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31 August 2023, Volume 42 Issue 7 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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Batch Extraction of 3D Model Data of Landscape Bridge Based on Rhino Grasshopper CHEN Suhua1,2, YU Zhiguang2, ZHOU Huan2, LI Ruiqi2 2023, 42(7): 1-7.  DOI: 10.3969/j.issn.1674-0696.2023.07.01 Abstract ( )   PDF (13524KB) ( )   The design of landscape bridges is based on reasonable structural stress, combined with emotional artistic expression, often forming complex special-shaped spatial curved surfaces. The complex bridge design increases the difficulty of design and construction. In order to analyze the data expression of the three-dimensional model of landscape bridge, a method to extract the three-dimensional model data of landscape bridge in batches based on Rhino Grasshopper software platform was developed by simplifying the design process through parametric strategy. The proposed method included five steps: segmenting, cutting, subdividing, extracting coordinates and outputting data. The proposed method was applied to the design and construction of Binhe West Road landscape bridge in Xining city. The results show that the maximum error of design parameters is 0.5%, which proves that the proposed method is effective, greatly improving design efficiency and construction quality. The written program algorithm has universality, providing ideas for BIM applications such as engineering quantity statistics and batch output of drawing and helping to promote BIM forward design. References | Related Articles | Metrics

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Structural Mechanical Properties of Large-Scale Beam Reaction System HUANG Feng1,2, ZHANG Ban2,3, LIU Xingchen1,2, YANG Zhengxu1,2, QU Miaodi1,2 2023, 42(7): 8-14.  DOI: 10.3969/j.issn.1674-0696.2023.07.02 Abstract ( )   PDF (10118KB) ( )   In order to break through the bottleneck of loading in tunnel scaled model experiments, a three-dimensional loading test system for underground structure was established in tunnel laboratory. The finite element model of the reaction system was established by ABAQUS, the strength and deformation law of the reaction beam were analyzed, and the rationality of the reaction system was verified. At the same time, 1 684 t tonnage static load test was carried out by the proposed system, and the deformation law of the reaction beam was obtained, which furtherly verified the effectiveness of the reaction system. Based on this, the mechanical characteristics of reaction beam and bolt under ultimate load were deeply studied, and the deformation law of reaction beam and bolt under ultimate load was obtained. The research results show that the bottom of the vertical rib, the middle of the horizontal rib, the two ends and bottom of the web and the horizontal direction of the bolt of the reaction beam have large deformation. When designing the reaction system, the section inertia moment of this part of the beam and the stiffness of the bolt should be strengthened to improve the safety and effectiveness of the reaction system. References | Related Articles | Metrics

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Multi-scale Assessment of Bridges Seismic Hazard Based on CRITIC-Entropy Weighting Method XIE Haoyu1,2, NIU Songshan1, ZHENG Wanshan1, TANG Guangwu1, ZHANG Wengang2 2023, 42(7): 15-20.  DOI: 10.3969/j.issn.1674-0696.2023.07.03 Abstract ( )   PDF (1764KB) ( )   The seismic hazard assessment of existing bridges in urban road networks is a complex and critical issue. In response to the shortcomings of existing evaluation methods that often relied on empirical judgment or considered factors affecting risk assessment, a multi-scale evaluation method was proposed. In the first scale, bridges within the road network were grouped by defining special road sections. And then in the second scale, the structure anti-seismic performance and the topological characteristics of the bridge in the road network were obtained by the modified structural vulnerability analysis method and the topological feature extraction method. At last, a CRITIC-entropy weighting method (EWM) combined method was used to comprehensively assign weights and calculate the comprehensive anti-seismic importance of bridges in the road network. The results show that the proposed method can realize the quantification of the decision-making process, and it can be used as a reliable basis for assessing the seismic hazard of bridges in the road network and judging the priority of anti-seismic reinforcement of urban bridges. References | Related Articles | Metrics

