Abstract:In order to study the performance differences between the strength composite pipe pile (SCP pile) and traditional pipe piles in foundation pit support, using indoor model tests and finite element simulation methods, the stress and deformation characteristics of SCP pile support structure during excavation are studied, and the influence of cement soil parameters on its support effect is revealed. The research results indicate that under experimental conditions, the support effect of cement soil wrapped pipe piles is significantly improved; Compared to traditional pipe piles, the horizontal displacement at the top of SCP piles decreases by 24.7% to 58.3%, the settlement of the outer soil decreases by 11.4% to 44.9% , and the bending moment of the pile body decreases by 10.9% to 24.6%.Cement soil can effectively improve the support capacity of pipe piles as supporting structures, and increasing the elastic modulus of cement soil and increasing its thickness can significantly enhance the sup-porting effect of reinforced composite piles. However, in contrast, increasing the thickness has a more prominent effect on the supporting effect.

Abstract:Aiming at the problem that the stress of each pile is different when the pile-soil coupling anti-slide pile is used to support the slope, taking a landslide control project in Jiangxi Province as the background, the Midas GTS NX finite element software is used to establish the pile-soil coupling anti-slide pile treatment model. The internal force and displacement variation of the structure under different pile length combinations are discussed, and the stress and deformation characteristics of the pile under different reinforcement methods are analyzed. The results show that the decrease of the anchorage ratio of the middle and rear piles will lead to the increase of the displacement and internal force of the front pile, and the decrease of the anchorage ratio of the pile will significantly reduce the bending moment and shear force. When the anchoring ratio of the rear pile is less than 1/3, the landslide thrust will not be transmitted to the stable stratum through the pile. By comparing the three reinforcement schemes, it is found that under the condition of meeting the safety requirements, the unified reinforcement of the pile is larger, the deformation of the pile is small, and the treatment effect and structural strength are better. When supporting a slope with a single load, the reinforcement method considering the force characteristics of the pile body is preferred. When supporting slopes with complex loads, the design method of separate reinforcement in each row is preferred.

Abstract:In order to accurately predict the influence of foundation pit excavation on adjacent pile foundation, this paper uses two-stage method to analyze the horizontal deformation and settlement of pile foundation based on Pasternak model. In the first stage, the horizontal displacement and vertical settlement of foundation soil at the axis of pile foundation caused by foundation pit excavation are calculated by the formula. In the second stage, the Pasternak model considering soil shear strain is used to simulate the deformation of pile foundation, and the horizontal deformation and settlement of adjacent pile foundation caused by foundation pit excavation are solved by superposition method, and a simplified calculation method is proposed. Based on the monitoring data of foundation pit construction of Hengqin-Mangzhou tunnel project, the accuracy of this method is verified by comparing the calculation results of this paper. The results show that the influence of foundation pit excavation on the lateral displacement and bending moment of adjacent pile foundation is mainly within the range of 0.4 times the excavation depth of foundation pit. The influence on the settlement of the pile is mainly in the range of 0.6 times the excavation depth. The method of reinforcing the adjacent soil by supporting structure can effectively reduce the surface settlement value near the supporting structure.

Abstract:In order to understand the stability and deformation mechanism of tunnel through fault zone,and to provide theoretical basis for scientific analysis of tunnel excavation through fault fracture zone, a large-scale direct shear test was carried out on the contact surface between the viscous mud-rock mass and the bedrock with joint surface,and the influence of normal pressure, stone content and rock dip angle on the interface mechanical properties of the viscous mud-bedrock contact surface was studied. The test results show that: The interfacial stress-strain relationship shows softening characteristics at low normal stress,and gradually transitions from weak softening to weak hardening with the increase of normal stress; The normal stress is positively correlated with the initial tangential modulus of the interface. The shear strength and stiffness of the interface increase with the increase of stone content; Compared with the block angle of 0°, the interface strength corresponding to the rock angle of 90° is improved; The internal friction angle of the interface has a linear positive correlation with the stone content, and the cohesion path has a negative correlation. When analyzing the stability and deformation mechanism of tunnel crossing fault zone, it is necessary to fully consider the influence of interface normal stress, stone content and rock inclination angle on interface strength.

