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61.
We report the observation of two types of Sommerfeld precursors (or forerunners) on the surface of a layer of mercury. When the fluid depth increases, we observe a transition between these two precursor surface waves in good agreement with the predictions of asymptotic analysis. At depths thin enough compared to the capillary length, high frequency precursors propagate ahead of the "main signal" and their period and amplitude, measured at a fixed point, increase in time. For larger depths, low frequency "precursors" follow the main signal with a decreasing period and amplitude. These behaviors are understood in the framework of the analysis first introduced for linear transient electromagnetic waves in a dielectric medium by Sommerfeld [Ann. Phys. (Leipzig) 44, 177 (1914)]] and Brillouin [Ann. Phys. (Leipzig) 44, 203 (1914)]]. 相似文献
62.
Etienne Laroche 《Probability Theory and Related Fields》1995,101(1):89-132
Résumé Nous considérons un système de spins sur
d
. Nous prouvons l'équivalence entre premièrement une condition faible de mélange deuxièmement le contrôle du trou dans le spectre et troisièmement celui de la constante de Sobolev logarithmique pour des potentiels de Gibbs de portée non nécessairement finie. Nous en tirons des conséquences sur la vitesse de convergence des semi-groupes dansL
2 et sur la décroissance des corrélations: il n'y a pas de régime intermédiaire entre un taux algébrique ent
–2d (resp. |j-k|–2d) et un taux exponentiel. Les résultats généraux sont montrés pour des spins à valeur dans une variété riemannienne compacte ou dans un espace fini.
Summary We consider a spin system on d . We prove the equivalence between first a weak mixing condition, secondly the controle of spectral gap and thirdly the controle of logarithmic Sobolev constants for non necessarily finite range Gibbs potentials. Hence we draw consequences concerning theL 2 decay to equilibrium and the correlations decay: there is no transitory rate between an algebraic decay ast –2d (resp. |j-k|–2d)and exponential decay. The general results are obtained for both continuous and discrete compact spins.
This article was processed by the authors using the LATEX style filepljour Im from Springer-Verlag 相似文献
63.
A novel hydrogel has been used for intracorneal implantation, in order to correct refractive errors of the eye. Our hydrogel is a polyanionic copolymer of acrylonitrile and sodium methallylsulfonate material (AN 69, made by HOSPAL, France). We describe here its formation, chemico-physical and biological properties (in vitro and in vivo), and its biomechanical behaviour when implanted into the cornea. 相似文献
64.
Two-Phase Flow Properties Prediction from Small-Scale Data Using Pore-Network Modeling 总被引:1,自引:0,他引:1
The objective of this work is to evaluate the prediction accuracy of network modeling to calculate transport properties of porous media based on the interpretation of mercury invasion capillary pressure curves only. A pore-scale modeling approach is used to model the multi-phase flow and calculate gas/oil relative permeability curves. The characteristics of the 3-D pore-network are defined with the requirement that the network model satisfactorily reproduces the capillary pressure curve (Pc curve), the porosity and the permeability. A sensitivity study on the effect of the input parameters on the prediction of capillary pressure and gas/oil relative permeability curves is presented. The simulations show that different input parameters can lead to similarly good reproductions of the experimental Pc, although the predicted relative permeabilities Kr are somewhat widespread. This means that the information derived from a mercury invasion Pc curve is not sufficient to characterize transport properties of a porous medium. The simulations indicate that more quantitative information on the wall roughness and the node/bond aspect ratio would be necessary to better constrain the problem. There is also evidence that in narrow pore size distributions pore body volume and pore throat radius are correlated while in broad pore size distributions they would be uncorrelated. 相似文献
65.
Creyssels M Dorbolo S Merlen A Laroche C Castaing B Falcon E 《The European physical journal. E, Soft matter》2007,23(3):255-264
We report on measurements of the electrical conductivity in both a 2D triangular lattice of metallic beads and in a chain
of beads. The voltage/current characteristics are qualitatively similar in both experiments. At low applied current, the voltage
is found to increase logarithmically in good agreement with a model of widely distributed resistances in series. At high enough
current, the voltage saturates due to the local welding of microcontacts between beads. The frequency dependence of the saturation
voltage gives an estimate of the size of these welded microcontacts. The DC value of the saturation voltage ( ≃ 0.4 V per
contact) gives an indirect measure of the number of welded contact carrying the current within the 2D lattice. Also, a new
measurement technique provides a map of the current paths within the 2D lattice of beads. For an isotropic compression of
the 2D granular medium, the current paths are localized in few discrete linear paths. This quasi-onedimensional nature of
the electrical conductivity thus explains the similarity between the characteristics in the 1D and 2D systems. 相似文献
66.
