西南交通大学学报

Analysis of Residential Accessibility of Stream Systems in Downtown Area of Nanjing

ZONG Yueguang, LIU Yingzi, WU Peng

2009, 22(6): 799-805.

[Abstract](1461)

Abstract:
To research the effect of the accessibility of stream systems on the distribution of residential areas,an accessibility analysis model was built in the module of GIS(geographic information system) software based on the shortest distance analysis method and the transport accessibility theory.ArcGIS9.2,a software,was used to determine the least time cost of different-class transportation and analyze the time-distance circle of the residential accessibility of stream systems and the distribution of newly-built residential areas in the downtown area of Nanjing,as an example,in the years 1990 and 2008.The analysis results show that from 1990 to 2008,residential areas within 5-min accessibility of stream systems decreased by about 10% in the downtown,those between 5-and 10-min accessibility and between 10-and 20-min accessibility increased respectively by about 5.8% and 5.4%,while residential areas with over 20-min accessibility did not change basically.About 80% of the newly-built residential areas in the downtown area were located within 10-min accessibility.It can be concluded that the proportion of residential areas within 5-min accessibility of stream systems has decreased in the downtown in the past 20 a,but the newly-built residential areas have displayed an obvious tendency towards water areas.

Vehicle-Bridge Coupling Vibration Analysis of PC Rail Beam of Straddle-Type Monorail Transportation

MA Jibing, PU Qianhui, HUO Xuejin

2009, 22(6): 806-811,829.

[Abstract](1795)

Abstract:
In order to discuss the dynamic responses of a straddle-type monorail transportation system,a dynamic model for a monorail vehicle with 15 DOFs(degrees of freedom) was established by employing the linear tire model.The radial rigidities,side-leaning effects and longitudinal slide-turning characteristics of running,steering and stabilizing tires are taken into account in this model.Dynamic responses of a PC(prestressed concrete) rail beam in a typical section of the straddle-type monorail transportation system in Chongqing City were calculated by using a self-compiled program and compared with field test results to show the correctness of the established dynamic model and the self-compiled program.

Influencing Factors of Ultimate Load-Bearing Capacity of Long-Span Composite Girder Cable-Stayed Bridge

LEI Yu, ZHAO Lei, LI Xi

2009, 22(6): 812-816.

[Abstract](1725)

Abstract:
In order to deeply research the effects of stay cable breaking,relative interface slip of composite girder and deck shear-lag effect on structural ultimate load-bearing capacity,Guanyinyan composite girder cable-stayed bridge in Jiangjin in Chongqing,as the engineering background,was investigated by considering geometrical nonlinearity,material nonlinearity,system transition and cumulative effect of displacements and stresses and adopting the theory of second kind static stability.The research results show that stay cable breaking,relative interface slip of composite girder and deck shear-lag effect have great influences on safety factor for the ultimate bearing-capacity of a long-span composite girder cable-stayed bridge,and the maximum variation of the safety factor resulted from them are respectively 23.0%,19.0% and 42.4%.The effect of stay cable breaking on the ultimate load-bearing capacity increases firstly and then decreases gradually,while the influences of the relative interface slip and the deck shear-lag effect behave mainly at the stage of short cantilever.

Performance-Based Damage Analysis for PC Continuous Rigid Frame Bridges

ZHANG Fang, QIAN Yongjiu, TANG Jishun

2009, 22(6): 817-822.

[Abstract](1693)

Abstract:
In order to find out the causes of the cracking and deflection of PC(prestressed concrete) continuous rigid frame bridges,a damage analysis method based on structure performance was proposed.In this method,the objective manifestations of structure performances are considered as the focus of attention,and the analysis of damage factors for structure performances is as the primary means.By comparing a large number of theoretical and test data and using load test data as a judgment basis to identify damage elements and damage degree,a more realistic performance level of a damaged bridge is obtained,and this performance level can be used as the basis of reliability evaluation and strengthening design.The damage analysis of a PC rigid frame bridge with a span of 160 m,as an example,shows that with the proposed method,the check coefficient of deflection can reach to 0.9.

