Drought,as the most catastrophic abiotic stress,poses a significant threat to the growth and development of plants.Among the mechanisms employed by plants to cope with drought-induced stress,abscisic acid(ABA)which is...Drought,as the most catastrophic abiotic stress,poses a significant threat to the growth and development of plants.Among the mechanisms employed by plants to cope with drought-induced stress,abscisic acid(ABA)which is the sesquiterpene hormone,occupies a pivotal role.A hypothesis has emerged that the exogenous application of ABA can positively influence the terpenoid content of Lavandula angustifolia cv Hidcote essential oil(EO),thereby conferring enhanced resilience to drought stress.A randomized complete block design experiment was conducted with three replicationsandfour irrigation regimes,including I4[30%-40%of field capacity(FC)],I3(50%-60%FC),I2(70%-80%FC),andI1(90%-100%FC)as control.Application of ABAspraying included three concentrations,A3(30μmol·L^(-1)ABA),A2(15μmol·L^(-1)ABA),and A1 as control(distilled water).Results revealed that drought significantly affected all studied traits except for relative water content(RWC)and shoot dry mass.The ABA impact application on the observed traits was found to be dependent upon the level of drought to which the plants were exposed.Specifically,the highest levels of flavonoid content,total antioxidant activity,peroxidase(POX)activity,and EO percentage were observed under I4A2 conditions.Conversely,the highest levels of superoxide dismutase(SOD)and catalase(CAT)activity,and proline were recorded under I4A3 conditions,while the highest EO yield was obtained under I3A2 conditions.Analysis of the EO revealed that there were common indicative compounds across the varying levels of droughtandABAapplication,including linalool,camphor,borneol,bornyl formate,andcaryophyllene oxide.Theproduction pattern ofmonoterpene and sesquiterpene compounds demonstrated a distinct trend,with the highest concentration of monoterpene hydrocarbon compounds(average of 12.92%)being observed in the I2A3 treatment group,andthe highest concentration of oxygenatedmonoterpenecompounds(average of 64.76%)being recorded in the I1A1 group.Conversely,the most significant levels of sesquiterpene hydrocarboncompounds(14.98%)andoxygenated sesquiterpene compounds(10.46%)were observed in the I4A3 and I4A1 groups,respectively,showing the efficacy of monoterpenes and sesquiterpenes from the action of ABA under drought conditions.The observed results indicated that the concentration of oxygenated monoterpene compounds decreases with an increase in drought level.Conversely,the application of ABA at any given drought level appears to resulted in increased concentrations of oxygenated monoterpene compounds in the same conditions.It may be concluded that plants under high-stress drought conditions allocate more terpene precursors to the production of sesquiterpene hydrocarbon compounds,aided by ABA with the same properties.展开更多
Collaborative changes in the hydro-sediment regime and erosional base level are vital factors that influence the evolution of wandering rivers.In the wandering Xiaobeiganliu reach of the Middle Yellow River(MYR),the r...Collaborative changes in the hydro-sediment regime and erosional base level are vital factors that influence the evolution of wandering rivers.In the wandering Xiaobeiganliu reach of the Middle Yellow River(MYR),the rapidly decreasing sediment discharge and lowering base level,i.e.,the Tongguan elevation,have resulted in new features of thalweg migration in river morphology.In this work,on the basis of topographic measurements of the reach from 2003–2021,the thalweg migration distance and intensity were calculated at both the section scale and reach scale.The results revealed that the annual sediment discharge decreased by 72%from 1986–2002,and the reach exhibited sustained scouring from deposition,leading to the Tongguan elevation decreasing by 1.69 m compared with that in 2002.Accordingly,the distance and intensity of thalweg migration have been reduced to varying degrees in both section and reach scales.The maximum section-scale thalweg migration distance was reduced by 11%,whereas the average thalweg migration distance and intensity at the reach scale decreased by 14%and 43%,respectively.During this sustained scouring period,the fluvial erosion intensity at the reach scale increased as the sediment discharge decreased.However,because the base level remained high,riverbed undercutting was deeply limited,which exacerbated lateral erosion of the bank and floodplain,enhancing thalweg migration.Flow-sediment regulation and training can be coupled to increase undercutting efficiency in the main channel and to protect banks from lateral erosion in river reach management.展开更多
The warming and thawing of permafrost are the primary factors that impact the stability of embankments in cold regions.However,due to uncertainties in thermal boundaries and soil properties,the stochastic modeling of ...The warming and thawing of permafrost are the primary factors that impact the stability of embankments in cold regions.However,due to uncertainties in thermal boundaries and soil properties,the stochastic modeling of thermal regimes is challenging and computationally expensive.To address this,we propose a knowledge-integrated deep learning method for predicting the stochastic thermal regime of embankments in permafrost regions.Geotechnical knowledge is embedded in the training data through numerical modeling,while the neural network learns the mapping from the thermal boundary and soil property fields to the temperature field.The effectiveness of our method is verified in comparison with monitoring data and numerical analysis results.Experimental results show that the proposed method achieves good accuracy with small coefficient of variation.It still provides satisfactory accuracy as the coefficient of variation increases.The proposed knowledge-integrated deep learning method provides an efficient approach to predict the stochastic thermal regime of heterogeneous embankments.It can also be used in other permafrost engineering investigations that require stochastic numerical modeling.展开更多
Semiconductor electronic devices are prone to charge accumulation during production and transportation,which usually causes device breakdown.Ionizers are widely used for electrostatic elimination,and utilizing semicon...Semiconductor electronic devices are prone to charge accumulation during production and transportation,which usually causes device breakdown.Ionizers are widely used for electrostatic elimination,and utilizing semiconductor silicon for the discharge needle material in ionizers can effectively prevent metal contamination.To investigate the discharge characteristics of silicon needles and their mode modulation mechanism,this study has established an experimental platform for silicon needle-plate discharge under positive polarity voltage.Discharge pulse parameters and optical signals were measured at varying electrode spacings.The experimental results reveal that silicon needle discharge progresses through four regimes:the spontaneous streamer,the periodic streamer,the cluster streamer,and the glow discharge.Among these,the pulse amplitude is most uniform and stable in the periodic streamer regime.In addition,shorter-gap discharge exhibits higher pulse amplitude and repetition frequency but is easier to transition into the filament regime.The formation process of a single pulse is closely related to the field strength in the ionization region near the needle tip.Hence,parameters such as the pulse rising edge time and falling edge time show minimal variation with voltage.The amount of charge generated per unit time is primarily influenced by the repetition frequency.Consequently,the electrostatic ionizer produces the highest,most stable,and most uniform charges if it operates in the periodic streamer regime.展开更多
