“实用性”用英语怎么说

我相信了他的新装置的实用性.I was persuaded of the usefulness of his new device.图5-2人物角色的实用性的简单示例.Figure 5 - 2 : A simplified example of how personas are useful.吉他的试验均未能激起任何关于电收尘原理的实用性研究.Guitar's experiments did not stimulate any...