A comprehensive understanding of vegetation responses to climate extremes is essential for predicting ecological risks.The Tianshan Mountains,the world's largest arid mountain system,are ecologically vulnerable to...A comprehensive understanding of vegetation responses to climate extremes is essential for predicting ecological risks.The Tianshan Mountains,the world's largest arid mountain system,are ecologically vulnerable to climate extremes,yet the spatiotemporal heterogeneity of vegetation responses is not well understood.To address this,we assessed changes in vegetation phenophases using the green-up date(GUD)and the monthly maximum vegetation index(MVI).Their relationship with climate extremes across seasons and geographic units was analyzed using Classification and Regression Tree and Principal Component Analysis.Results indicate that GUD advanced by 0.276 days/year,with MVI increasing in spring and decreasing in summer.On a yearly scale,nighttime heatwaves advanced GUD in all vegetation types at lower altitudes with higher snow cover,whereas daytime heatwaves delayed GUD in grasslands.On a monthly scale,early spring heatwaves generally benefitted vegetation,with positive effects decreasing from forests to grasslands:forests benefitted from March to May,forest-grassland from March to April,and grasslands only in March.By late summer,heatwaves were negatively correlated with MVI across all vegetation types.This study highlights the complex responses of vegetation to climate extremes and underscores the vulnerability of high-altitude,low snow-covered grasslands,which is crucial for guiding restoration efforts.展开更多
The ＂combined approach＂, which is suitable to represent subgrid land surface heterogeneity in both interpatch and intra-patch variabilities, is employed in the BiOsphere/Atmosphere Transfer Scheme （BATS） as a land...The ＂combined approach＂, which is suitable to represent subgrid land surface heterogeneity in both interpatch and intra-patch variabilities, is employed in the BiOsphere/Atmosphere Transfer Scheme （BATS） as a land surface component of the regional climate model RegCM3 to consider the heterogeneities in temperature and moisture at the land surface, and then annual-scale simulations for 5 years （1988-1992） were conducted. Results showed that on the annual scale, the model＇s response to the heterogeneities is quite sensitive, and that the effect of the temperature heterogeneity （TH） is more pronounced than the moisture heterogeneity （MH）. On the intraannual scale, TH may lead to more （less） precipitation in warm （cold） seasons, and hence lead to larger intraannual variability in precipitation; the major MH effects may be lagged by about 1 month during the warm, rainy seasons, inducing -6% more precipitation for some sub-regions. Additionally, the modeled climate for the northern sub-regions shows larger sensitivities to the land surface heterogeneities than those for the southern sub-regions. Since state-of-art land surface models seldom account for surface intra-patch variabilities, this study emphasizes the importance of including this kind of variability in the land surface models.展开更多
Sol-gel glassy films of the SiO2-TiO2-PO2.5-ErO2.5 system containing nanocrystallites of ErPO4, were obtained through suitable heat treatments. Variations in the shape and intensity of the Er3＋ photoluminescent signa...Sol-gel glassy films of the SiO2-TiO2-PO2.5-ErO2.5 system containing nanocrystallites of ErPO4, were obtained through suitable heat treatments. Variations in the shape and intensity of the Er3＋ photoluminescent signal around 1500 nm were linked to the nature of the host environment of the active ions; the specific features of the photoluminescent emission spectrum of the erbium 4113/2 metastable level were interpreted in terms of structural changes in the glassy films. The photoluminescent spectrum was found to be sensitive to the order （crystalline） or disorder （amorphous） of the Er3＋ ions neighbour within the glassy matrix. An amorphous envi- ronment led to a broadening of Er3＋ PL emission band while a crystalline one was responsible for a drastic photoluminescent band- width narrowing. The presence of nanoscale heterogeneities caused a drastic photoluminescence intensity decrease. Changes in the shape of the decay curve of fluorescence lifetime were found also structurally dependent on volumetric defects, occurrence of phase separation and Er3＋-Er3＋ clustering effects as well.展开更多
Geostatistical data plays a vibrant role for surface-based reservoir modeling through outcrop analogues,which is used to understand three-dimensional(3D)variability of petrophysical properties.The main purpose of this...Geostatistical data plays a vibrant role for surface-based reservoir modeling through outcrop analogues,which is used to understand three-dimensional(3D)variability of petrophysical properties.The main purpose of this study is to improvise the surface-based 3D geo-modeling to demonstrate petrophysical characteristics and heterogeneities of Sandakan reservoirs,NW Borneo.We used point cloud data from Light Detection and Ranging(Li DAR)to build high-resolution virtual outcrop modeling(VOM)onto which we mapped 6 different lithofacies.Porosity and permeability of core plugs were measured to determine the average variance of petrophysical properties for each lithofacies.By utilizing the integration of VOMs analogues and petrophysical properties in Petrel^(TM),we demonstrated the distribution and associations of all lithofacies in pseudo wells that have inherent thin beds heterogeneities in 3D geocellular model.The results concluded that the heterogeneity of thin beds in lithofacies is dependent on porosity and permeability with input dataset.According to the final model,cross-bedding sandstone(CBS),hummocky cross-stratified sandstone(HCSS)and trough cross-bedding sandstone(TCBS)show good reservoir quality due to high porosity ranging from:25.6%to 20.4%and,19.3%-14.5%,and permeability ranging from:74.03 mD to 66.84 mD and,64.86 mD to 21.01 mD.In contrast,massive to weak laminae sandstone(MWLS)and bioturbated sandstone(BS)show fair to poor reservoir quality,caused baffling of surrounding mud sediments in the reservoir lithofacies.Results also revealed that Li DAR based VOM with petrophysical properties can significantly reduce the risk and minimize the cost of reservoir modeling in petroleum industry.展开更多
From a practical point of view,grain structure heterogeneities are key parameters that control the rock response and still remains a challenge to incorporate in a quantitative manner.One of the less discussed topics i...From a practical point of view,grain structure heterogeneities are key parameters that control the rock response and still remains a challenge to incorporate in a quantitative manner.One of the less discussed topics in the context of the grain-based model(GBM)in the particle flow code(PFC)is the contact heterogeneities and the appropriate contact model to mimic the grain boundary behavior.Generally,the smooth joint(SJ)model and linear parallel bond(LPB)model are used to simulate the grain boundary behavior.However,the literature does not document the suitability of different models for specific problems.Another challenge in implementing GBM in PFC is that only a single bonding parameter is used at the grain boundaries.The aim of this study is to investigate the responses of a laboratory-scale specimen with SJ and LPB models,considering grain boundary heterogeneous and homogeneous contact parameters.Uniaxial and biaxial compression tests are performed to calibrate the response of Creighton granite.The stressestrain curves,volumetric dilation,inter-crack(crack in the grain boundary),and intra-crack(crack within the grain)development,and failure patterns associated with different contact models are examined.It was found that both the SJ and LPB models can reproduce the pre-peak behavior observed for a granitic rock type.However,the LPB model is unable to reproduce the post-peak behavior.Due to the large interlocking effect originating from the balls in contact and the ball size in the LPB model,local dilation is induced at the grain boundaries.This overestimates the volumetric dilation and residual shear strength.The LPB model tends to result in discontinuous inter-cracks and stress localization in the rock specimen,resulting in fine fragments at the rock surface during failure.展开更多
