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21.
Natural Hazards - In hydrological research, flood events can be analyzed by flood hydrograph coincidence. The duration of the flood hydrograph is a key variable to calculate the flood hydrograph... 相似文献
22.
CHEN Hao ZHOU Jinxing CAI Qiangguo LU Zhongchen & LI Zhongyan Institute of Geographic Sciences Natural Resources Research Chinese Academy of Sciences Beijing China Institute of Forestry Science Chinese Academy of Forestry Science Beijing China Research Center for Eco-Environment Sciences Chinese Academy of Sciences Beijing China Computing Institute of Science Engineering North China Electric Power University Beijing China 《中国科学D辑(英文版)》2005,48(2):230-240
Threshold of environmental elements in drainage basin sediment yield refers to, under effect of climate, underlying surface and human activity, a turning point of abrupt changes in drainage sediment yield related to environmental element characteristics. Previous studies on threshold of sediment yield of relevant drainage basins were mainly concentrated on impact of natural zones with a few researches on impact of other environmental elements. Particularly studies on compound environmental element threshold in drainage basin sediment yield remain blank today. Studies indicate that sediment yield in drainage basins is affected by compound interactions and complex actions. Based on single element analysis, the present paper gives quantitatively compound threshold of environmental elements affecting sediment yield of the drainage basin between Hekouzhen and Tongguan in the middle Yellow River by the method of multi-variant, polynomial formula regression analysis. 相似文献
23.
该文介绍了基于组件式GIS技术的决策气象服务系统建设的总体框架, 并阐述了系统的建设内容, 主要包括电子地图建设、气象制图输出、实时与历史资料检索、灾情分析、台风预警与损失评估以及参数化制图等功能; 同时对GIS应用于决策气象服务系统的若干关键技术问题进行了深入讨论与分析, 如数据共享与转换、气象要素插值算法、空间信息检索方法、基于插件技术的模型评估方法、三维可视化技术; 最后给出了相关结论, 并指出该系统将为全国综合性决策服务系统提供一个良好的建设思路。 相似文献
24.
Wang Kai-Rang Lin Jun Liu Lian-Guang Liu Chun-Ming Gao Guan-Nan 《Chinese Astronomy and Astrophysics》2012
Solar activities can cause the anomalies of electric power transmission systems, especially, for an extra-long distance transmission system. Using the data of coronal mass ejection (CME) from SOHO/LASCO (Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph), and the data of the geomagnetically induced current (GIC) and geomagnetic storm from the North China Electric Power University and Finnish Meteorological Institute, respectively, we analyze some important observational features and physical properties of the earth-directed halo CMEs associated with the GIC events. After classifying the observed halo CMEs according to their symmetry, it is found that the halo CMEs associated with GIC events are mainly the 3 types: completely symmetric, brightness-asymmetric, and outline-asymmetric. The geomagnetically induced current events driven by the three different types of halo CMEs have different characteristics in the intensity, duration, and period. We ?nd that the brightness-asymmetric halo CMEs are most likely to cause the major damage to the transmission systems. And that the geomagnetically induced current has also a good correlation with the time variation of geomagnetic ?eld. 相似文献
25.
《Ocean Engineering》2004,31(14-15):1859-1914
In this paper, a new state-space model of the potential-radiation hydrodynamics in moored ocean engineering floating structures and its parameter identification are presented. The raw data for this goal are the added mass and potential-damping matrices in frequency-discrete domain.In a preliminary study of existing approaches in the literature, two mathematical models and their estimation are comparatively analysed in detail. These served in the development of the new approach that shares certain main advantages of the previous approaches.The model is identified in a least-squares sense using a weighted norm and a free control parameter to accomplish a trade-off between quality and stability. This reduces numerical instability problems and also keeps the analytical and computational benefits of a parametric state-space model. The model can be conveniently expressed in any usual canonical form in state space.The application of the model acceptably accurate reproduces the behaviour of the potential-radiation hydrodynamic forces in time. Case studies involving a semisubmersible and buoys are shown to demonstrate the features of the proposed approach. 相似文献
26.
Natural Hazards - From now until 2030, China will be in a sprint to achieve reductions of 40–45% in carbon emission intensity by 2020 and 60–65% by 2030 compared to 2005; rigid... 相似文献
27.
气相色谱法测试土壤中分段石油烃的标准化定量方法初探 总被引:2,自引:1,他引:1
目前土壤样品中分段石油烃的分析方法中石油烃包括的碳原子数范围和采用的校准物质不统一,造成不同实验室的量值不具有可比性。为保证不同实验室之间结果的可比性,本文尝试建立一种石油烃相邻碳原子数标准化定量方法。该方法主要包括:(1)规定了石油烃包括的碳原子数范围为气相色谱峰中正己烷和正四十碳烷之间所有的烃(含正己烷);(2)总石油烃(TPH)分为挥发性石油烃(VPH)和半挥发性石油烃(SPH),分别选取碳原子数为6~10的5个正构烷烃作为VPH校准物质,选取碳原子数为10~40的31个正构烷烃作为SPH校准物质。采用平均响应因子法或一次线性回归法,建立校准物质的峰面积-浓度的校准关系;(3)采用相邻峰标准化校准方法,逐一定量所有的目标色谱峰;(4)计算正构烷烃含量、总石油烃含量和任意分段的石油烃含量。该方法为环境样品中石油烃分析方法的标准化建设提供了数据基础。 相似文献
28.
滦赤路位于北京市延庆区北部山区,由于公路依山势沿沟谷山坡修建,山高坡陡,两侧边坡存在较多的危岩体,威胁到过往车辆及行人的安全。在对滦赤路(延庆段)危岩体进行详细野外调查的基础上,结合危岩体发育区的地形地貌、地层岩性、地质构造等地质环境条件,选取了两处典型危岩体,分析了典型危岩体的发育特征,研究了危岩体的形成影响因素和失稳机理,评价了危岩体的稳定性,并针对典型危岩体提出了相应的防治措施建议。 相似文献
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