To study the effect of double circular holes on the mechanical properties of rocks and the crack extension process, a uniaxial compression model for rock specimens containing double circular holes was constructed, and the correctness and rationality of the numerical model were verified based on the comparison of the macroscopic mechanical parameters obtained from experiments and simulations. In addition, the crack extension process of specimens containing double circular holes and the evolution of the stress field around the circular holes were analyzed. The results show that the numerical simulation results are in good agreement with the experimental results；the initial tensile crack first sprouts at the upper and lower ends of the circular hole, and with the increase of axial stress, structural weak zones are usually formed at the left and right sides of the hole wall. The sprouting direction of the initial tensile crack is in the axial load-ing direction, independent of the orientation angle α, but the damage pattern of the specimen is influenced by the orientation angle α. The initial tensile crack is generated in the tensile stress concentration area；the tensile stress concentration area at the upper and lower ends of the circular hole moves and dissipates accordingly with the expansion of the initial tensile crack. The compressive stress concentration area of the stress component σ_yy is located on the left and right sides of the circular hole, while a shielding area of compressive stress is formed at the upper and lower ends of the circular hole, and the smaller the distance from the vertical center line of the circular hole, the stronger the shielding effect and the weaker the compressive stress.

With the development of civil aircraft design technology, the focus of today's passenger aircraft design transits from structural safety to cabin comfort, of which the vibration comfort is a key factor. From the perspective of passenger vibration comfort, We carried out the vibration transfer path test of a certain type of passenger aircraft under three working conditions, namely, the cruising condition, the low-altitude flight condition, and the runway running condition. Based on the test data of these conditions, the Vibration Transfer Path models were built, and the key factors affecting the vibration comfort were studied. The following conclusions are drawn:Under the cruising and low-altitude flight condition, the cabin vibration response mainly comes from the coupling of engine rotor excitation and the structure at the fundamental frequency and the double frequency；under the runway running condition, the vibration response in the cabin comes from the coupling of the main landing gear excitation and the structure in the low frequency range（especially 50 Hz）. This test not only provides a basis for the vibration reduction and isolation design of passenger cabins, but also fills the gap of the vibration comfort test and verification platform for all passenger aircraft in China.

The modeling of the passive dynamic walker of flexible legged rimless wheel is studied, and the influence of damping coefficient on system dynamics is analyzed. According to the geometric characteristics of the walker, the independent generalized coordinates are selected to describe the position of the system, and the second kind of Lagrange equation is used to establish the dynamic model of the passive dynamic walker of flexible legged rimless wheel. By analyzing the structure and physical properties of the flexible leg, it is concluded that the impact occurs in the tangential direction of the telescopic leg and the impact force is not transmitted between the leg and the ground in the radial direction during the impact stage, and a state jump model under the assumption of partial impact is proposed. The numerical simulation of passive dynamic walking of flexible legged rimless wheels using different damping parameters verifies the effective-ness of the proposed method. When a larger damping coefficient is selected, the double-limb support period of periodic walking accounts for 77.6% of the whole walking cycle, while the single-limb support period accounts for 22.4% of the whole walking cycle. The periodic walking can be achieved when the slope angle is in the range of 0.1-0.7 rad. The slope angle of the flexible legged rimless wheel that can passively and dynamically walk on decreases as the damping coefficient decreases.

Against the characteristic of large deformation for reinforced concrete（RC）frame, RC frame-frame truss composite wall（FTCW）structure was proposed, and two reinforced concrete（RC）frameframe truss composite wall（FTCW）specimens with a scale of 1∶2 were implemented for cyclic loading test. The seismic performance of bearing capacity, ductility and stiffness degradation were analyzed by the test phenomenon, hysteresis curves, backbone curves and stiffness degradation curves. The simulation of cyclic loading test was conducted by ABAQUS software, and the results were compared with the test results. The influence of the amount of infill FTCW, rebar ratio of RC frame columns, axial compression ratio, concrete strength, embedded angle steel and the layout direction of FTCW were analyzed. The test behav-iors showed that a multistage energy consuming system that FTCW worked before RC frame and the internal diagonal struts worked before the outer frame inside the FTCW, forming a multistage energy consumption system for the design purpose of earthquake resistant structures. The numerical analysis results showed that the most effective way to improve the bearing capacity of RC frame-FTCW was to increase the amount of filled FTCW, followed by increasing the rebar ratio of frame columns, and the improvement of increasing the concrete strength or adding angle steel for the internal diagonal struts were smaller. The improvement of axial compression ratio on the bearing capacity was unnoticeable. In addition, the layout direction of FTCW was significant, and the number and position of FTCW should be symmetrically arranged.

A large number of fission pores are generated in ceramic fuel under high burnup conditions, and the fission gas released into the crack cavity has a great influence on the crack propagation behavior. In this study, a dynamic crack propagation model under variable internal pressure is developed to address the dynamic cracking technique of the coupling effect between the internal pressure and crack propagation. The internal pressure in crack cavity varies with crack propagation, while the cracking behavior is simulta-neously affected by the pressure. The presented model is successfully applied to simulate the cracking behavior of ceramic fuel particles of high burnup structure, and the mechanical effect of fission gas release on crack propagation is studied. Based on the cohesive element, the crack initiation and propagation process are simulated, and the mechanical research method of gas release on crack propagation is established here. Furthermore, the effects of gas pressure on the crack initiation and propagation process in fuel particles are analyzed. The results show that the release of gas into the crack cavity can inhibit crack propagation based on gas pressure and crack geometry characteristics. For different initial gas pressures, the larger the initial gas pressure is, the longer the crack propagation length will be. The developed dynamic cracking simulation technique provides an analytical method and numerical foundation for accurately analyzing the failure of dispersion fuel meat. It also provides a method to study the coupling of load and crack propagation.

