An analytical complex mode superposition method was presented to solve the forced vibration problem of a taut cable with a concentrated viscous damper.The forced vibration problem of a cable-damper system under unit impulse excitation was transformed into an equivalent initial value problem.The system’s unit impulse response function was then derived based on the solution of the corresponding initial value problem, on the basis of which the response of the cable to an arbitrary concentrated load was derived through the Duhamel integral.The response of the cable to an arbitrarily distributed load was obtained by the principle of superposition.The characteristic of the proposed method lied in its utilization of the system’s analytical complex mode shapes during the modal superposition process, with all solutions provided in analytical form.An example involving the forced vibration of a cable-damper system excited by several typical loadings was provided to show the correctness and effectiveness of the method.

Deep underground engineering excavation is significantly impacted by high ground temperatures, high water pressure, high stress levels, and strong disturbance environments, posing immense challenges to the safe and efficient extraction of deep coal resources.The self-developed thermal-hydro-mechanical multi-field environment coupling device was used to simulate the complex environment of engineering rock mass, and the dynamic impact compression test of deep rock was carried out with the split Hopkinson pressure bar test system.The results show that the dynamic stress-strain curve conforms to the nonlinear characteristics, and is accompanied by a significant “plastic platform area”.Under the same hydro-mechanical coupling, the peak dynamic stress increases most at the hydrothermal temperature of 51-57 ℃, while the water pressure and average strain rate at different temperatures follow the logarithmic function distribution; with the increase of temperature, the relationship between peak dynamic stress and average strain rate changes from negative linear correlation to exponential decay, and the time history curves of strain rate and stress rate have the change rule of “increase-decrease-decrease”.As water pressure increases, the overall failure mode of rock exhibits a progressive trend of “compressive-shear crushing failure→oblique shear boundary failure→fracturing failure”.The opening width, propagation length, and number of primary cracks on its end faces and failure surfaces gradually decrease.Under multi-field coupling and impact load, the time history curve of rock dissipation energy decreases briefly.The relationship between incident energy and dissipation energy is approximately power function.There is a good linear positive correlation between energy transmission coefficient and water pressure.The average strain rate and energy dissipation coefficient increase with the increase of damage degree.

Under the theoretical framework of fracture mechanics of quasicrystal materials, the anti-plane problem for a finite crack propagation in a functionally graded one-dimensional hexagonal piezoelectric quasicrystal strip was analyzed by using the method of integral transformation technique.The material properties of the functionally graded piezoelectric quasicrystal materials vary continuously along the thickness direction, following an exponential function.With the help of Fourier cosine transformation, the partial differential equation boundary value problem describing the fracture problem was transformed into three sets of dual integral equations, which were subsequently solved numerically by adopting the Copson method.The explicit expressions for the phonon stress, phason stress, and electric field at the crack tip were obtained.On the basis of theoretical analysis, the influence laws of material gradient parameters, crack length, material thickness, material coupling coefficient and external loading on the fracture characteristics of materials were deeply explored through numerical examples.The results of numerical analysis indicate that increasing the coupling coefficient of the quasicrystal material will significantly inhibit crack propagation.Reasonable design of gradient parameters or gradient thickness can help reduce the stress concentration at the crack tip.Under the same load, applying phase fields or electric fields reduces the fracture toughness of the material.As the stress loads of phonon fields and phase fields increase, the dimensionless energy release rate continues to rise.This research result not only provides useful supplements and improvements to the fracture mechanics theory of functionally graded piezoelectric quasicrystal materials, but also brings new perspectives and ideas to this theoretical research.

The simulation of ground-based micro-low gravity environments is a necessary step before the formal deployment of a spacecraft’s deployable mechanisms. To ensure the safety of high-value test objects and to prevent potential damage from abnormal vibration phenomena during the experiment, preliminary tests are usually conducted using simulators to verify the reliability and safety of both the experimental scheme and the system. The abnormal vibration phenomena observed during the deployment process of a prototype reflector antenna is presented, along with the experimental investigation and mitigation measures, aiming to provide a reference for the design and analysis of similar tests. First, the characteristics of the instability phenomena during the simulator’s deployment process are introduced. Then, static tests and free response tests at fixed deployment angles as well as full deployment response tests were conducted and analyzed to reveal how the system’s dynamic characteristics vary with the deployment angle. The mode shape features associated with the abnormal vibration phenomena is identified. Finally, a mitigation strategy was proposed that involved reducing the mass of the force sensing module to weaken the transmission of vibrations, which significantly suppressed the vibrations of the reflector simulator. This approach provided reliable technical support for the ground test of the reflector antenna prototype, effectively reducing experimental risks and paving the way for the smooth execution of the ground test.

