To enhance the diversity and distribution uniformity of initial population,as well as to avoid local extrema in the Chimp Optimization Algorithm(CHOA),this paper improves the CHOA based on chaos initialization and Cau...To enhance the diversity and distribution uniformity of initial population,as well as to avoid local extrema in the Chimp Optimization Algorithm(CHOA),this paper improves the CHOA based on chaos initialization and Cauchy mutation.First,Sin chaos is introduced to improve the random population initialization scheme of the CHOA,which not only guarantees the diversity of the population,but also enhances the distribution uniformity of the initial population.Next,Cauchy mutation is added to optimize the global search ability of the CHOA in the process of position(threshold)updating to avoid the CHOA falling into local optima.Finally,an improved CHOA was formed through the combination of chaos initialization and Cauchy mutation(CICMCHOA),then taking fuzzy Kapur as the objective function,this paper applied CICMCHOA to natural and medical image segmentation,and compared it with four algorithms,including the improved Satin Bowerbird optimizer(ISBO),Cuckoo Search(ICS),etc.The experimental results deriving from visual and specific indicators demonstrate that CICMCHOA delivers superior segmentation effects in image segmentation.展开更多
Based on surface air temperature and precipitation observation data and NCEP/NCAR atmospheric reanalysis data,this study evaluates the prediction of East Asian summer climate during 1959–2016 undertaken by the CESM(C...Based on surface air temperature and precipitation observation data and NCEP/NCAR atmospheric reanalysis data,this study evaluates the prediction of East Asian summer climate during 1959–2016 undertaken by the CESM(Community Earth System Model)large-ensemble initialized decadal prediction(CESM-DPLE)project.The results demonstrate that CESM-DPLE can reasonably capture the basic features of the East Asian summer climate and associated main atmospheric circulation patterns.In general,the prediction skill is quite high for surface air temperature,but less so for precipitation,on the interannual timescale.CESM-DPLE reproduces the anomalies of mid-and highlatitude atmospheric circulation and the East Asian monsoon and climate reasonably well,all of which are attributed to the teleconnection wave train driven by the Atlantic Multidecadal Oscillation(AMO).A transition into the warm phase of the AMO after the late 1990s decreased the geopotential height and enhanced the strength of the monsoon in East Asia via the teleconnection wave train during summer,leading to excessive precipitation and warming over East Asia.Altogether,CESM-DPLE is capable of predicting the summer temperature in East Asia on the interannual timescale,as well as the interdecadal variations of East Asian summer climate associated with the transition of AMO phases in the late 1990s,albeit with certain inadequacies remaining.The CESM-DPLE project provides an important resource for investigating and predicting the East Asian climate on the interannual and decadal timescales.展开更多
During the initial impoundment period of a canyon-shaped reservoir,the water body fluctuated violently regarding water level,hydrological condition,and thermal stratification.These variations may alter the structure o...During the initial impoundment period of a canyon-shaped reservoir,the water body fluctuated violently regarding water level,hydrological condition,and thermal stratification.These variations may alter the structure of phytoplankton community,resulting in algal blooms and seriously threatening the ecological security of the reservoir.It is of great significance to understand the continuous changes of phytoplankton in the initial impoundment period for the protection of reservoir water quality.Therefore,a two-year in-situ monitoring study was conducted on water quality and phytoplankton in a representative canyonshaped reservoir named Sanhekou and the interannual changes of phytoplankton community and its response to environmental changes during the initial impoundment period were discussed at taxonomic versus functional classification levels.The results showed that the total nitrogen and permanganate index levels were relatively high in the first year due to rapid water storage and heavy rainfall input,and the more stable hydrological conditions in the second year promoted the increase of algae density and the transformation of community,and the proportion of cyanobacteria increased significantly.The succession order of phytoplankton in the first year of the initial impoundment periodwas Chlorophyta-Bacillariophyta-Chlorophyta,or J/F/X1-P/MP/W1-A/X1/MP,respectively.And the succession order in the second year was Cyanobacteria/Chlorophyta-Bacillariophyta-Chlorophyta,or L_(M)/G/P-P/A/X1-X1/J/G.Water temperature,relativewater column stability,mixing depth,and pHwere crucial factors affecting phytoplankton community succession.This study revealed the interannual succession law and driving factors of phytoplankton in the initial impoundment period and provided an important reference for the operation management and ecological protection of canyon-shaped reservoirs.展开更多
The models constructed by particle flow simulation method can effectively simulate the heterogeneous substance characteristics and failure behaviors of rocks.However,existing contact models overlook the rock cracks,an...The models constructed by particle flow simulation method can effectively simulate the heterogeneous substance characteristics and failure behaviors of rocks.However,existing contact models overlook the rock cracks,and the various simulation methods that do consider cracks still exhibit certain limitations.In this paper,based on Flat-Joint model and Linear Parallel Bond model,a crack contact model considering linked substance in the crack is proposed by splitting the crack contact into two portions:linked portion and unlinked portion for calculation.The new contact model considers the influence of crack closure on the contact force-displacement law.And a better compressive tensile strength ratio(UCS/T)was obtained by limiting the failure of the contact bond to be solely controlled by the contact force and moment of the linked portion.Then,by employing the FISH Model tool within the Particle Flow Code,the contact model was constructed and verified through contact force–displacement experiments and loading-unloading tests with cracked model.Finally,the contact model was tested through simulations of rock mechanics experiments.The results indicate that the contact model can effectively simulate the axial and lateral strain laws of rocks simultaneously and has a relatively good reproduction of the bi-modularity of rocks.展开更多
