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17 September 2021, Volume 40 Issue 09 Previous Issue   
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Transport+Big Data and Artificial Intelligence
Transportation Infrastructure Engineering
Transportation Equipment


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Transport+Big Data and Artificial Intelligence

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Flight Schedule Optimization in Multi-airport System Based on Particle Swarm Optimization Algorithm ZHU Jinfu1, MA Ruixin1,2, PENG Anna1, YAN Chen1 2021, 40(09): 1-8.  DOI: 10.3969/j.issn.1674-0696.2021.09.01 Abstract ( )   PDF (691KB) ( )   In view of the general problems of unbalanced development of China’s multi-airport system and high degree of homogenization of routes, a flight schedule optimization model was established to maximize the flight punctuality rate, airline market share, passenger loss time and flight function positioning index, and the flights with poor operation effect of the first level international hub airport were allocated to the surrounding airports. Under the conditions of meeting the takeoff and landing capacity constraints, flight uniqueness and flight continuity of each airport in the multi-airport system, an improved particle swarm optimization algorithm was designed to solve the problem. The flight schedule of Yangtze River Delta multi-airport system was taken as an example to verify. The research shows that the proposed model can effectively adjust the inefficient flights of the hub airport to the surrounding airports, which makes the flight distribution of each airport in the multi-airport system more balanced and effectively controls the change trend of flight sorties in each period, and the optimization effect is significant. References | Related Articles | Metrics

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Path Planning of UAV Based on Hybrid Ant Colony Algorithm under Greedy Strategy CAO Jianqiu, XU Peng,ZHANG Guangyan 2021, 40(09): 9-16.  DOI: 10.3969/j.issn.1674-0696.2021.09.02 Abstract ( )   PDF (1546KB) ( )   An improved ant-colony algorithm was proposed to correct the navigation error in the path planning of UAVs under complex environments. Based on ant colony algorithm, firstly, the fitness of particle swarm optimization algorithm was introduced into pheromone update as heuristic value in the proposed algorithm, which improved the original pheromone updating model. Besides, a greedy strategy was used to carry out pruning operations when selecting the correction points, which optimized the selection strategy of the algorithm. Finally, the A* algorithm was used to replace the random initialization process of the original algorithm, which modified the update method of pheromone and optimized the quality of the generated paths. For the planned path, the Dubins curve was used to smooth the track. The smoothed track could not only meet the track constraints, but also meet the performance constraints of the aircraft. The research results show that: in parameter setting, when the number of ant colony is large, setting smaller heuristic constant can get better results. A* algorithm is used to initialize the greedy ant colony algorithm, which can effectively accelerate the convergence speed of ant colony algorithm and improve the quality of solution. Experiments show that the improved algorithm reduces the track length by about 6% and the time by about 25%. References | Related Articles | Metrics

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Robot Path Planning Based on the Improved Sine Cosine Algorithm MA Yingying1, DU Nuannan2 2021, 40(09): 17-23.  DOI: 10.3969/j.issn.1674-0696.2021.09.03 Abstract ( )   PDF (1485KB) ( )   Aiming at the defects of low performance and poor accuracy of basic sine cosine algorithm (SCA), a hybrid sine cosine algorithm (HSCA) was designed and applied to the robot path planning problem (RPP). Firstly, HSCA combined the initial solution construction method based on opposition-based learning method. Meanwhile, meme grouping and the evolutionary mechanism of TLBO (teaching-learning-based optimization) were integrated by HSCA to strengthen the information exchange of subsequent solutions, which strived to enhance search performance. Aiming at RPP problem, the spline interpolation method was introduced by HSCA in the path curve planning process to ensure the solution accuracy and reduce the optimization dimension of the current problem. Finally, function optimization and path planning tests were carried out. The experiment results show that HSCA has better performance than the comparison algorithm. References | Related Articles | Metrics

