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
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
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
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
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
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
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
The spatial-temporal evolution of coherent structures （CS） is significant for turbulence control and drag re- duction. Among the CS, low and high speed streak structures show typical burst phenomena. The analysis wa...The spatial-temporal evolution of coherent structures （CS） is significant for turbulence control and drag re- duction. Among the CS, low and high speed streak structures show typical burst phenomena. The analysis was based on a time series of three-dimensional and three-component （3D-3C） velocity fields of the flat plate turbulent boundary layer （TBL） measured by a Tomographic and Time-resolved PIV （Tomo TRPIV） system. Using multi-resolution wavelet transform and conditional sampling method, we extracted the intrinsic topologies and found that the streak structures appear in bar-like patterns. Furthermore, we seized locations and velocity information of transient CS, and then calculated the propagation velocity of CS based on spatial-temporal cross-correlation scanning. This laid a foundation for further studies on relevant dynamics properties.展开更多
Studying the agricultural spatial distribution characteristics of Jianghan Plain from 2000 to 2018 and its spatial-temporal transformation with ecological space and urban space is of great significance for optimizing ...Studying the agricultural spatial distribution characteristics of Jianghan Plain from 2000 to 2018 and its spatial-temporal transformation with ecological space and urban space is of great significance for optimizing the spatial structure of the country, enhancing the supply capacity of agricultural products, and ensuring food security. The research results show that during the period from 2000 to 2018, the agricultural spatial concentration in the area along the “Xiaogan-Jingzhou” link was relatively high, and the areas with large declines were mainly distributed in the flat areas between the Yangtze River and Han River;the space is continuously reduced by the occupation of ecological space and urban space, and ecological space and urban space have been improved respectively;agricultural space has been transformed into ecological space, and the largest urban space has been transformed. Ecological space has been transformed into agricultural space and urban space. Less urban space has been transformed into agricultural space and ecological space.展开更多
The Three-River Source Region is an important ecological security barrier in China.Revealing the spati-otemporal evolution characteristics of its landscape types and ecological risks is of great significance for promo...The Three-River Source Region is an important ecological security barrier in China.Revealing the spati-otemporal evolution characteristics of its landscape types and ecological risks is of great significance for promoting ecological restoration and landscape pattern optimization in the Three-River Source Region.Selecting the Three-River Source Region for a case study and applying the land-use data from four periods(the 1990,2000,2010,and 2020),we constructed a landscape ecological risk assessment model for the region based on the landscape pattern index.We then quantitatively assessed the ecological risks and determined the characteristics of their spa-tial-temporal evolution.The results showed that:(1)The overall landscape ecological risk in the Three-River Source Region tended to decrease from northwest to southeast,and the distribution of landscape ecological risk was closely related to the natural plateau zones and the changes in land cover.(2)From 1990 to 2020,the areas covered by grasslands,water bodies,croplands,and construction land in the Three-River Source Region increased,while the areas of woodlands and unused land decreased.The spatial-temporal changes in the ecological landscape risk were consistent with the characteristics of the changes in the landscape types.The areas categorized as highest,higher,medium,lower and lowest risk areas,while highest and higher risk areas decreased by 9.76%,medium risk areas increased by 1.03%,lower risk areas increased by 8.99%,and lowest risk areas decreased by 0.26%,respectively.(3)Overall,the Three-River Source Region was dominated by very low to medium ecological risk,the areas of which accounted for more than 70%of the entire study area.Overall ecological risks are decreasing,and there is positive spatial autocorrelation of landscape ecological risks in adjacent evaluation units.展开更多
