Npswarn is the threshold that is used to signal the processes when space is getting low.

Npswarn是当空间变得较低时用于通知进程的阈值。

youdao

Infrared radiation heats up the pit membrane tissue, and TRPA1 channels open when a threshold temperature is reached, allowing ions to flow into the nerve cells and triggering an electrical signal.

红外线使窝器膜组织升温，当达到阈值后TRPA 1通路打开，离子流入神经细胞并催发电信号。

youdao

In this sense threshold means a sort of transition point like the threshold when an FM radio signal breaks through from being just static to being music (or maybe an AD).

从这个意义上讲，“threshold”意味着一种临界点，就像一个开关，使得FM无线电信号从静止状态到播放音乐状态(或者，也可能是一个广告)的忽然变化。

youdao

But now this mysterious property is up for sale, and so I find myself with a few other journalists on the other side of the doors, signing consent forms and handing in my mobile phone (whose signal had mysteriously vanished as soon as I crossed the threshold).

ECONOMIST: Snooker, piranhas and a hotline to Moscow