Black walnut shells are so hard they require special crackers.

黑核桃的壳相当硬，因此必须使用特殊的碎裂机。

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In her book, Ms. Arkins describes a different kind of ritual, involving "boats" made of walnut shells filled with wax.

在书中，阿金斯描述了另一种仪式，用核桃壳当“小船”，里面灌上蜡。

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One simple way that coal plant managers can adopt is to simply replace part of the coal they load into their plants (up to 20%) with dried biomass like sawdust, wood chips, dried walnut shells, etc.

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