This study deals with the use of high-order spectral/hp approximation functions in the finite element models of various nonlinear boundary-value and initial-value problems arising in the fields of structural mechanics and flows of viscous incompressible fluids. For many of these classes of problems, the high-order (typically, polynomial order p greater than or equal to 4) spectral/hp finite element technology offers many computational advantages over traditional low-order (i.e., p < 3) finite elements. For instance, higher-order spectral/hp finite element procedures allow us to develop robust structural elements for beams, plates, and shells in a purely displacement-based setting, which avoid all forms of numerical locking. The higher-order spectral/hp basis functions avoid the interpolation error in the numerical schemes, thereby making them accurate and stable. Furthermore, for fluid flows, when combined with least-squares variational principles, such technology allows us to develop efficient finite element models, that always yield a symmetric positive-definite (SPD) coefficient matrix, and thereby robust direct or iterative solvers can be used. The least-squares formulation avoids ad-hoc stabilization methods employed with traditional low-order weak-form Galerkin formulations. Also, the use of spectral/hp finite element technology results in a better conservation of physical quantities (e.g., dilatation, volume, and mass) and stable evolution of variables with time in the case of unsteady flows. The present study uses spectral/hp approximations in the (1) weak-form Galerkin finite element models of viscoelastic beams, (2) weak-form Galerkin displacement finite element models of shear-deformable elastic shell structures under thermal and mechanical loads, and (3) least-squares formulations for the Navier-Stokes equations governing flows of viscous incompressible fluids. Numerical simulations using the developed technology of several non-trivial benchmark problems are presented to illustrate the robustness of the higher-order spectral/hp based finite element technology.

Chemistry is often claimed to be difficult, irrelevant, and uninteresting to school students. Even students who enjoy doing science often have problems seeing themselves as being scientists. This thesis explores and challenges the negative perception of chemistry by investigating upper secondary students’ views on the subject. Based on students’ ideas for improving chemistry education to make the subject more interesting and meaningful, new learning approaches rooted in context-based learning (CBL) are presented. CBL approaches are applied in several countries to enhance interest, de-emphasise rote learning, and improve students’ higher order thinking. Students’ views on upper secondary school chemistry classes in combination with their problem- solving strategies and application of chemistry content knowledge when solving context-based chemistry tasks were investigated using a mixed methods approach. Questionnaire responses, written solutions to chemistry problems, classroom observations, and think-aloud interviews with upper secondary students at the Natural Science Programme and with experts working on context- based chemistry tasks were analysed to obtain a general overview and explore specific issues in detail. Several students were identified who had positive feelings about chemistry, found it interesting, and chose to continue with it beyond the compulsory level, mainly with the aim of future university studies or simply because they enjoyed it. Their suggestions for improving school chemistry by connecting it to everyday life prompted an exploration of CBL approaches. Studies on the cognitive learning outcomes arising from the students’ work on context-based tasks revealed that school chemistry heavily emphasises the recall of memorised facts. However, there is evidence of higher order thinking when students’ problem-solving processes are scaffolded using hints based on the Model of Hierarchical Complexity in Chemistry (MHC-C). In addition, the contextualisation of problems is identified as something that supports learning rather than distracting students. To conclude, the students in this thesis are interested in chemistry and enjoy chemistry education, and their motives for choosing to study chemistry at the post-compulsory level are related to their aspirations; students’ identity formation is important for their choices. Because students are accustomed to recalling facts and solving chemistry problems that have “one single correct answer”, they find more open problems that demand higher order thinking (e.g. knowledge transfer) unfamiliar and complex, suggesting that such processes should be practiced more often in school chemistry. / Kemi är ett skolämne som generellt anses vara både svårt, irrelevant och ointressant för ungdomar. Trots att det ändå finns ungdomar som uppskattar naturvetenskap i allmänhet