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19 November 2021, Volume 40 Issue 11 Previous Issue   
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Transportation+Big Data & Artificial Intelligence
Transportation Infrastructure Engineering
Transportation Equipment


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Transportation+Big Data & Artificial Intelligence

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Sea-Rail Intermodal Transport Path Selection for Japan-Korea Freight Based on CR Express LV Jing1, ZHANG Danyang2, JI Jiahui1 2021, 40(11): 1-8.  DOI: 10.3969/j.issn.1674-0696.2021.11.01 Abstract ( )   PDF (888KB) ( )   In order to meet the market needs of Japan-Korea fright transportation, a sea-rail intermodal transportation network of CR express was constructed. From the perspective of cargo owners, the cost and reliability functions were constructed according to the transportation process and infrastructure construction, and the 0-1 integer programming with the minimum cost and the highest reliability as the double-objective was carried out. According to the different emphasis requirements of the owner on the three elements of time, cost and reliability, the weights of different objective functions were determined. The double-objective problem was transformed into a single-objective function problem by the weighted summation and solved by genetic algorithm. Taking laptop and FMCG transportation from Busan port to Hamburg as an example, the optimal transportation scheme under different weights was obtained, and its time, cost and reliability were compared with those of the existing shipping routes. The results shows that the selected optimal path of sea-rail intermodal transport is superior to the existing shipping route in terms of time, reliability and total fee, and can meet the different needs of cargo owners. The overall reliability of the CR express sea-rail intermodal transport network is strong. References | Related Articles | Metrics

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Line Combination Selection Strategy in Less-Than-Carload Logistics YAN Fang, GUO Jun, CHEN Kai 2021, 40(11): 9-17.  DOI: 10.3969/j.issn.1674-0696.2021.11.02 Abstract ( )   PDF (571KB) ( )   The uncertainty of market demand makes enterprises often have temporary logistics demands. The supplementary role of logistics spot market procurement can effectively solve the above problem. In order to maximize the use of transport capacity and logistics network, reduce transportation costs and improve enterprise income, carriers often choose the combination of transportation routes in the form of transportation service combination auction. Aiming at the key problem how to select the appropriate combination of transportation routes in the auction of transportation service combination, from the perspective of LCL logistics carrier, a mathematical model aiming at maximizing revenue was established. Moreover, a solution strategy based on the synergy between shipping tasks was proposed, and the particle swarm optimization algorithm was used to verify the proposed model and synergy strategy through two different scale examples. In the small-scale example 1, the synergy strategy was the same as the solution of reverse elite particle swarm optimization algorithm, however, the operation time of synergy strategy was only 120.6s, which was 1775.1s less than that of reverse elite particle swarm optimization algorithm, and the solution time was shortened by 93.64%. In example 2, it took only 148.6s for the synergy strategy to obtain the optimal scheme, 4125.9s for the reverse elite particle swarm optimization algorithm to obtain the same optimal scheme, and the operation time was increased by 96.4%. The research results show that the solution strategy using synergy effect can obtain satisfactory decision results in both examples, and the computational complexity is small. When the solution quality is the same, the calculation time of synergy effect solution strategy is shorter. References | Related Articles | Metrics

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Travel Mode Choice of Commuters in Corridor Valley Pattern City of Loess Plateau Based on SVM PENG Hui,WANG Jianpo, ZHANG Na 2021, 40(11): 18-23.  DOI: 10.3969/j.issn.1674-0696.2021.11.03 Abstract ( )   PDF (435KB) ( )   Based on the large-scale survey data of residents travel, the travel mode choice behavior of travelers in Xining, a typical corridor valley pattern city of loess plateau was explored. Firstly, the socio-economic attributes and travel characteristics of individuals and families were extracted, and the choice of two commuting modes which meant private transportation mode including car travel and taxi travel and public transportation mode was taken as the target variable. Through the significance test, eight decision variables affecting the choice of travel mode were obtained. Then, for the valid samples of 29,960 travel records, the training sample set and test sample set were reasonably divided. Based on this, support vector machine (SVM) and traditional binomial logistic model (BL) were constructed respectively to identify the travel mode choice of commuters. The classification prediction accuracy, overall classification prediction accuracy and average absolute percentage error of three quantitative indicators were selected to compare the classification results of different models. The results show that compared with BL model, SVM has better fitting effect on classified data and good applicability for prediction of travel mode selection. Specifically, the prediction accuracy of SVM is 2.76% higher than that of the BL model for private transportation modes, and 8.08% higher for public transportation. The overall classification accuracy of SVM is 4.82% higher than that of BL model. References | Related Articles | Metrics

