B样条基转换矩阵的解析表示和计算公式

摘要B样条基的转换矩阵具有重要的理论和应用意义。本文研究其最基本的问题：存在性条件、解析表示和计算方法，利用差商展开系数得到了上述问题的有关结果，本文的结果为CAGD中B样条曲线的节点插入、节点删除、升阶、降阶、分割、组合等重要技术提供了一个统一的数学背景和实现方法。     

B样条基的转换矩阵及其应用

本文研究任意两个B样条基可转换的条件及转换矩阵，给出了关于转换矩阵元素的表示及性质等理论结果，并推导出了两个递推公式，为实际计算转换矩阵的元素提供了易于实现的数学方法。本文还讨论了B样条基转换矩阵在CAGD中的应用，特别讨论了B样条曲线的节点插入、升阶和分解问题。本文的结果为B样条曲线的节点插入、升阶、分解等运算提供了一个统一的数学模型和实现方法。     

周期B样条基转换矩阵的表示和计算

周期B样条基以一种简洁的形式表示闭B样条曲线.周期B样条基转换矩阵为闭B样条曲线及相关曲面的不同表示间的转换提供了一个数学模型.本文给出了周期B样条基转换矩阵的存在性条件,给出并证明了周期B样条基转换矩阵的一个简单的递归表示式.在此基础上,本文进一步给出了周期B样条基转换矩阵的计算公式和高效算法.周期B样条基转换矩阵为闭B样条曲线的节点插入、升阶、节点删除和降阶等基本运算提供了一个统一而简单的解决方法,本文给出了一些应用例子.     

二次带形状参数双曲B样条曲线

在空间Ω_5=span{1,sinh t,cosh t,sinh 2t,cosh 2t}上给出了二次带形状参数双曲B样条的基函数.由这组基组成的二次双曲B样条曲线是C~1连续的,同时具有很多与二次B样条曲线类似的性质和几何结构,并且可以精确表示双曲线.在控制多边形固定的情况下,可以通过调节形状参数的大小来进一步调整曲线的形状.     

基样条的Nikolskii型不等式

证明了基样条的Nikolskii型不等式‖s‖_p(R) ≤ 2 ( 1 + 4π) 2 ¹-qp πh1q-1p‖s‖_q(R) ,　 0 ＜p＜∞，其中s∈ _m,h，_m,h 表示以{jh+12（m - 1）h}_j∈z为节点的基样条空间。     

一类分层三角剖分下三次样条空间的维数

本文定义了平面单连通多边形域的一类较任意的三角剖分－分层三角剖分，并通过分析二元样条的积分协调条件，确定了分层三角剖分卜三次Ｃ^１作条函数空间的维数．     

基样条与整函数的极限性质

本文证明了‖smf-f‖ p→ 0 ( m→∞ )的必要条件是 f∈ Bπ,p,其中 Bπ,p=Bπ∩ Lp( R) ,Bπ表示指数 π型的整函数在R上限制是有界函数所构成的集合 ,smf 是在整数点对 f 插值的唯一确定的 m-1次基样条 .最终得到了关于整函数的一个等价刻划     

有理B—样条曲线的离散构造与保型性问题

在各种计算机辅助外型设计与制造中,曲线、曲面等几何造型是一个基本问题.这是因为现实客观世界中存在着许多不能用直线、平面和二次曲线(面)等简单几何模型所表示的几何实体,如汽车、船舶、飞机外型和地质、物理、医学等学科或领域中所遇到的一些     

T样条函数空间的局部支集基

Ｓｃｈｕｍａｋｅｒ，Ｌ．Ｌ．在其名著《ＳｐｌｉｎｅＦｕｎｃｔｉｏｎ：ＢａｓｉｃＴｈｅｏｒｙ》中第九章给出了Ｔｃｈｅｂｙｓｈ－ｅｆ样条函数空间的局部支集基定理，可惜其证明却是错的，本文给出了上述定理的正确证明．     

The Basis Number of Some Special Non-Planar Graphs

The basis number of a graph G was defined by Schmeichel to be the least integer h such that G has an h-fold basis for its cycle space. He proved that for m, n 5, the basis number b(K _m,n ) of the complete bipartite graph K _m,n is equal to 4 except for K _6,10, K _5,n and K _6,n with n = 5, 6, 7, 8. We determine the basis number of some particular non-planar graphs such as K _5,n and K _6,n , n = 5, 6, 7, 8, and r-cages for r = 5, 6, 7, 8, and the Robertson graph.     

