Les graphes argumentatifs interactifs sur Internet : sont-ils plus efficaces comme média du débat ou comme moyens de le représenter ?

Nous présentons les résultats d'une expérience menée dans le cadre du projet européen SCALE. Le but de cette recherche était d'étudier l'influence du type d'utilisation du graphe argumentatif durant des débats pédagogiques sur Internet. Précisément, il s'agissait de savoir sur le graphe argumentatif était plus efficace lorsqu'il était utilisé comme médium du débat (C1) ou comme moyen de le représenter (C2). Dans cet objectif, nous avons évalué à l'aide d'une méthode originale (ADAM), les différences entre des graphes argumentatifs construits individuellement avant et après le débat, et avons comparé ces différences entre les deux conditions expérimentales. Les résultats suggèrent une complémentarité entre les deux types d'utilisation des graphes argumentatifs dans le cadre d'un apprentissage conceptuel centré sur des questions socialement vives

Schématisation argumentative et co-élaboration de connaissances: le cas des interactions médiatisées par ordinateur

International audienceDans le cadre du projet européen SCALE (IST-1999) (Internet-based intelligent tool to Support Collaborative Argumentation-based Learning in secondary schools, http://www.euroscale.net), nous avons élaboré et étudié des situations d'apprentissage coopératif médiatisé par ordinateur au travers Internet. Il a s'agit de proposer une variété d'activités argumentatives — lecture et production de textes argumentatifs, élaboration de textes et schémas argumentatifs, interactions (ou débats) langagières et/ou schématiques — dans le but d'amener les élèves à élargir et à approfondir leurs connaissances d'un espace du débat particulier. Par la notion de « l'espace du débat », nous entendons l'espace cognitifsémiotique partagé, co-construit par les élèves au cours de leurs interactions argumentatives, en référence à une question débattue (Baker, Quignard, Lund & Séjourné, 2003 ; Quignard, Baker, Lund & Séjourné, 2003). Ce travail a conduit à la production d'outils de recherche permettant une analyse fine des processus interactifs d'élaboration des connaissances en relation avec des activités argumentatives

Near-infrared and Millimeter-wavelength Observations of Mol 160: A Massive Young Protostellar Core

We have discovered two compact sources of shocked H2 2.12-micron emission coincident with Mol 160 (IRAS 23385+6053), a massive star-forming core thought to be a precursor to an ultracompact HII region. The 2.12-micron sources lie within 2" (0.05 pc) of a millimeter-wavelength continuum peak where the column density is >= 10e24 cm$^{-2}$. We estimate that the ratio of molecular hydrogen luminosity to bolometric luminosity is > 0.2%, indicating a high ratio of mechanical to radiant luminosity. CS J=2-1 and HCO$^+$ J=1-0 observations with CARMA indicate that the protostellar molecular core has a peculiar velocity of ~ 2 km s$^{-1}$ with respect to its parent molecular cloud. We also observed 95 GHz CH3OH J=8$-7 Class I maser emission from several locations within the core. Comparison with previous observations of 44-GHz CH3OH maser emission shows the maser sources have a high mean ratio of 95-GHz to 44-GHz intensity. Our observations strengthen the case that Mol 160 (IRAS 23385+6053) is a rapidly accreting massive protostellar system in a very early phase of its evolution.Comment: 47 pages, 8 figures, 2 tables, accepted for publication in ApJ, 7 Dec 201

Two massive star-forming regions at early evolutionary stages

We report sensitive ATCA radio-continuum observations toward IRAS 15596-5301 and 16272-4837, two luminous objects (> 2x10^4 Lsun) thought to represent massive star-forming regions in early stages of evolution (due to previously undetected radio emission at the 1-sigma level of 2 mJy per beam). Also reported are 1.2-millimeter continuum and a series of molecular-line observations made with the SEST telescope. For IRAS 15596-5301, the observations reveal the presence of three distinct compact radio-continuum sources associated with a dense molecular core. We suggest that this core contains a cluster of B stars which are exciting compact HII regions that are in pressure equilibrium with the dense molecular surroundings. No radio continuum emission was detected from IRAS 16272-4837 (3-sigma limit of 0.2 mJy). However, a dense molecular core has been detected. The high luminosity and lack of radio emission from this massive core suggests that it hosts an embedded young massive protostar that is still undergoing an intense accretion phase. This scenario is supported by the observed characteristics of the line profiles and the presence of a bipolar outflow detected from observations of the SiO emission. We suggest that IRAS 16272-4837 is a bona fide massive star- forming region in a very early evolutionary stage, being the precursor of an ultra compact HII region.Comment: 25 pages, 9 figures, accepted for publication in The Astrophysical Journa

