Bernstein多项式凸性和非负性的计算机判别法

本文从多项式的零点分布入手，通过设定由多项式的系数的简单四则运算组成的判别式，由其符号来判断零点的范围，从而得到多项式的正性和凸性条件。     

定点算术数据通路的等价性检验方法

以vanishing多项式理想的极小强Gr-bner基为理论基础,提出一种针对定点算术数据通路的等价性检验方法.通过使用多项式函数建模定点数据通路的设计规范和寄存器传输级实现,将等价性检验问题转化为判断一个多项式函数是否为vanishing多项式、vanishing多项式理想的极小强Gr-bner基被用来有效地解决该问题.理论分析和实验结果表明,与现有的算法相比,该方法在时间消耗上具有一定的优势.     

一类不确定性系统的鲁棒正实性分析与综合

考虑一类具有多项式型不确定性系统的鲁棒正实性分析和综合问题。这类不确定模型是区间摄动和范数有界摄动系统的自然推广。给出了一个系统具有鲁棒扩展严格正实性 (ESPR)的充分条件 ,利用该条件可估计出使系统保持 ESPR的最大参数摄动范围。在 ESPR分析的基础上 ,进一步给出了ESPR控制器的存在条件和控制器的构造方法。通过凸优化算法 ,得到了所提出方法意义下具有最大摄动界的 ESPR控制器设计方法。     

Bezier曲面的凸性分析及保凸拼接

通过分析Bezier曲面局部凸的充要条件与控制顶点网格形状的关系,在几何上将网格的形状与曲面的凸性之间建立联系,导出Bezier曲面局部凸的几个充要条件。将凸性分析的结论应用到Bezier曲面拼接中,得到Bezier曲面保凸拼接的条件,并且证明带有公共边界线的两个局部凸Bezier曲面的Cn(n≥1)拼接后,仍然是凸的且凸性相同。最后,给出几个三次Bezier曲面保凸拼接实例。     

由一阶逻辑公式得到命题逻辑可满足性问题实例

命题逻辑可满足性(SAT)问题是计算机科学中的一个重要问题.近年来许多学者在这方面进行了大量的研究,提出了不少有效的算法.但是,很多实际问题如果用一组一阶逻辑公式来描述,往往更为自然.当解释的论域是一个固定大小的有限集合时,一阶逻辑公式的可满足性问题可以等价地归约为SAT问题.为了利用现有的高效SAT工具,提出了一种从一阶逻辑公式生成SAT问题实例的算法,并描述了一个自动的转换工具,给出了相应的实验结果.还讨论了通过增加公式来消除同构从而减小搜索空间的一些方法.实验表明,这一算法是有效的,可以用来解决数学研究和实际应用中的许多问题.     

参数凸曲线的性质及拐点判别算法

依据参数曲线凸性的原始几何定义,讨论了参数曲线的局部凸和全局凸性,得到了参数曲线局部凸和全局凸的若干性质。给出了参数曲线的拐点定义,讨论了参数曲线的拐点与局部性之间的关系,导出了参数曲线拐点判别的充要条件及算法。     

T样条调配函数线性无关性的判定算法

针对T样条调配函数的公开问题——T样条曲面表达式中的调配函数是否具有线性无关性,提出一种T样条调配函数线性无关性的验证算法.首先分析了T样条调配函数的数学性质,给出T样条调配函数线性无关的充要条件和充分条件,通过充分条件可以较容易地对一些特殊的T样条调配函数的线性无关性进行判定;然后结合充要条件和充分条件给出一种T样条调配函数线性无关性的验证算法.最后通过实例验证了该算法的有效性.文中结果对于开展T样条造型算法方面的研究有重要意义.     

曲线插值的一种具有还圆性的细分方法

传统的线性四点插值细分方法不能表示圆等非多项式曲线,为了解决这种 问题,基于几何特性提出了一种带有一个参数的四点插值型曲线细分方法。细分过程中,过 相邻三插值点作圆,过相邻二插值点的圆弧有两个中点,将其加权平均得到新插值点,文中 给出了插值公式和算法描述。所给方法具有还圆性,可以实现保凸性。实例分析对比了本方 法与多种细分方法的差异,说明本方法是有效的,当参数取值较小时,曲线靠近控制多边形。     

有理数域上二元多项式正定性的单点判定法

文中给出了一个用于判定有理数域上二元多项式正定性的算法,并利用Seidenberg代数曲线决定法证明了该算法的正确性.据此算法编制的Maple程序IsDefinite通过判定该多项式在平面上一个点处取值的符号就能够判定出该多项式是否正定.     

正交多项式拟合在EMD算法端点问题中的应用

经验模态分解(EMD)是由Huang等人提出的一种全新的针对非线性非平稳信号处理的算法.通过EMD,可以把一个信号分解为若干个固有模态函数(IMF),再将这些IMF进行希尔波特变换,从而得到具有真正意义的瞬时频率,因此解决了传统信号处理方法的不足之处。与此同时,EMD算法是一个全新的算法,本身也存在不足,如端点问题。文章在现有的解决方法的基础上,提出了用正交多项式拟合的方法来解决EMD的端点问题,并通过和已有算法的比较来证明这种方法的有效性。     

Wronskian-based tests for stability of polynomial combinations

In this paper, a stability criterion based on counting the real roots of two specific polynomials is formulated. To establish this result, it is shown that a hyperbolicity condition and a strict positivity of a polynomial Wronskian are necessary and sufficient for the stability of any real polynomial. This result is extended to the stability study of some linear combinations of polynomials. Necessary and sufficient conditions of stability are obtained for polynomial segments and planes.     

