西南交通大学学报

Aeolian Vibration Characteristics of Electrified High-Speed Railway Catenary

LIU Zhigang, SONG Yang, LIU Yucheng

2015, 28(1): 1-6. doi: 10.3969/j.issn.0258-2724.2015.01.001

[Abstract](1086)

Abstract:
In order to evaluate the influence of the aeolian vibration on catenaries in operation and calculate their amplitudes under different wind speeds, a formula of catenary aeolian vibration in the vertical direction was deduced based on the modal analysis method. By solving the vibration dynamic equations, the natural frequencies and vibration modes of the catenary were obtained first. Then the exciting force acting on the catenary was deduced. Finally, the aeolian vibration amplitudes of catenary with respect to each frequency under different wind speeds were calculated, and the relationship among the wind speed, frequency, and amplitude was analyzed. The results show that the maximum aeolian vibration amplitude of the catenary was less than 1 mm in general, and the aeolian vibration similar to that of transmission lines would not occur. In a numerical example, the maximal amplitude of the catenary occurs at the wind speed of 1.44 m/s, and only reaches 0.96 mm. Therefore, the aeolian vibration would not influence the operation of the electrified railway significantly.

Recognizing Running State of High-Speed Trains Based on Multifractal Theory and SVM

SUN Yongkui, YU Zhibin, JIN Weidong

2015, 28(1): 7-12. doi: 10.3969/j.issn.0258-2724.2015.01.002

[Abstract](1139)

Abstract:
In order to evaluate in-service performances of high-speed trains, a novel approach to recognize the running state of high-speed trains was proposed using the multifractal theory and the support vector machine (SVM). The relationship between the multifractal spectrum parameters and the train running states was analyzed after the multifractal spectrum of the vibration signal was calculated by multifractal theory. Then, high-speed train running states were identified by SVM, using the characteristics of the multifractal spectrum width, the fractal dimension difference, and the spectrum skewness. In addition, a recognition experiment was carried out for three typical conditions of a certain type train, including the normal condition, the anti-hunting damper malfunction, and the air spring damper malfunction, after the SVM with different velocities and the SVM with a velocity (160 km/h) were trained using their multifratal characteristics. As a result, a state recognition accuracy of more than 88.8% was obtained, which verified the effectiveness of the proposed method.

Analysis of Digital Voltage-Mode Controlled Buck Converter with Dual-Edge Constant on-Time Modulation

ZHOU Guohua, CHEN Xing, CUI Hengfeng

2015, 28(1): 13-19,35. doi: 10.3969/j.issn.0258-2724.2015.01.003

[Abstract](1272)

Abstract:
To improve the accuracy of output regulation in a switching converter with constant on-time (COT) modulation, dual-edge constant-on time (DCOT) modulation scheme for the switching converter in continuous conduction mode was proposed, based on the characteristics of COT modulation and dual-edge pulse-width modulation. The principle of digital voltage-mode controlled Buck converter with DCOT modulation was introduced. Moreover, its steady-state and transient performances were analyzed and compared with those of digital voltage-mode controlled Buck converter with COT modulation. The results show that digital voltage-mode controlled Buck converter with DCOT modulation improves output-regulation accuracy by 50% of peak-to-peak value of output voltage ripple and reduces the transient regulation time by one switching cycle. Finally, the simulation and experimental results validate the correctness of the theoretical analysis.

Research on the Control Strategy of Power System for Hybrid Electric Train

YANG Jibin, ZHANG Jiye, SONG Pengyun, CHEN Yanqiu

2015, 28(1): 20-26. doi: 10.3969/j.issn.0258-2724.2015.01.004

[Abstract](996)

Abstract:
In order to achieve a numerical simulation of hybrid electric trains, a mathematical model and a control strategy for the hybrid power system were proposed. By analyzing the coupling relationship between the hybrid power system and longitudinal dynamic system of a train, an algorithm based on the proposed control strategy was provided to calculate target speed profiles of the hybrid power train. In addition, using MATLAB/Simulink to build a system model for the train, simulation of the train's operation process on a railway line was made. The results show that the control strategy can meet the operational performance of the train, the automatic train operation (ATC) system can accurately control the train to track the target speed profiles, and 41% of the braking energy is recovered by the hybrid power system. Therefore, the system control strategy and the calculation algorithm of train target speed profiles can achieve the design goal.

