Author: "Alain Léger" / Language: english - Searchworks@Jio Institute Digital Library Search Results

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38 results on '"Alain Léger"'

1. On the coupling of large deformations and elastic-plasticity in the mechanics of a simple system

Author: Alain Léger, Alain Cimetière, Elaine Pratt, Institut Pprime (PPRIME), Université de Poitiers-ENSMA-Centre National de la Recherche Scientifique (CNRS), Surface, Interfaces et MAtériaux sous Contrainte SIMAC (SIMAC), Département Physique et Mécanique des Matériaux (Département Physique et Mécanique des Matériaux), Université de Poitiers-ENSMA-Centre National de la Recherche Scientifique (CNRS)-Université de Poitiers-ENSMA-Centre National de la Recherche Scientifique (CNRS)-Institut Pprime (PPRIME), Université de Poitiers-ENSMA-Centre National de la Recherche Scientifique (CNRS)-Université de Poitiers-ENSMA-Centre National de la Recherche Scientifique (CNRS), THALES Aerospace, THALES [France], Laboratoire de Mécanique et d'Acoustique [Marseille] (LMA ), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), and THALES
Subjects: Constitutive equation, [PHYS.MPHY]Physics [physics]/Mathematical Physics [math-ph], 02 engineering and technology, Kinematics, Plasticity, Tangent modulus, Incremental plasticity, Nonsmooth non linearity, Plastic buckling, [SPI.AUTO]Engineering Sciences [physics]/Automatic, 0203 mechanical engineering, [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph], [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], [PHYS.MECA.BIOM]Physics [physics]/Mechanics [physics]/Biomechanics [physics.med-ph], Bifurcation, Physics, [SPI.ACOU]Engineering Sciences [physics]/Acoustics [physics.class-ph], [PHYS.MECA.VIBR]Physics [physics]/Mechanics [physics]/Vibrations [physics.class-ph], Critical load, Mechanical Engineering, [SPI.FLUID]Engineering Sciences [physics]/Reactive fluid environment, [SPI.NRJ]Engineering Sciences [physics]/Electric power, [CHIM.MATE]Chemical Sciences/Material chemistry, Large deformations, [PHYS.MECA.MSMECA]Physics [physics]/Mechanics [physics]/Materials and structures in mechanics [physics.class-ph], 021001 nanoscience & nanotechnology, Condensed Matter Physics, [PHYS.MECA.ACOU]Physics [physics]/Mechanics [physics]/Acoustics [physics.class-ph], Nonlinear system, [SPI.ELEC]Engineering Sciences [physics]/Electromagnetism, 020303 mechanical engineering & transports, Classical mechanics, [CHIM.POLY]Chemical Sciences/Polymers, Buckling, Mechanics of Materials, Simple model, [PHYS.MECA.THER]Physics [physics]/Mechanics [physics]/Thermics [physics.class-ph], 0210 nano-technology
Abstract: International audience; The buckling and the post buckling of a simple model involving both large deformations and elastic-plasticity are studied. Plasticity is described by the classical incremental constitutive law involving in particular non regularized transition between plastic loading and elastic unloading. The kinematics is chosen in order to take into account any rotation, however large, without having to resort to approximations or asymptotic expansions. The work focusses essentially on the specificity of the coupling between these two types of nonlinearity. At small strains the global behavior is correctly given by Hutchinson's simple model involving the same elastic-plastic constitutive law and linearized deformations. But at very large strains, the response notably differs from that of Hutchinson's model. Indeed plasticity seems to have no effect and the behavior is that of a system involving the same nonlinear deformations but with a constant modulus. From the point of view of bifurcation analysis this result is qualitatively interesting due to the fact that the elastic-plastic constitutive law can be regarded as a strong, or non-smooth, nonlinearity, whereas large deformations is a smooth, we could say weaker, non linearity, so that the result contradicts the intuition that the strongest non linearity should be associated with the strongest bifurcation effect. The analysis is carried out using two different geometrical nonlinearities.
Published: 2019

2. Capillarity in pressure infiltration: improvements in characterization of high-temperature systems

Author: C. Bacciarini, Alain Léger, Raphaël Charvet, Willy Dufour, Ludger Weber, N. R. Calderon, and Andreas Mortensen
Subjects: 010302 applied physics, Materials science, Capillary action, Mechanical Engineering, Metal matrix composite, 02 engineering and technology, Penetration (firestop), 021001 nanoscience & nanotechnology, 01 natural sciences, Mechanics of Materials, 0103 physical sciences, Solid mechanics, General Materials Science, Wetting, Composite material, 0210 nano-technology, Saturation (chemistry), Relative permeability, Porosity
Abstract: In the pressure infiltration of metal matrix composites, molten metal is injected under external pressure into a porous preform of the reinforcing material. Equilibrium capillary parameters characterizing wetting for this process are summarized in plots of metal saturation versus applied pressure, also known as drainage curves. Such curves can be measured in our laboratory during a single experiment with an infiltration apparatus designed to track the rate of metal penetration into porous preforms under conditions characteristic of metal matrix composite processing (temperatures in excess of 1000 A degrees C and pressures in the order of 10 MPa). For such measurements to be valid, infiltration of the preform with molten metal must be mechanically quasi-static, i.e., the metal must flow at a rate sufficiently low for the metal pressure to be essentially uniform across the preform at all times. We examine this requirement quantitatively, using a finite-difference model that simulates the unsaturated unidirectional ingress of molten metal into a ceramic particle preform of finite width. We furthermore present improvements in the experimental apparatus developed in our laboratory to measure the entire drainage curve in a single experiment. We compare numerical results with new experimental data for the copper/alumina system to show (i) that pressurization rates sufficiently low for quasi-static infiltration can be produced with this apparatus, and (ii) that taking the relative permeability equal to the saturation yields better agreement with experiment than does the expression originally proposed by Brooks and Corey.
Published: 2018

3. A Smooth and Discontinuous Oscillator : Theory, Methodology and Applications

Author: Qingjie Cao, Alain Léger, Qingjie Cao, and Alain Léger
Subjects: Nonlinear theories, Chaotic behavior in systems
Abstract: This is the first book to introduce the irrational elliptic function series, providing a theoretical treatment for the smooth and discontinuous system and opening a new branch of applied mathematics. The discovery of the smooth and discontinuous (SD) oscillator and the SD attractors discussed in this book represents a further milestone in nonlinear dynamics, following on the discovery of the Ueda attractor in 1961 and Lorenz attractor in 1963.This particular system bears significant similarities to the Duffing oscillator, exhibiting the standard dynamics governed by the hyperbolic structure associated with the stationary state of the double well. However, there is a substantial departure in nonlinear dynamics from standard dynamics at the discontinuous stage. The constructed irrational elliptic function series, which offers a way to directly approach the nature dynamics analytically for both smooth and discontinuous behaviours including the unperturbed periodic motions and the perturbed chaotic attractors without any truncation, is of particular interest. Readers will also gain a deeper understanding of the actual nonlinear phenomena by means of a simple mechanical model: the theory, methodology, and the applications in various interlinked disciplines of sciences and engineering. This book offers a valuable resource for researchers, professionals and postgraduate students in mechanical engineering, non-linear dynamics, and related areas, such as nonlinear modelling in various fields of mathematics, physics and the engineering sciences.
Published: 2017

4. Qualitative Analysis of Nonsmooth Dynamics : A Simple Discrete System with Unilateral Contact and Coulomb Friction

Author: Alain Léger, Elaine Pratt, Alain Léger, and Elaine Pratt
Subjects: Qualitative research, Nonlinear mechanics, Differential equations, Nonlinear
Abstract: Qualitative Analysis of Nonsmooth Dynamics: A Simple Discrete System with Unilateral Contact and Coulomb Friction explores the effects of small and large deformations to understand how shocks, sliding, and stick phases affect the trajectories of mechanical systems. By analyzing these non-regularities successively this work explores the set of equilibria and properties of periodic solutions of elementary mechanical systems, where no classical results issued from the theory of ordinary differential equations are readily available, such as stability, continuation or approximation of solutions. The authors focus on unilateral contact in presence of Coulomb friction and show, in particular, how any regularization would greatly simplify the mathematics but lead to unacceptable physical responses. Explores the effects of small and large deformations to understand how shocks, sliding, and stick phases affect the trajectories of mechanical systems Includes theoretical results concerning the full investigation of the behavior under constant or oscillating loadings, even in the case of the simplest mechanical systems Provides a focus on unilateral contact in presence of Coulomb friction Helps you gain an accurate understanding of how the transition occurs to ensure the safe use of any machine involving rotating or sliding mechanisms
Published: 2016

5. On the equilibria and qualitative dynamics of a forced nonlinear oscillator with contact and friction

Author: Elaine Pratt, Alain Léger, Laboratoire de Mécanique et d'Acoustique [Marseille] (LMA ), Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM), Matériaux et Structures (M&S), Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM), Leger, Alain, Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), and Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Dynamical systems theory, mass-spring systems, non-smooth dynamics, Unilateral contact, 01 natural sciences, Simple (abstract algebra), 2010 Mathematics Subject Classification. Primary:70K42, Secondary:37M99, 0103 physical sciences, [PHYS.MECA.SOLID]Physics [physics]/Mechanics [physics]/Solid mechanics [physics.class-ph], Discrete Mathematics and Combinatorics, 010306 general physics, 010301 acoustics, Physics, [PHYS.MECA.SOLID] Physics [physics]/Mechanics [physics]/Solid mechanics [physics.class-ph], Applied Mathematics, SD oscillator, Dynamics (mechanics), equilibrium states, Mechanics, Coulomb friction, unilateral contact, Coupling (physics), Nonlinear system, Classical mechanics, Restoring force, Analysis
Abstract: International audience; After previous works related to the equilibrium states, this papergoes deeper into the study of the eect of coupling between smooth and non-smooth non-linearities on the qualitative behavior of low dimensional dynami-cal systems. The non-smooth non-linearity is due to non-regularized unilateralcontact and Coulomb friction while the smooth one is due to large strains ofa simple mass spring system, which lead to a nonlinear restoring force. Themain qualitative dierences with the case of a linear restoring force are due tothe shape of the set of equilibrium states.
Published: 2016

