西南交通大学学报

Calculation Method for Heavy-Haul Train Rushing Across Slope and Its Application

WANG Kaiyun, HUANG Chao

2015, 28(5): 771-775,795. doi: 10.3969/j.issn.0258-2724.2015.05.001

[Abstract](1073)

Abstract:
In order to investigate the uphill performance of heavy-haul trains, a multi-particle train model is built by the theory of train longitudinal dynamics, taking the plane and vertical sections of railway line into account. According to the principle that the train speed at the top of a slope should not be less than the calculation speed of locomotives, a calculation method of minimum speed is proposed for a heavy-haul train rushing across the slope. Then, taking a dedicated coal transportation line as an example, the method is applied to the problem of train rushing across a slope caused by the increase of train length in marshalling plan. The results show that the minimum speed of train rushing across the slope is 72.80 km/h. The running speed on the top of the slope and the calculated speed of the locomotive are 51.62 km/h and 51.50 km/h, respectively; and the difference between them is only 0.23%. This reflects the high precision of the proposed method.

Identifying Abnormal Noise of Vehicle Suspension Shock Absorber Based on Deep Belief Networks

HUANG Haibo, LI Renxian, YANG Qi, DING Weiping, YANG Mingliang

2015, 28(5): 776-782. doi: 10.3969/j.issn.0258-2724.2015.05.002

[Abstract](862)

Abstract:
Considering the complexity and non-expandability of extracting abnormal noise features of shock absorbers by experience and manual work, applications of deep belief networks (DBNs) to identification of vehicle suspension shock absorber's abnormal noise are discussed, and a complete identification process of shock absorber abnormal noise is proposed by combining the shock absorber's road test with its rig test. The method only needs to take the vibration acceleration signal of the shock absorber piston rod as input, and then process the signal by learning layer-wise features in the DBNs model to classify the sounds of shock absorbers. In addition, the identification accuracy by DBNs is compared with that by the classical BP neural network, support vector machine, and other three traditional abnormal noise identification methods. The results show that when only the original signal is used as input, the classification accuracy by DBNs is 96.7%, which is higher than that by the other five methods. This illustrates the superiority of the DBNs algorithm in identifying the abnormal noise of shock absorbers and may imply a wide prospect in engineering application.

Factors Influencing Subgrade Post-Construction Settlement of CFG Pile Composite Foundation in Wuhan-Guangzhou High-Speed Railway

ZHANG Feng, LIU Ying, XU Zhaoyi, LI Zhiyi

2015, 28(5): 783-788. doi: 10.3969/j.issn.0258-2724.2015.05.003

[Abstract](902)

Abstract:
In order to study the post-construction settlement of CFG(cement flyash gravel)pile composite foundation of high speed railway in soft soilI areas, finite element numerical simulations were made using ABAQUS software for several factors that influence the post-construction settlement of the CFG pile composite foundation in Wuhan-Guangzhou high-speed railway. On this basis, the influence degree and variation of each factor on the settlement was discussed to determine the main control factors of the settlement. The result shows that an increase in the elastic modulus or pile diameter will result in an increase in the stress ratio of pile to soil, and increasing the cushion thickness will decrease the stress ratio of pile to soil. When a combination of reinforced concrete pipe piles and CFG piles is used, the maximum settlement on the pile top is 2.01 mm, and uneven settlement is decreased by 46.5% compared with that using reinforced concrete pipe piles only.

Effect of Guide Vane beside Maintenance Rail on Vortex-Induced Vibration of Streamlined Box Girder

LIU Jun, LIAO Haili, WAN Jiawei, MA Cunming

2015, 28(5): 789-795. doi: 10.3969/j.issn.0258-2724.2015.05.004

[Abstract](909)

Abstract:
In order to study the vortex-induced vibration performance of streamlined box girders and seek effective mitigation measures, a long-span cable-stayed bridge with steel-box girder was taken as an example to investigate the vortex-induced vibration of the main girder through section model wind tunnel tests at a scale of 1:50. The two-dimensional flow field around the cross section of the main girder was modeled by computational fluid dynamic numerical simulation. The results show that alternate vortexes formation and shedding are repeated periodically behind the maintenance rails, which means that the rails have a significant impact on the vortex-induced vibration. The root mean square value of lift coefficient has a 24% reduction when the guide vanes move from the outside to the inside of the maintenance rails, implying that the vortex-induced vibration can be effectively mitigated by setting guide vans inside the maintenance rail.