och kemi i synnerhet, har de ofta problem att se sig själva som naturvetare eller kemister. Denna avhandling undersöker och ifrågasätter den negativa bilden av kemiämnet genom att till en början studera gymnasieelevers syn på kemi. Med utgångspunkt från naturvetarelevers förslag för att förbättra kemiundervisningen och göra ämnet mer intressant och meningsfullt, anknyter avhandlingen därefter till kontextbaserad kemi. Kontextbaserade kurser används i flera länder för att öka elevernas intresse, minska fokuseringen på utantillkunskaper och utveckla elevernas mer avancerade tänkande; med andra ord med målet att uppnå ett meningsfullt lärande. Vid kontextbaserade angreppssätt utgår man från ett sammanhang (kontexten), ofta något personligt eller samhälleligt, som ska vara relevant och intressant. Från dessa kontexter koncentreras därefter undervisningen på de ämneskunskaper man behöver ha för att förstå sammanhanget (s.k. need-to-know). Syftet med avhandlingen är att undersöka naturvetarelevers syn på gymnasiekemin, både deras intresse för ämnet och deras skäl att välja det naturvetenskapliga programmet på gymnasiet, samt elevernas problemlösningsförmåga och användande av ämneskunskaper när de löser kontextbaserade kemiuppgifter. Skälet att studera naturvetarelever på gymnasiet är att dessa elever uppfattas som möjliga framtida naturvetare eftersom de själva har valt naturvetenskaplig inriktning efter den obligatoriska grundskolan. Med hjälp av olika metoder (enkäter, klassrums- observationer, skriftliga lösningar till kemiuppgifter och intervjuer med både elever och experter som löser kemiuppgifter) har analyser genomförts för att dels får en allmän överblick, dels för att utforska specifika delar i detalj både gällande kognitiva och affektiva aspekter av lärande. Resultaten visar att flertalet elever har en positiv inställning till kemi, många tycker att ämnet är intressant och har valt att fortsätta läsa kemi efter den obligatoriska grundskolan främst med målet att studera vidare på universitetsnivå, men också eftersom de specifikt uppskattar kemi. Gymnasieeleverna lyfter fram lärarna som viktiga och lärarstyrda kemilektioner anses positivt, speciellt om lärarna är strukturerade i sin undervisning. Ett vanligt skäl till att välja naturvetenskapsprogrammet är också att man aktivt väljer utbildning med utgångspunkt från vilken skola man vill gå på, något som i denna avhandling tolkas som ett identitetsskapande. Elevernas förslag för att förbättra skolkemin genom att anknyta kemin till vardagen låg till grund för avhandlingens fortsatta inriktning mot kontextbaserade angreppssätt. Analyser av elevernas kognitiva resultat när de löser kontextbaserade kemiuppgifter visar att dagens skolkemi tydligt fokuserar på att memorera faktakunskaper. Eleverna är vana att använda utantillkunskaper när de löser kemiuppgifter eftersom uppgifterna, enligt eleverna, efterfrågar ”det rätta svaret”. Däremot visar studierna också att ett mer avancerat tänkande kan uppnås när elevernas problemlösning stöds av hjälp och ledtrådar som baseras på ett specifikt ramverk, MHC-C (Model of Hierarchical Complexity in Chemistry). När det gäller ämneskunskaperna som krävs för att lösa de kontextbaserade kemiuppgifterna är vissa kemibegrepp viktiga tröskelbegrepp (sk. threshold concepts). Med hjälp av medvetenhet om tröskelbegrepp, som exempelvis polaritet och elektronegativitet för löslighetsuppgifter inom den organiska kemin, kan en större helhetsförståelse för övergripande begrepp (crosscutting disciplinary concepts) som förhållandet mellan kemiska ämnens struktur och egenskaper förhoppningsvis uppnås. När det gäller affektiva resultat anser eleverna att kontexterna i uppgifterna både var intressanta och relevanta, främst när en personlig anknytning var tydlig. Dessutom visade sig kontexterna i uppgifterna vara positiva för lärandet, inte en distraktionsfaktor. Sammanfattningsvis konstateras att svenska elever på naturvetenskaps- programmet är intresserade av kemi och uppskattar kemiundervisningen, speciellt om kemin knyts till vardagen och att lärarna har en tydlig struktur i sin undervisning. Elevernas skäl att välja fortsatta kemistudier efter den obligatoriska grundskolan kan knytas till deras utbildningssträvan men också att elevers identitetsskapande är viktigt för deras gymnasieval. Med hjälp av kontextbaserade angreppssätt kan kemiundervisningen göras mer intressant och relevant samtidigt som elevernas problemlösningsförmåga kan utvecklas. När eleverna möter mer öppna frågor som kräver förklaringar och resonemang är de ovana vid detta och uppfattar uppgifterna komplicerade, samtidigt som de uppskattar denna typ av uppgifter eftersom de uppfattas relevanta och intressanta. Slutsatsen blir att elevernas förmåga till problemlösning av öppna frågor som både kräver faktakunskaper men också förklaringar och resonemang måste tränas oftare inom ramen för skolans kemi för att utveckla elevernas meningsfulla lärande.

