How criticality meets bifurcation in compressive failure of disordered solids

Continuum mechanics describes compressive failure as a standard bifurcation in the response of a material to an increasing load: damage, which initially grows uniformly in the material, localizes within a thin band at failure. Yet, experiments recording the acoustic activity preceding localization evidence power-law distributed failure precursors of increasing size, suggesting that compressive failure is a critical phenomenon. We examine here this apparent contradiction by probing the spatial organization of the damage activity and its evolution until localization during compression experiments of 2D cellular solids. The intermittent damage evolution measured in our experiments is adequately described by a non-stationary depinning equation derived from damage mechanics and reminiscent of critical phenomena. In this description, precursors are damage cascades emerging from the interplay between the material's disorder and the long-range stress redistributions following individual damage events. Yet, the divergence of their characteristic size close to failure, which we observe in our experiments, is not the signature of a transition towards criticality. Instead, the system remains at a fixed distance to the critical point at all stages of the damage evolution. The divergence results from the progressive loss of stability of the material as it is driven towards localization. Thus, our study shows that compressive failure is a standard bifurcation for which the material disorder plays a marginal role. It also shows that precursory activity constitute by-products of the evolution towards localization and can serve to build a predictive method to assess the residual lifetime of structures.Comment: 35 pages, 14 figures including the supplementary informatio

Early Eocene birds from La Borie, southern France

The early Eocene locality of La Borie is located in the village of Saint-Papoul, in southern France. These Eocene flu-vio-lacustrine clay deposits have yielded numerous vertebrate remains. Mammalian taxa found in the fossiliferous levels indicate an age near the reference level MP 8–9, which corresponds to the middle Ypresian, early Eocene. Here we provide a detailed description of the avian remains that were preliminarily reported in a recent study of the vertebrate fauna from La Borie. A maxilla, a quadrate, cervical vertebrae, a femur and two tibiotarsi are assigned to the giant ground bird Gastornis parisiensis (Gastornithidae). These new avian remains add to the fossil record of Gastornis, which is known from the late Paleocene to middle Eocene of Europe, early Eocene of Asia and early Eocene of North America. Gastornis parisiensis differs from the North American Gastornis giganteus in several features, including the more ventral position of the narial openings and the slender orbital process of quadrate. Two tibiotarsi and one tarsometatarsus are assigned to a new genus and species of Geranoididae, Galligeranoides boriensis gen. et sp. nov. So far, this family was known only from the early and middle Eocene of North America. The fossils from La Borie constitute the first record of the Geranoididae in Europe. We show that Gastornis coexisted with the Geranoididae in the early Eocene of both Europe (La Borie) and North America (Willwood Formation). The presence of Geranoididae and the large flightless bird Gastornis on either side of the present-day North Atlantic provides further evidence that a high-latitude land connection existed between Europe and North America in the early Eocene

Coupling Methodology within the Software Platform Alliances

CEA, ANDRA and EDF are jointly developing the software platform ALLIANCES which aim is to produce a tool for the simulation of nuclear waste storage and disposal repository. This type of simulations deals with highly coupled thermo-hydro-mechanical and chemical (T-H-M-C) processes. A key objective of Alliances is to give the capability for coupling algorithms development between existing codes. The aim of this paper is to present coupling methodology use in the context of this software platform.Comment: 7 page

Identification de compatibilités entre tags descripteurs de lieux et apprentissage automatique

International audienceLes travaux présentés dans cet article s'inscrivent dans le paradigme des recherches visant à acquérir des relations sémantiques à partir de folksonomies (ensemble de tags attribués à des ressources par des utilisateurs). Nous expérimentons plusieurs approches issues de l'état de l'art ainsi que l'apport de l'apprentissage automatique pour l'identification de relations entre tags. Nous obtenons dans le meilleur des cas un taux d'erreur de 23,7 % (relations non reconnues ou fausses), ce qui est encourageant au vu de la difficulté de la tâche (les annotateurs humains ont un taux de désaccord de 12%)

Implementation of the IFIP Digital Library in the HAL open publication repository

