To address the difficulty of balancing fuel economy and durability, an energy management strategy (SAC-V) for fuel cell hybrid electric buses was proposed by combining a bidirectional long short-term memory neural network (BiLSTMNN) with a soft actor-critic (SAC) algorithm. First, BiLSTMNN was applied to achieve short-term vehicle speed prediction. Second, the predicted speed and real-time vehicle states were jointly used as inputs to the SAC reinforcement learning agent, and constraint terms including hydrogen consumption, power battery state of charge deviation, and fuel cell degradation were introduced into the reward function to achieve dynamic coordinated optimization of vehicle fuel economy and powertrain durability. Finally, the proposed strategy was validated through offline simulation and hardware-in-the-loop tests. The research results show that, compared with the conventional SAC method and the deep deterministic policy gradient method, the proposed SAC-V strategy reduces equivalent hydrogen consumption, fuel cell power fluctuation, and fuel cell degradation rate by 3.46%, 35.56%, and 3.67%, respectively, exhibiting better overall performance and favorable real-time application potential in practical engineering.

Deep integration of traction power supply systems in electrified railways and new energy is an important measure to implement the national “carbon peaking and carbon neutrality” goal and promote the green transformation of rail transit. In view of the demand for large-scale integration of new energy, combined with the national direct connection strategy of green electricity, a technical scheme for the direct connection of green electricity in traction power supply systems was proposed, and its power flow control strategy was studied. Firstly, different schemes for direct connection of green electricity were compared and analyzed, and it was clarified that through-feeding power supply with direct connection of green electricity was the optimal choice to achieve a win-win situation for power grids and railways. On this basis, by considering grid support strength and coupling degree, three architectures of grid-structured through-feeding power supply physical systems with direct connection of green electricity were constructed. Power supply zones were formed based on the demarcation of section posts, realizing the matching of generation, consumption, and energy storage within power supply zones. Secondly, control logics of green electricity devices and energy storage devices under grid-connected/islanded modes were established, and a regulation system driven by controller information flows to direct energy flows was constructed. Based on electrical quantity information of section posts, train operation states and traction load powers were identified, realizing real-time power balance and autonomous coordinated control of generation, storage, and consumption under grid-connected/islanded modes. Finally, taking an actual reconstructed line as an example, the effectiveness and economy of the scheme were verified. Research results indicate that the through-feeding power supply with direct connection of green electricity is conducive to large-scale integration of new energy along railways. Meanwhile, it can solve dual pain points of negative sequence of power grids and power interruption zones of neutral sections in traction networks, achieving the core goals of zero grid interference and zero operation interruption. Through segmented and partitioned power supply and autonomous coordinated control of power flows, energy autonomy, operation autonomy, and control autonomy of the system are realized within respective jurisdiction sections of traction substations and traction green electricity stations. Combined with line data for economic analysis, by adopting lithium iron phosphate battery energy storage devices and considering two operation scenarios of grid-connected and islanded modes, preliminary cost recovery periods are approximately 3.9 years and 7.2 years, respectively.

To study the influence of guideway irregularity on ride comfort of 600 km/h high-speed maglev trains and to address the limitations of conventional dynamic models, which lack detailed descriptions of human biological structures and thus fail to reveal the complex interactions between vehicle body motion and resonance of human internal organs, an integrated full-chain “vehicle-guideway-human” coupled dynamic simulation method was proposed. First, a system simulation framework was established based on multibody dynamics and finite element theory, incorporating spatial flexible guideway beams, active levitation/guidance control algorithms, and multibody vehicle dynamics. Second, a 45 degrees of freedom (DOF) three-dimensional seated human biomechanical model was introduced to construct a full-system coupled dynamic model, thereby addressing the distortion at the human perception end in the vibration transmission path. Then, system modal analysis was employed to reveal the coupling mechanism between vehicle body motion and the resonance of human internal organs and skeletal system. Finally, the model was validated using measured data from the Shanghai high-speed maglev demonstration line. The results indicate that according to the standard (GB/T 5599—2019), the measured vertical and lateral ride quality indices are 2.33 (excellent) and 2.61 (good), respectively, while the simulated values are 2.28 and 2.56, with relative errors of only 2.15% and 1.92%, respectively. Furthermore, for the seat surface vibration directly perceived by the human body, the measured peak vertical and lateral accelerations are 0.915 m/s² and 1.115 m/s², respectively, with corresponding simulation errors controlled within 5.00% (0.76% and 2.91%, respectively). In the frequency domain, the model not only accurately reproduces the car body’s rigid body mode at approximately 1.5 Hz but also precisely captures the coupled resonance peaks in the 4.0–6.0 Hz band dominated by human biomechanical characteristics, thereby verifying the effectiveness of the model in refined ride comfort prediction.

To enhance the durability of structural members while ensuring ductility, a new glass fiber-reinforced polymer (GFRP)-steel hybrid reinforced (HRBS) column with a built-in spiral stirrup core column was proposed. Four HRBS columns were subjected to quasi-static loading tests, among which two HRBS columns underwent composite salt dry-wet cycling tests. The failure process, ultimate failure mode, hysteresis curves, skeleton curves, energy dissipation capacity, performance degradation, and residual displacement of the HRBS columns before and after composite salt dry-wet cycling were investigated. The results indicate that HRBS columns demonstrate good seismic performance both before and after composite salt dry-wet cycling, and all specimens exhibit flexural failure. Under conventional environments, the yield load and peak load of HRBS columns increase by 25.77% and 28.68%, respectively, with an increase in the core column diameter. In a composite salt environment, increasing the core column diameter improves the load-bearing capacity, displacement ductility factor, strength degradation factor, energy dissipation capacity, overall stiffness, and self-centering ability of the HRBS columns. After composite salt erosion, the yield load and peak load of specimens with a 200 mm core column diameter decrease by 17.65% and 15.77%, respectively, while the energy dissipation capacity and displacement ductility factor increase by 14.41% and 32.61%, respectively. Therefore, by designing an appropriate core column diameter, HRBS columns ensure good durability and overall seismic performance in both conventional and corrosive environments.

The air friction loss of a motor rotor increases rapidly with the increase in rotational speed. Especially for a high-speed motor supported by magnetic bearings, since the air-gap structure is complex, mastering its air friction loss characteristics is particularly important. A 2 MW、15 000 r/min high-speed permanent magnet motor with magnetic bearings was taken as the research object, and the entire air domain inside the motor was modeled. Firstly, based on the fine simulation technology of computational fluid dynamics (CFD), the distribution characteristics of air friction loss on the rotor surface were obtained. Then, the effects of rotational speed, ventilation wind speed, surface roughness height, air gap structure, and rotor eccentricity on the air friction loss characteristics of the rotor were analyzed in detail. Finally, a dual-motor drag test was conducted, and the air friction loss of the rotor was obtained by the loss separation method. The research results indicate that the air friction loss of the rotor is mainly concentrated in the air gap of the motor. At a rotational speed of 15 000 r/min and a ventilation wind speed of 2.5 m/s, it accounts for approximately 70.1% of the total air friction loss. Meanwhile, the air friction loss at the thrust collar cannot be ignored, accounting for about 23.9% of the total air friction loss under the non-ventilation condition. The synergistic thermal effect of cooling enhancement and loss increase caused by ventilation needs to be comprehensively considered. When the ventilation wind speed increases from 2.5 m/s to 5.0 m/s, the cooling heat transfer coefficient on the rotor surface increases from 315.7 W/(m²•℃) to 469.1 W/(m²•℃), and the air friction loss also increases by 3.13 kW. The maximum error between the experimentally measured values and the simulation calculation results is 8.60%.

In recent years, incidents of misoperation of relay protection devices caused by excitation inrush current have occurred multiple times when transformers are put into no-load operation by railway departments on site after modification, maintenance, or fault removal, which seriously affects power supply reliability. To ensure the safe and reliable operation of the railway power supply system, based on on-site investigations and comprehensive analysis of extensive literature, the hazards of excitation inrush current to electrical equipment and railway operation in the Chinese railway power supply system were systematically analyzed. Meanwhile, based on the electromagnetic equivalent model of transformers, a qualitative analysis of the formation causes of excitation inrush current was conducted, pointing out that residual magnetism and closing bias magnetism are the main factors affecting the magnitude of excitation inrush current. In addition, the current research status of Chinese and international scholars on suppressing excitation inrush current by coordinating residual magnetism and closing time, as well as adding external electrical components, was introduced, and the research progress of excitation inrush current waveform recognition technologies, such as the waveform feature method, time-frequency domain analysis method, and neural network method, was summarized. Finally, multi-scenario and full-characteristic transient simulation of excitation inrush current, the research and development and application of high-performance new materials and new structures for transformers, as well as waveform recognition technology based on new neural networks and its protection coordination measures were prospected, which were considered as key areas for future research.

In small-to-medium span highway girder bridges in China, laminated-rubber bearings are typically positioned between the steel plate at the beam bottom and the concrete padstone on the pier/abutment. While relevant specifications indicate that relative sliding can occur at the bearing-steel plate interface, under certain conditions, sliding is more prone to occur at the bearing-concrete padstone interface. To investigate the mechanical behavior of this interface, reciprocating compression-shear tests were conducted under three levels of contact pressure: low (8 MPa), medium (10 MPa), and high (12 MPa). A three-phase deformation and failure mechanism was revealed, a bulging failure criterion was established, the evolution laws of the shear modulus and friction coefficient were quantified, and a friction coefficient attenuation model was developed. The results show that the bearing hysteresis curves are characterized by a parallelogram shape with internal crescent-shaped abrupt loops. Bidirectional damage transfer occurs at the bearing-concrete interface, evidenced by bulging of the rubber cover layer on the bearing and the presence of rubber debris adhered to the concrete surface. In the sliding friction stage, the shear modulus decreases with increasing contact pressure and consistently remains below the code-specified dynamic shear modulus of 1200 kPa. The interface friction coefficient, measured to be below the code-suggested values of 0.25 and 0.30, exhibits a negative correlation with the contact pressure. It is recommended to control the bearing contact pressure below 10 MPa in practical engineering to avoid the risks of a sudden drop in the friction coefficient and bulging failure. The proposed models can provide a reference for the seismic design of small-to-medium span bridges.

Because of the train operation adjustment considering transfer under the railway line faults, minimizing the total train knock-on delay time and the number of passengers failing to transfer caused by railway line faults was taken as two objectives, and an optimization model for train operation adjustment under the influence of railway line faults was constructed. In light of the model as a large-scale hybrid integer programming model, an improved particle swarm based on Gaussian walk (IPS&GW) was designed. Road network composed of some upward-direction sections of the Beijing–Guangzhou Railway and downward-direction sections of the Zhengzhou–Xuzhou Railway was used to form a testing scenario. The proposed IPS&GW algorithm was used to solve the optimization model for train operation adjustment based on different train operation recovery strategies (strategy Ⅰ–strategy Ⅳ). The results show that compared to strategy Ⅰ, when the disturbance duration of railway line fault ranges from 10 to 30 minutes, the decreasing ratio of train knock-on delay time based on strategies Ⅱ, Ⅲ, and Ⅳ is respectively in the range from 82.5% to 86.6%, from 70.5% to 81.49%, and from 55.8% to 58.7%. The decreasing ratio of the total number of stranded passengers is respectively in the range from 28.3% to 39.1%, from 57.3% to 61.9%, and from 88.4% to 89.4%. Under different disturbance scenarios, a significant decrease in the number of passengers failing to transfer can be achieved by increasing the total train delay time by a certain amount. Finally, the proposed IPS&GW algorithm is compared with the traditional particle swarm optimization (PSO) algorithm. The former shows an advantage in the convergence speed of the objective function, so that the scheduled operation requirements for the train can be met, and the number of stranded passengers in the transfer hub stations is reduced.

To investigate the influence of soil layer dip on the dynamic failure of slopes, the failure characteristics and dynamic response laws of bedrock-overburden layered accumulation slopes with different soil layer dips under seismic action were studied based on shaking table model tests. By varying the bedrock-overburden interface dip, three types of slopes with linear, concave, and convex surfaces were designed. Shaking table model tests were subsequently conducted on these slopes, yielding the failure modes of the three types of slopes with various dips. By taking into account the acceleration amplification effect of slope failure, the soil stress state, and the Mohr-Coulomb strength theory, the dynamic response mechanism of slopes and the critical conditions for slope failure were explored. The test results show that the failure characteristics of the concave slope are concentrated in the upper soil layer during the slope failure process, while those of the convex slope are concentrated in the lower soil layer. By contrast, the linear slope exhibits a failure mode characterized by tensile cracking in the upper soil layer and shear sliding in the lower soil layer. Under the same seismic magnitude, the concave slope exhibits the smallest acceleration amplification coefficient, and the acceleration amplification effects of the linear slope, concave slope, and convex slope are concentrated at the slope crest, slope shoulder, and the rear edge of the slope crest, respectively. With the increase in the various dip coefficients, the critical acceleration for slope failure increases accordingly. The research results can provide a scientific basis for the anti-seismic design, stability evaluation, and disaster prevention and mitigation of engineering projects involving bedrock-overburden layered accumulation slopes.

