. Aquests triangles cúbics de Bézier interpolen la superfície; amb continuïtat C1 als nodes i C0 a les arestes. En virtut d'aquest plantejament, el nou element rep el nom de BEST (Bézier-enhanced shell triangle).L'element BEST aprofita totes les connectivitats nodals de cada triangle de la malla. El nombre de triangles que envolten cada node de la malla no afecta al càlcul dels vectors normals. L'element BEST és independent de la topologia de la malla.Es proposa un nou paradigma que consisteix en reconstruir la geometria d'un element triangular cúbic. Aquesta reconstrucció geomètrica aprofita les propietats de les funcions cúbiques B-spline (triangle cúbic de Bézier). D'aquesta manera l'autor crea un element de làmina que és conforme i basat en el continu.Un triangle cúbic de Bézier té 30 paràmetres (3 coordenades per cadascun dels 10 punts de control). Cal aplicar 30 condicions independents. 15 d'aquestes condicions es dedueixen de la posició dels 3 vèrtexs del triangle i dels vectors normals en els 3 vèrtexs.De les 15 condicions restants, 8 s'obtenen a partir de criteris de minimització de l'energia. Aquests criteris de minimització de l'energia serveixen per definir un element ben plantejat. L'autor desenvolupa 3 problemes reduïts per als 3 modes de deformació de la làmina: deformació de flexió, de membrana (extensió en el pla) i de tallant en el pla (rotació de barrina).Els únics graus de llibertat de l'element BEST són les posicions dels vèrtexs (9 variables). Els altres 21 paràmetres es resolen internament. Per obtenir aquests 21 paràmetres interns, cal resoldre 9 sistemes d'equacions lineals de rang 3 per cada element BEST.S'ha aplicat l'element BEST amb èxit al càlcul de làmines primes en règim lineal i geomètricament no-lineal fent servir un mètode implícit. La no-linealitat es planteja amb una formulació Lagrangiana total. Es demostra com es pot pre-integrar a través del gruix de manera eficient i precisa. Només cal avaluar les integrals a través del gruix un cop: a la configuració de referència. Només hi ha 14 integrals escalars a través del gruix per a cada punt de Gauss. Els exemples numèrics mostren que l'element BEST té potencial per convergir cúbicament. Però també hi ha dubtes de que aquest resultat es pugui reproduir de manera consistent per un ventall ampli de problemes. En problemes dominats per la deformació de tallant en el pla, la formulació emprada en aquesta tesi només assoleix convergència lineal. En exemples orientats a la deformació de membrana que incloguin curvatura, la convergència és quadràtica. L'element BEST pateix de bloqueig per membrana. L'autor suggereix desenvolupar en més profunditat la cinemàtica de les rotacions de barrina per resoldre el bloqueig per membrana.

This thesis details research undertaken in the investigation of the open-shell open-shell Van der Waals complexes between nitric oxide (NO) and oxygen (O₂) and between nitrogen dioxide (NO₂ ) and oxygen (O2 ). The Fourier transform microwave spectroscopy technique was used during the experimental work. Spectra were recorded for a mixture of NO and O₂ over the frequency range 7.0 to 18.2 GHz. Detailed ab initio calculations have been performed on the potential energy surface of both NO-O₂ and NO₂-O₂ using Multi-reference Rayleigh Schrodinger Second Order Perturbation Theory. These calculations were performed for the four distinct states of NO-O₂, ²A", ⁴A", ²A' and ⁴A', and for the two distinct states of NO,sub>2-O₂, ²A and ⁴A. Predicted rotational spectra have been generated by modelling the systems with a rigid-rotor Hamiltonians. The effective Hamiltonians included the rotational Hamiltonian, ℋ_rot, fine structure terms and hyperfine structure terms. It was not possible, for rationalizable reasons, to fit the predicted spectra for NO-O₂ to the experimental observations. Experimental details, calculation methods and rotational theory are discussed in the main body of the thesis. Predicted spectra, relevant calculations and other data is presented in the appendices.