交通运输工程学报

Strength and damage characteristic of cement stabilized cinder macadam base

ZHANG Xiang-dong, REN Kun

Abstract: In order to study the strength and damage characteristics of cement stabilized cinder macadam as a pavement base material, the optimal proportion of cement stabilized cinder macadam base under constraint conditions was obtained using the formula uniform test method.The ultrasonic wave velocity and unconfined compression strength of cement stabilized cinder macadam were tested through unconfined compression test and ultrasonic wave velocity test for different proportions, and the relationship between them was analyzed.Based on the ultrasonic wave velocity and the failure process of the specimens, the damage variable of cement stabilized cinder macadam was defined, the control threshold of damage development was proposed, and the constitutive relationship of cement stabilized cinder macadam base filler under unconfined compression was established.Analysis result shows that cement has a positive effect on the strength of the base material, while cinder has a negative effect on the strength of the material.The optimum proportion of cement stabilized cindermacadam is 5∶35∶60 (the mass ratio of cement, cinder and macadam).The strength of cement stabilized cinder macadam can reach 3.96 MPa, and it can be used as pavement base filler.As the compression strength increases, the ultrasonic wave velocity also increases, but the regularity between them is not strong.The test process can be divided into the compaction stage, elastic deformation stage, elastic-plastic deformation stage, and failure stage.Elastic deformation stage and elastic-plastic deformation stage can be distinguished by the change of ultrasonic wave velocity.The damage threshold of cement stabilized cinder macadam is determined to be 0.232 based on the ultrasonic wave velocity.The material can work with damage up to the damage threshold but cannot exceed it.More>

2018, 18(6): 1-9. doi: 10.19818/j.cnki.1671-1637.2018.06.001

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Gradation optimization of thermal resistant SMA-13 asphalt mixture

LIU Hai-peng, JIANG Ying-jun, XUE Jin-shun, FANG Jian, CHEN Zhe-jiang, LI Shou-wei

Abstract: In order to study the optimal dosage of refractory gravel in the thermal resistant SMA-13 asphalt mixture, the mixture proportion schemes were designed.In the schemes, the volume content of refractory gravel in the 2.36-4.75 mm ordinary aggregate was 100%, the volume content in the 4.75-9.5 mm ordinary aggregate was 20%, 40%, 60%, 80%, and 100%, respectively, and the volume content in the 9.5-13.2 mm ordinary aggregate was 10%, 20%, and 30%, respectively.The influence laws of refractory gravel content on the road property and heat resistant property of the SMA-13 asphalt mixture were studied, the optimum content ofrefractory gravel was put forward, and the road performance and thermal resistant performance of the SMA-13 asphalt mixture with this content were analyzed.Research result shows that compared with the ordinary SMA-13 asphalt mixture, when the 2.36-4.75 mm aggregate is entirely replaced by the refractory gravel, the road performance of the thermal resistant SMA-13 asphalt mixture reduces by about 3%, and the temperature of specimen decreases by about 1.4 ℃.When the 4.75-9.5 mm refractory gravel accounts for 60% of the same particle size of ordinary aggregates, the road performance of the thermal resistant SMA-13 asphalt mixture reduces by5%-10%, the temperature of the specimen decreases by about 5.7 ℃, and the heat resistance effect is obvious.When the content of the 4.75-9.5 mm refractory gravel is more than 60%, the road performance of the thermal resistant SMA-13 asphalt mixture decays rapidly, and the heat resistance effect is not obvious.When the content of the 4.75-9.5 mm refractory gravel is 60%-80%, the road performance of the thermal resistant SMA-13 asphalt mixture reduces by 10%-20%, and the temperature of the specimen decreases by less than 0.7 ℃.When the 9.5-13.2 mm refractory gravel accounts for 10%-20%of the same particle size of ordinary aggregates, the road performance of the thermal resistant SMA-13 asphalt mixture does not change basically, but the heat resistance effect is obvious.When the content reaches 20%, the road performance decreases by around 13%, and the temperature of the specimen decreases by about 7 ℃.When the content exceeds 20%, the road performance decreases sharply, the temperature of the specimen increases only by 0.1℃, and there is not heat resistance effect.Based on the best principle of cooling effect of the thermal resistant SMA-13 asphalt mixture, it is suggested that the contents of 2.36-4.75, 4.75-9.5and 9.5-13.2 mm refractory gravels account for 100%, 60%, and 20% of the same particle size of ordinary aggregates, respectively.More>

