In order to meet the requirements of high-voltage DC circuit breakers for rapidity actuation of their actuating mechanisms, a new electromagnetic repulsion mechanism was designed for 40.5 kV vacuum circuit breaker, which had high breaking and closing speeds and was suitable for quick disconnection. It consisted of a coil-plate and a double-coil mechanism connected in series.Firstly, the electromagnetic field simulation was carried out by the finite element method, the feasibility of the mechanism was initially verified by analyzing the electromagnetic repulsion,displacement/time characteristics and velocity/time characteristics. Then, the single-variable method was used to simulate and analyze its motion characteristics. the law of the influence of each parameter on the motion characteristics was obtained, and the optimization parameters were determined. Finally, in order to reduce the tripping bounce of the long-stroke fast electromagnetic repulsion mechanism, an electromagnetic buffer was designed. the effects of buffer current input time and buffer driving circuit parameters on buffer characteristics were analyzed. The results show that the new electromagnetic repulsion mechanism combines the advantages of the fast response of the coil-plate mechanism and the high drive efficiency of the double-coil mechanism,with its short response time, large motion speed and short full stroke time, and meet the need of quick disconnection. Under the parameter conditions of 3 500 μF capacitance and 1 200 V for the driving circuit and buffer circuit capacitance 3 500 μF capacitance and 1 300 V for the buffer circuit, the full travel time of the designedelectromagnetic repulsion mechanism is only 2.18 ms.

To study the damage characteristics of rock masses in cold regions under the coupling effect of freeze-thaw cycles and fatigue loads, freeze-thaw cycle tests, nuclear magnetic resonance microscopic tests, and triaxial compression fatigue macroscopic tests under different confining pressures were carried out on single crack marble. The pore structure expansion characteristics of fissured marble after freeze-thaw cycles, as well as the mechanical properties and deformation failure characteristics of fissured marble under freeze-thaw cycles and fatigue loads were analyzed. A single crack marble fatigue damage constitutive model based on Nishihara creep model was established by introducing damage variables under freeze-thaw and fatigue loads. The results showed that with the increase of freeze-thaw cycles, the mass loss rate and longitudinal wave velocity loss rate of fissured marble gradually increased. The nuclear magnetic resonance T₂ curve showed a three peak characteristic, with the whole curve shifting to the right. The second peak gradually connected with the third peak, and the total peak area continued to increase. There was a positive correlation between confining pressure and the fatigue strength of fissured marble. With the increase of confining pressure, the fatigue resistance and ductility of fissured marble increased, and the failure mode of the rock sample gradually changed from local shear failure to overall shear failure. The theoretical curve of the established fatigue damage constitutive model was basically consistent with the experimental data. The research results could provide reference for the prevention and control of rock engineering disasters in cold regions.

The stress-strain characteristics of gas hydrate-bearing sediments (GHBS) are essential for achieving safe and secure extraction of marine natural gas hydrate. To quantitatively investigate the influence of hydrate formation on the mechanical properties of GHBS, laboratory tests were conducted under different confining pressures and various hydrate saturations, and it was found that hydrate primarily enhanced the cohesive strength of GHBS, while the internal friction angle remained relatively unchanged. To comprehensively describe the intricate mechanical properties of GHBS, the previously established elastic-plastic constitutive model was employed for predictive purposes. A comparative analysis revealed that the constitutive model exhibited a certain level of applicability. Subsequently, a computer program was developed for the constitutive model by leveraging the UMAT user material subroutine interface provided by ABAQUS. The program was written in FORTRAN language and integrated into ABAQUS, facilitating the implementation of the constitutive model. To validate the effectiveness and stability of the developed model, finite element simulations were conducted on single elements as well as triaxial specimens of GHBS. The results of these simulations confirm the efficacy and reliability of the developed model.