Finite element modeling of dynamic frictional rupture with rate and state friction

Numerous laboratory experiments have demonstrated the dependence of the friction coefficient on the interfacial slip rate and the contact history, a behavior generically called rate and state friction. Although numerical models have been widely used for analyzing rate and state friction, in general they consider infinite elastic domains surrounding the sliding interface and rely on boundary integral formulations. Much less work has been dedicated to modeling finite size systems to account for interactions with boundaries. This paper investigates rate and state frictional interfaces in the context of finite size systems with the finite element method in explicit dynamics. We investigate the long term behavior of the sliding interface for two different friction laws: a velocity weakening law, for which the friction monotonously decreases with increasing sliding velocity, and a velocity weakening-strengthening law, for which the friction coefficient first decreases but then increases above a critical velocity. We show that for both friction laws at finite times, that is before wave reflections from the boundaries come back to the sliding interface, a temporary steady state sliding is reached, with a well-defined stress drop at the interface. This stress drop gives rise to a stress concentration and leads to an analogy between friction and fracture. However, at longer times, that is after multiple wave reflections, the stress drop is essentially zero, resulting in losing the analogy with fracture mechanics. Finally, the simulations reveal that velocity weakening is unstable at long time scales, as it results in an acceleration of the sliding blocks. On the other hand, velocity weakening-strengthening reaches a steady state sliding configuration

Élaboration et étude d'une situation d'apprentissage médiatisée par ordinateur pour le développement de la compréhension de l'espace du débat

Sommaire des pré-actes : http://archive-edutice.ccsd.cnrs.fr/edutice-00000318La vidéo de l'intervention et les questions de la salle sont accessibles sur http://webcast.in2p3.fr/tematice/baker.ramLa recherche présentée dans cet exposé a été réalisée dans le cadre du projet « SCALE » (Intelligent Support for Collaborative Argumentation-Based Learning, ou Guidage Intelligent pour L'Apprentissage Coopératif fondé sur l'Argumentation et l'Internet : http://www.euroscale.net), financé par le 5ème Plan IST (Information Society's Technologies) de l'Union Européenne. L'objectif pédagogique du projet est de comprendre comment concevoir des situations d'apprentissage coopératif pouvant conduire les élèves à élargir et à approfondir leur compréhension d'un espace du débat (cf. Golder, 1996). Cet objectif se situe à l'intersection de deux autres, devenues classiques : « apprendre à argumenter » et « argumenter pour apprendre ». Il s'agit en effet d'amener les élèves du secondaire à élaborer des connaissances qui sont de nature argumentative, grâce à leur implication dans l'activité argumentative que constitue le débat

Finite element model updating of a semi‐rigid moment resisting structure

Partial-strength composite steel–concrete moment-resisting frame structures can be designed to develop a ductile response in components of beam-to-column joints and column bases, including flexural yielding of beam end plates, shear yielding of column web panel zones and yielding of anchors. To evaluate the performance of a statically indeterminate structure under different earthquake intensities, a series of pseudo-dynamic, quasi-static cyclic and vibration tests were carried out at the European Laboratory for Structural Assessment of the Joint Research Centre at Ispra, Italy. The identified modal parameters from forced vibration tests at three different damage levels were used in order to quantify local and global damage indices by updating a 3D FE model of the structure with the non-linear Powell's Dog-Leg optimization method. Then, the Latin Hypercube Sampling technique, a variant of the Monte Carlo method, was employed to study the sensitivity of the updated parameters of the 3D model to modal inputs, caused by measurement noise. Rotations of beam-to-column joints and column bases, storey displacements and forces were employed during the final cyclic test in order to update a 2D FE model of the test structure. To avoid numerical instabilities during the detection of the non-linear behaviour of the structure, a novel technique based on the transformation of the origin coordinates in each half cycle was implemented. The identified joint behaviours allowed low-cycle fatigue energy-based damage indices to be applied. Copyright © 2009 John Wiley & Sons, Ltd