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.

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.

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.

In the past decade, approximately one-third of civil aviation safety incidents have been related to landing, with hard landings comprising one-fifth of these landing-related incidents. Hard landings not only damage aircraft structures but also can lead to aircraft destruction or loss of life in severe cases. However, statistical data on hard landings remain limited. This paper systematically analyzes hard landing criteria through a review of quantitative standards, simulation analysis, and machine learning techniques. It also conducts a statistical examination of 53 typical hard landing incidents of mainstream aircraft such as Boeing-737 and Airbus-A320 over the past decade, offering a detailed exploration of common structural damage patterns associated with hard landings. Results show that heavy landing incidents often cause damage of different degrees to the aircraft's landing gear, fuselage, wings, and other key components. Moreover, the extent of damage differs significantly among various types of heavy landing incidents.

In order to determine the influence of aggregate irregularity on the mechanical properties and failure morphology of concrete, Python programs were developed to generate randomly distributed aggregate models with different sharpness in ABAQUS, and the 0-thickness cohesive element and variable-thickness solid interface transition zone（ITZ）were established respectively. First, the reliability of model was determined by changing mesh size and friction coefficient between the loading pad and concrete compared with the experiment. Then, the quality of two ITZ modeling methods was analyzed. Finally, the uniaxial compression mechanical behavior of the three-dimensional meso-concrete model was analyzed from the aspects of stress-strain curve, fracture propagation, and energy dissipation. The simulation results show that the 0 thickness cohesive ITZ and the solid thickness ITZ model can predict the compressive strength of concrete, and the stress-strain curve and failure morphology of the ITZ model with solid thickness are more consistent with the experiment. The fracture propagation of concrete is obviously affected by the shape parameters of aggregate. The interior and surface of the spherical aggregate model are penetrating cracks. The strain energy of polyhedral aggregate model is larger, and there are many micro-cracks in the concrete, the possibility being compressed and destroyed into more fragments is higher. With the increase of aggregate irregularity, the compressive strength of concrete increases slightly, but the peak strain is not affected.

The objective of this paper is to study the mechanical characteristics of the interface between loess and geosynthetics, in hope of providing targeted suggestions for the design of reinforced loess projects. A large-scale interface shear apparatus was used to conduct direct shear tests on the geogrid-loess interface to study the effects of the moisture content and compaction degree of loess on the shear stress-shear displacement relationships, shear strength indices, and thickness of shear band of the geogrid-loess interface. The mechanism of the effects was analyzed, and the constitutive model of the geogrid-loess interface was discussed. The test results show that as the moisture content increases（not exceeding the plastic limit）, the shear stress-shear displacement curves of the geogrid-loess interface change from softening type to hardening type. The interface cohesion and friction angle significantly decrease with the increase of the moisture content, and thus the interface shear strength decreases accordingly. The thickness of shear band increases with the moisture content. The compaction degree of loess has little influence on the shear strength of the geogrid-soil interface, but it affects the thickness of shear band significantly. The thickness of shear band increases greatly when the compaction degree reaches 90%. Hence, the compaction degree of the backfill of reinforced loess engineering should not be less than 90%. The thickness of the shear band of geogrid-loess interface decreases continuously along the shear direction, with a maximum thickness of 3 cm approximately. This indicates that the shear band between the reinforcement and soil is the thinnest at the facing column in reinforced loess retaining walls. Hence, a flexible or integral facing column is recommended to be used in reinforced loess retaining walls. The hyperbolic interface constitutive model can effectively reflect the shear behavior of the geogrid-loess interface.

