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Interpréter avec Alceste (ou IramuteQ)
No full textInternational audienceUne analyse de discours assistée par ordinateur (ADAO) réalisée à l’aide d’un logiciel d’analyse statistique de données textuelles, tel qu’ALCESTE ou IramuteQ semble particulièrement appropriée dans le cadre d’analyses transversales de corpus volumineux. L’ADAO permet non seulement de limiter la perte d’informations, inhérente à une analyse manuelle des données d’un vaste corpus, mais favorise aussi la distanciation du chercheur par rapport à ses données. Dans le cadre de cette communication, nous montrerons, au travers d’exemples d’usages de ce type de logiciel dans nos recherches en SHS, la valeur heuristique de la démarche. Elle offre la possibilité à la fois de découvrir de manière inductive d’autres aspects non analysés du corpus et d’obtenir une forme de confirmation ou d’infirmation des résultats obtenus manuellement. L’usage d’outils numériques dans des travaux de recherche, lorsqu’ils peuvent se révéler un soutien à la démarche, est à considérer. Bien entendu, un logiciel ne fournit pas à lui seul les résultats d’une recherche. Il est paramétré en fonction des hypothèses du chercheur. Ce dernier doit ensuite analyser et interpréter les données classifiées. Cependant, ce recours à l’outil numérique se révèle être une aide précieuse et un atout dans une méthodologie de la complexité
Caractérisation de l'interaction fluide-structure d'un assemblage de coeur de réacteur sous forçage sismique
No full textWithin the framework of safety studies, it is necessary to have validated models of the fluid forces exerted on fuel assemblies in the event of an earthquake. In the PWR (Pressurized Water Reactor) technology used in France, fuel assemblies are made of cylindrical rods bundles arranged in a square array and subjected to an axial flow. In case of an earthquake, these assemblies are subjected to lateral oscillations. These vibrations can lead to the deformation of the assemblies. Test campaigns on real fuel assemblies have been carried out and have revealed the existence of dissipative fluid forces whose evolution and spatial distribution are still poorly documented. The objective of the present work is to contribute to the description of these forces in dynamics. The reference model for the description of the dynamics of slender structures under axial flow is the TLP model (Taylor-Lighthill-Païdoussis). In the literature this model has been validated for a structure very close to the cylinder bundle. Static studies performed on a cylinder in a bundle have shown a non-negligible influence of the extremities on the forces exerted by the fluid on the structure. The literature proposes few validation cases of the TLP model for more complex structures close to a fuel assembly. In order to evaluate the capacity of the model to describe the fluid forces exerted on a structure closer to a fuel assembly, a new test bench was designed and put into service. This test rig allows to laterally oscillate a cylinder bundle 5 x 5 with grids at each end in an axial flow. Force measurements at each grid give access to the resultant force of the structure. A numerical model completes this experimental approach and gives access to the distribution of forces in the structure. The forces obtained experimentally seem to indicate an important effect of the grids. The forces obtained from the simulations confirm the observations made on a bundle of cylinders and bring new elements on the distribution of the local forces as well as the influence of the extremities.Dans le cadre des études de sûreté, il est nécessaire de disposer de modèles validés des forces fluides s’exerçant sur des assemblages combustibles en cas de séisme. Dans la technologie REP (réacteur à eau pressurisée) utilisée en France, les assemblages sont constitués de faisceaux de crayons cylindriques disposés en réseau carré et soumis à un écoulement axial. En cas de séisme, ces assemblages sont soumis à des oscillations latérales. Ces vibrations peuvent mener à la déformation des assemblages. Des campagnes d’essais sur assemblage combustible réel ont été réalisées et ont mis en évidence l'existence de forces fluides dissipatives dont l'évolution et la répartition spatiale reste encore mal documentées. L'objectif des présents travaux est de contribuer à la description de ces forces en dynamique. Le modèle de référence pour la description de la dynamique des structures élancées sous écoulement axial est le modèle de TLP (Taylor-Lighthill-Païdoussis). Dans la littérature ce modèle a été validé pour une structure très proche du faisceau de cylindres. Des études statiques réalisées sur un cylindre dans un faisceau ont montré une influence non négligeable des extrémités sur les efforts exercés par le fluide sur la structure. La littérature propose peu de cas de validation du modèle TLP pour des structures plus complexes et proches d'un assemblage combustible. Afin d'évaluer la capacité du modèle à décrire les efforts fluides s'exerçant sur une structure plus proche d'un assemblage combustible, un nouveau banc d'essai a été conçu et mis en service. Ce banc d'essais permet de faire osciller latéralement un faisceau de cylindre 5 x 5 muni de grilles à chaque extrémité dans un écoulement axial. Des mesures de force au niveau de chaque grille donne accès à la résultante d'effort de la structure. Un modèle numérique complète cette approche expérimentale et donne accès à la répartition des efforts dans la structure. Les forces obtenues expérimentalement semble indiquer un effet important des grilles. Les forces issues des simulations confortent les observations faites sur un faisceau de cylindres et apportent de nouveaux éléments sur la répartition des efforts locaux ainsi que l'influence des extrémités
