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.

The study of meso-damage evolution in steel fiber concrete is important for the health inspection of in-service steel fiber concrete structures. A multi-channel acoustic emission system was used to collect acoustic emission signals from concrete and steel-fiber concrete specimens (steel fiber content of 15 and 45 kg/m3, respectively.) during splitting tests. Then, the damage characteristics of concrete and steel fiber concrete are analyzed by combining principal component analysis and k-means clustering algorithm. Research showed that steel fiber inhibits the propagation of cracks in concrete and effectively improve the post-peak toughness of concrete. The acoustic emission characteristics parameter of counts and energy changes reflect the meso-damage evolution process of macroscopic deformation and failure in steel fiber concrete. Finally, two damage mechanisms are identified for mortar matrix cracking and steel fiber pullout in steel fiber concrete. Compared with mortar matrix cracking, the acoustic emission signals generated by steel fiber pull-out behaviors have the characteristics of high count, high amplitude, strong energy, and long duration.

Combined with theoretical calculation, finite element simulation and experimental measurement, the optimization design method of acoustic maze structure based on acoustic black hole is studied, and a small-size and broadband sound absorption structure with 5.01 and 7.75octaves is given.First, based on the transfer matrix method, the mathematical model of acoustic black hole is established, the reflection coefficient of acoustic black hole is calculated, and the theoretical calculation results are compared with the finite element simulation results.Then, based on the admittance variation law of the acoustic black hole, the single and double side branch acoustic maze structures are designed. By optimizing the design, the matching of the maze structure and the admittance of the acoustic black hole is realized.Finally, based on the matching results of the admittance of the acoustic maze structure, the simulated annealing algorithm is used to construct the optimization model, and the small-sized acoustic maze structure with broadband sound absorption is obtained, and the 3D sample is printed for experimental verification.The results show that the double side branch pipe acoustic maze is used to replace the ring cavity in the acoustic black hole pipeline. After optimization, the admittance of the side branch pipe maze and the acoustic black hole can achieve perfect matching, and the small size design of the structure can be realized under the premise of maintaining the sound absorption performance. The effective sound absorption bandwidth of the optimized structure is 13.36 times that before optimization, and the octavesare3.94 times those before optimization.

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.

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.

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.

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.

Traditional force correction iterative hybrid test method uses a fixed model for restoring force correction, it has the problem of insufficient model accuracy causing increase in iteration rounds. Here, aiming at this problem, a force correction iterative hybrid test method based on adaptive model was proposed. This method could use restoring force correction values of all iteration rounds and true restoring force of physical substructure in each iteration round to build an adaptive model for iterating restoring force correction, and improve iteration’s convergence speed and accuracy. Taking a single-layer frame viscous damper seismic reduction structure as an example, effects of different weight distribution coefficients and initial model parameters on iteration convergence speed and accuracy were analyzed. Effects of structural natural vibration periods on this method were analyzed through separately verifying structures with different natural vibration periods. The results showed that different weight distribution coefficients and model parameters more largely affect iteration convergence speed and accuracy; when the weight distribution coefficient is 0.025 and the initial model parameter is 0.80, the proposed method’s iteration convergence speed and accuracy are much higher than those of traditional force correction iterative hybrid test method; the force correction iterative hybrid test method based on adaptive model has much better convergence speed and accuracy than traditional force correction iterative hybrid test method in different single-layer frame structures; for structures with a natural vibration period less than 1.0 s, the proposed method has more obvious advantages.

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.

