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10 January 2023, Volume 41 Issue 12 Previous Issue    Next Issue
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Transportation+Big Data & Artificial Intelligence
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Transportation+Big Data & Artificial Intelligence

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Traffic Capacity of Traffic Flow Mixed with Intelligent Assistant Driving Vehicle Platoons QIN Yanyan, CHEN Lingzhi 2022, 41(12): 1-10.  DOI: 10.3969/j.issn.1674-0696.2022.12.01 Abstract ( )   PDF (4768KB) ( )   Aiming at the traffic flow mixed with regular manual driving vehicles and intelligent assistant driving vehicle platoons, the characteristics of traffic capacity were analyzed. A probabilistic analytical expression of traffic flow mixed with intelligent assistant driving vehicles platoons was built. Meanwhile, the intelligent driver model and full velocity difference model were applied respectively as the car-following models of intelligent assistant driving vehicles and manual driving vehicles. Then, the fundamental diagram model of the mixed traffic flow was deprived. Based on this, the traffic capacity of mixed flow was analyzed. Finally, for the intelligent assistant driving vehicle market rate p, the maximum fleet size S of intelligent assistant driving fleet and the intelligent assistant driving level e, the parameter sensitivity analysis was carried out respectively. The research results show that the traffic capacity of the mixed flow improves with the increase of p. When p≤0.2, the traffic capacity improvement is not significant; when p≥0.4, the traffic capacity improves significantly. With the increase of p, the optimal value of the maximum platoon size S is also different. When p≤0.4, the optimal value of S is 2; when p≥0.6, the optimal value of S is 4. The effect of e on traffic capacity is greatly restricted by p. When p≤0.2, e has no significant effect on the improvement of traffic capacity; when p≥0.4, e has a significant impact on traffic capacity. References | Related Articles | Metrics

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Traffic Scene Target Detection Technology Based on Improved CenterNet ZHAO Fengkui, CHENG Haifei, SU Shanshan, ZHANG Yong 2022, 41(12): 11-17.  DOI: 10.3969/j.issn.1674-0696.2022.12.02 Abstract ( )   PDF (1546KB) ( )   Aiming at the problem of complex targets and serious occlusions in traffic scenes, which made objects difficult to detect, an objects detection algorithm based on improved CenterNet was proposed. The activation function ReLU function used by CenterNet had an output and gradient of 0 when the input value was negative, which caused that some neurons in CenterNet could not calculate the input information. LeakyReLU function had a very small value when the input value was less than 0. The problem of neuron death in the ReLU function can be solved by retaining the gradient value of neurons. The ReLU activation function in the CenterNet network was improved to the LeakyReLU function. Meanwhile, the backbone network had also been improved. Comprehensively considering the factors such as the number of floating-point operations and network depth, the original CenterNet backbone network was changed to ResNet-50 and the spatial pyramid pool structure (SPP) was added, which could better extract feature information. The neural network was retrained for traffic scenarios, and the neural network was tested by using test set data. The test results show that the recall rate and accuracy rate of target detection are improved after optimization of CenterNet algorithm. The comprehensive evaluation index F1 value has increased by 0.14 on average, and the mAP has increased from 83.18% to 87.35%. FPS has dropped slightly, but other performance indicators have improved significantly, indicating that the improved CenterNet target detection model has a higher ability of target detection in traffic scenes. References | Related Articles | Metrics

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Urban Parking Information Sharing Based on Fog Computing HU Yongshi1, FAN Yongqiang1, FAN Yongying2 2022, 41(12): 18-25.  DOI: 10.3969/j.issn.1674-0696.2022.12.03 Abstract ( )   PDF (6244KB) ( )   In order to alleviate the shortage of urban parking spaces and the low utilization rate of berth resources, from the perspective of parking space information sharing, a parking space information sharing model for fog computing was constructed, which revealed the influence of the geographical structure variables and the socio-economic structure explanatory variables on parking space information sharing in the two dimensions of time and space. The research results show that the berth information sharing period presents Poisson distribution. Moreover, the density of public transport network, the density of government units, parking rates and the proportion of people with an annual income of less than 100 000 yuan show a negative impact on parking space information sharing. While, the road network density, building density, living facility density, leisure and entertainment density, and job density promote the sharing of parking space information. References | Related Articles | Metrics

