Co3O4 catalysts prepared with different precipitants（NH3·H2O,KOH,NH4HCO3,K2CO3 and KHCO3）were investigated for the oxidation of formaldehyde（HCHO）.Among these,KHCO3-precipitated Co3O4（KHCO3-Co） was the most...Co3O4 catalysts prepared with different precipitants（NH3·H2O,KOH,NH4HCO3,K2CO3 and KHCO3）were investigated for the oxidation of formaldehyde（HCHO）.Among these,KHCO3-precipitated Co3O4（KHCO3-Co） was the most active low-temperature catalyst,and was able to completely oxidize HCHO at the 100-ppm level to CO2 at 90℃.In situ diffuse reflectance infrared spectroscopy demonstrated that hydroxyl groups on the catalyst surface were regenerated by K~＋ and CO3^（2-）,thus promoting the oxidation of HCHO.Moreover,H2-temperature programmed reduction and X-ray photoelectron spectroscopy showed that employing KHCO3 as the precipitant increased the Co^3＋/Co^2＋molar ratio on the surface of the Co3O4 catalyst,thus further promoting oxidation.Structural characterization revealed that catalysts precipitated with carbonate or bicarbonate reagents exhibited greater specific surface areas and pore volumes.Overall,these data suggest that the high activity observed during the Co3O4 catalyzed oxidation of HCHO can be primarily attributed to the presence of K~＋ and CO3^（2-） on the Co3O4 surface and the favorable Co^3＋/Co^2＋ ratio.展开更多
A series of Ni-CeO2 catalysts were prepared by co-precipitation method with Na2CO3, NaOH, and mixed precipitant （Na2CO3：NaOH; 1：1 ratio） as precipitant, respectively. The effect of the precipitants on the catalyti...A series of Ni-CeO2 catalysts were prepared by co-precipitation method with Na2CO3, NaOH, and mixed precipitant （Na2CO3：NaOH; 1：1 ratio） as precipitant, respectively. The effect of the precipitants on the catalytic performance, physical and chemical properties of Ni-CeO2 catalysts was investigated with the aid of X-ray diffraction （XRD）, Bmmaner-Emmett-Teller method （BET）, Fou- rier-transform infrared spectroscopy （FT-IR）, thermogravimetry （TG）, and H2-TPR characterizations. The Ni-CeO2 catalysts were exam- ined with respect to their catalytic performance for the reverse water-gas shift reaction, and their catalytic activities were ranked as： Ni-CeO2-CP （Na2CO3：NaOH=I：I）〉Ni-CeO2-CP（Na2CO3）〉Ni-CeO2-CP（NaOH）- Correlating to the characteristic results, it was found that the catalyst prepared by co-precipitation with mixed precipitant （Na2CO3：NaOH; 1：1 ratio） as precipitant hadthe most amount of oxygen vacancies accompanied with highly dispersed Ni particles, which made the corresponding Ni-CeO2-CP（Na2CO3：NaOH=I： 1） catalyst exhibit the highest catalytic activity. While the precipitant of Na2CO3 or NaOH resulted in less or no oxygen vacancies in Ni-CeO2 catalysts. As a result, Ni-CeO2-CP（Na2CO3） and Ni-CeO2-CP（NaOH） catalysts presented poor catalytic performance.展开更多
Novel precipitant prepared through carbonation with MgCl2 wastewater generated from rare earth extraction separation process and low-price dolomite as raw materials was studied in this paper. The purification methods ...Novel precipitant prepared through carbonation with MgCl2 wastewater generated from rare earth extraction separation process and low-price dolomite as raw materials was studied in this paper. The purification methods of novel precipitant by adding appropriate oxidizing agent were studied. It was found that optimal purification result could be achieved with sodium hypochlorite as iron removal reagent and the iron removal rate could reach up to 90% when the adding amount was 0.1 vol.%. During the preparation, the particle size and distribution of ceria-based polishing powder were affected obviously by the parameters such as concentration, reaction temperature and feeding rate. The results showed that ceria-based polishing powder with D50 =2.5-3.5 μm and the particle size distribution of 0.65-0.75 μm could be prepared when the concentration of CeCl3 was 0.6 mol/L, the reaction temperature was maintained at 50 °C and the feeding speed was controlled at 25 ml/min. Compared with commercial powder, the self-made polishing powder had roughly the same cutting amount, but the surface finish of polished glass was better than that of commercial polishing powder.展开更多
