In this paper,we study the extremal problem on Cartan-egg domain of the first type by using some inequalities.The extremal mapping and extremal value between the first type of Cartan-egg domain and the unit ball when ...In this paper,we study the extremal problem on Cartan-egg domain of the first type by using some inequalities.The extremal mapping and extremal value between the first type of Cartan-egg domain and the unit ball when k≤1 and k=2,m=2 are constructed.展开更多
In this paper we consider two problems. The first is connected with the optimal recovery of functions satisfyiog boundary conditions. The second is the characterization of the unique func- tion whose r-th derivative h...In this paper we consider two problems. The first is connected with the optimal recovery of functions satisfyiog boundary conditions. The second is the characterization of the unique func- tion whose r-th derivative has minimum L_∞-norm, taking given values of alternating signs and satis fying boundary conditions.展开更多
In this paper we construct circumscribed Hermitian ellipsoids of Hartogs domains of least volume and as an application, we obtain the Carathéodory extremal mappings between the Hartogs domains and the unit ball, ...In this paper we construct circumscribed Hermitian ellipsoids of Hartogs domains of least volume and as an application, we obtain the Carathéodory extremal mappings between the Hartogs domains and the unit ball, and also give an explicit formula for calculating the extremal values.展开更多
Let be an undirected graph. The maximum cycle packing problem in G then is to find a collection of edge-disjoint cycles C<sub>i</sup>in G such that s is maximum. In general, the maximum cycle packing probl...Let be an undirected graph. The maximum cycle packing problem in G then is to find a collection of edge-disjoint cycles C<sub>i</sup>in G such that s is maximum. In general, the maximum cycle packing problem is NP-hard. In this paper, it is shown for even graphs that if such a collection satisfies the condition that it minimizes the quantityon the set of all edge-disjoint cycle collections, then it is a maximum cycle packing. The paper shows that the determination of such a packing can be solved by a dynamic programming approach. For its solution, an-shortest path procedure on an appropriate acyclic networkis presented. It uses a particular monotonous node potential.展开更多
The present article is an account of results on univalent functions in multiply connected domains obtained by the author. It contains two rery simple proofs of Villat's formula; Schwarz's formula, Poisson'...The present article is an account of results on univalent functions in multiply connected domains obtained by the author. It contains two rery simple proofs of Villat's formula; Schwarz's formula, Poisson's formula and Poisson-Jensen formula in multiply connected domains; the differentiability theorem with respect to the parameter of analytic function family containing one parametric variable on multiply connected domains; variation theorem and parametric representation theorem of univalent functions in multiply connected domains; the solution of an extremal problem of differentiable functionals.展开更多
Some extremal properties of the integral of Legendre polynomials are given, which are of independent interest. Meanwhile they show that a conjecture of P. Erdos[1] is plausible and maybe provides some means to prove t...Some extremal properties of the integral of Legendre polynomials are given, which are of independent interest. Meanwhile they show that a conjecture of P. Erdos[1] is plausible and maybe provides some means to prove this conjecture.展开更多
