kx_e sin(theta0) "Plane wave direction, x"
ky_e -cos(theta0) "Plane wave direction, y"
k0 intop_pnt(acpr.k) "Free-field wave number"
kx k0*kx_e "Background plane wave, k_x"
ky k0*ky_e "Background plane wave, k_y"
Zn aveop_bnd(acpr.p_t/(nx*up(acpr.vx)+ny*up(acpr.vy))) "Specific surface impedance"
Pin intop_bnd(-acpr.I_by) "Incident power"
Pout intop_bnd(acpr.I_sy) "Outgoing power"
alpha 1-Pout/Pin "Absorption coefficient"