Aiming at the problem that the feature distribution of rolling bearing vibration data collected in variable working conditions is inconsistent and the label of the sample to be diagnosed is difficult to obtain, which leads to the difficulty of bearing fault diagnosis, this paper proposes a multi-source domain transfer diagnosis method of rolling bearing based on feature disentanglement and joint domain alignment. Firstly, in order to better extract the common features of the source domain and the target domain, the convolutional autoencoder and orthogonal constraint are used to disentangle the domain shared features and the domain private features, and the domain private features are filtered out and the domain shared features are retained for inter-domain alignment. Secondly, in order to reduce the feature distribution difference between the source domain and the target domain, the Multiple Kernel Maximum Mean Discrepancy (MK-MMD) and the Correlation Alignment method (CORAL) are used to construct the fusion metric. Finally, in order to avoid the decline of diagnostic accuracy caused by the negative impact of multi-source domain differences, the source adversarial module and the migration adversarial module are used to enhance the domain confusion between the source domain and between the source domain and the target domain, and the collaborative decision-making method is used to perform feature weighted fusion to reduce the interference of weak correlation domain features, and the final fault diagnosis recognition is realized. The proposed method is verified by experiments on rolling bearing fault data sets under two variable working conditions, and compared with the single-source domain diagnosis method and other multi-source domain diagnosis methods, which proves the effectiveness and superiority of the proposed method.

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. 

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.

The wheel polygon and rail corrugation as typical wheel-rail periodic wear of high-speed railway, aggravate wheel-rail vibration and affect driving safety. In order to explore the interaction under extreme conditions when wheel polygon and rail corrugation coexist, firstly, considering wheel-rail periodic wear of high-speed railway, the finite element model of wheel-rail system is established, and the frequency-dependent wheel-rail periodic wear competition mechanism is explored. Then, from the perspective of frequency-dependent wheel-rail periodic wears, the wheel-rail friction coupling vibration characteristics of wheel-rail periodic wears in the same/different phase contact are compared. Finally, from the perspective of frequency-independent wheel-rail periodic wears, the wheel-rail friction coupling vibration characteristics of the interaction of wheel-rail periodic wear are studied. Results show that under the extreme conditions of the coexistence of frequency-dependent wheel polygon and rail corrugation, the wheel-rail system is the most unstable. The instability of the wheel-rail system will be aggravated when the frequency-dependent wheel-rail periodic wear are in the same phase, and with the increase of wave depth, the difference in wheel-rail friction coupling vibration between the same phase and different phase will be increased. the closer the frequency-independent periodic wear frequency of wheel-rail is, the more obvious the influence on the stability of wheel-rail system is.

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.

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 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. 

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.

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 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.

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.

Transmission lines galloping is a low frequency, large amplitude vibration phenomenon caused by icing and strong wind, which seriously endanger affects the safety of the power grid. The galloping response and galloping control of 500 kV transmission line arewere studied by using numerical simulation method in this paper. Firstly, taking crescent-shaped, fan-shaped, and D-shaped ice covered split conductors as examples, the influence of wake effect and wind attack angle on the aerodynamic characteristics of the conductors under different ice covered shapes was studied. Based on the obtained aerodynamic coefficients, the aerodynamic load was calculated and the galloping response of the ice covered split conductors was studied. A new galloping control method for anti-galloping line spacing bars and phase spacing bars was proposed. By comparing the galloping displacement response of the central conductor in the span with the installation of ordinary inter line spacers, the results show that the installation of new anti-galloping inter line spacers can reduce the galloping response of single-phase split conductors by 93.18% (vertical direction) and 60.30% (horizontal direction); The installation of new anti-galloping phase and line spacing bars can reduce the galloping response of three-phase split conductors by 90.73% (vertical direction) and 86.05% (horizontal direction), the galloping control effect is significant. The research results of this paper provide a new method for the galloping control of ice covered split conductors.

