2013 Vol. 13, No. 6

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Road and railway engineering
Heat conduction experiment of asphalt mixture based on Fourier's heat conduction law
YAN Xi-li, LI Xu-mei, SUN Yi, XU Da
Abstract: Based on Fourier's heat conduction law and applying the principle of 1-D stable heat conduction, an experimental device in the form of double plane samples for heat conduction was self-developed, and the heat conduction experiments of 3 kinds of asphalt mixtures were done. The heat conductivities of asphalt mixtures at different temperatures were measured, and the heat conductibilities were studied. Experiment result shows that the heat conductivity of asphalt mixture changes with temperature, and increases linearly with the increase of temperature. There is not a great difference among the heat conductivity values of different asphalt mixtures at the same temperature, and the experimental device is stable and easy to handle.More>
2013, 13(6): 1-6.
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Multi-level clustering algorithm for crack detection of concrete surface
DONG An-guo, ZHANG Xian-yan, XUE Hong-zhi, SONG Jun
Abstract: In order to detect the crack and its width of concrete surface, the k-means clustering was applied for crack digital image, and binary image was got based on taking out entire suspected crack pixels from clustering results. The connected components of binary image were extracted according to the ubiety of pixels, the distance function of connected components was constructed considering connected components as clustering objects. Connected components could be clustered by spectral clustering algorithm, pseudo cracks were removed on the basis of crack features, and whole crack image was obtained. Numerical calculations of crack width were carried out twice by local rotation algorithm. Research result shows that multi-level clustering algorithm can get rid of more noises during extracting crack, and has stronger anti-noise ability compared with Canny operator and Sobel operator. When the crack width is calculated by local rotation algorithm, the average relative errors of calculated value and actual value are 3.86%and 2.40% respectively, so the algorithm has high accuracy and can be used for width calculations of all kinds of cracks.More>
2013, 13(6): 7-13.
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Operating speed characteristics of heavy vehicle on expressway uphill section
XU Jin-liang, LEI Bin, LI Nuo
Abstract: The traffic composition, heavy vehicle power, load mass and mass-to-power ratio of expressway in Inner Mongolia were analyzed, and the typical vehicle on expressway uphill section was determined. Based on the corrected speed prediction model, the operating speed curves of typical vehicle under different slope gradients (1%-6%), slope lengths, load masses (30, 40, 50, 55 t), mass-to-power ratios (80, 120, 160, 200 kg·kW-1) and initial speeds into slope (0, 20, 40, 60 km·h-1) were drawn, and the reasons of curve changes from vehicle dynamics perspective were studied. Analysis result shows that Foton Auman ETX9 heavy truck is the typical vehicle on the expressway for coal transportation in Inner Mongolia. When heavy vehicle runs on a certain slope, the vehicle speed will not decrease with the increase of slope length after reaching balancing speed. The bigger the slope gradient is, the faster the vehicle speed drops, the lower the final balancing speed is. The bigger the load mass is, the faster the vehicle speed drops. The smaller the mass-to-power ratio is, the better the vehicle climbing performance is. The higher the initial speed is, the longer the distance for vehicle to reach balancing speed is.More>
2013, 13(6): 14-19.
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Fatigue analysis of steel bar in box girder under vehicle load spectrum
YIN Guan-sheng, LIU Xiao-wei, HOU Xiu-hui
Abstract: The vehicle load spectrum was obtained by using traffic survey. The forces of traveling vehicle tires on the ground could be taken as instantaneous half-sine impact loads. Based on the pressure distribution change curve in the longitudinal direction of tire on the ground, a theoretical formula of vehicle dynamic amplification factor (DAF) was deduced. Combining the transient analysis method, the dynamic response was calculated when vehicles with different axles passed through bridge, the cyclic axial stress curves of steel bars in box girder were achieved, and these curves were classified by using rain-flow counting method.S-N curve of steel bar was got through tests, and bridge service life was calculated by using linear cumulative damage theory. Numerical simulation result shows that without considering the roughness degree of pavement, dynamic amplification factor fluctuates near zero before resonance point, and it reaches the maximum at resonance point, then it decreases with the increase of speed. There are no adverse effects on bridge service life under non-overloading traffic.More>
2013, 13(6): 20-27.
