HAL Portal UBS (Université Bretagne Sud)
Not a member yet
14201 research outputs found
Sort by
Dynamic in situ analysis of modern and ancient flax yarns: Impact of microstructure and aging
No full textInternational audienceFlax yarns are widely used in composites and textiles, yet their mechanical performance is limited by factors like microstructure and durability, necessitating in-depth investigation of their tensile behavior. This study aimed to evaluate the dynamic response of flax yarns under tensile loading, using in situ SEM tensile testing to reveal realtime failure mechanisms and microstructural behavior. Novelty lies in the unprecedented examination of 4,000year-old Egyptian yarns, offering unique insights into the effects of aging on fiber morphology and strength. This research included single and ply yarns from modern Egypt, France, and ancient Egypt. Findings indicate significant strength differences due to strong morphological variations. Morphological analysis demonstrates that, with aging, ancient yarns exhibit greater number of kink bands and fiber separation, indicating structural weakening and compound middle lamella (CML) degradation. Failure analysis revealed fiber breakage is the primary failure mode in modern yarns, contrasting with combined breakage and slippage in ancient yarns, indicating distinct degradation mechanisms. Kink-bands were identified as critical to tensile behavior, initiating cracks that propagate, causing fiber rupture and subsequent breakage in bundles within yarns. These results highlight the evolution in yarn production and durability, emphasizing the impact of fiber microstructure and aging on performance, contributing essential insights for advancing the mechanical performance of flax-based materials
De l’outil au dispositif de gestion pour appréhender la spécificité des organisations publiques
No full textInternational audienc
Couleurs, Races et Textes sacrés vus par les pasteurs africains-américains au XIXe et XXe siècles
No full textInternational audienc
Flexural Analysis of Porous Microbeams Based on the Modified Strain Gradient Theory Including Stretching Effects
No full textBonjour, Je viens d'ajouter la référence bibliographique à mon résumé, comme demandé. Merci pour votre patience et votre assistance. Bien cordialement,International audienceFlexural Analysis of Porous Microbeams Based on the Modified Strain Gradient Theory Including Stretching Effect
Investigating methane production potential of Sargassum muticum (Yendo) Fensholt via response surface methodology
No full textInternational audienc
: Transformaciones de Fourier fraccionarias hiperbólicas y teoría escalar de la difracción
No full textWe define hyperbolic fractional-order Fourier transformations by replacing the circular trigonometric functions in the integral expressions of conventional fractional-order Fourier transformations with hyperbolic trigonometric functions. We establish the composition laws of these hyperbolic transformations. We then use hyperbolic fractional-order Fourier transforms to mathematically represent Fresnel diffraction phenomena that cannot be described by conventional fractional Fourier transforms, due to their geometric configurations. Additionally, we apply appropriate compositions of these transformations to coherent optical imaging.Se definen las transformaciones de Fourier fraccionarias hiperbólicas, reemplazando las funciones trigonométricas circulares que aparecen en las integrales de definición de las transformaciones de Fourier fraccionarias habituales por funciones trigonométricas hiperbólicas. Se establecen las reglas de composición de estas transformaciones hiperbólicas, las cuales se utilizan posteriormente para representar matemáticamente los fenómenos de difracción de Fresnel que no pueden describirse mediante las transformaciones habituales, debido a que sus configuraciones geométricas no lo permiten. Además, se aplican productos de transformaciones hiperbólicas adecuados para la formación de imágenes geométricas coherentes.On définit les transformations de Fourier fractionnaires hyperboliques en remplaçant par des fonctions trigonométriques hyperboliques les fonctions trigonométriques circulaires qui apparaissent dans les intégrales définissant les habituelles transformations de Fourier fractionnaires. On établit les règles de compositions de ces transformations hyperboliques. On utilise ces dernières dans la représentation mathématique de phénomènes de diffraction de Fresnel qui ne peuvent pas être décrits par les transformations de Fourier fractionnaires usuelles, parce que leurs configurations géométriques ne s'y prêtent pas. On applique enfin les compositions appropriées de ces transformations à l'étude de l'imagerie géométrique cohérente
