The virtual community has become a new life style as for human,but the public's acceptance is relatively low at present.So the research about the mechanism of the influence on the cohesiveness and the collective e...The virtual community has become a new life style as for human,but the public's acceptance is relatively low at present.So the research about the mechanism of the influence on the cohesiveness and the collective efficiency in virtual community has an important theoretical value and practical value.In the paper,the key variables that affect virtual community cohesiveness are extracted from two aspects—self-perception of community members and community environment,and the influence mechanism model of virtual community cohesiveness and community collective efficiency is established based on Triadic Reciprocal Determinism.By means of the questionnaire on the community members and the empirical analysis,the key factors influencing cohesiveness of virtual community are brought up,as well as the mechanism that the four dimensions of cohesiveness work,on collective efficiency.According to the results,it is practically meaningful that the problems and insufficiency in the operation of existing virtual community are discovered,which guides the operating managers of the virtual community to formulate operation policy of the virtual community for operating managers to develop strategies.展开更多
The migration,accumulation,and high yield of hydrocarbons in tight sandstone reservoirs are closely tied to the natural fracture systems within the reservoirs.Large-scale fracture networks not only enhance reservoir s...The migration,accumulation,and high yield of hydrocarbons in tight sandstone reservoirs are closely tied to the natural fracture systems within the reservoirs.Large-scale fracture networks not only enhance reservoir seepage capacity but also influence effective productivity and subsequent fracturing reconstruction.Given the diverse mechanical behaviors,such as migration,penetration,or fracture arrest,traditional assumptions about fracture interaction criteria fail to address this complexity.To resolve these issues,a global cohesive element method is proposed to model random natural fractures.This approach verifies intersection models based on real-time stress conditions rather than pre-set criteria,enabling better characterization of interactions between hydraulic and natural fractures.Research has shown that the elastic modulus,horizontal stress difference,and fracturing fluid pumping rate significantly promote the expansion of hydraulic fractures.The use of low viscosity fracturing fluid can observe a decrease in the width of fractures near the wellbore,which may cause fractures to deflect when interacting with natural fractures.However,simulations under these conditions did not form a“complex network of fractures”.It is worth noting that when the local stress difference is zero,the result is close to the formation of this network.Excessive spacing will reduce the interaction between fractures,resulting in a decrease in the total length of fractures.By comprehensively analyzing these factors,an optimal combination can be identified,increasing the likelihood of achieving a“complex fracture network”.This paper thoroughly investigates hydraulic fracture propagation in naturally fractured reservoirs under various conditions,offering insights for developing efficient fracturing methods.展开更多
Slope failures,particularly in railway embankments during intense rainfall,are a major cause of economic damage and humanitarian loss.To forecast how shear cracks develop in slopes under heavy precipitation,we present...Slope failures,particularly in railway embankments during intense rainfall,are a major cause of economic damage and humanitarian loss.To forecast how shear cracks develop in slopes under heavy precipitation,we present a novel modeling framework:the Extended Cohesive Damage Element enhanced by soil moisture(SMECDE).The method first translates forecasted rainfall into soil moisture levels via an established correspondence.Then,recognizing that rainfall infiltration lowers soil cohesion—particularly at varying depths—we introduce a Soil Moisture Decoherence Model(SMDM)based on experimental data,which quantifies how cohesion degrades with moisture and how depth affects this process.By embedding SMDM within the ECDE technique,we investigate how shear fractures propagate under different moisture conditions throughout the slope profile.We apply SMECDE to a real railway embankment case to identify critical moisture thresholds and crack growth patterns.Validation is performed by comparing predictions against field measurements and weather station records,and further checked through simulations of large-scale plastic deformation in ABAQUS.展开更多
One of the main features of a communicative English classis activities, organized by the teacher and conducted by studentsperforming certain functions and involving different topics. Theuse of activities has gained mu...One of the main features of a communicative English classis activities, organized by the teacher and conducted by studentsperforming certain functions and involving different topics. Theuse of activities has gained much attention. However, the linkbetween activities seems to have been ignored. This paper is anattempt to explore the role of cohesiveness between activities incommunicative teaching. The cohesiveness can be eithermechanical or dynamic. The key is that dynamic cohesivenesscontributes to the atmosphere and effectiveness of communicativeEnglish classroom teaching.展开更多
