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The objective is to propose a methodology for assessing dynamic crack propagation laws under mixed-mode loading. Unlike quasi-static cases where the loading and the crack position can be easily established, in dynamic impact cases the loading conditions, the variation of the propagation parameters and the exact position of a crack are difficult to control. Thus, the determination of relevant constitutive crack propagation laws from dynamic crack propagation experiments is a rather challenging operation. Therefore, if one wants to evaluate dynamic crack propagation laws under mixed loading, one must perform numerical simulations and assess the quality of the laws by comparing numerical and experimental results. This process requires that the quality of both the numerical simulations and the experiments be perfectly controlled.Dynamic crack propagation experiments have been performed and two different techniques for measuring accurate crack tip position histories have been considered: very accurate crack tip localization by optical displacement sensor has been first used for transparent materials; then, an automatic method based on full-field displacement measurement has been developed for crack localization in all brittle materials whatever their opacity.Those experimental techniques have been carried out to study different cases of dynamic propagation: initiation in mode 1 or in mixed-mode, crack propagation, crack arrest, crack restart, interaction between two cracks, influence of a hole on the crack path, dynamic branching. Those experiments have been then numerically reproduced. A good fit of the experimental and numerical results is observed.; Les risques liés à la propagation de fissures sous impact sont encore très difficiles à estimer. La détermination de critères de rupture dynamique uniquement à partir de résultats expérimentaux reste délicate. Ainsi la première étape pour valider des lois de propagation de fissures sous impact passe par le développement d'outils de simulation numérique. Depuis les années 1970, de nombreux codes de calcul mécanique ont été dédiés à l'étude de la propagation de fissures, notamment dans le cas du phénomène de fatigue. La principale difficulté consiste dans la nécessité de suivre la géométrie de la fissure au cours du temps. Ces dernières années, des méthodes alternatives basées sur la partition de l'unité ont permis une description implicite des discontinuités mobiles. C'est le cas de la méthode des éléments finis étendue (X-FEM) qui paraît particulièrement adaptée à la simulation de la propagation dynamique de fissures sous chargement mixte où les trajets de fissures ne sont pas connus a priori. Si ces outils numériques permettent maintenant de représenter l'avancée dynamique d'une fissure, les résultats numériques doivent être comparés à des résultats expérimentaux pour s'assurer que les lois introduites sont physiquement fondées. Notre objectif est donc de développer conjointement des techniques expérimentales fiables et un outil de simulation numérique robuste pour l'étude des phénomènes hautement transitoires que sont l'initiation, la propagation, l'arrêt et le redémarrage de fissures sous impact.Des expériences de rupture dynamique ont donc été réalisées sur du Polyméthacrylate de méthyle (PMMA) durant lesquelles la mixité du chargement varie et des arrêts et redémarrages de fissures se produisent. Deux bancs d'essais différents ont été utilisé, le premier basé sur la technique des barres de Hopkinson (ou barres de Kolsky), le second mettant en jeu un vérin rapide. Le PMMA étant transparent, la position de la fissure au cours de l'essai a été acquise grâce à des caméras rapides mais aussi en utilisant un extensomètre optique (Zimmer), habituellement dédié à la mesure de déplacements macroscopiques d'un contraste noir/blanc. L'utilisation de cet extensomètre pour suivre la fissure au cours de l'essai a permis d'obtenir une localisation très précise de la pointe de la fissure en continu, permettant ainsi l'étude des phases transitoires de propagation. Afin d'étudier le même phénomène dans des matériaux opaques comme les aluminiums aéronautiques (Al 7075), des techniques de corrélation d'images numériques ont été employées en mouchetant les éprouvettes impactées. De nouveaux algorithmes ont été développés afin de traiter les images issues d'une caméra ultra-rapide (jusqu'à 400 000 images par seconde).Plusieurs géométries ont été envisagées afin d'étudier différents cas de propagation dynamique : initiation en mode I pur, initiation en mode mixte, propagation, arrêt, redémarrage, interaction entre deux fissures, influence d'un trou sur le trajet d'une fissure, branchement dynamique de fissures. Ces expériences ont ensuite été reproduites numériquement afin de valider les algorithmes et les critères de rupture choisis.

International audience

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.

In this work, high-pressure viscosity measurements for seven compositions of the binary mixture (x) HFE-7500 + (1 – x) diisopropyl ether were carried out. A set of 163 points have been measured cov...

