The progressive failure characteristics of geomaterial are a remarkable and challenging topic in geotechnical engineering.To study the effect of salt content and temperature on the progressive failure characteristics ...The progressive failure characteristics of geomaterial are a remarkable and challenging topic in geotechnical engineering.To study the effect of salt content and temperature on the progressive failure characteristics of frozen sodium sulfate saline sandy soil,a series of uniaxial compression tests were performed by integrating digital image correlation(DIC)technology into the testing apparatus.The evolution law of the uniaxial compression strength(UCS),the failure strain,and the formation of the shear band of the frozen sodium sulfate saline sandy soil were analyzed.The test results show that within the scope of this study,with the increase of salt content,both the UCS and the shear band angle initially decrease with increasing salt content before showing an increase.In contrast,the failure strain and the width of the shear band exhibit an initial increase followed by a decrease in the samples.In addition,to investigate the brittle failure characteristics of frozen sodium sulfate saline sandy soil,two classic brittleness evaluation methods were employed to quantitatively assess the brittleness level for the soil samples.The findings suggest that the failure characteristics under all test conditions in this study belong to the transition stage between brittle and ductile,indicating that frozen sodium sulfate saline sandy soil exhibits certain brittle behavior under uniaxial compression conditions,and the brittleness index basically decreases and then increases with the rise in salt content.展开更多
To investigate the temperature susceptibility and nonlinear memory effects of artificially frozen soil creep behavior,this study conducted uniaxial step-loading creep tests under controlled temperatures ranging from-1...To investigate the temperature susceptibility and nonlinear memory effects of artificially frozen soil creep behavior,this study conducted uniaxial step-loading creep tests under controlled temperatures ranging from-10℃to-20℃.The transient creep characteristics and steady-state creep rates of artificially frozen soils were systematically examined with respect to variations in temperature and stress.Experimental results demonstrate that decreasing temperatures lead to a decaying trend in the steady-state creep rate of silty frozen soil,confirming that low-temperature environments significantly inhibit plastic flow while enhancing material stiffness.Based on fractional calculus theory,a fractional derivative creep model was established.By incorporating temperature dependencies,the model was further improved to account for both stress and temperature effects.The model predictions align closely with experimental data,achieving over 91%agreement(standard deviation±1.8%),and effectively capture the stress-strain behavior of artificially frozen soil under varying thermal conditions.This research provides a reliable theoretical foundation for studying deformation characteristics in cold-regions engineering.展开更多
In order to explore the mechanical properties and microstructure changes of frozen saline silty clay in the Hexi region of Gansu Province,triaxial compression tests and scanning electron microscopy(SEM)analysis experi...In order to explore the mechanical properties and microstructure changes of frozen saline silty clay in the Hexi region of Gansu Province,triaxial compression tests and scanning electron microscopy(SEM)analysis experiment were conducted to explore the effects of moisture content,confining pressure,and temperature on the stress-strain characteristics and failure modes of frozen soil,as well as the changes in the internal microstructure of the sample.The experimental results show that the strength of frozen sulfate saline soil first increases and then decreases with the increase of moisture content,and the maximum strength corresponds to a moisture content of 15%.The changes in confining pressure and strength have the same trend.The lower the temperature,the greater the strength of the sample.During the entire loading process,the specimens undergo a gradual transition from volume shrinkage to volume expansion.Due to the strain harden behavior of the stress-strain curve throughout the entire loading process,the failure mode of the specimens is plastic failure.The internal microstructure of the sample gradually transitions from point-point contact and edge-point contact before shearing to edge-surface contact and edge-edge contact after shearing,and the pore size inside the sample increases after shearing,with a loose arrangement of the particle skeleton.The above research conclusions can lay a certain theoretical foun-dation for the engineering design and construction of sulfate saline soil in cold and arid areas.展开更多
Due to the high water content in warm frozen soil,the pore water pressure and pore ice pressure generated within the sample during loading significantlyinfluencethe deformation and strength of the soil skeleton.Theref...Due to the high water content in warm frozen soil,the pore water pressure and pore ice pressure generated within the sample during loading significantlyinfluencethe deformation and strength of the soil skeleton.Therefore,it is essential to develop a constitutive model for warm frozen soil that can capture the changes in ice pressure and water pressure.This study introduces a macro-meso constitutive model based on a binary-medium framework to describe the mechanical behavior of warm frozen soil.In this model,warm frozen soil is conceptualized as consisting of bonded and frictional elements from a meso perspective.The bonded elements are modeled using a macro-meso elastic constitutive approach based on poromechanics,while the frictional elements employ a macro-meso elastoplastic approach,also grounded in poromechanics.These two elements are then linked within the binarymedium model framework.By replicating the experimental curves of warm frozen soils,the theoretical results from the proposed model show excellent agreement with experimental data.This consistency indicates that the model effectively simulates the strain softening and volumetric expansion behaviors of warm frozen soil samples under various conditions.Additionally,the constitutive model predicts changes in unfrozen water pressure,frozen temperature,unfrozen water saturation,and porosity during the loading process of warm frozen soil samples.展开更多
Frost heave and thaw settlement in cold regions pose a significant threat to engineering construction.Optical frequency domain reflectometry(OFDR)based on Rayleigh scattering can be applied to monitor ground deformati...Frost heave and thaw settlement in cold regions pose a significant threat to engineering construction.Optical frequency domain reflectometry(OFDR)based on Rayleigh scattering can be applied to monitor ground deformation in frozen soil areas,where the interface behavior of soil-embedded fiber optic sensors governs the monitoring accuracy.In this paper,a series of pullout tests were conducted on fiber optic(FO)cables embedded in the frozen soil to investigate the cable‒soil interface behavior.An experimental study was performed on interaction effects,particularly focused on the water content of unfrozen soil,freezing duration,and differential distribution of water content in frozen soil.The highresolution axial strains of FO cables were obtained using a sensing interrogator,and were used to calculate the interface shear stress.The interfacial mechanical response was analytically modeled using the ideal elasto‒plastic and softening constitutive models.Three freezing periods,correlating with the phase change process between ice and water,were analyzed.The results shows that the freezing effect can amplify the peak shear stress at the cable-soil interface by eight times.A criterion for the interface coupling states was proposed by normalizing the pullout force‒displacement information.Additionally,the applicability of existing theoretical models was discussed by comparing the results of theoretical back‒calculations with experimental measurements.This study provides new insights into the progressive interfacial failure behavior between strain sensing cable and frozen soil,which can be used to assist the interpretation of FO monitoring results of frozen soil deformation.展开更多
