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
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
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
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
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 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
This paper investigates the mechanisms of rock failure related to axial splitting and shear failure due to hoop stresses in cylindrical specimens.The hoop stresses are caused by normal viscous stress.The rheological d...This paper investigates the mechanisms of rock failure related to axial splitting and shear failure due to hoop stresses in cylindrical specimens.The hoop stresses are caused by normal viscous stress.The rheological dynamics theory(RDT)is used,with the mechanical parameters being determined by P-and S-wave velocities.The angle of internal friction is determined by the ratio of Young's modulus and the dynamic modulus,while dynamic viscosity defines cohesion and normal viscous stress.The effect of frequency on cohesion is considered.The initial stress state is defined by the minimum cohesion at the elastic limit when axial splitting can occur.However,as radial cracks grow,the stress state becomes oblique and moves towards the shear plane.The maximum and nonlinear cohesions are defined by the rock parameters under compressive strength when the radial crack depth reaches a critical value.The efficacy and precision of RDT are validated through the presentation of ultrasonic measurements on sandstone and rock specimens sourced from the literature.The results presented in dimensionless diagrams can be utilized in microcrack zones in the absence of lateral pressure in rock masses that have undergone disintegration due to excavation.展开更多
The discourse marker ni hai bie shuo(你还别说)often appears at the beginning of a sentence,connecting to a rich variety of clause types.Its co-occurring words are mostly those expressing subjective evaluation.The subs...The discourse marker ni hai bie shuo(你还别说)often appears at the beginning of a sentence,connecting to a rich variety of clause types.Its co-occurring words are mostly those expressing subjective evaluation.The subsequent discourse it connects to mainly consists of three clause types:explanatory,resultative,and adversative.The basic semantic structure of the segment in which it appears is:(S1)+ni hai bie shuo+S2.It serves seven textual functions,such as the agreement function,negation function,reminding function,and topic-shifting function.展开更多
BACKGROUND Poorly cohesive gastric carcinomas are classified based on the proportion of signet-ring cell carcinoma(SRCC)components.In surgically resected gastric cancer,SRCC is diagnosed when the signet-ring cell(SRC)...BACKGROUND Poorly cohesive gastric carcinomas are classified based on the proportion of signet-ring cell carcinoma(SRCC)components.In surgically resected gastric cancer,SRCC is diagnosed when the signet-ring cell(SRC)component constitutes≥50%of the entire tumor,whereas poorly cohesive carcinoma(PCC)not otherwise specified is diagnosed when the proportion of the SRC component is<50%of the entire tumor.The SRCC proportion in PCC varies along the spectrum,and its prognostic significance in gastric cancer remains unclear.AIM To investigate how the proportion of SRCC affects tumor pathology,clinical outcomes,and prognosis and treatment decision-making.METHODS This retrospective study included 1066 patients with PCC who underwent gastric cancer surgery at Seoul National University Bundang Hospital from 2016 to 2023.Patients were classified into four groups based on the SRCC proportion:<10%,≥10%and<50%,≥50%and<90%,and≥90%.Clinicopathological and molecular data were compared between the groups.The correlation between SRCC proportion and pathological factors associated with indications for endoscopic resection in patients with early-stage gastric cancer(EGC)was analyzed.RESULTS A higher SRCC proportion was associated with smaller tumor size,lower tumor stage pathological tumor-nodemetastasis,and reduced rates of lymphatic,vascular,and neural invasion(P<0.001).Notably,the≥90%SRCC group exhibited the highest recurrence-free survival(P=0.0072)and overall survival(P=0.0002).In EGC,lower SRCC rates were correlated with increased ulceration,larger tumor size,and deeper submucosal invasion(P<0.001).CONCLUSION Higher SRCC proportions in the PCC correlate with lower tumor aggressiveness and improved prognosis.Its role in EGC should be validated as a factor influencing therapeutic strategies,including endoscopic submucosal dissection.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
