These devices "nc and maintenance" of professional practice play an important role in teaching, good effect.

这些设备在“数控加工与维修”专业的实践教学中发挥重要作用，效果很好。

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Sometimes they're startled, as when the MPAA slapped the sad, thoughtful "Blue Valentine" with an NC-17, which meant it couldn't play in many theaters, be advertised in many newspapers or probably be nominated for Oscars.

WSJ: Roger Ebert on Movie Ratings