Search results for "MECHANICS"
showing 10 items of 9361 documents
Residual a posteriori error estimation for frictional contact with Nitsche method
2023
We consider frictional contact problems in small strain elasticity discretized with finite elements and Nitsche method. Both bilateral and unilateral contact problems are taken into account, as well as both Tresca and Coulomb models for the friction. We derive residual a posteriori error estimates for each friction model, following [Chouly et al, IMA J. Numer. Anal. (38) 2018, pp. 921-954]. For the incomplete variant of Nitsche, we prove an upper bound for the dual norm of the residual, for Tresca and Coulomb friction, without any extra regularity and without a saturation assumption. Numerical experiments allow to assess the accuracy of the estimates and their interest for adaptive meshing …
Entropic model application to identify cross-sectional flow effect on velocity distribution in a large amplitude meandering channel
2020
Abstract Literature shows the application of the entropy concept in open channels flow. No existing research has been addressed to the application of the entropy concept for evaluating the effect of secondary flow which especially develops in curved channels. The purpose of this paper is to explore the possibility to evaluate the effect of the secondary flow on the stream-wise velocity distribution starting only from the knowledge of the surface velocity and the entropic concept application. The analysis is conducted with the aid of data collected in a large-amplitude meandering laboratory flume for two different values of the width-to-depth ratio. Results show that the location of the maxi…
ESTIMATION ET CORRECTION DES ERREURS SYSTEMATIQUES D'UN SYSTEME DE MESURE 3D ASSOCIANT SCANNER NAPPE LASER ET MMT
2012
Les techniques de mesure sans contact par scanning laser permettent d'acquérir un grand nombre de points, à une cadence très rapide. Elles sont de plus en plus utilisées pour des applications industrielles telles que la rétro-conception, le contrôle de forme,... Toutefois, les incertitudes de mesures sont plus importantes que celles obtenues par les techniques classiques de mesure par contact. Nous proposons une procédure de correction des erreurs systématiques basée sur démarche expérimentale et qui concerne la mesure de pièces présentant une surface mate (peu de présence de bruit spéculaire). Les paramètres retenus dans la procédure sont les paramètres de positionnement du capteur par rap…
Stress sensitivity of stylolite morphology
2009
International audience; Stylolites are rough surfaces that form by localized stress-induced dissolution. Using a set of limestone rock samples collected at different depths from a vertical section in Cirque de Navacelles (France), we study the influence of the lithostatic stress on the stylolites morphology on the basis of a recent morphogenesis model. We measured the roughness of a series of bedding-parallel stylolites and show that their morphology exhibits a scaling invariance with two self-affine scaling regimes separated by a crossover-length (L) at the millimeter scale consistent with previous studies. The importance of the present contribution is to estimate the stylolite formation s…
Influence of a Thiolate Chemical Layer on GaAs (100) Biofunctionalization: An Original Approach Coupling Atomic Force Microscopy and Mass Spectrometr…
2013
International audience; Widely used in microelectronics and optoelectronics; Gallium Arsenide (GaAs) is a III-V crystal with several interesting properties for microsystem and biosensor applications. Among these; its piezoelectric properties and the ability to directly biofunctionalize the bare surface, offer an opportunity to combine a highly sensitive transducer with a specific bio-interface; which are the two essential parts of a biosensor. To optimize the biorecognition part; it is necessary to control protein coverage and the binding affinity of the protein layer on the GaAs surface. In this paper; we investigate the potential of a specific chemical interface composed of thiolate molec…
Is individual- and school-level teacher burnout reduced by proactive strategies?
2021
There is provisional evidence that burnout may be contagious within professional communities via the crossover effect, referring to an inter-individual transmission of stress or strain. However, our understanding of effective means for tackling stressors is scarce. We tested a two-level path model to explore the interrelation between teachers’ proactive self- and co-regulative strategies and experienced burnout. The study sample comprised 1531 Finnish in-service teachers from 75 schools. The results showed that burnout symptoms varied both between individual teachers and between professional communities. Self- and co-regulative strategies serve partly different functions in regulating teach…
Discussion of “Three Simple Flumes for Flow Measurement in Open Channels” by Zohrab Samani
2018
In this paper the results on three simple flumes for flow measurements are discussed.
Simple flume with a central baffle
2016
Abstract In this paper the stage-discharge relationship of a flume with a central baffle is theoretically deduced using the Buckingham-Theorem of the dimensional analysis and the self-similarity theory. The new stage-discharge equation is calibrated by the measurements carried out by Peruginelli and Bonacci using a baffle having a given throat length and five different values of the contraction ratio. Finally, for a given throat length, a relationship linking the discharge with the upstream water depth, the contraction ratio and the contracted width is deduced.
Epigenetic regulation of sex differences in susceptibility to stress
2017
Under current diagnostics depression and stress related mood disorders have a higher occurrence in women than men. Little is known of the biological mechanisms contributing to these sex differences and how they may impact potential new therapeutics. Here we examine how DNA methylation contributes to sex specific stress vulnerability in adult animals. Mice of both sexes were exposed to variable stress and given a behavioral test battery to examine stress sensitivity. Female mice expressed depressionassociated behavior across all tests stress exposure whereas males were behaviorally resilient. Markers of pre and post-synaptic plasticity and spine morphology were examined using a combination o…
Fibre fragment distribution in a single-fibre composite tension test
2001
Abstract Single fibre fragmentation tests are performed for brittle fibres with Weibull strength distribution and different surface treatments. The fragmentation process is modelled and closed-form expressions for break spacing distribution are obtained. The model accounts for the effect of finite fibre length on the initial fragmentation as well as for break interaction on the advanced fragmentation stage. It is assumed that the exclusion zone due to fibre–matrix interface failure and stress recovery in the fibre is linearly dependent on the applied load. This assumption is validated experimentally. The derived theoretical average fragment length dependence on applied load is used to deter…