西南交通大学学报

Dynamic Response Study on Shallow Circular Composite-Lining Tunnels

GAO Bo, WANG Shuaishuai

2016, 29(4): 599-606. doi: 10.3969/j.issn.0258-2724.2016.04.001

[Abstract](580)

Abstract:
To investigate the dynamic response of shallow buried composite-lining tunnels, series solution of the dynamic stress concentration factor of double linings cylindrical cavities in an half elastic space were presented using the Fourier-Besselh method, as cavities were subjected to incident plane SV waves. The influence of the incident angle and frequency parameter on the dynamic stress concentration factor was discussed, then some conclusions were generated. The maximum dynamic stress concentration factor of the second lining is greater than that of the first lining in double linings tunnels. The dynamic stress concentration factor of the tunnel covered with buffer layers outside changes obviously, when the angle of incident SV waves is 0 and the frequency parameter is 0.25, the dynamic stress concentration factor of linings decreases by 20%. The incident angle and frequency parameter of plane SV waves have a significant influence on the dynamic stress concentration factor, with lager incident angle and frequency parameter, the values and distribution of dynamic stress factor become more complex.

Aerodynamic Effect Induced by High-Speed Train Entering into Tunnel in High Altitude Area

LUO Jianjun

2016, 29(4): 607-614. doi: 10.3969/j.issn.0258-2724.2016.04.002

[Abstract](650)

Abstract:
According to high altitude and low temperature climate conditions of midwestern and southwestern dangerous regions of China, a numerical simulation method of three dimensional compressible, viscous and unsteady compression waves induced by a high-speed train entering a tunnel was presented and aerodynamic effect also be studied.The results show that the range of the tunnel altitude has a profound effect on compression waves inside the tunel and micro-pressure waves at the tunnel exit. With the increase of altitude, the decrease of atmospheric pressure will cause a linear decrease of maximum and minimum value of compression waves and micro-pressure waves by 34% and 36% respectively, and has little influence on wave forms at measuring points.Besides, as temperature decreasing, the maximum and minimum value of compression waves and micro-pressure waves decrease linearly by 34% and 36% respectively.According to comparison, it assumes that altitude plays a much larger role in aerodynamic effect outside or inside the tunnel than temperature. At last, according to high altitude climate conditions of China and the principle that aims to make passengers comfortable, it provides that the tunnel area is 96 m2 when the CRH380B train runs at 350 km/h, 75.99 kPa and 250 K. This suggestion provides a guidance for sectional area designing of high-speed railway tunnel in high altitude and low temperature conditions.

Experimental Study on Pedestrian Behavior and Traffic Capacity of Cross Passage in Highway Tunnel

ZHANG Yuchun, XIANG Yue, HE Chuan, ZHANG Di, TANG Yuan

2016, 29(4): 615-620. doi: 10.3969/j.issn.0258-2724.2016.04.003

[Abstract](546)

Abstract:
In order to provide a foundation for cross passage design and fire risk evaluation in highway tunnel, an experimental platform of pedestrian evacuation from cross passages in highway tunnel was built and a software based on video image was developed to analyze pedestrian trajectories in the evacuation process. Pedestrians' evacuation behaviors and walking speeds in normal and emergency situations were studied with different cross passage widths (1.4-2.0 m), and the evacuation capacity of cross passages with different widths and illuminations was obtained based on the walking speed of pedestrians. The results show that in the order of entering the cross passage, pedestrians' walking speeds slow down, and the magnitude of speed reduction also gradually reduce. Compared with the earliest individuals to enter the cross passage, the latest individuals will reduce their walking speeds by 40%-50% in average. In addition, the width of the cross passage determines the layer numbers of pedestrians across the passage. With the passage width increasing, pedestrians' walking speed and passage traffic capacity both increase; specifically, every 0.1 m increase in the width of cross passage can bring an increase of 12.3-13.5 persons per minute in the traffic capacity. Under low illumination conditions, the traffic capacity of cross passage is about 15% lower than that in good illumination conditions, and pedestrians thus should pay more attention to enhance their self-protection.

