In this study, we developed an energy security evaluation model(ESEM) from three dimensions, energy supply-transport security, safety of energy utilization, and stability of political-socioeconomic environment, based ...In this study, we developed an energy security evaluation model(ESEM) from three dimensions, energy supply-transport security, safety of energy utilization, and stability of political-socioeconomic environment, based on the integrated application of subjective and objective weight allocation technique. Then the spatial-temporal evolution of global energy security pattern and its driving mechanism was analyzed with the method above, and the results are shown as follows:(1) since the 1990 s, the spatial patterns of global energy security have shown a deteriorating trend, with the growth of countries in at-risk type and relatively at-risk type.(2) The spatial distribution of countries with secure energy system shows a strong stability, and these countries are concentrated persistently in Western Europe and North America. The spatial evolution of countries with relatively secure energy system also presents a strong stability, which are mainly distributed in the periphery of the secure ones, namely Central and Southern Europe, South America and Eurasia, while countries with general energy system are mainly distributed in Asia, Africa and Southern Europe, and the spatial-temporal evolution of this type is the main cause for the deterioration of world energy security pattern. Countries with at-risk and relatively at-risk energy system are mainly concentrated in Africa, Asia, the Middle East and Eurasia, rendering spatial extension to the east and south.(3) In the past 20 years, the mechanism for world’s energy security pattern formation gradually transforms from the ‘unitary dimension dominated’ to the ‘binary dimension-dominated’, and the main factors influencing the global energy security pattern become more diverse.(4) In the pattern of world’s energy security, China’s performance on energy security has been the global average since the 1990 s, which shows a decreasing trend in safety of energy utilization dimension. Findings in this study can provide a reference for the government in terms of formulating strategic responses and policy options.展开更多
Formation and evolution of rural settlement patterns in Lianzhou City,Guangdong Province were analyzed from the perspective of space and time,on the basis of its gazetteer and relevant historical data.The results show...Formation and evolution of rural settlement patterns in Lianzhou City,Guangdong Province were analyzed from the perspective of space and time,on the basis of its gazetteer and relevant historical data.The results show that Lianzhou was first founded in the sixth year of Yuanding Period of the Western Han Dynasty,and its development could be roughly classified into 6 stages according to the construction of south–north traffic lines and regional development progress,and it witnessed the fastest development in the Ming and Qing Dynasty.In terms of spatial distribution,rural settlements in the local area show spatial continuity,Lianzhou Town is the core of rural settlement growth in the city,and towns with the most concentrated rural settlements in all stages are located in central-west and northeast parts of the city,and those with lower density of rural settlements are mostly located in minority regions in the north and mountainous areas in the east.On the basis of the above facts,the paper studies the influence of natural geological conditions,immigrant,traffic,economic development and ethnic composition on the establishment and development of rural settlements in Lianzhou City.展开更多
Currently, the agricultural growth in developed countries mainly relies on the improvement of productivity, which is also the target for China. Accordingly, the purpose of this study was to describe the spatial-tempor...Currently, the agricultural growth in developed countries mainly relies on the improvement of productivity, which is also the target for China. Accordingly, the purpose of this study was to describe the spatial-temporal evolution pattern of agricultural productivity, to reveal changes in total factor productivity in 2ooo-2olo, and analyze the impact of these changes in northwestern Sichuan plateau, China. Using data envelopment analysis （DEA） and the Malmquist Index, an in-depth study was conducted on agricultural productivity and changes in total factor productivity of 31 counties in northwestern Sichuan plateau. Results indicated that： （1） geographically, counties with optimal efficiency were mainly located in the north of northwestern Sichuan plateau and those with the lowest efficiency, in the south; （2） relative to pure technical efficiency, scale efficiency was the dominant factor in determining agricultural productivity; （3） the redundancy rate of input factors in zolo was slightly lower than that in zooo, thereby indicating an improved utilization of input factors to a certain extent and a great potential for further improving such utilization; （4） during the 2ooo-2olo period, the agricultural total factor productivity had an average annual growth rate of 8.3%, but the growth rates in various regions differed widely; （5） technical progress was the dominant factor promoting the improvement of total factor oroductivitv inagriculture. The disparities in spatial distribution may be due to the differences of natural conditions, former level agricultural productivity between counties. The findings are valuable for the government to make sustainable development policies for agriculture and improving agricultural development in northwestern Sichuan plateau.展开更多
The purpose of this study was to find out the spatial-temporal rules and driving force of cultivated land quality in Henan Province in the last ten years. Agricultural land grading factor evaluation was used to evalua...The purpose of this study was to find out the spatial-temporal rules and driving force of cultivated land quality in Henan Province in the last ten years. Agricultural land grading factor evaluation was used to evaluate the cultivated land quality of 2002 and 2012 in Henan Province, and to research the change laws. Method of correlation coefficient was employed to select the driving forces affecting cultivated land quality evolution. The results indicated that the cultivated land quality in Henan Province increased slightly in the last ten years in general, and in spatial there were unchanged regions, increased regions and decreased regions. The cultivated land quality in spatial presented the trend of good becoming better, bad becoming worse, which should be highly valued in cultivated land quality protection and management. Land development and consolidation projects had significant contributions to increasing the cultivated land quality. Driving forces between the sudden change regions and gradual change regions were significantly different. The paper concluded that the research on the spatial-temporal evolution and driving force of cultivated land quality based on cultivated land quality evolution had important academic significance and practical value.展开更多
In active rift basins, tectonism is extremely important for sequence stratigraphic patterns, affecting both the sequence architecture and internal makeup. Sequence stratigraphic framework of a Paleogene rift successio...In active rift basins, tectonism is extremely important for sequence stratigraphic patterns, affecting both the sequence architecture and internal makeup. Sequence stratigraphic framework of a Paleogene rift succession in Qiongdongnan Basin, northern South China Sea, was built using seismic profiles, complemented by well logs and cores. One first-order and three second-order sequences were identified on the basis of basin-scale unconformities, and seven third-order sequences are defined by unconformities along the basin margins and correlative conformities within the central basin. Through unconformity analysis and backstripping procedure, the Paleogene synrift tectonic evolution of deep- water area of Qiongdongnan Basin was proved to be episodic, which can be divided into rifting stage-I, rifting stage-II and rifting stage-III. Episodic rifting resulted in the formation of various types of struc- tural slope break belts, which controlled different architectures and internal makeup of sequences. This study enhances the understanding of the control of tectonic evolution on sequence stratigraphic pat- terns and establishes relevant patterns in a typical rift basin, and further proposes the favorable sand- stone reservoirs developing in different sequence stratigraphic patterns, which will be pretty helpful for subtle pool exploration in deepwater area of petroliferous basins.展开更多