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Simulation Study of Ship Overtaking Process Based on Hexagonal Cellular Automata FU Yuhui,MA Pengsen 2021, 40(09): 24-29.  DOI: 10.3969/j.issn.1674-0696.2021.09.04 Abstract ( )   PDF (3421KB) ( )   Based on the analysis and comparison of the existing ship traffic flow models based on cellular automata, a ship overtaking model based on regular hexagonal cellular automata was proposed, referring to the pedestrian evacuation model and road traffic flow model based on regular hexagonal cellular automata. In the proposed model, the ship motion space was divided into regular hexagon cells with appropriate size according to the actual situation, and each ship had seven motion directions including stationary. The approximate integer ratio of the ship speed was taken as the cell moving speed, and the update rules were formulated based on the ship dangerous field, ship field and moving boundary. And the ship overtaking process in open waters and restricted waters was simulated by MATLAB. The research results show that: compared with the restricted waters, ships in open waters have larger overtaking distance and transverse distance and longer time. The proposed model can truly reflect the actual ship overtaking process, and can play a certain reference role for the real ship overtaking and evaluation of route planning. References | Related Articles | Metrics

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The Impact of Government Behavior on Port Co-competition under Game Model LIU Cuilian, HUANG Yuming 2021, 40(09): 30-35.  DOI: 10.3969/j.issn.1674-0696.2021.09.05 Abstract ( )   PDF (537KB) ( )   The port is the node that provides cargo reloading and displacement services, undertaking a large number of cargo circulation operations. It is an important direction in the future to study the co-competition relationship between ports in order to realize the healthy development of port enterprises. There are many factors affecting the relationship between ports. By introducing the role of government, the game model between government and port enterprises was established by using evolutionary game theory, and the interaction between government and port was analyzed. MATLAB software was used for simulation experiment. The research shows that the direction of evolution is mainly related to the government revenue and the rectification cost of port enterprises. By controlling these two parameters, the co-competition relationship of port market can be adjusted. References | Related Articles | Metrics

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Transportation Service Procurement Mechanism Based on Reverse Multi-Attribute Online Auction WANG Yajuan1,2, LI Min1, SHAO Yuan3 2021, 40(09): 36-42.  DOI: 10.3969/j.issn.1674-0696.2021.09.06 Abstract ( )   PDF (444KB) ( )   In view of the low efficiency of transportation service procurement, which couldnt meet the needs of the carrier’s real-time transportation, the online auction method was used to study the transportation service procurement mechanism based on the multi-attribute requirements such as transportation time and service quality. The mechanism model with the goal of maximizing social welfare was established, and then the reverse multi-attribute online auction transportation service procurement mechanism was designed. The research results show that the proposed mechanism not only can realize the immediate decision-making of the shipper, allow the carrier to obtain transportation services at any time and improve transaction efficiency, but also can attract the carrier to participate in the auction voluntarily and encourage the carrier to disclose the real transportation cost, transportation time, service quality, arrival and departure time, which help to realize the fair and effective distribution of transportation services. Finally, an example is given to demonstrate the application of the proposed mechanism in practice. The proposed mechanism can provide theoretical basis, method guidance and technical support for the practice of transportation service procurement. References | Related Articles | Metrics

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Range of Inner Wheel Deviation Effect in Right Turn of Buse LI Yingshuai1, YAN Qiruo1, ZHAO Cong2 2021, 40(09): 43-48.  DOI: 10.3969/j.issn.1674-0696.2021.09.07 Abstract ( )   PDF (1664KB) ( )   Aiming at the malignant accidents caused by the difference in the inner wheels of large vehicles when turning right, mathematical modeling methods were used to investigate the actual situation of right-turning at bus intersections in Nanjing, and three theoretical models gradually tending to be more practical were established. The three theoretical models were analyzed and calculated, and different functions were used to express the trajectory of the inner front wheel and the inner rear wheel. And then the three no-stop areas of the inner wheel difference of the bus were obtained. Taking a certain intersection in Nanjing as a case study for analysis, the range of no-stop areas of three models is given: ①Model 1, 2 and 3 no-parking overlapping area, that is, the 1.0m crescent-shaped area at the widest point, is an absolutely prohibited area; ②Model 1 and 2 no-parking overlapping area, that is, the 1.7m crescent-shaped area at the widest point, is a relatively dangerous area. When driving in, close attention to the turning vehicle condition should be paid; ③Model 3 no-parking area, that is, the 2.5m crescent-shaped area at the widest point, is the place where road users should pay more attention and should not drive into the above area when there is a bus turning. The research results can provide a reference for the delineation of no-parking areas for non-motorized vehicles and pedestrians at intersections with different risk levels, so as to reduce the number of bus accidents at intersections and improve the safety and passing rate of buses at intersections and the reliability of road traffic facilities. References | Related Articles | Metrics