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Liner Refueling Strategy and Speed Optimization Considering Carbon Tax and Perishables LIU Cuilian, ZHANG Qunshu, WEI Wei 2021, 40(11): 24-31.  DOI: 10.3969/j.issn.1674-0696.2021.11.04 Abstract ( )   PDF (1299KB) ( )   Under the carbon tax mechanism, considering the special nature of perishables, it is an important decision for shipping companies to optimize liner speed and formulate fueling strategies. From the perspective of shipping companies, a mixed integer nonlinear programming model was established to achieve the minimum total cost of liner operation including fixed costs of ships, fueling costs, asset decay cost, refrigerated costs and carbon taxes. According to the characteristics of the proposed model, the piecewise linear approximation method was used to linearize and solve the fuel consumption function and perishable product deterioration function. Taking the actual liner route as an example, the effects of port fuel price, arrival time window and carbon tax rate on the decision-making of shipping companies were analyzed in turn. The research results can provide scientific basis for container liner companies transporting perishables to choose refueling ports, determine refueling volume and optimize speed. References | Related Articles | Metrics

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Optimization of Discharging Scheduling Based on Improved Salp Swarm Algorithm LI Changan1,3,4, ZHAO Delong2, WANG Guoyong2, WU Zhongqiang2, ZHANG Lijie1,3 2021, 40(11): 32-39.  DOI: 10.3969/j.issn.1674-0696.2021.11.05 Abstract ( )   PDF (1431KB) ( )   In the past, port coal discharge process mainly relied on the experience of workers for discharging operations, and there were problems such as long decision-making time, frequent operation conflicts, and excessive stagnation of train in the port. Taking the minimum time for trains in port as the overall optimization objective, on the premise of knowing the train arrival time and the corresponding relationship between stacking and coal types, a mathematical model of discharge scheduling was constructed, which considered the availability of working machinery, accessibility of operation process and their mutual constraints. Finally, the optimal scheduling method based on the improved salp swarm optimization algorithm was proposed. The adaptive inertia weight was introduced to effectively improve the convergence speed of the algorithm. Random Cauchy mutation strategy was introduced to effectively improve the optimization ability of the algorithm. The test results of the five test functions show that compared with the salp optimization algorithm, the adaptive salp optimization algorithm, particle swarm optimization algorithm and whale optimization algorithm, the improved salp optimization algorithm has faster convergence speed and higher accuracy. The simulation experiment of the actual data of port yard operation shows that the improved salp optimization algorithm can optimize and obtain the satisfactory discharge scheduling task, reduce the total time of the train in port and improve the overall work efficiency of the port. References | Related Articles | Metrics

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Satisfaction of Integration of Urban and Rural Public Transport Based on Structural Equation Model ZHU Xinglin, YAO Liang, LI Jianli, LIU Hongjun 2021, 40(11): 40-46.  DOI: 10.3969/j.issn.1674-0696.2021.11.06 Abstract ( )   PDF (1080KB) ( )   In order to lucubrate the deficiency in the integrated development of urban and rural public transport, the service quality of urban and rural public transport and the passenger satisfaction was targeted to improve. A county in Xinjiang province was taken as an example to conduct a questionnaire survey, which selected the perception of public transport environment, public transport convenience and public transport operation as the potential variables. Exploratory factor analysis was used to test the explanatory ability of the selected measurement variables to related problems. Based on the hypothesis of structural equation model (SEM), a satisfaction evaluation model of urban-rural public transport integration was constructed. On the basis of eligible adaptability of the proposed model, the operation results of the proposed model were analyzed and the corresponding optimization measures were put forward. The results indicate that the perception of public transport environment, public transport convenience and public transport operation are directly and positively correlated with satisfaction degree; the perception of public transportation convenience has the greatest influence on the satisfaction degree; the lack of urban and rural public transport information platform is the main factor which affects the convenience; improving ride comfort and driver passenger service quality in turn can effectively improve passenger satisfaction and urban and rural public transport service quality. References | Related Articles | Metrics

