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International audience; For particular structures like containment buildings of nuclear power plants, the study of the hydraulic behaviour is of great concern. These structures are indeed the third barrier used to protect the environment in case of accidents. The evolution of the leaking rate through the porous medium is closely related to the changes in the permeability during the ageing process of the structure. It is thus essential to know the relation between concrete degradation and the transfer property when the consequences of a mechanical loading on the hydraulic behaviour have to be evaluated. A chained approach is designed for this purpose. The mechanical behaviour is described by an elastic plastic damage formulation, where damage is responsible for the softening evolution while plasticity accounts for the development of irreversible strains. The drying process is evaluated according to a non-linear equation of diffusion. From the knowledge of the damage and the degree of saturation, a relation is proposed to calculate the permeability of concrete. Finally, the non-homogeneous distribution of the hydraulic conductivity is included in the hydraulic problem which is in fact the association of the mass balance equation for gas phase and Darcy law. From this methodology, it is shown how an indicator for the hydraulic flows can be deduced.

International audience; In this work, we compare four inhomogeneous square-well fluid models, only distinct in the approximation on the pair correlation function present in the attractive free energy term of the density functional theory (DFT). Various criteria can be considered to select or validate an approximation, depending on fundamental interests or for a specified application. Here the considered criteria of selection were the verification of sum rules, and the prediction of both the adsorbed quantity and the density profiles. Even if a model satisfies one of these criteria, it may fail to describe others, so they can be considered supplementary to each other and in no case redundant. According to this study, one can attach more importance to any of these criteria depending on the specific objectives intended for the model development and purpose. They can serve as references in the development of new DFT models, eventually with other criteria, according to the objective of the work and the accuracy desired.

A new Helmholtz free energy density functional is presented to predict the vapor-liquid interface of chainlike molecules. The functional is based on the last version of the statistical associating fluid theory for potentials of variable range for homogeneous Mie chainlike fluids (SAFT-VR Mie). Following the standard formalism, the density functional theory (SAFT-VR Mie DFT) is constructed using a perturbative approach in which the free energy density contains a reference term to describe all the short-range interactions treated at the local level, and a perturbative contribution to account for the attractive perturbation which incorporates the long-range dispersive interactions. In this first work, we use a mean-field version of the theory in which the pair correlations are neglected in the attractive term. The SAFT-VR Mie DFT formalism is used to examine the effect of molecular chain length and the repulsive exponent of the intermolecular potential on density profiles and surface tension of linear chains made up to six Mie (lr6) segments with different values of the repulsive exponent of the intermolecular potential. Theoretical predictions from the theory are compared directly with molecular simulation data for density profiles and surface tension of Mie chainlike molecules taken from the literature. Agreement between theory and simulation data is good for short-chain molecules at all thermodynamic conditions of coexistence considered. Once the theory has proven that is able to predict the interfacial properties, and particularly interfacial tension, the SAFT-VR Mie DFT formalism is used to predict the interfacial behavior of two new coarse-grained models for carbon dioxide and water recently proposed in the literature. In particular, the theoretical formalism, in combination with the coarse-grained models for carbon dioxide and water, is able to predict the interfacial properties of these important substances in a reasonable way., The authors thank helpful discussions with Carlos Avendaño andJosé Matías Garrido. We also acknowledge Centro de Supercom-putación de Galicia (CESGA, Santiago de Compostela, Spain) andMCIA (Mésocentre de Calcul Intensif Aquitain) of the Universitésde Bordeaux and Pau et Pays de l’Adour (France), for providingaccess to computing facilities and Ministerio de Economía, In-dustria y Competitividad through Grant with reference FIS2017-89361-C3-1-P co-financed by EU FEDER funds. Further financialsupport from Junta de Andalucía and Universidad de Huelva isalso acknowledged. J.A., J.M.M., and F.J.B. thankfully acknowl-edge the computer resources at Magerit and the technical supportprovided by the Spanish Supercomputing Network (RES) (ProjectQCM-2018-2-0042)., The authors thank helpful discussions with Carlos Avendaño and José Matías Garrido. We also acknowledge Centro de Supercomputación de Galicia (CESGA, Santiago de Compostela, Spain) and MCIA (Mésocentre de Calcul Intensif Aquitain) of the Universités de Bordeaux and Pau et Pays de l’Adour (France), for providing access to computing facilities and Ministerio de Economía, Industria y Competitividad through Grant with reference FIS2017- 89361-C3-1-P co-financed by EU FEDER funds. Further financial support from Junta de Andalucía and Universidad de Huelva is also acknowledged. J.A., J.M.M., and F.J.B. thankfully acknowledge the computer resources at Magerit and the technical support provided by the Spanish Supercomputing Network (RES) (Project QCM-2018-2-0042)

8 pags., 4 figs., Nonequilibrium temperature and concentration fluctuations inside a binary liquid mixture under the action of a temperature gradient relax back to equilibrium either due to conduction and diffusion at large wave numbers, or due to the quenching determined by gravity at small wave numbers. We investigate the dynamics of nonequilibrium fluctuations in a binary liquid mixture of polystyrene and toluene heated from above under stationary conditions in a thermodiffusion experiment. We show that the strong gravitational stabilization at small wave numbers determines the appearance of propagating modes of nonequilibrium fluctuations as detected through the structure function of shadowgraph images. The propagating modes are the combined effect of temperature and velocity nonequilibrium fluctuations induced by the buoyancy force. The experimental results are in good agreement with a fluctuating hydrodynamics theroretical model including the coupling of fluctuations of velocity, temperature and concentration., We gratefully acknowledge support from the European Space Agency (ESA) and the Centre National d’Etudes Spatiales (CNES) of France, specifically for supporting the acquisition of the fast camera that made it possible to observe the propagating mode described in this paper. F.C., L.G.F., and H.B. would like to thank E2S-UPPA for financial support. The research at the Complutense University was supported by Grant No. ESP2017-83544-C3-2-P of the Spanish Agencia Estatal de Investigación.

We propose an unequivocal top-down strategy to build state independent coarse-grained force fields based on the homonuclear Mie chain model. Then, this approach is applied to predict thermophysical properties (equilibrium, interfacial and transport) of nonassociating fluids from molecular simulations. Following the seminal work of Mejia et al. [Ind. Eng. Chem. Res. 2014, 53, 4131], the proposed top-down strategy is based on an extended corresponding states principle (i.e., requiring the critical temperature, one saturated liquid density and the acentric factor for each compound) enriched by the introduction of one reference viscosity in the parametrization procedure. Molecular simulations of the so-developed coarse-grained model representing various pure fluids (noble gas, n-alkanes, H2S, CO2, etc.) yield excellent results on the whole vapor–liquid equilibrium curve. Critical points, saturated densities, vapor pressures, and surface tensions are accurately predicted. Saturated liquid viscosities are as we...

