I teach a course on applied positive interventions and we have a service learning component as a part of that class.

我教积极干预应用,课程也包括一个服务教育部分。

哈佛公开课 - 幸福课课程节选

But since it is a component it can have a direction, too, so can go up l between negative l and positive l.

但因为它是个分量,它是有方向的，所以它可以,从负的l一直到正的。

麻省理工公开课 - 化学原理课程节选