In order to research the effect of rotation on the flow and heat transfer characteristics of heat convection system in a closed cavity, a series of numerical simulations were carried out on the air flow and heat transfer characteristics in a closed cavity. The distribution characteristics of velocity field and temperature field by different Rayleigh numbers and rotating Rayleigh numbers by horizontal and vertical temperature gradients were obtained, as well as the local and average Nusselt numbers on high temperature walls. The effect of rotation on the thermal convection system by two kinds of thermal boundary conditions was discussed. The results show that for the heat convection by horizontal temperature gradient, the gradual enhancement of rotation makes the flow characteristics change from single-cell to multi-cell, and enhances the heat transfer performance of heat convection. For heat convection by vertical temperature gradient, the enhancement of rotation makes the flow tend to the steady-state flow characteristics, that is, the flow stability is enhanced, and at a large Rayleigh number, the enhancement of rotational action will first inhibit and then strengthen the heat transfer performance. Given the same conditions, the convective heat transfer performance by horizontal temperature gradient is better than that by vertical temperature gradient, and the stronger the rotation effect is, the more obvious the feature is.

In order to reveal the unsteady flow characteristics during the pre-compression process of the radial wave rotor combustor, the pre-compression mechanism induced by complex wave systems under typical operating conditions was simulated and analyzed using three-dimensional unsteady simulations. The impact of pressure differential across intake and exhaust ports, as well as rotor speed, on the propagation behavior of compression waves within the channels was focused on. The results indicate that as compression waves propagate within the channels, they are influenced by the curvature of the curved channels, leading to wave reflection, refraction, and attenuation. This results in energy loss and waveform distortion, which affect the propagation path and speed of the compression waves. Although a higher pressure difference enhances the intensity of the compression waves, it exacerbates overfilling of the fuel and flow instability, increases thermodynamic losses, and significantly reduces the isentropic compression efficiency. The rotational speed affects the propagation characteristics of compression waves within the channels by adjusting the operational timing of the wave rotor. At 1 200 r/min, the opening time of the intake port is extended, causing the compression waves to reflect and form expansion waves that propagate in the reverse direction. This results in a pressure ratio within the channel of only 103% and a substantial decrease in isentropic compression efficiency.

The application of green NH₃-fuel on board has been widely regarded as a feasible way to realize the green and low-carbon transformation of the global shipping industry. However, the N₂O emission problem of marine NH₃-fuel engines has become one of the key technical bottlenecks hindering the development of ammonia-powered ships. To solve this problem, a series of TiO₂-supported transition metal oxide catalysts were prepared by impregnation method. The effect of transition metal element types on the N₂O removal performance of the catalysts was investigated, and the N₂O removal performance of Cu_x/TiO₂ catalysts was optimized. The results show that compared with Fe₅/TiO₂, Mn₅/TiO₂, Co₅/TiO₂ and Ni₅/TiO₂ catalysts, Cu₅/TiO₂ catalyst shows excellent catalytic activity, the N₂O conversion efficiency can reach 100% at 350 ℃. In addition, Cu₅/TiO₂ catalyst also has good water resistance. The experimental results show that 5% is the best Cu loading amount. X-ray diffraction, N₂ adsorption-desorption, H₂ temperature programmed reduction, O₂ temperature programmed desorption, and in-situ diffuse reflectance infrared Fourier transform spectroscopy were used to characterize the physicochemical properties and surface reaction intermediates of Cu₅/TiO₂ catalyst, and the relevant catalytic reaction mechanisms were discussed in depth from multiple perspectives. The characterization results show that compared with other Cu_x/TiO₂ catalysts, Cu₅/TiO₂ catalyst has higher dispersion of active species, specific surface area, oxygen vacancy content and stronger redox performance, which is conducive to its better catalytic activity. The main active species on the surface of Cu₅/TiO₂ catalyst are Cu²⁺ and Cu⁺ species, and the adsorption and deionization of N₂O is a key step in the catalytic reaction.