International audience; Aqueous biphasic systems (ABS) provide an alternative and efficient approach for the extraction, recovery and purification of biomolecules through their partitioning between two liquid aqueous phases. In this work, the ability of hydrophilic phosphonium-based ionic liquids (ILs) to form ABS with aqueous K 3PO 4 solutions was evaluated for the first time. Ternary phase diagrams, and respective tie-lines and tie-lines length, formed by distinct phosphonium-based ILs, water, and K 3PO 4 at 298 K, were measured and are reported. The studied phosphonium-based ILs have shown to be more effective in promoting ABS compared to the imidazolium-based counterparts with similar anions. Moreover, the extractive capability of such systems was assessed for distinct biomolecules (including amino acids, food colourants and alkaloids). Densities and viscosities of both aqueous phases, at the mass fraction compositions used for the biomolecules extraction, were also determined. The evaluated IL-based ABS have been shown to be prospective extraction media, particularly for hydrophobic biomolecules, with several advantages over conventional polymer-inorganic salt ABS. © 2010 by the authors.

International audience; The METSTOR project offers a methodology to look for potentially interesting CO2 storage areas in France at the initial stage, before the "site selection" step. Our tool, embodied in a Geographic Information System, is based on an interactive map of CO2 storage capacities. Other relevant information layers are included. The geographic layers are complemented with a series of online technical notices. It seems to be the first open online GIS that offers policy makers, businesses and the public at large an integrated access to that necessary information. Our prototype, limited mainly to the Paris Basin, is released online at www.metstor.fr.

International audience; The conditions for localization in a material described by a non-local damage-based constitutive relation coupled with a Kelvin type creep relation are derived in a closed form. The inception of a localized mode is considered as a bifurcation into a harmonic mode. The criterion of bifurcation is reduced to the classical form of singularity of a pseudo acoustic tensor; this tensor involves the elasto-damage strain and the total one at the inception of localization and the wavelength of the bifurcation mode through the Fourier transform of the weight function used in the definition of non-local damage. A geometrical approach was adopted to analyze localization for loading paths such that the elastic strain tensor is a fraction of the total strain tensor. Such loading paths include the general triaxial ones for which changes in the loading state occur only under time-independent processes (negligible creep strain during these changes of the stress state) and the uniaxial loading. The proposed coupled model preserves the properties of localization limiters; the minimum wavelength of the localization modes cannot be zero. The critical wavelength which is related to the width of the localization zone increases when the material parameter α (0 < α < 1), which is the fraction of creep strain entering into the evolution of damage, is decreasing. Under a certain condition on the growth of the loading function of damage and the initial state of deformation the critical wavelength decreases as the creep effect (creep strains) increases in accordance with experimental observations—increase of brittleness due to creep. In uniaxial tension, and for a specific yield function of concrete considered in this paper, this condition is fulfilled whenever the initial damage is in a region near the first occurrence of localization.

International audience; Molecular dynamics simulations of CH4, CO2, H2S and their mixtures, chosen as representative of acid gas mixtures, have been performed. Static properties (pressure or density) and dynamic properties (shear viscosity) have been computed. A comparison has been performed between results from three different models: a simple Lennard-Jones (LJ) model, an isotropic multipolar (IMP) one and the usual Lennard-Jones plus point charge (LJP). For pure fluids, a reasonable agreement is found between all three models and experiments except for CO2, for which the LJ model suffers from its lack of electrostatic contributions. Concerning CH4-H2S mixtures, results obtained using the three molecular models are consistent with each other for static and dynamic properties. In addition, no significant differences between the results obtained using both, Lorentz-Berthelot and Kong combining rules were noticed. For the CH4-H2S-CO2 mixture, the situation is different: a strong dependence of the pressure on the molecular models as well as on the combining rules, in the case of the LJP model, has been noted. Shear viscosity was found to be less dependent on the choice of models and combining rules. Thanks to simulations on H2S-CO2 mixtures, it has been found that the way cross interactions are treated between these two compounds explains the discrepancies for CH4-H2S-CO2 mixtures. For the systems studied, the IMP approximation seems to be the best option for engineering calculations of physical properties since it is quick to compute, ensures accuracy and is weakly dependent on the combining rules employed. In addition, it is shown that a van der Waals one fluid model combined with an accurate LJ Equation of State together with a correlation on viscosity is able to provide results consistent with simulations (on both LJ and IMP models). Such a result makes this correlative scheme a good alternative for industrial applications.

International audience; In this work we propose a new reduction method for phase equilibrium calculations using a general form of cubic equations of state (CEOS). The energy term in the CEOS is a quadratic form, which is diagonalized by applying a linear transformation. The number of the reduction parameters is related to the rank of the matrix C̄ with elements (1-Cij), where C ij denotes the binary interaction parameters (BIPs). The dimensionality of the problem depends only on the number of reduction parameters, and is independent of the number of components in the mixture.

International audience; The viscosity of the binary system ethanol + n-heptane has been measured with a falling-body viscometer for seven compositions as well as for the pure compounds in the temperature range 293.15-353.15 K and up to 100 MPa with an experimental uncertainty of ±2%. At 0.1 MPa, the viscosity has been measured with a classical capillary viscometer (Ubbelohde) with an uncertainty of ±1%. A total of 208 experimental data points are reported. The viscosity behavior of this binary system is interpreted as the results of changes in the free volume, and the breaking or weakening of hydrogen bonds. The excess activation energy for viscous flow of the mixtures is negative with a maximum absolute value of 0.3 kJ mol-1, indicating a very weakly interacting system. The data of this binary system as well as those recently measured for ethanol + toluene have been used to study the performance of some viscosity models with a physical and theoretical background. The evaluated models are based on the hard-sphere scheme, the concepts of the free-volume and the friction theory, and a model derived from molecular dynamics. In addition to these models, the simple compositional models by Grunberg-Nissan and Katti-Chaudhri have also been applied. Overall a satisfactory representation of the viscosity of these two binary ethanol + C7 hydrocarbon systems is found for the different models within the considered T, P range taking into account their simplicity.

