Philippe JEAN-PIERRE

---

• Type de publi. : Article dans une revue
• Date de publi. : 01/10/2008
• Auteurs : Charlotte Kounda-KikiJean-François PongePhilippe MoraCorinne Sarthou
• Organismes : Mécanismes adaptatifs : des organismes aux communautés Mécanismes adaptatifs : des organismes aux communautés Biogéochimie et écologie des milieux continentaux Mécanismes adaptatifs : des organismes aux communautés
• Publié dans Pedobiologia le 02/11/2020

---

Résumé : The common development of vegetation and soil is a central issue in plant succession. We hypothesized that areas of woody vegetation decay and accumulation on the ground (zones of destruction or 'micro-chablis') played a role in the successional development of vegetation patches on tropical inselbergs and that disturbance events could be inferred from the analysis of the organic matter accumulated along a successional gradient. The study was conducted in French Guiana (South America). Nine humus profiles (each comprised of a varying number of layers) were selected in shrub thickets (similar to 1 acre each) representative of three vegetation types of the rock savanna: canopies of pure Clusia minor (Clusiaceae), C. minor in mixture with Myrcia saxatilis (Myrtaceae) and zones of destruction. Using a dissecting microscope, a count point optical method for small soil volumes was employed to measure the volume ratio of each kind of humus component (107 categories) in the 62 layers sampled. Micro-morphotogicat data were analysed by correspondence analysis (CA). Humus profiles varied with canopy tree type and revealed traits of past as well. as trends for future plant succession. The lack of OL and OF horizons, and the presence of charred material differentiated the zones of destruction from other humus profiles and confirms the impact of spatially limited fires or lightning strikes in the cyclic development of vegetation patches.

---

Fichiers liés : articlehumus2.pdf

---

Source

---

• Type de publi. : Article dans une revue
• Date de publi. : 01/10/2008
• Auteurs : Tristan FerroirPierre BeckBertrand van de MoortèleMarcel BohnBruno ReynardAlexandre SimionoviciAhmed El GoresyPhilippe Gillet
• Organismes : Laboratoire de Sciences de la Terre Laboratoire de Planétologie de Grenoble Laboratoire de Sciences de la Terre Microsonde Ouest Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement Laboratoire de Sciences de la Terre Bavarian Research Institute of Experimental Geochemistry and Geophysics Laboratoire de Sciences de la Terre
• Publié dans Earth and Planetary Science Letters le 01/11/2020

---

Source

---

• Type de publi. : Article dans une revue
• Date de publi. : 01/10/2008
• Auteurs : Anatoli B. JuditskyPhilippe RigolletAlexandre Tsybakov
• Organismes : Statistique et Modélisation Stochatisque Laboratoire de Probabilités et Modèles Aléatoires Laboratoire de Probabilités et Modèles Aléatoires
• Publié dans Annals of Statistics le 28/10/2020

---

Résumé : Given a collection of $M$ different estimators or classifiers, we study the problem of model selection type aggregation, i.e., we construct a new estimator or classifier, called aggregate, which is nearly as good as the best among them with respect to a given risk criterion. We define our aggregate by a simple recursive procedure which solves an auxiliary stochastic linear programming problem related to the original non-linear one and constitutes a special case of the mirror averaging algorithm. We show that the aggregate satisfies sharp oracle inequalities under some general assumptions. The results allow one to construct in an easy way sharp adaptive nonparametric estimators for several problems including regression, classification and density estimation.

---

Fichiers liés : jrt3.pdf

---

Source

---

• Type de publi. : Article dans une revue
• Date de publi. : 01/10/2008
• Auteurs : Jérôme VialardG. R. FoltzMichael J. McphadenJean-Philippe DuvelClément de Boyer Montégut
• Organismes : Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques Laboratoire de Météorologie Dynamique (UMR 8539)
• Publié dans Geophysical Research Letters le 25/10/2020

