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Strong spin-orbital coupling-induced unusual magnetic and magnetocaloric features in YbVO 3 single crystals
No full textInternational audienceRVO 3 (R = rare earth) orthovanadates is a family of perovskites that reveals fascinating physical properties mainly arising from the strong coupling between spins, orbitals, and crystallographic structure. In this paper, we mainly focus on the magnetic and magnetocaloric properties of YbVO 3 single crystals grown by the floating-zone method. The prepared crystals unveil several phase transitions close to 104 K, 65 K and 20 K. The observed 104 K feature originates from the occurrence of a C-type antiferromagnetic ordering of V 3+ magnetic moments while that close to 65 K corresponds to the transformation of the established C-type spin ordering (SO) into a G-type antiferromagnetic ordering which is associated with a change in orbital ordering (OO) from G-type to C-type. The phase transition taking place close to 20 K is more probably attributed to the change of G-type SO into Ctype SO. On the other hand, the below 65 K ordering state constituted of G-type SO/C-type OO remains very stable even under sufficiently high magnetic fields (7 T). This underlines the weakness of f-d exchange couplings in the YbVO 3 vanadate being in contrast with other RVO 3 orthovanadates containing smaller rare earth elements such as DyVO 3 compound. Additionally, we particularly demonstrate that the complex electronic and magnetic structures of YbVO 3 results in interesting thermal effects over a wide range of temperature including a giant negative magnetocaloric effect close to 60 K. In fact, the maximum entropy change is found to be almost -12 J/kg K in the magnetic field change of 7 T applied along the c axis and the ab-plane at 64.25 K and 65.5 K, respectively. More interestingly, the strong magnetocrystalline anisotropy shown by the V 3+ sublattice results in a large rotating magnetocaloric effect (RMCE) at relatively high temperatures (60 K). This means that the refrigeration process can be achieved simply by spinning YbVO 3 single crystals in constant magnetic fields within the ac or bc planes instead varying the external magnetic field. Such RMCEs would open the avenue for the design of more efficient and compact magnetic refrigerators with simplified designs. Our experimental findings are discussed and analyzed in the framework of Density Functional Theory (DFT) calculations.</div
III-Nitride MEMS drum resonators on flexible metal substrates
No full textInternational audienceWe present a simple and efficient process for fabricating III-Nitride (III-N) mechanical resonators on flexible metal substrates. This method combines Van der Waals epitaxy of III-N epilayers with the deposition of a thick metal stressor atop the III-N layers. During thermal treatment, the 30 μm thick metal stressor deposited on a 300 nm AlGaN/500 nm GaN layer grown on a 3 nm two-dimensional hexagonal-Boron Nitride (2D h-BN) release layer, initiates a one-step Self-Lift-Off and Transfer (SLOT) process. This process effectively transfers the III-N heterostructure from the h-BN/Sapphire growth wafer to the flexible metal stressor substrate. Additional local etching of the metal stressor and deposition of front electrodes allow for releasing self-standing III-N layers with integrated actuation. Fabricated III-N MEMS drum resonators were analyzed using optical profilometry and laser Doppler vibrometer, enabling the observation of static deflections and distinct vibration modes. Finite element method (FEM) simulations were also performed to further understand experimental observations and assess the mechanical properties of the released III-N layers, particularly enabling the estimation of stress in the GaN and AlGaN released layers. This straightforward approach not only provides a practical solution for cost-effective III-N MEMS resonators but also ensures flexibility, and crack-free structures
Effect of Dissolved CO2 on the Hydraulic Performance of a Centrifugal Pump with Inducer under Cavitating Conditions
No full textInternational audienceAbstract This experimental study investigates the impact of dissolved gases specifically carbon dioxide (CO 2 ) on the hydraulic performance of a centrifugal pump equipped with an inducer. Tests were conducted at constant temperature in a closed-loop test rig using both degassed water and water containing 300 ppm in mass of dissolved CO 2 , corresponding to the maximum solubility of the gas at 0.2 bars. The experimental setup included a transparent test section and a high-speed camera operating at 1000 Hz, allowing detailed visualization of vapor cavity dynamics under cavitating flow regimes. The results demonstrate that the presence of dissolved CO 2 significantly impairs pump performance, especially at low flow rates, where head degradation occurs earlier and more gradually. In contrast, degassed water delays cavitation onset but results in a more abrupt performance drop once cavitation develops. These findings underscore the critical role of fluid quality and gas content in cavitation behavior and confirm previous observations made on the inducer- only configuration
Modélisation de l’interaction entre le membre résiduel et la prothèse chez la personne amputée d'un membre inférieur pour la conception numérique d’emboîtures
