Table 2

Results for the material parameters for different optimisation strategies for a sample of PIC181 at 25 °C: Proposed method with (p_∗) and without (${\mathit{p}}_{\mathbf{\ast }}^{\mathbf{\prime }}$) intermediate surrogate model optimisation and results of previously used method with analytically estimated initial values and block coordinate descent (BCD) steps in the final optimisation stage (${\mathit{p}}_{\mathbf{\ast }}^{\mathbf{″}}$) [11, 26]. Values of the objective function are calculated using the finite element (FE) model. Standard uncertainties for p_res are estimated by evaluating pseudo-inverse of the linearised model [18, 27]. The density (7800 kg m⁻³) is measured directly. *Actual estimate 3.8 ⋅ 10⁻¹¹ s⁻¹.

	Network	Surrog.	FE model	Network	FE model	Analytic	FE model	Rel. uncert.
	estimate	optim.	optim.	estimate	optim.	estim. [11]	BCD opt. [11]	of pres
	pinit	psur	pres	${\mathit{p}}_{\mathbf{init}}^{\mathbf{\prime }}$	${\mathit{p}}_{\mathbf{res}}^{\mathbf{\prime }}$	${\mathit{p}}_{\mathbf{ana}}^{\mathbf{″}}$	${\mathit{p}}_{\mathbf{res}}^{\mathbf{″}}$	${\mathit{u}}_{{\mathit{p}}_{\mathbf{res}}}$
$c_{11}^{\mathrm{E}}/\mathrm{GPa}$	142.63	142.59	141.21	142.63	141.24	130.63	136.80	3.6 ⋅ 10−4
$c_{12}^{\mathrm{E}}/\mathrm{GPa}$	78.12	76.11	82.29	78.12	82.27	72.22	58.42	2.5 ⋅ 10−3
$c_{13}^{\mathrm{E}}/\mathrm{GPa}$	82.06	80.79	80.36	82.06	80.37	72.22	77.81	2.9 ⋅ 10−3
$c_{33}^{\mathrm{E}}/\mathrm{GPa}$	138.40	137.14	137.19	138.40	137.19	130.63	136.93	6.3 ⋅ 10−3
$c_{44}^{\mathrm{E}}/\mathrm{GPa}$	27.61	30.09	29.85	27.61	29.85	29.20	26.97	7.4 ⋅ 10−3
${\epsilon }_{11}^{\mathrm{S}}/{\mathrm{nF}\mathrm{m}}^{-1}$	5.59	12.15	13.3	5.59	12.15	5.26	0.50	5.4 ⋅ 10−2
${\epsilon }_{33}^{\mathrm{S}}/{\mathrm{nF}\mathrm{m}}^{-1}$	5.63	5.34	5.38	5.63	5.34	5.26	5.30	4.0 ⋅ 10−3
$e_{15}/{\mathrm{C}\mathrm{m}}^{-2}$	9.79	13.29	13.22	9.79	13.22	8.51	6.65	3.6 ⋅ 10−2
$e_{31}/{\mathrm{C}\mathrm{m}}^{-2}$	−5.24	−4.50	−4.98	−5.24	−4.97	−2.55	−5.50	1.7 ⋅ 10−2
$e_{33}/{\mathrm{C}\mathrm{m}}^{-2}$	14.21	14.04	14.15	14.21	14.15	12.77	13.59	3.1 ⋅ 10−3
${\alpha }_{\mathrm{M}}/{\mathrm{ms}}^{-1}$	2.38	0∗	1.08	2.38	0.002	11.96	14.2	2.6 ⋅ 101
αK/ps	39.9	139	129	39.9	138	64.5	78.1	1.2 ⋅ 100
Obj. val.	26.8	17.8	3.98	26.8	3.98	117.5	20.5
Steps									–	27	20	–	36	–	321