谱半径

In this paper, we mainly study the spectrum of simple connected graphs and the the double cyclic graph, achieving some new results.

本文中我们主要考虑一般简单连通图的谱半径的可达上界，以及双圈图的树图的谱半径的界，并得到一些新的结论。

Using matrix theory,we present a sharp upper bound on the spectral radius of digraph s and strongly connected diagraphs.

利用矩阵理论，给出了简单有向图的谱半径可达上界和强连通有向图的谱半径上界

Missirlis in article [1]. At the same time, a sufficient condition for convergence of the PSD method is given to be compared when the coefficient matrix A of the linear system Ax = b is a symmetric, positively defective matrix. In §3.2, an example is given to state that the range of our sufficient condition is wider than theorem 3.3 of article [1]. On the other hand, following a.n analogous approach of [14] and starting the functional relationshipwe have a perfect analysis for the PSD method to converge and optimum valves for the involved parameters under different conditions.Under the assumptions that A is a consistent ordered matrix with nonvanishing diagonal elements and the eigenvalues of the Jacobi matrix of A are real,we get necessary and sufficient conditions for the PSD method to convergence.The result is equal to theorem 1 of article [9].Under the same condition, we can see the optimal parameter and of corresponding spectral radius of thePSD method in [8]:(2)When A is a consistent ordered matrix with nonvanishing diagonal elements and the eigenvalues of the Jacobi matrix of A are imaginary or zero,we get necessary and sufficient conditions for the PSD method to convergence.In chapter 3, the optimal parameter and of corresponding spectral radius of the PSD method are given by table 3.3. Moreover, under the assumption 0

Missirlis在文献[1]中定理3.3的不准确，同时给出了当线性方程组Ax=b的系数矩阵A为对称正定阵时，PSD迭代法收敛的一个充分条件与之比较，并且在§2.3中用实例说明了对于一部分矩阵而言本文得到的充分条件广于[1]中定理3.3的充分条件；另一方面，按照文献[14]的方法，我们从PSD迭代法的特征值λ与其Jacobi迭代矩阵B的特征值μ的关系式：出发，在不同条件下对PSD迭代法的收敛性和最优参数以及最优谱半径进行了完整的分析：(1)在系数矩阵A为(1，1)相容次序矩阵且对角元全不为零，其Jacobi迭代矩阵B的特征值全为实数的条件下，给出了PSD迭代法收敛的充分必要条件，此结果与[9]中的定理1等价，此时最优参数及最优谱半径由[8]得：(2)第三章表3.3中给出了，当系数矩阵A为(1，1)相容次序矩阵且对角元全不为零，其Jacobi迭代矩阵B的特征值全为纯虚数或零时的PSD迭代法的收敛范围和最优参数，并且我们可以得到当0

If the pattern has a low rate of convergence, the time of the human and machines will be wasted and the answer are not surely attainable.So,we must look for the patterns with the high rate of convergence or try to settle some parameters of the iteration patterns (for instance the overrelaxation parameter of SOR iterative method).

本文第二章针对AOR迭代法考察了当线性方程组的系数矩阵A为(1，1)相容次序矩阵且其Jacobi特征值为纯虚数或零时的迭代收敛范围，最优参数(即最优松弛因子和最优加速因子)及与之相应的谱半径，并将此最优谱半径与相应的SOR的进行比较，定量的给出在不同条件下，AOR和SOR迭代法各有其优越性，从而圆满的解决了在这两种迭代法之间如何适当的选择最佳迭代法的问题。

In the solution of the Difichlet boundary problem ofLaplace equations, we provide an effective method for determining the spectral radiusand the best slack variable of block basic iterative methods. At the same time, wepresent the spectral radius and the best slack variable of basic iterative methods from thenine-point difference scheme.

在解决Laplace方程Dirichlet边值问题上，文章为确定块基本迭代方法的谱半径和SOR方法最优松弛因子提供了一个有效的方法，并推导了九点差分格式下的块基本迭代方法的谱半径和SOR方法最优松弛因子。

We study the spectral radius of graphs with k cut edges, and the

利用移接变形的方法研究具有k条割边的图的谱半径的上界，给出了该图类谱半径达到最大和第二大的极图。

Let be the complement graph of G and let be the spectral radius of .

设G为n阶简单图，ρ为G的谱半径，ρ-为补图 G-的谱半径。

Finally, for the spectral radius of a graph with a cut vertex, we give an inequality concerning the spectral radius of the graph and its subgraphs.

最后，对于有割点的图的谱半径给出一个与子图的谱半径有关的一个不等式。

In this paper,lower bounds on the spectral radius of adjacency matrices of trees and perfect trees are discussed by algebraic method and edge switching of graph,and all trees which reach lower bounds on the spectral radius are obtained.

利用代数方法、图的边变换，以及树的邻接矩阵谱与L ap lacian谱的关系，研究树和完美树的邻接矩阵谱半径和L ap lacian谱半径的下界，给出达到下界的所有极树，得到的新结果改进了文献[2]的结论。

The orderings of trees with respect to Hosoya Index;2. Based on the former research of the order of trees and trees with perfect matching by professors Tian Feng and Yuan Xiying.

在田丰教授等对树的拉普拉斯谱半径排序以及袁西英等对完美匹配树的拉普拉斯谱半径排序研究的基础上，对完美匹配树的谱半径进行了进一步的研究。

With Death guitarist Schuldiner adopting vocal duties, the band made a major impact on the scene.

随着死亡的吉他手Schuldiner接受主唱的职务，乐队在现实中树立了重要的影响。

But he could still end up breakfasting on Swiss-government issue muesli because all six are accused of nicking around 45 million pounds they should have paid to FIFA.

不过他最后仍有可能沦为瑞士政府&议事餐桌&上的一道早餐，因为这所有六个人都被指控把本应支付给国际足联的大约4500万英镑骗了个精光。