[Objective] This study aimed to analyze the cause of the generation of short-term heavy precipitations in a regional heavy rainstorm in Shannxi Province. [Method] Taking a heavy rainstorm covering most parts of Shaanx...[Objective] This study aimed to analyze the cause of the generation of short-term heavy precipitations in a regional heavy rainstorm in Shannxi Province. [Method] Taking a heavy rainstorm covering most parts of Shaanxi Province in late July 2010 as an example, data of five Doppler weather radars in Shaanxi Province were employed for a detailed analysis of the evolution of the heavy rainstorm pro- cess. [Result] Besides the good large-scale weather background conditions, the de- velopment and evolution of some mesoscale and small-scale weather systems direct- ly led to short-term heavy precipitations during the heavy rainstorm process, involv- ing the intrusion of moderate IS-scale weak cold air and presence of small-scale wind shear, convergence and adverse wind area. In addition, small-scale convection echoes were arranged in lines and formed a ＂train effect＂, which would also con- tribute to the generation of short-term heavy precipitation. [Conclusion] This study provided basic information for more clear and in-depth analysis of the formation mechanism of short-term heavy precipitations.展开更多
Different multimodel ensemble methods are used to forecast precipitations in China, 1998, and their forecast skills are compared with those of individual models. Datasets were obtained from monthly simulations of eigh...Different multimodel ensemble methods are used to forecast precipitations in China, 1998, and their forecast skills are compared with those of individual models. Datasets were obtained from monthly simulations of eight models during the period of January 1979 to December 1998 from the “Climate of the 20th Century Experiment” （20C3M） for the Fourth IPCC Assessment Report. Climate Research Unit （CRU） data were chosen for the observation analysis field. Root mean square （RMS） error and correlation coeffi-cients （R） are used to measure the forecast skills. In addition, superensemble forecasts based on different input data and weights are analyzed. Results show that for original data, superensemble forecasting based on multiple linear regression （MLR） performs best. However, for bias-corrected data, the superensemble based on singular value decomposition （SVD） produces a lower RMS error and a higher R than in the MLR superensemble. It is an interesting result that the SVD superensemble based on bias-corrected data performs better than the MLR superensemble, but that the SVD superensemble based on original data is inferior to the corresponding MLR superensemble. In addition, weights calculated by different data formats are shown to affect the forecast skills of the superensembles. In comparison with the MLR superensemble, a slightly significant effect is present in the SVD superensemble. However, both the SVD and MLR superensembles based on different weight formats outperform the ensemble mean of bias-corrected data.展开更多
Annealing-regulated precipitation strengthening combined with cold-working is one of the most efficient strategies for resolving the conflict between strength and ductility in metals and alloys.However,precipitation c...Annealing-regulated precipitation strengthening combined with cold-working is one of the most efficient strategies for resolving the conflict between strength and ductility in metals and alloys.However,precipitation control and grain refinement are mutually contradictory due to the excellent phase stability of multicomponent alloys.This work utilizes the high-temperature extrusion and annealing to optimize the microstructures and mechanical properties of the Co_(34)Cr_(32)Ni_(27)Al_(3.5)Ti_(3.5) multicomponent alloy.Hot extrusion effectively reduces grain sizes and simultaneously accelerates the precipitation of coherent L12 nanoparticles inside the face-centered cubic(FCC)matrix and grain boundary precipitations(i.e.,submicron Cr-rich particles and L12-Ni 3(Ti,Al)precipitates),resulting in strongly reciprocal interaction between dislocation slip and hierarchical-scale precipitates.Subsequent annealing regulates grain sizes,dislocations,twins,and precipitates,further allowing to tailor mechanical properties.The high yield strength is attributed to the coupled precipitation strengthening effects from nanoscale coherent L12 particles inside grains and submicron grain boundary precipitates under the support of pre-existing dislocations.The excellent ductility results from the synergistic activation of dislocations,stacking faults,and twins during plastic deformation.The present study provides a promising approach for regulat-ing microstructures,especially defects,and enhancing the mechanical properties of multicomponent alloys.展开更多
