西南交通大学学报

Measurement Foundation of Railway Track Geometrical Parameters Based on Strapdown Inertial Technique

WANG Xuemei, NI Wenbo

2012, 25(3): 355-360. doi: 10.3969/j.issn.0258-2724.2012.03.001

[Abstract](1814)

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Abstract:
In order to found the datum plane of measurement of railway track geometrical parameters, a method to found the datum plane based on the strapdown inertial technique was researched to overcome the shortcomings of the traditional gyro platform. By analyzing the basic cant measurement principle, it was pointed out that attitude matrix calculation with a high accuracy is the key to the measurement of railway track geometrical parameters based on the strapdown inertial technique. Therefore, corresponding attitude, position and velocity differential equations for a train were founded based on the motion theory of rigid body. With a method based on rotary vector and quaternion, the calculations of attitude, position and velocity were analyzed and studied, and the multiple-sample algorithms were utilized to compensate for coning motion errors in attitude calculation and sculling errors in velocity calculation. The simulation results show that the multiple-sample algorithms are able to strongly decrease the accumulative errors with time in an inertial measurement system and improve the accuracy of a measurement system.

Calculation of Braking Force of Continuous Welded Rail on Large-Span Steel Truss Cable-Stayed Bridge

ZHAO Weihua, WANG Ping, CAO Yang

2012, 25(3): 361-366. doi: 10.3969/j.issn.0258-2724.2012.03.002

[Abstract](1786)

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In order to probe into the transmission mechanism of braking force on continuous welded rail (CWR) on a large-span steel truss cable-stayed bridge, a plane model for bridge-rail interaction was established based on the finite element method and the bridge-rail interaction theory. In this model, all structural characteristics, such as steel truss, stay cables, main towers, and viscous dampers, are involved. The influences of stay cable stiffness, main tower stiffness and viscous dampers on the braking force were analyzed, and a simplified algorithm for the braking force was proposed. The results show that braking force can meet the demands of paving CWR on cable-stayed bridges, and its distribution regularity is the same as that on conventional bridges; viscous dampers improve the bridge-rail interaction in train braking situation by reducing bridge-rail relative displacement and braking force; compared with the stiffness of main towers, the stiffness of stay cables has a great influence on the braking force, so it should be taken into account in CWR design of a cable-stayed bridge.

Dynamic Stability of Long-Span CFST Arch Bridge under Action of Near-Fault Ground Motions

XING Fan, ZHU Bing, ZHAO Canhui

2012, 25(3): 367-372. doi: 10.3969/j.issn.0258-2724.2012.03.003

[Abstract](1750)

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In order to research the dynamic stability performances of long-span CFST (concrete-filled steel tubular) arch bridges under the action of near-fault ground motions, an arch bridge with a 132 m main span was taken as the engineering background, and seismic records of the Chi-Chi earthquake in Taiwan, China were set as transverse inputs. The incremental dynamic analysis (IDA) was adopted to determine the critical load of dynamic instability. To increase the efficiency of IDA, the parallel high-performance numerical computing was employed. In addition, the problem of strengthening IDA curve cluster convergence was discussed. The research result shows that near-fault pulse-like ground motions are likely to bring about a great damage and result in nonlinear dynamical limit-load instability, and the corresponding critical load is decreased evidently. Weighted average peak ground acceleration, an new intensity measure, can make the discreteness of IDA curve cluster be improved significantly to avail to reveal the dynamic instability characteristics of CFST arch bridges caused by near-fault ground motions.

Effects of Hydrodynamic Pressure on Seismic Response of Continuous Rigid-Framed Bridge

YANG Wanli, LI Qiao

2012, 25(3): 373-378. doi: 10.3969/j.issn.0258-2724.2012.03.004

[Abstract](1400)

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The hydrodynamic pressure caused by inner water and outer water of thin-walled hollow piers under earthquake has an effect on the dynamic response of continuous rigid-framed bridges. In order to investigate the effect, a calculation model for the continuous rigid-framed part of Miaoziping Minjiang bridge, which is based on the finite element theory of fluid structure-interaction, was built by using ANSYS Fluid30 element to simulate water. The seismic response of the bridge was calculated by taking into account the gravity, longitudinal prestress, hydrodynamic pressure, and earthquake waves recorded by the nearest seismic station. The results show that hydrodynamic pressure has little influence on natural frequencies and mode shapes of the continuous rigid-framed bridge, and the maximum reduction rate of the first 30 natural frequencies is approximately 8%, increments of transverse displacement peaks of the box girder reach 10%-20%, the maximum increment of internal force peaks of the main piers reaches 170%, and this value is about 75% for the box girder; and, the earthquake wave acceleration and water depth are the important factors influencing the hydrodynamic pressure.

