IMPACT OF IRRADIATION HISTORY ON INVENTORY PREDICTION DATA FOR PWR FUEL

International audienceProcedures developed to allow generation of radio nuclide inventory data depend on fluxes and cross sections calculated by assembly spectrum codes. Their accuracy depends on the assembly spectrum code capacity to generate correct prediction data; otherwise corrections have to be made to eliminate the residual calculation/experiment discrepancies. In this work we present the effect of taking into account the temperature and boron history on predicted isotopic compositions (uranium and plutonium) of a 40 GWd/t UO 2 fuel

Distorted Born diffraction tomography: limits and applications to inverse the ultrasonic field scattered by an non-circular infinite elastic tube

International audienceThis study focuses on the application of ultrasonic diffraction tomography to noncircular 2D-cylindrical objects immersed in an infinite fluid. The distorted Born iterative method used to solve the inverse scattering problem be longs to the class of algebraic reconstruction algorithms. This method was developed to increase the order of application of the Born approximation (in the case of weakly-contrasted media) to higher orders. This yields quantitative in formation about the scatterer, such as the speed of sound and the attenuation. Quantitative ultrasonic imaging techniques of this kind are of great potential value in fields such as medicine, under water acoustics and non destructive testing

Ultrasonic Computed Tomography

Ultrasonic Computed Tomography (UCT) is a full digital imaging technique, which consists in numerically solving the inverse scattering problem associated to the forward scattering problem describing the interaction of ultrasonic waves with inhomogeneous media. For weakly inhomogeneous media such as soft tissues, various approximations of the solution of the forward problem (straight ray approximation, Born approximation...), leading to easy-to-implement approximations of the inverse scattering problem (back-projection or back-propagation algorithms) can be used. In the case of highly heterogeneous media such as bone surrounded by soft tissues, such approximations are no more valid. We present here two non-linear inversion schemes based on high-order approximations. These methods are conceived like the prolongation of the methods implemented in the weakly inhomogeneous case for soft tissues. The results show the feasibility of this UCT approach to bones and its potential to perform measurements in vivo

Efficient validation and construction of border arrays

In this article we present an on-line linear time and space algorithm to check if an integer array f is the border array of at least one string w built on a bounded or unbounded size alphabet Σ. We first show some relations between the border array of some string w and the skeleton of the DFA recognizing Σ ∗ · w, independently of the explicit knowledge of w. This enables us to design algorithms for validating and generating border arrays that outperform existing ones [4, 3]. The validating algorithm lowers the delay (time spent on one element of the array) from O(|w|) to O(min{|Σ|, |w|}) comparing to algorithms in [4, 3]. Finally we give some results on the numbers of distinct border arrays on some alphabet sizes.

Hälfte des Lebens

The paper is the written version of a previous lecture, held on the occasion of a new translation of Hölderlin’s poem Hälfte des Lebens by the world-known French scholar Jean-Pierre Lefebvre, who was a student of Paul Celan. The Sorbonne Emeritus, former member of the Board of the Hölderlin-Gesellschaft Tübingen and translator of Goethe, Hölderlin, Hegel and Heine, as well as of Rilke, Kafka, Brecht and Celan, discusses here in detail the task of the poet in his times, and of his interpreters and adapters. His new translation, A moitié de la vie, is reproduced at the bottom of the essay

Breast ductal computer phantoms

International audienceMost of breast cancers (85%) originate from the epithelium and develop first in the ductolobular structures. Therefore, the mammary epithelium should be investigated in priority by means of an anatomically guided examination. For this purpose (mass screening, surgery navigation), we develop a two-dimensional anatomic phantom which corresponds to an axial cut of the ductolobular structures and enables one to better understand the interaction of the breast composition with ultrasound. The different constitutive tissues are modeled as a random inhomogeneous continuum with density and sound speed fluctuations. Ultrasonic pulse propagation through the breast computer phantom has been simulated using a finite element time domain method (the phantom can be used with others propagation codes). The simulated Ductal Echographic image is compared with the Ductal Tomographic (DT) reconstruction. The preliminary results reveal a higher quality of DT both in terms of contrast and resolution

A 2-D anatomic breast ductal computer phantom for ultrasonic imaging

International audienceMost breast cancers (85%) originate from the epithelium and develop first in the ductolobular structures. In screening procedures, the mammary epithelium should therefore be investigated first by performing of an anatomically guided examination. For this purpose (mass screening, surgical guidance), we developed a two-dimensional anatomic phantom corresponding to an axial cross-section of the ductolobular structures, which makes it possible to better understand the interactions between the breast composition and ultrasound. The various constitutive tissues were modeled as a random inhomogeneous continuum with density and sound speed fluctuations. Ultrasonic pulse propagation through the breast computer phantom was simulated using a finite element time domain method (the phantom can be used with other propagation codes). The simulated Ductal Echographic image is compared with the Ductal Tomographic (DT) reconstruction. The preliminary results obtained show that the DT method is more satisfactory in terms of both the contrast and the resolution

Ultrasonic tomography of green wood using a non-parametric imaging algorithm with reflected waves

International audience• Ultrasonic computed tomography in reflection was used to assess the integrity of green wood. Qualitative reflectivity images were obtained from back-scattered measurements by reflection tomography, like ultrasound in medical applications. • The reconstruction algorithm was designed using, in particular, a linear approximation of the forward problem (Born approximation) and based on the assumption that a transversal cross section of wood is isotropic. The experimental device was composed of only one rotating emitter–receiver transducer to record and compute the projections. In this specific case, a tomographic projection was directly associated with a recorded signal. The qualitative aspect of this imaging technique was validated by performing a numerical simulation and tested on a small diameter green wood (Picea abies) log. • The images obtained were geometrically accurate considering the internal inclusions. It was, however, not possible in the simulation to differentiate the object shape from the background (coupling medium) because the reflectivity value associated with the object was too low. The image obtained with the spruce sample mainly showed the position of the bark as indicated by a very high contrast area. The proportion of transmitted energy was, however, sufficient to reconstruct the artificial inclusion within the sample