Climatic changes in the onset of spring in northern China associated with changes in the annual cycle and with a recent warming trend were quantified using a recently developed adaptive data analysis tool, the Ensembl...Climatic changes in the onset of spring in northern China associated with changes in the annual cycle and with a recent warming trend were quantified using a recently developed adaptive data analysis tool, the Ensemble Empirical Mode Decomposition. The study was based on a homogenized daily surface air temperature （SAT） dataset for the period 1955–2003. The annual cycle here is referred to as a refined modulated annual cycle （MAC）. The results show that spring at Beijing has arrived significantly earlier by about 2.98 d （10 yr）-1, of which about 1.85 d （10 yr）-1 is due to changes in the annual cycle and 1.13 d （10 yr）-1 due to the long-term warming trend. Variations in the MAC component explain about 92.5% of the total variance in the Beijing daily SAT series and could cause as much as a 20-day shift in the onset of spring from one year to another. The onset of spring has been advancing all over northern China, but more significant in the east than in the west part of the region. These differences are somehow unexplainable by the zonal pattern of the warming trend over the whole region, but can be explained by opposite changes in the spring phase of the MAC, i.e. advancing in the east while delaying in the west. In the east of northern China, the change in the spring phase of MAC explains 40%–60% of the spring onset trend and is attributable to a weakening Asian winter monsoon. The average sea level pressure in Siberia （55°–80°N, 50°–110°E）, an index of the strength of the winter monsoon, could serve as a potential short-term predictor for the onset of spring in the east of northern China.展开更多
癫痫是常见的神经系统疾病之一。癫痫发作的识别通常采用脑电测量记录中的癫痫发作起始点,以辅助医生进行诊断并对患者的发作状态报警。利用脑电信号的瞬态参数提出了一种自适应带宽特征,可用于提高癫痫发作检测精度。首先,利用经验模...癫痫是常见的神经系统疾病之一。癫痫发作的识别通常采用脑电测量记录中的癫痫发作起始点,以辅助医生进行诊断并对患者的发作状态报警。利用脑电信号的瞬态参数提出了一种自适应带宽特征,可用于提高癫痫发作检测精度。首先,利用经验模态分解(EMD)求得脑电信号的本征模态函数(IMF),并计算特定阶次IMF的解析信号;其次,利用该解析信号求解瞬时幅值与瞬时频率,对EEG信号的带宽特征添加权重,得到可用于癫痫检测的自适应带宽特征(Adaptive Bandwidth);最后,利用该特征完成癫痫发作检测。采用长达118 h 49 min的癫痫患者临床脑电数据进行实验,实验结果表明,自适应带宽特征的敏感性、特异性、准确性参数均比原特征取得明显提高。自适应带宽特征可提高癫痫发作检测精度并降低时间延迟,便于及时采取治疗措施,为临床检测提供了重要依据。展开更多
基金sponsored by the National Basic Research Program of China(Grant Nos. 2011CB952000, 2006CB400504)the Na-tional Natural Science Foundation of China (Grant No.41005039)+1 种基金Wu was sponsored by the National Science Foundation of USA (ATM-0917743)Yan was sponsored by the National Basic Research Program of China(Grant No. 2009CB421401)
文摘Climatic changes in the onset of spring in northern China associated with changes in the annual cycle and with a recent warming trend were quantified using a recently developed adaptive data analysis tool, the Ensemble Empirical Mode Decomposition. The study was based on a homogenized daily surface air temperature （SAT） dataset for the period 1955–2003. The annual cycle here is referred to as a refined modulated annual cycle （MAC）. The results show that spring at Beijing has arrived significantly earlier by about 2.98 d （10 yr）-1, of which about 1.85 d （10 yr）-1 is due to changes in the annual cycle and 1.13 d （10 yr）-1 due to the long-term warming trend. Variations in the MAC component explain about 92.5% of the total variance in the Beijing daily SAT series and could cause as much as a 20-day shift in the onset of spring from one year to another. The onset of spring has been advancing all over northern China, but more significant in the east than in the west part of the region. These differences are somehow unexplainable by the zonal pattern of the warming trend over the whole region, but can be explained by opposite changes in the spring phase of the MAC, i.e. advancing in the east while delaying in the west. In the east of northern China, the change in the spring phase of MAC explains 40%–60% of the spring onset trend and is attributable to a weakening Asian winter monsoon. The average sea level pressure in Siberia （55°–80°N, 50°–110°E）, an index of the strength of the winter monsoon, could serve as a potential short-term predictor for the onset of spring in the east of northern China.
文摘癫痫是常见的神经系统疾病之一。癫痫发作的识别通常采用脑电测量记录中的癫痫发作起始点,以辅助医生进行诊断并对患者的发作状态报警。利用脑电信号的瞬态参数提出了一种自适应带宽特征,可用于提高癫痫发作检测精度。首先,利用经验模态分解(EMD)求得脑电信号的本征模态函数(IMF),并计算特定阶次IMF的解析信号;其次,利用该解析信号求解瞬时幅值与瞬时频率,对EEG信号的带宽特征添加权重,得到可用于癫痫检测的自适应带宽特征(Adaptive Bandwidth);最后,利用该特征完成癫痫发作检测。采用长达118 h 49 min的癫痫患者临床脑电数据进行实验,实验结果表明,自适应带宽特征的敏感性、特异性、准确性参数均比原特征取得明显提高。自适应带宽特征可提高癫痫发作检测精度并降低时间延迟,便于及时采取治疗措施,为临床检测提供了重要依据。