Experimental Study on PBL Shear Connectors of Steel-Concrete Composite Bridge Considering Transverse Prestressing

ZHU Bing, WANG Xuewei

2016, 29(4): 621-631. doi: 10.3969/j.issn.0258-2724.2016.04.004

[Abstract](581)

Abstract:
In order to study the shear capacity and its influencing factors of PBL shear connectors for steel-concrete composite girder bridges, 33 specimens in 13 groups of three types were designed for push-out tests conducted in Xiaoshagou Bridge in Lanzhou, China. The failure modes, failure mechanisms, and influencing factors of shear capacity of these PBL shear connectors were analyzed comparatively. On this basis, a shear capacity calculation formula for PBL shear connectors considering the transverse prestressing effect was proposed. The results show that the shear capacity of PBL shear connectors could be effectively increased by increase of transverse rebar diameter, perforated rib diameter, and perforated rib thickness. The existence of transverse pretension stress accelerated the cracking of concrete, causing the strength and stiffness of concrete, perforated plate, and reinforcing rebars unable to exert their effect fully. As a result, the shear capacity of PBL shear connectors were reduced by about 10%. In addition, the constraint effect of transverse stress improved the strength and stiffness of concrete and delayed the concrete cracking, bringing the strength and stiffness of concrete, perforated plate, and reinforcing rebars into full play, and resulting in an significant improvement (20%) in the shear capacity of PBL shear connectors. The calculated results from the proposed formula close to the test results verified its effectiveness.

Dynamic Response of Superstructure of Prestressed Box-Girder Bridge to Over-High Truck Impact

TIAN Li, FENG Zhenning

2016, 29(4): 632-638. doi: 10.3969/j.issn.0258-2724.2016.04.005

[Abstract](589)

Abstract:
In order to reveal the damage of the prestressed box-girder bridge caused by over high truck impact, a comparative analysis between a numerical simulation and an impact experiment was conducted to study the dynamic response of the superstructure of a box-girder bridge. A three-dimensional separation model of the prestressed box-girder bridge superstructure, together with the coupling model of the truck and the bridge superstructure, was established using LS DYNA software. With this model, the damage of bridge and truck and the overall displacement of bridge were investigated when the truck impacted the bridge frontally at a speed of 80 km/h, and the dynamic responses of the bridge superstructure to impacts of the over-high truck at speeds of 30, 50, and 80 km/h were compared. The results show that when the truck hit the high mass bridge, the whole bridge damage was little and therefore the study should focus on its local damage; during the collision, the deformation of the truck carriage can result in the transformation of the frontal impact into a punching impact; both the impact force value and the displacement value of the impact area of the bridge are positively correlated with the truck speed, and the maximum displacement is 165 mm when the truck speed is 80 km/h.

Fatigue Life Prediction and Parameter Analysis of Girder New Detail

LIAO Ping, XIAO Lin, WEI Xing, ZHAO Renda, TANG Jishun

2016, 29(4): 639-644. doi: 10.3969/j.issn.0258-2724.2016.04.006

[Abstract](586)

Abstract:
In order to study the influence of the cope hole radius, shape and fillet weld size of the new detail of Hutong Railway Yangtze River Bridge girder on fatigue performance, the hot spot stress method was used to predict fatigue life, and the calculation results were compared with the experiment results of 9 welded specimens,then parameter analysis based on finite element models was conducted. The results show that:a little difference exists between fatigue life predicted by hot spot stress method and the results of fatigue experiments, which is within 15%; the mesh size of flange plate near the cope hole had little impact for hot spot stress, which is within 1.6%, two-point and three-point extrapolation method are feasible for this new detail; the fillet weld size and the cope hole radius have some influence on the maximum stress of flange plate and hot spot stress, the variation range is within 10%; the ratio of major and minor axes has a significant impact on the maximum stress of flange plate and web and hot spot stress,the variation range of web is 21.6%, however, the others are not beyond 10%. It is suggested that the welded detail with elliptical the cope hole can be used if the condition allowed, and large ratio of major and minor axes should be selected.

Influence of Tire Cornering Property on Ride Comfort Evaluation of Vehicles on Bridge

CHEN Ning, LI Yongle, XIANG Tianyu

2016, 29(4): 645-653. doi: 10.3969/j.issn.0258-2724.2016.04.007

[Abstract](569)

Abstract:
Vehicles driving on bridges under crosswind are affected simultaneously by the cornering force generated from the cornering property of tire and vibration responses of bridges, and the driver and passengers are prone to suffer the degradation of ride comfort. First, the cornering force expression of the tire is introduced into the lateral vibration equation of the wheel according to the nonlinear Dugoff tire model. A dynamic model of vehicle is established taking into account the cornering property of tire. Then, a framework for the wind-vehicle-bridge system is established by analyzing interactions among the natural wind, vehicles and bridges. Based on the framework, effects of the tire cornering property on evaluation of the ride comfort of vehicles under various influencing factors are studied. Results show that after taking the cornering property of tire into account, the ride comfort of vehicles can be improved by improving the lateral vibration status of vehicles. Under a crosswind of 25m/s and on good road surface conditions, the ride comfort indicator of the vehicle is improved by 20.6% when the cornering property of tire is considered.