Modeling and Verification of TSSM-Based CBTC Zone Controller for Urban Rail Transit

LI Yao, CHEN Rongwu, GUO Jin, KONG Lingjing, ZHOU Zheng

2015, 28(1): 27-35. doi: 10.3969/j.issn.0258-2724.2015.01.005

[Abstract](1213)

Abstract:
As a safe state machine lacks time property, a TSSM (timed safe state machine) modeling method was presented based on the synchronous design method of reactive system. The weak transition and synchronized transition were defined, and the ZC (zone controller) system model for urban rail transit was established. First, the operation environment, principle and functional requirements of ZC were analyzed, and according to the ZC features of reactive systems, the train management, ZC control, MA calculation and queue management sub-models of ZC system were built using TSSM in SCADE (safety critical application development environment). Then through the TSSM network model of ZC, the interaction information between the sub-models was analyzed. Finally, the safety features of ZC are formally expressed in Lustre, and the functional and performance requirements are examined by running data flow in Design Verifier. The result demonstrates the validity of the bounded liveness and safety properties of the TSSM model, which shows that ZC completely satisfies the functional and safety requirements.

Optimization and Design of Maglev System PID Controller Based on Particle Swarm Optimization Algorithm

SONG Rongrong, CHEN Zili

2015, 28(1): 36-43. doi: 10.3969/j.issn.0258-2724.2015.01.006

[Abstract](1077)

Abstract:
In order to improve the nonlinear and unstable characteristics of maglev systems, two nonlinear subsystems with different structures were transformed into linear ones with the same structure by differential geometry method, and then a PID controller that is based on the standard particle swarm optimization (PSO) was built. For the PSO algorithm, the fixed inertia weight (FIW), linear descend inertia weight (LIW), and linear differential descend inertia weight (LDW) were comparatively studied through simulation; among them the FIW was found more suitable and hence selected for electromagnet 1 and electromagnet 2. After optimization of controller parameters, the value of the FIW parameter C for electromagnets 1 and 2 was set to 0.5 and 0.49, respectively. In addition, a fuzzy comprehensive evaluation model was built to evaluate the anti-interference performance of the electromagnets 1 and 2, revealing that the two electromagnets both have a good anti-interference ability, and the membership degree of good is 0.561 9. Experimental results show that the optimized maglev system has a fairly good robustness.

Temperature Control of High-Power Self-Humidifying PEMFC with Air Cooling

YOU Zhiyu, CHENG Weirong, PENG Yun, LI Qi

2015, 28(1): 44-50. doi: 10.3969/j.issn.0258-2724.2015.01.007

[Abstract](1188)

Abstract:
To study the influence of temperature control on the stack output performance of high-power self-humidifying proton exchange membrane fuel cell (PEMFC) with air cooling, four control methods including fuzzy control, PID control, fuzzy-PID switching control, and adaptive fuzzy PID control are employed to test the stack. Results show that distinct differences exist in response performances of the stack among different control methods with load variations. More specifically, the fuzzy control has a greater influence on the output performance of the stack, resulting in obvious concentration polarization with heavy current output. In addition, when the load changes, problems of excessive overshoot in dynamic response and long regulation time exist in the fuzzy control, PID control, and fuzzy-PID switching control, while the adaptive fuzzyPID control has tiny overshoot and short regulation time. Compared with the PID temperature control, the adaptive fuzzy PID temperature control reduces the overshoot by at least 75%, and reduces the regulation time by at least 20%. By comprehensively evaluating the typical parameters such as regulation time, overshoot, control error, and the stack output performance, the adaptive fuzzyPID temperature control is favorable to improve the output performance of the high-power self-humidifying PEMFC with air cooling.

