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06 June 2023, Volume 42 Issue 5 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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Seismic Design Parameters of Partially Assembled Piers HE Shuanhai, ZHU Linhao, ZHU Zhao, LIU Zhi 2023, 42(5): 1-8.  DOI: 10.3969/j.issn.1674-0696.2023.05.01 Abstract ( )   PDF (6206KB) ( )   To promote the application of precast segmental piers in middle and high intensity seismic region, a partially assembled bridge pier consisting of a cast-in-place section at the pier bottom and a prefabricated section at the pier body, connected by unbonded prestressed steel bars, was proposed. A fiber element model was established to accurately simulate the stress characteristics of this type of bridge pier joint, and pseudo static hysteresis tests were conducted. The accuracy of the proposed model was verified through the test results. Then two sets of comparative experiments were designed by using the fibre element model to study and analyze the effects of two design parameters, namely the length of the cast-in-place section and the reinforcement ratio, on the seismic performance of partially assembled bridge piers. The results show that the horizontal ultimate load, residual displacement and energy dissipation of partially assembled piers increase with the increase of the length of cast-in-place segment. As the longitudinal reinforcement ratio increases, the horizontal ultimate load of the bridge pier gradually increases, while the residual displacement and energy dissipation of bridge pier decrease. When the reinforcement ratio reaches 1.48%, the horizontal ultimate load increases to a threshold and tends to be stable, and the residual displacement and energy dissipation capacity also tend to be stable. References | Related Articles | Metrics

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Influence Analysis of Steel Box Girder Structure on Temperature Field under Sunlight Conditions HUANG Haixin1, YAN Shisong1, LI Chunming2, KOU Zhitian1 2023, 42(5): 9-15.  DOI: 10.3969/j.issn.1674-0696.2023.05.02 Abstract ( )   PDF (966KB) ( )   The temperature field generated by steel box girders under sunlight conditions is an important factor to be considered in the design of bridge structures. Based on the basic theory of heat transfer and finite elements, a model of the temperature field of steel box girder under sunlight conditions was established by use of ABAQUS finite element software. Based on the comparison and verification with the field measured data, the influence of temperature distribution on the steel box girder was analyzed. The results show that the different orientation of the bridge affects the amount of solar radiation received by the web on both sides, which in turn leads to significant changes in the transverse temperature difference between the left and right webs of the box chamber. The ratio between the length of the flange plate and the height of the box girder is negatively correlated with the irradiated area of the web, and an increase in the irradiated area will expand the area of transverse temperature difference in the box chamber. A decrease in the inclination angle of the web will reduce the value of solar radiation received by the web. When the angle between the web and the top plate decreases by 15° from 90°, the transverse temperature difference between the two sides of the web decreases by about 20%. The shape and layout of the stiffening ribs are important factors affecting the local temperature field of the steel box girder. The temperature value of the open stiffener area is lower than that of the closed stiffener area, and increasing the height of the stiffener and reducing the layout spacing are beneficial for reducing local temperature. The most unfavorable combinations for the temperature field of steel box girder are summer, north-south orientation, short flange with high box girder and straight web. References | Related Articles | Metrics

