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26 September 2022, Volume 41 Issue 09 Previous Issue    Next Issue
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Transportation+Big Data & Artificial Intelligence
Transportation Infrastructure Engineering
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Transportation+Big Data & Artificial Intelligence

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Individual Metro Travel Prediction Based on Graph Convolution Gated Recurrent Network WENG Xiaoxiong, QIN Zhenlin, ZHANG Pengfei 2022, 41(09): 1-8.  DOI: 10.3969/j.issn.1674-0696.2022.09.01 Abstract ( )   PDF (1336KB) ( )   Aiming at the restriction of individual metro travel caused by geographic location, a spatiotemporal characteristic modelling method was proposed for the metro travel prediction task, which solved the problem that only the time characteristics of travel series were modeled, and the spatial characteristics in the data could not be fully mined in the past research. The proposed method firstly constructed the spatial features of individual travel series, extracted spatial features through graph convolutional neural network and fused the embedded vectors representing the spatiotemporal characteristics by using gating. And then, the gated recurrent networks were used to learn spatiotemporal features. The individual travel sequence data set constructed by Guangzhou Metro Yangchengtong card swiping data was verified, and the prediction accuracy of the proposed model was higher than that of the model that only modeled the time characteristics. Finally, by constructing artificial data with significant individual travel spatial characteristics and mixing them with real data in different proportions, it is verified that the proposed model can effectively learn the spatial characteristics of individual travel and has better robustness. References | Related Articles | Metrics

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Vehicle Re-identification Algorithm Based on Multi-granularity Feature Segmentation LAN Zhangli, WANG Chao, YANG Qingqing, JIN Hao 2022, 41(09): 9-17.  DOI: 10.3969/j.issn.1674-0696.2022.09.02 Abstract ( )   PDF (10307KB) ( )   In order to solve the problem that local feature extraction was insufficient and potentially significant local features were easy to be concealed in vehicle re-identification task, an algorithm based on multi-granularity feature segmentation was proposed. In the proposed algorithm, ResNeSt-50 which could realize the information exchange between channels was adopted as the backbone network to extract primary features. And the backbone network was copied into three independent branches, and the output feature map was segmented by multi-granularity along the vertical, horizontal and channel directions to extract the differentiated local features. In order to further enhance the ability of the network to extract discriminant feature information, the spatial attention module was embedded in each split-attention block of ResNeSt-50. The research results show that The mAP, Rank-1 and Rank-5 indexes of the proposed algorithm on the VeRi-776 dataset reach 85.92%, 97.67% and 98.53% respectively; on the three test sets of the VehicleID dataset, the Rank-1 index reaches 88.36%, 84.19% and 78.89% respectively, which is better than that of most of the existing mainstream algorithms. The research results show that the proposed algorithm is advanced and effective. References | Related Articles | Metrics

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Green Wave Control Method of Non-straight Path at Adjacent T-shaped Intersection ZHAO Xin1, FENG Lei1, LIN Haobo2, 3, CHEN Xi1, XIAO Yuzhou1 2022, 41(09): 18-25.  DOI: 10.3969/j.issn.1674-0696.2022.09.03 Abstract ( )   PDF (6072KB) ( )   Aiming at the coordinated control problem of non-straight paths at adjacent continuous T-shaped intersections, based on the MULTIBAND model, the effects of different path types and disturbance phases on the coordinated control performance were studied. By coupling the left-turn single-loop signal of the adjacent turning intersections, the double-loop signal of the virtual intersection was obtained and embedded in the coordination model, which indirectly converted the non-straight path into a straight path to process. The VISSIM simulation platform was used to simulate the road network around Jiefang Bridge in Guilin. The simulation data research results show that under the three traffic flow conditions, the travel delay of the controlled route is reduced by 22.27%, 14.64%, and 13.72% respectively, and the parking delay is reduced by 26.09%, 17.19%, and 15.81% respectively. The proposed control method can not only reduce the system delay, but also significantly reduce the delay and parking probability of the controlled path, and can adapt to different degrees of tidal flow, which verifies the scientificity and applicability of the proposed method. References | Related Articles | Metrics