A DV-HOP Localization Algorithm Against Wormhole Attacks in WSN

DENG Ping, ZHANG Hongjiang

2015, 28(1): 51-57,65. doi: 10.3969/j.issn.0258-2724.2015.01.008

[Abstract](1115)

Abstract:
In order to resist wormhole attacks and improve localization performance, a secure neighbor discovery based DV-HOP(NDDV) algorithm was proposed. Based on the abnormal hop number in the network node communication when wormhole attack occurs, NDDV can detect two kinds of wormhole links according to the path hop number difference between nodes, then search, find and filter wormhole links to ensure the correctness of DV-HOP hop number and hop distance, mitigate the impact of wormhole attacks, and enhance the node localization accuracy. In the simulation experiments, 144 nodes were positioned 150 times with different locator ratios. The results show that when the mean locator ratio is more than five, NDDV can effectively filter the wormhole links and improve the node localization accuracy. With the same average localization accuracy, NDDV has the locator ratio 17.5% smaller than LBDV (label-based DV-HOP localization against wormhole attacks).

Optimal Energy-Efficient Path Selection Scheme in OFDM-based DF Relay Networks

HUANG Gaoyong, FANG Xuming, CHEN Yu, ZHANG Qiangfeng

2015, 28(1): 58-65. doi: 10.3969/j.issn.0258-2724.2015.01.009

[Abstract](1048)

Abstract:
Based on a three-node orthogonal frequency division multiplexing (OFDM)-based relay transmission network and decode-and-forward (DF) relaying strategy, an optimal energy-efficient path selection scheme was proposed. By converting the fading values of both the relay and direct links into the equivalent path loss values, an optimal energy-efficient path selection criterion based on equivalent path loss exponent was presented. The effects of the circuit power consumption, bandwidth, data rate requirements and channel conditions on the system energy efficiency in the selection of transmission path were also analyzed. Simulation results show that the optimal energy-efficient transmission path depends on the bandwidth, data rate, and channel conditions, and satisfies the decision criteria of the optimal energy-efficient path. Comparing with the path selection scheme based on the maximum harmonic channel gain, when the distance between base station (BS) and mobile station (MS) equals 610 m, and data rates equal 5 and 6 Mbit/s respectively, the energy efficient values of the proposed scheme are increased by 11.8% and 40.5% respectively.

Optimization and Performance Analysis for Bandwidth Spectrum Sensing in Cognitive Radio

LIU Xin, ZHONG Weizhi

2015, 28(1): 66-71. doi: 10.3969/j.issn.0258-2724.2015.01.010

[Abstract](956)

Abstract:
To decrease interference to primary user (PU) in cognitive radio (CR), a bandwidth spectrum sensing model of secondary user (SU) over the whole frame was built through dividing the communication bandwidth into sensing frequency band and transmission frequency band, according to the status variation of PU. In this model, SU uses part of the bandwidth to perform spectrum sensing and the rest to transmit data in a frame. Subject to the constraints of the interference to PU and the false alarm probability of SU, the spectrum efficiency of SU was maximized through jointly optimizing sensing bandwidth proportion and detection probability. Using the MATLAB software to simulate the interference probability and the spectrum efficiency, it is found that compared to the conventional time spectrum sensing, the bandwidth spectrum sensing decreases the interference probability to PU by 30% with the false alarm probability of 0.5, and improves the spectrum efficiency of SU by 0.3 (bit/s)/Hz with the interference probability of 0.2.

Design of Solid State Modulator Coupled with Pulse Transformer of High-Turns Ratio

WANG Qingfeng, LIU Qingxiang, ZHANG Zhengquan, LI Xiangqiang

2015, 28(1): 72-76. doi: 10.3969/j.issn.0258-2724.2015.01.011

[Abstract](1197)

