ZeChipC: Time Series Interpolation Method Based on Lebesgue Sampling

In this paper, we present an interpolation method based on Lebesgue sampling that could help to develop systems based time series more efficiently. Our methods can transmit times series, frequently used in health monitoring, with the same level of accuracy but using much fewer data. Our method is based in Lebesgue sampling, which collects information depending on the values of the signal (e.g. the signal output is sampled when it crosses specific limits). Lebesgue sampling contains additional information about the shape of the signal in-between two sampled points. Using this information would allow generating an interpolated signal closer to the original one. In our contribution, we propose a novel time-series interpolation method designed explicitly for Lebesgue sampling called ZeChipC. ZeChipC is a combination of Zero-order hold and Piecewise Cubic Hermite Interpolating Polynomial(PCHIP) interpolation. ZeChipC includes new functionality to adapt the reconstructed signal to concave/convex regions. The proposed methods have been compared with state-of-the-art interpolation methods using Lebesgue sampling and have offered higher average performance

No detection of methane on Mars from early ExoMars Trace Gas Orbiter observations

The detection of methane on Mars has been interpreted as indicating that geochemical or biotic activities could persist on Mars today. A number of different measurements of methane show evidence of transient, locally elevated methane concentrations and seasonal variations in background methane concentrations. These measurements, however, are difficult to reconcile with our current understanding of the chemistry and physics of the Martian atmosphere, which-given methane's lifetime of several centuries-predicts an even, well mixed distribution of methane. Here we report highly sensitive measurements of the atmosphere of Mars in an attempt to detect methane, using the ACS and NOMAD instruments onboard the ESA-Roscosmos ExoMars Trace Gas Orbiter from April to August 2018. We did not detect any methane over a range of latitudes in both hemispheres, obtaining an upper limit for methane of about 0.05 parts per billion by volume, which is 10 to 100 times lower than previously reported positive detections. We suggest that reconciliation between the present findings and the background methane concentrations found in the Gale crater would require an unknown process that can rapidly remove or sequester methane from the lower atmosphere before it spreads globally

Martian dust storm impact on atmospheric H₂O and D/H observed by ExoMars Trace Gas Orbiter

Global dust storms on Mars are rare but can affect the Martian atmosphere for several months. They can cause changes in atmospheric dynamics and inflation of the atmosphere, primarily owing to solar heating of the dust. In turn, changes in atmospheric dynamics can affect the distribution of atmospheric water vapour, with potential implications for the atmospheric photochemistry and climate on Mars. Recent observations of the water vapour abundance in the Martian atmosphere during dust storm conditions revealed a high-altitude increase in atmospheric water vapour that was more pronounced at high northern latitudes, as well as a decrease in the water column at low latitudes. Here we present concurrent, high-resolution measurements of dust, water and semiheavy water (HDO) at the onset of a global dust storm, obtained by the NOMAD and ACS instruments onboard the ExoMars Trace Gas Orbiter. We report the vertical distribution of the HDO/H O ratio (D/H) from the planetary boundary layer up to an altitude of 80 kilometres. Our findings suggest that before the onset of the dust storm, HDO abundances were reduced to levels below detectability at altitudes above 40 kilometres. This decrease in HDO coincided with the presence of water-ice clouds. During the storm, an increase in the abundance of H2O and HDO was observed at altitudes between 40 and 80 kilometres. We propose that these increased abundances may be the result of warmer temperatures during the dust storm causing stronger atmospheric circulation and preventing ice cloud formation, which may confine water vapour to lower altitudes through gravitational fall and subsequent sublimation of ice crystals. The observed changes in H2O and HDO abundance occurred within a few days during the development of the dust storm, suggesting a fast impact of dust storms on the Martian atmosphere

Vers une terminologie pour une IA explicable entièrement contextualisée.

International audienc

Une terminologie pour une IA explicable contextualisée

International audienceL'Intelligence Artificielle explicable a connu un gain de popularité ces dernières années, grâce aux nouvelles législations promouvant le « droit à l'explication ». De nombreuses méthodes ont été récemment développées pour aider à comprendre les modèles dits « boîtes noires », mais la définition de ce qu'est une explication n'est pas encore clairement définie. De plus, la communauté s'accorde à dire que de nombreux termes importants n'ont pas de définition consensuelle. Dans cet article, nous passons en revue la littérature et montrons qu'il existe un problème majeur concernant les définitions des termes comme explicabilité ou interprétabilité. Pour résoudre ce problème, nous proposons une terminologie qui prend en compte le contexte d'un système d'IA. Cette terminologie est compatible avec la majorité des définitions vues dans la littérature, de sorte qu'elle puisse servir de base pour les travaux futurs. Nous discutons également des métriques permettant d'évaluer certaines propriétés définies dans cette terminologie

Des ontologies pour construire une architecture prédictive, classifier et expliquer

International audienceExplainable AI is gaining traction because of the widespread use of black box models in the industry. Many explanation methods are proposed to explain models without impacting their design. The literature describes a new architecture where an explainable model interacts with an explanation interface to generate explanations tailored for a user. We propose a novel image classification system that combines an ontology with machine learning models based on this architecture. It uses an ontology to add different labels to the same dataset and generates machine learning models to assess the class of an object and its different properties listed in the ontology. The outputs of these models are added to the ontology to verify that these predictions are consistent, using logical reasoning. The ontology can then be explored to understand the prediction and why it is consistent or not. This system can warn the user when a prediction is uncertain, which will help users to trust it

