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L'utilisation des techniques de nettoyage des marqueteries métalliques par abrasion mécanique a pu entraîner au cours du temps la disparition d’éléments décoratifs tels que la gravure en taille douce. Dans le cadre du projet interdisciplinaire de recherche appliquée à la restauration des meubles Boulle mené avec le musée du Louvre, le C2RMF a développé de nouvelles méthodes de nettoyage par gels de solvants, non dommageables pour la surface, en quantifiant les niveaux d’élimination de l’oxydation. Used over long periods of time, cleaning techniques for metal marquetry involving mechanical abrasion have led to the loss of decorative elements such as line-engraving. As part of the interdisciplinary applied research project undertaken with the Louvre on the restoration of Boulle furniture, the C2RMF developed new methods of cleaning metals with solvent gels, which do not harm the surface but remove discoloured layers.

We revisit binary decision trees from the perspective of partitions of the data. We introduce the notion of partitioning function, and we relate it to the growth function and to the VC dimension. We consider three types of features: real-valued, categorical ordinal and categorical nominal, with different split rules for each. For each feature type, we upper bound the partitioning function of the class of decision stumps before extending the bounds to the class of general decision tree (of any fixed structure) using a recursive approach. Using these new results, we are able to find the exact VC dimension of decision stumps on examples of $\ell$ real-valued features, which is given by the largest integer $d$ such that $2\ell \ge \binom{d}{\lfloor\frac{d}{2}\rfloor}$. Furthermore, we show that the VC dimension of a binary tree structure with $L_T$ leaves on examples of $\ell$ real-valued features is in $O(L_T \log(L_T\ell))$. Finally, we elaborate a pruning algorithm based on these results that performs better than the cost-complexity and reduced-error pruning algorithms on a number of data sets, with the advantage that no cross-validation is required., 79 pages. arXiv admin note: text overlap with arXiv:2010.07374

We introduce the inner theory or, more verbosely, isotropy Lawvere theory functor, which generalizes the isotropy group/monoid by assigning a Lawvere theory of coherently extendable arrows to each object of a category with finite powers. Then, we characterize the inner theory for categories of models of an algebraic (or, more generally, quasi-equational) theory, and note its relationship with a notion of definability for morphisms. Finally, we explore a variety of examples.

We significantly improve the generalization bounds for VC classes by using two main ideas. First, we consider the hypergeometric tail inversion to obtain a very tight non-uniform distribution-independent risk upper bound for VC classes. Second, we optimize the ghost sample trick to obtain a further non-negligible gain. These improvements are then used to derive a relative deviation bound, a multiclass margin bound, as well as a lower bound. Numerical comparisons show that the new bound is nearly never vacuous, and is tighter than other VC bounds for all reasonable data set sizes., Comment: 15 pages (body), 36 pages (appendices), 54 pages (total), 13 figures

International audience; Dans le cadre du projet interdisciplinaire de recherche appliquée à la restauration du mobilier Boulle mené par le musée du Louvre et le C2RMF, un protocole d’évaluation des principales méthodes de nettoyage chimique et mécanique a été élaboré, afin de comparer leur impact sur les parties métalliques et leurs décors gravés. C’est une méthode mixte qui a été jugée la plus efficace en termes de désoxydation et de respect du matériau : l’emploi de gels de solvants permettant un nettoyage chimique, accompagné d’une légère abrasion mécanique complémentaire, offre les résultats les plus convaincants.

International audience; Increasing the temporal resolution and instant coverage of velocity space of space plasma measurements is one of the key issues for experimentalists. Today the top-hat plasma analyzer appears to be the favorite solution due to its relative simplicity and the possibility to extend its application by adding a mass-analysis section and an electrostatic angular scanner. Similarly, great success has been achieved in MMS mission using such multiple top-hat analyzers to achieve unprecedented temporal resolution.An instantaneous angular coverage of charged particles measurements is an alternative approach to pursuing the goal of high time resolution. This was done with FONEMA 4-D and, to a lesser extent, by DYMIO instruments for Mars-96 and with the FIPS instrument for MESSENGER mission. In this paper we describe, along with precursors, a plasma analyzer with a 2π electrostatic mirror that was developed originally for the Phobos-Soil mission with a follow-up in the frame of the BepiColombo mission, and is under development for future Russian missions. Different versions of instrument are discussed along with their advantages and drawbacks.

