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  • Publication . Conference object . Part of book or chapter of book . 2020
    Open Access
    Authors: 
    Thomas Bonis; Nicolas Pronost; Saida Bouakaz;
    Publisher: Springer International Publishing
    Country: France
    Project: ANR | OMEGA (ANR-16-CE92-0042)

    International audience; Although predictive forward gait simulators have existed for a little while, only few sensitivity studies have been proposed. We present a study analysing precision, accuracy, stability and sensitivity of such simulator. We studied a gait simulator based on the trajectory mimicking method proposed by Lee et al. [1]. We assessed the effect of motion variation on the resulting gait simulation using the sensitivity analysis method proposed by Saltelli et al. [2]. Our method supports the use of this simulator for prediction.

  • Publication . Other literature type . Article . 2016
    Open Access English
    Authors: 
    Jacquin, L.; Brion, V.; Molton, P.; Sipp, D.; Dandois, J.; Deck, S.; Sartor, F.; Coustols, E.; Caruana, D.;
    Publisher: HAL CCSD
    Country: France

    L'article passe en revue les recherches menées à l'ONERA au cours des trente dernières années sur le buffet transsonique. Nous présentons d'abord le phénomène du buffet transsonique et nous expliquons son importance pour les applications aéronautiques. On distingue ensuite le buffet 2D produit par une aile bidimensionnelle et le buffet 3D qui caractérise les ailes en flèches d’envergure finie. Le buffet 2D se présente sous la forme d’une oscillation d’ensemble de tout l’écoulement couplant un déplacement de l’onde de choc et le décollement de la couche limite en aval de ce choc. Le buffet 3D prend quant à lui la forme d'une poche de perturbations localisées dans une portion limitée de l'aile. Nous rappelons que ces mécanismes ont d'abord été étudiés à l’ONERA dans les années 80 à travers une série de tests réalisés dans la soufflerie transsonique T2 à Toulouse et dans la grande soufflerie transsonique S2 de Modane. Ces travaux pionniers ont ensuite été approfondis dans la soufflerie S3Ch de Meudon de manière à élaborer une base de données complète du buffet 2D sur une aile 2D en régime turbulent, que nous décrivons. Cette base de données a été utilisée de façon extensive, à l’ONERA et dans d’autres institutions pour valider différents outils de simulation, ces derniers étant alors utilisés à leur tour pour étudier la physique du buffet. Nous illustrons cette collaboration entre la simulation et la physique en rappelant qu'une analyse de stabilité linéaire de solutions précises des équations de Navier-Stokes moyennées au sens de Reynolds (RANS) a permis de prouver que le buffet 2D provient d'un mécanisme d'instabilité globale. Nous passons également en revue des essais plus récents réalisés dans la soufflerie S3Ch sur le cas d'une aile 2D laminaire qui révèlent des comportements très distincts par rapport au cas turbulent. Cela illustre la sensibilité du buffet à la nature de la couche limite. Le dernier paragraphe du document donne un bref aperçu des simulations avancées de ces différents cas tests. Dans la conclusion, nous énumérons les perspectives de recherche sur le sujet, qui incluent aussi des thématiques méthodologiques plus générales telles que l'assimilation de données. The paper reviews research conducted at ONERA over the last thirty years on the transonic buffet. We first present the transonic buffet phenomenon and we explain its importance for aeronautical applications. Then, a distinction is made between the 2D buffet produced by an airfoil and the 3D buffet that characterizes swept wings of finite span. The 2D buffet amounts to a pure oscillation of the shock phase-locked with the detachment and reattachment of the boundary layer downstream, whereas the 3D buffet takes the form of a pocket of broadband perturbations located in a limitedportion of the wing. We recall that these mechanisms were first studied in the 1980s through a series of tests conducted in the transonic wind tunnel ONERA T2 at Toulouse and in the large transonic wind tunnel ONERA S2Ma at Modane. Since this pioneering work, progress in the measurement techniques has led to the constitution of a comprehensive database of the 2D buffet that we describe. This database, obtained in the wind tunnel ONERA S3Ch at Meudon, has been extensively used to validate various CFD tools, with the latter being used in turn to investigate the buffet physics. We illustrate this collaboration between simulation and physics by recalling that a linear stability analysis of accurate Reynolds-Averaged-Navier-Stokes (RANS) solutions made it possible to prove that the buffet on a 2D airfoil stems from a global instability mechanism.We also review more recent tests done in the case of a laminar airfoil, which reveal very distinct behaviors of the buffet flow. This illustrates how sensitive the buffet is to the nature of the boundary layer. The last section of the paper gives a short overview of advanced simulations for these different test cases. In the conclusion, we list research perspectives, which include some more general topics such as data assimilation.

