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 105.2 W, presenting the advantages of low force attenuation rate, good linearity, and low power consumption.

多体动力学；刚柔耦合；假设模态法；机电耦合；振动控制

The acoustic coating can be used by submarines to absorb sound waves and is a primary means of countering active sonar detection.With the continuous advancement of underwater detection technology, current acoustic coatings are being developed to achieve low-frequency broadband sound absorption in deep-sea environments.Traditional cavity-type coatings, due to their narrow absorption bandwidth and poor resistance to water pressure, are no longer able to meet application requirements.A novel sound-absorbing structure based on a circular tube honeycomb configuration was proposed in this paper.According to the equivalent layered medium theory, the theoretical solution of the absorption coefficient was derived using the transfer matrix method.A COMSOL finite element model was established to compare the theoretical results with simulation ones in detail, verifying the reliability of the finite element modal.The sound absorption mechanism was systematically analyzed, revealing that the introduction of the honeycomb structure induces shear vibration in the polyurethane, which enhances panel vibration and facilitates the conversion between longitudinal and transverse waves.Their coupling effect increase sound energy dissipation, achieving broadband sound absorption in the range of 1 091 Hz to 10 000 Hz, with an average absorption coefficient of 0.869.Both material parameters and the honeycomb structure impact the sound absorption performance.Higher loss factors and thicker honeycomb walls improve the sound absorption effect.The sound absorption performance under hydrostatic pressure was studied, and the results indicate that the structure can maintain its absorption stability under water pressure as high as 5.0 MPa.

Three-dimensional direct numerical simulations of the vortex-induced vibration of a pin-pin supported near-wall elastic cylinder at a Reynolds number of Re = 300 were conducted using the immersed boundary method based on embedded iteration. The aspect ratio of the slender cylinder was L /D = 25, while the gap ratio G/D ranged from 0.6 to 1.6. This corresponds to scenarios where the cylinder is fully covered by the boundary layer, partially submerged in the boundary layer, and completely outside the boundary layer, respectively. In the single-mode vibration regime, the vibration and the lift and drag coefficients of the cylinder at G/D = 0.6 and 1.1 are dominated by a single frequency. In contrast, at G/D = 1.6, two frequency components appear near the natural frequency. In the multi-mode vibration regime, the excitation and superposition of multiple modes cause the vibration and the lift and drag coefficients of the cylinder to exhibit a spatial-temporal distribution characterized by traveling waves. The merge of the upward-curling boundary layer and the wake vortices shed from the upper surface of the cylinder, together with the suppression of the vortices shed from the lower surface, leads to asymmetric vortex shedding. As the gap ratio increases, the suppression of vortex shedding weakens, and the wake sequentially exhibits the '1S', weak '2S', and '2S' vortex-shedding patterns. For multi-mode vibrations, the drag and lift spectra show the multi-frequency features while the streamwise and cross-flow vibrations are decoupled. 

Vortex-induced vibration (VIV) under the action of ocean currents is a primary cause of fatigue damage accumulation in marine risers. In actual marine environments, the flow direction of ocean currents is not constant but exhibits characteristics of multidirectional flow. In multidirectional flows, the orientation of the plane in which the catenary riser is located has a significant impact on the VIV response. Based on a numerical prediction model for VIV and a fatigue assessment method for structures in multidirectional flows, the fatigue damages of the riser in flows with different directions and velocities were calculated, and the VIV fatigue characteristics in multidirectional flows with significant and non-significant seasonal differences were analyzed. The results indicate that when in-plane and out-of-plane modes coexist and compete in the response within a multidirectional flow environment, the VIV fatigue damage is relatively small. The relationship between fatigue damage and the velocity of the external flow can be approximated by a power function or a double exponential function. When seasonal differences are not significant, fatigue damage varies dramatically with changes in the orientation of the riser; when seasonal differences are significant, fatigue damage varies more smoothly with changes in the orientation of the riser. Numerical calculations show that aligning the plane in which the riser is located at a specific angle with the dominant direction of the multidirectional flow can effectively reduce the VIV fatigue damage.

Piezoelectric smart metal corrosion sensors have already attracted much attention in pipeline corrosion monitoring, but most of them are in single output mode. The reliability of a single impedance signal is difficult to be effectively verified when facing complex and harsh corrosive environments. For this reason, a dual-port metal corrosion probe is designed based on electromechanical impedance technology and dual piezoelectric elements. The theoretical model of the probe under dual-port output was established, and the first resonance and anti-resonance frequencies were solved. The finite element simulation was used to verify the correctness of the theoretical model. In addition, artificial quantitative corrosion tests and wireless impedance measurement tests were carried out to investigate the quantitative corrosion monitoring performance of the probe as well as the online monitoring capability. The results show that the first resonance and anti-resonance frequencies of the dual-port output both increase with the decrease of the rod length, and the self-calibration function can be realized. The frequency values determined by the wireless impedance measurement system are in good agreement with the results of the traditional impedance analyzer. The research results provide a reference for the development of wireless self-calibration metal corrosion probes.