Abstract:
To improve the reliability and stability of solid-state modulator and avoid the plight that the semiconductor switch in series requires the voltage sharing and signal synchronization, a solid-state hard-tube modulator coupled with pulse transformer of high turns ratio was designed and its topology structure was presented. Based on the equivalent circuit model of pulse transformer, the effect of the distribution parameters of pulse transformer on the output waveform was analyzed using Laplace transform method. The characteristic coefficients of overshoot and rise time were calculated following the design requirements. Further, the structure of pulse transformer was optimized. The results show that the rise time change positively with the product of leakage inductance and parasitic capacitance, and the overshoot of the output waveform is directly proportional to the ratio of leakage inductance to parasitic capacitance. The optimized turn ratio of pulse transformer is increased from 1:30 to 1:70, and the primary voltage of 1 kV can meet the design requirements and ensure that the leakage inductance and parasitic capacitance also meet the demand of system. The experimental results show that rise time of high-voltage pulse waveform is 2.8 s, and the fall time is about 2 s when working voltage is 70 kV, load impendence is 1.4 k and the pulse width is 100 s; and the system can realize the stable operation for a long time in the 100 Hz full power conditions.

Experimental Study on Evolution of Wear Mechanism of Contact Strip with Electric Current

YANG Hongjuan, HU Yan, CHEN Guangxiong

2015, 28(1): 77-83. doi: 10.3969/j.issn.0258-2724.2015.01.012

[Abstract](1136)

Abstract:
In order to investigate the friction and wear behavior of the high-speed pantagraph-caternary system, a high speed ring-block wear tester was used to study the wear characteristics of carbon contact strip and the arc discharge phenomenon between the copper alloy contact wire and the carbon contact strip with electric current. The tests were conducted under the condition of electric current 200 A, normal load 70 N, and sliding speed 80-160 km/h. A optical microscope was used to observe the topography of the strip's wear surface. The results indicated that vibration and arc discharge occurred to the contact strip and intensified with sliding time; the arc discharge frequency increased first and then kept stable gradually. With the experimental time increasing, the average single arc discharge energy increased; the wear loss increased slowly first and then increased sharply. When the sliding speed was 160 km/h, the value of wear rate at the test time of 50 min (0.037 27 g/km) is 3 times that of 10 min (0.013 40 g/km). Under the high-speed operation conditions with electric current, the wear mechanism of the strip changed from a slight mechanical wear to a serious mechanical wear accompanied with slight arc erosion, and finally to a mechanical and arc erosion mixed wear.

Long-Term Load Spectrum Test of High-Speed Train Bogie

WANG Wenjing, WANG Yan, SUN Shouguang, LIANG Shulin

2015, 28(1): 84-89. doi: 10.3969/j.issn.0258-2724.2015.01.013

[Abstract](1317)

Abstract:
In order to establish the load spectra for high speed train bogies,a long-term on-track test of high speed train bogie loads was carried out on Wuhan-Guangzhou passenger dedicated line. The vertical load of axlebox spring and the lateral load of axlebox arm within a wheel profiling cycle were measured. The effect of wheel profiling on the load characteristics was evaluated for the typical service cases such as straight line running and curve passing. The loads for float-sinking, side-rolling, torsion, and lateral motion of bogie frame were derived from the measured loads of axlebox components and their spectra were compiled. The results indicate that the amplitudes of the axlebox spring vertical load, the axlebox arm lateral load, and frame loads decreased after the wheel profiling. In particular, the axlebox arm lateral load was reduced most significantly, by 50% and 40% under straight line running and curve passing conditions, respectively; and the wheel profiling improved the loading condition of bogie frame.

Influence of Rotational Inertia Errors on Simulation Results of Vehicle Collision Model

ZHANG Jian, ZHANG Xin, GAO Jingui, LI Jiang

2015, 28(1): 90-96. doi: 10.3969/j.issn.0258-2724.2015.01.014

[Abstract](1009)

Abstract:
To control effectively the influence of rotational inertia errors in the vehicle collision model on the simulation results, the influence rules were analyzed by perturbation theory. The influence degrees were investigated using the average slope of the pre-impact vehicle speed curve, the pre-impact vehicle speed angle curve, and the pre-impact angular velocity curve. According to the influence degrees, rotational inertia ranges that meet the demand of the simulation result accuracy could be determined. The result shows that when the rotational inertia error is controlled within 7.94%, the relative error of the simulation result is less or equal to 5%.