Fatigue Design Parameters for Orthotropic Steel Decks of Single Plane Cable-Stayed Bridges

YE Huawen, XU Xun, QIANG Shizhong, HOU Suwei

2012, 25(3): 379-386. doi: 10.3969/j.issn.0258-2724.2012.03.005

[Abstract](2375)

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Experiment and finite element analysis (FEA) were conducted on the orthotropic steel decks of two single plane cable-stayed bridges in Chongqing municipality, China, to verify the fatigue design parameters. A full scale specimen with the actual connection details of the longitudinal ribs, crossbeams and deck plates was used for fatigue test. Vertical and horizontal fatigue loads were applied to the specimen under equivalent applied stresses for 20 million cycles. FEA was done to extend the ranges of design parameters verified by fatigue tests, such as cutout shape (apple-shaped,key-shaped and circular), and thicknesses of plates and deck pavement. The experimental and FEA results shown that the crossbeam and pavement thickness played a significant role on fatigue performances of the orthotropic steel decks. The principal tension stress (13.7 MPa) near the apple-shaped cutout was the smallest compared with those near the key-shaped and circular cutouts, so that the apple-shaped cutout was the best in terms of fatigue performances. The plate at least 16 mm thick and the apple-shaped cutout were recommended for the crossbeam of the orthotropic steel decks.

Quantitative Hazard Assessment of Road Debris Flow in Wenchuan Earthquake Area: A Case Study of Xiaojia Ravine in Wenchuan County

XIANG Lingzhi, CUI Peng, ZHONG Dunlun, GE Yonggang, ZHU Xinghua, YANG Wei

2012, 25(3): 387-393. doi: 10.3969/j.issn.0258-2724.2012.03.006

[Abstract](2104)

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A quantitative assessment method of debris flow hazard to roads in Wenchuan earthquake areas was established based on the case study of Xiaojia ravine to assess serious debris flow disasters happening frequently in 3 years after the Wenchuan earthquake. The environmental and geology background and the basic parameters such as the area and gradient of Xiaojia ravine were anglicized through a field investigation and using the RS and GIS technologies. The total amount of once debris flow process calculated by the rain-storm and flood method and the method of completing the square was taken as the pile quantities. Pile scope parameters, including average pile thickness, length and width, were estimated by a regression expression derived from field investigation data. Then the damage degree of debris flow to the roads beside Yuzi river was calculated quantitatively by the geometric generalization method. The research shows that the total amount of once debris flow process is 41104 m3 under rainfall that occurs once every 50 years, the roads will be completely buried and the river blocked by the debris flow. The above results are basically coincident with the actual hazard situation.

Bending Mechanical Properties of Cement Concrete with Fiber Grid Reinforcement

YAN Xiangcheng, WENG Xingzhong, KOU Yanan, LIANG Lei, ZHANG Guangxian

2012, 25(3): 394-399. doi: 10.3969/j.issn.0258-2724.2012.03.007

[Abstract](1746)

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In order to investigate the influence of fiber grid type, surface treatment and coarse aggregate limiting grain size on bending mechanical properties of cement concrete, fourteen group specimens with dimensions of 150 mm150 mm600 mm were tested through four-point bending experiments. The failure processes of the specimens were analyzed, the mechanical mechanism of the interaction between fiber grid and cement concrete was discussed, and some suggestions about the use of fiber grid were proposed. The research result shows that brittle failure characterizes the damage of the specimens. Fiber grid greatly improves the bending mechanical properties of cement concrete, and the bending strength of cement concrete is improved by 6.62% to 31.40%. When coarse aggregate limiting grain size is 20 mm compared with 40 mm, the bending strength of cement concrete increases by 2.72% to 9.97%. The bending strength of cement concrete is improved by 8.30% to 11.88% when fiber grid surface is treated with epoxy resin.

