Molecular dynamics method is adopted to investigate the effect of different NaCl solutions concentrations on the bonding properties of the calcium silicate hydrate/γ-FeOOH(C-S-H/γ-FeOOH) interface. The effect mechanism of NaCl solution concentration is revealed from the interface ion evolution, radial distribution function, particle strength distribution, interaction energy and mechanical properties. The results show that as the concentration of NaCl solution increases, interlayer {\mathrm{Ca}}_{\mathrm{h}}^{2+} ions separate from the surface of C-S-H and diffuse to the interlayer solution, Na⁺ ions enter the C-S-H layer. {\mathrm{Ca}}_{\mathrm{h}}^{2+} ions adsorb Cl^- ions in the solution, resulting in the ion clusters of {\mathrm{Ca}}_{\mathrm{h}}^{2+} and Cl^- on the surface of C-S-H. In addition, the γ-FeOOH surface hydroxyl oscillation provides adsorption points for {{\mathrm{Na}}^{+}}^{}ions, resulting in the increase of Na⁺ ions on the γ-FeOOH surface. When the NaCl solution concentration increased, the RDF peak of Ca_h—O_s gradually decreased and the radial distribution function(RDF) peak of Ca_h—O_w, Ca_h—Cl, and Na—O_s gradually increases, consistent with the ionic strength distribution. Where, O_s is the oxygen on the silicon chain in C-S-H, and O_w is the oxygen in the interlayer solution water. {\mathrm{Ca}}_{\mathrm{h}}^{2+} ions form ionic bonds with O_w in water, leading to a reduction of Ca_h—O_s ionic bonds on the C-S-H surface. Since the strength and stability of Ca_h—O_s ionic bond are better than that of Ca_h—O_w,therefore, the C-S-H/γ-FeOOH interfacial interaction energy and peak stress both show a decreasing trend with the increase of NaCl solution concentration.

In order to solve the problems of imperfect fire risk management system and subjective and one-sided risk assessment methods of civil aviation transport aircraft, a comprehensive risk assessment method based on random forest ensemble algorithm was proposed for the analysis and evaluation of risk factor indicators. Firstly, according to the man machine environment management(MMEM) theory, the risk index system was established based on the investigation of the causes of aircraft fire accidents in the past 20 years, and then the scores of scholars and experts in related fields on the correlation between the indicators were collected, and the subjective risk index weight results were obtained by using the analytic network process(ANP) method. The causes of major aircraft fire accidents in the database in the past 20 years were counted and their prior probabilities were calculated by classification, and the Bayesian network(BN) dynamic analysis method was used for reverse reasoning to obtain the probability distribution of each risk factor. The random forest regression model was established to obtain the predicted value and importance of the characteristic index, and put forward scientific and effective suggestions for the fire risk control of the operating unit. The results show that the five indicators of missing dangerous goods in security inspection, failure to eliminate hidden dangers in time, component failure, bird strike, and high surface temperature are the most critical risk factors in aircraft fire accidents.

To achieve the integration of renewable energy utilization and CO₂ emission reduction technology, high-temperature gas field geothermal resource extraction was conducted via the CO₂ plume geothermal system, which merges the benefits of CO₂ sequestration with deep geothermal resource development, facilitating the concurrent sequestration of CO₂ during thermal extraction. Taking a high-temperature gas field as the target thermal storage, a three-dimensional thermal flow coupling model of cap rock thermal storage bedrock was constructed using COMSOL software to analyze the thermal compensation effect of the rock mass on both sides of the thermal storage and the relationship between the number of production wells and the system's thermal recovery performance. The findings indicate that during the advanced phases of the plume geothermal system's operation, when thermal compensation is considered, the fluid's temperature decline rate diminishes, resulting in an enhanced heat extraction rate and a greater heat extraction resource, while the thermal storage extraction degree is reduced, thereby extending the system's operational lifespan. It was discovered that increasing the number of production wells resulted in a smaller production fluid temperature decline. The operation of a CO₂ plume geothermal system demonstrates that the thermal compensation effect of cap rock and bedrock on thermal storage, along with an increase in the number of production wells, can extend the system's lifespan, offering theoretical insights for the optimisation and practical implementation of CO₂ plume geothermal systems in the future.

