HAL Portal UTC Université de Technologie de Compiègne
Not a member yet
11652 research outputs found
Sort by
Microrheometric study of damage and rupture of capsules in simple shear flow
No full textInternational audienceCapsules, which are potentially active fluid droplets enclosed in a thin elastic membrane, experience large deformations when placed in suspension. The induced fluid-structure interaction stresses can potentially lead to rupture of the capsule membrane. While numerous experimental studies have focused on the rheological behaviour of capsules until rupture, there remains a gap in understanding the evolution of their mechanical properties and the underlying mechanisms of damage and breakup under flow. We here investigate the damage and rupture of bioartificial microcapsules made of ovalbumin reticulated with terephthaloyl chloride and placed in simple shear flow. We characterize damage by identifying how the surface shear modulus of the capsule membrane changes over time. Rupture is then characterized by comparing the number and size distribution of capsules before and after exposure to shear, while varying the shear rates and time during which capsules are sheared. Our findings reveal how the percentage of ruptured capsules increases with their size, exposure time to shear, and the ratio of viscous to elastic forces at rupture
Time varying LQR-based optimal control of geometrically exact Reissner's beam model
No full textInternational audienceIn this work, we propose combining an advanced optimal control algorithm with a geometrically exact beam model. For simplicity, the 2D Reissner beam model is chosen to represent large displacements and rotations. The difficulty pertains to the nonlinear nature of beam kinematics affecting the tangent stiffness matrix, making it non-constant, which compromises direct use of optimal control methods for linear problems. Thus, we seek to accommodate a time varying control using linear-quadratic regulator (LQR) algorithm with the proposed geometrically nonlinear beam model. We provide a detailed theoretical formulation and its numerical implementation in a variational format form. Several illustrative numerical examples are provided to confirm an excellent performance of the proposed methodology.</div
Geometrically exact 3D beam theory with embedded strong discontinuities for modeling of localized failure in bending
No full textInternational audienceIn this work, we propose the elastoplastic model of a three-dimensional (3D) geometrically exact beam, which can capture localized bending deformation leading to a plastic hinge. This is a follow-up work to [27], where we only studied the fracture of fiber-like beam structures that break in mode I or mode II, here extended to handle beam-like behavior with bending failure and the main difficulty of the non-vectorial character of large 3D rotations. The Reissner model is chosen for representing the large elastic and large plastic deformations of such a beam model, which leads to the multiplicative decomposition of the rotation tensor. We shown how to replace this with the corresponding additive decomposition of the rotation vector derivatives, to be performed in the material description in the tangent space of SO(3) manifold in the initial configuration. The plasticity model for which we give a more detailed implementation employs a Rankin-like multi-surface plasticity criteria, where each moment vector component (i.e. torsion or bending) is considered separately. The non-local variational formulation is proposed to deal with the softening phenomena characteristic of localized bending failure, where the fracture energy is introduced as the main parameter for softening. The discrete approximation is built in terms of the embedded-discontinuity finite element method (ED-FEM), which introduces a jump in rotation vector that can be handled at the level of a particular beam element. This kind of approach builds upon the best approximation property of the FEM discrete approximation in the energy norm and provides the best-approximation property for the dissipated energy computations, and thus optimal computational accuracy if the quantity of interest is inelastic dissipation. The computations are carried out by the operator split method, which separates the computations of global state variables (displacements and moments) from local (plastic curvature) variables.Several illustrative examples are provided to confirm an excellent performance of the proposed methodology.</div
3D-environment and muscle contraction regulate the heterogeneity of myonuclei
No full textInternational audienceSkeletal muscle formation involves tight interactions between muscle cells and associated connective tissue fibroblasts. Every muscle displays the same type of organisation, they are innervated in the middle and attached at both extremities to tendons. Myonuclei are heterogeneous along myotubes and regionalised according to these middle and tip domains. During development, as soon as myotubes are formed, myonuclei at muscle tips facing developing tendons display their own molecular program. In addition to molecular heterogeneity, a subset of tip myonuclei has a fibroblastic origin different to the classical somitic origin, highlighting a cellular heterogeneity of myonuclei in foetal myotubes. To gain insights on the functional relevance of myonucleus heterogeneity during limb development, we used 2D culture and co-culture systems to dissociate autonomous processes (occurring in 2D-cultures) from 3D-environment of tissue development. We also assessed the role of muscle contraction in myonucleus heterogeneity in paralysed limb muscles. The regionalisation of cellular heterogeneity was not observed in 2D cell culture systems and paralyzed muscles. The molecular signature of MTJ myonuclei was lost in a dish and paralysed muscles indicating a requirement of 3D-enviroment and muscle contraction for MTJ formation. Tip genes that maintain a regionalized expression at myotube tips in cultures are linked to sarcomeres. The behaviour of regionalized markers in cultured myotubes and paralyzed muscles allows us to speculate whether the genes intervene in myogenesis, myotube attachment or MTJ formation
