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Electrostatic probe and laser photodetachment measurements in the hydrogen negative ion (H-) source "Prometheus I"
No full textInternational audienc
Crop insurance and pesticide use in French agriculture: an empirical analysis
No full textThis paper investigates the factors affecting the demand for crop–hail insurance and explores the potential relation with pesticide use for a sample of French farmers on the period 1993-2004, for the Meuse department. An econometric model involving two simultaneous equations with mixed censored/continuous dependent variables is estimated. Estimation results show that, in the case of rapeseed, insurance demand is significantly and positively related to pesticide use, but that the magnitude of this interaction is quite small. Insurance demand is positively influenced by the coefficient of variation of yield and the loss ratio, and is negatively influenced by Common Agricultural Policy subsidies and diversification of activity at farm level. These results shed light on the determinants of French farmers’ decisions related to risk management.Les auteurs étudient dans cet article les déterminants de la demande d’assurance récolte contre la grêle et ses potentielles interactions avec l’utilisation des pesticides pour un échantillon d’exploitations agricoles françaises sur la période 1993-2004, dans le département de la Meuse. Un modèle économétrique est bâti, correspondant à un système de deux équations simultanées où les variables indépendantes sont mixtes (censurée/continue). Lesrésultats des estimations montrent que, dans le cas du colza, la demande d’assurance est significativement et positivement associée à l’utilisation de pesticides, bien que l’ampleur de cette relation soit faible. La demande d’assurance est influencée positivement par le coefficient de variation du rendement et le loss ratio, et négativement par les aides de la Politique Agricole Commune et la diversification des activités. Ces résultats fournissent un éclairage sur les déterminants des décisions des agriculteurs français liées à la gestion du risque
Instrumentation for diagnostics and control of laser-accelerated proton (ion) beams
No full textInternational audienceSuitable instrumentation for laser-accelerated proton (ion) beams is critical for development of integrated, laser-driven ion accelerator systems. Instrumentation aimed at beam diagnostics and control must be applied to the driving laser pulse, the laser-plasma that forms at the target and the emergent proton (ion) bunch in a correlated way to develop these novel accelerators. This report is a brief overview of established diagnostic techniques and new developments based on material presented at the first workshop on 'Instrumentation for Diagnostics and Control of Laser-accelerated Proton (Ion) Beams' in Abingdon, UK. It includes radiochromic film (RCF), image plates (IP), micro-channel plates (MCP), Thomson spectrometers, prompt inline scintillators, time and space-resolved interferometry (TASRI) and nuclear activation schemes. Repetition-rated instrumentation requirements for target metrology are also addressed
Asymptotic analysis of small defects near a singular point in antiplane elasticity, with an application to the nucleation of a crack at a notch
No full textInternational audienceWe use matching asymptotic expansions to treat the antiplane elastic problem associated with a small defect located at the tip of a notch. In a first part, we develop the asymptotic method for any type of defect and present the sequential procedure which allows us to calculate the different terms of the inner and outer expansions at any order. This requires in particular separating in each term its singular part from its regular part. In a second part, the asymptotic method is applied to the case of a crack of variable length located at the tip of a given notch. We show that the first two nontrivial terms of the expansion of the energy release rate are sufficient to well approximate the dependence of the energy release rate on the crack length in the range of values of the length which are sufficient to treat the problem of nucleation. This problem is considered in the last part where we compare the nucleation and the propagation of a crack predicted by two different models: the classical Griffith law and the Francfort–Marigo law based on an energy minimization principle. Several numerical results illustrate the interest of the method
Jurisprudence et stratégie