Surface coating of synthetic materials is often considered to improve biomedical devices biocompatibility. In this study, we covalently bound fibronectin (FN) onto ammonia plasma-treated PTFE via two crosslinkers, namely glutaric anhydride (GA) and sulfosuccinimidyl-4-(p-maleimidophenyl)butyrate (sulfo-SMPB). With respect to clean PTFE, cell adhesion increased markedly on both FN grafted surfaces, although it was twice higher on PTFE-GA-FN than on PTFE-SMPB-FN. ELISA experiments performed with a polyclonal antibody revealed that the amount of FN is identical on both surfaces while monoclonal antibody specific to the RGD binding site clearly demonstrated a greater availability when FN is surface grafted through GA. These results provide evidence of a variation in protein conformation correlated with the surface conjugation strategy. 相似文献
67.
We report the observation of intermittency in gravity-capillary wave turbulence on the surface of mercury. We measure the temporal fluctuations of surface wave amplitude at a given location. We show that the shape of the probability density function of the local slope increments of the surface waves strongly changes across the time scales. The related structure functions and the flatness are found to be power laws of the time scale on more than one decade. The exponents of these power laws increase nonlinearly with the order of the structure function. All these observations show the intermittent nature of the increments of the local slope in wave turbulence. We discuss the possible origin of this intermittency. 相似文献
68.
Nonlinear Dynamics - This paper addresses the model reduction and the simulation of a damped Euler–Bernoulli–von Kármán pinned beam excited by a distributed force. This... 相似文献
69.
We report a Kinetic Monte Carlo (KMC) study of the diffusion of linear n-hexane (nC6) and 2,2-dimethylbutane (22DMB) mixture
in zeolite silicalite. We first investigated the loading dependences of single component self- and corrected diffusivities
of nC6 at 300 K. Anisotropic transition rates are implemented to account for the distribution of the molecules within the
zeolite framework. Repulsive guest-guest interactions are modeled using the parameter introduced by Reed and Ehrlich (Surf.
Sci. 102:588–601, 1981). The results are in good agreement with recent experimental Quasi Elastic Neutron Scattering data of Jobic et al. (J. Phys.
Chem. B 110:2195–2201, 2006), although the influence of the adsorption isotherm inflection is not reproduced. The binary diffusion study of nC6/22DMB
mixtures was performed by implementing the nC6 transition rates used for the single component study while 22DMB molecules
propagate via intersection-intersection hops. This KMC model allows for different saturation capacities and accounts for interactions
between molecules by introducing f
ij
parameters. Results show the large impact of guest-guest interactions between nC6 and 22DMB on both self- and corrected diffusivities
of the two components. Molecule-size effects are found to be predominant near 22DMB saturation capacity. Acceleration/deceleration
effects already described in the literature are confirmed. 相似文献
70.
Laroche I Wu X Masliyah JH Czarnecki J 《Journal of colloid and interface science》2002,250(2):316-326
In the commercial bitumen extraction operation, dynamic and static interaction forces between bitumen drops in water determine the likelihood of desirable bitumen coalescence at different process stages. These dynamic and static forces were measured using colloidal particle scattering and hydrodynamic force balance techniques, respectively. In the former technique, dynamic interactions are studied through droplet-droplet collision trajectory measurement. In the latter technique, the static attractive forces between droplets are determined when a doublet is separated with a known and adjustable hydrodynamic force. The dynamic force measurement implies the presence of rigid chains on bitumen surfaces. The mean chain lengths for deasphalted bitumen at pH 7, whole bitumen at pH 7, and whole bitumen at pH 8.5 are 50, 78, and 41 nm, respectively. However, the static force measurement indicates much shorter mean chain lengths (<9 nm) in these three bitumen systems. Shorter chain length indicates weaker repulsive force. This finding of a much weaker repulsion between bitumen droplets under static conditions has important implications on the commercial bitumen extraction operation. 相似文献