2018, 18(6): 10-17. doi: 10.19818/j.cnki.1671-1637.2018.06.002

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Durability evaluation of concrete in alpine salt marsh area based on gray system theory

FENG Zhong-ju, CHEN Si-xiao, XU Hao, YAO Xian-hua

Abstract: Based on the project of Qinghai Dexiang Highway, the evolution process and characteristics of the concrete's dynamic elastic modulus under the coupling effect of freezingthawing dry-wet cycle and salt corrosion were analyzed through the indoor damage test.Based on the grey system theory, the GM (1, 1) prediction models of the concrete's relative dynamic elastic modulus were established under different conditions, and the durabilities of the concretes with three mix ratios under two damage conditions were predicted by using the prediction models.According to the indoor damage test result and the prediction results of the GM (1, 1) models, thecompositions of the concrete were analyzed, and the influence of different mixtures on the durability of the concrete was studied.Research result shows that the relative errors of the prediction models for the concrete durability are within 6%, the posterior difference ratio is less than 0.35, and the small probability error is more than 0.95. Therefore, the prediction accuracy is higher.The durability of concrete varies greatly under different working conditions, and the effect degree of composite salt corrosion-curing freezing-thawing cycles is 42.8%-46.2% higher than the value of composite salt corrosion-immersion freezing-thawing cycles.The durability of the concrete mix proportion Ⅲ with fly ash, silica fume and expansive agent is the best and 50% higher than the value of standard mix proportion.Therefore, in order to ensure the durability of the concrete, the concrete mix proportion Ⅲ can be used as a reference in site concrete mix proportion design in similar areas.The simultaneous use of fly ash and slag will produce ettringite, which can seriously affect the durability of concrete.Compared with the reference mix ratio, the durability reduction rates of the concrete are more than 50% under different mix proportions.More>

2018, 18(6): 18-26. doi: 10.19818/j.cnki.1671-1637.2018.06.003

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Experiment on bearing capacity of bridge pile foundations in karst areas and reasonable rock-socketed depth

DONG Yun-xiu, FENG Zhong-ju, HAO Yu-meng, YAO Hong-sheng, ZHANG Xin-wang, XIE Fu-gui

Abstract: To study the bearing characteristics of bridge pile foundations in karst areas, with relevance to Xixie Overpass Project in Pingdingshan City, the pile foundatiion static load test was carried out.By placing strain sensors and displacement meters at the pile top and bottom, the internal forces of pile were measured, and pile top load (Q)-settlement (s) law of bridge in karst area was analyzed.Considering the limitations of current pile foundation design and combiningthe static load test results, the vertical ultimate bearing capacity of a single pile was predicted using different function models.Based on the wide beam mechanical model of rock-pile system and tensile-bending failure mode of karst cave roof, the calculation methods for the rock-socket depth of pile foundation were discussed, and an optimized calculation method for the rocksocketed depth of bridge pile foundations in karst areas was proposed.Research result shows that under different load levels, the Q-s curve exhibits slowly-varying developments.When the pile top load is small, the Q-s curve is basically linear.When the pile top load is greater than 6 000 kN, the Q-s curve becomes nonlinear.Although the pile is embedded deeply into limestone, it still shows typical friction pile characteristics.When loaded to 8 400 kN, the pile top settlement is3.69 mm, far less than the failure criterion of 0.03D (D is the pile diameter) or 40 mm.The pile tip resistance is 122.9 kN, accounting for only 1.6% of the pile top load.Bearing capacity of pile is still sufficient.Over the entire static load testing process, the stress state of pile is in the first stage of Kulhawy theory.The pile tip and side resistances develop synchronously.The fitting accuracy of hyperbola model is above 0.99 and the predicted value is determined to be safe.Thus, the model is recommended for use in similar projects.The proposed calculation method can reduce the rock-socketed depth of pile by 2.4 m, while meeting the requirements for safe thickness of karst cave roof, as well as bearing capacity and stability of pile foundation.More>

