Equation Icon  w(r,z) = --------Y--------{ σE (r,z)2 + (1 − 2σ) [(E (r,z) + E (r,z))2 2 (1 + σ )(1 − 2σ ) rr ϕϕ − 2E (r,z)E (r,z) + E (r,z)2]} (8.47 ) rr ϕϕ zz