Surthce elevation is tile basic data for geo-science. It is difficult to retrieve tidal-flats＇ elevation from a single Re- mote Sensing （RS） image because of the complicated sediment dynanical environment and huge ...Surthce elevation is tile basic data for geo-science. It is difficult to retrieve tidal-flats＇ elevation from a single Re- mote Sensing （RS） image because of the complicated sediment dynanical environment and huge spatial difference in tidal-flats＇ moisture content. A Digital Elevation Model （DEM） construction method for inconstant inter-tidal zone based on high tempo-resolution MODIS data set in a short period is proposed in a ease study on the Dongsha Sandbank of the Jiangsu Radial Tidal Sand-ridges. In the present study, a batch-preprocessing method based on image partition to handle massive MODIS IB images is developed and applied to 8163 scenes of MODIS images. The dataset of short-period and muhi-temporal MODIS images for inter-tidal flats＇ DEM inversion is selected and the usability of MODIS dataset is analyzed. Shorelines of the Dongsha Sandbank are extracted by use of batch supervised classification. In accord with tidal- 0 level forecasted by the Chenjiawu Tidal Gauge Station at the overpass moment of each RS image, DEMs of inter-tidal flats in January and sutmner（Jul, Aug and Sept）, 2003 are built under ArcG1S9.2. Studies show that： （1） The dataset of short-duration and muhi-phase MODIS images can be used to retrieve the historical DEM of tidal-flats at changeful tidal flats. （2） Aualysis on usability of MODIS images from Aqua and Terra indicates that there are more usable and higbquality MODIS images in spring, autumn and winter, but less in summer. Therefore, the period for building inter-tidal fiats＇ DEM is suggested to be one month in spring, autumn and winter and three months in summer.展开更多
The effect of temperature on molten zone length was investigated through simulation to optimize the control of molten zone length during the experimental process. The temperature gradient distribution within the molte...The effect of temperature on molten zone length was investigated through simulation to optimize the control of molten zone length during the experimental process. The temperature gradient distribution within the molten zone during zone refining was simulated using COMSOL Multiphysics software and experimentally validated. The simulated molten zone length showed good agreement with the actual measured length. The experimental study of tellurium purification by zone refining was conducted under the following conditions: three passes of zone refining, a hydrogen flow rate of 0.5 L/min, and molten zone movement speeds of 0.5 and 1.0 mm/min. The results demonstrated that the removal efficiencies of impurities such as Ca and Cu exceeded 95%, while the removal efficiency of phosphorus (P) reached over 70%. And the purity of tellurium reached 6N.展开更多
The interactions between clouds and aerosols represent one of the largest uncertainties in assessing the Earth's radiation budget, highlighting the importance of research on the transition zone(TZ) within the clou...The interactions between clouds and aerosols represent one of the largest uncertainties in assessing the Earth's radiation budget, highlighting the importance of research on the transition zone(TZ) within the cloud-aerosol continuum.This study assesses the global distribution of TZ conditions, analyzes its optical characteristics, and determines the cloud or aerosol types most commonly associated with them, using the cloud-aerosol discrimination(CAD) score of the CloudAerosol Lidar with Orthogonal Polarization(CALIOP) instrument on the CALIPSO satellite. The CAD score classifies clouds and aerosols by the probability density functions of attenuated backscatter, total color ratio, volume depolarization ratio, altitude, and latitude. After applying several filters to avoid artifacts, the TZ was identified as those atmospheric layers that cannot be clearly classified as clouds or aerosols, layers within the no-confidence range(NCR) of the CAD score, and cirrus fringes. The optical characteristics of NCR layers exhibit two main clusters: Cluster 1, with properties between high-altitude ice clouds and aerosols(e.g., wispy cloud fragments), and Cluster 2, with properties between water clouds and aerosols at lower altitudes(e.g., large hydrated aerosols). Our results highlight the significant ubiquity of TZ conditions, which appear in 9.5% of all profiles and comprise 6.4% of the detected layers. Cluster 1 and cirrus-fringe layers predominate near the ITCZ and in mid-latitudes, whereas Cluster 2 layers are more frequent over the oceans along the central West African and East Asian coasts, where elevated smoke and dusty marine aerosols are common.展开更多
This study investigates the microstructure and co-precipitation behavior of multicomponent(Ni(Al,Mn)and Cu)nanoparticles in the weld heat-affected zones of high-strength low-carbon steel.Through thermal simulations,th...This study investigates the microstructure and co-precipitation behavior of multicomponent(Ni(Al,Mn)and Cu)nanoparticles in the weld heat-affected zones of high-strength low-carbon steel.Through thermal simulations,the intercritical,fine-grained,and coarsegrained heat-affected zones were systematically characterized to elucidate the interplay between the microstructure,precipitation,and mechanical properties.At a heat input of 30 kJ·cm^(−1),Ni(Al,Mn)nanoparticles dissolve in the intercritical heat-affected zone,followed by dense reprecipitation coupled with significant coarsening of Cu particles during cooling,thereby retaining high strength but reducing impact toughness to(142±10)J(compared to(205±8)J of the base metal).The fine-grained heat-affected zone,under the same heat input,exhibits a refined ferritic-bainite matrix with a few fine Ni(Al,Mn)and slightly coarsened Cu particles,thus enhancing plastic deformation capacity and resulting in superior impact toughness of(196±7)J.Despite complete dissolution of original precipitates at peak temperatures in the coarse-grained heat-affected zone,re-precipitated nanoparticles provide effective strengthening effect,compensating for grain coarsening and dislocation recovery and resulting in an impressive impact toughness of(186±6)J.The toughening mechanism is primarily attributed to the synergistic actions of the matrix,precipitates,and deformation twins.These findings provide mechanistic and quantitative insights for developing processing-microstructure-property relationships in different welding heat-affected zones,and this framework can be further utilized to optimize welding parameters for tailored applications.展开更多
Wetlands are vital ecosystems that perform essential functions such as climate regulation,environmental purification,material circulation and energy flow.They play an essential role in global biogeochemical cycles,dri...Wetlands are vital ecosystems that perform essential functions such as climate regulation,environmental purification,material circulation and energy flow.They play an essential role in global biogeochemical cycles,driven primarily by microorganisms.Understanding the distribution of wetland microorganisms across different temperature zones is key to comprehending their ecological roles.A meta-analysis of 704 wetland soil samples on microbial communities was conducted,using statistical methods like analysis of variance,principal component analysis,non-metric nultidimensional scaling,and structural equation modeling to examine biogeography and diversity across temperature zones.Our findings revealed a clear latitudinal diversity gradient pattern,with the highest microbial abundance in the tropics and the lowest in the southern temperate zone,which differed significantly from other temperature zones.Proteobacteria(37.76%-51.04%),Acidobacteria(5.11%-30.70%)and Bacteroidetes(3.43%-16.16%)dominanted the bacterial communities.Notably,the southern temperate zone showed significant variations,with a higher prevalence of Acidobacteria(30.07%).To investigate the causes of this variability,we screened 177 core microbiome and identified latitude as the core environmental factor influencing microbial community composition.Moreover,soil microorganisms exhibited strong nitrogen cycling potentials(particularly nirD and nirB)and carbon cycling potentials(especially accA),with gene abundances showing little variation across temperature zones.Wetland bacterial communities also demonstrated high stability,with average variation degree index values ranging from 0.1 to 0.3.Our results improve the understanding of the diversity and biogeographic mechanisms of wetland bacterial communities and hold significant implications for the management and conservation of wetlands.展开更多
