The water-quenched(WQ)2195 Al−Li alloy was subjected to stretching at different temperatures,from room temperature(RT)to−196℃(CT),to investigate the effect of cryogenic deformation on the aging precipitation behavior...The water-quenched(WQ)2195 Al−Li alloy was subjected to stretching at different temperatures,from room temperature(RT)to−196℃(CT),to investigate the effect of cryogenic deformation on the aging precipitation behaviors and mechanical properties.The precipitation kinetics of the T1 phase and the microstructures in peak aging state were investigated through the differential scanning calorimetric(DSC)tests and electron microscopy observation.The results show that−196℃deformation produces a high dislocation density,which promotes the precipitation of the T1 phase and refines its sizes significantly.In addition,the grain boundary precipitates(GBPs)of−196℃-stretched samples are suppressed considerably due to the high dislocation density in the grain interiors,which increases the ductility.In comparison,the strength remains nearly constant.Thus,it is indicated that cryogenic forming has the potential to provide the shape and property control for the manufacture of critical components of aluminum alloys.展开更多
Manganese is a major impurity in acidic vanadium-bearing leaching solutions,but its effects on vanadium precipitation via hydrolysis and acidic ammonium salts remain unclear.In this study,vanadium-bearing leachates wi...Manganese is a major impurity in acidic vanadium-bearing leaching solutions,but its effects on vanadium precipitation via hydrolysis and acidic ammonium salts remain unclear.In this study,vanadium-bearing leachates with varying manganese concentrations(VL-cMn)were prepared through calcium,a calcium-manganese composite,and manganese-based roasting of vanadium slag(VS)to investigate the influence of manganese on vanadium precipitation behavior during hydrolysis precipitation(HP)and ammonium salt precipitation(AP),as well as the microscopic characteristics and purity of the resulting V_(2)O_(5) products.The results showed that increasing the pH mitigated the negative effects of Mn on the V precipitation rate during HP.However,as the manganese concentration increased from 5.69 to 15.38 g/L,the V precipitation rate gradually declined at higher temperatures and longer reaction times.The precipitates exhibited increased microstructural density,which might had contributed to the formation of Mn-bearing phases.Additionally,the average grain size of V_(2)O_(5) was reduced and the particles were increasingly agglomerated,leading to a 2.55%decrease in product purity.For AP,as manganese concentration increased,raising the pH counteracted the negative impact of Mn on the V precipitation rate and reduced the required amount of ammonium sulfate.Moreover,Mn was unevenly adsorbed on the surface of the precipitates.Although V_(2)O_(5) grains gradually shrank and became denser,there was no significant effect on the final product purity,which remained above 99.3%.In conclusion,roasting with added manganese salts influenced the hydrolysis of vanadium but had no significant effect on acidic ammonium salt precipitation.展开更多
Enzyme-Induced Carbonate Precipitation(EICP)is an innovative technique to improve soil strength and reduce permeability.However,the use of EICP for reinforcing underwater sand beds remains largely unexplored.To advanc...Enzyme-Induced Carbonate Precipitation(EICP)is an innovative technique to improve soil strength and reduce permeability.However,the use of EICP for reinforcing underwater sand beds remains largely unexplored.To advance EICP implementation in various geotechnical applications,this paper develops a model box system to investigate the effectiveness of the EICP technique in reinforcing underwater sand beds.An"injection-extraction"system is designed to facilitate the flow of the EICP solution through underwater sand layers.Key parameters,including conductivity,pH,and Ca^(2+)concentration of the solution,are measured and analyzed.Electrical resistivity tomography(ERT)is utilized to evaluate the reinforcement effect in the underwater sand bed.The permeability of the model is tested to verify the feasibility of EICP technology for strengthening underwater sands.Furthermore,scanning electron microscope(SEM)is performed to investigate the growth mechanisms of calcium carbonate(CaCO_(3))crystals.The results show that the permeability of the model decreases from 1.28×10^(-2)m/s to 9.66×10^(-5)m/s,representing a reduction of approximately three orders of magnitude.This verifies that the EICP technology can greatly reduce the permeability of underwater sand beds.With increasing grouting cycles,the resistivity of the underwater sand initially decreases and then increases.This variation in sand resistivity is significantly influenced by the ion concentration in the solution,resulting in marked differences in resistivity at various depths and positions within the sand.The findings from this study offer a theoretical basis for the application of EICP technology in reinforcing seabed foundations and supporting marine infrastructure such as offshore pipelines,wind turbines,and oil platforms.展开更多
Precipitation events,which follow a life cycle of initiation,development,and decay,represent the fundamental form of precipitation.Comprehensive and accurate detection of these events is crucial for effective water re...Precipitation events,which follow a life cycle of initiation,development,and decay,represent the fundamental form of precipitation.Comprehensive and accurate detection of these events is crucial for effective water resource management and flood control.However,current investigations on their spatio-temporal patterns remain limited,largely because of the lack of systematic detection indices that are specifically designed for precipitation events,which constrains event-scale research.In this study,we defined a set of precipitation event detection indices(PEDI)that consists of five conventional and fourteen extreme indices to characterize precipitation events from the perspectives of intensity,duration,and frequency.Applications of the PEDI revealed the spatial patterns of hourly precipitation events in China and its first-and second-order river basins from 2008 to 2017.Both conventional and extreme precipitation events displayed spatial distribution patterns that gradually decreased in intensity,duration,and frequency from southeast to northwest China.Compared with those in northwest China,the average values of most PEDIs in southeast China were usually 2-10 times greater for first-order river basins and 3-15 times greater for second-order basins.The PEDI could serve as a reference method for investigating precipitation events at global,regional,and basin scales.展开更多
Northeast China(NEC),a critical agricultural and ecological zone,has experienced intensified hydrological variability under global warming,with cascading impacts on food security and ecosystem resilience.This study ut...Northeast China(NEC),a critical agricultural and ecological zone,has experienced intensified hydrological variability under global warming,with cascading impacts on food security and ecosystem resilience.This study utilized observational data and two new generation reanalysis products(i.e.,the fifth major global reanalysis produced by ECMWF(ERA5)and the Japanese Reanalysis for Three Quarters of a Century(JRA-3Q))to investigate the shift changes in precipitation in NEC around 2000 and associated water vapor transport.The analysis identified a pivotal interdecadal shift in 1998/99,transitioning from moderate increases(17.5 mm/10 yr during 1980-1998)to accelerated but more variable precipitation growth(85.4 mm/10 yr post-1999).While the mean precipitation during the post-shift period decreased,enhanced anticyclonic circulation amplified moisture divergence over continental NEC,redirecting vapor flux toward coastal regions.Crucially,trajectory analysis demonstrated regime-dependent moisture sourcing:midlatitude westerlies dominated during wet extremes(44% of trajectories in 1998),whereas East Asian monsoon flows prevailed in drought years(36% of trajectories in 2007).The post-1998 period exhibited increased reliance on localized recycling(45%of mid-tropospheric trajectories),reflecting weakened monsoonal inflow.These findings highlight NEC’s growing vulnerability to competing moisture pathways and atmospheric blocking-a dual mechanism that explains rising extremes despite declining mean precipitation.By reconciling dataset discrepancies(ERA5 vs.JRA-3Q trends)and elucidating circulation-precipitation linkages,this work provides actionable insights for climate-resilient agriculture in NEC’s water-stressed ecosystems.展开更多