The mechanical behavior of cohesive soil is sensitized to drying-wetting cycles under confinements.However,the hydromechanical coupling effect has not been considered in current constitutive models.A macro-micro analy...The mechanical behavior of cohesive soil is sensitized to drying-wetting cycles under confinements.However,the hydromechanical coupling effect has not been considered in current constitutive models.A macro-micro analysis scheme is proposed in this paper to investigate the soil deformation behavior under the coupling of stress and drying-wetting cycles.A new device is developed based on CT(computerized tomography)workstation to apply certain normal and shear stresses on a soil specimen during drying-wetting cycles.A series of tests are conducted on a type of loess with various coupling of stress paths and drying-wetting cycles.At macroscopic level,stress sensor and laser sensor are used to acquire stress and strain,respectively.The shear and volumetric strain increase during the first few drying-wetting cycles and then become stable.The increase of the shear stress level or confining pressure would cause higher increase rate and the value of shear strain in the process of drying-wetting cycles.At microscopic level,the grayscale value(GSV)of CT scanning image is characterized as the proportion of soil particles to voids.A fabric state parameter is proposed to characterize soil microstructures under the influence of stress and drying-wetting cycle.Test results indicate that the macroand micro-responses show high consistence and relevance.The stress and drying-wetting cycles would both induce collapse of the soil microstructure,which dominants degradation of the soil mechanical properties.The evolution of the macro-mechanical property of soil exhibits a positive linear relationship with the micro-evolution of the fabric state parameter.展开更多
A coupled thermal-hydro-mechanical cohesive phase-field model for hydraulic fracturing in deep coal seams is presented.Heat exchange between the cold fluid and the hot rock is considered,and the thermal contribution t...A coupled thermal-hydro-mechanical cohesive phase-field model for hydraulic fracturing in deep coal seams is presented.Heat exchange between the cold fluid and the hot rock is considered,and the thermal contribution terms between the cold fluid and the hot rock are derived.Heat transfer obeys Fourier's law,and porosity is used to relate the thermodynamic parameters of the fracture and matrix domains.The net pressure difference between the fracture and the matrix is neglected,and thus the fluid flow is modeled by the unified fluid-governing equations.The evolution equations of porosity and Biot's coefficient during hydraulic fracturing are derived from their definitions.The effect of coal cleats is considered and modeled by Voronoi polygons,and this approach is shown to have high accuracy.The accuracy of the proposed model is verified by two sets of fracturing experiments in multilayer coal seams.Subsequently,the differences in fracture morphology,fluid pressure response,and fluid pressure distribution between direct fracturing of coal seams and indirect fracturing of shale interlayers are explored,and the effects of the cluster number and cluster spacing on fracture morphology for multi-cluster fracturing are also examined.The numerical results show that the proposed model is expected to be a powerful tool for the fracturing design and optimization of deep coalbed methane.展开更多
Grain boundary engineering plays a significant role in the improvement of strength and plasticity of alloys. However, in refractory high-entropy alloys, the susceptibility of grain boundaries to oxygen presents a bott...Grain boundary engineering plays a significant role in the improvement of strength and plasticity of alloys. However, in refractory high-entropy alloys, the susceptibility of grain boundaries to oxygen presents a bottleneck in achieving high mechanical performance. Creating a large number of clean grain boundaries in refractory high-entropy alloys is a challenge. In this study, an ultrafine-grained (UFG) NbMoTaW alloy with high grain-boundary cohesion was prepared by powder metallurgy, taking advantages of rapid hot-pressing sintering and full-process inert atmosphere protection from powder synthesis to sintering. By oxygen control and an increase in the proportion of grain boundaries, the segregation of oxygen and formation of oxides at grain boundaries were strongly mitigated, thus the intrinsic high cohesion of the interfaces was preserved. Compared to the coarse-grained alloys prepared by arc-melting and those sintered by traditional powder metallurgy methods, the UFG NbMoTaW alloy demonstrated simultaneously increased strength and plasticity at ambient temperature. The highly cohesive grain boundaries not only reduce brittle fractures effectively but also promote intragranular deformation. Consequently, the UFG NbMoTaW alloy achieved a high yield strength even at elevated temperatures, with a remarkable performance of 1117 MPa at 1200 ℃. This work provides a feasible solution for producing refractory high-entropy alloys with low impurity content, refined microstructure, and excellent mechanical performance.展开更多
