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20 November 2023, Volume 42 Issue 11 Previous Issue   
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Transportation+Big Data & Artificial Intelligence
Transportation Infrastructure Engineering
Transportation Equipment


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Transportation+Big Data & Artificial Intelligence

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Cable Replacement Scheme of Cable-Stayed Bridge Based on Joint Static and Dynamic Modification Model QI Dongchun1,2, WANG Yufei3, LI Qi1, ZHAO Zhiguo3 2023, 42(11): 1-8.  DOI: 10.3969/j.issn.1674-0696.2023.11.01 Abstract ( )   PDF (2461KB) ( )   A finite element model of double main beams was established by the grillage method, and a muti-objective optimization function based on joint static and dynamic measurement results was constructed and the function was solved by non-dominated sorting genetic algorithm. The model modification of a concrete cable-stayed bridge that had been in operation for many years was carried out. On this basis, the cable replacement sensitivity was analyzed, and the optimal cable replacement scheme was determined through the comparison of various cable replacement schemes. The research results show that the calculated values of static displacement and natural frequency after model modification are in good agreement with the measured values, which can better reflect the actual working state of the structure. For parallel steel wire cable-stayed bridges, the overrun tensile stress at the lower edge of concrete main beam is the primary consideration. And there is a relatively great risk in cable replacement, and the necessary reinforcement measures should be taken before cable replacement. References | Related Articles | Metrics

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Temperature Field during the Construction of Gussasphalt on Steel Bridge Deck WANG Tao1, HU Deyong1, WANG Hao2, CHANG Cheng1, WANG Min1 2023, 42(11): 9-14.  DOI: 10.3969/j.issn.1674-0696.2023.11.02 Abstract ( )   PDF (2555KB) ( )   The paving technics and environment have a great influence on the construction temperature field of gussasphalt on steel bridge deck. In order to optimize the paving technics and reduce the damage to the steel bridge deck structure caused by temperature deformation, based on the project of Wuhan Zhuankou Yangtze River Bridge, a three-dimensional finite element model was established with Abaqus software. And the temperature field of gussasphalt under different wind speeds and paving speeds was simulated based on the life-and-death unit control technology. And comparative analysis was conducted based on the monitoring data of the actual bridge. The research results show that: after the gussasphalt is paved, the surface temperature of the pavement layer shows a “three stage” trend of change, namely a sharp decline stage, a rapid decline stage and a slow decline stage. After 30 minutes of gussasphalt paving, the measured maximum temperature of the top plate of steel bridge deck is 103°C (138.6°C lower than the paving temperature), and the duration of this temperature is relatively short, approximately 8 minutes. Due to the heat absorption and heat resistance effects of the MMA waterproof-bonding layer, the time when the highest temperature occurs is about 13 minutes later than the time simulated by finite element analysis. In order to avoid the concentration of temperature stress on the steel bridge deck during paving, the paving speed of gussasphalt should be controlled between 2.5 m/min and 3.0 m/min. When the wind speed is greater than 3 m/s, the temperature loss of gussasphalt is more obvious. In order to reduce the influence of temperature loss on the workability of construction, the unloading point of gussasphalt should be as close to the paver as possible, and the distance should be controlled between 0.5 m and 1.5 m. References | Related Articles | Metrics

