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.
The revolving wing versus the flapping wing in the production of lift. (a) Downstroke and (b) upstroke. Only one typical stroke cycle is used in this test. The vertical dashed line represents the time period of wing acceleration. All forces are normalized by the same factor. (Online version in colour.)
