西南交通大学学报

Numerical Analysis of Train Impact Load with Finite Element Method

YAN Qixiang, LI Bin, ZHANG Meng, HE Chuan, YANG Wenbo, GENG Ping

2016, 29(1): 1-7. doi: 10.3969/j.issn.0258-2724.2016.01.001

[Abstract](1343)

Abstract:
In order to obtain the train impact load on shield tunnel to investigate the dynamic responses of shield tunnel segment under train impact load, a 3D numerical analysis model for train formation was established to obtain the time-history curves of train impact force at different impact velocities, train formations and oblique impact angles. The maximum train impact force and impact duration as functions of impact velocity and impact angle were researched. Based on the representative time-history curves, the dynamic responses of shield tunnel with different thickness double lining caused by train impact load were investigated. The research result shows that when train formation is certain, the maximum train impact force increases with the increases of impact velocity and impact angle; when impact angle is larger than 7.5, impact duration extends with the increase of impact velocity. From different times at which the maximum train impact force appears, the time-history curves of train impact force can be divided into two kinds of characteristic curve, and the first kind of characteristic curve with the maximum impact force appearing at the impact moment is in accordance with the Gauss multiple peak fitting formula, and 10 parameters can be used to achieve its approximate fitting. To increase secondary lining thickness can effectively reduce the dynamic responses of external segment lining under train impact load such as stress, velocity and acceleration as well as tension and compression damage zones.

Detection of Ballastless Track Diseases in High-Speed Railway Based on Ground Penetrating Radar

LIAO Hongjian, ZHU Qingnü, ZAN Yuewen, XIE Yongyong, SUN Junyu

2016, 29(1): 8-13. doi: 10.3969/j.issn.0258-2724.2016.01.002

[Abstract](1412)

Abstract:
A two-dimensional forward simulation was conducted to analyze slab ballastless track diseases in high-speed railway using the ground penetrating radar (GPR) technique. Based on the finite difference method, a two-dimensional forward simulation equation for GPR was deduced. By considering the different filling degrees and hardening progress of CA mortar layer, GPR geoelectric models for CRTSⅡ slab ballastless track were established and forward simulated, and the GPR picture features of the forward simulation were analyzed. The simulation results show that the forward simulation can clearly identify the interfaces between different dieletric layers and the number and location of reinforcement in slab ballastless track.

A Novel Method for Calculating Stress and Deformation of Supporting Pile Considering Pile-Soil Interaction

LI Tao, JIANG Yonghua, ZHU Lianhua, GUAN Chenlong

2016, 29(1): 14-21. doi: 10.3969/j.issn.0258-2724.2016.01.003

[Abstract](1061)

Abstract:
To study the pile-soil interaction on the internal force and deformation, a novel calculation method for calculating stress and deformation of supporting pile considering pile-soil interaction was proposed. This method treats the pile body above the excavation surface as a finite number of elastomers, the section below the excavation surface as Winker elastic foundation beam, and support structure as two-force elastic rod. The deformation compatibility between supporting pile and inner supporting system is also considered. Based on segmentation coordinate system and elastic beam-on-foundation system, the differential equation of pile deflection considering soil-pile-internal bracing interaction was proposed. By using this method and theoretical values of soil pressure, the lateral displacement and bending moment of supporting pile at different excavation depths were obtained and compared with the standard values and measured values. The results show that the calculated maximum lateral displacement of the supporting pile is 15.2% smaller than that of the standard method, and the calculated maximum bending moment is 26.2% smaller than that of the standard method, both of which are more close to the measured values.

Assessment of Rockfall Impact Force by Particle Flow Code Numerical Simulation Based on Discrete Element Model

WANG Yusuo, LI Junjie, LI Zhenghui, FENG Gaofei, WU Hao, HE Junnan

2016, 29(1): 22-29. doi: 10.3969/j.issn.0258-2724.2016.01.004

[Abstract](972)

