Particulate-reinforced metal matrix composites(PRMMCs)are difficult to machine due to the inclusion of hard,brittle reinforcing particles.Existing experimental investigations rarely reveal the complex material removal...Particulate-reinforced metal matrix composites(PRMMCs)are difficult to machine due to the inclusion of hard,brittle reinforcing particles.Existing experimental investigations rarely reveal the complex material removal mechanisms(MRMs)involved in the machining of PRMMCs.This paper develops a three-dimensional(3D)microstructure-based model for investigating the MRM and surface integrity of machined PRMMCs.To accurately mimic the actual microstructure of a PRMMC,polyhedrons were randomly distributed inside the matrix to represent irregular SiC particles.Particle fracture and matrix deformation and failure were taken into account.For the model’s capability comparison,a two-dimensional(2D)analysis was also conducted.Relevant cutting experiments showed that the established 3D model accurately predicted the material removal,chip morphology,machined surface finish,and cutting forces.It was found that the matrix-particle-tool interactions led to particle fractures,mainly in the primary shear and secondary deformation zones along the cutting path and beneath the machined surface.Particle fracture and dilodegment greatly influences the quality of a machined surface.It was also found that although a 2D model can reflect certain material removal features,its ability to predict microstructural variation is limited.展开更多
Ensemble-based analyses are useful to compare equiprobable scenarios of the reservoir models.However,they require a large suite of reservoir models to cover high uncertainty in heterogeneous and complex reservoir mode...Ensemble-based analyses are useful to compare equiprobable scenarios of the reservoir models.However,they require a large suite of reservoir models to cover high uncertainty in heterogeneous and complex reservoir models.For stable convergence in ensemble Kalman filter(EnKF),increasing ensemble size can be one of the solutions,but it causes high computational cost in large-scale reservoir systems.In this paper,we propose a preprocessing of good initial model selection to reduce the ensemble size,and then,EnKF is utilized to predict production performances stochastically.In the model selection scheme,representative models are chosen by using principal component analysis(PCA)and clustering analysis.The dimension of initial models is reduced using PCA,and the reduced models are grouped by clustering.Then,we choose and simulate representative models from the cluster groups to compare errors of production predictions with historical observation data.One representative model with the minimum error is considered as the best model,and we use the ensemble members near the best model in the cluster plane for applying EnKF.We demonstrate the proposed scheme for two 3D models that EnKF provides reliable assimilation results with much reduced computation time.展开更多
Carbon fiber(CF)/pyrolytic graphite(PG) composites are promising structural materials for molten salt reactors because of their superior performance.Due to the minor density difference between CF and PG, existing meth...Carbon fiber(CF)/pyrolytic graphite(PG) composites are promising structural materials for molten salt reactors because of their superior performance.Due to the minor density difference between CF and PG, existing methods are impractical for efficient three-dimensional characterization of CF/PG composites.Therefore, in this study, a method based on in-line phasecontrast X-ray microtomography was developed to solve the aforementioned problem.Experimental results demonstrate that the method is suitable for comprehensive characterization of CF/PG composites.The relationship between the microporous defects and fiber orientations of such composites was also elucidated.The findings can be useful for improving the manufacturing process of CF/PG composites.展开更多
Owing to the complexity of droughts,detailed assessments of drought events have become a key issue in water resource management and planning.In this study,three-dimensional copula models at Standard Precipitation Evap...Owing to the complexity of droughts,detailed assessments of drought events have become a key issue in water resource management and planning.In this study,three-dimensional copula models at Standard Precipitation Evapotranspiration Index(SPEI)-1,SPEI-3,SPEI-6,and SPEI-12 were used to assess drought risks in the Haihe River Basin(HRB)of China from 1961–2020.Drought duration,severity,and peak,as indicated by SPEI,were extracted based on run theory and fitted with suitable marginal distributions.The difference between the joint return period(Tor)and the co-occurrence return period(Tand)could explain the intrinsic correlation between drought characteristics.The smaller the difference,the stronger the correlation.The results showed that droughts in the north-western region of the HRB were characterized by high peak,intense severity,and long duration.In contrast,the eastern region exhibited a higher frequency of drought occurrence.Furthermore,the decreasing trend in precipitation dominated droughts,and topography of the northwest region creates the features of low annual precipitation with more days of precipitation.The drought events in the HRB were influenced by the phase shift between El Niño and La Niña.There was a strong negative phase coupling between SPEI-12 and Niño3.4(R^(2)≥0.77).The transition from La Niña to El Niño was responsible for severe droughts in the HRB.The El Niño-Southern Oscillation could predict droughts with lag times of 0.15–4.35 mon in mountainous areas.展开更多
The heterogeneity of unconventional reservoir rock tremendously affects its hydrofracturing behavior. A visual representation and accurate characterization of the three-dimensional （3D） growth and distribution of hy...The heterogeneity of unconventional reservoir rock tremendously affects its hydrofracturing behavior. A visual representation and accurate characterization of the three-dimensional （3D） growth and distribution of hydrofracturing cracks within heterogeneous rocks is of particular use to the design and implementation of hydrofracturing stimulation of unconventional reservoirs. However, because of the difficulties involved in visually representing and quantitatively characterizing a 3D hydrofracturing crack-network, this issue remains a challenge. In this paper, a novel method is proposed for physically visualizing and quantitatively characterizing the 3D hydrofracturing crack-network distributed through a heterogeneous structure based on a natural glutenite sample. This method incorporates X-ray microfocus computed tomography （μCT）, 3D printing models and hydrofracturing triaxial tests to represent visually the heterogeneous structure, and the 3D crack growth and distribution within a transparent rock model during hydrofracturing. The coupled effects of material heterogeneity and confining geostress on the 3D crack initiation and propagation were analyzed. The results indicate that the breakdown pressure of a heterogeneous rock model is significantly affected by material heterogeneity and confining geostress. The measured breakdown pressures of heterogeneous models are apparently different from those predicted by traditional theories. This study helps to elucidate the quantitative visualization and characterization of the mechanism and influencing factors that determine the hydrofracturing crack initiation and propagation in heterogeneous reservoir rocks.展开更多