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Reasonable Length of Transition Section of Parallel Acceleration Lane in Curved Section PAN Binhong, ZHANG Ranyang, LI Xiang, CHAI Hu, LIU Juan 2023, 42(7): 21-28.  DOI: 10.3969/j.issn.1674-0696.2023.07.04 Abstract ( )   PDF (4763KB) ( )   The length of the transition section directly affects the traffic safety at the end of the highway merge area. The regulations on the length of the transition section in JTG D20—2017 Highway Route Design Specification didnt consider the demand when the transition section of the acceleration lane was located in the curved section. And the insufficient length of the transition section located in the curved section may cause the roadside guardrail blocking the drivers line of sight, and there was a safety hazard of insufficient sight distance for parking at the end of the merge. The characteristics of the driving trajectory of the minibus in the transition section at the merge end and the intervisibility conditions for car drivers were analyzed. The hyperbolic tangent lane change model conforming to the actual lane change trajectory was adopted, the transition section meeting the stopping sight distance of the driver of the minibus was taken as the control element, and a parallel acceleration lane transition section length calculation model was constructed for the curve section. Based on the domestic and foreign research and the relevant vehicle operation speed survey data at the merge end, the values of key parameters in the proposed model were determined. Finally, a reasonable length value of parallel acceleration lane transition section on curved roadway was proposed. The study shows that the minimum length of parallel acceleration lane transition section of curved road section is positively correlated with the running speed of minibuses at the merge end, and negatively correlated with the width of hard shoulder and radius of circular curve on the right side of the mainline lane. The minimum length of parallel acceleration lane transition section specified in Highway Route Design Specification can meet the requirement of stopping sight distance when minibuses changing lanes at the merge end when the design speed of mainline is <100 km/h. When the design speed of the mainline is ≥100 km/h, it does not meet the requirement of stopping sight distance when minibuses changing lanes at the merge end, and there is a certain risk of traffic safety. It is recommended to determine the length of the parallel acceleration lane transition section according to the radius of curvature of the mainline and the width of the hard shoulder. References | Related Articles | Metrics

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Decay of Slip Resistance of Polyurethane Ultra-thin Wear Layer YU Miao1,2, LONG Chengliang1, LIU Quping3 2023, 42(7): 29-36.  DOI: 10.3969/j.issn.1674-0696.2023.07.05 Abstract ( )   PDF (4662KB) ( )   In order to study the slip resistance of polyurethane ultra-thin wear layer, the dynamic wear test and laser profile scanning test were combined to investigate the factors affecting the decay of the slip resistance of the wear layer and the evolution of the macroscopic texture characteristics of the road surface during this process. Through dynamic wear tests, the variation rule of dynamic friction coefficient (fDFC) changing with the wear time under different working conditions was analyzed. By means of laser profile scanning test, the surface elevation information of the wear layer was obtained, and the macroscopic texture index was calculated. Based on the correlation analysis of the indexes and the significance analysis of the regression equation, the relationship between the anti-slipping performance of the wear layer and the macroscopic texture was revealed. The research results show that the velocity, load, and aggregate mass loss all have an impact on the slip resistance of the wear layer. When velocity and load are taken as variables respectively, fDFC shows an exponential type of attenuation generally, and higher velocity and greater load will aggravate aggregate spalling, resulting in more easy decay of the slip resistance of the wear layer. 5 indexes such as the mean profile depth (hMPD), profile arithmetic average wavelength (λa), surface bearing index (kSBI), the newly introduced mass loss rate of the wear layer aggregate stage (σ) and stage total mass loss rate (ω) can establish a significant multivariate quadratic polynomial relationship with the slip resistance of the wear layer, which indicates that macroscopic texture and aggregate mass loss can accurately describe the slip resistance of the wear layer. References | Related Articles | Metrics

