Liquid metals: early contributions and some recent developments

We illustrate in this contribution the progress in the theoretical study of liquid metals made in the last decades, starting from the example of liquid gallium and the early work in Jean-Pierre Badiali's group. This was based on the combination of the perturbation theory with pseudo-potentials for the electrons and the liquid state theory for the ions. More recent developments combining ab initio and classical molecular dynamics simulations are finally illustrated on the example of glass forming alloys.Comment: 12 pages, 8 figure

Equilibrium route to colloidal gellation: mixtures of hard sphere-like colloids

The binodals and the non-ergodicity lines of a binary mixture of hard sphere-like particles with large size ratio are computed for studying the interplay between dynamic arrest and phase separation in depletion-driven colloidal mixtures. Contrarily to the case of hard core plus short range effective attraction, physical gellation without competition with the fluid-phase separation can occur in such mixtures. This behavior due to the oscillations in the depletion potential should concern all simple mixtures with non-ideal depletant, justifying further studies of their dynamic properties

Controlling the composition of a confined fluid by an electric field

Starting from a generic model of a pore/bulk mixture equilibrium, we propose a novel method for modulating the composition of the confined fluid without having to modify the bulk state. To achieve this, two basic mechanisms - sensitivity of the pore filling to the bulk thermodynamic state and electric field effect - are combined. We show by Monte Carlo simulation that the composition can be controlled both in a continuous and in a jumpwise way. Near the bulk demixing instability, we demonstrate a field induced population inversion in the pore. The conditions for the realization of this method should be best met with colloids, but being based on robust and generic mechanisms, it should also be applicable to some molecular fluids.Comment: 9 pages, 5 figure

A NOVEL MODEL AND TOOL FOR ENERGY RENOVATION PLANNING IN FRENCH RESIDENTIAL BUILDINGS AND DISTRICTS

International audienceEnergy renovation of existing buildings is important for energy consumption reduction. In fact, it attracted the interest of governments in several countries for its effectiveness (e.g., 38% consumption reduction by 2020 predicted in France). To achieve such rates, major incentivizing measures were taken by governments to facilitate the funding of energy-oriented renovation projects for final users (e.g., households, communities). Despite all these efforts, a lot of obstacles are yet to be overcome like the lack of interest and involvement of the population, the lack of understanding of the economic equation for renovation, unawareness of governmental aids and support. In fact, most of the population does not fully understand the long-term investment benefits of renovation and look at short term-centered benefits. By taking this into account, the aim of our study is to design, develop and implement a simulation model and decision-making tool to assist final users. The first objective of this tool is to shed the light on the advantages and the benefits of renovation to achieve a maximum awareness. To this end, we studied and highlighted three types of incentives: economical, ecological and comfort. The second objective is related to the technical aspects of the project, where users simulate one or several renovations with different characteristics such as insulation materials, space heater, glazing type. Based on the selected parameters, users will be provided with the cost of renovation works, and achievable yearly savings (energy, money, CO2, etc.). Consequently, the user can make the right decision that suits his needs

Calculated electrocapillary curve for a molten salt

If bulk properties of simple molten salts may be reasonably well understood in terms of the primitive model, the situation with respect to surface properties is less satisfactory. It has been shown that a simple model for the distributions at the free surface of a molten salt can give surface tension and surface energy in reasonable accord with experiment, provided that a factor guaranteeing local electroneutrality is introduced. In this model, properties are given in terms of bulk-salt distribution functions, for which the primitive model is used. The present work extends this model to the electrocapillary curve, i.e., variation of surface tension with surface charge density. The calculations are like those for the free surface, corresponding to the point of zero charge. The local electroneutrality correction, while extremely important for the magnitude of the surface tension, is much less important for its variation with surface charge, and hence the electrical capacitance. Our capacitances, derived from surface charges and potential drops derived from our model, are much too small, whereas the Gouy-Chapman model gives values which are much too large. The calculated variations of surface tension and potential drop with surface charge do not satisfy the thermodynamically derived Lippmann equations; neither does one obtain the same surface tension from different thermodynamically equivalent formulas. In order to understand the reasons and to improve the situation, we show how thermodynamic consistency may be restored to our model. Capacitances are still numerically much smaller than those reported experimentally

Axiomatisation d'un Lambda-Calcul avec Substitutions Explicites dans Coq

Projet COQNous présentons l'axiomatisation de la théorie du \Lenv-calcul dans le système Coq. Le principal résultat axiomatisé est la confluence de ce calcul. Par ailleurs, nous proposons un codage uniforme des systèmes de réécriture à une ou plusieurs sortes, sur lequel nous étudions la confluence locale