To clarify the occurrence characteristics and ecological risks of pollutants (e.g., heavy metals and organophosphate esters) in the construction wastewater of drill-and-blast tunnels, two tunnels under construction on the Qinghai-Xizang Plateau were taken as the research objects, and the water quality parameters, pollution characteristics, sources, and environmental risks of the construction wastewater and surrounding water bodies were analyzed. The research results indicate that the construction wastewater exhibits the characteristics of high turbidity (average of 43.7–100 NTU) and alkalinity (pH reaches 8.2–12.0) and contains high concentrations of petroleum pollutants (average concentration of 15.5–22.1 mg/L), which are mainly derived from pollutions such as mechanical lubricants; the metal elements are mainly Fe and Al, and the anions are mainly Cl⁻ and SO₄²⁻, whose main sources are the use of accelerators/coagulants and the dissolution and release of minerals; the total concentration range of OPFRs is 14.0–6 060 ng/L, and the main components include tributyl phosphate and tris (2-chloroethyl) phosphate, which may be sourced from construction materials and lubricants; the environmental risk assessment shows that the maximum value of the risk quotient of 2-ethylhexyl diphenyl phosphate in the tunnel construction wastewater and surface water reaches 0.68–1.83, indicating that it has moderate to high ecological risks, and the accumulation of tris (2-chloroisopropyl) phosphate and trioctyl phosphate in the tunnel construction wastewater is worthy of attention. The migration and transformation patterns of composite pollution during the construction process of high-altitude tunnels are revealed, providing a scientific basis for the optimization of green construction technologies and the precise control of pollutants.

Pantograph slide plates are one of the core components for high-speed trains to obtain electrical energy, and their performance directly affects the current collection quality of the pantograph-catenary system and the operational safety of trains. With the continuous improvement of the operational speed of high-speed railways and the increasing complexity of operational conditions, pantograph slide plates are required to operate stably for a long period under more severe working environments, which imposes higher requirements on their comprehensive performance. The development history of pantograph slide plates was systematically reviewed; the performance advantages and disadvantages of pantograph slide plates at various stages were introduced, and the composition, preparation processes, and research progress of carbon/graphite composite slide plates were summarized. Due to the advantages of light weight, good lubrication performance, and excellent electrical contact stability, carbon/graphite materials have become an important research direction for pantograph slide plates of high-speed trains. However, the further improvement of the performance of current carbon/graphite slide plates still faces many bottlenecks: inherent defects such as pores and microcracks introduced by preparation processes, insufficient interfacial bonding strength between the reinforcement phase and the matrix, and the agglomeration and disordered distribution of the reinforcement phase itself. There are key factors restricting the improvement of their performance. Optimization and surface modification of the reinforcement phase are effective methods to improve the comprehensive performance of carbon/graphite materials. Future research should focus on the design of multi-hybrid reinforcement phases, multi-scale interfacial regulation, and the construction of highly efficient conductive/thermally conductive networks under low filler content, so as to promote the research and development of high-performance carbon/graphite slide plates and their applications in high-speed railways.

At present, most of the studies on the shear strength parameters of waste soil are carried out based on laboratory waste soil samples, and the parameters obtained through laboratory tests are often quite different from the actual parameters, resulting in a large error in the calculation of waste landfill deformation. In view of the error problem caused by the laboratory test, by relying on the closure and restoration project of the waste landfill under construction, the influencing factors and change laws of the shear strength parameters of the waste soil were analyzed by carrying out the large-scale field direct shear test and the small-size laboratory direct shear test of the waste soil and making a comparison with the literature test results. The results show that the shear capability of waste soil is higher than that of traditional soil, and the shear stress continues to rise and tends to be stable with the increase of shear displacement. The density of waste soil is linearly and positively correlated with its shear strength. When the density increases from 750 kg/m³ to 950 kg/m³, the cohesion increases from 22.5 kPa to 34.5 kPa, and the friction angle decreases from 36.7° to 30.2°. The mean cohesion value (14.91 kPa) obtained by the small-size laboratory shear box test is 6.27 kPa lower than that of the large-size field test (21.18 kPa), and the mean friction angle (35.17°) is 6.61° higher than that of the field test (28.56°).

Quasi-static tests were conducted on three types of concrete-filled square steel tube (CFSST) column-H-shaped steel beam joints with external stiffening rings featuring different structures to investigate the seismic performance of prefabricated CFSST column-H-shaped steel beam joints with external stiffening rings. The bearing capacity, failure processes and modes, stress distribution in joint zones, and various seismic performance indicators were studied. The experimental results show that joint failures all occur near the beam ends, characterized by buckling and fracture failure of the beam sections outside the diaphragm. The hysteresis curves of the joints all exhibit a “spindle shape” with significant pinching effects. The loading process is essentially symmetric in the positive and negative directions, with a sliding segment of zero rotational stiffness observed in the curves. The ductility coefficient of joints ranges from 2.55 to 4.20, and the ultimate angle of rotation is between 0.032 rad and 0.062 rad, both exceeding the requirements specified in seismic codes. Compared to the integral external stiffening rings, the separate external stiffening rings exhibit increases of 60.7% in ductility and 209% in cumulative energy dissipation. Meanwhile, the cantilever energy-dissipating external stiffening rings show improvements of 38.1% in bearing capacity, 64.7% in ductility, and 400.3% in energy dissipation capacity over the integral connection. This indicates that the structural configuration of “separate multi-layer force transfer” and “dual-stage energy dissipation via cantilever segments and energy-dissipating cover plates” can effectively optimize the seismic performance of joints. There is sound agreement between the simulated and experimental hysteresis curves and failure modes, validating the numerical analysis reliability.

When maglev vehicles operate at an ultra-high speed, boundary conditions such as track irregularity and air resistance significantly affect the operational safety and stability of the vehicles. Based on the polymorphic coupled dynamic simulation test platform for rail transit, a dynamic model of an ultra-high-speed maglev model vehicle system was established, which considered conditions including superconducting pinning suspension and guiding force characteristics, air resistance, and track irregularity. The traction, coasting, and braking conditions achieving a maximum speed of 1,500 km/h on a 1.6 km test line were simulated. Based on the dynamic model, the vibration responses of the model vehicle system operating under different multiples of track irregularity amplitude, speeds, and limit clearances were simulated and analyzed. The results indicate that under a low-vacuum environment, when the track irregularity amplitude is 0.15 mm, and the maximum speed is 1,500 km/h, the mover exhibits a left-and-right swing vibration form during operation, and the maximum vertical displacement of the Dewar reaches 4.88 mm. As the operating speed of the model vehicle system increases, the system vibration strengthens, and the amplitudes of various dynamic indicators show an upward trend; an increase in the lateral limit clearance is beneficial to weaken the lateral vibration of the model vehicle system, while an increase in the vertical limit clearance intensifies the vertical vibration of the model vehicle system. The research results can provide a theoretical reference for the design of the ultra-high-speed maglev dynamic simulation test platform.

To improve the detection accuracy of the mover position of a primary segmented winding linear motor and reduce the direct current (DC) bias and harmonic interference introduced into the output signals of magnetoresistive sensors by harmonic magnetic fields, temperature variations, and other factors, a position detection method based on a frequency-adaptive cascaded delayed signal filter was investigated. First, a frequency-adaptive cascaded delayed signal filter was designed to suppress DC bias and multi-order harmonic disturbances by introducing signal delay and cascading the filters, thereby addressing the limitations of traditional methods, which required prior knowledge of harmonic orders and showed poor filtering performance for interferences near the fundamental frequency. Second, combined with type-Ⅲ phase-locked loop technology, quadrature phase locking was performed on the filtered signals to achieve synchronous extraction of the motor’s magnetic pole angle and mover position information. Finally, an experimental platform for the primary segmented winding linear motor was established to verify the filtering performance and position detection accuracy of the proposed method. The research results indicate that the proposed filtering method can effectively suppress harmonic voltages near the fundamental frequency and DC bias without relying on a motor model; under complex harmonic interference conditions, compared with the detection scheme combining traditional filters and phase-locked loops, it reduces the estimation error of the mover position of the linear motor by 68.75%.

To address two-phase flow problems with complex gas-liquid interface topology variation, a numerical simulation method capable of balancing computational efficiency and interface resolution accuracy was proposed. First, quadtree/octree Cartesian meshes with tree data structures were employed for spatial discretization. Adaptive mesh refinement was developed by leveraging the mesh’s hierarchical structures. Second, the continuum surface force (CSF) model was implemented within the adaptive mesh framework. By applying double convolution blurring to the volume fraction, the surface tension was smoothly distributed to the interface neighborhood, and the piecewise linear interface reconstruction technique was utilized to track the gas-liquid interface accurately. Subsequently, a mesh refinement criterion was established, and both the discrete error based on wavelet analysis of flow field velocity and the interface curvature distribution were considered, thereby achieving dynamic refinement in regions with sharp flow field variations and phase boundaries. Finally, the accuracy and reliability of the algorithm were validated through numerical examples of classic gas-liquid two-phase flow. The results show that in the verification of the Laplace law of surface tension, when the interface curvature is adopted as the refinement criterion, the computational error of internal and external pressure difference is only about 3.0%, which is significantly superior to the error range from 7.5% to 24% when using the volume fraction as the criterion, and its accuracy is consistent with that of uniform fine meshes. The proposed method can reduce the computational time consumption by approximately one order of magnitude compared with uniform fine meshes. In the numerical examples of surface tension waves, the root mean square error between the numerical solution and the theoretical solutions of regular modal can be reduced to the order of 10⁻⁵. In the simulation of a head-on collision between binary droplets, the experimentally observed dumbbell-shaped and diamond-shaped deformation sequences are reproduced, and the complex interface topology evolution details such as gas film rupture and the formation of tiny bubbles are captured.

In order to study the pullout characteristics of grouted enlarged toe precast pile (referred to as GET pile), a pullout experiment was carried out in a laboratory sand model box. Firstly, precast pile model with enlarged pile toe was assembled by connecting polyvinyl chloride (PVC) pipes and enlarged parts. Then, strain sensors were installed in the pile shaft, and the loading device and gravity sensor were arranged on the top of the piles. The pullout curves of different pile types were obtained by applying load on the top of the piles. Finally, the pullout bearing characteristics of the piles with equal cross section, piles with enlarged pile toe, and GET piles were compared, and the effects of enlarged base and grouting on pullout bearing characteristics were discussed. The experiment results show that GET pile can effectively improve the pile’s pullout bearing capacity. At small displacements, the pullout bearing capacity of piles with enlarged pile toe is twice that of piles with equal cross section and 5–6 times that of piles with pile side grouting. In addition, GET pile changes the mobilization characteristics of side friction resistance of the piles with equal cross section. The enlarged pile toe can increase the mobilization speed and maximum value of total side friction resistance and provide a certain amount of resistance at the pile end in the pullout process. Grouting can enhance the resistance on the pile side and the pile end, providing the initial total side friction resistance for the upper half of the pile shaft. There is a tendency to distribute more loads to the enlarged pile toe.

The system vibration caused by thrust ripple in double-sided linear induction motors (DSLIMs) is an urgent problem to be solved in precision control fields such as high-speed electromagnetic propulsion, rail transit, and industrial drives. An in-depth study on the secondary structure of DSLIMs was conducted, and an arrow-shaped secondary design was proposed to reduce thrust ripple. First, the key shape parameters of the arrow-shaped secondary design were derived. Three-dimensional finite element models of DSLIMs incorporating flat, square-misaligned, and arrow-shaped secondary designs were established to analyze their thrust output characteristics. Then, the eddy current distribution features and layered thrust distribution characteristics of different secondary structures were compared to elucidate the mechanism of thrust ripple suppression by the arrow-shaped secondary design. Finally, the thrust of the arrow-shaped secondary structure before and after optimization under motion conditions was compared using a three-dimensional transient finite element model. The results indicate that the optimized arrow-shaped secondary design improves the utilization of secondary conductors and enhances the thrust ripple suppression effect by optimizing the eddy current path in the end regions. In the region near the operational slip, the thrust ripple rate can be reduced to below 2%, and the thrust under the same mass can reach 21.51 kN, representing an increase of 1.03% compared with the square-misaligned secondary design.

To address the severe interference problem caused by non-orthogonal multiple access (NOMA) and device-to-device (D2D) technologies in enhancing the capacity of heterogeneous cellular networks, an efficient resource allocation algorithm was proposed to improve the system and rate. Firstly, a reconfigurable intelligent surface (RIS)-assisted heterogeneous cellular NOMA-D2D communication network model was constructed. Under the constraints of signal-to-noise ratio (SNR) of users, transmission power, and unit membrane of RIS phase shift, an optimization problem aiming to maximize the number of D2D users and rate was established. However, this problem was a mixed integer nonlinear problem and was difficult to solve directly. Therefore, it was decomposed into three sub-problems: D2D user-cellular user (CU) matching, D2D user power control, and RIS reflection phase shift optimization. Based on this, the D2D cluster channel allocation was completed by using the bipartite graph maximum matching algorithm, and a deep reinforcement learning algorithm based on a deep deterministic gradient strategy (DDPG) was proposed to jointly optimize the D2D transmission power and RIS phase shift matrix. Simulation results show that under the same conditions, the average value of the D2D link and rate of the proposed algorithm increases by 1.96%, 10.64%, and 14.29%, respectively, compared with that of the game algorithm, random phase shift algorithm, and RIS-assisted-free algorithm, verifying its effectiveness in interference suppression and spectral efficiency improvement.