Nonlinear Analysis and Simulation of Valley Current Controlled Flyback Converter

HE Shengzhong, XU Jianping, WU Songrong, ZHOU Guohua, WANG Jinping

2012, 25(3): 400-405. doi: 10.3969/j.issn.0258-2724.2012.03.008

[Abstract](1394)

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For parameter design of switching DC-DC converters, dynamic equations and a discrete mapping model of valley current controlled flyback converter were established, and its complex nonlinear dynamic behaviors were investigated using bifurcation diagram and Poincar map. In addition, the stability and bifurcation property for valley reference current and DC voltage were analyzed. The time-domain waveform and phase portrait were obtained through time domain models constructed under Matlab/Simulink. The results show that valley current controlled flyback converters have complex nonlinear dynamic behaviors. As circuit parameters vary, the converter changes from steady state to chaos by double period-double bifurcation and border-collision bifurcation.

Multi-granularity Complex Network Model Based on GIS

LI Yongshu, LIU Gang, ZHANG Shuaiyi

2012, 25(3): 406-412,419. doi: 10.3969/j.issn.0258-2724.2012.03.009

[Abstract](1808)

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For the purpose of enhancing the accuracy of the failure spreading and reliability analyses of an urban road network, three kinds of road failure were studied. Based on this, a multi-granularity complex network model was proposed based on the complex network theory, and a generalized network of urban transit was expressed as a multi-granularity road complex network by building granularity space. Experiments were carried out to validate the model by building the multi-granularity road complex network of Chengdu City, and then the failure spreading analysis and the reliability analysis towards random failure and malice failure were conducted. The results show that the multi-granularity complex network model is efficient to the failure spreading and reliability analyses of urban road networks to provide the advantage for the further study of fault dynamic inversion for urban road networks.

Dynamic Simulation Analysis of Bar Insulator Pollution in Strong Wind

SUN Jixing, WU Guangning, CHEN Weirong, GAO Guoqiang, CUI Yi, WANG Bo

2012, 25(3): 413-419. doi: 10.3969/j.issn.0258-2724.2012.03.010

[Abstract](1457)

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In order to probe into the pollution characters of the surface of an insulator used in high-speed railway, forces on polluted particles in a strong wind environment were analyzed, and a simulation model for pollution of QBJ-25/20 type bar insulator was established. By taking the pollution volume fraction of insulator shed as the index of pollution measure, the relationships between the volume fraction and wind velocity and wind coming angle were obtained. The research result shows that in a strong wind condition there is a negative exponential relationship between the volume fraction and the coming angle, and there exists the same rerelationship between the volume fraction and the wind velocity. The pollution on the upper surface of the shed is mainly influenced by the coming angle ranging from 0 to 90, while the pollution on the lower surface of the shed is seriously affected by the wind velocity. With the increase of polluted particles' diameters, the volume fraction shows a trend of first increase and then decrease.

Global Exponential Stability for a Class of Stochastic Nonlinear Interconnected Large-Scale Systems

SHI Jizhong, ZHANG Jiye

2012, 25(3): 420-426. doi: 10.3969/j.issn.0258-2724.2012.03.011

[Abstract](1488)

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In order to study the effects of random errors caused by vehicle modeling on interconnected large-scale systems like the automated highway vehicle system, the deterministic theory was extended to the random case theory, and a proper vector Lyapunov function was constructed using the matrix theory and the random case theory. By analyzing the stability of stochastic differential inequalities, a coefficient matrix of the random large-scale system and the solutions of the Lyapunov matrix function interconnected with large-scale system are used to construct a judgment matrix, and then obtain the sufficiency criterion for global exponential stability of the large-scale system: when the judgment matrix is a quasi-M-matrix, the global index of the large-scale system is stable. Simulation results show that the algorithm proposed in the paper has a rapid convergence rate, and the system can achieve stability in 20 s.