Rock residual strength,as an important input parameter,plays an indispensable role in proposing the reasonable and scientific scheme about stope design,underground tunnel excavation and stability evaluation of deep ch...Rock residual strength,as an important input parameter,plays an indispensable role in proposing the reasonable and scientific scheme about stope design,underground tunnel excavation and stability evaluation of deep chambers.Therefore,previous residual strength models of rocks established were reviewed.And corresponding related problems were stated.Subsequently,starting from the effects of bedding and whole life-cycle evolution process,series of triaxial mechanical tests of deep bedded sandstone with five bedding angles were conducted under different confining pressures.Then,six residual strength models considering the effects of bedding and whole life-cycle evolution process were established and evaluated.Finally,a cohesion loss model for determining residual strength of deep bedded sandstone was verified.The results showed that the effects of bedding and whole life-cycle evolution process had both significant influences on the evolution characteristic of residual strength of deep bedded sandstone.Additionally,residual strength parameters:residual cohesion and residual internal friction angle of deep bedded sandstone were not constant,which both significantly changed with increasing bedding angle.Besides,the cohesion loss model was the most suitable for determining and estimating the residual strength of bedded rocks,which could provide more accurate theoretical guidance for the stability control of deep chambers.展开更多
This study investigates the bond performance at the interfacial region shared by Ultra-High Performance Concrete(UHPC)and steel tubes through push-out tests.This study examines how changes in steel fiber volumetric ra...This study investigates the bond performance at the interfacial region shared by Ultra-High Performance Concrete(UHPC)and steel tubes through push-out tests.This study examines how changes in steel fiber volumetric ratio and thickness of steel tube influence the bond strength characteristics.The results show that as the enhancement of the steel tube wall thickness,the ultimate bond strength at the interface improves significantly,whereas the initial bond strength exhibits only slight variations.The influence of steel fiber volumetric ratio presents a nonlinear trend,with initial bond strength decreasing at low fiber content and increasing significantly as fiber content rises.Additionally,finite element(FE)simulations were applied to replicate the experimental conditions,and the outcomes showed strong correlation with the experimental data,confirming the exactitude of the FE model in predicting the bond behavior at the UHPC-Steel interface.These findings provide valuable insights for optimizing the design of UHPC-Filled steel tubes in high-performance structure.展开更多
1.A.Mertha,“‘Stressing Out’:Cadre Calibration and Affective Proximity to the CCP in Reform-Era China”,The China Quarterly,Vol.229,2017,pp.64-85.2.B.L.McCormick,“Book Review of‘The Chinese Communist Party's C...1.A.Mertha,“‘Stressing Out’:Cadre Calibration and Affective Proximity to the CCP in Reform-Era China”,The China Quarterly,Vol.229,2017,pp.64-85.2.B.L.McCormick,“Book Review of‘The Chinese Communist Party's Capacity to Rule:Ideology,Legitimacy and Party Cohesion’”,The China Journal,Vol.77,2017,pp.161-163.展开更多
This study aims to investigate the failure modes at the interface of semi-flexible pavement(SFP)materials.The cohesive and wetting properties of asphalt materials,as well as two types of grout(early strength cement gr...This study aims to investigate the failure modes at the interface of semi-flexible pavement(SFP)materials.The cohesive and wetting properties of asphalt materials,as well as two types of grout(early strength cement grout-ELS and high strength cement grout-CHS),were evaluated through pull-out tests and contact angle experiments.The rheological properties of the grout/asphalt mortar were assessed using dynamic shear rheometer(DSR)testing.The interaction coefficient,complex shear modulus,and complex viscosity coefficients of the grout/asphalt mortar were calculated to analyze the interaction between the grout and asphalt.Failure modes were identified through image analysis of semi-circular bending test(SCB)specimens.Results indicate that ELS specimens exhibit a lower grout/asphalt interface failure ratio compared to CHS specimens,due to the superior wettability and interaction of ELS grout.As the temperature increases,the proportions of cement fracture and aggregate failure decrease,while the proportion of asphalt cohesive failure surfaces increases.Furthermore,the bonding strength of SBS-modified asphalt with the grout exceeds that of pure asphalt.展开更多
Purpose:To explore how different types of research funding affect research papers,with implications for optimizing funding policies and promoting sustainable research development.Design/methodology/approach:We used so...Purpose:To explore how different types of research funding affect research papers,with implications for optimizing funding policies and promoting sustainable research development.Design/methodology/approach:We used social network analysis and citation analysis to compare the influence of funded and non-funded papers,as well as among different funding types.Multidimensional scaling and cohesive subgroup analysis revealed thematic differences.Findings:Funded papers do not always show higher academic influence than non-funded ones,but multifunded papers perform better than single-funded ones.Papers funded by international institutions and HKMT have a greater impact on the international academic community.Funded papers emphasize innovation and interdisciplinarity;non-funded papers focus more on classical theory application.Research limitations:This study used only the WoS Core Collection,potentially missing other funding sources.Practical implications:The findings inform the refinement of funding policies and support strategies that encourage impactful and innovative research.Originality/value:This study offers a multi-level empirical analysis of how funding shapes research influence and thematic trends.展开更多
