双中心分布 meaning in English

bicentric distribution

Secondly , the paper reviews the evolution of the scale structure of towns in county administrative areas . the spatial structure show changes from concentration to political regional balance , and changes to the grade - size differentiation . based on the cases , it summarizes four models : single - centre model , double - centre model , group - centre model and urban - radiation model
其次，总结全省县域城镇规模结构的演变，划分出密集化向均衡化再向等级化的阶段变迁，并结合具体案例归纳县域城镇空间分布的四种主要模式：向心集中型、双中心分布型、多核心分布型和城市辐射型。