Content-Based Fragile Audio Watermarking Algorithm in DCT Domain

ZHANG Jinquan, WANG Hongxia

2012, 25(3): 427-432. doi: 10.3969/j.issn.0258-2724.2012.03.012

[Abstract](1712)

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In order to realize the integrity authentication of audio files, a content-based fragile watermarking algorithm was proposed. To an one-dimensional sequence, the modification of alternating coefficient in DCT (discrete cosine transformation) will not change the sum of the sequence. Based on this property, an audio signal is segmented into frames. Then, samples are partitioned into sections for each frame. After absolute value of the sum of all samples in each section is computed, all absolute values are added in a frame. The result is quantized as a feature of the frame, and the quantization result is converted to a binary sequence as watermark. The watermark bits are embedded by modifying low frequency coefficient in DCT of each section with the quantization index modulation (QIM) method. Experimental results show that the fragile watermarking algorithm maintains good perceptual quality, the SNR (signal-to-noise ratio) values of watermarked audios are about 80 dB, and the algorithm is sensitive against additive noise, bit resolution transformation, sampling rate change, low-pass filtering and MP3 compression. Furthermore, it can detect and localize the tampered regions effectively.

Control of Superlong Bar LED Display Panel Based on Multiport Serial Flash

WU Zhiquan, JIN Wei, ZHU Yunfang, LI Qi

2012, 25(3): 433-438. doi: 10.3969/j.issn.0258-2724.2012.03.013

[Abstract](1474)

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In order to increase the display data output rate with the same system cost, an LED display control system based on multiport serial flash was proposed through analyzing the cell boards of the existing bar LED display panels. The system consists of high-speed 1T MCU (micro control unit) of STC12C5616 and multiport serial flash of SST26VF016B with serial peripheral interface (SPI). Based on the SPI high-speed clock of the MCU, the display data in the multi-port serial flash memory is directly sent to a superlong bar LED display panel by the way of direct memory access (DMA). Finally, by taking a 4 09664 monochromatic dot-matrix LED display as an example, the proposed control system was tested. The tested result shows that the display refresh rate is up to 62.5 Hz, and the effectiveness and feasibility of the proposed system are validated.

Vision-Based Detection of Moving Vehicles Using Wavelet Modulus History Images

QU Zhenshen, YU Mengmeng, JIANG Yonglin, WEN Fan, WANG Changhong

2012, 25(3): 439-445. doi: 10.3969/j.issn.0258-2724.2012.03.014

[Abstract](1466)

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To improve the robustness and accuracy of vehicle detection, a new detection method of moving vehicles was put forward based on background subtraction and wavelet decomposition modulus history images. First, wavelet decomposition was performed on the original image. In low frequency component, the Gaussian mixture model was used in conjunction with textural features to adaptively update the background image and label initial regions of moving objects. The high frequency component was used to calculate modulus value and obtain modulus history image through history frame accumulation. In view of the fact that vehicle objects have richer edge details than shadow regions, the edges were projected to x and y axes after object slant correction. Using the projection curves, the edge information was iteratively integrated with initial object regions to get final detection results. Experiment results show that compared with commonly used adaptive background extraction methods, the proposed method could detect vehicle objects accurately in practical traffic applications with a capture rate of 99.0% and an effective rate of 92.5%, and could effectively process the object conglutination caused by shadow with higher accuracy.

Comparison of Headways in Moving Block and Fallback Modes for CBTC System

HE Chengcai, YANG Tao

2012, 25(3): 446-450,457. doi: 10.3969/j.issn.0258-2724.2012.03.015

[Abstract](1705)

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In order to research the feature of headway in a Fallback mode and the difference to a normal mode for a CBTC (communication based train control) system, the basic principle of the CBTC system and the relative technology about moving block and Fallback modes were investigated, models for train headway in a CBTC Fallback mode were constructed, and headways in the moving block and Fallback modes for the CBTC system were simulated and calculated. The research shows that CBTC moving block and Fallback modes can meet the system requirements and achieve small train headway. Compared with the Fallback moving-like block mode, the moving block mode can achieve much smaller train headway (＜90 s).

Continuous Visible Reverse Nearest Neighbor Queries in Spatial Databases

YANG Zexue, HAO Zhongxiao

2012, 25(3): 451-457. doi: 10.3969/j.issn.0258-2724.2012.03.016

[Abstract](1290)

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In order to solve the problem of CRNN (continuous reverse nearest neighbor) query in an obstacle environment, the visibility was added to the CRNN query by taking obstacles into consideration, and a novel variant of CRNN queries, namely continuous visible reverse nearest neighbor (CVRNN) search, was introduced. The segment visibility judgment method and the corresponding pruning strategy were given. A CVRNN query processing algorithm was proposed. With this algorithm, a candidate set is gotten through a filter step, the wrong candidates were removed by a refinement step, and query results are founded through a splitting step. Experimental results show that the algorithm execution time increases linearly with the length of query line segment, and the proposed algorithm has a high query efficiency.

