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提出一种基于三角和双曲多项式加权的二次混合样条曲线,这种曲线具有二次非均匀B样条曲线相似性质.这里的权系数也是形状参数,称之为权参数,取值范围从区间[0,1]扩大到区间[-2.6482,3.9412].权参数的不同取值可以整体或局部地调整曲线的形状,并且权参数能像开关那样,使得曲线的各段能非常方便地在三角样条、双曲样条之间自由转换.不需要用重节点方法或解方程组,而只要令某个或某些权参数取-2.6482,曲线就能接插值于控制点或控制边.此外,还能精确表示椭圆(圆)和双曲线. 相似文献
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1引 言二次非均匀B样条曲线,由于结构简单,因而非常方便用于曲线曲面造型[1].但当控制多边形和节点向量给定后,曲线的形状是固定的.如果要调整曲线的形状,可以调整相应的控制顶点或节点向量,这意味着再一次计算曲线方程,计算量也随之增大.此外,二次非均匀B样条曲线不能表示除抛物线以外的圆锥曲线.有理形式的二次非均匀B样条曲线虽然可以表示一些圆锥曲线,权因子也具有调整曲线形状的作用,但权因子几何意义不明显,这对使用者来说是不方便的[2].为此,人们引入不同类型的非多项式、非有理形式的样条. 相似文献
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将B样条曲线转换为Bézier曲线,基于Bézier曲线间的光滑拼接的理论,研究了带多形状参数的Bézier曲线(CE-Bézier曲线)与均匀B样条曲线的拼接问题,得出均匀B样条曲线与CE-Bézier曲线的G0,G1,G2光滑拼接条件.在达到拼接条件的前提下,通过改变CE-Bézier曲线的形状参数的数值大小,可以灵活调整拼接曲线的形状. 相似文献
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构造了一组带形状参数的三次B样条曲线,该曲线与经典三次B样条曲线具有相同的基本性质,且可在不改变控制顶点的情况下,通过改变形状参数的取值实现对曲线形状的调整;选取适当的控制顶点,并对形状参数选取适当的取值,构造的三次λ-B样条曲线可以很好的逼近圆和椭圆;提供了插值于已知数据点的λ-B样条曲线的构造方法;最后,通过图例体现了新方法的有效性. 相似文献
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基于函数空间{1,sint,cost,sin~2t,sin~3t,cos~3t}构造了一种形状可调的三次三角Hermite插值样条.该样条不仅具有带参数的Hermite型插值样条的主要特性,而且在插值节点为等距时可自动满足C2连续,其形状还可通过所带的参数进行调节.在适当条件下,该样条对应的Ferguson曲线可精确表示工程中一些常见的曲线. 相似文献
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四次C-曲线的性质及其应用 总被引:20,自引:0,他引:20
以1,t,t2,t3,…为基底的Bézier曲线和B样条曲线是构造自由曲线、曲面强有力的工具.但是它们不能精确地表示某些圆锥曲线如圆弧、椭圆等,也不能精确地表示正弦曲线.本文利用一组新的基底sint,cost,t2,t,1,构造了两条新的曲线,这两条曲线依赖于参数α>0.当α→0时极限分别是四次Bézier曲线和四次B样条曲线,称之为四次C-曲线:四次C-Bézier曲线和四次C-B样条曲线.它们具有一般Bézier曲线和B样条曲线的性质:如端点插值,凸包,离散等,还可以精确的表示圆弧、椭圆及正弦曲线.作为应用,文章最后给出了四次C-Bézier曲线表示正弦曲线的条件. 相似文献
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利用三次非均匀有理B样条,给出了一种构造局部插值曲线的方法,生成的插值曲线是C2连续的.曲线表示式中带有一个局部形状参数,随着一个局部形状参数值的增大,所给曲线将局部地接近插值点构成的控制多边形.基于三次非均匀有理B样条函数的局部单调性和一种保单调性的准则,给出了所给插值曲线的保单调性的条件. 相似文献
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Kunyang Wang Feng Dai 《分析论及其应用》2007,23(1):50-63
As early as in 1990, Professor Sun Yongsheng, suggested his students at Beijing Normal University to consider research problems on the unit sphere. Under his guidance and encouragement his students started the research on spherical harmonic analysis and approximation. In this paper, we incompletely introduce the main achievements in this area obtained by our group and relative researchers during recent 5 years (2001-2005). The main topics are: convergence of Cesaro summability, a.e. and strong summability of Fourier-Laplace series; smoothness and K-functionals; Kolmogorov and linear widths. 相似文献
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Yuxian Zheng 《分析论及其应用》2006,22(2):136-140
In this paper, we study the commutators generalized by multipliers and a BMO function. Under some assumptions, we establish its boundedness properties from certain atomic Hardy space Hb^p(R^n) into the Lebesgue space L^p with p 〈 1. 相似文献
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H. H. Cuenya M.D. Lorenzo C. N. Rodriguez 《分析论及其应用》2007,23(2):162-170
In this paper we study best local quasi-rational approximation and best local approximation from finite dimensional subspaces of vectorial functions of several variables. Our approach extends and unifies several problems concerning best local multi-point approximation in different norms. 相似文献
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《中国科学 数学(英文版)》2014,(8)
<正>May 26,2014,Beijing Science is a human enterprise in the pursuit of knowledge.The scientific revolution that occurred in the 17th Century initiated the advances of modern science.The scientific knowledge system created by 相似文献
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《计算数学》2014,(2)
<正>August 10-14,2015Beijing,ChinaThe International Congress on Industrial and Applied Mathematics(ICIAM)is the premier international congress in the field of applied mathematics held every four years under the auspices of the International Council for Industrial and Applied Mathematics.From August 10 to 14,2015,mathematicians,scientists 相似文献
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W.M.Shah A.Liman 《分析论及其应用》2004,20(1):16-27
Let P(z)=∑↓j=0↑n ajx^j be a polynomial of degree n. In this paper we prove a more general result which interalia improves upon the bounds of a class of polynomials. We also prove a result which includes some extensions and generalizations of Enestrǒm-Kakeya theorem. 相似文献
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In this paper, the authors study the boundedness of the operator [μΩ, b], the commutator generated by a function b ∈ Lipβ(Rn)(0 <β≤ 1) and the Marcinkiewicz integrals μΩ, on the classical Hardy spaces and the Herz-type Hardy spaces in the case Ω∈ Lipα(Sn-1)(0 <α≤ 1). 相似文献
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Francois Chaplais 《分析论及其应用》2006,22(4):301-318
In applications it is useful to compute the local average empirical statistics on u. A very simple relation exists when of a function f(u) of an input u from the local averages are given by a Haar approximation. The question is to know if it holds for higher order approximation methods. To do so, it is necessary to use approximate product operators defined over linear approximation spaces. These products are characterized by a Strang and Fix like condition. An explicit construction of these product operators is exhibited for piecewise polynomial functions, using Hermite interpolation. The averaging relation which holds for the Haar approximation is then recovered when the product is defined by a two point Hermite interpolation. 相似文献
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A.Al-Shuaibi F.Al-Rawjih 《分析论及其应用》2004,20(1):28-34
Given the Laplace transform F(s) of a function f(t), we develop a new algorithm to find an approximation to f(t) by the use of the classical Jacobi polynomials. The main contribution of our work is the development of a new and very effective method to determine the coefficients in the finite series expansion that approximation f(t) in terms of Jacobi polynomials. Some numerical examples are illustrated. 相似文献