The geometrically nonlinear constant moment triangle based on the von Karman theory of thin plates is first described. This finite element, which is believed to be the simplest possible element to pass the totality of the von Karman patch test, is employed throughout the present work. It possesses the special characteristic of providing a tangent stiffness matrix which is accurate and without approximation. The stability of equilibrium of discrete conservative systems is discussed. The criteria which identify the critical points (limit and bifurcation), and the method of determination of the stability coefficients are presented in a simple matrix formulation which is suitable for computation. An alternative formulation which makes direct use of higher order directional derivatives of the total potential energy is also presented. Continuation along the stable equilibrium solution path is achieved by using a recently developed Newton method specially modified so that stable points are points of attraction. In conjunction with this solution technique, a branch switching method is introduced which directly computes any intersecting branches. Bifurcational buckling often exhibits huge structural changes and it is believed that the computation of the required switch procedure is performed here, and for the first time, in a satisfactory manner. Hence, both limit and bifurcation points can be treated without difficulty and with continuation into the post buckling regime. In this way, the ability to compute the stable equilibrium path throughout the load-deformation history is accomplished. Two numerical examples which exhibit bifurcational buckling are treated in detail and provide numerical evidence as to the ability of the employed techniques to handle even the most complex problems. Although only relatively coarse finite element meshes are used it is evident that the technique provides a powerful tool for any kind of thin elastic plate and shell problem. The thesis concludes with a proposal for an algorithm to automate the computation of the unknown parameter in the branch switching method.

Education is rapidly moving away from the instructional models of the 19th century and educationalists are now asserting that not only do students need to be able to learn by rote but also to be able to think in a more profound and complex manner. Students are required to develop new processes to handle the rapidly changing world that they are expected to take part in as they complete their formal learning. This change is evident in all the developed nations and Australian students are finding that they are being asked to demonstrate a range of higher order thinking skills in all their school subjects. Science courses in Queensland require students to be assessed on both complex reasoning and scientific process skills. Studies have shown that students can develop these skills in a number of ways that include the exposure to appropriate open-ended hands-on tasks. As higher order thinking skills underlie the development of both complex reasoning and scientific process, it is important that science educators take appropriate steps to facilitate the development of this level of thinking. This study examined the use of some higher order thinking skills by students using Information Technology in their science classroom. It investigated the degree to which students used their higher order thinking skills when engaged in a computer simulation of a complex science task. The study involved two pairs of Year 9 students, one pair each from the upper and lower quartiles of the year level, in a private Years 4 to 12 boys' school in an inner Brisbane suburb. All students had been immersed in Information Technology in Years 4 to 8 as part of a technology-across-the-curriculum project for all year levels in the school and at the time of the study were at the end of their second semester in Year 9. Students had worked with a large number of computer applications in all their subjects, averaging about one lesson in the computer room per day across all their subjects for the past year of schooling. The school also had a policy for learning and teaching that revolved around the development in students of critical thinking and, specifically in Science, complex reasoning, and scientific process skills. During this study, students engaged in a computer simulation requiring the application of skills and knowledge already learnt in their science course. The modules of this simulation developed an understanding of the essentials for life and the quantities of a range of items from water to seeds to land areas that would be required for a number of people that would be needed to staff the Lunar Base. Prompts were given on the way, which assisted students in their decision making. Students progressed through the various areas and stages of the development of the Lunar Base until they were satisfied that each area supported the others and that there was no imbalance that needed to be corrected. Once all stages had been completed, students were free to change variables and experiment further as they saw fit in order that they might produce the most self-sufficient Lunar Base possible. There was some evidence that the simulation did encourage the students in the pairs observed to think in greater depth about the materials and to argue their convictions in an improved manner. As well as the students appearing to increase in competency in argument over the period of time, the four students in their final interviews, spoke of feeling satisfied with the results of the lessons. The students also appeared more engrossed in their task and the pedagogy provided in the task was appreciated as it gave meaning to why they were required to learn scientific materials as well also presenting them with ways to find the knowledge for themselves.