A procedure is presented for the simultaneous prediction of fluid–fluid and solid–fluid equilibrium of light gases/heavy hydrocarbons systems under pressure. The objective of this work is to simplify the predictive approach previously proposed by the authors, making it more useful and accessible to users at the petroleum industry. The main modification with respect to the complex LCVM (linear combination of Huron–Vial and Michelsen) mixing rule that was previously used for the attractive term “a” of the equation of state (EOS). To avoid the use of a group contribution method, which is difficult to bring into play with real fluids, the LCVM mixing rule is here replaced by the classical quadratic van der Walls one-fluid mixing rule. The deviation that using this mixing rule introduces into the gamma–phi approach is cancelled by a new parameter , introduced in the calculation of the solid-phase activity coefficient. This procedure was tested for a large range of multicomponent systems where the parameter was fitted to match the wax appearance temperature (WAT) at atmospheric pressure. From the values obtained a correlation relating the parameter to the carbon number in the heavy fraction was developed, allowing a prediction of wax formation in petroleum fluids. It is shown that this approach can successfully be applied to the prediction of wax formation at high pressure for live oils. © 2005 American Institute of Chemical Engineers AIChE J, 51: 2089 –2097, 2005

International audience; The zeta potential of an air bubble suspended in an aqueous solution of mixed fluorocarbon and hydrocarbon anionic surfactants is studied over a wide range of concentrations and mixture compositions. The zeta potential is related to surfactant ion adsorption. The two surfactants, which exhibit an antipathy manifested by micellar demixing, compete for surface sites. The total surfactant adsorption is reduced when both surfactants are present. Adsorption phenomena are closely correlated to the micellar phase diagram.

International audience; Alternative approaches to the reduction of nitrobenzene for the aniline production using methane are being investigated. Solubility data of gases in aniline or aqueous aniline solutions are very scarce. In this work, high-pressure equilibrium data were measured for methane−aniline and methane−aniline−water systems at temperatures ranging from 293.15 to 373.15 K and pressures up to 100 MPa using a visual static method for detection of phase transitions. The influence of the temperature, pressure, and water on the solubility of methane in aniline was studied. It is shown that the solubility of methane in aniline increases with temperature and pressure and strongly decreases with the water content of the system.

The European Union Floods Directive requires the establishment of flood maps for high risk areas in all European member states by 2013. However, the current practice of flood mapping in Europe still shows some deficits. Firstly, flood maps are frequently seen as an information tool rather than a communication tool. This means that, for example, local stocks of knowledge are not incorporated. Secondly, the contents of flood maps often do not match the requirements of the end-users. Finally, flood maps are often designed and visualised in a way that cannot be easily understood by residents at risk and/or that is not suitable for the respective needs of public authorities in risk and event management. The RISK MAP project examined how end-user participation in the mapping process may be used to overcome these barriers and enhance the communicative power of flood maps, fundamentally increasing their effectiveness. Based on empirical findings from a participatory approach that incorporated interviews, workshops and eye-tracking tests, conducted in five European case studies, this paper outlines recommendations for user-specific enhancements of flood maps. More specific, recommendations are given with regard to (1) appropriate stakeholder participation processes, which allow incorporating local knowledge and preferences, (2) the improvement of the contents of flood maps by considering user-specific needs and (3) the improvement of the visualisation of risk maps in order to produce user-friendly and understandable risk maps for the user groups concerned. Furthermore, "idealised" maps for different user groups are presented: for strategic planning, emergency management and the public.

International audience; Natural materials (e.g. nacre, bone, and spider silk) exhibit unique and outstanding mechanical properties. This performance is due to highly evolved hierarchical designs. Building a comprehensive understanding of the multi-scale mechanisms that enable this performance represents a critical step toward realizing strong and tough bio-inspired materials. This paper details a multi-scale experimental investigation into the toughening mechanisms in natural nacre. By applying extended digital image correlation and other image processing techniques, quantitative information is extracted from otherwise prodominantly qualitative experiments. In situ three point bending fracture tests are performed to identify and quantify the toughening mechanisms involved during the fracture of natural nacre across multiple length scales. At the macro and micro scales, fracture tests performed in situ with a macro lens and optical microscope enable observation of spreading of damage outward from the crack tip. This spreading is quantified using an iso-contour technique to assess material toughness. At the nanoscale, fracture tests are performed in situ an atomic force microscope to link the larger-scale damage spreading to sliding within the tablet-based microstructure. To quantify the magnitude of sliding and its distribution, images from the in situ AFM fracture tests are analyzed using new algorithms based on digital image correlation techniques which allow for discontinuous displacement fields. Ultimately, this comprehensive methodology provides a framework for broad experimental investigations into the failure mechanisms of bio- and bio-inspired materials.

International audience; Nacre, the iridescent material in seashells, is one of many natural materials employing hierarchical structures to achieve high strength and toughness from relatively weak constituents. Incorporating these structures into composites is appealing as conventional engineering materials often sacrifice strength to improve toughness. Researchers hypothesize that nacre's toughness originates within its brick-and-mortar-like microstructure. Under loading, bricks slide relative to each other, propagating inelastic deformation over millimeter length scales. This leads to orders-of-magnitude increase in toughness. Here, we use in situ atomic force microscopy fracture experiments and digital image correlation to quantitatively prove that brick morphology (waviness) leads to transverse dilation and subsequent interfacial hardening during sliding, a previously hypothesized dominant toughening mechanism in nacre. By replicating this mechanism in a scaled-up model synthetic material, we find that it indeed leads to major improvements in energy dissipation. Ultimately, lessons from this investigation may be key to realizing the immense potential of widely pursued nanocomposites.

International audience; This paper deals with the development of a model for concrete subjected to dynamic loads. Shock waves are generated by Pulsed Arc Electro-hydraulic Discharges in water and applied to mortar samples. A diphasic model (liquid water and vapour) is implemented in order to describe the electrical discharge and the propagation of shock waves in water. An anisotropic damage model is devised, which takes account of the strain rate effect and the crack closure effect. Coupling between anisotropic damage and permeability is proposed in order to assess the variation of material permeability due to shock waves. Comparisons with experiments show a good correlation between the experimental and the numerical results.; Cette étude porte sur développement d'un modèle du béton sous chargement dynamique rapide. Le chargement dynamique est généré par des ondes de chocs dues à la décharge électrohydraulique d'un arc (PAED) sous l'eau. Un modèle actuel diphasique est qualifié et utilisé pour simuler la décharge électrique et la propagation des ondes dans l'eau. Un modèle d'endommagement anisotrope est développé qui prend en compte l'effet de vitesse de la déformation et la refermeture des fissures. Un couplage entre l'endommagement et la perméabilité anisotropique est proposé. Après la comparaison avec l'expérimentation, une bonne corrélation est observée entre les résultats expérimentaux et numériques.

