Modélisation de la fabrication directe de pièces par projection laser : application au Ti-6Al-4V

International audienceLa projection laser permet de fabriquer de façon relativement simple des pièces complexes, dont les dimensions sont proches des cotes finales. Le procédé s'accompagne néanmoins d'importantes variations locales de température, à l'origine d'une microstructure hétérogène, et de contraintes résiduelles difficiles à maîtriser. Une bonne manière d'aider au développement du procédé est de mettre en place sa simulation numérique, afin de prévoir la microstructure et les contraintes résiduelles. Des conditions laser adaptées et une stratégie de balayage optimisée doivent permettre d'obtenir la microstructure désirée et des contraintes résiduelles minimisées

La pollution industrielle et les sensibilités aux dégradations de l'environnement à Perpignan : acteurs, conflits, impacts (1810-1917)

François-Ignace Bonhommé, Tôlerie des forges d'Abainville, 1837 (21,7 cm x 30,1 cm) Au XIXe siècle, l'industrie se développe dans les villes françaises. Ces activités attirent une population nouvelle provoquant ainsi une croissance démographique importante. Les deux phénomènes cumulés modifient durablement l'environnement urbain et son rapport avec les sociétés. L'étude se propose ainsi de traiter la pollution industrielle et l'évolution des sensibilités aux dégradations de l'environnement. ..

La pollution industrielle et les sensibilités aux dégradations de l'environnement à Perpignan : acteurs, conflits, impacts (1810-1917)

François-Ignace Bonhommé, Tôlerie des forges d'Abainville, 1837 (21,7 cm x 30,1 cm) Au XIXe siècle, l'industrie se développe dans les villes françaises. Ces activités attirent une population nouvelle provoquant ainsi une croissance démographique importante. Les deux phénomènes cumulés modifient durablement l'environnement urbain et son rapport avec les sociétés. L'étude se propose ainsi de traiter la pollution industrielle et l'évolution des sensibilités aux dégradations de l'environnement. ..

Analytical and numerical modelling of the direct metal deposition laser process

International audienceThe direct metal deposition (DMD) laser process is a novel technique, well adapted for aeronautical applications, that allows the building of complex 3D geometries through the interaction between a powder nozzle system and a continuous laser beam. A three-step analytical and numerical approach was carried out to predict the shapes of manufactured structures and thermal loadings induced by the DMD process. First, powder temperature was calculated using a recent analytical model, then the geometry of walls was predicted by a combined numerical + analytical modelling using a discretization of the physical interaction domain, and finally, a finite element calculation was carried out on COMSOL 3.3 Multiphysics software to describe thermal behaviour during DMD of a titanium alloy. Our thermal model takes into account the moving interface during metal deposition with a specific function κ (t, x, y, z) allowing the conductivity front to move simultaneously with the moving laser source (with an appropriate spatial energy distribution), thus representing rather precisely the DMD process. This allowed us to provide an adequate representation of temperatures near the melt-pool, and to reproduce with a good accuracy thermal cycles and melt-pool dimensions during the construction of up to 25-layer walls. This was confirmed by comparisons with experimental thermocouple data T = f(t), and fast camera melt-pool recording

Does pre-testing promote better retention than post-testing?

International audienceCompared with other learning strategies, retrieval practice seems to promote superior long-term retention. This has been found mostly in conditions where learners take tests after being exposed to learning content. However, a pre-testing effect has also been demonstrated, with promising results. This raises the question, for a given amount of time dedicated to retrieval practice, whether learners should be tested before or after an initial exposure to learning content. Our experiment directly compares the benefits of post-testing and pre-testing relative to an extended reading condition, on a retention test 7 days later. We replicated both post-testing (d = 0.74) and pre-testing effects (d = 0.35), with significantly better retention in the former condition. Post-testing also promoted knowledge transfer to previously untested questions, whereas pre-testing did not. Our results thus suggest that it may be more fruitful to test students after than before exposure to learning content. npj Science of Learning (2019) 4:15 ; https://doi. INTRODUCTION The testing effect is a strong and well demonstrated effect. 1-5 As opposed to common learning practices such as reading, taking tests, and more generally retrieval practice during the learning phase contribute to better long term retention 6 by reducing the forgetting rate of information across time. 7 The benefits of retrieval practice have been demonstrated in both laboratory and classroom settings 8,9 and for both simple (e.g. word lists) and complex (e.g. prose passages) material. 10 In a meta-analysis, Rowland 11 reported a mean effect size of g = 0.50 [IC-95%: 0.42, 0.58] from 61 studies comparing the effects of testing vs. restudying on the ability to learn new information after a first exposure to learning contents. In another meta-analysis, Adesope et al. 12 found a mean effect size of g = 0.61 [IC-95%: 0.58 and 0.65] by comparing retrieval practice to other practices. The testing effect may also lead to better retention of previously untested information and to greater knowledge transfer than restudying. 13-15 A recent meta-analysis 16 on the transfer of retrieval practice effects found that retrieval practice yielded transferrable learning relative to a restudying control condition (d = 0.40, 95%CI [0.31 and 0.50]). However, transfer does not necessarily occur in all circumstances and with all types of content. 14 Pan and Rickard 16 made a distinction between untested application and inference questions and untested information seen during the first exposure to material. Interestingly, they found a transfer effect of retrieval practice on application and inference questions, but not on untested information seen during initial study. The testing effect has mainly been shown in the context of tests given after exposure to learning contents. However, a pre-testing effect has also been shown in laboratory settings with promising results. Indeed, taking a test before being exposed to learning content enhances retention compared with no retrieval practice. 17-23 Although the pre-testing effect was demonstrated on written materials (prose passages as well as paired words),

Does pre-testing promote better retention than post-testing ?

