National Information Infrastructures in Central and Eastern Europe: Perspectives from the Library Community

Information infrastructures (IIs) are a complex arrangement of people, technology, institutions, content, and conduits. Their development is shaped by the environment in which they evolve and the visions ascribed to them by the various actors. This article examines the assumptions, meanings, and definitions associated with IIs in four Central and Eastern European (CEE) countries: Czech Republic, Hungary, Poland, and Slovakia. In particular, it focuses on how one stakeholder group, the library community, frames the policy debates around IIs. In-depth interviews were conducted in 1999 with 49 library policymakers in 37 institutions. The data shed light on the respondents' collective story and visions and help us gain a better understanding of political and cultural differences in the development of IIs.     

谱约束下矩阵的最佳逼近

如何求出以给定的λi为特征值、以已知的qi为λi对应特征向量的n阶方阵的集合是矩阵分析和系统理论的重要问题.利用Kronecker积及矩阵的广义逆作为工具对这一问题做出回答,并给出了在相应的解集合中与给定矩阵的最佳逼近解的表达式.     

基于可调子块迭代的加速SAGE算法在PET图像重建中的应用

提出了一种可调子块迭代(RBI)方法加速空间交替广义期望最大(SAGE)算法的收敛性.新的可调子块迭代的空间交替广义期望最大算法(RBI-SAGE)组合了RBI算法和SAGE算法的优点用于加速正电子发射断层(PET)图像重建.RBI-SAGE将投影数据分成不连续的子块,每一次迭代仅包含一个这样的子块.在每一个子块中用SAGE算法序列更新参数.实验中,运用RBI-SAGE算法与SAGE算法对PET图像进行重建.结果表明,RBI-SAGE收敛性能比SAGE算法优越,且重建图像质量较高.     

酉不变范数下广义极分解的扰动界

设A是m×n且秩为r的复矩阵,存在m×n次酉矩阵Q和n×n半正定矩阵H使得A=QH。此分解称为A的广义极分解。本文给出了在任意酉不变范数下次酉矩阵Q和半正定矩阵H的扰动界。     

广义(3+1)维KPB方程的对称约化、精确解和守恒律

运用李对称方法得到了(3+1)维Kadomtsev Petviashvili Boussinesq(KPB)方程的对称和约化方程。进而,利用齐次平衡原理和椭圆函数方法得到了方程的精确解。最后,给出了该方程的守恒律。     

Iris Localization Algorithm Based on Improved Generalized Symmetry Transform

Accuracy and fastness of iris localization are very important in automatic iris recognition. A new fast iris localization algorithm based on improved generalized symmetry transform (GST) was proposed by utilizing iris symmetry. GST was improved in three aspects: 1 ) A new distance weight function is defined. The new weight function, which is effective in iris localization, utilized the characteristic of irises that the iris is a circular object and it has one inner boundary and one outer boundary. 2) Each calculation of the symmetry measurement of a pair of symmetry points was performed by taking one point of a pair as the starting point of the transformation. This is the most important reason for fast iris localization, due to which, repetitious computation was largely excluded. 3) A new phase weight function was proposed to adjust GST to locate circle target much better because the inner part of iris is darker than the outer part. The edge map of iris image was acquired and GST was only implemented on the edge point, which decreased computation without loss of accuracy. The modification of distance weight function and phase weight function leads to the accuracy of localization, and other ideass peed up the localization. Experiments show that the average speed of new algorithm is about 7.0-8.5 times as high as traditional ones including integro-differential operator and Hough transform method.     

非惯性参照系中的Lagrange方程

从非惯性参照系中的惯性力表达式出发，找出与之相对应的广义势函数U’，进一步写出与之相对应的类Lagrange函数表达式L″，从而推导出在非惯性参照系中的第二类Lagrange方程和保守力系的Lagrange方程，并通过实例说明在非惯性参照系中Lagrange方程的应用，从分析力学的角度提出了求解非惯性参照系中的动力学问题的一种方法。     

广义对数均值的单调性和凹凸性

拓广平均由K.B.Stolarsky给出定义并列出其各种形式,而大部分含有两个变量的平均值都是拓广平均值的某种特殊情形.文章给出拓广平均值的一类情形,并利用有关中值定理和导数工具着重讨论了此类平均值函数的单调性、凹凸性.     

约束非线性l1问题的极大熵方法

本文给出求解约束非线性l1问题的极大熵方法并证明了其收敛性。给出了极大熵与增广La grange乘子法相结合的算法 ,最后给出一个算例。     

关于强正则环的几个等价刻划

设R是一个环 ,如果对于任意的x ,y∈R ,有xy -yx∈C(R) ,那么下列条件等价 :( 1 )R是强正则环 ;( 2 )R是VonNeumann正则环 ;( 3)R是广义正则环 .设R是半可换环 ,则以下条件等价 :( 1 )R是强正则环 ;( 2 )R的每一个极大的本质的左理想是左GP -内射模 ;( 3)R的每一个极大的本质的右理想是右GP -内射模 .