Abstract:
To make a reasonable and effective assessment of rockfall impact force, a study on the impact force of falling down rockfall to a structure was carried out by using the method of PFC(particle flow code) based on the theory of DEM(discrete element model). The effects of rockfall height and gravity,and backfill soil thickness on the impact force were analyzed. The results of PFC numerical simulation were compared with those reached by other kinds of calculation methods. The results show that there is an obvious linear relationship between the impact force and the rockfall height or gravity. The linear variation range of the impact force with the changing of the rockfall height relates to the rockfall gravity, while the linear variation range of the impact force with the changing of the rockfall gravity relates to the backfill soil thickness. The impact force reduces by 50%-60% when the backfill soil thickness is 0.6 meter compared with no backfill soil. it tends to be stable when the backfill soil thickness is more than 2 meters, showing that there is a reasonable range of the backfill soil thickness. The total load of structure will increase if the backfill soil thickness exceeds the range. The method of PFC numerical simulation can simulate the effect of air acting on rockfall by setting damping coefficient, which makes the assessment of bigger size rockfall impact force more reasonable.

Limit State Design Method of Railway Tunnel Portal Based on Reliability Theory

MENG Guowang, ZHOU Jiamei, GAO Bo

2016, 29(1): 30-35,49. doi: 10.3969/j.issn.0258-2724.2016.01.005

[Abstract](960)

Abstract:
From the characteristics that limit state functions for the stability of a railway tunnel portal structure are nonlinear and the parameters are random, a new design method for railway tunnel portal structures was put forward based on the reliability theory. Limit state equations for railway tunnel portal structures were founded by analyzing the limit states of railway tunnel portal. Based on the reliability theory, reliability indices of a single-track railway tunnel portal with a design speed of 140 km/h were calculated as an example, target reliability indices for different limit states were determined from the calculated reliability indices of railway tunnel portal under three design speeds, including 16 kinds of portal forms and 22 kinds of portal categories, and partial resistance coefficients were calculated and optimized based on establishing the design expressions for different limit states. The research results show that major limit states of railway tunnel portal are cracking, crushing, overturning stability, sliding stability and insufficient foundation bearing capacity; the statistical characteristics of basic random variables in the limit state equations are the key whether reliability design of railway tunnel portal is accurate or not, and the determination of the reliability indices is the core issue in the limit state design of railway tunnel portal. The established method can be directly used to the limit state design of railway tunnel portal.

Analysis of Water Pressure in Ballastless Track Crack

CAO Shihao, YANG Rongshan, LIU Xueyi, SU Chengguang, GUO Likang

2016, 29(1): 36-42. doi: 10.3969/j.issn.0258-2724.2016.01.006

[Abstract](1248)

Abstract:
In the areas with sufficient rainfall and poor drainage, water in ballastless track has significant effect on the crack propagation. To analyze the distribution of water pressure and influential factors on water pressure in the ballastless track under high-frequency train load, based on the law of mass conservation and momentum theorem, the analytical expression of water pressure was deduced by using the control volume method. The finite element software ANSYS and CFX were used to analyze the influence of loading frequency, load amplitude, crack length and crack opening on water pressure. The theoretical results show that the maximum water pressure appears at the crack tip under loading, and decreases along the crack. The value of water pressure is proportional to load amplitude, square of loading frequency and inversely proportional to crack opening. At the frequency of 5 Hz and loading amplitude of 10 kN, the hydrodynamic pressure distributions resulted from experiment and theoretical computation are nearly identical, and the corresponding hydrodynamic pressure peaks are 0.177 and 0.161 kPa, respectively.

Test Principle and Test Scheme of Longitudinal Force in Continuous Welded Rail Using Resistance Strain Gauge

WANG Biao, XIE Kaize, XIAO Jieling, WANG Ping

2016, 29(1): 43-49. doi: 10.3969/j.issn.0258-2724.2016.01.007

[Abstract](909)

Abstract:
To test longitudinal force in continuous welded rails (CWRs), based on the bi-directional strain approach, a new test scheme using resistance strain gage was proposed. The test principle was systematically presented,and the errors of different test schemes were compared by taking into account the thermal output of resistance strain gage and uneven temperature distribution on the same rail section. The results show that, firstly, the test error mainly comes from uneven temperature distribution on the rail section. Secondly, when testing the longitudinal or vertical strain in CWRs, the thermal output of resistance strain gage and the influence of the longitudinal and vertical constraints of rail on the thermal output must be considered. In addition, all longitudinal force test schemes with resistance strain gage can not directly separate temperature force from the additional expansion force. Finally, the proposed scheme can offset bending strain caused by loads without additional compensation plate, and when both sides of the rail web have 2 ℃ temperature difference, compared to the two existing test schemes, the measurement error is reduced by 84.0% and 60.3%, respectively.

