Buried pipeline is an important part of oil and gas transportation. The subsidence of gob area will cause the corresponding subsidence of the pipeline passing through the gob area, resulting in pipeline deformation, fracture and other accidents. Taking Puxian-Hejin pipeline crossing coal mining subsidence area as the research background, 3D printing technology was used to make up for the mismatch in mechanical similarity between pipeline simulation materials and geotechnical simulation materials, and the coupling simulation experiment between pipeline and rock and soil was constructed. The mining response of buried pipeline caused by coal mining was analyzed, and the correlation between pipeline movement deformation and stratum movement deformation was established. The research shows that the buried pipeline and the underlying rock strata do not synchronously settlement, resulting in delamination between the overlying rock strata and the underlying rock strata. The pipeline bends and deforms under the overlying rock load and its own weight. When the delamination span is large enough, the bending tensile stress on the bottom of the pipeline exceeds the allowable stress, resulting in tensile failure. The subsidence value of the buried pipeline is about 1.21 times of the formation subsidence value, and only 18% of the horizontal deformation of the formation is transmitted to the pipeline. The research results have guiding significance for the safe laying and daily maintenance of pipelines in subsidence area.

Oil-based drilling fluids, favored for their superior stability and inhibitive properties in complex deep oil and gas strata, is constrained by a scarcity of efficient materials for leak prevention and plugging, thereby limiting their utilization. In response to this challenge, a homogenous and stable polymer, SMHDVD, was synthesized via solution polymerization, using acrylate monomers as the primary chain and incorporating functional monomers that offer resistance to high temperatures and enhanced bonding with the formation. The impact of different concentrations (0.1%, 0.3%, and 0.5%) of the crosslinking agent divinylbenzene on the polymer SMHDVD was also investigated. In-house plugging experiments have shown that SMHDVD significantly contributes to the plugging efficacy of oil-based drilling fluid systems, with a maximum reduction in cumulative drilling fluid loss of up to 68.7%, surpassing the performance of conventional plugging materials. It was observed through comparative studies that the incorporation of a crosslinking agent diminishes the sealing capacity of SMHDVD, and an increase in the crosslinking agent's concentration leads to a decline in the polymer's plugging performance. The polymeric plugging agent developed in this research offers a novel perspective for the prevention of oil-based drilling fluid leakage, with promising prospects for practical field application.

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.

Aiming at the problem that it is difficult to directly use external heat sink to dissipate heat for high-power electronic devices with short-time operation in external insulation condition, the phase-change material with low melting point and high volume enthalpy value was adopted to optimize the design of energy storage structure and realize temperature control for electronic devices. Firstly, based on the constraints of electronic device volume, weight, external environment, thermal power, working time, etc., combined with the thermal performance of phase change materials, an integrated design of heat dissipation structure was carried out. Secondly, according to the characteristics of phase change material(PCM), an equivalent specific heat capacity thermal analysis method based on temperature feedback was proposed. Finally, the thermal conductivity of three PCM including paraffin, carbon composite and liquid metal, was analyzed by numerical simulation, and the heat dissipation performance of the three PCM in specificenergy-storage structures was evaluated by using heat source temperature rise and temperature equalization as indicators, and an optimal phase-change energy-storage structure of the electronic devices was determined. The results show that the PCM can significantly control the temperature rise in a certain period of time, which meets the temperature control requirements of electronic devices in small volume and external adiabatic environment. The volume enthalpy of PCM represents the energy storage capacity per unit volume of PCM. The higher the volume enthalpy, the smaller the volume of PCM required. Liquid metal can obtain better thermal properties because of its large enthalpy and high thermal conductivity.

The non-lethal electric shock weapon is a research hotspot in the field of non-lethal weapons. In recent years, the research on wireless long-range electric shock bullets has become a key issue within this field. Therefore, aiming at the design of non-lethal long-range low-velocity electric shock bullet empennage, three airfoils of Clark Y, Eppler 387 and NACA-66 with good aerodynamic characteristics at low velocity were selected. The simulation results of NACA0012 airfoil at 30 m/s using CFD software were compared with the literature simulation results and wind tunnel test results to verify the algorithm's effectiveness. Subsequently, the aerodynamic characteristics of the three airfoils at low velocity were simulated, and the lift coefficient, drag coefficient and lift-drag ratio corresponding to different angles of attack at 30, 35 and 40 m/s were obtained respectively. The results show that at the same flight velocity, the lift coefficient and drag coefficient of the three airfoils gradually increase with the increase of the angle of attack, but the growth rate of the lift coefficient gradually decreases, and the growth rate of the drag coefficient gradually increases. The lift-to-drag ratio increases first and then decreases with the increase of the angle of attack. After comparison, it is found that the aerodynamic performance of the airfoil Eppler 387 is better than that of the other two airfoils. The velocity of 40 m/s and the angle of attack between 4° and 6° are the best working conditions, which can not only meet the structural design requirements of non-lethal long-range low-velocity electric shock bullets, but also produce less drag while providing as much rolling moment as possible.