To improve the torque transmission control accuracy of the shift clutch in hydraulic mechanical transmission (HMT) and enhance its shift quality, an adaptive sliding mode control method based on linear quadratic optimization was proposed. Firstly, the shift dynamics model of HMT and the numerical model of the clutch were constructed. Secondly, the optimal torque transmission trajectory of the shift clutch was solved under the target functional based on the linear quadratic optimization model. Combined with the dynamic friction coefficient model, the trajectory variable was converted into the expected oil pressure trajectory considering the time-varying effect of the lubricating oil film and the dynamic contact characteristics of the friction interface. Finally, the adaptive sliding mode control algorithm was used to track and control the expected oil pressure trajectory. Simulation results show that compared with the direct application of the linear quadratic control scheme, the proposed algorithm effectively improves the torque transmission control accuracy of the shift clutch, shortens the shift time by 13.8%, reduces the sliding friction work by 11.2%, and decreases the maximum shock by 39.1%. Experiments further confirm that the algorithm not only effectively improves the torque transmission control accuracy of the shift clutch but also improves the shift quality of HMT. The research results can provide a reference for the formulation of shift control strategies in the engineering application of HMT devices.

To address the design challenges of heat dissipation and energy efficiency caused by air friction loss in the air gap of high-speed permanent magnet motorized spindles, the formation mechanism of windage loss and the evolution laws of vortex flow under the coupled effect of stator slots and axial ventilation cooling were revealed. First, an ideal air-gap model with smooth walls and a realistic air-gap model containing 18 stator slots were established, respectively. Second, the independent impact of stator slots was quantitatively evaluated by comparing the energy dissipation differences between the two air-gap models under the condition of no axial ventilation. Finally, the nonlinear regulation effect of ventilation intensity on the internal flow field structure and energy dissipation characteristics of the air gap was systematically evaluated by applying axial cooling airflows at different velocities. The results indicate: 1) stator slots are the decisive factor leading to the surge of windage loss. Compared with the ideal air gap with smooth walls, the increase in additional loss caused by stator slots is nearly 80%. 2) In the air gap containing stator slots, the regulation of loss by axial ventilation exhibits significant non-monotonic and multi-stage characteristics: After weak axial ventilation is introduced, the loss decreases to the minimum at 2 m/s, with a decrease of more than 19%; when the flow velocity enters the critical range of 6–10 m/s, the flow field instability leads to a sharp surge in energy dissipation by over 26%; when the flow velocity exceeds 10 m/s, the vortex suppression effect dominates the flow field to restore stability, and the energy dissipation shows a steady and monotonic increasing trend after a sudden drop.

To provide a more realistic geometric irregularity spectrum for high-temperature superconducting (HTS) pinning-type maglev systems, the irregularity spectrum of permanent magnet (PM) tracks considering structural periodicity was investigated. To achieve the characterization and inversion of the PM track irregularity spectrum that incorporates structural periodicity, a finite element model of an HTS maglev bridge and its PM track was first built. Moving loads from a maglev train were then applied to the model to identify the most unfavorable loading position, and the displacement at this point was extracted as the dynamic irregularity. Next, by considering the deformation of the PM track caused by bridge creep camber and superimposing the periodic dynamic irregularity results from train loads, a sample of periodic track irregularity was formed. Furthermore, random assembly errors of the PM track were modeled using a white noise filtering method to obtain a sample of random geometric irregularity. This was then superimposed with the periodic irregularity to form the overall PM track irregularity spectrum. The irregularity spectrum was fitted using a 4th-order polynomial and a Lorentzian function, and the fitted spectrum was inversely transformed via the inverse Fourier transform to verify the effectiveness of the fitting method. Finally, the influence of train speed on the fitted irregularity spectrum was analyzed. The results show that train speed mainly affects the PM track irregularity spectrum in the wavelength range of 3–100 m; when the speed approaches the critical resonance speed of the bridge, the amplitude of the inverse-transformed irregularity becomes significantly larger. The irregularity spectrum obtained in this study can be readily applied in the dynamics calculations of HTS maglev vehicles, serving as input for the dynamic analysis and design optimization of HTS maglev trains operating at various speed levels.

To investigate the influence of rail corrugation coupled with wheel concave wear on the dynamics characteristics of the high-speed train’s wheel-rail system and determine the safety threshold for rail corrugation in high-speed railways, based on vehicle-track coupling dynamics theory and field-measured rail corrugation data of a certain line, a vehicle-track rigid flexible coupling dynamics model of the CRH3 high-speed train was established. Rail corrugation superimposed on the Wuhan–Guangzhou track irregularity spectrum was used as the excitation input.. The influence of rail corrugation with different wavelengths and depths on wheel-rail dynamics characteristics was explored, and the coupling effect of wheel concave wear at different operation mileages with rail corrugation on vehicle subsystem’s vibration acceleration was analyzed. Then, the safety threshold for rail corrugation was proposed. Results show that rail corrugation significantly increases the wheel-rail vertical force. The coupled action of wheel concave wear and rail corrugation further amplifies the wheel-rail force response, with more severe concave wear leading to greater wheel-rail forces. Worn wheels that have traveled 200 000 km show an 10.8% increase in wheel-rail vertical force compared to new wheels. By considering wheel concave wear, for high-speed trains operating at an average speed of 300 km/h, the recommended safety thresholds for rail corrugation of 50 mm, 80 mm, 100 mm, 120 mm, and 150 mm are wave depths of 0.023 mm, 0.036 mm, 0.05 mm, 0.054 mm, and 0.069 mm, respectively. In practical applications, maintenance strategies should be adjusted according to specific operating conditions and track structures, and grinding should be carried out promptly when wave depths exceed the safety thresholds.

Water and mud inrush is one of the common geological disasters in karst tunnels, which poses a severe threat to the safety of tunnel construction and long-term operation. Therefore, ensuring the safety of water-resistant rock mass at the face is the key to the prevention and control of water and mud inrush disasters. To ensure the stability of water-resistant rock mass at the face under the action of strong seepage, a mechanical analysis model of water-resistant rock mass in strong seepage fractures at the tunnel face was constructed. The drag force effect generated by the water flow on the wall of the penetrating fracture was fully considered, and the minimum safe thickness formula of the water-resistant rock mass in the karst tunnel under the action of strong seepage was systematically derived. Parameter sensitivity analysis and engineering examples were employed; the stability of the surrounding rock during tunnel excavation was further investigated by using the finite-difference software FLAC3D, considering penetrating fractures and water-rich karst cavities ahead of the tunnel face; the influence mechanism of key parameters on the stability of the water-resistant rock mass was discussed in depth. The results show that the increase of fracture opening significantly enhances the effect of the drag force. Under the condition of strong seepage, the fracture drag force has a significant adverse effect on the minimum safe thickness of the water-resistant rock mass, and its influence degree increases nonlinearly with the increase of fracture opening. In addition, the influence of fracture at different location distributions on the minimum safe thickness shows significant differences. It is found that there is a critical transition point (height ratio of cantilever beams Ⅰ and Ⅱ = 5.07∶4.93) at which the upper and lower beams and slabs of the fracture are destroyed synchronously, which further reveals the internal relationship between the fracture location and structural instability. The findings of this study can provide a theoretical basis and engineering guidance for designing the thickness of water-resistant rock mass in karst tunnel face, mitigating karst-related disasters (e.g., grouting sealing, fracture reinforcement, and seepage control), selecting monitoring and early-warning indicators, and conducting risk classification during construction.

To establish a wheel-rail broadband excitation model for numerical simulation and prediction of metro vibration noise, a study was conducted on the selection for long-wave irregularity of metro rail and wheel-rail short-wave roughness spectra based on measured data of long-wave irregularity of metro rail and rail surface roughness from Beijing metro lines, as well as wheel tread out-of-roundness (OOR) from Qingdao metro lines. Firstly, the Welch method was applied to the measured data of rail irregularity to estimate the power spectral density, and the expressions for the short-wave irregularity power spectrum of rail and the OOR power spectrum of wheel, as well as their fitting parameters were provided. In terms of long wavelength, typical rail spectra were selected according to the principle of similarity in individual high and low TQI values corresponding to speed classes. Regarding short wavelength, the short-wave irregularity power spectrum of the rail surface and the OOR power spectrum of the wheel were respectively divided into five grades based on quartiles, and a wheel-rail roughness spectrum was proposed by considering their coherence. The results show that the selected American sixth grade spectrum aligns well with the long-wave (1–42 m) irregularity power spectrum of metro lines with 80 km/h designed by Beijing, according to the principle of similarity in individual high and low TQI values. Both the short-wave irregularity power spectrum of the rail surface and the wheel OOR power spectrum exhibit a significantly skewed amplitude distribution under the same short wavelength. The wheel-rail roughness spectra of different levels in the short-wave range of 0.01–1.00 m are mainly dominated by the wheel OOR spectrum, and in severe cases, it even exceeds the short-wave spectrum recommended by the China Academy of Railway Sciences.

To investigate the flood resistance performance of traditional timber corridor bridges with cantilevered beams and the effectiveness of flood resistance measures, a quantitative analysis of flood loads and flood resistance performance was conducted under various flood conditions and flood resistance measures. First, flood loads on the superstructure of the corridor bridge were obtained using computational fluid dynamics (CFD) simulations, and the effects of water levels, flow velocities, and weatherboard removal were investigated. Next, the distribution of flood loads on main components was analyzed at the moment of maximum drag force of the superstructure. Finally, the flood resistance performance of the corridor bridge was assessed by calculating the sliding and overturning risks of the superstructure, and the enhancement effects of weatherboard removal and deck weighting on flood resistance performance were quantitatively evaluated. The results show that the drag force on the superstructure increases by 145.38% and 95.71% with the increase of water level and flow velocity, respectively. In the presence of weatherboards, the drag force is primarily distributed on the upstream weatherboard and the cantilever beams along the longitudinal axis of the bridge. After removing weatherboards, the drag force is mainly distributed on the cantilever beams along the longitudinal axis and the main beams. Under baseline flood conditions, the maximum drag force on the superstructure decreases by 17.79%; the reduction reaches 48.08% under high water level conditions; while an increase of 1.51% is observed under high flow velocity conditions. As the water level rises, the lift force acting on the superstructure increases rapidly and then stabilizes. Removing weatherboards can reduce the maximum lift force but leads to an earlier occurrence of the peak lift. The corridor bridge faces sliding failure risks under both high flow velocity and high water level conditions. When the uniformly distributed load added to the bridge deck reaches 4.0 kN/m², the stability of the corridor bridge under the most unfavorable conditions can be ensured. If weatherboards are simultaneously removed, the required uniformly distributed load on the bridge deck can be reduced to 0.5 kN/m² and 2.5 kN/m² under high flow velocity and high water level conditions, respectively.

The short primary linear induction motor (SPLIM) contains both longitudinal dynamic end effect and core saturation effect during operation, and its equivalent electromagnetic parameters are difficult to be calculated accurately by the traditional analytical method due to the mutual coupling and nonlinear influence of these two effects. To this end, the analytical calculation method of the equivalent electromagnetic parameters of SPLIM under the influence of multi-factor coupling was proposed. Firstly, the improved equivalent circuit of SPLIM under the influence of multi-factor coupling was analyzed. Secondly, the one-dimensional electromagnetic field model of SPLIM and the magnetic circuit considering the core reluctance were established, and the differential equations of the air-gap flux density containing the speed factor and core permeability were derived according to Ampère’s circuital law. The air-gap flux density at each position was calculated by the iterative method and the core magnetization curves. Next, the excitation inductance and secondary resistance under different operating conditions were calculated according to the magnetic chain method and the equivalent loss method, respectively. Finally, a transient field simulation model of SPLIM was established in ANSYS Maxwell. Results reveal that the maximum error between the analytical results for excitation inductance and the finite element results is 6.8%, while the maximum error between the analytical results for secondary resistance and the finite element results is 6.4%. The thrust calculated based on equivalent parameters is in good agreement with the experimental data, further validating the accuracy of the proposed analytical method.

To investigate the mechanical meso-mechanism and macroscopic response of coarse granular materials in rockfill dams, and to overcome the limitations of traditional continuum-based methods in simulating force chain evolution and particle breakage, a continuous-discontinuous deformation analysis method suitable for triaxial tests on coarse granular materials was developed. This method, based on the traditional discontinuous deformation analysis (DDA) framework, introduced a hybrid displacement mode to differentiate the mechanical responses of various blocks. Critical damping was employed to accelerate computational convergence, and a continuous-discontinuous simulation technique was proposed to characterize particle breakage. Through conventional triaxial numerical simulations, the deformation evolution, force chain development, particle breakage, and shear band formation during loading were analyzed, with particular emphasis on the effects of size and end friction. The results indicate that the simulation outcomes agree well with experimental data, reflecting both the macroscopic mechanical response and meso-mechanisms of coarse granular materials. The size effect leads to a 21.3% increase in peak stress under 0.4 MPa confining pressure, whereas its influence becomes negligible at 3.0 MPa. Under 3.0 MPa confining pressure, end friction contributes to an approximately 7.4% increase in peak stress. This study provides an effective numerical tool for further understanding the mechanical properties of coarse granular materials.