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Method for Determining Critical Speed of Curve-Slope Combination Section Based on Trucksim YAN Ying1, LIU Ge1, TIAN Min1, LIU Jiale1, MU Yan2 2021, 40(09): 49-54.  DOI: 10.3969/j.issn.1674-0696.2021.09.08 Abstract ( )   PDF (3162KB) ( )   In order to explore the relationship between different combinations of curve and slope and the critical vehicle speed when the vehicle was unstable, the 6-axis articulated train was selected as the experimental model. And a human-vehicle-road coupling system was established by the Trucksim software to carry out the vehicle instability simulation experiment under different curve-slope combinations. Based on the principle of least square, the critical speed prediction model of the curve-slope section was established by the fitting and regression analysis of the simulation results. Finally, the rationality of the proposed model was verified under a certain working condition. The results show that the critical speed predicted by the proposed model is close to that predicted by Lusetti model, and the calculation error is the smallest under a certain working condition. This study provides a safe and effective method for predicting the critical speed of vehicles in curved slope sections. References | Related Articles | Metrics

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Validity of Driving Simulation of Mandatory Lane-Changing Behavior during Highway Reconstruction and Expansion Period SUN Zhi1, ZHANG Yanning2, MENG Lingxiao1, LIU Xueqiang3 2021, 40(09): 55-59.  DOI: 10.3969/j.issn.1674-0696.2021.09.09 Abstract ( )   PDF (1442KB) ( )   In order to verify the validity of the driving simulation technology in the analysis of mandatory lane-changing behavior during highway reconstruction and expansion period, two kinds of experiments, field experiment and driving simulation, were carried out. Firstly, the speed and position information of vehicles were collected, and the behavior indexes such as the spot speed v, spot spacing Δd, and headway Δt were calculated; and then, non-parametric statistical testing method and regression model method were used to test the absolute and relative validity of each behavior index respectively. The results show that the driving simulation technology can be validly applied to analyze the mandatory lane-changing behavior in highway reconstruction and expansion period. The spot speed at the start of the mandatory lane-changing, the spot spacing and headway between the line-crossing spot and the beginning of construction section, and the spot spacing and headway between the end spot of lane-changing and the beginning of construction section show that drivers have more aggressive driving behaviors in driving simulation environment. References | Related Articles | Metrics

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Visual Characteristics of Colored Pavement at Entrance and Exit of Expressway Tunnel YUAN Jingyu, LIU Xiaojian, YAO Sheng, GAO Yuan, ZHANG Zhitao, WANG Zhide 2021, 40(09): 60-67.  DOI: 10.3969/j.issn.1674-0696.2021.09.10 Abstract ( )   PDF (7189KB) ( )   Laying colored pavement in expressway tunnel is considered to be one of the favorable measures to improve road traffic safety. In order to obtain a more reasonable color pavement design scheme and improve the driver’s driving attention, the method of virtual driving experiment was adopted. Red and yellow were selected as the color of the colored pavement to form a control group with the original pavement. Meanwhile, SketchUp and Lumion software were used to establish models and test videos that met the actual engineering requirements. Furthermore, the subjects’ fixation map, locus of fixation points and change characteristics of pupil area during the simulated driving were studied. The results show that laying colored pavement at the entrance and exit of the tunnel helps to improve the driver’s attention when driving. There are differences in drivers’ visual characteristics between the approaching segment and the exit segment of the colored pavement. After the yellow pavement is laid in the approaching segment of the tunnel, the drivers’ viewpoints are more concentrated than those on the red pavement, and the difference in the exit section is relatively smaller, in which the concentration of the red pavement is slightly higher. References | Related Articles | Metrics