The spectral element calculation method has the advantages of clear propagation mechanism and high computational efficiency in structural vibration analysis, but the calculation results are biased when dealing with complex structural spectral element matrix due to the equivalence problem of substructure. In this paper, an equivalent physical model of plate structure based on beam and spring vibrator substructure is proposed, and the spectral stiffness matrix of multi-period grid structure and vibrator grid structure is constructed, and the finite element models of the two structures are established for verification. By comparing the band gap and vibration response characteristics of the finite element and spectrum element grating model with that of the finite element plate model, the appropriate vibrator mass coefficient and band plate action coefficient of the two models are determined, and the accuracy of the calculation method is verified.

Vibration energy harvesting is a hot research field, and the existing research work mainly focuses on the free environmental space. In order to adapt to the extreme environment of limited and narrow space, a cut-out piezoelectric beam harvester with limiter is designed in this paper. The harvester is composed of a cut-out piezoelectric beam, two pairs of limiters and concentrated mass blocks. Based on the piezoelectric conservation relationship, the dynamics equation of the system is established. The effects of the distance of the limiter, the stiffness of the system, the external excitation amplitude and the electromechanical coupling coefficient on the frequency bandwidth, voltage and amplitude of the acquisition were analyzed by direct numerical integration method. By comparing with the linear harvester system without limiter, it is found that the acquisition frequency bandwidth, output voltage and power can be increased by reasonable limit spacing, proper stiffness, acceleration amplitude and piezoelectric coefficient. Finally, the correctness of the numerical analysis is verified by experiments.

Aiming at the rubbing fault between guide vane stem and head cover of a francis hydro-turbine under the effect of water flow, the finite element method combined with the fixed interface mode synthesis method was used to establish the reduced model of the guide vane stem-head cover system with rubbing fault. Then the effects of truncation number of guide vane stem and head cover on the first three-order natural frequencies of the model were discussed, respectively. Next, considering the pre-stressed effect caused by the water flow load and the local contact load between guide vane stem and head cover, the first three order natural frequencies obtained from the full and reduced models varying with hydrostatic load and friction coefficient were compared with each other. Finally, the effects of two contact states including near and near-far load end contacts on the dynamic behavior of the full and reduced models under single harmonic water flow excitation were compared with each other. The results showed that: (1) the first three natural frequencies of the system increase with the increasing hydrostatic load leading to the aggravation of local contact between guide vane stem and head cover, and a larger friction coefficient results in a larger hydrostatic load when switching from near-load end contact to near-far load end contact; (2) in the resonant state, the frequency spectrogram of guide vane stem-head cover rubbing-coupled system under the effect of single harmonic water flow presents integer multiples of the excitation frequency, and the amplitude amplification phenomenon appears at odd harmonics of the excitation frequency.

In view of the dynamic issues caused by the installation gap on the secondary lateral damper during the roller rig test of the electric multiple units trailer car. A Maxwell model for the secondary lateral damper was established considering installation gap, rubber joint stiffness, oil stiffness, and nonlinear damping characteristics. A dynamic co-simulation of the vehicle model and the damper models was further carried out to analyze the effects of different installation gaps on the damper on the dynamic performance of the vehicle. Meanwhile, all the models had been validated with bench tests. The research results are shown as follows. When the damper has an installation gap, the indicator diagram shows a deadband corresponding to the gap length after stroke reversal, reducing the damper’s ability to suppress vibration. The nonlinear critical speed decreases overall with the increase of the gap, and after the gap exceeds a certain value, the decrease in speed tends to level off, converging to the nonlinear critical speed for the complete failure condition of the secondary lateral dampers. The lateral ride quality index increases rapidly with the increase of the gap, and the evaluation grade undergoes an obvious change from excellent to good and then to qualified, significantly reducing the lateral ride quality of the vehicle running. The derailment coefficient and the wheelset lateral force increase relatively slowly with the increase of the gap, reducing the safety of the vehicle running to some extent. The research results are instructive for the fine modeling of long-service dampers and the operation and maintenance of vehicles.

