In order to study the prevention and control of power disaster induced by coal mining process, Brazilian splitting test of raw coal specimen was carried out to study the energy evolution law in the process of coal body tensile damage destruction, and the precursor information of coal body destabilization and destruction was identified. The results show that the coal body tensile damage process has significant nonlinear evolution characteristics, and it is possible to identify the critical point, destabilization point, and damage point of coal body damage. The energy evolution characteristics of coal body tensile damage in each stage are significantly different. In the elastic deformation stage, the input energy is mainly converted into elastic energy, and the dissipation energy remains stable, while in the destabilization stage, the dissipation-elasticity ratio shows a jumping growth. By calculating the energy release rate and energy dissipation rate, it is found that the index has abnormal response characteristics at the critical point, destabilization point and damage point of the coal body tensile process, and the appearance of the characteristic points all have significant precursor information. The nature of coal destabilization is the result of energy accumulation and dissipation, and the energy index of coal body can reveal the abnormal characteristics of energy evolution in the process of damage and destruction of the specimen, and identify the precursor information of coal body catastrophe, which is conducive to the over-warning, and escort for the safe mining of coal.

The pore structure of deep tight sandstone reservoir is complex and heterogeneous, and it is difficult to determine the influencing factors of pore microscopic parameters on the characteristics of gas-water phase permeability. Based on the fractal geometry theory, combined with the core mercury intrusion porosimetry (MIP) method, nuclear magnetic resonance (NMR) T₂ spectroscopy test and micron CT scanning results, the micro-pore throat parameters and various scale fractal dimensions of the reservoir were obtained. Through the mobile gas porosity and the maximum atmospheric phase relative permeability, the control mechanism of the fractal dimension and micro-pore throat structure parameters on the gas-water phase permeability characteristics was discussed. The results show that mercury injection and NMR fractal curves have obvious “three-stage” characteristics, and the total shape dimension of the reservoir describes the distribution of seepage and movable fluid more accurately when gas and water coexist. The maximum mercury saturation, average pore throat radius, total reservoir shape dimension and displacement pressure have significant effects on the mobile gas porosity during gas seepage. The average pore throat radius has a significant influence on the maximum effective gas phase relative permeability in gas seepage. The control mechanism of the micro-pore structure on the gas-water phase permeability can provide a powerful guide for the efficient development of water-producing gas reservoirs.

The research on the factors affecting the convenience of urban integrated transportation transfer can provide scientific basis and guidance for urban transportation planning. Based on the comprehensive transportation theory and transfer convenience theory, the logic of the comprehensive transportation transfer system was sorted out, and the comprehensive transportation transfer system diagram was drawn. Then, from the two perspectives of the comprehensive transportation hub station and the transfer origin-destination(OD) pair of a single station, Pearson correlation analysis, geographic detector model and multiple linear regression model were used to study the factors affecting the convenience of integrated transportation transfer. The results show that the transfer convenience of a single hub station is mainly related to the location of the hub station. Geographical distance, travel mode and number of travel stations are the main factors of the shortest transfer time, and the number of travel stations is the most important factor. Geographical distance, shortest highway mileage, travel mode and number of travel stations are the main factors of the least transfer cost, among which the travel mode and number of travel stations are the most important factors.

The problem of mine water pollution from abandoned mines after integration is becoming increasingly serious with the integration of coal resources and the merger and reorganisation of coal companies. An accurate understanding of the development mechanism of mine water quality in abandoned coal mines is an important prerequisite for the protection and use of mine water and the effective prevention and control of groundwater pollution. The leaching behaviour of Fe³⁺ and Mn²⁺ and the changes of related water quality indices were investigated by the long-term indoor water-coal immersion test based on the project practice of Shendong mining area. The results show that the solubility of Fe³⁺ is “wave-like”, and the solubility of both samples reaches the lowest value at the 84th day after immersion, while the solubility of Mn²⁺ remains relatively stable after a rapid reaction (the first day). The causes of solubility variations were further analysed by ion ratio coefficient method and Pearson correlation coefficient method, and it was found that mine water in goaf may be affected by mining activities, and the water quality of mine water is strongly influenced by the dissolution of silicate rocks and gypsum. The main water-rock interactions in mine water in the goaf area include the dissolution of silicate rocks and evaporative rocks and the alternating adsorption of cations. For the rational development and utilisation of mine water in China, it is of great importance to study the characteristic pollutant ion change law of mine water in the goaf area.

The path planning problem of electric vertical takeoff and landing (eVTOL) aircraft in urban scenarios was studied. Firstly, a three-dimensional urban space model was constructed using the hazard grid method. Considering the selected model of eVTOL, with range, operational risk, and altitude variation as objective functions, a path planning model for manned eVTOL with multiple constraints was developed, taking into account the characteristics of the aircraft and environmental limitations. Subsequently, an improved artificial electric field algorithm (IAEFA) was proposed, which enhances the traditional artificial electric field algorithm (AEFA) by introducing an adaptive Coulomb parameter and incorporating a decreasing coefficient in the Coulomb constant calculation for simulation-based solution. Experimental results demonstrate that the constructed model achieves the expected outcomes. The solution effectiveness of path planning using the improved algorithm surpasses that of traditional particle swarm optimization and artificial electric field methods, resulting in shorter range, minimal altitude variation, and enhanced safety during operations. Finally, based on comparative experiments, the value of the decreasing coefficient was determined. The optimal solution effectiveness of the improved algorithm is achieved when the decreasing coefficient is set to 1.5.