  • Open Access French
    Authors: 
    MORARU, George; FRANGEARD, Didier;
    Publisher: HAL CCSD
    Country: France

    La présente invention concerne le domaine de l’usinage par enlèvement de matière. L’invention a ainsi pour objet une machine d’usinage et, plus particulièrement, une machine de perçage ou de fraisage. La machine à la particularité d’intégrer deux moteurs électriques destinés à contrôler les mouvements d’avance et de rotation d’un outil, tout en permettant une action d’assistance vibratoire, particulièrement utile pour le perçage de matériaux difficiles à usiner. The present invention relates to the field of machining of materials by chip removal. The invention presents a special machine tool and, more particularly, a drilling or milling machine. The machine has the particularity of incorporating two electric motors for controlling the feed and rotation motions of a tool, while allowing a vibration assistance optional motion, particularly useful for drilling hard to machine materials . Contrats et collaboration ARTS / AEI

  • Publication . Article . Other literature type . 2008
    Open Access English
    Authors: 
    Chanhong Kim; Rasa Meskauskiene; Klaus Apel; Christophe Laloi;
    Publisher: HAL CCSD
    Country: France

    When plant cells are under environmental stress, several chemically distinct reactive oxygen species (ROS) are generated simultaneously in various intracellular compartments and these can cause oxidative damage or act as signals. The conditional flu mutant of Arabidopsis, which generates singlet oxygen in plastids during a dark-to-light transition, has allowed the biological activity of singlet oxygen to be determined, and the criteria to distinguish between cytotoxicity and signalling of this particular ROS to be defined. The genetic basis of singlet-oxygen-mediated signalling has been revealed by the mutation of two nuclear genes encoding the plastid proteins EXECUTER (EX)1 and EX2, which are sufficient to abrogate singlet-oxygen-dependent stress responses. Conversely, responses due to higher cytotoxic levels of singlet oxygen are not suppressed in the ex1/ex2 background. Whether singlet oxygen levels lower than those that trigger genetically controlled cell death activate acclimation is now under investigation.

  • Open Access English
    Authors: 
    Pierre Sans; Christine Boizoit-Szantai;
    Publisher: HAL CCSD
    Country: France

    International audience; The consumption of organic meat products has been characterized using the Kantar Worldpanel data col-lected from 2012 to 2014. Based on the price of the total quantity purchased and the amount spent on each purchase, several indicators were calculated and their values compared between organic households (OHs) and nonorganic households (NOHs). OHs were characterized according to sociodemographic and attitudi-nal variables. Finally, a logit model was constructed to determine the likelihood of belonging to the organic household category. Consumption is low in terms of the proportion of households that purchase organic meat (O-ME) and meat products (O-MPs), the average quantity purchased per year and per purchasing household (2 kg and 0.9 kg respectively), and purchasing frequency. These values are below those reported by questionnaire surveys which can be attributed to an attitude-behavior gap. The main organic meat prod-ucts purchased are bovine meat and pork processed products. Moreover, being part of a family with children and living in a big city increase the probability of purchasing O-ME and O-MPs. ,

  • Publication . Article . 1952
    Open Access French
    Authors: 
    Vinconneau;
    Publisher: HAL CCSD
    Country: France

    International audience

  • Publication . Preprint . Article . 2011
    Open Access English
    Authors: 
    Julian Rode; Marc Le Menestrel;
    Publisher: HAL CCSD
    Country: France

    International audience; We study the influence of decision power on fairness in the division of gains from productive activity. In an experimental setting, two actors are involved in generating a gain, but only one contributes actively by completing a task. In three treatments, decision power to divide the gain is assigned to (1) the inactive, (2) both the inactive and the active, (3) the active participant. Results show that changes in decision power not only affect allocations in accordance with previous research, but that they also alter fairness perceptions. In particular, full decision power significantly enhances self-serving interpretations of fairness. We discuss implications for organizational design.

