西南交通大学学报

Challenges in Construction of Railway and Highway from Sichuan to Tibet through Eastern Margin of Tibetan Plateau

YAO Lingkan, QIU Yanling, WEI Yongxing

2012, 25(5): 719-734. doi: 10.3969/j.issn.0258-2724.2012.05.001

[Abstract](1460)

PDF 2662KB(638)

Abstract:
The construction of railway and highway to Tibet through the eastern margin of the Tibetan Plateau has started step by step as the implementation of the Western Development Strategy. The controlling problems in the construction and the corresponding key techniques need to be studied urgently. The general information of railway and highway to Tibet through the eastern margin of the Tibetan Plateau was introduced. Some new challenges in the construction were discussed, including the crossing alternate plateau and ravine terrains in the north-south direction, the long-range threat of maritime valley glaciers and the line engineering design in fault creep deformation zones. A seismic hazard control method was proposed based on the case study of Xianshuihe. In this method, simple projects are adopted to reduce loss in design of individual engineering, and the expected annual operating cost is used to the comparison and selection of schemes. Meanwhile, for routes along deep-cut river, a higher elevation design was suggested to avoid the damage of valley disaster chain. Based on the above works, the framework of extreme disaster hazard control was established for macroscopic location design to provide references for the construction of railway and highway to Tibet and the scheme demonstration for the Kangding-Nyingchi line.

Design and Dynamical Analysis of New Light Deployable Bridge

GUAN Fuling, ZHOU Yijun, KUANG Qi, QIAN Lifeng

2012, 25(5): 735-740,747. doi: 10.3969/j.issn.0258-2724.2012.05.002

[Abstract](1644)

PDF 730KB(342)

Abstract:
To rapidly across ditches, valleys and other artificial or natural barriers for personnel, a new light deployable military bridge was developed. Scissors and sleeves are adopted to realize the axial deployment. A motor is used to drove a main cable to expand the bridge until it reaches a designed location, and then the bridge is locked. The functions in reducing deformation and enhancing bearing capacity were analyzed for the prestressed cable and brackets. A reduced-scale model for this bridge was made, and the test validation was carried out. The research results show that bridge deflection decreases from 1/114 to 1/386 because of setting the prestressed cable, and the bearing capacity increases by 35.1% due to the brackets. The structure can be successfully deployed and put into use, and the test result is in good agreement with the simulation one.

Stability Analysis of Edong Yangtze River Bridge during Construction

ZHAO Lei, SUN Caizhi, YANG Xingwang

2012, 25(5): 741-747. doi: 10.3969/j.issn.0258-2724.2012.05.003

[Abstract](1167)

PDF 867KB(574)

Abstract:
In order to research the change law of non-linear stability and its influencing factors of a long-span composite cable-stayed bridge during construction, by taking Edong Yangtze River bridge as research subject, LSB and ANSYS models were built based on the structure type and construction sequence of the bridge to calculate the non-linear stability safety factors during bridge construction and obtain the instability mode. The influencing law of non-linear factors to static stability was analyzed. In addition, the relationships among the stability during construction and steel-concrete connection position, cable-beam anchorage mode, temporary construction loads and cross-wind load were investigated. The research results show that the above factors have different effects on the stability during construction, but they are not controlling factors.

Elastic Modulus Reduction Method for Upper Bound Limit Analysis of Structure Containing Flaws

ZHANG Wei, LIU Liwen, YANG Lufeng, WU Wenlong

2012, 25(5): 748-753. doi: 10.3969/j.issn.0258-2724.2012.05.004

[Abstract](1187)

PDF 726KB(318)

Abstract:
In order to obtain the limit load of a structure containing flaws (SCF), an elastic modulus reduction method (EMRM) for upper bound limit analysis of SCF was proposed. The determination method for reference element bearing ratio was investigated to a stress concentration problem. An efficient elastic modulus adjustment strategy for SCF was proposed based on the reference element bearing ratio. Using this strategy and the linear elastic finite element method, stress and displacement fields under a limit state can be constructed. By introducing the upper bound limit load multiplier algorithm based on the virtual work principle and the reference volume concept, an efficient optimum solution of the limit load for the upper bound mathematic programming model was obtained. Numerical examples show that the proposed method can be applied to the limit analyses of structures containing cracks or slots and give a solution in 30 iteration steps with a difference within 5% relative to the analytical solution or other numerical solutions.