A novel Ni（II） coordination polymer [Ni（dtba）（4,4′-bpy）] （1, H2dtba = 2,2′-dithio- bisbenzoic acid, 4,4′-bpy = 4,4′-bipyridine） has been synthesized by H2dtba and Ni（CH3COO）2·4H2O with exo-bidentate...A novel Ni（II） coordination polymer [Ni（dtba）（4,4′-bpy）] （1, H2dtba = 2,2′-dithio- bisbenzoic acid, 4,4′-bpy = 4,4′-bipyridine） has been synthesized by H2dtba and Ni（CH3COO）2·4H2O with exo-bidentate rigid ligand 4,4′-bpy by using hydrothermal method, and its structure was determined by single-crystal X-ray diffraction. X-ray crystal structure analysis reveals that complex 1 crystallizes in monoclinic, space group Cc with a = 11.7624（9）, b = 18.7933（19）, c = 10.3071（11）, β = 97.6510（10）°, V = 2258.2（4）3, Z = 4, C24H16N2NiO4S2, Mr = 519.22, Dc = 1.527 g/cm3, μ = 1.079 mm-1 and F（000） = 1064. The structure was solved by direct methods and refined to R = 0.0434 and wR = 0.1000 for 3281 observed reflections （I 〉 2σ（I））. The coordination environment of Ni（II） is a distorted octahedron, and a three-dimensional structure was formed with the coordination effect of dtba2- and 4,4′-bpy ligands. The topological analysis reveals that the whole framework of 1 is a 2-nodal net of （52.6）（53.64.72.8） topology. The thermal stability and XRD pattern of 1 were also investigated展开更多
Fractures are crucial for unconventional hydrocarbon exploitation,but it is difficult to accurately observe the 3D spatial distribution characteristics of fractures.Microtomography(micro-CT)technology makes it possibl...Fractures are crucial for unconventional hydrocarbon exploitation,but it is difficult to accurately observe the 3D spatial distribution characteristics of fractures.Microtomography(micro-CT)technology makes it possible to observe the 3D structures of fractures at micro-scale.In this study,micron-CT scanning is conducted on multiple mud-shale samples of source rocks in the Permian Lucaogou Formation,Junggar Basin.The Avizo^(®) software is applied to process and segment the micron-CT images,so as to obtain the 3D fracture structure model inside rock core.Therefore,the independently-developed CTSTA program is adopted to quantitatively describe the micro-fractures inside rock core,including fracture dimension,extension direction and extension scale.Meanwhile,this study summarizes the classification characteristics of fractures and their anisotropy.On this basis,the fractal dimensions of fractures can also be extracted.Previous studies show that the geometric features of fractures have self-similarity at large and small scales,which can be described by exponential laws;and the fractal dimension is a typical exponent.Through the quantitative description or characterization of 3D fractures at micro-scale,the distribution characteristics of fractures in large scales could be known.展开更多
To address the challenge of visualizing internal defects within castings, ultrasonic nondestructive testing technology has been introduced for the detection and characterization of internal defects in castings. Ultras...To address the challenge of visualizing internal defects within castings, ultrasonic nondestructive testing technology has been introduced for the detection and characterization of internal defects in castings. Ultrasonic testing is widely utilized for detecting and characterizing internal defects in materials, thanks to its strong penetration ability, wide testing area, and fast scanning speed. However, traditional ultrasonic testing primarily relies on one-dimensional waveforms or two-dimensional images to analyze internal defects in billets, which hinders intuitive characterization of defect quantity, size, spatial distribution, and other relevant information. Consequently, a three-dimensional (3D) layered characterization method of billets internal quality based on scanning acoustic microscope (SAM) is proposed. The method starts with a layered focus scanning of the billet using SAM and pre-processing the obtained sequence of ultrasonic images. Next, the ray casting is employed to reconstruct 3D shape of defects in billets, allowing for characterization of their quality by obtaining characteristic information on defect spatial distributions, quantity, and sizes. To validate the effectiveness of the proposed method, specimens of 42CrMo billets are prepared using five different processes, and the method is employed to evaluate their internal quality. Finally, a comparison between the ultrasonic image and the metallographic image reveals a difference in dimensional accuracy of only 2.94%. The results indicate that the new method enables visualization of internal defect information in billets, serving as a valuable complement to the traditional method of characterizing their internal quality.展开更多
Incorporating structural-coupling constraint, known as the cross-gradients criterion, helps to improve the focussing trend in cross-plot of multiple physical properties. Based on this feature, a?post-processing techni...Incorporating structural-coupling constraint, known as the cross-gradients criterion, helps to improve the focussing trend in cross-plot of multiple physical properties. Based on this feature, a?post-processing technique is studied to characterize the lithological types of subsurface geological materials after joint inversion. A simple domain transform, which converts two kinds of participant physical properties into an artificial complex array, is adopted to extract anomalies manually from homogenous host rock. A synthetic example shows that structure-coupled joint inverted results tend to concentrate on the feature trends in the cross-plot, and the main geological targets are recovered well by a radius-azimuth plot. In a field data example, the lithological characterization?reveals that the main rock types interpreted in the study area agree with the geological information, thus demonstrating the feasibility of this technique.展开更多
One new polyoxotungstate complex H6Na2K4（H2W12O42）Cl2·14H2O 1 has been prepared in the beaker solution and characterized by elemental analysis and IR spectroscopy. Crystal data： H36Cl2K4W12Na2O56, Mr = 3411.77...One new polyoxotungstate complex H6Na2K4（H2W12O42）Cl2·14H2O 1 has been prepared in the beaker solution and characterized by elemental analysis and IR spectroscopy. Crystal data： H36Cl2K4W12Na2O56, Mr = 3411.77, monoclinic, space group P21/c, a = 11.5734（16）, b = 14.3136（19）, c = 15.459（2）A, β = 105.601（2）°, V = 2466.5（6）A^3, Z = 2, Dc = 4.594 g/cm^3, F（000） = 3008, μ = 28.447 mm^-1, R = 0.0574 and wR = 0.1239 （Ⅰ〉 2σ（Ⅰ））. Single-crystal X-ray diffraction analysis results reveal that a three-dimensional architecture in the title compound is constructed from the H2W12O42^10- units linked by potassium.展开更多
In the last two decades,significant research has been conducted in the field of automated extraction of rock mass discontinuity characteristics from three-dimensional(3D)models.This provides several methodologies for ...In the last two decades,significant research has been conducted in the field of automated extraction of rock mass discontinuity characteristics from three-dimensional(3D)models.This provides several methodologies for acquiring discontinuity measurements from 3D models,such as point clouds generated using laser scanning or photogrammetry.However,even with numerous automated and semiautomated methods presented in the literature,there is not one single method that can automatically characterize discontinuities accurately in a minimum of time.In this paper,we critically review all the existing methods proposed in the literature for the extraction of discontinuity characteristics such as joint sets and orientations,persistence,joint spacing,roughness and block size using point clouds,digital elevation maps,or meshes.As a result of this review,we identify the strengths and drawbacks of each method used for extracting those characteristics.We found that the approaches based on voxels and region growing are superior in extracting joint planes from 3D point clouds.Normal tensor voting with trace growth algorithm is a robust method for measuring joint trace length from 3D meshes.Spacing is estimated by calculating the perpendicular distance between joint planes.Several independent roughness indices are presented to quantify roughness from 3D surface models,but there is a need to incorporate these indices into automated methodologies.There is a lack of efficient algorithms for direct computation of block size from 3D rock mass surface models.展开更多