Review and Prospects on Constructing Technologies of Metro Tunnels Using Shield Tunnelling Method

HE Chuan, FENG Kun, FANG Yong

2015, 28(1): 97-109. doi: 10.3969/j.issn.0258-2724.2015.01.015

[Abstract](2319)

Abstract:
With the rapid development of metros in China, shield Tunnelling method, which is considered as a safe, environmental and quick construction method, has been widely applied in metro tunnel construction, and gradually become a hotspot in the world. In this paper, through review of the state-of-the-art of metro shield Tunnelling technologies and their latest new trends, technical problems in metro tunnel construction by shield Tunnelling method were discussed, and the related technology development and research progress in metro shield Tunnelling construction in recent years were summarized, including shield equipment manufacturing technology and shield selection technology, the environmental impact and control measures during shield construction, the behavior of shield tunnel lining structure under complex conditions, deterioration characteristics and durability of shield tunnel lining structure, and the impact and evaluation of disasters or accidents. Moreover, the technology development direction and research trends of metro shield tunnel in the near future are discussed in terms of manufacture and application of the special-face shields, constructing metro stations by enlarging shield tunnel, impact and assessment of disasters or accidents, system construction for lining structure safety assessment, repair and maintenance, etc.

Application of Flexible Shed-Tunnel Structure to Rock-Fall Hazard Prevention

LIU Chengqing, CHEN Linya, CHEN Chi, LI Junjun, ZHAO Shichun

2015, 28(1): 110-117. doi: 10.3969/j.issn.0258-2724.2015.01.016

[Abstract](1787)

Abstract:
To deal with the lack of research and design basis of flexible shed-tunnel structures, different types of protective structures for rock-fall hazards prevention and control were compared, according to the feature of widely distributed and concentrated mass of rock-fall hazards during traffic constructions in China. The structural characteristics of rigid and flexible shed-tunnel structures and the state-of-art-of in design theory, dynamic performance, stability performance, etc. were analyzed. Then, a numerical simulation was carried out using the finite element software ANSYS. The results show that under the same width, length, and protection level conditions, the flexible shed-tunnel structure has remarkable superiority in stress, construction, environmental protection, economy etc.; and hence is suitable for the rock-fall protection at the entrance and exit of highways and tunnels, especially in the emergency projects.

Influence of Inertial Effect of Compression Wave on Waveform Evolution

WANG Honglin, LEI Bo, BI Haiquan

2015, 28(1): 118-123. doi: 10.3969/j.issn.0258-2724.2015.01.017

[Abstract](894)

Abstract:
In order to accurately assess the micro-pressure wave outside tunnel exits, a theoretical formula of pressure gradient of wavefronts was deduced based on the one-dimensional plane wave equation and the flow characteristics of compression wave. The effects of propagation distance, and the amplitude and wavefront length of the initial compression wave on pressure gradient at different positions were analyzed using this theoretical formula. The results indicate that the pressure gradients significantly increase with propagation distance. When the propagation distance is close to the critical length, the pressure gradients show an abrupt change. With the same propagation distance, the pressure gradients increase along with the amplitude of the initial compression wave and decrease with the length of wavefront. When the propagation distance does not exceed the critical length, the relative error between the theoretical formula and numerical calculation is less than 6%, and the numerical results agrees well with measurements reported in literature.

Effects of Structural Quasi-static Components on Seismic Responses of Train-Track-Bridge System

LEI Hujun, LI Xiaozhen

2015, 28(1): 124-130,136. doi: 10.3969/j.issn.0258-2724.2015.01.018

[Abstract](1527)