Considering the high axial compression and concentrated flexural–shear actions at column base joints in underground frame structures, this study proposes a bolted semi-rigid column base joint exhibiting favorable seismic performance across a range of axial compression ratios. A reliable rotational stiffness model is essential for its structural application. Quasi-static tests were conducted to investigate the joint’s rotational behavior and flexural mechanism. Based on the results, an initial stiffness model was developed using the component method, incorporating a correction factor to account for nonlinear effects. A full-scale finite element model and nonlinear multivariate regression were employed to derive empirical expressions for this factor. The results revealed that moment resistance stems from the coordinated action of front and lateral connecting steel plates, confined square steel tubes, and concrete. At small rotations (0–0.7%), stiffness is primarily governed by the axial compression ratio and sectional dimensions, while at larger rotations, it is increasingly influenced by component parameters. Thus, desired joint stiffness can be achieved by adjusting these parameters to meet varying seismic performance demands. The proposed model showed a mean error of 10% and a standard deviation of 0.07, demonstrating high accuracy and broad applicability.

A dynamic model for grid-stiffened cylindrical shells under moving random loads was developed using the laminated stiffener method for full-field vibration uncertainty analysis. Spatiotemporal decoupling was achieved by separating the modal matrix of generalized state vectors in the reverberation-ray matrix method, significantly reducing the required sample size. A double-layer boosted long short-term memory neural network was proposed as a vibration response surrogate model, enabling fast and accurate full-field time-domain predictions. Parameter uncertainties were quantified with a probability distribution model, followed by uncertainty propagation analysis of the vibration response. Finite element simulations and Monte Carlo tests verified the method’s computational efficiency and prediction accuracy. The analysis incorporated uncertainties in material properties, geometric parameters, and external loads. Results indicate that the uncertain effects on the investigated structure exhibit diffusion characteristics under moving random loads, with the uncertainty in external load parameters playing a dominant role among all factors. Through parametric studies, the influence of stiffener geometry and external load parameters on the uncertainty in the dynamic response of the structure was revealed. These findings provide theoretical support for the engineering design and optimization of grid-stiffened cylindrical shells.

The folding device can effectively reduce the docking area of the shipborne helicopter, but the integration of the folding device will impact the vibration characteristics of the helicopter's horizontal tail drive shaft system. Based on the structural characteristics and transmission mode of the folding device, a dynamic model of the drum-tooth folding device was established. On this basis, a dynamic model of the horizontal tail drive shaft system with folding device was established using the finite element method and experimentally verified. The Newmark-β method was used to solve for the time domain waveform and axis trajectory of the horizontal tail drive shaft system with folding device, and its vibration characteristics were analyzed. Finally, the influence of the stiffness characteristics of the folding device on the vibration characteristics of the horizontal tail drive shaft system with the folding device was studied. The research results provide theoretical guidance for the structural design and selection of vibration suppression schemes for the horizontal tail drive shaft system with folding device.

Ocean-going vessels are continuously increasing in size and speed due to the advancement of shipbuilding technology and the expansion of global trade. However, larger and faster ships are more prone to hydroelastic effects with significant nonlinear vibrations even under moderate sea states. Therefore, accurately analyzing and evaluating ship hydroelasticity is of great importance for structural design optimization, safety assurance, and service reliability. In this study, a two-way coupled computational fluid dynamics–finite element method approach is employed to simulate the hydroelastic response of an ultra-large container ship in regular head waves and is validated against towing tank experiments using a segmented backbone model. The nonlinear responses induced by hydroelasticity are examined by comparing the influence of different sea states on the vertical bending moment at midship, and the contributions of wave-frequency and higher-frequency components are quantified through frequency-domain decomposition and time-domain reconstruction. The results show that when the wavelength matches the ship length, the structural response exhibits pronounced multi-frequency characteristics, with the higher-frequency component corresponding to a typical two-node vertical bending mode. Bow slamming triggers whipping, leading to nonlinear sectional loads near the bow that exceed the wave-frequency loads.

