西南交通大学学报

Fatigue Assessment of Orthotropic Steel Bridge Deck Based on Hot Spot Stress Method

PU Qianhui, GAO Liqiang, LIU Zhenbiao, SHI Zhou

2013, 26(3): 395-401. doi: 10.3969/j.issn.0258-2724.2013.03.001

[Abstract](1252)

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Abstract:
The hot spot stress method was applied to fatigue assessment to solve the problem of fatigue cracking in orthotropic steel bridge deck.In this method, the hot spot stresses at check positions were calculated using the linear extrapolation method of International Institute of Welding and the ANSYS sub-model method.Based on hot spot stress method, the process of fatigue assessment for orthotropic steel bridge deck was provided, and the related problems were investigated in a case study on Yongjiang railway cable-stayed bridge.The results show that compared with the nominal stress method, the hot spot stress method can better reflect the cracking essence of orthotropic steel bridge decks. The fatigue assessment made for the rib located at the joint between diaphragms and the rib of the orthotropic steel bridge deck of the Yongjiang bridge reveals that the fatigue life span of the structure is 73 years.

Mechanic Behavior of Steel-Concrete Composite Girder of Long-Span Cable-Stayed Bridge

WEI Xing, QIANG Shizhong

2013, 26(3): 402-408. doi: 10.3969/j.issn.0258-2724.2013.03.002

[Abstract](1499)

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In order to investigate the mechanic behavior of steel-concrete composite girder in long-span cable-stayed bridge, finite element method (FEM) analysis and specimen test of Guanyinyan Yangtze River bridge were carried out. By using FEM program ANSYS, a 3D model for girder section was founded, and elastic analyses of stress distribution of composite girder under different load cases were performed. By considering the nonlinear material properties and nonlinear slip of shear stud, elastic-plastic behaviors of composite girder were analyzed. A test specimen for composite girder with a scale of 1 to 2 was designed, and its static load test was carried out. Stresses at test points in cross section of composite girder bearing different load cases were obtained. The research results show that few relative slippage occurs between steel plate girder and concrete slab of composite girder bearing design load. Shear studs are qualified to resist interface shear and ensure a full composite action. The distribution of stresses in cross sections are similar to the assumption of plane cross-section. For the composite girder, steel girder mainly provides bending strength, while concrete slab provides compression strength mainly.

Structure-Borne Noise of Concrete Box-Girder and Its Influence Factors

ZHANG Xun, LI Xiaozhen, LIU Quanmin, WU Jinfeng, LI Yadong

2013, 26(3): 409-414. doi: 10.3969/j.issn.0258-2724.2013.03.003

[Abstract](1616)

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In order to research on structure-borne noise of box-girder and its influence factors, a simply-supported concrete box-girder with a span of 32 m was selected as the case study, its structure-borne noise was simulated by means of hybrid FEM-BEM method, and the computed results were validated by field measurements. On this basis, the influence laws of plate thickness and dip angle of web on structure-borne noise were probed into. The research results show that the dominate frequency ranges of box-girder vibration and structure-borne noise are 40.0 to 125.0 Hz and 31.5 to 100.0 Hz, respectively, and the peak frequency of noise around the bottom plate is 63.0 Hz. The structure-borne noise decreases with the increase of plate thickness, and the addition of top plate thickness is the most effective noise-reduction measure. The preferable dip angle of web is 0? to 12? for lower structure-borne noise of box-girder.

Landslide Responses of High Steep Hill with Two-Side Slopes under Ground Shaking

YANG Changwei, ZHANG Jianjing

2013, 26(3): 415-422. doi: 10.3969/j.issn.0258-2724.2013.03.004

[Abstract](1816)

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In order to study the landslide mechanisms and responses of a high steep hill with two-side slopes under ground shaking, a high steep hill with two-side slopes near national highway 213 was used as a prototype. A full process from initial deformation to sliding of the slope during ground shaking was simulated by the continuum-medium distinct element method (CDEM). The results show that the stress concentration phenomenon appeared at the top of the sliding mass firstly, and then some tension and shear failure points appeared there, which expanded toward the toe of the sliding mass from the top along the structural plane. At the same time, the number of tension failure points gradually increased. Finally, the toe of the sliding mass broke, and the sliding mass sheared out from the toe, resulting in the landslide. If external conditions such as material parameters were kept the same, the landslide occurrence in the middle of the slope would precede that at the foot, and the starting time of landslide and the arrival time of peak ground acceleration (PGA) were synchronous or the former lagged behind the latter slightly. The PGA of the input seismic wave was amplified with the increase of elevation, regardless of on the steep slope, on the lower slope side, or inside the slope. Generally, the vertical PGA amplification is larger than the horizontal one; the PGA amplification on a steep slope is larger than on a gentle slope, and the PGA amplification on a gentle slope is larger than inside the slope.