Transportation Infrastructure Engineering

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Dynamic Change Assessment of Ecosystem Services within Ecological Conservation Redline of Chongqing GUAN Dongjie, HUANG Danan, YIN Boling 2021, 40(09): 68-77.  DOI: 10.3969/j.issn.1674-0696.2021.09.11 Abstract ( )   PDF (10639KB) ( )   The integrate valuation of ecosystem services and tradeoffs (InVEST) model was used to calculate three ecosystem services respectively, such as the carbon storage, water supply and soil conservation of ecological conservation redline of Chongqing from 2015 to 2018. The results show that: ①The carbon storage in ecological conservation redline area of Chongqing is increased from 2015 to 2018, which is slightly from 6.8×107 t in 2015 to 7.1×107 t in 2018, with a change rate of 3.54%. ②The water supply is decreased slightly from 2015 to 2018, which is from 2.8×1010 mm in 2015 to 2.6×1010 mm in 2018, with a change rate of -7.70%. ③The soil conservation is decreased from 2015 to 2018, which is rapidly from 9.7×1010 t in 2015 to 7.8×1010 t in 2018, with a change rate of -19.74%. ④The comprehensive ecosystem service function of the study area is reduced. The comprehensive evaluation score of ecosystem service of ecological conservation redline in 2015 is 6.02 and that in 2018 is 5.57. References | Related Articles | Metrics

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Calculation and Analysis of the Influence of Foundation Pit Excavation on the Deformation of the Underlying Shield Tunnel XU Guoyuan, HUANG Siyuan 2021, 40(09): 78-85.  DOI: 10.3969/j.issn.1674-0696.2021.09.12 Abstract ( )   PDF (2630KB) ( )   In view of the influence of rectangular foundation pit excavation on the deformation of underlying tunnel, based on Mindlin’s classical solution, the formula to calculate the additional stress at the tunnel due to the excavation of foundation pits was derived, considering the influence of the residual stress at the bottom of the pit and the effect of the retaining pile. For the shield tunnel with buried depth more than 1.5 times the outer diameter of the tunnel, a spring layer was added onto the upper part of Pasternak model to consider the constraint of the overlying soil layer on the tunnel, and the deflection differential equation of foundation beam was established. The finite difference method was used to discretize the tunnel into independent node elements, so as to solve the longitudinal vertical displacement and horizontal displacement of the tunnel. Finally, it was compared with the tunnel deformation data obtained by finite element numerical simulation and engineering measurement. The research shows that: when the interaction between deeply-buried shield tunnel and soil is considered, compared with Pasternak model method, the proposed method can better reflect the real mechanical behavior between the two, and the obtained analytical solution is closer to the numerical solution, and its agreement with the measured value is also higher, which proves the rationality and superiority of the proposed method. In addition, the proposed method saves a lot of modeling work and can be used to preliminarily evaluate the influence of excavation of foundation pits on the longitudinal deformation of the underlying shield tunnel in the design. References | Related Articles | Metrics

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Protective Measures of Concealed Excavation of Metro Tunnel Crossing underneath High-Speed Railway Tunnel ZHOU Dingheng1, TIAN Xuejuan1, LI Changan1, MA Yongfeng2, LANG Yao1 2021, 40(09): 86-91.  DOI: 10.3969/j.issn.1674-0696.2021.09.13 Abstract ( )   PDF (3475KB) ( )   Taking interval tunnel from Dazhongsi station to Jimenqiao station of Beijing metro line 12 crossing underneath Jingzhang high-speed railway tunnel as the engineering background, the three-dimensional finite element numerical simulation of underground tunnel passing through Jingzhang tunnel was established, based on the protection design of high-speed railway tunnel. The variation characteristics of vertical displacement and transverse displacement of Jingzhang tunnel changing with construction steps were summarized. Through site monitoring, the results of the concealed excavation tunnel vault settlement and structural convergence were analyzed. Besides, the vertical displacement, lateral displacement, structural convergence and automatic monitoring results of Jingzhang tunnel were also analyzed in detail. The research results show that: firstly, the vertical displacement process of Jingzhang tunnel can be summarized as a two-stage “S” curve; secondly, the area within the front 16 m and the back 14 m of the center of Jingzhang tunnel is the area significantly affected by the crossing construction; thirdly, the vertical displacement of Jingzhang tunnel caused by the construction of the advanced and post tunnels accounts for 68.3% and 31.7% of the total vertical displacement respectively, and the construction of the advanced tunnel is the key stage of railway tunnel protection. Numerical calculation and field monitoring show that the spatial position change of the vertical displacement of the railway tunnel is obviously affected by the post construction tunnel. The transverse uneven settlement of Jingzhang tunnel is obvious, with the maximum value 1.267mm. Based on the field monitoring results, the relevant displacement of the underground tunnel and Jingzhang tunnel does not exceed 44% of the allowable value. It can be considered that the design parameters and construction protection scheme of the underground tunnel meet the protection requirements of railway tunnel. References | Related Articles | Metrics