Against a background of deepened globalization, the socio-spatial distribution characteristics of the employed population are one of the important perspectives that reflect the impact of globalization on urban social ...Against a background of deepened globalization, the socio-spatial distribution characteristics of the employed population are one of the important perspectives that reflect the impact of globalization on urban social space. Based on data of the population census of Shanghai in 2000 and 2010, using location quotient and index of dissimilarity, this paper analyzes the residential differentiation evolution in Shanghai from 2000 to 2010. The results show that except the high-end service industry, the residential differentiation of the employees in the other three types of industries has intensified but is not serious. In addition, the proportion of employees in high-end service industry within the Middle Ring has increased, while that of employees in the middle-and low-end service industry beyond the Middle Ring has increased, which further proves that globalization has an increasingly obvious impact on the socio-spatial differentiation in Shanghai. However, the adjustment in spatial development made by the Shanghai municipal government in response to globalization makes the socio-spatial evolution of Shanghai greatly different from the suburbanization of social elites in the West.展开更多
A composite electrocatalyst,CoMoNiO-S/NF-110(NF is nickel foam),was synthesized through electrodeposition,followed by pyrolysis and then the vulcanization process.CoMoNiO-S/NF-110 exhibited a structure where Ni3S2 and...A composite electrocatalyst,CoMoNiO-S/NF-110(NF is nickel foam),was synthesized through electrodeposition,followed by pyrolysis and then the vulcanization process.CoMoNiO-S/NF-110 exhibited a structure where Ni3S2 and Mo2S3 nanoparticles were integrated at the edges of Co3O4 nanosheets,creating a rich,heterogeneous interface that enhances the synergistic effects of each component.In an alkaline electrolyte,the synthesized CoMoNiO-S/NF-110 exhibited superior electrocatalytic performance for oxygen evolution reaction(OER),achieving current densities of 100 and 200 mA·cm^(-2) with low overpotentials of 199.4 and 224.4 mV,respectively,outperforming RuO2 and several high-performance Mo and Ni-based catalysts.This excellent performance is attributed to the rich interface formed between the components and active sites exposed by the defect structure.展开更多
The poor electrical conductivity of metal-organic frameworks(MOFs)limits their electrocatalytic performance in the oxygen evolution reaction(OER).In this study,a Py@Co-MOF composite material based on pyrene(Py)molecul...The poor electrical conductivity of metal-organic frameworks(MOFs)limits their electrocatalytic performance in the oxygen evolution reaction(OER).In this study,a Py@Co-MOF composite material based on pyrene(Py)molecules and{[Co2(BINDI)(DMA)_(2)]·DMA}_(n)(Co-MOF,H4BINDI=N,N'-bis(5-isophthalic acid)naphthalenediimide,DMA=N,N-dimethylacetamide)was synthesized via a one-pot method,leveragingπ-πinteractions between pyrene and Co-MOF to modulate electrical conductivity.Results demonstrate that the Py@Co-MOF catalyst exhibited significantly enhanced OER performance compared to pure Co-MOF or pyrene-based electrodes,achieving an overpotential of 246 mV at a current density of 10 mA·cm^(-2) along with excellent stability.Density functional theory(DFT)calculations reveal that the formation of O*in the second step is the rate-determining step(RDS)during the OER process on Co-MOF,with an energy barrier of 0.85 eV due to the weak adsorption affinity of the OH*intermediate for Co sites.CCDC:2419276.展开更多
The efficiency and stability of catalysts for photocatalytic hydrogen evolution(PHE)are largely governed by the charge transfer behaviors across the heterojunction interfaces.In this study,CuO,a typical semiconductor ...The efficiency and stability of catalysts for photocatalytic hydrogen evolution(PHE)are largely governed by the charge transfer behaviors across the heterojunction interfaces.In this study,CuO,a typical semiconductor featuring a broad spectral absorption range,is successfully employed as the electron acceptor to combine with CdS for constructing a S-scheme heterojunction.The optimized photocatalyst(CdSCuO2∶1)delivers an exceptional hydrogen evolution rate of 18.89 mmol/(g·h),4.15-fold higher compared with bare CdS.X-ray photoelectron spectroscopy(XPS)and ultraviolet-visible diffuse reflection absorption spectroscopy(UV-vis DRS)confirmed the S-scheme band structure of the composites.Moreover,the surface photovoltage(SPV)and electron paramagnetic resonance(EPR)indicated that the photogenerated electrons and photogenerated holes of CdS-CuO2∶1 were respectively transferred to the conduction band(CB)of CdS with a higher reduction potential and the valence band(VB)of CuO with a higher oxidation potential under illumination,as expected for the S-scheme mechanism.Density-functional-theory calculations of the electron density difference(EDD)disclose an interfacial electric field oriented from CdS to CuO.This built-in field suppresses charge recombination and accelerates carrier migration,rationalizing the markedly enhanced PHE activity.This study offers a novel strategy for designing S-scheme heterojunctions with high light harvesting and charge utilization toward sustainable solar-tohydrogen conversion.展开更多
