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Sophisticated study of time, frequency and statistical analysis for gradient-switching-induced potentials during MRI
No full textInternational audienceMagnetic resonance imaging (MRI) is a standard procedure in medical imaging, on a par with echography and tomodensitometry. In contrast to radiological procedures, no harmful radiation is produced. The constant development of magnetic resonance imaging (MRI) techniques has enabled the production of higher resolution images. The switching of magnetic field gradients for MRI imaging generates induced voltages that strongly interfere with the electrophysiological signals (EPs) collected simultaneously. When the bandwidth of the collection amplifiers is higher than 150 Hz, these induced voltages are difficult to eliminate. Understanding the behavior of these artefacts contributes to the development of new digital processing tools for better quality EPs. In this paper, we present a study of induced voltages collected in vitro using a device (350 Hz bandwidth). The experiments were conducted on a 1.5T MRI machine with two MRI sequences (fast spin echo (FSE) and cine gradient echo (CINE)) and three slice orientations. The recorded induced voltages were then segmented into extract patterns called “artefact puffs”. Two analysis series, “global” and “local”, were then performed. The study found that the temporal and frequency characteristics were specific to the sequences and orientations of the slice and that, despite the pseudo-periodic character of the artefacts, the variabilities within the same recording were significant. These evolutions were confirmed by two stationarity tests: the Kwiatkowski–Phillips–Schmidt–Shin (KPSS) and the time-frequency approach. The induced potentials, all stationary at the global scale, are no longer stationary at the local scale, which is an important issue in the design of optimal filters adapted to reduce MRI artifacts contaminating a large bandwidth, which varies between 0 and 500 Hz
Evaluation of Age and Sex Effects on Force Complexity and Fluctuation during isometric elbow flexion
No full textInternational audienceThis study attempts to examine the impact of age and gender on fluctuations in force output during voluntary muscle contractions and how this impacts task performance. More precisely, the study investigates how these fluctuations vary during an elbow flexion task at sub-maximal forces. Interestingly, the study found that elderly women exhibit lower steadiness, meaning they exhibit a diminished capacity to maintain a steady force output and lower complexity than young adults when dealing with high levels of contraction. This suggests that women may have a diminished ability to maintain a steady and adaptable force output during the elbow flexion task, which could affect their performance. However, the findings from this study show that the existence of notable differences in force fluctuations among diverse age groups was limited to specific levels of contraction. Thus, it can be deduced that various factors, apart from age alone, might contribute to the observed decrease in force fluctuations in this study. Additionally, there are differences in behavior between women and men
Opérateurs totalement informatifs et ordres linéaires partitionnés en révision de croyances
No full textNational audienceCet article traite d'opérateurs de révision des croyances qui conduisent à des situations totalement informées. Ce type de situation peut être représenté dans le cadre de révision de Katsuno et Mendelzon par une formule propositionnelle complète à partir de laquelle n'importe quelle formule ou sa négation peut être déduite. Nous caractérisons de tels opérateurs par un ensemble de postulats et fournissons un théorème de représentation qui conduit à totalement ordonner les interprétations. Nous présentons une famille d'opérateurs concrets basée sur des fonctions de départage. Néanmoins, les ordres linéaires sont extrêmement difficiles à obtenir dans la pratique. C'est pourquoi nous proposons dans une deuxième partie une structure ordonnée originale, appelée ordre linéaire partitionné (OLP). Ces structures peuvent être considérées comme des restrictions d'ordres linéaires indépendants, chacun d'entre eux représentant une situation locale totalement informée. Nous étudions les propriétés de la famille des OLP en termes d'expressivité, de représentations graphiques et de modèles interdits. Enfin, nous proposons des postulats rationnels et un théorème de représentation pour les opérateurs de révision aboutissant à un les OLP sur les interprétations, ainsi qu'un opérateur concret satisfaisant ces postulats
L’intelligence artificielle : usages et lien au sentiment d’efficacité personnelle à l’enseignement avec le numérique des enseignants du supérieur.