Morphology of hydraulic fracture surface has significant effects on oil and gas flow,proppant migration and fracture closure,which plays an important role in oil and gas fracturing stimulation.In this paper,we analyze...Morphology of hydraulic fracture surface has significant effects on oil and gas flow,proppant migration and fracture closure,which plays an important role in oil and gas fracturing stimulation.In this paper,we analyzed the fracture surface characteristics induced by supercritical carbon dioxide(SC-CO_(2))and water in open-hole and perforation completion conditions under triaxial stresses.A simple calculation method was proposed to quantitatively analyze the fracture surface area and roughness in macro-level based on three-dimensional(3D)scanning data.In micro-level,scanning electron micrograph(SEM)was used to analyze the features of fracture surface.The results showed that the surface area of the induced fracture increases with perforation angle for both SC-CO_(2)and water fracturing,and the surface area of SC-CO_(2)-induced fracture is 6.49%e58.57%larger than that of water-induced fracture.The fractal dimension and surface roughness of water-induced fractures increase with the increase in perforation angle,while those of SC-CO_(2)-induced fractures decrease with the increasing perforation angle.A considerable number of microcracks and particle peeling pits can be observed on SC-CO_(2)-induced fracture surface while there are more flat particle surfaces in water-induced fracture surface through SEM images,indicating that fractures tend to propagate along the boundary of the particle for SC-CO_(2)fracturing while water-induced fractures prefer to cut through particles.These findings are of great significance for analyzing fracture mechanism and evaluating fracturing stimulation performance.展开更多
Shield tunneling inevitably passes through a large number of pile foundations in urban areas.Thus,an accurate assessment of tunneling-induced pile displacement and potential damage becomes a critical part of shield co...Shield tunneling inevitably passes through a large number of pile foundations in urban areas.Thus,an accurate assessment of tunneling-induced pile displacement and potential damage becomes a critical part of shield construction.This study presents a mechanism research of pile-soil-tunnel interaction through Pasternak-based two-stage analysis method.In the first stage,based on Mindlin’s solution,the soil displacement fields induced by shield thrust force,cutterhead frictions,shield shell frictions and grouting pressure are derived.The analytical solution of threedimensional soil displacement field is established by introducing Pinto’s three-dimensional volume loss formula,which solves the problems that shield construction factors are not taken into account in Loganathan’s formula and only twodimensional soil displacement field can be obtained.In the second stage,based on Pasternak’s two-parameter foundation model,the analytical solution of pile displacement induced by shield tunneling in layered soil is derived.A case was found in the project of interval tunnels from Wanjiali Square to Furong District Government of Changsha Metro Line 5,where the shield tunnels were constructed near viaduct piles.The reliability of the analytical solution proposed in this study is verified by comparing with the field measured data and the results of finite element method(FEM).In addition,the comparisons of longitudinal,horizontal and vertical displacements of soil and pile foundation analyzed by the analytical solution and FEM provide corresponding theoretical basis,which has significant engineering guidance for similar projects.展开更多
Objective This study reports the first imported case of Lassa fever(LF)in China.Laboratory detection and molecular epidemiological analysis of the Lassa virus(LASV)from this case offer valuable insights for the preven...Objective This study reports the first imported case of Lassa fever(LF)in China.Laboratory detection and molecular epidemiological analysis of the Lassa virus(LASV)from this case offer valuable insights for the prevention and control of LF.Methods Samples of cerebrospinal fluid(CSF),blood,urine,saliva,and environmental materials were collected from the patient and their close contacts for LASV nucleotide detection.Whole-genome sequencing was performed on positive samples to analyze the genetic characteristics of the virus.Results LASV was detected in the patient’s CSF,blood,and urine,while all samples from close contacts and the environment tested negative.The virus belongs to the lineage IV strain and shares the highest homology with strains from Sierra Leone.The variability in the glycoprotein complex(GPC)among different strains ranged from 3.9%to 15.1%,higher than previously reported for the seven known lineages.Amino acid mutation analysis revealed multiple mutations within the GPC immunogenic epitopes,increasing strain diversity and potentially impacting immune response.Conclusion The case was confirmed through nucleotide detection,with no evidence of secondary transmission or viral spread.The LASV strain identified belongs to lineage IV,with broader GPC variability than previously reported.Mutations in the immune-related sites of GPC may affect immune responses,necessitating heightened vigilance regarding the virus.展开更多
Three-dimensional(3D)urban structures play a critical role in informing climate mitigation strategies aimed at the built environment and facilitating sustainable urban development.Regrettably,there exists a significan...Three-dimensional(3D)urban structures play a critical role in informing climate mitigation strategies aimed at the built environment and facilitating sustainable urban development.Regrettably,there exists a significant gap in detailed and consistent data on 3D building space structures with global coverage due to the challenges inherent in the data collection and model calibration processes.In this study,we constructed a global urban structure(GUS-3D)dataset,including building volume,height,and footprint information,at a 500 m spatial resolution using extensive satellite observation products and numerous reference building samples.Our analysis indicated that the total volume of buildings worldwide in2015 exceeded 1×10^(12)m^(3).Over the 1985 to 2015 period,we observed a slight increase in the magnitude of 3D building volume growth(i.e.,it increased from 166.02 km3 during the 1985–2000 period to 175.08km3 during the 2000–2015 period),while the expansion magnitudes of the two-dimensional(2D)building footprint(22.51×10^(3) vs 13.29×10^(3)km^(2))and urban extent(157×10^(3) vs 133.8×10^(3)km^(2))notably decreased.This trend highlights the significant increase in intensive vertical utilization of urban land.Furthermore,we identified significant heterogeneity in building space provision and inequality across cities worldwide.This inequality is particularly pronounced in many populous Asian cities,which has been overlooked in previous studies on economic inequality.The GUS-3D dataset shows great potential to deepen our understanding of the urban environment and creates new horizons for numerous 3D urban studies.展开更多