We designed and implemented an experimental methodology to investigate gas hydrate formation and growth around a water-guest meniscus in a thin glass capillary, thus mimicking pore-scale processes in sediments. The glass capillary acts as a high-pressure optical cell in a range of supercooling conditions from 0.1 °C, i.e., very close to hydrate dissociation conditions, to ∼35 °C, very near the metastability limit. Liquid or gaseous CO

Density and speed of sound of carbon dioxide + n-dodecane binary mixtures were measured at pressures from 10 to 70 MPa and at two temperatures around the critical temperature of carbon dioxide (303...

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.

Expanding the electrical double layer of minerals through low-salinity brine injection has been suggested as a possible enhanced oil recovery mechanism. To investigate this theory, we measured the ζ potential of different minerals, namely, sands from Fontainebleau, Ottawa, and Landes, a sample from a sandstone outcrop, and one crude oil. ζ-potential measurements can be used to quantify the surface charges of materials; therefore, experiments associated with this technique were performed to predict the behavior of repulsion or attraction between materials in different salinity and pH conditions. We showed that there is no significant difference between the ζ potentials of the tested materials. We did, however, observe that the different sands and sandstone have dissimilar adhesion behaviors. No correlation was found between the electrokinetic measurements performed on the minerals and their response to crude oil introduced into the system. The adhesion results obtained for the Landes and Ottawa sands were ...

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; A high-pressure bubbling sampler has been developed to trap and preconcentrate metals and metalloids from natural gas. This high-pressure sampler was designed to work at pressures up to 100 bar and be directly plugged into distribution and transportation networks. It consists of three vials in series, which contain 50 mL of metal trapping solution and the gas flows at the network pressure with a flow rate up to 40 L/min. The trapping solutions for mercury and other metals are permanganate/sulfuric acid or nitric acid/hydrogen peroxide according to standards EN 13211 and EN 14385. The sampler design, development, and validation steps are presented in this work. First, the trapping vials were tested in the laboratory, where argon gas was spiked with mercury at two different pressures that represented the distribution and transportation networks. The results show that more than 96% of the metal was trapped from the gas phase into the solution for both tested pressures. Moreover, more than 90% of the trapped metal was found in the first vial, which shows the good efficiency of the traps. Finally, the high-pressure bubbling sampler was tested in three field campaigns of natural gas sampling from a transportation network at 60 bar. Each sampling was performed for 5 days with a flow rate of 20 L/min, which makes a total volume of 140 Nm3 of sampled gas. The gas flowed through three vials of 50 mL, which makes a final preconcentration factor of 3 × 106. The trapping solutions were analyzed for trace metal concentrations using inductively coupled plasma mass spectrometry. The concentrations were 10–1 ng/Nm3 for barium, from 10–1 to 5 ng/Nm3 for tin, from 0.9 to 10 ng/Nm3 for arsenic and copper, and from 1 to 101 ng/Nm3 for aluminum, selenium, and zinc. The efficiency of the traps and the low measured concentrations make this high-pressure bubbling sampler a useful tool for trace element analyses in natural gas

National audience

International audience; This paper reports new measurements of the density of dimethyl adipate (DMA) and diisobutyl adipate (DiBA) over 12 isotherms from (293.15 to 403.15) K and 15 isobars from (0.1 to 140) MPa. The density of diethyl adipate (DEA) in the same conditions has already been published in a previous work. Viscosity data for the three fluids are also presented from (283.15 to 373.15) K at 0.1 MPa. The influence of the size of the adipate chains on the thermophysical properties has been analyzed. The correlation of the densities against pressure and temperature with the Tammann-Tait equation were used to obtain the isothermal compressibility and the isobaric thermal expansivity. The linear dependence between the tangent bulk modulus at atmospheric pressure and the secant bulk modulus at 100 MPa recently proposed by Kiselev et al. is also used in this work to calculate the isothermal compressibility at atmospheric pressure.

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.

Hexadecane assimilation by Marinobacter hydrocarbonoclasticus SP17 occurs through the formation of a biofilm at the alkane-water interface. In this study we focused on the interactions of cells with the alkane-water interface occurring during initiation of biofilm develop- ment. The behavior of cells at the interface was apprehended by investigating alterations of the mechanical properties of the interface during cell adsorption, using dynamic drop tensiometry measurements. It was found that after having reached the hexadecane-water interface, by a purely thermal diffusion process, cells released surface-active compounds (SACs) resulting in the formation of an interfacial visco- elastic film. Release of SACs was an active process requiring protein synthesis. This initial interaction occurred on meta- bolizable as well as non-metabolizable alkanes, indicating that at this stage cells are not affected by the nature of the alkane forming the interface. In contrast, at a later stage, the nature of the interface turned out to exert control over the behavior of the cells. The availability of a metabolizable alkane at the interface influenced cell activity, as revealed by cell cluster formation and differences in the interfacial elasticity. Biotechnol. Bioeng. 2010;105: 461-468. 2009 Wiley Periodicals, Inc.

