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Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
Display Method:
Fracture Mechanism of Cologne-Egg Fastener Clips in Rail Corrugation Sections
CUI Xiaolu, PENG Shuangqian, XU Jia, ZHONG Jianke, QI Yayun
 doi: 10.3969/j.issn.0258-2724.20230025
[Abstract](53) [FullText HTML](60) PDF 3743KB(5)
Abstract:

As typical rail damage of the railway, rail corrugation is often accompanied by the fastener clip fracture, which seriously affects the operation safety of the train. Moreover, the small-radius section of the Cologne-egg fastener experiences frequent rail corrugation. To explre the fracture mechanism of Cologne-egg fastener clips, firstly, the finite element model of the wheel set-rail-fastener system, including the complete Cologne-egg fastener model, was established baesd on the field investigation. Then, the resonant response of the Cologne-egg fastener clip was explored, considering the frictional coupling vibration of the wheel-rail system. Finally, the fatigue life of the Cologne-egg fastener clip was compared in the cases of with and without rail corrugation sections, and the fatigue damage of different clips was quantified. The results show that the dominant frequency of the frictional coupling vibration of the wheel-rail system is consistent with the first-mode constraint mode of the Cologne-egg fastener clip in the frequent rail corrugation sections, which indicates that the clip resonance induced by the frictional coupling vibration of the wheel-rail system is the main reason for the Cologne-egg fastener fracture. The frictional coupling vibration of the wheel-rail system is aggravated by the rail corrugation, which makes the clip life of the Cologne-egg fastener in the rail corrugation section decrease by 99.04% compared with that in the absence of rail corrugation section. The clip life is thus only 3.11% of the design clip life. Besides, the Cologne-egg fastener clip on the low gauge side is more prone to fatigue failure in the small-radius curved section, and the failure position is located on the inner side of the rear arch end of the clip.

Maximum Temperature in Bifurcated Tunnel Based on Synergistic Effect of Longitudinal Ventilation and Air Curtain
LI Tao, YANG Yunping, MI Chun, CHEN Zhengquan, WANG Chunxiang, CHEN Longfei, ZHANG Yuchun
 doi: 10.3969/j.issn.0258-2724.20230157
[Abstract](78) [FullText HTML](27) PDF 2383KB(9)
Abstract:

To investigate the effect of synergistic longitudinal ventilation and air curtain on the control of tunnel fire smoke in urban bifurcated tunnels, the 1∶10 small-sized bifurcated tunnel fire experiments were conducted, and the along-travel and maximum temperatures of bifurcated tunnels under the synergistic effect of longitudinal ventilation and air curtains were analyzed by taking into account the variables of longitudinal ventilation, jet velocity, angle, and thickness of air curtain. Firstly, the smoke and heat insulation effect of the air curtain was analyzed through 57 sets of small-sized tunnel fire experiments. Then, based on the dimensionless empirical correlation formula for the maximum temperature rise of the ceiling in a tunnel fire, a model of the maximum temperature rise under the synergistic effect of air curtain and longitudinal ventilation was constructed at a fixed heat release rate of 47.9 kW. Finally, the experimental values of the maximum temperature rise under different working conditions were compared with the predicted values of the theoretical models of the maximum temperature rise. The results show that an air curtain can effectively help longitudinal ventilation reduce the temperature in the main tunnel by up to 420 ℃ while effectively preventing smoke from entering the bifurcated tunnels. When the jet velocity of the air curtain is small, the increase in longitudinal wind speed can effectively prevent the accumulation of smoke in the bifurcation and improve the insulation efficiency of the air curtain on the smoke. In addition, the temperature of the smoke at the tunnel bifurcation point can be reduced by up to 170 ℃. The constructed theoretical model of the maximum temperature rise is compared with the experimental results, and the error between them is less than 10%.

Fixed Point Evolution Algorithm
SU Qinghua, HONG Nan, HU Zhongbo
 doi: 10.3969/j.issn.0258-2724.20220079
[Abstract](56) [FullText HTML](31) PDF 1811KB(13)
Abstract:

In order to design an efficient and robust evolution algorithm, the fixed point iteration idea in solving equations was first introduced into the optimization field. The optimization process of an evolution algorithm was regarded as the gradual display process of the fixed point of an equation in an iterative framework. On this basis, a novel evolution algorithm based on a mathematical model was developed, named fixed point evolution algorithm (FPEA). The reproduction operator of FPEA is a quadratic polynomial which is derived from a fixed point iteration model with the Aitken method. The overall framework of FPEA inherits the population-based iterative model of traditional evolution algorithms such as differential evolution algorithm. The experimental results show that the average ranking of the optimal value of FPEA ranks first among all the compared algorithms on CEC2014 and CEC2019 benchmark functions. The proposed algorithm can achieve the highest solution accuracy with a low computational overhead on four engineering constraint design problems among the compared algorithms including CSA and GPE.

Method of Splicing Constant Speed Signals with Short Signals During Wheelset Acceleration and Deceleration
ZHANG Wei, DONG Dawei, HUANG Yan, YAN Bing, HUA Chunrong, LYU Lumei, SONG Shizhe
 doi: 10.3969/j.issn.0258-2724.20220523
[Abstract](132) [FullText HTML](88) PDF 4151KB(30)
Abstract:

The characteristic value of train wheelsets is closely related to the speed, and the quantitative analysis of wheelset faults requires signals with a certain length collected at a certain speed. However, such a signal is difficult to be obtained by the system working in the variable speed condition. Therefore, a signal reconstruction method that did not require any velocimeters was proposed to realize the above quantitative analysis. This method used short signal segments to splice the constant speed signals under the acceleration and deceleration conditions. Firstly, a short-time Fourier transform (STFT) peak search method was adopted to obtain the speed curve and extract multiple signal segments passing through a specified speed. Secondly, the signal segments were converted into an angular domain signal, and the phase difference between signals was determined by cross-power spectra density (CPSD). Then, according to the phase difference and the length of the front signal, the splicing position of signals was obtained, and interpolation and fusion techniques were used to ensure the continuity of spliced signals. Finally, the spliced angular domain signal was resampled into the time domain signal. A rotor test bench with a similar wheelset structure has verified that during acceleration and deceleration of a cracked shaft, the frequency spectrums of the spliced signals of each speed obtained by this method are highly close to the frequency spectrums of the constant speed signals obtained by the experiment. The relative errors of the 1x and 3x values between the spliced signal of 15.0 Hz and the constant speed signal are only 0.9% and 1.0%, respectively. After adding noise to the signals to be spliced and shortening them to 1.5 cycles, the splicing phase error does not exceed 10°.

Fatigue Properties and Life Prediction of Ultrasonic Rolling EA4T Axle Steel
ZHANG Jiwang, ZHANG Haonan, YANG Bing, SU Kaixin, LI Hang
 doi: 10.3969/j.issn.0258-2724.20220257
[Abstract](246) [FullText HTML](93) PDF 2596KB(29)
Abstract:

In order to study the influence of surface ultrasonic rolling processing (SURP) on the fatigue properties of EA4T axle steel, the EA4T axle steel specimens were firstly treated by SURP technology, and the surface properties of the treated specimens were analyzed. The 3D surface morphologies, roughness, hardness, residual stress, full width at half maximum (FWHM), and crystal size were investigated. Then, the fatigue tests were carried out on the EA4T axle steel specimens using a rotary bending fatigue testing machine. The stress–fatigue life (S-N) curves and crack propagation behaviors were obtained, and the effect of SURP on fatigue properties and crack propagation behaviors of EA4T axle steels was analyzed. Finally, a back propagation (BP) neural network was used to establish the fatigue life prediction model of SURP EA4T axle steel, which took load stress amplitude, surface roughness, surface FWHM, surface hardness, hardened layer depth, surface residual stress, and depth of residual stress layer as input. In addition, the life of SURP EA4T axle steel specimens was predicted. The results show that SURP can reduce the surface roughness of the specimens to 0.17 μm and remove the groove morphology. Meanwhile, the surface hardness of the specimens is improved to 420 HV, and a surface residual stress of about −500 MPa and a residual stress layer with a depth of about 550 μm are introduced. There are conventional fatigue limits for grinding specimens, grinding with polishing specimens, as well as SURP specimens. The fatigue properties of grinding specimens and grinding with polishing specimens are basically the same, with a fatigue limit of 355 MPa. The fatigue property of SURP specimens is improved significantly, with a fatigue limit of 455 MPa, an increase of 28% compared with the grinding specimens. Fatigue fracture observations show that the fatigue cracks of all specimens initiate from the surface, and SURP cannot change the fatigue damage mechanism of the specimen. SURP can increase the threshold value of crack propagation of the specimen from 6.29 MPa·m1/2 to 11.21 MPa·m1/2, and it can slow down the crack initiation and propagation of short cracks, thus significantly improving the fatigue property of EA4T axle steel. The fatigue life prediction model of SURP EA4T axle steel has a prediction accuracy of 88.5%.

Formation Mechanism of Metro Wheel Polygonal Based on Vehicle-Track Coupling
SHI Yixuan, DAI Huanyun, MAO Qingzhou, SHI Huailong, WANG Qunsheng
 doi: 10.3969/j.issn.0258-2724.20220785
[Abstract](235) [FullText HTML](135) PDF 5626KB(45)
Abstract:

Wheel polygonal wear will deteriorate the vibration environment of rail vehicles, lead to resonance fatigue failure of structural components, and seriously threaten driving safety. To study the formation mechanism of wheel polygonal wear of metro vehicles, the dynamic line tracking test was carried out, and the vertical coupling finite element model and dynamics model of the track were established. In addition, the iterative simulation analysis of long-term wheel-track wear was carried out. The results show that the wheel polygonal wear of 7–9th order occurs in the measured vehicle, which leads to the forced vibration of 50–70 Hz, and the frequency is close to that of the P2 force during the coupling vibration of the wheel-track system. Through the iterative simulation analysis of wheel wear, it is determined that P2 force resonance of the wheel-rail system caused by periodic irregular rail joint weld is the root cause of the 7th–9th order wheel polygonal wear. Under the long-term action of P2 force, the floating slab track bed and the ladder sleeper track bed of steel spring will cause 8th and 15th order wheel polygonal wear, respectively.

