西南交通大学学报

Recent Advances of Research on Diexi Earthquake

HONG Shizhong

2014, 27(2): 185-194. doi: 10.3969/j.issn.0258-2724.2014.02.001

[Abstract](1325)

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Abstract:
On August 25, 1933, an M7.5 earthquake occurred in Diexi of Maoxian County, Sichuan Province, China. The strong earthquake caused a lot of landslides and collapses. The Diexi town was destroyed completely, and casualties were heavy. After 45 days, the barrier lake made by the earthquake burst to cause serious secondary flood. Recent advances of research on the earthquake were shown, including discovery of photographs about the earthquake and its secondary flood, discovery of the related investigation literatures carried out by geologist Chang Longqing and teachers and students of Sichuan University, discovery of other historical document about this earthquake, recent research production in seismogeology and geophysics, general works about the Diexi earthquake and works of seismosociology. Suggestions about further research on the Diexi earthquake were proposed.

Simulation of Construction Process of Loukouni Bridge in the Republic of Congo

WANG Yuanqing, ZONG Liang, ZHANG Longying, JIA Ruihua, SHI Gang

2014, 27(2): 195-201. doi: 10.3969/j.issn.0258-2724.2014.02.002

[Abstract](1002)

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Loukouni bridge is a deck type arch bridge with box section and is a part of the second stage of the first national road project of the Republic of Congo. This bridge will be constructed with cable erecting equipment. To make sure its construction safety, three methods, including the zero moment method, the zero displacement method and the invariable cable method, were used to calculate the cable force of fastening cable and the pre-camber of main arch during the construction. Live and dead elements provided by the general FE (finite element) software ANSYS were utilized to simulate the construction of the bridge. The research result shows that both the zero displacement method and the invariable cable method can meet the construction demand in terms of the shape of the arch, the stress of arch section and the deformation of the arch. In the two methods, the invariable cable method is better and should be the first choice applied to the Loukouni bridge. The trial zero displacement method is a simple and effective way to obtain the cable force.

Effects of Towers Random Sectional Bending Stiffness on Dynamic Characteristics of Large-Span Cable-Stayed Bridge

HUANG Bin, LI Yejun, ZHU Liping, ZHANG Weidong

2014, 27(2): 202-207. doi: 10.3969/j.issn.0258-2724.2014.02.003

[Abstract](1066)

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In order to investigate the dynamic characteristics of large span cable-stayed bridges with uncertain structural parameters, the plane FEM model of Edong Yangtze River bridge was established. In view of the randomness of sectional bending stiffness of the towers, the mean and standard deviation of the natural frequencies and vibration modes of the cable-stayed bridge were analyzed using recursive stochastic finite element method. Based on the calculated random dynamic parameters of this bridge, the effects of randomness of the towers' sectional bending stiffness on dynamic characteristics of large span cable-stayed bridge were discussed. The results show that when the variation coefficient of bending stiffness reaches 0.3, the randomness of the bending stiffness has great influence on the 18th, 19th, 29th, 34th, 37th, and 43th order in-plane natural frequencies and vibration modes of Edong Yangtze River bridge.

Anti-slip Performance of Interface between Carbon Fiber-Reinforced Plastic Main Cable and Cable Clamp for Large-Span Suspension Bridges

ZHUGE Ping, ZHANG Zihua, WANG Sicong, DING Yong, QIANG Shizhong

2014, 27(2): 208-212. doi: 10.3969/j.issn.0258-2724.2014.02.004

[Abstract](1125)