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Influencing Factors of Expressway Operation Service Satisfaction from the Public Perspective XIANG Pengcheng1,2, GAO Lu1, JIA Fuyuan1 2022, 41(12): 26-32.  DOI: 10.3969/j.issn.1674-0696.2022.12.04 Abstract ( )   PDF (1235KB) ( )   The influencing factors of expressway operation service satisfaction were studied from the public perspective. Based on the customer satisfaction theory, combined with the unique attributes of China’s expressway, the public satisfaction evaluation index system and evaluation model were established. Taking Chengdu-Suining-Chongqing Expressway as a case study, the empirical research was carried out. The fitting of the theoretical model and the influence degree of factors were verified by structural equation model. The results show that: ①the theoretical model has a good fitness (P=0.114, χ2/df=1.255); ② when α=0.001, the total effect of traffic capacity perception and environmental facilities perception on public satisfaction is the highest (β＞0.5), while corporate image only indirectly affects public satisfaction. References | Related Articles | Metrics

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Evolution and Motivation of Freight Transport Structure in Shandong Province Based on Information Entropy ZHANG Ruhua1, GUO Senyao1, SHI Qingli2 2022, 41(12): 33-40.  DOI: 10.3969/j.issn.1674-0696.2022.12.05 Abstract ( )   PDF (460KB) ( )   The freight structure refers to the proportion of various freight volumes in the total freight volume within a certain period and scope. Studying the influencing factors of freight structure can help the regional integrated transportation development to clarify its advantages and disadvantages, so as to adjust measures to local conditions and explore the optimal freight structure of the region. Information entropy was used to describe the freight structure, which could quantify the freight structure. The specific influencing factors of transportation structure could be studied by using push-pull effect model. Taking Shandong Province as an example, the information entropy was used to describe the comprehensive transportation and freight transport structure of Shandong Province and explore its evolution law. The gray correlation analysis method was used to explore the system influencing factors of the freight transport structure. Combined with the push-pull effect model, the impact of a single transportation mode on the freight structure was analyzed. The research indicates that the demographic factor has the greatest impact on the evolution of freight transport structure, which is mainly reflected in the impact on water freight volume. Studying the evolution and motivation of freight transport structure can analyze the reasonable scale and structure of regional freight transport from its own perspective, so as to maximize transport benefits. References | Related Articles | Metrics

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Evaluation Method of Urban Road Cross-Section Based on Projection Pursuit Method ZHANG Zhiqing, SONG Xin, FU Jinxiu 2022, 41(12): 41-47.  DOI: 10.3969/j.issn.1674-0696.2022.12.06 Abstract ( )   PDF (1627KB) ( )   In order to reduce the impact of subjective factors in the existing evaluation methods on the selection of cross section schemes in the design stage of urban roads, an evaluation index system for the selection of cross section schemes of urban roads was established from three aspects, such as traffic operation efficiency, traffic safety and resources and environment. Based on the basic principle of the projection pursuit, the projection index function was constructed, and the real number coding accelerated genetic algorithm was used to complete the optimization calculation of the optimal projection direction. The optimal weights of evaluation indexes were determined finally. A real number coding accelerated genetic algorithm -projection pursuit model for cross section evaluation was constructed and applied to a project case to compare with other evaluation methods. The results show that the projection pursuit evaluation results of the three kinds of typical cross-sections are 0.571, -0.145 and 0.465 respectively, and the fuzzy comprehensive evaluation results are 0.544, 0.427 and 0.537 respectively. By comparing the above two evaluation methods, it is found that the projection pursuit method can magnify the variability of cross section design factors in the results, thus reducing the impact of subjective factors on the evaluation results and making the selection of urban road cross-section design schemes more scientific and reasonable. References | Related Articles | Metrics