Combining an explainable model based on ontologies with an explanation interface to classify images

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Multidisciplinary Study of Marine Archives: Reconstruction of Sea-Level, Sediment Yields, Sediment Sources, Paleoclimate, Paleoceanography and Vertical Movement on Margins: Examples from the Western Mediterranean Sea

International audienceThe numerous processes (superficial and deep) occurring on margins, their origins, consequences, interactions and quantifications are only very partially described and understood. The identification of the relative role of factors is sometimes completely contradictory between authors. Here, we showed the results of a long-term multidecadal and multidisciplinary study (using geophysical, geological, stratigraphic, paleontological, geomorphologic, geochemical, microbiological and numerical models) in the Western Mediterranean Sea that acts as a natural laboratory at many different scales. We showed how sediments efficiently recorded at the same time: variations of glacio-eustatic sea-level changes, variations of sediments yield and sources, and also enabled quantifying vertical movements and geodynamic worldwide events but also detailed regional mass transport, turbidites and contourites deposits. They are also an archive of paleoclimatic, palaeoceanographic and diagenetic processes

Hydrothermal fluid flow structures at Solfatara volcano, Somma-Vesuvius volcanic complex and Mt. Etna.

Solfatara (Campi Flegrei):We present the first detailed 3-D Resistivity model of the Solfatara-Pisciarelli area, obtained from numerousERT surveys during the “MED-SUV” Project. This inversion was performed by taking into account 44 000ERT data points, as well as surface e-m resistivity measurements and the magneto-tellurics model from A.Siniscalchi et al. respectively as surface and bottom boundary conditions. The 3-D resistivity structure wellmatches with the CO2 flux, temperature and self-potential variations at the crater surface. This model clearlyhighlights the main geological units of the area (Monte Olibano, Solfatara crypto-dome, layers of eruptivedeposits), and the structures of hydrothermal fluids flow in the Solfatara crater. We particularly focus on theFangaia liquid plume, and the feeding system of Bocca Nuova and Bocca Grande fumaroles. We also presentthe time-lapse resistivity variations measured on the eastern flank of Solfatara that show the dynamics of thisactive hydrothermal system.Somma-Vesuvius:Vesuvius is perhaps the volcano with the highest risk in the world threatening the 800,000 residents living onits slopes. In March 2014 an extensive field work was carried out in the framework of the “MED-SUV”Project. The aim of this survey was to identify the hydrothermal system and its fluid circulation dynamics aswell as the structural boundaries associated to this volcanic complex. A high resolution deep ElectricalResistivity Tomography, 64 electrodes, 40m spacing, was performed along a NW-SE profile, 7km long,coupled with self-potential, temperature (30cm depth), and soil degassing (CO2) with a step of 20m. ERTmeasurements were performed with a Wenner configuration and reached 500m depth. Inside Somma caldera,the resistivity cross-section of Vesuvius cone displays a conductive body (20-100 ohm.m) located beneaththe present-day summit crater and interpreted as its hydrothermal system. This latter is also revealed by thecharacteristic “W” shape of self-potential signal showing with its minima a hydrothermal system of aboutMED-SUV Final MeetingRome 6 | 7 April 2016491,7km in diameter. The top of the hydrothermal system is at about 200-250m below the surface, except alongfour areas characterized by vertical rising of hydrothermal fluids up to the surface. These areas have beenevidenced by temperature anomalies (increase of 6-13°C). The largest structure allowing this preferential fluidflow is the 1906s crater rim, while the two others temperature peaks are located close to the present-dayfumarolic area. In the lower part of Vesuvius cone, outside of the hydrothermal system, it is possible to detecton both side of the edifice, a sub-vertical body of about 800-1000 ohm.m isolated by higher resistivity values(2500-3000 ohm.m). The more conductive body can be associated with a break in slope in the topography andalso to higher CO2 concentration. This structural boundary seems to fit with the 1631s crater rim.Etna:Between June and July 2015 a very deep ERT profile (Pole-Dipole configuration, 40m spacing betweenelectrodes and a remote electrode located at ~10km from the acquisition points) has been performed in theframework of the “MED-SUV” Project. Self-potential (SP), soil gas concentrations (CO2, 222Rn, 220Rn, He,H2 and CH4) and soil temperature (T) measurements were coupled to the ERT profile with a spacing of 20m(except for Rn: 40m). The NE-SW profile crossed Etnas summit craters in the middle of the 5720m ERTtotal length. Six roll along protocols of . of the dispositive (600m out of 2520m tot) have been carried outand, for the first time, a high resolution DC ERT profile reached the noticeable investigation depth of 900mbgl. The results clearly evidence the central shallow hydrothermal system of Mt Etna with large positive SPanomaly, high values of T, 222Rn, CO2, He, H2 and CH4, in the areas where the conductive bodies reach thesurface in correspondence of the summit craters and the 2014 eruptive vents (CO2, 222Rn and T). Structuralboundaries, such as the Elliptic Crater (EC), were highlighted by a sharp decrease of the SP inside the EC.The high activity of 220Rn (Thoron), outside the EC, highlights shallow gas source. The resistive bodyidentified just below the NE crater is probably due to the over-heated plume rising from the top of theshallow feeding system towards the surface