Observational studyaims at the approach to a dynamic system whose equation is undeterminable.

该方程组的有限时段上的采样值与给定序列重合。

He recalls a mother in her late 20s who came to him because she had an inoperable defect in her aorta that would rupture at some undeterminable time in the future, killing her instantly.

“我认为，激烈的面情绪有这样的作用，它可使我们正常的活动停，我们可一段时间内专注于某些事物”，他这样说到。