Let Fq be a finite field with q elements, where q is a power of an odd prime,In this paperl the authors consider a projective space PG(2v + δ + l, Fq) with dimension 2v + δ + l, partitioned into an affine space AG(2...Let Fq be a finite field with q elements, where q is a power of an odd prime,In this paperl the authors consider a projective space PG(2v + δ + l, Fq) with dimension 2v + δ + l, partitioned into an affine space AG(2v + δ + l, Fq) of dimension 2v + δ + l and a hyperplane H = PG(2v + δ + l - 1, Fq) of dimension 2v + δ + l - 1 at infinity, where l ≠0.The points of the hyperplane H are next partitioned into four subsets. A pair of points a and b of the affine space is defined to belong to class i if the line ab meets the subsct i of H. Finally, a family of four-class association schemes are constructed, and parameters are also computed.展开更多
Quadrics are of basic importance in Computer Graphics and Computer Aided Design. In this paper,we design a subdivision scheme based on the method suggested by G. Morin and J. Warren to generate conics and quadrics con...Quadrics are of basic importance in Computer Graphics and Computer Aided Design. In this paper,we design a subdivision scheme based on the method suggested by G. Morin and J. Warren to generate conics and quadrics conveniently. Given the control polygon(poly-hedron),the corresponding ellipse (ellipsoid)can be generated. The hyperbolas and hyperboloids are generated based on the generation of ellipses and ellipsoids by a simple transformation. The method in this paper is much simpler and easier to apply than those given by Eugenia Montiel et al.展开更多
This paper gets the Beltrami equations satisfied by a 1-quasiconformal map- ping, which are exactly CR or anti-CR equations on (2,2)-type quadric Q0. This means a 1-quasiconformal mapping on Q0 is CR or anti-CR. This ...This paper gets the Beltrami equations satisfied by a 1-quasiconformal map- ping, which are exactly CR or anti-CR equations on (2,2)-type quadric Q0. This means a 1-quasiconformal mapping on Q0 is CR or anti-CR. This reduces the determination of 1- quasiconformal mappings to a problem on the theory of several complex analysis. The result about the group of CR automorphisms is used to determine the unit component of group of 1-quasiconformal mappings.展开更多
This paper presents a novel algorithm for identifying quadric surfaces from scanned mechanical models. We make several important improvements over the existing variational 3D shape segmentation framework, which utiliz...This paper presents a novel algorithm for identifying quadric surfaces from scanned mechanical models. We make several important improvements over the existing variational 3D shape segmentation framework, which utilizes Lloyd's iteration. First, instead of using randomized initialization(which likely falls into non-optimal minimum), the RANSAC-based initialization approach is adopted. Given a good initialization, our method converges quickly than previous approaches. Second, in order to enhance the stability and the robustness, we carefully modify the distortion-minimizing flooding algorithm by using seed regions instead of seed triangles. Third, the geometric constraints are introduced into the optimization framework. The segmentation quality is further improved. We validate the efficiency and the robustness of our proposed method on various datasets, and demonstrate that our method outperforms state-of-art approaches.展开更多
