由线性微分算子决定的B-样条

首先,我们引进一些记号及定义.设 t=(t_i)_(-∞)~∞是非减的实数序列,对所有i都有t_i相似文献   

由线性微分算子决定的B-样条(Ⅱ)

本文继续[1]的工作,采用的记号及定义均依照该文.为明确起见,我们把与本文有关的一些记号及结果简述如下. 设t=(t_i)_(-∞)~( ∞)是非减的实数序列,t_i相似文献   

二维Qausi-Geostrophic方程的几何约束与非爆炸性

研究二维Qausi-Geostrophic(QG)方程水平集的动态演化过程.在"涡线"上"涡度"的最大值与全局"涡度"最大值可比的假设下,得到若"涡线"的长度L(t)被O(ln ln ||▽~⊥θ(·,t)||_∞)控制(被O(ln ln ||▽~⊥θ(·,t)||_∞)控制),曲率最大值K(t)与L(t)的乘积被O(ln ln ln ||▽~⊥θ(·,t)||_∞)控制(被O(ln ln ||▽~⊥θ(·,t)||_∞)控制),则||▽~⊥θ(·,t)||_∞)的增长阶数最多可达四重指数阶,这样二维QG方程在有限时间内无爆炸发生.     

关于corona(日冕)问题

设Δ={|z|<1},H~∞(Δ)表示Δ上一切有界解析函数全体所组成的函数族.它是一个Banach代数,因若f和g∈H~∞ (Δ),则fg∈H~∞(Δ),且||fg||_∞≤||f||_∞·||g||_∞.设对单位圆内任何一点z,令M_z={f∈H~∞(Δ):f(z)=0},则M_z是H~∞ (Δ)的一个极大理想.设 表示 H~∞(Δ)的极大理想空间,则它在弱拓扑下成为一个紧致的Hausdorff空间.若对z,|z|<1,则点赋值     

非线性单调型映射的广义拓扑度

本文引入(S)_ ~*型和拟(S)_ ~*型映射以及弱一次连续性概念。首先证明了拟(S)_ ~*型映射包含拟有界伪单调、伪单调、拟有界广义伪单调、弱-次连续(P)型和弱-次连续(S)_ ~*型映射。然后,利用Galerkin逼近建立了(S)_ ~*型映射和拟(S)_ ~*型映射的广义拓扑度。所得结果包含了F.E.Browder的一些主要结果。     

扰动区域最优控制的收敛性质

§1.引言设(?)_0为 R~n 中具有 C~1类边界 (?)_0 的有界开区域,(?)_0位于 (?)_0的一侧。考虑如下的最优控制问题:(?)(1.1)(?) J(v)=(?){‖u(v)-z_d‖_(L~2)~2(Ω0) N‖V‖_(L~2)~2(Ω_v)},(1.2)其中Δ为 R~n 中的 Laplace 微分算子,z_d∈L~2(Ω_0),(?)_0为 L~2(Ω_0)中的闭凸集,N 为正数,u(v)表示(1.1)的对应于 u∈(?)_0的解。     

定向集上鞅的推广

<正> 设(Ω,(?),P)是一个概率空间,N={1,2,…},((?)_n)_(n∈N)是(?)的上升子σ-代数列,T 是((?)_n)_(n∈N)有界停时的全体.一个((?)_n)_(n∈N)的适应可积随机变量序列(x_n)_(n∈N),若     

Quasi-shadowing Property on Random Partially Hyperbolic Sets

In this paper we investigate the quasi-shadowing property for C~1 random dynamical systems on their random partially hyperbolic sets. It is shown that for any pseudo orbit {xk}_(-∞)~(+∞)on a random partially hyperbolic set there exists a "center" pseudo orbit {yk}_(-∞)~(+∞)shadowing it in the sense that yk+1 is obtained from the image of yk by a motion along the center direction. Moreover, when the random partially hyperbolic set has a local product structure, the above "center" pseudo orbit {yk}_(-∞)~(+∞)can be chosen such that yk+1 and the image of yk lie in their common center leaf.     

带有Logistic源的吸引-排斥趋化性系统的整体有界性和渐近行为

该文研究了有界区域ΩR~N(N≥1)中,齐次Neumann边值条件下带有Logistic源的吸引-排斥趋化性系统u_t=Δu-▽·(u▽v)+μ_1u(1-u),0=Δv+w-v,w_t=Δw+▽·(w▽z)+μ_2w(1-w),0=△z-z+u,其中μ_1,μ_20.证明了对任何非负初值u_0(x),w_0(x)∈C(Ω),解(u(·,t),v(·,t),w(·,t),z(·,t))整体有界.此外,如果μ_1,μ_21/16,那么当t→∞时,解(u(·,t),u(·,t),w(·,t),z(·,t))在L~∞模意义下渐近收敛于常数平衡解(1,1,1,1).     

关于插值样条S_k~1(⊿_(mn)~((i)))

本文对 S_k~1(Δ_(mn)~(i))(i=1,2)插值问题给出一个一般性的研究方法,并以 S_4~1(Δ_(mn)~(1))为例,作了具体的应用,于是它的一类插值样条的存在、唯一性以及逼近度得以顺利解决.     