Restauraciones antiguas: enfoque estructural numérico para la identificación y reinterpretación de la secuencia constructiva del Medracen

[EN] This paper addresses the importance of a structural approach for identifying and interpreting building chronology, as well as for the establishment of historical stratigraphy. Through structural analyses, carried out on the oldest extant royal mausoleum in North Africa, the Medracen (4th-3rd century BC), located in eastern Algeria, it has been possible to identify building sequences and structural characteristics; a reinterpretation of its constructive sequence within a specific historical context was also suggested. A static linear Finite Element Method (FEM) analysis was performed on a simplified 3D model conceived with solid elements to assess the structural behaviour of the structure under the effect of its self-weight and to identify, consequently, its construction sequence. The equilibrium approach was effective in identifying the structure s geometry. Results show that Medracen s ancient restoration was a strengthening intervention strategy and had a symbolic aim related to the function of the funerary building. Restoration works, consisting of repairing specific parts of the building and adding an external cladding, as a whole architectural entity, contributed to reducing the effect of tensile stress, therefore, stabilizing the inner core. Besides, this same action was a means for the Numidian elite to transform an ancient monumental burial (sepulchrum) into a monument (monumentum) with cultural significance likely to convey socio-political messages relating to power and sovereignty. Therefore, we can speak of an evolutionary restoration that reflects the ambitions of the Numidian elite to become part of the Mediterranean orbit.[ES] Este artículo aborda la importancia del análisis estructural para la identificación e interpretación de la cronología de la construcción y el establecimiento de una estratigrafía histórica. A través de un análisis estructural, realizado sobre el mausoleo real más antiguo que se conserva en Argelia en el norte de África, el Medracen (siglos IV-III a.C.) localizado en su parte oriental, se han podido identificar algunas secuencias constructivas y características estructurales con el objetivo de sugerir una reinterpretación de su cronología constructiva enmarcada en un contexto histórico específico. Se realizó un análisis estático lineal por elementos finitos sobre un modelo 3D simplificado, concebido con elementos sólidos, para evaluar el comportamiento estructural del monumento bajo el efecto de su peso propio e identificar, en consecuencia, su secuencia constructiva. Por otro lado, el enfoque del equilibrio del conjunto fue eficaz para identificar la geometría de la estructura. Los resultados muestran que la antigua restauración de Medracen tuvo como meta una intervención de refuerzo y un objetivo simbólico relacionado con la función del edificio funerario. La restauración, consistente en la reparación de partes específicas del edificio y la adición de un paramento exterior, como entidad arquitectónica de pleno derecho, contribuyó a reducir el efecto de las tensiones de tracción, estabilizando así el núcleo interno. Además, esta misma acción fue un medio para que la élite Númida transformase un antiguo sepulcro (sepulchrum) en un monumento (monumentum) con significado cultural capaz de transmitir mensajes sociopolíticos relacionados con el poder y la soberanía. Por lo tanto, se puede hablar de una "restauración evolutiva" que refleja las ambiciones de la élite númida de integrarse en la órbita mediterránea.Amokrane, L.; Kassab, T.; Monjo-Carrio, J. (2022). Ancient restorations: computer-based structural approach for the identification and reinterpretation of the Medracen's constructive sequence. Virtual Archaeology Review. 13(27):33-48. https://doi.org/10.4995/var.2022.17394OJS3348132

Résolution des problèmes de décision de groupe par analyse bipolaire

On entend par décision de groupe ici, la sélection par plusieurs décideurs, d’une ou plusieurs alternatives dans un ensemble vaste d’alternatives. Du fait de l’existence de plusieurs acteurs, le processus de décision doit tenir compte des relations d’influence (positive ou négative) qui peuvent exister entre les acteurs de la décision. De même, l’évaluation des alternatives par rapport aux objectifs des décideurs doit se faire en considérant plusieurs critères ou attributs caractérisant ces alternatives positivement ou négativement. Cette dualité, que ce soit au niveau des relations entre décideurs ou au niveau des relations entre attributs caractérisant les alternatives et les objectifs, est prise en compte dans ce papier à travers la notion de bipolarité. Ainsi, les relations entre décideurs seront évaluées à travers des mesures de concordance et de discordance et les relations entre attributs et objectifs à travers les notions de supportabilité et de rejetabilité. Au final, pour chaque décideur une alternative sera évaluée, par deux mesures ; une mesure de sélectabilité qui agrège les aspects positifs de l’alternative et une mesure de rejetabilité qui agrège les aspects négatifs dans le formalisme des jeux satisfaisants. Un processus de recherche de consensus entre décideurs est proposé pour aboutir à une solution finale dans le cas où aucune alternative ne satisfait simultanément tous les décideurs