similarities and difference between the fcc and hcp structure
Close-packing of equal spheres There are two simple regular lattices that achieve this highest average density. They are called face-centered cubic (fcc) (also called cubic close packed) and hexagonal close-packed (hcp), based on their symmetry. Both are based upon sheets of spheres arranged at the vertices of a triangular tiling; they differ in how the sheets are stacked upon one another. The fcc lattice is also known to mathematicians as that generated by the A3 root system.[4]
FCC fairness doctrine The main agenda for the doctrine was to ensure that viewers were exposed to a diversity of viewpoints. In 1969 the United States Supreme Court upheld the FCC's general right to enforce the fairness doctrine where channels were limited. But the courts did not rule that the FCC was obliged to do so.[4] The courts reasoned that the scarcity of the broadcast spectrum, which limited the opportunity for access to the airwaves, created a need for the doctrine.