西南交通大学学报

Overview of Error Concealment for Video Transmission

PENG Qiang, ZHANG Lei, CHEN Jim X.

2009, 22(4): 473-483.

[Abstract](1589)

Abstract:
The history and present situation of researches on video error concealment were discussed.Several representative spatial and temporal error concealment algorithms were presented with an emphasis on edge detection based adaptive spatial error concealment,motion vectors extrapolation based error concealment,multi-step multi-weighted block-warping error concealment,and distortion based adaptive SVC FGS error concealment.Their applicability and performances in different error-prone transmission environments were analyzed.The development trend of the video error concealment technologies was predicted.

Hybrid Open-Close Loop FGS Coding Framework Based on Key Reference Frame

YIE Xiaotong, DENG Yun, CAI Lecai

2009, 22(4): 484-489.

[Abstract](1193)

Abstract:
A novel fine granularity scalability coding framework with hybrid open-close loop structures based on key reference pictures was proposed.In the framework,the open-loop structure with one prediction loop is adopted to code non-key frames to achieve the best coding efficiency;some key frames exploiting the close-loop structure with two prediction loops are periodically inserted to control drift caused by the open-loop structure.To optimally exploit the bandwidth,an optimized bit-stream extraction method was proposed to give more priority to the enhancement layer of key frames than that of non-key frames.Simulation results show that the proposed framework outperforms AR-FGS(FGS with adaptive reference) in JVT SVC(joint video team scalable video coding) by about 1 to 2 dB in a very wide rang of bit rate.

Effective Twice-Clustering Algorithm for Data Streams

HU Xuegang, CAO Yongzhao, WU Gongqing

2009, 22(4): 490-494.

[Abstract](1360)

Abstract:
In order to enhance the quality of data stream clustering towards noisy and unbalanced data,an effective twice-clustering algorithm for data streams,TCLUSA for short,was proposed.TCLUSA is based on the simple divide-and-conquer and separability theorems,uses DBSCAN(density-based spatial clustering of applications with noise) to get the average point of each cluster as its local result,and then achieves the final result by clustering all the average points using the k-means.The algorithm keeps all the average points by a layered structure.The theoretical analysis and experimental results demonstrate that the proposed algorithm can enhance clustering quality efficiently when data distribution is abnormal or a high dimensional data stream is dealt with.

Performance Testing-Oriented TTCN-3

LUO Hao

2009, 22(4): 495-500.

[Abstract](1386)

Abstract:
By analyzing the limitations of test verdict,timer and synchronization mechanism in the current TTCN-3 standard,the methodology for TTCN-3 based on performance testing description was investigated from three aspects,including performance extension of the current TTCN-3 core language,performance evaluation of the test system itself and redesign of the external function.Performance testing-oriented TTCN-3 was proposed and used in performance testing of IP routers.The test results indicate that the performance testing-oriented TTCN-3 not only simplifies the performance test description for IP routers but also makes the test results more reliable.

Radar Emitter Number Estimation Based on Principal Component Analysis

CHEN Taowei, JIN Weidong

2009, 22(4): 501-506.

[Abstract](1560)

Abstract:
To estimate the number of radar emitters in a complex electromagnetic condition,a novel information-theoretic criterion was formulated based on the characteristic of eigenvalues extracted from the principal component analysis of received pulse envelope vectors and arranged in a decreasing order.Computer simulation shows that compared with the existing information-theoretic criterion,the proposed criterion has a 29% improvement in average correct estimation rate and a 0.09 s improvement in average computational efficiency when SNR(signal-to-noise ratio) varies from 4 to 8 dB.

New Coherency Identification Approach and Its Application to Generator Tripping Algorithm

TAN Wei, ZHANG Xuemin, SHEN Chen

2009, 22(4): 507-512.

[Abstract](1531)

Abstract:
In order to forecast the unstable modes of an electric power system,a new generator coherency identification approach was proposed by analyzing the state matrix of the system in unstable state.In this method,the eigenvalues and right eigenvectors of the state matrix are calculated to forecast the dominant unstable mode of the system and identify groups of coherent generators.The stability margin of the system is calculated by extended equal-area criterion.Through sensitivity analysis,generator tripping locations and ratios are searched to produce the optimal emergency generator tripping control strategy.Simulation results on the revised IEEE-39 bus system were provided to verify the proposed method.The results show that the proposed generator coherency identification algorithm is effective,and that the generator tripping control strategy based on sensitivity analysis can successfully prevent the system from transient instability.

