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51.
Diem Ho 《Numerische Mathematik》1989,56(7):721-734
Summary The acceleration by Tchebychev iteration for solving nonsymmetric eigenvalue problems is dicussed. A simple algorithm is derived to obtain the optimal ellipse which passes through two eigenvalues in a complex plane relative to a reference complex eigenvalue. New criteria are established to identify the optimal ellipse of the eigenspectrum. The algorithm is fast, reliable and does not require a search for all possible ellipses which enclose the spectrum. The procedure is applicable to nonsymmetric linear systems as well. 相似文献
52.
A complete optical characterization in the visible region of thin copper oxide films has been performed by ellipsometry. Copper
oxide films of various thicknesses were grown on thick copper films by low temperature thermal oxidation at 125 °C in air
for different time intervals. The thickness and optical constants of the copper oxide films were determined in the visible
region by ellipsometric measurements. It was found that a linear time law is valid for the oxide growth in air at 125 °C.
The spectral behaviour of the optical constants and the value of the band gap in the oxide films determined by ellipsometry
in this study are in agreement with the behaviour of those of Cu2O, which have been obtained elsewhere through reflectance and transmittance methods. The band gap of copper oxide, determined
from the spectral behaviour of the absorption coefficient was about 2 eV, which is the generally accepted value for Cu2O. It was therefore concluded that the oxide composition of the surface film grown on copper is in the form of Cu2O (cuprous oxide). It was also shown that the reflectance spectra of the copper oxide–copper structures exhibit behaviour
expected from a single layer antireflection coating of Cu2O on Cu.
Received: 19 July 2001 / Accepted: 27 July 2001 / Published online: 17 October 2001 相似文献
53.
We describe a procedure for determining a few of the largest singular values of a large sparse matrix. The method by Golub and Kent which uses the method of modified moments for estimating the eigenvalues of operators used in iterative methods for the solution of linear systems of equations is appropriately modified in order to generate a sequence of bidiagonal matrices whose singular values approximate those of the original sparse matrix. A simple Lanczos recursion is proposed for determining the corresponding left and right singular vectors. The potential asynchronous computation of the bidiagonal matrices using modified moments with the iterations of an adapted Chebyshev semi-iterative (CSI) method is an attractive feature for parallel computers. Comparisons in efficiency and accuracy with an appropriate Lanczos algorithm (with selective re-orthogonalization) are presented on large sparse (rectangular) matrices arising from applications such as information retrieval and seismic reflection tomography. This procedure is essentially motivated by the theory of moments and Gauss quadrature.This author's work was supported by the National Science Foundation under grants NSF CCR-8717492 and CCR-910000N (NCSA), the U.S. Department of Energy under grant DOE DE-FG02-85ER25001, and the Air Force Office of Scientific Research under grant AFOSR-90-0044 while at the University of Illinois at Urbana-Champaign Center for Supercomputing Research and Development.This author's work was supported by the U.S. Army Research Office under grant DAAL03-90-G-0105, and the National Science Foundation under grant NSF DCR-8412314. 相似文献
54.
The qualitative behavior of buckled states of two different models of elastic beams is studied. It is assumed that random imperfections affect the governing nonlinear equations. It is shown that near the first critical value of the buckling load the stochastic bifurcation is described asymptotically by an algebraic equation whose coeffficients are Gaussian random variables. The corresponding asymptotic expansion for the displacement is to lowest order a Gaussian stochastic process.Work supported by NSF Grant No. DCR81-14726.Work supported by NSF Grant No. DMS87-01895. 相似文献
55.
PIC单片机在中央空调控制器中的应用 总被引:1,自引:0,他引:1
基于PIC 16F877/16C74单片机,设计了一种能满足用户尺寸要求的中央空调控制器。 相似文献
56.
This paper is based on the M. Sc. thesis written by the third author under the supervision of the first two authors. It was submitted to the University of Baghdad in 1986. 相似文献
57.
Vsevolod K. Malinovskii 《Acta Appl Math》1994,34(1-2):261-281
Edgeworth expansions for the distribution of a sequential least squares estimator in the random coefficient autoregressive (RCA) model are derived. The regenerative approach to second-order asymptotic analysis of Markov-type statistical models is developed. 相似文献
58.
Multiderivations of Coxeter arrangements 总被引:3,自引:0,他引:3
Hiroaki Terao 《Inventiones Mathematicae》2002,148(3):659-674
Let V be an ℓ-dimensional Euclidean space. Let G⊂O(V) be a finite irreducible orthogonal reflection group. Let ? be the corresponding Coxeter arrangement. Let S be the algebra of polynomial functions on V. For H∈? choose α
H
∈V
* such that H=ker(α
H
). For each nonnegative integer m, define the derivation module D
(m)
(?)={θ∈Der
S
|θ(α
H
)∈Sα
m
H
}. The module is known to be a free S-module of rank ℓ by K. Saito (1975) for m=1 and L. Solomon-H. Terao (1998) for m=2. The main result of this paper is that this is the case for all m. Moreover we explicitly construct a basis for D
(m)
(?). Their degrees are all equal to mh/2 (when m is even) or are equal to ((m−1)h/2)+m
i
(1≤i≤ℓ) (when m is odd). Here m
1≤···≤m
ℓ are the exponents of G and h=m
ℓ+1 is the Coxeter number. The construction heavily uses the primitive derivation D which plays a central role in the theory of flat generators by K. Saito (or equivalently the Frobenius manifold structure
for the orbit space of G). Some new results concerning the primitive derivation D are obtained in the course of proof of the main result.
Oblatum 27-XI-2001 & 4-XII-2001?Published online: 18 February 2002 相似文献
59.
François Métayer 《Archive for Mathematical Logic》1994,33(3):169-188
This work defines homology groups for proof-structures in multiplicative linear logic (see [Gir1], [Gir2], [Dan]). We will show that these groups characterize proof-nets among arbitrary proof-structures, thus obtaining a new correctness criterion and of course a new polynomial algorithm for testing correctness. This homology also bears information on sequentialization. An unexpected geometrical interpretation of the linear connectives is given in the last section. This paper exclusively focuses onabstract proof-structures, i.e. paired-graphs. The relation with actual proofs is investigated in [Gir1], [Gir2], [Dan], [Ret] and [Tro]. 相似文献
60.
多目标分数变分问题的对偶性 总被引:1,自引:0,他引:1
本文利用参数逼近在函数广义(F,ρ)-凸的条件下,建立了一类多目标式变分问题关于有效解的对偶理论。 相似文献