Evapotranspiration （ET） is the sum of soil or water body evaporation and plant transpiration from the earth surface and ocean to the atmosphere, and thus plays a significant role in regulating carbon and water resou...Evapotranspiration （ET） is the sum of soil or water body evaporation and plant transpiration from the earth surface and ocean to the atmosphere, and thus plays a significant role in regulating carbon and water resource cycles. The time-series data set from the remote sensing MOLDS product （MOD16） was used to study the spatial-temporal evolution of vegetation evapotranspiration in salinized areas during 2000-2014 by analyzing the variability, spatial patterns and Mann-Kendall （MK） nonparametric trends for the time series. The results indicate that inter-annual and intra-annual variations of ET across various vegetated areas show seasonal changes, with the abnormal months identified. The Cultivated land displays a greater degree of spatial heterogeneity and the spatial pattern of ET in the area covered by broadleaved deciduous forests corresponds to a higher ET rate and increased water consumption. Awidespread decline of ET is observed only in cultivated areas. However, agricultural cultivation doesn＇t worsen water shortage and soil salinization problems in the region, and water shortage problems are worsening for other vegetated areas. This research provides a basis of reference for the reasonable allocation of water resources and restructuring of vegetation patterns in salinized areas.展开更多
This article presents the findings of a study of the spheres of urban influence with regard to all cities in China(not including Hong Kong,Macao and Taiwan Province of China)in the years 1990,2000 and 2009.An optimize...This article presents the findings of a study of the spheres of urban influence with regard to all cities in China(not including Hong Kong,Macao and Taiwan Province of China)in the years 1990,2000 and 2009.An optimized gravity model with comprehensive time distance was used to carry out a detailed analysis of the spatial patterns of Chinese spheres of urban influence and the spatial characteristics of urban agglomerations.Such urban agglomerations are characterized by high density population and a developed economy,which are also considered as the national competition unit.This paper initially identifies four spatial patterns of urban agglomerations based on the spatial layout of city groups during their evolution.Some basic characteristics of urban agglomerations are outlined,including the number of cities,the size of cities and the functions of urban centers.These characteristics are examined by using statistical methods and Geographic Information System(GIS).The main findings from this research are that the development stages and structures of urban agglomerations in China vary significantly.It is also clear that the stages and evolution of spatial patterns are strongly affected and dominated by both policy and location factors.展开更多
Tectonism is of extreme importance to sequence stratigraphic patterns in continental sedimentary basins, affecting both the architectures and internal makeup of sequences. Sequence stratigraphic framework of the Paleo...Tectonism is of extreme importance to sequence stratigraphic patterns in continental sedimentary basins, affecting both the architectures and internal makeup of sequences. Sequence stratigraphic framework of the Paleogene system in the Fushan sag, northern South China Sea, was built using 3D and 2D seismic data, complemented by drilling cores and well logs data. One first-order, three second-order and seven third-order sequences were identified. Analysis of paleotectonic stress field, unconformities and subsidence history showed that the Paleogene tectonic evolution presented significant characteristics of multistage and episode, and can be divided into three stages： rifting stage I（initial rifting period）, rifting stage II（rapid subsidence period）, rifting stage III（fault-depressed diversionary period）. Partition of the west and east in tectonic activity was obvious. The west area showed relatively stronger tectonic activity than the east area, especially during the rifting stage II. Episodic rifting and lateral variations in tectonic activity resulted in a wide variety of structural slope break belts, which controlled both the sequence architectures and interval makeup, and strongly constrained the development of special facies zones or sand bodies that tended to form hydrocarbon accumulation. This paper classifies the genetic types of slope break belts and their relevant sequence stratigraphic patterns within the Fushan sag, and further discusses the tectonic evolution controls on sequence stratigraphic patterns, which suggests that vertical evolution paths of structural slope break belts and relevant sequence stratigraphic patterns as a response to the Paleogene tectonic evolution were strongly controlled by sag margin types and lateral variations of tectonic activity.展开更多
Migration plays an increasing role in China＇s economy since mobility rose and economic restructuring has proceeded during the last three decades. Given the background of most studies focusing on migration in a partic...Migration plays an increasing role in China＇s economy since mobility rose and economic restructuring has proceeded during the last three decades. Given the background of most studies focusing on migration in a particular period, there is a critical need to analyze the spatial-temporal patterns of migration. Using bicomponent trend mapping technique and interprovincial migration data during the periods 1985-1990, 1990-1995, 1995-2000, 2000- 2005, and 2005-2010 we analyze net-, in-, out-migration intensity, and their changes over time in this study. Strong spatial variations in migration intensity were found in China＇s interprovincial migration, and substantial increase in migration intensity was also detected in eastern China during 1985-2010. Eight key destinations are mostly located within the three rapidly growing economic zones of eastern China （Pearl River Delta, Yangtze River Delta and Beijing-Tianjin-Hebei Metropolitan Region）, and they are classified into three types： mature, emerging, and fluctuant origins, while most key origins are relatively undeveloped central and western provinces, which are exactly in accordance with China＇s economic development patterns. The results of bicomponent trend mapping indicate that, in a sense, the migration in the south was more active than the north over the last three decades. The result shows the new changing features of spatial-temporal patterns of China＇s interprovincial migration that Fan and Chen did not find out in their research. A series of social-economic changes including rural transformation, balanced regional development, and labor market changes should be paid more attention to explore China＇s future interprovincial migration.展开更多
In this work,we study the development,evolution,and migration of turbulent coherent structures in the turbulent boundary layer at Reτ=630 using time-resolved particle image velocimetry(TR-PIV).Multiple techniques,inc...In this work,we study the development,evolution,and migration of turbulent coherent structures in the turbulent boundary layer at Reτ=630 using time-resolved particle image velocimetry(TR-PIV).Multiple techniques,including multi-scale analysis,conditional averaging,cross-correlation,and spatial-temporal topological analysis are applied to extract the evolution principle,migration trajectory,and convection velocity vector of the targeted coherent structures from a Lagrangian perspective.The spanwise vortex structures with larger scale and intensity at a certain wall-normal height y were the main focus of the present study.In the statistical sense,spanwise vortex structures move away from the wall with the shape changing from a bulge to an ellipse,and finally to a circle.Two straight lines emerge from the mean transfer trajectory curve of the spanwise vortex,in which the horizontal one is located at the viscous sublayer(y^(+)<10),the other is a logarithmic straight line existing in the range of 50<y^(+)<120,and the inclination angle of the tangential migration path is fixed at around 12°.The streamwise convection velocity U_(c)of scaled spanwise vortex structures satisfies U_(c)/U_(∞)=0.5-0.6 below y=0.03δ(i.e.,U^(+)_(c)=11-13 undery^(+)=20).In particular,in the region of 50<y^(+)<120,the velocity growth curves of U_(c)and wall-normal convection velocity V_(c)follow the log-law distribution very well,and the slopes are consistent with that of the log-law region of the turbulent boundary layer.Our observations provide microscopic evidences of the logarithmic-linear distribution of the migration trajectory of spanwise vortex structures.展开更多
