In this study, a double-cable-beam-tower dynamic model was proposed for floating-type cable-stayed bridges, taking into account the vibrations of the tower, deck, and cables. The cables were modeled as tensioned strings, while both the deck and the tower were represented as Euler-Bernoulli beams with axial force effects considered. Based on this assumption, the corresponding axial and transverse differential equations of motion were derived, and the free vibration problem of the model was solved using the transfer matrix method. A floating-type railway cable-stayed bridge in Hunan was used as an engineering example, where the frequencies and mode shapes calculated with the proposed theory were presented and compared with ANSYS finite element results to verify the accuracy of the method. Furthermore, a detailed parametric analysis was conducted on key factors such as the elastic modulus, cable-beam angle, and initial cable force to investigate the variation patterns of the natural frequencies, thereby providing guidance for practical engineering applications. The results reveal that the natural frequencies exhibit distinct and abundant veering phenomena under parameter variations. 

Fatigue damage analysis is essential for engineering structures bearing various random loads. Non-Gaussian random loads and the mean stress caused by the superposition of dynamic and static loads make the prediction of fatigue damage more complex. Rain flow counting method requires a lot of computing time and cost when considering the mean stress of each stress cycle in non-Gaussian stochastic process. Although the frequency domain method can quickly estimate the fatigue damage rate, it is difficult to effectively consider the influence of each mean stress of rain flow. Therefore, based on the frequency-domain method proposed by Dirik and the power spectrum density correction method proposed by Niesalon and Bohm, the 
extreme gradient boosting (XG-Boost) model was established to predict broadband non-Gaussian fatigue damage considering the mean stress effect, and the sparrow search algorithm was used for optimization. 
Based on different power spectra, a large number of numerical simulations have been carried out for the fatigue strength index 
k-value of S-N curve, mean stress, ultimate tensile strength, skewness and kurtosis.
 The obtained database was used to enhance the generalization of the XG-Boost model, and the rain flow counting method was used to calculate the fatigue damage rate as an accurate reference. The final results show that the developed XG-Boost model can accurately predict non-Gaussian fatigue damage.

The main rotor is the primary vibration source in helicopters, transmitting alternating loads to the fuselage through the main reducer. To achieve effective suppression of the excitation force at the main rotor’s blade passage frequency, a focused vibration isolation platform employing struts with negative stiffness dynamic vibration absorber (NSDVA) was proposed for controlling rotor-fuselage vibration transmission. Firstly, a dynamic model of the main reducer-single strut with NSDVA-fuselage system was established. Parameter optimization targeting the reduction of the excitation force at the blade passage frequency was conducted, validating the mechanism of the NSDVA and the corresponding transmission control law. Secondly, based on the transfer matrix method, a dynamic model of the main reducer-four-strut vibration isolation platform with NSDVA-fuselage system was established to predict the vibration absorption performance at the blade passage frequency. Furthermore, based on disc spring and helical spring, the strut with NSDVA was designed, and the influence of the nonlinear stiffness of the disc spring on the system was analyzed. The results indicate that, compared with a traditional dynamic vibration absorber, NSDVA can reduce the required absorber mass while effectively broadening the vibration reduction bandwidth. The dynamic model of the main reducer-four struts-fuselage system established using the transfer matrix method shows good agreement with the finite element simulation results. Under the condition of a force transmissibility upper limit of 01, the isolation platform with NSDVA can achieve vibration reduction across a 9000 Hz bandwidth, offering an improvement of nearly 30 dB compared to a traditional dynamic vibration absorbers. The nonlinear effects of the disc spring within the strut with NSDVA are weak and can be approximately neglected. This research provides a theoretical foundation for the subsequent specific application of NSDVA in helicopter main reducer vibration isolation.

Membrane structures composed of high-strength fabric materials are extensively applied in civil engineering, aerospace, and marine engineering, where their vibration characteristics critically determine structural safety and reliability. This study investigates the influence of tension-shear coupling and ambient air on vibration modal properties of fabric membrane structures. An enhanced low-vacuum modal testing system was developed to conduct experimental studies on planar-tensioned fabric membranes, incorporating parameters such as environmental pressure, pretension levels, stress ratio, and yarn off-axis angles. Analysis reveals that fabric membranes exhibit relatively low air sensitivity, with a modal frequency increase of 34.73% under low-vacuum conditions. Vibration frequencies show a positive correlation with pretension levels, achieving a maximum increase of 69.77%. Furthermore, tension-shear coupling significantly affects vibration characteristics, where off-axis angle variations additionally alter modal shapes. These findings provide substantial theoretical and experimental support for modal analysis of membrane structures.