Numerical Simulation of Effect of Mountainous Topography on Wind Field at Bridge Site

YU Jianhan, LI Mingshui, LIAO Haili

2016, 29(4): 654-662. doi: 10.3969/j.issn.0258-2724.2016.04.008

[Abstract](641)

Abstract:
The influence of topographic features of mountainous area on the wind field distribution at bridge sites was investigated with a computational fluid dynamics software FLUENT by taking a long-span bridge crossing a deep valley as an engineering example. The simulation method was verified by comparing the numerical results with ones obtained from the wind tunnel testing. Through comparative analysis of cases with different wind directions, the distribution characteristics of wind velocity, wind attack angle and mean wind profiles at the bridge site under different flow directions were studied, and also the magnification factors caused by the effect of valley wind were discussed. The results show that the wind velocity distribution and wind profiles along the bridge deck would be influenced by the nearby mountains, and downward wind attack angle appears on this side; distortion of wind profile would happen at the lower part of the valley; and wind velocity accelerations would happen at the mid-span when the wind flow direction is aligned with the valley.

Method of Short-Term Wind Speed Forecasting Based on Generalized Autoregressive Conditional Heteroscedasticity Model

JIANG Yan, HUANG Guoqing, PENG Xinyan, LI Yongle

2016, 29(4): 663-669,742. doi: 10.3969/j.issn.0258-2724.2016.04.009

[Abstract](605)

Abstract:
In order to improve the security of the train operation, a short-term wind speed forecasting method was proposed based on a linear recursive auto-regressive integrated moving average (ARIMA) algorithm and a non-linear recursive generalized auto-regressive conditionally heteroscedastic (GARCH) algorithm (ARIMA-GARCH). Firstly, the non-stationarity embedded in the original wind speed data was pre-processed to eliminate its effect on the proposed model. Then, a linear recursive ARIMA model was build to predict wind speed. Finally, a non-linear recursive forecasting model was established based on the GARCH algorithm. Numerical example based on wind samples from field measurements The result shows that compared with the source data, the proposed approach has a higher prediction accuracy. With the increasing of prediction step, the mean absolute error only increases from 0.836 m/s to 1.272 m/s. The new method explains parts of the non-linear characteristics (heteroscedasticity) of wind speed time series and improves the prediction accuracy compared with the usual ARIMA approach. For instance, compared with the ARIMA model, the accuracy of mean absolute error of the six-step in advance forecast based on the GARCH model is improved by 11.54%.

Numerical Model of Asphalt Pavement Considering Transversely Isotropic Fatigue Damage

LIU Junqing, LI Qian, WANG Baoshi

2016, 29(4): 670-676. doi: 10.3969/j.issn.0258-2724.2016.04.010

[Abstract](601)

Abstract:
In order to study the fatigue damage in asphalt pavement, the damage that occurred in the tensile zone of pavement structure was assumed as being transversely isotropic. Based on this assumption, the asphalt pavement constitutive equation considering the transversely isotropic fatigue damage was derived. Then, using FORTRAN language to develop a material subroutine and a load subroutine, an ABAQUS finite element model of asphalt pavement was established based on the transversely isotropic fatigue damage theory. By analyzing the fatigue life of the model under different loads, the load-fatigue life curve was established in comparison with the test results to verify the reliability of the model. The distribution of damage degree and horizontal tensile stress in the pavement structure were studied by the finite element model. The results indicate that the fatigue damage mainly distributes at the base bottom near the middle line between the double wheels, where the fatigue crack appears first. With the load cycles increasing, the horizontal tensile stress decreases gradually, and its distribution in pavement structure changes. Its maximum position moves upward from the base bottom and transversely to the two sides from the middle line. The pavement life calculated by the proposed model is in good agreement with the experimental results, and the relative error is between 4.57% and 9.82%.

