The mechanical behavior of cohesive soil is sensitized to drying-wetting cycles under confinements.However,the hydromechanical coupling effect has not been considered in current constitutive models.A macro-micro analy...The mechanical behavior of cohesive soil is sensitized to drying-wetting cycles under confinements.However,the hydromechanical coupling effect has not been considered in current constitutive models.A macro-micro analysis scheme is proposed in this paper to investigate the soil deformation behavior under the coupling of stress and drying-wetting cycles.A new device is developed based on CT(computerized tomography)workstation to apply certain normal and shear stresses on a soil specimen during drying-wetting cycles.A series of tests are conducted on a type of loess with various coupling of stress paths and drying-wetting cycles.At macroscopic level,stress sensor and laser sensor are used to acquire stress and strain,respectively.The shear and volumetric strain increase during the first few drying-wetting cycles and then become stable.The increase of the shear stress level or confining pressure would cause higher increase rate and the value of shear strain in the process of drying-wetting cycles.At microscopic level,the grayscale value(GSV)of CT scanning image is characterized as the proportion of soil particles to voids.A fabric state parameter is proposed to characterize soil microstructures under the influence of stress and drying-wetting cycle.Test results indicate that the macroand micro-responses show high consistence and relevance.The stress and drying-wetting cycles would both induce collapse of the soil microstructure,which dominants degradation of the soil mechanical properties.The evolution of the macro-mechanical property of soil exhibits a positive linear relationship with the micro-evolution of the fabric state parameter.展开更多
Fissured clays exhibit unique geotechnical behaviors,with the stiffness characteristics evolving dynamically in response to environmental changes.To address this issue,reported here is a systematic assessment of how d...Fissured clays exhibit unique geotechnical behaviors,with the stiffness characteristics evolving dynamically in response to environmental changes.To address this issue,reported here is a systematic assessment of how dryingewetting(DW)cycles affect the small-strain stiffness characteristics of fissured clay.Resonant column tests are taken to examine the nonlinear attenuation behavior of the small-strain shear modulus(SSSM)and damping ratio of fissured clay under various DW cycle and consolidation pressure(25e200 kPa)conditions.Scanning electron microscopy(SEM)and computed tomography(CT)are employed to reveal the microstructure of fissured clay.The HardineDrnevich(H-D)model is used to describe the decay law of its SSSM,and the small strain stiffness characteristics of fissured soil are analyzed in view of damage mechanics.The results show that the SSSM of the fissured clay decreases as the DWcycles increase,with the greatest attenuation at original soil state.The damping ratio exhibits an incremental trend with escalating strain and a higher number of DW cycles.Regarding damage,DW cycles can lead to the formation of microcracks in the sample,and the aggregates disperse into smaller aggregates,which then aggregates again,resulting in structural damage.The damage variables of the samples under various confining pressures and DW cycles are analyzed based on the principle of strain damage.Finally,the volume changes and the distribution of different pore sizes obtained through CT are analyzed to investigate the stiffness attenuation under DW cycles.Additionally,the study examines the propagation direction of secondary cracks induced by primary fissures,which will play an important role in reduction of the stiffness.Our investigations contribute to understanding of soil mechanics and practical applications in areas where fissured clay is prevalent.展开更多
Numerous slope failures have been reported during periods of water level fluctuations.Understanding the influence of water on the creep behavior of joints is essential for evaluating the long-term stability of slopes....Numerous slope failures have been reported during periods of water level fluctuations.Understanding the influence of water on the creep behavior of joints is essential for evaluating the long-term stability of slopes.This study focuses on the effects of drying-wetting cycles and soaking conditions on the long-term behavior of sandstone joints.A total of 12 multi-stage shear creep tests are carried out on sandstone joints subjected to varying drying-wetting cycles under both soaking and un-soaking conditions.Based on the experimental results,the influences of drying-wetting cycles as well as soaking conditions on the microstructure,shear creep displacement,strength,and failure morphologies of sandstone joints are investigated comprehensively.Results indicate that increasing drying-wetting cycles not only yields larger shear creep displacements but also leads to a negative exponential decrease in the strength of sandstone joints.Besides,soaking conditions strongly influence the creep behavior of sandstone joints.The failure strength and long-term strength of sandstone joints for soaked samples decrease by 13.6%–29.0%and 19.4%–37.5%,respectively,as compared to unsoaked samples.Furthermore,four distinct stages in the shear creep process were identified according to the results obtained from multi-stage shear creep tests and computerized tomography scans,and three creep failure modes of sandstone joints are thus determined.Finally,the influence mechanism of drying-wetting cycles and soaking conditions on the creep failure modes of sandstone joints is revealed.Drying-wetting cycles and soaking conditions diminish the influence of asperities on the shear creep behavior of joints,thereby reducing the resistance of joints to long-term deformation.展开更多
Based on seawater immersion,drying-wetting cycles,carbonation and drying-wetting cycles for coral aggregate sea-water concrete(CASC)with different strength grades,the effect of carbonation and drying-wetting cycles on...Based on seawater immersion,drying-wetting cycles,carbonation and drying-wetting cycles for coral aggregate sea-water concrete(CASC)with different strength grades,the effect of carbonation and drying-wetting cycles on chloride diffusion be-havior of CASC is studied.The results show that the free surface chloride concentration(Cs),free chloride diffusion coefficient(Df)and time-dependent index(m)of CASC in the drying-wetting cycles is obviously higher than that in seawater immersion.The Df and m of CASC of carbonation and drying-wetting cycles is higher than that in the drying-wetting cycles.Carbonation increases the Df and m of CASC,which is against CASC to resist chloride corrosion.The corrosion possibility of CASC structures in different ex-posed areas is as follows:splash zone(carbonation and drying-wetting cycles)>tidal zone(drying-wetting cycles)>underwater zone(seawater immersion).Besides,the chloride diffusion rate of C65-CASC is 17.8%-63.4%higher than that of C65-ordinary aggre-gate concrete(OAC)in seawater immersion(underwater zone).Therefore,anti-corrosion measures should be adopted to improve the service life of CASC structure in the oceanic environment.展开更多
Cracks resulting from cyclic wetting and drying of expansive soils create discontinuities and anisotropy in the soil.The representative elementary volume(REV)defined by the continuous-media theory cannot be applied to...Cracks resulting from cyclic wetting and drying of expansive soils create discontinuities and anisotropy in the soil.The representative elementary volume(REV)defined by the continuous-media theory cannot be applied to cracked expansive soils that are considered discontinuous media.In this study,direct shear tests of three different scales(30 cm^(2),900 cm^(2),1963 cm^(2))and crack image analysis were carried out on undisturbed soil samples subjected to drying-wetting cycles in-situ.The REV size of expansive soil was investigated using the crack intensity factor(CIF)and soil cohesion.The results show that soil cohesion decreased with increasing sample area,and the development of secondary cracks further exacerbated the size effect of sample on cohesion of the soil.As shrinkage cracks developed,the REV size of the soil gradually increased and plateaued after 3−5 cycles.Under the same drying-wetting cycle conditions,the REV size determined using soil cohesion(REV-C)is 1.75 to 2.97 times the REV size determined using CIF(REV-CIF).Under the influence of shrinkage cracks,the average CIF is positively correlated with the REV size determined using different maximum permissible errors,with the coefficient of correlation greater than 0.9.A method for determining the REV-C based on crack image analysis is proposed,and the REV-C of expansive soil in the study area under different exposure times is given.展开更多
