This study utilized census data from Henan Province for the years 2000,2010,and 2020 to investigate the spatiotemporal evolution of population aging,defined by the proportion of the population aged 65 and above.Employ...This study utilized census data from Henan Province for the years 2000,2010,and 2020 to investigate the spatiotemporal evolution of population aging,defined by the proportion of the population aged 65 and above.Employing spatial analysis techniques such as spatial autocorrelation and the standard deviation ellipse,the research mapped out the progression and distribution of aging demographics.Furthermore,the study delved into the influencing factors of aging using an optimal parameters-based geographical detector.Results indicate a deepening degree of population aging in Henan Province,transitioning from an adult type to an old type structure.There is a marked positive spatial correlation among counties,with high-value aging areas initially decreasing,then increasing,and notably spreading from the central to the central and southern regions of the province.The center of gravity for population aging,specifically around Changge City and Xuchang City,exhibits a trajectory moving southeast before shifting northwest.Factor detection reveals that in 2000,2010,and 2020,the elderly dependency ratio predominantly influences the aging trend,with explanatory powers of 88.4%,87.9%,and 90.9%,respectively.Interaction analysis indicates that the interaction between the old-child ratio and the elderly dependency ratio has a strong explanatory power for the aging patterns in Henan Province,reaching 97.3%,97.0%,and 97.4%,respectively.展开更多
Cold storage is the vital infrastructure of cold chain logistics. In this study, we analyzed the spatial pattern evolution characteristics, spatial autocorrelation and influencing factors of cold storage in China by u...Cold storage is the vital infrastructure of cold chain logistics. In this study, we analyzed the spatial pattern evolution characteristics, spatial autocorrelation and influencing factors of cold storage in China by using kernel density estimation(KDE), spatial autocorrelation analysis(SAA), and spatial error model(SEM). Results showed that: 1) the spatial distribution of cold storage in China is unbalanced, and has evolved from ‘one core’ to ‘one core and many spots’, that is, ‘one core’ refers to the Bohai Rim region mainly including Beijing, Tianjin, Hebei, Shandong and Liaoning regions, and ‘many spots’ mainly include the high-density areas such as Shanghai, Fuzhou, Guangzhou, Zhengzhou, Hefei, Wuhan, ürümqi. 2) The distribution of cold storage has significant global spatial autocorrelation and local spatial autocorrelation, and the ‘High-High’ cluster area is the most stable, mainly concentrated in the Bohai Rim;the ‘Low-Low’ cluster area is grouped in the southern China. 3) Economic development level, population density, traffic accessibility, temperature and land price, all affect the location choice of cold storage in varying degrees, while the impact of market demand on it is not explicit.展开更多
We use the directional slacks-based measure of efficiency and inverse distance weighting method to analyze the spatial pattern evolution of the industrial green total factor productivity of 108 cities in the Yangtze R...We use the directional slacks-based measure of efficiency and inverse distance weighting method to analyze the spatial pattern evolution of the industrial green total factor productivity of 108 cities in the Yangtze River Economic Belt in 2003–2013.Results show that both the subprime mortgage crisis and ‘the new normal' had significant negative effects on productivity growth,leading to the different spatial patterns between 2003–2008 and 2009–2013.Before 2008,green poles had gathered around some capital cities and formed a tripartite pattern,which was a typical core-periphery pattern.Due to a combination of the polarization and the diffusion effects,capital cities became the growth poles and ‘core' regions,while surrounding areas became the ‘periphery'.This was mainly caused by the innate advantage of capital cities and ‘the rise of central China' strategy.After 2008,the tripartite pattern changed to a multi-poles pattern where green poles continuously and densely spread in the midstream and downstream areas.This is due to the regional difference in the leading effect of green poles.The leading effect of green poles in midstream and downstream areas has changed from polarization to diffusion,while the polarization effect still leads in the upstream area.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