To investigate the influence of subgrade deterioration on the damage behavior of airport cement concrete rigid pavements, a fragility analysis framework was developed based on conventional reliability theory and the capacity-demand ratio fitting method. This framework was employed to evaluate the failure probability of rigid pavements subjected to aircraft wheel loads under conditions of degraded subgrade stiffness. A simplified analysis model of airport rigid pavements was established using the general-purpose finite element software ABAQUS, with the maximum tensile strain at the bottom of the slab serving as the damage indicator for quantifying different damage states. Two types of subgrade stiffness degradation were considered: uniform and non-uniform. Fragility functions were constructed for each scenario to analyze the pavement failure probability across varying degrees of stiffness degradation. Additionally, by incorporating a wheel path distribution model for the main landing gear of commercial aircraft in China, the overall failure probability of pavements under realistic operating conditions was assessed. The results indicate that subgrade stiffness significantly influences the failure probability of rigid pavements. As the stiffness degrades, failure probabilities across all damage levels increase markedly, with the most notable rise occurring in the longitudinal joint regions. Increasing the surface layer thickness effectively enhances the pavement’s resistance to damage. Compared to the case of uniform subgrade stiffness, the presence of non-uniform stiffness distribution significantly increases the failure probability. When considering the wheel track distribution, the overall pavement failure probability falls between the failure probabilities corresponding to each specific wheel track, thereby providing a more realistic assessment of pavement failure risk under actual aircraft wheel loads. The proposed fragility analysis method under aircraft loading provides valuable support for performance evaluation and maintenance planning of airport rigid pavements. 

Linear resonant actuators (LRAs) are widely used in smartphones and other electronic devices. The consistency of their vibration sensation is a key parameter for evaluating the performance of actuators, so it is of great significance to carry out dynamic analysis and vibration control of LRAs. To overcome the limitation that traditional linear models cannot accurately describe the strong nonlinear characteristics of x-axis linear resonant actuators for smartphones, this study conducts research on nonlinear dynamic modeling, parameter analysis, and vibration control of the actuators. The linear actuator is simplified as a nonlinear two-degree-of-freedom mass-spring-damper system, with the nonlinear stiffness and nonlinear electromagnetic force of the system taken into account. The nonlinear stiffness and electromagnetic force are obtained through simulation, and the damping parameters of the system are further solved using the half-power bandwidth method based on measured data. For the two-degree-of-freedom nonlinear dynamic equation, the Runge-Kutta method is adopted for its solution. Test results show that the goodness-of-fit index Rnl between the theoretical prediction results and the measured results of the actuator is greater than 0.95, indicating that the model can accurately predict the vibration response of LRAs and effectively overcome the shortcomings of traditional linear models. Finally, based on the model established in this paper, an optimized current control strategy for LRAs is proposed, which realizes the consistent regulation of vibration responses in the full frequency band. Experimental results demonstrate that the proposed current control optimization strategy can reduce the deviation on the left side of the resonance peak by at least half, providing a new idea and approach for the consistency control of LRAs. 

In this study, a coupled computational fluid dynamics–discrete element method (CFD–DEM) is employed to systematically investigate the ice resistance characteristics and icebreaking mechanisms of a ship navigating in ice floe regions. Numerical simulations are performed using the STAR-CCM+ software. To ensure numerical reliability, mesh convergence is first conducted. Through multi-scale mesh refinement and sensitivity analyses, an optimal numerical model that balances computational efficiency and simulation accuracy is established. The effects of two key parameters—ship speed and ice floe thickness—on ice resistance are examined in detail, revealing their nonlinear influence on resistance characteristics. The intrinsic mechanisms linking ice resistance variation with fracture-induced energy dissipation during ship–ice interactions are clarified. Furthermore, from the perspectives of stress wave propagation, fracture modes, and kinetic energy transformation, the degree of ice fragmentation, crack propagation paths, and accumulation patterns of broken ice under different operating conditions are quantitatively evaluated and qualitatively analyzed. The results deepen the understanding of the multiphase coupled dynamic behavior of ship–ice–water interactions and provide a reliable numerical analysis approach and engineering reference for the optimization of polar ship performance and the design of ice-resistant structures.

As a typical underactuated and multi-degree-of-freedom coupled nonlinear system, tower cranes are highly susceptible to payload swing during luffing and slewing movements, significantly affecting positioning accuracy and operational safety. To address the trade-off between dynamic response speed and payload swing suppression in tower crane control, a positioning and anti-swing control strategy combining Composite Nonlinear Feedback (CNF) and energy-based control is proposed. Firstly, the dynamic model of the tower crane system is established and divided into two subsystems, luffing and slewing. Subsequently, CNF controllers are separately designed for each subsystem, wherein the linear feedback component ensures rapid dynamic response and the nonlinear feedback component effectively reduces system overshoot. Furthermore, an energy-based control law utilizing system kinetic and potential energy is introduced to enhance swing suppression and improve anti-disturbance capability. The asymptotic stability of the proposed system is rigorously proven through Lyapunov stability theory. Comparative simulations conducted on the Simulink platform demonstrate that the proposed combined CNF and energy control method significantly improves positioning accuracy, response speed, and disturbance rejection capability, showcasing superior robustness.

