W/Ta nanoscale metallic multilayer is a typical body-centered cubic/ body-centered cubic nanolayered composite，which is very promising for the application in nuclear fusion devices. Based on atomistic molecular dynamic（MD）simulations，we investigate the mechanical properties and plastic deformation mechanisms of W/Ta nanolayered composite under uniaxial tension，and further analyze the influence of modulation period on the mechanical response of W/Ta nanolayered composite. The results show that the W（110）/Ta（110）interface forms a misfit dislocation network，which can not only serve as the source for dislocation nucleation but also adsorb the dislocations in the metallic multilayer. The microstructure evolution analysis shows that，W/Ta nanolayered composite mainly experiences three deformation stages during stretching，i.e. linear elastic，plastic yield，and plastic flow stages. The dislocations firstly nucleate and propagate in the Ta layers，which leads to the sharp drop in the stress-strain curve. Subsequently，the dislocations in the Ta layers pass through the interfaces and enter into the W layers，and the propagation and slip of the dislocations in the W layers cause the yield of W layers. The yield of the sample is primarily determined by the Ta layers，and the plastic deformation in the flow stage is jointly governed by the dislocations and their evolution in both the W and Ta layers. With an increase of modulation period，the number of interfaces in the W/Ta metallic multilayer decreases，so that the nucleation of dislocations decreases as well as the amount of dislocations adsorbed by the interfaces decreases. In addition，the decreased number of the interface weakens the effect of hindering dislocations by interface. Therefore，the yield strength increases and the averaged plastic flow strength decreases.

The energy transfer efficiency and energy dissipation of coupled piecewise linear stiffness energy sink are studied. The equation of systematic slow-varying equations of the two-degree-of-freedom system coupled with the piecewise linear stiffness energy is derived by the complex variable-averaging method under 1∶1 internal resonance. The approximate expression of two extreme points of the slow-invariant manifold is obtained by using the polynomial approximation method，and the energy transfer efficiency equation and energy dissipation equation of the coupled piecewise linear stiffness energy sink system are obtained. The effects of piecewise gap and piecewise linear stiffness on energy transfer efficiency and the relationship between damping coefficient of the main structure and dissipation time are analyzed. The results indicate that the energy transfer efficiency of the system decreases as the piecewise gap of the coupled piecewise linear stiffness energy sink increases，while it increases with an increase of piecewise stiffness. Additionally，it decreases with an increase of the damping system of the main structure. Therefore，adjusting structural parameters，the piecewise linear stiffness energy sink can effectively mitigate vibrations within the main structure.

The camshaft is an important component that ensures the timely opening and closing of valve in marine diesel engines. Due to the poor contact lubrication state and excessive friction excitation，it is easy to cause larger interface torque on the camshaft. Considering the effects of transient excitation and interfacial friction，the tribo-dynamics model of the valve camshaft in V20 diesel engine is established. The forced vibration results of the camshaft are obtained，and the friction and lubrication performance of the cam-tappet pair is also analyzed under the fluctuating speed. The results show that，by thoroughly considering both the transient excitation and frictional excitation of each cam pair，the additional stress in each shaft section of the valve camshaft increases by about 4 MPa，while the transient speed fluctuation at the camshaft end increases by roughly ±30 r/min. Under the combined effects of speed fluctuation and surface roughness，the film thickness is dramatically reduced in some positions，especially in the cam base circle section where the film thickness decreases by about 0.3 μm. At the reverse motion position and nose of the cam，the temperature rise at the interface of the tappet exceeds the material’s scuffing temperature，thereby increasing the risk of scuffing wear.