In the proximity of an active fault, spatial variation of peak ground motion is significantly affected by the faulting mechanism. It has been observed that near fault ground motions consists of different characteristi...In the proximity of an active fault, spatial variation of peak ground motion is significantly affected by the faulting mechanism. It has been observed that near fault ground motions consists of different characteristics compared to the far fault ground motions. Near fault records, in the distance range of less than 100 m from the faults are not available except for few cases. Therefore numerical simulation of ground motions for such near-fault situations is necessary. In addition to the understanding of the phenomenon of near fault ground motion there is a need to enhance our understanding of the possible potential hazard that can be caused due to the future rupture activity by understanding the phenomenon of surface faulting. In this paper we propose numerical simulation based on discrete modeling to investigate the fault rupture propagation and its effect on the surface peak ground acceleration. In the present two dimensional study rupture propagation due to bedrock motion has been observed for different shear wave velocity. A model of size 1000× 150 m is selected for this purpose. It has been observed that as the stiffness of the media is decreasing, the affected surface is decreasing and also width of the shear crack zone is decreasing. Secondly, we attempted to study the ground motion on the surface due to the bedrock motion in presence of boulders in the soil media by keeping the boulder at different positions. We find that there is an increase in the shear zone as well as the PGA on the surface when the boulder is present on the foot wall and in the vicinity of the rupture zone. Finally, we performed the analysis using layered media and studied the affect of crack propagation and also the variation of peak accelerations. Findings from the study can be utilized to assess the damage potential of the near fault areas.展开更多
The influence of dose variation due to heterogeneities in narrow photon beams used in stereotactic radiosurgery has been investigated. Since the lateral electronic disequilibrium and existence of steep dose gradients ...The influence of dose variation due to heterogeneities in narrow photon beams used in stereotactic radiosurgery has been investigated. Since the lateral electronic disequilibrium and existence of steep dose gradients in small fields and the presence of heterogeneities can intensify these problems, in this study the effects of heterogeneities on 6 MV small photon beams produced by circular cone collimators with 5, 10, 15, 20 and 30 mm diameters are investigated. The heterogeneities include 3 cm Cork with density of 0.2 g/cm3 instead of lung and 3 cm Polytetrafluoroethylene (P.T.F.E) with density of 2.2 g/cm3 as bone. The measurements were carried out with EBT2 gafchromic and EDR2 radiographic films. Simulation was done by MCNP Monte Carlo Code (MCNP5). The depth dose curves in heterogeneous phantom were compared with homogeneous phantom. A good agreement was obtained within film and Monte Carlo calculations in presence of low density heterogeneity and also in the presence of high density heterogeneity. Monte Carlo results showed good agreement after stopping power correction.展开更多
In this research,a modeling approach of rainfall generator coupled with high resolution rainfall products were proposed to generate designed rainfall events under multiple spatial and temporal distributions,which was ...In this research,a modeling approach of rainfall generator coupled with high resolution rainfall products were proposed to generate designed rainfall events under multiple spatial and temporal distributions,which was then employed to analyze the impacts of spatial and temporal rainfall heterogeneities on peak runoff for watersheds.Three scenarios were developed under multiple degrees of impermeable underlying surface areas within an urban watershed in south China.Detailed runoff processes were analyzed through the adoption of a distributed hydrological model(GSSHA).A covariance analysis method combined with rainfall spatio-temporal heterogeneity characteristic were used to quantify heterogeneity effects on peak runoff.Results indicated that coupling short period(2008–2016)remotely rainfall data and RainyDay results could successfully reproduce designed rainfall events,spatio-temporal heterogeneity of rainfall contributed significantly to the peak runoff,which was greater than those by rainfall duration and capacity,and the increase in impermeable underlying surface enhanced the complexities of the effects.Over each rainfall duration with increasing rainfall return period,the indicator of rainfall peak coefficient(RWD)would decrease and then increase.Regarding the total rainfall center(tg),25 mm/h threshold rainfall spatial coverage(A25)decreased with increasing imperviousness,1-h maximum rainfall(Rmax)surged with increasing imperviousness at rainfall duration of 2 and 24 h.Innovations of this research lied in:combination of a rainfall generator model based on a stochastic storm transposition technique and remote-sensing rainfall data to generate designed rainfall events,a rainfall spatial and temporal heterogeneities index system was developed to reveal how the changing characteristics of rainfall distribution and the impacts on peak runoff,and in-depth analysis of the impacts on runoff peak under multiple urban development scenarios for increasing capability in flood control/prevention.展开更多
Water alternating gas(WAG)injection is a widely used strategy for enhancing oil recovery(EOR)during gas flooding,and the mechanisms,operating parameters,and influencing factors of which have been extensively studied.H...Water alternating gas(WAG)injection is a widely used strategy for enhancing oil recovery(EOR)during gas flooding,and the mechanisms,operating parameters,and influencing factors of which have been extensively studied.However,with respect to its capacity in expanding macroscopic sweep volume under varying heterogeneities,the related results appear inadequate.In this research,three cores with different heterogeneities were used and flooded by the joint water and CO_(2) WAG,then the effects of heterogeneity on oil recovery were determined.More importantly,the cores after CO_(2) WAG injection were investigated using the nuclear magnetic resonance(NMR)technique for remaining oil distribution research,which could help us to understand the capacity of CO_(2) WAG in enlarging sweep volume at different heterogeneities.The results show that the presence of heterogeneity may largely weaken the effectiveness of water flooding,the more severe the heterogeneity,the worse the water flooding.The WAG injection of CO_(2) performs well in EOR after water flooding for all the cores with different heterogeneities;however,it could barely form a complete or full sweep throughout the low-permeability region,and un-swept bypassed regions remain.The homogeneous core is better developed by the injection of the joint water and CO_(2) WAG than the heterogeneous and fractured cases.展开更多
