To prevent and contain mine gas explosion accidents, the explosion suppression performance of potassium salt powders and their action laws in the pipe network were deeply explored. In a pipe network with parallel pipelines, branching pipelines, and angular connecting pipelines, an experimental study on the suppression of gas explosions by three potassium salt powders, namely KHCO₃, K₂C₂O₄, and KH₂PO₄, driven by N₂, was carried out. The pyrolysis characteristics of the powders were studied through thermogravimetric(TG) analysis. By combining explosion experiments, the overpressure changes were monitored. The explosion overpressure and overpressure attenuation coefficient under the action of potassium salt powder were explored. Moreover, the explosion suppression mechanism was analyzed with the assistance of the Chemkin-Pro simulation software. The results indicate that after the explosion suppression by the three powders, the superposition and attenuation process of the shock wave pressure is eliminated, and the overpressure time-history curve exhibits a "single peak value" characteristic. Among them, the KHCO₃ powder has the best suppression effect on the explosion overpressure peak value, with a decrease range of 83.2% - 88.9%. K₂C₂O₄ ranks second, and KH₂PO₄ is relatively weaker. The pressure attenuation degree in the oblique angular connecting branch pipe 4 is greater than that in other branch pipes. Both the branch pipe 4 and the turning section can leverage their own structural characteristics to enhance the overpressure attenuation effect, and they are regarded as preferred locations for installing explosive inhibitors. KHCO₃ is able to maximize the utilization of this structural characteristic to enhance the explosion suppression effect. Additionally, the shock wave overpressure attenuation coefficient K₂ of the branch pipeline section shows a situation where it is less than 1.This phenomenon is found to be exacerbated by the addition of K₂C₂O₄ and KH₂PO₄ powders. Through the analysis using the Chemkin-Pro simulation software, it is concluded that the free radical content under the KHCO₃ working condition is the lowest, and the explosion suppression effect is the best, followed by the K₂C₂O₄ working condition, and finally the KH₂PO₄ working condition.

In order to alleviate the traffic congestion induced by different rainfall intensities, a dynamic control method of variable speed limit in merging zones considering rainfall intensity heterogeneity was proposed. The impacts of capacity reduction and vehicle lane-changing probability on the traffic flow state were comprehensively considered, and the dynamic relationship between rainfall intensity heterogeneity and vehicle free-flow speed was explored. Then, a traffic flow prediction model was constructed based on the cell transmission model. Taking into account the total travel time and total turnover, the variable speed limit optimization model was constructed, considering the influence of rainfall intensity heterogeneity on the variable speed limit value solution, and the optimal variable speed limit dynamic control method was obtained by using the particle swarm algorithm. Simulation and analysis of the evolution of traffic flow under different speed limit control methods were conducted. The results show that when implementing the RVSL under light, moderate, and heavy rainfall, the objective function is reduced by 8.41%, 40.57%, and 32.91% compared with variable speed limit (VSL), and by 17.48%, 55.14% and 44.69% compared with fixed speed limit (FSL). The method can effectively reduce congestion and improve the efficiency of the highway.

In order to enhance mine safety management, a ultra-large refined three-dimensional numerical model for an oversea ultra-large-scale block caving mine was established. The spatiotemporal evolution patterns of underground cave bodies and surface rock movement throughout the mining were simulated using FLAC^3D, and the safety of surface infrastructures was evaluated according to composite surface subsidence criteria. Results demonstrate that caving morphology development exhibits discontinuous, intermittent and leapfrogging characteristics. A definitive transition threshold exists in propagation modes - vertical caving dominates prior to surface breakthrough, shifting to lateral propagation afterwards. Caving crater expansion follows bimodal evolutionary patterns: initial rapid large-scale caving due to weak superficial strata, transitioning to velocity attenuation in mid-late stages through debris infill, ultimately forming cave zones with high spatial correlation to undercut areas and location. Evaluations based on composite subsidence criteria confirm that critical surface infrastructures remain outside the subsidence limit throughout the mining. Furthermore, the "priority exceedance" characteristic of curvature parameters proves effective as an early warning indicator for surface breakthrough.