Dynamic Reliability Calculation of Bridge Based on Quasi-non-integrable-Hamiltonian System Theory

HE Zhongying, WANG Genhui, YE Aijun, XIA Xiushen

2016, 29(1): 50-56. doi: 10.3969/j.issn.0258-2724.2016.01.008

[Abstract](790)

Abstract:
To improve the computation efficiency of bridge dynamic reliability, kinetic energy and potential energy of a railway bridge with nonlinear characteristics were expressed in the modal space, and the generalized momentum, the generalized velocity, the Hamiltonian function and the quasi-Hamiltonian system equation were established based on the quasi-Hamiltonian system theory. A quasi-non-integrable-Hamiltonian equation for a railroad concrete bridge was derived just considering its lateral and torsion displacements, and the backward Kolmogorov (BK) equation governing conditional reliability function and its corresponding quantitative boundary and initial conditions were obtained, and the central finite difference method was introduced to calculate the BK equation. The case research results show that the dynamic reliability of a nonlinear bridge structure and the peak value of probability density decrease as the primary energy increases, while they increase as the limit energy raises; and the contrastive analysis results of railway bridges with different spans are agreed with the actual situations, illustrating that the dynamic reliability calculation of railway bridges based on the quasi-non-integrable-Hamiltonian system theory is feasible.

Special Longitudinal Forces between Continuous Welded Rail and Long-Span Simply Supported Beam Bridge with High Piers and Their Influences

ZHANG Xun, SU Bin, LI Xiaozhen, ZHANG Jianqiang

2016, 29(1): 57-64. doi: 10.3969/j.issn.0258-2724.2016.01.009

[Abstract](905)

Abstract:
In order to investigate the special longitudinal forces between a continuous welded rail and a bridge caused by shrink and creep of the main girder and gradient temperature load of piers, a simply supported beam bridge with a standard span of 64 m was selected as the case study, and an rail-girder-pier-foundation integrated calculation model was established by finite element method (FEM) and bridge-rail interaction theory. On this basis, the influence laws of shrink and creep effects, gradient temperature modes, and pier height on longitudinal forces were probed into in comparison with four common types of longitudinal forces. The results show that the longitudinal force induced by shrink and creep of the main girder is dominated by the longitudinal shortening effect rather than the vertical bending effect. This kind of longitudinal force is higher than the contractility or bending force, and it causes a large horizontal force at abutments. The longitudinal forces caused by gradient temperature in exponential and linear distribution modes account for 20%- 30% and 50%- 100%, respectively, of the case of brake force. In general, the exponential distribution mode of gradient temperature is more reasonable as different parameters result in limited variations in longitudinal forces. Due consideration should be given to the formulation of reasonable and uniform gradient temperature load of piers.

Method for Analysis of Non-stationarity of Fluctuating Winds Based on Revised Local Recurrence Rate

LI Lixiao, XIAO Yiqing, ZHENG Bin, SONG Lili

2016, 29(1): 65-70. doi: 10.3969/j.issn.0258-2724.2016.01.010

[Abstract](797)

Abstract:
In order to overcome the misestimate of the non-stationarity of different signals by the recurrence trend (RT), the mutual information function and false nearest neighbors are employed to determine the time delay and minimum embedding dimension of the recurrence quantification analysis (RQA), respectively. Then a novel index, i.e., the standard deviation of normalized local recurrence rate (SDNLRR), which is based on the RQA, was proposed to quantify the non-stationary degree of the signals. Utilizing the SDNLRR, the non-stationarity of four basic signals (white noise signal, sinusoidal signal, amplitude-modulated signal and linear frequency modulation signal) and two field-observed fluctuating wind speed histories were analyzed and compared with the analysis results of RT. The results show that the proposed SDNLRR could offer a quantitative comparison of the non-stationarity of the above six signals with a 100% accuracy. The new method eliminates the misestimates of the sinusoidal signal and the stationary fluctuating wind speed signal in RT, and hence is more accurate than the RT estimation by 33.33%.