With basic information from 8353 archaeological sites, this study describes a holistic spatial-temporal distribution pattern of archaeological sites of the prehistoric culture sequence from 9.5 ka BP (ka BP = thousand...With basic information from 8353 archaeological sites, this study describes a holistic spatial-temporal distribution pattern of archaeological sites of the prehistoric culture sequence from 9.5 ka BP (ka BP = thousands of years before 0 BP, where "0 BP" is defined as the year AD 1950) to 2.3 ka BP in the region that extends from the Yanshan Mountains to the Liaohe River Plain(i.e., the Yan-Liao region) in northern China. Based on spatial statistics analysis – including the spatial density of the sites and Geographic Information System nearest-neighbour analysis, combined with a review of environmental and climatic data – this paper analyses cultural evolution, the spatial-temporal features of the archaeological sites and human activities against the backdrop of climatic and environmental changes in this region. The results reveal that prehistoric cultural evolution in the Yan-Liao region is extensively influenced by climatic and environmental changes. The Xinglongwa, Zhaobaogou and Fuhe cultures, which primarily developed during a habitable period from 8.5 ka BP to 6.0 ka BP with strong summer monsoons, have similar maximum density values, spatial patterns and subsistence strategies dominated by hunting-gathering. Significant changes occurred in the Hongshan and Lower Xiajiadian cultures, with a significant increase in numbers and densities of sites and a slump in average nearest-neighbour ratio when the environment began to deteriorate starting in 6.0 ka BP. Additionally, with the onset of a weak summer monsoon and the predominance of primitive agriculture, sites of these two cultures present a different type of concentric circle-shaped pattern in space. As the environment continuously deteriorated with increasing aridity and the spread of steppe, more sites were distributed towards the south, and primitive agriculture was replaced by livestock husbandry in the Upper Xiajiadian culture. The most densely populated areas of the studied cultures are centralized within a limited area. The Laohahe River and Jiaolaihe River basins formed the core area in which most archaeological sites were distributed during the strong summer monsoon period and the first few thousand years of the weak summer monsoon period.展开更多
Custom designed and built meso shear test equipment was used to examine the shear crack propagation in gassy coal under different gas pressures.The spatial-temporal evolution of gas migration pathways in the coal duri...Custom designed and built meso shear test equipment was used to examine the shear crack propagation in gassy coal under different gas pressures.The spatial-temporal evolution of gas migration pathways in the coal during shear loading was also researched.The results show that gas pressure can hasten crack growth at the shear fracture surface,can reduce the shear strength of gassy coal,and can accelerate the shear failure process.Shear failure in gassy coal exhibits five stages:the pre-crack stage;the stable crack growth stage;the unsteady crack growth stage;the fracture stage;and,finally,the friction crack stage.The shear breaking creates two kinds of crack,shear cracks and tensile cracks.Cracks first appear in the shear plane at both ends and then extend toward the center until a shear fracture surface forms.The direction of shear crack propagation diverges from the predetermined shear plane by an angle of about 5°-10°.展开更多
To comprehensively understand the law of urban-rural relationship and propose scientific measures of urban-rural coordinated development in Northeast China,this study uses the coupling coordination degree model and ge...To comprehensively understand the law of urban-rural relationship and propose scientific measures of urban-rural coordinated development in Northeast China,this study uses the coupling coordination degree model and geographically and temporally weighted regression(GTWR)model to analyze the spatial-temporal patterns and the corresponding driving mechanisms of its urban-rural coordination since 1990.The results are as follows.First,the urban-rural coupling coordination degree in Northeast China was very low and improved slowly,but its stages of evolution is a good interpretation of the strategic arrangements of China's urbanization.Second,the urban-rural coupling coordination degree in Northeast China had spatial differences and was characterized by central polarization,converging on urban agglomeration,which was high in the south and low in the north.Moreover,the gap between the north and south weakened.Third,the spatial-temporal evolution of the urban-rural coordination relationship in Northeast China was influenced by pulling from the central cities,pushing from rural transformation,and government regulations.The influence intensity of the three mechanisms was weak,but the pulling from the central cities was stronger than that of the other two mechanisms.Furthermore,the spatial difference between the three mechanisms determines the spatial pattern and its evolution of the urban-rural coordination relationship in Northeast China.Fourth,to promote the development of urban-rural coordination in Northeast China,it is essential to advance urban-rural economic correlation,enhance the government^role in regulating and guiding,and adopt different policies for each region in Northeast China.展开更多
Following a new train of thinking, this paper has explored first the potential information in the ground resistivitydata observed by the existing geoelectric observation system, investigated and proposed a new dimensi...Following a new train of thinking, this paper has explored first the potential information in the ground resistivitydata observed by the existing geoelectric observation system, investigated and proposed a new dimensionlessgeoelectric precursor factor, the degree of ground resistivity anisotropy, S, and studied the characteristics of dynamic evolution pattern of S during the seismogenic process. The results show that, during the seismogenic process, the degree of ground resistivity anisotropy (S) displays h process of 'normal' → 'abnormal strengthening(amplitude, range)' → 'abnormal weakening'→ 'earthquake occurrence'→ 'normal'. The earthquake wouldoccur at the time when the S value has entered the late stage of strengthening and turns to weaken and in the gradient belt on the margin ofS anomaly region. The dynamic evolution pattern ofS reflects the changes of the tectonicstress field during the seismogenic process. Therefore, it would be possible to trace the process of earthquake generation and occurrence from the dynamic evolution pattern ofS so as to service eaJ'thquake prediction.展开更多
Dykes are a special kind of intrusive rocks which were formed by deep magma intruded into the existing brittle fractures in the crust.Dykes swarms in different tectonic environments are very significant to re-construc...Dykes are a special kind of intrusive rocks which were formed by deep magma intruded into the existing brittle fractures in the crust.Dykes swarms in different tectonic environments are very significant to re-construct the展开更多
Exploring the spatial and temporal evolution characteristics of the border land use multifunctionality(LUMF)provides insights for taking advantage of border land use and optimizing border land use policies.Based on th...Exploring the spatial and temporal evolution characteristics of the border land use multifunctionality(LUMF)provides insights for taking advantage of border land use and optimizing border land use policies.Based on the improved Technique for Order Preference by Similarity to an Ideal Solution(TOPSIS)mode,this study identifies and evaluates the LUMFs in the China-Vietnam border area between 2000 and 2018 from the perspectives of agricultural production,social security,ecological service,landscape recreation,and national security.The results show that:1)The comprehensive land use functions in most counties and cities continued to be improved.2)The comprehensive land use function exhibits remarkable spatial divergence and aggregation characteristics.The high-value area of the agricultural production function and social security function evolves from the east to the west.In addition,the spatial evolution of ecological service function is complicated,without an obvious spatial divergence and aggregation pattern.The landscape recreation function shows different spatial differentiation characteristics in the early and middle stage,and forms a large cluster in the later stage.Finally,the spatial evolution pattern of the national security function is significant.3)Designing differentiated border land policies,improving border land use security,and establishing a long-term mechanism for ecological protection and ecological compensation can aid in optimizing the LUMF level in the border area.展开更多
