西南交通大学学报

Dynamic Analysis of Structural Adaptivity of Ballastless Track Substructure of High-Speed Railway

QIU Yanjun, FANG Mingjing, ZHANG Xiaojing, WEI Yongxing

2011, 24(2): 183-187. doi: 10.3969/j.issn.0258-2724.2011.02.001

[Abstract](2606)

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Abstract:
To discuss the adaptivity of track substructure of high-speed railway, the historical development of the structural analysis and design of track substructure was reviewed as the numerical analysis basis of the structural behavior of ballastless track substructure with a case study of Sui-Yu (Suining-Chongqing) high-speed railway. Dynamic responses of track substructure under the action of train loading were investigated using a finite element software, and the effects of train speed, axle loading and trackbed elastic modulus on the dynamic stress, vertical deflection and vertical acceleration of track bed were researched. The research results show that a sound track bed is essential to assure structural integrity and performance of railway lines and an asphalt railway substructure may be a good alternative.

Dynamic Analysis of Longitudinally Connected Ballastless Track on Earth Subgrade

XU Peng, CAI Chengbiao

2011, 24(2): 189-194. doi: 10.3969/j.issn.0258-2724.2011.02.002

[Abstract](2416)

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A coupled dynamic model of train-longitudinally connected ballastless track on earth subgrade was established. In the model, the track and subgrade were regarded as a layered viscoelastic body, which was modeled on continuum theory, and discretized with Galerkin method. The model was used to analyze the dynamics of ballastless track on earth subgrade of the Beijing-Tianjin high-speed railway as the CRH2-300 EMUs running at speeds of 300 and 350 km/h. The calculated results were compared with measured data, which verified reliability of the proposed model. The results show that the maximum stresses in CA（cement asphalt） mortar are 46.8—50.5 kPa, much less than the design specification of 15 MPa; dynamic deformations of subgrade decrease slowly with depth, while dynamic stresses decrease rapidly; dynamic stresses produced by a single bogie distribute about 5.00 and 3.25 m longitudinally and laterally, respectively; and the distribution of dynamic deformations in slab, CA mortar layer and supporting layer have a little difference along the depth direction.

Calculation of Wheel Wear Based on Semi-Hertzian Contact

DING Junjun, LI Fu, HUANG Yunhua

2011, 24(2): 195-200. doi: 10.3969/j.issn.0258-2724.2011.02.003

[Abstract](1399)

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To study the effect of wheel/rail contact theory on wheel wear calculation, wheel/rail contact stress and contact patch were analyzed using the semi-Hertzian contact theory, the Hertzian contact theory and the CONTACT program of Kalker's exact theory. Then, the creep forces under semi-Hertzian contact were solved by Kalker's simplified theory using the numerical program FASTSIM, and the wear depths of wheel profile were calculated based on Archard wear model. The results indicate that the contact patch and maximal contact stress calculated by semi-Hertzian theory are more closer to CONTACT's than that by Hertzian theory, because the varied curvatures in contact patch are considered in the semi-Hertzian theory; the error of creep forces between semi-Hertzian theory and CONTACT does not exceed 18%, except the lateral creep force in large spin creep condition; the computing time of the FASTSIM algorithm based on semi-Hertzian theory is 6 times that based on Hertzian theory and 1/166 of the CONTACT's; and, the wheel wear depth calculated by semi-Hertzian theory agrees well with CONTACT's when the elastic velocity is considered.

Effect of Spiral Transition Curve Length on Vehicle Path

LIN Yu, YANG Zhen, PAN Xiaodong

2011, 24(2): 200-204. doi: 10.3969/j.issn.0258-2724.2011.02.004

[Abstract](1632)

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In order to reveal the influence rule of spiral transition curve length on the path of a vehicle under free flow traffic states, a driver direction control model for highway alignment safety evaluation was put forward on the basis of the preselect optimal curvature method and by introducting the horizontal curve length-curvature alignment model. The simulation results show that when a vehicle enters a curve, its path has a tendency to shift inward the curve, while its path tends to shift outward the curve as it exits the curve. The length of a spiral transition curve has a significant impact on the path of a vehicle, the longer the spiral transition curve is, the smaller the lateral deviation of vehicle path is, whereas the greater it will be. To a symmetrical basic horizontal curve of second-class highways, the length of a spiral transition curve is suggested to be 0.4 to 0.6 times the radius of the curve.