To address the insufficient accuracy in reproducing coupled linear-angular vibration environments caused by transfer matrix measurement errors in traditional indirect simulation methods, a test method based on direct control of response points was proposed. A dual-shaker excitation system was designed, integrating spherical decoupling devices and an elastic suspension structure, achieving composite loading of angular and linear vibrations for aircraft. Cubic spline interpolation was applied to enhance the sampling rate of angular velocity data, resolving distortion issues in derivative calculations from low-sampled signals. By applying an incremental transfer function iterative correction strategy, the system's nonlinear deviations are suppressed stepwise, ultimately achieving more accurate reproduction in both time and frequency domains compared to traditional methods. Experimental results demonstrate that the response point direct control method effectively avoids transfer matrix error accumulation, while fringing function processing eliminates startup-shutdown impacts. Ultimately achieve a good match between test waveforms and telemetry data, validating the heaven-earth consistency. This study provides a systematic solution for ground simulation and assessment of complex vibration environments in aircraft.

To address the problem of bridge jumping caused by bridgehead subgrade settlement during the design of highway expansion and renovation, this paper conducts research on the design method of elevation gradient sections. The weighted root mean square value of acceleration is adopted as the evaluation index for the driving comfort of the elevation gradient section. Through uniform experimental design, the influence degree of driving speed, longitudinal slope difference, and longitudinal slope on the weighted root mean square value of acceleration is studied. Combined with regression analysis and significance test, the results show that the longitudinal slope difference is the key indicator affecting the design of the elevation gradient section. When the design speed is 120 km/h, ω is 0.3%; when the design speed is 100 km/h, ω is 0.35%; when the design speed is 80 km/h, ω is 0.45%. A segmented geometric model is constructed for the parking visual distance test, and the allowable settlement amount calculation formulas under different conditions are derived. It is proposed that the design of the elevation gradient section should be completed by combining the corresponding model for the safety check of parking visual distance. This paper provides quantitative indicators and engineering calculation methods for the design of the elevation gradient section of the bridgehead roadbed settlement during expressway expansion and reconstruction, effectively improving driving comfort and road traffic safety. 

The trend toward high-speed, lightweight designs presents new challenges for the stable operation of electric drive gear transmission systems, with vibration issues becoming increasingly prominent. Therefore, research on the nonlinear dynamic characteristics of the electric vehicle powertrain transmission system is carried out, a "bending torsion axis" coupled nonlinear dynamic model is established that incorporates the external characteristic curve of the motor. This model takes into account factors such as time-varying meshing stiffness, gear mesh error, and gear backlash. The influence of meshing frequency, damping ratio, and gear backlash on the system's bifurcation characteristics was thoroughly analyzed using Lyapunov exponent diagram, time-domain diagrams, phase diagrams, poincaré sections, and other methods. Additionally, vibration tests are conducted to verify the accuracy of the dynamic model established in this paper through vibration tests. The results indicate that as the meshing frequency increases, the system exhibits a rich array of dynamic characteristics. In the high-frequency range, its nonlinear behavior becomes more complex, overall presenting an overall motion state characterized by periodic, quasi-periodic, and chaotic alternations. Furthermore, appropriately increasing the damping ratio or reducing gear backlash can mitigate chaotic motion and enhance system stability.

This paper proposes a novel brake pedal feel emulator integrating a magnetorheological (MR) damper, a helical spring, and a rubber pad. First, guided by the target pedal force–travel characteristic curve, the mechanical structures of the pedal feel emulator and the MR damper are designed. Second, the operating principles of the pedal mechanism and the MR damper are systematically analyzed, and the corresponding control system is established. Finally, the system performance is validated through damper bench tests and a multi-mode pedal force testing platform. Experimental results demonstrate that the proposed device can accurately reproduce multi-mode nonlinear pedal force characteristics, exhibiting good dynamic response and tracking accuracy, thereby meeting the personalized pedal feel requirements of different drivers.

