In order to achieve the large-scale application of manufactured sand in railway high-strength concrete structure,a series of high-strength manufactured sand concrete(HMC)are prepared by taking the manufactured sand li...In order to achieve the large-scale application of manufactured sand in railway high-strength concrete structure,a series of high-strength manufactured sand concrete(HMC)are prepared by taking the manufactured sand lithology(tuff,limestone,basalt,granite),stone powder content(0,5%,10%,15%)and concrete strength grade(C60,C80,C100)as variables.The evolution of mechanical properties of HMC and the correlation between cubic compressive strength and other mechanical properties are studied.Compared to river sand,manufactured sand enhances the cubic compressive strength,axial compressive strength and elastic modulus of concrete,while its potential microcracks weaken the flexural strength and splitting tensile strength of concrete.Stone powder content displays both positive and negative effects on mechanical properties of HMC,and the stone powder content is suggested to be less than 10%.The empirical formulas between cubic compressive strength and other mechanical properties are proposed.展开更多
The endpoint carbon content in the converter is critical for the quality of steel products,and accurately predicting this parameter is an effective way to reduce alloy consumption and improve smelting efficiency.Howev...The endpoint carbon content in the converter is critical for the quality of steel products,and accurately predicting this parameter is an effective way to reduce alloy consumption and improve smelting efficiency.However,most scholars currently focus on modifying methods to enhance model accuracy,while overlooking the extent to which input parameters influence accuracy.To address this issue,in this study,a prediction model for the endpoint carbon content in the converter was developed using factor analysis(FA)and support vector machine(SVM)optimized by improved particle swarm optimization(IPSO).Analysis of the factors influencing the endpoint carbon content during the converter smelting process led to the identification of 21 input parameters.Subsequently,FA was used to reduce the dimensionality of the data and applied to the prediction model.The results demonstrate that the performance of the FA-IPSO-SVM model surpasses several existing methods,such as twin support vector regression and support vector machine.The model achieves hit rates of 89.59%,96.21%,and 98.74%within error ranges of±0.01%,±0.015%,and±0.02%,respectively.Finally,based on the prediction results obtained by sequentially removing input parameters,the parameters were classified into high influence(5%-7%),medium influence(2%-5%),and low influence(0-2%)categories according to their varying degrees of impact on prediction accuracy.This classi-fication provides a reference for selecting input parameters in future prediction models for endpoint carbon content.展开更多
In this study,compacted loess samples with varying compaction water content but identical dry density were prepared to investigate the evolution of their hydraulic conductivity and compression behavior.Additionally,en...In this study,compacted loess samples with varying compaction water content but identical dry density were prepared to investigate the evolution of their hydraulic conductivity and compression behavior.Additionally,environmental scanning electron microscopy(ESEM)and nuclear magnetic resonance(NMR)analyses were conducted to gain microstructural insights into loess behavior at the laboratory scale.The results indicate that the maximum saturated hydraulic conductivity is observed at the lowest compaction water content,particularly in the early stage of permeability tests.In particular,for loess compacted at water contents below the optimum(as determined by the modified Proctor compaction test),the hydraulic conductivity decreases throughout the permeability tests.Conversely,when the water content exceeds the optimum level,the hydraulic conductivity shows an increasing trend.In terms of compression behavior,when the as-compacted samples are loaded in oedometer conditions,an increase in material compressibility is observed with increasing compaction water content.Again,a different phenomenological behavior was observed when the compaction water content exceeded the optimum,i.e.an abrupt increase in loess compressibility.ESEM tests provide microstructural confirmation of this evidence,as the surface morphology of the compacted loess changes significantly with increasing compaction water content.The microstructural evolution was also quantified in terms of area ratio using image processing software.Finally,NMR was used to quantify the intra-and inter-aggregate water at different compaction water contents,once again highlighting a threshold for the presence or absence of inter-aggregate water similar to the optimum water content.展开更多
Carnitine(CAR) is a vital quaternary ammonium compound. However, the characteristics of CAR content and its influencing factors across different marine animal species remain poorly understood. This study examined the ...Carnitine(CAR) is a vital quaternary ammonium compound. However, the characteristics of CAR content and its influencing factors across different marine animal species remain poorly understood. This study examined the CAR content in 258 marine animals, representing 54 species across seven classes, collected from coastal and offshore regions of China and the Northwest Pacific Ocean(NWPO) between May 2020 and June 2022. The CAR content ranged from0.01 mmol/kg to 1.33 mmol/kg, with a mean value of(0.15 ± 0.18) mmol/kg(mean ± standard deviation). The highest CAR content was observed in Crustacea [(0.48 ± 0.38) mmol/kg], which was four times greater than the average CAR content in the other classes [(0.12 ± 0.11) mmol/kg]. Overall, the CAR content exhibited minor variation among marine animals, potentially because the carnitine pool maintains its dynamic balance. Additionally, significant correlations were observed between the CAR content and environmental factors in some species: a negative correlation with seawater temperature and positive correlations with latitude, seawater salinity, and depth. These results suggest that the CAR content in marine animals is influenced by environmental changes. This study provides theoretical insights for understanding the characteristics and influencing factors of CAR content in marine animals.展开更多
The present teaching content of the power electronics course is insufficient to cover the power electronics technology used in building electrical engineering.This paper analyzes the relationship between building elec...The present teaching content of the power electronics course is insufficient to cover the power electronics technology used in building electrical engineering.This paper analyzes the relationship between building electrical engineering and power electronics technology,investigates the main power electronics technology used in building electrical engineering,introduces the teaching content of current power electronics course,analyzes the insufficiency of current teaching content related to the practice of electrical engineering,and proposes the principles and directions for the reformation and innovation of the teaching content of the course of power electronics for the major of building electricity and intelligence.展开更多
Characterization and optimization of physical and chemical properties of drilling fluids are critical for the efficiency and success of drilling operations.In particular,maintaining the optimal levels of solids conten...Characterization and optimization of physical and chemical properties of drilling fluids are critical for the efficiency and success of drilling operations.In particular,maintaining the optimal levels of solids content is essential for achieving the most effective fluid performance.Proper management of solids content also reduces the risk of tool failures.Traditional solids content analysis methods,such as retort analysis,require substantial human intervention and time,which can lead to inaccuracies,time-management issues,and increased operational risks.In contrast to human-intensive methods,machine learning may offer a viable alternative for solids content estimation due to its pattern-recognition capability.In this study,a large set of laboratory reports of drilling-fluid analyses from 130 oil wells around the world were compiled to construct a comprehensive data set.The relationships among various rheological parameters were analyzed using statistical methods and machine learning algorithms.Several machine learning algorithms of diverse classes,namely linear(linear regression,ridge regression,and ElasticNet regression),kernel-based(support vector machine)and ensemble