We estimate the number of disjoint open subsets in Rn, which can support area-decreasing minimal graphs. This result generalizes the related results of Li-Wang and Tkachev for minimal hypersurfaces to higher codimensi...We estimate the number of disjoint open subsets in Rn, which can support area-decreasing minimal graphs. This result generalizes the related results of Li-Wang and Tkachev for minimal hypersurfaces to higher codimensional case.展开更多
In this paper,the authors derive H¨older gradient estimates for graphic functions of minimal graphs of arbitrary codimensions over bounded open sets of Euclidean space under some suitable conditions.
We use the concept of the inside-(a,η,h)domain to construct a subsolution to the Dirichlet problem for minimal graphs over convex domains in hyperbolic space.As an application,we prove that the Hölder exponent m...We use the concept of the inside-(a,η,h)domain to construct a subsolution to the Dirichlet problem for minimal graphs over convex domains in hyperbolic space.As an application,we prove that the Hölder exponent max{1/a,1/(n+1)}for the problem is optimal for any a∈[2,+∞].展开更多
In this paper, two methods of generating minimally persistent circle formation are presented. The proposed methods adopt a leader-follower strategy and all followers are firstly motivated to move into the leader's in...In this paper, two methods of generating minimally persistent circle formation are presented. The proposed methods adopt a leader-follower strategy and all followers are firstly motivated to move into the leader's interaction range. Based on the information about relative angle and relative distance, two numbering schemes are proposed to generate minimally persistent circle formation. Distributed control laws are also designed to maintain the desired relative distance between agents. The distinctive features of the proposed methods are as follows. First, only 2n - 3 unilateral communication links for n agents are needed during the circle formation process and thus the communication complexity can be reduced. In addition, the formation topology is kept fixed for the whole motion and achieves a self-stability property. Finally, each follower keeps a regualr interval with its neighbors and the formation converges to a uniform circle formation. Simulation results are also provided to demonstrate the effectiveness of the proposed methods.展开更多
This paper researched into some methods for generating min-weighted rigid graphs and min-weighted persistent graphs. Rigidity and persistence are currently used in various studies on coordination and control of autono...This paper researched into some methods for generating min-weighted rigid graphs and min-weighted persistent graphs. Rigidity and persistence are currently used in various studies on coordination and control of autonomous multi-agent formations. To minimize the communication complexity of formations and reduce energy consumption, this paper introduces the rigidity matrix and presents three algorithms for generating rain-weighted rigid and min- weighted persistent graphs. First, the existence of a min-weighted rigid graph is proved by using the rigidity matrix, and algorithm 1 is presented to generate the min-weighted rigid graphs. Second, the algorithm 2 based on the rigidity matrix is presented to direct the edges of min-weighted rigid graphs to generate min-weighted persistent graphs. Third, the formations with range constraints are considered, and algorithm 3 is presented to find whether a framework can form a min-weighted persistent formation. Finally, some simulations are given to show the efficiency of our research.展开更多
A. Kaneko and K. Ota proved that for a minimally (n, λ)-connected graph G, if |G| = p ≥ 3n - 1, then e(G) ≤ nλ(|G| - n); and if e(G) = nλ(|G| - n), then G is isomorphic to the graph Kn^λ,p-n whic...A. Kaneko and K. Ota proved that for a minimally (n, λ)-connected graph G, if |G| = p ≥ 3n - 1, then e(G) ≤ nλ(|G| - n); and if e(G) = nλ(|G| - n), then G is isomorphic to the graph Kn^λ,p-n which is obtained from the complete bipartite graph Kn,p-n by replacing each edge with A multiple edges; if 3n - 1 ≥ |G}≥ n + 1, then e(G) ≤λ(|G| + n)^2/8. In this paper, we determine all the minimally (n, λ)-connected graphs with order p and the maximum size λ(p+n)^2/8 for 3n- 1 ≥ p ≥ n+ 1 for 3n-1≥p≥n+1.展开更多
Let ψ be a certain set of graphs.A graph is called a minimizing graph in the set ψ if its least eigenvalue attains the minimum among all graphs in ψ.In this paper,we determine the unique minimizing graph in ψn,whe...Let ψ be a certain set of graphs.A graph is called a minimizing graph in the set ψ if its least eigenvalue attains the minimum among all graphs in ψ.In this paper,we determine the unique minimizing graph in ψn,where ψn denotes the set of connected graphs of order n with cut vertices.展开更多