Compressed natural gas（CNG）is most appropriate an alternative of conventional fuel for automobiles.However,emissions of carbon-monoxide and methane from such vehicles adversely affect human health and environment.Co...Compressed natural gas（CNG）is most appropriate an alternative of conventional fuel for automobiles.However,emissions of carbon-monoxide and methane from such vehicles adversely affect human health and environment.Consequently,to abate emissions from CNG vehicles,development of highly efficient and inexpensive catalysts is necessary.Thus,the present work attempts to scan the effects of precipitants（Na2CO3,KOH and urea）for nickel cobaltite（Ni Co2O4）catalysts prepared by co-precipitation from nitrate solutions and calcined in a lean CO-air mixture at 400℃.The catalysts were used for oxidation of a mixture of CO and CH4（1：1）.The catalysts were characterized by X-ray diffractometer,Brunauer–Emmett–Teller surface-area,X-ray photoelectron spectroscopy;temperature programmedreductionandScanningelectronmicroscopycoupledwith Energy-Dispersive X-Ray Spectroscopy.The Na2CO3was adjudged as the best precipitant for production of catalyst,which completely oxidized CO-CH4mixture at the lowest temperature（T（100）=350℃）.Whereas,for catalyst prepared using urea,T（100）=362℃.On the other hand the conversion of CO-CH4mixture over the catalyst synthesized by KOH limited to 97%even beyond 400℃.Further,the effect of higher calcination temperatures of 500 and600℃ was examined for the best catalyst.The total oxidation of the mixture was attained at higher temperatures of 375 and 410℃ over catalysts calcined at 500 and 600℃ respectively.Thus,the best precipitant established was Na2CO3and the optimum calcination temperature of 400℃ was found to synthesize the Ni Co2O4catalyst for the best performance in CO-CH4oxidation.展开更多
Heart Failure (HF) is a syndrome characterized by typical symptoms (e.g. breathlessness, ankle swelling and fatigue) that may be accompanied by signs (e.g. elevated jugular venous pressure, pulmonary crackles and peri...Heart Failure (HF) is a syndrome characterized by typical symptoms (e.g. breathlessness, ankle swelling and fatigue) that may be accompanied by signs (e.g. elevated jugular venous pressure, pulmonary crackles and peripheral oedema) caused by a structural and/or functional cardiac abnormality, resulting in a reduced cardiac output and/or elevated intracardiac pressures at rest or during stress. Clinical studies investigating the aetiological patterns of heart failure in Sub-Saharan Africa (SSA) revealed that hypertension, cardiomyopathy and rheumatic heart disease account for more than two-thirds of cardiac disease cases. The objective of this study therefore is to assess the pattern, precipitating factors and short term outcome of heart failure among patients admitted into our hospital. Method: The study was a prospective cross-sectional type conducted among in patients with heart failure in the medical ward of the hospital. Results: A total of three and fifty four (354) subjects were recruited into the study, comprising one hundred and twenty nine males (36.4%) and two hundred and twenty five (63.4%) females. Majority of the patients were admitted in NYHA functional class IV. This however improved to class II at discharge though few were discharged in NYHA class III. Heart failure secondary to progressive hypertensive heart disease was the most common (39.0%) followed by peripartum cardiomyopathy (22.6%) while idiopathic dilated cardiomyopathy (11.0%) and rheumatic heart disease (7.3%) were the third and fourth causes of heart failure respectively. The most common precipitating factor for heart failure in this study was chest infection (44.9%). In conclusion, the study revealed that progressive hypertensive heart disease was the leading cause of heart failure, followed by peripartum cardiomyopathy while idiopathic dilated cardiomyopathy and rheumatic heart disease were ranked third and fourth causes of heart failure respectively. Though myocardial infarction is on the increase, it was found to be the fifth cause of heart failure. The study also identified the following precipitants of heart failure in decreasing order of occurrence: chest infection, non-adherence to prescription, and urinary tract infection.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
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
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
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
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
