Express logistics is a direct reflection of intercity material flows and an important form of representation of urban connectivity.Taking 63 districts and counties in the Guangdong-Hong Kong-Macao Greater Bay Area as the basic research unit,this study constructed a 63 × 63 logistics linkage matrix based on logistics network data,and explored the spatial structure characteristics of logistics networks and their influencing factors by using social network analysis,GIS spatial analysis,and multi-scale geographically weighted regression(MGWR)models.The findings show that:1)The centrality of the network of districts and counties is basically consistent with the macro pattern of socioeconomic development level and town size,and the imbalance of logistics between districts and counties is notable,with Baiyun District having a prominent logistics function.2)The overall network has formed a multi-center structure of"three nuclei and two auxiliaries",with Guangzhou,Dongguan,and Shenzhen as the main cities,supplemented by Foshan and Zhongshan.The clustering and polarization of logistics links are significant,with network connections prioritized in core cities such as Guangzhou,Dongguan,and Shenzhen.3)The Guangdong-Hong Kong-Macao Greater Bay Area can be divided into four cohesive subgroups,which are characterized by a scattered distribution and zonal expansion,a typical core-periphery structure.4)The formation of logistics networks is mainly influenced by the size of the resident population and GDP,while GDP per capita,per capita disposable income of urban and rural residents,average wages of employed persons,and total retail sales of consumer goods also play an important role.The study is of significance for enriching the theory of urban networks,promoting the coordinated development of logistics,and enhancing the level of logistics services and the comprehensive competitiveness of urban agglomerations.

The planning of natural resource assets protection and utilization as well as territorial space planning is an essential tool to realize the "two unified" functions of natural resources management. In contrast to territorial space planning, there is a lack of basic research on planning for the protection and utilization of natural resource assets, and there is an urgent need to implement objectives, theoretical foundations, and basic framework issues. Firstly, the dialectical relationship between natural resource asset protection and utilization planning and territorial space planning and other related plans have been discussed according to the requirements of "two unified" functions. Secondly, the inner scientific logic of natural resources assets protection and utilization planning was proposed according to the perspective of "trinity" integrated management of resources, assets, and capital. Finally,with the fundamental goal of preserving and increasing the value of natural resource assets, the technical framework for planning for the protection and utilization of natural resource assets is built around the three essential links of development, circulation,and distribution for the sustainable realization of natural resource assets. The study aims to provide relevant ideas and model references for natural resources management agencies to prepare their plans.

城市群是新型城镇化的主题形态,在中国经济社会发展中具有重要地位,"流空间"理论的提出与发展为城市群研究提供了新视角.基于文献分析法对"流空间"视角下的城市群研究进行分析与梳理.研究发现:研究历程呈现出较显著的阶段性;研究主题与社会技术发展及政策指向密切相关;从研究热点来看,研究内容不断多元化,研究区域向中西部城市群拓展;研究作者呈现"部分集中,整体分散"的特点.最后对研究现状进行总结与展望.

研究了一个具有坏死核的双曲型肿瘤生长的Robin自由边界问题.该模型包含了一个描述营养物浓度变化的椭圆型方程,一个描述肿瘤半径的常微分方程和三个分别描述增殖细胞,休眠细胞和死亡细胞演化的一阶非线性双曲偏微分方程.通过特征线方法和Banach不动点定理证明了该模型整体解的存在唯一性.同时证明了当KR=0时,limt→+∞R(t)=+∞.

Regarding energy consumption for different degrees of nodes in a wireless sensor network , it proposed the energy cluster head selection mechanism , based on the cost of energy .In this mechanism , the first common node was seen as the cluster head node .Nodes, necessary node energy consumption , and the current energy surplus value were computed . With the proposed concepts and formulas , the above energy-related value was converted into the value of energy loss speed of the selected clusters at measur-able sensor nodes .Simulation results show that the algorithm has a better cluster head selection , and it can effectively extend the network life cycle .