This article designs a new fifth-order finite volume mapped unequal-sized weighted essentially non-oscillatory scheme(MUS-WENO)for solving hyperbolic conservation laws on structured meshes.One advantage is that the ne...This article designs a new fifth-order finite volume mapped unequal-sized weighted essentially non-oscillatory scheme(MUS-WENO)for solving hyperbolic conservation laws on structured meshes.One advantage is that the new mapped WENOtype spatial reconstruction is a convex combination of a quartic polynomial with two linear polynomials defined on unequal-sized central or biased spatial stencils.Then we propose the new mapped nonlinear weights and new mapping function to decrease the difference between the linear weights and nonlinear weights.This method has the characteristics of small truncation errors and high-order accuracy.And it could give optimal fifth-order convergence with a very tiny#even near critical points in smooth regions while suppressing spurious oscillations near strong discontinuities.Compared with the classical finite volume WENO schemes and mapped WENO(MWENO)schemes,the linear weights can be any positive numbers on the condition that their summation is one,which greatly reduces the calculation cost.Finally,we propose a new modified positivity-preserving method for solving some low density,low pressure,or low energy problems.Extensive numerical examples including some unsteadystate problems,steady-state problems,and extreme problems are used to testify to the efficiency of this new finite volume MUS-WENO scheme.展开更多
In extreme scenarios,classical high-order WENO schemes may result in non-physical states.The Positivity-Preserving Limiter(PP-Limiter)is often used to ensure positivity if CFL≤0.5 with a third-order TVD Runge-Kunta(R...In extreme scenarios,classical high-order WENO schemes may result in non-physical states.The Positivity-Preserving Limiter(PP-Limiter)is often used to ensure positivity if CFL≤0.5 with a third-order TVD Runge-Kunta(RK3)scheme.This study proposes two novel conservative WENO-Z methods:AT-PP and AO-PP to improve efficiency with 0.5<CFL<1 if desired.The AT-PP method detects negative cells after each RK3 stage posteriori and computes a new solution with the PPLimiter(CFL<0.5)for that step.The AO-PP method progressively lowers the WENO operator’s order and terminates with the first-order HLLC solver,proven positivitypreserving with CFL<1,only at negative cells at that RK3 stage.A single numerical flux enforces conservation at neighboring interfaces.Extensive 1D and 2D shocktube problems were conducted to illustrate the performance of AT-PP and AO-PP with CFL=0.9.Both methods outperformed the classical PP-Limiter in accuracy and resolution,while AO-PP performed better computationally in some cases.The AO-PP method is globally conservative and accurate,adaptiveness,and robustness while resolving fine-scale structures in smooth regions,capturing strong shocks and gradients with ENO-property,improving computational efficiency,and preserving the positivity,all without imposing a restrictive limit on the CFL condition.展开更多
In this work, we obtain good upper bounds for the diameter of any graph in terms of its minimum degree and its order, improving a classical theorem due to Erdos, Pach, Pollack and Tuza. We use these bounds in order to...In this work, we obtain good upper bounds for the diameter of any graph in terms of its minimum degree and its order, improving a classical theorem due to Erdos, Pach, Pollack and Tuza. We use these bounds in order to study hyperbolic graphs （in the Gromov sense）. To compute the hyperbolicity constant is an almost intractable problem, thus it is natural to try to bound it in terms of some parameters of the graph. Let H（n, δ0） be the set of graphs G with n vertices and minimum degree 50, and J（n, Δ） be the set of graphs G with n vertices and maximum degree A. We study the four following extremal problems on graphs： a（n,δ0） = min{δ（G） ｜ G ∈H（n, δ0）}, b（n, δ0） =- max{δ（G）｜ e ∈H（n, δ0）}, α（n, Δ） = min{δ（G） [ G ∈ J（n, Δ）} and β（n,Δ） = max{δ（G） ] G∈Π（n,Δ）}. In particular, we obtain bounds for b（n, δ0） and we compute the precise value of a（n, δ0）, α（n, Δ） and w（n, Δ） for all values of n, r0 and A, respectively.展开更多
The original version of the article was published in[1].Unfortunately,the original version of this article contains a mistake:in Theorem 6.2 appears thatβ(n,△)=(n-△+5)/4 but the correct statement isβ(n,△)=(n-△+4...The original version of the article was published in[1].Unfortunately,the original version of this article contains a mistake:in Theorem 6.2 appears thatβ(n,△)=(n-△+5)/4 but the correct statement isβ(n,△)=(n-△+4)/4.In this erratum we correct the theorem and give the correct proof.展开更多