We present lithofacies classifications for a tight gas sandstone reservoir by analyzing hierarchies of heterogeneities.We use principal component analysis(PCA)to overcome the two level of heterogeneities,which results...We present lithofacies classifications for a tight gas sandstone reservoir by analyzing hierarchies of heterogeneities.We use principal component analysis(PCA)to overcome the two level of heterogeneities,which results in a better lithofacies classification than the traditional cutoff method.The classical volumetric method is used for estimating oil/gas in-place resources in the petroleum industry since its inception is not accurate because it ignores the heterogeneities of and correlation between the petrophysical properties.We present the importance and methods of accounting for the heterogeneities of and correlation between petrophysical properties for more accurate hydrocarbon volumetric estimations.We also demonstrate the impacts of modeling the heterogeneities and correlation in porosity and hydrocarbon saturation for hydrocarbon volumetric estimations with a tight sandstone gas reservoir.Furthermore,geoscientists have traditionally considered that small-scale heterogeneities only impact subsurface fluid flow,but not impact the hydrocarbon resource volumetric estimation.We show the importance of modeling small-scale heterogeneities using fine cell size in reservoir modeling of unconventional resources for accurate resource assessment.展开更多
To describe the relationship between the whole material deformation behavior and each grain deformation behavior inmicro-forming,experimental and numerical modelling methods were employed.Tensile test results reveal t...To describe the relationship between the whole material deformation behavior and each grain deformation behavior inmicro-forming,experimental and numerical modelling methods were employed.Tensile test results reveal that contrary to the valueof flow stress,the scatter of flow stress decreases with the increase of thickness-to-grain diameter(T/d)ratio.Microhardnessevaluation results show that each grain owns unique deformation behavior and randomly distributes in each specimen.The specimenwith less number of grains would be more likely to form an easy deformation zone and produce the concentration of plasticdeformation.Based on the experiment results,a size-dependent model considering the effects of grain size,geometry size,and thedeformation behavior of each grain was developed.And the effectiveness and practicability of the size-dependent model wereverified by experimental results.展开更多
Homogeneous crystal nucleation is prone to formation of defects and often experiences heterogeneities,the inferences of which are crucial in processing crystalline materials and controlling their physical properties. ...Homogeneous crystal nucleation is prone to formation of defects and often experiences heterogeneities,the inferences of which are crucial in processing crystalline materials and controlling their physical properties. It has been debated in literature whether the associated heterogeneities are an integral part of the homogenous nucleation. In this study by integrating a probabilistic approach with large-scale molecular dynamics simulations based on the most advanced high-temperature interatomic potentials, we attempt to address the ambiguity over the sources and mechanisms of heterogeneities in homogenous nucleation during solidification of pure melts. Different classes of structured metals are investigated for this purpose,including face-centered cubic aluminum, body-centered cubic iron, and hexagonal close-packed magnesium. The results reveal, regardless of the element type or the solidified crystal structure, that the densification process of liquid metals is accompanied by short-range orderings of atoms prior to the formation of crystals, controlling the heterogeneities during homogenous nucleation.展开更多
The effect of annealing temperature on the development of microstructure and texture in an c~＋/3 titanium alloy Ti-6.5AI-3.SMo-l.5Zr-0.3Si （TCll） preformed by hot working was investigated with the aid of electron b...The effect of annealing temperature on the development of microstructure and texture in an c~＋/3 titanium alloy Ti-6.5AI-3.SMo-l.5Zr-0.3Si （TCll） preformed by hot working was investigated with the aid of electron back-scattered diffraction and X-ray diffraction measurements. It is shown that considerable microstructure and texture heterogeneities were developed in the cross-section of the hot-worked rod due to the non-uniform deformation. Subsequent annealing at 940 ℃ and 990 ℃ led to homogeneous microstructures with globular a grains, whereas a typical lamellar ca＋β microstructure was obtained after annealing at 1040 ℃. In the latter case, the Burgers orientation relationship was well preserved between the two phases in a single colony. The a lamellar within a given colony depicted similar crystallographic orientations and the boundary a grains shared the orientation of one of the neighboring c~ lamellar. In contrast, subsequent annealing had very limited effect on the main features of the textures, indicating strong inheritance of the texture heterogeneity in annealing. It is thus crucial to control the hot working process in order to achieve a high level of texture homogeneity in the final parts.展开更多
The prevailing mesoscale model MM5 (V3) is used to simulate a heavy rain case caused by interac- tion between a move-in front and topographical heterogeneities on Taiwan Island. It is found that both thermodynamic a...The prevailing mesoscale model MM5 (V3) is used to simulate a heavy rain case caused by interac- tion between a move-in front and topographical heterogeneities on Taiwan Island. It is found that both thermodynamic and dynamic ?elds along the front are heterogeneous in time and space. The heterogene- ity becomes more signi?cant as the e?ect of topography is added on. The heterogeneous distribution of physical variables along the front is the main reason for the heterogeneous frontal rain band; the optimum cooperation of the low level and upper level jet is another reason for the development of the rain band. Topography can strengthen the rainfall and causes extremely heavy rain cells. Updraft induced by topog- raphy extends to a rather low level, while the uplifted air by frontal circulation can reach to higher levels. The quasi-steady topographic circulation overlaps the frontal circulation when the front moves over Taiwan Island; the advantageous cooperation of various mesoscale conditions causes the large upward velocity on the windward side of the island.展开更多
