“…For the reaction-diffusion models discussed in this paper, determining the complete structure of the nodal set for Λ 1 (α, β) poses a challenging problem, both analytically and numerically [52]. To this end, some asymptotic behaviors of Λ 1 were studied in [26,27,99,139] in order to have a better understanding for this problem. Recently, the asymptotic behaviors for the principal eigenvalues of time-periodic parabolic operators were also studied, and we refer to [64,69,71,101,102,103,137].…”