The warming and thawing of permafrost are the primary factors that impact the stability of embankments in cold regions.However,due to uncertainties in thermal boundaries and soil properties,the stochastic modeling of ...The warming and thawing of permafrost are the primary factors that impact the stability of embankments in cold regions.However,due to uncertainties in thermal boundaries and soil properties,the stochastic modeling of thermal regimes is challenging and computationally expensive.To address this,we propose a knowledge-integrated deep learning method for predicting the stochastic thermal regime of embankments in permafrost regions.Geotechnical knowledge is embedded in the training data through numerical modeling,while the neural network learns the mapping from the thermal boundary and soil property fields to the temperature field.The effectiveness of our method is verified in comparison with monitoring data and numerical analysis results.Experimental results show that the proposed method achieves good accuracy with small coefficient of variation.It still provides satisfactory accuracy as the coefficient of variation increases.The proposed knowledge-integrated deep learning method provides an efficient approach to predict the stochastic thermal regime of heterogeneous embankments.It can also be used in other permafrost engineering investigations that require stochastic numerical modeling.展开更多
According to the announcement of General Administration of Quality Supervision,Inspection and Quarantine of the People's Republic of China,the risk of microbial items in frozen drinks is very high,and it is diffic...According to the announcement of General Administration of Quality Supervision,Inspection and Quarantine of the People's Republic of China,the risk of microbial items in frozen drinks is very high,and it is difficult to improve.For example,a recent spot check showed that 42 kinds of frozen drinks had microbial indicators exceeding the standard.Part of the reason is that the design of the production workshop is not conducive to the rapid removal of production water,resulting in continuous moisture throughout the workshop,which provides a breeding bed for microorganisms to breed and then contaminates the product.Therefore,research is carried out from the design point of view to fundamentally reduce the moisture in the workshop and build a dry workshop for frozen drinks production,so as to effectively reduce the risk of microbial contamination of frozen drinks.展开更多
Here,a seismic-response analysis model was proposed for evaluating the nonlinear seismic response of a pile-supported bridge pier under frozen and thawed soil conditions.The effect of a seasonally frozen soil layer on...Here,a seismic-response analysis model was proposed for evaluating the nonlinear seismic response of a pile-supported bridge pier under frozen and thawed soil conditions.The effect of a seasonally frozen soil layer on the seismic vulnerability of a pile-supported bridge pier was evaluated based on reliability theory.Although the frozen soil layer inhibited the seismic response of the ground surface to a certain extent,it exacerbated the acceleration response at the bridge pier top owing to the low radiation damping effect of the frozen soil layer.Furthermore,the frozen soil layer reduced the lateral displacement of the bridge pier top relative to the ground surface by approximately 80%,thereby preventing damage caused by earthquakes,such as falling girders.Compared to the thawed state of the ground surface,the bending moment of the bridge pier in frozen ground increases.However,the bending moment of the pile foundation in frozen ground decreases,thereby lessening the seismic vulnerability of the bridge pile foundation.The results of this can provide a reference for the seismic response analysis and seismic risk assessment of pile-supported bridges in seasonally frozen regions.展开更多
The potential of high-intensity lasers to influence nuclear decay processes has attracted considerable interest.This study quantitatively evaluated the effects of high-intensity lasers on α decay and cluster radioact...The potential of high-intensity lasers to influence nuclear decay processes has attracted considerable interest.This study quantitatively evaluated the effects of high-intensity lasers on α decay and cluster radioactivity.Our calculations revealed that,among the parent nuclei investigated,^(144)Nd is the most susceptible to laser-induced alterations,primarily because of its relatively low decay energy.Additionally,circularly polarized lasers exhibit a greater impact on decay modifications than linearly polarized lasers.Given the limited time resolution of current detectors,it is essential to account for the timeaveraging effect of the laser.By incorporating the effects of circular polarization,time averaging,and angular averaging,our theoretical predictions indicated that the modification of^(144)Nd decay could reach 0.1%at an intensity of 10^(27)W/cm^(2).However,this intensity significantly exceeds the current laser capability of 10^(23)W/cm^(2),and the predicted modification of 0.1%remains below the detection threshold of contemporary measurement techniques.Observing laser-assistedαdecay and^(14)C cluster radioactivity will likely remain unfeasible until both ultrahigh laser intensities and significant advancements in experimental resolution are achieved.展开更多
Objective:This study aims to develop a deep multiscale image learning system(DMILS)to differentiate malignant from benign thyroid follicular neoplasms on multiscale whole-slide images(WSIs)of intraoperative frozen pat...Objective:This study aims to develop a deep multiscale image learning system(DMILS)to differentiate malignant from benign thyroid follicular neoplasms on multiscale whole-slide images(WSIs)of intraoperative frozen pathological images.Methods:A total of 1,213 patients were divided into training and validation sets,an internal test set,a pooled external test set,and a pooled prospective test set at three centers.DMILS was constructed using a deep learningbased weakly supervised method based on multiscale WSIs at 10×,20×,and 40×magnifications.The performance of the DMILS was compared with that of a single magnification and validated in two pathologist-unidentified subsets.Results:The DMILS yielded good performance,with areas under the receiver operating characteristic curves(AUCs)of 0.848,0.857,0.810,and 0.787 in the training and validation sets,internal test set,pooled external test set,and pooled prospective test set,respectively.The AUC of the DMILS was higher than that of a single magnification,with 0.788 of 10×,0.824 of 20×,and 0.775 of 40×in the internal test set.Moreover,DMILS yielded satisfactory performance on the two pathologist-unidentified subsets.Furthermore,the most indicative region predicted by DMILS is the follicular epithelium.Conclusions:DMILS has good performance in differentiating thyroid follicular neoplasms on multiscale WSIs of intraoperative frozen pathological images.展开更多