Stabilizing the Hierarchical Basis by Approximate Wavelets,I: Theory

This paper proposes a stabilization of the classical hierarchical basis (HB) method by modifying the HB functions using some computationally feasible approximate L²-projections onto finite element spaces of relatively coarse levels. The corresponding multilevel additive and multiplicative algorithms give spectrally equivalent preconditioners, and one action of such a preconditioner is of optimal order computationally. The results are regularity-free for the continuous problem (second order elliptic) and can be applied to problems with rough coefficients and local refinement. © 1997 by John Wiley & Sons, Ltd.     

均布载荷作用下变厚度开顶扁球壳的非线性稳定问题

本文首先应用逐步加载法将具有硬中心的开顶扁球壳在均布载荷作用下的非线性微分方程组线性化,然后利用样条配点法解线性微分方程组,得到了临界载荷的数值．     

Convergence and Stability of the Truncated Euler-Maruyama Method for Stochastic Differential Equations with Piecewise Continuous Arguments

In this paper, we develop the truncated Euler-Maruyama (EM) method for stochastic differential equations with piecewise continuous arguments (SDEPCAs), and consider the strong convergence theory under the local Lipschitz condition plus the Khasminskii-type condition. The order of convergence is obtained. Moreover, we show that the truncated EM method can preserve the exponential mean square stability of SDEPCAs. Numerical examples are provided to support our conclusions.     

关于求解随机用户均衡问题的截断拟牛顿型信赖域法研究

信赖域法是一种保证全局收敛性的优化算法,为避免Hessian矩阵的计算,基于拟牛顿校正公式构造了求解带线性等式约束的非线性规划问题的截断拟牛顿型信赖域法.首先给出了截断拟牛顿型信赖域法的构造过程及具体步骤;然后针对随机用户均衡模型中变量和约束的特点对算法进行了修正,并将多种拟牛顿校正公式下所得结果与牛顿型信赖域法的结果进行了比较,结果发现基于对称秩1校正公式的信赖域法更为合适.最后基于数值算例结果得到了一些在算法编程过程中的重要结论,对其它形式信赖域法的编程实现具有一定的参考意义.     

简单图圈基长度的最大值

图的圈基是图的一个重要结构,一个圈基的长度是该圈基中所有圈的长度之和,本讲座了简单图的圈基长度的最大值,得到了如下结果：设基圈数为k,顶点数为n的简单图的圈基长度最大值为C^*,i)若k≥4且n ≥k 2时,C^*-kn;Ⅱ）若k=2,3,则对任意n≥4,C^*=kn-1,Ⅲ）若n(n≥5）为奇数,则对k(k≥4）的所有可能值,C^*=kn。     

球面混合插值的逼近性质

球面径向基函数(SBF)和多项式样条函数均为处理球面散乱数据的有效工具. 本文考虑由球面径向基函数与球面多项式函数组成的混合插值模型, 并利用最小二乘法求解该模型. 对于该插值模型, 首先, 给出带Bessel势的Sobolev空间中的Bernstein不等式, 然后利用该不等式建立逼近正定理,并进一步给出该插值工具的误差估计. 最后, 研究该插值方式(即利用最小二乘法求解混合插值模型)的稳定性.     

Morgan-Scott型剖分上的样条空间的奇异性

Multivariate spline function is an important research object and tool in Computational Geometry. The singularity of multivariate spline spaces is a difficult problem that is ineritable in the research of the structure of multivariate spline spaces. The aim of this paper is to reveal the geometric significance of the singularity of bivariate spline space over Morgan-Scott type triangulation by using some new concepts proposed by the first author such as characteristic ratio, characteristic mapping of lines （or ponits）, and characteristic number of algebraic curve. With these concepts and the relevant results, a polished necessary and sufficient conditions for the singularity of spline space S u＋1^u （△MS^u） are geometrically given for any smoothness u by recursion. Moreover, the famous Pascal＇s theorem is generalized to algebraic plane curves of degree n≥3.     

A greedy algorithm for partition of unity collocation method in pricing American options

A greedy algorithm in combination with radial basis functions partition of unity collocation (GRBF‐PUC) scheme is used as a locally meshless method for American option pricing. The radial basis function partition of unity method (RBF‐PUM) is a localization technique. Because of having interpolation matrices with large condition numbers, global approximants and some local ones suffer from instability. To overcome this, a greedy algorithm is added to RBF‐PUM. The greedy algorithm furnishes a subset of best nodes among the points X. Such nodes are then used as points of trial in a locally supported RBF approximant for each partition. Using of greedy selected points leads to decreasing the condition number of interpolation matrices and reducing the burdensome in pricing American options.     

The Dual Functionals for the Generalized Ball Basis of Wang-Said Type and Basis Transformation Formulas

The generalized Ball curves of Wang-Said type with a position parameter L not only unify the Wang-Ball curves and the Said-Ball curves, but also include several useful intermediate curves. This paper presents the dual functionals for the generalized Ball basis of Wang-Said type. The relevant basis transformation formulae are also worked out.