The chloride ion transmission model considering diffusion and convection was established respectively for different zones in concrete by analyzing chloride ion transmission mechanism under the dryingwetting cycles. Th...The chloride ion transmission model considering diffusion and convection was established respectively for different zones in concrete by analyzing chloride ion transmission mechanism under the dryingwetting cycles. The finite difference method was adopted to solve the model. The equation of chloride ion transmission model in the convection and diffusion zone of concrete was discreted by the group explicit scheme with right single point （GER method） and the equation in diffusion zone was discreted by FTCS difference scheme. According to relative humidity characteristics in concrete under drying-wetting cycles, the seepage velocity equation was formulated based on Kelvin Equation and Darcy＇s Law. The time-variant equations of chloride ion concentration of concrete surface and the boundary surface of the convection and diffusion zone were established. Based on the software MATLAB the numerical calculation was carried out by using the model and basic material parameters from the experiments. The calculation of chloride ion concentration distribution in concrete is in good agreement with the drying-wetting cycles experiments. It can be shown that the chloride ion transmission model and the seepage velocity equation are reasonable and practical. Studies have shown that the chloride ion transmission in concrete considering convection and diffusion under the drying-wetting cycles is the better correlation with the actual situation than that only considering the diffusion.展开更多
Enzyme-induced carbonate precipitation(EICP)has emerged promising in various geotechnical applications,and has been presented as an alternative to the traditional cementitious materials-based ground improvement method...Enzyme-induced carbonate precipitation(EICP)has emerged promising in various geotechnical applications,and has been presented as an alternative to the traditional cementitious materials-based ground improvement method.However,the study on mechanical properties and disintegration behavior of EICP-reinforced sea sand subjected to drying-wetting cycles are limited.This study investigated the mechanical properties and disintegration behavior of EICP-reinforced sea sand against the impact of drying-wetting(D-W)cycles.The uniaxial compressive strength(UCS)tests were performed to discuss the effect of drying-wetting cycles on the mechanical behavior of EICP-treated sea sand.The disintegration tests were conducted on EICP-treated sea sand to investigate the disintegration resistance of bio-cemented samples with various cementation levels.The microstructures of samples before and after disintegration were examined to disclose the disintegration mechanisms of EICP-reinforced sea sand.D-W cycles significantly affect the mechanical properties of EICP-reinforced sea sand,with UCS decreasing by 63.7%after undergoing 15 D-W cycles.The disintegration resistance index of specimens with a lower cementation level decreases significantly under the effect of D-W treatment.The higher disintegration resistance of specimens with higher cementation can be attributed to more crystals with better crystallinity formed in the contact point between sand particles within specimen.The crystals formed by soybean husk urease are mainly calcite and the crystallinity of spherical calcites would gradually change into larger rhombic calcite with further bio-grouting.The crystal with poor crystallinity is susceptible to the effect of D-W treatment,resulting in the obvious disintegration of EICP-reinforced sea sand.Overall,this study is expected to provide useful guidance on the long-term stability and drying-wetting disintegration mechanisms of EICP-reinforced sea sand.展开更多
Microbial-induced carbonate precipitation(MICP)technique has been adopted in geotechnical engineering widely.In this study,the effect of drying-wetting cycles on MICP-recycled shredded coconut coir(RSC)reinforced calc...Microbial-induced carbonate precipitation(MICP)technique has been adopted in geotechnical engineering widely.In this study,the effect of drying-wetting cycles on MICP-recycled shredded coconut coir(RSC)reinforced calcareous sand was studied,and the deterioration mechanism under drying-wetting cycles was revealed.Test results indicated that drying-wetting cycles exert an important influence on the durability of MICP-RSC reinforced specimens.With the increase of drying-wetting cycles N,the specimens demonstrated significant increase in mass loss rate and critical void ratio,decrease in maximum shear modulus,peak strength and toughness.Furthermore,an increase in the initial relative density reduced the deterioration of MICP-RSC reinforced specimens exposed to drying-wetting cycles.Higher initial relative density of the specimen correlates with an increased maximum shear modulus,peak stress and toughness,a decreased in permeability and critical void ratio.Microanalysis revealed that the generated calcium carbonate adhering to sand particles and RSC gradually dropped off with the increase of N,weakened cementation,and led to the deterioration of MICP-RSC reinforced specimens,which is consistent with the deterioration characteristics under drying-wetting cycles.展开更多
Enzyme-induced carbonate precipitation(EICP)is an emanating,eco-friendly and potentially sound technique that has presented promise in various geotechnical applications.However,the durability and microscopic character...Enzyme-induced carbonate precipitation(EICP)is an emanating,eco-friendly and potentially sound technique that has presented promise in various geotechnical applications.However,the durability and microscopic characteristics of EICP-treated specimens against the impact of drying-wetting(D-W)cycles is under-explored yet.This study investigates the evolution of mechanical behavior and pore charac-teristics of EICP-treated sea sand subjected to D-W cycles.The uniaxial compressive strength(UCS)tests,synchrotron radiation micro-computed tomography(micro-CT),and three-dimensional(3D)recon-struction of CT images were performed to study the multiscale evolution characteristics of EICP-reinforced sea sand under the effect of D-W cycles.The potential correlations between microstructure characteristics and macro-mechanical property deterioration were investigated using gray relational analysis(GRA).Results showed that the UCS of EICP-treated specimens decreases by 63.7% after 15 D-W cycles.The proportion of mesopores gradually decreases whereas the proportion of macropores in-creases due to the exfoliated calcium carbonate with increasing number of D-W cycles.The micro-structure in EICP-reinforced sea sand was gradually disintegrated,resulting in increasing pore size and development of pore shape from ellipsoidal to columnar and branched.The gray relational degree suggested that the weight loss rate and UCS deterioration were attributed to the development of branched pores with a size of 100-1000 m m under the action of D-W cycles.Overall,the results in this study provide a useful guidancee for the long-term stability and evolution characteristics of EICP-reinforced sea sand under D-W weathering conditions.展开更多
The influential depth of moisture transport in a concrete surface subject to drying-wetting cycles was analyzed numerically. The moisture transport was described by a diffusion model with different diffusivities for d...The influential depth of moisture transport in a concrete surface subject to drying-wetting cycles was analyzed numerically. The moisture transport was described by a diffusion model with different diffusivities for drying and wetting. A finite difference scheme was developed to solve the partial differential equations The influential depth was then investigated numerically for initially saturated and unsaturated concretes exposed to drying-wetting actions in marine environments using an equilibrium time ratio concept. The equilibrium time ratio was calculated numerically for a saturated condition and the moisture influential depth is shown to be a linear function of the square root of the drying time. However, this equilibrium time ratio does not exist for an unsaturated condition and the moisture influential depth depends on the initial saturation as well as the drying-wetting time ratio. The results indicate that this model gives more realistic predictions of moisture transport of in situ structural concrete and its durability.展开更多
