The transport of suspended particulate matter is a crucial aspect of studies on sediment source-to-sink processes.However,research on its transport patterns in high-erosion areas of low-latitude seas remains limited.T...The transport of suspended particulate matter is a crucial aspect of studies on sediment source-to-sink processes.However,research on its transport patterns in high-erosion areas of low-latitude seas remains limited.To elucidate modern land-sea interaction processes controlled by the monsoon climate,this study investigates the seasonal transport patterns and control mechanisms of suspended particulate matter in the western Sunda Shelf.Results reveal significant seasonal variations in the spatial distribution of suspended particulate matter concentrations,with elevated levels observed during autumn compared with spring.These differences are directly attributed to the East Asian monsoon,including seasonal monsoon precipitation and the associated transport dynamics.During the northeast monsoon,the Malay Peninsula serves as a primary source for the western sea area,with terrestrial materials from its rivers transported to the northern Gulf of Thailand.This transport pattern shifts to an S-shaped,clockwise circulation during upwelling events.Conversely,in the southwest monsoon,rivers in the northern Gulf of Thailand become the predominant sources for the Sunda Shelf,with terrestrial materials carried by clockwise currents toward the eastern Malay Peninsula.When upwelling occurs off the southern Indochina Peninsula,one branch heads toward the South China Sea and the other toward the southern tip of the Malay Peninsula.The seasonal variation in material sources is further supported by the distribution of clay minerals and the discrimination results of rare earth element proxies,including(La/Sm)UCC-(Gd/Yb)UCCand(La/Yb)UCC-(Gd/Yb)UCC,in surface sediments from the Sunda Shelf and surrounding marine areas.展开更多
One hundred and ten samples of rainwater were collected for chemical analysis at the summit of Huangshan Mountain, a high-altitude site in East China, from July 2010 to June 2011. The volume-weighted-mean （VWM） pH f...One hundred and ten samples of rainwater were collected for chemical analysis at the summit of Huangshan Mountain, a high-altitude site in East China, from July 2010 to June 2011. The volume-weighted-mean （VWM） pH for the whole sampling period was 5.03. SO2- and Ca2＋ were the most abundant anion and cation, respectively. The ionic concentrations varied monthly with the highest concentrations in winter/spring and the lowest in summer. Evident inter-correlations were found among most ions, indicating the common sources for some species and fully mixing characteristics of the alpine precipitation chemistry. The VWM ratio of [SO]-]/[NO3] was 2.54, suggesting the acidity of rainwater comes from both nitric and sulfuric acids. Compared with contemporary observations at other alpine continental sites in China, the precipitation at Huangshan Mountain was the least polluted, with the lowest ionic concentrations. Trajectories to Huangshan Mountain on rainy days could be classified into six groups. The rainwater with influencing air masses originating in Mongolia was the most polluted with limited effect. The emissions of Jiangxi, Anhui, Zhejiang and Jiangsu provinces had a strong influence on the overall rain chemistry at Huangshan Mountain. The rainwater with influencing air masses from Inner Mongolia was heavily polluted by anthropogenic pollutants.展开更多
Exploring transport patterns of soil contaminants is essential for solving the problem of heavy metal contamination in mine soils.In this study,contamination of Pb,Zn,and Cd in the mountain soils of the lead–zinc ore...Exploring transport patterns of soil contaminants is essential for solving the problem of heavy metal contamination in mine soils.In this study,contamination of Pb,Zn,and Cd in the mountain soils of the lead–zinc ore mines in Ganxi Township,Hengdong County,Hunan Province,China was investigated,and their transport patterns were further explored using a soil-column model and numerical simulation techniques.In total,111 mine soil samples were collected and placed into six experimental soil columns.By controlling the water flow,a control soil column group(CK),two mixed soil columns X1 with daily water flows of 1 and 5 L,and three mixed soil columns X3 with daily water flows of 2,3,and 4 L were evaluated.The results showed that