Preparation of Geopolymeric Concrete and Its Application to Rapid Repair of Cement Concrete Pavement

PENG Xiaoqin, YANG Tao, WANG Kaiyu, MENG Xiangjie

2011, 24(2): 205-210. doi: 10.3969/j.issn.0258-2724.2011.02.005

[Abstract](1411)

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To solve the problems of long traffic opening time and low durability of the existing cement concrete pavement repair materials, a geopolymeric concrete was developed and applied to rapid repair of cement concrete pavement. The influence of Portland cement dosage and activator to solid ratio on the early strength of geopolymer was studied experimentally, and the mechanical properties, adhesive strength, shrinkage of the geopolymeric concrete were investigated as well. The results show that the geopolymer has the highest early strength when the dosage of cement is 10%, and the activator to solid ratio is 0.75. The 8-hour flexural strength and compressive strength of the geopolymer concrete prepared are 3.25 and 43.6 MPa, respectively, and the 8-hour mechanical properties, adhesive strength, and shrinkage of the geopolymeric concrete meet the technical requirements of repair concrete.

Capillary Water Absorption Behavior of CA Mortar

ZENG Xiaohui, DENG Dehua, XIE Youjun

2011, 24(2): 211-216. doi: 10.3969/j.issn.0258-2724.2011.02.006

[Abstract](1182)

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In order to investigate the character of water transportation in cement-emulsified asphalt mortar (CA mortar) for CRTS (China railway track system) Ⅰ-type slab ballastless track (CRTS Ⅰ-type CA mortar), changes in the contact angle of water and mass of capillary water adsorption with time were tested, and the SEM (scanning electric microscopy) and EDS (energy dispersive spectrometer) were used to detect the fracture surfaces of the CA mortar. The research results show that like a normal porous material, the mass of capillary water adsorption of the CA mortar has a linear relationship with the extraction of time. The “sandwich structure” of the interface between CRTSⅠ-type CA mortar and a pouring bag is the reason for the large decrease of the capillary water adsorption coefficient. From the SEM analysis, an asphalt-rich film can be formed on the surface of the CA mortar by polishing to increase the contact angle of water and reduce about 45% of the capillary water adsorption coefficient. In addition, the nature fracture surface of the CA mortar at the perfusion port should be processed during the construction.

Prediction of Biaxial Fatigue of Steel Bridge Gusset Plate Based on Stress Field Intensity Method

ZHOU Shangmeng, LI Yadong

2011, 24(2): 217-222. doi: 10.3969/j.issn.0258-2724.2011.02.007

[Abstract](1544)

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In order to assess the biaxial or multi-axial fatigue behavior of some particular structure details of steel bridges, the stress field intensity method was applied to establish a field diameter solving model of steel bridge components. Based on that, the concept of effective field diameter was put forward by reference to the railway steel bridge design code, and an analysis model for solving the biaxial fatigue strength was built. Taking the steel bridge gusset plate as example, its fatigue strength can be calculated through the field diameter solving model, in an error of less than 15%. Furthermore, the biaxial fatigue strength of the steel bridge gusset plate was predicted by the analysis model for solving the biaxial fatigue strength, and the quantitative relation among the input loads in each direction was obtained. The results show that to keep the same fatigue life, when the load in the main direction increases, the load in the secondary direction should decrease in a magnitude -0.5 times less than the load increment in the main direction.