The coupling effects among the flow field,temperature distribution and structural deformation in a turbine cannot be ignored,particularly during flight cycles when the turbine experiences varied operational states.Rel...The coupling effects among the flow field,temperature distribution and structural deformation in a turbine cannot be ignored,particularly during flight cycles when the turbine experiences varied operational states.Relying solely on steady-state solutions cannot predict the detrimental effects caused by hysteresis.Consequently,this paper employs a quasi-steady-state fluid-thermalstructure multidisciplinary coupling solution method,integrating transient solid heat conduction with steady-state flow field and static structural deformation solutions.After conducting a numerical simulation of a three-dimensional,five-stage,low-pressure turbine air system,the following conclusions are drawn:when boundary conditions attain high-power states through processes that are numerically identical but in opposite directions,slight variations in solid deformation significantly impact the flow field;when boundary conditions attain high-power states through processes that are directionally consistent but have different numerical values,the influence of the boundary condition change rate on the flow field surpasses that of solid deformation.In terms of turbine design parameters,a large difference in stage-reaction between adjacent stages at the lower radius of the turbine can lead to significant changes in the disc cavity flow field during flight cycles.The difference in the stage-reaction of 0.23 at 10%blade height in adjacent stages may induce severe gas ingress in the stator disc cavity.Thus,it is crucial to minimize this difference and to appropriately extend the duration of the deceleration phase to ensure the turbine's safe operation.展开更多
The solar cycle(SC),a phenomenon caused by the quasi-periodic regular activities in the Sun,occurs approximately every 11 years.Intense solar activity can disrupt the Earth’s ionosphere,affecting communication and na...The solar cycle(SC),a phenomenon caused by the quasi-periodic regular activities in the Sun,occurs approximately every 11 years.Intense solar activity can disrupt the Earth’s ionosphere,affecting communication and navigation systems.Consequently,accurately predicting the intensity of the SC holds great significance,but predicting the SC involves a long-term time series,and many existing time series forecasting methods have fallen short in terms of accuracy and efficiency.The Time-series Dense Encoder model is a deep learning solution tailored for long time series prediction.Based on a multi-layer perceptron structure,it outperforms the best previously existing models in accuracy,while being efficiently trainable on general datasets.We propose a method based on this model for SC forecasting.Using a trained model,we predict the test set from SC 19 to SC 25 with an average mean absolute percentage error of 32.02,root mean square error of 30.3,mean absolute error of 23.32,and R^(2)(coefficient of determination)of 0.76,outperforming other deep learning models in terms of accuracy and training efficiency on sunspot number datasets.Subsequently,we use it to predict the peaks of SC 25 and SC 26.For SC 25,the peak time has ended,but a stronger peak is predicted for SC 26,of 199.3,within a range of 170.8-221.9,projected to occur during April 2034.展开更多
This study introduces superabsorbent polymers(SAP)into recycled concrete and,through freeze-thaw cycle tests,unconfined compressive strength tests,and nuclear magnetic resonance(NMR)analysis,evaluates the freeze-thaw ...This study introduces superabsorbent polymers(SAP)into recycled concrete and,through freeze-thaw cycle tests,unconfined compressive strength tests,and nuclear magnetic resonance(NMR)analysis,evaluates the freeze-thaw resistance and durability of recycled concrete samples under varying freeze-thaw cycles.The results indicate that an appropriate addition of SAP significantly enhances the freeze-thaw resistance of recycled concrete.After 200 freeze-thaw cycles,the RS0.6 sample retained good surface integrity,demonstrating the best performance.Compared to NAC,its mass loss decreased by 1.16%,the relative dynamic modulus improved by 7.01%,and the compressive strength loss rate decreased by 5.41%.Additionally,T2 spectrum analysis revealed that adding SAP optimized the pore structure of recycled concrete and mitigated pore development during freeze-thaw cycles.As the number of freeze-thaw cycles increased,the RS0.3 and RS0.6 samples demonstrated superior frost resistance compared to NAC.However,an excessive amount of SAP increased pore expansion during subsequent freeze-thaw cycles,ultimately weakening frost resistance.展开更多
The dust cycle is a crucial component of the present-day Martian climate system.This study examines its multitimescale variability using an optimized 50-year simulation with the fully interactive scheme from the Globa...The dust cycle is a crucial component of the present-day Martian climate system.This study examines its multitimescale variability using an optimized 50-year simulation with the fully interactive scheme from the Global Open Planetary Atmospheric Model for Mars(GoMars),a newly developed Mars General Circulation Model(MGCM).GoMars is able to reproduce the diurnal,seasonal,and interannual characteristics of the dust cycle in several key aspects,with high repeatability in diurnal and seasonal variations during non-global dust storm(non-GDS)years.The model’s“climatology”(non-GDS years ensemble mean)captures the seasonal pattern and magnitude of the vertical–meridional dust distribution,validated against Mars Climate Database and Mars Climate Sounder observations.In the absence of direct observations,the GoMars-simulated near-surface wind stress lifting flux is evaluated through comparisons with other MGCMs(e.g.,MarsWRF),revealing consistent seasonal and spatial patterns.As for the diurnal cycle,the peak dust devil lifting flux occurs at 1200–1300 local time,matching the Mars Pathfinder measurements.The model also successfully captures the intense dust devil activity in Amazonis,a region identified as a major dust devil hotspot based on observational data.In GDS years,GoMars effectively reproduces spontaneous GDSs,capturing their observed onset times,locations,and dust transport patterns as exhibited in specific Martian years.The model also simulates significant interannual variability,with irregular GDS intervals along with reasonable dust–atmosphere interactions.展开更多
Investigating the damage evolution of surrounding rock under thermal shock cycles is crucial for ensuring the stability of engineering rock masses.This study performed Brazilian splitting tests on granite specimens un...Investigating the damage evolution of surrounding rock under thermal shock cycles is crucial for ensuring the stability of engineering rock masses.This study performed Brazilian splitting tests on granite specimens under varying temperature and cycle conditions,employing acoustic emission monitoring,digital image correlation,and three-dimensional scanning technology.A systematic analysis was conducted on the patterns of damage evolution,failure precursor,and response mechanisms under combined thermal and cyclic loading.Experimental results show that both P-wave velocity and tensile strength degrade significantly with increasing temperature and cycle count,with temperature having a more pronounced effect than cycle count.Notably,damage evolution exhibits a dual-threshold behavior in which degradation accelerates markedly above 400℃ and stabilizes after 5 thermal cycles.Fracture surfaces evolve from initially planar to rugged morphologies,with peak-valley height differences at 600℃ being approximately three times greater than those at 200℃.Furthermore,based on acoustic emission energy entropy analysis,we introduce a novel failure precursor indicator where the sustained increase and critical surge in average entropy serve as reliable early-warning signals for impending rock failure.These findings establish a solid theoretical basis and practical methodology for damage assessment and instability early-warning systems in high-temperature rock engineering.展开更多