This study explores the initiation mechanisms of convective wind events,emphasizing their variability across different atmospheric circulation patterns.Historically,the inadequate feature categorization within multi-f...This study explores the initiation mechanisms of convective wind events,emphasizing their variability across different atmospheric circulation patterns.Historically,the inadequate feature categorization within multi-faceted forecast models has led to suboptimal forecast efficacy,particularly for events in dynamically weak forcing conditions during the warm season.To improve the prediction accuracy of convective wind events,this research introduces a novel approach that combines machine learning techniques to identify varying meteorological flow regimes.Convective winds(CWs)are defined as wind speeds reaching or exceeding 17.2 m s^(-1)and severe convective winds(SCWs)as speeds surpassing 24.5 m s^(-1).This study examines the spatial and temporal distribution of CW and SCW events from 2013 to 2021 and their circulation dynamics associated with three primary flow regimes:cold air advection,warm air advection,and quasibarotropic conditions.Key circulation features are used as input variables to construct an effective weather system pattern recognition model.This model employs an Adaptive Boosting(AdaBoost)algorithm combined with Random Under-Sampling(RUS)to address the class imbalance issue,achieving a recognition accuracy of 90.9%.Furthermore,utilizing factor analysis and Support Vector Machine(SVM)techniques,three specialized and independent probabilistic prediction models are developed based on the variance in predictor distributions across different flow regimes.By integrating the type of identification model with these prediction models,an enhanced comprehensive model is constructed.This advanced model autonomously identifies flow types and accordingly selects the most appropriate prediction model.Over a three-year validation period,this improved model outperformed the initially unclassified model in terms of prediction accuracy.Notably,for CWs and SCWs,the maximum Peirce Skill Score(PSS)increased from 0.530 and 0.702 to 0.628 and 0.726,respectively,and the corresponding maximum Threat Score(TS)improved from 0.087 and 0.024 to 0.120 and 0.026.These improvements were significant across all samples,with the cold air advection type showing the greatest enhancement due to the significant spatial variability of each factor.Additionally,the model improved forecast precision by prioritizing thermal factors,which played a key role in modulating false alarm rates in warm air advection and quasi-barotropic flow regimes.The results confirm the critical contribution of circulation feature recognition and segmented modeling to enhancing the adaptability and predictive accuracy of weather forecast models.展开更多
This study explores the combination of ultrasound technology with a detection algorithm to categorize flow regimes in bubble columns used for aeration in aquaculture.An ultrasonic velocity profiler is used to obtain t...This study explores the combination of ultrasound technology with a detection algorithm to categorize flow regimes in bubble columns used for aeration in aquaculture.An ultrasonic velocity profiler is used to obtain the standard deviation of the bubble velocity distributed throughout the column.The bubble velocity data for three known flow regimes were used to develop a probability density function(PDF)classification model.The experimental apparatus consisted of a circular tank equipped with a bubble generator and gas hold-up monitoring systems.The flow regimes of the experimental fluid were determined,and the classification was conducted via the PDF method.The results demonstrate that the classification accuracy is not lower than that of traditional machine learning methods.展开更多
The evolution of fretting wear behavior of zirconium alloy cladding tubes mated with dimples under the gross slip regime(GSR)was investigated.The findings revealed that the primary wear mechanisms under GSR were delam...The evolution of fretting wear behavior of zirconium alloy cladding tubes mated with dimples under the gross slip regime(GSR)was investigated.The findings revealed that the primary wear mechanisms under GSR were delamination,surface fatigue wear and abrasive wear,and the fretting damage rate mainly depends on delamination.The cross-sectional microstructure of the worn area could be divided into the third-body layer,tribologically transformed structure layer,and general deformation layer,with their formation mechanisms analyzed.Furthermore,the mechanism of wear-induced grain refinement was identified as dynamic recrystallization(DRX),including both continuous DRX and discontinuous DRX.Additionally,the processes of fretting wear and DRX were discussed.展开更多
Runoff observation uncertainty is a key unsolved issue in the hydrology community.Existing studies mainly focused on observation uncertainty sources and their impacts on simulation performance,but the impacts on chang...Runoff observation uncertainty is a key unsolved issue in the hydrology community.Existing studies mainly focused on observation uncertainty sources and their impacts on simulation performance,but the impacts on changes of flow regime characteristics remained rare.This study detects temporal changes in 16 flow regime metrics from five main components(i.e.,magnitude,frequency of events,variability,duration,and timing),and evaluates the effects of observation uncertainty on trends of flow regime metrics by adopting a normal distribution error model and using uncertainty width,significant change rate of slopes,coefficient of variation,and degree of deviation.The daily runoff series from 1971 to 2020 at five hydrological stations(i.e.,Huangheyan,Tangnaihai,and Lanzhou in the Yellow River Source Region,Xianyang in the Weihe River Catchment,and Heishiguan in the Yiluo River Catchment)in the water conservation zone of Yellow River are collected for our study.Results showed that:(1)Flow regimes showed significant increases in the low flow magnitude,and significant decreases in the high and average flow magnitude,variability and duration at all the five stations.The magnitude,variability and duration metrics decreased significantly,and the frequency metrics increased significantly at Heishiguan.The low flow magnitude and timing metrics increased significantly,while the high flow magnitude,frequency and variability metrics decreased significantly at Xianyang.The low flow magnitude and high flow timing metrics increased significantly,while the low flow frequency,high flow magnitude and variability metrics decreased significantly in the Yellow River Source Region.(2)Observation uncertainty remarkably impacted the changes of 28.75% of total flow regime metrics at all the stations.The trends of 11.25% of total metrics changed from significance to insignificance,while those of 17.5% of total metrics changed from insignificance to significance.For the rest metrics,the trends remained the same,i.e.,significant(18.75%)and insignificant(52.50%)trends.(3)Observation uncertainty had the greatest impacts on the frequency metrics,especially at Xianyang,followed by duration,variability,timing and magnitude metrics.展开更多
This study examines the nonlinear behaviors of a clamped-clamped porous pipe made of a functionally graded material(FGM)that conveys fluids and is equipped with a retaining clip,focusing on primary resonance and subcr...This study examines the nonlinear behaviors of a clamped-clamped porous pipe made of a functionally graded material(FGM)that conveys fluids and is equipped with a retaining clip,focusing on primary resonance and subcritical dynamics.The nonlinear governing equations for the FGM pipe are derived by the extended Hamilton's principle,and subsequently discretized through the application of the Galerkin method.The direct method of multi-scales is then used to solve the derived equations.A thorough analysis of various parameters,including the clip stiffness,the power-law index,the porosity,and the clip location,is conducted to gain a comprehensive understanding of the system's nonlinear dynamics.Through the analysis of the first natural frequency,the study highlights the influence of the flow velocity and the clip stiffness,while the comparisons with metallic pipes emphasize the role of FGM composition.The examination of the forced response curves reveals saddle-node bifurcations and their dependence on parameters such as the detuning parameter and the power-law index,offering valuable insights into the system's nonlinear resonant behavior.Furthermore,the frequency-response curves illustrate the hardening nonlinearities influenced by factors such as the porosity and the clip stiffness,revealing nuanced effects on the system response and resonance characteristics.This comprehensive analysis enhances the understanding of nonlinear behaviors in FGM porous pipes with a retaining clip,providing key insights for practical engineering applications in system design and optimization.展开更多
Background As an indigenous livestock species on the Tibetan Plateau,Tibetan sheep exhibit remarkable adaptability to low temperatures and nutrient-scarce environments.During the cold season,Tibetan sheep are typicall...Background As an indigenous livestock species on the Tibetan Plateau,Tibetan sheep exhibit remarkable adaptability to low temperatures and nutrient-scarce environments.During the cold season,Tibetan sheep are typically managed under two feeding regimes:barn feeding(BF)and traditional grazing(TG).However,the molecular mechanisms underlying their adaptation to these distinct management strategies remain unclear.This study aimed to investigate the adaptive strategies of rumen function in Tibetan sheep to cold-season feeding regimes by integrating analyses of rumen morphology,microbiome,metabolome,and transcriptome.Twelve healthy Tibetan sheep with similar body weights were assigned into two groups(BF vs.TG).At the end of the experiment,rumen tissues were subjected to histological observation.Multi-omics techniques were employed to evaluate the effects of cold-season feeding regimes on rumen function in Tibetan sheep.Results The ruminal papilla height,width,and muscular thickness were significantly higher in BF group.The relative abundances of Actinobacteria and Succiniclasticum were significantly elevated in the rumen of BF group,whereas Rikenellaceae,Gracilibacteria,and Lachnospiraceae showed higher abundances in the TG group.Metabolomic analysis identified 19 differential