Climate change has led human beings to take an interest in the study of meteorological and climatic phenomena. In fact, the main impact of climate change on different sectors of society is caused by extreme events sin...Climate change has led human beings to take an interest in the study of meteorological and climatic phenomena. In fact, the main impact of climate change on different sectors of society is caused by extreme events since the occurrence of extreme events leads to more impact related to change in mean climate. Unfortunately, the West African region is vulnerable to extreme rainfall impact because its economy is based on rain-fed agriculture. This study examined the seasonal variability of extreme rainfall in West Africa. Eight (8) climate indices were chosen from among the 27 defined by the Expert Team on Climate Change Detection and Indices (ETCCDI). The nonparametric Mann-Kendall test was used to assess the seasonal trends. The indices of the same types (frequency or intensity) were compared to assess the intra-seasonal variation of extreme precipitation. The results indicate that, regardless of the season, the Gulf of Guinea receives more rainfall than the Sahel. This phenomenon is due to the fact that the coastal part of West Africa is under the influence of evaporation which is observed at the Atlantic Ocean and during the monsoon, while the other part is dominated by the desert. Mann-Kendall’s test revealed upward and downward trends during each season. The increase in extreme rainfall trends in the number of consecutive dry days suggests that droughts, due to global warming, could be observed and could have severe consequences in terms of water availability, energy supply, agricultural yields and ecosystems in West Africa. In addition, it can lead to the loss of biodiversity and health issues. It is therefore essential for policymakers or decisions makers to determine strategies and mitigation measures against climate change and its impacts on populations.展开更多
Based on the available experimental phase equilibrium relations and aging precipitation sequences,the Mg–Gd–Y ternary system has been thermodynamically re-assessed by means of CALPHAD technique.To simulate the exper...Based on the available experimental phase equilibrium relations and aging precipitation sequences,the Mg–Gd–Y ternary system has been thermodynamically re-assessed by means of CALPHAD technique.To simulate the experimentally reported aging precipitation sequence,α(Mg)_(SS)(supersaturated)→GP zones(D019-type,metastable)→β’-Mg_(7)Gd(c-bco,metastable)→β_(1)-Mg_(3)Gd(fcc,metastable)→β-Mg_(5)Gd(fcc,stable)near the Mg–Gd side,andα(Mg)SS(supersaturated)→β’-Mg_(7)Y(c-bco,metastable)→β-Mg_(24)Y_(5)(bcc,stable)near the Mg–Y side,the effective nucleation driving forces obtained by deducting the nucleation resistances from the thermodynamic driving forces are calculated and analyzed.Two metastable components,GP zones(D019-type)andβ’(c-bco)ordered fromα(Mg)_(SS),do not exist in the stable equilibrium phase diagram but appear in the annealing process of typical alloys.The Redlich–Kister equations are adopted to describe three solution phases,Liquid,HCP_A3 and BCC_A2.The intermediate compounds Mg_(2)Y,Mg_(24)Y_(5),Mg_(2)Gd,Mg_(3)Gd and Mg_(5)Gd are expressed by the formulas of(Mg,Y)_(2/3)(Gd,Mg,Y)_(1/3),Mg_(24/29)(Gd,Mg,Y)_(4/29)Y1/29,(Gd,Mg)_(2/3)(Gd,Mg,Y)_(1/3),(Gd,Mg)_(3/4)(Gd,Mg,Y)_(1/4)and Mg_(5/6)(Gd,Mg,Y)_(1/6),respectively.In particular,the two-sublattice models(Gd,Mg,Y)_(1/2)(Gd,Mg,Y)_(1/2),(Gd,Mg,Y)_(3/4)(Gd,Mg,Y)_(1/4)and(Gd,Mg,Y)_(7/8)(Gd,Mg,Y)_(1/8)have been respectively used to describe the stable Mg(Gd,Y)(BCC_B2)alloy compound as well as the metastable GP zones(D019-type)andβ’(c-bco)phase,in order to cope with the order-disorder transitions.A set of self-consistent thermodynamic parameters has been obtained to ensure the thermodynamic calculations well consistent with the reported experimental data,containing not only the stable equilibrium phase diagram but also the aging precipitation sequence.展开更多
Time-course of oxygen stable isotopic ratios （i.e., δ^18O） as well as seasonal variation of δ^18O has been examined to investigate the characteristics, sources and the passing route of precipitations in Niigata Pr...Time-course of oxygen stable isotopic ratios （i.e., δ^18O） as well as seasonal variation of δ^18O has been examined to investigate the characteristics, sources and the passing route of precipitations in Niigata Prefecture. The precipitation samples have been mainly collected with a filtrating bulk sampler at the rooftop of Niigata University. Furthermore, backward trajectories analyses have been also conducted for these samples taken sequentially for a short period. Consequently, the following features have been mainly clarified for the precipitations in Niigata Prefecture： （1） the δ^18O values varied between -14.57%o and -3.86%0 in the precipitations of Niigata University; （2） as for the comparison among sampling points, the mean value of δ^18O at seaside spots （i.e., Niigata City： -6.93%0） is larger than that of inland spots （Sanjyo City： -8.68%0）; （3） δ^18O value was generally small in the rainy or typhoon season, and relatively large in summer; （4） decreasing δ^18O content with time is a predominant feature of sequentially sampled rainfalls as predicted by Rayleigh models of atmospheric vapor condensation.展开更多