To address the issues of uneven transverse distribution of compressive stress in existing carbon fiber-reinforced polymer (CFRP) plate anchorage technology, which leads to tearing failure of plates under tension and the difficulty in controlling bolt preload, a dual-curved CFRP plate anchorage was developed. This device’s main construction features were outer clamping plates with transverse arc surfaces to ensure uniform transverse distribution of compressive stress sustained by the CFRP plate and inner clamping plates with longitudinal arc surfaces to fully compress the middle section of the anchorage zone and avoid shear failure at the ends. The compressive displacement of the outer clamping plates was controlled by the limit plate to anchor the CFRP plate with the required preload. The anchorage performance test for six groups of new anchorage specimens was carried out to explore their stress-bearing principle. Finite element software ANSYS was used to perform stress simulation; the key parameters affecting anchorage performance were deeply analyzed; the stress-bearing performance of CFRP plate anchorage was compared with that of flat-plate anchorage. The results indicate that the thickness of the outer clamping plates is the dominant factor influencing the non-uniform transverse distribution of compressive stress sustained by CFRP plates. When the thickness of outer clamping plates is 27 mm, the CFRP plates exhibit a higher uniform transverse distribution of compressive stress, with a compressive stress difference of only 9.3 MPa between maximum and minimum values. The curved surface design of inner and outer clamping plates effectively optimizes the compressive stress distribution state of the CFRP plate, while minimizing stress difference among carbon fibers and resulting in significantly improved synchronization of transverse deformation of CFRP plates. Although the specimens ultimately fail in a tearing state, the new anchorage achieves an exceptional anchoring efficiency coefficient of 104.16%.

High-temperature active magnetic bearing technology is a key technology to replace traditional bearings and achieve stable operation under high-temperature and high-speed conditions. Its design complexity is significantly higher than that of ambient-temperature magnetic bearings. Based on relevant Chinese and international research literature, the research progress of high-temperature active magnetic bearings in four aspects, including material selection, mechanical system manufacturing processes and fail-safe mechanisms, high-temperature displacement sensor design, and rotor system modeling and dynamic characteristic analysis, was systematically reviewed. Furthermore, in-depth research in directions such as multi-physics coupled high-fidelity modeling, active vibration control strategies, multi-scenario application adaptability, and material-control-structure co-optimization was proposed as a future focus, to improve the reliability and engineering applicability of high-temperature magnetic bearing systems, and theoretical basis and technical support were provided for their stable operation in extreme environments.

As the seismic design philosophy of bridges gradually shifts from performance-based to resilience-oriented, the current research focus lies not only in ensuring structural safety under the action of earthquakes, but also in paying more attention to the preservation and recovery capacities of post-earthquake traffic function. Railway bridges serve as critical nodes in transportation networks, and their post-earthquake traffic capacity directly influences the operational efficiency of the lines and the recovery process of earthquake-stricken areas. Based on this, a shear-type viscoelastic damper was proposed to decrease track damage risk by controlling the relative transverse displacement of main beams, thereby enhancing the bridge’s post-earthquake traffic function. By taking a typical five-span railway simply-supported bridge as a case study, a comparative analysis was conducted on the traffic function vulnerability, post-earthquake function recovery capacity, and seismic resilience in the three constraint conditions of no constraint (NC), steel restrainer (SR) only, and SR combined with the shear-type viscoelastic damper (DP). The analytical results demonstrate that proposing the concept of a “component recovery weight coefficient” provides a quantitative index for determining the sequence of component repairs. Additionally, the proposed shear-type viscoelastic damper can significantly control the relative transverse displacement of main beams at beam ends, effectively reducing track alignment irregularity under the strong action of earthquakes and consequently enhancing the bridge’s post-earthquake traffic function. The addition of the viscoelastic damper to SR can notably shorten the post-earthquake repair time. In particular, under higher ground motion intensities, such as peak ground acceleration (PGA) of 0.8g, the repair time can be reduced by up to 9.1 days compared to the NC system. Furthermore, the DP configuration demonstrates significantly better post-earthquake residual traffic function and seismic resilience indices than the SR and NC configurations at various PGA levels. For instance, under PGA=0.4g, the post-earthquake residual traffic function improves by 20.0% and 56.9%, and seismic resilience increases by 13.1% and 34.4% respectively, confirming the remarkable effectiveness of this device in enhancing both post-earthquake traffic function and seismic resilience of bridges.

Fabric anisotropy is an important factor affecting the mechanical properties of sandy soil, and the formation disturbance caused by shield tunnel excavation in sandy soil is largely affected by the mechanical properties of the overlying sandy soil. This study utilizes the two-dimensional discrete element method to model particles as overlapping ellipse-like clusters, specifically arranging the long-axis orientation to create sand samples with varying anisotropy. The long-axis orientation and horizontal deposition direction form the bedding plane. A two-dimensional RVE biaxial test shows that the peak friction angle initially decreases and then increases with the bedding angle, aligning with experimental findings. Subsequently, strata with different bedding angles are generated, and tunnel excavation is analyzed based on Park's stratum loss model. In anisotropic strata, the disturbance range exhibits asymmetry about the tunnel's central axis. The surface settlement curve divides into three zones: influence, expansion, and weakening. The effect of bedding angle is evident only in the influence and expansion zones. Maximum settlement occurs at a bedding angle of 0°, while it is minimized at 45°. As the bedding angle increases, maximum settlement trends upward on the left side and downward on the right side of 45°. The principal stress deflection of the tunnel correlates with the displacement-induced asymmetry. In the samples with bedding angles of 0° and 90°, the main direction of the distribution of the contact normal did not change.

A fuzzy dual-adaptive zero-power control method based on a high-order sliding mode observer was proposed to address issues of saturation, response lag, and insufficient disturbance rejection caused by current integration in the zero-power control of permanent magnet electromagnetic hybrid suspension systems. The method comprehensively considered both no-load lifting and load variation operating conditions. First, based on the system mathematical model, a high-order sliding mode observer was designed to estimate the lumped disturbance and error variation rate. Second, feedforward compensation was introduced into the proportional derivative (PD) controller according to the observer output, achieving fast and stable tracking of the suspension gap and dynamic compensation of disturbance forces. Further analysis was conducted on the impact of current integration on dynamic and steady-state performance under both no-load lifting and load variation conditions. Finally, a fuzzy dual-adaptive algorithm was proposed. A two-dimensional fuzzy algorithm was used to optimize the integral coefficient of the current loop online, while the learning rate was dynamically adjusted based on a hyperbolic tangent function, enabling adaptive adjustment of the integral gain weight according to the system dynamics. This effectively suppressed integral saturation and improved system response speed. The research results show that under no-load lifting conditions, the simulation and experimental response time of the proposed method is 0.12 s and 0.25 s, respectively, with no overshoot. Under sudden load variation conditions, the simulation and experimental response time is 0.10 s and 0.15 s, without overshoot. Under continuous load variation conditions, the current error does not exceed ±0.35 A, and no overshoot occurs. Compared with methods using fixed learning rates and fixed current integral coefficients, the proposed method reduces response time by at least 14.2% with zero overshoot.

To investigate the effects of continuous braking conditions on the maximum temperature and temperature difference of wheel tread and clarify thermal load characteristics of the wheel, continuous braking tests on the super-long large ramp were conducted on a 1∶1 brake test bench, with the friction pair of brake shoe and wheel tread taken as the research object. The distribution pattern of tread temperature during braking was analyzed by changing three key parameters: braking pressure, speed, and duration. Results demonstrate that when the braking speed increases from 40 km/h to 70 km/h, the maximum temperature during the three braking phases (0–1 200 s, 1 200–2 400 s, and 2 400–3 600 s) increases by 97%, 118%, and 86%, respectively, and the maximum temperature difference rises by 113%, 150%, and 128%, respectively. The increase in braking speed exerts a greater influence on temperature difference during the first two stages, which is attributable to the lower temperature of the initial friction surface and the wear-resistant properties of brake shoe contact areas that constrain expansion of contact areas. At a braking speed of 70 km/h, when the braking pressure increases from 3 kN to 7 kN, the maximum tread temperature increases from 321 ℃ to 436 ℃, representing a 36% increase. The increase in the braking pressure enhances the friction power and amplifies the effect of local contact on the friction temperature, which further exacerbates the uneven distribution of tread temperature. Under the braking pressure of 3 kN, augmentation of speed from 40 km/h to 70 km/h increases the maximum tread temperature from 176 ℃ to 328 ℃, representing an 86% increase. Increasing the braking speed can boost braking energy and increase braking power, which significantly expands the high-temperature regions. This study can provide a reference for analyzing the tread braking performance and developing operational strategies of rolling stock under super-long large ramps.

In order to meet the requirements for driving performance of railway bridges, it is necessary to control the smoothness of the bridge alignment. Based on the analysis of driving stability, the sensitive wavelength range of the vehicle body was determined. The amplitude of the completed bridge alignment within the range was adopted as the evaluation criterion. From the perspective of ensuring driving performance, by considering the self-adjustment capability of ballastless tracks and the relationship between the track surface alignment and the completed bridge alignment, the expression of the irregularity limit value for the completed bridge alignment was derived. A seven-span continuous steel truss girder bridge was taken as the research object. The irregularity amplitude of the completed bridge alignment within the sensitive wavelength range of the vehicle body was controlled according to the derived expression. A method for controlling the smoothness of the girder assembly alignment based on the target alignment of the completed bridge was proposed by combining Akima spline curve with the girder assembly curve. The research results show that the sensitive wavelength of the vehicle body is less than 200 m at driving speeds of trains ranging from 250 km/h to 350 km/h. If a seven-span continuous steel truss girder bridge is taken as an example, the irregularity limit values for the completed bridge alignment within the sensitive wavelength ranges of the vehicle body corresponding to speeds of 350 km/h, 300 km/h, and 250 km/h are 24, 26 mm, and 29 mm, respectively. The irregularity amplitude within a 0–200 m wavelength range of the girder assembly alignment can be evaluated and controlled through the proposed method for controlling the smoothness of the girder assembly alignment.

To clarify the distribution and migration characteristics of volatile organic compounds (VOCs) in organic pollution sites, 120 soil and 48 soil gas sampling holes were arranged at a site where a chemical plant was once located, and 97 pairs of soil/soil gas samples were collected from 14 holes in the heavily polluted area. The pollutant concentrations in the samples were determined through laboratory analysis. The distribution characteristics of the pollutants were analyzed using Sufer software, and the distribution and migration characteristics of trichloroethylene (TCE) were interpreted in combination with the stratigraphic lithology. The applicability of two models for predicting the content of soil gas VOCs was analyzed with predicted and measured values. The results show that as the hole depth increases, the TCE concentration in the soil in the heavily polluted area decreases with an exceedance rate of 50.4%. The maximum value is in the clayey silt layer (1610 mg/kg), exceeding the standard by 2300 times. The TCE concentration in soil gas first increases and then decreases, with the maximum value occurring in the sandy soil layer (643 mg/m³), exceeding the standard by 546 times with an exceedance rate of 97.9%. The TCE concentration in soil and soil gas outside the heavily polluted area first increases and then decreases with soil depth, and the exceedance rate is 6.6% and 54.9%, respectively. The horizontal migration of TCE is weaker than its vertical migration. The area that exceeds the standard first increases and then decreases with soil depth, and the average exceedance area is 7.3 × 10³ m². TCE in soil gas spreads rapidly from the heavily polluted area to the surrounding areas. The exceedance area covers the entire chemical plant area and pollutes the area outside the chemical plant. The average exceedance area is 2.4 × 10⁴ m². Based on the soil TCE concentration, both the linear model and the dual equilibrium desorption (DED) model can predict the soil gas TCE concentration. The proportion of data points with a prediction error of one order of magnitude or less for the two models is 78.6% and 71.4% for the fill and sandy soil, respectively. Regression analysis shows that the DED model predicts soil gas TCE concentrations more close to the actual values for fill (irreversible adsorption degree f = 0.1), silty clay (f = 1.0), and clayey silt (f = 0), while the linear model and DED model yield relatively close predictions of soil gas TCE concentrations for sandy soil. When a pollution assessment and secondary development of similar sites are conducted, the concentrations of soil gas pollutants should be monitored or predicted to avoid underestimating the degree and scope of site pollution.

To investigate the stability of the bogie in a straddle-type monorail vehicle, the Hopf bifurcation characteristics of the straddle-type monorail vehicle bogie system were analyzed based on the spatial perturbations of the mechanical properties under the wheel-rail contact relationship. Firstly, a three-degree-of-freedom nonlinear dynamic model of the vehicle bogie, incorporating spatial perturbations, was established. Secondly, the Hurwitz stability criterion was employed to solve for the critical speed of the bogie system, and the type of Hopf bifurcation was identified via the center manifold stability index. The theoretical results were further validated numerically using the MATCONT toolbox. Finally, the influence of different spatial perturbation conditions on the stability of the bogie system was discussed. The research results show that at a motion state of low speeds, the bogie primarily exhibits rolling motion with a frequency of 2.4 Hz; at a motion state of medium and high speeds, the motion is dominated by coupled yawing and rolling, with frequencies ranging from 1.3 Hz to 2.4 Hz. When the speed reaches 163.563 24 km/h, the system undergoes a supercritical Hopf bifurcation, resulting in the emergence of a stable limit cycle; at a speed of 163.563 60 km/h, a saddle-node bifurcation occurs, leading to an unstable limit cycle. Under spatial perturbations, the critical speed of the bogie decreases with increasing radial stiffness of the guiding wheel and radial damping of the stabilizing wheel but increases with greater radial damping of the guiding wheel, radial stiffness of the stabilizing wheel, as well as the radial stiffness and damping of the running wheel. Moreover, changes in the structural parameters of the bogie can induce transitions between supercritical and subcritical Hopf bifurcations. To avoid subcritical Hopf bifurcations that may cause abrupt changes in the system’s motion state, the structural parameters of the bogie should be carefully designed.