In order to meet the service requirements of artificial cartilage foam (ACF) in a wide temperature range, the tensile, tearing and 100-800J drop hammer impact tests at three temperature points (low temperature, normal temperature, high temperature (10℃, 23℃, 40℃) were carried out on the ACF with a density of 380kg•m⁻³at -40℃~70℃. The effects of temperature on its static and dynamic mechanical properties and energy absorption mechanism were systematically revealed. The results show that ACF material has significant temperature sensitivity. With the increase of temperature, the tensile strength and tear strength gradually decrease, showing a typical thermal response behavior from "rigid brittle" to "viscoelastic flexible"; The young's modulus changes nonlinearly with temperature and has a turning point, and a significant turning point occurs at -10℃~10℃, which reveals that the macro mechanical response characteristics of the material change significantly in the temperature range; ACF shows typical "Three-stage" compression response in the process of falling weight impact. At low temperature and normal temperature, the energy absorption rate of low energy level 100J after three impacts is higher than 85%; At high temperature of 40℃, the energy absorption rate of 100J energy level material decreases to about 60%, but with the increase of energy level, the energy absorption rate gradually increases, and it can rise to 96% at 800J high energy level. The fluctuation of peak load and maximum displacement of each temperature group after multiple impacts is less than 10%, which verifies the self recovery and impact resistance stability of the material. The mechanical properties and energy absorption mechanism of ACF are obviously affected by the synergistic effect of temperature and impact energy. In practical engineering applications, the appropriate material structure and service conditions should be selected according to the specific ambient temperature and load level, so as to give full play to the efficient buffer and protection potential of ACF in aerospace, transportation, sports protection and other fields.

To explore the influence mechanism of additional harmonic excitation on the vortex-induced vibration and flow field structure of rigid-flexible coupled wave-excited cone-cylinders, a three-dimensional fluid-structure interaction computational model of such cone-cylinders was established based on overlapping grid and dynamic mesh technologies. Spectral analysis was performed on the displacement time-history curves of the rigid-flexible coupled wavy cylinder. The results show that: when the frequency of the additional harmonic excitation equals the natural frequency of the structure, the amplitude of the wavy cylinder is effectively increased and the lock-in range is expanded; when the frequency of the additional harmonic excitation matches the structural modal frequency, the amplitude of the wavy cylinder reaches the maximum; when the additional harmonic excitation is a harmonic of the structural natural frequency, the additional excitation can couple with the harmonic modes in the flow field, enabling the wavy cylinder to exhibit a relatively large amplitude even when the frequency of the additional excitation is far from the structural modal frequency. These findings indicate that enhanced flow-induced vibration of the wavy cylinder is achieved under appropriate control parameters of the additional harmonic excitation, which is expected to improve the energy harvesting efficiency of bladeless wind turbines.

The damage evolution of grouted composites under cyclic blasting loads in water-rich strata was investigated. Cyclic impact tests on granite residual soil grouted with three materials (C, MC, MCS) at initial moisture contents (ω0) of 16%–32% were conducted using a confined SHPB system, with energy dissipation and SEM analysis. Results show that the dynamic behavior depends strongly on ω0 and material type. Stress-strain curves transition from elastic to plastic flow type, accompanied by strength/stiffness degradation and strain increase. High ω0 exacerbates degradation, reducing the strength retention of C grout to 47% at ω0=32%. MC grout provides the highest initial strength, whereas MCS grout exhibits superior damage resistance, characterized by lower initial damage D (0.715 at ω0=32%), stable growth rate G2, and higher damage tolerance. Microstructure analysis indicates that high ω0 increases porosity and weakens interfaces, while the dense gel network and integrated interface of MCS grout underlie its excellent damage control. The coupled mechanism, in which ω0 presets the initial damage state and grout material governs the evolution path, is clarified, providing a theoretical basis for material selection in tunneling through water-rich strata.

In order to investigate the damage characteristics of coal-rock-like combined body interface under impact load, according to the engineering background of 1331(1) working face of Zhujidong coal mine, the coal-rock-like combined body specimens were prepared by using similar materials, uniaxial compression test was carried out to test the mechanical crushing characteristics of the assemblage specimens under the range of low loading rate, and the Separate Hopkins Pressure Bar (SHPB) test system and ultra-high-speed video camera system were utilized, and the impact test on the coal-rock-like combined body under two impact air pressures of 0.3 MPa and 0.4 MPa was carried out by using DIC digital image technology. The impact test was carried out under two impact air pressures of 0.3 MPa and 0.4 MPa on the coal-rock-like combined body, and the dynamic stress-strain characteristics, displacement change rule and damage characteristics of the coal-rock-like combined body were comparatively analyzed based on the DIC digital image technology, under the situation that the stress wave entered into the coal body from the rock body. The results show that: ① The coal-rock-like combined body with close strength and large difference in wave impedance will show the phenomenon of equal double peaks in the stress-strain curve under the impact load, and the phenomenon is more obvious under the impact air pressure. ② When the coal-rock-like combined body is subjected to impact loading, the axial strain field appears in the coal body near the interface, and the second high strain field appears in the coal body far away from the interface and expands to the interface over time; in the transverse strain field, the first and the second high strain areas are located in the coal body far away from the interface and the position of the main crack, respectively; and the low-strain area appears near the coal-rock interface under different impact pressures; the strain at each moment of high impact pressure is more obvious than that under impact pressure. The strain peaks at each moment of high impact air pressure are 1.260, 1.094 and 0.382 times of the strain peaks of low impact air pressure, respectively, and the high impact air pressure has a weakening effect on the interface effect. ③ In the vertical direction, the displacement near the interface gradually appears as a step change zone, and it appears earlier under high impact air pressure. In the horizontal direction, the zone of sudden change in displacement near the interface appears, and the zone of sudden change in displacement is larger under high impact air pressure. ④ When the impact air pressure increased from 0.3 MPa to 0.4 MPa, the fractal dimension of the clasts increased from 0.658 to 2.071, and the average grain size of the clasts decreased from 27.194 mm to 12.297 mm, which was 54.8%. The results provide a research basis for studying the deformation and destabilization of the surrounding rock in dynamic pressure roadways by using coal-like rock materials.