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Performance Enhancement Mechanism of Silane Coupling Agent on Semi-flexible Pavement Materials CHENG Peifeng, MA Guangtao, ZHANG Zhanming,LI Yiming 2023, 42(7): 37-44.  DOI: 10.3969/j.issn.1674-0696.2023.07.06 Abstract ( )   PDF (10690KB) ( )   In order to study the influence rule and the action mechanism of adding silane coupling agent on the performance of semi-flexible pavement materials, Marshall stability test, rutting test, low temperature bending test, freeze-thaw splitting test and other tests were adopted to test the mechanical properties and road performance of semi-flexible pavement materials with different dosage of silane coupling agents. And the optimal dosage of silane coupling agent was also determined. The micro-modification mechanism of silane coupling agent based on the interface modification principle was observed by instruments such as a high magnification instrument. The results show that with the increase of the dosage of silane coupling agent, the high temperature performance, low temperature performance and water stability of the semi-flexible pavement have all been improved to varying degrees. At the same time, there is a peak effect of its dosage on performance. The Marshall stability, dynamic stability, bending tensile strain, and freeze-thaw splitting strength ratio all reach their peak at around 0.5%. After exceeding the peak, the performance decreases with the increase of the dosage. Finally, the optimal dosage of silane coupling agent is determined to be 0.5%. The interface tightness is quantitatively reflected by measuring the changes in connectivity porosity and perfusion rate. Combined with observation and comparison, it can be clearly observed that silane coupling agents can react between cement-based grouting materials and asphalt mixtures through a series of chemical reactions, thereby altering the morphology of the cement-asphalt interface, by comparing the cement asphalt interface of the semi-flexible pavement material under the optimal dosage of silane coupling agent and that of the ordinary semi-flexible pavement material. The stability of cement-asphalt interface is effectively improved and the cracks at the cement asphalt interface are reduced. Combined with performance tests, silane coupling agents can improve the mechanical and road performance of semi-flexible pavement through interface optimization. References | Related Articles | Metrics

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Uniformity of Asphalt Mixture Paved with Spiral Distribution Based on EDEM CAO Yuanwen1, MEI Yuhang1, ZHOU Shihua1, XIE Lidan2, CHEN Zuo3 2023, 42(7): 45-51.  DOI: 10.3969/j.issn.1674-0696.2023.07.07 Abstract ( )   PDF (12336KB) ( )   In order to explore the influence of the structural parameters and working parameters of the spiral distribution system of the paver on the uniformity of asphalt mixture paving, the contact relationship among the asphalt mixture particles was analyzed, and the three-dimensional solid modeling of the spiral distributor was carried out. The mass ratio deviation coefficient Sc was proposed to use as a uniformity evaluation index. According to the simulation of various related parameters such as different screw diameters, pitches and material level coefficients, the relationship variation curve of Sc was obtained. Finally, the actual measurement results of paving uniformity engineering were analyzed by digital image technology. The results show that the paving uniformity law of the simulation analysis and the measured uniformity law of the project have good consistency. References | Related Articles | Metrics

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Dynamic Response of Under-Rail Support Failure Based on the Principle of Virtual Work YANG Hongyin1,2, WU Nanhao1, CAO Hongyou3, ZHANG Wei1, LIU Zhangjun1 2023, 42(7): 52-59.  DOI: 10.3969/j.issn.1674-0696.2023.07.08 Abstract ( )   PDF (2168KB) ( )   Regarding trains, tracks and bridges as three substructures, the dynamic coupling equations of the above three were deduced based on the principle of virtual work. The sub-equations were assembled into a coupled matrix of train-track-bridge according to the way of taking a seat according to the number. Discrete spring-damping connections were used between the track and the bridge subsystem. When the under-rail support failed due to the damage of the under-rail structure, the calculation model should remove the spring-damping corresponding to the lower end of the track and the bridge, and then modify the stiffness matrix and damping matrix of the original assembly. Aiming at the problem of under-rail support failure, the proposed method was used to analyze the variation rule of dynamic response of the track and the bridge. The results show that the under-rail support failure changes the continuous track support stiffness, resulting in a drastic change in the wheel-rail contact force when the vehicle passes through the failure area. When only considering the dynamic unevenness of the track, the foundation support defect under the track has little effect on the displacement response of the bridge, but it will aggravate the acceleration response of the bridge. The greater the scope of under-rail support failure, the greater the wheel-rail contact force and bridge acceleration. For track displacement and acceleration, both will increase significantly with the expansion of the under-rail support failure area and the increase of train travel speed. References | Related Articles | Metrics

