Compétences sur l'internet : adaptation, résistance des utilisateurs de P2P et mobilisation des internautes pour intervenir dans le débat public

International audienceThis communication aims to present collaboratives practices, share of information, exchanges between netsurfers, networks of training and capacities of organization, mobilization and debates on the Internet.Cette communication vise à présenter des pratiques collaboratives, de partage d'information, d'échanges entre internautes, des réseaux d'apprentissage et des capacités d'organisation, de mobilisation et de débats sur l'internet

Quality Measures of Parameter Tuning for Aggregated Multi-Objective Temporal Planning

Parameter tuning is recognized today as a crucial ingredient when tackling an optimization problem. Several meta-optimization methods have been proposed to find the best parameter set for a given optimization algorithm and (set of) problem instances. When the objective of the optimization is some scalar quality of the solution given by the target algorithm, this quality is also used as the basis for the quality of parameter sets. But in the case of multi-objective optimization by aggregation, the set of solutions is given by several single-objective runs with different weights on the objectives, and it turns out that the hypervolume of the final population of each single-objective run might be a better indicator of the global performance of the aggregation method than the best fitness in its population. This paper discusses this issue on a case study in multi-objective temporal planning using the evolutionary planner DaE-YAHSP and the meta-optimizer ParamILS. The results clearly show how ParamILS makes a difference between both approaches, and demonstrate that indeed, in this context, using the hypervolume indicator as ParamILS target is the best choice. Other issues pertaining to parameter tuning in the proposed context are also discussed.Comment: arXiv admin note: substantial text overlap with arXiv:1305.116

Divide-and-Evolve: a New Memetic Scheme for Domain-Independent Temporal Planning

An original approach, termed Divide-and-Evolve is proposed to hybridize Evolutionary Algorithms (EAs) with Operational Research (OR) methods in the domain of Temporal Planning Problems (TPPs). Whereas standard Memetic Algorithms use local search methods to improve the evolutionary solutions, and thus fail when the local method stops working on the complete problem, the Divide-and-Evolve approach splits the problem at hand into several, hopefully easier, sub-problems, and can thus solve globally problems that are intractable when directly fed into deterministic OR algorithms. But the most prominent advantage of the Divide-and-Evolve approach is that it immediately opens up an avenue for multi-objective optimization, even though the OR method that is used is single-objective. Proof of concept approach on the standard (single-objective) Zeno transportation benchmark is given, and a small original multi-objective benchmark is proposed in the same Zeno framework to assess the multi-objective capabilities of the proposed methodology, a breakthrough in Temporal Planning

Divide-and-Evolve : une nouvelle méta-heuristique pour la planification temporelle indépendante du domaine

Traduction en français de l'article Divide-and-Evolve: a New Memetic Scheme for Domain-Independent Temporal Planning, présenté à la conférence EvoCOP 2006 à Budapest, http://hal.inria.fr/inria-00000975/en/Une approche originale dénommée Divide-and-Evolve est proposée pour l'hybridation des Algorithmes Évolutionnaires (AEs) avec des méthodes d'Intelligence Artificielle dans le domaine des Problèmes de Planification Temporelle (PPTs). Alors que les algorithmes mémétiques standards utilisent des méthodes locales de résolution pour améliorer les solutions évolutionnaires, l'approche Divide-and-Evolve divise arbitrairement le problème en plusieurs sous-problèmes (que l'on espère plus faciles), et peut ainsi résoudre globalement des problèmes hors d'atteinte lorsque directement fournis en entrée d'algorithmes spécialisés classiques. Mais le principal avantage de l'approche Divide-and-Evolve est qu'elle ouvre immédiatement une avenue pour l'optimisation multi-objectifs, même avec une méthode spécialisée mono-objectif. La preuve du concept de cette approche sur le benchmark de transport standard Zeno (mono-objectif) est donnée, et un petit benchmark multi-objectifs original est proposé dans ce même cadre Zeno pour montrer les possibilités multi-objectifs de la méthodologie proposée, une percée dans la planification temporelle