The Almus Fault Zone(AFZ)is one of the major splay faults of the North Anatolian Fault Zone(NAFZ)and is important for understanding its tectonic features and assessing regional seismic hazards.This research presents t...The Almus Fault Zone(AFZ)is one of the major splay faults of the North Anatolian Fault Zone(NAFZ)and is important for understanding its tectonic features and assessing regional seismic hazards.This research presents the integration of morphometric indices to quantitatively assess the spatial variation of tectonic activity along the AFZ.The AFZ is an active fault with both strike-slip and normal fault components and consists of two main branches,Mercimekdağı-Çamdere Fault(MÇF)and Tokat Fault(TF)segments.This study aims to assess the relative tectonic activity of the AFZ using various morphometric indices,based on a 10 m resolution DEM,with the aid of ArcGIS and MATLAB software.For this purpose,morphometric indices such as hypsometric integral(HI:0.35-0.65),mountain front sinuosity(Smf:1.3-1.44),valley floor width-height ratio(Vf:0.15-2.28),asymmetry factor(AF:23-77),drainage basin shape(Bs:1.13-6.10)and normalized steepness index(ksn:1-498)were applied to 53 drainage basins.When the Smf and mean Vf indices results were evaluated,it was calculated that the uplift ratio of the region was more than 0.5 mm/yr.The spatial distribution of the relative tectonic activity(Iat)of the area was revealed by combining the obtained morphometric indices analysis results.According to the Iat result,it was concluded that the MercimekdağıÇamdere Fault and Tokat Fault segments have high tectonic activity,but the Mercimekdağı-Çamdere Fault segment has higher tectonic activity.The results obtained were also confirmed by field observations.This research provides valuable information for the evaluation of tectonic activity in drainage systems controlled by splay faults.展开更多
The Guanxian-Anxian fault zone in the Longmen Shan,Sichuan,China,exhibits long-term creep-slip but ruptured during the 2008 Wenchuan earthquake,challenging the view that creeping faults rarely generate strong earthqua...The Guanxian-Anxian fault zone in the Longmen Shan,Sichuan,China,exhibits long-term creep-slip but ruptured during the 2008 Wenchuan earthquake,challenging the view that creeping faults rarely generate strong earthquakes.To investigate the transition from creep-slip to stick-slip,we analyzed fault rocks from the WFSD-3,using microstructural observations,XRD,μXRF,Raman spectroscopy,and quartz grain size statistics.Fault rocks show intense foliation,pressure-solution structures,and abundant clay minerals,reflecting long-term aseismic creep.At the interface between black and gray fault gouges at~1249.98 m,microstructures indicate stick-slip behavior,including truncated grains,angular fragments,and finer grain sizes.Here,clay content drops sharply while strong minerals(quartz,feldspar,calcite,dolomite)increase.Elemental mapping shows Al and K enriched in black gouge,whereas Ca and Si in gray gouge;Raman spectroscopy indicates possible graphitization;the finest quartz grains occur in black gouge.These features mark co-seismic principal slip zone of the Wenchuan earthquake.We propose that fluid-driven transformation of strong minerals into clays facilitates creep-slip,whereas localized precipitation of strong minerals strengthens the fault,causing stress accumulation and controlling the creep-slip to stick-slip transition.This mechanism has implications for reassessing seismic hazards of creeping faults.展开更多
Ensuring national food security amidst rapid population growth and increasing extreme weather events remains a critical global challenge.However,the extent to which agricultural modernization in China enhances grain y...Ensuring national food security amidst rapid population growth and increasing extreme weather events remains a critical global challenge.However,the extent to which agricultural modernization in China enhances grain yield and contributes to food security remains unclear.Therefore,using panel data from 327 Chinese cities(2013–2021),this study employs spatial econometric models to analyze the spatial spillover effects of agricultural modernization level(AML)on grain yield and to reveal regional heterogeneity across nine major agricultural zones.The results showed a cumulative grain yield increase of 23.7 million tons,with peak productivity concentrated along the Hu Line and declining eastward and westward.AML also exhibited a steady increase but a clear spatial gradient,decreasing from coastal to inland regions,with the highest level observed in Southern China(SC).A key finding was that a 1%increase in AML directly raised local grain yield by an average of 4.185%,accompanied by significant positive spillover effects on neighboring regions.Regional variations revealed distinct patterns:the direct effects of AML were more pronounced in southern and eastern zones,while spillover effects dominated in northern and western zones.The largest positive direct impact of AML on grain yield was observed in the SC(8.499%),while Middle-Lower Yangtze Plain ranked second but exhibited the strongest positive spatial spillover effect(4.534%).These findings highlight the critical role of agricultural modernization in promoting grain production and provide a solid basis for optimizing regional agricultural systems,ensuring food security,and advancing sustainable agriculture.展开更多
Anaerobic ammonium oxidation(anammox)plays a vital role in the global nitrogen cycle by mitigating reactive nitrogen.In recent years,its ecological importance has drawn increasing attention.Despite its widespread occu...Anaerobic ammonium oxidation(anammox)plays a vital role in the global nitrogen cycle by mitigating reactive nitrogen.In recent years,its ecological importance has drawn increasing attention.Despite its widespread occurrence,the distribution and quantitative contribution of anammox to global nitrogen loss remain unclear.We collected 390 reported anammox activity measurements which were obtained using 15N isotope tracing techniques and analyzed anammox rate and environmental factors including soil/sediment and water property using generalized additive models(GAMs).Moreover,based on the division of the anammox activity region,we estimated anammox-driven nitrogen loss across different ecosystems including wetlands and oxygen minimum zones(OMZs)ecosystems.Our findings revealed that soil moisture content was the most significant predictor of anammox activity in wetlands ecosystems.Paddy fields contributed 51%of anammox-driven nitrogen loss(32.0 Tg N/yr),followed by rivers/lakes(29%)and wetlands(20%).Asia emerged as the dominant region for anammoxdriven nitrogen loss(30.7 Tg N/yr),with paddy fields making a substantial contribution.North America was the second-largest contributor(25.4 Tg N/yr),with rivers/lakes being the main sources of nitrogen loss.In OMZs ecosystems,nitrate and dissolved oxygen were key factors influencing anammox rates.OMZs were hotspots for anammox,with peak activity at 300 m depth and nitrogen loss totaling 68.6 Tg N/yr,mostly between 100 and 500 m depths.This study underscores the critical role of anammox in global nitrogen cycling and offers a basis for environmental nitrogen management through predictive anammox modeling.展开更多
An innovative real-time monitoring method for surrounding rock damage based on microseismic time-lapse double-difference tomography is proposed for delayed dynamic damage identification and insufficient detection of a...An innovative real-time monitoring method for surrounding rock damage based on microseismic time-lapse double-difference tomography is proposed for delayed dynamic damage identification and insufficient detection of adverse geological conditions in deep-buried tunnel construction.The installation techniques for microseismic sensors were optimized by mounting sensors at bolt ends which significantly improves signal-to-noise ratio(SNR)and anti-interference capability compared to conventional borehole placement.Subsequently,a 3D wave velocity evolution model that incorporates construction-induced disturbances was established,enabling the first visualization of spatiotemporal variations in surrounding rock wave velocity.It finds significant wave velocity reduction near the tunnel face,with roof and floor damage zones extending 40–50 m;wave velocities approaching undisturbed levels at 15 m ahead of the working face and on the laterally undisturbed side;pronounced spatial asymmetry in wave velocity distribution—values on the left side exceed those on the right,with a clear stress concentration or transition zone located 10–15 m;and systematically lower velocities behind the face than in front,indicating asymmetric rock damage development.These results provide essential theoretical support and practical guidance for optimizing dynamic construction strategies,enabling real-time adjustment of support parameters,and establishing safety early warning systems in deep-buried tunnel engineering.展开更多
Nereididae is a prolific annelid family widely distributed in the world oceans,especially in the Indo-Pacific Convergence Zone(IPCZ).However,its biogeographic pattern remains unexplored in IPCZ.To contribute to the un...Nereididae is a prolific annelid family widely distributed in the world oceans,especially in the Indo-Pacific Convergence Zone(IPCZ).However,its biogeographic pattern remains unexplored in IPCZ.To contribute to the understanding of biodiversity and biogeography of Nereididae in the IPCZ,we integrated historical data of species distributions with those of model-predicted ones to determine the biogeographic patterns of nereid species,from which we projected to its future distribution patterns for 2090-2100 under different climate scenarios(SSP1-1.9 and SSP5-8.5).Functional diversity within IPCZ was assessed using functional richness,functional evenness,and functional disparity.Divergence times within Nereididae were estimated using three DNA marker genes(COI,16S,and 18S rRNA),and a time tree was constructed based on a strict molecular clock model.The IPCZ was established as a key Nereididae biodiversity hotspot through distribution modelling of 256 species(44 genera),and temperature emerging as the predominant climatic driver of species distribution patterns.The distribution of species and functional diversity is notable for its non-centralized pattern.We projected that by the end of the century,areas of medium-to-high species richness will expand significantly under the low-emission SSP1-1.9 climate scenario.However,under the high-emission SSP5-8.5 scenario,the suitability of these regions significantly declines,posing an increasingly severe threat to biodiversity.In addition,by molecular clock analysis,we revealed that the evolutionary divergence of extant nereidid species occurred mainly in the Cretaceous and Jurassic,suggesting that paleogeographical and environmental events,such as oceanic anoxic events,might have played a pivotal role in shaping the evolutionary trajectory and ecological adaptations of marine annelids.These findings highlight the importance of considering both current biodiversity patterns and historical contexts in conservation planning,and provided insights into the potential factors on the biogeographic distribution and evolutionary processes of Nereididae.展开更多
