基于西安市菜鸟驿站和中国邮政速递的POI(point of interest,兴趣点)数据,综合运用数理统计、文本词频分析、空间分析等方法,解析菜鸟驿站的依托组织形式与服务对象类型,空间分布特征与区位选择特征,及其与中国邮政速递的空间竞合关系...基于西安市菜鸟驿站和中国邮政速递的POI(point of interest,兴趣点)数据,综合运用数理统计、文本词频分析、空间分析等方法,解析菜鸟驿站的依托组织形式与服务对象类型,空间分布特征与区位选择特征,及其与中国邮政速递的空间竞合关系。研究发现:①菜鸟驿站依托类型以商品销售型为主,社会服务型和个体店铺型次之;其服务对象以社区为主,商业街区、大学城次之;②菜鸟驿站空间上呈现“中心城区多,周边区县少”的“内密外疏”格局,并沿东北-西南走向分布;③区位选择特征,大尺度表现为以钟楼为中心,随距离增加,驿站数量呈现出低-高-低的分布规律;小尺度则在与服务对象出入口距离区间[100,300]内存在二维正态分布;④菜鸟驿站与目标对象直线可达距离平均位于200m范围以内,且街区活力点与其服务对象主体相适应;⑤邮政站点与菜鸟驿站均由中心城区向外围区县扩张式发展,前者分布范围更广,二者在地理邻近竞争二者中趋于协同发展。展开更多
Silica aerogel was prepared by a sol-gel method with combination of freeze drying.The aerogel was filled with TiCl4 in autoclave and used to fabricate a hierarchical structure of TiO_(2) nanofiber shell and SiO_(2) ae...Silica aerogel was prepared by a sol-gel method with combination of freeze drying.The aerogel was filled with TiCl4 in autoclave and used to fabricate a hierarchical structure of TiO_(2) nanofiber shell and SiO_(2) aerogel core(SiO_(2)@TiO_(2)).The TiO_(2) nanofibers with a diameter of 10-15 nm were highly crystalline and mainly grew along the(101)or(001)planes,favoring charge migration along the growth axis of the fibers.The photoluminescence(PL)emission spectra show that the TiO_(2) nanofibers exhibited much lower PL intensity than P25.The free standing TiO2 nanofibers loaded with CuO had a band gap of 3.04 eV.When CuO was hierarchically loaded on the nanofiber surface and into the aerogel core(SiO_(2)/CuO@TiO_(2)/CuO),the absorption edge significantly red shifted,and the band gap was further narrowed to 2.66 eV.Meanwhile,Fe^(3+)implanted TiO_(2) nanofibers on the aerogel surface(SiO_(2)@Fe-TiO_(2))were also fabricated in the same strategy.The CuO loaded nanofibers(SiO_(2)/CuO@Fe-TiO_(2)/CuO)had a band gap of 2.62 eV.The photocatalytic reduction of CO_(2) was performed under light irradiation by a 300 W Xe-lamp for 4 h.The methanol yield over the SiO_(2)/CuO@Fe-TiO_(2)/CuO reached~2,400 μmol·gcat^(-1) in the absence of sacrificial agent.展开更多
文摘基于西安市菜鸟驿站和中国邮政速递的POI(point of interest,兴趣点)数据,综合运用数理统计、文本词频分析、空间分析等方法,解析菜鸟驿站的依托组织形式与服务对象类型,空间分布特征与区位选择特征,及其与中国邮政速递的空间竞合关系。研究发现:①菜鸟驿站依托类型以商品销售型为主,社会服务型和个体店铺型次之;其服务对象以社区为主,商业街区、大学城次之;②菜鸟驿站空间上呈现“中心城区多,周边区县少”的“内密外疏”格局,并沿东北-西南走向分布;③区位选择特征,大尺度表现为以钟楼为中心,随距离增加,驿站数量呈现出低-高-低的分布规律;小尺度则在与服务对象出入口距离区间[100,300]内存在二维正态分布;④菜鸟驿站与目标对象直线可达距离平均位于200m范围以内,且街区活力点与其服务对象主体相适应;⑤邮政站点与菜鸟驿站均由中心城区向外围区县扩张式发展,前者分布范围更广,二者在地理邻近竞争二者中趋于协同发展。
基金The authors acknowledgement the financial supports from the Key R&D Planning Project of Hainan Province(No.ZDYF2020015)the Research Lab Construction of Hainan University(No.ZY2019HN09)the National Natural Science Foundation of China(No.51761010).
文摘Silica aerogel was prepared by a sol-gel method with combination of freeze drying.The aerogel was filled with TiCl4 in autoclave and used to fabricate a hierarchical structure of TiO_(2) nanofiber shell and SiO_(2) aerogel core(SiO_(2)@TiO_(2)).The TiO_(2) nanofibers with a diameter of 10-15 nm were highly crystalline and mainly grew along the(101)or(001)planes,favoring charge migration along the growth axis of the fibers.The photoluminescence(PL)emission spectra show that the TiO_(2) nanofibers exhibited much lower PL intensity than P25.The free standing TiO2 nanofibers loaded with CuO had a band gap of 3.04 eV.When CuO was hierarchically loaded on the nanofiber surface and into the aerogel core(SiO_(2)/CuO@TiO_(2)/CuO),the absorption edge significantly red shifted,and the band gap was further narrowed to 2.66 eV.Meanwhile,Fe^(3+)implanted TiO_(2) nanofibers on the aerogel surface(SiO_(2)@Fe-TiO_(2))were also fabricated in the same strategy.The CuO loaded nanofibers(SiO_(2)/CuO@Fe-TiO_(2)/CuO)had a band gap of 2.62 eV.The photocatalytic reduction of CO_(2) was performed under light irradiation by a 300 W Xe-lamp for 4 h.The methanol yield over the SiO_(2)/CuO@Fe-TiO_(2)/CuO reached~2,400 μmol·gcat^(-1) in the absence of sacrificial agent.