Variable marking intervention in expressway weaving sections based on the cellular automaton was proposed by combining the advantage that variable markings can flexibly change the marking form according to the needs of traffic scenarios and provide more marking control strategies to solve the problems of fixed marking control in the weaving sections of urban expressways, with the intervention effect evaluated. First, the cellular automaton model was built based on the three-phase traffic flow theory to provide a basis for fuzzy controller building. Second, the strategy library of active variable marking intervention was generated, and the fuzzy controller was constructed to realize the full-time simulation of weaving section scenarios under variable marking control. By selecting the coil data of weaving sections and typical traffic flow data during peak periods in Shanghai as the traffic flow input for full-time simulation, the output was obtained for the marking control scheme. Finally, the intervention effect was evaluated in terms of operation efficiency, potential accident risk and pollutant emission. The results show that the average delays of the scenarios of real working conditions and designed working conditions are significantly reduced under variable marking intervention compared with ordinary markings, with the average delay of the designed working conditions decreasing from 71 to 48 s. The number of hazardous scenarios under variable marking intervention in real working conditions is reduced by 23.4% compared with ordinary markings. The mean values of several important pollutants emitted by the vehicles are significantly reduced.

In view of the problems of low efficiency and high cost associated with current three-dimensional (3D) printing methods for fabricating physical terrain models, a rapid printing method for terrain models based on improved K-dimensional (KD) tree spatial segmentation was proposed, aiming to enhance printing efficiency and reduce material consumption. First, the correlation between digital terrain model features and 3D printing parameters was analyzed to establish a rule set of spatial segmentation constraints. Subsequently, an improved KD tree model integrating dimension adaptation and size constraints was constructed, overcoming the rigid limitations of positions and dimensions in traditional segmentation and achieving refined segmentation for the terrain model and effective removal of underground sections. Building upon this foundation, a rapid spatial segmentation algorithm incorporating a greedy strategy was designed. This algorithm maximized the hollowed-out volume of the base by pursuing locally optimal segments. Micro terrain areas were integrated by means of regional clustering to optimize the sub-block segmentation results. For each terrain unit after segmentation, a rapid prototyping method based on block-based parallel and inverted printing was proposed. Fine support structures at four corners prevented model distortion while enabling substantial base hollowing and reducing material consumption and printing time. Finally, an experimental environment was established; case experiments and analysis were carried out; five typical disaster terrain data, including earthquakes, wildfires, floods, landslides, and debris flows, were selected for printing validation under conditions of varying resolutions and spatial scales. Research results demonstrate that the proposed method effectively overcomes the rigid limitations of traditional segmentation and the problem of model sagging distortion in fused deposition modeling. Across cases of the five disaster types, the approach achieves an average reduction of 17.69% in 3D printing time and 28.98% in material consumption. This facilitates rapid and low-cost physical terrain model printing with high applicability across diverse terrains.

Aiming at the problem of poor controllability of deformation recovery in the process of transverse elliptic deformation of shield tunnel treated by traditional stratum grouting, the experimental study on transverse elliptic deformation of shield tunnel treated by capsular bag grouting was carried out innovatively. Two different capsular bag layout schemes were adopted in the experiment. The analysis of the test results shows that the tunnel has a vertical elliptical deformation near the grouting point, and the additional earth pressure, tunnel diameter and deflection deformation near the grouting point change the most, showing a gradual decreasing trend along the two ends of the tunnel. Under the same amount of grouting, vertical grouting can better control the transverse elliptic deformation of the existing tunnel, and the side bottom grouting can realize the recovery effect of the transverse elliptic deformation of the tunnel while uplifting the tunnel and effectively reducing the settlement of the tunnel during operation. When grouting at the bottom of the tunnel side, due to the influence of the gravity of the built tunnel, the deformation of the tunnel caused by grouting is lower than that caused by vertical grouting during the expansion process of the bag. Therefore, it is suggested to increase the grouting amount appropriately in the grouting process to achieve the expected recovery effect of transverse ellipse deformation. After grouting, the capsular bag presents a cylindrical shape with wide middle and narrow sides. The capsular bag grouting method can effectively limit the slurry diffusion path, and the slurry is squeezed and diffused in the capsular bag, so that the local pressure of the tunnel increases rapidly, and the recovery effect of transverse ellipse deformation is remarkable. Vertical grouting at the side of the tunnel has a significant effect on the recovery of transverse ellipse deformation, but excessive grouting pressure and other reasons can easily induce problems such as dislocation of shield tunnel segments. It is suggested that when the transverse ellipse deformation of the shield tunnel exceeds the limit, the grouting point should be arranged at the bottom of the tunnel side, that is, about 30°～60°away from both sides of the tunnel.

Mitigating axle load transfer by optimizing structural parameters of locomotives is a primary strategy for enhancing adhesion utilization. To address the unclear mechanism by which the traction rod of a locomotive affects axle load transfer, a theoretical calculation model for axle load transfer given the rotation of the traction rod was established based on quasi-static equilibrium. The influence of the traction rod parameters on axle load transfer was explored based on the Sobol sensitivity analysis. Further analysis investigated the influence of traction force magnitude, stiffness of rubber sleeves, and position of the traction rod on axle load transfer. The results show that when the rotation of the traction rod is considered, the calculation results of the theoretical model are closer to those of the Simpack model, and the theoretical model exhibits significantly higher computational efficiency than the dynamics model. The initial tilt angle of the traction rod has a greater effect on axle load transfer than other traction rod parameters, and the rotation of the traction rod causes the load on each axle to vary nonlinearly with the traction force. As the radial stiffness of rubber sleeves of the traction rod exceeds 160 MN/m, the change in the locomotive’s axle load transfer tends to be gentle. As the deflection stiffness of rubber sleeves of the traction rod increases from 20 N m/rad to 500 N m/rad, the locomotive’s axle load transfer increases by 25.7%. As the height between the end of the traction rod frame and the rail surface increases from 0.05 m to 0.80 m, the locomotive’s axle load transfer increases by 84.3%. As the longitudinal distance between the end of the traction rod frame and the frame centroid increases from 0.5 m to 3.5 m, the locomotive’s axle load transfer decreases by 30.4%. The rotation angle of the traction rod approaches 0 when the initial tilt angle of the traction rod is around 11°. The axle load transfer of the second and third wheelsets approaches 0 when the initial tilt angle of the traction rod is between 13° and 14°.

In view of the complex light environment problems such as sudden light changes, dimness, and glare in highway tunnels, a lane line recognition method, improved Hough & least squares (IHLS), based on embedded artificial intelligence (AI) is proposed. It used the improved Hough transform algorithm to carry out Hough transform for detecting straight lines at lane feature points, and employed the least squares method (LS) for curve fitting to identify curved lane lines. Real-time brightness detection and AI-based enhancement were performed on the captured image by embedding AI vision processing algorithm on the in-vehicle camera. The image was enhanced by the zero-reference deep curve estimation (Zero-DCE) model. The edge detection was performed by the improved Otsu method, and the dynamic region of interest (DROI) was divided by pixel statistics. The image was enhanced and smoothed by guided filtering to improve the accuracy of lane line recognition. The experiment on the proposed method was based on the Liupanshan Tunnel of Qingdao-Lanzhou Expressway. Compared with the LS algorithm, the IHLS algorithm shows a mean intersection over union (MIoU) index increased by 4.14%, average precision (AP) increased by 3.08%, and running time (RT) increased by 0.01 s. Compared with Hough transform, the algorithm presents an MIoU index increased by 4.18%, AP increased by 2.88%, and RT increased by 0.01 s. The IHLS algorithm embedded with AI visual processing solves the optical problems such as machine vision overexposure, color imbalance, and distortion, and realizes real-time recognition and tracking of lane lines in complex light environments.

To mitigate the deformation and upward arching defects prone to occur in the longitudinally continuous ballastless track structures of high-speed railway under high-temperature conditions, a reflective insulation coating with medium brightness and high reflective properties was formulated by using self-made fluorine-modified black pigments. This coating can effectively control the temperature while avoiding the visual damage caused by conventional white reflective coating with high brightness to people seeing it. The molecular structure of the self-made fluorine-modified black pigment was characterized by infrared spectroscopy. The mechanism underlying the high solar reflectance performance of the self-made black pigment was elucidated by using a UV-VIS-NIR spectrophotometer, with a comparison made against conventional cool pigments. Based on this, a reflective thermal insulation coating with medium brightness was developed, and the properties of the film-formed coating, including temperature control, adhesion, and durability, were tested. Furthermore, the full-scale track slab structures under natural exposure conditions were coated, and long-term temperature monitoring and analysis were conducted to evaluate the actual temperature control effect of the coating. The results show that the self-made fluorine-modified black pigment can effectively improve the solar reflectance performance of the reflective thermal insulation coating with medium brightness through the transparency characteristics of its near-infrared band. The solar reflectivity of the self-made coating can be increased by more than 7.2% compared to the coating with medium brightness by using conventional pigments. The insulation temperature difference under simulated solar radiation can be increased by more than 3.0 ℃. The coating possesses good uniformity, adhesion, and resistance to ultraviolet-induced aging. Under typical sunny conditions, it can reduce the surface peak temperature of a full-scale track slab structure by more than 10.0 ℃, the daily temperature difference on the surface by 5.0–10.0 ℃, and the longitudinal positive temperature gradient of the track slab by about 50%.

Accurate and uninterrupted position information is crucial for ensuring the safe and efficient operation of rail transit trains. However, realizing seamless and precise positioning still poses a significant challenge for current train positioning systems operating in complex environments such as tunnels, elevated tracks, urban canyons, and suburban areas. Resilient positioning, navigation, and timing (PNT) system can produce continuous, reliable, and robust position information by integrating diverse PNT information sources. It can withstand hazards, adapt to risks, and counteract interference, offering a viable solution to the aforementioned challenges and demonstrating significant potential in fields such as military defense and aerospace. To promote the application and development of this technology in the rail transit sector, the navigation, positioning, and timing requirements of users of the rail transit industry were analyzed. According to the existing navigation and positioning capabilities of rail transit systems, the concept and framework of a resilient PNT system tailored for rail transit was proposed. Given the unique characteristics of rail transit PNT, the fundamental characteristics and evaluation metrics of the resilient PNT system of rail transit were summarized, and the relationship between resilience and accuracy, integrity, continuity, availability, and other indicators was elaborated. On the basis of multi-source PNT sensors, including global navigation satellite system (GNSS), responders, and 5G-railway (5G-R), the key technologies of the resilient PNT technology system and information fusion for rail transit were discussed. In conclusion, deep fusion of multi-source information and resilient fusion architecture are important research directions for achieving continuous seamless positioning in future rail transit.

To address the issues such as the high density and corrosion susceptibility of traditional steel-polymer fiber hybrid systems, the hybrid effects of three types of polymer fibers, namely polyvinyl alcohol (PVA) fibers, polypropylene (PP) fibers, and polyoxymethylene (POM) fibers, on the workability and mechanical properties of fiber-reinforced cementitious composites (FRCC) were investigated. A total of 12 groups of specimens were designed, including single fiber and different combinations of hybrid fibers, including PVA and POM, PVA and PP, and POM and PP. Flowability, compressive, bending, uniaxial tensile, and four-point bending tests were conducted. The performance of each group was systematically analyzed and comprehensively evaluated, while the hybrid fiber mechanism was also analyzed using a high-resolution optical microscope. The results have shown that hybrid fibers can effectively compensate for the shortcomings of single fibers, significantly enhancing the overall performance of FRCC. The flowability of A0.5M1.5P0 increases by 18.62% compared to the single PVA fiber. The bending strength of A1M1P0 is 14.53 MPa, a 24.94% improvement over the single POM fiber. The compressive strength of A0M1.5P0.5 is 73.33 MPa, a 25.50% increase over the single PP fiber. A1.5M0.5P0 exhibits the best tensile performance, with a tensile strength of 3.36 MPa and strain energy density of 54.2 kJ/m³, showing increases of 54.13% and 2158.33%, respectively, compared to the single POM fiber. The bending strength of A1M1P0 is 9.03 MPa, a 51.26% improvement over the single PVA fiber, while the equivalent bending strength of 3.89 MPa shows a 77.63% increase over the single POM fiber. Based on the comprehensive evaluation of the radar chart, A1.5M0.5P0 exhibits the best overall performance. Two fibers with different physical properties produce a synergistic effect when hybridized. For example, PVA fibers limit crack propagation, while POM fibers dissipate energy through deformation during crack propagation. The synergy of PVA and POM fibers enhances the toughness and load-bearing capacity of the composite material.

To study the noise reduction performance of 3D printed special-shaped noise barrier for high-speed railways, the geometric models of the noise barrier were established by using three-dimensional modeling software, and the noise reduction model of a special-shaped noise barrier for high-speed railways under three sound source modes was established. Based on the acoustic indirect boundary element method, the optimal design parameters of a special-shaped noise barrier were obtained by comparing the noise reduction effect, sound field distribution, spectrum characters, and insertion loss characteristics of the special-shaped noise barrier under different wave distances, wave heights, and barrier heights. The effects of different barrier-line center distances and train speeds on the noise reduction effect of a special-shaped noise barrier were compared and analyzed. The results show that the special-shaped noise barrier has a significant noise reduction advantage for the middle and far field points, the field points in the sound shadow area, and the middle and high frequency noise above 630 Hz. Compared with that of the vertical noise barrier, the additional noise reduction gain of the special-shaped noise barrier can be obtained when the optimized wave distance is in the range of 3.2–4.0 m, and the additional noise reduction effect can reach 1.7 dB (A). In the case of a certain wave distance, with the increase of wave height, the noise reduction effect of the special-shaped noise barrier is enhanced, and the maximum can reach 15–17 dB (A). The additional insertion loss of the special-shaped noise barrier is 1.8 dB (A) when the wave distance is 4 m, and the wave height is 600 mm. When the special-shaped noise barrier height increases by 1 m, the sound pressure level of the four standard field points decreases by 1.6–4.8 dB (A), which mainly acts on the range of 5–10 m near the barrier area and the high frequency cut-off area in space. The additional noise reduction is attenuated from the area to both sides. In the range of 3–4 m, the barrier-line center distance has little effect on the noise reduction level of the special-shaped noise barrier, and the recommended value of the parameter is 3.4–3.6 m. As the train speed increases, the insertion loss of the special-shaped noise barrier decreases. When the train speed is increased from 300 km/h to 340 km/h, the insertion loss of the field point under different working conditions is reduced by 0.17–0.34 dB (A) and 0.55–0.63 dB (A), respectively.

