In the tracking stage, track face using kalman filter and skin-color feature, if fail to track then turn into detecting stage.

跟踪阶段用卡尔曼滤波器结合肤色特征跟踪人脸，如果跟踪失败，转入检测阶段。

youdao

But even if those efforts fail, it is too soon to know just how strong the new rules will be.

VOA: special.2010.07.23

Then if you fail to pay on the mortgage--pay off the debt -the lender can seize the property and sell it.

然而如果你无法偿还贷款,贷方可以没收这项财产并出售

耶鲁公开课 - 金融市场课程节选

If the person has not mastered the basic concept, the person must fail, must get four or less.

如果他没有掌握基本的概念，那就一定不能通过考试，只得十分之四或更少。

麻省理工公开课 - 固态化学导论课程节选

But customers forfeit the 0% rate if they if fail to pay on time more than once.

BBC: NEWS | Programmes | Moneybox | Barclaycard promises credit card clarity

They will fail if they continue along this path, and they will fail if they pull out.

BBC: NEWS | Middle East | Iran leader condemns US 'stupidity'

We need to make it impossible for the taxpayers to be holding the bag when big institutions fail, if they fail.

WHITEHOUSE: Press Briefing