This study investigated the characteristics and mechanisms of summer regional persistent extreme precipitation events(RPEPEs)over South China(SC)modulated by distinct intensity regimes of 10-30-day intraseasonal oscil...This study investigated the characteristics and mechanisms of summer regional persistent extreme precipitation events(RPEPEs)over South China(SC)modulated by distinct intensity regimes of 10-30-day intraseasonal oscillation(ISO).Diagnostic analyses revealed that the spatiotemporal evolution of RPEPEs exhibits robust phase-locking with the 10-30-day intraseasonal precipitation.By classifying RPEPEs into strong-ISO(SRPEPE)and weak-ISO(WRPEPE)composites based on the amplitude of 10-30-day filtered precipitation,we demonstrate a 14.6%enhancement in peak precipitation intensity during SRPEPEs compared to WRPEPEs.These distinct precipitation regimes are governed by fundamentally different Rossby wave teleconnection patterns over Eurasia.During SRPEPEs,a robust southeastward-propagating 10-30-day Rossby wave train originating from the Barents Sea traverses midlatitude Eurasia,effectively perturbing the northwestern Pacific upper-level circulation and establishing a favorable dynamic environment over SC.In contrast,WRPEPEs are associated with weaker eastward-propagating wave trains constrained along the subtropical jet stream.The horizontal convergence of background moisture driven by 10-30-day winds significantly amplifies lower-tropospheric humidity during SRPEPEs.The thermal advection of background temperature by 10-30-day geostrophic winds enhances baroclinic instability and vertical motion,intensifying precipitation under these moisture conditions.展开更多
China launched its first spaceborne Precipitation Measurement Radar(PMR)on the FY-3G satellite in April 2023.To achieve the scientific goal of measuring the three-dimensional precipitation structure,evaluating the qua...China launched its first spaceborne Precipitation Measurement Radar(PMR)on the FY-3G satellite in April 2023.To achieve the scientific goal of measuring the three-dimensional precipitation structure,evaluating the quantitative measurement ability of the PMR is critical.China operates more than 250 weather radars over the mainland.Consistency of the spaceborne radar with ground-based radars will enhance precipitation measurement ability,especially over oceans and mountains where observations are sparse.Additionally,the spaceborne radar can be used to evaluate the spatial and temporal homogeneity of the ground-based radar network.This paper focuses on comparing the PMR onboard the FY-3G satellite with S-band China New Generation Weather Radars(CINRADs).A comparison algorithm between the PMR and CINRADs has been developed,incorporating detailed quality control,attenuation correction,data optimization,spatiotemporal matching,non-uniform beam filling constraint,uniformity constraint,and frequency correction.The matched data in typical months of four seasons were selected to carry out the comparison.The data consistency between the PMR and CINRADs was analyzed.The correlation coefficient is 0.87,the deviation is 0.89 dB,and the standard deviation is 2.50 dB,based on 98226 matching samples.The results show the radar reflectivity of the PMR is quite comparable to that of the CINRADs,demonstrating that the PMR data quality is satisfactory and can be used to verify and correct data consistency among multiple ground-based radars.This work also paves the way for data fusion and joint application of satellite and ground radars in the future.展开更多
Using multi-source reanalysis data,this study examines the relationship between the tropical Pacific-Atlantic SST Dipole Mode(TPA-DM)and summer precipitation in North China(NCSP)on the interannual timescale during the...Using multi-source reanalysis data,this study examines the relationship between the tropical Pacific-Atlantic SST Dipole Mode(TPA-DM)and summer precipitation in North China(NCSP)on the interannual timescale during the period of 1979-2022.The results show that the TPA-DM,the dominant pattern of interannual variability in the tropical Pacific and Atlantic regions,exhibits a significant negative correlation with NCSP.The positive phase of TPA-DM induces subsidence over the Maritime Continent through a zonal circulation pattern,which initiates a Pacific-Japan-like wave train along the East Asian coast.The circulation anomalies lead to moisture deficits and convergence subsidence over North China,leading to below-normal rainfall.Further analysis reveals that cooler SST in the Southern Tropical Atlantic facilitates the persistence of the TPA-DM by stimulating the anomalous Walker circulation associated with wind-evaporation-SST-convection feedback.展开更多
The northeastern permafrost region of China is one of the most vulnerable areas to climate warming in midlatitude areas.Despite this,the specific pathways of water vapor circulation and transport in this area remain p...The northeastern permafrost region of China is one of the most vulnerable areas to climate warming in midlatitude areas.Despite this,the specific pathways of water vapor circulation and transport in this area remain poorly understood.Additionally,there is ongoing debate on whether the oxygen isotope of precipitation(δ^(18)O_(p))is primarily influenced by the temperature or the precipitation amount effects.Tree-ring samples were collected from various sites and tree species across the region,and 12 stable oxygen isotopes(δ18Oc)series constructed to investigate the water vapor signals embedded within.Our findings revealed consistentδ18Oc variations across different sites and species,reflecting relative humidity signals during the growing season(June to September)(r=−0.764,P<0.001,n=40).By applying an improved model to simulateδ^(18)O_(p),a“temperature effect”was identified.Bothδ18Oc andδ^(18)O_(p) provided valuable insights into the regional water vapor circulation,withδ18Oc offering a stronger climate signal.A binary linear regression model further revealed thatδ^(18)O_(p) had a greater influence onδ18Oc than relative humidity.The regional climate is primarily driven by the East Asian summer monsoon and large-scale water vapor circulation associated with the El Niño-Southern Oscillation.Because of future warming and drying trends,trees in this region are expected to face increasing drought stress.展开更多
Global land monsoon precipitation(GLMP)is highly sensitive to changes in interhemispheric thermal contrast(ITC).Amplified interhemispheric asymmetries of GLMP due to enhanced ITC driven by high-level anthropogenic emi...Global land monsoon precipitation(GLMP)is highly sensitive to changes in interhemispheric thermal contrast(ITC).Amplified interhemispheric asymmetries of GLMP due to enhanced ITC driven by high-level anthropogenic emissions are expected to simultaneously increase the probability of regional floods and droughts,threatening ecosystems within global terrestrial monsoon regions and the freshwater supply for billions of residents in these areas.In this study,the responses of GLMP to the evolution of ITC toward the carbon neutrality goal are assessed using multimodel outputs from a new model intercomparison project(CovidMIP).The results show that the Northern Hemisphere-Southern Hemisphere(NH-SH)asymmetry of GLMP in boreal summer weakens during the 2040s,as a persistent reduction in well-mixed greenhouse gas(WMGHG)emissions leads to a downward trend in the ITC after 2040.At the same time,the reduction in WMGHG emissions dampens the Eastern Hemisphere-Western Hemisphere(EH-WH)asymmetry of GLMP by inducing La Niña-like cooling and enhancing moisture transport to Inner America.The resulting increases in land monsoon precipitation(LMP)may alleviate drought under the global warming scenario by about 19%-25%and 7%-9%in the WH and SH monsoon regions,respectively.However,a persistent reduction in aerosol emissions in Asia will dominate the increases in LMP in this region until the mid-21st century,and these increases may be approximately 23%-60%of the growth under the global warming scenario.Our results highlight the different rates of response of aerosol and WMGHG concentrations to the carbon neutrality goal,leading to various changes in LMP at global and regional scales.展开更多