Datasheet: where is requirements engineering gone? A case in Benchmarking Mobile Robotics
No full textInternational audienceThe lifecycle of a system is extended from its early conception to its retirement of service. The lifespan of Unmanned Ground Vehicles (UGVs) can be expected to last over 50 years in the defence market. In this context, the rising complexity of UGV systems imposes engineering steps that would ensure both capabilities of the system and resilience to its future inclusion in a system-of-system context. During its operational usage, the UGV is supposed to be manoeuvred for specifically designed purposes following user manual datasheet of the components off-the-shelf (COTS) that were integrated. This paper exposes the public user datasheet relevance compared to the system engineering requirements that are the artefacts of system design architecture. The use of connecting COTS user manual to system requirements is discussed, all the more if the systems are to be re-used in a system production line
Channeling Acceleration in Crystals and Nanostructures and Studies of Solid Plasmas: New Opportunities
No full textInternational audiencePlasma wakefield acceleration (PWA) has shown illustrious progress over the past two decades of active research and resulted in an impressive demonstration of O(10 GeV) particle acceleration in O(1 m) long single structures. While already potentially sufficient for some applications, like, e.g., FELs, the traditional laser- and beam-driven acceleration in gaseous plasma faces enormous challenges when it comes to the design of the PWA-based O(1-10 TeV) high energy colliders due to the complexity of energy staging, low average geometric gradients, and unprecedented transverse and longitudinal stability requirements. Channeling acceleration in solid-state plasma of crystals or nanostructures, e.g., carbon nanotubes (CNTs) or alumna honeycomb holes, has the promise of ultra-high accelerating gradients O(1-10 TeV/m), continuous focusing of channeling particles without need of staging, and ultimately small equilibrium beam emittances naturally obtained while accelerating
Technical Feasibility of Supervision of Stretching Exercises by a Humanoid Robot Coach for Chronic Low Back Pain: The R-COOL Randomized Trial
No full textInternational audienceAdherence to exercise programs for chronic low back pain (CLBP) is a major issue. The R-COOL feasibility study evaluated humanoid robot supervision of exercise for CLBP. Aims are as follows: (1) compare stretching sessions between the robot and a physiotherapist (control), (2) compare clinical outcomes between groups, and (3) evaluate participant perceptions of usability and satisfaction and therapist acceptability of the robot system. Prospective, randomized, controlled, single-blind, 2-centre study comparing a 3-week (3 hours/day, 5 days/week) physical activity program. Stretching sessions (30 minutes/day) were supervised by a physiotherapist (control) or the robot. Primary outcome: daily physical activity time (adherence). Secondary outcomes: lumbar pain, disability and fear and beliefs, participant perception of usability (system usability scale) and satisfaction, and physiotherapist acceptability (technology acceptance model). Clinical outcomes were compared between groups with a Student t -test and perceptions with a Wilcoxon test. Data from 27 participants were analysed ( n = 15 control and n = 12 robot group). Daily physical activity time did not differ between groups, but adherence declined (number of movements performed with the robot decreased from 82% in the first week to 72% in the second and 47% in the third). None of the clinical outcomes differed between groups. The median system usability scale score was lower in the robot group: 58 (IQR 11.8) points vs. 87 (IQR 9.4) in the control group at 3 weeks ( p < 0.001 ). Median physiotherapist rating of the technology acceptance model was <3 points, suggesting a negative opinion of the robot. In conclusion, adherence to robot exercise reduced over time; however, lumbar pain, disability, or fear and beliefs did not differ between groups. The results of the participant questionnaires showed that they were willing to use such a system, although several technical issues suggested the KERAAL system could be improved to provide fully autonomous supervision of physical activity sessions
Control of the acoustic waves generated by intense laser filamentation in water
