The Cu0.9Cr0.1Zr alloy was deformed through continuous equal channel angular pressing(C-ECAP)through Route A,followed by liquid nitrogen cryogenic rolling(CR)and aging treated at 450℃.The microstructure,mechanical pr...The Cu0.9Cr0.1Zr alloy was deformed through continuous equal channel angular pressing(C-ECAP)through Route A,followed by liquid nitrogen cryogenic rolling(CR)and aging treated at 450℃.The microstructure,mechanical properties,and conductivity of the alloy were detected by electron back-scattered diffractometer,energy dispersive spectroscope,X-ray diffractometer,scanning electron microscope,and transmission electron microscope.The evolution mechanism of the texture during the deformation process and its influence on mechanical properties were analyzed.The results show that directional shear bands form in the CuCrZr alloy during the C-ECAP process,and the preferred orientation of the microstructure is consistent with the rolling direction.After deformation,the number of precipitated phases(mainly Cr)increases with the prolongation of aging time,accompanied by the appearance of micro-nanostructured fibrous structure in the alloy.After C-ECAP for three passes,75%CR deformation,and aging at 450℃ for 2 h,the tensile strength,microhardness,and conductivity reach 538 MPa,168 HV,and 80%IACS,respectively.CR,aging heat treatment,and formation of recrystallization texture are all conducive to the improvement of conductivity.展开更多
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 a potential ground improvement method that can reduce the permeability of sands.However,the traditional mathematical models are hard to accurately predict the permeabilit...Enzyme-induced carbonate precipitation(EICP)is a potential ground improvement method that can reduce the permeability of sands.However,the traditional mathematical models are hard to accurately predict the permeability of EICP-treated sands.In this study,the mathematical model was established for predicting the permeability of EICP-treated sands based on Kozeny-Carman equation.The effects of calcium carbonate precipitation on the porosity,tortuosity,and specific surface area of the EICP-treated sands were considered in the model.To validate the model,the bio-cemented sand column tests with different grain size distributions(coarse,medium,and fine sands)and treatment numbers(6,8,and 10 times)were conducted.The calcium carbonate content(CCC)and permeability of EICP-treated sands were measured.The validation of the model was confirmed through a comparative analysis of theoretical and experimental results.Furthermore,the impacts of porosity,particle size,CCC,and specific surface area on the hydraulic conductivity of EICP-treated sands were analyzed.The results showed that the model can reflect the hydraulic conductivity of EICP-treated sands under different particle size distributions and degrees of cementation,demonstrating broad applicability.Parametric analysis indicated the hydraulic conductivity gradually decreases with increasing CCC and specific surface area.Conversely,the hydraulic conductivity gradually increases with increasing porosity(n)and particle size(d50),with porosity exhibiting a significantly higher sensitivity than particle size.In summary,this study contributes theoretical foundations for the practical implementation of EICP technology in reducing soil permeability.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
To reveal the influence mechanism of Nb/Ti microalloying on the mechanical property of ferritic stainless steel,the grain size,phase composition,microhardness,mechanical properties and fracture morphology are characte...To reveal the influence mechanism of Nb/Ti microalloying on the mechanical property of ferritic stainless steel,the grain size,phase composition,microhardness,mechanical properties and fracture morphology are characterized and analyzed for ferritic stainless steel with single addition of Ti stabilizing element and composite addition of Nb and Ti stabilizing elements.The influence mechanism of Ti and Nb stabilizing elements is elucidated on microstructure and mechanical properties of ferritic stainless steel.Results indicate that the grains are bigger(20-60µm)for ferritic stainless steel containing 0.09 wt.%Ti(F-Ti-ss).The average grain size is about 43.9µm.Meanwhile,there are many granular TiN precipitates with big size.For ferritic stainless steel with Nb and Ti stabilizing elements(F-Nb-Ti-ss),the grains are small(8-22µm),and average grain size is about 17.3µm.There are a few granular TiN precipitates with small size.Furthermore,many nanoscale(Fe,Cr,Nb)C phases precipitate at grain boundary,which plays a role in refining grain size.Compared with mechanical properties of F-Ti-ss(506 MPa and 28.2%),both the ultimate tensile strength and elongation are improved for F-Nb-Ti-ss(573 MPa and 30.5%).The ultimate tensile strength is increased by 13.2%.The main reason is that grains are obviously refined and a large number of nanoscale phases precipitate at grain boundary for F-Nb-Ti-ss.Therefore,strengthening effect is obvious and grain deformation is more uniform during tensile test.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