With the development of Web service technology, using composite services to satisfy users' requirements has become an inevitable tendency. Goal changes caused by changing requirements of users may directly drive t...With the development of Web service technology, using composite services to satisfy users' requirements has become an inevitable tendency. Goal changes caused by changing requirements of users may directly drive the corresponding evolution of service composition. However, most researches focus on how to compose services, and little efforts have been placed on how to evolve the composite services with changing requirements. In this paper, the service composition patterns are defined based on workflow patterns, and the changes of service composition patterns are analyzed according to changing goals. Finally, a case study is given to demonstrate the feasibility of the proposed approach.展开更多
The complex and volatile international landscape has significantly impacted global grain supply security. This study uses a complex network analysis model to examine the evolution and trends of the global major grain ...The complex and volatile international landscape has significantly impacted global grain supply security. This study uses a complex network analysis model to examine the evolution and trends of the global major grain trade from 1990 to 2020, focusing on network topology, centrality ranking, and community structure. There are three major findings. First, the global major grain trade network has expanded in scale, with a growing emphasis on diversification and balance. During the study period, the United States, Canada, China, and Brazil were the core nodes of the network. Grain-exporting countries were mainly situated in Asia, the Americas, and Europe, and importing countries in Asia, Africa, and Europe. Second, a significant increase in the number of high centrality countries with high export capacity occurred, benefiting from natural advantages such as fertile land and favorable climates. Third, the main global grain trade network is divided into four communities, with the Americas-Europe community being the largest and most widespread. The formation of the community pattern was influenced by geographic proximity, driven by the core exporting countries. Therefore, the world needs to enhance the existing trade model, promote the multi-polarization of the grain trade network, and establish a global vision for the future community. Countries and regions should participate actively in global grain trade security governance and institutional reform, expand trade links with other countries, and optimize import and export policies to reduce trade risks.展开更多
To clarify the connotations and extensions of urban resilience,this study focuses on the Chengdu-Chongqing Economic Circle with 16 cities as research subjects.A comprehensive evaluation index system was constructed to...To clarify the connotations and extensions of urban resilience,this study focuses on the Chengdu-Chongqing Economic Circle with 16 cities as research subjects.A comprehensive evaluation index system was constructed to measure the resilience of each city from 2003 to 2020.The spatial-temporal evolution characteristics were analyzed using Kernel density estimation,standard deviation ellipse,and spatial Markov chain analysis,and the spatial Tobit model was introduced to discover the influencing factors.The results indicate the following:①Urban resilience in the Chengdu-Chongqing Economic Circle displays an upward trend,with the center of gravity moving to the southwest,and the polarization phenomenon intensifying.②The urban resilience level in a region has certain spatial and geographical dependence,while the probability of urban resilience transfer differs in adjacent cities with different resilience levels.③Urban centrality,economic scale,openness level,and financial development promote urban resilience,whereas government scale significantly inhibits it.Finally,this paper proposes countermeasures and suggestions to improve the urban resilience of the Chengdu-Chongqing Economic Circle.展开更多
Accessibility is an important tool</span></span><span><span><span style="font-family:""> </span></span></span><span style="font-family:Verdana;&qu...Accessibility is an important tool</span></span><span><span><span style="font-family:""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">to evaluate the maturity of a regional traffic network structure</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> which </span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">describes the traffic convenience in the traffic</span><span style="font-family:Verdana;"> network. </span><span style="font-family:Verdana;">The paper defines a new accessibility index by using the resident pop</span><span style="font-family:Verdana;">ulation weighted average value of the sum of inverse of the traveling time </span><span style="font-family:Verdana;">distance and time threshold coming from ordinary traffic network, and then uses this accessibility index to analyze the spatial-temporal characteristics of Henan highway network, as well as its evolution patterns from 2005 to 2020. The results show that with the expansion and improvement of Henan highway network, city accessibility level has been significantly improved, spatial convergence is obvious, the cities in the north central are always High-High aggregation area, the cities in the south are always Low-Low aggregation area, gradually forming the characteristics of Northwest high and Southeast low, relative balance between East and West. There is some non-conforming phenomenon in highway mileage growth and improvement of the city accessibility levels, but this situation is being weakened, the highway network layout is gradually rationalized, the spatial distribution of city accessibility and that of population are beginning to converge.展开更多
基金National Natural Science Foundation of China,No.41671126,No.41171147Special Funds for Scientific Research Institutes from Science&Technology Department of Fujian Province,No.2016R1032-5
文摘In this study, we developed an energy security evaluation model(ESEM) from three dimensions, energy supply-transport security, safety of energy utilization, and stability of political-socioeconomic environment, based on the integrated application of subjective and objective weight allocation technique. Then the spatial-temporal evolution of global energy security pattern and its driving mechanism was analyzed with the method above, and the results are shown as follows:(1) since the 1990 s, the spatial patterns of global energy security have shown a deteriorating trend, with the growth of countries in at-risk type and relatively at-risk type.(2) The spatial distribution of countries with secure energy system shows a strong stability, and these countries are concentrated persistently in Western Europe and North America. The spatial evolution of countries with relatively secure energy system also presents a strong stability, which are mainly distributed in the periphery of the secure ones, namely Central and Southern Europe, South America and Eurasia, while countries with general energy system are mainly distributed in Asia, Africa and Southern Europe, and the spatial-temporal evolution of this type is the main cause for the deterioration of world energy security pattern. Countries with at-risk and relatively at-risk energy system are mainly concentrated in Africa, Asia, the Middle East and Eurasia, rendering spatial extension to the east and south.(3) In the past 20 years, the mechanism for world’s energy security pattern formation gradually transforms from the ‘unitary dimension dominated’ to the ‘binary dimension-dominated’, and the main factors influencing the global energy security pattern become more diverse.(4) In the pattern of world’s energy security, China’s performance on energy security has been the global average since the 1990 s, which shows a decreasing trend in safety of energy utilization dimension. Findings in this study can provide a reference for the government in terms of formulating strategic responses and policy options.