Effect of Notch and Tack Coat on the Interface Shear Performance between Asphalt Layers

LIU Hongpo, QIU Yanjun, JIANG Xin

2016, 29(4): 677-683. doi: 10.3969/j.issn.0258-2724.2016.04.011

[Abstract](524)

Abstract:
In order to evaluate the important order and significance of the type of asphalt mixtures (A) on both sides of the interface of pavement surface course, the notch (B) in the interface, the tack coat (C), and the two-way interactions (AB, AC and BC) of the three factors that influence the interlayer shear strength, the orthogonal design was applied to make the test scheme. Three types of composite Marshall specimens were prepared by compaction method. The lower layer of specimens was 19 mm nominal maximum aggregate size (NMAS) dense-graded asphalt mixture (AC-20); and the upper layer was 13 mm NMAS dense-graded asphalt mixture (AC-13), AC-20, or 13 mm NMAS open-graded friction courses (OGFC-13), respectively. There were four treatments for the specimens interfaces, namely, neither notch nor tack coat (NNNT), no notch but tack coat (NNYT), no tack coat but notch (YNNT), and both notch and tack coat (YNYT). The interfaces of the specimens were directly sheared by the homemade interface shearing apparatus at 25℃. The results show that the average shear strength of the NNYT, YNNT, and YNYT interface is increased by 23.8%, 42.9%, and 53.9% respectively, compared with the average shear strength of the NNNT interface. By variance analysis, the effect of the three factors and their interactions on the shear bond strength can be ranked in a descending order as A, B, C, BC, AC, and AB. The A, B, C, and the interaction of BC are highly significant factors, and the interactions AB and AC are subordinate factors.

Predictive Model of Subgrade Deformation Beneath Aluminum Sandwich Panel

ZHOU Shaohui, CAI Liangcai, XU Wei, CEN Guoping

2016, 29(4): 684-689. doi: 10.3969/j.issn.0258-2724.2016.04.012

[Abstract](591)

Abstract:
In order to study the subgrade deformation beneath the sandwich panel which was subjected to repeated aircraft load, four aluminum honeycomb sandwich panels with different thickness and strength were trafficked and the soil plastic deformation was surveyed. The performance data were analyzed and presented graphically to build a simple predictive model including traffic times and base strength. The simplify model was revised and compared with conventional models. The results show that the soil deformation is in proportion to the logarithm of times, and inversely proportional to base strength. Fatigue cracking is the main failure reason of pavement structures. The maximum traffic times calculated by three different design equations are 4.071013, 288, and 487 990 respectively when pavement D is installed over the soil with 70MPa strength.

Seismic Performance of Short-Pier Shear Walls:Theoretical Analysis and Numerical Simulation

LIU Chengqing, WEI Xiaodan, NI Xiangyong

2016, 29(4): 690-696. doi: 10.3969/j.issn.0258-2724.2016.04.013

[Abstract](575)

Abstract:
To research the seismic performance of short-pier shear walls, firstly, influences of the constraints at the edges were considered, and the theoretical calculation equations of the ultimate axial compression ratio were established based on the plane section assumption and critical reinforcement of short-pier shear walls sections, in addition, the numerical simulation was conducted to study the seismic performance of short-pier shear walls. Then the ultimate axial compression ratio was obtained by the calculation theory. through changing the axial compression ratio of numerical models, influences of the axial compression ratio on seismic performance of short-pier shear walls were analyzed when the axial compression ratio was smaller or larger than the ultimate axial compression ratio. At last, the seismic performance of short-pier shear walls with different height-thickness ratios was studied. Results show that the ratios of the calculated and test results of skeleton curves characteristic points are between 0.86 and 1.08, and the numerical simulation results have a good agreement with the test results; when the axial compression ratio of short-pier shear walls is less than the ultimate axial compression ratio, with the axial compression ratio increasing 0.1, the horizontal bearing capacity increases about 7.81%, and the ductility reduces about 4.52%; when the axial compression ratio of short-pier shear walls is more than the ultimate axial compression ratio, with the axial compression ratio increasing 0.1, the horizontal bearing capacity reduces about 5.50%, and the ductility reduces about 6.85%, the accuracy of the calculation theory for ultimate axial compression ratio is verified. In the case of equal section areas, shear walls with a big cross section height-thickness ratio can have a good seismic performance.

