  Random walks with a fixed bias direction on randomly diluted cubic lattices
far above the percolation threshold exhibit log-periodic oscillations in the
effective exponent versus time. A scaling argument accounts for the numerical
results in the limit of large biases and small dilution and shows the
importance of the interplay of these two ingredients in the generation of the
log-periodicity. These results show that log-periodicity is the dominant effect
compared to previous predictions of and reports on anomalous diffusion.