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Setting Threshold of Right-Turn Protective Phase under the Condition of Comity to Pedestrians ZHANG Zhiyong, HUANG Xincan, SHAO Yue 2022, 41(09): 26-35.  DOI: 10.3969/j.issn.1674-0696.2022.09.04 Abstract ( )   PDF (7384KB) ( )   In order to scientifically set the right-turn protective phase of signalized intersection under the detailed rules of comity to pedestrians, the spatial and temporal distribution characteristics of pedestrian-vehicle interaction and two-way pedestrian crossing street were analyzed by the field investigation of several intersections in Beijing. Based on the acceptable gap theory, a delay model of pedestrian-vehicle interaction under the influence of yielding rate and two-way pedestrian crossing street was established. The sensitivity analysis of the parameters in the proposed model was carried out, and the conditions for setting right-turn protective phase were proposed from the perspective of safety and operating efficiency. The results show that when the right-turn vehicle flow is not saturated, the right-turn vehicle flow reaches 100 veh/h, and the two-way pedestrian crossing street flow reaches more than 1700 ped/h, it is appropriate to set the right-turn protective phase. The more pedestrian flow crossing the street, the lower the demand of setting threshold value of right-turn protective phase on vehicle flow. With the increase of vehicle flow, the demand of setting threshold value of right-turn protective phase on pedestrian flow tends to decrease firstly and then increase. The higher vehicle yielding rate, the lower the demand of setting threshold value of right-turn protective phase on flow and the smaller the delay increment after setting right-turn protective phase. References | Related Articles | Metrics

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Driving Safety Distance of Urban Road in Cold Regions Based on Separation Facilities FENG Tianjun1, YANG Xiayu1, XIA Chunting2, LIANG Chunyan1, LI Henan3 2022, 41(09): 36-40.  DOI: 10.3969/j.issn.1674-0696.2022.09.05 Abstract ( )   PDF (882KB) ( )   In order to improve the driving safety of urban road in cold regions and maximize the function and effectiveness of traffic facilities, the data of guardrail height H, vehicle speed V and driving safety distance W of road separation facilities in four road sections of Yatai Street, Yatai Street Expressway and Huizhan Street in Changchun city and Jilin Street in Jilin city were collected on the spot. The probability distribution of W was analyzed by SPSS software and mathematical statistics. The functional relationship model between H, V and W of urban roads in cold regions was constructed, and the proposed model was verified by an example. The results show that when H is constant, W and V corresponding to H basically obey normal distribution. W is significantly correlated with V and H, and there is a linear relationship among them. Considering safety, efficiency and economy, the minimum values and comfort values for driving safety distance of urban road in cold regions corresponding to H are recommended. References | Related Articles | Metrics

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Injury Severity Analysis of the Elderly in Collision Accidents at Intersections PAN Yiyong, WU Jingting, SHI Ying 2022, 41(09): 41-46.  DOI: 10.3969/j.issn.1674-0696.2022.09.06 Abstract ( )   PDF (415KB) ( )   In order to study the factors affecting the injury severity of the elderly in collision at intersections and explore the heterogeneity unobserved in the collision accidents, the injury severity model of the elderly in the intersection collision accident was constructed based on the latent category Logit model. Taking the severity of accident injury as the dependent variable, 12 independent variables were selected from five aspects such as people, vehicle, road, built environment, and road environment. Latent category Logit model was used to construct accident injury severity model, and parameter estimation and pseudo-elastic analysis were carried out. The research results demonstrate that motorcycles, darkness and no light at night, the top / bottom of the mountain, and the speed of 50~60 km/h have heterogeneous effects on the severity of accident injuries. In the built environment, there is no shopping center in the 300 m buffer zone of the intersection, which is negatively correlated with minor injury accidents. References | Related Articles | Metrics