metabolites between the two groups,including upregulated compounds in BF group(fumaric acid,maltose,L-phenylalanine,and L-alanine)and TG group(e.g.,phenylacetic acid,salicyluric acid and ferulic acid).These metabolites were predominantly enriched in phenylalanine metabolism,alanine,aspartate and glutamate metabolism,and phenylalanine,tyrosine and tryptophan biosynthesis pathways.Additionally,210 differentially expressed genes(DEGs)were identified in rumen epithelium:100 upregulated DEGs in the BF group were enriched in nutrient metabolism-related pathways(e.g.,fatty acid degradation and PPAR signaling pathway),while 110 upregulated DEGs in the TG group were associated with immune-related pathways(e.g.,p53 signaling pathway and glutathione metabolism).Conclusions Among these,we observed distinct rumen functional responses to different cold-season feeding regimes in Tibetan sheep and revealed energy allocation strategies mediated by host-microbe interactions.In the BF group,Tibetan sheep adopted a"metabolic efficiency-priority"strategy,driving rumen microbiota to maximize energy capture from high-nutrient diets to support host growth.In contrast,the TG group exhibited an"environmental adaptation-priority"strategy,where rumen microbiota prioritized cellulose degradation and anti-inflammatory functions,reallocating energy toward homeostasis maintenance at the expense of rumen development and growth performance.展开更多
[Objective] To clarify the effects of different straw retention regimes on soil fertility in double cropping paddy field. [Method] The effects of different straw reten- tion regimes on total organic carbon （CToc）, a...[Objective] To clarify the effects of different straw retention regimes on soil fertility in double cropping paddy field. [Method] The effects of different straw reten- tion regimes on total organic carbon （CToc）, active carbon （CA） and mineralized carbon （CM） were analyzed, and carbon pool active （A）, carbon pool active index （A/）, carbon pool index （CPI） and carbon pool management index （CPMi） for each treat- ment were calculated. [Result] Compared with the unfertilized treatment （CK）, CToc, CA, CM and the available ratio of soil carbon were increased in the treatment of re- turning early season and late season rice straws to field. With the same nutrient application, CToc, CA and the available ratio of soil carbon in the field with straw re- turned to field were higher than that of straw incineration and no straw returning, and the change in soil CA content was more significant. The difference in CPMI be- tween different treatments reached significant or very significant level, and the value was in the order of straw directly returned to field 〉 straw returned to field after in- cineration 〉 no straw returned to field. [Conclusion] This study provided theoretical bases for the increase of soil CA content and soil fertility in double rice fields.展开更多
[Objective] The aim was to find a suitable weaning regime, including weaning period and weaning feed, for Angui//a mormorata glass eels. [Method] A weaning processing experiment was conducted indoor in fiberglass tank...[Objective] The aim was to find a suitable weaning regime, including weaning period and weaning feed, for Angui//a mormorata glass eels. [Method] A weaning processing experiment was conducted indoor in fiberglass tanks, two kinds of artificial feeds （eel grower powder feed and eel grower piece feed） were selected as weaning diets against a control group fed on natural food （minced octopus flesh）, two weaning periods, 5 and 15 d, were introduced in weaning experiment. [Result] The growth rate and survival rate of the groups with 15-day＇s weaning period were higher than that of the groups with 5-day＇s weaning period, revealing that a 20% increase every 3 d from 0% to 100% in the proportion of grower paste in the minced octopus flesh during weaning is suitable for A. mormorata glass eels. [Conclusion] A. mormorata glass eels can be weaned from natural food to the commer- cially available eel grower feeds over a certain weaning period, and of the artificial feeds with same ingredients and nutrient, A. mormorata glass eels accepted powder feed more readily over 28 d than piece feed.展开更多
Purpose-This paper provides a comprehensive analysis of the Brazilian freight railway system,examining the efficacy of the current concession renewal model in light of persistent structural problems such as market con...Purpose-This paper provides a comprehensive analysis of the Brazilian freight railway system,examining the efficacy of the current concession renewal model in light of persistent structural problems such as market concentration,cargo dependence on export commodities and underutilization of the network.Situating Brazil within the broader international debate on railway reforms,the paper evaluates whether the ongoing early renewal of concessions can deliver a more diversified and competitive freight system.Design/methodology/approach-The study adopts a sequential mixed-methods research design that integrates longitudinal quantitative analysis with qualitative institutional and policy evaluation.The quantitative component examines time-series indicators published by ANTT,DNIT and INFRA S.A.from 1999 to 2023 to identify structural patterns in traffic growth,investment,safety and market concentration.The qualitative component employs a process-tracing logic to reconstruct the evolution of concession renewals and the implementation of Railway Law 14.273/2021,drawing on concepts from regulatory economics,institutional theory and industrial organization.These empirical streams are synthesized through an analytical framework that connects three dimensions-regulatory design,market structure and system performance-allowing for a systematic assessment of how Brazil’s institutional configuration shapes incentives,competitive dynamics and network utilization.Findings-The analysis confirms that the early renewal of concessions has successfully secured substantial private investment for capacity expansion on existing trunk lines.However,it has perpetuated the vertically integrated model,reinforcing the market power of incumbent operators and failing to significantly promote intramodal competition or cargo diversification.The system remains dominated by iron ore and agricultural commodities,with general cargo representing a minuscule share.The new authorization regime and short-line railway policies present a viable pathway for market opening but face significant operational and institutional barriers to implementation.Originality/value-This research offers a timely and critical assessment of a pivotal moment in Brazilian railway policy.It moves beyond a simplistic evaluation of volume growth to a structural analysis of market failures and the interplay between concession renewal and regulatory innovation.The findings provide actionable insights for policymakers in Brazil and other emerging economies seeking to balance private investment with public interest goals in railway infrastructure,highlighting the necessity of complementary,pro-competitive measures alongside financial investment.展开更多
Accurate prediction of flood events is important for flood control and risk management.Machine learning techniques contributed greatly to advances in flood predictions,and existing studies mainly focused on predicting...Accurate prediction of flood events is important for flood control and risk management.Machine learning techniques contributed greatly to advances in flood predictions,and existing studies mainly focused on predicting flood resource variables using single or hybrid machine learning techniques.However,class-based flood predictions have rarely been investigated,which can aid in quickly diagnosing comprehensive flood characteristics and proposing targeted management strategies.This study proposed a prediction approach of flood regime metrics and event classes coupling machine learning algorithms with clustering-deduced membership degrees.Five algorithms were adopted for this exploration.Results showed that the class membership degrees accurately determined event classes with class hit rates up to 100%,compared with the four classes clustered from nine regime metrics.The nonlinear algorithms(Multiple Linear Regression,Random Forest,and least squares-Support Vector Machine)outperformed the linear techniques(Multiple Linear Regression and Stepwise Regression)in predicting flood regime metrics.The proposed approach well predicted flood event classes with average class hit rates of 66.0%-85.4%and 47.2%-76.0%in calibration and validation periods,respectively,particularly for the slow and late flood events.The predictive capability of the proposed prediction approach for flood regime metrics and classes was considerably stronger than that of hydrological modeling approach.展开更多