In order to mitigate the recoil impact and muzzle vibration of a 30 mm aircraft cannon during continuous firing, an asymmetric curved passage design in the recoil reducer is proposed, which generates counter-thrust and dynamic couples through asymmetric gas ejection from the upper and lower end surfaces. The initial conditions are determined based on the two-phase internal ballistics theory, and the transient flow of the gas in the asymmetric passage is simulated using the dynamic mesh method to obtain the variation curves of the flow field and aerodynamic forces. The results show that the dynamic peak values of the upper and lower passages differ by 0.18 ms, with a maximum aerodynamic force difference of 9.2%, effectively forming a dynamic couple. The lateral linear displacement and velocity at the muzzle are reduced by 22% and 19.3%, respectively, while the lateral angular displacement and angular velocity are decreased by 15.9% and 19.9%, respectively. The vibration is significantly suppressed without generating lateral forces, and the impact on the fuselage is markedly weakened. 

Negative Poisson's ratio structures exhibit transverse deformation opposite to conventional materials (lateral contraction under compression and expansion under tension), enabling complex deformation paths and energy dissipation under dynamic loads. To optimize energy dissipation under cyclic loading, a Bayesian optimization-based multi-objective parameter design method was proposed to tackle the strong nonlinear coupling between mechanical responses and geometric parameters. Finite element simulation combined with Bayesian optimization analyzed the influence of 7D geometric parameters on the equivalent plastic deformation ratio and cumulative plastic deformation. The results show that the bayonet-type negative Poisson structure achieves over 80% equivalent plastic deformation ratio through multi-cell collaborative deformation via Bayesian optimization, improving deformation uniformity. The machine learning attribute of Bayesian optimization provides a global optimization framework for high-dimensional complex systems, enhancing the optimization process.

To balance accuracy and efficiency in the dynamic modeling of bolted joint structures, this paper proposes an equivalent modeling method based on a variable spring stiffness-damping surface model. The method accounts for the stiffness characteristics of the joint interface and, more importantly, incorporates an equivalent representation of interface damping. A quantitative relationship is established among the contact pressure distribution governed by bolt preload, the frictional energy dissipation mechanism, and the evolution of interface stiffness and damping. Accordingly, a set of equivalent interface stiffness–damping parameter identification procedures suitable for finite element modeling is developed. To improve modeling efficiency, an automated finite element modeling plugin based on ABAQUS and Python has been developed, enabling agile model construction and parametric adjustments for complex bolted joint structures. Using a standardized bolted beam structure (Brake-Reuß model) and a multi-bolt lap-joint plate structure as case studies, modal tests are conducted and compared with traditional modeling approaches. The results show that the proposed method predicts the modal frequencies of the Brake–Reuß model with errors below 3%, and the MAC values exceed 0.94. Compared with conventional modeling approaches—such as full tie constraints (errors up to 11.24%) and partial tie constraints (errors up to 6.77%)—the proposed method significantly improves prediction accuracy and effectively captures the stiffness and damping variations under different preload levels. Additionally, the method achieves modal frequency prediction errors below 4% for the multi-bolt lap-joint structure. Overall, the proposed method enables efficient and accurate finite element modeling of bolted joints while maintaining high fidelity, offering a feasible and broadly applicable solution for the dynamic analysis of complex engineering structures.