A graph property is any class of graphs that is closed under isomorphisms, A graph property P is hereditary if it is closed under taking subgraphs; it is compositive if for any graphs
Let B(G) denote the bipartite double cover of a non-bipartite graph G with v ≥ 2 vertices and s edges. We prove that G is a perfect 2-matching covered graph if and only if B(G) is a 1-extendable graph. Furthermor...Let B(G) denote the bipartite double cover of a non-bipartite graph G with v ≥ 2 vertices and s edges. We prove that G is a perfect 2-matching covered graph if and only if B(G) is a 1-extendable graph. Furthermore, we prove that B(G) is a minimally l-extendable graph if and only if G is a minimally perfect 2-matching covered graph and for each e = xy ∈ E(G), there is an independent set S in G such that |ГG(S)| = |S| + 1, x ∈ S and |ГG-xy(S)| = |S| Then, we construct a digraph D from B(G) or G and show that D is a strongly connected digraph if and only if G is a perfect 2-matching covered graph. So we design an algorithm in O(x√vε) time that determines whether G is a perfect 2-matching covered graph or not.展开更多
We analyze a common feature of p-Kemeny AGGregation(p-KAGG) and p-One-Sided Crossing Minimization(p-OSCM) to provide new insights and findings of interest to both the graph drawing community and the social choice ...We analyze a common feature of p-Kemeny AGGregation(p-KAGG) and p-One-Sided Crossing Minimization(p-OSCM) to provide new insights and findings of interest to both the graph drawing community and the social choice community. We obtain parameterized subexponential-time algorithms for p-KAGG—a problem in social choice theory—and for p-OSCM—a problem in graph drawing. These algorithms run in time O*(2O(√k log k)),where k is the parameter, and significantly improve the previous best algorithms with running times O.1.403k/and O.1.4656k/, respectively. We also study natural "above-guarantee" versions of these problems and show them to be fixed parameter tractable. In fact, we show that the above-guarantee versions of these problems are equivalent to a weighted variant of p-directed feedback arc set. Our results for the above-guarantee version of p-KAGG reveal an interesting contrast. We show that when the number of "votes" in the input to p-KAGG is odd the above guarantee version can still be solved in time O*(2O(√k log k)), while if it is even then the problem cannot have a subexponential time algorithm unless the exponential time hypothesis fails(equivalently, unless FPT D M[1]).展开更多
基金supported by zhongdian grantof NSFC (A010501)NSFC-NSF (1081112053)supported by NSFC (10701025)
文摘We estimate the number of disjoint open subsets in Rn, which can support area-decreasing minimal graphs. This result generalizes the related results of Li-Wang and Tkachev for minimal hypersurfaces to higher codimensional case.
基金supported by the National Natural Science Foundation of China(Nos.11871156,11922106,11531012)。
文摘In this paper,the authors derive H¨older gradient estimates for graphic functions of minimal graphs of arbitrary codimensions over bounded open sets of Euclidean space under some suitable conditions.
基金This work was supported in part by the Natural Science Foundation of Beijing Municipality(No.1212002)the National Natural Science Foundation of China(Grant Nos.12071017,11871432).
文摘We use the concept of the inside-(a,η,h)domain to construct a subsolution to the Dirichlet problem for minimal graphs over convex domains in hyperbolic space.As an application,we prove that the Hölder exponent max{1/a,1/(n+1)}for the problem is optimal for any a∈[2,+∞].
基金Project supported by the National Basic Research Program of China (Grant No.2010CB731800)the National Natural Science Foundation of China (Grant Nos.60934003,61074065,and 61375105)the Natural Science Foundation of Hebei Province,China (Grant No.F2012203119)
文摘In this paper, two methods of generating minimally persistent circle formation are presented. The proposed methods adopt a leader-follower strategy and all followers are firstly motivated to move into the leader's interaction range. Based on the information about relative angle and relative distance, two numbering schemes are proposed to generate minimally persistent circle formation. Distributed control laws are also designed to maintain the desired relative distance between agents. The distinctive features of the proposed methods are as follows. First, only 2n - 3 unilateral communication links for n agents are needed during the circle formation process and thus the communication complexity can be reduced. In addition, the formation topology is kept fixed for the whole motion and achieves a self-stability property. Finally, each follower keeps a regualr interval with its neighbors and the formation converges to a uniform circle formation. Simulation results are also provided to demonstrate the effectiveness of the proposed methods.