Hyperpath Searching Algorithm Method Based on Signal Delay at Intersections
DU Muqing, JU Ziyan, LI Dawei
 doi: 10.3969/j.issn.0258-2724.20220387
[Abstract](102) [FullText HTML](23) PDF 2118KB(10)
Abstract:

The periodic change of intersection signals in urban road systems leads to the uncertain delay of vehicle travel. In order to reduce the delays of vehicles at signal-controlled intersections, an improved hyperpath searching algorithm was proposed with the minimization of travel time on the road segments and the expected delay at the intersections as the optimization goal. First, according to the probability distribution function of vehicles arriving at the intersection, the expected waiting time and the turning movement proportion were derived. Then, the high-performance hyperpath searching algorithm was developed with the introduction of the label setting algorithm. Finally, the improved hyperpath searching algorithm was applied to the road network at Xinjiekou area, Nanjing, and the optimal hyperpath set was used to evaluate the applicability of the algorithm. The results show that compared with the shortest path strategy, hyperpath searching algorithm reduces the intersection delay and the total travel time by 67.1% and 22.3%, respectively as drivers shift to a driving route in the optimal hyperpath set. Furthermore, the hyperpath-based strategy can optimize the trip distribution in the road network, alleviating traffic congestion and contributing to flow equilibrium.

Method for Compressing Departure Tracking Interval of High-Speed Trains Based on Pre-departure Strategy
LU Gongyuan, HU Liuyang, PENG Hui, ZHANG Hongxiang, ZHANG Shoushuai
 doi: 10.3969/j.issn.0258-2724.20220064
[Abstract](77) [FullText HTML](27) PDF 2384KB(7)
Abstract:

The departure tracking interval is one of the main bottlenecks that limit the 3-minute tracking operation of trains, and compressing the departure tracking interval can effectively improve line capacity. The departure tracking process of high-speed trains was first analyzed, and a pre-departure annunciator was set at a certain distance inside the outbound annunciator, making the train have a certain initial speed and shortening the remaining outbound distance when the outbound annunciator was open. At the same time, the principle of “failure-oriented safety” for the pre-departure process was put forward to ensure that the train did not cross the outbound annunciator. Then, based on the analysis of factors affecting the compression of departure tracking interval, the curves of train control mode under different pre-departure schemes were studied. Finally, the high-speed yard of Shanghai Hongqiao Station was studied, and the results show that the departure tracking interval can be compressed by the proposed method. The compression effect increases first and then decreases with the increase in the pre-departure distance, and the maximum compressible departure tracking interval can be more than 26 s if the pre-departure distance reaches 200 m of the effective lengths of the arrival-departure track.

Determination of Influence Range of Urban Traffic Congestion and Identification of Key Road Sections
ZHAO Xueting, HU Liwei, KOU Fangling
 doi: 10.3969/j.issn.0258-2724.20220413
[Abstract](94) [FullText HTML](24) PDF 4679KB(26)
Abstract:

In order to determine the influence range of non-point source traffic congestion and identify key road sections, the risk field strength theory and the regional growth method were introduced to improve the plume model. The maximum and core influence ranges were determined, and key road sections were identified. First, the “source-path-sink” of non-point source traffic congestion was defined, and the “source” risk field strength model of non-point source traffic congestion was constructed based on the traffic survey data and traffic status data in Guiyang in 2021. By considering the traffic influence of different land use properties and the adjustment coefficient of different road grades for calibration, the identification model of the maximum influence range was established based on different “source” risks, and the regional growth method was introduced to establish a model for determining the influence range of the core area of the road section. Finally, based on the traffic volume, length, and time of the road section, the damage evaluation index of the road section with traffic congestion was constructed, and quantitative research on the degree of traffic congestion was carried out. The original model, the improved model, and the actual situation were compared. The results show that different land use properties and different road grades have different influences on traffic congestion in road sections. The improved identification model of influence range based on different “source” risks is more effective, and the prediction accuracy is increased by 3.54%, which is closer to the actual situation. With the regional growth method, the accuracy of the influence range of the core area of the road section with traffic congestion is higher, which is 2.66% different from the actual situation. In summary, a new idea for the delineation of the cumulative risk range of urban non-point source traffic congestion and the determination of key risk paths is provided, also serving as a theoretical basis for further governance of different types of traffic congestion.

Lightweight Detection of Railway Object Intrusion Based on Spectral Pooling and Shuffled-Convolutional Block Attention Module Enhancement
CHEN Yong, WANG Zhen, ZHANG Jiaojiao
 doi: 10.3969/j.issn.0258-2724.20220074
[Abstract](61) [FullText HTML](24) PDF 3113KB(7)
Abstract:

In infrared low-light scenes, railway object intrusion detection faces low detection accuracy, and it is difficult to achieve lightweight real-time detection. Therefore, a lightweight detection method of railway object intrusion based on convolutional block attention module (CBAM) enhancement was proposed. Firstly, the Darknet53 feature extraction network was improved by deep separable convolution to achieve lightweight extraction of railway object intrusion characteristics in infrared low-light scenes. Secondly, semantic-guided infrared spectral pooling was used for feature enhancement to improve the feature quality of infrared image downsampling. Then, a shuffled-CBAM (shuffled-CBAM) was proposed to achieve feature extraction and fusion of key infrared targets and improve the accuracy of infrared target detection. Finally, the lightweight anchor-free network was used to predict the output result of railway object intrusion, overcoming the deficiency of poor real-time performance due to non-maximum value suppression operation with anchor frame detection, and it reduced calculation load and speeded up the detection efficiency. The experimental results show that the lightweight model has higher detection accuracy, and the size of the model is reduced by 179.01 MB after the improvement. The detection rate is increased to 39 frames/s, which is 3.9 times that of the YOLOv4 method. Compared with other detection methods, the proposed method can detect infrared railway object intrusion quickly and accurately.

Consolidation Solution of Aquitard Induced by Dropping of Groundwater Table with Continuous Drainage Boundary
JIANG Liuhui, LI Chuanxun, WU Wenbing, MEI Guoxiong
 doi: 10.3969/j.issn.0258-2724.20220473
[Abstract](172) [FullText HTML](83) PDF 1964KB(28)
Abstract:

In order to investigate the influence of the drainage boundary, which can better reflect the actual permeability, on the land subsidence caused by over-exploitation of groundwater, firstly, a one-dimensional consolidation model of aquitard caused by the dropping of groundwater table in phreatic aquifer with continuous drainage boundary was established by introducing the continuous drainage boundary, where the pore pressure decayed exponentially with time. Secondly, the general analytical solutions of the model and the analytical solutions of two special precipitation models for the instantaneous dropping of the groundwater table and the single-stage and constant-rate dropping of the groundwater table were obtained by using the method of separate variables. Then, the correctness of the analytical theory in this paper was preliminarily verified by the degeneracy of the analytical solutions under certain conditions. Finally, the single-stage and constant-rate dropping of the groundwater table was taken as an example, and the consolidation curves of the aquitard under different interface parameters B were calculated based on the analytical solutions. In addition, the influence of interface parameter B on the consolidation behaviors was analyzed emphatically. The results show that the maximum error rate is 13% by comparing the theoretically calculated settlement curve with the experimental settlement curve, which further indicates that the continuous drainage boundary is closer to the actual permeable boundary. Furthermore, larger interface parameter B indicates (better water permeability of the drainage boundary) a faster pore pressure dissipation rate, faster consolidation rate, and shorter consolidation time, but the final consolidation state is not affected.

Short-Period Error Suppression Method of PCB-Based Inductive Linear Displacement Sensor
TANG Qifu, LI Mi, ZHAO Jing, GUO Yangting, PENG Song
 doi: 10.3969/j.issn.0258-2724.20220450
[Abstract](179) [FullText HTML](70) PDF 3114KB(28)
Abstract:

In the linear displacement measurement, the printed circuit board (PCB)-based new inductive displacement sensors is easy to lead to short-period errors in manufacturing, assembly, and other process links because of its large pitch. Among the types of short-period errors caused, the first-order and fourth-order errors are the most common short-period errors in PCB-based inductive linear displacement sensors. Therefore, in order to reduce the first-order and fourth-order errors, the generation mechanism of these two kinds of errors was first studied from the output signals, and then an error self-correction method that did not depend on external reference was proposed. Firstly, the sources of short-period first-order and fourth-order errors and the functions of the two errors with the original sine (SIN) and cosine (COS) signals of the sensor were analyzed theoretically. Then, a short-period error function model based on the characteristics of the original SIN and COS signals of the sensor was established, and the corresponding parameters of the first-order and fourth-order errors in the error function model were calculated based on the measured data of the sensor prototype. Finally, the first-order and fourth-order error models were used for the error compensation of the sensor prototype. The results of prototype experiments show that the peak-to-peak value of the error after compensation is reduced from 51.6 μm to 36.2 μm. The short-period first-order error is reduced by about 64.5%, and the short-period fourth-order error is reduced by about 83.0%.

Simulation Research on Coupling Relationship Between Energy Distribution and Dynamic Response of High-Speed Solenoid Valves
ZHAO Jianhui, CHEN Wenfei, YANG Guichun, CHEN Jingyan
 doi: 10.3969/j.issn.0258-2724.20220452
[Abstract](332) [FullText HTML](64) PDF 2347KB(28)
Abstract:

In order to study the energy distribution inside the high-speed solenoid valve and the coupling relationship between the energy parameters and the dynamic response, the performance of the high-speed solenoid valve was optimized. Firstly, the dynamic model of the high-speed solenoid valve was established based on the finite element method, and the accuracy of the model was validated through the experimental data. Secondly, based on the D-optimal design of experiments and the method of least squares, the response surface prediction model of the solenoid valve’s dynamic response characteristics was constructed, with the energy parameters as the factors. Finally, based on the meta-analysis method, the simulation analysis of the dynamic response of the high-speed solenoid valve with significant energy parameters and parameter interactions was carried out. The results show that the eddy energy E1 is the relatively sensitive parameter affecting the response time of high-speed solenoid valve opening To among the single parameters, and To increases by about 25% with the increase in E1. The interaction between E1 and damping energy E3 and between E1 and Joule energy E4 is the highly sensitive parameter affecting To, and the interaction between E1 and E4 is the highly sensitive parameter affecting the response time of closing Tc. The results also find that the factors that play a dominant role in the interaction parameters change with the range of values.