Triangular Mesh Segmentation Based on Spherical Images

MA Yuankui, ZHANG Shusheng, BAI Xiaoliang, FAN Haitao

2012, 25(3): 458-464. doi: 10.3969/j.issn.0258-2724.2012.03.017

[Abstract](1642)

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In order to manage and reuse triangular mesh models with local shapes, a segmenting method for triangular mesh models based on spherical images was proposed. With this method geometric signals of a triangular mesh model are mapped into spherical images through spherical parameterization and partition of a sphere. Then the spherical images are segmented by sophisticated image processing algorithms of region growing and region merging. Finally, the segmentation result of the spherical images is mapped into the related triangular mesh model. Experimental results show that the proposed method is effective to non-uniform, low-resolution triangular mesh models, the impact of accuracy of estimated geometric signals on segmentation results is reduced, and the segmentation result does not need to be post-processed.

Re-adhesion Optimization Control Strategy for Metro Traction

LIN Wenli, LIU Zhigang, FANG Youtong

2012, 25(3): 465-470. doi: 10.3969/j.issn.0258-2724.2012.03.018

[Abstract](1280)

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To make full use of the adhesion force between wheels and tracks and guarantee the train traction/brake performances, a re-adhesion optimization control strategy based on full-dimension state observer was proposed. When detecting slip/slide phenomena, this method could realize the optimal adhesion utilization by searching the adhesion summit zone quickly and adjusting the given torque dynamically according to the calculated AC motor torque and rotor angular velocity. The closed-loop poles assignment was introduced to ensure the control system stability and dynamic response performance. The proposed control strategy was simulated through a MATLAB/Simulink model and then verified by field experiments. The experimental results show that the whole re-adhesion efficiency using the proposed control strategy is greater than 80%, which meets the metro traction demands.

Calculation Errors of Performance Parameters of Hydraulic Torque Converter and Their Corrections

LUO Hong, WANG Tengteng, LI Xingquan, LI Yingqiang

2012, 25(3): 471-476. doi: 10.3969/j.issn.0258-2724.2012.03.019

[Abstract](1723)

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In order to improve the numerical simulation precision of hydraulic torque converters, the performance parameters, including torque ratio, efficiency and pump capacity factor, were calculated by the CFD (computational fluid dynamics) method. Calculation errors of the performance parameters were analyzed, and the corresponding correction methods were proposed. Through analyzing the impact of compensating fluid flow on the calculation error of pump capacity factor, its correction method was proposed. The results show that the neglect of friction loss and compensative flow in numerical simulations will result in calculation errors of the performance parameters of a hydraulic torque converter. The error correction method for friction loss can decrease the maximal relative errors of torque ratio and efficiency from 16.2% to 13.9%, and the error correction method for pump capacity factor can decrease its maximal relative error from 13.9% to 7.3%.

Rear Axle Compliance Steering Performance Analysis of Five-Link Dependent Rear Suspension

PAN Xiao, LIN Yi, CHEN Xiaokai, WANG Dongcheng

2012, 25(3): 477-483. doi: 10.3969/j.issn.0258-2724.2012.03.020

[Abstract](1436)

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In order to study the handing stability of vehicles with five-link dependent rear suspension, a linear three-degrees-of-freedom handling model of the vehicle including rear axle compliance steering was established. The influences of the rear axle compliance steering on the vehicle under-steering characteristics were analyzed by the frequency domain method. The results show that the longitudinal location of the upper links intersection point and the bush stiffness of the upper links influence the vehicle under-steering characteristics. When the intersection point is located 1.65 m from the rear axle and the bush bending stiffness is 1.5 kNm/rad, the vehicle under-steering performance is optimal. The simulation results of the theoretical model agree well with the experimental ones.