2018, 18(6): 27-36. doi: 10.19818/j.cnki.1671-1637.2018.06.004

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Mechanical properties of shield tunnel with inclined bolt joint and temperature distribution law under fire

ZHANG Wen-jun, ZHANG Xin-xin, SONG Xiao-long

Abstract: A three-dimensional solid model of circumferential composite segments and the circumferential inclined bolted joint was established using the finite element calculation software ABAQUS.The nonlinearity of the composite segment material was considered, and the elastoplastic constitutive model was adopted.The mechanical properties of the circumferential inclined bolted joint under normal temperature were analyzed.According to the heating up curve of HC, the heat transfer characteristics of the joint model were analyzed, and the temperature distribution laws of the composite segment lining and the circumferential inclined bolted joint under fire were studied.Analysis result shows that the use of a high-strength bolt can effectively reduce the opening of the joint and increase the joint stiffness.For high-strength bolts, the maximum axial stress of the inclined bolt is easy to yield at the initial stage, and the increase inbending moment and axial force of the joint has little influence on the stress of the bolt, but has more influence on deformation of the bolt.When the negative bending moment of the joint increases from 7 kN·m to 122 kN·m, the axial force of the joint increases from 368 kN to 734 kN, and the maximum strain of the inclined bolt increases by 1.6 times.When the positive bending moment of the joint increases from 53 kN·m to 182 kN·m, and the axial force of the joint increases from 903 kN to 1 056 kN, the maximum strain of the inclined bolt increases by 5.9 times.Under the normal temperature, a special antisymmetric distribution of the axial stress of the inclined bolt is shown near the seam.The axial stresses of the inclined bolt, except the joints are equal, is about 400 MPa, and the maximum absolute value of the axial stress at the joint can reach 700 MPa.In a fire, the fastest temperature rise is at the hand hole, and if the temperature reaches its highest, it can reach 1 000 ℃ in 80 min.The temperature of concrete at the seam reaches a stable temperature after 100 min, and at the nut after 150 min.This stable temperature is about 1 000℃.More>

2018, 18(6): 37-49. doi: 10.19818/j.cnki.1671-1637.2018.06.005

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Three-dimensional high-order continuous curve alignment design of horizontal and vertical overlapping region of high-speed railways