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.

Second order selective harmonic repetitive control(SOSHRC) strategy with good frequency adaptability and dynamic performance, is widely used in grid-connected inverter control. To address the problems of the traditional SOSHRC strategy, such as the difficulty of using the stability analysis method and the conservative stability criterion, a novel second order selective harmonic repetitive control and proportional control(SOSHRC-PC) was proposed. Firstly, the structure and principle of the novel SOSHRC were designed, the novel SOSHRC-PC control strategy was introduced. Then, the stability and parameter design methods of the novel SOSHRC-PC controller were analyzed. Finally, a three-phase grid-connected inverter based on the novel second-order (6k ± 1) harmonic repetitive control and proportional control was constructed, and the simulation results show that the proposed control strategy has great steady state and dynamic performance.

The reactive power optimization and reconfiguration of traditional distribution network are mostly studied separately, lacking the coordination and cooperation of different optimization techniques. A mathematical model of reactive power and reconfiguration collaborative optimization of active distribution network was established. Combined with the two optimization methods of reactive power optimization and reconfiguration of distribution network, the coordinated operation of the two was realized according to the actual situation of distribution network. Taking the minimum annual comprehensive cost as the objective function, the improved grey wolf algorithm was used to solve the problem under the constraints of network power balance, node voltage amplitude and network radial operation. Aiming at the problems of low population diversity, easy to fall into local optimal solution and slow running speed of traditional grey wolf algorithm, it is proposed to increase the explosion mechanism of fireworks algorithm on the basis of grey wolf update strategy. At the same time, in order to improve the computational efficiency and solution accuracy, the fireworks algorithm was used for integer solution optimization, and the nonlinear programming algorithm was introduced to optimize the continuous solution. The IEEE33 node distribution network was taken as an example to verify four different scenarios. The results show that the proposed collaborative optimization model can effectively reduce the network loss and annual comprehensive cost, suppress the node voltage fluctuation level, and show the superiority of the improved algorithm in convergence speed and calculation accuracy.

Aiming at the problem that the unordered charging of large-scale electric truck (ET) increases the peak load of the grid and affects the power quality, a cluster division and two-tier optimal scheduling strategy for peak load balancing scenarios were proposed. Firstly, the demand response model of ET participating in power grid peak regulation was established considering real-time road flow and multi-energy consumption factors. With logistics factors as characteristic quantities, ET was divided into day-ahead clusters by an improved fuzzy clustering algorithm. Secondly, based on the clustering results, combined with the different interests of power grid dispatching and enterprise users, a two-tier scheduling model was established under the framework of master-slave game considering the flexible time window to solve the charging and discharging power of pure electric heavy duty card in the cluster in real time. Finally, particle swarm optimization based on Kriging model was used to speed up the solving of the model. The simulation results of ET data in a logistics area show that the two-tier scheduling strategy based on cluster division and flexible time window can better smooth the load curve and reduce the scheduling deviation of clusters. At the same time, Kriging optimization algorithm is more fast in solving the two-tier optimization model.

An adaptive predefined-time prescribed performance backstepping fault-tolerant control strategy is presented based on radial basis function (RBF) neural networks, event-trigger mechanism and hysteresis quantizer for the attitude control problem of quadrotor unmanned aerial vehicle (UAV) with actuator faults. Firstly, the dynamic model of the quadrotor UAV system was constructed, and the attitude model was reconstructed by incorporating the actuator fault model. Secondly, by designing a class of time-varying functions, the error variables required for backstepping control were transformed. Thirdly, the nonlinear function approximation capability of RBF neural networks was utilized to estimate derivatives of virtual control laws and the actuator fault with unknown parameters. Finally, to reduce the update frequency of the actuator, a combination of event-trigger mechanism and hysteresis quantizer was used to design the control input. Stability of the closed-loop system was demonstrated through Lyapunov stability theory. The effectiveness of the proposed algorithm was verified through MATLAB. It is concluded that the designed event-triggered quantized controllers have a lower update frequency compared to controllers designed using only event-triggered techniques.