This article introduces the engine important parts cylinder head valve pipe hole and sealing trip on their technical method and analyse used in the machining center.

介绍了发动机上重要部件汽缸盖中气门导管孔和密封带在加工中心上的工艺方法，并对其进行了分析。

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The head is a concave dish of permanent magnet with a hole in the center.

照射头部是一带有中心孔的永磁体凹形圆盘；

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Mutations of Sonic hedgehog in people may result in babies with a single eye or a hole in the center of their head.

FORBES: Magazine Article