Many complex systems are frequently subject to the influence of uncertain disturbances,which can exert a profound effect on the critical transitions(CTs),potentially resulting in catastrophic consequences.Consequently...Many complex systems are frequently subject to the influence of uncertain disturbances,which can exert a profound effect on the critical transitions(CTs),potentially resulting in catastrophic consequences.Consequently,it is of uttermost importance to provide warnings for noise-induced CTs in various applications.Although capturing certain generic symptoms of transition behaviors from observational and simulated data poses a challenging problem,this work attempts to extract information regarding CTs from simulated data of a Gaussian white noise-induced tri-stable system.Using the extended dynamic mode decomposition(EDMD)algorithm,we initially obtain finite-dimensional approximations of both the stochastic Koopman operator and the generator.Subsequently,the drift parameters and the noise intensity within the system are identified from the simulated data.Utilizing the identified system,the parameter-dependent basin of the unsafe regime(PDBUR)is quantified,enabling data-driven early warning of Gaussian white noise-induced CTs.Finally,an error analysis is carried out to verify the effectiveness of the data-driven results.Our findings may serve as a paradigm for understanding and predicting noise-induced CTs in complex systems based on data.展开更多
This study investigates the influence of different curing regimes on the microstructure and macro properties of ultra-high performance fiber reinforced cementitious composite （UHPFRCC）, and aims to discover whether ...This study investigates the influence of different curing regimes on the microstructure and macro properties of ultra-high performance fiber reinforced cementitious composite （UHPFRCC）, and aims to discover whether it is possible to produce qualified UHPFRCC using different curing regimes. A control mix of UHPFRCC is prepared. The mechanical performance and the short-term durability of the UHPFRCC matrix under three curing regimes are studied. In addition, the microstructures of the UHPFRCC matrix with different curing conditions are analyzed by combining scanning electron microscopy （SEM） and mercury intrusion porosimetry （MIP）. The results explore how different UHPFRCC curing regimes affect its microstructure and how the microstructure affects its macro behavior. Heat and steam curing for 3 d is succeeded to produce the UHPFRCC with nearly the same mechanical properties and durability as those of the 90 d standard curing. However, the heat cured UHPFRCC does not show great resistance to chloride-ion penetration.展开更多
Sequential extraction procedure was applied to assess the dynamics of solid-phase transformation of added Cu, Pb, Cd, and Hg in a typical Chinese paddy soil incubated under three moisture regimes （75% field capacity,...Sequential extraction procedure was applied to assess the dynamics of solid-phase transformation of added Cu, Pb, Cd, and Hg in a typical Chinese paddy soil incubated under three moisture regimes （75% field capacity, wetting-drying cycle, and flooding）. The heavy metals spiked in the soil were time-dependently transferred from the easily extractable fraction （the exchangeable fraction） into less labile fractions （Fe-Mn oxide- and organic matter-bound fractions）, and thus reduced lability of the metals. No significant changes were found for the carbonate-bound and residual fractions of the heavy metals in the soil during the whole incubation. Change rate of the mobility factor （MF）, a proportion of weakly bound fractions （exchangeable and carbonate-bound） in the total metal of soil, reflected the transformation rate of metal speciation from the labile fractions toward stable fractions. It was found that soil moisture regime did not change the direction and pathways of transformation of metal speciation, but it significantly affected the transformation rate. In general, the paddy soil under flooding regime had higher metal reactivity compared with 75% field capacity and wetting-drying cycle regimes, resulting in the more complete movement of metals toward stable fractions. This might be related to the increased pH, precipitation of the metals with sulfides and higher concentration of amorphous Fe oxides under submerged condition.展开更多
A synthesis is given in this paper on late Mesozoic deformation pattern in the zones around the Ordos Basin based on lithostratigraphic and structural analyses. A relative chronology of the late Mesozoic tectonic stre...A synthesis is given in this paper on late Mesozoic deformation pattern in the zones around the Ordos Basin based on lithostratigraphic and structural analyses. A relative chronology of the late Mesozoic tectonic stress evolution was established from the field analyses of fault kinematics and constrained by stratigraphic contact relationships. The results show alternation of tectonic compressional and extensional regimes. The Ordos Basin and its surroundings were in weak N-S to NNE-SSW extension during the Early to Middle Jurassic, which reactivated E-W-trending basement fractures. The tectonic regime changed to a multi-directional compressional one during the Late Jurassic, which resulted in crustal shortening deformation along the marginal zones of the Ordos Basin. Then it changed to an extensional one during the Early Cretaceous, which rifted the western, northwestern and southeastern margins of the Ordos Basin. A NW-SE compression occurred during the Late Cretaceous and caused the termination of sedimentation and uplift of the Ordos Basin. This phased evolution of the late Mesozoic tectonic stress regimes and associated deformation pattern around the Ordos Basin best records the changes in regional geodynamic settings in East Asia, from the Early to Middle Jurassic post-orogenic extension following the Triassic collision between the North and South China Blocks, to the Late Jurassic multi-directional compressions produced by synchronous convergence of the three plates （the Siberian Plate to the north, Paleo-Pacific Plate to the east and Lhasa Block to the west） towards the East Asian continent. Early Cretaceous extension might be the response to collapse and lithospheric thinning of the North China Craton.展开更多
A field experiment was conducted from 1999 to 2002 to compare and evaluate the effects of nutrient and water regimes on paddy soil quality by investigating soil chemical and microbiological parameters. Four nutrient r...A field experiment was conducted from 1999 to 2002 to compare and evaluate the effects of nutrient and water regimes on paddy soil quality by investigating soil chemical and microbiological parameters. Four nutrient regimes, a control, chemical fertilizers only (CF), chemical fertilizers with swine manure (SM), and chemical fertilizers with wheat straw (WS), and two soil moisture regimes, continuous waterlogging (CWL) and alternate wetting and drying (AWD), were investigated. With SM and WS total organic carbon and total nitrogen in the paddy soil were significantly higher (P < 0.05) than those with CF. A similar effect for organic amendments was observed in the soil light fraction organic C (LFOC), water-soluble carbohydrates (WSC), and water-soluble organic C (WSOC). CWL, in particular when swine manure was incorporated into the paddy soil, markedly decreased soil redox potential (Eh) and increased total active reducing substances (ARS). Meanwhile, as compared to CF, SM and WS significantly (P < 0.05) increased soil microbial biomass C (MBC) and mineralizable carbon, with differences in AWD being higher than CWL. In addition, SM and WS treatments significantly (P < 0.05) improved rice above-ground biomass and grain yield, with AWD being greater than CWL. Thus, for ecologically sustainable agricultural management of paddy soils, long-term waterlogging should be avoided when organic manure was incorporated into paddy soil.展开更多
Since the mid-late Eocene, North China has been subjected to extensional stress, resulting in the formation and development of basins. The dynamic origin of this crustal extension has long been an issue of debate. Thi...Since the mid-late Eocene, North China has been subjected to extensional stress, resulting in the formation and development of basins. The dynamic origin of this crustal extension has long been an issue of debate. This paper presents the results of kinematic analyses of faults obtained from two seperated areas in North China. In the Weihe graben situated on the southernmost margin of the Ordos block, analyses of fault kinematics were coupled with an analysis of the basin's subsidence history. Three successive extensional tectonic phases accompaning the basin's formation and development have been distinguished. The Palaeogene extension was oriented in a WNW-ESE direction; the Neogene extension in a NE-SW direction and the Pliocene-Quaternary extension in a NW-SE direction. Such changes have also been recorded by fault kinematics along the southern Tanlu fault zone. This has been demonstrated by three successive sets of fault striations indicating normal dip slip resulting from NW-SE extension, then left-lateral slip with a normal component resulting from NE-SW extension, and right-lateral slip with a minor normal component, respectively. The kinematic history of faults and their chronological evolution indicate changes in continental dynamics acting in North China over Cenozoic time.展开更多
基金We appreciate the financial support of this work by Gorgan University of Agricultural Sciences and Natural Resources from Golestan Province(Grant No.9413184180).
