关于空间(k1,k2)-拟正则映射

本文考虑空间 (k1,k2 ) -拟正则映射的 Lp(p >n)可积性 ,以及当 k1→ 1 ,k2 → 0时 p的渐近行为 .     

基于空间压缩和无穷级数的空间碎片碰撞概率快速算法

空间碎片碰撞概率的计算可以转化为2维正态分布概率密度函数(PDF)在圆域内的积分问题,针对以往方法的不足,首先通过空间压缩将不等方差PDF在圆域内的积分化为等方差PDF在椭圆区域内的积分,并将椭圆区域用与其面积相等的圆区域近似,化为等方差PDF在圆域内的积分,对引入的误差进行了讨论.该积分可以表示为首项与递推公式已知的无穷级数形式,可取级数前任意有限项的和作为概率积分的近似,并且给出了截断误差上限的表达式.根据近似结果分析了最大概率的表达式和此时的位置误差参数.以一次实际发生的碰撞为例对该方法进行了验证,并与另外两种进行了比较,结果表明该方法是一种精度高速度快的方法.     

On the Convergence of Fourier Series in the Space L1

We establish necessary and sufficient conditions for the convergence in the mean of trigonometric series whose coefficients satisfy the Boas–Telyakovskii conditions.     

On the Dynamics of

We investigate the existence of unbounded solutions and the period-two convergence of solutions of the equation in the title with the parameter γ positive, the remaining parameters nonnegative, and with nonnegative initial conditions.     

关于拟常曲率空间中2 -调和子流形

该文研究拟常曲率空间中的紧致2 -调和子流形,得到了这类子流形成为极小子流形的关于第二基本形式模长的Pinching定理及推广的J.Simons型积分不等式     

Banach空间的p— Asplund 伴随空间

我们称一个定义在Banach空间E上的连续凸函数f具有Frechet可微性质（FDP）,如果E上的每个实值凸函数g≤f均在E一个稠密的Gδ－子集上Frechet可微。本文主要证明了：对任何Banach空间E,均存在一个局部凸相容拓扑p使得1）（E,p)是Hausdorff局部凸空间;2） E上的每个范数连续具有FDP的凸函数均是p－连续的;3）每个p-连续的凸函数均具有FDP ;4）p等价某个范数拓扑当且仅不E是Asplund空间。     

On the Stability of Equilibria in Two-Degrees-of- Freedom Hamiltonian Systems Under Resonances

We consider the problem of stability of equilibrium points in Hamiltonian systems of two degrees of freedom under resonances. Determining the stability or instability is based on a geometrical criterion based on how two surfaces, related with the normal form, intersect one another. The equivalence of this criterion with a result of Cabral and Meyer is proved. With this geometrical procedure, the hypothesis may be extended to more general cases.     

关于局部对称空间中2-调和子流形

本文研究局部对称完备黎曼流形中的紧致2－调和子流形，得到了这类流形第二基本模式长平方的Pinching定理及推广的J．Simons型积分不等式。     

On Conformal Curves in 2-Dimensional de Sitter Space

In this paper, we examine the pseudo-spherical curves, which are equivalent to each other under the conformal maps preserving a fixed point in the de Sitter 2-space, by using the Clifford algebra Cl _2,1. Also, we find the parametric equations of de Sitter loxodromes.     

On the Dynamics of Gear Shifting

Continuously or discretely variable transmissions are used in a variety of machines to match prime mover characteristics to varying loads. In most cases, the transmissions provide a fairly rigid constraint on the motions of inertial elements associated with the prime mover and the load although compliance will allow some high frequency oscillatory behavior. In this paper, compliance effects are neglected and the emphasis is on correct representations of impulsive forces associated with rapid gear ratio changes. The aim is to represent jumps in speeds, momenta and energy at the shifting times. This allows an efficient computer model of the overall system dynamics to be made without the necessity of representing the high frequency dynamics of the transmission itself. Bond graph models of automotive systems will be used to illustrate some of the pitfalls associated with models of various types of shiftable transmissions but the concepts apply to a wide variety of machines.     

On the Dynamics of Elastic Strips

Summary. {The dynamics of elastic strips, i.e., long thin rods with noncircular cross section, is analyzed by studying the solutions of the appropriate Kirchhoff equations. First, it is shown that if a naturally straight strip is deformed into a helix, the only equilibrium helical configurations are those with no internal twist and whose principal bending direction is either along the normal or the binormal. Second, the linear stability of a straight twisted strip under tension is analyzed, showing the possibility of both pitchfork and Hopf bifurcations depending on the external and geometric constraints. Third, nonlinear amplitude equations are derived describing the dynamics close to the different bifurcation regimes. Finally, special analytical solutions to these equations are used to describe the buckling of strips. In particular, finite-length solutions with a variety of boundary conditions are considered. } Received February 16, 1999; accepted October 24, 2000 Online publication February 20, 2001     

On the Dynamics of Belt Drives

In modelling the dynamics of belt drives, one has to distinguish between taut and slack belts. While the former can be described by a linear model, the latter is inherently nonlinear and needs a more sophisticated analysis. The paper at hand presents an analytical approach to modelling slack belts in plane motion. To simplify the setting, the pulleys are assumed to have equal radii, such that only one quarter of the total system needs to be considered. The extension to a more general geometry is straightforward. The belt is assumed to have non-zero bending stiffness. The slackness of the belt should be high enough to allow .exural vibrations even if the belt is inextensible. The static and the stationary solutions are formulated analytically in terms of elliptic functions. As a preliminary study, the special case of a travelling string is considered yielding a .rst insight into the complexity of belt dynamics. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

伪黎曼空间型的2一调和类空子流形

用活动标架法给出常曲率的伪黎曼流形的类空子流形为2-调和的充要条件,研究平均曲率为零的一些条件.     

Resonances for steplike potentials: Forward and inverse results

We consider resonances associated to the one dimensional Schrödinger operator , where if x_M$"> and if , with . We obtain asymptotics of the resonance-counting function for several regions. Moreover, we show that in several situations, the resonances, , and determine uniquely up to translation.

     

Resonances in bounded media: Nonlinear and boundary effects

We study the response of nonlinear wave systems in bounded domains at or near resonance. There are typically two qualitatively distinct types of response which may be observed relating to whether or not higher harmonics are themselves resonant. We introduce a variety of nonlinear model problems at or near resonance and study the subsequent response. We explain how the features of this problem such as the form of nonlinearity, boundary conditions, and the nature of spectrum play a fundamental role in the qualitative nature of the response. Numerical simulations are carried out to provide further explanation and comparison with analytic approximations. The results of this study provide a better understanding of the impact and interplay between nonlinear and boundary effects and thus in turn will contribute to providing new insights into various physically motivated problems in acoustics and other settings.     

On the Quaternionic B 2-Slant Helices in the Euclidean Space E 4

In this paper we give a new definition of harmonic curvature functions in terms of B ₂ and we define a new kind of slant helix which we call quaternionic B ₂–slant helix in 4–dimensional Euclidean space E ⁴ by using the new harmonic curvature functions. Also we define a vector field D which we call Darboux quaternion of the real quaternionic B ₂–slant helix in 4–dimensional Euclidean space E ⁴ and we give a new characterization such as: "a: I ì \mathbb R ? E⁴{``\alpha : I \subset {\mathbb R} \rightarrow E^4} is a quaternionic B ₂–slant helix ${\Leftrightarrow H^\prime_2 -KH_{1} = 0"}${\Leftrightarrow H^\prime_2 -KH_{1} = 0"} where H ₂, H ₁ are harmonic curvature functions and K is the principal curvature function of the curve α.