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In order to solve the slip problem between main cable and clamp at saddles of large-span suspension bridges, the anti-slip performance of the interface between carbon fiber reinforced plastic (CFRP) cable and cable clamp was investigated. The frictional coefficient calculation formula of the interface was derived according to the equilibrium condition between the cable tension and the friction force on the interface. Based on this formula, the friction coefficient of the cable-clamp interface was obtained through laboratory model test using a cable composed of 19 CFRP tendons. Then, the test results of frictional coefficient were used to analyze the anti-slip performance of the main cable-clamp system of a CFRP cable suspension bridge with a main span of 3 500 m, where the CFRP tendons had a spirally indented surface. The results show that the friction coefficient of the CFRP main cable-cable clamp interface is up to 0.331, which is higher than that of steel cable, and meet the requirement of engineering application. Therefore, when the CFRP tendons with a spirally indented surface are applied to the main cables of large-span suspension bridges, the cable-clamp interface is good enough to meet the requirement in anti-slip performance even if the cable clamps are designed in conventional shape and with an inner surface not granulated specially.

Fatigue Reliability Analysis of Multi-loading Suspension Bridges Considering Nonlinear Accumulative Damage

CHEN Zhiwei, XU Youlin

2014, 27(2): 213-219. doi: 10.3969/j.issn.0258-2724.2014.02.005

[Abstract](1940)

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Taking into account uncertainties in the nonlinear process of fatigue damage accumulation for fatigue reliability analysis of multi-loading long-span bridges, a fatigue reliability assessment method for a long suspension bridge under combined highway, railway, and wind loadings was proposed using a continuum damage model (CDM). First, the CDM based on continuum damage mechanics was briefly introduced, and main model parameters were analyzed. Then, a simplified CDM was proposed for further application to bridge structures. A limit state function for fatigue reliability analysis based on CDM was defined by introducing proper random variables into the CDM. The Monte Carlo simulation (MCS) was adopted to generate the random variables and to calculate the failure probability. Finally, the Tsing Ma Bridge in Hong Kong was taken as a case study, and the failure probabilities of the bridge at the end of 120 years were estimated for different loading scenarios. The results indicate that the health condition of the bridge in fatigue is satisfactory under the current traffic conditions, but attentions should be paid to future traffic growth because it will largely accelerate the damage growth.

Probability Density Evolution Method of Nonlinear Random Vibration Analysis

PENG Yongbo, LI Jie

2014, 27(2): 220-226. doi: 10.3969/j.issn.0258-2724.2014.02.006

[Abstract](1076)

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In order to reveal the applicability of the probability density evolution method in nonlinear random vibration analysis, a comparative research of the probability density evolution method and the classical nonlinear random vibration analysis was carried out by investigating the nonlinear responses of a class of randomly base-driven Duffing oscillators using the probability density evolution method (PDEM), the adaptive polynomial chaos expansion (APCE) and the Monte Carlo simulation (MCS). A physically based stochastic ground motion model was employed, and represented by a Karhunen-Love expansion in the application of the APCE. This discrete representation can be viewed as a projection of the physical vector space into the Gaussian vector space. Numerical results reveal that the solution processes of the three approaches are identical to weakly nonlinear systems, while they are approximately identical to strongly nonlinear systems though errors resulted from numerical techniques and artificial truncations are amplified, indicating that the solution of the PDEM is equivalent to that of the classical nonlinear random vibration analysis in the mean-square sense. The PDEM, moreover, goes a step further than the classical nonlinear random vibration analysis since the probability density function of responses and the dynamic reliability of systems can be simultaneously provided by the PDEM. The other methods, however, need much more computational efforts to obtain high order statistics of responses.

Probability Density Evolution Analysis for Stochastic Dynamic Seismic Responses of Structures Based on Improved Point Estimation Method

SONG Pengyan, LÜ, Dagang, YU Xiaohui, WANG Guangyuan

2014, 27(2): 227-232. doi: 10.3969/j.issn.0258-2724.2014.02.007

[Abstract](1246)

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Abstract:
In order to obtain the law of probability densities of structural responses varying with time, a new moment-based approach for analysis of probability density evolution of nonlinear stochastic dynamic responses of structures was developed, by combining an improved point estimation method (IPEM) with the maximum entropy theory and the probability density evolution theory for stochastic dynamics of structures. The proposed method was then used to perform probabilistic density evolution analysis and parameter sensitivity analysis of a reinforced concrete (RC) frame structure designed according to Chinese codes, selecting the top displacement and global seismic damage index of the structure under earthquake as response parameters, and taking into account the uncertainty of structural parameters. The results show that the steel yield strength, the structural damping ratio, and concrete gravity density have dominant influences on structural displacement, with a sensitivity of more than 10%.

