  We have studied changes in charge-density-wave strain under application of
square-wave currents of variable amplitude and frequency by numerically solving
the phase-slip augmented diffusion model introduced by Adelman et al (Phys.
Rev. B 53, 1833 (1996)). The frequency dependence of the strain, at each
position and amplitude, was fit to a modified harmonic oscillator expression,
and the position and current dependence of the fitting parameters determined.
In particular, the delay time (1/resonant frequency) vanishes adjacent to the
contact and grows with distance from the contact, and both the delay time and
relaxation time decrease rapidly with increasing current (and phase-slip rate),
as experimentally observed in the electro-optic response of blue bronze. We
have also found that pinning the phase at the contacts causes more rapid
changes in strain between the contacts than allowing the phase to flow outside
the contacts.