Transportation Infrastructure Engineering

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Dynamic Characteristics of Truck Load Influenced by Manholes and Pavement around Manholes ZHAO Quanman1,2, WANG Xinjun1, LU Xiaojin1, LIU Jifa3, HU Wenjun1 2023, 42(7): 60-68.  DOI: 10.3969/j.issn.1674-0696.2023.07.09 Abstract ( )   PDF (2080KB) ( )   In order to analyze the dynamic characteristics of truck load when passing the manhole and its surrounding pavement surfaces, the type and scope of pavement disease around manholes were determined by the investigation of pavement disease around manholes. Considering the deformation and vibration of manhole cover, the multi-degree-of-freedom vibration model of truck-manhole cover coupling was established, and the variation rules and influencing factors of truck load impact coefficient changing with time were analyzed. The research results show that under the excitation of the smoothness of the manhole and the pavement around manholes, the load impact coefficient of the truck reaches its maximum value when the truck drives from the pavement around manholes into the normal pavement, and the truck load is 1.35 times as large as the static load. The degree of influence of various factors on the dynamic characteristics of truck load is ranked in descending order: the height difference caused by pavement surface diseases around the manhole is greater than the settlement of the manhole, the rate of slope change, the driving speed, and the stiffness coefficient of the manhole cover. Therefore, the smoothness of the pavement surface when the truck passes the manhole and its surrounding pavement surface is the reason for whether the impact effect of truck load is significant, and it is also one of the main factors causing frequent damage to the manhole surrounding pavement surface. References | Related Articles | Metrics

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Solution Method of Radial Basis Function Approximation for Elastic Foundation Beam and Plate LIN Junzhi1,2, YANG Di1, XU Jiqing1,3 2023, 42(7): 69-75.  DOI: 10.3969/j.issn.1674-0696.2023.07.10 Abstract ( )   PDF (2914KB) ( )   Based on Winkler model, a new method was proposed to solve the deflection of elastic foundation beam and plate. The approximate solution of deflection was obtained by using the collocation method of weighted residual method combined with radial basis function approximation. The proposed method didn’t need mesh and integration, which was a strong form solution of one-to-one correspondence between the number of unknowns and the number of equations. The numerical results show that the approximate solution is in good agreement with the theoretical solution, and the computational effect is equivalent to that of the hybrid boundary method, which is superior to that of the sliding least square method. In addition, according to the boundary conditions, the physical meaning of the additional unknown quantity is given, and part of the characteristic matrix is constructed into the unit matrix, to reduce the difficulty of solving the equations to be solved and the error, which provides a new idea for the compilation of the additional rows of the characteristic matrix. References | Related Articles | Metrics

