The principle of the hydraulic drifter is introduced，and the process of drilling into rocks by the drifter is established as a physical model of rock with three-degree-of-freedom dry friction. The concept of rate of penetration （ROP） is introduced. The stick and non-stick modes are studied，explaining the differences between these two types of motion. The periodic trajectories of the nonlinear piecewise smooth dynamical system mathematical model are segmented. By using the pseudo-arclength continuation method and Floquet theory，the angular frequency and amplitude of the hydraulic force are taken as control parameters to obtain stable periodic trajectories and the point of maximum ROP. Bifurcations such as period-doubling bifurcation，saddle-node bifurcation，and torus bifurcation are discovered. The data acquisition system for drilling rocks with a hydraulic drifter is introduced，and the displacement and velocity of the piston obtained from the model and experiments are compared. The results indicate that to make the drifter work on the period-1 trajectory，the range of angular frequency should be ω<6.814，and the range of amplitude should be 0.03<a<3.051. There is a strong correlation between the experiments and the model，and compared with the experiment，the piston in the model undergoes deceleration before colliding with the drill tool，adding an impact deceleration stroke.

Reconstructing the sound field environment inside the aircraft cabin during actual flight in a laboratory environment can provide a means for analyzing the acoustic environment inside the aircraft cabin，subjective evaluation，and noise reduction design. Based on the principle of sound pressure matching，this paper adopts a regularization method based on the L-curve method to solve the problem of inverse transformation of ill conditioned matrices. The effectiveness of the method in solving ill conditioned problems and improving reconstruction accuracy is demonstrated through simulation examples. Independently designed and built an aircraft cabin sound field reconstruction system. Conduct flight tests on transport aircraft，measure the noise at the pilot’s ear position under typical flight conditions，and use it as the target sound field. By using the sound pressure matching method，the full flight profile sound field reconstruction was achieved through the aircraft cabin sound field reconstruction system. Through sound field reconstruction experiments and subjective evaluation experiments，it shows that the reconstruction error in each frequency band of the one-third octave band is within 3 dB （A），and the subjective auditory fidelity and restoration are relatively high，providing support for subsequent analysis and subjective evaluation of the aircraft cabin acoustic environment.

Research on magnetically levitated rotors has been heavily influenced by studies on slender shaft magnetic levitated rotors. In the study on a certain magnetically levitated flat rotor for a centrifugal pump structure，both experiments and finite element analysis revealed that the support characteristics of the radial permanent magnetic bearings，with the same dual-ring structure，exhibited the significant differences from the known experience when applied to flat rotors. The translational stiffness and torsional stiffness showed substantial variations. This paper analyzes the variations in translational and torsional stiffness of permanent magnetic radial bearings for flat rotors based on changes in the bearing’s structural dimensions. Based on the analysis，a flat rotor magnetic levitation structure is proposed，which can increase and adjust the torsional stiffness of the permanent magnetic bearings，while also allowing for a rational ratio between translational and torsional stiffness. A finite element analysis is used to identify the structural conditions that yield maximum translational and rotational stiffness. The effectiveness of the proposed methodology is subsequently validated.

According to certain selection criteria，this paper selects 8 mainshock-aftershock events and 560 mainshock-aftershock sequences from NGA-West2 ground motion database，uses ASK14 ground motion prediction equation to carry out residual analysis on the mainshock-aftershock sequences，obtains the intra event residual of mainshock-aftershock sequences at each station，and standardizes them. According to the geostatistical semivariogram method，the exponential semivariogram model and the manual fitting method are used to calculate the spatial autocorrelation of the spectral acceleration period of the mainshock-aftershock sequence. Since the Pearson linear correlation coefficient can better measure the linear relationship between the fixed-distance variables，the Pearson linear correlation coefficient is used to calculate the cross-correlation of the normalized intra-event residuals between different spectral acceleration periods of the mainshock-aftershock sequence without considering the spatial cross-correlation. According to Markov’s hypothesis，the spatial information is introduced into the calculation of the cross-correlation，and then the expression of the change of the spatial cross-correlation with the spatial distance （h） is obtained. The results show that the mainshock is significantly different from aftershocks in terms of spatial autocorrelation and cross-correlation characteristics，and aftershocks generally have higher spatial correlation in the long-period stage. Neglecting the spatial correlation between the mainshock and aftershocks or using the characteristics of the mainshock to replace the characteristics of the aftershocks will adversely affect the research on earthquake hazard analysis，damage assessment，and the synthesis of main and aftershock sequences.

In order to achieve rapid construction and reliable connection of precast RC frames，a sleeve-type fully-bolted joint is proposed. The ends of the prefabricated components are reinforced with a steel sleeve-concrete combination. High-strength bolts are pre-built in the sleeve area，and the precast components are rapidly installed using a connection plate. A total of four test specimens were designed for different thicknesses of connecting cover plates. The horizontal hysteresis test study obtained the damage mode，load-displacement hysteresis curve，ultimate bearing capacity，ductility and energy dissipation capacity of this type of joint. The results show that the new joint has a 43% higher ultimate load，70% higher initial stiffness and nearly 50% higher ductility than the cast-in-place joint，and the equivalent viscous damping coefficient is increased by about two times，which shows better seismic performance. Strain analysis reveals that the cover plate at the joints shows a “stress increase”，but the effect on the overall performance is not apparent. As the thickness of the connection plate increases，the squeezing effect of the sleeve on the concrete increases. Therefore，a connection stiffness ratio of 1.6 is more reasonable. Finally，based on the test results，a trifold moment-turning angle model is established，and the calculated results agree with the test values.