This article discusses the influence of compressive shock waves on the permeability of cementitious materials. Shock waves are generated in water by Pulsed Arc Electrohydraulic Discharges (PAED). The practical aim is to increase the intrinsic permeability of the specimens. The maximum pressure amplitude of the shock wave is 250 MPa. It generates damage in the specimens and the evolution of damage is correlated with the intrinsic permeability of the mortar. A threshold of pressure is observed. From this threshold, the increase of permeability is linear in a semi-log plot. The influence of repeated shocks on permeability is also discussed. Qualitative X Ray Tomography illustrates the evolution of the microstructure of the material leading to the increase of permeability. Comparative results from mercury intrusion porosimetry (MIP) show that the micro-structural damage process starts at the sub-micrometric level and that the characteristic size of pores of growing volume increases. Cement and Concrete Research, ISSN : 0008-8846, DOI : 10.1016/j.cemconres.2010.07.005, Issue : 12, Volume : 40, pp. 1631–1638, December 2010.

International audience; The Gradient Theory of fluid interfaces is for the first time combined with the SAFT-VR Mie EOS to model the interfacial properties of the water/CO2 mixture. As a preliminary test of the performance of the coupling between both theories, liquid-vapor interfacial properties of pure water have been determined. The complex temperature dependence of the surface tension of water can be accurately reproduced, and the interfacial thickness is in good agreement with experimental data and simulation results. The water/CO2 mixture presents several types of interfaces as the liquid water may be in contact with gaseous, liquid, or supercritical CO2. Here, the interfacial tension of the water/CO2 mixture is modeled accurately by the gradient theory with a unique value of the crossed influence parameter over a broad range of thermodynamic conditions. The interfacial density profiles show a systematic adsorption of CO2 in the interface. Moreover, when approaching the saturation pressure of CO2, a prewetting transition is highlighted. The adsorption isotherm of CO2 is computed as well in the case of a gas/liquid interface and compared with experimental data. The good agreement obtained is an indirect proof of the consistency of interfacial density profiles computed with the gradient theory for this mixture and confirms that the gradient theory is suitable and reliable to describe the microstructure of complex fluid interfaces.

International audience; Damage models are capable to represent initiation and somehow crack propagation in a continuum framework. Thus crack openings are not explicitly described. However for concrete structures durability analysis, crack opening through transfer properties is a key issue. Therefore, in this contribution we present a new approach that is able from a continuum modelling to locate a crack from internal variable field and then to estimate crack opening along its path. Results compared to experimental measures for a three point bending test are in a good agreement with an error lower than 10% for widely opened crack (40μm).

International audience; The objective of the GeoCarbone-Injectivity project was to develop a methodology to study the complex phenomena involved in the near wellbore region during CO2 injection. This paper presents an overview of the program and results of the project, and some further necessary developments. The proposed methodology is based on experiments and simulations at the core scale, in order to understand (physical modelling and definition of constitutive laws) and quantify (calibration of simulation tools) the mechanisms involved in injectivity variations: fluid/rock interactions, transport mechanisms, geomechanical effects. These mechanisms and the associated parameters have then to be integrated in the models at the wellbore scale. The methodology has been applied for the study of a potential injection of CO2 in the Dogger geological formation of the Paris Basin, in collaboration with the other ANR GeoCarbone projects.

International audience; The present contribution aims at providing a closer insight on boundary effects in non local damage modelling. From micromechanics, we show that on a boundary interaction stress components normal to the surface should vanish. These interaction stresses are at the origin of non locality and therefore the material response of points located on the boundary should be partially local. Then, we discuss a tentative modification of the classical non local damage model aimed at accounting for this effect due to existing boundaries and also boundaries that arise from crack propagation. One-dimensional computations show that the profiles of damage are quite different compared to those obtained with the original formulation. The region in which damage is equal to 1 is small. The modified model performs better at complete failure, with a consistent description of discontinuity of the displacement field after failure.

International audience; A novel Modified Rachford-Rice equation is developed for three-phase equilibrium calculations in hydrocarbon-water systems, based on the free-water assumption, i.e., the water-rich liquid phase consists of pure water only. In the inner loop of the flash algorithm, the three-phase problem (consisting in a system of two non-linear equations) is replaced by a pseudo-two-phase problem (consisting in a non-linear equation). Unlike previous formulations, the new Modified Rachford-Rice function is guaranteed to monotonically decrease between two adjacent asymptotes. The negative flash concept is used, and a search window is proposed for the vapor fraction. The new free-water flash method proved to be robust, and excellent agreement between full three-phase flash and pseudo-two-phase free-water flash was obtained for various test problems. The proposed method is very useful in compositional reservoir simulation of certain oil recovery methods and in process simulation.

International audience; Abstract This paper deals with the dynamics of a single-degree-of-freedom unilateral damage oscillator. Using appropriate internal variables, the hysteretic dynamic system can be written as a nonsmooth autonomous system. The free dynamics of such a nonlinear system are simply reduced to periodic motion, eventually attractive trajectories, and divergent motion. The direct Lyapunov method is used to investigate the stability of the free damage system. A critical energy is highlighted that the oscillator can support while remaining stable. The natural frequency of the periodic motion depends on the stationary value of the damage internal variable. The inelastic forced oscillator, however, can exhibit very complex phenomena. When the damage parameter remains stationary, the dynamics are similar to those of an elastic oscillator with nonsymmetric stiffness. The dynamics appear to be controlled by the initial perturbations. Chaotic motions may appear in such a system, specifically for severely damaged oscillators. It is numerically shown that chaos is observed in the vicinity of the divergence zone (the collapse). This closeness of both behaviors-chaos and divergence-is probably related to the perturbation of the homoclinic orbit associated with the critical energy. © 2010. Journal of Mechanics of Materials and Structures.

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International audience; Some insights on boundary effects in nonlocal damage modelling are addressed. Interaction stresses that are at the origin of nonlocality are expected to vanish at the boundary of a solid, in the normal direction to this boundary. Existing models do not account for such an effect. We introduce tentative modifications of the classical nonlocal damage model aimed at accounting for this boundary layer effect in a continuum modelling setting. Computations show that some nonnegligible differences may be observed between the classical and modified formulations. In a one dimensional spalling test, only the modified formulation provides a spall of finite nonzero thickness, whereas spalls smaller than the internal length cannot be obtained according to the original formulation. For the same set of model parameters, including the internal length, the fracture energy derived from the size effect test method is also very different according to both approaches. Parameters in the size effect laws for notched and unnotched specimens, obtained from computation of geometrically similar bending beams, are more consistent with the modified nonlocal model compared to the original nonlocal formulation.

