  Nonlinear self-modulation of the dust acoustic waves is studied, in the
presence of non-thermal (non-Maxwellian) ion and electron populations. By
employing a multiple scale technique, a nonlinear Schrodinger-type equation
(NLSE) is derived for the wave amplitude. The influence of non-thermality, in
addition to obliqueness (between the propagation and modulation directions), on
the conditions for modulational instability to occur is discussed. Different
types of localized solutions (envelope excitations) which may possibly occur
are discussed, and the dependence of their characteristics on physical
parameters is traced. The ion deviation from a Maxwellian distribution comes
out to be more important than the electron analogous deviation alone. Both
yield a de-stabilizing effect on (the amplitude of) DAWs propagating in a dusty
plasma with negative dust grains. The opposite effect, namely a tendency
towards amplitude stabilization, is found for the case of positively charged
dust presence in the plasma.