To investigate driving workload on mountainous expressways, a naturalistic driving study was conducted utilizing an eye tracker to capture drivers' eye movement data in a realistic driving environment. Employing the change rate of pupil area, average saccade time, blink frequency, and fixation time ratio as primary indicators, a quantitative driving workload model was formulated through a combined weighting approach. This model aimed to reveal the driving workload evolution mechanism in typical scenarios of mountain expressways such as bridge and tunnel clusters, tunnel clusters, and short distances between tunnels and intersections. A clustering algorithm was applied to determine the classification thresholds for driving workload, thereby identifying high-risk scenarios characterized by heightened workload. The results show that the types of bridges within bridge-tunnel groups, the length of connection sections between tunnel groups, and the proximity of tunnels to interchanges significantly influence driving workload. A positive correlation was observed between driving workload and bridge size, whereas driving workload exhibited a negative correlation with the length of connection sections between tunnel groups and the distance from tunnels to interchanges. The thresholds of high, medium and low intensity levels of driving workload on mountain expressway are 0.54 and 0.26. Scenarios with bridge-tunnel groups composed of large or super-large bridges, tunnel groups with distances less than 300 m, and tunnel-to-interchange sections with distances less than 400 m were classified as high-risk driving workload scenarios. It is advisable to implement an intelligent lighting system within expressway tunnels, establish light-reducing structures at tunnel entrances, and in scenarios where tunnels are located in close proximity to interchanges, consider installing designated lane-changing zones within suitable tunnel sections to facilitate smooth lane transitions.

Because Hainan Province is located in the tropics, it is often hit by extreme weather such as typhoons and rains, so it is very prone to geological disasters such as slope collapse and landslides, which eventually cause irreparable losses. In order to improve the stability of tropical soil slope in a green and environmentally friendly way, the slope was strengthened by microbial induced calcium carbonate precipitation (MICP) technology and carpet grass root slope consolidation. Suitable microbial strains were first screened out, and the preparation process of related microbial agents was optimized. Subsequently, carpet grass root system was implanted in the slope soil indoors, and MICP treatment was carried out after the formation of the root-soil complex. Subsequently, a series of laboratory tests and numerical simulation analyses were carried out to evaluate the reinforcement effect of this technology. The results showed that MICP technology and plant root treatment complemented each other in terms of mechanical brittleness and integrity of slope, and significantly improved the unconfined compressive strength and shear strength performance of soil, effectively enhanced the stability of slope, and reduced the risk of slope erosion. Finally, the numerical simulation verification was carried out by using Abaqus finite element software, which enhanced the reliability of the research results. It can be seen that the MICP combined with carpet grass root reinforcement method provides an effective reinforcement method for tropical soil slopes, which not only improves the mechanical properties of slopes, but also promotes ecological restoration and environmental sustainability. This result provides a new technical approach for the ecological reinforcement of slopes in tropical areas, and has certain theoretical and practical significance for protecting the ecological environment and reducing the risk of geological disasters.

To meet the increasingly refined individual-level traffic management and travel service needs in the new era, a vehicle travel destination prediction method that comprehensively considers temporal and spatial correlation was proposed based on the traditional prediction method based on historical trajectories. Using data from video AI recognition and vehicle satellite positioning, the vehicle stopping points were identified to segment the vehicle's full-day travel trajectories and establish a historical vehicle travel trajectory database. By studying the temporal and spatial characteristics of vehicle travel, a calculation method for the temporal and spatial correlation of vehicle travel trajectories was proposed, and a vehicle travel destination prediction model was constructed using temporal and spatial correlation as weights. Taking the vehicle travel in Futian Central District of Shenzhen as an example, four typical vehicle travel trajectories including private cars and taxis were selected to establish a model prediction accuracy evaluation function. The prediction accuracy of travel destinations for different types of travel and different degrees of trajectory completion was analyzed and compared with the historical trajectory-based prediction method. The results show that the prediction accuracy of travel destinations for different types of vehicles is basically positively correlated with the degree of trajectory completion. When the trajectory completion rate reaches 80%, the accuracy of travel prediction basically reaches over 80%. Compared with the traditional prediction method based on historical trajectories, the prediction method considering temporal and spatial correlation has higher prediction accuracy, especially for taxis services with no fixed commuting travel characteristics. The prediction accuracy of travel destinations has been improved by more than 16%. The research results can better meet the needs of global traffic management.

