Design of synergic development mechanism for Beijing Tianjin and Hebei 并列题名：Design of synergic development mechanism for Beijing Tianjin and Hebei Research on synergetic development of the metropolitan city agglomeration in Beijing, Tianjin and Hebei 并列题名：Research on synergetic development of the metropolitan city agglomeration in Beijing, Tianjin and Hebei Interpreting the synergic development mechanism of developing economies