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991.
We compare various algorithms for constructing a matrix of order $n$ whose Pareto spectrum contains a prescribed set $\Lambda =\{\lambda _1,\ldots , \lambda _p\}$ of reals. In order to avoid overdetermination one assumes that $p$ does not exceed $n^2.$ The inverse Pareto eigenvalue problem under consideration is formulated as an underdetermined system of nonlinear equations. We also address the issue of computing Lorentz spectra and solving inverse Lorentz eigenvalue problems. 相似文献
992.
Alberto Abbondandolo 《Journal of Fixed Point Theory and Applications》2013,13(2):397-430
In this expository article we study the question of the existence of periodic orbits of prescribed energy for classical Hamiltonian systems on compact configuration spaces.We use a variational approach, by studying how the behavior of the free period Lagrangian action functional changes when the energy crosses certain values, known as the Mañé critical values. 相似文献
993.
Alberto Seeger 《Set-Valued and Variational Analysis》2013,21(3):503-516
This work establishes a localization result for the solutions to a class of extremal problems involving invariant sets and invariant functions. The concept of invariance is relative to a special collection of linear endomorphisms on some Euclidean space. 相似文献
994.
995.
We consider the problem of placing n points in the unit square in such a way as to maximize their minimum pairwise distance m. Starting from two properties of the optimal solution presented by Locatelli and Raber in [Discrete Applied Mathematics 122 (1–3) (2002) 139–166], and using the known theoretical lower and upper bounds, we derive some constraints for tightening the original formulation of the problem. 相似文献
996.
Elena Barcucci Alberto Del Lungo Elisa Pergola 《Journal of Difference Equations and Applications》2013,19(4-5):435-490
In this Paper, we illustrate a method (called the ECO method) for enumerating some classes of combinatorial objects. The basic idea of this method is the following: by means of an operator that performs a "local expansion" on the objects, we give some recursive constructions of these classes. We use these constructions to deduce some new funtional equations verified by classes' generating functions. By solving the functional equations, we enumerate the combinatorial objects according to various parameters. We show some applications of the method referring to some classical combinatorial objects, such as: trees, paths, polyminoes and permutations 相似文献
997.
Alberto del Valle 《代数通讯》2013,41(4):1257-1269
The formula dim(A+B)=dim(A)+dim(B)-dim(A∩B) works when ‘dim’ stands for the dimension of subspaces A,B of any vector space. In general, however, it does no longer hold if 'dim' means the uniform (or Goldie) dimension of submodules A,B of a module M over a ring R, and in fact the left hand side may be infinite while the right hand side is finite. In this paper we shall give a characterization of those modules M in which the formula holds for any two submodules A,B, as well as some conditions in the ring R which guarantee that dim(A+B) is finite whenever A and B are finite dimensional R-modules. 相似文献
998.
Alberto Sapora Pietro Cornetti Alberto Carpinteri 《Communications in Nonlinear Science & Numerical Simulation》2013,18(1):63-74
In the present paper, the wave propagation in one-dimensional elastic continua, characterized by nonlocal interactions modeled by fractional calculus, is investigated. Spatial derivatives of non-integer order 1 < α < 2 are involved in the governing equation, which is solved by fractional finite differences. The influence of long-range interactions is then analyzed as α varies: the resonant frequencies and the standing waves of a nonlocal bar are evaluated and the deviations from the classical (local) ones, recovered by imposing α = 2, are discussed. 相似文献
999.
Alberto Boscaggin Maurizio Garrione 《NoDEA : Nonlinear Differential Equations and Applications》2013,20(3):825-843
We consider the planar Hamiltonian system $$Ju^{\prime} = \nabla F(u) + \nabla_u R(t,u), \quad t \in [0,T], \,u \in \mathbb{R}^2,$$ with F(u) positive and positively 2-homogeneous and ${\nabla_{u}R(t, u)}$ sublinear in u. By means of an Ahmad-Lazer-Paul type condition, we prove the existence of a T-periodic solution when the system is at resonance. The proof exploits a symplectic change of coordinates which transforms the problem into a perturbation of a linear one. The relationship with the Landesman–Lazer condition is analyzed, as well. 相似文献
1000.
Douglas R. Anderson Alberto Cabada 《Journal of Difference Equations and Applications》2013,19(9):919-935
We are concerned with the existence and form of positive solutions to a third-order multi-point boundary-value problem on time scales with mixed derivatives. We find and utilize the Green function for the corresponding homogeneous right-focal problem as the kernel of an integral equation of Hammerstein-type. Two examples are included to illustrate the results. 相似文献