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681.
Freshwater mills historically were found throughout England serving a wide variety of uses. The decline in the need for water power over the last 100 years saw a reduction in the number of operational mills. Despite this decline, the associated river structures were rarely removed and many of these have exceeded their design life and have failed or are now starting to fail, with important geomorphological implications for the river. This paper investigates the geomorphological impacts of mills and their structures on English rivers, and considers their legacy for the contemporary management of these systems. 相似文献
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684.
Angelo Turco 《GeoJournal》2004,60(4):329-337
Territorial symbolism in sub-Saharan Africa calls to mind multiple forms of knowledge. More particularly, territorial significance
is fed both by magical and sacred beliefs and by knowledge based on empirical observation and concrete practices. These two
types of knowledge differ widely as to their nature, the procedures by which they are formed, and the cultural values they
embody. Nevertheless, semantic interaction between mythical knowledge and technical knowledge is remarkably rich. By blurring
the distinction between mythos and techne, this semantic interaction seems to constitute an important cultural tool for building feelings of social security in that
it reinforces and stabilizes socio-geographic patterns, and more especially those which regulate access to space and natural
resources.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
685.
Assessment of downstream trends in channel gradient, total and specific stream power: a GIS approach
Geographic Information Systems (GIS) analyses of Digital Elevation Models (DEMs) coupled with catchment area based discharge estimation techniques provide a relatively simple means of modelling contiguous downstream trends in channel gradient, total stream power, and in riverscapes conducive to regime analysis, also specific stream power. For a small, high relief, coastal catchment in SE Australia, good agreement was obtained between channel gradients derived from a 25 m cell-size DEM and field survey equivalents over distances of several kilometres, indicating that channel gradients derived from DEMs can have a reasonable degree of absolute as well as relative accuracy over multi-kilometre reach scales. Assessment of downstream rates of change in channel gradient and specific stream power across four river systems suggests that some of the river reaches most responsive to high magnitude floods occur in zones where these variables rapidly decrease downstream. Modelling of downstream trends in channel gradient, total and specific stream power from catchment-wide DEMs has potential to provide a framework with which to investigate conceptual and empirical models between channel gradient, stream power and the form and dynamics of river systems. 相似文献
686.
山西数字遥测地震台网各子台台址地脉动噪声分析 总被引:4,自引:0,他引:4
通过对山西数字遥测地震台网11个子台台址背景噪声进行分析和计算,得出了各台址背景噪声地脉动速度均方根值(RMS值)、观测动态范围、噪声信号功率谱。结果表明各台址背景噪声水平基本符合数字地震观测技术规范要求。 相似文献
687.
高分辨率数字航测相机现状和思考 总被引:4,自引:0,他引:4
本文根据国内外数字航测相机发展的实际情况,对于新型数字航测相机视场角、影像分辨率、像移补偿、摄影间隔和影像存贮器容量、相机系统的动态定位与定向以及真彩色与多光谱摄影等技术问题进行了分析并给出了相应的结论。 相似文献
688.
通过对秦沈客运专线一路桥过渡段路基动应力的现场实测,得到了行车速度对无缝线路桥路过渡段路基动应力的影响特征,同时,定义了速度动力系数的概念,并得到了过渡段路基中速度动力系数变化规律。同时提出随行车速度的提高,必存在一个临界车速使得列车在通过路桥过渡段时,其动响应(动应力、动应变、动位移、振动加速度等)变化总趋势发生改变。研究结果对铁路客运专线过渡段的设计和施工有参考意义。 相似文献
689.
云南地震数字遥测台网子台地动噪声分析 总被引:6,自引:1,他引:6
介绍了云南数字遥测台网的基本情况,阐述了地动噪声有效值和功率谱的计算方法。对选取的资料进行预处理后,计算分析了云南数字遥测台网全部子台的地动噪声水平,按地动噪声水平对子台进行了分类。指出了地动噪声分析对台网建设的作用。 相似文献
690.
Ethiopia and the Eastern Nile Basin 总被引:1,自引:0,他引:1