LI Ming, WEI Qing-chao, PAN Zi-hua, ZANG Chuan-zhen, QIN Xiao-chun, SHI Jin

Abstract: For the phenomenon that the horizontal and vertical overlapping region of curves is of geometric continuity degradation and then leads to sudden change of train motion state, based on the Frenet frame of three-dimensional curve, a three-dimensional carbody motion state model was established by combining curvature and torsion.The relationship among curvature, torsion, acceleration and jerk of carbody was obtained, and then the influence of geometric continuity order of three-dimensional curve on carbody motion was analyzed from three-dimensional point ofview by this model.Considering the geometric continuity requirement for curvature and torsion, an alignment selection method minimizing the changes of curvature and torsion in curve was proposed.A three-dimensional Euler curve was used to establish a high-order continuous curve in horizontal and vertical overlapping region.Research result shows that there is a geometric continuity degradation at the connection point of the traditional horizontal and vertical overlapping region of curves, and it is first order geometric continuity only.The curvature and torsion play dominant roles in the acceleration and jerk of trains. Geometric continuity degradation is the main reason for the sudden increase in vertical jerk.The vertical jerk of twodimensional design curve at the connection point is 1.206-1.264 m·s^-3, exceeding the passenger comfort threshold value (0.240 m·s^-3), so it is difficult to realize the high-order geometric continuity of two-dimensional alignment.The proposed curve design method has clear definitions on curvature and torsion at connection points, so it can easily achieve high-order geometric continuity at connection points without geometric continuity degradation.The changes of curvature and torsion in this curve are minimized.The proposed curve can effectively reduce the adverse effects on carbody motion caused by changes of curve parameters.The acceleration and jerk are continuous and meet the threshold values over the entire curve, realizing the second order geometric continuity.The maximum vertical jerk is 0.149 m·s^-3, 62.0% of threshold value, and 11.7%-12.3% of that of two-dimensional design.The proposed curve effectively improves the running stability of train and passenger comfort.The difference between paths of the proposed curve and the two-dimensional design is small.When the difference in gradient is 2%-3%, the horizontal and vertical coordinate differences are 0.907-2.305 and 1.085-2.498 m, respectively.the design parameters of the proposed curve are also used as calculation parameters of the carbody motion state, so this curve can be directly applied to the optimized design according to train running conditions.More>

2018, 18(6): 50-60. doi: 10.19818/j.cnki.1671-1637.2018.06.006

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Deflection force and displacement of CRTS Ⅲ slab track on bridge under train load

ZHANG Peng-fei, GUI Hao, LEI Xiao-yan, GAO Liang

Abstract: To study the loading and deformation of independently developed China rail track system (CRTS) Ⅲ slab tracks in the operation stage, based on the beam-slab-rail interacting principle, with full consideration of both the dimensions and mechanical properties of detail structures such as rail, track slab, self-compacting concrete layer, and bed plate, a refined space coupling model for continuous welded rails of CRTS Ⅲ slab tracks on a high-speed railway bridge was established using finite element method.The deflection force and displacement of rails andbridge structure under train load were calculated.The effects of load action length, longitudinal resistance of fasteners and longitudinal stiffness of fixed bearings atop the abutments on deflection force, and displacement were analyzed.Analysis result indicates that with the entire bridge loaded, the deflection force of the rail on the multi-span simply supported beam bridge is expressed as tension at the supports and as pressure on the mid-span.While the deflection force of the rail on the main bridge of the long-span continuous beam is expressed as tension on both sides and as pressure on the mid-span.Under the single-line loaded condition, the deflection forces of the loaded side rail on the two bridges reach 38 and 53 kN, and is approximately half of the results under the double-line loaded condition.The maximum longitudinal force and displacement of track and bridge structures will not occur under the same condition.Thus the most unfavorable condition shall be selected based on the different parts to be examined and calculated, to set the concentrated force in ZK train load to the mid-span position.The application of small resistance fasteners changes the stress and deformation acting on the rails, with the maximum deflection forces on rail of the simply supported beam bridge and continuous beam bridge decrease by 35% and 22% respectively, and the maximum longitudinal displacement on rail decrease by 7% and 5% respectively. On the contrary, the relative displacement between track slab and rail increase by 26% and 30%, which necessitates continual observation to keep rail creeping under control.From the perspective of safety and durability of tracks and bridge structures, it is proposed that the longitudinal stiffness atop the abutments be kept within 1.0-1.5 times of the design value.More>

2018, 18(6): 61-72. doi: 10.19818/j.cnki.1671-1637.2018.06.007

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Application performance of buses fueled with waste cooking oil-based B10 biodiesel

