Before revision:  In particular, we  is formed by either one or two orthogonal orientations, \mathcal{O}=\{0^\circ\} or \mathcal{O}=\{0^\circ,90^\circ\}.
After revision:  In particular, we consider the case when the set \mathcal{O is formed by either one or two orthogonal orientations, \mathcal{O}=\{0^\circ\} or \mathcal{O}=\{0^\circ,90^\circ\}.