There's no way to choose consistently a normal vector for the Mobius strip So, that's what we call a non-orientable surface.
为Mobius带选一个始终如一的的法向量是不可能的,这就是所谓的不可定向的曲面。
2
Corrugation problem in the car trunk sealing strip edges is analyzed with the highly non-linear finite element analysis software (MARC). The structure and material is optimized.
Like a smoking and non-smoking section, the restaurant will have a naked and non-naked section, and a changing room for those who want to strip down while they chow down.