Figure 1.

Basis functions $h_i\left(\tau \right)$ (13), $i=1,\dots ,5$, of the relaxation spectrum model ${\overline{H}}_N\left(\tau \right)$ (12) for time sampling instants: (a) $t_i=10, 30, 50, 70, 90 \mathrm{s}$ and (b) $t_i=0.1, 0.5, 1, 1.5, 2 \mathrm{s}$.