Distribution Regularities of Landslides Induced by Wenchuan Earthquake, Lushan Earthquake and Nepal Earthquake

GUO Chenwen, YAO Lingkan, DUAN Shusu, HUANG Yidan

2016, 29(1): 71-77. doi: 10.3969/j.issn.0258-2724.2016.01.011

[Abstract](870)

Abstract:
In order to study the distribution laws of landslides induced by earthquakes, the distribution regularities of landslides were investigated statistically based on the data of 22 302 landslides induced by the Wenchuan earthquake, 1 608 landslides induced by the Lushan earthquake, and 919 landslides induced by the Nepal earthquake using GIS techniques, and the relationships of the landslides with distance from coseismic fault, lithology, slope position and slope shape were discussed. The research results show that the landslides induced by the three earthquakes were more serious in hard rock zones than in soft rock zones and in complex slope shape zones than in simple slope shape zones. Moreover, the distributions of these landslides shown a hanging wall and footwall effect. The distributions of the landslides shown a fault effect in ordinary circumstances, otherwise, thefault effect did not exist in intensity anomaly. The landslides had a characteristic, i.e., they were more serious in high slope position only when seismic intensity was not less than intensity Ⅸ.

Management Algorithm of Point-Cloud Data Based on Octree Concerned with Adaptive Levels of Detail

ZHANG Junfeng, XU Dehe, WANG Xiaodong

2016, 29(1): 78-84. doi: 10.3969/j.issn.0258-2724.2016.01.012

[Abstract](844)

Abstract:
Large-scale point-cloud data are not easy to organize effectively and have great redundancy at dynamic visualization, and it is hard to realize the adaptive display. Aiming at these problems, a new algorithm concerned with the levels of detail (LOD) of point-cloud expression on the basis of octree structure was proposed. The algorithm assigned every scanning point into an octree node, and integrated top-down division with down-top calculation as the pretreatment strategy to reduce the amount of real-time calculation. Then it made any region meet the accuracy requirement and display speed automatically by building conservative simulation-error evaluation criteria. Furthermore, with the help of acceleration methods, large-scale point-cloud data could be organized effectively and expressed smoothly with little data redundancy. Preliminary experiments show that the algorithm has abilities to overcome the shortcoming of the classical R-tree methods; meanwhile, with the support of optimized pretreatment and assistant acceleration methods, the amount of real-time calculation is small and the time of each frame can hold within 0.04 s easily.

Optimization of Classical Domains for High-Speed Train Transmission System

LIU Yumei, ZHAO Congcong, XIONG Mingye, ZHANG Zhiyuan, QIAO Ningguo

2016, 29(1): 85-90,120. doi: 10.3969/j.issn.0258-2724.2016.01.013

[Abstract](797)

Abstract:
In order to monitor the operating condition of a high-speed train transmission system, matter elements that present the operating condition of components of the transmission system were established by the extension theory, and an optimization method for determining the classical domains of characteristic parameters of the matter element that presents a component's normal operating condition was proposed. In this method, a fitness function was constructed using the maximum comprehensive correlative degree (MCCD) between a component's sample sets and its normal operating condition. Then, the parallel particle swarm optimization (PSO) algorithm was adopted to solve the fitness function and determine the classical domains. In addition, the optimization results of classical domains were compared with those determined by the statistical method. The results show that the maximum and average of MCCDs obtained from the optimization results of classical domains are improved by 3.63% and 2.51%, respectively, which demonstrates that the optimization results of classical domains more conform to components' actual operating conditions.

Curve-Passing Dynamic Performance of Portal Bogie with Forced Steering Mechanism

WANG Boming, CHEN Hongyu, LI Zhize, TAN Hongyuan

2016, 29(1): 91-97. doi: 10.3969/j.issn.0258-2724.2016.01.014

[Abstract](815)

Abstract:
In order to predict the curve-passing dynamic performance of ultra-low-floor (ULF) trams, the configuration of the forced steering mechanism and its working principles were analyzed, theoretical formulas of related steering parameters were derived, and a curve-passing dynamic model was built. By using computer simulation, the influences of the forced steering mechanism on vehicles' curve-passing dynamic performance were assessed, and a comparison on four curve-passing dynamic indexes was made between vehicles with and without forced steering mechanism. As a result, the wheel-rail lateral force and the derailment coefficient in the two cases showed no difference, but the angle of attack of the vehicle with the forced steering mechanism was reduced by nearly 60%(about 0.5), and the wheel-rail wear coefficient of wheel pairs in positions No. 1 and No.2 was reduced more than 10 kN(). In addition, the curve-passing performance of vehicles were predicted in different curve radiuses. It was found that when the curve radius was over 100 m, the vehicles showed good curv-passing dynamic performance; and when the curve radius was less than 100 m, the response of curve-passing dynamic indexes became sensitive. On the whole the vehicles with a forced steering mechanism have good small radius curve-passing performance.