No full textInternational audienceSi l'on part du principe que la stratégie viserait, en son principe même, la création de jurisprudences nouvelles puisqu'elle consiste à concevoir ex ante et à faire advenir des formes nouvelles qui ne seront évidentes et donc discutables qu'ex post, alors ce sont les catégories mêmes que l'on juge pertinentes pour l'agir stratégique qui méritent d'être rediscutées. Successivement, la thèse d'une conception jurisprudentielle de la stratégie, que l'on se propose de travailler de manière heuristique à partir du concept de "Black Hole" est discutée dans ses motifs et ses principes avant d'en évaluer ses conséquences. C'est ainsi qu'une réflexion sur nos "(im-)pensables" et nos 'im-possibles" (partie 1) permet d'argumenter à nouveaux frais la question de nos "(in-)existences" et de nos "(in)-consistances" (partie 2). Cette réflexion, qui suit délibérément l'invitation deleuzienne à se situer "à la pointe de son savoir" conclue par l'importance, parmi d'autres thèmes, de l'activité de (ré-)création stratégique
Experimental study and modeling of the mechanical behavior of SiC/SiC composite tubes
No full textInternational audienc
Coupler l'analyse géométrique et la théorie de la viabilité pour explorer les dynamiques des systèmes : application à un système alimentaire
No full text[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]MOTIVEInternational audienceThis paper addresses the issue of studying a food complex system in a reverse engineering manner with the aim of identifying the set of all possible actions that makes it reach a quality target with respect to manufacturing constraints. Once the set of actions is identified, several criteria can be considered to identify interesting trajectories and control policies. A viability approach, coupling the viability theory and a geometric approach of robustness, is proposed to study complex dynamical systems. It can be implemented for several types of systems, from linear to non linear or hybrid systems. The proposed framework was adapted to a living food system: a ripening model of Camembert cheese to identify the set of states and actions (capture basin) from which it is possible to reach a predefined quality target. Within the set of viable trajectories, particular trajectories that improve the Camembert cheese ripening process are identified using the proposed approach. The results are applied at a pilot scale and are discussed in this paper
A new Mars Climate Database v5.1
No full textInternational audienceWhat is the Mars Climate Database? The Mars Climate Database (MCD) is a database of meteorological fields derived from General Circulation Model (GCM) numerical simulations of the Martian atmosphere and validated using available observational data. The MCD includes complementary post-processing schemes such as high spatial resolution interpolation of environmental data and means of reconstructing the variability thereof. The GCM is developed at Laboratoire de Météorologie Dynamique du CNRS (Paris, France) [1-3] in collaboration with the Open University (UK), the Oxford University (UK) and the Instituto de Astrofisica de Andalucia (Spain) with support from the European Space Agency (ESA) and the Centre National d'Etudes Spatiales (CNES). The MCD is freely distributed and intended to be useful and used in the framework of engineering applications as well as in the context of scientific studies which require accurate knowledge of the state of the Martian atmosphere. The MCD may be accessed either online (in a somewhat simplified form) via an interactive server available at http://www-mars.lmd.jussieu.fr (useful for moderate needs), or from the complete version which includes advanced access and post-processing software (contact [email protected] and/or [email protected] to obtain a free copy). Overview of MCDv5 contents: The MCD provides mean values and statistics of the main meteorological variables (atmospheric temperature, density, pressure and winds) as well as atmospheric composition (including dust and water vapor and ice content), as the GCM from which the datasets are obtained includes water cycle [4-6], chemistry [7,8], and ionosphere [9,10] models. The database extends up to and including the thermosphere[11-13] (~350km). Since the influence of Extreme Ultra Violet (EUV) input from the sun is significant in the latter, 3 EUV scenarios (solar minimum, average and maximum inputs) account for the impact of the various states of the solar cycle
Dynamique non-inertielle de bulle(s) et/ou particule(s) solide(s) au voisinage de la surface d’un liquide soumis à la gravité