The freeze-thaw cycles of frozen soil could significantly affect its thermo-hydro-mechanical-chemical(THMC)properties,causing the frost heaving and thawing settlement.The microscale essence is the water-ice phase tran...The freeze-thaw cycles of frozen soil could significantly affect its thermo-hydro-mechanical-chemical(THMC)properties,causing the frost heaving and thawing settlement.The microscale essence is the water-ice phase transition,but the microscale details are still poorly understood,especially at ultra-low temperatures.Nuclear magnetic resonance(NMR)technology and molecular dynamics(MD)simulation method were performed to explore the freeze-thaw behaviors of montmorillonite clay under temperature of 210e293 K.Then,the water-ice phase transition,freeze-thaw hysteresis,ice nucleation mechanism,and surface effect of clay at an atomistic level were discussed.A classification method of different types of unfrozen water through NMR experiment was proposed,including bulk,capillary,and bound water.Here,it is found that:(1)the freeze-thaw process of frozen soil at the macroscale was essentially the occurrence of ice-water phase transition at the microscale.(2)The freeze-thaw hysteresis was caused by different growth and melting rates of ice crystals,where the ice growth/nucleation on clay surface(i.e.freeze process)was more difficult to develop.(3)The surface effect of clay was essential for the ice nucleation and the existence of bound water.For example,little unfrozen water still existed in unfrozen soil even at 213 K.(4)For unsaturated frozen soil,the quasi-liquid water was an essential component of unfrozen water that cannot be ignored.This work could provide an atomistic insight to unravel the atomistic origin of the freeze-thaw mechanism of montmorillonite clay and complement relevant experimental evidence.展开更多
The artificial ground-freezing method is the main technical means for the excavation of mines and tunnels through the water-rich sand layer,and the comprehensive understanding of the mechanical properties of frozen sa...The artificial ground-freezing method is the main technical means for the excavation of mines and tunnels through the water-rich sand layer,and the comprehensive understanding of the mechanical properties of frozen saturated sand and the stress-strain relationship under complex stress can provide important guidance.In this study,a series of true triaxial tests of frozen saturated sand samples were conducted.Combined with the test data,the effects of temperature and medium principal stress ratio(b)on the strength and deformation characteristics of frozen saturated sand are discussed.In addition,a cohesion tensor is introduced to the Wu-Lin hypoplastic model.A scalar value is used to characterize the effect of temperature on the strength of frozen soil.The defect that the original model cannot describe the tensile capacity of frozen soil under low stress conditions is clearly solved.In addition,the cumulative deformation state variable is introduced to improve the response performance of the model in triaxial compression tests.The hypoplastic model of frozen soil has shown good performance in simulating triaxial compression tests at different temperatures and medium principal stress ratios.展开更多
The pile-plate structure has proven highly effective support for high-speed railway subgrades,particularly in poor geological conditions.Although its efficacy in non-frozen regions is well-established,its potential in...The pile-plate structure has proven highly effective support for high-speed railway subgrades,particularly in poor geological conditions.Although its efficacy in non-frozen regions is well-established,its potential in frozen regions remains underexplored.In seasonally frozen areas,F-T(freeze-thaw)cycles threaten subgrade stability,necessitating research on pile-plate structure’s behavior under such conditions.To address this challenge,a scaled model experiment was conducted on a silty sand foundation,simulating F-T cycles using temperature control devices.Key parameters,including soil temperature,frozen depth,and displacement,were systematically monitored.Results indicate that the bearing plate functions as an effective insulation layer,significantly reducing sub-zero temperature penetration.Additionally,the anchoring action of the piles mitigates frost heave in the foundation soil,while the plate middle restrains soil deformation more effectively due to increased constraint.The thermal insulation provided by the plate maintains higher soil temperatures,delaying the onset of freezing.By the end of each freezing stage,the vertical displacement in the natural subgrade is approximately 4 times greater than that beneath the pile-plate structure.Furthermore,the frost depth is about 1.3-1.4 times and 1.6-4.9 times greater than that measured below the plate edge and middle,respectively.These insights contribute to the development of more resilient designs for high-speed railway subgrades in seasonally frozen regions,offering engineers a robust,scientifically-backed foundation for future infrastructure projects.展开更多
Due to the presence of ice and unfrozen water in pores of frozen rock,the rock fracture behaviors are susceptible to temperature.In this study,the potential thawing-induced softening effects on the fracture behaviors ...Due to the presence of ice and unfrozen water in pores of frozen rock,the rock fracture behaviors are susceptible to temperature.In this study,the potential thawing-induced softening effects on the fracture behaviors of frozen rock is evaluated by testing the tension fracture toughness(KIC)of frozen rock at different temperatures(i.e.-20℃,-15℃,-12℃,-10℃,-8℃,-6℃,-4℃,-2℃,and 0℃).Acoustic emission(AE)and digital image correlation(DIC)methods are utilized to analyze the microcrack propagation during fracturing.The melting of pore ice is measured using nuclear magnetic resonance(NMR)method.The results indicate that:(1)The KIC of frozen rock decreases moderately between-20℃ and-4℃,and rapidly between-4℃ and 0℃.(2)At-20℃ to-4℃,the fracturing process,deduced from the DIC results at the notch tip,exhibits three stages:elastic deformation,microcrack propagation and microcrack coalescence.However,at-4℃e0℃,only the latter two stages are observed.(3)At-4℃e0℃,the AE activities during fracturing are less than that at-20℃ to-4℃,while more small events are reported.(4)The NMR results demonstrate a reverse variation trend in pore ice content with increasing temperature,that is,a moderate decrease is followed by a sharp decrease and-4℃ is exactly the critical temperature.Next,we interpret the thawing-induced softening effect by linking the evolution in microscopic structure of frozen rock with its macroscopic fracture behaviors as follow:from-20℃ to-4℃,the thickening of the unfrozen water film diminishes the cementation strength between ice and rock skeleton,leading to the decrease in fracture parameters.From-4℃ to 0℃,the cementation effect of ice almost vanishes,and the filling effect of pore ice is reduced significantly,which facilitates microcrack propagation and thus the easier fracture of frozen rocks.展开更多
The soil freezing characteristic curve(SFCC)plays a fundamental role in comprehending thermohydraulic behavior and numerical simulation of frozen soil.This study proposes a dynamic model to uniformly express SFCCs ami...The soil freezing characteristic curve(SFCC)plays a fundamental role in comprehending thermohydraulic behavior and numerical simulation of frozen soil.This study proposes a dynamic model to uniformly express SFCCs amidst varying total water contents throughout the freezing-thawing process.Firstly,a general model is proposed,wherein the unfrozen water content at arbitrary temperature is determined as the lesser of the current total water content and the reference value derived from saturated SFCC.The dynamic performance of this model is verified through test data.Subsequently,in accordance with electric double layer(EDL)theory,the theoretical residual and minimum temperatures in SFCC are calculated to be-14.5℃to-20℃for clay particles and-260℃,respectively.To ensure that the SFCC curve ends at minimum temperature,a correction function is introduced into the general model.Furthermore,a simplified dynamic model is proposed and investigated,necessitating only three parameters inherited from the general model.Additionally,both general and simplified models are evaluated based on a test database and proven to fit the test data exactly across the entire temperature range.Typical recommended parameter values for various types of soils are summarized.Overall,this study provides not only a theoretical basis for most empirical equations but also proposes a new and more general equation to describe the SFCC.展开更多