The loaded rock experiences multiple stages of deformation.It starts with the formation of microcracks at low stresses(crack initiation,CI)and then transitions into unstable crack propagation(crack damage,CD)near the ...The loaded rock experiences multiple stages of deformation.It starts with the formation of microcracks at low stresses(crack initiation,CI)and then transitions into unstable crack propagation(crack damage,CD)near the ultimate strength.In this study,both the acoustic emission method(AEM)and the ultrasonic testing method(UTM)were used to examine the characteristics of AE parameters(b-value,peak frequency,frequency-band energy ratio,and fractal dimension)and ultrasonic(ULT)properties(velocity,amplitude,energy attenuation,and scattering attenuation)of bedded shale at CI,CD,and ultimate strength.The comparison involved analyzing the strain-based method(SBM),AEM,and UTM to determine the thresholds for damage stress.A fuzzy comprehensive evaluation model(FCEM)was created to describe the damage thresholds and hazard assessment.The results indicate that the optimal AE and ULT parameters for identifying CI and CD stress are ringing count,ultrasonic amplitude,energy attenuation,and scattering attenuation of the S-wave.Besides,damage thresholds were detected earlier by AE monitoring,ranging from 3 MPa to 10 MPa.CI and CD identified by UTM occurred later than SBM and AEM,and were in the range of 12 MPa.The b-value,peak frequency,energy ratio in the low-frequency band(0e62.5 kHz),correlation dimension,and sandbox dimension showed low values at the peak stress,while the energy ratio in a moderate-frequency band(187.5e281.25 kHz)and amplitude showed high values.The successful application of FCEM to laboratory testing of shales has demonstrated its ability to quantitatively identify AE/ULT precursors of seismic hazards associated with rock failure.展开更多
Aiming at mitigating the high risks associated with conventional explosive blasting,this study developed a safe directional fracturing technique,i.e.instantaneous expansion with a single fracture(IESF),using a coal-ba...Aiming at mitigating the high risks associated with conventional explosive blasting,this study developed a safe directional fracturing technique,i.e.instantaneous expansion with a single fracture(IESF),using a coal-based solid waste expanding agent.First,the mechanism of directional fracturing blasting by the IESF was analyzed,and the criterion of directional crack initiation was established.On this basis,laboratory experiments and numerical simulations were conducted to systematically evaluate the directional fracturing blasting performance of the IESF.The results indicate that the IESF presents an excellent directional fracturing effect,with average surface undulation differences ranging from 8.1 mm to 22.7 mm on the fracture surfaces.Moreover,during concrete fracturing tests,the stresses and strains in the fracturing direction are measured to be 2.16-3.71 times and 8 times larger than those in the nonfracturing direction,respectively.Finally,the IESF technique was implemented for no-pillar mining with gob-side entry retaining through roof cutting and pressure relief in an underground coal mine.The IESF technique effectively created directional cracks in the roof without causing severe roadway deformation,achieving an average cutting rate and maximum roadway deformation of 94%and 197 mm,respectively.These on-site test results verified its excellent directional rock fracturing performance.The IESF technique,which is safe,efficient,and green,has considerable application prospects in the field of rock mechanics and engineering.展开更多
Evaluation of hydromechanical shear behavior of unsaturated soils is still a challenging issue. The time and cost needed for conducting precise experimental investigation on shear behavior of unsaturated soils have en...Evaluation of hydromechanical shear behavior of unsaturated soils is still a challenging issue. The time and cost needed for conducting precise experimental investigation on shear behavior of unsaturated soils have encouraged several investigators to develop analytical, empirical, or semi-empirical models for predicting the shear behavior of unsaturated soils. However, most of the previously proposed models are for specimens subjected to the isotropic state of stress, without considering the effect of initial shear stress. In this study, a hydromechanical constitutive model is proposed for unsaturated collapsible soils during shearing, with consideration of the effect of the initial shear stress. The model implements an effective stress-based disturbed state concept (DSC) to predict the stress-strain behavior of the soil. Accordingly, material/state variables were defined for both the start of the shearing stage and the critical state of the soil. A series of laboratory tests was performed using a fully automated unsaturated triaxial device to verify the proposed model. The experimental program included 23 suction-controlled unsaturated triaxial shear tests on reconstituted specimens of Gorgan clayey loess wetted to different levels of suctions under both isotropic and anisotropic stress states. The results show excellent agreement between the prediction by the proposed model and the experimental results.展开更多
