The switching of power devices in servo drive can lead to bus voltage ripple, which may result in performance degradation, electromagnetic interference, and harmonic issues in permanent magnet synchronous motor AC servo systems. To address these issues, the influence of the switching process of power device on the voltage ripple of bus was analyzed and studied for the DC power supply servo drive system. Firstly, based on the working principle of PMSM (permanent magnet synchronous motor)and SVPWM (space vector pulse width modulation) algorithm, the ripple current of the busbar capacitor was analyzed. Then, according to the law of charge conservation, the relationship between the busbar capacitance, busbar voltage and current amplitude under the seven-stage and five-stage SVPWM modulation was analyzed theoretically, and its simplified expression was given. Finally, the theoretical results were verified by simulation experiments.

The anti-corrosion maintenance workload of railway fasteners and bolts in China is large, and the cost of manual lubrication operation is high, the efficiency is low, and the labor intensity is high, and there are problems such as operation safety risks and ballast pollution. In order to solve this series of problems, an automatic lubrication device based on PLC(programmable logic controller)control that can automatically lubricate fasteners and bolts on railway tracks was developed to realize the efficiency, intelligence and automation of the construction process. Optimize the design of the equipment’s traveling mechanism, lubrication system, fastener bolt identification and sensing device, control system, etc. The adjustable spraying structure was innovatively designed to realize the oil coating operation of different types of tracks, and the sensor device that can adapt to the change of the height and position of the rail fastener bolts was innovatively designed, so as to realize the accurate identification of the track fastener bolts with different height distribution. According to the characteristics of anti-rust grease, the quantitative atomization technology of the device was analyzed and optimized. Delta’s DVP ES2-24MR PLC is connected to an external actuator, which processes data through the PLC to control the corresponding sensors in real time, and uses compensation algorithms to achieve accurate control of the equipment oil coating operation. The experiment shows that the automatic lubrication device shortens a large number of construction periods, solves the pollution phenomena such as inaccurate lubrication, oil dripping and wire pulling of the existing mechanical lubricating machine, and the device can effectively guarantee the quality and safety of the lubrication operation, effectively improve the construction efficiency and reduce the construction cost.

Bonding with existing concrete is one of the important application situations of self-compacting concrete. With the aim of investigating the bonding characteristics between DSSC (desert sand self-compacting concrete) and other existing concrete, the bond-casting test, bonding interface splitting tensile strength and sand-filling method was used to determinate the failure mode and analyze the influence of concrete type and interface treatment method on the bonding characteristics between old and new concrete. Scanning electron microscope was used to photograph the micro-morphological characteristics of the bonding interface and determinate the distribution of gap width. The results show that the bonding performance is stronger when the linear grooving is consistent with the loading direction. Compared with linear groove cutting, the drilling interface is more efficient in interface efficiency and bonding strength. Low water-to-cement ratio reduces the bond interface gap. The effect of desert sand on the reduction of the bond interface gap is more significant with low water-to-cement ratio.

The problem of scheduling and collaborative decision-making in airport metroplex or terminal areas can be significantly approached by obtaining accurate ETA (estimated time of arrival). Traditional methods are short of the ability to fine-tune the arrival metering nodes. The accurate quantitative estimation of large-volume and complex flight traffic situations is hard to achieved especially under the influence of highly dynamic environments in a medium to long term. An ETA correction method based on error feedback was proposed. Based on the aircraft performance parameters, an aircraft kinematics model was firstly constructed combined with route planning and meteorological data, which was used to give a preliminary ETA prediction through the calculation of 4D trajectory then. After that an error sequence would be constructed by comparing the difference between ATA (actual time of arrival) and the predicted results, with it the next error could be predicted using the error feedback model and the results obtained previously would be corrected. Finally, the arrival flights to a large hub airport were taken as examples to conduct a simulation, in which the rate of error within ±5 minutes that predicted 30 minutes in advance was chosen as the evaluation criteria. The simulation results show that the accuracy of ETA prediction can be improved by more than 25% in bad weather after corrected by the proposed method when compared with traditional means.