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Bearing Characteristics of the Frame Wharf Structure with High-Filled Bank Slope under the Influence of Variable Amplitude Water Level HE Linlin1,2,3, LI Zhisong1, ZHAO Chenyu1, QIAN Jin1 2023, 42(7): 76-86.  DOI: 10.3969/j.issn.1674-0696.2023.07.11 Abstract ( )   PDF (7414KB) ( )   The periodic variable amplitude water level in the reservoir area causes a weakening of the shear strength parameters of the high-filled bank slope soil, which in turn causes a decrease in the stability of the frame dock structure. Therefore, it is necessary to carry out the study on bearing characteristics of the frame wharf with high-filled bank slope under the influence of variable amplitude water level. Firstly, based on the simplified calculation method established for bank slope stability under variable amplitude water level, and considering the influence rule of soil saturation and water level cycles on soil strength parameters, a simplified analysis method for the bearing characteristics of wharf structures was established considering the comprehensive effects of permeability, soil saturation, and variable amplitude water level cycles. Then, with the help of ABAQUS finite element software, a three-dimensional finite element calculation model for the high-filled slope frame wharf structure was established, and the bearing characteristics of an actual wharf engineering were analyzed by applying the proposed method. The results show that the combined effect of saturation, variable amplitude water level cycles, and permeability on the vertical bearing capacity of the slope frame wharf is not significant. However, the increase in saturation and the number of water level cycles slightly increases the horizontal ultimate bearing capacity of the wharf structure. Under the impact load, the horizontal ultimate bearing capacity of the wharf structure with 90% saturation of the soil increases by 6.4% compared with that with 14% saturation of the soil, and the horizontal ultimate impact capacity when water levels are cycling 100 times increases by 3.3% compared with that when the water levels are cycling one time. The changes in saturation and water level cycles after considering the permeability have a significant impact on the displacement of the bank slope soil. Among them, the plastic penetration zone of the bank slope and the area with the largest displacement change concentrate below the retaining wall at the top of the slope and around the first and second rows of pile foundation soil of the bank slope.The relevant research results can provide a certain reference for similar engineering designs. References | Related Articles | Metrics

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Prediction and Cause Analysis of Freeway Traffic Accident Severity Based on Bayesian Network CHENG Wei1, MA Mingwei1, ZHANG Xiaolong2 2023, 42(7): 87-95.  DOI: 10.3969/j.issn.1674-0696.2023.07.12 Abstract ( )   PDF (4510KB) ( )   In order to study the freeway traffic safety in depth, the mechanism of freeway traffic accidents and the influence of various factors on the severity of freeway traffic accidents were analyzed. 1939 traffic accidents on Shanghai-Kunming Expressway in Qujing City from 2017 to 2019 were collected for research. Taking the accident severity as dependent variable, 19 influencing factors related to the accident severity were selected as independent variables under four categories such as people, vehicle, road and environment. Based on tree-enhanced Bayesian network, a prediction model of accident severity was established by data fusion method, and the influence relationships among various factors were quantified. The key causes were found by feature screening, and the reasoning analysis based on case studies was carried out. The results show that the key factors affecting the severity of traffic accidents on freeways are successively weather conditions, sight distance conditions, road conditions, etc. The prediction accuracy of the proposed model for the severity of freeway accidents can reach 84.27%, which is higher than that of the traditional Bayesian method, and the validity of the proposed model is well verified. According to the main causes of the accident, some improvement suggestions are put forward, which can provide accurate accident information to assist decision-making for traffic management departments, speed up the accident response and improve the emergency command ability. References | Related Articles | Metrics

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Safety Risk Analysis of Car-Following Behavior on Highway in Rainy Environment QIN Yanyan, ZHU Li, ZHU Yiwen, TANG Honghui 2023, 42(7): 96-105.  DOI: 10.3969/j.issn.1674-0696.2023.07.13 Abstract ( )   PDF (3135KB) ( )   The safety hazards of driving in rainy environments are prominent. The safety risks of rear-end collisions caused by car-following in rainy enviorment was analyzed. First of all, considering two conditions such as normal acceleration and deceleration of vehicles and sudden braking in a rainy environment, the safety simulation scenarios were designed, and a car-following model calibrated by basing on real driving data was also used to carry out simulation test on the safety risk of car-following behavior. Secondly, according to the simulation data, three different types of safety evaluation indicators such as ITC, DRAC and DSS, were applied to evaluate the safety risk for different rainfall and car-following scenarios. Finally, the statistical testing was used to analyze the applicability of the three safety evaluation indicators such as ITC, DRAC and DSS. The research results show that in the two car-following scenarios, as the rainfall increases, the risk of collisions in car-following behavior increases and and the time of potential collision risk also increases. Taking the speed of 20 m/s and DSS as an example, under different weather conditions in normal acceleration and deceleration scenarios, the DSS indicates the possibility time of collision risk in 0 seconds for clear weather, 90.9 seconds for light rain and 100 seconds for heavy rain. Under different weather conditions in the emergency braking scenario, the DSS indicates the possibility time of collision risk in 7.0 seconds for clear weather, 14.3 seconds for light rain and 20.7 seconds for heavy rain. For different rainfall and car-following scenarios, the applicability of DSS evaluation index is better than that of ITC evaluation index and DRAC evaluation index. References | Related Articles | Metrics