Stability Analysis of Reinforced Earth Retaining Wall under Earthquake

JIA Liang, ZHU Yanpeng, LAI Chunjing

2016, 29(4): 697-703. doi: 10.3969/j.issn.0258-2724.2016.04.014

[Abstract](621)

Abstract:
To calculate the stability factor of reinforced earth retaining wall under earthquake, a stability analysis model was set up based on the upper bound limit theory by considering the effect of the reinforcement strip and selecting the logarithmic spiral as the integral slip surface. The stability factor equation was developed through deduction of the external power made by sliding mass gravity behind the retaining wall, the external power of earthquake on sliding mass, the internal power of soil cohesion of the potential failure surface, and the reinforcement strip on soil friction. The stability factor of reinforced retaining wall under earthquake was calculated using the genetic algorithm. The results show that after considering the reinforcement, the stability factor obtained by the dynamic model of failure surface is 1.337, which is 0.08 higher than the stability factor calculated by the method from Code for Design of Highway Reinforced Earth Engineering. This suggest, taking the anti-sliding effect of reinforcement into accout during the stability analysis is reasonable.

Evaluation Methods for Post-Earthquake Damage State of Ancient Masonry Buildings

PAN Yi, LI Lingjiao, YAO Yunyi, WANG Huiqin

2016, 29(4): 704-713. doi: 10.3969/j.issn.0258-2724.2016.04.015

[Abstract](576)

Abstract:
Evaluating the damage sate of ancient masonry buildings after earthquake involves many impact factors which are uncertain and correlated. In order to evaluate accurately the post-earthquake damage state of ancient masonry buildings, an ancient masonry building is divided into subsoil, foundation, and superstructure; and 11 indictors are selected as evaluation factors. Using membership function and analogy to build the judgment matrix, the weight coefficient vector is determined by analytic hierarchy process, and a fuzzy comprehensive evaluation model with two phases and three levels is built. Taking a watchtower in the Qiang village as an example, the model is applied to evaluate its damage state after Wenchuan earthquake. The results show that according to the fuzzy comprehensive evaluation model, the watchtower suffered moderate damage after the earthquake, with an assessment grade of B, which is consistent with the actual destruction state of the tower. This suggests that the proposed model can accurately reflects the damage state of ancient masonry buildings after earthquake, and therefore can be used as a basis to provide strengthening or maintenance measures for ancient masonry buildings damaged by earthquake.

Failure Mechanism of Civil Membrane-Structure Architecture with Gas Rib

HE Taibi, WANG Shuai, YAN Qipeng, ZHANG Qianwen, YUAN Ye

2016, 29(4): 714-720. doi: 10.3969/j.issn.0258-2724.2016.04.016

[Abstract](581)

Abstract:
In order to study the stability of a long-span membrane structure in varied environment, tensile tests of the membrane materials were carried out. A 1:1 geometric model of the membrane structure architecture was established using SOLIDWORKS software. Based on the finite element theory, a static analysis model for the membrane structure was proposed to obtain its equivalent stress nephogram. To simplify the analysis steps, parametric modeling of ANSYS software was employed to establish the static analysis model at cross connector of the membrane structure, with which variation rules of the membrane structure were analyzed under different temperatures, gas rib diameters, and internal pressures. The results show that for membrane structures with a diameter of 335 mm, the maximum stress in membrane surface increased from 48.14 to 58.84 MPa as the internal pressure increased from 0.018 to 0.022 MPa, which would greatly increase the load of membrane materials. If taking no account of the security coefficient, the appropriate temperature of membrane materials would decrease from 70 to below 56℃, indicating that membrane structures made of the membrane material cannot sustain high temperature working conditions.

Research on Grids Width of Herringbone Water-Sediment Separation Structure for Debris Flow Defense

XIE Tao, WEI Fangqiang, YANG Hongjuan, XIE Xiangping

2016, 29(4): 721-728. doi: 10.3969/j.issn.0258-2724.2016.04.017

[Abstract](543)

Abstract:
A new herringbone water-sediment separation structure was designed to separate coarse sediment from debris flow. The width of water-sediment separation grids is key to separation effectiveness. A formula for grids width was proposed by theoretical analysis, A optimal width discriminant of grids was gived by theoretical analysis, that is, the movement time of sediment larger than design separation diameter sliding down grids is equals to that of the residual debris getting through grids. And then, model tests were developed to revise the formula. Only gravitational effect is considered, based on the above analysis, the theoretical formula consisting of the width and depth of overflow gate and the incline angle of grids is established. Tests results demonstrate that measured values are 1.53 times larger than theoretical ones, and the correlation coefficient is 0.93. The coefficient can be used to revise theoretical models.

