Comprehensive evaluation and spatial-temporal evolution characteristics of urban resilience in Chengdu-Chongqing Economic Circle

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.

Spatial-temporal evolution of vegetation evapotranspiration in Hebei Province,China

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.

Spatial-temporal Evolution of the Urban-rural Coordination Relationship in Northeast China in 1990-2018

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.

Spatial-temporal Evolution Analysis on Land Use Multifunctionality in the China-Vietnam Border Area

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.

The Analysis of Spatial-Temporal Evolution of City Accessibility Based on Highway Network in Henan Province in China

Accessibility is an important tool to evaluate the maturity of a regional traffic network structure which describes the traffic convenience in the traffic network. The paper defines a new accessibility index by using the resident population weighted average value of the sum of inverse of the traveling time 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.

Spatial-temporal evolution of gas migration pathways in coal during shear loading

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°.

The spatial-temporal evolution of coherent structures in log law region of turbulent boundary layer

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.

Spatial-Temporal Evolution Characteristics and Driving Factors of Agricultural Space in Jianghan Plain from the Perspective of “Three-Zone Space”

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.

Spatial-temporal Evolution Pattern of Agricultural Productivity in Northwestern Sichuan Plateau

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 2000-2010,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 2010 was slightly lower than that in 2000,thereby indicating an improved utilization of input factors to a certain extent and a great potential for further improving such utilization;(4) during the 2000-2010 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 productivity in agriculture.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.

Deformable Catalytic Material Derived from Mechanical Flexibility for Hydrogen Evolution Reaction

Deformable catalytic material with excellent flexible structure is a new type of catalyst that has been applied in various chemical reactions,especially electrocatalytic hydrogen evolution reaction(HER).In recent years,deformable catalysts for HER have made great progress and would become a research hotspot.The catalytic activities of deformable catalysts could be adjustable by the strain engineering and surface reconfiguration.The surface curvature of flexible catalytic materials is closely related to the electrocatalytic HER properties.Here,firstly,we systematically summarized self-adaptive catalytic performance of deformable catalysts and various micro–nanostructures evolution in catalytic HER process.Secondly,a series of strategies to design highly active catalysts based on the mechanical flexibility of lowdimensional nanomaterials were summarized.Last but not least,we presented the challenges and prospects of the study of flexible and deformable micro–nanostructures of electrocatalysts,which would further deepen the understanding of catalytic mechanisms of deformable HER catalyst.

Microwave shock motivating the Sr substitution of 2D porous GdFeO_(3) perovskite for highly active oxygen evolution

The incorporation of partial A-site substitution in perovskite oxides represents a promising strategy for precisely controlling the electronic configuration and enhancing its intrinsic catalytic activity.Conventional methods for A-site substitution typically involve prolonged high-temperature processes.While these processes promote the development of unique nanostructures with highly exposed active sites,they often result in the uncontrolled configuration of introduced elements.Herein,we present a novel approach for synthesizing two-dimensional(2D)porous GdFeO_(3) perovskite with A-site strontium(Sr)substitution utilizing microwave shock method.This technique enables precise control of the Sr content and simultaneous construction of 2D porous structures in one step,capitalizing on the advantages of rapid heating and cooling(temperature~1100 K,rate~70 K s^(-1)).The active sites of this oxygen-rich defect structure can be clearly revealed through the simulation of the electronic configuration and the comprehensive analysis of the crystal structure.For electrocatalytic oxygen evolution reaction application,the synthesized 2D porous Gd_(0.8)Sr_(0.2)FeO_(3) electrocatalyst exhibits an exceptional overpotential of 294 mV at a current density of 10 mA cm^(-2)and a small Tafel slope of 55.85 mV dec^(-1)in alkaline electrolytes.This study offers a fresh perspective on designing crystal configurations and the construction of nanostructures in perovskite.