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Sunshine Gradient Temperature Effect of Concrete-Filled Steel Tubular Arch Rib GUO Zengwei, ZHANG Yali, YANG Yifan, ZHOU Shuixing 2023, 42(5): 16-24.  DOI: 10.3969/j.issn.1674-0696.2023.05.03 Abstract ( )   PDF (1331KB) ( )   In order to explore the gradient temperature effect of concrete-filled steel tubular arch rib under sunlight radiation, a thermo-mechanical coupling model considering the interface contact state between steel tube and concrete was established, which was based on the real-time collection of the surface temperature of the steel tube in the Minjiang River Bridge project in Qianwei, Sichuan Province. The gradient temperature and stress analysis of concrete-filled steel tubular arch ribs were carried out and the time-varying laws of the cross-sectional gradient temperature along the diameter D direction and the spatial distribution mode of steel tube-concrete interface contact stress of the concrete-filled steel tubular arch bridge in service in Sichuan under the influence of sunlight were revealed. Moreover, the radial gradient temperature calculation formula and characteristic parameter values were given. The research shows that the radial temperature distribution of CFST section is seriously inhomogeneous under the influence of sunlight. The temperature gradient within the depth range of D/8 from the steel pipe top is about 5 ℃ higher than the recommended value in JTG D60—2015 and about 8 ℃ higher than that in TB 10092—2017. In addition, at D/2, it is only 50% of the recommended value in TB 10092-2017. The interface stress between steel pipe and concrete exhibits an alternating phenomenon of “tension-compression” within one day, with peak tensile stress reaching 0.8 MPa at 14:00 and 15:00. Therefore, the appropriate measures should be taken in the process of design and construction to make an expansion compressive stress of the concrete inside the tube exceed 0.8 MPa, so as to avoid the bond void phenomenon of the concrete inside the tube. References | Related Articles | Metrics

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Combined Prediction Model of Bridge Deformation Response Based on EEMD-LSTM MENG Qingcheng1, LI Mingjian1, HU Lei1, WAN Da1, WU Haojie1, QI Xin2 2023, 42(5): 25-34.  DOI: 10.3969/j.issn.1674-0696.2023.05.04 Abstract ( )   PDF (1156KB) ( )   In order to accurately predict the deformation response of bridge structure, an EEMD-LSTM combined model was proposed, in which the iForest algorithm was used to denoise the original deformation data of the bridge, the Ensemble Empirical Mode Decomposition (EEMD) method was used to decompose the bridge deformation data, and the Long Short-Term Memory (LSTM) deep learning method was used to predict the obtained multi-scale deformation components. Taking Wuhan Zhuankou Yangtze River Bridge as the research object, RMSE, MAE, MAPE and R2 were selected as evaluation indexes to verify the proposed model. The research results show that compared with the single LSTM, SVM and Bayesian model, the EEMD-LSTM model has good robustness, applicability, and higher prediction accuracy. References | Related Articles | Metrics

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Driving Quality Prediction of Highway Asphalt Pavement Based on PCA-GA-LSSVMR CAO Xuejuan1, LI Xiaoyu1, WU Bowen2, HAO Zengheng3 2023, 42(5): 35-43.  DOI: 10.3969/j.issn.1674-0696.2023.05.05 Abstract ( )   PDF (996KB) ( )   To realize accurate prediction of highway driving quality and save maintenance cost, in the context of machine learning theory, a PCA-GA-LSSVMR-based prediction model for driving quality of highway was proposed based on historical pavement performance data. Firstly, the box plot analysis method and min-max standardization method were used to pre-process the road performance data, screen out abnormal data and normalize the data to ensure the reliability of data quality. Then the PCA-GA-LSSVMR model was used in Rstudio software to predict the driving quality and compared with the SVMR model and PCA-LSSSVMR model. The study shows that the linear regression determination coefficient of the proposed model is 0.835, and the model has the best stability. The root mean square error is 2.394, indicating that the model has the smallest prediction error. The average prediction accuracy of the model is 86%, which can effectively evaluate the driving quality of asphalt pavement. References | Related Articles | Metrics