A series of acoustic emission(AE)-integrated conventional triaxial compression tests(CTTs)were conducted to evaluate the mechanical properties of hard red sandstone.Under conventional triaxial stress states,the crack ...A series of acoustic emission(AE)-integrated conventional triaxial compression tests(CTTs)were conducted to evaluate the mechanical properties of hard red sandstone.Under conventional triaxial stress states,the crack closure stress,crack initiation stress,and damage stress ranged in 13.75%-22.34%,31.84%-42.19%,and 63.85%-75.93%of the peak strength of sandstone,respectively.The AE parameters reflected the confining pressure(σ3)effect on microcrack propagation,withσ3=5 MPa identified as the threshold affecting both the timing of numerous AE hits and the distribution range of peak frequencies of AE signals before the final failure of each specimen.The AE property analysis showed that shear cracks played a dominant role in rock failure in CCTs,which ranged in 60%-85%of the total number of cracks.A smallerσ3 value promoted shear failure,whereas a largerσ3 value inhibited it.Furthermore,the appropriate dataset selection range to accurately calculate the cohesion force and internal friction angle in CTTs and variable-angle shear tests was determined.展开更多
The development of geological lamination in shale reservoirs influences fracture propagation during hydraulic stimulation,and the fracture generation mechanism as it propagates through the laminated interface is close...The development of geological lamination in shale reservoirs influences fracture propagation during hydraulic stimulation,and the fracture generation mechanism as it propagates through the laminated interface is closely related to fracturing effects.In this paper,the laminated shale was selected to conduct three-point bending experiments using digital image correlation(DIC)and acoustic emission(AE)techniques,which revealed that the propagation path of cross-layer fractures exhibits dislocation features.The cohesive fracture mechanism of cross-layer fractures is investigated from the viewpoint of the fracture process zone(FPZ),which displays the characteristics of intermittence and dislocation during fracture development.A computational criterion for predicting the dislocation of cross-layer fracture at the interface is proposed,which shows that the maximum dislocation range does not exceed 72%of the FPZ length.Considering the mechanical differences between adjacent layers of laminated shale,the cohesive zone model of cross-layer fracture is discussed,from which the constitutive relationship and fracture energy during FPZ development are characterized,and the discontinuous nature of the constitutive relationship is found.This study improves the understanding of the geometry and cohesive fracture mechanism of the cross-layer fracture and provides valuable insights for field fracturing in shale reservoirs.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(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 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.
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.
文摘This paper investigates the mechanisms of rock failure related to axial splitting and shear failure due to hoop stresses in cylindrical specimens.The hoop stresses are caused by normal viscous stress.The rheological dynamics theory(RDT)is used,with the mechanical parameters being determined by P-and S-wave velocities.The angle of internal friction is determined by the ratio of Young's modulus and the dynamic modulus,while dynamic viscosity defines cohesion and normal viscous stress.The effect of frequency on cohesion is considered.The initial stress state is defined by the minimum cohesion at the elastic limit when axial splitting can occur.However,as radial cracks grow,the stress state becomes oblique and moves towards the shear plane.The maximum and nonlinear cohesions are defined by the rock parameters under compressive strength when the radial crack depth reaches a critical value.The efficacy and precision of RDT are validated through the presentation of ultrasonic measurements on sandstone and rock specimens sourced from the literature.The results presented in dimensionless diagrams can be utilized in microcrack zones in the absence of lateral pressure in rock masses that have undergone disintegration due to excavation.
文摘The discourse marker ni hai bie shuo(你还别说)often appears at the beginning of a sentence,connecting to a rich variety of clause types.Its co-occurring words are mostly those expressing subjective evaluation.The subsequent discourse it connects to mainly consists of three clause types:explanatory,resultative,and adversative.The basic semantic structure of the segment in which it appears is:(S1)+ni hai bie shuo+S2.It serves seven textual functions,such as the agreement function,negation function,reminding function,and topic-shifting function.