By using nondegenerate and degenerate quadrics in projective space over finite fields of characteristic 2, some association schemes were canstructed and their parameters were computed by the authors (see Adv. in Math....By using nondegenerate and degenerate quadrics in projective space over finite fields of characteristic 2, some association schemes were canstructed and their parameters were computed by the authors (see Adv. in Math., 3(2000), 120-128 and Acta Math. Appl. Sinica, 1(1999), 96-103). In this note, their polynomial properties,eigenmatrices, imprimitivities, association subschemes and related quotient associa-tion schemes are studied.展开更多
We propose a conjecture relevant to Galkin’s lower bound conjecture,and verify it for the blow-ups of a four-dimensional quadric at a point or along a projective plane.We also show that Conjecture O holds in these tw...We propose a conjecture relevant to Galkin’s lower bound conjecture,and verify it for the blow-ups of a four-dimensional quadric at a point or along a projective plane.We also show that Conjecture O holds in these two cases.展开更多
A Clifford deformation of a Koszul Frobenius algebra E is a finite dimensional Z_(2)-graded algebra E(θ),which corresponds to a noncommutative quadric hypersurface E^(!)/(z)for some central regular element z∈E_(2)^(...A Clifford deformation of a Koszul Frobenius algebra E is a finite dimensional Z_(2)-graded algebra E(θ),which corresponds to a noncommutative quadric hypersurface E^(!)/(z)for some central regular element z∈E_(2)^(!).It turns out that the bounded derived category D^(b)(gr_(Z_(2))E(θ))is equivalent to the stable category of the maximal Cohen-Macaulay modules over E^(!)/(z)provided that E!is noetherian.As a consequence,E^(!)/(z)is a noncommutative isolated singularity if and only if the corresponding Clifford deformation E(θ)is a semisimple Z_(2)-graded algebra.The preceding equivalence of triangulated categories also indicates that Clifford deformations of trivial extensions of a Koszul Frobenius algebra are related to Knörrer's periodicity theorem for quadric hypersurfaces.As an application,we recover Knörrer's periodicity theorem without using matrix factorizations.展开更多
In this letter we assume that F_q is a finite field with q elements, where q is a power of 2. Let N={x^2+x|x∈F_q} and choose a fixed element α of F_q not belonging to N. Theorem 1. Under affine transformations any q...In this letter we assume that F_q is a finite field with q elements, where q is a power of 2. Let N={x^2+x|x∈F_q} and choose a fixed element α of F_q not belonging to N. Theorem 1. Under affine transformations any quadric in AG(n, F_q), where q is even, can be carried into a quadric with one of the following quadratic equations as its equation:展开更多
The problem of a hollow thick-wall cylinder subject to quadric function pressures is solved with a new stress function, thus laying the basis for solving the spatial symmetric deformation of a hollow cylinder subject ...The problem of a hollow thick-wall cylinder subject to quadric function pressures is solved with a new stress function, thus laying the basis for solving the spatial symmetric deformation of a hollow cylinder subject to arbitrarily distributed pressures.展开更多
To this day for special m and small |c|, solvable, c are obtained about general equations x^2-my^2=c with positive squarefree integer m and integer c by Ankeny, Mollin et al. Afterwards, Zhang in ref. [1] greatly deve...To this day for special m and small |c|, solvable, c are obtained about general equations x^2-my^2=c with positive squarefree integer m and integer c by Ankeny, Mollin et al. Afterwards, Zhang in ref. [1] greatly developed their correspondent results and gave all proper integer solutions and solvable c about the equations for general m. Then Lu in ref. [2] gave results for small |q| about general binary quadric indefinite展开更多
We introduce a new notion of pseudo-anti commuting Ricci tensor for real hypersurfaces in the noncompact complex hyperbolic quadric Q^(m?)= SO_2~0,_m/SO_2SO_m and give a complete classi?cation of these hypersurfaces.