The deep tunnels are prone to mud and water inrush disasters when crossing water-rich weak zones.A good understanding the hydromechanical behavior of the water-rich weak zone in deep tunnels is the prerequisite for de...The deep tunnels are prone to mud and water inrush disasters when crossing water-rich weak zones.A good understanding the hydromechanical behavior of the water-rich weak zone in deep tunnels is the prerequisite for determining the limit support pressure on the tunnel face.However,the seepage forces within the water-rich weak zone are not well estimated in existing models.To overcome this,an analytical model is proposed in this study to determine the limit support pressure of a deep tunnel crossing the water-rich weak zone.The seepage force in the water-rich weak zone is obtained by solving a group of Laplace equations about the hydraulic head,avoiding complex physical and mathematical approximation in existing models.Besides,the seepage boundary conditions in the water-rich weak zone are considered at the nodes on the Neumann boundary and the Dirichlet boundary.The effectiveness of the proposed model is then validated by numerical simulations and engineering practice.It shows that the proposed model has higher accuracy and wider applicability in estimating the hydraulic head.The proposed model can be used for stability analysis of tunnel faces.展开更多
Against the backdrop of accelerated development of new forms of trade,the question of whether rapid expansion of cross-border e-commerce(CBEC)can help to reduce carbon emissions among Chinese enterprises is of great s...Against the backdrop of accelerated development of new forms of trade,the question of whether rapid expansion of cross-border e-commerce(CBEC)can help to reduce carbon emissions among Chinese enterprises is of great significance for seizing new opportunities in foreign trade,and advancing firms’green and low-carbon transformation.This study treats the creation of CBEC pilot zones as a quasi-natural experiment,employing panel data from Chinese A-share listed companies matched with city-level information from 2006 to 2021.We construct a multi-period difference-in-differences model to identify the impact of CBEC pilot zone policy on corporate carbon emissions.Our findings indicate the construction of these pilot zones significantly reduces firms’carbon emissions intensity,and the results are robust across multiple tests.We show the pilot zone initiative contributes to emission reductions by enhancing the adoption of digital infrastructure,promoting green technological innovation,and increasing environmental awareness among enterprises.Quantile regressions reveal pilot zones exert a more pronounced carbon-reduction effect on firms characterized by high carbon emissions intensity and advanced levels of digital transformation.Moreover,the policy effect is especially significant in heavily polluting industries,and regions with weaker governmental environmental regulations or lower public environmental concerns.This study makes an innovative contribution to the literature by empirically verifying the environmental governance effect of establishing CBEC pilot zones,and offers practical guidance for governments in formulating cross-border e-commerce policies and for enterprises pursuing low carbon development.展开更多
The concurrent exploration of shale oil wells in the Gulong Sag of the Songliao Basin has uncovered promising hydrocarbon shows in the Fuyu pay zone of the Lower Cretaceous Quantou Formation.To assess the hydrocarbon ...The concurrent exploration of shale oil wells in the Gulong Sag of the Songliao Basin has uncovered promising hydrocarbon shows in the Fuyu pay zone of the Lower Cretaceous Quantou Formation.To assess the hydrocarbon exploration potential of the Fuyu pay zone,this study systematically analyzes the main controlling factors for hydrocarbon accumulation,including source rock conditions,reservoir characteristics and migration capacity,in the deep area of the Gulong Sag,using seismic,drilling and core data,and reveals the hydrocarbon enrichment mechanism and accumulation model.The results indicate that the source rocks in the first member of Cretaceous Qingshankou Formation(Qing-1 Member)in the Gulong Sag are widely distributed,characterized by high quality,large area,high maturity and high hydrocarbon generation intensity,providing an ample oil source for the Fuyu pay zone.The Fuyu pay zone in the Gulong Sag features multi-phase channel sand bodies and beach-bar sands that are laterally superimposed and vertically stacked,forming large-scale sand-rich reservoir assemblages,which provide the storage space for tight oil enrichment.Influenced by overpressure pore preservation and dissolution-enhanced porosity,the porosity of the Fuyu pay zone can reach up to 13%,meeting the reservoir conditions necessary for large-scale tight oil enrichment.The episodic opening of hydrocarbon-source connected faults during the hydrocarbon expulsion period,combined with source-reservoir pressure differentials,drives the efficient charging and enrichment of hydrocarbons into the underlying tight reservoirs.The hydrocarbon accumulation model of the Fuyu pay zone is summarized as“source-reservoir juxtaposition,overpressure charging,lateral source-reservoir connection+vertical fault-directed bidirectional hydrocarbon supply,continuous sand body distribution,and large-scale enrichment in fault-horst belts”.A new insight for the deep area of the Gulong Sag is proposed as being sand-rich,having superior reservoirs,and being oil-rich.This insight guided the deployment of three risk exploration wells.The Well HT1H achieved a high-yield industrial oil flow rate of 35.27 t/d during testing,discovering light tight oil with low density and low viscosity.Through horizontal well volumetric fracturing treatment,the Well HT1H achieved the first high-yield breakthrough of tight oil in the deep area of the Gulong Sag,confirming the presence of geological conditions for large-scale hydrocarbon accumulation in this area.This expands the potential for hundred-million-ton tight oil resource additions in the Songliao Basin and deepens the theoretical understanding of continental tight oil accumulation.展开更多
Investigating the detonation reaction zone structures of high explosives is significant for understanding detonation reaction mechanism.This study employed an integrated approach combining machine learning prediction,...Investigating the detonation reaction zone structures of high explosives is significant for understanding detonation reaction mechanism.This study employed an integrated approach combining machine learning prediction,theoretical calculation,and experimental characterization to determine the detonation reaction zone width of CL-20-based aluminized explosive.In this study,the detonation reaction zone refers to the reaction zone between the von Neumann(VN)peak and sonic point,which usually means the so-called detonation driving zone(DDZ).For the machine learning prediction,an ensemble model integrating Random Forest and Support Vector Regression was developed to predict the reaction zone width using a dataset of 19 publicly available samples.For the theoretical calculation,the Wood-Kirkwood(W-K)detonation theory model was utilized to implement numerical calculation of the reaction zone structures,incorporating chemical reaction kinetics to describe the detonation reaction progress.In experimental characterization,the Photon Doppler Velocimetry(PDV)was applied with LiF as the optical window to measure the particle velocity profile of detonation products and derive the reaction zone width.The results indicate that the reaction zone width values are 0.25 mm,0.28 mm,and 0.26 mm obtained from machine learning prediction,theoretical calculation,and experimental characterization,respectively.The corresponding velocities at the Chapman-Jouguet(CJ)point are 1,938 m/s,2,047 m/s,and 1,982 m/s,respectively.The maximum relative deviation in reaction zone width among three methods is approximately 7.7%,while that for CJ particle velocity is approximately 3.3%.These results from all three methods agree well within engineering error.This validates the effectiveness of integrating machine learning prediction,theoretical calculation and advanced experimental techniques for studying the detonation reaction zone structures of high explosives.This research provides insights into the detonation reaction mechanism and reaction zone characteristics of CL-20-based aluminized explosive.展开更多
