Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Restriction emerged around a vertex. A folding angle is defined as the right figure: complete unfolding is represented as ρi=0. Positive direction (Valley folding) is defined the right-handed screw direction from considered vertex outwards.