To address the problem of multi-missile cooperative interception against maneuvering targets at a prespecified impact time and desired Line-of-Sight(LOS)angles in ThreeDimensional(3D)space,this paper proposes a 3D lea...To address the problem of multi-missile cooperative interception against maneuvering targets at a prespecified impact time and desired Line-of-Sight(LOS)angles in ThreeDimensional(3D)space,this paper proposes a 3D leader-following cooperative interception guidance law.First,in the LOS direction of the leader,an impact time-controlled guidance law is derived based on the fixed-time stability theory,which enables the leader to complete the interception task at a prespecified impact time.Next,in the LOS direction of the followers,by introducing a time consensus tracking error function,a fixed-time consensus tracking guidance law is investigated to guarantee the consensus tracking convergence of the time-to-go.Then,in the direction normal to the LOS,by combining the designed global integral sliding mode surface and the second-order Sliding Mode Control(SMC)theory,an innovative 3D LOS-angle-constrained interception guidance law is developed,which eliminates the reaching phase in the traditional sliding mode guidance laws and effectively saves energy consumption.Moreover,it effectively suppresses the chattering phenomenon while avoiding the singularity issue,and compensates for unknown interference caused by target maneuvering online,making it convenient for practical engineering applications.Finally,theoretical proof analysis and multiple sets of numerical simulation results verify the effectiveness,superiority,and robustness of the investigated guidance law.展开更多
Mesoscale eddies play vital roles in ocean processes.Although previous studies focused on eddy surface features and individual three-dimensional(3D)eddy cases in the northwestern Pacific Ocean,the analysis of unique e...Mesoscale eddies play vital roles in ocean processes.Although previous studies focused on eddy surface features and individual three-dimensional(3D)eddy cases in the northwestern Pacific Ocean,the analysis of unique eddy3D regional characteristics is still lacking.A 3D eddy detection scheme is applied to 9 years(2000-2008)of eddyresolving Regional Ocean Modeling System(ROMS)output to obtain a 3D eddy dataset from the surface to a depth of 1000 m in the northwestern Pacific Ocean(15°-35°N,120°-145°E).The 3D characteristics of mesoscale eddies are analyzed in two regions,namely,Box1(Subtropical Countercurrent,15°-25°N,120°-145°E)and Box2(Southern Kuroshio Extension,25°-35°N,120°-145°E).In Box1,the current is characterized by strong vertical shear and weak horizontal shear.In Box2,the current is characterized by the strong Kuroshio,topographic effect,and the westward propagation of Rossby waves.The results indicate the importance of baroclinic instability in Box1,whereas in Box2,both the barotropic and baroclinic instability are important.Moreover,the mesoscale eddies’properties in Box1 and Box2 are distinct.The eddies in Box1 have larger number and radius but a shorter lifetime.By contrast,Box2 has fewer eddies,which have smaller radius but longer lifetime.Vertically,more eddies are detected at the subsurface than at the surface in both regions;the depth of 650 m is the turning point in Box1.Above this depth,the number of cyclonic eddies(CEs)is larger than that of anticyclonic eddies(AEs).In Box2,the number of CEs is dominant vertically.Eddy kinetic energy(EKE)and mean normalized relative vorticity in Box2are significantly higher than those in Box1.With increasing depth,the attenuation trend of EKE and relative vorticity of Box1 become greater than those of Box2.Furthermore,the upper ocean(about 300 m in depth)contains 68.6%of the eddies(instantaneous eddy).Only 16.6%of the eddies extend to 1000 m.In addition,about87%of the eddies are bowl-shaped eddies in the two regions.Only about 3%are cone-shaped eddies.With increasing depth of the eddies,the proportion of bowl-shaped eddies gradually decreases.Conversely,the coneand lens-shaped eddies are equal in number at 700-1000 m,accounting for about 30%each.Studying the 3D characteristics of eddies in two different regions of the northwestern Pacific Ocean is an important stepping stone for discussing the different eddy generation mechanisms.展开更多
An appropriate Monte Carlo method was developed to simulate the three-dimensional normal grain growth more completely. Comparative investigation on the three-dimensional and the cross-sectional characteristics of norm...An appropriate Monte Carlo method was developed to simulate the three-dimensional normal grain growth more completely. Comparative investigation on the three-dimensional and the cross-sectional characteristics of normal grain growth was done. It was found that the time exponent of grain growth determined from cross-section exhibits the same rule of increasing slowly with time and approaching the theoretical value n = 0.5 of steadygrain growth as the three-dimensional (3-D) system. From change of the number of grains per unit area with timemeasured in cross-section, the state of 3-D normal grain growth may be predicted. The gtain size distribution incross-section is different from that in 3-D system and can not express the evolution characteristic of the 3-D distribution. Furthermore, there exists statistical connection between the topological parameters in cross-section and thosein three-dimensions.展开更多
With the ongoing depletion of fossil fuels,energy and environmental issues have become increasingly critical,necessitating the search for effective solutions.Catalysis,being one of the hallmarks of modern industry,off...With the ongoing depletion of fossil fuels,energy and environmental issues have become increasingly critical,necessitating the search for effective solutions.Catalysis,being one of the hallmarks of modern industry,offers a promising avenue for researchers.However,the question of how to significantly enhance the performance of catalysts has gradually drawn the attention of scholars.Defect engineering,a commonly employed and effective approach to improve catalyst activity,has become a significant research focus in the catalysis field in recent years.Nonmetal vacancies have received extensive attention due to their simple form.Consequently,exploration of metal vacancies has remained stagnant for a considerable period,resulting in a scarcity of comprehensive reviews on this topic.Therefore,based on the latest research findings,this paper summarizes and consolidates the construction strategies for metal vacancies,characterization techniques,and their roles in typical energy and environmental catalytic reactions.Additionally,it outlines potential challenges in the future,aiming to provide valuable references for researchers interested in investigating metal vacancies.展开更多
文摘Particulate-reinforced metal matrix composites(PRMMCs)are difficult to machine due to the inclusion of hard,brittle reinforcing particles.Existing experimental investigations rarely reveal the complex material removal mechanisms(MRMs)involved in the machining of PRMMCs.This paper develops a three-dimensional(3D)microstructure-based model for investigating the MRM and surface integrity of machined PRMMCs.To accurately mimic the actual microstructure of a PRMMC,polyhedrons were randomly distributed inside the matrix to represent irregular SiC particles.Particle fracture and matrix deformation and failure were taken into account.For the model’s capability comparison,a two-dimensional(2D)analysis was also conducted.Relevant cutting experiments showed that the established 3D model accurately predicted the material removal,chip morphology,machined surface finish,and cutting forces.It was found that the matrix-particle-tool interactions led to particle fractures,mainly in the primary shear and secondary deformation zones along the cutting path and beneath the machined surface.Particle fracture and dilodegment greatly influences the quality of a machined surface.It was also found that although a 2D model can reflect certain material removal features,its ability to predict microstructural variation is limited.