Based on reanalysis data from 1979 to 2021,this study explores the spatial distribution of the Southern Indian Ocean Dipole(SIOD)and its individual and synergistic effects with the El Niño-Southern Oscillation(EN...Based on reanalysis data from 1979 to 2021,this study explores the spatial distribution of the Southern Indian Ocean Dipole(SIOD)and its individual and synergistic effects with the El Niño-Southern Oscillation(ENSO)on summer precipitation in China.The inverse phase spatial distribution of sea surface temperature anomalies(SSTAs)in the southwest and northeast of the southern Indian Ocean is defined as the SIOD.Positive SIOD events(positive SSTAs in the southwest,negative SSTAs in the northeast)are associated with La Niña events(Central Pacific(CP)type),while negative SIOD events(negative SSTAs in the southwest,positive SSTAs in the northeast)are associated with El Niño events(Eastern Pacific(EP)type).Both SIOD and ENSO have certain impacts on summer precipitation in China.Precipitation in the Yangtze River basin decreases,while precipitation in southern China increases during pure positive SIOD(P_PSIOD)events.During pure negative SIOD(P_NSIOD)events,the changes in precipitation are exactly the opposite of those during P_PSIOD events,which may be due to differences in the cross-equatorial flow in the southern Indian Ocean,particularly in low-level Australian cross-equatorial flow.When positive SIOD and CP-type La Niña events occur simultaneously(PSIOD+La_Niña),precipitation increases in the Yangtze-Huaihe River basin,while it decreases in northern China.When negative SIOD and EP-type El Niño events occur simultaneously(NSIOD+El_Niño),precipitation in the Yangtze-Huaihe River basin is significantly lower than during P_NSIOD events.This is caused by differences in water vapor originating from the Pacific Ocean during different events.展开更多
Northeast China serves as an important crop production region.Accurately forecasting summer precipitation in Northeast China(NEC-PR)has been a challenge due to its wide range of time scales influenced by varying clima...Northeast China serves as an important crop production region.Accurately forecasting summer precipitation in Northeast China(NEC-PR)has been a challenge due to its wide range of time scales influenced by varying climatic conditions.This study presents a scale separation hybrid statistical model with recurrent neural network(SS-RNN)to predict the summer monthly NEC-PR.The SS-RNN model decomposes the multiple scales of the NEC-PR into several spatiotemporal intrinsic mode functions covering annual to decadal time scales.This strategy provides a way to derive appropriate predictors and establish predictive models for the primary spatial modes of the NEC-PR at various time scales.Our results demonstrate substantial improvements by the SS-RNN model in predicting the summer monthly NEC-PR as compared with dynamic models,particularly in predicting the spatial pattern of the NEC-PR.In this paper we take August,the month of the highest NEC-PR,to assess our model skill.Independent forecasts of the August NEC-PR over the period 2021–24 achieve significant spatial anomaly correlation coefficients,reaching a maximum value of 0.83.Additional verifications by station observations show that the model hits most station anomalies,achieving a mean predictive skill score of 90.展开更多
Precipitation nowcasting is of great importance for disaster prevention and mitigation.However,precipitation is a complex spatio-temporal phenomenon influenced by various underlying physical factors.Even slight change...Precipitation nowcasting is of great importance for disaster prevention and mitigation.However,precipitation is a complex spatio-temporal phenomenon influenced by various underlying physical factors.Even slight changes in the initial precipitation field can have a significant impact on the future precipitation patterns,making the nowcasting of short-term high-resolution precipitation a major challenge.Traditional deep learning methods often have difficulty capturing the long-term spatial dependence of precipitation and are usually at a low resolution.To address these issues,based upon the Simpler yet Better Video Prediction(SimVP)framework,we proposed a deep generative neural network that incorporates the Simple Parameter-Free Attention Module(SimAM)and Generative Adversarial Networks(GANs)for short-term high-resolution precipitation event forecasting.Through an adversarial training strategy,critical precipitation features were extracted from complex radar echo images.During the adversarial learning process,the dynamic competition between the generator and the discriminator could continuously enhance the model in prediction accuracy and resolution for short-term precipitation.Experimental results demonstrate that the proposed method could effectively forecast short-term precipitation events on various scales and showed the best overall performance among existing methods.展开更多
The microstructural evolution of Cu−19Ni−6Cr−7Mn alloy during aging treatment was investigated.After aging for 120 min at 500℃,the alloy exhibited excellent mechanical properties,including a tensile strength of 978 M...The microstructural evolution of Cu−19Ni−6Cr−7Mn alloy during aging treatment was investigated.After aging for 120 min at 500℃,the alloy exhibited excellent mechanical properties,including a tensile strength of 978 MPa and an elastic modulus of 145.8 GPa.After aging for 240 min at 500℃,the elastic modulus of the alloy reached 149.5 GPa,which was among the highest values reported for Cu alloys.It was worth mentioning that the tensile strength increased rapidly from 740 to 934 MPa after aging for 5 min at 500℃,which was close to the maximum tensile strength(978 MPa).Analysis of the underlying strengthening mechanisms and phase transformation behavior revealed that the Cu−19Ni−6Cr−7Mn alloy underwent spinodal decomposition and DO_(22) ordering during the first 5 min of aging at 500℃,and L1_(2) ordered phases and bcc-Cr precipitates appeared.Therefore,the enhanced mechanical properties of the Cu−19Ni−6Cr−7Mn alloy can be attributed to the stress field generated by spinodal decomposition and the presence of nanoscale ordered phase and Cr precipitates.展开更多
Microbially induced calcium carbonate precipitation(MICP)is an eco-friendly technology for soil improvement.Although numerous experiments have been conducted to solidify sand foundations using MICP,the mechanisms by w...Microbially induced calcium carbonate precipitation(MICP)is an eco-friendly technology for soil improvement.Although numerous experiments have been conducted to solidify sand foundations using MICP,the mechanisms by which grain interfacial morphologies influencethe MICP process remain unclear.This study utilized 3D-printed flowcells with different boundary morphologies to investigate the effects of interfacial morphologies on the MICP process.CaCO_(3)precipitation characteristics were investigated through microscopic observation and image quantificationanalysis.The results indicate that low flowvelocities near the interface promote bacterial accumulation due to reduced hydrodynamic shear forces.Rough interfaces,compared to smooth ones,enhance bacterial adsorption owing to the larger regions of low flowvelocity,increased surface area,and the formation of local eddies,which promote greater CaCO_(3)precipitation.Compared to the regions away from the interface,a higher abundance of small CaCO_(3)crystals is observed near the interface because of the high urease activity from bacteria and the reduced shear-induced entrainment due to the low flowvelocity.Besides,larger crystals also preferentially precipitate in proximity to interfaces as the low flowvelocity enhances crystal growth according to the particle attachment theory.The presence of rough interfaces further reduces flowvelocities,leading to the precipitation of larger and more densely packed CaCO_(3)crystals.Therefore,rough interfaces promote the microbially induced calcium carbonate precipitation.This work is expected to enhance the understanding of microbially induced calcium carbonate precipitation characteristics on solid surfaces such as soil grains and contribute to the optimization of MICP applications.展开更多