Dynamic Response of Bogie in Failure Modes of High-Speed EMU Air Spring

QI Zhuang, LI Fu, DING Junjun, HUANG Yunhua, YU Dalian

2016, 29(1): 98-104. doi: 10.3969/j.issn.0258-2724.2016.01.015

[Abstract](896)

Abstract:
In order to simulate the failure states of a high-speed EMU's air spring, a 3D coupled dynamics model of the air spring system was established by the theory of pneumatics and the function fitting method. A co-simulation by combination of the 3D coupled model of air spring and the vehicle MBS dynamics model of EMU was carried out to study the dynamics response of the high-speed EMU bogie in the failure modes of air spring. The results of air spring leakage analysis show that the possibility of the vehicle instability caused by the leakage of air spring is little, but the leakage will cause the ride comfort to deteriorate. The peak values of vehicle vertical and horizontal safety indexes appear when the leakage area is 15 mm2 and 30 mm2, respectively. The action of the differential pressure valve can effectively guarantee the vehicle dynamics performance in the air spring leakage process. The results of vehicle curving performance analysis show that, if the direction of the vehicle passing a curve is consistent with the leakage side of the air spring, the wheel load reduction rate is about 20% higher than that on a straight track. The failure of the differential pressure valve and the leveling valve will affect the vehicle dynamics performance to some extent, but the dynamics indexes can still meet the safety requirement.

Research on Numerical Analysis and Dust Collection Efficiency of Reverse Blowing Pickup Mouth

XI Yuan, CHENG Kai, LOU Xitong, CHENG Lei, ZHANG Qinguo, HU Yanjuan

2016, 29(1): 105-112. doi: 10.3969/j.issn.0258-2724.2016.01.016

[Abstract](850)

Abstract:
In order to improve dust collection efficiency, the computational fluid dynamics (CFD) technology was used to calculate the flow field of reverse blowing pickup mouth, analyze the structural parameters influence on the dust collection efficiency, and calculate the dust collection efficiency combined with the gas-solid flow model. The results show that when the ratio between outlet diameter and width is less than 0.47 and the dip angle is less than 105,the dust collection efficiency can improved by increasing the outlet diameter and dip angle.Airflow velocity is high and the direction is close to the ground when reverse blowing pickup mouth is near the ground. There is no leakage to bring about secondary pollution. The overall removal efficiency declines by 27%when traveling speed increases from 5 km/h to 15 km/h, in which the grade efficiency of 45 and 152 m particle diameter respectively decrease by 9%and 33%.

Holistic High-Speed Train Subsystem Simulation Platform Based on CAD/CAE Integration

TANG Zhao, ZHU Yunrui, NIE Yinyu, ZHANG Weihua

2016, 29(1): 113-120. doi: 10.3969/j.issn.0258-2724.2016.01.017

[Abstract](912)

Abstract:
To enable general-purpose commercial multi-body dynamics and finite element software to meet the requirements of simulation and modeling of a high-speed train subsystem, an extensible and flexible framework was set up by utilizing open-source components and the dynamic encapsulating technology. As a case study, a high-speed train pantograph-catenary subsystem simulation platform (TPL. PC) was developed based on this framework. The application result shows that the proposed framework can provide all necessary functions for the high-speed train simulation platform, such as geometric modeling, mesh generation and editing, numerical solution, and 3D real-time visualization. In addition, it can overcome the difficulty of interoperability of geometry models and simulation models in above aspects among different subsystems, which makes the temporal data produced by iterative computation and the result data exchange smoothly.

