On chromatic and flow polynomial unique graphs

It is known that the chromatic polynomial and flow polynomial of a graph are two important evaluations of its Tutte polynomial, both of which contain much information of the graph. Much research is done on graphs determined entirely by their chromatic polynomials and Tutte polynomials, respectively. Oxley asked which classes of graphs or matroids are determined by their chromatic and flow polynomials together. In this paper, we found several classes of graphs with this property. We first study which graphic parameters are determined by the flow polynomials. Then we study flow-unique graphs. Finally, we show that several classes of graphs, ladders, Möbius ladders and squares of n-cycle are determined by their chromatic polynomials and flow polynomials together. A direct consequence of our theorem is a result of de Mier and Noy [A. de Mier, M. Noy, On graphs determined by their Tutte polynomial, Graphs Comb. 20 (2004) 105-119] that these classes of graphs are Tutte polynomial unique.     

关于群的定义

群是基本的代数系统,群的定义对左(右)单位和左(右)逆元是成立的,而对左单位元和右逆元不一定成立。本文证明了群的定义对唯一左单位元和右逆元是成立的。     

关于非线性两点边界值问题u″ g(t,u)=f(t),u(0)=u(2π)=0的解的存在性和唯一性

本文给出了ｍａｘ＿ｍｉｎ原理的一个非变分形式，证明了非线性两点边界值问题ｕ″＋ｇ（ｔ，ｕ）＝ｆ（ｔ），ｕ（０）＝ｕ（２π）＝０的解的一个存在性和唯一性定理·     

广义绝对值方程算例分析

分别给出了广义绝对值方程存在唯一解的算例、存在多个解的算例以及无解的算例,并分析了这些算例中矩阵奇异值的特点.     

Comparing bacterial genomes from linear orders of patterns

We compare complete genomes from common words denoted MUMs for maximum unique matches. They allow to transform each genome into a linear order. We first evaluate the minimum length of a MUM shared by two genomes to be significant. Secondly, we compute maximal common chains of elements, that are in the same order in genomes. From these chains we define conserved genome segments as long DNA fragments having MUMs in the same order and with a bounded gap length between them. The resulting small number of segments allow to detect main evolutionary events as reversal or transposition of these fragments.     

The second expansion of the solution for a singular elliptic boundary value problem

In this paper we analyze the second expansion of the unique solution near the boundary to the singular Dirichlet problem −Δu=b(x)g(u), u>0, x∈Ω, u_|∂Ω=0, where Ω is a bounded domain with smooth boundary in RN, g∈C¹((0,∞),(0,∞)), g is decreasing on (0,∞) with and g is normalised regularly varying at zero with index −γ (γ>1), , is positive in Ω, may be vanishing on the boundary.     

Inverse scattering by an inhomogeneous penetrable obstacle in a piecewise homogeneous medium

This paper is concerned with the inverse problem of scattering of time-harmonic acoustic waves by an inhomogeneous penetrable obstacle in a piecewise homogeneous medium. The well-posedness of the direct problem is first established by using the integral equation method. We then proceed to establish two tools that play important roles for the inverse problem: one is a mixed reciprocity relation and the other is a priori estimates of the solution on some part of the interfaces between the layered media. For the inverse problem, we prove in this paper that both the penetrable interfaces and the possible inside inhomogeneity can be uniquely determined from a knowledge of the far field pattern for incident plane waves.     

一类完全三部图的色唯一性

用P(G,λ)表示简单图G的色多项式.设G是一个给定的简单图,若对任意简单图H,当P(H,λ)=P(G,λ)时都有H和G同构(记为H≌G),则称图G是色唯一的.本文证明了以下结果:设n,k,△都为非负整数,其中k≥0,△∈{4,5},若n≥1/3k~2+1/3△~2-1/3k△-1/3k-1/3△+4/3,则完全三部图K(n,n+△,n+k)是色唯一的.同时还给出了一个猜想.     

On a Counterexample Concerning Unique Continuation for Elliptic Equations in Divergence Form

We construct a second order elliptic equation in divergence form in3, with a nonzero solution which vanishes in a half-space.The coefficients are -Hölder continuous of any order < 1. This improves a previous counterexample of Miller (1972, 1974).Moreover, we obtain coefficients which belong to a finer class ofsmoothness, expressed in terms of the modulus of continuity.     

关于图θ（a,b,c,d,e）的色性

在两个顶点之间用五条长分别是ａ，ｂ，ｃ，ｄ，ｅ的内部不交的路连接而形成的图记为θ（ａ，ｂ，ｃ，ｄ，ｅ），其中ａ≤ｂ≤ｃ≤ｄ≤ｅ，本文讨论了它的色性．得出了θ（ａ，ｂ，ｃ，ｄ，ｅ）是色唯一的一个充分条件．