Effect of Fire Fighting Water on Compressive Strength of Concrete in Tunnel Fire

WANG Zhen, LI Guhua, ZHANG Zejiang, HUANG Tao

2011, 24(2): 223-227. doi: 10.3969/j.issn.0258-2724.2011.02.008

[Abstract](1482)

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In order to investigate the influences of fire fighting water on the mechanical properties of HPC (high porfomance concrete) in a tunnel fire, the variation of the characteristics of samples with fire temperature was researched experimentally, the effect of fire fighting water on the residual compressive strength of HPC was analyzed, and the fitting relationship between the residual compressive strength and fire temperature was given. The research results show that fire fighting water affects the residual compressive strength of HPC greatly. Generally, under a natural cooling condition, the the residual compressive strength of HPC decreases with temperature raising, but goes up slightly at 300 ℃. Under a water injection cooling condition, the residual compressive strength of HPC decreases all the time. Under the same temperature, the residual compressive strength is lower under the water injection cooling condition than under the natural cooling condition, and the greatest residual compressive strength under the natural cooling condition is 1.3 times of that under the water injection cooling condition.

Experimental Investigation and Design of Artificial Structures Controlling Dam-Break Floods

CHEN Xiaoqing, ZHAO Wanyu, GAOQuan, JIAShitao, ZHU Xinghua

2011, 24(2): 228-234. doi: 10.3969/j.issn.0258-2724.2011.02.009

[Abstract](1174)

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In order to verify the control effect of different artificial structures in dealing with barrier dam-break floods, flume model tests were conducted in lab on tetrahedral entity structure (TES), tetrahedral entity structure group (TESG), tetrahedral frame structure (TFS) and tetrahedral frame structure group (TFSG). The research results show that throwing artificial structures has an important effect on the control of barrier dam-break floods, and compared with no throwing artificial structures, throwing artificial structures can effectively reduce peak break-out floods by 26.6% to 61.7%. Different artificial structures have different control effects, and optimal structures are in sequence TFSG, TESG, TFS and TES. In addition, increasing unit weight of artificial structures can improve the control effect.

Differences between Fault-Normal and Fault-Parallel Components of Horizontal Ground Motion in Wenchuan Earthquake

YANG Yongqiang, XIE Lili, LI Ming, HU Jinjun

2011, 24(2): 235-240. doi: 10.3969/j.issn.0258-2724.2011.02.010

[Abstract](1450)

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Totally 113 groups of horizontal ground motion were selected from the Wenchuan earthquake to study the influence of fault strike on horizontal ground motion. Differences between fault-normal (FN) and fault-parallel (FP) components were researched by comparing the peak ground acceleration, duration, response spectra, amplification factor and characteristic period. The research results show that when fault distance is less than 50 km, peak ground acceleration of the FN component is larger than that of the FP component, and the mean ratio of their peak ground accelerations is slightly affected by site conditions; durations of the two components both increase with the fault distance. When the fault distance is less than 100 km, the difference of their durations under site class Ⅰ is larger than that under site class Ⅱ. In near-fault areas, the mean ratio of their response spectra is larger than that of their amplification factors, and the differences of their response spectra and amplification factors are more obvious under site class Ⅰ than under site class Ⅱ; characteristic periods of the two components show a sufficient difference, and site conditions have a large effect on the mean ratio and difference of their characteristic periods.

Availability of ITRF Frames in High Precision Satellite Positioning

GAO Shuzhao, HUANG Dingfa

2011, 24(2): 241-246. doi: 10.3969/j.issn.0258-2724.2011.02.011

[Abstract](1201)

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For the multi-source selection of coordinates and velocities of IGS (International Global Navigation Satellite System Service) tracking stations, the coordinates and velocities of 4 IGS tracking stations in China were collected from 4 international organizations, and they were converted to the same reference frame and specified epoch to compare them. The comparison results show that the coordinates and velocities from the different international organizations are consistent well in the ITRF (international terrestrial reference frame) 2005, but the coordinates and velocities of a few IGS tracking stations are discrepant in the ITRF2000. Therefore, in order to reduce the impact of the difference on high precision satellite positioning, coordinates and velocities from different international organizations should be compared before adjustment calculation, and the latest data should be adopted.