The socio-economic activities of Niger rely on agriculture which is strongly affected by changes in precipitation during the rainy season.The ultimate aim of this study is to assess the projected changes of precipitat...The socio-economic activities of Niger rely on agriculture which is strongly affected by changes in precipitation during the rainy season.The ultimate aim of this study is to assess the projected changes of precipitation over Niger under the Representative Concentration Pathways(RCP)scenarios 4.5(RCP 4.5)and RCP 8.5 using multi-RCM(Multi-Regional Climate)model approach.The observation data are from CHIRPS(Climate Hazards Group InfraRed Precipitation with Station)and the RCMs are from the SMHI(Swedish Meteorological and Hydrological Institute)model(RCA4)driven by ten(10)different GCMs(General Circulation Model)(e.g.,CCCma,CSIRO,ICHEC,IPSL,MIROC,MOHC-HadGEM2,MPI,NCC-NorESM1,NOOA,and NRCM)within the framework of CORDEX(Coordinated Regional Climate Downscaling Experiment)Africa experiment.The reference and projections periods in this study are respectively 1981-2005 for the present and 2011-2100 for the near,medium and far future divided into three periods,2011 to 2040(P1),2041 to 2070(P2)and 2071 to 2100(P3).The methodology used,consists of assessing the performance of the multi-RCMs of RCA4 model(with respect of CHIRPS)in simulating the precipitations changes by computing the spatial distribution and anomalies of precipitations;and their indices of RMSE(Root Mean Square Error),the bias,SPI(Standardized Precipitation Anomaly Index),correlation coefficient,statistical t-test,spatial evolution rate and the rate of temporal change.After the validation of the multi-RCMs RCA4 models,the ensemble mean of the models is used to assess the projected changes of precipitations over Niger in the future.The results show that most of the multi-RCMs capture the four climatic zone except for IPSL.While the ensemble mean of the models simulates(as compared to CHIRPS)more accurately the monthly,annual precipitations anomalies and their indices than individual’s models in the reference period,some RCMs(e.g.,CSIRO-IPSL and CCCma-HadGEM)poorly reproduce them.The projected changes of precipitations indicate for the scenario RCP 4.5 respectively a moderately surplus of precipitation years in the period P1 and moderately deficit years in the period P2 while the period P3 shows a small upward precipitation trend.In contrary,for the scenario RCP 8.5,all the three periods(P1,P2 and P3)indicate an intensification of precipitation leading to a longer wet period which may lead to extreme precipitations and flooding.Moreover,both scenarios have projected an increase of total monthly precipitation in May and September and a decrease in July and August respectively which will likely lead to an early onset and late cessation of the rainy season;and a shift of the peak of the rainy season.Therefore,this study shows the need of a monitoring system for the projected changes of precipitation in the near future to anticipate urgent action in wet/dry periods to adapt to a changing climate.展开更多
In January 2018</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> a high record of monthly total precipitation in northern</span><...In January 2018</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> a high record of monthly total precipitation in northern</span><span style="font-family:Verdana;"> China drew our attention. The precipitation amount is 4 times more than that in normal winters over the past 30 years. Up to now, many research</span><span style="font-family:Verdana;">es</span><span style="font-family:""><span style="font-family:Verdana;"> over the world focus on the intensity of precipitations or the number of intense precipitations, however, no sufficient study is investigated in the continuous </span><span style="font-family:Verdana;">mod</span><span style="font-family:Verdana;">erate precipitations. The abnormal precipitation in January 2018 in northern China is a typical case of the continuous moderate precipitation. The research region is composed by the northern part of the farming-pastoral zone </span><span style="font-family:Verdana;">and the Hulunbuir Grassland. The main method in this study consists of</span><span style="font-family:Verdana;"> ana</span><span style="font-family:Verdana;">lyzing the abnormal precipitation month by identifying the precipitation</span><span style="font-family:Verdana;"> types and locations, and exploring the atmospheric circulations at the moment of typical </span><span style="font-family:Verdana;">precipitations. The research found that the continuity is the key point for</span><span style="font-family:Verdana;"> high precipitation amount in January 2018 in Northern China. Besides, this continuity is caused by frequent appearance of cyclones in the vicinity.