No full textThis thesis is devoted to the bubble(s) and solid particle(s) interactions near the surface of a liquid subject to gravity. Such case occurs during industrial glass process when bubbles and impurities, driven by gravity, gather below the surface of the liquid molten glass. The present work numerically investigates, in the viscous flow regime, the evolution in time of each interface (bubbles and molten glass surface) shape together with the thickness of the film occurring between two closes surfaces (drainage phenomenon). On each interface a competition takes place between different forces: the capillary one modeled by the interface uniform surface tension, the gravity one and the viscous one due to the liquid flow. The relative magnitude of these effects is estimated using the Bond number (comparing the gravity term to the capillary term) and the capillary number (comparing the viscous term to the capillary term) which are of the same order for particles with negligible inertia. The surface tension effect has been then quantified and discussed in a large range of Bond number for one bubble, several bubble(s) and clusters made of bubble(s) and solid particle(s).La thèse porte sur les interactions entre des bulles et/ou des particules solides situées à proximité de la frontière d'un liquide soumis à l'action de la pesanteur. Cette situation est notamment rencontrée pour les bains de verre liquide dans lesquels les bulles et les impuretés se concentrent sous l'action de la seule gravité au voisinage immédiat de la surface du verre. Ce travail étudie numériquement, dans le cadre des écoulements visqueux, l'évolution temporelle de la déformation de chaque interface (bulle(s) et surface du verre) et de l'épaisseur du film liquide entre deux surfaces proches (phénomène de drainage). Sur chaque interface interviennent des forces capillaires (mesurées par la tension de surface uniforme), des forces de pesanteur et enfin des forces visqueuses dues à l'écoulement. L'importance relative de ces efforts est mesurée par le nombre de Bond (comparant termes de gravité et termes capillaires) et le nombre capillaire (comparant termes visqueux et termes capillaires) qui pour nos particules d'inertie négligeable sont du même ordre de grandeur. L'influence des tensions de surface et du nombre de Bond a ainsi été mise en évidence et commentées dans les cas d'une seule bulle, de plusieurs bulles et enfin de bulles et de sphères solides
Accuracy assessment of water vapour measurements from in-situ and remote sensing techniques during the DEMEVAP 2011 campaign
No full textInternational audienceThe Development of Methodologies for Water Vapour Measurement (DEMEVAP) project aims at assessing and improving humidity sounding techniques and establishing a reference system based on the combination of Raman lidars, ground-based sensors and GPS. Such a system may be used for climate monitoring, radiosonde bias detection and correction, satellite measurement calibration/validation, and mm-level geodetic positioning with Global Navigation Satellite Systems. A field experiment was conducted in September-October 2011 at Observatoire de Haute Provence (OHP). Two Raman lidars (IGN mobile lidar and OHP NDACC lidar), a stellar spectrometer (SOPHIE), a differential absorption spectrometer (SAOZ), a sun photometer (AERONET), 5 GPS receivers and 4 types of radiosondes (Vaisala RS92, MODEM M2K2-DC and M10, and Meteolabor Snow-White) participated in the campaign. A total of 26 balloons with multiple radiosondes were flown during 16 clear nights. This paper presents preliminary findings from the analysis of all these datasets. Several classical Raman lidar calibration methods are evaluated which use either Vaisala RS92 measurements, point capacitive humidity measurements, or GPS integrated water vapour (IWV) measurements. A novel method proposed by Bosser et al. (2010) is also tested. It consists in calibrating the lidar measurements during the GPS data processing. The methods achieve a repeatability of 4-5 %. Changes in calibration factor of IGN Raman lidar are evidenced which are attributed to frequent optical re-alignments. When modelling and correcting the changes as a linear function of time, the precision of the calibration factors improves to 2-3 %. However, the variations in the calibration factor, and hence the absolute accuracy, between methods and types of reference data remain at the level of 7 %. The intercomparison of radiosonde measurements shows good agreement between RS92 and Snow-White measurements up to 12 km. An overall dry bias is found in the measurements from both MODEM radiosondes. Investigation of situations with low RH values (< 10 %RH) in the lower and middle troposphere reveals, on occasion, a lower RH detection limit in the Snow-White measurements compared to RS92 due to a saturation of the Peltier device. However, on other occasions, a dry bias is found in RS92, instead. On average, both RS92 and Snow-White measurements show a slight moist bias at night-time compared to GPS IWV, while the MODEM measurements show a large dry bias. The IWV measurements from SOPHIE (night-time) and SAOZ (daytime) spectrometers, AERONET photometer (daytime) and calibrated Raman lidar (night-time) showed excellent agreement with the GPS IWV measurements