No full textFor lower limb prosthesis users, the prosthetic socket, which connects the prosthetic limb to the residual limb, is a critical interface. It must provide safe control of the prosthesis, while ensuring the user's comfort, as a poor socket fit can lead to pain, irritation, or even pressure ulcers. Traditionally, sockets are designed from a plaster cast of the residual limb, in a time-consuming, quasi-artisanal process requiring great expertise. Indeed, a slight rectification in the socket shape can have a major impact on the user’s comfort and mobility.To speed up this process and improve its repeatability, a digital alternative has been introduced. The socket can now be designed from a 3D scan of the residual limb, using Computer-Aided Design and Manufacturing (CAD/CAM) tools. This evolution paves the way for the integration of more quantitative tools into this workflow, to guide the prosthetist in the rectification process. This thesis is part of the ANR IMPRINT project, which proposes to integrate a biomechanical model of the residual limb/socket assembly, in order to estimate a number of mechanical indicators of socket fit before its manufacture.The first part of this thesis presents a state-of-the-art review of solutions for optimizing socket design. The interface pressure between the residual limb and the socket has been identified as a relevant mechanical indicator of socket fit. As a result, numerous models, based on the Finite Element (FE) method, have been developed to estimate this parameter. However, most of them have only been implemented on a single subject and have never been validated experimentally, which is a major barrier to their transfer to clinical practice.The aim of this thesis was therefore to develop and evaluate a subject-specific FE model for estimating interface pressure, with a view to its integration into CAD/CAM software.The lack of validation of FE models can be explained by the limitations of available pressure measurement systems in terms of accuracy and ease of use. The second chapter therefore focuses on the development of an accurate, robust and affordable solution, based on 3D printing and force sensors, for measuring interface pressure.The third chapter presents the development of a subject-specific FE model of the residual limb/socket assembly to estimate interface pressure, and its evaluation on 6 transtibial amputees using the aforementioned measurement system. To our knowledge, this is the first study in the literature to evaluate a FE model of the residual limb and socket on such a large cohort. The results highlight the impact of individual characteristics on model accuracy, and the importance of evaluating it on a larger number of subjects. A sensitivity study was carried out with the dual aim of improving the model's accuracy and simplifying it for clinical transfer. Two critical parameters were identified - the external geometry of the residual limb, and soft tissue compressibility - opening up two avenues for future research.The last chapter of the thesis addresses two additional barriers to clinical adoption. A first section explores the use of a statistical shape model to estimate the internal geometry of the residual limb without the need for clinically inaccessible medical imaging systems. The second presents a semi-automated socket rectification method based on FE modelling, intended to help interpret pressure data.Altogether, this work demonstrates the feasibility of prosthetic socket rectification guided by a subject-specific Finite Element model, and marks a first step towards the development of biomechanical tools to assist prosthetists in optimizing and accelerating socket design.Pour les utilisateurs de prothèse de membre inférieur, l’emboîture prothétique, qui fait le lien entre la prothèse et le membre résiduel, est une interface critique. Elle doit assurer un contrôle efficace de la prothèse, sans être inconfortable, car un mauvais ajustement peut entraîner des douleurs, des irritations, voire des escarres. Elle est conventionnellement conçue à partir d’un moulage en plâtre du membre résiduel, selon un processus chronophage et quasi-artisanal, qui nécessite une grande expertise. En effet, une rectification minime de la paroi peut avoir un impact majeur sur le ressenti et la mobilité de l’utilisateur.Pour accélérer ce processus et améliorer sa répétabilité, une alternative numérique se démocratise peu à peu. L’emboîture peut désormais être conçue à partir d’un scan 3D du membre résiduel, avec des outils de Conception et Fabrication Assistée par Ordinateur (CFAO). Cette évolution ouvre la voie à l’intégration d’outils quantitatifs dans le processus de rectification pour guider le prothésiste. Le projet ANR IMPRINT, dans lequel s’inscrit cette thèse, propose d’intégrer un modèle biomécanique du couple membre résiduel/emboîture, permettant d’estimer des indicateurs quantitatifs de l’ajustement de l’emboîture en amont de sa fabrication.La première partie de ce manuscrit présente un état de l’art des solutions pour optimiser la conception de l’emboîture. La distribution de pression à l’interface avec le membre résiduel a été identifiée comme un indicateur mécanique de l’ajustement de l’emboîture. De nombreux