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 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
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 a...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
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
The development of cost-effective,strong,and ductile alloys for various temperatures is crucial but challenging for the modern industry.In this study,we designed a series of novel L1_(2)-strengthened(Fe_(58.98)Ni_(31....The development of cost-effective,strong,and ductile alloys for various temperatures is crucial but challenging for the modern industry.In this study,we designed a series of novel L1_(2)-strengthened(Fe_(58.98)Ni_(31.7)Al_(6)Ti_(3)Zr_(0.1)C_(0.2)B_(0.02))_(100-x)Cr_(x)(x=0,4,8,and 13 at%)Fe-based medium-entropy alloys(MEAs).The alloy with 8%Cr content demonstrated optimal mechanical properties from-196℃to 700℃,outperforming numerous MEAs and austenitic stainless steels.At 25℃,it exhibited a yield strength and elongation of~843 MPa and 23%,respectively.Both strength and ductility improved as the temperature decreased from 25℃to-196℃.The excellent mechanical properties at 25℃are attributed to the synergistic effects of L1_(2)nanoprecipitates,dislocations,slip bands,and stacking faults.In the sample deformed at-196℃,Lomer-Cottrell locks were also observed.Furthermore,at 700℃,the MEA maintains a high yield strength of~766 MPa and elongations of 26%,which is attributed to the shearing of L1_(2)precipitate and dislocation slips.This study provides a foundation for developing advanced alloys for use across a wide temperature range.展开更多
Overcoming the strength-ductility trade-off in alloys without complex post-processing remains a critical challenge.Here,we designed a hierarchical heterostructure of micro-cellular segregation(MCS)and supranano precip...Overcoming the strength-ductility trade-off in alloys without complex post-processing remains a critical challenge.Here,we designed a hierarchical heterostructure of micro-cellular segregation(MCS)and supranano precipitates(SNPs)in the directly cast medium-entropy alloy(MEA),achieving higher strength without a significant loss of plasticity.This MCS-SNP alloy exhibits a superior combination of tensile strength(~922 MPa)and elongation(~32%)compared with most traditional ascast face-centered cubic(FCC)alloys.The MCS impedes the movement of the slip bands and maintains the flow stress in the work-hardening process.The SNPs enhance the pinning effect of dislocations,providing an additional source of work hardening together with microbands.The synergistic effect of MCS and SNP generates significant back stress at both micro and nano scales.The findings of this study provide a promising strategy for designing high-performance casting alloys with integrated microscale cellular segregation and supranano precipitate structures.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
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Supported by Special Fund for National Weather Service Forecaster of China (CMAYBY2011-050)~~
文摘[Objective] This study aimed to analyze the cause of the generation of short-term heavy precipitations in a regional heavy rainstorm in Shannxi Province. [Method] Taking a heavy rainstorm covering most parts of Shaanxi Province in late July 2010 as an example, data of five Doppler weather radars in Shaanxi Province were employed for a detailed analysis of the evolution of the heavy rainstorm pro- cess. [Result] Besides the good large-scale weather background conditions, the de- velopment and evolution of some mesoscale and small-scale weather systems direct- ly led to short-term heavy precipitations during the heavy rainstorm process, involv- ing the intrusion of moderate IS-scale weak cold air and presence of small-scale wind shear, convergence and adverse wind area. In addition, small-scale convection echoes were arranged in lines and formed a ＂train effect＂, which would also con- tribute to the generation of short-term heavy precipitation. [Conclusion] This study provided basic information for more clear and in-depth analysis of the formation mechanism of short-term heavy precipitations.