The magnetic flux leakage detection technology has been widely used in the field of ferromagnetic material defect detection, in which the magnetic dipole method is currently the most widely used mathematical method for predicting magnetic flux leakage from structural defects. The magnetic dipole method is primarily employed for predicting the magnetic flux leakage signal of regular defects. The unit magnetic dipole band superposition model can be used to predict the magnetic flux leakage signal of complex defects. The magnetic charge density of complex defects needs to be calculated when the model is used for prediction. However, the magnetic charge density distribution of complex defects is inhomogeneous, and the calculation is complex. Therefore, a calculation method of discrete magnetic charge density field was proposed for calculating the magnetic charge density of three-dimensional irregular defects. The computational complexity of the model was reduced by using this method and the magnetic flux leakage signal of three-dimensional irregular defects can be quickly and exactly obtained. Comparison between the signal predicted by the unit magnetic dipole band superposition model based on discrete magnetic charge density field and the signal simulated by COMSOL software demonstrates the feasibility of the method. Experimental results show that the prediction performance of the model has been significantly improved by using this method, the maximum prediction error is reduced by 90.08%, and the calculation time is reduced by 97.43%, thus a fast and effective solution for the calculation of the magnetic charge distribution of three-dimensional irregular defects is provided.

The effect of water flooding development in low permeability reservoir is generally poor, and CO₂ flooding can effectively improve the degree of crude oil recovery. In order to analyze various factors affecting the effect of CO₂-assisted gravity flooding, based on the research mechanism of gas-injection-assisted gravity flooding, a mechanism model of one injection and one production was established to analyze the influence law of geological factors and development factors, and the orthogonal experimental design method and Shapley value method were used for multi-factor analysis. The results show that the positive rhythm reservoir is more suitable for CO₂-assisted gravity flooding. Reservoir dip angle, average permeability and gas injection velocity are positively correlated with development effect. The ratio of vertical permeability to horizontal permeability and the difference of permeability stage were negatively correlated with the development effect. If the ratio of gas injection and dimensionless horizontal well section length is set to 0.8, the CO₂-assisted gravity flooding effect can be effectively improved. The ratio of vertical permeability to horizontal permeability has the highest influence on CO₂-assisted gravity flooding. The research results provide technical guidance and theoretical support for improving the development effect of CO₂-assisted gravity flooding in low permeability reservoirs.

With the transition from traditional centralized power systems to distributed energy systems, harmonics are produced due to the penetration of renewable energy, resulting in additional losses. Distribution network loss accounts for more than half of the total system loss and is the focus of network loss reduction. A network reconstruction method based on improved binary particle swarm optimization algorithm was proposed to reduce distribution network loss. Firstly, considering the influence of harmonic wave on network loss and the harmonic effect of the line under high frequency current, the line impedance was modified. Then, the total loss of the network was calculated using the corrected impedance, and a probabilistic reverse learning approach suitable for binary algorithms was creatively proposed, integrating the theory of the good point set to obtain uniform and diverse initial particles. Finally, taking the modified 33 node power system as an example, the optimization objective was to minimize the total loss and obtain the optimal topology structure of the distribution network. The experimental results show that the distribution network reconstruction considering harmonic factors has played a good role in reducing the loss of distribution network.

As China’s mountainous regions host more and more gas pipelines, incidents involving natural gas leaks that cause harm to the environment or injure people are growing increasingly common. To investigate the diffusion behavior and vertical hazard distance of leakage gas in mountainous regions, a three-dimensional model of pipeline-soil-air was created with CFD software. The impacts of various obstructions, soil types, burial depths, leak hole shapes, and leak directions on the propagation of natural gas pipeline leaks and hazard distances were studied separately. The results show that in proportion to the direction angle between the buoyant force and the leakage hole, the vertical hazard distance and the rate of gas diffusion to the ground decrease. Diffusion rates and hazard ranges are larger for square and triangle leaking holes compared to circular ones. As soil porosity and granularity increase, the rate at which escaping gases diffuse into the soil increases steadily. The time it takes for the gas leak to release will vary depending on the burial depth, and as soil burial depth increases, so will the vertical hazard distance. Obstructions will alter the diffusion path of the leaking gas and accelerate the vertical hazard distance. Culverts will allow the gas to accumulate in the ditch to form an area of high concentration.

Henan Province has abundant geothermal resources, with the northern and central regions having undergone extensive exploration and large-scale development. However, the southern region of Henan has been subject to limited exploration efforts, resulting in a scarcity of drilling data. Consequently, research on its structural characteristics, stratigraphic distribution, geothermal geological characteristics and resource potential is relatively underdeveloped. This knowledge gap poses challenges in meeting the demands for industrialization and large-scale development. Based on regional geological characteristics and two-dimensional seismic interpretation results, the research on geothermal geological characteristics, resource evaluation and favorable area prediction in Zhumadian area were carried out on the basis of previous studies. The results show that Zhumadian structure is located in five secondary structural units: Wuyang Depression, Zhumadian-Huaibin Depression, Pingyu Uplift and Changshan uplift in the southwest of Zhoukou Depression and Biyang Depression in the east of Nanxiang Basin. In Zhumadian area, the geothermal geological conditions are poor in Zhengyang and Chishan, which are located in the uplift area of Changshan Mountain. There are three sets of stratified heat reservoirs in Neogene, Paleogene sandstone and Cambrian-Ordovician carbonate rocks in this area, and the total static resources are about 115×10¹⁵ kJ. It is predicted that Biyang County urban area, Xincai County urban area and the west of Yicheng District are the most favorable areas for geothermal resources development, with moderate depth of heat storage, large water inflow and high temperature.