Centrifuge Model Test of Clay Tunnel with Embedded Small Duct Grouting

XU Ming

2013, 26(3): 423-427,434. doi: 10.3969/j.issn.0258-2724.2013.03.005

[Abstract](1512)

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Plane strain centrifuge model tests were carried out to investigate the influence of small duct grouting range on tunnel stability and ground subsidence. The consolidation principle and performance optimization of advanced duct grouting were discussed. The tests were carried out in a circular cavity with stiff resin inclusions embedded around the periphery of the tunnel in over-consolidated clay in plane strain. The experimental results show that with the extension of ducts' circumferential setting range, tunnel stability is improved, tunnel plastic zone and slip plane transfer from tunnel crown to its invert, and deep soil becomes involved in bearing load. The shoulder reinforcement scheme is one of economic ways to improve the consolidation effect in accordance with the findings. When the cover-span ratio equals to 2, this scheme can be reduce the maximum ground subsidence in clay tunnel construction by 10%.

Capillary Penetration Diffusion Model for Backfill Grouting of Shield Tunnel

YE Fei, LIU Yanpeng, GOU Changfei, ZHANG Jinlong, ZHOU Zhuo

2013, 26(3): 428-434. doi: 10.3969/j.issn.0258-2724.2013.03.006

[Abstract](1249)

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In order to discuss the calculating method of diffusion radius and pressure on segments of backfill grouting, a mechanical model for penetration diffusion in surrounding soils was set up by simplifying grouting penetration as transfusion in soil capillary tubes with uneven bore diameters. Based on the cylinder diffusion theory and the assumption that grout is as Bingham fluid, under the premise of bring the equivalent porosity to replace the soil porosity, the calculation formula of the diffusion radius and the pressure on segments of backfill grouting were obtained through simulating the penetration process of grout in single capillary tube. Then, the relations between grouting pressure, time, and the diffusion radius, pressure on segments were discussed through a detail example. The result shows that the increase rate of the pressure on segments is bigger than that of the grouts diffusion radius under different grouting time and pressure, and the total capillary area on the grouts flowing frontal surface is in proportion to diffusion radius when keep the influence depth of tail gap and the soil equivalent porosity unchanged.

Electromagnetic Wave CT Detection Standard of Karst Roadbed Grouting

HU Yi, XIE Qiang, ZHAO Wen, ZHENG Lining

2013, 26(3): 441-447,454. doi: 10.3969/j.issn.0258-2724.2013.03.008

[Abstract](1026)

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To investigate the detection standard of electromagnetic wave CT of karst roadbed grouting, 64 sections in the karst roadbed test areas of Nanning-Guangzhou railway were tested using the electromagnetic wave CT, the differences of electromagnetic wave absorption coefficients before and after grouting of clay, pebble soil and karst cave were analyzed. The results show that in grouting qualified karst roadbed, the difference of electromagnetic wave absorption coefficients before and after grouting is below 0.1 dB/m to clay and about 0.2 dB/m to pebble soil, respectively; and it is above 0.4 dB/m to karst caves, mainly from 0.6 to 1.2 dB/m. The electromagnetic wave CT detection standard of karst roadbed grouting for Nanning-Guangzhou railway is that the difference of absorption coefficients before and after grouting is above 0.2 dB/m to pebble soil and over 0.4 dB/m to karst caves.