tree-based(gradient boosting,XGBoost,and random forests)algorithms,were trained and tuned to estimate solids content from other readily available drilling fluid properties.Input variables were kept consistent across all models for interpretation and comparison purposes.In the final stage,different evaluation metrics were employed to evaluate and compare the performance of different classes of machine learning models.Among all algorithms tested,random forests algorithm was found to be the best predictive model resulting in consistently high accuracy.Further optimization of the random forests model resulted in a mean absolute percentage error(MAPE)of 3.9%and 9.6%and R^(2) of 0.99 and 0.93 for the training and testing sets,respectively.Analysis of residuals,their histograms and Q-Q normality plots showed Gaussian distributions with residuals that are scattered around a mean of zero within error ranges of±1%and±4%,for training and testing,respectively.The selected model was further validated by applying the rheological measurements from mud samples taken from an offshore well from the Gulf of Mexico.The model was able to estimate total solids content in those four mud samples with an average absolute error of 1.08% of total solids content.The model was then used to develop a web-based graphical-user-interface(GUI)application,which can be practically used at the rig site by engineers to optimize drilling fluid programs.The proposed model can complement automation workflows that are designed to measure fundamental rheological properties in real time during drilling operations.While a standard retort test can take approximately 2 h at the rig site,such kind of real-time estimations can help the rig personnel to timely optimize drilling fluids,with a potential of saving 2920 man-hours in a given year for a single drilling rig.展开更多
Tight oil is the most viable target for unconventional oil and gas exploration, but the complexity of micro-/nanopore throat systems significantly affects the oil content of reservoirs. To investigate the causes of he...Tight oil is the most viable target for unconventional oil and gas exploration, but the complexity of micro-/nanopore throat systems significantly affects the oil content of reservoirs. To investigate the causes of heterogeneity in oil-bearing reservoirs, a high-pressure mercury injection experiment combined with fractal theory was conducted to analyze the micro pore throat structure characteristics of the tight sandstone of Chang 7 Member reservoirs in the Ordos Basin. The factors controlling the variations in oil content among tight sandstone samples were identified based on mineral composition characteristics. The results indicate that the pore throat radius distribution is mainly unimodal an bimodal. In oil-bearing samples, the pore throat distributions align well with the corresponding permeability contribution curves, while in oil-free samples, there is a clear deviation from these curves. Mesopore throats exert the greatest influence on seepage capacity. Differences in fractal characteristics are primarily reflected in D1 values, with oil-free samples exhibiting D1 values close to 3, indicating an extremely nonuniform pore throat structure at this scale. The content of quartz, plagioclase, and chlorite is significantly higher in oil-bearing samples than in oil-free samples, whereas calcite content is lower in oil-bearing samples. There is a positive correlation between the contents of quartz, plagioclase, and chlorite with D1;their increased presence contributes to a more favorable pore throat structure.Conversely, the calcite contents show an inverse relationship with D1. Cementation increases the complexity of pore throat structures, while multiple diagenetic processes simultaneously control these characteristics, leading to variations in oil content.展开更多
Peanut kernels rich in oil,particularly those with oleic acid as their primary fatty acid,are in high demand among consumers,the food industry,and farmers due to their superior nutritional content,extended shelf life,...Peanut kernels rich in oil,particularly those with oleic acid as their primary fatty acid,are in high demand among consumers,the food industry,and farmers due to their superior nutritional content,extended shelf life,and health benefits.The oil content and fatty acid composition are governed by multiple genetic factors.Identifying the quantitative trait loci(QTLs)related to these attributes will facilitate marker-assisted selection and genomic selection,thus enhancing quality-focused peanut breeding programs.For this purpose,we developed a population of 521 recombinant inbred lines(RILs)and tested their kernel quality traits across five different environments.We identified two major and stable QTLs for oil content,qOCAh12.1 and qOCAh16.1.The markers linked to these QTLs were designed by Kompetitive allele-specific PCR(KASP)and subsequently validated.Moreover,we found that the superior haplotype of oil content in the qOCAh16.1 region was conserved within the plant introduction(PI)germplasm cluster,as evidenced by a diverse peanut accession panel.In addition,we determined that qAh09 and qAh19.1,which harbor the key gene encoding fatty acid desaturase 2(FAD2),influence all seven fatty acids,palmitic,stearic,oleic,linoleic,arachidic,gadoleic,and behenic acids.Regarding the protein content and the long-chain saturated fatty acid behenic acid,qAh07 emerged as the major and stable QTL,accounting for over 10%of the phenotypic variation explained(PVE).These findings can enhance marker-assisted selection in peanut breeding,with the aim of improving the oil content,and deepen our understanding of the genetic mechanisms that shape fatty acid composition.展开更多
To elucidate the effect of calcite-regulated activated carbon(AC)structure on low-temperature denitrification performance of SCR catalysts,this work prepared a series of Mn-Ce/De-AC-xCaCO_(3)(x is the calcite content ...To elucidate the effect of calcite-regulated activated carbon(AC)structure on low-temperature denitrification performance of SCR catalysts,this work prepared a series of Mn-Ce/De-AC-xCaCO_(3)(x is the calcite content in coal)catalysts were prepared by the incipient wetness impregnation method,followed by acid washing to remove calcium-containing minerals.Comprehensive characterization and low-temperature denitrification tests revealed that calcite-induced structural modulation of coal-derived AC significantly enhances catalytic activity.Specifically,NO conversion increased from 88.3%of Mn-Ce/De-AC to 91.7%of Mn-Ce/De-AC-1CaCO_(3)(210℃).The improved SCR denitrification activity results from the enhancement of physicochemical properties including higher Mn^(4+)content and Ce^(4+)/Ce^(3+)ratio,an abundance of chemisorbed oxygen and acidic sites,which could strengthen the SCR reaction pathways(richer NH_(3)activated species and bidentate nitrate active species).Therefore,NO removal is enhanced.展开更多
The methane adsorption capacity,gas content,and carbon isotope characteristics of coal are crucial parameters that determine the productivity of coalbed methane(CBM)wells and their development potential.In this paper,...The methane adsorption capacity,gas content,and carbon isotope characteristics of coal are crucial parameters that determine the productivity of coalbed methane(CBM)wells and their development potential.In this paper,test analyses of methane adsorption,gas content and carbon isotope of methane were carried out using 89 samples from the No.3 coal seam in the southwestern part of the Qinshui Basin.Their characteristics and correlations were analyzed.A relationship model between methane adsorption,gas content,carbon isotopes,coal metamorphism and material composition were established,and its controlling mechanism was investigated.The results indicate that the distribution patterns of Langmuir volume and Langmuir pressure in No.3 coal seam are mainly determined by the material composition and the thermal evolution level.The methane gas content in coal is mainly affected by the burial depth,microcosmic co mposition,mineral conte nt,moisture content and ash yield,adsorption capacity and metamorphism of the coal.The methane carbon isotope(δ^(13)C_(1))values in the natural desorbed gas from No.3 coal seam range from-26.95%to-57.80‰,with a mean value of-34.53‰.δ^(13)C_(1)in coal shows a two-stage variation pattern with increasing in vitrinite reflectance(R_(max)^(o)).When R_(max)^(o)is blow 3.0%,δ^(13)C_(1)values of methane in coal become progressively heavier with increasing R_(max)^(o).When R_(max)^(o)reaches or exceeds 3.0%,δ^(13)C_(1)values exhibit a lightning trend with furth er increases in R_(max)^(o),which is primarily controlled by the carbon isotope fractionation effects during thermal evolution.展开更多