HU Zhi-yuan, LIN Piao-qi, HUANG Wen-ming, TAN Pi-qiang, LOU Di-ming

Abstract: The application research of buses certified to meet China Ⅲ and Ⅴ emission standards (referred to as "China Ⅲ buses" and "China Ⅴ buses"), which are fueled with diesel and waste cooking oil-based B10 biodiesel, was investigated.The influences of using waste cooking oilbased B10 biodiesel on the power performance, fuel economy, emission performance, and reliability of buses were analyzed in comparison with using pure diesel.Analysis result shows that power performances such as maximum speed, and acceleration time at full throttle from 25 to 70 km·h^-1 and from 0 to 70 km·h^-1 for the B10-fueled China Ⅲ and Ⅴ buses are at the same level with diesel-fueled buses.The emissions of HC, CO, PM, and solid particulate number of PM_2.5 emitted by B10-fueled China Ⅲ and Ⅴ buses are lower than that in diesel-fueled buses.Among these emissions, HC from B10-fueled China Ⅲ and Ⅴ buses reduce by 7.1% and 11.1%, CO by 9.2% and 8.0%, PM by 36.8% and 8.4%, and solid particulate number reduce by 4.7% and 23.5%, respectively.Waste cooking oil-based biodiesel blends of B10 have different effects on the NO_x emissions of China Ⅲ and Ⅴ buses.The emissions of NO_x from a B10-fueled China Ⅲ bus are 7.9% higher than that from a diesel-fueled bus, while a B10-fueled China Ⅴ bus emits 11.2% less NO_x compared with the diesel-fueled buses.During the test operation for sixteen months, the trend for the monthly average fuel consumption of China Ⅲ and Ⅴ buses fueled with two kinds of fuel, is the same with time.Owing to the running of the vehicle air conditioning in summer, the monthly average fuel consumption of buses is much higher in summer (from July to September).The monthly average fuel consumption samples of both diesel-fueled and B10-fueled China Ⅲ and Ⅴ buses obey the normal distribution, and the mean of the probability distributions are 38.67, 38.60, 39.06, and 39.27 L, respectively.Compared with the diesel-fueled buses, the failure rate of the B10-fueled buses connected with the fuel circuit is slightly higher, and the failure rates of oil-water separators and fuel filters take up large portions of maintenance.To improve the reliability of the B10-fueled buses, some key indicators such as oxidation stability and the water content of biodiesel made from used cooking oil should be controlled.More>

2018, 18(6): 73-81. doi: 10.19818/j.cnki.1671-1637.2018.06.008

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Anomaly detection of automobile braking curves

NING Hang, NAN Chun-li, YANG Lan, ZHAO Xiang-mo, LIU Hao-xue, ZHOU Dan

Abstract: The anomaly detection methods of automobile braking curves were studied.The features of the depressing-releasing-depressing anomaly were analyzed.The detection conditions and changing trends of the braking curves were considered.The braking data were clustered based on the cosine similarity and relative error.The segmentation algorithm of the braking curves was established.The braking curves were divided into blocking segment, rising segment, continuous segment, and releasing segment, and the corresponding data subsets were extracted.9 120 braking force curves from 3 inspection institutions were manually screened and analyzed, the three anomalous features including braking advance, depressing-releasing-depressing and braking growth lag were summarized, and the corresponding anomaly detection algorithms were given. For more difficult to identify the depressing-releasing-depressing anomaly, the subsequence with the longest continuous and descending trend in the ascending segment was searched according to the dynamic programming idea.The distance ratio of the subsequence in theascending segment was calculated, and compared with the corresponding experiential value to determine whether the subsequence was anomalous or not.Research result shows that the lowdimensional braking data can be clustered into blocking segment, rising segment, continuous segment, and releasing segment according to the cosine similarity only when the dimensions are not higher than 32.For the high-dimensional data, because their dimensions are higher than 32, the demarcation point has less influence on the overall sequence similarity.In this case, the relative error of the demarcation point must be combined with the similarity to constrain the clustering result for determining the blocking segment, rising segment, continuous segment, and releasing segment of the braking curve.Since the distance ratio of the depressing-releasingdepressing subsequence in the ascending segment is 9.8% and larger than the empirical value of 8.2%, the braking curve has depressing-releasing-depressing anomaly. This is correct, therefore, the method is reliable.More>

