Coke oven gas(COG)and natural gas(NG),both high-calorific by-products derived from the steel industry,have gained prominence as alternative fuels in the sintering process,thereby supporting dual objectives of emission...Coke oven gas(COG)and natural gas(NG),both high-calorific by-products derived from the steel industry,have gained prominence as alternative fuels in the sintering process,thereby supporting dual objectives of emission reduction and carbon neutrality.While existing research on hydrogen-rich gas injection has predominantly concentrated on conventional thin-bed sintering,investigations into its application within thick-bed sintering remain comparatively scarce.Thick-bed sintering,recognized for enhancing energy efficiency and increasing sinter output,encounters challenges such as uneven heat distribution and diminished permeability,which can negatively impact process efficiency and product quality.To address these issues,sinter pot experiments were conducted to assess the effects of NG and COG injection on thick-bed sintering performance.Findings reveal that NG injection in thick beds mirrors the behavior observed in conventional thin-bed sintering,effectively optimizing the process and achieving a carbon reduction potential exceeding 10%.In contrast,COG injection in thick-bed conditions demonstrates notable differences,substantially lowering the solid fuel consumption rate but detrimentally affecting sinter strength and overall production.However,by optimizing the timing of COG injection,it is feasible to improve sinter yield while concurrently reducing solid fuel usage.These outcomes provide valuable insights for the advancement of gas injection technologies in thick-bed sintering,thereby contributing to energy conservation and emission mitigation efforts within the sintering industry.展开更多
The West Lake area and water system in West Lake scenic area of Hangzhou City directly affect the soil properties of waterfront lawn beds,which in turn have a significant impact on the growth of waterfront lawns.In or...The West Lake area and water system in West Lake scenic area of Hangzhou City directly affect the soil properties of waterfront lawn beds,which in turn have a significant impact on the growth of waterfront lawns.In order to further improve the quality of lawns,the conditions of 10 waterfront lawn beds in West Lake scenic area were tested and analyzed.The results showed that the waterfront lawn beds in West Lake scenic area were prone to salinization,with moderate or high pH values,moderate overall organic matter content,relatively sufficient nitrogen and phosphorus elements,and relatively deficient potassium elements.The contents of exchangeable calcium in all samples were higher than the lower limit,and the contents of exchangeable sodium,exchangeable magnesium,and available manganese in the soil were moderate or low,while the contents of available copper were moderate or high.展开更多
Seagrass beds are crucial coastal ecosystems,functioning as vital blue carbon sinks and natural ecological barriers.However,these ecosystems are increasingly threatened by global climate events,coastal development,and...Seagrass beds are crucial coastal ecosystems,functioning as vital blue carbon sinks and natural ecological barriers.However,these ecosystems are increasingly threatened by global climate events,coastal development,and water eutrophication,making them some of the most endangered ecosystems worldwide.In the Yellow Sea and Bohai Sea regions,seagrass bed assessment and monitoring have been largely overlooked.Thus,strengthening research efforts is necessary to identify current distribution patterns and long-term changes in seagrass bed resources.This study focused on a seagrass bed in Sanggou Bay,Rongcheng,using remote sensing(RS)and geographic information system technologies to analyze multisource satellite data from the US Landsat and Chinese resource satellite series.By combining RS indexes with historical survey data,large-scale temporal and geographic distribution data for seagrass beds were obtained in the study area from 1985 to 2022.The spatial distribution and evolution trends of the seagrass bed were analyzed using a water depth inversion model,and the factors driving its degradation were identified.Results indicated that the seagrass bed area in Sanggou Bay fluctuated between 100 and 140 km^(2) from 1985 to 2010.During 2010–2013,dynamic changes in the seagrass bed area increased,with a considerable decrease in its overall size.After 2014,changes were minimal,indicating a notably stable state.Seagrass bed degradation in Sanggou Bay is influenced by high-intensity human activities,pollution from coastal land sources,raft cultures,underwater terrain conditions,and sedimentary environmental factors.The findings offer essential insights for developing seagrass restoration and protection strategies in Sanggou Bay and contribute to the broader scientific efforts for coastal ecosystem conservation and rehabilitation.展开更多
This study presents a detailed experimental evaluation of a newly developed mechanistic scale-up methodology for gas-solid fluidized beds.Traditional scale-up approaches typically rely on matching global dimensionless...This study presents a detailed experimental evaluation of a newly developed mechanistic scale-up methodology for gas-solid fluidized beds.Traditional scale-up approaches typically rely on matching global dimensionless groups,which often fail to ensure local hydrodynamic similarity.In contrast,the new mechanistic method aims to achieve scale-up by matching the radial profiles of gas holdup between geometrically similar beds at corresponding dimensionless axial positions(z/Dc).This approach is based on the premise that when gas holdup profiles align,other key hydrodynamic parameters—such as solids holdup and particle velocity—also become similar.To validate this methodology,experiments were conducted in two fluidized beds with inner diameters of 14 cm and 44 cm.Optical probes and gamma ray densitometry(GRD)were used to measure local gas holdup,solids holdup,and particle velocity at multiple axial and radial positions.The results show that matched gas holdup profiles led to mean absolute deviations(MAD)below 3%in solids holdup and particle velocity,confirming hydrodynamic similarity.In contrast,unmatched profiles resulted in significant deviations across all parameters.展开更多
Cracking of early-age concrete can occur in the track beds of high-speed railways due to changes in material properties,environmental effects,and construction processes.This is a multi-field,time-varying issue involvi...Cracking of early-age concrete can occur in the track beds of high-speed railways due to changes in material properties,environmental effects,and construction processes.This is a multi-field,time-varying issue involving hydro-thermo-chemo-mechanical coupling.However,to date,research has not adequately described the early-age cracking mechanisms in track beds,and few risk control measures have been proposed.To solve this problem,we incorporated the hydration degree of concrete into multi-field coupling equations for early-age concrete,and set boundary conditions that account for environmental influences and various stress factors that typically cause early creep of concrete.A four-field coupled risk prediction model was built based on hydro-thermo-chemo-mechanical properties,and was used to calculate and analyze various time-varying behavior(including the risk and form of cracking)in the hydro,thermo,chemo,and mechanical fields of early-age concrete.Finally,we focused on material-related factors(maximum heat of hydration and peak heat release time),environmental factors(temperature difference between day and night,average daily cooling rate,and intensity of solar radiation),and construction technique factors(molding temperature,pouring time,and thermal insulation coefficient).The influence of these factors on the early-age cracking risk of the track bed was analyzed,and risk control measures against early cracking were proposed accordingly.展开更多
