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浙江大学学报(理学版)  2022, Vol. 49 Issue (5): 555-563    DOI: 10.3785/j.issn.1008-9497.2022.05.006
数学与计算机科学     
非均匀二型三角剖分二元二次样条的数值积分公式
钱江1,2(),王凡3
1.河海大学 理学院,江苏 南京 211100
2.海岸灾害及防护教育部重点实验室(河海大学),江苏 南京 210098
3.南京农业大学 理学院,江苏 南京 210095
Numerical integration formulas of bivariate quadratic splines upon non-uniform type-2 triangulation
Jiang QIAN1,2(),Fan WANG3
1.College of Science,Hohai University,Nanjing 211100,China
2.Key Laboratory of Coastal Disaster and Defence (Hohai University),Ministry of Education,Nanjing 210098,China
3.College of Science,Nanjing Agricultural University,Nanjing 210095,China
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摘要:

给出了构成矩形域的4个三角形子区域的二元样条拟插值算子的等价形式,对这4个三角形子区域分别建立了数值积分公式,相加后得到一般矩形域上的数值积分公式,同时给出了构造数值积分公式所需的结点处的函数值与相应的求积系数。进一步,利用算子范数、连续模及拟插值算子的保多项式性,针对具有不同连续性的被积函数,得到了相应的数值积分公式的求积余项。研究表明,提出的数值积分公式不仅具有较高的计算精度,而且计算量约为二元张量积型求积公式的1/5。数值算例进一步说明了数值积分公式的有效性。

关键词: 多元样条光滑余因子协调法二元数值积分样条拟插值B网    
Abstract:

In the paper, equivalent representations of the spline quasi-interpolation are presented over four triangular sub-domains contained in a general rectangular domain. Moreover, the direct bivariate numerical integration formulas are constructed over the four triangular sub-domains, while summing them yields the integration formula over the general rectangular domain. For illustration, the necessary function values and the corresponding integration coefficients are listed in several tables. Furthermore, based on the norm of the operator, the module of continuity and the reproduction of bivariate polynomials, error estimations of the numerical integration are derived for continuously differential functions with different orders. The computational cost of the proposed method is approximately 1/5 of that based on tensor-product-type quadratic splines. Numerical examples show the validity of the proposed numerical integration approach.

Key words: multivariate spline    conformality of smoothing cofactor method    bivariate numerical integration    spline quasi-interpolation    B-net
收稿日期: 2021-04-06 出版日期: 2022-09-14
CLC:  O 241.5  
基金资助: 江苏省自然科学基金青年基金项目(BK20160853);河海大学中央高校基本科研业务费项目(2019B19414);海岸灾害与防护教育部重点实验室开放基金项目(河海大学202011);国家留学基金资助出国留学项目(访问学者201806715010)
作者简介: 钱江(1981—),ORCID: https://orcid.org/0000-0002-0526-5660,男,博士,副教授,主要从事数值逼近与计算几何研究,E-mail:qianjianghhu@sina.com.
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引用本文:

钱江, 王凡. 非均匀二型三角剖分二元二次样条的数值积分公式[J]. 浙江大学学报(理学版), 2022, 49(5): 555-563.

Jiang QIAN, Fan WANG. Numerical integration formulas of bivariate quadratic splines upon non-uniform type-2 triangulation. Journal of Zhejiang University (Science Edition), 2022, 49(5): 555-563.

链接本文:

https://www.zjujournals.com/sci/CN/10.3785/j.issn.1008-9497.2022.05.006        https://www.zjujournals.com/sci/CN/Y2022/V49/I5/555

