CO_(2) released by soil serves as an important link between terrestrial ecosystems and atmospheric CO_(2), whose small chang‐es may significantly affect the global carbon cycle. In order to reveal the spatio-temporal...CO_(2) released by soil serves as an important link between terrestrial ecosystems and atmospheric CO_(2), whose small chang‐es may significantly affect the global carbon cycle. In order to reveal the spatio-temporal variations of CO_(2) concentrations in deep loess, this paper takes Qingliangsi Gully watershed in northwestern Shanxi Province, China as an example to sys‐tematically study soil CO_(2)concentration and its spatio-temporal variations and carbon sink significance under different watershed locations and different land use types. Results show that: (1) The release potential of the loess soil is larger in the depth range of 2 m, which is much more likely to be the CO_(2) release area. (2) Grassland and forest are more advanta‐geous in terms of soil microbial activity and soil carbon reserve compared with farmland. In addition, the change of land use type from farmland to grassland can increase soil organic carbon reserve, which is of far-reaching significance to the global carbon cycle. This is especially true in an area like the Loess Plateau with densely covered hills, gullies, and serious soil erosion in an area of 64×104 km2. (3) In the study area, the diurnal concentration of soil CO_(2) at different depths shows a weak "high-low-high-low" trend from 08:00 to 07:00 next day;and in deep soil it has a lag time compared with the daily change of temperature, generally about 4−12 h, which may be caused largely by the more compact loess structure. It is worth pointing out that the Loess Plateau in China, with a thickness of the loess of tens to hundreds of meters, has the most abundant soil resources in the world, and also stores a large amount of terrestrial soil carbon, which carries the hope of promoting the research of global carbon cycle.展开更多
Time-domain distance protection shows superior performance for transmission lines integrated with renewable energy sources (RESs).However,in 35-110 kV renewable power transmission systems,the inhomogeneity of the mixe...Time-domain distance protection shows superior performance for transmission lines integrated with renewable energy sources (RESs).However,in 35-110 kV renewable power transmission systems,the inhomogeneity of the mixed overhead lines (OHLs) and underground cables (UGCs) negatively affects the feasibility of distance protection.This paper proposes a robust algorithm of time-domain distance protection for renewable power transmission system with the mixed OHLs and UGCs.First,based on the time-domain mathematical model,the accuracy and robustness of the conventional algorithm under inhomogeneous line parameters are evaluated.To solve the “0/0” problem caused by weak signals,the singular value decomposition-based least squares method (SVD-LSM) is adopted to avoid calculation outliers and improve the protection reliability.Meanwhile,a weighting method based on Euclidean norm is designed to overcome the problem of computational non-convergence.It also ensures the protection operation speed by using a short time window.In addition,a distance correction method is designed for mixed lines to improve the accuracy of fault location.On the basis,a prototype of the protection device is developed,and extensive hardware-in-the-loop (HIL) tests are performed to verify its feasibility and superiority.In addition,the prototype of the protection device has been applied to actual renewable power transmission systems.展开更多
To the Editor:The latest variant of concern,Omicron,has become the dominant global variant immediately after it was first reported in November 2021.[1]It contains>30 mutations in the spike protein,with 17 mutations...To the Editor:The latest variant of concern,Omicron,has become the dominant global variant immediately after it was first reported in November 2021.[1]It contains>30 mutations in the spike protein,with 17 mutations in the receptor-binding domain,rendering it with increased transmissibility and capacity for immune evasion.[1,2]Moreover,the waning of protection has been observed over time since the coronavirus disease 2019(COVID-19)vaccination.[3]Therefore,a booster is highly recommended.A large-scale study in the UK assessing the effectiveness of the booster vaccination with either the BNT162b2 or mRNA-1273 indicated that the booster shot substantially increased protection against symptomatic infection in patients with the confirmed Omicron variant infection.[3]However,although the laboratory study has illustrated that the homologous booster with the inactivated COVID-19 vaccine could also yield potent neutralizing activity against the Omicron variant,[4]clinical evidence regarding the effectiveness of this vaccination program is limited.展开更多
基金supported by the National Natural Science Foundation, Grant No. 41671213the Fundamental Research Funds for the Central Universities, No. GK201803055Shaanxi prov‐ince Postdoctoral Science Foundation No. 2016 BSHEDZZ27.
