Acoustic propagation in random media using polynomial chaos expansions

International audienceSound propagation in the atmosphere is highly dependent on the information to specify the waveguide parameters. For real-world applications, there is considerable uncertainty regarding this information, and it is more realistic to consider the wind and temperature profiles as random functions, with associated probability distribution functions. Even though the numerical methods currently-in-use allow accurate results for a given atmosphere, high dimensionality of the random functions severely limits the ability to compute the random process representing the acoustic field, and some form of sampling reduction is necessary. In this work we use polynomial chaos (gPC)-based metamodels to represent the effect of large-scale features onto the acoustic normal modes. The impact of small-scale atmospheric structures is modelled using a perturbative approach of the coupling matrix. This two-level approach allows to estimate the statistical influence of each mode as the frequency varies. An excellent agreement is obtained with the gPC-based propagation model, with a few realizations of the random process, when compared with the Monte Carlo approach, with its thousands of realizations

Infrasound propagation in multiple-scale ran- dom media using generalized polynomial chaos

International audienceInfrasound propagation in realistic environments is highly dependent on the information to specify the waveguide parameters. For real-world applications, there is considerable uncertainty regarding this information, and it is more realistic to consider the wind and temperature profiles as random functions, with associated probability distribution functions reflecting phenomena that are filtered out in the available data. Even though the numerical methods currently-in-use allow accurate results for a given atmosphere, high dimensionality of the random functions severely limits the ability to compute the random process representing the acoustic field, and some form of sampling reduction is necessary. In this work, we use polynomial chaos (gPC)-based metamodels to represent the effect of large-scale atmospheric variability onto the acoustic normal modes. The impact of small-scale atmospheric structures is modelled using a perturbative approach of the coupling matrix. This multi-level approach allows to estimate the statistical influence of each mode as the frequency varies. An excellent agreement is obtained with the gPC-based propagation model, with a few realizations of the random process, when compared with the Monte Carlo approach, with its thousands of realizations. Furthermore, the gPC framework allows computing easily the Sobol indices without supplementary cost, which is essential for sensitivity studies

La démocratie à l'épreuve du conflit

Poser la question de la place et de la valeur du conflit en démocratie n’est pas inédit. La philosophie politique au XXe siècle le fait déjà abondamment, tant pour contester le consensualisme de la démocratie délibérative, que pour interroger les limites du libéralisme sur la question des dangers que représentent les conflits radicaux, et proposer, de manière très diverse, une valorisation de l’agonistique. Pour autant, de nombreux événements récents, notamment des mouvements sociaux contestataires, reposent cette question avec acuité. Est-ce à dire que l’on assiste à une intensification des conflits sociaux de nos jours, et ce pour le bien de nos démocraties ? Le conflit peut-il, de manière pertinente, servir de principe politique ? Les contributions qui suivent ont la particularité d’interroger la conflictualité démocratique contemporaine soit directement, soit de manière plus large en la liant à des questions plus anciennes – révélant ainsi toute sa complexité. Questions regarding the role and value of social conflict in democracy are nothing new. This issue has been extensively discussed in 20th century political philosophy, where scholars have brought into question the consensualism of deliberative democracy as well as the limited ways in which liberalism responds to real crises. They have proposed, in various ways, agonism as a viable and valuable alternative. Moreover, contemporary social movements renew the call for more analysis on the role of social conflict. Are we facilitating an intensification of social conflict in our present day? Does this act in the interests of democracy? Can conflict serve a political principal? The following contributions examine the democratic potential of agonism, either directly or through a broader approach that engages longstanding questions in the field – revealing its complexity

CONCERTO : Digital processing for finding and tuning LEKIDs

We describe the on-line algorithms developed to probe Lumped Element Kinetic Inductance Detectors (LEKID) in this paper. LEKIDs are millimeter wavelength detectors for astronomy. LEKID arrays are currently operated in different instruments as: NIKA2 at the IRAM telescope in Spain, KISS at the Teide Observatory telescope in Tenerife, and CONCERTO at the APEX 12-meter telescope in Chile. LEKIDs are superconducting microwave resonators able to detect the incoming light at millimeter wavelengths and they are well adapted for frequency multiplexing (currently up to 360 pixels on a single microwave guide). Nevertheless, their use for astronomical observations requires specific readout and acquisition systems both to deal with the instrumental and multiplexing complexity, and to adapt to the observational requirements (e.g. fast sampling rate, background variations, on-line calibration, photometric accuracy, etc). This paper presents the different steps of treatment from identifying the resonance frequency of each LEKID to the continuous automatic control of drifting LEKID resonance frequencies induced by background variations

CONCERTO : Digital processing for finding and tuning LEKIDs

We describe the on-line algorithms developed to probe Lumped Element Kinetic Inductance Detectors (LEKID) in this paper. LEKIDs are millimeter wavelength detectors for astronomy. LEKID arrays are currently operated in different instruments as: NIKA2 at the IRAM telescope in Spain, KISS at the Teide Observatory telescope in Tenerife, and CONCERTO at the APEX 12-meter telescope in Chile. LEKIDs are superconducting microwave resonators able to detect the incoming light at millimeter wavelengths and they are well adapted for frequency multiplexing (currently up to 360 pixels on a single microwave guide). Nevertheless, their use for astronomical observations requires specific readout and acquisition systems both to deal with the instrumental and multiplexing complexity, and to adapt to the observational requirements (e.g. fast sampling rate, background variations, on-line calibration, photometric accuracy, etc). This paper presents the different steps of treatment from identifying the resonance frequency of each LEKID to the continuous automatic control of drifting LEKID resonance frequencies induced by background variations