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Evaluation Method of Intersection Signal Control Efficiency Based on Data Envelopment Analysis XU Jianmin, LIU Kun 2021, 40(11): 47-52.  DOI: 10.3969/j.issn.1674-0696.2021.11.07 Abstract ( )   PDF (1061KB) ( )   With the continuous increase of urban vehicle ownership, the operation efficiency of many urban intersections is not high, frequent congestion occurs and the signal control efficiency is difficult to match the actual traffic situation. China lacks a unified standard for the efficiency evaluation of intersection signal control scheme. In order to evaluate the efficiency of signalized intersection control scheme and provide reference for relevant departments to select intersection signal scheme, data envelopment analysis (DEA) method was used to select intersection vehicle queue length, average driving delay and parking times as evaluation input indexes, green light utilization rate and traffic volume as evaluation output indexes. Finally, an example was selected for verification. The simulation results show that the proposed evaluation method of intersection signal control efficiency is feasible. References | Related Articles | Metrics

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Guiding Method of Vehicles Changing Lane at Highway Bottleneck in Cooperative Vehicle Infrastructure System JIAO Pengpeng, YUN Xu, AN Yu 2021, 40(11): 53-59.  DOI: 10.3969/j.issn.1674-0696.2021.11.08 Abstract ( )   PDF (1763KB) ( )   Frequent vehicle lane changes occurred at bottleneck areas due to the occurrence of traffic incidents on highway. In order to improve the traffic efficiency and safety performance of vehicles at the bottleneck area of the highway, the superiority of the cooperative vehicle infrastructure system (CVIS) was discussed, and a lane-change guidance method for the vehicle at highway bottleneck area in CVIS was proposed. The lane changing consideration factors of traditional vehicles and intelligent vehicles were defined in the form of establishing discrete selection model. The utility functions of free lane change and forced lane change were defined according to the location of the vehicle. Considering the velocity density relationship of macro traffic flow under different permeability, the expected lane change probability was sovled and introduced into the cell transmission model considering lateral traffic flow to simulate the macro traffic flow lane changing behaviour, so as to guide the intelligent vehicles from the upstream of the bottleneck. The proposed vehicle lane change guidance method was used to simulate the macro traffic flow numerically. And five groups of traffic flow under different permeability were set. The research results show that in cooperative vehicle infrastructure system, all the total travel time of traffic flow with different permeability through the bottleneck area decreases. When the permeability is 1, the corresponding total travel time is the smallest, which is 296.21s. When the permeability changes from 0.4 to 0.6, the total travel time decreases most significantly, which is 8.3%. When the permeability changes from 0.8 to 1, the reduction of total travel time is the smallest, which is 2.7%. Therefore, using the prposed guidance method to guide the traffic flow with permeability of 0.6 has the most significant effect. After using the guidance method, the density of each lane tends to be balanced, which can effectively alleviate the blocking wave propagating upstream at the bottleneck area. References | Related Articles | Metrics

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Traffic Short-Term Prediction Generated by Wavelet Decomposition and BP Neural Network of Traffic Zone ZHAO Yi, SHEN Linghong, MA Jianxiao, QIU Xuanli 2021, 40(11): 60-66.  DOI: 10.3969/j.issn.1674-0696.2021.11.09 Abstract ( )   PDF (2230KB) ( )   A short-term prediction method based on wavelet analysis and BP neural network was proposed to meet the short-term prediction demand of traffic zone’s generated traffic. The dbN wavelet function was used by the proposed prediction method to decompose the traffic zone’s generated traffic. And the BP neural network was used to predict each waveform with different frequency bands after decomposition in a short time. Finally, the short-term prediction results of the traffic zone’s generated traffic can be obtained by waveform reconstruction. On the basis of constructing the short-term prediction model of comprehensive wavelet analysis and BP neural network, some actually generated traffic data of the traffic zone were collected, and a comparison model of short-term prediction was constructed to test the prediction accuracy of the proposed model. The test results show that the combined prediction model of wavelet analysis and BP neural network has higher accuracy than BP neural network does alone in predicting the short-term generated traffic of the traffic zone. References | Related Articles | Metrics

