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近几十年来中国北方极端气候变化对比研究 被引量:1
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作者 齐秀堃 唐耀 +1 位作者 周颖 李冬玲 《自然科学》 2017年第1期79-87,共9页
极端气候事件是一个包括诸多气象灾害事件的复杂系统,已成为当今国际社会普遍关注的热点问题。通过搜集近50年来中国东北、华北及西北地区的极端高温、极端低温事件的记录,利用Photoshop软件进行数据整理分析发现:华北地区极端最高气温... 极端气候事件是一个包括诸多气象灾害事件的复杂系统,已成为当今国际社会普遍关注的热点问题。通过搜集近50年来中国东北、华北及西北地区的极端高温、极端低温事件的记录,利用Photoshop软件进行数据整理分析发现:华北地区极端最高气温上升速率较大,东北地区极端最低气温的上升速率最大,其次是华北地区;东北地区降水量减少,极端降水事件增多、增强,旱涝灾害频发;华北地区极端降水量明显减少,极端降水事件发生频次减少、强度减弱,有干旱的趋势;西北地区极端降水事件增多、增强,大多数地区干旱事件增多。这些表明由于全球气候变暖的加快,中国大部分地区极端高温事件增多、增强,极端低温事件减少、减弱,极端降水事件频发。 展开更多
关键词 极端气候事件 时空变化 影响因素
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Critical power of keyhole formation in CW Nd:YAG laser deep penetration welding 被引量:1
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作者 秦国梁 齐秀堃 林尚扬 《China Welding》 EI CAS 2007年第1期36-40,共5页
The energy model was founded to calculate the critical power of keyhole formation by using the limit principle in CW ( continuous wave ) Nd: YAG laser deep penetration welding process. The model was validated by ex... The energy model was founded to calculate the critical power of keyhole formation by using the limit principle in CW ( continuous wave ) Nd: YAG laser deep penetration welding process. The model was validated by experiments. The results show that '.there are two errors between the calculated critical power of keyhole formation and that of experiments : one is that the calculated results is less than those of experiments, which is caused by not considering the energy loss by heat conduction in the model of keyhole formation. The other is that there is 0. 9 mm error between the axis of the calculated curve of critical power with location of laser focus and that of experimental curve, which is induced by the excursion of laser focus in laser deep penetration welding. At last, the two errors were revised according to the analyses of the errors. 展开更多
关键词 laser deep penetration welding keyhole formation critical power error analysis
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