Serbisütherapy(ST)is a distinctive external treatment modality within traditional Mongolian medicine(TMM),historically developed within a nomadic cultural framework.This study presents a comprehensive philologica...Serbisütherapy(ST)is a distinctive external treatment modality within traditional Mongolian medicine(TMM),historically developed within a nomadic cultural framework.This study presents a comprehensive philological and historical analysis of ST,tracing its evolution from early battlefield applications to contemporary clinical use.By critically examining classical Mongolian medical texts alongside modern case studies,we aim to systematize ST’s therapeutic methods,indications,and limitations,while exploring its mechanisms of action through both traditional theory and modern biomedical perspectives.ST has undergone significant transformation,shifting from whole-body cavity immersion in the 13th century to targeted,organ-specific applications in modern practice.Its four primary methods–Covering,Mounted,Organ Placement,and Suction–demonstrate efficacy in treating cold-natured diseases,musculoskeletal disorders,gynecological conditions,and certain emergencies.ST embodies the core principles of TMM,particularly the balance of the“Three Roots”and the correction of cold-induced pathologies through heat.Despite challenges related to standardization,cultural translation,and regulatory acceptance,ST holds translational potential for integrative medicine.Future research should prioritize mechanistic validation,clinical standardization,and the development of biocompatible thermal technologies to bridge traditional practice with modern healthcare systems.展开更多
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
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
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
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
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.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.
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.
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.
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supported by the National Natural Science Foundation of China(11332006,11272233,and 11411130150)the National Basic Research Programm of China(2012CB720101)
文摘The spatial-temporal evolution of coherent structures （CS） is significant for turbulence control and drag re- duction. Among the CS, low and high speed streak structures show typical burst phenomena. The analysis was based on a time series of three-dimensional and three-component （3D-3C） velocity fields of the flat plate turbulent boundary layer （TBL） measured by a Tomographic and Time-resolved PIV （Tomo TRPIV） system. Using multi-resolution wavelet transform and conditional sampling method, we extracted the intrinsic topologies and found that the streak structures appear in bar-like patterns. Furthermore, we seized locations and velocity information of transient CS, and then calculated the propagation velocity of CS based on spatial-temporal cross-correlation scanning. This laid a foundation for further studies on relevant dynamics properties.
文摘Studying the agricultural spatial distribution characteristics of Jianghan Plain from 2000 to 2018 and its spatial-temporal transformation with ecological space and urban space is of great significance for optimizing the spatial structure of the country, enhancing the supply capacity of agricultural products, and ensuring food security. The research results show that during the period from 2000 to 2018, the agricultural spatial concentration in the area along the “Xiaogan-Jingzhou” link was relatively high, and the areas with large declines were mainly distributed in the flat areas between the Yangtze River and Han River;the space is continuously reduced by the occupation of ecological space and urban space, and ecological space and urban space have been improved respectively;agricultural space has been transformed into ecological space, and the largest urban space has been transformed. Ecological space has been transformed into agricultural space and urban space. Less urban space has been transformed into agricultural space and ecological space.
