Equation Icon  U J+1∕2− Δt-L− UJ+1 ∕2 = U J + Δt- (L − L− )U J, N 2 N N N 2 N N N J+1 Δt + J+1 J+1∕2 Δt ( +) J+1∕2 U N − ---L NU N = U N + --- LN − L N UN , (130 ) 2 2