To analyze the impact of bubbles on the mechanical behavior of glasses,by controlling the refining time,we prepared three borosilicate glasses with the same composition and different porosity.By the analysis software ...To analyze the impact of bubbles on the mechanical behavior of glasses,by controlling the refining time,we prepared three borosilicate glasses with the same composition and different porosity.By the analysis software integrated within the optical microscope,the diameter and number of the bubbles on the surface of three borosilicate glasses were quantified.From the hardness and crack initiation resistance(CR),we built the relationship between the porosity and the mechanical performance of these borosilicate glasses.展开更多
The microstructural evolution of a cold-rolled and intercritical annealed medium-Mn steel(Fe-0.10C-5Mn)was investigated during uniaxial tensile testing.In-situ observations under scanning electron microscopy,transmiss...The microstructural evolution of a cold-rolled and intercritical annealed medium-Mn steel(Fe-0.10C-5Mn)was investigated during uniaxial tensile testing.In-situ observations under scanning electron microscopy,transmission electron microscopy,and X-ray diffraction analysis were conducted to characterize the progressive transformation-induced plasticity process and associated fracture initiation mechanisms.These findings were discussed with the local strain measurements via digital image correlation.The results indicated that Lüders band formation in the steel was limited to 1.5%strain,which was mainly due to the early-stage martensitic phase transformation of a very small amount of the less stable large-sized retained austenite(RA),which led to localized stress concentrations and strain hardening and further retardation of yielding.The small-sized RA exhibited high stability and progressively transformed into martensite and contributed to a stably extended Portevin-Le Chatelier effect.The volume fraction of RA gradually decreased from 26.8%to 8.2%prior to fracture.In the late deformation stage,fracture initiation primarily occurred at the austenite/martensite and ferrite/martensite interfaces and the ferrite phase.展开更多
We study the two-dimensional(2D)Cauchy problem of nonhomogeneous Boussinesq system for magnetohydrodynamics convection without heat diffusion in the whole plane.Based on delicate weighted estimates,we derive the globa...We study the two-dimensional(2D)Cauchy problem of nonhomogeneous Boussinesq system for magnetohydrodynamics convection without heat diffusion in the whole plane.Based on delicate weighted estimates,we derive the global existence and uniqueness of strong solutions.In particular,the initial data can be arbitrarily large and the initial density may contain vacuum states and even have compact support.展开更多
The hot compression curves and deformed microstructures were investigated under various hot deformation conditions in three states:hot isostatic pressing(HIP,A1),HIP+hot extrusion at 1100℃(A2),and HIP+hot extrusion a...The hot compression curves and deformed microstructures were investigated under various hot deformation conditions in three states:hot isostatic pressing(HIP,A1),HIP+hot extrusion at 1100℃(A2),and HIP+hot extrusion at 1150℃(A3).The results show that A2 sample,extruded at 1100℃ with uniform γ+γ′duplex microstructures,demonstrates excellent hot deformation behavior at both 1050 and 1100℃.The true stress-true strain curves of A2 sample maintain a hardening-softening equilibrium over a larger strain range,with post-deformation average grain size of 5μm.The as-HIPed A1 sample and 1150℃ extruded A3 sample exhibit a softening region in deformation curves at 1050℃,and the grain microstructures reflect an incomplete recrystallized state,i.e.combination of fine recrystallized grains and initial larger grains,characterized by a necklace-like microstructure.The predominant recrystallization mechanism for these samples is strain-induced boundary migration.At 1150℃ with a strain rate of 0.001 s^(-1),the influence of the initial microstructure on hot deformation behavior and resultant microstructure is relatively less pronounced,and postdeformation microstructures are fully recrystallized grains.Fine-grained microstructures are conducive to maximizing the hot deformation potential of alloy.By judiciously adjusting deformation regimes,a fine and uniform deformed microstructure can be obtained.展开更多
As a negative electrode material for lithium-ion batteries,silicon monoxide(SiO)suffers from dramatic volume changes during cycling,causing excessive stress within the electrode and resulting in electrode deformation ...As a negative electrode material for lithium-ion batteries,silicon monoxide(SiO)suffers from dramatic volume changes during cycling,causing excessive stress within the electrode and resulting in electrode deformation and fragmentation.This ultimately leads to a decrease in cell capacity.The trends of volume expansion and capacity change of the SiO/graphite(SiO/C)composite electrode during cycling were investigated via in situ expansion monitoring.First,a series of expansion test schemes were designed,and the linear relationship between negative electrode expansion and cell capacity degradation was quantitatively analyzed.Then,the effects of different initial pressures on the long-term cycling performance of the cell were evaluated.Finally,the mechanism of their effects was analyzed by scanning electron microscope.The results show that after 50 cycles,the cell capacity decreases from 2.556 mAh to 1.689 mAh,with a capacity retention ratio(CRR)of only 66.08%.A linear relationship between the capacity retention ratio and thickness expansion was found.Electrochemical measurements and scanning electron microscope images demonstrate that intense stress inhibits the lithiation of the negative electrode and that the electrode is more susceptible to irreversible damage during cycling.Overall,these results reveal the relationship between the cycling performance of SiO and the internal pressure of the electrode from a macroscopic point of view,which provides some reference for the application of SiO/C composite electrodes in lithium-ion batteries.展开更多