International audience; The serviceability of concrete structures is a coupled problem in which fracture and damage are coupled with several environmental attacks. In this paper, we start with the description of chemo-mechanical damage and the case of calcium leaching which is relevant to waste containment vessels. The second example of implementation of continuum damage models discussed deals with coupled damage permeability effects. In the case of diffuse damage, the material permeability is controlled by the decrease of average stiffness due to micro-cracking. After a macro-crack has formed, permeability is controlled by a power function of the crack opening (Poiseuille flow). A relationship between permeability and damage, consistent with the two above asymptotic cases, is defined.; La durabilité de structures en béton est un problème dans lequel la rupture et l'endommagement sont couplés aux différentes attaques de l'environnement. Nous commençons par illustrer un tel couplage avec la lixiviation et la modélisation chimiomécanique de l'endommagement dans les bétons. Les couplages entre l'endommagement et les propriétés de transport du béton sont le deuxième exemple traité. Dans le cas d'un endommagement diffus, la perméabilité du matériau est contrôlée par la diminution de raideur moyenne due à la microfissuration. Lorsqu'une macrofissure s'est formée, la perméabilité est contrôlée par une fonction puissance de l'ouverture de fissure (écoulement de Poiseuille). Une relation entre la perméabilité et l'endommagement est définie, en accord avec ces deux cas limites.

Beta-heterosubstituted acrylonitriles correspond to the formal addition of nucleophiles on cyanoacetylene. Acrylonitriles substituted with an amino, methoxy, mercapto group, or halogeno atom have been synthesized. Rearrangements between Z and E stereoisomers or tautomerizations have been studied by NMR spectroscopy and by quantum calculations. The photoelectron spectra were recorded and analyzed with the aid of a time-dependent density functional theory, ab initio OVGF, and so-called "corrected" ionization energy calculations. The electronic structure of the studied species was determined, and strong differences between beta-heterosubstituted acrylonitriles and the corresponding nitrile-free heteroalkenes were clearly documented. A "push-pull" effect was noticed, due to the combined donor effect of the substituent on one side of the carbon-carbon double bond and the electron-withdrawing effect of the nitrile group on the other side. Thus, the presence of a nitrile group strongly stabilizes the electronic structure. The efficient pi-donor contribution of the NH(2) and SH groups was evidenced.

International audience; Experimental tests exhibit a strong interaction between material damage and transport properties of concrete. There are at least two asymptotic cases where some theoretical modeling exists: in the case of diffuse cracking, the material permeability should be controlled by damage, e.g., by the decrease of average stiffness due to microcracking. In the case of localized microcracking, and after a macrocrack has formed, permeability should be controlled by a power function of the crack opening (Poiseuille flow). For quasi-brittle materials with evolving microstructure due to mechanical loads, a transition regime on the evolution of permeability between these two asymptotic cases is expected. In this contribution, we define a relationship between permeability and damage that is consistent with the two above configurations. One of the key issues is to relate the crack opening to the state variables in the continuum approach, so that the two asymptotic cases are expressed in the same variable system and can be matched. A simplified approach is used for this purpose. The permeability law is then derived using a mixing formula that weights each asymptotic regime with damage. To illustrate the influence of the matching law on structural response, finite-element simulations of a Brazilian splitting test and a comparison with existing test data are presented.

Extensive nonequilibrium molecular dynamics (NEMD) simulations have been carried out in order to estimate the Newtonian shear viscosity of a fluid composed of short chains (up to 16 segments) of jointed spheres [Lennard-Jones chain (LJC)] over a large range of thermodynamic conditions. Using the NEMD results, it is shown that the zero-density contribution decreases with the chain length for a given temperature and is simply proportional to ${N}^{\ensuremath{-}1∕2}$, where $N$ is the number of spheres composing the chain. In addition, it has been noticed that the residual shear viscosity is proportional to the chain length. Then, using these results, a relation is proposed to correlate the shear viscosity of the LJC fluid using the LJ fluid (the monomer) as a reference. It is shown that this correlation is able to provide an excellent estimation of the LJC fluid viscosity compared to NEMD results for $N\ensuremath{\leqslant}16$ over the domain $0\ensuremath{\leqslant}{\ensuremath{\rho}}^{*}\ensuremath{\leqslant}1.1$ and $0.7\ensuremath{\leqslant}{T}^{*}\ensuremath{\leqslant}6$. Finally, it is shown that the LJC model is unambiguously more efficient than a simple LJ approximation when applied to estimate the shear viscosity of $n$-butane, if only the sphere or segment diameter is used as an adjustable parameter in both models.

International audience; In this work, is presented an empirical correlation on the thermal conductivity of the Lennard-Jones fluid based on extensive non-equilibrium molecular dynamics simulations results (103 points). Finite size and cutoff radius effects are investigated and taken into account to develop the correlation. This last, composed of low density, residual and critical enhancement contributions, is built for a wide range of thermodynamics states, even at the vicinity of the critical point, and yields an average absolute deviation of 1.29 % compared to our simulations. In addition, a careful analysis of the different contributions to the microscopic flux is carried out which sheds light on the underlying mechanism of the results. Finally, are discussed the limitations of the proposed model when applied to real simple fluids and mixtures using a standard corresponding states scheme and the van der Waals one-fluid approximation.

International audience; The phase behaviour of the {CO2 (1) + cis-decalin (2)} binary system has been experimentally studied at temperatures ranging from (292.75 to 373.75) K. Saturation pressures, ranging from (15.9 to 490.5) bar, were obtained using a variable volume high-pressure cell by visual observation of phase transitions at constant overall composition. For this system, no literature data are available and the results obtained in this study reveal the occurrence of vapor–liquid, liquid–liquid, and vapor–liquid–liquid phase transitions in the investigated temperature range. A total of 133 experimental points are reported including bubble points, dew points, liquid–liquid phase equilibria, and coordinates of the three-phase line. The experimental data can be reasonably predicted by the PPR78 model in which the temperature-dependent binary interaction parameter is calculated by a group contribution method.