---

Résumé : A moored buoy was recently deployed at 8°S, 67°E in the shallow thermocline region of the Indian Ocean known as ''Seychelles-Chagos Thermocline Ridge'' (SCTR), where the Madden Julian Oscillation (MJO) is associated with strong sea surface temperature (SST) variability. We use observations from this mooring to describe the oceanic signature of two MJOs between November 2007 and February 2008. The four-month average upper ocean heat balance was largely between heating by atmospheric forcing (2.0 +/- 0.3°C/month) and a significant cooling by subsurface processes (-2.2 +/- 0.8°C/month), consistent with climatological Ekman pumping in the region. The two MJO events resulted in strong intraseasonal SST variations (1.5 to 2°C in ~20 days) in the SCTR. At the mooring site, atmospheric fluxes dominated the upper ocean heat balance at the MJO timescale, with the net surface heat flux into the ocean decreasing from an average 105 W m^-2 during suppressed phases to 15 W m^-2 during active phases of the MJO. It is difficult to establish if MJO-induced variations of subsurface processes also contributed to the cooling because of large uncertainty in this term. Lateral advection had no systematic fluctuations on MJO timescales, but cannot be neglected at the mooring site.

---

Fichiers liés : 2008GL035238.pdf

---

Source

---

• Type de publi. : Communication dans un congrès
• Date de publi. : 30/09/2008
• Auteurs : Mehdi AlouiniDaniel DolfiT. MerletJean-Pierre HuignardPhilippe DelayeRobert Frey
• Organismes : Institut de Physique de Rennes Thales Research and Technology [Palaiseau] Thales Research and Technology [Palaiseau] Thales Air Systems Thales Research and Technology [Palaiseau] Laboratoire Charles Fabry de l'Institut d'Optique / Manolia Laboratoire Charles Fabry de l'Institut d'Optique / Manolia

---

Résumé : Raman amplification of optically carried RF signals is shown to be a good alternative to erbium-doped-fiber amplification. In the case of continuous RF signal, RIN levels as low as -160 dB/Hz, limited by the laser source, are obtained. Moreover, when the RF signal is no more continuous, such as real radar waveforms, we evidence that Raman amplification overcomes erbium-doped-fiber amplification. Improvement of the pulse-to-pulse RF phase stability of 17 dB is observed. This result is attributed to the nature of Raman amplification, which does not involve transient variations of the population inversion across the whole spectral range covered by radar waveforms.

---

Source

---

• Type de publi. : Pré-publication, Document de travail
• Date de publi. : 25/09/2008
• Auteurs : Christophe MartayanYves FrematRonny BlommeAnthony JonckheereMarcelo BorgesBertrand de BatzBernard LeroyRosanna SordoJean-Claude BouretFabrice MartinsJean ZorecCoralie NeinerYael NazéEvelyne AlecianMichele FloquetAnne-Marie HubertDanielle BriotAnatholy MiroshnichenkoIndrek KolkaPh. SteeThierry LanzGeorges Meynet
• Organismes : Royal Observatory of Belgium = Observatoire Royal de Belgique Galaxies, Etoiles, Physique, Instrumentation Royal Observatory of Belgium = Observatoire Royal de Belgique Royal Observatory of Belgium = Observatoire Royal de Belgique Royal Observatory of Belgium = Observatoire Royal de Belgique Observatoire de la Côte d'Azur Galaxies, Etoiles, Physique, Instrumentation Laboratoire d'études spatiales et d'instrumentation en astrophysique Padova Observatory, Italy Laboratoire d'Astrophysique de Marseille Groupe de Recherche en Astronomie et Astrophysique du Languedoc Institut d'Astrophysique de Paris Galaxies, Etoiles, Physique, Instrumentation Institut d'Astrophysique de Liège, Belgium RMC Kingston, Canada Galaxies, Etoiles, Physique, Instrumentation Galaxies, Etoiles, Physique, Instrumentation Galaxies, Etoiles, Physique, Instrumentation Université de Caroline du Nord à Chapel Hill = University of North Carolina [Chapel Hill] Tartu Observatory Observatoire de la Côte d'Azur Department of Astronomy [College Park] Observatoire Astronomique de l'Université de Genève

---

Résumé : The Gaia satellite will be launched at the end of 2011. It will observe at least 1 billion stars, and among them several million emission line stars and hot stars. Gaia will provide parallaxes for each star and spectra for stars till V magnitude equal to 17. After a general description of Gaia, we present the codes and methods, which are currently developed by our team. They will provide automatically the astrophysical parameters and spectral classification for the hot and emission line stars in the Milky Way and other close Local Group galaxies such as the Magellanic Clouds.

