Vectorial interpolation using radial-basis-like functions

AbstractThis paper deals with vector field interpolation, i.e., the data are R3 values located in scattered R3 points, while the interpolating function is a function from R3 into R3. In order to take into account possible connections between the components of the interpolant, we derive it by solving a variational spline problem involving the rotational and the divergence of the interpolant, and depending on a parameter ρ significative of the balance of the rotational part and of the divergence part, and on the order m of derivatives of the rotational and divergence involved in the minimized seminorm. We so obtain interpolants whose expression is σ(x) = Σni=1 Φ(x − xi)ai + pm−1(x), where Φ is some 3 × 3 matrix function, pm−1 is a degree m − 1 vectorial polynomial, and where the ai are R3-vectors. Besides, the ai meet a relation generalizing the usual orthogonality to all polynomials of degree at most m − 1. For ρ = 1, we find the usual m-harmonic splines in each component of σ. Numerical examples show the interest of the method, and we compare the so-obtained functions with the ones obtained by Matlab's procedures

Wind and Temperature Networking Applied to Aircraft Trajectory Prediction

International audienceTrajectory prediction estimates the future position of aircraft along their planned trajectories in order to detect potential conflicts and to optimize air space occupancy. This prediction is a critical task in the Air Traffic Control (ATC) process and has been studied for many years. For the future automation processes developed in the SESAR [19], NextGen [15] and CARATS [3] projects, such trajectory prediction will be even more critical. As there is always a deviation between the predicted wind (from the weather forecasts) and the encountered wind, the main longitudinal (along-track) error source between the predicted and the actual trajectory is linked to wind estimation. Even if the main longitudinal (along-track) error source between the predicted and the actual trajectory is linked to wind estimation, temperature wrong estimation may also lead to ETE1 prediction errors. In a previous paper [11] we measured the potential benefit produced by sharing wind measures between aircraft. In the present paper we will try to improve the trajectory prediction by sharing the wind and the temperature information between aircraft. Addressing the temperature came when we noticed that at least the cruising phase of many flight was performed at constant Mach number. Maintaining a given Mach number under changing temperatures equals changing the true air speed. Based on the current performances of Air Traffic Control systems , controllers are able to efficiently detect conflict 20 minutes in advance ; for a larger time horizon (look-ahead time), the induced trajectory prediction uncertainty strongly reduces the reliability of the conflict detection. The goal of this work is to measure the potential benefit produced by sharing wind/temperature measures between aircraft (this concept will be called Wind/Temp Networking (WTN)). To reach this goal, aircraft measure (temperature and pressure) and calculate (wind and density) their local atmospheric data and broadcast them to the other aircraft. Having such distributed weather information, each aircraft is able to compute an enhanced local wind/temperature map as a function of location (3D) and time. These updated wind/temp fields could be shared with other aircraft and/or with ground systems. Using this enhanced weather information, each aircraft is able to improve drastically its own trajectory prediction. This concept has been simulated in the French airspace with 8 000 flights. Comparisons have been investigated on trajectory prediction performances with and without wind/temp networking. Statistics have been conducted in order to measure the benefit of such concept in both time and space dimensions showing higher improvement in high traffic areas, as expected