2018, 18(6): 82-92. doi: 10.19818/j.cnki.1671-1637.2018.06.009

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Test on aerodynamic performance of high-speed train in cryogenic wind tunnel

LIU Feng-hua

Abstract: The aerodynamic performances of China high-speed train HST, France high-speed train TGV and Germany high-speed train ICE3 were compared by testing them in a cryogenic wind tunnel.Based on the EN 14067 and TSI standards, the drag, lift and rolling moment of these trains under different yaw angles were tested on aluminum material models.Particle image velocimetry (PIV) was used to measure the flow field around the train, and the interaction mechanism and aerodynamic phenomenon between high-speed train and air were obtained.The calculation fluid dynamic (CFD) method was used to simulate the actual operation of high-speed trains, and the results were compared with those obtained from the cryogenic wind tunnel test.Research result indicates that under the yaw angle of 0°-10°, the order of absolute value of train drag coefficient from large to small is HST, ICE3 and TGV.When the yaw angle is 0°, the drag coefficients of the three kinds of trains are 0.223, 0.166 and 0.140, respectively.Under the yawangle of 0°-5°, the order of absolute value of train lift coefficient from large to small is TGV, ICE3 and HST, and their values are all close to 0. The lift forces of ICE3 and HST are positive and are pointed to the rail surface, the lift force of TGV is negative and the train receives an upward force.Under the yaw angle of 0°-5°, the order of absolute value of train rolling moment coefficient from large to small is TGV, HST and ICE3.When the yaw angle is 0°, the rolling moment coefficients of the three kinds of trains are 0.021, 0.019, and 0.011, respectively.Flow separation occurs at the transition of the head curved surface for the double-layer design of the HST high-speed train head.It increases the train friction and pressure drag and causes the drag coefficient of HST high-speed train to be larger than that of TGV and ICE3, but the drag coefficient is within the limit of 0.25 of the technical requirements for high-speed train head design, and the performances of lift force and rolling moment are superior.It makes the train have good stability.It can meet the aerodynamic engineering requirements of head design for high-speed train.More>

2018, 18(6): 93-100. doi: 10.19818/j.cnki.1671-1637.2018.06.010

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Soft measurement method for temperature monitoring data of train axle

XIE Guo, ZHANG Yong-yan, SHANGGUAN An-qi, DU Xu-long, HEI Xin-hong, GAO Qiao-sheng, WANG Yue-kuan

Abstract: To solve the high misdiagnosis and missing report rates of existing axle temperature monitoring system caused by data missing, a soft measurement method based on the characteristic analysis of axle temperature monitoring data was proposed.By analyzing the layout and correlation of axle temperature monitoring points, the source data range of soft measurement for monitoring data was determined.By using the self-organizing feature mapping algorithm, the intrinsic dimension of axle temperature data was determined.The data were clustered through source data normalization, winning region definition and membership degree optimization.By introducing the multi-dimensional scaling analysis method, the dimension reduction of axle temperature data in the internal class was realized through data space quantization and similarityas well as eigenvalue decomposition of the distance matrix. The multi-dimensional scaling analysis method was reused to reduce the dimension of data between external classes.A step-bystep dimension reduction method was proposed, and an equilibrium strategy was built to maximize the amount of information and minimize the calculations.The stacked auto encoder of a deep learning method was utilized to extract the internal characteristics of data between external classes, and a soft measurement model of axle temperature missing data was constructed.Research result shows that the time efficiency of the soft measurement method based on the dimension reduced data is 14.25% higher than that based on original data.The accuracies of the two methods maintain a similar level.When one-dimensional data is missed, the average accuracy of soft measurement data can reach 99.83%.When two-dimensional data is missed, the average accuracy can achieve 99.75%.When three-or four-dimensional data is missed, the average accuracy can arrive at 99.16%.Under the conditions that the maximum allowable error and error tolerance are 2.5% and 1.0%, respectively, as long as the dimension of missing data is not higher than four, the method can effectively recover the missing data with high accuracy and efficiency.More>