基金supported by The Ministry of Trade,Industry,and Energy(20172510102090,20142520100440,20162010201980)Global PhD Fellowship Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(2015H1A2A1030756)supported by the National Research Foundation of Korea(NRF)Grant(No.2018R1C1B5045260).
文摘Ensemble-based analyses are useful to compare equiprobable scenarios of the reservoir models.However,they require a large suite of reservoir models to cover high uncertainty in heterogeneous and complex reservoir models.For stable convergence in ensemble Kalman filter(EnKF),increasing ensemble size can be one of the solutions,but it causes high computational cost in large-scale reservoir systems.In this paper,we propose a preprocessing of good initial model selection to reduce the ensemble size,and then,EnKF is utilized to predict production performances stochastically.In the model selection scheme,representative models are chosen by using principal component analysis(PCA)and clustering analysis.The dimension of initial models is reduced using PCA,and the reduced models are grouped by clustering.Then,we choose and simulate representative models from the cluster groups to compare errors of production predictions with historical observation data.One representative model with the minimum error is considered as the best model,and we use the ensemble members near the best model in the cluster plane for applying EnKF.We demonstrate the proposed scheme for two 3D models that EnKF provides reliable assimilation results with much reduced computation time.
基金supported by the National Key Research and Development Program of China (Nos.2017YFA0206004,2017YFA0206002, 2018YFC1200204, and 2017YFA0403801)the National Natural Science Foundation of China(NSFC)(No.81430087)。
文摘Carbon fiber(CF)/pyrolytic graphite(PG) composites are promising structural materials for molten salt reactors because of their superior performance.Due to the minor density difference between CF and PG, existing methods are impractical for efficient three-dimensional characterization of CF/PG composites.Therefore, in this study, a method based on in-line phasecontrast X-ray microtomography was developed to solve the aforementioned problem.Experimental results demonstrate that the method is suitable for comprehensive characterization of CF/PG composites.The relationship between the microporous defects and fiber orientations of such composites was also elucidated.The findings can be useful for improving the manufacturing process of CF/PG composites.
基金Under the auspices of the Shandong Provincial Natural Science Foundation(No.ZR2024ME171,ZR2024QD207)the National Natural Science Foundation of China(No.41471160,42377077)。
文摘Owing to the complexity of droughts,detailed assessments of drought events have become a key issue in water resource management and planning.In this study,three-dimensional copula models at Standard Precipitation Evapotranspiration Index(SPEI)-1,SPEI-3,SPEI-6,and SPEI-12 were used to assess drought risks in the Haihe River Basin(HRB)of China from 1961–2020.Drought duration,severity,and peak,as indicated by SPEI,were extracted based on run theory and fitted with suitable marginal distributions.The difference between the joint return period(Tor)and the co-occurrence return period(Tand)could explain the intrinsic correlation between drought characteristics.The smaller the difference,the stronger the correlation.The results showed that droughts in the north-western region of the HRB were characterized by high peak,intense severity,and long duration.In contrast,the eastern region exhibited a higher frequency of drought occurrence.Furthermore,the decreasing trend in precipitation dominated droughts,and topography of the northwest region creates the features of low annual precipitation with more days of precipitation.The drought events in the HRB were influenced by the phase shift between El Niño and La Niña.There was a strong negative phase coupling between SPEI-12 and Niño3.4(R^(2)≥0.77).The transition from La Niña to El Niño was responsible for severe droughts in the HRB.The El Niño-Southern Oscillation could predict droughts with lag times of 0.15–4.35 mon in mountainous areas.
基金We gratefully acknowledge the financial support of the National Natural Science Foundation of China （Grants 51374213 and 51674251）, National Natural Science Fund for Distinguished Young Scholars of China （Grant 51125017）, Science Fund for Creative Research Groups of the National Natural Science Foundation of China （Grant 51421003）, Fund for Innovative Research and Development Group Program of Jiangsu Province （Grant 2014-27）, and the Priority Academic Program Development of Jiangsu Higher Education Institutions （Grant PAPD 2014）.
文摘The heterogeneity of unconventional reservoir rock tremendously affects its hydrofracturing behavior. A visual representation and accurate characterization of the three-dimensional （3D） growth and distribution of hydrofracturing cracks within heterogeneous rocks is of particular use to the design and implementation of hydrofracturing stimulation of unconventional reservoirs. However, because of the difficulties involved in visually representing and quantitatively characterizing a 3D hydrofracturing crack-network, this issue remains a challenge. In this paper, a novel method is proposed for physically visualizing and quantitatively characterizing the 3D hydrofracturing crack-network distributed through a heterogeneous structure based on a natural glutenite sample. This method incorporates X-ray microfocus computed tomography （μCT）, 3D printing models and hydrofracturing triaxial tests to represent visually the heterogeneous structure, and the 3D crack growth and distribution within a transparent rock model during hydrofracturing. The coupled effects of material heterogeneity and confining geostress on the 3D crack initiation and propagation were analyzed. The results indicate that the breakdown pressure of a heterogeneous rock model is significantly affected by material heterogeneity and confining geostress. The measured breakdown pressures of heterogeneous models are apparently different from those predicted by traditional theories. This study helps to elucidate the quantitative visualization and characterization of the mechanism and influencing factors that determine the hydrofracturing crack initiation and propagation in heterogeneous reservoir rocks.