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Experimental Study on Bus Evacuation Time under 5MW Fire in Full-Scale Tunnel AN Wenjuan1,2, FANG Lei3, XIE Yaohua2, LI Yuanzhe2 2021, 40(11): 67-73.  DOI: 10.3969/j.issn.1674-0696.2021.11.10 Abstract ( )   PDF (2436KB) ( )   In order to study the evacuation time of drivers and passengers within bus in the case of fire incidents in tunnel, and improve the safety of tunnel operation, an evacuation experiment of drivers and passengers within bus was conducted in a full-scale experimental tunnel. The oil basin fire combustion scene was constructed, and the bus personnel evacuation test was carried out under four groups of working conditions such as different number of people and different paths. The evacuation time inside and outside the bus for each experiment group was recorded. Then the evacuation time of experiment results were compared with the calculation results by empirical formula. The experiment results show that the evacuation time inside the bus was greater than that outside the bus with good vision and less obstacle interference in the experiment environment, and the more evacuees, the greater the gap between them. It is indicated that the evacuation within bus is a bottleneck of the whole evacuation process, and it is necessary to strengthen the evacuation education and training under emergencies for bus drivers and passengers, so as to improve the evacuation efficiency inside buses. When there are multiple exits available, 99% of the participants choose to escape from the nearest exit away from the fire source, resulting in a queue at the exit. Therefore, it is necessary to strengthen the guidance of evacuation path and emergency exit in the tunnel, so as to avoid blind obedience in group evacuation and improve evacuation efficiency. Furthermore, the comparison results show that when using the empirical formula to calculate the evacuation time, the influence of the number of evacuees on the average passage speed of pedestrian flow, the influence of fire scale and evacuation environment on the evacuation speed outside the vehicle, and the difference between the number of actually used exits and the number of available exits should be fully considered in combination with the actual situation, so as to reasonably set the parameter values and improve the accuracy of the calculation results. References | Related Articles | Metrics

Transportation Infrastructure Engineering

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Change and Driving Factors of Urban Construction Land in Chongqing Based on Geodetector MU Fengyun1, LI Qiuyan2, MA Ying3, CHEN Lin4, LONG Qiuyue5, YANG Meng6 2021, 40(11): 74-81.  DOI: 10.3969/j.issn.1674-0696.2021.11.11 Abstract ( )   PDF (4894KB) ( )   With the acceleration of urbanization in China, the disorderly expansion of urban construction land has caused the loss of arable land, the inefficiency of land use and the disorder of urban spatial structure. Taking Chongqing as an example, based on the analysis of the spatial and temporal evolution of urban construction land from 2000 to 2015, the driving factors of the area change of urban construction land were discussed by entropy method and geodetector. The results show that: ① In terms of time, in recent 15 years, the growth rate of urban construction land in Chongqing has taken the lead in fluctuating growth, then tended to be flat, and the area of urban construction land in Chongqing has increased by 259.09% compared with 2000; spatially, Morans I shows that the distribution of urban construction land has spatial agglomeration, the urban construction land in the nine districts of the main city has grown significantly, while the area of the economically slower areas such as Wushan and Fengjie County has not changed significantly. ② The use of entropy method and geodetector shows that the main factors affecting the change of urban construction land are the industrial scale and population size, and the location conditions are less affected. Urbanization rate, GDP, output value of secondary industry, output value of tertiary industry and other factors have enhanced interaction to influence the change of urban construction land, but the degree of interaction is different. The research results provide a scientific basis to identify the changes and driving factors of urban construction land as well as guide the rational allocation of urban construction land. References | Related Articles | Metrics

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Classification of Soft Surrounding Rock of Tunnel Based on Normal Cloud Theory LIANG Huiru1, WANG Yongdong2, PENG Hao2, LIU Junfeng1, YAN Xin2 2021, 40(11): 82-87.  DOI: 10.3969/j.issn.1674-0696.2021.11.12 Abstract ( )   PDF (3439KB) ( )   The normal cloud theory was applied to the classification of soft surrounding rock of tunnel.删 Four indexes for soft rock including uniaxial compressive strength Rc, integrity coefficient Kv, cohesion c and softening coefficient Kf were selected. The classification system of soft surrounding rock of tunnel based on normal cloud theory was constructed and verified with engineering cases. Taking the actual excavation surrounding rock grade as the reference standard, the results of surrounding rock classification obtained by normal cloud method and BQ method were compared and analyzed. The results show that the surrounding rock grade obtained by normal cloud method is more consistent with the actual excavation surrounding rock grade than that obtained by BQ method, which verifies the feasibility of surrounding rock classification system of soft tunnel based on normal cloud theory. The normal cloud method surrounding rock classification system can be used as a new classification method for soft surrounding rock of tunnel. References | Related Articles | Metrics