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Research Progress on Thermal Stress of Asphalt Pavement ZHU Hongzhou1,2, LEI Lei2, CHEN Ruipu2, LIU Yufeng3 2023, 42(5): 44-53.  DOI: 10.3969/j.issn.1674-0696.2023.05.06 Abstract ( )   PDF (578KB) ( )   As a non-ignorable environmental factor in the service process of asphalt pavement, the temperature has attracted extensive attention at home and abroad. Temperature change can cause different temperature stresses to occur inside the pavement structure. In order to master its main research methods and current situation, it was analyzed from three aspects such theoretical analysis, numerical simulation and experimental research. The application scenarios and limitations of different methods were systematically summarized, providing reference for further improvement of research methods. The research results show that the viscoelasticity, stress history and relaxation effect of materials are successively considered in the theoretical analysis method, and the research tends to be gradually improved. Judycki analysis method considers the rheological and viscoelastic properties of materials, which is more in line with the actual stress characteristics of pavement than Monismith analysis method and Hills & Brien analysis method. However, due to some assumptions in the theoretical analysis, there is a deviation between the thermal stress prediction model and the actual value. So, the follow-up research can start with the material characteristics of asphalt mixture, considering the viscoelastic characteristics, to improve the theoretical model and the application scope and accuracy of the theoretical formula. Secondly, the numerical simulation method can scientifically and efficiently study the influence law of different stress states, parameter values and environmental factors on the service performance of asphalt pavement, but the rationality of the model depends on the selection of material parameters. So, the follow-up research should take the scientific definition and comprehensive acquisition of material parameters as the starting point. Finally, the indoor experiment TSRST has high international recognition and is often used as a measurement standard of whether the analytical method is reasonable or not. And the full-scale pavement test loop is more scientific than the indoor test, which has the convenience of space, technology and time. It is the most effective method to study the actual response of pavement structure. The analysis of full-scale loop data may become a follow-up research hotspot. References | Related Articles | Metrics

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Structure Bearing Capacity of Underside Groove-Shaped Precast Block Pavement LI Yueguang, SUN Qiang, ZHOU Bingqing 2023, 42(5): 54-60.  DOI: 10.3969/j.issn.1674-0696.2023.05.07 Abstract ( )   PDF (1006KB) ( )   The underside rectangular groove was selected as the structural type, and the indoor bearing plate method was used to conduct bending test research on the underside groove-shaped prefabricated block pavement. The deflection values of precast block pavement under different conditions such as different base layer types, sand cushion types, sand cushion thickness, and precast block types were studied by experiment. The critical deflection value L was used to evaluate the structural bearing capacity of the precast block pavement. The results show that for the same pavement structure combination, as the thickness of the sand cushion increases, the critical deflection value of prefabricated pavement structure increases, and the structure bearing capacity decreases. The structure bearing capacity of the precast block pavement with sand cushion mixed with 30% gravel is better than that with the ordinary sand cushion. The structure bearing capacity of the underside groove-shaped interlocking precast block USB pavement is better than that of the interlocking precast block IB pavement. The structure bearing performance of underside groove-shaped precast block pavement is better than that of ordinary precast block pavement. And the structure bearing performance of precast block pavement can be improved by selecting proper pavement base and sand cushion. References | Related Articles | Metrics

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Experimental Study on Dynamic Deformation and Dynamic Strength Characteristics of Expansive Soil of Qinchong Expressway in Guangxi TANG Xianyuan1, 2 ,WANG Shihai3, MA Jieling1，LUO Jie1 2023, 42(5): 61-69.  DOI: 10.3969/j.issn.1674-0696.2023.05.08 Abstract ( )   PDF (1069KB) ( )   To study the dynamic deformation and dynamic strength characteristics of expansive soil under long-term cyclic loading, the indoor dynamic triaxial tests were carried out on expansive soil of Qinchong Expressway in Guangxi. The effects of confining pressure and dynamic stress on the axial cumulative deformation and dynamic strength characteristics of expansive soil were analyzed. The research results show that the relationship between the axial cumulative strain of expansive soil and the vibration times presents a stable development trend when the dynamic stress is small, and a destructive development trend when the dynamic stress is large. A modified hyperbolic cumulative deformation prediction model considering the stable and destructive development trends is established, and the fitting parameters under different confining pressures and dynamic stresses are obtained. The inclination of hysteresis curve of expansive soil gradually decreases with the increase of vibration times. The shape of hysteresis curve changes from full shuttle to willow flocculent strip. With the increase of confining pressure, the hysteresis curve gradually approaches to the direction of dynamic stress axis, the slope gradually increases, and the dynamic strain gradually decreases. The dynamic strength of expansive soil shows a power function curve attenuation law with the increase of failure vibration times Nf. The dynamic cohesion cd and the dynamic internal friction angle φd decrease linearly with the increase of lgN in the semi-logarithmic coordinate, and the decrease rate of cd is greater than that of φd. After normalizing the dynamic and static strength index parameters, the normalized formula of the strength index of expansive soil changing with different failure vibration times lgN is obtained. References | Related Articles | Metrics