In order to obtain more accurate and refined dynamic characteristics of the flat boom tower crane，the field test of the dynamic response of the typical freestanding flat boom tower crane was carried out considering the influence of lifting positions，lifting heights （rope lengths） and lifting weights. The test results show that the vibration along the boom axial direction and vertical direction has good synchronization. However，the response correlation between the horizontal direction of the vertical boom and the axial and vertical direction of the tower crane boom is relatively low. The natural frequencies identified by the half-power bandwidth method and the SSI-COV method are basically the same，with the difference of lifting positions，rope lengths and lifting weights，the natural frequencies of flat boom tower crane will fluctuate around the natural frequency under no load. There are some differences in the identification results of the damping ratio between the two methods，in most working conditions，the damping ratio identified by the SSI-COV method is smaller than that identified by the half power bandwidth method. Based on orthogonal test analysis，the influence of the above factors on the natural frequency and damping ratio of the tower crane is not significant，and there is no main effect. In addition，the finite element model of the flat arm tower crane is optimized，and the frequency of the updated model is in good agreement with the test results. The boom vibration mode function under no-load condition was fitted，the amplitude distribution along the boom length exhibits an approximately linear，however，when the lifting weight appears at the end or root of the boom，the boom vibration mode may show an obvious nonliner characteristics.

Based on the three-dimensional elasticity theory，the smooth stochastic response model of three-dimensional sandwiched cylindrical shells is established by using the unified series method and the pseudo-excitation method （PEM）. The cylindrical shell subdomains are divided according to the interlayer property differences of the sandwich material，and the kinetic energy，strain energy，boundary potential energy and smooth random excitation work of each subdomain are established by using three-dimensional elasticity theory combined with the virtual excitation method. The mechanical coordination conditions between the layered subdomains are converted into coupling condition energies by the coupling penalty function method，and then the overall energy generalization of the sandwiched cylindrical shell is obtained by superposing the energies of each subdomain. The displacement components of each subdomain are constructed using a unified level expression and solved by combining the Rayleigh-Ritz method to obtain the stochastic response of the three-dimensional sandwiched cylindrical shell structure. The correctness of the stochastic response model is verified by comparison with literature and finite element results. Finally，the effects of thickness-to-radius ratio，lay-up angle of laminated-functional gradient sandwich material and power-law index on the random response of three-dimensional sandwiched cylindrical shell are analyzed.

Statistical energy analysis （SEA） is a widely used method for analyzing the high-frequency dynamic response of mechanical structures. The reasonable division of subsystems is one of the critical basises for SEA. In this paper，an automatic identification method of SEA subsystem based on order-reduced modal energy density and hierarchical cluster analysis is developed. First，the structural modal energy densities in the high-frequency band are obtained through the discrete finite element model. Then，the main features of the modal energies are extracted through the proper orthogonal decomposition. The similarity of the modal energy density between different elements is analyzed by hierarchical cluster analysis. Finally，the number of statistical energy analysis subsystems and the corresponding structural elements are identified. The T-shaped plates，I-shaped plates，and engine combustion chamber are taken as simulation models to verify the effectiveness of the proposed method. Simulation results show that the coupling relationship between components，the number of subsystems，and corresponding elements can be automatically identified by the proposed method. Then，the SEA model can be established efficiently and accurately.

In view of the light weight，small space and small amplitude requirements of electronic equipment for vibration isolation structure，the paper focuses on the isolation of low frequency vibration from its base. By introducing the cross-braced configuration，a concave cross braced plate model is proposed，the influence law of structural parameters on its low frequency vibration isolation performance is illustrated. Then，based on the design concept of cross-bracing，a concave sandwich phononic crystal structure model is proposed，and the influence mechanism of geometric parameters on its frequency response characteristics is revealed. After geometric parameter optimization and experimental verification，the vibration isolation structure model has excellent vibration attenuation characteristics in the low and wide frequency band. In 100~500 Hz，the attenuation efficiency of acceleration power spectral density above 70%. In 35~80 Hz，and 500~2000 Hz，the attenuation efficiency of acceleration power spectral density above 40%. Working displacement of the vibration isolation structure under 3 times standard deviation confidence is less than 3 mm. Therefore，it is suitable for the isolation of low frequency random vibration. In addition，the model has broad application prospects owing to its advantages of light weight，small volume，large bearing capacity and strong universality.

In order to solve the engineering problems of strict convergence condition of traditional decentralized algorithm and huge computation amount of centralized algorithm in vibration active control of complex systems，this paper combines network topology cooperation strategy and FxLMS algorithm to design a novel active vibration control algorithm based on network topology cooperation，and selects a simplified airframe model of a helicopter as the controlled object. The simulation study of active vibration control with a scale of 20×20 （20 actuators and 20 error sensors） is carried out. The results show that the algorithm based on network topology can achieve the same vibration reduction effect as the centralized algorithm while significantly reducing the computation amount，which is an advantage that the decentralized algorithm and the centralized algorithm do not have. The mean vibration decreases about 34.3 dB under single-frequency control，and about 12.6 dB under multi-frequency control. At the same time，the characteristics of secondary path coupling are properly simplified，which is conducive to the value of convergence coefficient，and the effectiveness and superiority of this algorithm for active vibration control of helicopter complex system are fully verified.