Compared with traditional energy sources,wind power has a lower environmental impact.However,emissions are still generated across the life cycle of wind turbines,from production to recycling.As wind power rapidly deve...Compared with traditional energy sources,wind power has a lower environmental impact.However,emissions are still generated across the life cycle of wind turbines,from production to recycling.As wind power rapidly develops and deployment increases,these impacts are becoming increasingly evident.A comprehensive understanding of these impacts is crucial for sustainable development.Based on the harmonization of previous detailed life cycle assessment(LCA)studies,this study develops a simplified LCA model that estimates the life cycle environmental impacts of wind turbines based on their nominal power.Using this simplified LCA model,we assess the global warming potential(GWP),acidification potential(AP),and cumulative energy demand(CED)of wind power at the regional scale for 2022 and under three future scenarios(high-power wind turbine promotion,reduced wind curtailment,and a comprehensive development scenario).The results indicate that in 2022,the life cycle GWP,AP,and CED of wind power in western China were 10.76 g CO_(2) eq/kWh,0.177 g SO_(2) eq/kWh,and 17.6 kJ/kWh,respectively.Scenario simulations suggest that reducing wind curtailment is the most effective approach for reducing emissions in Inner Mongolia,Gansu,Qinghai,Ningxia,and Xinjiang,producing average decreases of 8.64%in GWP,8.39%in AP,and 9.26%in CED.In contrast,for Guangxi,Chongqing,Sichuan,Guizhou,Yunnan,Xizang,and Shaanxi,the promotion of high-power wind turbines provides greater environmental benefits than reducing curtailment,producing average decreases of 3.45%,3.09%,and 4.29%in GWP,AP,and CED,respectively.These findings help clarify the environmental impact of wind power across its life cycle at the regional scale and provide theoretical references for the direction of future wind power development and the formulation of related policies.展开更多
Hair loss,a multifactorial disorder characterized by follicular miniaturization and excessive shedding,significantly impairs psychological well-being and quality of life.Cyperus rotundus rhizome(CR),a traditional Chin...Hair loss,a multifactorial disorder characterized by follicular miniaturization and excessive shedding,significantly impairs psychological well-being and quality of life.Cyperus rotundus rhizome(CR),a traditional Chinese medicine used for various ailments,has not been evaluated for efficacy in treating hair loss.This study presents the first comprehensive assessment of the hair growth-promoting effects of ethanol extract from CR on mouse primary dermal papilla cells(MDPCs)and human immortalized hair DPCs(IHHDPCs),employing cell counting kit-8(CCK-8),scratch assay,reverse transcription-quantitative polymerase chain reaction(RT-q PCR),and Western blot(WB).CR treatment activated the Wnt/β-Catenin signaling pathway by upregulating Wnt10b,increasingβ-Catenin protein levels and promoting its nuclear translocation,while simultaneously downregulating transforming growth factor-beta 1(TGF-β1),BMP4,and dickkopf-related protein 1(DKK1)in MDPCs.These molecular changes enhanced cell proliferation and increased secretion of key growth factors—insulin-like growth factor 1(IGF1),keratinocyte growth factor(KGF),and vascular endothelial growth factor(VEGF)—thereby stimulating hair growth and prolonging the anagen phase,which was confirmed in an ex vivo hair follicle(HF)organ culture model.Chromatographic analysis identified the petroleum ether fraction(CRP),enriched in sesquiterpenes,as the primary bioactive component.Both CR and CRP promoted IHHDPC proliferation,migration,and growth factor expression through activation of the Wnt/β-Catenin pathway,with CRP exhibiting superior bioactivity.Furthermore,both treatments stimulated HF cycling,increased follicular density,and upregulated Ki67 andβ-Catenin expression in the dorsal skin of C57BL/6 mice.Collectively,these findings demonstrate that CR and CRP promote hair growth and modulate the hair cycle via enhancement of Wnt/β-Catenin signaling,providing a scientific basis for the potential clinical application of C.rotundus rhizomes in hair loss therapy and the development of related pharmaceuticals or cosmetics.展开更多
Freeze-thaw cycles(FTCs)have an important effect on soil aggregate stability by altering soil structures,thereby influencing soil wind and water erosion on the eastern Qinghai-Tibet Plateau.However,the effects of FTCs...Freeze-thaw cycles(FTCs)have an important effect on soil aggregate stability by altering soil structures,thereby influencing soil wind and water erosion on the eastern Qinghai-Tibet Plateau.However,the effects of FTCs on the stability of these soils remain unclear.Here,we conducted freeze-thaw simulations in laboratory to investigate the effects of FTCs(0 to 15 cycles)on the wet-and dry-sieving aggregate stability of undisturbed sandy loam from Maqu county,which was treated with different initial soil moisture contents(1%to 25%in increments of 4%)and initial aggregate diameters(<2,2-5,5-10,and 10-15 mm).Results show that soil aggregates with initial diameters larger than 2 mm exhibit higher soil organic carbon contents(1.45%-1.57%)and silt contents(34.63%-35.52%)than those smaller than 2 mm(0.93%and 31.38%,respectively).The stability of both wet-and dry-sieving aggregates increases with larger initial diameters.Increasing initial soil moisture content from 1%to 25%reduces aggregate stability,with reductions of 2.4%-88.0%for wet-sieving aggregates and 2.1%-25.5%for dry-sieving aggregates(>2 mm).With increasing FTCs,wet-sieving aggregate(>2 mm)stability exhibits a fluctuating upward trend,with increases of 79.2%-87.4%after 15 FTCs,while dry-sieving aggregate(>2 mm)stability decreases significantly(5.7%-21.7%)upon the first FTC and remains unchanged thereafter.The stability of both the wet-and dry-sieving aggregates smaller than 2 mm remains unchanged with increasing FTCs(p>0.05).SOC content decreases by 22.3%on average with increasing FTCs from 1 to 15 and shows no significant correlations with wet-and dry-sieving aggregate stability.Higher silt content(r=0.39,p<0.05)and lower sand content(r=-0.38,p<0.05)enhances the wet-sieving aggregate stability of sandy loam.Frequent FTCs tend to improve wet-sieving aggregate stability but reduce dry-sieving aggregate stability in the sandy loam.The findings provide certain guidance for preventing freeze-thaw-induced wind erosion.展开更多
The conversion of CO_(2) into high value added chemicals via the Fischer-Tropsch synthesis(FTS)reaction has attracted significant attention.The surface oxygenation environment is a significant factor influencing the p...The conversion of CO_(2) into high value added chemicals via the Fischer-Tropsch synthesis(FTS)reaction has attracted significant attention.The surface oxygenation environment is a significant factor influencing the performance of the catalyst.In this work,spin-polarized density-functional theory calculations have been used to investigate the adsorption and reactions of CO_(2) and H to generate CH4 and CH3OH on Fe_(5)C_(2)(100)surfaces with varying OH∗coverage.On the pure Fe_(5)C_(2)(100)surface,surface C^(∗) preferentially reacts with hydrogen to form CH4,exposing C^(∗) vacancy.CO_(2) favors adsorbing on the C^(∗) vacancy to further dissociating and activating.The co-adsorption of OH∗promotes the C^(∗) cycle process by facilitating the hydrogenation of C^(∗).The Fe_(5)C_(2) surface with an oxide interface is favorable for reducing FexOy,thereby maintaining the dynamic stability of the surface.Therefore,surface oxidation is inevitably involved in the entire C^(∗) cycle of the FTS reaction and regulates the relative content of iron oxides and iron carbides.Our work can contribute to the rational modulation of the surface C^(∗) cycle,thereby enhancing catalyst performance.展开更多
Lithium-oxygen(Li-O_(2))battery is favored among“beyond lithiumion”technologies for sustainability because of its exceptional energy density.Major impediments are the poor cycle stability and grievous capacity degra...Lithium-oxygen(Li-O_(2))battery is favored among“beyond lithiumion”technologies for sustainability because of its exceptional energy density.Major impediments are the poor cycle stability and grievous capacity degradation at high current densities.We address these issues by a“killing two birds with one stone”O_(2)-pressure protocol.It first resolves efficient O_(2) mass transport at high rates..The accelerated reaction kinetics optimizes the composition and growth pathway of discharge products.This protocol secondly achieves protection of Li anodes via densifying corrosion layers on them.Consequently,the battery delivers both ultrahigh discharge capacity(>9,000 mAh g^(-1))at 3,000 mA g^(-1) and excellent cycling stability.Under a dual-strategy effect of high-pressure O_(2) and artificial protection layers,the battery actualizes over 11-fold increase in cycle life of 5,170 h(2,585 cycles).The strategy opens avenues for advancing Li-O_(2) batteries towards practical application and confers the extension to other gas-based batteries.展开更多
基金funded by National Key R&D Program of China(Grant No.2023YFC3007001)Beijing Natural Science Foundation(Grant No.8244053)China Postdoctoral Science Foundation(Grant No.2024M754065).