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Flight Area Layout Optimization of Airfield with Minimum Fuel Consumption Based on Improved Genetic Algorithm LI Runing1, FENG Xing2 2022, 41(12): 48-55.  DOI: 10.3969/j.issn.1674-0696.2022.12.07 Abstract ( )   PDF (2070KB) ( )   To achieve a reduction of aircraft fuel consumption at the airport flight area, according to the structural characteristics of the airport flight area, an improved genetic algorithm design was completed, and optimization studies were carried out for the airport stand allocation and flight area layout. Through the analysis of the location of runway, taxiway, connecting lane and apron in the airfield area and the distribution form of parking stands, based on the fuel consumption of different types of aircraft, the fuel consumption simulation model of airport airfield with the configuration of single runway and linear parking lot distribution was established. Taking the minimum fuel consumption in airfield as the optimization objective, the fitness function design was completed. A mixed coding method of real number coding and binary coding was designed, which could meet the needs of both the aircraft stand allocation and the coding of the structural parameters of the flight area. The mapping of mixed coding genes to feasible solutions and the design of evolutionary operations for gene selection, crossover and mutation were completed. Penalty function was used to reduce the influence of infeasible genes on feasible genes in the evolution process. The optimal preservation strategy was adopted to ensure that the optimal individual gene was not destroyed in the evolution process, and the efficiency and accuracy of genetic algorithm optimization was improved. In order to verify the effectiveness of the proposed optimization method, the airfield with one runway one taxiway configuration and straight-line stand distribution was optimized. The optimization results show that: the improved genetic algorithm can be used to effectively optimize the parameters of the airfield to achieve the minimum fuel consumption of the aircraft, with fast convergence speed and high quality. References | Related Articles | Metrics

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Port Efficiency of Eight Cities along the Yangtze River in Jiangsu Province Based on DEA Game Cross Efficiency—SDM model JIANG Huiyuan, DING Jianjun 2022, 41(12): 56-61.  DOI: 10.3969/j.issn.1674-0696.2022.12.08 Abstract ( )   PDF (1243KB) ( )   The eight cities along the Yangtze River in Jiangsu province are important transportation nodes in the Yangtze River Delta, and their port efficiency has important research significance. According to the port background and data statistics, the factor analysis method was used to obtain three input indicators, including economic input, infrastructure construction and intermodal facility construction. And then the DEA game cross efficiency model was used to measure the port efficiency and analyze its space-time characteristics. Finally, spatial Durbin model (SDM) was used to furtherly analyze the spatial effect between port efficiency and influencing factors. The efficiency measurement research results show that the efficiency values of the eight ports along the Yangtze River in Jiangsu province from 2012 to 2019 fluctuate in time, with an overall upward trend; spatially, they are high in the middle and low on both sides. Global spatial autocorrelation analysis shows that the port efficiency has a significantly negative spatial correlation. The SDM analysis results show that the port efficiency of the eight cities along the river is positively correlated with the input of economic resources and the construction of intermodal facilities, and negatively correlated with the port infrastructure and the efficiency of surrounding ports. References | Related Articles | Metrics

Transportation Infrastructure Engineering

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Research Progress of Stay Cable Disease Detection Robot ZHANG Hong1,2, YUAN Ye2, XIA Runchuan2, ZHOU Jianting1,2, CHEN Yue1,2 2022, 41(12): 62-69.  DOI: 10.3969/j.issn.1674-0696.2022.12.09 Abstract ( )   PDF (7851KB) ( )   Robot detection is the most suitable detection method for stay cable diseases because of its comprehensive, accurate, timely, and reliable characteristics. The application status of robot in cable disease detection was summarized, the mechanical climbing system and disease detection system of robot were analyzed, and the development trend was prospected. The analysis results show that the wheel climbing mode has the problem of excessive clamping force and cannot pass through the special obstacles on the stay cable. The visual inspection system can quickly and accurately self-identify and detect the apparent diseases of stay cables with smooth surfaces; however, there is a lack of research on self-identification detection of cables with non-smooth surfaces, and the self-identification model of apparent diseases needs to be improved. Cable wire damage detection system based on MFL can be used to quantitatively characterize the cable wire damage inside the stay cable, but there is still a lack of uniform and universal MFL evaluation index and a model that can automatically identify the cable wire damage. References | Related Articles | Metrics