Grain boundaries(GBs)are often known as intergranular cracking sources in alloys at high temperatures,resulting in limited high-temperature strength and ductility.Here,we propose a GB-dual-carbide(de-noted as GB-DC)st...Grain boundaries(GBs)are often known as intergranular cracking sources in alloys at high temperatures,resulting in limited high-temperature strength and ductility.Here,we propose a GB-dual-carbide(de-noted as GB-DC)strengthening strategy and have developed a high-performance(NiCoFeCr)_(99)Nb0.5 C_(0.5) high-entropy alloy(HEA)with exceptional strength-ductility synergy at 1073 K.Chain-like coherent M23 C6 carbides have been successfully introduced at GBs and remain a cube parallel crystallographic orientation with the face-centered cubic(FCC)matrix during deformation.Nano-scale NbC particles are distributed alternatively between M_(23)C_(6) carbides and inhibit their coarsening.Both strength and duc-tility of the GB-DC HEA increase dramatically at strain rates ranging from 10^(−4) to 10^(−2) s^(−1) at 1073 K,compared with those of the single-phase NiCoFeCr HEA.Specifically,yield strength of 142 MPa,ultimate tensile strength of 283 MPa,and elongation of 34%were obtained,which are twice that of the refer-ence NiCoFeCr HEA(82 MPa,172 MPa,and 18%,respectively).EBSD investigations demonstrated that chain-like carbides enhance the GB cohesion at high temperature,and TEM analysis revealed that dislo-cations can go through the coherent phase boundaries(CPBs)and activate dipoles inner M_(23)C_(6) carbides,which weakened the stress concentration in GBs.This substantially reduces the critical stress for dislo-cation generation and transmission to a stress level lower than that required for intergranular fracture.Theoretical estimation suggests that carbides result in a much higher activation energy(∼510 kJ/mol)for GB sliding and a rather low interface energy(∼101 mJ/m^(2))compared with the GB energy(1000 mJ/m^(2)),which rationalizes the enhanced GB cohesion by carbides.展开更多
A comprehensive numerical investigation into mixed⁃mode delamination is presented in this study.It aims to assess the impact of thermal and friction effects through mixed⁃mode flexure crack propagation testing.Finite ...A comprehensive numerical investigation into mixed⁃mode delamination is presented in this study.It aims to assess the impact of thermal and friction effects through mixed⁃mode flexure crack propagation testing.Finite element analysis was employed to model the delamination process,incorporating a contact cohesive zone model.This model couples the traction⁃separation law,the contact law,and the Coulomb friction law simultaneously.The thermomechanical analysis in this study is performed using a sequentially coupled approach,implemented with the finite element software ABAQUS.The findings underscore the importance of this study.展开更多
Shale reservoirs are characterized by numerous geological discontinuities,such as bedding planes,and exhibit pronounced heterogeneity across rock layers separated by these planes.Bedding planes often possess distinct ...Shale reservoirs are characterized by numerous geological discontinuities,such as bedding planes,and exhibit pronounced heterogeneity across rock layers separated by these planes.Bedding planes often possess distinct mechanical properties compared to the surrounding rock matrix,particularly in terms of damage and fracture behavior.Consequently,vertical propagation of hydraulic fractures is influenced by both bedding planes and the heterogeneity.In this study,a numerical investigation into the height growth of hydraulic fractures was conducted using the finite element method,incorporating zero-thickness cohesive elements.The analysis explored the effects of bedding planes,toughness contrasts between layers,and variations in in-situ stress across different strata.The results reveal that hydraulic fractures are more likely to propagate along bedding planes instead of traversing them and extending vertically into barrier layers when(1)bedding strength is low,(2)stress contrast between layers is high,and(3)toughness contrast is significant.Furthermore,for a given bedding strength,increased stress contrast or higher toughness contrast between layers elevate hydraulic fracture extension pressure.When a substantial stress difference exists between layers(Lc 0.4),hydraulic=fractures preferentially propagate along bedding planes.Conversely,as bedding strength increases,the propagation distance along bedding planes decreases,accompanied by an amplified horizontal compressive stress field.Notably,when the stress difference is sufficiently small(SD a phenomenon termed“stress rolling”emerges,wherein<-0.2),hydraulic fractures deviate from vertical growth and instead extend along a near-horizontal trajectory.展开更多
基金This work has been supported by National Natural Science Foundation of China （No. 71271032）.
