Nuclear-resonance beamline at ESRF

Summary The Nuclear-Resonance Beamline at ESRF is dedicated to the excitation of nuclear levels by synchrotron radiation. The source of radiation and optical elements are optimized to provide an intense, highly monochromatic, collimated and stable X-ray beam of small cross-section at the M?ssbauer transition energies between 6 keV and 30 keV. The set-up of the beamline allows to perform studies in diffraction, small-angle scattering, forward scattering and incoherent scattering. Equipment is available to maintain the sample at variable temperature and magnetic field. Fast detectors and timing electronics serve to separate the delayed nuclear scattering from the ?prompt? electronic scattering and to measure the time spectra of nuclear radiation with sub-nanosecond resolution. The general layout and the parameters of the beamline are reported. Typical domains of applications are discussed and illustrated by first experimental results. Paper presented at ICAME-95, Rimini, 10–16 September 1995.     

Dynamics of Inhomogeneous Chains of Coupled Quadratic Maps

A new effective local analysis method is elaborated for coupled map dynamics. In contrast to the previously suggested methods, it allows visually investigating the evolution of synchronization and complex-behavior domains for a distributed medium described by a set of maps. The efficiency of the method is demonstrated with examples of ring and flow models of diffusively coupled quadratic maps. An analysis of a ring chain in the presence of space defects reveals some new global-behavior phenomena.     

Adsorption thermodynamics of monomers on diluted-bonds triangular lattices

The surface of amorphous solids cannot be usually represented by a regular lattice of adsorbing sites. One of the main characteristics of such surfaces is a variable connectivity for each site. A simple model consisting of a triangular lattice where a fraction of bonds (interactions) is suppressed at random is used here to find out, by using Monte Carlo simulations, how the adsorption thermodynamics of repulsively interacting monomers is modified with respect to the same process in the regular lattice. Adsorption isotherm, differential heat of adsorption and adsorbed phase entropy calculations are carried out showing and interpreting the effects of the variable connectivity. In particular, it is found that the order-disorder phase transition observed for the regular lattice survives, though with modifications, above a critical mean connectivity.     

一类非齐次A-调和方程组很弱解的性质

该文应用Hodge分解定理，得到了非齐次A—调和方程组-Di(A^ij(x,Du)) Difj(i(x)=0,j=1,…，m的很弱解是弱解，进一步，利用Morrey空间法与Campanato空间法以及齐次化方法，作者得出了该方程的很弱解是局部Hoelder连续的，并且得出了Hoelder连续指数μ与λ之间的多值函数关系式．     

Influence of capillary effects on strength of non-saturated porous mediaInfluence des effets capillaires sur la résistance d'un milieu poreux non saturé

The mechanical behavior of a partially saturated porous medium is addressed by means of a micro-to-macro reasoning. First, an estimate of the quadratic average over the solid phase of the equivalent shear strain is proposed. The latter is used in the framework of a nonlinear homogenization technique (‘modified secant’ method) in order to model the nonlinear poroelastic behavior in partially saturated conditions. The determination of the macroscopic strength criterion is then considered. Finally, the influence of membrane tension effects on strength is investigated. To cite this article: L. Dormieux et al., C. R. Mecanique 334 (2006).     

大型稀疏矩阵的不完全因子分解法及预处理

本文对大型稀疏阵线性方程组的不完全因子分解及预处理法进行了研究。对对称正定阵和Ｌ阵分别提出了非对角元乘子不完全因子分解法的分解公式。对分解Ａ＝Ｍ－Ｎ，得到了当Ａ为对称正定时，Ｍ亦为对称正定，当Ａ为Ｌ阵时，分解为正规分裂等结果。并研究了预处理ＣＧ加速，最后的数值例子表明本文给出了的算法效果是良好的。     

Measuring the extent of phase separation during polymerization of composite latex particles using modulated temperature DSC

The morphological features of composite latex particles predominantly develop during the polymerization process and depend upon a significant number of variables. In this study, we have concentrated on the relative polarities of the two polymers in the particles and the rate at which we added the monomers during semibatch reactions containing the seed polymer latex. Our particular interest was to develop data that could reveal the extent of polymer phase separation as a function of the amount of monomer fed, and to characterize the morphology resulting from it. While TEM is the most common analytical technique employed, we show in this paper that modulated temperature DSC can generate data that allows us to follow the phase separation process as the monomer feed progresses. By considering the possibilities of having “phases” within the particles of pure polymer, homogeneously mixed (but nonequilibrium) polymers, gradient and interfacial polymer, we have been able to quite successfully simulate the DSC data. This results in quantitative estimates of the relative amounts of these “phases” and their polymer compositions. Combining these results with TEM photos showing the spatial characteristics of the morphology, we can achieve a much greater understanding of the physical structure of the composite latex particles. In many cases we find that phase separation is far from complete at the end of the reaction process. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2790–2806, 2005     

Ray aberrations of two-dimensional oblique lattices on the self-image plane

We extend the geometrical theory of aberration for a self-imaging system to the case of two-dimensional oblique lattices. In our approach, the fundamental translation vectors of the lattice are not restricted in both length and orientation. Evaluating the disturbance of light through the oblique lattice under coherent illumination, we find the conditions of constraint which limit the self-imaging of the oblique lattice. Various types of oblique lattices are shown to obey the self-imaging conditions. We derive the equations to trace the optical paths of self-imaging rays and then analyze the ray aberrations which arise from the difference between the optical paths of a self-imaging ray and of the corresponding actual ray. The ray aberrations are shown to disappear when the periods of the lattice are large compared with the wavelength of light. We find that the ray aberrations carried by self-imaged oblique lattices are totally undercorrected and the aberrated image patches are displaced along the direction tangent vector of a chief ray.     

A Non Homogeneous Riemann Solver for shallow water and two phase flows

In this work we consider a two steps finite volume scheme, recently developed to solve nonhomogeneous systems. The first step of the scheme depends on a diffusion control parameter which we modulate, using the limiters theory. Results on Shallow water equations and two phase flows are presented.     

A constructive semantics for non‐deducibility

This paper provides a constructive topological semantics for non‐deducibility of a first order intuitionistic formula. Formal topology theory, in particular the recently introduced notion of a binary positivity predicate, and co‐induction are two needful tools. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)