  • Open Access
    Authors: 
    Jean-Paul Blaizot; Jean-Yves Ollitrault;
    Publisher: American Physical Society (APS)
    Country: France

    We study fermionic excitations in a cold ultrarelativistic plasma. We construct explicitly the quantum states associated with the two branches which develop in the excitation spectrum as the chemical potential is raised. The collective nature of the long wavelength excitations is clearly exhibited. Email contact: ollie@amoco.saclay.cea.fr Comment: Saclay-T93/018 Email: ollie@amoco.saclay.cea.fr

  • Open Access English
    Authors: 
    F. Said; C. Chauvin;
    Publisher: HAL CCSD
    Country: France

    International audience; —This paper presents a study carried out within the context of Level 3 automated driving. It aims to characterize drivers takeover behaviour by exploring quantitative data related to the driver's performance (vehicle data) and qualitative data (user experience expressed in post-activity interviews). For this purpose, several techniques of multivariate analysis were used such as clustering of variables and units. This study illustrates that user experience is associated with the magnitude of actions related to lateral and longitudinal control; positive experience being associated with smoother actions, whereas negative feelings were associated with rougher ones. Furthermore, two main driver's profiles emerged; they are described by two latent variables, one of which is quality of the actions. Future research will investigate the determinants of these profiles.

  • Open Access English
    Authors: 
    Y Caballero; Vincent Jomelli; Pierre Chevallier; Pierre Ribstein;
    Publisher: HAL CCSD
    Country: France

    Abstract The hydrological processes within slope deposits are not well known, particularly for high tropical mountains with climatic conditions giving seasonal contrasts in the hydrological cycle. Measurements have been taken in a high Andean valley of the Cordillera Real (Bolivia) with the aim to determine the role of the slope deposits in the framework of a hydraulic modelling. Different transfer time measurements combined with morphometrical and sedimentological analysis were carried out on three talus slopes and two moraines during the rainy season. After injection of salt, the electrical conductivity of the water in slope deposits springs is monitored to estimate transfer velocities. The hydrological behaviour of these slope deposits depends on the season. In the dry season, all the water infiltrates and there is no visible outlet. During the wet season, one part soaks in and gives springs down slope. The lag times estimated by the measurement of tracer velocity demonstrate that these slope deposits delayed the flow depending on the type of deposit. The delay is at least 24 h in the case of the talus slopes and more than 48 h in the case of lateral moraines.

Advanced search in
Research products
arrow_drop_down
Searching FieldsTerms
Any field
arrow_drop_down
includes
arrow_drop_down
Include:
798,714 Research products, page 1 of 79,872
  • Publication . Conference object . Part of book or chapter of book . 2020
    Open Access
    Authors: 
    Thomas Bonis; Nicolas Pronost; Saida Bouakaz;
    Publisher: Springer International Publishing
    Country: France
    Project: ANR | OMEGA (ANR-16-CE92-0042)

    International audience; Although predictive forward gait simulators have existed for a little while, only few sensitivity studies have been proposed. We present a study analysing precision, accuracy, stability and sensitivity of such simulator. We studied a gait simulator based on the trajectory mimicking method proposed by Lee et al. [1]. We assessed the effect of motion variation on the resulting gait simulation using the sensitivity analysis method proposed by Saltelli et al. [2]. Our method supports the use of this simulator for prediction.

  • Publication . Other literature type . Article . 2016
    Open Access English
    Authors: 
    Jacquin, L.; Brion, V.; Molton, P.; Sipp, D.; Dandois, J.; Deck, S.; Sartor, F.; Coustols, E.; Caruana, D.;
    Publisher: HAL CCSD
    Country: France