In this study a phenomenographic theoretical perspective is taken as departure for research on manifested critical thinking in civics among Swedish ninth-grade compulsory school students. According to the phenomenographic perspective students’ manifestations of critical thinking are linked to the way of experiencing the phenomena inducing a manifestation of critical thinking. Thus differences between students’ manifestations of critical thinking are linked to differences in the way of experiencing the phenomena inducing a manifestation of critical thinking. The empirical investigation in this study revolves around how 19 ninth-grade students experience four different tasks designed to induce manifestations of critical thinking. In broad terms the main aim of the study is to describe the students’ different ways of experiencing each specific task and furthermore, to link each specific way of experiencing a specific task to a specific type of manifested critical thinking in relation to that task. A more overarching aim is to offer and test the phenomenographic theoretical perspective as a way of conducting research on manifested critical thinking. The empirical results show how the way of experiencing a specific task plays a decisive roll for the type of manifested critical thinking, made possible in relation to the specific task. A more complex way of experiencing the task can be linked to a more complex manifestation of critical thinking in relation to the task. A less complex way of experiencing the task can be linked to a less complex manifestation of critical thinking in relation to the task. The study also suggests how these empirical results can be used in a pedagogical situation in order to enhance students manifested critical thinking in civics. Concerning the more overarching aim the study strongly points to a further use of the phenomenographic perspective when conducting research on students manifested critical thinking.

Contexte & Motivation:Les installations électriques des bâtiments se détériorent au fil du temps et leur gravité et leur taux de détérioration dépendent de facteurs environnementaux (chaleur, humidité, réactions chimiques corrosives et vieillies isolations) ou d'actions externes indésirables telles que la manipulation humaine erronée, qui conduit à des charges ou des câbles/réseaux endommagés.L'European Fire Academy (EFA) et de nombreuses compagnies d'assurance indiquent que 25% des incendies de bâtiments sont d'origine électrique. Ces incendies peuvent être déclenchés par des circuits surchargés, des court-circuits, des courants de fuite à la terre, des surtensions et / ou des défauts d'arc électrique dans les connexions et les câbles.Les protections électriques classiques telles que les disjoncteurs et les disjoncteurs différentiels offrent une protection insuffisante. Par exemple, en cas de défauts d'arcs en série, la valeur du courant de défaut d'arc reste inférieure à la valeur du courant nominal, car elle est limitée par la résistance du carbone généré par le défaut d'arc. Dans ce cas, toute protection existante peut détecter ce type de faute.Détection de défaut d'arc : approche de traitement du signalDans le cadre de ce travail, l'objectif a été de détecter chaque instant d'arc, ce qui, pour un réseau alternatif, permettrait d'identifier correctement chaque arc dans chaque demi-cycle de réseau où il se produit.En fonction de la caractéristique numérique utilisée à des fins de détection, nous avons introduit différentes classes de méthodes:• Caractéristiques énergétiques (bandes étroite et large bande)• Caractéristiques statistiques (moments statistiques, analyse de la corrélation etc.)• Caractéristiques basées sur un model (ex. modelés AR, ARMA etc.)• Caractéristiques data-driven (utiliser Phase Space Embedding pour les séries temporelles)Chaque approche a été testée et évaluée sur une base de données de signaux construite avec soin, capable de fournir la variabilité du monde réel, dans un cadre d'évaluation statistique qui permet de trouver des seuils appropriés et leurs plages associées. Il donne également des performances relatives, d'une fonctionnalité à l'autre, en fonction de la façon dont les plages de seuils couvrent tout l'espace des caractéristiques.Une approche prometteuse est montrée avec un résultat intermédiaire sur la figure 8. La configuration est plutôt courante, avec une charge résistive (R-Load) en fonctionnement normal, avec un gradateur allumé et ajouté dans la configuration et un arc persistant apparaissant dans le circuit.Il suffit d'analyser simplement la forme d'onde du courant 50 Hz, car même lors d'une simple inspection visuelle, il est difficile d'identifier l'origine du