Mechanical Behavior of Cemented Sand Considering Particle Breakage

LI Bo, CHEN Yulong

2016, 29(4): 729-735. doi: 10.3969/j.issn.0258-2724.2016.04.018

[Abstract](588)

Abstract:
In order to study the effect of bonding proportion on behaviors of cemented sand combined with particle breakage effect, the conception of particle breakage was introduced and cemented sand behaviors were studied by numerical simulation with the built contact bond model in PFC3D. A series of triaxial compression tests on cemented sand of different bond proportions were carried out. Then, the simulated results were compared with the test results on artificially cemented sand from laboratory tests. The micromechanical responses were analyzed by numerical simulation. Results show that the discrete element method model is able to capture the main mechanical behaviors of cemented sand. Compared with uncemented sand, cemented sand has greater strength, and shows strain-softening in stress-strain curve and transition from compaction to shear-dilation in volumetric strain. The macromechanical responses of cemented sand (stress-strain relationship and dilatancy) are closely associated with the micromechanical responses. Bond breakage ratio and rate are low at the initial loading stage and then rapidly increase after yielding point. Bond breakage rate peaks at peak strength and deceases afterward, while the bond breakage ratio increases slowly and become stable. A sample with lower bond proportion and bond strength has higher bond breakage ratio and rate. High bond proportion leads to more broken particles and dilation in volume. When bond proportions are 0 and 100% respectively, particle breakage ratio increases from 1.13% to 10.96%. In contrast to uncemented sand, the bond develops the shear band, and larger and more concentrated contact force.

Algorithm for Eliminating Interactions Between Fundamental Wave and Harmonics in Phasor Estimation

LIANG Jianying, LIU Zhiming

2016, 29(4): 736-742. doi: 10.3969/j.issn.0258-2724.2016.04.019

[Abstract](521)

Abstract:
The fundamental and harmonic component of signal would interact between each other, leading to the measurement deviation. Thus, an algorithm was proposed, which is able to simultaneously measure both fundamental and harmonic waves and eliminate their interactions. First, the Taylor model was used to express the time-varying model of signal containing harmonic component. Several phasor estimations for different frequencies in one data window were obtained using the frequency-domain information; Then these phasor estimations were used to estimate the model parameters denoting time-variation and harmonic component. Tests on ideal signals and electric motor units trial data were conducted, and the results show that, at the cost of increasing about 5.4% of computational cost, the proposed algorithm can effectively eliminate the interactions between fundamental and harmonic components of signal, and the maximum measurement error and variance of the fundamental and harmonics measurement were decreased by 21.3% and 2.7%, respectively.

Prediction of Traction Load for New Electrified Railway

ZHANG Liyan, LI Qunzhan, ZHU Yi

2016, 29(4): 743-749. doi: 10.3969/j.issn.0258-2724.2016.04.020

[Abstract](563)

Abstract:
A statistical forecasting method based on the measured data is proposed to evaluate the influence of a new electrified railway on the power quality of power grid. Through analysis of statistical distribution characteristics of a large number of traction load test data, parameters such as the charged effective coefficient, maximum value, variance, and skewness coefficient are selected to describe the main characteristics of the traction load in probability distribution. Using the fuzzy C-means clustering algorithm, 42 groups of measured data are divided into 10 types. Based on the characteristic values of traction load provided by railway design departments, the probability model of the new electrified railway can be derived from the above 10 types, and its probability distribution function (PDF) is accordingly obtained. Finally, the feeder currents in traction substation of the new electrified railway are predicted by Monte Carlo sampling method. The validity of the method is verified by the fitting curves of PDF using the predicted data and the mean square error of PDF is less than 0.1.

Starting Characteristics of Linear Motor in Evacuated Tube HTS Side-Suspended Maglev System

ZHOU Dajin, CUI Chenyu, MA Jiaqing, ZHAO Lifeng, ZHANG Yong, ZHAO Yong

2016, 29(4): 750-758. doi: 10.3969/j.issn.0258-2724.2016.04.021

[Abstract](495)

Abstract:
In order to gain a greater starting thrust and higher running acceleration in evacuated tube HTS (high temperature superconductor) side-suspended maglev vehicle, and improve running stability at high speeds, a 2D simulation model for linear motor was established by studying the driving system of evacuated-tube HTS side-suspended maglev. The characteristics of the starting-thrust and normal force of the motor with different secondary plates were studied by finite element simulation and experiments. The results show that the secondary plates of different materials and thicknesses have significantly effects on the operation of maglev vehicle. When a 2 mm-thick commercial-purity aluminum plate was used as the motor secondary, the maglev vehicle could achieve higher starting thrust and accelerating performance with a high synchronous-speed. Meanwhile, low density of aluminum plate reduces the total weight of the maglev vehicle and it provides a levitation force in the hanging direction, which increases the running stability of the maglev vehicle.