文摘The virtual community has become a new life style as for human,but the public's acceptance is relatively low at present.So the research about the mechanism of the influence on the cohesiveness and the collective efficiency in virtual community has an important theoretical value and practical value.In the paper,the key variables that affect virtual community cohesiveness are extracted from two aspects—self-perception of community members and community environment,and the influence mechanism model of virtual community cohesiveness and community collective efficiency is established based on Triadic Reciprocal Determinism.By means of the questionnaire on the community members and the empirical analysis,the key factors influencing cohesiveness of virtual community are brought up,as well as the mechanism that the four dimensions of cohesiveness work,on collective efficiency.According to the results,it is practically meaningful that the problems and insufficiency in the operation of existing virtual community are discovered,which guides the operating managers of the virtual community to formulate operation policy of the virtual community for operating managers to develop strategies.
基金supported by the National Natural Science Foundation of China(52074313).
文摘The migration,accumulation,and high yield of hydrocarbons in tight sandstone reservoirs are closely tied to the natural fracture systems within the reservoirs.Large-scale fracture networks not only enhance reservoir seepage capacity but also influence effective productivity and subsequent fracturing reconstruction.Given the diverse mechanical behaviors,such as migration,penetration,or fracture arrest,traditional assumptions about fracture interaction criteria fail to address this complexity.To resolve these issues,a global cohesive element method is proposed to model random natural fractures.This approach verifies intersection models based on real-time stress conditions rather than pre-set criteria,enabling better characterization of interactions between hydraulic and natural fractures.Research has shown that the elastic modulus,horizontal stress difference,and fracturing fluid pumping rate significantly promote the expansion of hydraulic fractures.The use of low viscosity fracturing fluid can observe a decrease in the width of fractures near the wellbore,which may cause fractures to deflect when interacting with natural fractures.However,simulations under these conditions did not form a“complex network of fractures”.It is worth noting that when the local stress difference is zero,the result is close to the formation of this network.Excessive spacing will reduce the interaction between fractures,resulting in a decrease in the total length of fractures.By comprehensively analyzing these factors,an optimal combination can be identified,increasing the likelihood of achieving a“complex fracture network”.This paper thoroughly investigates hydraulic fracture propagation in naturally fractured reservoirs under various conditions,offering insights for developing efficient fracturing methods.
文摘Slope failures,particularly in railway embankments during intense rainfall,are a major cause of economic damage and humanitarian loss.To forecast how shear cracks develop in slopes under heavy precipitation,we present a novel modeling framework:the Extended Cohesive Damage Element enhanced by soil moisture(SMECDE).The method first translates forecasted rainfall into soil moisture levels via an established correspondence.Then,recognizing that rainfall infiltration lowers soil cohesion—particularly at varying depths—we introduce a Soil Moisture Decoherence Model(SMDM)based on experimental data,which quantifies how cohesion degrades with moisture and how depth affects this process.By embedding SMDM within the ECDE technique,we investigate how shear fractures propagate under different moisture conditions throughout the slope profile.We apply SMECDE to a real railway embankment case to identify critical moisture thresholds and crack growth patterns.Validation is performed by comparing predictions against field measurements and weather station records,and further checked through simulations of large-scale plastic deformation in ABAQUS.
文摘One of the main features of a communicative English classis activities, organized by the teacher and conducted by studentsperforming certain functions and involving different topics. Theuse of activities has gained much attention. However, the linkbetween activities seems to have been ignored. This paper is anattempt to explore the role of cohesiveness between activities incommunicative teaching. The cohesiveness can be eithermechanical or dynamic. The key is that dynamic cohesivenesscontributes to the atmosphere and effectiveness of communicativeEnglish classroom teaching.
基金funded by National Key R&D Program of China(Grant No.2023YFC3007001)Beijing Natural Science Foundation(Grant No.8244053)China Postdoctoral Science Foundation(Grant No.2024M754065).