    L'article passe en revue les recherches menées à l'ONERA au cours des trente dernières années sur le buffet transsonique. Nous présentons d'abord le phénomène du buffet transsonique et nous expliquons son importance pour les applications aéronautiques. On distingue ensuite le buffet 2D produit par une aile bidimensionnelle et le buffet 3D qui caractérise les ailes en flèches d’envergure finie. Le buffet 2D se présente sous la forme d’une oscillation d’ensemble de tout l’écoulement couplant un déplacement de l’onde de choc et le décollement de la couche limite en aval de ce choc. Le buffet 3D prend quant à lui la forme d'une poche de perturbations localisées dans une portion limitée de l'aile. Nous rappelons que ces mécanismes ont d'abord été étudiés à l’ONERA dans les années 80 à travers une série de tests réalisés dans la soufflerie transsonique T2 à Toulouse et dans la grande soufflerie transsonique S2 de Modane. Ces travaux pionniers ont ensuite été approfondis dans la soufflerie S3Ch de Meudon de manière à élaborer une base de données complète du buffet 2D sur une aile 2D en régime turbulent, que nous décrivons. Cette base de données a été utilisée de façon extensive, à l’ONERA et dans d’autres institutions pour valider différents outils de simulation, ces derniers étant alors utilisés à leur tour pour étudier la physique du buffet. Nous illustrons cette collaboration entre la simulation et la physique en rappelant qu'une analyse de stabilité linéaire de solutions précises des équations de Navier-Stokes moyennées au sens de Reynolds (RANS) a permis de prouver que le buffet 2D provient d'un mécanisme d'instabilité globale. Nous passons également en revue des essais plus récents réalisés dans la soufflerie S3Ch sur le cas d'une aile 2D laminaire qui révèlent des comportements très distincts par rapport au cas turbulent. Cela illustre la sensibilité du buffet à la nature de la couche limite. Le dernier paragraphe du document donne un bref aperçu des simulations avancées de ces différents cas tests. Dans la conclusion, nous énumérons les perspectives de recherche sur le sujet, qui incluent aussi des thématiques méthodologiques plus générales telles que l'assimilation de données. The paper reviews research conducted at ONERA over the last thirty years on the transonic buffet. We first present the transonic buffet phenomenon and we explain its importance for aeronautical applications. Then, a distinction is made between the 2D buffet produced by an airfoil and the 3D buffet that characterizes swept wings of finite span. The 2D buffet amounts to a pure oscillation of the shock phase-locked with the detachment and reattachment of the boundary layer downstream, whereas the 3D buffet takes the form of a pocket of broadband perturbations located in a limitedportion of the wing. We recall that these mechanisms were first studied in the 1980s through a series of tests conducted in the transonic wind tunnel ONERA T2 at Toulouse and in the large transonic wind tunnel ONERA S2Ma at Modane. Since this pioneering work, progress in the measurement techniques has led to the constitution of a comprehensive database of the 2D buffet that we describe. This database, obtained in the wind tunnel ONERA S3Ch at Meudon, has been extensively used to validate various CFD tools, with the latter being used in turn to investigate the buffet physics. We illustrate this collaboration between simulation and physics by recalling that a linear stability analysis of accurate Reynolds-Averaged-Navier-Stokes (RANS) solutions made it possible to prove that the buffet on a 2D airfoil stems from a global instability mechanism.We also review more recent tests done in the case of a laminar airfoil, which reveal very distinct behaviors of the buffet flow. This illustrates how sensitive the buffet is to the nature of the boundary layer. The last section of the paper gives a short overview of advanced simulations for these different test cases. In the conclusion, we list research perspectives, which include some more general topics such as data assimilation.

  • Open Access French
    Authors: 
    MORARU, George; FRANGEARD, Didier;
    Publisher: HAL CCSD
    Country: France

    La présente invention concerne le domaine de l’usinage par enlèvement de matière. L’invention a ainsi pour objet une machine d’usinage et, plus particulièrement, une machine de perçage ou de fraisage. La machine à la particularité d’intégrer deux moteurs électriques destinés à contrôler les mouvements d’avance et de rotation d’un outil, tout en permettant une action d’assistance vibratoire, particulièrement utile pour le perçage de matériaux difficiles à usiner. The present invention relates to the field of machining of materials by chip removal. The invention presents a special machine tool and, more particularly, a drilling or milling machine. The machine has the particularity of incorporating two electric motors for controlling the feed and rotation motions of a tool, while allowing a vibration assistance optional motion, particularly useful for drilling hard to machine materials . Contrats et collaboration ARTS / AEI

  • Publication . Article . Other literature type . 2008
    Open Access English
    Authors: 
    Chanhong Kim; Rasa Meskauskiene; Klaus Apel; Christophe Laloi;
    Publisher: HAL CCSD
    Country: France

    When plant cells are under environmental stress, several chemically distinct reactive oxygen species (ROS) are generated simultaneously in various intracellular compartments and these can cause oxidative damage or act as signals. The conditional flu mutant of Arabidopsis, which generates singlet oxygen in plastids during a dark-to-light transition, has allowed the biological activity of singlet oxygen to be determined, and the criteria to distinguish between cytotoxicity and signalling of this particular ROS to be defined. The genetic basis of singlet-oxygen-mediated signalling has been revealed by the mutation of two nuclear genes encoding the plastid proteins EXECUTER (EX)1 and EX2, which are sufficient to abrogate singlet-oxygen-dependent stress responses. Conversely, responses due to higher cytotoxic levels of singlet oxygen are not suppressed in the ex1/ex2 background. Whether singlet oxygen levels lower than those that trigger genetically controlled cell death activate acclimation is now under investigation.