Investigation of the motif activity of transcription regulators in pancreatic β-like cell subpopulations differentiated from human induced pluripotent stem cells
No full textInternational audiencePancreatic β-cells are composed of different subtypes that play a key role in the control of insulin secretion and thereby control glucose homeostasis. In vitro differentiation of human induced pluripotent stem cells (hiPSCs) into 3D spheroids leads to the generation of β-cell subtypes and thus to the development of islet-like structures. Using this cutting-edge cell model, the aim of the study was to decipher the signaling signature that underlines β-cell subtypes, with a focus on the search for the activity of motifs of important transcription regulators (TRs). The investigation was performed using data from previous single-cell sequencing analysis introduced into the integrated system for motif activity response analysis (ISMARA) of transcription regulators. We extracted the matrix of important TRs activated in the β-cell subpopulation and bi-hormonal-like β-cells. Based on these TRs and their targets, we built specific regulatory networks for main cell subpopulations. Our data confirmed the transcriptomic heterogeneity of the β-cell subtype lineage and suggested a mechanism that could account for the differentiation of β-cell subtypes during pancreas development. We do believe that our findings could be instrumental for understanding the mechanisms that affect the balance of β-cell subtypes, leading to impaired insulin secretion in type 2 diabetes
Optimisation de la co-digestion anaérobie en voies liquide et solide par couplage de plans de mélange d’expérimentations multi-échelles en laboratoire
No full textThis work aims to propose a method for optimizing anaerobic digestion, for both liquid and solid-state, with the goal of improving the efficiency of the process. The optimization is primarily monitored by analyzing the different proportions of substrates and their impacts on methane production. The first stage of this study focuses on optimizing the liquid-state anaerobic digestion by testing various compositions of complex substrates, including horse waste, sewage sludge, and the organic fraction of municipal solid waste. To achieve this, a mixture design methodology was used allowing the reduction of the number of experiments while maintaining results’ accuracy, saving both time and space. The obtained results enabled the development of a cubic polynomial model capable of predicting methane production based on different co-substrate compositions and their interactions. This model includes coefficients for individual substrates, combinations of two substrates, as well as the interactions between all three substrates simultaneously. The second stage of the study explores whether the co-digestion of these same substrates is also beneficial in the solid-state anaerobic digestion, focusing on operational conditions, particularly the optimal substrate proportions for achieving a high methane yield. The same experimental design was applied. However, for this part, a custom-designed pilot was conceived to conduct the experiments, minimizing human intervention, experimental time, and space requirements. This pilot includes 15 reactors, each with a 5-liter capacity, designed using specific software and fabricated with a 3D printer. This technology reduced both the cost and production time by a factor of three. The experimental results were incorporated into a mathematical model to predict methane production based on the substrate composition. It is important to note that the three substrates used in this study have highly variable and complex physico-chemical properties, presenting significant scientific and technical challenges. The final objective of this approach is to propose a methodology for optimizing anaerobic digestion, both in liquid and solid states, for three complex and distinct substrates, allowing the prediction of methane production and the determination of optimal substrate compositions. This is a conceptual methodology that will facilitate the study of specific substrates under well-defined operational conditions.Ce travail a pour objectif de proposer une méthode d’optimisation de la digestion anaérobie en voie liquide et en voie solide, dans le but d’améliorer l’efficacité de ce processus. L’optimisation est suivie principalement en analysant les différentes proportions des substrats et leurs impacts sur la production de méthane. La première étape de cette étude consiste à optimiser le processus de la digestion anaérobie en voie liquide en testant diverses compositions de substrats complexes, notamment le fumier équin, les boues urbaines et la fraction organique des ordures ménagères. Pour ce faire, un plan de mélange a été utilisé, permettant de réduire le nombre d’expériences à effectuer tout en maintenant la précision des résultats, et tout en gagnant en temps et en espace. Les résultats obtenus ont permis de développer un modèle polynomial cubique capable de prédire la production de méthane en fonction des différentes compositions en co-substrats et de leurs interactions. Ce modèle inclut les coefficients des substrats individuels, les combinaisons des substrats deux à deux, ainsi que les interactions entre les trois substrats simultanément. La deuxième étape de l’étude examine si la co-digestion des mêmes substrats présente également un intérêt en voie solide, en se concentrant sur les conditions opératoires, et plus spécifiquement, les proportions optimales des substrats pour obtenir un rendement élevé en méthane. Le même plan d’expériences a été utilisé. En revanche, pour cette partie, un pilote a été conçu sur mesure afin de réaliser les expériences tout en minimisant l’intervention humaine, le temps expérimental et l’espace requis. Ce pilote comporte 15 réacteurs de 5 litres chacun, conçus à l’aide d’un logiciel spécifique, et fabriqués avec une imprimante 3D. Cette technologie a permis de réduire les coûts et le délai de fabrication par un facteur de 3. Les résultats expérimentaux obtenus ont été intégrés dans un modèle mathématique de prédiction de la production de méthane en fonction de la composition des substrats. Il est important de souligner que les trois substrats utilisés présentent des caractéristiques physico-chimiques très variées et complexes à gérer, ce qui pose des défis scientifiques et techniques significatifs dans cette étude. L’objectif final de cette démarche est de proposer une méthodologie d’optimisation de la digestion anaérobie, en voie liquide et en voie solide, pour trois substrats complexes et différents, permettant de prédire la production de méthane et de déterminer les compositions optimales de substrats. C’est une méthodologie conceptuelle qui permettra d’étudier des substrats spécifiques dans des conditions opératoires bien définies