Interferometric Combination for Persistent Scatterer Interferometry Considering Interferometric Phase Noise and Its Application to Subsidence Monitoring

NIE Yunju, LIU Guoxiang, SHI Jinfeng, YU Bing, CHENG Penggen, ZHANG Rui, LI Tao

2013, 26(3): 448-454. doi: 10.3969/j.issn.0258-2724.2013.03.009

[Abstract](1069)

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In order to improve the accuracy of persistent scatterer interferometric (PSI) synthetic aperture radar for monitoring ground deformation, an improved interferometric combination mode was proposed by considering the thresholds of both spatial and temporal baselines, and taking into account the noise level in interferometric phases of all interferometric pairs. Experiments of subsidence monitoring using the proposed interferometric mode were performed using 16 high resolution SAR images collected by the X-band radar sensor onboard the German satellite TerraSAR-X over Shanghai. The results show that the minimum interferometric pairs (92) and the maximum persistent scatterer (PS) points (27 026) can be obtained by the proposed method. Compared with the ground-based measurements, the subsidence rate derived by the PSI technique has an error of ?3.89 mm/a, with a precision being 1.86-3.00 times higher than that of other available modes. This demonstrates the effectiveness and reliability of the proposed interferometric mode.

Comparison of Short Arc Integral Approach and Average Acceleration Approach in Gravity Field Recovery

HUANG Qiang, FAN Dongming

2013, 26(3): 455-459,480. doi: 10.3969/j.issn.0258-2724.2013.03.010

[Abstract](835)

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In order to compare the short arc integral approach with the average acceleration approach, two Fortran programs were compiled respectively. Two 90 degrees and orders gravity field models, Model_Arc (for the short arc integral approach) and Model_Acc (for the average acceleration approach), were recovered based on the programs and GOCE (gravity field and steady-state ocean circulation explorer) orbits. The results show that the maximal geoid error is respectively 4 cm at 80 degrees to the Model_Acc and 10 cm at 90 degrees to the Model_arc, the precisions of the Model_Acc and Model_Arc are higher than those of the models based on CHAMP (challenging mini-satellite payload) and GRACE (gravity recovery and climate experiment) orbits. The superiority of the Model_Acc over model GO_CONS_GCF_2_TIM_R3 is accuracy before 80 degrees, while the superiority of the Model_Arc over the Model_Acc is consumed time.

A New Secure Digital Camera Model Based on State Parameter

HE Hongjie, CHEN Fan, YIN Zhongke

2013, 26(3): 460-466. doi: 10.3969/j.issn.0258-2724.2013.03.011

[Abstract](932)

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The current secure digital camera (SDC) model can not identify the secondary capture image and have to validate the integrity of watermarked images taken by it. To address these problems, a state parameter based SDC model is proposed by generating and transferring secret key which is used to produce a watermarked image. The cascade chaotic mapping is used to generate the camera key for the proposed SDC model. By the application of the plaintext data including camera key and state parameters in the image creation, such as viewfinder mode, focus, and time, the secret key is produced by Hash function. The confidentiality and anti-counterfeiting of secret key for the proposed SDC model were validated and one to many nonlinear mapping between the camera and the secret key was established. Experimental results demonstrate that the bit number variation of secret key follows approximately uniform distribution when the camera key or scene parameter is changed.

Testing Dielectric Properties of Biological Material by Dynamic Frequency Sweep Method for Multimode Cavity

LU Zhiyuan, HOU Jianqiang, HAN Rixia, CHEN Rui, NIU Zhongqi

2013, 26(3): 467-472. doi: 10.3969/j.issn.0258-2724.2013.03.012

[Abstract](1009)

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The microwave nondestructive testing on dielectric constant of material needs several times to tune cavity system, which leads to low efficiency and high cost. Based on the cavity perturbation theory, an electromagnetic separation test system was designed, in which the TE10p (p is the odd number) oscillation mode was selected. A dynamic frequency sweep method for multiple oscillation modes in a cavity was proposed to measure the dielectric constant and electromagnetic energy loss for different kinds of trees. This method can simultaneously measure the dielectric constants and loss characteristics at three different frequencies, which greatly reduces the error caused by tuning cavity size in the single-frequency measurements. Repetitive test results on the dielectric constant of the polyltef material with the proposed method have error of lesser than 1％.

Joint Rate and Power Control Based on Dynamic Game Theory in Data Link System

HE Gang, BAI Peng, PENG Weidong, ZHAO Hongyan, SU Xi, LIN Jinfu, WANG Mingfang

2013, 26(3): 473-480. doi: 10.3969/j.issn.0258-2724.2013.03.013

[Abstract](1004)

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As IFDL(intra flight data link) is required to support heterogeneous operations and the transmission of large amounts of battlefield information, it is necessary to perform joint control over different transmission rates and powers for each node. To fulfill this purpose, an algorithm based on dynamic game theory is proposed. By applying this algorithm, the transmission rate and power are optimized, and the existence and uniqueness of the Nash equilibrium are proved. The simulation results show that compared to the fixed rate and distributed power control algorithm using static game theory, this algorithm has improved the transmission rate of each node by 50.92% at least, the convergence of transmission rate by 50%, and the convergence of transmission power by 80%, which demonstrates that it can facilitate the stability and fairness of the IFDL system.