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Sensitivity Analysis of Stability Influential Factors of New Assembled Retaining Wall WU Guoyin1, WANG Kui1, YI Pengying2, LI Ke2 2021, 40(09): 92-100.  DOI: 10.3969/j.issn.1674-0696.2021.09.14 Abstract ( )   PDF (3661KB) ( )   Compared with the traditional gravity retaining wall, the new assembled retaining wall has the advantages such as small self-weight, low requirements for foundation bearing capacity, strong adaptability, saving materials and short construction time, and can achieve the purposes of energy saving, water saving, material saving and environmental protection. It is an important direction of retaining wall design and research. Compared with the traditional gravity retaining wall, the deformation and stability problems caused by the reduction of wall self-weight and the splicing of assembly structure needed to be considered more. Therefore, the stability of assembled retaining wall was focused and discussed. Firstly, based on the study of the stability of the traditional gravity retaining wall, the inclined wall back retaining wall was taken as an example, and the relevant safety coefficients of the retaining wall were calculated according to the norm. And then the sensitivity analysis method was used to analyze the effects of the bulk density of the filler in the wall, the internal friction angle of the backfill and the inclination angle of the wall back on the stability of the new assembled retaining wall one by one. Finally, the influence degree of various factors on the stability of retaining wall was studied, and the main factors affecting the stability of retaining wall were found out. The problems that should be paid attention to in the design of the new type of assembly inclined wall back retaining wall are put forward, which provides a certain basis for the design of the new assembled retaining wall. References | Related Articles | Metrics

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Comparative Experimental Study on Frost Heave Deformation of Saturated Sandstone under Closed and Open Unidirectional Freezing Conditions XIA Caichu1,2, CHEN Tianhao1, LI Qiang3 2021, 40(09): 101-108.  DOI: 10.3969/j.issn.1674-0696.2021.09.15 Abstract ( )   PDF (1462KB) ( )   In order to study the law of frost heave deformation of tunnel surrounding rock in cold area in practical engineering, the comparative tests of frost heave deformation of saturated sandstone under closed and open unidirectional freezing conditions were carried out respectively. The law of frost heave deformation of saturated sandstone under different environmental conditions was studied and a comparative analysis was made. The test results show that the saturated sandstone presents uneven frost heave characteristics under closed and open unidirectional freezing conditions, and the change process of frost heave strain is the same in two groups of tests, but the frost heaving rate and strain value of each temperature gradient under closed condition are slightly higher than those under open condition. With the same temperature gradient, it is found that the uneven coefficient of frost heave under open condition is slightly smaller than that under closed condition, but the growth rate of uneven coefficient of frost heave with temperature gradient under open condition is faster than that under closed condition. The changes of temperature field in the two groups of tests are divided into three stages: rapid decline, slow decline and stability. The total deformation of the specimen in the freezing direction has three-stage characteristics. The first two stages of two groups of tests are similar, which are cold shrinkage and slow growth stages. But the third stage is rapid growth stage in the open condition, with a linear growth trend. In the closed condition, it enters the stable stage, and the deformation volume tends to be stable. Through the comparative test, it can be found that the specimen is in-situ frost heaving under the closed condition, and in-situ frost heaving first and then partial frost heaving due to the supplement of external water under the open condition. References | Related Articles | Metrics