Abstract:
In order to discuss the effects of structural quasi-static components on the running safety of a train running over a high-speed railway bridge subjected to earthquake action, two dynamic models for a train-track-bridge system subjected to seismic excitation were set up by considering the seismic force boundaries of subgrade and bridge in relative coordinates and absolute coordinates, and the seismic force boundaries were processed respectively by the relative movement method and the large mass method. A rigid-continuous combination beam bridge with spans of 48 m+580 m+48 m was taken as an example, and the effects of structural quasi-static components in different directions on the seismic responses of the train-track-bridge system were analyzed. The research results show that the transversal quasi-static component causes a significant increase in dynamic responses, including the transversal displacements of bridge and rail, derailment coefficient and wheel unloading rate. The longitudinal and vertical quasi-static components have little effect on the seismic responses of the coupling system. When the quasi-static components of all three directions are considered, the derailment coefficient and wheel unloading rate of train increase significantly, their relative errors increase with the raising of train speed and the maximum relative errors can reach 30.5% and 22.2%, respectively. So, if the effects of structural quasi-static components are ignored to a train running through a bridge under earthquake action at a high speed, the dynamic responses of vehicle will be substantially undervalued to lead to an incorrect judgment of the running safety.

Iterative Algorithm of HSR Ballastless Track Realignment Calculation Based on MCO Model

WEI Hui, ZHU Hongtao, ZHAO Guotang, WAN Jian, WANG Zhiyong

2015, 28(1): 131-136. doi: 10.3969/j.issn.0258-2724.2015.01.019

[Abstract](1257)

Abstract:
To avoid the over-reliance on measuring track outer geometry for ballastless track fine adjustment, a computing method of track realignment on the basis of track irregularities was proposed. Through establishing the vector models of track irregularities based on the inertia trajectory of track inspecting instrument, a successive over-relaxation iteration algorithm was constructed for the numerical solution of realignment value, and its convergence and its convergence rate were analyzed. The proposed method has been applied to the fine adjustment of ballastless track in certain high-speed railway to prove its effectiveness by kinematical survey. The research indicates that the computing method is convergent, and after finite iteration, the realignment value to meet the requirements of track irregularities can be obtained. The track quality index obtained by the kinematical survey is 2.26, being comparable to absolute adjustment.

Numerical Analysis of Static Crushed Behavior of Railway Ballast

ZHANG Xu, ZHAO Chunfa, ZHAI Wanming

2015, 28(1): 137-143. doi: 10.3969/j.issn.0258-2724.2015.01.020

[Abstract](1072)

Abstract:
In order to reveal the static compressive behavior and breakage mechanism of railway ballast, the discrete element method was applied to simulate its crushed behavior under statically loading between two flat platens. A laser scanner was used to obtain the three dimensional morphology of a ballast. Discrete element models for the ballast with a realistic shape were constructed using hexagonal close packed agglomerates. Contact and bond behaviors between particles were defined in these models. History of load-displacement, distribution evolution of force chain and broken bonds in the ballast during the crush process were analyzed. The numerical results show that the characteristic strength of railway ballast follows a Weibull distribution, being consistent with the existing experimental results. Stress concentration at ballast surface and local crush due to sharp corner and surface irregularity induce the initial rotation of ballast and the change of its contact state, resulting in variation of force chain distribution in the ballast and a short drop of load. During the stable elastic response phase, contact forces between some parts of elements gradually increase with the enlargement of load and then exceed the bond strength, thus broken bonds exist in the ballast. When the number of broken bonds dramatically increases and reaches a certain scale, the ballast is crushed due to the rapid propagation of internal micro cracks.

Triaxial CT Tests of Meso-Structure Evolution of Remodeled Cohesive Soil in Hefei

ZHU Baolong, WU Xiyong, LI Xiaoning, WEI Jiuping

2015, 28(1): 144-149. doi: 10.3969/j.issn.0258-2724.2015.01.021

[Abstract](957)

Abstract:
In order to investigate the meso-structure characteristic of unsaturated cohesive soil, unsaturated consolidated-drained triaxial shear tests for remodeled cohesive soil in Heifei were carried out under different suctions and net confining pressures with CT (computed tomography) multi-function triaxial apparatus, and the CT images and corresponding CT data (CT data average and variance) of its inner structure evolution were obtained. The research result shows that net confining pressure has a great effect on the meso-structure evolution of soil. When the net confining pressure is low, original holes in soil disappear, unsaturated cohesive soil will generate cracks rapidly after transient compaction, and the width and length of cracks extend with time. The larger the suction is, the more significant the crack propagation is. The CT data average decreases by 0.26% to 4.16% compared with the original value, while the CT data variance increases by 15.82% to 37.80% compared with the original variance to indicate that soil density becomes nonuniform. When the net confining pressure is high, soil as a whole is compacted and almost does not generate cracks. Compared with the original values, the CT data average increases by 1.22% to 14.87%, and the variance decreases by 10.02% to 83.37% to indicate that soil density becomes uniform and the soil body is more compact.

