Local and global electrochemical impedances applied to the corrosion behaviour of an AZ91 magnesium alloy

The electrochemical behaviour of an AZ91 magnesium alloy was investigated in a low aggressive medium by means of local and global electrochemical impedance measurements. The results were compared to those obtained on a pure magnesium sample. It was possible to show the individual contribution of each phase constituting the alloy, and it was observed that the corrosion mechanism of the two phases was the same, controlled by the Mg dissolution. However, local impedance diagrams clearly indicated that the kinetics dissolution of the b-phase was slower than that of the a-phase, which was in good agreement with SEM observations

Galvanic coupling between copper and aluminium in a thin-layer cell

The Al/Cu coupling was investigated in a thin-layer cell formed by a large Cu electrode and an Al microelectrode embedded in an insulator placed above the Cu electrode. By using a scanning electrochemical microscope (SECM) the thickness of the thin layer was perfectly controlledwith a precision in the micrometer range. A copper deposit on an electrochemical quartz crystal microbalance (EQCM) was also used as SECM substrate to quantify the copper dissolution rate. It was shown that such an experimental set-up allows to mimic the galvanic corrosion of intermetallic particles embedded in the aluminium matrix of the 2XXX series aluminium alloys. The combination of the SECM and the EQCM permitted the evaluation of the corrosion rate of copper at the corrosion potential of the 2024 Al alloy, whereas cyclic voltammetry performed on the SECM tip indicated the enrichment in Cu2+ ions in the thin electrolyte layer

La traduction des textes émotifs : un défi paradoxal

Dans cette communication l’accent est mis sur les problèmes que posent en général les rapports entre langage et émotions et plus particulièrement ceux que rencontrent un traducteur ou un interprète. L’expression des émotions constitue un défi au langage mais les huamins ne renoncent pas. Le rapport implicitation/explicitation, l’usage des métaphores et l’articulation intermodale des types de signes, constituent la panoplie de moyens d’expression particulièrement utiles pour relever un tel défi. Mais lorsque l’interprète ou/et le traducteur tentent de traduire un discours ou un texte émotif, leur tâche risque d’être difficile. Toutefois malgré les limites inévitables de l’entreprise quand il s’agit de traduire des textes émotifs, la situation n’est pas désespérée pourvu que l’on adopte une perspective pragmatique. Un traducteur (interprète) qui pratique son art dans une perspective pragmatique, peut déjà contribuer beaucoup au partage des émotions. En ce cas, son art ressemble à une paraphrase dans une autre langue, paraphrase qui sait s’adapter aux implicites et aux contextes des publics et lecteurs réels ou potentiels. Certes il faut prendre en compte les différences de conditions de référenciation pour la traduction et pour l’interprétation. Il est ainsi pertinent de partir d’une réflexion sur les problèmes que pose la traduction et de l’interprétation des discours et textes émotifs, pour renouveler l’étude psycholinguistique de la complexité du langage. Il importe d’élaborer en effet, une problématique pluridisciplinaire (traductologie et psycholinguistique) afin de définir ces « universaux psychologiques » qui en deçà des variétés de langues et de cultures fondent le passage d’une langue à l’autre.In this paper, the accent is on the problems posed by the relations between language and emotions, especially those encountered by a translator or an interpreter. Expressing emotions presents a challenge to language, but human beings keep trying. The relation between the implicit and the explicit, the use of metaphors, and the intermodal articulation of types of signs constitute the set of expressive tools best adapted to this challenge. When, however, the interpreter and/or translator tries to translate an emotional discourse or text, their task is likely to be difficult. Nevertheless, despite the inevitable limitations on possible success, the situation is not hopeless, provided one adopts a pragmatic perspective. A translator or interpreter who applies such a perspective can contribute considerably to the sharing of emotions. In this case, his art resembles paraphrasing in another language, but these are paraphrases adapted to the implicit knowledge and contexts of their real or potential audiences. In addition, of course, one must take into account the differences in referential conditions between translation and interpretation. Thus we see the relevance of taking this set of problems as a starting point for a renewed interest in the psycholinguistic study of the complexity of language. One must in fact establish a multidisciplinary framework, combining translation studies with psycholinguistics, in order to define the “psychological universals” which, at a deeper level than the variation among languages and cultures, form the basis of expressing one language in another