The application of carbon capture systems on ships is technically constrained by limited onboard space and the weight of the conventional absorption tower.The rotating packed bed(RPB)has emerged as a promising alterna...The application of carbon capture systems on ships is technically constrained by limited onboard space and the weight of the conventional absorption tower.The rotating packed bed(RPB)has emerged as a promising alternative due to its small footprint and high mass transfer performance.However,despite its advantages,the structural and vibration stability of RPBs at high rotational speed remains insufficiently studied,and no international design standards currently exist for RPBs.To address this gap,this study performed a comprehensive finite element analysis(FEA)using ANSYS to investigate the structural and dynamic characteristics of an RPB.A three-dimensional model was developed to evaluate the effects of material selection(316 stainless steel,aluminum alloy,titanium alloy),bearing stiffness,and unbalanced mass on deformation,stress,and natural frequencies.In the structural analysis,316 stainless steel exhibited the highest von Mises stress and deformation.However,it was confirmed that all three materials did not exceed their yield strengths at the maximum rotating speed.Modal analysis and Campbell diagrams showed no resonance risk within the rated speed range,and increased bearing stiffness led to higher natural frequencies and improved stability.The findings provide quantitative design guidance for material selection,bearing stiffness optimization,and vibration control in high-rotational-speed RPB systems.This study contributes to establishing a foundational framework for the mechanical reliability and standardization of marine carbon capture units.展开更多
Methods and procedures of three-dimensional （3D） characterization of the pore structure features in the packed ore particle bed are focused. X-ray computed tomography was applied to deriving the cross-sectional imag...Methods and procedures of three-dimensional （3D） characterization of the pore structure features in the packed ore particle bed are focused. X-ray computed tomography was applied to deriving the cross-sectional images of specimens with single particle size of 1-2, 2-3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-9, 9-10 ram. Based on the in-house developed 3D image analysis programs using Matlab, the volume porosity, pore size distribution and degree of connectivity were calculated and analyzed in detail. The results indicate that the volume porosity, the mean diameter of pores and the effective pore size （d50） increase with the increasing of particle size. Lognormal distribution or Gauss distribution is mostly suitable to model the pore size distribution. The degree of connectivity investigated on the basis of cluster-labeling algorithm also increases with increasing the particle size approximately.展开更多
A Markov chain-based stochastic model （MCM） is developed to simulate the movement of particles in a 2D bubbling fluidized bed （BFB）. The state spaces are determined by the discretized physical cells of the bed, an...A Markov chain-based stochastic model （MCM） is developed to simulate the movement of particles in a 2D bubbling fluidized bed （BFB）. The state spaces are determined by the discretized physical cells of the bed, and the transition probability matrix is directly calculated by the results of a discrete element method （DEM） simulation. The Markov property of the BFB is discussed by the comparison results calculated from both static and dynamic transition probability matrices. The static matrix is calculated based on the Markov chain while the dynamic matrix is calculated based on the memory property of the particle movement. Results show that the difference in the trends of particle movement between the static and dynamic matrix calculation is very small. Besides, the particle mixing curves of the MCM and DEM have the same trend and similar numerical values, and the details show the time averaged characteristic of the MCM and also expose its shortcoming in describing the instantaneous particle dynamics in the BFB.展开更多
A dual-phase synergistic enhancement method was adopted to strengthen the Al-Mn-Mg-Sc-Zr alloy fabricated by laser powder bed fusion(LPBF)by leveraging the unique advantages of Er and TiB_(2).Spherical powders of 0.5w...A dual-phase synergistic enhancement method was adopted to strengthen the Al-Mn-Mg-Sc-Zr alloy fabricated by laser powder bed fusion(LPBF)by leveraging the unique advantages of Er and TiB_(2).Spherical powders of 0.5wt%Er-1wt%TiB_(2)/Al-Mn-Mg-Sc-Zr nanocomposite were prepared using vacuum homogenization technique,and the density of samples prepared through the LPBF process reached 99.8%.The strengthening and toughening mechanisms of Er-TiB_(2)were investigated.The results show that Al_(3)Er diffraction peaks are detected by X-ray diffraction analysis,and texture strength decreases according to electron backscatter diffraction results.The added Er and TiB_(2)nano-reinforcing phases act as heterogeneous nucleation sites during the LPBF forming process,hindering grain growth and effectively refining the grains.After incorporating the Er-TiB_(2)dual-phase nano-reinforcing phases,the tensile strength and elongation at break of the LPBF-deposited samples reach 550 MPa and 18.7%,which are 13.4%and 26.4%higher than those of the matrix material,respectively.展开更多
Laser powder bed fusion(LPBF)is highly suitable for forming 18Ni300 mold steel,thanks to its excellent capability in manufacturing complex shapes and outstanding capacity for regulating microstructures.It is widely us...Laser powder bed fusion(LPBF)is highly suitable for forming 18Ni300 mold steel,thanks to its excellent capability in manufacturing complex shapes and outstanding capacity for regulating microstructures.It is widely used in fields such as injection molding,die casting,and stamping dies.Adding reinforcing particles into steel is an effective means to improve its performance.Nb/18Ni300 composites were fabricated by LPBF using two kinds of Nb powders with different particle sizes,and their microstructures and properties were studied.The results show that the unmelted Nb particles are uniformly distributed in the 18Ni300 matrix and the grains are refined,which is particularly pronounced with fine Nb particles.In addition,element diffusion occurs between the particles and the matrix.The main phases of the base alloy are α-Fe and a small amount of γ-Fe.With the addition of Nb,part of the α-Fe is transformed into γ-Fe,and unmelted Nb phases appear.The addition of Nb also enhances the hardness and wear resistance of the composites but slightly reduces their tensile properties.After aging treatment,the molten pools and grain boundaries become blurred,grains are further refined,and the interfaces around the particles are thinned.The aging treatment also promotes the formation of reverted austenite.The hardness,ultimate tensile strength,and volumetric wear rate of the base alloy reach 51.9 HRC,1704 MPa,and 17.8×10^(-6) mm^(3)/(N·m),respectively.In contrast,the sample added with fine Nb particles has the highest hardness(56.1 HRC),ultimate tensile strength(1892 MPa)and yield strength(1842 MPa),and the volume wear rate of the sample added with coarse Nb particles is reduced by 90%to 1.7×10^(-6) mm^(3)/(N·m).展开更多
