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地闪回击电流是雷电的一个重要特征参数。其测量数据的积累对于雷电防护技术的提高具有重要意义。目前国内外的雷电研究人员通过矮塔、高塔直接观测，人工引雷观测和电场电流关系反衍的方法对地闪回击电流进行了大量的观测研究，并取得了丰富的观测资料。观测表明，负地闪首次回击电流平均为30kA，继后回击电流平均12kA。正地闪回击电流平均为35kA，有时可达几百kA。不同地区地闪回击电流平均值略有不同。高塔测量是主要的雷电流参量直接测量方法，但不同高度测量的地闪回击电流无论峰值还是波形都存在一定的差异。人工引发闪电和自然闪电继后回击雷电流的测量结果较为一致。间接估测雷电流参数的方法随着地闪回击模式的发展将成为主要的方法之一。 相似文献
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巴比塔是《圣经》故事中提到的一座通天塔,他由诺亚的后代所建。《旧约·创世纪》第11章曾有这样一段描述：古时候,天下人都说一种语言。人们在向东迁移的进修,走到一个叫示拿的地方,发现一片平原,就住下来。他们计划修一座高塔,塔顶要高耸入云,直达天庭,以显示人们的力量和团结。塔很快就建起来了。这惊动了天庭的耶和华。他见到塔越建越高,心中十分嫉妒。 相似文献
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平遥古城位于山西省中部,始建于西周宣王时期（前827～前782年）,明代洪武三年（1370年）扩建,距今已有2700多年的历史。迄今为止,它还较为完好地保留着明、清时期县城的基本风貌。 相似文献
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在天津众多的高楼中,有这样一座高塔,它伫立在天津城区南部,255米的高度使其傲立于群楼之中,它就是为气象人所熟悉的大气边界层气象观测塔。 相似文献
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The study aimed to assess the response of ep- and hemiedaphic Collembola communities （activity, richness, community structure） to a disturbance, the subsequent management regime and to the season （summer, winter） in a High Tatra Mountainsspruce forest destroyed by a windstorm. Fire and clear-cut resulted in an initial increase in the activity of Collembola inhabiting open areas, opportunistic or generalist species, while forest specialists diminished in numbers or disappeared. Our results indicated that treatment with non-extracted fallen trees （NEX） provided a better chance for forest species to survive compared with their survival in open habitats of extracted （EXT） and wildfire （FIR） treatments. Great species’ potential of NEX treatment was indicated by Chao2 estimator and activity/species rarefaction curves. Communities of NEX treatment were more similar to the reference （REF） treatment, documented by ordination and cluster analyses. Thus, leaving fallen timber after a windthrow to natural process of succession is suitable for survival of forest species and maintenance of diversity in forests restoration than timber extraction. Community structure in wildfire （FIR） stands was the most dissimilar to the other treatments. Most of the species trapped in this treatment belonged to hemiedaphic life forms, while the activity of larger epedaphic species diminished. In contrast, the highest number of trapped Collembola in EXT treatment was connected with the larger-bodied epigeic species with fast dispersal ability. The trapping period affected both the number of individuals and species richness; Collembola activity and species diversity in the individual treatments were lower in winter compared with the summer period. Several species increased activity during the winter period, namelyFolsomia penicula, Friesea mirabilis, F. truncata,Hypogastrura socialisand Protaphorura aurantiaca. 相似文献
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