Aiming at the issues of excessive drag caused by shock wave effects and high-pressure suppression in local windward areas during high-speed rocket sled tests, a disc-shaped spike cantilever structure was employed. This structure reduces the intensity of the bow shock wave and envelops the rocket sled within the shock wave cone, thereby reducing aerodynamic impact and alleviating high-pressure drag. The study focused on a monorail rocket sled tests with a maximum operating Mach number of 3, combining numerical simulation methods with the test results to obtain the influence of spike on the aerodynamic characteristics of rocket sleds and verify the effectiveness of this configuration. The research indicates that the spike maintains reliable structural integrity and can reduce aerodynamic pitching moments by 69.60% under the operating condition of Mach 3, significantly enhancing orbital operational stability. When the Mach number exceeds 0.8, the spike shows a significant drag reduction effect, with the drag reduction rate increasing with the Mach number, reaching 36.87% at Mach number of 3, and it has minimal impact on the lift of the rocket sled, but its cooling effect is not significant. The pressure distribution on the spike surface has good symmetry, with little influence from ground effects and the asymmetric structure of the rocket sled. However, the area of -90° to -51.5° of the hemispherical head of the rocket sled is within the influence range of the slippers and the rail.

This study investigates the temperature-dependent modal characteristics of tire structure-acoustic cavity coupled systems. A tire theoretical model was developed by integrating the flexible ring theory with acoustic resonance theory and the ideal gas law, incorporating temperature correction factors for material properties. Through combined theoretical modelling and experimental validation, the influence mechanisms of temperature variations on system modal properties are revealed. The results show that: The effect of tire structure-acoustic cavity coupling induces nonlinear natural frequency-temperature dependencies—for low-order modes, the temperature effect on material parameters dominates, leading to frequency reduction with temperature rise, whereas for high-order modes, the tire cavity pressure effect becomes predominant, causing frequency increase;  The established coupled model achieves prediction errors below 4% for in-plane and acoustic cavity modes within the 6.5 °C - 56.2 °C temperature range.

Debris flow impacts are a major cause of bridge damage and collapse in mountainous regions. In this study, a coupled DEM-FEM numerical model was developed to investigate the dynamic response and chained failure mechanisms of double-column reinforced concrete bridge piers under continuous debris flow impacts of varying intensities. By analyzing the variations in debris flow kinetic energy and structural resistance during impact, the influence of impact intensity on the overturning resistance of the bridge structure was examined, and an impact intensity index and classification system were proposed. The results show that debris flow impacts exhibit climbing and flow-around diffusion characteristics when interacting with bridge piers. Two typical failure modes were identified under different impact intensities: localized damage and global overturning. When the impact force exceeds a certain threshold, the cumulative effect of sustained impacts leads to progressive local damage and eventual overturning failure. The critical thresholds for no damage, local damage, and overall overturning of the inner pier are 27.97×10²kN, 29.22×10²kN, and 39.59×10²kN, respectively. Under moderate impact intensity, the stress state at the base of the inner pier transitions from compression to tension, exhibiting a stress reversal effect that causes tensile cracking failure. Under high-intensity impacts, a chained failure path of “concrete tensile cracking-joint compression-shear failure-longitudinal reinforcement yielding” is observed. The instability of the outer pier arises from system-level cooperative failure rather than direct impact domination. This study overcomes the limitations of traditional single-impact-force evaluations and provides theoretical foundations and threshold parameters for the impact-resistant design of bridges subjected to debris flows.

During tunnel drilling and blasting construction, the blasting vibration signals detected are often interfered with by multiple noises. The paper proposes a noise reduction method based on ICEEMDAN and WTD, aiming to more accurately remove noise while minimizing the loss of effective blasting vibration signal components. Additionally, WOA is introduced to improve ICEEMDAN, optimizing the selection of Nstd and NE during the decomposition process to further enhance the decomposition effectiveness of ICEEMDAN. To verify the feasibility of the method, the authors conducted simulation signal experiments and applied it to the processing of blasting vibration signals in the drilling and blasting construction section of the Qingdao Jiaozhou Bay Second Submarine Tunnel. The results show: Compared with CEEMDAN-WTD, EMD-WTD, MEEMD-LMS, and WTD, the self-optimizing ICEEMDAN-WTD proposed in this study demonstrates superior comprehensive performance. Through the processing and analysis of simulated signals and actual blasting vibration signals, the method achieves the best performance in three evaluation indicators: SNR, RMSE, and r. In practical engineering applications, the noise-reduced signals obtained by this method can more effectively eliminate noise above 200 Hz while reducing the loss of effective signal components below 200 Hz. Therefore, the self-optimizing ICEEMDAN-WTD method proposed by the authors has significant advantages in the processing of blasting vibration signals and can provide more accurate data support for controlling blasting vibration disasters in tunnel engineering.