Accurate prediction of vibration velocity in tunnel blasting engineering is of great significance for construction safety control and environmental impact assessment. To further improve the prediction accuracy of tunnel blast-induced vibration, this study addresses the limitations of the traditional Blood-Sucking Leech Optimizer (BSLO), which is prone to falling into local optima and exhibits slow convergence when dealing with multimodal and high-dimensional optimisation problems, and proposes an Improved Blood-Sucking Leech Optimizer (IBSLO). Based on the original BSLO mathematical model, the algorithm incorporates a host resource balancing mechanism to achieve adaptive migration and dynamic resource updating of search agents, thereby effectively enhancing population diversity and global optimisation capability. Comparative verification using twelve benchmark test functions demonstrates that IBSLO achieves significantly better convergence accuracy, stability and global search performance than BSLO and other traditional optimisation algorithms. On this basis, IBSLO is employed to optimise the hyperparameters of the Least Squares Support Vector Machine (LSSVM), and an IBSLO-LSSVM model for predicting tunnel blast-induced vibration velocity is developed. The results show that, compared with the BSLO-LSSVM, LSSVM and BP models, the IBSLO-LSSVM achieves a higher level of agreement between predicted and measured values, with the maximum prediction error reduced by 11.23%, 30.98% and 40.83%, respectively. The research findings can provide useful reference for blasting safety control and the optimisation of blasting parameter design in tunnel engineering.

Common buffers are unable to provide smooth cushioning over a limited short distance under high-speed heavy impact, which remains a technical challenge difficult to address in current drop impact tests. Therefore, a new type of multi-stage hydraulic cushioning system was developed, clarifying the working principle of the hydraulic cushioning system; based on Hertz contact theory, considering the effect of hysteretic damping factors on material energy dissipation, a continuous collision contact force equation for the cushioning system was established; the mechanical behavior of the multi-stage cushioning throttle hole structure at different cushioning stages was analyzed, and a dynamic model of the coupled contact-collision and cushioning hydraulic system was constructed. A high-speed heavy-impact test platform for the hydraulic buffering system is built, and the impact tests of the system under different impact velocities and different cushioning contact materials are completed. Comparing and analyzing the test and simulation results, the proposed modeling method is validated for accurately describing the cushioning process of the system; the dynamic characteristics of the hydraulic buffering system under different operating conditions and materials are studied in detail, and the influence laws of contact collision behavior on the cushioning performance of the system are clarified. The results show that the modeling method based on combined contact-collision and buffering coupling can accurately simulate the dynamic behavior characteristics of the buffering system. Moreover, the newly developed multi-stage hydraulic buffering system can achieve smooth buffering within a limited distance, providing an effective solution for buffering issues in the field of high-speed heavy-load drop impact protection.

Based on the impact deformation behavior of concave honeycomb array multi-cell structures with circular arc-curves, a target deformation mode hypothesis is proposed to optimize impact resistance and energy absorption performance. Combined with curved beam deformation theory, four parameter gradient distribution design schemes were developed, systematically studying the triggering mechanism of the target deformation mode under each scheme, as well as its effects on peak collision force and specific energy absorption. The study shows that the X-GS structure is more likely to trigger an “X”-shaped deformation at the early stage of impact compression, with better negative Poisson's ratio effect and impact energy absorption performance than the N-GS structure; the Y-GS structure is more likely to trigger an “I”-shaped deformation, which can buffer the peak collision force; the XY~GS structure can simultaneously trigger both“X”- and “I”-shaped deformations at the early stage of compression, and all cells achieve stable and ideal compression cohesion in the later stage, making its impact resistance and energy absorption performance the most outstanding. By reasonably designing the spatial gradient distribution of cell parameters in the honeycomb multi-cell structure, the impact deformation mode can be effectively regulated, the negative Poisson's ratio effect can be enhanced, and significant improvements in impact resistance and energy absorption performance can be achieved. 