Optimisation du trafic aérien en tenant compte des conditions météorologiques

National audienceDans le cadre des systèmes de gestion du trafic aérien du futur, nous nous intéressons ici au concept "Free Flight" dans lequel les avions ne sont plus astreints à suivre des trajectoires définies par des routes aériennes et pourraient ainsi rechercher des trajectoires optimisées relativement à un critère de coût. Dans les travaux présentés ici, le choix s'est porté sur la minimisation du temps de vol en exploitant les conditions météorologiques, tout en minimisant la congestion engendrée par l'ensemble des vols.La méthodologie mise en œuvre se déroule en deux étapes. La première consiste à calculer la trajectoire optimale en temps de vol de manière indépendante pour chaque avion. Cette planification est effectuée à l'aide d'un algorithme basé sur la méthode Ordered Upwind. A partir de ces trajectoires, nous calculons une métrique de congestion simple pour nous permettre d'évaluer la complexité du trafic. La métrique choisie ici correspond au nombre d'avions présents dans un voisinage défini à un temps donné.La deuxième étape a pour but de modifier les trajectoires initiales afin de minimiser la congestion globale du trafic. Pour cela, un algorithme de Recuit Simulé est appliqué de la façon suivante. A chaque itération, une trajectoire est tirée aléatoirement. Elle est recalculée, à l'aide de l'algorithme de la première étape, en pénalisant les zones congestionnées pour obtenir la trajectoire optimisée pour le critère pénalisé. Nous réévaluons ensuite la complexité du trafic avec cette nouvelle trajectoire.L'adaptation de l'algorithme Ordered Upwind sur la sphère, nous a permis de travailler avec des données réelles de vent et de trafic sur un espace aérien à l'échelle européenne

Wind-Optimal Path Planning: Application to Aircraft Trajectories

International audienceIn this paper, an algorithm to plan a continuous wind-optimal path is proposed, and simulations are made for aircraft trajectories. We consider a mobile which can move in a two dimensional space. The mobile is controlled only by the heading direction, the speed of the mobile is assumed to be constant. The objective is to plan the optimal path avoiding obstacles and taking into account wind currents. The algorithm is based on Ordered Upwind Method which gives an optimality proof for the solution. The algorithm is then extended to spherical coordinates in order to be able to handle long paths

Le sanwen, de l’époque classique à l’époque moderne

Cet article retrace brièvement l’histoire du sanwen, en insistant sur la variété des écrits qu’il recouvre et sur la difficulté à le définir en tant que genre. À l’époque classique, le wen constituait avec le shi (poésie) la totalité de la littérature lettrée, dont étaient exclus les écrits romanesques et le théâtre. Souvent opposé à la prose fictionnelle (xiaoshuo), il entretient cependant avec elle des rapports complexes, et plus que le caractère non fictionnel, c’est l’engagement personnel de l’auteur qui semble en être la caractéristique essentielle. La Révolution littéraire du début du xxe siècle entraîne une recomposition du paysage littéraire : le sanwen, débarrassé des textes considérés comme non littéraires au sens moderne du terme, devient un des quatre grands genres aux côtés de la poésie, du roman et du théâtre. De nouveaux termes comme zawen ou xiaopinwen apparaissent pour désigner des types spécifiques de prose littéraire. Comme par le passé, les frontières entre fiction et non fiction ne sont pas étanches. Quoi qu’il en soit, le sanwen demeure très prisé pour l’image de profondeur et de distinction qu’il véhicule.This article briefly traces the history of sanwen, emphasizing the variety of writings it covers and the difficulty of defining it as a genre. In the classical period, the wen constituted with the shi (poetry) the whole of the highbrow literature, which did not comprise fiction and theater. Often opposed to fictional prose (xiaoshuo), it nevertheless maintains a complex relationship with the latter, and more than its being non-fictional, it is the personal commitment of the author that seems to be its essential characteristic. The Literary Revolution of the early 20th century entailed a reshaping of the literary landscape: sanwen, from which texts considered non-literary in the modern sense were excluded, became one of the four major genres alongside poetry, fiction and theater. New terms emerged, like zawen or xiaopinwen, to refer to specific types of literary prose. As in the past, the boundaries between fiction and non-fiction are not impervious. However, sanwen is still held in high esteem for the image of depth and distinction it conveys