Braking Energy Utilization in Urban Rail Transit: Status and Prospects
LIU Jizong, ZHANG Zutao, WANG Hao, KONG Lingji, YI Minyi, ZHU Zhongyin
 doi: 10.3969/j.issn.0258-2724.20220676
[Abstract](380) [FullText HTML](381) PDF 4077KB(65)
Abstract:

The development of urban rail transit plays an important role in alleviating urban traffic congestion, and its regenerative braking energy utilization technology has attracted much attention. At present, the inverter regenerative braking energy utilization technology includes the topology structure of the feedback circuit, vehicle-network voltage relationship, and feedback device optimization. Other regenerative braking energy utilization technologies include various energy storage types such as supercapacitor energy storage, flywheel energy storage, and battery energy storage. On this basis, the regenerative braking energy utilization technology in urban rail transit based on inverter feedback and energy storage feedback was systematically and comprehensively reviewed, and the characteristics, trends, and key research issues in the development process of the technology were pointed out in terms of improving energy storage density, system stability, and device life, so as to provide guidance for further exploration and commercial development in this field. In addition, the research trends of regenerative braking energy utilization technology in urban rail transit were analyzed, and future research can focus on system topology optimization, energy storage capacity, system stability, service life, and technical and economic analysis.

Numerical Analysis of Multiphysics Coupling of Grout Penetration
CHEN Feng, YANG Jie, ZHANG Chong, YU Zhen, LIU Xianfeng
 doi: 10.3969/j.issn.0258-2724.20220763
[Abstract](206) [FullText HTML](52) PDF 2504KB(29)
Abstract:

Grout penetration in the unsaturated formation is a complex multiphysics process. In order to analyze more accurately the penetration characteristics of grout in saturated and unsaturated formations and estimate the range of grout penetration and grout compaction area, a multiphysics coupling model for unsaturated porous media was developed based on mixture theory. A novel five-degree-of-freedom eight-node quadrilateral axisymmetric Serendipity element was constructed through the secondary development of ABAQUS, so as to realize the numerical solution of soil deformation, soil porosity, pore pressure, and grout concentration distribution during grouting. The state variables, such as soil saturation and permeability coefficient, were updated in real time. The effects of grout water-cement ratio, grouting pressure, initial dry density, and water content of soil on the grouting in silty sand were analyzed with a three-dimensional axisymmetric grouting example, and the fitting curves of horizontal and vertical diffusion distance of grout with the above factors were obtained. The results show that the range of grout penetration is most significantly influenced by the water-cement ratio, followed by the grouting pressure, and it is least influenced by the water content and dry density of soil; the range of grout penetration increases with the increase in the water-cement ratio, especially when the water-cement ratio is greater than 1.0; a compacted area will be formed around the grouting pipe, where the soil is simultaneously subject to the grouting pressure and pore pressure; with the increase in the distance from the grouting pipe, the porosity of the soil gradually decreases in the compacted area and gradually recovers outside the compacted area, while the compacted area increases with the increase in the grouting pressure. The research results can provide theoretical guidance for calculating the grouting reinforcement in the soil.

Wind-Induced Vibration of 400 km/h Trains with Vertical Sound Barrier on Highspeed Railway Bridge
LI Xiaozhen, ZHANG Xiaobang, ZHENG Jing, XU Hong, CHEN Feng
 doi: 10.3969/j.issn.0258-2724.20220033
[Abstract](217) [FullText HTML](133) PDF 2044KB(47)
Abstract:

The increasing speed of high-speed trains makes the dynamic problem of sound barriers prominent. In this study, the dynamic amplification factor of vertical sound barriers caused by high-speed trains was taken as the research object to explore the vibration characteristics and influencing parameters of vertical sound barriers. Firstly, the finite element model of the vertical sound barrier on a high-speed railway bridge was established, and its basic dynamic characteristics were analyzed. Then, the vibration law of the sound barrier under the fluctuating wind load of 400 km/h train was studied, and the dynamic amplification factor of the sound barrier steel structure was calculated based on it. Finally, the vibration response and dynamic amplification factor of the sound barrier were analyzed with multiple parameters. The results show that the dynamic amplification factor of the sound barrier column with a height of 5.0 m is about 2.76 when the train’s speed is 400 km/h. The distance between the installed sound barrier and the center line of the track is increased from 3.8 m to 4.7 m, and the dynamic amplification factor of the bending moment response is reduced by 0.3. The dynamic magnification factors of the bending moment responses of sound barrier columns with a height of 2.3, 3.3, and 5.0 m are 1.64, 2.52, and 2.76, respectively. The transverse displacement of the top is increased from 0.45 mm to 3.80 mm, while the bending moment of the bottom is increased by 26.8% and 60.8%, respectively. Increasing the height of the sound barrier is not conducive to the vibration characteristics of the structure.

Line Shape of Boundary Transition Section of Terrain Model at Bridge Sites in Complex Mountainous Areas
ZHANG Mingjin, YAN Tingyuan, HU Bo, CHEN Hongyu, LI Yongle
 doi: 10.3969/j.issn.0258-2724.20220282
[Abstract](155) [FullText HTML](82) PDF 2242KB(34)
Abstract:

The curve of the transition section of the terrain model at bridge sites in complex mountainous areas directly affects the accuracy of the wind tunnel experiment or numerical simulation results. To study the ideal form of line shape used in the boundary transition section of the terrain model at the bridge site, the principle of constructing line shape of the transition section was put forward based on the two ideas of setting up the transition section. The numerical simulation method was used to compare the three types of typical line shapes of the transition section in terms of the flow separation characteristics, mean wind speed profiles, wind attack angle profiles, and distribution of turbulent kinetic energy along the route under the uniform flow. The influence law of the slope change of the transition section on the flow field was also explored. The results show that the sine-squared curve exhibits superior characteristics compared with other line shapes, with a maximum shear stress difference of 3.77 × 10−3 Pa at the same location in terms of flow separation characteristics, a maximum wind speed difference of 0.09 m/s in terms of transitional performance of wind, and a maximum turbulent kinetic energy difference of 1.46 × 10−3 J. These findings provide important insights for selecting the line shape of the transition section of the terrain model at bridge sites.

Analysis of Bending Natural Vibration Characteristics of Box Girder Based on Additional Deflection for Shear Lag
ZHANG Yuyuan, ZHANG Yuanhai, ZHANG Hui
 doi: 10.3969/j.issn.0258-2724.20220618
[Abstract](159) [FullText HTML](76) PDF 2041KB(35)
Abstract:

In order to reveal the influence of the bending space effect on natural vibration frequency weakening, the additional deflection caused by the shear lag effect was selected as the generalized displacement, and the warping additional deformation of box girder was incorporated into the total kinetic energy of the system. The bending variational solution of the natural vibration frequency of box girder considering the influence of shear deformation, shear lag, and their double effects was established by using the Hamilton principle. The difference ratio parameter of spatial effect on natural vibration frequency weakening was introduced, and the influence of the section size and the side-to-middle span on the difference ratio parameter was analyzed in detail. The example analysis shows that the analytical solution of the natural vibration frequency of the box girder considering shear derformation and double effects is in good agreement with the finite element numerical solution. A larger frequency order indicates a greater weakening degree of each effect to the natural vibration frequency. The double effect is the most significant, which reduces the natural vibration frequency of simply supported and continuous box girders by 4.72% and 4.80% respectively for the first-order frequency. The larger span width ratio, width-to-height ratio, and side-to-middle span ratio indicate a smaller difference ratio of natural vibration frequency. A larger plate width ratio is accompanied by a smaller difference ratio of natural vibration frequency considering shear lag and double effect and a larger difference ratio of natural vibration frequency considering shear derformation . At the same span width ratio, shear lag and shear derformation effects weaken the natural vibration frequency to the same extent. At the different width-to-height ratio ratios, the shear lag effect weakens the natural vibration frequency to almost the same extent, and the shear derformation effect has a more significant impact. Low-order natural vibration frequency can be calculated using a box girder without a cantilever plate.

Characteristics and Significance of New Geological Tectonic Activities in Niba Mountain Fault Zone
DENG Ronggui, ZHONG Zhibin, WANG Wenpo, WANG Yuanyuan, ZHANG Jin, LIU Yuancheng
 doi: 10.3969/j.issn.0258-2724.20220376
[Abstract](158) [FullText HTML](58) PDF 5236KB(25)
Abstract:

New geological phenomena have been found in the structural geological mapping of Niba Mountain tunnel field of Ya’an to Xichang section of Beijing−Kunming Expressway. To demonstrate the nature of the Niba Mountain fault zone and new tectonic phenomena of regional geological tectonic significance, using quartz particle morphology scan, geological mechanics and rockmass mechanics theory and numerical simulation analysis method, first elaborated the area of Niba Mountain tunnel engineering geological environment and the new tectonic phenomena, and then discusses the Niba Mountain fault zone boundary faults and tectonic activity, Secondly, the regional geological tectonic significance of the neotectonic phenomenon is discussed. Finally, the existence of the neotectonic phenomenon and the rationality of the evidence of the regional tectonic new framework are demonstrated by numerical simulation analysis. The results show that: 1) the Niba Mountain fault zone has obvious neotectonic activity characteristics; 2) the Niba Mountain fault zone to which the new tectonic deformation phenomenon belongs has genetic homology with the Xianshuihe active fault zone in the “Y” shaped active tectonic zone in western Sichuan, which is the southeast extension of the Xianshuihe fault zone; 3) the Niba Mountain fault zone and its southeastern extension fault (Ebian−Mabian−Leibo segment) and the “Y” shaped active tectonic zone in western Sichuan constitute the original “X” type tectonic model, and have the conditions for the breeding of moderate and strong earthquake activities.