In order to investigate the influence of air pressure and ventilation speed on the flashover critical conditions of cable fires in long-narrow confined spaces under plateau environments, a functional equation between the flashover critical ceiling temperature and air pressure and ventilation speed was derived based on dimensional analysis. A cable fire model in a long-narrow confined space was established using Fire Dynamics Simulator (FDS) to study the critical flashover temperature during fire development under different air pressures (101, 90, 77, and 65 kPa) and ventilation speeds (0, 0.5, 1.0, and 1.5 m/s). The results show that the flashover critical ceiling temperature of cable fires in long-narrow confined spaces is relatively high, ranging from 720.7 to 877.3 ℃. The flashover critical ceiling temperature follows a power-law relationship with air pressure and ventilation speed, while showing a decreasing trend with increasing pressure and ventilation speed. The established model provides reasonable predictions for the flashover critical ceiling temperature of cable fires in long-narrow confined spaces under both natural ventilation and longitudinal ventilation scenarios. The model prediction results agree well with the numerical simulation results.

In order to improve the grouting efficiency and accuracy of phosphogypsum based self-produced gas expansion slurry, the change in density of phosphogypsum based self-produced gas expansion slurry with time was analyzed. Based on fluid mechanics theory and the time-varying model of slurry density, a mathematical model of the seepage diffusion pressure of the slurry during the self-produced gas expansion stage was established. Through a self-built phosphogypsum based self-produced gas expansion slurry similar model experiment system, the seepage pressure variation of phosphogypsum based self-produced gas expansion slurry in the fracture network during the self expansion stage was studied, and the mathematical model of the seepage diffusion pressure of the slurry was modified to verify the rationality of the modified mathematical model of seepage diffusion pressure. The results show that the trend of slurry density over time follows a negative exponential power characteristic. During the self expansion process, the diffusion area of the slurry increases and the increase in diffusion area of the slurry becomes smaller and smaller. The relative error between the theoretical and experimental results of the seepage pressure at the monitoring point does not exceed 10%, proving the rationality of the modified mathematical model for seepage diffusion pressure.

In order to address the issue of uneven filtration velocity distribution on the filter bag surface in a baghouse dust collector, a new design method for filter bags with non-uniform permeability was proposed. Using Fluent software and User-Defined Function (UDF), the impact of non-uniform permeability on the filtration velocity distribution across the bag surface was simulated under the design filtration velocity condition (1.0 m/min). The results indicate that the filtration velocity of uniformly permeable filter bags gradually increases along the axis of the bag from bottom to top, and the uniformity of filtration velocity distribution decreases with the increase in bag length. By optimizing the permeability of filter bags with different lengths of 5, 7 and 10 m, the maximum filtration velocity on the surface of filter bags is reduced from 1.60, 2.32 and 3.34 m/min to 1.30, 1.31 and 1.38 m/min, respectively. Moreover, the uniformity index of filtration velocity distribution on the surface of the filter bag is significantly improved, from 0.736, 0.459, 0.210 to 0.854, 0.868, 0.892, respectively.

In order to study the dynamic law and differential response of coal deformation for different gases in the whole process of adsorption-desorption, the deformation test was carried out under the conditions of adsorption-desorption of CO₂, CH₄ and N₂ in primary coal by utilizing the dynamic test platform for adsorption / desorption deformation of coal bodies. The results show that the adsorption strain of each gas changes with time in Langmuir form, and the coal bodies with the strong adsorption gases exhibit larger deformation and faster response. The body strain of different adsorbed gases in the process of desorption decreases with the increase of desorption amount in a nearly linear manner, and the desorption shrinkage of the strong adsorption gas is more significant, but the residual deformation is also larger, and the residual body strain of CO₂ is twice that of CH₄, and that of CH₄ is almost twice that of N₂. With the same desorption gas amount, the shrinkage deformation caused by CH₄ is the most obvious, and the shrinkage deformation caused by CO₂ and N₂ is about 1/3 of it. In the whole process of adsorption and desorption, the adsorption strain is anisotropic and changing constantly, and the adsorption strain in the direction perpendicular to the bedding is always larger than that parallel to the bedding. The change of anisotropy coefficient of CO₂ is the largest, that of N₂ is the next, and that of CH₄ is the smallest.

