1 Decoherence-free subspaces, subspace of a system's Hilbert space where the system is decoupled from the environment.  Dynamic Frequency Selection, part of the IEEE 802.11h wireless standard.
The American Psychological Association (APA) is a scientific and professional organization that represents psychologists in the United States.
American Protective Association: American Protective Association (APA), in U.S. history, an anti-Catholic, anti-immigrant group that briefly acquired a membership greater than 2,000,000 during the 1890s. A