Fig. 2

a β-curves in stretching sheet case. Physically meaningful solutions correspond to β > 0. I corresponds to β in Eq. 17I,  II corresponds to β in Eq. 17II, III corresponds to β in Eq. 17III, IV corresponds to β in Eq. 17IV. b β-curves in shrinking sheet case. Physically meaningful solutions correspond to β > 0. I corresponds to β in Eq. 17I, II corresponds to β in Eq. 17II, III corresponds to β in Eq. 17III, IV corresponds to β in Eq. 17IV