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Optimization for Reasonable Location of Auxiliary Pier of Composite Girder Cable-Stayed Bridge YAN Donghuang, DAI Mingyu, CHEN Changsong 2022, 41(12): 70-76.  DOI: 10.3969/j.issn.1674-0696.2022.12.10 Abstract ( )   PDF (2111KB) ( )   In order to study the influence of auxiliary pier position on the internal force of composite girder cable-stayed bridge, a composite girder cable-stayed bridge with a span of 1380m in Hubei province was taken as the object. 9 kinds of auxiliary pier position schemes were designed and finite element models were established respectively. 7 key indexes were selected, including the stress amplitude of the lower edge of the steel main girder, the stress amplitude of the upper edge of the concrete slab, the vertical deformation amplitude of the main girder, the stress amplitude of the stay cable, the bending moment amplitude of the main tower root, the bending moment amplitude of the lower beam of the main tower, and the bending moment amplitude of the tower column in the main tower. The internal forces of the 9 scheme models were compared and analyzed, and the reasonable location range of the auxiliary pier was obtained according to a single index. Using the comprehensive evaluation method of variation coefficient and standard score method, based on the principle of regression, the reasonable location of auxiliary pier for comprehensive evaluation of all indicators was determined. The results show that: for the stress amplitude of the composite girder, vertical deformation amplitude of composite girder, stress amplitude of stay cable and bending moment amplitude of main tower, the reasonable location range of the auxiliary pier is 0.230L~0.320L, 0.300L~0.320L, 0.275L~0.320L and 0.360L ~0.410L. Considering all indicators comprehensively, the optimal reasonable location of the auxiliary pier of the composite girder cable-stayed bridge is 0.285L away from the side pier (L is the side span). References | Related Articles | Metrics

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Evaluation Method for Fire Resistance of Main Cable of Three-Tower Self-anchored Suspension Bridge MA Rujin1, ZOU Mingming2 2022, 41(12): 77-84.  DOI: 10.3969/j.issn.1674-0696.2022.12.11 Abstract ( )   PDF (1496KB) ( )   A simplified evaluation method for fire resistance of bridge structures was proposed. Firstly, the time history curve of component temperature field under vehicle-induced fire was obtained by conducting component heat-transfer analysis. The thermal-structural coupling model of the whole bridge was established, and the static response analysis and safety of the whole bridge under high temperature were evaluated. Then, taking a steel-concrete simply supported beam specimen as the object, the temperature field and static response of members under fire were analyzed by numerical simulation, and the analysis results were compared with the test results to verify the accuracy of the proposed model. Finally, based on the engineering background of a suspension bridge, the heat-transfer analysis and structural response analysis of components under fire conditions of four types of vehicles, such as oil tankers, trucks, buses and cars, were carried out. According to the self-defined cable damage assessment criteria, the local damage of the main cable was evaluated by the proposed evaluation method. The research shows that the most serious damage to the structure is caused by the fire of the oil tanker. The maximum temperature of the main cable can reach 830 ℃. Although the mid-span deflection increases by only 160 mm, the main cable suffers serious irreversible damage. The proposed method can be used to analyze the fire resistance and safety of long-span cable supported bridges. References | Related Articles | Metrics

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Influencing Factors of Technical Interface Quality of Railway Bridge and Tunnel Engineering BAO Xueying1, WEN Yuanyuan1, HU Suoting2, 3, BAN Xinlin2, 3, XU Jianchao2, 3 2022, 41(12): 85-93.  DOI: 10.3969/j.issn.1674-0696.2022.12.12 Abstract ( )   PDF (6951KB) ( )   In order to improve the quality of technical interface of railway bridge and tunnel engineering, based on the unique natural environment in difficult and dangerous mountainous areas and the characteristics of bridge and tunnel construction, the influencing factors of technical interface quality were identified from five aspects: personnel, materials, equipment, method and environment. Based on the analysis of the action mechanism of influencing factors, research hypotheses were put forward and scheme design was carried out. The path coefficient analysis results were obtained by using the structural equation model. On this basis, the Bayesian network model was constructed to obtain the probability reasoning results and test the consistency of the results. Finally, Lasa-Linzhi section railway was taken as the research object to verify the hypothesis. The research shows that personnel, materials and environment have a great impact on the quality of technical interface, and the personnel aspect is mainly reflected in the technology, quality and coordination of relevant personnel directly engaged in interface construction; The material aspect is mainly reflected in the quality performance of interface construction materials, the perfection of relevant quality acceptance standards and material storage conditions; The environmental aspect is mainly reflected in the natural environment, space environment and relevant quality management system of the technical interface construction, which should be focused on management. References | Related Articles | Metrics

