HAL Portal IOGS (nstitut d'Optique Graduate School)
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Extreme near-field heat transfer between silica surfaces
No full textInternational audienceDespite recent experiments exhibiting an impressive enhancement in radiative heat flux between parallel planar silica surfaces with gap sizes of about 10 nm, the exploration of sub-nanometric gap distances remains unexplored. In this work, by employing non-equilibrium molecular dynamics (NEMD) simulations, we study the heat transfer between two SiO2 plates in both their amorphous and crystalline forms. When the gap size is 2 nm, we find that the heat transfer coefficient experiences a substantial ∼30-fold increase compared to the experimental value at the gap size of 10 nm confirming the dependence on the distance inversely quadratic as predicted by the fluctuational electrodynamics (FE) theory. Comparative analysis between NEMD and FE reveals a generally good agreement, particularly for amorphous silica. Spectral heat transfer analysis demonstrates the profound influence of gap size on heat transfer, with peaks corresponding to the resonances of dielectric function. Deviations from the fluctuational electrodynamics theory at smaller gap sizes are interpreted in the context of acoustic phonon tunneling and the effects of a gradient of permittivity close to the surfaces
Blood flow velocity in skin microvasculature by line-field confocal optical coherence tomography (LC-OCT) at two different acquisition speeds
No full textInternational audienceLC-OCT enabled manual tracking of individual cell motion in the upper dermal microvessels. Blood flow velocity was on average 2.5 times higher (173 vs 70 µm/s) when measured at 40 vs 8 frames per second
Algorithme de lumière structurée pour le calcul de mesure d'erreur 3D longue distance
No full textInternational audienceThe 3D acquisition of an indoor scene with colorimetric information is currently achieved by vision systems using structured light. The existing solutions are specific to small scenes at short distances. In the case of larger scenes where the vision system is far from the analysed objects, i.e. more than 4 m from the acquisition system, the solutions do not enable scene acquisition with a measurement error of the order of a millimetre. From existing algorithms in the literature, the method, Bi-Frequency and Gray Code Phase Shifting (B-GCPS) combining two structured light algorithms is proposed. The main idea consists in using several reference planes to minimize the measurement error. Our method uses the Gray Code + Phase Shifting (GC+PS) algorithm to assist in the acquisition of reference planes and the selection of the most relevant ones. Then, the Bi-frequency algorithm estimates the 3D coordinates of the scene with a very low measurement error, thanks to different reference planes acquired previously. With the proposed method, the acquisition of long distances scenes higher than 2 m in width and length is possible, with a very low measurement error. This method reduces the measurement error on the 3 axes (X, Y, Z) by at least 400, in the order of a millimetre
SENSE-LM : A Synergy between a Language Model and Sensorimotor Representations for Auditory and Olfactory Information Extraction
No full textInternational audienceThe five human senses – vision, taste, smell, hearing, and touch – are key concepts that shape human perception of the world. The extraction of sensory references (i.e., expressions that evoke the presence of a sensory experience) in textual corpus is a challenge of high interest, with many applications in various areas. In this paper, we propose SENSE-LM, an information extraction system tailored for the discovery of sensory references in large collections of textual documents. Based on the novel idea of combining the strength of large language models and linguistic resources such as sensorimotor norms, it addresses the task of sensory information extraction at a coarse-grained (sentence binary classification) and fine-grained (sensory term extraction) level.Our evaluation of SENSE-LM for two sensory functions, Olfaction and Audition, and comparison with state-of-the-art methods emphasize a significant leap forward in automating these complex tasks
Theia : Astrométrie différentielle à haute précision pour les exoplanètes et la matière noire
No full textInternational audienceHigh precision differential Astrometry is the branch of astronomy that evaluates the relative position, distance and motion of celestial objects with respect to the stars present in the field of view.A mission called Theia has been submitted in 2022 for ESA's M7 call for missions, using a diffraction-limited telescope about 1m in diameter and with a field of view of 0.5 degrees, capable of achieving sub-microsecond angular accuracy. Such precision makes it possible to study the nature of dark matter in our galaxy and to reveal the architecture of exoplanetary systems close to the Sun, down to the mass of the Earth. But for the moment the technology readiness levels (TRL) of the detector plane and the telescope stability are too low. The aim of the experimental tests presented in this poster is to improve the TRL of 2 specific aspects: the calibration of new detectors with very large number of pixels and the calibration of the field distortion thanks to the stars in the field of view.First, a key element of such a space telescope is the focal plane, which must be calibrated spatially with an extreme precision down to the 1e-5 pixel level. Previous work has shown that this is possible with small detector matrices (Crouzier et al. 2016, A&A 595, A108). The goal is now to check the performances and validate this method with the new very large detectors. Pyxalis, a company based near Grenoble, is developing very large detectors that have a low noise level and high sensitivity. The aim is to use this type of detectors for a laboratory demonstration, to ensure that the performance achieved meets the required specifications.In addition, recent work on telescope stability (Malbet et al. 2022, SPIE 12180, 1F) has shown that the reference stars in the field of the telescope can be used as actual metrology sources in order to compute the distortion function of the field. The second goal of these test bed is to experimentally show the performances of this new field calibration method. This poster will present the latest developments of these laboratory experiments
CHARM High-energy Ions for Micro Electronics Reliability Assurance (CHIMERA)
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Temperature Cycling Effects on Infrared Radiation-Induced Attenuation of Silica-based Optical Fibers
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Exploration des architectures des systèmes exoplanétaires proches par astrométrie spatiale à haute précision
No full textNational audienceL'astrométrie est la branche de l'astronomie qui évalue la position, la distance et le mouvement des étoiles et des autres objets célestes. L'astrométrie globale consiste à relier des étoiles ayant de grandes distances angulaires dans un réseau où chaque étoile est connectée à un grand nombre d'autres étoiles dans toutes les directions. La condition de fermeture du réseau assure la réduction des erreurs de position de toutes les étoiles. Pour accroître la précision de mesure sur certains objets astronomiques spécifiques, il convient de consacrer plus de temps d'observation pour déterminer leur position relative par rapport aux étoiles présentes dans le champ de vue, ce que l'on appelle astrométrie relative ou astrométrie différentielle. Lors de la dernière étude prospective de l'ESA, le Senior Committee a reconnu qu'après Gaia, "les prochaines étapes de l'astrométrie spatiale pourraient consister à améliorer d'un ordre de grandeur la précision astrométrique relative" (section 3.1.7). Une mission appelée Theia a été soumise en 2022 pour l'appel M7 de l'ESA, utilisant un télescope limité par la diffraction d'environ 1 m de diamètre et avec un champ de vue de 0,5 degré, capable d'atteindre une précision inférieure à la micro-seconde d'angle. Une telle précision permet d'étudier d'obtenir l'architecture des systèmes exoplanétaires proches du Soleil jusqu'à la masse de la Terre. Nous présenterons le principe de ce projet de mission spatiale, les capacités de détection et en quoi ce projet de classe M pourrait être bénéfique à la fois pour comprendre les architectures des systèmes exoplanétaires proches, mais aussi permettre d'identifier des sources d'intérêt pour des missions interférométriques et/ou coronographiques chargées de caractériser spectralement ces exoplanètes proches