In December 2024,SAMR(SAC)released the Report on Standardization Achievements of the 10th Anniversary of the Belt and Road Initiative(BRI),which summarizes the fruitful results of standardization since the BRI was pro...In December 2024,SAMR(SAC)released the Report on Standardization Achievements of the 10th Anniversary of the Belt and Road Initiative(BRI),which summarizes the fruitful results of standardization since the BRI was proposed in 2013.展开更多
China and Thailand are connected by mountains and rivers.Both countries enjoy cultural proximity and a deep and enduring friendship rooted in mutual understanding.As close partners who stand by each other through thic...China and Thailand are connected by mountains and rivers.Both countries enjoy cultural proximity and a deep and enduring friendship rooted in mutual understanding.As close partners who stand by each other through thick and thin,the two countries have seen cooperation reach new heights under the framework of the Belt and Road Initiative(BRI).Bilateral ties have made significant strides across various sectors,with data highlighting increasingly close collaboration in trade,investment,tourism,and cultural exchange.China has remained Thailand’s largest trading partner for 12 consecutive years and is also Thailand’s biggest export market for agricultural products as well as its top source of foreign direct investment(FDI).Meanwhile,Thailand continues to be one of the most popular travel destinations for Chinese tourists.展开更多
Since its inception,the Belt and Road Initiative(BRI)has emerged as a global platform for international cooperation,with infrastructure connectivity at its core.Infrastructure,often referred to as the“lifeblood”of e...Since its inception,the Belt and Road Initiative(BRI)has emerged as a global platform for international cooperation,with infrastructure connectivity at its core.Infrastructure,often referred to as the“lifeblood”of economic and social development,plays a pivotal role in breaking bottlenecks,bridging regional gaps,and driving inclusive growth-particularly in developing regions where inadequate infrastructure has long hindered progress.展开更多
At a time when humanity grapples with intersecting deficits in peace,development,security and governance,civilizations stand at a crossroads.As traditional Western-led solutions falter,China’s Global Civilization Ini...At a time when humanity grapples with intersecting deficits in peace,development,security and governance,civilizations stand at a crossroads.As traditional Western-led solutions falter,China’s Global Civilization Initiative(GCI)emerges as a transformative framework,translating historical wisdom into actionable strategies.Recent forums like the 11th Nishan Forum on World Civilizations and the Global Civilizations Dialogue Ministerial Meeting underscore growing consensus on core principles:equality,mutual learning,inclusive dialogue,and collaborative response to global challenges.As Chinese President Xi Jinping pointed out in his congratulatory letter to the Global Civilizations Dialogue Ministerial Meeting,“History shows that exchanges and mutual learning among civilizations are essential for civilizations to flourish and for human progress to be made.”展开更多
As energy cooperation under the Belt and Road Initiative continues to deepen,both traditional and new energy projects require a diverse range of talents in fields such as engineering technology,management,environmenta...As energy cooperation under the Belt and Road Initiative continues to deepen,both traditional and new energy projects require a diverse range of talents in fields such as engineering technology,management,environmental protection,and finance.However,the current talent supply faces structural deficiencies,including a lack of international perspective among local talent,a shortage of interdisciplinary talents,and an inadequate framework for transnational mobility and educational cooperation,which severely constrains project implementation efficiency.展开更多
Events in the first few days of September have confirmed what was already in motion.A new rhythm in world affairs is emerging.In Tianjin,a metropolis in north China,Chinese President Xi Jinping launched the Global Gov...Events in the first few days of September have confirmed what was already in motion.A new rhythm in world affairs is emerging.In Tianjin,a metropolis in north China,Chinese President Xi Jinping launched the Global Governance Initiative(GGI)at the Shanghai Cooperation Organisation(SCO)Summit.In Beijing,China’s capital,President Xi reviewed troops during a military parade to mark the 80th Anniversary of the Victory in the Chinese People’s War of Resistance Against Japanese Aggression and the World Anti-Fascist War.展开更多
Across more than a decade of joint Belt and Road Initiative(BRI)promotion,China and Singapore have forged a robust collaboration framework that has yielded substantial results.As the international landscape grows incr...Across more than a decade of joint Belt and Road Initiative(BRI)promotion,China and Singapore have forged a robust collaboration framework that has yielded substantial results.As the international landscape grows increasingly complex,bilateral ties between the two countries continue to strengthen.Leveraging its strategic geographical location,trade connectivity,and developed financial infrastructure,Singapore continues to attract a growing number of Chinese businesses,with over 100,000 entrepreneurs from China’s Zhejiang Province now navigating these changing tides in pursuit of new growth opportunities.Since its inception,the Zhejiang(S)Entrepreneurs Association(ZJEA)has remained committed to promoting resource integration including private capital and talent.It has actively supported Zhejiang entrepreneurs seeking to expand business in Southeast Asia,while also facilitating greater investment by Singaporean companies in Zhejiang.展开更多
基金This work is supported by Natural Science Foundation of Anhui under Grant 1908085MF207,KJ2020A1215,KJ2021A1251 and 2023AH052856the Excellent Youth Talent Support Foundation of Anhui underGrant gxyqZD2021142the Quality Engineering Project of Anhui under Grant 2021jyxm1117,2021kcszsfkc307,2022xsxx158 and 2022jcbs043.