Coastal tidal creeks are important channels for exchanges of material and energy between sea and land,and play an important role in the ecological protection of tidal flats.Although tidal creeks have evolved different...Coastal tidal creeks are important channels for exchanges of material and energy between sea and land,and play an important role in the ecological protection of tidal flats.Although tidal creeks have evolved differently in various regions,the evolutionary process of tidal creeks in the Huanghe(Yellow)River delta of China,one of the most active deltas worldwide,is not entirely clear.Therefore,the evolution of tidal creeks in the delta from 1981 to 2021 was investigated by quantitatively analysing the tidal creeks and developing a standard for dividing their evolution periods.Visual interpretation and supervised classification methods were applied to the Landsat images to extract the tidal creek network,and 17 groups of tidal creek systems were selected.Results indicate that Creek S 1 was the most developed creek for having 113 tidal creeks totaling 65.8 km in length,while Creek E 3 had the fastest growth rate for having average annual increase of 1.9 km.Meanwhile,the level of tidal creeks increased,the average and median lengths of tidal creeks increased,and the number of tidal creeks decreased since 1981.The evolution of the tidal creek system could be divided into four stages,namely,rising,developing,stabilizing,and degrading.Analyses of a representative tidal creek show that there was no degenerated tidal creek during the rising period,with an increase in the number of 50 and a length increase of 57.9 km between 1981 and 1989.The proportion of new tidal creeks in the developing period was more than 50%and the new tidal creeks in the stabilizing period were equal to the degraded tidal creeks.Extinct tidal creeks were greater than 50%during the degrading period.There was no fixed order of tidal creek evolution in each period,and there may be a skip in evolution.Our findings provided a reference for studying the evolution of tidal creeks.展开更多
The convection in an annular container with heated bottom,cooled top and insulated side walls are studied by both linear instability analysis and direct numerical simulation.The onset of convection is investigated by ...The convection in an annular container with heated bottom,cooled top and insulated side walls are studied by both linear instability analysis and direct numerical simulation.The onset of convection is investigated by linear stability analysis and corresponding pattern selection mechanisms are discussed.The nonlinear evolution of different flow patterns and the convective heat transfer are simulated.The transition to oscillatory flow is also given by stability analysis where the base flow is a steady three dimensional flow.The stability predictions are in good agreement with the numerical simulations,including both the growth rate and the dimensionless frequency.展开更多
As an important indicator of the structural and functional stability of wetland landscapes,hydrological connectivity plays an important role in maintaining the stability of wetland ecosystems.Large-scale human activit...As an important indicator of the structural and functional stability of wetland landscapes,hydrological connectivity plays an important role in maintaining the stability of wetland ecosystems.Large-scale human activities have led to significant changes in the hydrological connectivity pattern of wetlands in Naoli River Basin since 1950 s.Combined with the availability of wetland habitat and the spreading capacity of aquatic birds,hydrological connectivity indices of marsh wetlands were calculated in the studied area,and the temporal and spatial changes were analyzed from 1950 s to 2015.The results indicate that:(1)the hydrological connectivity index of the marsh wetlands shows a growth trend with increasing distance threshold.All patches of marsh wetlands linked together when the distance threshold reached 35--40 km;(2)the optimal distance of hydrological connectivity is about 10 km for marsh wetlands of whole Naoli River Basin;(3)the total hydrological connectivity of marsh wetlands decreased in the Naoli River Basin from 1950 s to 2015.Although the hydrological connectivity index increased after 2005,the fragmentation of the landscape has not been improved.The analysis of the wetland hydrological connectivity can provide a scientific basis for the ecological restoration and protection of the wetland in the Naoli River Basin.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
Quantum pattern recognition algorithm for two-qubit systems has been implemented by quantum adiabatic evolution. We will estimate required running time for this algorithm by means of an analytical solution of time- de...Quantum pattern recognition algorithm for two-qubit systems has been implemented by quantum adiabatic evolution. We will estimate required running time for this algorithm by means of an analytical solution of time- dependent Hamiltonian since the time complexity of adiabatic quantum evolution is a limitation on the quantum computing. These results can be useful for experimental implementation.展开更多