Calculation of Longitudinal Connected Slab Reinforcement Considering Expansion and Contraction of Bridge

CHEN Xiaoping

2012, 25(5): 754-760. doi: 10.3969/j.issn.0258-2724.2012.05.005

[Abstract](1341)

PDF 893KB(578)

Abstract:
To optimize the reinforcement design of longitudinal connected slab for CRTSⅡ-type slab ballastless track on bridge, a computational method of stiffness reduction on the longitudinal connected slab was derived. Longitudinal forces acting on the longitudinal connected slab were analyzed. It was proposed that the reinforcement design of longitudinal connected slab should take the longitudinal force resulted from bridge expansion or contraction into account, and its combination coefficient was determined. Based on the limited state method, a new computational method of the reinforcement of longitudinal connected slab was presented by taking the longitudinal force due to bridge expansion or contraction into account. An example about the reinforcement design of longitudinal connected slab on a continuous beam bridge was provided. The research results show that the new method is beneficial to the durability of longitudinal connected slab, especially for a long-span continuous beam bridges.

Adaptive Mutation Disturbance Particle Swarm Optimization Algorithm Based on Personal Best Position

LIU Zhigang, ZENG Jiajun, HAN Zhiwei

2012, 25(5): 761-768. doi: 10.3969/j.issn.0258-2724.2012.05.006

[Abstract](1305)

PDF 955KB(642)

Abstract:
In order to overcome the disadvantage of the particle swarm optimization (PSO) that it easily falls into local optimum, an adaptive mutation disturbance particle swarm optimization (AMDPSO) algorithm based on personal best position was proposed. This algorithm is based on PSO, and the disturbance is considered. When the adaptive conditions are met, the mutation operation of particles is performed based on the personal best position. The proposed algorithm was applied to 6 test functions and compared with IWPSO (inertia weight particle swarm optimization), CFPSO (constriction factor particle swarm optimization) and DE (differential evolution). The research results show that the AMDPSO has a good convergence rate and optimization capability, and can easily escape the local optimum and keep the population diversity.

Adaptive Foreground Detection Based on Weighted Kernel Density Estimation

JIANG Peng, JIN Weidong

2012, 25(5): 769-775. doi: 10.3969/j.issn.0258-2724.2012.05.007

[Abstract](1136)

PDF 873KB(441)

Abstract:
In order to avoid the impacts of moving foreground on background modeling in training stage, an adaptive foreground detection method based on weighted kernel density estimation (KDE) was proposed. In this method, temporal stable pixels are assigned more weights, and a weighted KDE background model is established to reduce the interference of foreground during background model building. Based on this background model, a strategy for dynamic foreground threshold was proposed. With the spatial consistency of foreground, "holes" in foreground are filled and thresholds are updated in the same time. The experimental results show that the proposed foreground detection method is able to achieve over 90% precise and recall rates in various scenes even under the condition that there are moving objects, and it outperforms the conventional background subtraction methods.

Realization of Computer-Aided Aircraft Tolerance Design

GUO Changhong, ZHAN Zaiji, WANG Zhenyu

2012, 25(5): 776-783. doi: 10.3969/j.issn.0258-2724.2012.05.008

[Abstract](1114)

PDF 926KB(314)

Abstract:
In order to solve the problem of aircraft tolerances computerization, the modeling techniques of aircraft tolerance were researched. Using UG (UniGraphics) second development technology and VC++, computer-aided aircraft tolerance optimization design modules were developed in the UG platform to realize computer-aided aircraft tolerance analysis and tolerance distribution. A practical and reliable aircraft tolerance database was created to realize aircraft tolerance automatic inquiry. Finally, the applied examples of aircraft tolerance analysis and tolerance distribution were given. The examples verify the correctness of the research results to complete the preliminary computerization of aircraft tolerance design and provide a technical reference for digital design of aircraft tolerances.

