可变上限属性控制哪些字符被忽略，只在替代属性不是不可忽略的情况下这些字符才是有意义的。

The variable top attribute controls which characters to ignore and is only meaningful if the alternate attribute is not non-ignorable.

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常规的、不可变径的钻柱稳定器现在依然是井斜控制井底钻具组合中不可缺少的组件。

The ordinary non-adjustable stabilizer is still now an indispensable element of DHA(Down-Hole Assembly) for controlling well inclination.

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