Copper manufactured by laser powder bed fusion(LPBF)process typically exhibits poor strength-ductility coordination,and the addition of strengthening phases is an effective way to address this issue.To explore the eff...Copper manufactured by laser powder bed fusion(LPBF)process typically exhibits poor strength-ductility coordination,and the addition of strengthening phases is an effective way to address this issue.To explore the effects of strengthening phases on Cu,Cu-carbon nanotubes(CNTs)composites were prepared using LPBF technique with Cu-CNTs mixed powder as the matrix.The formability,microstructure,mechanical properties,electrical conductivity,and thermal properties were studied.The result shows that the prepared composites have high relative density.The addition of CNTs results in inhomogeneous equiaxed grains at the edges of the molten pool and columnar grains at the center.Compared with pure copper,the overall mechanical properties of the composite are improved:tensile strength increases by 52.8%and elongation increases by 146.4%;the electrical and thermal properties are also enhanced:thermal conductivity increases by 10.8%and electrical conductivity increases by 12.7%.展开更多
As the primary functional component of a fusion reactor,the fusion blanket pebble bed,composed of numerous particles,is crucial for tritium breeding,neutron multiplication,and radiation shielding.Particles within trit...As the primary functional component of a fusion reactor,the fusion blanket pebble bed,composed of numerous particles,is crucial for tritium breeding,neutron multiplication,and radiation shielding.Particles within tritium-breeding pebble beds are subjected to prolonged neutron irradiation,high thermal loads,and strong magnetic fields in fusion environments.Such conditions render them susceptible to pulverization and fragmentation.The resulting fragments and powders migrate and are deposited into the gas channel,driven by the purge gas.The reduction in the effective flow area of the gas increases the flow resistance,resulting in tritium retention,degraded heat transfer,and other adverse effects.These conditions impair the thermodynamic properties of the pebble beds and hinder the self-maintenance of tritium.Limited information exists on powder migration and clogging mechanisms in fusion blanket pebble beds,particularly under diverse physical conditions.The aim of this study was to use a computational fluid dynamics model coupled with the discrete element method(CFD-DEM)to numerically explore powder migration and clogging in pebble beds.The model considers factors such as breeder orientation,purge velocity,powder size distribution,and friction coefficient.We propose two migration and clogging mechanisms.One involves powder with a large particle size,and the other does not.The results indicate that the powder migration velocity progresses through three stages:rapid decay,linear decay,and stability.Pebble-bed clogging manifests in two forms:extensive superficial clogging and uniform internal clogging.Two fitted curves were used to depict the migration and clogging tendencies.The powder size distribution significantly influenced the powder migration.The breeder orientation,powder size,and friction coefficient affected the distribution of the clogging powders.However,the impact of the purge velocity on powder migration and clogging in pebble beds was limited,and this effect varied significantly with different particle size ratios.Based on the analysis,a formula is proposed to characterize the behavior of the powder in the pebble beds.The results of this study can aid in analyzing and predicting powder dynamics in pebble beds.展开更多
Ecological floating bed is an important biological remediation method for water pollution control.During the removal of excess nutrients and pollutants,changes in environmental factors affect the characteristics of mi...Ecological floating bed is an important biological remediation method for water pollution control.During the removal of excess nutrients and pollutants,changes in environmental factors affect the characteristics of microorganisms in aquatic ecosystems.To understand the influences of ecological floating beds on size-fractionated microorganisms,we investigated the community assembly and nitrogen metabolic characteristics of three size-fractionated microorganism groups in the ecological floating bed area,using 18S rDNA,16S rDNA metabarcoding,and metagenomic sequencing techniques.Firstly,we discovered substantial differences between size-fractionated groups in the diversity and compositions of both microeukaryotic and bacterial communities,as well as the influences of floating beds on specific groups.The floating beds appeared to provide more habitats for heterotrophs and symbiotes while potentially inhibiting the growth of certain phytoplankton(cyanobacteria).Secondly,we observed that microeukaryotic and bacterial communities were predominantly influenced by stochastic and deterministic processes,respectively,and they both exhibited distinct patterns across different size-fractionated groups.Notably,microeukaryotic community assembly demonstrated a greater sensitivity to ecological floating beds,as indicated by an increase in dispersal limitation processes.Finally,the nitrogen metabolism functional genes revealed that microbes associated with large-sized particles played a crucial role in dissimilatory nitrate reduction to ammonium(DNRA)and denitrification processes within the floating bed area,thereby facilitating the removal of excess nitrogen nutrients from the water.In contrast,freeliving microorganisms from small-sized groups were linked mainly to the genes involved in nitrogen assimilation and assimilatory nitrate reduction to ammonium(ANRA)processes.These findings help understand the impact of ecological floating beds on the diversity and functional characteristics of microorganism communities in different size-fractionated groups.展开更多
In this paper,a novel method for investigating the particle-crushing behavior of breeding particles in a fusion blanket is proposed.The fractal theory and Weibull distribution are combined to establish a theoretical m...In this paper,a novel method for investigating the particle-crushing behavior of breeding particles in a fusion blanket is proposed.The fractal theory and Weibull distribution are combined to establish a theoretical model,and its validity was verified using a simple impact test.A crushable discrete element method(DEM)framework is built based on the previously established theoretical model.The tensile strength,which considers the fractal theory,size effect,and Weibull variation,was assigned to each generated particle.The assigned strength is then used for crush detection by comparing it with its maximum tensile stress.Mass conservation is ensured by inserting a series of sub-particles whose total mass was equal to the quality loss.Based on the crushable DEM framework,a numerical simulation of the crushing behavior of a pebble bed with hollow cylindrical geometry under a uniaxial compression test was performed.The results of this investigation showed that the particle withstands the external load by contact and sliding at the beginning of the compression process,and the results confirmed that crushing can be considered an important method of resisting the increasing external load.A relatively regular particle arrangement aids in resisting the load and reduces the occurrence of particle crushing.However,a limit exists to the promotion of resistance.When the strain increases beyond this limit,the distribution of the crushing position tends to be isotropic over the entire pebble bed.The theoretical model and crushable DEM framework provide a new method for exploring the pebble bed in a fusion reactor,considering particle crushing.展开更多