Interval TypeⅡ Fuzzy Model Simplification Based on Orthogonal Transformation Methods

YAO Lan, XIAO Jian, JIANG Yulian

2013, 26(3): 481-486. doi: 10.3969/j.issn.0258-2724.2013.03.014

[Abstract](901)

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As the effective singular value is hard to determine in the singular value decomposition-QR (SVD-QR), QR decomposition with column pivoting (pivoted-QR) was proposed to analyze the fuzzy model structure. By applying it to the two firing strength matrices of the fuzzy model, the absolute values of R-diagonal elements were used as a rule ranking index, and specific rule was located according to the position of element with the value of each column of Π equaling one. Finally, a chaos time series was predicted with the SVD-QR and pivoted-QR, and adaptability of important rules selected by both methods were compared with different samples. The simulation results indicate that the two methods are clearly distinct in the selection of a set of important fuzzy rules. The error of pivoted-QR is 0.108 6 in average, much less than that of the QR. The errors of pivoted-QR with different input samples are close, demonstrating that it has better generalization performance.

An LCL Composite Resonant-Type Bi-directional Contactless Power Transfer Mode

DAI Xin, SHI Hui, SUN Yue

2013, 26(3): 487-493,519. doi: 10.3969/j.issn.0258-2724.2013.03.015

[Abstract](952)

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Classical single-load bi-directional inductive power transfer systems have some drawbacks such as low resonant capacity and high voltage and current stress of switching devices. Based on LCL composite resonance, a bi-directional power energy transfer mode using symmetric topology was proposed. The impedance model for alternating current was presented and the gain between the input and output was deduced. By analyzing the frequency responses and the output power under different loads and coupling coefficients, an output voltage regulation method was proposed, which runs in the bi-operation mode between energy injection and free running. Furthermore, a duty cycle control method for the bi-operation mode was also proposed to guarantee the stability of output voltage. The simulation and experimental results indicate that the proposed mode can achieve bi-directional energy transmission and the output voltage ripple less than 0.3 V. Moreover, this mode is simple and easy for implementation.

Stress Corrosion Behavior of Car-Body Aluminum Alloy for High Speed Train

JIANG Chao, CHEN Hui, WANG Xiaoming, MA Jijun, LI Hengkui

2013, 26(3): 500-506. doi: 10.3969/j.issn.0258-2724.2013.03.017

[Abstract](958)

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In order to ensure the safety and reliability of the series 5,6 and 7 aluminum alloy components of high-speed trains, specimens were tested using constant loading technique and constant displacement technique for the stress corrosion cracking. Mechanical incisions and fatigue cracks were prefabricated on the samples, which were then tested by applying a constant load or constant displacement. Experimental results showed that the series 7N01P-T4 alloy, with a critical stress intensity factor KⅠSCC of less than 11.238 MPa·m1/2  and a limit stress of less than 224.3 MPa, underperforms the series of 5083P-H111 and 6005A-T6 in the stress corrosion resistance, but the three series of aluminum alloy all met the requirements. Typical characteristics of stress corrosion caused by hydrogen embitterment of catholic reaction were found near the crack source region, but the characteristics of hydrogen-induced cracking were found near the fatigue region, which was consistent with the distribution of straight-line trenches on the fracture.

Numerical Simulation of Railway Vehicle Impacts

SUN Shulei, LI Fu, HUANG Yunhua, DING Junjun

2013, 26(3): 507-512. doi: 10.3969/j.issn.0258-2724.2013.03.018

[Abstract](1134)

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In order to study the effect of vehicle impacts on vehicle safety, a modified draft gear dynamic model was built in Simulink based on theory of draft gear, and a full degree-of-freedom (DOF) model of C80 freight car and K6 bogie were built in UM based on the vehicle system dynamics and a coupler model. The vehicle impact was co-simulated by combination of above models using Simulink and UM. The results indicate that the problem of energy dissipation on the transition curve can be solved and the characteristic of draft gear can be simulated by the correction model; the impact between two groups of vehicles is more harmful than that between a vehicle and a group of vehicles; low-amplitude and high-frequency coupler force is generated by the mass of the coupler and follower plate; the coupler force of the full-DOF impact model is 21.7% less than that of singe-DOF model due to the suspension; a coupling relationship between longitudinal, lateral, and vertical directions can be found in the vehicle impact, so the rail-wheel vertical force increases with an increase in the impact mass and the height of center of gravity, and the rail-wheel lateral force increases with an increase in the longitudinal force or a decrease in curve radius.