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Influence of Proportioning on the Performance of Inert Slurry in Shield Tunnel Construction CHENG Xuesong1,2, ZHAO Linsong2, ZHENG Gang1,2, SUO Xiaoming3, WU Xinliu3 2023, 42(11): 15-20.  DOI: 10.3969/j.issn.1674-0696.2023.11.03 Abstract ( )   PDF (1213KB) ( )   Five factors (the water to binder ratio X1, ratio of cementitious material to sand X2, ratio of fly ash to lime X3, ratio of bentonite to water X4, and ratio of water reducing agent to cementitious material X5), and three levels were selected to conduct orthogonal experiments of inert slurry. The influence laws of various factors on the consistency (cone penetration P), setting time ts, and consolidation shrinkage rate ε, 28-day compressive strength f28 and bleeding rate η of inert slurry were analyzed. Partial least squares regression (PLS) was used to obtain regression formulas for various performance indicators of inert slurry based on five factors. The PLS regression values of various performance indicators were compared with the test values to verify the rationality of the regression formula. In the experiment, water reducing agents (X5=0, 0.002, 0.004, 0.006, 0.008) and CMC thickeners (dosage 0, 0.05%, 0.10%, 0.15%, 0.20%) were added to the reference inert slurry, and the cone penetration P, bleeding rate η, viscosity μ, and flowability F of the prepared inert slurry were measured. The modification effects of water reducing agents and CMC thickeners were analyzed, and the engineering geological applicability of inert slurry was discussed. The results show that the water to binder ratio has a significant impact on all indicators, the ratio of cementitious material to sand has a significant impact on the setting time and consolidation shrinkage rate, the ratio of bentonite to water and ratio of water reducing agent to cementitious material have a significant impact on the cone penetration and bleeding rate, and the overall impact of ratio of fly ash to lime is relatively small. The PLS regression formula can be used to optimize the proportion of inert slurry. When proportioning the slurry, an appropriate amount of water reducing agent can be added to reduce the water to binder ratio while ensuring the required consistency requirements. An appropriate amount of CMC thickener can also be added to improve the viscosity of the slurry. References | Related Articles | Metrics

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Diffusion Fusion of Old and New Asphalt in Recycled Asphalt Based on Ficks Second Law TIAN Xiaoge1, YAO Shilin1, LU Xuerong1, DOU Wenli2, CHANG Huiqin3 2023, 42(11): 21-27.  DOI: 10.3969/j.issn.1674-0696.2023.11.04 Abstract ( )   PDF (1641KB) ( )   In order to study the degree of diffusion fusion of old and new asphalt at different diffusion times and temperatures, the aging asphalt with a diameter of 25mm and thickness of 2mm and new asphalt double-layer asphalt samples were prepared to carry out dynamic shear rheological tests. The complex shear modulus G* was used as the characterization parameter of the performance of double-layer asphalt samples, and the theoretical G* values of double-layer samples with different fusion degrees were calculated based on Fick’s second law theory, so that the fusion degree of new and old asphalt in double-layer asphalt samples was calculated by iterative method and according to the measured value of G*. Two-factor ANOVA was used to evaluate the significance of time and temperature on the degree of diffusion fusion. The results show that the complex shear modulus can describe the diffusion fusion of old and new asphalt in recycled asphalt, and it has a good linear relationship with the new asphalt content, which can be used as a characterization parameter for performance change. 70# base asphalt and 90# base asphalt have diffusion rates of the same magnitude, both of which are around 10-7, and the diffusion rate of both kinds of recycled asphalt increases exponentially with temperature change. From the two-factor ANOVA analysis, it is found that the diffusion time and temperature have a significant impact on the degree of diffusion fusion of new and old asphalt. References | Related Articles | Metrics

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Influence of Tire Road Coupling Contact Behavior on the Decay of Skid Resistance of Asphalt Pavement YU Miao1, ZHANG Zhengji1, LUO Yansheng2, ZHAO Xiaoning1, LIU Shikang1 2023, 42(11): 28-35.  DOI: 10.3969/j.issn.1674-0696.2023.11.05 Abstract ( )   PDF (3642KB) ( )   In order to clarify the tire road coupling contact behavior and decay process of skid resistance of asphalt pavement under the driving state of vehicles, based on the influencing factors of road durability, orthogonal tests were carried out on the surface design of AC-13, SM-13 and OGFC-13 asphalt pavement with different coarse aggregates, and the variation rules of tire road coupling contact behavior and skid resistance of asphalt pavement were compared and analyzed. The relationship between the tire road coupling contact behavior of different asphalt mixtures and the decay of skid resistance of asphalt mixtures was discussed. The influence of tire road coupling contact behavior on skid resistance of asphalt mixture was summarized. The analysis results show that under the driving state of vehicles, the road durability factors, such as traffic load grade, heavy traffic occurrence time and heavy traffic duration, have little influence on the tire road contact area of asphalt pavement, but have significant influence on the decay of skid resistance of various asphalt pavement. The tire road coupling friction behavior under the driving state of a car is different from the tire road coupling friction behavior under the braking state of a car, and there is no significant correlation with the decay of the skid resistance of asphalt pavement. Therefore, it is only necessary to consider the road surface friction coefficient as the main indicator for evaluating the anti-slip performance, when the decay rules of skid resistance of asphalt pavement are studied under the driving state of vehicles. References | Related Articles | Metrics