文摘The mechanical behavior of cohesive soil is sensitized to drying-wetting cycles under confinements.However,the hydromechanical coupling effect has not been considered in current constitutive models.A macro-micro analysis scheme is proposed in this paper to investigate the soil deformation behavior under the coupling of stress and drying-wetting cycles.A new device is developed based on CT(computerized tomography)workstation to apply certain normal and shear stresses on a soil specimen during drying-wetting cycles.A series of tests are conducted on a type of loess with various coupling of stress paths and drying-wetting cycles.At macroscopic level,stress sensor and laser sensor are used to acquire stress and strain,respectively.The shear and volumetric strain increase during the first few drying-wetting cycles and then become stable.The increase of the shear stress level or confining pressure would cause higher increase rate and the value of shear strain in the process of drying-wetting cycles.At microscopic level,the grayscale value(GSV)of CT scanning image is characterized as the proportion of soil particles to voids.A fabric state parameter is proposed to characterize soil microstructures under the influence of stress and drying-wetting cycle.Test results indicate that the macroand micro-responses show high consistence and relevance.The stress and drying-wetting cycles would both induce collapse of the soil microstructure,which dominants degradation of the soil mechanical properties.The evolution of the macro-mechanical property of soil exhibits a positive linear relationship with the micro-evolution of the fabric state parameter.
基金the financial support of the National Key Research and Development Program of China(Grant No.2019YFC1509901).
文摘Fissured clays exhibit unique geotechnical behaviors,with the stiffness characteristics evolving dynamically in response to environmental changes.To address this issue,reported here is a systematic assessment of how dryingewetting(DW)cycles affect the small-strain stiffness characteristics of fissured clay.Resonant column tests are taken to examine the nonlinear attenuation behavior of the small-strain shear modulus(SSSM)and damping ratio of fissured clay under various DW cycle and consolidation pressure(25e200 kPa)conditions.Scanning electron microscopy(SEM)and computed tomography(CT)are employed to reveal the microstructure of fissured clay.The HardineDrnevich(H-D)model is used to describe the decay law of its SSSM,and the small strain stiffness characteristics of fissured soil are analyzed in view of damage mechanics.The results show that the SSSM of the fissured clay decreases as the DWcycles increase,with the greatest attenuation at original soil state.The damping ratio exhibits an incremental trend with escalating strain and a higher number of DW cycles.Regarding damage,DW cycles can lead to the formation of microcracks in the sample,and the aggregates disperse into smaller aggregates,which then aggregates again,resulting in structural damage.The damage variables of the samples under various confining pressures and DW cycles are analyzed based on the principle of strain damage.Finally,the volume changes and the distribution of different pore sizes obtained through CT are analyzed to investigate the stiffness attenuation under DW cycles.Additionally,the study examines the propagation direction of secondary cracks induced by primary fissures,which will play an important role in reduction of the stiffness.Our investigations contribute to understanding of soil mechanics and practical applications in areas where fissured clay is prevalent.
基金financial support from the National Natural Science Foundation of China(Grant Nos.52479108,52408391)the Fundamental Research Funds for the Central Universities(2042024kf0032)+1 种基金the Postdoctoral Fellowship Program(Grade C)of China Postdoctoral Science Foundation(Grant No.GZC20241283)the Natural Science Foundation of Hubei Province,China(No.2024AFB160)。
文摘Numerous slope failures have been reported during periods of water level fluctuations.Understanding the influence of water on the creep behavior of joints is essential for evaluating the long-term stability of slopes.This study focuses on the effects of drying-wetting cycles and soaking conditions on the long-term behavior of sandstone joints.A total of 12 multi-stage shear creep tests are carried out on sandstone joints subjected to varying drying-wetting cycles under both soaking and un-soaking conditions.Based on the experimental results,the influences of drying-wetting cycles as well as soaking conditions on the microstructure,shear creep displacement,strength,and failure morphologies of sandstone joints are investigated comprehensively.Results indicate that increasing drying-wetting cycles not only yields larger shear creep displacements but also leads to a negative exponential decrease in the strength of sandstone joints.Besides,soaking conditions strongly influence the creep behavior of sandstone joints.The failure strength and long-term strength of sandstone joints for soaked samples decrease by 13.6%–29.0%and 19.4%–37.5%,respectively,as compared to unsoaked samples.Furthermore,four distinct stages in the shear creep process were identified according to the results obtained from multi-stage shear creep tests and computerized tomography scans,and three creep failure modes of sandstone joints are thus determined.Finally,the influence mechanism of drying-wetting cycles and soaking conditions on the creep failure modes of sandstone joints is revealed.Drying-wetting cycles and soaking conditions diminish the influence of asperities on the shear creep behavior of joints,thereby reducing the resistance of joints to long-term deformation.
基金sup-ports from the National Natural Science Foundation of China(Nos.11832013 and 51878350)the Fundamental Research Funds for the Central Universities(No.B210202023)+5 种基金the Young Scientific and Technological Talents to Support Project of Jiangsu Association for Science and Technology(No.027)the Water Conservancy Science and Technology Project of Jiangsu Province(No.2020017)the Postdoctoral Research Funding Program of Ji-angsu Province(No.2021K133B)the Ningbo Science and Technology Innovation Project(No.2020Z040)the Nantong Science and Technology Plan Project(No.JC 2020120)the Open Research Fund of Changjiang River Research Institute of Changjiang Water Resources Com-mittee(No.CKWV2021879/KY).
文摘Based on seawater immersion,drying-wetting cycles,carbonation and drying-wetting cycles for coral aggregate sea-water concrete(CASC)with different strength grades,the effect of carbonation and drying-wetting cycles on chloride diffusion be-havior of CASC is studied.The results show that the free surface chloride concentration(Cs),free chloride diffusion coefficient(Df)and time-dependent index(m)of CASC in the drying-wetting cycles is obviously higher than that in seawater immersion.The Df and m of CASC of carbonation and drying-wetting cycles is higher than that in the drying-wetting cycles.Carbonation increases the Df and m of CASC,which is against CASC to resist chloride corrosion.The corrosion possibility of CASC structures in different ex-posed areas is as follows:splash zone(carbonation and drying-wetting cycles)>tidal zone(drying-wetting cycles)>underwater zone(seawater immersion).Besides,the chloride diffusion rate of C65-CASC is 17.8%-63.4%higher than that of C65-ordinary aggre-gate concrete(OAC)in seawater immersion(underwater zone).Therefore,anti-corrosion measures should be adopted to improve the service life of CASC structure in the oceanic environment.
基金Project(41472240)supported by the National Natural Science Foundation of ChinaProjects(2015B25514,2015B17214)supported by the Fundamental Research Funds for the Central Universities,China。
文摘Cracks resulting from cyclic wetting and drying of expansive soils create discontinuities and anisotropy in the soil.The representative elementary volume(REV)defined by the continuous-media theory cannot be applied to cracked expansive soils that are considered discontinuous media.In this study,direct shear tests of three different scales(30 cm^(2),900 cm^(2),1963 cm^(2))and crack image analysis were carried out on undisturbed soil samples subjected to drying-wetting cycles in-situ.The REV size of expansive soil was investigated using the crack intensity factor(CIF)and soil cohesion.The results show that soil cohesion decreased with increasing sample area,and the development of secondary cracks further exacerbated the size effect of sample on cohesion of the soil.As shrinkage cracks developed,the REV size of the soil gradually increased and plateaued after 3−5 cycles.Under the same drying-wetting cycle conditions,the REV size determined using soil cohesion(REV-C)is 1.75 to 2.97 times the REV size determined using CIF(REV-CIF).Under the influence of shrinkage cracks,the average CIF is positively correlated with the REV size determined using different maximum permissible errors,with the coefficient of correlation greater than 0.9.A method for determining the REV-C based on crack image analysis is proposed,and the REV-C of expansive soil in the study area under different exposure times is given.