International audience; In the presence of a large excess of asphaltenes in oil phase, an interfacial tension anomaly (a small bump of the order of 1 mN/m), is found to correspond to the optimum formulation where the fastest water-in-oil emulsion breaking is observed. This correspondence, also observed for other systems, indicates that strong interaction should occur between asphaltenes and demulsifiers. Therefore, the optimum formulation would correspond to a situation where there is enough demulsifier to remove the asphaltenic interfacial gel by orogenic displacement, but not too much to cause adsorption of large asphaltenic/demulsifier complexes which would slow down emulsion drainage.

International audience; This work reports the density data (352 points) of two 2-alkylamines (2-aminobutane and 2-aminooctane; branched amines) at 12 temperatures between (293.15 and 403.15) K and pressures up to 140 MPa (every 10 MPa) which allows studying the influence of the chain length. An Anton Paar vibrating tube densimeter, calibrated with an uncertainty of ± 5·10−4 g·cm−3 was used to perform these measurements. The experimental density data were fitted with the Tait-like equation with low standard deviations (less than 2·10−4 g·cm−3). These data were used to derive the isobaric thermal expansivity and the isothermal compressibility.

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; The present work propose a methodology combining acoustic, volumetric and calorimetric measurements in order to characterize thermophysical behaviors of heavy oils under conditions similar to those encountered during their production and/or transportation. Ultrasonic velocity measurements were performed in two heavy oils from 283.15 to 373.15 K at pressures up to 20 MPa. Further volumetric measurements, i.e. density, were carried out in the same ranges while heat capacity was determined at the only atmospheric pressure from 300.15 to 373.15 K. Comparisons between direct ultrasonic velocity measurements and calculated speed of sound from its thermodynamic definition which involves both volumetric and calorimetric measurements exhibit a strong divergence below a temperature of 320 K. This difference between the two sets of data means that thermodynamic consistency is not complete, which can mean a singular thermophysical behavior of such fluids.

International audience; The melting temperatures of nine n-alkylbenzenes (undecylbenzene, dodecylbenzene, tridecylbenzene, tetradecylbenzene, pentadecylbenzene, hexadecylbenzene, heptadecylbenzene, octadecylbenzene, and nonadecylbenzene) were measured by means of a high-pressure microscope up to 100 MPa. The experimental device used in this work allowed the distinction between stable and metastable solid phases. The influences of the alkyl chain length and pressure on the melting temperatures of the stable solid phases are discussed.

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; An optical fiber extrinsic sensor for measurement of changes in the refractive index of liquids confined in chambers for high pressure and temperature experiments is described. One head sensor composed by two fibers is fixed in front of a high pressure and temperature cell filled with the sample. The operation principle is based in the reflectivity dependence in the refractive index of the glass–liquid interface. Excellent results and a sensitivity of 10−5 RI were obtained for pure liquids. The applicability of the sensor is demonstrated following the changes in the refractive index for pure liquids at different pressure and temperatures and by measuring the asphaltenes and wax precipitation in crude oils under pressure. The extrinsic probe designed for refractive index measurement proves to be a reliable tool for measuring heavy organics deposition in crude oils under high pressures and temperatures where the sample to be measured is not very accessible.

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.

International audience; In this work, two asphaltenes derived from the same set of source rocks, C1 from a crude oil and C2 from an oil sand, were studied, concerning their adsorption/occlusion properties. From the adsorbed components, saturated and aromatic hydrocarbon distributions are distinctly different for these two asphaltenes. For example, some n-alkanes and alkyl-branched alkanes were found adsorbed in C2 asphaltenes, whereas only some cyclic compounds, particularly terpanes were detected from C1 asphaltenes. This difference is due to their different evolution processes in oil reservoirs, and the exchangeability between asphaltene-sorption compounds and those from outside of the bulk phase is different for these two asphaltenes. However, from the asphaltene-occlusion compounds, saturated hydrocarbons show almost the same distribution features. This is consistent with the fact that these two asphaltenes were derived from the same set of source rocks, therefore, occluded almost the same original oils from the source rocks. The experimental results suggest that substantial microporous units exist inside the macromolecular structures of asphaltenes and the asphaltene-derived adsorption/occlusion phenomena extensively occur in oil reservoirs. It seems that asphaltene occlusion should have taken place before asphaltene was detached from kerogen.