文摘Different multimodel ensemble methods are used to forecast precipitations in China, 1998, and their forecast skills are compared with those of individual models. Datasets were obtained from monthly simulations of eight models during the period of January 1979 to December 1998 from the “Climate of the 20th Century Experiment” （20C3M） for the Fourth IPCC Assessment Report. Climate Research Unit （CRU） data were chosen for the observation analysis field. Root mean square （RMS） error and correlation coeffi-cients （R） are used to measure the forecast skills. In addition, superensemble forecasts based on different input data and weights are analyzed. Results show that for original data, superensemble forecasting based on multiple linear regression （MLR） performs best. However, for bias-corrected data, the superensemble based on singular value decomposition （SVD） produces a lower RMS error and a higher R than in the MLR superensemble. It is an interesting result that the SVD superensemble based on bias-corrected data performs better than the MLR superensemble, but that the SVD superensemble based on original data is inferior to the corresponding MLR superensemble. In addition, weights calculated by different data formats are shown to affect the forecast skills of the superensembles. In comparison with the MLR superensemble, a slightly significant effect is present in the SVD superensemble. However, both the SVD and MLR superensembles based on different weight formats outperform the ensemble mean of bias-corrected data.
基金financially supported by the National Natural Science Foun-dation of China (No.51871132)the opening project of the State Key Laboratory of Explosion Science and Technology (Beijing Insti-tutes of Technology) (No.KFJJ21-08M)+4 种基金the Shenzhen Science and Technology Program (No.JCYJ20210324121011031)the Free Exploring Basic Research Project of Shenzhen Virtual University Park (No.2021Szvup069)the Natural Science Foundation of Shandong Province (No.ZR2020ME002)Additional support from the China Scholarship Council (CSC,No.201906220226)the Ministry of Education and Science of the Russian Federation within the frame-work of the Increase Competitiveness Program of MISiS (No.K1-2022-032)is gratefully acknowledged.
文摘Annealing-regulated precipitation strengthening combined with cold-working is one of the most efficient strategies for resolving the conflict between strength and ductility in metals and alloys.However,precipitation control and grain refinement are mutually contradictory due to the excellent phase stability of multicomponent alloys.This work utilizes the high-temperature extrusion and annealing to optimize the microstructures and mechanical properties of the Co_(34)Cr_(32)Ni_(27)Al_(3.5)Ti_(3.5) multicomponent alloy.Hot extrusion effectively reduces grain sizes and simultaneously accelerates the precipitation of coherent L12 nanoparticles inside the face-centered cubic(FCC)matrix and grain boundary precipitations(i.e.,submicron Cr-rich particles and L12-Ni 3(Ti,Al)precipitates),resulting in strongly reciprocal interaction between dislocation slip and hierarchical-scale precipitates.Subsequent annealing regulates grain sizes,dislocations,twins,and precipitates,further allowing to tailor mechanical properties.The high yield strength is attributed to the coupled precipitation strengthening effects from nanoscale coherent L12 particles inside grains and submicron grain boundary precipitates under the support of pre-existing dislocations.The excellent ductility results from the synergistic activation of dislocations,stacking faults,and twins during plastic deformation.The present study provides a promising approach for regulat-ing microstructures,especially defects,and enhancing the mechanical properties of multicomponent alloys.
