In order to comprehensively analyze and compare the characteristics and utilization value of the new wheat variety Jingdong 23, the performance of Jingdong 23 was compared with a control variety based on the results i...In order to comprehensively analyze and compare the characteristics and utilization value of the new wheat variety Jingdong 23, the performance of Jingdong 23 was compared with a control variety based on the results in Beijing water con- servation regional test. The characteristics and yield structures of Jingdong 23 were analyzed. The results showed that the three factors of yield of Jingdong 23 were coordinated and the average yield of Jingdong 23 ranked in the first place among the 14 tested varieties (ten-location tests). On average, the yield of Jingdong 23 was 4.5% more than that of the control Jingdong 8 in water conservation regional test and production test in Beijing. Jingdong 23 has a good adaptability, high and stable yield.展开更多
Farmland protection and delimitation in the urban fringe considers not only natural factors but also the spatial characters and site factors. Taking Daxing District, Beijing in China as a case study, this paper used l...Farmland protection and delimitation in the urban fringe considers not only natural factors but also the spatial characters and site factors. Taking Daxing District, Beijing in China as a case study, this paper used landscape ecology and power-law methods to ana- lyze and evaluate farmland loss during the period of 2004~2007 based on the interpretation results of SPOT5 remote sensing images in 2004 and 2007. At the patch level, we selected four landscape indices, namely patch size, shape index, the nearest neighbor distance between farmland and construction land (including residential land and other construction land), and cropping type, to evaluate the risk of farmland loss and establish a farmland site analysis indicator system. The results showed that patch size and shape index have a sig- nificant positive correlation with farmland loss, whereas the distance to construction land has a clear negative correlation with farmland loss. As regards cropping type, fallow farmland is much easier for non-agriculUlral use than cultivated farmland. The relative transition ratio among vegetable land, fallow farmland and cultivated farmland is 1 : 5.6 : 1. The patch size of lost farmland follows a power-law distribution, indicating that not only small parcels but also large parcels can be lost. Patch size less than 4 ha or more than 15 ha is in high loss risk, between 4 ha and 10 ha in medium loss risk, and larger than 10 ha and less than 15 ha in low risk. Farmland with a more regular shape has a higher likelihood of loss. Patch shape index less than 2.0 is in high loss risk, between 2.0 and 3.0 in medium loss risk, and larger than 3.0 in low risk. Construction land has a varying impact on farmland loss, the residential land effeeted distance is 1000 m, and that of the other construction land is 2000 m. This analysis showed the relationships between site factors and farmland loss, and the analysis framework can provide support and reference for farmland protection and delimitation of prime farmland in China.展开更多
Due to long-term over-exploitation of groundwater in Beijing Municipality, regional groundwater funnels have formed and land subsidence has been induced. By combining a groundwater monitoring network, GPS monitor- ing...Due to long-term over-exploitation of groundwater in Beijing Municipality, regional groundwater funnels have formed and land subsidence has been induced. By combining a groundwater monitoring network, GPS monitor- ing network data, radar satellite SAR data, GIS and other new technologies, a coupled process model based on the dy- namic variation of groundwater and the deformation response of land subsidence has been established. The dynamic variation of groundwater fimnels and the land subsidence response process were analyzed systematically in Beijing. Study results indicate that current groundwater funnel areas are distributed mainly in the southwest of Shunyi District, the northeast of Chaoyang District and the northwest of Tongzhou District, with an average decline rate of groundwa- ter level of 2.66 rn/yr and a maximum of 3.82 m/yr in the center of the funnels. Seasonal and interannual differences exist in the response model of land subsidence to groundwater funnels with uneven spatial and temporal distribution, where the maximum land subsidence rate was about --41.08 mm/yr and the area with a subsidence rate greater than 30 mm/yr was about 1637.29 km2. Although a consistency was revealed to exist between a groundwater funnel and the spatial distribution characteristics of the corresponding land subsidence funnel, this consistency was not perfect. The results showed that the response model of land subsidence to the dynamic variation of groundwater was more revealing when combining conventional technologies with InSAR, GIS, GPS, providing a new strategy for environmental and hydrogeological research and a scientific basis for regional land subsidence control.展开更多
To investigate aerosol optical properties in the Beijing metropolitan area, aerosol absorption coefficient (Ab), scattering coefficient (So), and fine particulate matter (PM2.5) were measured in the Beijing urba...To investigate aerosol optical properties in the Beijing metropolitan area, aerosol absorption coefficient (Ab), scattering coefficient (So), and fine particulate matter (PM2.5) were measured in the Beijing urban area from 20 May to 30 August 2009. The average Ab, So, single scat- tering albedo (SSA), and PM2.5 concentration were 58.0±39.5 M m^-1, 343.5±353.7 M m 1, 0.80±0.10 and 63.6+50.0 μg m^-3, respectively, during the observation period. Ab, Sc, and SSA all showed single peak diurnal variations, with their maximum values being measured at 0500, 1000, and 1300 local time, respectively. Ab and Sc had a strong positive correlation with PM2.5, and Ab, Sc, and PM25 all had positive correlations with relative humidity and negative correlations with wind speed.展开更多
AIM: To investigate the genetic characteristics and pathogenicity of hepatitis E virus (HEV) and assess the potential risk factors for sporadic hepatitis E.