Lateral Deformation of Cellular Diaphragm Wall at Excavation Stage

LIANG Sejia, XU Wei, CHEN Yu

2015, 28(1): 150-155,172. doi: 10.3969/j.issn.0258-2724.2015.01.022

[Abstract](1215)

Abstract:
To get the general rules of stress and deformation of cellular diaphragm wall, a centrifugal model test and field monitoring were made to analyze the lateral deformation rule, effects of design parameters on wall deformation, and relationship between maximum lateral displacement and excavation depth. The research results show that horizontal displacement of wall top is large and gravitated, and front and back walls have a similar deformation rule. Excavation depth, front and rear walls' spacing, partition wall spacing, soil property and temporary bracing have great effects on the horizontal displacement. Compared with anchored diaphragm wall, cellular diaphragm wall has large and strong integral rigidity and resistance, its maximum lateral displacement is on average about 0.15% to 0.5% of excavation depth, meeting the basic deformation requirement of deep foundation pit in soft soil areas.

Determination Method of Slip Surface of Reinforced Soil Slope Subjected to Seismic Load

JIANG Wei, SU Qian, ZHANG Xiaoxi, ZHOU Heng

2015, 28(1): 156-160. doi: 10.3969/j.issn.0258-2724.2015.01.023

[Abstract](1077)

Abstract:
In order to reasonably determinate the position of slip surface of a reinforced soil slope, a method, a horizontal slice method, was proposed for reinforced soil slopes subjected to seismic loads on the basis of the limit equilibrium theory. In this method, the slip surface is assumed to be a composite linear surface. The expression of reinforced soil tension, a multivariate function related to slip surface parameters, was derived based on the force equilibrium conditions of reinforced soil slopes, and solved with the software Mathematics to obtain the slip surface and the reinforced soil tension. In addition, slip surfaces obtained with the proposed method and the existing methods were compared to show its correctness. The research results show that the steeper the slope angle is, the closer the positions of potential slip surfaces based on the proposed method and the existing methods are. The slip surface moves outward constantly with the increases of internal friction angle and cohesion as well as with the reduction of horizontal seismic acceleration coefficient.

Aerial Image Registration Based on Bayesian Decision Theory

ZHANG Shuaiyi, LI Yongshu, CAI Guolin

2015, 28(1): 161-166. doi: 10.3969/j.issn.0258-2724.2015.01.024

[Abstract](978)

Abstract:
To eliminate the influence of projection difference on aerial image registration in object monitoring, a new image registration method was proposed based on Bayesian decision theory. Distribution rule of projection difference was derived and its impact on image registration was analyzed. A large number of feature matches were extracted to calculate the distribution parameters within the pre-set training sample area. The distribution rule was tested with KIT AIS dataset, and the registered images before and after eliminating projection difference were compared. The difference image results show an improved visual effect and 10% entropy decrease after elimination, which proves that the proposed algorithm is effective to improving the accuracy of aerial image registration.

Spatio-Temporal Meeting Analysis of Vehicles Based on Floating Car Data

SHEN Jingwei, ZHANG Hongtao, ZHOU Tinggang

2015, 28(1): 167-172. doi: 10.3969/j.issn.0258-2724.2015.01.025

[Abstract](1184)

Abstract:
In order to investigate the spatial-temporal relationships of discrete spatial-temporal data, spatio-temporal trajectory was taken as a link, and an analysis method for spatio-temporal meeting of vehicles based on FCD (floating car data) was proposed. The map matching method was used to spatially interpolate FCD to attain the continuous trajectories of vehicles. A linear interpolation method based on the timestamp and trajectory of two adjacent sample points was proposed to acquire the timestamp of any point in the trajectory. The spatial meeting relationship of vehicles in different temporal relationships was discussed using the Allen's interval based temporal logic and the spatial relationship theory. Experiments on spatio-temporal trajectory acquirement and spatio-temporal meeting analysis were conducted, and the spatio-temporal meeting relationships of vehicles were discussed. The experiment results show that the proposed spatio-temporal analysis method can solve the spatial-temporal relationships analysis problem of discrete spatial-temporal data.