Optimization of Variable Blank Holder Forces in Sheet Metal Forming Based on RBF Neural Network Model

XIE Yanmin, HE Yujun, TIAN Yin

2016, 29(1): 121-127. doi: 10.3969/j.issn.0258-2724.2016.01.018

[Abstract](1069)

Abstract:
In order to solve the difficulty of training the hidden layer nodes in radial basis function (RBF) neural network during the optimization of variable blank holder forces,a RBF neural network based on the artificial immune algorithm was established by taking advantages of artificial intelligence algorithms, and then used to approximate a nonlinear function. Using both the block blank holder technology and the variable blank holder force control technology, numerical simulations were conducted in Dynaform to obtain the forming data, and an approximate model of RBF neural network was established between the variable blank holder forces and the forming quality. The approximate model was optimized by artificial immune algorithm to obtain the optimal blank holder force parameters. In addition, the method was applied to the S-rail stamping. The results show that compared with that before optimization, the maximum wrinkle amount was reduced by 89.53%, and wrinkles could be effectively controlled by the optimized variable blank holder forces.

Simulation of Temporary Traffic Bottleneck on Highways Based on Cellular Automaton

JIANG Xinguo, XIA Liang

2016, 29(1): 128-137. doi: 10.3969/j.issn.0258-2724.2016.01.019

[Abstract](938)

Abstract:
To study the influence of the forced lane changing and the distribution of conflict points on the temporary traffic bottleneck flow of freeways, a cellular automaton model was proposed considering the driver's changing psychology behavior. The new model combines the rule of forced lane changing with the NaSch (NS) model and the symmetric two-lane cellular automaton (STCA) model. Under open boundary, the relationship between the traffic flow at the bottleneck, the lane-changing frequency and the car arrival rate were obtained by simulation with different safe lane-changing probabilities, forced lane changing probabilities, distance between conflict areas, and length of conflict area. The results show that safe lane-changing behavior has little influence on the flow. The main factor decreasing the maximum flow is the forced lane changing behavior at the bottleneck. When the safe lane-changing probability is 0.5 and the forced lane changing probability changes from 0.0 to 0.1, the maximum flow decreases by 17%. The length of conflict area helps to reduce the traffic congestion at the bottleneck. When the range length of conflict area changes from 1 to 4 cells, the critical car arrival rate increases by 4%. The traffic conflict area has significant influence on the traffic safety risk, which could increase with the lane-changing probability.

Applicability Analysis of Triparametric Fundamental Equations for Pedestrian Traffic Flow

YE Jianhong, CHEN Xiaohong

2016, 29(1): 138-144. doi: 10.3969/j.issn.0258-2724.2016.01.020

[Abstract](917)

Abstract:
To verify whether the fundamental equations among traffic volume, density and speed hold for pedestrian traffic flow, methods of analogy analysis and error analysis were used to establish the methodology and procedures for examining the applicability of the fundamental equations. Pedestrian traffic data including volume, density, and speed on level walkways and stairways were collected. The observed density values were compared with those converted by the fundamental equations to analyze the errors between them. The results show that for the pedestrian flow on walking facilities with boundaries, the relative error of parameter conversion by using the fundamental equations could reach more than 20%-25% in very low and high density conditions. What's worse, the application of fundamental equations likely leads to a wrong conclusion that the pedestrian flow and speed can be still high in high density conditions, and even loses some high-density data. The truth is that the traffic flow fundamental equations do not hold strictly under real pedestrian traffic conditions, and hence should not be applied for parametric calculation in theoretical research of pedestrian traffic capacity.

Routing Optimization Model and Algorithm for Out-of-Gauge Freights in Multiple Flow Railway Network

CHEN Hao, WANG Wenxian, LI Xueqin

2016, 29(1): 145-151. doi: 10.3969/j.issn.0258-2724.2016.01.021

[Abstract](843)

Abstract:
In order to distribute the out-of-gauge freights reasonably to paths in railway network, a multi-objective optimization model was built for route selection of multi-direction out-of-gauge freights. In the model, the minimum transport route mileage, the minimum haulage time, and the minimum interference to the normal operation of the existing railway lines were taken as targets; and the distance between railway out-of-gauge freights and structure gauge, the railway transport capacity, and the loading capacity of the bridge along the way were used as constraints. According to the model characteristics, a multi-objective hybrid genetic algorithm was proposed to solve the model. In the algorithm, the natural array coding mode, together with cross and mutation operators, were designed to fit the constraints, and a simulated annealing strategy was introduced to enhance its neighborhood search capability. In addition, the proposed method was applied to the complex network containing 14 node stations and 23 sections to verify its validity. The application results show that the objective function values obtained by the proposed model and algorithm are superior to those obtained by genetic algorithm and annealing algorithm. Therefore, this method provides a technical measure for the decision-making of path selection in out-of-gauge freights transportation.