基金Sponsored by Fundamental Research Funds for the Central Universities(GK201303006)National Natural Science Foundation of China(41171139)Key Projects of Humanities and Social Sciences Research Base of Guangdong Colleges and Universities(09JDXM84001)
文摘Formation and evolution of rural settlement patterns in Lianzhou City,Guangdong Province were analyzed from the perspective of space and time,on the basis of its gazetteer and relevant historical data.The results show that Lianzhou was first founded in the sixth year of Yuanding Period of the Western Han Dynasty,and its development could be roughly classified into 6 stages according to the construction of south–north traffic lines and regional development progress,and it witnessed the fastest development in the Ming and Qing Dynasty.In terms of spatial distribution,rural settlements in the local area show spatial continuity,Lianzhou Town is the core of rural settlement growth in the city,and towns with the most concentrated rural settlements in all stages are located in central-west and northeast parts of the city,and those with lower density of rural settlements are mostly located in minority regions in the north and mountainous areas in the east.On the basis of the above facts,the paper studies the influence of natural geological conditions,immigrant,traffic,economic development and ethnic composition on the establishment and development of rural settlements in Lianzhou City.
基金funded by the Knowledge Innovation Project of the Chinese Academy of Sciences (Grant No. KSCX2-YW-NF-01)Spark Program projects (Grant No. 2010GA600017)
文摘Currently, the agricultural growth in developed countries mainly relies on the improvement of productivity, which is also the target for China. Accordingly, the purpose of this study was to describe the spatial-temporal evolution pattern of agricultural productivity, to reveal changes in total factor productivity in 2ooo-2olo, and analyze the impact of these changes in northwestern Sichuan plateau, China. Using data envelopment analysis （DEA） and the Malmquist Index, an in-depth study was conducted on agricultural productivity and changes in total factor productivity of 31 counties in northwestern Sichuan plateau. Results indicated that： （1） geographically, counties with optimal efficiency were mainly located in the north of northwestern Sichuan plateau and those with the lowest efficiency, in the south; （2） relative to pure technical efficiency, scale efficiency was the dominant factor in determining agricultural productivity; （3） the redundancy rate of input factors in zolo was slightly lower than that in zooo, thereby indicating an improved utilization of input factors to a certain extent and a great potential for further improving such utilization; （4） during the 2ooo-2olo period, the agricultural total factor productivity had an average annual growth rate of 8.3%, but the growth rates in various regions differed widely; （5） technical progress was the dominant factor promoting the improvement of total factor oroductivitv inagriculture. The disparities in spatial distribution may be due to the differences of natural conditions, former level agricultural productivity between counties. The findings are valuable for the government to make sustainable development policies for agriculture and improving agricultural development in northwestern Sichuan plateau.
文摘The purpose of this study was to find out the spatial-temporal rules and driving force of cultivated land quality in Henan Province in the last ten years. Agricultural land grading factor evaluation was used to evaluate the cultivated land quality of 2002 and 2012 in Henan Province, and to research the change laws. Method of correlation coefficient was employed to select the driving forces affecting cultivated land quality evolution. The results indicated that the cultivated land quality in Henan Province increased slightly in the last ten years in general, and in spatial there were unchanged regions, increased regions and decreased regions. The cultivated land quality in spatial presented the trend of good becoming better, bad becoming worse, which should be highly valued in cultivated land quality protection and management. Land development and consolidation projects had significant contributions to increasing the cultivated land quality. Driving forces between the sudden change regions and gradual change regions were significantly different. The paper concluded that the research on the spatial-temporal evolution and driving force of cultivated land quality based on cultivated land quality evolution had important academic significance and practical value.
基金supported by the National Science Foundation of China (NSFC) (Nos. 41272122, 41202074 and 41172123)the Major National Science and Technology Programs in the "Twelfth Five-Year" Plan of China (No. 2011ZX05009-002-02)+1 种基金the Open Research Program Foundation of Teaching Laboratory of China University of Geosciencesthe Foundation of Key Laboratory of Tectonics and Petroleum Resources (China University of Geosciences) of Ministry of Education (No. TPR-2013-14)
文摘In active rift basins, tectonism is extremely important for sequence stratigraphic patterns, affecting both the sequence architecture and internal makeup. Sequence stratigraphic framework of a Paleogene rift succession in Qiongdongnan Basin, northern South China Sea, was built using seismic profiles, complemented by well logs and cores. One first-order and three second-order sequences were identified on the basis of basin-scale unconformities, and seven third-order sequences are defined by unconformities along the basin margins and correlative conformities within the central basin. Through unconformity analysis and backstripping procedure, the Paleogene synrift tectonic evolution of deep- water area of Qiongdongnan Basin was proved to be episodic, which can be divided into rifting stage-I, rifting stage-II and rifting stage-III. Episodic rifting resulted in the formation of various types of struc- tural slope break belts, which controlled different architectures and internal makeup of sequences. This study enhances the understanding of the control of tectonic evolution on sequence stratigraphic pat- terns and establishes relevant patterns in a typical rift basin, and further proposes the favorable sand- stone reservoirs developing in different sequence stratigraphic patterns, which will be pretty helpful for subtle pool exploration in deepwater area of petroliferous basins.