2018, 18(6): 101-111. doi: 10.19818/j.cnki.1671-1637.2018.06.011

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Index characteristics of expressway transportation volume based on toll collection data

YAN Sheng-yu, XIAO Run-mou

Abstract: Based on highway network toll collection system database of China in 2017, by the means of the sampling investigation data at typical toll stations, the structural properties of transportation volume indicators of Chinese expressway network were analyzed.Analysis result shows that the total traveling distance of vehicles on the expressway from 2010 to 2017 continuously increased.The total traveling distance for 2017 was 6.80×10¹¹ veh·km, and the distances of the passenger vehicles and trucks were 4.70×10¹¹ and 2.10×10¹¹ veh·km, respectively.In 2017, passenger transportation volume was 22.965 billion, passenger transportation turnover was 1 688.605 billion person·km, passenger average traveling distance was 72.96 km, and passenger transportation density was 1 257.47×10⁴ person·km·km^-1.Compared with 2016, these four indexes increased by 11.72%, 9.13%, 3.07%, and 4.21%, respectively.The passenger turnover of commercial vehicles was 505.571 billion person·km, and increased by 1.76% year on year.Type-Ⅰ passenger vehicles accounted for 95.70% of total traffic flow, and its passenger transportation volume and passenger transportation turnover maintained a rapid growth rate.The passenger transportation volume was 16.528 billion, passenger transportation turnover was 1 086.280 billion person·km, and they increased by15.25% and 11.60%, respectively, compared with 2016.In 2017, the freight transportation volume, freight transportation turnover, average transportation distance of trucks, and freight transportation density of expressway were 170.45×10⁸ t, 287.05×10¹⁰ t·km, 167.89 km, and 2 138.32×10⁴ t·km·km^-1, respectively.Compared with the transportation data in 2016, these four indexes increased by 15.33%, 16.17%, 0.42%, and 11.37%, respectively.The 2-axles-truck had the largest traffic flow, which accounted for 41.14%of the total trucks traffic flow.The proportion of unload trucks was 26.81%, and the proportion of transportation within and across provinces are 43.80% and 15.67%, respectively.In 2017, The overall index of expressway transportation kept a steady increase, and the freight volume, cargo type and cargo value were the results of the economic restructuring of freight transportation.More>

2018, 18(6): 112-120. doi: 10.19818/j.cnki.1671-1637.2018.06.012

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Estimation method of crowding cost in urban rail transit carriages

FANG De-wei, HE Dong-po, WANG Li-feng, CHEN Xi, SUN Xiang-long

Abstract: The discrete choice analysis and contingent valuation method were used to design a double-bounded dichotomous questionnaire to calculate the total generalized cost of rail transit, including the crowding degrees.The passenger densities in the carriage was reduced by extending the travel time of passengers in the carriage, and the equivalent travel efficiencies were obtained under different crowding degrees in the carriage.The passengers' choice probability for two rounds of bidding was obtained from the questionnaire feedback.The bivariate probit estimators and random utility estimators were used to deduce the standardized value of the time marginal disutility, and then the time multiplier was obtained to estimate the passengers' willingness to travel longer and the willingness to pay.Based on the data obtained from the survey of 15 representative platforms of Beijing Metro Lines 1and 5in 2015-2016, a linear regression analysis was made for the time multiplier under six crowding degrees in the rail transit carriage.Analysis result shows that there is a linear relationship between the passenger density in the carriage and the time multiplier, but an inverse proportion between the crowding degrees after improvementand the generalized cost in the carriage.Traveler's willingness to pay increases with the reduction of crowding degree in the carriage.When the crowding degree improves from 5 person·m^-2 to 4 person·m^-2, the willingness to pay for peak hours in the morning and evening is RMB 1.58 and 3.02, respectively.When the crowding degree improves from 5 person·m^-2 to 3.5 person·m^-2, the willingness to pay for peak hours in the morning and evening increase to RMB 2.47 and 4.99, respectively.Therefore, traveler's average payment willingness in the evening peak is approximate twice that in the morning peak, and there are significant differences in the payment willingness for the improved crowding degree at different periods.More>