Extraction and Calibration of Trajectory Characteristics of Vehicles at Intersections

JIANG Sheng, WANG Dianhai, QU Zhaowei, HU Hongyu

2012, 25(5): 784-789. doi: 10.3969/j.issn.0258-2724.2012.05.009

[Abstract](1016)

PDF 698KB(351)

Abstract:
In order to probe into the running characteristics of vehicles at intersections, the composite feature extraction algorithm was used to obtain the trajectory characteristics of vehicles in images. Based on the algorithm of polygon linear scan calibration, considering the influence of the distortion of CCD (charge-coupled device) camera and introducing center deviation factor, an MRSCCO (multi-region scanning calibration considering about center offset) algorithm was proposed to transform the trajectory features of images into real motion features. Finally, data extracted using this algorithm were compared with both results obtained by the algorithm of polygon linear scan calibration and real data. The experimental results show that the proposed algorithm can effectively extract the trajectories of vehicles at intersections and accurately express the relevant characteristics. Compared with the real vehicle speed, the vehicle speed obtained by the MRSCCO algorithm has an error of less than 4%.

Image Alignment Algorithm for Multi-projector Display System Based on Structured Light

XIAO Chao, YANG Hongyu, SU Xianyu

2012, 25(5): 790-796. doi: 10.3969/j.issn.0258-2724.2012.05.010

[Abstract](1190)

PDF 969KB(447)

Abstract:
In order to solve the problem of image alignment in a multi-projector display system, an image alignment algorithm based on the structured light projection technique was proposed. The algorithm uses intersection points of phase-equal lines to establish the mapping relation between projector images and camera images. For an arbitrary pixel point on projector images, it has a horizontal phase value and a vertical phase value. In horizontal phase unwrapping diagram of camera images, a series of discrete coordinate points with a phase value equal to the horizontal phase value of this pixel point is found, and these discrete points are fit to a horizontal phase-equal line. In the same way, a vertical phase-equal line of the pixel point can be obtained. And the intersection point of the horizontal and vertical phase-equal lines is the pixel point on camera images corresponding to the projector pixel. The analytic expressions of display wall and the internal parameters of a camera are not necessary for the proposed algorithm, so the algorithm is suitable for curved display walls with arbitrary smooth surface. The comparison experiments between aligned images and original images show that the peak signal to noise ratio reaches 27.904 and the structure similarity is 0.972 4 to demonstrate that the proposed algorithm can improve image alignment accuracy effectively.

Received Signal Strength Indicator Circuit for Wireless Communication Systems

HE Xiaofeng, MA Chengyan, YE Tianchun, GAN Yebin, JIN Yuhua

2012, 25(5): 797-805. doi: 10.3969/j.issn.0258-2724.2012.05.011

[Abstract](1233)

PDF 946KB(455)

Abstract:
To solve the problems that accuracy of traditional signal strength indicator circuit is low and resistance to temperature and process variations is not enough strong, a system model for RSSI (received signal strength indicator) circuit was set up. The relationship between limiting amplifier gain and signal strength detection unit error was derived, and measures to decrease the error were obtained. Through analyses ways to reduce gain change with temperature and process under the condition of improving accuracy were gained. Based on the analyses, a gain-enhanced structure was introduced to improve the accuracy of limiting amplifier gain and raise its ability to resist temperature and process variations. The designed circuit uses 0.18 μm bulk silicon (CMOS) technology with 1.8 V power supply, and its area is 500 μm × 200 μm. The test results show that the dynamic gain range of the circuit can reach 55 dB while test temperature changes from -40 ℃ to 85 ℃. The circuit can provide a bandwidth greater than 55 MHz and its detection error is less than 1.5 dB. The power consumption of the circuit is 1.89 mW, and its detection accuracy is up to 1.5 dB.

Multi-agent-Based Coordination Control of Continuous Cophase Traction Power Supply System

ZHAO Yanling, LI Qunzhan

2012, 25(5): 806-813. doi: 10.3969/j.issn.0258-2724.2012.05.012

[Abstract](1319)

PDF 1010KB(550)

Abstract:
In order to solve the problems of power quality, electric section-phase insulator of the traction power supply system for electrified railway, which will affect the high-speed and heavy-load train running normally, a viewpoint on establishing an intelligent traction power supply system based on multi-agent was put forward, and the system structure and development methods were discussed. The agents' functions were proposed and the coordination and collaboration problems were described. To solve the problems of parallel running and power flow dispatch of traction substations, the coordination control strategy between substations was used. The numerical simulation of the proposed system for Beijing-Shanghai high-speed railway was executed. The simulation results show that the level-two autonomous control strategy with the coordination agent involved is significantly better than any other way, and it can realize power flow dispatch between traction substations, and make the disturbed node voltage recover to the initial value, so the whole voltage level of a power supply system can be ensured.

