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Natural Hazards - The 2013 outbreak of smog in China triggered unprecedented public attention in the country, which played a critical role in crisis communication and management. This study... 相似文献
974.
Underdamped slug tests with unsaturated‐saturated flows by considering effects of wellbore skins
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An analytical solution is presented for the slug tests conducted in a partially penetrating well in an unconfined aquifer affected from above by an unsaturated zone. The solution considers the effects of wellbore skin and oscillatory responses on underdamped slug tests. The flow in the saturated zone is described by a two‐dimensional, axially symmetric governing equation, and the flow in the unsaturated zone above the water table by a linearized one‐dimensional Richards' equation. The unsaturated medium properties are represented by the exponential constitutive relationships. A Laplace domain solution is derived using the Laplace and finite Fourier transform and the solution in the real‐time domain is evaluated using the numerical inverse Laplace transform method. The solution derived in this study is more general and reduces to the most commonly used solutions for slug tests in their specified conditions. It is found that the unsaturated flow has a significant impact on the slug test conducted in an unconfined aquifer. The impact of unsaturated flow on such a slug test is enhanced with a larger anisotropy ratio, a shorter well screen length, a shorter distance between the well screen and the water table, or a larger well screen radius. The impact of unsaturated flow on slug tests decreases as the degree of penetration (the length of well screen) increases. For a fixed well screen length, the impact of unsaturated flow on slug tests decreases as the distance between the centre of screen and the water table increases. A large dimensionless well screen radius (>0.01) leads to significant effects of unsaturated flow on slug tests. The unsaturated flow reduces the oscillatory responses to underdamped slug tests. The unsaturated zone has significant impact on slug test under high‐permeability wellbore skin. 相似文献
975.
We investigate the periodicity in the PMOD composite of the daily total solar irradiance (TSI) from 21 September 1978 to 9 June
2009. Besides the Schwabe cycle period (10.32 years), the quasi-rotation period is found to be statistically significant in
TSI, whose value is about 32 days, longer than that in sunspot activity (27 days), and it intermittently appears around the
sunspot maximum times. The quasi-rotation period in TSI is inferred to be mainly caused by sunspot activity, but to be modulated
by bright features as well. It was previously found that variations of TSI over a Schwabe solar cycle mainly come from the
combination of the sunspots’ blocking and the intensification due to bright faculae, plages, and network elements, with a
slight dominance of the bright-feature effect during the maximum of the Schwabe cycle. For the sunspot-blocking and the bright-feature
effect to contribute to TSI over a Schwabe solar cycle, the former is inferred to lead the latter by 29 days at least. 相似文献
976.
利用2007—2010年近4年的探空资料对比新疆中、北部地区乌鲁木齐、伊宁、克拉玛依、北塔山4个采用GTS (U)-2型P波段雷达-电子探空仪的探空站及其周围的阿勒泰、阿克苏和库尔勒3个采用GTS1型L波段雷达-电子探空仪的探空站的探空记录与预报场的偏差值,发现采用GTS1型探空仪的3个探空站的探空记录不仅在同一观测时段而且08:00(北京时,下同) 与20:00两个不同的观测时段与预报场差值的差异小;4个采用GTS (U)-2型探空仪的探空站的探空记录与预报场的差值在同一观测时间的差异小,但08:00和20:00的差异很大;且GTS (U)-2型探空仪与GTS1型探空仪20:00获取的探空记录与预报场差值的差异小,但08:00探空记录的差异大。综合对比结果表明:2007年1月—2010年3月新疆自治区采用的GTS (U)-2型探空仪的探空记录08:00可能存在问题,用户在数据资料分析时需要特别注意。 相似文献
977.
分布式水文模型全局敏感性高效分析方法研究(英文) 总被引:4,自引:0,他引:4
Sensitivity analysis of hydrological model is the key for model uncertainty quantification. However, how to effectively validate model and identify the dominant parameters for distributed hydrological models is a bottle-neck to achieve parameters optimization. For this reason, a new approach was proposed in this paper, in which the support vector machine was used to construct the response surface at first. Then it integrates the SVM-based response surface with the Sobol’ method, i.e. the RSMSobol’ method, to quantify the parameter sensitivities. In this work, the distributed time-variant gain model (DTVGM) was applied to the Huaihe River Basin, which was used as a case to verify its validity and feasibility. We selected three objective functions (i.e. water balance coefficient WB, Nash-Sutcliffe efficiency coefficient NS, and correlation coefficient RC) to assess the model performance as the output responses for sensitivity analysis. The results show that the parameters g1 and g2 are most important for all the objective functions, and they are almost the same to that of the classical approach. Furthermore, the RSMSobol method can not only achieve the quantification of the sensitivity, and also reduce the computational cost, with good accuracy compared to the classical approach. And this approach will be effective and reliable in the global sensitivity analysis for a complex modelling system. 相似文献
978.
邯郸石龙群的成因与年代研究 总被引:1,自引:0,他引:1
在野外调查的基础上,从地质学的角度对河北省南部邯郸县姜窑村出土的石龙群的成因及其形成年代进行了分析。结果表明,由1条大龙和9条小龙组成的石龙群是钙质胶结的洺河古河道沙体,形成于距今4万年前的晚更新世晚期,对应于玉木早冰期华北平原第Ⅲ古河道发育期。石龙沙体上的横切V形裂口是古河道沙体在干缩过程中形成的横切裂隙,沿古河道沙体下泄的富含碳酸钙的地下水在此渗出是形成裂隙两侧脊状突起和"龙爪"的直接原因,新构造运动可能是造成紫山断块隆升并迫使洺河改道和石龙群整体向北东方向翘首的直接原因。 相似文献
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