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Drivers Dynamic Visual Characteristics in Different Distraction States on Prairie Highways LYU Zhen, QI Chunhua, ZHU Shoulin 2022, 41(09): 47-54.  DOI: 10.3969/j.issn.1674-0696.2022.09.07 Abstract ( )   PDF (5205KB) ( )   Driving distraction has a great impact on the drivers perception of the road environment. In order to analyze the impact of different distraction states on the the visual perception characteristics of drivers on the prairie highway, 14 drivers were selected to carry out a driving simulation test in a typical prairie highway driving scene. And the I view X HED eye tracker was used to collect drivers gaze and saccade data under three states, which included normal driving, cognitive distraction (hands-free voice) and compound distraction (receiving and sending mobile phone information). The gaze transfer theory, entropy theory and statistical methods were used to compare and analyze the typical visual characteristics indexes such as gaze duration, saccade frequency, gaze transfer probability and gaze entropy of drivers under normal driving and two different distracted states. Andrews curve was used to reduce dimension to visualize the difference of visual characteristics in different states. The data analysis results show that the average gaze duration of cognitive distraction is significantly longer than that of normal driving, while that of compound distraction is significantly shorter than that of normal driving; the saccade frequency is the highest in compound distraction and the lowest in cognitive distraction. Compared with the normal driving state, the drivers gaze transfer in cognitive distraction is more distributed among the interest areas in front of the road, the transfer paths are concentrated, and the disorder of gaze point transfer is small. The drivers transfer probability between the vehicle and the front of the road increases significantly in compound distraction, and the gaze entropy also increases dramatically. It is indicated that the effect of compound distraction is greater in terms of perceptual characteristics. References | Related Articles | Metrics

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Speed Optimization of Multiple Ships Based on Ice Condition of Arctic Route during Navigation Period MIN Dequan, JIANG Kejian, LIU Ru 2022, 41(09): 55-62.  DOI: 10.3969/j.issn.1674-0696.2022.09.08 Abstract ( )   PDF (1520KB) ( )   Aiming at the problem of ship speed optimization in the arctic route, a multi-objective mixed integer speed optimization model was established based on the ice data during the navigation period and the ship resistance model. With linear weighting and discretization methods, the established model was transformed and split by single target. Combined with the segment division and the calculation examples of various ships, the MATLAB software was used to solve the proposed model, and the optimal speed under the minimum target of ship operation cost and ship operation time was obtained. In the set ice segment, the maximum reduction of the average speed of the four example ships were up to 14.53%, 14.12%, 11.41% and 13.67%. References | Related Articles | Metrics

Transportation Infrastructure Engineering

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Mainstream Line Characteristics of Spur Dike Reach Based on Typical Flood Process WANG Pingyi1,2, ZHANG Fan1,3, MOU Ping1 2022, 41(09): 63-69.  DOI: 10.3969/j.issn.1674-0696.2022.09.09 Abstract ( )   PDF (1919KB) ( )   In order to explore the comprehensive influence of spur dike construction and naturally unsteady incoming flow on the main streamline of the channel, the unsteady flow two-dimensional shallow water model was used to calculate the flow field distribution of the regulation reach of a single spur dike in the upper reaches of the Yangtze River during a typical flood process. And the characteristics of the mainstream line of the reach and its impact on navigation safety were analyzed. The spatial and temporal variation characteristics of the mainstream were defined and calculated. The research shows that the mainstream line of the spur dike regulation reach has significant characteristics of zoning along the way, and it is recommended to divide the reach along the flow direction into 6 characteristic intervals with the dam axis as the boundary. The mainstream line in the near area behind the dam is the most tortuous and unstable (the tortuous degree is severe, the wandering swing degree is drastic, and the maximum swing amplitude reaches 30% of the river width). A stable deflection of nearly 40° from the opposite bank to the bank where the dam is located occurs in the reach near the dam axis, which affects navigation safety. At a distance of 8.4 times the dam length at the upstream and 23.6 times the dam length at the downstream from the dam axis, the mainstream line is straight and stable, which does not affect the navigation safety during the flood. References | Related Articles | Metrics