With the increasing number of vehicles in large-and medium-sized cities challenges in urban traffic management, control, and road planning are being faced. Taxi GPS trajectory data is a novel data source that can be u...With the increasing number of vehicles in large-and medium-sized cities challenges in urban traffic management, control, and road planning are being faced. Taxi GPS trajectory data is a novel data source that can be used to study the potential dynamic traffic characteristics of urban roads, and thus identify locations that show a notable lack of road planning. Considering that road traffic characteristics on their own are insufficient for a comprehensive understanding of urban traffic, we develop a road traffic characteristic time series clustering model to analyze the relationship between urban road traffic characteristics and road grade based on existing taxi trajectory data. We select the main urban area of Nanjing as our study area and use the taxi trajectory data of a single month for evaluating our method. The experiments show that the clustering model exhibit good performance and can be successfully used for road traffic characteristic classification. Moreover, we analyze the correlation between traffic characteristics and road grade to identify road segments with planning designs that do not match the actual traffic demands.展开更多
Based on online observations of fine particulate matter(PM2.5) for five consecutive years from January 2013 to December 2017 in Beijing, combined with simultaneous measurement of gaseous precursors and meteorological ...Based on online observations of fine particulate matter(PM2.5) for five consecutive years from January 2013 to December 2017 in Beijing, combined with simultaneous measurement of gaseous precursors and meteorological parameters, the evolution and meteorological causes of fineparticle explosive growth(FPEG) events were analyzed. During the 5-year observation period,132 FPEG events were observed and these events were further divided into three types(3-, 6-, and 9-h events) according to their evolution duration. The majority of FPEG events were observed in winter under the conditions of higher gas precursor concentrations and unfavorable meteorological conditions. The average concentration of PM2.5 during winter FPEG events changed little from 2013 to 2016, whereas it decreased significantly in 2017, in accordance with the similar variation of gaseous species(SO2, NO2, and CO). In addition, the higher wind speeds and lowest relative humidity observed in 2017 were also conducive to the decrease in PM2.5. The evolutions of FPEG events and normal haze episodes were analyzed, revealing that the rate of increase in NO2 was much greater than that of SO2, suggesting more of a contribution from mobile sources than stationary sources. The polar Plot results suggest that the transportation from the southeast area of Beijing plays a major role in the formation of 3-h events, whereas local emissions is the main contributory factor for 9-h events and normal haze episodes. However, further quantitative analysis regarding the contributions of these factors is still needed.展开更多
In the metropolises of China, the metro plays an increasingly important role in commuting because of its efficiency, affordability, and cleanliness. This paper attempts to explore the relationship between walking acce...In the metropolises of China, the metro plays an increasingly important role in commuting because of its efficiency, affordability, and cleanliness. This paper attempts to explore the relationship between walking access distance to metro stations and the demographic characteristics of passengers, such as age, monthly income, travel frequency, gender, and travel purpose, as well as the influence of the urban context. Nanjing Metro Line 2 is selected as the case study. By using different methods such as a questionnaire survey, spatial decay function, analysis of covariance(ANOVA), network analysis of routes, and K-means cluster analysis, it is suggested that demographic characteristics have a significant impact on the pedestrian walking distance, with the exception of gender. Furthermore, the paper finds a spatial decay effect in walking access distance, the decay rate of which, however, varies across stations. Terminal stations have a larger pedestrian catchment area than in regular and exchange stations. Moreover, the passengers of Nanjing Metro Line 2 can be classified into six groups according to their demographic characteristics, among which education and occupation are vital indicators in determining their willingness to walk to the stations. Middle-class passengers have a higher dependence on the metro and tend to walk longer than other groups do. This study provides an important reference for planners and transport sectors to optimize land-use and transport infrastructures.展开更多
Based on the consumer questionnaires of the three traditional retailing centers,Qianmen,Wangfujing and Xidan in Beijing,this article analyzes the present features of consumer composition in the three retailing centers...Based on the consumer questionnaires of the three traditional retailing centers,Qianmen,Wangfujing and Xidan in Beijing,this article analyzes the present features of consumer composition in the three retailing centers.What is more,the evolution course and function transition of traditional retailing centers is revealed based on the changing of consumer composition in different times.Lastly,the renewal method and development trends of traditional retailing centers are discussed based on the evaluation results in consumers'perspective.展开更多
