In actual industrial production, different operating conditions lead to variations in data distribution, posing a challenge for bearing fault diagnosis under different working conditions. To address this issue, a fault diagnosis method based on multi-adversarial and balanced distribution adaptation was proposed. Firstly, an improved residual network was used to directly extract domain-invariant features from the original vibration signals, enhancing feature extraction efficiency while preserving rich fault feature information. Secondly, a domain adaptation method combining correlation alignment and multi-adversarial domain adaptation was proposed, which can simultaneously align marginal distribution and conditional distribution of source domain and target domain to minimize data distribution differences between domains.Thirdly, the balanced distribution adaptation method was improved with designing a balance factor to allocate weights to the marginal distribution and conditional distribution in the adaptation process, so as to enhance cross-domain fault diagnosis effect. Finally, the effectiveness of the proposed method was validated using publicly available bearing fault datasets. Experimental results show that compared to popular domain adaptation methods, the proposed method achieves higher fault diagnosis accuracy, showing practical application value in bearing fault diagnosis tasks under different working conditions.

Autonomous underwater vehicles (AUVs) are widely used in various fields such as hydrological monitoring, underwater exploration, and patrol reconnaissance, due to their mobility, robustness, and extensive operational range. To ensure the safe and efficient completion of various tasks, the research on motion control technology for AUVs is of paramount importance. This paper provides a chronological overview of the development of AUVs, focusing on typical products both domestically and internationally, with an emphasis on motion control technologies. Additionally, it presents the "Sheng Whale I" AUV developed by the team, along with its motion control technology. Based on the current state of AUV motion control research, strategies can be classified into path tracking, trajectory tracking, and stabilization control. Research in this field primarily focuses on the design of guidance schemes and the optimization of controllers. The main challenges affecting AUV motion control systems include model uncertainties, external disturbances, and actuator saturation. To address these challenges, intelligent control techniques such as deep reinforcement learning, sliding mode control, active disturbance rejection control, neural networks, adaptive control, S-plane control, and fuzzy control have been widely applied. These methods effectively mitigate the impact of changes in the AUV's dynamic model, as well as environmental disturbances like waves and ocean currents, on tracking accuracy. For actuator saturation issues, model predictive control, deep reinforcement learning, and sliding mode control have shown particularly promising results. Existing research indicates that information-based AUVs are numerous, and the motion control systems of AUVs demonstrate significant advantages in terms of accuracy and robustness. Future developments in AUVs will focus on long-range vehicles powered by renewable energy and multi-mode AUVs equipped with autonomous maneuvering capabilities. Additionally, the trend in AUV motion control will shift towards low-power motion control and swarm motion control.

Under variable operating conditions, the training set and testing set of the deep learning-based train wheelset bearing fault diagnosis model usually come from different operating conditions, and the domain shift problem caused by the distribution difference of vibration signals under different operating conditions leads to the diagnosis accuracy reduction. The domain adaptation-based bearing fault diagnosis method under variable operating condition needs to obtain sample of the target domain to participate in the training process, which is infeasible in engineering practice. Thus the domain adaptation-based method is not suitable for bearing fault diagnosis of unseen conditions. Aiming at the above problems, an operating condition domain generalization fault diagnosis method based on multi-scale CNN and two-stage attention mechanism network model (TSAMCNN) is proposed in this paper. First, the multi-scale feature extraction module can extract richer fault information in the time-domain vibration signals from multiple scales. Then, the two-stage attention module can adaptively enhance the fault-sensitive features and suppress the condition-sensitive and useless features from both the channel and space dimensions. The model is ultimately capable of extracting condition-invariant fault features, which is the key to achieving the operating condition domain generalization fault diagnosis. Through the variable speed and the variable load bearing fault diagnosis experiments, it is proved that the proposed TSAMCNN model can improve the accuracy of bearing fault diagnosis, noise immunity performance and operating condition domain generalization ability. In addition, the weight vectors of the two-stage attention mechanism and the features extracted by each module of the model are visualised and analysed to improve the model interpretability.

Harmonic drive is a transmission mechanism that relies on controllable deformation produced by flexible components, which are subjected to continuous alternating stress. As a result, the risk of failure is significantly higher than that of conventional transmission mechanisms. Changes on the fault location, kinematic relationship, and bearing area may cause interval distribution and periodic transformation of fault characteristic frequency. The running of harmonic drive based on the close coordination of several rotational components in narrow space, the transmission of single fault may cause the appearance of fault characteristics of multiple faults, the fault location is difficult. Therefore, an equivalent method is proposed to clarify the time-varying patterns of flexible bearing fault frequency by equating the kinematic relationship of continuous transient with that of conventional bearing. The calculation procedure of fault characteristic frequency for circular spline, flex-spline, flexible bearing, and cross roller bearing is presented. A fault simulation experiment is conducted to validate the theoretical analysis, fault characteristics for multiple faults are provided. The results show that the experiment results are consistent with the theoretical analysis, and the fault characteristic frequency can be obtained based on the proposed method.

In order to solve the problem of low fault diagnosis accuracy, this paper proposes a bearing fault diagnosis method based on feature cross-attention mechanism fusion and develops the CNN-BiTCN-CATTM model. The original signal is reconstructed using variational mode decomposition and fast fourier transform, while bidirectional temporal convolutional networks (BiTCN) and convolutional neural networks (CNN) are used to extract time-frequency features. The cross-attention mechanism (CATTM) is applied to fuse these features, fully capturing fault characteristics from the original signal. Experiments show that in an environment with Gaussian white noise (SNR = 9.32, standard deviation = 2.98), the CNN-BiTCN-CATTM model achieves a bearing fault classification accuracy of 99.88%, which is about 22.79%, 4.85%, and 4.19% higher than using CNN, BiTCN, and CNN-SATTM, respectively. Even with Gaussian white noise (SNR = 3.31, standard deviation = 5.96), the model still achieves a diagnostic accuracy of 96.12%. The CNN-BiTCN-CATTM model effectively extracts deep fault features and significantly improves fault classification accuracy.

