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为了更好地学习和贯彻近期中央领导重要讲话精神,本刊从本期开始,在“大讲堂”中连续刊登有关学习中央领导重要讲话精神的体会文章,为关注国土资源管理事业发展的广大作者和读者开辟一块相互学习、交流的平台,为保护耕地、节约集约用地创造良好的社会氛围: 相似文献
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在乙醇存在下,以偶氮胂Ⅲ为指示剂,乙二胺、磺基水杨酸为掩蔽剂,EDTA容量法直接测定稀土萃取分离工艺负载有机相中稀土浓度。省去了有机相的反萃取分离过程,提高了测定的准确度。对不同浓度的稀土有机相样品进行测定,其相对标准偏差(n=5)在1.00—0.29%范围。方法适合于环烷酸体系萃取分离稀土元素工艺各级水相、有机相中稀土浓度的直接测定。 相似文献
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The flow past various mechanical cavity, which is a common structure on the surface of the underwater vehicle, and generating hydrodynamic noise has attracted considerable attention in recent years. In this paper, a hybrid method is presented to investigate the hydrodynamic noise induced by mechanical cavities with various shapes. With this method, the noise sources in the near wall turbulences or in the wake are computed by the large eddy simulation (LES) and the generation and propagation of the acoustic waves are solved by the Ffowcs Williams-Hawkings (FW-H) acoustic analogy method with acoustic source terms extracted from the time-dependent solutions of the unsteady flow. The feasibility and reliability of the current method was verified by comparing with experimental data (Wang, 2009). The 2D cavity models with different cross-section shapes and 3D cavity models with different cavity mouth shapes (rectangular and circular) are developed to study the influence of cavity shape on the hydrodynamic noise. By comparing the flow mechanisms, wall pressure fluctuations, near-field and far-field sound propagation distributions, it is found that the quadrangular cavity with equal depths of leading-edge and trailing-edge is preferred for its inducing lower hydrodynamic noise than the cylindrical cavity does. 相似文献
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为了更好地学习和贯彻近期中央领导重要讲话精神,本刊从本期开始,在“大讲堂”中连续刊登有关学习中央领导重要讲话精神的体会文章,为关注国土资源管理事业发展的广大作者和读者开辟一块相互学习、交流的平台,为保护耕地、节约集约用地创造良好的社会氛围: 相似文献
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本方法提出在硫代锑酸钠、多硫化钠、硫代硫酸钠、亚硫酸钠、硫酸钠等多种价态的硫化合物共存下,直接测定锑电解液中硫化钠的方法。即在5%的氢氧化钠溶液中,以亚硝基铁氰化钠为指示剂,用铁氰化钾标准溶液直接滴定锑电解液中的硫化钠。试验了不同价态的硫化合物对测定的影响,提 相似文献
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