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Experimental Study on Mechanical Characteristics of Micro-steel Pipe Pile at Soil-Rock Interface in Deep Foundation Pit BAI Xiaoyu1, SU Hang1, ZHANG Pengfei2, HAN Jianyong3, ZHANG Li1 2023, 42(11): 36-42.  DOI: 10.3969/j.issn.1674-0696.2023.11.06 Abstract ( )   PDF (1994KB) ( )   Based on a foundation pit project of Qingdao Metro, field tests of the micro-steel pipe pile supporting structure were carried out by placing resistance-type strain gauges symmetrically on the outer wall of the micro-steel pipe pile and earth pressure boxes on the pile facing the earth. The pile bending moment and pile side earth pressure data of three parts such as soil layer, soil-rock interface and rock layer were collected respectively. The evolution characteristics of pile side pressure and pile bending moment at soil-rock interface during excavation of foundation pit were analyzed, and the variation law of pile side pressure and pile bending moment of the inner row micro-steel pipe pile changing with the excavation depth of foundation pit in the quaternary soil layer, soil-rock interface and rock layer was studied. The results show that with the increase of foundation pit excavation depth, the soil pressure values on pile side in soil layer and rock layer show a trend of first decreasing and then increasing, then decreasing and then increasing, and then continuously increasing. The soil pressure on the pile side at the soil-rock interface shows a trend of wavy increase, and the increase is large, which belongs to the weak point of the soil layer stress. The prestressed anchor (cable) support can effectively coordinate the internal force of the pile body and limit the occurrence of large deformation of the pile body, so as to avoid the growth of the bending moment of the pile. The bending moment value of the micro-steel pipe pile near the soil-rock joint surface is small and the growth is slow. The soil pressure on the pile side is greatly influenced by the spatiotemporal effect of excavation of the foundation pit. References | Related Articles | Metrics

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Experimental Study on Influence of Rock Content on Seepage Characteristics of Soil-Rock Backfill HUANG Feng1, 2, YANG Zhengxu1, 2, ZHOU Qihong3, LIU Xingcheng1, 2, ZHANG Ban1, 2 2023, 42(11): 43-49.  DOI: 10.3969/j.issn.1674-0696.2023.11.07 Abstract ( )   PDF (6213KB) ( )   The shallow surface of southwest mountainous cities is mostly soil-rock backfill strata, and the sensitivity law of soil-rock gradation of soil-rock backfill seepage characteristics is difficult to grasp. Under the condition of rainfall infiltration, shallow tunnel and deep foundation pit excavation often induce surface subsidence and slope collapse. Based on the particle gradation of the site soil-rock backfill, the sensitivity of rock content and the loss of fine particles in the permeability coefficient of backfill were studied by indoor constant head test. It is found that the permeability coefficient of soil-rock backfill increases exponentially with the increase of rock content, and begins to increase sharply when the rock content is 60%. Under poor gradation, poor cohesion and adhesion between coarse and fine particles in soil-rock backfill are the main reasons for the loss of fine particles, and the loss of fine particles presents a change process from small to large and then to stable with the extension of seepage time. In practice, the block stone content of the site soil-rock backfill can be reasonably adjusted according to the permeability requirements of the stratum. At the same time, the loss of fine grained soil of the high stone content soil-rock backfill should be focused to ensure the stability of the construction stratum. References | Related Articles | Metrics