The paper explores the connection of Graph-Lagrangians and its maximum cliques for 3-uniform hypergraphs. Motzkin and Straus showed that the Graph-Lagrangian of a graph is the Graph-Lagrangian of its maximum cliques. ...The paper explores the connection of Graph-Lagrangians and its maximum cliques for 3-uniform hypergraphs. Motzkin and Straus showed that the Graph-Lagrangian of a graph is the Graph-Lagrangian of its maximum cliques. This connection provided a new proof of Turin classical result on the Turan density of complete graphs. Since then, Graph-Lagrangian has become a useful tool in extremal problems for hypergraphs. Peng and Zhao attempted to explore the relationship between the Graph-Lagrangian of a hypergraph and the order of its maximum cliques for hypergraphs when the number of edges is in certain range. They showed that if G is a 3-uniform graph with m edges containing a clique of order t - 1, then A（G） = A（[t- 1]（3）） provided （t31） ≤ m ≤ （3^t1） ＋ （2^rt-2）. They also conjectured： If G is an r-uniform graph with m edges not containing a clique of order t - 1, then A（G） 〈 A（[t - 1]（r）） provided （r^t-1） ≤ m ≤ （r^t-1） ＋ （r-1^t-2）. It has been shown that to verify this conjecture for 3-uniform graphs, it is sufficient to verify the conjecture for left-compressed 3-uniform graphs with m = （3^t-1） ＋ （2^t-2）. Regarding this conjecture, we show： If G is a left-compressed 3-uniform graph on the vertex set It] with m edges and lit - 1]（3） ／ E（G）｜=- p, then A（G） 〈 A（[t - 1]（3）） provided m = （3^t-1） ＋ （2^t-2） and t ≥ 17p/2 ＋ 11.展开更多
Frankl and Füredi in [1] conjectured that the r-graph with m edges formed by taking the first m sets in the colex ordering of N^（r） has the largest Lagrangian of all r-graphs with m edges.Denote this r-graph by...Frankl and Füredi in [1] conjectured that the r-graph with m edges formed by taking the first m sets in the colex ordering of N^（r） has the largest Lagrangian of all r-graphs with m edges.Denote this r-graph by Cr,m and the Lagrangian of a hypergraph by λ（G）.In this paper,we first show that if（3^t-1） ≤m〈（3^t）,G is a left-compressed 3-graph with m edges and on vertex set[t],the triple with minimum colex ordering in G^c is（t — 2 — i）（t — 2）t,then λ（G） ≤λ（C3,m）.As an implication,the conjecture of Frankl and Fiiredi is true for（3^t）-6≤m≤（3^t）.展开更多
基金Supported by the SF of Jiangsu Province Education(07KJB110115)
文摘In this paper,we study the extremal problem on Cartan-egg domain of the first type by using some inequalities.The extremal mapping and extremal value between the first type of Cartan-egg domain and the unit ball when k≤1 and k=2,m=2 are constructed.
基金Partially supported by Ministry of Science under Project MM--414.
文摘In this paper we consider two problems. The first is connected with the optimal recovery of functions satisfyiog boundary conditions. The second is the characterization of the unique func- tion whose r-th derivative has minimum L_∞-norm, taking given values of alternating signs and satis fying boundary conditions.
基金supported in part by the National Natural Science Foundation of China(Grant No.10171068)the National Natural Science Foundation of Beijing(Grant No.1012004).
文摘In this paper we study some extremal problems between the Hua domain of the first type and the unit ball.
基金supported by National Natural Science Foundation of China (Grant No. 10771144)the BeijingNatural Science Foundation (Grant No. 1082005)the Korea Research Foundation Grant Funded by KoreaGovernment (MOEHRD, Basic Research Promotion Fund) (Grant No. KRF-2005-070-C00007)
文摘In this paper we construct circumscribed Hermitian ellipsoids of Hartogs domains of least volume and as an application, we obtain the Carathéodory extremal mappings between the Hartogs domains and the unit ball, and also give an explicit formula for calculating the extremal values.
