Equation Icon  { ( ) 2 4 2𝜃e3-1∕2(1 + 1.781𝜃1e.34) 𝜃e < 1, fei = ne¯nσT cαfmec × 9𝜃eπ (73 ) 2π [ln(1.123𝜃e + 0.48) + 1.5] 𝜃e ≥ 1.