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Height optimization of windbreak wall with holes on high-speed railway bridge
ZHANG Jie, GAO Guang-jun, LI Jing-juan
Abstract: Based on 3D steady N-S equation and k-ε double-equation turbulent model, the influence of height of windbreak wall with holes on high-speed railway bridge on train aerodynamic performance was simulated by using finite volume method. The relationships among train overturning moment, wind speed at catenary position and the height were analyzed, and the accuracy of present numerical method was validated combining with wind tunnel test. Analysis result shows that after the installment of windbreak wall, the equivalent coefficient absolute values of lateral force and overturning moment decrease speedily with the increase of the height. At the same height, the equivalent coefficient of lift force of train located at leeward line is as half as that at windward line. As there are no windbreak wall or train on bridge, the lateral wind speeds at two lines'catenary position are almost equal, the speeds rise sharply by 28.9% and 27.2%respectively when the train passes windward line and leeward line. After the installment of windbreak wall, the lateral wind speed at catenary position tends to decline with the increase of the height, and the leeward line wind speed reduces rapidly. Whether it is single-side or doubleside windbreak wall, the reasonable height of windbreak wall with holes on high-speed railway bridge is 2.8m.More>
2013, 13(6): 28-35.
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Transportation vehicle engineering
Load-shedding method based on suction effect to improve wind drag of high-speed train
XI Yan-hong, MAO Jun, GAO Liang, YANG Guo-wei
Abstract: In order to improve the safety of train in crosswind, a new method for safety control using suction effect was discussed to control the separation of airflow boundary layers and to decrease the crosswind aerodynamic force on train. Taking CRH high-speed train of China as prototype, the pumping chambers were added in train body, and the outer surface of train was connected with pumping chambers by slots. When train was running at high speed, airflow was sucked into pumping chambers through slots to form suction effect. Analysis result indicates that the installing of pumping chambers and slots can make the pressure inside train lower than its outside airflow pressure when train is running at high speed. The separation of airflow boundary layers can be effectively controlled. The crosswind aerodynamic force on train decreases. Slot inclination angle has significant effect on decreasing crosswind aerodynamic force. When inclination angle is 30°, the decrease of total resistance is 7.21%. The decrease of lateral force is 4.85% for the first vehicle, 2.71% for the middle vehicle, and 90.48% for the last vehicle. The decrease of lift is 8.21% for the first vehicle, 12.56% for the middle vehicle, and 7.69% for the last vehicle. The decrease of overturning moment is 5.29% for the first vehicle, 8.84% for the middle vehicle, and 57.56% for the last vehicle. Slot inclination angle has different effects on the aerodynamic load-shedding rates of different vehicles. The impact of slot inclination angle on the last vehicle is greatest.More>
2013, 13(6): 36-46.
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Influence of wheelset wear and wheel radius difference on dynamics performances of high-speed train
HAN Peng, ZHANG Wei-hua, LI Yan, HUANG Guan-hua
Abstract: Wheel profiles of working high-speed train were traced in test to study the change rules of shape and position of rolling radius difference function with worn profiles and wheel radius difference. The dynamics model of high-speed train was set up based on the parameters of working high-speed train to calculate nonlinear critical speeds, stabilities, and curve passing performances under different conditions of worn profiles and wheel radius difference. The relationship between rolling radius difference function and vehicle dynamics performances was described by the calculation of dynamic equilibrium points at different wheel-rail contacts under straight and curve passing conditions of high-speed train. Analysis result indicates that profile wear and radius difference may change the shape and position of rolling radius difference function, cause the change of equilibrium points of wheel-rail contact and lead to the significant change of vehicle system dynamics performances at the end. On straight line, when the running distance of vehicle reaches 1.98×105 km, vehicle critical speed declines from 530 km·h-1 to 300 km·h-1 with the increase of profile wear. Vehicle riding index increases from 1.60 to 1.87. As wheel radius difference changes from-0.5 mm to 0.5 mm, the critical speed declines by 80 km·h-1, while the riding index increases by 0.10. On curve line, with the increase of profile wear, wheelrail lateral force increases from 6.7 kN to 15.9 kN. Derailment coefficient increases from 0.12 to 0.23. Elkins wear index increases from 0.005 to 0.018. As the wheel radius difference changes from-0.5 mm to 0.5 mm, wheel-rail lateral force decreases by 3-6 kN, derailment coefficient decreases by 0.03-0.10, and Elkins wear index decreases by 0.003-0.010.More>
2013, 13(6): 47-53.
