  We apply the adaptive time-dependent Density Matrix Renormalization Group
method (tDMRG) to the study of transport properties of quantum-dot systems
connected to metallic leads. Finite-size effects make the usual tDMRG
description of the Kondo regime a numerically demanding task. We show that such
effects can be attenuated by describing the leads by "Wilson chains", in which
the hopping matrix elements decay exponentially away from the impurity ($t_n
\propto \Lambda^{-n/2}$). For a given system size and in the linear response
regime, results for $\Lambda > 1$ show several improvements over the undamped,
$\Lambda=1$ case: perfect conductance is obtained deeper in the strongly
interacting regime and current plateaus remain well defined for longer time
scales. Similar improvements were obtained in the finite-bias regime up to bias
voltages of the order of the Kondo temperature. These results show that, with
the proposed modification, the tDMRG characterization of Kondo correlations in
the transport properties can be substantially improved, while it turns out to
be sufficient to work with much smaller system sizes. We discuss the numerical
cost of this approach with respect to the necessary system sizes and the
entanglement growth during the time-evolution.