基金The National Natural Science Foundation of China (42171223)The National Social Science Foundation of China (19BJY205)+1 种基金The Department of Education Youth Science and Technology Talent Growth Fund of Guizhou ([2022]107)The Mountain Discipline Construction Project of Minzu Normal University of Xingyi (XKJS202332)。
文摘The Three-River Source Region is an important ecological security barrier in China.Revealing the spati-otemporal evolution characteristics of its landscape types and ecological risks is of great significance for promoting ecological restoration and landscape pattern optimization in the Three-River Source Region.Selecting the Three-River Source Region for a case study and applying the land-use data from four periods(the 1990,2000,2010,and 2020),we constructed a landscape ecological risk assessment model for the region based on the landscape pattern index.We then quantitatively assessed the ecological risks and determined the characteristics of their spa-tial-temporal evolution.The results showed that:(1)The overall landscape ecological risk in the Three-River Source Region tended to decrease from northwest to southeast,and the distribution of landscape ecological risk was closely related to the natural plateau zones and the changes in land cover.(2)From 1990 to 2020,the areas covered by grasslands,water bodies,croplands,and construction land in the Three-River Source Region increased,while the areas of woodlands and unused land decreased.The spatial-temporal changes in the ecological landscape risk were consistent with the characteristics of the changes in the landscape types.The areas categorized as highest,higher,medium,lower and lowest risk areas,while highest and higher risk areas decreased by 9.76%,medium risk areas increased by 1.03%,lower risk areas increased by 8.99%,and lowest risk areas decreased by 0.26%,respectively.(3)Overall,the Three-River Source Region was dominated by very low to medium ecological risk,the areas of which accounted for more than 70%of the entire study area.Overall ecological risks are decreasing,and there is positive spatial autocorrelation of landscape ecological risks in adjacent evaluation units.
基金funded by National Natural Science Foundation of China(No.41501170)the special fund for basic scientific research of colleges and universities under the jurisdiction of the Central Government(No.0100219175)
文摘Against a background of deepened globalization, the socio-spatial distribution characteristics of the employed population are one of the important perspectives that reflect the impact of globalization on urban social space. Based on data of the population census of Shanghai in 2000 and 2010, using location quotient and index of dissimilarity, this paper analyzes the residential differentiation evolution in Shanghai from 2000 to 2010. The results show that except the high-end service industry, the residential differentiation of the employees in the other three types of industries has intensified but is not serious. In addition, the proportion of employees in high-end service industry within the Middle Ring has increased, while that of employees in the middle-and low-end service industry beyond the Middle Ring has increased, which further proves that globalization has an increasingly obvious impact on the socio-spatial differentiation in Shanghai. However, the adjustment in spatial development made by the Shanghai municipal government in response to globalization makes the socio-spatial evolution of Shanghai greatly different from the suburbanization of social elites in the West.
文摘A composite electrocatalyst,CoMoNiO-S/NF-110(NF is nickel foam),was synthesized through electrodeposition,followed by pyrolysis and then the vulcanization process.CoMoNiO-S/NF-110 exhibited a structure where Ni3S2 and Mo2S3 nanoparticles were integrated at the edges of Co3O4 nanosheets,creating a rich,heterogeneous interface that enhances the synergistic effects of each component.In an alkaline electrolyte,the synthesized CoMoNiO-S/NF-110 exhibited superior electrocatalytic performance for oxygen evolution reaction(OER),achieving current densities of 100 and 200 mA·cm^(-2) with low overpotentials of 199.4 and 224.4 mV,respectively,outperforming RuO2 and several high-performance Mo and Ni-based catalysts.This excellent performance is attributed to the rich interface formed between the components and active sites exposed by the defect structure.