the residual fraction of Pb accounted for 71.93%of the content on average,whereas the exchangeable fractions of Zn,Cd,and Fe-Mn oxide-bound fractions of Zn and Cd accounted for 28.60%,31.07%,and 43.2%and 53.54%of the content,respectively.Pb,Zn,and Cd in the soils of the CK,X1,and X3 groups mainly were accumulated at a depth from approximately 0 to 20 cm,and the content at this depth accounted for 60.09%of that at a 0~40 cm depth.The soil at a depth range of 0~10 cm was most seriously contaminated,and the proportion of content was 32.39%of that at a 0~40 cm depth.Numerical simulation showed that on the 5 th day,the pollutant transport range was 0~24 cm,and on the 9 th day,the pollutant transport range exceeded 40 cm.On the 15 th day,the transport capacity of pollutants at depths of 0~40 cm was close to the stable state,but the soil at a depth of 0~10 cm was still heavily polluted.These results reflect the transport pattern of heavy metal pollutants in the soil of lead–zinc ore mines and may provide a reliable scientific support for the prevention of heavy metal contamination in mine environments.展开更多
On the basis of the in situ data of DO2, pH, SiO2. PO4-P, NO3-N and NO2-N collected in the north of the East China Sea during 1987-1988, the following points are mainly expounded.1.The inorgonic nutrients are obviousl...On the basis of the in situ data of DO2, pH, SiO2. PO4-P, NO3-N and NO2-N collected in the north of the East China Sea during 1987-1988, the following points are mainly expounded.1.The inorgonic nutrients are obviously affected by continent runoff in the north of the East China Sea. Their distributions are characteristic of its distribution of terrigenous materials.2.There are three transport paths of nutrients from the shelf to the Kuroshio area. The first is mixing-diffusing-advec-tion and upwelling process, the process of biology and biochemistry belongs to the second, and the sinking process is the last one.3.The swing of the Kuroshio axis affectes both the range of the migration of substances through mixing-diffusing-advec-tion process and the upwelling degree of the subsurface Kuroshio water to the shelf.4.Most part of the substances sink as macroparticles to the deep layer before reaching the Kuroshio area.展开更多
Clay mineral compositions of 199 offshore surface sediment samples collected from the Hangzhou Bay have been analyzed. The clay minerals in the sediments from the Hangzhou Bay are dominated by illite(58.7%, on average...Clay mineral compositions of 199 offshore surface sediment samples collected from the Hangzhou Bay have been analyzed. The clay minerals in the sediments from the Hangzhou Bay are dominated by illite(58.7%, on average), followed by chlorite(20.3%), kaolinite(16.9%) and smectite(4.1%). Two provinces were classified by Q-mode cluster analysis. Class Ⅰ with relatively low amounts of illite and smectite is widely distributed in the Hangzhou Bay, especially concentrated in the top and mouth of the bay, and the northern and southern nearshore areas. Class Ⅱ with comparatively high amounts of illite and smectite is mainly concentrated in the central part of the bay with the water depth of 8–10 m. By comparing clay mineral compositions with the neighbouring regions, we can find that the sediments in the Hangzhou Bay are mainly influenced by the resuspension and repeated deposition of particles from the Yangtze River due to the strong dynamic environment. In particular, the clay fraction of Class Ⅰ is mainly supplied by the Yangtze River, while the sediments of Class Ⅱ are mixture of the clay minerals carried by the Yangtze River and Qiantang River. In general, the distributions of clay minerals in the northern bay are affected by Yangtze River runoff, coastal current and flood tide together, and in the southern they are mainly affected by the Qiantang River runoff and ebb tide.展开更多