The characteristics of the reinforced soil interface are the basis of the design of the reinforced structure. The method of stitching transverse rib geotextile reinforcement is a new reinforcement technology for the improvement of traditional geotextiles. It improves the interaction of the reinforced soil interface through three-dimensional reinforcement and gives full play to the advantages of high strength of geotextiles. In order to study the influence of the number and height of transverse ribs on the characteristics of the reinforced soil interface, the discrete element numerical simulation of the direct shear test was carried out according to the indoor test results, and the mechanical response of the reinforced soil interface under different number and height of transverse ribs was analyzed from the macroscopic and mesoscopic parameters. The results show that the shear strength of the reinforced soil interface can be significantly improved by stitching the transverse rib geotextile. The shear stress-displacement curve is mainly divided into two parts: linear growth stage and stable stage. With the increase of the number and height of the transverse ribs, the overall shear strength of the geotextile increases. When the ratio of the height of the transverse ribs to the thickness of the soil layer is 0.5, the shear strength of the interface is significantly improved and the strain value on each transverse rib is more uniform. Therefore, it is recommended that the height of the transverse ribs is 0.5 times the reinforcement spacing in practical application. With the increase of the number of transverse ribs, the quasi-cohesive force increases obviously and the quasi-friction angle changes little. With the increase of the height of transverse ribs, the quasi-friction angle increases obviously and the quasi-cohesive force changes little. In the process of direct shear test, the strain of the paving part of the geotextile and the strain on the transverse rib increase with the increase of the number and height of the transverse ribs. The maximum strain is at the joint of the two. The strain of the first transverse rib is the largest and the fastest increase, which makes the joint of the transverse rib become the key of the whole system. Therefore, the height, setting position and stitching strength of the first transverse rib should be paid attention to in practical application. This study can provide a reference for the engineering application and further research of geotextiles as reinforcement materials.

In order to improve the path planning ability and efficiency of AUV (autonomous underwater vehicle), an AUV path planning algorithm based on the community information transmission mechanism was proposed. Firstly, based on the community information transmission mechanism, the global short and long connection operators were designed to achieve the optimal search of the neighborhood of the planned path points and the probabilistic search outside the neighborhood. Then, the local short and long connection operators were designed, which implements the search for four boundary derived points of the path center point and the connections of feasible paths outside the derived points. Finally, the AUV path planning algorithm flow was completed. Six simulation and two seabed map simulation tests show that, compared with other algorithms, the algorithm has the advantages of strong planning ability, high planning efficiency, and smooth planning path.

In order to solve the problem of real-time monitoring and accurate prediction of structural deformation of platform doors on high-speed railway lines, an artificial intelligence-based neural network method was used. Structural deformation data of platform doors, involving 210 different conditions of train length, blocking ratio, installation distance, and speed, were selected as training samples for the network model. Two neural network models, CNN(convolutional neural network) and K-Fold(K-Fold cross-validation) optimized GRNN(general regression neural network), were used to establish predictive models for platform door structural deformation under different working conditions of high-speed railways. These models were compared and verified with the remaining sample data. The research shows that both models effectively predict the operation and maintenance data of railway platform door structures. The K-Fold optimized GRNN model is superior to the CNN model in prediction accuracy. The Mean Square Error of the K-Fold optimized GRNN model is maintained within 0.22, and theRoot Mean Square Error is within 0.27, which is at the leading level in the field. The K-Fold optimized GRNN model better predicts the structural deformation of platform doors when trains pass, providing data references for the design and maintenance of high-speed railway platform doors.