Zn's natural degradability and biocompatibility make it a promising candidate for implants,however,its mechanical properties remain insufficient for bone applications.In this study,the performance of Zn was enhanc...Zn's natural degradability and biocompatibility make it a promising candidate for implants,however,its mechanical properties remain insufficient for bone applications.In this study,the performance of Zn was enhanced by developing Zn-Cu alloys via laser powder bed fusion(LPBF).Optimal LPBF parameters for forming stable tracks were achieved by adjusting laser power and scanning speed.Under optimized conditions of 100 W and 100 mm/s,high density(99.58%)Zn-Cu alloys with improved hardness(68.2 HV)and yield strength(160 MPa)were achieved.These improvements are attributed to solid solution strengthening,segregation strengthening,and grain refinement.The Zn-Cu alloys also demonstrated favorable degradation behavior,with a rate of 0.16 mm/year.This degradation is primarily driven by micro-galvanic corrosion between the CuZn 5 phase and Zn matrix,along with refined grains and increased grain boundary density.This work demonstrates a viable strategy for fabricating Zn-based implants with enhanced structural integrity and mechanical performance via LPBF.展开更多
Targeting Chang'E-8 mission'in-situ resource utilization(ISRU)for sustainable lunar habitats,laser powder bed fusion(LPBF)provides a viable pathway for in-situ additive manufacturing of lunar regolith.To eluci...Targeting Chang'E-8 mission'in-situ resource utilization(ISRU)for sustainable lunar habitats,laser powder bed fusion(LPBF)provides a viable pathway for in-situ additive manufacturing of lunar regolith.To elucidate mission relevant mechanical behavior and failure mechanisms of LPBF fabricated lunar regolith simulants,mare type and highland type simulant specimens were produced.Microstructural characterization,mechanical test coupled with three-dimensional digital image correlation(3D-DIC),and an energy-dissipation framework were employed for comprehensive analysis.The pristine highland specimens achieved 5.79 MPa and a peak strain of 0.13(50 mm×50 mm×30 mm),significantly outperforming their mare counterparts.Wire-cutting to 20 mm×20 mm×20 mm lowered strength by~20%and peak strain to 0.04,indicating cutting-induced defects reduce ductility.All specimens displayed multipeaked stress–strain curves.3D-DIC revealed band-type strain localization in pristine highland samples,diffuse strain patterns in cut highland samples,and highly tortuous,network-type bands in mare samples;the anisotropy index was also quantified.Fragmented particles exhibited fractal dimensions ranging from 1.6 to 2.0(size 1.25–9 mm).Energy evolution progressed through three distinct stages:elastic energy storage,progressive energy dissipation delaying crack propagation,and final unstable collapse.An energy-based damage model was established and validated.The data and methods developed support Chang'E-8 missions'ISRU demonstrations and establish a transferable framework toward sustainable lunar habitats.展开更多
The densification characterization,phase constitution,precipitation evolution and mechanical performance of Al−Mg−Sc−Zr alloy processed by laser powder bed fusion(LPBF)were systematically investigated.Moreover,the evo...The densification characterization,phase constitution,precipitation evolution and mechanical performance of Al−Mg−Sc−Zr alloy processed by laser powder bed fusion(LPBF)were systematically investigated.Moreover,the evolution of phase constitution and precipitation behavior after heat treatment were characterized by using X-ray diffraction(XRD)and transmission electron microscope(TEM)analysis.The ultimate tensile strength(UTS)of as-built samples ranged from 396.8 to 414.6 MPa as the scanning speed decreased from 1600 to 1000 mm/s.After post heat treatment,the yield strength(YS)increased to(513.1±1.3)MPa,while the UTS increased from(414.6±5.1)to(539.2±1.5)MPa.The significant improvement of mechanical performance was ascribed to the formation of secondary Al3(Sc,Zr)precipitates.展开更多
Laser remelting(LR)was used as an auxiliary post-treatment process for the Ti6Al4V titanium alloys fabricated by laser powder bed fusion(LPBF).Optical microscope(OM),scanning electron microscope(SEM)and electron back ...Laser remelting(LR)was used as an auxiliary post-treatment process for the Ti6Al4V titanium alloys fabricated by laser powder bed fusion(LPBF).Optical microscope(OM),scanning electron microscope(SEM)and electron back scattering diffraction(EBSD)observations showed that the grains in melted zone(MZ)transformed into equiaxial grains with an average size of 1.31μm,and the grains in heat affected zone(HAZ)were refined.Moreover,the texture intensity dropped significantly from 13.86 to 6.35 in MZ and 10.79 in HAZ.The temperature gradient(G)to solidification rate(R)ratio decreased when the laser scanning speed slowed down to a certain extent in the LR process,which effectively improved the highly preferred orientation and filled the hole defects in the surface of LPBF-Ti6Al4V.Furthermore,the hardness,wear resistance and corrosion resistance of the surface of the LPBF samples were improved by LR treatment.展开更多
Lacustrine deposits exposed at Daohugou, Inner Mongolia, China, have yielded superbly preserved vertebrate fossils. The fossil beds were first misinterpreted as of Early Cretaceous age, based on alleged occurrences of...Lacustrine deposits exposed at Daohugou, Inner Mongolia, China, have yielded superbly preserved vertebrate fossils. The fossil beds were first misinterpreted as of Early Cretaceous age, based on alleged occurrences of key fossils of the Jehol Biota. Compelling evidence revealed by more rigorous research involving regional biostratigraphy, radiometric dating, and paleontology supports the Middle Jurassic age of the fossil beds. Despite the awesome evidence for the Middle Jurassic age of the Daohugou beds, the age dispute has been resurrected recently by invoking an overturned stratigraphic sequence. A careful review of the data, however, found no evidence that this sequence has been overturned. In addition, many of the assumptions, on which the conjecture of the fossil beds being post- Middle Jurassic is imprudently based, are self-contradictory or otherwise misleading. Thus, the post- Middle Jurassic age of the Daohugou beds as an unfounded conclusion can readily be dismissed.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52474347)Postdoctoral Science Foundation of China(Grant No.2024T171095)the Fundamental Research Funds for the Central Universities(Grant No.2024CDJXY003).
文摘Coke oven gas(COG)and natural gas(NG),both high-calorific by-products derived from the steel industry,have gained prominence as alternative fuels in the sintering process,thereby supporting dual objectives of emission reduction and carbon neutrality.While existing research on hydrogen-rich gas injection has predominantly concentrated on conventional thin-bed sintering,investigations into its application within thick-bed sintering remain comparatively scarce.Thick-bed sintering,recognized for enhancing energy efficiency and increasing sinter output,encounters challenges such as uneven heat distribution and diminished permeability,which can negatively impact process efficiency and product quality.To address these issues,sinter pot experiments were conducted to assess the effects of NG and COG injection on thick-bed sintering performance.Findings reveal that NG injection in thick beds mirrors the behavior observed in conventional thin-bed sintering,effectively optimizing the process and achieving a carbon reduction potential exceeding 10%.In contrast,COG injection in thick-bed conditions demonstrates notable differences,substantially lowering the solid fuel consumption rate but detrimentally affecting sinter strength and overall production.However,by optimizing the timing of COG injection,it is feasible to improve sinter yield while concurrently reducing solid fuel usage.These outcomes provide valuable insights for the advancement of gas injection technologies in thick-bed sintering,thereby contributing to energy conservation and emission mitigation efforts within the sintering industry.