Model for Determination of Vehicle Trajectories in Three-Dimensional Roll-Over Crashes

CAO Yi, PEI Yulong, FU Chuanyun

2013, 26(3): 513-519. doi: 10.3969/j.issn.0258-2724.2013.03.019

[Abstract](1165)

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In order to reconstruct three-dimensional vehicle collision accidents, the critical conditions of vehicle pitching and rolling were derived in the vehicle's three-dimensional coordinate system by analyzing the relationship between collision impulse moment and inverse gravity moment. The movement trajectory model of vehicle rolling with ground reaction force was constructed according to the kinematics theory and the relationship of kinetic energy conversion. For a real accident case, a comparative study between the reconstruction analysis results and the vehicle traces remained in the accident scene was conducted using the accident reconstruction system based on the above model and PC-Crash. The results show that the vehicle stationary position and attitude reconstructed by the model are consistent with the actual state in the accident scene; the reconstructed trajectories are consistent with those remained in the accident scene, except a smaller curvature of the passenger car's left front wheel.

Competitive Network Equilibrium Based on Express-Delivery Transport Organization Plan

NI Linglin, SHI Feng

2013, 26(3): 525-531. doi: 10.3969/j.issn.0258-2724.2013.03.021

[Abstract](1099)

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In order to analyze the contributing factors of express-delivery price, the research attempts to evaluate the express-delivery operation procedures based on the union's express-delivery organization plan, consumer behaviors, behaviors of related transport enterprises as well as the equilibrium condition in competitive express-delivery market. The paper adopts the variational inequality and builds the express-delivery market competitive network equilibrium model, and uses a modified projection algorithm to solve this model. Case studies demonstrate that express price is proportional to the average weight, the cost of transport and express-delivery enterprises, the exchange cost between consumer and express enterprises, while is disproportional with the competition of transport and express market, and the competitiveness of express-delivery enterprises is weakened with the increasing transaction cost between the consumer and express enterprises.

Passenger-Flow Spatial Distribution Model of Urban Rail Transit

SHANG Bin, ZHANG Xiaoning

2013, 26(3): 539-545. doi: 10.3969/j.issn.0258-2724.2013.03.023

[Abstract](1382)

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In order to analyze the variation of urban rail transit (URT) passenger flow against the distance from the city center, a model characterizing the passenger spatial distribution of urban rail system was proposed, which was based on the deterioration model of pavement performance. The model was verified using the real passenger flow data of URT in Shanghai and Beijing. The results show that the larger the value of the important node coefficient K, the more important the important node station and the larger the passenger volume will be. When the shape parameter β is larger than 1, the trend curve of passenger flow is inverse S shaped; when β is less than 1, the trend curve of passenger flow is concave. In addition, the urban scale parameter reflects the radiation range of rail transit. When the value of α is near 15 km, the connection line of urban scale parameter is near the Outer Ring Road in Shanghai, indicating that the URT passenger flow is mainly concentrated in the main urban areas. The predicted variation of URT forecasting passenger flow against the distance from the city center is accordance with the actual situation.

Method for Computing On-Line Bus Stop Capacity

SUN Feng, WANG Dianhai, MA Dongfang

2013, 26(3): 546-552. doi: 10.3969/j.issn.0258-2724.2013.03.024

[Abstract](1026)

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In order to improve the precision of calculation of bus stop capacity, the servicing process of buses at on-line stops was analyzed using the bus trajectories according to metropolitan bus operation status. On this basis, a method for computing on-line bus stop capacity was developed taking into account both the queue probability and the dwell time distribution. Then, the dwell time distribution function was fitted to the field-observed data of Hangzhou city; Kolmogorov-Smirnov (K-S) test shows that the log-normal distribution has the best goodness of fit, with the K-S value of two traffic periods being 0.083 9 and 0.050 6, respectively.The capacities of three kinds of bus stops were computed by MATLAB programming with different parameters of dwell time distribution. The results indicate that the capacity of bus stop with different berths decreases from 44.4% to 47.3% as the natural logarithmic mean of the dwell time μ increases. In addition, the capacity of bus stops was obtained by simulation using VISSIM software. The average relative error between the calculated and simulated results is 6.5%.