The present paper aimed to assess the sediment distribution pattern,mode of transport,and its interaction with hydrodynamic and topographic conditions at different depths and regions along the east coast of India.Abou...The present paper aimed to assess the sediment distribution pattern,mode of transport,and its interaction with hydrodynamic and topographic conditions at different depths and regions along the east coast of India.About 900 surficial sediment samples were collected and analysed on a monthly basis for the Chennai coastal region at 32 stations from 2013 to 2015.The study region is classified into four types,such as beach,inlet,5 m,and 10 m depth.Sediment textural and grain size trend analyses were conducted to achieve the objectives.Sediment characteristics for the region were recorded as sandy,equally dominated by unimodal and bimodal at the beach,while unimodal at shallow depths(5 and 15 m).The sediments were medium sand to coarse sand at the beach,mostly fine followed by medium at 5 and 15 m depths.The sediment sorting is dominated by moderately well-sorted sediments;the skew-ness of beach sediments was negative,while nearshore sediments were found positive;average kurtosis values of sediments were noticed to be mesokurtic.The CM plot depicts that the sediments were mostly derived by tractive current,and the modes of transport are“bottom suspension and rolling”and“graded suspension no rolling”at beach locations and shallow water depths,respectively.The GSTA analysis reveals the annual average sediment transport pattern is northerly.The numerical hydrodynamic study confirms the GSTA and CM plot analysis.The study reveals a stable sedimentary environment south of the Chennai port and instability in the northern part.The study includes large spatiotemporal nearshore sediment data with hydrodynamic conditions,immensely helpful to coastal stake-holders and researchers.展开更多
This paper reviews the process of transportation construction in China and investigates the developmental and spatial characteristics of transportation patterns. The principles of transportation evolution including st...This paper reviews the process of transportation construction in China and investigates the developmental and spatial characteristics of transportation patterns. The principles of transportation evolution including stages, structures and orders are systematically analyzed. The investigation shows that China’s transportation construction mode has upgraded from investment-driven scale expansion to uality improvement driven by efficiency and promotion. The rapid growth and development of transportation networks has significantly influenced economic and social activities in time and space. The resulting spatial convergence and dominance have improved distribution, promoting development of the socioeconomic structure. Regional development that has traditionally been based on corridors has changed into a networked mode centered on cities and metropolitan areas. The transportation pattern follows evolutionary principles. China has been moving from a hierarchical structure to a cascade structure. Simultaneously, the socioeconomic pattern has changed from an axis to a hub-and-spoke structure with a preliminary ordered network. As transportation networks grow, China’s functional spatial structure and ordered network will gradually become stabilized and balanced.展开更多
Consideration of gender equality in transportation planning is quite a new phenomenon. However, its significance is discussed widely by several researchers, particularly, in developing countries. In Kandahar city of A...Consideration of gender equality in transportation planning is quite a new phenomenon. However, its significance is discussed widely by several researchers, particularly, in developing countries. In Kandahar city of Afghanistan, women have limited choices when it comes to using transportation services. With respect to some cultural, social, contextual, environmental, technological and physical barriers;women do not receive equal services from the current transport sectors. Using Revealed Preference and Stated Preference techniques, a survey was conducted in Kandahar city to identify the differences between trip patterns and transportation needs among men and women of the city. Our findings show distinct and clear disparities in socio-demographic characteristics of men and women of Kandahar city leading to trip disparities. Almost all of women do not own any types of personal vehicles, they are less educated and do not have jobs. Likewise, there is a considerable gap between trip characteristics and patterns of men and women. Majority of female trips are for educational purposes while male trips are more dispersed over multiple activities. Motorcycle is the most dominant and preferred mode for men, while women are mostly walking or using available public transit. Compared to men, women were recorded to have lesser trips per day over short distances. Transportation choices of women are also limited to walking, accompanying other male members of family or using public modes. However, men are generally using their private cars, motorcycles and bicycles together with all those options available for women. The results of Multinomial Logit Model showed that all selected variables such as vehicle ownership, income, travel cost and time will be significant factors for mode choice behavior of men, though for female respondents travel time and travel cost are main factors.展开更多
