HAL-Université de Bretagne Occidentale
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Static and Vibration Analysis of Two-phase Peridynamic Rods or Strings under General Boundary Conditions — Exact, FDM and FEM Approaches
No full textInternational audienceStatic and dynamic analysis of two-phase peridynamic one-dimensional systems is thoroughly investigated in this paper for various boundary conditions by exact and numerical approaches. Such a nonlocal study concerns the axial or torsional responses of two-phase peridynamic rods or the behavior of a two-phase peridynamic string. For a normalized exponential kernel, the integro-differential equation of the two-phase peridynamic problem can be converted as a linear higher-order differential equation with constant coefficients. Exact static solutions of fixed–fixed and fixed–free two-phase peridynamic axial rod (TPPAR) under uniform distributed loading and concentrated force are analytically derived. It is shown that the pure peridynamic rod problem can be ill-posed due to a conflict between the natural boundary condition and the peridynamic constitutive boundary condition. The two-phase peridynamic problem may be justified from physical arguments, and is also seen as a regularized peridynamic problem. The exact eigen-frequencies of the two-phase peridynamic rods are also analytically obtained for various boundary conditions, including fixed–free, fixed–fixed or free–free boundary conditions. These theoretical approaches are corroborated by numerical investigations based on Finite Difference Method (FDM), Finite Element Method (FEM), exact FEM and variational iterative methods. Two FDM schemes are presented for the statics and the vibration of two-phase peridynamic rods, with convergence orders of 1 and 2, respectively. Moreover, three different FE procedures are proposed as: (1) FEM for direct solving the integro-differential equations of two-phase peridynamic one-dimensional system, (2) FEM for discretizing the pure differential equations, and (3) Exact FEM to obtain both the exact stiffness matrix and exact dynamic stiffness matrix of two-phase peridynamic one-dimensional system, based on Eisenberger’s methodology. The order of convergence for the first and the second proposed FEM is equal to 2 and 4, according to the type of selected finite elements. Moreover, the third proposed FEM based on the exact shape function of the peridynamic problem gives the exact solution from one single FEM element. In addition, the variational iterative method of Stodola–Vianello is successfully applied to the two-phase peridynamic eigenvalue problems
Exact solutions for the static bending of nonlocal higher-order shear beams under various boundary conditions
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Formalisme représentationnel et méchanique quantique en espace-temps courbe
No full textWe extend the representation frame formalism, previously introduced to reinterpret key cosmological observations within a static Einstein Universe, to the non-relativistic quantum domain. In this approach, each observer is associated with a at representation referential Robs , constructed as the tangent space to the physical spatial manifold U at the observer's position. The representation map T : U → Robs preserves radial distances while rescaling transverse directions according to the spatial curvature, yielding an observer-centric Euclidean space in which all measurements are performed. Because Robs admits a flat Euclidean structure, the laws of quantum mechanics can be defined there using the standard Schrödinger formalism, avoiding some of the usual difficulties associated with quantisation on curved manifolds. We derive the correspondence between the observer's Hamiltonian and its counterpart on U , showing that the resulting quantum dynamics is intrinsically observer dependent, though consistent with the underlying static geometry. Applications to the hydrogen atom in the Einstein Universe and near a black hole illustrate how curvature effects manifest as deformations of the effective potential perceived by the observer.Nous étendons le formalisme des cadres de représentation, introduit précédemment pour réinterpréter des observations cosmologiques clés dans le cadre d'un Univers d'Einstein statique, au domaine quantique non relativiste. Dans cette approche, chaque observateur est associé à un référentiel de représentation Robs, construit comme l'espace tangent à la variété spatiale physique U à la position de l'observateur. L'application de représentation T : U → Robs préserve les distances radiales tout en redimensionnant les directions transversales selon la courbure spatiale, ce qui donne un espace euclidien centré sur l'observateur dans lequel toutes les mesures sont effectuées. Puisque Robs admet une structure euclidienne plate, les lois de la mécanique quantique peuvent y être définies à l'aide du formalisme de Schrödinger standard, évitant ainsi certaines difficultés habituelles liées à la quantification sur les variétés courbes. Nous établissons la correspondance entre l'hamiltonien de l'observateur et son homologue sur U, montrant que la dynamique quantique résultante dépend intrinsèquement de l'observateur, tout en restant cohérente avec la géométrie statique sous-jacente. Les applications à l'atome d'hydrogène dans l'univers d'Einstein et à proximité d'un trou noir illustrent comment les effets de courbure se manifestent par des déformations du potentiel effectif perçues par l'observateur
Evolving paradigms in pulmonary hypertension: Highlights of the 6th French Pulmonary Hypertension Network Meeting
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Plongée dans les collections : une histoire du protestantisme en Bretagne, sous le regard du pays de Galles
No full texthttps://bylg.hypotheses.org/3201Présentation d'une pièce documentaire incomplète trouvée au sein des collections d'ouvrages de la Bibliothèque Yves-Le-Gallo, qui s'est revelée être l'extrait d'une thèse sur l'histoire du protestantisme en Bretagne initiée par Dewi Morris-Jones
Impacts immédiats et saisonniers de tempêtes estivales sur l'océan et la glace de mer en Arctique
