Measurements of turbulent flow fields in a stilling basin of multi-horizontal submerged jets were made with the single- camera Particle Image Velocimetry （PIV）. The particle images were captured, processed, and subs...Measurements of turbulent flow fields in a stilling basin of multi-horizontal submerged jets were made with the single- camera Particle Image Velocimetry （PIV）. The particle images were captured, processed, and subsequently used to characterize the flow in terms of the 2-D velocity and vorticity distributions. This study shows that the maximum close-to-bed velocity in the stilling basin is approximately reduced by 60%, comparing to the jet velocity at the outlet of orifices. The jet velocity is distributed evenly at the latter half of the stilling basin and the time-averaged velocity of the cross section is reduced by 77%-85%, comparing to the jet velocity at the outlet of orifices. These results show that the vortices with horizontal axes are continuously repeated during the form-merge-split-disappear process. The vertical vortices are continuously formed and disappeared, they appear randomly near the slab and intermittently reach the slab of the stilling basin. The range of these vortices is small. Vortices with horizontal axes and ver- tical vortices do not coincide in space and the vortices with horizontal axes only affect the position of the tail of the vertical vortices attached to the slab of the stilling basin.展开更多
目的全面深入了解抗生素污染的研究状况和发展趋势,为该领域相关研究工作者提供有力参考。方法采用文献计量学方法,以Web of Science核心合集数据库为数据源,利用数据库文献检索分析功能和Excel软件对1990—2018发表的抗生素污染相关领...目的全面深入了解抗生素污染的研究状况和发展趋势,为该领域相关研究工作者提供有力参考。方法采用文献计量学方法,以Web of Science核心合集数据库为数据源,利用数据库文献检索分析功能和Excel软件对1990—2018发表的抗生素污染相关领域的研究文献进行检索与整理,从发文年代、发文国家/地区、研究机构、期刊分布等方面进行统计和分析。结果①研究抗生素污染的全球发文量呈上升趋势,美国相关文献的篇均引用次数和H指数都遥遥领先于其他国家,发文量不及中国,但中国的文献发表质量还不够高。②针对抗生素污染相关领域开展研究的机构较多,其中美国的机构研究水平较高。③相关文献大多发表在环境、生物、健康、化学等领域的刊物上。结论有关抗生素污染的研究文献在逐年增加;中国和美国对抗生素污染领域的研究有着更高的影响力,而美国的研究文献质量较高且更全面。抗生素污染带来的环境问题以及对人类健康水平的影响已引起相关学者的注意,我国还要继续加强对相关领域的研究。展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 51279118, 50479062)the Key Projects in the National Science and Technology Pillar Program (Grant No. 2008BAB29B04)
文摘Measurements of turbulent flow fields in a stilling basin of multi-horizontal submerged jets were made with the single- camera Particle Image Velocimetry （PIV）. The particle images were captured, processed, and subsequently used to characterize the flow in terms of the 2-D velocity and vorticity distributions. This study shows that the maximum close-to-bed velocity in the stilling basin is approximately reduced by 60%, comparing to the jet velocity at the outlet of orifices. The jet velocity is distributed evenly at the latter half of the stilling basin and the time-averaged velocity of the cross section is reduced by 77%-85%, comparing to the jet velocity at the outlet of orifices. These results show that the vortices with horizontal axes are continuously repeated during the form-merge-split-disappear process. The vertical vortices are continuously formed and disappeared, they appear randomly near the slab and intermittently reach the slab of the stilling basin. The range of these vortices is small. Vortices with horizontal axes and ver- tical vortices do not coincide in space and the vortices with horizontal axes only affect the position of the tail of the vertical vortices attached to the slab of the stilling basin.
文摘目的全面深入了解抗生素污染的研究状况和发展趋势,为该领域相关研究工作者提供有力参考。方法采用文献计量学方法,以Web of Science核心合集数据库为数据源,利用数据库文献检索分析功能和Excel软件对1990—2018发表的抗生素污染相关领域的研究文献进行检索与整理,从发文年代、发文国家/地区、研究机构、期刊分布等方面进行统计和分析。结果①研究抗生素污染的全球发文量呈上升趋势,美国相关文献的篇均引用次数和H指数都遥遥领先于其他国家,发文量不及中国,但中国的文献发表质量还不够高。②针对抗生素污染相关领域开展研究的机构较多,其中美国的机构研究水平较高。③相关文献大多发表在环境、生物、健康、化学等领域的刊物上。结论有关抗生素污染的研究文献在逐年增加;中国和美国对抗生素污染领域的研究有着更高的影响力,而美国的研究文献质量较高且更全面。抗生素污染带来的环境问题以及对人类健康水平的影响已引起相关学者的注意,我国还要继续加强对相关领域的研究。