Utilizing phase change materials and carrier materials to prepare phase change particles, replacing concrete aggregates for the production of phase change concrete, represents a novel technique for enhancing the durability of concrete in cold regions. In order to investigate the correlation between the compressive strength of PCC and its pore characteristics, a novel type of phase change particles with cement-encapsulated, named EPC₁₄, was prepared by using n-tetradecane (C₁₄) and EP (expanded perlite) as raw materials. Subsequently, phase change concrete (PCC-EPC₁₄) was prepared by replacing fine aggregates at an equal volume. The PCC-EPC₁₄s underwent 50, 100, 150, and 200 freeze-thaw cycles. Then, uniaxial compression tests and nuclear magnetic resonance tests were uesd to test the compressive strength and pore characteristics of the PCC-EPC₁₄s. Finally, the fractal dimension of the PCC-EPC₁₄ was calculated using fractal theory, and the relationship between compressive strength and fractal dimension was analyzed. The results show that the optimal volume replacement ratio of phase change particles to fine aggregates is 20%. At this ratio, the PCC-EPC₁₄(20%) exhibites the maximum NMR (nuclear magnetic resonance) fractal dimension, minimum porosity, and maximum compressive strength after 200 freeze-thaw cycles. Additionally, a proportional relationship is observed between compressive strength and NMR fractal dimension, while an inverse relationship is found with relaxation time signal area.

The rheological parameters of drilling fluid have an important impact on accurately predicting the hydraulic parameters of deepwater and ultra-deepwater drilling wells. The rheological experiments were carried out on commonly used HEM(high efficient mud) drilling fluids and synthetic-based drilling fluids in the deep waters of the South China Sea under conditions of 4 to 210 ℃ and 30 to 180 MPa. The variation laws of rheological parameters such as apparent viscosity, plastic viscosity, and dynamic shear stress with temperature and pressure were revealed in a wide range of temperature and pressure. Based on the experimental data, nine existing rheological models were compared and evaluated. It was found that the Ross model is suitable for synthetic-based drilling fluid, and the Herschel-Bulkley model is suitable for HEM drilling fluid. On this basis, a general predictive model for rheological parameters of HEM and synthetic-based drilling fluids was created, which is applicable to alternating high and low temperatures, high and low pressures. The maximum error of this model is 11.95%, with an average error of 0.62%, which is better than existing models.The bottom hole pressure error is 0.28% when using HEM drilling fluid and 0.181% when using synthetic drilling fluid, which can meet the requirement of deep water drilling in the South China Sea.

In response to the common problem of secondary lining cracking in double-arch tunnel without middle drift, how to improve its mechanical characteristics to ensure the safety of tunnel construction and operation is the focus of this study. Based on the arch section of Yijin Expressway Huangjiaoping Tunnel Project, numerical simulation method was adopted, the influence of support parameters such as the thickness of the initial support, the spacing of the steel frame, and the thickness of the secondary lining of the advanced tunnel on the displacement of surrounding rock, the mechanics characteristics of the initial support and the secondary lining of the advanced tunnel were deeply studied, and reasonable and optimized support parameters were proposed. The results show that as the thickness of the initial support increases or the spacing of the steel frame decreases, the displacement of the surrounding rock of the advanced tunnel and the principal stress of the secondary lining continue to decrease, and the principal stress of the initial support continues to increase. Among them, the maximum tensile stress of the secondary lining decreases significantly. When the thickness of the initial support is 0.28 m or the spacing of the steel frame is 0.5 m, the maximum tensile stress decreases by about 15% compared with the most unfavorable condition. As the thickness of the secondary lining increases, the displacement of surrounding rock, the principal stress of the initial support and the secondary lining of the advanced tunnel decrease significantly. Compared with the thickness of the secondary lining of 0.7 m and the thickness of the secondary lining of 0.5 m, the maximum tensile stress of the secondary lining is reduced by 23.8%. Therefore, moderately increasing the thickness of the initial support or decreasing the spacing of the steel frame or increasing the thickness of the secondary lining can effectively improve the stress of the secondary lining. It is suggested that the thickness of the initial support of the advanced tunnel should be 0.28 m, the spacing of the steel frame should be 0.5 m, the corresponding steel frame type is I22b, and the thickness of the secondary lining should be 0.7 m under the shallow buried state of V-class surrounding rock.