Surface albedo,as one of the important properties of the underlying surface,has a significant impact on the surface energy balance in cold regions.However,due to the complexity of the factors affecting surface albedo,...Surface albedo,as one of the important properties of the underlying surface,has a significant impact on the surface energy balance in cold regions.However,due to the complexity of the factors affecting surface albedo,existing calculations still contain inaccuracies.Therefore,this study conducted surface albedo experiments on loess with different water contents and temperatures.By analyzing the surface albedo measurements of samples with varying temperature and water content levels,as well as the soil freezing characteristic curve(SFCC)and soil-water characteristic curve(SWCC)of loess,the study explores the influence of soil temperature and water content on the surface albedo of loess.The results indicate that both the temperature and water content of loess jointly affect surface albedo.During the process of albedo change,there exists a water content threshold that alters the trend of surface albedo.Soil temperature influences surface albedo by affecting the content of pore ice and liquid water within the soil.When the water content of loess is relatively low,the surface albedo decreases as the unfrozen water content decreases.However,this trend changes as the water content of loess increases.Additionally,a decrease in soil temperature lowers the moisture content threshold during the changes in surface albedo.This study provides a reference for exploring and determining the surface energy balance in cold regions under the background of warm and humid climates,as well as for establishing thermal calculation boundaries.展开更多
Vehicular networks enable seamless connectivity for exchanging emergency and infotainment content.However,retrieving infotainment data from remote servers often introduces high delays,degrading the Quality of Service(...Vehicular networks enable seamless connectivity for exchanging emergency and infotainment content.However,retrieving infotainment data from remote servers often introduces high delays,degrading the Quality of Service(QoS).To overcome this,caching frequently requested content at fog-enabled Road Side Units(RSUs)reduces communication latency.Yet,the limited caching capacity of RSUs makes it impractical to store all contents with varying sizes and popularity.This research proposes an efficient content caching algorithm that adapts to dynamic vehicular demands on highways to maximize request satisfaction.The scheme is evaluated against Intelligent Content Caching(ICC)and Random Caching(RC).The obtained results show that our proposed scheme entertains more contentrequesting vehicles as compared to ICC and RC,with 33%and 41%more downloaded data in 28%and 35%less amount of time from ICC and RC schemes,respectively.展开更多
This study systematically investigates the effects of Al content on the microstructure,tensile properties,and high-cycle fatigue behavior of extruded Mg-xAl-Zn-Ca-Y(SENx)alloys.The results reveal that all extruded all...This study systematically investigates the effects of Al content on the microstructure,tensile properties,and high-cycle fatigue behavior of extruded Mg-xAl-Zn-Ca-Y(SENx)alloys.The results reveal that all extruded alloys exhibit fully recrystallized microstructures with undissolved second-phase particles enriched with Ca and Y.The average grain size varies non-monotonically with Al content due to the competing effects of recrystallization kinetics,solute drag,and particle band distribution.As Al content increases,tensile strength increases,while ductility decreases.Notably,despite its relatively coarse grain structure,the SEN9 alloy exhibits significantly higher yield strength than the SEN6 alloy.This improvement is mainly attributed to additional precipitation strengthening from fine Mg_(17)Al_(12)discontinuous precipitates formed along grain boundaries.Meanwhile,the reduced elongation observed in the SEN9 and SEN11 alloys is attributed to premature fracture at coarse Mg_(17)(Al,Zn,Ca)_(12)particle bands aligned along the extrusion direction.From the SEN1 to SEN9 alloys,the fatigue strength(FS)increases approximately linearly with ultimate tensile strength(UTS),reaching 170 MPa.However,this FS-UTS proportionality fails in the SEN11 alloy,where FS falls to 120 MPa despite the highest UTS.This deviation from the FS-UTS correlation that is observed for the lower-Al-content alloys is attributed to the clustered distribution of coarse Mg_(17)(Al,Zn,Ca)_(12)particles in the SEN11 alloy,which promotes early crack initiation under cyclic loading.These findings emphasize the importance of controlled Al addition in enhancing both strength and fatigue resistance while also highlighting the adverse effects of excessive Al content owing to microstructural embrittlement.展开更多
Gas injection-enhanced underground coal combustion for heat extraction represents a disruptive chemical fluidized extraction method of coal resources.Coal seam combustion dynamics provide crucial underpinnings for eng...Gas injection-enhanced underground coal combustion for heat extraction represents a disruptive chemical fluidized extraction method of coal resources.Coal seam combustion dynamics provide crucial underpinnings for engineering realization.This study establishes an experimental system for monitoring temperature field evolution during gas-assisted combustion in cylindrical coal cores,investigating the influence of moisture content(0%,16%,24%)on gas-assisted combustion kinetics.Results showed moisture content significantly influences combustion:higher levels(16%-24%)delay high-temperature expansion(0-1 h)due to evaporation energy absorption,but subsequently enhance efficiency through pore formation and oxygen diffusion,achieving 1120-1230°C peaks.Dry coal exhibits rapid initial combustion(peak temperature of 1130°C within 1 h)but weaker sustained reactions.The temperature field evolves from localized hotspots to an elliptical high-temperature zone,with axial expansion rates surpassing radial rates,driven by thermal buoyancy and convective heat transfer.Moisture’s dual role is revealed:initially as a thermodynamic inhibitor and later as a promoter by increasing pore diameter and oxygen diffusion coefficients.An optimal moisture content of 16%balances initial heat loss with enhanced reactivity,offering practical insights for optimizing gas injection and thermal recovery in underground coal combustion.展开更多
This study was conducted to investigate the air oxygen content inside and outside a Phyllostachys edulis forest in Qishan Forest Park throughout all four seasons.(1)Regarding the overall annual variation in oxygen con...This study was conducted to investigate the air oxygen content inside and outside a Phyllostachys edulis forest in Qishan Forest Park throughout all four seasons.(1)Regarding the overall annual variation in oxygen content in both environments,comparative analysis of the annual average oxygen concentration showed that the average inside the forest was 22.13%,while the value outside it was 21.39%.The annual average oxygen concentration inside the forest was 3.34%higher than that outside the forest.(2)Regarding the seasonal variation in oxygen content at both sites,the oxygen concentration inside the forest was consistently higher than that outside the forest in all four seasons.The oxygen concentrations inside the forest were 22.1%,21.9%,21.8%,and 21.5%in spring,summer,autumn,and winter,respectively,while outside the forest,they were 22.0%,21.8%,21.7%,and 21.4%for the same seasons,respectively.(3)The diurnal variation trends of oxygen concentration at both sites were similar throughout all four seasons,exhibiting a single-peak and double-trough curve pattern.The peak period occurred at 13:00 in spring,summer,and winter,and at 9:00 in autumn.The trough periods were observed at 7:00 and between 21:00 and 23:00 or at 5:00.展开更多