Pressure Control System for Rail Grinding Based on Chamber Adjustment

NIE Meng, LI Jianyong, SHEN Haikuo

2015, 28(5): 796-802. doi: 10.3969/j.issn.0258-2724.2015.05.005

[Abstract](776)

Abstract:
To reduce the pressure fluctuation during rail grinding operation, a new rail grinding pressure control system was proposed by adding a chamber adjuster into the traditional pneumatic constant pressure control system. The chamber adjuster consisted of a gas holder and a proportional flow valve. It could absorb the shock pressure exerting on the system to reduce the pressure fluctuation and supplement energy for the system when delivery pressure was needed to accelerate system response. To ensure the accuracy and stability of the rail grinding pressure control, the rail grinding pressure system with chamber adjuster adopted a double closed-loop control system based on variable structure control, and the controller was designed according to the control characteristic of each closed loop. In addition, the characteristics of the proposed control system were verified by numerical simulation and grinding experiments, and compared with those of the traditional rail grinding pressure control system. The results show that the chamber adjustment control system could reduce 76.8% of the pressure fluctuation in the traditional pressure control system.

Web Geographic Information Services-Based Acquisition Method of Digital Terrain Data for Highway Location

NIE Liangtao, YI Sirong, LI Yang

2015, 28(5): 803-810. doi: 10.3969/j.issn.0258-2724.2015.05.006

[Abstract](921)

Abstract:
In the initial stage of a highway planning, obsolete topographic maps and the difficulty and high economic costs in acquiring digital terrain data always present challenges for digital location design. To address these challenges, a method based on comprehensive analysis of current geographic information resources available in the open network was proposed. It makes use of the shuttle radar topography mission (SRTM) data and Google Maps images to acquire the digital elevation model (DEM) and digital orthophoto map (DOM) for modeling in the virtual geographical environment (VGE) of highway digital location system. Then, a method for quick download of Google Maps image tiles was developed; a globally nonlinear and locally linear compression algorithm for the transformation of Google Maps images based on the divide-conquer method was proposed to realize quick match with SRTM data. Finally, terrain data acquisition and modeling test were conducted to verify the proposed method. The results show that stable, quick, and automatic download of image tiles can be achieved by automatically calculating tile URL address, using libcurl library functions and multithread downloading technology. The resolution of the acquired DOM is greater than 0.2 m. After data match with DEM, the constructed VGE meets the requirements of highway digital location design in the initial planning stage.

3D Discrete Element Analysis of Selection of Sleeper Types on High-Speed Railway Bridge

XIAO Hong, GAO Liang, HOU Bowen

2015, 28(5): 811-816. doi: 10.3969/j.issn.0258-2724.2015.05.007

[Abstract](943)

Abstract:
In order to select a reasonable sleeper type used for a high-speed railway bridge, based on a comprehensive investigation of sleeper types, sleeper-ballast bed models for type Ⅲ sleeper, broad sleeper, ladder sleeper and frame sleeper were established using the discrete element software PFC 3D, and numerical analyses of ballast track structures for high-speed railway bridges were carried out. The research result shows that the four sleeper types have a large track frame rigidity and a long-time ability to sustain track geometry and stability. Contact forces between broad sleeper as well as frame sleeper and ballast bed are relatively small and distribute more evenly, and compared with type Ⅲ sleeper, broad sleeper and frame sleepe are more suitable for ballast track structures on high-speed railway bridges. However, the advantages of frame sleeper are not so obvious and its corresponding maintenance equipment has not been developed, so broad sleeper should be adopted for high-speed railway bridges in China.

