The problem of heating the solar corona requires the conversion of magnetic energy into thermal energy. Presently, there are two promising mechanisms for heating the solar corona: wave heating and nanoflare heating. In this thesis, we consider nanoflare heating only. Previous modelling has shown that the kink instability can trigger energy release and heating in large scale loops, as the field rapidly relaxes to a lower energy state under the Taylor relaxation theory. Two distinct experiments were developed to understand the coronal heating problem: the avalanche effect within a multiple loop system, and the importance of thermal conduction and optically thin radiation during the evolution of the kinked-unstable coronal magnetic field. The first experiment showed that a kink-unstable thread can also destabilise nearby threads under some conditions. The second experiment showed that the inclusion of thermal conduction and optically thin radiation causes significant change to the internal energy of the coronal loop. After the initial instability occurs, there is continual heating throughout the relaxation process. Our simulation results show that the data is consistent with observation values, and the relaxation process can take over 200 seconds to reach the final relaxed state. The inclusion of both effects perhaps provides a more realistic and rapid heating experiment compared to previous investigations.

No description available.

The compressive strength of unidirectional (UD) carbon fibre reinforced plastics (CFRPs) is often only 60-70% of their tensile strength owing to premature failure associated with kink-band formation. The sudden and complex nature of kink-band formation has been hindering the progress in experimental studies on the evolution of damage in compressive failure. A better understanding of the damage mechanisms associated with kink-band formation can help to design more reliable composite structures. Therefore, the principal aim of this project is to identify, in three dimensions (3D), the key damage mechanisms underlying the initiation and propagation of kink bands in UD carbon fibre/epoxy composite. A new manufacturing method is developed to fabricate high-quality UD T700/epoxy cylindrical rods for axial compression tests and high-resolution imaging of kink bands by post mortem and in situ X-ray computed tomography (CT). The morphology of kink bands is visualised in 3D by segmenting fibre breaks at kink-band boundaries and representative longitudinal splits. The geometrical parameters of each fully developed kink band are consistent through the specimen. Radiographs obtained from ultra-fast synchrotron imaging show that a kink band initiates and propagates across the specimen in less than 1.2 ms. A scenario of kink-band failure is proposed: fibre buckling and longitudinal splitting occur prior to fibre breakage, which forms kink-band boundaries and eventually the morphology of multiple kink bands develops suddenly. 3D tomographs of the fast and unstable kink-band formation could not be captured in the axial compression experiments. Therefore, a testing method of loading notched UD carbon fibre (T800, T700 and T300)/epoxy beams using a four-point bending (FPB) fixture is developed to enable monitoring of more stable initiation and propagation of kink bands by in situ X-ray CT. Kink-band formation is significantly slowed in the FPB tests. Fibre micro-buckling accompanied by splitting, could initiate the formation of kink bands. In the T700/epoxy system, the early initiation stage of fibre micro-buckling without fracture is captured, and the critical radius of curvature of unbroken fibres prior to fracture is ～130micro metre. Unloading causes significant recovery of fibre curvature (radius of curvature ～280 micro metre) and a reduction of 10-20º in fibre rotation angle within the kink band. The results show that in situ 3D characterisation of kink bands is essential as fibre buckling is a 3D phenomenon, resulting in development of both in-plane and out-of-plane kink bands. Understanding of kink-band formation in 3D will help to establish strategies to improve the compressive strength of CFRP composites by depressing kink-band formation; in this respect lateral constraint conferred by strong interfaces is a key aspect.

Historically, kinky sexualities and sexual behaviors have been understood as pathological or perverse. Such misunderstandings and misrepresentations have contributed to the development and perpetuation of kink stigma. The aim of this retrospective, cross-sectional, correlational research study was to explore the potential relationship(s) between pathology, personality, and kinky sexual behaviors/roles in adulthood. Guided by queer-feminist theory, the research questions addressed whether personality traits, experiences of childhood trauma, or a combination thereof, were predictors for kinky behaviors/roles in adulthood. A multi measure, anonymous, and confidential survey was distributed online including the Childhood Traumatic Events Scale as a childhood trauma questionnaire, the Mini-IPIP, and the sadomasochism checklist. Multiple regression analyses were used, and the results showed that experiences of childhood trauma, personality characteristics, or the combination of both were not significant predictors for kinky sexual behaviors in adulthood. Among the sample surveyed, there were no significant relationships found between the variables to provide sufficient evidence to support the negative perceptions and stigmatization of the kinky population. These findings contribute to social change by better informing deficiencies in the historical pathology-based and personality-based academic literature on kinky sexualities. Additionally, the findings of the present study provide others with an increased awareness and understanding of the kink community and lifestyles which benefits evolving society and psychological professionals, scholars, and the kink community.

