30.Now Tom has obtained ________ from his boss to

30.Now Tom has obtained ________ from his boss to extend the field of his inves

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晶闸管装置中不采用过电压、过电流保护,选用较高电压和电流等级的晶闸管行不行?

晶闸管装置中不采用过电压、过电流保护,选用较高电压和电流等级的晶闸管行不行?

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变速器在换挡时,为避免同时挂入两档,必须装设自锁装置。

变速器在换挡时,为避免同时挂入两档,必须装设自锁装置。

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