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。
Mainly , it includes the outside mode of upgrade and the inside ones . outside mode has new centre mode of upgrade ( set up new city centre district and set up modern cbd ) and many cores the mode of upgrade mainly ( the upgrade mode of the satellite town up 主要包括城市中心区外部更新模式和内部更新模式，外部更新模式主要有新中心更新模式(建立新的城市中心区和建立现代cbd )和多核心更新模式(卫星城更新模式、副中心更新模式) ，内部更新模式主要有局部更新模式(建立初级cbd 、居住区更新模式、建立步行街、城市开放空间更新)和整体更新模式。
Sustainable development is the aim all the city planning experts pursued , in this paper a few advanced overseas planning principles are introduced , the process of the city development is studied and the utilization of urban underground space to promote the multi - center compact city mode is suggested 摘要可持续发展是所有城市规划师一直追求的目标，文章通过分析国外几种新的规划理念，研究了城市的发展历程，提出了多核心紧凑型城市空间规划模式的架构，对利用地下空间促进该模式实现的途径和方法进行了研究和探讨。
While a control packet is processed at each switching node , an all optical light path is set up dynamically for the corresponding data packet . switching node architecture and scheduling algorithm have great influence on packet loss rate in obs network . this paper proposed a port modularized scheduling policy that combines these two aspects , with the aim of reducing burst packet loss rate 其中严格的端口模块化策略可以避免m p p交换结构的内部阻塞,在单核心节点的网络上使丢失率降到0 ,但不适用于多核心节点的多跳网络;修改的端口模块化算法通过设置合适的参数,平衡各个节点上调度资源的使用,在全网达到较低的丢失率。
Recently , new urbanism becomes popular , which holds to develop both insides and outsides of city . according to function , city area can be divided into cbd , industrial area , residential area and so on . these areas " arrangement in city space shows some rules such as the fan shape , multi - corns 本文从经济地理角度出发，在时间维度上，探讨了“城市化?逆城市化?新都市主义”的发展过程；在空间维度上，阐述了商业、工业、住宅等城市职能分区和同心圆、扇形、多核心等城市地域空间结构理论。