This study investigated the characteristics and mechanisms of summer regional persistent extreme precipitation events(RPEPEs)over South China(SC)modulated by distinct intensity regimes of 10-30-day intraseasonal oscil...This study investigated the characteristics and mechanisms of summer regional persistent extreme precipitation events(RPEPEs)over South China(SC)modulated by distinct intensity regimes of 10-30-day intraseasonal oscillation(ISO).Diagnostic analyses revealed that the spatiotemporal evolution of RPEPEs exhibits robust phase-locking with the 10-30-day intraseasonal precipitation.By classifying RPEPEs into strong-ISO(SRPEPE)and weak-ISO(WRPEPE)composites based on the amplitude of 10-30-day filtered precipitation,we demonstrate a 14.6%enhancement in peak precipitation intensity during SRPEPEs compared to WRPEPEs.These distinct precipitation regimes are governed by fundamentally different Rossby wave teleconnection patterns over Eurasia.During SRPEPEs,a robust southeastward-propagating 10-30-day Rossby wave train originating from the Barents Sea traverses midlatitude Eurasia,effectively perturbing the northwestern Pacific upper-level circulation and establishing a favorable dynamic environment over SC.In contrast,WRPEPEs are associated with weaker eastward-propagating wave trains constrained along the subtropical jet stream.The horizontal convergence of background moisture driven by 10-30-day winds significantly amplifies lower-tropospheric humidity during SRPEPEs.The thermal advection of background temperature by 10-30-day geostrophic winds enhances baroclinic instability and vertical motion,intensifying precipitation under these moisture conditions.展开更多
Recent studies have confirmed the critical and essential role of elemental hydrolysis in metallogenic processes,such as metal migration and precipitation.However,the kinetic processes,characteristics,and formation mec...Recent studies have confirmed the critical and essential role of elemental hydrolysis in metallogenic processes,such as metal migration and precipitation.However,the kinetic processes,characteristics,and formation mechanisms of hydrolyzed precipitates require further comprehensive investigation.This paper is based on a systematic investigation of the hydrolysis mechanisms of Pb and Zn in various systems under ambient temperature and pressure,the storage conditions of the hydrolyzed precipitates,and the characterization of these precipitates.The results indicate that the hydrolysis behaviors of Pb and Zn exhibit significant differences across various systems.Within the monometallic regime,there is a pronounced disparity in the hydrolysis rates between Pb ions and Zn ions.Pb ions demonstrate a substantially higher degree of hydrolysis,a trend that persists over time and remains largely unaffected by the fluid retention or isolation"phenomenon in the surrounding environment.Both hydrolytic precipitation rates were observed to decrease in the mixed system,with Zn ions exhibiting less reduction than Pb ions.After hydrolysis,hydrolyzed precipitates can remain in the fluid environment for extended periods of time,which can lead to re-dissolution.Over time,this re-dissolution can increase,eventually leading to significant loss of hydrolyzed precipitates.The hydrolyzed precipitates obtained from the experiments primarily consisted of alkaline carbonates of Pb and Zn.Notably,the crystalline characteristics of the hydrolysis products of Pb and Zn ions exhibited significant differences across various experimental systems;however,the crystallographic characteristics of the primary hydrolysis products are essentially identical to those of their corresponding natural counterparts.Based on the findings from physical phase analysis and previous research,it is concluded that the hydrolysis process consists of three main stages:oxides/hydroxides,carbonates,and alkali carbonates.In the Pb-Zn-NaCl-H_(2)O system,the proportion of the basic carbonate products of Pb and Zn is 6:2.This research offers an in-depth analysis of the hydrolysis dynamics of lead and zinc under ambient temperature and pressure conditions.Furthermore,it characterizes the crystallization features of the hydrolyzed precipitates and reconstructs the three stages of the formation process.This study holds significant scientific value for understanding the metallogenic mechanisms of Pb and Zn.展开更多
To investigate the effects of extrusion temperature on the microstructure and mechanical properties of WE43 magnesium alloy,extrusion experiments were conducted under 330,380,430,and 450℃,and the extrusion ratio was ...To investigate the effects of extrusion temperature on the microstructure and mechanical properties of WE43 magnesium alloy,extrusion experiments were conducted under 330,380,430,and 450℃,and the extrusion ratio was 16.The experimental results indicate that,at a low temperature of 330℃,the alloy precipitates a large amount of second phases rich in Zr elements.Moreover,the texture strength and kernel average misorientation value are the highest,with values of 27.77 and 0.71,respectively.The increase in extrusion temperature leads to a gradual decrease in texture strength and kernel