Important information about small-scale heterogeneities is hardly accessible by the traditional deterministic seismic tomography. Fluctuations of the phase and the logarithmic amplitude of direct teleseismic plane P w...Important information about small-scale heterogeneities is hardly accessible by the traditional deterministic seismic tomography. Fluctuations of the phase and the logarithmic amplitude of direct teleseismic plane P waves can be used to characterize small-scale heterogeneities. Seismic data recorded by the Hi-CLIMB array are used to analyze the average power spectrum of the small-scale velocity heterogeneities under Tibet. Coherence functions of the logarithmic amplitude and the phase fluctuations due to different earthquakes from different back azimuths show consistent characteristics, indicating that fluctuations are due to heterogeneities under the stations. Assuming that the heterogeneities are statistically stationary and distributed within a layer, we invert for the average heterogeneity spectrum by fitting both the logarithmic amplitude and the phase coherence data. Multiscale nature of the heterogeneity is evident. The inverted power spectrum is ＂red＂ at the large-scale end, meaning that the power spectrum decreases as the length scale decreases. Such a decreasing trend stops at smaller scales -20-50 km and 10 km. This may indicate that mantle convection is not effective in destroying smaller heterogeneities.展开更多
To address the charging infrastructure challenges associated with slow electric vehicle(EV)industry growth,this study investigates the collaboration between private charging-pile-sharing platforms struggling with prof...To address the charging infrastructure challenges associated with slow electric vehicle(EV)industry growth,this study investigates the collaboration between private charging-pile-sharing platforms struggling with profitability and automotive companies.This collaboration is crucial,as it demands a balanced price and service quality management due to consumer expectations.This paper introduces a Stackelberg game model to explore the relationship between a charging platform and an automotive company.Through numerical analysis,we assess how this cooperation might improve the platform’s efficiency and benefit society,potentially overcoming existing industry hurdles.Our findings indicate that such partnerships could benefit all parties involved,despite possible negative environmental impacts.However,after collaborat-ing,platforms may increase consumer prices and payments to suppliers,potentially lowering service quality for brand-associated consumers due to a compromise between shorter waiting times and service quality.This research offers valu-able insights for stakeholders on the effects of cooperation,enabling better strategic decisions in the EV charging sector.展开更多
By GIS and ENVI,TM/ETM remote sensing images of five districts(Yuelu District,Furong District,Yuhua District,Tianxin District and Kaifu District) in Changsha City center in 2005,2010 and 2015 were interpreted.Moreover...By GIS and ENVI,TM/ETM remote sensing images of five districts(Yuelu District,Furong District,Yuhua District,Tianxin District and Kaifu District) in Changsha City center in 2005,2010 and 2015 were interpreted.Moreover,distribution chart for ecological background factors in 2020 was simulated by using CA-Markov module in IDRISI.Using principal component analysis,evaluation model for ecological background quality of the city was established.Via circle analysi s,GS+semi variance function analysis,hot spot area analysis and grey correlation analysis,integrated analysis and evaluation on spatial heterogeneity evolution of ecological background quality in research region were conducted.Results showed that firstly Changsha overall has formed ecological pattern of landscape island city,but ecological background started to show the evolution trend of high heterogeneity and fragmentation under the construction land expansion,and ecological background quality of the city declined from 0.300,6 to 0.257,1 during 2005-2020.Secondly,ecological background quality of Changsha City had typical circle and axial gradient structure,and "eco tone" had the most violent evolution.Thirdly,spatial structure of ecological background quality had region,time and direction heterogeneities,and spatial heterogeneity of region was the most important.Fourthly,hot spot area distribution of ecological background quality evolution showed the "frog jump" trend of gathering in marginal zone and diffusing to peripheral zone.Fifthly,in driving factors of ecological background quality,industrialization rate had the highest grey correlation degree(0.842,1),and grey absolute correlation degree between ecological background quality in Yuelu District and industrialization rate was the highest(0.603,1).展开更多
Deep learning in electron microscopy(EM)data analysis is predominantly supervised,relying on manually labeled data.This dependence limits scalability and slows the development of highthroughput EM characterization of ...Deep learning in electron microscopy(EM)data analysis is predominantly supervised,relying on manually labeled data.This dependence limits scalability and slows the development of highthroughput EM characterization of materials.While simulation-based approaches provide an alternative,they often struggle with morphological heterogeneity,contrast complexity,and experimental artifacts,reducing their real-world effectiveness.Weintroduce EMcopilot,a closed-loop generative learning framework that enables label-free EM segmentation.EMcopilot leverages the general vision model to extract morphological priors and employs a conditional generative adversarial network to generate contrast-aware images.An EM-specificdomain adapter further enhances realism by modeling key microscope-specific perturbations.Benchmark results show that EMcopilot-trained models not only achieve segmentation accuracy comparable to human-annotated models but also outperform them in detecting nanoparticles in poor-contrast regions and spatially clustered configurations,overcoming inherent human biases in annotation.By illustrating how generative models distill and transform complex EM features into a robust training resource in a self-supervised manner,EMcopilot provides a scalable solution for automated microscopy analysis.展开更多
The extensive tracing of Nd, Sr and Pb isotopes has revealed that there exist high-degree heterogeneities in suboceanic mantle and mantle anomalies of the Southern Hemisphere on a large scale (DUPAL, high <sup>8...The extensive tracing of Nd, Sr and Pb isotopes has revealed that there exist high-degree heterogeneities in suboceanic mantle and mantle anomalies of the Southern Hemisphere on a large scale (DUPAL, high <sup>87</sup>Sr/<sup>86</sup>Sr, and HIMU, high μ value, i. e. <sup>238</sup> U/<sup>204</sup>pb). Recently, the isotopic tracing of the Cenozoic Volcanics from the continent of China has confirmed that there exists a general tendency that the subcontinental mantle of eastern China was en-展开更多