An Improved Integrated Evaluation Method on Operation Performance of Air Traffic Control Based on BP Network

ZHANG Jianping, HU Minghua, WU Zhenya, ZHANG Ruiping

2013, 26(3): 553-558. doi: 10.3969/j.issn.0258-2724.2013.03.025

[Abstract](1696)

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To improve the integrated evaluation on the operation performance of air traffic control, a general index system was established, including density of air traffic flow, safety performance, efficiency performance and workload of air traffic controller, and a classification evaluation method by means of artificial intelligence was presented on the basis of back propagation network model. Taking the Chengdu terminal area for example, under the condition of segregated operation on two parallel runways, a BP network model of 12-7-5 in topology was set up after 60 typical samples were collected for network training and test, and applied for classification evaluation for 40 exam samples. In comparison with another integrated evaluation method based on principal component analysis, both of the evaluation results were in agreement.

Interval Robust Optimization of Airline Network Designing

WU Xiaohuan, ZHU Jinfu, WU Weiwei, GAO Qiang

2013, 26(3): 559-564. doi: 10.3969/j.issn.0258-2724.2013.03.026

[Abstract](1069)

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In order to determine the specific locations of hubs and optimize the path design of origin-destination (OD) flows of airline network, an interval scenario set was defined and a new absolute interval robust optimization model was established, taking into account the uncertainty of design parameters OD flows and unit flow cost of the hub-and-spoke network.The model was solved by combination of the modified shortest path algorithm with artificial intelligence algorithms, and then verified in two numerical cases using the classic data for airline network design and the OD data of Chinese airline network, respectively. The results show that the optimal solutions obtained from the absolute interval robust optimization model have global optimality, and the deterministic robust optimization model is a special case of the proposed model under pessimistic rules when the values of the OD flows and cost of unit flow are determined; the correlation coefficient of the two groups of objective values obtained from pessimistic and optimistic rules is more than 0.99 in different scenarios. In the standard example under the pessimistic rule, the optimal objective value calculated from the proposed model, after normalized, is 784.47, which is 16.65% less than the optimal objective value of the deterministic optimization model and 29.07% less than the optimal objective value of the relative interval robust optimization model.

Aircraft Initial Taxiing Route Planning Based on Petri Net and Genetic Algorithm

ZHU Xinping, TANG Xinmin, HAN Songchen

2013, 26(3): 565-573. doi: 10.3969/j.issn.0258-2724.2013.03.027

[Abstract](1627)

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For the precision guidance of aircraft movement under the control of the advanced surface movement guidance and control system (A-SMGCS), airport surface was divided into typical operation units, such as taxiway intersection and line segment. A modular surface operation model was built based on the extended timed place Petri net (ETPPN), and used to code chromosomes. Then, algorithms for chromosome validation and amendment, crossover and mutation were proposed respectively, taking the surface operation rules into account. Using the daily operation data collected from runway 01 at Beijing Capital International Airport, and the initial taxiing routes were planned for each flight using the model and algorithms. The result demonstrates that, compared with the node-link model, the proposed model could depict surface operation rules more thoroughly and avoid generating illegal routes. The computation time of initial taxi routes for each flight is less than 10 s, which meets the requirement of A-SMGCS. In addition, as the aircraft taxi speed adjustment process is taken into account by the model, the traffic situation could be described more closely to the real surface operation.

Effect of Temperature on Stabilizing Process of Aerobic Bioreactor Landfill

QIU Zhongping, LIAN Hongmin, LIU Yang, WANG Shu, GONG Zhengjun, ZHOU Liping

2013, 26(3): 574-579. doi: 10.3969/j.issn.0258-2724.2013.03.028

[Abstract](1020)

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Variations of the features of leachate and components of landfill at different temperatures were simulated experimentally to study the effect of temperature on the stabilizing process of aerobic bioreactor landfill.The results indicated that the concentration of chemical oxygen demand (COD) and ammonia nitrogen of leachate decreased more rapidly at higher temperature between 20-40 ℃. Moreover, the concentration of ammonia nitrogen at 40 ℃ reached the threshold limit value specified by GB16889—2008 standards after 56 d, which is 84 d earlier than that at 20 ℃. Higher temperature between 20-40 ℃ would result in a less leachate yield and a more remarkable decline in moisture content of solid waste and total organic carbon (TOC) in the whole landfill process, and thus brought a thorough degradation of wastes. When the landfill was finished, it subsided and stabilized rapidly. Therefore, higher temperature is beneficial for acceleration of stabilization of landfill.