文摘BACKGROUND Poorly cohesive gastric carcinomas are classified based on the proportion of signet-ring cell carcinoma(SRCC)components.In surgically resected gastric cancer,SRCC is diagnosed when the signet-ring cell(SRC)component constitutes≥50%of the entire tumor,whereas poorly cohesive carcinoma(PCC)not otherwise specified is diagnosed when the proportion of the SRC component is<50%of the entire tumor.The SRCC proportion in PCC varies along the spectrum,and its prognostic significance in gastric cancer remains unclear.AIM To investigate how the proportion of SRCC affects tumor pathology,clinical outcomes,and prognosis and treatment decision-making.METHODS This retrospective study included 1066 patients with PCC who underwent gastric cancer surgery at Seoul National University Bundang Hospital from 2016 to 2023.Patients were classified into four groups based on the SRCC proportion:<10%,≥10%and<50%,≥50%and<90%,and≥90%.Clinicopathological and molecular data were compared between the groups.The correlation between SRCC proportion and pathological factors associated with indications for endoscopic resection in patients with early-stage gastric cancer(EGC)was analyzed.RESULTS A higher SRCC proportion was associated with smaller tumor size,lower tumor stage pathological tumor-nodemetastasis,and reduced rates of lymphatic,vascular,and neural invasion(P<0.001).Notably,the≥90%SRCC group exhibited the highest recurrence-free survival(P=0.0072)and overall survival(P=0.0002).In EGC,lower SRCC rates were correlated with increased ulceration,larger tumor size,and deeper submucosal invasion(P<0.001).CONCLUSION Higher SRCC proportions in the PCC correlate with lower tumor aggressiveness and improved prognosis.Its role in EGC should be validated as a factor influencing therapeutic strategies,including endoscopic submucosal dissection.
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partially supported by the National Natural Science Foundation of China(No.52104112)the Science and Technology Innovation Program of Hunan Province,China(Nos.2021RC3007,2020RC3090)by the Fundamental Research Funds for the Central Universities of Central South University,China(No.2024ZZTS0060)。
文摘A series of acoustic emission(AE)-integrated conventional triaxial compression tests(CTTs)were conducted to evaluate the mechanical properties of hard red sandstone.Under conventional triaxial stress states,the crack closure stress,crack initiation stress,and damage stress ranged in 13.75%-22.34%,31.84%-42.19%,and 63.85%-75.93%of the peak strength of sandstone,respectively.The AE parameters reflected the confining pressure(σ3)effect on microcrack propagation,withσ3=5 MPa identified as the threshold affecting both the timing of numerous AE hits and the distribution range of peak frequencies of AE signals before the final failure of each specimen.The AE property analysis showed that shear cracks played a dominant role in rock failure in CCTs,which ranged in 60%-85%of the total number of cracks.A smallerσ3 value promoted shear failure,whereas a largerσ3 value inhibited it.Furthermore,the appropriate dataset selection range to accurately calculate the cohesion force and internal friction angle in CTTs and variable-angle shear tests was determined.
基金financiallysupported by the Excellent Young Fund of Sinopec Petroleum Exploration and Production Research Institute(Grant No.YK2024009)the National Natural Science Foundation of China(Grant Nos.U23B6004 and 51925405).
文摘The development of geological lamination in shale reservoirs influences fracture propagation during hydraulic stimulation,and the fracture generation mechanism as it propagates through the laminated interface is closely related to fracturing effects.In this paper,the laminated shale was selected to conduct three-point bending experiments using digital image correlation(DIC)and acoustic emission(AE)techniques,which revealed that the propagation path of cross-layer fractures exhibits dislocation features.The cohesive fracture mechanism of cross-layer fractures is investigated from the viewpoint of the fracture process zone(FPZ),which displays the characteristics of intermittence and dislocation during fracture development.A computational criterion for predicting the dislocation of cross-layer fracture at the interface is proposed,which shows that the maximum dislocation range does not exceed 72%of the FPZ length.Considering the mechanical differences between adjacent layers of laminated shale,the cohesive zone model of cross-layer fracture is discussed,from which the constitutive relationship and fracture energy during FPZ development are characterized,and the discontinuous nature of the constitutive relationship is found.This study improves the understanding of the geometry and cohesive fracture mechanism of the cross-layer fracture and provides valuable insights for field fracturing in shale reservoirs.