International audience; In this work, using extensive molecular dynamics simulations of several thermophysical properties, it is proposed to analyze possible relationships (in the corresponding states sense) between monoatomic fluids for which the repulsive interactions are modeled by an inverse n-power form, the Lennard-Jones 12-6 (LJ), or by an exponential one, the exponential-6 (Exp-6). To compare results between them, two possible definitions of Exp-6 potentials “equivalent” to the LJ one are proposed. In pure fluids, for a large range of thermodynamic conditions, the properties computed are the surface tension, liquid/vapour equilibrium densities, one-phase potential energy, pressure, isometric heat capacity, thermal pressure coefficient and self-diffusion, shear viscosity, thermal conductivity. Additionally, thermodiffusion (Soret effect) has been considered in “isotopic” equimolar mixtures. It is shown that, despites similarities exhibited by alike radial distribution functions, differences exist between the thermodynamic properties values provided by the LJ fluid and the two “equivalent” Exp-6 fluids. Nevertheless, quite surprisingly, when temperature and density are used as inputs, all three direct transport properties are shown to be nearly independent of the choice of the potential tested. Unexpectedly, these similarities hold even for thermodiffusion which is a priori very sensitive to the nature of the interactions. These results indicate that the use of an Exp-6 potential form to describe non bonded/non polar interaction in molecular simulation is an alternative (more physically acceptable) to the LJ potential when dealing simultaneously with thermodynamic and transport properties. However, when only transport properties are considered (including thermodiffusion), the Exp-6 potential form should not lead to any differences compared to the LJ one.

Ionic liquids are attracting great attention nowadays due to their interesting properties which make them useful in a broad range of applications including reaction media or separation/capture of environmentally hazardous gases such as carbon dioxide. In many cases, for practical and/or economical reasons, the use of aqueous solutions of ILs would be preferable to their use as pure compounds. In this work, high pressure equilibrium data for the {carbon dioxide (CO2) + tri-iso-butyl(methyl)phosphonium tosylate [iBu3MeP][TOS] + water system were measured at temperatures ranging from (276 to 370) K and pressures up to 100 MPa. Measurements were performed using a high-pressure cell with a sapphire window that allows direct observation of the liquid–vapour transition. Mixtures with different IL concentrations were studied in order to check the influence of the amount of IL on the solubility of CO2 in the aqueous mixture. The results show that the presence of IL enhances the solubility of CO2 in the (IL + water) system revealing a salting-in effect of the IL on the solubility of CO2. The appearance of a three phase region was observed for IL concentrations higher than 4 mol% of IL in water when working at pressures between 4 and 8 MPa and temperatures between (280 and 305) K. In this range, the upper limit of the VLE region observed is shown to increase with the temperature being almost independent of the IL initial concentration in the mixture., Fundação para a Ciência e a Tecnologia (FCT), FEDER, CICECO, University of Aveiro

International audience; An approach based on molecular dynamics results on Lennard-Jones spheres is proposed to model the viscosity of hydrogen sulfide, H2S. The molecular parameters, that have a strong physical meaning, are the depth of the potential, and the length at which the potential is null (the “molecular diameter”), which take into account the dipolar moment of the hydrogen sulphide through an isotropic dipolar approximation. The interest of the method is that the adjustment does not involve any viscosity data because only density values have been used in order to estimate the molecular parameters. Consequently, the model is entirely predictive. A comparison between the data generated by our model, REFPROP7 and REFPROP8 database and the few available experimental viscosity data (dilute gas and saturated liquid) is performed and clearly demonstrates the performance of this predictive model. It is even shown that this model is, without fitting, slightly better than REFPROP7 and REFPROP8 which uses viscosity experimental database to adjust their parameters. In addition, in typical petroleum reservoirs conditions, it is shown that non negligible deviations appear when comparing results predicted by REFPROP7, REFPROP8 and the model proposed. Due to its predictive nature, we believe that the values evaluated by the proposed model make sense in such reservoir conditions, at least for industrial purposes. Moreover, the scheme proposed is shown to be very easily extended to deal with mixtures involving H2S with the limit that the Lennard-Jones fluid model is appropriate for the other species of the mixtures.

Thermosolutal convection of a water–ethanol binary mixture, with a 50% mass fraction, at a high pressure of 750 bar, in a three-dimensional horizontal cavity, filled with an aluminum oxide (Al2O3) porous medium, is numerically investigated. Such investigation is examined in terms of the compositional separation versus the thermal conductivity and permeability of Al2O3 porous medium. The thermal diffusion, or Soret effect, is analyzed globally with a separation ratio and locally with the distributions of ethanol mole fraction on the horizontal and vertical lines in the center of the porous cavity. The Soret coefficient of ethanol at 30 °C was found to vary between −0.00699 and −0.00610 when pressure increases from 1 to 750 bar, leading to a ± 13.74 % relative variation around the mean value. On the other hand, the Soret coefficient of ethanol at 750 bar will vary from −0.00697 to −0.00534 when the temperature increases from 10 to 50 °C, leading to ± 26.48 % relative variation around the mean value. The details of the compositional separation at the steady state of thermosolutal convection are also applied to study the characteristics of Soret effect. When the value of permeability is less than 104 md, the compositional separation in the cavity is evident. However, when the value of permeability is larger than 104 md, the thermosolutal convection creates a mixing of the substances and the separation is diminished. Recommendations are made for the experimental design based on the results of numerical analysis.

International audience; Crack opening governs many transfer properties that play a pivotal role in durability analyses. Instead of trying to combine continuum and discrete models in computational analyses, it would be attractive to derive from the continuum approach an estimate of crack opening, without considering the explicit description of a discontinuous displacement field in the computational model. This is the prime objective of this contribution. The derivation is based on the comparison between two continuous variables: the distribution if the effective non local strain that controls damage and an analytical distribution of the effective non local variable that derives from a strong discontinuity analysis. Close to complete failure, these distributions should be very close to each other. Their comparison provides two quantities: the displacement jump across the crack [U] and the distance between the two profiles. This distance is an error indicator defining how close the damage distribution is from that corresponding to a crack surrounded by a fracture process zone. It may subsequently serve in continuous/discrete models in order to define the threshold below which the continuum approach is close enough to the discrete one in order to switch descriptions. The estimation of the crack opening is illustrated on a one-dimensional example and the error between the profiles issued from discontinuous and FE analyses is found to be of a few percents close to complete failure.

International audience; This paper reports viscosity data for mixtures containing a refrigerant (HFC-134a) and a lubricant (triethylene glycol dimethyether, TriEGDME, or tetraethylene glycol dimethyl ether, TEGDME), at 12% of TriEGDME or 14% mass fraction of TEGDME. The measurements (140 data points) were obtained at various pressures (between 10 and 140 MPa) in the monophasic liquid state from 293.15 to 373.15 K. Because HFC-134a and the polyethers are not in the same single phase at normal pressure and temperature (the refrigerant is a gas, whereas the polyethers are liquids), accurate measurements of their mixtures require specific procedures for preparation of the samples and filling of the apparatus. A specially designed isobaric-transfer falling-body viscometer is used in this work. The viscosities of the mixtures are, on average, 40% higher than that of the pure refrigerant, and this increase is more noticeable at low temperatures. The experimental viscosities have been used to check the predictive and correlation ability of several viscosity models (mixing rules, Geller and Davis method, self-referencing model, hard-sphere theory, free-volume model, and friction theory). Most of the studied models underestimate the dynamic viscosity values over all of the temperature and pressure ranges investigated.

