结构塑性设计优化理论

2—2 园板的举例轴线对称荷载的园板是最简单的例子,无论怎样都保持一般壳体问题的所有基本特性.有一个用特尔斯克(Tresca)材料做的简支夹芯园板.承受均匀分布荷载,在园环中有相等的γ种θ(图2)弯曲的主要比率Kr和Kθ仅仅是通过主要的弯矩M_γ和M_θ而归结为应变.屈服的轨迹已消楚的知道,如图3所示的特尔斯克六方晶体.     

三大前沿技术助力打造货运安全

从使用封条到使用卫星，货物的安全得益于科技的发展。新生的智能技术和检测技术为货运安全提供了新的解决思路，但再好的技术也要使用得当，否则也将一无是处。     

Who Gains from the Demographic Dividend? Forecasting Income by Age

Changes in the population age structure are known to influence the total income per person, but little is known about whether the changes are equally shared across the population or are concentrated on particular age groups and/or birth cohorts. The answer to this question has potentially important implications for income inequality, human capital investment, and fertility decision-making. We propose a new model of intergenerational transfers which distinguishes between the effects of changes in population structure and the effects of changes in family age structure. Using age-specific data from annual income and expenditure surveys of Taiwan between 1978 and 1998, we show that changes in age structure have had a very favorable effect on Taiwan's income growth. The gains are not equally shared by all age groups, however. Children and young adults have benefited the most, while the elderly have benefited the least. The population and family age structures have independent effects on per capita income; the effect of the population age structure is most important. Generational differences in per capita income are closely related to intergenerational differences in earnings, suggesting only a weak form of altruism. Finally, we predict that, on average, population aging will adversely influence the per capita income growth in Taiwan in the coming decades.     

Headship rates and the household formation process in Great Britain

"This paper looks at the changes in headship rates in Great Britain over the period 1960-1979, and attempts to explain them in terms of economic variables, such as real income and the real cost of housing. Such variables are found to be significant for some household types, but not for others. Notably, young single person household formation appears to be more supply constrained and to respond to appropriate supply variables." Furthermore, "some comparisons are made with similar studies done on similar data from the USA and France. These studies reveal a number of features in common, but also some differences, and these are commented upon."     

Waves of migration: a new situation

An attempt is made to forecast migration trends affecting those countries that were formerly part of the Soviet Union. "The new migratory trends are characterized by at least three fundamentally important elements: the ouster of the newly arrived population from the social niche that it had recently occupied, emigration from overpopulated regions, and growing emigration beyond the borders of the former Union."     

PLANNING FOR ECONOMIC DEVELOPMENT:The COMMUNITY ECONOMIC DEVELOPMENT PLAN

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Current issues in European migration

The authors examine recent migration patterns into and within the European Union. Issues involving asylum and migration policy are discussed, and problems caused by differing naturalization practices in different countries are considered. Skill patterns of migrants and problems in labor markets are also investigated.