Cable-Beam Vibration Correlation of Railway Low-Pylon Cable-Stayed Bridge Subjected to Train Load

LI Xiaozhen, LIU Zhenjie, XIN Lifeng, LIU Dejun

2015, 28(5): 817-822,844. doi: 10.3969/j.issn.0258-2724.2015.05.008

[Abstract](769)

Abstract:
In order to investigate the vibration correlation of a low-pylon cable-stayed bridge and its cable components under different running speeds, the interaction between the whole structure and its cables was considered by taking a railway low-pylon cable-stayed bridge with a main span of 115 m+95 m as an engineering background, and the vibration responses of beams and towers and the local vibration responses of cables were obtained with the method of numerical integration based on the train-track-bridge coupling vibration theory. The research result indicates that the cable-beam vibration correlation under a train load is essentially an energy transfer process. The vibration energy transfers easily in the condition that the frequency of displacement excitation at cable end is close to the nature frequency of cables. When a train is passing through a bridge at a design speed of 225 to 350 km/h and the excitation frequency is close to the nature frequency of cables, the resonance of cables will occur under external excitation, but the resonant amplitudes are not great, local vibration amplitudes of cables being less than 3 mm.

Practical Formulas to Calculate Suspender Tension Based on Frequency

ZHANG Rongling, YANG Zijiang, ZHU Xuehui, LIANG Qingfu, XU Ruipeng

2015, 28(5): 823-829. doi: 10.3969/j.issn.0258-2724.2015.05.009

[Abstract](1642)

Abstract:
In order to analyze the influence of frequency on suspender tension, a partial differential equation of motion is established for the suspender according to its vibration mechanical properties and dynamic equilibrium. Then, a computational formula for the frequency and suspender force is built taking into account the influence of flexural rigidity, rotational inertia, shear deformation, and the coupling of rotational inertia and shear deformation. Comparing frequencies of different orders and fitting frequency difference for various lengths of suspenders leads to the finding that the fundamental frequency worked out using high-order differential frequency will contain a positive error and thus causes a positive deviation in the cable force. On this basis, the modified value for the first-order frequency is then obtained and practical formulas for calculating the cable force are proposed. In a case study, the proposed formulas are compared with the string vibration formula and the formula that takes the bending stiffness into consideration. The result show that using the practical formulas, the error between the calculated suspender tension and the measured value is no more than 5%, which validates the practical formulas.

Fabrication Error Propagation Properties of Key Components of Large-Span Cable-Stayed Bridges with Steel Box Girder

ZHANG Qinghua, HUANG Can, BU Yizhi, LI Qiao

2015, 28(5): 830-837. doi: 10.3969/j.issn.0258-2724.2015.05.010

[Abstract](902)

Abstract:
To clarify the fabrication errors' propagating properties in the construction control of a large-span cable-stayed bridge, the effect characteristics of the manufacture errors of key components during the whole construction procedure were investigated. An error propagation equation was developed based on geometrically nonlinear equilibrium equations. By taking Sutong bridge, a typical large-span cable-stayed, as research object, an in-depth discussion concerning the forming process, effect characteristics and propagation properties of manufacturing errors was carried out. The research results show that the theoretical method established is feasible and appropriate to analyze and expound the error effects accompanying whole-procedure construction control. There are significant differences among the fabrication error propagation properties of different types of components. With the increase of cantilever length, the error effect of the angle fabrication error between main girder segments is convergent, while the error effect of the length fabrication error is not, so scientific error control schemes are necessary for better control effect.

Seismic Responses of Lengzhuguan Slope During Kangding Ms5.8 Earthquake

WANG Yunsheng, HE Jianxian, LUO Yonghong, HE Zihao, LIU Yong, ZHANG Lei

2015, 28(5): 838-844. doi: 10.3969/j.issn.0258-2724.2015.05.011

[Abstract](904)

Abstract:
In order to reveal the characteristics of the peak acceleration at different depths of a slope and seismic landslide formation mechanism, a strong earthquake monitoring array was set up in both sides of the Lengzhuguan slope. Five strong vibrograph at different depths but the same altitude were triggered by Kangding Ms 5.8 earthquake occurred on December 25th, 2014. The data reveals that the horizontal peak acceleration at each monitoring site decreases with the increase of depth. It decreases greatly within the surface range of 0 to 45 m and at the inner slope falls at a slow rate. At the monitoring site (99 m from the hole) the horizontal peak acceleration is about 0.6 times the one at the hole. The acceleration response spectrum shows that the amplitudes at monitoring sites decay with the increase of the depth, and the dynamic magnification factor of standard spectra is less than 3.5. Fourier spectrum shows that the amplitudes also decrease gradually from the outside hole to the inside slope, and near the hole, the components of the spectrum become complex.