défaut d'arc et s'il est stable ou s'il s'éteint après (ou où). En mesurant correctement le bruit de défaut d'arc haute fréquence et en sélectionnant correctement la bande passante, nous parvenons à obtenir un signal beaucoup plus facile à traiter. L'arc est difficile à détecter en raison de la variation de l'intensité énergétique d'un réseau à l'autre (encore plus: pour un même réseau, ajouter / enlever des charges ou des rallonges modifie la distribution d'amplitude et de fréquence de l'arc). Par conséquent, nous exploitons le caractère aléatoire intrinsèque de l'arc, ce qui permet une variabilité suffisante d'une réalisation d'arc à une autre.En conclusion, nous proposons une nouvelle méthodologie de traitement du signal pour la détection des défauts d'arc, à mettre en œuvre dans un algorithme de produit AFDD. En outre, une autre approche est présentée, basée sur l'analyse de diagramme de phase, qui permet la séparation entre les arcs et les signaux de communication, ce qui est également un grand défi dans ce domaine. / Context & Motivation:Electrical installations in buildings deteriorate, over time and the severity and rate of deterioration depend on environmental factors (such as heat, humidity, corrosive chemical reactions and aging insulations) and unwanted external actions (such as human mishandling, that leads to damaged devices or cables/network).Caution is mandatory when handling electrical installations, seeing that potential hazards include electric shocks, burns, explosions and fire, if proper safety precautions are ignored or neglected. The European Fire Academy (EFA) and many property and casualty insurance companies report that 25% of building fires are electrical in origin. These fires can be triggered by overloaded circuits, short-circuits, earth leakage currents, overvoltage and/or electrical arc faults in connections and cables.Classical electrical protection such as circuit breakers and RCDs offer insufficient protection. For example, in case of series arc faults, the arc fault current value remains below the rated current value, since it is limited by the resistance of the carbon generated by the arc fault and by the load itself. In this case, no existing protection can detect such kind of fault.Arc Fault Detection: Signal Processing ApproachIn the context of this work, the objective has been to detect each instant of arcing, which for an AC network, would mean correctly identifying each arcing in each network half-cycle where it occurs.Depending on the numerical feature used for detection purposes, we introduced different classes of methods:• Energy-related features (narrow and wideband)• Statistical features (statistical moments, correlation analysis etc.)• Model-based features (using numerical models, such as AR, for example)• Data-driven features (using Phase Space Embedding for time series)Each approach has been tested & evaluated on a carefully constructed signal database, capable of supplying real-world variability, within a statistical evaluation framework which enables finding suitable thresholds and their appropriate ranges. It also gives relative performances, from one feature to another, based on how threshold ranges cover the entire feature space.A promising approach is shown with an intermediary result in Figure 9. The configuration is rather common, with a resistive load (R – Load) in normal operation, with a dimmer being turned on and added in the configuration and a persistent arc appearing in the circuit.Figure 9 Resistive load, dimmer and persistent arcing – processing result (example).Simply analyzing the 50Hz line current waveform is insufficient, as even at a simple visual inspection there is difficulty in identifying where the arc fault ignites and if it is a stable one, or if it extinguishes afterwards (or where). By correctly measuring the high frequency arc fault noise and with correct selection of the bandwidth, we manage to obtain a signal much easier to process further on. Arcing is inherently difficult to detect, due to high frequency energy intensity variation from one network to another (even more: for the same network, adding/removing loads or extension cords will change the amplitude and frequency distribution of the arc fault energy). Therefore, we exploit the intrinsic randomness of arcing, which enables sufficient variability from one arcing realization to another.To conclude, we propose a new signal processing methodology for arc fault detection, to be implemented in an AFDD product algorithm. Also, another approach is presented, based on phase diagram analysis, that allows the separation between the arcs and communication signals, which is also a great challenge in this field.