Mountain area is an important geographical unit of land,and its ecology is sensitive and fragile.Over the past few decades,human activities have caused dramatic changes in land use in mountainous areas,which caused ch...Mountain area is an important geographical unit of land,and its ecology is sensitive and fragile.Over the past few decades,human activities have caused dramatic changes in land use in mountainous areas,which caused changes in landscape patterns and impacts on the ecological environment.It is unknown how the mechanism of land use affects the landscape pattern at different scales.The Hantai District,a typical human settlement in the mountain area in Shaanxi,China,was chosen as the study area.Based on the remote sensing images,the mathematical models and landscape indexes were adopted to evaluate the impact of land use change from 1998 to 2017 on the landscape pattern at different scales,and its main driving forces were analyzed.The results showed that the urbanized land expanded largest from 15.39%to 24.30%,and cultivated land experienced the largest decline from 43.54%to 35.35%.Changes in land use have made the patch morphology of most land types developed from a natural random to a sawtooth shape,and its spatial pattern evolved from a ruleset to a fragmented expansion.This reflects the continuous strengthening of human intervention in the process of regional development.Under the jurisdiction of Hantai District,the biggest change in landscape pattern is in Hanzhong City and Qili Town.The improved economy and increasing population and urbanization rate were the main factors that cause these changes.This research could provide necessary information for understanding the evolution mechanism of land resources in mountainous human settlements for mountainous areas with significant geomorphic differentiation.展开更多
Various pattern evolutions are presented in one- and two-dimensional spatially coupled phase-conjugate systems （SCPCSs）. As the system parameters change, different patterns are obtained from the period-doubling of k...Various pattern evolutions are presented in one- and two-dimensional spatially coupled phase-conjugate systems （SCPCSs）. As the system parameters change, different patterns are obtained from the period-doubling of kink-antikinks in space to the spatiotemporal chaos in a one-dimensional SCPCS. The homogeneous symmetric states induce symmetry breaking from the four corners and the boundaries, finally leading to spatiotemporal chaos with the increase of the iteration time in a two-dimensional SCPCS. Numerical simulations are very helpful for understanding the complex optical phenomena.展开更多
Based on data of fault movement surveying, we simulate the evolution process of three dimensional stress field in North China by three dimensional finite element method. Evolutional patterns in one-year time scale fro...Based on data of fault movement surveying, we simulate the evolution process of three dimensional stress field in North China by three dimensional finite element method. Evolutional patterns in one-year time scale from 1986 to 1997 have been illustrated and the evolution characteristics of stress field have been analyzed. In comparison with the seismic activity among that time interval in North China, we have primarily discussed the relationship between the evolution of stress field and seismic activity.展开更多
Lakes are important ecological water sources in the Bashang Plateau. Its expansion or shrinkage directly affects the ecological security of the plateau and its surrounding areas. In this study, Landsat images from 198...Lakes are important ecological water sources in the Bashang Plateau. Its expansion or shrinkage directly affects the ecological security of the plateau and its surrounding areas. In this study, Landsat images from 1984 to 2015 were selected to monitor the area of lakes in the Bashang Plateau and to analyze the spatiotemporal evolution and driving forces of lakes in the Bashang Plateau. The results showed that there were 47 lakes in the Bashang Plateau in 2015, with a total area of 37.63 km2, mainly distributed in the central and western regions of the region. From 1984 to 2015, the lakes in Bashang Plateau showed a shrinking trend. At the same time, there are obvious stage differences in lake changes. During 1984-1996, the number of lakes increased by 99 and the total area increased by 124.43 km2. From 1996 to 2015, the number of lakes decreased by 142, and the total area decreased by 183.96 km2. Before 1996, climate change was the dominant factor. However, the shrinkage of lakes after 1996 is the result of climate change and human activities. Among them, the large-scale planting of water consuming crops such as vegetables is the main human activity mode leading to lake shrinkage. This study will help to understand the expansion and contraction factors of the Bashang Plateau lakes in Hebei province and provide a reference for the future protection and management of the lakes.展开更多
