To balance stope stability with mining economy and to inform stope span design in similar engineering projects, a comprehensive investigation was conducted on the stope span and its stability, using the -200 m level of a copper mine as a case study. The Mathews stability chart method was adopted to evaluate the stope stability by calculating the rock mass stability index and hydraulic radius, thereby defining a reasonable range of stable stope spans. Based on the analysis, four stope span scenarios were designed and numerically simulated using finite difference software to study the stope responses. Comparative analyses were performed on roof displacements and the characteristics of plastic zones in the surrounding rock. The results show that as the stope span increases from 12 m to 18 m, vertical displacement of the roof increases gradually, and the volume of the plastic zone fluctuates slightly. However, when the span reaches 20 m, a significant increase in roof displacement and a sudden expansion of the plastic zone which leads to through-going failure is observed, severely compromising roof stability. An optimal stope span of 18 m is recommended for the -200 m level of the copper mine. The stope span design of mining should consider the influence of factors such as orebody occurrence conditions, safety and efficiency.

In order to clarify the influence of droop angle on suspended cable fire spread characteristics, a cable combustion test platform was constructed. The cable combustion tests with different droop angles (θ) and different cross-sectional areas (S) were carried out. The results show that the flame presents an axisymmetric conical state when the cable is arranged horizontally. When the droop angle is greater than 0°, as the combustion progresses, the flame shape transits from a multi-branched cone to an extended state along the cable direction. The flame spread behavior of cable can be divided into three stages: the advance of the pyrolysis front in stage I increases FSR, the interaction between thermal convection and thermal radiation in stage II leads to a rapid increase of FSR. Stage III thermal radiation dominates the continuous increase of FSR. The radiation heat flux generated by combustion plays a leading role in the increase of FSR. The rapid increase of radiation heat flux and the appearance of peak value are consistent with the three stages of fire spread, which can be used as a sign of the increase stage. The increase of θ and the decrease of S will promote the increase of FSR. According to the Stephen-Boltzmann law, the relationship between θ and S for the increase of FSR is proposed, and the theoretical index of the relationship is in good agreement with the experimental index.

To prevent accidents caused by miners' unsafe behaviors induced by physical fatigue and reduce the impact of physical fatigue on safe behaviors abality, a physical fatigue response test was carried out. First, forty adult male participants were equally divided into two groups, with each group induced to develop MEF and MPF respectively. Subsequently, a series of operational performance tests were conducted to measure attention level, reaction speed, judgment accuracy, and body coordination ability. Then, paired sample t-tests were employed to analyze pre- and post-fatigue behavioral data, investigating the effects of physiological fatigue on safety-related performance capabilities. Finally, evidence-based management recommendations were formulated according to the analytical results. The findings reveal that muscular endurance fatigue significantly compromise attention levels through its effects on mean pupil diameter(P<0.01), blink frequency(P<0.01), and saccadic rate(P<0.05). While muscular explosive power fatigue also demonstrates measurable influence on attentional performance as evidenced by altered pupil diameter(P<0.01), its effect magnitude is statistically inferior to that of endurance fatigue. Also, muscular explosive power fatigue reduces the body coordination ability, as both hand-eye coordination ability(P<0.05) and fine operation ability(P<0.05)have significantly declined. However, muscle explosive fatigue does have a certain improvement effect on reaction speed, with simple reaction time increasing by 0.028 s(P<0.01) and comprehensive reaction time increasing by 0.020 s(P<0.01). Physiological fatigue has no significant impact on judgment accuracy.

In order to improve the efficiency of gas extraction, numerical simulation methods were employed to analyze the characteristics of changes in gas volume fraction, gas breakthrough time, coal permeability, CH₄ extraction rate, and extraction quantity under different gas injection pressures. The results show that after flue gas injection, the volume fraction of CH₄ shows a downward trend, while the volume fractions of CO₂, N₂ and O₂ show an upward trend. The increase in injection pressure will shorten the breakthrough time of each gas in the flue gas, reduce the permeability of the coal seam and increase the gas extraction volume. At 180 days of extraction, the gas injection pressure increased from 0.5 MPa to 2.5 MPa, the coal seam permeability decreased from 8.722 7×10^-17 m² to 8.711 5×10^-17 m², and the extraction volume increased from 449.01 m³ to 715.30 m³. The gas drainage rate shows the variation characteristics of rising - falling - rising - falling. From the perspective of the influence of gas injection pressure on drainage, the gas injection pressure has a relatively small impact on the drainage in the first two stages.

To address wellbore instability caused by differences in the physical-mechanical properties of coal-rock and gangue seams, this study established a numerical model for borehole collapse in deep horizontal wells with composite coal-rock layers. The model leveraged triaxial compression test data on coal-rock and gangue mechanics, integrating composite material failure criteria with poroelastic coupling equations. This model was used to simulate how coal-gangue configurations affect peripheral collapse pressure in horizontal wells and analyze the influence of interface positioning and dip angles on collapse pressure distribution. The results show that significant differences in mineral composition ratios between coal and gangue create compromised cementation strength at interfaces, where coal samples fracture more readily due to lower strength. Disparities in physical-mechanical properties and weak interfacial bonding cause pronounced pressure discontinuity at contacts when drilling traverses varied composites. While interface position dictates coal-gangue collapse pressure differentials, dip angle variations not only modulate peak collapse pressure magnitudes but also trigger migration of extreme-value locations along the borehole wall.

