Discrte Ordinate semi-transparent boundary

gts

Hi,

I have the following problem: A thin horizontal plate having an initial temperature Ti is cooled and in the same time heated by conduction and radiation. We have the top external temperature Th and the bottom external temperature Tc. (Th>Ti>Tc). How should I prescribe the boundary conditions for temperature and radiation if the boundaries are semi-transparent specular.

Thank you.