R-1 homogeneous stability R+1 stability against spatial distrubance: ,R-I P R+l (S,τ if P <1 D<Da), systems is always stable, against any perturbation both spatial and temporal1 1 + − > R R Q homogeneous stability: stability against spatial distrubance: 1 1 + − > R R P Q s I I’(s,τ) I 9 if P < 1 (Di<Da), systems is always stable, against any perturbation both spatial and temporal