Mesure de la vitesse de déplacement d'un arc de coupure sur une electrode plane

Dans cet article les auteurs montrent comment ils ont mesuré la vitesse de déplacement sur une surface plane métallique, d'un pied d'arc électrique parcouru par un courant compris entre 500 et 3 000 A. Le dispositif expérimental réalisé permet d'effectuer les mesures nécessaires en temps réel sans perturber le phénomène. Les résultats illustrent le caractère instable du plasma et montrent que le déplacement s'effectue de manière aléatoire

Étude des grandeurs caractéristiques de la tache cathodique d'un arc électrique

The cathode of an electric arc burning freely in air was studied during a half-wave of a sinusoidal, 50 Hz current. For mean intensities ranging from 500 to 2 000 A, five characteristic parameters for the cathode spot were determined : the mean radius a, the temperature T, the electric field E, the total current density J, and the fraction s of the current density due to electrons. The experimental measurement of the erosion of the cathode together with five simultaneous equations enabled the parameters above to be obtained for copper and silver electrodes. The first part of the results gives mean values. The second part shows the changes occuring in the cathode spot as a function of time for the half-wave of the current.On étudie la cathode d'un arc électrique brulant librement dans l'air pendant une demi-alternance d'un courant sinusoïdal de fréquence 50 Hz. Nous avons déterminé pour des intensités moyennes variant entre 500 et 2 000 A cinq grandeurs physiques caractéristiques de la tache cathodique : le rayon moyen a, la température T, le champ électrique E, la densité totale de courant J et la fonction s de la densité de courant due aux électrons. La mesure expérimentale de l'érosion de la cathode associée à un système de cinq équations a permis d'obtenir ces grandeurs pour des électrodes en cuivre et en argent. La première partie des résultats donne des valeurs moyennes, tandis que la deuxième partie montre l'évolution de la tache cathodique en fonction du temps pour la demi-alternance de courant

Contamination d'un plasma d'argon par des vapeurs anodiques de cuivre

The region close to the copper anode (1 mm to 1 cm) of a stabilized arc discharge in argon (15 A and 30 A) is studied. An important drop in temperature due to the metal vapor as well as the concentric and peripherical copper distribution are shown up. The copper concentration is between 10-2 and 10-5. The method allowing to compute the different parameters is given.La région proche de l'anode en cuivre (1 mm à 1 cm) d'un arc stabilisé sous atmosphère d'argon (15 A et 30 A) est étudiée. Un abaissement de température important dû à la présence des vapeurs métalliques ainsi que la répartition concentrique et périphérique du cuivre sont mis en évidence. La concentration en cuivre se situe entre 10-2 et 10-5. La méthode permettant de calculer les différents paramètres à partir des valeurs expérimentales est indiquée

Etude expérimentale d'une décharge d'arc électrique contaminée par des vapeurs d'isolants

Through an experimental investigation, it was shown that vapours originating from some industrial insulators cause an increase in the temperature, electric field and thermal conductivity of the column of an electric arc as well as a shortening of the arc extinction time. The measurements were carried out spectrometrically and using a probing method.Une étude expérimentale a permis de montrer que la présence de vapeurs issues de certains isolants industriels entraîne une augmentation de la température, du champ électrique et de la conductivité thermique de la colonne d'un arc électrique ainsi qu'une diminution du temps d'extinction de l'arc. Les mesures sont faites par spectrométrie et par une méthode de sondes

Influence of the nature of the metal on the conductivity of an argon-metal plasma

Number of materials: 16The importance of the value of the metal first ionisation potential in a low temperature region (T<8000K) is shown through a theoretical investigation of plasmas contaminated by various metals, for a temperature range between 5000K and 14000K

Ionic association and interactions in aqueous methylsulfate alkyl-imidazolium-based ionic liquids

International audienceSeveral experimental techniques were used to study ionic association and interactions in aqueous [C1C2Im][MeSO4], 1-ethyl-3-methylimidazolium methylsulfate, and [C1C4Im][MeSO4], 1-butyl-3-methylimidazolium methylsulfate. Two transport properties, viscosity and electrical conductivity, were determined for these two binary mixtures. For a better assessment of the ionic association and the perturbation of water into the molecular structure of the ionic liquid, diffusion coefficients of ions and water molecules were obtained by NMR spectroscopy while molecular interactions were probed by IR spectroscopy.The comparison of the two ionic liquids shows that for the shorter alkyl chain the viscosity was lower and the electrical conductivity was higher. While the viscosity of the mixture drops already with small additions of water, the electrical conductivity of the solution is only significantly increased for high water concentrations. A maximum is observed for compositions around xwater = (0.90 to 0.95). The SO3 asymmetric stretching band of the IR spectrum can be used as a probe to observe the evolution of the structure around the anion which was mainly occurring for high concentrations of water. Several experimental techniques show than the main change in the ionic association was only observed for high water contents (water mole fraction > 0.8)

Mesure de la vitesse de déplacement d'un arc de coupure sur une electrode plane

In the present work, the authors explain their way of measuring the speed at which the spot of an electric arc moves along a flat metallic surface, when carrying a current from 500 to 3 000 A. The set-up devised enables the necessary measurements to be made in real time without perturbing the process. The results illustrate the unsteady character of plasma and show that the motion occurs randomly.Dans cet article les auteurs montrent comment ils ont mesuré la vitesse de déplacement sur une surface plane métallique, d'un pied d'arc électrique parcouru par un courant compris entre 500 et 3 000 A. Le dispositif expérimental réalisé permet d'effectuer les mesures nécessaires en temps réel sans perturber le phénomène. Les résultats illustrent le caractère instable du plasma et montrent que le déplacement s'effectue de manière aléatoire

Elaboration of Bi-based Nanoparticles by reactive magnetron sputtering on Ionic Liquid for photocatalytic applications.