Experimental Investigation of Fatigue Behavior of Tension Steel Plate Reinforced with Prestressed CFRP Laminates

YE Huawen, KÖ, NIG Christian, UMMENHOFER Thomas, QIANG Shizhong

2009, 22(6): 823-829.

[Abstract](1671)

Abstract:
To properly estimate the fatigue performances of a steel structure reinforced with prestressed CFRP(carbon fiber reinforcement polymer) plates,a modified Paris’ equation based on effective stress intensity factor range was presented to analyze the propagation of fatigue cracks.The effects of stress ratio,CFRP stiffness,prestress and adhesive property on fatigue crack growth were investigated through the fatigue tests of central cracked specimens.The experimental results show that the fatigue lives of reinforced specimens extend greatly,more than 16 times that of an un-reinforced specimen,and that their theoretically predicted results are more conservative than the experimental results.The prestress,rather than the properties of CFRP and adhesive,dominates the fatigue behavior of a reinforced specimen.The stress ratio plays a significant role in the fatigue life of a reinforced specimen.Therefore,the proper estimation of traffic loading is the foundation of effective reinforcement.

Detection of Gross Errors in DEM Based on Principal Components Analysis

YANG Xiaoyun, CEN Minyi, LIANG Xin

2009, 22(6): 830-834,854.

[Abstract](1507)

Abstract:
To probe into the effect of error spatial distribution on the detection rate of gross error for a digital elevation model(DEM),two different models,spike-like and pyramid-like gross error models,were constructed.Data with different gross error rates of 0.2% to 3.0% were simulated and added to DEM randomly.A detection algorithm based on the principal components analysis(PCA) was used for tests.The result shows that whether gross errors are spatially correlated or not,the detection rate decreases with increasing of the gross error rate.To a spike-like gross error,when the rate is below 1.0%,almost all gross errors can be found out.While to a pyramid-like gross error,the detection efficiency decreases to 50% when the rate is equal to 1.0%.It can be found that the spatial relativity and a high gross error rate will cut down the detection rate of the algorithm.

Simulation Analysis of Dynamic Characteristic of Harmonics for High-Speed Locomotive Running at Rated Power

GUO Lei, LI Qunzhan, LIU Wei, XIE Shaofeng

2009, 22(6): 835-840.

[Abstract](1773)

Abstract:
An analytical method for calculating the dynamic characteristic of the harmonics of high-speed locomotives running at a rated power was presented by analyzing the generation process of harmonic voltage and the characteristics of harmonic impedance of a traction power supply system.Based on the double Fourier series and the Bessel function,the expression of harmonic voltage of a PWM(pulse width modulation) rectifier was deduced.Based on the distributed parameter model the formula of calculating harmonic impedance for an overhead contact system was derived,and from the formula,series resonances and parallel resonances were analyzed.Frequency spectrum characteristics of harmonic voltage and harmonic current under the condition that a high-speed locomotive runs at a rated power were simulated and analyzed.The research results indicate that the frequency spectrum characteristics of both harmonic current and harmonic voltage vary,especially the former;series resonances occur at some frequency and the resonance position depends on locomotive position along the line;harmonic current contents are small,and the main contents are the 3rd to 9th and series resonance harmonics.

Optimal Compensation Models in Cophase Power Supply System

ZHANG Xiufeng, LÜ, Xiaoqin, LIAN Jisan

2009, 22(6): 841-847.

[Abstract](1652)

Abstract:
To balance the three phases,filter the harmonics and compensate the reactive power in a cophase power supply system,two optimal compensation models were proposed: the minimum waveform distortion model,which can get best waveform quality,and the optimum resistance model,which can get optimum load.Then,the compensation effects of the two models with distortion voltages were analyzed by simulation.The results show that the former can only get fundamental active current,and the latter can transform an unbalanced single phase into a balanced three-(or two-or four-) phase resistant load.The two models have the same compensation characteristics under voltages without distortion and unbalance,and there are differences under voltages with distortion and unbalance.

Probability Distribution of Feeder Current of Traction Substation

ZHANG Liyan, LI Qunzhan, XIE Shaofeng, CHEN Minwu

2009, 22(6): 848-854.