Research on Thermal Aging Characteristics of Vehicle-Mounted Cable Terminal Stress Control Tube and Its Influence on Insulation Performance
SUN Chuanming, LIU Kai, ZHANG Pengpeng, XIN Dongli, GAO Bo, LI Guangjian, WU Guangning
 doi: 10.3969/j.issn.0258-2724.20220164
[Abstract](80) [FullText HTML](54) PDF 3010KB(38)
Abstract:

In order to determine the thermal aging characteristics of the vehicle-mounted cable terminal stress control tube and its influence on the insulation performance of cable terminal under thermal aging conditions, firstly, the macro-dielectric characteristics and micro-aging law of vehicle-mounted cable terminal stress control tube were determined through experimental research. Secondly, based on the analysis of the electrical conductivity, polarization, and loss characteristics of the stress tube material under thermal aging, the dielectric characteristic curves under different aging periods were obtained. Finally, a finite element model of the electric field of the vehicle-mounted cable terminal was established by considering the aging characteristics of the stress control tube, and the electric field distribution of the cable terminal of the stress control tube was calculated based on the dielectric parameters under thermal aging. The results show that the electrical conductivity increases most significantly at 140 °C and reaches the maximum value of 1.1 ´ 10−10 S/m at a field intensity of 50 kV/m. The relative dielectric constant reaches the minimum value of 14.00 at high temperature (140 °C) for 20 days. In addition, trap hindrances such as folding and breaking of polymer long chain are enhanced during pyrolysis reaction, and the dielectric loss increases. In terms of functional group characteristics and microstructure of the stress control tube, thermal aging results in pyrolytic polymerization of olefin polymers in stress control tube materials, forming chemical stereoscopic defects. In addition, the cracking of polymer spherulites and the formation of inorganic oxidation products on the surface of the stress control tube sample are intensified, and the physical and chemical properties of the sample surface are changed. Simulation results show that under thermal aging conditions, the electric field distortion area inside the cable terminal presents a trend of expanding, creeps along the stress control tube towards the terminal high voltage, and finally stabilizes at the junction of the main insulation layer of ethylene propylene rubber (EPR) and stress control tube.

Crossing Power Governance Approach of Continuous Power Supply System in Electrified Railway
LI Qunzhan, PENG You, HUANG Xiaohong, WANG Hanlin, REN Tao
 doi: 10.3969/j.issn.0258-2724.20220887
[Abstract](121) [FullText HTML](48) PDF 2232KB(11)
Abstract:

A novel crossing power governance approach was proposed to mitigate the effects of crossing power in the traction power supply system while taking regenerative braking energy utilization into account. First, the power flow under different operating conditions was derived based on the structure of the continuous power supply system, and the method for detecting crossing power was analyzed. Second, a power transfer and energy storage unit was set using the single-phase combined co-phase traction substation, and the working mechanism of the improved system was analyzed. Then, a cooperative control strategy of crossing power governance was proposed by combining the upper control strategy of power distribution and negative sequence satisfactory compensation with the lower control strategy of converter control. Finally, the amount of crossing power was calculated using the experimental data of a railway line, and the cost-effectiveness of the governance measure was evaluated. In addition, the accuracy and efficacy of the proposed scheme were verified by simulation. The research results show that the proposed system and its control strategy can effectively mitigate the crossing power and regenerative braking energy, with the utilization rate of the crossing power of the power transfer and energy storage unit exceeding 70% in the case of traction substation and traction network loss. The system is highly economical and feasible.

Theoretical Study on Uplift Calculation of Embedded Twelve Ground Screws of Transmission Angle Steel Tower
HE Songyang, YAN Xiuqing, LI Zhengliang, LIU Xiangyun, LI Zhong, GONG Tao
 doi: 10.3969/j.issn.0258-2724.20230011
[Abstract](57) [FullText HTML](27) PDF 3589KB(5)
Abstract:

In order to solve the problem of ground screw connection under large load of transmission angle steel tower, an embedded twelve ground screw joint structure was proposed. Based on the plastic yield line theory of stiffness difference evolution, the influence of the position of ground screws and the stiffness difference between ground screws and tower foot plates was considered, and the theoretical formula of uneven internal force between embedded ground screws and external ground screws under uplift load was derived. Then, combined with 24 sets of refined numerical analysis, the influence of different ground screw diameters, ground screw spacings, and tower foot plate thicknesses on the differences in uplift forces of internal and external ground screws was studied, and the correction coefficient of stiffness difference was calibrated. Finally, the theoretical formula was verified by 72 sets of numerical experiments. The research results show that the embedded twelve ground screw structure can improve the uplift bearing capacity of the joint by 40%–50% compared with the traditional eight ground screw structure; when the internal ground screw is arranged on the orthogonal line of the external ground screw, the uneven distribution coefficient of internal force of the internal and external ground screws under the uplift load is about 1.1, and it does not change with the diameter of the ground screw and the thickness of the tower foot plate. When the internal screw is close to the external screw along the diagonal, the uneven distribution coefficient of the internal force of the internal screw will decrease, but when the thickness of the tower foot plate increases, the uneven distribution coefficient will increase. The calculation results based on the plastic yield line theory of stiffness difference evolution of the tower foot plate are compared with the numerical simulation results. The average value of the ratio of the theoretical uneven distribution coefficient to the numerical uneven distribution coefficient is 1.01, and the coefficient of variation is 0.03.

Optimization Analysis and Monitoring of Construction Process of Open Spherical Reticulated Shell Structure with a Large Rise-to-Span Ratio
SHI Kairong, LIN Zhiyi, JIANG Zhengrong, CHEN Chunguang, CHEN Yiqiao, LIANG Jun
 doi: 10.3969/j.issn.0258-2724.20220228
[Abstract](139) [FullText HTML](76) PDF 2570KB(15)
Abstract:

To ensure the construction safety of the complex spatial grid structure, the optimization analysis and monitoring of the construction process were carried out. An open single-layer spherical reticulated shell structure with a large rise-to-span ratio was taken as an example, and the construction process of this complex special-shaped structure was simulated through finite element analysis (FEA). By changing the boundary conditions of the support, the shape of the rib axis, and the support mode of the temporary support jig frame, different FEA models were established. The stress variations of key members and the structural displacement were analyzed to optimize the construction process. On this basis, the arc rod model with a temporary support jig frame was used as the final calculation model for construction process simulation, and the calculation results before and after unloading were compared with the on-site monitoring data to verify the accuracy of the FEA model in simulating the construction process. The failure sensitivity of the temporary support jig frame was further studied to avoid structural safety problems. The results show that the FEA model is consistent with the actual structure. The stress of each measuring point before and after unloading changes slightly, and the maximum tensile and compressive stress changes are 10.61 MPa and −5.67 MPa, respectively. The special-shaped spherical reticulated shell with a large rise-to-span ratio is in a controllable state during construction. The failure of a certain temporary support jig frame would have a great influence on member stress and structural displacement in the adjacent area. The maximum change of the member stress is 28 MPa, and that of the vertical displacement is 13 mm. Therefore, the reliability of the support jig frame shall be ensured during the construction.

Display Method:
Rail Transit “Network-Source-Storage-Vehicle” Collaborative Energy Supply Technology System
GAO Shibin, LUO Jiaming, CHEN Weirong, HU Haitao, TU Chunming, CHEN Yanbo, XIAO Fan, WANG Feikuan
2024, 59(5): 959-979, 989.   doi: 10.3969/j.issn.0258-2724.20220210
[Abstract](333) [FullText HTML](204) PDF 8327KB(112)
Abstract:

In order to minimize energy consumption in rail transit systems, the coordinated power supply technology of “network-source-storage-vehicle” integrates with renewable energy power generation systems along the line. This approach establishes a new coordinated power supply technology system that enables efficient energy utilization across time and space. This paper comprehensively analyzes the fundamental composition and characteristic types of physical, informational, and social architectures within the coordinated power supply system. Building upon this analysis, it introduces a temporal and spatial matching evaluation method for "load-source" based on the core concept of asset energization from a systemic comprehensive evaluation and operational perspective. Furthermore, it elaborates on important technological systems such as multi-source integration, protection reconstruction, and elastic evaluation. Emphasizing efficient energy-saving operations, it focuses on high-efficiency and high-resilience energy self-consistency technology through coordination among network, source, storage, and vehicle components. Additionally, leveraging artificial intelligence and information technology tools is proposed to construct multi-level energy management systems aimed at achieving effective coupling of diverse energy flows while ensuring safe, stable, and cost-effective operation of the system. The paper systematically summarizes key technologies related to the “network-source-storage-vehicle” coordinated energy supply system for rail transit including architectural characteristics; evaluation; optimization; safe operation; as well as coordinated operation of the system. It also outlines technical composition systems relevant to coordinated energy supply systems providing valuable references for engineering practices.

Current-Mode Variable Frequency Control Technique for Single-Inductor Dual-Output Switching Converter with Independent Charge and Discharge Sequence
HE Mingzhi, LIN Runze, ZHOU Shuhan, FENG Pei, LI Huan, WANG Dengfeng
2024, 59(5): 980-989.   doi: 10.3969/j.issn.0258-2724.20220535
[Abstract](283) [FullText HTML](100) PDF 4094KB(59)
Abstract:

Single-inductor dual-output (SIDO) switching converters with shared charge and discharge sequence have problems of the large inductor current ripple and cross-regulation between output branches, and the control circuit fails to work normally under the wide range of changes in circuit parameters. To solve these problems, a current-mode variable frequency control (C-VF) technique with an independent charge and discharge sequence was proposed. First, the working principle of the converter in continuous conduction mode (CCM) was specifically described, and the open-loop transfer function of the main circuit was derived. Furthermore, a closed-loop small signal model was constructed, and the closed-loop cross-regulation impedance transfer functions were derived. The cross-regulation characteristics of the converter with different output voltages and load currents were analyzed in detail. Finally, simulation and experimental verification were carried out. The results show that compared with the shared charge and discharge sequence, the C-VF CCM SIDO buck convert with independent charge and discharge sequence reduces the cross-regulation and improves the transient load response performance. When the load voltages of the two branches are different, decreasing the load of one branch can reduce the cross-regulation of this branch to another one. When the output voltages of the two branches are the same, but the loads are different, the branch with heavy loads has small cross-regulation on the branch with light load.