average misorientation value.The strength of the alloy is the highest at an extrusion temperature of 330℃.Its tensile yield stress is 254.7 MPa and ultimate tensile strength is 302.7 MPa,respectively.As the extrusion temperature increases,the strength of the alloy gradually decreases.At an extrusion temperature of 450℃,the tensile yield stress is 181.3 MPa and ultimate tensile strength is 265.7 MPa,respectively.The elongation first increases and then decreases,with an elongation of 20.9%at an extrusion temperature of 330℃.At an extrusion temperature of 430℃,the elongation reaches its maximum value,which is 23.6%.At an extrusion temperature of 450℃,the elongation reaches its lowest value,which is 16.4%.展开更多
This study investigates the width of the secondary eyewall(SE)immediately following its formation in tropical cyclones with surface environmental winds aligned and counter-aligned with environmental vertical wind shea...This study investigates the width of the secondary eyewall(SE)immediately following its formation in tropical cyclones with surface environmental winds aligned and counter-aligned with environmental vertical wind shear(VWS),using idealized numerical experiments.Results reveal that the SE develops greater radial extent when surface winds align with VWS compared to counter-aligned conditions.In alignment configurations,shear-enhanced surface winds on the right flank amplify surface enthalpy fluxes,thereby elevating boundary-layer entropy within the downshear outer-core region.Subsequently,more vigorous outer rainbands develop,inducing marked acceleration of tangential winds in the outer core preceding SE formation.The resultant radial expansion of supergradient winds near the boundary-layer top triggers widespread convective activity immediately beyond the inner core.Progressive axisymmetrization of this convective forcing ultimately generates an expansive SE structure.展开更多
Selective laser melting(SLM)is an advanced additive manufacturing technique that enables the fabrication of complex metal components with high density,precision,and design flexibility.A novel Sc-free Al-4.58Mg-1.17Mn-...Selective laser melting(SLM)is an advanced additive manufacturing technique that enables the fabrication of complex metal components with high density,precision,and design flexibility.A novel Sc-free Al-4.58Mg-1.17Mn-1.59Zr-1.45Ti alloy was successfully fabricated via SLM,achieving a relative density of~99.89%.The microstructure of the as-fabricated alloy was characterized by scanning electron microscopy and transmission electron microscopy,which revealed refined equiaxed grains,a high density of low-angle grain boundaries and dislocation structures,as well as Mg segregation along grain boundaries.Additionally,a variety of dispersed precipitates were identified,including Mg-containing oxides,L1_(2)-Al_(3)(Ti_(x),Zr_(1−x)),and Al_(3)Zr particles.Room-temperature tensile tests showed that the alloy exhibits an excellent combination of strength and ductility,with a yield strength of 453.2±12 MPa,an ultimate tensile strength of 515.1±8 MPa,and an elongation of 22.5%±0.3%.The high strength was attributed to the combined effects of grain boundary strengthening,solid solution strengthening,precipitation strengthening,and dislocation strengthening.The developed Sc-free Al-Mg-Mn-Zr-Ti alloy demonstrates significant potential as an economical high-strength lightweight material for SLM-based manufacturing applications.展开更多
基金supported by the National Natural Science Foundation of China(21577088)~~
文摘Co3O4 catalysts prepared with different precipitants（NH3·H2O,KOH,NH4HCO3,K2CO3 and KHCO3）were investigated for the oxidation of formaldehyde（HCHO）.Among these,KHCO3-precipitated Co3O4（KHCO3-Co） was the most active low-temperature catalyst,and was able to completely oxidize HCHO at the 100-ppm level to CO2 at 90℃.In situ diffuse reflectance infrared spectroscopy demonstrated that hydroxyl groups on the catalyst surface were regenerated by K~＋ and CO3^（2-）,thus promoting the oxidation of HCHO.Moreover,H2-temperature programmed reduction and X-ray photoelectron spectroscopy showed that employing KHCO3 as the precipitant increased the Co^3＋/Co^2＋molar ratio on the surface of the Co3O4 catalyst,thus further promoting oxidation.Structural characterization revealed that catalysts precipitated with carbonate or bicarbonate reagents exhibited greater specific surface areas and pore volumes.Overall,these data suggest that the high activity observed during the Co3O4 catalyzed oxidation of HCHO can be primarily attributed to the presence of K~＋ and CO3^（2-） on the Co3O4 surface and the favorable Co^3＋/Co^2＋ ratio.