Autumn rain in western China(ARWC)is a unique and significant precipitation phenomenon that occurs during the summer-to-winter transition of the atmospheric circulation.Using the fifth generation of global climate and...Autumn rain in western China(ARWC)is a unique and significant precipitation phenomenon that occurs during the summer-to-winter transition of the atmospheric circulation.Using the fifth generation of global climate and weather reanalysis data from the European Centre for Medium-Range Weather Forecasts and CN05.1 grid precipitation data,this study examined the anomalous characteristics and mechanisms of ARWC by combining the synergistic effect of the westerly jet and meridional wind.Over the past 60 years,ARWC has exhibited significant interdecadal and interannual variations,as well as a north-south seesaw pattern.The westerly jet index(meridional wind index)exhibited a negative(positive)correlation with precipitation in the northern autumn rain zone(NARZ),and a positive(negative)correlation with precipitation in the southern autumn rain zone(SARZ).The coupling of a weak meridional southerly wind with a southward westerly jet and a strong meridional southerly wind with a northward westerly jet are the two primary modes that synergistically influence the ARWC.These synergistic effects cause significant atmospheric changes throughout the troposphere.The contrasting circulation structure,temperature advection,vertical motion,and water vapor flux contributed to the opposite precipitation anomalies observed in the NARZ and SARZ.A new comprehensive index that reflects the coupled synergistic effect is proposed to characterize the anomalous changes in ARWC.This study improves the understanding of the anomalous characteristics and mechanisms of ARWC.展开更多
Rapid colonization by invasive plants threatened local biodiversity worldwide;however,their distributional hotspots and future habitat shifts remain poorly understood in developing nations such as Nigeria.Using MaxEnt...Rapid colonization by invasive plants threatened local biodiversity worldwide;however,their distributional hotspots and future habitat shifts remain poorly understood in developing nations such as Nigeria.Using MaxEnt model,we investigated present and future habitat suitability for two aggressive invaders,C.odorata and T.diversifolia,across Nigeria's urban landscapes.We used a dataset consisting of 327 and 108 occurrence points for C.odorata and T.diversifolia,respectively,along with twenty-three(23)environmental variables to identify occurrence and areas of concern under current climatic fluctuations.The results revealed that the model performed strongly(AUC>0.85)and identified precipitation seasonality as the dominant predictor for both species.The finding indicates that precipitation seasonality of≤59 CV,isothermality of≥57%and precipitation of wettest month of≥170 mm enhance niche occupancy of C.odorata,while precipitation seasonality of 62-70 CV,precipitation of wettest quarter and maximum temperature of warmest month of≥450 mm and 35℃,respectively enhance that of T.differsifolia.Current predictions place C.odorata primarily along the southern coast,while T.diversifolia is most suitable in the southwest and extends into the northcentral.Future suitable area for C.odorata will slightly expand by 2050 and 2070,encroaching into southeastern and some central states.In contrast,T.diversifolia contracts under CNRM-CM5 but shows a modest expansion under GFDL-CM3.These projections indicate that climate change may reinforce the dominance of C.odorata in southern Nigeria,whereas T.differsifolia may exhibit divergent trajectories from southern to certain northern states in the future.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
Smart pesticide delivery systems based on stimuli-responsive nanocarriers have attracted considerable attention because of their potential to enhance pesticide efficiency while reducing environmental risks.In this stu...Smart pesticide delivery systems based on stimuli-responsive nanocarriers have attracted considerable attention because of their potential to enhance pesticide efficiency while reducing environmental risks.In this study,a novel p H/glutathione dual-responsive pesticide delivery system was constructed through the synthesis of disulfide-bridged hollow mesoporous organosilica nanospheres(HMONs)via the St??ber method,followed by poly(acrylic acid)(PAA)coating through distillation-precipitation polymerization to form HMONs@PAA nanocomposites.The resulting abamectin-loaded system(Abamectin-HMONs@PAA)demonstrated a 12.73% pesticide loading capacity and significantly improved photostability,retaining twice as much active ingredient as free abamectin after 250 h of UV irradiation(36 W).Release studies revealed p H-and glutathione-dependent characteristics,with cumulative releases in acidic conditions exceeding those in neutral and alkaline environments by 18.66% and 40.98%,respectively,and a 14.2% increase in glutathione-containing solution(0.2 mmol·L^(-1) in 70% ethanol)after 97 h.Bioassays showed superior performance against Plutella xylostella,with a 13.33% reduction in survival rate compared to conventional suspension at equivalent dosage(40 mg·L^(-1)),while maintaining efficacy after extensive rainfall simulation(20 events over 10 days).This study provides a promising approach for developing environmentally responsive nanopesticides with enhanced durability and controlled-release properties,offering significant potential for sustainable crop protection.展开更多