Gemini Frontier Fields: Wide-field Adaptive Optics KsK_s-band Imaging of the Galaxy Clusters MACS J0416.1-2403 and Abell 2744

We have observed two of the six Frontier Fields galaxy clusters, MACS J0416.1-2403 and Abell 2744, using the Gemini Multi-Conjugate Adaptive Optics System (GeMS) and the Gemini South Adaptive Optics Imager (GSAOI). With 0.08"-0.10" FWHM our data are nearly diffraction-limited over a 100"x100" wide area. GeMS/GSAOI complements the Hubble Space Telescope (HST) redwards of 1.6microns with twice the angular resolution. We reach a 5 sigma depth of Ks = 25.6 mag (AB) for compact sources. In this paper we describe the observations, the data processing and the initial public data release. We provide fully calibrated, co-added images matching the native GSAOI pixel scale as well as the larger plate scales of the HST release, adding to the legacy value of the Frontier Fields. Our work demonstrates that even for fields at high galactic latitude, where natural guide stars are rare, current multi-conjugated adaptive optics technology at 8m-telescopes has opened a new window on the distant Universe. Observations of a third Frontier Field, Abell 370, are planned.Comment: Accepted for publication in ApJS; significantly revised compared to the first submissio

Combinatorial Mesh Optimization

International audienceA new mesh optimization framework for 3D triangular surface meshes is presented, which formulates the task as an energy minimization problem in the same spirit as in Hoppe et al. (SIGGRAPH’93: Proceedings of the 20th Annual Conference on Computer Graphics and Interactive Techniques, 1993). The desired mesh properties are controlled through a global energy function including data attached terms measuring the fidelity to the original mesh, shape potentials favoring high quality triangles, and connectivity as well as budget terms controlling the sampling density. The optimization algorithm modifies mesh connectivity as well as the vertex positions. Solutions for the vertex repositioning step are obtained by a discrete graph cut algorithm examining global combinations of local candidates.Results on various 3D meshes compare favorably to recent state-of-the-art algorithms. Applications consist in optimizing triangular meshes and in simplifying meshes, while maintaining high mesh quality. Targeted areas are the improvement of the accuracy of numerical simulations, the convergence of numerical schemes, improvements of mesh rendering (normal field smoothness) or improvements of the geometric prediction in mesh compression technique

Origem dos microagregados em solos com horizonte B latossólico

Os microagregados, característicos do horizonte B latossólico, podem ser formados a partir de processos físicos, geoquímicos e biológicos. Apesar da quantidade de trabalhos realizados sobre este tema, poucos tem discutido a hierarquia entre os processos que formam estes microagregados. O objetivo deste trabalho foi estudar a gênese dos microagregados numa seqüência de solos localizada em Piracicaba (SP), Brasil. Os solos foram classificados como Nitossolos Vermelhos Eutroférricos latossólicos e desenvolvem-se a partir de sedimentos argilosos vermelhos do Quaternário e diabásio. Para atingir o objetivo deste trabalho foram utilizadas técnicas de microscopia ótica, análise de imagens, microscopia eletrônica de varredura e quantificações elementares de ferro através de fluorescência de raio-X. As investigações micromorfológicas mostraram a presença de três tipos de microagregados: (i) microagregados ovais com grãos de quartzo bem selecionados no seu interior; (ii) microagregados ovais sem grãos de quartzo ou grãos de quartzo mal selecionados no seu interior; e (iii) microagregados poliédricos densos. Estas evidencias morfológicas junto com os dados elementares de ferro e a microscopia eletrônica de varredura mostraram a contribuição de mais de um processo na formação dos microagregados: (i) a ação mecânica da mesofauna seria responsável pela formação do primeiro tipo de microagregados; (ii) processos geoquímicos e biológicos estariam formando o segundo tipo de microagregados; e (iii) a fissuração da matriz do solo por processos de contração e expansão formariam o terceiro tipo de microagregados.Microaggregates that characterize ferralic soils have been hypothesized to have physical, geochemical and/or biological origins. Despite of many studies, the hierarchy between these processes that form microaggregates has seldom been reported. The objective of this work was to study the genesis of microaggregates in a sequence of Ferralic Nitisols developed on Quaternary red clayey sediments and diabase in Piracicaba (SP), Brazil. This issue was tackled by combining optical microscopy, image analysis, scanning electron microscopy and elemental iron quantifications by X-ray fluorescence. Micromorphological investigations showed three different types of microaggregates: (i) oval microaggregates with well sorted quartz grains in their interior; (ii) oval microaggregates without or with poorly sorted quartz grains in their interior; and (iii) dense polyedric microaggregates. These morphological evidences, together with the elemental iron determinations and scanning electron microscopy, revealed the contribution of more than one process for microaggregate formation: (i) the mechanical action of the mesofauna would form the first type of microaggregates (ii) geochemical and biological processes would form the second type and (iii) the fissuration of the soil matrix by expansion and compression processes would form the third type