Groundwater level(GWL)is a key indicator used to accurately assess groundwater resources and form the foundation for ef-fective groundwater management.This paper integrates a Gate Recurrent Unit(GRU)model with a Multi...Groundwater level(GWL)is a key indicator used to accurately assess groundwater resources and form the foundation for ef-fective groundwater management.This paper integrates a Gate Recurrent Unit(GRU)model with a Multi-head Self-attention mechan-ism(MSAM-GRU)to simulate GWLs in both confined and unconfined aquifers simultaneously.The model innovatively captures the lag times between GWLs in the unconfined aquifer and precipitation,as well as between GWLs in the confined aquifer and the upper aquifer.We have assessed the effectiveness of the proposed model using a case study in the Beijing Plain,China from January 2005 to December 2020.With the consideration of lag times,the results indicated that the MSAM-GRU model exhibits a maximum 67%and 73%reduction in RMSE compared to the Attention mechanism-GRU(AM-GRU)and GRU model,respectively.MSAM-GRU model exhibited a 31%reduction in RMSE and a 0.12 increase in R^(2) compared to the same model that do not account for lag time.In Region I,the shortest lag time of GWL in the unconfined aquifer was two months,while that in the confined aquifer was three months,indicating a longer delayed response in the confined aquifer.MSAM-GRU model considering lag time,was then applied to simulate the GWLs in the unconfined aquifer under different scenarios and to analyze whether GWL fluctuations affect subway operations.The simulation res-ults showed that under the scenario 1,the GWL in the unconfined aquifer would rise above the depth of subway station floor,threaten-ing the operation of subways.This study can provide reliable technical support for the accurate simulation of GWLs in multi-aquifer systems.展开更多
Precipitation is often used for the preparation of La(OH)_(3)with precipitants of liquid alkali and ammonia.To solve the problems of high cost and wastewater pollution caused by common precipitants,the active MgO synt...Precipitation is often used for the preparation of La(OH)_(3)with precipitants of liquid alkali and ammonia.To solve the problems of high cost and wastewater pollution caused by common precipitants,the active MgO synthesized by pyrolysis was used as the precipitant to prepare La(OH)_(3).The species distribution of LaCl_(3)and LaCl_(3)-MgCl_(2)mixed system solution was calculated,and the kinetic analysis of the precipi-tation process was carried out to confirm the key factors influencing the precipitation of La(OH)_(3).The results show that La(OH)_(3)with D_(50)of 5.57μm,a specific surface area of 25.70 m^(2)/g,a rod-like shape,and MgO content of 0.044 wt%,was successfully prepared by adding active MgO.The precipitation ratio of La reaches 99.92%.The La(OH)_(3)precipitation is controlled by the diffusion process.The activity of MgO has a significant influence on MgO content in the precipitate.The preparation of La(OH)_(3)by active MgO provides a potential way for an eco-friendly preparation method of rare earth.展开更多
Cu-Ti alloys are a kind of elastic copper alloys with excellent comprehensive properties.They are often used in electronic and electrical fields.However,discontinuous precipitation may occur during the preparation pro...Cu-Ti alloys are a kind of elastic copper alloys with excellent comprehensive properties.They are often used in electronic and electrical fields.However,discontinuous precipitation may occur during the preparation process of Cu-Ti alloys,and they can lead to the significant deterioration of mechanical properties.To solve this problem,three Cu-Ti alloys with various Fe contents(Cu-2.7Ti,Cu-2.7Ti-0.1Fe and Cu-2.7Ti-0.2Fe)were designed and prepared in this paper to investigate the effects of Fe on the discontinuous precipitation.The results showed that after aging at any given aging time and temperature,the area fraction of cellular structure decreased with the increase of Fe content.The addition of Fe into Cu-Ti alloys resulted in Fe doping inβ'-Cu_(4)Ti phase andβ-Cu_(4)Ti phase.For 450℃/144 h-aged Cu-2.7Ti-0.2Fe alloy,the Fe content inβ'-Cu_(4)Ti phase andβ-Cu_(4)Ti phase was 1.59 at%and 0.90 at%,respectively.The tensile tests showed that under the same aging treatment conditions,Cu-2.7Ti-0.2Fe alloy possessed better mechanical properties.First-principles calculation confirmed that the thermodynamic stability ofβ'-Cu_(4)Ti phase was enhanced by decreasing its cohesive energy through Fe doping.At the same time,the enthalpy of formation ofβ-Cu_(4)Ti phase was generally increased by Fe doping,making it difficult to generate.In short,Fe addition in Cu-Ti alloys suppressed discontinuous precipitation by Fe doping in the precipitates and helped to improve mechanical properties.展开更多
Accurate seasonal precipitation forecasts,especially for extreme events,are crucial to preventing meteorological hazards and their potential impacts on national development,social activity,and security.However,the int...Accurate seasonal precipitation forecasts,especially for extreme events,are crucial to preventing meteorological hazards and their potential impacts on national development,social activity,and security.However,the intensity of summer precipitation is often largely underestimated in many current dynamic models.This study uses a deep learning method called Cycle-Consistent Generative Adversarial Networks(CycleGAN)to improve the seasonal forecasts for June-JulyAugust precipitation in southeastern China by the Nanjing University of Information Science and Technology Climate Forecast System(NUIST-CFS 1.0).The results suggest that the CycleGAN-based model significantly improves the accuracy in predicting the spatiotemporal distribution of summer precipitation compared to the traditional quantile mapping(QM)method.Using the unpaired bias-correction model,we can also obtain advanced forecasts of the frequency,intensity,and duration of extreme precipitation events over the dynamic model predictions.This study expands the potential applications of deep learning models toward improving seasonal precipitation forecasts.展开更多
Titanium alloys engineered in structural applications achieve ultrahigh strength primarily through precipitation strengthening of secondary α-phase(αs)during aging,while they often experience compromised ductility a...Titanium alloys engineered in structural applications achieve ultrahigh strength primarily through precipitation strengthening of secondary α-phase(αs)during aging,while they often experience compromised ductility and toughness due to traditional strength-toughness tradeoff.In this study,we propose a novel strategy to address this conflict by introducing deformation kinks prior to conventional cold rolling(CR)and aging processes.These kinks are produced by cold forging(CF)to create macroscopic lamellar structures in β-grains,which alter strain partitioning during subsequent CR and ultimately tailor α_(s)-precipitation upon aging.As a result,an ultrafine duplex(αe+β)-structure is formed within kink interi-ors,while hierarchicalαs-precipitates are generated in the external β-matrix.This unique microstructure effectively enhances dislocation activity,promotes uniform plastic strain distribution and impedes crack propagation.Consequently,a simple Ti-V binary titanium alloy exhibits exceptional properties with ultra-high strength∼1636 MPa,decent ductility∼5.4% and appreciable fracture toughness∼36.1 MPa m^(1/2).The synergetic properties surpass those obtained through traditional CR and aging processes for the alloy and even outperform numerous multielement engineering titanium alloys reported in literature.Our findings open up a new avenue for overcoming the strength-toughness tradeoffof ultrahigh-strength titanium alloys,and also offer a facile production route towards structural materials for advanced performance.展开更多
基金financially supported by the National Key Research and Development Program of China (No. 2019YFA0708801)the National Natural Science Foundation of China (No. 51875125)。
文摘The water-quenched(WQ)2195 Al−Li alloy was subjected to stretching at different temperatures,from room temperature(RT)to−196℃(CT),to investigate the effect of cryogenic deformation on the aging precipitation behaviors and mechanical properties.The precipitation kinetics of the T1 phase and the microstructures in peak aging state were investigated through the differential scanning calorimetric(DSC)tests and electron microscopy observation.The results show that−196℃deformation produces a high dislocation density,which promotes the precipitation of the T1 phase and refines its sizes significantly.In addition,the grain boundary precipitates(GBPs)of−196℃-stretched samples are suppressed considerably due to the high dislocation density in the grain interiors,which increases the ductility.In comparison,the strength remains nearly constant.Thus,it is indicated that cryogenic forming has the potential to provide the shape and property control for the manufacture of critical components of aluminum alloys.