The warm and ice-rich frozen soil is characterized by high unfrozen water content, low shear strength and large compressibility, which is unreliable to meet the stability requirements of engineering infrastructures an...The warm and ice-rich frozen soil is characterized by high unfrozen water content, low shear strength and large compressibility, which is unreliable to meet the stability requirements of engineering infrastructures and foundations in permafrost regions. In this study, a novel approach for stabilizing the warm and ice-rich frozen soil with sulphoaluminate cement was proposed based on chemical stabilization. The mechanical behaviors of the stabilized soil, such as strength and stress-strain relationship, were investigated through a series of triaxial compression tests conducted at -1.0℃, and the mechanism of strength variations of the stabilized soil was also explained based on scanning electron microscope test. The investigations indicated that the strength of stabilized soil to resist failure has been improved, and the linear Mohr-Coulomb criteria can accurately reflect the shear strength of stabilized soil under various applied confining pressure. The increase in both curing age and cement mixing ratio were favorable to the growth of cohesion and internal friction angle. More importantly, the strength improvement mechanism of the stabilized soil is attributed to the formation of structural skeleton and the generation of cementitious hydration products within itself. Therefore, the investigations conducted in this study provide valuable references for chemical stabilization of warm and ice-rich frozen ground, thereby providing a basis for in-situ ground improvement for reinforcing warm and ice-rich permafrost foundations by soil-cement column installation.展开更多
In view of the problem that crystalline particles cause wall vibration at a low temperature,based on two-phase flow model,computational fuid dynamics is used to conduct the numerical simulation of internal flows when ...In view of the problem that crystalline particles cause wall vibration at a low temperature,based on two-phase flow model,computational fuid dynamics is used to conduct the numerical simulation of internal flows when the valve openings are 20%,60%and 100%respectively.The molten salt fow may be changed under strict conditions and produce forced vibration of the inner parts of molten salt particle shock valve body.Euler two-phase flow model is used for different molten salt sizes to extract temporal pressure pulse information and conduct statistical data processing analysis.The influence of the molten salt crystallization of molten salt particles on the fow and pressure pulse strength is analyzed.The results show that the crystallization of molten salt has a serious impact on the vibration of the valve body,especially in the throttle rate.The valve oscillation caused by the pressure pulsation mostly occurs from the small opening rate.As the opening increases,the pressure pulse threshold and its change trend decrease.展开更多
Owing to its exceptional casting performance,substantial utilization of recycled sand,and environmen-tally sustainable characteristics,frozen sand mold casting technology has found extensive application across diverse...Owing to its exceptional casting performance,substantial utilization of recycled sand,and environmen-tally sustainable characteristics,frozen sand mold casting technology has found extensive application across diverse sectors,including aerospace,power machinery,and the automotive industry.The focus of the present study was on the development of frozen sand mold formulations tailored for efficient machin-ing,guided by the performance and cutting fracture mechanism of frozen sand molds.A regional tem-perature control device was developed for the purpose of conducting cryogenic cutting experiments on frozen sand molds with varying geometrical characteristics and molding materials.The impact of milling process parameters on the dimension accuracy of both sand molds and castings,as well as castings’surface roughness,were systematically investigated by a whole-process error flow control method.The findings indicate that precise and efficient processing of complicated sand molds was achievable by using sand particles with sizes ranging from 106 to 212μm,and water content between 4 and 5 wt.%,freezing temperature below-25℃,and cutting temperature within the range of-5 to 0℃.Through the frozen-casting of representative components,it was validated that the machining error of the frozen sand mold was within±0.25 mm.Additionally,the dimensional accuracy of the flywheel shell casting conformed to the CT8 specifications.This study provides theoretical guidance for the selection of frozen-casting sand formulations and close-loop control of process size chains for complex metal parts,as well as an overall solution for the realization of sustainable development of green casting.展开更多
Compared to the resin sand mold casting process, frozen casting is more environmentally friendly, providing a better working environment and enhanced supercooling degree. The interfacial heat transfer coefficient (IHT...Compared to the resin sand mold casting process, frozen casting is more environmentally friendly, providing a better working environment and enhanced supercooling degree. The interfacial heat transfer coefficient (IHTC) between frozen sand mold and metal is an important parameter that significantly influences the final mechanical properties and microstructure of the castings. This paper solved the inverse heat conduction problem using the finite difference method (FDM). In addition, the conjugate gradient method (CGM) was adopted to calculate the temperature distribution and heat flux in the molten metal. At the same time, the particle swarm optimization algorithm (PSO) was used in temperature distribution determination in frozen sand mold. The interfacial heat transfer coefficient (IHTC) was estimated during the solidification of ZL101. The results showed a good agreement between calculated and experimental data, obtaining accurate casting interface temperature Tm, frozen sand mold interface temperature Ts, heat flux q, and IHTC. The analysis of the IHTC variation revealed a water content value within the range of 4 wt.% to 5 wt.% resulted in IHTC in two types of interpretation, called ‘fluctuation type’ and ‘turning type’.展开更多
Quantum discord, one of the famous quantum correlations, has been recently generalized to multipartite systems by Radhakrishnan et al. Here we give analytical solutions of the quantum discord for a family of N-qubit q...Quantum discord, one of the famous quantum correlations, has been recently generalized to multipartite systems by Radhakrishnan et al. Here we give analytical solutions of the quantum discord for a family of N-qubit quantum states. For the bipartite system, we derive a zero quantum discord which will remain unchanged under the phase damping channel. For multiparitite systems, it is found that the quantum discord can be classified into three categories and the quantum discord for odd-partite systems can exhibit freezing under the phase damping channel, while the freezing does not exist in the even-partite systems.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.42372312,and 42172299)the Pyramid Talent Training Project of Beijing University of Civil Engineering and Architecture(Grant No.JDYC20220807).