文摘To enhance the diversity and distribution uniformity of initial population,as well as to avoid local extrema in the Chimp Optimization Algorithm(CHOA),this paper improves the CHOA based on chaos initialization and Cauchy mutation.First,Sin chaos is introduced to improve the random population initialization scheme of the CHOA,which not only guarantees the diversity of the population,but also enhances the distribution uniformity of the initial population.Next,Cauchy mutation is added to optimize the global search ability of the CHOA in the process of position(threshold)updating to avoid the CHOA falling into local optima.Finally,an improved CHOA was formed through the combination of chaos initialization and Cauchy mutation(CICMCHOA),then taking fuzzy Kapur as the objective function,this paper applied CICMCHOA to natural and medical image segmentation,and compared it with four algorithms,including the improved Satin Bowerbird optimizer(ISBO),Cuckoo Search(ICS),etc.The experimental results deriving from visual and specific indicators demonstrate that CICMCHOA delivers superior segmentation effects in image segmentation.
基金Supported by the National Key Research and Development Program of China(2016YFA0600704)National Natural Science Foundation of China(41421004 and 41875104)。
文摘Based on surface air temperature and precipitation observation data and NCEP/NCAR atmospheric reanalysis data,this study evaluates the prediction of East Asian summer climate during 1959–2016 undertaken by the CESM(Community Earth System Model)large-ensemble initialized decadal prediction(CESM-DPLE)project.The results demonstrate that CESM-DPLE can reasonably capture the basic features of the East Asian summer climate and associated main atmospheric circulation patterns.In general,the prediction skill is quite high for surface air temperature,but less so for precipitation,on the interannual timescale.CESM-DPLE reproduces the anomalies of mid-and highlatitude atmospheric circulation and the East Asian monsoon and climate reasonably well,all of which are attributed to the teleconnection wave train driven by the Atlantic Multidecadal Oscillation(AMO).A transition into the warm phase of the AMO after the late 1990s decreased the geopotential height and enhanced the strength of the monsoon in East Asia via the teleconnection wave train during summer,leading to excessive precipitation and warming over East Asia.Altogether,CESM-DPLE is capable of predicting the summer temperature in East Asia on the interannual timescale,as well as the interdecadal variations of East Asian summer climate associated with the transition of AMO phases in the late 1990s,albeit with certain inadequacies remaining.The CESM-DPLE project provides an important resource for investigating and predicting the East Asian climate on the interannual and decadal timescales.
基金supported by the National Key R&D Program of China(No.2022YFC3203602)the Natural Science Foundation of China(No.52370018)+1 种基金Shaanxi Provincial Youth Innovation Team Project(No.22JP040)Shaanxi Provincial Key Scientific and Technological Innovation Team(No.2023-CX-TD-32).
文摘During the initial impoundment period of a canyon-shaped reservoir,the water body fluctuated violently regarding water level,hydrological condition,and thermal stratification.These variations may alter the structure of phytoplankton community,resulting in algal blooms and seriously threatening the ecological security of the reservoir.It is of great significance to understand the continuous changes of phytoplankton in the initial impoundment period for the protection of reservoir water quality.Therefore,a two-year in-situ monitoring study was conducted on water quality and phytoplankton in a representative canyonshaped reservoir named Sanhekou and the interannual changes of phytoplankton community and its response to environmental changes during the initial impoundment period were discussed at taxonomic versus functional classification levels.The results showed that the total nitrogen and permanganate index levels were relatively high in the first year due to rapid water storage and heavy rainfall input,and the more stable hydrological conditions in the second year promoted the increase of algae density and the transformation of community,and the proportion of cyanobacteria increased significantly.The succession order of phytoplankton in the first year of the initial impoundment periodwas Chlorophyta-Bacillariophyta-Chlorophyta,or J/F/X1-P/MP/W1-A/X1/MP,respectively.And the succession order in the second year was Cyanobacteria/Chlorophyta-Bacillariophyta-Chlorophyta,or L_(M)/G/P-P/A/X1-X1/J/G.Water temperature,relativewater column stability,mixing depth,and pHwere crucial factors affecting phytoplankton community succession.This study revealed the interannual succession law and driving factors of phytoplankton in the initial impoundment period and provided an important reference for the operation management and ecological protection of canyon-shaped reservoirs.