文摘The mechanical behavior of cohesive soil is sensitized to drying-wetting cycles under confinements.However,the hydromechanical coupling effect has not been considered in current constitutive models.A macro-micro analysis scheme is proposed in this paper to investigate the soil deformation behavior under the coupling of stress and drying-wetting cycles.A new device is developed based on CT(computerized tomography)workstation to apply certain normal and shear stresses on a soil specimen during drying-wetting cycles.A series of tests are conducted on a type of loess with various coupling of stress paths and drying-wetting cycles.At macroscopic level,stress sensor and laser sensor are used to acquire stress and strain,respectively.The shear and volumetric strain increase during the first few drying-wetting cycles and then become stable.The increase of the shear stress level or confining pressure would cause higher increase rate and the value of shear strain in the process of drying-wetting cycles.At microscopic level,the grayscale value(GSV)of CT scanning image is characterized as the proportion of soil particles to voids.A fabric state parameter is proposed to characterize soil microstructures under the influence of stress and drying-wetting cycle.Test results indicate that the macroand micro-responses show high consistence and relevance.The stress and drying-wetting cycles would both induce collapse of the soil microstructure,which dominants degradation of the soil mechanical properties.The evolution of the macro-mechanical property of soil exhibits a positive linear relationship with the micro-evolution of the fabric state parameter.
基金Project supported by the National Natural Science Foundation of China(No.42202314)。
文摘A coupled thermal-hydro-mechanical cohesive phase-field model for hydraulic fracturing in deep coal seams is presented.Heat exchange between the cold fluid and the hot rock is considered,and the thermal contribution terms between the cold fluid and the hot rock are derived.Heat transfer obeys Fourier's law,and porosity is used to relate the thermodynamic parameters of the fracture and matrix domains.The net pressure difference between the fracture and the matrix is neglected,and thus the fluid flow is modeled by the unified fluid-governing equations.The evolution equations of porosity and Biot's coefficient during hydraulic fracturing are derived from their definitions.The effect of coal cleats is considered and modeled by Voronoi polygons,and this approach is shown to have high accuracy.The accuracy of the proposed model is verified by two sets of fracturing experiments in multilayer coal seams.Subsequently,the differences in fracture morphology,fluid pressure response,and fluid pressure distribution between direct fracturing of coal seams and indirect fracturing of shale interlayers are explored,and the effects of the cluster number and cluster spacing on fracture morphology for multi-cluster fracturing are also examined.The numerical results show that the proposed model is expected to be a powerful tool for the fracturing design and optimization of deep coalbed methane.
基金supported by the National Natural Science Foundation of China(Nos.52371128,52304378,52101031 and 92163107).
文摘Grain boundary engineering plays a significant role in the improvement of strength and plasticity of alloys. However, in refractory high-entropy alloys, the susceptibility of grain boundaries to oxygen presents a bottleneck in achieving high mechanical performance. Creating a large number of clean grain boundaries in refractory high-entropy alloys is a challenge. In this study, an ultrafine-grained (UFG) NbMoTaW alloy with high grain-boundary cohesion was prepared by powder metallurgy, taking advantages of rapid hot-pressing sintering and full-process inert atmosphere protection from powder synthesis to sintering. By oxygen control and an increase in the proportion of grain boundaries, the segregation of oxygen and formation of oxides at grain boundaries were strongly mitigated, thus the intrinsic high cohesion of the interfaces was preserved. Compared to the coarse-grained alloys prepared by arc-melting and those sintered by traditional powder metallurgy methods, the UFG NbMoTaW alloy demonstrated simultaneously increased strength and plasticity at ambient temperature. The highly cohesive grain boundaries not only reduce brittle fractures effectively but also promote intragranular deformation. Consequently, the UFG NbMoTaW alloy achieved a high yield strength even at elevated temperatures, with a remarkable performance of 1117 MPa at 1200 ℃. This work provides a feasible solution for producing refractory high-entropy alloys with low impurity content, refined microstructure, and excellent mechanical performance.