文摘The poor electrical conductivity of metal-organic frameworks(MOFs)limits their electrocatalytic performance in the oxygen evolution reaction(OER).In this study,a Py@Co-MOF composite material based on pyrene(Py)molecules and{[Co2(BINDI)(DMA)_(2)]·DMA}_(n)(Co-MOF,H4BINDI=N,N'-bis(5-isophthalic acid)naphthalenediimide,DMA=N,N-dimethylacetamide)was synthesized via a one-pot method,leveragingπ-πinteractions between pyrene and Co-MOF to modulate electrical conductivity.Results demonstrate that the Py@Co-MOF catalyst exhibited significantly enhanced OER performance compared to pure Co-MOF or pyrene-based electrodes,achieving an overpotential of 246 mV at a current density of 10 mA·cm^(-2) along with excellent stability.Density functional theory(DFT)calculations reveal that the formation of O*in the second step is the rate-determining step(RDS)during the OER process on Co-MOF,with an energy barrier of 0.85 eV due to the weak adsorption affinity of the OH*intermediate for Co sites.CCDC:2419276.
文摘The efficiency and stability of catalysts for photocatalytic hydrogen evolution(PHE)are largely governed by the charge transfer behaviors across the heterojunction interfaces.In this study,CuO,a typical semiconductor featuring a broad spectral absorption range,is successfully employed as the electron acceptor to combine with CdS for constructing a S-scheme heterojunction.The optimized photocatalyst(CdSCuO2∶1)delivers an exceptional hydrogen evolution rate of 18.89 mmol/(g·h),4.15-fold higher compared with bare CdS.X-ray photoelectron spectroscopy(XPS)and ultraviolet-visible diffuse reflection absorption spectroscopy(UV-vis DRS)confirmed the S-scheme band structure of the composites.Moreover,the surface photovoltage(SPV)and electron paramagnetic resonance(EPR)indicated that the photogenerated electrons and photogenerated holes of CdS-CuO2∶1 were respectively transferred to the conduction band(CB)of CdS with a higher reduction potential and the valence band(VB)of CuO with a higher oxidation potential under illumination,as expected for the S-scheme mechanism.Density-functional-theory calculations of the electron density difference(EDD)disclose an interfacial electric field oriented from CdS to CuO.This built-in field suppresses charge recombination and accelerates carrier migration,rationalizing the markedly enhanced PHE activity.This study offers a novel strategy for designing S-scheme heterojunctions with high light harvesting and charge utilization toward sustainable solar-tohydrogen conversion.
基金supported by The China Ethnic Medicine Association Research Grant(No.2023MY055-81)Science and Technology Program of the Joint Fund of Scientific Research for the Public Hospitals of Inner Mongolia Academy of Medical Sciences(2023GLLHD177,2023GLLH0174)Inner Mongolia Autonomous Region Regional Medical Center for Specialized Care(2025).
文摘Serbisütherapy(ST)is a distinctive external treatment modality within traditional Mongolian medicine(TMM),historically developed within a nomadic cultural framework.This study presents a comprehensive philological and historical analysis of ST,tracing its evolution from early battlefield applications to contemporary clinical use.By critically examining classical Mongolian medical texts alongside modern case studies,we aim to systematize ST’s therapeutic methods,indications,and limitations,while exploring its mechanisms of action through both traditional theory and modern biomedical perspectives.ST has undergone significant transformation,shifting from whole-body cavity immersion in the 13th century to targeted,organ-specific applications in modern practice.Its four primary methods–Covering,Mounted,Organ Placement,and Suction–demonstrate efficacy in treating cold-natured diseases,musculoskeletal disorders,gynecological conditions,and certain emergencies.ST embodies the core principles of TMM,particularly the balance of the“Three Roots”and the correction of cold-induced pathologies through heat.Despite challenges related to standardization,cultural translation,and regulatory acceptance,ST holds translational potential for integrative medicine.Future research should prioritize mechanistic validation,clinical standardization,and the development of biocompatible thermal technologies to bridge traditional practice with modern healthcare systems.
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.