Buffer material and metal disposal containers are the key engineering barriers in the geological disposal of high-level radioactive waste.The durability of disposal containers largely depends on the water con-tent in ...Buffer material and metal disposal containers are the key engineering barriers in the geological disposal of high-level radioactive waste.The durability of disposal containers largely depends on the water con-tent in buffer material.This work focused on investigating the corrosion evolution of NiCu low alloy steel in compacted GMZ bentonite with different water contents for 270 d by using weight loss,electrochemi-cal measurements,and various methods for analyzing corrosion products.As the water content increased from 13%to 20%,the water in the bentonite transformed from an unsaturated to a critical saturated state,and the corrosion rate of NiCu steel clearly increased.In these two systems,the oxygen could mi-grate to the thin liquid film on the steel surface through the air pores in the bentonite in the gas phase and undergo cathodic reduction.Meanwhile,it oxidized the ferrous hydrolysis products into ferric corro-sion products and formed a rust layer,which could block the diffusion of oxygen.At that moment,the cathodic process of NiCu steel corrosion changed to rust reduction.When the water content continually increased to 30%and 40%,the compacted bentonite was in a saturation state,and the corrosion rate of NiCu steel was significantly decreased.This was because most pores among the bentonite particles were occupied by a large amount of free water,which hindered the diffusion of oxygen and inhibited its cathodic reduction.Furthermore,it restrained the oxidation of ferrous corrosion products,which greatly weakened the cathodic depolarization of rust,leading to the cathodic process being dominated by the hydrogen evolution reaction.展开更多
The nine typical Shanghai soils are usually silty clay or clay,which appears inconsistent with their low clay content in the relevant publications.The literature review shows that the documented clay content of Shangh...The nine typical Shanghai soils are usually silty clay or clay,which appears inconsistent with their low clay content in the relevant publications.The literature review shows that the documented clay content of Shanghai soils ranges from 0%to 30.8%by weight.This inconsistency may stem from two factors:(1)the Shanghai soil classification system relies solely on the plasticity index for soil naming;and(2)the conventional steel sieving method cannot separate the clay from the fine soils(clay and silt mixtures).This paper aims to accurately determine the clay content in Shanghai soils.It uses nylon cloth sieves with apertures ranging from 0.063 mm to 0.0008 mm and completely separates the clay particles from the fine soils.The nine typical Shanghai soils are tested and sieved into distinct subgroups of clay,silt,sand,and gravel particles.Results demonstrate clay content ranges from 18.99%to 79.33%,substantially higher than literature values and consistent with their names of either silty clay or clay.Macro,micro,and scanning electron microscope(SEM)images reveal effective separation of clay,silt,sand,and gravel particles.The clay exhibits cohesive properties,while the silt,sand,and gravel comprise clean,non-cohesive individual particles.The clay and silt fractions are confirmed to be within their respective sieving limits by SEM-based particle size measurements.Additionally,Atterberg limits testing highlights the high plasticity of the clay particles and the non-plastic nature of the silt particles.展开更多
With the rising global demand for energy and growing awareness of environmental sustainability,hydrogen energy has emerged as a promising clean and efficient alternative.Supported by national policies,both basic and a...With the rising global demand for energy and growing awareness of environmental sustainability,hydrogen energy has emerged as a promising clean and efficient alternative.Supported by national policies,both basic and applied research in hydrogen and hydrogen energy have seen significant advancements in recent years.Reflecting these developments,the teaching of“hydrogen element and hydrogen energy”in college level inorganic chemistry has gradually expanded.In the context of the new era,there is an urgent need to reform and enrich this teaching content to cultivate students’comprehensive abilities and align with the country’s evolving demand for talent in the energy sector.This paper analyzes current challenges in the teaching of hydrogen energy within college chemistry curricula and proposes targeted strategies to optimize instructional content.The goal is to offer practical insights and references for educators seeking to improve the effectiveness and relevance of hydrogen energy education.展开更多
Biotite content critically influences rock mechanical behavior and threatens underground engineering stability.Uniaxial compression tests with acoustic emission(AE)monitoring were conducted on granite pegmatite sample...Biotite content critically influences rock mechanical behavior and threatens underground engineering stability.Uniaxial compression tests with acoustic emission(AE)monitoring were conducted on granite pegmatite samples having varying biotite content.Peak frequency distribution analysis,rise angleaverage frequency(RA-AF)analysis,multifractal theory,and a dynamic multifractal algorithm were applied to explore the relationship between damage evolution and AE characteristics.Results indicate that increased biotite content reduces uniaxial compressive strength and elastic modulus,enhances plastic deformation,and increases the proportion of shear cracks.The segmented evolution of the dynamic multifractal parameter Δα_(m) is biotite-dependent.Oscillations during the elastic phase signify localized shear crack initiation and propagation;their attenuation in the plastic phase reflects frictional closure along biotite cleavage planes,promoting elastic energy storage and delaying release.AE-based damage models and time-varying signals characterize rock damage progression.Stress concentrations around biotite minerals foster localized shear band formation,leading to concentrated shear failure at lower damage levels.Higher biotite content accelerates crack propagation,while smooth cleavage planes lower the fracture energy threshold,reducing strength and stiffness.These findings enhance understanding of biotite-influenced progressive rock damage and underpin stability monitoring and early-warning systems for underground engineering.展开更多
Aerosol hygroscopicity and liquid water content(ALWC)have important influences on the environmental and climate effect of aerosols.In this study,we measured the hygroscopic growth factors(GF)of particles with dry diam...Aerosol hygroscopicity and liquid water content(ALWC)have important influences on the environmental and climate effect of aerosols.In this study,we measured the hygroscopic growth factors(GF)of particles with dry diameters of 40,80,150,and 200 nm during the wintertime in Nanjing.Both the GF-derived hygroscopicity parameter(κ_(gf))and ALWC increased with particle size,but displayed differing diurnal variations,withκ_(gf)peaking around the midday,while ALWC peaking in the early morning.Nitrate,ammonium and oxygenated organic aerosols(OOA)were found as the chemical components mostly strongly correlated with ALWC.A closure study suggests that during midday photo-oxidation and nighttime high ALWC periods,theκof organic aerosols(κ_(org))was underestimated when using previous parameterizations.Accordingly,we re-constructed parameterizations forκ_(org)and the oxidation level of organics for these periods,which indicates a higher hygroscopicity of photochemically formed OOA than the aqueous OOA,yet both being much higher than the generally assumed OOA hygroscopicity.Additionally,in a typical high ALWC episode,concurrently increased ALWC,nitrate,OOA as well as aerosol surface area and mass concentrations were observed under elevated ambient RH.This strongly indicates a coupled effect that the hygroscopic secondary aerosols,in particular nitratewith strong hygroscopicity,led to large increase in ALWC,which in turn synergistically boosted nitrate and OOA formation by heterogeneous/aqueous reactions.Such interaction may represent an important mechanism contributing to enhanced formation of secondary aerosols and rapid growth of fine particulate matter under relatively high RH conditions.展开更多
基金Funded by the National Natural Science Foundation of China(Nos.U1934206,52108260)China Academy of Railway Sciences Fund(No.2021YJ078)+1 种基金Railway Engineering Construction Standard Project(No.2023-BZWW-006)New Cornerstone Science Foundation through the XPLORER PRIZE。
文摘In order to achieve the large-scale application of manufactured sand in railway high-strength concrete structure,a series of high-strength manufactured sand concrete(HMC)are prepared by taking the manufactured sand lithology(tuff,limestone,basalt,granite),stone powder content(0,5%,10%,15%)and concrete strength grade(C60,C80,C100)as variables.The evolution of mechanical properties of HMC and the correlation between cubic compressive strength and other mechanical properties are studied.Compared to river sand,manufactured sand enhances the cubic compressive strength,axial compressive strength and elastic modulus of concrete,while its potential microcracks weaken the flexural strength and splitting tensile strength of concrete.Stone powder content displays both positive and negative effects on mechanical properties of HMC,and the stone powder content is suggested to be less than 10%.The empirical formulas between cubic compressive strength and other mechanical properties are proposed.