Numerical Simulation of Wave Forces on Large Circular Cylinder Based on -Coordinate and Immersed Boundary Method

KANG Azhen, ZHU Bing, XING Fan

2014, 27(2): 233-239. doi: 10.3969/j.issn.0258-2724.2014.02.008

[Abstract](1060)

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To investigate the wave forces acting on a large circular cylinder under wave effects, a three-dimensional numerical model for the interaction of three-dimensional waves and a structure was established based on the multiple-layer -coordinate transformation model used to simulate time-dependent free surface. Wave forces acting on a large circular cylinder were simulated numerically, the immersed boundary method (IBM) was used to deal with the irregular structure surface. The results indicate that the numerical simulation result of wave forces and moment on a large circular cylinder has a good agreement with experimental results and analytical solutions. Horizontal wave force and moment increase at a low wave number and decrease at a high wave number. Vertical force decreases with the increase of wave number. The established numerical model can well simulate wave forces and moment on a structure.

Optimization Analysis of Height and Distance of Shelter Wind Wall for High-Speed Railway

YE Kun, LI Renxian

2014, 27(2): 240-246. doi: 10.3969/j.issn.0258-2724.2014.02.009

[Abstract](1285)

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Based on the Navier-Storkes equations of viscous compressible fluid and the k- two-equation turbulent model, side forces and rolling moments acting on a train were calculated by means of the finite volume method. The effects of shelter wind wall on transverse aerodynamic forces acting on trains were investigated numerically, and the optimal height and distance of shelter wind wall were obtained, including 275 cases of straight railway and curved railway with different radii under different wall heights and wall distances. The research results show that the optimal height and distance of shelter wind walls on a straight railway line are about 1.90 and 3.90 m respectively when train speed is 200 to 400 km/h and transverse wind speed 20 to 40 m/s. When a train runs on a curved railway line with a radius of 1 000 to 7 000 m, the optimal height decreases linearly with the increase of the radius, while the optimal distance is about 4.50 m with little relation to the radius. Wind speed and train speed have a few effects on the optimal wall height and distance. If wall height is too low or wall distance is too small, the direction of side forces and rolling moments acting on the head and rear cars are different.

Peak Pressure Estimation Method of Wind Loads on Low-Rise Building Based on Field Measurement

HUANG Peng, CAI Bin, QUAN Yong, GU Ming

2014, 27(2): 247-253. doi: 10.3969/j.issn.0258-2724.2014.02.010

[Abstract](1068)

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Abstract:
The peak pressure estimation methods of field measurement-based wind loads on low-rise buildings were investigated for the design of wind resistance on low-rise buildings. Based on pressure data measured on the roof of the test building during monsoon climate at the wind engineering field measurement base constructed on seashore beside Pudong International Airport of Shanghai by the State Key Laboratory of Disaster Reduction in Civil Engineering of Tongji University, including a full-scale low-rise building with adjustable roof pitches and two anemometer towers respectively with a height of 10 and 40 m, the distribution characteristics of wind pressures were analyzed, and the validity of the peak value estimation method to use the extreme pressure of short time interval samples to estimate that of long time interval samples from field measurement data was discussed. The research result shows that as for the flow separation region, the probability distributions of wind pressure coefficient have non-Gaussian features and a good agreement with the Gamma and lognormal distributions. When the time-history curve of wind pressures on the roof are divided into several sub-sections and the relationships of typeⅠEVD (extreme value distribution) parameters between parent section and sub-sections are used to estimate peak pressures, the estimated peak pressures are more accurate than observed extreme values, and the optimal length of a sub-section can be determined by the auto-correlation analysis of the parent section. For the full-scale data the extreme value distribution has a good conformity with type Ⅰ EVD when sub-section data are divided by the optimal length, and the peak pressure estimation method based on type Ⅰ EVD for short time interval samples has reliable results.