In view of the deficiency of the research on the prevention and control of bolt anchoring in engineering rock mass, the method of cooperative prevention and control analysis based on bolt pre-tightening force was put forward, and the cooperative prevention and control test of bolt, anchor agent and surrounding rock based on bolt pre-tightening force was carried out, the variation law of pre-tightening force of bolt was obtained and the cooperative prevention and control state of bolt anchoring was identified. The results indicate that improving the synergy between anchoring agents and the surrounding rock of anchoring holes, as well as between anchor rods and anchoring agents, is beneficial for their synergistic evolution and can effectively enhance the prevention and control effect. A method for determining the collaborative state of anchor rod anchoring is provided, which can comprehensively determine the collaborative state of anchor rod anchoring through the relaxation process curve and relaxation degree of anchor rod pre-tightening force. Increasing the contact surface between the anchor rod pad and the surrounding rock on the free face is beneficial for their synergistic evolution. Based on the application and monitoring of pre-tightening force, a method for determining the overall coordination degree of anchor rod anchoring prevention and control has been developed, and strategies for improving the coordination degree of each part of anchor rod anchoring have been proposed. During design, special attention should be paid to the coordination of each part of anchor rod anchoring to ensure that they can perform at their best and be in their optimal state. The research results have good guidance and reference significance for the anchoring mechanism, monitoring, prediction and prevention of prestressed anchor rods in engineering rock masses.

The Unmanned aerial vehicles three-dimensional path planning problem is a combinatorial optimization problem to find the optimal path between the starting point and the endpoint in complex three-dimensional environment, but most path planning algorithms struggle to find feasible paths within acceptable time and precision range, therefore, a dynamic multi-subswarm salp swarm algorithm based on K-means++ clustering optimization was proposed to address the aforementioned issue. Firstly, a new cost function incorporating height cost was proposed within the three-dimensional environment model. The path planning problem was converted into a multi-dimensional function optimization issue. Secondly, the population was clustered using the K-means++ clustering algorithm, and a dynamic multi-subswarm mechanism was designed to balance the algorithm's global search and local exploitation. Each subswarm collaborates with multiple strategies for improvement, avoiding the algorithm from being trapped in local optima while enhancing global optimization capability. Finally, after validating the algorithm against five algorithms ISSA, MSNSSA, IBSO, MBFPA, and SSA using 12 CEC2017 benchmark test functions, it was applied to solve the optimal path planning problem in three-dimensional environments. Simulation results under different environmental models demonstrate that the algorithm's average effective path rate is increased by 15.5%, 11%, 23%, 20.5% and 18% compared to the other five algorithms, confirming its excellent optimization capability in complex environments.

In China's shale gas exploration and development, skid-mounted equipment is typically used due to its ease of disassembly, transportation, and reassembly. This equipment is often operated in high-pressure and high-temperature environments. As a result, faults are more likely to occur. To prevent production accidents and eliminate safety hazards, regular monitoring and fault diagnosis of skid-mounted gathering and transportation equipment are essential. Only relatively independent and discrete fault information is typically provided by conventional fault diagnosis methods. The relationships between faults are not uncovered. In response, a two-stage association analysis technique was proposed to analyze fault data from shale gas gathering and transportation skid-mounted equipment. The relationships between faults and defect type distributions were identified, providing valuable guidance for equipment maintenance and process optimization. It has been demonstrated through experiments on real data that the method proposed accurately identifies the relationships between defect locations and the distribution of defect types in skid-mounted equipment. A new solution is provided for the preventive detection and optimized design of gathering and transportation skid-mounted systems.

In order to reveal the unsteady flow characteristics during the pre-compression process of the radial wave rotor combustor, the pre-compression mechanism induced by complex wave systems under typical operating conditions was simulated and analyzed using three-dimensional unsteady simulations. The impact of pressure differential across intake and exhaust ports, as well as rotor speed, on the propagation behavior of compression waves within the channels was focused on. The results indicate that as compression waves propagate within the channels, they are influenced by the curvature of the curved channels, leading to wave reflection, refraction, and attenuation. This results in energy loss and waveform distortion, which affect the propagation path and speed of the compression waves. Although a higher pressure difference enhances the intensity of the compression waves, it exacerbates overfilling of the fuel and flow instability, increases thermodynamic losses, and significantly reduces the isentropic compression efficiency. The rotational speed affects the propagation characteristics of compression waves within the channels by adjusting the operational timing of the wave rotor. At 1 200 r/min, the opening time of the intake port is extended, causing the compression waves to reflect and form expansion waves that propagate in the reverse direction. This results in a pressure ratio within the channel of only 103% and a substantial decrease in isentropic compression efficiency.