Seismic Fragility of Irregular Continuous Rigid Frame Bridge

DONG Jun, SHAN Deshan, ZHANG Erhua, MA Teng

2015, 28(5): 845-851,878. doi: 10.3969/j.issn.0258-2724.2015.05.012

[Abstract](861)

Abstract:
To investigate the seismic performances of irregular bridges, a seismic vulnerability model for a typical irregular highway bridge was created. By considering the uncertainties of an earthquake and bridge parameters, a model sample database was generated by adopting the sampling method to carry out the seismic vulnerability analysis of a bridge. To obtain the structural dynamic responses, a nonlinear time-history analysis was carried out for the sample database by using the software OpenSees. On the basis of the research on the distribution characteristics of time-history curves of inflection point and the curvature envelope of each pier, pier and bearing damage indexes were determined. The fragility curves of dangerous bridge members were generated by using the probabilistic seismic demand analysis approach, and the first-order reliability theory was employed to generate the fragility curve of a bridge system. The research results show that bearings are easy to damage to an irregular bridge subject to an earthquake action. Compared with its members, an irregular bridge system has a high failure probability. The fragility curves obtained can be used to evaluate the seismic performances of an irregular bridge and provide an evidence for post-earthquake damage identification.

Probabilistic Seismic Capacity Model for High Pier of CFST Composite Column

HUANG Zhitang, QIANG Shizhong, CUI Shengai

2015, 28(5): 852-857. doi: 10.3969/j.issn.0258-2724.2015.05.013

[Abstract](776)

Abstract:
In order to assess the seismic performances of high pier of concrete-filled steel tube (CFST) composite column, curvature was chosen as the performance indicator. The whole eccentric compression process for section samples of CFST composite column was simulated by the Latin hypercube sampling (LHS) and the numerical analysis method. Based on damage patterns, 4 limit states of slight damage, moderate damage, severe damage and complete damage were defined and quantified. Cubic polynomial regression analyses for statistical characteristic values of curvature indicator as a function of axial force were carried out, and a probabilistic seismic capacity model for high pier of CFST composite column with axial force as the variable was built. The results show that the damage characteristics of reinforced concrete (RC) and CFST are shown by the dividing line of outer confined concrete damage. Curvature indicators of the4 damage limit states under different axial forces obey lognormal distributions, and their mean values decrease with the increase of axial force.

Analysis of Damping Effect in Two-Stage Energy Dissipation Damping System of Buckling Restrained Braces

PAN Yi, GENG Pengfei, GUO Yangzhao, YI Luxing

2015, 28(5): 858-865. doi: 10.3969/j.issn.0258-2724.2015.05.014

[Abstract](869)

Abstract:
To solve the problems of the great seismic force and poor anti-seismic performance of normal energy dissipation system of buckling restrained braces in high seismic regions, it was proposed to design two-stage energy dissipation system of buckling restrained braces. With reference to one engineering example in high earthquake intensity area, the two energy dissipation systems were designed according to the principle that the lateral deformations were equal. Besides, two corresponding numerical models were established by using SAP2000.Then energy dissipation effect of two-stage energy dissipation system of buckling restrained braces was investigated through model analysis, response spectrum analysis and elastic time history analysis under the frequent earthquakes, and elastic-plastic time history analysis under the rare earthquakes. The research results indicate that compared with the normal energy dissipation system of buckling restrained braces, stiffness of two-stage energy dissipation system of buckling restrained braces is reduced, seismic force decreases significantly, and development of plastic hinges is postponed. The force of the buckling restrained braces decreases notably, anti-seismic performance is improved obviously.