文摘Climate change has led human beings to take an interest in the study of meteorological and climatic phenomena. In fact, the main impact of climate change on different sectors of society is caused by extreme events since the occurrence of extreme events leads to more impact related to change in mean climate. Unfortunately, the West African region is vulnerable to extreme rainfall impact because its economy is based on rain-fed agriculture. This study examined the seasonal variability of extreme rainfall in West Africa. Eight (8) climate indices were chosen from among the 27 defined by the Expert Team on Climate Change Detection and Indices (ETCCDI). The nonparametric Mann-Kendall test was used to assess the seasonal trends. The indices of the same types (frequency or intensity) were compared to assess the intra-seasonal variation of extreme precipitation. The results indicate that, regardless of the season, the Gulf of Guinea receives more rainfall than the Sahel. This phenomenon is due to the fact that the coastal part of West Africa is under the influence of evaporation which is observed at the Atlantic Ocean and during the monsoon, while the other part is dominated by the desert. Mann-Kendall’s test revealed upward and downward trends during each season. The increase in extreme rainfall trends in the number of consecutive dry days suggests that droughts, due to global warming, could be observed and could have severe consequences in terms of water availability, energy supply, agricultural yields and ecosystems in West Africa. In addition, it can lead to the loss of biodiversity and health issues. It is therefore essential for policymakers or decisions makers to determine strategies and mitigation measures against climate change and its impacts on populations.
基金the National Key Research and Development Program of China(No.2016YFB0701201)the National Natural Science Foundation of China(No.52071011)for the financial supports.
文摘Based on the available experimental phase equilibrium relations and aging precipitation sequences,the Mg–Gd–Y ternary system has been thermodynamically re-assessed by means of CALPHAD technique.To simulate the experimentally reported aging precipitation sequence,α(Mg)_(SS)(supersaturated)→GP zones(D019-type,metastable)→β’-Mg_(7)Gd(c-bco,metastable)→β_(1)-Mg_(3)Gd(fcc,metastable)→β-Mg_(5)Gd(fcc,stable)near the Mg–Gd side,andα(Mg)SS(supersaturated)→β’-Mg_(7)Y(c-bco,metastable)→β-Mg_(24)Y_(5)(bcc,stable)near the Mg–Y side,the effective nucleation driving forces obtained by deducting the nucleation resistances from the thermodynamic driving forces are calculated and analyzed.Two metastable components,GP zones(D019-type)andβ’(c-bco)ordered fromα(Mg)_(SS),do not exist in the stable equilibrium phase diagram but appear in the annealing process of typical alloys.The Redlich–Kister equations are adopted to describe three solution phases,Liquid,HCP_A3 and BCC_A2.The intermediate compounds Mg_(2)Y,Mg_(24)Y_(5),Mg_(2)Gd,Mg_(3)Gd and Mg_(5)Gd are expressed by the formulas of(Mg,Y)_(2/3)(Gd,Mg,Y)_(1/3),Mg_(24/29)(Gd,Mg,Y)_(4/29)Y1/29,(Gd,Mg)_(2/3)(Gd,Mg,Y)_(1/3),(Gd,Mg)_(3/4)(Gd,Mg,Y)_(1/4)and Mg_(5/6)(Gd,Mg,Y)_(1/6),respectively.In particular,the two-sublattice models(Gd,Mg,Y)_(1/2)(Gd,Mg,Y)_(1/2),(Gd,Mg,Y)_(3/4)(Gd,Mg,Y)_(1/4)and(Gd,Mg,Y)_(7/8)(Gd,Mg,Y)_(1/8)have been respectively used to describe the stable Mg(Gd,Y)(BCC_B2)alloy compound as well as the metastable GP zones(D019-type)andβ’(c-bco)phase,in order to cope with the order-disorder transitions.A set of self-consistent thermodynamic parameters has been obtained to ensure the thermodynamic calculations well consistent with the reported experimental data,containing not only the stable equilibrium phase diagram but also the aging precipitation sequence.