基金financially supported by the National Natural Science Foundation of China(No.52174297).
文摘The endpoint carbon content in the converter is critical for the quality of steel products,and accurately predicting this parameter is an effective way to reduce alloy consumption and improve smelting efficiency.However,most scholars currently focus on modifying methods to enhance model accuracy,while overlooking the extent to which input parameters influence accuracy.To address this issue,in this study,a prediction model for the endpoint carbon content in the converter was developed using factor analysis(FA)and support vector machine(SVM)optimized by improved particle swarm optimization(IPSO).Analysis of the factors influencing the endpoint carbon content during the converter smelting process led to the identification of 21 input parameters.Subsequently,FA was used to reduce the dimensionality of the data and applied to the prediction model.The results demonstrate that the performance of the FA-IPSO-SVM model surpasses several existing methods,such as twin support vector regression and support vector machine.The model achieves hit rates of 89.59%,96.21%,and 98.74%within error ranges of±0.01%,±0.015%,and±0.02%,respectively.Finally,based on the prediction results obtained by sequentially removing input parameters,the parameters were classified into high influence(5%-7%),medium influence(2%-5%),and low influence(0-2%)categories according to their varying degrees of impact on prediction accuracy.This classi-fication provides a reference for selecting input parameters in future prediction models for endpoint carbon content.
基金the China Postdoctoral Science Foundation(Grant No.2024MD753992)Shaanxi Geotechnical Mechanics and Engineering Young Talent Support Program Project(Grant No.YESS2024005)the National Natural Science Foundation of China(Grant No.41931285).
文摘In this study,compacted loess samples with varying compaction water content but identical dry density were prepared to investigate the evolution of their hydraulic conductivity and compression behavior.Additionally,environmental scanning electron microscopy(ESEM)and nuclear magnetic resonance(NMR)analyses were conducted to gain microstructural insights into loess behavior at the laboratory scale.The results indicate that the maximum saturated hydraulic conductivity is observed at the lowest compaction water content,particularly in the early stage of permeability tests.In particular,for loess compacted at water contents below the optimum(as determined by the modified Proctor compaction test),the hydraulic conductivity decreases throughout the permeability tests.Conversely,when the water content exceeds the optimum level,the hydraulic conductivity shows an increasing trend.In terms of compression behavior,when the as-compacted samples are loaded in oedometer conditions,an increase in material compressibility is observed with increasing compaction water content.Again,a different phenomenological behavior was observed when the compaction water content exceeded the optimum,i.e.an abrupt increase in loess compressibility.ESEM tests provide microstructural confirmation of this evidence,as the surface morphology of the compacted loess changes significantly with increasing compaction water content.The microstructural evolution was also quantified in terms of area ratio using image processing software.Finally,NMR was used to quantify the intra-and inter-aggregate water at different compaction water contents,once again highlighting a threshold for the presence or absence of inter-aggregate water similar to the optimum water content.
基金The Shandong Provincial Natural Science Foundation of China under contract No.ZR2022MD055Youth Program of National Natural Science Foundation of China under contract No. 41606097Central Public interest Scientific Institution Basal Research Fund of CAFS under contract No. 2023TD53。
文摘Carnitine(CAR) is a vital quaternary ammonium compound. However, the characteristics of CAR content and its influencing factors across different marine animal species remain poorly understood. This study examined the CAR content in 258 marine animals, representing 54 species across seven classes, collected from coastal and offshore regions of China and the Northwest Pacific Ocean(NWPO) between May 2020 and June 2022. The CAR content ranged from0.01 mmol/kg to 1.33 mmol/kg, with a mean value of(0.15 ± 0.18) mmol/kg(mean ± standard deviation). The highest CAR content was observed in Crustacea [(0.48 ± 0.38) mmol/kg], which was four times greater than the average CAR content in the other classes [(0.12 ± 0.11) mmol/kg]. Overall, the CAR content exhibited minor variation among marine animals, potentially because the carnitine pool maintains its dynamic balance. Additionally, significant correlations were observed between the CAR content and environmental factors in some species: a negative correlation with seawater temperature and positive correlations with latitude, seawater salinity, and depth. These results suggest that the CAR content in marine animals is influenced by environmental changes. This study provides theoretical insights for understanding the characteristics and influencing factors of CAR content in marine animals.
基金Cloud Course of Beijing University of Civil Engineering and Architecture at Super Star Learning(YC240109)。
文摘The present teaching content of the power electronics course is insufficient to cover the power electronics technology used in building electrical engineering.This paper analyzes the relationship between building electrical engineering and power electronics technology,investigates the main power electronics technology used in building electrical engineering,introduces the teaching content of current power electronics course,analyzes the insufficiency of current teaching content related to the practice of electrical engineering,and proposes the principles and directions for the reformation and innovation of the teaching content of the course of power electronics for the major of building electricity and intelligence.
文摘Characterization and optimization of physical and chemical properties of drilling fluids are critical for the efficiency and success of drilling operations.In particular,maintaining the optimal levels of solids content is essential for achieving the most effective fluid performance.Proper management of solids content also reduces the risk of tool failures.Traditional solids content analysis methods,such as retort analysis,require substantial human intervention and time,which can lead to inaccuracies,time-management issues,and increased operational risks.In contrast to human-intensive methods,machine learning may offer a viable alternative for solids content estimation due to its pattern-recognition capability.In this study,a large set of laboratory reports of drilling-fluid analyses from 130 oil wells around the world were compiled to construct a comprehensive data set.The relationships among various rheological parameters were analyzed using statistical methods and machine learning algorithms.Several machine learning algorithms of diverse classes,namely linear(linear regression,ridge regression,and ElasticNet regression),kernel-based(support vector machine)and ensemble tree-based(gradient boosting,XGBoost,and random forests)algorithms,were trained and tuned to estimate solids content from other readily available drilling fluid properties.Input variables were kept consistent across all models for interpretation and comparison purposes.In the final stage,different evaluation metrics were employed to evaluate and compare the performance of different classes of machine learning models.Among all algorithms tested,random forests algorithm was found to be the best predictive model resulting in consistently high accuracy.Further optimization of the random forests model resulted in a mean absolute percentage error(MAPE)of 3.9%and 9.6%and R^(2) of 0.99 and 0.93 for the training and testing sets,respectively.Analysis of residuals,their histograms and Q-Q normality plots showed Gaussian distributions with residuals that are scattered around a mean of zero within error ranges of±1%and±4%,for training and testing,respectively.The selected model was further validated by applying the rheological measurements from mud samples taken from an offshore well from the Gulf of Mexico.The model was able to estimate total solids content in those four mud samples with an average absolute error of 1.08% of total solids content.The model was then used to develop a web-based graphical-user-interface(GUI)application,which can be practically used at the rig site by engineers to optimize drilling fluid programs.The proposed model can complement automation workflows that are designed to measure fundamental rheological properties in real time during drilling operations.While a standard retort test can take approximately 2 h at the rig site,such kind of real-time estimations can help the rig personnel to timely optimize drilling fluids,with a potential of saving 2920 man-hours in a given year for a single drilling rig.
