关于等价嵌入于存贮线性有限自动机问题

本文应用模的手段研究域上线性有限自动机等价嵌入于其中存贮类型的问题,分别得到可等价嵌入的一个充分条件与不可等价嵌入的一个充要条件。     

Finite bases for finitely generated,relatively congruence distributive quasivarieties

In [21], D. Pigozzi has proved in a non-constructive way that every relatively congruence distributive quasivariety of finite type generated by a finite set of finite algebras is finitely axiomatizable. In this paper we show that the non-constructive parts of Pigozzi's argument can be replaced by constructive ones. As a result we obtain a method of constructing a finite set of quasi-equational axioms for each relatively congruence distributive quasivariety generated by a given finite set of finite algebras of finite type. The method can also be applied to finitely generated congruence distributive varieties.Presented by Joel Berman.     

Simple Product-Form Bounds for Queueing Networks with Finite Clusters

Queueing networks are studied with finite capacities for clusters of stations, rather than for individual stations. First, an instructive tandem cluster example is studied to show that a product-form modification method for networks with finite stations can be extended to networks with finite clusters. Next, general results are established by which finite clusters can be regarded as finite aggregate stations. By these results product-form modifications for finite stations can be extended to product-form modifications for finite clusters by just considering a network at cluster level. This may lead to simple performance bounds. A number of illustrative examples with numerical support are provided.     

Abelian quotients and orbit sizes of linear groups

Let G be a finite group,and let V be a completely reducible faithful finite G-module(i.e.,G ≤GL(V),where V is a finite vector space which is a direct sum of irreducible G-submodules).It has been known for a long time that if G is abelian,then G has a regular orbit on V.In this paper we show that G has an orbit of size at least |G/G′| on V.This generalizes earlier work of the authors,where the same bound was proved under the additional hypothesis that G is solvable.For completely reducible modules it also strengthens the 1989 result |G/G′| |V| by Aschbacher and Guralnick.     

Inner Homomorphisms and Positive-Conditional Terms

We establish the criterion for two finite or uniformly locally finite algebras of a finite signature to be positive-conditionally rational equivalent (in terms of semigroups of inner homomorphisms of these algebras) and the criterion for two finite algebras to be strongly similar (in terms of expanded semigroups of inner homomorphisms of those algebras).     

输入存贮线性有限自动机的弱可逆性

应用输入存贮线性有限自动机的结构矩阵讨论了输入存贮线性有限自动机的弱可逆性,得出输入存贮线性有限自动机延迟0步弱可逆的充要条件、延迟τ步弱可逆和严格延迟τ步弱可逆的充分条件,由此条件得出延迟τ步弱可逆和严格延迟τ步弱可逆的输入存贮线性有限自动机的构造方法并且求出延迟0步弱可逆输入存贮线性有限自动机的一个弱逆.     

The Conservation and Convergence of Two Finite Difference Schemes for KdV Equations with Initial and Boundary Value Conditions

Korteweg-de Vries equation is a nonlinear evolutionary partial differential equation that is of third order in space. For the approximation to this equation with the initial and boundary value conditions using the finite difference method, the difficulty is how to construct matched finite difference schemes at all the inner grid points. In this paper, two finite difference schemes are constructed for the problem. The accuracy is second-order in time and first-order in space. The first scheme is a two-level nonlinear implicit finite difference scheme and the second one is a three-level linearized finite difference scheme. The Browder fixed point theorem is used to prove the existence of the nonlinear implicit finite difference scheme. The conservation, boundedness, stability, convergence of these schemes are discussed and analyzed by the energy method together with other techniques. The two-level nonlinear finite difference scheme is proved to be unconditionally convergent and the three-level linearized one is proved to be conditionally convergent. Some numerical examples illustrate the efficiency of the proposed finite difference schemes.     

An Iterative FEM for Solving Wave Problems of a Halfspace

An iterative finite element method for solving wave problems of a halfspace is presented in this paper. The halfspace is first truncated by introducing a fictive finite boundary on which some fictive boundary conditions must be imposed. A finite computational domain is in each iteration subjected to actual boundary conditions on real boundary and to fictive Dirichlet or Neumann boundary conditions on the fictive boundary. The radiation condition is satisfied by using DtN operator. The DtN operator is not introduce in the finite element formulation on the fictive boundary so any finite elements can be used. The method is simple and specially useful for computing higher harmonics.     

On stationary equilibria of a single-controller stochastic game

We consider a two-person, general-sum, rational-data, undiscounted stochastic game in which one player (player II) controls the transition probabilities. We show that the set of stationary equilibrium points is the union of a finite number of sets such that, every element of each of these sets can be constructed from a finite number of extreme equilibrium strategies for player I and from a finite number of pseudo-extreme equilibrium strategies for player II. These extreme and pseudo-extreme strategies can themselves be constructed by finite (but inefficient) algorithms. Analogous results can also be established in the more straightforward case of discounted single-controller games.     