[Abstract](1403)

Abstract:
Based on the theory of stochastic process and the method of numerical analysis,probability density function for the feeder current of traction substations was fitted by using the β-function and the statistical analysis of extensive recorded data of the feeder current.Feeder current samples were obtained by using the Monte Carlo method to supply more detailed information for the procedure analysis of the feeder current.A comparison between the simulation results and recorded data of the feeder current shows the same statistical regularity to verify the effectiveness of the adopted approach.

Simulation of High-Speed Pantograph Dynamic Performance Based on Finite Element Model and Aerodynamic Pantograph Model

WU Yan, WU Junyong, ZHENG Jihao

2009, 22(6): 855-859.

[Abstract](1881)

Abstract:
A coupled finite element model for the pantograph-catenary system and an aerodynamic pantograph model were built.Based on the models,the dynamic current collection and aerodynamic performances of the pantograph were studied using MSC-Marc and STAR-CD simulation software.In the finite element model,the pantograph and catenary subsystems are integrated into a whole system through contact coupling between them,to simulate the dynamic behavior of the pantograph-catenary system.Then,the aerodynamic performance of the high-speed pantograph was simulated on the three-dimensional aerodynamic pantograph model.The simulation results show that the dynamic uplift and average contact force of simple suspension are smaller than those of stitched suspension.When the train speed reaches 250 km/h,the additional uplift force caused by the high speed air flow on pantograph is about 12 N and the drag force is about 550 N.

Robust Strictly Passive Control of Uncertain Descriptor Systems

WANG Cuihong, HUANG Tianmin

2009, 22(6): 860-864,911.

[Abstract](1597)

Abstract:
The strictly passive realness and strictly passive control of an uncertain linear descriptor system was investigated.To solve the problem of equality restriction in strictly passive conditions of a descriptor system,the relationship between the fast and slow subsystems of a descriptor system was described by using a relaxed variable,and a new sufficient condition was presented to ensure that a descriptor system is strictly passive in terms of strict linear matrix inequality(LMI).Based on the sufficient condition,a robust strictly passive controller was designed and a numerical example was given to show the designed controller can ensure that a closed-loop system is strictly passive.

IIR Digital Filter Design via Seeker Optimization Algorithm

DAI Chao-Hua, CHEN Wei-Rong, SHU Yun-Fang, ZHENG Yong-Kang, LI Ai

2009, 22(6): 871-876.

[Abstract](2736)

Abstract:
To further improve the performances of infinite impulse response(IIR) digital filters,a new approach based on the seeker optimization algorithm(SOA) was proposed for IIR digital filter design.The SOA is aimed to simulate the random action in human searching behaviors for solving an optimization problem through the update of seekers’ positions.In the algorithm,the search direction is determined by the empirical gradients based on evaluating the responses to the changes of the seekers’ positions,and the step length is decided by uncertainty reasoning based on a simple fuzzy rule.The performance of the SOA was investigated by two typical cases of IIR digital filter design.The simulation results show that compared with the differential evolution(DE) and three modified particle swarm optimization(PSO) algorithms,the proposed approach has both a good global search ability and a fast convergence speed,as a result,the SOA can be efficiently used for the design of IIR digital filters.

Data-Driven Q-Learning in Dynamic Environment

SHEN Yuanxia, WANG Guoyin

2009, 22(6): 877-881.

[Abstract](1596)

Abstract:
It is difficult for reinforcement learning to balance between the exploration of untested actions and the exploitation of known optimum actions in dynamic environment.To address this problem,a data-driven Q-learning algorithm was proposed.In this algorithm,the information system of behavior is constructed for each agent.Then the trigger mechanism of environment is build by the uncertainty of knowledge in the information system of behavior to trace the environmental change.The dynamic information of the environment is used to exploit new environment by the trigger mechanism to achieve the balance between the exploration of untested actions and the exploitation of know optimum actions.The proposed algorithm was applied to grid-world navigation tasks.The simulation results show that compared with the Q-learning,simulated annealing Q-learning(SAQ) and recency-based exploration(RBE) Q-learning algorithms,the proposed algorithm has a high learning efficiency.