No full textInternational audienceExperiments and simulations are performed to study filamentation and generation of acoustic waves in water by loosely focused multi-millijoules laser pulses. When the laser pulse duration is increased from femtosecond to nanosecond duration, a transition is observed from a filamentary propagation with extended and low energy density deposition to a localized breakdown, related to high energy density deposition. The transition suggests that Kerr selffocusing plays a major role in the beam propagation dynamics. As a result, the shape, the amplitude and the spectrum of the resulting pressure wave present a strong dependence on the laser pulse duration
Molecular diagnosis of alveolar echinococcosis in patients based on frozen and formalin-fixed paraffin-embedded tissue samples
No full textInternational audienceConfirmed diagnosis of alveolar echinococcosis (AE) is based on pathological criteria and molecular evidence. This parasite-borne disease, caused by the cestode Echinococcus multilocularis, sparingly involves humans as a dead-end host. In humans, the parasite mainly colonizes the liver but can colonize any organ and cause atypical forms, often difficult to characterize clinically. Moreover, molecular methods may be suitable to make the diagnosis of AE in cases of atypical forms, extra-hepatic localizations, or immunosuppressed patients. The aim of this study was to determine the most relevant published PCR techniques, for diagnosis of AE in patients and adopt the best strategy for molecular diagnosis depending on the nature of the tested sample. In this study, we evaluated nine end-point PCR assays and one real-time PCR assay (qPCR), targeting mitochondrial genes, using a total of 89 frozen or formalin-fixed paraffin-embedded (FFPE) samples from either 48 AE or 9 cystic echinococcosis patients. Targeted fragment-genes ranged from 84 to 529 bp. Six PCR assays were able to amplify the DNA of 100% of the frozen AE-samples and for one PCR, 69.8% of the FFPE AE-samples. The 16S rrnL PCR (84 bp) was positive in PCR for 77% of the AE samples and in qPCR for 86.5%. The sensitivity of the PCR assays was higher for fresh samples and FFPE samples stored for less than 5 years. The qPCR assay further increased sensitivity for the tested samples, confirming the need for the development of an Echinococcus spp. qPCR to improve the molecular diagnosis of echinococcoses
Very High-Resolution Satellite-Derived Bathymetry and Habitat Mapping Using Pleiades-1 and ICESat-2
No full textInternational audienceAccurate and reliable bathymetric data are needed for a wide diversity of marine research and management applications. Satellite-derived bathymetry represents a time saving method to map large shallow waters of remote regions compared to the current costly in situ measurement techniques. This study aims to create very high-resolution (VHR) bathymetry and habitat mapping in Mayotte island waters (Indian Ocean) by fusing 0.5 m Pleiades-1 passive multispectral imagery and active ICESat-2 LiDAR bathymetry. ICESat-2 georeferenced photons were filtered to remove noise and corrected for water column refraction. The bathymetric point clouds were validated using the French naval hydrographic and oceanographic service Litto3D® dataset and then used to calibrate the multispectral image to produce a digital depth model (DDM). The latter enabled the creation of a digital albedo model used to classify benthic habitats. ICESat-2 provided bathymetry down to 15 m depth with a vertical accuracy of bathymetry estimates reaching 0.89 m. The benthic habitats map produced using the maximum likelihood supervised classification provided an overall accuracy of 96.62%. This study successfully produced a VHR DDM solely from satellite data. Digital models of higher accuracy were further discussed in the light of the recent and near-future launch of higher spectral and spatial resolution satellites
Improvement of hierarchical matrices for 3D elastodynamic problems with a complex wavenumber
No full textInternational audienceIt is well known in the literature that standard hierarchical matrix (H-matrix) based methods, although very efficient for asymptotically smooth kernels, are not optimal for oscillatory kernels. In a previous paper, we have shown that the method should nevertheless be used in the mechanical engineering community due to its still important data-compression rate and its straightforward implementation compared to H 2-matrix, or directional, approaches. Since in practice, not all materials are purely elastic it is important to be able to consider visco-elastic cases. In this context, we study the effect of the introduction of a complex wavenumber on the accuracy and efficiency of H-matrix based fast methods for solving dense linear systems arising from the discretization of the elastodynamic (and Helmholtz) Green's tensors. Interestingly, such configurations are also encountered in the context of the solution of transient purely elastic problems with the convolution quadrature method. Relying on the theory proposed in [12] for H 2-matrices for Helmholtz problems, we study the influence of the introduction of damping on the data compression rate of standard H-matrices. We propose an improvement of H-matrix based fast methods for this kind of configuration. This work is complementary to the recent work [12]. Here, in addition to addressing another physical problem, we consider standard H-matrices, derive a simple criterion to introduce additional compression and we perform extensive numerical experiments