Generalized Kelvin Creep Damage Model and Its Parameters' Intelligent Identification

XU Guowen, HE Chuan, DAI Cong, WANG Shimin

2015, 28(5): 866-871. doi: 10.3969/j.issn.0258-2724.2015.05.015

[Abstract](826)

Abstract:
In order to describe the characteristics of rock rheological deformation better, a generalized Kelvin creep damage model considering the deterioration effects in creep process was proposed, and its finite difference scheme was derived. Based on the interface platform of software FLAC3D, the model was developed using C++ language. Furthermore, an intelligent algorithm combining PSO (particle swarm optimization) algorithm, SA (simulated annealing) algorithm and FLAC3D was put forward and adopted to determine the rheological parameters in the model based on the existing experimental data. The research results show that the proposed model can reflect visco-elastic-plastic properties and damage characteristics of rock, and simulate the two-stage creep effect of rock in a low stress condition and three-stage creep effect of rock in a high stress condition. The algorithm can converge to the global optimal solution in some 40 steps as long as inversion parameters are selected appropriately.

Calculation Model for Axial Rigidity of CHS Y-Type Joints

ZHAO Bida, LIU Chengqing, ZHANG Shengye, ZHANG Jiansheng

2015, 28(5): 872-878. doi: 10.3969/j.issn.0258-2724.2015.05.016

[Abstract](993)

Abstract:
In order to establish a practical parameterization calculation formula for the axial rigidity of a circular hollow section (CHS) Y-type joint, a semicircular arch model for Y-type joint rigidity was developed based on the round-direction model and the relationship between local deformation of a joint and its axial rigidity, and a theoretical formula for the axial rigidity was established. With the help of the Taylor series, the complex theoretical formula was simplified to the product of an exponential function and a power function embodying the interaction effect between independent variables. In addition, the secondary influence factor, brace-to-chord thickness ratio, was omitted in the light of the single-parameter analysis result from finite element analyses (FEA). As a result, a practical formula for the axial rigidity of a Y-type joint was obtained through a multiple nonlinear regression analysis. The results show that the axial rigidity is directly proportional to elastic modulus of steel, reciprocal of sine-square of the angle between branch and chord in plane and chord diameter, brace-to-chord diameter ratio and chord diameter-to-thickness ratio have significant effects on the axial rigidity, and relative errors between axial rigidity values obtained by the practical formula and the FEA and existing test results are basically less than 8%.

Experimental Investigation of Bracket sets of 1st Eave of Taihe Palace in the Forbidden City under Vertical Loads

ZHOU Qian, YAN Weiming, MU Chenxi, YANG Hui

2015, 28(5): 879-885. doi: 10.3969/j.issn.0258-2724.2015.05.017

[Abstract](691)

Abstract:
To effectively protect Chinese ancient timber buildings, bracket sets (tou-kung) of 1st eave of Taihe Palace in the Forbidden City were taken as an example to investigate the bearing performances of Chinese ancient liujin type of bracket sets under vertical loads. Based on constitution characteristics of intermediate set, column set and corner set, models with a geometrical scaled ratio of 1 to 2 were built, and experiments under vertical loading were carried out. By the experiments, damage modes, internal forces and deformation of the bracket sets were discussed. In addition, a calculation model for vertical stiffness of the bracket sets was deduced. The experimental results show that under vertical loads, the top 2-layer parts of the bracket sets are easy to damage. Compared with the underparts, the upper parts of the bracket sets bear more loads. In three types of the bracket sets, i.e., column set, corner set and intermediate set, column set and intermediate set have respectively the largest and smallest ultimate bearing capacities; intermediate set has the greatest deformation and residual deformation, and corner set comes second; compared with column set, intermediate set has a great ductility performance, while the ductility performance of corner set is small. The internal force of back part of the balance arm is small. Under vertical loads, the calculation model for vertical stiffness of the bracket sets can be simplified as a 3-line model.

