一种四次有理插值样条及其逼近性质

1引言有理样条函数是多项式样条函数的一种自然推广,但由于有理样条空间的复杂性,所以有关它的研究成果不象多项式样条那样完美,许多问题还值得进一步的研究．近几十年来,有理插值样条,特别是有理三次有理插值样条,由于它们在曲线曲面设计中的应用,已有许多学者进行了深入研究,取得了一系列的成果(见[1]-[7])．但四次有理插值样条由于其构造所花费的计算量太大以及在使用上很不方便而让人们忽视了其重要的应用价值,因此很少有人研究他们．实际上,在某些情况下四次有理插值样条有其独特的应用效果,如文[8]建立的一种具有局部插值性质的分母为二次的四次有理样条,即一个剖分     

复二次B样条曲线

本文在复平面单位圆弧上引进了复二次Ｂ样条曲线，讨论了它的一些几何性质．实质上它是分段帕斯卡蜗线段的Ｃ１合成曲线．调整控制点可使某段曲线为圆孤．     

对称性与局部支集样条函数构造

1引言令D为二维串连通区域,用不可约代数曲线对D进行剖分西,得胞腔。,i—l,…,N．D上n次广阶光滑的样条函数空间定义为S：（D,凸）一｛f6or（D）,f。一片;6尺｝在两相邻胞腔。和个上,SESZ（D,凸）满足其中l。为人与4的公共内网线,q。称为S在l。上的光滑余因子．进而分片多项式S6s：（,凸）,当且仅当在任一内网线上存在光滑余因子,且在任一内网点A处满足协调条件Zc／xx。一。其中求和对所有以A为一端点的内网线进行［”‘j．以上定义和基本结果是文1中给出的．这种方法称为光滑余因子协条法．此外在多元样条函数的研究…     

小波理论在无单元方法中权函数研究的应用

小波理论中多分辨率分析(MRA),可以提供在不同分辨率下分析表达信息的有效途径．基于样条小波多分辨率分析,将无单元中的权函数投影到尺度空间去研究,尝试一种新的权函数研究方法,并给出了算例．     

带有给定凸切线多边形的保形五次样条逼近

本讨论带有给定切线多边形的保形逼近问题．给出了一条与给定切线多边形相切的保形五次参数祥条曲线。     

双周期二次样条的插值逼近

§1.引言 考虑矩形区域Ω=[0,1]?[0,1],Δ_(mn)~((2))为Ω的均匀四方向网,它将Ω分成4mn个小三角形单元. 样条空间 S_2~1(Δ_(mn)~((2)))由满足以下条件的S(x,y)组成:     

紧支撑样条小波插值及其应用

基于紧支撑样条小波函数插值与定积分的思想,给出了由紧支撑样条小波插值函数构造数值积分公式的方法．并将该方法应用于二次、三次、四次和五次紧支撑样条小波函数,得到了相应的数值积分公式．最后,通过数值例子验证,发现该方法得到的数值积分公式是准确的,且具有较高精度．     

广义Ball样条曲线及三角域上曲面的升阶公式和转换算法

Ｔ．Ｎ．Ｔ．Ｇｏｏｄｍａｎ在［９］和［１０］中给出了广义Ｂａｌｌ样条曲线、曲面的奇次升阶公式和有关性质，但未给出偶次广义Ｂａｌｌ样条形式。     

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．     

一类基于l1模的最佳二次样条插值

本文讨论了二次样条插值的定解条件,在l_1模意义下给出了一类最佳二次样条插值的概念,以及寻找最佳二次样条插值的定解条件的方法.最后讨论了误差估计问题,并给出了实际算例.     

Halphen pencils on quartic threefolds

For any smooth quartic threefold in P⁴ we classify pencils on it whose general element is an irreducible surface birational to a surface of Kodaira dimension zero.     

Odd order Brauer–Manin obstruction on diagonal quartic surfaces

We determine the odd order torsion subgroup of the Brauer group of diagonal quartic surfaces over the field of rational numbers. We show that a non-constant Brauer element of odd order always obstructs weak approximation but never the Hasse principle.     