Codigestion de boues activées avec une fraction organique d'ordures ménagères et du fumier équin en réacteurs semi-continus thermophile et mésophile
No full textInternational audienc
Full harmonic spectrum calculation of magnetic pressures in synchronous permanent magnet machines based on a new realistic partial analytical model: application to SVPWM and DPWM2
No full textInternational audiencePurposeThe purpose of this paper is to propose a new method that allows to compare the magnetic pressures of different pulse width modulation (PWM) strategies in a fast and efficient way.Design/methodology/approachThe voltage harmonics are determined using the double Fourier integral. As for current harmonics and waveforms, a new generic model based on the Park transformation and a dq model of the machine was established taking saturation into consideration. The obtained analytical waveforms are then injected into a finite element software to compute magnetic pressures using nodal forces.FindingsThe overall proposed method allows to accelerate the calculations and the comparison of different PWM strategies and operating points as an analytical model is used to generate current waveforms.Originality/valueWhile the analytical expressions of voltage harmonics are already provided in the literature for the space vector pulse width modulation, they had to be calculated for the discontinuous pulse width modulation. In this paper, the obtained expressions are provided. For current harmonics, different models based on a linear and a nonlinear model of the machine are presented in the referenced papers; however, these models are not generic and are limited to the second range of harmonics (two times the switching frequency). A new generic model is then established and used in this paper after being validated experimentally. And finally, the direct injection of analytical current waveforms in a finite element software to perform any magnetic computation is very efficient
Inferring from an Imprecise Plackett–Luce model: application to label ranking
No full textInternational audienceThe Plackett–Luce model is a popular parametric probabilistic model to define distributions between rankings of objects, modelling for instance observed preferences of users or ranked performances of algorithms. Since such observations may be scarce (users may provide partial preferences, or not all algorithms are run for a given experiment), it may be useful to consider the case where the parameters of the Plackett–Luce model are imprecisely known. In this paper, we first introduce the imprecise Plackett–Luce model, induced by a set of parameters (for instance, parameters with a high relative likelihood). Given a set of possible parameters for the model, we then provide an efficient algorithm to make cautious inferences, returning sets of possible optimal rankings (for instance in the form of partial orders). We illustrate the use of our imprecise model on label ranking, a specific kind of supervised learning
Accompagnement à la certification « AFAQ Service Biomédical » de niveau 1
No full textSince 1997, French biomedical services have been following standards and regulations to guarantee the safety and performance of medical devices. However, these standards have not been widely adopted, and ISO 9001:2015, known as the benchmark standard for quality management, is only applied in 10% of French biomedical departments.To stimulate interest in quality management among hospital biomedical departments, AFIB and AAMB have developed the "AFAQ Service Biomédical" certification, which is compatible with ISO 9001 requirements. This certification aims to adopt a progressive and cheaper approach than ISO 9001, while at the same time facilitating the establishment of a quality management system in biomedical services.The main objective of our project is to facilitate the implementation of level 1 of the "AFAQ Service Biomédical" certification within healthcare establishments, by developing a self-diagnostic tool enabling biomedical departments to assess their compliance with the three themes of level 1 certification.Depuis 1997, les services biomédicaux français suivent des normes et réglementations pour garantir la sécurité et la performance des dispositifs médicaux. Cependant, ces normes n'ont pas été largement adoptées, et l'ISO 9001:2015, qui constitue la norme de référence en matière de gestion de la qualité n’est appliquée que dans 10% des services biomédicaux français. Pour susciter l'intérêt des services biomédicaux hospitaliers pour le management de la qualité, l'AFIB et l'AAMB ont développé la certification « AFAQ Service Biomédical » compatible avec les exigences de l'ISO 9001. Cette certification vise à adopter une approche progressive et moins coûteuse que l'ISO 9001, tout en visant à faciliter l'établissement d'un système de gestion de la qualité dans les services biomédicaux. L'objectif principal de notre projet est de faciliter la mise en place du niveau 1 de la certification « AFAQ Service Biomédical » au sein des établissements de santé, par le développement d’un outil d'auto-diagnostic permettant aux services biomédicaux d'évaluer leur conformité aux trois thèmes du niveau 1 de la certification