Mathematical Bio-Economics 2.0 for Sustainable Fisheries
No full textInternational audienceReconciling food security, economic development, and biodiversity conservation in the face of global changes is a major challenge. The sustainable uses of marine biodiversity in the context of climate change, invasive species, water pollution, and demographic growth is an example of this bio-economic challenge. There is a need for quantitative methods, models, scenarios, and indicators to support policies addressing this issue. Although bio-economic models for marine resources date back to the 1950s and are still used in fisheries management and policy design, they need major improvements, extensions, and breakthroughs. This paper proposes to design a Mathematical Bio-Economics 2.0 (MBE2) for Sustainable Fisheries to advance the development of bio-economic models and scenarios for the management of fisheries and marine ecosystems confronted with unprecedented global change. These models and scenarios should make both ecological and socioeconomic sense while being well-posed mathematically and numerically. To achieve this, we propose to base the MBE2 framework for Sustainable Fisheries on four research axes regarding the mathematics and modeling of: (i) ecosystem-based fisheries management; (ii) criteria of sustainability; (iii) criteria of resilience; and (iv) governance and strategic interactions. The associated methodology of MBE2 draws mainly on dynamic systems theory, optimal and viable controls of systems, game theory, and stochastic approaches. Our analysis, which is based on these four axes, allows us to identify the main methodological gaps to fill compared to current models for fisheries management. | IntroductionBalancing biodiversity conservation with food security and the preservation of a broader set of ecosystem services (ESs), in a context of ecological transition and climate change, is one of the greatest challenges of the century. The creation and development of the IPBES (International Platform for Biodiversity and Ecosystem Services) at the interface of decision-support and scientific knowledge is in direct line with these concerns.</div
Numerical investigations of the vibration damping properties of carbon/flax hybrid fiber-reinforced composite structures with perturbation method
No full textInternational audienc
Perturbations of Vector Bundle whose Curvature Form Solves a Polynomial Equation
No full textWe investigate the behaviour of local perturbations of a wide class of geometric PDEs on holomorphic Hermitian vector bundles over a compact complex manifold. Our main goal is to study the existence of solutions near an initial solution under small deformations of both the holomorphic structure of the bundle and the parameters of the equation. Inspired by techniques from geometric invariant theory and the moment map framework, under suitable assumptions on the initial solution, we establish a local Kobayashi-Hitchin correspondence. A perturbed bundle admits a solution to the equation if and only if it satisfies a local polystability condition. We also show additional results, such as continuity and uniqueness of solutions when they exist, and a local version of the Kempf-Ness theorem. We also provide a local version of the Jordan-Hölder and Harder-Narasimhan filtrations
Réfugiés polonais et politisation en Sarthe sous la monarchie de Juillet
No full textInternational audienceCet article propose d’étudier trois moments polonais sous la monarchie de Juillet à partir du cas de la Sarthe. En 1831, l’émotion suscitée par l’insurrection de Varsovie ouvre des perspectives de mobilisations populaires. Les libéraux couvrent la ville de drapeau polonais. Quand arrivent les premiers réfugiés, l’enthousiasme est perceptible et la solidarité se met en place. Sur le terrain, un droit d’asile en formation se bricole. Par ce biais, on peut apercevoir des fragments du quotidien de ces étrangers. Ni oisifs, ni passifs, certains participent aux activités politiques de la vie locale. Autour de l’année 1846, quand Cracovie est écrasée par l’armée autrichienne, les engagements polonais et démocratiques se mêlent à nouveau sur le terrain. L’espérance est réciproque, « pas faite à sens unique ». Au fond, les réfugiés polonais ont aussi mis en circulation une culture politique participant à donner à la Sarthe l’image d’« une île républicaine au milieu de la France monarchique »