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Optimization of Cable Force of a Tied Arch Bridge Based on Improved Particle Swarm Optimization YANG Yaxun , ZHANG Yuhang, CHAI Wenhao, WU Fuyong 2022, 41(09): 70-75.  DOI: 10.3969/j.issn.1674-0696.2022.09.10 Abstract ( )   PDF (3380KB) ( )   In order to determine the reasonable cable force of tied arch bridge, the improvement and optimization of the algorithm was realized by improving the inertia weight of particle swarm intelligence optimization algorithm. The objective function of the cable was obtained by combining the optimization objective with the influence matrix principle. Then, the proposed algorithm was combined with the objective function by using the finite element and numerical analysis software to realize the automatic adjustment of the suspender and cable forces, which achieved the purpose of reasonable stress and uniform linear shape of the completed state of the arch bridge. The optimization results show that applying the improved particle swarm optimization algorithm to solve the cable force of tied arch bridge can achieve the effect of fast convergence, reasonable cable force and error within the allowable range. The proposed method provides an efficient solution scheme for cable force calculation in practical construction control. References | Related Articles | Metrics

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Comparative Study on Mechanical Performances of Multi-layer Structure Wire Rope Strands of Different Laying Types CHEN Yuanpei1, QIN Wei2, HE Yituan1 2022, 41(09): 76-84.  DOI: 10.3969/j.issn.1674-0696.2022.09.11 Abstract ( )   PDF (9150KB) ( )   In order to explore the influence rule of laying types on the service performance of the multi-layer structure wire rope strands, the mechanical properties of the cross-twisted and co-direction twisted multi-layer structure wire rope strands were comparatively analyzed. Firstly, the parametric equations of the cross-twisted and co-direction twisted multi-layer structure wire rope strands were derived, and the geometric models of the two kinds of strands were established. Furtherly, with the consideration of the factors such as the laying types, the elasto-plasticity of the steel wires and the interwire frictional contact, the overall and local performances of the strands subjected to an axial tension were compared and analyzed through finite element simulation. The results show that the axial force and von Mises stress of the cross-twisted and co-direction twisted strands subjected to the same axial tensile strain are close to each other, and both of them have the nonlinear behavior. The plastic deformation of the cross-twisted strand is larger than that of the co-direction twisted strand. The stress distribution of the two is generally uniform. The stress of the cross-twisted strand is concentrated on the contact part between the inner helical layer and outer helical layer, while that of the co-direction twisted strand is concentrated between the core layer and inner helical layer. Compared with the co-direction twisted strand, the cross-twisted strand has a better anti-rotation property and less stress concentration. References | Related Articles | Metrics

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Applicability of 2D Arc Consistent Viscoelastic Boundary Element YE Dan1,2, ZHOU Jianting1, YIN Shangzhi3 2022, 41(09): 85-90.  DOI: 10.3969/j.issn.1674-0696.2022.09.12 Abstract ( )   PDF (1717KB) ( )   Based on the viscoelastic artificial boundary element theory, the traditional straight artificial boundary was changed, and a new idea of using 2D arc consistent viscoelastic boundary element to simulate the artificial boundary of semi-infinite domain was proposed. Through case study, the establishment idea and the specific process set in the finite element software were introduced in detail, and the reliability of the 2D arc consistent viscoelastic boundary element model was checked. Meanwhile, the effects of the input source frequency domain, the elastic constants of the medium and the thickness of the element on the calculation results were discussed in depth, and the application range of the 2D arc consistent viscoelastic boundary element was given. The results show that the proposed element has better accuracy and stability than the common viscoelastic boundary element, which is simpler to use. References | Related Articles | Metrics