基金supported by the Natural Science Foundation of Heilongjiang Province(No.ZD2021E006)the National Natural Science Foundation of China(Nos.52174075 and 52074110).
文摘The models constructed by particle flow simulation method can effectively simulate the heterogeneous substance characteristics and failure behaviors of rocks.However,existing contact models overlook the rock cracks,and the various simulation methods that do consider cracks still exhibit certain limitations.In this paper,based on Flat-Joint model and Linear Parallel Bond model,a crack contact model considering linked substance in the crack is proposed by splitting the crack contact into two portions:linked portion and unlinked portion for calculation.The new contact model considers the influence of crack closure on the contact force-displacement law.And a better compressive tensile strength ratio(UCS/T)was obtained by limiting the failure of the contact bond to be solely controlled by the contact force and moment of the linked portion.Then,by employing the FISH Model tool within the Particle Flow Code,the contact model was constructed and verified through contact force–displacement experiments and loading-unloading tests with cracked model.Finally,the contact model was tested through simulations of rock mechanics experiments.The results indicate that the contact model can effectively simulate the axial and lateral strain laws of rocks simultaneously and has a relatively good reproduction of the bi-modularity of rocks.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.U20A20266 and 12302503)Scientific and technological research projects in Sichuan province(Grant No.2024NSFSC0973).
文摘The loaded rock experiences multiple stages of deformation.It starts with the formation of microcracks at low stresses(crack initiation,CI)and then transitions into unstable crack propagation(crack damage,CD)near the ultimate strength.In this study,both the acoustic emission method(AEM)and the ultrasonic testing method(UTM)were used to examine the characteristics of AE parameters(b-value,peak frequency,frequency-band energy ratio,and fractal dimension)and ultrasonic(ULT)properties(velocity,amplitude,energy attenuation,and scattering attenuation)of bedded shale at CI,CD,and ultimate strength.The comparison involved analyzing the strain-based method(SBM),AEM,and UTM to determine the thresholds for damage stress.A fuzzy comprehensive evaluation model(FCEM)was created to describe the damage thresholds and hazard assessment.The results indicate that the optimal AE and ULT parameters for identifying CI and CD stress are ringing count,ultrasonic amplitude,energy attenuation,and scattering attenuation of the S-wave.Besides,damage thresholds were detected earlier by AE monitoring,ranging from 3 MPa to 10 MPa.CI and CD identified by UTM occurred later than SBM and AEM,and were in the range of 12 MPa.The b-value,peak frequency,energy ratio in the low-frequency band(0e62.5 kHz),correlation dimension,and sandbox dimension showed low values at the peak stress,while the energy ratio in a moderate-frequency band(187.5e281.25 kHz)and amplitude showed high values.The successful application of FCEM to laboratory testing of shales has demonstrated its ability to quantitatively identify AE/ULT precursors of seismic hazards associated with rock failure.
基金supported by the National Natural Science Foundation of China(Grant No.52404155)State Key Laboratory of Mining Disaster Prevention and Control(Shandong University of Science and Technology)+1 种基金Ministry of Education(Grant No.JMDPC202402)supported by the opening project of State Key Laboratory of Explosion Science and Safety Protection(Beijing Institute of Technology).The opening project number is KFJJ24-20M.
文摘Aiming at mitigating the high risks associated with conventional explosive blasting,this study developed a safe directional fracturing technique,i.e.instantaneous expansion with a single fracture(IESF),using a coal-based solid waste expanding agent.First,the mechanism of directional fracturing blasting by the IESF was analyzed,and the criterion of directional crack initiation was established.On this basis,laboratory experiments and numerical simulations were conducted to systematically evaluate the directional fracturing blasting performance of the IESF.The results indicate that the IESF presents an excellent directional fracturing effect,with average surface undulation differences ranging from 8.1 mm to 22.7 mm on the fracture surfaces.Moreover,during concrete fracturing tests,the stresses and strains in the fracturing direction are measured to be 2.16-3.71 times and 8 times larger than those in the nonfracturing direction,respectively.Finally,the IESF technique was implemented for no-pillar mining with gob-side entry retaining through roof cutting and pressure relief in an underground coal mine.The IESF technique effectively created directional cracks in the roof without causing severe roadway deformation,achieving an average cutting rate and maximum roadway deformation of 94%and 197 mm,respectively.These on-site test results verified its excellent directional rock fracturing performance.The IESF technique,which is safe,efficient,and green,has considerable application prospects in the field of rock mechanics and engineering.