The blasting stress waves generated by blasting pressure relief in rock burst roadways induce high-frequency disturbances in the surrounding rock of the roadway. This subjects the bolts to transient cyclic impacts, which easily trigger fatigue damage and failure of the bolts. To address this issue, a combination of theoretical derivation, numerical simulation, and underground field measurement was employed to systematically study the dynamic response characteristics of bolts under blasting dynamic loads. A one-dimensional free vibration model of bolts under blasting dynamic loads was established, and the differences in vibration modes of bolts under two anchorage conditions (end anchorage and full anchorage) were analyzed by combining the natural modes of the bolts. Additionally, an evolution equation for bolt fatigue damage under dynamic loads was constructed, revealing the influence mechanism of impact dynamic loads on the fatigue life of bolts.The research results indicate the following:① Blasting dynamic loads continuously impact the bolts, leading to the accumulation of fatigue damage. This damage accumulation process follows the evolutionary law of crack initiation, propagation, and eventual overall fracture failure.② The greater the amplitude of the dynamic load and the closer its frequency is to the natural frequency of the bolt, the more significant the attenuation of the bolt's fatigue life.③ Compared with full anchorage, end anchorage is more prone to resonance effects under dynamic loads, resulting in the amplification of blasting stress wave amplitude and early failure of the bolts.④ The loss rate of bolt working resistance decreases in a negative exponential trend as the distance from the blasting source increases. The working resistance of bolts in the blasting side and roof decreases more significantly than that in the non-blasting side.The research findings of this study provide new insights for analyzing the vibration response mechanism of bolts under blasting dynamic loads, and hold important theoretical significance and engineering application value for the support system design of deep mines, the optimization of blasting parameters, and disaster prevention and control.

To address the complex distribution of explosion overpressure fields in confined structures and the absence of effective empirical formulas, this study proposes a reconstruction method based on dataset augmentation and improved neural network modeling. The initial dataset is built using limited experimental data, while additional multi-equivalent samples are generated through 3D numerical simulations to augment the data. An improved neural network model is trained on the augmented dataset. Its performance is validated using internal samples, and further tested on unseen equivalent experimental data to reconstruct the overpressure field. Results show that with training on a multi-equivalent joint dataset, the model achieves an average relative error of 4.43% and a coefficient of determination (R²) of 0.9533. When applied to other equivalent conditions, the trained model yields an average relative error of 6.77%, The effectiveness of the data-driven modeling strategy in small-yield ranges and complex implosion environments with regular structures has been validated, providing a promising approach for research on this type of problem.

The pulse-type bedrock ground motion parameters are of great significance for earthquake disaster analysis and seismic design of underground structures. In view of this, based on the data of KiK-net strong earthquake observation network, this study selected 17 commonly used engineering ground motion parameters covering the three elements of the pulse-type bedrock ground motion to construct a database. Then, the bedrock ground motion parameters are regarded as high-dimensional random variables, the surface ground motion parameters and the ground motion influence factor parameters are regarded as high-dimensional conditional variables, and the conditional denoising diffusion neural network is used to establish its probability distribution model. After training the conditional denoising diffusion neural network with database data, the inversion and prediction of bedrock ground motion parameters can be realized. which can be applied to design quayside gantry crane systems. Finally, three stations are selected to compare the prediction results of the model with the traditional empirical formula and the equivalent linearization method. The fitting accuracy R2 is increased by about 17.97 % and 9.55 % respectively, indicating the rationality and advancement of the model established in this study.

