为揭示江苏克氏原螯虾养殖环境中抗生素的分布特征和污染现状,利用超高效液相色谱-串联质谱法(UPLC-MS/MS)调查浦口和盱眙两个地区4个典型养殖塘水和沉积物中抗生素的残留情况。共检出14种抗生素(包括4种大环内酯类、2种四环素类、4种...为揭示江苏克氏原螯虾养殖环境中抗生素的分布特征和污染现状,利用超高效液相色谱-串联质谱法(UPLC-MS/MS)调查浦口和盱眙两个地区4个典型养殖塘水和沉积物中抗生素的残留情况。共检出14种抗生素(包括4种大环内酯类、2种四环素类、4种喹诺酮类和4种磺胺类),除浦口两养殖塘水体中的CTCHCL、OFL和AZI(浓度分别为16.528~57.140ng L-1和9.803~47.400 ng L-1),其他抗生素均以低浓度存在。抗生素浓度与水质指标的相关性分析结果表明,抗生素在水环境中的降解可能受水体富营养化、有机污染程度等水质状况的影响。基于RQs值对养殖环境中的抗生素进行风险评估,它们对生态系统中浮游动物的生长基本不会造成威胁;对藻类等浮游植物而言,浦口养殖水体中部分大环内酯类(SP、CTM)和喹诺酮类(O FL)抗生素具有中高度风险(0.161≤RQs≤2.92),盱眙养殖环境中目标抗生素生态风险较低(RQs≤0.181)。研究表明,江苏(特别是盱眙)克氏原螯虾养殖水体中抗生素污染水平相对较低,但仍存在一定的生态风险。建议采取全面的抗生素控制措施,以保护水产养殖生态系统的健康。展开更多
针对现有轨迹聚类算法中对轨迹之间的时空关联性考虑不足以及全局唯一距离阈值带来的算法的时空复杂度高以及聚类精度低的问题,提出了一种基于轨迹间时空关联性的数据聚类算法(The Data Clustering Algorithm Based on Spatio-temporal ...针对现有轨迹聚类算法中对轨迹之间的时空关联性考虑不足以及全局唯一距离阈值带来的算法的时空复杂度高以及聚类精度低的问题,提出了一种基于轨迹间时空关联性的数据聚类算法(The Data Clustering Algorithm Based on Spatio-temporal Correlation between Trajectories,DSCBT)。该方法主要包含两个阶段,在第一阶段中,首先根据最短停留时间限制和半径r确定初始中心代表点,然后将所在簇的最大距离作为该初始中心代表点对应的半径R,最后根据最短移动时间约束合并相邻的初始中心代表点并调整半径R,得到中心代表点集。第二阶段主要处理新增轨迹数据,首先将轨迹点与中心代表点集进行匹配,删除匹配成功的点产生新轨迹,然后对有聚类价值的新增轨迹执行第一阶段的操作,最后更新中心点集并完成聚类。实验结果表明,该算法能够有效降低算法的时间复杂度并提高聚类精度。展开更多
By reviewing the current situation of Sri Lanka's debt problem, as well as its nature, causes and relation with Chinese loans, this article argues that the loans from China are neither the main source nor the main...By reviewing the current situation of Sri Lanka's debt problem, as well as its nature, causes and relation with Chinese loans, this article argues that the loans from China are neither the main source nor the main cause of Sri Lanka's debt problem. Instead, the projects they financed will bring promising economic returns to Sri Lanka in the long run.展开更多
Among the major countries in the world,Russia and India are two that have always maintained relatively stable relations.However,recent years have witnessed profound transitions in the regional and global strategic env...Among the major countries in the world,Russia and India are two that have always maintained relatively stable relations.However,recent years have witnessed profound transitions in the regional and global strategic environments,hence increasing divergence between their foreign policy strategies.Furthermore,the traditional drivers of cooperation between the two countries are weakening,such that their disagreements are accumulating in plain sight.Their perceptions and policies surrounding the Indo-Pacific,in particular,have created significant strategic discord.In the foreseeable future,the foundational basis for strategic cooperation between Russia and India will not be fundamentally shaken,but reversing the trend of their drifting foreign policies will prove to be difficult.The gap between the two sides will continue to exist and is likely to further enlarge.The trajectory of Russia-India relations will entail changes in the international and regional landscapes.Overall,a stable Russia-India relationship is in China’s best interest.展开更多