Assessment on Safety of Steel Reinforced Shotcrete Support for Tunnels

YANG Chengyong, OUYANG Jie, LU Jinghui

2014, 27(2): 254-259. doi: 10.3969/j.issn.0258-2724.2014.02.011

[Abstract](1035)

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A displacement-based method was proposed to evaluate the safety of steel reinforced shotcrete support for tunnels under construction. Based on shotcrete creep experiment, a GL2000 model was modified and employed to describe the creep of shotcrete. Formulas to calculate the axial deformation and curvature change of the support were obtained. Formulas to compute the internal forces of the support with creep considered were given, and performance functions to a cross-section of the support were put forward. At last, a case study was done for a tunnel on the Wuhan-Guangzhou railway line. The case research result shows that results based on the proposed method are consistent with in-situ situations. Calculated reliability indices fall into the interval required by the related Chinese codes. Creep causes the shotcrete to relax to result in large reliability indices, but the increase of the indices is smaller than those for plain shotcrete and lattice girder reinforced shotcrete supports.

Stress Mechanism of Lining Structure of High Geothermal and Deep-Buried Tunnel

WANG Yusuo, YE Yuezhong, YANG Chao, TANG Jianhui, CHEN Long, ZENG Hongfei

2014, 27(2): 260-267. doi: 10.3969/j.issn.0258-2724.2014.02.012

[Abstract](1412)

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To study the behavior of stress varying with the ambient temperature in lining structures of high geothermal and deep-buried tunnels, a laboratory model test was designed to measure the structural stress of a tunnel model at various temperatures. Then, a numerical simulation analysis of the model test was conducted. A comparison of the two groups of data revealed that the axial force values obtained by model test were approximately 20% larger than the simulated values, but their distribution trend are similar, and the structural safety factors were approximately equal. Taking a tunneling project as an example, the numerical simulation method was adopted to analyze the effect of insulating layer on the stress characteristics and safety of the tunnel lining structure at 60 ℃ under a buried depth of 1 000 m. The results show that the insulating layer has a small effect on both the internal force distribution pattern of the supporting structure and the internal force of the primary lining and the cast concrete lining. The insulting layer, however, can remarkably improve the stress state of the secondary lining, and the minimum safety factor of the tunnel's secondary lining structure increases from 2.0 without a insulting layer to 4.0 when the insulting layer is set.

Two-Dimensional Magnetotelluric Tipper and Apparent Tipper：Simulation and Application

YU Nian, HU Xiangyun, WANG Xuben, LI Jian

2014, 27(2): 268-275. doi: 10.3969/j.issn.0258-2724.2014.02.013

[Abstract](1023)

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In order to analyze abnormal responses of 2D magnetotelluric tipper data, a tipper data forward calculation was developed using the finite element quadrilateral mesh, and a forward numerical simulation of the abnormal body, inclined faults, static effects, and terrains was made based on their theoretical models. The derivation and calculation of the apparent tipper data were improved, and the tipper and apparent tipper were compared. As an application example, the apparent tipper was calculated using the transversal electric (TE)-mode apparent resistivity and phase data during the audio-magnetotelluric (AMT) exploration of the Zhongyi tunnel on the newly built Lijiang-Shangrila railway. The results show that the tipper can reflect the abnormal lateral boundary and fault apparently, and is only affected by the static displacement and topography at mid-high frequency band above 1 Hz, where the tipper and apparent tipper data have a good correspondence. In addition, the apparent tipper data can not only locate the fracture zone of the tunnel and reflect the position, scale, and trend of main faults effectively, but also can reflect the more subtle abnormal structures.

