The Danjiangkou Reservoir is the water source for the middle route of the South-to-North Water Diversion Project in China. Thus, its water quality status is of great concern. Five water quality indicators （dissolved ...The Danjiangkou Reservoir is the water source for the middle route of the South-to-North Water Diversion Project in China. Thus, its water quality status is of great concern. Five water quality indicators （dissolved oxygen, permanganate index, ammonia nitrogen, total nitrogen, and total phosphorus）, were measured at three monitoring sites （the Danjiangkou Reservoir dam, the Hejiawan and the Jiangbei bridge）, to investigate changing trends, and spatiotemporal characteristics of water quality in the Danjiangkou Reservoir area from January 2006 to May 2012. We then applied a Bayesian statistical method to evaluate the water quality comprehensively. The normal distribution sampling method was used to calculate likelihood, and the entropy weight method was used to determine indicator weights for variables of interest in to the study. The results indicated that concentrations of all five indicators increased during the last six years. In addition, the water quality in the reservoir was worse during the wet season （from May to October）, than during the dry season （from November to April of the next year）. Overall, the probability of the water＇s belonging to quality category of type lI, according to environmental quality standards for surface water in China, was 27.7%-33.7%, larger than that of its belonging to the other four water quality types. The increasing concentrations of nutrients could result in eutrophication of the Danjiangkou Reser- voir. This method reduced the subjectivity that is commonly associated with determining indicator weights and artificial classifications, achieving more reliable results. These results indicate that it is important for the interbasin water diversion project to implement integrated water quality management in the Danjiangkou Reservoir area.展开更多
A dual-polarized multiple-input multiple-output(MIMO)antenna is proposed for 5G base stations.Each antenna element consists of two orthogonally placed fan-shaped dipole elements and45°dual-polarized feed-ing str...A dual-polarized multiple-input multiple-output(MIMO)antenna is proposed for 5G base stations.Each antenna element consists of two orthogonally placed fan-shaped dipole elements and45°dual-polarized feed-ing structures are used to achieve broadband operation.The resonant frequency of the array element is from 3.3 to 4.2 GHz,which covers the mainstream spectrum allocations of 5G mobile networks.H-shaped coupling elements are used to improve the isolation between the neighboring antenna elements and the mutual coupling is reduced by over 4 dB.The envelope correlation of a 2×2 array is provided for verification.展开更多
To the Editor:Montegazza in 1866 was the first to suggest banks for frozen human semen.[1]In 1981,China's first human sperm bank was successfully established at the CITIC Xiangya Hospital.During the previous four ...To the Editor:Montegazza in 1866 was the first to suggest banks for frozen human semen.[1]In 1981,China's first human sperm bank was successfully established at the CITIC Xiangya Hospital.During the previous four decades,from 1981 to 2020,there were 27 human sperm banks in Chinese mainland.Human sperm banks provide cryopreservation of spermatozoa services for males needing to preserve fertility for an extended period in the Chinese mainland.展开更多
基金Acknowledgements This study was supported by the National Science and Technology Support Program （No. 2011BAC12B02）, the National Science Foundation for Innovative Research Group （No. 51121003）, and the Outstanding Doctoral Thesis Fund of Beijing Normal University （No. 105512GK）. We are grateful to the editors and anonymous reviewers＇ careful review of this paper, whom have contributed substantially to improving the paper.
文摘The Danjiangkou Reservoir is the water source for the middle route of the South-to-North Water Diversion Project in China. Thus, its water quality status is of great concern. Five water quality indicators （dissolved oxygen, permanganate index, ammonia nitrogen, total nitrogen, and total phosphorus）, were measured at three monitoring sites （the Danjiangkou Reservoir dam, the Hejiawan and the Jiangbei bridge）, to investigate changing trends, and spatiotemporal characteristics of water quality in the Danjiangkou Reservoir area from January 2006 to May 2012. We then applied a Bayesian statistical method to evaluate the water quality comprehensively. The normal distribution sampling method was used to calculate likelihood, and the entropy weight method was used to determine indicator weights for variables of interest in to the study. The results indicated that concentrations of all five indicators increased during the last six years. In addition, the water quality in the reservoir was worse during the wet season （from May to October）, than during the dry season （from November to April of the next year）. Overall, the probability of the water＇s belonging to quality category of type lI, according to environmental quality standards for surface water in China, was 27.7%-33.7%, larger than that of its belonging to the other four water quality types. The increasing concentrations of nutrients could result in eutrophication of the Danjiangkou Reser- voir. This method reduced the subjectivity that is commonly associated with determining indicator weights and artificial classifications, achieving more reliable results. These results indicate that it is important for the interbasin water diversion project to implement integrated water quality management in the Danjiangkou Reservoir area.
文摘A dual-polarized multiple-input multiple-output(MIMO)antenna is proposed for 5G base stations.Each antenna element consists of two orthogonally placed fan-shaped dipole elements and45°dual-polarized feed-ing structures are used to achieve broadband operation.The resonant frequency of the array element is from 3.3 to 4.2 GHz,which covers the mainstream spectrum allocations of 5G mobile networks.H-shaped coupling elements are used to improve the isolation between the neighboring antenna elements and the mutual coupling is reduced by over 4 dB.The envelope correlation of a 2×2 array is provided for verification.
基金Guangzhou Municipal Science and Technology Bureau(No.202002030480)Guangdong Provincial Natural Science Foundation(No.2021A1515011544)。
文摘To the Editor:Montegazza in 1866 was the first to suggest banks for frozen human semen.[1]In 1981,China's first human sperm bank was successfully established at the CITIC Xiangya Hospital.During the previous four decades,from 1981 to 2020,there were 27 human sperm banks in Chinese mainland.Human sperm banks provide cryopreservation of spermatozoa services for males needing to preserve fertility for an extended period in the Chinese mainland.