基金financial support from the National Key Research and Development Program of China(2017YFC1502404)the National Natural Science Foundation of China(41601562 and 41761014)+1 种基金the China Institute of Water Resources and Hydropower Research Team Construction and Talent Development Project(JZ0145B752017)the Research Project for Young Teachers of Fujian Province,China(JAT160085)
文摘Evapotranspiration （ET） is the sum of soil or water body evaporation and plant transpiration from the earth surface and ocean to the atmosphere, and thus plays a significant role in regulating carbon and water resource cycles. The time-series data set from the remote sensing MOLDS product （MOD16） was used to study the spatial-temporal evolution of vegetation evapotranspiration in salinized areas during 2000-2014 by analyzing the variability, spatial patterns and Mann-Kendall （MK） nonparametric trends for the time series. The results indicate that inter-annual and intra-annual variations of ET across various vegetated areas show seasonal changes, with the abnormal months identified. The Cultivated land displays a greater degree of spatial heterogeneity and the spatial pattern of ET in the area covered by broadleaved deciduous forests corresponds to a higher ET rate and increased water consumption. Awidespread decline of ET is observed only in cultivated areas. However, agricultural cultivation doesn＇t worsen water shortage and soil salinization problems in the region, and water shortage problems are worsening for other vegetated areas. This research provides a basis of reference for the reasonable allocation of water resources and restructuring of vegetation patterns in salinized areas.
基金Under the auspices of National Natural Science Foundation of China(No.40901088,41271174)
文摘This article presents the findings of a study of the spheres of urban influence with regard to all cities in China(not including Hong Kong,Macao and Taiwan Province of China)in the years 1990,2000 and 2009.An optimized gravity model with comprehensive time distance was used to carry out a detailed analysis of the spatial patterns of Chinese spheres of urban influence and the spatial characteristics of urban agglomerations.Such urban agglomerations are characterized by high density population and a developed economy,which are also considered as the national competition unit.This paper initially identifies four spatial patterns of urban agglomerations based on the spatial layout of city groups during their evolution.Some basic characteristics of urban agglomerations are outlined,including the number of cities,the size of cities and the functions of urban centers.These characteristics are examined by using statistical methods and Geographic Information System(GIS).The main findings from this research are that the development stages and structures of urban agglomerations in China vary significantly.It is also clear that the stages and evolution of spatial patterns are strongly affected and dominated by both policy and location factors.
基金supported by the National Natural Science Foundation of China (Nos. 41272122, 41202074)
文摘Tectonism is of extreme importance to sequence stratigraphic patterns in continental sedimentary basins, affecting both the architectures and internal makeup of sequences. Sequence stratigraphic framework of the Paleogene system in the Fushan sag, northern South China Sea, was built using 3D and 2D seismic data, complemented by drilling cores and well logs data. One first-order, three second-order and seven third-order sequences were identified. Analysis of paleotectonic stress field, unconformities and subsidence history showed that the Paleogene tectonic evolution presented significant characteristics of multistage and episode, and can be divided into three stages： rifting stage I（initial rifting period）, rifting stage II（rapid subsidence period）, rifting stage III（fault-depressed diversionary period）. Partition of the west and east in tectonic activity was obvious. The west area showed relatively stronger tectonic activity than the east area, especially during the rifting stage II. Episodic rifting and lateral variations in tectonic activity resulted in a wide variety of structural slope break belts, which controlled both the sequence architectures and interval makeup, and strongly constrained the development of special facies zones or sand bodies that tended to form hydrocarbon accumulation. This paper classifies the genetic types of slope break belts and their relevant sequence stratigraphic patterns within the Fushan sag, and further discusses the tectonic evolution controls on sequence stratigraphic patterns, which suggests that vertical evolution paths of structural slope break belts and relevant sequence stratigraphic patterns as a response to the Paleogene tectonic evolution were strongly controlled by sag margin types and lateral variations of tectonic activity.
基金National Basic Research Program of China （973 Program）, No.2012CB95570001 Key Research Program of the Chinese Academy of Sciences, No.KZZD-EW-06-04+1 种基金 National Natural Science Foundation of China, No.41301121 National Key Technologies R＆D Program of China, No.2012BAJ15B02
文摘Migration plays an increasing role in China＇s economy since mobility rose and economic restructuring has proceeded during the last three decades. Given the background of most studies focusing on migration in a particular period, there is a critical need to analyze the spatial-temporal patterns of migration. Using bicomponent trend mapping technique and interprovincial migration data during the periods 1985-1990, 1990-1995, 1995-2000, 2000- 2005, and 2005-2010 we analyze net-, in-, out-migration intensity, and their changes over time in this study. Strong spatial variations in migration intensity were found in China＇s interprovincial migration, and substantial increase in migration intensity was also detected in eastern China during 1985-2010. Eight key destinations are mostly located within the three rapidly growing economic zones of eastern China （Pearl River Delta, Yangtze River Delta and Beijing-Tianjin-Hebei Metropolitan Region）, and they are classified into three types： mature, emerging, and fluctuant origins, while most key origins are relatively undeveloped central and western provinces, which are exactly in accordance with China＇s economic development patterns. The results of bicomponent trend mapping indicate that, in a sense, the migration in the south was more active than the north over the last three decades. The result shows the new changing features of spatial-temporal patterns of China＇s interprovincial migration that Fan and Chen did not find out in their research. A series of social-economic changes including rural transformation, balanced regional development, and labor market changes should be paid more attention to explore China＇s future interprovincial migration.
基金the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.11802195)the National Natural Science Foundation of China(Grant Nos.12172242,and 11972251)+2 种基金the Key Program of the National Natural Science Foundation of China(Grant No.11732010)Sino-German International Cooperation Project supported by Sino-German Science Center(GZ1575)the Natural Science Foundation for Young Scientists of Shanxi Province,China(Grant No.201801D221027).