基金Project supported by Natural Science Foundation of Zhejiang Province(Y4110220)Foundation of the Zhejiang Provincial Department of Education(Y200908245)Foundation of the Dinghai Academy of Science and Technology(201006)
文摘A series of Ni-CeO2 catalysts were prepared by co-precipitation method with Na2CO3, NaOH, and mixed precipitant （Na2CO3：NaOH; 1：1 ratio） as precipitant, respectively. The effect of the precipitants on the catalytic performance, physical and chemical properties of Ni-CeO2 catalysts was investigated with the aid of X-ray diffraction （XRD）, Bmmaner-Emmett-Teller method （BET）, Fou- rier-transform infrared spectroscopy （FT-IR）, thermogravimetry （TG）, and H2-TPR characterizations. The Ni-CeO2 catalysts were exam- ined with respect to their catalytic performance for the reverse water-gas shift reaction, and their catalytic activities were ranked as： Ni-CeO2-CP （Na2CO3：NaOH=I：I）〉Ni-CeO2-CP（Na2CO3）〉Ni-CeO2-CP（NaOH）- Correlating to the characteristic results, it was found that the catalyst prepared by co-precipitation with mixed precipitant （Na2CO3：NaOH; 1：1 ratio） as precipitant hadthe most amount of oxygen vacancies accompanied with highly dispersed Ni particles, which made the corresponding Ni-CeO2-CP（Na2CO3：NaOH=I： 1） catalyst exhibit the highest catalytic activity. While the precipitant of Na2CO3 or NaOH resulted in less or no oxygen vacancies in Ni-CeO2 catalysts. As a result, Ni-CeO2-CP（Na2CO3） and Ni-CeO2-CP（NaOH） catalysts presented poor catalytic performance.
基金Project supported by The National High Technology Research and Development Program of China(863Program:2010AA03A405)Twelfth Five-Year National Science and Technology Pillar Program(2012BAE01B02)
文摘Novel precipitant prepared through carbonation with MgCl2 wastewater generated from rare earth extraction separation process and low-price dolomite as raw materials was studied in this paper. The purification methods of novel precipitant by adding appropriate oxidizing agent were studied. It was found that optimal purification result could be achieved with sodium hypochlorite as iron removal reagent and the iron removal rate could reach up to 90% when the adding amount was 0.1 vol.%. During the preparation, the particle size and distribution of ceria-based polishing powder were affected obviously by the parameters such as concentration, reaction temperature and feeding rate. The results showed that ceria-based polishing powder with D50 =2.5-3.5 μm and the particle size distribution of 0.65-0.75 μm could be prepared when the concentration of CeCl3 was 0.6 mol/L, the reaction temperature was maintained at 50 °C and the feeding speed was controlled at 25 ml/min. Compared with commercial powder, the self-made polishing powder had roughly the same cutting amount, but the surface finish of polished glass was better than that of commercial polishing powder.