High-speed penetration of ogive-nose projectiles into thick concrete targets:Tests and a projectile nose evolution model

The majority of the projectiles used in the hypersonic penetration study are solid flat-nosed cylindrical projectiles with a diameter of less than 20 mm.This study aims to fill the gap in the experimental and analytical study of the evolution of the nose shape of larger hollow projectiles under hypersonic penetration.In the hypersonic penetration test,eight ogive-nose AerMet100 steel projectiles with a diameter of 40 mm were launched to hit concrete targets with impact velocities that ranged from 1351 to 1877 m/s.Severe erosion of the projectiles was observed during high-speed penetration of heterogeneous targets,and apparent localized mushrooming occurred in the front nose of recovered projectiles.By examining the damage to projectiles,a linear relationship was found between the relative length reduction rate and the initial kinetic energy of projectiles in different penetration tests.Furthermore,microscopic analysis revealed the forming mechanism of the localized mushrooming phenomenon for eroding penetration,i.e.,material spall erosion abrasion mechanism,material flow and redistribution abrasion mechanism and localized radial upsetting deformation mechanism.Finally,a model of highspeed penetration that included erosion was established on the basis of a model of the evolution of the projectile nose that considers radial upsetting;the model was validated by test data from the literature and the present study.Depending upon the impact velocity,v0,the projectile nose may behave as undistorted,radially distorted or hemispherical.Due to the effects of abrasion of the projectile and enhancement of radial upsetting on the duration and amplitude of the secondary rising segment in the pulse shape of projectile deceleration,the predicted DOP had an upper limit.

Carbon Emission Effects Driven by Evolution of Chinese Dietary Structure from 1987 to 2020

Exploring carbon emission effects based on the evolution of residents’ dietary structure to achieve the carbon neutrality goal and mitigate climate change is an important task.This study took China as the research object(data excluding Hong Kong,Macao and Taiwan) and used the carbon emission coefficient method to quantitatively measure the food carbon emissions from 1987–2020,then analyzed the carbon emission effects under the evolution of dietary structure.The results showed that during the study period,the Chinese dietary structure gradually changed to a high-carbon consumption pattern.The dietary structure of urban residents developed to a balanced one,while that of rural residents developed to a high-quality one.During the study period,the per capita food carbon emissions and total food consumption of Chinese showed an increasing trend.The per capita food carbon emissions of residents in urban and rural showed an overall upward trend.The total food carbon emissions in urban increased significantly,while that in rural increased first and then decreased.The influence of beef and mutton on carbon emissions is the highest in dietary structure.Compared with the balanced dietary pattern,the food carbon emissions of Chinese residents had not yet reached the peak,but were evolving to a high-carbon consumption pattern.

Tuning electronic structure of RuO_(2)by single atom Zn and oxygen vacancies to boost oxygen evolution reaction in acidic medium

The poor stability of RuO_(2)electrocatalysts has been the primary obstacles for their practical application in polymer electrolyte membrane electrolyzers.To dramatically enhance the durability of RuO_(2)to construct activity-stability trade-off model is full of significance but challenging.Herein,a single atom Zn stabilized RuO_(2)with enriched oxygen vacancies(SA Zn-RuO_(2))is developed as a promising alternative to iridium oxide for acidic oxygen evolution reaction(OER).Compared with commercial RuO_(2),the enhanced Ru–O bond strength of SA Zn-RuO_(2)by forming Zn-O-Ru local structure motif is favorable to stabilize surface Ru,while the electrons transferred from Zn single atoms to adjacent Ru atoms protects the Ru active sites from overoxidation.Simultaneously,the optimized surrounding electronic structure of Ru sites in SA ZnRuO_(2)decreases the adsorption energies of OER intermediates to reduce the reaction barrier.As a result,the representative SA Zn-RuO_(2)exhibits a low overpotential of 210 mV to achieve 10 mA cm^(-2)and a greatly enhanced durability than commercial RuO_(2).This work provides a promising dual-engineering strategy by coupling single atom doping and vacancy for the tradeoff of high activity and catalytic stability toward acidic OER.