Contactless Power Transfer System with Stabilized Frequency and High Efficiency Based on Impedance Conversion

XIA Chenyang, ZHANG Yanbing, WU Xiaojie, SUN Yue, ZUO Lan, LI Chaowei

2012, 25(5): 814-819. doi: 10.3969/j.issn.0258-2724.2012.05.013

[Abstract](1491)

PDF 696KB(407)

Abstract:
Aimed at the problem that the variation of load resistance can seriously affect the resonant frequency and efficiency of a contactless power transfer (CPT) system, a stabilized frequency and high efficiency CPT system design method based on impedance conversion was put forward to improve its frequency stability and efficiency. According to the theory that switching converters can realize impedance conversion, a switching converter was added to the secondary circuit, the duty cycle of the converter was controlled to realize the equivalent impedance conversion, and the resonance compensation parameters of the CPT system were optimized for achieving stable frequency and high efficiency. Through resonance compensation and impedance conversion analysis, the calculation equations for the key parameters were built up, and the analytical resolution of the switch duty cycle and the load resistance were obtained. Experimental result shows that when the resistance changes from 1 to 10 Ω, the efficiency of the CPT system can always keep 67.0% through adjustment of the duty cycle.

Solution for Speed Sensorless Control System Restarting at Unknown Speed of Traction Motor

XIONG Chenglin, FENG Xiaoyun, SONG Wensheng

2012, 25(5): 820-825,831. doi: 10.3969/j.issn.0258-2724.2012.05.014

[Abstract](1062)

PDF 705KB(507)

Abstract:
In order to solve the problem that a traction motor may restart at unknown speed when a speed sensorless control system is applied in electric traction drives, a new strategy using regenerative mode to replace coasting mode is presented on the basis of analyzing the train's operating state and the root causes of this problem, and the effectiveness of this method is verified by numerical simulation using Matlab/Simulink. Taking the parameters of the electric multiple unit (EMU) CRH3 and the electric locomotive HXD3 for example, the influence of this strategy on speed and running time of the motor train is calculated. The results show that compared with those of passing the phase insulator under coasting mode, the loss in both of speed and running time is less than 2% for the EMU running at a speed more than 200 km/h, and less than 7% for heavy haul freight train running at more than 60 km/h.

Numerical Simulation of Two-Dimensional Laminar Flow around Circular Cylinder with Splitter Plate

HE Chuan, DUAN Zhiqiang

2012, 25(5): 826-831. doi: 10.3969/j.issn.0258-2724.2012.05.015

[Abstract](1578)

PDF 689KB(397)

Abstract:
In order to study the effect of splitter plate on flows past through a circular cylinder, the finite volume method, unstructured grids, and the laminar flow model were used to solve the two-dimensional incompressible N-S equation. A thin plate was placed along the horizontal centerline downstream of the circular cylinder, and the flow past this circular cylinder was simulated with a two-dimensional model at Reynolds number 200. The change in the contour of instantaneous velocity, Strouhal number, and the average drag coefficient with the plate length were then obtained. Numerical results indicate that the splitter plate can effectively suppress the vortex shedding of the cylinder, weaken the energy dissipation in the wake region, and reduce the Strouhal number. The vortices are confined to the sides of the plate stably and symmetrically, and the vortex shedding behind the circular cylinder disappear completely when the length of the splitter plate is seven times more than the diameter of the circular cylinder (i.e., L/D≥7), then the flow field behind the circular cylinder changes into streamlines. Meanwhile, the drag coefficient continuously decreases along with the plate length. When the plate length is seven times the cylinder diameter, the drag coefficient decreases from 1.43 to 0.87, by about 40%.

Unsteady Characteristics of Vortex Breakdown over Delta Wing

ZHANG Minglu, YANG Yiren, LÜ, Zhiyong

2012, 25(5): 832-835. doi: 10.3969/j.issn.0258-2724.2012.05.016

[Abstract](874)

PDF 461KB(303)

Abstract:
In order to investigate the unsteady characteristics of the broken vortices over delta wing after the leading edge vortices were broken down, experiments of dynamic pressure measurement were carried out on the surface of the 75? sweep delta wing in a wind tunnel. Experimental results show that the root mean square (RMS) pressure fluctuation is positively correlated with the fluid state of leading edge vortices on the top surface of delta wing. At the angle of attack region with leading edge vortices breakdown, the maximal RMS pressure fluctuation is 33 Pa. With increasing angle of attack, the variation of buffeting strength has the same tendency as that of RMS pressure fluctuation. Analysis of the pressure signal shows that the pressure fluctuations over the delta wing are mainly caused by the spiral wave of the broken-down vortex flow, which leads to the buffeting of the delta wing.

