Here, they employed a movement velocity-based threshold to determine set discontinuation.

在这里，他们采用了一个基于运动速度的阈值来确定组数的中止。

As it often happens in English, there is no simple rule to determine whether a set of nouns countable or uncountable. Sorry.

正如在英语中经常发生的那样，没有一劳永逸的规则来确定一组名词是可数还是不可数。抱歉。