Modelling of standard and specialty fibre-based systems using finite element methods

We report on the investigation of an approach for modelling light transmission through systems consisting of several jointed optical fibres, in which the analytical modelling of the waveguides was replaced by Finite Element Modelling (FEM) simulations. To validate this approach we first performed FEM analysis of standard fibres and used this to evaluate the coupling efficiency between two singlemode fibres under different conditions. The results of these simulations were successfully compared with those obtained using classical analytical approaches, by demonstrating a maximum loss deviation of about 0.4 %. Further, we performed other more complex simulations that we compared again to the analytical models. FEM simulations allow addressing any type of guiding structure, without limitations on the complexity of the geometrical waveguide cross section and involved materials. We propose as example of application the modelling of the light transmitted through a system made of a hollow core photonic crystal fibre spliced between two singlemode standard optical fibres, and qualitatively compare the results of the simulation with experimental results.Comment: Proceedings article, SPIE conference "Fiber Lasers and Glass Photonics: Materials through Applications

Calculs 3d prédictifs pour la conception d'alvéoles de stockage de déchets radioactifs HAVL

National audienceFor the "HA cells" experimentation in the URL of Bure (Andra), coupled mechanical modelings (creep or hydraulic behavior) were carried out to predict the expected behavior of argillites during excavation of a disposal cell (stresses, displacements, EDZ). These predictions are then compared to in situ measurements (displacement and pore pressure).Dans le cadre de l'expérimentation "alvéoles HA" au laboratoire souterrain de recherche de Bure (Andra), des modélisations mécaniques couplées (comportement différé ou hydraulique) ont été réalisées pour prédire le comportement attendu des argilites à l'excavation d'une alvéole (contraintes, déplacements, EDZ). Elles sont ensuite comparées avec les mesures in situ (déplacements et pression interstitielle)

Ultrasonic sounding and monitoring of the excavation damaged zone in relation with drift support

International audienceUnder high in situ stresses, the excavation of underground openings generally causes the creation of a disturbed (EdZ: Excavation disturbed Zone) and/or damaged (EDZ: Excavation Damaged Zone) zone, resulting from the initiation and growth of cracks and fractures and from the pre-existing stress redistribution. The EdZ or EDZ changes the mechanical and hydromechanical properties which in return, constitute a potential risk for the performance of the geologic and/or engineered structures in the context of waste underground storage. Ultrasonic experiments have been implemented to characterize the EDZ extension around drifts and its evolution in time according to the structural support type (soft or rigid) and the environmental conditions. Those studies consist of two experimental components: (1) the prior auscultation of the floor and sidewalls of the gallery by ultrasonic transmission tomography, (2) the monitoring of the time-dependant evolution of EDZ and the analysis of measurable changes in the propagation of ultrasonic waves in the medium term. A code for computing these continuous in situ velocity measurements into the elastic has been developed. Then, the five dynamic elastic constants for the assumed transverse isotropic character of the rock are derived as a function of time and the distance from the drift wall. Performed a few months after the excavation of the galleries, the tomography shows that ultrasonic velocities are higher in the orthoradial direction (both in the concrete support and rock). This velocity field highlights clearly the damaged zone and induced stress shift

Calcifying Bowel Inflammation: A Case Report

We report about a previously healthy 72-year-old woman, presented with 6 days of left lower quadrant abdominal pain and constipation. There was no report of fever, melena, hematochezia or change in appetite. The physical exam demonstrated a distended abdomen with palpable left lower quadrant pain, without guarding. CT showed images compatible with a sigmoid diverticulitis and a calcification of the sigmoid colon. After antibiotic threatment, a colonoscopy was performed which revealed the presence of a shell in the sigmoid colon. Our case illustrates the need for a colonoscopy following an attack of diverticulitis to look for a cancer or rarely a foreign body

Baroquisme et humanisme et humanisme dans l’élégie de Robert Garnier sur le trépas de Ronsard

L’Élégie sur le trespas de feu Monsieur de Ronsard a été publiée en 1586 avec les pièces constituant le Tombeau de P. de Ronsard et en même temps que l’édition posthume du poète. Sombre année, où le roi légitime est prisonnier de la Ligue, tandis qu’Henri de Navarre vient par une bulle du Pape d’apprendre sa déchéance des droits à la couronne. Une période confuse et sanglante a commencé qui s’achèvera bientôt par le double assassinat du duc de Guise et d’Henri III. L’inquiétude du poète perce..

Ultrasonic velocity survey in Callovo-Oxfordian argillaceous rock during shaft excavation

International audienceThe excavation of a deep underground structure induces a stress field redistribution that could create an excavation-damaged zone (EDZ). The study of the EDZ is important in the framework of nuclear waste storage, where such EDZ could constitute a preferential pathway of stored material towards the biosphere. Analysis of ultrasonic wave propagation across the rock media around the excavation is one technique that can be used to characterize such zones. This method has been applied in the Meuse/Haute-Marne Underground Research Laboratory (URL) in France to characterize the initialization and evolution of damage around the URL access shaft. To achieve this, a device comprising 21 ultrasonic sensors was spread out at different distances from the shaft wall, at depths between -465 and -475 m. A transversely isotropic model enabled the measured experimental velocities on each ray path during shaft excavation to be integrated. The results highlighted the initialization and extension of the damage as the shaft front proceeded. They also showed a polarization of the velocity field and an oscillation of the transversal isotropy with a preferential orientation of the stress release and the microcracking. Monitoring of the velocity field also highlighted some significantly different behaviour linked to the complex mechanical behaviour of the argillaceous rock