International audience; The assessment of the diffuse damage and the crack opening are key parameters for estimating the integrity and the strength of concrete structures in the face of environmental attacks ruled by diffusion and/or Darcy's transfers. Continuum enhanced approaches to concrete fracture are able to represent diffuse damage, crack initiation and propagation. They regard damage process as an ultimate consequence of a gradual loss of material integrity. These models, however, do not predict the crack opening. Therefore, we propose to compute the crack opening using cinematic equivalence at failure between a continuous and a discontinuous description. For this purpose, we consider a discontinuous displacement field with a given jump from which we compute the equivalent non‐local strain. From a classical finite element computation we obtain a distribution of the non‐local strain provided by an integral or gradient damage model. The displacement jump is computed assuming that both non‐local strains are equal at the location of a crack. Finally, using this displacement jump, permeability of a cracked concrete may be determined with Poiseuille's law. This approach will be validated against experimental results on loaded discs in Brazilian splitting test.

Molecular dynamics (MD) simulations of direct and derivative thermodynamic properties of the Mie n-6 fluid (n=8, 10, and 12) have been performed for liquid to supercritical states. Using the results, an in depth test of the monomer-monomer interaction estimation of a recently derived statistical associating fluid theory of variable range (SAFT-VR) equation of state [Lafitte et al., J. Chem. Phys., 124, 024509 (2006)] has been carried out based on the Mie n-6 potential. For pure fluids, using an appropriate scaling, MD simulations show that density and isometric heat capacity are nearly independent of n, whereas sound velocity and thermal pressure coefficient tend to increase with n. In addition, the results show that predictions provided by the equation of state are consistent with those coming from MD and catch correctly the trends of each property with n except for the heat capacity. The comparison is next extended to binary mixtures with components differing only in the value of the n parameter and which demonstrate the reliability of the scheme (MX1b) used by Lafitte et al. to deal with this parameter in the SAFT-VR equation of state. In addition, a new empirical one-fluid approximation of the n parameter is proposed thanks to MD simulations, which very favorably compare with the one-fluid model on n previously proposed in the literature. The consistency of this approximation is addressed by making use of it in combination with the SAFT-VR Mie equation of state. It is shown that using such an approach, which is easier to handle than the MX1b one, yields slightly improved results compared to those of the MX1b.

International audience; During growth on n-alkanes, the marine bacterium Marinobacter hydrocarbonoclasticus SP17 formed a biofilm at the alkane–water interface. We showed that hexadecane degradation was correlated with biofilm development and that alkane uptake is localized in the biofilm but not in the bulk medium. Biofilms were observed in cultures on metabolizable n-alkanes (C8–C28) and n-alcohols (C12 and C16), but were formed neither on non-metabolizable alkanes (pristane, heptamethylnonane and n-C32) nor on inert substrata (glass, polystyrene and Permanox®). This substratum specificity indicates that biofilm formation is determined by the presence of an interface between an insoluble substrate and the aqueous phase. Simultaneously with biofilm growth, planktonic cells were released from the biofilm. Detached cells were in a non-growing state, implying that the growing population was exclusively located within the biofilm. Planktonic and sessile cells exhibited differences in their ultrastructure and lipid content. Biofilm cells contained a large amount of wax esters (0.47 mg/mg protein) in rounded or irregularly shaped cytoplasmic inclusions, whereas detached cells displayed rod-shaped inclusions and contained 5 times fewer wax esters (0.10 mg/mg protein) than their sessile counterparts. This study points out the inter-relationship between biofilm formation, insoluble substrate uptake and lipid storage.

The master asymptotic behavior of the usual parachor correlations, expressing surface tension sigma as a power law of the density difference rho(L)-rho(V) between coexisting liquid and vapor, is analyzed for a series of pure compounds close to their liquid-vapor critical point, using only four critical parameters (beta(c))-1 , alpha(c) , Z(c) , and Y(c) , for each fluid. This is accomplished by the scale dilatation method of the fluid variables where, in addition to the energy unit (beta(c))-1 and the length unit alpha(c) , the dimensionless numbers Z(c) and Y(c) are the characteristic scale factors of the ordering field along the critical isotherm and of the temperature field along the critical isochore, respectively. The scale dilatation method is then formally analogous to the basic system-dependent formulation of the renormalization theory. Accounting for the hyperscaling law delta-1/delta+1=eta-2/2d , we show that the Ising-like asymptotic value pi(a) of the parachor exponent is unequivocally linked to the critical exponents eta or delta by pi(a)/d-1=2/d-(2-eta)=delta+1/d (here d=3 is the space dimension). Such mixed hyperscaling laws combine either the exponent eta or the exponent delta , which characterizes bulk critical properties of d dimension along the critical isotherm or exactly at the critical point, with the parachor exponent pi(a) which characterizes interfacial properties of d-1 dimension in the nonhomogeneous domain. Then we show that the asymptotic (symmetric) power law [abstract; see text] is the two-dimensional critical equation of state of the liquid-gas interface between the two-phase system at constant total (critical) density rho(c) . This power law complements the asymptotic (antisymmetric) form [abstract; see text] of the three-dimensional critical equation of state for a fluid of density rho not equal to rho_(c) and pressure p not equal to p_(c) , maintained at constant (critical) temperature T=T_(c)} [mu_(rho)(mu_(rho,c)) is the specific (critical) chemical potential; p_(c) is the critical pressure; and T_(c) is the critical temperature]. We demonstrate the existence of the related universal amplitude combination [abstract; see text] = universal constant, constructed with the amplitudes D_(rho)(sigma) and D_(rho)(c) , separating then the respective contributions of each scale factor Y_(c) and Z_(c) , characteristic of each thermodynamic path, i.e., the critical isochore and the critical isotherm (or the critical point), respectively. The main consequences of these theoretical estimations are discussed in light of engineering applications and process simulations where parachor correlations constitute one of the most practical methods for estimating surface tension from density and capillary rise measurements.