文摘Drought,as the most catastrophic abiotic stress,poses a significant threat to the growth and development of plants.Among the mechanisms employed by plants to cope with drought-induced stress,abscisic acid(ABA)which is the sesquiterpene hormone,occupies a pivotal role.A hypothesis has emerged that the exogenous application of ABA can positively influence the terpenoid content of Lavandula angustifolia cv Hidcote essential oil(EO),thereby conferring enhanced resilience to drought stress.A randomized complete block design experiment was conducted with three replicationsandfour irrigation regimes,including I4[30%-40%of field capacity(FC)],I3(50%-60%FC),I2(70%-80%FC),andI1(90%-100%FC)as control.Application of ABAspraying included three concentrations,A3(30μmol·L^(-1)ABA),A2(15μmol·L^(-1)ABA),and A1 as control(distilled water).Results revealed that drought significantly affected all studied traits except for relative water content(RWC)and shoot dry mass.The ABA impact application on the observed traits was found to be dependent upon the level of drought to which the plants were exposed.Specifically,the highest levels of flavonoid content,total antioxidant activity,peroxidase(POX)activity,and EO percentage were observed under I4A2 conditions.Conversely,the highest levels of superoxide dismutase(SOD)and catalase(CAT)activity,and proline were recorded under I4A3 conditions,while the highest EO yield was obtained under I3A2 conditions.Analysis of the EO revealed that there were common indicative compounds across the varying levels of droughtandABAapplication,including linalool,camphor,borneol,bornyl formate,andcaryophyllene oxide.Theproduction pattern ofmonoterpene and sesquiterpene compounds demonstrated a distinct trend,with the highest concentration of monoterpene hydrocarbon compounds(average of 12.92%)being observed in the I2A3 treatment group,andthe highest concentration of oxygenatedmonoterpenecompounds(average of 64.76%)being recorded in the I1A1 group.Conversely,the most significant levels of sesquiterpene hydrocarboncompounds(14.98%)andoxygenated sesquiterpene compounds(10.46%)were observed in the I4A3 and I4A1 groups,respectively,showing the efficacy of monoterpenes and sesquiterpenes from the action of ABA under drought conditions.The observed results indicated that the concentration of oxygenated monoterpene compounds decreases with an increase in drought level.Conversely,the application of ABA at any given drought level appears to resulted in increased concentrations of oxygenated monoterpene compounds in the same conditions.It may be concluded that plants under high-stress drought conditions allocate more terpene precursors to the production of sesquiterpene hydrocarbon compounds,aided by ABA with the same properties.
基金National Key R&D Program of China,No.2023YFC3206205National Natural Science Foundation of China,No.U22A20237Independent Research Project of Yellow River Engineering Consulting Co.,Ltd.,No.2025KY001。
文摘Collaborative changes in the hydro-sediment regime and erosional base level are vital factors that influence the evolution of wandering rivers.In the wandering Xiaobeiganliu reach of the Middle Yellow River(MYR),the rapidly decreasing sediment discharge and lowering base level,i.e.,the Tongguan elevation,have resulted in new features of thalweg migration in river morphology.In this work,on the basis of topographic measurements of the reach from 2003–2021,the thalweg migration distance and intensity were calculated at both the section scale and reach scale.The results revealed that the annual sediment discharge decreased by 72%from 1986–2002,and the reach exhibited sustained scouring from deposition,leading to the Tongguan elevation decreasing by 1.69 m compared with that in 2002.Accordingly,the distance and intensity of thalweg migration have been reduced to varying degrees in both section and reach scales.The maximum section-scale thalweg migration distance was reduced by 11%,whereas the average thalweg migration distance and intensity at the reach scale decreased by 14%and 43%,respectively.During this sustained scouring period,the fluvial erosion intensity at the reach scale increased as the sediment discharge decreased.However,because the base level remained high,riverbed undercutting was deeply limited,which exacerbated lateral erosion of the bank and floodplain,enhancing thalweg migration.Flow-sediment regulation and training can be coupled to increase undercutting efficiency in the main channel and to protect banks from lateral erosion in river reach management.
基金funding support from the National Natural Science Foundation of China(Grant Nos.42277161,42230709).
文摘The warming and thawing of permafrost are the primary factors that impact the stability of embankments in cold regions.However,due to uncertainties in thermal boundaries and soil properties,the stochastic modeling of thermal regimes is challenging and computationally expensive.To address this,we propose a knowledge-integrated deep learning method for predicting the stochastic thermal regime of embankments in permafrost regions.Geotechnical knowledge is embedded in the training data through numerical modeling,while the neural network learns the mapping from the thermal boundary and soil property fields to the temperature field.The effectiveness of our method is verified in comparison with monitoring data and numerical analysis results.Experimental results show that the proposed method achieves good accuracy with small coefficient of variation.It still provides satisfactory accuracy as the coefficient of variation increases.The proposed knowledge-integrated deep learning method provides an efficient approach to predict the stochastic thermal regime of heterogeneous embankments.It can also be used in other permafrost engineering investigations that require stochastic numerical modeling.
基金financially supported by Wuxi Yanping Electronic Technology Co.Ltd.
文摘Semiconductor electronic devices are prone to charge accumulation during production and transportation,which usually causes device breakdown.Ionizers are widely used for electrostatic elimination,and utilizing semiconductor silicon for the discharge needle material in ionizers can effectively prevent metal contamination.To investigate the discharge characteristics of silicon needles and their mode modulation mechanism,this study has established an experimental platform for silicon needle-plate discharge under positive polarity voltage.Discharge pulse parameters and optical signals were measured at varying electrode spacings.The experimental results reveal that silicon needle discharge progresses through four regimes:the spontaneous streamer,the periodic streamer,the cluster streamer,and the glow discharge.Among these,the pulse amplitude is most uniform and stable in the periodic streamer regime.In addition,shorter-gap discharge exhibits higher pulse amplitude and repetition frequency but is easier to transition into the filament regime.The formation process of a single pulse is closely related to the field strength in the ionization region near the needle tip.Hence,parameters such as the pulse rising edge time and falling edge time show minimal variation with voltage.The amount of charge generated per unit time is primarily influenced by the repetition frequency.Consequently,the electrostatic ionizer produces the highest,most stable,and most uniform charges if it operates in the periodic streamer regime.
