Search results for "flux"

Optimal control of the atmospheric arc of a space shuttle and numerical simulations with multiple-shooting method

2005

This article, continuation of previous works, presents the applications of geometric optimal control theory to the analysis of the Earth re-entry problem for a space shuttle where the control is the angle of bank, the cost is the total amount of thermal flux, and the system is subject to state constraints on the thermal flux, the normal acceleration and the dynamic pressure. Our analysis is based on the evaluation of the reachable set using the maximum principle and direct computations with the boundary conditions according to the CNES research project\footnote{The project is partially supported by the Centre National d'Etude Spatiales.}. The optimal solution is approximated by a concatenat…

Une approche géométrique du contrôle optimal de l'arc atmosphérique de la navette spatiale

2002

L'objectif de ce travail est de faire quelques remarques géométriques et des calculs préliminaires pour construire l'arc atmosphérique optimal d'une navette spatiale (problème de rentrée sur Terre ou programme d'exploration de Mars). Le système décrivant les trajectoires est de dimension 6, le contrôle est l'angle de gîte cinématique et le coût est l'intégrale du flux thermique. Par ailleurs il y a des contraintes sur l'état (flux thermique, accélération normale et pression dynamique). Notre étude est essentiellement géométrique et fondée sur une évaluation de l'ensemble des états accessibles en tenant compte des contraintes sur l'état. On esquisse une analyse des extrémales du Principe du …

Un enregistrement des flux sédimentaires sous glaciaires dans le lac du front de la mer de glace (Chamonix-France) : Bilans perspectives

2003

Modelling biogeochemical processes in sediments from the north-western Adriatic Sea: response to enhanced particulate organic carbon fluxes

2018

This work presents the result of a study carried out in the north-western Adriatic Sea, by combining two different types of biogeochemical models with field sampling efforts. A longline mussel farm was taken as a local source of perturbation to the natural particulate organic carbon (POC) downward flux. This flux was first quantified by means of a pelagic model of POC deposition coupled to sediment trap data, and its effects on sediment bioirrigation capacity and organic matter (OM) degradation pathways were investigated constraining an early diagenesis model by using original data collected in sediment porewater. The measurements were performed at stations located inside and outside the ar…

New hypothesis on the ploidy of the hybrid species Phytopthora alni subsp. alni

2012

EA MERS CT3 Affiche (+ résumé mais sans mention de C. Revellin sur le résumé (oubli de C. Husson)); Alder decline caused by the Phytophthora alni complex is one of the most important diseases in natural ecosystems in Europe in the last 20 years. The emergence of Phytophthora alni subsp. alni (Paa), the pathogen responsible for the epidemics, is linked to an interspecific hybridization event between two parental species: Phytophthora alni subsp. multiformis (Pam) and Phytophthora alni subsp. uniformis (Pau). One of these parental species, Pau that has been isolated in several European countries and in North America, specifically in Alaska and Oregon, is exotic to Europe and a diploid species…

Study of yeast-yeast interactions in fermentative medium

2019

Alcoholic fermentation is the main step for winemaking, mainly performed by the yeast Saccharomyces cerevisiae. But other wine yeasts called non-Saccharomyces may contribute to alcoholic fermentation and improve the wine aroma complexity. The recurrent problem with the use of these non-Saccharomyces yeasts is their trend to die off prematurely during alcoholic fermentation, leading to a lack of their interesting aromatic properties searched in the desired wine. This phenomenon appears to be mainly due to interactions with S. cerevisiae. These interactions are most of the time negatives but remain unclear because of the species and strain specific response. That is why several studies focuse…

Semantic-aware news feeds management framework

2010

In the Web, RSS and Atom (feeds) are probably the most popular and highly utilized XML formats which allow web communities, publishing industries, web services, etc. to publish and exchange XML documents. In addition, they allow a user to consume data/information easily without roaming from site to site using software applications. Here, the user registers her favorite feed providers; and each provider sends the list of news items changed since the last download. However, registering a number of feed sources in feed aggregators cause both heterogeneity and information overloading problems. Besides, none of the existing RSS/feed aggregators provide an approach that integrates (merges) feeds …

Upper limit on the cosmic-ray photon fraction at EeV energies from the Pierre Auger Observatory

2009

From direct observations of the longitudinal development of ultra-high energy air showers performed with the Pierre Auger Observatory, upper limits of 3.8%, 2.4%, 3.5% and 11.7% (at 95% c.l.) are obtained on the fraction of cosmic-ray photons above 2, 3, 5 and 10 EeV (1 EeV equivalent to 10(18) eV), respectively. These are the first experimental limits on ultra-high energy photons at energies below 10 EeV. The results complement previous constraints on top-down models from array data and they reduce systematic uncertainties in the interpretation of shower data in terms of primary flux, nuclear composition and proton-air cross-section.

Search for neutrino-induced cascades with five years of AMANDA data

2010

Contains fulltext : 97339.pdf (Publisher’s version ) (Closed access) We report on the search for electromagnetic and hadronic showers ("cascades") produced by a diffuse flux of extraterrestrial neutrinos in the AMANDA neutrino telescope. Data for this analysis were recorded during 1001 days of detector livetime in the years 2000-2004. The observed event rates are consistent with the background expectation from atmospheric neutrinos and muons. An upper limit is derived for the diffuse flux of neutrinos of all flavors assuming a flavor ratio of v(e):v(mu):v(tau) = 1:1:1 at the detection site. The all-flavor flux of neutrinos with an energy spectrum Phi proportional to E(-2) is less than 5.0 x…

Inférence de la résistance du paysage au flux de gènes à l'aide de modèles gravitaires intégrant des variables intra-populationnelles

2021

International audience; Modéliser les mouvements de dispersion nécessite d'associer aux éléments paysagers des valeurs de coût caractérisant leur résistance aux déplacements. En landscape genetics, l'inférence de ces valeurs se fait à partir de mesures de différenciation génétique entre populations. Bien que l'hétérogénéité spatiale des tailles de populations puisse aussi influencer de façon significative la différenciation génétique, les variables intra-populationnelles sont rarement prises en compte dans ce type d'inférence. Nous avons étudié à quel point la prise en compte de ces variables pouvait améliorer l'inférence des coûts. Pour cela, nous avons simulé des flux de gènes entre 60 po…