In this paper, the effects of doping elements（Re and Ru）content on the stability and occupancy orientation of a Ni-Al binary model nickel-based single-crystal superalloy are studied by using first-principles calculations. The results show that the total energy of the system decreases gradually with the increase of the content of Re and Ru elements, which suggests that the stability of the system is improved. The system using Ru to replace Ni has the lowest stability, while the stability of system is the best by using Re to replace Al. Therefore, Re and Ru are more inclined to replace Al, which is consistent with the previous experimental results. Meanwhile, compared to other contents of Re and Ru, when Re and Ru with the content of about 1.4% are used to replace Al, the substitution formation energy is the lowest. Furthermore, two different stacking fault modes are obtained by deleting a layer of atoms in the Ni-Al binary model. Research on these two stacking fault modes indicates that replacing Al with Re and Ru can improve the stability of the systems, and systems containing Re are more stable, which have lower substitution formation energy compared to replacing Al with Ru. However, for different stacking fault modes, when replacing Al with Re and Ru, the content of Re and Ru is different for the best of a stable system and the lowest of substitution formation energy and stacking fault energy. Replacing Al with Re results in a better stability in stacking fault systems, but the content of Re in the most stable system depends on the selected stacking fault mode.

Hypersonic aircraft face extremely high aerodynamic resistance and heating during flight, posing a threat to flight safety and stability. Taguchi-gray correlation method is utilized to study the impact of size on the resistance and heat reduction performance of hypersonic aircraft. An orthogonal test is conducted, wherein design factors such as spike length-diameter ratio, airway diameter ratio, pneumatic disk diameter ratio, and lateral jet angle are considered. The response targets comprise total flight resistance, peak pressure coefficient, and Stanton number. Test results are obtained through numerical simulation. The findings indicate that the flight resistance is most significantly affected by the length-diameter ratio of the spike，while the lateral jet angle has the least effect. In regard to the peak pressure coefficient and Stanton number，the size factors exhibit a similar rank of influence. Among these factors，the length-diameter ratio of the pneumatic disk exerts the most significant impact. Increasing the length-diameter ratio of the spike and the diameter ratio of the pneumatic disk can effectively improve overall resistance and heat reduction performance. However，it should be noted that as the size increases，the lifting efficiency gradually diminishes. In comparison to the optimal group of orthogonal design，the optimized configuration demonstrates an overall performance improvement of 4.6%，thus indicating a favorable optimization effect.

The anti-yaw vibration devices currently used in high-speed trains are hydraulic dampers, whose damping characteristics cannot be adjusted according to the changes in the vehicle's operating state and environmental conditions, resulting in poor ride quality and stability for the vehicle. A semi-active damper based on magnetorheological technology combined with intelligent control technology can solve this problem. In this paper, a three-coil magnetorheological damper has been developed with adjustable damping characteristics based on the technical specifications of the anti-yaw damper. The multi-physical field of the damper is simulated, and damping performance of the damper is tested under different excitation currents, amplitudes, frequencies, and coil combinations. The results show that the magnetic circuit design of the damper is reasonable and complies with the technical requirements for anti-yaw dampers, with a maximum output force of 46 kN and an adjustable dynamic coefficient of 28. In addition, an analysis is conducted on the magnetic field distribution at varying coil spacings. The findings indicate that a critical distance exists between the coils, and the critical distance of this damper is 0.69 times the width of the coil, beyond which the magnetic field distribution becomes non-uniform. The change in magnetic flux density at the effective damping channel will stop when a certain part of the magnetic circuit reaches saturation.

Aiming at the demand for torsional capacity of high-power offshore wind power supporting structure, the full-range torsional mechanism of tapered concrete-filled double skin steel tubular（TCFDST）members was examined under the large hollow ratio, high taper degree, and out-of-code diameter-to-thickness（D/t）ratio. The characteristics of torque-angle curve could be divided into the elastic stage, elasticplastic, plastic strengthening stage, and failure stage. Influence of key parameters on ultimate bearing capacity and stiffness was revealed. The hollow ratio and strengths of steel and concrete were positively correlated with the ultimate torque and stiffness；D/t ratios of outer or inner tubes had negative relationship to it；the axial compression ratios had positive relationship within the limited value，and inversely，it was negatively correlative. A method based on laminated tube theory was proposed to calculate the torque-angle curves of TCFDST members. Subsequently，the hierarchical integration method was established and verified based on the Chinese code and relevant literature，for calculating the ultimate torsional capacity of concrete-filled double skin steel tubular members，and the difference of various methods in determining N-T curve was also analyzed. The research results in this paper can provide valuable reference for the application of TCFDST members with large hollow ratios，large taper degree，and out-of-code D/t ratios in wind power projects.

The classic fiber model based on Euler-Bernoulli beam theory overlooks the influence of shear deformation on the section of the beam. In order to establish a more accurate creep analysis method for reinforced concrete fiber beam elements, this paper proposes a fiber beam element considering shear effects based on Timoshenko beam theory. The stiffness matrix of the fiber beam element is derived, and the finite element equation for the equivalent nodal force of creep analysis based on concrete creep analysis initial strain method is obtained. Finally, a finite element method for creep analysis of reinforced concrete fiber beam elements is established. A computing program is developed in FORTRAN language, and elastic analysis for normal beam and reinforced concrete beam, and creep analysis for reinforced concrete beam are conducted. The results are compared with analytical solutions, commercial software and other literature, indicating that the proposed method can accurately consider the shear effects and clearly define the behaviors of steel and concrete in the creep performance of reinforced concrete beams. Moreover, including steel in the creep analysis model can effectively improve the accuracy of the results.