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Burgers Model with Elastic Limit LIU Ke 2022, 41(09): 91-96.  DOI: 10.3969/j.issn.1674-0696.2022.09.13 Abstract ( )   PDF (2189KB) ( )   In order to study the plastic deformation accumulation of asphalt mixture, Burgers model was used to fit the creep process of gussasphalt at 60 ℃. However, the plastic viscous deformation rate calculated by the inversion parameters was always greater than the measured total deformation rate, and the calculated residual strain was far less than the measured value. Although the defect of residual strain was overcome by using the improved model with instantaneous plastic strain, the deformation rate still had a large deviation, which made the subsequent loading and unloading process incalculable. In view of the above problems, a new Burgers model with elastic limit σe was constructed. The new model and Burgers model were identical equation. But the instantaneous deformation was separated into elastic terms and plastic terms through σe, and viscoelastic deformation in Burgers model was separated into viscoelastic terms and viscoplastic terms. The proportion of the two separations was the same, and the stress-strain relationship in plastic and elastic stages was the same. The physical mechanism of the viscoplastic term added in the new model was the plastic dislocation and rotation of meso-components. In the subsequent loading, due to the material hardening, the load was equal to σe. The Burgers model with σe as the load was obtained by the term elimination of the new model. The fitting results show that the new model not only solves the deformation rate problem of the improved model with instantaneous plastic strain, but also can accurately calculate the subsequent loading and unloading process, which provides a tool for the calculation of plastic cumulative deformation of asphalt mixture. References | Related Articles | Metrics

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Moving Single Camera BSV and Its Application in Structural Surface Crack Measurement MA Hua, LIANG Yixing, YANG Guang 2022, 41(09): 97-101.  DOI: 10.3969/j.issn.1674-0696.2022.09.14 Abstract ( )   PDF (3580KB) ( )   In order to improve the flexibility and convenience of the measurement of structure surface cracks, a measurement method based on binocular stereo vision with single moving camera was proposed. Firstly, when the precise internal parameters of the camera were known, the images of the cracks were collected from two perspectives respectively. Then, the motion estimation of the camera was performed according to the acquired images, so as to solve the motion parameters of the two positions before and after the camera. Furtherly, crack edge detection based on Canny algorithm was carried out. Finally, the binocular stereo vision model for crack measurement was established according to the internal parameters of the camera, the motion parameters and the edge information of the crack image. The measurement test results show that within the measuring distance of 2m, the relative measuring error of the crack is less than 5%, which can effectively verify the measuring accuracy of the proposed measuring method. References | Related Articles | Metrics

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A Fast Test and Evaluation Method for Spatial Distribution of Moisture Field of Highway Subgrade YUAN Ganglie, CHE Ailan 2022, 41(09): 102-109.  DOI: 10.3969/j.issn.1674-0696.2022.09.15 Abstract ( )   PDF (11160KB) ( )   In order to evaluate the spatial distribution of moisture field of subgrade soil, a fast test and evaluation method of spatial distribution of moisture field of highway subgrade based on vibration test and electrical measurement was studied. A section of subgrade of an expressway under construction in a rainy and humid area was selected as an equal scale test subgrade model. The moisture field of the subgrade was changed by the water injection system. Three subgrade models Ⅰ, Ⅱ and Ⅲ were designed, and the designed moisture content was 17%, 19% and 20% respectively. 4 kinds of methods such as vibration test, temperature and humidity sensor test, high-density surface wave test and electrical measurement were used for testing respectively. The test indicators included moisture content of subgrade soil ω, elastic wave amplitude A, shear wave velocity Vshear and apparent resistivity ρs. The attenuation rate and resistivity distribution of elastic wave vibration were analyzed, and the spatial distribution of subgrade moisture field was evaluated. The apparent resistivity measured by the electrical measurement was converted into water content ωρ, which was compared with the moisture content ωsensor measured by the temperature and humidity sensor. The results show that as the moisture content of the subgrade increases from 17% to 20%, the vibration attenuation rate of subgrade increases by 20%~30%, and the shear wave velocity decreases by 16%, which verifies that the vibration test can quickly evaluate the change of subgrade moisture field; and the absolute value of relative error of moisture content ωρ converted by electrical measurement method and ωsensor converted by the temperature and humidity sensor test, is in the range of 1%~3%, which verifies that the electrical measurement method can accurately evaluate the spatial distribution of subgrade moisture field. References | Related Articles | Metrics