Some new maximum VC classes

Set systems of finite VC dimension are frequently used in applications relating to machine learning theory and statistics. Two simple types of VC classes which have been widely studied are the maximum classes (those which are extremal with respect to Sauer's lemma) and so-called Dudley classes, which arise as sets of positivity for linearly parameterized functions. These two types of VC class were related by Floyd, who gave sufficient conditions for when a Dudley class is maximum. It is widely known that Floyd's condition applies to positive Euclidean half-spaces and certain other classes, such as sets of positivity for univariate polynomials.In this paper we show that Floyd's lemma applies to a wider class of linearly parameterized functions than has been formally recognized to date. In particular we show that, modulo some minor technicalities, the sets of positivity for any linear combination of real analytic functions is maximum on points in general position. This includes sets of positivity for multivariate polynomials as a special case.     

Stability Analysis of Time-Delay Systems With Incommensurate Delays Using Positive Polynomials

We present a new stability condition for linear time-delay systems (TDS) with multiple incommensurate delays based on the Rekasius substitution and positive polynomials. The condition is checked by testing the positivity of multivariate polynomials in certain domains. For this purpose, we propose two alternative algorithms based on linear programming and sum of squares methods, respectively. The efficiency and accuracy of the algorithms is compared in an example to alternative stability conditions taken from the literature.      

Robustness analysis of polynomials with polynomial parameterdependency using Bernstein expansion

This paper considers the robust stability verification of polynomials with coefficients depending polynomially on parameters varying in given intervals. Two algorithms are presented, both rely on the expansion of a multivariate polynomial into Bernstein polynomials. The first one is an improvement of the so-called Bernstein algorithm and checks the Hurwitz determinant for positivity over the parameter set. The second one is based on the analysis of the value set of the family of polynomials and profits from the convex hull property of the Bernstein polynomials. Numerical results to real-world control problems are presented showing the efficiency of both algorithms     

Termination of the F5 algorithm

The F5 algorithm, which calculates the Gröbner basis of an ideal generated by homogeneous polynomials, was proposed by Faugère in 2002; simultaneously, the correctness of this algorithm was proved under the condition of termination. However, termination itself was demonstrated only for a regular sequence of polynomials. In this paper, it is proved that the algorithm terminates for any input data. First, it is shown that if the algorithm does not terminate, it eventually generates two polynomials where the first is a reductor for the second. However, it is not argued that such a reduction is permitted by all the criteria introduced in F5. Next, it is shown that if such a pair exists, then there exists another pair for which the reduction is permitted by all the criteria, which is impossible.     

区间多项式族根分布不变性的一个充分条件

本文利用广义剔零原理，讨论了区间多项式族根分布问题，得到一区间多项式族具有相同的根分布的充分条件是某一同次多项式在负实轴上是严格正实的，且族中有一元有此分布。     

On the complete instability of interval polynomials

In this paper, we study “complete instability” of interval polynomials, which is the counterpart of classical robust stability. That is, the objective is to check if all polynomials in the family are unstable. If not, a subsequent goal is to find a stable polynomial. To this end, we first propose a randomized algorithm which is based on a (recursive) necessary condition for Hurwitz stability. The second contribution of this paper is to provide a probability-one estimate of the volume of stable polynomials. These results are based on a combination of deterministic and randomized methods. Finally, we present two numerical examples and simulations showing the efficiency of the proposed methodology for small and medium-size problems.     

An improved EZ-GCD algorithm for multivariate polynomials

The EZ-GCD algorithm often has the bad-zero problem, which has a remarkable influence on polynomials with higher-degree terms. In this paper, by applying special ideals, the EZ-GCD algorithm for sparse polynomials is improved. This improved algorithm greatly reduces computational complexity because of the sparseness of polynomials. The author expects that the use of these ideals will be useful as a resolution for obtaining a GCD of sparse multivariate polynomials with higher-degree terms.     

Decomposition of ordinary difference polynomials

In this paper, we present an algorithm to decompose ordinary non-linear difference polynomials with rational functions as coefficients. The algorithm provides an effective reduction of the decomposition of difference polynomials to the decomposition of linear difference polynomials over the same coefficient field. The algorithm is implemented in Maple for the constant coefficient case. Experimental results show that the algorithm is quite effective and can be used to decompose difference polynomials with thousands of terms.     

用泛函网络求任意高阶多项式的近似根

本文提出了一种新的基于泛函网络的多项式求根模型及学习算法，而泛函网络的参数利用解线性不等式组，可得到所求任意高阶多项式近似根的一般参数表达式。文章还讨论了基于泛函网络的多项式求根学习算法实现的一些技术问题，相对传统方法，能够有效地获得任意多项式对应根的参数表达式。