文摘The progressive failure characteristics of geomaterial are a remarkable and challenging topic in geotechnical engineering.To study the effect of salt content and temperature on the progressive failure characteristics of frozen sodium sulfate saline sandy soil,a series of uniaxial compression tests were performed by integrating digital image correlation(DIC)technology into the testing apparatus.The evolution law of the uniaxial compression strength(UCS),the failure strain,and the formation of the shear band of the frozen sodium sulfate saline sandy soil were analyzed.The test results show that within the scope of this study,with the increase of salt content,both the UCS and the shear band angle initially decrease with increasing salt content before showing an increase.In contrast,the failure strain and the width of the shear band exhibit an initial increase followed by a decrease in the samples.In addition,to investigate the brittle failure characteristics of frozen sodium sulfate saline sandy soil,two classic brittleness evaluation methods were employed to quantitatively assess the brittleness level for the soil samples.The findings suggest that the failure characteristics under all test conditions in this study belong to the transition stage between brittle and ductile,indicating that frozen sodium sulfate saline sandy soil exhibits certain brittle behavior under uniaxial compression conditions,and the brittleness index basically decreases and then increases with the rise in salt content.
基金National Key Research and Development Program of China“Structural Stability Assessment Techniques and Demonstration for Masonry Ancient Pagodas”(2023YFF0906005)。
文摘To investigate the temperature susceptibility and nonlinear memory effects of artificially frozen soil creep behavior,this study conducted uniaxial step-loading creep tests under controlled temperatures ranging from-10℃to-20℃.The transient creep characteristics and steady-state creep rates of artificially frozen soils were systematically examined with respect to variations in temperature and stress.Experimental results demonstrate that decreasing temperatures lead to a decaying trend in the steady-state creep rate of silty frozen soil,confirming that low-temperature environments significantly inhibit plastic flow while enhancing material stiffness.Based on fractional calculus theory,a fractional derivative creep model was established.By incorporating temperature dependencies,the model was further improved to account for both stress and temperature effects.The model predictions align closely with experimental data,achieving over 91%agreement(standard deviation±1.8%),and effectively capture the stress-strain behavior of artificially frozen soil under varying thermal conditions.This research provides a reliable theoretical foundation for studying deformation characteristics in cold-regions engineering.
基金supported by the National Natural Science Foun-dation of China(12362032)the Key Research and Development Pro-gram of Gansu Province-Social Development(23YFFA0063).
文摘In order to explore the mechanical properties and microstructure changes of frozen saline silty clay in the Hexi region of Gansu Province,triaxial compression tests and scanning electron microscopy(SEM)analysis experiment were conducted to explore the effects of moisture content,confining pressure,and temperature on the stress-strain characteristics and failure modes of frozen soil,as well as the changes in the internal microstructure of the sample.The experimental results show that the strength of frozen sulfate saline soil first increases and then decreases with the increase of moisture content,and the maximum strength corresponds to a moisture content of 15%.The changes in confining pressure and strength have the same trend.The lower the temperature,the greater the strength of the sample.During the entire loading process,the specimens undergo a gradual transition from volume shrinkage to volume expansion.Due to the strain harden behavior of the stress-strain curve throughout the entire loading process,the failure mode of the specimens is plastic failure.The internal microstructure of the sample gradually transitions from point-point contact and edge-point contact before shearing to edge-surface contact and edge-edge contact after shearing,and the pore size inside the sample increases after shearing,with a loose arrangement of the particle skeleton.The above research conclusions can lay a certain theoretical foun-dation for the engineering design and construction of sulfate saline soil in cold and arid areas.
基金the financial support from the funding of the National Natural Science Foundation of China(NSFC)(Grant Nos.42401160 and U22A20596)the Science and Technology Plan Project of Linzhi(Grant No.SYQ2024-13).
文摘Due to the high water content in warm frozen soil,the pore water pressure and pore ice pressure generated within the sample during loading significantlyinfluencethe deformation and strength of the soil skeleton.Therefore,it is essential to develop a constitutive model for warm frozen soil that can capture the changes in ice pressure and water pressure.This study introduces a macro-meso constitutive model based on a binary-medium framework to describe the mechanical behavior of warm frozen soil.In this model,warm frozen soil is conceptualized as consisting of bonded and frictional elements from a meso perspective.The bonded elements are modeled using a macro-meso elastic constitutive approach based on poromechanics,while the frictional elements employ a macro-meso elastoplastic approach,also grounded in poromechanics.These two elements are then linked within the binarymedium model framework.By replicating the experimental curves of warm frozen soils,the theoretical results from the proposed model show excellent agreement with experimental data.This consistency indicates that the model effectively simulates the strain softening and volumetric expansion behaviors of warm frozen soil samples under various conditions.Additionally,the constitutive model predicts changes in unfrozen water pressure,frozen temperature,unfrozen water saturation,and porosity during the loading process of warm frozen soil samples.
基金the National Key Research and Development Program of China(Grant No.2023YFF1303501)the National Science Fund for Distinguished Young Scholars of China(Grant No.42225702)the Open Fund of State Key Laboratory of Frozen Soil Engineering(Grant No.SKLFSE201814).
文摘Frost heave and thaw settlement in cold regions pose a significant threat to engineering construction.Optical frequency domain reflectometry(OFDR)based on Rayleigh scattering can be applied to monitor ground deformation in frozen soil areas,where the interface behavior of soil-embedded fiber optic sensors governs the monitoring accuracy.In this paper,a series of pullout tests were conducted on fiber optic(FO)cables embedded in the frozen soil to investigate the cable‒soil interface behavior.An experimental study was performed on interaction effects,particularly focused on the water content of unfrozen soil,freezing duration,and differential distribution of water content in frozen soil.The highresolution axial strains of FO cables were obtained using a sensing interrogator,and were used to calculate the interface shear stress.The interfacial mechanical response was analytically modeled using the ideal elasto‒plastic and softening constitutive models.Three freezing periods,correlating with the phase change process between ice and water,were analyzed.The results shows that the freezing effect can amplify the peak shear stress at the cable-soil interface by eight times.A criterion for the interface coupling states was proposed by normalizing the pullout force‒displacement information.Additionally,the applicability of existing theoretical models was discussed by comparing the results of theoretical back‒calculations with experimental measurements.This study provides new insights into the progressive interfacial failure behavior between strain sensing cable and frozen soil,which can be used to assist the interpretation of FO monitoring results of frozen soil deformation.