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Expansion and Shrinkage Characteristics of Red Clay and Lime Composite Modified Phyllite ZHAO Xiushao1, 2, CHEN Zixi1, 2, RAO Jianglong1, 2, CHENG An1, 2, ZHAO Linhao1, 2 2023, 42(11): 50-56.  DOI: 10.3969/j.issn.1674-0696.2023.11.08 Abstract ( )   PDF (3906KB) ( )   In order to reduce the expansion rate of phyllite and the shrinkage rate of red clay, a physical-chemical combined method for improving phyllite was proposed. 24 different combination improvement schemes were designed with a mass mixing ratio of 0, 20%, 40%, 60%, 80%, and 100% for red clay, and a mass mixing ratio of 0, 3%, 5%, and 8% for lime. The expansion and shrinkage characteristics of the composite modified soil were analyzed through the test on the expansion and shrinkage of the fully weathered phyllite composite modified soil, and the mechanism of the dilatation and shrinkage characteristics of the red clay and lime composite modified phyllite was explained from the microscopic perspective. The test results show that the evolution law of the free expansion rate is similar to that of the no-load expansion rate. The expansion rate decreases with the increase of the red clay blending ratio. With the increase of the lime content, the expansion rate firstly decreases rapidly and then tends to be stable, and the optimal lime dosage is 3%. After adding lime, the expansion force firstly decreases and then increases with the red clay blending ratio and reaches the lowest when the red clay blending ratio is 60%. When the lime content is greater than 3%, the improvement effect is not significantly improved compared to the lime content of 3%. The linear shrinkage rate of soil samples decreases with the decrease of the red clay blending ratio and the increase of the lime content, and the decrease is relatively small when the lime content is greater than 3%. The comprehensive shrinkage test results show that the effect of reducing the shrinkage deformation of red clay with phyllite soil is better than that with lime. With each lime content, the shrinkage limits all firstly decrease and then increase with the increase of the red clay blending ratio and reach the lowest when the red clay blending ratio is about 40%. Based on the results of the expansion and shrinkage test, it is suggested that the optimal dosage is 40%~60% for red clay and 3% for lime. At this time, the free expansion rate is reduced by 24%~26%, and the no-load expansion rate is reduced by 25.9%~27.0%; the expansion force is reduced by 639~593 kPa, and the linear shrinkage rate is reduced by 0.7%~0.8%. References | Related Articles | Metrics

Transportation Infrastructure Engineering

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Influence of Nano-SiO2-CSH Composite Regulator on the Properties of Cement Concrete ZHU Yunsheng1,3, XIAO Yuzhen1,3, DIAO Xigang2, LIU Yang2, XU Lin2 2023, 42(11): 57-62.  DOI: 10.3969/j.issn.1674-0696.2023.11.09 Abstract ( )   PDF (4488KB) ( )   Improving the early strength of cement concrete can effectively shorten the demolding and tension waiting time of prestressed precast members，so as to shorten the construction period. However, using traditional early strength accelerator to improve the early strength of the cement concrete often affects its durability or workability. In order to solve this problem, the effect of compound regulating agent made of nanometer silica and calcium silicate hydrate on the early performance, volume stability and durability of concrete was studied, and the effect of compound regulating agent on the microstructure of cement concrete was observed by SEM test. The research shows that the use of compound regulating agent can improve the workability, early compressive strength and durability as well as reduce drying shrinkage rate of cement concrete. When the content of the compound regulating agent content is 1.0%, compared with the reference group, the slump and expansion of concrete increases by 11.9% and 17.6%, the emptying time of the inverted slump cylinder decreases by 26.5%，the 3d compressive strength increases by 14.4%, the 56d electric flux decreases by 32.7% and the 56d drying shrinkage rate decreases by 39.7%. Through SEM test, it is found that the compound regulating agent can make cement more compact, reduce the defects of concrete interface transition zone and furtherly refine fly ash particles. References | Related Articles | Metrics

