Archive Ouverte INSA Lyon
Not a member yet
75807 research outputs found
Sort by
Theory of Bauschinger and Some Other Memory Effects in Glassy Polymers
No full textInternational audienceWe proposed recently that the strain hardening of glassy polymers is attributed to the increase of free energy barriers for α-relaxation as a consequence of local orientation of Kuhn segments during the course of deformation. As the chains have been signicantly oriented at the Kuhn segments scale, the contribution of Kuhn segments orientation to free energy barriers may become large and may then overcompensate the decrease of free energy barriers due to the increasing stress, the latter being responsible for yield and the onset of plastic ow. We show that the slow relaxation of Kuhn segments orientation explains the various memory eects observed in the strain hardening regime and generically named Bauschinger eect. It explains the fact that the stress-strain curve of a second deformation after some waiting time at some point in the strain hardening regime rejoins the reference curve, and that a yield stress is present for this second deformation. Indeed, the degrees of freedom which control the free energy barriers associated to yield relax on the time scale of the experiment, whereas Kuhn segments orientations, that is the degrees of freedom which control the free energy barriers associated to plastic ow in the strain hardening regime, relax slowly. We calculate the evolution of the relaxation time distributions, as well as that of the dominant relaxation time and of the Kuhn segments orientations, during successive deformations (tractiontraction, traction-compression, compression-traction, compression-compression). These predictions could be tested experimentally
Recherche de references sensorielles dans des collections de documents multimodaux issus de fonds patrimoniaux
No full textInternational audienc
Implementation of Energy based Hysteresis Model with Harmonic Balance method
No full textInternational audienceCircuit type simulation softwares (like SPICE) are routinely used in power electronics systems to analyze a large variety of topologies and parameter combinations (duty cycle, frequency, input/output voltages, . . . ). The magnetic components are usually considered linear in these simulations. This article discusses the feasability of implementing the Energy Based Hysteresys Model (EBHM) into a harmonic balance simulation in order to obtain efficiently, the steady response of a power electronic topology including the saturation and hysteresis effect of the magnetic component.</div
Frankia Root Nodulation Alters the Molecular Defence Responses Against Phytophthora alni Infection in Alnus glutinosa
No full textInternational audienceThe expression of mechanisms involved in plant stress responses has recently been described during the interactions between Frankia and Alnus glutinosa . In the present study, we sought to investigate the ability of A. glutinosa to activate its defence mechanisms when infected by the pathogen Phytophthora alni , specifically in relation to the presence of Frankia in the root tissues. We report that nodulated plants with Frankia exhibit distinct immune responses when exposed to P. alni infection. This study is based on a comprehensive multi‐omics approach, incorporating transcriptomic, proteomic and hormone analyses to better understand the molecular dynamics involved. Our findings reveal that A. glutinosa plants nodulated with Frankia trigger specific defence mechanisms within their roots in response to P. alni infection, compared to non‐nodulated plants. Additionally, these plants also initiate a more pronounced widespread defence reaction, highlighting the intricate interactions between the host plant, its symbiotic partner and the pathogen. Interestingly, the results suggest that the presence of Frankia in the root tissues influences how A. glutinosa regulates its immune system, especially in the context of P. alni infection. Furthermore, we propose that A. glutinosa plants may employ defence mechanisms not only to fight the pathogen but also to control the growth of their symbiont
En quête de précision : Un benchmark open-source et un solveur polyvalent pour le Graphical Lasso
No full textNational audienceNous proposons un benchmark open source des principaux algorithmes d'optimisation et leurs implémentations pour la résolution du Graphical Lasso, afin d'aider les praticiens à choisir la meilleure option en fonction de leur cas d'usage. Notre benchmark est public, customisable et intégré à l'écosystème benchopt [Moreau et al., 2022] afin de favoriser la recherche ouverte et reproductible. Nous publions également une implémentation efficace d'un solveur par descente de blocs de coordonnées, avec des fonctionnalités avancées comme les pénalités pondérées, ainsi que diverses pénalités. Il permet ainsi d'utiliser la régularisation nonconvexe, dont nous démontrons empiriquement la supériorité. Afin d'assurer une large diffusion et un impact pratique significatif, ce solveur est intégré à l'écosystème scikit-learn via le package skglm [Bertrand et al., 2022]
Damping cable-driven parallel robot vibrations using active vibration control methods