基金funding support from the National Natural Science Foundation of China(Grant Nos.42277161,42230709).
文摘The warming and thawing of permafrost are the primary factors that impact the stability of embankments in cold regions.However,due to uncertainties in thermal boundaries and soil properties,the stochastic modeling of thermal regimes is challenging and computationally expensive.To address this,we propose a knowledge-integrated deep learning method for predicting the stochastic thermal regime of embankments in permafrost regions.Geotechnical knowledge is embedded in the training data through numerical modeling,while the neural network learns the mapping from the thermal boundary and soil property fields to the temperature field.The effectiveness of our method is verified in comparison with monitoring data and numerical analysis results.Experimental results show that the proposed method achieves good accuracy with small coefficient of variation.It still provides satisfactory accuracy as the coefficient of variation increases.The proposed knowledge-integrated deep learning method provides an efficient approach to predict the stochastic thermal regime of heterogeneous embankments.It can also be used in other permafrost engineering investigations that require stochastic numerical modeling.
文摘According to the announcement of General Administration of Quality Supervision,Inspection and Quarantine of the People's Republic of China,the risk of microbial items in frozen drinks is very high,and it is difficult to improve.For example,a recent spot check showed that 42 kinds of frozen drinks had microbial indicators exceeding the standard.Part of the reason is that the design of the production workshop is not conducive to the rapid removal of production water,resulting in continuous moisture throughout the workshop,which provides a breeding bed for microorganisms to breed and then contaminates the product.Therefore,research is carried out from the design point of view to fundamentally reduce the moisture in the workshop and build a dry workshop for frozen drinks production,so as to effectively reduce the risk of microbial contamination of frozen drinks.
基金National Natural Science Foundation of China under Grant Nos.52068045,U21A2012 and 41825015。
文摘Here,a seismic-response analysis model was proposed for evaluating the nonlinear seismic response of a pile-supported bridge pier under frozen and thawed soil conditions.The effect of a seasonally frozen soil layer on the seismic vulnerability of a pile-supported bridge pier was evaluated based on reliability theory.Although the frozen soil layer inhibited the seismic response of the ground surface to a certain extent,it exacerbated the acceleration response at the bridge pier top owing to the low radiation damping effect of the frozen soil layer.Furthermore,the frozen soil layer reduced the lateral displacement of the bridge pier top relative to the ground surface by approximately 80%,thereby preventing damage caused by earthquakes,such as falling girders.Compared to the thawed state of the ground surface,the bending moment of the bridge pier in frozen ground increases.However,the bending moment of the pile foundation in frozen ground decreases,thereby lessening the seismic vulnerability of the bridge pile foundation.The results of this can provide a reference for the seismic response analysis and seismic risk assessment of pile-supported bridges in seasonally frozen regions.
基金supported by the National Natural Science Foundation of China(Nos.12475136 and 12075327)。
文摘The potential of high-intensity lasers to influence nuclear decay processes has attracted considerable interest.This study quantitatively evaluated the effects of high-intensity lasers on α decay and cluster radioactivity.Our calculations revealed that,among the parent nuclei investigated,^(144)Nd is the most susceptible to laser-induced alterations,primarily because of its relatively low decay energy.Additionally,circularly polarized lasers exhibit a greater impact on decay modifications than linearly polarized lasers.Given the limited time resolution of current detectors,it is essential to account for the timeaveraging effect of the laser.By incorporating the effects of circular polarization,time averaging,and angular averaging,our theoretical predictions indicated that the modification of^(144)Nd decay could reach 0.1%at an intensity of 10^(27)W/cm^(2).However,this intensity significantly exceeds the current laser capability of 10^(23)W/cm^(2),and the predicted modification of 0.1%remains below the detection threshold of contemporary measurement techniques.Observing laser-assistedαdecay and^(14)C cluster radioactivity will likely remain unfeasible until both ultrahigh laser intensities and significant advancements in experimental resolution are achieved.
基金supported by the Taishan Scholar Project(No.ts20190991,tsqn202211378)the Key R&D Project of Shandong Province(No.2022CXPT023)the General Program of National Natural Science Foundation of China(No.82371933)。
文摘Objective:This study aims to develop a deep multiscale image learning system(DMILS)to differentiate malignant from benign thyroid follicular neoplasms on multiscale whole-slide images(WSIs)of intraoperative frozen pathological images.Methods:A total of 1,213 patients were divided into training and validation sets,an internal test set,a pooled external test set,and a pooled prospective test set at three centers.DMILS was constructed using a deep learningbased weakly supervised method based on multiscale WSIs at 10×,20×,and 40×magnifications.The performance of the DMILS was compared with that of a single magnification and validated in two pathologist-unidentified subsets.Results:The DMILS yielded good performance,with areas under the receiver operating characteristic curves(AUCs)of 0.848,0.857,0.810,and 0.787 in the training and validation sets,internal test set,pooled external test set,and pooled prospective test set,respectively.The AUC of the DMILS was higher than that of a single magnification,with 0.788 of 10×,0.824 of 20×,and 0.775 of 40×in the internal test set.Moreover,DMILS yielded satisfactory performance on the two pathologist-unidentified subsets.Furthermore,the most indicative region predicted by DMILS is the follicular epithelium.Conclusions:DMILS has good performance in differentiating thyroid follicular neoplasms on multiscale WSIs of intraoperative frozen pathological images.
基金financially supported by the Open Fund of State Key Laboratory of Frozen Soil Engineering(Grant No.SKLFSE202104)the Natural Science Foundation of GuangDong Basic and Applied Basic Research Foundation(Grant No.2024A1515011853)the Research Grants Council(RGC)of Hong Kong Special Administrative Region Government(HKSARG)of China(Grant Nos.:N_PolyU534/20).