6. Microarcsecond astrometric observatory Theia: from dark matter to compact objects and nearby earths

Author: Renaud Goullioud, Mike Shao, Douglas Spolyar, Fabien Malbet, Lucas Labadie, Antoine Crouzier, Celine Boehm, Berry Holl, Guillem Anglada Escudé, Alberto Krone-Martins, Alessandro Sozzetti, and Alain Léger
Subjects: Physics, Cosmic Vision, Planetary habitability, 010308 nuclear & particles physics, Dark matter, Astronomy, Astrometry, 01 natural sciences, Exoplanet, Astrobiology, law.invention, Telescope, Planet, Observatory, law, 0103 physical sciences, 010303 astronomy & astrophysics
Abstract: Theia is a logical successor to Gaia, as a focused, very high precision astrometry mission which addresses two key science objectives of the ESA Cosmic Vision program: the nature of dark matter and the search for habitable planets. Theia addresses a number of other science cases strongly synergistic with ongoing/planned missions, such as the nature of compact objects, motions of stars in young stellar clusters, follow-up of Gaia objects of interest. Theia s "point and stare" operational mode will enable us to answer some of the most profound questions that the results of the Gaias survey will ask. Extremely-high-precision astrometry at 1-μas level can only be reached from space. The Theia spacecraft, which will carry a 0.8-m telescope, is foreseen to operate at L2 for 3,5 years. The preliminary Theia mission assessment allowed us to identify a safe and robust mission architecture that demonstrates the mission feasibility within the Soyuz ST launch envelope and a small M-class mission cost cap. We present here these features of the mission that has been submitted to the last ESA M4 call in January 2015.
Published: 2016

7. Stability in the obstacle problem for a shallow shell

Author: Bernadette Miara, Alain Léger, Laboratoire de Mécanique et d'Acoustique [Marseille] (LMA ), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Modélisation et Simulation Numérique (MOSIM), École Supérieure d'Ingénieurs en Électronique et Électrotechnique, and Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)
Subjects: Applied Mathematics, 010102 general mathematics, Mathematical analysis, Scalar (mathematics), Unilateral contact, Nash–Moser theorem, 02 engineering and technology, stability, [SPI.MECA.SOLID]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Solid mechanics [physics.class-ph], Curvature, 01 natural sciences, Free boundary, 020303 mechanical engineering & transports, 0203 mechanical engineering, obstacle problem, Obstacle, Variational inequality, Obstacle problem, Free boundary problem, Vector field, 0101 mathematics, Analysis, Mathematics, unilateral contact
Abstract: International audience; This work deals with the variation of the solution to an obstacle problem with respect to the variation of its parameters. More precisely, a mechanical structure is pushed by some external forces against an obstacle in such a way that the equilibrium solution involves a part of the domain in which the structure is strictly in contact with the obstacle. It is known from the theory of variational inequalities that studying the variation of the solution as the external forces vary amounts to studying the variation of the boundary of this contact zone. This problem has been studied in previous works in the scalar case, and it was open in the general case where the unknown is a vector field, due to the coupling between the components. As a first step, the present work considers the case of a linearly elastic shallow membrane shell where the coupling between the in-plane and normal components of the displacement arises from the curvature.Read More: http://www.worldscientific.com/doi/abs/10.1142/S0219530514500225
Published: 2016

8. Dynamics of elastic bodies connected by a thin soft viscoelastic layer

Author: Somsak Orankitjaroen, Christian Licht, Ahmed Ould Khaoua, Alain Léger, Modélisation Mathématique en Mécanique (M3), Laboratoire de Mécanique et Génie Civil (LMGC), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Matériaux et Structures (M&S), Laboratoire de Mécanique et d'Acoustique [Marseille] (LMA ), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Department of Mathematics, Mahidol University [Bangkok], Département de Mathématiques, and Universite Los Andes
Subjects: Bonding problem, Wave propagation, General Mathematics, Variational convergence, 02 engineering and technology, [SPI.MECA.SOLID]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Solid mechanics [physics.class-ph], 01 natural sciences, Viscoelasticity, 010305 fluids & plasmas, [PHYS.MECA.MEMA]Physics [physics]/Mechanics [physics]/Mechanics of materials [physics.class-ph], symbols.namesake, [PHYS.MECA.STRU]Physics [physics]/Mechanics [physics]/Structural mechanics [physics.class-ph], 0203 mechanical engineering, 0103 physical sciences, Convergence (routing), [SPI.MECA.MEMA]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Mechanics of materials [physics.class-ph], [PHYS.MECA.SOLID]Physics [physics]/Mechanics [physics]/Solid mechanics [physics.class-ph], Limit (mathematics), Mathematics, Kelvin-Voigt viscoelasticity, Applied Mathematics, Mathematical analysis, Hilbert space, Dissipation, Nonlinear system, 020303 mechanical engineering & transports, Trotter's theory, [SPI.MECA.STRU]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Structural mechanics [physics.class-ph], symbols, Approximation of semigroups, Quasistatic process
Abstract: International audience; A dynamic study was performed on a structure consisting of two three-dimensional linearly elastic bodies connected by a thin soft nonlinear Kelvin-Voigt viscoelastic adhesive layer. The adhesive is assumed to be viscoelastic of Kelvin-Voigt generalized type, which makes it possible to deal with a relatively wide range of physical behavior by choosing suitable dissipation potentials. In the static and purely elastic case, convergence results when geometrical and mechanical parameters tend to zero have already been obtained using variational convergence methods. To obtain convergence results in the dynamic case, the main tool, as in the quasistatic case, is a nonlinear version of Trotter's theory of approximation of semigroups acting on variable Hilbert spaces. The limit problem involves a mechanical constraint imposed along the surface to which the layer shrinks. The meaning of this limit with respect to the relative behavior of the parameters is discussed. The problem applies in particular to wave phenomena in bonded domains.
Published: 2013

9. A fully nonlinear oscillator with contact and friction

Author: Elaine Pratt, Alain Léger, Qingjie Cao, Matériaux et Structures (M&S), Laboratoire de Mécanique et d'Acoustique [Marseille] (LMA ), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), School of Civil Engineering [Harbin] (HIT), Harbin Institute of Technology (HIT), and Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)
Subjects: Work (thermodynamics), Unilateral contact, Dynamical systems theory, Equilibrium states, Aerospace Engineering, Ocean Engineering, 02 engineering and technology, [SPI.MECA.SOLID]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Solid mechanics [physics.class-ph], 01 natural sciences, Stability (probability), Mass-spring system, 0203 mechanical engineering, SD-oscillator, Simple (abstract algebra), 0103 physical sciences, Attractor, [PHYS.MECA.SOLID]Physics [physics]/Mechanics [physics]/Solid mechanics [physics.class-ph], Electrical and Electronic Engineering, 010301 acoustics, Physics, Coupling, [PHYS.MECA.VIBR]Physics [physics]/Mechanics [physics]/Vibrations [physics.class-ph], Nonsmooth dynamics, Applied Mathematics, Mechanical Engineering, [SPI.MECA.VIBR]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Vibrations [physics.class-ph], Nonlinear system, 020303 mechanical engineering & transports, Classical mechanics, Coulomb friction, Control and Systems Engineering
Abstract: International audience; In order to understand the effects of the coupling between smooth and nonsmooth nonlinearities in dynamical systems, we introduce a simple mechanical model containing the exact expression of nonlinear strains together with non-regularized unilateral contact and Coulomb friction conditions. This model is suggested both by previous work dealing with unilateral contact conditions and by work closer to classical dynamical systems which has recently led to the introduction of a new attractor. The main part of the paper concerns the investigation of the set of equilibrium states which turns out to be much more intricate than when the strains were linearized. Then the paper ends by suggesting some possible paths towards the study of the stability of these equilibria and of the qualitative dynamics.
Published: 2012

10. The far future of exoplanet direct characterization

Author: Thomas Henning, William C. Danchi, Alan J. Penny, Glenn J. White, René Liseau, Alain Léger, Carlos Eiroa, Lisa Kaltenegger, Francesco Paresce, Franck Selsis, Andreas Quirrenbach, Malcolm Fridlund, Jonathan I. Lunine, Giovanna Tinetti, Huub Roettgering, Jean Schneider, Daphne Stam, Tom Herbst, Helmut Lammer, Charles Beichman, Observatoire de Paris - Site de Meudon (OBSPM), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA)-European Space Agency (ESA), SLAC National Accelerator Laboratory (SLAC), Stanford University, Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Space Research Institute of Austrian Academy of Sciences (IWF), Austrian Academy of Sciences (OeAW), European Southern Observatory (ESO), Landessternwarte Königstuhl [ZAH] (LSW), Universität Heidelberg [Heidelberg], Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1, NASA Goddard Space Flight Center (GSFC), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, SRON Netherlands Institute for Space Research (SRON), University College of London [London] (UCL), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Agence Spatiale Européenne = European Space Agency (ESA)-Agence Spatiale Européenne = European Space Agency (ESA), Universität Heidelberg [Heidelberg] = Heidelberg University, Universiteit Leiden, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Université Sciences et Technologies - Bordeaux 1 (UB)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP), 010504 meteorology & atmospheric sciences, Computer science, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Spectrum Analysis, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, Direct imaging, Astrophysics, 01 natural sciences, Agricultural and Biological Sciences (miscellaneous), Exoplanet, Characterization (materials science), Astrobiology, Space and Planetary Science, 0103 physical sciences, Fourth generation, Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Forecasting, Astrophysics - Earth and Planetary Astrophysics, 0105 earth and related environmental sciences
Abstract: In this outlook we describe what could be the next steps of the direct characterization of habitable exoplanets after first the medium and large mission projects and investigate the benefits of the spectroscopic and direct imaging approaches. We show that after third and fourth generation missions foreseeable for the next 100 years, we will face a very long era before being able to see directly the morphology of extrasolar organisms., Draft of a paper accepted in Astrobiology
Published: 2010