Optimal Design of No-Load Airgap Flux Density of Permanent Magnet Synchronous Motor

XU Yinglei, LI Qunzhan, WANG Tao

2009, 22(4): 513-516,540.

[Abstract](2050)

Abstract:
To improve the back-EMF(electromotive force) waveform of PMSM(permanent magnet synchronous motor),the waveform of no-load airgap flux density of radial V-shaped magnet configuration of PMSM was analyzed.The eccentricity airgap was got by changing the pole shoe’s shape.Asymmetric airgap was used to improve the waveform of airgap magnetic field.The waveform of the airgap magnetic field and the harmonic content were analyzed with the finite element method under the eccentricity of 15.2,20.2,25.6,35.6 and 50.6 mm to obtain the eccentricity-airgap flux filed curve and the optimal eccentricity.Numerical calculation and measured results of electromagnetic field show that through the optimal design of eccentricity,the back-EMF waveform of no load is close to sinusoidal distribution and the total harmonic distortion is 0.5%,as a result,the waveform of no-load airgap flux density gets improved.

Optimization Model of Passenger Transfer Network for Integrated Transportation

ZHANG Yiying, PENG Qiyuan

2009, 22(4): 517-522.

[Abstract](1699)

Abstract:
To resolve multi-modal transport coordination problem during passenger transfer,a optimization model of passenger transfer network for integrated transformation,with the shortest travel time and the least expense taken as optimization objectives,was built according to the characteristics and structure of passenger transfer network.Then,the multi-objective functions were integrated into a single-objective function through weighted summation of the shortest travel time and the least expense.The model was solved by genetic algorithm,and the solution procedure was described.An application example was demonstrated,and the results verified the effectiveness of the proposed model and algorithm.

Adaptive Path Selection in Stochastic and Time-Dependent Traffic Networks

CHEN Jingrong, YU Jianning, LI Yinzhen

2009, 22(4): 523-529.

[Abstract](1541)

Abstract:
The travel time for each road section at different time was defined as a discrete random variable according to the stochastic and time dependent properties of travel time in traffic networks.Based on this,an adaptive path selection model was built in stochastic,time dependent networks,and an algorithm with polynomial time complexity was given.By this model,travelers can obtain adaptive paths from all nodes to a specified destination with the least expected time,and then select an optimal route to their destination at any node according to the arrival time.In the end,an illustrative example verified the effectiveness of the algorithm.

Improvement of Elitism Preservation and Optimum Selection of Multi-objective Particle Swarm Optimization Algorithm

YU Jin, HE Zhengyou, QIAN Qingquan

2009, 22(4): 530-534,563.

[Abstract](1692)

Abstract:
In order to improve the performance of MOPSO(multi-objective particle swarm optimization) algorithm for solving multiple objective problems,decrease the calculation complexity and ameliorate the convergence of this algorithm,a modified MOPSO algorithm was proposed.In this modified algorithm,the extended dominance(E-dominance) method is used to confirm the preference among all solutions and determine the best global position of current generation particles randomly.The modified algorithm considers the convergence and diversity of solutions.In addition,an exterior population file is utilized to preserve the elitist solutions and a non-linear function is used to map the objective space into a finite domain where the preference and distribution of the solutions are considered.Series of classical testing problems were investigated numerically.The simulation results show that this modified MOPSO algorithm surpasses the initial MOPSO and NSGA2(non-dominated sorting genetic algorithms 2) algorithms in the calculation complexity and the convergence when a multi-objective optimization problem possesses over three objectives.

Experimental Psychology Study on Relationship between Fatigue and Driving Time

MA Yanli, WANG Yaowu, PEI Yulong

2009, 22(4): 535-540.

[Abstract](1819)

Abstract:
Based on an analysis of influences of fatigue on driving safety,experimental psychology tests and subjective fatigue investigation were conducted to study the effects of continuous driving time on driver’s fatigue.The results show that a break of at least 30 min must be taken after 3.5 h continuous driving.

Probability Model for Driver Attention State under High Driving Load

GUO Zizheng, CHEN Chongshuang, CHEN Yaqing

2009, 22(4): 541-546.