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Performance of High Modulus Asphalt and Its Definition Standard ZHANG Zhengqi1, LU Chuan1, WANG Suqing1,2, LI Naiqiang3, LI Hongwei3 2021, 40(09): 109-116.  DOI: 10.3969/j.issn.1674-0696.2021.09.16 Abstract ( )   PDF (3142KB) ( )   In order to determine the definition standard of high modulus asphalt, three kinds of high modulus modifiers were selected to modify the base asphalt. The softening point, penetration, ductility, viscosity, complex shear modulus, rutting factor and PG grading index of the prepared high modulus modified asphalt were tested by conventional performance test and rheological performance test. And the dynamic modulus and dynamic stability parameters of asphalt concrete prepared from the three kinds of high modulus asphalt were tested by uniaxial compression test and rutting test. On this basis, the regularity, discrimination and consistency of various indexes were analyzed. Through the correlation analysis between the performance indexes of high modulus modified asphalt and the dynamic modulus of high modulus asphalt concrete, the definition standard of high modulus asphalt was established with complex shear modulus as the key index and penetration index system as the auxiliary index. It is suggested that the complex shear modulus of high modulus asphalt G* (60 C, 10 Hz, 0.1%) should be greater than 66.43 kPa, G* (60 ℃, 10 Hz, 12%) should be greater than 12.8 kpa and the softening point should be greater than 61.6 ℃. References | Related Articles | Metrics

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Performance of Ultra-High Content Rubber Modified Asphalt CAI Bin1, YU Gongxin2, LI Yanwei1, XUE Shanguang1 2021, 40(09): 117-123.  DOI: 10.3969/j.issn.1674-0696.2021.09.17 Abstract ( )   PDF (8387KB) ( )   In order to improve the content of rubber powder in rubber modified asphalt and increase the utilization ratio of waste rubber powder, aiming at the low content of rubber powder in rubber powder modified asphalt at present, the preparation process of rubber powder modified asphalt was optimized to prepare ultra-high content (40%) rubber powder modified asphalt. The basic properties and aging properties of ultra-high content rubber powder modified asphalt were studied by three indicators test, TFOT test and PAV test. Based on DSR test and BBR test, the PG grading performance of ultra-high content rubber powder modified asphalt was determined. The tensile test was used to evaluate the viscosity and toughness of ultra-high content rubber powder modified asphalt. TGA test, fluorescence microscopy test and SEM test were used to reveal the micro-properties of asphalt modified with ultra-high content rubber powder. The results show that the rotational viscosity of ultra-high content rubber powder modified asphalt is lower than 4.0 Pa·s at 180 ℃, and its low temperature crack resistance and aging resistance are better than those of conventional rubber powder modified asphalt. The high temperature rutting resistance of ultra-high content rubber powder modified asphalt decreases slightly, but its fatigue limit temperature is lower than that of conventional rubber powder modified asphalt, and its performance grade is determined to be PG 88-34. Flexibility of ultra-high content rubber powder modified asphalt accounts for 88.0% of the viscosity toughness, which is 2.1 times as much as that of conventional rubber powder modified asphalt. At 180 ℃, the thermal stability of asphalt modified with ultra-high rubber powder content is the best. On the basis of retaining a certain elastic core, the excess rubber powder is degraded into fine particles and dissolved in asphalt, which determines the good storage stability in macroscopic performance. References | Related Articles | Metrics

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Key Influencing Factors of Fatigue Performance of Asphalt Stabilized Macadam ZHU Hongzhou1，2, PAN Yue1, WANG Daqian1, HU Lanxin1, HE Zhaoyi2 2021, 40(09): 124-130.  DOI: 10.3969/j.issn.1674-0696.2021.09.18 Abstract ( )   PDF (2797KB) ( )   In order to determine the key factors affecting the fatigue performance of asphalt stabilized macadam base, based on two kinds of dense asphalt stabilized macadam mixtures such as ATB25 and ATB30, 9 types of aggregate gradation and 3 types of asphalt were selected, and 10 items of material test data of 13 kinds of mixture specimens were taken as the reference column; the k value and n value in the fatigue equation of asphalt stabilized macadam were taken as the comparison column. The grey entropy analysis that affected the fatigue performance of asphalt stabilized macadam was carried out. The influence degree of different parameters on the fatigue performance of asphalt stabilized macadam was obtained. Furtherly, on this basis, the statistical research method of correspondence analysis was used to unify the relevant conclusions. The research results show that asphalt saturation and asphalt aggregate ratio of asphalt mixture are the two key factors affecting the fatigue performance of asphalt macadam stabilized base. The asphalt saturation affects the asphalt volume percentage and the ratio of the mineral material gap, while the change of asphalt aggregate ratio will cause the change of asphalt saturation and asphalt film thickness, which will significantly affect the fatigue life of asphalt mixture. References | Related Articles | Metrics