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Influencing Factors of Dynamic Modulus of SRX Polymer Stable Gradation Crushed Stone ZHANG Xinqiang1, TANG Boming1,2, ZHU Hongzhou1,2, OU Li1 2022, 41(12): 94-98.  DOI: 10.3969/j.issn.1674-0696.2022.12.13 Abstract ( )   PDF (7128KB) ( )   In order to study the influencing factors of the dynamic modulus of SRX polymer stabilized graded crushed stone and the action mechanism of SRX polymer, the orthogonal analysis method was used to study the influence of SRX content (0.25%, 0.5%, 0.75%), curing age (2, 6, 10 d) and confining pressure (34, 69, 103 kPa) on the dynamic modulus. Moreover, the action mechanism of SRX polymer was analyzed based on SEM. The results show that the addition of SRX polymer can significantly increase the dynamic modulus of graded crushed stone, and the stable graded crushed stone of SRX polymer exhibits a stronger stress dependence. Curing time has the most significant effect on the dynamic modulus of SRX polymer stabilized graded crushed stone, followed by SRX content and confining pressure. SRX polymer is uniformly coated on the surface of graded crushed stone, forming a layer of dense mucosa on the aggregate surface, and different aggregates are bonded to each other by SRX polymer. References | Related Articles | Metrics

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Model Test on the Half-Filled and Half-Excavated Subgrade in Loess Area WAN Qi1,2, YAN Changgen1, ZHANG Xiaoming1, 3, YANG Xiaohua1, BAO Han1 2022, 41(12): 99-103.  DOI: 10.3969/j.issn.1674-0696.2022.12.14 Abstract ( )   PDF (4383KB) ( )   Aim at the problem of water-induced damaged subgrade in Longdong loess area, the treatment technology of capillary barrier layer combined with vertical and horizontal blind ditches was proposed, taking the half-filled and half-excavated subgrade as the research object. Through the subgrade model tests under three working conditions, the variation law of the internal humidity of the subgrade under the action of simulated top ponding infiltration and groundwater capillarity was analyzed. Research results show that setting blind ditch on the upper part of the subgrade can promote the early water drainage of the subgrade; setting capillary retarding layer at the base of fill road can effectively block the rise of underground capillary water and ensure that the volume moisture content of filled subgrade and slope is in a relatively stable state (25.5%). The volume moisture content of each soil layer of the subgrade increases significantly under the comparison condition without any setting, moreover, the difference of the volume moisture content of the soil layer at subgrade filling and excavation junction reaches 20%. Thus, it can be seen that the significant difference of moisture content at subgrade filling and excavation junction may be the main reason for settlement, deformation and even slipping of subgrade in subsequent operation. References | Related Articles | Metrics

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Experimental Study on Non-equilibrium Flow and Instability Characteristics on Macropores Slope under Rainfall Conditions LI Shanghui1, QUE Yun2, ZHAN Xiaojun2 2022, 41(12): 104-111.  DOI: 10.3969/j.issn.1674-0696.2022.12.15 Abstract ( )   PDF (9361KB) ( )   In order to reveal non-equilibrium migration and characteristics of instability of macropores slopes under rainfall conditions, an indoor two-stage slope model with 30 artificial macropores was designed. Two rain intensities 30 and 80 mm/h were applied respectively. Volumetric moisture content θ, pore water pressure p, soil pressure σ, displacement u, slope surface velocity v and cumulative discharge q and other indicators at the top, middle and foot of the slope were tested. And the displacement nephogram was identified by PhotoInfor image processing technology to analyze the hydraulic response law and instability failure process of macroporous slope under different rainfall intensities. The results show that the greater the rainfall intensity, the closer the response time of θ at the foot, middle and top of the slope, the more significant the non-equilibrium flow phenomenon; furthermore, the easier it is to accumulate water at the foot of the slope, the easier it is to form an erosion ditch at the top of the slope, which causes the secondary increase of p at the foot of slope and the advance of pressure relief time at the top of slope. The σ at the top and foot of the slope increases with the increase of rainfall intensity, and then decreases slowly after reaching the peak value. Finally, the σ is released associated with local collapse of slope. The u increases slowly with the increase of rainfall duration and reaches the peak when the slope collapses locally. The greater the rainfall intensity, the greater the peak value of u at the top and step of slope, and the earlier the time to reach the peak value. The peak value of q and v increases with the increase of rainfall intensity. When the rainfall intensity is small, the macropore slope mainly suffers from shallow local sliding fracture. When the rainfall intensity is large, the macropore slope mainly suffers from shallow local scour failure. References | Related Articles | Metrics

