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Study of Thermomechanical Behavior of Refractory Materials Under Thermal Gradient. Part I – Presentation of ATHORNA Device and Experimental Protocol
No full textInternational audienceBackground: Improving the understanding of how a refractory material responds to thermal shocks and allowing the validation of finite element models require a valuable tool for experimental data collection.Objective: This paper introduces an innovative, sophisticated, and highly reliable experimental device designed to apply a controlled cyclic thermal gradient in a disk-shaped ceramic refractory sample and to simultaneously monitor thermome-chanical response and potential damage.Methods: This device, named Advanced measurements for in-situ Thermomechanical monitORing of large sample uNder thermal grAdient, is based on a CO2 laser beam to generate a calibrated thermal flux sequence at the top face while accu-rately measuring temperature field at the bottom face by an infrared camera. The displacement field of the bottom face is also continuously monitored by a stereo-vision system, enabling a precise measurement of 3D displacements and, thus, of the local strains. An accurate monitoring of the crack extension is performed thanks to the Two-Part Digital Image Correla-tion technique.Results: Throughout the thermal cycling sequence applied to an exemplar sample, the device has proved to be a robust and reliable system able to provide very accurate experiment data in terms of displacement, strain, temperature fields and crack length/opening.Conclusions: This device represents a significant advancement in in-situ monitoring of a refractory sample and contributes to the comprehensive characterization of materials under thermal gradients. More investigations and comparison with ther-momechanical Finite Element modelling are shown in a second part of this paper
La méthode des recherches en ligne par mots clés successives, apports et limites
No full textInternational audienceCette communication a eu lieu dans le cadre du séminaire Méthodes, ici consacré aux ressources numériques, organisé par le laboratoire GRESCO. Celle-ci visait à montrer comment des recherches par mots clés successives via des moteurs de recherche, en vue de réaliser une prosopograhie, ont permis d'esquisser un espace social, et conduit à redéfinir l'objet de la recherche. Elle est ensuite revenue sur les apports et les limites de cette méthode de collecte des données en ligne, ainsi que sur les questions spécifiques posées par les types de matériaux récoltés, leur diversité et leurs conditions de production
Les Blancs de Saint-Domingue sous le gouvernement de Toussaint Louverture, 1798-1802
No full textInternational audienceUnder Toussaint Louverture’s government, the white population of Saint-Domingue had shrunk to a tiny minority, concentrated in the coastal towns or scattered across the countryside. Their living conditions were very different from those of the colonists who had taken refuge in the United States and Jamaica, or of the homeowners who had sought shelter in France. During the Southern War (1799-1800), these few thousand white civilians were instrumentalized by the two rival parties of Toussaint and Rigaud, and often became victims of the conflict. Once domestic peace had returned, Toussaint Louverture, victorious, surrounded himself with many of them to run his proto-state, relying on white landowners for economic and political reasons. However, when Leclerc’s expedition arrived in February 1802, the Black Governor unleashed large-scale roundups against the white men at his mercy, followed by massacres.Sous le gouvernement de Toussaint Louverture, les Blancs vivant à Saint-Domingue ne constituent plus qu’une infime minorité de la population, concentrée dans les villes côtières ou éparpillée dans les campagnes. Leurs conditions d’existence sont bien différentes de celles des colons réfugiés aux États-Unis et à la Jamaïque ou des propriétaires d’habitations à l’abri en France. Lors de la guerre du Sud (1799-1800), ces quelques milliers de civils blancs sont instrumentalisés par les deux partis rivaux de Toussaint et Rigaud, et souvent victimes du conflit. La paix intérieure revenue, Toussaint Louverture, victorieux, s’entoure de nombre d’entre eux pour faire fonctionner son proto-État et s’appuie sur des propriétaires blancs pour des raisons économiques et politiques. Toutefois, à l’arrivée de l’expédition de Leclerc en février 1802, le Gouverneur noir déclenche des rafles de grande ampleur contre les hommes blancs à sa merci, suivies de massacres
Early sensorimotor restriction in rats induces age-dependent mitochondrial alterations in skeletal muscles and brain structures
