Detection And Correction Of Under-/Overexposed Optical Soundtracks By Coupling Image And Audio Signal Processing

International audienceFilm restoration using image processing, has been an active research field during the last years. However, the restoration of the soundtrack has been mainly performed in the sound domain, using signal processing methods, despite the fact that it is recorded as a continuous image between the images of the film and the perforations. While the very few published approaches focus on removing dust particles or concealing larger corrupted areas, no published works are devoted to the restoration of soundtracks degraded by substantial underexposure or overexposure. Digital restoration of optical soundtracks is an unexploited application field and, besides, scientifically rich, because it allows mixing both image and signal processing approaches. After introducing the principles of optical soundtrack recording and playback, this contribution focuses on our first approaches to detect and cancel the effects of under and overexposure. We intentionally choose to get a quantification of the effect of bad exposure in the 1D audio signal domain instead of 2D image domain. Our measurement is sent as feedback value to an image processing stage where the correction takes place, building up a "digital image and audio signal" closed loop processing. The approach is validated on both simulated alterations and real data

Structure and Evolution of the Lunar Procellarum Region as Revealed by GRAIL Gravity Data

The Procellarum region is a broad area on the nearside of the Moon that is characterized by low elevations, thin crust, and high surface concentrations of the heat-producing elements uranium, thorium, and potassium. The Procellarum region has been interpreted as an ancient impact basin approximately 3200 km in diameter, though supporting evidence at the surface would have been largely obscured as a result of the great antiquity and poor preservation of any diagnostic features. Here we use data from the Gravity Recovery and Interior Laboratory (GRAIL) mission to examine the subsurface structure of Procellarum. The Bouguer gravity anomalies and gravity gradients reveal a pattern of narrow linear anomalies that border the Procellarum region and are interpreted to be the frozen remnants of lava-filled rifts and the underlying feeder dikes that served as the magma plumbing system for much of the nearside mare volcanism. The discontinuous surface structures that were earlier interpreted as remnants of an impact basin rim are shown in GRAIL data to be a part of this continuous set of quasi-rectangular border structures with angular intersections, contrary to the expected circular or elliptical shape of an impact basin. The spatial pattern of magmatic-tectonic structures bounding Procellarum is consistent with their formation in response to thermal stresses produced by the differential cooling of the province relative to its surroundings, coupled with magmatic activity driven by the elevated heat flux in the region

Approche numérique du couplage par effets de marée entre transferts thermiques internes et évolution orbitale des corps planétaires

Les effets de marée qui ont lieu au sein de certains corps du Système Solaire et probablement dans un grand nombre des planètes extrasolaires détectées jusqu à présent associent la friction visqueuse produite par la déformation cyclique de leurs enveloppes internes et éventuellement externes (atmosphère et océans) à une modification de leurs paramètres orbitaux. La dissipation d énergie de marée étant fortement dépendante de la rhéologie et donc de la température, il existe naturellement un couplage entre ces effets et les transferts de chaleur au sein des corps planétaires. Cette thèse a été dédiée à la construction d un modèle numérique permettant de simuler de manière cohérente la convection thermique dans un manteau planétaire compressible, à viscosité variable et soumis à un chauffage de marée hétérogène, ainsi que l évolution orbitale du corps. Les équations de conservation pour la dynamique du manteau sont traitées via une méthode en volumes finis dans la géométrie bidimensionnelle d anneau sphérique ; cette dernière permet d approximer des transferts thermiques tridimensionnels sphériques en gardant des temps de calcul raisonnables. En particulier, un solveur mécanique multigrille et un schéma à haute résolution pour l advection de la chaleur ont été implémentés. La dissipation de marée qui influence l évolution orbitale est ensuite évaluée via une solution semi-analytique dérivée au cours de ce travail. Deux applications préliminaires sont présentées pour examiner, d une part, l influence de la compressibilité dans le traitement du problème de convection couplée avec la dissipation de marée et, d autre part, l effet de ce couplage sur l évolution orbitale.Tidal effects that occur in some objects of the Solar System, and probably in a great part of the extrasolar planets detected so far, associate the viscous friction induced by the periodic deformation of their internal, possibly external layers (atmosphere and oceans), to a change of their orbital parameters. Since tidal dissipation strongly depends on rheology, hence on temperature, there is a natural coupling between these effects and heat transfer inside planetary bodies. This thesis was devoted to the building of a numerical model that self-consistently simulates thermal convection in a compressible mantle with variable viscosity and subjected to heterogeneous tidal heating, and the orbital evolution of the body. Conservation equations for mantle dynamics are treated by a finite volume method based on the bi-dimensional spherical annulus geometry; this approach approximates three-dimensional heat transfer while keeping moderate computational time. In particular, a multigrid mechanical solver and a high resolution advection scheme for the heat equation were implemented. The dissipation of tidal energy, which influences orbital evolution, is then computed through a semi-analytical solution derived during this work. Two preliminary applications are presented to investigate, on one hand the influence of compressibility in the treatment of the convection problem coupled with tidal dissipation and, on the other hand the effect of this coupling on orbital evolution.NANTES-BU Sciences (441092104) / SudocSudocFranceF

Climate-driven deposition of water ice and the formation of mounds in craters in Mars’ north polar region

This paper explores the origins and evolution of ice-rich interior mounds found within craters of the north polar region of Mars. We present a systematic study of impact craters above 65°N, and identify 18 craters that have interior mounds. At least 11 of these mounds are composed of water ice and geometric similarities suggest that dune-covered mounds may also have a water ice core. The mounds are found in the deeper craters in the north polar area and we suggest that these form a specific microclimate favorable for mound initiation and growth. It is likely that at least seven of the mounds have evolved as individual outliers, rather than conterminous with the main polar cap. Our observations suggest that the mounds are built up by atmospheric deposition, similar to that of the north polar layered deposits. Using a combination of remote sensing techniques enabling topographic, spectral, radar and image data analyses, we have documented the morphology, composition and stratigraphy of selected mounds. We advance and test four hypotheses for formation of these mounds: artesian outpouring from a deep aquifer, hydrothermal activation of ground ice, remnants of a more extensive polar cap, and atmospheric deposition on ice caps in meteorologically isolated locations. We propose that during periods when the perihelion was located in northern summer (most recently 10–25 ka before present) the microclimate in these craters retarded the sublimation of CO2 and water ice in northern spring, thus creating a cold trap for volatiles released as the seasonal cap retreated. This created a thick enough deposit of water ice to withstand sublimation over the summer and initiate a positive feedback leading to mound-building. Mounds without complete dune-cover may be in dynamic equilibrium with the ambient climate and show evidence of both present-day and past periods of erosion and aggradation. We conclude that the water ice mounds formed in deep impact craters in Mars’ north polar region may contain sensitive records of past polar climate that may enhance our understanding of the CO2–H2O system in the polar regions

GRAIL gravity constraints on the vertical and lateral density structure of the lunar crust

International audienceWe analyzed data from the Gravity Recovery and Interior Laboratory (GRAIL) mission using a localized admittance approach to map out spatial variations in the vertical density structure of the lunar crust. Mare regions are characterized by a distinct decrease in density with depth, while the farside is characterized by an increase in density with depth at an average gradient of ∼35 kg m −3 km −1 and typical surface porosities of at least 20%. The Apollo 12 and 14 landing site region has a similar density structure to the farside, permitting a comparison with seismic velocity profiles. The interior of the South Pole-Aitken (SP-A) impact basin appears distinct with a near-surface low-density (porous) layer 2-3 times thinner than the rest of the farside. This result suggests that redistribution of material during the large SPA impact likely played a major role in sculpting the lunar crust