This paper presents a simplified structural model for continuous variable cross-section single-pile foundations of offshore wind turbines, considering the water-pile-soil interaction, using the Euler-Bernoulli beam theory. The simplified model is solved using the differential transform method to obtain the transverse vibration control equation. The investigation focuses on the impact of tower diameter, transition section height, water-added mass, impeller-nacelle assembly mass, and the stiffness of three springs on the transverse natural frequency. The results show that the influence of the bottom diameter of the variable cross-section tower on the natural frequency is greater than that of the top diameter. In offshore wind turbine installations with greater water depths, the effect of water-added mass on the structural natural frequency cannot be overlooked. The transverse natural frequency of the wind turbine decreases as the impeller-nacelle assembly mass increases. The sensitivity of the soil modulus to the spring stiffness is ranked as follows: horizontal spring > coupling spring > rotational spring. Similarly, the sensitivity of the natural frequency to the spring stiffness is ranked as: coupling spring > horizontal spring > rotational spring. When variations occur in the soil modulus, the primary influence on the natural frequency is predominantly exerted by the horizontal spring and the coupling spring.

Higher-order harmonics of crowd loads may can lead to an increase in the dynamic response of high-frequency floors, resulting in serviceability and safety issues. This study aims to analyze the effect of different indoor layouts on the human-induced vibration of high-frequency floors. First, a random load model for high-frequency floors is established by combining the social force model (SFM) and a pedestrian load model. Next, a computational model for human-induced vibration of high-frequency floors is developed, taking into account human-structure interaction (HSI). A high-frequency floor with a fundamental frequency of 10.35 Hz is tested to validate the reasonableness of the computational model when applied to different layout configurations. Finally, the serviceability of the floor with different layout forms under random crowd walking conditions is evaluated using the global assessment method for human-induced vibration, with probabilistic results provided. The results show that for human-induced vibration problem in high-frequency floors, the influence of high-order vibration modes must be considered. Under the random walking conditions for five people, the dynamic response of the floor with different layouts is reduced after considering HIS, with a maximum reduction of 13.33% in peak acceleration and a maximum reduction of 12% in probability value of serviceability. The serviceability of the floor varies with the different layout configuration. Specifically, the probability of serviceability problems is highest for the floor with a discussion room layout, followed by the classroom layout, with the meeting room layout the lowest probability.

Aiming at the vibration problem of rotating pre-twisted beams in engineering, an effective modeling method is proposed to study their vibration characteristics. Rotating experiments are designed to verify the accuracy of theoretical research. By adjusting the boundary spring stiffness, different boundary conditions are simulated. The displacement field is expanded using the modified Fourier series method, and the motion equation of the rotating beam is derived using the Rayleigh-Litz method. Based on the theoretical research, vibration tests of rotating straight beams and pre-twisted beams with different sizes are designed. The accuracy of this method is verified by comparing the theoretical calculations with finite element simulations and experimental results. The possibility of elastic boundaries is also verified through error analysis. The results show that the natural frequency of the beam increases with the increase in rotating speed and thickness. The increase in pre-twist angle has a minimal effect on the first-order natural frequency but significantly reduces the second-order natural frequency.

The narrowband active control system is suitable for controlling low-frequency harmonic noise. In practical applications, the problem of reference signal mismatch caused by the rapid frequency changes of the original noise will seriously degrade the performance of the narrowband active control system. Existing frequency estimation algorithms often struggle to balance the speed, accuracy, and computational complexity required to track the actual frequency. This paper proposes a Notch-HAQSE frequency estimation algorithm for narrowband active control, which extracts any number of line spectrum frequency components from the reference sensor signal by combining a notch filter with a high-precision single-frequency estimation algorithm based on DFT coefficients (HAQSE). The synthesized reference signal is sent to the controller to complete secondary signal updating. Simulation and experimental results show that, compared with other frequency estimation methods used in active control, the proposed method accurately identifies and rapidly tracks multiple frequencies while significantly reducing computational complexity. It effectively addresses the problem of reference signal mismatch and multi-line spectrum vibration noise control.