Two-Stage Optimization Algorithm for Stop Schedule Plan of High-Speed Train

HUANG Jian, PENG Qiyuan

2012, 25(3): 484-489. doi: 10.3969/j.issn.0258-2724.2012.03.021

[Abstract](1181)

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To improve optimization efficiency of the stop schedule plan of high-speed trains, the main factors influencing train stop schedule plans were analyzed based on the principles of stop schedule plan of high-speed trains. An optimization model was proposed, in which passengers' traveling convenience and generalized cost were considered. A two-stage algorithm was designed to solve the optimization model. Prior knowledge was used to find a local optimum solution quickly at the first stage, and Tabu search was applied to find a global optimal solution at the second stage where the local optimum solution obtained at the first stage was taken as its input. An optimization example of train stop schedule plan of a high-speed railway was presented. The result shown that the efficiency of the proposed two-stage algorithm was 30% higher than that of Tabu search only.

Evaluation of Coordination between Railway Transportation and Open-Pit Mining Based on Efficacy and Coupling

LI Xin, SHANG Tao, ZHOU Wei

2012, 25(3): 490-494. doi: 10.3969/j.issn.0258-2724.2012.03.022

[Abstract](1294)

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In order to evaluate the coordination relationship between railway transportation system and open-pit production, a coupling degree model is established under the capacity-coupling theory. This model quantitatively analyzes the coordination level of mine production and transportation systems as well as the effects of subsystems and system parameters on the whole open-pit mining system. Besides, the indices of open-pit mining and haulage equipments, the parameters choice of wagon quantity, load and fluctuation in railway transportation are discussed, and an isometric transformation is applied using an improved efficacy method. Finally, a case study is conducted to verify the model ability in reflecting the real productivity. The results show that compared with expectation, a lower daily average number of wagons has a larger effect on the system coordination level, with only 20% contribution ratio of the minimum value of other indexes; however, the unbalanced factor of trains has a smaller effect on the system coordination. Moreover, the coupling index will be raised by 17% if the daily average number of wagons is increased to 80% of the original plan.

Repairing Unit Location Problem in Background of Mobile Battle

YE Qing, SONG Jianshe, CHEN Chunxia

2012, 25(3): 495-501. doi: 10.3969/j.issn.0258-2724.2012.03.023

[Abstract](1572)

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To solve the problem of rational location of repairing units and improve the timeliness of the battlefield-repairing, a new location model with double coverage standards was constructed based on Laplace criterion of uncertainty decision and aiming at the maximum of edge covering ratio of the whole road network by supposing that task demands occur at any point of the network. An improved genetic-tabu algorithm was designed to solve this model. A group of initial solutions was obtained by the area-dividing clustering method. To avoid the generation of too many infeasible solutions in searching, the heuristic strategy was adopted at cross choosing. The results show that the proposed algorithm has a low computational complexity, and the precision problem of the location model based on edge demands is solved without increasing the network dimensions.

Using ADAMS to Assess Dynamic Load of Pavement during Aircraft Landing

LIANG Lei, GU Qiangkang, LIU Guodong, ZHANG Renyi, JIANG Le

2012, 25(3): 502-508. doi: 10.3969/j.issn.0258-2724.2012.03.024

[Abstract](2146)

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In order to provide a rational dynamic load coefficient for airport rigid pavement design and reduce the workload of the pavement dynamic load test, the software ADAMS was used to analyze the dynamic response mechanisms of the vertical load, longitudinal load, and lateral load on the pavement. The loading sensitivity of the pavement was analyzed by independently varying pitch angle, roll angle, initial descending rate, and initial ground clearance. In addition, different roughness levels of pavements were generated by the white noise linear filtering method to study the effect of roughness level on the dynamic load response of pavements. The results show that when the initial descending speed increases from 0 to 3 m/s, the dynamic load coefficient increases from 0.677 to 1.623; the horizontal load during aircraft landing is mainly in the longitudinal direction; and the peak value of aircraft dynamic load on level H pavement increases 68.71% than level A pavement.

Optimization Algorithm for Flexible Job-Shop Scheduling Problem Based on Heuristic Rules and Adjustment of Critical Paths

SHUAI Qi, YAO Xifan

2012, 25(3): 509-515. doi: 10.3969/j.issn.0258-2724.2012.03.025

[Abstract](1315)

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In order to overcome the disadvantages of long computing time and unstable result of traditional evolutionary algorithms in solving the optimization for large flexible job-shop problems (FJSPs), a heuristic critical path approach (HCPA) was proposed. This method first uses a heuristic rule to get some preliminary schedules. Then, critical workpieces and key process of these preliminary schedules are searched and critical paths are locally adjusted using some heuristic rules for better solutions. Finally, the optimal schedule of FJSP is obtained by comparison among these solutions. The proposed approach was applied to benchmark FJSPs, and the solutions were compared with those of other approaches. The results show that for the 1510 FJSP, the values of evaluation indexes computed by the proposed method are nearly the same as those by the integrated genetic algorithm, but the computing time (only 3.2 s) is reduced by 42%. The large FJSPs of 2310 and 2510 are also calculated, reflecting that introduction of heuristic rules can improve the computing efficiency and solution stability; compared with the traditional evolutionary algorithms, the proposed method is more suitable for real-time solution of difficult FJSPs.