文摘In this work,we study the development,evolution,and migration of turbulent coherent structures in the turbulent boundary layer at Reτ=630 using time-resolved particle image velocimetry(TR-PIV).Multiple techniques,including multi-scale analysis,conditional averaging,cross-correlation,and spatial-temporal topological analysis are applied to extract the evolution principle,migration trajectory,and convection velocity vector of the targeted coherent structures from a Lagrangian perspective.The spanwise vortex structures with larger scale and intensity at a certain wall-normal height y were the main focus of the present study.In the statistical sense,spanwise vortex structures move away from the wall with the shape changing from a bulge to an ellipse,and finally to a circle.Two straight lines emerge from the mean transfer trajectory curve of the spanwise vortex,in which the horizontal one is located at the viscous sublayer(y^(+)<10),the other is a logarithmic straight line existing in the range of 50<y^(+)<120,and the inclination angle of the tangential migration path is fixed at around 12°.The streamwise convection velocity U_(c)of scaled spanwise vortex structures satisfies U_(c)/U_(∞)=0.5-0.6 below y=0.03δ(i.e.,U^(+)_(c)=11-13 undery^(+)=20).In particular,in the region of 50<y^(+)<120,the velocity growth curves of U_(c)and wall-normal convection velocity V_(c)follow the log-law distribution very well,and the slopes are consistent with that of the log-law region of the turbulent boundary layer.Our observations provide microscopic evidences of the logarithmic-linear distribution of the migration trajectory of spanwise vortex structures.
基金National Natural Science Foundation of China,No.41371148Major Program of National Social Science Fund of China,No.13&ZD082
文摘With basic information from 8353 archaeological sites, this study describes a holistic spatial-temporal distribution pattern of archaeological sites of the prehistoric culture sequence from 9.5 ka BP (ka BP = thousands of years before 0 BP, where "0 BP" is defined as the year AD 1950) to 2.3 ka BP in the region that extends from the Yanshan Mountains to the Liaohe River Plain(i.e., the Yan-Liao region) in northern China. Based on spatial statistics analysis – including the spatial density of the sites and Geographic Information System nearest-neighbour analysis, combined with a review of environmental and climatic data – this paper analyses cultural evolution, the spatial-temporal features of the archaeological sites and human activities against the backdrop of climatic and environmental changes in this region. The results reveal that prehistoric cultural evolution in the Yan-Liao region is extensively influenced by climatic and environmental changes. The Xinglongwa, Zhaobaogou and Fuhe cultures, which primarily developed during a habitable period from 8.5 ka BP to 6.0 ka BP with strong summer monsoons, have similar maximum density values, spatial patterns and subsistence strategies dominated by hunting-gathering. Significant changes occurred in the Hongshan and Lower Xiajiadian cultures, with a significant increase in numbers and densities of sites and a slump in average nearest-neighbour ratio when the environment began to deteriorate starting in 6.0 ka BP. Additionally, with the onset of a weak summer monsoon and the predominance of primitive agriculture, sites of these two cultures present a different type of concentric circle-shaped pattern in space. As the environment continuously deteriorated with increasing aridity and the spread of steppe, more sites were distributed towards the south, and primitive agriculture was replaced by livestock husbandry in the Upper Xiajiadian culture. The most densely populated areas of the studied cultures are centralized within a limited area. The Laohahe River and Jiaolaihe River basins formed the core area in which most archaeological sites were distributed during the strong summer monsoon period and the first few thousand years of the weak summer monsoon period.
基金supported in part by the State Key Basic Research Program of China(No.2011CB201203)in part by the General Project of the National Natural Science Foundation of China(No.50974141)the Fundamental Research Funds for the Central Universities(No.CDJZR12240055)
文摘Custom designed and built meso shear test equipment was used to examine the shear crack propagation in gassy coal under different gas pressures.The spatial-temporal evolution of gas migration pathways in the coal during shear loading was also researched.The results show that gas pressure can hasten crack growth at the shear fracture surface,can reduce the shear strength of gassy coal,and can accelerate the shear failure process.Shear failure in gassy coal exhibits five stages:the pre-crack stage;the stable crack growth stage;the unsteady crack growth stage;the fracture stage;and,finally,the friction crack stage.The shear breaking creates two kinds of crack,shear cracks and tensile cracks.Cracks first appear in the shear plane at both ends and then extend toward the center until a shear fracture surface forms.The direction of shear crack propagation diverges from the predetermined shear plane by an angle of about 5°-10°.
基金Under the auspices of National Natural Science Foundation of China(No.41401182,41501173)Youth Fund for Humanities and Social Sciences of the Ministry of Education of China(No.19YJC630177)+2 种基金Natural Science Foundation of Heilongjiang Province(No.LH2019D008)University Nursing Program for Young Scholars with Creative Talents in Heilongjiang Province(No.UNPYSCT-2018194)Talent Introduction Project of Southwest University(No.SWU019020)。
文摘To comprehensively understand the law of urban-rural relationship and propose scientific measures of urban-rural coordinated development in Northeast China,this study uses the coupling coordination degree model and geographically and temporally weighted regression(GTWR)model to analyze the spatial-temporal patterns and the corresponding driving mechanisms of its urban-rural coordination since 1990.The results are as follows.First,the urban-rural coupling coordination degree in Northeast China was very low and improved slowly,but its stages of evolution is a good interpretation of the strategic arrangements of China's urbanization.Second,the urban-rural coupling coordination degree in Northeast China had spatial differences and was characterized by central polarization,converging on urban agglomeration,which was high in the south and low in the north.Moreover,the gap between the north and south weakened.Third,the spatial-temporal evolution of the urban-rural coordination relationship in Northeast China was influenced by pulling from the central cities,pushing from rural transformation,and government regulations.The influence intensity of the three mechanisms was weak,but the pulling from the central cities was stronger than that of the other two mechanisms.Furthermore,the spatial difference between the three mechanisms determines the spatial pattern and its evolution of the urban-rural coordination relationship in Northeast China.Fourth,to promote the development of urban-rural coordination in Northeast China,it is essential to advance urban-rural economic correlation,enhance the government^role in regulating and guiding,and adopt different policies for each region in Northeast China.
文摘Following a new train of thinking, this paper has explored first the potential information in the ground resistivitydata observed by the existing geoelectric observation system, investigated and proposed a new dimensionlessgeoelectric precursor factor, the degree of ground resistivity anisotropy, S, and studied the characteristics of dynamic evolution pattern of S during the seismogenic process. The results show that, during the seismogenic process, the degree of ground resistivity anisotropy (S) displays h process of 'normal' → 'abnormal strengthening(amplitude, range)' → 'abnormal weakening'→ 'earthquake occurrence'→ 'normal'. The earthquake wouldoccur at the time when the S value has entered the late stage of strengthening and turns to weaken and in the gradient belt on the margin ofS anomaly region. The dynamic evolution pattern ofS reflects the changes of the tectonicstress field during the seismogenic process. Therefore, it would be possible to trace the process of earthquake generation and occurrence from the dynamic evolution pattern ofS so as to service eaJ'thquake prediction.