The development of a new precipitation-strengthened Ni-based superalloy relies on a seemingly contradictory yet crucial trade-off between‘easy-to-deform’and‘high strength’.Commercial Haynes 282(Ni-20Cr-10Co-8.5Mo-...The development of a new precipitation-strengthened Ni-based superalloy relies on a seemingly contradictory yet crucial trade-off between‘easy-to-deform’and‘high strength’.Commercial Haynes 282(Ni-20Cr-10Co-8.5Mo-2.1Ti-1.5Al)has a good balance of mechanical properties and formability,but it still faces growing concerns regarding material cost and applicability due to the high concentration of Co(∼10 wt%).Therefore,it is necessary to develop Co-free,easy-to-deform and low-cost alloys with thermomechanical processing capabilities and mechanical properties comparable to those of Haynes 282.Both Ni and Fe are selected to replace Co,because the atomic sizes of Fe,Ni and Co are almost identical(∼0.125 nm).Moreover,the moduli of Co and Fe are all 82 GPa,which is only 7%higher than that of Ni(76 GPa).The effects of Co substitution by Ni/Fe on the alloy microstructures and mechanical properties are investigated.Substitution of Co with Ni/Fe does not change the size and volume fraction of theγ′phase,nor does it change the partitioning behavior of elements between theγmatrix andγ′phase.The substitution of Co with Ni/Fe only slightly changes the type of precipitates on grain boundaries(GBs).The newly developed‘Co-free 282’low-cost alloys are not susceptible to stress-accelerated GB oxidation and exhibit great mechanical properties(tensile and creep),which are comparable to the 282 alloy.Current findings not only broaden the alloy selection for applications in extreme environments,but also represent an important trend in the field of precipitation-strengthened superalloys and high/medium entropy alloys to reduce the dependence on strategic high-cost metal Co.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
Recent studies have confirmed the critical and essential role of elemental hydrolysis in metallogenic processes,such as metal migration and precipitation.However,the kinetic processes,characteristics,and formation mec...Recent studies have confirmed the critical and essential role of elemental hydrolysis in metallogenic processes,such as metal migration and precipitation.However,the kinetic processes,characteristics,and formation mechanisms of hydrolyzed precipitates require further comprehensive investigation.This paper is based on a systematic investigation of the hydrolysis mechanisms of Pb and Zn in various systems under ambient temperature and pressure,the storage conditions of the hydrolyzed precipitates,and the characterization of these precipitates.The results indicate that the hydrolysis behaviors of Pb and Zn exhibit significant differences across various systems.Within the monometallic regime,there is a pronounced disparity in the hydrolysis rates between Pb ions and Zn ions.Pb ions demonstrate a substantially higher degree of hydrolysis,a trend that persists over time and remains largely unaffected by the fluid retention or isolation"phenomenon in the surrounding environment.Both hydrolytic precipitation rates were observed to decrease in the mixed system,with Zn ions exhibiting less reduction than Pb ions.After hydrolysis,hydrolyzed precipitates can remain in the fluid environment for extended periods of time,which can lead to re-dissolution.Over time,this re-dissolution can increase,eventually leading to significant loss of hydrolyzed precipitates.The hydrolyzed precipitates obtained from the experiments primarily consisted of alkaline carbonates of Pb and Zn.Notably,the crystalline characteristics of the hydrolysis products of Pb and Zn ions exhibited significant differences across various experimental systems;however,the crystallographic characteristics of the primary hydrolysis products are essentially identical to those of their corresponding natural counterparts.Based on the findings from physical phase analysis and previous research,it is concluded that the hydrolysis process consists of three main stages:oxides/hydroxides,carbonates,and alkali carbonates.In the Pb-Zn-NaCl-H_(2)O system,the proportion of the basic carbonate products of Pb and Zn is 6:2.This research offers an in-depth analysis of the hydrolysis dynamics of lead and zinc under ambient temperature and pressure conditions.Furthermore,it characterizes the crystallization features of the hydrolyzed precipitates and reconstructs the three stages of the formation process.This study holds significant scientific value for understanding the metallogenic mechanisms of Pb and Zn.展开更多
基金Gansu Provincial Department of Education Industrial Support Program Project(2025CYZC-069)Central Government-Guided Local Science and Technology Development Fund Project(25ZYJE002)National Natural Science Foundation of China(51861022,51261016)。
文摘The Cu0.9Cr0.1Zr alloy was deformed through continuous equal channel angular pressing(C-ECAP)through Route A,followed by liquid nitrogen cryogenic rolling(CR)and aging treated at 450℃.The microstructure,mechanical properties,and conductivity of the alloy were detected by electron back-scattered diffractometer,energy dispersive spectroscope,X-ray diffractometer,scanning electron microscope,and transmission electron microscope.The evolution mechanism of the texture during the deformation process and its influence on mechanical properties were analyzed.The results show that directional shear bands form in the CuCrZr alloy during the C-ECAP process,and the preferred orientation of the microstructure is consistent with the rolling direction.After deformation,the number of precipitated phases(mainly Cr)increases with the prolongation of aging time,accompanied by the appearance of micro-nanostructured fibrous structure in the alloy.After C-ECAP for three passes,75%CR deformation,and aging at 450℃ for 2 h,the tensile strength,microhardness,and conductivity reach 538 MPa,168 HV,and 80%IACS,respectively.CR,aging heat treatment,and formation of recrystallization texture are all conducive to the improvement of conductivity.
