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大型锻件中疏松缺陷压实条件研究 被引量:10
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作者 任运来 聂绍珉 +1 位作者 陈颖 DuanX 《机械工程学报》 EI CAS CSCD 北大核心 2003年第3期126-129,共4页
利用对数应变的可加性和体积可压缩材料的塑性方程,建立了大型锻件中疏松孔隙率与应力和变形的解析关系式,进而得到疏松压实条件。应力和应变状态对疏松压实有各自不可替代的作用。静水应力的存在是疏松压实的必要条件。压实过程初期,... 利用对数应变的可加性和体积可压缩材料的塑性方程,建立了大型锻件中疏松孔隙率与应力和变形的解析关系式,进而得到疏松压实条件。应力和应变状态对疏松压实有各自不可替代的作用。静水应力的存在是疏松压实的必要条件。压实过程初期,静水应力起主要作用,压实过程后期,变形起减小应力值的作用。利用铅质疏松材料的压实试验,检验了疏松材料中孔隙率与应力、变形的关系,表明所得的疏松压实条件可作为实际生产的参考依据。 展开更多
关键词 材料加工 塑性力学 塑性成形 大椴件
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英美国家公园体制比较及启示 被引量:21
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作者 徐菲菲 Dorothy Fox 《旅游学刊》 CSSCI 北大核心 2015年第6期5-8,共4页
中国国家公园体制建设是当前政界、业界与学界关注的热点。世界各国国家公园的设立背景、目的、程序、任务、土地、资金、机构等不尽相同,但均适应并体现了各国的政治、经济、社会文化特征。本文通过英美国家公园体制的比较,旨在促进... 中国国家公园体制建设是当前政界、业界与学界关注的热点。世界各国国家公园的设立背景、目的、程序、任务、土地、资金、机构等不尽相同,但均适应并体现了各国的政治、经济、社会文化特征。本文通过英美国家公园体制的比较,旨在促进我国国家公园的体制建设与持续发展。 展开更多
关键词 国家公园 体制比较 社会文化特征 体制建设 设立背景 持续发展 土地 资金
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Predicting ecological regime shift under climate change: New modelling techniques and potential of molecular-based approaches
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作者 Richard STAFFORD V. Anne SMITH +2 位作者 Dirk HUSMEIER Thomas GRIMA Barbara-ann GUINN 《Current Zoology》 SCIE CAS CSCD 2013年第3期403-417,共15页
Ecological regime shift is the rapid transition from one stable community structure to another, often ecologically infe- rior, stable community. Such regime shifts are especially common in shallow marine communities, ... Ecological regime shift is the rapid transition from one stable community structure to another, often ecologically infe- rior, stable community. Such regime shifts are especially common in shallow marine communities, such as the transition of kelp forests to algal turfs that harbour far lower biodiversity. Stable regimes in communities are a result of balanced interactions be- tween species, and predicting new regimes therefore requires an evaluation of new species interactions, as well as the resilience of the 'stable' position. While computational optimisation techniques can predict new potential regimes, predicting the most likely community state of the various options produced is currently educated guess work. In this study we integrate a stable regime op- timisation approach with a Bayesian network used to infer prior knowledge of the likely stress of climate change (or, in practice, any other disturbance) on each component species of a representative rocky shore community model. Combining the results, by calculating the product of the match between resilient computational predictions and the posterior probabilities of the Bayesian network, gives a refined set of model predictors, and demonstrates the use of the process in determining community changes, as might occur through processes such as climate change. To inform Bayesian priors, we conduct a review of molecular approaches applied to the analysis of the transcriptome of rocky shore organisms, and show how such an approach could be linked to meas- ureable stress variables in the field. Hence species-specific microarrays could be designed as biomarkers of in situ stress, and used to inform predictive modelling approaches such as those described here. 展开更多
关键词 Regime shift Phase shift Altemative stable state INTERTIDAL Food web RESILIENCE
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