Control Method of Vehicle Directional Stability for Automobile Anti-lock Braking System

ZHENG Taixiong, MA Fulei, YANG Yong

2014, 27(2): 276-282. doi: 10.3969/j.issn.0258-2724.2014.02.014

[Abstract](1083)

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In order to maintain vehicle directional stability during the emergency braking, a control method of controlling the brake wheel cylinder pressure difference between the front wheels was put forward. The control process of the anti-lock braking system (ABS) is divided into first control and conventional control. In the first control, the rotational speed difference between front wheels is used to identify the road condition provided that the front wheels are not locking. According to the identification result, the conventional control adopts the method of synchronous pressurization for the front wheels and independent control for the rear wheels on single cohesion coefficient roads,and adopts modified low selector control for front wheels and independent control for the rear wheels on split cohesion coefficient roads. In addition, according to the test methods and procedure specified by the national standards, braking tests were carried out on four typical roads in a test field. The steering correction angle of the vehicle during the tests was less than 30 within 2 s, much less than the 120 in national standards, which shows the effectiveness of the control method.

Rollover Control Strategy Based on Vehicle Stability Control System

OU Jian, CHENG Xiangchuan, ZHOU Xinhua, YANG Echuan, ZHANG Yong

2014, 27(2): 283-290. doi: 10.3969/j.issn.0258-2724.2014.02.015

[Abstract](1121)

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To enhance the rollover control function of vehicles in extreme conditions, a vehicle dynamics model with 8 degrees of freedom covering yaw and roll motions was established, and an integrated control strategy with emergency roll control was proposed based on the direct yaw control of the traditional electronic stability control (ESC) system. The roll coefficient was calculated using the vehicle lateral acceleration provided by the standard ESC sensor. The emergency roll control was activated when the roll coefficient exceeded its reference value, and the vehicle rollover got controlled effectively by adjusting the lateral acceleration in time. The results of fishhook test simulation on direct yaw control and integrated control show that under the direct yaw control strategy, the vehicle has the ability to resist rollover under continuous small steering wheel angle, but cannot resist rollover in extreme conditions with a big steering wheel angle. In contrast, the integrated control strategy improves the ability to resist the rollover in the extreme conditions and enhances the rollover control function of the vehicle ESC system.

Influence of Valves Parameters on Damping Characteristics of Hydraulic Shock Absorber for High-Speed Trains

YANG Mingliang, LI Renxian, DING Weiping, ZHANG Song, DING Wei

2014, 27(2): 291-296. doi: 10.3969/j.issn.0258-2724.2014.02.016

[Abstract](1134)

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A form of hydraulic shock absorber structure widely used for high-speed trains was studied to reveal the quantitative relationship between the damping characteristics of hydraulic shock absorber and valves parameters. The damping force generating mechanism was analyzed using fluid dynamics principle and hydraulic transmission technology. Then, a damping force calculation model was constructed and verified for the recovery stroke, and the influences of valves parameters on damping characteristics of the hydraulic shock absorber for high-speed trains were discussed. The results show that the diameter of the throttle holes was the major factor to impact the shock absorber's damping characteristics before the valves opened, and the damping force changed up to 52.4%. In contrast, the diameter of the recovery hole was the major factor to impact the shock absorber's damping characteristics after the valves opened, and the damping force changed up to 80.1%. According to the conclusion, the performance design and tuning guidelines for high-speed train shock absorbers are proposed.

