“…Accordingly, these works cannot determine the global interface shape of cell, the location of cell's tip and bottom, the total length of cell, the concentration of the impurity at cell's tip and bottom, and, in particular, the mathematical relationships between all these important quantities and the operating conditions. There are also many numerical works in the literature in recent years [10,11]. The numerical works may show the global patterns of cellular array, they, however, cannot explore the properties of singularity of the system at the bottom of root, nor provide the profound mechanisms behind the phenomenon.…”