文摘Time-course of oxygen stable isotopic ratios （i.e., δ^18O） as well as seasonal variation of δ^18O has been examined to investigate the characteristics, sources and the passing route of precipitations in Niigata Prefecture. The precipitation samples have been mainly collected with a filtrating bulk sampler at the rooftop of Niigata University. Furthermore, backward trajectories analyses have been also conducted for these samples taken sequentially for a short period. Consequently, the following features have been mainly clarified for the precipitations in Niigata Prefecture： （1） the δ^18O values varied between -14.57%o and -3.86%0 in the precipitations of Niigata University; （2） as for the comparison among sampling points, the mean value of δ^18O at seaside spots （i.e., Niigata City： -6.93%0） is larger than that of inland spots （Sanjyo City： -8.68%0）; （3） δ^18O value was generally small in the rainy or typhoon season, and relatively large in summer; （4） decreasing δ^18O content with time is a predominant feature of sequentially sampled rainfalls as predicted by Rayleigh models of atmospheric vapor condensation.
基金We thank the late Professor Fode MADE for his contribution in this work,may his soul stay in peace in paradise.
文摘The socio-economic activities of Niger rely on agriculture which is strongly affected by changes in precipitation during the rainy season.The ultimate aim of this study is to assess the projected changes of precipitation over Niger under the Representative Concentration Pathways(RCP)scenarios 4.5(RCP 4.5)and RCP 8.5 using multi-RCM(Multi-Regional Climate)model approach.The observation data are from CHIRPS(Climate Hazards Group InfraRed Precipitation with Station)and the RCMs are from the SMHI(Swedish Meteorological and Hydrological Institute)model(RCA4)driven by ten(10)different GCMs(General Circulation Model)(e.g.,CCCma,CSIRO,ICHEC,IPSL,MIROC,MOHC-HadGEM2,MPI,NCC-NorESM1,NOOA,and NRCM)within the framework of CORDEX(Coordinated Regional Climate Downscaling Experiment)Africa experiment.The reference and projections periods in this study are respectively 1981-2005 for the present and 2011-2100 for the near,medium and far future divided into three periods,2011 to 2040(P1),2041 to 2070(P2)and 2071 to 2100(P3).The methodology used,consists of assessing the performance of the multi-RCMs of RCA4 model(with respect of CHIRPS)in simulating the precipitations changes by computing the spatial distribution and anomalies of precipitations;and their indices of RMSE(Root Mean Square Error),the bias,SPI(Standardized Precipitation Anomaly Index),correlation coefficient,statistical t-test,spatial evolution rate and the rate of temporal change.After the validation of the multi-RCMs RCA4 models,the ensemble mean of the models is used to assess the projected changes of precipitations over Niger in the future.The results show that most of the multi-RCMs capture the four climatic zone except for IPSL.While the ensemble mean of the models simulates(as compared to CHIRPS)more accurately the monthly,annual precipitations anomalies and their indices than individual’s models in the reference period,some RCMs(e.g.,CSIRO-IPSL and CCCma-HadGEM)poorly reproduce them.The projected changes of precipitations indicate for the scenario RCP 4.5 respectively a moderately surplus of precipitation years in the period P1 and moderately deficit years in the period P2 while the period P3 shows a small upward precipitation trend.In contrary,for the scenario RCP 8.5,all the three periods(P1,P2 and P3)indicate an intensification of precipitation leading to a longer wet period which may lead to extreme precipitations and flooding.Moreover,both scenarios have projected an increase of total monthly precipitation in May and September and a decrease in July and August respectively which will likely lead to an early onset and late cessation of the rainy season;and a shift of the peak of the rainy season.Therefore,this study shows the need of a monitoring system for the projected changes of precipitation in the near future to anticipate urgent action in wet/dry periods to adapt to a changing climate.
