In order to study the pollution characteristics and potential ecological risks of heavy metals in soil of Xiangtan lotus planting area,the contents of Mn,Cu,As,Cd,Pb and Cr in soil and lotus seeds were analyzed in six...In order to study the pollution characteristics and potential ecological risks of heavy metals in soil of Xiangtan lotus planting area,the contents of Mn,Cu,As,Cd,Pb and Cr in soil and lotus seeds were analyzed in six main lotus planting areas.The comprehensive potential ecological risks of heavy metals in soil were evaluated by the potential ecological hazard index.The results showed that Cd concentration(mean value)was higher than the risk screening value and lower than the risk control value,and other heavy metals were lower or close to the risk screening value.The ecological risks of each element from large to small were Cd,Pb,As,Cu,Cr and Mn.The average value of the comprehensive ecological hazard index of the six sites was 224.7,which was a medium level of pollution risk.The lotus seeds corresponding to each site were also polluted by heavy metals to a certain extent,and Cd and Pb in the seeds exceeded the standard.Through the above analysis,the heavy metals in the soil of the lotus planting area presented a medium ecological risk.In order to ensure the safety of lotus production,it is necessary to strengthen the soil testing and management in the lotus planting area.展开更多
Based on the previous research on the model of rainstorm weather with low-level jet in Xiangtan,using the classification result of radar echo characteristics,the wind profile data provided by new generation of weather...Based on the previous research on the model of rainstorm weather with low-level jet in Xiangtan,using the classification result of radar echo characteristics,the wind profile data provided by new generation of weather radar in Changsha and hourly rainfall data,a thorough study of the heavy rainfall from 2 to 5 July 2016 in Xiangtan was conducted. It was concluded that heavy precipitation had the characteristics of the WPSH pattern of rainstorm with low-level jet at early stage,and then it converted to cold shear jet pattern in latter stage. When low-level southwest jet began to have momentum download,that is to say,there was more than 12 m/s of southwest jet below 1 km,and it rapidly strengthened and expanded downward,it was conducive to the occurrence of short-term rainstorm. The low-level jet would not immediately cause a strong precipitation when it reached the station,with a certain lag. A positive correlation existed between the increase of low-level jet index and precipitation intensity,and low-level jet index could predict the occurrence of heavy rainfall and rain intensity.展开更多
Objectives:To explore the level of active aging and correlates among rural elderly in Xiangtan County,China.Methods:A cross-sectional survey was conducted from July to November 2019.A total of 945 rural elderly from 3...Objectives:To explore the level of active aging and correlates among rural elderly in Xiangtan County,China.Methods:A cross-sectional survey was conducted from July to November 2019.A total of 945 rural elderly from 3 towns in Xiangtan County,China,were investigated by using the positive aging evaluation questionnaire(PAEQ),the activity of daily living scale(ADL),and the depression in old-age scale(DIA-S).Results:The average score in the PAEQ among the rural elderly of Xiangtan County was 72.81(range=21-105).A moderate negative correlation was found between the score in the PAEQ and those in the ADL(r=−0.361)and DIA-S(r=−0.495).Symptoms of depression(β:−0.321,P=0.001),number of chronic diseases(β:−0.281,P=0.001),subjective economic status(β:0.239,P=0.001),ADL(β:−0.196,P=0.001),education(β:0.126,P=0.001),number of children(β:0.097,P=0.001),and marital status(β:−0.060,P=0.001)were significantly associated with levels of active aging in rural elderly,whereas gender and age were not independently related to active aging.Conclusions:The level of active aging is at a moderately high level in the Chinese elderly in rural areas in Xiangtan County.The focus group of active aging in rural areas should be elderly people suffering from chronic diseases,physical decline,poor education and economic conditions,childlessness,and those without partners.展开更多
目前数据中心网络(data center network,DCN)的负载均衡方法存在对大小流的调度缺乏全局实时检测等不足,部分大流会造成拥塞、负载不均衡和带宽碎片等问题.针对上述问题,提出了一种SDN网络流量负载均衡算法—DSA-D.首先,对流量进行分类...目前数据中心网络(data center network,DCN)的负载均衡方法存在对大小流的调度缺乏全局实时检测等不足,部分大流会造成拥塞、负载不均衡和带宽碎片等问题.针对上述问题,提出了一种SDN网络流量负载均衡算法—DSA-D.首先,对流量进行分类,为大流计算所有源至目的主机可达路径的最短跳数路径集;然后,根据LLDP和ECHO测量链路时延以求得时延最优路径集;最后,采用概率拟合算法分配路径,实现数据中心网络流量负载均衡.在相同场景下的实验结果表明,与ECMP、Hedera和DIFF算法相比,DSA-D算法具有更好的吞吐量、链路带宽利用率和平均往返时延.展开更多
基金Supported by Provincial and Municipal Joint Fund of Self Science Fund in Hunan Province(2019JJ60045)Hunan Department of Education Project(18K063)+1 种基金Open Fund Project of Hunan Key Laboratory(E22007)College Student Innovation and Entrepreneurship Training Project in Hunan Province(S143528).