Transportation Infrastructure Engineering

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Deformation of Ballastless Track under Uneven Settlement Based on Winkler Foundation Composite Beam YAN Jianwei1,2, XIONG Ming1,2, TAN Xin1,2 2023, 42(5): 70-77.  DOI: 10.3969/j.issn.1674-0696.2023.05.09 Abstract ( )   PDF (923KB) ( )   Aiming at the structure of double-block ballastless track, a Winkler foundation composite beam analytical model was established to predict the bending deformation of the track during uneven settlement of a concave-cosine soil subgrade. And by comparing and verifying the beam body finite element model considering the nonlinear contact between the track and subgrade, the critical conditions applicable to the Winkler foundation composite beam model for predicting track deformation, namely the critical conditions triggered by the nonlinear contact between the track and subgrade, were determined. The research shows that under the condition of small settlement amplitude/wavelength, the predicted results of the two models are in good agreement. While, under the condition of large settlement amplitude/wavelength, the predication results of rail deformation of the analytical model are larger. The finite element simulation results of the beam body show that there is a significant void phenomenon between the track and the roadbed, with a contact stress of 0. The critical conditions triggered by the nonlinear contact between the track and subgrade are given, that is, when the wavelength of uneven settlement is 10, 15, 20, 25 m, the critical settlement amplitude of Winkler foundation composite beam model is 1, 3, 10, 30 mm respectively, and when it is greater than the critical settlement amplitude, the contact nonlinearity between the track and the roadbed begins to trigger. The settlement wavelength-critical settlement amplitude curve of Winkler foundation composite beam is obtained, which provides theoretical basis and calculation method for rapid and accurate prediction of rail surface deformation under uneven settlement conditions of the subgrade. References | Related Articles | Metrics

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Surface Deformation Monitoringof Chongqing Donggang Area Based on InSAR LI Huarong, DAI Shuanglin 2023, 42(5): 78-84.  DOI: 10.3969/j.issn.1674-0696.2023.05.10 Abstract ( )   PDF (3420KB) ( )   For the settlement monitoring of the high-fill area, taking Chongqing Donggang as the research area, the PS-InSAR technology was used to obtain PS points of the research area, and these points were introduced into the SBAS-InSAR technology process as ground control points, so that the surface deformation field in the research area can be inverted. The accuracy evaluation of the deformation results and traditional leveling measurement results was carried out and compared with the surface deformation results obtained by the unimproved SBAS-InSAR technology. The research results show that introducing GCP screened by PS-InSAR technology into the SBAS-InSAR processing process has reliability and practicality and is suitable for settlement monitoring of high-fill sites. References | Related Articles | Metrics

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Motion Response of Cylindrical Floating Breakwater Based on AQWA YUAN Peiyin, LI Yufeng, ZHANG Zhe 2023, 42(5): 85-91.  DOI: 10.3969/j.issn.1674-0696.2023.05.11 Abstract ( )   PDF (1514KB) ( )   Based on the three-dimensional potential flow theory, the hydrodynamic research of the cylindrical floating breakwater was carried out by the method of numerical analysis, which was by use of the hydrodynamic analysis software AQWA. The amplitude response operators of the breakwater under different wave directions, the additional mass at different water depths, the motion response of the breakwater, and the cable tension were obtained by calculation. The research results show that the sway, surge and heave motions of the proposed floating breakwater are mainly caused by low-frequency motions. Since the mooring lines are mostly bow and stern lines, the amplitude of the surge motion of the floating body in the time domain is relatively small, which is one order of magnitude smaller than the amplitude of the sway and heave motions. References | Related Articles | Metrics