11. Geophysical and atmospheric evolution of habitable planets

Author: Günter Stangl, Glenn J. White, Thomas Henning, Doris Breuer, W. Hausleitner, Helfried K. Biernat, Jean-Mathias Grießmeier, Andreas Quirrenbach, Jonathan I. Lunine, Hannes Gröller, Eric Chassefière, Tom Herbst, Charles Beichman, Yuri N. Kulikov, Richard Lundin, Alan J. Penny, Herbert Lichtenegger, René Liseau, Uwe Motschmann, Helmut Lammer, Carlos Eiroa, Lisa Kaltenegger, Francesco Paresce, Tilman Spohn, Petra Odert, John Parnell, François Leblanc, Heike Rauer, Nikolai V. Erkaev, Esa Kallio, A. Stadelmann, Jean Schneider, Huub Röttgering, Martin Leitzinger, Maxim L. Khodachenko, Alain Léger, Arnold Hanslmeier, Giovanna Tinetti, Siegfried J. Bauer, William C. Danchi, Frances Westall, Malcolm Fridlund, Daphne Stam, Franck Selsis, Space Research Institute of Austrian Academy of Sciences (IWF), Austrian Academy of Sciences (OeAW), Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire aquitain des sciences de l'univers (OASU), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Interactions et dynamique des environnements de surface (IDES), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), DLR Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] (DLR), Netherlands Institute for Radio Astronomy (ASTRON), Polar Geophysical Institute of Russian Academy of Sciences (PGI), Russian Academy of Sciences [Moscow] (RAS), Institute of Computational Modelling of the Russian Academy of Sciences (ICM SB RAS), Siberian Branch of the Russian Academy of Sciences (SB RAS), Finnish Meteorological Institute (FMI), Swedish Institute of Space Physics [Kiruna] (IRF), Centre de biophysique moléculaire (CBM), Université d'Orléans (UO)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Institute of Physics [Graz], Karl-Franzens-Universität [Graz, Autriche], NASA ExoPlanet Science Institute (NExScI), California Institute of Technology (CALTECH), NASA Goddard Space Flight Center (GSFC), Universidad Autonoma de Madrid (UAM), Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA)-European Space Agency (ESA), Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, Institut d'astrophysique spatiale (IAS), Department of Radio and Space Science [Göteborg], Chalmers University of Technology [Göteborg], Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Institut für Theoretische Physik [Braunschweig], Technische Universität Braunschweig = Technical University of Braunschweig [Braunschweig], Istituto Nazionale di Astrofisica (INAF), Department of Geology and Petroleum Geology [Aberdeen], University of Aberdeen, STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), Landessternwarte Königstuhl [ZAH] (LSW), Universität Heidelberg [Heidelberg], Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Observatoire de Paris - Site de Meudon (OBSPM), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), SRON Netherlands Institute for Space Research (SRON), University College of London [London] (UCL), Department of Physics and Astronomy [Milton Keynes], The Open University [Milton Keynes] (OU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université d'Orléans (UO)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Karl-Franzens-Universität Graz, Universidad Autónoma de Madrid (UAM), Agence Spatiale Européenne = European Space Agency (ESA)-Agence Spatiale Européenne = European Space Agency (ESA), Harvard University-Smithsonian Institution, Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Universität Heidelberg [Heidelberg] = Heidelberg University, and Universiteit Leiden
Subjects: 010504 meteorology & atmospheric sciences, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Kepler-69c, Habitability, Rare Earth hypothesis, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Planets, Environment, 01 natural sciences, Astrobiology, Physics::Geophysics, Eccentric Jupiter, Magnetics, Galactic habitable zone, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Terrestrial planets, 010303 astronomy & astrophysics, Physics::Atmospheric and Oceanic Physics, 0105 earth and related environmental sciences, Radiation, Planetary habitability, Atmosphere, Astronomy, Water, Geophysics, Agricultural and Biological Sciences (miscellaneous), Habitability of orange dwarf systems, Earth analog, 13. Climate action, Space and Planetary Science, Atmosphere evolution, Terrestrial planet, Astrophysics::Earth and Planetary Astrophysics, Evolution, Planetary, Geology
Abstract: International audience; The evolution of Earth-like habitable planets is a complex process that depends on the geodynamical and geophysical environments. In particular, it is necessary that plate tectonics remain active over billions of years. These geophysically active environments are strongly coupled to a planet's host star parameters, such as mass, luminosity and activity, orbit location of the habitable zone, and the planet's initial water inventory. Depending on the host star's radiation and particle flux evolution, the composition in the thermosphere, and the availability of an active magnetic dynamo, the atmospheres of Earth-like planets within their habitable zones are differently affected due to thermal and nonthermal escape processes. For some planets, strong atmospheric escape could even effect the stability of the atmosphere
Published: 2010

12. Eyepiece focus and vergence/accommodation conflict: Implications for night-vision devices

Author: Marie Charbonneau, Bernard Claverie, Alain Léger, Orange Labs R&D [Rennes], France Télécom, Laboratoire de l'intégration, du matériau au système (IMS), and Centre National de la Recherche Scientifique (CNRS)-Institut Polytechnique de Bordeaux-Université Sciences et Technologies - Bordeaux 1
Subjects: accommodation, [SPI.OTHER]Engineering Sciences [physics]/Other, Visual acuity, Computer science, focus adjustment, hyperstereopsis, Vergence, telestereoscope, vergence, [SHS]Humanities and Social Sciences, [SPI]Engineering Sciences [physics], Eyepiece, Night-vision goggles, medicine, Computer vision, Electrical and Electronic Engineering, Focus (computing), business.industry, [SCCO.NEUR]Cognitive science/Neuroscience, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, Short distance, [SCCO.PSYC]Cognitive science/Psychology, Artificial intelligence, medicine.symptom, business, Accommodation, Night vision device, Landolt C
Abstract: International audience; – Aviation increasingly conducts night operations using night-vision devices. However, design of some aspects may limit performance. As pointed out by Kotulak, vergence/accommodation mismatch in NVDs, usually due to eyepiece focus misadjustments, is sometimes a source of visual acuity (VA) decrement. The increased separation between sensors, existing in some binocular helmet-mounted displays, was also identified to be potentially responsible for decreased VA at short distances. Based upon knowledge pertaining to vergence and accommodation, a study was performed to better understand the problem of dissociation accommodation/convergence. Different conditions of intero-cular separation and viewing distances were used. Twelve subjects participated and were asked to resolve Landolt C charts using night-vision goggles. The results show that, with the eyepiece focus fixed at 10 m, the decrease in VA is roughly proportional to the interocular separation, when looking at short distances. A fixed eyepiece focus at 4 m considerably reduces the conflict and results in improved VA. An additional experiment was conducted to investigate the effect of fixing the objective lenses focus at infinity. With this setting, the decrease in VA at a short distance was such that effects of the mismatch accommodation/convergence are no longer apparent regardless of the interocular separation.
Published: 2010

13. The Search for Worlds Like Our Own

Author: Peter R. Lawson, Oliver P. Lay, Luigi D'Arcio, Mikael Kilter, Franck Selsis, William C. Danchi, Jonathan I. Lunine, René Liseau, Charles Beichman, Tom Herbst, Charles Hanot, Alan J. Penny, Thomas Henning, Huub Röttgering, Carlos Eiroa, Philippe Gondoin, Lisa Kaltenegger, Francesco Paresce, Anna-Maria Stankov, Malcolm Fridlund, Christian Erd, Michael Devirian, A. Karlsson, Jean Schneider, Roland den Hartog, Glenn J. White, Olivier Absil, Kenneth J. Johnston, Alain Léger, Giovanna Tinetti, Daniel R. Coulter, Daphne Stam, Andreas Quirrenbach, Denis Defrere, Helmut Lammer, Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA)-European Space Agency (ESA), Universidad Autonoma de Madrid (UAM), Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Space Research Institute of Austrian Academy of Sciences (IWF), Austrian Academy of Sciences (OeAW), Department of Radio and Space Science [Göteborg], Chalmers University of Technology [Göteborg], Istituto Nazionale di Astrofisica (INAF), STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), Landessternwarte Königstuhl [ZAH] (LSW), Universität Heidelberg [Heidelberg], Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1, Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Department of Physics and Astronomy [Milton Keynes], The Open University [Milton Keynes] (OU), Institut d'Astrophysique et de Géophysique [Liège], Université de Liège, University College of London [London] (UCL), NASA ExoPlanet Science Institute (NExScI), California Institute of Technology (CALTECH), NASA Goddard Space Flight Center (GSFC), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Harvard-Smithsonian Center for Astrophysics (CfA), and Smithsonian Institution-Harvard University [Cambridge]
Subjects: Time Factors, 010504 meteorology & atmospheric sciences, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], media_common.quotation_subject, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Planets, 01 natural sciences, Kepler, Astrobiology, Life, Planet, Heresy, 0103 physical sciences, Humans, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, media_common, Copernicus, Physics, Habitability, Atmosphere, Agricultural and Biological Sciences (miscellaneous), Exoplanet, Space and Planetary Science, Research Design, Darwin (spacecraft), Solar System, Classics
Abstract: International audience; The direct detection of Earth-like exoplanets orbiting nearby stars and the characterization of such planets -- particularly, their evolution, their atmospheres, and their ability to host life -- constitute a significant problem. The quest for other worlds as abodes of life has been one of mankind's great questions for several millennia. For instance, as stated by Epicurus 300 BC: Other worlds, with plants and other living things, some of them similar and some of them different from ours, must exist. Demokritos from Abdera (460-370 BC), the man who invented the concept of indivisible small parts - atoms - also held the belief that other worlds exist around the stars and that some of these worlds may be inhabited by life-forms. The idea of the plurality of worlds and of life on them has since been held by scientists like Johannes Kepler and William Herschel, among many others. Here, one must also mention Giordano Bruno. Born in 1548, Bruno studied in France and came into contact with the teachings of Nicolas Copernicus. He wrote the book De l'Infinito, Universo e Mondi in 1584, in which he claimed that the Universe was infinite, that it contained an infinite amount of worlds like Earth, and that these worlds were inhabited by intelligent beings. At the time, this was extremely controversial, and eventually Bruno was arrested by the church and burned at the stake in Rome in 1600, as a heretic, for promoting this and other equally confrontational issues (though it is unclear exactly which idea was the one that ultimately brought him to his end). In all the aforementioned cases, the opinions and results were arrived at through reasoning not by experiment. We have only recently acquired the technological capability to observe planets orbiting stars other than 6our Sun; acquisition of this capability has been a remarkable feat of our time. We show in this introduction to the Habitability Primer that mankind is at the dawning of an age when, by way of the scientific method and 21st-century technology, we will be able to answer this fascinating controversial issue that has persisted for at least 2500 years.
Published: 2010

