The coal dynamic characteristic stress identification under dynamic load is important for guiding underground mineral mining and predicting underground dynamic disasters.In this article,the dynamic compression test of...The coal dynamic characteristic stress identification under dynamic load is important for guiding underground mineral mining and predicting underground dynamic disasters.In this article,the dynamic compression test of anthracite under five strain rates is carried out,the evolution law of three kinds of crack characteristic stress is analyzed,and a prediction model of the crack characteristic stress threshold considering the strain rate effect is established.Then,the rationality of crack characteristic stress under dynamic loading is discussed from the damage evolution standpoint,and the crack extension response mechanism during dynamic compression of anthracite is discussed.The result shows that the crack characteristic stress threshold is significantly influenced by the strain rate.The three characteristic stress thresholds are positively correlated with the strain rate,but the ratios to the crest stress gradually decrease.The increase in the strain rate strongly contributes to the crack extension behavior of anthracite.In the crack unstable extension phase,because of the increase of the strain rate,anthracite shows more energy dissipation under the same deformation in association with the stress concentration effect and the dynamic strength enhancement effect.The crack propagation rate is increased,the crack propagation path of the section is more complex,and more severe damage occurs before the dynamic failure of anthracite,which leads to even more severe damage.展开更多
Neuromorphic computing simulates the operation of biological brain function for information processing and can potentially solve the bottleneck of the Von Neumann architecture.Inspired by the real characteristics of p...Neuromorphic computing simulates the operation of biological brain function for information processing and can potentially solve the bottleneck of the Von Neumann architecture.Inspired by the real characteristics of physical memristive devices,we propose a threshold-type nonlinear voltage-controlled memristor mathematical model which is used to design a novel memristor-based crossbar array.The presented crossbar array can simulate the synaptic weight in real number field rather than only positive number field.Theoretical analysis and simulation results of a 2×2 image inversion operation validate the feasibility of the proposed crossbar array and the necessary training and inference functions.Finally,the presented crossbar array is used to construct the neural network and then applied in the handwritten digit recognition.The Mixed National Institute of Standards and Technology(MNIST)database is adopted to train this neural network and it achieves a satisfactory accuracy.展开更多
A series of acoustic emission(AE)-integrated conventional triaxial compression tests(CTTs)were conducted to evaluate the mechanical properties of hard red sandstone.Under conventional triaxial stress states,the crack ...A series of acoustic emission(AE)-integrated conventional triaxial compression tests(CTTs)were conducted to evaluate the mechanical properties of hard red sandstone.Under conventional triaxial stress states,the crack closure stress,crack initiation stress,and damage stress ranged in 13.75%-22.34%,31.84%-42.19%,and 63.85%-75.93%of the peak strength of sandstone,respectively.The AE parameters reflected the confining pressure(σ3)effect on microcrack propagation,withσ3=5 MPa identified as the threshold affecting both the timing of numerous AE hits and the distribution range of peak frequencies of AE signals before the final failure of each specimen.The AE property analysis showed that shear cracks played a dominant role in rock failure in CCTs,which ranged in 60%-85%of the total number of cracks.A smallerσ3 value promoted shear failure,whereas a largerσ3 value inhibited it.Furthermore,the appropriate dataset selection range to accurately calculate the cohesion force and internal friction angle in CTTs and variable-angle shear tests was determined.展开更多
基金National Natural Science Foundation of China,Grant/Award Numbers:12072363,12372373,51934007,52104234,52174091。
文摘The coal dynamic characteristic stress identification under dynamic load is important for guiding underground mineral mining and predicting underground dynamic disasters.In this article,the dynamic compression test of anthracite under five strain rates is carried out,the evolution law of three kinds of crack characteristic stress is analyzed,and a prediction model of the crack characteristic stress threshold considering the strain rate effect is established.Then,the rationality of crack characteristic stress under dynamic loading is discussed from the damage evolution standpoint,and the crack extension response mechanism during dynamic compression of anthracite is discussed.The result shows that the crack characteristic stress threshold is significantly influenced by the strain rate.The three characteristic stress thresholds are positively correlated with the strain rate,but the ratios to the crest stress gradually decrease.The increase in the strain rate strongly contributes to the crack extension behavior of anthracite.In the crack unstable extension phase,because of the increase of the strain rate,anthracite shows more energy dissipation under the same deformation in association with the stress concentration effect and the dynamic strength enhancement effect.The crack propagation rate is increased,the crack propagation path of the section is more complex,and more severe damage occurs before the dynamic failure of anthracite,which leads to even more severe damage.
基金supported by the National Natural Science Foundation of China(61801154,61771176)the Zhejiang Provincial Natural Science Foundation of China(LY20F010008).
文摘Neuromorphic computing simulates the operation of biological brain function for information processing and can potentially solve the bottleneck of the Von Neumann architecture.Inspired by the real characteristics of physical memristive devices,we propose a threshold-type nonlinear voltage-controlled memristor mathematical model which is used to design a novel memristor-based crossbar array.The presented crossbar array can simulate the synaptic weight in real number field rather than only positive number field.Theoretical analysis and simulation results of a 2×2 image inversion operation validate the feasibility of the proposed crossbar array and the necessary training and inference functions.Finally,the presented crossbar array is used to construct the neural network and then applied in the handwritten digit recognition.The Mixed National Institute of Standards and Technology(MNIST)database is adopted to train this neural network and it achieves a satisfactory accuracy.
基金partially supported by the National Natural Science Foundation of China(No.52104112)the Science and Technology Innovation Program of Hunan Province,China(Nos.2021RC3007,2020RC3090)by the Fundamental Research Funds for the Central Universities of Central South University,China(No.2024ZZTS0060)。
文摘A series of acoustic emission(AE)-integrated conventional triaxial compression tests(CTTs)were conducted to evaluate the mechanical properties of hard red sandstone.Under conventional triaxial stress states,the crack closure stress,crack initiation stress,and damage stress ranged in 13.75%-22.34%,31.84%-42.19%,and 63.85%-75.93%of the peak strength of sandstone,respectively.The AE parameters reflected the confining pressure(σ3)effect on microcrack propagation,withσ3=5 MPa identified as the threshold affecting both the timing of numerous AE hits and the distribution range of peak frequencies of AE signals before the final failure of each specimen.The AE property analysis showed that shear cracks played a dominant role in rock failure in CCTs,which ranged in 60%-85%of the total number of cracks.A smallerσ3 value promoted shear failure,whereas a largerσ3 value inhibited it.Furthermore,the appropriate dataset selection range to accurately calculate the cohesion force and internal friction angle in CTTs and variable-angle shear tests was determined.