Sensor Selection Optimization for Monitoring System of Large-Scale Group-Pile Foundation

TANG Yong, CHEN Zhijian

2011, 24(2): 247-252. doi: 10.3969/j.issn.0258-2724.2011.02.012

[Abstract](1488)

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In order to optimize the sensor system for a large-scale group-pile foundation and properly select sensor types, a multi-sensor optimization model was established, and the genetic algorithm was used to solve this optimal problem. In this model, the cost of the sensor system is set as the objective function, and the reliability of the voting system is taken as the constraint conditions. The reduction coefficient of environmental factor was put forward to consider the influence of sensor installation environment on the system reliability, its determination way was given, and it was used to revise the sensor reliability under different environments. In addition, the sensor system of Sutong bridge foundation was taken as an example to prove the optimization model. The research result shows that with the help of the established model, the cost can be saved nearly 10% under the precondition of the system reliability.

Automatic Generation of Railway Initial Horizontal Alignment Based on Optimal Route Analysis

HAN Chunhua, YI Sirong, YANG Yang

2011, 24(2): 252-258. doi: 10.3969/j.issn.0258-2724.2011.02.013

[Abstract](1193)

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In order to make the initial horizontal alignment of railway line more practical and meet the design code, a method for automatic generation of railway horizontal alignment was proposed based on knowledge reasoning and optimal route analysis in raster data format. First, the Dijkstra algorithm was improved by using Knight's neighboring pattern of 16 cells and taking account, in a construction cost model, of the influence of design slope on the bridge and tunnel construction costs and target speed of railway line on its length concerning cost. Then, the improved Dijkstra algorithm was used to propose an optimal route among the existing control points. Finally, by gradual dichotomy and automatic configuration of the horizontal curve, the vectorized optimal route was converted to an initial horizontal alignment that meets the design code. An actual application in a GIS-based railway location intelligent environment manifested that the proposed method can generate a satisfactory initial railway horizontal alignment. Compared with the conventional method, the proposed method can save more than 90% time in the design of local railway horizontal alignment.

Influence of Mechanical Parameter Errors on Pre-impact Speed of Vehicles in Vehicle Collision Models

ZHANG Jian, ZHANG Xin

2011, 24(2): 259-263. doi: 10.3969/j.issn.0258-2724.2011.02.014

[Abstract](1201)

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In order to measure accurately the influence of mechanical parameter errors on the pre-impact speed of vehicles in vehicle collision models，an influence analysis method was built by matrix theory. According to common error forms，the influence of mechanical parameter errors in one model with a centroid origin and another model with a collision center origin on the pre-impact speed of a vehicle was analyzed through a vehicle collision case. The result shows that under the constraint that the relative error in pre-impact speed is not more than 3%，the maximum margin of mechanical parameter error is ±9.7% in the model with a centroid origin, and ±8.7% in the model with a collision center origin.

Reliability Analysis of Urban Rail Transit Vehicle's Door System Based on GO Method

CAI Guoqiang, ZHOU Liming, LI Xi, JIA Limin

2011, 24(2): 264-270. doi: 10.3969/j.issn.0258-2724.2011.02.015

[Abstract](1426)

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In order to simplify the calculation of parallel redundancy operators, the characteristic value calculation method of GO operators was used to study the signal failure rate distribution characteristics of the parallel redundancy operators. The feasibility was validated that the repairable system with low-level redundancy could be hypothesized and treated as an exponential distribution unit. Then, an improved algorithm of the parallel redundancy operators in GO model was proposed and applied to the reliability analysis of urban rail transit vehicle's door system. The results show that for the input signal with exponential distribution, the output signal of parallel operator has a non-exponential characteristic; the improved algorithm can simplify the calculation process of the reliability analysis of urban rail transit vehicle's door system by eliminating 10 intermediate variables and 3 calculation steps in the original algorithm.

Numerical Simulation of Temperature Distribution of Induction Plasma Torch in Preparation of Superfine Powder

CHEN Xiao'an, SHANG Fujun, SONG Shuncheng

2011, 24(2): 271-276. doi: 10.3969/j.issn.0258-2724.2011.02.016

[Abstract](1573)

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To obtain the temperature field of the radio frequency induction plasma torch in preparation of superfine powder, the governing equations for the coupled electric field, temperature field and flow field were set up based on heat transfer, electromagnetic theory, and incompressible Navier-Stocks equations. A numerical simulation of the electrothermal effect and fluid-thermal interaction in powder preparation were simulated using the finite element method, to obtain the velocity distribution and temperature distribution of the plasma torch in the flow process. The results show that a vortex exists in the plasma heating region, and the highest temperature point is not on the axial line of the region. The higher the power input, the smaller the distance between the highest temperature region and the coil for skin effect. Under the same gas flux condition, the distance between the highest temperature point and the coil is 0.062 m when the power input is 2 kW, and 0.039 m when the power input is 5 kW.