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)the“Foal Eagle Program”Youth Top-notch Talent Project of Fujian Province,China(Grant No.00387088).
文摘Enzyme-induced carbonate precipitation(EICP)is a potential ground improvement method that can reduce the permeability of sands.However,the traditional mathematical models are hard to accurately predict the permeability of EICP-treated sands.In this study,the mathematical model was established for predicting the permeability of EICP-treated sands based on Kozeny-Carman equation.The effects of calcium carbonate precipitation on the porosity,tortuosity,and specific surface area of the EICP-treated sands were considered in the model.To validate the model,the bio-cemented sand column tests with different grain size distributions(coarse,medium,and fine sands)and treatment numbers(6,8,and 10 times)were conducted.The calcium carbonate content(CCC)and permeability of EICP-treated sands were measured.The validation of the model was confirmed through a comparative analysis of theoretical and experimental results.Furthermore,the impacts of porosity,particle size,CCC,and specific surface area on the hydraulic conductivity of EICP-treated sands were analyzed.The results showed that the model can reflect the hydraulic conductivity of EICP-treated sands under different particle size distributions and degrees of cementation,demonstrating broad applicability.Parametric analysis indicated the hydraulic conductivity gradually decreases with increasing CCC and specific surface area.Conversely,the hydraulic conductivity gradually increases with increasing porosity(n)and particle size(d50),with porosity exhibiting a significantly higher sensitivity than particle size.In summary,this study contributes theoretical foundations for the practical implementation of EICP technology in reducing soil permeability.
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the National Key Research and Development Program of China(Grant No.2023YFB3712400)the National Natural Science Foundation of China(Grant Nos.52027805 and 52204381)Fundamental Research Funds for the Central Universities(Grant No.FRF-TP-24-002A).
文摘To reveal the influence mechanism of Nb/Ti microalloying on the mechanical property of ferritic stainless steel,the grain size,phase composition,microhardness,mechanical properties and fracture morphology are characterized and analyzed for ferritic stainless steel with single addition of Ti stabilizing element and composite addition of Nb and Ti stabilizing elements.The influence mechanism of Ti and Nb stabilizing elements is elucidated on microstructure and mechanical properties of ferritic stainless steel.Results indicate that the grains are bigger(20-60µm)for ferritic stainless steel containing 0.09 wt.%Ti(F-Ti-ss).The average grain size is about 43.9µm.Meanwhile,there are many granular TiN precipitates with big size.For ferritic stainless steel with Nb and Ti stabilizing elements(F-Nb-Ti-ss),the grains are small(8-22µm),and average grain size is about 17.3µm.There are a few granular TiN precipitates with small size.Furthermore,many nanoscale(Fe,Cr,Nb)C phases precipitate at grain boundary,which plays a role in refining grain size.Compared with mechanical properties of F-Ti-ss(506 MPa and 28.2%),both the ultimate tensile strength and elongation are improved for F-Nb-Ti-ss(573 MPa and 30.5%).The ultimate tensile strength is increased by 13.2%.The main reason is that grains are obviously refined and a large number of nanoscale phases precipitate at grain boundary for F-Nb-Ti-ss.Therefore,strengthening effect is obvious and grain deformation is more uniform during tensile test.