基金Guangdong S&T Program(2024A1111120024)CMA Innovation and Development Fund(CXFZ2024J014)+3 种基金CMA Youth Innovation Team(CMA2024QN01)PRB Meteorological Open Research Fund(ZJLY202425-GD02)GBA Meteorological S&T Program(GHMA2024Y04)Guangzhou Meteorological Research Project(Z202401)。
文摘This study explores the initiation mechanisms of convective wind events,emphasizing their variability across different atmospheric circulation patterns.Historically,the inadequate feature categorization within multi-faceted forecast models has led to suboptimal forecast efficacy,particularly for events in dynamically weak forcing conditions during the warm season.To improve the prediction accuracy of convective wind events,this research introduces a novel approach that combines machine learning techniques to identify varying meteorological flow regimes.Convective winds(CWs)are defined as wind speeds reaching or exceeding 17.2 m s^(-1)and severe convective winds(SCWs)as speeds surpassing 24.5 m s^(-1).This study examines the spatial and temporal distribution of CW and SCW events from 2013 to 2021 and their circulation dynamics associated with three primary flow regimes:cold air advection,warm air advection,and quasibarotropic conditions.Key circulation features are used as input variables to construct an effective weather system pattern recognition model.This model employs an Adaptive Boosting(AdaBoost)algorithm combined with Random Under-Sampling(RUS)to address the class imbalance issue,achieving a recognition accuracy of 90.9%.Furthermore,utilizing factor analysis and Support Vector Machine(SVM)techniques,three specialized and independent probabilistic prediction models are developed based on the variance in predictor distributions across different flow regimes.By integrating the type of identification model with these prediction models,an enhanced comprehensive model is constructed.This advanced model autonomously identifies flow types and accordingly selects the most appropriate prediction model.Over a three-year validation period,this improved model outperformed the initially unclassified model in terms of prediction accuracy.Notably,for CWs and SCWs,the maximum Peirce Skill Score(PSS)increased from 0.530 and 0.702 to 0.628 and 0.726,respectively,and the corresponding maximum Threat Score(TS)improved from 0.087 and 0.024 to 0.120 and 0.026.These improvements were significant across all samples,with the cold air advection type showing the greatest enhancement due to the significant spatial variability of each factor.Additionally,the model improved forecast precision by prioritizing thermal factors,which played a key role in modulating false alarm rates in warm air advection and quasi-barotropic flow regimes.The results confirm the critical contribution of circulation feature recognition and segmented modeling to enhancing the adaptability and predictive accuracy of weather forecast models.
基金supported by the Center of Excellence on Instru-mentation Technology and Automation(CEITA),Department of Instru-mentation and Electronics Engineering,Faculty of Engineering,King Mongkut’s University of Technology North Bangkok,Thailand。
文摘This study explores the combination of ultrasound technology with a detection algorithm to categorize flow regimes in bubble columns used for aeration in aquaculture.An ultrasonic velocity profiler is used to obtain the standard deviation of the bubble velocity distributed throughout the column.The bubble velocity data for three known flow regimes were used to develop a probability density function(PDF)classification model.The experimental apparatus consisted of a circular tank equipped with a bubble generator and gas hold-up monitoring systems.The flow regimes of the experimental fluid were determined,and the classification was conducted via the PDF method.The results demonstrate that the classification accuracy is not lower than that of traditional machine learning methods.
基金supported by the National Natural Science Foundation of China(No.52105221)the Postdoctoral Fellowship Program(Grade C)of China Postdoctoral Science Foundation(No.GZC20232749)+1 种基金the Youth Innovation Promotion Assessment CAS(No.2022187)the IMR Innovation Fund(No.2024-PY13).
文摘The evolution of fretting wear behavior of zirconium alloy cladding tubes mated with dimples under the gross slip regime(GSR)was investigated.The findings revealed that the primary wear mechanisms under GSR were delamination,surface fatigue wear and abrasive wear,and the fretting damage rate mainly depends on delamination.The cross-sectional microstructure of the worn area could be divided into the third-body layer,tribologically transformed structure layer,and general deformation layer,with their formation mechanisms analyzed.Furthermore,the mechanism of wear-induced grain refinement was identified as dynamic recrystallization(DRX),including both continuous DRX and discontinuous DRX.Additionally,the processes of fretting wear and DRX were discussed.
基金National Key Research and Development Program of China,No.2021YFC3201102National Natural Science Foundation of China,No.42071041,No.42171047。
文摘Runoff observation uncertainty is a key unsolved issue in the hydrology community.Existing studies mainly focused on observation uncertainty sources and their impacts on simulation performance,but the impacts on changes of flow regime characteristics remained rare.This study detects temporal changes in 16 flow regime metrics from five main components(i.e.,magnitude,frequency of events,variability,duration,and timing),and evaluates the effects of observation uncertainty on trends of flow regime metrics by adopting a normal distribution error model and using uncertainty width,significant change rate of slopes,coefficient of variation,and degree of deviation.The daily runoff series from 1971 to 2020 at five hydrological stations(i.e.,Huangheyan,Tangnaihai,and Lanzhou in the Yellow River Source Region,Xianyang in the Weihe River Catchment,and Heishiguan in the Yiluo River Catchment)in the water conservation zone of Yellow River are collected for our study.Results showed that:(1)Flow regimes showed significant increases in the low flow magnitude,and significant decreases in the high and average flow magnitude,variability and duration at all the five stations.The magnitude,variability and duration metrics decreased significantly,and the frequency metrics increased significantly at Heishiguan.The low flow magnitude and timing metrics increased significantly,while the high flow magnitude,frequency and variability metrics decreased significantly at Xianyang.The low flow magnitude and high flow timing metrics increased significantly,while the low flow frequency,high flow magnitude and variability metrics decreased significantly in the Yellow River Source Region.(2)Observation uncertainty remarkably impacted the changes of 28.75% of total flow regime metrics at all the stations.The trends of 11.25% of total metrics changed from significance to insignificance,while those of 17.5% of total metrics changed from insignificance to significance.For the rest metrics,the trends remained the same,i.e.,significant(18.75%)and insignificant(52.50%)trends.(3)Observation uncertainty had the greatest impacts on the frequency metrics,especially at Xianyang,followed by duration,variability,timing and magnitude metrics.
文摘This study examines the nonlinear behaviors of a clamped-clamped porous pipe made of a functionally graded material(FGM)that conveys fluids and is equipped with a retaining clip,focusing on primary resonance and subcritical dynamics.The nonlinear governing equations for the FGM pipe are derived by the extended Hamilton's principle,and subsequently discretized through the application of the Galerkin method.The direct method of multi-scales is then used to solve the derived equations.A thorough analysis of various parameters,including the clip stiffness,the power-law index,the porosity,and the clip location,is conducted to gain a comprehensive understanding of the system's nonlinear dynamics.Through the analysis of the first natural frequency,the study highlights the influence of the flow velocity and the clip stiffness,while the comparisons with metallic pipes emphasize the role of FGM composition.The examination of the forced response curves reveals saddle-node bifurcations and their dependence on parameters such as the detuning parameter and the power-law index,offering valuable insights into the system's nonlinear resonant behavior.Furthermore,the frequency-response curves illustrate the hardening nonlinearities influenced by factors such as the porosity and the clip stiffness,revealing nuanced effects on the system response and resonance characteristics.This comprehensive analysis enhances the understanding of nonlinear behaviors in FGM porous pipes with a retaining clip,providing key insights for practical engineering applications in system design and optimization.
基金funded by the Chief Scientist Program of Qinghai Province(2024-SF-102)the Joint Special Project of Sanjiangyuan National Park(LHZX-2023-02).