基金supported by National Natural Science Foundation of China(Nos.52204309,52174277 and 52374300)Fundamental Funds for the Central Universities(No.N2425026)。
文摘Manganese is a major impurity in acidic vanadium-bearing leaching solutions,but its effects on vanadium precipitation via hydrolysis and acidic ammonium salts remain unclear.In this study,vanadium-bearing leachates with varying manganese concentrations(VL-cMn)were prepared through calcium,a calcium-manganese composite,and manganese-based roasting of vanadium slag(VS)to investigate the influence of manganese on vanadium precipitation behavior during hydrolysis precipitation(HP)and ammonium salt precipitation(AP),as well as the microscopic characteristics and purity of the resulting V_(2)O_(5) products.The results showed that increasing the pH mitigated the negative effects of Mn on the V precipitation rate during HP.However,as the manganese concentration increased from 5.69 to 15.38 g/L,the V precipitation rate gradually declined at higher temperatures and longer reaction times.The precipitates exhibited increased microstructural density,which might had contributed to the formation of Mn-bearing phases.Additionally,the average grain size of V_(2)O_(5) was reduced and the particles were increasingly agglomerated,leading to a 2.55%decrease in product purity.For AP,as manganese concentration increased,raising the pH counteracted the negative impact of Mn on the V precipitation rate and reduced the required amount of ammonium sulfate.Moreover,Mn was unevenly adsorbed on the surface of the precipitates.Although V_(2)O_(5) grains gradually shrank and became denser,there was no significant effect on the final product purity,which remained above 99.3%.In conclusion,roasting with added manganese salts influenced the hydrolysis of vanadium but had no significant effect on acidic ammonium salt precipitation.
基金supported by the National Youth Top-notch Talent Support Program of China(Grant No.00389335)the National Natural Science Foundation of China(Grant No.52378392)+1 种基金the“Foal Eagle Program”Youth Top-notch Talent Project of Fujian Province(Grant No.00387088)supports are gratefully acknowledged.
文摘Enzyme-Induced Carbonate Precipitation(EICP)is an innovative technique to improve soil strength and reduce permeability.However,the use of EICP for reinforcing underwater sand beds remains largely unexplored.To advance EICP implementation in various geotechnical applications,this paper develops a model box system to investigate the effectiveness of the EICP technique in reinforcing underwater sand beds.An"injection-extraction"system is designed to facilitate the flow of the EICP solution through underwater sand layers.Key parameters,including conductivity,pH,and Ca^(2+)concentration of the solution,are measured and analyzed.Electrical resistivity tomography(ERT)is utilized to evaluate the reinforcement effect in the underwater sand bed.The permeability of the model is tested to verify the feasibility of EICP technology for strengthening underwater sands.Furthermore,scanning electron microscope(SEM)is performed to investigate the growth mechanisms of calcium carbonate(CaCO_(3))crystals.The results show that the permeability of the model decreases from 1.28×10^(-2)m/s to 9.66×10^(-5)m/s,representing a reduction of approximately three orders of magnitude.This verifies that the EICP technology can greatly reduce the permeability of underwater sand beds.With increasing grouting cycles,the resistivity of the underwater sand initially decreases and then increases.This variation in sand resistivity is significantly influenced by the ion concentration in the solution,resulting in marked differences in resistivity at various depths and positions within the sand.The findings from this study offer a theoretical basis for the application of EICP technology in reinforcing seabed foundations and supporting marine infrastructure such as offshore pipelines,wind turbines,and oil platforms.
基金National Key Research and Development Program of China,No.2023YFC3206605,No.2021YFC3201102National Natural Science Foundation of China,No.41971035。
文摘Precipitation events,which follow a life cycle of initiation,development,and decay,represent the fundamental form of precipitation.Comprehensive and accurate detection of these events is crucial for effective water resource management and flood control.However,current investigations on their spatio-temporal patterns remain limited,largely because of the lack of systematic detection indices that are specifically designed for precipitation events,which constrains event-scale research.In this study,we defined a set of precipitation event detection indices(PEDI)that consists of five conventional and fourteen extreme indices to characterize precipitation events from the perspectives of intensity,duration,and frequency.Applications of the PEDI revealed the spatial patterns of hourly precipitation events in China and its first-and second-order river basins from 2008 to 2017.Both conventional and extreme precipitation events displayed spatial distribution patterns that gradually decreased in intensity,duration,and frequency from southeast to northwest China.Compared with those in northwest China,the average values of most PEDIs in southeast China were usually 2-10 times greater for first-order river basins and 3-15 times greater for second-order basins.The PEDI could serve as a reference method for investigating precipitation events at global,regional,and basin scales.
基金supported by the National Natural Science Foundation of China[grant numbers 42275185 and 42205032]the Fundamental Research Funds for the Central Universities[grant number B250201118]。
文摘Northeast China(NEC),a critical agricultural and ecological zone,has experienced intensified hydrological variability under global warming,with cascading impacts on food security and ecosystem resilience.This study utilized observational data and two new generation reanalysis products(i.e.,the fifth major global reanalysis produced by ECMWF(ERA5)and the Japanese Reanalysis for Three Quarters of a Century(JRA-3Q))to investigate the shift changes in precipitation in NEC around 2000 and associated water vapor transport.The analysis identified a pivotal interdecadal shift in 1998/99,transitioning from moderate increases(17.5 mm/10 yr during 1980-1998)to accelerated but more variable precipitation growth(85.4 mm/10 yr post-1999).While the mean precipitation during the post-shift period decreased,enhanced anticyclonic circulation amplified moisture divergence over continental NEC,redirecting vapor flux toward coastal regions.Crucially,trajectory analysis demonstrated regime-dependent moisture sourcing:midlatitude westerlies dominated during wet extremes(44% of trajectories in 1998),whereas East Asian monsoon flows prevailed in drought years(36% of trajectories in 2007).The post-1998 period exhibited increased reliance on localized recycling(45%of mid-tropospheric trajectories),reflecting weakened monsoonal inflow.These findings highlight NEC’s growing vulnerability to competing moisture pathways and atmospheric blocking-a dual mechanism that explains rising extremes despite declining mean precipitation.By reconciling dataset discrepancies(ERA5 vs.JRA-3Q trends)and elucidating circulation-precipitation linkages,this work provides actionable insights for climate-resilient agriculture in NEC’s water-stressed ecosystems.
基金the comments of three reviewers which substantially enhanced the quality of this manuscript.This research is jointly sponsored by the National Natural Science Foundation of China(grant 42575038)the National Key Research and Development Program of China(grant 2022YFF0801702)the National Natural Science Foundation of China(grant 42206257 and 42205163).