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Design and Hydrodynamic Characteristics of Ship Emergency Mooring System in Shallow Water Area of Three Gorges Reservoir Area YUAN Peiyin, ZHANG Zhe, LI Yufeng 2023, 42(11): 63-71.  DOI: 10.3969/j.issn.1674-0696.2023.11.10 Abstract ( )   PDF (3384KB) ( )   The process of standardization, upsizing and specialization of inland river ships is constantly accelerating. When ships sail in the Three Gorges Reservoir area in wind, wave, and current environments, they often encounter problems such as severe swaying motion, speed reduction, unstable heading and difficult maneuvering. Therefore, the reliability of ship emergency mooring system design in shallow waters of the Three Gorges Reservoir area has become an urgent problem to be solved in the field of ship engineering. Taking the typical ship in the Three Gorges Reservoir area as the research object, a numerical model of the ship emergency mooring system was established by use of ANASYS-AQWA, which was based on the three-dimensional potential flow theory. The design of different cable layout schemes was optimized, and the amplitude of ship motion response and cable tension with different mooring schemes were compared and analyzed. The research shows that compared with the cable arrangement scheme of the 4-4 mooring system, the cable arrangement scheme of the 4-2-2 mooring system has more rationality and superiority in terms of balancing the tension of the mooring cable. The proposed research method can provide a scientific and reliable theoretical basis for the design of emergency mooring system scheme for ships in shallow waters of the Three Gorges Reservoir area. References | Related Articles | Metrics

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Urban Waterlogging Disaster Resilience Evaluation Based on RAGA-PP JIAO Liudan, TANG Lian, HUO Xiaosen, ZHANG Yu 2023, 42(11): 72-79.  DOI: 10.3969/j.issn.1674-0696.2023.11.11 Abstract ( )   PDF (493KB) ( )   The intensification of global temperature changes has caused frequent urban natural disaster events related to climate, seriously affecting the public safety of cities. At present, the construction of the urban waterlogging disaster resilience evaluation system is mostly from the perspective of various components of urban systems, and the subjective evaluation methods are used in the evaluation model construction. Based on this, 27 specific indicators were selected to establish resilience evaluation system for urban waterlogging disaster from 3 aspects such as resistance, recovery capability and adaptive capacity, and the urban waterlogging disaster resilience evaluation model based on the projection pursuit model was established. The real code accelerated genetic algorithm was adopted to optimize the solution. For high-dimensional data, the proposed model could directly identify its structure and features from the data itself, avoiding the limitations of subjective judgment and making the evaluation results more authentic and reliable. Finally, the proposed model was used to evaluate and analyze the resilience of urban waterlogging disasters in 18 prefecture level cities in Henan Province. The research results show that there are obvious differences in the resilience levels of urban waterlogging disasters in 18 prefecture level cities in Henan Province, among which Zhengzhou has the highest resilience evaluation value, followed by Luoyang and Jiaozuo, and Puyang has the lowest resilience evaluation value. The medical conditions, economic level and infrastructure construction have a great impact on the resilience level of urban waterlogging disasters. References | Related Articles | Metrics

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Evaluation Method and Application of Tunnel Construction Safety Risk Based on K-Means Clustering Model WU Bo1, ZHU Linping1, LI Yangbo1, LIU Cong1, XIA Chengming2 2023, 42(11): 80-87.  DOI: 10.3969/j.issn.1674-0696.2023.11.12 Abstract ( )   PDF (619KB) ( )   Tunnel construction safety risks are affected by many factors, and deep mining for risk information is an effective way to improve the accuracy of risk evaluation results. The K-Means clustering algorithm was introduced into the comprehensive calculation of the traditional LEC method, and a tunnel construction safety risk evaluation model based on K-Means clustering was established. Firstly, the risks in the whole process of tunnel construction were identified by WBS-RBS method, and the risk event set was constructed. Then the accident likelihood, personnel exposure time and severity of accident consequences were taken as the tunnel construction safety risk evaluation indexes, and the linguistic multi-attribute decision method was used to transform the risk evaluation information into a data set, and the K-Means clustering algorithm were used to process the data set and determine the event risk level based on the clustering results. Finally, the propesed model was applied to the construction risk analysis of Wenbishan No. 1 tunnel cavern project. The results show that the risk evaluation results of the proposed model match with reality, and the analysis results can provide a reference for decision making in tunnel construction risk control. References | Related Articles | Metrics

