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Radiated Sound and Transmitted Vibration Following the Ball/Racket Impact of a Tennis Serve
No full textInternational audienceShock-induced vibrations transmitted from the racket to the tennis player's upper limb have interested researchers, whether for investigating their effect on injury risk, or for designing new equipment. Measuring these vibrations is, however, very challenging in an ecological playing situation: sensors must be of very high quality in order to precisely measure high-energy and broad-frequency signals, as well as non-invasive in order to allow the players to perform their usual movements. The working hypothesis of this paper is that contactless sound recordings of the ball/racket impact carry the same information as direct vibratory measurements. The present study focuses on the tennis serve, as being tennis' most energy-demanding stroke, therefore possibly being the most traumatic stroke for the upper limb. This article aims (a) to evaluate the propagation of vibration from the racket to the upper limb; and (b) to identify correlations with acoustic signals collected simultaneously. Eight expert tennis players performed serves with three rackets and two ball spin effects. Accelerometers measured the vibration on the racket and at five locations on the upper limb, and a microphone measured the impact sound. Resulting signals were analyzed in terms of energy and spectral descriptors. Results showed that flat serves produced louder sounds, higher vibration levels, lower acoustic spectral centroids, and higher vibratory spectral centroids than kick serves. The racket only had a marginal influence. Similarities between acoustic and vibratory measurements were found (levels were correlated), but so were differences (spectral centroids tended to be negatively correlated), encouraging further studies on the link between sound and vibration for the in situ measurement of shock-induced vibration.</div
Business text classification with imbalanced data and moderately large label spaces for digital transformation
No full textInternational audienceAbstract Digital transformation refers to an organization’s use of digital technology to improve its products, services, and operations, aligning them with evolving business requirements. To demonstrate this transformative process, we present a real-life case study where a company seeks to automate the classification of their textual data rather than relying on manual methods. Transitioning to automated classification involves deploying machine learning models, which rely on pre-labeled datasets for training and making predictions on new data. However, upon receiving the dataset from the company, we faced challenges due to the imbalanced distribution of labels and moderately large label spaces. To tackle text classification with such a business dataset, we evaluated four distinct methods for multi-label text classification: fine-tuned Bidirectional Encoder Representations from Transformers (BERT), Binary Relevance, Classifier Chains, and Label Powerset. The results revealed that fine-tuned BERT significantly outperformed the other methods across key metrics like Accuracy, F1-score, Precision, and Recall. Binary Relevance also displayed competence in handling the dataset effectively, while Classifier Chains and Label Powerset exhibited comparatively less impressive performance. These findings highlight the remarkable effectiveness of fine-tuned BERT model and the Binary Relevance classifier in multi-label text classification tasks, particularly when dealing with imbalanced training datasets and moderately large label spaces. This positions them as valuable assets for businesses aiming to automate data classification in the digital transformation era
Threshold of Saturation Degree of Unsaturated Sand to Cause Liquefaction Considering the Sample Volumetric Strain: Modelization and Experimental Laboratory Investigation
No full textInternational audienceThis paper aims to determine a non-liquefiable domain corresponding to the threshold of saturation degree where liquefaction does not occur under cyclic loading. To determine this threshold, sample volumetric strain at liquefaction state of unsaturated soil was modeled considering the suction. In low saturation degree zones, capillary suction is taken into account. In a high saturation degree zone, spherical suction caused by surface tension of air bubbles is considered by using its microscopic analysis and its equivalent size. Finally, three series of experimental tests have been made to give the data and verify the presented model
A new methodology for anisotropic yield surface description using model order reduction techniques and invariant neural network
No full textInternational audienceIn this paper, we present a general methodology that we call spectral neural network (SNN) which enables to generate automatically knowing a few datapoints (eight at most), a sound and plausible yield surface for any variations of a given anisotropic material, e.g. batches of the same material or same type of material produced by a different supplier. It relies on the use of a reliable parametrization of a performant analytic orthotropic yield function for the generation of a large database of yield surface shapes and the singular value decomposition method to create a reduced basis. For a specific material, a surrogate model for the reduced basis coordinates is further constructed using few additional datapoints. The dense neural network is built such as to ensure that the invariance requirements dictated by the material symmetry as well as the convexity of the yield surface are automatically enforced. The capabilities of this new methodology are demonstrated for hexagonal closed packed materials titanium materials, which are known to be particularly challenging to model due to their anisotropy and tension–compression asymmetry. Furthermore, we show that the SNN methodology can be extended such as to include variations of multiple materials of vastly different plastic behavior and yield surface shapes. The in-depth analysis presented reveals the benefits and limits of the hybrid data-driven models for description of anisotropic plasticity