Damage evolution of rock-encased-backfill structure under stepwise cyclic triaxial loading

Rock-encased-backfill(RB)structures are common in underground mining,for example in the cut-andfill and stoping methods.To understand the effects of cyclic excavation and blasting activities on the damage of these RB structures,a series of triaxial stepwise-increasing-amplitude cyclic loading experiments was conducted with cylindrical RB specimens(rock on outside,backfill on inside)with different volume fractions of rock(VF=0.48,0.61,0.73,and 0.84),confining pressures(0,6,9,and 12 MPa),and cyclic loading rates(200,300,400,and 500 N/s).The damage evolution and meso-crack formation during the cyclic tests were analyzed with results from stress-strain hysteresis loops,acoustic emission events,and post-failure X-ray 3D fracture morphology.The results showed significant differences between cyclic and monotonic loadings of RB specimens,particularly with regard to the generation of shear microcracks,the development of stress memory and strain hardening,and the contact forces and associated friction that develops along the rock-backfill interface.One important finding is that as a function of the number of cycles,the elastic strain increases linearly and the dissipated energy increases exponentially.Also,compared with monotonic loading,the cyclic strain hardening characteristics are more sensitive to rising confining pressures during the initial compaction stage.Another finding is that compared with monotonic loading,more shear microcracks are generated during every reloading stage,but these microcracks tend to be dispersed and lessen the likelihood of large shear fracture formation.The transition from elastic to plastic behavior varies depending on the parameters of each test(confinement,volume fraction,and cyclic rate),and an interesting finding was that the transformation to plastic behavior is significantly lower under the conditions of 0.73 rock volume fraction,400 N/s cyclic loading rate,and 9 MPa confinement.All the findings have important practical implications on the ability of backfill to support underground excavations.

Multivariate Time Series Anomaly Detection Based on Spatial-Temporal Network and Transformer in Industrial Internet of Things

In the Industrial Internet of Things(IIoT),sensors generate time series data to reflect the working state.When the systems are attacked,timely identification of outliers in time series is critical to ensure security.Although many anomaly detection methods have been proposed,the temporal correlation of the time series over the same sensor and the state(spatial)correlation between different sensors are rarely considered simultaneously in these methods.Owing to the superior capability of Transformer in learning time series features.This paper proposes a time series anomaly detection method based on a spatial-temporal network and an improved Transformer.Additionally,the methods based on graph neural networks typically include a graph structure learning module and an anomaly detection module,which are interdependent.However,in the initial phase of training,since neither of the modules has reached an optimal state,their performance may influence each other.This scenario makes the end-to-end training approach hard to effectively direct the learning trajectory of each module.This interdependence between the modules,coupled with the initial instability,may cause the model to find it hard to find the optimal solution during the training process,resulting in unsatisfactory results.We introduce an adaptive graph structure learning method to obtain the optimal model parameters and graph structure.Experiments on two publicly available datasets demonstrate that the proposed method attains higher anomaly detection results than other methods.

Study on Spatial-Temporal Evolution of Residential Differentiation in Shanghai from an Employee Perspective

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.

Origin and evolution of a new tetraploid mangrove species in an intertidal zone

Polyploidy is a major factor in the evolution of plants,yet we know little about the origin and evolution of polyploidy in intertidal species.This study aimed to identify the evolutionary transitions in three truemangrove species of the genus Acanthus distributed in the Indo-West Pacific region.For this purpose,we took an integrative approach that combined data on morphology,cytology,climatic niche,phylogeny,and biogeography of 493 samples from 42 geographic sites.Our results show that the Acanthus ilicifolius lineage distributed east of the Thai-Malay Peninsula possesses a tetraploid karyotype,which is morphologically distinct from that of the lineage on the west side.The haplotype networks and phylogenetic trees for the chloroplast genome and eight nuclear genes reveal that the tetraploid species has two sub-genomes,one each from A.ilicifolius and A.ebracteatus,the paternal and maternal parents,respectively.Population structure analysis also supports the hybrid speciation history of the new tetraploid species.The two sub-genomes of the tetraploid species diverged from their diploid progenitors during the Pleistocene.Environmental niche models revealed that the tetraploid species not only occupied the near-entire niche space of the diploids,but also expanded into novel environments.Our findings suggest that A.ilicifolius species distributed on the east side of the Thai-Malay Peninsula should be regarded as a new species,A.tetraploideus,which originated from hybridization between A.ilicifolius and A.ebracteatus,followed by chromosome doubling.This is the first report of a true-mangrove allopolyploid species that can reproduce sexually and clonally reproduction,which explains the long-term adaptive potential of the species.