Main Valve Structure Design for Water Medium Low-Pressure Large-Flow Pilot Operated Solenoid Valve

ZHAO Jiyun, ZHANG Desheng, LIU Lei, DING Haigang

2014, 27(2): 297-301. doi: 10.3969/j.issn.0258-2724.2014.02.017

[Abstract](937)

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In order to achieve the basic requirements of the large-power valve-control coupling for control valve quick response, high flow capacity, and anti-blocking ability, the main valve with a tail cone structure was designed for a water medium low-pressure large-flow pilot solenoid valve group. The influences of spring stiffness, throttle nozzles diameter, and other parameters on the dynamic and static characteristics of the valve were analyzed using the AMESim simulation software, and accordingly the optimized parameters combination of the solenoid valve group was determined. In addition, a pure water hydraulic test-bed was built to measure the response characteristics of the valve group. The results show that the normal working pressure drop of the designed solenoid valve group is about 0.07 MPa, the opening time is 0.3-0.4 s, and the closing time is about 1 s. The valve group possesses a good low pressure characteristic and a fast response characteristic, which can satisfy the requirements of large-power valve-control coupling.

Wheel-Rail Wear on Heavy Haul Lines and Its Influences on Running Stability of Trains

XIONG Jiayang, DENG Yongquan, CAO Yabo, LI Li, JIN Xuesong

2014, 27(2): 302-309. doi: 10.3969/j.issn.0258-2724.2014.02.018

[Abstract](1568)

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The development and application of heavy haul railways in China and other countries were reviewed. Typical wheel-rail wear that occurred on heavy haul railway lines was elaborated, including the wheel flange wear, hollow wear on the wheel tread, wheel ovalization, eccentric wear of wheels, side wear at rail gauge corner, rail corrugation, wheel flats, and rail burns. Then, the wheel-rail wear of heavy haul railways was studied mainly from two aspects: the mechanical behavior of the wheel-rail interaction system; and the mechanism and development of the wheel-rail wear, influences of factors and possible counter measures. Moreover, effects of wheel-rail wear on the wheel-rail contact, the vehicle-track interaction, and the running stability and comfort of trains were discussed. Finally, research methods and technical routes were proposed to study the derailment safety problems of heavy haul trains under different worn conditions. With them, the derailment mechanism of heavy haul trains, key influential factors, and their rules under different worn conditions are expected to be worked out using numerical simulation.

Algorithm for Computing Reliability Evolution of Internetware

ZHANG Jing, LEI Hang

2014, 27(2): 310-316. doi: 10.3969/j.issn.0258-2724.2014.02.019

[Abstract](1108)

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To calculate and evaluate the reliability change of Internetware system in the Internet environment, the reliability transition matrix of Internetware system was constructed using Internetware system architecture and considering the accumulation effects of Internetware reliability change. The reliability evolution calculation model and the evolution trend model were established. On the basis of discrete time Markov chain (DTMC) theory and convolution principle, the reliability evolution calculation model was proposed, and the corresponding algorithm was designed. According to the fine-grained quantitative analysis of reliability, reliability change, and reliability change accumulation, the computation complexity of the designed algorithm is decreased to O(Nlog2N). The simulation results using MATLAB show that the proposed model and algorithm can effectively implement the evolution analysis of Internetware reliability, and improve 7% more in reliability evolutionary tendency than the traditional non-homogeneous Poisson process (NHPP).

Combinational Modeling Method of Virtual High-Speed Railway Scene Based on Entity-Relationship Conceptual Model

ZHU Jun, WANG Jinhong, HU Ya, PENG Zilong, ZHANG Ali

2014, 27(2): 317-322. doi: 10.3969/j.issn.0258-2724.2014.02.020

[Abstract](1376)

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By analyzing the object entity and the three dimensional relations of virtual high-speed railway scene, a combinational modeling method based on entity-relationship conceptual model was proposed. The conceptual model of virtual high-speed railway scene was designed, which includes three levels, namely entity level, relation level and scene level. Then some key technologies such as modeling flowchart, mapping and combination of primitive models were discussed in detail. Finally a prototype system was implemented for modeling experiment on a case study region. The experimental results show that 110 km line scene modeling can be finished within 2 min. The proposed method can efficiently clarify various relations between scene object entities. It supports fast organization and the modeling of virtual high-speed railway scene.