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Driving Behavior Patterns Recognition Method in High-Speed Conditions Based on Multi-source Parameters LIU Tong, XU Lei, ZHANG Xuelian, PENG Jinshuan 2023, 42(11): 88-97.  DOI: 10.3969/j.issn.1674-0696.2023.11.13 Abstract ( )   PDF (2263KB) ( )   Recognizing the current driving behavior patterns of vehicles accurately is an urgent technical problem to be solved in the field of autonomous driving. To analyze driving behavior patterns accurately and improve the accuracy and reliability of the recognition model, the multi-source parameter information such as the driving behavior data and visual characteristic data of 20 drivers under high-speed conditions was collected through the naturalistic driving test, and four typical driving behavior patterns (free driving, car following, left and right lane changes) and multi-source parameter coupling characteristics were analyzed. Four types of driving behavior patterns index sets were determined based on the principal component method, random forest decision tree and support vector machine were used to establish recognition models. The recognition results were compared after model training and learning, the model with better recognition effect was furtherly optimized, and the temporal variation characteristics of the recognition accuracy of the optimized model for four types of driving behavior patterns were analyzed. The results show that the total recognition rates of the support vector machine model, the random forest decision tree model, and the random forest optimization model based on the multi-layer perceptron neural network are 89.4%, 90.5% and 91.9%, respectively. AUC (area under the curve) values of the optimized model are all greater than 0.93 under four driving behavior patterns, which can better recognize the current driving behavior patterns. In addition, the recognition accuracy of the random forest optimization model for four types of driving patterns shows a trend of first increasing and then gradually becoming stable over time, and the recognition accuracies of the car following and free driving patterns at the same time are greater than that of left and right lane changes. The results will provide technical support and theoretical basis for the decision-making and control strategy formulation of high-level auto drive system. References | Related Articles | Metrics

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Emergency Evolution of Dangerous Goods Transportation Accidents Based on System Dynamics SHEN Xiaoyan1, LAN Qian1, HUA Jun2, SUI Xinyu1 2023, 42(11): 98-107.  DOI: 10.3969/j.issn.1674-0696.2023.11.14 Abstract ( )   PDF (6352KB) ( )   Improving the emergency response capacity of dangerous goods transportation accidents can effectively reduce the severity of accidents. Taking the emergency response system for dangerous goods road transportation accidents as the research object, the system was divided into four subsystems: accident information processing, rescue materials delivery, personnel rescue and evacuation as well as vehicle evacuation. On this basis, the causal mechanism and the loop diagrams of for the emergency response process were established by use of the principles of system dynamics. And combined with VENSIM software, a system flow diagram of emergency response process was constructed, and the relationship equations of each variable were constructed. Firstly, six factors were selected as parameters to analyze the sensitivity of the proposed model, including the number of dispatching transportation vehicles, the informatization level of warehousing, task execution speed, information feedback time, the delay time of traffic control and the distance from rescue institutions. Then, the influence of factors such as on-site material demand gap, number of people in safe areas, number of vehicles in safe areas, amount of on-site information, and system dynamic evolution behavior on the observed values was analyzed. The results show that when the number of dispatching transportation vehicles is doubled, the peak value of on-site material inventory increases by 27%, the task execution speed increases by 8.9% and the execution speed of emergency disposal increases by 8.8%. The delay time of traffic control is shortened by 360 s, the number of vehicles to be evacuated reduces by 116, the distance from rescue institutions is shortened by 60% and the rescue rate reaches its peak 1 238 seconds ahead of schedule. References | Related Articles | Metrics

