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Hermant A.,Directorate General of Armaments
Optimal Control Applications and Methods | Year: 2011

This paper deals with the optimal control problem of the atmospheric reentry of a space shuttle with a second-order state constraint on the thermal flux. We solve the problem using the shooting algorithm combined with an homotopy method, which automatically determines the structure of the optimal trajectory (composed of one boundary arc and one touch point). © 2010 John Wiley & Sons, Ltd. Source

Bourlier C.,University of Nantes | Pinel N.,University of Nantes | Kubicke G.,Directorate General of Armaments
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2013

In this article, the fields scattered by coated cylinders, a rough layer, and an object below a rough surface are computed by the efficient propagation-inside-layer-expansion (PILE) method combined with the physical optics (PO) approximation to accelerate the calculation of the local interactions on the non-illuminated scatterer, which is assumed to be perfectly conducting. The PILE method is based on the method of moments, and the impedance matrix of the two scatterers is then inverted by blocks from a Taylor series expansion of the inverse of the Schur complement. Its main interest is that it is rigorous, with a simple formulation and a straightforward physical interpretation. In addition, one of the advantages of PILE is to be able to hybridize methods (rigorous or asymptotic) valid for a single scatterer. Then, in high frequencies, the hybridization with PO allows us to significantly reduce the complexity in comparison to a direct lower-upper inversion of the impedance matrix of the two scatterers without loss in accuracy. © 2013 Optical Society of America. Source

Plestan F.,CNRS Research Institute of Communication and Cybernetics of Nantes | Moulay E.,University of Poitiers | Glumineau A.,CNRS Research Institute of Communication and Cybernetics of Nantes | Cheviron T.,Directorate General of Armaments
Automatica | Year: 2010

This paper proposes a new second-order sliding mode output feedback controller. This is developed in the case of finite sampling frequency and uses only output information in order to ensure desired trajectory tracking with high accuracy in a finite time in spite of uncertainties and perturbations. This new strategy is evaluated in simulations on an academic example. © 2010 Elsevier Ltd. All rights reserved. Source

Bontemps J.-D.,French National Institute for Agricultural Research | Herve J.-C.,Directorate General of Armaments | Dhote J.-F.,Office National des Forets ONF
Forest Ecology and Management | Year: 2010

While forest productivity is usually inferred from height growth indices, retrospective analyses of tree rings have been intensively used to assess long-term trends in forest productivity. However, radial growth is sensitive to the degree of competition between trees and influenced by management practices or local disturbances. Whether radial growth is accurate for diagnosing and quantifying productivity changes remains a debated question. In a previous study (Bontemps et al., 2009), we assessed historical variations in dominant height growth of even-aged stands of common beech in north-eastern France as a proxy for their productivity changes. The analysis was based on a sampling design including 14 pairs of young/old (75/150 yr) neighbour stands growing under the same site conditions. Dominant height was reconstructed from stem analyses and was compared between generations using a statistical modelling procedure. In this analysis, we tested whether radial and height growth of dominant trees may provide compatible indications on long-term trends. We therefore measured and analysed the radial growth of dominant trees at breast height for the same sampled trees. The effects of site, developmental stage, and calendar date were separated by applying a similar modelling approach. Consideration of the developmental stage effect led to the formulation of an original growth equation. Analysis of radial growth revealed: (i) a long-term positive increase; (ii) a magnitude of +50% over the last century; and (iii) growth declines in the 1940s and 1990s. These features were remarkably similar to those reported on dominant height, and indicated that radial growth of dominant trees delivered a sound picture of productivity changes. The radial growth chronology also differed by showing a more acute acceleration phase in the early century, and a recent but significant difference between stand generations. © 2010 Elsevier B.V. All rights reserved. Source

Gilles J.,Directorate General of Armaments | Meyer Y.,Ecole Normale Superieure de Cachan
IEEE Transactions on Image Processing | Year: 2010

In this paper, we present some theoretical results about a structures-textures image decomposition model which was proposed by the second author. We prove a theorem which gives the behavior of this model in different cases. Finally, as a consequence of the theorem we derive an algorithm for the detection of long and thin objects applied to a road networks detection application in aerial or satellite images. © 2006 IEEE. Source

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