In tunnel drilling and blasting operations through hard rock formations, the restraining effect of surrounding rock and fracture toughness significantly reduce cycle advance length and borehole utilization rate. To improve excavation efficiency, this study introduced a bottom-hole longitudinal shaped charge (BLSC) structure adapted from military and industrial shaped charge applications. The mechanism of BLSC was investigated through integrated numerical simulations and field tests. The results show that: The penetration damage of shaped charge jet to rock primarily occurs during the quasi-steady stage. In the near-penetration region, compressive stress failure dominates, forming an impact fragmentation zone, while in the far-penetration region, shear strain failure prevails under combined shock and stress waves, generating a crack zone. Compared to conventional cylindrical charges, BLSC significantly increases bottom hole pressure and effective stress while reducing their attenuation rates. The liner's confinement effect enhances detonation energy concentration, resulting in substantially higher wall pressure at BLSC positions than conventional charges. BLSC produces more extensive surrounding rock fragmentation and crack propagation compared to conventional cylindrical charges. When implemented in cut holes, it promotes earlier formation of through-going fractures in confined deep rock masses and facilitates better interconnection of directional cracks at borehole bottoms. Compared with the conventional blasting in test section, the local test of the upper bench BLSC blasting increas the average blast hole utilization rate of cutting holes by 12.6% and the average cycle advance by 0.17 m. In the full-section blasting systematic test, the average blast hole utilization rate of surrounding holes increased by 6% and the average cycle advance increased by 0.32 m. The research results demonstrate the feasibility of tunnel bottom-hole longitudinal shaped charge blasting, providing a novel technical approach to enhance drilling and blasting efficiency in hard rock tunnel excavation.

Long-span parallel double-box-girder bridges are increasingly deployed in high-traffic infrastructure applications, and their aerodynamic characteristics differ significantly from those of single box girders due to aerodynamic interference effects between the two girders. Therefore, a novel numerical identification method for aerodynamic admittance functions (AAF) based on the Adjustable Harmonic Multi-Frequency Spectral Synthesis method is proposed. This method takes into account the differences between the longitudinal (u-) and vertical (w-) components of the wind turbulence. Accordingly, the characteristics of AAF for the parallel highway-track box girders under aerodynamic interference conditions are further investigated. First, the influence of turbulence characteristics on the AAFs of the two girders was analyzed. It was found that the AAF of the upstream highway girder is insensitive to variations in turbulence parameters, whereas the AAF of the downstream track girder decreases with increasing turbulence intensity in the low-frequency region (k1 ≤ 0.15). Secondly, the aerodynamic interference effects of the upstream highway girder on the downstream track girder's AAF were analyzed. It was found that the longitudinal component of AAF (u-AAF) is less susceptible to aerodynamic interference, whereas the vertical component of AAF (w-AAF) is significantly affected, exhibiting a notable increase particularly in the higher-frequency range (k1 > 0.15). Subsequently, a comparative analysis was conducted on the differences between the u- and w- AAFs for the two girders. It was found that the u-AAF consistently exceeded the w-AAF. Finally, for the u-AAF and w-AAF respectively, a comparison was made between the upstream highway girder and the downstream track girder. It was found that the magnitude relationship between the two girders exhibits distinct variation patterns in terms of both u-AAF and w-AAF, which are influenced by the wind attack angle and the frequency. The outcomes of this study serve as a valuable reference for the accurate analysis of buffeting responses in long-span parallel double-box-girder bridges.

To comprehensively improve the hydrodynamic and acoustic performance of the pump-jet propulsor, the hub profile was parametrically represented using Bézier curves. Four key parameters—the inlet radius (r1), the radius at the rotor center (r₂), the radius at the stator center (r₃), and the axial length of the hub (d)—were selected as optimization variables. A synergistic optimization study of hydrodynamic and acoustic performance was conducted using a combination of numerical simulation and orthogonal experiments. The results show that, without loss of thrust, the optimized model achieved a 3.9% increase in open-water efficiency and a 3.2 dB reduction in sound pressure level under rated conditions, verifying the feasibility and effectiveness of hub profile optimization in synergistically enhancing pump-jet performance. The radius at the stator center had the most significant impact on open-water efficiency, while the radius at the rotor center most notably influenced rotor noise. A larger inlet hub radius and a moderate axial length improved the overall performance of the pump-jet propulsor. By designing a smooth curvature distribution and improving compatibility with the blade profile, the optimized hub contour effectively suppressed boundary layer separation and vortex generation in the flow passage, thereby enhancing flow stability and uniformity, reducing noise amplitude, and improving its spatial distribution.