Cyclohexene is an important raw material in the production of nylon.Selective hydrogenation of benzene is a key method for preparing cyclohexene.However,the Ru catalysts used in current industrial processes still face...Cyclohexene is an important raw material in the production of nylon.Selective hydrogenation of benzene is a key method for preparing cyclohexene.However,the Ru catalysts used in current industrial processes still face challenges,including high metal usage,high process costs,and low cyclohexene yield.This study utilizes existing literature data combined with machine learning methods to analyze the factors influencing benzene conversion,cyclohexene selectivity,and yield in the benzene hydrogenation to cyclohexene reaction.It constructs predictive models based on XGBoost and Random Forest algorithms.After analysis,it was found that reaction time,Ru content,and space velocity are key factors influencing cyclohexene yield,selectivity,and benzene conversion.Shapley Additive Explanations(SHAP)analysis and feature importance analysis further revealed the contribution of each variable to the reaction outcomes.Additionally,we randomly generated one million variable combinations using the Dirichlet distribution to attempt to predict high-yield catalyst formulations.This paper provides new insights into the application of machine learning in heterogeneous catalysis and offers some reference for further research.展开更多
基金National Natural Science Foundation of China,No.41871025The Third Xinjiang Scientific Expedition Program,No.2022xjkk0100+1 种基金The Natural Science Foundation of Shanghai,No.24ZR1440400The Young Talent Development Program in the Humanities at Shanghai Jiao Tong University,No.2025QN034。
文摘A comprehensive understanding of vegetation responses to climate extremes is essential for predicting ecological risks.The Tianshan Mountains,the world's largest arid mountain system,are ecologically vulnerable to climate extremes,yet the spatiotemporal heterogeneity of vegetation responses is not well understood.To address this,we assessed changes in vegetation phenophases using the green-up date(GUD)and the monthly maximum vegetation index(MVI).Their relationship with climate extremes across seasons and geographic units was analyzed using Classification and Regression Tree and Principal Component Analysis.Results indicate that GUD advanced by 0.276 days/year,with MVI increasing in spring and decreasing in summer.On a yearly scale,nighttime heatwaves advanced GUD in all vegetation types at lower altitudes with higher snow cover,whereas daytime heatwaves delayed GUD in grasslands.On a monthly scale,early spring heatwaves generally benefitted vegetation,with positive effects decreasing from forests to grasslands:forests benefitted from March to May,forest-grassland from March to April,and grasslands only in March.By late summer,heatwaves were negatively correlated with MVI across all vegetation types.This study highlights the complex responses of vegetation to climate extremes and underscores the vulnerability of high-altitude,low snow-covered grasslands,which is crucial for guiding restoration efforts.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(IAP09306)the National Natural Science Foundation of China under Grant Nos. 40875067 and 40675040the National Basic Research Program of China under Grant No.2006CB400505
文摘The ＂combined approach＂, which is suitable to represent subgrid land surface heterogeneity in both interpatch and intra-patch variabilities, is employed in the BiOsphere/Atmosphere Transfer Scheme （BATS） as a land surface component of the regional climate model RegCM3 to consider the heterogeneities in temperature and moisture at the land surface, and then annual-scale simulations for 5 years （1988-1992） were conducted. Results showed that on the annual scale, the model＇s response to the heterogeneities is quite sensitive, and that the effect of the temperature heterogeneity （TH） is more pronounced than the moisture heterogeneity （MH）. On the intraannual scale, TH may lead to more （less） precipitation in warm （cold） seasons, and hence lead to larger intraannual variability in precipitation; the major MH effects may be lagged by about 1 month during the warm, rainy seasons, inducing -6% more precipitation for some sub-regions. Additionally, the modeled climate for the northern sub-regions shows larger sensitivities to the land surface heterogeneities than those for the southern sub-regions. Since state-of-art land surface models seldom account for surface intra-patch variabilities, this study emphasizes the importance of including this kind of variability in the land surface models.
文摘Sol-gel glassy films of the SiO2-TiO2-PO2.5-ErO2.5 system containing nanocrystallites of ErPO4, were obtained through suitable heat treatments. Variations in the shape and intensity of the Er3＋ photoluminescent signal around 1500 nm were linked to the nature of the host environment of the active ions; the specific features of the photoluminescent emission spectrum of the erbium 4113/2 metastable level were interpreted in terms of structural changes in the glassy films. The photoluminescent spectrum was found to be sensitive to the order （crystalline） or disorder （amorphous） of the Er3＋ ions neighbour within the glassy matrix. An amorphous envi- ronment led to a broadening of Er3＋ PL emission band while a crystalline one was responsible for a drastic photoluminescent band- width narrowing. The presence of nanoscale heterogeneities caused a drastic photoluminescence intensity decrease. Changes in the shape of the decay curve of fluorescence lifetime were found also structurally dependent on volumetric defects, occurrence of phase separation and Er3＋-Er3＋ clustering effects as well.
文摘Geostatistical data plays a vibrant role for surface-based reservoir modeling through outcrop analogues,which is used to understand three-dimensional(3D)variability of petrophysical properties.The main purpose of this study is to improvise the surface-based 3D geo-modeling to demonstrate petrophysical characteristics and heterogeneities of Sandakan reservoirs,NW Borneo.We used point cloud data from Light Detection and Ranging(Li DAR)to build high-resolution virtual outcrop modeling(VOM)onto which we mapped 6 different lithofacies.Porosity and permeability of core plugs were measured to determine the average variance of petrophysical properties for each lithofacies.By utilizing the integration of VOMs analogues and petrophysical properties in Petrel^(TM),we demonstrated the distribution and associations of all lithofacies in pseudo wells that have inherent thin beds heterogeneities in 3D geocellular model.The results concluded that the heterogeneity of thin beds in lithofacies is dependent on porosity and permeability with input dataset.According to the final model,cross-bedding sandstone(CBS),hummocky cross-stratified sandstone(HCSS)and trough cross-bedding sandstone(TCBS)show good reservoir quality due to high porosity ranging from:25.6%to 20.4%and,19.3%-14.5%,and permeability ranging from:74.03 mD to 66.84 mD and,64.86 mD to 21.01 mD.In contrast,massive to weak laminae sandstone(MWLS)and bioturbated sandstone(BS)show fair to poor reservoir quality,caused baffling of surrounding mud sediments in the reservoir lithofacies.Results also revealed that Li DAR based VOM with petrophysical properties can significantly reduce the risk and minimize the cost of reservoir modeling in petroleum industry.
基金Supports from the University Transportation Center for Underground Transportation Infrastructure(UTC-UTI)at the Colorado School of Mines for funding this research under Grant No.69A3551747118 from the US Department of Transportation(DOT)the Fundamental Research Funds for the Central Universities under Grant No.A0920502052401-210 are gratefully acknowledged.