Desertification is the most serious environmental problem in the world today. Fractal feature of granularity composition was studied by using the fractal theory in view of desertification soil in Fuxin district, there...Desertification is the most serious environmental problem in the world today. Fractal feature of granularity composition was studied by using the fractal theory in view of desertification soil in Fuxin district, thereby evolution patterns of desertification was promulgated. The result shows that the self-formation degree of the developing desertification areas is higher than the relatively steady desertification areas. Evolution of desertification is beginning of forming sandy soil of framework composition, and then the sandy soil be came complex by the effect of environment, climate and anthropo-activity.展开更多
People's attitudes towards public events or products may change overtime,rather than staying on the same state.Understanding how sentiments change overtime is an interesting and important problem with many applica...People's attitudes towards public events or products may change overtime,rather than staying on the same state.Understanding how sentiments change overtime is an interesting and important problem with many applications.Given a certain public event or product,a user's sentiments expressed in microblog stream can be regarded as a vector.In this paper,we define a novel problem of sentiment evolution analysis,and develop a simple yet effective method to detect sentiment evolution in user-level for public events.We firstly propose a multidimensional sentiment model with hierarchical structure to model user's complicate sentiments.Based on this model,we use FP-growth tree algorithm to mine frequent sentiment patterns and perform sentiment evolution analysis by Kullback-Leibler divergence.Moreover,we develop an improve Affinity Propagation algorithm to detect why people change their sentiments.Experimental evaluations on real data sets show that sentiment evolution could be implemented effectively using our method proposed in this article.展开更多
Transition from old to new economic drivers(TONED) is of great significance for optimizing economic structures. Using a combination of methods including entropy weight technique for order preference by similarity to i...Transition from old to new economic drivers(TONED) is of great significance for optimizing economic structures. Using a combination of methods including entropy weight technique for order preference by similarity to ideal solution, geospatial analysis, and optimal parameter geodetector, this study investigates the patterns and mechanisms of China's TONED in the prefecture-level cities from 2011 to 2020. The findings reveal that(1) the TONED exhibited a spatial distribution characterized by higher levels in the east and lower levels in the west, along with a pyramidal hierarchy of levels. The distribution of hot and cold spots roughly followed the Heihe-Yulin line.(2) The informatization levels, openness to the outside world, and urbanization played a dominant role in the TONED. The types of dual-factor interactions exhibited both dual-factor enhancement and non-linear enhancement effects.(3) The eastern and central regions were more likely to promote the TONED through enhanced informatization levels, whereas the western region relied more on increasing openness. This study finds that the TONED results from the combined effects of three geographical natures, each playing a distinct role. The recommendations provided can serve as a reference for China and other developing countries to implement the TONED in the context of deglobalization.展开更多
The global value chains have become the core skeleton of the global economy.As a large-scale international cooperation initiative,the Belt and Road Initiative(BRI hereafter)may have a significant impact on the global ...The global value chains have become the core skeleton of the global economy.As a large-scale international cooperation initiative,the Belt and Road Initiative(BRI hereafter)may have a significant impact on the global economic landscape.In this context,the spatiotemporal pattern and evolution of the value chain connection of the Silk Road countries and whether the BRI will promote the value chain connections between China and these countries are important research questions for understanding the changing global economic landscape.This paper employs input-output analysis,network analysis and difference-in-differences based on Propensity Score Matching(PSM-DID)to conduct an in-depth quantitative study of these questions.The results show that,first,the overall value chain connection between China and the Silk Road countries has been rising since 2001.From the perspective of geographical distribution,Southeast Asia is the highest value chain connection region with China,and the growth in the central and eastern Europe is the most significant,whereas the central Asia is the lowest value connection region.From the perspective of complex network analysis,China’s position in the network of value flow among the Silk Road countries has been increasing continuously,and it has been in the lead position since 2008.Besides,the implementation of the BRI has had a significant positive influence on the overall value chain connection between China and the Silk Road countries,but this positive influence is limited to the central and eastern Europe region,whereas it is not significant in other regions.Finally,this paper suggests that to promote the development of value chain connection,the Silk Road countries need to develop more specific policies related to value chains.Policymakers need to be able to correctly identify the comparative advantages of the region and the types of value chains that are compatible with them and then find suitable partners and formulate targeted promotion policies.展开更多
