What method is rice grains and stones

Husk and stones could be separated from grains by handpicking. Husk is separated from heavier seeds of grain by winnowing. Difference in the size of particles in a mixture is utilised to separate them by the process of sieving and filtration.

An informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.