Search results for " Statistics"
showing 10 items of 1891 documents
Ecrits sur les processus aléatoires, Analyse spectrale des processus alpha stables
2012
International audience
Frequency composition of traction and tillage forces on a mole plough
1997
International audience
Continuous optimal control sensitivity analysis with AD
2000
In order to apply a parametric method to a minimum time control problem in celestial mechanics, a sensitivity analysis is performed. The analysis is continuous in the sense that it is done in the infinite dimensional control setting. The resulting sufficient second order condition is evaluated by means of automatic differentiation, while the associated sensitivity derivative is computed by continuous reverse differentiation. The numerical results are given for several examples of orbit transfer, also illustrating the advantages of automatic differentiation over finite differences for the computation of gradients on the discretized problem.
Coplanar control of a satellite around the Earth
2001
We investigate the minimum time transfer of a satellite around the Earth. Using an optimal control model, we study the controllability of the system and propose a geometrical analysis of the optimal command structure. Furthermore, in order to solve the problem numerically, a new parametric technique is introduced for which convergence properties are established.
Solving chance constrained optimal control problems in aerospace via Kernel Density Estimation
2017
International audience; The goal of this paper is to show how non-parametric statistics can be used to solve some chance constrained optimization and optimal control problems. We use the Kernel Density Estimation method to approximate the probability density function of a random variable with unknown distribution , from a relatively small sample. We then show how this technique can be applied and implemented for a class of problems including the God-dard problem and the trajectory optimization of an Ariane 5-like launcher.
Seasonal reproducibility and predictability of the West African Monsoon in coupled GCMs
2009
In the framework of the ENSEMBLES FP6 project, an ensemble prediction system based on five different state-of-the-art European coupled models has been developed. This study evaluates the performance of these models for forecasting the West African monsoon (WAM) at the monthly time scale. From simulations started the 1 May of each year and covering the period 1991–2001, the reproducibility and potential predictability (PP) of key parameters of the WAM—rainfall, zonal and meridional wind at four levels from the surface to 200 hPa, and specific humidity, from July to September—are assessed. The Sahelian rainfall mode of variability is not accurately reproduced contrary to the Guinean rainfall …
Construction de Modèles Prédictifs pour l'Analyse des Relations Oiseaux-Paysage
2013
National audience; Cet article présente une comparaison de trois méthodes (Modèles Linéaires Généralisés, Réseaux de Neurones, Machines Vecteurs Supports) et de différentes combinaisons de prétraitements de données (filtrage, arrondi, analyse factorielle, sélection de paramètres). L'objectif de cette comparaison est de définir quel est le processus qui permet de construire le meilleur modèle prédictif, dans le cadre de la prédiction d'abondances d'espèces d'oiseaux à partir de variables décrivant le paysage. Nous comparerons les modèles grâce à l'erreur moyenne absolue et à l'information mutuelle. Cette comparaison a montré qu'aucune technique étudiée ne permet de construire des modèles pré…
Visualizing linguistic variation in a network of Latin documents and scribes
2018
This article explores whether and how network visualization can benefit philological and historical-linguistic study. This is illustrated with a corpus-based investigation of scribes' language use in a lemmatized and morphologically annotated corpus of documentary Latin (Late Latin Charter Treebank, LLCT2). We extract four continuous linguistic variables from LLCT2 and utilize a gradient colour palette in Gephi to visualize the variable values as node attributes in a trimodal network which consists of the documents, writers, and writing locations underlying the same corpus. We call this network the "LLCT2 network". The geographical coordinates of the location nodes form an approximate map, …
Territoires urbains en transition. Monographie d’un quartier populaire en résilience écologique, Editions Universitaires de Dijon, décembre 2015
2015
National audience; Que faites-vous pour la planète? Vous prenez le vélo pour aller travailler? Vous recyclez des tissus pour fabriquer et peut-être vendre des vêtements? Vous avez choisi une pratique sportive durable dans un club près de chez vous? Vous mangez bio? Vous utilisez les réseaux sociaux pour faire connaître vos éco-gestes à vos voisins ou à l'autre bout du monde? Imaginez... A quoi pourrait ressembler un quartier populaire en 2050, si on ne fait rien pour protéger l’environnement ou, à l'inverse, si on fait tout pour le préserver?Une équipe pluridisciplinaire a enquêté durant deux ans, entre 2012 et 2014, auprès de la population d'un de ces quartiers, la Fontaine d'Ouche, en pro…