文摘Evaluation of hydromechanical shear behavior of unsaturated soils is still a challenging issue. The time and cost needed for conducting precise experimental investigation on shear behavior of unsaturated soils have encouraged several investigators to develop analytical, empirical, or semi-empirical models for predicting the shear behavior of unsaturated soils. However, most of the previously proposed models are for specimens subjected to the isotropic state of stress, without considering the effect of initial shear stress. In this study, a hydromechanical constitutive model is proposed for unsaturated collapsible soils during shearing, with consideration of the effect of the initial shear stress. The model implements an effective stress-based disturbed state concept (DSC) to predict the stress-strain behavior of the soil. Accordingly, material/state variables were defined for both the start of the shearing stage and the critical state of the soil. A series of laboratory tests was performed using a fully automated unsaturated triaxial device to verify the proposed model. The experimental program included 23 suction-controlled unsaturated triaxial shear tests on reconstituted specimens of Gorgan clayey loess wetted to different levels of suctions under both isotropic and anisotropic stress states. The results show excellent agreement between the prediction by the proposed model and the experimental results.
基金Funded by the National Natural Science Foundation of China(No.52172007)。
文摘To analyze the impact of bubbles on the mechanical behavior of glasses,by controlling the refining time,we prepared three borosilicate glasses with the same composition and different porosity.By the analysis software integrated within the optical microscope,the diameter and number of the bubbles on the surface of three borosilicate glasses were quantified.From the hardness and crack initiation resistance(CR),we built the relationship between the porosity and the mechanical performance of these borosilicate glasses.
基金supported by the National Key R&D Program of China(No.2017YFB0304402)。
文摘The microstructural evolution of a cold-rolled and intercritical annealed medium-Mn steel(Fe-0.10C-5Mn)was investigated during uniaxial tensile testing.In-situ observations under scanning electron microscopy,transmission electron microscopy,and X-ray diffraction analysis were conducted to characterize the progressive transformation-induced plasticity process and associated fracture initiation mechanisms.These findings were discussed with the local strain measurements via digital image correlation.The results indicated that Lüders band formation in the steel was limited to 1.5%strain,which was mainly due to the early-stage martensitic phase transformation of a very small amount of the less stable large-sized retained austenite(RA),which led to localized stress concentrations and strain hardening and further retardation of yielding.The small-sized RA exhibited high stability and progressively transformed into martensite and contributed to a stably extended Portevin-Le Chatelier effect.The volume fraction of RA gradually decreased from 26.8%to 8.2%prior to fracture.In the late deformation stage,fracture initiation primarily occurred at the austenite/martensite and ferrite/martensite interfaces and the ferrite phase.
文摘We study the two-dimensional(2D)Cauchy problem of nonhomogeneous Boussinesq system for magnetohydrodynamics convection without heat diffusion in the whole plane.Based on delicate weighted estimates,we derive the global existence and uniqueness of strong solutions.In particular,the initial data can be arbitrarily large and the initial density may contain vacuum states and even have compact support.
基金Shenzhen Science and Technology Program(KJZD20230923113900001)Project of Industry and Information Technology Bureau of Shenzhen Municipality(201806071403422960)。
文摘The hot compression curves and deformed microstructures were investigated under various hot deformation conditions in three states:hot isostatic pressing(HIP,A1),HIP+hot extrusion at 1100℃(A2),and HIP+hot extrusion at 1150℃(A3).The results show that A2 sample,extruded at 1100℃ with uniform γ+γ′duplex microstructures,demonstrates excellent hot deformation behavior at both 1050 and 1100℃.The true stress-true strain curves of A2 sample maintain a hardening-softening equilibrium over a larger strain range,with post-deformation average grain size of 5μm.The as-HIPed A1 sample and 1150℃ extruded A3 sample exhibit a softening region in deformation curves at 1050℃,and the grain microstructures reflect an incomplete recrystallized state,i.e.combination of fine recrystallized grains and initial larger grains,characterized by a necklace-like microstructure.The predominant recrystallization mechanism for these samples is strain-induced boundary migration.At 1150℃ with a strain rate of 0.001 s^(-1),the influence of the initial microstructure on hot deformation behavior and resultant microstructure is relatively less pronounced,and postdeformation microstructures are fully recrystallized grains.Fine-grained microstructures are conducive to maximizing the hot deformation potential of alloy.By judiciously adjusting deformation regimes,a fine and uniform deformed microstructure can be obtained.
基金supported by the Fundamental Research Funds for the Central Universities(WK2090000055)Anhui Provincial Natural Science Foundation of China(2308085QG231).
