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贵州夏季降水异常的小波分析 被引量:5
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作者 伍红雨 《贵州气象》 2001年第1期8-9,共2页
利用 1951~ 1999年贵州省 19站月平均降水资料 ,应用小波分析的方法分析了贵州夏季降水的周期振荡特征和年际及年代际变化特征。结果表明 :贵州夏季降水具有多尺度振荡的特点 ,且振荡的周期具有显著的年际、年代际变化。
关键词 贵州 夏季 降水 小波分析 降水资料 年代际变化 周期振荡特征
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中国灾害性对流天气日数的时空变化特征 被引量:10
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作者 孔锋 杨萍 +2 位作者 王品 吕丽莉 孙劭 《长江流域资源与环境》 CAS CSSCI CSCD 北大核心 2018年第11期2518-2528,共11页
采用1961~2016年中国2 481站的冰雹、大风、雷暴和闪电日数数据,利用多种数理统计方法,分析了中国4种灾害性对流天气日数时空分布特征、周期变化规律和气候突变特征。结果表明:(1)在时间上,中国4种灾害性对流天气日数呈减少趋势,且冰雹... 采用1961~2016年中国2 481站的冰雹、大风、雷暴和闪电日数数据,利用多种数理统计方法,分析了中国4种灾害性对流天气日数时空分布特征、周期变化规律和气候突变特征。结果表明:(1)在时间上,中国4种灾害性对流天气日数呈减少趋势,且冰雹和雷暴日数具有"先增-后减"的分段变化特征。中国冰雹、大风、雷暴和闪电日数分别具有3~5 a、2~3 a、1~2 a和1~4 a左右的振荡周期,且冰雹和雷暴日数分别于2002和1992年发生突变。(2)在空间上,青藏高原-四川西部地区是冰雹、大风和雷暴日数的高值分布区。同时长江以南地区也是雷暴日数的高值分布区。华南及其同纬度的西南地区是闪电日数的高值分布区。(3)在趋势上,中国冰雹日数主要在青藏高原地区呈减少趋势。大风日数变化趋势呈东部减少-中部不变-西部增减镶嵌的空间格局。雷暴日数在西藏、华北、重庆、浙江和黑龙江西北部呈增加趋势。中国闪电日数变化趋势在长江以南地区减少明显。(4)在波动上,中国冰雹日数在东南地区波动较大,大风日数在胡焕庸线以东波动较大。中国雷暴日数波动特征呈西北高-东南低的空间格局,闪电日数除在新疆北部和华南地区波动动较小外,其它地区波动相对较大。 展开更多
关键词 灾害性天气 冰雹-大风-雷暴-闪电 时空格局 周期振荡特征 突变检验
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Periodic switching oscillation and mechanism in a periodically switched BZ reaction 被引量:4
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作者 LI XiangHong ZHANG Chun +1 位作者 YU Yue BI QinSheng 《Science China(Technological Sciences)》 SCIE EI CAS 2012年第10期2820-2828,共9页
By introducing periodic switching signal associated with illumination to the Originator,a switched mathematical model has been established.The bifurcation sets are derived based on the characteristics of the equilibri... By introducing periodic switching signal associated with illumination to the Originator,a switched mathematical model has been established.The bifurcation sets are derived based on the characteristics of the equilibrium points.Two types of periodic oscillation,such as 2T-focus/cycle periodic switching and 2T-focus/focus periodic switching,have been observed,the mechanism of which is presented through the switching relationship.The distribution of eigenvalues related to the equilibrium points determined by two subsystems is discussed to interpret oscillation-increasing and oscillation-decreasing cascades of the periodic oscillations.Furthermore,the invariant subspaces of the equilibrium point are investigated to reveal the mechanism of dynamical phenomena in the periodic switching. 展开更多
关键词 photosensitive BZ reaction bifurcation mechanism periodic switching oscillation-increasing cascades
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Stability switches in a Cohen-Grossberg neural network with multi-delays 被引量:1
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作者 Wenying Duan 《International Journal of Biomathematics》 2017年第5期345-359,共15页
In this paper, we consider a Cohen-Grossberg neural network with three delays. Regard- ing time delays as a parameter, we investigate the effect of time delays on its dynamics. We show that there exist stability switc... In this paper, we consider a Cohen-Grossberg neural network with three delays. Regard- ing time delays as a parameter, we investigate the effect of time delays on its dynamics. We show that there exist stability switches for time delays under certain conditions and the conditions for the existence of periodic oscillations are given by discussing the associated characteristic equation. Numerical simulations are given to illustrate the obtained results and interesting network behaviors are observed, such as multiple stability switches of the network equilibrium and synchronous (asynchronous) oscillations. 展开更多
关键词 Cohen-Grossberg neural networks DELAYS stability switches
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