基金supported by the National Natural Science Foundation for Distinguished Young Scholars of China (Grant No 60525303)the National Natural Science Foundation of China (Grant No 60704009)Doctor Fund of Yanshan University (Grant NoB203)
文摘This paper researched into some methods for generating min-weighted rigid graphs and min-weighted persistent graphs. Rigidity and persistence are currently used in various studies on coordination and control of autonomous multi-agent formations. To minimize the communication complexity of formations and reduce energy consumption, this paper introduces the rigidity matrix and presents three algorithms for generating rain-weighted rigid and min- weighted persistent graphs. First, the existence of a min-weighted rigid graph is proved by using the rigidity matrix, and algorithm 1 is presented to generate the min-weighted rigid graphs. Second, the algorithm 2 based on the rigidity matrix is presented to direct the edges of min-weighted rigid graphs to generate min-weighted persistent graphs. Third, the formations with range constraints are considered, and algorithm 3 is presented to find whether a framework can form a min-weighted persistent formation. Finally, some simulations are given to show the efficiency of our research.
基金This research is supported by the National Natural Science Foundation of China.
文摘A. Kaneko and K. Ota proved that for a minimally (n, λ)-connected graph G, if |G| = p ≥ 3n - 1, then e(G) ≤ nλ(|G| - n); and if e(G) = nλ(|G| - n), then G is isomorphic to the graph Kn^λ,p-n which is obtained from the complete bipartite graph Kn,p-n by replacing each edge with A multiple edges; if 3n - 1 ≥ |G}≥ n + 1, then e(G) ≤λ(|G| + n)^2/8. In this paper, we determine all the minimally (n, λ)-connected graphs with order p and the maximum size λ(p+n)^2/8 for 3n- 1 ≥ p ≥ n+ 1 for 3n-1≥p≥n+1.
基金Supported by the Supported by the National Natural Science Foundation of China (Grant No. 11071002)Key Project of Chinese Ministry of Education (Grant No. 210091)+4 种基金Anhui Provincial Natural Science Foundation(Grant No. 10040606Y33)Anhui University Innovation Team Project (Grant No. KJTD001B)Project of Anhui Province for Young Teachers Research Support in Universities (Grant No. 2008JQl021)Project of Anhui Province for Excellent Young Talents in Universities (Grant No. 2009SQRZ017ZD)the Natural Science Foundation of Department of Education of Anhui Province (Grant No. KJ2010B136)
文摘Let ψ be a certain set of graphs.A graph is called a minimizing graph in the set ψ if its least eigenvalue attains the minimum among all graphs in ψ.In this paper,we determine the unique minimizing graph in ψn,where ψn denotes the set of connected graphs of order n with cut vertices.
文摘A graph property is any class of graphs that is closed under isomorphisms, A graph property P is hereditary if it is closed under taking subgraphs; it is compositive if for any graphs
基金Acknowledgements The authors would like to thank the referees very much for their careful reading and their very instructive suggestions which improve this paper greatly. This work was supported in part by the National Natural Science Foundation of China (Grant No. 11201158).
文摘Let B(G) denote the bipartite double cover of a non-bipartite graph G with v ≥ 2 vertices and s edges. We prove that G is a perfect 2-matching covered graph if and only if B(G) is a 1-extendable graph. Furthermore, we prove that B(G) is a minimally l-extendable graph if and only if G is a minimally perfect 2-matching covered graph and for each e = xy ∈ E(G), there is an independent set S in G such that |ГG(S)| = |S| + 1, x ∈ S and |ГG-xy(S)| = |S| Then, we construct a digraph D from B(G) or G and show that D is a strongly connected digraph if and only if G is a perfect 2-matching covered graph. So we design an algorithm in O(x√vε) time that determines whether G is a perfect 2-matching covered graph or not.
基金supported by a GermanNorwegian PPP grantsupported by the Indo-German Max Planck Center for Computer Science (IMPECS)
文摘We analyze a common feature of p-Kemeny AGGregation(p-KAGG) and p-One-Sided Crossing Minimization(p-OSCM) to provide new insights and findings of interest to both the graph drawing community and the social choice community. We obtain parameterized subexponential-time algorithms for p-KAGG—a problem in social choice theory—and for p-OSCM—a problem in graph drawing. These algorithms run in time O*(2O(√k log k)),where k is the parameter, and significantly improve the previous best algorithms with running times O.1.403k/and O.1.4656k/, respectively. We also study natural "above-guarantee" versions of these problems and show them to be fixed parameter tractable. In fact, we show that the above-guarantee versions of these problems are equivalent to a weighted variant of p-directed feedback arc set. Our results for the above-guarantee version of p-KAGG reveal an interesting contrast. We show that when the number of "votes" in the input to p-KAGG is odd the above guarantee version can still be solved in time O*(2O(√k log k)), while if it is even then the problem cannot have a subexponential time algorithm unless the exponential time hypothesis fails(equivalently, unless FPT D M[1]).