  We calculate within a Bose-Hubbard tight-binding model the matter-wave flow
driven by a constant force through a Bose-Einstein condensate of Rb 87 atoms in
various types of quasi-onedimensional arrays of potential wells. Interference
patterns are obtained when beam splitting is induced by creating energy
minigaps either through period doubling or through quasi-periodicity governed
by the Fibonacci series. The generation of such condensate modulations by means
of optical-laser structures is also discussed.