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National Natural Science Foundation of China(42030611)Second Tibetan Plateau Scientific Expedition and Research(STEP)Program(2019QZKK0103)。
文摘Autumn rain in western China(ARWC)is a unique and significant precipitation phenomenon that occurs during the summer-to-winter transition of the atmospheric circulation.Using the fifth generation of global climate and weather reanalysis data from the European Centre for Medium-Range Weather Forecasts and CN05.1 grid precipitation data,this study examined the anomalous characteristics and mechanisms of ARWC by combining the synergistic effect of the westerly jet and meridional wind.Over the past 60 years,ARWC has exhibited significant interdecadal and interannual variations,as well as a north-south seesaw pattern.The westerly jet index(meridional wind index)exhibited a negative(positive)correlation with precipitation in the northern autumn rain zone(NARZ),and a positive(negative)correlation with precipitation in the southern autumn rain zone(SARZ).The coupling of a weak meridional southerly wind with a southward westerly jet and a strong meridional southerly wind with a northward westerly jet are the two primary modes that synergistically influence the ARWC.These synergistic effects cause significant atmospheric changes throughout the troposphere.The contrasting circulation structure,temperature advection,vertical motion,and water vapor flux contributed to the opposite precipitation anomalies observed in the NARZ and SARZ.A new comprehensive index that reflects the coupled synergistic effect is proposed to characterize the anomalous changes in ARWC.This study improves the understanding of the anomalous characteristics and mechanisms of ARWC.
文摘Rapid colonization by invasive plants threatened local biodiversity worldwide;however,their distributional hotspots and future habitat shifts remain poorly understood in developing nations such as Nigeria.Using MaxEnt model,we investigated present and future habitat suitability for two aggressive invaders,C.odorata and T.diversifolia,across Nigeria's urban landscapes.We used a dataset consisting of 327 and 108 occurrence points for C.odorata and T.diversifolia,respectively,along with twenty-three(23)environmental variables to identify occurrence and areas of concern under current climatic fluctuations.The results revealed that the model performed strongly(AUC>0.85)and identified precipitation seasonality as the dominant predictor for both species.The finding indicates that precipitation seasonality of≤59 CV,isothermality of≥57%and precipitation of wettest month of≥170 mm enhance niche occupancy of C.odorata,while precipitation seasonality of 62-70 CV,precipitation of wettest quarter and maximum temperature of warmest month of≥450 mm and 35℃,respectively enhance that of T.differsifolia.Current predictions place C.odorata primarily along the southern coast,while T.diversifolia is most suitable in the southwest and extends into the northcentral.Future suitable area for C.odorata will slightly expand by 2050 and 2070,encroaching into southeastern and some central states.In contrast,T.diversifolia contracts under CNRM-CM5 but shows a modest expansion under GFDL-CM3.These projections indicate that climate change may reinforce the dominance of C.odorata in southern Nigeria,whereas T.differsifolia may exhibit divergent trajectories from southern to certain northern states in the future.
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financially supported by the Jiangsu Forestry Science and Technology Innovation and Promotion Project(No.LYKJ-Nanjing[2022]02)the Jiangsu Agricultural Science and Technology Innovation Fund(No.CX(23)3090)。
文摘Smart pesticide delivery systems based on stimuli-responsive nanocarriers have attracted considerable attention because of their potential to enhance pesticide efficiency while reducing environmental risks.In this study,a novel p H/glutathione dual-responsive pesticide delivery system was constructed through the synthesis of disulfide-bridged hollow mesoporous organosilica nanospheres(HMONs)via the St??ber method,followed by poly(acrylic acid)(PAA)coating through distillation-precipitation polymerization to form HMONs@PAA nanocomposites.The resulting abamectin-loaded system(Abamectin-HMONs@PAA)demonstrated a 12.73% pesticide loading capacity and significantly improved photostability,retaining twice as much active ingredient as free abamectin after 250 h of UV irradiation(36 W).Release studies revealed p H-and glutathione-dependent characteristics,with cumulative releases in acidic conditions exceeding those in neutral and alkaline environments by 18.66% and 40.98%,respectively,and a 14.2% increase in glutathione-containing solution(0.2 mmol·L^(-1) in 70% ethanol)after 97 h.Bioassays showed superior performance against Plutella xylostella,with a 13.33% reduction in survival rate compared to conventional suspension at equivalent dosage(40 mg·L^(-1)),while maintaining efficacy after extensive rainfall simulation(20 events over 10 days).This study provides a promising approach for developing environmentally responsive nanopesticides with enhanced durability and controlled-release properties,offering significant potential for sustainable crop protection.
