  This paper is concerned with some nonlinear propagation phenomena for
reaction-advection-diffusion equations with Kolmogrov-Petrovsky-Piskunov (KPP)
type nonlinearities in general periodic domains or in infinite cylinders with
oscillating boundaries. Having a variational formula for the minimal speed of
propagation involving eigenvalue problems ( proved in Berestycki, Hamel and
Nadirashvili \cite{BHN1}), we consider the minimal speed of propagation as a
function of diffusion factors, reaction factors and periodicity parameters.
There we study the limits, the asymptotic behaviors and the variations of the
considered functions with respect to these parameters. The last section treats
a homogenization problem as an application of the results in the previous
sections in order to find the limit of the minimal speed when the periodicity
cell is very small.