An Adaptive Localization Algorithm Based on Particle Filter for Wireless Sensor Networks

DENG Ping, WU Xiaomei

2014, 27(2): 323-329. doi: 10.3969/j.issn.0258-2724.2014.02.021

[Abstract](1296)

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As the number of particles of the dynamic sampling based adaptive Monte Carlo boxed (AMCB) algorithm is too small at some localization time slots and the optimal inheritance of the particles can not be ensured, an improved particle filter localization algorithm named AMCB* was proposed. To solve the problem that the localization accuracy of the AMCB algorithm is low when the anchor node density is low and nodes are in bad network condition, an adaptive localization algorithm based on particle filter in WSN named NAMCB was proposed. NAMCB sets reasonable number of particles, localization mode and filtering condition based on the evaluation to the network condition of nodes at each localization time slot. In tests, when 80 nodes were continuously positioned 125 times, the average localization error of NAMCB was 0.344 2 times of node communication radius, and the average sampling number was 84. Compared with AMCB, both were reduced by 12.26% and 4.55% respectively.

Influence of Geometric Parameter Design on Performance of Capacitive Proximity Sensors

LI Nan, HAN Ying

2014, 27(2): 330-336. doi: 10.3969/j.issn.0258-2724.2014.02.022

[Abstract](979)

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To deal with the weak signal strength in the measurement of capacitive proximity sensors, the effects of geometric parameter design were investigated, and the sensor measurement performance was greatly improved by the geometric parameter optimization. The comprehensive evaluation standards of sensor performance were presented, including penetration depth, signal strength and noise tolerance, measurement sensitivity and dynamic range. For round capacitive proximity sensors, the effects of the surface area on sensor performance were analyzed. Four different structures including rectangular, round, interdigital and spiral-shaped sensors were designed. In the same conditions, the electric field distributions of the sensors with four structures were simulated and the measured fringe capacitance was compared. The results indicate that the geometric parameters have remarkable influence on the measured signal strength and measurement sensitivity; comparing with rectangular and round sensors, the measurement sensitivity of interdigital and spiral-shaped sesnros was increased by 66.8% and 33.5%.

Ranking Method for Node Importance Based on Efficiency Matrix

FAN Wenli, LIU Zhigang

2014, 27(2): 337-342. doi: 10.3969/j.issn.0258-2724.2014.02.023

[Abstract](1123)

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In order to improve the accuracy of the node importance evaluation in complex networks, a novel evaluation method based on efficiency matrix was proposed through analysis of the impact of non-adjacent nodes on the node importance evaluation by using the complex network theory. This method combined both the local and global node importance comprehensively, and overcame the limitations of depending on just the adjacent nodes in the node importance evaluation. The cascading failures by removing important nodes on the ARPA network show that when the top 2 important nodes are removed, the size of the biggest subgraph based on the proposed method falls by 23.8% compared with that based on the node importance evaluation method, which further verifies the accuracy of the proposed method.

Pollution Distribution Characteristic of High-Speed Train Roof Insulator and Its Optimization Strategy

SUN Jixing, LUO Shucai, WU Guangning, GAO Guoqiang, YANG Kunsong, HU Xueyong

2014, 27(2): 343-350. doi: 10.3969/j.issn.0258-2724.2014.02.024

[Abstract](1049)

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In order to solve the pollution accumulating problem of high-speed train roof insulators in rainy and foggy winter environment, a hydrodynamic simulation model was built to study the pollution distribution characteristics of the roof insulators. The movement and forces of pollution particles in high-speed gas flow were analyzed by theory of fluid mechanics, and the particles' adhesion and separation behaviors after colliding to insulator surface were discussed by theory of agglomerating fluidization. On this basis, the optimization strategy to reduce the surface contamination was proposed. Analysis results show that the pollution at windward and lee sides of a roof insulator is more serious than that at lateral side in high speed air flow at low temperature. The pollutant mainly accumulates at the root of insulator shed at windward and lee sides, and only a little is adhered evenly on the insulator shed surface at lateral side. When the shed has no ribs, pollution is less and more uniform. In addition, the pollution density increases with an increase in the shed lower inclination angle, but decreases with an increase in the shed spacing. To achieve the minimum pollution density, the roof insulator shed should has no ribs on its lower surface, the shed upper inclination angle should be 8, and the shed lower inclination angle 0.