基金supported by the National Natural Science Foundation of China(Grant Nos.52471019 and 52571019)the Zhejiang Provincial Natural Science Foundation of China under Grant No.LR24E010001.
文摘The development of a new precipitation-strengthened Ni-based superalloy relies on a seemingly contradictory yet crucial trade-off between‘easy-to-deform’and‘high strength’.Commercial Haynes 282(Ni-20Cr-10Co-8.5Mo-2.1Ti-1.5Al)has a good balance of mechanical properties and formability,but it still faces growing concerns regarding material cost and applicability due to the high concentration of Co(∼10 wt%).Therefore,it is necessary to develop Co-free,easy-to-deform and low-cost alloys with thermomechanical processing capabilities and mechanical properties comparable to those of Haynes 282.Both Ni and Fe are selected to replace Co,because the atomic sizes of Fe,Ni and Co are almost identical(∼0.125 nm).Moreover,the moduli of Co and Fe are all 82 GPa,which is only 7%higher than that of Ni(76 GPa).The effects of Co substitution by Ni/Fe on the alloy microstructures and mechanical properties are investigated.Substitution of Co with Ni/Fe does not change the size and volume fraction of theγ′phase,nor does it change the partitioning behavior of elements between theγmatrix andγ′phase.The substitution of Co with Ni/Fe only slightly changes the type of precipitates on grain boundaries(GBs).The newly developed‘Co-free 282’low-cost alloys are not susceptible to stress-accelerated GB oxidation and exhibit great mechanical properties(tensile and creep),which are comparable to the 282 alloy.Current findings not only broaden the alloy selection for applications in extreme environments,but also represent an important trend in the field of precipitation-strengthened superalloys and high/medium entropy alloys to reduce the dependence on strategic high-cost metal Co.
基金sponsored by the National Natural Science Foundation of China (grant 42575038)the National Key Research and Development Program of China (grant2022YFF0801702)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financed jointly by the National Natural Science Foundation of China(42472127,42172086)the Yunnan Major Science and Technological Projects(202202AG050014)+2 种基金the Yunnan Major Project of Basic Research(202401BN070001-002)Yunnan Mineral Resources Prediction and Evaluation Engineering Research Center(2011)Innovation Team Program of Kunming University of Science and Technology,Yunnan Province。
文摘Recent studies have confirmed the critical and essential role of elemental hydrolysis in metallogenic processes,such as metal migration and precipitation.However,the kinetic processes,characteristics,and formation mechanisms of hydrolyzed precipitates require further comprehensive investigation.This paper is based on a systematic investigation of the hydrolysis mechanisms of Pb and Zn in various systems under ambient temperature and pressure,the storage conditions of the hydrolyzed precipitates,and the characterization of these precipitates.The results indicate that the hydrolysis behaviors of Pb and Zn exhibit significant differences across various systems.Within the monometallic regime,there is a pronounced disparity in the hydrolysis rates between Pb ions and Zn ions.Pb ions demonstrate a substantially higher degree of hydrolysis,a trend that persists over time and remains largely unaffected by the fluid retention or isolation"phenomenon in the surrounding environment.Both hydrolytic precipitation rates were observed to decrease in the mixed system,with Zn ions exhibiting less reduction than Pb ions.After hydrolysis,hydrolyzed precipitates can remain in the fluid environment for extended periods of time,which can lead to re-dissolution.Over time,this re-dissolution can increase,eventually leading to significant loss of hydrolyzed precipitates.The hydrolyzed precipitates obtained from the experiments primarily consisted of alkaline carbonates of Pb and Zn.Notably,the crystalline characteristics of the hydrolysis products of Pb and Zn ions exhibited significant differences across various experimental systems;however,the crystallographic characteristics of the primary hydrolysis products are essentially identical to those of their corresponding natural counterparts.Based on the findings from physical phase analysis and previous research,it is concluded that the hydrolysis process consists of three main stages:oxides/hydroxides,carbonates,and alkali carbonates.In the Pb-Zn-NaCl-H_(2)O system,the proportion of the basic carbonate products of Pb and Zn is 6:2.This research offers an in-depth analysis of the hydrolysis dynamics of lead and zinc under ambient temperature and pressure conditions.Furthermore,it characterizes the crystallization features of the hydrolyzed precipitates and reconstructs the three stages of the formation process.This study holds significant scientific value for understanding the metallogenic mechanisms of Pb and Zn.