Test Study on Stability Control of Locomotive Coupler in Heavy Haul Combined Train

YANG Junjie, LIU Jianxin, LUO Shihui, FENG Quanbao

2009, 22(6): 882-886.

[Abstract](1878)

Abstract:
To control the dynamic stability of locomotive couplers in heavy haul combined trains,a formula for calculating the maximum free swing angle of heavy-haul locomotive couplers was derived from the stability principle of the coupler and the geometric relation between the coupler and carbody on rails.Taking some locomotive driving a heavy train in Datong-Qinhuangdao line with coupler & draft gear DFC-E100 as an example,the effect of the lateral swing of the coupler for the middle locomotive on locomotive operation security was studied by tests.In the tests,the coupler longitudinal force was increased gradually by changing the haul weight,organization mode,and braking mode of the train,and the security parameters such as locomotive derailment factor,wheel unloading rate,and lateral wheelset force were measured in different operating conditions.The results show that the lateral swing angle of the locomotive coupler would increase with the coupler longitudinal force under the action of coupler pressing force.The bigger the maximum lateral swing angle of the coupler is,the bigger the security parameters of the locomotive are,and the bigger the risk of locomotive derailment is.With engineering errors taken into consideration,the maximum free swing angle of the locomotive coupler should be controlled in the range of 2.5°~3.5°.

Global Exponential Synchronization of Impulsive Chaotic Neural Networks

XU Xiaohui, CAO Yu, ZHANG Jiye

2009, 22(6): 887-892.

[Abstract](1642)

Abstract:
To study the dynamical behaviors of impulsive neural networks,the global exponential synchronization of a class of impulsive chaotic neural networks with time-varying delays was analyzed based on the conception of drive-response.On the assumption that the activation functions increased monotonously,inequalities were constructed using weighted coefficients,self-feedback functions and activation functions of the neural network.The equations of sufficient condition for global exponential synchronization of drive and response systems were obtained based on the theory of vector Lyapunov function,and all the equations were negative.The result of a numerical simulation demonstrated the correctness of the sufficient condition.

Bayesian Estimation of Vehicle Dynamic Performance by Rail Measurement

CHEN Lei, ZENG Yuqing, YU Weidong

2009, 22(6): 893-899.

[Abstract](1686)

Abstract:
An assessment technique that assesses vehicle dynamic performance using the data of rail measurement was developed by Bayesian estimation principle.The assessing data of dynamic performance were obtained from the on-board and on-ground monitoring in the 35×104 km reliability tests of China speed up wagons at the velocity of 120 km/h.A probability model about the relationship between on-ground and on-board monitoring data was built by applying the Parzen’s window method and an improved two-dimensional interpolation technique to smoothen the probability density functions.The derailment coefficient of the speed up wagons was assessed according to the on-ground data.The result shows that the derailment coefficient of the existing speed up wagons in China is up to 1.2613.

Estimation Method of Humping Time in Marshalling Yard

JING Yun, WANG Ciguang, XUE feng, MU feng

2009, 22(6): 900-905.

[Abstract](1408)

Abstract:
To solve the problem that the humping time for trains is highly uncertain during the break up operation in marshalling yard,a regression model was built for interval estimation of the humping time,in which the humping time for a train is used as the dependent variable and the number of cuts in break up operation as the independent variable.With the obtained interval estimate value,the humping time of each train is expressed as a fuzzy set to solve for its λ-cut set and obtain the point estimate value of the humping time.The result of a case study involving 16 trains for hump operation shows that the estimation error of the point estimate value obtained by the model is 50% lower than that estimated by the current humping time standard.

Optimization of Seat Comfort of High-Speed Train

CHEN Xiang, XU Bochu, ZHANG Weihua

2009, 22(6): 906-911.

[Abstract](1895)

Abstract:
To improve the ride comfort of high-speed trains,a questionnaire about the seat comfort of CRH2 high-speed train was carried out.The factors influencing the seat comfort were determined with multiple regression analysis based on the results of the questionnaire,body data of Chinese people,and the seat design theory combined with the ergonomics.Seat dimensions that suit to Chinese people was presented: the seat back angle is 100° to 120°,the width and height of seat back are less than 415 and 729 mm,respectively,and the headrest is 700 to 859 mm above the seat surface.