Seed movement is a key hub for the management of Spartina alterniflora.Seed transport patterns under varying dominant wind directions and initiation rates were evaluated by tidal model combined with ecological model.B...Seed movement is a key hub for the management of Spartina alterniflora.Seed transport patterns under varying dominant wind directions and initiation rates were evaluated by tidal model combined with ecological model.Before the simulation,S.alterniflora distribution in the research area was determined and seed deposition rate was measured experimentally.Research findings indicated that:1)Wind direction affected the primary direction of seed dispersal for S.alterniflora.2)A positive correlation was discovered between wind speed and the distance traveled by S.alterniflora seeds,such that seeds showed the longest displacement under prevailing summer winds,with maximum displacement of up to 25 m.3)Starting velocity played a key role in the determination of the extent of S.alterniflora seed dispersal.Specifically,when initiation flow velocity reached 0.1 m s^(-1),seed transport range was maximized.Furthermore,as time progressed,seed transport range continued to expand.展开更多
尽管基于城市轨道交通自动售检票(automatic fare collection,AFC)系统采集的智能卡数据(smart card data,SCD)能够精准记录人们的出行时间和地点,但无法直接反映出行目的或活动类型.本研究提出一种方法,将约束种子K-means算法的站点聚...尽管基于城市轨道交通自动售检票(automatic fare collection,AFC)系统采集的智能卡数据(smart card data,SCD)能够精准记录人们的出行时间和地点,但无法直接反映出行目的或活动类型.本研究提出一种方法,将约束种子K-means算法的站点聚类与隐含狄利克雷分布(latent Dirichlet allocation,LDA)模型的客流出行目的挖掘相结合,以揭示城市轨道交通客流出行数据中的潜在活动模式.首先,基于车站周边的人口特征、客流特征及兴趣点(points of interest,POI)分布,使用约束种子K-means算法将站点划分为8类:就业集聚型、居住集聚型、职住复合型、商业中心型、旅游景点型、综合枢纽型、对外枢纽型以及客流培育型.其次,基于出站时间、活动时长、起点车站类型以及终点车站类型构建了LDA模型.该模型成功识别出5类主要活动,分别为购物消费、工作、回家、休闲旅游及其他.此外,这些模式进一步细分为若干子主题,每个子主题在时间和空间特征上具有显著差异,为深入理解节假日城市轨道交通客流出行行为提供了理论支持.展开更多
基金the Basic Scientific Fund for National Public Research Institutes of China(No.2023Q03)the National Natural Science Foundation of China(Nos.42476078,42306091)+2 种基金the National Programme on Global Change and Air-Sea Interaction(Nos.GASI-04-HYDZ-02,GASI-02-SCS-CJB01)the China-Malaysia Cooperation Project‘Effect on Variability of Seasonal Monsoon on Sedimentary Process in Peninsular Malaysia Waters’the China-Thailand Cooperation Project‘Research on Vulnerability of Coastal Zone’。
文摘The transport of suspended particulate matter is a crucial aspect of studies on sediment source-to-sink processes.However,research on its transport patterns in high-erosion areas of low-latitude seas remains limited.To elucidate modern land-sea interaction processes controlled by the monsoon climate,this study investigates the seasonal transport patterns and control mechanisms of suspended particulate matter in the western Sunda Shelf.Results reveal significant seasonal variations in the spatial distribution of suspended particulate matter concentrations,with elevated levels observed during autumn compared with spring.These differences are directly attributed to the East Asian monsoon,including seasonal monsoon precipitation and the associated transport dynamics.During the northeast monsoon,the Malay Peninsula serves as a primary source for the western sea area,with terrestrial materials from its rivers transported to the northern Gulf of Thailand.This transport pattern shifts to an S-shaped,clockwise circulation during upwelling events.Conversely,in the southwest monsoon,rivers in the northern Gulf of Thailand become the predominant sources for the Sunda Shelf,with terrestrial materials carried by clockwise currents toward the eastern Malay Peninsula.When upwelling occurs off the southern Indochina Peninsula,one branch heads toward the South China Sea and the other toward the southern tip of the Malay Peninsula.The seasonal variation in material sources is further supported by the distribution of clay minerals and the discrimination results of rare earth element proxies,including(La/Sm)UCC-(Gd/Yb)UCCand(La/Yb)UCC-(Gd/Yb)UCC,in surface sediments from the Sunda Shelf and surrounding marine areas.