14. Dynamical Habitability of Planetary Systems

Author: Glenn J. White, Richard P. Schwarz, Barbara Funk, Helmut Lammer, Tom Herbst, René Liseau, William C. Danchi, Carlos Eiroa, Malcolm Fridlund, Lisa Kaltenegger, Francesco Paresce, Alan J. Penny, Andreas Quirrenbach, Huub Röttgering, Elke Pilat-Lohinger, Jonathan I. Lunine, Jean Schneider, Alain Léger, Giovanna Tinetti, Eric Bois, Daphne Stam, Rudolf Dvorak, Franck Selsis, Thomas Henning, Charles Beichman, Laboratoire de Cosmologie, Astrophysique Stellaire & Solaire, de Planétologie et de Mécanique des Fluides (CASSIOPEE), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Observatoire de la Côte d'Azur (OCA), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), NASA ExoPlanet Science Institute (NExScI), California Institute of Technology (CALTECH), NASA Goddard Space Flight Center (GSFC), Universidad Autonoma de Madrid (UAM), Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA)-European Space Agency (ESA), Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Harvard-Smithsonian Center for Astrophysics (CfA), Smithsonian Institution-Harvard University [Cambridge], Space Research Institute of Austrian Academy of Sciences (IWF), Austrian Academy of Sciences (OeAW), Department of Radio and Space Science [Göteborg], Chalmers University of Technology [Göteborg], Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Istituto Nazionale di Astrofisica (INAF), STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), Landessternwarte Königstuhl [ZAH] (LSW), Universität Heidelberg [Heidelberg], Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1, Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Observatoire de Paris - Site de Meudon (OBSPM), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), SRON Netherlands Institute for Space Research (SRON), University College of London [London] (UCL), Department of Physics and Astronomy [Milton Keynes], and The Open University [Milton Keynes] (OU)
Subjects: Physics, 010504 meteorology & atmospheric sciences, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Planets, Astronomy, Planetary system, 01 natural sciences, Agricultural and Biological Sciences (miscellaneous), Habitability of orange dwarf systems, Exoplanet, Astrobiology, Kepler-47, 13. Climate action, Space and Planetary Science, Planet, Jupiter, 0103 physical sciences, Terrestrial planet, Solar System, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Planetary mass, 0105 earth and related environmental sciences, Planetary migration
Abstract: International audience; The problem of the stability of planetary systems, a question that concerns only multiplanetary systems that host at least two planets, is discussed. The problem of mean motion resonances is addressed prior to discussion of the dynamical structure of the more than 350 known planets. The difference with regard to our own Solar System with eight planets on low eccentricity is evident in that 60% of the known extrasolar planets have orbits with eccentricity e > 0.2. We theoretically highlight the studies concerning possible terrestrial planets in systems with a Jupiter-like planet. We emphasize that an orbit of a particular nature only will keep a planet within the habitable zone around a host star with respect to the semimajor axis and its eccentricity. In addition, some results are given for individual systems (e.g., Gl777A) with regard to the stability of orbits within habitable zones. We also review what is known about the orbits of planets in double-star systems around only one component (e.g., gamma Cephei) and around both stars (e.g., eclipsing binaries).
Published: 2010

15. Co-evolution of atmospheres, life, and climate

Author: René Liseau, Lisa Kaltenegger, Francesco Paresce, Glenn J. White, Thomas Henning, Daphne Stam, Malcolm Fridlund, Andreas Quirrenbach, Huub Röttgering, Alan J. Penny, Helmut Lammer, Tom Herbst, Heike Rauer, Giovanna Tinetti, J. Schneider, Jonathan I. Lunine, Carlos Eiroa, Alain Léger, William C. Danchi, Charles Beichman, Franck Selsis, John Lee Grenfell, DLR Institute of Planetary Research, German Aerospace Center (DLR), Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1, Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Harvard-Smithsonian Center for Astrophysics (CfA), Smithsonian Institution-Harvard University [Cambridge], NASA ExoPlanet Science Institute (NExScI), California Institute of Technology (CALTECH), NASA Goddard Space Flight Center (GSFC), Universidad Autonoma de Madrid (UAM), Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA)-European Space Agency (ESA), Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Space Research Institute of Austrian Academy of Sciences (IWF), Austrian Academy of Sciences (OeAW), Department of Radio and Space Science [Göteborg], Chalmers University of Technology [Göteborg], Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Istituto Nazionale di Astrofisica (INAF), STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), Landessternwarte Königstuhl [ZAH] (LSW), Universität Heidelberg [Heidelberg], Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Observatoire de Paris - Site de Meudon (OBSPM), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), SRON Netherlands Institute for Space Research (SRON), University College of London [London] (UCL), Department of Physics and Astronomy [Milton Keynes], and The Open University [Milton Keynes] (OU)
Subjects: Atmospheres, 010504 meteorology & atmospheric sciences, Ultraviolet Rays, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Climate, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Planets, FOS: Physical sciences, chemistry.chemical_element, Geologic record, 01 natural sciences, Oxygen, Astrobiology, Atmosphere, Ozone, Planet, 0103 physical sciences, Ozone layer, Photosynthesis, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Earth and Planetary Astrophysics (astro-ph.EP), Exoplanets, Early Earth, Biomarker, Agricultural and Biological Sciences (miscellaneous), Exoplanet, chemistry, 13. Climate action, Space and Planetary Science, Greenhouse gas, Sunlight, Environmental science, Solar System, Evolution, Planetary, Astrophysics - Earth and Planetary Astrophysics
Abstract: After Earth's origin, our host star, the Sun, was shining 20–25% less brightly than today. Without greenhouselike\ud conditions to warm the atmosphere, our early planet would have been an ice ball, and life may never have evolved. But life did evolve, which indicates that greenhouse gases must have been present on early Earth to warm the planet. Evidence from the geological record indicates an abundance of the greenhouse gas CO2. CH4 was probably present as well; and, in this regard, methanogenic bacteria, which belong to a diverse group of anaerobic prokaryotes that ferment CO2 plus H2 to CH4, may have contributed to modification of the early atmosphere. Molecular oxygen was not present, as is indicated by the study of rocks from that era, which contain iron carbonate rather than iron oxide. Multicellular organisms originated as cells within colonies\ud that became increasingly specialized. The development of photosynthesis allowed the Sun's energy to be harvested directly by life-forms. The resultant oxygen accumulated in the atmosphere and formed the ozone layer in the upper atmosphere. Aided by the absorption of harmful UV radiation in the ozone layer, life colonized Earth's surface. Our own planet is a very good example of how life-forms modified the atmosphere over the planets' lifetime. We show that these facts have to be taken into account when we discover and characterize atmospheres of Earth-like exoplanets. If life has originated and evolved on a planet, then it should be expected that a strong co-evolution occurred between life and the atmosphere, the result of which is the planet's climate.
Published: 2010

16. Stability in unilateral contact problems with dry friction

Author: Elaine Pratt, Michel Saint Jean, Alain Léger, Laboratoire de Mécanique et d'Acoustique [Marseille] (LMA ), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Pratt, Elaine, and Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)
Subjects: [PHYS.MECA.SOLID] Physics [physics]/Mechanics [physics]/Solid mechanics [physics.class-ph], Conjecture, Dynamical systems theory, Computation, Complex system, Unilateral contact, Perturbation (astronomy), 02 engineering and technology, [SPI.MECA.SOLID]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Solid mechanics [physics.class-ph], Coulomb friction, 01 natural sciences, 020303 mechanical engineering & transports, Classical mechanics, 0203 mechanical engineering, Phase space, 0103 physical sciences, [PHYS.MECA.SOLID]Physics [physics]/Mechanics [physics]/Solid mechanics [physics.class-ph], [SPI.MECA.SOLID] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Solid mechanics [physics.class-ph], 010301 acoustics, ComputingMilieux_MISCELLANEOUS, Mathematics
Abstract: We discuss stability in the case of systems with unilateral contact and Coulomb friction. Classical stability results for dynamical systems concern perturbations of the initial data in a classical phase space. Here we establish results concerning the trajectories issued from a perturbation of the external forces. With such a notion of stability a conjecture is given that we back up in detail by analytical computations in the case of a simple model and that we begin to extend to more complex systems.
Published: 2009

17. Darwin—an experimental astronomy mission to search for extrasolar planets

Author: Hervé Cottin, Helmut Lammer, Thomas Henning, Denis Mourard, Willy Benz, Carlos Eiroa, Charles Beichman, Olivier Absil, Glenn J. White, Denis Defrere, Andreas Quirrenbach, Laurent M. Mugnier, Frances Westall, Charles S. Cockell, C. Moutou, Alain Léger, René Liseau, Pascale Bordé, Malcolm Fridlund, Huub Röttgering, Lucas Labadie, Eugene Serabyn, B. Chazelas, Marc Ollivier, Stefan Martin, Tom Herbst, Lisa Kaltenegger, Oliver P. Lay, Kenneth J. Johnston, William C. Danchi, Ralf Launhardt, Francesco Paresce, Yves Rabbia, Franck Selsis, Vincent Coudé du Foresto, Peter R. Lawson, Nuno C. Santos, Daniel Rouan, Alain Chelli, A. Brack, Jan-Willem den Herder, Dimitri Mawet, Planetary and Space Sciences Research Institute [Milton Keynes] (PSSRI), Centre for Earth, Planetary, Space and Astronomical Research [Milton Keynes] (CEPSAR), The Open University [Milton Keynes] (OU)-The Open University [Milton Keynes] (OU), Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Institut d'astrophysique spatiale (IAS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Grenoble (LAOG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), California Institute of Technology (CALTECH), Physikalisches Institut [Bern], Universität Bern [Bern], Centre de biophysique moléculaire (CBM), Université d'Orléans (UO)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA (UMR_7583)), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA)-European Space Agency (ESA), Space Research Institute of Austrian Academy of Sciences (IWF), Austrian Academy of Sciences (OeAW), SPEC Inc., Laboratoire de Recherche en Informatique (LRI), Université Paris-Sud - Paris 11 (UP11)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Hippolyte Fizeau (FIZEAU), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Marseille (LAM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), ONERA - The French Aerospace Lab [Châtillon], ONERA-Université Paris Saclay (COmUE), European Southern Observatory (ESO), Landessternwarte Königstuhl [ZAH] (LSW), Universität Heidelberg [Heidelberg], Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Centro de Astrofísica da Universidade do Porto (CAUP), Universidade do Porto, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire aquitain des sciences de l'univers (OASU), Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Engineering Department, University of Cambridge [UK] (CAM), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Universität Bern [Bern] (UNIBE), Université d'Orléans (UO)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Agence Spatiale Européenne = European Space Agency (ESA)-Agence Spatiale Européenne = European Space Agency (ESA), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Université Nice Sophia Antipolis (1965 - 2019) (UNS), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Universität Heidelberg [Heidelberg] = Heidelberg University, Universiteit Leiden, Universidade do Porto = University of Porto, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université d'Orléans (UO)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), ONERA, and Universidade do Porto [Porto]
Subjects: Systematic error, Physics, Cosmic Vision, Habitable zone, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Exoplanets, Exomoon, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Astronomy, Astronomy and Astrophysics, 01 natural sciences, Exoplanet, Astrobiology, 010309 optics, Direct imaging of exoplanets, Space and Planetary Science, Primary (astronomy), 0103 physical sciences, Darwin (spacecraft), Nulling interferometry, Interferometer, 010303 astronomy & astrophysics, Circumstellar habitable zone
Abstract: International audience; As a response to ESA call for mission concepts for its Cosmic Vision 2015–2025 plan, we propose a mission called Darwin. Its primary goal is the study of terrestrial extrasolar planets and the search for life on them. In this paper, we describe different characteristics of the instrument.
Published: 2009