有限秩的可解群的正则自同构

设G是有限秩的剩余有限可解群或是有限秩的剩余有限可解群的有限扩张,α是G的一个索数p阶正则自同构且φ:G→G(g→[g,α])是满射,则G是幂零类不超过h(p)的幂零群,其中h(p)是只与p有关的函数.     

最小二乘法及光滑问题不规则剖分上有限元解的超收敛分析

对有限元近似解提出一种通用的超收敛框架,该框架是对有限元解在另一有限维空间中作最小二乘逼近,中证明新构造的逼近解具有局部和整体上的超收敛,与所有已知的超收敛结果不同的是,该框架给出的超收敛结果对区域的有限元剖分没有附加任何一致性或对称性要求,这种得用小二乘作超收剑的技巧可以很简单地推广到混合有限元法,斯托克斯方程及重调方程的有限元法。     

Tamely uniform orders

The following two results are proven.

(i) Let G be a finitely generated torsion-free linear group. If every torsion-free section of G is an R-group, then G is soluble of finite rank. Conversely, if G has finite rank, then it has a subgroup of finite index, in which every torsion-free section is an R-group.

Let G be a finitely generated torsion-free soluble group. If in every torsion-free section of G the normalizer of each isolated subgroup is isolated, then G has finite rank. Conversely, if G has finite rank, then it has a subgroup K of finite index such that in every torsion-free section of K the normalizer of each isolated subgroup is isolated.     

剩余有限minimax 可解群的几乎正则自同构

设G 是一个剩余有限的minimax 可解群, α 是G 的几乎正则自同构, 则G/[G, α] 是有限群, 并且(1) 当α^p = 1 时, G 有一个指数有限的幂零群其幂零类不超过h(p), 其中h(p) 是只与素数p 有关的函数.(2) 当α² = 1 时, G 有一个指数有限的Abel 特征子群且[G, α]′ 是有限群.关键词剩余有限minimax 可解群几乎正则自同构     

Congruence-preserving extensions of finite lattices to sectionally complemented lattices

In 1962, the authors proved that every finite distributive lattice can be represented as the congruence lattice of a finite sectionally complemented lattice. In 1992, M. Tischendorf verified that every finite lattice has a congruence-preserving extension to an atomistic lattice. In this paper, we bring these two results together. We prove that every finite lattice has a congruence-preserving extension to a finite sectionally complemented lattice.

     

Finite abundant semigroups in which the idempotents form a subsemigroup

We consider certain abundant semigroups in which the idempotents form a subsemigroup, and which we call bountiful semigroups. We find a simple criterion for a finite bountiful semigroup to be a member of the join of the pseudovarieties of finite groups and finite aperiodic semigroups.     

Nonconforming finite element methods on quadrilateral meshes

It is well known that it is comparatively difcult to design nonconforming fnite elements on quadrilateral meshes by using Gauss-Legendre points on each edge of triangulations.One reason lies in that these degrees of freedom associated with these Gauss-Legendre points are not all linearly independent for usual expected polynomial spaces,which explains why only several lower order nonconforming quadrilateral fnite elements can be found in literature.The present paper proposes two families of nonconforming fnite elements of any odd order and one family of nonconforming fnite elements of any even order on quadrilateral meshes.Degrees of freedom are given for these elements,which are proved to be well-defned for their corresponding shape function spaces in a unifying way.These elements generalize three lower order nonconforming fnite elements on quadrilaterals to any order.In addition,these nonconforming fnite element spaces are shown to be full spaces which is somehow not discussed for nonconforming fnite elements in literature before.     

On the hamiltonicity of line graphs of locally finite, 6‐edge‐connected graphs

The topological approach to the study of infinite graphs of Diestel and KÜhn has enabled several results on Hamilton cycles in finite graphs to be extended to locally finite graphs. We consider the result that the line graph of a finite 4‐edge‐connected graph is hamiltonian. We prove a weaker version of this result for infinite graphs: The line graph of locally finite, 6‐edge‐connected graph with a finite number of ends, each of which is thin, is hamiltonian.     

A second-order finite difference method for the resolution of a boundary value problem associated to a modified Poisson equation in spherical coordinates

We propose a second-order finite difference method which may be used for a self-contained and efficient numerical resolution of a boundary value problem involving a modified Poisson equation written in spherical coordinates and a Robin type boundary condition. We compare on two realistic examples issued from the combustion of a coal char particle the efficiency of this second-order finite difference method with that of the classical finite difference method and of the finite element method.     

Finite Homomorphic Images of Groups of Finite Rank

Let π be a finite set of primes. We prove that each soluble group of finite rank contains a finite index subgroup whose every finite homomorphic π-image is nilpotent. A similar assertion is proved for a finitely generated group of finite rank. These statements are obtained as a consequence of the following result of the article: Each soluble pro-π-group of finite rank has an open normal pronilpotent subgroup.