Frequency-Domain Reliability Analysis of Tuned Mass Damper System by First-Passage Theory

TAN Ping, LIU Liangkun, LI Xiangxiu, ZHANG Ying, ZHOU Fulin

2015, 28(5): 886-890,941. doi: 10.3969/j.issn.0258-2724.2015.05.018

[Abstract](830)

Abstract:
In order to investigate the frequency-domain characteristic of reliability and the damping performance of a tuned mass damper (TMD) system, the probability distribution formula about the spectral moment of cut-off frequency of a structure under random excitations is derived based on the first-passage failure criterion, and the frequency-domain probability density is solved using the forward difference scheme. Then, the frequency-domain probability information of the TMD system is also analyzed by the above method. The results show that the frequency-domain probability density is negative, and the frequency-domain probability tends to the value calculated by the first-passage failure criterion as the frequency band increases. For a structure without control, the percentage of the reliability reduction at the first two mode frequencies are 59.23% and 35.45%, respectively, while counterparts of the TMD system are 34.54% and 55.92%. The frequency-domain reliability analysis reveals that the TMD system has a reliable damping effect, mainly by controlling the first mode vibration of the structure.

Route Decision Model under the Environment of Multi-source Information

LIU Lan, LUO Chen, YIN Junsong, MA Yafeng

2015, 28(5): 891-897. doi: 10.3969/j.issn.0258-2724.2015.05.019

[Abstract](795)

Abstract:
Aimed at the route choice process integrated with the subjective perception and objective analysis that cannot be quantified, the intuitionistic fuzzy set theory is applied to quantify the selection results of route decision, in which the subjective and objective intuitionistic fuzzy numbers are constructed by the establishment of the dual membership function, and decision-making functions are set up with the membership degree and hesitating membership degree of intuitionistic fuzzy numbers. Drawing lessons from evidence conflicting ideas of evidence theory, a function projection method is proposed to solve the distribution problem of hesitating degree function. Then, a logarithmic growth model is applied to determine dynamic weights and quantify temporal characteristics of multi-source information, and a route decision model is established to analyze the driving decision-making behavior. Finally, an example derived from traffic practices demonstrates that the approximate membership degrees of go and change decision are calculated as 0.767 and 0.233, respectively, with the decision-making functions under a multivariate information environment including experiences, traffic management and control, roads, and congestion.

Trailer Scheduling Optimization and Simulation Based on Petri Net

CAI Wenxue, ZHONG Guanheng, HU Qinghao, ZHONG Huiling

2015, 28(5): 898-904. doi: 10.3969/j.issn.0258-2724.2015.05.020

[Abstract](853)

Abstract:
To solve the problem with excessive trailers obstructing major traffic paths outside container terminals, a hybrid Petri net (HPN) model with optimal scheduling strategy is created by optimizing trailer arrivals using non-stationary Poisson distribution to simulate arrival pattern. It can be applied to trailer arrivals and operation process of inland container terminals in the Pearl River Delta. Based on the HPN model, an Arena simulation model of Sanshui Port is constructed, where data is collected and analyzed through a process analyzer (PAN) to calculate the number of trailers per arrival and hence evaluate the effectiveness of scheduling strategy. Simulation results show that the obstruction can be effectively alleviated by optimizing the scheduling strategy, while the waiting time of trailers and the quantity of awaiting trailers are reduced by up to 87% and 26% separately after optimization.

A Secure Electronic Voting Scheme Based on Linkable Ring Signature against Fraud from the Third Party

ZHANG Wenfang, XIONG Dan, WANG Xiaomin

2015, 28(5): 905-911,941. doi: 10.3969/j.issn.0258-2724.2015.05.021

[Abstract](679)

Abstract:
In order to solve the puzzles existing in electronic voting, such as vote collision, the third party deceiving voters, relying anonymous communication channel to send votes and vote inefficiency, a secure and efficient electronic voting scheme was designed. The scheme, based on the principle of electronic voting, uses linkable ring signature to register anonymously, applies blind signature to blind ballot, and introduces sequence identity code to ensure the uniqueness of the votes. The proposed scheme not only meets the basic security requirements for electronic voting protocol,but also has the function of the anti vote collision, allowing voters to abstain at any stage, not depending on any trusted third party and anonymous communication channel, while at the same time it possesses high efficiency. The comparisons show that the voting time complexity of proposed scheme is only 961 mode multiplication and independent of the size of the voters, which is at least increased by 42.9% in contrast to the existing schemes under the same security, and suitable for large group election.