International audience; The density of the asymmetrical binary system composed of ethanol and heptane has been measured (630 points) for nine different compositions including the pure compounds at five temperatures in the range (293.15 to 333.15) K and 14 isobars up to 65 MPa with a vibrating-tube densimeter, The experimental uncertainty is estimated to be 0.5 kg·m-3. The isothermal compressibility, the isobaric thermal expansion, and the excess molar volume have been derived from the experimental density data, revealing that a volume expansion occurs for this binary system. The results have been interpreted as due to changes in the molecular free-volume, disruption of the order molecular structure, and the breaking of hydrogen bonds within the self-associating alcohol.

International audience; Commercial ethoxylated nonionic surfactant mixtures containing alcohol cosurfactant exhibit a three-phase behavior whose formulation strongly varies with the water/oil ratio. As a consequence, a change in water/oil ratio can result in a sequence of up to three different emulsion inversion processes, through a combination of formulation and composition effects.

International audience; Density data (196 points) for 1-phenyldecane (decylbenzene) and for 1-phenylundecane (undecylbenzene) at several temperatures between (293.15 and 353.15) K and pressures up to 65 MPa are reported. A vibrating tube densimeter with an uncertainty of ±5 × 10-4 g·cm -3 was used to perform these measurements. The experimental density data were fitted with the Tait-like equation with standard deviations ≤1.5 × 10-4 g·cm-3. The isobaric thermal expansivity, αp, and the isothermal compressibility, K T, have been evaluated, calculating these derivative density properties using the Tait-like equation.

International audience; Seven asphaltene samples and six octylated asphaltene (OA) derivatives were analyzed using laser desorption ionization-time-of-flight (LDI-TOF) mass spectrometry (abbreviated as MS) and vapor pressure osmometry (VPO) techniques. Molecular weight distributions (MWDs) that were determined using MS spanned, for all asphaltenes samples and their octylated counterparts, a similar range, from ∼100 Da to ∼10 000 Da. For asphaltenes, the number-average molecular weight (Mn) and weight-average molecular weight (Mw) afforded values in the 1900 ± 200 and 3200 ± 400 intervals, respectively. Consistently heavier values were observed for the OA derivatives (Mn ≈ 2300 ± 200 and Mw ≈ 3600 ± 200). To select the adequate laser power for these measurements, experiments at different laser powers were performed, to increase volatility and reduce fragmentation to a minimum. Several other experiments were performed to validate these results. First, good agreement between the measured and calculated Mn values was observed for OA materials (calculated from asphaltene Mn and n, the number of octyl groups introduced, as determined from elemental analysis); second, Mn values, as measured by VPO and MS, were determined to be equal, within an average standard deviation of ±27.0%. These results and calculations strongly suggest that the MWD, the molecular weight range, and the molecular weight averages determined using the present MS technique are reasonable estimates of the molecular weight properties of asphaltenes and not the result of artifacts such as fragmentation, polymerization, incomplete volatilization, etc., which may be occurring during the MS experiment.

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; The partitioning of ethoxylated alkylphenol surfactant species between oil and water depends on all physicochemical variables which are likely to alter the balance of affinity of the surfactant for the oil and water phases. Experimental data indicate how the logarithm of the partitioning coefficient varies with the oligomer characteristics (degree of ethoxylation, alkyl chain length), the phase nature (oil alkane carbon number, aqueous phase salinity), and cosurfactant (n-pentanol) content.

International audience; Experimental determinations versus pressure of the nonlinear acoustic parameter B/A have been conducted for methanol, 1-butanol and 1-octanol in the pressure range 0-50 MPa and temperature range 303.15-373.15 K. These measurements proceed from an experimental technique based on a phase comparison method allowing to measure the change in sound speed with the pressure for an isentropic process. The value of B/A is found to decrease with increasing pressure and seems to be an increasing function of temperature. A comparison with the data determined numerically by the classical thermodynamic method has also been performed.