Taking the shell-and-tube heat exchanger as the research object, the acoustic transfer characteristics of its tube range are solved based on the combined plane wave-mode matching method. The heat exchanger is divided into different acoustic regions according to the sound field distribution inside the heat exchanger, the heat exchanger tube bundle with smaller tube diameter uses the plane wave theory to calculate the acoustic transfer matrix, and the inlet/outlet header with larger tube diameter uses the three-dimensional mode-matching method to calculate its acoustic transfer matrix, and the acoustic pressure at the axial interfaces is used to solve the tube-range acoustic transfer characteristics of the shell and tube heat exchanger under the continuity conditions of the sound pressure and the plasmonic vibration velocity. Using the method of this paper and the three-dimensional finite element simulation method to calculate the tube-range sound transfer characteristics of the shell-and-tube heat exchanger in the frequency range of 10Hz-2000Hz, the method of this paper has a higher computational efficiency and a consistent computational accuracy compared with the results of the three-dimensional finite element simulation. Then, the influence of different parameters on the sound transmission characteristics of heat exchanger tube range is analyzed by this calculation method.

The stochastic transition dynamics between periodic solutions in complex nonlinear systems is of great significance for the stability and reliability of the systems. Aiming at multi-stable stochastic systems under periodic external excitation, this paper constructs the Euler-Lagrange equation satisfied by the most probable transition path using the variational principle based on the Onsager-Machlup action functional theory, and solves the most probable transition path of the system by integrating an improved physics-informed neural networks. Furthermore, this methodological framework is applied to a stochastic membrane acoustic  metamaterial model, yielding high-precision numerical solutions for the transition paths between the bistable periodic solutions of the model. On this basis, the effects of periodic excitation and noise on the stochastic transition paths of the system are discussed. The research shows that periodic excitation and noise can alter the transition position, transition time, and transition path, providing theoretical guidance for the effective design of membrane acoustic metamaterial models.

To investigate the natural frequencies, vibration modes, and overall dynamic behavior of a new small-radius curved railway trough–box hybrid continuous bridge, a theoretical formula for the natural frequency similarity ratio between the prototype and scaled models is derived based on the Euler–Bernoulli beam theory, combined with elastic similarity laws and dimensional analysis, and is applicable to arbitrary boundary conditions and variable cross-sections.According to the (72+72)m continuous curve trough-box-section hybrid bridge in Jieyang - Huilai railway, a 1/8 scale model with curve radius of 800m and a dual-equal-span layout of (9+9)m was designed and tested. Finite element simulation analyses were then performed for both the full-scale bridge and the scaled model. The hammering method was used to perform point excitation tests to obtain the natural vibration characteristics of the model under cantilever and continuous beam conditions, and the impact coefficient of the beam was also obtained by impact tests. The results indicate that, the proposed natural frequency similarity ratio model for straight variable-section continuous beams is applicable to the design of scaled models for both straight and curved variable-section continuous beams; the measured longitudinal impact coefficient is 1.31-1.36 and remains within the code limits.The parametric analysis indicates that the transverse constraints have the most significant influence on the natural frequencies and vibration modes of the curved trough–box hybrid continuous beam; the curvature radius and prestress level have limited effects on the overall dynamic characteristics.

Field measurements of vibration acceleration were conducted on the ground surface and within adjacent buildings above a typical small-radius curved section of Xi’an Metro Line 5 to analyze the characteristics of train-induced environmental and structural vibrations. Based on acceleration time histories and spectral analysis, one-third octave band analysis and Z vibration level indices were applied to investigate the horizontal and vertical vibration features at different surface distances and within building structures. Furthermore, the vibration dose value (VDV) was employed to evaluate the effects of short-term vibration and long-term exposure on human comfort. The results show that ground vibration acceleration generally attenuates with increasing horizontal distance from the track but exhibits a significant amplification zone within approximately 10-15m, with horizontal vibrations being notably greater than vertical ones. Dominant vibration frequencies range from 40 to 80Hz, with a peak near 63Hz. The maximum ground Z vibration level reaches 98dB, while the maximum horizontal band level reaches 102dB, exceeding the limit values by about 15-36%. Building vibrations decrease overall with floor height, exhibiting coexisting characteristics of low-frequency transmission and local high-frequency amplification. Vibrations measured on floor slabs are greater than those at wall corners, and the horizontal vibration level along the track direction shows a trend of initial decrease followed by increase, with the proportion of Z vibration level exceedance ranging from 3% to 25%. VDV results show that a single train passage produces vibration levels below the reference value of 0.4 m/s1.75, corresponding to slight perceptibility. However, considering cumulative daily exposure under regular operation, most measurement points exceed this limit, reaching uncomfortable or even very uncomfortable levels.