No full textInternational audienceA cable-driven parallel robot (CDPR) is a manipulator characterized by its end-effector (EE) being connected to the frame by cables. An electric motor/winch system enables the adjustment of each cable length and tension. The primary drawback of cables lies in their low stiffness, resulting in EE vibrations along the trajectory. For applications requiring high accuracy, such as additive manufacturing for instance, this issue presents a significant obstacle to the development of high-precision CDPRs. There is thus a need in damping these EE vibrations. Active vibration control can be defined as a method or system designed to mitigate or suppress undesirable vibrations in structural systems by using sensors, actuators, and control algorithms. This approach involves the detection of vibrations through sensors, the processing of this information via a control unit, and the generation of counteracting forces or displacements through actuators to minimize or eliminate the vibrations. These methods can thus be applied to CDPRs. Nevertheless, the CDPR modal properties can fundamentally change depending on the EE position, requiring careful consideration in vibration control algorithms. This study, therefore, focuses on presenting different approaches to damp EE vibrations along trajectories using active vibration control methods, while also taking into account the evolution of modal properties to ensure accuracy without any loss of performance
Linear-Time Transport with Rectified Flows
No full textInternational audienceMatching probability distributions allows to compare or interpolate them, or model their manifold. Optimal transport is a tool that solves this matching problem. However, despite the development of numerous exact and approximate algorithms, these approaches remain too slow for large datasets due to the inherent challenge of optimizing transport plans. Taking intuitions from recent advances in rectified flows we propose an algorithm that, while not resulting in optimal transport plans, produces transport plans from uniform densities to densities stored on grids that resemble the optimal ones in practice. Our algorithm has linear-time complexity with respect to the problem size and is embarrassingly parallel. It is also trivial to implement, essentially computing three summed-area tables and advecting particles with velocities easily computed from these tables using simple arithmetic. This already allows for applications such as stippling and area-preserving mesh parameterization. Combined with linearized transport ideas, we further extend our approach to match two non-uniform distributions. This allows for wider applications such as shape interpolation or barycenters, matching the quality of more complex optimal or approximate transport solvers while resulting in orders of magnitude speedups. We illustrate our applications in 2D and 3D
Error Bounds for a Kernel-Based Constrained Optimal Smoothing Approximation
No full textThis paper establishes error bounds for the convergence of a piecewise linear approximation of the constrained optimal smoothing problem posed in a reproducing kernel Hilbert space (RKHS). This problem can be reformulated as a Bayesian estimation problem involving a Gaussian process related to the kernel of the RKHS. Consequently, error bounds can be interpreted as a quantification of the maximum a posteriori (MAP) accuracy. To our knowledge, no error bounds have been proposed for this type of problem so far. The convergence results are provided as a function of the grid size, the regularity of the kernel, and the distance from the kernel interpolant of the approximation to the set of constraints. Inspired by the MaxMod algorithm from recent literature, which sequentially allocates knots for the piecewise linear approximation, we conduct our analysis for non-equispaced knots. These knots are even allowed to be non-dense, which impacts the definition of the optimal smoothing solution and our error bound quantifiers. Finally, we illustrate our theorems through several numerical experiments involving constraints such as boundedness and monotonicity
Évaluation du contrôle climatique sur l’érosion dans des cirques glaciaires alpins : comparaison entre les périodes du Néoglaciaire et du Dryas Récent
No full textInternational audienceGlacial cirques are key indicators of interactions between glaciers, climate, and topography. Moraine formation in glacial cirques is mainly influenced by periglacial and subglacial erosion processes, glacier dynamics, and topography. The intensity and spatio-temporal variability of erosion processes are climate-driven, yet climate is rarely considered in moraine formation. In this study, moraines formed during periods of glacier advances in several high-altitude cirques of the Mont Blanc, Aiguilles Rouges, and Gran Paradiso massifs were used as proxies for erosion to assess climate influence. We compared moraines from two periods: the Younger Dryas (cold and dry) and the Neoglacial (temperate and humid). A PDD glacial model was used to calibrate climate variations for these two periods relative to a reference period (1979–2014). Denudation rates were calculated from moraine volumes derived from high-resolution LiDAR DEM. Two extreme moraines formation-time hypotheses allowed the calculation of minimum and maximum values: 0.05 to 0.11 mm·a –1 and 0.10 to 0.23 mm·a –1 during the Younger Dryas; 0.12 to 0.45 mm·a –1 and 0.24 to 0.90 mm·a –1 during the Neoglacial. Furthermore, denudation rates correlated positively with mean annual temperature and precipitation in the studied cirques. These results could highlight those climatic parameters exert both spatial and temporal control on erosion in glacial cirques, with erosion being significantly accentuated under more temperate and humid climates compared to colder and dryer climates
An improved TCAD simulation procedure for platinum diffused silicon power diodes
No full textInternational audienceSilicon bipolar power diodes require carrier lifetime engineering to reduce switching time. Platinum diffusion is the most used method to achieve lifetime reduction. Platinum diffusion in silicon is a well understood process, however, its modeling for TCAD device simulations is lacking. In this paper, we propose a new physically precise method of modeling platinum induced defects in silicon power diodes. We show that the precision of this new method enables truly predictive simulation of silicon power diodes