Computational modeling of elasticity using methods of particles

El método de los elementos finitos es un método numérico bien establecido que se puede utilizar para predecir el comportamiento mecánico en las ciencias de los materiales. Sin embargo, su dependencia de los elementos implica límites y problemas en ciertas aplicaciones de ingeniería. Es por eso por lo que ha surgido el concepto de eliminar la malla o, al menos, limitar la dependencia en los elementos. Así, se han desarrollado los métodos llamados “meshfree” (los métodos sin malla) que se siguen investigados y mejorados hoy en día. En este trabajo, se estudian los métodos sin malla para aplicaciones de elastoestática, y en particular el “global Radial Point Interpolation Method (RPIM)” y el “Local Radial Point Interpolation Method (LRPIM)”. Él objetive de este trabajo de fin de máster es comprender los procedimientos de solución de los métodos sin malla y los desafíos que se presentan. Por lo tanto, problemas mecánicos sencillos servirán de soportes y de ejemplos para ilustrar los conceptos subyacentes. Además, gracias a los códigos informáticos proporcionados en (G. R. Liu e Y. T. Gu, 2005), se detallan los problemas de implementación debidos al RPIM global y al LRPIM, y se utilizan y modifican los algoritmos para estudiar aplicaciones triviales. Entonces, estos dos métodos se aplican a un problema de mecánica en 2D: un voladizo sometido a una carga parabólica en su extremo derecho, para la que se conoce la solución analítica. Así, se puede cuantificar y estudiar la precisión de la solución.The Finite Element method is a well-established and common numerical method that can be used predict the mechanical behaviour in material sciences. Nevertheless, its strong reliance with the elements implies limits and issues for certain engineering problems. That is why the concept of eliminating the mesh or at least, limiting its dependence has come. Hence, the so-called meshfree methods have been developed and still investigated and improved nowadays. In this work, meshfree methods are discussed for elasto-static mechanics applications, and in particular the global Radial Point Interpolation Method (RPIM) and the Local Radial Point Interpolation Method (LRPIM). The aim of this master thesis is to understand and go through the meshfree methods solution procedures and challenges. Hence, simple mechanics problems will serve as supports and examples to illustrate the concepts behind such numerical methods. More, thanks to the computer codes provided in (G. R. Liu and Y. T. Gu, 2005), the implementation issues due to the global RPIM and LRPIM are detailed, and the algorithms are used and modified for studies on simple applications. These two methods are applied to a 2D mechanics problem: a cantilever beam subjected to a parabolic load at its right end, for which the analytical solution is known. Thus, the meshfree method parameters that affect the solution accuracy can be highlighted and discussed.Incomin

Localized approach to galvanic coupling in an aluminum–magnesium system

The corrosion behavior of a pure aluminum/pure magnesium couple in a weakly conductive sodium sulfate solution was investigated. Potential and current distributions on the surface of the model couple at the beginning of immersion were obtained by solving the Laplace equation using a finite element method algorithm. Magnesium acted as the anode of the system while oxygen and water were reduced on aluminum. Calculations predicted a large current peak at the Al/Mg interface related to a local increase in both Mg dissolution and oxygen and water reduction on aluminum, leading to a local pH increase. Optical and scanning electron microscope observations confirmed the strong dissolution of magnesium concomitantly with depassivation of aluminum at the Al/Mg interface. Local electrochemical impedance spectroscopy showed the detrimental effects of the galvanic coupling both on aluminum and magnesium

Classic China and the Yangtze

Suggested readings for the Penn Alumni Travel event in China. See the Library Guide for this bibliography here