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Optimization of wind resistance for heavy truck
YANG Fan, HU Yang-yang, WANG Jian-hua
Abstract: To optimize the drag coefficient of heavy truck, the effect of rear spoilers and linking seals between cab and packing case was tested, in which the relative motion between truck and road and the pressed deformations of tires in real running under windless conditions were considered. The numerical simulation using commercial computational fluid dynamics software FLUENT and low-speed wind tunnel experiments were carried out to investigate the airflow characteristics around the US standard Class 8 truck and the drag coefficients of truck with different add-on devices. Analysis result indicates that by attaching the proper add-on devices, such as linking seals and rear spoilers, the rear vortices and front airflow sparation of packing case reduce, which results in the significant reduction of drag coefficient. At commercial speed of 90 km·h-1, drag coefficient decreases by 16.2% and its minimum value is 0.485 4.More>
2013, 13(6): 54-60.
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Measurement method of vehicle yaw rate with smartphone
CHEN Zhi-jun, WU Chao-zhong, HUANG Zhen, MA Jie, GAO Yan
Abstract: Vehicle yaw rates were measured by smartphone and high-precision inertial navigation system (INS). The influence of smartphone places on the measurement accuracy of yaw rate was analyzed. A self-adaptive weighted fusion algorithm was applied to reduce the measurement error of built-in gyroscope and orientation sensor of smartphone. The extreme value theory of multivariable function was used to obtain the optimal weighting factors of two sensors. The best value of yaw rate was calculated by weighted summation. Analysis result indicates that the impact of smartphone position on the measurement accuracy is very small. When smartphone is not fixed at center of gravity, the maximal relative errors of yaw rates measured by two sensors of smartphone are 0.739 7% and 0.923 8%, respectively. Average absolute error between fused data and INS data is 0.607 7 (°) ·s-1. Compared with the data measured by two sensors of smartphone, the average absolute error reduces by 34.3% and 50.0%, respectively. The variance of fused data declines and rapidly converges as the number of measurement increases. The convergent time is about 6 s.More>
2013, 13(6): 61-68.
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Transportation planning and management
Optimization model and ACO of ship assignment for international liner transportation
JIAO Xin-long, LIU Xue-lian, WANG Ren-xiang, ZHAO Ya-peng
Abstract: Aiming at the ship assignment problem of international liner transportation, the traditional dynamic ship assignment models were analyzed. Based on the fixed routes, ship types and ship amount, the influences of freight volume, port charge, fuel cost and river-crossing cost were analyzed. The minium operating cost was taken as objective function, ship amount and ship transportation volume were taken as constraint conditions, and a new optimization model of ship assignment was set up. Based on the neighborhood search technology, ant colony optimization (ACO) was used to solve the model, and example verification was carried out by using three typical routes. Calculation result shows that when the freight transportation demand can be satisfied, the optimization costs of the three typical routes are 133 723 000, 93 339 000, 139 464 000 yuan respectively, the total cost is 366 526 000 yuan and reduces by 1 106 000 yuan. By using genetic algorithm, the costs of the three typical routes are 134 051 000, 93 416 000, 140 127 000 yuan respectively, the total cost is 367 594 000 yuan. By using simulated annealing algorithm, the costs of the three typical routes are 133 985 000, 93 397 000, 139 859 000 yuan respectively, the total cost is 367 241 000 yuan. The optimization model of ship assignment for international liner transportation is feasible, and ACO has good advantage on the optimization model of ship assignment.More>
2013, 13(6): 69-75.