[Abstract](1670)

Abstract:
To study the shifting progress of driver’s attention under high driving load,a probability model for driver’s attention state during a short period and a approximate solution algorithm were presented based on the Markov process theory.This model is not directly applicable to a long period because it does not meet the homogeneous requirement at driving state transition points,This problem could be solved by cutting the long period into small fractions.Practical data were used for simulation,and the result shows that the overall error of the model was 2.83%.

Response of Noise Barrier for Existing Railway Bridges under Impulsive Pressure Induced by High-Speed Train

L? Jianpin, ZHANG Jiwen, LIAO Jianzhou, HU Weinan, TU Yongming

2009, 22(4): 547-551.

[Abstract](2067)

Abstract:
A finite element model for noise barriers of the existing railway bridges was built by using an SAP2000(structural analysis programme) software.In this model,the connections between stop plank and H-type steel columns are simulated using displacement springs and rotation springs.The dynamic responses of noise barriers for three types of railway bridges with a span of 16,24 or 32 m were analyzed by considering both multiple support excitation and uniform excitation.The distribution characteristics of displacement amplitude,bending moment amplitude and dynamic magnification coefficient of noise barriers were investigated.The research results show that the factor of traveling-wave effect of noise barriers are below 1 for the three types of railway bridges.The maximum displacement of the columns and the bending moment of the cantilever beam decrease with the increase of bridge span.The maximum displacement of the columns for a 16 m span bridge reaches 15.5 mm due to the deficient stiffness of its cantilever beam.

Dynamic Performances of Pantograph-Catenary System with Double Pantographs

ZHOU Ning, ZHANG Weihua

2009, 22(4): 552-557.

[Abstract](1639)

Abstract:
Finite element models for the catenary and the double pantographs were derived.The latter was simplified as a multi-lumped-mass system.The two models was coupled by contact elements to form a pantograph-catenary system model,and its dynamic equilibrium equations were presented.The parameters in the pantograph-catenary system model were calculated with the time integration method.The results show that the rear pantograph has a little influence on the current collection performance of the front pantograph,and the front pantograph has an obvious impact on the rear pantograph.The space between the two pantographs has not obvious effect on uplift and contact force of the front pantograph,and has obvious impact on those of the rear pantograph.The current collection performance of the rear pantograph is the worst when the space between the two pantographs is 90 or 150 m,and the preferable space is 200 or 210 m.

Experimental Research on Bearing Behavior of New-to-Old Concrete Interface in Arch Bridge Strengthening

ZHANG Jing, WANG Zhenling, QIAN Yongjiu

2009, 22(4): 564-568.

[Abstract](1598)

Abstract:
Two models of arch ring were made to research the bearing behaviors of new-to-old concrete interface in arch bridge strengthening.Destructive experiments were carried out on the two models to investigate their failure characteristics and service behaviors and the distributions of stress and strain on new-to-old concrete interface.The experimental result shows that the shear-bearing capacity of the interface is given by the bond of new and old concrete without embedded steel bars at the early stage of loading.When shear stress increases to the bond shear strength of new and old concrete,the shear-bearing capacity of the interface is mainly given by embedded steel bars.The distribution of bond shear stress on the interface is different in different regions at the stage from yielding of longitudinal reinforcement to the failure of specimens.At the stage,the bond shear stress decreases linearly in the region near cradks,does not change in the region away from cracks and increases linearly in the region away far from cracks.

Multi-regression Analysis of In-situ Stress Field in Deep River Valley

LIANG Yao, ZHAO Gang, YANG Tao

2009, 22(4): 569-573.

[Abstract](1289)

Abstract:
Based on the geological characteristics of deep river valleys,factors inflencing in-situ stress fields were analyzed.It was strongly believed that valley development is an important factor affecting in-situ stress fields besides self-weight and geological structures.An in-situ stress field was simulated by the multi-regression method and thought to be the sum of a self-weight stress field affected by river valley development and a tectonic stress field.The research result shows that the regressed stresses considering the development and evolution of a deep river valley by steps are close to the measured ones,and the regressed stress field characterizes a relaxation at the shallow surface of a deep river valley and a concentration at its bottom.

Prediction Model for Buried Personnel Probabilty in Earthquake

XIAO Dongsheng, HUANG Dingfa, CHEN Weifeng, PENG Jinchuan

2009, 22(4): 574-579.