基金co-supported by National Natural Science Foundation of China (Project number 41502201)"Western Light" project of Chinese Academy of Sciences (XBBS201301)
文摘Dykes are a special kind of intrusive rocks which were formed by deep magma intruded into the existing brittle fractures in the crust.Dykes swarms in different tectonic environments are very significant to re-construct the
基金Under the auspices of National Natural Science Project(No.42161046)National Social Science Project(No.21CJY075)+2 种基金Guangxi Natural Science Project(No.2021JJB150070)Guangxi Philosophy and Social Science Project(No.20FJY027)Guangxi First-class Discipline Applied Economics Construction Project Fund(Guangxi Education and Scientific Research(No.[2022]No.1))。
文摘Exploring the spatial and temporal evolution characteristics of the border land use multifunctionality(LUMF)provides insights for taking advantage of border land use and optimizing border land use policies.Based on the improved Technique for Order Preference by Similarity to an Ideal Solution(TOPSIS)mode,this study identifies and evaluates the LUMFs in the China-Vietnam border area between 2000 and 2018 from the perspectives of agricultural production,social security,ecological service,landscape recreation,and national security.The results show that:1)The comprehensive land use functions in most counties and cities continued to be improved.2)The comprehensive land use function exhibits remarkable spatial divergence and aggregation characteristics.The high-value area of the agricultural production function and social security function evolves from the east to the west.In addition,the spatial evolution of ecological service function is complicated,without an obvious spatial divergence and aggregation pattern.The landscape recreation function shows different spatial differentiation characteristics in the early and middle stage,and forms a large cluster in the later stage.Finally,the spatial evolution pattern of the national security function is significant.3)Designing differentiated border land policies,improving border land use security,and establishing a long-term mechanism for ecological protection and ecological compensation can aid in optimizing the LUMF level in the border area.
基金National Natural Science Foundation of China (No. 60970017 )Fundamental Research Funds for the Central Universities,China (No. 3101034,No. 6082008,No. 201121102020004)
文摘With the development of Web service technology, using composite services to satisfy users' requirements has become an inevitable tendency. Goal changes caused by changing requirements of users may directly drive the corresponding evolution of service composition. However, most researches focus on how to compose services, and little efforts have been placed on how to evolve the composite services with changing requirements. In this paper, the service composition patterns are defined based on workflow patterns, and the changes of service composition patterns are analyzed according to changing goals. Finally, a case study is given to demonstrate the feasibility of the proposed approach.
基金funded by the National Natural Science Foundation of China(42271313)the Chinese Academy of Agricultural Sciences Innovation Project(CAAS-ASTIP2021-AII)the Central Public-interest Scientific Institution Basal Research Fund,China(JBYW-AII-2022-06,JBYWAII-2022-40)。
文摘The complex and volatile international landscape has significantly impacted global grain supply security. This study uses a complex network analysis model to examine the evolution and trends of the global major grain trade from 1990 to 2020, focusing on network topology, centrality ranking, and community structure. There are three major findings. First, the global major grain trade network has expanded in scale, with a growing emphasis on diversification and balance. During the study period, the United States, Canada, China, and Brazil were the core nodes of the network. Grain-exporting countries were mainly situated in Asia, the Americas, and Europe, and importing countries in Asia, Africa, and Europe. Second, a significant increase in the number of high centrality countries with high export capacity occurred, benefiting from natural advantages such as fertile land and favorable climates. Third, the main global grain trade network is divided into four communities, with the Americas-Europe community being the largest and most widespread. The formation of the community pattern was influenced by geographic proximity, driven by the core exporting countries. Therefore, the world needs to enhance the existing trade model, promote the multi-polarization of the grain trade network, and establish a global vision for the future community. Countries and regions should participate actively in global grain trade security governance and institutional reform, expand trade links with other countries, and optimize import and export policies to reduce trade risks.
基金supported by the Graduate Research and Innovation Project of Chongqing Normal University[Grant No.YKC23035],comprehensive evaluation,and driving factors of urban resilience in the Chengdu-Chongqing Economic Circle.
文摘To clarify the connotations and extensions of urban resilience,this study focuses on the Chengdu-Chongqing Economic Circle with 16 cities as research subjects.A comprehensive evaluation index system was constructed to measure the resilience of each city from 2003 to 2020.The spatial-temporal evolution characteristics were analyzed using Kernel density estimation,standard deviation ellipse,and spatial Markov chain analysis,and the spatial Tobit model was introduced to discover the influencing factors.The results indicate the following:①Urban resilience in the Chengdu-Chongqing Economic Circle displays an upward trend,with the center of gravity moving to the southwest,and the polarization phenomenon intensifying.②The urban resilience level in a region has certain spatial and geographical dependence,while the probability of urban resilience transfer differs in adjacent cities with different resilience levels.③Urban centrality,economic scale,openness level,and financial development promote urban resilience,whereas government scale significantly inhibits it.Finally,this paper proposes countermeasures and suggestions to improve the urban resilience of the Chengdu-Chongqing Economic Circle.
文摘Accessibility is an important tool</span></span><span><span><span style="font-family:""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">to evaluate the maturity of a regional traffic network structure</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> which </span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">describes the traffic convenience in the traffic</span><span style="font-family:Verdana;"> network. </span><span style="font-family:Verdana;">The paper defines a new accessibility index by using the resident pop</span><span style="font-family:Verdana;">ulation weighted average value of the sum of inverse of the traveling time </span><span style="font-family:Verdana;">distance and time threshold coming from ordinary traffic network, and then uses this accessibility index to analyze the spatial-temporal characteristics of Henan highway network, as well as its evolution patterns from 2005 to 2020. The results show that with the expansion and improvement of Henan highway network, city accessibility level has been significantly improved, spatial convergence is obvious, the cities in the north central are always High-High aggregation area, the cities in the south are always Low-Low aggregation area, gradually forming the characteristics of Northwest high and Southeast low, relative balance between East and West. There is some non-conforming phenomenon in highway mileage growth and improvement of the city accessibility levels, but this situation is being weakened, the highway network layout is gradually rationalized, the spatial distribution of city accessibility and that of population are beginning to converge.