To investigate the propagation laws of energy waves generated by nearshore underwater borehole blasting and to evaluate the destructive effects of seismic waves and water shock waves on reservoir dam, as well as the damaging effects of seismic waves on reservoir shore pits, this study was conducted based on the underwater borehole blasting project at the water intake of the Second Water Source Project in Guilin City. Using a fully coupled Lagrangian-Eulerian algorithm, numerical simulations of nearshore underwater borehole blasting were carried out to analyze the changes in propagation patterns and attenuation laws of blasting energy waves, as well as the dynamic response characteristics of the reservoir dam and shore pits. The results indicated that: 1) The attenuation characteristics of the water shock wave peak pressure with the scaled distance charge (Q1/3/R), dam vibration velocity time history curve and the variation pattern of dam peak vibration velocity observed in field tests showed a high degree of consistency with the numerical simulation results. Both field tests and numerical simulations demonstrated that the attenuation characteristics of water shock wave peak pressure closely matched Cole's empirical formula, confirming the reliability of the numerical simulation model for underwater borehole blasting. 2) Based on an intuitive analysis of the propagation and attenuation characteristics of water shock waves in reservoir water and seismic waves in the reservoir bottom rock mass, the propagation process of blasting energy waves was divided into three stages: explosion stage, diffusion stage, and attenuation stage. The influence ranges of seismic waves and water shock waves caused by the propagation of energy waves, with a medium vibration velocity of v=0.1cm/s, were 270m and 206.28m, respectively, and both did not reach the foot of the reservoir dam. 3) The peak pressure of water shock waves significantly attenuated with increasing distance from the explosion center and depth. Based on the blast similarity analogy method, a dual-factor empirical calculation formula for water shock wave pressure, considering both explosion center distance and underwater depth, was established, which can be used to reliably predict the peak pressure of water shock waves at any position in the water area. 4) The propagation of blasting energy waves in the reservoir dam caused significant dynamic responses in the core wall and the dam body. The vibration response in the bottom region of the dam’s blast-facing side was intense, and localized damage occurred in the dam foot area. The peak vibration velocity at the monitoring point at the dam bottom reached 0.17cm/s, which is below the standard limit of 2.5cm/s, indicating that the dam was preliminarily in a safe and stable state; the maximum damage ratio at the dam foot was only 25%. To ensure the absolute safety of the dam, appropriate vibration isolation and protective measures should be considered. 5) The propagation of blast-induced seismic waves in the reservoir shore rock mass triggered sequential dynamic responses on the blast-facing side, bottom, side, and back-blast side of the pit. The peak stress and peak vibration velocity were highest at the top of the blast-facing side of the pit. Close-range high-charge blasting could adversely affect the safety and stability of the shore pit, necessitating strict reinforcement and vibration isolation measures in engineering practice. The findings can also provide a reference for analyzing the propagation laws of energy waves and assessing adverse impacts in similar engineering blasting projects.

Precision optical instruments in aircraft and ships face increasingly stringent requirements for the vibration environment, and active control methods via the Stewart platform have attracted extensive attention. Firstly, the development of Stewart active vibration isolation platform at home and abroad was investigated, and the main performance indicators such as payload (Kg), active bandwidth (Hz) and maximum amplitude attenuation (dB) were summarized. Secondly, the key technologies on Stewart active vibration isolation platform, including Stewart platform configuration, isotropic and dynamic stability, coupling factors and decoupling methods, dynamic modeling methods, nonlinear and hysteresis phenomena of smart material actuators, and active control algorithms, were summarized in detail. The study discussed how the main performance indicators were enhanced by these key technologies and identified unresolved issues； then, the advantages of multi-channel coupled adaptive algorithm using Stewart isolation platform in complex and time-varying vibration environment were summarized. Finally, the further development of Stewart active vibration isolation platforms in precision optical instruments was prospected. 

Due to the low stiffness of serial industrial robots, the robotic milling process is prone to chatter due to the improper selection of processing parameters or robot pose, which will reduce the surface quality of the workpiece and damage the robot equipment.In order to predict the chatter stability of robotic milling, the variation of robot end stiffness along with the spatial pose was studied by constructing the stiffness model of the robot.The dynamic model of the spindle system was constructed, then the influence of the speed effect on the dynamic characteristics of the tool tip was studied, and the mapping function between the spindle speed and the natural frequency of the tool tip was constructed by data fitting method.A robotic milling dynamic model considering the coupling effects between the robot and spindle system was proposed.The damping ratio and modal mass at the tool tip of the robotic milling system were obtained by hammer experiments, and the stability lobe diagram of the robotic milling system considering different factors was obtained.The variation law of milling chatter stability under the coupling effects of the robot-spindle system was revealed and verified by experiments.The results show that the stability lobe diagram obtained when considering the robot-spindle system coupling effects is more consistent with the actual milling state, which can effectively improve the prediction accuracy of robotic milling chatter stability.

Transmission lines are subjected to dynamic loads such as wind loads, conductor vibrations, and dancing for a long time, resulting in loss of bolt preload or even loosening, which seriously affects the safety of transmission towers and lines.The joints of the tower are usually connected by bolts, which bear the shear force and lateral vibration load.However, relevant codes only specify that the tightening torque of bolts should achieve the purpose of tightening and preventing loosening, and other factors that affect the anti-loosening characteristics are often ignored, which may affect the long-term tightening state and daily operation and maintenance of bolts.Transverse vibration tests were conducted on 6.8 grade M16 rough high-strength bolts commonly used in transmission towers, and the effects of different frequencies, amplitudes, and torques on the bolt preload and fastening characteristics were studied.Then, a simulation analysis of the anti-loosening characteristics of bolts under transverse vibration load was carried out, and the results were compared and verified with the test results and specifications.The bolt deformation and thread area stress under transverse vibration state, as well as the bolt loosening law under different initial preloads were investigated.The results show that the decline curve of preload can be divided into two stages: rapid decrease and steady decrease.When the transverse vibration frequency is lower, the amplitude is larger, and the torque is smaller, the bolt is more likely to loosen.Under transverse vibration load, the stress distribution in the threaded area is uneven, with an overall trapezoidal distribution.Furthermore, the stress distribution of the thread gradually decreases from the screw section towards the free end, and the maximum stress point moves from the middle position to both sides.The higher the preload, the better the anti-loosening performance.Therefore, it can be seen that the preload force corresponding to the torque method specified in the code is relatively low.It is recommended to use preload force control and take 0.5 to 0.6 times the yield tightening axial force.