DAE: Planning as Artificial Evolution -- (Deterministic part)

International audienceThe sub-optimal DAE planner implements the stochastic approach for domain-independent planning decomposition. The purpose of this planner is to optimize the makespan, or the number of actions, by generating ordered sequences of intermediate goals via a process of artificial evolution. For the evolutionary part we used the Evolving Objects (EO) library, and to solve each intermediate subproblem we used the constraint-based optimal temporal planner CPT. Therefore DAE can only solve problems that CPT can solve. Compression of subplans into a global solution plan is also achieved efficiently with CPT by exploiting causalities found so far. Because the selection of predicates for intermediate goal generation is still an open question, we have submitted two planners DAE1 and DAE2 that use different strategies for the generation of intermediate goals. An empirical formula has been defined to set a limit on the number of backtracks allowed for solving the intermediate subproblems

Tables de transposition pour la satisfaction de contraintes

Dans ce papier, nous proposons une approche basée sur la reconnaissance d'états dans le cadre de la résolution du problème de satisfaction de contraintes (CSP). L'idée principale consiste en la mémorisation d'états pendant la recherche de manière à prévenir la résolution de sous-réseaux similaires. Les techniques classiques évitent la réapparition de conflits précédemment rencontrés en enregistrant des ensembles conflits (conflict sets). Ceci contraste avec notre approche basée sur les états qui mémorise des sous-réseaux déjà explorés, c'est à dire une photographie de certains domaines sélectionnés. Ces informations sont ensuite exploitées pour éviter soit le parcours d'états in consistants, soit de recalculer l'ensemble des solutions de ces sous-réseaux. Les deux approches présentent une certaine complémentarité : en effet différents états peuvent être évités à partir d'une même instantiation partielle ou ensemble conflits tandis que différentes instantiations partielles peuvent mener à un même état qui n'a besoin d'être exploré qu'une seule fois. De plus notre méthode permet de détecter et casser dynamiquement certaines formes de symétries (notamment l'interchangeabilité au voisinage). Les résultats expérimentaux obtenus laissent entrevoir des perspectives promette uses pour la recherche basée sur les états

Recherche dirigée par le dernier conflit

Dans ce papier, nous proposons une nouvelle approche pour guider la recherche vers la source des conflits. Son principe est le suivant : après chaque conflit, la dernière variable assignée est sélectionnée en priorité tant que le réseau de contraintes est inconsistant. Ceci permet de découvrir la variable coupable la plus récente (i.e. à l'origine de l'échec) en remontant la branche courante de la feuille vers la racine de l'arbre de recherche. Autrement dit, l'heuristique de choix de variables est violée jusqu'au moment où un retour-arrière sur la variable coupable est effectué et que l'on découvre une valeur singleton consistante. En conséquence, ce type de raisonnement, qui représente un moyen original d'éviter le thrashing, peut facilement être intégré à de nombreux algorithmes de recherche. Les expérimentations effectuées sur un large éventail d'instances démontrent l'efficacité de cette approche