文摘This study investigated the characteristics and mechanisms of summer regional persistent extreme precipitation events(RPEPEs)over South China(SC)modulated by distinct intensity regimes of 10-30-day intraseasonal oscillation(ISO).Diagnostic analyses revealed that the spatiotemporal evolution of RPEPEs exhibits robust phase-locking with the 10-30-day intraseasonal precipitation.By classifying RPEPEs into strong-ISO(SRPEPE)and weak-ISO(WRPEPE)composites based on the amplitude of 10-30-day filtered precipitation,we demonstrate a 14.6%enhancement in peak precipitation intensity during SRPEPEs compared to WRPEPEs.These distinct precipitation regimes are governed by fundamentally different Rossby wave teleconnection patterns over Eurasia.During SRPEPEs,a robust southeastward-propagating 10-30-day Rossby wave train originating from the Barents Sea traverses midlatitude Eurasia,effectively perturbing the northwestern Pacific upper-level circulation and establishing a favorable dynamic environment over SC.In contrast,WRPEPEs are associated with weaker eastward-propagating wave trains constrained along the subtropical jet stream.The horizontal convergence of background moisture driven by 10-30-day winds significantly amplifies lower-tropospheric humidity during SRPEPEs.The thermal advection of background temperature by 10-30-day geostrophic winds enhances baroclinic instability and vertical motion,intensifying precipitation under these moisture conditions.
基金jointly supported by the National Natural Science Foundation of China(Grant U2442214)the China Meteorological Administration Youth Innovation Team(Grant No.CMA2024QN10)+1 种基金the National Defense Science and Technology Bureau’s 14th Five-Year Civil Aerospace Preresearch Project(Grant Nos.D030303 and D040204)the International Space Water Cycle Observation Constellation Program(Grant No.183311KYSB20200015).
文摘China launched its first spaceborne Precipitation Measurement Radar(PMR)on the FY-3G satellite in April 2023.To achieve the scientific goal of measuring the three-dimensional precipitation structure,evaluating the quantitative measurement ability of the PMR is critical.China operates more than 250 weather radars over the mainland.Consistency of the spaceborne radar with ground-based radars will enhance precipitation measurement ability,especially over oceans and mountains where observations are sparse.Additionally,the spaceborne radar can be used to evaluate the spatial and temporal homogeneity of the ground-based radar network.This paper focuses on comparing the PMR onboard the FY-3G satellite with S-band China New Generation Weather Radars(CINRADs).A comparison algorithm between the PMR and CINRADs has been developed,incorporating detailed quality control,attenuation correction,data optimization,spatiotemporal matching,non-uniform beam filling constraint,uniformity constraint,and frequency correction.The matched data in typical months of four seasons were selected to carry out the comparison.The data consistency between the PMR and CINRADs was analyzed.The correlation coefficient is 0.87,the deviation is 0.89 dB,and the standard deviation is 2.50 dB,based on 98226 matching samples.The results show the radar reflectivity of the PMR is quite comparable to that of the CINRADs,demonstrating that the PMR data quality is satisfactory and can be used to verify and correct data consistency among multiple ground-based radars.This work also paves the way for data fusion and joint application of satellite and ground radars in the future.
基金jointly supported by the Second Tibetan Plateau Scientific Expedition and Research Program[grant number-ber 2019QZKK0103]the National Natural Science Foundation of China[grant number 42293294]the China Meteorological Admin-istration Climate Change Special Program[grant number QBZ202303]。
文摘Using multi-source reanalysis data,this study examines the relationship between the tropical Pacific-Atlantic SST Dipole Mode(TPA-DM)and summer precipitation in North China(NCSP)on the interannual timescale during the period of 1979-2022.The results show that the TPA-DM,the dominant pattern of interannual variability in the tropical Pacific and Atlantic regions,exhibits a significant negative correlation with NCSP.The positive phase of TPA-DM induces subsidence over the Maritime Continent through a zonal circulation pattern,which initiates a Pacific-Japan-like wave train along the East Asian coast.The circulation anomalies lead to moisture deficits and convergence subsidence over North China,leading to below-normal rainfall.Further analysis reveals that cooler SST in the Southern Tropical Atlantic facilitates the persistence of the TPA-DM by stimulating the anomalous Walker circulation associated with wind-evaporation-SST-convection feedback.
基金supported by the National Natural Science Foundation of China(Grant Nos.42173080 and 42488201)the Chinese Academy of Sciences(Grant No.XDB40010300)the Young Talent Support Plan of Xi’an Jiaotong University.
文摘The northeastern permafrost region of China is one of the most vulnerable areas to climate warming in midlatitude areas.Despite this,the specific pathways of water vapor circulation and transport in this area remain poorly understood.Additionally,there is ongoing debate on whether the oxygen isotope of precipitation(δ^(18)O_(p))is primarily influenced by the temperature or the precipitation amount effects.Tree-ring samples were collected from various sites and tree species across the region,and 12 stable oxygen isotopes(δ18Oc)series constructed to investigate the water vapor signals embedded within.Our findings revealed consistentδ18Oc variations across different sites and species,reflecting relative humidity signals during the growing season(June to September)(r=−0.764,P<0.001,n=40).By applying an improved model to simulateδ^(18)O_(p),a“temperature effect”was identified.Bothδ18Oc andδ^(18)O_(p) provided valuable insights into the regional water vapor circulation,withδ18Oc offering a stronger climate signal.A binary linear regression model further revealed thatδ^(18)O_(p) had a greater influence onδ18Oc than relative humidity.The regional climate is primarily driven by the East Asian summer monsoon and large-scale water vapor circulation associated with the El Niño-Southern Oscillation.Because of future warming and drying trends,trees in this region are expected to face increasing drought stress.
基金funded by the National Natural Science Foundation of China(Grant No.42275039)the Meteorological Joint Fund by NSF and CMA(Grant No.U2342224)+1 种基金the National Key R&D Program of China(Grant No.2022YFC3701202)the S&T Development Fund of CAMS(Grant No.2024KJ019)。
文摘Global land monsoon precipitation(GLMP)is highly sensitive to changes in interhemispheric thermal contrast(ITC).Amplified interhemispheric asymmetries of GLMP due to enhanced ITC driven by high-level anthropogenic emissions are expected to simultaneously increase the probability of regional floods and droughts,threatening ecosystems within global terrestrial monsoon regions and the freshwater supply for billions of residents in these areas.In this study,the responses of GLMP to the evolution of ITC toward the carbon neutrality goal are assessed using multimodel outputs from a new model intercomparison project(CovidMIP).The results show that the Northern Hemisphere-Southern Hemisphere(NH-SH)asymmetry of GLMP in boreal summer weakens during the 2040s,as a persistent reduction in well-mixed greenhouse gas(WMGHG)emissions leads to a downward trend in the ITC after 2040.At the same time,the reduction in WMGHG emissions dampens the Eastern Hemisphere-Western Hemisphere(EH-WH)asymmetry of GLMP by inducing La Niña-like cooling and enhancing moisture transport to Inner America.The resulting increases in land monsoon precipitation(LMP)may alleviate drought under the global warming scenario by about 19%-25%and 7%-9%in the WH and SH monsoon regions,respectively.However,a persistent reduction in aerosol emissions in Asia will dominate the increases in LMP in this region until the mid-21st century,and these increases may be approximately 23%-60%of the growth under the global warming scenario.Our results highlight the different rates of response of aerosol and WMGHG concentrations to the carbon neutrality goal,leading to various changes in LMP at global and regional scales.