基金the National Natural Science Foundation of China (No. 20771006, 20901004 and 20801025)
文摘A novel Ni（II） coordination polymer [Ni（dtba）（4,4′-bpy）] （1, H2dtba = 2,2′-dithio- bisbenzoic acid, 4,4′-bpy = 4,4′-bipyridine） has been synthesized by H2dtba and Ni（CH3COO）2·4H2O with exo-bidentate rigid ligand 4,4′-bpy by using hydrothermal method, and its structure was determined by single-crystal X-ray diffraction. X-ray crystal structure analysis reveals that complex 1 crystallizes in monoclinic, space group Cc with a = 11.7624（9）, b = 18.7933（19）, c = 10.3071（11）, β = 97.6510（10）°, V = 2258.2（4）3, Z = 4, C24H16N2NiO4S2, Mr = 519.22, Dc = 1.527 g/cm3, μ = 1.079 mm-1 and F（000） = 1064. The structure was solved by direct methods and refined to R = 0.0434 and wR = 0.1000 for 3281 observed reflections （I 〉 2σ（I））. The coordination environment of Ni（II） is a distorted octahedron, and a three-dimensional structure was formed with the coordination effect of dtba2- and 4,4′-bpy ligands. The topological analysis reveals that the whole framework of 1 is a 2-nodal net of （52.6）（53.64.72.8） topology. The thermal stability and XRD pattern of 1 were also investigated
基金This work was financially supported by the National Basic Research Program of China(973 Project)"Formation mechanism and enrichment law of China's terrestrial tight oil(shale oil)"(2014CB239004).
文摘Fractures are crucial for unconventional hydrocarbon exploitation,but it is difficult to accurately observe the 3D spatial distribution characteristics of fractures.Microtomography(micro-CT)technology makes it possible to observe the 3D structures of fractures at micro-scale.In this study,micron-CT scanning is conducted on multiple mud-shale samples of source rocks in the Permian Lucaogou Formation,Junggar Basin.The Avizo^(®) software is applied to process and segment the micron-CT images,so as to obtain the 3D fracture structure model inside rock core.Therefore,the independently-developed CTSTA program is adopted to quantitatively describe the micro-fractures inside rock core,including fracture dimension,extension direction and extension scale.Meanwhile,this study summarizes the classification characteristics of fractures and their anisotropy.On this basis,the fractal dimensions of fractures can also be extracted.Previous studies show that the geometric features of fractures have self-similarity at large and small scales,which can be described by exponential laws;and the fractal dimension is a typical exponent.Through the quantitative description or characterization of 3D fractures at micro-scale,the distribution characteristics of fractures in large scales could be known.
基金supported by the joint funds of the National Natural Science Foundation of China (Grant No. U22A20186)the Open Foundation of Key Laboratory of Metallurgical Equipment and Control Technology (Wuhan University of Science and Technology) Ministry of Education (Grant No. MECOF2019804)the Foundation of Key Technologies R&D Program of Guangdong Province (Grant No. 2020B0101130007).
文摘To address the challenge of visualizing internal defects within castings, ultrasonic nondestructive testing technology has been introduced for the detection and characterization of internal defects in castings. Ultrasonic testing is widely utilized for detecting and characterizing internal defects in materials, thanks to its strong penetration ability, wide testing area, and fast scanning speed. However, traditional ultrasonic testing primarily relies on one-dimensional waveforms or two-dimensional images to analyze internal defects in billets, which hinders intuitive characterization of defect quantity, size, spatial distribution, and other relevant information. Consequently, a three-dimensional (3D) layered characterization method of billets internal quality based on scanning acoustic microscope (SAM) is proposed. The method starts with a layered focus scanning of the billet using SAM and pre-processing the obtained sequence of ultrasonic images. Next, the ray casting is employed to reconstruct 3D shape of defects in billets, allowing for characterization of their quality by obtaining characteristic information on defect spatial distributions, quantity, and sizes. To validate the effectiveness of the proposed method, specimens of 42CrMo billets are prepared using five different processes, and the method is employed to evaluate their internal quality. Finally, a comparison between the ultrasonic image and the metallographic image reveals a difference in dimensional accuracy of only 2.94%. The results indicate that the new method enables visualization of internal defect information in billets, serving as a valuable complement to the traditional method of characterizing their internal quality.
文摘Incorporating structural-coupling constraint, known as the cross-gradients criterion, helps to improve the focussing trend in cross-plot of multiple physical properties. Based on this feature, a?post-processing technique is studied to characterize the lithological types of subsurface geological materials after joint inversion. A simple domain transform, which converts two kinds of participant physical properties into an artificial complex array, is adopted to extract anomalies manually from homogenous host rock. A synthetic example shows that structure-coupled joint inverted results tend to concentrate on the feature trends in the cross-plot, and the main geological targets are recovered well by a radius-azimuth plot. In a field data example, the lithological characterization?reveals that the main rock types interpreted in the study area agree with the geological information, thus demonstrating the feasibility of this technique.
基金The work was supported by NNSFC (No. 20501011)Liaocheng University (31801)
文摘One new polyoxotungstate complex H6Na2K4（H2W12O42）Cl2·14H2O 1 has been prepared in the beaker solution and characterized by elemental analysis and IR spectroscopy. Crystal data： H36Cl2K4W12Na2O56, Mr = 3411.77, monoclinic, space group P21/c, a = 11.5734（16）, b = 14.3136（19）, c = 15.459（2）A, β = 105.601（2）°, V = 2466.5（6）A^3, Z = 2, Dc = 4.594 g/cm^3, F（000） = 3008, μ = 28.447 mm^-1, R = 0.0574 and wR = 0.1239 （Ⅰ〉 2σ（Ⅰ））. Single-crystal X-ray diffraction analysis results reveal that a three-dimensional architecture in the title compound is constructed from the H2W12O42^10- units linked by potassium.
基金funded by the U.S.National Institute for Occupational Safety and Health(NIOSH)under the Contract No.75D30119C06044。
文摘In the last two decades,significant research has been conducted in the field of automated extraction of rock mass discontinuity characteristics from three-dimensional(3D)models.This provides several methodologies for acquiring discontinuity measurements from 3D models,such as point clouds generated using laser scanning or photogrammetry.However,even with numerous automated and semiautomated methods presented in the literature,there is not one single method that can automatically characterize discontinuities accurately in a minimum of time.In this paper,we critically review all the existing methods proposed in the literature for the extraction of discontinuity characteristics such as joint sets and orientations,persistence,joint spacing,roughness and block size using point clouds,digital elevation maps,or meshes.As a result of this review,we identify the strengths and drawbacks of each method used for extracting those characteristics.We found that the approaches based on voxels and region growing are superior in extracting joint planes from 3D point clouds.Normal tensor voting with trace growth algorithm is a robust method for measuring joint trace length from 3D meshes.Spacing is estimated by calculating the perpendicular distance between joint planes.Several independent roughness indices are presented to quantify roughness from 3D surface models,but there is a need to incorporate these indices into automated methodologies.There is a lack of efficient algorithms for direct computation of block size from 3D rock mass surface models.