[purpose]In order to research the full frequency domain vibration problem of vehicle-track structure,[method] a dynamic model and algorithm for the vehicle-ballastless track structure coupling system is constructed based on the spectral geometry method.The Rayleigh-Ritz method is applied to derive the stiffness matrix,damping matrix,mass matrix of the track structure spectral geometry element and coupling virtual spring stiffness matrix between elements.The dynamic equation of the vehicle-track structure coupling system is solved by the spectral geometry method,and the vibration response of the vehicle track structure in the full frequency domain is obtained.The influence of track structure element size on convergence and computational efficiency is analyzed,and the range of virtual spring stiffness coefficients for the rail,slab,and support layer is discussed.Compared with the finite element method,the correctness and efficiency of the spectral geometry method is verified.As an application example,the vibration response of the vehicle-track structure coupling system is analyzed under the excitation of random track irregularities.[result]The research results indicate that,while ensuring computational accuracy,larger track structure element sizes for calculation can be used by spectral geometry method,while smaller track structure element sizes can be used by finite element method,Therefore,the computational efficiency of spectral geometry method is much higher than that of finite element method;When the element sizes are 3.25m and 6.5m,the computational efficiency of the spectral geometry method is higher,which can be used as the reference element sizes for analyzing the dynamic problems of vehicle-track structure coupling systems based on the spectral geometry method;The reasonable value for the virtual spring stiffness of the rail, slab,and support layer is greater than or equal to 105 times the bending stiffness of the corresponding components.The displacement amplitude frequency curves of the car body and bogie alternate with numerous peaks and valleys,which are caused by the phase difference of track irregularity excitation between the four wheel sets for the vehicle system;The frequency at the valley of the vertical displacement amplitude frequency curve of the car body and bogie corresponds to the fixed distance filtering and wheelbase filtering frequencies of the vehicle respectively.[Conclusion]The research results offer an efficient and accurate numerical method for solving the dynamic problems of vehicle-track structure coupling systems in the full frequency domain,and provide technical support for vibration reduction analysis and design of vehicle-track structure systems.

To analyze the dynamic performance of variable-angle ply porous fiber-reinforced sandwich composite panels under simply supported boundary conditions, the vibration differential equations for the porous double-layer sandwich panels were established based on the layerwise theory and the Rayleigh-Ritz method. These equations were subsequently solved using the Navier method. The dynamic characteristics at various ply angles were analyzed using Abaqus and the modal tests were performed with [0°/90°] and [±45°] ply orientations to validate the accuracy of the theoretical model. A parametric analysis of the porous double-layer sandwich panel was conducted using the theoretical model, followed by structural optimization using a genetic algorithm. The research reveals that laminated panels with a porosity of 94.854% and fiber ply angles in multiples of 45° exhibit outstanding dynamic performance. These results provide a reference for the design and manufacture of such structures.

In order to control the horizontal and vertical vibrations of semisubmersible wind turbine, a multi-direction and multi-position TMD deployment method is proposed, which involves arranging H-TMD in the nacelle and V-TMD in the platform. To study the vibration reduction effect of this TMD deployment method, A fully coupled numerical model of semisubmersible wind turbine with multi-directional multi-position TMD was established, and the dynamic response of semisubmersible wind turbine under wind wave combined action was analyzed using OpenFAST simulation. The results show that the vibration reduction control effect of arranging multi-direction and multi-position TMD is better than that of single position TMD, and arranging low-frequency H-TMD in the nacelle and V-TMD in the platform is the optimal arrangement scheme, which can achieve average standard deviation control rates of 13.97%, 32.85%, 15.21%, and 2.86% for pitch, roll, heave, and tower longitudinal vibration of semisubmersible wind turbine.

To enhance the sealing performance of piston rings in Stirling engines, the mechanical properties of piston rings under differential pressure were first analyzed through numerical simulation. This analysis investigated the effects of four structural parameters—assembly interference (δ), floating ring axial thickness (σ), floating ring outer diameter (D), and bowl lip depth (L)—on the sealing performance of the piston rings. Subsequently, the response surface methodology (RSM) was employed to optimize these four structural parameters, aiming to determine the optimal combination that aligns the contact pressure at the piston ring-cylinder liner interface with the target values established by experimental results. The findings indicate that the maximum contact pressure at the sealing interface between the floating ring and the cylinder liner increases with δ, increases and then decreases with σ, decreases and then increases with D, and remains relatively stable before increasing with L. Optimization results were analyzed using regression coefficients and ANOVA. The estimated regression coefficients and ANOVA revealed varying influences of the structural parameters, with σ exerting the most significant effect on the maximum contact pressure, followed by L and D, while δ had the least impact. Additionally, the interaction between σ and L significantly affected the response. When δ is set to 0.03 mm, σ to 1.05 mm, D to 55.6 mm, and L to 0.95 mm, the maximum contact pressure on the sealing surface of piston ring I decreases from 12.124 MPa to 10.717 MPa, whereas that on piston ring II increases from 4.027 MPa to 4.3287 MPa. Validation using the THT07-135 high-temperature friction and wear experimental machine demonstrated that post-optimization, the temperature rise of the friction surface decreases, the coefficient of friction increases, and the wear rate decreases significantly. These results confirm the scientific and effective nature of the optimization design. This inverse-guided optimization approach provides an effective solution for the development of high-performance seals.