This contribution presents a review of the works carried out at R&DO in Nantes, in collaboration with Electricite de France. The aim is the study of sensitive structures like containment vessels of nuclear power plants, and the evaluation of their gas tightness more specifically. The objective is the computation of the leakage rate of vessels subjected to internal pressure (typically during integrity tests). It requires the evaluation of the material permeability, as a function of the moisture content in concrete and of the amount of damage. We focus mainly on the relationship between gas permeability, material damage and cracking. Experimental tests prove strong interaction between mechanical state and transport properties of concrete (see e.g. Choinska et al. 2007) and there exist at least two asymptotic cases where some theoretical modelling exists: In the case of diffuse damage, analysis of discrete lattices show that the material permeability should be controlled by the decrease of average stiffness due to micro- cracking (Chatzigeorgiou et al. 2005). Such a relationship has been checked experimentally by Picandet et al. (2001).

The sorption of carbon dioxide in glassy Poly(lactic acid) (PLA) films was studied by quartz crystal microbalance (QCM) at high pressures. Two thermal treat- ments, melted and quenched, were performed in PLA with two different L:D contents, 80:20 and 98:2, films and compared with a third thermal protocol, annealed, and used in a previous work. The results obtained show that for pressures higher than 2 MPa, the carbon dioxide solubility is larger in PLA 80:20 than in PLA 98:2, indicating that the L:D plays a dominant role on this property. The thermal treatments only affect the gas solubility in PLA 98:2. Sorption isotherms at temperatures 303, 313, and 323 K, below the glass transition temperature of the polymer, and pressures up to 5 MPa were measured and analyzed with three different models, the dual-mode sorp- tion model, the Flory-Huggins equation, and a modified dual-mode sorption model where the Henry's law term was substituted by the Flory-Huggins equation. This last model performs especially well for CO2 in PLA 80:20, due to the convex upward curvature of the solubility isotherms for that system. V C 2007 Wiley Periodicals, Inc.

International audience; In order to study the influence of stereoisomeric effects on the volumetric properties, an extensive experimental study of the density of the binary system composed of the two stereoisomeric molecular forms of decalin – cis and trans – have been measured (294 points) for 7 different compositions including the pure compounds at 3 temperatures (303.15, 323.15 and 343.15 K) and 14 isobars up to 65 MPa with a vibrating-tube densimeter. The experimental relative uncertainty is estimated to be 0.05%. The isothermal compressibility and the isobaric thermal expansivity have been derived and discussed with respect to their behavior due to stereoisomerism. These results have been interpreted as due to the molecular structure as well as changes in the molecular distance and free volume. Three different types of equations of state (EoS) are studied in order to investigate how they take the stereoisomeric influence and effect into account through their required model parameters, revealing that some model parameters are influenced by stereoisomerism, whereas other parameters are not. In all cases for the density, the models are able to distinguish between the two stereoisomeric decalin compounds. The considered models are the PR EoS, the PC-SAFT approach and a molecular dynamics approach. Further, based on the analysis of the model parameters performed on the pure compounds, it has been found that the use of simple mixing rules without introducing any binary interaction parameters is sufficient in order to predict the density of cis- + trans-decalin mixtures with the same accuracy in comparison with the experimental values as obtained for the pure compounds.

International audience; We present the master (i.e., unique) behavior of the squared capillary length—the so-called Sugden factor—as a function of the temperaturelike field along the critical isochore, asymptotically close to the gas-liquid critical point of about twenty (one-component) fluids. This master behavior is obtained using the scale dilatation of the relevant physical fields of the one-component fluids. The scale dilatation method introduces the fluid-dependent scale factors in a manner analog to the linear relations between physical fields and scaling fields needed by the renormalization theory applied to any physical system belonging to the Ising-like universality class. The master behavior for the Sugden factor satisfies hyperscaling. It can be asymptotically fitted by the leading terms of the theoretical crossover functions for the correlation length and the susceptibility in the homogeneous domain, recently obtained from massive renormalization in field theory. In the absence of corresponding estimation of the theoretical crossover functions for the interfacial tension, we define the range of the temperaturelike field where the master leading power law can be practically used to predict the singular behavior of the Sugden factor, in conformity with the theoretical description provided by the massive renormalization scheme within the extended asymptotic domain of the one-component fluid “subclass.”

International audience; In this work, a new algorithm is proposed to compute single particle (infinite dilution) thermodiffusion using Non-Equilibrium Molecular Dynamics simulations through the estimation of the thermophoretic force that applies on a solute particle. This scheme is shown to provide consistent results for simple Lennard-Jones fluids and for model nanofluids (spherical non-metallic nanoparticles + Lennard-Jones fluid) where it appears that thermodiffusion amplitude, as well as thermal conductivity, decrease with nanoparticles concentration. Then, in nanofluids in the liquid state, by changing the nature of the nanoparticle (size, mass and internal stiffness) and of the solvent (quality and viscosity) various trends are exhibited. In all cases the single particle thermodiffusion is positive, i.e. the nanoparticle tends to migrate toward the cold area. The single particle thermal diffusion 2 coefficient is shown to be independent of the size of the nanoparticle (diameter of 0.8 to 4 nm), whereas it increases with the quality of the solvent and is inversely proportional to the viscosity of the fluid. In addition, this coefficient is shown to be independent of the mass of the nanoparticle and to increase with the stiffness of the nanoparticle internal bonds. Besides, for these configurations, the mass diffusion coefficient behavior appears to be consistent with a Stokes-Einstein like law.

International audience; Models based on the corresponding-states principle have been extensively used for several equilibrium and transport properties of different pure and mixed fluids. Some limitations, however, have been encountered with regard to its application to long chain or polar molecules. Following previous studies, where it was shown that the corresponding-states principle could be used to predict thermophysical properties such as vapor–liquid interfacial tension, vapor pressure, liquid density, viscosity, and thermal conductivity of long-chain alkanes, the application of the corresponding-states principle to the estimation of speeds of sound, with a special emphasis on the less studied heavier n-alkane members, is presented. Results are compared with more than four thousand experimental data points as a function of temperature and pressure for n-alkanes ranging from ethane up to n-hexatriacontane. Average deviations are less than 2%, demonstrating the reliability of the proposed model for the estimation of speeds of sound.

International audience; Because their affinities for the oil and water phases vary considerably with the number of ethylene oxide units in their hydrophilic group, the ethoxylated nonionic species occurring in commercial products tend to behave in a non-collective way, with the low ethoxylation oligomers partitioning mostly in the oil phase. This results in a surfactant mixture at the interface which is more hydrophilic than the one which was introduced in the system in the first place. The pseudophase model is used to study the partitioning in Winsor III type systems, and to estimate the deviation of the interfacial mixture composition from the overall one. New results indicate that the selective partitioning into the oil phase increases when the oil phase becomes aromatic, when the total surfactant concentration decreases and when the water-to-oil ratio decreases.