Automatic identificationof discontinuities is a key focus in rock slope research.Conventional methods typically target small areas,which limits efficiencyand applicability for complex discontinuities in large-scale ro...Automatic identificationof discontinuities is a key focus in rock slope research.Conventional methods typically target small areas,which limits efficiencyand applicability for complex discontinuities in large-scale rock slopes.This study uses multi-angle unmanned aerial vehicle(UAV)nap-of-the-object photogrammetry to construct a high-definitionthree-dimensional(3D)point cloud model of the slope.The edge-firstconnection algorithm identifiesall edge points of discontinuities in the point cloud and completes recognition through simple connection analysis.This method avoids the complex calculations required for sequentially identifying discontinuity edges in conventional methods and achieves significantacceleration through algorithm optimization and parallel computation support.Based on this algorithm,the RockDiscontinuity Identification(RD ID)software is developed and applied to identify numerous highly disordered discontinuities on the Xulong slope in the Jinsha River suture zone.Processing tens of millions of point clouds within approximately 2 h demonstrates exceptional computational efficiency.The automatic algorithm accurately identifiesnearly 80%of planar discontinuities,with orientations and trace lengths closely matching manual results,highlighting its potential for large-scale rock outcrop applications.Comparisons with region growing algorithms further emphasize its effectiveness and accuracy.However,the algorithm struggles to identify linear discontinuities,which are a major source of error.Additionally,high roughness and smooth edges of discontinuities affect recognition accuracy,indicating areas for further improvement.展开更多
The number and diversity of inhibitory neurons(INs)increased substantially during mammalian brain evolution.However,the generative mechanisms of the vast repertoire of human INs remain elusive.We performed spatial and...The number and diversity of inhibitory neurons(INs)increased substantially during mammalian brain evolution.However,the generative mechanisms of the vast repertoire of human INs remain elusive.We performed spatial and single-cell transcriptomics of human medial ganglionic eminence(hMGE),a pivotal source of cortical and subpallial INs,and built the trajectories of hMGE-derived cells during brain development.We identified spatiotemporally and molecularly segregated progenitor cell populations fated to produce distinct IN types.展开更多
Systematically analyzing the impact mechanisms of policy on Land Use Conflict(LUC)is crucial for constructing effective conflict mitigation strategies.However,previous research on how policy influences LUC remains rel...Systematically analyzing the impact mechanisms of policy on Land Use Conflict(LUC)is crucial for constructing effective conflict mitigation strategies.However,previous research on how policy influences LUC remains relatively limited.Focusing on the indirect driving role of policy on LUC,this study proposed County Development Level(CDL)under Major Function Oriented Zone Planning(MFOZP)guidance as an intermediary variable,bridging the implicit influence of MFOZP and the explicit changes in LUC.Using the Beijing-Tianjin-Hebei(BTH)region in China as a case study,we analyzed the spatio-temporal evolution characteristics of LUC and CDL for the periods 2000-2010 and 2010-2020,before and after MFOZP implementation.Panel models and Geographically Weighted Regression(GWR)were employed to explore the mechanism by which CDL influences LUC under MFOZP guidance.The results show that:1)MFOZP implementation effectively alleviates land use pressure from regional development,with LUC continuously declining at a rate of 2.41%,while CDL exhibits slight growth(3.84%),during 2010-2020.2)Under MFOZP guidance,CDL reduces pressure on Land Use Structure Conflict(LUSC)and Land Use Process Conflict(LUPC),enhances its inhibitory effect on Land Use Function Conflict(LUFC),and significantly contributes to LUC coordination,with notable spatial heterogeneity.3)The coupling relationship between CDL and LUC has improved post-implementation.Based on this,tailored LUC coordination strategies are proposed for different functional zones.This study confirms the effectiveness of MFOZP in coordinating LUC and provides a scientific reference for LUC research under policy frameworks and the governance of LUC in the BTH region.展开更多
A brief review is made on the theory of the Lagrangian residual circulation and inter-tidal transports in a convectively weakly nonlinear system. In the review the emphasis is put on the systematical development of th...A brief review is made on the theory of the Lagrangian residual circulation and inter-tidal transports in a convectively weakly nonlinear system. In the review the emphasis is put on the systematical development of the theory and its weakness of convectively weakly nonlinear approximation. The fundamentals of a Lagrangian tidally-averaged theory on circulation with inter-tidal transport processes have been proposed for a general nonlinear coastal/estuarine system. The Lagrangian residual velocity is strictly de- fined, and it has been verified to be able to embody the velocity field of circulation. A new concept of the concentration for inter- tidal transport processes is presented. The concentration describing the inter-tidal transport processes should be a ＂Lagrangian inter-tidal concentration＂ defined and named, but not the Eulcrian tidally-averaged concentration used traditionally. The circulation described here contains a set of infinite temporal-spatial fields of velocity/concentration, each of which corresponds to a specific value of tidal phases varying continuously over one tidal cycle. When the convectively weakly nonlinear condition（ with a smaller order of eddy diffusion and sources） is approximately satisfied, a set of infinite temporal-spatial fields of velocity/concentration can be reduced to a single one.. the mass transport velocity/the Eulerian tidally averaged concentration as exhibited traditionally.展开更多
Diaspore traits and germination of four non-viviparous mangrove species in Hong Kong,Lumnitzera racemosa(Jack.)Voigt..Heritiera littoralis(Drgand.)Ait.,Excoecaria agallocha L.and Acanthus ilicifolius L.,were investiga...Diaspore traits and germination of four non-viviparous mangrove species in Hong Kong,Lumnitzera racemosa(Jack.)Voigt..Heritiera littoralis(Drgand.)Ait.,Excoecaria agallocha L.and Acanthus ilicifolius L.,were investigated.L.racemosa fruits planted immediately after collection failed to germinate but those stored in wet condition for 35 or 50 d were successfully germinated.This suggested that L.racemosa had endogenous and morphological seed dormancy,with embryos continued to develop during the dormant period.Germination rates of L.racemosa decreased with increasing salinity and no germina-tion was found at salinities over 25 ppt(ppt,parts per thausand).H.littoralis seeds were easily germinated if the fruit coat was artificially removed.Fruit dissection significantly shortened time for root initiation and leaf expansion.E.agallocha and A.ilicifolius seeds were also easy to germinate,initiating roots within 2 and 3 d,respectively.In terms of germination,A.ilicifolius had more tolerance to high salinity than L.racemosa.The four species exhibited three types of adaptation to unstable environments:(1)prolonged diaspore longevity as shown in L.racemosa and H.littoralis;(2)shortened rooting time as in E.agallocha and A.ilicifolius;and(3)produced sinking diaspores in L.racemosa.Diaspore buoyancy was one of the most important factors in determining inter-tidal zonation of non-viviparous mangrove species.Among the four species,L racemosa was distributed in the most seaward zones because its diaspores were sinkers while diaspores of H.littoralis,E.agallocha and A,ilicifolius,more abundant at backshore locations,were floaters.Root initiation was also important in influencing the inter-tidal zonation of the three species whose diaspores were floaters.H.littoralis with the longest rooting time,as compared to E.agallocha and A.ilicifolius,was distributed in the most backshore zone.None of other factors including salinity of seawater,animal predation,diaspore size and seedling dimension could account for inter-tidal zonation of theses pecies.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos .40701117 andJ0630535)
文摘Surthce elevation is tile basic data for geo-science. It is difficult to retrieve tidal-flats＇ elevation from a single Re- mote Sensing （RS） image because of the complicated sediment dynanical environment and huge spatial difference in tidal-flats＇ moisture content. A Digital Elevation Model （DEM） construction method for inconstant inter-tidal zone based on high tempo-resolution MODIS data set in a short period is proposed in a ease study on the Dongsha Sandbank of the Jiangsu Radial Tidal Sand-ridges. In the present study, a batch-preprocessing method based on image partition to handle massive MODIS IB images is developed and applied to 8163 scenes of MODIS images. The dataset of short-period and muhi-temporal MODIS images for inter-tidal flats＇ DEM inversion is selected and the usability of MODIS dataset is analyzed. Shorelines of the Dongsha Sandbank are extracted by use of batch supervised classification. In accord with tidal- 0 level forecasted by the Chenjiawu Tidal Gauge Station at the overpass moment of each RS image, DEMs of inter-tidal flats in January and sutmner（Jul, Aug and Sept）, 2003 are built under ArcG1S9.2. Studies show that： （1） The dataset of short-duration and muhi-phase MODIS images can be used to retrieve the historical DEM of tidal-flats at changeful tidal flats. （2） Aualysis on usability of MODIS images from Aqua and Terra indicates that there are more usable and higbquality MODIS images in spring, autumn and winter, but less in summer. Therefore, the period for building inter-tidal fiats＇ DEM is suggested to be one month in spring, autumn and winter and three months in summer.