文摘Background As an indigenous livestock species on the Tibetan Plateau,Tibetan sheep exhibit remarkable adaptability to low temperatures and nutrient-scarce environments.During the cold season,Tibetan sheep are typically managed under two feeding regimes:barn feeding(BF)and traditional grazing(TG).However,the molecular mechanisms underlying their adaptation to these distinct management strategies remain unclear.This study aimed to investigate the adaptive strategies of rumen function in Tibetan sheep to cold-season feeding regimes by integrating analyses of rumen morphology,microbiome,metabolome,and transcriptome.Twelve healthy Tibetan sheep with similar body weights were assigned into two groups(BF vs.TG).At the end of the experiment,rumen tissues were subjected to histological observation.Multi-omics techniques were employed to evaluate the effects of cold-season feeding regimes on rumen function in Tibetan sheep.Results The ruminal papilla height,width,and muscular thickness were significantly higher in BF group.The relative abundances of Actinobacteria and Succiniclasticum were significantly elevated in the rumen of BF group,whereas Rikenellaceae,Gracilibacteria,and Lachnospiraceae showed higher abundances in the TG group.Metabolomic analysis identified 19 differential metabolites between the two groups,including upregulated compounds in BF group(fumaric acid,maltose,L-phenylalanine,and L-alanine)and TG group(e.g.,phenylacetic acid,salicyluric acid and ferulic acid).These metabolites were predominantly enriched in phenylalanine metabolism,alanine,aspartate and glutamate metabolism,and phenylalanine,tyrosine and tryptophan biosynthesis pathways.Additionally,210 differentially expressed genes(DEGs)were identified in rumen epithelium:100 upregulated DEGs in the BF group were enriched in nutrient metabolism-related pathways(e.g.,fatty acid degradation and PPAR signaling pathway),while 110 upregulated DEGs in the TG group were associated with immune-related pathways(e.g.,p53 signaling pathway and glutathione metabolism).Conclusions Among these,we observed distinct rumen functional responses to different cold-season feeding regimes in Tibetan sheep and revealed energy allocation strategies mediated by host-microbe interactions.In the BF group,Tibetan sheep adopted a"metabolic efficiency-priority"strategy,driving rumen microbiota to maximize energy capture from high-nutrient diets to support host growth.In contrast,the TG group exhibited an"environmental adaptation-priority"strategy,where rumen microbiota prioritized cellulose degradation and anti-inflammatory functions,reallocating energy toward homeostasis maintenance at the expense of rumen development and growth performance.
基金Supported by the National Key Technology R&D Program during the Eleventh Five-year Plan Period,China(2006BAD02A04)the Key Technology R&D Program of Jiangxi Province,China(2009BNA03800)~~
文摘[Objective] To clarify the effects of different straw retention regimes on soil fertility in double cropping paddy field. [Method] The effects of different straw reten- tion regimes on total organic carbon （CToc）, active carbon （CA） and mineralized carbon （CM） were analyzed, and carbon pool active （A）, carbon pool active index （A/）, carbon pool index （CPI） and carbon pool management index （CPMi） for each treat- ment were calculated. [Result] Compared with the unfertilized treatment （CK）, CToc, CA, CM and the available ratio of soil carbon were increased in the treatment of re- turning early season and late season rice straws to field. With the same nutrient application, CToc, CA and the available ratio of soil carbon in the field with straw re- turned to field were higher than that of straw incineration and no straw returning, and the change in soil CA content was more significant. The difference in CPMI be- tween different treatments reached significant or very significant level, and the value was in the order of straw directly returned to field 〉 straw returned to field after in- cineration 〉 no straw returned to field. [Conclusion] This study provided theoretical bases for the increase of soil CA content and soil fertility in double rice fields.
基金Supported by Xiamen Marine Research and Development Institute [K10102(1)]~~
文摘[Objective] The aim was to find a suitable weaning regime, including weaning period and weaning feed, for Angui//a mormorata glass eels. [Method] A weaning processing experiment was conducted indoor in fiberglass tanks, two kinds of artificial feeds （eel grower powder feed and eel grower piece feed） were selected as weaning diets against a control group fed on natural food （minced octopus flesh）, two weaning periods, 5 and 15 d, were introduced in weaning experiment. [Result] The growth rate and survival rate of the groups with 15-day＇s weaning period were higher than that of the groups with 5-day＇s weaning period, revealing that a 20% increase every 3 d from 0% to 100% in the proportion of grower paste in the minced octopus flesh during weaning is suitable for A. mormorata glass eels. [Conclusion] A. mormorata glass eels can be weaned from natural food to the commer- cially available eel grower feeds over a certain weaning period, and of the artificial feeds with same ingredients and nutrient, A. mormorata glass eels accepted powder feed more readily over 28 d than piece feed.
文摘Purpose-This paper provides a comprehensive analysis of the Brazilian freight railway system,examining the efficacy of the current concession renewal model in light of persistent structural problems such as market concentration,cargo dependence on export commodities and underutilization of the network.Situating Brazil within the broader international debate on railway reforms,the paper evaluates whether the ongoing early renewal of concessions can deliver a more diversified and competitive freight system.Design/methodology/approach-The study adopts a sequential mixed-methods research design that integrates longitudinal quantitative analysis with qualitative institutional and policy evaluation.The quantitative component examines time-series indicators published by ANTT,DNIT and INFRA S.A.from 1999 to 2023 to identify structural patterns in traffic growth,investment,safety and market concentration.The qualitative component employs a process-tracing logic to reconstruct the evolution of concession renewals and the implementation of Railway Law 14.273/2021,drawing on concepts from regulatory economics,institutional theory and industrial organization.These empirical streams are synthesized through an analytical framework that connects three dimensions-regulatory design,market structure and system performance-allowing for a systematic assessment of how Brazil’s institutional configuration shapes incentives,competitive dynamics and network utilization.Findings-The analysis confirms that the early renewal of concessions has successfully secured substantial private investment for capacity expansion on existing trunk lines.However,it has perpetuated the vertically integrated model,reinforcing the market power of incumbent operators and failing to significantly promote intramodal competition or cargo diversification.The system remains dominated by iron ore and agricultural commodities,with general cargo representing a minuscule share.The new authorization regime and short-line railway policies present a viable pathway for market opening but face significant operational and institutional barriers to implementation.Originality/value-This research offers a timely and critical assessment of a pivotal moment in Brazilian railway policy.It moves beyond a simplistic evaluation of volume growth to a structural analysis of market failures and the interplay between concession renewal and regulatory innovation.The findings provide actionable insights for policymakers in Brazil and other emerging economies seeking to balance private investment with public interest goals in railway infrastructure,highlighting the necessity of complementary,pro-competitive measures alongside financial investment.
基金National Key Research and Development Program of China,No.2023YFC3006704National Natural Science Foundation of China,No.42171047CAS-CSIRO Partnership Joint Project of 2024,No.177GJHZ2023097MI。
文摘Accurate prediction of flood events is important for flood control and risk management.Machine learning techniques contributed greatly to advances in flood predictions,and existing studies mainly focused on predicting flood resource variables using single or hybrid machine learning techniques.However,class-based flood predictions have rarely been investigated,which can aid in quickly diagnosing comprehensive flood characteristics and proposing targeted management strategies.This study proposed a prediction approach of flood regime metrics and event classes coupling machine learning algorithms with clustering-deduced membership degrees.Five algorithms were adopted for this exploration.Results showed that the class membership degrees accurately determined event classes with class hit rates up to 100%,compared with the four classes clustered from nine regime metrics.The nonlinear algorithms(Multiple Linear Regression,Random Forest,and least squares-Support Vector Machine)outperformed the linear techniques(Multiple Linear Regression and Stepwise Regression)in predicting flood regime metrics.The proposed approach well predicted flood event classes with average class hit rates of 66.0%-85.4%and 47.2%-76.0%in calibration and validation periods,respectively,particularly for the slow and late flood events.The predictive capability of the proposed prediction approach for flood regime metrics and classes was considerably stronger than that of hydrological modeling approach.
