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。     

朱德与中共第一代领导集体的形成

朱德进入中共中央第一代领导集体 ,凭藉的是他的卓越的军事贡献和丰富的政治经验。从“红军之父”到“中国军人的伟大导师” ,从“人民的救星”到“党的领袖” ,既表明了他对党和人民事业的无限忠诚 ,也蕴含着党和人民给予他的极大光荣 ,反映了他追求进步 ,服从真理 ,实事求是 ,不断创新的卓越品质。第一代领导集体形成的标志时期是党的七大。朱德在第一代领导集体中的地位非常重要 ,他实际上起了一个稳定的中和的作用 ;从194 5年到 195 6年 ,朱德在中共中央和中央军委的职务、地位和威望仅次于毛泽东。     

Demographic Shifts in the Czech Republic after 1989: A Second Demographic Transition View

A dramatic change in fertility,family formation and living arrangements tookplace in the Czech Republic over the 1990s. Theestablishment of democracy, profound socialtransformation and transition to the marketeconomy affected the values and demographicbehaviour of the young Czech generation. Thispaper examines whether these demographic shiftscan be interpreted within the framework of thesecond demographic transition. The theoreticalpart discusses the idea of the transition,outlining three distinctive conceptualisations.Two of them – the view of the transition as aprogression of characteristic interrelateddemographic changes and a broader viewstressing the importance of underlyingideational factors – fit the Czech situationvery well. A comparison with the Netherlandsreveals that the onset of the transition in theCzech Republic may be clearly located in thefirst half of the 1990s, lagging two decadesbehind the Netherlands.     

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。     

Family Cap and Nonmarital Fertility: The Racial Conditioning of Policy Effects

Using an experimental design, this research examines the effect of the nation's first family cap on the births, abortions, and contraception use of over 8,000 women receiving public assistance in New Jersey. The family cap denies additional cash benefits to children conceived while the mother is receiving public assistance. Our research shows that a targeted welfare benefit manipulation does influence fertility behavior; however, the effect is conditioned by race. We find that Black women in the experimental group have a 21% lower birth rate and a 32% higher abortion rate than Black women in the control group. We do not find a birth effect for Hispanic or White women. We discuss the policy implications of the effects of a segmented family cap.     

Trade-Offs Between Formal Home Health Care and Informal Family CareGiving

Using 1994 National Long Term Care Survey data, we estimated logistic regressions of formal and informal home health care use and hours. Home health care use and intensity were differentially impacted by chronic conditions, are higher for Medicaid enrollees and rural or small town residents, but lower for HMO enrollees. Decreases in the probability of home health care use increased informal instrumental activities of daily living (IADL) support four hours and decreased informal activities of daily living (ADL) support eight hours weekly. IADL caregiving substituted for formal care, but ADL caregiving declined with reductions in formal care. Public policy reducing formal home health care access may reduce informal ADL caregiving and increase informal IADL caregiving, producing net declines in support.     

社会资本与我国家族企业的发展

改革开放以来,我国家族企业迅速崛起。此现象按新古典经济学的理论无法解释,因为家族企业创业时既缺少物质资本,又缺少人力资本,也没有技术支持,甚至连存在的合法性都成问题。其实,经济增长不仅需要物质资本和人力资本,还需要社会资本。家族企业之所以在夹缝中突起,很大程度依靠其深厚的社会资本。但也要看到,如果社会资本不能应经济发展而提高,就可能走向反面,成为家族企业发展的障碍。     

Working Time,Gender and Family: An East‐West European Comparison

This article provides a comparison of three West European countries with five Central East European countries in respect of working time and the integration of work and family life. The countries are the Netherlands, Sweden and the UK in West Europe and Bulgaria, the Czech Republic, Hungary, Romania and Slovenia in Central East Europe. As well as providing an East–West comparison, the article also takes into account the differing institutional and policy contexts in the selected countries and the different routes to flexibility. A further aim of the article is to extend our understanding of the culture and values which underpin the organization of family and work in each country. Whilst there is a clear East–West divide, all eight countries demonstrate diverse routes to flexibility and different mixes of social policies and gender cultures which have lead to considerable differences in the integration of work and family life.     

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.