Regarding the dynamic problems of composite thin-walled cylindrical shells with multiple elliptical perforations, this paper proposes a semi-analytical modeling method based on the energy superimposition. Combined with the Rayleigh-Ritz method, Love's first approximation theory and second kind of Chebyshev polynomials, a semi-analytical model for free vibration of the hard-coated thin-walled cylindrical shells with multiple elliptical perforations uniformly distributed in the circumferential direction is established. The comparison between the calculated and experimental natural frequencies verifies the correctness and rationality of the semi-analytical model. On this basis, the influences of elliptical perforation schemes (including the axial length, axial and circumferential perforation numbers) on vibration and damping characteristics of the shell are analyzed emphatically. The results show that the perforations would first lead to a reduction in natural frequencies compared to non-perforated structures. As the axial perforation number increases, the natural frequencies show a trend of first decreasing and then increasing. As the length of the elliptical axis increases, the natural frequency of the shell continuously decreases, and the larger the axial perforations, the greater the frequency reduction. As the circumferential perforation number increases, the natural frequencies and modal loss factor of the shell also show a significant downward trend. However, when the circumferential perforation number is twice that of the circumferential wave, the natural frequencies gradually increase as well as the modal loss factor reaches its peak.

This paper establishes a simplified model of the bladeless wind turbine and derives the formula for its power generation efficiency. Numerical simulations were conducted using computational fluid dynamics software Fluent and user-defined functions (UDF), studying the vortex-induced vibration characteristics and power generation efficiency of single and dual degree-of-freedom bladeless wind turbines under different reduced wind speeds. The study shows that the difference in the degrees of freedom of the wind turbine significantly affects its vibration response, aerodynamic characteristics, and power generation efficiency. The vibration amplitude initially increases and then decreases as the reduced wind speed increases, remaining stable in certain wind speed ranges. The vibration trajectory of the dual degree-of-freedom wind turbine at reduced wind speeds primarily forms a figure-eight pattern, exhibiting multi-frequency vibrations when the wind speed approaches the natural frequency, with the trajectory becoming chaotic. The power generation efficiency follows a trend of increasing first and then decreasing with the reduced wind speed, with the efficiency of the dual degree-of-freedom wind turbine being higher than that of the single degree-of-freedom wind turbine. At a reduced wind speed of Ur = 2.4, the maximum power generation efficiency of the single degree-of-freedom wind turbine is 25.19%; at Ur = 3.4, the maximum power generation efficiency of the dual degree-of-freedom wind turbine is 57.14%. Power generation efficiency is influenced by the combined effects of incoming wind speed, vibration velocity, and lift-drag coefficients. With changes in degrees of freedom and reduced wind speeds, the wake vortex shedding patterns of the wind turbine also vary. The vortex shedding patterns of the three-dimensional bladeless wind turbine at different heights in the span direction are similar to those of the two-dimensional wind turbine, but due to smaller vortices in the surrounding flow field, the energy loss is higher, leading to a slightly lower power generation efficiency compared to the two-dimensional bladeless wind turbine.

In this paper, by using the Smoothed Particle Hydrodynamics (SPH) method combined with the MoorDyn dynamic mooring cable numerical model, a computational model to study the motion responses and mooring forces of moored floating bodies on the three-dimensional stepped seabed under wave-driven conditions had been developed. We used the experimental data to verify and compare its applicability and accuracy. Further, the effects of the Kollagan-Carpenter number (KC number), the period T, the spacing between floating bodies d, and the seabed height h on the motion responses and mooring forces of the moored floating bodies which are located at the upstream and downstream of the stepped seabed (moored floating bodies I and II, respectively) are systematically investigated. It was found that the KC number has a motivational effect on the motion response and mooring forces of moored floating bodies I and II. As T increases, the motion response phases of moored floating bodies I and II are significantly shifted, and the amplitude of the mooring forces on the two floating bodies has a tendency to increase. The effect of d on the motion responses of moored floating bodies I and II is small, and the phases corresponding to the amplitude of the mooring forces on the two floating bodies under different d show significant shifts. As h increases, the motion response of the moored floating body I is weakened while the motion response of the moored body II is enhanced, and the amplitude of the mooring forces on the two moored floating bodies shows a similar trend. The removal of the moored floating body I resulted in intensification of the moored floating body II motion response.