In complex hilly terrain, the wind field around interfered hills is influenced by nearby hills, which affects the wind-induced fatigue damage of the tension suspension-braced transmission structure. Therefore, the effect of occluding hills must be considered in the analysis of wind-induced fatigue. In order to analyze the influence of occluding hills on the wind-induced fatigue damage of the transmission structure in complex hilly terrain, wind tunnel tests on the wind filed characteristics of complex hilly terrain were first conducted. Based on the test results, the variation of the mean velocity correction factor and the fluctuating velocity correction factor of the wind field around interfered hills, with different slopes, heights and interval distances of occluding hills, were studied, and a corresponding distribution model was proposed. Next, a nonlinear finite element model for wind-induced vibration of the tension suspension-braced transmission structure considering the effect of occluding hills was established using the nonlinear finite element method. Then the time domain rain-flow method and the Miner’s linear cumulative damage theory were applied to estimate the wind-induced damage to the structure. Finally, a two-span tension suspension-braced transmission structure was selected as a case study, and considering the effect of occluding hills, the wind-induced fatigue damage was analyzed using the proposed model. The results show that: the fatigue damage in each part increases initially and then decreases as the slope of the occluding hills increases. The heights of occluding hills have little effect on the fatigue damage of each part, with no obvious trend. When the interval distances between occluding hills is between 0 m and 600 m, the fatigue damage in each part gradually decreases as the distance increases. However, when the interval distance is between 600 m and 800 m, the fatigue damage of each part suddenly increases as the distance increases. Under the influence of the same occluding hill, the fatigue damage of the end of the conductor and the supporting-conductor suspension cable is greater than that at the mid-span.

This study investigates the influence of installation methods on the optimization design and vibration reduction performance of a novel tuned mass damper inerter (NTMDI). Firstly, the mechanical model of NTMDI-R (reverse-installed NTMDI)is introduced in detail, and its optimization design of NTMDI-R is performed using classical fixed-point theory, resulting in analytical expressions for the optimal structural parameters of NTMDI-R. Subsequently, a comparative study is conducted to analyze the vibration reduction effects of NTMDI-R and four existing classical tuned mass dampers (TMD, TMDI, VTMD, and NTMDI)under harmonic and random excitations, while also investigating the influence of installation methods on the vibration reduction performance of NTMDI-R. The results demonstrate that the optimized parameters of the two dampers (NTMDI and NTMDI-R) differ, and the installation method has a significant impact on their vibration reduction performance. When the apparent mass ratio β is less than 0.1, NTMDI-R exhibits a lower vibration reduction effect compared to NTMDI. However, when β exceeds 0.1, the vibration reduction effect of NTMDI-R becomes similar to that of NTMDI. Therefore, when adopting NTMDI for structural vibration reduction, the installation direction should be specified. Under base acceleration and load force conditions, the vibration reduction effect of NTMDI-R is reduced by 3.9% and 4.7%, respectively, compared to NTMDI.

To gain a deeper insight into the sorting of main launching noise sources in underwater weapons, different sub-noise sources and their contribution to the overall radiation noise are analyzed through both analytical and experimental research, focusing on the typical gas-water tank launching device trial model. The acoustic transmission channels of launching noise include hull structure and the seawater-connected domain formed by the pipeline system through which the weapons travels. In the concluded thirteen sub-noise sources, the primary components include 4 structural vibration noises and one impact vibration noise. The former are caused by gas tank seat vibration, tank cylinder wall vibration, torpedo tube wall vibration and piston axial fluctuating force source, all of which radiate noise through two transmission channels. The impact vibration is induced by the piston striking the end wall of the tank and radiates noise mainly through the connected domain. The jet noise radiated by the tube exit flow is comparable to the radiation noise of a quasi-quiet submarine in navigation and makes less contribution to the overall launching noise. The airborne noise of the launching device presents broadband white noise with stepwise elevation, mainly concentrated in high-frequency band, with minimal contribution to the structural vibration noise. The vertical vibration of the gas tank seat and the radial vibration of the tank cylinder wall are significantly affected by the piston’s startup and end crash. The instantaneous vertical impact peak value is one order of magnitude higher than a typical ship diesel engine’s periodic vibration. The radial vibration pulse peak of the tube wall is corresponded to the moment of the piston’s end crash. The ranking of the average vibration levels for the three vibration sources is as follows: gas tank seat vibration, tank cylinder wall vibration, and tube wall vibration.