The occurrence of disasters in deep mining engineering has been confirmed to be closely related to the external dynamic disturbances and geological discontinuities.Thus,a combined finite-element method was employed to...The occurrence of disasters in deep mining engineering has been confirmed to be closely related to the external dynamic disturbances and geological discontinuities.Thus,a combined finite-element method was employed to simulate the failure process of an underground cavern,which provided insights into the failure mechanism of deep hard rock affected by factors such as the dynamic stress-wave amplitudes,disturbance direction,and dip angles of the structural plane.The crack-propagation process,stress-field distribution,displacement,velocity of failed rock,and failure zone around the circular cavern were analyzed to identify the dynamic response and failure properties of the underground structures.The simulation results indicate that the dynamic disturbance direction had less influence on the dynamic response for the constant in situ stress state,while the failure intensity and damage range around the cavern always exhibited a monotonically increasing trend with an increase in the dynamic load.The crack distribution around the circular cavern exhibited an asymmetric pattern,possibly owing to the stress-wave reflection behavior and attenuation effect along the propagation route.Geological discontinuities significantly affected the stability of nearby caverns subjected to dynamic disturbances,during which the failure intensity exhibited the pattern of an initial increase followed by a decrease with an increase in the dip angle of the structural plane.Additionally,the dynamic disturbance direction led to variations in the crack distribution for specific structural planes and stress states.These results indicate that the failure behavior should be the integrated response of the excavation unloading effect,geological conditions,and external dynamic disturbances.展开更多
Higher-order exceptional points(EPs), which appear as multifold degeneracies in the spectra of non-Hermitian systems, are garnering extensive attention in various multidisciplinary fields. However, constructing higher...Higher-order exceptional points(EPs), which appear as multifold degeneracies in the spectra of non-Hermitian systems, are garnering extensive attention in various multidisciplinary fields. However, constructing higher-order EPs still remains a challenge due to the strict requirement of the system symmetries. Here we demonstrate that higher-order EPs can be judiciously fabricated in parity–time(PT)-symmetric staggered rhombic lattices by introducing not only on-site gain/loss but also non-Hermitian couplings. Zero-energy flatbands persist and symmetry-protected third-order EPs(EP3s) arise in these systems owing to the non-Hermitian chiral/sublattice symmetry, but distinct phase transitions and propagation dynamics occur. Specifically, the EP3 arises at the Brillouin zone(BZ) boundary in the presence of on-site gain/loss. The single-site excitations display an exponential power increase in the PT-broken phase. Meanwhile, a nearly flatband sustains when a small lattice perturbation is applied. For the lattices with non-Hermitian couplings, however, the EP3 appears at the BZ center. Quite remarkably, our analysis unveils a dynamical delocalization-localization transition for the excitation of the dispersive bands and a quartic power increase beyond the EP3. Our scheme provides a new platform toward the investigation of the higher-order EPs and can be further extended to the study of topological phase transitions or nonlinear processes associated with higher-order EPs.展开更多
Coal-related accidents are prevalent in China, often attributed to the intricate geology and challenging workingconditions of mines. This study seeks to determine the patterns of these accidents by examining the chara...Coal-related accidents are prevalent in China, often attributed to the intricate geology and challenging workingconditions of mines. This study seeks to determine the patterns of these accidents by examining the characteristicsof an accidents database, considering regional, temporal, mining method, and classification distribution characteristics. The analysis centers on all significant coal accidents (involving three or more fatalities) that occurredin China from 2017 to 2022, as documented in China’s (excluding Hong Kong, Macao, and Taiwan) national coalmining safety accident report. Over the most recent six years, roof falls and gas explosions have emerged as themost common types of accident. Case studies were conducted to comprehensively investigate the histories andunderlying causes of these incidents. Countermeasures are proposed from three perspectives: prospective measures, optimization strategies, and enterprise management.展开更多
Atom interferometer has been proven to be a powerful tool for precision metrology. Here we propose a cavity-aided nonlinear atom interferometer, based on the quasi-periodic spin mixing dynamics of an atomic spin-1 Bos...Atom interferometer has been proven to be a powerful tool for precision metrology. Here we propose a cavity-aided nonlinear atom interferometer, based on the quasi-periodic spin mixing dynamics of an atomic spin-1 Bose−Einstein condensate trapped in an optical cavity. We unravel that the phase sensitivity can be greatly enhanced with the cavity-mediated nonlinear interaction. The influence of encoding phase, splitting time and recombining time on phase sensitivity are carefully studied. In addition, we demonstrate a dynamical phase transition in the system. Around the criticality, a small cavity light field variation can arouse a strong response of the atomic condensate, which can serve as a new resource for enhanced sensing. This work provides a robust protocol for cavity-enhanced metrology.展开更多
基金The authors would like to acknowledge the financial supports from the National Natural Science Foundation of China(Grant Nos.52004143,51774194)the Open fund for State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines,the China Postdoctoral Science Foundation(No.2020M670781)the NSFC-Shandong Joint fund(Grant No.U1806208).