[Abstract](1354)

Abstract:
To meet the demand of fast response and lifesaving assistant decision-making,a model for buried personnel probabilty in an earthquake was established based on collapsing ratio and in-building probabilty by analyzing factors influencing the buried personnel probabilty.In this model,the in-building probabilty is used as the prior probability.By taking elementary and middle schools in the disaster areas in the Wenchuan earthquake as examples,the situation of buried personnel was explained with the established model,and its precision was analyzed with the error theory.The analysis result shows that the precision of the established model is about ±0.2.

Particle Flow Numerical Simulation of Landslip of Loose Slope under Seismic Loading

YANG Qinghua, YAO Lingkan, YANG Ming

2009, 22(4): 580-584.

[Abstract](2000)

Abstract:
The landslip process and law of loose slopes under seismic loading were investigated by using PFC2D(particle flow code in two dimensions) based on the discrete element method.In the numerical simulation,the effect of seismic intensity on the landslip of loose slopes was analyzed by changing the angle of underside due to pseudo-static method,and the numerical simulation results were compared with the exsiting centrifugal test ones.The research results show that the landslip law of loose slopes can be analyzed effectively by a particle flow code model.Under seismic intensities of 5,6 to 7 or 8 degree,landslip scale is respectively about 5%,18% and 45%,and departure from the critical slope is less than 1.0°,1.0° to 2.0° and about 10°,respectively.The numerical simulation results are consistent with the exsiting centrifuge experimental ones.The research provides a reference for the aseismatic design of loose slopes and the evaluation of river and road barrage.

Spatio-temporal Visualization Method of Spatial Interaction between Regions

CHENG Hongxia, LI Yongshu, LIN Yuejiang

2009, 22(4): 585-589.

[Abstract](1344)

Abstract:
The existing visualization methods for spatial interaction between regions lack comparability and are limited by time points.In order to overcome these shortcomings,a spatio-temporal visualization method of spatial interaction between regions was proposed.In this method,the center point of every region is taken as the centre point of its visualization result,the total spatial interaction between regions and the spatial interaction between regions at different time points are calculated respectively to determine the radius and angle of visualization results by using the spatial interaction model.By taking the seven regions of Sichuan Province as research objects,the spatio-temporal visualization of spatial interaction between regions was realized.The experimental results show that this method is of high legibility and comparability.

Soil Respiration of Three Typical Subtropical Forest Ecosystems in Tianmu Mountain of China

LIU Yuanyue, JIANG Hong, QIU Zhongping, YUAN Huanying, LI Yahong

2009, 22(4): 590-594.

[Abstract](1207)

Abstract:
The soil respiration(SR) of three typical forest ecosystems,which were Chinese fir,broadleaf evergreen and Phyllostachys pubescens,were measured by the infrared system(LI-8100) in situ in West Tianmu Mountain of Chinese subtropical area,to study the relationship between the fluxes of CO2 released from this soil carbon pool and the change of the regional climatic environment.The results indicated that the diurnal soil respiration in the three stands almost varied in a single-peaked pattern.Among the three stands,the annual average CO2 efflux rate of Phyllostachys pubscens(3.82 μmo l/(m2·s)) was the greatest,that of broadleaf evergreen(2.23 μmo l/(m2·s))was the lowest,and that of Chinese fir(2.35 μmo l/(m2·s))was in between them.Generally,soil respiration rate increased with soil temperature.In summer(August),the CO2 effluxes of the three stands rose to the maximum,but dropped greatly in winter(November).Soil moisture was in a negative linear correlation with SR,and together with soil temperature,had mutual effects on SR.In conclusion,the environmental factors interacted with each other and influenced the process of SR.

Wet Surface Modification of Calcium Silicate Hydrate Superfine Powder

PENG Xiaoqin, HE Fang, ZHANG Le, QI Xuejun, TIAN Yuanyan

2009, 22(4): 595-599.

[Abstract](1424)

Abstract:
Four kinds of modifiers were chosen to conduct wet modification experiments for calcium silicate hydrate to improve its compatibility with polymer materials.The modifier with the best modification effect was optimally selected to do orthogonal experiments to investigate the effects of modifier quantity,concentration of calcium silicate hydrate in the slurry,and modification temperature and time on surface modification of calcium silicate hydrate.Under the optimal condition,the active index of the modified product increased from 0 to 95%,and the oil absorption value decreased from 86.5 mL/100 g to 69.5 mL/100 g.Infrared analysis shows that chemical adsorption of the optimally selected modifier happens on the surfaces of the calcium silicate hydrate powders,resulting in their organization.

