Wave propagation in unbounded layered media with a new formulation of Axisymmetric Scaled Boundary Finite Element Method (AXI-SBFEM) is derived. Dividing the general three-dimensional unbounded domain into a number of independent two-dimensional ones, the problem could be solved by a significant reduction in required storage and computational time. The equations of the corresponding Axisymmetri...

Two permutation classes, the X-class and subpermutations of increasing oscillation are shown to exhibit an exponential Wilf-collapse. This means that number distinct enumerations principal subclasses each these classes grows much more slowly than class itself whereas a priori, based only on symmetries class, there is no reason expect this. The underlying cause collapse in both cases ability app...