“…Experimental results for the effects of thermal oxidation reported by Imai et al [21] show a smooth decreasing trend, and are in good agreement with those obtained by Pickup et al [20]. As described in the Appendix, Young's modulus is related to the pore fraction contained in the material or model by Knudsen's semi-empirical equation [24,25]: where E 0 is the virtually 'pore-free' Young's modulus and b P is the decay factor (see Appendix).…”