To determine the accuracy of the light hydrocarbon parameter obtained from the headspace gas, crude oils and associated gases from six wells in the western part of the Qaidam Basin were collected. The composition and carbon isotopes of individual light hydrocarbons from headspace gas and natural gas were analyzed and compared. The results show that the content of C₅—C₇ light hydrocarbons obtained from headspace gas is higher than that in natural gas, but the relative contents of each light hydrocarbon obtained from two methods are similar. It is found that light hydrocarbon parameters calculated from headspace gas and natural gas share similar results in studying the genesis type, generation temperature and other aspects, but get different results in evaluating the maturity by using heptane and isoheptane values. Besides, the carbon isotopes of individual light hydrocarbons in headspace gas are greater than those in natural gas, among which cyclo-alkanes have the smallest carbon isotope difference. Particularly, the carbon isotopes of methylcyclohexane (δ¹³C_MCC6) in the headspace gas are close to those in natural gas. Therefore, the main parameters of light hydrocarbons and δ¹³C_MCC6 can be accurately obtained from the headspace gas of crude oil. The research results provide a basis for enriching the application of light hydrocarbon geochemistry in oil and gas accumulation.

The conflict between coal resource extraction and ecological environmental protection is particularly pronounced in the Gaojialiang coal mine of Inner Mongolia. To accurately characterize the deformation extent and evolutionary patterns of mining-induced ground subsidence within the study area, small baseline subset interferometric synthetic aperture radar (SBAS-InSAR) technology combined with Sentinel-1 radar remote sensing data were utilized to obtain the annual average deformation velocity and time-series cumulative deformation over three primary panels. Additionally, the Kriging interpolation method was employed to predict and supplement data in decoherence regions, ensuring comprehensive coverage of the deformation field. The results show that three distinct subsidence zones are identified, spatially correlated with the mined-out areas of panels 203, 301, and 401, respectively. The subsidence is characterized by slow deformation, with a peak annual average deformation velocity of approximately -34 mm/a. The temporal initiation and spatial propagation of subsidence in the three panels align closely with the actual mining sequence and operational conditions. Among these, panel 401 exhibited the largest subsidence area, covering approximately 4.56 km², with a maximum cumulative deformation of -189 mm, followed by panels 301 and 203 in descending order. Ground fractures identified through high-resolution optical remote sensing imagery are consistent with field investigations, predominantly distributed in the zones of maximum deformation intensity. Based on the deformation characteristics and fractures distribution, three high-risk geohazard zones are delineated within the study area. The primary driver of ground subsidence is attributed to longwall mining activities, while geological structures and precipitation infiltration also contributed to the deformation process. SBAS-InSAR technology has good application effects in monitoring large-scale mining-induced ground subsidence, and can provide crucial technical and data support for geological disaster prevention and ecological environment restoration in Gaojialiang mining area.

In order to study the applicability of the assembled subway station structure in the liquefiable site of the seismic fortification area, based on the engineering practice of Shuangfeng Station of Changchun Metro, the seismic response analysis of the assembled subway station structure in the liquefiable stratum was carried out by using the finite difference software FLAC^3D. Compared with the calculation results of the corresponding cast-in-place subway station conditions, the pore water pressure of the foundation, the dynamic response and floating characteristics of the subway station structure and the deformation characteristics of the assembled subway station structure were studied. The results show that, similar to the calculation condition of cast-in-place underground structure, in the calculation condition of assembled subway station in liquefiable site, the pore pressure ratio of site soil shows three stages: initial slow increase stage, middle rapid increase stage and final gentle stage. When the seismic intensity is high, the underground structure has a significant inhibitory effect on the liquefaction of the surrounding soil. The acceleration response of the prefabricated station structure is smaller than that of the cast-in-place structure, which reflects its flexible adaptation to the deformation of the terrain in the liquefiable site. The connection between the side wall and the middle plate is the key part of structural strength control. When the intensity of the input ground motion is low, the vertical displacement changes of the structure are manifested at different positions of the bottom plate show the development stage of a small amount of sinking at the beginning, then a sharp rise, and finally a downward trend, but with the increase of the intensity of the ground motion, this phenomenon is gradually not obvious. The deformation of the assembled subway station structure under horizontal ground motion is closer to the shear deformation. Its flexible connection is easier to adapt to the larger vertical relative deformation than the rigid connection of the cast-in-place station, and its anti-overturning ability is better.