Friction and Wear Performance of Pantograph-Catenary System in Electrified Railways: State of the Art
ZHOU Ning, ZHI Xingshuai, ZHANG Jing, ZHENG Wei, LUO Chaoji, ZHANG Weihua
2024, 59(5): 990-1005, 1022.   doi: 10.3969/j.issn.0258-2724.20220053
[Abstract](209) [FullText HTML](210) PDF 3552KB(67)
Abstract:

For pantograph-catenary contact pairs in electrified railways operating in normal and abnormal states, the friction and wear performance of pantograph strip differentiates in a wear cycle, highlighted by differences in wear rate and wear profile. When abnormal wear occurs, the wear rate of pantograph strip will have a multifold increase or even dozens of times increase, but the wear profile acts differently, revealing partial eccentric wear, wavy wear, and penetrating wear. The similarities and differences in current-carrying friction and wear platforms are summarized for pantograph-catenary systems, as well as the advantages and disadvantages of contact and non-contact detection methods. The influential factors and evolution law are analyzed in view of the structure and parameters, train operation parameters, current-carrying parameters and external environment of pantograph-catenary system. Following above work, the state of the art of pantograph-catenary wear models, including mechanism analysis model and data fitting model, are analyzed extensively, and the prospective direction and development trend are put forward, such as, the equivalent simulation of a pantograph-catenary friction pair in real service under laboratory conditions, online high-precision detection of pantograph-catenary wear performance, simulation and optimization of pantograph-catenary wear performance in complex climatic conditions and multi-physical field coupling, pantograph-catenary wear prediction using big data and intelligent algorithms, intelligent operation and maintenance strategies, and capability maintenance in the whole life cycle.

Identification of Vulnerable Lines in Power Grid Based on Power Flow Correlation Network
FAN Wenli, YE Yurun, LI Quanyou, XIAO Yeqi, XIONG Liying, HE Xiaofeng
2024, 59(5): 1006-1013.   doi: 10.3969/j.issn.0258-2724.20210535
[Abstract](225) [FullText HTML](104) PDF 1928KB(95)
Abstract:

Global blackouts have indicated that vulnerable lines in the power system would bring great operation risk and threaten system security. In view of this, the identification of vulnerable lines in the power system was carried out according to the transfer characteristics of the active power flows in the case of a two-stage cascading failure. First, from the perspective of system operation, the relationship between the lines was weighted in terms of the transferred active power flows when the power system had a two-stage cascading failure, and a bidirectional weighted power flow correlation network was constructed. Then, an improved E-index-based identification method for vulnerable lines was proposed to quantify line vulnerability in cascading failures. The results show that the average value at risk and the average conditional value at risk of the top eight vulnerable lines in the identified results are 3 453.73 MW and 187.82 MW respectively for the IEEE-39 bus system, which are much higher than those obtained from other methods. Meanwhile, the residual load rate of the system is only 43.4% after the static intentional attack, and the number of power islands in the system increases rapidly.

Throughput Performance Analysis and Optimization of Energy Harvesting Wireless Sensor Network Based on Simultaneous Wireless Information and Power Transfer
LI Cuiran, YANG Qian, XIE Jianli, LYU Anqi
2024, 59(5): 1014-1022.   doi: 10.3969/j.issn.0258-2724.20220625
[Abstract](244) [FullText HTML](102) PDF 2296KB(64)
Abstract:

In view of two-hop multi-relay transmission in energy harvesting wireless sensor networks (WSN), a wireless radio frequency power beacon (PB)-assisted energy harvesting relay model based on simultaneous wireless information and power transfer (SWIPT) was constructed. Under the condition that the relay node has the characteristics of capturing the source node, loop self interference, and PB signal energy, the outage probability and throughput of the destination node using two different receiving strategies, namely, selection combining (SC) and maximal ratio combining (MRC), were derived. Then, under multiple constraints such as ensuring communication quality of service (QoS), a relay selection algorithm was proposed to jointly optimize the time switching factor and power splitting factor with the goal of maximizing the throughput. Simulation and numerical results show that the PB transmit power, time switching factor, number of antennas, and power splitting factor significantly affect the system’s outage probability and throughput. When PB transmit power is 6 dBW, and the number of antennas is 3, compared with the random relay selection algorithm and the max-min relay selection algorithm, the system’s throughput gains under the SC strategy are 0.29 and 0.15 bit/(s·Hz), respectively, and those under the MRC strategy are 0.32 and 0.16 bit/(s·Hz), respectively.

Testing Modeling Method for Engineering Testing of High-Speed Railway Signaling System
SHI Zengshu, LI Yao, GUO Jin, ZHANG Yadong
2024, 59(5): 1023-1033.   doi: 10.3969/j.issn.0258-2724.20220674
[Abstract](251) [FullText HTML](59) PDF 2203KB(63)
Abstract:

The engineering testing of a high-speed railway signaling system (HSRSS) focuses on the complex behavior relationship and state synchronization among various equipment in the system. Since the testing modeling method for engineering testing lacks complex behavior interaction and synchronization mechanism, the engineering testing modeling method and test case generation method of HSRSS based on an extended finite state machine (EFSM) were proposed. First, the engineering testing characteristics of HSRSS were analyzed, and the testing modeling requirements for complex event interaction and state synchronization were proposed. Based on the theory of finite state machine, the state events and hierarchy were extended to meet the modeling requirements for complex behavior relationships and state synchronization in engineering testing of HSRSS. The formal definition of EFSM was given by using Z specification language. The pattern and synchronization mechanism of EFSM were defined. Then, the algorithm of transforming the EFSM into a timed automata (TA) was put forward, and the test case generation algorithm of TA was used to automatically generate test cases for engineering testing of HSRSS. Finally, with the route control in engineering testing of HSRSS as an example, an EFSM model was established, and test cases were generated. In addition, the generated test cases were evaluated through mutation analysis. The result shows that the test cases have a mutation score of 1 when testing state mutation and signal expression mutation, and they have good coverage, which can meet the requirements of engineering testing of HSRSS.

Effect of Measured Wheel-Rail Creep Curves on Rail Wear
WANG Ping, SONG Juan, YANG Chunkai, AN Boyang, CHEN Rong
2024, 59(5): 1034-1042.   doi: 10.3969/j.issn.0258-2724.20220392
[Abstract](266) [FullText HTML](185) PDF 2415KB(84)
Abstract:

The wheel-rail creep curve influences dynamic wheel-rail interaction, which further affects rail wear. To study the effect of the measured wheel-rail creep curve on rail wear, parameters suitable for the Polach model and modified FASTSIM algorithm were obtained based on the least square method, and measured creep curves at the running speed of 40–400 km/h of the vehicle were simulated. After that, the vehicle system dynamics model was established in the SIMPACK, and measured creep curves were considered through the Polach model. Finally, the Kik-Piotrowski model and modified FASTSIM algorithm were used to calculate the non-Hertzian rolling contact, and rail wear was predicted by the USFD model. The discrepancies of rail wear under ideal and measured creep curves were compared. The research shows that the rail wear depth under the ideal creep curve is more obvious than that under the measured creep curve. As more vehicles pass the rail, the rail wear distribution range under ideal conditions is larger, and the distribution ranges of inner and outer rail are respectively 1.5 and 1.3 times those under the measured creep curve; the friction coefficient and wear rate significantly influence the magnitude and distribution range of rail wear, so it is necessary to consider the measured wheel-rail creep curve in vehicle dynamics simulation and rail wear calculation. A pre-processing program is developed to determine parameters of the measured creep curve, which can serve for vehicle dynamics simulation and rail wear calculation and effectively guide maintenance work such as rail grinding.

Research Progress on Buckling of Longitudinal Reinforcement Under Earthquake
LI Xi, YANG Hao
2024, 59(5): 1043-1057.   doi: 10.3969/j.issn.0258-2724.20220549
[Abstract](190) [FullText HTML](79) PDF 2377KB(51)
Abstract:

During the outbreak of an earthquake, the pier columns in reinforced concrete (RC) structures are usually subjected to horizontal forces and vertical forces under reciprocating loads. When the transverse constraints in the structure are insufficient, the longitudinal reinforcement may have obvious transverse deformation. The bearing capacity and ductility of the structure are thus significantly reduced, and it is difficult to repair. Therefore, it is of great significance for structural design and construction to study the buckling mechanism of longitudinal reinforcements under compression. Firstly, the research on longitudinal reinforcement buckling based on the direct compression test of a single reinforcement was summarized, and the analysis shows that the main influencing factors of reinforcement buckling are the slenderness ratio and yield strength. Secondly, the research progress of reinforcement buckling based on the direct compression test of RC short columns was summarized, and the possible factors influencing longitudinal reinforcement buckling under complex interaction were described. Moreover, combined with the development status of civil engineering, the research progress of longitudinal reinforcement buckling in pier columns with new materials and structures was discussed. Finally, it is concluded that the current research on longitudinal reinforcement buckling lacks a theoretical method for determining the direction and extent of reinforcement buckling. Further investigations are needed to address the overall buckling issues of longitudinal reinforcements and the longitudinal reinforcement buckling concerns in novel structures. Subsequent studies should comprehensively consider the effect of factors such as corrosion, loading history, cross-sectional geometry, and interactions among materials on longitudinal reinforcement buckling.

Calculation Method for Reinforcement Stress in Ultra-High Performance Concrete Beams Considering Bond-Slip Effect
SUN Yongxin, LIN Pengzhen, YANG Zijiang
2024, 59(5): 1058-1067.   doi: 10.3969/j.issn.0258-2724.20230130
[Abstract](189) [FullText HTML](53) PDF 2112KB(42)
Abstract:

Four-point bending tests were conducted on six ultra-high performance concrete T-shaped (UHPC-T) section beams to establish a reinforcement stress calculation method for reinforced UHPC beams and study the variation law of reinforcement stress. Based on the mechanism of force balance and deformation coordination between reinforcement and UHPC, a reinforcement stress calculation formula was derived using the differential equations of equilibrium, deformation, and bond-slip established by micro elements, which could comprehensively reflect the influence of bond-slip between reinforcement and UHPC interfaces and the contribution of steel fibers to tensile strength. By simplifying the calculation of the strain non-uniformity coefficient and the reinforcement stress in cracked sections, a simplified formula for reinforcement stress suitable for engineering applications was proposed. The results show that the increase in reinforcement stress under unit load decreases with the increase in reinforcement ratio, but it is not related to the change in steel fiber volume fraction. Compared with ordinary concrete beams, the reinforcement stress in UHPC beams is relatively small in the cracked section, but the uneven distribution of reinforcement stress between adjacent cracks is intensified. The calculation value of the suggested formula for reinforcement stress is in good agreement with the experimental values in this article and existing literature. The average ratio of the calculated value of the simplified formula for reinforcement stress to the experimental value is 1.03, and the coefficient of variation is 0.06, indicating that this simplified formula can be used for calculating reinforcement stress in UHPC beams.