Urban Vehicle Routing Based on Ant Colony Algorithm

LIU Jingyu, FANG Yanjun

2009, 22(6): 912-917.

[Abstract](1692)

Abstract:
To solve the problem of urban traffic vehicle routing,an improved ant colony system(ACS) algorithm was proposed.The algorithm focuses on both distance and time costs of path planning.Its search rules and flow charts were given.Based on extensive simulation results,the effects of parameters of the algorithm on the convergence performance,including convergence rate and convergence accuracy,were discussed,and a set of empirical parameters were obtained.The reasons for fake optimal paths involved in the search were analyzed.Further,the algorithm was optimized by controlling the convergence rate and forcing the convergence toward to the optimal path.The simulation result indicates that the optimization is effective in restraining fake optimal paths and has a convergence rate within 2 cycles per search.

Assessment of Longitudinal Collision Risk on Parallel Routes Based on Communication,Navigation,and Surveillance Performances

ZHANG Zhaoning, LIU Jimin, Wang Lili

2009, 22(6): 918-925.

[Abstract](2163)

Abstract:
In order to study the positioning errors and longitudinal collision risk of flights and their influence factors under communication,navigation and surveillance(CNS),the CNS errors were analyzed and a formula for calculating the longitudinal overlap probability on parallel routes was derived based on Reich model.Hereby,a CNS-based assessment model of longitudinal collision risk on parallel routes was established.The result of a numerical example shows that the collision risk on the given parallel routes in RCP400,RNP10 and RSP20 conditions is 3.0×10-10,satisfying the safety target level specified by the International Civil Aviation Organization.Therefore,the assessment model is feasible.

Event-Driven Dynamic Ground Holding Policy for Single Runways

WANG Fei, XU Xiaohao, ZHANG Jing

2009, 22(6): 926-932.

[Abstract](1631)

Abstract:
In order to ensure flight safety,make full use of airport capacity,and reduce flight delay cost effectively,an event-driven dynamic ground holding policy(GHP) model for single runways was established.The model was then solved by a two-stage hierarchical optimization algorithm.The results of a numeric simulation show that by the event-driven policy,the total delay cost was reduced by 19.6% compared with that by time-driven model;and that the calculation complexity was reduced by 24.3% compared with that by linear programming method.

Dynamic Taxiway Routing Algorithm Based on Conflict Avoidance

WANG Yanjun, HU Minghua, SU Wei

2009, 22(6): 933-939.

[Abstract](3227)

Abstract:
To solve the taxi path assignment problem of aircrafts on airport surface,a dynamic taxiway routing algorithm that is based on the time-dependent shortest path(TDSP) algorithm was proposed according to the dynamic characteristic of taxiway system.Three different types of taxi conflict,together with taxi priority,were defined based on the airport ground operation.The taxiway delay functions for different taxi conflicts and taxi priorities were constructed,on the basis of which the algorithm of dynamic taxi path assignment was realized.Simulation results show that when the runway capacity reaches 32 aircrafts per hour,compared with a static taxiway assignment method,the proposed dynamic algorithm can achieve 3 min per aircraft reduction in the average taxi time,and 3.5 min per aircraft movement in the ground delay.

Wigner Functions for Eigenstates of Arbitrary Power of Annihilation Operators

LAN Haijiang, WEI Lianfu

2009, 22(6): 940-945.

[Abstract](1520)

Abstract:
Wigner functions for the eigenstates of arbitrary power of annihilation operators were reconstructed using their expressions in Fock presentations.The distribution of the reconstructed Wigner functions in phase spaces was analyzed,based on which the nonclassical properties of these eigenstates were discussed.The results show that,the distribution of the Wigner functions for these eigenstates depend on the eigenvalues of the annihilation operators;the eignestates of the annihilation operators of the first power(i.e.,coherent states) are quasiclassical(their Wigner functions are always non-negative),and those of higher powers obviously exhibit nonclassical properties(their Wigner functions may become negative).

Analytical Model of Brillouin Scattering Spectrum Measurements in Fibre-Optic Distributed Sensing Systems

XIAO Shanghui, LI Li

2009, 22(6): 946-950.