Nonlinear energy sink (NES) has broad application prospects in passive control.However, studies in this filed mainly focus on unidirectional vibration absorbers to limit its applicability to multi-directional vibrations in practical applications.Here, a multi-directional NES was designed using 2 sets of mutually orthogonal steel wire structures to realize adaptive vibration absorption in any direction of a single vibrator space.Multi-directional vibration governing equations of the system were established based on Lagrange equation, and the harmonic balance method was used for approximate analytical analysis of the system’s steady-state response.The fourth-order Runge-Kutta method was used for numerical verification, and then the vibration reduction effect of the multi-directional NES was studied.The results showed that the multi-directional single vibrator NES can effectively suppress multi-directional vibrations and it is equally effective for any unidirectional excitation. This study can provide a reference for application and design of NES in multi-directional vibration control.

The geometric condition of railway tracks is crucial for the operational safety and ride comfort of trains. Therefore, research on the analysis of track irregularities, track quality assessment, and prediction of track irregularity development is of importantsignificant practical significance. This paper reviews recent Recent research on the assessment and prediction of track geometry was reviewed in this paper, including the analysis distribution characteristics analysis of track irregularity, track serviceability assessment, and prediction of track irregularity development. The advancements and shortcomings of existing research is was discussed and future research directions of relevant topics are were analyzed. It is found that in the study of track regularity distribution, there is a need to further integrate dynamic and static track inspection data, as well as to further investigate the data feature in the sensitive and weak track sections. Regarding track quality assessment methods, time-domain methods is predominant, whilst the frequency-domain methods are still under development. Further research is needed to investigate the relationship between time- and frequency-domain indexes, and to establish a comprehensive track quality assessment scheme incorporating wavelength parameters. In terms of track irregularity development prediction, compared to ballasted tracks and conventional railways, research on ballastless tracks and high-speed railways is relatively limited, and relevant studies inadequately consider the evolution of track structural performance. Future efforts should focus on constructing predictive models that meet the requirements of maintenance work based on actual environmental and factors. 

As one of the basic engineering units, elastic beam systems are widely used in various fields, including architecture, aerospace, ocean engineering, and others.It is of great engineering significance to control the vibration level of elastic beam systems.To reveal the potential application of double-coupling nonlinear oscillators(DCNO) in the vibration control of double-beam systems, a dynamic behavior prediction model of double-beam systems with DCNOs was established, where the Lagrange method was used to predict the dynamic behavior of the double-beam system.On the basis of ensuring the correctness of the numerical results, the typical operating mode of the DCNO was studied, and the influence of the DCNO parameters on the dynamic behavior of the double-beam system was discussed.The results show that the introduction of the DCNOs can effectively realize the synchronous vibration control of each substructure of the double-beam system.On the one hand, when the DCNO is in the multi-frequency linear/nonlinear vibration control mode, the vibration of each sub-beam in the main resonance region of the double-beam system is effectively suppressed.Additionally, the multi-frequency nonlinear vibration control mode excites the complicated vibration responses of the double-beam system, resulting in the unidirectional transmission of vibration energy in time domain between elastic beams and DCNOs.On the other hand, according to the vibration control requirements, the working mode and vibration control effect of DCNOs can be realized by adjusting its core control parameters.Setting appropriate core control parameters for DCNOs is conducive to enhancing the vibration control effect of the DCNOs on the main resonance region of the double-beam system.

As the core component of active vibration control, a novel Ampere force electromagnetic actuator based on the Halbach magnetic pole array was designed, featuring high force density and low output force fluctuation rate. The multi-physical field coupling relationship of the electromagnetic actuator was analyzed, and a coupled model of the electromagnetic field and energy consumption field was established. In this model, the energy consumption field was modeled by the neural network surrogate model method to enhance the computational efficiency. The NSGA-II optimization algorithm was employed to conduct multi-objective optimization design, and the improved entropy weight decision-making theory was combined to obtain the optimal combination of design parameters. A prototype of the electromagnetic actuator was fabricated and experimental analysis was carried out. The results show that: In the 30-250Hz frequency band, the force constant of the actuator can reach 20 N/A, and the nonlinearity is less than 10%. When the peak current is 8 A at 250 Hz, the energy consumption of the actuator is 105.20 W, presenting the advantages of low force attenuation rate, good linearity, and low power consumption.

When tape springs are applied in the form of winding and stretching in spatially deployable structures, the problem of loosening often occurs.Here, a multi-tape spring winding and loosening model was proposed, in which a loosened winding segment was divided into an external Archimedean spiral expansion zone and an internal semi-circular arc transition zone, and a strain energy analytical model was established.According to the principle of minimum potential energy, stable loosening inner diameter and stable loosening form were solved, and critical center body radius, stable tip force and critical tip force were derived.A finite element model for multi-tape spring winding and loosening was established using the software ABAQUS, and the numerical analysis results of stable loosening inner diameter, stable loosening form, critical center body radius and critical tip force were compared with the theoretical model calculation results.Tests were conducted to verify stable loosening form and stable loosening inner diameter, and prove the correctness of the theoretical model.

The transfer learning method has made great progress in solving the problem of unsupervised fault diagnosis of gearbox. However, due to the differences in the distribution of gearbox data, noise and interference, and the limitations of the model, most of the methods are not effective in migrating complex gearbox datasets, and there are still few studies on the interpretability of network inputs. In this paper, we propose an improved domain-adversarial neural network (IDANN). The improved time-frequency network is used as a feature extractor to provide interpretability and noise reduction when the signal is fed into the network, and then the class-level alignment method of the target domain is added to the domain adversarial network, and two classifiers are used to detect the target samples close to the decision boundary to enhance the migration performance. The effectiveness and reliability of IDANN are verified on the Southeast University gearbox dataset and straddle-type monorail gearbox, and the performance of IDANN under noise conditions is tested on the Case Western Reserve University bearing dataset, and the experimental results show that IDANN has excellent diagnostic performance and robustness. 