文摘The occurrence of disasters in deep mining engineering has been confirmed to be closely related to the external dynamic disturbances and geological discontinuities.Thus,a combined finite-element method was employed to simulate the failure process of an underground cavern,which provided insights into the failure mechanism of deep hard rock affected by factors such as the dynamic stress-wave amplitudes,disturbance direction,and dip angles of the structural plane.The crack-propagation process,stress-field distribution,displacement,velocity of failed rock,and failure zone around the circular cavern were analyzed to identify the dynamic response and failure properties of the underground structures.The simulation results indicate that the dynamic disturbance direction had less influence on the dynamic response for the constant in situ stress state,while the failure intensity and damage range around the cavern always exhibited a monotonically increasing trend with an increase in the dynamic load.The crack distribution around the circular cavern exhibited an asymmetric pattern,possibly owing to the stress-wave reflection behavior and attenuation effect along the propagation route.Geological discontinuities significantly affected the stability of nearby caverns subjected to dynamic disturbances,during which the failure intensity exhibited the pattern of an initial increase followed by a decrease with an increase in the dip angle of the structural plane.Additionally,the dynamic disturbance direction led to variations in the crack distribution for specific structural planes and stress states.These results indicate that the failure behavior should be the integrated response of the excavation unloading effect,geological conditions,and external dynamic disturbances.
基金National Key Research and Development Program of China(2021YFA0718300,2021YFA1400243,2021YFA1400900)National Natural Science Foundation of China(11922408,12074105,12074106,12134006,12234012,12247146,61835013)111 Project(B07013)
文摘Higher-order exceptional points(EPs), which appear as multifold degeneracies in the spectra of non-Hermitian systems, are garnering extensive attention in various multidisciplinary fields. However, constructing higher-order EPs still remains a challenge due to the strict requirement of the system symmetries. Here we demonstrate that higher-order EPs can be judiciously fabricated in parity–time(PT)-symmetric staggered rhombic lattices by introducing not only on-site gain/loss but also non-Hermitian couplings. Zero-energy flatbands persist and symmetry-protected third-order EPs(EP3s) arise in these systems owing to the non-Hermitian chiral/sublattice symmetry, but distinct phase transitions and propagation dynamics occur. Specifically, the EP3 arises at the Brillouin zone(BZ) boundary in the presence of on-site gain/loss. The single-site excitations display an exponential power increase in the PT-broken phase. Meanwhile, a nearly flatband sustains when a small lattice perturbation is applied. For the lattices with non-Hermitian couplings, however, the EP3 appears at the BZ center. Quite remarkably, our analysis unveils a dynamical delocalization-localization transition for the excitation of the dispersive bands and a quartic power increase beyond the EP3. Our scheme provides a new platform toward the investigation of the higher-order EPs and can be further extended to the study of topological phase transitions or nonlinear processes associated with higher-order EPs.
基金support from the National Natural Science Foundation of China(52204142)Key Program of National Natural Science Foundation of China(52130403)+1 种基金Liaoning Provincial Central Leading Local Science and Technology Development Special Project(2023JH6/100100050)Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines(DM2023Z01).
文摘Coal-related accidents are prevalent in China, often attributed to the intricate geology and challenging workingconditions of mines. This study seeks to determine the patterns of these accidents by examining the characteristicsof an accidents database, considering regional, temporal, mining method, and classification distribution characteristics. The analysis centers on all significant coal accidents (involving three or more fatalities) that occurredin China from 2017 to 2022, as documented in China’s (excluding Hong Kong, Macao, and Taiwan) national coalmining safety accident report. Over the most recent six years, roof falls and gas explosions have emerged as themost common types of accident. Case studies were conducted to comprehensively investigate the histories andunderlying causes of these incidents. Countermeasures are proposed from three perspectives: prospective measures, optimization strategies, and enterprise management.
文摘Atom interferometer has been proven to be a powerful tool for precision metrology. Here we propose a cavity-aided nonlinear atom interferometer, based on the quasi-periodic spin mixing dynamics of an atomic spin-1 Bose−Einstein condensate trapped in an optical cavity. We unravel that the phase sensitivity can be greatly enhanced with the cavity-mediated nonlinear interaction. The influence of encoding phase, splitting time and recombining time on phase sensitivity are carefully studied. In addition, we demonstrate a dynamical phase transition in the system. Around the criticality, a small cavity light field variation can arouse a strong response of the atomic condensate, which can serve as a new resource for enhanced sensing. This work provides a robust protocol for cavity-enhanced metrology.