基金supported by the National Natural Science Foundation of China (Grant No. 42002139)the Basic Prospective Project of SINOPEC (Grant No. P23240-3)。
文摘Tight oil is the most viable target for unconventional oil and gas exploration, but the complexity of micro-/nanopore throat systems significantly affects the oil content of reservoirs. To investigate the causes of heterogeneity in oil-bearing reservoirs, a high-pressure mercury injection experiment combined with fractal theory was conducted to analyze the micro pore throat structure characteristics of the tight sandstone of Chang 7 Member reservoirs in the Ordos Basin. The factors controlling the variations in oil content among tight sandstone samples were identified based on mineral composition characteristics. The results indicate that the pore throat radius distribution is mainly unimodal an bimodal. In oil-bearing samples, the pore throat distributions align well with the corresponding permeability contribution curves, while in oil-free samples, there is a clear deviation from these curves. Mesopore throats exert the greatest influence on seepage capacity. Differences in fractal characteristics are primarily reflected in D1 values, with oil-free samples exhibiting D1 values close to 3, indicating an extremely nonuniform pore throat structure at this scale. The content of quartz, plagioclase, and chlorite is significantly higher in oil-bearing samples than in oil-free samples, whereas calcite content is lower in oil-bearing samples. There is a positive correlation between the contents of quartz, plagioclase, and chlorite with D1;their increased presence contributes to a more favorable pore throat structure.Conversely, the calcite contents show an inverse relationship with D1. Cementation increases the complexity of pore throat structures, while multiple diagenetic processes simultaneously control these characteristics, leading to variations in oil content.
基金supported by the National Key R&D Program of China(2022YFD1200400)the earmarked fund for CARS-13,the Major Science and Technology Projects of Henan Province,China(221100110300)the Henan Provincial R&D Program of Interregional Cooperation for Local Scientific and Technological Development Guided by Central Government,China(YDZX20214100004191)。
文摘Peanut kernels rich in oil,particularly those with oleic acid as their primary fatty acid,are in high demand among consumers,the food industry,and farmers due to their superior nutritional content,extended shelf life,and health benefits.The oil content and fatty acid composition are governed by multiple genetic factors.Identifying the quantitative trait loci(QTLs)related to these attributes will facilitate marker-assisted selection and genomic selection,thus enhancing quality-focused peanut breeding programs.For this purpose,we developed a population of 521 recombinant inbred lines(RILs)and tested their kernel quality traits across five different environments.We identified two major and stable QTLs for oil content,qOCAh12.1 and qOCAh16.1.The markers linked to these QTLs were designed by Kompetitive allele-specific PCR(KASP)and subsequently validated.Moreover,we found that the superior haplotype of oil content in the qOCAh16.1 region was conserved within the plant introduction(PI)germplasm cluster,as evidenced by a diverse peanut accession panel.In addition,we determined that qAh09 and qAh19.1,which harbor the key gene encoding fatty acid desaturase 2(FAD2),influence all seven fatty acids,palmitic,stearic,oleic,linoleic,arachidic,gadoleic,and behenic acids.Regarding the protein content and the long-chain saturated fatty acid behenic acid,qAh07 emerged as the major and stable QTL,accounting for over 10%of the phenotypic variation explained(PVE).These findings can enhance marker-assisted selection in peanut breeding,with the aim of improving the oil content,and deepen our understanding of the genetic mechanisms that shape fatty acid composition.
基金Supported by the Science and Technology Cooperation and Exchange special project of Cooperation of Shanxi Province(202404041101014)the Fundamental Research Program of Shanxi Province(202403021212333)+3 种基金the Joint Funds of the National Natural Science Foundation of China(U24A20555)the Lvliang Key R&D of University-Local Cooperation(2023XDHZ10)the Initiation Fund for Doctoral Research of Taiyuan University of Science and Technology(20242026)the Outstanding Doctor Funding Award of Shanxi Province(20242080).
文摘To elucidate the effect of calcite-regulated activated carbon(AC)structure on low-temperature denitrification performance of SCR catalysts,this work prepared a series of Mn-Ce/De-AC-xCaCO_(3)(x is the calcite content in coal)catalysts were prepared by the incipient wetness impregnation method,followed by acid washing to remove calcium-containing minerals.Comprehensive characterization and low-temperature denitrification tests revealed that calcite-induced structural modulation of coal-derived AC significantly enhances catalytic activity.Specifically,NO conversion increased from 88.3%of Mn-Ce/De-AC to 91.7%of Mn-Ce/De-AC-1CaCO_(3)(210℃).The improved SCR denitrification activity results from the enhancement of physicochemical properties including higher Mn^(4+)content and Ce^(4+)/Ce^(3+)ratio,an abundance of chemisorbed oxygen and acidic sites,which could strengthen the SCR reaction pathways(richer NH_(3)activated species and bidentate nitrate active species).Therefore,NO removal is enhanced.
基金supported by the National Natural Science Foundation of China(No.42372192)Shanxi Province science and technology plan joint unveiling project(No.20201101002)。
文摘The methane adsorption capacity,gas content,and carbon isotope characteristics of coal are crucial parameters that determine the productivity of coalbed methane(CBM)wells and their development potential.In this paper,test analyses of methane adsorption,gas content and carbon isotope of methane were carried out using 89 samples from the No.3 coal seam in the southwestern part of the Qinshui Basin.Their characteristics and correlations were analyzed.A relationship model between methane adsorption,gas content,carbon isotopes,coal metamorphism and material composition were established,and its controlling mechanism was investigated.The results indicate that the distribution patterns of Langmuir volume and Langmuir pressure in No.3 coal seam are mainly determined by the material composition and the thermal evolution level.The methane gas content in coal is mainly affected by the burial depth,microcosmic co mposition,mineral conte nt,moisture content and ash yield,adsorption capacity and metamorphism of the coal.The methane carbon isotope(δ^(13)C_(1))values in the natural desorbed gas from No.3 coal seam range from-26.95%to-57.80‰,with a mean value of-34.53‰.δ^(13)C_(1)in coal shows a two-stage variation pattern with increasing in vitrinite reflectance(R_(max)^(o)).When R_(max)^(o)is blow 3.0%,δ^(13)C_(1)values of methane in coal become progressively heavier with increasing R_(max)^(o).When R_(max)^(o)reaches or exceeds 3.0%,δ^(13)C_(1)values exhibit a lightning trend with furth er increases in R_(max)^(o),which is primarily controlled by the carbon isotope fractionation effects during thermal evolution.