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Quantification of the impact of water as an impurity on standard physico-chemical properties of ionic liquids

International audienceThe objective of this work was to quantify the effect of the presence of water as impurity in ionic liquids. First, density and viscosity of five ionic liquids as well as their aqueous solutions were measured. For hydrophobic dried ionic liquids, traces of water (50 ppm) have measurable impact neither on the density nor on the viscosity values. In the concentration range studied (up to 5000 ppm), a linear evolution of the molar volume of the mixture with the mole fraction composition is observed. Practically, this allows to estimate the density of an neat ionic liquid provided (i) the water quantity and (ii) the density of the undried sample are known. This is particularly useful for hydrophilic ionic liquids that are difficult to dry. In the studied concentration range, a linear evolution of the relative viscosity was also depicted as a function of the mass fraction composition. It is thus possible to evaluate the viscosity of the pure ionic liquid knowing the water quantity and the viscosity of the undried sample. The comparison of the results obtained using two viscosimeters confirms that a Stabinger viscosimeter is appropriate to precisely measure ionic liquids viscosities. Second, NMR and IR spectroscopies were used to characterize the pure ionic liquids and their solutions with water. The sensitivity of IR spectroscopy does allow neither the quantification nor the detection of water below 1 mol%. With NMR spectroscopy, water can be quantified using either the intensity or the chemical shift of the water proton peak for mole fractions as low as 200 ppm. It is even possible to detect water in the dried hydrophobic ionic liquids, few ppm of water, as long as the water peak does not overlap the ionic liquid signal

Article original SociaBillyQuizz, un jeu pour l&apos;entraînement aux habiletés sociales chez l&apos;enfant et l&apos;adolescent : étude exploratoire The SociaBillyQuizz game: A mediation for social skills training in children and adolescents

Résumé Contexte. -Le SociaBillyQuizz est un jeu thérapeutique élaboré pour servir de médiation à des groupes d&apos;entraînement aux habiletés sociales (GEHS) chez les enfants et adolescents. Il sollicite, de manière ludique, différentes dimensions : l&apos;exposition, les cognitions, la communication, l&apos;imagination et l&apos;expression émotionnelle. Abstract Background. -The SociaBillyQuizz is a therapeutic game designed for social skills training groups with children and adolescents. Using an entertaining method, this media requests several dimensions: exposure, cognition, communication skills, imagination, emotional expression and sign decoding. In this preliminary study, the setting includes two groups of six adolescents, one with social anxiety disorder and the other with Asperger syndrome. Objective. -To evaluate, in an exploratory study, the effects of a therapeutic device involving this game for these two clinically different groups of adolescents. Methods. -During 26 of 1 hour weekly sessions, two adolescents groups participate to a program including the SociaBillyQuizz and cognitive behavioral therapies. The groups are moderated by two therapists. The SociaBillyQuizz is a board game for two to six players; its goal is to collect points by answering instructions from the different thematic cards. There are four thematic cards: action cards (players have to do something), brainstorming cards (players have to use their imagination and demonstrate cognitive flexibility), interview cards (players have to express themselves about what they think or feel) and mystery cards (unexpected instructions). According to the groups&apos; clinical characteristics, * Auteur correspondant. Pourre et al. / Neuropsychiatrie de l&apos;enfance et de l&apos;adolescence 60 (2012) [155][156][157][158][159] some aims are specifically highlighted. In the anxiety disorder group, the cognitive dimension is privileged and in the Asperger syndrome group, we emphasise the pretend, cognitive flexibility and theory of mind. The effects are measured by the Rathus Assertiveness Schedule and the Fear Avoidance Hierarchy (FAH) for the social anxiety disorder group and by the Faux Pas Recognition Test and the Social Responsiveness Scale (parent version) for the Asperger group. Results. -These assessment tools indicate, for both groups, a significant increase of the scores corroborating the observed clinical effects. For eleven of the twelve adolescents, a clinical interview 6 months after the retest shows a continuity of therapeutic benefit. Discussion. -These early results suggest that a social skills training device featuring the SociaBillyQuizz produces clinical improvements in these two groups of adolescents. In future researches, with control group and more complete follow-up, nature and effectiveness of its contribution should be specified. Conclusion. -In this preliminary study, the SociaBillyQuizz appears to be an interesting therapeutic tool that can increase implication, motivation, participation and cohesiveness of the group. It also makes easier the cognitive-behavioural-strategies learning