Extreme waves have a profound impact on coastal infrastructure;thus,understanding the variation law of risky analysis and disaster prevention in coastal zones is necessary.This paper analyzed the spatiotemporal charac...Extreme waves have a profound impact on coastal infrastructure;thus,understanding the variation law of risky analysis and disaster prevention in coastal zones is necessary.This paper analyzed the spatiotemporal characteristics of extreme wave heights adjacent to China from 1979 to 2018 based on the ERA5 datasets.Nonstationary extreme value analysis is undertaken in eight repre-sentative points to investigate the trends in the values of 50-and 100-year wave heights.Results show that the mean value of extreme waves is the largest in the eastern part of Taiwan Island and the smallest in the Bohai Sea from 1979 to 2018.Only the extreme wave height in the northeastern part of Taiwan Island shows a significant increase trend in the study area.Nonstationary analysis shows remarkable variations in the values of 50-and 100-year significant wave heights in eight points.Considering the annual mean change,E1,E2,S1,and S2 present an increasing trend,while S3 shows a decreasing trend.Most points for the seasonal mean change demon-strate an increasing trend in spring and winter,while other points show a decreasing trend in summer and autumn.Notably,the E1 point growth rate is large in autumn,which is related to the change in typhoon intensity and the northward movement of the typhoon path.展开更多
随着数据规模的增长,集中式环境下的查询算法已无法满足对大规模数据的查询需求,对此提出一种分布式动态Skyline查询(Distributed Dynamic Skyline Query,DDSQ)算法。DDSQ算法包含本地计算和合并计算两个过程。本地计算中,基于B树索引...随着数据规模的增长,集中式环境下的查询算法已无法满足对大规模数据的查询需求,对此提出一种分布式动态Skyline查询(Distributed Dynamic Skyline Query,DDSQ)算法。DDSQ算法包含本地计算和合并计算两个过程。本地计算中,基于B树索引提出基础扫描算法(Basic Scan Algorithm based on B-tree,BSAB)来快速计算分布式动态Skyline候选集;提出优化的扫描算法(Optimized Scan Algorithm based on B-tree,OSAB),与BSAB相比,OSAB进一步减少了扫描空间,提高了计算效率。合并计算中,采用轮转策略对动态Skyline候选集进行合并计算。通过一系列实验验证了DDSQ算法的有效性。展开更多
基金support of the Natural Science Foundation of China(No.51909114)the Major Research Grant(Nos.U1806227,U1906231)from the National Natural Science Foundation of China(NSFC).
文摘Extreme waves have a profound impact on coastal infrastructure;thus,understanding the variation law of risky analysis and disaster prevention in coastal zones is necessary.This paper analyzed the spatiotemporal characteristics of extreme wave heights adjacent to China from 1979 to 2018 based on the ERA5 datasets.Nonstationary extreme value analysis is undertaken in eight repre-sentative points to investigate the trends in the values of 50-and 100-year wave heights.Results show that the mean value of extreme waves is the largest in the eastern part of Taiwan Island and the smallest in the Bohai Sea from 1979 to 2018.Only the extreme wave height in the northeastern part of Taiwan Island shows a significant increase trend in the study area.Nonstationary analysis shows remarkable variations in the values of 50-and 100-year significant wave heights in eight points.Considering the annual mean change,E1,E2,S1,and S2 present an increasing trend,while S3 shows a decreasing trend.Most points for the seasonal mean change demon-strate an increasing trend in spring and winter,while other points show a decreasing trend in summer and autumn.Notably,the E1 point growth rate is large in autumn,which is related to the change in typhoon intensity and the northward movement of the typhoon path.
文摘随着数据规模的增长,集中式环境下的查询算法已无法满足对大规模数据的查询需求,对此提出一种分布式动态Skyline查询(Distributed Dynamic Skyline Query,DDSQ)算法。DDSQ算法包含本地计算和合并计算两个过程。本地计算中,基于B树索引提出基础扫描算法(Basic Scan Algorithm based on B-tree,BSAB)来快速计算分布式动态Skyline候选集;提出优化的扫描算法(Optimized Scan Algorithm based on B-tree,OSAB),与BSAB相比,OSAB进一步减少了扫描空间,提高了计算效率。合并计算中,采用轮转策略对动态Skyline候选集进行合并计算。通过一系列实验验证了DDSQ算法的有效性。