基金supported by the National Natural Science Foundation of China(42261028)the Chinese Academy of Sciences“Light of West China”Program for Western Young Scholars(23JR6KA027)+3 种基金the Science Foundation for Distinguished Young Scholars of Gansu Province(24JRRA167)the Key Research and Development Program on Ecological Civilization Construction of Gansu Province(25YFFA012)Gansu Provincial Science and Technology Plan Fund Project(24CXGA063)Scientific Research Projects on Ecological and Environmental Protection in Heilongjiang Province in 2023(Grant No.:HST2023ZR005)。
文摘Surface albedo,as one of the important properties of the underlying surface,has a significant impact on the surface energy balance in cold regions.However,due to the complexity of the factors affecting surface albedo,existing calculations still contain inaccuracies.Therefore,this study conducted surface albedo experiments on loess with different water contents and temperatures.By analyzing the surface albedo measurements of samples with varying temperature and water content levels,as well as the soil freezing characteristic curve(SFCC)and soil-water characteristic curve(SWCC)of loess,the study explores the influence of soil temperature and water content on the surface albedo of loess.The results indicate that both the temperature and water content of loess jointly affect surface albedo.During the process of albedo change,there exists a water content threshold that alters the trend of surface albedo.Soil temperature influences surface albedo by affecting the content of pore ice and liquid water within the soil.When the water content of loess is relatively low,the surface albedo decreases as the unfrozen water content decreases.However,this trend changes as the water content of loess increases.Additionally,a decrease in soil temperature lowers the moisture content threshold during the changes in surface albedo.This study provides a reference for exploring and determining the surface energy balance in cold regions under the background of warm and humid climates,as well as for establishing thermal calculation boundaries.
基金supported and funded by the Deanship of Scientific Research at Imam Mohammad Ibn Saud Islamic University(IMSIU)(grant number IMSIU-DDRSP2504).
文摘Vehicular networks enable seamless connectivity for exchanging emergency and infotainment content.However,retrieving infotainment data from remote servers often introduces high delays,degrading the Quality of Service(QoS).To overcome this,caching frequently requested content at fog-enabled Road Side Units(RSUs)reduces communication latency.Yet,the limited caching capacity of RSUs makes it impractical to store all contents with varying sizes and popularity.This research proposes an efficient content caching algorithm that adapts to dynamic vehicular demands on highways to maximize request satisfaction.The scheme is evaluated against Intelligent Content Caching(ICC)and Random Caching(RC).The obtained results show that our proposed scheme entertains more contentrequesting vehicles as compared to ICC and RC,with 33%and 41%more downloaded data in 28%and 35%less amount of time from ICC and RC schemes,respectively.
基金supported by the Materials and Components Technology Development Program(No.20024843)funded by the Ministry of Trade,Industry&Energy(MOTIE,South Korea)the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.RS-2024-00450561).
文摘This study systematically investigates the effects of Al content on the microstructure,tensile properties,and high-cycle fatigue behavior of extruded Mg-xAl-Zn-Ca-Y(SENx)alloys.The results reveal that all extruded alloys exhibit fully recrystallized microstructures with undissolved second-phase particles enriched with Ca and Y.The average grain size varies non-monotonically with Al content due to the competing effects of recrystallization kinetics,solute drag,and particle band distribution.As Al content increases,tensile strength increases,while ductility decreases.Notably,despite its relatively coarse grain structure,the SEN9 alloy exhibits significantly higher yield strength than the SEN6 alloy.This improvement is mainly attributed to additional precipitation strengthening from fine Mg_(17)Al_(12)discontinuous precipitates formed along grain boundaries.Meanwhile,the reduced elongation observed in the SEN9 and SEN11 alloys is attributed to premature fracture at coarse Mg_(17)(Al,Zn,Ca)_(12)particle bands aligned along the extrusion direction.From the SEN1 to SEN9 alloys,the fatigue strength(FS)increases approximately linearly with ultimate tensile strength(UTS),reaching 170 MPa.However,this FS-UTS proportionality fails in the SEN11 alloy,where FS falls to 120 MPa despite the highest UTS.This deviation from the FS-UTS correlation that is observed for the lower-Al-content alloys is attributed to the clustered distribution of coarse Mg_(17)(Al,Zn,Ca)_(12)particles in the SEN11 alloy,which promotes early crack initiation under cyclic loading.These findings emphasize the importance of controlled Al addition in enhancing both strength and fatigue resistance while also highlighting the adverse effects of excessive Al content owing to microstructural embrittlement.
基金supported by the Key Project of Chongqing Special Program for Technological Innovation and Application Development(CSTB2024TIAD-KPX0099)the Graduate Research Innovation Project of Chongqing,China(CYB240050),the Fundamental Research Funds for the Central Universities(2025CDJZKKYJH-14)the State Key Laboratory of Coal Mine Disaster Dynamics and Control for 2030 major project(2011DA105287-MX2030-202101).
文摘Gas injection-enhanced underground coal combustion for heat extraction represents a disruptive chemical fluidized extraction method of coal resources.Coal seam combustion dynamics provide crucial underpinnings for engineering realization.This study establishes an experimental system for monitoring temperature field evolution during gas-assisted combustion in cylindrical coal cores,investigating the influence of moisture content(0%,16%,24%)on gas-assisted combustion kinetics.Results showed moisture content significantly influences combustion:higher levels(16%-24%)delay high-temperature expansion(0-1 h)due to evaporation energy absorption,but subsequently enhance efficiency through pore formation and oxygen diffusion,achieving 1120-1230°C peaks.Dry coal exhibits rapid initial combustion(peak temperature of 1130°C within 1 h)but weaker sustained reactions.The temperature field evolves from localized hotspots to an elliptical high-temperature zone,with axial expansion rates surpassing radial rates,driven by thermal buoyancy and convective heat transfer.Moisture’s dual role is revealed:initially as a thermodynamic inhibitor and later as a promoter by increasing pore diameter and oxygen diffusion coefficients.An optimal moisture content of 16%balances initial heat loss with enhanced reactivity,offering practical insights for optimizing gas injection and thermal recovery in underground coal combustion.
基金Supported by Science and Technology Project of Beijing Municipal Administration Center of Parks (ZX2019ZX2017).
文摘This study was conducted to investigate the air oxygen content inside and outside a Phyllostachys edulis forest in Qishan Forest Park throughout all four seasons.(1)Regarding the overall annual variation in oxygen content in both environments,comparative analysis of the annual average oxygen concentration showed that the average inside the forest was 22.13%,while the value outside it was 21.39%.The annual average oxygen concentration inside the forest was 3.34%higher than that outside the forest.(2)Regarding the seasonal variation in oxygen content at both sites,the oxygen concentration inside the forest was consistently higher than that outside the forest in all four seasons.The oxygen concentrations inside the forest were 22.1%,21.9%,21.8%,and 21.5%in spring,summer,autumn,and winter,respectively,while outside the forest,they were 22.0%,21.8%,21.7%,and 21.4%for the same seasons,respectively.(3)The diurnal variation trends of oxygen concentration at both sites were similar throughout all four seasons,exhibiting a single-peak and double-trough curve pattern.The peak period occurred at 13:00 in spring,summer,and winter,and at 9:00 in autumn.The trough periods were observed at 7:00 and between 21:00 and 23:00 or at 5:00.