Synergy Model of Vertical Structure of High-Speed Railway Dispatching System

DENG Nian, PENG Qiyuan

2016, 29(1): 152-160. doi: 10.3969/j.issn.0258-2724.2016.01.022

[Abstract](1121)

Abstract:
Three dispatching schemes for high-speed railway network would be built in China, namely the centralized scheme, regionally centralized scheme and access-based scheme. In order to study synergy of dispatching system, management and organizational structure of different schemes were analyzed and compared. By combining with the synergistic theory, the concept of synergic order degree of dispatching system was proposed. With the goal of realizing vertical structure synergy of dispatching system, general order degree models in different dispatching schemes were constructed by the information entropy theory. And on this basis the quantitative selection method about dispatching schemes was proposed.Finally,validity was verified by a case analysis.The results indicate that the order degree of organization structure can be improved by 0.05 to 0.10 through seting regional control center when the system has 60 dispatcher stations,and it can be effectively increased by 0.1 through reasonable configuration scheme of the secondary management control center.

Occupant Evacuation Simulation Model during Civil Aircraft Emergency

DU Hongbing, ZHANG Qingqing, CHEN Chen

2016, 29(1): 161-167. doi: 10.3969/j.issn.0258-2724.2016.01.023

[Abstract](1281)

Abstract:
A computer simulation to verify occupant evacuation within 90 s during aircraft emergency can supply beneficial information for the full-scale evacuation experiment in the initial airworthiness certification of the advanced regional jet (ARJ) developed by China. Based on cellular automata and multi-agent theory, a civil aircraft cabin occupant emergency evacuation model (CACOEM) was established. In the model, considering their psychology in an emergency circumstance of aircraft, occupants were classified into different roles according to their distinctive features of behavior; four sub-models, i.e., civil aircraft cabin model, occupants' characteristics model, occupants' behavior model, and occupants' movement model were involved. In addition, simulation software CabinEvacu was developed and applied to the regional commercial aircrafts with 100 seats. According to the requirements on passenger age-sex proportion in Transport Aircraft Airworthiness Standards: Transport Category Airplanes (CCAR25-R4), 1000 times of occupant emergency evacuation simulations were made in a scenario where three hatches are opened in front, middle, and rear areas, respectively. The results show that the average evacuation time is 68.7 s, which is consistent with the result obtained by the evacuation test simulation and investigation algorithm (ETSIA).

Design and Switching Control of Power Supply Coils Applied to ICPT-Based Electric Vehicles

SU Yugang, ZHANG Shuai, XU Yong, TANG Chunsen

2016, 29(1): 168-176. doi: 10.3969/j.issn.0258-2724.2016.01.024

[Abstract](882)

Abstract:
For the inductively coupled power transfer (ICPT) system of electric vehicles (EVs) with cascading power supply coils, there is a sharp drop of the mutual inductance and difficult to detect the EV position when the power supply coils switch. To deal with this, a novel embeddable power supply coil was developed. The design method for the parameters of the coil was also presented based on the constant principle and computational methods of mutual inductance. Besides, a position detection sensor with double coils was designed. The parameter design method of the sensor, the suppression strategy for the power flow disturbance to the sensor, and the switching control strategy of the cascading power supply coils were presented. Finally, based on the simulations on Ansoft Maxwell, Matlab/Simulink and ICPT experiment platform, the results were verified. The relative fluctuation ratios of mutual inductance and the pickup voltage are about 8% and 10% respectively. The position detection sensor with double coils can reliably detect the position of EV in the energy channel of 40 kHz electromagnetic field.