The manipulator mechanism of space station with clearance is taken as the research object, and the influence of motion pair wear on the motion output accuracy of the mechanism is analyzed. Firstly, the dynamic modeling of the mechanism is carried out by combining the Lankarani-Nikravesh contact impact force model and the LuGre stagnation-slip friction model, and the relationship function between wear depth and puncture depth and stiffness coefficient is established. Secondly, the dynamic response characteristics of the system under different clearance conditions are explored. Finally, the simulation results are combined with the Archard model to analyze the wear of the motion pair under different conditions, reconstruct the irregular clearance surface, and solve the effect of wear on the dynamic response of the system. The results show that for the open-loop mechanism, the closer the clearance position is to the end effector, the greater the influence on the end effector is. The wear of the kinematic pair connected to the spacecraft body is more serious. Under the irregular clearance, the time of velocity and acceleration fluctuation lags behind that of the regular clearance.

In space operations, solar panels mounted on satellites needed to adjust their position and orientation to achieve optimal illumination angles for energy replenishment. These flexible structures exhibited low modal frequencies, making them prone to excitation and slow to dampen residual vibrations. The solar panels on satellites are typically multi-flexible structures. The T-shaped design can simulate the vibrational characteristics of multi-flexible structures under external factors. Considering the operational features of solar panels, a trapezoidal trajectory motion was designed to observe the vibrations of the flexible beams, along with a control scheme. An active vibration control strategy was developed for the designed T-shaped movable three-flexible beam measurement and control experimental platform. System identification was performed, and an RBF neural network-based nonsingular fast terminal sliding mode controller (RBF-NFTSMC) was designed for active vibration control. Due to the significant excitation caused by trapezoidal trajectory motion, trapezoidal trajectory excitation was applied to the flexible beam. After the trajectory motion was completed, active control experiments with the RBF-NFTSM controller were conducted. The experimental results demonstrate that the RBF-NFTSMC outperforms traditional high-gain PD controllers in suppressing residual vibrations more effectively.

The operational environment of the Ram Air Turbine (RAT) on aircraft is characterized by randomness in wind speed, flight altitude, and temperature, necessitating stable operation across diverse working conditions. A control model is established for the RAT speed control system under the influence of incoming air, and stability analysis is conducted under various operating conditions. Initially, based on turbine operating principles, a dynamic model is formulated for the speed control system of a RAT, capable of reflecting the true response of the turbine. Subsequently, the speed control system is approximated linearly near the speed equilibrium state to derive a closed-loop control model that can describe system stability under load disturbance. By combining the simulation results of the dynamic model with the theoretical calculations of the control model, the response characteristics of the turbine under load impact are analyzed. Ultimately, the stability of the speed control system is evaluated, and the stability laws of the speed control system in different operational environments are systematically investigated. The numerical simulation results indicate that the closed-loop control model accurately reflects the stability of the RAT speed control system, with system stability being weakest in operational conditions of high wind speed and low flight altitude.

In order to realize the intelligent multi-component fault diagnosis of bearings, rotors and gears in a mechanical transmission system under low speed, weak faults and few measurement points, a fault diagnosis method based on improved vibration-mapped gray texture images (GTIs) and multi-scale lightweight convolutional neural network is proposed. An improved gray texture image with enhanced features is obtained by robust local binary pattern (RLBP) on the traditional gray image. Based on the standard convolutional neural network (CNN), a multi-scale lightweight CNN (MSLCNN) model is constructed by adding batch normalization, multi-scale convolution and simplified full connection layer. The fault diagnosis experiment under 700r/min and a single measurement point is designed, and seven typical faults of bearings, rotors and gears are simulated. The investigation shows that the model parameters of the proposed fault diagnosis method are 0.30M, the floating point operations (FLOPs) are 127.22M, the model size is 1.17MB, and the average diagnostic accuracy is 98.42%. It provides a new feasible path for the data-driven multi-component fault diagnosis of the mechanical transmission system based on the deep learning.

Cavitation, one of destabilizing factors in the operation of water jet propulsion pumps, not only induces a drop in hydraulic performance, but also triggers vibration and noise. For improving the resolution accuracy of cavitation vibrational signal, SSA-VMD integration algorithm was proposed on the basis of VMD with the minimum arrangement entropy coefficients as fitness function, and the identification of modes number and penalty parameter was improved. Cavitation visualization and simultaneous acquisition of vibration signals from multiple sources were then tested. SSA-VMD decomposition, total energy, component energy, and correlation calculations of vibration signal were performed. Effective access to the vibration energy change law, and spectral energy distribution of characteristic measurement point and axial under two states. The results provide reference and an fast and effective method for experimental study of cavitation prediction and vibration mechanism, which is of practical significance for guaranteeing efficient and stable navigation of water jet propulsion ships.

