In his past research, the P.I. has studied the behavior of waves in random systems of various geometries and in quasiperiodic systems. In the course of this work, he has been able to identify some systems which are particularly "clean" and he proposes to use these special geometries to answer some current open questions in l.t. condensed-matter physics. Specifically, he proposes to study: - 1) scaling and dimensional cross-over for 4He using a glass capillary array; 2) the difference between local and non-local non-linear interactions in random systems and quasiperiodic systems; 3) 2D, strong, Anderson localization as a function of the amount of disorder; and 4) the superfluid transition with 4He permeated by a variable weak-link array (generated with standing e.m. waves from crossed laser beams), with the possibility of observing a controlled Bose glass transition.