Figure 6.

(a) The SHMs and (b) the parameter sensitivity spectra (PSS) for the modified Hoffmann model. (a) The analysis when the time domain is restricted to (i, iii) 0≤t≤200 (i.e. T=200) and (ii,iv) when this is 0≤t≤1000. (b) The PSS show that in both cases ((i) 0≤t≤200 and (ii) 0≤t≤1000), only very few parameters k_j have sensitivities greater than one thousandth of the maximum one. However, the dominant parameters for the two cases are different. In (b(i)), we note that ka4, k1, ka7, ka1 and klr2 are the most sensitive and that these primarily affect the variables at the times that are coloured red in (a(iii)). As for figure 3, the maxima and minima have been marked with pink and white bars, respectively, on the heat maps for the $f_{i,m}^{(d)}$ so that one can quickly check which are sensitive to any parameter and then determine which parameters using the PSS.