基金Project supported by the National Natural Science Foundation of China(No.12402033)the National Natural Science Foundation for Distinguished Young Scholars of China(No.52225211)。
文摘Many complex systems are frequently subject to the influence of uncertain disturbances,which can exert a profound effect on the critical transitions(CTs),potentially resulting in catastrophic consequences.Consequently,it is of uttermost importance to provide warnings for noise-induced CTs in various applications.Although capturing certain generic symptoms of transition behaviors from observational and simulated data poses a challenging problem,this work attempts to extract information regarding CTs from simulated data of a Gaussian white noise-induced tri-stable system.Using the extended dynamic mode decomposition(EDMD)algorithm,we initially obtain finite-dimensional approximations of both the stochastic Koopman operator and the generator.Subsequently,the drift parameters and the noise intensity within the system are identified from the simulated data.Utilizing the identified system,the parameter-dependent basin of the unsafe regime(PDBUR)is quantified,enabling data-driven early warning of Gaussian white noise-induced CTs.Finally,an error analysis is carried out to verify the effectiveness of the data-driven results.Our findings may serve as a paradigm for understanding and predicting noise-induced CTs in complex systems based on data.
基金The Scholarship Supported by the China Scholarship Councilthe Technical Research Program from NV Bekaert SA of Belgiumthe National Natural Science Foundation of China(No.50908047)
文摘This study investigates the influence of different curing regimes on the microstructure and macro properties of ultra-high performance fiber reinforced cementitious composite （UHPFRCC）, and aims to discover whether it is possible to produce qualified UHPFRCC using different curing regimes. A control mix of UHPFRCC is prepared. The mechanical performance and the short-term durability of the UHPFRCC matrix under three curing regimes are studied. In addition, the microstructures of the UHPFRCC matrix with different curing conditions are analyzed by combining scanning electron microscopy （SEM） and mercury intrusion porosimetry （MIP）. The results explore how different UHPFRCC curing regimes affect its microstructure and how the microstructure affects its macro behavior. Heat and steam curing for 3 d is succeeded to produce the UHPFRCC with nearly the same mechanical properties and durability as those of the 90 d standard curing. However, the heat cured UHPFRCC does not show great resistance to chloride-ion penetration.
基金supported by the National Basic Research Program (973) of China (No. 2005CB121104)the National Natural Science Foundation of China (No.41071145)
文摘Sequential extraction procedure was applied to assess the dynamics of solid-phase transformation of added Cu, Pb, Cd, and Hg in a typical Chinese paddy soil incubated under three moisture regimes （75% field capacity, wetting-drying cycle, and flooding）. The heavy metals spiked in the soil were time-dependently transferred from the easily extractable fraction （the exchangeable fraction） into less labile fractions （Fe-Mn oxide- and organic matter-bound fractions）, and thus reduced lability of the metals. No significant changes were found for the carbonate-bound and residual fractions of the heavy metals in the soil during the whole incubation. Change rate of the mobility factor （MF）, a proportion of weakly bound fractions （exchangeable and carbonate-bound） in the total metal of soil, reflected the transformation rate of metal speciation from the labile fractions toward stable fractions. It was found that soil moisture regime did not change the direction and pathways of transformation of metal speciation, but it significantly affected the transformation rate. In general, the paddy soil under flooding regime had higher metal reactivity compared with 75% field capacity and wetting-drying cycle regimes, resulting in the more complete movement of metals toward stable fractions. This might be related to the increased pH, precipitation of the metals with sulfides and higher concentration of amorphous Fe oxides under submerged condition.
基金funded by Sino-Probe 08-01the National Natural Science Foundation of China(grant No40572120)
文摘A synthesis is given in this paper on late Mesozoic deformation pattern in the zones around the Ordos Basin based on lithostratigraphic and structural analyses. A relative chronology of the late Mesozoic tectonic stress evolution was established from the field analyses of fault kinematics and constrained by stratigraphic contact relationships. The results show alternation of tectonic compressional and extensional regimes. The Ordos Basin and its surroundings were in weak N-S to NNE-SSW extension during the Early to Middle Jurassic, which reactivated E-W-trending basement fractures. The tectonic regime changed to a multi-directional compressional one during the Late Jurassic, which resulted in crustal shortening deformation along the marginal zones of the Ordos Basin. Then it changed to an extensional one during the Early Cretaceous, which rifted the western, northwestern and southeastern margins of the Ordos Basin. A NW-SE compression occurred during the Late Cretaceous and caused the termination of sedimentation and uplift of the Ordos Basin. This phased evolution of the late Mesozoic tectonic stress regimes and associated deformation pattern around the Ordos Basin best records the changes in regional geodynamic settings in East Asia, from the Early to Middle Jurassic post-orogenic extension following the Triassic collision between the North and South China Blocks, to the Late Jurassic multi-directional compressions produced by synchronous convergence of the three plates （the Siberian Plate to the north, Paleo-Pacific Plate to the east and Lhasa Block to the west） towards the East Asian continent. Early Cretaceous extension might be the response to collapse and lithospheric thinning of the North China Craton.
基金1Project supported by the Knowledge Innovative Program of the Chinese Academy of Sciences (No. KZCX2-413) andthe National High Technology Research and Development Program of China (863 Program) (No. 2002AA601012).
文摘A field experiment was conducted from 1999 to 2002 to compare and evaluate the effects of nutrient and water regimes on paddy soil quality by investigating soil chemical and microbiological parameters. Four nutrient regimes, a control, chemical fertilizers only (CF), chemical fertilizers with swine manure (SM), and chemical fertilizers with wheat straw (WS), and two soil moisture regimes, continuous waterlogging (CWL) and alternate wetting and drying (AWD), were investigated. With SM and WS total organic carbon and total nitrogen in the paddy soil were significantly higher (P < 0.05) than those with CF. A similar effect for organic amendments was observed in the soil light fraction organic C (LFOC), water-soluble carbohydrates (WSC), and water-soluble organic C (WSOC). CWL, in particular when swine manure was incorporated into the paddy soil, markedly decreased soil redox potential (Eh) and increased total active reducing substances (ARS). Meanwhile, as compared to CF, SM and WS significantly (P < 0.05) increased soil microbial biomass C (MBC) and mineralizable carbon, with differences in AWD being higher than CWL. In addition, SM and WS treatments significantly (P < 0.05) improved rice above-ground biomass and grain yield, with AWD being greater than CWL. Thus, for ecologically sustainable agricultural management of paddy soils, long-term waterlogging should be avoided when organic manure was incorporated into paddy soil.
基金supported by the programmes"Dynamique et Billan de la Terre","Imageric et Structure de la Terre"(Tectoscope)of In-stitut National des Sciences de l'Univers(INSU)and Centre National de la Recherche Scientifiquc(Paris,France).
文摘Since the mid-late Eocene, North China has been subjected to extensional stress, resulting in the formation and development of basins. The dynamic origin of this crustal extension has long been an issue of debate. This paper presents the results of kinematic analyses of faults obtained from two seperated areas in North China. In the Weihe graben situated on the southernmost margin of the Ordos block, analyses of fault kinematics were coupled with an analysis of the basin's subsidence history. Three successive extensional tectonic phases accompaning the basin's formation and development have been distinguished. The Palaeogene extension was oriented in a WNW-ESE direction; the Neogene extension in a NE-SW direction and the Pliocene-Quaternary extension in a NW-SE direction. Such changes have also been recorded by fault kinematics along the southern Tanlu fault zone. This has been demonstrated by three successive sets of fault striations indicating normal dip slip resulting from NW-SE extension, then left-lateral slip with a normal component resulting from NE-SW extension, and right-lateral slip with a minor normal component, respectively. The kinematic history of faults and their chronological evolution indicate changes in continental dynamics acting in North China over Cenozoic time.