Numerical Simulation of Ultrasonic Wave Propagation in Wheel/Rail Material

DENG Weili

2012, 25(5): 836-841,848. doi: 10.3969/j.issn.0258-2724.2012.05.017

[Abstract](1502)

PDF 677KB(469)

Abstract:
To enhance the application of ultrasonic waves to rail flaw detection and train safety monitoring, a finite model was introduced to study the ultrasonic sound field distribution characters. In this model, the acoustic field due to ultrasonic propagating in rail was simulated with different frequencies and sizes of ultrasonic sources. The distribution of acoustic pressure on central axis was plotted; and the relationships between ultrasonic near field length, spread angle, frequency, and source size were discussed. The results show that among the models with the same source size, the one with a frequency of 1.0 MHz has the longest near-field length and the best spread angle; and among the models with the same ultrasonic frequency, the one with a source size of 40 mm has the longest near-field length and the best spread angle.

Load Control of Ship Accelerating Process Based on PI Controller

HUANG Bin, WANG Yongsheng

2012, 25(5): 842-848. doi: 10.3969/j.issn.0258-2724.2012.05.018

[Abstract](1251)

PDF 728KB(474)

Abstract:
A simulation model for a combined diesel or gas turbine (CODOG) propulsion system was built in Matlab/Simulink, and the veracity of this model was validated using the trail data of actual ship. Through the model, two existing accelerating control approaches were simulated and their flexibility was evaluated. The result shows that during the emergent accelerating process, the main engine is overloaded seriously; during the natural accelerating process, however, the redundancy of the engine power is big and the flexibility is low. To improve the flexibility, a method using PI controller was proposed to design the "engine-propeller" combined control curve of the accelerating process. In this method, the controller uses the engine power redundancy to adjust the increasing ratio of engine speed and propeller pitch during the accelerating process. Simulation result shows that using this method to control the accelerating process, the engine overloading can be avoided, and the increasing ratio of the ship velocity is about 70% faster than the natural accelerating process.

Application of Multirate Unscented Kalman Filter to State Estimation in Vehicle's Active Front Steering System

ZHOU Cong, XIAO Jian, WANG Song

2012, 25(5): 849-854,894. doi: 10.3969/j.issn.0258-2724.2012.05.019

[Abstract](1190)

PDF 624KB(400)

Abstract:
In order to improve the control quality of the single-rate digital control strategy in a complex system, an input multirate unscented Kalman filter (IMRUKF) was developed by combination of multirate digital control systems and the unscented Kalman filter (UKF) algorithm. The IMRUKF algorithm was applied to estimate the yaw rate, slip angle, and longitudinal velocity of the active front steering (AFS) system of vehicles. Then, a co-simulation and a Monte Carlo experiment were carried out using Carsim and Simulink. The results show that IMRUKF improves the ability of the state estimator by integrating multi-input information. Compared with the single-rate UKF algorithm, the IMRUKF algorithm has a higher stability and a smaller estimation error (with a reduction in the error of around 4.0% to 48.7%).

Design and Performance Analysis of Efficient Semi-active Energy-Regenerative Suspension

YANG Heli

2012, 25(5): 855-860. doi: 10.3969/j.issn.0258-2724.2012.05.020

[Abstract](1372)

PDF 714KB(299)

Abstract:
On the basis of normal gear and rack type suspension, an efficient semi-active energy-regenerative suspension was designed to improve the damping properties and energy-regenerative characteristics of gear and rack type suspension. This suspension consists of a NdFeB permanent magnet generator, a variable-speed mechanism, a reversing gear and an impact protection device. The simulation and experiment for the efficient semi-active suspension were made. The research results show that compared with the gear and rack type suspension, the rotary inertia and volume of generator rotor of the semi-active energy-regenerative suspension are reduced by 71% and about 40% respectively, exciting power is saved by 20 to 30 W, and dead zone is decreased from -0.22-0.22 m/s to -0.04-0.04 m/s. Furthermore, damping and energy-regenerative characteristics are improved, and energy conversion efficiency raises from about 20% to over 50%. Compared with the passive suspension, the maximum value of dynamic tyre load, the maximum vertical acceleration of sprung mass and suspension dynamic deflection all are decreased by over 20%.