Stability Analysis and Evaluation of a Tunnel Entrance Slope Under Complex Disaster-Prone Environments
XU Zhengxuan, LIN Zhiheng, LIU Yunpeng, NIE Xiaofang, REN Li, ZHANG Zhilong
2024, 59(5): 1068-1077, 1085.   doi: 10.3969/j.issn.0258-2724.20220361
[Abstract](248) [FullText HTML](113) PDF 5430KB(69)
Abstract:

Influenced by rainfall, strong earthquakes, and intensive engineering activities, the slope at the tunnel entrance may experience collapses, landslides, debris flows, and other geological disasters, especially under the complex conditions of violent earthquakes, high geostress, abrupt slopes, and extremely cold environments. To explore the stability of tunnel entrance slopes under different working conditions in complex disaster-prone environments, the Jiarishan tunnel in southwest China was taken as an example, and a “space-air-ground” integrated investigation technology combining unmanned aerial vehicle (UAV) photography, surface trenching, laboratory experiments, field tests, and cave surveys was employed to obtain accurate engineering geological information. Typical failure characteristics of the studied slope were systematically revealed, and the two failure causes and evolution models of the slope were discussed. In addition, the slope stability under different working conditions was qualitatively analyzed using the limit equilibrium method and three-dimensional numerical simulation. The results indicate that the stability factor of the slope at the Jiarishan tunnel entrance is always greater than 1.15 under natural, rainstorm, and earthquake working conditions. Overall, the slope is stable except for the local deformation and instability of the shallow horizon of the posterior margin. This research can provide theoretical guidance and technical support for similar tunnels in terms of siting, construction, and operation safety.

Theoretical and Test Study of Impact Force and Impact Depth of Falling Rocks on Buffering Soil Layers
WANG Yusuo, YANG Junxiang, XIAO Zongyang, LI Chuanbao, TIAN Siming, WANG Wei, YAO Qingchen, ZHAO Zhuang
2024, 59(5): 1078-1085.   doi: 10.3969/j.issn.0258-2724.20230303
[Abstract](179) [FullText HTML](72) PDF 2313KB(39)
Abstract:

To elucidate the applicability and feasibility of the calculation methods for impact force and impact depth of falling rocks based on Hertz contact theory, as well as the determination method for the reinforcement coefficient of buffering soil layers, full-scale model tests, inversion analysis, and mathematical statistics methods were employed. The falling rock impact tests were carried out, involving cubic rock and conical rock with a spherical top, each with a volume of approximately 1 m³ and a weight of about 2 t. They were dropped from heights ranging from 1 to 10 m onto buffering soil layers with thicknesses of 0.5–2 m. Then, the reinforcement coefficient of buffering sand layers was determined, and theoretical and test results for impact force and impact depth of falling rocks were comparatively analyzed. The research conclusions are as follows: Based on inversion analysis of the test results, it is recommended that the reinforcement coefficient of buffering sand layers within the 99.7% confidence interval should range from 0.25 GN/m5/2 to 10.00 GN/m5/2. The theoretically calculated average impact force of cubic rock is 140% larger than the test value, while that of conical rock with a spherical top is 21% larger than the test value. The theoretically calculated average impact depth of cubic rock is 112% larger than the test value, while that of conical rock with a spherical top is 5% larger than the test value. Within the 99.7% confidence interval of the reinforcement coefficient, the range of calculated impact force and impact depth of rock can encompass 100% of the test results. Under the same conditions, the test value of the impact depth of conical rock with a spherical top is greater than that of cubic rock. The impact depth increases with the increase in the thickness of the buffering layer, while the variability in the impact force of falling rocks shows no significant correlation with the rock shape and buffering layer thickness.

Experimental Comparison of Horseshoe Prefabricated and Spray Anchor Initial Support Structures
BAI Zhongkun, BI Chengcheng, ZHAO Xiuwang, XUE Yongtao
2024, 59(5): 1086-1094.   doi: 10.3969/j.issn.0258-2724.20220197
[Abstract](225) [FullText HTML](103) PDF 3826KB(37)
Abstract:

In order to study the mechanical deformation characteristics of the new horseshoe prefabricated initial support structure and compare its difference with the spray anchor initial support structure, the prototype loading tests of two types of structures were carried out. The structural design, lining prefabrication, test loading, and result analysis were introduced systematically, and the test results were deeply analyzed. The results show that the ultimate bearing capacity of the prefabricated initial support structure is 2.80 times the design load, and that of the spray anchor initial support structure is 1.32 times the design load. The ultimate bearing capacity of the former is about 2.10 times that of the latter. The prefabricated initial support structure is affected by the positive bending moment and negative axial force at the vault and the arch waist, as well as the negative bending moment and positive axial force at the arch shoulder and the arch bottom. The spray anchor initial support structure is similar. The maximum moment and the maximum axial force of the prefabricated initial support structure are about 1.39 and 1.45 times that of the spray anchor initial support structure near the destruction phase, respectively. The concave and convex deformation trend of the prefabricated initial support structure is basically the same as that of the spray anchor initial support structure. The right arch shoulder is convex, and the right arch waist is concave, with steel and concrete spalling when the structure is damaged, and the ultimate deformation capacity of the prefabricated initial support structure is about 1.20 times that of the spray anchor initial support structure.

Characteristics and Calculation Method of Impact Load in Rockburst Tunnel
LUO Xun, YANG Jie, TIAN Hongtao, LIU Dagang, WANG Xiaoyong
2024, 59(5): 1095-1103.   doi: 10.3969/j.issn.0258-2724.20220373
[Abstract](259) [FullText HTML](121) PDF 1872KB(60)
Abstract:

The hard and brittle surrounding rock in tunnels is prone to rockburst under high ground stress conditions. Currently, the support structure design for rockburst tunnels in China mainly adopts the engineering analogy method. In order to quantify the impact load of the rockburst on the support structure, the energy conversion relationship during the rockburst process was analyzed from an energy perspective. Then, the kinetic energy theorem and energy conservation principle were used to calculate the impact load. Combined with the loose pressure of the tunnel, a load calculation method for rockburst in tunnels was proposed. At the same time, the influence of different factors such as tunnel diameter on the range of rockburst action was explored. Finally, the rationality was verified based on the rockburst section of a high ground stress tunnel. The research results indicate that the dynamic load factor in the formula for rockburst impact load is positively correlated with the structural stiffness used for tunnel support. Under the same span and ground stress conditions, the rockburst depth of a circular tunnel is smaller than that of a horseshoe tunnel, and the lateral range of the rockburst is larger than that of a horseshoe tunnel. Under the same tunnel shape and ground stress conditions, as the tunnel span increases, the depth and lateral range of the rockburst also increase. Under the same tunnel shape and span conditions, a higher ground stress value indicates a greater depth and lateral range of the rockburst. The rockburst load of Grade Ⅱ surrounding rock in a single-track tunnel ranges from 12.02 kPa to 337.75 kPa, and that of Grade Ⅲ surrounding rock in a single-track tunnel ranges from 25.36 kPa to 352.12 kPa. Moreover, the rockburst load of Grade Ⅱ surrounding rock in a double-track tunnel ranges from 8.54 kPa to 288.55 kPa, and that of Grade Ⅲ surrounding rock in a double-track tunnel ranges from 33.11 kPa to 300.83 kPa.

Experimental Investigation of Relative Humidity Response in Early-Age Concrete Under Tensile Stress
ZHAO Haitao, DING Jian, YANG Guo, XIANG Yu, XU Wen, CHEN Yuzhi
2024, 59(5): 1104-1112.   doi: 10.3969/j.issn.0258-2724.20220134
[Abstract](281) [FullText HTML](91) PDF 3079KB(43)
Abstract:

In order to systematically investigate the response law of the internal relative humidity of concrete at an early age to different tensile stress levels, a test method of the internal relative humidity of the concrete under constant axial tension was developed in this paper, and the response law of the relative humidity under different tensile stresses was studied experimentally. According to the experimental results and theoretical analysis, a linear model of the relative humidity and tensile stress of early-age concrete under one-side drying conditions was presented. The results show that the tensile stress causes the instantaneous decrease in the internal relative humidity of the concrete. When the tensile stress increases from 0.8 MPa to 3.2 MPa, the relative humidity change at the depth of 50, 75, and 100 mm of the concrete increases from 0.5%, 0.4%, and 0.3% to 0.8%, 0.7%, and 0.6%, respectively. At the same time, with the increase in tensile stress, the decrease in the relative humidity gradually increases. Under the same tensile stress, the response of relative humidity of the concrete, close to the exposed surface, to tensile stress which is is more obvious. The relative humidity gradually recovers during the tensile stress loading, and the time is about 2.5 h. A similar phenomenon also occurs during the compressive stress loading, and the time is about 20.0 h. Therefore, the relative humidity recovery time is shorter during the tensile stress loading.

Effect of Fly Ash and Silica Fume Contents on Mechanical Properties of Alkali-Activated Slag-Based Concrete
XIA Dongtao, WU Chen, CUI Kai, WU Fanghong, LI Biao, WANG Yu, YU Shiting, LI Yaowei
2024, 59(5): 1113-1122.   doi: 10.3969/j.issn.0258-2724.20230036
[Abstract](186) [FullText HTML](106) PDF 2619KB(54)
Abstract:

In order to study the effect of fly ash and silica fume contents on the properties of alkali-activated slag-based concrete (AASC), the changes in setting time, cubic compressive strength, cubic splitting tensile strength, flexural strength, and elastic modulus of AASC were investigated by conducting tests on setting time and basic mechanical properties. Based on the test results, a regression analysis method was used to establish the conversion relationship equation of cubic splitting tensile strength, flexural strength, and elastic modulus with cubic compressive strength, and the effect of fly ash and silica fume on the properties of AASC was revealed according to the microstructure and phase composition. The results show that the fly ash and silica fume can prolong the setting time of AASC; the mechanical property indicators of AASC tend to strengthen and then weaken with the increase in the contents of fly ash and silica fume, and the optimal contents of fly ash and silica fume are 20% and 10%, respectively. The proposed empirical formulae for cubic splitting tensile strength, flexural strength, and elastic modulus of AASC have a high fitting precision. The appropriate contents of fly ash (silica fume≤20%) and silica fume (silica fume≤10%) can promote the hydration reaction of AASC and the denser microstructures.