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Research Progress on Origin and Electrical Resistivity Characteristics of Soil-Rock Composite Medium CHEN Songlin1, WANG Kui1, ZHAO Mingjie2 2022, 41(12): 112-119.  DOI: 10.3969/j.issn.1674-0696.2022.12.16 Abstract ( )   PDF (6378KB) ( )   Different from the traditional engineering geological material—soil, as a new geotechnical medium material, the soil-rock composite medium is attracting more and more researchers’ attention. Based on the literature reading and collection, from the perspective of the source of the block rock material, the geological origin of soil-rock composite medium was mainly divided into four types: weathering, freezing-thawing, scouring and karstification. Then, the soil-rock threshold, the electrical conductivity of soil and rock, the connection and proportion of soil and rock were discussed. Thirdly, starting from several different influencing factors, such as water content, compaction degree, soil-rock ratio, porosity, the performance rules of resistivity characteristics of soil-rock composite medium under different influencing factors were summarized. Finally, the problems and shorts in the current research on resistivity characteristics of the soil-rock composite medium and the future research focus were discussed. References | Related Articles | Metrics

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Creep Characteristics of Interactive Marine Terrestrial Deposit Soil Based on Fractal Derivative GAO Luchao1, CHEN Hede2, HE Zirui3, HUA Xin4, HU Chuankai4 2022, 41(12): 120-127.  DOI: 10.3969/j.issn.1674-0696.2022.12.17 Abstract ( )   PDF (2862KB) ( )   Interactive marine terrestrial (IMT) deposit soil is formed in the complex depositional environment, and its creep characteristics are different from other deposit soils. By substituting the Newton dashpots with fractal dashpots, the fractal creep model was established to describe the creep characteristics of IMT deposit soils based on the theory of fractal derivative. The consolidation drained triaxial creep test of Ningbo deposit soils was employed to study the creep deformation and stress-strain relationship. Combined with the creep test results of deposit soils in Ningbo and Dalian, the fractional creep model and the classical element model were compared. The calculation results show that the creep deformation of Ningbo deposit soils has obvious nonlinear characteristics. Compared with the classical element model, the fractional creep model is more suitable for describing the creep deformation of IMT deposit soils, which has the characteristics of high accuracy and few parameters. Moreover, the fractal creep model can effectively characterize the accelerated creep deformation stage of deposit soil. The research results can provide a theoretical reference for the analysis of the creep characteristics of the IMT deposit soils. References | Related Articles | Metrics

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Quantity of Pebble Movement Based on Acoustical Real-Time Monitoring YANG Shengfa1,2, YAN Luyao1, ZHANG Peng1, TIAN Mi1 2022, 41(12): 128-133.  DOI: 10.3969/j.issn.1674-0696.2022.12.18 Abstract ( )   PDF (4050KB) ( )   Bedload transport in natural rivers has strong randomness, and the traditional bedload sampling method can not carry out continuous dynamic monitoring of bedload transport process, which affects the process of research on bedload transport characteristics. In view of the advantages of the acoustic method in the prototype observation of pebble transport, which could be dynamically monitored and had high temporal and spatial resolution, the movement quantity of pebbles was explored by use of the pebble impact signal, combined with the energy variation characteristics of pebble impact audio. The research shows that in the process of single pebble movement, the number of collisions with the bed surface is positively correlated with the flow velocity, but not significantly correlated with the pebble particle size. Based on the test data, an empirical formula for the number of pebble collisions and the flow velocity is established to further calculate the number of pebble movements, which provides a theoretical support for the prototype observation of the acoustic pebble transport. References | Related Articles | Metrics