modèles, reposant sur la méthode des Éléments Finis (EF), ont donc été introduits pour estimer ce paramètre. Cependant, la majorité de ces modèles n’ont été implémentés que sur un seul sujet et n’ont pas été validés expérimentalement, ce qui constitue un frein majeur à leur transfert en pratique clinique.Ce travail de thèse visait donc à développer et évaluer un modèle EF personnalisé pour estimer la pression à l’interface, en vue de son intégration dans un logiciel de CFAO.L’absence de validation des modèles EF s’explique en partie par les limites des systèmes de mesure de pression disponibles en termes de précision et de praticité. Le second chapitre présente donc le développement d’une solution précise, robuste et abordable, reposant sur l’impression 3D et des capteurs de force, pour mesurer la pression à l’interface.La troisième partie présente le développement d’un modèle EF personnalisé de l’ensemble membre résiduel/emboîture pour estimer la pression à l’interface, et son évaluation sur 6 personnes amputées transtibiales à l’aide du système de mesure susmentionné. Il s’agit de la première étude de la littérature à évaluer un modèle EF de ce type sur une telle cohorte. Les résultats soulignent l’impact des caractéristiques individuelles sur la précision du modèle, et l’importance de l’évaluation sur plus de sujets. Une étude de sensibilité a été menée dans le double objectif d’améliorer la précision du modèle, et de le simplifier en vue d’un transfert clinique. Deux paramètres critiques ont été identifiés - la géométrie externe du membre résiduel, et la compressibilité des tissus mous - ouvrant deux axes de recherche.Enfin, la dernière partie aborde deux verrous au transfert clinique d’un tel outil. Une première section explore l’utilisation d’un modèle statistique pour estimer la géométrie interne du membre résiduel sans avoir recours à des systèmes d’imagerie médicale peu accessibles. La seconde propose une méthodologie semi-automatique de rectification de l’emboîture basée sur le modèle EF pour aider à l’interprétation des données de pression.Finalement, ces travaux démontrent la faisabilité d’une rectification de l’emboîture guidée par un modèle EF personnalisé, et constituent une première étape vers le développement d’outils biomécaniques destinés aux prothésistes pour optimiser et accélérer la conception des emboîtures
Posture and ventilation in the playing of wind musical instruments: a pilot experiment
No full textPerformance sportive et musicale : geste, contrôle, perception; GSAM - Acoustique Musicale: GAP - Voix et ParoleNational audienceFor wind instrumentalists, breath control is essential for sound production. It requires a "non-respiratory" use of muscles whose primary function is respiratory. These muscles also contribute to maintaining posture, resulting in a interaction between the ventilatory and postural systems. Observing that wind instrumentalists move to varying degrees while playing, depending on the instrument and the musical instruction, we aim to investigate the relationships between the musical task, breathing strategies, and movement, which involve temporal variations in posture. Are the musicians’ movements intended to emphasize musical expression independently of the respiratory cycle ? To explore this, we record various instrumental control parameters, acoustic signals, and biomechanical data during musical performance : mouth and instrumental pressure using pressure sensors, mouth position and opening area with a camera-mirror system attached to the instrument, radiated acoustic pressure using two microphones, and thoracic volume variations and postural oscillations of body segments with an optoelectronic motion capture system. We will present the results obtained during the musical performance on the transverse flute. The selected musical excerpt comes from an Etude chosen for its simple and regular musical structure, allowing the imposition of specific breathing instructions that alter the respiratory cycle period. The analyses will integrate instrumental control, the use of the respiratory and postural systems, and the musical structure
Illusion of Control in Gambling Behavior in a Non-Clinical Sample of Adults Aged 40–75
No full textInternational audienceThe illusion of control (IoC) is a cognitive distortion implicated in risky and problem gam-bling. This study aimed to validate a comprehensive IoC measure, the Multi-Dimensional Rating Scale for Illusion of Control in Gambling (EEMDIC), in a large non-clinical sam-ple of adult and aging gamblers, and to clarify how IoC relates to gambling severity, game type, and age. A total of 1,311 participants aged 40–75 completed the EEMDIC, the Prob-lem Gambling Severity Index (PGSI), and questions on gambling habits and sociodemo-graphics. Exploratory (n = 649) and confirmatory (n = 662) factor analyses assessed scale structure. ANOVAs, linear regressions, Mann–Whitney U tests, and Spearman correlations examined associations with game category, PGSI scores, education, occupation, and age. Factor analyses supported a reduced 14-item EEMDIC with four coherent factors: Luck, Skill, Strategy, and Rituals/Superstitious Behaviors. Higher EEMDIC scores, especially on primary-control dimensions (Skill, Strategy), were associated with greater gambling severity and engagement in strategic betting (sports, horse racing). Education correlated negatively with IoC, and occupational differences emerged. Age was modestly but sig-nificantly associated with lower IoC: it explained ≈ 2.8% of total variance and 0.9–4.1% across factors. Framing on gains or losses showed no age effect after controlling for PGSI. The EEMDIC is a reliable, multidimensional tool distinguishing primary and secondary control beliefs. Findings link primary-control beliefs to gambling harm and show modest age-related declines in IoC. The scale can inform targeted prevention and tailored inter-ventions across game types and sociodemographic groups
