Extension of a B-spline curve or surface is a useful function in a CAD system. This paper presents an algorithm for extending cubic B-spline curves or surfaces to one or more target points. To keep the extension curve...Extension of a B-spline curve or surface is a useful function in a CAD system. This paper presents an algorithm for extending cubic B-spline curves or surfaces to one or more target points. To keep the extension curve segment GC^2-continuous with the original one, a family of cubic polynomial interpolation curves can be constructed. One curve is chosen as the solution from a sub-class of such a family by setting one GC^2 parameter to be zero and determining the second GC^2 parameter by minimizing the strain energy. To simplify the final curve representation, the extension segment is reparameterized to achieve C-continuity with the given B-spline curve, and then knot removal from the curve is done. As a result, a sub-optimized solution subject to the given constraints and criteria is obtained. Additionally, new control points of the extension B-spline segment can be determined by solving lower triangular linear equations. Some computing examples for comparing our method and other methods are given.展开更多
We introduce and study the minimal inner-Σ-Ω-groups and the minimal outer-Σ-■-groups.Then we give some applications and obtain some interesting results,including characterizations of nilpotent,supersolvable,solvab...We introduce and study the minimal inner-Σ-Ω-groups and the minimal outer-Σ-■-groups.Then we give some applications and obtain some interesting results,including characterizations of nilpotent,supersolvable,solvable,and p-closed groups in terms of the join of two conjugate cyclic subgroups having the same property.展开更多
In this paper,we investigate truncated l2\l1-2 minimization and its associated alternating direction method of multipliers(ADMM)algorithm for recovering the block sparse signals.Based on the block restricted isometry ...In this paper,we investigate truncated l2\l1-2 minimization and its associated alternating direction method of multipliers(ADMM)algorithm for recovering the block sparse signals.Based on the block restricted isometry property(Block-RIP),a theoretical analysis is presen ted to guarantee the validity of proposed method.Our theore tical resul ts not only show a less error upper bound,but also promote the former recovery condition of truncated l1-2 method for sparse signal recovery.Besides,the algorithm has been compared with some state-of-the-art algorithms and numerical experiments have shown excellent performances on recovering the block sparse signals.展开更多
This paper presents a fast algorithm （BS2 Algorithm） for fitting C 1 surfaces to scat- tered data points. By using energy minimization, the bivariate spline space S 2 1（△ m,n （2） ） is introduced to construct a ...This paper presents a fast algorithm （BS2 Algorithm） for fitting C 1 surfaces to scat- tered data points. By using energy minimization, the bivariate spline space S 2 1（△ m,n （2） ） is introduced to construct a Cl-continuous piecewise quadratic surface through a set of irregularly 3D points. Moreover, a multilevel method is also presented. Some experimental results show that the accuracy is satisfactory. Furthermore, the BS2 Algorithm is more suitable for fitting surfaces if the given data points have some measurement errors.展开更多
文摘Extension of a B-spline curve or surface is a useful function in a CAD system. This paper presents an algorithm for extending cubic B-spline curves or surfaces to one or more target points. To keep the extension curve segment GC^2-continuous with the original one, a family of cubic polynomial interpolation curves can be constructed. One curve is chosen as the solution from a sub-class of such a family by setting one GC^2 parameter to be zero and determining the second GC^2 parameter by minimizing the strain energy. To simplify the final curve representation, the extension segment is reparameterized to achieve C-continuity with the given B-spline curve, and then knot removal from the curve is done. As a result, a sub-optimized solution subject to the given constraints and criteria is obtained. Additionally, new control points of the extension B-spline segment can be determined by solving lower triangular linear equations. Some computing examples for comparing our method and other methods are given.
基金supported by National Natural Science Foundation of China (Grant No.10871032)the Natural Science Foundation of Jiangsu Province (Grant No. BK2008156)
文摘We introduce and study the minimal inner-Σ-Ω-groups and the minimal outer-Σ-■-groups.Then we give some applications and obtain some interesting results,including characterizations of nilpotent,supersolvable,solvable,and p-closed groups in terms of the join of two conjugate cyclic subgroups having the same property.
基金The authors would like to thank reviewers for valuable comments.This work was supported by Natural Science Foundation of China(Grant Nos.61673015,61273020)Fundamental Research Funds for the Central Universities(Grant Nos.XDJK2015A007,XDJK 2018C076,SWU1809002).
文摘In this paper,we investigate truncated l2\l1-2 minimization and its associated alternating direction method of multipliers(ADMM)algorithm for recovering the block sparse signals.Based on the block restricted isometry property(Block-RIP),a theoretical analysis is presen ted to guarantee the validity of proposed method.Our theore tical resul ts not only show a less error upper bound,but also promote the former recovery condition of truncated l1-2 method for sparse signal recovery.Besides,the algorithm has been compared with some state-of-the-art algorithms and numerical experiments have shown excellent performances on recovering the block sparse signals.
基金Acknowledgments. This work was supported by the National Natural Science Foundation of China （Nos. U0935004,11071031,11071037,10801024）, and the Fundamental Funds for the Central Universities. should be changed to Acknowledgments. This work is partly supported by the National Natural Science Foundation of China （Nos. U0935004,11071031,10801024）, the Fundamental Funds for the Central Universities （DUT10ZD112, DUT11LK34）, and National Engineering Research Center of Digital Life, Guangzhou 510006, China.
文摘This paper presents a fast algorithm （BS2 Algorithm） for fitting C 1 surfaces to scat- tered data points. By using energy minimization, the bivariate spline space S 2 1（△ m,n （2） ） is introduced to construct a Cl-continuous piecewise quadratic surface through a set of irregularly 3D points. Moreover, a multilevel method is also presented. Some experimental results show that the accuracy is satisfactory. Furthermore, the BS2 Algorithm is more suitable for fitting surfaces if the given data points have some measurement errors.