基金Sponsored by Key Project of Hangzhou Science and Technology Bureau(20191203B78).
文摘The West Lake area and water system in West Lake scenic area of Hangzhou City directly affect the soil properties of waterfront lawn beds,which in turn have a significant impact on the growth of waterfront lawns.In order to further improve the quality of lawns,the conditions of 10 waterfront lawn beds in West Lake scenic area were tested and analyzed.The results showed that the waterfront lawn beds in West Lake scenic area were prone to salinization,with moderate or high pH values,moderate overall organic matter content,relatively sufficient nitrogen and phosphorus elements,and relatively deficient potassium elements.The contents of exchangeable calcium in all samples were higher than the lower limit,and the contents of exchangeable sodium,exchangeable magnesium,and available manganese in the soil were moderate or low,while the contents of available copper were moderate or high.
基金supported by the Marine S&T Fund of Shandong Province for Pilot National Laboratory for Marine Science and Technology(Qingdao)(No.2022QNLM 050302-4)the Geological Survey Project of the China Geological Survey(No.DD20230071)+1 种基金the China Geological Survey Project‘Investigation and Monitoring of the Coastal Geological Environment of the Yangtze River Estuary’(No.DD20242714)the cooperation fund of Collaborative Research on Marine Geological Environment and Hazards in the Yangtze River Delta and Red River Delta.
文摘Seagrass beds are crucial coastal ecosystems,functioning as vital blue carbon sinks and natural ecological barriers.However,these ecosystems are increasingly threatened by global climate events,coastal development,and water eutrophication,making them some of the most endangered ecosystems worldwide.In the Yellow Sea and Bohai Sea regions,seagrass bed assessment and monitoring have been largely overlooked.Thus,strengthening research efforts is necessary to identify current distribution patterns and long-term changes in seagrass bed resources.This study focused on a seagrass bed in Sanggou Bay,Rongcheng,using remote sensing(RS)and geographic information system technologies to analyze multisource satellite data from the US Landsat and Chinese resource satellite series.By combining RS indexes with historical survey data,large-scale temporal and geographic distribution data for seagrass beds were obtained in the study area from 1985 to 2022.The spatial distribution and evolution trends of the seagrass bed were analyzed using a water depth inversion model,and the factors driving its degradation were identified.Results indicated that the seagrass bed area in Sanggou Bay fluctuated between 100 and 140 km^(2) from 1985 to 2010.During 2010–2013,dynamic changes in the seagrass bed area increased,with a considerable decrease in its overall size.After 2014,changes were minimal,indicating a notably stable state.Seagrass bed degradation in Sanggou Bay is influenced by high-intensity human activities,pollution from coastal land sources,raft cultures,underwater terrain conditions,and sedimentary environmental factors.The findings offer essential insights for developing seagrass restoration and protection strategies in Sanggou Bay and contribute to the broader scientific efforts for coastal ecosystem conservation and rehabilitation.
文摘This study presents a detailed experimental evaluation of a newly developed mechanistic scale-up methodology for gas-solid fluidized beds.Traditional scale-up approaches typically rely on matching global dimensionless groups,which often fail to ensure local hydrodynamic similarity.In contrast,the new mechanistic method aims to achieve scale-up by matching the radial profiles of gas holdup between geometrically similar beds at corresponding dimensionless axial positions(z/Dc).This approach is based on the premise that when gas holdup profiles align,other key hydrodynamic parameters—such as solids holdup and particle velocity—also become similar.To validate this methodology,experiments were conducted in two fluidized beds with inner diameters of 14 cm and 44 cm.Optical probes and gamma ray densitometry(GRD)were used to measure local gas holdup,solids holdup,and particle velocity at multiple axial and radial positions.The results show that matched gas holdup profiles led to mean absolute deviations(MAD)below 3%in solids holdup and particle velocity,confirming hydrodynamic similarity.In contrast,unmatched profiles resulted in significant deviations across all parameters.
基金supported by the National Key R&D Program of China(No.2021YFF0502100)the National Natural Science Foundation of China(Nos.52278461 and 52308467).
文摘Cracking of early-age concrete can occur in the track beds of high-speed railways due to changes in material properties,environmental effects,and construction processes.This is a multi-field,time-varying issue involving hydro-thermo-chemo-mechanical coupling.However,to date,research has not adequately described the early-age cracking mechanisms in track beds,and few risk control measures have been proposed.To solve this problem,we incorporated the hydration degree of concrete into multi-field coupling equations for early-age concrete,and set boundary conditions that account for environmental influences and various stress factors that typically cause early creep of concrete.A four-field coupled risk prediction model was built based on hydro-thermo-chemo-mechanical properties,and was used to calculate and analyze various time-varying behavior(including the risk and form of cracking)in the hydro,thermo,chemo,and mechanical fields of early-age concrete.Finally,we focused on material-related factors(maximum heat of hydration and peak heat release time),environmental factors(temperature difference between day and night,average daily cooling rate,and intensity of solar radiation),and construction technique factors(molding temperature,pouring time,and thermal insulation coefficient).The influence of these factors on the early-age cracking risk of the track bed was analyzed,and risk control measures against early cracking were proposed accordingly.
基金support of the Korea Institute of Industrial Technology and Promotion,with the financial resources of the government(Ministry of Trade,Industry,and Energy)in 2024.(RS-2024-00424595,project to train high-quality researchers for the next generation of marine mobility industry innovation).
文摘The application of carbon capture systems on ships is technically constrained by limited onboard space and the weight of the conventional absorption tower.The rotating packed bed(RPB)has emerged as a promising alternative due to its small footprint and high mass transfer performance.However,despite its advantages,the structural and vibration stability of RPBs at high rotational speed remains insufficiently studied,and no international design standards currently exist for RPBs.To address this gap,this study performed a comprehensive finite element analysis(FEA)using ANSYS to investigate the structural and dynamic characteristics of an RPB.A three-dimensional model was developed to evaluate the effects of material selection(316 stainless steel,aluminum alloy,titanium alloy),bearing stiffness,and unbalanced mass on deformation,stress,and natural frequencies.In the structural analysis,316 stainless steel exhibited the highest von Mises stress and deformation.However,it was confirmed that all three materials did not exceed their yield strengths at the maximum rotating speed.Modal analysis and Campbell diagrams showed no resonance risk within the rated speed range,and increased bearing stiffness led to higher natural frequencies and improved stability.The findings provide quantitative design guidance for material selection,bearing stiffness optimization,and vibration control in high-rotational-speed RPB systems.This study contributes to establishing a foundational framework for the mechanical reliability and standardization of marine carbon capture units.