文摘The freeze-thaw cycles of frozen soil could significantly affect its thermo-hydro-mechanical-chemical(THMC)properties,causing the frost heaving and thawing settlement.The microscale essence is the water-ice phase transition,but the microscale details are still poorly understood,especially at ultra-low temperatures.Nuclear magnetic resonance(NMR)technology and molecular dynamics(MD)simulation method were performed to explore the freeze-thaw behaviors of montmorillonite clay under temperature of 210e293 K.Then,the water-ice phase transition,freeze-thaw hysteresis,ice nucleation mechanism,and surface effect of clay at an atomistic level were discussed.A classification method of different types of unfrozen water through NMR experiment was proposed,including bulk,capillary,and bound water.Here,it is found that:(1)the freeze-thaw process of frozen soil at the macroscale was essentially the occurrence of ice-water phase transition at the microscale.(2)The freeze-thaw hysteresis was caused by different growth and melting rates of ice crystals,where the ice growth/nucleation on clay surface(i.e.freeze process)was more difficult to develop.(3)The surface effect of clay was essential for the ice nucleation and the existence of bound water.For example,little unfrozen water still existed in unfrozen soil even at 213 K.(4)For unsaturated frozen soil,the quasi-liquid water was an essential component of unfrozen water that cannot be ignored.This work could provide an atomistic insight to unravel the atomistic origin of the freeze-thaw mechanism of montmorillonite clay and complement relevant experimental evidence.
基金support provided by the Open Project Foundation for Key Laboratories of Universities in Fujian Province(KF-T18014)the Scientific Research Project of Shaanxi Coalfield Geology Group Co.,Ltd.(SMDZ-2019CX-7).
文摘The artificial ground-freezing method is the main technical means for the excavation of mines and tunnels through the water-rich sand layer,and the comprehensive understanding of the mechanical properties of frozen saturated sand and the stress-strain relationship under complex stress can provide important guidance.In this study,a series of true triaxial tests of frozen saturated sand samples were conducted.Combined with the test data,the effects of temperature and medium principal stress ratio(b)on the strength and deformation characteristics of frozen saturated sand are discussed.In addition,a cohesion tensor is introduced to the Wu-Lin hypoplastic model.A scalar value is used to characterize the effect of temperature on the strength of frozen soil.The defect that the original model cannot describe the tensile capacity of frozen soil under low stress conditions is clearly solved.In addition,the cumulative deformation state variable is introduced to improve the response performance of the model in triaxial compression tests.The hypoplastic model of frozen soil has shown good performance in simulating triaxial compression tests at different temperatures and medium principal stress ratios.
基金The authors express their gratitude to the financial support from National Key R&D Program of China(No.2023YFB2604001)National Natural Science Foundation of China(No.52478475,No.52378463 and No.52168066).
文摘The pile-plate structure has proven highly effective support for high-speed railway subgrades,particularly in poor geological conditions.Although its efficacy in non-frozen regions is well-established,its potential in frozen regions remains underexplored.In seasonally frozen areas,F-T(freeze-thaw)cycles threaten subgrade stability,necessitating research on pile-plate structure’s behavior under such conditions.To address this challenge,a scaled model experiment was conducted on a silty sand foundation,simulating F-T cycles using temperature control devices.Key parameters,including soil temperature,frozen depth,and displacement,were systematically monitored.Results indicate that the bearing plate functions as an effective insulation layer,significantly reducing sub-zero temperature penetration.Additionally,the anchoring action of the piles mitigates frost heave in the foundation soil,while the plate middle restrains soil deformation more effectively due to increased constraint.The thermal insulation provided by the plate maintains higher soil temperatures,delaying the onset of freezing.By the end of each freezing stage,the vertical displacement in the natural subgrade is approximately 4 times greater than that beneath the pile-plate structure.Furthermore,the frost depth is about 1.3-1.4 times and 1.6-4.9 times greater than that measured below the plate edge and middle,respectively.These insights contribute to the development of more resilient designs for high-speed railway subgrades in seasonally frozen regions,offering engineers a robust,scientifically-backed foundation for future infrastructure projects.
基金We acknowledge the funding support from the National Natural Science Foundation of China(Grant No.42271148).
文摘Due to the presence of ice and unfrozen water in pores of frozen rock,the rock fracture behaviors are susceptible to temperature.In this study,the potential thawing-induced softening effects on the fracture behaviors of frozen rock is evaluated by testing the tension fracture toughness(KIC)of frozen rock at different temperatures(i.e.-20℃,-15℃,-12℃,-10℃,-8℃,-6℃,-4℃,-2℃,and 0℃).Acoustic emission(AE)and digital image correlation(DIC)methods are utilized to analyze the microcrack propagation during fracturing.The melting of pore ice is measured using nuclear magnetic resonance(NMR)method.The results indicate that:(1)The KIC of frozen rock decreases moderately between-20℃ and-4℃,and rapidly between-4℃ and 0℃.(2)At-20℃ to-4℃,the fracturing process,deduced from the DIC results at the notch tip,exhibits three stages:elastic deformation,microcrack propagation and microcrack coalescence.However,at-4℃e0℃,only the latter two stages are observed.(3)At-4℃e0℃,the AE activities during fracturing are less than that at-20℃ to-4℃,while more small events are reported.(4)The NMR results demonstrate a reverse variation trend in pore ice content with increasing temperature,that is,a moderate decrease is followed by a sharp decrease and-4℃ is exactly the critical temperature.Next,we interpret the thawing-induced softening effect by linking the evolution in microscopic structure of frozen rock with its macroscopic fracture behaviors as follow:from-20℃ to-4℃,the thickening of the unfrozen water film diminishes the cementation strength between ice and rock skeleton,leading to the decrease in fracture parameters.From-4℃ to 0℃,the cementation effect of ice almost vanishes,and the filling effect of pore ice is reduced significantly,which facilitates microcrack propagation and thus the easier fracture of frozen rocks.
基金supported by the National Natural Science Foundation of China(Grant No.51979002)the Fundamental Research Funds for the Central Universities(Grant No.2022YJS080).