Rational cubic/quartic Said-Ball conics

In CAGD, the Said-Ball representation for a polynomial curve has two advantages over the Bézier representation, since the degrees of Said-Ball basis are distributed in a step type. One advantage is that the recursive algorithm of Said-Ball curve for evaluating a polynomial curve runs twice as fast as the de Casteljau algorithm of Bézier curve. Another is that the operations of degree elevation and reduction for a polynomial curve in Said-Ball form are simpler and faster than in Bézier form. However, Said-Ball curve can not exactly represent conics which are usually used in aircraft and machine element design. To further extend the utilization of Said-Ball curve, this paper deduces the representation theory of rational cubic and quartic Said-Ball conics, according to the necessary and sufficient conditions for conic representation in rational low degree Bézier form and the transformation formula from Bernstein basis to Said-Ball basis. The results include the judging method for whether a rational quartic Said-Ball curve is a conic section and design method for presenting a given conic section in rational quartic Said-Ball form. Many experimental curves are given for confirming that our approaches are correct and effective.     

A computational approach to Lüroth quartics

A plane quartic curve is called Lüroth if it contains the ten vertices of a complete pentalateral. White and Miller constructed in 1909 a covariant quartic fourfold, associated to any plane quartic. We review their construction and we show how it gives a computational tool to detect if a plane quartic is Lüroth. As a byproduct, we show that the 28 bitangents of a general plane quartic correspond to 28 singular points of the associated White–Miller quartic fourfold.     

Finite element method by using quartic B‐splines

In this article, we discuss a kind of finite element method by using quartic B‐splines to solve Dirichlet problem for elliptic equations. Bivariate spline proper subspace of S(Δ) satisfying homogeneous boundary conditions on Type‐2 triangulations and quadratic B‐spline interpolating boundary functions are primarily constructed. Linear and nonlinear elliptic equations are solved by Galerkin quartic B‐spline finite element method. Numerical examples are provided to illustrate the proposed method is flexible. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 27: 818–828, 2011     

C2 Continuous Quartic Hermite Spline Curves with Shape Parameters

In order to relieve the deficiency of the usual cubic Hermite spline curves, the quartic Hermite spline curves with shape parameters is further studied in this work. The interpolation error and estimator of the quartic Hermite spline curves are given. And the characteristics of the quartic Hermite spline curves are discussed. The quartic Hermite spline curves not only have the same interpolation and conti-nuity properties of the usual cubic Hermite spline curves, but also can achieve local or global shape adjustment and C2 continuity by the shape parameters when the interpolation conditions are fixed.     

Quartic theta hypergeometric series

Four classes of quartic theta hypergeometric series are investigated by means of the modified Abel lemma on summation by parts. Several transformations are proved that express the quartic series in terms of well-poised, quadratic and cubic ones. Thirty new summation formulae for terminating quartic theta hypergeometric series are derived consequently.     

C 1 Quadratic and C 2 Quartic Macro-Elements on a Modified Morgan-Scott Triangulation

In this paper, we construct a quadratic composite finite element of class C ¹ and quartic composite finite element of class C ² on a new triangulation τ ₁₀ which is obtained by splitting each triangle of a given triangulation τ into ten smaller subtriangles. These new elements can be used for constructing spline spaces with local basis that can be applied for solving some Hermite interpolation problems with optimal approximation order.     

An efficient algorithm for computing the roots of general quadratic,cubic and quartic equations

While the solution to deriving the roots of the general quadratic equation is adequately covered in a typical classroom environment, the same is not true for the general cubic and quartic equations. To the best of our knowledge, we do not see the roots of the general cubic or quartic equation discussed in any typical algebra textbook at the undergraduate level. In this paper, we propose an efficient algorithm in order to calculate the roots of the general quadratic, cubic and quartic equations. Examples are given to demonstrate the usefulness of this proposed algorithm.