Robot Visual Servoing Control Based on Redundant Features of Sub-pixel Accuracy

ZHANG Guoliang, WANG Zhanni, WANG Tian, DU Jixiang

2016, 29(4): 759-766. doi: 10.3969/j.issn.0258-2724.2016.04.022

[Abstract](545)

Abstract:
To overcome the dependency of a robot visual servoing system on calibration accuracy and pose estimation, a redundant featurebased robot visual servoing control method was proposed via fusing object feature recognition and visual servoing in different stages respectively. Firstly, to address the issue of largescale computation on image processing, a recursive greedy data compression algorithm based on curve vector was designed to speed up the feature extraction process. Secondly, to improve the measurement precision of feature in image space, a subpixel feature extraction method was studied based on the principle of vector orthogonallity. Furthermore, experimental rule of object recognition was proposed based on cooperative object shape and polygon shape fitting. Finally, based on the theory of image visual servoing and the method of task function, redundant visual features in subpixels were selected directly as feedback signals to build controlling model of robot visual servoing. The theoretical analysis and experimental results show that the servoing features can be extracted quickly and stably in complex environments, and the proposed method was robust to the calibration error and depth estimation error.

Pilot Protection Principle Based on Traveling Wave Amplitude Comparison Considering the Characteristics of Transfer Function

LIU Xingmao, LIN Sheng, ZHENG Gao, HE Zhengyou

2016, 29(4): 767-775. doi: 10.3969/j.issn.0258-2724.2016.04.023

[Abstract](493)

Abstract:
In order to accurately describe the propagation process of traveling wave and its attenuation law in the transmission line, and explore fault information that it carries for the transmission line protection, the equivalent circuit of Thevenin type for the lossy uniform transmission line was analyzed and the lumped equivalent circuit of the faulted network was built by transforming the transmission line wave equations in the time domain into the Laplace domain. On the basis of the lumped equivalent circuit, the mathematical relationship of the initial backward traveling waves on both ends of the faulted line was deduced, and the algorithm of the travelling wave based pilot protection was proposed, while the transfer function of the transmission line was taken into consideration. S transform was used to extract the initial traveling waves, and the attenuation ratio of the initial backward traveling waves on both ends of the line was calculated. The proposed algorithm determines whether a fault is internal or external to the protected zone according to the ratio value. The simulation data from PSCAD/EMTDC was applied to verify the proposed algorithm. The simulation results show that the ratio is greater than 0.81 when the internal fault occurs, and it almost equals to zero when the external fault occurs, indicating that the algorithm can reliably identify internal and external faults, and is not affected by the adverse factors of the error of line model, circuit parameter uncertainty, etc.

Adaptive Optimization of Radio Frequency Identification with Gauss Traversal and Harmony Search Network in Internet of Things

CHEN Liwei, TANG Quanhua

2016, 29(4): 776-784. doi: 10.3969/j.issn.0258-2724.2016.04.024

[Abstract](532)

Abstract:
To handle the large amount of data and complexity in the radio frequency identification process of the Internet of things, and overcome the disadvantages of lower complexity and recognition accuracy in the traditional algorithms, an algorithm was proposed to achieve the adaptive optimization of radio frequency identification with Gauss traversal and harmony search network in internet of things. First, the harmony search algorithm was used to optimize the design of the network. In order to solve the problems of the low optimizing accuracy and high computational complexity, the ergodicity of Gaussian function was applied to introducing control parameter in the improvisation process of the algorithm, which improves the pertinence for different evolution periods. The theoretical analysis for parameter selection was presented as well. Secondly, the optimization model of the radio frequency identification for the Internet of things was studied, and the improved adaptive optimization objective was proposed to achieve the equilibrium optimization of the performance index. Finally, the proposed algorithm was compared with the RPSOAS, CDE and C-MC algorithm, showing that, in the RFID (radio frequency identification network) experiment with 1000 m1000 m region and the 100000 tags, the convergence rate is 7.215 6, increased by more than 29.6%.