In order to quickly and accurately locate the location of damage to the top tension riser (TTR), avoid the economic and environmental hazards caused by riser damage. A TTR damage identification method based on wavelet packet transform is proposed. Analyzing the acceleration dynamic response before and after TTR damage, relevant information about the evolution of the structure with damage is extracted as damage features. Firstly, the vibration acceleration signal of the riser is decomposed into wavelet packet components of different frequency bands using wavelet packet decomposition. Then, the wavelet packet energy of each sub-band is calculated and summed, and the wavelet packet energy curvature is obtained using the second-order difference method. Reducing the elastic modulus of the unit to simulate damage, the difference in energy curvature before and after damage is used as an indicator for identifying and locating riser damage. Research was conducted on TTR simulation models with different damage scenarios, and the effects of noise interference, unit partitioning, and local quality changes on the localization performance of the method were analyzed. The results indicate that this method can provide accurate location of riser damage, has a certain anti-interference ability against noise effects, and is not affected by unit division, and is insensitive to local quality changes in the riser.

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.

In the monitoring of high-pressure servo motor, traditional methods face significant challenges due to the scarcity of fault data, which is difficult to acquire, and the inherent uncertainty of fault occurrences, with normal samples vastly outnumbering fault samples. To address these issues, this paper proposes a state monitoring system for high-pressure servo motor based on Support Vector Data Description (SVDD) for anomaly detection and Support Vector Machine (SVM) for fault diagnosis. Initially, time-domain (T), frequency-domain (F), and wavelet packet subband energy (W) features are extracted from raw data. These features are then fused and normalized to form a new multidimensional feature vector, TFW. Subsequently, a Convolutional Neural Network (CNN) is employed to deeply mine the TFW, generating more expressive features, TFWCNN, which serve as inputs to the SVDD and SVM models. An experimental platform for simulating high-pressure servo motor faults was constructed to collect data and validate the proposed method. The results indicate that on three dynamic datasets with different valve opening positions, the F1 scores for SVDD anomaly detection are 0.9991, 0.9978, and 0.9760, and for SVM fault diagnosis, the F1 scores are 0.9988, 0.9950, and 0.9867, respectively. These findings not only demonstrate the superior performance of the proposed method in the state monitoring of high-pressure servo motor but also highlight the efficacy and accuracy of deep TFWCNN features. Furthermore, this study provides an effective technical solution for similar turbine state monitoring and diagnostic systems.

In the context of life prediction for components, dynamic environments complicate the degradation process. To ensure the reliability of components during actual operation, a time-varying drift kernel filter based on Bayesian framework is proposed in time-varying operating environment. Firstly, the Wiener model is employed to characterize the degradation process, and the state space equation is constructed utilizing the multi-source mapping function. Next, the Bayesian online mutation point detection is employed, utilizing prior knowledge to predict and update the posterior probability of particles to determine the location of the mutation point. Then, the drift kernel filter is used to adaptively allocate weights and select different kernel functions for particle resampling before and after change points. This approach enhances prediction accuracy. Finally, the effectiveness of the drift kernel filter is verified through the C-MAPSS dataset. 

The noise resulting from the impact of carrier-based aircraft wake on the deflector plate seriously threatens the health and safety of ground crew , as well as the instruments and equipment on the aircraft carrier. This problem can be simplified to the noise of high-speed jets impacting the deflector plate. A numerical method combining three-dimensional Large eddy simulation (LES) and FW-H acoustic analogy was employed to investigate the impact of incorporating porous media onto the swash plate’s surface on both the high-speed jet impingement flow field and the acoustic field . The study revealed the noise reduction trends associated with variations in the physical properties of the porous media. Additionally, it analyzed in detail the mechanisms by which porous media influence several types of typical noise, starting from the root cause of flow changes. It is shown that porous media can effectively reduce the discrete monotone and turbulent mixing noise in the jet impingement flow field. An optimal combination of physical parameters exists, offering the best noise reduction effect. For instance, the porous model with a thickness of 20mm and PPI of 30 can reduce the discrete monotone near 2312Hz up to 19.79dB, This results in the total upstream SPL reduction of 6.92dB; the suppression of discrete noise by porous media is based on the following principles: porous media affect the stability between the third and forth shock grille, thereby destroying the self-excitation conditions that are closely related to the formation of the feedback loop. The effect of the porous medium on the turbulent mixing noise originates from its destructive impact on the large-scale vortices and its adsorptive effect on the small-scale vortices. This not only suppresses or transfers the low and medium-frequency broadband noise but also effectively reduces the turbulence kinetic energy intensity and pressure fluctuations near the wall surface.

