关于有限群的可解性

利用极大子群的几乎正规的概念得到了有限群为可解群的若干充要条件．     

模糊集的无穷扩展原理

从普通集族{Xt}t?T（T为无限集）的直积Ⅱt?TXt出发，给出模糊集族At?F(Xt)(t?T)的直积概念；将通常的映射?：Ⅱt?TXt→Y扩展为模糊集族的直积Ⅱt?TF(Xt)到Y上的模糊集F(Y)的映射。     

对民族文化深层底蕴与旅游资源开发的思考--以吉林省延边朝鲜族自治州为例

朝鲜族的民族文化底蕴是中国朝鲜族两重性文化长期积淀的结果。在长期的历史发展过程中 ,朝鲜族形成了注重秩序、积极入世、民族传统心理与现代意识集于一身、重视结果而忽略过程的民族性格 ,在这种民族意识的支配下 ,延边注重旅游资源的有序开发 ,注重品牌效应 ,也重视打造民俗形象     

Robustness of a Class of Partial Diallel Cross Designs to the Unavailability of a Complete Block of Observations

Complete and partial diallel cross designs are examined as to their construction and robustness against the loss of a block of observations. A simple generalized inverse is found for the information matrix of the line effects, which allows evaluation of expressions for the variances of the line-effect differences with and without the missing block. A-efficiencies, based on average variances of the elementary contrasts of the line-effects, suggest that these designs are fairly robust. The loss of efficiency is generally less than 10%, but it is shown that specific comparisons might suffer a loss of efficiency of as much as 40%.     

Children's gender- and age-based categorization in similarity and induction tasks

The present studies examined children's and adults' preferences for gender- or age-based categorization using similarity and inductive inference tasks. Four-year-olds, 6-year-olds, and adults looked at pictures of people and decided which of two was more like a target (similarity condition) or which shared a novel age- or gender-related property with the target (inference condition). Age or gender-based matches were possible. The results are consistent with previous findings that gender-based classification decreases with age. However, they also demonstrate that children use gender more for judging similarity than for making inferences about novel properties. Distinct patterns emerge from the two tasks: 6-year-olds and adults in both conditions categorize more by age than gender; 4-year-olds categorize by gender more than age in the similarity task, but by age more in the induction task. Only adults differentiated by property in the inference condition. These findings suggest that the salience of gender categories cannot entirely be attributed to their inductive potential. Gender has a salience beyond what would be predicted by its power for directing novel generalizations.     

试述台湾少年团在抗战中的宣传活动

1937年开始的抗日战争是中华民族抗击日本侵略的战争。大陆的中华儿女和海外炎黄子孙,包括广大的台港澳同胞都参加了抗战。他们当中,不仅有青壮年,还有老人和儿童。台湾少年团只是活跃在祖国抗日战场上的千万个儿童抗日团体之一,但其抗日活动有鲜明的特点。本文拟通过对台湾少年团在抗战中的宣传鼓动活动的考述,突出台湾少年为民族解放战争作出的贡献,再现其爱国精神和期盼祖国统一的心愿。     

5次交错群A_5的10阶子群的一个构造方法

A5的元最大阶数是5,使用有限群的Lagrange定理,A5的10阶子群元的阶只可能是2,5。但由于拉格朗日定理的逆不成立,因此是否存在A5的10阶子群仍是问题。该文通过对5-循环置换各次方幂的计算及其研究,找到A5的10阶子群元的构成规律,并使用构造性方法给出了5次交错群A5的6个10阶子群。     

一类非线性波动方程的新精确解

利用李群对称方法,通过构造变换不变量,将一类1 1维非线性波动方程化为常微分方程,得到了这一类非线性波动方程的一些新的显式精确解,包括孤子解、三角函数解和椭圆函数周期解。     

科技创新是现代化高校发展的重要标志

近年来,高校作为国家科技创新体系的重要组成部分,大力加强科学研究。北京大学让本科生提前介入科研,培养科研创新能力。高校创办的具有特色的大学科技园、高科技产业群,逐步发展成为普遍趋势,高校已经成为中国基础研究的主力军。高校现有的人才资源有效结合起来,就形成一批充满活力的科技创新集体。     

The Chinese-speaking Muslims (Dungans) of Central Asia: A Case of Multiple Identities in a Changing Context

Chinese-speaking Muslims, called Dungans in Central Asia and Huizu in China, were forced to migrate to present-day Kazakhstan, Kyrgyzstan and Uzbekistan at the end of the nineteenth century. They reconstructed their identity through interrelations with local populations and the soviet categorisation of nationality. But after 1991, their status has being gradually destabilised owing to the changes in economic, social and political rules as well as citizenship regulations in these countries. They have to readapt to the new situation created by the independence of the three former Soviet Republics, which has challenged their unity.