基金financial support from the National Key Research and Development Program of China(No.2023YFC2907904)the National Natural Science Foundation of China(Nos.52374364,52104355,52074363)+1 种基金National Sustainable Development Agenda Innovation Demonstration Zones:Provincial Special“Open Competition”Project in Chenzhou,China(No.2022sfq57)Postdoctoral Innovation Talent Support Program,China(No.BX20230438)。
文摘The effect of temperature on molten zone length was investigated through simulation to optimize the control of molten zone length during the experimental process. The temperature gradient distribution within the molten zone during zone refining was simulated using COMSOL Multiphysics software and experimentally validated. The simulated molten zone length showed good agreement with the actual measured length. The experimental study of tellurium purification by zone refining was conducted under the following conditions: three passes of zone refining, a hydrogen flow rate of 0.5 L/min, and molten zone movement speeds of 0.5 and 1.0 mm/min. The results demonstrated that the removal efficiencies of impurities such as Ca and Cu exceeded 95%, while the removal efficiency of phosphorus (P) reached over 70%. And the purity of tellurium reached 6N.
基金funded through project NUBOLOSYTI (PID2023149972NB-100) of the Spanish Ministry of Science and Innovation (MICINN)supported by an IFUdG 2022 fellowship。
文摘The interactions between clouds and aerosols represent one of the largest uncertainties in assessing the Earth's radiation budget, highlighting the importance of research on the transition zone(TZ) within the cloud-aerosol continuum.This study assesses the global distribution of TZ conditions, analyzes its optical characteristics, and determines the cloud or aerosol types most commonly associated with them, using the cloud-aerosol discrimination(CAD) score of the CloudAerosol Lidar with Orthogonal Polarization(CALIOP) instrument on the CALIPSO satellite. The CAD score classifies clouds and aerosols by the probability density functions of attenuated backscatter, total color ratio, volume depolarization ratio, altitude, and latitude. After applying several filters to avoid artifacts, the TZ was identified as those atmospheric layers that cannot be clearly classified as clouds or aerosols, layers within the no-confidence range(NCR) of the CAD score, and cirrus fringes. The optical characteristics of NCR layers exhibit two main clusters: Cluster 1, with properties between high-altitude ice clouds and aerosols(e.g., wispy cloud fragments), and Cluster 2, with properties between water clouds and aerosols at lower altitudes(e.g., large hydrated aerosols). Our results highlight the significant ubiquity of TZ conditions, which appear in 9.5% of all profiles and comprise 6.4% of the detected layers. Cluster 1 and cirrus-fringe layers predominate near the ITCZ and in mid-latitudes, whereas Cluster 2 layers are more frequent over the oceans along the central West African and East Asian coasts, where elevated smoke and dusty marine aerosols are common.
基金supported by the National Natural Science Foundation of China(No.U2330110)Youth Science Foundation Project(Category A)of Liaoning Province,China(No.2025JH6/101100006).
文摘This study investigates the microstructure and co-precipitation behavior of multicomponent(Ni(Al,Mn)and Cu)nanoparticles in the weld heat-affected zones of high-strength low-carbon steel.Through thermal simulations,the intercritical,fine-grained,and coarsegrained heat-affected zones were systematically characterized to elucidate the interplay between the microstructure,precipitation,and mechanical properties.At a heat input of 30 kJ·cm^(−1),Ni(Al,Mn)nanoparticles dissolve in the intercritical heat-affected zone,followed by dense reprecipitation coupled with significant coarsening of Cu particles during cooling,thereby retaining high strength but reducing impact toughness to(142±10)J(compared to(205±8)J of the base metal).The fine-grained heat-affected zone,under the same heat input,exhibits a refined ferritic-bainite matrix with a few fine Ni(Al,Mn)and slightly coarsened Cu particles,thus enhancing plastic deformation capacity and resulting in superior impact toughness of(196±7)J.Despite complete dissolution of original precipitates at peak temperatures in the coarse-grained heat-affected zone,re-precipitated nanoparticles provide effective strengthening effect,compensating for grain coarsening and dislocation recovery and resulting in an impressive impact toughness of(186±6)J.The toughening mechanism is primarily attributed to the synergistic actions of the matrix,precipitates,and deformation twins.These findings provide mechanistic and quantitative insights for developing processing-microstructure-property relationships in different welding heat-affected zones,and this framework can be further utilized to optimize welding parameters for tailored applications.
基金supported by the National Natural Science Foundation of China(No.52070019).
文摘Wetlands are vital ecosystems that perform essential functions such as climate regulation,environmental purification,material circulation and energy flow.They play an essential role in global biogeochemical cycles,driven primarily by microorganisms.Understanding the distribution of wetland microorganisms across different temperature zones is key to comprehending their ecological roles.A meta-analysis of 704 wetland soil samples on microbial communities was conducted,using statistical methods like analysis of variance,principal component analysis,non-metric nultidimensional scaling,and structural equation modeling to examine biogeography and diversity across temperature zones.Our findings revealed a clear latitudinal diversity gradient pattern,with the highest microbial abundance in the tropics and the lowest in the southern temperate zone,which differed significantly from other temperature zones.Proteobacteria(37.76%-51.04%),Acidobacteria(5.11%-30.70%)and Bacteroidetes(3.43%-16.16%)dominanted the bacterial communities.Notably,the southern temperate zone showed significant variations,with a higher prevalence of Acidobacteria(30.07%).To investigate the causes of this variability,we screened 177 core microbiome and identified latitude as the core environmental factor influencing microbial community composition.Moreover,soil microorganisms exhibited strong nitrogen cycling potentials(particularly nirD and nirB)and carbon cycling potentials(especially accA),with gene abundances showing little variation across temperature zones.Wetland bacterial communities also demonstrated high stability,with average variation degree index values ranging from 0.1 to 0.3.Our results improve the understanding of the diversity and biogeographic mechanisms of wetland bacterial communities and hold significant implications for the management and conservation of wetlands.
