Contrôle de l'équilibre des humains virtuels

Ce chapitre aborde le problème de l'analyse de l'équilibre et de la synthèse par la ommande de la coordination des mouvements d'humains virtuels pour la simulation réaliste d'activités physiques quotidiennes ou professionnelles. nous discutons dans un premier temps les notions d'équilibre postural et de stabilité de cet équilibre dans le cadre particulier des mannequins numériques. Nous introduisons un modèle mécanique pour des mannequins en interaction physique avec l'environnement. À partir d'une formulation générale du problème de l'équilibre, nous examinons un certain nombre de moyens proposés pour caractériser et quantifier la stabilité de l'équilibre des systèmes mécaniques contraints. Nous introduisons la notion de perturbation admissible pour la dynamique posturale vis-à-vis des contraintes de persistance et de non-glissement des appuis. Enfin, nous proposons des techniques de synthèse par la commande de fonctions motrices pour une coordination de l'ensemble du système postural et de manipulation satisfaisant explicitement les contraintes d'équilibre des appuis

Qu’est-ce que le vivant ? Matières inanimées, avez-vous donc une âme ?

Depuis toujours, l’homme cherche à définir, explorer et utiliser le vivant, cette chose, cette substance, cette force vitale… En réalité, la vie n’est pas une entité mais une somme de processus complexes, dépendants de l’organisation de la matière. Dans cette contribution, nous effeuillons d’abord les visions de différentes civilisations anciennes concernant cette question. Une confrontation de ces représentations issues du passé avec les approches scientifiques actuelles est ensuite présentée. Une discussion autour d’une vision actuelle du vivant et la présentation de résultats préliminaires expérimentaux, obtenus au sein du laboratoire, terminent ce texte.Historically, men have sought to define, explore and use life, this thing, this substance, this strength… In fact, life is not an entity but an addition of complex processes, which depends on the organization of the matter at the molecular level. In this contribution, we first present several descriptions and representations of life coming from old civilizations. These ancient descriptions are compared with current scientific approaches. A discussion about a current representation of the living and some preliminary experimental results obtained in the laboratory, complete the text

Efficiency of dispersive wave generation in dual concentric core microstructured fiber

We describe the generation of powerful dispersive waves that are observed when pumping a dual concentric core microstructured fiber by means of a sub-nanosecond laser emitting at the wavelength of~1064 nm. The presence of three zeros in the dispersion curve, their spectral separation from the pump wavelength, and the complex dynamics of solitons originated by the pump pulse break-up, all contribute to boost the amplitude of the dispersive wave on the long-wavelength side of the pump. The measured conversion efficiency towards the dispersive wave at 1548 nm is as high as 50%. Our experimental analysis of the output spectra is completed by the acquisition of the time delays of the different spectral components. Numerical simulations and an analytical perturbative analysis identify the central wavelength of the red-shifted pump solitons and the dispersion profile of the fiber as the key parameters for determining the efficiency of the dispersive wave generation process.Comment: 11 pages, 12 figure

Bragg-Scattering conversion at telecom wavelengths towards the photon counting regime

9openopenKatarzyna Krupa; Alessandro Tonello; Victor Kozlov; Vincent Couderc; Philippe Di Bin; Stefan Wabnitz; Alain Barthelemy; Laurent Labonte; Sebastien TanzilliKatarzyna, Krupa; Alessandro, Tonello; Kozlov, Victor; Vincent, Couderc; Philippe Di, Bin; Wabnitz, Stefan; Alain, Barthelemy; Laurent, Labonte; Sebastien, Tanzill

Visible supercontinuum generation controlled by intermodal four-wave mixing in micro-structured fibre

International audienceWe present an experimental and numerical study of supercontinuum generation extended in the visible part of the spectrum by using a selective optical coupling of the pump wave in the largely anomalous dispersion regime. The broadband frequency generation is induced by an initial four-wave mixing process that converts the pump wave at 1064 nm into 831 nm anti-Stokes and 1478 nm Stokes wavelengths. Phase matching is ensured on such a large frequency shift thanks to a microstructured multimodal fiber with a specific design. Continuum generation is therefore enhanced around the two generated sideband

A functional model of tree growth and tree architecture.

A new approach for modelling plant growth using the software AMAPpara is presented. This software takes into consideration knowledge about plant architecture which has been accumulated at the Plant Modelling Unit of CIRAD for several years, and introduces physiological concepts in order to simulate the dynamic functioning of trees. The plant is considered as a serial connection of vegetative organs which conduct water from the roots to the leaves. Another simple description of the plant as a network of parallel pipes is also presented which allows an analytical formulation of growth to be written. This recurring formula is used for very simple architectures and is useful to understand the role of each organ in water transport and assimilate production. Growth simulations are presented which show the influence of modifications in architecture on plant development

Le Marais des Paluns

Les zones humides méditerranéennes sont au cœur de multiples enjeux environnementaux. Les zones humides de la Palun connectées à l’étang de Berre sont une zone spéciale de conservation située à l’aval d’un bassin versant anthropisé. Une contamination diffuse et cumulative dans le temps des sédiments y a été identifiée. C’est dans ce contexte qu’un travail a été mené sur un procédé de traitement des eaux du bassin versant de la Palun pour favoriser la résilience du marais récepteur face à la pollution chronique. Les possibilités de réalisation d’une zone humide artificielle en amont du marais, dédiée à l’épuration des eaux, ont été réfléchies en lien avec les usages et les attentes parfois divergentes des acteurs du territoire. La réparation des atteintes environnementales dans le contexte socio-économique contraint de l’étang de Berre a été interrogée à partir des savoirs issus de l’écologie de la restauration et de la sociologie.Mediterranean wetlands are subject to many environmental issues. The Palun wetlands in connection with the industrialized Berre lagoon are a special area of conservation located downstream of an anthropised watershed and where diffuse and cumulative contaminations of the sediments were detected. A work was then carried out on a water treatment process in the Palun watershed to promote the resilience of the receiving marsh. The possibilities of creating a constructed wetland upstream to treat all waters have been reflected in connection with the potential divergent uses and expectations of the territory actors. Repairing environmental damages in the particular socio-economic context of the Berre lagoon was considered from the knowledge of restoration ecology and sociology

Efficacy and safety of enoxaparin versus unfractionated heparin during percutaneous coronary intervention: systematic review and meta-analysis

Objective To determine the efficacy and safety of enoxaparin compared with unfractionated heparin during percutaneous coronary intervention

A Note on Encodings of Phylogenetic Networks of Bounded Level

Driven by the need for better models that allow one to shed light into the question how life's diversity has evolved, phylogenetic networks have now joined phylogenetic trees in the center of phylogenetics research. Like phylogenetic trees, such networks canonically induce collections of phylogenetic trees, clusters, and triplets, respectively. Thus it is not surprising that many network approaches aim to reconstruct a phylogenetic network from such collections. Related to the well-studied perfect phylogeny problem, the following question is of fundamental importance in this context: When does one of the above collections encode (i.e. uniquely describe) the network that induces it? In this note, we present a complete answer to this question for the special case of a level-1 (phylogenetic) network by characterizing those level-1 networks for which an encoding in terms of one (or equivalently all) of the above collections exists. Given that this type of network forms the first layer of the rich hierarchy of level-k networks, k a non-negative integer, it is natural to wonder whether our arguments could be extended to members of that hierarchy for higher values for k. By giving examples, we show that this is not the case