When a tunnel crosses a water-rich fault fracture zone, it is very easy to produce a water surge accident under a series of construction disturbances. In order to study the effects of fault zone width, dip angle and water pressure on tunnel water inflow, Yingshan tunnel was used as the engineering background, field tests were carried out, and an orthogonal test scheme was designed to carry out numerical simulation of coupled flow-solidity in the fault zone under multifactorial conditions, so as to analyze the sensitivity of the fault zone width, dip angle and water pressure on the water inflow of the tunnel. The results show that the tunnel water inflow increases with the increase of fault zone thickness, dip angle and water pressure, and the factors affecting the tunnel water inflow are water pressure, dip angle and width of the fault zone. The numerical simulation results are in good agreement with the field monitoring results. The results can provide theoretical references for the prediction of water influx in water-rich tunnels and the prevention and control technology.

In order to solve the problems of imperfect fire risk management system and subjective and one-sided risk assessment methods of civil aviation transport aircraft, a comprehensive risk assessment method based on random forest ensemble algorithm was proposed for the analysis and evaluation of risk factor indicators. Firstly, according to the man machine environment management(MMEM) theory, the risk index system was established based on the investigation of the causes of aircraft fire accidents in the past 20 years, and then the scores of scholars and experts in related fields on the correlation between the indicators were collected, and the subjective risk index weight results were obtained by using the analytic network process(ANP) method. The causes of major aircraft fire accidents in the database in the past 20 years were counted and their prior probabilities were calculated by classification, and the Bayesian network(BN) dynamic analysis method was used for reverse reasoning to obtain the probability distribution of each risk factor. The random forest regression model was established to obtain the predicted value and importance of the characteristic index, and put forward scientific and effective suggestions for the fire risk control of the operating unit. The results show that the five indicators of missing dangerous goods in security inspection, failure to eliminate hidden dangers in time, component failure, bird strike, and high surface temperature are the most critical risk factors in aircraft fire accidents.

In recent years, artificial intelligence has demonstrated strong pattern recognition and classification capabilities across various fields, providing new insights for lithology identification. Starting from three methods: support vector machines, neural networks, and ensemble learning, the basic principles, advantages and disadvantages of these machine learning algorithms were reviewed, as well as their research progress and application in the field of uranium ore bed lithology identification. The results show that machine learning can effectively identify the correlation between logging data and different lithologies through model training, transforming the process of lithology identification into a machine learning process. This can greatly improve the automation level and accuracy of lithology identification, holding significant practical importance and a broad development prospect.

The systematic construction of a biomechanical analysis of the full swing technique is considered essential to addressing the core issues and resolving technical problems from their root causes. Targeted special physical training is a powerful guarantee for the full utilization of technical skills. The research findings on the golf full swing technique were reviewed, its biomechanical characteristics were discussed and summarized. By further analyzing the strengths and weaknesses of full swing techniques in players of different genders and skill levels, rational recommendations for physical training were proposed, providing valuable insights for optimizing athletes' full swing techniques and enhancing the level of scientific training. During the full swing, the limbs follow the principle of proximal-to-distal motion, and muscle contractions adhere to the stretch-shortening cycle principle. Weight transfer is rationally adjusted based on specific swing patterns, and the terminal joint release effect is strengthened, contributing to the maximization of clubhead speed. In the downswing, the peak angular velocities of turnk and hip axial rotations, along with the timing and the peak speed of wrist release, are identified as the primary factors influencing clubhead speed. These factors also represent the key technical differences between male and female players. Strength and conditioning is regarded as a crucial pathway for improving full swing performance. Golfers are advised to focus on developing specific physical qualities, including upper limb muscle strength and explosiveness, lower limb muscle strength and explosiveness, as well as core stability and rotational power.

The mechanical properties of carbon fiber reinforced polymer (CFRP) composites are significantly impacted by residual stresses, which can even induce material cracking. Consequently, the accurate measurement of interlayer non-uniform residual stresses in CFRP laminates is of paramount importance for improving their manufacturing processes. The incremental hole-drilling method was employed to measure the interlayer non-uniform residual stresses in CFRP laminates. Finite element simulation was used to calculate the standard coefficient matrix between the released residual stresses and strains released in each layer. Coefficient matrix in conjunction with the measured strains was utilized to compute the residual stresses within each layer of the CFRP. The results indicate that the CFRP laminates exhibit an overall stress distribution characterized by compressive stresses externally and tensile stresses internally along the thickness direction. Furthermore, the measurement variance of residual stresses increases with the increase in drilling depth, and the interlayer residual stress values and their non-uniformity are higher in the layers closer to the center of the plate.