No full textIn the Arctic, storms play a critical role in affecting sea ice and ocean dynamics by enhancing air-sea interactions, mixing, and ice deformation. However, their longerterm seasonal impacts, particularly in summer when sea ice is reduced, remain unclear.This thesis explores the seasonal influence of summer storms in the Canadian Basin using two coupled ice-ocean models. First, a onedimensional model (NEMO-SI3) is used to assess the effects of idealized storms, revealing that anomalies in mixed layer depth and heat content can persist for weeks, delaying autumn sea ice formation and accelerating winter sea ice growth. Then, a three-dimensional model (NEMO-LIM3) is used to show that while one-dimensional processes dominate in the initial weeks after a synthetic Arctic cyclone occurs, advective processes gradually attenuate these anomalies over time. Thus, delay in the freeze up date may be observed due to a cyclone, but long-term impacts in sea ice thickness are less pronounced. These findings highlight the complex interplay between storms and ice-ocean systems, with implications for seasonal ice forecasting.Dans l’Arctique, les tempêtes jouent un rôle essentiel dans la dynamique de la glace de mer et des océans en renforçant les interactions air-mer, le mélange et la déformation de la glace. Cependant, leurs impacts saisonniers à plus long terme, en particulier en été lorsque la glace de mer est réduite, restent peu clairs. Cette thèse explore l’influence saisonnière des tempêtes d’été dans le bassin canadien en utilisant deux modèles couplés glace-océan. D’abord, un modèle unidimensionnel (NEMO-SI3) est utilisé pour évaluer les effets de tempêtes idéalisées, révélant que les anomalies dans la profondeur de la couche de mélange et le contenu thermique peuvent persister pendant des semaines, retardant la formation de la glace de mer en automne et accélérant la croissance de la glace de mer en hiver. Ensuite, un modèle tridimensionnel (NEMO-LIM3) est utilisé pour montrer que si les processus unidimensionnels dominent dans les premières semaines suivant un cyclone arctique synthétique, les processus advectifs atténuent progressivement ces anomalies au fil du temps. Ainsi, un cyclone peut entrainer un retard dans la date de formation de la glace, mais les impacts à long terme sur l’épaisseur de la glace de mer sont moins prononcés. Ces résultats mettent en évidence l’interaction complexe entre les tempêtes et le système glace-océan, avec des implications pour la prévision saisonnière de la glace
Identity by descent analysis uncovering a founder event in a novel hereditary small vessel cerebral disease
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A secular sea level hindcast (1900-2015) to investigate extreme surges variability and trends in the North Atlantic
No full textInternational audienceChanges in extreme sea levels, combined with the growth of coastal population, are critical factors in evaluating the risks related to coastal flooding. Thus, studying the variability and trends of storm surges, a major contributor to extreme sea levels, becomes essential for coastal protection policies. We developed in the North Atlantic the first hourly surge hindcast covering the full 20th century (1900-2015) on a 0.1 • grid, and called ClimEx hindcast. We validated the hindcast against 34 long-term tide gauges. The model shows overall very good performance for surges (Root Mean Square Error of 9.3 cm on average), and good performance for extreme surges, despite an overall underestimation. To investigate the variability and trends in storm surges, we performed a non-stationary extreme value analysis on modeled and observed storm surges. The seasonality of storm surges is highly dependent on the area. The seasonal amplitude varies from typically 10 cm, to more than 40 cm in the North Sea. The storm surge season occurs around December-January in the north of the domain (above 40 • N), due to winter extra-tropical cyclones, and around September-October in the south-west, due to tropical cyclones. The dependence of storm surges with the North Atlantic Oscillation extends from the coasts to the deep ocean, and is positive above 50 • N and negative below. Observed storm surges show mostly non significant or small trends (< ± 1 mm/yr), while the model displays positive trends almost everywhere, possibly due to inhomogeneities in the atmospheric forcing dataset prior to 1950
Efficient Hardware Primitives for Interval Contractors in Robotics and Integration to a Custom RISC-V ISA Extension
No full textInternational audienceInterval analysis is commonly used in mobile robotics to solve nonlinear problems. Typical implementations mostly rely on software libraries which perform poorly on low-power embedded devices. This article shows how interval primitives can be ported on FPGA and integrated to the RISC-V architecture using a custom ISA extension called xinterval. The novelty of this approach is the emphasis on elementary interval contractors which are higher-level abstractions than plain interval arithmetic especially well suited for robotics applications
The influence of habitat heterogeneity and disturbance on benthic community structure in deep-sea polymetallic nodule environments and management implications for seabed mining
No full textInternational audienceHabitat heterogeneity is known to influence faunal community structure, but its influence on deep-sea benthic communities remains understudied, particularly for polymetallic nodule environments in abyssal waters. As nodules are currently of interest for mining, understanding the potential impact of this disturbance on habitat heterogeneity, and the subsequent effect on faunal communities, becomes critical for developing environmental management plans. Although some aspects of the influence of habitat heterogeneity on the nodule-associated fauna have been studied, the influence on multiple size components of the benthic community across varying spatial scales has not yet been fully assessed, and the current metrics by which habitat heterogeneity is measured may be insufficient. This review synthesizes existing research regarding habitat heterogeneity, the influence of disturbance on habitat heterogeneity, and the influence of this heterogeneity on metazoan fauna (megafauna, macrofauna, and meiofauna) in polymetallic nodule environments across spatial scales. Current gaps in knowledge and the implications of this knowledge for the management of proposed deep-seabed mining are also discussed