文摘The soil freezing characteristic curve(SFCC)plays a fundamental role in comprehending thermohydraulic behavior and numerical simulation of frozen soil.This study proposes a dynamic model to uniformly express SFCCs amidst varying total water contents throughout the freezing-thawing process.Firstly,a general model is proposed,wherein the unfrozen water content at arbitrary temperature is determined as the lesser of the current total water content and the reference value derived from saturated SFCC.The dynamic performance of this model is verified through test data.Subsequently,in accordance with electric double layer(EDL)theory,the theoretical residual and minimum temperatures in SFCC are calculated to be-14.5℃to-20℃for clay particles and-260℃,respectively.To ensure that the SFCC curve ends at minimum temperature,a correction function is introduced into the general model.Furthermore,a simplified dynamic model is proposed and investigated,necessitating only three parameters inherited from the general model.Additionally,both general and simplified models are evaluated based on a test database and proven to fit the test data exactly across the entire temperature range.Typical recommended parameter values for various types of soils are summarized.Overall,this study provides not only a theoretical basis for most empirical equations but also proposes a new and more general equation to describe the SFCC.
基金supported by the National Natural Science Foundation of China (No. 41471062, No. 41971085, No. 41971086)。
文摘The warm and ice-rich frozen soil is characterized by high unfrozen water content, low shear strength and large compressibility, which is unreliable to meet the stability requirements of engineering infrastructures and foundations in permafrost regions. In this study, a novel approach for stabilizing the warm and ice-rich frozen soil with sulphoaluminate cement was proposed based on chemical stabilization. The mechanical behaviors of the stabilized soil, such as strength and stress-strain relationship, were investigated through a series of triaxial compression tests conducted at -1.0℃, and the mechanism of strength variations of the stabilized soil was also explained based on scanning electron microscope test. The investigations indicated that the strength of stabilized soil to resist failure has been improved, and the linear Mohr-Coulomb criteria can accurately reflect the shear strength of stabilized soil under various applied confining pressure. The increase in both curing age and cement mixing ratio were favorable to the growth of cohesion and internal friction angle. More importantly, the strength improvement mechanism of the stabilized soil is attributed to the formation of structural skeleton and the generation of cementitious hydration products within itself. Therefore, the investigations conducted in this study provide valuable references for chemical stabilization of warm and ice-rich frozen ground, thereby providing a basis for in-situ ground improvement for reinforcing warm and ice-rich permafrost foundations by soil-cement column installation.
基金the National Natural Science Foundation of China(No.51569012)。
文摘In view of the problem that crystalline particles cause wall vibration at a low temperature,based on two-phase flow model,computational fuid dynamics is used to conduct the numerical simulation of internal flows when the valve openings are 20%,60%and 100%respectively.The molten salt fow may be changed under strict conditions and produce forced vibration of the inner parts of molten salt particle shock valve body.Euler two-phase flow model is used for different molten salt sizes to extract temporal pressure pulse information and conduct statistical data processing analysis.The influence of the molten salt crystallization of molten salt particles on the fow and pressure pulse strength is analyzed.The results show that the crystallization of molten salt has a serious impact on the vibration of the valve body,especially in the throttle rate.The valve oscillation caused by the pressure pulsation mostly occurs from the small opening rate.As the opening increases,the pressure pulse threshold and its change trend decrease.
基金supported by the National Key R&D Program of China(grant No.2021YFB3401200)the Jiangsu Provincial Basic Research Program(Natural Science Foundation)Youth Fund(grant No.BK20230885)the Special Technical Project for Equipment Pre-research(grantNo.30104040302).
文摘Owing to its exceptional casting performance,substantial utilization of recycled sand,and environmen-tally sustainable characteristics,frozen sand mold casting technology has found extensive application across diverse sectors,including aerospace,power machinery,and the automotive industry.The focus of the present study was on the development of frozen sand mold formulations tailored for efficient machin-ing,guided by the performance and cutting fracture mechanism of frozen sand molds.A regional tem-perature control device was developed for the purpose of conducting cryogenic cutting experiments on frozen sand molds with varying geometrical characteristics and molding materials.The impact of milling process parameters on the dimension accuracy of both sand molds and castings,as well as castings’surface roughness,were systematically investigated by a whole-process error flow control method.The findings indicate that precise and efficient processing of complicated sand molds was achievable by using sand particles with sizes ranging from 106 to 212μm,and water content between 4 and 5 wt.%,freezing temperature below-25℃,and cutting temperature within the range of-5 to 0℃.Through the frozen-casting of representative components,it was validated that the machining error of the frozen sand mold was within±0.25 mm.Additionally,the dimensional accuracy of the flywheel shell casting conformed to the CT8 specifications.This study provides theoretical guidance for the selection of frozen-casting sand formulations and close-loop control of process size chains for complex metal parts,as well as an overall solution for the realization of sustainable development of green casting.
基金supported by the National Key R&D Program of China(No.2021YFB3401200)the Jiangsu Provincial Basic Research Program(Natural Science Foundation)Youth Fund(No.BK20230885).
文摘Compared to the resin sand mold casting process, frozen casting is more environmentally friendly, providing a better working environment and enhanced supercooling degree. The interfacial heat transfer coefficient (IHTC) between frozen sand mold and metal is an important parameter that significantly influences the final mechanical properties and microstructure of the castings. This paper solved the inverse heat conduction problem using the finite difference method (FDM). In addition, the conjugate gradient method (CGM) was adopted to calculate the temperature distribution and heat flux in the molten metal. At the same time, the particle swarm optimization algorithm (PSO) was used in temperature distribution determination in frozen sand mold. The interfacial heat transfer coefficient (IHTC) was estimated during the solidification of ZL101. The results showed a good agreement between calculated and experimental data, obtaining accurate casting interface temperature Tm, frozen sand mold interface temperature Ts, heat flux q, and IHTC. The analysis of the IHTC variation revealed a water content value within the range of 4 wt.% to 5 wt.% resulted in IHTC in two types of interpretation, called ‘fluctuation type’ and ‘turning type’.
基金partially supported by the National Natural Science Foundation of China (Grant No. 11601338)。
文摘Quantum discord, one of the famous quantum correlations, has been recently generalized to multipartite systems by Radhakrishnan et al. Here we give analytical solutions of the quantum discord for a family of N-qubit quantum states. For the bipartite system, we derive a zero quantum discord which will remain unchanged under the phase damping channel. For multiparitite systems, it is found that the quantum discord can be classified into three categories and the quantum discord for odd-partite systems can exhibit freezing under the phase damping channel, while the freezing does not exist in the even-partite systems.
