Orléans, France


Orléans, France
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Iubini S.,CNRS Center for Molecular Biophysics | Boada O.,Telecommunications Institute of Portugal | Omar Y.,Telecommunications Institute of Portugal | Omar Y.,University of Lisbon | And 2 more authors.
New Journal of Physics | Year: 2015

The role of noise in the transport properties of quantum excitations is a topic of great importance in many fields, from organic semiconductors for technological applications to light-harvesting complexes in photosynthesis. In this paper we study a semi-classical model where a tight-binding Hamiltonian is fully coupled to an underlying spatially extended nonlinear chain of atoms. We show that the transport properties of a quantum excitation are subtly modulated by (i) the specific type (local versus non-local) of exciton-phonon coupling and by (ii) nonlinear effects of the underlying lattice. We report a non-monotonic dependence of the exciton diffusion coefficient on temperature, in agreement with earlier predictions, as a direct consequence of the lattice-induced fluctuations in the hopping rates due to long-wavelength vibrational modes. A standard measure of transport efficiency confirms that both nonlinearity in the underlying lattice and off-diagonal exciton-phonon coupling promote transport efficiency at high temperatures, preventing the Zeno-like quench observed in other models lacking an explicit noise-providing dynamical system. © 2015 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Ammar M.R.,French National Center for Scientific Research | Ammar M.R.,UniversitedOrleans | Charon E.,CNRS ENS Geology Laboratory | Charon E.,University Paris - Sud | And 6 more authors.
Spectroscopy Letters | Year: 2011

Polished section of Acapulco meteorite was used for the structural examination of graphitic matter by Raman microspectroscopy. The polishing process was shown to be necessary for the samples, where carbon matter is embedded in metallic phases. However, this process is known to drastically change the Raman spectrum, inducing unacceptable errors in the intrinsic structural characterization of these carbon materials. The deconvolution of spectra shows that the G-band width, related to the only bond stretching of sp2 atoms, gives real structural information, even on polished carbon, whereas the common intensity ratio ID=IG, which is too sensitive to polishing process, has to be avoided. Copyright © Taylor & Francis Group, LLC.

Hellbourg G.,CNRS Nançay Radioastronomy Station | Hellbourg G.,Netherlands Institute for Radio Astronomy | Trainini T.,University of Toulon | Weber R.,CNRS Nançay Radioastronomy Station | And 4 more authors.
European Signal Processing Conference | Year: 2012

Radio astronomical data are increasingly corrupted by human telecommunication activities. Therefore, Radio Frequency Interferences (RFI) mitigation becomes an important step in the data processing flow, in particular for phased radio telescope array. In this framework, the preliminary step is to retrieve the RFI spatial information. This article presents three new techniques in radio astronomy allowing the estimation of the RFI spatial signature. These techniques are based on subspace decomposition of time-lagged correlation matrices or cyclic correlation matrices, and on a Blind Source Separation approach. Compared to classical methods, these approaches improve the quality of the spatial filtering obtained on the raw uncalibrated sky map. © 2012 EURASIP.

All studies during the last six decades have stated that sciomyzid larvae are strictly malacophagous. However, the Afrotropical sciomyzid Sepedonella nana species was found in this study to feed only on the small freshwater oligochaete, Aulophorus furcatus. The divergent oligophagous feeding behaviour of this species was investigated. The physical attributes of the egg, first-, second- and third-instar larvae, and the puparium are described. Four types of sensilla-coeloconicum, trichodeum, chaeticum, and styloconicum-are present with a characteristic distribution on each tagma. Each thoracic segment is distinguished by presence of a pair of Keilin's organ on ventral surface. Each abdominal segment has eleven pairs of the same sensilla types; their variable locations are presented. Population dynamics of the adults are shown from our field investigations in permanent and temporary freshwater biotopes during 1996-2008. The life cycle of the species is presented from our field observations and laboratory experiments. Among the 62 species of Afrotropical Sciomyzidae, this is the eighth species for which life-cycle is entirely resolved. © 2011 Magnolia Press.

Fadlallah Y.,Institute Telecom | Aissa-El-Bey A.,Institute Telecom | Abed-Meraim K.,UniversitedOrleans | Amis K.,Institute Telecom | Pyndiah R.,Institute Telecom
IEEE Wireless Communications Letters | Year: 2013

In this paper we address the decoding problem in the K-user MIMO interference channel assuming an interference alignment (IA) design. We aim to decode robustly the desired signal without having a full Channel State Information (CSI) (i.e. precoders knowledge) at the receivers. We show the equivalency between the IA model and the Semi-Blind Source Separation model (SBSS). Then, we prove that this equivalence allows the use of techniques employed in source separation for extracting the desired signal free of interference, even though dependency exists between some components of the source signal in the SBSS model. Our simulation results illustrate a BER performance very close to the MMSE receiver with full-CSI. © 2013 IEEE.

Le Rousseau J.,UniversitedOrleans | Lebeau G.,University of Nice Sophia Antipolis
ESAIM - Control, Optimisation and Calculus of Variations | Year: 2012

Local and global Carleman estimates play a central role in the study of some partial differential equations regarding questions such as unique continuation and controllability. We survey and prove such estimates in the case of elliptic and parabolic operators by means of semi-classical microlocal techniques. Optimality results for these estimates and some of their consequences are presented. We point out the connexion of these optimality results to the local phase-space geometry after conjugation with the weight function. Firstly, we introduce local Carleman estimates for elliptic operators and deduce unique continuation properties as well as interpolation inequalities. These latter inequalities yield a remarkable spectral inequality and the null controllability of the heat equation. Secondly, we prove Carleman estimates for parabolic operators. We state them locally in space at first, and patch them together to obtain a global estimate. This second approach also yields the null controllability of the heat equation. ©2011 EDP Sciences, SMAI.

Seers P.,École de Technologie Supérieure of Montreal | Foucher F.,UniversitedOrleans | Mounaim-Rousselle C.,UniversitedOrleans
International Journal of Engine Research | Year: 2013

Oxygen-enriched air combustion has been extensively studied, but not for internal-combustion engines. This paper presents how oxygen-enriched intake air influences early flame growth and the combustion process, and looks at how oxygen (O2) enrichment translates into resistance to carbon dioxide (CO2) dilution. The experiments were conducted with an optical single-cylinder engine instrumented with an in-cylinder pressure transducer and a high-speed camera to monitor early flame growth. During the experiments, O2 concentrations were varied from 18% to 29%, while CO2 was varied from 0% to 35%. The main findings are that O2 addition speeds up the combustion process and renders the flame more resistant to CO 2 dilution. It was observed that the amount of CO2 can be significantly increased to reduce the combustion process to a level similar to that with air. Finally, laminar flame speed correlated well with early flame growth and fully developed turbulent combustion periods. © IMechE 2013.

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