为弥补传统的广义线性模型(generalized linear model,GLM)方法的不足,并探索模式识别在运动脑科学当中的应用价值。使用支持向量机(support vector machine,SVM)模式识别算法,以低频振幅(fractional amplitude of low-frequency fluctu...为弥补传统的广义线性模型(generalized linear model,GLM)方法的不足,并探索模式识别在运动脑科学当中的应用价值。使用支持向量机(support vector machine,SVM)模式识别算法,以低频振幅(fractional amplitude of low-frequency fluctuations,fALFF)、局部一致性(regional homogeneity,ReHo)和度中心度(degree centrality,DC)作为学习特征,对射击运动组和滑冰运动组(分类1)、射击运动组和对照组(分类2)以及速滑运动组和对照组(分类3)之间进行二分类,并计算每一个脑区在分类算法当中的权重。使用留一交叉验证法计算分类正确率,使用总的准确率、接受者操作特性曲线(receiver operating characteristic curve,ROC)、以及预测准确率来衡量机器分类算法的优劣性。结果表明:分类1中SVM算法的正确率较高且分类效果更稳定,总的准确率(total accuracy,tACC)可以维持在96.67%以上,曲线下面积(area under curve,AUC)均为1,说明SVM算法对区分不同项目运动员脑静息态功能特征时更有优势;在分类2和分类3中,SVM算法效果取决于使用的指标。其中,使用fALFF或者综合使用三个静息态指标的分类效果较稳定(tACC均在80%以上,AUC均在0.88以上);小脑在分类1算法中占较多的权重,提示不同运动项目运动员的脑功能活动之间差异最明显的部位主要在小脑上。而分类2和3中,除了小脑,还有一些与运动执行和控制及其他功能活动相关的脑区参与了算法的构成。通过SVM分类算法的应用获得较为理想的结果,展示了模式识别方法在运动科学领域的应用价值。研究成果有助于体育科学研究者从新的角度更加全面地理解运动与脑的关系。展开更多
This study investigates the roles of the boreal summer intraseasonal oscillation(BSISO)in the diurnal rainfall cycle over Hainan Island during the warm season(April-September)using 20-year satellite-based precipitatio...This study investigates the roles of the boreal summer intraseasonal oscillation(BSISO)in the diurnal rainfall cycle over Hainan Island during the warm season(April-September)using 20-year satellite-based precipitation,ERA5 and the outgoing longwave radiation data with the phase composite analysis method.Results show that the spatial distributions of the hourly rainfall anomaly significantly change under the BSISO phases 1-8 while no clear variations are found on the daily and anomaly daily area-averaged rainfall over the island.During the BSISO phase 1,the rainfall anomaly distinctly increases in the morning over the southwest and late afternoon over the northeast of the island,while suppressed convection occurs in the early afternoon over the southwest area.Under this circumstance,strong low-level westerly winds bring abundant moisture into the island,which helps initiate the nocturnal-morning convection over the south coastal area,and drives the convergence region of sea breeze fronts to concentrate into the northwest.Opposite to Phase 1,an almost completely reversed diurnal cycle of rainfall anomaly is found in Phase 5,whereas a positive anomalous rainfall peak is observed in the early afternoon over the center while negative peaks are found in the morning and late afternoon over the southwest and northeast,owing to a strong low-level northeasterly anomaly flow,which causes relatively low moisture and enlarges a sea-breeze convergence area over the island.During Phase 8,strongest moisture is found over the island all through the day,which tends to produce highest rainfall in the afternoon with enhanced anomalous northerly.These results further indicate that multiscale interactions between the large-scale circulations and local land-sea breeze circulations play important roles in modulating diurnal precipitation cycles over the tropical island.展开更多
基金National Natural Science Foundation of China(41905096)Key Laboratory of South China Sea Meteorological Disaster Prevention and Mitigation of Hainan Province(SCSF202004)。
文摘This study investigates the roles of the boreal summer intraseasonal oscillation(BSISO)in the diurnal rainfall cycle over Hainan Island during the warm season(April-September)using 20-year satellite-based precipitation,ERA5 and the outgoing longwave radiation data with the phase composite analysis method.Results show that the spatial distributions of the hourly rainfall anomaly significantly change under the BSISO phases 1-8 while no clear variations are found on the daily and anomaly daily area-averaged rainfall over the island.During the BSISO phase 1,the rainfall anomaly distinctly increases in the morning over the southwest and late afternoon over the northeast of the island,while suppressed convection occurs in the early afternoon over the southwest area.Under this circumstance,strong low-level westerly winds bring abundant moisture into the island,which helps initiate the nocturnal-morning convection over the south coastal area,and drives the convergence region of sea breeze fronts to concentrate into the northwest.Opposite to Phase 1,an almost completely reversed diurnal cycle of rainfall anomaly is found in Phase 5,whereas a positive anomalous rainfall peak is observed in the early afternoon over the center while negative peaks are found in the morning and late afternoon over the southwest and northeast,owing to a strong low-level northeasterly anomaly flow,which causes relatively low moisture and enlarges a sea-breeze convergence area over the island.During Phase 8,strongest moisture is found over the island all through the day,which tends to produce highest rainfall in the afternoon with enhanced anomalous northerly.These results further indicate that multiscale interactions between the large-scale circulations and local land-sea breeze circulations play important roles in modulating diurnal precipitation cycles over the tropical island.
