Darboux Coverings and Rational Reductions of the KP Hierarchy

We use the method of Darboux coverings to discuss the invariant submanifolds of the KP equations presented as conservation laws in the space of monic Laurent series in the spectral parameter (the space of the Hamiltonian densities). We identify a special class of these submanifolds with the rational invariant submanifolds entering matrix models of two-dimensional gravity recently characterized by Dickey and Krichever. Four examples of the general procedure are provided.     

The Maximum or Minimum Number of Rational Points on Genus Three Curves over Finite Fields

We show that for all finite fields F_q, there exists a curve C over F_q of genus 3 such that the number of rational points on C is within 3 of the Serre–Weil upper or lower bound. For some q, we also obtain improvements on the upper bound for the number of rational points on a genus 3 curve over F_q.with an Appendix by Jean-Pierre Serre     

固定床传热参数中的等价关系

本文根据二维拟均相模型与二维非均相模型的等价条件建立了两种模型的传热参数之间的关系,所得结果适用于不存在床高效应的床层。根据本文的结果,只要用径向温度分布法测得床层的温度数据并反向拟合出二维拟均相模型中的传热参数,就可以在此基础上计算得到二维非均相模型中的传热参数,如此则为二维非均相模型的实际应用奠定了基础。     

A new linearized method for Benjamin‐Bona‐Mahony equations

In this article, a new method called linearized and rational approximation method based on differential quadrature method (DQM) is proposed for the Benjamin‐Bona‐Mahony (BBM) equation on a semi‐infinite interval. Numerical result indicates the high accuracy and relatively little computational effort of this method. © 2004 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2004     

齐次平衡法和浅水波中WBK方程的精确分析解

Based on the homogenous balance method and with the help of mathematica, the Backlund transformation and the transfer heat equation are derived. Analyzing the heat-transfer equation, the multiple soliton solutions and other exact analytical solution for Whitham-Broer-Kaup equations(WBK) are derived. These solutions contain Fan‘s, Xie‘s and Yan‘s results and other new types of analytical solutions, such as rational function solutions and periodic solutions. The method can also be applied to solve more nonlinear differential equations.     

Classification of hypersurfaces with parallel Mbius second fundamental form in S~(n+1)

Let M~n(n≥2) be an immersed umbilic-free hypersurface in the (n+1)-dimensional unit sphere S~(n+1). Then M~n is associated with a so-called Mobius metric g,and a Mobius second fundamental form B which are invariants of M~n under the Mobiustransformation group of S~(n+1). In this paper, we classify all umbilic-free hypersurfaces withparallel Mobius second fundamental form.     

管理信息系统的发展与展望

近年来，随着信息技术的飞速发展和管理的不断创新，管理信息系统的概念正在突破原有的界限．向着系统发展的网络化、系统开发方法的理性统一化以及系统运行的智能化的方向发展。本就此进行讨论，并提出一些看法。     

There exist non‐isomorphic STS(19) with equivalent point codes

The rows of a point by block incidence matrix of a design can be used to generate a code, the point code of the design. It is known that binary point codes of non‐isomorphic Steiner triple systems of order hr STS(v), are inequivalent when v ≤ 15, but whether this also holds for higher orders has been open. In the current paper, an example of two non‐isomorphic STS(19) with equivalent point codes is presented. © 2004 Wiley Periodicals, Inc.