Bearing Combination-Based Fusion Algorithm for Heterogeneous Sensors Track Data

HUANG Youpeng, WU Hanbao, ZHANG Zhiyun

2011, 24(2): 277-281. doi: 10.3969/j.issn.0258-2724.2011.02.017

[Abstract](1287)

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To the track data fusion caused by the difference between the measurement spaces of a 2D radar and a bearing-only sensor, a fusion algorithm for heterogeneous sensors track data was proposed based on bearing combination. With this algorithm, bearing measure of the target track detected by the radar and the bearing-only sensor relative to the same coordinate system is calculated by taking the platform of the bearing-only sensor as a data fusion center, and the bearing precision is mounted with an approximation method. Then, the bearings are combined with the weighted average method based on the optimal weight allocation. Finally, the target track detected by the radar is corrected using the combined bearing, and the corrected target track is taken as the fusion track. This algorithm gives the precision of the fusion track while it gets the fusion track. The simulation results show that compared with the precision of a radar track, the precision of the fusion track is improved by 25.23% in average.

Factors Influencing Dielectric Frequency Responses of Oil-Paper Insulation

LIU Jun, WU Guangning, ZHOU Lijun, MIN Yingji

2011, 24(2): 282-287. doi: 10.3969/j.issn.0258-2724.2011.02.018

[Abstract](1330)

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The dielectric frequency response method was used to model an oil-paper insulation system. The time domain dielectric response function and its frequency response were derived. An experimental system was designed to measure the dielectric frequency responses of oil-paper insulation at different temperatures. Also, the dielectric frequency response of the pure impregnated paper was calculated. The results show that the errors caused by the oil gap were not significant, with the maximum error being less than 10%. Significant dielectric loss of oil-paper insulation occurred in low frequencies, but not in high frequency. As the temperature increases, the shapes of oil-paper dielectric frequency response curves almost keep the same, and move to high frequency direction. The logarithm of dielectric loss of oil-paper is linear to reciprocal of temperature when frequency is constant.

Recent Development on Consensus-Based Kalman Filtering in Multi-agent Systems

MA Lei, SHI Xizhi

2011, 24(2): 287-293. doi: 10.3969/j.issn.0258-2724.2011.02.019

[Abstract](1694)

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Recent development of the distributed Kalman filtering using the consensus method was addressed. The concept, convergence and performance analysis of consensus problems in multi-agent systems were introduced, and several aspects of the consensus-based Kalman filtering were discussed in details, including filter construction based on local communication, information weighting and parameter optimization. Finally, some frontiers of the research on the consensus method， such as information loss, quantized consensus and stochastic asynchronous algorithms, were briefly discussed to promote the related research.

PHAF-Based Detection of Multi-component LFM Emitter Signal

Rong Haina, Zhan Gexiang, Jin Weidong

2011, 24(2): 294-302. doi: 10.3969/j.issn.0258-2724.2011.02.020

[Abstract](1293)

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To effectively detect a multi-component emitter signal (MCES) composed of several signal components with different energies and serious overlapping in the time-frequency plane, a detection method based on product high-order ambiguity function (PHAF) was proposed. By using a strategy of peeling onion, this method sequentially detects signal components in light of their energy magnitudes. In the process of detection, the signal components with strong energy are first detected and then are deleted from the original signal so that the signal components with weak energy are not interfered by the cross-terms and other signal components. Through multiplying several high-order ambiguity functions with different time-delays, the method strengthens the useful signal components, weakens noises and effectively detects the multi-component emitter signal with a low signal-to-noise ratio. The analysis and test results show that the proposed method can effectively detect multi-component emitter signals with serious overlapping in the time-frequency plane, and that the relative detection error is less than 2.457×10-4 and 7.560×10-2 for the signal components with strong energy and the ones with weak energy, respectively; and to noised signals, it is respectively less than 1.300×10-3 and 7.330×10-2 for the two kinds of the signal components.