Microdynamic mechanical properties and fracture evolution mechanism of monzogabbro with a true triaxial multilevel disturbance method

The far-field microdynamic disturbance caused by the excavation of deep mineral resources and underground engineering can induce surrounding rock damage in high-stress conditions and even lead to disasters.However,the mechanical properties and damage/fracture evolution mechanisms of deep rock induced by microdynamic disturbance under three-dimensional stress states are unclear.Therefore,a true triaxial multilevel disturbance test method is proposed,which can completely simulate natural geostress,excavation stress redistribution(such as stress unloading,concentration and rotation),and subsequently the microdynamic disturbance triggering damaged rock failure.Based on a dynamic true triaxial test platform,true triaxial microdynamic disturbance tests under different frequency and amplitudes were carried out on monzogabbro.The results show that increasing amplitude or decreasing frequency diminishes the failure strength of monzogabbro.Deformation modulus gradually decreases during disturbance failure.As frequency and amplitude increase,the degradation rate of deformation modulus decreases slightly,disturbance dissipated energy increases significantly,and disturbance deformation anisotropy strengthens obviously.A damage model has been proposed to quantitatively characterize the disturbance-induced damage evolution at different frequency and amplitude under true triaxial stress.Before disturbance failure,the micro-tensile crack mechanism is dominant,and the micro-shear crack mechanism increases significantly at failure.With the increase of amplitude and frequency,the micro-shear crack mechanism increases.When approaching disturbance failure,the acoustic emission fractal dimension changes from a stable value to local large oscillation,and finally increases sharply to a high value at failure.Finally,the disturbance-induced failure mechanism of surrounding rock in deep engineering is clearly elucidated.

Hydrochemical Characteristics and Evolution of Underground Brine in Lop Nur,Northwestern China

Lop Nur is located at the eastmost end of the Tarim Basin in Xinjiang,Northwestern China.This study reviews the hydrochemical characteristics and evolution of underground brine in Lop Nur,based on analytical data from 429 water samples(mainly brine).It is found that in the NE-SW direction,from the periphery to the Luobei sub-depression,while the hydrochemical type varies from the sodium sulfate subtype(S)to the magnesium sulfate subtype(M),the corresponding brine in the phase diagram transfers from the thenardite phase(Then)area,through the bloedite phase(Blo),epsomite phase(Eps),picromerite phase(Picro),finally reaching the sylvite phase(Syl)area.As for the degree of evolution,the sequence is the periphery<Luobei horizontally and the overlying glauberite brine<the underlying clastic brine vertically.It is concluded that the oxygen and hydrogen isotopic compositions of the brine have evidently been affected through the effects of evaporation and altitude,as well as the changes in local water circulation in recent years.Boron and chloride isotopic compositions show that the glauberite brine is formed under more arid conditions than the clastic one.The strontium isotopic composition indicates that the Lop Nur brine primarily originates from surface water;however,deep recharge may also be involved in the evolution of the brine,according to previous noble gas studies.It is confirmed that the brine in Lop Nur has become enriched with potassium prior to halite precipitation over the full course of the salt lake's evolution.Based on chemical compositions of brine from drillhole LDK01 and previous lithological studies,the evolution of the salt lake can be divided into three stages and it is inferred that the brine in Lop Nur may have undergone at least two significant concentration-dilution periods.