Dynamic complex scene analysis with the fractal embedding method

We present a new image sequence analysis method for automatic and real-time extraction of transitory and complex motions in natural scenes. We show how to extract these motions as multidimensional point clusters obtained from the temporal embedding of grey level variations, in five successive steps: embedding, fractal indexing, point chaining, cluster identification and data extraction. We develop the two main algorithms: fractal space filling indexing and chaining in order to access directly to the relevant information. To illustrate our method, we present an automatic system for early smoke source detection through the processing of landscape images by extracting fugitive and various movements within a small spot of pixels affected by the smoke. We show how to modify the embedding technique used to obtain the data points coordinates to produce many other applications for the fractal embedding method, for example the recognition of complex moving or varying shapes objects.Nous présentons une nouvelle méthode d'analyse de séquences d'images adaptée à l'extraction automatique en temps réel de mouvements localisés dans des scènes naturelles. Nous montrons comment extraire ces mouvements sous la forme de voisinages de points formés dans un espace de très grande dimension par le plongement temporel des variations de niveaux de gris des pixels d'une même enveloppe. Nous présentons tout d'abord notre méthode d'extraction rapide des voisinages dans cet espace multidimensionnel. Ses étapes principales sont l'indexation et le chaînage des points : l'indexation des points se fait selon une courbe fractale qui remplit l'espace, et le chaînage des points indexés permet un accès immédiat aux points voisins. Nous validons ensuite la méthode dans le cas du plongement temporel d'enveloppes de pixels rendus dynamiques par la présence de fumée. L'application est un détecteur des feux de forêts capable de faire la distinction entre des enveloppes causées par une source de fumée ou par tout autre phénomène dynamique pouvant apparaître localement dans un paysage. On exploite les propriétés caractéristiques des mouvements fugitifs et diversifiés qui sont causés par les bouffées de fumée, même à l'intérieur de petites enveloppes de pixels. Nous généralisons ensuite les perspectives d'utilisation de la méthode du plongement fractal en envisageant d'autres types d'applications par l'extraction de caractéristiques autres que des mouvements

Activation dimension of EEG :a cue tool with a real time algorithm

This article presents a fast, robust and practical method for direct quantification of brain activity computed on scalp electroencephalogram (EEG) data. This new indicator called Activation Dimension (DA) is based on the well-known correlation dimension D2. The results of DA calculation from several EEG corroborate our claim in the study of activation of EEG by cognitive task, desactivation of EEG during sleep wake cycles and during anesthesia.Cet article présente une nouvelle méthode de quantification directe de l’activité cérébrale enregistrée par électroencéphalographie (EEG), qui présente l’avantage d’être à la fois rapide et bien adaptée à la dynamique de l’EEG. Nous introduisons la notion de dimension d’activation dont le calcul commence comme celui de la dimension de corrélation D2. Les résultats de calcul obtenus pour différents états d’activation pendant une tache cognitive, un état de sommeil ou une anesthésie montrent que la dimension d’activation, que nous allons introduire, est alors un bon estimateur de l’activité cérébrale

Simulations of the solar orbiter spacecraft interactions with the solar wind: effects on RPW and SWA/EAS measurements

International audienceWe present numerical simulations of the future Solar Orbiter spacecraft/plasma interactions performed with the Spacecraft Plasma Interaction System (SPIS) software. This spacecraft, to be launched in October 2018, is dedicated to the Sun observation with in-situ and remote sensing instruments, brought as close as 0.28 A.U. from our star. In this hot and dense environment, the entire satellite will be submitted to high radiations and temperatures (up to 10 Solar constants). Material responses to environment constraints (heat, U.V. flux, photoemission, secondary electron emission under electron impact – SEEE – or under proton impact - SEEP) might bias the scientific instrument measurements. Our interest is focused on two instruments: the Radio and Plasma Waves (RPW) and the Electron Analyzer System (EAS)

Solar wind plasma interaction with solar probe plus spacecraft

International audience3-D PIC (Particle In Cell) simulations of spacecraft-plasma interactions in the solar wind context of the Solar Probe Plus mission are presented. The SPIS software is used to simulate a simplified probe in the near-Sun environment (at a distance of 0.044 AU or 9.5 RS from the Sun surface). We begin this study with a cross comparison of SPIS with another PIC code, aiming at providing the static potential structure surrounding a spacecraft in a high photoelectron environment. This paper presents then a sensitivity study using generic SPIS capabilities, investigating the role of some physical phenomena and numerical models. It confirms that in the near- sun environment, the Solar Probe Plus spacecraft would rather be negatively charged, despite the high yield of photoemission. This negative potential is explained through the dense sheath of photoelectrons and secondary electrons both emitted with low energies (2-3 eV). Due to this low energy of emission, these particles are not ejected at an infinite distance of the spacecraft and would rather surround it. As involved densities of photoelectrons can reach 106 cm-3 (compared to ambient ions and electrons densities of about 7 × 103 cm-3), those populations affect the surrounding plasma potential generating potential barriers for low energy electrons, leading to high recollection. This charging could interfere with the low energy (up to a few tens of eV) plasma sensors and particle detectors, by biasing the particle distribution functions measured by the instruments. Moreover, if the spacecraft charges to large negative potentials, the problem will be more severe as low energy electrons will not be seen at all. The importance of the modelling requirements in terms of precise prediction of spacecraft potential is also discussed

Study and Simulation of Low Energy Plasma Measurement on Solar Orbiter

International audienceThe flux of particles collected by scientific low energy detectors are sensitive to absolute and differential potentials, and may include both ambient and secondary particles emitted by the spacecraft itself. This work presents numerical models of particle detector behaviour on Solar Orbiter, using the SPIS software. The results presented in this paper show the necessity to take into account the spacecraft plasma interactions at the earlier stage of scientific missions' definition, as well as during measurement interpretation. It demonstrates that electrons emitted in the vicinity of the detectors may be the main contributor to low energy electron measurements pollution