Influences of Ice Load and Air Damping on Dynamic Current Collection of Pantograph-Iced Catenary

DUAN Fuchuan, LIU Zhigang, SONG Yang, ZHANG Jing

2016, 29(1): 177-187. doi: 10.3969/j.issn.0258-2724.2016.01.025

[Abstract](921)

Abstract:
In order to study the influences of the icing and environmental wind on pantograph-catenary current collection, based on modal analysis method, the differential equations of motion for icing catenary were deduced considering the influence of icing on the catenary mass and stiffness. Then pantograph-catenary equation of motion is adjusted by introducing the term of air damping caused by static wind load. Then, utilizing a lumped-mass pantograph model, the contact force with different ice thicknesses, wind speeds and angles of attack is calculated. The results show that without wind, the increase of ice thickness leads to a poor contact performance of pantograph-catenary system. When there is static wind load, the wind direction is the main factors affecting the contact performance of the pantograph-catenary system, because the aerodynamic damping of catenary is changed by icing. While the more closely the wind flows to the horizon direction, the less it affects the contact performance of pantograph-catenary system.

A New (k+2, k) Hadamard Minimum Storage Regenerating Code

ZHANG Sina, TANG Xiaohu, LI Jie

2016, 29(1): 188-192,200. doi: 10.3969/j.issn.0258-2724.2016.01.026

[Abstract](854)

Abstract:
To reduce the storage capacity of nodes in distributed storage systems, a new (k+2, k) Hadamard Minimum Storage Regenerating (MSR) code was constructed. Each coding matrix is related to two values, from which the diagonal elements of this coding matrix are selected. These two values appear in the coding matrix in a repeating pattern, but with different repeating cycles for different matrices. Based on the structure of the coding matrix, a repair strategy was constructed. The repair strategy divides symbols in the failed node into /2 groups with two symbols in each group, then the two symbols are recovered by downloading one symbol from each of the other k+1 nodes. If the two values related to each coding matrix are unequal, the new Hadamard MSR code can optimally repair systematic nodes. If the sum of two values related to each coding matrix is nonzero and the k values are the same, the new Hadamard MSR code can optimally repair the first parity node. If the sum of the inverse of two values related to each coding matrix is one, the new Hadamard MSR code can optimally repair the second parity node. The new code reduces the storage capacity to the bond for Hadamard MSR code. Further, it can optimally repair all systematic nodes and one parity node.

Electrocardiography Monitoring System Based on Wireless Communication

NING Wenshuang, LIANG Ting, YUAN Yong J

2016, 29(1): 193-200. doi: 10.3969/j.issn.0258-2724.2016.01.027

[Abstract](748)

Abstract:
To assist the doctors in assessing drug effects and monitor the recovery of patients, the mobile medical monitoring system was designed in this paper, which utilizes electrocardiography (ECG) signals. ECG sensors were adopted to gather signals from monitoring sites. Both ECG signal acquisition and transmission were controlled by an ARM chip. GPRS network and Internet network were used for the remote wireless data transmission. In either a monitoring center or community hospital, SOCKET technology was utilized to develop network applications. The end-user friendly interface was visually established, and patient database and ECG database were administrated by the monitoring center with SQL database. When the sampling frequency of ECG sensors is 200 Hz, the Nyquist sampling theorem was satisfied and the acquisition precision is up to 5 mV, which can obtain accurate ECG P, Q, R, S, T waveforms. ARM processor has the merits of high performance, low power consumption and real-time analysis. The developed system not only realizes remote, real-time monitoring and alarming for ECG, but also provides the functions such as waveform playback and QRS waveform detection, which can be extended to other applications of physiological signal monitoring system.

Mechanical Properties Analysis of Coronary Stent Based on Medical Images

XU Jiang, YANG Jie, YANG Ji, HUANG Nan, LIU Yaling

2016, 29(1): 201-208. doi: 10.3969/j.issn.0258-2724.2016.01.028

[Abstract](843)

Abstract:
In order to find a simple method to build the coronary artery stenosis model based on medical images, a simplified narrow coronary artery-stent coupling finite element (FE) model based on CT images was built using the feature contour extraction method. The mechanical properties of the stent in an ideal coronary artery stenosis was then studied using the CT-based FE model in comparison with the ideal simplified artery FE model. In addition, some clinical study results were used to verify the rationality of the two models. The results show that some differences in mechanical properties existed between the two models, such as the stress distribution, expansion stiffness, recoil rate, dog bone rate, and the mean area of blood vessel. For the CT-based model, the mean stress of vessel was 1.22 MPa and the minimal area of vessel after stent implantation was 6.1 mm2, while they were 1.54 MPa and 5.1 mm2, respectively, in the ideal simplified model. The results obtained by the CT-based simplified model was more close to the clinical results than the ideal simplified model.

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2016 Vol. 29, No. 1