The authors gratefully acknowledge the GENCI/CINES for HPC resources/computer time (Project cpt2130).; International audience; The importance of having reliable calculation tools to interpret and predict the electronic properties of BN-aromatics is directly linked to the growing interest for these very promising new systems in the field of materials science, biomedical research, or energy sustainability. Ionization energy (IE) is one of the most important parameters to approach the electronic structure of molecules. It can be theoretically estimated, but in order to evaluate their persistence and propose the most reliable tools for the evaluation of different electronic properties of existent or only imagined BN-containing compounds, we took as reference experimental values of ionization energies provided by ultra-violet photoelectron spectroscopy (UV-PES) in gas phase-the only technique giving access to the energy levels of filled molecular orbitals. Thus, a set of 21 aromatic molecules containing B-N bonds and B-N-B patterns has been merged for a comparison between experimental IEs obtained by UV-PES and various theoretical approaches for their estimation. Time-Dependent Density Functional Theory (TD-DFT) methods using B3LYP and long-range corrected CAM-B3LYP functionals are used, combined with the ΔSCF approach, and compared with electron propagator theory such as outer valence Green's function (OVGF, P3) and symmetry adapted cluster-configuration interaction ab initio methods. Direct Kohn-Sham estimation and "corrected" Kohn-Sham estimation are also given. The deviation between experimental and theoretical values is computed for each molecule, and a statistical study is performed over the average and the root mean square for the whole set and sub-sets of molecules. It is shown that (i) ΔSCF+TDDFT(CAM-B3LYP), OVGF, and P3 are the most efficient way for a good agreement with UV-PES values, (ii) a CAM-B3LYP range-separated hybrid functional is significantly better than B3LYP for the purpose, especially for extended conjugated systems, and (iii) the "corrected" Kohn-Sham result is a fast and simple way to predict IEs.

International audience; With a view to evaluate the risk of asphaltene to flocculate in crude oils, an experimental device based on an acoustic technique of phase comparison has been developed. The operational method and the results concerning the influence of the precipitant concentration on crude-solvent mixtures at 323 K and atmospheric pressure thus obtained are presented. On the basis of the measurements carried out, it is shown that flocculation caused a sufficiently important change in the output phase signal which thus can be used as an indicator of the phenomenon. (C) 2000 Elsevier Science B.V. All rights reserved. With a view to evaluate the risk of asphaltene to flocculate in crude oils, an experimental device based on an acoustic technique of phase comparison has been developed. The operational method and the results concerning the influence of the precipitant concentration on crude-solvent mixtures at 323 K and atmospheric pressure thus obtained are presented. On the basis of the measurements carried out, it is shown that flocculation caused a sufficiently important change in the output phase signal which thus can be used as an indicator of the phenomenon.

International audience; The spinning bubble tensiometer technique provides a handy tool to measure the ζ potential at the air-water surface. The method is used to estimate the variation of the ζ potential at the surface of aqueous solutions containing binary mixtures of surfactants (anionic, nonionic, and fluorocarbon anionic). The evidence on molecular interactions at the air-water surface is compared with the information deduced from the critical micelle concentration experimental data. The spinning bubble tensiometer technique provides a handy tool to measure the ζ potential at the air-water surface. The method is used to estimate the variation of the ζ potential at the surface of aqueous solutions containing binary mixtures of surfactants (anionic, nonionic, and fluorocarbon anionic). The evidence on molecular interactions at the air-water surface is compared with the information deduced from the critical micelle concentration experimental data.

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

International audience

International audience; This work examines the performance of composite panels when subjected to underwater impulsive loads. The scaled fluid-structure experimental methodology developed by Espinosa and co-workers was employed. Failure modes, damage mechanisms and their distributions were identified and quantified for composite monolithic and sandwich panels subjected to typical blast loadings. The temporal evolutions of panel deflection and center deflection histories were obtained from shadow Moiré fringes acquired in real time by means of high speed photography. A linear relationship of zero intercept between peak center deflections versus applied impulse per areal mass was obtained for composite monolithic panels. For composite sandwich panels, the relationship between maximum center deflection versus applied impulse per areal mass was found to be approximately bilinear but with a higher slope. Performance improvement of sandwich versus monolithic composite panels was, therefore, established specially at sufficiently high impulses per areal mass (I0/M¯>170 m s−1). Severe failure was observed in solid panels subjected to impulses per areal mass larger than 300 m s−1. Extensive fiber fracture occurred in the center of the panels, where cracks formed a cross pattern through the plate thickness and delamination was very extensive on the sample edges due to bending effects. Similar levels of damage were observed in sandwich panels but at much higher impulses per areal mass. The experimental work reported in this paper encompasses not only characterization of the dynamic performance of monolithic and sandwich panels but also post-mortem characterization by means of both non-destructive and microscopy techniques. The spatial distribution of delamination and matrix cracking were quantified, as a function of applied impulse, in both monolithic and sandwich panels. The extent of core crushing was also quantified in the case of sandwich panels. The quantified variables represent ideal metrics against which model predictive capabilities can be assessed.