2018, 18(6): 121-130. doi: 10.19818/j.cnki.1671-1637.2018.06.013

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Review of control switch and safety of human-computer driving intelligent vehicle

WU Chao-zhong, WU Hao-ran, LYU Neng-chao

Abstract: On the basis of the features and tendencies of intelligent vehicle technology, the concept of human-computer driving was proposed.The taxonomy methods of the control switch of intelligent vehicles were analyzed in terms of the initiator, urgency, and schedule.The features and applications of two taxonomy methods were discussed in a generalized and narrow sense.The characteristics of human factors in the field of human-computer driving and its influence on the safety of control switch were analyzed in terms of the driver awareness, workload, and response.The experimental methods and human-machine interaction forms of control switch weresummarized, and the problems and further developments of the safety were pointed.Analysis result indicates that the application scope of human-computer driving intelligent vehicle is L2-L3 automated driving, and the characteristic is the cooperation of human and computer to complete the dynamic driving tasks.The safety of the control switch situations, which is initiated by the system and passively taken over by the driver, has been given special attention.The key to ensure the safety of control switch is that the driver can effectively recognize and evaluate the current driving state, take over the vehicle operation, and finally avoid the potential hazard.Human factors have a severe impact on the safety and stability of the control switch, mainly manifested as the loss of situation awareness, sudden change of workload before and after handover, uncertainty of the influence of secondary tasks, and significant differences of driver response in different scenarios.The main research in this field also include the evaluation of taking over performance, optimization of switching timing and human-machine interaction, and the improvement of experimental methods.More>

2018, 18(6): 131-141. doi: 10.19818/j.cnki.1671-1637.2018.06.014

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Vehicle multi-target detection method based on YOLO v2 algorithm under darknet framework

LI Xun, LIU Yao, LI Peng-fei, ZHANG Lei, ZHAO Zheng-fan

Abstract: To improve the detection rate and robustness of the traditional road vehicle detection methods that need to extract different features as the scenes change, a vehicle multi-target detection method based on the YOLO v2 algorithm under the darknet framework was proposed.The YOLO-voc network model was improved according to the changes of the scenes and traffic flows of target road sections.The classification training model was obtained based on the ImageNet data and fine-tuning technology.The parameters of the improved algorithm were adjusted according to the training results and vehicle target characteristics.Lastly, the vehiclemulti-target detection method in YOLO-vocRV network model was obtained and more suitable for road vehicle detection.In order to verify the validity and completeness of the detection method, the vehicle multi-target detection experiment was carried based on different traffic densities.At the same time, the improved method was compared with the YOLO-voc and YOLO9000 model.The multi-target detection test result was analyzed by the improved YOLO-vocRV network model based on 20 000 iterations.Test result shows that in the blocking flow condition, the detection rates of the YOLO9000 network model, YOLO-voc network model and improved network model YOLO-vocRV are 93.71%, 94.48% and 96.95%, respectively, so the detection rate of the YOLO-vocRV model is the highest.The precision and recall rate of the YOLO-vocRV model are gathered at 0.95, so it loses less recall rate under the condition of obtaining better precision, and agood compromise is achieved.After the mixed-sample training, the detection rate of vehicle multi-target detection method based on the YOLO-vocRV model is 99.11% in the free flow state, 97.62% in the synchronous flow state, and 97.14% in the blocking flow state, so it has little false detection rate and good robustness.More>

2018, 18(6): 142-158. doi: 10.19818/j.cnki.1671-1637.2018.06.015

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2018 Vol. 18, No. 6

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