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Improved Cooperative Merging Model of Expressway On-Ramp in Intelligent Internet Connection Environment XIAO Daiquan, KANG Shengyang, XU Xuecai, SHEN Zhenwu, YUAN Quan 2023, 42(5): 92-100.  DOI: 10.3969/j.issn.1674-0696.2023.05.12 Abstract ( )   PDF (1525KB) ( )   In order to solve the traffic congestion located at expressway on-ramp during peak periods, based on intelligent internet connection for collaborative merging control and the thought of virtual platoon, an improved collaborative merging model was constructed, which could simultaneously reflect vehicle collaborative merging and collaborative lane-changing. With the simulation platform constructed by Python and VISSIM, the effectiveness of the proposed model was evaluated by selecting indicators such as road network traffic efficiency, on-ramp queue length, and designated distance travel time. A comparative analysis was conducted on the improvement effect of road network traffic efficiency in scenarios where there was no control, collaborative merging control and improved collaborative merging control of virtual platoon. The results reveal that compared with no control, under the control of the improved collaborative merging and collaborative merging control of virtual platoon, the average delay of the road network is reduced by 65.3% and 59.0% respectively, and the traffic efficiency of the entrance area is also improved. Meanwhile, both types of control can reduce the travel time of vehicles during peak hours, while the improved collaborative merging control of virtual platoon has better traffic efficiency. References | Related Articles | Metrics

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Influence of Real-Time Risk Early Warning System at Unsignalized Intersection on Driver's Behavior GUO Fengxiang1, XIONG Changan1,2, NI Dingan1, SU Yu2, YANG Wenchen2 2023, 42(5): 101-108.  DOI: 10.3969/j.issn.1674-0696.2023.05.13 Abstract ( )   PDF (1673KB) ( )   In order to test the warning effect of real-time risk early warning system at unsignalized intersection and understand its influence on drivers behavior characteristics, three virtual simulation scenarios of road intersections were built to carry out driving simulation experiments. Physiological behavior data such as TSDNN, TRMSSD, NLF-norm and NLF/HF were obtained, and driving operation behavior data such as average vehicle speed, standard deviation of vehicle speed and variation coefficient of vehicle speed were collected. Statistical analysis was conducted on the behavior characteristics of the test drivers, and the impact of RTCRWS on driver behavior was studied. The warning effect of RTCRWS under different traffic conditions was comprehensively evaluated by factor analysis method. The research results show that RTCRWS has a good warning effect on the driver groups, which can improve the safety level of unsignalized intersection, reduce the speed of drivers passing through the unsignalized intersection and alleviate the tension of drivens. The warning effect of RTCRWS varies among drivers under different traffic conditions. The psychological tension level of drivers decreases in order of no warning for mild traffic flow, warning for mild traffic flow and warning for severe traffic flow. References | Related Articles | Metrics

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Key Influencing Factors of Urban Rail Transit Station Resilience under Rainstorm Disaster JIAO Liudan, LI Dongrong, ZHANG Yu, HUO Xiaosen 2023, 42(5): 109-115.  DOI: 10.3969/j.issn.1674-0696.2023.05.14 Abstract ( )   PDF (582KB) ( )   It is of great significance to study the key influencing factors of rainstorm disaster on station resilience to ensure the safe travel of residents. Firstly, 20 factors affecting station resilience were selected from the three attributes of resilience (resistance, resilience, and adaptability). Then, taking the adjacency relationship between influencing factors as the research data, the CONCOR method of cohesive subgroup analysis in social network analysis (SNA) was used to analyze the relationship of secondary group structure in factor network. Finally, the centrality analysis of SNA was used to screen out the key influencing factors of station resilience. The research results show that the key influencing factors of station resilience under rainstorm disaster are: flood control monitoring capability, flood control water retaining capability, personnel evacuation efficiency, flood control drainage capability, flood control fund investment, personnel coordination and cooperation capability, flood control emergency plan system and flood control training drill. References | Related Articles | Metrics