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Research and Judgment of Asphalt Regeneration Performance Based on Routine, Fatigue and Healing-Fatigue Tests CHEN Long1, CHEN Hongbin2, HE Zhaoyi3, LI Peng1, WANG Xiaodong4 2022, 41(09): 110-118.  DOI: 10.3969/j.issn.1674-0696.2022.09.16 Abstract ( )   PDF (3817KB) ( )   To master the regeneration performance of reclaimed asphalt adequately, the conventional mechanics properties test, fatigue properties test and fatigue-healing-fatigue properties test were carried out respectively, and the waste matrix asphalt and waste SBS modified asphalt with different aging degree were evaluated by adding 4%~12% regenerant. And the regeneration laws of different evaluation methods and their characteristic indexes were compared and discussed. The results show that when the amount of rejuvenation agent is increased by 2%, each conventional mechanical performance indes of reclaimed matrix asphalt and SBS modified asphalt is restored gradually by linear equation or polynomial function, while the complex shear modulus G* and fatigue life Nf are attenuated by equal range, and the healing index HI is increased by 10%~30% remarkably. Moreover, the improvement effect of rejuvenation agent on waste matrix asphalt and long-term aging asphalt are significantly higher than that of waste SBS modified asphalt and short-term aging asphalt, and the change rule of each behavior result under the stress control mode is clearer than that under the strain control mode. Taking the original asphalt as the performance recovery benchmark, when the fatigue performance test is used for evaluation, the amount of rejuvenation agent required is the most, which is 12% or more. When the conventional mechanics test is used for evaluation, the amount of rejuvenation agent required is the modest, which is 10%~12% or more, and the lower limit value is taken when the high temperature performance indexes are used. When the fatigue-healing-fatigue performance test is used for evaluation, the amount of rejuvenation agent required is the least, which is usually in the range of 8%~12%. It is recommended to apply the fatigue-healing-fatigue test and healing index HI instead of the fatigue test and complex shear modulus G* and fatigue life Nf to judge the recovery of rheological mechanical properties of reclaimed asphalt. References | Related Articles | Metrics

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Influence of High Cold and Large Temperature Difference on Performance of Asphalt and Asphalt Mixture CAO Haibo1, 2, WANG Shuangjie1, 2, ZHU Hongzhou1 2022, 41(09): 119-124.  DOI: 10.3969/j.issn.1674-0696.2022.09.17 Abstract ( )   PDF (754KB) ( )   Through indoor simulation of high-cold and large temperature difference conditions, the changes of asphalt performance under high-cold and large temperature difference conditions were studied by using asphalt penetration, softening point, ductility, bending creep stiffness and dynamic shear rheology tests. The results show that the variation range of each index of asphalt is small, and the influence of high-cold and large temperature difference conditions on the performance of asphalt is small. The performance change of asphalt mixture under high-cold and large temperature difference conditions was studied by using TSRST, low-temperature bending and freeze-thaw splitting tests. The results show that the condition of high-cold and large temperature difference has a great influence on the low temperature performance of asphalt mixture. The type of asphalt and asphalt mixture has a significant influence on the performance of asphalt mixture under high-cold and large temperature difference conditions, among which the modified asphalt is better than the matrix asphalt, and SMA asphalt mixture is better than AC asphalt mixture. References | Related Articles | Metrics

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Molding Temperature of Asphalt Mixture Based on Volume Parameters and Road Performance FENG Zhengang1, JIAO Xiaolai1, WANG Shujuan2, ZHANG Jian3, YAO Dongdong2 2022, 41(09): 125-131.  DOI: 10.3969/j.issn.1674-0696.2022.09.18 Abstract ( )   PDF (953KB) ( )   The mix ratio of two kinds of asphalt mixtures (AC-20 and SMA-13) was designed through the Marshall test. The specimens for rutting and Marshall test of the two kinds of asphalt mixtures were prepared at five different temperatures (130 ℃, 140 ℃, 150 ℃, 160 ℃ and 170 ℃). The influence of the molding temperature on different volume parameters and pavement performance of the two asphalt mixtures was evaluated. The results show that with the increase of molding temperature, the void ratio and voids in mineral aggregate of the asphalt mixture gradually decrease, while the bulk density and asphalt saturation gradually increase; the high temperature stability gradually increases, while the low temperature cracking resistance and the water stability tend to increase first and then decrease. Based on the variation law of volume parameters and road performance of asphalt mixture changing with forming temperature, it is recommended that the molding temperature of AC-20 should not be higher than 140 ℃, and the molding temperature of SMA-13 should not be higher than 150 ℃. References | Related Articles | Metrics