基金Projects(2024YFC3013801,2022YFC3004602)supported by the National Key R&D Program of ChinaProjects(U23B2093,52034009)supported by the National Natural Science Foundation of China。
文摘Rock residual strength,as an important input parameter,plays an indispensable role in proposing the reasonable and scientific scheme about stope design,underground tunnel excavation and stability evaluation of deep chambers.Therefore,previous residual strength models of rocks established were reviewed.And corresponding related problems were stated.Subsequently,starting from the effects of bedding and whole life-cycle evolution process,series of triaxial mechanical tests of deep bedded sandstone with five bedding angles were conducted under different confining pressures.Then,six residual strength models considering the effects of bedding and whole life-cycle evolution process were established and evaluated.Finally,a cohesion loss model for determining residual strength of deep bedded sandstone was verified.The results showed that the effects of bedding and whole life-cycle evolution process had both significant influences on the evolution characteristic of residual strength of deep bedded sandstone.Additionally,residual strength parameters:residual cohesion and residual internal friction angle of deep bedded sandstone were not constant,which both significantly changed with increasing bedding angle.Besides,the cohesion loss model was the most suitable for determining and estimating the residual strength of bedded rocks,which could provide more accurate theoretical guidance for the stability control of deep chambers.
基金supported by grants from the Natural Science Foundation of Fujian Province(2021J011062)Minjiang Scholars Funding(GY-633Z21067).
文摘This study investigates the bond performance at the interfacial region shared by Ultra-High Performance Concrete(UHPC)and steel tubes through push-out tests.This study examines how changes in steel fiber volumetric ratio and thickness of steel tube influence the bond strength characteristics.The results show that as the enhancement of the steel tube wall thickness,the ultimate bond strength at the interface improves significantly,whereas the initial bond strength exhibits only slight variations.The influence of steel fiber volumetric ratio presents a nonlinear trend,with initial bond strength decreasing at low fiber content and increasing significantly as fiber content rises.Additionally,finite element(FE)simulations were applied to replicate the experimental conditions,and the outcomes showed strong correlation with the experimental data,confirming the exactitude of the FE model in predicting the bond behavior at the UHPC-Steel interface.These findings provide valuable insights for optimizing the design of UHPC-Filled steel tubes in high-performance structure.
文摘1.A.Mertha,“‘Stressing Out’:Cadre Calibration and Affective Proximity to the CCP in Reform-Era China”,The China Quarterly,Vol.229,2017,pp.64-85.2.B.L.McCormick,“Book Review of‘The Chinese Communist Party's Capacity to Rule:Ideology,Legitimacy and Party Cohesion’”,The China Journal,Vol.77,2017,pp.161-163.
基金Funded by the Science and Technology Program Special Fund of Jiangsu Province(Frontier Leading Technology Basic Research)Major Projects(No.BK20222004)the National Natural Science Foundation of China(No.52078241)the New Cornerstone Science Foundation through the XPLORER PRIZE。
文摘This study aims to investigate the failure modes at the interface of semi-flexible pavement(SFP)materials.The cohesive and wetting properties of asphalt materials,as well as two types of grout(early strength cement grout-ELS and high strength cement grout-CHS),were evaluated through pull-out tests and contact angle experiments.The rheological properties of the grout/asphalt mortar were assessed using dynamic shear rheometer(DSR)testing.The interaction coefficient,complex shear modulus,and complex viscosity coefficients of the grout/asphalt mortar were calculated to analyze the interaction between the grout and asphalt.Failure modes were identified through image analysis of semi-circular bending test(SCB)specimens.Results indicate that ELS specimens exhibit a lower grout/asphalt interface failure ratio compared to CHS specimens,due to the superior wettability and interaction of ELS grout.As the temperature increases,the proportions of cement fracture and aggregate failure decrease,while the proportion of asphalt cohesive failure surfaces increases.Furthermore,the bonding strength of SBS-modified asphalt with the grout exceeds that of pure asphalt.
基金supported by the National Natural Science Foundation of China(Grant No.72304169)Natural Science Foundation of Shandong Province(Grant No.ZR2023QG113)+1 种基金Youth Innovation Teams in Higher Education Institutions of Shandong Province(Grant No.2023RW007)the Fundamental Research Funds of Shandong University(Grant No.23RWZX29).
文摘Purpose:To explore how different types of research funding affect research papers,with implications for optimizing funding policies and promoting sustainable research development.Design/methodology/approach:We used social network analysis and citation analysis to compare the influence of funded and non-funded papers,as well as among different funding types.Multidimensional scaling and cohesive subgroup analysis revealed thematic differences.Findings:Funded papers do not always show higher academic influence than non-funded ones,but multifunded papers perform better than single-funded ones.Papers funded by international institutions and HKMT have a greater impact on the international academic community.Funded papers emphasize innovation and interdisciplinarity;non-funded papers focus more on classical theory application.Research limitations:This study used only the WoS Core Collection,potentially missing other funding sources.Practical implications:The findings inform the refinement of funding policies and support strategies that encourage impactful and innovative research.Originality/value:This study offers a multi-level empirical analysis of how funding shapes research influence and thematic trends.
