Phase-Space Volume of Regions of Trapped Motion: Multiple Ring Components and Arcs

The phase--space volume of regions of regular or trapped motion, for bounded or scattering systems with two degrees of freedom respectively, displays universal properties. In particular, sudden reductions in the phase-space volume or gaps are observed at specific values of the parameter which tunes the dynamics; these locations are approximated by the stability resonances. The latter are defined by a resonant condition on the stability exponents of a central linearly stable periodic orbit. We show that, for more than two degrees of freedom, these resonances can be excited opening up gaps, which effectively separate and reduce the regions of trapped motion in phase space. Using the scattering approach to narrow rings and a billiard system as example, we demonstrate that this mechanism yields rings with two or more components. Arcs are also obtained, specifically when an additional (mean-motion) resonance condition is met. We obtain a complete representation of the phase-space volume occupied by the regions of trapped motion.Comment: 19 pages, 17 figure

Méthode de fusion multi-capteurs pour des opérations de suivi de lignes de culture et de traversabilité

Conférence AXEMA-EURAGENG 2017, Paris, FRA, 25-/02/2017 - 25/02/2017International audiencePrecision agriculture vehicles need autonomous navigation in cultures to carry out their tasks, such as planting, maintenance and harvesting in cultures such as vegetable, vineyard, or horticulture. The detection of natural objects like trunks, grass, leaf, or obstacles in front of vehicle in crop row is crucial for safe navigation. Sensors such as LiDAR devices or Time Of Flight cameras (TOF), allow to obtain geometric data in natural environment, using information of an Inertial Measurement Unit (IMU), for measurement accuracy. Fusion of geometric information with a color camera data improves the natural object identification, using some color classification technique, such as Support Vector Machine (SVM), considering two object classes, either solid objects such as crop or tree branch, and other elements like grass, leaf and soil. Agricultural vehicles can use these geometric and colorimetric data in real time, to follow crop rows and detect obstacles while executing various precision agriculture operations. In this application, perception sensors embedded on a light mobile robot were used to detect and identify natural objects in agricultural crops, working in various fields, with or without soil perturbation, with different speeds and several vegetation levels to achieve crop row tracking tasks, from a desired lateral deviation between robot and crop line, or traversability operations which consisted to take a decision in vehicle navigation, according to the size and nature of the detected objects, in front of vehicle. The vehicle could cross or avoid the object, or it must stop, for big solid obstacles

Is Indoor Tanning the Next Tobacco?

Marketers of indoor tanning services have directed major promotional efforts toward young adults, and their tactics in pursuing this market segment have been limited by only weak regulation (Greenman and Jones 2010). Although most young indoor tanners acknowledge the link between skin cancer and tanning, they desire the immediate benefits of a tan and regard skin cancer as a distant threat, something as hard for them to imagine as old age itself (Hillhouse 2011). The authors compare the marketing practices of the indoor tanning industry with the practices of the tobacco industry prior to present day regulations

Spectral statistics of the k-body random-interaction model

We reconsider the question of the spectral statistics of the k-body random-interaction model, investigated recently by Benet, Rupp, and Weidenmueller, who concluded that the spectral statistics are Poissonian. The binary-correlation method that these authors used involves formal manipulations of divergent series. We argue that Borel summation does not suffice to define these divergent series without further (arbitrary) regularization, and that this constitutes a significant gap in the demonstration of Poissonian statistics. Our conclusion is that the spectral statistics of the k-body random-interaction model remains an open question.Comment: 17 pages, no figure

Motion Control of a heterogeneous fleet of mobile robots: Formation control for achieving agriculture task

International audienceLa nécessité de réduire l'impact environnemental des activités agricoles, tout en préservant le niveau de production pour satisfaire la demande croissante des populations nécessite une étude de nouveaux outils de production. Les robots mobiles peuvent constituer une solution prometteuse, puisque les dispositifs autonomes peuvent permettre une augmentation des niveaux de production, tout en préservant l'environnement grâce à leur grande précision. Dans cet article, l'utilisation de plusieurs robots mobiles autonomes pour effectuer l'opération sur le terrain est étudiée. En particulier, les techniques prédictives sont également proposées pour tenir compte des retards induits par des actionneurs à basse altitude. Les capacités de l'approche proposée sont étudiées au moyen d'expériences de la pleine échelle. / The necessity of decreasing the environmental impact of agricultural activities, while preserving the level of production to satisfy growing population demands requires investigation of new production tools. Mobile robots may constitute a promising solution, since autonomous devices may allow increasing production levels, while preserving the environment thanks to their high accuracy. In this paper, the use of several autonomous mobile robots to perform field operation is investigated. In particular, predictive techniques are also proposed to account for delays induced by low-level actuators. Capabilities of the proposed approach are investigated through full scale experiments

Fluctuations of wave functions about their classical average

Quantum-classical correspondence for the average shape of eigenfunctions and the local spectral density of states are well-known facts. In this paper, the fluctuations that quantum mechanical wave functions present around the classical value are discussed. A simple random matrix model leads to a Gaussian distribution of the amplitudes. We compare this prediction with numerical calculations in chaotic models of coupled quartic oscillators. The expectation is broadly confirmed, but deviations due to scars are observed.Comment: 9 pages, 6 figures. Sent to J. Phys.

Level Repulsion in Constrained Gaussian Random-Matrix Ensembles

Introducing sets of constraints, we define new classes of random-matrix ensembles, the constrained Gaussian unitary (CGUE) and the deformed Gaussian unitary (DGUE) ensembles. The latter interpolate between the GUE and the CGUE. We derive a sufficient condition for GUE-type level repulsion to persist in the presence of constraints. For special classes of constraints, we extend this approach to the orthogonal and to the symplectic ensembles. A generalized Fourier theorem relates the spectral properties of the constraining ensembles with those of the constrained ones. We find that in the DGUEs, level repulsion always prevails at a sufficiently short distance and may be lifted only in the limit of strictly enforced constraints.Comment: 20 pages, no figures. New section adde

Effect of phase relaxation on quantum superpositions in complex collisions

We study the effect of phase relaxation on coherent superpositions of rotating clockwise and anticlockwise wave packets in the regime of strongly overlapping resonances of the intermediate complex. Such highly excited deformed complexes may be created in binary collisions of heavy ions, molecules and atomic clusters. It is shown that phase relaxation leads to a reduction of the interference fringes, thus mimicking the effect of decoherence. This reduction is crucial for the determination of the phase--relaxation width from the data on the excitation function oscillations in heavy--ion collisions and bimolecular chemical reactions. The difference between the effects of phase relaxation and decoherence is discussed.Comment: Extended revised version; 9 pages and 3 colour ps figure