Acquisition System for Three-Dimensional Surface Texture of Asphalt Pavement Based on Digital Image Processing

LIU Yamin, HAN Sen, XU Ouming

2014, 27(2): 351-357. doi: 10.3969/j.issn.0258-2724.2014.02.025

[Abstract](1092)

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In order to make an objective and true evaluation on three-dimension surface texture of asphalt pavement, an acquisition system for surface three-dimensional texture of asphalt pavement was developed based on the digital image processing. First, the classical Lambertian diffuse model was used to obtain three red, green, blue images. Then photometric stereo method was employed to calculated the surface gradients in x and y directions with the reflection intensity of three images. Finally the Frankot-Chellappa global integration algorithm was applied to making the Fourier transformation of the gradients. Thus the heights were obtained and the surface texture was reconstructed. The results indicate that the accuracy of height value obtained by the acquisition system is 0.000 1 mm, which meets the requirement for analysis of texture depth; the correlation coefficient between the results of this system and the traditional sand patch test is 0.887 5, which demonstrates that this acquisition system is practical.

Road System Optimum Equilibrium Model Based on Mean-Excess Travel Time

QIN Juan, PU Yun, LÜ, Biao

2014, 27(2): 358-366. doi: 10.3969/j.issn.0258-2724.2014.02.026

[Abstract](1085)

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In order to study the effects on traffic assignment of travelers' route choice behaviors under random perturbations, the mean-excess travel time (METT) was assumed to describe travelers' route choice criteria. According to the theory of marginal cost pricing, the calculation formula for marginal cost pricing was derived under stochastic supply and demand. Then, a traffic assignment system equilibrium model was built and formulated as an equivalent variational inequality,and a self-adaptive projection and contraction method was used to solve the model. The results of numerical experiments show that when the ratio of origin-destination (OD) demand coefficient was 1.0 and the ratio of degradation of link capacity was 0.5, the marginal cost toll of route 1, compared with those by use of mean travel time and travel time budget to choose paths, was increased by 11.27% and 3.58%, respectively. When the reliability of travel time was 0.9, the marginal cost toll of route 1 were found to be 20.22% and 4.30% higher than those using the mean travel time and travel time budget as a basis for route choice, respectively.

Blood Compatibility of Titanium Oxide Powder after High Temperature Annealing

ZHAO Ansha, WANG Zhao, ZHOU Shuo, ZHU Xiaohua, XIE Xiao, HUANG Nan

2014, 27(2): 367-372. doi: 10.3969/j.issn.0258-2724.2014.02.027

[Abstract](931)

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Abstract:
Vacuum annealing was used to prepare the Ti-O powder at different annealing temperatures. The structure and surface properties were characterized by X-ray diffraction, Zeta potential test and surface area measurement respectively. Bradford method was applied to determine the adsorption and desorption of fibrinogen on the powder, and Fourier transform infrared spectroscopy was used to analyze the change of secondary structure of adsorbed fibrinogen on the samples. Then flow cytometry was used to measure the degree of platelets activation. The results show that after 800 ℃ annealing process, the crystal structure of Ti-O powder transformed from anatase to rutile with 10 times less total surface area and more negative charges, and the amount of fibrinogen adsorption was decreased to 67g and retained its normal conformation. Less platelet was activated by the annealed Ti-O powder, which proves that it has an excellent blood-compatibility.

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2014 Vol. 27, No. 2