International audienceInria, the French National Institute for computer science and applied mathematics has been involved for more than 10 years in defining policies and services related to Open Access to scientific information. In 2014, Inria became a partner of the French national infrastructure CCSD, which, together with CNRS and the University of Lyon, develops repository and editorial services for the higher education and research domain. In particular, the HAL publication repository has become a reference platform for the national open access landscape (https://hal.archives-ouvertes.fr).The International Federation for Information Processing (IFIP) has partnered with Inria to manage their Digital Library on HAL as a corpus of open access papers in information and communication technologies. The IFIP DL is organized as a series of collections (proceedings, books, journals), including embargoed material initially published by commercial publishers such as Springer, ACM or IEEE, as well as publications issued in conjunction to IFIP events (workshops and conferences).IFIP and Inria have designed a comprehensive workflow to integrate legacy and new content to the digital library by means of a series of validation and transformation processes of XML based description of the metadata associated to each document. Such information comprises a variety of precise descriptors related to bibliography, affiliation and technical descriptions. At the end of the complete process it is eventually transformed into a representation compliant to the TEI (Text Encoding Initiative) guidelines. The use of a TEI based representation anticipates further management of scholarly content a (XML based) full text with the prospect of re-publishing capacities in additional formats (e.g. ePub)..The integration workflow for IFIP content is based upon a two-step process:- The validation and enrichment of the data delivered by the publisher, where pdf and Springer meta-data are grouped together and further information related to IFIP technical committees is being added;.- The ingestion proper within HAL, by means of an XSLT transform from the enriched Springer format into the standard TEI-based HAL back-office format followed by an upload through a SWORD interface..Furthermore, various additional processes (generation of tables of content, thematic collection management, de-duplication of content when some documents already exist in HAL) and actuated on the fly during the integration of each volume. Such processes rely in particular upon the rich API available on HAL..An important step in the integration of IFIP content on HAL is to check all affiliation information (Institutions, laboratories and research teams) against the integrated authorities database associated to HAL: AuréHAL (https://aurehal.archives-ouvertes.fr). This facilitates the production of precise indicators for the digital library (e.g. co-authorship patterns) and ensures the precise monitoring of further usage statistics.Finally each volume of IFIP DL is a HAL collection with personal design (html pages written manually with a tool provided by HAL) and offer some metrics like number of hits and downloads..The current IFIP DL is visible under: https://hal.inria.fr//IFIP, all disembargoed documents being available under a CC-BY licence

Ornement architectural et expression constructive : concepts d’hier et débats d’aujourd’hui

Si le retour de l’ornement sur la scène architecturale n’est plus tout à fait un phénomène récent, il semble avoir trouvé de nouvelles motivations dans les transformations qui ont infléchi le travail de conception architecturale au cours des deux dernières décennies. Il a également bénéficié d’un riche contexte historiographique, mettant en exergue la fécondité des théories de l’ornement de la seconde moitié du xixe siècle. L’article développe l’hypothèse selon laquelle ces théories peuvent aider à construire un appareil analytique utile à la compréhension des œuvres contemporaines. Elles suggèrent en effet des outils conceptuels applicables à un vaste spectre de productions. Nourries par des ambitions pédagogiques, motivées par un contexte d’incertitude esthétique, elles interrogent les évolutions technologiques, les changements de matériaux, les interactions entre les déterminations fonctionnelle, technique et symbolique de la forme. En analysant les démarches ornementales de quelques architectes contemporains, il s’agit de souligner le réinvestissement d’une poétique architectonique liée aux motifs constructifs et à leur potentiel mémoriel.While the return of the ornament to architecture is not an altogether recent phenomenon, it seems that in the last two decades some transformations in architectural conceptualisation have offered it new incentives. This "comeback" has also been favored by a rich historiographical context, emphasizing the fruitfulness of theories of ornament from the second half of the nineteenth century. This article elaborates the hypothesis that these theories can help to elaborate an analytical apparatus useful to the understanding of contemporary works. Indeed, they offer conceptual tools that are applicable to a vast variety of productions. Nourished by pedagogical ambitions and motivated by a context of esthetic uncertainty, these works question recent technological evolutions, changes in the field of materials, and interactions between the functional, technical and symbolical aspects of forms. The analysis of the use of ornament by several contemporary architects brings to the fore the resurgence of an architectural poetics that has to do with constructive motives and with their memorial potential

Influence de la position dans l’épaisseur des reprises de plis sur le comportement statique et en fatigue pour un stratifié carbone/époxy + Influence of ply-drop position in thickness direction on static and fatigue loading behaviour of carbon fibre/ epoxy laminates

L'influence de la position dans l'épaisseur des reprises de plis sur l'endommagement sous chargement en fatigue (R = -1) et la durée de vie a été étudiée. Deux configurations avec une variation de la position des reprises ont été comparées. Les stratifiés de base sont les mêmes pour les deux configurations et passent de 20 à 12 plis. Des essais mécaniques ont été menés pour identifier les modes et les lieux d'endommagement par observation des deux bords des éprouvettes pendant le chargement cyclique. La cinétique des derniers cycles jusqu'à la rupture finale a été observée. Une différence de la durée de vie entre les deux configurations testées a été trouvée. Un modèle éléments finis a été mis en place pour étudier les différences d'évolution de l'endommagement observées expérimentalement. Cette approche, basée sur un dialogue modèle global et modèle local, permet d'obtenir l'état de contrainte interlaminaire autour de chaque reprise de plis. Les résultats numériques sont en bon accord avec les observations expérimentales