Search results for " PRIN"
showing 10 items of 1809 documents
Discrete and differential homotopy in circular restricted three-body control
2010
The planar circular restricted three-body problem is considered. The control enters linearly in the equation of motion to model the thrust of the third body. The minimum time optimal control problem has two scalar parameters: The ratio of the primaries masses which embeds the two-body problem into the three-body one, and the upper bound on the control norm. Regular extremals of the maximum principle are computed by shooting thanks to continuations with respect to both parameters. Discrete and di erential homotopy are compared in connection with second order sucient conditions in optimal control. Homotopy with respect to control bound gives evidence of various topological structures of extr…
Optimal control with state constraints and the space shuttle re-entry problem
2003
In this article, we initialize the analysis under generic assumptions of the small \textit{time optimal synthesis} for single input systems with \textit{state constraints}. We use geometric methods to evaluate \textit{the small time reachable set} and necessary optimality conditions. Our work is motivated by the \textit{optimal control of the atmospheric arc for the re-entry of a space shuttle}, where the vehicle is subject to constraints on the thermal flux and on the normal acceleration. A \textit{multiple shooting technique} is finally applied to compute the optimal longitudinal arc.
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.
Fracture of Honeycombs Produced by Additive Manufacturing
2022
Publisher Copyright: © 2021 World Scientific Publishing Europe Ltd. Lattice materials, such as honeycombs, are remarkable in their ability to combine high stiffness, strength and toughness at low density. In addition, the recent and pervasive development of additive manufacturing technologies makes it easier to produce these cellular materials and opens new possibilities to improve their properties by implementing small modifications to their microstructure. Such developments open new opportunities towards the design of new classes of architectured materials. For example, recent computational studies have shown that honeycombs with lattice density gradients have a fracture energy under tens…
Plasma diagnostic tools for ECR ion sources : What can we learn from these experiments for the next generation sources
2019
International audience; The order-of-magnitude performance leaps of ECR ion sources over the past decades result from improvements to the magnetic plasma confinement, increases in the microwave heating frequency, and techniques to stabilize the plasma at high densities. Parallel to the technical development of the ion sources themselves, significant effort has been directed into the development of their plasma diagnostic tools. We review the recent results of Electron Cyclotron Resonance Ion Source (ECRIS) plasma diagnostics highlighting a number of selected examples of plasma density, electron energy distribution, and ion confinement time measurements, obtained mostly with the second-gener…
Field-free molecular alignment induced by elliptically polarized laser pulses: Noninvasive three-dimensional characterization
2007
International audience; An investigation of field-free molecular alignment produced by elliptically polarized laser pulses is reported. Experiments are conducted in CO2 at room temperature. A noninvasive all-optical technique, based on the cross defocusing of a probe pulse, is used to measure the alignment along two orthogonal directions which is sufficient to provide a three-dimensional characterization. The field-free molecular alignment produced by a laser of elliptical polarization is in good agreement in terms of amplitude and shape with theoretical predictions. It turns out to be almost equivalent to the superposition of the effects that one would obtain with two individual cross-pola…
Coherent superposition of current flows in an atomtronic quantum interference device
2015
We consider a correlated Bose gas tightly confined into a ring shaped lattice, in the presence of an artificial gauge potential inducing a persistent current through it. A weak link painted on the ring acts as a source of coherent back-scattering for the propagating gas, interfering with the forward scattered current. This system defines an atomic counterpart of the rf-SQUID: the atomtronics quantum interference device (AQUID). The goal of the present study is to corroborate the emergence of an effective two-level system in such a setup and to assess its quality, in terms of its inner resolution and its separation from the rest of the many-body spectrum, across the different physical regime…
Digital and handcrafting processes applied to sound-studies of archaeological bone flutes
2016
International audience; Bone flutes make use of a naturally hollow raw-material. As nature does not produce duplicates, each bone has its own inner cavity, and thus its own sound-potential. This morphological variation implies acoustical specificities, thus making it impossible to handcraft a true and exact sound-replica in another bone. This phenomenon has been observed in a handcrafting context and has led us to conduct two series of experiments (the first-one using handcrafting process, the second-one using 3D process) in order to investigate its exact influence on acoustics as well as on sound-interpretation based on replicas. The comparison of the results has shed light upon epistemolo…
La généralisation des enquêtes judiciaires et la construction du pouvoir princier dans le duché de Bourgogne (xiie-xiiie siècles)
2011
Ce projet est une étude historique du processus de généralisation de l'enquête judiciaire dans le duché de Bourgogne pendant les xiie et xiiie siècles. À partir de l'analyse des actes de la pratique et de la documentation ducale et papale, on étudiera comment les cours juridiques laïques et ecclésiastiques se sont adaptées aux transformations et innovations juridiques et procédurales à partir du xiie siècle, et surtout au xiiie siècle. Cette recherche s'articule autour de deux perspectives, que l'on ne doit pas considérer séparément. Il s'agit, d'une part, de l'analyse des procédures et leurs liens avec le droit savant, et, d'autre part, des rapports des enquêtes judiciaires avec la constru…
Vix: The Temptation of the City
2019
International audience; Ancient and modern geographers tend to use three criteria to define cities: a population above 5,000 inhabitants, the presence of a variety of activities, and a network connecting them with other establishments. Plato, Herodotus, Pausanias, and many others had preceded them in attempting to establish a paradigm for the city or polis. The Celtic princely seat on Vix-Mont Lassois is considered a coherent and organised entity, consisting of a quasi-urban space. At Vix, the latest investigations (2016‑2019) have revealed remains that suggest the possibility of harbour installations on the banks of the Seine. The notion of urbanisation or proto-urbanisation has been put f…