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Average waiting time model for passengers transfering from high-speed railway to bus
PEI Yu-long, SHEN Xiang-hao, ZHOU Kan
Abstract: The characteristics of the waiting times of passengers transfering from high-speed railway to bus were analyzed, the actual arrival times of passengers at bus stations in high-speed railway hubs were tested, the distribution of passenger arrival times was fitted, and K-S test was carried out. Based on probabilistic theory, the average waiting time model was set up by considering the limitation of bus carrying capacity, the validity of the proposed model was verified, and the influences of the arrival time intervals of high-speed train and bus, transfer passenger amount, bus carrying capacity and bus punctuality rate on the average waiting time of passengers were simulated. Simulation result indicates that when the arrival time interval of highspeed train is 10 min and the arrival time interval of bus increases from 200 sto 600 s, the average waiting time of transfer passengers increases from 120 sto 1 000 s. When bus carrying capacity is 50 people·veh-1 and transfer passenger amount increases from 50 to 200, the average waiting time of transfer passengers increases from 100 sto 900 s. When the average arrival time interval of bus is 200 sand the standard deviation of bus arrival time interval increases from 0 to 400 s, the average waiting time of transfer passengers increases from 110 sto 800 s. The average waiting time of transfer passengers has a positive correlation with bus arrival time interval, a negative correlation with the arrival time interval of high-speed train, apositive correlation with transfer passenger amount, and a negative correlation with bus punctuality rate.More>
2013, 13(6): 76-82.
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Determination method of equilibrium scale for highway network
LIANG Guo-hua, ZHANG Jing-feng, LEI Jian, MA Rong-guo, ZHANG Zhang-sheng
Abstract: Based on the concept of highway network equilibrium scale, the second-class highway was taken as the standard grade highway, the calculation method of equivalent mileage and equivalent coefficient was proposed, and the regressing model of terrain correction coefficient for highway network was established. The shortcomings and characteristics of traditional methods such as territory coefficient method and connectivity method were analyzed. The traditional calculation method of highway network equilibrium scale was adjusted. The minimum comprehensive Gini coefficient was taken as judging criterion, the range of equilibrium scale interval was adjusted, the calculation flow of equilibrium scale proportion was established, the systematic determination method of equilibrium scale for highway network was proposed, and example verification was carried out by using the highway network in Yunnan Province. Analysis result shows that the terrain correction coefficient of freeway in Qujing is the minimum, and is 1.12. The terrain correction coefficient of the fourth-class highway and substandard highway in Diqing is the maximum, and is 1.92. The equilibrium scale mileage in Nujiang is the minimum, and is 549 km. The equilibrium scale mileage in Qujing is the maximum, and is 4 753 km. By using the proposed method, the Gini coefficients of population, economy and area for highway network in Yunnan Province are 0.02, 0.19, 0.15, reduce by 0.15, 0.29, 0.18 respectively, the three Gini coefficients meet absolute equilibrium standard.More>
2013, 13(6): 83-89.
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Modeling and simulation of collaborative flight based on multi-agent technique
YE Bo-jia, HU Ming-hua, TIAN Yong
Abstract: The flight risk of aircraft agent flying in air corridor was studied by using multi-agent modeling and simulation technique. According to the flight aim, main function and interior structure of aircraft agent in air corridor, the inference rule and collaborative state were analyzed, the interactive structure of collaborative flight was put out, and simulation experiment was carried out by using hybrid simulation method. Simulation result shows that when the maximum and minimum cruising speeds of large-sized aircraft are 880, 620 km·h-1 respectively, the maximum and minimum cruising speeds of medium-sized aircraft are 790, 525 km·h-1 respectively, and the maximum and minimum accelerations of the two aircrafts are 0.608 and-0.780 m·s-2, the aircraft flight state in air corridor can be divided into four typical conditions. Under condition 1, aircraft speed is always 745.17 km·h-1, and the total flight time is 708 s. Under condition 2, aircraft adjusts its speed according to the leading aircraft, the initial and maximum speeds are 658, 778 km·h-1, and the total flight time is 648 s. Under condition 3, aircraft changes its flight line in air corridor in order to avoid flight conflict, and the total flight time is 744 s. Under condition 4, aircraft breaks away from air corridor for safety problem, and the total flight time is 66 s. The proposed model can meet the actual requirement.More>
2013, 13(6): 90-98.