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Evaluation of Green and Low-Carbon Construction Scheme of Highway Engineering Based on Double Objectives of “Carbon Neutralization” and Cost LI Hongdi, ZHOU Yunzi 2023, 42(7): 106-112.  DOI: 10.3969/j.issn.1674-0696.2023.07.14 Abstract ( )   PDF (772KB) ( )   Green and low-carbon construction of highway engineering can effectively reduce environmental pollution. However, the construction scheme of a unit project in the construction project cannot achieve “carbon neutralization” and can only form a construction scheme for low-carbon emissions that are “carbon neutralization”. At the same time, it is necessary to adhere to a green and low-carbon construction plan under reasonable cost control. The highway engineering construction scheme was studied from the double objectives of carbon neutralization concept and cost of construction scheme, and the highway engineering construction system was compared to a dissipative system. According to the concept of “carbon neutralization”, a positive and negative entropy model was introduced. Based on the type of impact on the construction system, carbon emissions and cost were interpreted as positive entropy values of the construction system, and carbon absorption was interpreted as negative entropy values of the construction system. According to the model formula, the PSR model was used to establish the evaluation index system of green and low-carbon construction of highway engineering based on the concept of “carbon neutralization”, and the weights required by the positive and negative entropy model were obtained. The total entropy of the construction system was thereby calculated, and the entropy values of different construction schemes were compared. The impacts of cost and green and low-carbon of construction scheme were comprehensively analyzed and compared, and three scenarios were established to evaluate the construction scheme, and then the overall superior construction scheme was selected. The research results show that the total entropy value of the construction scheme using ecological block prefabricated parts is less than that of the construction scheme using traditional prefabricated parts, and the former construction scheme is more consistent with the double objectives of “carbon neutralization” and cost. References | Related Articles | Metrics

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Tunnel Lighting Environment Evaluation Based on Improved Entropy Method YAN Zihai1, LI Shuo2, GAN Penglu1, LIANG Sinong1 2023, 42(7): 113-119.  DOI: 10.3969/j.issn.1674-0696.2023.07.15 Abstract ( )   PDF (1275KB) ( )   Aiming at the problems of strong subjectivity and single evaluation index in the existing tunnel lighting environment evaluation methods, the evaluation indicators were selected from four aspects: light source, traffic conditions, ventilation conditions and spatial visibility. The improved entropy method was used to clarify the impact degree of each evaluation indicator, and combining the model simplification based on BP neural network and the safety level classification based on clustering analysis, a tunnel lighting environment evaluation system was constructed. The research results show that the weight calculation results fully reflect the information contained in the measured data itself and solve the problem of the large index weight value due to the large degree of data dispersion. The simplified model for lighting environment evaluation based on BP neural network has high calculation accuracy, and the fitting judgment coefficient R2=0.934 is calculated. After inspection, the mean and median changes in pupil area are basically consistent with the variation pattern of the evaluation value. The evaluation value W can effectively evaluate the comprehensive risk level of the tunnel interior lighting environment. References | Related Articles | Metrics