In this paper, the crimped expansion mechanism with complex multi-region contact is simplified to a variable-length flexible component attached with a rigid disk, and the multi-body system dynamics model is established to realize efficient simulation. Firstly, a variable-length beam is modeled using the absolute nodal coordinate formulation described by arbitrary Lagrangian–Eulerian method (ALE-ANCF), and then the complex contact problem is simplified into constraint relation of moving boundary. A method for adding and deleting nodes is presented which can effectively solve the singularity and accuracy problems caused by the change of element length. On this basis, rigid-flexible coupling dynamic model for the multibody system is established, and the numerical solution of the dynamic equations is realized by an implicit algorithm. The effectiveness of the modeling method is verified by examples of sliding rope and moving pulley. Finally, a simplified dynamic model of the rolled deployable mechanism inflatable deployment system is developed, in which arbitrary Lagrangian-Eulerian moving mesh is used to track the real-time position of the rolled deployable mechanism, accurately capture the moving boundary points, and quickly determine the contact behavior. The influence of air pressure and adhesion force on the development dynamic characteristics is analyzed. By controlling the distribution of adhesion force, the uniform deployment of the rolled deployable mechanism is achieved, which holds practical engineering significance.

The impact vibration test is widely used in modal analysis, because of its convenience, low cost, and efficiency in identifying multiple modes with a single impact.To achieve efficient and accurate estimation and uncertainty quantification of modal parameters in the impact test, a fast Bayesian fast Fourier transform method was proposed.The likelihood function was first developed based on the equation of motion and the complex normal assumption of measurement error, and the Laplace approximation was then adopted to obtain the posterior distribution of modal parameters, i.e., fitting the posterior distribution with a Gaussian distribution, whose mean was computed by minimizing the negative log likelihood function (NLLF) while the covariance matrix was obtained by taking the inverse of the Hessian matrix of NLLF at the posterior mean.A coordinate descent algorithm was proposed to minimize the NLLF taking advantage of the analytical gradient of NLLF.The Hessian matrix was obtained via the calculus of complex matrix, allowing an efficient implementation.Finally, the performance of the proposed method was validated through synthetic and laboratory data.A comparison with the methods based on free and ambient vibration tests was also provided, respectively.

Damage analysis of ground building under blast loading has significant practical guidance for developing combat strike strategies and engineering protection design. The LS-DYNA finite element analysis software is used to reproduce the existing near-field explosion test of the reinforced concrete (RC) masonry-infilled frame structure, which fully verifies the applicability of the adopted refined numerical simulation method. Combined with the hybrid element modeling method of building structures, a simulation analysis is carried out on the dynamic response of the three-story masonry-infilled RC frame under the explosion of typical warheads (100kg and 200kg TNT equivalent). The propagation of blast waves inside the structure and structural damage characteristics are investigated. Based on the equivalent single-degree-of-freedom (SDOF)method, the damage degrees of RC beams, columns, slabs and infill walls under blast loads are predicted, and a damage assessment method for building structures under internal explosions is established. Its applicability is verified by comparing with the refined numerical simulation results. It indicates that, under 100kg and 200kg TNT explosion conditions, the overall functionality and structural damage degrees of the building in the refined numerical simulation are both moderate and slight. The corresponding damage degrees obtained by the equivalent SDOF simplified assessment are consistent with the refined numerical simulation results. In addition, it can be seen from the damage degree of members that compared with load-bearing components, i.e. slabs, beams and columns, masonry infill walls are more prone to failure, resulting in a larger damage range of rooms in the horizontal direction within the floor.

In order to explore the wind vibration characteristics of bladeless wind turbines, a bladeless wind turbine with a height of 3 m and a rated power of 100 W was taken as the research object. Firstly, the finite element model of the wind turbine is established, the natural mode information is calculated, and the wind-induced vibration is predicted. Subsequently, a full-scale model of the turbine was tested in a wind tunnel. Finally, the experimental results are compared with the theoretical prediction results, and the wind-induced vibration law is comprehensively analyzed. The results show that the cross-wind displacement at the top of the fan increases first and then decreases with the increase of wind speed, showing a typical vortex phenomenon, so there is no need to consider safety measures such as braking system in high wind speed environment. At the same time, when the wind speed is stable, the displacement time history of the top of the fan is close to the standard sinusoidal curve, showing stable wind-induced vibration. In addition, the aerodynamic characteristics of the wind turbine in all directions are also about the same, with good adaptability to all wind directions, and there is no need to rely on an additional yaw system to cope with wind direction changes.

Given the issues of imbalanced attention mechanisms, conservative pooling strategies, and the loss function's inability to comprehensively consider information from all classes leads to the learned features being relatively scattered in the FasterVit network, a rolling bearing fault diagnosis method based on the CFasterVit-TFAM and COS-UMAP models is proposed. The model consists of the FasterVit-TFAM network, the COS-UMAP dimensionality reduction algorithm, and the activation function CMSD-Softmax. Firstly, a new attention mechanism TFAM is proposed and combined with the FasterVit network to improve the balance and representation ability of information attention in the FasterVit network. Secondly, the COS-UMAP dimensionality reduction algorithm is used to replace the last pooling operation before the fully connected layer of the FasterVit network, effectively filtering and retaining important features in multidimensional data. Finally, replacing the cross-entropy loss function in the Softmax activation function with the mean standard deviation loss function allows for a more comprehensive learning of features and improves the model's generalization. The XJTU rolling bearing mixed fault experiment results show that the diagnostic accuracy of the TFAM attention mechanism is increased by 8% compared to other attention mechanisms, and the diagnostic accuracy of the COS-UMAP is increased by 15.8% compared to other dimensionality reduction algorithms. The diagnostic accuracy of the CMSD is increased by 0.5% compared to the cross entropy loss function. The proposed model achieves a recognition accuracy of 99.6% for fault samples, which is 1.4% higher than that of FasterVit and 7.8% higher than that of other network models. The simulation results of the rolling bearing dataset from Southeast University show that the proposed model achieves a recognition rate of 98.6% for fault samples, which is 2.2% higher than that of FasterVit. The average training time per round is reduced by 16.92 seconds, which is a maximum improvement of 12.2% compared to other network models, effectively improving the accuracy and generalization performance of the rolling bearing fault diagnosis model.