A regional seismic resilience assessment method based on GIS is proposed to improve the accuracy and coverage of evaluating urban bridge networks under earthquakes. The method analyzes road network density in ArcGIS Pro using kernel density estimation. By integrating the density grid-based DBSCAN clustering algorithm with the boundaries of urban residential land, this method enables the division of urban spatial regions and the identification of multiple transportation hotspot areas. Road network data of each area are extracted from ArcGIS attribute tables to build bridge network topology models. Incremental dynamic analysis (IDA) is used to evaluate bridge vulnerability. Monte Carlo sampling estimates bridge damage distributions under different peak ground accelerations to describe performance degradation. A gravity model and the trip attraction strength of points of interest (POIs) are used to generate interregional travel demand. The Frank-Wolfe algorithm balances network flow and calculates total travel time before and after earthquakes. Functional resilience indicators of each regional bridge network are calculated, standardized, and weighted by the number of POIs to obtain the overall resilience of the urban bridge system. Results show that higher PGA leads to significant traffic degradation: total travel time increases about 20 times, travel distance grows by 143%, and average speed decreases despite partial recovery potential. When peak ground acceleration rises by 0.1 g, traffic system performance declines by 10–15%, and overall resilience weakens. The results confirm that the proposed method can effectively describe the functional degradation and recovery of urban bridge networks under seismic disturbance and provide a scientific basis for earthquake risk assessment and seismic planning of urban transportation systems.

The long-period velocity pulses of near-fault pulse-like ground motions can induce resonant responses in base-isolated structures. This resonance not only challenges traditional dampers in synergistically controlling displacement and acceleration but also results in limited seismic mitigation efficiency. To address this issue, a Negative Stiffness Amplification System (NSAS) is incorporated into the base isolation layer. By adjusting the equivalent structural stiffness to suppress resonant responses and enhance mitigation efficiency, this study investigates the influence of pulse parameters on the seismic performance of NSAS-equipped structures using idealized velocity pulse excitations. The control effectiveness of NSAS under real near-fault pulse-like records is also analyzed. Engineering applicability is verified through time-history response analysis of the base-isolated structure. Results show that the seismic performance of NSAS is more significantly influenced by the pulse period (Tp). Within the resonant region (Tp≈Ts), NSAS demonstrates notable superiority over the traditional Viscoelastic Damper (VED), achieving optimization rates for displacement and acceleration reduction of up to 15.73% and 31.73%, respectively. Furthermore, time-history analyses based on 94 real near-fault pulse-like ground motion records confirm that NSAS enables synergistic control of inter-story drift and floor acceleration. The maximum average reduction rates reach 18.79% for inter-story drift and 10.52% for floor acceleration, verifying the advantages of NSAS in enhancing seismic mitigation efficiency and its engineering applicability under near-fault pulse-like earthquakes.

Traditional time-frequency analysis methods are difficult to provide high-resolution time-frequency distributions for fast-varying and slow-varying features, which hinders accurate identification of equipment operational status. To address this issue, this paper proposes a morphology-improved multi-synchronous-transient squeezing transform for mechanical fault diagnosis. First, the method estimates the instantaneous frequency and group delay by performing short-time Fourier transform. Then, morphological operations are used to construct morphology-improved multiple squeezing operator, thereby reducing the number of unassigned points caused by multiple squeezing operator. Finally, the morphology-improved multiple squeezing operator is applied to carry out the synchronous-transient squeezing transform, enhancing the resolution of time-frequency representation for both fast and slow time-varying features. Simulation and engineering case studies were conducted. The results demonstrate that proposed method outperforms traditional time-frequency squeezing methods.

To address the problems of strong noise, weak impulsive features, and limited fault recognition accuracy in vibration signals of mining slurry pump rolling bearings, a fault diagnosis method combining adaptive clustering stagewise orthogonal matching pursuit (AcStOMP) denoising and a grey wolf optimizer–support vector machine (GWO-SVM) is proposed. First, an overcomplete dictionary is constructed using a Laplace wavelet basis that is highly consistent with the attenuated oscillatory impulsive characteristics of bearing faults. Based on AcStOMP, matching atoms are adaptively searched within the dictionary and sparse representation coefficients are solved to achieve high-precision reconstruction of impulsive transient components, thereby effectively extracting true fault features from a strong noise background. Subsequently, five time-domain and three frequency-domain dimensionless indicators are extracted from the reconstructed signal to form a fault feature set, and redundant features are eliminated using SHAP (SHapley Additive exPlanations) feature contribution analysis, which reduces model complexity while maintaining diagnostic performance. Finally, the parameters of the support vector machine are optimized using the grey wolf optimizer to realize accurate bearing fault identification. Experimental results based on vibration data collected from SKF22324C bearings in an industrial site demonstrate that the proposed method achieves excellent diagnostic performance under four operating conditions—normal, inner race fault, rolling element fault, and compound inner race-rolling element fault—with an average classification accuracy of 98.26% ± 0.78%.