The peak overpressure of underwater explosion induced shock waves in water is mainly based on the Kuhl formula, without considering the mechanism of underwater drilling and blasting induced shock waves in water. In response to the lack of reliable prediction methods for overpressure caused by underwater drilling and blasting induced water shock waves, this paper first theoretically analyzes the rock breaking and water shock wave excitation process of the blasting system composed of water explosives rock mass. Furthermore, by comparing the theoretical and numerical solutions of the peak pressure of the water hammer wave under the action of explosive stress waves, it was found that when the explosive stress wave first entered the elastic deformation zone, the numerical solution was relatively small, indicating that the rock mass's elastic-plastic deformation zone gradually transitioned from the plastic deformation zone to the elastic deformation zone, and as the distance increased, it entered the elastic deformation zone of the rock mass. The fitting effect between the numerical solution and the theoretical solution was good. Furthermore, based on the SPH-FEM coupling method, the motion process of detonation product particles around the blast hole was simulated, and combined with the single hole underwater blasting test data from the Yangtze River channel construction project site, the waveform characteristics of water hammer waves were compared and verified. The research results indicate that there are three mechanisms for underwater drilling and blasting to excite shock waves in water. After the explosive detonates in the borehole, the stress wave of the explosion will undergo a complex process of transmission and reflection when it encounters the interface between rock and water. Some will reflect back from the interface, while others will transmit and excite shock waves in the water at the interface; As the detonation wave propagates, the explosive gas is subsequently ejected from the borehole opening, triggering a shock wave in the water; Affected by the explosion shock wave, the blast hole cavity begins to undergo radial dynamic expansion, followed by further crack propagation, completing the bulging and fragmentation of the rock mass, causing the explosion generated gas to expand and escape into the water from the cracks in the rock mass bulge, and exciting underwater shock waves.

To analyze the damage characteristics of module charge dropping in a variety of ground environment, a dynamic finite element model of the modular charge was established on the basis of nonlinear finite element theory. The drop impact process of the modular charge was simulated using ANSYS/LS-DYNA software. A numerical simulation was conducted to evaluate the impact of dropping postures and ground characteristics on the stress, strain, and acceleration responses of module charge. The stress, strain and acceleration data of the modular charge when it was dropped from a height of 2m onto three different types of ground: sand, concrete, and Q235 steel plate, with three dropping postures: bottom-downward vertical drop, horizontal drop, and a 45° inclined drop. The primary objective is to examine the deformation and damage characteristics of combustible cartridges, with a particular emphasis on the influence of drop posture and ground characteristic. The results show that the ranking of module charge rupture risk is: inclined 45° dropping, horizontal dropping, and bottom down vertical dropping. The harder the ground is, the greater the stress, strain, and overload will be, and the time to reach the peak value will be shorter. Under the three dropping posture conditions, the nitrocellulose collides with each other but do not break, and the safety risk area is located at the bottom of the combustible cartridge. The rupture occurred at a 45° inclined drop to both the concrete ground and the Q235 steel plate. The damage modes observed include localised denting, matrix cracking and shearing. These research findings can be utilized as a reference for the improvement of the structural design of module charges.  

Previous studies have demonstrated that that facade ribs serve as an effective aerodynamic optimization measure, significantly reducing wind loads on high-rise buildings. However, the optimal arrangement of facade ribs under minimal wind loads in practical engineering remains unclear. Conventional numerical simulations and wind tunnel test methods can only obtain limited optimization schemes for rib layouts, and the optimization process is time-consuming and labor-intensive. Therefore, this paper utilizes a multi-objective optimization procedure combining Large Eddy Simulation (LES), Back Propagation Neural Network (BPNN), and Non-Dominated Sorting Genetic Algorithm (NSGA-II) to assess the optimal layout parameters for facade ribs corresponding to minimal wind loads. The results demonstrate that the BPNN surrogate model can rapidly capture the complex nonlinear relationship between rib layout parameters and target wind loads, revealing notable differences in the load variation trends on the overall force on the model and on ribs positioned at different locations. The mean drag and fluctuating lift of models of windward ribs and upstream sidewall ribs have opposite trend.  The loads on the windward ribs and upstream side ribs exhibit opposite trends compared to the total lift and drag on the model. Due to the influence of vortex shedding, the loads on the downstream side ribs and leeward ribs are more complex. The genetic algorithm NSGA-II effectively evaluates the optimal trade-off solutions among multiple objective wind loads. The optimal layout parameters, specifically the position ratio b/D and extension length d/D, fall within the ranges of 0.14-0.17 and 0.073-0.077, respectively, with a b/d ratio of approximately 2. These optimal arrangement parameters provide balance for wind loads on both the model and the ribs, offering references for engineers and designers in wind-resistant design using facade ribs. 