Vibrotactile Cues with Net Lateral Forces Resulting from a Travelling Wave
No full textInternational audienceUltrasonic travelling waves possess the capability to induce net shear forces on the finger pulp, which finds utility in various applications. This study specifically investigates their potential in generating vibrotactile cues through force modulation. Two experiments are outlined herein. In the first, we assess the detection threshold, estimated at 1.5 μm peak-peak for a modulation frequency of 75 Hz. Remarkably, this threshold closely aligns with that observed in conventional vibrotactile indentation and remains consistent regardless of the force modulation method employed. In the second experiment, we correlate the amplitude of a travelling wave tactile display with the vibration amplitude of a shaker to achieve equivalent vibration intensity. Our findings reveal a substantial amplitude ratio range experienced on the travelling wave device, spanning from 24 to 155, which is pivotal in optimizing vibrotactile stimulator design. Additionally, we demonstrate that vibrations below 1 μm yield negligible net lateral forces on the finger pulp. These results underscore the potential of ultrasonic travelling waves in enhancing tactile feedback systems
Evaluating the Effectiveness of Avatar-Based Collaboration in XR for Pump Station Training Scenarios
No full textInternational audienceImmersive Virtual Reality (iVR) and Augmented Reality (AR) have become increasingly accessible tools for enhancing learning and training experiences. This study aims to evaluate the effectiveness of avatar-based collaboration within each platform, particularly in the context of pump station training scenarios, so an application was developed: EduAvatars: Pumpstation XR. A total of four concepts were prepared: on-site AR instruction with avatar, on-site AR instruction without avatar but with manual, iVR instruction with avatar, and iVR instruction without avatar but with manual. In each concept, users are supposed to proceed with two experimental tasks: speed control and bypass control, following the same procedure: check valves and level indicators. The usability of this application was validated as a preliminary study, and the results are promising for its introduction to lectures to improve student learning. The preliminary results indicate user satisfaction with the integration of EduAvatars and a significant interest in using it frequently. However, our work also discusses identified areas for improvement
Fixturing-driven determination of multi-product assembly plans in the context of product variety and reconfiguration
No full textInternational audienceThe design and use of assembly systems for more than one dedicated product becomes more important to manufacturing industries as product variety increases and lot sizes decrease. Since their introduction in the late 90’s, reconfigurable production systems have become a lever to enable those multi-product assembly systems. The question remains how can the needed reconfiguration degree be defined and how can be determined where in the assembly line reconfiguration makes sense. A new method for fixturing driven determination of multi-product assembly plans is presented in this paper to answer this question. It relies on LCS/SCS analysis of the assembly plan signature of a product variety. A case study is furnished to illustrate the application of the new approac
Spatialisation, fusion et enrichissement d'imagerie multimodale pour les Sciences du Patrimoine
No full textDigital heritage is becoming an effervescent concept at the crossroads of many disciplinary fields. By extension the multi-faceted Cultural heritage asset, as object of study, is at the center of interdisciplinary studies, essentially from digital-born documentation procedures and technologies where real-based modeling or sensing is a key feature. As a matter of fact, the imaging tools and 2D/3D digitization technologies mobilized today to survey, document and study heritage artifacts offer many perspectives and investigation paths to improve the shared knowledge around a heritage object. However, while the need of digital knowledge and expertise is developing in kind as well as in number, the also variable methods mobilized are facing the challenge of multimodality. As a core notion of this dissertation, the multimodality is understood and justified by the overgrowing need to gather and interlink various digital resources (including multiple sensors, scales of observation, spectral or temporal layers) in order to allow a crossing of views and expertise. This work is inspired by a systemic approach where the mechanisms and the data stream, from the raw instrumental data captured in-situ to the knowledge extraction and representation is explored by (re)usable strategies exploiting the richness of the multimodal scenarios. Starting from a critical review of the acquisition-processing-interpretation sequence, this thesis proposes innovative ways to improve key steps such as data fusion and data provenance. A global strategy is proposed to better articulate the instrumental, computational and analytical phases toward the construction of a digital twin of heritage object. This research work is structured by three contributions proposing at different crucial intersections of the system, so-called strategic actions, to increase the informative potential of 2D/3D multimodal modeling. The coherence of the explored tracks, allows in particular to reveal reasoned, and pragmatic approaches based on the multimodal digitization and potentially being able to contribute to the upcoming challenges in terms of correlation of spatio-temporal semantically enriched data.Le Patrimoine Culturel est un objet d’étude protéiforme, désormais au centre d’enjeux documentaires interdisciplinaires, dont les procédures et les technologies numériques jouent un rôle prépondérant. Le Patrimoine Numérique s’installe comme une notion en effervescence, située à l’intersection de nombreux domaines de connaissances. Les