Atypical sexual behavior is often viewed from a perspective of pathology and non-clinical samples are not typically used in research. The current exploratory research is a qualitative study that examined the etiological perspectives of Adult Baby/ Diaper Lover (ABDL) behavior from members of an online ABDL community. Archival survey data from an online sample (N = 1,795) of ABDL participants were used. The theories informing this research included attachment theory and the sexual health model. Research questions included an examination of: (a) what we can be learn from the way an ABDL individual perceives the origin of ABDL behavior, (b) differences in the way participants find their ABDL interests, and (c) the origin beliefs of participants from a community sample compare to the results from historical data. Thematic analysis was used to analyze the archival survey data, and grounded theory was used to forward a theory about the etiology of ABDL. Participants suggested that ABDL may not be the result of a mental health condition or a trauma history. The majority of participants believe their ABDL behaviors are connected to childhood experiences, which partially dovetails with current theories on the etiology of paraphilias. Although some participants believe ABDL behaviors are related to toilet training, most do not. Most participants endorse a wide range of explanations for their ABDL interests and behaviors. The environmental shaping theory of ABDL is based on data from this study and both supports and conflicts with historical research on paraphilia. This study contributes to positive social change by allowing clinicians and scholars the opportunity to hear the voices of a stigmatized group and understand them better. An increased awareness of sexual diversity can allow for greater acceptance and less stigmatization in the mental health and medical fields.

In order to investigate the formation of different types of pit shapes on the crystalline surfaces, a mathematical model has been considered, which does not take into account surface diffusion and which defines the removal or transformation of different characteristic sites on the surface according to a set of frequencies. The characteristic sites are defined according to Terrace-Ledge-Kink model for the simple cubic crystal. With the help of the geometry of the step systems, specific conditions have been obtained under which the step systems considered could be obtained for a pit of monoatomic thickness. The dissolution of a simple cubic crystal has been simulated according to a set of probabilities. / Thesis / Master of Engineering (ME)

No description available.

The Fermi-Pasta-Ulam-Tsingou (FPUT) lattice became of great mathematical interest when it was observed that it exhibited a near-recurrence of its initial condition, despite it being a nonlinear system. This behavior was explained by showing that the Korteweg-de Vries (KdV) equation serves as a continuum limit for the FPUT and has soliton solutions. Much work has been done into analyzing the solitary wave solutions of the FPUT and the relationship between the lattice and its continuum limit. For certain potentials the modified KdV (mKdV) instead serves as the continuum limit for the FPUT. However, there has been little research done to examine how the defocusing mKdV can be used a modulation equation for the FPUT or how the kink solutions of the mKdV relate to solutions of the FPUT. This thesis first addresses the existence of kink-like solutions of the FPUT and shows that their profiles can be approximated by the profiles of the kink solutions of the mKdV. Next, it is shown that the defocusing mKdV can be used more widely as a modulation equation for small-amplitude, long-wavelength solutions of the FPUT lattice. Finally, the issue of stability of the kink-like solutions is discussed, and some results toward linear stability are given.