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Location Allocation of Container Yard from the Perspective of Determining Tasks ZHENG Yunfeng, LIU Ruilin, RAO Benshun, ZHOU Xiaobin, ZHANG Guoqing 2023, 42(7): 120-127.  DOI: 10.3969/j.issn.1674-0696.2023.07.16 Abstract ( )   PDF (900KB) ( )   In order to allocate yard resources reasonably and improve the working efficiency of terminals, the allocation of container slots in container yards was studied. Considering the factors such as the destination, time, container weight of ships arriving at the dock, a container allocation model of the yard was established, with the goal of minimizing the sum of the driving cost and the container turnover cost of the yard bridge. In order to enhance the global search ability of the algorithm, based on the view of determining tasks, the process of bay selection and box arranglment in bay was regarded as a whole, a genetic algorithm for searching the box arrangement position in the whole region was designed to solve the model and the specific box location scheduling allocation scheme was obtained. The effectiveness of the proposed algorithm was verified by simulation and compared with Yalmip software. Examples of different scales were solved to verify the performance of the proposed algorithm. The results show that the proposed algorithm can effectively solve the problem of storage space allocation in actual production operation and can also provide a better solution in a short time when solving large-scale examples. References | Related Articles | Metrics

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Influence Analysis of Urban Built Environment on the Return Quantity of Shared Bikes WANG Zhenbao1, LI Huiqing1, LIU Zhou2 2023, 42(7): 128-135.  DOI: 10.3969/j.issn.1674-0696.2023.07.17 Abstract ( )   PDF (3634KB) ( )   After determining the optimal spatial unit collection method of dockless bike-sharing passenger flow, the influence degree of urban built environment on the return amount of shared bike was analyzed. Taking Xiamen island as an example, the spatial unit return amount obtained from the collection of shared bike return location data was taken as the dependent variable, and the built environment index that calculated each spatial unit was taken as the independent variable. The regression analysis on eight spatial unit division methods was carried out by using the ordinary least square method (OLS), geographical weighted regression (GWR) and multi-scale geographical weighted regression (MGWR) models. The spatial unit division method with the best goodness of fit was determined and the spatial heterogeneity of the impact degree of built environment variables was analyzed. The results show that: ① the MGWR model using traffic zoning for shared bike return amount aggregation has the best fit; ② the density of corporate interest points, the density of buildings, the number of intersections and the number of electronic fences for shared bike are positively correlated with the number of returned bikes; the spatial closure, the density of interest points in scientific research and education, the distance to the nearest subway station and the diversity of interest points are negatively correlated with the number of returned bikes. The distance to the nearest bus stop is negatively correlated in the southwest, and positively correlated in the northwest, north and northeast. The research ideas and methods provide a reference for the accuracy of the prediction model of the shared bike return amount, and the spatial heterogeneity results of the influence degree of built environment variables provide a scientific basis for proposing differentiated built environment renewal strategies in different locations. References | Related Articles | Metrics

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Airport Real-Time Capacity Extraction and Deep Ensemble Spatiotemporal Distribution Prediction Modeling ZANG Haipei，ZHU Jinfu，GAO Qiang 2023, 42(7): 136-145.  DOI: 10.3969/j.issn.1674-0696.2023.07.18 Abstract ( )   PDF (9288KB) ( )   For the network structure of civil aviation transportation, evaluating the operation capacity of a single airport can only be used for flight scheduling, while predicting the spatiotemporal distribution of airport network capacity has guiding significance for flight operation control. In order to reflect the impact of complex weather on the airport real-time capacity, the big data of weather and flight operations of China civil aviation was adopted, and the data mining technology was used to extract the real-time capacity of the airport. And the nonlinear mapping relationship between weather and capacity was also studied. A model that converted weather spatiotemporal distribution prediction into airport capacity spatiotemporal distribution prediction was established by using various machine learning algorithms such as neural networks. Moreover, on the basis of analyzing the prediction results of a single model, the neural network weighted feature fusion layer was used to construct a deep ensemble prediction model, which deeply integrated multiple algorithms to further improve the accuracy of real-time airport capacity prediction. Finally, the multi-seasonal weather data of airport network in Eastern China was used to verify the accuracy of the proposed model in predicting the real-time capacity of the airport under complex weather conditions. It is found by the research that the prediction accuracy of each model decreases with the increase of unit time, and the deep neural network has a strong ability to learn nonlinear weather characteristics. The construction of deep neural network through fusion ensemble learning has effectively improved the prediction accuracy of real-time airport capacity. The proposed deep ensemble prediction model satisfies the requirements of obtaining the real-time capacity of future airports in a short time, which can provide decision-making basis for civil aviation transportation and reduce flight delays.It satisfies the requirement of obtaining the real-time capacity of future airports in a short time, and can provide decision basis for the dynamic operation of the airport and reduce flight delays. References | Related Articles | Metrics