Programas sofrem diversas modificações ao longo das etapas de desenvolvimento, implantação e manutenção. A evolução de um software pode ter várias causas: correção de erros, inclusão de novas funcionalidades ou até mesmo, como é o caso de programas orientados a aspecto, transformações estruturais podem fazer parte da semântica do sistema. Apesar de modificações serem comuns, não é tarefa trivial prever como estas afetam o comportamento dos programas, já que os componentes de software normalmente interagem de forma complexa, o que faz com que mesmo pequenas alterações possam introduzir comportamentos indesejados. Transformação de grafos, também conhecida como reescrita de grafos, é um importante paradigma para modelagem e análise de sistemas. Modelos baseados em transformação de grafos, como gramáticas de grafos, permitem uma modelagem ao mesmo tempo intuitiva e com semântica precisa, permitindo a aplicação de técnicas de análise como verificação de modelos e análise de par crítico no estudo do comportamento de sistemas. A teoria por trás de transformação de grafos vem sendo desenvolvida a várias décadas, e atualmente está descrita de uma forma bastante abstrata. Contudo, ainda não possui uma definição natural de reescritas de alta ordem, que facilitaria a definição de evolução de especificações compostas por regras de reescrita de grafo, tais como gramáticas de grafos. Nesta tese são abordadas a modelagem e a análise de sistemas sob modificações programadas no contexto de gramáticas de grafos. A generalização da abordagem de pushout duplo para reescrita de grafos é utilizada como o princípio geral para descrever, simultaneamente, a semântica do sistema e modificações estruturais. Para tal, introduzimos uma noção de reescrita de segunda ordem para modificar a estrutura de regras de transformação de grafos, e usando isso, definimos modelos equipados simultaneamente de regras de primeira e segunda ordem, chamados gramáticas de grafos de segunda ordem. Através destes modelos podemos representar simultaneamente transformações estruturais e execução do sistema, e relacionar formalmente ambos tipos de reescrita. Também propomos novas técnicas para investigar o efeito da modificação de regras sobre a aplicação destas. Finalmente, como um exemplo de aplicação da teoria, caracterizamos construções de sistemas orientados a aspectos através de gramáticas de grafos de segunda ordem, e discutimos como utilizar as novas técnicas para estudar o efeito da combinação aspectual sobre o sistema inicial. / Software systems are not static entities: they usually undergo several changes along their development and maintenance cycles. Software evolution may be required for several reasons, such as the inclusion of new functionalities, the correction of errors or even as part of the system semantics, as it is the case of aspect-oriented systems. However, it is usually not trivial to foresee how structural changes can affect the system behaviour, since system components often interact in very complex ways, and even trivial modifications may introduce new problems. Graph transformation, also known as graph rewriting, has been used throughout the years as an important paradigm for system modelling and analysis. Models based on graph transformation, such as graph grammars, allow an intuitive but formal representation of the system behaviour, allowing the usage of analysis techniques such as model checking and static analysis of rule interaction. The theory behind graph transformation is quite general, and has been studied since the 1970s. However, it still lacks a general notion of higher-order rewriting that would allow a natural definition of model transformations for graph grammars. The lack of general second-order characterization presents difficulties for employing graph grammars as targets of model transformations, and studying how model transformations affect their natural behaviour. In this thesis we address the problem of modelling and analysing systems undergoing programmed modifications in the context of graph grammars. We use the generalization of the double-pushout approach for graph rewriting as a principle for defining simultaneously the system semantics and structural modifications. To achieve this, we introduce a notion of second-order graph rewriting that acts on graph transformation rules. Based on secondorder rewriting we are able to define second-order graph grammars, models equipped with a first-order layer, representing the original system execution, and a second-order layer, representing a model transformation. Using second-order graph grammar we can encode simultaneously model transformations and system execution, allowing us to formally relate them. Moreover, we propose new techniques to investigate the effect of rule modification over their effect on graphs. As an application example, we characterize aspect-oriented constructions for graph grammars, and discuss how to relate the aspect weaving layer with the base system semantics.

