[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 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
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.