18. Tests of achromatic phase shifters performed on the SYNAPSE test bench: a progress report

Author: Pavel Gabor, Peter A. Schuller, Bruno Chazelas, Michel Decaudin, Alain Labèque, Philippe Duret, Yves Rabbia, Ralf Launhardt, Jean Gay, Zoran Sodnik, Marc Barillot, Frank Brachet, Thomas Laurent, Sophie Jacquinod, Denis Vandormael, Jérôme Loicq, Dimitri Mawet, Marc Ollivier, Alain Léger, Schöller, Markus, Danchi, William C., and Delplancke, Françoise
Subjects: Physics, Test bench, business.industry, Astrophysics (astro-ph), Phase (waves), FOS: Physical sciences, Astrophysics, Space exploration, law.invention, Interferometry, Optics, Achromatic lens, law, Darwin (spacecraft), Prism, business, Phase shift module
Abstract: The achromatic phase shifter (APS) is a component of the Bracewell nulling interferometer studied in preparation for future space missions (viz. Darwin/TPF-I) focusing on spectroscopic study of Earth-like exo-planets. Several possible designs of such an optical subsystem exist. Four approaches were selected for further study. Thales Alenia Space developed a dielectric prism APS. A focus crossing APS prototype was developed by the OCA, Nice, France. A field reversal APS prototype was prepared by the MPIA in Heidelberg, Germany. Centre Spatial de Li\`ege develops a concept based on Fresnel's rhombs. This paper presents a progress report on the current work aiming at evaluating these prototypes on the SYNAPSE test bench at the Institut d'Astrophysique Spatiale in Orsay, France.
Published: 2008

19. Semantic Web Take-Off in a European Industry Perspective

Author: Jean Charlet, Johannes Heinecke, Lyndon Nixon, Pavel Shvaiko, Alain Léger, Paola Marcella Hobson, François Goasdoué, France Télécom Recherche & Développement (FT R&D), France Télécom, Freie Universität Berlin, Università degli Studi di Trento (UNITN), Laboratoire de Santé Publique et Informatique Médicale (SPIM), Institut National de la Santé et de la Recherche Médicale (INSERM), Motorola Labs (MOTOROLA), Motorola, Laboratoire de Recherche en Informatique (LRI), Université Paris-Sud - Paris 11 (UP11)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), Integration of data and knowledge distributed over the web (GEMO), Université Paris-Sud - Paris 11 (UP11)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-Inria Saclay - Ile de France, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Roberto Garcia, France Télécom Recherche & Développement ( FT R&D ), Freie Universität Berlin [Berlin], Università di Trento, Laboratoire de Santé Publique et Informatique Médicale ( SPIM ), Institut National de la Santé et de la Recherche Médicale ( INSERM ), Motorola Labs ( MOTOROLA ), Laboratoire de Recherche en Informatique ( LRI ), Université Paris-Sud - Paris 11 ( UP11 ) -Institut National de Recherche en Informatique et en Automatique ( Inria ) -CentraleSupélec-Centre National de la Recherche Scientifique ( CNRS ), Integration of data and knowledge distributed over the web ( GEMO ), Université Paris-Sud - Paris 11 ( UP11 ) -Institut National de Recherche en Informatique et en Automatique ( Inria ) -CentraleSupélec-Centre National de la Recherche Scientifique ( CNRS ) -Université Paris-Sud - Paris 11 ( UP11 ) -Institut National de Recherche en Informatique et en Automatique ( Inria ) -CentraleSupélec-Centre National de la Recherche Scientifique ( CNRS ) -Inria Saclay - Ile de France, Institut National de Recherche en Informatique et en Automatique ( Inria ), and Goasdoué, François
Subjects: [INFO.INFO-AI] Computer Science [cs]/Artificial Intelligence [cs.AI], Knowledge management, Knowledge representation and reasoning, [INFO.INFO-WB] Computer Science [cs]/Web, Computer science, [ INFO.INFO-WB ] Computer Science [cs]/Web, 02 engineering and technology, Ontology (information science), computer.software_genre, Social Semantic Web, [INFO.INFO-AI]Computer Science [cs]/Artificial Intelligence [cs.AI], Semantic computing, 020204 information systems, Collaborative filtering, 0202 electrical engineering, electronic engineering, information engineering, [INFO.INFO-DB] Computer Science [cs]/Databases [cs.DB], [ INFO.INFO-AI ] Computer Science [cs]/Artificial Intelligence [cs.AI], Semantic Web, [INFO.INFO-DB]Computer Science [cs]/Databases [cs.DB], business.industry, [INFO.INFO-WB]Computer Science [cs]/Web, Data science, [ INFO.INFO-DB ] Computer Science [cs]/Databases [cs.DB], Domain knowledge, 020201 artificial intelligence & image processing, Web service, business, computer
Abstract: Semantic Web technology is being increasingly applied in a large spectrum of applications in which domain knowledge is conceptualized and formalized (e.g., by means of an ontology) in order to support diversified and automated knowledge processing (e.g., reasoning) performed by a machine. Moreover, through an optimal combination of (cognitive) human reasoning and (automated) machine processing (mimicking reasoning); it becomes possible for humans and machines to share more and more complementary tasks. The spectrum of applications is extremely large and to name a few: corporate portals and knowledge management, e-commerce, e-work, e-business, healthcare, e-government, natural language understanding and automated translation, information search, data and services integration, social networks and collaborative filtering, knowledge mining, business intelligence and so on. From a social and economic perspective, this emerging technology should contribute to growth in economic wealth, but it must also show clear cut value for everyday activities through technological transparency and efficiency. The penetration of Semantic Web technology in industry and in services is progressing slowly but accelerating as new success stories are reported. In this chapter we present ongoing work in the cross-fertilization between industry and academia. In particular, we present a collection of application fields and use cases from enterprises which are interested in the promises of Semantic Web technology. The use cases are focused on the key knowledge processing components that will unlock the deployment of the technology in industry. The chapter ends with the presentation of the current state of the technology and future trends as seen by prominent actors in the field.
Published: 2008

20. Towards the Composition of Stateful and Independent Semantic Web Services

Author: Freddy Lecue, Alexandre Delteil, Alain Léger, Six, Grégory, Département Systèmes Multi-Agents (SMA-ENSMSE), École des Mines de Saint-Étienne (Mines Saint-Étienne MSE), and Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Centre G2I
Subjects: Web standards, medicine.medical_specialty, business.industry, Computer science, Distributed computing, computer.software_genre, Social Semantic Web, Stateful firewall, Scalability, medicine, Semantic Web Stack, Web service, business, WS-Policy, Semantic Web, computer, Web modeling, ComputingMilieux_MISCELLANEOUS
Abstract: Most of the work on automated semantic Web service composition has focused so far on two main levels of composition i.e., functional level and process level composition (respectively FLC and PLC from now). The former level of composition considered Web services as atomic components that can be executed in a single request-response step whereas the latter level studies in more details the protocol and the behavioural features of Web services. Since PLC i.e., a time and particularly space consuming level of composition makes difficult the scalability of composition-based applications, it seems interesting to restrict the composition of stateful but (only) independent Web services. Such a restriction make possible the composition of a large number of Web services in industrial scenarios, the whole with convincing results. In this paper we suggest to study the advantages to apply FLC together with β-composition in order to perform an automated end to end composition of stateful and independent services. In particular we focus on computational complexity results concerning the two models of composition i.e., the well-known PLC vs. the newest FLC+β-composition. Moreover we prove that FLC is an interesting and necessary level of composition to significantly reduce computational complexity not only in space but also in time.
Published: 2008

21. Singular perturbation analysis of the buckling of circular cylindrical shells

Author: Alain Léger, Radhi Abdelmoula, Laboratoire de Mécanique et d'Acoustique [Marseille] (LMA ), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM), and Leger, Alain
Subjects: Singular perturbation, Asymptotic analysis, Critical load, [PHYS.MECA.STRU] Physics [physics]/Mechanics [physics]/Structural mechanics [physics.class-ph], Explicit formulae, Mechanical Engineering, 010102 general mathematics, Mathematical analysis, General Physics and Astronomy, Boundary (topology), 02 engineering and technology, 01 natural sciences, Boundary layer, 020303 mechanical engineering & transports, [PHYS.MECA.STRU]Physics [physics]/Mechanics [physics]/Structural mechanics [physics.class-ph], 0203 mechanical engineering, Buckling, Mechanics of Materials, [SPI.MECA.STRU]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Structural mechanics [physics.class-ph], General Materials Science, [SPI.MECA.STRU] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Structural mechanics [physics.class-ph], Boundary value problem, 0101 mathematics, ComputingMilieux_MISCELLANEOUS, Mathematics
Abstract: This paper deals with the buckling of thin cylindrical shells with very large Batdorf parameters under external pressure. We first perform a simplified analysis from which we obtain explicit formulae for the critical load. An asymptotic analysis is carried out with a view to determining the effects of the boundary conditions on the critical loads and buckling shapes. The inverse of the Batdorf parameter is the convenient small parameter of the analysis. Among the whole set of boundary conditions, the axial boundary conditions are found to be have crucially important at the first order. This analysis also shows the existence of boundary layers in which the remaining boundary conditions are only significant at the second order, at the very most.
Published: 2008

22. DL Reasoning and AI Planning for Web Service Composition

Author: Alexandre Delteil, Alain Léger, Freddy Lecue, Six, Grégory, Département Systèmes Multi-Agents (SMA-ENSMSE), École des Mines de Saint-Étienne (Mines Saint-Étienne MSE), and Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Centre G2I
Subjects: Theoretical computer science, Knowledge representation and reasoning, Programming language, Computer science, computer.software_genre, GeneralLiterature_MISCELLANEOUS, Description logic, Automated planning and scheduling, Automated reasoning, Situation calculus, Web service, computer, Semantic Web, Logic programming, ComputingMilieux_MISCELLANEOUS
Abstract: We claim that a key feature for correct and effective web service composition, and one that has largely been ignored,is the joint consideration of (semantic) causal links and causal laws, respectively in area of description logics (DL) and AI planning. In this paper we propose a means of specifying both causal links and laws into Web service composition by integrating DL reasoning and situation calculus. To this end an augmented and adapted version of the logic programming language Golog i.e., sclGolog is presented as a natural formalism not only for reasoning about the latter links and laws, but also for automatically composing services. sclGolog operates as an offline interpreter that supports n-ary sensing actions to retrieve conditional compositions of services. Lastly sclGolog has been implemented and tested in the context of telecommunication scenarios.
Published: 2008

