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排序方式: 共有851条查询结果,搜索用时 271 毫秒
41.
Muluken E. Muche Sumathy Sinnathamby Rajbir Parmar Christopher D. Knightes John M. Johnston Kurt Wolfe S. Thomas Purucker Michael J. Cyterski Deron Smith 《Journal of the American Water Resources Association》2020,56(3):486-506
Gridded precipitation datasets are becoming a convenient substitute for gauge measurements in hydrological modeling; however, these data have not been fully evaluated across a range of conditions. We compared four gridded datasets (Daily Surface Weather and Climatological Summaries [DAYMET], North American Land Data Assimilation System [NLDAS], Global Land Data Assimilation System [GLDAS], and Parameter‐elevation Regressions on Independent Slopes Model [PRISM]) as precipitation data sources and evaluated how they affected hydrologic model performance when compared with a gauged dataset, Global Historical Climatology Network‐Daily (GHCN‐D). Analyses were performed for the Delaware Watershed at Perry Lake in eastern Kansas. Precipitation indices for DAYMET and PRISM precipitation closely matched GHCN‐D, whereas NLDAS and GLDAS showed weaker correlations. We also used these precipitation data as input to the Soil and Water Assessment Tool (SWAT) model that confirmed similar trends in streamflow simulation. For stations with complete data, GHCN‐D based SWAT‐simulated streamflow variability better than gridded precipitation data. During low flow periods we found PRISM performed better, whereas both DAYMET and NLDAS performed better in high flow years. Our results demonstrate that combining gridded precipitation sources with gauge‐based measurements can improve hydrologic model performance, especially for extreme events. 相似文献
42.
微量元素对双孢蘑菇菌丝生长的影响 总被引:3,自引:0,他引:3
聋用固体平板和液体摇瓶培养试验方法,研究了Zn2+、Cu2+、Co2+、Mo(VI)、Mn2+等5种微量元素对双孢蘑菇2796菌丝生长的影响。通过测定各处理组的菌丝干重、胞内多糖、过氧化物酶活和菌丝生长势等生长参数表明,双孢蘑菇在添加上述5种浓度为20—40mg/L的微量元素时,对菌丝生长势、胞内多糖量和胞外蛋白量等都有促进作用,加入的浓度不同其促进程度也不同。加入Mn2+促进菌丝生长的效果最明显,使菌丝干重达最高值(200mg/100ml),胞内多糖量高达23mg/100ml,分别比对照组增加200%和400%,但添加高浓度的微量元素则会抑制菌丝的生长。 相似文献
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How to Constrain Multi‐Objective Calibrations of the SWAT Model Using Water Balance Components 下载免费PDF全文
Matthias Pfannerstill Katrin Bieger Björn Guse David D. Bosch Nicola Fohrer Jeffrey G. Arnold 《Journal of the American Water Resources Association》2017,53(3):532-546
Accurate discharge simulation is one of the most common objectives of hydrological modeling studies. However, a good simulation of discharge is not necessarily the result of a realistic simulation of hydrological processes within the catchment. We propose an evaluation framework that considers both discharge and water balance components as evaluation criteria for calibration of the Soil and Water Assessment Tool (SWAT). In this study, we integrated average annual values of surface runoff, groundwater flow, and evapotranspiration in the model evaluation procedure to constrain the selection of good model runs for the Little River Experimental Watershed in Georgia, United States. For evaluating water balance and discharge dynamics, the Nash‐Sutcliffe efficiency (NSE) and percent bias (PBIAS) were used. In addition, the ratio of root mean square error and standard deviation of measured data (RSR) was calculated for individual segments of the flow duration curve to identify the best model runs in terms of discharge magnitude. Our results indicate that good statistics for discharge do not guarantee realistic simulations of individual water balance components. Therefore, we recommend constraining the ranges of water balance components to achieve a more realistic simulation of the entire hydrological system, even if tradeoffs between good statistics for discharge simulations and reasonable amounts of the water balance components are unavoidable. Editor's note : This paper is part of the featured series on SWAT Applications for Emerging Hydrologic and Water Quality Challenges. See the February 2017 issue for the introduction and background to the series. 相似文献
47.
文中简述了摆管淋水试验装置的基本结构及其常见的校准方式,对其中的“摆角校准”这一技术难点提出了可行的解决方案并作了较详尽的说明分析。 相似文献
48.
Cascade-based attack vulnerability on the US power grid 总被引:5,自引:0,他引:5
The vulnerability of real-life networks subject to intentional attacks has been one of the outstanding challenges in the study of the network safety. Applying the real data of the US power grid, we compare the effects of two different attacks for the network robustness against cascading failures, i.e., removal by either the descending or ascending orders of the loads. Adopting the initial load of a node j to be Lj=[kj(ΣmΓjkm)]α with kj and Γj being the degree of the node j and the set of its neighboring nodes, respectively, where α is a tunable parameter and governs the strength of the initial load of a node, we investigate the response of the US power grid under two attacks during the cascading propagation. In the case of α<0.7, our investigation by the numerical simulations leads to a counterintuitive finding on the US power grid that the attack on the nodes with the lowest loads is more harmful than the attack on the ones with the highest loads. In addition, the almost same effect of two attacks in the case of α=0.7 may be useful in furthering studies on the control and defense of cascading failures in the US power grid. 相似文献
49.
沙尘试验设备参数的测量,目前没有相关的标准和指导文件。本文给出沙尘试验设备参数测量的一般方法,主要介绍了一种沙尘浓度测量方法。 相似文献
50.
实验基于企业污水站的改造工程,研究了MBR对玉米深加工废水的处理效果并对工艺运行参数优化提出建议.结果表明,该工艺对COD的去除率可以达到90%以上,出水稳定在26 mg/L左右;出水NH4-N达到1 mg/L以下;TN去除率达到70%以上,出水TN达到10 mg/L以下,出水完全达到排放标准.通过4种工况的比较,说明在污泥浓度8 g/L左右,曝气池内DO在3 mg/L左右,MBR内DO>4 mg/L,好氧段停留时间13.5 h,并保证3h以上的缺氧段水力停留段时间的条件下,A/O+ MBR工艺可以有效去除玉米深加工废水中的污染物. 相似文献