基金Humanities and Social Science Project of the Ministry of Education(NO.17YJCZH041)。
文摘This study utilized census data from Henan Province for the years 2000,2010,and 2020 to investigate the spatiotemporal evolution of population aging,defined by the proportion of the population aged 65 and above.Employing spatial analysis techniques such as spatial autocorrelation and the standard deviation ellipse,the research mapped out the progression and distribution of aging demographics.Furthermore,the study delved into the influencing factors of aging using an optimal parameters-based geographical detector.Results indicate a deepening degree of population aging in Henan Province,transitioning from an adult type to an old type structure.There is a marked positive spatial correlation among counties,with high-value aging areas initially decreasing,then increasing,and notably spreading from the central to the central and southern regions of the province.The center of gravity for population aging,specifically around Changge City and Xuchang City,exhibits a trajectory moving southeast before shifting northwest.Factor detection reveals that in 2000,2010,and 2020,the elderly dependency ratio predominantly influences the aging trend,with explanatory powers of 88.4%,87.9%,and 90.9%,respectively.Interaction analysis indicates that the interaction between the old-child ratio and the elderly dependency ratio has a strong explanatory power for the aging patterns in Henan Province,reaching 97.3%,97.0%,and 97.4%,respectively.
基金Under the auspices of the National Social Science Fund of China(No.15BGL185,19XJL004)General Project of Humanities and Social Sciences Research and Planning Fund of Ministry of Education(No.19YJA790097)+1 种基金Social Science Fund of Fujian Province(No.FJ2017C080)A Key Discipline of Henan University of Animal Husbandry and Economy‘Business Enterprise Management’(No.MXK2016201)。
文摘Cold storage is the vital infrastructure of cold chain logistics. In this study, we analyzed the spatial pattern evolution characteristics, spatial autocorrelation and influencing factors of cold storage in China by using kernel density estimation(KDE), spatial autocorrelation analysis(SAA), and spatial error model(SEM). Results showed that: 1) the spatial distribution of cold storage in China is unbalanced, and has evolved from ‘one core’ to ‘one core and many spots’, that is, ‘one core’ refers to the Bohai Rim region mainly including Beijing, Tianjin, Hebei, Shandong and Liaoning regions, and ‘many spots’ mainly include the high-density areas such as Shanghai, Fuzhou, Guangzhou, Zhengzhou, Hefei, Wuhan, ürümqi. 2) The distribution of cold storage has significant global spatial autocorrelation and local spatial autocorrelation, and the ‘High-High’ cluster area is the most stable, mainly concentrated in the Bohai Rim;the ‘Low-Low’ cluster area is grouped in the southern China. 3) Economic development level, population density, traffic accessibility, temperature and land price, all affect the location choice of cold storage in varying degrees, while the impact of market demand on it is not explicit.
基金Under the auspices of the post-funded project of National Social Science Foundation of China(No.16FJL009)
文摘We use the directional slacks-based measure of efficiency and inverse distance weighting method to analyze the spatial pattern evolution of the industrial green total factor productivity of 108 cities in the Yangtze River Economic Belt in 2003–2013.Results show that both the subprime mortgage crisis and ‘the new normal' had significant negative effects on productivity growth,leading to the different spatial patterns between 2003–2008 and 2009–2013.Before 2008,green poles had gathered around some capital cities and formed a tripartite pattern,which was a typical core-periphery pattern.Due to a combination of the polarization and the diffusion effects,capital cities became the growth poles and ‘core' regions,while surrounding areas became the ‘periphery'.This was mainly caused by the innate advantage of capital cities and ‘the rise of central China' strategy.After 2008,the tripartite pattern changed to a multi-poles pattern where green poles continuously and densely spread in the midstream and downstream areas.This is due to the regional difference in the leading effect of green poles.The leading effect of green poles in midstream and downstream areas has changed from polarization to diffusion,while the polarization effect still leads in the upstream area.