[Abstract](1537)

Abstract:
Under the condition that the pulse widths are near or below the photon lifetime,i.e.10 ns,scattering spectrum properties of fibre-optic distributed sensing systems were analyzed and discussed.A nonlinear Pseudo-Voigt(P-V) analytical model was established by optimal combination of Lorentzian and Gaussian profiles for Brillouin scattering spectrum in fiber-optic distributed sensing systems.The P-V model and the Levenberg-Marquardt(L-M) nonlinear least square algorithm were applied to curve fitting and optimal parameter estimation of measured data of Brillouin scattering spectrum.Better fitting and higher resolution for parameter estimation were obtained with the proposed method compared to the conventional Lorentzian and Gaussian profiles.

Solution to Geomagnetic Systems in Areas with Smooth Magnetic Fields

KOU Yimin, MA Guangcheng, WANG Changhong

2009, 22(6): 951-957.

[Abstract](1576)

Abstract:
To solve the divergence problem of traditional Kalman filter-based geomagnetic navigation systems caused by their unobservability in the areas with smooth magnetic fields,a new algorithm was proposed.The algorithm uses linearized planes to fit a smooth magnetic field,the vector properties of the magnetic field to construct linear equations,and multi-level submaps to realize fast and accurate position estimation.The observation equation of the Kalman filter was constructed based upon the position estimation.Theoretical analysis and simulations proved the effectiveness of the algorithm.

Surface Cleanliness Level Detection by Imaging Method for Precision Optical Elements

ZHU Xiaolong, WANG Yi, XIE Zhijiang, LIU Changchun, CHU Hongyu

2009, 22(6): 958-962.

[Abstract](1699)

Abstract:
To avoid the disturbance of flaws and improve the accuracy in measurement of surface cleanliness-level of precise optical elements,an image detection system based on machine vision method was proposed,in which a set of movable clamping fixtures for optical elements of various sizes and a three-dimensional electronic control platform were designed.In image processing,Canny edge detection operator was used to extract image edges,and the convex hull method was employed to obtain enclosed areas for the detected object.Then,a test vector was composed by the characteristic parameters extracted from the geometric space,gray-level space and spectrum domain of the enclosed area,and analyzed by relevance vector machine(RVM) method to recognize particle and non-particle contaminants on surface.Based on the results,the cleanliness-level grade of the precision optical elements can be obtained.

Electrical Properties of Ce-Doped WO3 Thin Film

DONG Liang, WANG Yu, LI Dezhu, LI Tongye, YAN Zhongming

2009, 22(6): 963-967.

[Abstract](1793)

Abstract:
Ce-doped WO3 thin films were fabricated by DC reactive magnetron sputtering on glass substrates and annealed in dry air at 550℃ for 1 h.The effects of sputtering power on electrical properties of the film were investigated.X-ray diffraction(XRD) and scanning electron microscopy(SEM) analyses were performed to characterize the film.The experimental results show that Ce-doping caused WO3 crystals to grow along the preferred orientation(b-axis) with island structures,and the film displayed the highest nonlinear coefficient of 7.92 when the sputtering powers for Ce and W were 40 W and 160 W,respectively.

Analysis of Products from Thermal Decomposition of Waste Computer Mainboard

WANG Songtao, GUO Yuwen, ZHANG Jianqiang

2009, 22(6): 968-974.

[Abstract](1294)

Abstract:
The pyrolysis characteristics and thermal decomposition products of waste computer mainboards were investigated by the TG-FTIR(thermogravimetric analyzer-Fourier transform infrared spectroscopy),a duct-furnace pyrolysis system and the GC-MS(gas chromatography-mass spectrometer).The results show that waste computer mainboards have an acute mass loss from 300 to 460℃ and about 20% of mass is lost at this stage,and the loss velocity over 600℃ is very slow.The thermal decomposition products of a waste computer mainboard include aromatic compounds comprised of 8 to 15 carbon atoms such as phenol,organic compounds with 1 to 4 carbon atoms and bromized organic compounds.These products mainly come from the decomposition of the organic polymer and tetrabromobisphenol A in waste computer mainboards.

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2009 Vol. 22, No. 6