Search results for "Dynamic"
showing 10 items of 12329 documents
Spontaneous emission of an atom in a dynamical photonic crystal
2014
A structured environment such as a photonic crystal can strongly affect radiative properties of an atomic system, for example the spontaneous emission process. Recently there has been also an increasing interest on dynamical photonic crystal, that is photonic crystals whose dielectric properties change on time. We consider the spontaneous emission of an atom placed inside a photonic crystal with time-dependent properties (dynamical photonic crystal). We investigate the atomic spontaneous emission in two different regimes, weak and strong coupling, assuming a small, periodic and adiabatic perturbation of the crystal. In the weak coupling case, we analytically obtain the spontaneous emission …
Electrophysiological and hemodynamic mismatch responses in rats listening to human speech syllables
2016
International audience; Speech is a complex auditory stimulus which is processed according to several time-scales. Whereas consonant discrimination is required to resolve rapid acoustic events, voice perception relies on slower cues. Humans, right from preterm ages, are particularly efficient to encode temporal cues. To compare the capacities of preterms to those observed in other mammals, we tested anesthetized adult rats by using exactly the same paradigm as that used in preterm neonates. We simultaneously recorded neural (using ECoG) and hemodynamic responses (using fNIRS) to series of human speech syllables and investigated the brain response to a change of consonant (ba vs. ga) and to …
Animated and interactive cartography to improve the understanding of the regional dynamics
2013
International audience
Génération expérimentale de solitons de cut-off dans une ligne électrique non linéaire
2015
National audience; Nous étudions le phénomène de supratransmission dans un milieu non linéaire discret, soumis, à une excitation périodique dont la fréquence appartient à la bande interdite. Nous montrons l’existence d’un seuil de tension au dessus duquel l’instabilité modulationnelle (IM) va se développer dans la ligne, valeur de seuil dépendant de la fréquence d’excitation. Si elle n’empêche pas l’apparition de l’IM par supratransmission, la dissipation présente dans la ligne est un obstacle à la génération des solitons de cut-off, obstacle que nous sommes parvenus à contourner par un choix approprié de l’amplitude de l’excitation.
Typology of pentad circulation anomalies over the Eastern Africa - Western Indian Ocean region, and their relationship with rainfall
2005
International audience; The aim of this study was to classify the most frequently observed atmospheric circula- tion anomaly patterns in eastern Africa and the adjacent Indian Ocean. As an example of the useful- ness of such a classification, the second objective was to test whether these patterns account for intraseasonal rainfall anomalies in the region. A partitioning algorithm, known as dynamical cluster analysis, was therefore applied to the zonal (U)and meridional (V)components of the wind anom- alies, obtained from the NCEP-NCAR Reanalysis R-2 at the pentad (5 d) timescale. The 3 geopoten- tial levels 850, 700 and 200 hPa were combined. Focus is on the transition seasons (March to Ma…
Meson exchange and isobar current effects in nuclear photon scattering
1980
Explicit expressions of meson exchange and isobar current contributions to the nuclear two-photon amplitude are derived in the non-relativistic limit. In connection with this amplitude the requirement of gauge invariance on the photon scattering amplitude and on the nuclear electromagnetic interaction operator is discussed in detail.
Flame atomic absorption analysis of gold in jewelry samples
1990
A new procedure is proposed for the determination of gold by flame atomic absorption in jewelry samples. The method is based on the acid digestion of 10 mg of sample in a microwave oven and on the on-line dilution, using a three-way valve. The dynamic range of the technique is extended to 100 mg/l gold solutions and using a weighted bracketing method for the treatment of the results, accuracy errors lower than 2% can be found in the analysis of real samples as compared with those obtained by fire assay. The method is very fast and implies only little damage to the jewelry samples.
A Divergence-Free High-Resolution Code for MHD
2001
We describe a 2.5D numerical code to solve the equations of ideal magnetohydrodynamics (MHD). The numerical code, based on high-resolution shock-capturing (HRSC) techniques, solves the equations written in conservation form and computes the numerical fluxes using a linearized Riemann solver. A special procedure is used to force the conservation of magnetic flux along the time.
Polymer-polymer interaction, in the presence of a solvent as measured by viscometry
2001
Dilute solution viscometry experiments have been carried out in five ternary polymer systems solvent(1)/polymer(2)/polymer(3). Values of the specific viscosity of polymer (3) in a ‘binary solvent’ formed by polymer(2) + solvent(1) have been used to determine the compatibility of the polymer blends. Krigbaum and Wall formalism has been used to predict compatibility which relies on an interaction parameter that depends on the concentration, weight fraction and molar mass of each polymer. To reduce the dependences and to clarify the criterion of compatibility, a parameter independent of polymer (3) composition and molar mass has been deduced. This parameter shows the same behaviour with polyme…
Critical micellization density: A small-angle-scattering structural study of the monomer-aggregate transition of block copolymers in supercriticalCO2
2000
In this paper we report a small-angle neutron-scattering investigation of micelle formation by the fluorocarbon-hydrocarbon block copolymer, polyvinyl acetate-b-poly (1,1,2,2-tetrahydroperfluoro-octyl acrylate) in supercritical CO{sub 2} (scCO{sub 2}) at 313 K. At high pressure the copolymer is in a monomeric state with a random coil structure, while at low pressure the polymer forms spherical aggregates stable in a wide range of thermodynamic conditions. By profiling pressure, a sharp monomer-micelle transition is obtained due to the tuning of the solvating ability of scCO{sub 2}. We confirm the previous finding that this aggregate-monomer transition is driven by the gradual penetration of…