Subjects: Other Disciplines >> Synthetic discipline submitted time 2023-03-28 Cooperative journals: 《中国科学院院刊》
Abstract： The problem of sandy desertification in Tibet is one of important regions of desertification research in China, the important progresses in the research on sandy desertification in Tibet in recent thirty years are concluded in the paper, such as finding out the status and characteristics of spatial and temporal change in recent years of sandy desertification in Tibet as well as its driving factors, establishing the theoretical system of sandy desertification in Tibet including the classification system of sandy desertification land and geological-historical evolutionary process of sandy desertification as well as the features of river valley aeolian landform in Tibet, building the combating strategy and control technical system of sandy desertification in Tibet with special plateau features. On the basic analysis of status and development trends as well as the control results of sandy desertification in Tibet, the future combating idea of sandy desertification in Tibet are forward given.
Subjects: Geosciences >> Geography submitted time 2022-02-11 Cooperative journals: 《干旱区地理》
Abstract：当下城市网络研究中存在相对重结构特征测度、轻影响机理分析的问题，而在城市网络影响机理的研究中，又存在重理论定性的宏观描述或基于独立变量的常规性统计分析，轻从图论、结构视角的城市网络微观发育机理研究。因此，从结构关系依赖视角出发，基于苹果手机2019年供 应商数据构建研发型、生产型、代工服务型全球化城市网络，运用指数随机图模型的微观构型测度城市网络的生长发育机理。结果表明：（1）互惠性与中介效应在3类城市网络普遍存在，深刻影响城市网络的通性发育机理。（2）偏好依附过程与接收者、发送者效应是解释城市网络等级中心性发育的结构机理，二者都体现了城市网络发育中以入度为核心的路径依赖现象。（3）三角形结构（传递三角形与循环三方组）和同质性是促进城市网络集群发育、富人俱乐部现象的微观基础，同质性对城市网络的发育机理主要体现在核心城市间的联结关系上。（4）企业路径依赖与距离是影响城市网络发育的核心外生因素。其中，对距离的分类讨论发现，地理邻近性对3类城市网络存在便在性影响。认知邻近性在研发型城市网络对长距离联系的影响与敏感度更大；在生产型城市网络中对中等距离有正向影响，代工服务型城市网络对短距离阈值敏感。该研究对丰富与拓展现有城市网络影响机理的研究视角有重要意义。
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