No full textInternational audienceA sedentary lifestyle can lead to motor and cognitive deficits, increasing the risk of neurodegenerative diseases in ageing. Emerging hypotheses suggest that these functional alterations may be related to energy metabolism. Indeed, ATP produced by mitochondria is essential for muscle contraction, neurotransmission and brain plasticity processes. Although a sedentary lifestyle has been associated with mitochondrial alterations in skeletal muscle, the potential effects on brain structures have yet to be investigated. The present study aimed to determine whether early sensorimotor restriction (SMR) alters mitochondrial metabolism in rat muscles and brain structures. Enzyme activities of citrate synthase (CS) and respiratory chain complexes I, II and IV were measured using a spectrophotometric technique and mitochondrial respiration was assessed using high-resolution respirometry in two hind limb muscles [soleus and extensor digitorum longus (EDL)] and four brain structures (sensorimotor cortex, striatum, prefrontal cortex and hippocampus) in control rats and rats experiencing early SMR from birth to day 28. Mitochondrial enzyme activities decreased in the soleus (complexes I and II), in the EDL (complex I) and in the hippocampus (complexes I and IV) in an age-dependent manner, whereas no effect was observed in other brain structures. CS activity decreases in the soleus and increases transiently in the striatum and sensorimotor cortex at postnatal day 15. Mitochondrial respiration was reduced in the soleus and in the sensorimotor cortex (CI and CI+CII). Early SMR appears to induce quantitative and qualitative mitochondrial alterations in skeletal muscles and certain brain structures involved in cognitive and motor processes
Triboelectric Charging and Electrostatic Separation of Granular Plastic Wastes Exposed to Long-Term Action of High Levels of Ambient Humidity
No full textInternational audienceTribo-electrostatic separation of granular plastic wastes is a complex phenomenon depending on several parameters, including the relative humidity of ambient air. The work presented in this paper aimed at studying the effect of storage environmental conditions on triboelectric charging and electrostatic separation. The experiments were conducted on four types ofmm-size granular polymers, ABS, PS, PE, and PP, placed in a climatic chamber for 48 h to 96 h under controlled humidity. The thermal machine of the climatic chamber allowed humidity to be regulated at 82% ± 4% for a temperature of 19 °C ± 1 °C. The granules stored under these conditions will be designated as “humid.” Their water content was measured with a thermal balance and compared with “normal” granules, kept at ambient humidity varying between polymer granules increased by at least 10% after 48 h of exposure 46%and52%, at 18 °C±1 °C.Thewater content ofeachofthe four to the high relative humidity ambient conditions. The thin water layer formed at the particle’s surface can explain their modified triboelectric behavior. The recovery and purity of the products collected after the tribo-electrostatic separation of the ABS/PS and PE/PP mixtures were poorer for the “humid” granules due to the less efficient tribocharging in the fluidized bed device
« Le handicap, ça se voit. »
No full textPartie : Le handicap : réalité médicale ou construction sociale ?Plan— Le handicap invisible et le monde du travail— Le corps médical et l’entourage face au handicap invisibl
From Net Neutrality to Technological Neutrality: What Axiological Neutrality for the 21st Century Connected Scholar?
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Whistling side-view mirrors: Modelling ladder-type structure tonal noise from flow intermittency
No full textInternational audienceWhistling side-view mirror flows are investigated experimentally. Two designs are considered: the baseline, and a controlled one, whose cap is equipped with a protruding step, used as a vortex generator to turn the boundary layer turbulent upstream of the trailing edge. The acoustic field is measured with microphones while the inflow velocity is decreasing from 50 to 15 m s-1. Hot-wire anemometry and time-resolved particle image velocimetry are performed at 26 and 34 m s-1, synchronised with microphones, allowing whistling source localisation. Although the feedback loop that generates the tonal noise emission is deactivated in the controlled case in the step region, a switch from single tone to ladder-type structure tones is noticed on the outer side of this side-view mirror. This is associated with a flow intermittency in that region, at a low frequency corresponding to the peak distance. Fluctuation maps at the whistling frequencies are qualitatively different too, suggesting that, in the controlled case, the feedback loop is only active during the phase of the intermittent process when the shear layer deviates outward. This interpretation is supported by the estimation of a higher convection velocity of the fluctuations in the shear layer. Introducing the intermittency into time series models allows to reproduce the ladder-type structure, that is the harmonic jumps when the velocity increases. A Fourier analysis shows that whatever the vortex passing frequency over the trailing edge (e.g. as fixed by the feedback loop), the spectrum is made of harmonics of the intermittency frequency only. However, the specific velocities of rung changes on the ladder results from a higher growth rate of the passing frequency with velocity