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Maturity Model of Metro Emergency Response Capability Based on Improved Unascertained Measure ZHANG Peng, JIANG Yifan, ZHAN Yuxin 2023, 42(5): 116-123.  DOI: 10.3969/j.issn.1674-0696.2023.05.15 Abstract ( )   PDF (754KB) ( )   The research on the emergency response capability maturity of subway emergencies is helpful for subway operating companies to evaluate and improve emergency management. Based on the capability maturity model and unascertained measurement theory, a maturity evaluation model for subway emergency response capabilities was constructed. From the perspective of pre-event, during event and post-event, a subway emergency response capability evaluation index system was established, and the factors affecting the subway emergency response capability were divided into 6 types of first-level indicators and 19 second-level indicators. 6 types of first-level indicators included organization and system, monitoring and preparation capabilities, emergency rescue capabilities, emergency handling capabilities, emergency recovery capabilities as well as accident summarization and analysis. The G1 method and the entropy weight theory were combined to determine the weight of each indicator, and the blind number theory and the unascertained measurement theory were used to improve the unascertained measurement model to deal with the uncertainty and ambiguity in evaluating the emergency response capability for handling subway emergencies. Taking Chengdu Metro as an example, the emergency response capability maturity evaluation was conducted to verify the rationality and practicability of the proposed model. The results show that the overall emergency response capability of Chengdu Metro is at the normative level. Among them, the maturity scores of organization and system as well as emergency rescue capabilities are relatively high, but the monitoring and preparation capabilities and emergency response capabilities need to be further improved. References | Related Articles | Metrics

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Cause Analysis of Traffic Accidents in Jinan Based on GIS FENG Haixia，NING Erwei，WANG Qi，LI Jian 2023, 42(5): 124-131.  DOI: 10.3969/j.issn.1674-0696.2023.05.16 Abstract ( )   PDF (989KB) ( )   In order to reduce traffic accidents and ensure peoples normal life and personal safety, identifying traffic accident-prone areas and analyzing the causes of accidents are the key to reduce accidents. Taking Jinan as the research area, based on the traffic accident data of Jinan in 2018, the spatial characteristics and causes of traffic accidents in Jinan were studied by the methods such as kernel density analysis, accident equivalent combined with buffer zone analysis and geographic weighted regression analysis. Meanwhile, the corresponding improvement measures were proposed. The research results show that the accident sites have obvious aggregation, and six accident-prone areas in Jinan have been identified. The lack of road physical isolation and roadside protection facilities are the main reasons for the accident-prone areas. The number of vehicles, highway mileage, GDP and population have a great impact on the number of regional accidents, and they are positively correlated with the number of accidents, among which the number of vehicles has the greatest impact. The correlation regression coefficient of the GWR model constructed on the basis of the number of vehicles and highway mileage is as high as 0.75, which can provide timely warning and improve corresponding transportation facilities for accident-prone areas in various regions according to the proposed model. This study is of great significance to reduce the occurrence of traffic accidents and improve the level of traffic safety. References | Related Articles | Metrics

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Calculation of the Maximum Number of People Gathered at Passenger Stations Based on Travel Characteristics TANG Qiusheng,XU Hao,ZHANG Yonghui,XIONG Yang,SUN Lingbo 2023, 42(5): 132-138.  DOI: 10.3969/j.issn.1674-0696.2023.05.17 Abstract ( )   PDF (578KB) ( )   In order to achieve the accurate calculation of the maximum number of people gathered at bus terminals, on the basis of the current research results of the maximum number of people gathered at passenger stations, the influence mechanism between the travel characteristics and the arrival time of passengers was further explored. Statistical analysis was conducted on the arrival time propensity of shuttle bus passengers under different departure environments at the same station, and it was found that passengers had significant differences in their arrival time due to different travel characteristics. On the basis of ensuring convenient data acquisition, five travel characteristics were selected to predict the arrival time of passengers. Furthermore, a calculation model for the maximum number of people gathered at a station considering the difference in passenger arrival time was constructed. Taking Chongqing Chenjiaping Bus Station as an example for case study, the effectiveness of the proposed method was verified. References | Related Articles | Metrics