Energy Efficiency Resource Reuse for Device-to-Device Communication

LIU Yanping, FANG Xuming

2016, 29(4): 785-791. doi: 10.3969/j.issn.0258-2724.2016.04.025

[Abstract](467)

Abstract:
Energy efficiency is an important problem in mobile communication. Resource reuse and power allocation strategy based on energy efficiency was proposed for energy efficiency resource reuse of D2D (device-to-device) communication coexisting with traditional cellular communication, in which the QoS (quality of service) requirements of D2D pairs and cellular users and circuit consumption power were taken into account. The existence of the optimal power allocation of the D2D pairs was analyzed, and the closed expression of the optimal power was also obtained using fractional programming theory. Simulation results show that, compared to the existing schemes, the proposed scheme achieves the best energy efficiency while guaranteeing the sum-rate of 1.7 Mbit/s to 3 Mbit/s, and energy efficient of the proposed scheme is improved 36.25% compared to the maximum sum-rate algorithm when the requirements of QoS are low and slightly higher than the energy-saving based power allocation algorithm when the requirements of QoS are high.

Simultaneous Fault Diagnosis Method Based on Improved Sparse Bayesian Extreme Learning Machine

YE Qing, LIU Changhua, PAN Hao

2016, 29(4): 792-799. doi: 10.3969/j.issn.0258-2724.2016.04.026

[Abstract](582)

Abstract:
In order to identify simultaneous faults of the main reducer, an adaptive threshold denoising was adopted for intrinsic mode functions (IMFs) with high frequency and an interval threshold denoising was adopted for IMFs with low frequency, which are obtained from ensemble empirical mode decomposition (EEMD) of vibration signal, to eliminate noises. Then, a paired multi-label classification (PMLC) strategy was established, and probability classifiers based on PMLC and sparse Bayesian extreme learning machine (SBELM) were constructed with single fault samples; an optimal decision threshold was generated by using the grid searching method to convert the probability output obtained from classifiers into final simultaneous fault modes. On this basis, a simultaneous fault diagnosis (SFD) method based on adaptive threshold de-noising and SBELM was proposed. Its performance was verified using real samples of the main reducer. The experiment results show that the diagnostic accuracy of the method is 96.1%, which is 5% higher than that of methods based on probabilistic neural network (PNN) and support vector machine (SVM); its training time and execution time are 131.4 and 61.3ms, respectively, approximately 70% shorter than those of the method based on SVM.

4D Trajectory Prediction and Uncertainty Analysis for Departure Aircraft

ZHANG Junfeng, GE Tengteng, CHEN Qiang, WANG Fei

2016, 29(4): 800-806. doi: 10.3969/j.issn.0258-2724.2016.04.027

[Abstract](661)

Abstract:
In order to accelerate the implementation of trajectory-based operation (TBO), a new four-dimensional (4D) aircraft trajectory prediction approach that is based on aircraft continuous dynamics and discrete dynamics model was presented to predict trajectories of departure aircraft by dividing the departure operation into taking-off and climbing phases. Through in-depth analysis of factors such as the model construction, aircraft intent, initial state, performance parameters, and environmental information, the uncertainty in 4D aircraft trajectory prediction was reduced and the accuracy of prediction was improved. Taking the domestic flight CQH8867 from ZSPD to ZUCK as an example, a simulation was conducted to verify the validity of the proposed method, in which the position error and time error were chosen as the evaluation criteria, and the influences of the takeoff mass, top-of-climb (TOC) altitude, wind speed and wind direction on the departure aircraft 4D trajectory prediction were taken into account. Results show that the proposed algorithm can control the error between expected and actual time of arrival at departure fix within 1 min to meet the demand for air traffic management.

Short-Term Traffic Flow Prediction of Airspace Sectors Based on Bayesian Estimation Theory

CHEN Dan, HU Minghua, ZHANG Honghai, YIN Jianan

2016, 29(4): 807-814. doi: 10.3969/j.issn.0258-2724.2016.04.028

[Abstract](578)

Abstract:
To accurately forecast the air traffic flow distribution in airspace sectors and its development trend in the future, a short-term traffic flow prediction method based on Bayesian estimation theory is proposed. First, the operational history data of various sectors in the airspace system are extracted by parsing raw radar data of the aircraft within the airspace system. On this basis, an aggregate multi-sector traffic flow model is established. Then, Bayesian estimation theory is adopted to predict the future trend of airspace sector traffic flow and its uncertainty intervals by estimating and updating the optimal parameter of the aggregate multi-sector traffic flow model dynamically. Finally, the proposed method is verified on a set of operational history data of five air route sectors, taking 5 min as one time step to predict the short-term air traffic flow in the next one hour. The results show that the absolute error of the predicted results of more than 85% time steps is less than 3, the average absolute error is less than 2, and the stability of the predicted results is well. The proposed method can adequately reflect the dynamics and uncertainty in the airspace system operation, and hence is well in line with the practice.

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2016 Vol. 29, No. 4