This thesis explores the extent to which the doxastic ‘should' is information-sensitive and the implications of this for a number of debates in normative epistemology. The doxastic ‘should' is a special case of the deontic modal ‘should' and occurs in sentences such as ‘You shouldn't believe everything you read online'. In the recent semantics literature, it has been suggested that the deontic ‘should' is information-sensitive, meaning that sentences of the form ‘S should do A' are relativized to information-states. After a short introductory chapter, I survey the relevant semantics literature in chapter 2 and provide a simplified contextualist semantics for the doxastic ‘should', according to which the truth-conditions of sentences containing the doxastic ‘should' vary with the information-state provided by their context of utterance. In chapters 3 to 6, I discuss the different kinds of information-states the doxastic ‘should' can be relativized to and how the respective relativization matters for normative epistemology. Chapter 3 argues that the doxastic ‘should' has a subjective and an objective sense and that this distinction solves the apparent conflict between subjective epistemic norms and the truth norm for belief. Chapter 4 addresses the question of how one should react to misleading higher-order evidence. I propose that two seemingly opposing views on this issue, Steadfastness and Concilliationism, are both correct. In a sense of ‘should' that is relativized to one's first-order evidence, one should remain steadfast in the face of misleading higher-order evidence, but in another sense, which is relativized to one's higher-order evidence, one shouldn't. In chapters 5 and 6, I argue that when we advise others on what they should believe, we talk about what they should believe in light of their and our joint evidence. Chapter 7 concludes this thesis with a defence of contextualist semantics for the doxastic ‘should' against truth-relativist challenges.

Le principe d'invariance de jauge local est au centre de la physique des particules moderne. Dans le modèle standard (MS), il repose sur le groupe de jauge ad hoc SU(3)_c x SU(2)_L x U(1)_Y. L'idée d'étendre ce groupe de jauge est particulièrement attrayante dans une perspective de ``Grand Unified Theory'' (GUT) où le MS est la limite basse énergie d'une théorie plus fondamentale basée sur un groupe de jauge beaucoup plus large tel que SO(10) ou E(6). En effet, lors de la brisure de symétrie du groupe de GUT au MS, des facteurs de groupe non-brisés supplémentaires, tels que U(1) ou SU(2), peuvent apparaitre. Ce manuscrit est consacré à la phénoménologie de modèles avec un groupe de jauge étendu. En particulier, les études présentées sont centrées sur les modèles basés sur le groupe de jauge SU(2) x SU(2) x U(1) dénotés G(221). De manière générique, ces modèles prédisent de nouveaux bosons de jauges, Z' et W'.Après une brève présentation des modèles G(221), un nouveau code publique, PyR@TE, qui permet de déterminer les équations du groupe de renormalisation à deux boucles pour une théorie de jauge arbitraire est introduit. Ce code est ensuite utilisé pour déterminer les RGEs des modèles de la classe G(221). La suite du manuscrit est dédiée à la présentation des résultats obtenus sur le calcul des corrections radiatives QCD de la production électrofaible d'une paire de quarks top dans le cadre des modèles G(221), i.e. en présence d'un nouveau boson de jauge Z'. Ces résultats font l'objet d'une implémentation dans le générateur d'événements Monte Carlo POWHEG BOX et les premiers résultats numériques obtenus sont présentés. Les derniers développements concernant le calcul des corrections QCD à la production électrofaible de single-top sont également revus. Enfin, la dernière partie de ce manuscrit est consacrée à l'étude de l'impact de nouvelles résonances W', Z', telles que celles présentes dans les modèles G(221), sur l'interaction des neutrinos d'ultra-haute énergie dans l'atmosphère. Ces interactions sont recherchées par l'observatoire Pierre Auger dans les douches de particules produites par l'interaction des rayons cosmiques avec les particules de l'atmosphère. / The principle of local gauge invariance is a pillar of modern particle physics theories and in the SM relies on the ad-hoc gauge group structure SU(3)_c x SU(2)_L x U(1)_Y. Extending this gauge group is very well motivated in a Grand Unified Theory (GUT) perspective in which