The flight stability of explosively formed projectiles (EFP) directly determines their impact orientation, velocity, and dispersion, which in turn affects the penetration performance of the EFP. To enhance the penetration power of hypersonic EFPs (Mach 4-7), a review of the current configurations and flight stability of EFPs was conducted. Models of EFPs with high aspect ratio tail skirts and corrugated fins were established, and a numerical method for calculating the aerodynamic parameters of hypersonic EFPs was developed and validated. The effects of structural parameters of finned EFPs—such as root height, tooth width, and solidity—on lift-to-drag ratio, center of pressure, and flight stability were analyzed. Additionally, the influence of structural asymmetry and roll motion on the static aerodynamic parameters of tail-skirted and finned EFPs was investigated. Based on this, the flight dynamics differential equations of EFP were established and validated. The effects of structural asymmetry and roll motion on ballistic radial displacement were analyzed. Additionally, the impact of liner material on the long-range velocity decay of spherical, tail-skirted, and finned EFPs was studied, and a quantitative analysis was conducted to assess how flight stability influences the residual velocity retention of EFPs. The study indicates that conventional stability criteria for finned projectiles remain applicable to the hypersonic air trajectory of EFPs. Introducing a low-speed roll motion through inclined corrugated fins significantly enhances the air trajectory dispersion of asymmetrical EFPs. The optimized finned EFP presented in this paper exhibits excellent flight stability and superior residual velocity retention, offering a standard configuration reference for designing high-penetration EFP warheads.

Damage to transformer windings caused by external short circuits is usually not only related to a single short-circuit process, but also to gradual deformation of windings caused by successive short-circuit impacts to generate irreversible cumulative deformation and reduce their anti-short-circuit ability. Here, firstly, a 110.0 kV transformer was remade to conduct multiple short-circuit impulse tests. Cumulative effect of short-circuit impacts on mechanical state damage of windings was verified by measuring changes of reactance and axial pressure of windings. Then, effects of cumulative effect on vibration characteristics of windings were revealed through time domain and frequency domain analyses of vibration signals on surface of fuel tank and axial impact force of windings. Wigner-Ville distribution method was used to process vibration signals, construct time-frequency matrix for realizing feature extraction, and calculate the membership degree of winding mechanical state based on fuzzy C-means clustering algorithm, a method for quantifying the cumulative effect of winding deformation was proposed, and the criterion for severe winding deformation was determined. According to the experimental results, it can be seen that the variation law of vibration characteristic parameters is highly consistent with the change rate of reactance and axial pressure. The study results can be applied in mechanical state assessment and early fault warning of windings, and provide important engineering reference value for safe and stable operation of transformers.

A bandgap control method based on XOY plane cell element Z-axis dimension folding is proposed for negative Poisson's ratio mechanical metamaterials used for vibration reduction. Based on the three-dimensional folded cell element method and corresponding three-dimensional Bloch-Floquet periodic boundary conditions, the finite element method is applied to numerically calculate the band curves of three types of negative Poisson's ratio metamaterials (arrow shaped, star shaped, and inner hexagonal) and the vibration level drop of the samples. The reasons for the band gap changes of these mechanical metamaterials are analyzed from the perspective of vibration modes. The sensitivity of different band curves to folding angles is reflected in the local stiffness of the corresponding vibration modes of the cell, and stiffness changes can generate or eliminate band gaps. Research has shown that when the bandgap control method of cell folding is applied to three types of metamaterial cells, their band structures all exhibit similar band gap evolution patterns. By controlling the geometric shape of the cells through folding angle, the movement of the band curve can be controlled. Under specific folding angles, new directional band gaps can be generated in the band structure of metamaterials, and the original directional band gaps will also disappear. Taking the arrow shaped cell as an example, a metamaterial sample was made, and the accuracy of the numerical calculation results and the band gap variation law were verified through frequency sweep experiments. The first directional band gap in the energy band structure changed from 3989.2Hz to 4204.4Hz to 3843.4Hz to 4176.5Hz. 

多体动力学；刚柔耦合；假设模态法；机电耦合；振动控制

Based on the research background of twin rotor actuator, a single drive twin rotor actuator active control device is proposed in this paper, which is mainly composed of mass block, space transmission gear group, motor and controller. The centrifugal force generated when the rotor is driven by the gear is used as the active control force to reduce the structural vibration. Compared with the traditional active mass damper, this design not only does not need to consider the linear travel limit of the guide rail, but also solves the problem that the motor in the dual drive twin rotor actuator is difficult to synchronize through structural optimization, and realizes more efficient and stable vibration control. In order to study the vibration damping performance of the single drive twin rotor actuator, firstly, the mechanical model of the single drive twin rotor actuator system, the single degree of freedom structure and the state equation of the single driven twin rotor actuator are established based on the mechanical analysis of Lagrange equation. Secondly, a controller combining pole assignment method and Super-Twisting Sliding mode control algorithm is designed for vibration reduction of single drive twin rotor actuator system, and the control parameters contained in the controller are optimized based on the improved Dung beetle optimization algorithm. Compared with other control algorithms, the proposed method not only enables easier acquisition of controller parameters but also eliminates tedious trial-and-error tuning, thereby streamlining practical engineering im-plementation. Finally, the stability of the system is proved by the Lyapunov function, and the feasibility and effec-tiveness of the Super-Twisting sliding mode control algorithm based on the single drive twin rotor actuator system are verified by the simulation experiments.

Blasting-induced vibrations significantly threaten the safety of adjacent structures. Barrier hole, as one of the effective methods for mitigating such vibrations, has been widely employed in rock engineering. However, the layout scheme of the barrier holes often relies on empirical methods, and the current standards for assessing the effectiveness of vibration reduction are typically limited to specific measurement points, which cannot comprehensively represent the spatial distribution of vibration impacts behind barrier holes. In this paper, to systematically investigate the vibration reduction and isolation effect of barrier holes, numerical simulations were carried out based on the engineering background of the Zhentou dam apron blasting excavation project. Firstly, the effectiveness of LS-DYNA software and the equivalent blasting load method in modeling the vibration reduction and isolation effect of barrier holes was verified through small-scale blast experiments. Subsequently, the effects of various parameters of barrier holes on vibration reduction and isolation characteristics were investigated. Simulation results indicated that the area with the optimal vibration reduction effect is located directly behind the region where the barrier holes are arranged. With the increase in the number of barrier hole rows, barrier hole depth, distance between the barrier holes and blast area, and the number of holes in a single row, the effective vibration reduction area increases. The peak vibration reduction rate significantly increases with the increase of the number of barrier hole rows but decreases with the increase of the distance between the barrier holes and the blast area, and is affected by both the depth of the barrier hole and the depth of the blast hole. Compared with the vibration reduction rate of a specific measuring point, the effective vibration reduction area can reflect the regional distribution of the vibration reduction effect and is not affected by the location of the measurement point. The correlation analysis of the vibration reduction and isolation effect based on different barrier hole parameters showed that the effective vibration reduction area is most correlated with the depth of barrier holes, followed by the number of barrier hole rows and the distance between the barrier holes and the blast area. The peak vibration reduction rate is most correlated with the number of barrier hole rows, and the concentrated vibration reduction rate is closely related to the number and depth of barrier hole rows. The research findings in this study provided a reference for the layout of barrier holes, optimizing vibration mitigation to safeguard adjacent structures.