Wind Loads on Linear Fresnel Reflectors’ Technology: A Numerical Study

AbstractThe wind effect on the Fresnel technology is one of the main design stresses for the metallic structure, primary reflectors, receivers and solar tracking system. Therefore,in order to quantify its impact and compare it to a more mature technology(the Parabolic Trough),a first study of the wind load on a Linear Fresnel Reflector(LFR)collector with an air-stable absorber tube receiver (with protective cover glass) has been undertaken. The drag, lift and momentum coefficients of the receiver and primary reflectors have been calculated using a bi-dimensional CFD model based on the COMSOL Multiphysics® software. The impact of the transversal wind speed has been studied. Moreover, the interaction between the receiver and the primary reflectors has been quantified. Finally, a comparison to Parabolic Trough collectors has been made, which confirms the much lower windload of LFR technology for an equal mirror aperture area, and thus the much lighter structures required for resisting these wind loads and/or the larger operation range with respect to wind speed

Noël Dutrait (ed.): L'Ecriture romanesque et théâtrale de Gao Xingjian.

This volume contains a collection of sixteen papers presented at the conference on the work of Gao Xinjiang, which was organised by the research team on Chinese literature and translation at the University of Provence, and was held on January 28th and 29th 2005. There is a introductory text by Noël Dutrait, who also authored one of the papers, and the volume concludes with a post-script and a selective bibliography of Gao's works available in French. The latter omits, among other items, extra..

Lu Xun, Errances (Wandering)

The vagaries of publishing have seen the simultaneous appearance in France of two complete versions of Lu Xun’s collection Wandering, only seven of whose eleven texts had hitherto been available in French. The one by Sébastian Veg, being considered here, is a scholarly edition, accompanied by copious amounts of critical material in the form of very detailed footnotes and “notes” offering a personal interpretation for each of the short stories. The whole is complemented by the annotated transl..

Aircraft trajectory forecasting using local functional regression in Sobolev space

International audienceThis paper considers the problem of short to mid-term aircraft trajectory prediction, that is, the estimation of where an aircraft will be located over a 10-30 min time horizon. Such a problem is central in decision support tools, especially in conflict detection and resolution algorithms. It also appears when an air traffic controller observes traffic on the radar screen and tries to identify convergent aircraft, which may be in conflict in the near future. An innovative approach for aircraft trajectory prediction is presented in this paper. This approach is based on local linear functional regression that considers data preprocessing, localizing and solving linear regression using wavelet decomposition. This algorithm takes into account only past radar tracks, and does not use any physical or aeronautical parameters. This approach has been successfully applied to aircraft trajectories between several airports on the data set that is one year air traffic over France. The method is intrinsic and independent from airspace structure

De Lu Xun à Deng Tuo : les vicissitudes du zawen dans la Chine maoïste

Si Lu Xun est célébré comme le maître incontesté du zawen, l’essai polémique dans lequel il s’est illustré a été attaqué dès les années 1930 par ceux qui niaient toute valeur littéraire à ces petits textes de circonstance, avant que le contexte de la guerre ne conduise certains critiques de gauche à encourager un type d’écrits plus direct et plus simple. Mais c’est Mao lui-même qui sonnera le glas du zawen à la Lu Xun, en posant des limites explicites aux velléités contestataires des auteurs. L’article examine trois moments au cours desquels des écrivains ont tenté de redonner au zawen toute sa dimension critique : les années 1941 et 1942 à Yan’an, les Cent Fleurs et la période qui a suivi le Grand Bond en avant. Une place particulière est consacrée aux Yanshan yehua et à leur auteur, Deng Tuo, dont la fin tragique couronne des décennies de vicissitudes du zawen.Although Lu Xun is celebrated as the undisputed master of the zawen, the polemical essay for which he became famous was debased in the 1930s by those who denied any literary value to these small occasional texts, before the context of the war led some leftist critics to encourage a more straightforward and plain style of writing. But it was Mao himself who sounded the death knell for the zawen à la Lu Xun, by setting explicit limits to the oppositional stance of the authors. The article examines three moments during which writers attempted to restore the zawen to its full critical dimension: the years 1941 and 1942 in Yan’an, the Hundred Flowers period and the years following the Great Leap Forward. A special place is devoted to Yanshan yehua and its author, Deng Tuo, whose tragic end exemplifies decades of vicissitudes for the zawen