文摘From a practical point of view,grain structure heterogeneities are key parameters that control the rock response and still remains a challenge to incorporate in a quantitative manner.One of the less discussed topics in the context of the grain-based model(GBM)in the particle flow code(PFC)is the contact heterogeneities and the appropriate contact model to mimic the grain boundary behavior.Generally,the smooth joint(SJ)model and linear parallel bond(LPB)model are used to simulate the grain boundary behavior.However,the literature does not document the suitability of different models for specific problems.Another challenge in implementing GBM in PFC is that only a single bonding parameter is used at the grain boundaries.The aim of this study is to investigate the responses of a laboratory-scale specimen with SJ and LPB models,considering grain boundary heterogeneous and homogeneous contact parameters.Uniaxial and biaxial compression tests are performed to calibrate the response of Creighton granite.The stressestrain curves,volumetric dilation,inter-crack(crack in the grain boundary),and intra-crack(crack within the grain)development,and failure patterns associated with different contact models are examined.It was found that both the SJ and LPB models can reproduce the pre-peak behavior observed for a granitic rock type.However,the LPB model is unable to reproduce the post-peak behavior.Due to the large interlocking effect originating from the balls in contact and the ball size in the LPB model,local dilation is induced at the grain boundaries.This overestimates the volumetric dilation and residual shear strength.The LPB model tends to result in discontinuous inter-cracks and stress localization in the rock specimen,resulting in fine fragments at the rock surface during failure.
文摘In the proximity of an active fault, spatial variation of peak ground motion is significantly affected by the faulting mechanism. It has been observed that near fault ground motions consists of different characteristics compared to the far fault ground motions. Near fault records, in the distance range of less than 100 m from the faults are not available except for few cases. Therefore numerical simulation of ground motions for such near-fault situations is necessary. In addition to the understanding of the phenomenon of near fault ground motion there is a need to enhance our understanding of the possible potential hazard that can be caused due to the future rupture activity by understanding the phenomenon of surface faulting. In this paper we propose numerical simulation based on discrete modeling to investigate the fault rupture propagation and its effect on the surface peak ground acceleration. In the present two dimensional study rupture propagation due to bedrock motion has been observed for different shear wave velocity. A model of size 1000× 150 m is selected for this purpose. It has been observed that as the stiffness of the media is decreasing, the affected surface is decreasing and also width of the shear crack zone is decreasing. Secondly, we attempted to study the ground motion on the surface due to the bedrock motion in presence of boulders in the soil media by keeping the boulder at different positions. We find that there is an increase in the shear zone as well as the PGA on the surface when the boulder is present on the foot wall and in the vicinity of the rupture zone. Finally, we performed the analysis using layered media and studied the affect of crack propagation and also the variation of peak accelerations. Findings from the study can be utilized to assess the damage potential of the near fault areas.
文摘The influence of dose variation due to heterogeneities in narrow photon beams used in stereotactic radiosurgery has been investigated. Since the lateral electronic disequilibrium and existence of steep dose gradients in small fields and the presence of heterogeneities can intensify these problems, in this study the effects of heterogeneities on 6 MV small photon beams produced by circular cone collimators with 5, 10, 15, 20 and 30 mm diameters are investigated. The heterogeneities include 3 cm Cork with density of 0.2 g/cm3 instead of lung and 3 cm Polytetrafluoroethylene (P.T.F.E) with density of 2.2 g/cm3 as bone. The measurements were carried out with EBT2 gafchromic and EDR2 radiographic films. Simulation was done by MCNP Monte Carlo Code (MCNP5). The depth dose curves in heterogeneous phantom were compared with homogeneous phantom. A good agreement was obtained within film and Monte Carlo calculations in presence of low density heterogeneity and also in the presence of high density heterogeneity. Monte Carlo results showed good agreement after stopping power correction.
基金Program for Guangdong Introducing Innovative and Entrepreneurial Teams,Grant/Award Number:2021ZT09Key-Area Research and Development Program of Guangdong Province,Grant/Award Number:2020B1111380003National Natural Science Foundation of China,Grant/Award Number:U20A20117。
文摘In this research,a modeling approach of rainfall generator coupled with high resolution rainfall products were proposed to generate designed rainfall events under multiple spatial and temporal distributions,which was then employed to analyze the impacts of spatial and temporal rainfall heterogeneities on peak runoff for watersheds.Three scenarios were developed under multiple degrees of impermeable underlying surface areas within an urban watershed in south China.Detailed runoff processes were analyzed through the adoption of a distributed hydrological model(GSSHA).A covariance analysis method combined with rainfall spatio-temporal heterogeneity characteristic were used to quantify heterogeneity effects on peak runoff.Results indicated that coupling short period(2008–2016)remotely rainfall data and RainyDay results could successfully reproduce designed rainfall events,spatio-temporal heterogeneity of rainfall contributed significantly to the peak runoff,which was greater than those by rainfall duration and capacity,and the increase in impermeable underlying surface enhanced the complexities of the effects.Over each rainfall duration with increasing rainfall return period,the indicator of rainfall peak coefficient(RWD)would decrease and then increase.Regarding the total rainfall center(tg),25 mm/h threshold rainfall spatial coverage(A25)decreased with increasing imperviousness,1-h maximum rainfall(Rmax)surged with increasing imperviousness at rainfall duration of 2 and 24 h.Innovations of this research lied in:combination of a rainfall generator model based on a stochastic storm transposition technique and remote-sensing rainfall data to generate designed rainfall events,a rainfall spatial and temporal heterogeneities index system was developed to reveal how the changing characteristics of rainfall distribution and the impacts on peak runoff,and in-depth analysis of the impacts on runoff peak under multiple urban development scenarios for increasing capability in flood control/prevention.
基金Project(KFJJ-TZ-2019-3)supported by the Open Project of Shaanxi Key Laboratory of Advanced Stimulation Technology for Oil&Gas Reservoirs,ChinaProjects(51504275,51974344)supported by the National Natural Science Foundation of China。
文摘Water alternating gas(WAG)injection is a widely used strategy for enhancing oil recovery(EOR)during gas flooding,and the mechanisms,operating parameters,and influencing factors of which have been extensively studied.However,with respect to its capacity in expanding macroscopic sweep volume under varying heterogeneities,the related results appear inadequate.In this research,three cores with different heterogeneities were used and flooded by the joint water and CO_(2) WAG,then the effects of heterogeneity on oil recovery were determined.More importantly,the cores after CO_(2) WAG injection were investigated using the nuclear magnetic resonance(NMR)technique for remaining oil distribution research,which could help us to understand the capacity of CO_(2) WAG in enlarging sweep volume at different heterogeneities.The results show that the presence of heterogeneity may largely weaken the effectiveness of water flooding,the more severe the heterogeneity,the worse the water flooding.The WAG injection of CO_(2) performs well in EOR after water flooding for all the cores with different heterogeneities;however,it could barely form a complete or full sweep throughout the low-permeability region,and un-swept bypassed regions remain.The homogeneous core is better developed by the injection of the joint water and CO_(2) WAG than the heterogeneous and fractured cases.