基金sponsored by the fund of National Natural Sci-ence Foundation of China(Grant No.52371028 and 52271097)the State Key Laboratory of Solidification Processing in NPU(Grant No.SKLSP202401)the Fundamental Research Funds for the Central Universities,HUST(No.2023JYCXJJ016).
文摘Grain boundaries(GBs)are often known as intergranular cracking sources in alloys at high temperatures,resulting in limited high-temperature strength and ductility.Here,we propose a GB-dual-carbide(de-noted as GB-DC)strengthening strategy and have developed a high-performance(NiCoFeCr)_(99)Nb0.5 C_(0.5) high-entropy alloy(HEA)with exceptional strength-ductility synergy at 1073 K.Chain-like coherent M23 C6 carbides have been successfully introduced at GBs and remain a cube parallel crystallographic orientation with the face-centered cubic(FCC)matrix during deformation.Nano-scale NbC particles are distributed alternatively between M_(23)C_(6) carbides and inhibit their coarsening.Both strength and duc-tility of the GB-DC HEA increase dramatically at strain rates ranging from 10^(−4) to 10^(−2) s^(−1) at 1073 K,compared with those of the single-phase NiCoFeCr HEA.Specifically,yield strength of 142 MPa,ultimate tensile strength of 283 MPa,and elongation of 34%were obtained,which are twice that of the refer-ence NiCoFeCr HEA(82 MPa,172 MPa,and 18%,respectively).EBSD investigations demonstrated that chain-like carbides enhance the GB cohesion at high temperature,and TEM analysis revealed that dislo-cations can go through the coherent phase boundaries(CPBs)and activate dipoles inner M_(23)C_(6) carbides,which weakened the stress concentration in GBs.This substantially reduces the critical stress for dislo-cation generation and transmission to a stress level lower than that required for intergranular fracture.Theoretical estimation suggests that carbides result in a much higher activation energy(∼510 kJ/mol)for GB sliding and a rather low interface energy(∼101 mJ/m^(2))compared with the GB energy(1000 mJ/m^(2)),which rationalizes the enhanced GB cohesion by carbides.
文摘A comprehensive numerical investigation into mixed⁃mode delamination is presented in this study.It aims to assess the impact of thermal and friction effects through mixed⁃mode flexure crack propagation testing.Finite element analysis was employed to model the delamination process,incorporating a contact cohesive zone model.This model couples the traction⁃separation law,the contact law,and the Coulomb friction law simultaneously.The thermomechanical analysis in this study is performed using a sequentially coupled approach,implemented with the finite element software ABAQUS.The findings underscore the importance of this study.
基金the National Natural Science Foundation of China(No.52204052)the NationalNatural Science Foundation of China(No.U23B20156)the Sichuan Science and Technology Program(No.2023NSFSC0933).
文摘Shale reservoirs are characterized by numerous geological discontinuities,such as bedding planes,and exhibit pronounced heterogeneity across rock layers separated by these planes.Bedding planes often possess distinct mechanical properties compared to the surrounding rock matrix,particularly in terms of damage and fracture behavior.Consequently,vertical propagation of hydraulic fractures is influenced by both bedding planes and the heterogeneity.In this study,a numerical investigation into the height growth of hydraulic fractures was conducted using the finite element method,incorporating zero-thickness cohesive elements.The analysis explored the effects of bedding planes,toughness contrasts between layers,and variations in in-situ stress across different strata.The results reveal that hydraulic fractures are more likely to propagate along bedding planes instead of traversing them and extending vertically into barrier layers when(1)bedding strength is low,(2)stress contrast between layers is high,and(3)toughness contrast is significant.Furthermore,for a given bedding strength,increased stress contrast or higher toughness contrast between layers elevate hydraulic fracture extension pressure.When a substantial stress difference exists between layers(Lc 0.4),hydraulic=fractures preferentially propagate along bedding planes.Conversely,as bedding strength increases,the propagation distance along bedding planes decreases,accompanied by an amplified horizontal compressive stress field.Notably,when the stress difference is sufficiently small(SD a phenomenon termed“stress rolling”emerges,wherein<-0.2),hydraulic fractures deviate from vertical growth and instead extend along a near-horizontal trajectory.