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Evaluation and Optimization of Hub-Airport Transit Connectivity YE Zhijian, HU Luodan, GAO Wei 2023, 42(11): 108-117.  DOI: 10.3969/j.issn.1674-0696.2023.11.15 Abstract ( )   PDF (1472KB) ( )   In order to improve the punctuality rate and connectivity efficiency of hub airport flight operation, based on the definition of individual and total number of transit connection hits of inbound flights, a dual objective slot planning and adjustment model was established, with the goal of maximizing the number of transit connection hits and minimizing the amount of time adjustment and with the constraint conditions of the unplanned delays, runway capacity, and corridor opening capacity. Particle swarm optimization algorithm and linear programming algorithm were used to solve. The proposed model and algorithm were validated with an example of adjusting the flight schedule of Daxing Airport, and the influencing factors of the number of transit connection hits were analyzed by numerical simulation combined with correlation coefficient analysis method. The research results show that the proposed schedule adjustment method can effectively eliminate the delay caused by unreasonable planning, and the number of transit connection hits after optimization is significantly increased. The proposed schedule adjustment method provides a theoretical basis for improving the transit connectivity of hub airports and establishes a benchmark for the comparison of transit connectivity between different airports. References | Related Articles | Metrics

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Path Planning Algorithm of Autonomous Vehicle Based on Improved RRT ZHANG Yong, GAO Feng, ZHAO Fengkui 2023, 42(11): 118-125.  DOI: 10.3969/j.issn.1674-0696.2023.11.16 Abstract ( )   PDF (3011KB) ( )   Under urban road conditions, road constraints are more complex, and the path planning effect of RRT and target-based Bg-RRT algorithms is not good, which is prone to cause problems such as node redundancy and low smoothness of search path. Aiming at these problems, an improved RRT algorithm based on the force field optimization sampling area was proposed. Firstly, the proposed algorithm dynamically optimized the sampling area based on the road environment and vehicle position, then adjusted the sampling area in real time based on the maximum angle constraint of the force field and the vehicle, and finally adopted a dynamic step selection strategy based on safety distance and 270-degree collision detection. On this basis, greedy thinking and curvature constraint were combined to post-process the path. Simulation experiment was carried out on the improved algorithm. The research results show that the improved algorithm reduces the number of nodes by 72.16%, improves the path search efficiency by 83.57%, and ensures the smoothness of the path meanwhile. The effectiveness and adaptability of the proposed algorithm are verified. References | Related Articles | Metrics

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Short-Term Traffic Flow Prediction with Structure-Optimized Deep Belief Network ZHANG Yan1, LIAO Xiaoye1, YANG Shumin2, XIN Dongrong3 2023, 42(11): 126-133.  DOI: 10.3969/j.issn.1674-0696.2023.11.17 Abstract ( )   PDF (2812KB) ( )   To address the issues of excessive reliance on time series training data, insufficient consideration of spatial correlation, and overly fixed selection forms of model structural parameters in short-term traffic flow prediction, a structure-optimized short-term traffic flow prediction method for deep belief networks was proposed. The proposed model could simultaneously train three kinds of traffic data related to the traffic volume of the predicted nodes, enhance the spatial and temporal correlation of the prediction, and overcome the defect that the training data relied too much on time series. Meanwhile, the proposed model optimized the structure of the deep belief network short-term traffic flow prediction model and proposed an improved flower pollination algorithm to optimize the hidden layer structure parameters of the prediction model, avoiding the problem that the prediction results of the model were trapped in local optimal solutions and the practicality was reduced due to the overly fixed selection forms of model structural parameters. The feasibility of the proposed prediction model was evaluated by collecting the relevant traffic volume data of two intersections in Fuzhou. At the same time, the MFPA-DBN model was compared with the deep belief network model with different hidden layer structures, GA-LSTM, CNN-SVR and TGWO-BP models. The experimental results show that under the same training data conditions, the short-term traffic flow prediction method based on MFPA-DBN is feasible and effective, its prediction accuracy is better than that of other depth learning prediction models, and the real-time performance can also meet the actual requirements. References | Related Articles | Metrics