The small pore throat radius, high starting pressure gradient, poor formation physical property and large gas production difference of horizontal wells after fracturing in tight sandstone reservoirs seriously affect the increase of tight gas reserves and production. In view of the above problems, the production dynamics of gas wells under different levels of sweet spots in the eastern Ordos Basin were analyzed, and a new tight gas fracturing method based on sweet spot distribution was proposed. Based on the evaluation of rock mechanics parameters, energy storage coefficient and argillaceous content parameters, the evaluation model of geological sweet spot and engineering sweet spot was established, and the reservoir quality of tight sandstone gas reservoir was divided by fuzzy comprehensive evaluation method. According to different sweet spot types, the production characteristics and sweet spot distribution characteristics of Class I, II and III horizontal wells were summarized, and three fracturing modes based on geological sweet spot and engineering sweet spot were formed. The results show that when the horizontal well is drilled in Class I geological sweet spot and Class I engineering sweet spot, the cumulative gas production is higher than expected (Class I well), and a larger fracturing scale and displacement can be adopted to maximize the economic benefit (Model 1). When the horizontal well is drilled in Class I geological sweet spot and Class II engineering sweet spot combination, the cumulative gas production is lower than Class I well (Class II well), and the fracturing scale should be reduced appropriately to pursue a certain production capacity and economic benefit (Model 2). When horizontal wells are drilled in geological sweet spots below Class II and combinations of Class I/II engineering sweet spots, the production effect is the worst (Class III wells), and the fracturing scale should be controlled by reducing displacement to avoid the fracture from entering the risk layer and obtain a certain production rate (Model 3). The above new fracturing method was applied to a newly drilled horizontal well in a tight gas reservoir, and the open flow and gas production of the horizontal well after fracturing reached the expectation, which has certain guiding significance for the development of tight sandstone gas reservoir.

In order to solve the problems of the traditional interactive multiple model (IMM) algorithm in vehicle target tracking, such as the model probability change is not obvious and the tracking accuracy is insufficient, an improved adaptive IMM-UKF(unscented Kalman filter) algorithm was proposed. Firstly, the vehicle motion model was established by using uniform speed straight line, uniform acceleration straight line and uniform turning, and the vehicle target was tracked by unscented Kalman filter. Then, the probability change rate of sub model was used as the correction parameter of IMM algorithm, and different correction strategies were adopted for the main diagonal and non main diagonal elements of Markov matrix. Finally, the decision window was set to modify the main diagonal element of the normalized Markov matrix to expand the probability of matching model. The results show that the probability of the improved algorithm model changes more obviously, and the root mean square errors of position and velocity are less than the original algorithm, which effectively improves the tracking accuracy.

The explosive popularity of the new generation of artificial intelligence technologies will profoundly impact the risk experience of perceptual subjects within risk societies. Factor analysis and multiple indicators and multiple causes (MIMIC) model were used to study 12 risk scenarios of generative AI, besides four indicators reflecting the public's risk perception and five dimensions affecting the public's risk perception were explored. The results show that the public's perception of the risks of generative AI can be reflected by expectations of safety, technology, user and corporate regulatory. The public's risk perception is affected by its subjective evaluation of technology risks, macro risks, equity risks, subject risks and application risks, among which both equity risks and macro risks have the most significant impact. It shows that the public's risk perception of generative artificial intelligence is mainly characterized by “self-oriented” and “precautionary”. On this basis, the public's risk perception of generative artificial intelligence from the perspectives of history and culture, risk communication and technology governance was analyzed further, and corresponding countermeasures was put forward.

To investigate the mechanisms of floor heave and support methods for large-section inclined shafts in highly expansive and weak rock, a case study was conducted on the main inclined shaft of a mine in the Yaojie Coal and Electricity Group. Through field surveys and laboratory tests, characteristics such as low rock mass strength, poor integrity, high clay content, and softening and swelling upon water exposure were identified. A Flac3D numerical model was established to simulate the deformation patterns of the tunnel under actual engineering conditions, elucidating the mechanisms of floor heave deformation in large-section soft rock inclined shafts. Three optimized prevention strategies were summarized, and an optimized support scheme of “inverse floor arch and anchor cable” was proposed based on the original support design. Field measurement data indicated that the optimized support scheme significantly improved the floor heave control in soft rock tunnels, enhanced the bearing capacity of the surrounding rock, reduced floor heave deformation, and achieved stability control of the tunnel surrounding rock. This provides an important reference for the control of floor heave in large-section shallow soft rock inclined shafts.