文摘The Almus Fault Zone(AFZ)is one of the major splay faults of the North Anatolian Fault Zone(NAFZ)and is important for understanding its tectonic features and assessing regional seismic hazards.This research presents the integration of morphometric indices to quantitatively assess the spatial variation of tectonic activity along the AFZ.The AFZ is an active fault with both strike-slip and normal fault components and consists of two main branches,Mercimekdağı-Çamdere Fault(MÇF)and Tokat Fault(TF)segments.This study aims to assess the relative tectonic activity of the AFZ using various morphometric indices,based on a 10 m resolution DEM,with the aid of ArcGIS and MATLAB software.For this purpose,morphometric indices such as hypsometric integral(HI:0.35-0.65),mountain front sinuosity(Smf:1.3-1.44),valley floor width-height ratio(Vf:0.15-2.28),asymmetry factor(AF:23-77),drainage basin shape(Bs:1.13-6.10)and normalized steepness index(ksn:1-498)were applied to 53 drainage basins.When the Smf and mean Vf indices results were evaluated,it was calculated that the uplift ratio of the region was more than 0.5 mm/yr.The spatial distribution of the relative tectonic activity(Iat)of the area was revealed by combining the obtained morphometric indices analysis results.According to the Iat result,it was concluded that the MercimekdağıÇamdere Fault and Tokat Fault segments have high tectonic activity,but the Mercimekdağı-Çamdere Fault segment has higher tectonic activity.The results obtained were also confirmed by field observations.This research provides valuable information for the evaluation of tectonic activity in drainage systems controlled by splay faults.
基金supported by the National Natural Science Foundation of China(42230312,42272270,42172262,42372266)the Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project(2024ZD1000500)the China Geological Survey Project(DD20240041).
文摘The Guanxian-Anxian fault zone in the Longmen Shan,Sichuan,China,exhibits long-term creep-slip but ruptured during the 2008 Wenchuan earthquake,challenging the view that creeping faults rarely generate strong earthquakes.To investigate the transition from creep-slip to stick-slip,we analyzed fault rocks from the WFSD-3,using microstructural observations,XRD,μXRF,Raman spectroscopy,and quartz grain size statistics.Fault rocks show intense foliation,pressure-solution structures,and abundant clay minerals,reflecting long-term aseismic creep.At the interface between black and gray fault gouges at~1249.98 m,microstructures indicate stick-slip behavior,including truncated grains,angular fragments,and finer grain sizes.Here,clay content drops sharply while strong minerals(quartz,feldspar,calcite,dolomite)increase.Elemental mapping shows Al and K enriched in black gouge,whereas Ca and Si in gray gouge;Raman spectroscopy indicates possible graphitization;the finest quartz grains occur in black gouge.These features mark co-seismic principal slip zone of the Wenchuan earthquake.We propose that fluid-driven transformation of strong minerals into clays facilitates creep-slip,whereas localized precipitation of strong minerals strengthens the fault,causing stress accumulation and controlling the creep-slip to stick-slip transition.This mechanism has implications for reassessing seismic hazards of creeping faults.
基金National Natural Science Foundation of China,No.42471455,No.42230113National Key Research and Development Program of China,No.2022YFC3800804-01。
文摘Ensuring national food security amidst rapid population growth and increasing extreme weather events remains a critical global challenge.However,the extent to which agricultural modernization in China enhances grain yield and contributes to food security remains unclear.Therefore,using panel data from 327 Chinese cities(2013–2021),this study employs spatial econometric models to analyze the spatial spillover effects of agricultural modernization level(AML)on grain yield and to reveal regional heterogeneity across nine major agricultural zones.The results showed a cumulative grain yield increase of 23.7 million tons,with peak productivity concentrated along the Hu Line and declining eastward and westward.AML also exhibited a steady increase but a clear spatial gradient,decreasing from coastal to inland regions,with the highest level observed in Southern China(SC).A key finding was that a 1%increase in AML directly raised local grain yield by an average of 4.185%,accompanied by significant positive spillover effects on neighboring regions.Regional variations revealed distinct patterns:the direct effects of AML were more pronounced in southern and eastern zones,while spillover effects dominated in northern and western zones.The largest positive direct impact of AML on grain yield was observed in the SC(8.499%),while Middle-Lower Yangtze Plain ranked second but exhibited the strongest positive spatial spillover effect(4.534%).These findings highlight the critical role of agricultural modernization in promoting grain production and provide a solid basis for optimizing regional agricultural systems,ensuring food security,and advancing sustainable agriculture.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB0750400)the National Natural Science Foundation of China(Nos.91851204,42177063,and 52370185)+1 种基金the Special project of eco-environmental technology for peak carbon dioxide emissions and carbon neutrality(No.RCEES-TDZ-2021-20)the State Key Joint Laboratory of Environmental Simulation and Pollution Control(Research Center for Eco-environmental Sciences,Chinese Academy of Sciences)(No.24Z01ESPCR).
文摘Anaerobic ammonium oxidation(anammox)plays a vital role in the global nitrogen cycle by mitigating reactive nitrogen.In recent years,its ecological importance has drawn increasing attention.Despite its widespread occurrence,the distribution and quantitative contribution of anammox to global nitrogen loss remain unclear.We collected 390 reported anammox activity measurements which were obtained using 15N isotope tracing techniques and analyzed anammox rate and environmental factors including soil/sediment and water property using generalized additive models(GAMs).Moreover,based on the division of the anammox activity region,we estimated anammox-driven nitrogen loss across different ecosystems including wetlands and oxygen minimum zones(OMZs)ecosystems.Our findings revealed that soil moisture content was the most significant predictor of anammox activity in wetlands ecosystems.Paddy fields contributed 51%of anammox-driven nitrogen loss(32.0 Tg N/yr),followed by rivers/lakes(29%)and wetlands(20%).Asia emerged as the dominant region for anammoxdriven nitrogen loss(30.7 Tg N/yr),with paddy fields making a substantial contribution.North America was the second-largest contributor(25.4 Tg N/yr),with rivers/lakes being the main sources of nitrogen loss.In OMZs ecosystems,nitrate and dissolved oxygen were key factors influencing anammox rates.OMZs were hotspots for anammox,with peak activity at 300 m depth and nitrogen loss totaling 68.6 Tg N/yr,mostly between 100 and 500 m depths.This study underscores the critical role of anammox in global nitrogen cycling and offers a basis for environmental nitrogen management through predictive anammox modeling.
基金support of the National Natural Science Foundation of China(No.52274176)the Guangdong Province Key Areas R&D Program(No.2022B0101070001)+5 种基金Chongqing Elite Innovation and Entrepreneurship Leading talent Project(No.CQYC20220302517)the Chongqing Natural Science Foundation Innovation and Development Joint Fund(No.CSTB2022NSCQ-LZX0079)the National Key Research and Development Program Young Scientists Project(No.2022YFC2905700)the Chongqing Municipal Education Commission“Shuangcheng Economic Circle Construction in Chengdu-Chongqing Area”Science and Technology Innovation Project(No.KJCX2020031)the Fundamental Research Funds for the Central Universities(No.2024CDJGF-009)the Key Project for Technological Innovation and Application Development in Chongqing(No.CSTB2025TIAD-KPX0029).
文摘An innovative real-time monitoring method for surrounding rock damage based on microseismic time-lapse double-difference tomography is proposed for delayed dynamic damage identification and insufficient detection of adverse geological conditions in deep-buried tunnel construction.The installation techniques for microseismic sensors were optimized by mounting sensors at bolt ends which significantly improves signal-to-noise ratio(SNR)and anti-interference capability compared to conventional borehole placement.Subsequently,a 3D wave velocity evolution model that incorporates construction-induced disturbances was established,enabling the first visualization of spatiotemporal variations in surrounding rock wave velocity.It finds significant wave velocity reduction near the tunnel face,with roof and floor damage zones extending 40–50 m;wave velocities approaching undisturbed levels at 15 m ahead of the working face and on the laterally undisturbed side;pronounced spatial asymmetry in wave velocity distribution—values on the left side exceed those on the right,with a clear stress concentration or transition zone located 10–15 m;and systematically lower velocities behind the face than in front,indicating asymmetric rock damage development.These results provide essential theoretical support and practical guidance for optimizing dynamic construction strategies,enabling real-time adjustment of support parameters,and establishing safety early warning systems in deep-buried tunnel engineering.
