École normale supérieure de Cachan

About: École normale supérieure de Cachan is a education organization based out in Cachan, Île-de-France, France. It is known for research contribution in the topics: Decidability & Nonlinear system. The organization has 2717 authors who have published 5585 publications receiving 175925 citations.

Luminescence properties of hexagonal boron nitride: Cathodoluminescence and photoluminescence spectroscopy measurements

Abstract: M. G. Silly,1,2 P. Jaffrennou,1,2,4 J. Barjon,3 J.-S. Lauret,4 F. Ducastelle,1,* A. Loiseau,1 E. Obraztsova,5 B. Attal-Tretout,2 and E. Rosencher2 1Laboratoire d’Etude des Microstructures, ONERA-CNRS, Boite Postale 72, 92322 Châtillon Cedex, France 2Departement de Mesures Physiques, ONERA, Chemin de la Huniere, 91761 Palaiseau Cedex, France 3Groupe d’Etude de la Matiere Condensee, Universite de Versailles St. Quentin, CNRS Bellevue, 1 place Aristide Briand, 92195 Meudon Cedex, France 4Laboratoire de Photonique Quantique et Moleculaire, Institut d’Alembert, Ecole Normale Superieure de Cachan, 61 Avenue du President Wilson, 94235 Cachan Cedex, France 5A. M. Prokhorov General Physics Institute of Russian Academy of Sciences, 38 Vavilov Street, 119991 Moscow, Russia Received 27 July 2006; revised manuscript received 21 December 2006; published 12 February 2007

Triple-star candidates among the kepler binaries

Abstract: We present the results of a search through the photometric database of Kepler eclipsing binaries looking for evidence of hierarchical triple-star systems. The presence of a third star orbiting the binary can be inferred from eclipse timing variations. We apply a simple algorithm in an automated determination of the eclipse times for all 2157 binaries. The ''calculated'' eclipse times, based on a constant period model, are subtracted from those observed. The resulting O - C (observed minus calculated times) curves are then visually inspected for periodicities in order to find triple-star candidates. After eliminating false positives due to the beat frequency between the {approx}1/2 hr Kepler cadence and the binary period, 39 candidate triple systems were identified. The periodic O - C curves for these candidates were then fit for contributions from both the classical Roemer delay and so-called physical delay, in an attempt to extract a number of the system parameters of the triple. We discuss the limitations of the information that can be inferred from these O - C curves without further supplemental input, e.g., ground-based spectroscopy. Based on the limited range of orbital periods for the triple-star systems to which this search is sensitive, we can extrapolatemore » to estimate that at least 20% of all close binaries have tertiary companions.« less

Durability of reactive powder composites: influence of silica fume on the leaching properties of very low water/binder pastes

Abstract: Reactive Powder Composites are new cement-based materials which could be used for the storage of nuclear wastes thanks to their excellent microstructural properties. This paper studies their durability when submitted in the laboratory to a water leaching attack. In order to understand the behaviour of the hydrates (CSH), the study was carried out on a pure cement paste and on a cement + silica fume paste. The beneficial effect of silica fume is demonstrated from considerations on the calcium leaching, from XRD analysis, from SEM observations and from the tritium diffusion and pore distribution analysis. It was found that the leaching greatly affects the microstructure, especially that of the anhydrous cement grains remaining in the paste.