Transportation Equipment

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Numerical Research on the Hydrodynamic Characteristics of Ship Passing Spur Dike JI Nan, HUANG Haodong, LUO Yi, LI Haoran 2023, 42(7): 146-154.  DOI: 10.3969/j.issn.1674-0696.2023.07.19 Abstract ( )   PDF (17666KB) ( )   Spur dike is a common hydraulic structure, which will affect the flow of river and the hydrodynamic characteristics of passing ships. Based on the RANS equation, VOF method was used to process free surface, and Realizable k-ε turbulence model was combined to numerically simulate the hydrodynamic characteristics of ships passing through spur dike. Firstly, the hydrodynamic characteristics of the spur dike and the ship were numerically simulated and compared with the experimental data, which proved the rationality of the numerical simulation method. Then, the flow velocity and the relative position of the ship spur dike were used as the variation parameters to calculate the hydrodynamic characteristics of the ship and the channel flow field domain, and the force characteristics of the ship and the variation pattern of the navigation attitude were obtained. The results show that the presence of ships makes the flow field behind the spur dike oscillate unsteadily. When the ship passes through the spur dike, the peak value of transverse force appears at about 0.25 times of the ship length in front of the spur dike (X/Lpp=-0.25), the peak value of longitudinal force appears at the position of the axis of the spur dike. The positive peak value of heading turning moment appears at the position of 0.5 times of the ship length behind the spur dike (=0.5), and the negative peak value appears at the position of 0.5 times of the ship length in front of spur dike (X/Lpp=-0.5). With the increase of water flow velocity, the increment of force and moment of ship is the most significant in the range of one ship length in front and rear of the spur dike (-1 References | Related Articles | Metrics

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Numenical Calculation and Experiment of Flow Field of Rotary Vane Compressor Oil-Gas Separator LIU Jin1, HE Zeyin1,2, TAO Pingan1, LIU Hongmei1, XIANG Yin1,2, RAN Zhixiang2 2023, 42(7): 155-160.  DOI: 10.3969/j.issn.1674-0696.2023.07.20 Abstract ( )   PDF (6995KB) ( )   In order to solve the problem of low separation efficiency of small diameter oil droplets by oil-gas separator used in rotary vane compressor, a new two-stage oil-gas separation pipe structure was proposed. Firstly, based on the SST k-ω turbulence model and the discrete phase model (DPM), the numerical model of multiphase flow in the oil-gas separator was established. The velocity distribution of the flow field and the movement trajectory of oil droplets were analyzed. The law of separation efficiency of centrifugal oil-gas separator was studied, and the scheme for improving the separator structure was proposed, in which a secondary separation pipe was added in the main exhaust pipe of the separator to increase the collision probability between oil droplets and the wall surface and thus increase the oil-gas separation efficiency. A calibration test bench for oil droplets in a centrifugal oil-gas separator was built, and experimental research on oil droplet separation in a centrifugal oil-gas separator was conducted. The research results show that the newly established secondary separation pipe has improved the separation efficiency of oil droplets of various diameters, especially for small diameter oil droplets, with an increase of nearly 20%. The problem of poor separation effect of the separator for oil droplets of small diameters has been effectively solved by the optimization results. References | Related Articles | Metrics