Search results for "Engineering sciences"
showing 10 items of 2347 documents
Definition and performance evaluation of a robust SVM based fall dectection system
2012
International audience
Emulating the Effects of Radiation-Induced Soft-Errors for the Reliability Assessment of Neural Networks
2021
International audience; Convolutional Neural Networks (CNNs) are currently one of the most widely used predictive models in machine learning. Recent studies have demonstrated that hardware faults induced by radiation fields, including cosmic rays, may significantly impact the CNN inference leading to wrong predictions. Therefore, ensuring the reliability of CNNs is crucial, especially for safety-critical systems. In the literature, several works propose reliability assessments of CNNs mainly based on statistically injected faults. This work presents a software emulator capable of injecting real faults retrieved from radiation tests. Specifically, from the device characterisation of a DRAM m…
The application of a reduced volume method for the simulation of the characterisation of a carbon fibre pressure vessel
2018
International audience; The characteristics of advanced composite materials make them ideally suited for use in pressure vessels for storing gas as fuel for ground transport vehicles. It has been found that the failure process starts with randomly distributed fibre breaks and as the loading continues, they coalesce into clusters of fibre breaks which lead to failure [4]. However, improvements are needed to reduce computational times when performing full-scale simulations. The reduced volume method is therefore applied to the stochastic fibre break model related to the concept of an integral range. This method allows the calculation for a certain volume of a laminate that statistically repre…
Comparison of the accumulation of fibre breaks occurring in a unidirectional carbon/epoxy composite identified in a multi-scale micro-mechanical mode…
2010
National audience; A model to predict fibre break accumulation that takes into account all physical phenomena at the origin of the fibre break (i.e. the random nature, stress transfer due to breaks, fibre debonding and viscosity of the matrix) shows clearly that the failure of a unidirectional composite structure results in the formation of random fibre breaks which at higher loads coalesce into clusters of broken fibres. The object of the study is to experimentally confirm this scenario. Many techniques exist to detect the failure of carbon fibre composites, however none of them offer a resolution that allows this goal to be achieved in a non-destructive manner and in three dimensions. Hig…
Effect of the Time Dependent Loading of Type IV Cylinders using a Multiscale Model
2019
International audience; The current requirements for composite cylinders are still based on an arbitrary approach derived from the behaviour of metal structures, that the designed burst pressure should be at least 2.5 times the maximum in-service pressure [1]. This could lead to an over-designed composite cylinder for which the weight saving would be less than optimum. Moreover, predicting the lifetime of composite cylinders is a challenging task due to their anisotropic characteristics. A federal research institute in Germany (BAM) has proposed a minimum load-cycle requirement that mitigates this issue by using a Monte-Carlo analysis of the burst test results [2-3]. To enrich this study, m…
CONVERSIONS DE FREQUENCE ULTRA LARGE BANDE PAR MELANGE A QUATRE ONDES INTERMODAL EN CASCADE DANS LES FIBRES MULTIMODES
2017
International audience; Nous mettons en évidence des effets de conversion spectrale paramétrique avec des décalages spectraux très importants (~200THz) dans une fibre à gradient d'indice qui, pompée avec une source laser picoseconde à 1064nm, supporte quatre modes de propagation. À travers des études expérimentales, analytiques et numériques détaillées, nous montrons que les multiples raies paramétriques sont générées par un processus en cascade complexe faisant intervenir des mélanges à quatre ondes intermodaux. Les longueurs d'onde paramétriques résultantes s'étendent dans le visible jusqu'à 410nm et dans le proche infrarouge jusqu'à 1355nm. MOTS-CLEFS : dynamique spatio-temporelle ; conv…
Analyse multiéchelle d'un composite textile
2010
National audience; On propose dans cette étude d'expliquer le comportement mécanique d'un composite textile au travers d'un processus multiéchelle. Les propriétés mécaniques nécessaires à la réalisation des calculs ont été déterminées par une étude expérimentale préalable.
Analyse multiéchelle d'un composite textile = Multiscale analysis of a textile composite
2009
National audience; On propose dans cette étude de comprendre le comportement mécanique d'un composite textile. Pour ce faire, l'étude se scinde en deux parties distinctes. Dans cet article, nous présentons la modélisation multiéchelle qui fait suite à une étude expérimentale. Son objectif est double : comprendre la nature du comportement macroscopique observé et expliquer l'origine des endommagements susceptibles d'apparaître. L'étude expérimentale du matériau fait l'objet d'un premier article.
Multi-agent control architecture for RFID cyberphysical robotic systems initial validation of tagged objects detection and identification using Playe…
2016
International audience; The objective of this paper is to describe and validate a multi-agent architecture proposed to control RFID Cyber-Physical Robotic Systems. This environment may contain human operators, robots (mobiles, manipulators, mobile manipulators, etc.), places (workrooms, walls, etc.) and other objects (tables, chairs, etc.). The proposed control architecture is composed of two types of agents dispatched on two levels. We find at the Organization level a Supervisory agent to allow operators to configure, manage and interact with the overall control system. At the Control level, we distinguish the Robots agents, to each robot (mobiles, manipulators or mobile manipulators) is a…
Détection et discrimination par émission acoustique des endommagements dans les composites stratifiés d'unidirectionnels ; rupture de fibre, macro et…
2010
National audience; On présente dans cette étude la discrimination des phénomènes de ruptures de fibre, de microfissuration intralaminaire, de macrofissuration intralaminaire ainsi que du microdélaminage au sein des composites stratifiés d'unidirectionnels orientés, dans le cadre d'une méthode de détection des endommagements basée sur la technique de l'Emission Acoustique. Ces résultats expérimentaux sont confrontés aux prévisions issues d'un modèle de comportement de matériaux composites unidirectionnels, basés sur la physique des phénomènes à l'échelle des constituants. Plus précisément, ce modèle prend notamment en compte : le caractère aléatoire des ruptures de fibres, les transfert de c…