Based on the local, migratory and subsection characteristics of main roof fall of longwall face, the main roof was divided into some plate group, and plate group mechanical model was established.

针对长壁工作面顶板垮落具有局部、分段、迁移的时空特征，将长壁工作面采场顶板划分成若干个相互铰接的薄板，建立了薄板组力学模型。

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In addition to migratory dolphins, the marine biologists have concluded that a group of 60 larger, bottlenose dolphins live permanently in the Bosphorus.

NPR: Dolphins Dodge Danger in the Bosphorus Strait