Transportation Equipment

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Obstacle Avoidance Strategy for Mobile Robots in Dynamic Environment YU Tengwei1, LIU Changli2 2021, 40(09): 131-136.  DOI: 10.3969/j.issn.1674-0696.2021.09.19 Abstract ( )   PDF (1975KB) ( )   In recent years, the optimization algorithm proposed for the traditional artificial potential field (APF) method that was easy to fall into the local minimum problem still had the problems such as low applicability and low computational efficiency. Based on the shortcomings of some improved algorithms, a sampling-based rapidly exploring random tree (RRT) algorithm was innovatively introduced to pre-select a number of temporary target points on a static known map, which avoided the mobile robot from falling into the local minimum value area when the artificial potential field method was used. Meanwhile, the mobile robot carried out the obstacle avoidance strategy of real-time path planning in dynamic obstacle environment. Simulation test results show that the proposed method is simple and easy to implement; meanwhile, it combines the advantages of complete probability and good convergence of RRT algorithm with small calculation and high real-time performance of APF algorithm, which can adapt to the changes of dynamic environment and meet the requirements of dynamic obstacle avoidance of mobile robot. References | Related Articles | Metrics

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Intelligent Vehicle Path Planning Method Based on Steering Constraints in Complex Obstacle Environment JIANG Kang, WANG Hao, CHEN Jiajia 2021, 40(09): 137-144.  DOI: 10.3969/j.issn.1674-0696.2021.09.20 Abstract ( )   PDF (5059KB) ( )   Aiming at the problems of unsmooth, unsafe, and slow generation of the generated path in the traditional path planning algorithm, Bi-RRT was used to study the path planning algorithm in unmanned driving. Firstly, the vehicle’s own steering constraints was used to construct a node expansion space that met the vehicle kinematics requirements. Then, the target bias sampling strategy and two-way search were used to greatly improve the planning speed of the RRT algorithm. At the same time, the KD tree was used to define the nearest neighbor point in combination with the maximum curvature constraint. Finally, the generated path was pruned and subjected to safety collision detection and Bezier curve smoothing to make it more in line with the dynamic characteristics of the vehicle. The research results show that the improved Bi-RRT algorithm has a significant improvement in search speed and algorithm overhead, and the generated path is also smoother, which proves the effectiveness, practicability and adaptability of the proposed algorithm. References | Related Articles | Metrics

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Optimization Design of Penalty Function Particle Swarm Optimization Algorithm for Angular Contact Ball Bearings HU Qiguo1, DU Chunchao1, WU Mingqin1, YANG Xuejiao1, CAO Lijie2 2021, 40(09): 145-150.  DOI: 10.3969/j.issn.1674-0696.2021.09.21 Abstract ( )   PDF (970KB) ( )   In order to improve the performance of angular contact ball bearings, a multi-objective optimization model of double-row angular contact ball bearing structure was established with the rated dynamic load and rated static load of double-row angular contact ball bearings as the optimization target. Aiming at the defects that ordinary particle swarm algorithm was easy to fall into local optimum and couldn’t effectively solve the optimization problem with constraints, a penalty term was added into the objective function to transform the optimization problem with constraints into an unconstrained optimization problem, which was based on the standard particle swarm optimization algorithm. Taking the 3210 angular contact ball bearing as an example, the proposed penalty function particle swarm optimization algorithm was used to optimize the design. After optimization, the rated value of dynamic load and static load of the bearing were increased by 66.46% and 70.60% respectively. The results show that the performance of angular contact ball bearing can be improved by using penalty function particle swarm optimization algorithm. References | Related Articles | Metrics