文摘为揭示江苏克氏原螯虾养殖环境中抗生素的分布特征和污染现状,利用超高效液相色谱-串联质谱法(UPLC-MS/MS)调查浦口和盱眙两个地区4个典型养殖塘水和沉积物中抗生素的残留情况。共检出14种抗生素(包括4种大环内酯类、2种四环素类、4种喹诺酮类和4种磺胺类),除浦口两养殖塘水体中的CTCHCL、OFL和AZI(浓度分别为16.528~57.140ng L-1和9.803~47.400 ng L-1),其他抗生素均以低浓度存在。抗生素浓度与水质指标的相关性分析结果表明,抗生素在水环境中的降解可能受水体富营养化、有机污染程度等水质状况的影响。基于RQs值对养殖环境中的抗生素进行风险评估,它们对生态系统中浮游动物的生长基本不会造成威胁;对藻类等浮游植物而言,浦口养殖水体中部分大环内酯类(SP、CTM)和喹诺酮类(O FL)抗生素具有中高度风险(0.161≤RQs≤2.92),盱眙养殖环境中目标抗生素生态风险较低(RQs≤0.181)。研究表明,江苏(特别是盱眙)克氏原螯虾养殖水体中抗生素污染水平相对较低,但仍存在一定的生态风险。建议采取全面的抗生素控制措施,以保护水产养殖生态系统的健康。
文摘针对现有轨迹聚类算法中对轨迹之间的时空关联性考虑不足以及全局唯一距离阈值带来的算法的时空复杂度高以及聚类精度低的问题,提出了一种基于轨迹间时空关联性的数据聚类算法(The Data Clustering Algorithm Based on Spatio-temporal Correlation between Trajectories,DSCBT)。该方法主要包含两个阶段,在第一阶段中,首先根据最短停留时间限制和半径r确定初始中心代表点,然后将所在簇的最大距离作为该初始中心代表点对应的半径R,最后根据最短移动时间约束合并相邻的初始中心代表点并调整半径R,得到中心代表点集。第二阶段主要处理新增轨迹数据,首先将轨迹点与中心代表点集进行匹配,删除匹配成功的点产生新轨迹,然后对有聚类价值的新增轨迹执行第一阶段的操作,最后更新中心点集并完成聚类。实验结果表明,该算法能够有效降低算法的时间复杂度并提高聚类精度。
文摘By reviewing the current situation of Sri Lanka's debt problem, as well as its nature, causes and relation with Chinese loans, this article argues that the loans from China are neither the main source nor the main cause of Sri Lanka's debt problem. Instead, the projects they financed will bring promising economic returns to Sri Lanka in the long run.
基金the result of the initial research of a key project supported by the National Social Science Fund of China(NSSFC)on the“Indo-Pacific Sea Lane Security Support System in the Context of the‘Belt and Road Initiative’”(Grant No.:19AGJ002)。
文摘Among the major countries in the world,Russia and India are two that have always maintained relatively stable relations.However,recent years have witnessed profound transitions in the regional and global strategic environments,hence increasing divergence between their foreign policy strategies.Furthermore,the traditional drivers of cooperation between the two countries are weakening,such that their disagreements are accumulating in plain sight.Their perceptions and policies surrounding the Indo-Pacific,in particular,have created significant strategic discord.In the foreseeable future,the foundational basis for strategic cooperation between Russia and India will not be fundamentally shaken,but reversing the trend of their drifting foreign policies will prove to be difficult.The gap between the two sides will continue to exist and is likely to further enlarge.The trajectory of Russia-India relations will entail changes in the international and regional landscapes.Overall,a stable Russia-India relationship is in China’s best interest.