基金supported by the National Natural Science Foundation of China(Nos.52173304 and U1867216)the National Key R&D Program of China(No.2022YFB3207600)China Scholarship Council(No.2018SLJ014508).
文摘Buffer material and metal disposal containers are the key engineering barriers in the geological disposal of high-level radioactive waste.The durability of disposal containers largely depends on the water con-tent in buffer material.This work focused on investigating the corrosion evolution of NiCu low alloy steel in compacted GMZ bentonite with different water contents for 270 d by using weight loss,electrochemi-cal measurements,and various methods for analyzing corrosion products.As the water content increased from 13%to 20%,the water in the bentonite transformed from an unsaturated to a critical saturated state,and the corrosion rate of NiCu steel clearly increased.In these two systems,the oxygen could mi-grate to the thin liquid film on the steel surface through the air pores in the bentonite in the gas phase and undergo cathodic reduction.Meanwhile,it oxidized the ferrous hydrolysis products into ferric corro-sion products and formed a rust layer,which could block the diffusion of oxygen.At that moment,the cathodic process of NiCu steel corrosion changed to rust reduction.When the water content continually increased to 30%and 40%,the compacted bentonite was in a saturation state,and the corrosion rate of NiCu steel was significantly decreased.This was because most pores among the bentonite particles were occupied by a large amount of free water,which hindered the diffusion of oxygen and inhibited its cathodic reduction.Furthermore,it restrained the oxidation of ferrous corrosion products,which greatly weakened the cathodic depolarization of rust,leading to the cathodic process being dominated by the hydrogen evolution reaction.
基金supported by the Research Grant Council of the Hong Kong Special Administrative Region,China(Grant Nos.HKU 17207518 and R5037-18).
文摘The nine typical Shanghai soils are usually silty clay or clay,which appears inconsistent with their low clay content in the relevant publications.The literature review shows that the documented clay content of Shanghai soils ranges from 0%to 30.8%by weight.This inconsistency may stem from two factors:(1)the Shanghai soil classification system relies solely on the plasticity index for soil naming;and(2)the conventional steel sieving method cannot separate the clay from the fine soils(clay and silt mixtures).This paper aims to accurately determine the clay content in Shanghai soils.It uses nylon cloth sieves with apertures ranging from 0.063 mm to 0.0008 mm and completely separates the clay particles from the fine soils.The nine typical Shanghai soils are tested and sieved into distinct subgroups of clay,silt,sand,and gravel particles.Results demonstrate clay content ranges from 18.99%to 79.33%,substantially higher than literature values and consistent with their names of either silty clay or clay.Macro,micro,and scanning electron microscope(SEM)images reveal effective separation of clay,silt,sand,and gravel particles.The clay exhibits cohesive properties,while the silt,sand,and gravel comprise clean,non-cohesive individual particles.The clay and silt fractions are confirmed to be within their respective sieving limits by SEM-based particle size measurements.Additionally,Atterberg limits testing highlights the high plasticity of the clay particles and the non-plastic nature of the silt particles.
文摘With the rising global demand for energy and growing awareness of environmental sustainability,hydrogen energy has emerged as a promising clean and efficient alternative.Supported by national policies,both basic and applied research in hydrogen and hydrogen energy have seen significant advancements in recent years.Reflecting these developments,the teaching of“hydrogen element and hydrogen energy”in college level inorganic chemistry has gradually expanded.In the context of the new era,there is an urgent need to reform and enrich this teaching content to cultivate students’comprehensive abilities and align with the country’s evolving demand for talent in the energy sector.This paper analyzes current challenges in the teaching of hydrogen energy within college chemistry curricula and proposes targeted strategies to optimize instructional content.The goal is to offer practical insights and references for educators seeking to improve the effectiveness and relevance of hydrogen energy education.
基金provided by the National Key R&D Program of China(No.2024YFC3012605)the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project(Nos.SKLGP2022Z001,SKLGP2023Z029 and SKLGP2022K027)。
文摘Biotite content critically influences rock mechanical behavior and threatens underground engineering stability.Uniaxial compression tests with acoustic emission(AE)monitoring were conducted on granite pegmatite samples having varying biotite content.Peak frequency distribution analysis,rise angleaverage frequency(RA-AF)analysis,multifractal theory,and a dynamic multifractal algorithm were applied to explore the relationship between damage evolution and AE characteristics.Results indicate that increased biotite content reduces uniaxial compressive strength and elastic modulus,enhances plastic deformation,and increases the proportion of shear cracks.The segmented evolution of the dynamic multifractal parameter Δα_(m) is biotite-dependent.Oscillations during the elastic phase signify localized shear crack initiation and propagation;their attenuation in the plastic phase reflects frictional closure along biotite cleavage planes,promoting elastic energy storage and delaying release.AE-based damage models and time-varying signals characterize rock damage progression.Stress concentrations around biotite minerals foster localized shear band formation,leading to concentrated shear failure at lower damage levels.Higher biotite content accelerates crack propagation,while smooth cleavage planes lower the fracture energy threshold,reducing strength and stiffness.These findings enhance understanding of biotite-influenced progressive rock damage and underpin stability monitoring and early-warning systems for underground engineering.
基金supported by the National Natural Science Foundation of China(Nos.42275116 and 41975172).
文摘Aerosol hygroscopicity and liquid water content(ALWC)have important influences on the environmental and climate effect of aerosols.In this study,we measured the hygroscopic growth factors(GF)of particles with dry diameters of 40,80,150,and 200 nm during the wintertime in Nanjing.Both the GF-derived hygroscopicity parameter(κ_(gf))and ALWC increased with particle size,but displayed differing diurnal variations,withκ_(gf)peaking around the midday,while ALWC peaking in the early morning.Nitrate,ammonium and oxygenated organic aerosols(OOA)were found as the chemical components mostly strongly correlated with ALWC.A closure study suggests that during midday photo-oxidation and nighttime high ALWC periods,theκof organic aerosols(κ_(org))was underestimated when using previous parameterizations.Accordingly,we re-constructed parameterizations forκ_(org)and the oxidation level of organics for these periods,which indicates a higher hygroscopicity of photochemically formed OOA than the aqueous OOA,yet both being much higher than the generally assumed OOA hygroscopicity.Additionally,in a typical high ALWC episode,concurrently increased ALWC,nitrate,OOA as well as aerosol surface area and mass concentrations were observed under elevated ambient RH.This strongly indicates a coupled effect that the hygroscopic secondary aerosols,in particular nitratewith strong hygroscopicity,led to large increase in ALWC,which in turn synergistically boosted nitrate and OOA formation by heterogeneous/aqueous reactions.Such interaction may represent an important mechanism contributing to enhanced formation of secondary aerosols and rapid growth of fine particulate matter under relatively high RH conditions.
