排序方式: 共有441条查询结果,搜索用时 15 毫秒
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中世纪英格兰运输役起源于庄园领主的物资供应需求,随着12、13世纪市场的激增以及运输条件的改善,市场型运输役逐渐普及。运输役一般由农民上层承担,其运输距离、目的地、运输种类等都受习俗制约。运输役衰落的原因主要有直营领地的衰落、运输的专职化以及私下交易的流行。运输役的兴衰与中世纪英格兰市场培育密切相关,是市场已有一定发育但还不太成熟的产物。 相似文献
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构造了一个由数量老龄化、结构老龄化和密度老龄化三个指标所组成的综合老龄化指数(CAI),并建立了一套人口老龄化空间类型划分方案,运用多尺度空间自相关分析对长春市人口老龄化空间的时空演变及空间类型进行研究。结果表明:①长春市近10年出现了老年人口郊区化的趋势,人口老龄化空间的“中心-边缘”分布格局在10年内没有发生显著改变,但空间扩散趋势十分明显,东部和南部近郊区出现了明显的人口老化趋势。②长春市形成了残留老化、集聚老化、自然老化和集聚稀释四种不同的人口老龄化类型区。城市核心区和远郊区形成以非老年人口大量流失为基本特征的残留老化型地区,而近郊区则形成以年轻人口大量涌入为特征的集聚稀释型地区,人口老龄化空间整体上呈现出一种城市中心区和远郊区的老化程度高于近郊区的夹层结构。 相似文献
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JAMES D. LEE SIYUAN SHEN MAJID T. MANZARI YIN-LIN SHEN 《Journal of Earthquake Engineering》2013,17(1):67-96
The dynamic finite element equations of a two-dimensional structure made of axial-flexural frame elements with tendon-driven actuators have been derived. A critical review of classical optimal control theory is made with respect to its application to the control of structure under seismic excitations. Seven control algorithms, including two newly proposed algorithms, have been described, investigated and discussed. The need of an optimal observer, Kalman filter, is discussed. The validity of separation theorem applicable to the optimal stochastic control of structure for earthquake resistance is shown. How the control system perform under the circumstances of actuator saturation is also shown. Several numerical examples are worked out to demonstrate and compare the efficiency and limitations of those control algorithms. 相似文献
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基于旅游行为的旅游目的地空间层次与管理 总被引:1,自引:0,他引:1
关于旅游目的地的空间研究比较丰富,视点主要在于经济与地理空间。但是,旅游业是市场导向非常明显的行业,从旅游行为角度研究旅游目的地的空间层次更具有现实意义,对指导旅游目的地的开发和管理更具有操作性。本论文从旅游行为导向、管理方便性角度,融入社区理念,提出了新的旅游目的地解读,将其划分为三个空间层次,即游览服务区、社区服务区和社会服务区,并分析了它的空间层次结构关系和主要要素。论文最后从规范管理角度提出管理层次与关系。 相似文献
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淮海经济区城市空间影响范围与城市经济区划分 总被引:3,自引:0,他引:3
运用因子分析法求取淮海经济区20个地级市的综合实力指数及等级划分。根据城市综合实力指数和等级划分,选取4个一级城市作为中心城市,然后运用断裂点公式计算中心城市与邻近城市的空间影响距离。再根据空间影响距离划分各中心城市经济影响区范围。最后以城市经济影响区为基础,综合考虑各城市的区域特征、发展潜力、现有经济规划、历史习惯和人文特征,确定城市经济区界限。研究淮海经济区城市经济区形成和划分的目的是指明各城市在整个区域内劳动地域分工中的地位,了解城市经济发展现状和主要特点。 相似文献
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中国乡村城市化研究:起源、概念、进展与展望 总被引:17,自引:0,他引:17
本文回顾了20世纪80年代以来我国乡村城市化研究的起源,对乡村城市化和自下而上城市化两个概念进行了辨析,对近20年来乡村城市化研究的内容、进展以及存在的主要问题进行了评述,并对未来乡村城市化研究的方向作出了展望。 相似文献
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钟兴麒 《中国边疆史地研究》2000,(1)
本文在1986年发表《唐代安西四镇之一的碎叶位置新探》一文的基础上,详检有关碎叶史事,从时空两方面综合分析,其绝大部分发生在哈密碎叶及其周围。巴尔喀什湖附近的碎叶,从乌质勒徙其牙帐以后,在整个四镇存在期间,一直是突骑施安身立命之处。裴行俭留王方翼于安西筑碎叶城,位于其东归途中的伊州(哈密),不可能在今新疆玛纳斯河以西。《资治通鉴》胡三省注,把王方翼筑碎叶城,放在焉耆都督府名下,是因为焉耆王龙嫩突在突骑施占据焉耆后隋唐军移徙伊州碎叶,该地曾长期作为焉耆都督府的侨置治所。“碎叶”(Suyab),突厥语意为两水交汇处,西域有多处以“碎叶”为地名,对有关史事必须具体分析,以免张冠李戴。 相似文献
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Chen Xin 《Frontiers of History in China》2006,1(2):199
Use, truth and time constitute the basic elements of the epistemological structure of history. That structure went through three stages: pre-modern (from ancient times to the late eighteenth century, before the professionalization of history took place), modern (the period of professional history, from the late eighteenth century to the 1970s), and post modern (post 1970s). In these three stages, use, truth, and time successively occupied the core of the epistemological structure of history. Postmodernist history, which puts time at the core of its epistemology, is an extreme form of historicism. Even more than historicism, it has emphasized the determining effect of time and change on historical truth and historical consciousness. The privatization of historical narrative and reading has prodded history to become experimental. Experimental history no longer proclaims the truth about the past. Instead, under specific historical circumstances, it strives to produce texts that will be recognized by individual historians and provides these texts to readers, who will make their own judgments. Whether these texts are true will be decided through the uses they produce. In this way, any historiographical practice will be an experiment conducted by an historian in the present and that will consist in searching for the truth about the past. The success of this experiment will depend entirely on the experimental environment, that is, on the conditions provided by the reading environment. 相似文献