Abstract:Due to the long-term repeated loading, surface defects occur in high-speed railway steel rails. In order to improve the accuracy and speed of surface defect detection for multiple classes and scales of steel rails in complex scenarios, a steel rail surface defect segmentation network based on multimodal fusion (DAFNet) is designed. Firstly, a steel rail surface defect dataset containing visible light and infrared channels is constructed, and an improved dual-branch network architecture is adopted to increase segmentation speed. Simultaneously, a bimodal adaptive fusion module (BAFM) is designed to achieve adaptive feature fusion, improving the segmentation accuracy of steel rail surface defects in complex scenarios. Additionally, a spatial detail extraction module (SDEM) and a key information enhancement module (KIEM) are designed to further enhance the perception of defect edges and address the low contrast between defects and backgrounds in complex scenarios. Experiments show that the accuracy and mIoU of the designed network segmentation reach 68.13% and 59.96% respectively, which are significantly better than other mainstream networks. Moreover, FLOPs, parameter quantity, and model size are 17.41 GFLOPs, 1.38 M, and 5.67 MB respectively, which are better than most mainstream networks. The designed network significantly improves the segmentation accuracy of steel rail surface defects and has a high segmentation speed, which is of great significance for ensuring the safe operation of high-speed railways.

Abstract:This paper studies the impact of Shanghai—Kunming high-speed railway on the tourism economy of cities along the line from 2007 to 2019 and its mechanism. Firstly, a multi-period double-difference method was used to assess the promotion effect of the opening of high-speed rail on the tourism economic development of cities along the route. Secondly, through the dynamic effect model, the long-term economic effect of high-speed rail construction is discussed, and the results show that the effect persists. Finally, the intermediary effect model and Bootstrap test were used to analyze the mechanism of high-speed rail, and it was found that tourism scientific and technological innovation had the highest proportion of intermediary effect in promoting tourism economy by high-speed rail, which was superior to tourism industry structure and traffic development. The overall results show that the opening of high-speed rail has a positive and lasting impact on the tourism economy of the cities along the line. With the passage of the construction cycle, tourism scientific and technological innovation has gradually become a key way to achieving high-quality tourism economic development.

Abstract:Addressing the issue of slot scheduling, this study employs a hierarchical allocating strategy and introduces the value of slot to construct a dual-objective optimizationmodel that balances fairness and efficiency.The validity of model is verified using historical data from a Level 3 airport in China. A comprehensive analysis of slot scheduling acrossdifferent levels, airlines, and date typesreveals the complexity of the process. Furthermore, the concept of overload allocation is introduced, and the offset evaluation criteria are redefined through the tolerance parameter, exploring the impact of optimal tolerance levels on slot scheduling. The results indicate that,compared to a single-objective model, the dual-objective model enhances fairness by only 0.30% and maximum slot displacement by 3.28%, while improving fairness by 26.00%. Moreover, the adjustment among airlines are more balanced, and historical requests are more likely to achieve fair allocation. Displacement on weekdays are observed to be lower than those on non-weekdays, exhibiting superior fairness(0.02%). Saturdays exhibit the highest displacement and the poorest fairness(1.11%). The optimal tolerance level is identified as 2 slots,which reduces overload allocation by 47.78%. This research provides novel insights into the slot scheduling and hold considerable reference value for airlines in the process of schedule.

Abstract:The development of intelligent connected vehicles has placed higher demands on automotive braking systems, and traditional braking systems are gradually being replaced by brake-by-wire systems. With their outstanding response speed and control precision, brake-by-wire systems have become the core execution foundation for achieving high-level autonomous driving and even unmanned driving. This paper systematically reviews and summarizes the development history, architecture, classification, key technologies, and applications of the brake-by-wire systems for intelligent connected vehicles; analyzes the structural schemes and advantages and disadvantages of different types of brake-by-wire systems, and combs and analyzes key technologies such as master cylinder hydraulic pressure control, wheel cylinder hydraulic pressure control, wheel cylinder hydraulic pressure estimation, solenoid valve control, and clamping force control. It also outlines two active safety control technologies based on brake-by-wire systems: ABS and AEB, as well as brake energy recovery technology. It analyzes and summarizes the current challenges faced by intelligent connected vehicle brake-by-wire technology and its future development trends. The brake-by-wire technology for intelligent connected vehicles is evolving from EHB to EMB, but it still faces many challenges such as insufficient motor power and compatibility issues of electronic components. There is an urgent need to improve the system’s integration and redundancy to meet the reliability and safety requirements of high-level autonomous driving.