To investigate the influence of finite-element mesh geometry on seismic wave simulation results and its theoretical mechanism, a series of numerical experiments have been conducted on the scattering problem of SH waves in valley topography using quadrilateral, triangular, or rectangular elements of varying sizes. The accuracy and computational efficiency are analyzed in combination with grid dispersion theory. The main research findings are as follows: (1) When the mesh sizes are 1/20, 1/15, 1/12, 1/10, 1/7.5, and 1/5 of the minimum wavelength, the grid dispersion errors are 0.62%, 1.1%, 1.69%, 2.44%, 4.27%, and 9.41%, and the numerical simulation errors are approximate <1%, <1%, 2%, 4%, 10%, and 28%, respectively. Thus, the first two mesh sizes are highly accurate. (2) The influence of mesh geometry on accuracy is manifested that variation in element size with direction also leads to directional variation in accuracy. Therefore, highly-irregular elements face a significant challenge in balancing the accuracy in long-edge direction and the computational efficiency in short-edge direction. (3) Moreover, mesh size and geometry play a dominant role in computational efficiency. The primary mechanism is that the stable time step in explicit time integration is proportional to the element size in short-edge direction. Consequently, triangular elements or other irregular elements allow for considerably smaller time steps compared to square elements. (4) The all-square element model has the advantages of simplicity and high-efficiency. Our preliminary investigation demonstrates that its step-like interface mesh generates only minor error waves, confirming the feasibility of this model. This study provides practical guidance for finite element modeling of seismic response of complex sites. 

Historical seismic damage investigations have shown that bearing uplift is a critical cause of bridge structural failures, especially in long-span arch bridges where spatial vibration of the main arch amplifies the dynamic response of spandrel structures. To evaluate the influence of bearing uplift on the seismic behavior of such bridges, a nonlinear collision mechanical model incorporating uplift effects was developed. Using a typical long-span concrete-filled steel tube (CFST) arch bridge as an engineering case, this study systematically examines the mechanisms and consequences of bearing uplift under near-fault pulse (NF-P), near-fault non-pulse (NF-NP), and far-field (FF) ground motions. Results indicate that the bearing uplift process consists of three distinct stages: girder-bearing compression, girder uplift, and girder-bearing collision. Bearings located at girder-ends and mid-span are most vulnerable to uplift, showing larger vertical displacements, higher uplift frequency, and longer uplift duration. Among the considered seismic scenarios, NF-P ground motions are the most likely to trigger bearing uplift, with the lowest threshold peak acceleration. In addition to intensifying vertical collision forces, bearing uplift also leads to redistribution of compressive forces among adjacent bearings, resulting in abrupt load increases in non-uplifted bearings. Furthermore, bearing uplift significantly amplifies the internal forces in cap beams, as well as the torsional and in-plane bending responses of the girder, while having limited influence on out-of-plane girder bending. Neglecting these uplift effects may lead to a severe underestimation of seismic responses and potential risks in long-span CFST arch bridges, underscoring the importance of considering this phenomenon in seismic design.

Conventional rocking substructures targeted rare earthquakes, with dampers at the base to mitigate seismic response. Under design‑level earthquakes, rocking amplitude was small and damper stroke was limited. To improve moderate‑earthquake performance, a multi‑level energy‑dissipating rocking system with negative‑stiffness device and variable‑stiffness connections was proposed. The mechanism amplified rocking amplitude under design‑level earthquakes to increase damper stroke; deformation of variable‑stiffness connections reduced substructure impact on the main structure; under rare earthquakes, connections transitioned to rigid links to constrain deformation. Elastic–plastic time‑history analyses were conducted to compare representative systems. The results show that peak floor acceleration, floor shear and inter‑story drift are reduced by 28%, 18% and 2.8% under design‑level earthquakes and by 6%, 6% and 3% under rare earthquakes. A simplified multi‑degree‑of‑freedom model was developed using OpenSees to investigate effects of connection stiffness, negative stiffness and damping ratio. A single‑degree‑of‑freedom elastic model was proposed and optimized using generalized fixed‑point theory combined with acceleration–displacement optimization. 

To address the limitations of conventional seismic fragility analysis methods, a semi-parametric TKC method that balances computational accuracy and efficiency was introduced for component-level analysis, along with an R-vine Copula-based system-level approach that effectively accounts for the correlation of component responses. A two-level “component–system” fragility analysis is conducted. The rationality and accuracy of the proposed methods were validated through comparison with the first-order boundary method. To investigate the damage characteristics and seismic performance of a typical railway seismic isolated bridge system, taking a 7×32  m seismically isolated simply supported beam bridge with double-track railway as the case study, a refined nonlinear dynamic analysis model of the track–bridge system was established, enabling fragility analyses at both component and system levels. A three-level seismic performance evaluation framework tailored for railway seismic isolation bridges was developed to comprehensively assess bridge seismic performance. Results indicate that seismic-isolation bearings are the most vulnerable components under seismic action, followed by tracks and piers. The bearing system predominantly controls slight and moderate damage states, while the track system governs severe damage and complete failure. Accordingly, practical engineering should prioritize enhancing seismic design of the bearing system and implement necessary measures to improve track system seismic capacity, ensuring overall bridge system performance meets intended standards.