Influence of Temperature on Performance and Microporous Structure of Foamed Concrete During Pouring Period
LIU Xin, YAO Yunlong, ZHANG Siqing, SHI Yunqiang, HONG Baoning
2024, 59(5): 1123-1131.   doi: 10.3969/j.issn.0258-2724.20220179
[Abstract](279) [FullText HTML](94) PDF 4344KB(42)
Abstract:

Foamed concrete is susceptible to environmental factors such as temperature during the period from pouring to curing and molding, and adverse environmental factors can lead to performance degradation and deterioration of foamed concrete after curing and molding. In order to study the performance and microporous structure of foamed concrete affected by temperature (−15–70 ℃) during the pouring period, a single factor indoor test program was designed by using dry density, compressive strength, and water absorption to evaluate the physical property of foamed concrete, the construction quality, and the operational durability of foamed concrete, respectively. In addition, the evolution of the microporous structure of foamed concrete was analyzed by using an image data acquisition system and Image J software. The results show that the dry density of foamed concrete generally decreases in a stepwise manner as the temperature rises. The compressive strength first decreases, then increases, and finally decreases. The water absorption rate takes 0 ℃ as the cut-off point, and it tends to increase and then decrease when the temperature decreases or increases. The equivalent pore size shows a trend of increasing, decreasing, and increasing. The pore roundness value first increases and then decreases. The fractal dimension of pore distribution first decreases and then becomes larger. The results of macroscopic performance and microporous structure show that the recommended temperature range for the construction of foamed concrete during the pouring period is −5–40 ℃.

Investigation of FRP-Confined UHPC Circular Stub Columns Under Axial Compression
MA Kaize, HAN Xiao, HE Tengwei, BAI Jingzhu
2024, 59(5): 1132-1139.   doi: 10.3969/j.issn.0258-2724.20220332
[Abstract](269) [FullText HTML](95) PDF 2219KB(46)
Abstract:

In order to study the influences of the number of fiber reinforced polymer (FRP) layers, the type of FRP, and the volume of steel fiber on the axial compression performance of ultra-high performance concrete (UHPC) circular stub columns, 21 FRP-confined UHPC circular stub columns were tested under axial compression. The typical failure characteristics and stress mechanism of the specimens were analyzed. In addition, the influence of various parameters on the ultimate strength and ultimate strain of the specimens was studied. The experimental results show that the ultimate strength of UHPC circular stub columns can be improved by increasing the number of FRP layers. The ultimate strength of C12, C22, and C32 is 17.8%, 25.4%, and 23.4% higher than that of C11, C21, and C31, respectively. With the increase in the volume of steel fiber, the ultimate strength and ultimate strain, and the ductility of UHPC circular stub columns are improved. The ultimate strength and ultimate strain of C31 are increased by 2.9% and 15.1%, respectively, compared with C21, as well as 4.7% and 50%, respectively, compared with C11. Under the same FRP layers and volume of steel fiber, the improvement of the ultimate strength of confined UHPC circular stub columns by carbon fiber reinforced polymer (CFRP) is significantly better than that by glass fiber reinforced polymer (GFRP). The ultimate strength of C11, C12, and C13 is 9.7%, 7.8%, and 7.2% higher than that of G11, G12, and G13, respectively. In view of the constraint of the steel fiber, calculation models of compressive strength and ultimate strain of FRP-confined UHPC circular stub columns are proposed. Furthermore, the constitutive model of FRP-confined UHPC is given.

Non-uniform Corrosion and Load Bearing Capacity Deterioration Tests of Reinforced Concrete Beams Under Load and Chloride Salt Environment
LAI Jun, CAI Jian, ZUO Zhiliang, FENG Yinian
2024, 59(5): 1140-1147, 1157.   doi: 10.3969/j.issn.0258-2724.20220038
[Abstract](200) [FullText HTML](63) PDF 2967KB(37)
Abstract:

To explore how sustained loading and drying-wetting cycles of chloride salt affect the flexural behavior of reinforced concrete (RC) beams, the corrosion tests and flexural capacity tests of 19 RC beams were carried out at first. The effects of various sustained loading grades and drying-wetting cycle periods were studied on the crack distribution, the mass corrosion rate of longitudinal reinforcements, and the flexural behavior of corroded members. The relationship was summarized between the maximum and average mass corrosion rate of longitudinal reinforcements and the flexural bearing capacity reduction ratio. The study results show that the corrosion degree of longitudinal reinforcements was higher in the pure bending segment than in other areas, and distributed non-uniformly along the circumference of the longitudinal reinforcements. There was no noticeable correlation between the position of the extreme mass corrosion rate of longitudinal reinforcements and the occurrence position of initial transverse cracks. The maximum mass corrosion rate of longitudinal reinforcements increased with the loading grade and drying-wetting cycle period, and was more notably affected by the drying-wetting cycle period. The peak load of the beam decreased after corrosion. When the mass corrosion rate of the longitudinal reinforcements was low (average value below 3% or maximum value above 6%), the correlation between the mass corrosion rate and the reduction ratio of bearing capacity was low, and the maximum mass corrosion rate has less correlation with the reduction ratio of bearing capacity than the average mass corrosion rate. When the mass corrosion rate of longitudinal reinforcements increased (average value above 3% or maximum value above 6%), both the maximum and the average mass corrosion rates of longitudinal reinforcements had an increased correlation with the reduction ratio of bearing capacity. When the average mass corrosion rate of longitudinal reinforcements is the same, the reduction of bearing capacity of specimens with natural corrosion is higher than that of specimens with external current corrosion.

Vehicle Trajectory Reconstruction Model of Signalized Intersection in Connected Automated Environments
YANG Tao, MA Yuqin, LIU Meng, YAO Zhihong, JIANG Yangsheng
2024, 59(5): 1148-1157.   doi: 10.3969/j.issn.0258-2724.20220321
[Abstract](373) [FullText HTML](154) PDF 2466KB(66)
Abstract:

Vehicle trajectory data provides abundant spatial-temporal traffic flow information, which can be used for traffic research. Traditional vehicle trajectory models mostly focus on the artificial driving environment and fail to consider the impact of mixed traffic flows composed of regular vehicles (RVs), connected vehicles (CVs), and connected automated vehicles (CAVs). To solve this problem, a full sample vehicle trajectory reconstruction model of signalized intersections in connected automated environments was proposed. Firstly, the composition of vehicles at signalized intersections of urban roads and the passage of queues in connected automated environments were analyzed. Secondly, a model for estimating the number of trajectories of mixed traffic flows on urban roads was constructed, and the concept of virtual vehicles was further proposed to estimate the traffic status of different vehicles according to the queuing of front and rear vehicles. Finally, a numerical simulation test was designed to analyze the influence of traffic flow density and penetration rate of CAVs and CVs on the model, and the model was verified by NGSIM data. The results show that the error of the number and position of the model decreases with the increase in traffic flow density and the penetration rate of CAVs and CVs. For example, when the traffic flow density increases from 20 veh/km to 50 veh/km, both the error of the number and position of the model shows a decreasing trend, and the maximum error is no more than 6.88% and 8.02 m. Compared with that of CVs, the penetration rate of CAVs has a greater impact on the model results.

Influence of Location Frequency on Travel Mode Extraction Using Cellular Phone Data
WANG Yanchen, YANG Fei, LI Rongling, ZHOU Tao
2024, 59(5): 1158-1166.   doi: 10.3969/j.issn.0258-2724.20220136
[Abstract](351) [FullText HTML](80) PDF 1914KB(48)
Abstract:

As a key factor affecting location quality of cellular phone data, location frequency has an important influence on the extraction accuracy of travel mode. In order to quantify the change rule between the location frequency and accuracy of travel mode extraction, a travel mode extraction model based on random forest is proposed. Second, with the help of communication operators, through a field data collection, individual cellular phone data and corresponding real travel information were simultaneously acquired. The dataset is used to verify the travel mode extraction model. Finally, a series of cellular phone datasets with different location frequencies are built through data sampling. With this series of datasets, the extraction accuracy of traffic modes under different location frequencies is evaluated. The evaluation results show that the overall extraction accuracy for walking, non-motorized vehicles, cars, and buses is 79.2%, and the sensitivity of each travel mode to location frequency is different. The sensitivity of non-motorized vehicles and buses is higher, and the sensitivity of walking and cars is relatively low. As the location frequency is decreased from 48 seconds per data to 241 seconds per data, the overall accuracy of non-motorize vehicles and buses is decreased by 19.2% and 21.5%, respectively, while that of walking and car is decreased by 12.8% and 11.5%, respectively. Owning to the requirements of extraction accuracy and computing efficiency, 60 seconds per data is recommended as the optimal threshold for user screening and data sampling.

Simulation Study of Influence of Structural Parameters on Entrainment Coefficient of Ejector Based on Response Surface Method
JIA Demin, WANG Xiaoyan, WANG Peilun, YU Binbin, XU Yu, CHEN Xiumin, ZHAO Jianhui
2024, 59(5): 1167-1175.   doi: 10.3969/j.issn.0258-2724.20220232
[Abstract](284) [FullText HTML](206) PDF 3329KB(52)
Abstract:

To analyze the significant influencing factors of the entrainment coefficient of the ejector, a two-dimensional numerical model of the compressible flow of the ejector with air as the working medium was established, and its calculation accuracy was validated by the experimental data. Meanwhile, the calculation matrix was designed by utilizing the D-optimal experimental design method. Based on the least-squares method, the response surface prediction model of the entrainment coefficient with a second-order form was constructed, and the significant parameters of the ejection coefficient and their interaction were simulated based on the constructed model. The research results show that the coincidence between the predicted and calculated values of the entrainment coefficients proves the accuracy of the response surface prediction model; the interaction between the length of the diffuser section, the mixing section length, the diameter of the mixing section, and the distance from the nozzle outlet to the inlet of the mixing section, the interaction between the mixing section diameter and mixing section length, and the interaction between the mixing section length and the diffusion angle of the diffuser section are the key factors affecting the entrainment coefficient because their P-values are less than 0.001. Meanwhile, the interaction of the diffusion angle of the diffuser section, the distance from the nozzle outlet to the inlet of the mixing section and the length of the diffuser section, and the interaction between the length of the mixing section and the distance from the nozzle outlet to the inlet of the mixing section have an important influence on the entrainment coefficient. Therefore, they are the main parameters affecting the entrainment coefficient. In addition, it is found that among the significant interaction of parameters, the significant factors affecting the entrainment coefficient will change with the value range of the two parameters with significant interaction.