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Intelligent Monitoring Platform of Frame Bridge Underpassing Existing Railway Based on BIM ZHENG Mingxin1, 2, 3, DU Zizhen1, 3, KANG Meng1, 3, XU Pengwei1, 3 2021, 40(11): 88-93.  DOI: 10.3969/j.issn.1674-0696.2021.11.13 Abstract ( )   PDF (2525KB) ( )   Based on summarizing a large number of frame bridge monitoring projects and BIM technology engineering applications, the intelligent monitoring platform of frame bridge existing railway underpassing based on BIM Technology was explored and developed. The construction practice of Xiakeng first road frame bridge underpassing Fengcheng street, Yongding District, Longyan City was taken as an exapmple, which integrated the automatic monitoring system, video security monitoring system, cloud data storage and the integrated early warning system. By giving full play to the features of BIM technology, such as real-time visualization, information sharing, the monitoring information of frame bridge jacking construction was quickly and accurately transmitted to the participating units through BIM model. The automatic technology of collection, storage, analysis and processing of the monitoring data was combined with the early warning system. The monitoring data were analyzed and fitted in real time to predict the deformation trend, so as to ensure the safe construction of the frame bridge underpassing the existing railway. References | Related Articles | Metrics

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Reasonable Angle of Arch Hinge Diagonal Web Member of Concrete Filled Steel Tubular Arch Bridge WANG Weimin1, GAO Hejie2, ZHOU Shuixing3, XIE Yao3 2021, 40(11): 94-100.  DOI: 10.3969/j.issn.1674-0696.2021.11.14 Abstract ( )   PDF (833KB) ( )   The steel tubular arch segments of concrete filled steel tubular (CFST) arch bridge were usually constructed by cantilevering assembly method with cable hoisting. In order to adjust the installation alignments of arch rib, temporary arch hinge was often set at the springing. The arch hinge structures were simplified as the ideal truss and the rigid frame structure respectively. Firstly, according to the balance principle of force system, the consistent expression of the axial force of the diagonal web member of the ideal truss was derived. The ratio of the Euler critical load to the axial force was defined as the stability coefficient of the web member, the relationship between the stability coefficient and the angle between the web member was established, and the angle value corresponding to the maximum stability coefficient of the web member was obtained. Secondly, based on the principle of force method, the calculation expressions of moment and axial force at the end of triangular rigid frame were derived. The correctness of the calculation formula was verified by a calculation example. On this basis, the change law of the angle between the internal force of arch hinged rigid frame and diagonal web member was further studied. According to the structural requirements of the code for design of highway concrete filled steel tubular arch bridge that the angle between the main and branch pipes should not be less than 30°, it is concluded that the angle between the diagonal web members of arch hinge is more reasonable between 60° and 100°, which verifies the rationality of the arch hinge structural design of some built CFST arch bridges in China. References | Related Articles | Metrics

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Improved Algorithm for Design Position of Composite Circular Curve Splay Saddle DENG Xiaokang, DENG Hengyao 2021, 40(11): 101-105.  DOI: 10.3969/j.issn.1674-0696.2021.11.15 Abstract ( )   PDF (415KB) ( )   Based on the analysis of the main cable shape, the mechanical and geometric relationship between the main cable and the cable saddle of the suspension bridge, an improved algorithm for the design position of the compound circular curve splay saddle was proposed. The geometric conditions of the main cable and saddle were used to establish the equations, and the position of the compound circular curve splay saddle could be obtained only by solving the one-dimensional nonlinear equation with dichotomy. The proposed algorithm gives the solution interval of dichotomy to solve the nonlinear equation, and the calculation process can ensure the solution convergence without any initial value. The examples show that the improved algorithm has better accuracy. References | Related Articles | Metrics

