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1.
Received September 14, 2000; revised September 25, 2001 相似文献
2.
利用α-甲基苯乙烯合成佳乐麝香的研究 总被引:1,自引:0,他引:1
介绍一种新的佳乐麝香合成方法,并就反应的参数对反应过程的影响进行了探讨。 相似文献
3.
4.
Fritz Schwarz 《Computing》2000,65(2):155-167
The largest group of Lie symmetries that a third-order ordinary differential equation (ode) may allow has seven parameters.
Equations sharing this property belong to a single equivalence class with a canonical representative v
′′′(u)=0. Due to this simple canonical form, any equation belonging to this equivalence class may be identified in terms of certain
constraints for its coefficients. Furthermore a set of equations for the transformation functions to canonical form may be
set up for which large classes of solutions may be determined algorithmically. Based on these steps a solution algorithm is described for any equation with this symmetry type which resembles a similar
scheme for second order equations with projective symmetry group.
Received March 9, 2000; revised June 8, 2000 相似文献
5.
We propose an efficient algorithm for computing a unit lower triangular n×n matrix with prescribed singular values of O(n
2) cost. This is a solution of the question raised by N. J. Higham in [4, Problem 26.3, p. 528].
Received July 21, 1999; revised November 4, 1999 相似文献
6.
We propose a cascadic multigrid algorithm for a semilinear indefinite elliptic problem. We use a standard finite element
discretization with piecewise linear finite elements. The arising nonlinear equations are solved by a cascadic organization
of Newton's method with frozen derivative on a sequence of nested grids. This gives a simple version of a multigrid method
without projections on coarser grids. The cascadic multigrid algorithm starts on a comparatively coarse grid where the number
of unknowns is small enough to obtain an approximate solution within sufficiently high precision without substantial computational
effort. On each finer grid we perform exactly one Newton step taking the approximate solution from the coarsest grid as initial
guess. The linear Newton systems are solved iteratively by a Jacobi-type iteration with special parameters using the approximate
solution from the previous grid as initial guess. We prove that for a sufficiently fine initial grid and for a sufficiently
good start approximation the algorithm yields an approximate solution within the discretization error on the finest grid and
that the method has multigrid complexity with logarithmic multiplier.
Received February 1999, revised July 13, 1999 相似文献
7.
Walter Zulehner 《Computing》2000,65(3):227-246
In this paper smoothing properties are shown for a class of iterative methods for saddle point problems with smoothing rates
of the order 1/m, where m is the number of smoothing steps. This generalizes recent results by Braess and Sarazin, who could prove this rates for methods
where, in the context of the Stokes problem, the pressure correction equation is solved exactly, which is not needed here.
Received December 4, 1998; revised April 14, 2000 相似文献
8.
用VHDL-AMS进行概念设计 总被引:4,自引:3,他引:1
VHDL-AMS是VHDL向模拟和混合信号领域的诉展,VHLD-AMS为设计者提供了在概念级处理复杂系统的能力,随着VHDL-AMS的标准化,将诞生处理复杂的模拟和混合信号模型的有效的模拟器,文中介绍了VHLD-AMS模拟扩展的主要内容,展示了一个混合模式模拟环境,并给出了模拟解算器的构成,讨论了连续和离散模拟的同步问题;用4个例子说明VHDL-AMS在概念设计中的应用。 相似文献
9.
A. Goldsztejn 《Computing》2007,79(1):53-60
The Krawczyk and the Hansen-Sengupta interval operators are closely related to the interval Newton operator. These interval
operators can be used as existence tests to prove existence of solutions for systems of equations. It is well known that the
Krawczyk operator existence test is less powerful that the Hansen-Sengupta operator existence test, the latter being less
powerful than the interval Newton operator existence test. In 2004, Frommer et al. proposed an existence test based on the
Poincaré-Miranda theorem and proved that it is more powerful than the Krawczyk existence test. In this paper, we complete
the classification of these four existence tests showing that, in practice, the Hansen-Sengupta existence test is actually
more powerful than the existence test proposed by Frommer et al. 相似文献
10.
One-leg methods and linear multistep methods are two class of important numerical methods applied to stiff initial value
problems of ordinary differential equations. The purpose of this paper is to present some convergence results of A-stable
one-leg and linear multistep methods for one-parameter multiply stiff singular perturbation problems and their corresponding
reduced problems which are a class of stiff differential-algebraic equations.
Received April 14, 2000; revised June 30, 2000 相似文献