Dense Crowd Counting Network Based on Multi-scale Perception
LI Hengchao, LIU Xianglian, LIU Peng, FENG Bin
2024, 59(5): 1176-1183, 1214.   doi: 10.3969/j.issn.0258-2724.20220823
[Abstract](247) [FullText HTML](76) PDF 1980KB(54)
Abstract:

A dense crowd counting network based on multi-scale perception was proposed to solve the problems of diverse target scales and large-scale changes of crowds in dense crowd scenes. Firstly, since the small-scale targets account for a relatively large proportion of the images, a dilated convolution module was introduced based on the visual geometry group 2016 (VGG-16) network to mine the detailed information in the images. Then, by utilizing the multi-scale information of the target, a novel context-aware module was designed to extract the contrast features between different scales. Finally, In view of the continuous change of target scales, the multi-scale feature aggregation module was designed to improve the sampling range of dense scales, enhance the interaction of multi-scale information, and thus improve the model performance. The experimental results show that mean absolute errors (MAEs) of the proposed method are 62.5, 6.9, and 156.5, and the root mean square errors (RMSEs) are 95.7, 11.0, and 223.3 on ShangHai Tech (Part_A/Part_B) and UCF_CC_50 datasets, respectively. Compared with the optimal method of comparison model, the MAE and RMSE are reduced by 1.1% and 4.3% on the UCF_QNRF dataset and by 8.7% and 13.9% on the NWPU dataset.

Correspondence Calculation of Three-Dimensional Point Cloud Model Based on Attention Mechanism
YANG Jun, GAO Zhiming, LI Jintai, ZHANG Chen
2024, 59(5): 1184-1193.   doi: 10.3969/j.issn.0258-2724.20220682
[Abstract](247) [FullText HTML](65) PDF 2234KB(43)
Abstract:

The existing deep learning methods have low precision and poor generalization ability in calculating dense correspondence between non-rigid point cloud models. To address these issues, a novel method for calculating unsupervised three-dimensional (3D) point cloud model correspondence based on a feature sequence attention mechanism was proposed. Firstly, the feature extraction module was used to extract the features of the input point cloud model pair. Secondly, the transformer module learned context information by capturing self-attention and cross-attention and generated a soft mapping matrix through the correspondence prediction module. Finally, the reconstruction module reconstructed the point cloud model based on the obtained soft mapping matrix and used the unsupervised loss function to complete training. The experimental results on FAUST, SHREC’19, and SMAL datasets show that the average correspondence errors of this algorithm are 5.1, 5.8, and 5.4, respectively, which are lower than those of the classical algorithms including 3D-CODED, Elementary Structures, and CorrNet3D. The correspondence between non-rigid 3D point cloud models calculated by the proposed algorithm has higher accuracy and stronger generalization ability.

Knowledge Fusion Method of High-Speed Train Based on Knowledge Graph
WANG Shuying, LI Xue, LI Rong, ZHANG Haizhu
2024, 59(5): 1194-1203.   doi: 10.3969/j.issn.0258-2724.20220193
[Abstract](299) [FullText HTML](98) PDF 2135KB(76)
Abstract:

To address challenges of unclear correlation, intricate knowledge retrieval, and difficult knowledge application across diverse domains of high-speed trains, the organizational structure involving multi-source heterogeneous knowledge pertaining to high-speed trains was first analyzed, and a knowledge graph pattern layer and knowledge graph of the high-speed train domain was developed based on the product structure tree and stage domain of high-speed trains. Subsequently, the bidirectional encoder transformer-bidirectional long short-term memory network-conditional random field (BERT-BILSTM-CRF) model was employed for entity recognition, so as to establish the mapping of stage domain ontology. Then, the entity attributes of high-speed trains were categorized into structured and unstructured attributes. The Levenshtein distance and the continuous bag of words-bidirectional long short-term memory network (CBOW-BILSTM) model were utilized to calculate the similarity of corresponding attributes, resulting in aligned entity pairs. Ultimately, the knowledge fusion graph of high-speed train domain fusion was constructed by using the coding structure tree of high-speed train products for mapping and fusion. The proposed method was applied to high-speed train bogies for verification. The results reveal that in terms of named entity recognition, the entity recognition accuracy of the BERT-BILSTM-CRF model reaches 91%. In terms of entity alignment, the F1 values (the harmonic mean of accuracy and recall) of entity similarity calculated by the Levenshtein distance and the CBOW-BILSTM model are 82% and 83%, respectively.

Infrared and Visible Image Fusion Based on Attention Mechanism and Illumination-Aware Network
YANG Yanchun, YAN Yan, WANG Ke
2024, 59(5): 1204-1214.   doi: 10.3969/j.issn.0258-2724.20230529
[Abstract](154) [FullText HTML](28) PDF 5457KB(37)
Abstract:

Some image fusion methods do not fully consider the illumination conditions in the image environment, resulting in insufficient brightness of infrared targets and overall low brightness of the image in the fused image, thereby affecting the clarity of texture details. To address these issues, an infrared and visible image fusion algorithm based on attention mechanism and illumination-aware network was proposed. Firstly, before training the fusion network, the illumination-aware network was used to calculate the probability that the current scene was daytime or nighttime and apply it to the loss function of the fusion network, so as to guide the training of the fusion network. Then, in the feature extraction part of the network, spatial attention mechanism and depthwise separable convolution were used to extract features from the source image. After obtaining spatial salient information, it was input into a convolutional neural network (CNN) to extract deep features. Finally, the deep feature information was concatenated for image reconstruction to obtain the final fused image. The experimental results show that the method proposed in this paper improves mutual information (MI), visual fidelity (VIF), average gradient (AG), fusion quality (Qabf), and spatial frequency (SF) by an average of 39.33%, 11.29%, 26.27%, 47.11%, and 39.01%, respectively. At the same time, it can effectively preserve the brightness of infrared targets in the fused images, including rich texture detail information.

Interpretability of Modulation Recognition Network Based on Time-Frequency Gradient-Weighted Class Activation Mapping
LIANG Xianming, NI Fan, CHEN Wenjie, ZHANG Jiashu
2024, 59(5): 1215-1224.   doi: 10.3969/j.issn.0258-2724.20210791
[Abstract](297) [FullText HTML](97) PDF 4891KB(42)
Abstract:

Aiming at the poor interpretability of modulation recognition methods based on time-frequency deep learning, an interpretable framework of a modulation recognition network is proposed, utilizing time-frequency gradient-weighted class activation mapping (Grad-CAM). Through the key features of the hidden layer in the Grad-CAM visual deep model, the significance of the deep features extracted from the network hidden layer are illustrated in terms of correct and error recognition, revealing the decline of network performance in the environment of low signal-to-noise ratio (SNR). The contribution values of different convolution cores at each network layer are quantified and sorted to determine the network redundancy. The simulation results verify the interpretable framework of the time-frequency deep learning network for modulation recognition. The interpretable analysis results reflect that there is a large amount of noise present in the feature extraction region of the network in a low signal-to-noise ratio environment, and the tested modulation recognition network exhibits a high degree of redundancy.

Edge-Aware Semi-Supervised Built-up Area Extraction Using Multi-Temporal Synthetic Aperture Radar Images
CHEN Shuailin, YANG Wen, LI Hengchao, TAPETE Deodato, BALZ Timo
2024, 59(5): 1225-1234.   doi: 10.3969/j.issn.0258-2724.20220807
[Abstract](184) [FullText HTML](60) PDF 2330KB(39)
Abstract:

To address the challenges of identifying and annotating built-up areas in synthetic aperture radar (SAR) images, a novel semi-supervised method for extracting built-up areas that combined improved pseudo-labeling techniques with an edge enhancement strategy was proposed. Initially, SAR images from the same location but at different time were introduced as a natural data augmentation method, and the pseudo-labels were determined by voting based on the prediction results of multi-temporal images. Subsequently, an edge-enhancement auxiliary module was designed, which corrected the body features of the built-up areas through feature map warping and improved edge features with skip connections. Separate supervision for the body and edge features was performed. Moreover, a dataset for extracting built-up areas in multi-temporal SAR images, which included two types of sensors and two urban areas, was constructed. This dataset contains 1,000 annotated images and 800 groups of unlabeled temporal images. Experimental validations based on this dataset have demonstrated that on the constructed test set, the baseline method trained with full data achieves an intersection over union (IoU) of 63.43%, while the proposed method reaches an IoU of 63.46% and 68.24% when using 10% and full data, respectively. Remarkably, using only 10% of the annotated data, the proposed method can achieve the precision that the baseline method has obtained with full annotated data.

Traffic Speed Prediction in Merging Zone of Urban Expressway Based on Bidirectional Long Short-Term Memory Network
XIE Jiming, XIA Yulan, QIN Yaqin, ZHAO Rongda, LIU Bing, DUAN Guozhong, CHEN Jinhong
2024, 59(5): 1235-1244.   doi: 10.3969/j.issn.0258-2724.20220005
[Abstract](260) [FullText HTML](77) PDF 3386KB(73)
Abstract:

Accurate prediction of microscopic traffic parameters in atypical complex scenes is a prerequisite to ensure stable operation of the intelligent vehicle infrastructure cooperative systems (IVICS). To solve the problem of vehicle speed distribution disorder and difficulty in prediction caused by bottleneck phenomenon during peak hours in the merging area under IVICS conditions, First, using the UAV video, the full-sample high-precision vehicle trajectory data of the intertwined area during peak hours are extracted from a wide-area view. Then, as bidirectional long short-term memory (Bi-LSTM) networks cost long time and affect the prediction performance of the model when training parameters are manually set, a BHO-Bi-LSTM (bayesian hyperparameter optimization bidirectional long short-term memory) integrated vehicle speed prediction model based on Bayesian hyperparameters optimization is proposed. Finally, the classical multiple linear regression model and Bi-LSTM model of vehicle speed prediction are constructed for comparison. The results show that the BHO-Bi-LSTM model outperforms other models, with a goodness-of-fit and rank correlation of 91.05% and 94.87%, respectively, and error mean, error standard deviation, mean square error, root mean square error, and normalized root mean square error of 0.0561, 0.4556, 0.2106, 0.4589, and 0.0785, respectively, which can overcome the disadvantage in prediction of complicated traffic speeds during peak hours.