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11.
12.
Sedimentation and erosion processes in sedimentary basins can be modeled by a parabolic equation with a limiter on the fluxes and a constraint on the time variation.This limiter happens to satisfy a stationary scalar hyperbolic inequality,within a constraint,for which the authors prove the existence and the uniqueness of the solution.Actually,this solution is shown to be the maximal element of a convenient convex set of functions.The existence proof is obtained thanks to the use of a numerical scheme. 相似文献
13.
The purpose of this article is to support the idea that “whenever we can prove a limit theorem in the classical sense for a dynamical system, we can prove a suitable almost-sure version based on an empirical measure with log-average”. We follow three different approaches: martingale methods, spectral methods and induction arguments. Our results apply, among others, to Axiom A maps or flows, to systems inducing a Gibbs–Markov map, and to the stadium billiard. 相似文献
14.
The palladium-catalyzed α-arylation of ketones on solid support is described. Using modified Buchwald-Hartwig reaction conditions, the coupling of immobilized 4-bromobenzamide with various aromatic, heteroaromatic, and aliphatic ketones was investigated. Subsequent cleavage from the resin provided the desired α-aryl ketones almost in moderate to high yields and good to excellent purities. The scope and limitations of this protocol will be discussed. 相似文献
15.
We consider an M/G/1 queue with symmetric service discipline. The class of symmetric service disciplines contains, in particular, the preemptive
last-come-first-served discipline and the processor-sharing discipline. It has been conjectured in Kella et al. [1] that the
marginal distribution of the queue length at any time is identical for all symmetric disciplines if the queue starts empty.
In this paper we show that this conjecture is true if service requirements have an Erlang distribution. We also show by a
counterexample, involving the hyperexponential distribution, that the conjecture is generally not true.
AMS Subject Classifications Primary—60K25; Secondary—90B22 相似文献
16.
A phenanthridinium salt was prepared in four steps, including an intramolecular CH-arylation and a hydride abstraction reaction. Treatment with sterically demanding bases does not lead to the corresponding carbene, but rather to addition products: the planar-constrained geometry significantly enhances the electrophilicity over the acidity of C-aryl iminium salts. 相似文献
17.
18.
A two-fraction model that makes it possible to calculate analytically the complex dielectric permittivity of ice in the far infrared and submillimeter wavelength ranges is proposed. The librational and vibrational fractions are considered. The first fraction, consisting of rigid dipoles executing anharmonic reorientations in defects of the structure, gives rise to the librational band of ice at 800 cm?1. The second fraction consists of elastically vibrating oppositely charged H-bonded molecules. This fraction describes two bands of ice in the range 100–300 cm?1, and the nonresonant background of dielectric losses in the submillimeter wavelength range. The dielectric permittivity spectra of ice calculated for the temperature of ?7°C are consistent with the experimental spectra. The spectra of ice at the temperature ?30°C are predicted. 相似文献
19.
Various approaches and standards for transferring mathematical objects between different computer programs in multimedia environment in the framework of the OpenMath project are described. The use of these standards might revolutionize the exchange of mathematical information caused by the development of computer algebra tools and telecommunication possibilities. The standards make it possible to create databases and easily save and use mathematical objects obtained in different applications, e.g., to exchange the data obtained in different computer algebra systems and place information on the Internet. Bibliography: 9 titles. 相似文献
20.
Frédéric Coquel Thierry Gallouët Jean-Marc Hérard Nicolas Seguin 《Comptes Rendus Mathematique》2002,334(10):927-932
Closure laws for interfacial pressure and interfacial velocity are proposed within the frame work of two-pressure two-phase flow models. These enable us to ensure positivity of void fractions, mass fractions and internal energies when investigating field by field waves in the Riemann problem. To cite this article: F. Coquel et al., C. R. Acad. Sci. Paris, Ser. I 334 (2002) 927–932. 相似文献