LA STEAM EXPLOSION : PRINCIPE ET ACTION SUR LES MATERIAUX LIGNOCELLULOSIQUES

La steam explosion est un procédé thermomécanochimique qui va permettre la déstructuration de la matière lignocellulosique par l’action combinée de la chaleur issue de la vapeur, des hydrolyses induites par la formation d’acides organiques et du cisaillement résultant de la chute brutale de pression. Le procédé est composé de deux phases distinctes. D’une part, le vapocraquage qui consiste à faire pénétrer par diffusion, puis à condenser, la vapeur sous haute pression à l’intérieur de la structure du matériau. L’eau condensée à température élevée va initier l’hydrolyse des groupements acétyles contenus dans les xylanes et induire la formation d’acides organiques. Selon la sévérité des conditions (pression, température), les acides vont catalyser l’hydrolyse des fractions hémicellulosiques, induire des modifications dans la structure des lignines et modifier le degré de cristallinité de la fraction cellulosique. D’autre part, la décompression explosive. Cette phase est provoquée par une chute brutale de pression qui va entraîner la revaporisation d’une partie de l’eau condensée. L’expension brutale de la vapeur va induire des forces de cisaillement qui vont modifier les propriétés physiques (granulométrie, surface spécifique, rétention d’eau…) du matériau.LIGNOFUE

ModHel'X, un outil expérimental pour la modélisation multi-paradigmes

National audienceLa modélisation multi-paradigmes vise à permettre la modélisation d’un système en utilisant pour chacune de ses sous-parties le formalisme (ou paradigme) de modélisation le plus adapté. Nous nous intéressons plus spécifiquement à la modélisation du comportement de systèmes : dans ce cadre, il est nécessaire de pouvoir combiner la sémantique des différents formalismes utilisés dans un modèle de sorte à déterminer le comportement global du système modélisé. Nous avons conç̧u un outil appelé ModHel’X qui permet a) de décrire les formalismes de modélisation utilisés grâce au concept de modèle de calcul, b) de décrire l’adaptation sémantique à la frontière entre deux formalismes, c) de construire des modèles faisant appel à plusieurs de ces formalismes et d) de simuler le comportement de tels modèles

An Ambient Assisted Living Framework with Automatic Self-Diagnosis

International audienceAs the population in many countries is steadily aging, allowing elderly people to stay longer at home is a growing concern. Ambient Assisted Living (AAL) proposes new techniques to help people remain autonomous, based on ambient intelligence. We present an ontology-based framework in which ontologies enable the expression of users' preferences in order to personalize the system behavior. They are also used for the discovery and interconnection of devices, the storage and retrieval of collected data and the transmission of actions. Basing everything on ontologies allows the designer to express the behavior of the system using high-level logic rules. To render AAL systems as autonomous as possible, devices that fail should be detected at runtime. For this reason, the framework offers a diagnosis service that builds a prediction model of the values detected by sensors. It is based on information discovered opportunistically at run-time and knowledge about physical laws. The framework monitors the run-time behavior of the AAL system and uses the prediction model to detect inconsistencies and hence faults. Therefore, fault detection is totally dynamic and opportunistic; there are no pre-defined control loops. This paper describes an actual implementation, with precise technological details, in order to prove the feasibility of the technical choices, and provide implementation ideas for future projects

Recent developments and prospects for the production of biofuels in the EU: Can they really be "Part of Solution"?

The European Union has launched an ambitious policy aiming at increasing the use of biofuels in land transport “with a view to contributing to objectives such as meeting climate change commitments, environmentally friendly security of supply and promoting renewable energy sources”. Another motivation, at least for some member states, is that the development of biofuels is expected to provide larger outlets for domestic farm products and new employment opportunities in rural areas and make future adjustments of the Common agricultural policy easier. The EU policy of support to energy crops, tax exemption for biofuels and mandatory incorporation targets in some member states, has resulted in a significant increase in the demand and supply of biofuels. The market share of biofuels remains modest (1 % in 2005 in the EU-25) but has increased dramatically over the last few months. The paper provides an analysis of recent developments and prospects for the production and utilization of biofuels in the EU. Its presents the potential benefits of biofuels in the EU as well as their possible drawbacks. In particular, it addresses the three related issues of energy efficiency, environmental benefits and cost competitiveness of EU biofuels.Resource /Energy Economics and Policy,

Heterogeneous Model Composition in ModHel'X: the Power Window Case Study

This paper describes an heterogeneous model of a power window which is available on the ReMoDD repository. This model uses timed finite state machines for modeling the controller of the power window, synchronous data flows for modeling the mechanical part of the window, and discrete events for modeling the communications between the components on the car's bus. An important aspect of this model is the specification of the semantic adaptation between the heterogeneous parts of the model. This semantic adaptation is made for data, control, and time. The semantic adaptation of control and time relies on the TESL library which is an implementation of the model of time used in the ModHel'X platform. The model can be run using a simulation scenario with a graphical display of the outputs. The semantic adaptation can be disabled in order to show how it affects the behavior of the model. The demo can also be run with a graphical interface and a user in the loop

Automatic Optimisation of Reliable Collaborative Services in OLSR Mobile Ad Hoc Networks

