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.
Cross-section views of different quasi-continuous structures. (a) A conical surface; (b) a cylindrical surface; (c) a parabolic surface. Red dashed lines represent the desired continuous profiles for special applications. Point F in (b) and (c) stands for the focal point of the surface.