基金the project under the SERC SR/S3/CE/0062/2010 by the Department of Science and Technology, India
文摘Compressed natural gas（CNG）is most appropriate an alternative of conventional fuel for automobiles.However,emissions of carbon-monoxide and methane from such vehicles adversely affect human health and environment.Consequently,to abate emissions from CNG vehicles,development of highly efficient and inexpensive catalysts is necessary.Thus,the present work attempts to scan the effects of precipitants（Na2CO3,KOH and urea）for nickel cobaltite（Ni Co2O4）catalysts prepared by co-precipitation from nitrate solutions and calcined in a lean CO-air mixture at 400℃.The catalysts were used for oxidation of a mixture of CO and CH4（1：1）.The catalysts were characterized by X-ray diffractometer,Brunauer–Emmett–Teller surface-area,X-ray photoelectron spectroscopy;temperature programmedreductionandScanningelectronmicroscopycoupledwith Energy-Dispersive X-Ray Spectroscopy.The Na2CO3was adjudged as the best precipitant for production of catalyst,which completely oxidized CO-CH4mixture at the lowest temperature（T（100）=350℃）.Whereas,for catalyst prepared using urea,T（100）=362℃.On the other hand the conversion of CO-CH4mixture over the catalyst synthesized by KOH limited to 97%even beyond 400℃.Further,the effect of higher calcination temperatures of 500 and600℃ was examined for the best catalyst.The total oxidation of the mixture was attained at higher temperatures of 375 and 410℃ over catalysts calcined at 500 and 600℃ respectively.Thus,the best precipitant established was Na2CO3and the optimum calcination temperature of 400℃ was found to synthesize the Ni Co2O4catalyst for the best performance in CO-CH4oxidation.
文摘Heart Failure (HF) is a syndrome characterized by typical symptoms (e.g. breathlessness, ankle swelling and fatigue) that may be accompanied by signs (e.g. elevated jugular venous pressure, pulmonary crackles and peripheral oedema) caused by a structural and/or functional cardiac abnormality, resulting in a reduced cardiac output and/or elevated intracardiac pressures at rest or during stress. Clinical studies investigating the aetiological patterns of heart failure in Sub-Saharan Africa (SSA) revealed that hypertension, cardiomyopathy and rheumatic heart disease account for more than two-thirds of cardiac disease cases. The objective of this study therefore is to assess the pattern, precipitating factors and short term outcome of heart failure among patients admitted into our hospital. Method: The study was a prospective cross-sectional type conducted among in patients with heart failure in the medical ward of the hospital. Results: A total of three and fifty four (354) subjects were recruited into the study, comprising one hundred and twenty nine males (36.4%) and two hundred and twenty five (63.4%) females. Majority of the patients were admitted in NYHA functional class IV. This however improved to class II at discharge though few were discharged in NYHA class III. Heart failure secondary to progressive hypertensive heart disease was the most common (39.0%) followed by peripartum cardiomyopathy (22.6%) while idiopathic dilated cardiomyopathy (11.0%) and rheumatic heart disease (7.3%) were the third and fourth causes of heart failure respectively. The most common precipitating factor for heart failure in this study was chest infection (44.9%). In conclusion, the study revealed that progressive hypertensive heart disease was the leading cause of heart failure, followed by peripartum cardiomyopathy while idiopathic dilated cardiomyopathy and rheumatic heart disease were ranked third and fourth causes of heart failure respectively. Though myocardial infarction is on the increase, it was found to be the fifth cause of heart failure. The study also identified the following precipitants of heart failure in decreasing order of occurrence: chest infection, non-adherence to prescription, and urinary tract infection.
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the comments of three reviewers which substantially enhanced the quality of this manuscript.This research is jointly sponsored by the National Natural Science Foundation of China(grant 42575038)the National Key Research and Development Program of China(grant 2022YFF0801702)the National Natural Science Foundation of China(grant 42206257 and 42205163).
文摘This study investigated the characteristics and mechanisms of summer regional persistent extreme precipitation events(RPEPEs)over South China(SC)modulated by distinct intensity regimes of 10-30-day intraseasonal oscillation(ISO).Diagnostic analyses revealed that the spatiotemporal evolution of RPEPEs exhibits robust phase-locking with the 10-30-day intraseasonal precipitation.By classifying RPEPEs into strong-ISO(SRPEPE)and weak-ISO(WRPEPE)composites based on the amplitude of 10-30-day filtered precipitation,we demonstrate a 14.6%enhancement in peak precipitation intensity during SRPEPEs compared to WRPEPEs.These distinct precipitation regimes are governed by fundamentally different Rossby wave teleconnection patterns over Eurasia.During SRPEPEs,a robust southeastward-propagating 10-30-day Rossby wave train originating from the Barents Sea traverses midlatitude Eurasia,effectively perturbing the northwestern Pacific upper-level circulation and establishing a favorable dynamic environment over SC.In contrast,WRPEPEs are associated with weaker eastward-propagating wave trains constrained along the subtropical jet stream.The horizontal convergence of background moisture driven by 10-30-day winds significantly amplifies lower-tropospheric humidity during SRPEPEs.The thermal advection of background temperature by 10-30-day geostrophic winds enhances baroclinic instability and vertical motion,intensifying precipitation under these moisture conditions.
