One New Caledonian crow, called Betty, bent some straight wire into a hook and used it to lift a small bucket of her favourite food from a vertical pipe.
A new calculation mode of the earth stress of vertical fracture is built based on generalized Hook 's law in this paper, which is suitable to hydraulic fracturing cracks.
该文基于广义虎克定律，建立了适用于水力压裂裂缝为垂直裂缝的地应力计算模式。
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A practical hook structure of band saws with carriage and the fine adjustment structure of the vertical stake of the carriage are introduced.