techniques d'imageries mobilisées dans les Sciences du Patrimoine pour relever, documenter et examiner les objets patrimoniaux offrent de nombreuses perspectives d’investigation pour améliorer les connaissances partagées autour d’un objet d'étude devenu hybride, à l'interface entre le Réel et le Virtuel. Pour autant, à l’heure où ce savoir-faire numérique se développe, l'ensemble des méthodes et des outils mobilisés se heurtent au défi de la multimodalité. Cette problématique, au cœur de ce projet de thèse, se reflète par la nécessité croissante de mettre en coopération une variété de ressources numériques (comprenant une multiplicité de capteurs, d’échelles d’observations, de couches spectrales ou temporelles) dans l’objectif de permettre une croisée des regards et des expertises. Cette thèse propose d'appréhender les flux de numérisation 2D et 3D par une approche systémique visant à consolider le continuum informationnel reliant les données instrumentales capturées "in-situ" aux connaissances qu’il est possible d’en extraire. Ce travail de recherche explore différentes stratégies pour faire fructifier la richesse et la diversité des scenarios multimodaux. Les contributions principales se développent autour d'une relecture de la triade Acquisition -- Traitement -- Interprétation, en la mettant en interaction avec des thématiques telles que la Spatialisation, la Fusion et l'Enrichissement des données. Différentes approches sont proposées afin de mieux articuler les phases d’instrumentales, computationnelles et analytiques permettant d'augmenter le potentiel informatif des modélisations 2D/3D multimodales. Les pistes explorées sont appuyées par une série de travaux et d'expérimentations faisant émerger des synergies possibles pour explorer la corrélation de données spatio-temporelles sémantiquement enrichies basées sur des numérisations multimodales
Asymmetry and intermittency in the rheo-inertial transition to turbulence in pipe flow
No full textInternational audienceTransition to turbulence in pipe has been extensively studied but is still not completely understood and even more for non-Newtonian fluids. We focus here on yield stress shear-thinning fluids and the mechanism leading to the transition in pipe, the so-called rheo-inertial transition to turbulence. An experimental setup has enabled us to identify flow regimes in a cylindrical pipe, using both flow visualizations and pressure drops measurements for a range of Reynolds numbers. We delimited the non-Newtonian specific regime in the laminar-turbulent transition triggered at a critical Reynolds number below the turbulent puffs onset. This pre-transition regime is associated with a velocity profile asymmetry in which its degree and position evolve as the Reynolds number increases. The origin for the stability of this rheo-inertial regime is discussed, as it could be due to a competition between the nonlinear contributions of rheological behavior and flow inertia. Beyond this regime, we quantified the intermittence of puff transit, revealing the delay to turbulence. We spotted for the first time a different rheo-inertial transitional behavior in the intermittency evolution vs Reynolds number, displaying a smoother transition on a broader range. Finally, the critical Reynolds numbers for different yield stresses are compared with previous works, and the novelty is the linear increase in the delay to turbulent puffs with the yield stress
Correlated IR-SEM-TEM studies of three different grains from Ryugu: From the initial material to post-accretional processes
No full textInternational audienceIn order to better constrain the alteration history of the Ryugu parent body, we performed a multi-analytical study combining scanning electron microscopy, transmission electron microscopy and infrared spectroscopy on sections extracted from the three fragments A0064-FO019, A0064-FO021 and C0002-FO019 returned from Ryugu by the Hayabusa2 space mission. The three sections show large differences in terms of structure, mineralogy and infrared signature. Section A0064-FO019 resembles the major Ryugu lithology with the presence of both fine-grained phyllosilicates (fg-phyllos) with embedded nanosulfides and coarse-grained phyllosilicates (cg-phyllos), whereas section C0002-FO019 belongs to the group of the less altered lithologies with the presence of anhydrous minerals embedded in a partially amorphous matrix. Section A0064-FO021 also belongs to this group but shows two different lithologies, a compact amorphous one and a more porous and very fractured one showing the presence of Na-rich phosphate, calcite and olivine. The two less altered lithologies (sections A0064-FO021 and C0002-FO019) show the presence of numerous mineralogical features similar to those observed in cometary interplanetary dust particles, ultra-carbonaceous Antarctic micrometeorites or in the CM Paris meteorite, i.e. amorphous and partially crystallized matrix with GEMS-like ghosts objects, whisker olivine, phosphide, or FeNi metal. This supports an outer solar system origin common with that of cometary material for the Ryugu parent body. Combined with the results of Nakamura et al. (2022b) reporting the presence of a lithology showing the presence of GEMS-like objects, we propose that section C0002-FO019 represents the onset of aqueous alteration of such primitive materials. The cg-phyllos and fg-phyllos of section A0064-FO019, i.e. of the major Ryugu lithology, representing the advanced stage of alteration, exhibit distinctive IR signatures with a higher abundance of oxygen-rich functional groups in the organic matter (OM) from the cg-phyllos. We thus suggest the following chronology of formation and evolution for Ryugu: (1) accretion of highly porous aggregate of GEMS-like units with fine-grained high-temperature anhydrous silicates, (2) onset of alteration with the dissolution of primary nanosulfides and development of amorphous/partially crystallized material in the pores, (3) crystallization of fg-phyllos with a second generation of sulfides, (4) later formation of cg-phyllos devoid of nanosulfides and their associated oxygen-rich OM in a more water-rich environment