Performance Research on Full-Duplex Relay Selection Scheme

ZHONG Fujian, ZHAO Yongchi

2015, 28(5): 912-916. doi: 10.3969/j.issn.0258-2724.2015.05.022

[Abstract](747)

Abstract:
To improve spectral efficiency of the cooperative communication system, the communication system with full-duplex relay was investigated. First, the conventional proactive opportunistic relaying and the optimal full-duplex relay selection were introduced. Then, an incremental full-duplex relay scheme was proposed based on the optimal full-duplex relay selection. Next, the outage performance of the proactive opportunistic relaying used in the full-duplex relay network was analyzed, and the accurate closed form expressions of the outage probabilities of these three schemes were derived. Furthermore, the approximations of the outage probabilities in the high signal-to-noise ratio (SNR) regime were obtained. At last, the theoretical results of the proposed scheme were verified by numerical simulations. The simulation results show that the outage performance of the proactive opportunistic relaying and the optimal full-duplex relay selection tends to platform effect in high SNR, and the outage performance of incremental full-duplex relay scheme is improved with the increasing SNR. Meanwhile, the outage performance of incremental full-duplex relay scheme is the best, the outage performance of the proactive opportunistic relaying is the worst.

Model-Based Test Case Automatic Generation of CTCS-3 Train Control System

LÜ, Jidong, ZHU Xiaolin, LI Kaicheng, TANG Tao, WANG Haifeng

2015, 28(5): 917-927. doi: 10.3969/j.issn.0258-2724.2015.05.023

[Abstract](815)

Abstract:
In order to improve the test case generation efficiency of the CTCS-3 train control system, a test case automatic generation method is proposed based on formal models of hybrid communication sequential process (HCSP) and timed automata. Then, timing models for operation scenarios in the train control system are built to verify its real-time function. Based on the timing models, test case automatic generation algorithms are designed for three domain independent coverage criteria, including all location, all edge and definition-use pair in the train control system. Taking the typical radio block center (RBC) handover scenario as an example, 100% function coverage test suites with all-location, all-edge and definition-use pair test coverage criteria are automatically derived. In addition, the efficiency of the test case generation method is analyzed from the aspects of test suite number, time consumption, and memory cost. The results show that among the three 100% function coverage test suites, the user-defined pair test criterion consumes a minimum time of 0.2 s and a minimum memory of 9.4 blocks, and the proposed method can enhance the test case generation efficiency by a maximum of 30% in the train control system.

Two-Stage Optimal Schedule Model for Active Distribution Network

ZHUANG Huimin, XIAO Jian

2015, 28(5): 928-934. doi: 10.3969/j.issn.0258-2724.2015.05.024

[Abstract](761)

Abstract:
In order to alleviate the impact of forecast errors of renewable energy sources and loads on the active distribution scheduler and to solve the over-voltage problem caused by distributed generation (DG), a two-stage optimal schedule model was presented by integrating a day-ahead economic scheduler with an intra-day rolling dispatch. First, the day-ahead optimization model was made with the minimum operation cost as the objective. Then taking the minimum dispatch cost and network loss as the objective, the intra-day scheduler was made by applying the DG active power curtailment and reactive power as the slack variables. Finally, the two-stage optimal schedule model was verified using the IEEE34-node distribution networks. The numerical results show that the proposed approach can reduce the distribution network operation cost and network loss by 3.27% and 0.22%, respectively, and can adjust the bus voltages out of limits to their normal ranges.

Analysis of Aeroacoustics Characteristics for Pantograph of High-Speed Trains

DU Jian, LIANG Jianying, TIAN Aiqin

2015, 28(5): 935-941. doi: 10.3969/j.issn.0258-2724.2015.05.025

[Abstract](839)

Abstract:
In order to study aerodynamic noise source distribution and frequency spectrum for the pantograph of high-speed trains, the flow field for the pantograph of high-speed trains was calculated using the computational fluid dynamics method, and the fluctuating pressure on the surface of the pantograph was obtained. On this basis, the far-field aerodynamic noise for the pantograph was computed using the FW-H equation. Computational results show that the aerodynamic noise for the pantograph of high-speed trains has obvious directivity, which is not affected by the train speed, and the total sound pressure level of the far-field measurement points reaches the maximum near the 10~20. Moreover, the total sound pressure level increases significantly with the train speed. The far-field aerodynamic noise has obvious main frequency that increases with the train speed. The beam at the top of the pantograph is a main contributor to the aerodynamic noise for the pantograph.