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 Natural Science Foundation of Shandong Province(No.ZR2021ME167)the Key Research and Development Program of Shandong Province(No.2022CXGC010401)。
文摘Coastal tidal creeks are important channels for exchanges of material and energy between sea and land,and play an important role in the ecological protection of tidal flats.Although tidal creeks have evolved differently in various regions,the evolutionary process of tidal creeks in the Huanghe(Yellow)River delta of China,one of the most active deltas worldwide,is not entirely clear.Therefore,the evolution of tidal creeks in the delta from 1981 to 2021 was investigated by quantitatively analysing the tidal creeks and developing a standard for dividing their evolution periods.Visual interpretation and supervised classification methods were applied to the Landsat images to extract the tidal creek network,and 17 groups of tidal creek systems were selected.Results indicate that Creek S 1 was the most developed creek for having 113 tidal creeks totaling 65.8 km in length,while Creek E 3 had the fastest growth rate for having average annual increase of 1.9 km.Meanwhile,the level of tidal creeks increased,the average and median lengths of tidal creeks increased,and the number of tidal creeks decreased since 1981.The evolution of the tidal creek system could be divided into four stages,namely,rising,developing,stabilizing,and degrading.Analyses of a representative tidal creek show that there was no degenerated tidal creek during the rising period,with an increase in the number of 50 and a length increase of 57.9 km between 1981 and 1989.The proportion of new tidal creeks in the developing period was more than 50%and the new tidal creeks in the stabilizing period were equal to the degraded tidal creeks.Extinct tidal creeks were greater than 50%during the degrading period.There was no fixed order of tidal creek evolution in each period,and there may be a skip in evolution.Our findings provided a reference for studying the evolution of tidal creeks.
基金supported by the National Natural Science Foundation of China (Grant No. 11072238)the 111 Project of China (Grant No. B07-033)
文摘The convection in an annular container with heated bottom,cooled top and insulated side walls are studied by both linear instability analysis and direct numerical simulation.The onset of convection is investigated by linear stability analysis and corresponding pattern selection mechanisms are discussed.The nonlinear evolution of different flow patterns and the convective heat transfer are simulated.The transition to oscillatory flow is also given by stability analysis where the base flow is a steady three dimensional flow.The stability predictions are in good agreement with the numerical simulations,including both the growth rate and the dimensionless frequency.
基金Supported by projects of National Natural Science Foundation of China (No. 41771103)National Key R&D Program of China (No. 2016YFC0500204)。
文摘As an important indicator of the structural and functional stability of wetland landscapes,hydrological connectivity plays an important role in maintaining the stability of wetland ecosystems.Large-scale human activities have led to significant changes in the hydrological connectivity pattern of wetlands in Naoli River Basin since 1950 s.Combined with the availability of wetland habitat and the spreading capacity of aquatic birds,hydrological connectivity indices of marsh wetlands were calculated in the studied area,and the temporal and spatial changes were analyzed from 1950 s to 2015.The results indicate that:(1)the hydrological connectivity index of the marsh wetlands shows a growth trend with increasing distance threshold.All patches of marsh wetlands linked together when the distance threshold reached 35--40 km;(2)the optimal distance of hydrological connectivity is about 10 km for marsh wetlands of whole Naoli River Basin;(3)the total hydrological connectivity of marsh wetlands decreased in the Naoli River Basin from 1950 s to 2015.Although the hydrological connectivity index increased after 2005,the fragmentation of the landscape has not been improved.The analysis of the wetland hydrological connectivity can provide a scientific basis for the ecological restoration and protection of the wetland in the Naoli River Basin.
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.
文摘Quantum pattern recognition algorithm for two-qubit systems has been implemented by quantum adiabatic evolution. We will estimate required running time for this algorithm by means of an analytical solution of time- dependent Hamiltonian since the time complexity of adiabatic quantum evolution is a limitation on the quantum computing. These results can be useful for experimental implementation.