the SM is the low-energy limit of a more fundamental theory based on a larger gauge group like SO(10) or E(6). Indeed, the symmetry breaking (SB) of the underlying GUT gauge group, down to the SM one, leaves some additional group factors unbroken, such as U(1) or SU(2). In this spirit, we focus in this manuscript on the phenomenology of extended gauge group models and on the new heavy neutral and charged resonances, generically called Z' and W' predicted by these.In this manuscript we present different aspects of the phenomenology of the G(221) models. After reviewing these extensions, we present a public tool, PyR@TE, that aims at automating the calculation of RGEs at two-loop for arbitrary gauge theories and exemplify its use with the G(221) models. In a second part, we present our results for the calculation of the QCD corrections to the electroweak top-pair production as well as their implementation in a general purpose Monte Carlo generator allowing for a consistent matching of next-to-leading order (NLO) matrix elements with parton shower algorithms, the POWHEG BOX. We then review the status of our calculation of the QCD corrections to the electroweak single-top production. Finally, we present a different aspect of the phenomenology of new heavy resonances, Z', W' by studying their impact on the interaction of ultra-high energy neutrinos in the atmosphere. For definiteness we consider the Pierre Auger Observatory, which is sensible to showers initiated by neutrinos of extreme energies up to 10E12 GeV

Submitted by Pedro Henrique Fusco Nogueira null (pedrofusconogueira@gmail.com) on 2018-03-04T20:59:18Z No. of bitstreams: 1 Dissertação Final.pdf: 530386 bytes, checksum: 67ed197e0d666d071b9b062d11c6ee5f (MD5) / Approved for entry into archive by Pamella Benevides Gonçalves null (pamella@feg.unesp.br) on 2018-03-05T19:05:49Z (GMT) No. of bitstreams: 1 nogueira_phf_me_guara.pdf: 530386 bytes, checksum: 67ed197e0d666d071b9b062d11c6ee5f (MD5) / Made available in DSpace on 2018-03-05T19:05:49Z (GMT). No. of bitstreams: 1 nogueira_phf_me_guara.pdf: 530386 bytes, checksum: 67ed197e0d666d071b9b062d11c6ee5f (MD5) Previous issue date: 2018-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho buscamos encontrar a teoria mais geral para partículas massivas de spin-2 via tensor simétrico. Começamos expondo o caminho que seguiremos para calcular a amplitude de dois pontos saturada por fontes e obter o conteúdo físico de uma dada teoria livre. Como primeira tentativa partimos de uma teoria semelhante a teoria de Fierz-Pauli, mas com termo de massa generalizado. Após isto exploramos uma densidade lagrangiana mais geral, com no máximo duas derivadas. Em ambos os casos retornamos a teoria de Fierz-Pauli como a única viável. Em busca de maior generalidade, posteriormente, propomos uma densidade lagrangiana com coeficientes arbitrários e com potência arbitrária nas derivadas, relacionamos os coeficientes desta teoria com os coeficientes da densidade lagrangiana encontrada anteriormente na literatura via imersão de Euler das equações de Fierz Pauli, o propósito foi verificar se existe uma teoria mais geral que esta última. Por último, a fim de complementar o assunto tratado neste trabalho, verificaremos as consequências de uma dada simetria local no conteúdo físico de uma teoria, de spin-2 massiva. / In this project we seek to find the most general theory for massive particles of spin-2 through symmetric tensor. We begin by the path we will follow to calculate the amplitude of two points, saturated by sources, and obtain physical contente of a free theory. As first attempt, we started with a theory similar to the Fierz-Pauli’s theory, but with a generalized mass term. After this we explored a more general Lagrangian density, with two derivatives in the most. In both cases we return to the Fierz-Pauli’s theory as the only viable one. In search of a greater generality, we later propoused a Lafrangian density with arbitrary coefficients and arbitrary power in the derivatives. We related the coefficients of this theory with the Lagrangian density’s coefficients found previously in the literature through imersão de Euler of the Fierz-Pauli’s equations. The purpose was to verify if there is a more general theory than this last one. Finally, in order to complemente the subject discussed in this paper, we will verify the consequences of a certain local symmetry on the physical contente of a massive spin-2 theory