International audienceFuture Network based Operations (NbO) will strongly rely on Mobile Ad hoc Networks (MANET), due to urban area, tactical mobility and assymetric operation management. These networks will support multiple collaborative services, such as sensor to shooters, reachback, maintenance of Common Operational Picture (COP). Both networks and services will have to be managed with no or limited operator intervention, still providing reliable behavior in spite of aggressive environments. At routing level, we present how to preserve 2-connectivity by adapting the Optimised Link State Routing Protocol (OLSR). We also introduce the concept of active subnet management to retrieve maximal operational gain from collaborative services. Following a constraint solving method, the paper shows how to maximise the subnet of actors, while satisfying 2-connectivity, reactivity and communication quality constraints. We demonstrate the approach on simulating real world NbO

Use of 13C-NMR in structural elucidation of polysaccharides: case of locust bean gum

Locust bean gum (LBG) galactomannans are polysaccharides consisting of a β-(1→4) D-mannopyranosyl backbone substituted to varying degrees in α-(1→6) with single D-galactopyranosyl residues. This basic structure is the same for all galactomannans (Fig. 2). However, when locust bean gum is extracted at different temperatures, the generated fractions exhibit different properties in aqueous solution (viscosity, viscoelasticity, gel formation, thermohydrolysis resistance, etc.). This means that there are differences within the fine structure of the polymers (although the basic structure is the same). Analysis of [13C]-NMR spectra of galactomannans, in combination with other techniques, can provide capital information about fine structural elucidation of the polymers. The method specifies the distribution of lateral galactosyls along the main chain of mannans. Two fractions extracted from locust bean gum at 25 and 80 °C (respectively GM25 and GM80) were comparatively studied by [13C]-NMR. Mannosyls/Galactosyls (M/G) ratios can be determined by considering the intensities of C-1 mannose and galactose signals in [13C]-NMR spectra. This method provides results relatively close to those obtained by GC-MS analysis. Spectra also showed that resonance from C4 of D-mannose residues were split, in evident dependence upon the nearest-neighbor probabilities (“diad frequencies”) of D-galactosyl groups along the mannan chains (Fig. 2). Diad frequencies were obtained by integrating C4(Man) peak areas. F11, F21/F12 and F22 gave respectively the di-, mono- or non-substituted mannose pairs proportions. High percentages of F11 and F22 therefore indicate a more non-homogeneous distribution of lateral galactosyls along the polysaccharide backbone as observed for GM80. The percentages of total lateral substituents obtained by C4(Man) peak analysis [F11 + (F21 or F12)/2] were fairly well correlated with M/G ratios. Splitting of the C-6 substituted D-mannose resonance provides, therefore the basis for determining the next-nearest-neighbor probabilities (triad frequencies) (Fig. 2). However, the spectrum is often not sufficiently resolved to accurately quantify and interpret the results

Building Heterogeneous Models at Runtime to Detect Faults in Ambient-Intelligent Environments

International audienceThis paper introduces an approach for fault detection in ambient-intelligent environments. It proposes to compute predictions for sensor values, to be compared with actual values. As ambient environments are highly dynamic, one cannot pre-determine a prediction method. Therefore, our approach relies on (a) the modeling of sensors, actuators and physical effects that link them, and (b) the automatic construction at run-time of a heterogeneous prediction model. The prediction model can then be executed on a heterogeneous modeling platform such as ModHel'X, which yields predicted sensor values

Comparison of hip joint mechanical energetics in table tennis forehand and backhand drives: a preliminary study

Hip joints are highly involved in table tennis. Some authors found both pelvic angular velocity and hip joint torques are related to the racket velocity. Others have also demonstrated how some of the best players have higher ranges of motion of the lower-limb joints. Therefore, the mechanical work generated by the playing-side-hip can be seen as indicator of the playing intensity associated with different strokes. The aim of this study was to quantify the hip joint mechanical work and power during four classical strokes. Motion capture acquisitions were performed on two international players. A biplanar radiographic acquisition was also performed to personalize the biomechanical model. Hip joint velocity and torques were calculated on the dominant side, allowing mechanical power and work to be calculated between the end of backswing and the ball impact. The highest level of mechanical work from the hip joint was found for forehand drive against backspin and forehand topspin drive with pivot. A backhand drive required the lowest hip mechanical work, and the forehand drive against topspin was found to be intermediate. The lower work required from the backhand stroke makes it suitable as a waiting stroke

Une sémantique multi-paradigme pour simuler des modèles SysML avec SystemC-AMS

National audienceDans le contexte de la modélisation de systèmes, SysML apparait comme un langage pivot de spécification et de documentation. Ses diagrammes permettent la définition de la structure et du comportement de systèmes. La flexibilité de SysML a pour incon-vénient qu'il n'existe pas de méthode standard pour définir leur sémantique. Ce problème est flagrant dans la conception de systèmes hétérogènes, où différentes sémantiques opéra-tionnelles peuvent être utilisées. Cet article présente une manière de donner une sémantique opérationnelle aux éléments de SysML sous la forme de transformations vers le langage SystemC-AMS, permettant ainsi la simulation de modèles SysML