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101.
研究偶次中立型泛函微分方程,给出了该微分方程解的振荡性的充分条件,得到了一些新的结果并给出了一些示例。 相似文献
102.
PIAO Daxiong 《中国科学A辑(英文版)》2001,44(9)
In this paper, we investigate the existence and uniqueness of new almost periodic type solutions, so-called pseudo almost periodic solutions for the systems of differential equations with piecewise constant argument by means of introducing the notion of pseudo almost periodic vector sequences. 相似文献
103.
104.
Vladimir A. Mandelshtam Howard S. Taylor A.J. Shaka 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1998,133(2):304-312
A new non-Fourier data processing algorithm, the filter diagonalization method (FDM), is presented and applied to phase-sensitive 1D and 2D NMR spectra. FDM extracts parameters (peak positions, linewidths, amplitudes, and phases) directly from the time-domain data by fitting the data to a sum of damped complex sinusoids. Grounded in a quantum-mechanical formalism, FDM shares some of the features of linear prediction and other linear algebraic approaches, but is numerically more efficient, scaling like the fast Fourier transform algorithm with respect to data size, and has the ability to correctly handle spectra with thousands or even millions of lines where the competing methods break down. Results obtained on complex spectra are promising. 相似文献
105.
106.
The main purpose of this paper is to investigate high dimensional limiting behaviors, as m becomes infinite (m → ∞), of matrix statistics on the Stiefel manifold Vk, m, which consists of m × k (m ≥ k) matrices X such that X′X = Ik. The results extend those of Watson. Let X be a random matrix on Vk, m. We present a matrix decomposition of X as the sum of mutually orthogonal singular value decompositions of the projections P
X and P
X, where
and
are each a subspace of Rm of dimension p and their orthogonal compliment, respectively (p ≥ k and m ≥ k + p). Based on this decomposition of X, the invariant measure on Vk, m is expressed as the product of the measures on the component subspaces. Some distributions related to these decompositions are obtained for some population distributions on Vk, m. We show the limiting normalities, as m → ∞, of some matrix statistics derived from the uniform distribution and the distributions having densities of the general forms f(P
X) and f(m1/2P
X) on Vk, m. Subsequently, applications of these high dimensional limit theorems are considered in some testing problems. 相似文献
107.
108.
We investigate the non-diagonal normal forms of a quadratic form on , in particular for n = 3. For this case it is shown that the set of normal forms is the closure of a 5-dimensional submanifold in the 6-dimensional
Grassmannian of 2-dimensional subspaces of .
Received: 27 June 2008 相似文献
109.
A. Alsaad A. Ahmad 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(1):65-77
Theoretical results are presented regarding the incorporation of Scandium into wurtzite GaN and InN binaries. The electric,
optical and piezoelectric properties of the resulting ScGaN and ScInN systems are reported by using first-principles Local-density
approximation (LDA) within density functional theory (DFT), Berry phase approach within modern theory of polarization and
phonon calculations within the density functional perturbation theory. Our results predict the existence of breaking-symmetry
structural phase transition in ordered Sc0.5Ga0.5N and Sc0.5In0.5N alloys when subjected to a compressive or tensile strain. Moreover, our results demonstrate the existence of symmetry preserving pressure-induced isostructural phase transitions
in ordered ScGaN and ScInN systems for different Sc concentrations. It has been shown that the existence of isostructural
phase transitions leads to dramatic changes in optical, acoustic, and piezoelectric properties of ordered ScGaN and ScInN
systems under high pressure. In particular, this study demonstrates that the existence of first-order isostructural phase
transitions in Sc1Ga1N2 at a critical hydrostatic pressure of 12.3 GPa leads to a huge enhancement of piezoelectricity (i.e., the e
33 piezoelectric coefficient adopts a huge value as large as 13 C/m2). In addition, It has been shown that ordered Sc0.5Ga0.5N and Sc0.5In0.5N alloys exhibit tremendous piezoelectric response, associated with a breaking-symmetry phase transition from nonpolar P63/mcc(D6h) space group to a polar P63
mc(C6v) structure, at fixed Ga, In and Sc compositions, as a function of the in-plane compressive and tensile strains. We also reveal
the reason behind, and consequences of, these unusual properties associated with the strain-induced and pressure-induced structural
phase transitions in the novel ScGaN and ScInN ordered structures. 相似文献
110.
This paper studies the existence of solutions of first order impulsive functional differential equations with lower and upper solutions in the reversed order, obtains the sufficient conditions for the existence of solutions by establishing a new comparison principle and using the monotone iterative technique. A concrete example is presented and solved to illustrate the obtained results. 相似文献