文摘As a negative electrode material for lithium-ion batteries,silicon monoxide(SiO)suffers from dramatic volume changes during cycling,causing excessive stress within the electrode and resulting in electrode deformation and fragmentation.This ultimately leads to a decrease in cell capacity.The trends of volume expansion and capacity change of the SiO/graphite(SiO/C)composite electrode during cycling were investigated via in situ expansion monitoring.First,a series of expansion test schemes were designed,and the linear relationship between negative electrode expansion and cell capacity degradation was quantitatively analyzed.Then,the effects of different initial pressures on the long-term cycling performance of the cell were evaluated.Finally,the mechanism of their effects was analyzed by scanning electron microscope.The results show that after 50 cycles,the cell capacity decreases from 2.556 mAh to 1.689 mAh,with a capacity retention ratio(CRR)of only 66.08%.A linear relationship between the capacity retention ratio and thickness expansion was found.Electrochemical measurements and scanning electron microscope images demonstrate that intense stress inhibits the lithiation of the negative electrode and that the electrode is more susceptible to irreversible damage during cycling.Overall,these results reveal the relationship between the cycling performance of SiO and the internal pressure of the electrode from a macroscopic point of view,which provides some reference for the application of SiO/C composite electrodes in lithium-ion batteries.
文摘In December 2024,SAMR(SAC)released the Report on Standardization Achievements of the 10th Anniversary of the Belt and Road Initiative(BRI),which summarizes the fruitful results of standardization since the BRI was proposed in 2013.
文摘China and Thailand are connected by mountains and rivers.Both countries enjoy cultural proximity and a deep and enduring friendship rooted in mutual understanding.As close partners who stand by each other through thick and thin,the two countries have seen cooperation reach new heights under the framework of the Belt and Road Initiative(BRI).Bilateral ties have made significant strides across various sectors,with data highlighting increasingly close collaboration in trade,investment,tourism,and cultural exchange.China has remained Thailand’s largest trading partner for 12 consecutive years and is also Thailand’s biggest export market for agricultural products as well as its top source of foreign direct investment(FDI).Meanwhile,Thailand continues to be one of the most popular travel destinations for Chinese tourists.
文摘Since its inception,the Belt and Road Initiative(BRI)has emerged as a global platform for international cooperation,with infrastructure connectivity at its core.Infrastructure,often referred to as the“lifeblood”of economic and social development,plays a pivotal role in breaking bottlenecks,bridging regional gaps,and driving inclusive growth-particularly in developing regions where inadequate infrastructure has long hindered progress.
文摘At a time when humanity grapples with intersecting deficits in peace,development,security and governance,civilizations stand at a crossroads.As traditional Western-led solutions falter,China’s Global Civilization Initiative(GCI)emerges as a transformative framework,translating historical wisdom into actionable strategies.Recent forums like the 11th Nishan Forum on World Civilizations and the Global Civilizations Dialogue Ministerial Meeting underscore growing consensus on core principles:equality,mutual learning,inclusive dialogue,and collaborative response to global challenges.As Chinese President Xi Jinping pointed out in his congratulatory letter to the Global Civilizations Dialogue Ministerial Meeting,“History shows that exchanges and mutual learning among civilizations are essential for civilizations to flourish and for human progress to be made.”
基金2024 Western Project of the National Social Science Fund,"Research on Promotion Strategies and Implementation Paths for High-Quality Energy Cooperation under the Belt and Road Initiative"(No.24XGJ002)PetroChina Southwest Oil&Gasfield Company Scientific Research Project,"Research on the Construction of Professional Technical Talent Teams in the PetroChina Southwest Oil&Gasfield Company"(No.2024D111-01-03)Chengdu soft science research project titled"Research on the Path to Achieve High-quality Clean Energy Cooperation between Chengdu and Countries along the Belt and Road"(No.2025-RK00-00088-ZF).
文摘As energy cooperation under the Belt and Road Initiative continues to deepen,both traditional and new energy projects require a diverse range of talents in fields such as engineering technology,management,environmental protection,and finance.However,the current talent supply faces structural deficiencies,including a lack of international perspective among local talent,a shortage of interdisciplinary talents,and an inadequate framework for transnational mobility and educational cooperation,which severely constrains project implementation efficiency.
文摘Events in the first few days of September have confirmed what was already in motion.A new rhythm in world affairs is emerging.In Tianjin,a metropolis in north China,Chinese President Xi Jinping launched the Global Governance Initiative(GGI)at the Shanghai Cooperation Organisation(SCO)Summit.In Beijing,China’s capital,President Xi reviewed troops during a military parade to mark the 80th Anniversary of the Victory in the Chinese People’s War of Resistance Against Japanese Aggression and the World Anti-Fascist War.
文摘Across more than a decade of joint Belt and Road Initiative(BRI)promotion,China and Singapore have forged a robust collaboration framework that has yielded substantial results.As the international landscape grows increasingly complex,bilateral ties between the two countries continue to strengthen.Leveraging its strategic geographical location,trade connectivity,and developed financial infrastructure,Singapore continues to attract a growing number of Chinese businesses,with over 100,000 entrepreneurs from China’s Zhejiang Province now navigating these changing tides in pursuit of new growth opportunities.Since its inception,the Zhejiang(S)Entrepreneurs Association(ZJEA)has remained committed to promoting resource integration including private capital and talent.It has actively supported Zhejiang entrepreneurs seeking to expand business in Southeast Asia,while also facilitating greater investment by Singaporean companies in Zhejiang.