Transportation Equipment

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Research Progress and Prospect of Switching Human-Machine Driving of Intelligent Vehicle ZHANG Lingyu1, WANG Li1, ZHANG Lili2, ZHANG Xiao3, SUN Dehui1 2022, 41(09): 132-141.  DOI: 10.3969/j.issn.1674-0696.2022.09.19 Abstract ( )   PDF (3468KB) ( )   The transition stage from manual driving to autonomous driving in human-machine driving will exist for a long time and become one of the difficulties that need to be broken through in the development of intelligent vehicles. In order to further study human-machine driving, the definition, classification and research methods of human-machine driving at home and abroad was combed. The existing problems of vehicle in single vehicle intelligent human-machine driving was summarized, and the solution was put forward. It was shown that the main problems at the perception and decision levels were the limited range of environmental perception and the local optimization of decision results. Then, in view of the rise of vehicle infrastructure cooperative technology in recent years, based on the idea of technology change that broke the limitation of single point thinking with systematic thinking, the new method brought by the idea for the enhancement of the perception of human-machine driving vehicles and the collaborative decision-making of driving modes was analyzed. Finally, according to the participation degree of “human-vehicle-road-cloud” traffic elements, the development stages of human-machine driving were divided; meanwhile, a preliminary solution to the problems existing in the current research on human-machine driving of intelligent vehicles was proposed. References | Related Articles | Metrics

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Numerical Simulation of Temperature Field and Residual Stress in Flat Plate Butt Welding CUI Huwei, FAN Kaijing 2022, 41(09): 142-148.  DOI: 10.3969/j.issn.1674-0696.2022.09.20 Abstract ( )   PDF (4390KB) ( )   In order to analyze the influence of welding process parameters on the distribution of temperature and stress after butt welding of flat plate, the moving loading of Gaussian heat source was realized by using the function loading function of ANSYS on the basis of thermoelastic-plastic finite element method. Furthermore, the influence of welding parameters such as welding current, effective arc heating radius and welding speed on the temperature field and residual stress field of flat plate butt welding was analyzed by ANSYS finite element software. The research results show that the peak value of temperature field decreases with the increase of welding speed and increases with the increase of effective arc heating radius and welding current. The peak value of residual stress along the weld joint increases with the increase of welding speed, effective arc heating radius and welding current. References | Related Articles | Metrics

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Multi-objective Optimization of Composite Thermal Management System of Lithium-ion Battery ZHANG Furen1, YI Mengfei1, WANG Pengwei2, ZHANG Lin1, LI Shiyuan1 2022, 41(09): 149-156.  DOI: 10.3969/j.issn.1674-0696.2022.09.21 Abstract ( )   PDF (5805KB) ( )   In order to alleviate the serious heat accumulation during rapid charge and discharge of lithium-ion battery pack, the advantages of traditional U-type and Z-type parallel air-cooled battery thermal management system (BTMS) were integrated, and a new I-type BTMS(I-BTMS) was proposed. Firstly, the charge and discharge experiments of square lithium-ion battery were carried out and the temperature rise characteristics at different rates were studied to obtain thermophysical parameters, which was verified with the results of the computational fluid dynamics (CFD) model of the battery. Then, based on the verified CFD method, it was found that the cooling efficiency of I-BTMS was higher than that of U-BTM and Z-BTMS under the same boundary conditions. Finally, the initial I-BTMS was optimized by air-liquid composite cooling mode with the addition of air duct partition and mini-channel liquid cooling plate. The design points obtained by the optimal Latin hypercube sampling were numerically calculated by combining CFD method with multi-objective optimization, and based on NSGA-Ⅱ genetic algorithm, the cooling performance of the system was optimized by multiple objectives. The optimal solution of iterative convergence shows that the maximum temperature and maximum temperature difference of the battery pack are reduced by 9.08% and 70.19%, respectively, compared with the initial I-BTMS. References | Related Articles | Metrics