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921.
Radulescu O. Janssen T. Etrillard J. 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(3):385-398
We compare within an unifying formalism the dynamical properties of modulated and composite aperiodic (incommensurate) crystals.
We discuss the concept of inner polarization and we define an inner polarization parameter β that distinguishes between different
acoustic modes of aperiodic crystals. Although this concept has its limitations, we show that it can be used to extract valuable
information from neutron coherent inelastic scattering experiments. Within certain conditions, the ratio between the dynamic
and the static structure factors at various Bragg peaks depends only on β. We show how the knowledge of β for modes of an
unknown structure can be used to decide whether the structure is composite or modulated. The same information can be used
to predict scattered intensity within unexplored regions of the reciprocal space, being thus a guide for experiments.
Received 9 June 2002 Published online 14 October 2002
RID="a"
ID="a"e-mail: Ovidiu.Radulescu@univ-rennes1.fr 相似文献
922.
E. Cappelluti C. Grimaldi L. Pietronero 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(4):511-517
In small Fermi energy metals, disorder can deeply modify superconducting state properties leading to a strong suppression
of the critical temperature Tc. In this paper, we show that also normal state properties can be seriously influenced by disorder when the Fermi energy E
F is sufficiently small. We calculate the normal state spin susceptibility χ for a narrow band electron-phonon coupled metal
as a function of the non-magnetic impurity scattering rate . We find that as soon as is comparable to E
F, χ is strongly reduced with respect to its value in the clean limit. The effects of the electron-phonon interaction including
the nonadiabatic corrections are discussed. Our results strongly suggest that the recent finding on irradiated MgB2 samples can be naturally explained in terms of small E
F values associated with the σ-bands of the boron plane, sustaining therefore the hypothesis that MgB2 is a nonadiabatic metal.
Received 31 July 2002 / Received in final form 21 September 2002 Published online 31 December 2002 相似文献
923.
Phillip Griffith 《Transactions of the American Mathematical Society》2001,353(1):77-93
The main result states: if is a module finite extension of excellent local normal domains which is unramified in codimension two and if represents a deformation of the completion of , then there is a corresponding -algebra deformation such that the ring homomorphism represents a deformation of . The main application is to the ascent of the arithmetic Cohen-Macaulay property for an étale map of smooth projective varieties over an algebraically closed field. 相似文献
924.
Let X, X
1, X
2,... be a sequence of independent and identically distributed random variables with common distribution function F. Denote by F
n
the distribution function of centered and normed sum S
n
. Let F belong to the domain of attraction of the standard normal law , that is, lim F
n
(x)= (x), as n , uniformly in x . We obtain extended asymptotic expansions for the particular case where the distribution function F has the density p(x) = cx
––1 ln(x), x > r, where 2, , c > 0, and r > 1. We write the classical asymptotic expansion (in powers of n
–1/2) and then add new terms of orders n
–/2 ln
n, n
–/2 ln-1
n, etc., where 0. 相似文献
925.
Qiya Hu 《高等学校计算数学学报(英文版)》2008,1(4):383-409
A class of normal-like derivatives for functions with low regularity defined on Lipschitz domains are introduced and studied.It is shown that the new normal-like derivatives,which are called the generalized normal derivatives,preserve the major prop- erties of the existing standard normal derivatives.The generalized normal derivatives are then applied to analyze the convergence of domain decomposition methods (DDMs) with nonmatching grids and discontinuous Galerkin (DG) methods for second-order el- liptic problems.The approximate solutions generated by these methods still possess the optimal energy-norm error estimates,even if the exact solutions to the underlying elliptic problems admit very low regularities. 相似文献
926.
FAN Hong-Yi LOU Sen-Yue 《理论物理通讯》2008,49(3):613-616
We introduce bivariate normal distribution operator for state vector [ψ) and find that its marginal distribution leads to one-dimensional normal distribution corresponding to the measurement probability |λ,v〈x|.ψ〉|^2, where |x〉λ,v is the coordinate-momentum intermediate representation. As a by-product, the one-dimensional normal distribution in statistics can be explained as a Radon transform of two-dimensional Gaussian function. 相似文献
927.
Maik Nowak 《Rheologica Acta》2001,40(4):366-372
The first normal stress differences N
1 of a highly dilute cationic surfactant solution are investigated in a cone-and-plate rheometer. In continuation of a previous
paper (Nowak 1998), where the buildup of a shear induced structure in such a solution was attained after a reduced deformation,
the N
1 turned out to be in proportion to the square of the shear rate γ˙ reduced by a critical value γ˙
c
in a first range above γ˙
c
. At higher shear rates the N
1 tend to lower values than predicted by this relation.
Relaxation experiments were performed in the same geometry to determine the characteristic time scales of the shear induced
state's decay. In the lower range above &γdot;
c
the stress decay is a monoexponential process, while a second time constant has to be introduced to describe the relaxation
in that range, where the N
1 deviate from the parabolic dependence of the reduced shear rate.
Received: 10 May 1999 Accepted: 15 November 2000 相似文献
928.
929.
This paper is concerned with an homogeneous isotropic linear elastic strip, in plane strain. It is supposed that its lateral
boundaries are displacement-free and that the deformation is generated by actions on the ends. A cross-sectional measure of
deformation, complementing that of a previous paper, is defined and shown to satisfy a generalised convexity condition in
the axial variable x
1, for materials with negative Poisson's ratio σ. An enhanced measure is subsequently defined, and, in the case of a semi-infinite
strip, is shown to yield pointwise exponential decay estimates for both the axial and the transverse displacement components
for materials with positive Poisson's ratio.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
930.
林升光 《数学物理学报(A辑)》2001,(2)
该文讨论强度为随机变量X 应力为复合x2-更新过程{Y(t),t ∈[0,T]}时结构可靠度的 渐近正态性问题.获得在设计基准期[0,T] 内结构可靠度表达式和结构可靠度渐近正态估计. 相似文献