In order to characterize the distribution law of active earth pressure with depth for a circular platform foundation pit under transient infiltrations, this study derived the slip line equation for the active earth pressure of circular platform foundation pits. The derivation was based on the strength equation of generalized effective stress for unsaturated soils and matric suction under transient infiltration conditions. Subsequently, the differential iterative method was adopted to obtain the slip line solution of active earth pressure for circular platform foundation pits under transient infiltrations. Last, the accuracy of the obtained slip line solution was verified, and an influencing factor analysis was conducted. The results indicate that the obtained slip line solution, compared with the existing solutions, can reasonably account for comprehen-sive influences of transient infiltration（time, infiltration ratio, nonlinear profiles of suction stress）, soil types（sand, silt, clay）, foundation pit model parameters（wall dip angle, wall-soil friction angle）, and the circumferential stress coefficient on the active earth pressure of foundation pits. The accuracy of the obtained slip line solution of active earth pressure under specific reduced conditions is demonstrated by comparing it with the slip line solution of circular platform foundation pits in saturated soils（when suction stress is zero）, and the limit equilibrium solution of plane retaining walls under transient infiltrations（when the radius of foundation pit tends to infinity）reported in the literature. The influence of time and infiltration ratio on the value and distribution of active earth pressure is most pronounced for foundation pits in clay, followed by foundation pits in silt. However, it is negligible for foundation pits in sand, which is caused by nonlinear profiles of suction stress for different soils. The active earth pressure of foundation pits decreases significantly with the increase of wall dip angle, wall-soil friction angle and circumferential stress coefficient, while its distribution and change with depth are closely related to soil types.

In order to investigate a structure with better mechanical properties, this paper proposes a square honeycomb lattice sandwich cylindrical shell structure, which combines metal thin-walled tubes and honeycomb structures. The mechanical behavior of the sandwich cylindrical shell structure with a square honeycomb as the core under radial compressive loads is studied by experimental and numerical methods. By comparing the results of two research methods, the accuracy of the finite element model is verified, and the deformation mode of the structure under radial compressive loads is analyzed, and the reinforcement mechanism of the structure is discussed. The results show that the rectangular honeycomb lattice sandwich cylin-drical shell structure will undergo three deformation stages:elastic stage, plastic stage and collapsibility stage under radial compression load. Compared with the simple superposition of single-layer cylindrical shells and cores, the load-bearing and energy absorption of the square honeycomb lattice sandwich cylindrical shell are greatly improved. The structure is mainly coupled and reinforced by the formation of plastic hinges and the debonding between the square honeycomb core and the inner and outer cylindrical shells.

Large flexible appendages of flexible spacecraft are characterised by their large scale and low stiffness, resulting in vibration of large flexible appendages that can seriously affect the attitude precision of the spacecraft. Information fusion preview control is combined with fuzzy control to construct the attitude controller. According to the information fusion theory, the spacecraft's desired trajectory and system dynamics information are fused, the optimal preview control law is derived. The optimal preview control law can be easily obtained due to the information fusion control has a simple design process and low computational burden. In real engineering, the control torque generated by the actuator is limited. The fuzzy controller is employed to adjust the parameters of the control law on-line in order to satisfy the requirements of limitation. Simulation results show that the designed control strategy with high control performance can effectively suppress the vibration of the flexible appendages, and the attitude angle can reach the desired value accurately and quickly. The proposed control strategy can be served as a reference for the engineering application of large flexible spacecraft attitude control.

In order to enhance the seismic performance of reinforced concrete columns, a method of embedding steel wire mesh to strengthen concrete columns was proposed. A total of six specimens including reinforced concrete column, four steel mesh-reinforced columns, and one stirrup-reinforced column were designed and poured. Constant axial pressure was applied to the specimens and horizontal quasi-static cyclic loading was carried out. The failure patterns, crack distribution, hysteretic characteristics, ductility, and energy dissipation capacity of each specimen were tested. The seismic performances of steel wire mesh-reinforced specimens and stirrup-reinforced specimens with the same equivalent stirrup ratio were compared and analyzed, and the effects of steel mesh layers and configuration height range on the seismic perform-ance of members were discussed. The research results show that the proper configuration of steel mesh can effectively restrict the formation and development of column sectional crack and“diagonal crack”, and transform the bending-shear failure mode of the specimen into bending failure mode. Therefore, compared with the reference specimen and stirrup-reinforced specimen, the wire mesh-reinforced specimen shows greater initial stiffness, better ductile deformation and cumulative energy dissipation capacity. The research results preliminarily clarify the relationship between the number of wire mesh layers, height range and ductile deformation capacity, stiffness degradation, and energy dissipation capacity of specimens, and the related results can provide reference for the design of embedded wire mesh-reinforced concrete columns.