23. Mathematical justification of the obstacle problem in the case of a shallow shell

Author: Bernadette Miara, Alain Léger, Laboratoire de Mécanique et d'Acoustique [Marseille] (LMA ), Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM), Modélisation et Simulation Numérique (MOSIM), École Supérieure d'Ingénieurs en Électronique et Électrotechnique, and Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Mechanical Engineering, 010102 general mathematics, Mathematical analysis, 74B99 - 74K25 - 74M15, Unilateral contact, Elasticity (physics), [SPI.MECA.SOLID]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Solid mechanics [physics.class-ph], 16. Peace & justice, 01 natural sciences, 010101 applied mathematics, Sobolev space, [PHYS.MECA.STRU]Physics [physics]/Mechanics [physics]/Structural mechanics [physics.class-ph], Mechanics of Materials, [SPI.MECA.STRU]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Structural mechanics [physics.class-ph], Obstacle, Obstacle problem, [PHYS.MECA.SOLID]Physics [physics]/Mechanics [physics]/Solid mechanics [physics.class-ph], Shallow shell, General Materials Science, Equilibrium problem, 0101 mathematics, Signorini problem, ComputingMilieux_MISCELLANEOUS, Mathematics
Abstract: This paper deals with the asymptotic formulation and justification of a mechanical model for a shallow shell in frictionless unilateral contact with an obstacle. The first three parts of the paper concern the formulation of the equilibrium problem. Special attention is paid to the contact conditions, which are usual within two or three dimensional elasticity, but which are not so usual in shell theories. Lastly the limit problem is formulated in the main part of the paper and a convergence result is presented. Two points are worth stressing here. First, we point out that unlike classical bilateral shell models justifications, the functional framework of the present analysis involves cones. Secondly, while the cones result from a positivity condition on the boundary as long as the thickness parameter is finite, leading to a Signorini problem in the Sobolev space H1, the cone results from a positivity condition in the domain, giving rise to a so-called obstacle problem in the Sobolev space H2 at the limit.
Published: 2008

24. Mass loss from 'Hot Jupiters'—Implications for CoRoT discoveries, Part II: Long time thermal atmospheric evaporation modeling

Author: Yu. N. Kulikov, Magali Deleuil, D. Langmayr, T. Penz, Nikolai V. Erkaev, Helmut Lammer, Alain Léger, Giuseppina Micela, Cesare Cecchi-Pestellini, Helfried K. Biernat, Pierre Barge, Franck Selsis, INAF - Osservatorio Astronomico di Palermo, Istituto Nazionale di Astrofisica (INAF), Institute of Computational Modelling, Russian Academy of Sciences [Moscow] (RAS), Polar Geophysical Institute of Russian Academy of Sciences (PGI), Space Research Institute of Austrian Academy of Sciences (IWF), Austrian Academy of Sciences (OeAW), INAF - Osservatorio Astronomico di Palermo (OAPa), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire aquitain des sciences de l'univers (OASU), Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Marseille (LAM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), and Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES)
Subjects: Physics, 010504 meteorology & atmospheric sciences, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Astronomy and Astrophysics, Astrophysics, 7. Clean energy, 01 natural sciences, Exoplanet, Atmosphere, 13. Climate action, Space and Planetary Science, 0103 physical sciences, Tidal force, Hot Jupiter, Astrophysics::Solar and Stellar Astrophysics, Roche lobe, Astrophysics::Earth and Planetary Astrophysics, Thermosphere, 010303 astronomy & astrophysics, Planetary mass, Stellar evolution, 0105 earth and related environmental sciences
Abstract: We investigate the efficiency of the atmospheric mass loss due to hydrodynamic blow-off over the lifetime of the exoplanet HD209458b by studying numerically its hydrogen wind for host star X-ray and EUV (XUV) fluxes between 1 and 100 times that of the present Sun. We apply a time-dependent numerical algorithm which is able to solve the system of hydrodynamic equations straight through the transonic point of the flow including Roche lobe effects. The mass loss rates are calculated as functions of the absorbed energy in the thermosphere. Depending on the heating efficiency for a hydrogen-rich thermosphere the maximum temperature obtained in our study at 1.5 R pl by neglecting IR cooling is about 5000–10,000 K for heating efficiencies of 10% and 60%, respectively. We find that the upper atmosphere of HD209458b experiences hydrodynamic blow-off even at such low temperatures if one does not neglect gravitational effects caused by the proximity of the planet to its Roche lobe boundary. Depending on the heating efficiency, we find from the solution of the hydrodynamic equations of mass, momentum, and energy balance that energy-limited mass loss rate estimations overestimate the realistic mass loss rate at present time for HD209458b by several times. Using the maximum heating efficiency for hydrogen–rich atmospheres of 60% we find that HD209458b may experience an atmospheric mass loss rate at present time of about 3.5 × 10 10 g s - 1 . The mass loss rate evolves to higher values for higher XUV fluxes expected during the early period of the planet's host star evolution, reaching values of several times 10 12 g s - 1 . The integrated mass loss is found to be between 1.8% and 4.4% of the present mass of HD209458b. We found that the influence of the stellar tidal forces on atmospheric loss (the Roche lobe effect) is not significant at 0.045 AU. For a similar exoplanet, but at closer orbital distances ⩽ 0.02 AU , the combined effect of the Roche lobe and the high XUV radiation result in much higher thermal loss rates of about 2.6 × 10 11 g s - 1 and even more for early stages. This leads to a total loss over 4 Gyr of 27.5% of the planetary mass.
Published: 2008

25. Critical oscillations of mass-spring systems due to nonsmooth friction

Author: Alain Léger, Elaine Pratt, Michel Saint Jean, Laboratoire de Mécanique et d'Acoustique [Marseille] (LMA ), Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM), and Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Bilateral contact, Computation, 02 engineering and technology, Interval (mathematics), [SPI.MECA.SOLID]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Solid mechanics [physics.class-ph], 01 natural sciences, 0203 mechanical engineering, Simple (abstract algebra), 0103 physical sciences, [PHYS.MECA.SOLID]Physics [physics]/Mechanics [physics]/Solid mechanics [physics.class-ph], Mass-spring systems, Contact dynamics, 010301 acoustics, ComputingMilieux_MISCELLANEOUS, [PHYS.MECA.VIBR]Physics [physics]/Mechanics [physics]/Vibrations [physics.class-ph], Physics, Nonsmooth dynamics, Mechanical Engineering, [SPI.MECA.VIBR]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Vibrations [physics.class-ph], Mechanics, [SPI.MECA]Engineering Sciences [physics]/Mechanics [physics.med-ph], Shock absorber, Coulomb friction, 020303 mechanical engineering & transports, Trajectory, Benchmark (computing), Constant (mathematics)
Abstract: International audience; Critical values of the parameters governing the dynamics of simple systems appear when Coulomb friction is not regularized. We explore such systems using a method based on the fact that under constant or analytical data the trajectory exists, is unique and is also sufficiently regular. In fact these properties justify elementary analytical computations on successive time intervals where the condition used to connect the solution from one interval to the other is due to the regularity. Although the systems are simple the dynamics turn out to be quite complex and thus furnish an interesting benchmark for contact dynamics numerical codes. Among other possible applications we choose to present here how to use a mass-spring chain with Coulomb friction to slow down in a progressive and regular manner an oncoming mass with a given initial velocity.
Published: 2008

26. Stability of equilibrium states in a simple system with unilateral contact and Coulomb friction

Author: Stéphanie Basseville, Alain Léger, Laboratoire de Mécanique et d'Acoustique [Marseille] (LMA ), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), École des Mines de Paris, and Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)
Subjects: Cauchy problem, Well-posed problem, Unilateral contact, Discrete dynamics, Mechanical Engineering, Mathematical analysis, Time evolution, 02 engineering and technology, [PHYS.MECA]Physics [physics]/Mechanics [physics], [SPI.MECA]Engineering Sciences [physics]/Mechanics [physics.med-ph], 01 natural sciences, Stability (probability), Mechanical system, 020303 mechanical engineering & transports, Classical mechanics, Coulomb friction, 0203 mechanical engineering, Equilibrium thermodynamics, Simple (abstract algebra), 0103 physical sciences, Klarbring’s system, 010301 acoustics, Stability, Mathematics
Abstract: International audience; The aim of this paper is to study the stability of equilibrium states in a mechanical system involving unilateral contact with Coulomb friction. Since the assumptions made in classical stability theorems are not satisfied with this class of systems, we return to the basic definitions of stability by studying the time evolution of the distance between a given equilibrium and the solution of a Cauchy problem where the initial conditions are in a neighborhood of the equilibrium. It was recently established that the dynamics is well posed in the case of analytical data. In the present study, we focus in particular on the stability of the equilibrium states under a constant force and deal only with a simple mass-spring system in $\mathbb{R}^2$.
Published: 2006

27. Exploring the dynamics of a simple system involving Coulomb friction

Author: Elaine Pratt, Alain Léger, Laboratoire de Mécanique et d'Acoustique [Marseille] (LMA ), Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM), C.M. Soarez and al, Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), and Pratt, Elaine
Subjects: Physics, [PHYS.MECA.STRU] Physics [physics]/Mechanics [physics]/Structural mechanics [physics.class-ph], Computation, Work (physics), Dynamics (mechanics), Range (mathematics), Classical mechanics, Amplitude, [PHYS.MECA.STRU]Physics [physics]/Mechanics [physics]/Structural mechanics [physics.class-ph], Spring (device), Simple (abstract algebra), [SPI.MECA.STRU]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Structural mechanics [physics.class-ph], [SPI.MECA.STRU] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Structural mechanics [physics.class-ph], Uniqueness
Abstract: The work presented here consists in an exhaustive study of a simple mass-spring system involving Coulomb friction. The aim was to gain some insight into the behaviour of a chain of masses in frictionnal contact. If it is simple to explicit the analytical solution of a single mass system, the analytical solution for a two mass system is already far more complicated. We thus consider two masses linked by a spring in bilateral contact with Coulomb friction and submitted to an external force applied onto one of the masses. The existence, uniqueness and regularity of the dynamics of the system is established through a recent paper [1]. Once the uniqueness is ensured it is simple to exhibit the explicit solution for certain values of the external force (i.e. when the amplitude of the force is either small or large). When the amplitude of the external force belongs to a certain intermediate range the dynamics turns out to be more interesting. The solution can be calculated analytically, however as the computation becomes rapidly tiresome, we use a symbolic calculus tool to compute a solution corresponding to a given external force.
Published: 2006