基金supported by funds from the Scientific Research Projects of High-level Talents of the Department of Human Resources and Social Security of Anhui Province (Grant No.2009Z019)the State Key Laboratory of Atmospheric Boundary Physics and Atmospheric Chemistry (Grant No.LAPC-KF-201105)
文摘One hundred and ten samples of rainwater were collected for chemical analysis at the summit of Huangshan Mountain, a high-altitude site in East China, from July 2010 to June 2011. The volume-weighted-mean （VWM） pH for the whole sampling period was 5.03. SO2- and Ca2＋ were the most abundant anion and cation, respectively. The ionic concentrations varied monthly with the highest concentrations in winter/spring and the lowest in summer. Evident inter-correlations were found among most ions, indicating the common sources for some species and fully mixing characteristics of the alpine precipitation chemistry. The VWM ratio of [SO]-]/[NO3] was 2.54, suggesting the acidity of rainwater comes from both nitric and sulfuric acids. Compared with contemporary observations at other alpine continental sites in China, the precipitation at Huangshan Mountain was the least polluted, with the lowest ionic concentrations. Trajectories to Huangshan Mountain on rainy days could be classified into six groups. The rainwater with influencing air masses originating in Mongolia was the most polluted with limited effect. The emissions of Jiangxi, Anhui, Zhejiang and Jiangsu provinces had a strong influence on the overall rain chemistry at Huangshan Mountain. The rainwater with influencing air masses from Inner Mongolia was heavily polluted by anthropogenic pollutants.
基金funded by the Natural Science Foundation of Hunan Province,grant number“2021JJ30679”the Hunan Provincial Department of Education General Project,grant number“19C1744”。
文摘Exploring transport patterns of soil contaminants is essential for solving the problem of heavy metal contamination in mine soils.In this study,contamination of Pb,Zn,and Cd in the mountain soils of the lead–zinc ore mines in Ganxi Township,Hengdong County,Hunan Province,China was investigated,and their transport patterns were further explored using a soil-column model and numerical simulation techniques.In total,111 mine soil samples were collected and placed into six experimental soil columns.By controlling the water flow,a control soil column group(CK),two mixed soil columns X1 with daily water flows of 1 and 5 L,and three mixed soil columns X3 with daily water flows of 2,3,and 4 L were evaluated.The results showed that the residual fraction of Pb accounted for 71.93%of the content on average,whereas the exchangeable fractions of Zn,Cd,and Fe-Mn oxide-bound fractions of Zn and Cd accounted for 28.60%,31.07%,and 43.2%and 53.54%of the content,respectively.Pb,Zn,and Cd in the soils of the CK,X1,and X3 groups mainly were accumulated at a depth from approximately 0 to 20 cm,and the content at this depth accounted for 60.09%of that at a 0~40 cm depth.The soil at a depth range of 0~10 cm was most seriously contaminated,and the proportion of content was 32.39%of that at a 0~40 cm depth.Numerical simulation showed that on the 5 th day,the pollutant transport range was 0~24 cm,and on the 9 th day,the pollutant transport range exceeded 40 cm.On the 15 th day,the transport capacity of pollutants at depths of 0~40 cm was close to the stable state,but the soil at a depth of 0~10 cm was still heavily polluted.These results reflect the transport pattern of heavy metal pollutants in the soil of lead–zinc ore mines and may provide a reliable scientific support for the prevention of heavy metal contamination in mine environments.
文摘On the basis of the in situ data of DO2, pH, SiO2. PO4-P, NO3-N and NO2-N collected in the north of the East China Sea during 1987-1988, the following points are mainly expounded.1.The inorgonic nutrients are obviously affected by continent runoff in the north of the East China Sea. Their distributions are characteristic of its distribution of terrigenous materials.2.There are three transport paths of nutrients from the shelf to the Kuroshio area. The first is mixing-diffusing-advec-tion and upwelling process, the process of biology and biochemistry belongs to the second, and the sinking process is the last one.3.The swing of the Kuroshio axis affectes both the range of the migration of substances through mixing-diffusing-advec-tion process and the upwelling degree of the subsurface Kuroshio water to the shelf.4.Most part of the substances sink as macroparticles to the deep layer before reaching the Kuroshio area.