基金funded by Natural Science Foundation of China(51378067)the Natural Science Foundation of Shaanxi(806215594019)。
文摘Mountain area is an important geographical unit of land,and its ecology is sensitive and fragile.Over the past few decades,human activities have caused dramatic changes in land use in mountainous areas,which caused changes in landscape patterns and impacts on the ecological environment.It is unknown how the mechanism of land use affects the landscape pattern at different scales.The Hantai District,a typical human settlement in the mountain area in Shaanxi,China,was chosen as the study area.Based on the remote sensing images,the mathematical models and landscape indexes were adopted to evaluate the impact of land use change from 1998 to 2017 on the landscape pattern at different scales,and its main driving forces were analyzed.The results showed that the urbanized land expanded largest from 15.39%to 24.30%,and cultivated land experienced the largest decline from 43.54%to 35.35%.Changes in land use have made the patch morphology of most land types developed from a natural random to a sawtooth shape,and its spatial pattern evolved from a ruleset to a fragmented expansion.This reflects the continuous strengthening of human intervention in the process of regional development.Under the jurisdiction of Hantai District,the biggest change in landscape pattern is in Hanzhong City and Qili Town.The improved economy and increasing population and urbanization rate were the main factors that cause these changes.This research could provide necessary information for understanding the evolution mechanism of land resources in mountainous human settlements for mountainous areas with significant geomorphic differentiation.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10847110)
文摘Various pattern evolutions are presented in one- and two-dimensional spatially coupled phase-conjugate systems （SCPCSs）. As the system parameters change, different patterns are obtained from the period-doubling of kink-antikinks in space to the spatiotemporal chaos in a one-dimensional SCPCS. The homogeneous symmetric states induce symmetry breaking from the four corners and the boundaries, finally leading to spatiotemporal chaos with the increase of the iteration time in a two-dimensional SCPCS. Numerical simulations are very helpful for understanding the complex optical phenomena.
基金State Natural Science Foundation of China (49574223)Key Project (95-04-04-03-01) from China Seismological Bureau under (Nint
文摘Based on data of fault movement surveying, we simulate the evolution process of three dimensional stress field in North China by three dimensional finite element method. Evolutional patterns in one-year time scale from 1986 to 1997 have been illustrated and the evolution characteristics of stress field have been analyzed. In comparison with the seismic activity among that time interval in North China, we have primarily discussed the relationship between the evolution of stress field and seismic activity.
文摘Lakes are important ecological water sources in the Bashang Plateau. Its expansion or shrinkage directly affects the ecological security of the plateau and its surrounding areas. In this study, Landsat images from 1984 to 2015 were selected to monitor the area of lakes in the Bashang Plateau and to analyze the spatiotemporal evolution and driving forces of lakes in the Bashang Plateau. The results showed that there were 47 lakes in the Bashang Plateau in 2015, with a total area of 37.63 km2, mainly distributed in the central and western regions of the region. From 1984 to 2015, the lakes in Bashang Plateau showed a shrinking trend. At the same time, there are obvious stage differences in lake changes. During 1984-1996, the number of lakes increased by 99 and the total area increased by 124.43 km2. From 1996 to 2015, the number of lakes decreased by 142, and the total area decreased by 183.96 km2. Before 1996, climate change was the dominant factor. However, the shrinkage of lakes after 1996 is the result of climate change and human activities. Among them, the large-scale planting of water consuming crops such as vegetables is the main human activity mode leading to lake shrinkage. This study will help to understand the expansion and contraction factors of the Bashang Plateau lakes in Hebei province and provide a reference for the future protection and management of the lakes.
文摘Desertification is the most serious environmental problem in the world today. Fractal feature of granularity composition was studied by using the fractal theory in view of desertification soil in Fuxin district, thereby evolution patterns of desertification was promulgated. The result shows that the self-formation degree of the developing desertification areas is higher than the relatively steady desertification areas. Evolution of desertification is beginning of forming sandy soil of framework composition, and then the sandy soil be came complex by the effect of environment, climate and anthropo-activity.