In cross-domain fault diagnosis of rotating machinery, significant data distribution differences exist between different equipment and operating conditions. Existing domain adaptation methods suffer from insufficient feature discriminability and pseudo-label noise interference, resulting in low diagnostic accuracy. A cross-domain fault diagnosis method based on dynamic margin and confidence calibration (DMCC) was proposed to address these problems. A prototype-driven dynamic margin mechanism was designed to maintain prototype representations of fault categories and dynamically adjust separation margins according to inter-category similarities, imposing stronger separation constraints on similar fault categories to enhance feature discriminability. A confidence calibration alignment strategy was constructed using prediction confidence of target domain samples to adaptively weight domain alignment losses, suppressing negative effects of low-quality pseudo-labels in conditional domain alignment. The two mechanisms were combined through an end-to-end optimization framework and validated on 12 cross-domain tasks constructed from four datasets containing bearings and gearboxes. Experimental results show that the method achieves average accuracies of 83.85% and 91.79% on cross-device and cross-condition fault diagnosis tasks respectively; the proposed method outperforms existing mainstream domain adaptation methods; the approach demonstrates good cross-domain generalization capability.

Aiming at the challenges in identifying bearing degradation onset and subtle inter-signal variations, this paper proposes a novel method for early warning and remaining useful life (RUL) prediction based on state feature energy ratio and fine-grained network updates. The approach combines nonlinear energy operator with Savitzky-Golay filtering to extract transient energy features and suppress noise. The energy ratio identifies degradation onset by computing prominent frequency energy proportion in envelope signals. The prediction network employs causal convolution and bidirectional learning in training process to capture local features and subtle temporal variations, enhanced by a fine-grained update mechanism. Validated on XJTU-SY and CQJTU-CJB datasets, the method demonstrates effective early degradation alarm and precise RUL prediction. 

Considering the rotor tilt, a gas film model of a 4-degree-of-freedom aerostatic journal bearing is established, and the perturbed Reynolds equations with flow disturbance term are obtained through theoretical derivation. The finite difference method is used to solve the coupled perturbation Reynolds equations, and the effects of rotor tilt angles, eccentricity, rotating speed, gas supply pressure, and perturbation frequency ratio on the dynamic characteristics of bearings are studied. The results show that increasing the rotor tilt angles, eccentricity, and gas supply pressure can increase the main stiffness coefficients and main damping coefficients of the bearing at the same time. Increasing the ratio of rotating speed and perturbation frequency ratio can improve the main stiffness coefficients of the bearing, but reduce the main damping coefficients of the bearing; In addition, with the increase of perturbation frequency ratio, the values of damping coefficients of bearings gradually approach zero.

To address the problem of strong noise contamination in acoustic emission (AE) signals generated during rock fracture, a novel denoising method based on Artificial Lemming Algorithm (ALA) optimized Variational Mode Decomposition (VMD) combined with an improved wavelet threshold (IWT) technique is proposed. The ALA is employed to optimize the number of modes and the penalty factor of VMD. The correlation coefficients between the decomposed intrinsic mode functions (IMFs) and the original AE signal are calculated, and a threshold is set to classify the intrinsic mode functions into noise-dominant and signal-dominant components. To overcome the limitation of traditional wavelet threshold denoising in adaptively selecting the wavelet basis function and decomposition level, the optimal wavelet basis and decomposition level are determined based on the characteristics of rock fracture AE signals, as well as the signal-to-noise ratio (SNR) and root mean square error (RMSE) of the denoised signal. Subsequently, the noisy components are denoised using the IWT method and then reconstructed to obtain the denoised AE signal. Experimental results on both simulated and real AE signals show that the proposed ALA-VMD-IWT algorithm improves the signal-to-noise ratio by 44.63% and reduces the root mean square error by 32.97%, demonstrating its superior noise suppression capability and higher denoising accuracy. The proposed method provides a reliable foundation for subsequent rock characterization based on AE signal analysis.

