设施选址对提高居民生活质量至关重要,利用地理可达相似性聚类对空间元素进行分类是求解此类问题的重要方法。然而,现有的应用于地理可达性分析的聚类算法存在地理可达性测度不准确、不涉及簇中心选取或簇中心不可达等缺陷,不能有效求...设施选址对提高居民生活质量至关重要,利用地理可达相似性聚类对空间元素进行分类是求解此类问题的重要方法。然而,现有的应用于地理可达性分析的聚类算法存在地理可达性测度不准确、不涉及簇中心选取或簇中心不可达等缺陷,不能有效求解真实场景下的设施选址问题。基于此,本文提出一种基于可达距离的模糊C均值聚类算法(Fuzzy C-Means based on Reachable Distance,FCM-RD)。FCM-RD算法改造了经典FCM算法的目标函数、隶属度函数和簇中心函数,使其适用基于可达距离的聚类分析。其次,以沿路网的最短路径距离作为可达距离衡量元素间的地理可达相似性,将聚类元素的二维地理坐标映射为路网坐标,并以此设计簇中心迭代机制,实现在聚类过程中以可达距离迭代不受约束的可达簇中心。同时,对所提簇中心迭代机制的有效性进行理论分析和实验验证,结果表明,FCM-RD算法在每次迭代中所选的各簇簇中心唯一且为当前簇类目标函数最小值点。最后,基于真实地理场景的仿真实验表明,相比基准算法,FCM-RD不仅能获得位置不受限的可达簇中心,而且能获得更好的聚类效果,为实际场景下的地理空间聚类方案提供了有效且精准的解决方案。展开更多
Pharmaceutical services contribute to the rational use of medicines by ensuring the provision of appropriate, safe and effective pharmacotherapies. Thus, it is important to investigate whether the geographical distrib...Pharmaceutical services contribute to the rational use of medicines by ensuring the provision of appropriate, safe and effective pharmacotherapies. Thus, it is important to investigate whether the geographical distribution of pharmacies causes inequalities in access in countries like Brazil, where there is no federal law regulating the opening of new establishments (in contrast to many European countries). This study analyzed the accessibility of community pharmacies in the city of Sao Mateus, Espírito Santo, Brazil. The authors obtained the geographical coordinates of pharmacies and healthfacilities, which scanned and georeferenced the study area. The 40 pharmacies included in the spatial analysis presented a heterogeneous distribution, with the existence of neighborhoods with an accumulation of pharmacies and others with no pharmacies. The authors found that only 43.7% of the study area received pharmaceutical service coverage, when buffer zones of 350 meters are incorporated, and that most of the districts have a minimum distance of 100 meters between health facilities and pharmacies. It was concluded that the use of GIS proved to be very suitable for analysis of pharmaceutical services, enabling knowledge of the local situation and serving as a stimulus for future studies.展开更多
学区规划的合理性和科学性是基础教育管理工作的重要内容之一。文中以汉中市主城区的中小学为研究对象,借助GIS(Geographical Information System)服务区分析和两步移动搜寻法,基于城市路网、居民区、中小学校数据和人口统计资料,分析...学区规划的合理性和科学性是基础教育管理工作的重要内容之一。文中以汉中市主城区的中小学为研究对象,借助GIS(Geographical Information System)服务区分析和两步移动搜寻法,基于城市路网、居民区、中小学校数据和人口统计资料,分析汉中市主城区16所小学、5所初级中学的服务范围、时间和距离可达性。结果表明:汉中市主城区的中小学学校分布和可达性均具有不平衡性,距离和时间可达性由中心城区向城郊地区递减。其中,3所小学的平均可达时间大于20 min,平均距离成本大于1 km,可达性较差;中学和小学空间分布不均衡,中心城区过于密集,且学区区划范围偏小,城市郊区中小学校分布少且学区区划范围较大。此外,适当完善城市基础道路设施建设和提高路网密度,形成主城区和郊区路网一体化,可提升城市中小学校的可达性。展开更多
文摘设施选址对提高居民生活质量至关重要,利用地理可达相似性聚类对空间元素进行分类是求解此类问题的重要方法。然而,现有的应用于地理可达性分析的聚类算法存在地理可达性测度不准确、不涉及簇中心选取或簇中心不可达等缺陷,不能有效求解真实场景下的设施选址问题。基于此,本文提出一种基于可达距离的模糊C均值聚类算法(Fuzzy C-Means based on Reachable Distance,FCM-RD)。FCM-RD算法改造了经典FCM算法的目标函数、隶属度函数和簇中心函数,使其适用基于可达距离的聚类分析。其次,以沿路网的最短路径距离作为可达距离衡量元素间的地理可达相似性,将聚类元素的二维地理坐标映射为路网坐标,并以此设计簇中心迭代机制,实现在聚类过程中以可达距离迭代不受约束的可达簇中心。同时,对所提簇中心迭代机制的有效性进行理论分析和实验验证,结果表明,FCM-RD算法在每次迭代中所选的各簇簇中心唯一且为当前簇类目标函数最小值点。最后,基于真实地理场景的仿真实验表明,相比基准算法,FCM-RD不仅能获得位置不受限的可达簇中心,而且能获得更好的聚类效果,为实际场景下的地理空间聚类方案提供了有效且精准的解决方案。
文摘Pharmaceutical services contribute to the rational use of medicines by ensuring the provision of appropriate, safe and effective pharmacotherapies. Thus, it is important to investigate whether the geographical distribution of pharmacies causes inequalities in access in countries like Brazil, where there is no federal law regulating the opening of new establishments (in contrast to many European countries). This study analyzed the accessibility of community pharmacies in the city of Sao Mateus, Espírito Santo, Brazil. The authors obtained the geographical coordinates of pharmacies and healthfacilities, which scanned and georeferenced the study area. The 40 pharmacies included in the spatial analysis presented a heterogeneous distribution, with the existence of neighborhoods with an accumulation of pharmacies and others with no pharmacies. The authors found that only 43.7% of the study area received pharmaceutical service coverage, when buffer zones of 350 meters are incorporated, and that most of the districts have a minimum distance of 100 meters between health facilities and pharmacies. It was concluded that the use of GIS proved to be very suitable for analysis of pharmaceutical services, enabling knowledge of the local situation and serving as a stimulus for future studies.
文摘学区规划的合理性和科学性是基础教育管理工作的重要内容之一。文中以汉中市主城区的中小学为研究对象,借助GIS(Geographical Information System)服务区分析和两步移动搜寻法,基于城市路网、居民区、中小学校数据和人口统计资料,分析汉中市主城区16所小学、5所初级中学的服务范围、时间和距离可达性。结果表明:汉中市主城区的中小学学校分布和可达性均具有不平衡性,距离和时间可达性由中心城区向城郊地区递减。其中,3所小学的平均可达时间大于20 min,平均距离成本大于1 km,可达性较差;中学和小学空间分布不均衡,中心城区过于密集,且学区区划范围偏小,城市郊区中小学校分布少且学区区划范围较大。此外,适当完善城市基础道路设施建设和提高路网密度,形成主城区和郊区路网一体化,可提升城市中小学校的可达性。