Traffic Assignment Model Based on Cumulative Prospect Theory for Stochastic Road Network with Heterogeneous Users

LÜ, Biao, LIU Haixu, PU Yun, WANG Keming, GUO Qian

2015, 28(1): 173-182. doi: 10.3969/j.issn.0258-2724.2015.01.026

[Abstract](1277)

Abstract:
Due to travelers' bounded rationality and their differences of risk taking behaviors in route choice, the travelers were divided into four types, who respectively adopted travel time budget (travel time reliability being less than 50%), expected travel time, travel time budget (travel time reliability being more than 50%), and mean-excess travel time as their reference point for route choice. The calculation formulas of the prospect value for four types of travelers when the traffic demand follows a log-normal distribution and the link capacity follows a uniform distribution were derived, and a user equilibrium model was built and formulated as an equivalent variational inequality. The experimental results show that the parameter setting of cumulative prospect theory would have a great impact on the traffic assignment. Specifically, the route prospects of all types of travelers tend to increase with an increase in the gain sensitivity coefficient, and the change of the third and fourth types of travelers is more significant than that of the first and second types of travelers; the route prospects of all types of travelers tend to decrease with an increase in the loss sensitivity coefficient and the loss aversion coefficient, and the change of the first and second types of travelers is more significant than that of the third and fourth types of travelers; as the perception probability coefficient increases, the route prospects of the first and second types of travelers tend to decrease but that of the third and fourth types of travelers tend to increase.

Speeding Behavior Analysis Based on Structural Equation Model

YANG Jingshuai

2015, 28(1): 183-188. doi: 10.3969/j.issn.0258-2724.2015.01.027

[Abstract](1187)

Abstract:
In order to identify and quantify the causal relationships between drives' compliance with speed limit signs or warning messages and its associated factors in different traffic conditions, the data of 534 driver questionnaire surveys were analyzed by exploratory factor analysis and structural equation model. The analysis results indicate that the structural equation model provides a good fit with the observed values of variables, all the fit indices values are more than 0.9 and can better meet the criterion. The findings reveal that drivers' satisfaction with speed limit is the most significant variable that positively affecting drivers' compliance with speed limit instructions under conditions of low and high hazard perception. Drivers' personal factors, including age, driving experiences, speeding citation numbers, and driving frequency, are the second significant variables. Based on the present study, recommendations of improving the drivers' acceptation and satisfaction with speed limit, increasing drivers' risk of speeding behaviors are suggested, which would be effective measures to enhance drivers' compliance with speed limit instructions.

Congestion Identification of Crossing Air Routes Based on Gray Clustering Method

LI Shanmei, XU Xiaohao, WANG Chao, WANG Fei

2015, 28(1): 189-197. doi: 10.3969/j.issn.0258-2724.2015.01.028

[Abstract](1147)

Abstract:
In order to reduce the cognitive load of air traffic managers for congestion of crossing air routes, the limitations of the congestion identification measurements was analyzed. According to the formation process of traffic congestion, a definition of crossing air routes congestion based on flying inflow and flying outflow rates was established. On this basis, indexes for measuring traffic congestion of crossing air routes, including retention degree, aggregation degree, and equivalent traffic volume, was proposed to establish an aggregation model of crossing air routes. Then, a congestion identification method of crossing air routes was built by gray clustering theory, and verified by numerical simulation. The results show that the congestion status is the result of interaction between macroscopic dynamic features and complicated microscopic features; the proposed method has an identification precision of 90% and a simple and feasible calculation process.

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2015 Vol. 28, No. 1