PHM and Active Maintenance for High-Speed Railway Traction Power Supply System

WANG Qi, HE Zhengyou, LIN Sheng, FENG Ding, LI Zhaoyang

2015, 28(5): 942-952. doi: 10.3969/j.issn.0258-2724.2015.05.026

[Abstract](1320)

Abstract:
As China's high-speed railways enter into a comprehensive operation and maintenance period, many problems are exposed such as binary judgment of system and equipment states, fault diagnosis after fault occurrence and passive maintenance. To deal with these problems, the prognostics and health management (PHM) and active maintenance in the traction power supply system of high-speed railway were introduced. The characteristics of traction power supply system such as multiple temporal and spatial scales, dynamics and stochastics were taken into account. By applying multi-scale transform, temporal and spatial joint analysis and stochastic process, the goals of fault prognostics, health status assessment, reliability and risk analysis, and maintenance decision and optimization were achieved. The results indicate that the theoretical application of PHM and active maintenance can process massive data in traction power supply system, show the health status of systems and equipment comprehensively, predict and forecast failures, and make the optimum maintenance decisions. The PHM and active maintenance can realize prompt response when the traction power supply system operates in an unhealthy state. It can restore the health operation by sensing, assessing, predicting, diagnosing and decision making of the health monitoring and intelligent maintenance system.

Modeling and Dynamic Analysis of Thermal Management System for Fuel Cell Locomotive

GUO Ai, CHEN Weirong, LIU Zhixiang, LI Qi

2015, 28(5): 953-960. doi: 10.3969/j.issn.0258-2724.2015.05.027

[Abstract](926)

Abstract:
To improve the efficiency and dynamic performance of fuel cell locomotives, a control-oriented thermal management model with a fan in the radiator and a coolant circulation pump was built by the law of mass conservation, the first law of thermodynamics, and the affinity law. Based on this model, the influences of the control parameters including the bypass ratio, the coolant circulation pump voltage, and the radiator fan voltage on the stack temperature, temperature difference, and system efficiency were studied. The results showed that, the bypass valve would influence the stack temperature and its temperature difference partially, and change the response time of the thermal system, but almost has no effect on the system efficiency; the circulation pump was able to adjust the temperature difference between the inlet and outlet of the stack to make it to be a proper value; with the same temperature difference, the system efficiency will be higher with lower circulation pump voltage; the radiator fan could not only adjust the stack temperature and the response time of thermal system, but also influence the temperature difference and system efficiency.

Permeability Characteristics of High-Order Harmonics of Traction Network for Three-Phase Power System

ZHAO Yuanzhe, LI Qunzhan, ZHOU Fulin, ZHU Peng

2015, 28(5): 961-969. doi: 10.3969/j.issn.0258-2724.2015.05.028

[Abstract](2312)

Abstract:
In order to study the influences of the high order harmonics of traction network on three-phase power system, the harmonic model of impedance-matching balanced transformer was established to analyze the permeability characteristics of high-order harmonics for public grid high-voltage three-phase system, and the harmonic model of the inverse Scott transformer was established to analyze the permeability characteristics of high-order harmonics for the low-voltage three-phase system of traction substation. The traction substation with severe harmonic distortion was measured, and the harmonic measured data were analyzed and compared with those resulted from harmonic models of impedance-matching balanced transformer and inverse Scott transformer. A filtering scheme based on Y-type wave-trap high-pass filter was proposed which is applied to the low-voltage three-phase system of traction substation, and a set of filtering devices was developed. The results show that the high-order harmonics less penetrate into the high-voltage three-phase system, but significantly into the low voltage three-phase system of traction substation. After filtering, the harmonic distortion rate of a-phase voltage at traction substation is reduced from 12.25% to 1.94%, and the harmonic distortion rates of b-phase and c-phase are also significantly reduced. This indicates that the developed device can filter the high-order harmonics and effectively improve the power supply quality of the low-voltage three-phase system.

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2015 Vol. 28, No. 5