基金National Natural Science Foundation of China(Grant No.51804318)the China Postdoctoral Science Foundation Founded Project(Grant No.2019M650963)National Key Basic Research and Development Program of China(Grant No.2014CB239203).
文摘Morphology of hydraulic fracture surface has significant effects on oil and gas flow,proppant migration and fracture closure,which plays an important role in oil and gas fracturing stimulation.In this paper,we analyzed the fracture surface characteristics induced by supercritical carbon dioxide(SC-CO_(2))and water in open-hole and perforation completion conditions under triaxial stresses.A simple calculation method was proposed to quantitatively analyze the fracture surface area and roughness in macro-level based on three-dimensional(3D)scanning data.In micro-level,scanning electron micrograph(SEM)was used to analyze the features of fracture surface.The results showed that the surface area of the induced fracture increases with perforation angle for both SC-CO_(2)and water fracturing,and the surface area of SC-CO_(2)-induced fracture is 6.49%e58.57%larger than that of water-induced fracture.The fractal dimension and surface roughness of water-induced fractures increase with the increase in perforation angle,while those of SC-CO_(2)-induced fractures decrease with the increasing perforation angle.A considerable number of microcracks and particle peeling pits can be observed on SC-CO_(2)-induced fracture surface while there are more flat particle surfaces in water-induced fracture surface through SEM images,indicating that fractures tend to propagate along the boundary of the particle for SC-CO_(2)fracturing while water-induced fractures prefer to cut through particles.These findings are of great significance for analyzing fracture mechanism and evaluating fracturing stimulation performance.
基金Project(52078060) supported by the National Natural Science Foundation of ChinaProject(2020JJ4606)supported by the Natural Science Foundation of Hunan Province,China+1 种基金Project(2018IC19) supported by the International Cooperation and Development Project of Double-First-Class Scientific Research in Changsha University of Science&Technology,ChinaProject(18ZDXK05) supported by Innovative Program of Key Disciplines with Advantages and Characteristics of Civil Engineering of Changsha University of Science&Technology,China。
文摘Shield tunneling inevitably passes through a large number of pile foundations in urban areas.Thus,an accurate assessment of tunneling-induced pile displacement and potential damage becomes a critical part of shield construction.This study presents a mechanism research of pile-soil-tunnel interaction through Pasternak-based two-stage analysis method.In the first stage,based on Mindlin’s solution,the soil displacement fields induced by shield thrust force,cutterhead frictions,shield shell frictions and grouting pressure are derived.The analytical solution of threedimensional soil displacement field is established by introducing Pinto’s three-dimensional volume loss formula,which solves the problems that shield construction factors are not taken into account in Loganathan’s formula and only twodimensional soil displacement field can be obtained.In the second stage,based on Pasternak’s two-parameter foundation model,the analytical solution of pile displacement induced by shield tunneling in layered soil is derived.A case was found in the project of interval tunnels from Wanjiali Square to Furong District Government of Changsha Metro Line 5,where the shield tunnels were constructed near viaduct piles.The reliability of the analytical solution proposed in this study is verified by comparing with the field measured data and the results of finite element method(FEM).In addition,the comparisons of longitudinal,horizontal and vertical displacements of soil and pile foundation analyzed by the analytical solution and FEM provide corresponding theoretical basis,which has significant engineering guidance for similar projects.
基金supported by Public Health Talent Training and Surport Plan(National Administration of Disease Prevention and Control)Research and application of new technology for rapid monitoring and tracing of emergent infectious diseases among entry-exit population(2024YFFK0056)Monitoring,Early warning and Response of Major Infectious Diseases(2022ZDZX0017).
文摘Objective This study reports the first imported case of Lassa fever(LF)in China.Laboratory detection and molecular epidemiological analysis of the Lassa virus(LASV)from this case offer valuable insights for the prevention and control of LF.Methods Samples of cerebrospinal fluid(CSF),blood,urine,saliva,and environmental materials were collected from the patient and their close contacts for LASV nucleotide detection.Whole-genome sequencing was performed on positive samples to analyze the genetic characteristics of the virus.Results LASV was detected in the patient’s CSF,blood,and urine,while all samples from close contacts and the environment tested negative.The virus belongs to the lineage IV strain and shares the highest homology with strains from Sierra Leone.The variability in the glycoprotein complex(GPC)among different strains ranged from 3.9%to 15.1%,higher than previously reported for the seven known lineages.Amino acid mutation analysis revealed multiple mutations within the GPC immunogenic epitopes,increasing strain diversity and potentially impacting immune response.Conclusion The case was confirmed through nucleotide detection,with no evidence of secondary transmission or viral spread.The LASV strain identified belongs to lineage IV,with broader GPC variability than previously reported.Mutations in the immune-related sites of GPC may affect immune responses,necessitating heightened vigilance regarding the virus.
基金supported by the National Science Fund for Distinguished Young Scholars(42225107)the National Natural Science Foundation of China(42001326,42371414,42171409,and 42271419)+1 种基金the Natural Science Foundation of Guangdong Province of China(2022A1515012207)the Basic and Applied Basic Research Project of Guangzhou Science and Technology Planning(202201011539)。
文摘Three-dimensional(3D)urban structures play a critical role in informing climate mitigation strategies aimed at the built environment and facilitating sustainable urban development.Regrettably,there exists a significant gap in detailed and consistent data on 3D building space structures with global coverage due to the challenges inherent in the data collection and model calibration processes.In this study,we constructed a global urban structure(GUS-3D)dataset,including building volume,height,and footprint information,at a 500 m spatial resolution using extensive satellite observation products and numerous reference building samples.Our analysis indicated that the total volume of buildings worldwide in2015 exceeded 1×10^(12)m^(3).Over the 1985 to 2015 period,we observed a slight increase in the magnitude of 3D building volume growth(i.e.,it increased from 166.02 km3 during the 1985–2000 period to 175.08km3 during the 2000–2015 period),while the expansion magnitudes of the two-dimensional(2D)building footprint(22.51×10^(3) vs 13.29×10^(3)km^(2))and urban extent(157×10^(3) vs 133.8×10^(3)km^(2))notably decreased.This trend highlights the significant increase in intensive vertical utilization of urban land.Furthermore,we identified significant heterogeneity in building space provision and inequality across cities worldwide.This inequality is particularly pronounced in many populous Asian cities,which has been overlooked in previous studies on economic inequality.The GUS-3D dataset shows great potential to deepen our understanding of the urban environment and creates new horizons for numerous 3D urban studies.