Parameter Estimation of Co-channel Multi-signals Based on Cyclic Spectrum Amplitude

YU Ningyu, MA Hongguang, SHI Rong, YUZ hibin

2011, 24(2): 303-309. doi: 10.3969/j.issn.0258-2724.2011.02.021

[Abstract](1168)

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To solve the problem that the signal received by a non-cooperative receiver in communication reconnaissance is interfered by co-channel signals, a new algorithm based on cyclic spectrum amplitude was proposed to estimate the carrier frequencies and chip width of multi-signals. This algorithm is suitable for signals with low SNR (signal-to-noise ratio) and can implement blind estimation without prior knowledge of pseudorandom sequences, and it avoids the impact and interference of stationary noises by searching in nonzero cyclic frequencies. The simulations indicate that when the power ratio is 1 to 1, the correct probability of carrier frequencies can reach 100% for SNR=-9 dB, and the correct probability of chip width can reach 99% for SNR=-4 dB.

Key Management Scheme for Clustered Wireless Sensor Networks

YU Wangke, MA Wenping, CHEN Hefeng

2011, 24(2): 310-314. doi: 10.3969/j.issn.0258-2724.2011.02.022

[Abstract](1546)

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In order to overcome the limitations in power, computation, storage space and band width, a key management scheme for clustered wireless sensor networks was presented. Combinatorial design is adopted in this scheme so that the nodes in the same cluster can directly establish shared keys while the ones in different clusters can set up a multi-path key through the base station. The theoretical and simulation results show that with the key management scheme, the probability of network connectivity is 1 when the number of node's keys is more than 10.

Efficient and Secure Authentication Scheme for Vehicular Ad Hoc Networks

LIU Hui, LI Hui, MA Zhanxin

2011, 24(2): 315-520. doi: 10.3969/j.issn.0258-2724.2011.02.023

[Abstract](979)

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In order to resolve the safety problem in vehicular ad hoc networks (VANET), an efficient privacy-preserving scheme was proposed for VANET message authentication, which is based on the bilinear pairing technique for large-scale group communication and synthetically considers the actual situation of the VANET according to digital signature principles. In the scheme, vehicles are classified into private ones and public ones. The messages from private vehicles are verified by group signature, and those from public vehicles and roadside units (RSU) by identity-based signature. Furthermore, batch technique is introduced to accelerate the verification of accumulated messages, and quantitative comparison and determination is employed to handle the conflicting information. As a result, the information authentication efficiency is improved by about 33%, in comparison to that of the conventional schemes. Finally, an experimental simulation was conducted to confirm the efficiency of the proposed scheme in various application scenarios. The results show that the scheme is robust and scalable, and meets the requests of VANET.

Reliable Network Design Based on Partial Stochastic User Equilibrium

PU Yun, LIU Haixu

2011, 24(2): 321-325. doi: 10.3969/j.issn.0258-2724.2011.02.024

[Abstract](1585)

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To reduce the performance uncertainty caused by traffic accidents in a road network, the partial stochastic user equilibrium was used to describe the status of a road network under the impact of accidents, and a bi-level programming model for reliable network design problem was formulated. In the upper level model, the expected total travel time (ETTT) is adopted as a reliability measure, and the optimization objective is to minimize the weighted sum of the investment costs and the ETTT. The lower level model predicts the traffic flow pattern during accidents by generalizing the partial user equilibrium model to account for not only the partial impact of traffic accidents but also the imperfect information that travelers perceive. A Monte Carlo simulation-based genetic algorithm was provided to solve the bi-level model. The results of a numerical example show that, compared with the existing deterministic method, the proposed model can yield more robust solutions; under three demand levels of 100, 150, 200 veh/h, the average increase of social costs is 18%, but the increase rate of social cost decrease with the increase of demand.

