WHITEHEAD GROUPS OF MODULE EXTENSIONS

When R satisfies (strong unit) 1-stable range and M is a R-R-bimodule, theauthors calculate that K1(R ∞ M) ≌ U(R ∞ M)/L(R ∞ M). As applications, the authors also calculate some Whitehead groups for exchange rings with artinian primitive factors.Key words Whitehead group, module extension, (strong unit) 1-stable range     

On the boundedness of topological categories

Let K be a complete and cocomplete category with a given proper (E,M)-factorization. K is called well-bounded if K is moreover bounded with a generator and cowellpowered with respect to the given factorization. Freyd-Kelly proved the following theorem about well-bounded categories: Let K be a well-bounded category and let Γ be a class of cylinders in the small category C¹, and let all but a set of these cylinders be cones. Then Γ(C,K) is a reflective subcategory of [C,K]. The main results of this paper are: (I) If F: K→L is a Top-functor and L is well-bounded, then K is well-bounded. (II) If U is an E-reflective subcategory of a well-bounded category,then U is again wellbounded. As a corollary one obtains for instance that all coreflective and all epireflective subcategories of the category of topological spaces are well-bounded.     

On the divisibility of the class number of the imaginary quadratic field ℚ (\sqrt {a^2 - 4k^n } )

LetD be a positive integer which is square free, and leth (–D) denote the class number of the imaginary quadratic field 2e (–D). In this paper we prove that ifD' exp exp exp 1000,D=4k –a ², wherea, k andn are integers witha>0,k>1,n>1, then

A test of convergence of Fourier series with respect to multiplicative systems,analogous to the Jordan test

, {p _n} _n=0 (p₀=1, _n2 n2). : x f(t) V(G)

弹性介质中正交各向异性微管的屈曲分析

已有实验表明,处于细胞质中的微管可以比自由微管承受更大的压力而不发生屈曲．基于嵌入式碳纳米管屈曲的Winkler模型,利用正交各向异性情形的Winkler模型研究了细胞质中充当细胞骨架的微管的屈曲行为．计算表明,本模型可以较好地预测嵌入弹性介质中的微管较自由微管承受更大屈曲压力这一现象,而且所得到的临界屈曲压力与微管受压屈曲的实验值吻合\．同时,所得的结果也表明周围介质与微管的相互作用可以极大地提高微管抵抗屈曲的能力,该结果很好地阐释了介质与微管相互作用从而提高微管抗屈曲压力的相互作用机制\．模拟结果表明,所给出的模型可以对嵌入弹性介质中的微管的屈曲行为进行很好地模拟．     

φ-Derivations on Strongly Double Triangle Subspace Lattice Algebras

Let D = {{0},K,L,M,X } be a strongly double triangle subspace lattice on a non- zero complex reflexive Banach space X ,which satisfies that one of three sums K + L,L + M and M + K is closed.It is shown that local φ-derivations and φ-derivations at zero point on AlgD are generalized φ-derivations.     

From Lie algebras of vector fields to algebraic group actions

The action of an affine algebraic group G on an algebraic variety V can be differentiated to a representation of the Lie algebra L(G) of G by derivations on the sheaf of regular functions on V . Conversely, if one has a finite-dimensional Lie algebra L and a homomorphism ρ : L → Der_K(K[U]) for an affine algebraic variety U, one may wonder whether it comes from an algebraic group action on U or on a variety V containing U as an open subset. In this paper, we prove two results on this integration problem. First, if L acts faithfully and locally finitely on K[U], then it can be embedded in L(G), for some affine algebraic group G acting on U, in such a way that the representation of L(G) corresponding to that action restricts to ρ on L. In the second theorem, we assume from the start that L = L(G) for some connected affine algebraic group G and show that some technical but necessary conditions on ρ allow us to integrate ρ to an action of G on an algebraic variety V containing U as an open dense subset. In the interesting cases where L is nilpotent or semisimple, there is a natural choice for G, and our technical conditions take a more appealing form.     

Finite element approximation of a sixth order nonlinear degenerate parabolic equation

Summary. We consider a finite element approximation of the sixth order nonlinear degenerate parabolic equation where generically for any given In addition to showing well-posedness of our approximation, we prove convergence in space dimensions $d \leq 3$. Furthermore an iterative scheme for solving the resulting nonlinear discrete system is analysed. Finally some numerical experiments in one and two space dimensions are presented. Mathematics Subject Classification (2000): 65M60, 65M12, 35K55, 35K65, 35K35Supported by the EPSRC, U.K. through grant GR/M29689.Supported by the EPSRC, and by the DAAD through a Doktorandenstipendium     

A Netform System for Resource Planning in the U.S. Bureau of Land Management

We report an effective model and solution procedure for a major resource management problem of the U.S. Bureau of Land Management (B.L.M.), enabling large practical applications to be solved 20-300 times faster than previously possible. The resulting system has proved a useful analysis tool, providing model interaction capabilities that are employed routinely by the B.L.M. an average of 700 times a month throughout the U.S.     

基于鞅空间M(ln~+M)~p,L(ln~+L)~p与K(ln~+K)~p的关系研究

旨在利用概率方法探讨鞅空间K2与M1之间的鞅空间包含变化关系.首先提出了新的鞅空间M(ln+M)p,L(ln+L)p以及K(ln+K)p(其中p 1)的定义,并证明了其空间包含关系.