In order to establish a seismic design method for the buckling-restrained braced reinforced concrete (BRB-RC) frame structures based on resilience, the quantitative index of resilience level was introduced, the classification of the seismic resilience level of the building was established, the calculation assumption based on functional loss to control the resilience index was proposed. A quantitative relationship of multi-level functional loss of the building was established, and the method to control component damage and engineering demand parameters based on building function loss was proposed. According to the working mechanism for BRB-RC frame, the design method based on resilience was determined, and the design process was established. The design method was applied to the seismic design of a 5-story BRB-RC frame structure and the nonlinear dynamic analyses of the structure subjected to large earthquake were performed. The analysis results show that the inter-story drift ratio and inter-story shear force distribution of the structure meet the design requirements, and the proposed method can achieve the expected seismic resilience target. 

In order to study the seismic performance of the assembled steel fully recycled concrete frame-recycled concrete infilled wall structure, a cast-in-place steel reinforced concrete frame (control group) and two assembled steel reinforced recycled concrete frames with a scale ratio of 1:2.5 were designed. The mechanical properties such as hysteresis curve, skeleton curve, stiffness degradation, energy dissipation capacity, strength degradation and inter-story displacement angle of assembled steel reinforced fully recycled concrete were investigated by low cyclic loading test. The results show that the failure modes of the assembled steel fully recycled concrete frame and the cast-in-place ordinary concrete frame are similar, both of which are manifested as the failure of the plastic hinge zone at the beam end and the column bottom. The stiffness degradation of prefabricated steel reinforced recycled concrete frame is more obvious than that of cast-in-place ordinary concrete frame, and the maximum reduction is about 62.54 %. The energy dissipation capacity of the prefabricated steel reinforced recycled concrete frame with infill wall is the best, which is about 22.22 % higher than that of the cast-in-place steel reinforced concrete frame. The strength degradation coefficient of cast-in-place ordinary steel reinforced concrete frame and assembled steel reinforced recycled concrete frame is between 0.89 and 0.91, and the strength degradation coefficient of assembled steel reinforced recycled concrete frame with infilled wall is between 0.77 and 0.82. The displacement ductility coefficient of the assembled steel reinforced recycled concrete frame is about 2.14 ~ 4.63, which is about 118.40 % higher than that of the cast-in-place ordinary concrete structure. The ultimate inter-story displacement angle of cast-in-place steel ordinary concrete frame and assembled steel recycled concrete frame is between 1/39 and 1/28. The strain test results show that the bearing capacity of the structure is mainly controlled by the normal stress on the section. The plastic hinge begins to form at the beam end, and finally forms at the bottom of the column. The failure belongs to the beam hinge mechanism, which meets the seismic requirements of strong column and weak beam.

The number of components and fault types of the shore bridge gearbox is large, and the fault data is difficult to obtain, and its diagnosis faces the problem of small sample and multiple classification. To address the above problems, a fault diagnosis method based on frequency domain vibration image (FDVI) and conditional denoising diffusion probabilistic model (CDDPM) is proposed. Firstly, the obtained vibration signals are transformed into images using the FDVI method, fully characterizing the characteristic information of vibration signals for each fault. Then, the CDDPM is used to expand the small sample data, and the labeling information is input to the model to control the generation of fault sample categories, while skip-layer sampling is used to accelerate the sample generation speed. Input the expanded sample set into a convolutional neural network classifier for training to improve the classifier's performance in diagnosing multi class faults with small samples. The small-sample diagnostic experiments on the 17 faults in the CWRU dataset and the 29 faults in the shore bridge scaling experimental platform dataset show that: after the sample expansion, the fault recognition rate of the CWRU dataset is increased from 89.86% to 99.30%; the fault recognition rate of the shore bridge dataset is increased from 68.63% to 99.30%. The above analysis shows that the proposed method can accomplish the task of multi-class fault diagnosis for shore bridge gearboxes under small sample conditions.

The cooling blade is the core component of the heavy-duty gas turbine, which is used under severe service conditions and often fails due to excessive vibration.It is of practical significance to accurately understand the vibration mechanism of cooling blades for design and maintenance of gas turbine blades.In this paper, a NACA0012 airfoil blade was taken as an example.The blade was simplified into a rotating cantilever flow tube with a single-axisymmetric section, which contained unequal large double channels, based on the Euler-Bernoulli beam theory.An axial-chord-flap-torsion coupling dynamic model was established by using the assumed mode method and the Lagrange method.By comparing the results with the reference, the accuracy of the dynamic model in this study was confirmed.The effects of fluid flow velocity, infusion tube rotation speed, axial-chord coupling and flap-torsion coupling effect on the natural frequencies of the system were studied.It is found that the rotational speed has different effects on the stiffening effect of each degree of freedom, resulting in complex modal sequence exchange phenomenon.The axial-chord couplings, and the flap-torsion couplings could induce the modal steering phenomenon, resulting in a decrease or increase in the different natural frequencies.For Euler-Bernoulli beams with large slenderness, the influence of the single-axisymmetric section mainly focuses on the flap-torsional stiffness coupling.Within a certain speed range, the flap-torsion coupling effects may induce flutter instability in the system.In addition, the axial force showing a hardening effect on the torsional vibration of one-dimensional components, as discussed in present paper, represents an extension and advancement of the material concerning one-dimensional wave equations within the current curriculum of vibration mechanics.Furthermore, the contributions of structural dynamics modeling and the associated numerical methodologies presented herein are deemed suitable for inclusion as supplementary reading material in both undergraduate and graduate vibration mechanics courses.