Strength Characterization by Vibrational Analysis of Building Demolition Wood to Assess Reuse Potential
No full textInternational audienceThe objective of the study is to develop a methodology for strength characterization by vibrational analysis of a batch of wood from building demolitions with a view to its reuse. This approach is part of an experimental deconstruction/reconstruction project located in the Vosges "département" of France and led by the social housing landlord, VOSGELIS. The main constraint related to this intention of reuse is the obtention of the strength class of the elements, which is not recorded in the standards. The comparative study of different nondestructive technologies has shown that the values of the longitudinal dynamic modulus of elasticity obtained by the vibrational method are closer on average (15%) to the actual value obtained by the bending tests than those obtained by the ultrasonic method (35%). A portable measuring bench suitable for the deconstruction site was also developed during the study for the utilization of the vibrational method. The values of the dynamic modules of elasticity obtained on this bench are close, on average, to the values of the modulus of elasticity obtained by bending tests executed on a test slab (13%). This study made it possible to extend the use of the NF EN 14081-2+A1 standard to woods from building demolitions. However, this standard needs to be adapted for the classification of that typology of wood, with a reference batch constituted of 15 to 20 samples.</div
Robotized Incremental Sheet Forming trajectory control using deep neural network for force/torque compensator and task-space error tracking controller
No full textInternational audienceIn Robotized Incremental Sheet Forming (ISF), achieving precise geometrical accuracy is a challenging task due to trajectory tool center point (TCP) position errors at the forming tool attached to the robot’s end-effector. These errors primarily arise from external disturbance forces and torques generated during the interaction between the forming tool and the elastic metal sheet. While jointtorque space controllers can mitigate reaction forces and torques through dynamic modeling, jointspace control has inherent limitations, particularly for industrial high-load robots like the ABB IRB 8700. To overcome these challenges, thiswork implements an external force/torque (F/T) compensator in task-space using a deep neural network. The network predicts trajectory errors induced by reaction forces and torques measured via a 6-axis F/T sensor. Additionally, the forming tool’s trajectory is precisely monitored using a laser tracker, which serves as a feedback mechanism in a closed-loop task-space error-tracking controller. This controller detects and corrects trajectory deviations in real time. By integrating the F/T compensator and the task-space error-tracking controller, the proposed approach effectively compensates for reaction forces and torques while addressing additional errors introduced by other process-related factors. This integration results in significantly enhanced accuracy in robotic incremental forming processes
Reassessing Carbon Black’s Role in the Thermo-Oxidative Ageing of Elastomers
No full textInternational audienceThis study explores the impact of carbon black on the structure-property relationships of natural rubber during thermo-oxidative ageing. Natural rubber samples containing 27% mass of carbon black were subjected to ageing in air at temperatures ranging from 70 °C to 115 °C for up to 270 days. The ageing process was monitored in terms of oxygen consumption, swelling, and tensile testing. Results revealed a substantial reduction in crosslink density, highlighting chain scission as the dominant process. Tensile properties were significantly affected, showing decreases in modulus, elongation at break, and stress at break. A comparison with previous studies on unfilled natural rubber shed light on the role of carbon black during oxidation. Our findings suggest that carbon black plays a minor role in macromolecular network modifications for similar exposure conditions. More specifically, we analyze the validity of structure–property relationships between the average crosslink density and mechanical properties during thermo-oxidative ageing regardless of whether the elastomer contains carbon black filler. These results illustrate a new strategy for studying the aging of filled elastomers
A Lattice Boltzmann kernel on GPU for real-time 3D aerodynamical digital twin
No full textInternational audienceA Lattice Boltzmann kernel on GPU for real-time 3D aerodynamical digital twi