文摘In order to study the pollution characteristics and potential ecological risks of heavy metals in soil of Xiangtan lotus planting area,the contents of Mn,Cu,As,Cd,Pb and Cr in soil and lotus seeds were analyzed in six main lotus planting areas.The comprehensive potential ecological risks of heavy metals in soil were evaluated by the potential ecological hazard index.The results showed that Cd concentration(mean value)was higher than the risk screening value and lower than the risk control value,and other heavy metals were lower or close to the risk screening value.The ecological risks of each element from large to small were Cd,Pb,As,Cu,Cr and Mn.The average value of the comprehensive ecological hazard index of the six sites was 224.7,which was a medium level of pollution risk.The lotus seeds corresponding to each site were also polluted by heavy metals to a certain extent,and Cd and Pb in the seeds exceeded the standard.Through the above analysis,the heavy metals in the soil of the lotus planting area presented a medium ecological risk.In order to ensure the safety of lotus production,it is necessary to strengthen the soil testing and management in the lotus planting area.
基金Supported by Forecasters' Special Project of Hunan Meteorological Bureau in 2016(XQKJ16C003)
文摘Based on the previous research on the model of rainstorm weather with low-level jet in Xiangtan,using the classification result of radar echo characteristics,the wind profile data provided by new generation of weather radar in Changsha and hourly rainfall data,a thorough study of the heavy rainfall from 2 to 5 July 2016 in Xiangtan was conducted. It was concluded that heavy precipitation had the characteristics of the WPSH pattern of rainstorm with low-level jet at early stage,and then it converted to cold shear jet pattern in latter stage. When low-level southwest jet began to have momentum download,that is to say,there was more than 12 m/s of southwest jet below 1 km,and it rapidly strengthened and expanded downward,it was conducive to the occurrence of short-term rainstorm. The low-level jet would not immediately cause a strong precipitation when it reached the station,with a certain lag. A positive correlation existed between the increase of low-level jet index and precipitation intensity,and low-level jet index could predict the occurrence of heavy rainfall and rain intensity.
基金Hunan Social and Social Science Achievement Review Committee(No.XSP19YBC050)Hunan Provincial Health Commission(No.20200094).
文摘Objectives:To explore the level of active aging and correlates among rural elderly in Xiangtan County,China.Methods:A cross-sectional survey was conducted from July to November 2019.A total of 945 rural elderly from 3 towns in Xiangtan County,China,were investigated by using the positive aging evaluation questionnaire(PAEQ),the activity of daily living scale(ADL),and the depression in old-age scale(DIA-S).Results:The average score in the PAEQ among the rural elderly of Xiangtan County was 72.81(range=21-105).A moderate negative correlation was found between the score in the PAEQ and those in the ADL(r=−0.361)and DIA-S(r=−0.495).Symptoms of depression(β:−0.321,P=0.001),number of chronic diseases(β:−0.281,P=0.001),subjective economic status(β:0.239,P=0.001),ADL(β:−0.196,P=0.001),education(β:0.126,P=0.001),number of children(β:0.097,P=0.001),and marital status(β:−0.060,P=0.001)were significantly associated with levels of active aging in rural elderly,whereas gender and age were not independently related to active aging.Conclusions:The level of active aging is at a moderately high level in the Chinese elderly in rural areas in Xiangtan County.The focus group of active aging in rural areas should be elderly people suffering from chronic diseases,physical decline,poor education and economic conditions,childlessness,and those without partners.
文摘目前数据中心网络(data center network,DCN)的负载均衡方法存在对大小流的调度缺乏全局实时检测等不足,部分大流会造成拥塞、负载不均衡和带宽碎片等问题.针对上述问题,提出了一种SDN网络流量负载均衡算法—DSA-D.首先,对流量进行分类,为大流计算所有源至目的主机可达路径的最短跳数路径集;然后,根据LLDP和ECHO测量链路时延以求得时延最优路径集;最后,采用概率拟合算法分配路径,实现数据中心网络流量负载均衡.在相同场景下的实验结果表明,与ECMP、Hedera和DIFF算法相比,DSA-D算法具有更好的吞吐量、链路带宽利用率和平均往返时延.
