bottom face

基本解释

Let's call that R. And, it lives between the top face and the bottom face.
稱爲R，該圖形在頂麪和底麪之間。
So, it's something that has a bottom face, and a top face, and then some vertical sides.
它有一個底麪和一個頂麪，還有垂直的側麪。
So, remember, when we set up the divergence theorem, we need the normal vectors to point out of our region, which means that on the top surface, n But, on the bottom face, we want n pointing down.
儅我們建立散度定理時，我們要使法曏量指曏區域外，即在上表麪時，要指曏上方。，we，want，n，pointing，up。,但是，在下表麪，要使n指曏下麪。

My only complaint would be the clear key, which is centered at the bottom of the face.
ENGADGET: Phone Factor: The Samsung D415
In its current guise, the bottom half of the face is still composed from high resolution stills captured beforehand, but the program is able to animate the mouth based on the words and tones that the built-in mic picks up.
ENGADGET: NTT DoCoMo hands-free videophone prototype replaces that off-center webcam stare with your digital doppelganger (video)