基金Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB42000000)the National Natural Science Foundation of China(No.42376092)the Marine S&T Fund of Shandong Province for Pilot National Laboratory for Marine Science and Technology(No.2022QNLM030004)。
文摘Nereididae is a prolific annelid family widely distributed in the world oceans,especially in the Indo-Pacific Convergence Zone(IPCZ).However,its biogeographic pattern remains unexplored in IPCZ.To contribute to the understanding of biodiversity and biogeography of Nereididae in the IPCZ,we integrated historical data of species distributions with those of model-predicted ones to determine the biogeographic patterns of nereid species,from which we projected to its future distribution patterns for 2090-2100 under different climate scenarios(SSP1-1.9 and SSP5-8.5).Functional diversity within IPCZ was assessed using functional richness,functional evenness,and functional disparity.Divergence times within Nereididae were estimated using three DNA marker genes(COI,16S,and 18S rRNA),and a time tree was constructed based on a strict molecular clock model.The IPCZ was established as a key Nereididae biodiversity hotspot through distribution modelling of 256 species(44 genera),and temperature emerging as the predominant climatic driver of species distribution patterns.The distribution of species and functional diversity is notable for its non-centralized pattern.We projected that by the end of the century,areas of medium-to-high species richness will expand significantly under the low-emission SSP1-1.9 climate scenario.However,under the high-emission SSP5-8.5 scenario,the suitability of these regions significantly declines,posing an increasingly severe threat to biodiversity.In addition,by molecular clock analysis,we revealed that the evolutionary divergence of extant nereidid species occurred mainly in the Cretaceous and Jurassic,suggesting that paleogeographical and environmental events,such as oceanic anoxic events,might have played a pivotal role in shaping the evolutionary trajectory and ecological adaptations of marine annelids.These findings highlight the importance of considering both current biodiversity patterns and historical contexts in conservation planning,and provided insights into the potential factors on the biogeographic distribution and evolutionary processes of Nereididae.
基金support from the National Natural Science Foun-dation of China(Grant Nos.U24A20599 and 42277173)the National Science and Technology Major Project of China(Grant No.2024ZD1004300)is gratefully acknowledged.
文摘The deep tunnels are prone to mud and water inrush disasters when crossing water-rich weak zones.A good understanding the hydromechanical behavior of the water-rich weak zone in deep tunnels is the prerequisite for determining the limit support pressure on the tunnel face.However,the seepage forces within the water-rich weak zone are not well estimated in existing models.To overcome this,an analytical model is proposed in this study to determine the limit support pressure of a deep tunnel crossing the water-rich weak zone.The seepage force in the water-rich weak zone is obtained by solving a group of Laplace equations about the hydraulic head,avoiding complex physical and mathematical approximation in existing models.Besides,the seepage boundary conditions in the water-rich weak zone are considered at the nodes on the Neumann boundary and the Dirichlet boundary.The effectiveness of the proposed model is then validated by numerical simulations and engineering practice.It shows that the proposed model has higher accuracy and wider applicability in estimating the hydraulic head.The proposed model can be used for stability analysis of tunnel faces.
基金support provided by the National Natural Science Foundation of China[Grant No.72204202]2025 Annual Research Program of the China Society for Commercial Statistics[Grant No.2025STY10]General Project of Philosophy Society in Jiangsu Province Universities[Grant Nos.2023SJYB0923 and 2025SJYB0708].
文摘Against the backdrop of accelerated development of new forms of trade,the question of whether rapid expansion of cross-border e-commerce(CBEC)can help to reduce carbon emissions among Chinese enterprises is of great significance for seizing new opportunities in foreign trade,and advancing firms’green and low-carbon transformation.This study treats the creation of CBEC pilot zones as a quasi-natural experiment,employing panel data from Chinese A-share listed companies matched with city-level information from 2006 to 2021.We construct a multi-period difference-in-differences model to identify the impact of CBEC pilot zone policy on corporate carbon emissions.Our findings indicate the construction of these pilot zones significantly reduces firms’carbon emissions intensity,and the results are robust across multiple tests.We show the pilot zone initiative contributes to emission reductions by enhancing the adoption of digital infrastructure,promoting green technological innovation,and increasing environmental awareness among enterprises.Quantile regressions reveal pilot zones exert a more pronounced carbon-reduction effect on firms characterized by high carbon emissions intensity and advanced levels of digital transformation.Moreover,the policy effect is especially significant in heavily polluting industries,and regions with weaker governmental environmental regulations or lower public environmental concerns.This study makes an innovative contribution to the literature by empirically verifying the environmental governance effect of establishing CBEC pilot zones,and offers practical guidance for governments in formulating cross-border e-commerce policies and for enterprises pursuing low carbon development.
基金Supported by the PetroChina Oil,Gas and New Energy Division Science and Technology Special Project(2023YQX10102)。
文摘The concurrent exploration of shale oil wells in the Gulong Sag of the Songliao Basin has uncovered promising hydrocarbon shows in the Fuyu pay zone of the Lower Cretaceous Quantou Formation.To assess the hydrocarbon exploration potential of the Fuyu pay zone,this study systematically analyzes the main controlling factors for hydrocarbon accumulation,including source rock conditions,reservoir characteristics and migration capacity,in the deep area of the Gulong Sag,using seismic,drilling and core data,and reveals the hydrocarbon enrichment mechanism and accumulation model.The results indicate that the source rocks in the first member of Cretaceous Qingshankou Formation(Qing-1 Member)in the Gulong Sag are widely distributed,characterized by high quality,large area,high maturity and high hydrocarbon generation intensity,providing an ample oil source for the Fuyu pay zone.The Fuyu pay zone in the Gulong Sag features multi-phase channel sand bodies and beach-bar sands that are laterally superimposed and vertically stacked,forming large-scale sand-rich reservoir assemblages,which provide the storage space for tight oil enrichment.Influenced by overpressure pore preservation and dissolution-enhanced porosity,the porosity of the Fuyu pay zone can reach up to 13%,meeting the reservoir conditions necessary for large-scale tight oil enrichment.The episodic opening of hydrocarbon-source connected faults during the hydrocarbon expulsion period,combined with source-reservoir pressure differentials,drives the efficient charging and enrichment of hydrocarbons into the underlying tight reservoirs.The hydrocarbon accumulation model of the Fuyu pay zone is summarized as“source-reservoir juxtaposition,overpressure charging,lateral source-reservoir connection+vertical fault-directed bidirectional hydrocarbon supply,continuous sand body distribution,and large-scale enrichment in fault-horst belts”.A new insight for the deep area of the Gulong Sag is proposed as being sand-rich,having superior reservoirs,and being oil-rich.This insight guided the deployment of three risk exploration wells.The Well HT1H achieved a high-yield industrial oil flow rate of 35.27 t/d during testing,discovering light tight oil with low density and low viscosity.Through horizontal well volumetric fracturing treatment,the Well HT1H achieved the first high-yield breakthrough of tight oil in the deep area of the Gulong Sag,confirming the presence of geological conditions for large-scale hydrocarbon accumulation in this area.This expands the potential for hundred-million-ton tight oil resource additions in the Songliao Basin and deepens the theoretical understanding of continental tight oil accumulation.
