Quasi-zero stiffness （QZS） vibration isolation，by introducing stiffness nonlinearity，effectively addresses the inherent contradiction between load-bearing capacity and isolation bandwidth in conventional linear isolators. As a result，it exhibits superior low-frequency isolation performance. The core challenge in realizing QZS isolation lies in designing mechanical structures whose force-displacement curves simultaneously demonstrate high static stiffness and low dynamic stiffness. Focusing on QZS isolation design methodologies，this paper first outlines the fundamental principles of QZS isolation and categorizes the traditional approaches according to the means of stiffness nonlinearization into four groups： geometric motion nonlinearity，geometric deformation nonlinearity，magnetic nonlinearity，and stress-strain nonlinearity. Subsequently，it introduces emerging design strategies based on nonlinear positive-stiffness structures，including hardening and softening types，and compares them with conventional approaches，with particular attention to their differences in static and dynamic behavior. Finally，the paper summarizes and discusses future directions from the perspectives of negative-stiffness structure design，QZS characteristic tuning，and potential applications，aiming to provide a comprehensive overview of the latest research progress and to offer insights into future development trends of QZS isolation systems.

The theoretical framework of Hertzian contact model for soft sphere collisions is well-established； however limited research has been done on the collision between rigid particles and elastoplastic materials. In this study，a novel damping form is introduced by incorporating the elastoplastic half-space contact constitutive relationship，and a viscoelastoplastic collision model between hard spherical particles and polyurethane surfaces is established. The nonlinear dynamic equations for particle and elastoplastic surface collision are derived. Furthermore，by conducting experiments to measure the coefficient of restitution for coal pellets colliding with polyurethane，the Meyer's index of the polyurethane material and the damping coefficient in the dynamic equations are determined. Additionally，the correctness of the damping model proposed in this study is validated by considering different damping forms in the equations. The changes in contact force at different stages are analyzed under various damping coefficients. The variations of displacement，velocity，and contact force during the collision process between particles and elastoplastic polyurethane are investigated. The results reveal that with an increase in the initial collision velocity，the irreversible plastic deformation of polyurethane increases from 1.636×10^-4 m to 5.657×10^-4 m，the coefficient of restitution decreases from 0.583 2 to 0.501 2，the collision time decreases from 6.963×10^-4 s to 4.737×10^-4 s，and the proportion of plastic compression stage decreases from 59.81% to 59.04%.The model established in this paper can be used in scenarios where particles collide with softer planes，such as the separation of metal ores and particle dampers. This paper provides theoretical support for the transportation，collision，impact，and separation of particle systems.

Aiming at the chatter problem in the process of milling screw rotors，a chatter monitoring method based on RelifF algorithm to the least square support vector machine （RF-LSSVM） is proposed. Firstly，the vibration signals in the milling process of the screw rotor are decomposed，and feature extraction and selection are performed using the variational modal （VMD） and the RelifF algorithm. Secondly，the penalty factor，kernel parameter，the number of near neighbor samples of RelifF algorithm and the length of dimension reduction feature of LSSVM are iteratively optimized using the enhanced whale optimization algorithm （E-WOA）. Finally，a flutter identification model is established by inputting the reduced-dimensional flutter eigenvector matrix and outputting the flutter occurrence state. The experimental results show that the proposed VMD-RF-LSSVM model has a higher recognition accuracy than the unoptimized variational modal decomposition-support vector machine （VMD-SVM） model，reaching 99.5% accuracy. The proposed method can effectively monitor the chatter problem in the screw milling process，provides a thought for the optimization of the screw milling processing.

A parameter identification method is proposed to accurately capture the nonlinear dynamic characteristics of dielectric elastomer actuators （DEAs）. First，the response signal of the actuator is acquired under swept-frequency excitation using the time-frequency analysis capability of the transient-extracting transform （TET）. Then，the harmonic and fundamental frequency components are separated and extracted，and the transfer functions for each component are computed to derive the overall transfer function of the DEA. Finally，the results are compared with experimental data. The proposed method achieves a fitting accuracy of 92.11% for the fundamental frequency transfer function and 90.35% for the second harmonic transfer function. This approach does not require prior knowledge of material properties or free energy density functions，and incorporates the influence of high-order harmonic components，offering a novel solution for parameter identification in electroactive material structures.

Aiming at the multi-source noise of inertial navigation in the attitude estimation of coal mine bolting jumbo，a noise reduction method of inertial navigation heterogeneous signal is proposed based on noise sensitive prior and improved variational mode decomposition（VMD），which avoids the over-decomposition and under-decomposition problems caused by the parameter fixation. Firstly，the noise sensitivity difference of the heterogeneous signals （acceleration and angular velocity） of coal mine bolting jumbo is investigated by using the variation of the signal characteristics in the time and frequency domains. Secondly，according to the noise-sensitive characteristics，the dual decomposition layer and energy fluctuation model are constructed，so that the decomposition parameters have the ability of adaptive optimization and the synchronous optimal decomposition of the inertial-guide heterogeneous signals is realized. Based on the Pearson correlation coefficient （PCC），the modal component screening parameter，correlation coefficient P，is designed to consider the noise sensitivity difference，to achieve screening practical modal components and simultaneous noise reduction of heterogeneous signals. Finally，the proposed method is compared with the noise reduction results of complementary ensemble empirical mode decomposition （CEEMD） and improved complete ensemble empirical mode decomposition with adaptive noise （ICEEMDAN）. The results show that the method proposed in this paper considers the noise sensitivity differences of heterogeneous signals，thereby improving the signal-to-noise ratio of inertial measurement and enhancing the attitude initialization accuracy of bolting jumbo. The pitch error is reduced by 81.818 %，and the yaw error is reduced by 87.958 %，which lays a good foundation for accurate roadway support.

