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741.
Tim D. Keane Christopher K. Sass 《Journal of the American Water Resources Association》2017,53(6):1513-1529
This paper recounts our predictions of channel evolution of the Black Vermillion River (BVR) and sediment yields associated with the evolutionary sequence. Channel design parameters allowed for the prediction of stable channel form and coincident sediment yields. Measured erosion rates and basin‐specific bank erosion curves aided in prediction of the stream channel succession time frame. This understanding is critical in determining how and when to mitigate a myriad of instability consequences. The BVR drains approximately 1,062 km2 in the glaciated region of Northeast Kansas. Once tallgrass prairie, the basin has been modified extensively for agricultural production. As such, channelization has shortened the river by nearly 26 km from pre‐European dimensions; shortening combined with the construction of numerous flow‐through structures have produced dramatic impacts on discharge and sediment dynamics. Nine stream reaches were established within three main tributaries of the BVR in 2007. Reaches averaged 490 m in length, were surveyed, and assessed for channel stability, while resurveys were conducted annually through 2010 to monitor change. This work illustrates the association of current stream state, in‐channel sediment contributions, and prediction of future erosion rates based on stream evolution informed by multiple models. Our findings suggest greater and more rapid sedimentation of a federal reservoir than has been predicted using standard sediment prediction methods. 相似文献
742.
This study used Programmable System-on-Chip to make a fuel cell controller to manage the fuel cell operating environment. When a proton exchange membrane fuel cell is reacting, its performance is closely related to the operating conditions, such as temperature, water management, etc. This article investigates purge time interval control and the related characteristics. The controller developed in this study is free from additional power requirements, using only the power provided by the fuel cell. 相似文献
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选取了6种有代表性的挥发性有机化合物(VOCs),异丙醇、二氯甲烷、乙酸乙烯酯、正己烷、苯和四氯化碳,实测了这些VOCs在气体采样罐(SUMMA罐)中的存储稳定性。结果表明:苯、正己烷和二氯甲烷在采样罐中均较稳定,其含量在84 d的存储期内基本无变化;乙酸乙烯酯在6个VOCs中最不稳定,在普通和惰性采样罐中含量均明显下降;异丙醇和四氯化碳的稳定性与采样罐的类型有关,在普通采样罐内含量下降明显,而在惰性采样罐内则相对稳定。实际监测工作中,为提高VOCs分析的准确性,如目标分析物有含氧类(醇,酮,酯等)或含卤素类VOCs,则采样后需尽快分析,同时尽量选择惰性采样罐为采样容器。 相似文献
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用高铝陶瓷球磨加工在120℃下烘干30h的风砂土、黑土和暗棕壤土壤样品。用X-射线荧光光谱法等分析样品中Cu,F3,Ti等元素,做均匀度检验,结果表明样品均匀。定值分析采用NA、ICP-MS等18种不同原理的分析技术。在1年多时间里,用X-射线荧光光谱法做稳定性实验,表明样品稳定。在IBM计算机上处理获取的全部数据。用Grubbs、多重比较S法等剔除离群值,求出最佳估计值。以最佳估计值按定值原则确 相似文献
750.
An equilibrator for sampling the partial pressures of halomethanes in seawater was designed and built, incorporating semipermeable membrane tubing to carry the gas phase. The equilibrator was tested for its ability to equilibrate chloromethane, bromomethane, iodomethane, and CFC-11. The residence time required for these halomethanes to equilibrate in the tubing (30 to 60 s) was determined experimentally. In a laboratory test, concentrations calculated from equilibrator measurements and based on published solubility values were found to differ by 6% to 16% from concentrations measured with a purge-and-trap apparatus, but uncertainties in the solubility values are likely to contribute significantly to the differences. In a comparison at sea, no significant difference was found between the semipermeable membrane equilibrator and another, more conventional equilibrator, except a 1.3% difference for CFC-11. This study demonstrates the feasibility of using semipermeable membranes in this and related applications. 相似文献