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3我国及国外关于城市环境噪声的规定 为了控制城市环境噪声,我国自上世纪80年代就制定了一系列法律、法规、标准及规定,分别就环境噪声中的工业生产噪声、交通运输噪声、社会生活噪声、建筑施工噪声的控制做出了一些规定. 相似文献
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Zhaowei Liu Yongcan Chen Dejun Zhu Erqing Hui Chunbo Jiang 《Environmental Fluid Mechanics》2012,12(4):341-346
An analytical solution for the vertical profiles of the horizontal velocity of channel flow with submerged shrub-like vegetation is investigated in this paper. At first, a shape function is proposed to fit the diameter change of different types of shrub-like vegetation. Using the momentum theorem and the mixing-length turbulence model, an analytical solution for the vertical profile of the horizontal velocity within the vegetation is obtained. The velocity distribution of the whole column is determined in tandem with the logarithmic velocity profile above the vegetation. The solution is compared with experimental data in excellent agreement. The results show that the flow above the vegetation has a logarithmic velocity profile while the flow within the vegetation is impacted greatly by the shape and density of vegetation. The flows within shrub-like vegetations are non-uniform and vary inversely with the shrub diameter. 相似文献
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为了研究活性污泥系统中丝状菌的存在与污泥气液传质的关系,实验测量了不同絮体结构丝状菌污泥对体积溶氧传质系数(kLa)的影响,并考察了改善气液传质效率对控制丝状菌膨胀的影响。实验结果表明,丝状菌对气液传质的影响主要取决于丝状菌的沉淀性能而不是丝状菌的数量。在由于溶氧不足导致丝状菌膨胀的条件下,可以通过改善丝状菌絮体结构提高系统的气液传质效率,即通过絮体结构调控消除溶氧不足的外在条件,从而实现了控制丝状菌膨胀的目的。研究成果以改善丝状菌结构为手段,从微生物本身出发提高系统曝气效果,为控制丝状菌膨胀提供了新的思路。 相似文献