基金supported by the National Natural Science Foundation of China[grant numbers 41975087,U2242212,and 41975085]supported by the National Natural Science Foundation of China[grant number U2242212]。
文摘Based on reanalysis data from 1979 to 2021,this study explores the spatial distribution of the Southern Indian Ocean Dipole(SIOD)and its individual and synergistic effects with the El Niño-Southern Oscillation(ENSO)on summer precipitation in China.The inverse phase spatial distribution of sea surface temperature anomalies(SSTAs)in the southwest and northeast of the southern Indian Ocean is defined as the SIOD.Positive SIOD events(positive SSTAs in the southwest,negative SSTAs in the northeast)are associated with La Niña events(Central Pacific(CP)type),while negative SIOD events(negative SSTAs in the southwest,positive SSTAs in the northeast)are associated with El Niño events(Eastern Pacific(EP)type).Both SIOD and ENSO have certain impacts on summer precipitation in China.Precipitation in the Yangtze River basin decreases,while precipitation in southern China increases during pure positive SIOD(P_PSIOD)events.During pure negative SIOD(P_NSIOD)events,the changes in precipitation are exactly the opposite of those during P_PSIOD events,which may be due to differences in the cross-equatorial flow in the southern Indian Ocean,particularly in low-level Australian cross-equatorial flow.When positive SIOD and CP-type La Niña events occur simultaneously(PSIOD+La_Niña),precipitation increases in the Yangtze-Huaihe River basin,while it decreases in northern China.When negative SIOD and EP-type El Niño events occur simultaneously(NSIOD+El_Niño),precipitation in the Yangtze-Huaihe River basin is significantly lower than during P_NSIOD events.This is caused by differences in water vapor originating from the Pacific Ocean during different events.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFC3002803)the National Key Research and Development Program of China(Grant No.2024YFF0808402)the National Natural Science Foundation of China(Grant No.42375169)。
文摘Northeast China serves as an important crop production region.Accurately forecasting summer precipitation in Northeast China(NEC-PR)has been a challenge due to its wide range of time scales influenced by varying climatic conditions.This study presents a scale separation hybrid statistical model with recurrent neural network(SS-RNN)to predict the summer monthly NEC-PR.The SS-RNN model decomposes the multiple scales of the NEC-PR into several spatiotemporal intrinsic mode functions covering annual to decadal time scales.This strategy provides a way to derive appropriate predictors and establish predictive models for the primary spatial modes of the NEC-PR at various time scales.Our results demonstrate substantial improvements by the SS-RNN model in predicting the summer monthly NEC-PR as compared with dynamic models,particularly in predicting the spatial pattern of the NEC-PR.In this paper we take August,the month of the highest NEC-PR,to assess our model skill.Independent forecasts of the August NEC-PR over the period 2021–24 achieve significant spatial anomaly correlation coefficients,reaching a maximum value of 0.83.Additional verifications by station observations show that the model hits most station anomalies,achieving a mean predictive skill score of 90.
基金Supported by the National Natural Science Foundation of China(No.42306214)the Postdoctoral Innovative Talents Support Program of Shandong Province(No.SDBX2022026)+1 种基金the China Postdoctoral Science Foundation(No.2023M733533)the Special Research Assistant Project of the Chinese Academy of Sciences in 2022。
文摘Precipitation nowcasting is of great importance for disaster prevention and mitigation.However,precipitation is a complex spatio-temporal phenomenon influenced by various underlying physical factors.Even slight changes in the initial precipitation field can have a significant impact on the future precipitation patterns,making the nowcasting of short-term high-resolution precipitation a major challenge.Traditional deep learning methods often have difficulty capturing the long-term spatial dependence of precipitation and are usually at a low resolution.To address these issues,based upon the Simpler yet Better Video Prediction(SimVP)framework,we proposed a deep generative neural network that incorporates the Simple Parameter-Free Attention Module(SimAM)and Generative Adversarial Networks(GANs)for short-term high-resolution precipitation event forecasting.Through an adversarial training strategy,critical precipitation features were extracted from complex radar echo images.During the adversarial learning process,the dynamic competition between the generator and the discriminator could continuously enhance the model in prediction accuracy and resolution for short-term precipitation.Experimental results demonstrate that the proposed method could effectively forecast short-term precipitation events on various scales and showed the best overall performance among existing methods.
基金supported by the National Key R&D Program of China (No. 2021YFB3700700)the Henan Province Top Talent Training Program Project, China (No. 244500510020)the High-level Talent Research Start-up Project Funding of Henan Academy of Sciences, China (No. 242017001)。
文摘The microstructural evolution of Cu−19Ni−6Cr−7Mn alloy during aging treatment was investigated.After aging for 120 min at 500℃,the alloy exhibited excellent mechanical properties,including a tensile strength of 978 MPa and an elastic modulus of 145.8 GPa.After aging for 240 min at 500℃,the elastic modulus of the alloy reached 149.5 GPa,which was among the highest values reported for Cu alloys.It was worth mentioning that the tensile strength increased rapidly from 740 to 934 MPa after aging for 5 min at 500℃,which was close to the maximum tensile strength(978 MPa).Analysis of the underlying strengthening mechanisms and phase transformation behavior revealed that the Cu−19Ni−6Cr−7Mn alloy underwent spinodal decomposition and DO_(22) ordering during the first 5 min of aging at 500℃,and L1_(2) ordered phases and bcc-Cr precipitates appeared.Therefore,the enhanced mechanical properties of the Cu−19Ni−6Cr−7Mn alloy can be attributed to the stress field generated by spinodal decomposition and the presence of nanoscale ordered phase and Cr precipitates.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFC3707900)National Natural Science Foundation of China(Grant No.42230710,42525201)Key task project for joint research and development of the Yangtze River Delta Science and Technology Innovation Community(Grant No.2022CSJGG1200).
文摘Microbially induced calcium carbonate precipitation(MICP)is an eco-friendly technology for soil improvement.Although numerous experiments have been conducted to solidify sand foundations using MICP,the mechanisms by which grain interfacial morphologies influencethe MICP process remain unclear.This study utilized 3D-printed flowcells with different boundary morphologies to investigate the effects of interfacial morphologies on the MICP process.CaCO_(3)precipitation characteristics were investigated through microscopic observation and image quantificationanalysis.The results indicate that low flowvelocities near the interface promote bacterial accumulation due to reduced hydrodynamic shear forces.Rough interfaces,compared to smooth ones,enhance bacterial adsorption owing to the larger regions of low flowvelocity,increased surface area,and the formation of local eddies,which promote greater CaCO_(3)precipitation.Compared to the regions away from the interface,a higher abundance of small CaCO_(3)crystals is observed near the interface because of the high urease activity from bacteria and the reduced shear-induced entrainment due to the low flowvelocity.Besides,larger crystals also preferentially precipitate in proximity to interfaces as the low flowvelocity enhances crystal growth according to the particle attachment theory.The presence of rough interfaces further reduces flowvelocities,leading to the precipitation of larger and more densely packed CaCO_(3)crystals.Therefore,rough interfaces promote the microbially induced calcium carbonate precipitation.This work is expected to enhance the understanding of microbially induced calcium carbonate precipitation characteristics on solid surfaces such as soil grains and contribute to the optimization of MICP applications.