Abstract:In order to obtain the trend of the properties of magnetorheological elastomer (MRE) with the applied magnetic flux density and excitation frequency, MREs with different ratios were prepared to investigate the relative MR effects and shear modulus properties. Three kinds of MRE samples were prepared based on the silicone rubber and silicone oil mass fraction ratio of 3∶2, and high viscosity silicone oil was selected to analyze the changes of energy storage modulus and shear modulus with magnetic flux density under oscillatory shear mode with different ratios, different shear strains, and shear frequencies, as well as the trends of MRE normal force under different preloads. The experimental results show that the energy storage modulus, shear modulus and normal force of MRE increase with the increase of magnetic flux density. The results indicate that the maximum change of the MRE normal force increases by 31.6% when the preload is increased from 5 N to 25 N. When the magnetic flux density increases from 0 to 0.8 T, the maximum energy storage modulus of sample 3 is 2.25 MPa, with a maximum relative MRE effect of 1 465.60%, and the maximum shear modulus of sample 3 is 2.25 MPa,which is an increase of 1 400.00% compared to the zero-field case. This experiment shows that MRE is suitable for high-frequency and low-shear strain application, and iron powder with 80% mass fraction can effectively improve the mechanical properties of MRE.

Abstract:In order to solve the problem of low hardness and poor wear resistance of 40CrNiMoA steel, a heat treatment process was designed, and three different quenching mediums were used, including water, salt solution and oil, to carry out high-frequency quenching and low-temperature tempering heat treatment of 40CrNiMoA steel. The HV-2000 Vickers hardness tester was used to test the surface hardness of the sample after heat treatment, and the SFT-2M ball-disc friction and wear testing machine was used to test its wear resistance. The results show that when the quenching medium was salt solution, the tempered martensite was smaller, and the surface hardness of the specimen after heat treatment was the highest, reaching 431.2 HV_0.2, and the wear was the smallest. After quenching in salt solution, fine tempered martensite can be obtained, resulting in increased hardness of 40CrNiMoA steel, less wear of the specimen and enhanced wear resistance.

Abstract:Aluminum matrix composites are a type of excellent structural material, however, their poor weldability necessitates significant improvements in joint properties. Ti was introduced into a CoCrNi-reinforced AlSi12 filler during laser powder-filled welding of SiC_p/6061Al composites to investigate its influence on the welded joints. The results show that the Ti is evenly distributed in the weld, and TiNi3 phase is formed around the CoCrNi phase, Additionally, the CoCrNi phase changes from the coarse dendritic shape to the fine triangular shape, contributing to solid solution strengthening, dispersion strengthening, and fine grain strengthening. The interface of the fusion zone of the welded joint was clear, with no reaction products generated at the interface,forming a good physical metallurgical interface. After adding Ti to the welding filler, the weld hardness increased by 30%, and the tensile strength and extension of the welded joint increased at the same time. When performing SiC_p/6061Al laser filler welding, adding Ti to CoCrNi reinforced AlSi12 mixed filler can effectively improve the quality of welded joints and improve mechanical properties.

Abstract:The Clar covering polynomial of molecular graphs is a method to characterize the electronic structure of conjugated systems. By studying the Clar covering polynomials of plane bipartite graphs, the resonance theory of related molecular graphs and their properties can be thoroughly investigated. Based on the theorem related to Clar covering polynomials of plane bipartite graphs, the method of generating functions is utilized to compute Clar covering polynomials of plane bipartite graphs. Recurrence relationship for Clar covering polynomials of a special class of graphs are derived. In turn, explicit expressions the Clar covering polynomials of two classes of catacondensed plane bipartite graphs are computed using the generating function method. On the Clar covering polynomials of plane bipartite graphs, it is possible to understand the electronic structure of chemical molecules, predict their chemical properties and reaction behavior, and design new molecular structures.