文摘Let be an undirected graph. The maximum cycle packing problem in G then is to find a collection of edge-disjoint cycles C<sub>i</sup>in G such that s is maximum. In general, the maximum cycle packing problem is NP-hard. In this paper, it is shown for even graphs that if such a collection satisfies the condition that it minimizes the quantityon the set of all edge-disjoint cycle collections, then it is a maximum cycle packing. The paper shows that the determination of such a packing can be solved by a dynamic programming approach. For its solution, an-shortest path procedure on an appropriate acyclic networkis presented. It uses a particular monotonous node potential.
文摘The present article is an account of results on univalent functions in multiply connected domains obtained by the author. It contains two rery simple proofs of Villat's formula; Schwarz's formula, Poisson's formula and Poisson-Jensen formula in multiply connected domains; the differentiability theorem with respect to the parameter of analytic function family containing one parametric variable on multiply connected domains; variation theorem and parametric representation theorem of univalent functions in multiply connected domains; the solution of an extremal problem of differentiable functionals.
基金the National Natural Science Foundation of China (No.19671082).
文摘Some extremal properties of the integral of Legendre polynomials are given, which are of independent interest. Meanwhile they show that a conjecture of P. Erdos[1] is plausible and maybe provides some means to prove this conjecture.
基金supported by National Natural Science Foundation of China(NSFC)grant No.11872210supported by National Natural Science Foundation of China(NSFC)grant No.11872210 and Grant No.MCMS-I-0120G01.
文摘This article designs a new fifth-order finite volume mapped unequal-sized weighted essentially non-oscillatory scheme(MUS-WENO)for solving hyperbolic conservation laws on structured meshes.One advantage is that the new mapped WENOtype spatial reconstruction is a convex combination of a quartic polynomial with two linear polynomials defined on unequal-sized central or biased spatial stencils.Then we propose the new mapped nonlinear weights and new mapping function to decrease the difference between the linear weights and nonlinear weights.This method has the characteristics of small truncation errors and high-order accuracy.And it could give optimal fifth-order convergence with a very tiny#even near critical points in smooth regions while suppressing spurious oscillations near strong discontinuities.Compared with the classical finite volume WENO schemes and mapped WENO(MWENO)schemes,the linear weights can be any positive numbers on the condition that their summation is one,which greatly reduces the calculation cost.Finally,we propose a new modified positivity-preserving method for solving some low density,low pressure,or low energy problems.Extensive numerical examples including some unsteadystate problems,steady-state problems,and extreme problems are used to testify to the efficiency of this new finite volume MUS-WENO scheme.
基金support provided by the National Natural Science Foundation of China(No.12301530)China Postdoctoral Science Foundation(No.2023M733348)for this research+1 种基金support provided by the Shandong Provincial Natural Science Foundation(No.ZR2022MA012)Hong Kong Research Grant Council GRF Grant.
文摘In extreme scenarios,classical high-order WENO schemes may result in non-physical states.The Positivity-Preserving Limiter(PP-Limiter)is often used to ensure positivity if CFL≤0.5 with a third-order TVD Runge-Kunta(RK3)scheme.This study proposes two novel conservative WENO-Z methods:AT-PP and AO-PP to improve efficiency with 0.5<CFL<1 if desired.The AT-PP method detects negative cells after each RK3 stage posteriori and computes a new solution with the PPLimiter(CFL<0.5)for that step.The AO-PP method progressively lowers the WENO operator’s order and terminates with the first-order HLLC solver,proven positivitypreserving with CFL<1,only at negative cells at that RK3 stage.A single numerical flux enforces conservation at neighboring interfaces.Extensive 1D and 2D shocktube problems were conducted to illustrate the performance of AT-PP and AO-PP with CFL=0.9.Both methods outperformed the classical PP-Limiter in accuracy and resolution,while AO-PP performed better computationally in some cases.The AO-PP method is globally conservative and accurate,adaptiveness,and robustness while resolving fine-scale structures in smooth regions,capturing strong shocks and gradients with ENO-property,improving computational efficiency,and preserving the positivity,all without imposing a restrictive limit on the CFL condition.