图1  S21(Δmn(2))的最小八边形支集
f22(i,j)b22(i,j)I22(i,j)
fi-12,j-12b13II(i-1,j-1)Ai'Bj'
fi+12,j-12b20(i,j-1)94+Ai+Ai+1'Bj'
fi+32,j-12b1II(i+1,j-1)Ai+1Bj'
fi-12,j+12b12(i-1,j)34+BjAi'
fi+12,j+12b22(i,j)34Ai+94Bj+34Ai+1'+14Bj+1'+AiBj+Ai+1'Bj
fi+32,j+12b6(i+1,j)34+BjAi+1
fi+12,j+32b7(i,j+1)14Bj+1
表1  与样条函数b22(i,j)对应的f22(i,j)和I22(i,j)
f24(i,j)b24(i,j)I24(i,j)
fi+32,j-12b1I(i+1,j-1)Ai+1Bj'
fi+32,j+12b17(i+1,j)94+Bj+Bj+1'Ai+1
fi+32,j+32b5II(i+1,j+1)Ai+1Bj+1
fi+12,j-12b16(i,j-1)34+Ai+1'Bj'
fi+12,j+12b24(i,j)14Ai+34Bj+94Ai+1'+34Bj+1'+Ai+1'Bj+Ai+1'Bj+1'
fi+12,j+32b10(i,j+1)34+Ai+1'Bj+1
fi-12,j+12b11(i-1,j)14Ai'
表2  与样条函数b24(i,j)对应的f24(i,j)和I24(i,j) (splinesb24(i,j))
f19(i,j)b19(i,j)I19(i,j)
fi+32,j+32b5I(i+1,j+1)Ai+1Bj+1
fi+12,j+32b21(i,j+1)94+Ai+Ai+1'Bj+1
fi-12,j+32b9I(i-1,j+1)Ai'Bj+1
fi+32,j+12b4(i+1,j)34+Bj+1'Ai+1
fi+12,j+12b19(i,j)34Ai+14Bj+34Ai+1'+94Bj+1'+AiBj+1'+Ai+1'Bj+1'
fi-12,j+12b14(i-1,j)34+Bj+1'Ai'
fi+12,j-12b15(i,j-1)14Bj'
表3  与样条函数b19(i,j)对应的f19(i,j)和I19(i,j) (splinesb19(i,j))
f18(i,j)b18(i,j)I18(i,j)
fi-12,j+32b9II(i-1,j+1)Ai'Bj+1
fi-12,j+12b23(i-1,j)94+Bj+Bj+1'Ai'
fi-12,j-12b13I(i-1,j-1)Ai'Bj'
fi+12,j+32b8(i,j+1)34+AiBj+1
fi+12,j+12b18(i,j)94Ai+34Bj+14Ai+1'+34Bj+1'+AiBj+Ai'Bj+1'
fi+12,j-12b2(i,j-1)34+AiBj'
fi+32,j+12b3(i+1,j)14Ai+1
表4  与样条函数b18(i,j)对应的f18(i,j)和I18(i,j) (splinesb18(i,j))
f(i,j)I(i,j)
fi-12,j-122Ai'Bj'
fi+12,j-122(2+Ai+Ai+1')Bj'
fi+32,j-122Ai+1Bj'
fi-12,j+122(2+Bj+Bj+1')Ai'
fi+12,j+122(Ai+Ai+1'+2)(Bj+Bj+1'+2)-8
fi+32,j+122(2+Bj+Bj+1')Ai+1
fi-12,j+322Ai'Bj+1
fi+12,j+322(2+Ai+Ai+1')Bj+1
fi+32,j+322Ai+1Bj+1
表5  f(i,j)及其对应的I(i,j)
图2  矩形域上八边形支集的平移过程
积分区域真值近似值误差
[0.05,0.70]?[0.06,0.10]0.024 509 90.023 308 5-0.001 201 4
[0.05,0.70]?[0.06,0.30]0.141 885 20.129 004 5-0.012 880 7
[0.05,0.70]?[0.06,0.40]0.196 043 10.178 989 9-0.017 053 2
[0.05,0.70]?[0.06,0.50]0.246 670 80.230 373 1-0.016 297 7
[0.05,0.70]?[0.06,0.55]0.270 624 30.255 576 4-0.015 047 9
表6  算例1数值积分的真值、近似值与误差
积分区域真值近似值误差
[0.05,0.70]?[0.06,0.55]0.606 920 20.578 508 0-0.028 412 1
表7  算例2数值积分的真值、近似值与误差
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