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The Tseng-wen River is a small mountainous river in southern Taiwan that has distinct dry and flood seasons. Several lines of evidence have revealed that the depositional system at the mouth of the river has transformed from a deltaic system to an estuarine system. The evidence includes long to short-term shoreline changes, geomorphology of the river mouth, mixed sediment sources inside the river mouth, mixing and suspended sediment characteristics inside the river mouth, and the grain-size distribution patterns on the river bed. Unlike the long-term evolution of many other coastal systems, the transformation at the Tseng-wen River mouth is largely caused by the building of a reservoir in the middle reaches of the river. The present study provides an example that coastal environments can be influenced by human activities farther inland on a time scale much faster than what would occur naturally. 相似文献
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An annual in situ corrosion experiment of carbon steel and low alloy steel is reported in this paper. The results show that the corrosion rate varies with the beginning month of immersion. The corrosion rates of 09CuWSn steel panels immersed at the end of April and May when larger fouling organisms grow heavily are 0.1180 and 0.1342 mm/y respectively, 相似文献
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汶川地震次生地质灾害数量多、分布广且类型复杂,严重威胁灾区人民的生命财产安全。为了分析次生地质灾害发育分布规律,并用于减灾防灾,急需一种有效的方法来对现场调查获取的大量地质灾害数据进行管理。以信息建模理论为指导,运用统一建模语言UML,并结合GIS空间数据模型分析,以建立面向对象的空间数据模型,及实现海量地灾信息综合管理为目的,研发了汶川地震次生地质灾害信息综合管理系统(WIMS)。利用GIS的强大空间图形管理能力、数据库技术以及网络开发等技术,以发布图形服务与数据服务的方式实现地质灾害数据共享,解决了空间数据编辑及提升地图访问速度的关键技术问题。该系统不仅能够为灾害管理部门制定防治方案提供一定的参考依据,并且能够为广大群众提供一个认识地质灾害的公共平台,提高全民防灾意识。 相似文献
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Abstract– Simulants of lunar dust are needed when researching the lunar environment. However, unlike the true lunar dust, today’s simulants do not contain nanophase iron. Two different processes have been developed to fabricate nanophase iron to be used as part of a lunar dust simulant. (1) The first is to sequentially treat a mixture of ferric chloride, fluorinated carbon, and soda lime glass beads at about 300 °C in nitrogen, at room temperature in air, and then at 1050 °C in nitrogen. The product includes glass beads that are gray in color, can be attracted by a magnet, and contains α‐iron nanoparticles (which seem to slowly lose their lattice structure in ambient air during a period of 12 months). This product may have some similarity to the lunar glassy agglutinate, which contains FeO. (2) The second is to heat a mixture of carbon black and a lunar simulant (a mixed metal oxide that includes iron oxide) at 1050 °C in nitrogen. This process simulates lunar dust reactions with the carbon in a micrometeorite at the time of impact. The product contains a chemically modified simulant that can be attracted by a magnet and has a surface layer whose iron concentration increased during the reaction. The iron was found to be α‐iron and Fe3O4 nanoparticles, which appear to grow after the fabrication process. This growth became undetectable after 6 months of ambient air storage, but may last for several years or longer. 相似文献
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本文首先用北京和南京的总辐射及日照记录,比较了几种计算总辐射经验公式的精确程度,然后用哈蒙等人设计的图解,由日照求出中国东部总辐射的分布。 相似文献
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本文将遗传算法（GA）应用于非监督训练,提高了遥感数据的分类精度。遗传竞争学习算法（GA-CL）综合了遗传算法和简单的竞争学习算法,可用于改进非监督训练的结果。遗传算法在典型样本聚类的过程中可以避免得到局部最优值。Jeffries-Matusita（J-M）距离法是通过统计测量两个训练类别之间的分离度,可用于评价这种算法。将此算法应用于TM数据的结果显示,遗传算法改进了简单的竞争学习算法,与其他非监督训练算法相比,其提供了K-均值,GA-K-均值和简单的竞争学习算法。 相似文献