文摘To address the problem of multi-missile cooperative interception against maneuvering targets at a prespecified impact time and desired Line-of-Sight(LOS)angles in ThreeDimensional(3D)space,this paper proposes a 3D leader-following cooperative interception guidance law.First,in the LOS direction of the leader,an impact time-controlled guidance law is derived based on the fixed-time stability theory,which enables the leader to complete the interception task at a prespecified impact time.Next,in the LOS direction of the followers,by introducing a time consensus tracking error function,a fixed-time consensus tracking guidance law is investigated to guarantee the consensus tracking convergence of the time-to-go.Then,in the direction normal to the LOS,by combining the designed global integral sliding mode surface and the second-order Sliding Mode Control(SMC)theory,an innovative 3D LOS-angle-constrained interception guidance law is developed,which eliminates the reaching phase in the traditional sliding mode guidance laws and effectively saves energy consumption.Moreover,it effectively suppresses the chattering phenomenon while avoiding the singularity issue,and compensates for unknown interference caused by target maneuvering online,making it convenient for practical engineering applications.Finally,theoretical proof analysis and multiple sets of numerical simulation results verify the effectiveness,superiority,and robustness of the investigated guidance law.
基金The National Natural Science Foundation of China under contract Nos NSFC 41806030 and 42076021the China Ocean Mineral Resources Research and Development Association Program under contract No.DY135-E2-3-01+4 种基金the Basic Scientific Research Business Expenses of Zhejiang Provincial Universities under contract No.2020J00007the project of State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology,Chinese Academy of Sciences under contract No.LTO1807the project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)under contract No.SML2020SP007the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)under contract No.311020004the Strategic Priority Research Program of Chinese Academy of Sciences under contract No.XDB42000000。
文摘Mesoscale eddies play vital roles in ocean processes.Although previous studies focused on eddy surface features and individual three-dimensional(3D)eddy cases in the northwestern Pacific Ocean,the analysis of unique eddy3D regional characteristics is still lacking.A 3D eddy detection scheme is applied to 9 years(2000-2008)of eddyresolving Regional Ocean Modeling System(ROMS)output to obtain a 3D eddy dataset from the surface to a depth of 1000 m in the northwestern Pacific Ocean(15°-35°N,120°-145°E).The 3D characteristics of mesoscale eddies are analyzed in two regions,namely,Box1(Subtropical Countercurrent,15°-25°N,120°-145°E)and Box2(Southern Kuroshio Extension,25°-35°N,120°-145°E).In Box1,the current is characterized by strong vertical shear and weak horizontal shear.In Box2,the current is characterized by the strong Kuroshio,topographic effect,and the westward propagation of Rossby waves.The results indicate the importance of baroclinic instability in Box1,whereas in Box2,both the barotropic and baroclinic instability are important.Moreover,the mesoscale eddies’properties in Box1 and Box2 are distinct.The eddies in Box1 have larger number and radius but a shorter lifetime.By contrast,Box2 has fewer eddies,which have smaller radius but longer lifetime.Vertically,more eddies are detected at the subsurface than at the surface in both regions;the depth of 650 m is the turning point in Box1.Above this depth,the number of cyclonic eddies(CEs)is larger than that of anticyclonic eddies(AEs).In Box2,the number of CEs is dominant vertically.Eddy kinetic energy(EKE)and mean normalized relative vorticity in Box2are significantly higher than those in Box1.With increasing depth,the attenuation trend of EKE and relative vorticity of Box1 become greater than those of Box2.Furthermore,the upper ocean(about 300 m in depth)contains 68.6%of the eddies(instantaneous eddy).Only 16.6%of the eddies extend to 1000 m.In addition,about87%of the eddies are bowl-shaped eddies in the two regions.Only about 3%are cone-shaped eddies.With increasing depth of the eddies,the proportion of bowl-shaped eddies gradually decreases.Conversely,the coneand lens-shaped eddies are equal in number at 700-1000 m,accounting for about 30%each.Studying the 3D characteristics of eddies in two different regions of the northwestern Pacific Ocean is an important stepping stone for discussing the different eddy generation mechanisms.
文摘An appropriate Monte Carlo method was developed to simulate the three-dimensional normal grain growth more completely. Comparative investigation on the three-dimensional and the cross-sectional characteristics of normal grain growth was done. It was found that the time exponent of grain growth determined from cross-section exhibits the same rule of increasing slowly with time and approaching the theoretical value n = 0.5 of steadygrain growth as the three-dimensional (3-D) system. From change of the number of grains per unit area with timemeasured in cross-section, the state of 3-D normal grain growth may be predicted. The gtain size distribution incross-section is different from that in 3-D system and can not express the evolution characteristic of the 3-D distribution. Furthermore, there exists statistical connection between the topological parameters in cross-section and thosein three-dimensions.
基金financially supported by National Key R&D Program of China(2021YFB3500702)National Natural Science Foundation of China(Nos.21677010 and 51808037)Special fund of Beijing Key Laboratory of Indoor Air Quality Evaluation and Control(No.BZ0344KF21-04).
文摘With the ongoing depletion of fossil fuels,energy and environmental issues have become increasingly critical,necessitating the search for effective solutions.Catalysis,being one of the hallmarks of modern industry,offers a promising avenue for researchers.However,the question of how to significantly enhance the performance of catalysts has gradually drawn the attention of scholars.Defect engineering,a commonly employed and effective approach to improve catalyst activity,has become a significant research focus in the catalysis field in recent years.Nonmetal vacancies have received extensive attention due to their simple form.Consequently,exploration of metal vacancies has remained stagnant for a considerable period,resulting in a scarcity of comprehensive reviews on this topic.Therefore,based on the latest research findings,this paper summarizes and consolidates the construction strategies for metal vacancies,characterization techniques,and their roles in typical energy and environmental catalytic reactions.Additionally,it outlines potential challenges in the future,aiming to provide valuable references for researchers interested in investigating metal vacancies.