Bivariate Free Knot Splines

We consider the least squares approximation of gridded 2D data by tensor product splines with free knots. The smoothing functional to be minimized—a generalization of the univariate Schoenberg functional—is chosen in such a way that the solution of the bivariate problem separates into the solution of a sequence of univariate problems in case of fixed knots. The resulting optimization problem is a constrained separable least squares problem with tensor product structure. Based on some ideas developed by the authors for the univariate case, an efficient method for solving the specially structured 2D problem is proposed, analyzed and tested on hand of some examples from the literature.     

Polyharmonic cardinal splines: A minimization property

Polyharmonic cardinal splines are distributions which are annihilated by iterates of the Laplacian in the complement of a lattice in Euclidean n-space and satisfy certain continuity conditions. Some of the basic properties were recorded in our earlier paper on the subject. Here we show that such splines solve a variational problem analogous to the univariate case considered by I. J. Schoenberg.     

Inverse spectral problem for normal matrices and the Gauss-Lucas theorem

We establish an analog of the Cauchy-Poincare interlacing theorem for normal matrices in terms of majorization, and we provide a solution to the corresponding inverse spectral problem. Using this solution we generalize and extend the Gauss-Lucas theorem and prove the old conjecture of de Bruijn-Springer on the location of the roots of a complex polynomial and its derivative and an analog of Rolle's theorem, conjectured by Schoenberg.

     

On the numerical solution of the generalized Prandtl equation using variation-diminishing splines

Convergence results are proved for Cauchy principal value integrals of the Schoenberg variation-diminishing splines and its first derivative. The use of such splines in the numerical solution of the Prandtl and generalized Prandtl integral equations is proposed. A Nyström-type method and a modified Nyström method are used and compared computationally.     

样条函数精度的某些问题研究

样条函数的精度是Schoenberg于1946年在[20]中首次提到的．本文在Schoenberg 工作的基础上,进一步讨论了这种样条的精度和跨度之间的联系,并且构造了某些特殊样条满足精度最大条件下的跨度最小．然后,我们还讨论了当一元样条的问题推广到多元的时候,如何将所要考虑的问题用多元的工具加以描述,从而能够将某些特殊的多元box样条的精度和跨度之间的联系做进一步的研究．     

Schoenberg’s polynomial B-splines of odd degrees: A brief review of application

A brief overview of applications of Schoenberg’s polynomial B-splines of odd degrees in mathematical statistics, computational mathematics, and statistical radio engineering is provided. Exact formulas for the found Schoenberg B-spline of 15th degree are presented. High-quality approximations of smooth functions with an infinite Fourier transform by functions with a finite Fourier transform are found.     

An optimization method for solving some differential algebraic equations

In this paper, the problem of differential algebraic equations has been solved via Chebyshev integral method combined with an optimization method. Two approaches are used based on the index of the problem: in the first, the proposed method is applied on the original problem and in the second, the index of the problem is decreased and the modified problem is solved. An optimization technique is proposed to solve the resulting algebraic equations. Numerical results are included to confirm the efficiency and accuracy of the method.     

Quasi-interpolatory splines based on Schoenberg points

By using the Schoenberg points as quasi-interpolatory points, we achieve both generality and economy in contrast to previous sets, which achieve either generality or economy, but not both. The price we pay is a more complicated theory and weaker error bounds, although the order of convergence is unchanged. Applications to numerical integration are given and numerical examples show that the accuracy achieved, using the Schoenberg points, is comparable to that using other sets.

     

Riemannian Newton-type methods for joint diagonalization on the Stiefel manifold with application to independent component analysis

The joint approximate diagonalization of non-commuting symmetric matrices is an important process in independent component analysis. This problem can be formulated as an optimization problem on the Stiefel manifold that can be solved using Riemannian optimization techniques. Among the available optimization techniques, this study utilizes the Riemannian Newton’s method for the joint diagonalization problem on the Stiefel manifold, which has quadratic convergence. In particular, the resultant Newton’s equation can be effectively solved by means of the Kronecker product and the vec and veck operators, which reduce the dimension of the equation to that of the Stiefel manifold. Numerical experiments are performed to show that the proposed method improves the accuracy of the approximate solution to this problem. The proposed method is also applied to independent component analysis for the image separation problem. The proposed Newton method further leads to a novel and fast Riemannian trust-region Newton method for the joint diagonalization problem.     

Numerical solution of the inverse electrocardiography problem with the use of the Tikhonov regularization method

The inverse electrocardiography problem related to medical diagnostics is considered in terms of potentials. Within the framework of the quasi-stationary model of the electric field of the heart, the solution of the problem is reduced to the solution of the Cauchy problem for the Laplace equation in R ³. A numerical algorithm based on the Tikhonov regularization method is proposed for the solution of this problem. The Cauchy problem for the Laplace equation is reduced to an operator equation of the first kind, which is solved via minimization of the Tikhonov functional with the regularization parameter chosen according to the discrepancy principle. In addition, an algorithm based on numerical solution of the corresponding Euler equation is proposed for minimization of the Tikhonov functional. The Euler equation is solved using an iteration method that involves solution of mixed boundary value problems for the Laplace equation. An individual mixed problem is solved by means of the method of boundary integral equations of the potential theory. In the study, the inverse electrocardiography problem is solved in region Ω close to the real geometry of the torso and heart.