基金Funded by the National Natural Science Foundation of China(Nos.51278495,51174291)the Open Fund of Nation Engineering Laboratory for High Speed Railway Construction(No.HSR2013011)
文摘The chloride ion transmission model considering diffusion and convection was established respectively for different zones in concrete by analyzing chloride ion transmission mechanism under the dryingwetting cycles. The finite difference method was adopted to solve the model. The equation of chloride ion transmission model in the convection and diffusion zone of concrete was discreted by the group explicit scheme with right single point （GER method） and the equation in diffusion zone was discreted by FTCS difference scheme. According to relative humidity characteristics in concrete under drying-wetting cycles, the seepage velocity equation was formulated based on Kelvin Equation and Darcy＇s Law. The time-variant equations of chloride ion concentration of concrete surface and the boundary surface of the convection and diffusion zone were established. Based on the software MATLAB the numerical calculation was carried out by using the model and basic material parameters from the experiments. The calculation of chloride ion concentration distribution in concrete is in good agreement with the drying-wetting cycles experiments. It can be shown that the chloride ion transmission model and the seepage velocity equation are reasonable and practical. Studies have shown that the chloride ion transmission in concrete considering convection and diffusion under the drying-wetting cycles is the better correlation with the actual situation than that only considering the diffusion.
基金support of National Natural Science Foundation of China(Grant nos.41972276,52108307)"Foal Eagle Program"Youth Top-notch Talent Project of Fujian Province(Grant no.00387088)+1 种基金Natural Science Foundation of Fujian Province(Grant no.2020J06013)Qishan Scholar Project of Fuzhou University(Grant nos.XRC-22015,GXRC21047).
文摘Enzyme-induced carbonate precipitation(EICP)has emerged promising in various geotechnical applications,and has been presented as an alternative to the traditional cementitious materials-based ground improvement method.However,the study on mechanical properties and disintegration behavior of EICP-reinforced sea sand subjected to drying-wetting cycles are limited.This study investigated the mechanical properties and disintegration behavior of EICP-reinforced sea sand against the impact of drying-wetting(D-W)cycles.The uniaxial compressive strength(UCS)tests were performed to discuss the effect of drying-wetting cycles on the mechanical behavior of EICP-treated sea sand.The disintegration tests were conducted on EICP-treated sea sand to investigate the disintegration resistance of bio-cemented samples with various cementation levels.The microstructures of samples before and after disintegration were examined to disclose the disintegration mechanisms of EICP-reinforced sea sand.D-W cycles significantly affect the mechanical properties of EICP-reinforced sea sand,with UCS decreasing by 63.7%after undergoing 15 D-W cycles.The disintegration resistance index of specimens with a lower cementation level decreases significantly under the effect of D-W treatment.The higher disintegration resistance of specimens with higher cementation can be attributed to more crystals with better crystallinity formed in the contact point between sand particles within specimen.The crystals formed by soybean husk urease are mainly calcite and the crystallinity of spherical calcites would gradually change into larger rhombic calcite with further bio-grouting.The crystal with poor crystallinity is susceptible to the effect of D-W treatment,resulting in the obvious disintegration of EICP-reinforced sea sand.Overall,this study is expected to provide useful guidance on the long-term stability and drying-wetting disintegration mechanisms of EICP-reinforced sea sand.
基金support from the National Natural Science Foundations of China(No.52171282,41831280)Shandong Provincial Key Research and Development Plan,China(No.2021ZLGX04)supported by Taishan Scholars of Shandong Province,China(No.tsqn202306098).
文摘Microbial-induced carbonate precipitation(MICP)technique has been adopted in geotechnical engineering widely.In this study,the effect of drying-wetting cycles on MICP-recycled shredded coconut coir(RSC)reinforced calcareous sand was studied,and the deterioration mechanism under drying-wetting cycles was revealed.Test results indicated that drying-wetting cycles exert an important influence on the durability of MICP-RSC reinforced specimens.With the increase of drying-wetting cycles N,the specimens demonstrated significant increase in mass loss rate and critical void ratio,decrease in maximum shear modulus,peak strength and toughness.Furthermore,an increase in the initial relative density reduced the deterioration of MICP-RSC reinforced specimens exposed to drying-wetting cycles.Higher initial relative density of the specimen correlates with an increased maximum shear modulus,peak stress and toughness,a decreased in permeability and critical void ratio.Microanalysis revealed that the generated calcium carbonate adhering to sand particles and RSC gradually dropped off with the increase of N,weakened cementation,and led to the deterioration of MICP-RSC reinforced specimens,which is consistent with the deterioration characteristics under drying-wetting cycles.
基金The authors gratefully acknowledge the financial support of National NaturalScience Foundation of China(Grant No.41972276)Natural Science Foundation of Fujian Province,China(Grant No.2020J06013)"Foal Eagle Program"Youth Top-notch Talent Project of Fujian Province,China(Grant No.00387088).
文摘Enzyme-induced carbonate precipitation(EICP)is an emanating,eco-friendly and potentially sound technique that has presented promise in various geotechnical applications.However,the durability and microscopic characteristics of EICP-treated specimens against the impact of drying-wetting(D-W)cycles is under-explored yet.This study investigates the evolution of mechanical behavior and pore charac-teristics of EICP-treated sea sand subjected to D-W cycles.The uniaxial compressive strength(UCS)tests,synchrotron radiation micro-computed tomography(micro-CT),and three-dimensional(3D)recon-struction of CT images were performed to study the multiscale evolution characteristics of EICP-reinforced sea sand under the effect of D-W cycles.The potential correlations between microstructure characteristics and macro-mechanical property deterioration were investigated using gray relational analysis(GRA).Results showed that the UCS of EICP-treated specimens decreases by 63.7% after 15 D-W cycles.The proportion of mesopores gradually decreases whereas the proportion of macropores in-creases due to the exfoliated calcium carbonate with increasing number of D-W cycles.The micro-structure in EICP-reinforced sea sand was gradually disintegrated,resulting in increasing pore size and development of pore shape from ellipsoidal to columnar and branched.The gray relational degree suggested that the weight loss rate and UCS deterioration were attributed to the development of branched pores with a size of 100-1000 m m under the action of D-W cycles.Overall,the results in this study provide a useful guidancee for the long-term stability and evolution characteristics of EICP-reinforced sea sand under D-W weathering conditions.
基金the National Natural Science Foundation of China (No. 50538060)
文摘The influential depth of moisture transport in a concrete surface subject to drying-wetting cycles was analyzed numerically. The moisture transport was described by a diffusion model with different diffusivities for drying and wetting. A finite difference scheme was developed to solve the partial differential equations The influential depth was then investigated numerically for initially saturated and unsaturated concretes exposed to drying-wetting actions in marine environments using an equilibrium time ratio concept. The equilibrium time ratio was calculated numerically for a saturated condition and the moisture influential depth is shown to be a linear function of the square root of the drying time. However, this equilibrium time ratio does not exist for an unsaturated condition and the moisture influential depth depends on the initial saturation as well as the drying-wetting time ratio. The results indicate that this model gives more realistic predictions of moisture transport of in situ structural concrete and its durability.