基金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.
基金Funded by the Fundamental Research Program of Shanxi Province(No.202203021211191)。
文摘To investigate the effects of extrusion temperature on the microstructure and mechanical properties of WE43 magnesium alloy,extrusion experiments were conducted under 330,380,430,and 450℃,and the extrusion ratio was 16.The experimental results indicate that,at a low temperature of 330℃,the alloy precipitates a large amount of second phases rich in Zr elements.Moreover,the texture strength and kernel average misorientation value are the highest,with values of 27.77 and 0.71,respectively.The increase in extrusion temperature leads to a gradual decrease in texture strength and kernel average misorientation value.The strength of the alloy is the highest at an extrusion temperature of 330℃.Its tensile yield stress is 254.7 MPa and ultimate tensile strength is 302.7 MPa,respectively.As the extrusion temperature increases,the strength of the alloy gradually decreases.At an extrusion temperature of 450℃,the tensile yield stress is 181.3 MPa and ultimate tensile strength is 265.7 MPa,respectively.The elongation first increases and then decreases,with an elongation of 20.9%at an extrusion temperature of 330℃.At an extrusion temperature of 430℃,the elongation reaches its maximum value,which is 23.6%.At an extrusion temperature of 450℃,the elongation reaches its lowest value,which is 16.4%.
基金jointly supported by the National Natural Science Foundation of China[grant numbers U2342202,42175005,and 42175016]the Qing Lan Project[grant number R2023Q06]。
文摘This study investigates the width of the secondary eyewall(SE)immediately following its formation in tropical cyclones with surface environmental winds aligned and counter-aligned with environmental vertical wind shear(VWS),using idealized numerical experiments.Results reveal that the SE develops greater radial extent when surface winds align with VWS compared to counter-aligned conditions.In alignment configurations,shear-enhanced surface winds on the right flank amplify surface enthalpy fluxes,thereby elevating boundary-layer entropy within the downshear outer-core region.Subsequently,more vigorous outer rainbands develop,inducing marked acceleration of tangential winds in the outer core preceding SE formation.The resultant radial expansion of supergradient winds near the boundary-layer top triggers widespread convective activity immediately beyond the inner core.Progressive axisymmetrization of this convective forcing ultimately generates an expansive SE structure.
基金supported by the Jilin Scientific and Technological Development Program(No.20240302108GX)the National Natural Science Foundation of China(Nos.51974032,52174355,51874043,and 51604034).
文摘Selective laser melting(SLM)is an advanced additive manufacturing technique that enables the fabrication of complex metal components with high density,precision,and design flexibility.A novel Sc-free Al-4.58Mg-1.17Mn-1.59Zr-1.45Ti alloy was successfully fabricated via SLM,achieving a relative density of~99.89%.The microstructure of the as-fabricated alloy was characterized by scanning electron microscopy and transmission electron microscopy,which revealed refined equiaxed grains,a high density of low-angle grain boundaries and dislocation structures,as well as Mg segregation along grain boundaries.Additionally,a variety of dispersed precipitates were identified,including Mg-containing oxides,L1_(2)-Al_(3)(Ti_(x),Zr_(1−x)),and Al_(3)Zr particles.Room-temperature tensile tests showed that the alloy exhibits an excellent combination of strength and ductility,with a yield strength of 453.2±12 MPa,an ultimate tensile strength of 515.1±8 MPa,and an elongation of 22.5%±0.3%.The high strength was attributed to the combined effects of grain boundary strengthening,solid solution strengthening,precipitation strengthening,and dislocation strengthening.The developed Sc-free Al-Mg-Mn-Zr-Ti alloy demonstrates significant potential as an economical high-strength lightweight material for SLM-based manufacturing applications.