Aiming at the limitations of traditional synthetic aperture radar interferometry (InSAR) technology in monitoring karst collapse, a small baseline subset (SBAS)-InSAR surface deformation monitoring method integrating permanent scatterer (PS) technology was proposed to monitor the deformation characteristics of shallowly buried karst collapse groups. The study area was deliberately selected as the Dongdiu District in Libo County, Qiannan Prefecture, Guizhou Province. A dataset composed of 83 Sentinel-1A imagery acquisitions from January 30, 2020, to December 21, 2022, was thoroughly compiled and subsequently analyzed by time-series InSAR in a rigorous manner. The results show that during the period from 2020 to 2022, the collapse-prone areas undergo a phase of accelerated development in deformation rate. The monitoring results closely mirror the actual boundaries of the delineated collapse zones. The maximum deformation rate recorded within the collapse zones is -167.5 mm/a, predominantly occurring in regions with the most concentrated collapses. Moreover, a novel set of criteria for identifying karst collapse clusters was introduced, which was based on time-series InSAR technology. These criteria were founded on the analysis of the uniformity in the trends of deformation accumulation curves and the detection of local abrupt changes among any three interconnected points within the monitoring area. Such features were proposed as early indicators of the development of clustered karst collapses. The research findings are anticipated to provide valuable perspectives for the identification and characterization of the developmental processes associated with clustered, shallowly buried karst collapses.

Basalt laterite weathering profile is very suitable for studying the geochemical behavior of elements under extreme weathering. A laterite weathering profile developed on the Middle Pleistocene Duowen Formation basalt in Lingao County, northwestern Hainan Island was reported. Detailed analysis of main-trace elements, pH, Eh and cation exchange capacity (CEC) were carried out on 84 profile samples. The migration and redistribution behavior of elements in the profile was studied by mass balance calculation. The laterite weathering profile of Lingao in Hainan Island has high Fe₂O₃(17.0%~41.6%) and Al₂O₃(15.3%~28.4%), low SiO₂(10.6%~43.6%), and very high chemical index of alteration (CIA) (average 99.3). It reflects that the weathering profile has experienced strong chemical weathering with Fe and Al enrichment, and desiliconization under extreme weathering conditions. The mass balance calculation results show that alkali metals and alkaline earth metals are mostly lost along the whole pofile with a high degree. Among the transition metals, Sc, Cu and Zn are leached to a high degree in the section, V and Ni are enriched in the top and Ⅳ layer of the saprolite, respectively, and high field strength element (HFSE) are leached with different degrees in the profile. Among the redox sensitive elements, Fe mainly precipitates and accumulates in the form of Fe (OH)₃ at the top of the saprolite. Cr exists as water-insoluble Cr₂O₃ in the profile and is enriched at the top of the saprolite. Mn and Co exist in the form of soluble Mn²⁺ and Co²⁺, and their enrichment is caused by the dissolution of oxides containing Mn²⁺ and Co²⁺ during weathering. U precipitates and accumulates in the form of UO₂ at the bottom of the saprolite, while U in other layers exists in the form of soluble UO₂CO₃ and $\mathrm{UO}_{2}^{2+}$. The enrichment behavior is related to the adsorption of iron hydroxide in the profile. The slight enrichment of uranium throughout the profile may be due to groundwater introduction. It is found that the formation of ferrite laterite in Lingao section should be caused by the obvious leaching of Al and the enrichment of Fe at the top of the saprolite, while the ferrite laterite in Wenchang section is the product of both Fe and Al enrichment, which is helpful to understand the difference between the laterite weathering products of basalt in northeast and northwest Hainan Island, and has certain indicative significance for the development and utilization of mineral resources in the future.