Due to the long lead time and high cost for the preparation of rubber isolator prototypes and impact performance testing, simulation analysis is needed to evaluate the feasibility of the design or selection of structure and material before the preparation of prototypes. Referring to the drop impact test method of isolator, a finite element model for impact performance simulation analysis of vibration isolators is established in LS-DYNA, and the Mooney-Rivlin-Maxwell model is chosen as the rubber visco-hyperelastic constitutive model. In order to obtain the parameters of the constitutive model of the rubber material under the impact condition, the rubber material used in the isolator is made into a sphere, and the impact test and finite element simulation analysis of the rubber sphere and steel plate are carried out. A generalized regression neural network (GRNN) is established, and the optimized GRNN model and test data are used to predict the parameters of the constitutive model of rubber material. Carry out the impact simulation and analysis of rubber isolator, the simulation is close to the test results, and the established finite element simulation and analysis model can be used to evaluate the impact performance of the isolator, which provides a reference method to carry out the simulation and analysis of the impact performance of rubber isolators and the acquisition of the parameters of the constitutive model of rubber material under the impact condition.

Inerters are widely used as a new type of structural control element in structural vibration systems, but are less studied in bogie motor suspensions. Three kinds of inerter-stiffness-damping (ISD) motor frame suspension bogie lateral dynamics models are established. The equivalent conicity is simulated by smooth fitting curves, the measured track spectrum is used as the excitation input of the bogie system. The integrated value of the root-mean-square (RMS) of the acceleration at the end of the frame is used as the optimization objective function. The parameters of ISD frame suspension and the original frame suspension structure (SD) are optimized and their stability is analyzed by the subtractive averaging optimizer optimization algorithm (SABO). Parameters of the ISD frame suspension and the original frame suspension structure (SD) through the subtractive average optimizer algorithm (SABO) and analyze their stability. The results showed that the ISD tandem-parallel structure has the best effect in reducing the vibration response of the bogie, and its stability is the best under the new wheel-rail matching and the late stage after wheel reprofiling, and its linear critical speed can be increased by 215.6 km/h compared with that of the SD structure. The ISD triple-parallel structure has stability indexes that are slightly lower than that of the SD structure, and the ISD triple-tandem structure deteriorates the lateral stability of the bogie and reduces its critical speed. At the same time, its integrated root-mean-square and maximal  root-mean-square are lower than that of the original frame suspension structure (SD). Its integrated  root-mean-square and maximum  root-mean-square are the most sensitive to speed changes, which is not conducive to improving the lateral stability of the bogie. The results of the study can provide a reference for the design of motor elastic suspensions for high-speed EMUs.

Aiming at the problem that the damping characteristics of vehicle hydro-pneumatic spring cannot be adaptively adjusted according to road and driving conditions, and it is difficult to achieve sufficient safety and comfortBased on the insufficient adaptive damping capability with the various road and running conditions for hydro-pneumatic spring in vehicles, which cannot obtain satisfactory safety and serviceability,, a design theory of semi-active magnetorheological (MR) hydro-pneumatic spring is was proposed. Based on the MR mechanism and vibration-damping theory of vehicle suspension, a novel MR hydro-pneumatic spring with two-way damping force controllability for vehicles has beenwas designed. Mechanical principle of this MR prototype is was discussed with MR valve. Considering the compressibility of liquid and gas, squeezing strengthening effect of MR fluid and local loss, the theoretical models of output damping force and elastic force are were derived. The effects of Mechanical mechanical variations ,with piston length, gap width and gas pressure, with on output mechanical properties were have been qualitatively and quantitatively analyzed based on the derived model. Comparing with the measured results of the experimental prototype, the proposed theoretical models can precisely describe the mechanical performance under various excitations. The output force increases with the increasing increase the of excitation amplitude, frequency and the applied currents. These findings provide the theory and hardware base for optimization design of MR hydro-pneumatic spring for vehicles.

The dynamic impact problem under moving load is closely related to bridge design, operation and maintenance, and involves the economy and service safety of bridge structure construction. At present, many studies mainly focus on the dynamic amplification of vehicle crossing the bridge, and the dynamic amplification coefficient of a single vehicle crossing the bridge is often not equal to the dynamic load coefficient used in the design stage of the bridge. Based on the numerical simulation of the dynamic response of the vehicle-bridge-pier coupling system model, the definition and calculation method of the bridge impact factor (BIF) were given. Aiming at a high-pier and long-span girder bridge, the BIF calculation and influencing factors were studied, and the influence of speed limit and pavement roughness on BIF was analyzed. The results show that BIF is an inherent characteristic parameter related to the bridge state, which is closely related to the allowable load, limited speed and pavement smoothness of the bridge. BIF increases with the increase of the speed limit, but when the speed limit exceeds the most unfavorable speed, BIF remains unchanged. Road roughness has a more significant effect on BIF, and BIF is further amplified with the increase of road roughness. When the bridge deck deteriorates, bridge deck pavement repair or speed limit can be implemented to ensure that the BIF is within the allowable range. This study reveals the value and evolution law of bridge BIF, which can provide guidance and reference for the design and operation and maintenance management of the same type of bridge.

To solve the problem of fault feature extraction and intelligent diagnosis of rolling bearing signals, this paper proposed a bearing fault diagnosis method, based on successive variational mode decomposition (SVMD) and convolutional block attention module-residual neural network (CBAM-ResNet). It entailed decomposing bearing vibration signals using SVMD into a series of intrinsic mode components. The selection of components with distinct fault features was determined based on envelope entropy and kurtosis fusion evaluation indicators, followed by a reconstruction process. The reconstructed signals underwent transformation into time-frequency images using Short-Time Fourier Transform. After that, CBAM was able to capture the features of the graphic features adaptively, and the time-frequency images of the reconstructed signal were input into CBAM-ResNet model for feature extraction and fault pattern recognition. In the process of CBAM-ResNet model training, transfer learning was used to initialize ResNet model parameters to improve the generalization of the model. Compared with other traditional models, the classification accuracy of the proposed model is as high as 96.68%, and it has stronger fault feature extraction ability. The experimental results show that CBAM-ResNet model also has high recognition accuracy under variable working conditions.