基金Under the auspices of the National Key Research and Development Program of China(No.2024YFC3713102)。
文摘Groundwater level(GWL)is a key indicator used to accurately assess groundwater resources and form the foundation for ef-fective groundwater management.This paper integrates a Gate Recurrent Unit(GRU)model with a Multi-head Self-attention mechan-ism(MSAM-GRU)to simulate GWLs in both confined and unconfined aquifers simultaneously.The model innovatively captures the lag times between GWLs in the unconfined aquifer and precipitation,as well as between GWLs in the confined aquifer and the upper aquifer.We have assessed the effectiveness of the proposed model using a case study in the Beijing Plain,China from January 2005 to December 2020.With the consideration of lag times,the results indicated that the MSAM-GRU model exhibits a maximum 67%and 73%reduction in RMSE compared to the Attention mechanism-GRU(AM-GRU)and GRU model,respectively.MSAM-GRU model exhibited a 31%reduction in RMSE and a 0.12 increase in R^(2) compared to the same model that do not account for lag time.In Region I,the shortest lag time of GWL in the unconfined aquifer was two months,while that in the confined aquifer was three months,indicating a longer delayed response in the confined aquifer.MSAM-GRU model considering lag time,was then applied to simulate the GWLs in the unconfined aquifer under different scenarios and to analyze whether GWL fluctuations affect subway operations.The simulation res-ults showed that under the scenario 1,the GWL in the unconfined aquifer would rise above the depth of subway station floor,threaten-ing the operation of subways.This study can provide reliable technical support for the accurate simulation of GWLs in multi-aquifer systems.
基金the National Key Research and Development Program of China(2022YFB3504503)the National Natural Science Foundation of China(52274355)the Gansu Province Science and Technology Major Special Project,China(22ZD6GD061).
文摘Precipitation is often used for the preparation of La(OH)_(3)with precipitants of liquid alkali and ammonia.To solve the problems of high cost and wastewater pollution caused by common precipitants,the active MgO synthesized by pyrolysis was used as the precipitant to prepare La(OH)_(3).The species distribution of LaCl_(3)and LaCl_(3)-MgCl_(2)mixed system solution was calculated,and the kinetic analysis of the precipi-tation process was carried out to confirm the key factors influencing the precipitation of La(OH)_(3).The results show that La(OH)_(3)with D_(50)of 5.57μm,a specific surface area of 25.70 m^(2)/g,a rod-like shape,and MgO content of 0.044 wt%,was successfully prepared by adding active MgO.The precipitation ratio of La reaches 99.92%.The La(OH)_(3)precipitation is controlled by the diffusion process.The activity of MgO has a significant influence on MgO content in the precipitate.The preparation of La(OH)_(3)by active MgO provides a potential way for an eco-friendly preparation method of rare earth.
基金supported by the National Natural Science Foundation of China(No.U2202255)Hunan Provincial Natural Science Foundation of China(No.2024JJ2076)the Key Technology Research Program of Ningbo(No.2023Z092).
文摘Cu-Ti alloys are a kind of elastic copper alloys with excellent comprehensive properties.They are often used in electronic and electrical fields.However,discontinuous precipitation may occur during the preparation process of Cu-Ti alloys,and they can lead to the significant deterioration of mechanical properties.To solve this problem,three Cu-Ti alloys with various Fe contents(Cu-2.7Ti,Cu-2.7Ti-0.1Fe and Cu-2.7Ti-0.2Fe)were designed and prepared in this paper to investigate the effects of Fe on the discontinuous precipitation.The results showed that after aging at any given aging time and temperature,the area fraction of cellular structure decreased with the increase of Fe content.The addition of Fe into Cu-Ti alloys resulted in Fe doping inβ'-Cu_(4)Ti phase andβ-Cu_(4)Ti phase.For 450℃/144 h-aged Cu-2.7Ti-0.2Fe alloy,the Fe content inβ'-Cu_(4)Ti phase andβ-Cu_(4)Ti phase was 1.59 at%and 0.90 at%,respectively.The tensile tests showed that under the same aging treatment conditions,Cu-2.7Ti-0.2Fe alloy possessed better mechanical properties.First-principles calculation confirmed that the thermodynamic stability ofβ'-Cu_(4)Ti phase was enhanced by decreasing its cohesive energy through Fe doping.At the same time,the enthalpy of formation ofβ-Cu_(4)Ti phase was generally increased by Fe doping,making it difficult to generate.In short,Fe addition in Cu-Ti alloys suppressed discontinuous precipitation by Fe doping in the precipitates and helped to improve mechanical properties.
基金supported by the National Key Research and Development Program of China(Grant No.2020YFA0608000)the National Natural Science Foundation of China(Grant No.42030605)+1 种基金CAAI-MindSpore Academic Fund Research Projects(CAAIXSJLJJ2023MindSpore11)the program of China Scholarships Council(No.CXXM2101180001)。
文摘Accurate seasonal precipitation forecasts,especially for extreme events,are crucial to preventing meteorological hazards and their potential impacts on national development,social activity,and security.However,the intensity of summer precipitation is often largely underestimated in many current dynamic models.This study uses a deep learning method called Cycle-Consistent Generative Adversarial Networks(CycleGAN)to improve the seasonal forecasts for June-JulyAugust precipitation in southeastern China by the Nanjing University of Information Science and Technology Climate Forecast System(NUIST-CFS 1.0).The results suggest that the CycleGAN-based model significantly improves the accuracy in predicting the spatiotemporal distribution of summer precipitation compared to the traditional quantile mapping(QM)method.Using the unpaired bias-correction model,we can also obtain advanced forecasts of the frequency,intensity,and duration of extreme precipitation events over the dynamic model predictions.This study expands the potential applications of deep learning models toward improving seasonal precipitation forecasts.
基金supported by the National Natural Science Foundation of China(Nos.52271113,92163201)Jinyu Zhang is grateful for the Shaanxi Province Youth Innovation Team(No.22JP042)Shaanxi Province Innovation Team Project(2024RS-CXTD-58).
文摘Titanium alloys engineered in structural applications achieve ultrahigh strength primarily through precipitation strengthening of secondary α-phase(αs)during aging,while they often experience compromised ductility and toughness due to traditional strength-toughness tradeoff.In this study,we propose a novel strategy to address this conflict by introducing deformation kinks prior to conventional cold rolling(CR)and aging processes.These kinks are produced by cold forging(CF)to create macroscopic lamellar structures in β-grains,which alter strain partitioning during subsequent CR and ultimately tailor α_(s)-precipitation upon aging.As a result,an ultrafine duplex(αe+β)-structure is formed within kink interi-ors,while hierarchicalαs-precipitates are generated in the external β-matrix.This unique microstructure effectively enhances dislocation activity,promotes uniform plastic strain distribution and impedes crack propagation.Consequently,a simple Ti-V binary titanium alloy exhibits exceptional properties with ultra-high strength∼1636 MPa,decent ductility∼5.4% and appreciable fracture toughness∼36.1 MPa m^(1/2).The synergetic properties surpass those obtained through traditional CR and aging processes for the alloy and even outperform numerous multielement engineering titanium alloys reported in literature.Our findings open up a new avenue for overcoming the strength-toughness tradeoffof ultrahigh-strength titanium alloys,and also offer a facile production route towards structural materials for advanced performance.
