Pressure dependent friction on granular slopes close to avalanche

We investigate the sliding of objects on an inclined granular surface close to the avalanche threshold. Our experiments show that the stability is driven by the surface deformations. Heavy objects generate footprint-like deformations which stabilize the objects on the slopes. Light objects do not disturb the sandy surfaces and are also stable. For intermediate weights, the deformations of the surface destabilize the objects and generate sliding. A characteristic pressure for which the solid friction is minimal is evidenced. Applications to the locomotion of devices and animals on sandy slopes as a function of their mass are proposed

Eye-Sat: A 3U Student CubeSat from CNES Packed with Technology

Eye-Sat will observe the Zodiacal light, the Sun light scattered by interplanetary dust. It is a diffuse and faint white glow. Equipped with its small home-made telescope, this 3U CubeSat will measure the zodiacal light’s intensity and linear polarization ratio. The payload’s optics has a focal length of 50 mm and a diameter of 25 mm for a field of view of +/- 6.5°. Two rotating wheels bear spectral and polarizing filters. For one year Eye-Sat will produce more than 500 GB of data which will be downloaded to the ground thanks to a high data rate X-band link. Moreover, scientific objectives impose severe requirements on the attitude determination and control system such as a 0.25° 3-axis pointing accuracy. To fulfil these requirements, Eye-Sat comprises a star tracker and four reaction wheels. Eye-sat will also welcome new technologies on board to demonstrate their applicability in space environment and to test their in-orbit performances: - C&DH module will combine a dual-core ARM9 microprocessor (CPU frequency up to 1GHz) and a FPGA - Flight software will be based on Time and Space Partitioning technology - S-band TTC transceiver - X-band transmitter for scientific data - Solar panels will be deployed by self-blocking and self-deployable composite hinges - Hold-on and Release Mechanisms based on the thermal knife concept - 3DPlus camera with a CMOS detector from CMOSIS - Innovative black coating from Cilas Eye-Sat is a Student CubeSat which belongs to JANUS, a CNES’ program that supports French Universities in developing their CubeSat projects. The specificity of Eye-Sat is that it has been developed within the French Space Agency since 2012, with more than 200 students involved. After passing a successful qualification review before a board of CNES agents in October 2018, the project team is now in the Assembling, Integration and Validation phase with the flight model. Launch is due on October/November 2019, on a Soyouz rocket from French Guyana, with COSMOS Sky-Med from the Italian Space Agency and Cheops from the European Space Agency

EyeSat: A Great Student Adventure Within the French Space Agency Leading Up to Lessons Learned From Orbit

EyeSat has been a tremendous, challenging and successful student project. With 250 students over 7 years, CNES has achieved to put in orbit a 3U CubeSat that carries tens of state-of-the art innovative nanosatellite subsystems resulting from R&D programs carried out within the French space ecosystem. Launched in December 18, 2019, EyeSat has proved to be fully functional in orbit and has started its mission to map the intensity and the polarization direction of the zodiacal light. Housekeeping data, acquired over the past 5 months, has been analyzed by the team. Precious comparisons have been made between design and simulation results on the one hand and actual data on the other. Now, the private company U-Space, created in 2018, leverages those lessons learned from EyeSat and provides space missions based on high-performance nanosatellites

Reference-less Quality Estimation of Text Simplification Systems

International audienceThe evaluation of text simplification (TS) systems remains an open challenge. As the task has common points with machine translation (MT), TS is often evaluated using MT metrics such as BLEU. However, such metrics require high quality reference data, which is rarely available for TS. TS has the advantage over MT of being a monolingual task, which allows for direct comparisons to be made between the simplified text and its original version. In this paper, we compare multiple approaches to reference-less quality estimation of sentence-level text simplification systems, based on the dataset used for the QATS 2016 shared task. We distinguish three different dimensions: gram-maticality, meaning preservation and simplicity. We show that n-gram-based MT metrics such as BLEU and METEOR correlate the most with human judgment of grammaticality and meaning preservation, whereas simplicity is best evaluated by basic length-based metrics

Episode H5N8 d'influenza aviaire en France en 2016-2017 : quel rôle pour la faune sauvage ?

L'influenza aviaire (IA) est une menace permanente, qui arrive parfois en Europe par le biais des oiseaux migrateurs. Un dispositif de surveillance est en place en permanence pour surveiller les mortalités dans l'avifaune, et particulièrement celles des oiseaux d'eau migrateurs. En octobre 2016, un épisode d'IA H5N8 qui était surveillé depuis sa survenue en République de Touva (Fédération de Russie, avril 2016) s'est déclaré en Europe. Il a entraîné des pertes conséquentes dans certaines populations d'oiseaux sauvages en Europe, ainsi que dans des filières avicoles. La situation en France s'est révélée paradoxale : l'atteinte a été majeure dans la filière avicole de canards gras du Sud- Ouest, mais les cas dans la faune sauvage sont restés peu nombreux et circonscrits. Ce n'est pas faute d'avoir renforcé la surveillance, soit événementielle (analyse des oiseaux trouvés morts) soit active autour des foyers domestiques. Plus de 800 cadavres d'oiseaux sauvages ont été analysés, dont beaucoup d'anatidés, 90 ont été détectés infectés regroupés en 55 cas dans l'avifaune libre et captive, et dix sites stratégiques ont fait l'objet d'une recherche intensifiée des cadavres et n'ont permis de trouver aucun cas positif supplémentaire. Plus de 300 oiseaux commensaux des élevages domestiques foyers ont été analysés et se sont tous révélés négatifs. Les performances du système de surveillance ne semblent pas pouvoir être mises en cause, et il apparaît donc qu'il y a bien eu des différences de circulation du virus par rapport à nos voisins d'outre-Rhin, mal expliquées à ce stade mais la situation en France est similaire à celle observée en Italie et en Espagne cet hiver, et correspond assez bien à l'épisode H5N8 qui avait circulé en Europe fin 2014/début 2015, sans toucher la France. (Résumé d'auteur

Morphological diversity and locomotory instability of the prey of antlions

Nous avons étudié les mécanismes d’interaction entre le piège du fourmilion, une dépression conique dans le sable, et ses proies. Nous avons identifié un spectre optimal de proies, pesant environ 2 à 3 mg, par une expérience d’écologie comportementale sur des fourmis. Les proies plus petites et plus grosses sont moins capturées, pour des raisons différentes. Nous avons également découvert que la compacité du milieu granulaire où les fourmilions construisent influence la probabilité de capture. Le piège garde donc en mémoire l’état du milieu, avec des conséquences sur l’alimentation du prédateur.We studied the interactions between an antlion pit, a conical depression in sand, and its prey. We identified an optimal range of prey size with a behavioural ecology experiment with ants. Prey that are lighter or heavier are less captured, for different causes, than prey of around 2 and 3 mg. We also found that the compaction of the granular medium where antlion built impacts on the probability of capture of prey. The pit so has a memory of the initial state of the immediate soil environment, with consequences for the predator success