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; Microchromatography using permeation through gels with the increasing exclusion limit (5000, 400000 and 20000000 Da) was combined with high resolution (R = 4000) ICP MS to measure the distribution of Co, Cr, Fe, Ni, S, Si, V and Zn as a function of the molecular mass fraction of crude oil and oil vacuum distillation residue. The accuracy of the simultaneous multielement determination was verified by the flow-injection-ICP MS analysis of certified reference materials (wear-metals in lubricating oils: SRM 1084a and SRM 1085b). The method allowed the acquisition of chromatograms with high sensitivity competitive existing methods, showing element- and sample origin-dependent morphology.

Short-range correlations of the molecular orientations in liquid n-alkanes have been extensively studied from depolarized Rayleigh scattering and thermodynamic measurements. These correlations between segments induce structural anisotropy in the fluid bulk. This phenomenon, which is characteristic of linear chain molecules when the constituting segments are nor freely jointed, but interact through a given angular potential, is then present in the linear n-Cn series, increasing its magnitude with chain length, and it is therefore less relevant or even completely absent in branched alkanes. This intermolecular effect is clearly revealed in second-order excess magnitudes such as heat capacities when the linear molecule is mixed with one whose structure approaches sphericity. The mixing process of different aspect ratio chain molecules is thought to modify the original pure fluid structure, by producing a diminution of the orientational order previously existing between pure n-alkane chains. However, second-order thermodynamics quantities of pure liquids C(P), ( partial differentialv/ partial differentialT)(P), and ( partial differentialv/ partial differentialP)(P) are known to be very sensitive to the specific interactions occurring at the microscopic level. In other words, the behavior of these derived properties versus temperature and pressure can be regarded as response functions of the complexity of the microscopic interactions. Thus, the purpose of the present work is to rationalize the orientational order evolution with both temperature and molecular chain length from the analysis of pure fluid properties. To this aim, we focused on two linear alkanes, n-octane (n-C(8)) and n-hexadecane (n-C(16)), and two of their branched isomers, i.e., 2,2,4-trimethylpentane (br-C(8)) and 2,2,4,4,6,8,8-heptamethylnonane (br-C(16)). For each compound, we propose a combined study from direct experimental determination of second-order derivative properties and Monte Carlo simulations. We performed density rho, speed of sound c, and isobaric heat capacity C(P) measurements in broad ranges of pressure and temperature allowing a complete thermodynamic characterization of these compounds. Monte Carlo simulations provide a link between the molecular scale model and the experimental thermodynamic properties. Additional information about the microscopic structure of the simulated fluid model was derived, through the calculation of the radius of gyration and average end-to-end distances. Orientational order is clearly revealed by the experimental residual heat capacity trend of pure linear alkanes. The close agreement observed between this experimental macroscopic property and the calculated theoretical structural parameters support the conclusion that the orientational order between segments of linear molecules should be regarded as a conformational effect due to the flexibility of the chain.

International audience; Molecular dynamics simulations of surface tensions of short flexible Lennard-Jones chains, composed of 2, 3, 4, and 5 segments, have been performed in this work. Using the simulation results, it is shown that the reduced surface tension depends only on the chain length and the reduced temperature. As a consequence, simple three parameters corresponding states using the acentric factor is shown to yield an excellent estimation of the reduced surface tension of the flexible Lennard-Jones chain fluid model. In addition, it has been noticed that the reduced surface tension of this fluid model is a unique function of the coexisting liquid and vapor reduced densities i.e., there exist a universal Parachor behavior for all chain lengths tested. When applied to real fluids, this universal behavior holds rather well for a large class of real species which can be nonspherical, nonlinear, and even polar. Only the surface tension of hydrogen-bonding compounds seems to largely deviate from this universal Parachor behavior. These interesting features of the surface tension, written in appropriate scaled forms, can probably be used to improve molecular models, in particular, those on which modern molecular based equations of state rely on.