基金supported by the Important National Science Technology Specific Projects of China(No.2016ZX05010-001-003).
文摘We present lithofacies classifications for a tight gas sandstone reservoir by analyzing hierarchies of heterogeneities.We use principal component analysis(PCA)to overcome the two level of heterogeneities,which results in a better lithofacies classification than the traditional cutoff method.The classical volumetric method is used for estimating oil/gas in-place resources in the petroleum industry since its inception is not accurate because it ignores the heterogeneities of and correlation between the petrophysical properties.We present the importance and methods of accounting for the heterogeneities of and correlation between petrophysical properties for more accurate hydrocarbon volumetric estimations.We also demonstrate the impacts of modeling the heterogeneities and correlation in porosity and hydrocarbon saturation for hydrocarbon volumetric estimations with a tight sandstone gas reservoir.Furthermore,geoscientists have traditionally considered that small-scale heterogeneities only impact subsurface fluid flow,but not impact the hydrocarbon resource volumetric estimation.We show the importance of modeling small-scale heterogeneities using fine cell size in reservoir modeling of unconventional resources for accurate resource assessment.
文摘To describe the relationship between the whole material deformation behavior and each grain deformation behavior inmicro-forming,experimental and numerical modelling methods were employed.Tensile test results reveal that contrary to the valueof flow stress,the scatter of flow stress decreases with the increase of thickness-to-grain diameter(T/d)ratio.Microhardnessevaluation results show that each grain owns unique deformation behavior and randomly distributes in each specimen.The specimenwith less number of grains would be more likely to form an easy deformation zone and produce the concentration of plasticdeformation.Based on the experiment results,a size-dependent model considering the effects of grain size,geometry size,and thedeformation behavior of each grain was developed.And the effectiveness and practicability of the size-dependent model wereverified by experimental results.
基金financially supported by the National Science Foundation (Nos.NSF-CMMI 1855491 and NSF-CMMI 2031800)。
文摘Homogeneous crystal nucleation is prone to formation of defects and often experiences heterogeneities,the inferences of which are crucial in processing crystalline materials and controlling their physical properties. It has been debated in literature whether the associated heterogeneities are an integral part of the homogenous nucleation. In this study by integrating a probabilistic approach with large-scale molecular dynamics simulations based on the most advanced high-temperature interatomic potentials, we attempt to address the ambiguity over the sources and mechanisms of heterogeneities in homogenous nucleation during solidification of pure melts. Different classes of structured metals are investigated for this purpose,including face-centered cubic aluminum, body-centered cubic iron, and hexagonal close-packed magnesium. The results reveal, regardless of the element type or the solidified crystal structure, that the densification process of liquid metals is accompanied by short-range orderings of atoms prior to the formation of crystals, controlling the heterogeneities during homogenous nucleation.
基金financial support of the National Basic Research Program of China(No.2007CB613803)
文摘The effect of annealing temperature on the development of microstructure and texture in an c~＋/3 titanium alloy Ti-6.5AI-3.SMo-l.5Zr-0.3Si （TCll） preformed by hot working was investigated with the aid of electron back-scattered diffraction and X-ray diffraction measurements. It is shown that considerable microstructure and texture heterogeneities were developed in the cross-section of the hot-worked rod due to the non-uniform deformation. Subsequent annealing at 940 ℃ and 990 ℃ led to homogeneous microstructures with globular a grains, whereas a typical lamellar ca＋β microstructure was obtained after annealing at 1040 ℃. In the latter case, the Burgers orientation relationship was well preserved between the two phases in a single colony. The a lamellar within a given colony depicted similar crystallographic orientations and the boundary a grains shared the orientation of one of the neighboring c~ lamellar. In contrast, subsequent annealing had very limited effect on the main features of the textures, indicating strong inheritance of the texture heterogeneity in annealing. It is thus crucial to control the hot working process in order to achieve a high level of texture homogeneity in the final parts.
基金National Natural Science Foundation of China(Grant Nos.40175012 , 90302015)The Innovation Program of Chincse Academy of Sciences(Grant No.ZKCX2-sw-210) the National Key Basic Research Development Progran of MSTC(Grant No.G1999043400).
文摘The prevailing mesoscale model MM5 (V3) is used to simulate a heavy rain case caused by interac- tion between a move-in front and topographical heterogeneities on Taiwan Island. It is found that both thermodynamic and dynamic ?elds along the front are heterogeneous in time and space. The heterogene- ity becomes more signi?cant as the e?ect of topography is added on. The heterogeneous distribution of physical variables along the front is the main reason for the heterogeneous frontal rain band; the optimum cooperation of the low level and upper level jet is another reason for the development of the rain band. Topography can strengthen the rainfall and causes extremely heavy rain cells. Updraft induced by topog- raphy extends to a rather low level, while the uplifted air by frontal circulation can reach to higher levels. The quasi-steady topographic circulation overlaps the frontal circulation when the front moves over Taiwan Island; the advantageous cooperation of various mesoscale conditions causes the large upward velocity on the windward side of the island.
文摘Important information about small-scale heterogeneities is hardly accessible by the traditional deterministic seismic tomography. Fluctuations of the phase and the logarithmic amplitude of direct teleseismic plane P waves can be used to characterize small-scale heterogeneities. Seismic data recorded by the Hi-CLIMB array are used to analyze the average power spectrum of the small-scale velocity heterogeneities under Tibet. Coherence functions of the logarithmic amplitude and the phase fluctuations due to different earthquakes from different back azimuths show consistent characteristics, indicating that fluctuations are due to heterogeneities under the stations. Assuming that the heterogeneities are statistically stationary and distributed within a layer, we invert for the average heterogeneity spectrum by fitting both the logarithmic amplitude and the phase coherence data. Multiscale nature of the heterogeneity is evident. The inverted power spectrum is ＂red＂ at the large-scale end, meaning that the power spectrum decreases as the length scale decreases. Such a decreasing trend stops at smaller scales -20-50 km and 10 km. This may indicate that mantle convection is not effective in destroying smaller heterogeneities.
