As the unit of deployment (and as the artifact that exists in the file system), the JAR is a very practical unit of reuse but it lacks some of the other characteristics of a good module.

作为一个部署单元(和文件系统中存在的工件)，JAR是一个非常实用的重用单元，但它缺乏作为一个好模块的其他一些特征。

youdao

On a more practical level, the unit is compact, USB-powered, and has a built-in audio-interface (no extra sound card required for headphone monitoring).

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Often a PhD was required just to operate a RS unit and this still took a great amount of time and experience, not at all practical for medical applications.

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