基金Supported in part by two grants from Ministerio de Economía y Competitividad,Spain:MTM2013-46374-P and MTM2015-69323-REDT
文摘In this work, we obtain good upper bounds for the diameter of any graph in terms of its minimum degree and its order, improving a classical theorem due to Erdos, Pach, Pollack and Tuza. We use these bounds in order to study hyperbolic graphs （in the Gromov sense）. To compute the hyperbolicity constant is an almost intractable problem, thus it is natural to try to bound it in terms of some parameters of the graph. Let H（n, δ0） be the set of graphs G with n vertices and minimum degree 50, and J（n, Δ） be the set of graphs G with n vertices and maximum degree A. We study the four following extremal problems on graphs： a（n,δ0） = min{δ（G） ｜ G ∈H（n, δ0）}, b（n, δ0） =- max{δ（G）｜ e ∈H（n, δ0）}, α（n, Δ） = min{δ（G） [ G ∈ J（n, Δ）} and β（n,Δ） = max{δ（G） ] G∈Π（n,Δ）}. In particular, we obtain bounds for b（n, δ0） and we compute the precise value of a（n, δ0）, α（n, Δ） and w（n, Δ） for all values of n, r0 and A, respectively.
基金Supported by two grants from Ministerio de Economía y Competitividad,Spain(Grant Nos.MTM2013-46374-P and MTM2015-69323-REDT)
文摘The original version of the article was published in[1].Unfortunately,the original version of this article contains a mistake:in Theorem 6.2 appears thatβ(n,△)=(n-△+5)/4 but the correct statement isβ(n,△)=(n-△+4)/4.In this erratum we correct the theorem and give the correct proof.
基金Supported in part by National Natural Science Foundation of China(Grant No.11271116)
文摘The paper explores the connection of Graph-Lagrangians and its maximum cliques for 3-uniform hypergraphs. Motzkin and Straus showed that the Graph-Lagrangian of a graph is the Graph-Lagrangian of its maximum cliques. This connection provided a new proof of Turin classical result on the Turan density of complete graphs. Since then, Graph-Lagrangian has become a useful tool in extremal problems for hypergraphs. Peng and Zhao attempted to explore the relationship between the Graph-Lagrangian of a hypergraph and the order of its maximum cliques for hypergraphs when the number of edges is in certain range. They showed that if G is a 3-uniform graph with m edges containing a clique of order t - 1, then A（G） = A（[t- 1]（3）） provided （t31） ≤ m ≤ （3^t1） ＋ （2^rt-2）. They also conjectured： If G is an r-uniform graph with m edges not containing a clique of order t - 1, then A（G） 〈 A（[t - 1]（r）） provided （r^t-1） ≤ m ≤ （r^t-1） ＋ （r-1^t-2）. It has been shown that to verify this conjecture for 3-uniform graphs, it is sufficient to verify the conjecture for left-compressed 3-uniform graphs with m = （3^t-1） ＋ （2^t-2）. Regarding this conjecture, we show： If G is a left-compressed 3-uniform graph on the vertex set It] with m edges and lit - 1]（3） ／ E（G）｜=- p, then A（G） 〈 A（[t - 1]（3）） provided m = （3^t-1） ＋ （2^t-2） and t ≥ 17p/2 ＋ 11.
基金Supported by Chinese Universities Scientic Fund(No.N140504004)the National Natural Science Foundation of China(No.11271116)
文摘Frankl and Füredi in [1] conjectured that the r-graph with m edges formed by taking the first m sets in the colex ordering of N^（r） has the largest Lagrangian of all r-graphs with m edges.Denote this r-graph by Cr,m and the Lagrangian of a hypergraph by λ（G）.In this paper,we first show that if（3^t-1） ≤m〈（3^t）,G is a left-compressed 3-graph with m edges and on vertex set[t],the triple with minimum colex ordering in G^c is（t — 2 — i）（t — 2）t,then λ（G） ≤λ（C3,m）.As an implication,the conjecture of Frankl and Fiiredi is true for（3^t）-6≤m≤（3^t）.