Multi-objective 0-1 Linear Programming Model for Combined Location-Routing Problem in Hazardous Waste Logistics System

Shai Bin, ZHAOJ iahong

2011, 24(2): 326-332. doi: 10.3969/j.issn.0258-2724.2011.02.025

[Abstract](1345)

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An improved multi-objective 0-1 mixed-integer linear programming model for the location-routing problem in hazardous waste logistics was proposed, in which the optimization objectives are to minimize total costs and risks, and the constraints include waste types and treatment technologies, capacity and operation costs of treatment centers. A TOPSIS (technique for order preference by similarity to an ideal solution) algorithm was designed to solve this multi-objective model. The feasibility and advantage of the proposed model was demonstrated through a representative example taken from literature. Comparing with an exiting model, the proposed model reduced the risk by 7.69% at the expense of a little rise in cost by 0.70%.

Improved Ant Colony System Algorithm for Waste Collection Vehicle Routing Problem

LIU Jie, LI UDan, HE Yanfeng

2011, 24(2): 333-339. doi: 10.3969/j.issn.0258-2724.2011.02.026

[Abstract](1367)

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In order to solve the waste collection vehicle routing problem with intermediate facilities (WCVRP-IF) and reduce the route length and overlaps between two different vehicle routes, a clustering-based multiple ant colony system (CMACS) algorithm was proposed. This CMACS algorithm possesses a set of new strategies to construct solutions, including clustering-based strategy, improved global pheromone update rule and cross operator. Tests on two standard instances were conducted, their deviations being 0 and 2.13% from the best known solution, respectively. In addition, a comparison between calculated results based on different ant colony algorithms was made. The research results show that the length and compactness of the optimal route calculated by the proposed algorithm with a clustering-based strategy is 4.90% shorter and 83.33% smaller respectively than those of the optimal route calculated by the traditional ant colony system algorithm. The contribution degree of different strategies is successively the clustering-based strategy, the global pheromone update rule and the cross operator.

Airspace Sector Probabilistic Traffic Demand Prediction Model

TIAN Wen, HU Minghua

2011, 24(2): 340-346. doi: 10.3969/j.issn.0258-2724.2011.02.027

[Abstract](1856)

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In order to predict the traffic demands and variations for a future time interval in an airspace sector, the influence of the aircraft flight time on the probabilistic traffic demand prediction was analyzed from the point of uncertainty with a simplified airspace structure. The probabilistic distribution functions for the sector entry time, sector exit time and sector transit time were established by analysis of the randomicity of the sector entry, exit and transit process. On this basis, an airspace sector probabilistic traffic demand prediction model was developed, and a heuristic algorithm was designed. A simulation was performed to verify the proposed model and algorithm using real flight data. The result shows that the sector congestion predicted by the model and algorithm occurs during 10:00-11:00. Compared with the traditional deterministic methods, the proposed method can reduce 30 min of congestion period avoid unnecessary flow management during the period 9:30-10:00, and thus alleviate the air traffic controllers' workload.

Revenue-and-Expense Sharing Contract for Closed-Loop Supply Chain Coordination in Multiple Retail Markets

CHEN Yanru, TANG Xiaoping, XIAO Qinxin

2011, 24(2): 347-353. doi: 10.3969/j.issn.0258-2724.2011.02.028

[Abstract](1092)

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With assumptions that the sale price affected the demand directly and the recycling price and the effort level of recycling affected the recycling amount, supply chain coordination models under centralized, decentralized and revenue-and-expense sharing contracts were proposed. Optimal decisions and profits of the participants in a closed-loop supply chain were analyzed. The study reveals that profits of forward and reserve supply chain under the decentralized contract are lower than those under the centralized one in a multiple retail market. Under the revenue-and-expense sharing contract, a perfect coordination of a closed-loop supply chain can be obtained with a proper wholesale price and a fair distribution of expenses, and the wholesale price, instead of conventional revenue distribution, is to be determined through negotiation. A numeric example was presented to demonstrate feasibility of the revenue-and-expense sharing contract

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2011 Vol. 24, No. 2