文摘In January 2018</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> a high record of monthly total precipitation in northern</span><span style="font-family:Verdana;"> China drew our attention. The precipitation amount is 4 times more than that in normal winters over the past 30 years. Up to now, many research</span><span style="font-family:Verdana;">es</span><span style="font-family:""><span style="font-family:Verdana;"> over the world focus on the intensity of precipitations or the number of intense precipitations, however, no sufficient study is investigated in the continuous </span><span style="font-family:Verdana;">mod</span><span style="font-family:Verdana;">erate precipitations. The abnormal precipitation in January 2018 in northern China is a typical case of the continuous moderate precipitation. The research region is composed by the northern part of the farming-pastoral zone </span><span style="font-family:Verdana;">and the Hulunbuir Grassland. The main method in this study consists of</span><span style="font-family:Verdana;"> ana</span><span style="font-family:Verdana;">lyzing the abnormal precipitation month by identifying the precipitation</span><span style="font-family:Verdana;"> types and locations, and exploring the atmospheric circulations at the moment of typical </span><span style="font-family:Verdana;">precipitations. The research found that the continuity is the key point for</span><span style="font-family:Verdana;"> high precipitation amount in January 2018 in Northern China. Besides, this continuity is caused by frequent appearance of cyclones in the vicinity.
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.
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supported by the National Natural Science Foundation of China(Grant Nos.52101053,52371078)。
文摘The development of cost-effective,strong,and ductile alloys for various temperatures is crucial but challenging for the modern industry.In this study,we designed a series of novel L1_(2)-strengthened(Fe_(58.98)Ni_(31.7)Al_(6)Ti_(3)Zr_(0.1)C_(0.2)B_(0.02))_(100-x)Cr_(x)(x=0,4,8,and 13 at%)Fe-based medium-entropy alloys(MEAs).The alloy with 8%Cr content demonstrated optimal mechanical properties from-196℃to 700℃,outperforming numerous MEAs and austenitic stainless steels.At 25℃,it exhibited a yield strength and elongation of~843 MPa and 23%,respectively.Both strength and ductility improved as the temperature decreased from 25℃to-196℃.The excellent mechanical properties at 25℃are attributed to the synergistic effects of L1_(2)nanoprecipitates,dislocations,slip bands,and stacking faults.In the sample deformed at-196℃,Lomer-Cottrell locks were also observed.Furthermore,at 700℃,the MEA maintains a high yield strength of~766 MPa and elongations of 26%,which is attributed to the shearing of L1_(2)precipitate and dislocation slips.This study provides a foundation for developing advanced alloys for use across a wide temperature range.
基金supported by the National Natural Science Foundation of China(Grant Nos.52401215,52271149,52301209,52401214,52201183)the Shanghai Magnolia Talent Plan Pujiang Project(Grant No.24PJD035)+3 种基金the Open Research Fund of Songshan Lake Materials Laboratory(Grant No.2023SLABFN07)the Technology Plan Program of Shanghai Municipal Commission of Science and Technology(Grant No.25CL2902300)the Shanghai Science and Technology Innovation Action Plan(Grant No.24CL2901500)the Shanghai Municipal Explorer Program(Grant No.25TS1401900)。
文摘Overcoming the strength-ductility trade-off in alloys without complex post-processing remains a critical challenge.Here,we designed a hierarchical heterostructure of micro-cellular segregation(MCS)and supranano precipitates(SNPs)in the directly cast medium-entropy alloy(MEA),achieving higher strength without a significant loss of plasticity.This MCS-SNP alloy exhibits a superior combination of tensile strength(~922 MPa)and elongation(~32%)compared with most traditional ascast face-centered cubic(FCC)alloys.The MCS impedes the movement of the slip bands and maintains the flow stress in the work-hardening process.The SNPs enhance the pinning effect of dislocations,providing an additional source of work hardening together with microbands.The synergistic effect of MCS and SNP generates significant back stress at both micro and nano scales.The findings of this study provide a promising strategy for designing high-performance casting alloys with integrated microscale cellular segregation and supranano precipitate structures.
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.