To address the challenge of balancing low-frequency noise and ventilation in urban rail transit systems, a low-frequency ventilation acoustic metamaterial combining the Venturi effect and the Helmholtz effect has been designed. This structure guides and compresses airflow through a Venturi tube while constructing a Helmholtz cavity to achieve discrete resonance, enabling coupling between continuous propagation modes and discrete local resonance in the low-frequency range. This generates a Fano-like effect to enhance sound transmission loss. Simulation results indicate that, at the same resonance frequency, when the neck is centred at the throat of the Venturi tube, the structure achieves the strongest acoustic energy coupling and maximum transmission loss, reaching 59.8 dB. Additionally, steady-state turbulence simulations show that the maximum wind speed of this structure is four times that of a traditional straight cylindrical pipe structure, verifying its excellent ventilation performance. Low-frequency sound insulation performance was tested using the four-microphone method, with results showing a sound insulation peak of 40.45 dB at 485 Hz, consistent with simulation results. This metamaterial structure provides a new approach for noise reduction in rail transit systems, offering tunable and integrable solutions.

This paper investigates the influence of wavy leading-edge blade and wavy leading-edge/serrated trailing-edge blade on the aerodynamic noise generated by traction motor cooling fan using arc array measurement technology. Experimental measurements are conducted on motor noise with baseline fan, wavy leading-edge fan, and wavy leading-edge/serrated trailing-edge fan, analyzing variations in far-field acoustic directivity and overall sound power level. The experimental results show that the bionic configurations effectively reduce motor noise, achieving a maximum reduction of 1.1 dBA in overall sound power level, while maintaining neutral impact on the far-field acoustic directivity. The bionic configurations exhibit notable suppression effects on noise within the 500 Hz to 2000 Hz, achieving up to 10.7 dBA reduction in sound power level. The serrated leading-edge reduces noise in the air intake region, while the wavy leading-edge/serrated trailing-edge demonstrates notable noise suppression across the full circumferential range. Moreover, the wavy leading-edge/serrated trailing-edge demonstrates superior noise suppression performance compared to the wavy leading-edge alone.

Magnetic bearing technology demonstrates broad application prospects across various fields, with its performance being crucial for the stability and reliability of rotating machinery systems. However, in complex real-world operating environments, maglev bearing systems inevitably encounter various forms of electromagnetic interference (EMI). These interferences infiltrate the control system through different coupling paths, leading to a significant reduction in levitation precision, which in turn affects the overall system performance. To effectively suppress these detrimental electromagnetic interferences and ensure the normal and stable operation of maglev bearing systems, implementing a rational grounding strategy is a crucial and indispensable key measure. In a maglev bearing system, a scientifically sound grounding method can effectively establish an equipotential reference point, providing a low-impedance return path for various signals generated within the system. This low-impedance path can significantly suppress the propagation of both common-mode and differential-mode interference, thereby reducing noise effects on sensitive signals. Inappropriate grounding methods can lead to problems such as ground loops, common-mode voltages, and crosstalk, causing inherently weak sensor signals to be submerged in noise and severely undermining the stability and precision of the control system. Therefore, in-depth and systematic research into the grounding methods for maglev bearing systems is essential to ensure their high-precision and high-reliability operation. This paper aims to thoroughly investigate the specific impact and underlying causes of different grounding methods for various components within a maglev bearing system, including the bearing itself, the driver, the controller, and the DC power supply, on control signal stability and levitation precision. Through experimental comparisons, the effects of 19 different grounding schemes on the maglev bearing rotor displacement signals were analyzed, and the optimal grounding method was selected for testing during the acceleration/deceleration process and at maximum speed. The experimental results demonstrate that optimizing grounding methods can effectively enhance levitation stability, and this study also provides valuable optimized grounding strategies for the anti-interference design and engineering implementation of maglev bearing systems, contributing to an improvement in their stability and reliability in practical applications.