基金Projects(50934002,51074013,51304076,51104100)supported by the National Natural Science Foundation of ChinaProject(IRT0950)supported by the Program for Changjiang Scholars Innovative Research Team in Universities,ChinaProject(2012M510007)supported by China Postdoctoral Science Foundation
文摘Methods and procedures of three-dimensional （3D） characterization of the pore structure features in the packed ore particle bed are focused. X-ray computed tomography was applied to deriving the cross-sectional images of specimens with single particle size of 1-2, 2-3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-9, 9-10 ram. Based on the in-house developed 3D image analysis programs using Matlab, the volume porosity, pore size distribution and degree of connectivity were calculated and analyzed in detail. The results indicate that the volume porosity, the mean diameter of pores and the effective pore size （d50） increase with the increasing of particle size. Lognormal distribution or Gauss distribution is mostly suitable to model the pore size distribution. The degree of connectivity investigated on the basis of cluster-labeling algorithm also increases with increasing the particle size approximately.
基金The National Science Foundation of China(No.51276036,51306035)the Fundamental Research Funds for the Central Universities(No.KYLX_0114)
文摘A Markov chain-based stochastic model （MCM） is developed to simulate the movement of particles in a 2D bubbling fluidized bed （BFB）. The state spaces are determined by the discretized physical cells of the bed, and the transition probability matrix is directly calculated by the results of a discrete element method （DEM） simulation. The Markov property of the BFB is discussed by the comparison results calculated from both static and dynamic transition probability matrices. The static matrix is calculated based on the Markov chain while the dynamic matrix is calculated based on the memory property of the particle movement. Results show that the difference in the trends of particle movement between the static and dynamic matrix calculation is very small. Besides, the particle mixing curves of the MCM and DEM have the same trend and similar numerical values, and the details show the time averaged characteristic of the MCM and also expose its shortcoming in describing the instantaneous particle dynamics in the BFB.
基金Shaanxi Province Qin Chuangyuan“Scientist+Engineer”Team Construction Project(2022KXJ-071)2022 Qin Chuangyuan Achievement Transformation Incubation Capacity Improvement Project(2022JH-ZHFHTS-0012)+8 种基金Shaanxi Province Key Research and Development Plan-“Two Chains”Integration Key Project-Qin Chuangyuan General Window Industrial Cluster Project(2023QCY-LL-02)Xixian New Area Science and Technology Plan(2022-YXYJ-003,2022-XXCY-010)2024 Scientific Research Project of Shaanxi National Defense Industry Vocational and Technical College(Gfy24-07)Shaanxi Vocational and Technical Education Association 2024 Vocational Education Teaching Reform Research Topic(2024SZX354)National Natural Science Foundation of China(U24A20115)2024 Shaanxi Provincial Education Department Service Local Special Scientific Research Program Project-Industrialization Cultivation Project(24JC005,24JC063)Shaanxi Province“14th Five-Year Plan”Education Science Plan,2024 Project(SGH24Y3181)National Key Research and Development Program of China(2023YFB4606400)Longmen Laboratory Frontier Exploration Topics Project(LMQYTSKT003)。
文摘A dual-phase synergistic enhancement method was adopted to strengthen the Al-Mn-Mg-Sc-Zr alloy fabricated by laser powder bed fusion(LPBF)by leveraging the unique advantages of Er and TiB_(2).Spherical powders of 0.5wt%Er-1wt%TiB_(2)/Al-Mn-Mg-Sc-Zr nanocomposite were prepared using vacuum homogenization technique,and the density of samples prepared through the LPBF process reached 99.8%.The strengthening and toughening mechanisms of Er-TiB_(2)were investigated.The results show that Al_(3)Er diffraction peaks are detected by X-ray diffraction analysis,and texture strength decreases according to electron backscatter diffraction results.The added Er and TiB_(2)nano-reinforcing phases act as heterogeneous nucleation sites during the LPBF forming process,hindering grain growth and effectively refining the grains.After incorporating the Er-TiB_(2)dual-phase nano-reinforcing phases,the tensile strength and elongation at break of the LPBF-deposited samples reach 550 MPa and 18.7%,which are 13.4%and 26.4%higher than those of the matrix material,respectively.
基金Key-Area Research and Development Program of Guangdong Province(2023B0909020004)Project of Innovation Research Team in Zhongshan(CXTD2023006)+1 种基金Natural Science Foundation of Guangdong Province(2023A1515011573)Zhongshan Social Welfare Science and Technology Research Project(2024B2022)。
文摘Laser powder bed fusion(LPBF)is highly suitable for forming 18Ni300 mold steel,thanks to its excellent capability in manufacturing complex shapes and outstanding capacity for regulating microstructures.It is widely used in fields such as injection molding,die casting,and stamping dies.Adding reinforcing particles into steel is an effective means to improve its performance.Nb/18Ni300 composites were fabricated by LPBF using two kinds of Nb powders with different particle sizes,and their microstructures and properties were studied.The results show that the unmelted Nb particles are uniformly distributed in the 18Ni300 matrix and the grains are refined,which is particularly pronounced with fine Nb particles.In addition,element diffusion occurs between the particles and the matrix.The main phases of the base alloy are α-Fe and a small amount of γ-Fe.With the addition of Nb,part of the α-Fe is transformed into γ-Fe,and unmelted Nb phases appear.The addition of Nb also enhances the hardness and wear resistance of the composites but slightly reduces their tensile properties.After aging treatment,the molten pools and grain boundaries become blurred,grains are further refined,and the interfaces around the particles are thinned.The aging treatment also promotes the formation of reverted austenite.The hardness,ultimate tensile strength,and volumetric wear rate of the base alloy reach 51.9 HRC,1704 MPa,and 17.8×10^(-6) mm^(3)/(N·m),respectively.In contrast,the sample added with fine Nb particles has the highest hardness(56.1 HRC),ultimate tensile strength(1892 MPa)and yield strength(1842 MPa),and the volume wear rate of the sample added with coarse Nb particles is reduced by 90%to 1.7×10^(-6) mm^(3)/(N·m).