The Fast Iterative Shrinkage Threshold algorithm based on Fast Fourier transform (FFT-FISTA) has high computational efficiency, as it ignores the spatial variation of the point spread function and the winding error, resulting in the loss of sound source recognition performance. The improved algorithm takes the output of function beamforming as the iterative input of FFT-FISTA algorithm, establishes a linear equation system of function beamforming, sound source distribution and rising power spatial transfer invariant point spread function, and solves it iteratively based on the fast Fourier transform under the periodic boundary condition. The calculated non-periodic function is changed into a periodic function, which solves the problem of wavenumber leakage caused by the zero-filling boundary, which can improve the accuracy of the operation and further improve the imaging performance. The main lobe of the point spread function is sharpened by exponential operation, and the applicability of the assumption of spatial transfer invariance of the point spread function is expanded. The simulation and experimental results show that, compared with the conventional FFT-FISTA algorithm, the improved algorithm can improve the spatial resolution and dynamic range of the imaging, and expand the effective imaging area of the FFT-FISTA algorithm, and the experimental results of compressed gas leakage verify the effectiveness of the improved algorithm. 

Masonry pagodas are important cultural heritage buildings,with a relatively large number of existing examples and distinguished by their unique structural forms and the relatively large number of existing examples. Due to their high aspect ratios and relatively low shear strength, these pagodas exhibit notable dynamic responses under seismic actions, making them highly susceptible to damage. This study examines the The structural features of these pagodas were examined in this study, summarizing the patterns of seismic damage in various structural forms were summarized. It compiles and analyzes The formulas for calculating the natural vibration periods of these structures were compiled and analyzed and compares the results of in-situ dynamic tests were compared. Focusing on key issues related to damage identification, dynamic response, damage mechanisms, and vibration control, the analysis highlights highlighted the fundamental patterns of seismic response in masonry ancient pagodas and the mechanical mechanisms of seismic damage formation and control. By integrating research on damage identification, this study also analyzes the basic characteristics of dynamic responses were also analyzed obtained from shaking table tests and numerical analyses, and summarizing the variations in seismic responses of the pagodas were summarized. Analyzing the damage modes of masonry ancient pagodas under seismic actions, this study examines the seismic damage mechanisms of the pagodas, organizes existing reliability assessment methods, clarifies the influence of foundation soil on the seismic response of the pagoda structure, and identifies key issues in the restoration and seismic control of ancient pagodas. Based on the failure mode of masonry pagodas under seismic action, the seismic failure mechanism of the pagodas was analyzed, the existing reliability evaluation methods were sorted out, the influence of foundation soil on the seismic response of the pagoda structure was clarified, and the key issues of restoration and seismic reduction control of thepagodas were identified. This work provides valuable insights for the seismic research and performance enhancement of masonry ancient pagodas.

 In order to solve the problem of excessive system recoil caused by the large kinetic energy of the muzzle of a 40mm submerged bullet artillery gun, a composite recoil reduction technology that combines the muzzle brake and expanding wave technology is proposed. Based on this technology, the internal ballistic equation of the submerged bullet expanding wave artillery was established, and the change rule of the chamber pressure, velocity and body tube force with time during the internal ballistic period was analyzed. On this basis, based on the three-dimensional non-constant Navier-Stocks equation, combined with the dynamic mesh technology, the numerical simulation of the breech flow field during the after-effect period of the submerged projectile gun is carried out, which focuses on revealing the influence of the gunpowder and gas flow on the force characteristics of the retractor, and comparing and analyzing the recoil and recoil impulse change characteristics of the two submerged projectile guns containing the composite recoil reduction technology and the two types of submerged projectile guns without this technology in the entire internal ballistic path and the after-effect period. The results of the study show that the recoil and recoil impulse of the two types of submerged projectiles with the composite recoil reduction technology and without the technology are analyzed in comparison. The results of the study show that the composite recoil reduction technology can effectively reduce the recoil force of the submerged projectile gun and reduce the recoil impulse from 1720.36 N-s to 306.04 N-s, with a recoil reduction efficiency of 82.2%, while keeping the muzzle velocity of the projectile unchanged.

The double cone shaped charge has a strong destructive effect on armored targets. Tests and high precision simulations are of great significance for improving the destructive performance of shaped charge. To study the effect of different structures and materials of conical shaped charges on the penetration property of steel target plates, five kinds of biconical shaped charge liners with different structures are designed, and the influence of different materials (copper and high entropy alloy) and shell on the penetration properties of biconical shaped charge jet are considered. The static armor-piercing test of the shaped charge jet penetrating the steel target plate is carried out. Based on the fluid elastoplastic governing equations, a high-precision Euler algorithm for the formation and penetration simulation of shaped charge jet is constructed, and the numerical simulation of the experimental conditions is carried out with the constructed program. The reliability of the self-constructed high-precision numerical method is verified by comparison of numerical simulation and experiment. The results show that the head velocity and length of the jet decreases with the increase of the inner cone angle, while the effective penetration mass and penetration depth increase gradually. For the copper and high-entropy alloy shaped charge liners with the same structure, the difference in penetration diameter and depth is not significant. The head velocity of the high-entropy alloy jet is larger, and the penetration diameter of the high-entropy alloy is more consistent from top to bottom.

Accurately identifying and locating internal defects is crucial for ensuring safety and durability of concrete structures. The impact echo (IE) method has unique advantages for concrete structures with only a single inspection surface. When using IE method for testing internal defects in concrete structures, the difficulty lies in analyzing features of IE signals and classifying and identifying defects. Here, a method for identifying internal defects in concrete was proposed based on deep learning of time-frequency maps of IE signals. Firstly, IE tests were conducted for concrete slabs containing different types of defects including holes, honeycombs and cracks. Then, the original IE signals were converted into time-frequency maps with short-time Fourier transform and continuous wavelet transform, respectively. Finally, 2 types of time-frequency maps were combined for data expansion to construct datasets containing defect types, hole sizes and crack depth time-frequency maps. 3 types of deep learning models of Swin Transformer, Vision Transformer and ResNet18 were used for training. Based on the relevant evaluation indexes of deep learning models, performances of different deep learning models under different datasets were analyzed, and the classification and recognition effects of models on defects were compared. The results showed that Swin Transformer performs the best among 3 models, its correctness rate is over 95.00% in defect type classification, and it has good recognition performance.