文摘CO_(2) released by soil serves as an important link between terrestrial ecosystems and atmospheric CO_(2), whose small chang‐es may significantly affect the global carbon cycle. In order to reveal the spatio-temporal variations of CO_(2) concentrations in deep loess, this paper takes Qingliangsi Gully watershed in northwestern Shanxi Province, China as an example to sys‐tematically study soil CO_(2)concentration and its spatio-temporal variations and carbon sink significance under different watershed locations and different land use types. Results show that: (1) The release potential of the loess soil is larger in the depth range of 2 m, which is much more likely to be the CO_(2) release area. (2) Grassland and forest are more advanta‐geous in terms of soil microbial activity and soil carbon reserve compared with farmland. In addition, the change of land use type from farmland to grassland can increase soil organic carbon reserve, which is of far-reaching significance to the global carbon cycle. This is especially true in an area like the Loess Plateau with densely covered hills, gullies, and serious soil erosion in an area of 64×104 km2. (3) In the study area, the diurnal concentration of soil CO_(2) at different depths shows a weak "high-low-high-low" trend from 08:00 to 07:00 next day;and in deep soil it has a lag time compared with the daily change of temperature, generally about 4−12 h, which may be caused largely by the more compact loess structure. It is worth pointing out that the Loess Plateau in China, with a thickness of the loess of tens to hundreds of meters, has the most abundant soil resources in the world, and also stores a large amount of terrestrial soil carbon, which carries the hope of promoting the research of global carbon cycle.
基金supported in part by State Key Laboratory of Technology and Equipment for Defense Against Power System Operational Risks(No.SGTYHT/20-JS-221)the National Natural Science Foundation of China for Distinguished Young Scholars(No.52025071)the Natural Science Foundation of Tianjin,China(No.22JCQNJC01030).
文摘Time-domain distance protection shows superior performance for transmission lines integrated with renewable energy sources (RESs).However,in 35-110 kV renewable power transmission systems,the inhomogeneity of the mixed overhead lines (OHLs) and underground cables (UGCs) negatively affects the feasibility of distance protection.This paper proposes a robust algorithm of time-domain distance protection for renewable power transmission system with the mixed OHLs and UGCs.First,based on the time-domain mathematical model,the accuracy and robustness of the conventional algorithm under inhomogeneous line parameters are evaluated.To solve the “0/0” problem caused by weak signals,the singular value decomposition-based least squares method (SVD-LSM) is adopted to avoid calculation outliers and improve the protection reliability.Meanwhile,a weighting method based on Euclidean norm is designed to overcome the problem of computational non-convergence.It also ensures the protection operation speed by using a short time window.In addition,a distance correction method is designed for mixed lines to improve the accuracy of fault location.On the basis,a prototype of the protection device is developed,and extensive hardware-in-the-loop (HIL) tests are performed to verify its feasibility and superiority.In addition,the prototype of the protection device has been applied to actual renewable power transmission systems.
基金Key Research and Development Project of the Science and Technology Department of Sichuan Province(No.2021YFS0003,Zygd18020)High-level Talents Fund of the Wuhu Municipal Government(No.2021-134)
文摘To the Editor:The latest variant of concern,Omicron,has become the dominant global variant immediately after it was first reported in November 2021.[1]It contains>30 mutations in the spike protein,with 17 mutations in the receptor-binding domain,rendering it with increased transmissibility and capacity for immune evasion.[1,2]Moreover,the waning of protection has been observed over time since the coronavirus disease 2019(COVID-19)vaccination.[3]Therefore,a booster is highly recommended.A large-scale study in the UK assessing the effectiveness of the booster vaccination with either the BNT162b2 or mRNA-1273 indicated that the booster shot substantially increased protection against symptomatic infection in patients with the confirmed Omicron variant infection.[3]However,although the laboratory study has illustrated that the homologous booster with the inactivated COVID-19 vaccine could also yield potent neutralizing activity against the Omicron variant,[4]clinical evidence regarding the effectiveness of this vaccination program is limited.