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Safety evaluation model of long-steep downgrade section for montane highway based on driving workload
LIN Sheng, LIU Jian-bei, YAN Ying, LUO Jing, YUAN Zhen-zhou
Abstract: The existing psychological and physiological driving indexes and safety evaluation methods were analyzed, the practical vehicle test on the continuous long-steep downgrade sections of typical montane highway was put out, and the 23 549 heart rate variability (HRV) indexes of 27 truck drivers on 22 test sections were collected. Heart rate variability was taken as driving workload, the driving workload model related with longitudinal slope degree, slope length and vehicle speed was set up, and the interval range of driving comfort level on long-steep downgrade section was determined. Based on the threshold division range of driving workload, the relationship between driving workload and longitudinal slope index was analyzed, and example verification was carried out. Verification result indicates that when vehicle speed is not more than 75 km·h-1 and slope degree is from-6% to-3%, the determined risk sections contain all the accident frequent sections by using the proposed model. There are 38 traffic accidents on the determined highest-risk section and 11 traffic accidents on the determined higher-risk section, and the ratio of the death toll on the two risk sections to the total death toll is 84%. The evaluation result is consistent with the actual traffic accident distribution, so the proposed model is effective.More>
2013, 13(6): 99-106.
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Traffic information engineering and control
Adaptive demodulation method for balise uplink-signal
ZHAO Hui-bing, QUAN Hong-yu, LIANG Di
Abstract: The characteristic of balise uplink-signal was analyzed. An adaptive demodulation method for balise uplink-signal was introduced. The frequency of uplink-signal was tracked by using adaptive least mean square (LMS) algorithm. The signal was demodulated according to the calculated tracking residual. The demodulation performance was verified according to the Eurobalise test specification and then compared with zero-crossing detection method and noncoherent demodulation method. Simulation result shows that adaptive demodulation method can meet the demodulation performance requirements when there exists extreme migration of uplinksignal. When the signal to noise ratio (SNR) is 7 dB, the error rate of adaptive demodulation method is almost 0, while the error rates of the zero-crossing detection method and the noncoherent demodulation method are 0.163 and 0.001 respectively. The adaptive demodulation method is simple to utilize and has strong anti-interference ability. It provides a foundation for the reliable application of balise in comparative harsh electromagnetic environment.More>
2013, 13(6): 107-112.
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Aircraft attitude estimation method based on CKF
HAN Ping, GAN Hao-liang, HE Wei-kun, ALAZARD Daniel
Abstract: In order to improve the estimation accuracy of aircraft attitude in nonlinear model, a nonlinear estimation model based on the quaternion and the sensors with less accuracy and higher noise was established, and the cubature Kalman filter(CKF) algorithm based on spherical-radial cubature rules was applied to estimate the attitude. The model and algorithm were verified by using the real flying data. The estimation results of cubature Kalman filter algorithm, extended Kalman filter (EKF) algorithm and central difference Kalman filter (CDKF) algorithm were compared. Comparison result indicates that the estimation precision and stability of CKF are higher, its estimation time and error are minimum, and the derivation and adjustable parameters are not required in the estimation. 1 tab, 7 figs, 15 refs.More>
2013, 13(6): 113-118.
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Study status and prospect of traffic signal control for over-saturated intersection
LI Rui-min
Abstract: In order to relieve the serious congestion at signalized intersections, the development course and research status of traffic signal control at over-saturated intersection were summarized, and future development trend was analyzed. The various control objectives of over-saturated traffic flow were introduced, including the minimum delay, the maximum capacity and the queue limitation etc. Several kinds of traffic signal control models and algorithms at over-saturated intersection were analyzed, such as linear programming and optimization models, mixed integer linear programming models and other models based on soft computing and artificial intelligence techniques etc. The traffic signal control under over-saturated condition which was supported by the typical traffic simulation platform and signal control optimization software was summarized, as well as the traffic signal control methods at over-saturated intersection in some typical traffic control systems. Analysis result indicates that according to the traffic flow characteristics at oversaturated intersection, some problems need to be solved by the control methods, including too much parameters, computational complexity and lower computation efficiency etc. In oversaturated network, traffic flow characteristics, integrated optimization model, highly efficient solving algorithm and technology, simulation platform and demonstration application are the future research trends which need to concentrate on.More>
2013, 13(6): 119-126.
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