Experiments in Vitro of Biofuel Cell for Implantable Medical Devices

LIN Jieqiong, ZHOU Xiaoqin, MA Long

2009, 22(4): 600-603,619.

[Abstract](1575)

Abstract:
A prototype device of an implantable biofuel cell(BFC) that utilizes body fluid was developed,and experiments in vitro were carried out for the implantable BFC in a simulated physiological environment of human body,to investigate the influences of the concentration,temperature,and pH value of glucose solution on the electric current output of the BFC prototype device.The experimental results show that as the concentration of glucose solution decreased,the electric current output of the BFC decreased,and the sustaining time of power supply of the BFC shortened.On the other hand,the electric current increased with the decrease of the pH value of the glucose solution.Lifting the temperature of the reaction solution would cause oscillation to occur to the current output of the BFC.

Dynamic Characteristic Modeling and Control of Proton Exchange Membrane Fuel Cell

LI Qi, CHEN Weirong, JIA Junbo, CHAM Yew Thean, HAN Ming

2009, 22(4): 604-608.

[Abstract](1890)

Abstract:
To solve the problem that the current model of proton exchange membrane fuel cell(PEMFC) is hard to be used in the design of control systems,a dynamic model of PEMFC was established with Matlab-Simulink,and a fuzzy logic controller(FLC) was designed based on this dynamic model.The combined application of fuzzy control and proportion-integral-differential(PID) control was adopted to control the output voltage of a PEMFC system.The simulation results show that the established model can reflect the dynamic characteristic of PEMFC systems,and the combined technique of fuzzy control and PID control can restrain the disturbance to improve the output characteristic of PEMFC systems and ensure their stability.The proposed model can be utilized to design the real-time control system of PEMFC.

Traffic Impact Analysis of MCBD in Urban Planning:Case Research on Pearl River New Town in Chengdu

GENG Huamin, JIANG Yangsheng, ZHONG Yongyan

2009, 22(4): 609-614.

[Abstract](1596)

Abstract:
By taking the Pearl River new town in Chengdu as an example,the method of traffic impact analysis of minitype central business districts(MCBD) was presented.Great effects of the traffic impact analysis on location-selection for urban planning and support for the sustainable development of MCBD were discoursed upon.The research provides a reference for the scientific planning of MCBD.

Far-Field Divergence Angle and Directionality of One Dimensional Off-Axis Gaussian Beams

JI Guangming, XU Bicai, JI Xiaoling

2009, 22(4): 615-619.

[Abstract](1387)

Abstract:
Based on the Huygens-Fresnel principle,the analytical expression for the far-field divergence angle of one-dimensional off-axis Gaussian beams propagating in free space was derived using the integral transform technique to study the properties of the far-field divergence angle and the directionality.The results show that the far-field divergence angle of an one-dimensional off-axis Gaussian beam decreases with an increase in beam number and a decrease in relative separation distance between subbeams,it varies a little when the beam number and the relative separation distances between subbeams are large enough,and under a certain condition,an one-dimensional off-axis Gaussian beam has the same directionality as an one Gaussian beam does.

Modeling and Simulation of CONWIP Systems Based on Petri Net

KANG Jie, LI Liang

2009, 22(4): 620-624.

[Abstract](1692)

Abstract:
A hierarchical Petri net model for CONWIP(constant work in process) production control systems was built.Based on this model,the CONWIP system was simulated by software Arena,and compared with the MRP(material requirement planning) system and the Kanban system in terms of the amount of WIP(work in process),average processing time,and average operation ratio.The results show that the CONWIP system is superior to the other two systems,since it can control the amount of WIP effectively and bring the production capacity of machines into full play.

Automated Supply Chain Coordination by Probability Conversion Rule

ZHOU Jianpin, ZHANG Qin

2009, 22(4): 625-630.

[Abstract](1697)

Abstract:
To improve efficiency,transparency and goal synergy in supply chain coordination of multi-agent system,a probability conversion rule for automating the coordination among supply chain agents was proposed based on the mapping correlation among agent belief,intention and policy space.Then,the policy space transformation,intersection generation and coordinating process guiding of the coordinating agents were achieved using the affine transformation rule as the probability conversion rule.An application example was presented to illustrate the automated coordination process,and the results showed the feasibility and effectiveness of the proposed method.

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2009 Vol. 22, No. 4