With the widespread adoption of location- aware technology, obtaining long-sequence, massive and high-accuracy spatiotemporal trajectory data of individuals has become increasingly popular in various geographic studie...With the widespread adoption of location- aware technology, obtaining long-sequence, massive and high-accuracy spatiotemporal trajectory data of individuals has become increasingly popular in various geographic studies. Trajectory data of taxis, one of the most widely used inner-city travel modes, contain rich information about both road network traffic and travel behavior of passengers. Such data can be used to study the microscopic activity patterns of individuals as well as the macro system of urban spatial structures. This paper focuses on trajectories obtained from GPS-enabled taxis and their applications for mining urban commuting patterns. A novel approach is proposed to discover spatiotemporal patterns of household travel from the taxi trajectory dataset with a large number of point locations. The approach involves three critical steps： spatial clustering of taxi origin-destination （OD） based on urban traffic grids to discover potentially meaningful places, identifying thresh- old values from statistics of the OD clusters to extract urban jobs-housing structures, and visualization of analytic results to understand the spatial distribution and temporal trends of the revealed urban structures and implied household commuting behavior. A case study with a taxi trajectory dataset in Shanghai, China is presented to demonstrate and evaluate the proposed method.展开更多
Soil moisture variability in natural landscapes has been widely studied; however, less attention has been paid to its variability in the urban landscapes with respect to the possible influence of texture stratificatio...Soil moisture variability in natural landscapes has been widely studied; however, less attention has been paid to its variability in the urban landscapes with respect to the possible influence of texture stratification and irrigation management. Therefore, a case study was carried out in the Beijing Olympic Forest Park to continuously monitor the soil in three typical profiles from 26 April to 11 November 2010. The texture stratification significantly affected the vertical distribution of moisture in the non- irrigated profile where moisture was mostly below field capacity. In the profile where irrigation was sufficient to maintain moisture above field capacity, gravity flow led to increased moisture with depth and thus eliminated the influence of texture. In the non-irrigated sites, the upper layer （above 80 cm） exhibited long-term moisture persis- tence with the time scale approximating the average rainfall interval. However, a coarse-textured layer wea- kened the influence of rainfall, and a fine-textured layer weakened the influence of evapotranspiration, both of which resulted in random noise-like moisture series in the deeper layers. At the irrigated site, frequent irrigation neutralized the influence of evapotranspiration in the upper layer （above 60 em） and overshadowed the influence of rainfall in the deeper layer. As a result, the moisture level in the upper layer also behaved as a random noise-like series; whereas due to deep transpiration, the moisture of the deep layer had a persistence time-scale longer than a month, consistent with characteristic time-scales found for deep transpiration.展开更多
本文回顾性分析了19例晚期肝癌伴门脉癌栓病人的介入治疗疗效和肝动脉栓塞的安全性。结果显示19例中有13例肿瘤不同程度的缩小,全部是经加用碘油或明胶海绵栓塞肝动脉的病例。在抗癌药物加碘油、明胶海绵栓塞的肝动脉组中,9例门脉显影者...本文回顾性分析了19例晚期肝癌伴门脉癌栓病人的介入治疗疗效和肝动脉栓塞的安全性。结果显示19例中有13例肿瘤不同程度的缩小,全部是经加用碘油或明胶海绵栓塞肝动脉的病例。在抗癌药物加碘油、明胶海绵栓塞的肝动脉组中,9例门脉显影者仅1例 ALT 和 AST 升高,而3例门脉未显影者全部升高。因此作者认为:对伴有门脉癌栓的晚期肝癌,只要间接门脉造影显示门静脉,亦应加用碘油和明胶海绵栓塞肝动脉。但对门脉未显影者,用碘油栓塞是安全的,但不宜用明胶海绵栓塞。展开更多
基金This research is sponsored by the National High Technology Research and Development of China （No. 2013AA 12A402）, the National Natural Science Foundation of China （Grant Nos. 40771138, 41101371, and 41301484） and the Zhejiang Province Key Scientific and Technological Project （No. 2013C01124）. Thanks to Dr. Zhongwei Deng for providing taxi trajectory data of Shanghai, China.
文摘With the widespread adoption of location- aware technology, obtaining long-sequence, massive and high-accuracy spatiotemporal trajectory data of individuals has become increasingly popular in various geographic studies. Trajectory data of taxis, one of the most widely used inner-city travel modes, contain rich information about both road network traffic and travel behavior of passengers. Such data can be used to study the microscopic activity patterns of individuals as well as the macro system of urban spatial structures. This paper focuses on trajectories obtained from GPS-enabled taxis and their applications for mining urban commuting patterns. A novel approach is proposed to discover spatiotemporal patterns of household travel from the taxi trajectory dataset with a large number of point locations. The approach involves three critical steps： spatial clustering of taxi origin-destination （OD） based on urban traffic grids to discover potentially meaningful places, identifying thresh- old values from statistics of the OD clusters to extract urban jobs-housing structures, and visualization of analytic results to understand the spatial distribution and temporal trends of the revealed urban structures and implied household commuting behavior. A case study with a taxi trajectory dataset in Shanghai, China is presented to demonstrate and evaluate the proposed method.
文摘Soil moisture variability in natural landscapes has been widely studied; however, less attention has been paid to its variability in the urban landscapes with respect to the possible influence of texture stratification and irrigation management. Therefore, a case study was carried out in the Beijing Olympic Forest Park to continuously monitor the soil in three typical profiles from 26 April to 11 November 2010. The texture stratification significantly affected the vertical distribution of moisture in the non- irrigated profile where moisture was mostly below field capacity. In the profile where irrigation was sufficient to maintain moisture above field capacity, gravity flow led to increased moisture with depth and thus eliminated the influence of texture. In the non-irrigated sites, the upper layer （above 80 cm） exhibited long-term moisture persis- tence with the time scale approximating the average rainfall interval. However, a coarse-textured layer wea- kened the influence of rainfall, and a fine-textured layer weakened the influence of evapotranspiration, both of which resulted in random noise-like moisture series in the deeper layers. At the irrigated site, frequent irrigation neutralized the influence of evapotranspiration in the upper layer （above 60 em） and overshadowed the influence of rainfall in the deeper layer. As a result, the moisture level in the upper layer also behaved as a random noise-like series; whereas due to deep transpiration, the moisture of the deep layer had a persistence time-scale longer than a month, consistent with characteristic time-scales found for deep transpiration.
文摘本文回顾性分析了19例晚期肝癌伴门脉癌栓病人的介入治疗疗效和肝动脉栓塞的安全性。结果显示19例中有13例肿瘤不同程度的缩小,全部是经加用碘油或明胶海绵栓塞肝动脉的病例。在抗癌药物加碘油、明胶海绵栓塞的肝动脉组中,9例门脉显影者仅1例 ALT 和 AST 升高,而3例门脉未显影者全部升高。因此作者认为:对伴有门脉癌栓的晚期肝癌,只要间接门脉造影显示门静脉,亦应加用碘油和明胶海绵栓塞肝动脉。但对门脉未显影者,用碘油栓塞是安全的,但不宜用明胶海绵栓塞。