Delay Map Matching Algorithm of Mass GPS Data Based on Topological Judgment

WANG Zhijian, WANG Li, WANG Jian

2012, 25(5): 861-866. doi: 10.3969/j.issn.0258-2724.2012.05.021

[Abstract](1085)

PDF 783KB(348)

Abstract:
Traditional algorithms for vehicle map matching can not be applied directly because of lengthy GPS date cycle, low relevance of road topology structure and a number of data in the processing of floating car data collection. For this reason, a new algorithm of delay map matching was proposed based on a road topology structure under the condition that a vehicle can not match the data at the first time. The actual testing data indicate that the new algorithm has a great instantaneity and accuracy in map matching to effectively solve the problem of traffic data collection in complex intersections and viaduct areas.

Judgment of Train Operation Conflict and Its Implementation for High-Speed Railway

WEN Chao, PENG Qiyuan, CHEN Yuhong

2012, 25(5): 867-873. doi: 10.3969/j.issn.0258-2724.2012.05.022

[Abstract](1486)

PDF 857KB(472)

Abstract:
In order to improve railway traffic control level and ensure railway operation safety, the judgment methods for 7 types of train operation conflicts were studied, including time interval conflicts between two adjacent trains at stations, conflicts of section occupation, utilization conflict of arrival and departure track, conflicts between train running and maintenance work, conflicts between train running and passenger transfer time, connecting time conflicts of electric multiple units (EMUs), and time conflicts of cross-line trains. According to the judging rules of high-speed train operation conflicts, the calculation criteria for temporal relation of event time slice was established using the theory of time topology matrix, and the time logic checking of train events was realized. The job of train operation conflict judging is divided into two parts, i.e., the utilization conflict of arrival and departure tracks and the other types of conflicts, for high-speed rail system. In addition, the judgment methodology and processes were described. A application instance shows that the method that combines the conflict judging rules with the time topology matrix can successfully judge the various types of real-time train operation conflicts and meet the demands of high-speed railway traffic control.

Multi-objective Model for Logistics Distribution Programming Considering Logistics Service Level

GUO Xiaofang, WANG Yuping

2012, 25(5): 874-880. doi: 10.3969/j.issn.0258-2724.2012.05.023

[Abstract](1029)

PDF 870KB(584)

Abstract:
To improve the customer satisfaction on the service of logistics distribution, a multi-objective optimization model for logistics distribution programming under the three-level supply chain was developed. In this model, minimization of total expenses and maximization of logistics service level were optimization objectives, and the influence of both the commodity processing ability and distribution time on the logistics service level was taken into account. Given that there is no single optimal solution for multi-objective optimization problems, a preference-based multi-objective evolutionary algorithm for solving the model was proposed with a pre-defined preference area and randomly generated weight vector used to establish the fitness function. The results show that by solving the model, ten non-inferior solutions are obtained, each of which represents a distribution program. The ten solutions without exception lie in the subjective preference area of the decision maker and reflect the conflict relationship between total expenses and logistics service level.

Solving the Mode Selection Problem with Fixed Transportation Cost in Intermodal Transportation

LI Yu, ZHAO Jun, WU Gang, CHEN Jiaqi

2012, 25(5): 881-887. doi: 10.3969/j.issn.0258-2724.2012.05.024

[Abstract](1201)

PDF 892KB(453)

Abstract:
To organize the intermodal transportation in a more cost-effective way, the problem of selecting the transportation mode in each link along the transportation route of an intermodal shipment was addressed by taking into account the fixed and variable transportation cost simultaneously. Aiming at minimize the total cost including transportation cost, transfer cost, and penalty cost, and taking the shipment delivery time and transportation capacity as constraints, a mixed integer linear programming model was proposed, and a corresponding integer-based encoding genetic algorithm was designed. Computational results show that the proposed model can find much better solutions when compared with the existing model that does not consider the fixed transportation cost. For 15 random instances with 20 to 100 links and 5 to 20 transportation modes, the present algorithm find much better solutions than the commercial optimization solver LINGO within the same computation time of 60 seconds for 2 large-scale instances, achieving an average total cost-saving of 0.75%. This proves the efficiency of the proposed algorithm for large-scale instances.

