A Littlewood-Paley type inequality

In this note we prove the following theorem: Let u be a harmonic function in the unit ball and . Then there is a constant C = C(p, n) such that

Boosts in an Arbitrary Direction and Maximal Causal Velocities in a Deformed Minkowski Space

We discuss boosts in a deformed Minkowski space, i.e., a four-dimensional spacetime with metric coefficients depending on nonmetric coordinates (in particular on the energy). The general form of a boost in an arbitrary direction is derived in the case of space anisotropy. Two maximal trivector velocities are mathematically possible, an isotropic and an anisotropic one. However, only the anisotropic velocity has physical meaning, being invariant indeed under deformed boosts.     

Uniform Continuity of a Family of Weakly Regular Set Functions on Topological Spaces

Conditions for the uniform continuity of a family of weakly regular set functions defined on an algebra of subsets of a -topological space (T,) and taking values in an arbitrary topological space are found.     

Iterated monoidal categories

We develop a notion of an n-fold monoidal category and show that it corresponds in a precise way to the notion of an n-fold loop space. Specifically, the group completion of the nerve of such a category is an n-fold loop space, and free n-fold monoidal categories give rise to a finite simplicial operad of the same homotopy type as the classical little cubes operad used to parametrize the higher H-space structure of an n-fold loop space. We also show directly that this operad has the same homotopy type as the n-th Smith filtration of the Barratt-Eccles operad and the n-th filtration of Berger's complete graph operad. Moreover, this operad contains an equivalent preoperad which gives rise to Milgram's small model for when n=2 and is very closely related to Milgram's model of for n>2.     

Smoothing Properties and Approximation of Time Derivatives for Parabolic Equations: Variable Time Steps

We study smoothing properties and approximation of time derivatives for time discretization schemes with variable time steps for a homogeneous parabolic problem formulated as an abstract initial value problem in a Banach space. The time stepping methods are based on using rational approximations to the exponential function which are A()-stable for suitable (0,/2] with unit bounded maximum norm. First- and second-order approximations of time derivatives based on using difference quotients are considered. Smoothing properties are derived and error estimates are established under the so-called increasing quasi-quasiuniform assumption on the time steps.     

立体车库钢结构系统失效树分析及软件研制

基于有限元理论 ,结合优化准则法 ,提出了立体停车库钢结构系统失效树理论分析方法 ,开发了计算软件FTA ,算例结果表明 :根据结构规模和具体特征选择合理的控制参数 ,不仅可以提高计算效率 ,而且可以保证计算的准确性 ;失效树中第一个失效元件是导致其余元件失效的根源 ,加强第一个失效元件 ,是保证结构系统不失效的最合理、最经济的方法 ;本文提出的分析计算方法及其软件FTA是有效的。     

多复变中Dp和H∝及βp空间的一些关系

在 Cⁿ中的单位球上, 讨论了Dirichlet 型空间D_p和广义Bloch空间β^q的相互包含关系以及D_p 和Hardy空间H^∝之间的点乘子,根据 p 的一些不同情形对M(H^∝, D_p ) 和 M( D_p , H^∝) 进行了刻划.     

计算机在地理空间概念教学中的应用

空间性是地理学科的重要特征 依据地理空间概念的特点 ,结合地理教学的实际 ,指出了常用软件Mapinfo、powerpoint在地理空间概念教学中的重要作用     

On the N-exciton normalization factor

The N-ground-state-exciton normalization factor, namely 〈v| B ₀ ^N B ₀ ^dagN| v〉 = N!F _N, with B ₀ ^d ag the exact ground state exciton creation operator, differs from N! because the excitons are not perfect bosons. The quantity F_N turns out to be crucial for problems dealing with interacting excitons. Indeed, the excitons feel each other not only through the Coulomb interaction but also through Pauli exclusion between their components. A quite novel purely Pauli contribution exists in their many-body effects, which relies directly on F_N. Following procedures used in the commutation technique we recently introduced to treat interacting close-to-bosons, and in the BCS theory of superconductivity, we rederive important relations verified by the F_N's. We also give new explicit expressions of F_N valid for η = Na _x ³/ small but N ² a _x ³/ large, as F_N does not read in terms of η but Nη, the exciton number N being possibly huge in macroscopic samples. Due to this superextensivity, F_N does not appear alone in physical quantities, but through ratios like F _{N + p}/F _N. We end this work by giving the η expansion of these ratios, useful for all purely Pauli many-body effects. Received 30 May 2002 / Received in final form 12 October 2002 Published online 27 January 2003 RID="a" ID="a"e-mail: combescot@gps.jussieu.fr     

The structure of XLPE and the distribution of space charge

The formation and accumulation of space charge under charge treatment are investigated using PWP method. The interaction between space charge and the structure of XLPE is measured using infrared spectroscopy (IR) method. The related mechanism about space charge distribution and the structure of XLPE are discussed.