  • Open Access English
    Authors: 
    Pierre Sans; Christine Boizoit-Szantai;
    Publisher: HAL CCSD
    Country: France

    International audience; The consumption of organic meat products has been characterized using the Kantar Worldpanel data col-lected from 2012 to 2014. Based on the price of the total quantity purchased and the amount spent on each purchase, several indicators were calculated and their values compared between organic households (OHs) and nonorganic households (NOHs). OHs were characterized according to sociodemographic and attitudi-nal variables. Finally, a logit model was constructed to determine the likelihood of belonging to the organic household category. Consumption is low in terms of the proportion of households that purchase organic meat (O-ME) and meat products (O-MPs), the average quantity purchased per year and per purchasing household (2 kg and 0.9 kg respectively), and purchasing frequency. These values are below those reported by questionnaire surveys which can be attributed to an attitude-behavior gap. The main organic meat prod-ucts purchased are bovine meat and pork processed products. Moreover, being part of a family with children and living in a big city increase the probability of purchasing O-ME and O-MPs. ,

  • Publication . Article . 1952
    Open Access French
    Authors: 
    Vinconneau;
    Publisher: HAL CCSD
    Country: France

    International audience

  • Publication . Preprint . Article . 2011
    Open Access English
    Authors: 
    Julian Rode; Marc Le Menestrel;
    Publisher: HAL CCSD
    Country: France

    International audience; We study the influence of decision power on fairness in the division of gains from productive activity. In an experimental setting, two actors are involved in generating a gain, but only one contributes actively by completing a task. In three treatments, decision power to divide the gain is assigned to (1) the inactive, (2) both the inactive and the active, (3) the active participant. Results show that changes in decision power not only affect allocations in accordance with previous research, but that they also alter fairness perceptions. In particular, full decision power significantly enhances self-serving interpretations of fairness. We discuss implications for organizational design.

  • Open Access
    Authors: 
    Jean-Paul Blaizot; Jean-Yves Ollitrault;
    Publisher: American Physical Society (APS)
    Country: France

    We study fermionic excitations in a cold ultrarelativistic plasma. We construct explicitly the quantum states associated with the two branches which develop in the excitation spectrum as the chemical potential is raised. The collective nature of the long wavelength excitations is clearly exhibited. Email contact: ollie@amoco.saclay.cea.fr Comment: Saclay-T93/018 Email: ollie@amoco.saclay.cea.fr

  • Open Access English
    Authors: 
    F. Said; C. Chauvin;
    Publisher: HAL CCSD
    Country: France

    International audience; —This paper presents a study carried out within the context of Level 3 automated driving. It aims to characterize drivers takeover behaviour by exploring quantitative data related to the driver's performance (vehicle data) and qualitative data (user experience expressed in post-activity interviews). For this purpose, several techniques of multivariate analysis were used such as clustering of variables and units. This study illustrates that user experience is associated with the magnitude of actions related to lateral and longitudinal control; positive experience being associated with smoother actions, whereas negative feelings were associated with rougher ones. Furthermore, two main driver's profiles emerged; they are described by two latent variables, one of which is quality of the actions. Future research will investigate the determinants of these profiles.

  • Open Access English
    Authors: 
    Y Caballero; Vincent Jomelli; Pierre Chevallier; Pierre Ribstein;
    Publisher: HAL CCSD
    Country: France

    Abstract The hydrological processes within slope deposits are not well known, particularly for high tropical mountains with climatic conditions giving seasonal contrasts in the hydrological cycle. Measurements have been taken in a high Andean valley of the Cordillera Real (Bolivia) with the aim to determine the role of the slope deposits in the framework of a hydraulic modelling. Different transfer time measurements combined with morphometrical and sedimentological analysis were carried out on three talus slopes and two moraines during the rainy season. After injection of salt, the electrical conductivity of the water in slope deposits springs is monitored to estimate transfer velocities. The hydrological behaviour of these slope deposits depends on the season. In the dry season, all the water infiltrates and there is no visible outlet. During the wet season, one part soaks in and gives springs down slope. The lag times estimated by the measurement of tracer velocity demonstrate that these slope deposits delayed the flow depending on the type of deposit. The delay is at least 24 h in the case of the talus slopes and more than 48 h in the case of lateral moraines.

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