at intervals和on occassion都可以表示间断,请问二者有何区别?

on occasion后面可以接从句,它的意思是“在.场合".at interval不能这样用,但是它的前面可以有修饰语,表示间隔情况如何.
at intervals or at ...intervals
1）with time between:
例a）Buses to the city leave at regular intervals.
b）The runners started at 5-minute intervals.
2 with spaces between:
Flaming torches were positioned at intervals along the terrace.

在间隔或在。。。 间隔
和时间的 1 ）在:之间
对城市的例一辆）公共汽车留在固定的间隔。
b ）跑步者在 5 点开始- 分钟间隔。
2 由于空间在:之间
燃烧的火把被放置在间隔沿着台地