The reasonable layer selection is the main influencing factors for gas drainage by high level borehole, the borehole parameters is based on the caving & fracture zone height of gob.

高位钻孔抽放最主要的影响因素是合理层位选择，其钻孔参数应根据采空区冒落带及裂隙带高度来设计。

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This is the first time we are cleaning at that height, in the death zone.

曾七次登上世界最高峰的纳姆格亚尔 夏尔巴说：“这是我们第一次在死亡区这么高的地带清理垃圾，难度很大，也很危险。”

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Based on the fractal characteristic of concrete material, the relation between fracture toughness and height of crack zone is analyzed.

根据混凝土材料裂纹的分形特性，分析了混凝土的断裂韧度与裂纹带高度之间的变化关系。

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One example of continuous observation of ecological change is provided by the Nenets in Northwest Russia, who report increases in the height of willow and alder shrubs in the tundra zone.

UNESCO: EDUCATION