基金funded by China-ASEAN maritime cooperation fund: Comparative Study of Holocene Sedimentary Evolution of the Yangtze River Delta and the Red River Deltathe National Natural Science Foundation of China (Nos. 4170 6074 and 41506107)+1 种基金the China Geological Survey (No. DD20160145)the Basic Fund of Ministry of Science Foundation of China (No. 2013FY112200)
文摘Clay mineral compositions of 199 offshore surface sediment samples collected from the Hangzhou Bay have been analyzed. The clay minerals in the sediments from the Hangzhou Bay are dominated by illite(58.7%, on average), followed by chlorite(20.3%), kaolinite(16.9%) and smectite(4.1%). Two provinces were classified by Q-mode cluster analysis. Class Ⅰ with relatively low amounts of illite and smectite is widely distributed in the Hangzhou Bay, especially concentrated in the top and mouth of the bay, and the northern and southern nearshore areas. Class Ⅱ with comparatively high amounts of illite and smectite is mainly concentrated in the central part of the bay with the water depth of 8–10 m. By comparing clay mineral compositions with the neighbouring regions, we can find that the sediments in the Hangzhou Bay are mainly influenced by the resuspension and repeated deposition of particles from the Yangtze River due to the strong dynamic environment. In particular, the clay fraction of Class Ⅰ is mainly supplied by the Yangtze River, while the sediments of Class Ⅱ are mixture of the clay minerals carried by the Yangtze River and Qiantang River. In general, the distributions of clay minerals in the northern bay are affected by Yangtze River runoff, coastal current and flood tide together, and in the southern they are mainly affected by the Qiantang River runoff and ebb tide.
基金study was part of the project on“Water Quality Prediction,Chennai”This manuscript has an NCCR contribution no-NCCR/MS/407.
文摘The present paper aimed to assess the sediment distribution pattern,mode of transport,and its interaction with hydrodynamic and topographic conditions at different depths and regions along the east coast of India.About 900 surficial sediment samples were collected and analysed on a monthly basis for the Chennai coastal region at 32 stations from 2013 to 2015.The study region is classified into four types,such as beach,inlet,5 m,and 10 m depth.Sediment textural and grain size trend analyses were conducted to achieve the objectives.Sediment characteristics for the region were recorded as sandy,equally dominated by unimodal and bimodal at the beach,while unimodal at shallow depths(5 and 15 m).The sediments were medium sand to coarse sand at the beach,mostly fine followed by medium at 5 and 15 m depths.The sediment sorting is dominated by moderately well-sorted sediments;the skew-ness of beach sediments was negative,while nearshore sediments were found positive;average kurtosis values of sediments were noticed to be mesokurtic.The CM plot depicts that the sediments were mostly derived by tractive current,and the modes of transport are“bottom suspension and rolling”and“graded suspension no rolling”at beach locations and shallow water depths,respectively.The GSTA analysis reveals the annual average sediment transport pattern is northerly.The numerical hydrodynamic study confirms the GSTA and CM plot analysis.The study reveals a stable sedimentary environment south of the Chennai port and instability in the northern part.The study includes large spatiotemporal nearshore sediment data with hydrodynamic conditions,immensely helpful to coastal stake-holders and researchers.