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Vehicle Distance Detection Method Based on MTCNN Algorithm DING Baiqun, LI Jingyu 2023, 42(5): 139-144.  DOI: 10.3969/j.issn.1674-0696.2023.05.18 Abstract ( )   PDF (1621KB) ( )   Monocular vision detection system has simple structure as well as better real time with low cost and convenient and fast detection services, but its detection accuracy is lower than that of the multi-ocular vision system and is highly dependent on the calculation methods. The current vehicle ranging method using monocular vision does not fully consider the error problem caused by multi-scale vehicles, which affects its detection accuracy. A vehicle distance detection method based on multi-task cascaded convolutional neural network (MTCNN) was established, which could calculate space between vehicles through the P4P principle with the vehicle license plate as the target, using the monocular camera to collect front vehicle images and MTCNN algorithm so as to obtain the corner coordinates of the license plate. The proposed method was not related to the size of the vehicle type or road undulation, but only to the quality of license plate image recognition and calculation, which can effectively reduce errors caused by other factors. The test shows that the proposed vehicle distance measurement method uses MTCNN and P4P algorithms to analyze and calculate the video images of the front vehicle, achieving high-precision distance detection. The average error of distance detection within a range of 27 meters is 2.77%, with an average error of 2.52% for detection between 3 and 27 meters. It has high stability in a larger distance measurement range. References | Related Articles | Metrics

Transportation Equipment

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Design and Structure Optimization of SCR Mixer Based on CFD WANG Guoxian1, WU Hongjing1, 2, WU Huawei2, ZHAO Qian2, YANG Xiaobing3 2023, 42(5): 145-151.  DOI: 10.3969/j.issn.1674-0696.2023.05.19 Abstract ( )   PDF (1374KB) ( )   In order to improve the ammonia distribution uniformity of diesel selective catalytic reduction (SCR) post-treatment system, two different mixer structures, fan-shaped and louver, were designed. The two mixer structures were optimized by using computational fluid dynamics (CFD) technology. For the optimized two mixer schemes, the velocity uniformity, ammonia uniformity and pressure loss were simulated, analyzed and compared. The CFD analysis results show that the louver mixer structure has higher ammonia distribution uniformity at the front end of the catalyst carrier, and the pressure loss of the louver mixer is less than that of the fan-shaped one. Further analysis of the impact of exhaust flow and exhaust temperature on ammonia uniformity shows that an increase in exhaust flow leads to a decrease of ammonia uniformity index, while an increase in exhaust temperature leads to an increase of ammonia uniformity index. The ammonia uniformity index of louver type is always higher than that of fan-shaped structure. Overall, the louvered structure mixer is superior to the fan-shaped structure. References | Related Articles | Metrics

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Driving Instability Threshold of Wheel Loader Based on Improved Dynamics Equation CAO Yuanwen1, ZHOU Shihua1, MEI Yuhang1, XIE Lidan2, SONG Shubin3 2023, 42(5): 152-160.  DOI: 10.3969/j.issn.1674-0696.2023.05.20 Abstract ( )   PDF (995KB) ( )   In order to obtain the instability threshold of the motion parameters of the wheel loader under different road conditions, based on the analysis of the degree of freedom of the traditional wheel loader, an improved driving dynamics equation that can reflect the changes of the driving trajectory and the force changes of the front and rear bodies was established. The main influencing factors of driving instability of wheel loader were analyzed by taking the lateral load transfer rate (LTR) as the index. Finally, the motion parameter instability threshold range was determined. The research results show that the increase of the driving speed and steering speed of the wheel loader, the increase of the slope angle and the driving steering angle will seriously aggravate the risk of tipping instability of the wheel loader. Among them, driving speed and steering angle have the most serious impact on driving stability. References | Related Articles | Metrics