Dominique Delcourt Present Adress : Director LPC2E UMR 7328 CNRS Orléans; International audience; Observations from the MESSENGER spacecraft have considerably enhanced our understanding of the plasma environment at Mercury. In particular, measurements from the Fast Imaging Plasma Spectrometer (FIPS) provide evidences of a variety of ion species of planetary origin (He+, O+, Na+) in the northern dayside cusp and in the nightside plasma sheet. A more comprehensive view of Mercury's plasma environment will be provided by the Bepi Colombo mission that will be launched in 2018. Onboard the Bepi Colombo MMO spacecraft, the MPPE (Mercury Plasma/Particle Experiment) consortium gathers different sensors dedicated to particle measurements. Among these sensors, the Mass Spectrum Analyzer (MSA) is the instrument dedicated to plasma composition analysis. It consists of a top-hat for energy analysis followed by a Time-Of-Flight (TOF) chamber to derive the ion mass. Taking advantage of the spacecraft rotation, MSA will measure three-dimensional distribution functions in one spin (4 s), from energies characteristic of exospheric populations (in the eV range) up to plasma sheet energies (up to ~38 keV/q). A notable feature of the MSA instrument is that the TOF chamber is polarized with a linear electric field that leads to isochronous TOFs and enhanced mass resolution (typically, m/∆m ≈ 40 for ions with energies up to 13 keV/q). At Mercury, this capability is of paramount importance to thoroughly characterize the wide variety of ion species originating from the planet surface. It is thus anticipated that MSA will provide unprecedented information on ion populations in the Hermean environment and hence improve our understanding of the coupling processes at work.

International audience; The objective of the ICE (Instrument Champ Electrique) experiment on board DEMETER is to provide a nearly continuous survey of the electromagnetic and/or electrostatic waves that may arise from the coupling of seismic activity with the upper atmosphere and ionosphere. To this aim it makes use of 4 spherical electrodes with embedded preamplifiers that are deployed by stacer booms at approximately 4 in from the satellite. Measurements are made over a wide frequency range from DC to 3.175 MHz, subdivided in the signal processing unit in four frequency channels DC/ULF, ELF, VLF and HF. Three axis measurements are available in the DC/ULF range for all modes of operation of DEMETER and in the ELF range in the DEMETER Burst modes. In the VLF and HF ranges and in ELF during DEMETER Survey modes only one axis of measurement is available that can be selected by telecommand. We present in this paper a general description of the instrument and its modes of operation and in-flight performances. The sensitivity is similar to 0.1-0.2 mu V/mHz(1/2) from similar to 100 Hz through the HF range and the dynamical range is > 80 dB in ELF and VLF and about 42 dB in HF. In order to illustrate the instrument capabilities, we briefly describe a number of observations from the first months of operation in various regions along the orbit from the equator to high latitudes.

Le bilan synthétique des activités du laboratoire d'entomologie du CIRAD-FLHOR Martinique est présenté. Les trois principaux thèmes d'études sont annoncés: La lutte intégrée en cultures maraîchères, les travaux de faunistique en verger d'Agrumes, les premières études bibliographiques sur la mouche des fruits Anastrepha obliqua. En maraîchage, une présentation du programme d'étude de Plutella xylostella et de son complexe parasitaire en Martinique initié en février 2000, est faite. Les objectifs et les premiers résultats faunistiques sont mentionnés. Les essais sur la mise au point de méthodes de lutte chimique raisonnée sont présentés avant restitution dans un compte-rendu d'expérimentation. L'étude de lutte raisonnée contre Diaphania hyalinata, la pyrale des cucurbitacées est résumée, ainsi que les perspectives d'études de ce ravageur. Un rapport donnera les résultats d'un essai de mise au point de méthode de lutte (test du Lufénuron, de l'Indoxacarb, du BT, par rapport à un témoin non traité et une référence toxique (Lannat). En diversification fruitière, un inventaire faunistique de l'entomofaune du verger d'Agrumes a été réalisé. Le présent rapport donne les premiers résultats des prospections des ravageurs , de leurs prédateurs et parasitoïdes, avec une estimation de l'efficacité du contrôle biologique endémique pour chaque ravageur. Les perspectives d'études plus approfondies sont données. En matière de mouche de la Goyave Anastrepha obliqua (Tephritidae), une étude bibliographique et les perspectives d'études à lancer sur ce ravageur sont donnés.

BepiColombo Mio (previously called MMO: Mercury Magnetospheric Orbiter) was successfully launched by Ariane 5 from Kourou, French Guiana on October 20, 2018. The Mercury Plasma/Particle Experiment (MPPE) is a comprehensive instrument package onboard Mio spacecraft used for plasma, high-energy particle and energetic neutral atom measurements. It consists of seven sensors including two Mercury Electron Analyzers (MEA1 and MEA2), Mercury Ion Analyzer (MIA), Mass Spectrum Analyzer (MSA), High Energy Particle instrument for electron (HEP-ele), High Energy Particle instrument for ion (HEP-ion), and Energetic Neutrals Analyzer (ENA). Significant efforts were made pre-flight to calibrate all of the MPPE sensors at the appropriate facilities on the ground. High voltage commissioning of MPPE analyzers was successfully performed between June and August 2019 and in February 2020 following the completion of the low voltage commissioning in November 2018. Although all of the MPPE analyzers are now ready to begin observation, the full service performance has been delayed until Mio’s arrival at Mercury. Most of the fields of view (FOVs) of the MPPE analyzers are blocked by the thermal shield surrounding the Mio spacecraft during the cruising phase. Together with other instruments on Mio including Magnetic Field Investigation (MGF) and Plasma Wave Investigation (PWI) that measure plasma field parameters, MPPE will contribute to the comprehensive understanding of the plasma environment around Mercury when BepiColombo/Mio begins observation after arriving at the planet Mercury in December 2025.