28. On automating Web services discovery

Author: Alain Léger, Mohand-Said Hacid, Christophe Rey, Farouk Toumani, Boualem Benatallah, Computer Science and Engineering [Sydney] (CSE), University of New South Wales [Sydney] (UNSW), Base de Données (BD), Laboratoire d'InfoRmatique en Image et Systèmes d'information (LIRIS), Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-École Centrale de Lyon (ECL), Université de Lyon-Université Lumière - Lyon 2 (UL2)-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Université Lumière - Lyon 2 (UL2), France Télécom Recherche & Développement (FT R&D), France Télécom, Laboratoire d'Informatique, de Modélisation et d'optimisation des Systèmes (LIMOS), SIGMA Clermont (SIGMA Clermont)-Université d'Auvergne - Clermont-Ferrand I (UdA)-Ecole Nationale Supérieure des Mines de St Etienne-Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP), Université Lumière - Lyon 2 (UL2)-École Centrale de Lyon (ECL), Université de Lyon-Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Lumière - Lyon 2 (UL2)-École Centrale de Lyon (ECL), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), and Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Université d'Auvergne - Clermont-Ferrand I (UdA)-SIGMA Clermont (SIGMA Clermont)-Ecole Nationale Supérieure des Mines de St Etienne (ENSM ST-ETIENNE)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Service (systems architecture), Information retrieval, Computer science, business.industry, Service discovery, Context (language use), 02 engineering and technology, Ontology (information science), computer.software_genre, World Wide Web, Description logic, Web Services Discovery, Knowledge base, Hardware and Architecture, 020204 information systems, 0202 electrical engineering, electronic engineering, information engineering, Ontology, 020201 artificial intelligence & image processing, [INFO]Computer Science [cs], Web service, business, computer, Information Systems
Abstract: International audience; One of the challenging problems that Web service technology faces is the ability to effectively discover services based on their capabilities. We present an approach to tackling this problem in the context of description logics (DLs). We formalize service discovery as a new instance of the problem of rewriting concepts using terminologies. We call this new instance the best covering problem. We provide a formalization of the best covering problem in the framework of DL-based ontologies and propose a hypergraph-based algorithm to effectively compute best covers of a given request. We propose a novel matchmaking algorithm that takes as input a service request (or query) Q and an ontology T of services and finds a set of services called a “best cover” of Q whose descriptions contain as much common information with Q as possible and as little extra information with respect to Q as possible. We have implemented the proposed discovery technique and used the developed prototype in the context of the Multilingual Knowledge Based European Electronic Marketplace (MKBEEM) project.
Published: 2005

29. Nulling interferometry for the Darwin Mission: polychromatic laboratory test bench

Author: Frank Brachet, Alain Labèque, B. Pellet, Marc Ollivier, Alain Léger, Thierry Lépine, Veronique Hervier, Claude Lizambert, Bruno Chazelas, Claude Valette, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, Wavefront, Test bench, business.industry, Laser, Exoplanet, law.invention, Interferometry, Optics, Achromatic lens, law, Astronomical interferometer, business, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], High dynamic range
Abstract: The Darwin mission is a project of the European Space Agency that should allow around 2015 the search for extrasolar planets and a spectral analysis of their potential atmospheres in order to detect gases and particularly tracers of life. The basic concept of the instrument is a Bracewell nulling interferometer. It allows high angular resolution and high dynamic range. However, this concept, proposed 25 years ago, is very difficult to implement with high rejection factor and has to be demonstrated in laboratory before being applied in space. Theoretical and numerical approaches of the question highlight strong difficulties : - The need for very clean and homogeneous wavefronts, in terms of intensity, phase and polarisation distribution ; - The need for achromatic optical devices working in a wide spectral range (typically 6 to 18 microns for the space mission). A solution to the first point is the optical filtering which has been successfully experimentally demonstrated at 10 microns using a single mode laser. We focus now on the second point and operate a test bench working in the near infrared, where the background constraints are reduced. We present this test bench and the first encouraging results in the 2-4 microns spectral range. We particularly focus on recent optical developments concerning achromatic component, and particularly the beam combiners and the phase shifter, which are keypoints of the nulling interferometry principle. Finally, we present the future of this experimental demonstration, in the thermal infrared, covering the real and whole spectral range of Darwin.
Published: 2004

30. Sur le flambage plastique de l'éprouvette cruciforme

Author: Michel Potier-Ferry, Alain Léger, Alain Cimetière, Laboratoire de Mécanique et d'Acoustique [Marseille] (LMA ), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), and Leger, Alain
Subjects: Marketing, 020303 mechanical engineering & transports, 0203 mechanical engineering, Strategy and Management, Media Technology, General Materials Science, 02 engineering and technology, [SPI.MECA]Engineering Sciences [physics]/Mechanics [physics.med-ph], [SPI.MECA] Engineering Sciences [physics]/Mechanics [physics.med-ph], 021001 nanoscience & nanotechnology, 0210 nano-technology, ComputingMilieux_MISCELLANEOUS
Abstract: Resume On construit un potentiel de vitesses grace a l'introduction d'une serie d'hypotheses de comportement, dont on commente l'interpretation physique. Introduit dans les equations quasi-statiques, ce potentiel permet de rediscuter le probleme generique du flambage plastique de l'eprouvette cruciforme. On obtient sur l'axe du parametre de charge un intervalle dont tous les points sont des points de bifurcation. Ce resultat est qualitativement interessant d'un point de vue d'analyse spectrale. En effet, il etait jusqu'a present admis que l'existence d'un tel continuum est la consequence de la presence de discontinuites de modules dans le comportement, alors qu'ici tout est tres regulier. Pour citer cet article : A. Cimetiere et al., C. R. Mecanique 332 (2004).
Published: 2004

31. A New Family of Planets ? Öcean Planets\'

Author: Alain Labèque, Helmut Lammer, Claude Valette, D. Despois, Marc Ollivier, Frank Brachet, Dimitri Mawet, Christophe Sotin, Franck Selsis, Bruno Chazelas, Tristan Guillot, Alain Léger, Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Cosmologie, Astrophysique Stellaire & Solaire, de Planétologie et de Mécanique des Fluides (CASSIOPEE), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire aquitain des sciences de l'univers (OASU), and arXiv, Import
Subjects: Physics, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Astrophysics (astro-ph), Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy, Astronomy and Astrophysics, [SDU.ASTR] Sciences of the Universe [physics]/Astrophysics [astro-ph], Astrophysics, Space exploration, Exoplanet, Physics::Geophysics, Astrobiology, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], [PHYS.ASTR.CO] Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Space and Planetary Science, Planet, Biosignature, Terrestrial planet, Astrophysics::Solar and Stellar Astrophysics, Darwin (spacecraft), Ocean planet, Astrophysics::Earth and Planetary Astrophysics, Planetary mass
Abstract: A new family of planets is considered which is between rochy terrestrial planets and gaseous giant ones: "Ocean-Planets". We present the possible formation, composition and internal models of these putative planets, including that of their ocean, as well as their possible Exobiology interest. These planets should be detectable by planet detection missions such as Eddington and Kepler, and possibly COROT (lauch scheduled in 2006). They would be ideal targets for spectroscopic missions such as Darwin/TPF., 15 pages, 3 figures submitted to Icarus notes (10 july 2003)
Published: 2004

32. Ultrasonic Wave Propagation in Non Homogeneous Media

Author: Alain Leger, Marc Deschamps, Alain Leger, and Marc Deschamps
Subjects: Ultrasonic waves--Congresses, Ultrasonic testing--Congresses, Inhomogeneous materials--Nondestructive testing--Congresses
Abstract: Non Destructive Testing and Non Destructive Evaluation using Ultrasounds covers an important field of applications and requires a wide range of fundamental theoretical, numerical and experimental investigations. In the present volume, the reader will find some relevant research results on wave propagation in complex materials and structures which are concerned with today's problems on composites, bonding, guided waves, contact or damage, imaging and structural noise. The fifth meeting of the Anglo-French Research Group on'Wave propagation in non homogeneous media with a view to Non Destructive testing'was held in Anglet, France, June 2-6, 2008.
Published: 2009

33. Investigation of the equilibrium states and their stability for a simple model with unilateral contact and Coulomb friction

Author: Stéphanie Basseville, Elaine Pratt, Alain Léger, Pratt, Elaine, Laboratoire de Mécanique et d'Acoustique [Marseille] (LMA ), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)
Subjects: Physics, Lyapunov stability, [PHYS.MECA.STRU] Physics [physics]/Mechanics [physics]/Structural mechanics [physics.class-ph], Mechanical Engineering, Numerical analysis, Stiffness, Unilateral contact, Stability (probability), Instability, Mechanical system, [PHYS.MECA.STRU]Physics [physics]/Mechanics [physics]/Structural mechanics [physics.class-ph], Classical mechanics, Exponential stability, [SPI.MECA.STRU]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Structural mechanics [physics.class-ph], medicine, [SPI.MECA.STRU] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Structural mechanics [physics.class-ph], medicine.symptom, ComputingMilieux_MISCELLANEOUS
Abstract: We are interested in the stability properties of the equilibrium states of a simple mechanical system with unilateral contact and Coulomb friction. First, we give a complete description of the set of solutions that the equilibrium problem may have, depending on the stiffness coefficients, on the external forces and on the friction coefficient. In the second part, we present the stability properties of all these equilibrium states, obtained by appropriate numerical experiments.
Published: 2003

34. Exo-planet detection with the COROT space mission. I. A multi-transit detection criterion

Author: Pascal Bordé, Daniel Rouan, Alain Léger, Departement de recherche SPAtiale (DESPA), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and arXiv, Import
Subjects: Physics, 010504 meteorology & atmospheric sciences, Stellar population, Detection threshold, Astrophysics (astro-ph), General Physics and Astronomy, Astronomy, FOS: Physical sciences, Astrophysics, Star (graph theory), Space (mathematics), 01 natural sciences, Galaxy, Exoplanet, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], [PHYS.ASTR.CO] Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Transit (astronomy), Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract: We present a detection criterion for exo-planets to be used with the space mission COROT. This criterion is based on the transit method, which suggests the observation of star dimming caused by partial occulations by planetary companions. When at least three transits are observed, we show that a cross-correlation technique can yield a detection threshold, thus enabling the evaluation of the number of possible detections, assuming a model for the stellar population in the Galaxy., Comment: 7 pages, 4 figures
Published: 2001

35. Etude des performances d'un banc interférométrique en frange noire dans le cadre de la préparation de la mission Darwin