基金National Natural Science Foundation of China,No.41771134Strategic Priority Research Program of the Chinese Academy of Sciences,No.XDA19040403
文摘This paper reviews the process of transportation construction in China and investigates the developmental and spatial characteristics of transportation patterns. The principles of transportation evolution including stages, structures and orders are systematically analyzed. The investigation shows that China’s transportation construction mode has upgraded from investment-driven scale expansion to uality improvement driven by efficiency and promotion. The rapid growth and development of transportation networks has significantly influenced economic and social activities in time and space. The resulting spatial convergence and dominance have improved distribution, promoting development of the socioeconomic structure. Regional development that has traditionally been based on corridors has changed into a networked mode centered on cities and metropolitan areas. The transportation pattern follows evolutionary principles. China has been moving from a hierarchical structure to a cascade structure. Simultaneously, the socioeconomic pattern has changed from an axis to a hub-and-spoke structure with a preliminary ordered network. As transportation networks grow, China’s functional spatial structure and ordered network will gradually become stabilized and balanced.
文摘Consideration of gender equality in transportation planning is quite a new phenomenon. However, its significance is discussed widely by several researchers, particularly, in developing countries. In Kandahar city of Afghanistan, women have limited choices when it comes to using transportation services. With respect to some cultural, social, contextual, environmental, technological and physical barriers;women do not receive equal services from the current transport sectors. Using Revealed Preference and Stated Preference techniques, a survey was conducted in Kandahar city to identify the differences between trip patterns and transportation needs among men and women of the city. Our findings show distinct and clear disparities in socio-demographic characteristics of men and women of Kandahar city leading to trip disparities. Almost all of women do not own any types of personal vehicles, they are less educated and do not have jobs. Likewise, there is a considerable gap between trip characteristics and patterns of men and women. Majority of female trips are for educational purposes while male trips are more dispersed over multiple activities. Motorcycle is the most dominant and preferred mode for men, while women are mostly walking or using available public transit. Compared to men, women were recorded to have lesser trips per day over short distances. Transportation choices of women are also limited to walking, accompanying other male members of family or using public modes. However, men are generally using their private cars, motorcycles and bicycles together with all those options available for women. The results of Multinomial Logit Model showed that all selected variables such as vehicle ownership, income, travel cost and time will be significant factors for mode choice behavior of men, though for female respondents travel time and travel cost are main factors.
基金supported by the National Natural Science Foundation of China Joint Fund Projects(No.U21A20164)。
文摘Seed movement is a key hub for the management of Spartina alterniflora.Seed transport patterns under varying dominant wind directions and initiation rates were evaluated by tidal model combined with ecological model.Before the simulation,S.alterniflora distribution in the research area was determined and seed deposition rate was measured experimentally.Research findings indicated that:1)Wind direction affected the primary direction of seed dispersal for S.alterniflora.2)A positive correlation was discovered between wind speed and the distance traveled by S.alterniflora seeds,such that seeds showed the longest displacement under prevailing summer winds,with maximum displacement of up to 25 m.3)Starting velocity played a key role in the determination of the extent of S.alterniflora seed dispersal.Specifically,when initiation flow velocity reached 0.1 m s^(-1),seed transport range was maximized.Furthermore,as time progressed,seed transport range continued to expand.
文摘尽管基于城市轨道交通自动售检票(automatic fare collection,AFC)系统采集的智能卡数据(smart card data,SCD)能够精准记录人们的出行时间和地点,但无法直接反映出行目的或活动类型.本研究提出一种方法,将约束种子K-means算法的站点聚类与隐含狄利克雷分布(latent Dirichlet allocation,LDA)模型的客流出行目的挖掘相结合,以揭示城市轨道交通客流出行数据中的潜在活动模式.首先,基于车站周边的人口特征、客流特征及兴趣点(points of interest,POI)分布,使用约束种子K-means算法将站点划分为8类:就业集聚型、居住集聚型、职住复合型、商业中心型、旅游景点型、综合枢纽型、对外枢纽型以及客流培育型.其次,基于出站时间、活动时长、起点车站类型以及终点车站类型构建了LDA模型.该模型成功识别出5类主要活动,分别为购物消费、工作、回家、休闲旅游及其他.此外,这些模式进一步细分为若干子主题,每个子主题在时间和空间特征上具有显著差异,为深入理解节假日城市轨道交通客流出行行为提供了理论支持.