In high-pressure common rail systems under multiple injections, the pressure waves induced by the pilot injection cause fluctuations in the main injection quantity, thereby reducing in-cylinder combustion efficiency and increasing pollutant emissions. A data-driven prediction model for the main injection quantity based on Gaussian process regression (GPR) was proposed to achieve the accurate control of injection quantity under multiple injections. First, D-optimal design and a second-order response surface method were employed to build a response surface model for the main injection quantity by utilizing rail pressure, pilot-injection pulse width, pilot-main injection interval, and main-injection pulse width as factors. Analysis of variance indicates that the four operating parameters all have extremely significant effects on the main injection quantity. Then, based on a self-developed multi-physics coupled digital simulation platform, a dataset containing 528 operating conditions was constructed, and the model was trained. On this basis, several combinations of mean functions (zero, constant, linear, and quadratic polynomials) and different kernel functions (SEiso, RQard, and Matérn) were systematically compared, and the linear mean function combined with the rational quadratic kernel function was identified as the optimal configuration. Results show that in test conditions, the mean absolute percentage error (MAPE) of main injection quantity predicted by the GPR-based model is 0.347% and the coefficient of determination R² is 0.9996, with predictions at different main-pulse widths and pilot-main intervals clustered closely around the regression line. In non-test conditions, the model can still accurately reproduce the fluctuation law of the main injection quantity with varying pilot-main intervals, and features lower error and higher consistency than BP, GR, and SVR models. The proposed GPR-based data-driven model under multiple injections is proved to have both high prediction accuracy and sound generalization capability, providing model support for the precise control of high-pressure common rail systems under multiple injections.

Bus stops play a role of connection and transfer in the travel chain of residents, and the density of slow-moving heterogeneous groups in the areas is high, thus increasing the possibility of traffic conflicts among them. To conduct an in-depth study on the causal mechanisms of traffic conflicts and the heterogeneity among influencing factors for the slow-moving heterogeneous groups in bus stop areas, data of 20 bus stops from December 2022 to March 2023 was collected by taking four types of bus stops in Kunming as the research object, and the motion characteristics of slow-moving heterogeneous groups were analyzed. The severity of conflicts was determined based on the Dutch objective conflict technique for operation and research (DOCTOR) method, and a random parameter Logit model was constructed in consideration of the mean and variance heterogeneity to better identify the heterogeneity of random parameters. The results show that in terms of random parameter distributions, the lateral conflict and non-motorized lane width for pedestrians obey normal distributions with means of 0.455 and −0.541 and variances of 0.872² and 1.214², respectively. The yielding and high speed of cyclists obey normal distributions with means of −0.399 and 0.745 and variances of 1.274² and 1.043², respectively. In terms of mean heterogeneity, there is mean heterogeneity for lateral conflicts with respect to the high speed of pedestrians and for non-motorized lane width at island-type linear bus stops, and there is mean heterogeneity for yielding of cyclists with respect to riding on sidewalks and for the high speed of cyclists with respect to the cyclist density. In terms of variance heterogeneity, there is variance heterogeneity for the parameter of non-motorized lane width among the elderly and for the parameter of the high speed among female cyclists. The average marginal effect coefficients are further calculated to quantify the extent to which the factors contribute to the severity of traffic conflicts. After analysis, the probability of a serious traffic conflict is the highest for alighting passengers in the pedestrian group and for reverse cyclists in the cyclist group.

In order to reveal the air pressure variation law and the subsidence mechanism in covered karst soil cave induced by precipitation, according to the theory of short gas pipe submerged flow, calculation methods of gas seepage flow, air pressure, and stability coefficient in ellipsoid cave were obtained. MATLAB program was compiled based on finite difference numerical solutions. The feasibility of calculation methods was verified through indoor model tests of subsidence induced by precipitation in a karst soil cave. The example analysis has shown that the gas state parameters (flow and pressure) and stability coefficient of the cave evolved from the initial state to drastic variations in the early stage of precipitation, then shifted to gradual changes in the later stage, and finally returned to the initial state. The maximum peak flow of soil cave induced by precipitation is positively correlated with the length of the semi-minor axis b of the ellipsoid cave, and negatively correlated with the ratio of semi-major axis and semi-minor axis $ a / b $, and arch height. The minimum peak air pressure is positively correlated with $ a / b $, $ b $, and arch height. The arrival time of the minimum peak air pressure is positively correlated with arch height, and negatively correlated with $ a / b $, while the effect of $ b $ is negligible. The minimum peak stability coefficient of soil cave induced by precipitation is positively correlated with $ a / b $ and arch height and negatively correlated with $ b $. The arrival time of the minimum peak stability coefficient is positively correlated with arch height, and negatively correlated with $ a / b $, while the effect of $ b $is negligible.

To address the insufficient durability of recycled concrete structures in the Hetao irrigated saline soil region, a typical geomorphological environment in the area was simulated, and concrete specimens were placed in a dry, wet, and freeze-thaw environment to investigate the erosion regularity and mechanism of sodium sulfate. Concrete type, water-cement ratio, and sodium sulfate solution concentration were employed as experimental variables. The quality evaluation parameter ƞ_a and the dynamic elastic modulus evaluation parameter ƞ_b were selected as key evaluation parameters to establish a comprehensive damage evaluation index. Based on this, a two-parameter Weibull reliability analysis was conducted, and a sensitivity analysis of each influencing factor was performed using grey relational grade. The results show that ordinary concrete exhibits better erosion resistance than recycled concrete; after the fourth cycle, the ƞ_b value of ordinary concrete is four times that of recycled concrete. Furthermore, appropriately reducing the water-cement ratio can improve the erosion resistance of recycled concrete. Under the influence of multiple factors, the damage to recycled concrete is caused by the cumulative effects of sodium sulfate crystallization expansion and chemical corrosion. The sodium sulfate with a higher concentration leads to faster damage development. After three cycles, the ƞ_b value of the RC-0.46-0% group is still 0.051, while the ƞ_b value of the RC-0.46-10% group is −0.066, indicating that the specimen has already been destroyed. The Weibull distribution function can effectively describe the erosion damage process of recycled concrete. By establishing an accelerated life reliability function, the service life of the specimen can be intuitively predicted, and the prediction results are consistent with the experimental results. According to the analysis results of the grey relational grade, after four cycles, the ƞ_a value of the specimen with a water-cement ratio of 0.53 is 0.36 and 0.65 lower than that of the specimens with water-cement ratios of 0.46 and 0.39, respectively, while the ƞ_b values of the latter two groups of specimens are basically the same, Therefore, the water-cement ratio is the main factor influencing the durability of recycled concrete.

Magnetic suspension bearings are devices that suspend the rotating shaft at an equilibrium position by magnetic force action, thereby eliminating the contact friction between rotors and stators. Different from the support methods of traditional bearings, magnetic suspension bearings exhibit significant advantages in rotational speed increase, control precision optimization, and low energy consumption, achieving the core demands of high-speed operation, precise control, and zero-friction operation. Magnetic suspension bearings have been widely applied in key fields such as industrial manufacturing, flywheel energy storage, aerospace, and high-speed machine tools. However, with the increasing demand of modern industries for high-performance bearings and the continuous deepening of the concept of low carbon and environmental protection, the technical improvement and performance breakthrough of magnetic suspension bearings have become an urgent requirement of industry development. The relevant research also catches extensive attention from academia and industry. Research progress in magnetic suspension bearings was reviewed systematically. The classification system was first clarified based on the magnetic suspension force generation method (attractive type and repulsive type), followed by reviewing core research content of magnetic suspension bearing systems such as topological structure design, mathematical modeling, and control strategies. The current state of the art in technical research was comprehensively presented. Although phased achievement has been made in basic theory and engineering applications, core technical bottlenecks remain, including stability control under high-temperature/high-speed operating conditions, permanent magnet demagnetization protection, system integration and miniaturization, and cost control. Future research should focus on deepening of multi-field coupling mechanisms, the integration of intelligent control algorithms, and the design of lightweight and low-cost systems, so as to provide technical support for the large-scale application of magnetic suspension bearings under more extreme operating conditions and in broader fields.

Magnetic fluid vibration energy harvesters demonstrate distinct technical advantages in low-frequency vibration environments and broad application prospects in fields such as mechanical vibration monitoring, micro-nano sensors, and power supply for wearable devices. With the increasing energy demand and the growing prominence of environmental issues, the development of efficient and reliable vibration energy harvesting technologies has become a current research hotspot. By applying magnetic fluids to vibration energy harvesters, the frequency response threshold of the energy harvesters can be reduced, and their energy harvesting efficiency can be improved. This innovative design broadens the application scope of vibration energy harvesters and provides a stable energy source for microelectronic devices, holding significant theoretical and practical value. This paper reviewed the current research status of magnetic fluid vibration energy harvesters in China and abroad, elaborated on the latest research progress of electromagnetic and triboelectric vibration energy harvesters, and on this basis, analyzes the influence of the performance of magnetic fluid materials and wall surface characteristics on the electrical output performance of magnetic fluid vibration energy harvesters. The surface roughness and hydrophobicity of the wall material can also significantly affect the output performance of triboelectric energy harvesters. Therefore, how to optimize the performance of magnetic fluid materials and wall surface characteristics to improve the output performance of energy harvesters, and design efficient energy management systems to achieve stable energy output and effective utilization, are important research directions for the future. The future development trends of magnetic fluid vibration energy harvesters were prospected, so as to provide references for related research.

To investigate the mechanical characteristics of large-diameter shield tunnel segment structures under ultimate loads, a multifunctional shield tunnel structure loading device was used to conduct a prototype loading failure test on the shield tunnel segment structure of the Sutong gas-insulated metal-enclosed transmission line (GIL) utility tunnel project. The mechanical response laws of deformation, internal force, joint deformation, bolt and steel bar strain of the segment structure under ultimate load were analyzed. Based on the crack morphology, the failure characteristics and mechanisms of the segment structure were revealed. The results show that the deformation of the segment structure presents a horizontal duck egg shape, the bending moment presents a butterfly shape, and the axial force presents a circular shape. The maximum single point change rate is 10.3‰, the maximum positive bending moment is 3896 kN•m, and the maximum axial force is 17099.28 kN. The maximum bolt strain is 1871 με, far less than the yield strain, and the maximum steel bar strain is 2213 με, exceeding its yield strain. The safety margin for the deformation indicator of the segment structure is between 0.92 and 1.72, while for the strength indicator, it is between 0.10 and 0.16. The strength indicator reaches the ultimate failure value before the deformation indicator. Reinforcement yielding or the main crack penetration is recommended as the judgment criterion of the ultimate limit state for the normal serviceability of the segment structure. Cracks of the segment structure first appear in the middle of the segment B3. When the load is 1778.4 kN, multiple cracks penetrate through the inner and outer arc surfaces of the arch crown and arch bottom, with the maximum widths of the cracks on the inner and outer arc surfaces reaching 4.5 mm and 11.5 mm, respectively. The steel bar of the segment B3 reaches the yield condition, and the segment structure is damaged due to local instability.

To address the low accuracy of numerical simulation in traditional friction models during the prediction of the forming process of ultra-high strength steel, the influence of sliding speed and normal load on the friction behavior of ultra-high strength steel CP780 was investigated using a stamping friction testing machine of self-developed ultra-high strength steel. A dynamic friction coefficient model related to sliding speed and normal load for ultra-high strength steel stamping and forming was established, and the proposed model was verified by integrating U-bending experiments with numerical simulations. Research findings indicate that the friction coefficient of CP780 sheet materials increases with increasing sliding speed and decreases with increasing load. Under conditions of low load and low speed, the wear mechanism of CP780 sheet materials is primarily dominated by ploughing effects; under conditions of high speed and high load, the wear mechanism involves both ploughing effects and partial adhesive effects. A comparison of rebound test values from U-bending experiments with numerical simulation results reveals that the error in the rebound angle α predicted by the dynamic friction model is 1.509%, and the error in the predicted rebound angle β is 0.348%. In contrast, the error in the rebound angle α predicted by the traditional constant friction coefficient model is as high as 12.483%, and the error in the predicted rebound angle β is as high as 4.994%. The dynamic friction model developed in this study demonstrates greater precision in predicting rebound angles and significantly enhances the accuracy of numerical simulations for formed parts.