文摘Investigating the detonation reaction zone structures of high explosives is significant for understanding detonation reaction mechanism.This study employed an integrated approach combining machine learning prediction,theoretical calculation,and experimental characterization to determine the detonation reaction zone width of CL-20-based aluminized explosive.In this study,the detonation reaction zone refers to the reaction zone between the von Neumann(VN)peak and sonic point,which usually means the so-called detonation driving zone(DDZ).For the machine learning prediction,an ensemble model integrating Random Forest and Support Vector Regression was developed to predict the reaction zone width using a dataset of 19 publicly available samples.For the theoretical calculation,the Wood-Kirkwood(W-K)detonation theory model was utilized to implement numerical calculation of the reaction zone structures,incorporating chemical reaction kinetics to describe the detonation reaction progress.In experimental characterization,the Photon Doppler Velocimetry(PDV)was applied with LiF as the optical window to measure the particle velocity profile of detonation products and derive the reaction zone width.The results indicate that the reaction zone width values are 0.25 mm,0.28 mm,and 0.26 mm obtained from machine learning prediction,theoretical calculation,and experimental characterization,respectively.The corresponding velocities at the Chapman-Jouguet(CJ)point are 1,938 m/s,2,047 m/s,and 1,982 m/s,respectively.The maximum relative deviation in reaction zone width among three methods is approximately 7.7%,while that for CJ particle velocity is approximately 3.3%.These results from all three methods agree well within engineering error.This validates the effectiveness of integrating machine learning prediction,theoretical calculation and advanced experimental techniques for studying the detonation reaction zone structures of high explosives.This research provides insights into the detonation reaction mechanism and reaction zone characteristics of CL-20-based aluminized explosive.
基金supported by the National Key R&D Program of China(Grant No.2022YFC3080200)the China Postdoctoral Science Foundation(Grant No.2023M731264)the Science and Technology Development Plan Project of Jilin Province,China(Grant No.20250602007RC).
文摘Automatic identificationof discontinuities is a key focus in rock slope research.Conventional methods typically target small areas,which limits efficiencyand applicability for complex discontinuities in large-scale rock slopes.This study uses multi-angle unmanned aerial vehicle(UAV)nap-of-the-object photogrammetry to construct a high-definitionthree-dimensional(3D)point cloud model of the slope.The edge-firstconnection algorithm identifiesall edge points of discontinuities in the point cloud and completes recognition through simple connection analysis.This method avoids the complex calculations required for sequentially identifying discontinuity edges in conventional methods and achieves significantacceleration through algorithm optimization and parallel computation support.Based on this algorithm,the RockDiscontinuity Identification(RD ID)software is developed and applied to identify numerous highly disordered discontinuities on the Xulong slope in the Jinsha River suture zone.Processing tens of millions of point clouds within approximately 2 h demonstrates exceptional computational efficiency.The automatic algorithm accurately identifiesnearly 80%of planar discontinuities,with orientations and trace lengths closely matching manual results,highlighting its potential for large-scale rock outcrop applications.Comparisons with region growing algorithms further emphasize its effectiveness and accuracy.However,the algorithm struggles to identify linear discontinuities,which are a major source of error.Additionally,high roughness and smooth edges of discontinuities affect recognition accuracy,indicating areas for further improvement.
文摘The number and diversity of inhibitory neurons(INs)increased substantially during mammalian brain evolution.However,the generative mechanisms of the vast repertoire of human INs remain elusive.We performed spatial and single-cell transcriptomics of human medial ganglionic eminence(hMGE),a pivotal source of cortical and subpallial INs,and built the trajectories of hMGE-derived cells during brain development.We identified spatiotemporally and molecularly segregated progenitor cell populations fated to produce distinct IN types.
基金Under the auspices of the National Key Research and Development Program of China(No.2018YFD1100803)the Fundamental Research Fund for the Central Universities(Ph.D.Top Innovative Talents Fund of CUMTB)(No.BBJ2024029)。
文摘Systematically analyzing the impact mechanisms of policy on Land Use Conflict(LUC)is crucial for constructing effective conflict mitigation strategies.However,previous research on how policy influences LUC remains relatively limited.Focusing on the indirect driving role of policy on LUC,this study proposed County Development Level(CDL)under Major Function Oriented Zone Planning(MFOZP)guidance as an intermediary variable,bridging the implicit influence of MFOZP and the explicit changes in LUC.Using the Beijing-Tianjin-Hebei(BTH)region in China as a case study,we analyzed the spatio-temporal evolution characteristics of LUC and CDL for the periods 2000-2010 and 2010-2020,before and after MFOZP implementation.Panel models and Geographically Weighted Regression(GWR)were employed to explore the mechanism by which CDL influences LUC under MFOZP guidance.The results show that:1)MFOZP implementation effectively alleviates land use pressure from regional development,with LUC continuously declining at a rate of 2.41%,while CDL exhibits slight growth(3.84%),during 2010-2020.2)Under MFOZP guidance,CDL reduces pressure on Land Use Structure Conflict(LUSC)and Land Use Process Conflict(LUPC),enhances its inhibitory effect on Land Use Function Conflict(LUFC),and significantly contributes to LUC coordination,with notable spatial heterogeneity.3)The coupling relationship between CDL and LUC has improved post-implementation.Based on this,tailored LUC coordination strategies are proposed for different functional zones.This study confirms the effectiveness of MFOZP in coordinating LUC and provides a scientific reference for LUC research under policy frameworks and the governance of LUC in the BTH region.
基金The National Key Basic Research Science Foundation ("973"project) of China under contract No. 2002CB412402the National Natu-ral Science Foundation of China under contract No. 40276007the Program for New Century Excellent Talents in University of China NCET-05-0592
文摘A brief review is made on the theory of the Lagrangian residual circulation and inter-tidal transports in a convectively weakly nonlinear system. In the review the emphasis is put on the systematical development of the theory and its weakness of convectively weakly nonlinear approximation. The fundamentals of a Lagrangian tidally-averaged theory on circulation with inter-tidal transport processes have been proposed for a general nonlinear coastal/estuarine system. The Lagrangian residual velocity is strictly de- fined, and it has been verified to be able to embody the velocity field of circulation. A new concept of the concentration for inter- tidal transport processes is presented. The concentration describing the inter-tidal transport processes should be a ＂Lagrangian inter-tidal concentration＂ defined and named, but not the Eulcrian tidally-averaged concentration used traditionally. The circulation described here contains a set of infinite temporal-spatial fields of velocity/concentration, each of which corresponds to a specific value of tidal phases varying continuously over one tidal cycle. When the convectively weakly nonlinear condition（ with a smaller order of eddy diffusion and sources） is approximately satisfied, a set of infinite temporal-spatial fields of velocity/concentration can be reduced to a single one.. the mass transport velocity/the Eulerian tidally averaged concentration as exhibited traditionally.
文摘Diaspore traits and germination of four non-viviparous mangrove species in Hong Kong,Lumnitzera racemosa(Jack.)Voigt..Heritiera littoralis(Drgand.)Ait.,Excoecaria agallocha L.and Acanthus ilicifolius L.,were investigated.L.racemosa fruits planted immediately after collection failed to germinate but those stored in wet condition for 35 or 50 d were successfully germinated.This suggested that L.racemosa had endogenous and morphological seed dormancy,with embryos continued to develop during the dormant period.Germination rates of L.racemosa decreased with increasing salinity and no germina-tion was found at salinities over 25 ppt(ppt,parts per thausand).H.littoralis seeds were easily germinated if the fruit coat was artificially removed.Fruit dissection significantly shortened time for root initiation and leaf expansion.E.agallocha and A.ilicifolius seeds were also easy to germinate,initiating roots within 2 and 3 d,respectively.In terms of germination,A.ilicifolius had more tolerance to high salinity than L.racemosa.The four species exhibited three types of adaptation to unstable environments:(1)prolonged diaspore longevity as shown in L.racemosa and H.littoralis;(2)shortened rooting time as in E.agallocha and A.ilicifolius;and(3)produced sinking diaspores in L.racemosa.Diaspore buoyancy was one of the most important factors in determining inter-tidal zonation of non-viviparous mangrove species.Among the four species,L racemosa was distributed in the most seaward zones because its diaspores were sinkers while diaspores of H.littoralis,E.agallocha and A,ilicifolius,more abundant at backshore locations,were floaters.Root initiation was also important in influencing the inter-tidal zonation of the three species whose diaspores were floaters.H.littoralis with the longest rooting time,as compared to E.agallocha and A.ilicifolius,was distributed in the most backshore zone.None of other factors including salinity of seawater,animal predation,diaspore size and seedling dimension could account for inter-tidal zonation of theses pecies.