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Highway Axle Load Spectrum Analysis Using Old Vehicle Types under the New Specification ZHAO Yao1, ZHANG Zhongya2, ZHU Yujie3 2021, 40(11): 106-113.  DOI: 10.3969/j.issn.1674-0696.2021.11.16 Abstract ( )   PDF (2251KB) ( )   With the implement of the Specifications for Design of Highway Asphalt Pavement (2017 version), the transform between the new and old vehicle classification standards has become a problem in asphalt pavement design. All vehicle data used were collected by expressway toll management system from Henan Province, in 2015. A transform method was firstly proposed, 6 types of vehicles classified by old specification were transformed into 11 types of vehicles under the 2017 version of specification. The representative values of axle load spectrum parameters in Henan Province were then calculated. According to the axle load spectrum parameters and the requirements of the new specification, the equivalent design axle load conversion coefficient of various vehicle types in asphalt pavement design was calculated, and the representative value of equivalent design axle load conversion coefficient in Henan Province was determined. The results indicate that the proposed transform method for old and new vehicle types is feasible. However, when the vehicle overload is serious, the equivalent design axle load conversion coefficient calculated by the standard method still can not accurately reflect the actual situation. References | Related Articles | Metrics

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Concrete Internal Defect Detection Based on Infrared Image Enhancement Algorithm ZHENG Dan, TAN Shuaishuai 2021, 40(11): 114-117.  DOI: 10.3969/j.issn.1674-0696.2021.11.17 Abstract ( )   PDF (4597KB) ( )   The traditional infrared detection method has low resolution and its defect characteristics were not obvious on account of the poor thermal conductivity of concrete. In view of the problems above, a concrete internal defect detection method combining infrared thermal image and enhanced image algorithm was proposed. The infrared detection tests of concrete with defects of different depths and sizes were carried out. The infrared detection images were processed by means of combining time-domain fitting with CLAHE algorithm, and the defect recognition effects before and after processing were compared. The test results show that the temperature difference required for defect identification decreases from 0.3 ℃ to 0.1 ℃ after the application of algorithm and the edge details are optimized, which improves the accuracy and practical range of infrared image concrete internal defect detection. The proposed method expands the application range of infrared thermography in concrete nondestructive testing. References | Related Articles | Metrics

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Molecular Dynamics Simulation of Nano-ZnO Modified Asphalt SU Manman1, SI Chundi2, ZHANG Hongliang3 2021, 40(11): 118-127.  DOI: 10.3969/j.issn.1674-0696.2021.11.18 Abstract ( )   PDF (9869KB) ( )   In order to reveal the mechanism of nano-ZnO modifier improving the physical properties of asphalt, the molecular dynamics simulation technology was used to simulate nano-ZnO modified asphalt. The asphalt molecular model was constructed by the representative compounds of four fractions of asphalt, combined with the test results of element content of matrix asphalt and the relative content of four fractions. Models of nano-ZnO with different particle sizes and nano-ZnO/asphalt blends were built according to the morphological characteristics of nano-ZnO. The interaction between nano-ZnO and asphalt molecules was calculated by molecular dynamics method, and the diffusion properties of nano-ZnO in asphalt were analyzed. Moreover, the influence of nano-ZnO on physical modulus and the molecular structure of asphalt was investigated. According to the molecular dynamics simulation results, the modification mechanism of nano-ZnO modified asphalt was revealed. Research results show that when the simulation temperature is about 150 ℃, the van der Waals interaction and non-bonding interaction of nano-ZnO/asphalt blends reach the maximum, whose architecture is the most stable. Nano-ZnO particles increase the bulk modulus, shear modulus and elastic modulus of asphalt system and improve the high temperature performance of asphalt, so as to improve the shear resistance of asphalt. Meanwhile, nano-ZnO enlarges the centroid distance between asphaltenes and resins system molecules, alleviates of the accumulation of strong polar fractions, strengthens the ductility of branched chains between molecules and increases the compactness of asphalt structure, which contributes to a more stable colloidal structure and better physical properties of asphalt. References | Related Articles | Metrics