To investigate the collapse performance of reinforced concrete (RC) frame structures under high temperatures, this paper utilizes ABAQUS finite element software to establish a finite element model for a two-story RC frame structure with instantaneous corner column removal. Based on the full validation of the model's accuracy, the study examines the impact of different durations and areas of fire exposure on the dynamic response of the RC frame structure to progressive collapse following corner column failure, through sequential thermo-mechanical coupling modeling. Furthermore, considering the uncertainty of parameters, a probabilistic assessment of the resistance to progressive collapse of RC frame structures under high temperatures is conducted. The results show that with the increase of fire time, when the first layer corner lattice is exposed to fire, the maximum peak displacement of the structure without columns increases by 153.26% compared with that at room temperature, and its resistance mechanism is mainly cantilever action and vierendeel effect, and the tensile membrane effect occurs when 60min is exposed to fire. When the first and second floor corner grids are exposed to fire, the maximum peak displacement of the structure after column removal is increased by 145.81%. Compared with the first layer corner lattice exposed to fire, the vierendeel effect is weakened, but when exposed to fire 60min, the floor produces a more obvious tensile membrane effect to resist collapse. Based on the uncertainty of structure and load, the cumulative distribution function obtained by fitting can better evaluate the collapse probability of RC frame structure at high temperature.

Dynamic compaction vibration affects the safety and stability of slopes. Existing studies often use indoor model tests and numerical calculations to determine the impact of dynamic compaction vibration waves on slopes, and few analytical methods use wave mechanics theory. In order to reveal the principle of the amplification effect of loess slopes under dynamic compaction vibration, based on the ray propagation theory of wave mechanics, this paper analyzes the propagation law of dynamic compaction vibration waves in slopes with positive and negative elevations, and deduces the analytical solution of the displacement amplification factor of particles inside the slope. Using the analytic hierarchy process, factors that may affect slope stability such as tamping energy, slope height and slope are sorted according to the calculation results of the weight coefficient. Based on the field conditions, different plans were selected to analyze the change laws of the displacement amplification factors of different particles in the slope body. The results show that under the action of low-frequency waves, the particle near the top of the slope tends to produce a large amplification factor, and the amplification effect at the top of the slope is more obvious. As the incident frequency of vibration waves increases, the particle amplification factor in the area near the top of the slope decreases relatively, but at the same time, there are many areas where amplification factors are concentrated, and the amplification factor values in these areas are large, indicating that partial collapse of the slope is prone to occur in these areas. The steep and gentle slope shape has a great influence on the amplification effect of slope particles. The steeper the slope inclination, the more obvious the amplification effect, which means that the steeper the slope, the more likely the slope is to collapse. This analytical solution calculation method is simple and practical, and can provide guidance for engineering practice.

The substation switchgear is critical equipment in power systems. Traditional seismic vulnerability analysis only considers the structural failure of equipment, neglecting associated functional failure mechanisms. In order to account for structure-function related failure modes, a vulnerability assessment framework for switchgear is established to generate simulated seismic responses based on the optimized Copula function. Taking the 800kV isolating switch as an example, a simulation model was developed based on test data to obtain original seismic response samples. This model was used to fit the marginal distribution function and build a Copula function to generate a large number of simulated response data to evaluate the structure-function joint failure probabilities. The results show that the simulated data generated by this framework can effectively reflect the correlation of the original samples; ignoring functional failure modes can underestimate the actual failure probability by up to 50%; at the current manufacturing level, it is difficult to significantly improve equipment reliability through material strength alone. Based on this framework, the design acceptance criteria for equipment strength and functional indicators can be effectively determined.

The MS 6.2 Jishishan earthquake, which occurred near Qinghai Province, caused significant seismic damage to buildings in many counties, affecting rural buildings in particular. The results indicate that rural buildings with wooden and brick (or earth)-wood structures experienced greater damage compare with those with masonry and reinforced concrete (RC) frame structures. In wooden structures, the cooperative deformation between wooden frames and rammed earth walls or brick walls is poor. The pressure from the walls can easily cause splitting, pull-out-tenoning, and even complete de-tenoning at the mortise and tenon joints of the wooden frames. In some brick (or earth)-wood structures, the connection between the wooden roofs and the load-bearing walls is inadequate, posing the risk of roof displacement and collapse. A small number of brick-concrete and RC frame structures also suffered significant earthquake damage due to inadequate design and poor construction quality. Additionally, the site selection for rural buildings requires careful consideration to avoid the impact of potential secondary disasters. Based on this investigation and historical seismic data, several recommendations were put forward regarding standard formulation, structural system optimization, construction quality improvement, non-structural element enhancement, and location selection. These suggestions aim to guide the seismic design and repair of rural buildings in the Qinghai earthquake region and beyond.