Equation Icon  1 Y [ ( w (r,z) = ----------------- σE (r,z)2 + (1 − 2σ) Err(r,z)2 2(1 + σ)(1 − 2σ) )] +E ϕϕ(r,z)2 + Ezz(r,z)2 + 2Erz(r,z)2 (8.111 )