Velocity structure beneath active faults in the Beijing area has been discussed,based on the digital crustal model of velocity from deep seismic sounding profiles and tomography imaging of P waves. We found that there...Velocity structure beneath active faults in the Beijing area has been discussed,based on the digital crustal model of velocity from deep seismic sounding profiles and tomography imaging of P waves. We found that there exists nearly vertical deep faults beneath the Shunyi Depression and the Machiko Depression,which are very likely to be seismogenic faults in the future. In the superficial crust,the north segment of the Shunyi-QianmenLiangxiang fault,the north segment of the Huangzhuang-Gaoliying fault and the Qinghe fault show a trend to converge but without intersecting with vertical deep faults. This kind of seismo-tectonic state has great potential to generate large earthquakes.展开更多
Taking Beijing as an example and based on the census data,macro-level population statistical data and 2004~2013 marriage registration data,this paper makes a contrastive analysis on the characteristics and changing tr...Taking Beijing as an example and based on the census data,macro-level population statistical data and 2004~2013 marriage registration data,this paper makes a contrastive analysis on the characteristics and changing trends of local residents,migrants and temporary migrants. Relative to the local residents,the migrants generally have household registry of central districts and higher educational level and occupational layer. Temporary migrants have relatively complicated population structure but differentiate during the process of marriage matching. 'Two-place marriages'form a stable group of new permanent migrants and meanwhile imply a sizable group of latent dependent migrants. This will produce great infl uences on the general population structure and the aging process,which may also lead to some confl icts and problems. The government should be prepared with policy responses so as to promote the benign development of population diversifi cation in megalopolis.展开更多
基金Supported by Science and Technology Projects of Crop Seed Industry of National SciTech Support Plan(2011BAD35B03)~~
文摘In order to comprehensively analyze and compare the characteristics and utilization value of the new wheat variety Jingdong 23, the performance of Jingdong 23 was compared with a control variety based on the results in Beijing water con- servation regional test. The characteristics and yield structures of Jingdong 23 were analyzed. The results showed that the three factors of yield of Jingdong 23 were coordinated and the average yield of Jingdong 23 ranked in the first place among the 14 tested varieties (ten-location tests). On average, the yield of Jingdong 23 was 4.5% more than that of the control Jingdong 8 in water conservation regional test and production test in Beijing. Jingdong 23 has a good adaptability, high and stable yield.
基金Under the auspices of National Natural Science Foundation of China(No.41130526)Beijing Municipal Natural Science Foundation(No.8122020)
文摘Farmland protection and delimitation in the urban fringe considers not only natural factors but also the spatial characters and site factors. Taking Daxing District, Beijing in China as a case study, this paper used landscape ecology and power-law methods to ana- lyze and evaluate farmland loss during the period of 2004~2007 based on the interpretation results of SPOT5 remote sensing images in 2004 and 2007. At the patch level, we selected four landscape indices, namely patch size, shape index, the nearest neighbor distance between farmland and construction land (including residential land and other construction land), and cropping type, to evaluate the risk of farmland loss and establish a farmland site analysis indicator system. The results showed that patch size and shape index have a sig- nificant positive correlation with farmland loss, whereas the distance to construction land has a clear negative correlation with farmland loss. As regards cropping type, fallow farmland is much easier for non-agriculUlral use than cultivated farmland. The relative transition ratio among vegetable land, fallow farmland and cultivated farmland is 1 : 5.6 : 1. The patch size of lost farmland follows a power-law distribution, indicating that not only small parcels but also large parcels can be lost. Patch size less than 4 ha or more than 15 ha is in high loss risk, between 4 ha and 10 ha in medium loss risk, and larger than 10 ha and less than 15 ha in low risk. Farmland with a more regular shape has a higher likelihood of loss. Patch shape index less than 2.0 is in high loss risk, between 2.0 and 3.0 in medium loss risk, and larger than 3.0 in low risk. Construction land has a varying impact on farmland loss, the residential land effeeted distance is 1000 m, and that of the other construction land is 2000 m. This analysis showed the relationships between site factors and farmland loss, and the analysis framework can provide support and reference for farmland protection and delimitation of prime farmland in China.
