Search results for "centri"

IM-17: a new zeolitic material, synthesis and structure elucidation from electron diffraction ADT data and Rietveld analysis

2014

International audience; The synthesis and the structure of IM-17, a new germanosilicate with a novel zeolitic topology, prepared hydrothermally with decamethonium as the organic structure directing agent, are reported. The structure of calcined and partially rehydrated IM-17 of chemical formula per unit cell |(H2O)14.4|[Si136.50Ge39.50O352] was solved ab initio using electron diffraction ADT data in the acentric Amm2 (setting Cm2m) space group and refined by the Rietveld method. This new zeolite framework type contains a 3D pore system made of intersecting 12, 10 and 8-ring channels.

Geometric optimal control of elliptic Keplerian orbits

2005

This article deals with the transfer of a satellite between Keplerian orbits. We study the controllability properties of the system and make a preliminary analysis of the time optimal control using the maximum principle. Second order sufficient conditions are also given. Finally, the time optimal trajectory to transfer the system from an initial low orbit with large eccentricity to a terminal geostationary orbit is obtained numerically.

Optimizing Hough transform for fertilizer spreading optical control

2006

International audience; In Europe, centrifugal spreading is a widely used method for agricultural soil fertilization. In this broadcasting method, fertilizer particles fall onto a spinning disk, are accelerated by a vane, and afterward are ejected into the field. To predict and control the spread pattern, a low-cost, embeddable technology adapted to farm implements must be developed. We focus on obtaining the velocity and the direction of fertilizer granules when they begin their flight by means of a simple imaging system. We first show that the outlet angle of the vane is a bounded value and that its measurement provides the outlet velocity of the particle. Consequently, a simple camera un…

A 3-D simulation with virtual stereo rig for centrifugal fertilizer spreading

2012

International audience; Stereovision can be used to characterize of the fertilizer centrifugal spreading process and to control the spreading fertilizer distribution pattern on the ground reference. Fertilizer grains, however, resemble each other and the grain images contain little information on texture. Therefore, the accuracy of stereo matching algorithms in literature cannot be used as a reference for stereo images of fertilizer grains. In order to evaluate stereo matching algorithms applied to images of grains a generator of synthetic stereo particle images is presented in this paper. The particle stereo image generator consists of two main parts: the particle 3D position generator and…

Ressources naturelles et développement dans le monde tropical : les contradictions entre dynamiques écologiques, reproduction sociale et ordre économ…

2013

Natural resources are in the midst of contradictory dynamics. While they are essential to the reproduction of societies and life, actual organization of the world economy subordinates them to logics of accumulation. In addition to the fact that these logics don't take into account (consider) the physical limits inside of which humanity evolves, they induce problematic socio-ecological inequalities at different scales. Indeed, actual international economic order tends to generate ecologically unequal exchanges, which disrupt the development of primary exporting countries and threaten the most vulnerable populations and ecosystems inside of them.Tropics are the typical context in which such c…

Eccentricity in Mervyn Peake’s work

2013

International audience; Ce chapitre analyse l’un des motifs principaux de l’œuvre de Mervyn Peake: l’excentricité et ses modes d’expression textuelle et picturale dans Letters from a Lost Uncle (1948) et Figures of Speech (1954), au sein de l’intertexte formé par les biographies d’excentriques et le nonsense.

Interview in Will Self's radio programme "The Death of the Eccentric" on Radio 4 (Archive 4)https://www.bbc.co.uk/programmes/m0006kt6

2019

Altération des performances neuromusculaires après un exercice physique prolongé. Analyse comparée d'une épreuve de marathon et de triathlon

1998

The aim of this study was to compare the effects of a marathon and a triathlon on isometric and dynamic neuromuscular performances. Seven triathletes took part in 3 experimental situations : a 2 h 15 mn triathlon (TRI) (30 min swimming, 60 min cycling and 45 min running), a 2 h 15 mn marathon (MA) and a 45 min isolated run done at triathlon speed. The results showed a reduction of the isometric endurance time for knee extensor muscles (35 % of maximal voluntary contraction) after TRI (41 ± 24 %) and after MA (59 ± 19 %). The height of rise of the center of gravity of the counter-movement jumps (CMJ) was also significantly lower after MA (-12 ± 1 cm) than after TRI (-2,5 0,5 cm). Kinetic ana…

Building scenarios for a LUTI model : articulation of spaced based models and an agent based model

2013

International audience

Urban Economics in Retrospect: Continuity or Change ?

2000

International audience