We introduce the notion of commuting Ricci tensor for real hypersurfaces in the complex quadric Q^m= SO_(m+2)/SO_mSO_2. It is shown that the commuting Ricci tensor gives that the unit normal vector field N becomes A-p...We introduce the notion of commuting Ricci tensor for real hypersurfaces in the complex quadric Q^m= SO_(m+2)/SO_mSO_2. It is shown that the commuting Ricci tensor gives that the unit normal vector field N becomes A-principal or A-isotropic. Then according to each case, we give a complete classification of Hopf real hypersurfaces in Q^m= SO_(m+2)/SO_mSO_2 with commuting Ricci tensor.展开更多
This paper proposes an improved algorithm to construct moving quadrics from moving planes that follow a tensor product surface with no base points, assuming that there are no moving planes of low degree following the ...This paper proposes an improved algorithm to construct moving quadrics from moving planes that follow a tensor product surface with no base points, assuming that there are no moving planes of low degree following the surface. These moving quadrics provide an efficient method to implicitize the tensor product surface which outperforms a previous approach by the present authors.展开更多
Let F<sub>q</sub> be a finite field with q elements, where q is a power of a prime, and let AG （n, F<sub>q</sub> ）be the n-dimensional aftine space over F<sub>q</sub>. The set of ...Let F<sub>q</sub> be a finite field with q elements, where q is a power of a prime, and let AG （n, F<sub>q</sub> ）be the n-dimensional aftine space over F<sub>q</sub>. The set of points （x<sub>1</sub>, x<sub>2</sub>,…,x<sub>n</sub> ） in AG（n, F<sub>q</sub>） which satisfy a quadratic展开更多
文摘Let Fq be a finite field with q elements, where q is a power of an odd prime,In this paperl the authors consider a projective space PG(2v + δ + l, Fq) with dimension 2v + δ + l, partitioned into an affine space AG(2v + δ + l, Fq) of dimension 2v + δ + l and a hyperplane H = PG(2v + δ + l - 1, Fq) of dimension 2v + δ + l - 1 at infinity, where l ≠0.The points of the hyperplane H are next partitioned into four subsets. A pair of points a and b of the affine space is defined to belong to class i if the line ab meets the subsct i of H. Finally, a family of four-class association schemes are constructed, and parameters are also computed.
基金This work is supported by NKBRSF on Mathematical Mechanics(G1998030600),the National Natural Science Foundation of China(19971087,69603009)and the Doctoral Program(20010358003)and TRAPOYT of MOE,China.
文摘Quadrics are of basic importance in Computer Graphics and Computer Aided Design. In this paper,we design a subdivision scheme based on the method suggested by G. Morin and J. Warren to generate conics and quadrics conveniently. Given the control polygon(poly-hedron),the corresponding ellipse (ellipsoid)can be generated. The hyperbolas and hyperboloids are generated based on the generation of ellipses and ellipsoids by a simple transformation. The method in this paper is much simpler and easier to apply than those given by Eugenia Montiel et al.
基金Supported by the National Natural Science Foundation of China (10571155)
文摘This paper gets the Beltrami equations satisfied by a 1-quasiconformal map- ping, which are exactly CR or anti-CR equations on (2,2)-type quadric Q0. This means a 1-quasiconformal mapping on Q0 is CR or anti-CR. This reduces the determination of 1- quasiconformal mappings to a problem on the theory of several complex analysis. The result about the group of CR automorphisms is used to determine the unit component of group of 1-quasiconformal mappings.
基金Supported by the National Natural Science Foundation of China(61372168,61620106003 and 61331018)
文摘This paper presents a novel algorithm for identifying quadric surfaces from scanned mechanical models. We make several important improvements over the existing variational 3D shape segmentation framework, which utilizes Lloyd's iteration. First, instead of using randomized initialization(which likely falls into non-optimal minimum), the RANSAC-based initialization approach is adopted. Given a good initialization, our method converges quickly than previous approaches. Second, in order to enhance the stability and the robustness, we carefully modify the distortion-minimizing flooding algorithm by using seed regions instead of seed triangles. Third, the geometric constraints are introduced into the optimization framework. The segmentation quality is further improved. We validate the efficiency and the robustness of our proposed method on various datasets, and demonstrate that our method outperforms state-of-art approaches.
基金The NNSF (19571024) of China Hebei Province Education Committee Fund (98103).
文摘By using nondegenerate and degenerate quadrics in projective space over finite fields of characteristic 2, some association schemes were canstructed and their parameters were computed by the authors (see Adv. in Math., 3(2000), 120-128 and Acta Math. Appl. Sinica, 1(1999), 96-103). In this note, their polynomial properties,eigenmatrices, imprimitivities, association subschemes and related quotient associa-tion schemes are studied.