基金Under the auspices of Program of International S&T Cooperation (No. 2010DFA92400)Non-profit Industry Financial Program of the Ministry of Water Resources (No. 200901091)+2 种基金Beijing Municipal Natural Science Foundation (No. 8101002)Beijing Municipal Education Commission Plans to Focus Science and Technology Projects (No. KZ201010028030)National Natural Science Foundation of China (No. 41130744,41171335)
文摘Due to long-term over-exploitation of groundwater in Beijing Municipality, regional groundwater funnels have formed and land subsidence has been induced. By combining a groundwater monitoring network, GPS monitor- ing network data, radar satellite SAR data, GIS and other new technologies, a coupled process model based on the dy- namic variation of groundwater and the deformation response of land subsidence has been established. The dynamic variation of groundwater fimnels and the land subsidence response process were analyzed systematically in Beijing. Study results indicate that current groundwater funnel areas are distributed mainly in the southwest of Shunyi District, the northeast of Chaoyang District and the northwest of Tongzhou District, with an average decline rate of groundwa- ter level of 2.66 rn/yr and a maximum of 3.82 m/yr in the center of the funnels. Seasonal and interannual differences exist in the response model of land subsidence to groundwater funnels with uneven spatial and temporal distribution, where the maximum land subsidence rate was about --41.08 mm/yr and the area with a subsidence rate greater than 30 mm/yr was about 1637.29 km2. Although a consistency was revealed to exist between a groundwater funnel and the spatial distribution characteristics of the corresponding land subsidence funnel, this consistency was not perfect. The results showed that the response model of land subsidence to the dynamic variation of groundwater was more revealing when combining conventional technologies with InSAR, GIS, GPS, providing a new strategy for environmental and hydrogeological research and a scientific basis for regional land subsidence control.
基金supported by the Pilot Project of the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.KZCX2-YW-Q11-03)the Research and Development Special Fund for Public Welfare Industry(Meteorology) of the China Meteorological Administration(Grant No. GYHY201006047)+2 种基金the Special Scientific Research Funds for Environment Protection Commonweal Section(Grant No.200809143)the Innovation Method Fund of China(Grant No.2008IM020500)the Ministry of Science and Technology of China(Grant No. 2010DFA22770)
文摘To investigate aerosol optical properties in the Beijing metropolitan area, aerosol absorption coefficient (Ab), scattering coefficient (So), and fine particulate matter (PM2.5) were measured in the Beijing urban area from 20 May to 30 August 2009. The average Ab, So, single scat- tering albedo (SSA), and PM2.5 concentration were 58.0±39.5 M m^-1, 343.5±353.7 M m 1, 0.80±0.10 and 63.6+50.0 μg m^-3, respectively, during the observation period. Ab, Sc, and SSA all showed single peak diurnal variations, with their maximum values being measured at 0500, 1000, and 1300 local time, respectively. Ab and Sc had a strong positive correlation with PM2.5, and Ab, Sc, and PM25 all had positive correlations with relative humidity and negative correlations with wind speed.
基金Supported by The 863 National High Technology Research and Development Program of China,No.2006A02Z453the National Natural Science Foundation of China,No.30570063
文摘AIM: To investigate the genetic characteristics and pathogenicity of hepatitis E virus (HEV) and assess the potential risk factors for sporadic hepatitis E.
基金Under the auspices of National Natural Science Foundation of China(No.41571377)
文摘With the increasing number of vehicles in large-and medium-sized cities challenges in urban traffic management, control, and road planning are being faced. Taxi GPS trajectory data is a novel data source that can be used to study the potential dynamic traffic characteristics of urban roads, and thus identify locations that show a notable lack of road planning. Considering that road traffic characteristics on their own are insufficient for a comprehensive understanding of urban traffic, we develop a road traffic characteristic time series clustering model to analyze the relationship between urban road traffic characteristics and road grade based on existing taxi trajectory data. We select the main urban area of Nanjing as our study area and use the taxi trajectory data of a single month for evaluating our method. The experiments show that the clustering model exhibit good performance and can be successfully used for road traffic characteristic classification. Moreover, we analyze the correlation between traffic characteristics and road grade to identify road segments with planning designs that do not match the actual traffic demands.