Transportation Equipment

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Optimization and Verification of the Lightweight Engine Room Bracket of Electrical Vehicle DING Mingde1, ZHANG Peng2, LIU Bo3 2021, 40(11): 128-134.  DOI: 10.3969/j.issn.1674-0696.2021.11.19 Abstract ( )   PDF (16513KB) ( )   In order to meet the lightweight requirements of pure electric vehicles, a compound material lightweight development was carried out for the engine room support assembly of a pure electric vehicle of Changan. Sheet molding compound (SMC) was selected based on performance and cost factors, and CAE analysis and bench fatigue vibration test were carried out for the SMC engine room support assembly. According to the test analysis results, the analysis model and structure optimization were carried out, and the optimized SMC nacelle support assembly was verified by test. Research results show that the suspension weight has a great impact on the performance of the composite engine room support assembly, and CAE modeling should reflect the suspension weight. The analysis model and the improved SMC engine room support assembly can meet the requirements of strength and fatigue durability. Compared with the metal engine room bracket assembly, SMC component can achieve a 2kg weight reduction with a weight reduction rate of 31.3%, whose lightweight effect is obvious. Compared with the cost of metal parts, the cost of SMC components only increases by 20 yuan, and the cost of weight reduction per kilogram is 10 yuan. The cost increase is acceptable and has the prospect of mass application. The application of SMC composite materials can greatly reduce the production process, cancel the welding process and significantly reduce the energy consumption. At the same time, it reduces emissions and resource consumption. It conforms to the national energy conservation and environmental protection policy and provides a good direction for the lightweight development of pure electric vehicles and automotive structural functional parts. References | Related Articles | Metrics

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Operation Characteristics of Free Piston Engine with Energy Storage Spring LI Yanxiao, YANG Jun, XU Chuanyan 2021, 40(11): 135-141.  DOI: 10.3969/j.issn.1674-0696.2021.11.20 Abstract ( )   PDF (846KB) ( )   In order to improve the free piston engine performance such as operating frequency, indicated efficiency, operation stability, a design scheme of FPE internal combustion power generation system with energy storage spring was proposed. The working principle of the proposed system was analyzed. The coupling calculation model of system dynamics and in-cylinder thermodynamics was established, and the effectiveness of the proposed model was verified by experiments. The influence of energy storage spring on the operating characteristics of FPE system was studied by numerical simulation. Results show that: with the increase of energy storage spring stiffness, the displacement and velocity of FPE piston tend to sinusoidal variation curve, and the opening time of inlet and exhaust ports is pushed back; the greater the stiffness of the energy storage spring, the lower the peak pressure and mechanical efficiency in the cylinder, the higher the peak piston speed, system operating frequency and output power, and the higher the indicating efficiency when the stiffness of the energy storage spring is 100 ~ 200 kN/m. In addition, the setting of energy storage spring can reduce the fluctuation range of peak pressure and compression ratio in FPE cylinder, and effectively restrain the influence of combustion cycle fluctuation and accidental misfire on the operation stability of the system. References | Related Articles | Metrics

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Impact Analysis of Hydraulic Shock Absorber Failure on the Dynamics Performance of Straddle Type Monorail Vehicle DU Zixue, MA Jiabing 2021, 40(11): 142-148.  DOI: 10.3969/j.issn.1674-0696.2021.11.21 Abstract ( )   PDF (5109KB) ( )   Taking a domestic straddle type monorail vehicle as the research object, a dynamic simulation model of straddle type monorail was established by using dynamic simulation software, and the influence of different failure conditions of hydraulic damper on the performance of vehicle dynamics was analyzed. The overturning coefficient, the radial force of the horizontal wheel, the rolling angle of the car body and the running stability index were investigated. The analysis results show that the overturning stability, anti-derailment stability and running safety of the vehicle will be worse under the failure conditions of the hydraulic damper at different positions during the operation of the vehicle on the curve track. In case of condition 5 or 6, the dynamic performance is the worst, which will seriously affect the stable operation of the vehicle, so it is necessary to slow down, stop and evacuate the passengers. When the vehicle runs at the maximum running speed of 75KM/h on the straight track, the lateral and vertical stability of the vehicle under different failure conditions of the hydraulic shock absorber is compared with that under normal operation conditions, the lateral stability is less influenced, but the vertical stability of the vehicle is more affected. References | Related Articles | Metrics