基金supported by the National Science and Tech-nology Major Project,China(No.J2019-II-0012-0032)。
文摘The coupling effects among the flow field,temperature distribution and structural deformation in a turbine cannot be ignored,particularly during flight cycles when the turbine experiences varied operational states.Relying solely on steady-state solutions cannot predict the detrimental effects caused by hysteresis.Consequently,this paper employs a quasi-steady-state fluid-thermalstructure multidisciplinary coupling solution method,integrating transient solid heat conduction with steady-state flow field and static structural deformation solutions.After conducting a numerical simulation of a three-dimensional,five-stage,low-pressure turbine air system,the following conclusions are drawn:when boundary conditions attain high-power states through processes that are numerically identical but in opposite directions,slight variations in solid deformation significantly impact the flow field;when boundary conditions attain high-power states through processes that are directionally consistent but have different numerical values,the influence of the boundary condition change rate on the flow field surpasses that of solid deformation.In terms of turbine design parameters,a large difference in stage-reaction between adjacent stages at the lower radius of the turbine can lead to significant changes in the disc cavity flow field during flight cycles.The difference in the stage-reaction of 0.23 at 10%blade height in adjacent stages may induce severe gas ingress in the stator disc cavity.Thus,it is crucial to minimize this difference and to appropriately extend the duration of the deceleration phase to ensure the turbine's safe operation.
基金supported by the Academic Research Projects of Beijing Union University(ZK20202204)the National Natural Science Foundation of China(12250005,12073040,12273059,11973056,12003051,11573037,12073041,11427901,11572005,11611530679 and 12473052)+1 种基金the Strategic Priority Research Program of the China Academy of Sciences(XDB0560000,XDA15052200,XDB09040200,XDA15010700,XDB0560301,and XDA15320102)the Chinese Meridian Project(CMP).
文摘The solar cycle(SC),a phenomenon caused by the quasi-periodic regular activities in the Sun,occurs approximately every 11 years.Intense solar activity can disrupt the Earth’s ionosphere,affecting communication and navigation systems.Consequently,accurately predicting the intensity of the SC holds great significance,but predicting the SC involves a long-term time series,and many existing time series forecasting methods have fallen short in terms of accuracy and efficiency.The Time-series Dense Encoder model is a deep learning solution tailored for long time series prediction.Based on a multi-layer perceptron structure,it outperforms the best previously existing models in accuracy,while being efficiently trainable on general datasets.We propose a method based on this model for SC forecasting.Using a trained model,we predict the test set from SC 19 to SC 25 with an average mean absolute percentage error of 32.02,root mean square error of 30.3,mean absolute error of 23.32,and R^(2)(coefficient of determination)of 0.76,outperforming other deep learning models in terms of accuracy and training efficiency on sunspot number datasets.Subsequently,we use it to predict the peaks of SC 25 and SC 26.For SC 25,the peak time has ended,but a stronger peak is predicted for SC 26,of 199.3,within a range of 170.8-221.9,projected to occur during April 2034.
基金Funded by the Science and Technology Program of Gansu Province(Nos.25JRRA497,23ZDFA017)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB0950000)High-level Talent Funding of Kashi。
文摘This study introduces superabsorbent polymers(SAP)into recycled concrete and,through freeze-thaw cycle tests,unconfined compressive strength tests,and nuclear magnetic resonance(NMR)analysis,evaluates the freeze-thaw resistance and durability of recycled concrete samples under varying freeze-thaw cycles.The results indicate that an appropriate addition of SAP significantly enhances the freeze-thaw resistance of recycled concrete.After 200 freeze-thaw cycles,the RS0.6 sample retained good surface integrity,demonstrating the best performance.Compared to NAC,its mass loss decreased by 1.16%,the relative dynamic modulus improved by 7.01%,and the compressive strength loss rate decreased by 5.41%.Additionally,T2 spectrum analysis revealed that adding SAP optimized the pore structure of recycled concrete and mitigated pore development during freeze-thaw cycles.As the number of freeze-thaw cycles increased,the RS0.3 and RS0.6 samples demonstrated superior frost resistance compared to NAC.However,an excessive amount of SAP increased pore expansion during subsequent freeze-thaw cycles,ultimately weakening frost resistance.
基金jointly supported by the National Natural Science Foundation of China(Grant No.42475135)the Key Technology Research Project of TW-3(TW3006)the IAP’s basic scientific research project during the 14th Five-Year Plan Period.
文摘The dust cycle is a crucial component of the present-day Martian climate system.This study examines its multitimescale variability using an optimized 50-year simulation with the fully interactive scheme from the Global Open Planetary Atmospheric Model for Mars(GoMars),a newly developed Mars General Circulation Model(MGCM).GoMars is able to reproduce the diurnal,seasonal,and interannual characteristics of the dust cycle in several key aspects,with high repeatability in diurnal and seasonal variations during non-global dust storm(non-GDS)years.The model’s“climatology”(non-GDS years ensemble mean)captures the seasonal pattern and magnitude of the vertical–meridional dust distribution,validated against Mars Climate Database and Mars Climate Sounder observations.In the absence of direct observations,the GoMars-simulated near-surface wind stress lifting flux is evaluated through comparisons with other MGCMs(e.g.,MarsWRF),revealing consistent seasonal and spatial patterns.As for the diurnal cycle,the peak dust devil lifting flux occurs at 1200–1300 local time,matching the Mars Pathfinder measurements.The model also successfully captures the intense dust devil activity in Amazonis,a region identified as a major dust devil hotspot based on observational data.In GDS years,GoMars effectively reproduces spontaneous GDSs,capturing their observed onset times,locations,and dust transport patterns as exhibited in specific Martian years.The model also simulates significant interannual variability,with irregular GDS intervals along with reasonable dust–atmosphere interactions.
基金supported by National Natural Science Foundation of China (Nos.52264006,52364004,and 52464005)the Guizhou Provincial Science and Technology Foundation (No.GCC[2022]005-1)。
文摘Investigating the damage evolution of surrounding rock under thermal shock cycles is crucial for ensuring the stability of engineering rock masses.This study performed Brazilian splitting tests on granite specimens under varying temperature and cycle conditions,employing acoustic emission monitoring,digital image correlation,and three-dimensional scanning technology.A systematic analysis was conducted on the patterns of damage evolution,failure precursor,and response mechanisms under combined thermal and cyclic loading.Experimental results show that both P-wave velocity and tensile strength degrade significantly with increasing temperature and cycle count,with temperature having a more pronounced effect than cycle count.Notably,damage evolution exhibits a dual-threshold behavior in which degradation accelerates markedly above 400℃ and stabilizes after 5 thermal cycles.Fracture surfaces evolve from initially planar to rugged morphologies,with peak-valley height differences at 600℃ being approximately three times greater than those at 200℃.Furthermore,based on acoustic emission energy entropy analysis,we introduce a novel failure precursor indicator where the sustained increase and critical surge in average entropy serve as reliable early-warning signals for impending rock failure.These findings establish a solid theoretical basis and practical methodology for damage assessment and instability early-warning systems in high-temperature rock engineering.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFF1303405).
文摘Compared with traditional energy sources,wind power has a lower environmental impact.However,emissions are still generated across the life cycle of wind turbines,from production to recycling.As wind power rapidly develops and deployment increases,these impacts are becoming increasingly evident.A comprehensive understanding of these impacts is crucial for sustainable development.Based on the harmonization of previous detailed life cycle assessment(LCA)studies,this study develops a simplified LCA model that estimates the life cycle environmental impacts of wind turbines based on their nominal power.Using this simplified LCA model,we assess the global warming potential(GWP),acidification potential(AP),and cumulative energy demand(CED)of wind power at the regional scale for 2022 and under three future scenarios(high-power wind turbine promotion,reduced wind curtailment,and a comprehensive development scenario).The results indicate that in 2022,the life cycle GWP,AP,and CED of wind power in western China were 10.76 g CO_(2) eq/kWh,0.177 g SO_(2) eq/kWh,and 17.6 kJ/kWh,respectively.Scenario simulations suggest that reducing wind curtailment is the most effective approach for reducing emissions in Inner Mongolia,Gansu,Qinghai,Ningxia,and Xinjiang,producing average decreases of 8.64%in GWP,8.39%in AP,and 9.26%in CED.In contrast,for Guangxi,Chongqing,Sichuan,Guizhou,Yunnan,Xizang,and Shaanxi,the promotion of high-power wind turbines provides greater environmental benefits than reducing curtailment,producing average decreases of 3.45%,3.09%,and 4.29%in GWP,AP,and CED,respectively.These findings help clarify the environmental impact of wind power across its life cycle at the regional scale and provide theoretical references for the direction of future wind power development and the formulation of related policies.