基金supported by NSFC Grant(Grant Nos.11890662 and 11831017)supported by NSFC Grant(Grant Nos.12271532 and 11831017)+2 种基金supported by NSFC Grant(Grant No.11831017)Guangdong Introducing Innovative and Enterpreneurial Teams(Grant No.2017ZT07X355)supported by Guangdong Basic and Applied Basic Research Foundation(Grant No.2020A1515010876)。
文摘We propose a conjecture relevant to Galkin’s lower bound conjecture,and verify it for the blow-ups of a four-dimensional quadric at a point or along a projective plane.We also show that Conjecture O holds in these two cases.
基金supported by ZJNSF(LY19A010011)NSFC(11971141,12371017)supported by NSFC(11971449,12131015,12371042).
文摘A Clifford deformation of a Koszul Frobenius algebra E is a finite dimensional Z_(2)-graded algebra E(θ),which corresponds to a noncommutative quadric hypersurface E^(!)/(z)for some central regular element z∈E_(2)^(!).It turns out that the bounded derived category D^(b)(gr_(Z_(2))E(θ))is equivalent to the stable category of the maximal Cohen-Macaulay modules over E^(!)/(z)provided that E!is noetherian.As a consequence,E^(!)/(z)is a noncommutative isolated singularity if and only if the corresponding Clifford deformation E(θ)is a semisimple Z_(2)-graded algebra.The preceding equivalence of triangulated categories also indicates that Clifford deformations of trivial extensions of a Koszul Frobenius algebra are related to Knörrer's periodicity theorem for quadric hypersurfaces.As an application,we recover Knörrer's periodicity theorem without using matrix factorizations.
文摘In this letter we assume that F_q is a finite field with q elements, where q is a power of 2. Let N={x^2+x|x∈F_q} and choose a fixed element α of F_q not belonging to N. Theorem 1. Under affine transformations any quadric in AG(n, F_q), where q is even, can be carried into a quadric with one of the following quadratic equations as its equation:
文摘The problem of a hollow thick-wall cylinder subject to quadric function pressures is solved with a new stress function, thus laying the basis for solving the spatial symmetric deformation of a hollow cylinder subject to arbitrarily distributed pressures.
文摘To this day for special m and small |c|, solvable, c are obtained about general equations x^2-my^2=c with positive squarefree integer m and integer c by Ankeny, Mollin et al. Afterwards, Zhang in ref. [1] greatly developed their correspondent results and gave all proper integer solutions and solvable c about the equations for general m. Then Lu in ref. [2] gave results for small |q| about general binary quadric indefinite
基金supported by National Research Foundation of Korea (Grant No. NRF2015-R1A2A1A-01002459)
文摘We introduce a new notion of pseudo-anti commuting Ricci tensor for real hypersurfaces in the noncompact complex hyperbolic quadric Q^(m?)= SO_2~0,_m/SO_2SO_m and give a complete classi?cation of these hypersurfaces.
基金supported by National Research Foundation of Korea (Grant No. NRF2015-R1A2A1A-01002459)
文摘We introduce the notion of commuting Ricci tensor for real hypersurfaces in the complex quadric Q^m= SO_(m+2)/SO_mSO_2. It is shown that the commuting Ricci tensor gives that the unit normal vector field N becomes A-principal or A-isotropic. Then according to each case, we give a complete classification of Hopf real hypersurfaces in Q^m= SO_(m+2)/SO_mSO_2 with commuting Ricci tensor.
基金supported by the National Natural Science Foundation of China under Grant Nos.11271328and 11571338the Zhejiang Provincial Natural Science Foundation under Grant No.Y7080068
文摘This paper proposes an improved algorithm to construct moving quadrics from moving planes that follow a tensor product surface with no base points, assuming that there are no moving planes of low degree following the surface. These moving quadrics provide an efficient method to implicitize the tensor product surface which outperforms a previous approach by the present authors.
文摘Let F<sub>q</sub> be a finite field with q elements, where q is a power of a prime, and let AG （n, F<sub>q</sub> ）be the n-dimensional aftine space over F<sub>q</sub>. The set of points （x<sub>1</sub>, x<sub>2</sub>,…,x<sub>n</sub> ） in AG（n, F<sub>q</sub>） which satisfy a quadratic