Transportation Equipment

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Influence of Stepped Flow Channel on the Performance of Proton Exchange Membrane Fuel Cell AN Zhiguo, ZHANG Dongyang, ZHANG Zhen, YAN Zhirui 2022, 41(12): 134-140.  DOI: 10.3969/j.issn.1674-0696.2022.12.19 Abstract ( )   PDF (5683KB) ( )   Reasonable design of flow channel will effectively improve the performance of proton exchange membrane fuel cell (PEMFC). A novel stepped flow channel model was established for PEMFC, and the numerical simulation experiments were carried out according to two proposed experimental schemes. The effects of the structure parameters of the stepped flow channel on the distribution of oxygen and water mass fractions, pressure drop in the flow channel and electrochemical characteristics of PEMFC were studied by comparing with the conventional flow channel. The results show that, compared with the conventional flow channel structure, the stepped flow channel structure will effectively improve the uniformity of oxygen distribution and water distribution in the cell, and its maximum power density will be increased by 13.58%, but it will produce a big pressure drop in the flow channel. When the inlet and outlet height of flow channel of PEMFC is fixed, the pressure drop in flow channel will be reduced with the increase of the number of steps, and the maximum pressure drop can be reduced by 24.9%. References | Related Articles | Metrics

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Numerical Simulation of Aerodynamic Characteristics of Automobile Tail Based on Mira Model LI Peng1, ZHU Li1, SONG Jie2,3 2022, 41(12): 141-150.  DOI: 10.3969/j.issn.1674-0696.2022.12.20 Abstract ( )   PDF (23336KB) ( )   The influence of vehicle aerodynamic characteristics on its performance plays a more and more important role with the improvement of vehicle speed. Using the method of CFD numerical simulation, taking Mira model as the research object, the prototype and the model with rear spoiler were simulated. By studying the flow field and velocity around the model, the effects of different tail Mira models, the installation of rear spoiler and the rear spoiler with different section shapes and angles of attack on the aerodynamic characteristics were analyzed. The research shows that there are obvious differences in the wake structure due to different body tail shapes, which has a great impact on the aerodynamic characteristics of the vehicle. At the same time, properly installing the rear spoiler at the rear of the vehicle can well optimize the wake structure of the vehicle body, so as to improve the aerodynamic characteristics of the vehicle. References | Related Articles | Metrics

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A CACC Data Accuracy Improvement Method Based on Improved Kalman Filtering in V2X Environment ZHAO Hongzhuan1, LU Ningning1, CHEN Jianpen1, ZHAN Xin2, XU Enyong2 2022, 41(12): 151-156.  DOI: 10.3969/j.issn.1674-0696.2022.12.21 Abstract ( )   PDF (917KB) ( )   Aiming at the problem of noise in acquiring cooperative adaptive cruise control (CACC) vehicle state data (including displacement, speed, acceleration, etc.) through vehicle-to-vehicle and vehicle-to-road communication in V2X environment, a method to improve the accuracy of CACC vehicle driving data based on improved Kalman filtering algorithm was proposed, considering the change of velocity azimuth angle of the vehicles when driving on the curve. According to the geometric relationship of the CACC vehicle driving on the curve, by taking into account the changes of vehicle driving displacement, speed and other driving states at the previous time and the current time, the optimal estimation of vehicle driving state was made for the driving data after improved Kalman filtering, so as to improve the accuracy of CACC vehicle driving state data. The improved Kalman filtering algorithm was established through the joint simulation platform of CarSim and Simulink to simulate and verify the data obtained by CACC vehicles during the course of driving on the curve. The simulation results show that the improved Kalman filtering algorithm makes the accuracy of vehicle driving displacement MSE increase by 81.04% and RMSE increase by 56.96%, which is closer to the expected value and has better accuracy. References | Related Articles | Metrics