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971.
In this paper, the structure of the critical group of the graph K
m
× C
n
is determined, where m, n ≥ 3. 相似文献
972.
Juan Alberto Rodriguez-Velazquez José María Sigarreta Ismael Gonzalez Yero Sergio Bermudo 《数学学报(英文版)》2011,27(3):497-504
A defensive (offensive) k-alliance in Γ = (V,E) is a set S ⊆ V such that every υ in S (in the boundary of S) has at least k more neighbors in S than it has in V / S. A set X ⊆ V is defensive (offensive) k-alliance free, if for all defensive (offensive) k-alliance S, S/X ≠ ∅, i.e., X does not contain any defensive (offensive) k-alliance as a subset. A set Y ⊆ V is a defensive (offensive) k-alliance cover, if for all defensive (offensive) k-alliance S, S ∩ Y ≠ ∅, i.e., Y contains at least one vertex from each defensive (offensive) k-alliance of Γ. In this paper we show several mathematical properties of defensive (offensive) k-alliance free sets and defensive (offensive) k-alliance cover sets, including tight bounds on their cardinality. 相似文献
973.
For the planar Z
2-equivariant cubic systems having two elementary focuses, the characterization of a bi-center problem and shortened expressions
of the first six Liapunov constants are completely discussed. The necessary and sufficient conditions for the existence of
the bi-center are obtained. All possible first integrals are given. Under small Z
2-equivariant cubic perturbations, the conclusion that there exist at most 12 small-amplitude limit cycles with the scheme
〈6 ∐ 6〉 is proved. 相似文献
974.
In two real Banach spaces, we shall present two conditions, under one of which each nonexpansive mapping must be an isometry. 相似文献
975.
Observations of sampling are often subject to rounding, but are modeled as though they were unrounded. This paper examines
the impact of rounding errors on parameter estimation with multi-layer ranked set sampling. It shows that the rounding errors
seriously distort the behavior of covariance matrix estimate, and lead to inconsistent estimation. Taking this into account,
we present a new approach to implement the estimation for this model, and further establish the strong consistency and asymptotic
normality of the proposed estimators. Simulation experiments show that our estimates based on rounded multi-layer ranked set
sampling are always more efficient than those based on rounded simple random sampling. 相似文献
976.
Bingquan Ji Luming Zhang Xuanxuan Zhou 《Numerical Methods for Partial Differential Equations》2019,35(3):1056-1079
In this article, a compact finite difference method is developed for the periodic initial value problem of the N‐coupled nonlinear Klein–Gordon equations. The present scheme is proved to preserve the total energy in the discrete sense. Due to the difficulty in obtaining the priori estimate from the discrete energy conservation law, the cut‐off function technique is employed to prove the convergence, which shows the new scheme possesses second order accuracy in time and fourth order accuracy in space, respectively. Additionally, several numerical results are reported to confirm our theoretical analysis. Lastly, we apply the reliable method to simulate and study the collisions of solitary waves numerically. 相似文献
977.
In this article, we study the second-order optimality conditions for a class of circular conic optimization problem. First, the explicit expressions of the tangent cone and the second-order tangent set for a given circular cone are derived. Then, we establish the closed-form formulation of critical cone and calculate the “sigma” term of the aforementioned optimization problem. At last, in light of tools of variational analysis, we present the associated no gap second-order optimality conditions. Compared to analogous results in the literature, our approach is intuitive and straightforward, which can be manipulated and verified. An example is illustrated to this end. 相似文献
978.
Stevo Stevi 《Mathematical Methods in the Applied Sciences》2019,42(18):6315-6338
By using generalized invariants, we describe a method for solving a class of higher‐order nonautonomous difference equations. Solvability of the equations of order two, three, and four are studied in detail. Our results explain and extend some problems in the literature. As far as we know, the case when the order is four is considered for the first time in this paper. For the equations of second order, we also give an explanation how they can be obtained in a natural way. 相似文献
979.
In this work, we consider the Lie point symmetry analysis of a strongly nonlinear partial differential equation of third order, the ∞‐Polylaplacian, in two spatial dimensions. This equation is a higher order generalization of the ∞‐Laplacian, also known as Aronsson's equation, and arises as the analog of the Euler–Lagrange equations of a second‐order variational principle in L∞. We obtain its full symmetry group, one‐dimensional Lie subalgebras and the corresponding symmetry reductions to ordinary differential equations. Finally, we use the Lie symmetries to construct new invariant ∞‐Polyharmonic functions. 相似文献
980.
Let H2(γ) be the Hilbert space over the bidisk D2 generated by a positive sequence γ={γnm}n,m ≥ 0. In this paper, we prove that the Beurling type theorem holds for the shift operator on H2(γ) with γ={γnm}n,m ≥ 0 satisfying certain series of inequalities. As a corollary, we give several applications to a class of classical analytic reproducing kernel Hilbert spaces over the bidisk D2. 相似文献