基金supported by the National Natural Science Foundation of China(72474034,72104034)Humanities and Social Science Fund of the Ministry of Education of China(21YJC630037,22XJC910001)China Postdoctoral Science Foundation(2022T150072)。
文摘To address the charging infrastructure challenges associated with slow electric vehicle(EV)industry growth,this study investigates the collaboration between private charging-pile-sharing platforms struggling with profitability and automotive companies.This collaboration is crucial,as it demands a balanced price and service quality management due to consumer expectations.This paper introduces a Stackelberg game model to explore the relationship between a charging platform and an automotive company.Through numerical analysis,we assess how this cooperation might improve the platform’s efficiency and benefit society,potentially overcoming existing industry hurdles.Our findings indicate that such partnerships could benefit all parties involved,despite possible negative environmental impacts.However,after collaborat-ing,platforms may increase consumer prices and payments to suppliers,potentially lowering service quality for brand-associated consumers due to a compromise between shorter waiting times and service quality.This research offers valu-able insights for stakeholders on the effects of cooperation,enabling better strategic decisions in the EV charging sector.
基金Sponsored by National Natural Science Fund(51578454)
文摘By GIS and ENVI,TM/ETM remote sensing images of five districts(Yuelu District,Furong District,Yuhua District,Tianxin District and Kaifu District) in Changsha City center in 2005,2010 and 2015 were interpreted.Moreover,distribution chart for ecological background factors in 2020 was simulated by using CA-Markov module in IDRISI.Using principal component analysis,evaluation model for ecological background quality of the city was established.Via circle analysi s,GS+semi variance function analysis,hot spot area analysis and grey correlation analysis,integrated analysis and evaluation on spatial heterogeneity evolution of ecological background quality in research region were conducted.Results showed that firstly Changsha overall has formed ecological pattern of landscape island city,but ecological background started to show the evolution trend of high heterogeneity and fragmentation under the construction land expansion,and ecological background quality of the city declined from 0.300,6 to 0.257,1 during 2005-2020.Secondly,ecological background quality of Changsha City had typical circle and axial gradient structure,and "eco tone" had the most violent evolution.Thirdly,spatial structure of ecological background quality had region,time and direction heterogeneities,and spatial heterogeneity of region was the most important.Fourthly,hot spot area distribution of ecological background quality evolution showed the "frog jump" trend of gathering in marginal zone and diffusing to peripheral zone.Fifthly,in driving factors of ecological background quality,industrialization rate had the highest grey correlation degree(0.842,1),and grey absolute correlation degree between ecological background quality in Yuelu District and industrialization rate was the highest(0.603,1).
基金support from the National Research Foundation(NRF)Singapore,under its NRF Fellowship(NRF-NRFF11-2019-0002)Singapore Low-Carbon Energy Research Program Funding Initiative hosted under A*STAR(Grant No.U2305d4003).We thank Dr.Jen-It Wong,Senior Application Engineer of JEOL Asia Pte Ltd,for his help in configuring computer connections for the in-situ experiments.
文摘Deep learning in electron microscopy(EM)data analysis is predominantly supervised,relying on manually labeled data.This dependence limits scalability and slows the development of highthroughput EM characterization of materials.While simulation-based approaches provide an alternative,they often struggle with morphological heterogeneity,contrast complexity,and experimental artifacts,reducing their real-world effectiveness.Weintroduce EMcopilot,a closed-loop generative learning framework that enables label-free EM segmentation.EMcopilot leverages the general vision model to extract morphological priors and employs a conditional generative adversarial network to generate contrast-aware images.An EM-specificdomain adapter further enhances realism by modeling key microscope-specific perturbations.Benchmark results show that EMcopilot-trained models not only achieve segmentation accuracy comparable to human-annotated models but also outperform them in detecting nanoparticles in poor-contrast regions and spatially clustered configurations,overcoming inherent human biases in annotation.By illustrating how generative models distill and transform complex EM features into a robust training resource in a self-supervised manner,EMcopilot provides a scalable solution for automated microscopy analysis.
基金Project supported by the National Natural Science Foundation of China.
文摘The extensive tracing of Nd, Sr and Pb isotopes has revealed that there exist high-degree heterogeneities in suboceanic mantle and mantle anomalies of the Southern Hemisphere on a large scale (DUPAL, high <sup>87</sup>Sr/<sup>86</sup>Sr, and HIMU, high μ value, i. e. <sup>238</sup> U/<sup>204</sup>pb). Recently, the isotopic tracing of the Cenozoic Volcanics from the continent of China has confirmed that there exists a general tendency that the subcontinental mantle of eastern China was en-
基金Supported by CAS Basic and Interdisciplinary Frontier Scientific Research Pilot Project(XDB1190300,XDB1190302)Youth Innovation Promotion Association CAS(Y2021056)+1 种基金Joint Fund of the Yulin University and the Dalian National Laboratory for Clean Energy(YLU-DNL Fund 2022007)The special fund for Science and Technology Innovation Teams of Shanxi Province(202304051001007)。
文摘Cyclohexene is an important raw material in the production of nylon.Selective hydrogenation of benzene is a key method for preparing cyclohexene.However,the Ru catalysts used in current industrial processes still face challenges,including high metal usage,high process costs,and low cyclohexene yield.This study utilizes existing literature data combined with machine learning methods to analyze the factors influencing benzene conversion,cyclohexene selectivity,and yield in the benzene hydrogenation to cyclohexene reaction.It constructs predictive models based on XGBoost and Random Forest algorithms.After analysis,it was found that reaction time,Ru content,and space velocity are key factors influencing cyclohexene yield,selectivity,and benzene conversion.Shapley Additive Explanations(SHAP)analysis and feature importance analysis further revealed the contribution of each variable to the reaction outcomes.Additionally,we randomly generated one million variable combinations using the Dirichlet distribution to attempt to predict high-yield catalyst formulations.This paper provides new insights into the application of machine learning in heterogeneous catalysis and offers some reference for further research.