We report an experiment that examined the learning effects of pre-testing and post-testing on long term memory with a web based environment, in comparison with a reading only condition

Non-lesional status epilepticus in a patient with coronavirus disease 2019

International audienceA 59-year-old man with a history of atrial fibrillation and treated obstructive sleep apnea presented to the emergency department on March 26, 2020 with fever, dry cough, dyspnea and headache. He had no history of personal or familial seizures. A first reverse-transcriptase–polymerase-chain-reaction (RT-PCR) of nasopharyngeal swab test for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was negative but SARS-CoV-2 infection was subsequently confirmed by RT-PCR assay performed on tracheal secretions and by computed tomography scan of the chest. The illness rapidly progressed to hypoxemic respiratory failure warranting the initiation of invasive mechanical ventilation on March 28. Lung bacterial overinfection by Hafnia alveii and Proteus vulgaris was diagnosed and sequentially treated with amoxicillin-clavulanic acid/rovamycine (7 days), tazobactam-piperacillin (5 days) and finally with cefepime (7 days). Deep sedation with midazolam was stopped on April 8 and the patient was extubated the following day.From April 10, the patient started to exhibit short episodes of impaired consciousness together with confusion and behavioral disturbances. Forty-nine minute electroencephalogram (EEG), performed when the patient was awake but confused, showed background fluctuating alertness with preserved responses to simple orders (Fig. 1b) and two widespread long rhythmic delta discharges with superimposed spikes in predominantly frontal localization simultaneous with impaired awareness (Fig. 1c), highly suggestive of epileptic seizures. The first seizure lasted 6 minutes (Fig. 1c), followed by a moderate interictal frontal activity (Fig. 1d) and the second seizure lasted at least 5 minutes (Fig. 1e), leading to the diagnosis of non-convulsive status epilepticus. Laboratory blood tests and brain MRI were normal; plasma cefepime concentrations were within the normal range. Routine cerebrospinal fluid (CSF) analysis was unremarkable and CSF SARS-CoV2 RT-PCR was negative. Clobazam (30 mg/day) and levetiracetam (1.5 g/day) were introduced. On April 14, the patient had only one brief episode of impaired consciousness and his long-term EEG monitoring was normal. He is now clinically stable and discharged from ICU

An innovative approach to reproduce the biodeterioration of industrial cementitious products in a sewer environment. Part I: Test design

WOS:000357909400024International audienceA test method to evaluate biogenic resistance of cementitious pipe products intended for sewer networks is presented. It consisted in inoculating pipes with a highly diverse microbial consortium (urban wastewater treatment plant), and trickling a feeding solution containing a safe and soluble reduced sulfur source, thiosulfate, over the inoculated surface in order to select a sulfur-oxidizing activity. Thiosulfate was used in the form of an aqueous solution, which facilitated the monitoring of (i) the bacterial activity by sulfur mass balances in the liquid phase, and thus quantification of acid production, and of (ii) the leaching of cementitious ions. Cement-based linings made of (i) blast furnace slag cement and (ii) calcium aluminates cement were tested. Results showed the selection of sulfur-oxidizing bacteria and the production of biogenic acid. Differences were shown between the linings in terms of Ca and Al dissolution. Biomass characterization highlighted the influence of the lining composition on colonization. (C) 2014 Elsevier Ltd. All rights reserved

Innovative approach to simulating the biodeterioration of industrial cementitious products in sewer environment. Part II: Validation on CAC and BFSC linings

WOS:000367483000036International audienceThe development of a new test method for evaluating the resistance of manufactured cementitious products to biogenic acid attack, labeled BAC-Test for Biogenic Acid Concrete Test, was reported in Part I of this paper. The performance of the test in terms of sulfur-oxidizing bacteria selection and acid and sulfate production has been validated previously. In this second part, the representativeness of the degradation mechanisms of the cementitious materials is explored. Two segments of industrial pipes - ductile cast iron coated with cementitious linings (blast furnace slag cement (BFSC) and calcium aluminate cement (CAC) mortars) - were exposed to the test for 107 days. Then linings were analyzed by SEM coupled with EDS, EPMA, and XRD. Significant differences between BFSC and CAC linings were highlighted. Abundant cracking of the BFSC lining was observed, caused by precipitation of secondary ettringite, while no cracking was observed in the CAC lining. The CAC outer layer was composed mainly of AH(3) gel. The decalcification front was deeper in the BFSC matrix than in the CAC one. (C) 2015 Elsevier Ltd. All rights reserved