基金supported by the Start-up Fund of China Pharmaceutical University(No.3150020057)。
文摘Hair loss,a multifactorial disorder characterized by follicular miniaturization and excessive shedding,significantly impairs psychological well-being and quality of life.Cyperus rotundus rhizome(CR),a traditional Chinese medicine used for various ailments,has not been evaluated for efficacy in treating hair loss.This study presents the first comprehensive assessment of the hair growth-promoting effects of ethanol extract from CR on mouse primary dermal papilla cells(MDPCs)and human immortalized hair DPCs(IHHDPCs),employing cell counting kit-8(CCK-8),scratch assay,reverse transcription-quantitative polymerase chain reaction(RT-q PCR),and Western blot(WB).CR treatment activated the Wnt/β-Catenin signaling pathway by upregulating Wnt10b,increasingβ-Catenin protein levels and promoting its nuclear translocation,while simultaneously downregulating transforming growth factor-beta 1(TGF-β1),BMP4,and dickkopf-related protein 1(DKK1)in MDPCs.These molecular changes enhanced cell proliferation and increased secretion of key growth factors—insulin-like growth factor 1(IGF1),keratinocyte growth factor(KGF),and vascular endothelial growth factor(VEGF)—thereby stimulating hair growth and prolonging the anagen phase,which was confirmed in an ex vivo hair follicle(HF)organ culture model.Chromatographic analysis identified the petroleum ether fraction(CRP),enriched in sesquiterpenes,as the primary bioactive component.Both CR and CRP promoted IHHDPC proliferation,migration,and growth factor expression through activation of the Wnt/β-Catenin pathway,with CRP exhibiting superior bioactivity.Furthermore,both treatments stimulated HF cycling,increased follicular density,and upregulated Ki67 andβ-Catenin expression in the dorsal skin of C57BL/6 mice.Collectively,these findings demonstrate that CR and CRP promote hair growth and modulate the hair cycle via enhancement of Wnt/β-Catenin signaling,providing a scientific basis for the potential clinical application of C.rotundus rhizomes in hair loss therapy and the development of related pharmaceuticals or cosmetics.
基金supported by National Natural Science Foundation of China(Grant No.42201080)Young Scientific and Technological Talents Program of Shaanxi Province(Grant No.2025ZC-KJXX-57)Special Scientific Research Program of the Shaanxi Provincial Department of Education(Grant No.21JK0967)。
文摘Freeze-thaw cycles(FTCs)have an important effect on soil aggregate stability by altering soil structures,thereby influencing soil wind and water erosion on the eastern Qinghai-Tibet Plateau.However,the effects of FTCs on the stability of these soils remain unclear.Here,we conducted freeze-thaw simulations in laboratory to investigate the effects of FTCs(0 to 15 cycles)on the wet-and dry-sieving aggregate stability of undisturbed sandy loam from Maqu county,which was treated with different initial soil moisture contents(1%to 25%in increments of 4%)and initial aggregate diameters(<2,2-5,5-10,and 10-15 mm).Results show that soil aggregates with initial diameters larger than 2 mm exhibit higher soil organic carbon contents(1.45%-1.57%)and silt contents(34.63%-35.52%)than those smaller than 2 mm(0.93%and 31.38%,respectively).The stability of both wet-and dry-sieving aggregates increases with larger initial diameters.Increasing initial soil moisture content from 1%to 25%reduces aggregate stability,with reductions of 2.4%-88.0%for wet-sieving aggregates and 2.1%-25.5%for dry-sieving aggregates(>2 mm).With increasing FTCs,wet-sieving aggregate(>2 mm)stability exhibits a fluctuating upward trend,with increases of 79.2%-87.4%after 15 FTCs,while dry-sieving aggregate(>2 mm)stability decreases significantly(5.7%-21.7%)upon the first FTC and remains unchanged thereafter.The stability of both the wet-and dry-sieving aggregates smaller than 2 mm remains unchanged with increasing FTCs(p>0.05).SOC content decreases by 22.3%on average with increasing FTCs from 1 to 15 and shows no significant correlations with wet-and dry-sieving aggregate stability.Higher silt content(r=0.39,p<0.05)and lower sand content(r=-0.38,p<0.05)enhances the wet-sieving aggregate stability of sandy loam.Frequent FTCs tend to improve wet-sieving aggregate stability but reduce dry-sieving aggregate stability in the sandy loam.The findings provide certain guidance for preventing freeze-thaw-induced wind erosion.
基金the National Natural Science Foundation of China(22002008,22202226,22468042)Ningxia Key Research and Development Project(2022BEE03002,2022 BSB03056)+1 种基金the Fourth Batch of Ningxia Youth Talents Supporting Program(TJGC2019022)West Light Foundation of the Chinese Academy of Sciences(XAB2019AW02).
文摘The conversion of CO_(2) into high value added chemicals via the Fischer-Tropsch synthesis(FTS)reaction has attracted significant attention.The surface oxygenation environment is a significant factor influencing the performance of the catalyst.In this work,spin-polarized density-functional theory calculations have been used to investigate the adsorption and reactions of CO_(2) and H to generate CH4 and CH3OH on Fe_(5)C_(2)(100)surfaces with varying OH∗coverage.On the pure Fe_(5)C_(2)(100)surface,surface C^(∗) preferentially reacts with hydrogen to form CH4,exposing C^(∗) vacancy.CO_(2) favors adsorbing on the C^(∗) vacancy to further dissociating and activating.The co-adsorption of OH∗promotes the C^(∗) cycle process by facilitating the hydrogenation of C^(∗).The Fe_(5)C_(2) surface with an oxide interface is favorable for reducing FexOy,thereby maintaining the dynamic stability of the surface.Therefore,surface oxidation is inevitably involved in the entire C^(∗) cycle of the FTS reaction and regulates the relative content of iron oxides and iron carbides.Our work can contribute to the rational modulation of the surface C^(∗) cycle,thereby enhancing catalyst performance.
基金support from the Major basic research project of Natural Science Foundation of Shandong Province(No.ZR2023ZD12)Singapore National Research Foundation Investigatorship(No.NRFNRFI08-2022-0009)NUS R&G Postdoc Fellowship Program.
文摘Lithium-oxygen(Li-O_(2))battery is favored among“beyond lithiumion”technologies for sustainability because of its exceptional energy density.Major impediments are the poor cycle stability and grievous capacity degradation at high current densities.We address these issues by a“killing two birds with one stone”O_(2)-pressure protocol.It first resolves efficient O_(2) mass transport at high rates..The accelerated reaction kinetics optimizes the composition and growth pathway of discharge products.This protocol secondly achieves protection of Li anodes via densifying corrosion layers on them.Consequently,the battery delivers both ultrahigh discharge capacity(>9,000 mAh g^(-1))at 3,000 mA g^(-1) and excellent cycling stability.Under a dual-strategy effect of high-pressure O_(2) and artificial protection layers,the battery actualizes over 11-fold increase in cycle life of 5,170 h(2,585 cycles).The strategy opens avenues for advancing Li-O_(2) batteries towards practical application and confers the extension to other gas-based batteries.
