Figure 8.

Error distributions of IQA kriging models. a) oxygen $E_{\mathrm{S}\mathrm{e}\mathrm{l}\mathrm{f}}$, b) oxygen $E_{\mathrm{I}\mathrm{n}\mathrm{t}\mathrm{e}\mathrm{r}}$, c) hydrogen $E_{\mathrm{S}\mathrm{e}\mathrm{l}\mathrm{f}}$, d) hydrogen $E_{\mathrm{I}\mathrm{n}\mathrm{t}\mathrm{e}\mathrm{r}}$. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]