The navigation congestion problem in water control projects is often caused by the unbalanced allocation of cargo flow for dam-passing ships. To address this issue, a cargo flow distribution optimization model was established to achieve dual objectives of minimizing the total additional cost for dam-crossing ships and waiting time. Furthermore, the service charge mechanism oriented to the dam-crossing mode of the new waterway was further introduced, and its influence on the transfer law of ship cargo flow was analyzed. Then, a non-dominated sorting genetic algorithm (NSGA)-II was applied to solve the model, and the dam-crossing ship cargo flow allocation optimization scheme was proposed. Finally, by taking the Three Gorges water control project as an example, the effectiveness of the proposed model and algorithm was verified. The results demonstrate that the algorithm successfully obtains multiple sets of Pareto frontier solutions and provides diversified ship cargo flow allocation schemes. The total additional cost of dam-crossing ships is significantly negatively correlated with their waiting time. The cargo flow allocation schemes of the dam-crossing system with dual and multiple modes can achieve the objectives of effectively reducing costs and improving efficiency. The optimized scheme with a multi-mode system reduces the total additional cost for dam-crossing ships and waiting time by 67.1% and 0.5%, respectively. Compared with the initial scheduling scheme, the proposed ship cargo flow allocation scheme results in a mode shift of at least 33.4% of the ship cargo flow, which alleviates navigation congestion in water control projects. Moreover, a reasonable service charge rate for the new waterway can effectively reduce the cost and improve the efficiency of dam-crossing ships.

One significant challenge in railway transportation organization is how to quickly develop high-quality wagon flow routing schemes while considering complex constraints such as line capacity, with the aim of minimizing total transportation costs. Given the distinct tree structure of wagon flow routes, all the wagon flow towards the same destination station was considered as a whole, and the concept of in-tree was proposed. By doing so, the flow routing problem could be transformed into determining the in-tree scheme for each destination station (i.e., root node). On this basis, the classic arc-based multi-commodity flow model was reformulated using the in-tree selection variables. Subsequently, a two-stage solution approach was proposed in consideration of the structure of the reformulated model. The first-stage model aimed to generate a pool of promising in-tree schemes by using the column generation algorithm. The second-stage model was intended to select the best in-tree scheme for each root and obtain the wagon flow routes. Finally, by using basic data from the railway network in Southwest China, test instances of varying network scales were constructed to evaluate the algorithm’s performance. The results demonstrate that the proposed method can obtain near-optimal solutions within a short computation time. Compared to CPLEX, the column generation algorithm achieves higher solution efficiency; compared to a simulated annealing algorithm, it delivers better solution quality. The in-tree model exhibits lower model complexity and higher computational efficiency than the traditional arc-based model.

The support structure of wheels is an important component of post-treatment reaction vessels. To improve the safety strength of the reaction vessels, the support system adopts a statically indeterminate structure. In view of the strength of supporting rollers and load-bearing characteristics of the system, based on the energy method, Lagrange multipliers were introduced and the law of energy conservation was combined to calculate the normal forces on each roller, thus solving the bending stress and contact stress. A simple 3D model was built, and by adopting finite element software, the stress distribution and variation laws of each roller were analyzed, with the results verified via experiments. The load distribution factor was defined, and the influence laws of manufacturing errors on the load distribution factor were analyzed by utilizing SPSSAU. The results show that the maximum bending stress of the roller is 42 MPa, which is much smaller than the yield strength of the material. The maximum error between the finite element simulation results and theoretical results is about 8%, and the accuracy of the proposed method was verified by strain experiments on rollers. The load distribution factor negatively correlates with the curvature radius of the roller surface, and positively correlates with the curvature radius of the wheel surface.

To improve the anti-disturbance capability of the electromagnetic levitation system, an adaptive nonsingular terminal sliding mode control based on disturbance upper bound compensation (ANTSMC-DUBC) was proposed. The strategy used nonsingular terminal sliding mode control based on disturbance upper bound compensation (NTSMC-DUBC) to speed up the convergence of the system state and avoid singularity. The disturbance compensation term in the reaching control law can suppress the lumped disturbance, so that a smaller switching gain can be selected to reduce chattering. A switching gain that can adaptively change with the state of the sliding mode function was designed to ensure the dynamic performance of the system while improving the steady state performance and the efficiency of disturbance compensation. The theoretical derivation proved that the designed levitation controller satisfied the Lyapunov stability criterion. The experimental results show that the proposed ANTSMC-DUBC controller exhibits good steady state and dynamic performance in signal tracking, anti-disturbance, and load variation tests, and demonstrates excellent anti-disturbance when facing internal and external disturbances in the system. Compared with that of NTSMC, the gap fluctuation of ANTSMC-DUBC is less than 0.21 mm under the equivalent external disturbance, and the system root mean square error and time-weighted absolute error are reduced by 56.26% and 57.57%, respectively. The maximum gap fluctuation is 0.22 mm with no steady state error when the 1.5 kg load variation is performed.

To enhance the economic efficiency of the traction power supply system of high-speed maglev, an optimization design method integrating power supply partitions and stator segment length was developed using the improved genetic algorithm. Firstly, a mathematical model of the traction system was established through analysis of equivalent circuits under dual-feeding mode. The effective range of power supply partitions was determined to be 20–40 km through comprehensive consideration of tracking intervals and traction performance constraints. Then, the design length of the stator segment was 600–2 000 m according to step-switching control and traction performance constraints. On this basis, the dynamically-constrained adaptive genetic algorithm was employed to optimize the design of the power supply partitions and stator segment length, so as to minimize the overall economic cost. Finally, the Shanghai–Hangzhou maglev planning line and the Shanghai maglev demonstration line were selected as validation subjects. Through hardware-in-the-loop simulations, dynamic train operation data was acquired to compare the comprehensive economic cost of the traction system before and after optimization. Results show that for the Shanghai–Hangzhou line, the traditional design scheme requires seven 27 km power supply partitions of equal length. In contrast, the optimized scheme uses six differentiated partitions, among which the partition at the ends is 20 km, and the central partition is about 37 km. This reduces the comprehensive economic cost by 14.25%. For the Shanghai maglev demonstration line, the existing scheme uses 25 stator segments with a length of about 1 200 m each. The optimized scheme produces 26 unequal-length segments, forming a current-matched layout with shorter segments for higher current and longer segments for lower current, which reduces the comprehensive economic cost by 19.1%.

To achieve digital modeling and performance evaluation of ancient stone arch bridges, the reverse modeling method was explored based on unmanned aerial vehicle (UAV) oblique photography and image contour extraction technology. Firstly, the UAV was used to collect multi-view sequence images of the stone arch bridge. Secondly, based on the structure from motion (SfM) and multi-view stereo (MVS) algorithms, a three-dimensional (3D) model of stone arch bridges was constructed. Then, based on the characteristics of color difference between stone blocks and mortar, as well as the geometric regularity of stone blocks, strategies of color difference enhancement and small-area impurity filtering were proposed to improve the Canny edge detection. Subsequently, the real scale was calibrated based on ground control points, and the finite element model was generated through parametric modeling using the extracted contour coordinates. Finally, the proposed method was applied to model the Toulong Bridge and analyze its performance, and compared with experimental results. The study has shown that no obvious diseases are detected on the surface of the 3D real-scene model of the Toulong Bridge, with the maximum dimensional error of 0.8%. The maximum calculation error of the deflection of the finite element model is 2.1%. These indicate that the method can accurately reflect the geometric shape and mechanical properties of ancient stone arch bridges, providing technical support for their digital protection and performance evaluation.

Gas migration is prevalent in unsaturated loess foundations. Research into gas migration laws and catastrophe driving mechanisms holds great significance for urban construction, the evaluation of infrastructure service safety, and the interpretation of the loess catastrophe issue in the Loess Plateau. Therefore, by considering the transverse isotropy of loess foundations, an improved triaxial apparatus for unsaturated loess was used to conduct gas permeability tests on undisturbed soil samples (with different humidity and stress levels) and remolded soil samples (with various dry densities). The gas migration characteristics and gas catastrophe driving mechanism within transversely isotropic unsaturated loess were summarized, and a corresponding gas permeability coefficient model was proposed. The results indicate that with increases in density, moisture content, and stress level, both gas flow rate and gas permeability coefficient in transversely isotropic unsaturated loess exhibit a distinct trend of initial decrease followed by stabilization. Specifically, when the dry density is less than or equal to 1.51 g/cm³; the moisture content is less than or equal to 12.5%, and the vertical stress is less than or equal to 100 kPa, the observed decrease in gas permeability coefficient is less than 30%. Conversely, beyond these thresholds, the decay accelerates. Fundamentally, these factors induce compressed internal air pore volume, reduced pore connectivity, and increased tortuosity of gas flow paths, ultimately diminishing the gas permeability performance. Under the influence of density, moisture content, and stress level, the gas migration within transversely isotropic unsaturated loess collectively demonstrates a “suppression, pressurization, and driving” catastrophe mechanism. The research findings can not only improve the accuracy of gas permeability calculation in unsaturated loess and enrich the theory of gas leakage prevention and control but also offer valuable reference for the prevention and control of loess foundation catastrophe induced by pressurized gas.

Due to the unique structural form of stone masonry walls in traditional Tibetan architecture, the complexity of the material composition, and the interference of environmental factors, the accurate detection of hidden damage in the wall is extremely challenging. To address the limitations of traditional methods in target signal identification, experimental data obtained from ground-penetrating radar (GPR) testing of Tibetan stone masonry walls were used to verify the reliability of the numerical simulation results. Then, the propagation characteristics of the effective wave were systematically analyzed, with the focus on the effects of different GPR antenna center frequencies, GPR spacing from the wall, and crack width on the echo characteristics. Finally, the successive variational mode decomposition (SVMD) method was applied for signal decomposition and reconstruction. Its stability, applicability in target signal identification, and its advantages over existing techniques were evaluated across varying noise levels and crack widths. The results have shown that when the SVMD method is applied to the noise reduction of GPR signals in masonry walls of traditional Tibetan architecture under specific conditions, it improves the signal-to-noise ratio by 58.36% and 18.67% compared to the empirical mode decomposition (EMD) and variational mode decomposition (VMD) methods, respectively. It can effectively separate the target signals, background wall signals, and noise signals, providing reliable technical support for extracting damage characteristics in masonry walls of traditional Tibetan architecture.

To clarify the seismic behavior of earthen-stone masonry walls in traditional Tibetan dwellings in Western Sichuan, four earthen-stone masonry wall specimens were designed, fabricated, and used for conducting quasi-static loading tests. Timber wall reinforcement installation, wall tapering, and wall window openings were adopted as the main parameters to study their influence mechanisms on the seismic behavior of earthen-stone masonry walls. Through the tests, the horizontal load–displacement curves of the earthen-stone masonry walls were obtained, and key seismic performance indicators including bearing capacity, deformation capacity, stiffness, ductility, and energy dissipation capacity were analyzed. The influence of wall openings and timber wall reinforcement installation on the failure mode of the wall was discussed, and a comparative analysis of the shear strength between the earthen-stone masonry walls in Tibetan dwellings and ordinary brick masonry walls was conducted. The research results indicate that the earthen-stone masonry walls in Tibetan dwellings in Western Sichuan generally exhibit good seismic behavior and deformation capacity. In this test, the average shear strength per unit area of each wall component reaches 0.16 N/mm², and the ultimate deformation capacity is in the range of 2.4%–3.0%, with its deformability showing obvious advantages compared with ordinary brick masonry walls. Both window openings and timber wall reinforcement installation affect the failure morphology and failure mode of the walls. Compared with walls without timber wall reinforcement, the shear strength and energy dissipation capacity of walls equipped with timber wall reinforcement are increased by approximately 27% and 37%, respectively. Meanwhile, the number and width of shear cracks are significantly reduced.

Obtaining the vibrational characteristics of independent substructures from global structures is crucial. The conventional isolated substructure method with time series (SIM-TS) suffers from increased computational errors due to excessively small singular values under noisy conditions. To address this, an improved ISM-TS method named ISIM-TS is proposed, aiming to achieve higher accuracy in substructure modal parameter identification. First, based on SIM-TS, an adaptive truncated singular value decomposition technique was introduced, optimizing the decomposition results by dynamically adjusting the truncation threshold. The ISIM-TS was combined with the covariance-driven stochastic subspace method (SSI-COV) to establish a new substructure modal identification framework, termed ISIM-TS-SSI-COV. Then, the feasibility of the proposed framework was verified via a classical five-degree-of-freedom (5-DOF) numerical simulation. Finally, this method was applied to identify the dynamic characteristics of a substructure in a Tibetan ancient architecture. The numerical results demonstrate that the improved method enhances the identification accuracy of the substructure, particularly reducing the identification error of the second-order frequency by 71.4%, under 1% noise. Furthermore, based on response data acquired under ambient excitation, the proposed method successfully identifies the first two natural frequencies of the substructure as 12.18 Hz and 13.31 Hz, respectively.