基金This study was supported by The Ministry of Science and Technology of the people's Republic of China:[Grant Numbers 2017YFC0210000 and 2016YFC0202700]the National Natural Science Foundation of China:[Grant Number 41705110].
文摘Based on online observations of fine particulate matter(PM2.5) for five consecutive years from January 2013 to December 2017 in Beijing, combined with simultaneous measurement of gaseous precursors and meteorological parameters, the evolution and meteorological causes of fineparticle explosive growth(FPEG) events were analyzed. During the 5-year observation period,132 FPEG events were observed and these events were further divided into three types(3-, 6-, and 9-h events) according to their evolution duration. The majority of FPEG events were observed in winter under the conditions of higher gas precursor concentrations and unfavorable meteorological conditions. The average concentration of PM2.5 during winter FPEG events changed little from 2013 to 2016, whereas it decreased significantly in 2017, in accordance with the similar variation of gaseous species(SO2, NO2, and CO). In addition, the higher wind speeds and lowest relative humidity observed in 2017 were also conducive to the decrease in PM2.5. The evolutions of FPEG events and normal haze episodes were analyzed, revealing that the rate of increase in NO2 was much greater than that of SO2, suggesting more of a contribution from mobile sources than stationary sources. The polar Plot results suggest that the transportation from the southeast area of Beijing plays a major role in the formation of 3-h events, whereas local emissions is the main contributory factor for 9-h events and normal haze episodes. However, further quantitative analysis regarding the contributions of these factors is still needed.
基金Under the auspices of National Nature Science Foundation of China(No.41701180)
文摘In the metropolises of China, the metro plays an increasingly important role in commuting because of its efficiency, affordability, and cleanliness. This paper attempts to explore the relationship between walking access distance to metro stations and the demographic characteristics of passengers, such as age, monthly income, travel frequency, gender, and travel purpose, as well as the influence of the urban context. Nanjing Metro Line 2 is selected as the case study. By using different methods such as a questionnaire survey, spatial decay function, analysis of covariance(ANOVA), network analysis of routes, and K-means cluster analysis, it is suggested that demographic characteristics have a significant impact on the pedestrian walking distance, with the exception of gender. Furthermore, the paper finds a spatial decay effect in walking access distance, the decay rate of which, however, varies across stations. Terminal stations have a larger pedestrian catchment area than in regular and exchange stations. Moreover, the passengers of Nanjing Metro Line 2 can be classified into six groups according to their demographic characteristics, among which education and occupation are vital indicators in determining their willingness to walk to the stations. Middle-class passengers have a higher dependence on the metro and tend to walk longer than other groups do. This study provides an important reference for planners and transport sectors to optimize land-use and transport infrastructures.
文摘Based on the consumer questionnaires of the three traditional retailing centers,Qianmen,Wangfujing and Xidan in Beijing,this article analyzes the present features of consumer composition in the three retailing centers.What is more,the evolution course and function transition of traditional retailing centers is revealed based on the changing of consumer composition in different times.Lastly,the renewal method and development trends of traditional retailing centers are discussed based on the evaluation results in consumers'perspective.
基金sponsored by the National Science & Technology Pillar Program (2006BAC13B01-0203)the Specific Earthquake Scientific Research Program (200808008),China
文摘Velocity structure beneath active faults in the Beijing area has been discussed,based on the digital crustal model of velocity from deep seismic sounding profiles and tomography imaging of P waves. We found that there exists nearly vertical deep faults beneath the Shunyi Depression and the Machiko Depression,which are very likely to be seismogenic faults in the future. In the superficial crust,the north segment of the Shunyi-QianmenLiangxiang fault,the north segment of the Huangzhuang-Gaoliying fault and the Qinghe fault show a trend to converge but without intersecting with vertical deep faults. This kind of seismo-tectonic state has great potential to generate large earthquakes.
文摘Taking Beijing as an example and based on the census data,macro-level population statistical data and 2004~2013 marriage registration data,this paper makes a contrastive analysis on the characteristics and changing trends of local residents,migrants and temporary migrants. Relative to the local residents,the migrants generally have household registry of central districts and higher educational level and occupational layer. Temporary migrants have relatively complicated population structure but differentiate during the process of marriage matching. 'Two-place marriages'form a stable group of new permanent migrants and meanwhile imply a sizable group of latent dependent migrants. This will produce great infl uences on the general population structure and the aging process,which may also lead to some confl icts and problems. The government should be prepared with policy responses so as to promote the benign development of population diversifi cation in megalopolis.