Plate Load Test Investigation of Dynamic Compaction Effect of Gravel Soil

HUANG Da, JIN Huahui, WU Xiongwei

2013, 26(3): 435-440,454. doi: 10.3969/j.issn.0258-2724.2013.03.007

[Abstract](1107)

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In order to deeply probe into influences of gravel content and distribution on bearing capacity and differential settlement, 18 plate loading tests were carried out on 3 dynamic compaction foundations with different gravel contents. The research result shows that the dynamic compaction foundation of gravel soil has a better bearing capacity with a mean of above 250 kPa. The non-uniform bearing capacity and differential settlement of foundation are more obvious with the increase of gravel content and uneven distribution. For dynamic compaction foundation with a high gravel content and uneven distribution, great differential settlement occurs when load is close to or reaches at its bearing capacity. The differential settlement can be as large as 3 to 4 times because of the difference of grave content of a dynamic compaction foundation in Kai County in Chongqing.

Research on Load's Tracking Control for Crane's Motor Driving System

MA Lili, CHENG Wenming, ZHONG Bin

2013, 26(3): 494-499. doi: 10.3969/j.issn.0258-2724.2013.03.016

[Abstract](1088)

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In order to control a crane motor to real-time track the abrupt load torque with a given rotational speed for the motor driving system, the equivalent moment of inertia and equivalent load torque on the rotor of the hoisting mechanism and the dynamic equation of the motor driving system were derived through equivalent conversion. Then a system of synchronous rotating coordinates was constructed according to rotor flux linkage orientation, and a vector variable frequency control system for tracking load torque was designed based on the slip angle frequency. The results of a case study show that the starting time of the close-loop control system with no load was 0.34 s faster than that of the open-loop system, the motor could start stably, and the difference of electromagnetic torque's peak value was 148 Nm between the open-loop system and the close-loop control system. In addition, the electric power consumption of the motor in the close-loop control system was less than that in the open-loop system; especially at the motor's starting stage, the motor peak power of the open-loop system was 2.5 times that of the close-loop control system. In brief, under the designed close-loop control, the motor could save about 50% energy during the starting stage and about 30% during the stable running stage.

Algorithm for Origin-Destination Matrix Estimation of Mutil-mode Network Bus Route

ZHANG Yi

2013, 26(3): 520-524. doi: 10.3969/j.issn.0258-2724.2013.03.020

[Abstract](1135)

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In order to analyze the impact of urban rail transit on the travel mode choice of conventional bus passengers, an algorithm for origin-destination matrix estimation of conventional bus passenger flow under the impact of urban rail transit was developed in MATLAB by using Dijkstra's algorithm to calculate the path with shortest travel time, where the minimum travel time was taken as the objective in travel mode choice. Compared with the traditional gravity model, this method can avoid the complicated process of estimating the impedance coefficient. The result of a case study show that in order to choose urban rail transit, the passenger flow at 43.7% of bus stations have increased to 2.73 times that before the advent of urban rail transit, and 56.3% of original bus passengers choose the urban rail transit system to substitute bus.

Causal Mechanism of Difference between Experienced and Novice Drivers in Hazard Perception Based on Fuzzy Signal Detection Theory

TANG Zhihui, CHENG Jie, FANG Zhengnan

2013, 26(3): 532-538. doi: 10.3969/j.issn.0258-2724.2013.03.022

[Abstract](1189)

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Abstract:
In order to reduce the rate of accidents of novice drivers, a hazard perception and rating test was designed using a driving simulator by the fuzzy signal detection theory. Through the test, causes of difference between experienced and novice drivers in hazard perception performance were analyzed. The results show that the difference between the experienced and novice drivers in hazard perception results from the difference of response bias, such that more liberal responses are associated with faster latencies and more conservative responses lead to slower latencies. The correlation coefficient between response bias and latency is 0.81 for the trained novice drivers, 0.63 for the untrained novice drivers, and 0.75 for the experienced drivers. Therefore, it is recommended to reduce the hazard threshold of the novice driver through training.

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2013 Vol. 26, No. 3