Search results for "circular"
showing 10 items of 856 documents
Riemannian metric of the averaged energy minimization problem in orbital transfer with low thrust
2007
Abstract This article deals with the optimal transfer of a satellite between Keplerian orbits using low propulsion and is based on preliminary results of Epenoy et al. (1997) where the optimal trajectories of the energy minimization problem are approximated using averaging techniques. The averaged Hamiltonian system is explicitly computed. It is related to a Riemannian problem whose distance is an approximation of the value function. The extremal curves are analyzed, proving that the system remains integrable in the coplanar case. It is also checked that the metric associated with coplanar transfers towards a circular orbit is flat. Smoothness of small Riemannian spheres ensures global opti…
On local optima in minimum time control of the restricted three-body problem
2016
International audience; The structure of local minima for time minimization in the controlled three-body problem is studied. Several homotopies are systematically used to unfold the structure of these local minimizers, and the resulting singularity of the path associated with the value function is analyzed numerically.
Time Versus Energy in the Averaged Optimal Coplanar Kepler Transfer towards Circular Orbits
2015
International audience; The aim of this note is to compare the averaged optimal coplanar transfer towards circular orbits when the costs are the transfer time transfer and the energy consumption. While the energy case leads to analyze a 2D Riemannian metric using the standard tools of Riemannian geometry (curvature computations, geodesic convexity), the time minimal case is associated to a Finsler metric which is not smooth. Nevertheless a qualitative analysis of the geodesic flow is given in this article to describe the optimal transfers. In particular we prove geodesic convexity of the elliptic domain.
On the optimal control of the circular restricted three body problem
2011
The context of this work is space mechanics. More precisely, we aim at computing low thrust transfers in the Earth-Moon system modeled by the circular restricted three-body problem. The goal is to calculate the optimal steering of the spacecraft engine with respect to two optimization criteria: Final time and fuel consumption. The contributions of this thesis are of two kinds. Geometric, first, as we study the controllability of the system together with the geometry of the transfers (structure of the command) by means of geometric control tools. Numerical, then, different homotopic methods being developed. A two-three body continuation is used to compute minimum time trajectories, and then …
Minimum fuel control of the planar circular restricted three-body problem
2012
The circular restricted three-body problem is considered to model the dynamics of an artificial body submitted to the attraction of two planets. Minimization of the fuel consumption of the spacecraft during the transfer, e.g. from the Earth to the Moon, is considered. In the light of the controllability results of Caillau and Daoud (SIAM J Control Optim, 2012), existence for this optimal control problem is discussed under simplifying assumptions. Thanks to Pontryagin maximum principle, the properties of fuel minimizing controls is detailed, revealing a bang-bang structure which is typical of L1-minimization problems. Because of the resulting non-smoothness of the Hamiltonian two-point bound…
Observation of light-by-light polarization control and stabilization in optical fibre for telecommunication applications
2010
International audience; In many photonics applications, especially in optical fibre based systems, the state of polarization of light remains so far an elusive uncontrolled variable, which can dramatically affect the performances of that systems and which one would like to control as finely as possible. Here, we experimentally demonstrate light-by-light polarization control via a nonlinear effect occurring in single mode optical fibre. We observe a polarization attraction and stabilization of a 10 Gbit/s optical telecommunication signal around 1550 nm. We also validate the potentiality of the device to annihilate very fast nanosecond polarization bursts. This result confirms yet another fas…
Investigating the Viability of Multi-Recycling of Asphalt Mixtures through a Preliminary Binder Level Characterization
2022
The incorporation of reclaimed asphalt (RA) in hot mix asphalt mixtures is widely considered a sustainable solution for road infrastructure development. Under the scope of the circular economy (CE), the multiple recycling capability of RA has to be assessed in order to ensure its performance at each recycling cycle and also its viability with different additives. The performance of asphalt mixtures with RA strongly depends on the type of rejuvenator, binder, and their degree of blending in the mix. For this reason, it is essential to know the properties of the aged binder extracted from RA to better understand its rheological properties and optimal dosage of rejuvenation to design a satisfa…
Agro-tourism Structures, SARS-CoV-2: the Role of Water
2022
The agro-tourism environmental sustainability and its circular economy approaches represent the keys for the future development of the sector and in term of tourist presences, thanks to their growing attractivity. Water is one of the most used inputs in agro-tourism structures for internal (drinking, cooking, cleaning, etc.) and outdoor use (for agriculture and green areas management). In the scientific literature, the outdoor water use was more studied with regard the agro-tourism structures. The aim of the present paper is first to check and understand how the water consumption of an agro-tourism structure is managed and to propose solutions for its reduction, all in agreement with circul…
Circularité de l'information entre patients autour des pratiques alimentaires
2016
International audience; Dans le cadre de cette communication, nous souhaitons étudier la production et le traitement d’informations entre patients atteints du cancer, afin de partager leurs expériences, leurs connaissances à l’intérieur de communautés numériques empiriquement et durablement construites. Pour des patients atteints du cancer la transmission et le partage d’information sont vitaux, tout particulièrement pour ce qui concerne les bonnes pratiques, les pratiques de prévention (Hugol-Gential, 2015). L’alimentation est un paramètre essentiel dans le processus de soin tant au plan physiologique qu’au plan psychologique (Hartwell, 2013). Dans un contexte très important de reprise en …
Evolution des conceptions de l'organisation de l'ADN mitochondrial par des études de la stérilité mâle cytoplasmique des plantes
1985
Notice présente dans BelInra (https://belinra.inra.fr/gestion/catalog.php?categ=isbd&id=83504); il s'agit d'un type de produit dont les métadonnées ne correspondent pas aux métadonnées attendues dans les autres types de produit : DISSERTATION; Evolution des conceptions de l'organisation de l'ADN mitochondrial par des études de la stérilité mâle cytoplasmique des plantes