Currently, most Min-Zhe timber arch lounge bridges suffer from the lack of detailed blueprint documentation, leading to unsatisfactory preservation effects and insufficient research on fire spread patterns and disaster prevention. To solve these problems, a digital reconstruction technology based on three-dimensional scanning and BIM parameterization was proposed to construct the digital twins of timber arch lounge bridges, and a BIM-fire dynamics simulator (FDS) was used to analyze the fire spread patterns and fire prevention strategies of such bridges. Firstly, the original point cloud model of Helong Bridge was obtained through on-site three-dimensional scanning, and after registration, denoising, and thinning processes, a BIM parametric digital twin was established to calculate its fire load density. Secondly, the IFC format was adopted to realize the interaction between BIM and FDS, and the fire digital twin of the timber arch lounge bridge was established. Simulation analysis was conducted through parameters such as heat release rate (HRR), fire spread phenomenon, visibility, temperature, and harmful gas concentration, and the fire spread patterns were derived by simulating and analyzing multiple typical fire source scenarios in FDS. Finally, fire prevention optimization strategies such as material flame-retardant treatment, bridge deck non-combustible transformation, and sprinkler system layout were discussed. The research results indicate that the fire load density of the timber arch lounge bridge is as high as 4 017.764 MJ/m², far exceeding that of typical Chinese and foreign buildings, thus posing an extremely high fire risk. Among multiple typical fire source scenarios, excluding HRR mutation values, the HRR peaks of the arch structure and bridge bottom working conditions are stable at 100 MW and 95 MW, respectively. The HRR peaks of the bridge center and bridge head working conditions are stable at 88 MW and 70 MW, respectively. The HRR of the bridge side bottom and bridge top working conditions does not reach the peak within 1 000 seconds, with maximum values of 55 MW and 22 MW. Therefore, the fire risk of ignition under the bridge is the highest, followed by ignition on the bridge deck, while the fire risks of roof ignition and ignition at the bridge side bottom are relatively low. Through fire simulation and quantitative analysis of multiple fire parameters, it is confirmed that the three fire prevention measures can delay the fire spread of timber arch lounge bridges, and the upper and lower fire compartments, wood flame retardancy, and sprinkler systems reduce the HRR peak by 23 MW, 39 MW, and 63 MW, respectively. The research results can serve as the basis for information storage, quantitative analysis of fire spread, and preventive protection of timber arch lounge bridges and provide technical support for the long-term safe operation and maintenance of cultural heritage buildings.

As the intelligent technologies continuously develop, the transportation system is shifting toward autonomous and unmanned operation modes. To clarify the technical characteristics and functional advantages of autonomous transportation systems (ATS) at different autonomy levels, this paper deconstructs ATS into five layers of the system, scenario, function, technology, and service by quantifying the generational evolution standards of ATS, evaluating system topology, and simulating and analyzing the generational evolution paths of ATS. Meanwhile, in terms of the linkages between traffic scenarios, traffic entities, and traffic services, it employs the quantized values of technological types and their development levels required by each function as the link cost, and proposes a hierarchical evolvable architecture model for ATS based on classical network theory. Finally, by taking the priority passage service under road intersection scenarios as an example, the interaction relationship between ATS traffic entities, functional realization, and information flow is analyzed in depth by calibrating the link cost via questionnaires. The results show that increasing interoperable linkages can significantly improve the autonomy level of ATS, with the key milestone for full autonomy being “human participation reduced to less than 10%”. The proposed hierarchical evolvable architecture model provides a quantitative analysis framework for ATS generational evolution, filling the gap of existing theories in system-level dynamic evolution modeling. The findings can assist transportation authorities in ATS development planning and provide a quantitative basis for priority setting in technological research and development.

To ensure the safe and efficient operation of full-face tunnel boring machines (TBMs) in complex terrains, it is essential to clarify the load characteristics of cutters in the multi-cutter collaborative rock-breaking condition and to analyze the performance of cutter profiles in different geological strata. Therefore, a numerical discrete element model based on the particle-flow method for the multi-cutter collaborative rock-breaking condition was established. The load characteristics of flat-tipped and circle-tipped cutters under varying rock strength and rotational speeds of cutterheads were investigated. Additionally, multi-cutter rock-breaking experiments were conducted to verify the accuracy of the numerical analysis results. The findings indicate that under a given penetration depth, the circle-tipped cutter exhibits a normal total thrust that is 23%−50% lower than that of the flat-tipped cutter, along with a reduction in rock-breaking volume and specific energy by 10%−20%. The load of cutters at different installation radii varies. The innermost and outermost cutters only collaborate in rock breaking with adjacent single-sided cutters, so the cutting force is approximately 30% higher than that of the adjacent cutter. Consequently, the mean and the standard deviation of cutting forces show a “W”-shaped distribution, with higher values at both ends and lower values in the middle as the installation radius increases. The mean and standard deviation of the normal forces for both cutter profiles are positively correlated. However, at the same level of normal thrust, the flat-tipped cutter exhibits a 37%−50% lower standard deviation of normal force, which means the circle-tipped cutter may lead to more severe vibrations. Additionally, the cutting forces for both types of cutters increase with an elevation in the rotational speed of the cutterhead. The flat-tipped cutter exhibits greater sensitivity to variations in the rotational speed.

To enhance the accuracy and efficiency of crack detection of ancient bridges and address the issues of information loss and secondary damage caused by traditional sensor detection methods, a crack identification and measurement method was proposed based on an improved you only look once 11 (YOLO11) and SegFormer. First, to overcome the limitations of the YOLO11 model, including its large parameter size and restricted inference speed, the you only look once-crack detect (YOLO-CD) object detection model was introduced. The StarNet lightweight backbone network was employed to reduce computational costs. The HSANet neck network was integrated to enhance the ability to preserve the crack edge detail, and an optimized spatial context detection (OSCD) head was designed to improve multi-scale detection efficiency. Second, an enhanced SegFormer-HF semantic segmentation model was proposed, which incorporated a feature fusion module (FFM) and a high-low frequency decomposition block (HLFDB) to mitigate information loss during sampling and improve semantic consistency in crack segmentation. Finally, a joint detection-segmentation framework was developed, combining a skeleton line algorithm to achieve automatic calculations of crack length and width. Based on the experiments conducted on the crack dataset of ancient bridges, the results have demonstrated that the YOLO-CD model achieves F1 score, mAP50, and mAP50-95 values of 67.8%, 71.5%, and 46.4%, respectively, while reducing floating-point operations (GFLOPs) by 47.6% compared to YOLO11. The SegFormer-HF model achieves superior performance with F1-score, mIoU, and mPA of 91.50%, 90.51%, and 85.15%, respectively, outperforming existing mainstream models. The results validate that the proposed method achieves higher efficiency and compact model size while balancing detection speed and accuracy, which is suitable for deployment on mobile devices such as cameras and drones.

The conservation of ancient stone arch bridges is severely hindered by drawing deficiency, difficult on-site survey, and structural deterioration. These obstacles make it difficult to acquire the geometric parameters required for refined mechanical models and to reproduce the real damage state of individual blocks. As a result, refined mechanical models can hardly be established effectively. To solve the problem, a finite-element (FE) modeling strategy of ancient stone arch bridges based on masonry structure gap image recognition is proposed. First, a dataset with a large number of labeled contours of blocks in stone arch bridges was constructed, and a trained YOLOv8 convolutional neural network was used for instance segmentation of the block contours on the bridge images. Second, the recognition results were post-processed with the Douglas–Peucker algorithm, and key geometric information of individual blocks was extracted. Finally, a parametric modeling procedure was developed: an ABAQUS parametric modeling script was developed to automatically generate a separate FE model that faithfully replicates the actual masonry structure, with contact interfaces defined between blocks for subsequent FE simulation analysis. The results show that under self-weight and deck loads, the peak principal stress in the arch rib predicted by the separate FE model is about 1.2 times that given by a conventional monolithic FE model, and conspicuous stress concentrations appear at masonry defects. The separate model can more accurately reproduce the block distribution and local defects of the actual bridge. It has significant advantages for revealing the damage mechanism of the masonry structure of ancient bridges, and provides a new perspective and method for the mechanical simulation study of ancient bridge protection.

The large eddy simulation (LES) was employed to make a transient simulation of the flow field within the grid flocculation tank to investigate the evolutionary characteristics of the jet vortex flow structure of flow field within the grid flocculation tank. The grid flow field was analyzed from both two-dimensional and three-dimensional perspectives. The results indicate that a jet vortex flow field is formed immediately behind mesh holes as fluid flows through a grid plate. Due to shear, entrainment, and mixing between jet and background fluid, a backflow vortex zone is formed in the region behind the grid, accompanied by a continuously developing vortex ring structure along the side wall. The vortex ring structure causes varying degrees of deformation and displacement at the front of the jet, while also suppressing its forward movement. The vortices are mainly located within the boundary layer of the jet, with rapid changes occurring in their structure at its forefront. This area exhibits both maximum size and intensity. The most significant variations in vortex structure intensity are observed near the side wall, where the vortex structures of each jet display mirror symmetry about its axis. Additionally, the front of the three-dimensional vortex structure resembles a coronal formation. As the jet develops forward, the coronal structure will extend and swell to become larger and then will eventually discrete and detach. The distribution of vortex structure at each moment exhibits mirror symmetry with respect to the bisector of the flow field, while the variation process of the flow field morphology demonstrates a trend from the side wall towards the center of the flow field.

To address the issue that the asymmetric basic type calculation model, which the intersection method relies on in highway alignment design, fails to perform calculations when turning curves include incomplete transition curves, the asymmetric basic type calculation model was used as the foundation. By analyzing the causes of the model’s failure in solving incomplete transition curve scenarios, the structure and solution logic of the calculation model were optimized and improved, and an asymmetric general type calculation model was further proposed. This new model introduced a novel definition of transition curve direction. It classified transition curves into two categories, positive and negative, by judging the relationship between the curvature change trend of the transition curve and the route’s traveling direction. Then, based on the positional order of the transition curve within a single curve, a special local coordinate system was established. Through geometric derivation, the tangential growth value and curve offset value of the incomplete transition curve were obtained, enabling the subsequent use of the asymmetric basic type calculation model for further solution. The research has shown that the asymmetric general type calculation model eliminates the restrictions of the asymmetric basic type model on alignment combination types, allowing the curvature radii at the start and end points of transition curves to be arbitrary values. By comparing the calculation results of the same complex curve segment with those obtained using the traditional element method, the differences in the calculated mileage values and coordinates of the control stakes are both less than 1 mm, which meets the engineering accuracy requirements.

To reduce the structural and ground safety risks caused by the high-speed air–water mixture during geyser events in baffle-drop shafts, a numerical simulation was conducted to investigate the influence of void fraction and connecting pipe diameter on shaft pressure and geyser intensity. The variation patterns of impact loads on the baffles at the shaft bottom were analyzed, proposing the installation of a throttling orifice at the shaft midpoint to control the geyser intensity. The results show that the pressure in the connecting pipe first reduces and then increases with rising void fraction, reaching a minimum within the range of 0.2–0.4. Among the three diameter ratios considered, the geyser intensity reaches its maximum when the diameter of the connecting pipe is half that of the shaft. The impact load on the baffles decreases continuously from bottom to top, and for any given baffle, the impact load near the partition wall and shaft wall is greater than that at the baffle’s edge. Installing a throttling orifice at the shaft midpoint can effectively control the geyser intensity, and the impact load on the throttling orifice is 10 times greater than that on the bottom baffle. These findings provide a reference for the safe operation of urban deep tunnel drainage systems.

To enhance the industrialization level of the prefabricated bridge pier and develop connection forms compatible with the performance of the ultra-high performance concrete (UHPC) pier, an external prestressed connection joint and its tensioning process were proposed. The feasibility of this configuration and technique was validated through full-scale tests. Combined with finite element analysis, the influence of joint prestress and axial compression ratio on the performance of the UHPC pier was investigated, and a design method for prestressed joints based on the capacity design method was proposed. The research results have shown that the prefabricated pier with the external prestressed connection joint experiences typical bending failure, with the UHPC concrete of the pier body being crushed, but no interfacial separation occurs at the interface between the pier and the cap. The stress variation of the prestressed high-strength reinforcement is basically proportional to the horizontal load of the pier, with the maximum variation amplitude of only 9%, indicating that the connection performance of the external prestressed connection joint used in the specimen has reliable connection performance and good overall structural performance. When the tension force of the high-strength reinforcement in the pier is small, joint opening occurs at the interface between the pier and the cap, reducing the stiffness of the prefabricated bridge pier, but it has little effect on the peak load-bearing capacity of the specimen.

Micro-pressure waves are generated and noise is induced when the initial compression wave generated during the entry of a high-speed metro train into a tunnel propagates to the tunnel exit. In some cases, sonic booms may also occur, resulting in serious environmental problems for residents. To effectively control the micro-pressure wave noise at tunnel exits, numerical simulation studies on the acoustic characteristics of micro-pressure wave noise were conducted, and an acoustic suppression structure targeting low-frequency micro-pressure wave noise was proposed. Firstly, large eddy simulation (LES) was employed to obtain near-field unsteady flow field data at the tunnel exit, using the Ffowcs Williams-Hawkings (FW-H) acoustic analogy to predict the type of micro-pressure wave noise sources. Secondly, based on the unsteady flow field data, the acoustic finite element method (AFEM) was utilized to compute the far-field radiation of micro-pressure wave noise and analyze the mitigating effect of acoustic structures of the tunnel exit on micro-pressure wave noise. Finally, the accuracy of the numerical methods was validated through a moving model test. The results indicate that at a train speed of 160 km/h, dipole noise predominates in the micro-pressure wave noise at the tunnel exit. Dipole noise radiates outward in a semi-ellipsoidal shape, with its energy mainly concentrated below 20 Hz and a peak frequency being 4 Hz. The attenuation of dipole noise in the tunnel exit direction follows an exponential decay law. Adding acoustic structures at the tunnel exit significantly reduces micro-pressure wave noise. Specifically, the sound pressure levels (SPLs) outside the tunnel exit across various longitudinal planes decrease by approximately 3.00 dB. At the designated measurement points, located at 20 m and 50 m, the SPLs are reduced by 3.54 dB and 2.62 dB, respectively.