To address the issue of metallic objects around a balise affecting its electromagnetic transmission performance，a balise antenna model is established in electromagnetic simulation software. The simulation experiments are carried out by varying three parameters：the metal surface area，the vertical distance between the metal surface and the balise，and the metal surface thickness. The uplink signal amplitude curves of the balise under different parameters are obtained，and the transmission performance metrics are calculated to analyze the impact. Results show that： a larger metal surface area leads to lower performance metrics，such as a reduced number of safety message frames received by the balise transmission module （BTM），with a more significant degradation and greater interference from the sidelobe region. When the metal area is greater than 320 mm×320 mm，the uplink field strength consistency requirement can no longer be met. A greater absolute distance between the metal surface and the balise results in less interference from the sidelobe region，and the distance must be greater than 123 mm to satisfy the field strength consistency requirement. Increased metal surface thickness causes greater interference from the sidelobe region，and the thickness should not exceed 1 mm.

To investigate the fault mechanism of blade cracks and to analyze the effects of blade crack on the three-dimensional （3D） tip clearance of the rotor system，while comprehensively considering blade radial deformation，flap-wise bending，and chordwise bending，this paper develops a novel dynamic model of the rotor system based on continuum theory. With the blade breathing crack model under the three-dimensional stress state，a 3D tip clearance dynamic response model of rotor system with blade cracks is further established. The accuracy of the dynamic model is validated by comparing it with the finite element model and experiments. On this basis，the effect of blade crack depth and location on the 3D tip clearance in rotor system is further analyzed. The results show that the amplitudes of the high frequency doubling component of the 3D tip clearance increase with crack depth，while both the fundamental frequency and the high frequency doubling component of the 3D tip clearance show a non-monootonic trend as the relative crack location increases. The research results provide theoretical guidance for research on monitoring and diagnosis method of aero-engine blade crack based on 3D tip clearance.

In order to improve the fault detection performance of wheelset bearings under small sample image conditions，a machine vision inspection method based on a novel multi-resolution siamese neural network （MrSNN） is proposed for surface defect detection of wheelset bearings. First，the siamese neural network （SNN） is used as the basic model framework. A multi-resolution convolution fusion block （MrCFB） containing convolution kernels of different sizes and dilation factors is constructed to comprehensively extract the detailed features and contour features from images. Then，a dual attention mechanism combining channel and spatial information is adopted to recalibrate the multi-resolution feature weights，further enhancing the image feature extraction capability of the model. Finally，the algorithm is validated through the detection and analysis of four types of wheelset bearings images： normal，scratched，pitted and spalled. Experimental results show that the recognition rate for the three types of faulty images reaches 100%，the recognition rate for normal images is 95%，and the overall recognition accuracy is 98.75%. The recognition accuracy is superior to that of traditional SNN and YOLO-V5 models.

To study the influence of subway wheel polygons on low-frequency vibration of the car body，the polygon wear of wheels of a subway line is investigated，on the basis of grasping the distribution characteristics of wheel polygons of subway lines. A vertical dynamic model of elastic car body considering wheel polygons is established，by the time-domain integral solution method. The relationship between wheel polygon excitation frequency and low frequency vibration of vehicle body is studied. By comparing the low-frequency vibration of wheel polygons of different orders，the effect of changes in the operating speed of metro vehicles under service conditions and changes in the radius of wheel wear on the polygonal action of the wheel body is discussed separately. It is shown that a wheel polygon of order 1—3 at common operating speeds generate a low-frequency excitation frequency of 0—20 Hz，and when the excitation frequency is close to the first-order droop frequency of 10.2 Hz resonance will occur. At the beginning of service，the influence of the second order wheel polygon becomes severe on the low frequency vibration of the car body. With the wear of the wheel radius during service，the influence of the first three order wheel polygon changes on the vibration law of the car body. This paper provides a good reference value for service subway operation and wheel maintenance.

The transient vibration of a vertical axis washing machine is strong in the dehydration process，so a new planar variable damping structure is proposed to reduce the transient vibration. Firstly，the kinetic energy and potential energy of various rigid bodies of the washer are deduced，the generalized forces of the suspension structure are described，the force of the liquid balancer is analyzed，and the vibration model of the vertical axis washing machine is established using Lagrange's equation. The working principle of the planar damping structure is explored，its damping force is described and its suppression effect on transient vibration of the washer is verified. Secondly，the influence of the planar damping structure on dynamic characteristics of the washer is evaluated，the bifurcation theory is employed to analyze stability of the system. Furthermore，the distributions of the stable regions of the system is analyzed，and the appropriate disengaging speed range of the damping structure is obtained. Finally，the effect of the damping structure for suppressing transient suppression of the washer is validated though experiments，and the appropriate disengaging speed of the structure is analyzed. The results show that the planar damping structure can suppress transient vibrations effectively with little influence on other dynamic characteristics of the washer.