No full textInternational audienceThis study investigates the utilization of artificial intelligence (AI) in higher education teaching and its correlation with the instructors' sense of personal efficacy in digital pedagogy. Through a rigorous examination of AI applications, instructional strategies, and educators' perceptions, the research aims to elucidate the intricate nexus between technological integration, pedagogical effectiveness, and individual confidence levels among university faculty. Employing a multidimensional framework, the study explores how AI intersects with diverse facets of teaching methodologies and contributes to the enhancement of educators' professional competencies. The findings of this inquiry offer valuable insights into the evolving landscape of AI-assisted teaching practices and shed light on the nuanced dynamics shaping educators' perceptions and practices in the digital era
Incompatible-mode geometrically non-linear finite element for micropolar elasticity
No full textInternational audienceIn this work a new three-dimensional geometrically non-linear hexahedral micropolar finite element enhanced with incompatible modes is presented. The analytical model is expressed in terms of Biot-like stress and couple-stress tensors and corresponding Biot-like strain and curvature tensors, with a linear, elastic and isotropic constitutive law. The numerical model is derived based on the principle of virtual work, and the residual derivation together with the linearisation and static condensation procedure is given in detail. The newly developed finite element is tested against the analytical solution of the geometrically non-linear micropolar pure bending problem and the element accuracy and robustness is compared against hexahedral Lagrangian finite elements of first and second order on several numerical examples. It is shown that the newly presented element is fast convergent, more robust and more accurate than the available Lagrangian elements. Moreover, the operator split and static condensation provide for a significantly lower computational cost than standard elements
Discrete Element Modelling (DEM) of a granular material mixer: Zirconium sponge
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Overcoming the added mass effect in FSI calculations relating to dynamic squat
No full textInternational audienceThis paper presents a corrected partitioned scheme for investigating fluid–structure interaction (FSI) generatedby ship squat in presence of transient effects. A theoretical example describing the motion of a piston enclosedin a U-tube gives rise to an analysis of the divergence effect resulting from added mass, and it has beenconcluded that divergence always occurs when the mass in motion is less than the added mass. An added-mass-corrected scheme is proposed to guarantee the convergence of the coupling scheme irrespective of themass ratio. This corrected scheme is successfully applied to the ship dynamics in an analysis of ship squat viaa non-stationary potential fluid flow approach. The results of our coupled calculations have been comparedto the squat stability models detailed in Alderf et al. (2010); Alderf et al. (2015) in which transient effectswere neglected in the fluid flow solver. Finally, energy transfers between the ship’s motion and the fluid flowhave been analyzed. We confirm the energy conservation capability of the proposed fluid–structure couplingscheme in relation to the transient response of the ship
Effective Adaptive Large Neighborhood Search for a firefighters timetabling problem
No full textInternational audienceEvery year, wildfires accentuated by global warming, cause economic and ecological losses, and often, human casualties. Increasing operational capacity of firefighter crews is of utmost importance to better face the forest fire period that yearly occurs. In this study, we investigate the real-world firefighters timetabling problem of the INFOCA institution, Andalusia (Spain). The main issue is to achieve maximum operational capability while taking into account work regulation constraints. This paper proposes an Integer Linear Programming (ILP) formulation that makes it feasible to solve small/medium instances to optimality. We put forward a matheuristic (ILPH) based on the ILP formulation, and we obtain solutions for larger instances. We propose an Adaptive Large Neighbourhood Search metaheuristic (ALNS) to obtain better results for larger instances and we use a version of the ILPH as one of the constructive methods. The ALNS obtains all the optimal solutions found by the ILP on small instances. It yields better solutions than the ILPH matheuristic on larger instances within shorter processing times. We report on experiments performed on datasets generated using real-world data of the INFOCA institution. The work was initiated as part of the GEO-SAFE project *
« Je t’aime, moi non plus ? »: Les émotions et les sociologues (de la culture)
No full textInternational audienceThis article is informed by the observation that, while emotions are at the heart of cultural works and practices, until recently little research in France had focused on the multiple and reciprocal links between the two. The first part of this article considers the reasons for this paradox. Over and above the division of scientific labour, it highlights the importance of the polysemy, vagueness, and ambiguity of the concept of emotions. These characteristics have made it difficult to appropriate and to use it empirically, particularly in the sociology of art and of culture, where scientific rationalism has long prevailed. The second part of the article points out that the sociology of emotions has distanced itself from cultural practices and works because of its predilection for both theoretical (structuralist) approaches and empirical interactionist analyses. Finally, the last part shows that, while emotions have received little or no attention in explanations of the love of art, they have appeared from the margins in the works of feminist Cultural Studies and of the French scholars who have drawn on it to characterize the lifestyles of young working-class women.Cet article part d’un constat paradoxal : alors que les émotions sont au cœur des œuvres et des pratiques culturelles, jusqu’à récemment, peu de recherches, en France, se sont intéressées aux liens multiples et réciproques qu’entretiennent culture et émotions. La première partie du texte revient sur les raisons de ce paradoxe. Au-delà de la division du travail scientifique, elle met en avant le rôle central du caractère polysémique, flou et ambigu de la notion d’émotions – ce qui a rendu son appropriation et son usage empirique difficiles, notamment dans un domaine, la sociologie de l’art ou de la culture, où le rationalisme scientifique a longtemps dominé. La deuxième partie souligne de façon réciproque la mise à distance des pratiques et œuvres culturelles par la sociologie des émotions, en raison d’un penchant pour les approches théoriques et pour les analyses empiriques interactionnistes. Enfin, la dernière partie montre que si les émotions ont peu été prises en compte dans l’explication de l’amour de l’art, elles sont apparues depuis les marges, dans les travaux des Cultural Studies féministes et de leurs importateurs français sur les subcultures féminines
Bio-composites based on cellulosic fibers from agro-industrial waste filled PP matrix: production and properties
No full textInternational audienceThe aim of this work is the valorisation of bagasse cane by-product for the development of a new bio-composite based on Polypropylene (PP) reinforced with different cellulose derivatives. In this study, the effect of fiber’s chemical surface treatments on the thermal and mechanical performance of PP was investigated, in particular, a comparison between three chemical treatments (alkali, bleaching, and coupling agent). Bio-composite materials were prepared using twin-screw extrusion followed by injection molding by mixing PP pellet with 5 to 10 Wt.% of raw bagasse cane (RBC), alkali bagasse cane (ABC) and cellulose microfibers (CMF), as well as CMF with Styrene-(ethylene-butene)-styrene three-block co-polymer grafted with maleic anhydride (SEBS-g-MA) as coupling agent. Overall, the thermal analysis reveals that the addition of fibers reduces the thermal stability of the reinforced PP. The mechanical results show an improvement in the values of Yung’s modulus, tensile strength and hardness of the reinforced PP compared to neat PP. However, a remarkable decrease was obtained in elongation at break and toughness for all reinforced composites compared to neat PP. These findings clearly show the advantages in the use of thermoplastic matrix reinforced with cellulosic fibers