功能梯度材料复合板的热应力计算分析     

张开银  张建刚  吕运冰 《广东海洋大学学报》1997,(1)

对金属－功能梯度材料－陶瓷复合板结构进行了热应力分析，导出了功能梯度材料连续模型的温度分布及热应力分布的计算表达式，并就Zro2／NiCrAl梯度材料热应力分布的解析解和有限元解进行了比较。计算结果表明：功能梯度材料连续板模型，便于结构的热应力分析和结构的优化设计，有利于梯度材料结构的非均等分层，可进一步减缓层间的应力突变和残余应力。  相似文献   

中国城市体系的工业职能结构   总被引：21，自引：1，他引：20  

田文祝  周一星 《地理研究》1991,10(1):12-23

本文应用聚类分析方法对中国城市市区的工业职能进行了分类,并结合纳尔逊统计分析方法对聚类分析结果作了适当调整及补充,将中国1984年295个城市分成四个大类、十八个亚类和四十三个职能组。在工业职能分类的基础上,通过16个工业部门在全部城市中的分布特点的分析,初步概括了中国城市体系工业职能结构的特征。最后,运用分类结果,对中国城市工业的经济效盆从投入、产出两个方面进行了应用研究。  相似文献   

温州市域城镇体系规划构想     

董黎明 《地理学报》1987,(3)

本文在温州市域城镇体系规划实践的基础上,侧重分析影响城镇发展的地理背景和经济因素,应用城市地理学的基本理论探讨城镇体系的等级规模结构、职能分工系统及空间分布网络,并强调要发挥各级中心城市的作用。  相似文献   

Approaches to defining a planetary boundary for biodiversity     

《Global Environmental Change》2014

The idea that there is an identifiable set of boundaries, beyond which anthropogenic change will put the Earth system outside a safe operating space for humanity, is attracting interest in the scientific community and gaining support in the environmental policy world. Rockstrom et al. (2009) identify nine such boundaries and highlight biodiversity loss as being the single boundary where current rates of extinction put the Earth system furthest outside the safe operating space. Here we review the evidence to support a boundary based on extinction rates and identify weaknesses with this metric and its bearing on humanity's needs. While changes to biodiversity are of undisputed importance, we show that both extinction rate and species richness are weak metrics for this purpose, and they do not scale well from local to regional or global levels. We develop alternative approaches to determine biodiversity loss boundaries and extend our analysis to consider large-scale responses in the Earth system that could affect its suitability for complex human societies which in turn are mediated by the biosphere. We suggest three facets of biodiversity on which a boundary could be based: the genetic library of life; functional type diversity; and biome condition and extent. For each of these we explore the science needed to indicate how it might be measured and how changes would affect human societies. In addition to these three facets, we show how biodiversity's role in supporting a safe operating space for humanity may lie primarily in its interactions with other boundaries, suggesting an immediate area of focus for scientists and policymakers.  相似文献