---

Fichiers liés : martayan2_talk.pdf

---

Source

---

• Type de publi. :
• Date de publi. : 25/09/2008
• Auteurs : Pierre GibotChristian MasquelierJean‐marie TarasconStéphane LevasseurPhilippe Carlach
• Organismes : Laboratoire réactivité et chimie des solides - UMR CNRS 7314 UPJV Laboratoire réactivité et chimie des solides - UMR CNRS 7314 UPJV UMICORE Research UMICORE Research

---

Source

---

• Type de publi. : Communication dans un congrès
• Date de publi. : 22/09/2008
• Auteurs : Xing MeiPhilippe DecaudinBao-Gang HuXiaopeng Zhang
• Organismes : Laboratoire Franco-Chinois d'Informatique, d'Automatique et de Mathématiques Appliquées Virtual environments for animation and image synthesis of natural objects Laboratoire Franco-Chinois d'Informatique, d'Automatique et de Mathématiques Appliquées Laboratoire Franco-Chinois d'Informatique, d'Automatique et de Mathématiques Appliquées

---

Résumé : Level set methods have been extensively used to track the dynamical interfaces between different materials for physically based simulation, geometry modeling, oceanic modeling and other scientific and engineering applications. Due to the inherent Eulerian characteristics, interface evolution based on level set usually suffers from numerical diffusion, sharp feature missing and mass loss. Although some effective methods such as Particle Level Set (PLS) and Marker Level Set (MLS) have been proposed to tackle these difficulties, the complicated correction process and the high computational cost pose severe limitations for real-time applications. In this paper we provide an efficient parallel implementation of the Marker Level Set method on latest graphics hardware. Each step of the MLS method is fully mapped on GPU with an innovative combination of different computation techniques. Relying on GPU's parallelism and flexible programmability, the method provides real-time performance for large size 2D examples and moderate 3D examples, which is significantly faster than previous CPU based methods.

---

Fichiers liés : MarkerLevelSetGPU.pdf

---

Source

---

• Type de publi. : Chapître d'ouvrage
• Date de publi. : 18/09/2008
• Auteurs : Charles BostAudrey JaegerW. HuinPhilippe KoubbiLewis G HalseyN. HanuiseY. Handrich
• Organismes : Centre d'Études Biologiques de Chizé Centre d'Études Biologiques de Chizé Centre d'Études Biologiques de Chizé Laboratoire d'océanographie de Villefranche School of Human and Life Sciences Centre d'Études Biologiques de Chizé Institut Pluridisciplinaire Hubert Curien Institut Pluridisciplinaire Hubert Curien

---

Résumé : Seabirds constitute a key group of marine top-predators. While foraging seabirds prey mostly on schooling pelagic fish, crustaceans and squids. Because seabirds distribute over a wide spatial range they are sensitive to physical and biotic changes at several temporal scales. In the last 20 years bio-logging science has revolutionized our knowledge of how seabirds can act as monitors of prey stocks. One of the most interesting applications of data loggers on seabirds is determination of the distribution and availability of prey on which we have little knowledge such as mesopelagic fish, squid, and krill. There are now known to be several variables measurable by data loggers which estimate the number of prey caught by free-ranging seabirds. Such data loggers, in combined deployment on seabirds with time-depth or movement loggers (which record acceleration in one or more dimensions) provide data sets representing dependable indices of prey availability. While knowledge of seabird behaviour continues to improve, we still know little about the relationships between seabird behaviour and prey density/availability. Unravelling these relationships is a key step to calibrating the proxies of prey availability recorded by data loggers. Continuing to develop the use of instrumented seabirds as bio-indicators of marine resources is important in the quest to understand marine ecosystems and the conservation of top-predators.

---

Source

---

• Type de publi. : Communication dans un congrès
• Date de publi. : 17/09/2008
• Auteurs : Jean-Pierre MathieuJonas HoffmannGilles RoehrichPhilippe Mallein
• Organismes : Audencia Business School

---

Source