基金National Key Research and Development Program of China(2023YFB4606400)Supported by Longmen Laboratory Frontier Exploration Topics(LMQYTSKT003)。
文摘Copper manufactured by laser powder bed fusion(LPBF)process typically exhibits poor strength-ductility coordination,and the addition of strengthening phases is an effective way to address this issue.To explore the effects of strengthening phases on Cu,Cu-carbon nanotubes(CNTs)composites were prepared using LPBF technique with Cu-CNTs mixed powder as the matrix.The formability,microstructure,mechanical properties,electrical conductivity,and thermal properties were studied.The result shows that the prepared composites have high relative density.The addition of CNTs results in inhomogeneous equiaxed grains at the edges of the molten pool and columnar grains at the center.Compared with pure copper,the overall mechanical properties of the composite are improved:tensile strength increases by 52.8%and elongation increases by 146.4%;the electrical and thermal properties are also enhanced:thermal conductivity increases by 10.8%and electrical conductivity increases by 12.7%.
文摘As the primary functional component of a fusion reactor,the fusion blanket pebble bed,composed of numerous particles,is crucial for tritium breeding,neutron multiplication,and radiation shielding.Particles within tritium-breeding pebble beds are subjected to prolonged neutron irradiation,high thermal loads,and strong magnetic fields in fusion environments.Such conditions render them susceptible to pulverization and fragmentation.The resulting fragments and powders migrate and are deposited into the gas channel,driven by the purge gas.The reduction in the effective flow area of the gas increases the flow resistance,resulting in tritium retention,degraded heat transfer,and other adverse effects.These conditions impair the thermodynamic properties of the pebble beds and hinder the self-maintenance of tritium.Limited information exists on powder migration and clogging mechanisms in fusion blanket pebble beds,particularly under diverse physical conditions.The aim of this study was to use a computational fluid dynamics model coupled with the discrete element method(CFD-DEM)to numerically explore powder migration and clogging in pebble beds.The model considers factors such as breeder orientation,purge velocity,powder size distribution,and friction coefficient.We propose two migration and clogging mechanisms.One involves powder with a large particle size,and the other does not.The results indicate that the powder migration velocity progresses through three stages:rapid decay,linear decay,and stability.Pebble-bed clogging manifests in two forms:extensive superficial clogging and uniform internal clogging.Two fitted curves were used to depict the migration and clogging tendencies.The powder size distribution significantly influenced the powder migration.The breeder orientation,powder size,and friction coefficient affected the distribution of the clogging powders.However,the impact of the purge velocity on powder migration and clogging in pebble beds was limited,and this effect varied significantly with different particle size ratios.Based on the analysis,a formula is proposed to characterize the behavior of the powder in the pebble beds.The results of this study can aid in analyzing and predicting powder dynamics in pebble beds.
基金Supported by the National Natural Science Foundation of China(Nos.42141003,42176147)the National Key Research and Development Program of China(No.2022YFF0802204)the Xiamen Key Laboratory of Urban Sea Ecological Conservation and Restoration(USER)(Nos.USER2021-1,USER2021-5)。
文摘Ecological floating bed is an important biological remediation method for water pollution control.During the removal of excess nutrients and pollutants,changes in environmental factors affect the characteristics of microorganisms in aquatic ecosystems.To understand the influences of ecological floating beds on size-fractionated microorganisms,we investigated the community assembly and nitrogen metabolic characteristics of three size-fractionated microorganism groups in the ecological floating bed area,using 18S rDNA,16S rDNA metabarcoding,and metagenomic sequencing techniques.Firstly,we discovered substantial differences between size-fractionated groups in the diversity and compositions of both microeukaryotic and bacterial communities,as well as the influences of floating beds on specific groups.The floating beds appeared to provide more habitats for heterotrophs and symbiotes while potentially inhibiting the growth of certain phytoplankton(cyanobacteria).Secondly,we observed that microeukaryotic and bacterial communities were predominantly influenced by stochastic and deterministic processes,respectively,and they both exhibited distinct patterns across different size-fractionated groups.Notably,microeukaryotic community assembly demonstrated a greater sensitivity to ecological floating beds,as indicated by an increase in dispersal limitation processes.Finally,the nitrogen metabolism functional genes revealed that microbes associated with large-sized particles played a crucial role in dissimilatory nitrate reduction to ammonium(DNRA)and denitrification processes within the floating bed area,thereby facilitating the removal of excess nitrogen nutrients from the water.In contrast,freeliving microorganisms from small-sized groups were linked mainly to the genes involved in nitrogen assimilation and assimilatory nitrate reduction to ammonium(ANRA)processes.These findings help understand the impact of ecological floating beds on the diversity and functional characteristics of microorganism communities in different size-fractionated groups.
基金supported by Anhui Provincial Natural Science Foundation(2408085QA030)Natural Science Research Project of Anhui Educational Committee,China(2022AH050825)+3 种基金Medical Special Cultivation Project of Anhui University of Science and Technology(YZ2023H2C008)the Excellent Research and Innovation Team of Anhui Province,China(2022AH010052)the Scientific Research Foundation for High-level Talents of Anhui University of Science and Technology,China(2021yjrc51)Collaborative Innovation Program of Hefei Science Center,CAS,China(2019HSC-CIP006).
文摘In this paper,a novel method for investigating the particle-crushing behavior of breeding particles in a fusion blanket is proposed.The fractal theory and Weibull distribution are combined to establish a theoretical model,and its validity was verified using a simple impact test.A crushable discrete element method(DEM)framework is built based on the previously established theoretical model.The tensile strength,which considers the fractal theory,size effect,and Weibull variation,was assigned to each generated particle.The assigned strength is then used for crush detection by comparing it with its maximum tensile stress.Mass conservation is ensured by inserting a series of sub-particles whose total mass was equal to the quality loss.Based on the crushable DEM framework,a numerical simulation of the crushing behavior of a pebble bed with hollow cylindrical geometry under a uniaxial compression test was performed.The results of this investigation showed that the particle withstands the external load by contact and sliding at the beginning of the compression process,and the results confirmed that crushing can be considered an important method of resisting the increasing external load.A relatively regular particle arrangement aids in resisting the load and reduces the occurrence of particle crushing.However,a limit exists to the promotion of resistance.When the strain increases beyond this limit,the distribution of the crushing position tends to be isotropic over the entire pebble bed.The theoretical model and crushable DEM framework provide a new method for exploring the pebble bed in a fusion reactor,considering particle crushing.