CONCERTO : Digital processing for finding and tuning LEKIDs

We describe the on-line algorithms developed to probe Lumped Element Kinetic Inductance Detectors (LEKID) in this paper. LEKIDs are millimeter wavelength detectors for astronomy. LEKID arrays are currently operated in different instruments as: NIKA2 at the IRAM telescope in Spain, KISS at the Teide Observatory telescope in Tenerife, and CONCERTO at the APEX 12-meter telescope in Chile. LEKIDs are superconducting microwave resonators able to detect the incoming light at millimeter wavelengths and they are well adapted for frequency multiplexing (currently up to 360 pixels on a single microwave guide). Nevertheless, their use for astronomical observations requires specific readout and acquisition systems both to deal with the instrumental and multiplexing complexity, and to adapt to the observational requirements (e.g. fast sampling rate, background variations, on-line calibration, photometric accuracy, etc). This paper presents the different steps of treatment from identifying the resonance frequency of each LEKID to the continuous automatic control of drifting LEKID resonance frequencies induced by background variations

Doc’CISMeF : un outil de recherche Internet orienté vers l’enseignement et la formation à distance en médecine

Contexte : les ressources disponibles sur l’Internet concernant l’enseignement et la formation dans le domaine de la médecine sont en croissance exponentielle. L’objectif de Doc’CISMeF est de créer un outil de recherche générique fondé sur un modèle d’information qui encapsule le thésaurus MeSH. Pour indexer les ressources de qualité, Doc’CISMeF utilise 4 niveaux hiérarchiques : méta-terme, mot-clé, qualificatif et type de ressources. Deux recherches sont possibles dans Doc’CISMeF : une recherche simple qui permet à l’utilisateur de saisir un terme ou une expression ; si ce terme appartient à notre modèle d’information, il sera explosé, c’est-à-dire que Doc’CISMeF affichera toutes les ressources indexées avec des termes hiérarchiquement inférieurs. La recherche avancée permet des requêtes plus complexes, combinant avec des opérateurs booléens, méta-termes, mots-clés, qualificatifs et types de ressources, mais aussi tous les champs de Doc’CISMeF, comme par exemple la cible d’une ressource éducative, notamment le cycle d’études. Doc’CISMeF utilise deux outils standards pour organiser l’information : le thésaurus MeSH et le format de données et de méta-données Dublin Core. Les champs de Doc’CISMeF sont : titre, auteur, description, site éditeur, date, identifiant, format, langue, mots-clés et type de ressources, institution, ville, département ou province ou état, pays, public concerné, coût, parrainage. Doc’CISMeF est un des outils de recherche qui sera utilisé au sein de la future Université Médicale Virtuelle Francophone

Doc'CISMeF: A Search Tool Based on "Encapsulated" MeSH Thesaurus

Abstract In the year 2000, the Internet became a major source of health information for the health professional and the Netizen. The objective of Doc'CISMeF (D'C

Violence(s) de la préhistoire à nos jours

De nos jours, violences et insécurité occupent une place importante dans les médias et semblent la préoccupation majeure de la société. Qu'en était-il autrefois ? Les violences étaient-elles omniprésentes ? Une évolution des notions de normes sociales et d'infraction à celles-ci s'est-elle produite ? Cet ouvrage, publication d'un colloque tenu à l'université de Perpignan, regroupe les points de vue d'historiens, d'archéologues et de juristes. Ceux-ci proposent diverses interprétations des sources narratives, normatives, des traités juridiques, des archives judiciaires qui permettent d'approcher violences individuelles et violences collectives. Quelques communications traitent des rapports entre l'État et la violence, rapports qui peuvent être éclairés par le droit pénal, la répression des violences, les lois d'exception. Les pratiques actuelles de l'État fixant des limites juridiques au travail des historiens sont aussi abordées.Colloque subventionné par l'Université de Perpignan Via Domitia, le département d'histoire, le CRHISM, l'école Doctorale, la mairie de Perpignan, la région Languedoc-Roussillon. Ouvrage publié avec le concours du CRHISM

The KISS Experiment

Mapping millimetre continuum emission has become a key issue in modern multi-wavelength astrophysics. In particular, spectrum imaging at low-frequency resolution is an asset for characterising the clusters of galaxies via the Sunyaev–Zel’dovich effect. In this context, we have built a ground-based spectrum-imager named KIDs Interferometer Spectrum Survey (KISS). This instrument is based on two 316-pixel arrays of Kinetic Inductance Detectors (KID) cooled to 150 mK by a custom dilution refrigerator-based cryostat. By using Ti–Al and Al absorbers, we can cover a wide frequency range between 80 and 300 GHz. In order to preserve a large instantaneous field of view ∼ 1 , the spectrometer is based on a Fourier transform interferometer. This represents a technological challenge due to the fast scanning speed that is needed to overcome the effects of background atmospheric fluctuations. KISS is installed at the QUIJOTE 2.25 m telescope in Tenerife since February 2019 and is currently in its commissioning phase. In this report, we present an overview of the instrument and the latest results.With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737