Il est couramment admis que la déformation plastique des phases MAX est dueau glissement de dislocations dans les plans de base s'organisant en empilements et murs. Cesderniers peuvent former des zones de désorientation locale appelées kink bands. Cependant, lesmécanismes élémentaires et le rôle exact des défauts microstructuraux sont encore mal connus. Cemanuscrit présente une étude expérimentale multi-échelle des mécanismes de déformation de laphase MAX Ti2AlN. A l'échelle macroscopique, deux types d'expériences ont été menés. Des essaisde compression in-situ à température et pression ambiantes couplés à la diffraction neutroniqueont permis de mieux comprendre le comportement des différentes familles de grains dans le Ti2AlNpolycristallin. Des essais de compression sous pression de confinement ont également été réalisés dela température ambiante jusqu'à 900 °C. À l'échelle mésoscopique, les microstructures des surfacesdéformées ont été observées par MEB et AFM. Ces observations complétées par des essais denanoindentation ont montré que la forme des grains et leur orientation par rapport à la directionde sollicitation gouvernent l'apparition de déformations intra- et inter-granulaires ainsi que lalocalisation de la plasticité. Finalement à l'échelle microscopique, une étude détaillée par METdes échantillons déformés sous pression de confinement a révélé la présence de configurations dedislocations inédites dans les phases MAX, telles que des réactions entre dislocations, des dipôleset des dislocations hors plan de base. À la vue de ces résultats nouveaux, les propriétés mécaniquesdes phases MAX sont rediscutées. / It is commonly believed that plastic deformation mechanisms of MAX phases consistin basal dislocation glide, thus forming pile-ups and walls. The latter can form local disorientationareas, known as kink bands. Nevertheless, the elementary mechanisms and the exact role ofmicrostructural defects are not fully understood yet. This thesis report presents a multi-scale experimentalstudy of deformation mechanisms of the Ti2AlN MAX phase. At the macroscopic scale,two kinds of experiments were performed. In-situ compression tests at room temperature coupledwith neutron diffraction brought new insight into the deformation behavior of the different grainfamilies in the polycrystalline Ti2AlN. Compression tests from the room temperature to 900 °Cunder confining pressure were also performed. At the mesoscopic scale, deformed surface microstructureswere observed by SEM and AFM. These observations associated with nanoindentationtests showed that grain shape and orientation relative to the stress direction control formationof intra- and inter- granular strains and plasticity localization. Finally, at the microscopic scale,a detailed dislocation study of samples deformed under confining pressure revealed the presenceof dislocation configurations never observed before in MAX phases, such as dislocation reactions,dislocation dipoles and out-of-basal plane dislocations. In the light of these new results, mechanicalproperties of MAX phases are discussed.

L'objectif principal de cette thèse concerne la mise en oeuvre d'une méthoded'éléments finis stabilisés pour la simulation des plasmas de fusion. Pour cela,nous avons d'abord dérivé les modèles magnétohydrodynamiques depuis lemodèle cinétique. Les modèles MHD sont généralement utilisés pour simuler lesinstabilités macroscopiques des plasmas. Nous nous sommes concentrés sur lemodèles de la MHD complète. Ensuite, l'approche numérique est décrite dans lecadre de la stabilisation Variationelle Multi-Échelles (VMS). Cette stabilisationvient ajouter un terme à la formulation faible pour mimer les effets des échellesnon-résolues sur celles résolues. Si les effets de ces sous-échelles ne sont paspris en compte lorsque l'on traite des écoulements dominés par convection,comme dans le cadre des plasmas de fusion, le schéma numérique conduit àdes résultats non-physiques. Une étude détaillée de l'instabilité de « Kinkinterne » a été faite ainsi qu'une étude préliminaire des plasmas avec point-Xayant pour but la validation du schéma numérique développé ici / The main objective of this thesis concerns the implementation of a robuststabilized finite element method for simulating fusion plasmas. For that, we firstderive the magnetohydrodynamic models from the kinetic model. MHD modelsare generally used for macroscopic simulations of plasma instabilities. Weconcentrate ou efforts on the full MHD model. Next, the numerical approach isdescribed in the context of the Variational Multi-Scale (VMS) stabilization. Thisstabilization comes to add a term to the weak formulation to mimics the effectsof the unresolved scales over the coarse scales. If the effects of these subscalesare not taken into account when dealing with fluxes dominated byconvection, as it is the cases for fusion plasmas, the numerical scheme canlead to unphysical results. A detailed study of the resistive internal kinkinstability has been done as well as an introductory study of the so called Xpointplasmas in order to validate the numerical scheme developed here