基金Projects(52571276,52275395,U24A20120,52475362)supported by the National Natural Science Foundation of ChinaProject(2025JJ30015)supported by the Hunan Provincial Natural Science Foundation,China+3 种基金Project(2023RC3046)supported by the Science and Technology Innovation Program of Hunan Province,ChinaProject(2023YFB4605800)supported by National Key Research and Development Program of ChinaProject(2023CXQD023)supported by the Central South University Innovation-Driven Research Programme,ChinaProject supported by the State Key Laboratory of Precision Manufacturing for Extreme Service Performance,Central South University,China。
文摘Zn's natural degradability and biocompatibility make it a promising candidate for implants,however,its mechanical properties remain insufficient for bone applications.In this study,the performance of Zn was enhanced by developing Zn-Cu alloys via laser powder bed fusion(LPBF).Optimal LPBF parameters for forming stable tracks were achieved by adjusting laser power and scanning speed.Under optimized conditions of 100 W and 100 mm/s,high density(99.58%)Zn-Cu alloys with improved hardness(68.2 HV)and yield strength(160 MPa)were achieved.These improvements are attributed to solid solution strengthening,segregation strengthening,and grain refinement.The Zn-Cu alloys also demonstrated favorable degradation behavior,with a rate of 0.16 mm/year.This degradation is primarily driven by micro-galvanic corrosion between the CuZn 5 phase and Zn matrix,along with refined grains and increased grain boundary density.This work demonstrates a viable strategy for fabricating Zn-based implants with enhanced structural integrity and mechanical performance via LPBF.
基金supported by the Young Student Project of National Natural Science Foundation of China(No.525B2139)the National Key Research and Development Program of China(Nos.2023YFB3711300 and 2021YFF0500301)the Space Application System of China Manned Space Program(No.KJZ-YYWCL404)。
文摘Targeting Chang'E-8 mission'in-situ resource utilization(ISRU)for sustainable lunar habitats,laser powder bed fusion(LPBF)provides a viable pathway for in-situ additive manufacturing of lunar regolith.To elucidate mission relevant mechanical behavior and failure mechanisms of LPBF fabricated lunar regolith simulants,mare type and highland type simulant specimens were produced.Microstructural characterization,mechanical test coupled with three-dimensional digital image correlation(3D-DIC),and an energy-dissipation framework were employed for comprehensive analysis.The pristine highland specimens achieved 5.79 MPa and a peak strain of 0.13(50 mm×50 mm×30 mm),significantly outperforming their mare counterparts.Wire-cutting to 20 mm×20 mm×20 mm lowered strength by~20%and peak strain to 0.04,indicating cutting-induced defects reduce ductility.All specimens displayed multipeaked stress–strain curves.3D-DIC revealed band-type strain localization in pristine highland samples,diffuse strain patterns in cut highland samples,and highly tortuous,network-type bands in mare samples;the anisotropy index was also quantified.Fragmented particles exhibited fractal dimensions ranging from 1.6 to 2.0(size 1.25–9 mm).Energy evolution progressed through three distinct stages:elastic energy storage,progressive energy dissipation delaying crack propagation,and final unstable collapse.An energy-based damage model was established and validated.The data and methods developed support Chang'E-8 missions'ISRU demonstrations and establish a transferable framework toward sustainable lunar habitats.
基金support of the Research and Development Program in Key Areas of Guangdong Province,China(No.2019B090907001)the Science and Technology Program of Guangdong Province,China(No.2014B010129002)the National Key R&D Program of China(No.2017YFB0305800)。
文摘The densification characterization,phase constitution,precipitation evolution and mechanical performance of Al−Mg−Sc−Zr alloy processed by laser powder bed fusion(LPBF)were systematically investigated.Moreover,the evolution of phase constitution and precipitation behavior after heat treatment were characterized by using X-ray diffraction(XRD)and transmission electron microscope(TEM)analysis.The ultimate tensile strength(UTS)of as-built samples ranged from 396.8 to 414.6 MPa as the scanning speed decreased from 1600 to 1000 mm/s.After post heat treatment,the yield strength(YS)increased to(513.1±1.3)MPa,while the UTS increased from(414.6±5.1)to(539.2±1.5)MPa.The significant improvement of mechanical performance was ascribed to the formation of secondary Al3(Sc,Zr)precipitates.
基金supported by the National Natural Science Foundation of China(No.51871243)the National Key Laboratory of Strength and Structural Integrity,China(No.ASSIKFJJ202304001)+3 种基金the State Key Laboratory of Precision Blasting and Hubei Key Laboratory of Blasting Engineering,China(No.PBSKL2022C01)the Guangdong-Hong Kong-Macao Joint Laboratory for Neutron Scattering Science and Technology,China(No.HT-CSNS-DG-CD-0092/2021)the Shock and Vibration of Engineering Materials and Structures Key Laboratory of Sichuan Province,China(No.22kfgk06)the Hubei Longzhong Laboratory,China(No.2022KF-08)。
文摘Laser remelting(LR)was used as an auxiliary post-treatment process for the Ti6Al4V titanium alloys fabricated by laser powder bed fusion(LPBF).Optical microscope(OM),scanning electron microscope(SEM)and electron back scattering diffraction(EBSD)observations showed that the grains in melted zone(MZ)transformed into equiaxial grains with an average size of 1.31μm,and the grains in heat affected zone(HAZ)were refined.Moreover,the texture intensity dropped significantly from 13.86 to 6.35 in MZ and 10.79 in HAZ.The temperature gradient(G)to solidification rate(R)ratio decreased when the laser scanning speed slowed down to a certain extent in the LR process,which effectively improved the highly preferred orientation and filled the hole defects in the surface of LPBF-Ti6Al4V.Furthermore,the hardness,wear resistance and corrosion resistance of the surface of the LPBF samples were improved by LR treatment.
基金The research was supported by the National Natural Science Foundation of China （grant #40272006, 30430100, 30370184）RFDP of the Chinese Ministry of Education, and RCQJ Project of Beijing Municipal Commission of Education. Thanks are given to Prof. R. C. Fox （University of Alberta） for reading and improving the manuscript.
文摘Lacustrine deposits exposed at Daohugou, Inner Mongolia, China, have yielded superbly preserved vertebrate fossils. The fossil beds were first misinterpreted as of Early Cretaceous age, based on alleged occurrences of key fossils of the Jehol Biota. Compelling evidence revealed by more rigorous research involving regional biostratigraphy, radiometric dating, and paleontology supports the Middle Jurassic age of the fossil beds. Despite the awesome evidence for the Middle Jurassic age of the Daohugou beds, the age dispute has been resurrected recently by invoking an overturned stratigraphic sequence. A careful review of the data, however, found no evidence that this sequence has been overturned. In addition, many of the assumptions, on which the conjecture of the fossil beds being post- Middle Jurassic is imprudently based, are self-contradictory or otherwise misleading. Thus, the post- Middle Jurassic age of the Daohugou beds as an unfounded conclusion can readily be dismissed.