Stochastic Mean-Excess User Equilibrium Model with Multiple Classes and Elastic Demand

LV Biao, PU Yun, LIU Haixu

2012, 25(3): 516-525. doi: 10.3969/j.issn.0258-2724.2012.03.026

[Abstract](2128)

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In order to accurately describe travelers' route choice behaviors for avoiding risks caused by uncertainties about travel time in a stochastic road network, the calculation formula of mean-excess travel time was derived for conditions when the traffic demand of commuters follows a log-normal distribution and the link capacity follows a Beta distribution, and a stochastic mean-excess user equilibrium model with multiple classes and elastic demand was built and formulated as an equivalent variational inequality. In the model, travelers' perception errors on travel time and the effects on traffic demand caused by the road network service level were taken into account. The results show that, as the demand variation level and degradation degree of link capacity increase, when the ratio of variance to mean increases from 0.5 to 2.0 and the parameters (l, m) of Beta distribution change from (90,10) to (10,10), the average minimum perceived mean-excess travel time increases 48.5% for commuters and 99.2% for non-commuters.

Product Family Design Based on Mechanism of Population Evolution

NIE Yong, YIN Guofu, ZHAO Xiufen

2012, 25(3): 526-532. doi: 10.3969/j.issn.0258-2724.2012.03.027

[Abstract](1498)

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In order to attain a rapid response to customers' individualized needs in market segments, a process model of product family evolutionary design was established according to the biological evolutionism. Based on the definitions of product genes and product allelic genes, a new four-layer product family genetic structure was built. In addition, product family fitness models in two dimensions, i.e., customer needs in marketplace and production efficiency in design and manufacture environment, were constructed by quantitative analysis of customer needs in market and the production efficiency. Meanwhile, a multi-directional evolution algorithm that supports the whole product family evolution was proposed. Taking a car product family design for example, simulation results of the product family evolutionary process show that after 20 generations, the product family develops into the optimal solution which meets the needs in small, compact and medium car market segments and has high product efficiency. Therefore, the method proposed for product family evolutionary design can effectively meet customers' individualized needs in market segments.

Exprimental Study on Acceleration of Landfill Stabilization Process Using Bioaugmentation Technology

QIU Zhongping

2012, 25(3): 533-537. doi: 10.3969/j.issn.0258-2724.2012.03.028

[Abstract](1867)

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In order to overcome the drawbacks of traditional methods in landfill treatment, such as slow degradation of organic waste, long-lasting stabilization, and complicated operation and management, a new bioaugmentation technology was proposed to accelerate the stabilization of landfill processing. Through indoor simulation experiments, a composite microbial system was introduced, and its influences on the landfill waste stabilization of bioreactor landfill was studied. The results show that the multifunctional microbe community accelerated the biodegradation of organic waste: A landfill temperature rise of 0.8-5.0 ℃ was observed in the landfill during the early and mid stages, and the pH value in landfill increased rapidly over 8.0 and became stable 208 days earlier than the control. Moreover, compared with the control group, the composite microbial system in the experimental group reduced the COD (chemical oxygen demand) concentration of leachate more obviously, which remained at about 3 000 mg/L after 505 days of anaerobic landfilling. The concentration of ammonia nitrogen decreased more rapidly, keeping lower than the control after 463 days, and reaching the level below 25 mg/L after 700 days, which meet discharge requirements of ammonia nitrogen in leachate specified by the National Standard for Pollution Control on the Landfill Site of Municipal Solid Waste (GB 168892008). The composite microbial system also increased the deposition capability as much as by 27.39%, 19.23% and 14.81% when compared with the control group at the early, mid, and end stages of landfill processing, respectively.

2012, 25(3): 538-538.

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2012 Vol. 25, No. 3