To study the influence of similar scenario knowledge transfer on the subjective probability of safety accidents of engineers under avoidance behavior, the scenario similarity variable was introduced, and a subjective probability evolution model for safety accidents among engineering personnel groups was constructed and simulated. The results show that knowledge transfer in similar scenarios accelerates the convergence of the mean subjective probability, and reduces the subjective probability differences between individuals and scenarios, but also leads to the underestimation of accident rates in high-accident-rate scenarios. There is a "high-risk" accident scenario with the largest number of fatalities, where the accident rate ranges from 0.4 to 0.8. When there is a significant mortality rate difference between two scenarios, scenario knowledge transfer reduces losses only if the low-mortality-scenario has a higher accident rate than the high-mortality one. With close mortality rates but greatly varying accident rates, incomplete knowledge transfer may cause greater losses.

To improve the safety of EP in application fields, Calcium Terephthalate(CaT), a metal-organic framework (MOF) material, was utilized synergistically with the liquid flame retardant bisphenol A bis (diphenyl phosphate) (BDP) to flame-retardant modify the EP/PPO system. The flame retardant properties were characterized using the limiting oxygen index, vertical burning test, and cone calorimeter tests. The curing kinetics and pyrolysis kinetics of the modified EP/PPO system were investigated using the Kissinger, FWO (Flynn-Wall-Ozawa), and Crane equations. The results show that when 8% BDP and 2% CaT are added to EP, the composite exhibits good flame retardant performance. 34.5% of the limiting oxygen index is reached. V-0 rating of the vertical burning test is achieved. The peak heat release rate and the total heat release are reduced by 76.6% and 51.5% respectively compared to pure EP. The incorporation of CaT is found to be beneficial for the curing reaction. The optimal curing temperature could be determined by extrapolation from non-isothermal differential scanning calorimetry curves. It is an initial stage at 100 ℃, followed by 120 ℃, and finally 170 ℃. Analysis of non-isothermal thermogravimetric analysis curves and pyrolysis kinetics demonstrates that EP/PPO system exhibits lower activation energy.

In order to address the issue of sudden changes in pressure and flow on the stability of the tethered UAV during high-rise firefighting, the water hammer effect in the vertical pipe cable during the start pump and pump stop was simulated using Bentley Hammer software. The vertical height of the pipe cable was controlled from 160 to 220 m, and the transportation flow was set from 260 to 320 L/min. The variation laws of pressure, flow and water hammer force at the locations of the pump and tethered UAV were analyzed. The results show that the water hammer phenomenon during the start pump and pump stops can be divided into the static/steady state stage, the sudden rise/drop stage, and the steady state/oscillation weakening stage. When starting the pump, the water hammer force at the ground pump end is proportional to the pipe cable height, with the maximum water hammer force increasing from 7 176.502 N to 8 413.785 N, indicating a stronger impact and a delayed response. The water hammer force of the UAV end is minimally affected by the pipe cable height. When the pump is stopped, the maximum water hammer force at the ground pump end increases with the pipe cable height, from 4 316.401 N to 7 219.388 N, increasing the risk of pipeline rupture. The reverse water hammer force at the UAV end is inversely proportional to the pipe cable height, decreasing from 10 616 N to 8 158.870 N, indicating that a lower pipe cable height is more likely to induce the UAV attitude instability. Regarding the transport flow, during pump start-up, the transport flow has a small impact on the peak water hammer force. When the pump is stopped, the peak water hammer force at the ground pump end is proportional to flow, increasing from 6 693.8 N to 7 541.606 N, increasing the risk of damage. The peak reverse water hammer force at the UAV end decreases with the increase of flow, from 9 866.063 N to 8 471.582 N. The smaller the flow rate, the more likely it is to cause damage to the tethering system.