基金ACKNOWLEDGEMENTS The authors would like to thank the reviewers for their detailed reviews and constructive comments, which have helped improve the quality of this paper. The research was supported in part by National Basic Research Program of China （973 Program, No. 2013CB329601, No. 2013CB329604）, National Natural Science Foundation of China （No.91124002, 61372191, 61472433, 61202362, 11301302）, and China Postdoctoral Science Foundation （2013M542560）. All opinions, findings, conclusions and recommendations in this paper are those of the authors and do not necessarily reflect the views of the funding agencies.
文摘People's attitudes towards public events or products may change overtime,rather than staying on the same state.Understanding how sentiments change overtime is an interesting and important problem with many applications.Given a certain public event or product,a user's sentiments expressed in microblog stream can be regarded as a vector.In this paper,we define a novel problem of sentiment evolution analysis,and develop a simple yet effective method to detect sentiment evolution in user-level for public events.We firstly propose a multidimensional sentiment model with hierarchical structure to model user's complicate sentiments.Based on this model,we use FP-growth tree algorithm to mine frequent sentiment patterns and perform sentiment evolution analysis by Kullback-Leibler divergence.Moreover,we develop an improve Affinity Propagation algorithm to detect why people change their sentiments.Experimental evaluations on real data sets show that sentiment evolution could be implemented effectively using our method proposed in this article.
基金National Natural Science Foundation of China,No.42371188National Social Science Foundation of China,No.20BJL104+2 种基金Major Project of Key Research Bases of Humanities and Social Sciences,Ministry of Education,No.22JJD790016Major Project of Applied Research in Philosophy and Social Sciences at Colleges and Universities in Henan Province,No.2023-YYZD-03Program of Excellence for Graduate Students of Henan University,No.SYLYC2023123。
文摘Transition from old to new economic drivers(TONED) is of great significance for optimizing economic structures. Using a combination of methods including entropy weight technique for order preference by similarity to ideal solution, geospatial analysis, and optimal parameter geodetector, this study investigates the patterns and mechanisms of China's TONED in the prefecture-level cities from 2011 to 2020. The findings reveal that(1) the TONED exhibited a spatial distribution characterized by higher levels in the east and lower levels in the west, along with a pyramidal hierarchy of levels. The distribution of hot and cold spots roughly followed the Heihe-Yulin line.(2) The informatization levels, openness to the outside world, and urbanization played a dominant role in the TONED. The types of dual-factor interactions exhibited both dual-factor enhancement and non-linear enhancement effects.(3) The eastern and central regions were more likely to promote the TONED through enhanced informatization levels, whereas the western region relied more on increasing openness. This study finds that the TONED results from the combined effects of three geographical natures, each playing a distinct role. The recommendations provided can serve as a reference for China and other developing countries to implement the TONED in the context of deglobalization.
基金Under the auspices of Priority Research Program of Chinese Academy of Sciences(No.XDA20080000)。
文摘The global value chains have become the core skeleton of the global economy.As a large-scale international cooperation initiative,the Belt and Road Initiative(BRI hereafter)may have a significant impact on the global economic landscape.In this context,the spatiotemporal pattern and evolution of the value chain connection of the Silk Road countries and whether the BRI will promote the value chain connections between China and these countries are important research questions for understanding the changing global economic landscape.This paper employs input-output analysis,network analysis and difference-in-differences based on Propensity Score Matching(PSM-DID)to conduct an in-depth quantitative study of these questions.The results show that,first,the overall value chain connection between China and the Silk Road countries has been rising since 2001.From the perspective of geographical distribution,Southeast Asia is the highest value chain connection region with China,and the growth in the central and eastern Europe is the most significant,whereas the central Asia is the lowest value connection region.From the perspective of complex network analysis,China’s position in the network of value flow among the Silk Road countries has been increasing continuously,and it has been in the lead position since 2008.Besides,the implementation of the BRI has had a significant positive influence on the overall value chain connection between China and the Silk Road countries,but this positive influence is limited to the central and eastern Europe region,whereas it is not significant in other regions.Finally,this paper suggests that to promote the development of value chain connection,the Silk Road countries need to develop more specific policies related to value chains.Policymakers need to be able to correctly identify the comparative advantages of the region and the types of value chains that are compatible with them and then find suitable partners and formulate targeted promotion policies.
