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排序方式: 共有635条查询结果,搜索用时 15 毫秒
1.
In this paper we consider a wavelet algorithm for the piecewise constant collocation method applied to the boundary element solution of a first kind integral equation arising in acoustic scattering. The conventional stiffness matrix is transformed into the corresponding matrix with respect to wavelet bases, and it is approximated by a compressed matrix. Finally, the stiffness matrix is multiplied by diagonal preconditioners such that the resulting matrix of the system of linear equations is well conditioned and sparse. Using this matrix, the boundary integral equation can be solved effectively. 相似文献
2.
Eiji Yanagida 《Journal of Dynamics and Differential Equations》2007,19(4):895-914
This paper is concerned with the irregular behavior of solutions for Fisher’s equation when initial data do not decay in a
regular way at the spatial infinity. In the one-dimensional case, we show the existence of a solution whose profile and average
speed are not convergent. In the higher-dimensional case, we show the existence of expanding fronts with arbitrarily prescribed
profiles. We also show the existence of irregularly expanding fronts whose profile varies in time. Proofs are based on some
estimate of the difference of two distinct solutions and a comparison technique.
Dedicated to Professor Pavol Brunovsky on his 70th birthday. 相似文献
3.
Let Ω be a region in ℝn and letp = Pi )
i
1m
, be a partition ofΩ into a finite number of closed subsets having piecewise C2 boundaries of finite(n - 1 )dimensional measure. Let τ:Ω→Ω be piecewise C2 onP where, τi = τ|pi is aC
2 diffeomorphism onto its image, and expanding in the sense that there exists α > 1 such that for anyi = 1, 2,...,m ‖Dτi
-1 ‖ < α-1, where Dτi
-1 is the derivative matrixτ
i
- 1 and |‖·‖ is the Euclidean matrix norm. By means of an example, we will show that the simple bound of one-dimensional dynamics
cannot be generalized to higher dimensions. In fact, we will construct a piecewise expanding C2 transformation on a fixed partition with a finite number of elements in ℝ2, but which has an arbitrarily large number of ergodic, absolutely continuous invariant measures 相似文献
4.
Bernard Bialecki 《Numerical Algorithms》1994,8(2):167-184
Cyclic reduction and Fourier analysis-cyclic reduction (FACR) methods are presented for the solution of the linear systems which arise when orthogonal spline collocation with piecewise Hermite bicubics is applied to boundary value problems for certain separable partial differential equations on a rectangle. On anN×N uniform partition, the cyclic reduction and Fourier analysis-cyclic reduction methods requireO(N
2log2
N) andO(N
2log2log2
N) arithmetic operations, respectively. 相似文献
5.
Vasiliy A. Ustimenko 《Acta Appl Math》2002,74(2):117-153
A combinatorial method of encryption with a similarity to the classical scheme of linear coding has been suggested by the author. The general idea is to treat vertices of a graph as messages and arcs of a certain length as encryption tools. We will study the quality of such an encryption in the case of graphs of high girth by comparing the probability to guess the message, (vertex) at random with the probability of breaking the key, i.e. guessing the encoding arc. In fact, the quality is good for graphs which are close to the Erdös bound, defined by the Even Cycle Theorem.In the case of parallelotopic graphs, there is a uniform way to match arcs with strings in a certain alphabet. Among parallelotopic graphs we distinguish linguistic graphs of affine type whose vertices (messages) and arcs (encoding tools) both could be naturally identified with vectors over the GF(q), and neighbors of the vertex defined by a system of linear equations. We will discuss families of linguistic and parallelotopic graphs of increasing girth as the source for assymmetric cryptographic functions and related open key algorithms.Several constructions of families of linguistic graphs of high girth with good quality, complexity and expansion coefficients will be considered. Some of those constructions have been obtained via group-theoretical and geometrical techniques. 相似文献
6.
In this paper, we present a new algorithm to estimate a regression function in a fixed design regression model, by piecewise
(standard and trigonometric) polynomials computed with an automatic choice of the knots of the subdivision and of the degrees
of the polynomials on each sub-interval. First we give the theoretical background underlying the method: the theoretical performances
of our penalized least-squares estimator are based on non-asymptotic evaluations of a mean-square type risk. Then we explain
how the algorithm is built and possibly accelerated (to face the case when the number of observations is great), how the penalty
term is chosen and why it contains some constants requiring an empirical calibration. Lastly, a comparison with some well-known
or recent wavelet methods is made: this brings out that our algorithm behaves in a very competitive way in term of denoising
and of compression. 相似文献
7.
8.
对薄层柱壳爆炸膨胀断裂过程的研究 总被引:10,自引:2,他引:8
本文提出了一个用于描述动态破坏发展过程的损伤度函数。从这个损伤度函数出发,把材料特征性方程取为强化粘塑性本构方程形式,导出了薄层柱壳爆炸膨胀运动在两种近似下(恒定膨胀速度近似合恒定应变速率近似)断裂判据的解析表达式。结果分析表明,在上述条件下,存在着一个动态断裂“塑性峰”,在这个峰值条件的应变率下,柱壳出现贯穿断裂时刻的应变最大。以软钢为算例,本断裂判据可以比较好地解释Иванов和陈大年等给出的实验结果。这时,动态断裂“塑性峰”对应的应变率为4×104 s-1,相应的应变约为60%~80%。 相似文献
9.
P. S. Szczepaniak 《Journal of Optimization Theory and Applications》1989,63(3):459-468
This paper deals with dynamic systems described by nonlinear differential-difference equations of retarded type. The problem considered is to determine the initial function and certain system parameters which minimize a given cost functional. A computational method is presented and some convergence results are given. Numerical examples of linear and nonlinear systems are also included. 相似文献
10.
ONBAHADURASYMPTOTICEFFICIENCYINASEMIPARAMETRICREGRESSIONMODELLIANGHUA(梁华);CHENGPING(成平)(InstituteofSystemsScience,theChineseA... 相似文献