Aiming at the problems of poor noise immunity and insufficient model training of traditional deep learning models in a small-sample and strong noise environment, a method based on Adaptive Maximum Second -order Cyclostationarity Blind Deconvolution (ACYCBD) combining Markov (ACYCBD) combined with Markov Transition Field (MTF) and MobileViT for rolling bearing fault diagnosis. Firstly, the impact signal of bearing faults under strong noise background is enhanced by parameter-adaptive CYCBD algorithm to reduce the influence of strong background noise, then, MTF is used to transform the preprocessed one-dimensional bearing vibration signal into a two-dimensional feature image with temporal correlation, and finally, the MTF image is inputted into the MobileViT network for training to get the fault diagnosis results, which is applied to the Southeast University Gearbox dataset and Shenyang University of Technology laboratory rolling bearing dataset to verify the fault identification accuracy of the proposed method in small sample strong noise conditions, the results show that, in the small sample strong noise conditions, ACYCBD processed data, the trained model has a higher accuracy, compared to maximum correlated kurtosis deconvolution, variational mode decomposition, ensemble empirical mode decompositionaccuracy increased by 1.73, 1.99, 2.2 After using MTF for modal transformation, the accuracy is 2.59, 3.12 and 2.72 percentage points higher than that of Gramian angular field, continuous wavelet transform and RP, respectively; comparing with other deep learning models, the method proposed in this paper has higher anti-interference ability and generalization performance under the above conditions. 

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.

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.

To promote the development of parachute-free airdrop technology, the impact characteristics of parachute-free airdrop box with composite structure were studied, and the impact response and failure modes were analyzed. Theoretically analyzing the protection mechanism of the parachute-free airdrop box, followed by in-depth simulation using finite element method. The simulation results show that the goods with edge drop and angle drop have large displacement, serious box deformation and long impact duration; the impact energy absorption rate of parachute-free airdrop box is more than 80%, and the efficient energy absorption provides a strong guarantee for goods safety; compared with edge drop and angle drop, the peak acceleration and average impact force of goods are larger for face drop; when the edge drop and the angle drop, the stress and strain level of the parachute-free airdrop box is higher than the face drop. The study shows that the safety of goods is related to the impact area and foam impact thickness, smaller impact area and larger foam thickness can reduce the risk of goods damage; the failure of parachute-free airdrop box is related to their impact area, larger impact area can effectively reduce the degree of impact failure and improve the safety of goods.

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. 

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.

The pulley-rope system in hoisting mechanism of crane is prone to vibrate and tilt during operation process, which seriously reduces efficiency and increases safety hazard. When dealing with the real-time change of the contact state between pulley and rope, the assumption that the element node is bound to the material point leads to the fact that the element shape function hardly describes the circular curves of each section, and the element size needs to be reduced, which lowers solving efficiency. In this study, spatial description method was introduced to divide ropes in different contact states by the boundary points of the contact area on the pulley. Arc interpolation and Hermite interpolation were used to describe the shapes of the ropes in different sections, and the material velocity and material acceleration of each node were obtained. Considering the axial deformation of the rope, the dynamic equation was established according to the principle of virtual power. By comparing with ADAMS, the effectiveness of the method proposed in this paper is verified, and the pulley rope system commonly used in hoisting equipment is modeled. The influence of combination of pulleys and rope, lifting weight and distance of pulleys on the rotation degrees of pulley frame was studied. The modeling method of pulley-rope system proposed in this study provides the necessary theoretical support for engineering practice.

多体动力学；刚柔耦合；假设模态法；机电耦合；振动控制

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.

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.

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.

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.

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 principle of equal limiting penetration velocity is employed to derive an equivalent model applicable to thin target plates of different steel materials, designed to resist the penetration of pointed ovoid bullets. This is achieved through the use of magnitude analysis. The finite element software LS-DYNA was employed to simulate the vertical penetration of the 12.7mm armor-piercing bullet core through the 30CrMnSi target plate and the 45 steel target plate. The resulting equivalent thickness was used to determine the coefficients of the equivalent model for both the 30CrMnSi target plate and the 45 steel target plate. Furthermore, the 30CrMnSi target plate and its equivalent 45 steel target plate were employed in 12.7mm armor-piercing bullet core penetration experiments. The two limit penetration speed error was less than 2.7%. This verifies the correctness of the equivalent model. Additionally, the study can be used to validate the penetration of a bullet through a rocket engine, which is equivalent to the aforementioned experiments. This provides a theoretical basis and data reference.

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.

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.