In order to enhance the proficiency of general aviation pilots in walk-around inspections and ensure aviation safety, eye-tracking technology was employed to measure and analyze the completion rates and fixation behavior characteristics of pilots categorized by experience level. Based on the walk-around checklists and inspection procedures, Diamond DA-40D aircraft was divided into six Areas of Interest (AOI), including the engine, wings, fuselage, landing gear, and empennage. During the participants' walk-around inspections, the completion rates of the walk-around checks and the characteristics of fixation behavior for these six AOI were recorded by means of an eye tracker. The results show that the completion rates of inspections in five AOI, including the empennage, engine, right wing, left wing, and left landing gear, were significantly higher in the veteran group than in the novice group. With the increase in flight experience, the completion rates of general aviation pilots' walk-around inspections gradually improve. Significantly higher total fixation durations and total fixation counts were observed in the experienced group compared to the novice group across five AOI: the engine, right landing gear, right wing, left wing, and left landing gear. A significantly longer average fixation duration on the engine AOI was demonstrated by the novice group relative to the experienced group. Recommendations are provided for training to place greater emphasis on the empennage section, right wing, left wing, and left landing gear areas. Additionally, enhancement of novices' inspection capabilities regarding the engine and left landing gear areas is suggested.

In order to capture the evolving landscape of research on emergency-synergy in public health emergencies and systematically synthesize key studies and their characteristics in this domain, this study employed the scientific knowledge mapping tool CiteSpace to conduct a visual analysis of relevant literature from the past decade. Data were retrieved from core collections of China National Knowledge Infrastructure (CNKI) and Web of Science (WOS). Concurrently, existing research findings were systematically examined across five dimensions: synergistic models, mechanisms, subjects, decision-making processes, and model construction. The results indicate that research output on emergency-synergy in public health emergencies grew steadily alongside the progression of Corona Virus Disease 2019(COVID-19) pandemic, with a subsequent decline as the pandemic subsided. Overall publication volume in this field remains modest: the retrieval yielded 121 academic papers, 306 master's and doctoral theses, and 54 foreign-language documents. Research focus is predominantly concentrated in areas such as emergency management, collaboration mechanisms, and multi-stakeholder synergy. The analysis further reveals that evolutionary game theory and dynamic disease transmission theory have gained significant traction among researchers in modeling emergency-synergy. The synergistic mechanism featuring "government leadership, multi-party participation, and clear division of responsibilities" has garnered widespread recognition within the academic community. Nevertheless, challenges persist regarding the practical implementation of multi-subject emergency synergy under government leadership, warranting further in-depth investigation. It is projected that future research will advance toward theoretical refinement of emergency-synergy governance models and the diversification of synergistic subjects.

To optimize vehicle design and improve road safety, the effect of the NBLEH on pedestrians head injuries during ground contact was investigated. The impact with the ground AIS 1+ pedestrian landing injury cases was selected, and data analysis along with multicollinearity tests was conducted. The results show that as the NBLEH increases, the severity of pedestrian head injuries exhibits a corresponding upward trend. Through Logistic regression analysis, it is further revealed that for AIS 2+ head injuries in adult pedestrians can be jointly predicted by vehicle speed, age, and NBLEH. Specifically, the risk of injuries is increased with higher values of NBLEH, faster speeds, and older ages. Analysis of real accident videos demonstrates that a smaller NBLEH results in increased full-body rotation angles of pedestrians. However, once NBLEH surpasses 0.9, the rotation angle notably diminishes. The collision force transmission and the pedestrian's landing posture are altered by different values of NBLEH. Additionally, cadaver crash tests were conducted using two types of vehicles with different front-end heights to establish test conditions with different NBLEH values. The results indicate that NBLEH not only influences the timing of head contact with the ground, but also that there is an interaction between head landing posture and collision speed, further complicating head injuries. Parametric simulation studies reinforced that NBLEH significantly influences factors such as posture, angle, timing, and speed during pedestrian head-to-ground contact, thereby increasing the complexity and uncertainty of surrounding injury mechanisms. The simulation results show that both vehicle speed and NBLEH influence the pedestrian flip angle, with NBLEH values less than 1 producing larger pedestrian flip angles than values greater than 1.

In order to more accurately capture the evolutionary patterns of disaster risks and facilitate scientific risk assessment, this study innovatively integrated the dual natural and social attributes of disasters. By leveraging the outcomes from event extraction, event relationship identification, and event generalization, a method based on causal association strength was developed to mine event logic. Subsequently, an emergency event evolutionary graph was constructed for assessing chain-reaction disaster risks. Combined with a similarity matching method that incorporates the multi-dimensional attributes of disaster events, an empirical study was conducted using earthquake disasters as a case study. The results demonstrate that the proposed disaster risk assessment framework based on the event evolutionary graph can rapidly identify historical earthquake events with high similarity to the Luding earthquake case. Furthermore, by leveraging the intrinsic interconnections and evolutionary paths among risks revealed by the graph, the framework can predict secondary disasters (e.g., landslide-dammed lakes) and derivative social risks (e.g., rumor propagation).

To address the issues of an incomplete indicator system and oversimplified weight determination in current lifting machinery safety evaluation, a safety evaluation indicator system for lifting machinery was constructed based on Man, Machine, Milieu, Management(4M) factors theory and 95 lifting machinery accident investigation reports from 2019 to 2023. The BWM was employed to determine subjective weights, while an CRITIC method was introduced to determine objective weights. By applying game theory combination weighting, the subjective and objective weights were integrated to form composite weights, thereby enabling the weighting and evaluation of the established indicator system. The results reveal that human factors are the primary cause of lifting machinery accidents. During safety inspections of operators, particular attention should be paid to their safety awareness and technical proficiency. In safety inspections of lifting machinery, the effectiveness of safety protection devices and the structural integrity of key components should be emphasized. The model outputs are highly consistent with key safety indicators in the on-site inspection records, confirming the effectiveness of the proposed model in the safety evaluation of lifting machinery.