Author: Gabor, Pavel, Institut d'astrophysique spatiale (IAS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Sud - Paris 11 (UP11), Université Paris Sud - Paris XI, Alain Léger(alain.leger@ias.u-psud.fr), Darwin, and TPFI
Subjects: nulling interferometry, infrared instrumentation, achromatic phase shifters, planètes extrasolaires, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], extrasolar planets, déphaseurs achromatiques, optical path difference stabilisation, haute résolution angulaire, interférométrie en frange noire, stabilisation de la différence de marche optique, instrumentation infrarouge, high angular resolution
Abstract: Preparations for a future interferometric flagship space mission (Darwin, TPF-I) are under way in order to study Earth-like extrasolar planets in the habitable zones of their parent stars, and more particularly to estimate the proportion of such exoplanets with atmospheric compositions suggesting the presence of biotic photosynthesis. Nulling interferometry operating in the spectral band between 6 and 18 µm may allow distinguishing the emissions of the exoplanet from those of its star and the ambient diffuse sources. The thesis summarises the experimental work performed on the SYNAPSE test bed at the Institut d'Astrophysique Spatiale in Orsay. The bench was tested in the K band, from 2.0 to 2.5 µm, as well as with a laser at 3.39 µm. The results confirm the trend observed by other research groups, viz., the performance is better in monochromatic light than in broadband (nulling ratios of 1E-5 monochromatic, and 3E-4 broad band). Extensive experimental study of this phenomenon is described. In addition to these efforts aiming at a better grasp of nulling interferometry as such, we tested an Achromatic Phase Shifter prototype (a key element in broadband nulling) based on the through-focus principle. We developed a technique of optical path difference stabilisation, where interferometrically combined flux is measured while dithering the optical path difference. We reached stability levels comparable to those required for the future space mission.; Une future mission spatiale (Darwin, TPF-I) est en préparation pour étudier les planètes extrasolaires telluriques dans les zones habitables respectives de leurs étoiles, notamment, pour établir combien, parmi ces exoplanètes, ont une composition atmosphérique indiquant la présence de la photosynthèse biotique. Travaillant dans la bande spectrale de 6 à 18 m, l'interfèrométrie en frange noire doit permettre de distinguer le flux lumineux de l'exoplanète de celui de son étoile ainsi que des sources diffuses. La thèse résume les travaux expérimentaux conduits sur le banc Synapse à l'Institut d'Atrophysique Spatiale à Orsay. Le banc a été testé dans la bande K, de 2.0 à 2.5 µm, ainsi qu'avec une source laser à 3.39 µm. Les fibres optiques monomodes sont employées comme filtres du front d'onde. Le banc utilise deux paires (une dans chacun des deux bras) de prismes dispersifs qui servent de compensateur du chromatisme et de d´ephaseur achromatique. Les résultats confirment la tendance observée par d'autres équipes : les performances sont meilleures en lumière monochromatique qu'en bande large (taux d'extinction : 1E-5 monochromatique et 3E-4 bande large). Des études expérimentales extensives de ce phénomène sont décrites. A part ces travaux portant sur le principe de l'interférométrie en frange noire, nous avons testé un prototype du déphaseur achromatique basé sur le passage par un foyer optique. Nous avons d´eveloppé une technique pour stabiliser la différence de marche, mesurant le flux recombiné en modulant la différence de marche. Nous avons obtenu des niveaux de stabilité comparables à ceux qui sont nécessaires pour la future mission spatiale.
Published: 2009

36. A study of the performance of a nulling interferometer testbed preparatory to the Darwin mission

Author: Gabor, Pavel, Gabor, Pavel, Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Paris Sud - Paris XI, Alain Léger(alain.leger@ias.u-psud.fr), Darwin, and TPFI
Subjects: nulling interferometry, achromatic phase shifters, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], déphaseurs achromatiques, optical path difference stabilisation, haute résolution angulaire, interférométrie en frange noire, stabilisation de la différence de marche optique, [SDU.ASTR] Sciences of the Universe [physics]/Astrophysics [astro-ph], infrared instrumentation, planètes extrasolaires, extrasolar planets, instrumentation infrarouge, high angular resolution
Abstract: Preparations for a future interferometric flagship space mission (Darwin, TPF-I) are under way in order to study Earth-like extrasolar planets in the habitable zones of their parent stars, and more particularly to estimate the proportion of such exoplanets with atmospheric compositions suggesting the presence of biotic photosynthesis. Nulling interferometry operating in the spectral band between 6 and 18 µm may allow distinguishing the emissions of the exoplanet from those of its star and the ambient diffuse sources. The thesis summarises the experimental work performed on the SYNAPSE test bed at the Institut d'Astrophysique Spatiale in Orsay. The bench was tested in the K band, from 2.0 to 2.5 µm, as well as with a laser at 3.39 µm. The results confirm the trend observed by other research groups, viz., the performance is better in monochromatic light than in broadband (nulling ratios of 1E-5 monochromatic, and 3E-4 broad band). Extensive experimental study of this phenomenon is described. In addition to these efforts aiming at a better grasp of nulling interferometry as such, we tested an Achromatic Phase Shifter prototype (a key element in broadband nulling) based on the through-focus principle. We developed a technique of optical path difference stabilisation, where interferometrically combined flux is measured while dithering the optical path difference. We reached stability levels comparable to those required for the future space mission., Une future mission spatiale (Darwin, TPF-I) est en préparation pour étudier les planètes extrasolaires telluriques dans les zones habitables respectives de leurs étoiles, notamment, pour établir combien, parmi ces exoplanètes, ont une composition atmosphérique indiquant la présence de la photosynthèse biotique. Travaillant dans la bande spectrale de 6 à 18 m, l'interfèrométrie en frange noire doit permettre de distinguer le flux lumineux de l'exoplanète de celui de son étoile ainsi que des sources diffuses. La thèse résume les travaux expérimentaux conduits sur le banc Synapse à l'Institut d'Atrophysique Spatiale à Orsay. Le banc a été testé dans la bande K, de 2.0 à 2.5 µm, ainsi qu'avec une source laser à 3.39 µm. Les fibres optiques monomodes sont employées comme filtres du front d'onde. Le banc utilise deux paires (une dans chacun des deux bras) de prismes dispersifs qui servent de compensateur du chromatisme et de d´ephaseur achromatique. Les résultats confirment la tendance observée par d'autres équipes : les performances sont meilleures en lumière monochromatique qu'en bande large (taux d'extinction : 1E-5 monochromatique et 3E-4 bande large). Des études expérimentales extensives de ce phénomène sont décrites. A part ces travaux portant sur le principe de l'interférométrie en frange noire, nous avons testé un prototype du déphaseur achromatique basé sur le passage par un foyer optique. Nous avons d´eveloppé une technique pour stabiliser la différence de marche, mesurant le flux recombiné en modulant la différence de marche. Nous avons obtenu des niveaux de stabilité comparables à ceux qui sont nécessaires pour la future mission spatiale.
Published: 2009

37. Proc. 4th ECAI 2008 workshop on Context and ontologies (C&O)

Author: Bouquet, Paolo, Euzenat, Jérôme, Ghidini, Chiara, Mcguinness, Deborah, de Paiva, Valeria, Qi, Gulin, Serafini, Luciano, Shvaiko, Pavel, Wache, Holger, Léger, Alain, Department of Information Engineering and Computer Science (DISI), University of Trento [Trento], Computer mediated exchange of structured knowledge (EXMO), Inria Grenoble - Rhône-Alpes, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Laboratoire d'Informatique de Grenoble (LIG), Université Pierre Mendès France - Grenoble 2 (UPMF)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre Mendès France - Grenoble 2 (UPMF)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS), Fondazione Bruno Kessler [Trento, Italy] (FBK), Stanford Artificial Intelligence Laboratory [Stanford] (SAIL), Stanford University, Palo Alto Research Center (PARC), Xerox Company, Institut für Angewandte Informatik und Formale Beschreibungsverfahren [Karlsruhe] (AIFB), Universität Karlsruhe (TH), Informatica Trentina [Trento], Department of Computer Science - Vrije Universiteit, Vrije Universiteit Brussel (VUB), Orange Labs R&D [Rennes], France Télécom, Paolo Bouquet, Jérôme Euzenat, Chiara Ghidini, Deborah McGuinness, Valeria de Paiva, Gulin Qi, Luciano Serafini, Pavel Shvaiko, Holger Wache, Alain Léger, Laboratoire d'Informatique de Grenoble (LIG), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre Mendès France - Grenoble 2 (UPMF)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre Mendès France - Grenoble 2 (UPMF)-Université Joseph Fourier - Grenoble 1 (UJF)-Inria Grenoble - Rhône-Alpes, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre Mendès France - Grenoble 2 (UPMF)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre Mendès France - Grenoble 2 (UPMF)-Université Joseph Fourier - Grenoble 1 (UJF), Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Laboratoire d'Informatique de Grenoble (LIG ), and Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])
Subjects: [INFO.INFO-WB]Computer Science [cs]/Web, ComputingMilieux_MISCELLANEOUS, [INFO.INFO-AI]Computer Science [cs]/Artificial Intelligence [cs.AI]
Abstract: bouquet2008a; International audience; No abstract available.
Published: 2008

38. Context and ontologies: theory and practice

Author: Shvaiko, Pavel, Euzenat, Jérôme, Léger, Alain, McGuinness, Deborah, Wache, Holger, Department of Information Engineering and Computer Science (DISI), University of Trento [Trento], Computer mediated exchange of structured knowledge (EXMO), Inria Grenoble - Rhône-Alpes, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Orange Labs R&D [Rennes], France Télécom, Stanford Artificial Intelligence Laboratory [Stanford] (SAIL), Stanford University, Department of Computer Science - Vrije Universiteit, Vrije Universiteit Brussel (VUB), Pavel Shvaiko, Jérôme Euzenat, Alain Léger, Deborah McGuinness, Holger Wache, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Laboratoire d'Informatique de Grenoble (LIG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Laboratoire d'Informatique de Grenoble (LIG), Université Pierre Mendès France - Grenoble 2 (UPMF)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre Mendès France - Grenoble 2 (UPMF)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre Mendès France - Grenoble 2 (UPMF)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre Mendès France - Grenoble 2 (UPMF)-Université Joseph Fourier - Grenoble 1 (UJF), Laboratoire d'Informatique de Grenoble (LIG), and Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre Mendès France - Grenoble 2 (UPMF)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre Mendès France - Grenoble 2 (UPMF)-Université Joseph Fourier - Grenoble 1 (UJF)-Inria Grenoble - Rhône-Alpes
Subjects: [INFO.INFO-WB]Computer Science [cs]/Web, ComputingMilieux_MISCELLANEOUS, [INFO.INFO-AI]Computer Science [cs]/Artificial Intelligence [cs.AI]
Abstract: shvaiko2005b; International audience; No abstract available.
Published: 2005

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