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Fluctuation Trend and Space Prediction of Bus Passenger Flows Based on FIG-SVM HE Qingling, PEI Yulong, XU Huizhi, HOU Lin 2023, 42(11): 134-140.  DOI: 10.3969/j.issn.1674-0696.2023.11.18 Abstract ( )   PDF (3129KB) ( )   According to the fluctuation characteristics of bus passenger flows time series and the correlation between influencing factors, the bus passenger flows were divided into time windows with the length of 7 d. The time window sample data information was granularized through fuzzy theory, and the time series after granulation of three sets of fuzzy information such as LOW, R and UP were obtained. The support vector machine model was used to predict, and the fluctuation trend and spatial range of bus passenger flows were obtained. The proposed model was used to empirically study the 245 d IC data of No. 1 bus in Harbin. The results show that the proposed model has higher accuracy than ARMA and GA-BP model and can effectively predict the fluctuation trend and space of bus passenger flows. References | Related Articles | Metrics

Transportation Equipment

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New Adaptive Sliding Mode Fault-Tolerant Control for Phase Failure of Marine Six Phase Propulsion Motor Based on PSO-RBF Optimization SHI Weifeng, ZHU Beizhi, XIE Jialing 2023, 42(11): 141-148.  DOI: 10.3969/j.issn.1674-0696.2023.11.19 Abstract ( )   PDF (2229KB) ( )   In order to improve the fault-tolerant ability and output ability under fault conditions of permanent magnet synchronous propulsion motor, a new adaptive sliding mode fault-tolerant control method based on PSO-RBF optimization was proposed for the phase failure of propulsion motor in marine electric propulsion system. The switching gain of sliding mode controller was adjusted in real time by use of the learning ability of neural network, and the parameters of neural network were optimized by particle swarm optimization algorithm. Then the fault-tolerant control strategy was adopted to adjust the phase and amplitude of the other healthy phase currents after phase failure, so as to realize the rapid convergence and chattering weakening of the marine propulsion motor under normal operation and fault conditions, and then improve the fault-tolerant control performance of the propulsion motor. The simulation results show that compared with the traditional sliding mode control, the speed recovery time of the proposed method is shortened by 1.7 s, the steady-state error of speed is reduced by 0.17%, and the steady-state error of torque is reduced by 7% under phase failure conditions. The more stable operation of marine propulsion motor, the better the control performance after fault. References | Related Articles | Metrics

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Suppression Mechanism of Rail Corrugation by Rail Vibration Absorber in the Short Sleeper Section CUI Xiaolu1, XU Xiaotian1, WEN Xiaoxia1, LYU Dong1, TANG Jinwei2 2023, 42(11): 149-156.  DOI: 10.3969/j.issn.1674-0696.2023.11.20 Abstract ( )   PDF (6965KB) ( )   As one of the significant damage problems on subway tracks, the rail corrugation has not been effectively solved so far. The rail vibration absorber has a good inhibition effect on the rail corrugation, but its suppression mechanism is still not clear. Firstly, according to the on-site investigation of Shuangbei-Shijingpo of Chongqing Metro Line 1, the dynamic model of the vehicle-track system with short sleepers supporting small radius curves was established, and the dynamic characteristics of the subway vehicle passing through the small radius curve section were studied. Then, combining with field tests and dynamic analysis results, based on the viewpoint of rail corrugation induced by frictional self-excited vibration in wheel-rail system, a finite element model of wheelset-rail-absorber system was established. Correspondingly, the suppression mechanism of rail vibration absorber on rail corrugation was studied from the perspective of frequency domain and time domain by complex eigenvalue analysis and instantaneous dynamic analysis. The inhibition effect of rail bottom absorber and rail waist absorber were compared, and the influence rule of key parameters of the rail vibration absorber on the rail corrugation was also analyzed. The research results show that the rail vibration absorber can effectively suppress the frictional self-excited vibration, thereby inhibiting the generation and development of rail corrugation. The rail bottom shock absorber and the rail waist absorber have a similar inhibition effect on the rail corrugation. Meanwhile, increasing the mass ratio and connection stiffness of the rail vibration absorber within a certain range can reduce the possibility of frictional self-excitation vibration of the wheelset-rail-absorber system. References | Related Articles | Metrics