Monte Carlo Simulation of Electron Transport and X-Ray Generation. II. Radiative Processes and Examples in Electron Probe Microanalysis

Theoretical models for Monte Carlo simulation of radiative processes, i.e. bremsstrahlung and characteristic x-ray emission, are presented. Possible strategies for simulating electron transport are briefly described. For mechanisms involving energy loss and angular deflections, difficulties for strict implementation of accurate numerical differential cross sections still remain due to the strong correlations between these variables. Practical solutions for the case of inelastic collisions and bremsstrahlung emission are described. Comparisons of simulation results with experimental data for several problems of interest in electron probe microanalysis are presented.     

Un modèle mathématique de cyclone

The source waves are some particular solutions to genuinely non linear hyperbolic systems with a source term, whose propagation velocity is a constant determined by the roots of this source term. We propose a system of 2 equations on a 2 dimension space, which model the velocity field of the atmosphere near the ground. The source term is made of three parts: a given pressure gradient, a friction or aspiration effect and the Coriolis force. In the case where these parameters are constant, we build a solution which is a constant outside a circular crown. The internal circle represents the eye's wall of the hurricane and corresponds to a share shock wave. The external circle is a set generating the bifurcation which actually models the hurricane. To cite this article: A.-Y. LeRoux et al., C. R. Acad. Sci. Paris, Ser. I 339 (2004).     

Quasi-free divisors and duality

We prove a duality theorem for some logarithmic $\text{D}$-modules associated with a class of divisors. We also give some results for the locally quasi-homogeneous case. To cite this article: F.J. Castro-Jiménez, J.M. Ucha-Enr??quez, C. R. Acad. Sci. Paris, Ser. I 338 (2004).     

KxCoO2·yH2O(x《0.2,y≤0.8)的晶体结构、输运及磁学性质

利用熔融KOH和Co3O4在较低温度(480℃)下反应制备出K0.36CoO2,然后用高锰酸钾溶液和饱和的过硫酸钾溶液进行氧化处理.氧化的同时伴随有水分子嵌入.K0.36CoO2用高锰酸钾和过硫酸钾溶液处理后分别得到K0.12CoO2·0.8H2O和K0.16CO2·0.6H2O.这两种化合物都属于六角晶系,表现出金属行为,脱水后主相变为正交结构并且呈现出半导体特性.K0.16CoO2·0.6H2O在56K附近可能存在自旋玻璃转变行为或其他涨落.随着钾含量的减少和水含量的增多,样品的自旋玻璃行为受到抑制或发生磁性相分离.样品K0.12CoO2·0.8H2O在零场冷却和有场冷却曲线上的分叉现象基本上消失.还讨论了产生KxCoO2与NaxCoO2体系结构和物性差别的原因.     

Stable boundary layers in a diffusion problem with nonlinear reaction at the boundary

We prove the existence of nonconstant stable stationary solutions of an evolution problem with a nonlinear reaction acting on the boundary. These solutions present layers at certain points of the boundary. We also study the behavior of these solutions as the small parameter appearing in the equation approaches zero and show some stability properties of the profiles given by these equilibrium solutions.     

Comparison of Several Calibration Procedures for Glass Electrodes in Proton Concentration

Several reported procedures for calibrating glass electrodes in proton concentration are compared. Some recommendations for non-experts are also given. The examined procedures can be classified into two broad categories, namely: those based on direct potential difference measurements of solutions of known proton concentration and those that use one or several pH standards to calibrate the electrode and subsequently measure the pH of solutions containing known proton concentrations. With a single buffer, the two types of procedures lead to equivalent results. However, if two pH buffers are used, the slope of the calibration graph in proton concentration will differ from the real electrode slope to an extent proportional to the difference between the liquid junction potentials of the two buffers. Therefore, any other method is preferable under these circumstances.     

Principes de grandes déviations pour des processus de « coarse graining »

We improve the Large Deviations Principle satisfied by a Coarse Grained process already analyzed by Boucher, Ellis and Turkington [Ann. Probab. 27 (1999) 297–324]. To cite this article: J. Trashorras, C. R. Acad. Sci. Paris, Ser. I 336 (2003).     

土壤盐渍化的研究进展

根据近年来国内外土壤学者在土壤盐渍化的研究成果，从土壤盐渍化的基本理论，改良方法以及预测预报方面的研究，综述了土壤盐渍化的研究现状，通过分析土壤盐渍化研究多方面存在的问题，对其发展趋势和今后研究重点进行了展望，望能为进一步的深入研究工作提供帮助．