Car-Following Model Based on Optimal Distance and Its Characteristics Analysis

YANG Da, PU Yun, YANG Fei, ZHU Liling

2012, 25(5): 888-894. doi: 10.3969/j.issn.0258-2724.2012.05.025

[Abstract](1461)

PDF 829KB(588)

Abstract:
To reveal the mechanism of car-following behaviors more accurately, a car-following optimal distance model (ODM) was proposed based on analysis of the optimal distance function, under an assumption that drivers in a car-following process always tend to maintain an optimal spacing distance. Then, the ODM and Gipps' car-following model were calibrated and evaluated using the next generation simulation (NGSIM) data. The numerical simulation method was adopted to analyze the acceleration characteristic of the ODM and its ability in reproducing the macroscopic phenomena of traffic flow. The results show that the simulation accuracy of the ODM in acceleration, velocity and distance MAE (mean average error) is 0.36 m/s2, 0.99 m/s and 0.73 m higher than that of the Gipps' model; the ODM can reproduce the stable state and shock wave phenomenon of traffic flow, and always tends to choose an acceleration that can make the distance between successive vehicles equal or just fluctuate about the optimal distance value in the stable state.

Analysis Model of Transport Aircraft Veering off Runway during Landing Phase

HUO Zhiqin, RU Yi, HAN Songchen

2012, 25(5): 895-900. doi: 10.3969/j.issn.0258-2724.2012.05.026

[Abstract](1054)

PDF 710KB(334)

Abstract:
In order to overcome the flaws of traditional fault tree analysis which can only describe two states: normal or fault, a combined method based on fault tree (FT) and Bayesian Network (BN) for landing aircraft veering off runway analysis was put forward. The new method not only took the advantages of logical analysis of fault tree but also the function of the description of polymorphic events and probability calculation of Bayesian network. In addition, a transform algorithm from FT to BN was proposed to solve the model. Based on the data about aircraft veering off runway during landing phase of Civil Aviation Administration of China from 1996 to 2010, the key factors causing runway excursion landing accidents of aircrafts were determined and then ranked by their importance. The result indicates that standing water, dysfunction of thrust reverser or airbrake, complex weather conditions, deficiency of piloting technology, jammed nose wheel steering, night operation or adverse influence from lights, failure of crew resource management, accumulated ice or snow should be the key concerns whose posterior probability are greater than 0.3; and targeted preventive measures should be developed toward the major risky factors. The analysis result produced by the model is consistent with the fact.

Measuring Traffic Conflict of Single Ship Crossing Ship Flow Based on Integrative Distance Index

CHENG Zhiyou, LIU Qing, HE Detao, LI Zhite

2012, 25(5): 901-906. doi: 10.3969/j.issn.0258-2724.2012.05.027

[Abstract](1108)

PDF 800KB(257)

Abstract:
To supervise the traffic risk of single ship crossing ship flow in waters, an integrative distance index was proposed to measure the traffic conflict of single ship crossing ship flow by considering the impact of single ship crossing's dynamic course and associated multi-objects. A primary model was built to measure the traffic conflict of single ship crossing ship flow according to the inverse ratio relation between the integrative distance index and traffic conflict. Then, the criteria in mild, moderate, and severe traffic conflict conditions for single ship crossing ship flow were confirmed by comparison between the criterion from 85 percentile cumulated frequency value analysis based on expert questionnaire data and the probability interval at 95% of the observed integrative distance index data in corresponding conditions. The results show that measuring model can exactly reflect the impact of the three parameters of integrative distance index on the traffic conflict of single ship crossing ship flow. When the value of the three parameters increases simultaneously, the traffic conflict borne by single ship decreases; when the value of anyone parameter decreases, however, the traffic conflict borne by single ship increases. The criteria proposed in this paper applies to cases when visibility is 0.8 to 6.0 n mile in the inner waters, ship length is 60 to 180 m, ship speed is 3 to 13 kn, and the impacts of wind, current and wave are negligible.

Search Advance Search

Journal Search

Search Type

NewsMore

instruction for authors

Read this journal

LinksMore

2012 Vol. 25, No. 5