On the stored and dissipated energies in heterogeneous rate-independent materials. Application to a quasi-brittle energetic material under tensile loading.

International audienceThe present paper is the first part of a work that aims at building a dissipative model of microcrack friction in quasi-brittle energetic materials. The latter is viewed as an assembly of elementary cells containing the most salient features of the heterogeneous microstructure of an energetic material. It is intended here to build an analytical model describing the mechanical and energetic response of such an elementary cell under confined tension. This is achieved by applying a previously published theory that allows for the determination of the amount of dissipated and stored energies in heterogeneous dissipative structures containing microcracks and other dissipative components

A comprehensive revision of the summation method for the prediction of reactor antineutrino fluxes and spectra

The summation method for the calculation of reactor $\bar{\nu}_e$ fluxes and spectra is methodically revised and improved. For the first time, a complete uncertainty budget accounting for all known effects likely to impact these calculations is proposed. Uncertainties of a few percents at low energies and ranging up to 20% at high energies are obtained on the calculation of a typical reactor $\bar{\nu}_e$ spectrum. Although huge improvements have been achieved over the past decade, the quality and incompleteness of the present day evaluated nuclear decay data still limit the accuracy of the calculations and therefore dominate by far these uncertainties. Pushing the $\beta$-decay modeling of the thousands of branches making a reactor $\bar{\nu}_e$ spectrum to a high level of details comparatively brings modest changes. In particular, including nuclear structure calculations in the evaluation of the non-unique forbidden transitions gives a smaller impact than anticipated in past studies. Finally, this new modeling is challenged against state-of-the-art predictions and measurements. While a good agreement is observed with the most recent Inverse Beta Decay measurements of reactor $\bar{\nu}_e$ fluxes and spectra, it is unable to properly describe the reference aggregate $\beta$ spectra measured at the Institut Laue-Langevin High-Flux reactor in the 80s. This result adds to recent suspicions $\beta$ the reliability of these data and preferentially points toward a misprediction of the $^{235}$U $\bar{\nu}_e$ spectrum.Comment: 34 pages, 16 figures. Submitted to PR

Identification d'une loi d'endommagement de plâtre à partir de mesures de champs de déplacements

Le plâtre est aujourd’hui le matériau le plus utilisé en construction. Il est crucial pour les producteurs de plaques de plâtre de fabriquer des panneaux de gypse qui soient légers et qui satisfassent aux tests normatifs. Il faut donc connaître les mécanismes d’endommagement et de rupture de la plaque de plâtre, par exemple lors d’un essai de flexion. Des plaques de plâtre ont été testées en flexion 4 points jusqu'à la rupture. La corrélation d’images numériques (CIN) est utilisée pour suivre la cinématique de l’essai et la dégradation progressive associée. Il est proposé d'identifier le comportement de la plaque de plâtre grâce à une description continue et homogénéisée (de type poutre) où la dégradation progressive de la rigidité de la plaque est décrite par un paramètre d’endommagement. Plusieurs formes algébriques qui décrivent l’évolution de l’endommagement en fonction de la courbure locale de la poutre ont été testées, conduisant à une évaluation comparable de la loi d’endommagement. Une forme algébrique simple avec seuil est choisie pour illustrer les résultats de l'identification. Une procédure d’identification spécifique est présentée où les imperfections expérimentales sont prises en compte. Le processus de rupture de la plaque de plâtre en flexion 4 points est discuté en relation avec la courbe effort-déflexion et les différents champs de déplacement mesurés par CIN. La fissuration du plâtre dans la zone tendue de la poutre est détectée comme étant le premier événement de la séquence conduisant à la rupture de l’échantillon, mais la fissure ne se propage pas dans toute l’épaisseur et ne conduit pas à la rupture brutale de l’échantillon car le papier tendu est capable de supporter le transfert de charge. Juste avant rupture, l’échantillon contient de multiples fissures plus ou moins parallèles à la direction de chargement

Project Final Report – FREEDOM ICT-248891

This document is the final publishable summary report of the objective and work carried out within the European Project FREEDOM, ICT-248891.This document is the final publishable summary report of the objective and work carried out within the European Project FREEDOM, ICT-248891.Preprin

ALTA: Asynchronous Loss Tolerant Algorithms for Grid Computing

International audienceThis paper describes an environment dedicated to the building of efficient scientific applications for the Grid on top of unreliable communication networks. Nowadays, scientific computing appli-cations are usually built on top of reliable communication proto-cols (such as TCP). Nevertheless, the additional cost introduced by the reliability layer is not negligible in wide area network-based grid environments. On the other hand, data loss in communications may have a dramatic impact over the performance – if not over the correctness – of classical parallel algorithms. However, a particular class of parallel iterative algorithms hap-pens to be tolerant to such losses. This is the class of asynchronous iterative algorithms, which are commonly used in large scientific applications. They are particularly prone to a good communica-tion/computation overlap since processors are no more synchro-nized. In this study, we aim at proposing a new architecture suit-able for the development of asynchronous iterative algorithms tolerant to message losses

On the needs and requirements arising from connected and automated driving

Future 5G systems have set a goal to support mission-critical Vehicle-to-Everything (V2X) communications and they contribute to an important step towards connected and automated driving. To achieve this goal, the communication technologies should be designed based on a solid understanding of the new V2X applications and the related requirements and challenges. In this regard, we provide a description of the main V2X application categories and their representative use cases selected based on an analysis of the future needs of cooperative and automated driving. We also present a methodology on how to derive the network related requirements from the automotive specific requirements. The methodology can be used to analyze the key requirements of both existing and future V2X use cases

Towards Massive Connectivity Support for Scalable mMTC Communications in 5G networks

The fifth generation of cellular communication systems is foreseen to enable a multitude of new applications and use cases with very different requirements. A new 5G multiservice air interface needs to enhance broadband performance as well as provide new levels of reliability, latency and supported number of users. In this paper we focus on the massive Machine Type Communications (mMTC) service within a multi-service air interface. Specifically, we present an overview of different physical and medium access techniques to address the problem of a massive number of access attempts in mMTC and discuss the protocol performance of these solutions in a common evaluation framework

Altimetry for the future: Building on 25 years of progress

In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the ‘‘Green” Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments’ development and satellite missions’ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion