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【Objective】To study the reinforcement effect of steel plate thickness and anchor strength on the joint of shield tunnel.【Method】Using ABAQUS finite element software, establish left and right half standard block pipe joint models with an inner diameter of 5.4m and an outer diameter of 6m. Based on a load structure calculation model, study the mechanical properties of steel plate adhesive reinforced subway tunnel pipe joint. 【Result】The research results indicate that the mechanical properties of reinforced pipe joints are influenced by three aspects: concrete matrix, steel plate, and anchor bolt. The bending stiffness of steel plate reinforced joints is significantly improved. A 10mm steel plate can increase the joint stiffness by 40%. When the thickness of the steel plate is 20mm-30mm, the bending moment of the structure continuously increases under external loads. In the later stage, structural damage mainly concentrates on the joint surface, near the handhole, and below the loading point. A steel plate thickness exceeding 20mm does not cause significant changes in the structural damage mode. The stress of the steel plate is concentrated at the support far away from the joint surface, proving that the steel plate can fully exert the stress advantage of the composite structure under this thickness. 【Conclusion】When the number of anchor bolts is fixed, increasing the diameter can effectively improve the collaborative stress of the reinforced pipe joint. Due to the limitation of concrete strength in the compressed area of the joint, the stiffness increases of the joint decreases with the increase of steel plate thickness. The optimal thickness is 10-20mm steel plate; An anchor bolt diameter greater than M16 ensures effective connection between structures.
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【Object】In order to explore the vibration characteristics of high-speed train gearbox housing under the coupling excitation of wheel polygon and rail corrugation.【Method】The rigid-flexible coupling dynamic model of wheelset, gearbox housing and track was established. Three vibration acceleration sensors were arranged in the gearbox housing, and dynamic simulation was carried out under different working conditions to analyze the vibration acceleration of each measuring point of gearbox housing.【Result】Under the wheel-rail coupling excitation, at the same speed, when the wheel polygon is 23 order and the amplitude is 0.01 mm, the root mean square value of the vibration acceleration of each measuring point is the largest, and the wheel polygon has the greatest influence on the measuring point B in the three measuring points. Under the excitation of rail corrugation, the root mean square value of vibration acceleration of measuring point B is the largest among the three measuring points under the combined action of harmonic torque of traction motor and gear meshing. The root mean square value of vibration acceleration of measuring points A and C increases with the increase of amplitude. Compared with the wheel-rail coupling excitation with broad spectrum, the vibration frequency caused by wheel-rail excitation is close to the fifth order natural frequency of the gearbox housing, which induces resonance.【Conclusion】The resonance can be avoided by changing the speed of the train or changing the structure of the gearbox. This study provides a reference for the design of the gearbox structure.
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【Objective】To investigate the impact of surface surcharge on the settlement of adjacent tunnels, 【Method】a two-stage analysis method was adopted. In the first stage, the Boussinesq solution calculates the vertical additional force exerted on nearby subway tunnels due to surface surcharge. In the second stage, the subway tunnel is modeled as an Euler beam supported on the Pasternak foundation, simplifying the structural representation. Utilizing the Rayleigh Ritz method, functional expressions for each system component are formulated, leading to the establishment of the total energy equation. The control equation is subsequently solved through the application of the variational principle. 【Result】The obtained results are compared to measured data to validate the effectiveness of the proposed method. The research explores the impact of offset distance (d), tunnel burial depth (z), surcharge (p), and surcharge range (B and L) on settlement. 【Conclusion】The research findings indicate a significant impact on settlement within the range of (0.5-1) L directly below and on both sides of the surcharge; As d increases, the maximum settlement of the tunnel gradually decreases; There is a linear relationship between p and wmax and the larger the pile surcharge, the greater the maximum settlement; Increasing L and B initially leads to gradual settlement increase, followed by stabilization. L exerts a greater influence on wmax compared to B.
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Remote sensing image object detection has a wide range of applications in intelligent transport, such as dynamic monitoring of road network operation status, intelligent law enforcement on roads, and intelligent monitoring of road disasters. Due to the characteristics of small and dense targets, large scale changes, and arbitrary direction distribution in remote sensing images, general object detectors have poor detection performance when directly applied to remote sensing images. To address these challenges,this paper proposes a remote sensing image object detection algorithm based on improved Retinanet. First, the model introduces Improved Downsampling Module (IDM) on the base feature extraction network ResNet50, which performs multiple down-sampling processing on features, and then dynamically selects the spatial receptive field using the convolution kernel selection mechanism to model the multi-scale semantic information of the scene. Finally, the classification and regression results of the target object are obtained. Experimental results show that the proposed method improves the mAP by 3.2% on the large-scale remote sensing image object detection dataset DOTA compared to the original Retinanet network, enabling more accurate localization and identification of remote sensing targets.
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【Objective】The Clar covering polynomial of molecular graphs is a method to characterize the electronic structure of conjugated systems. By studying the Clar covering polynomials of plane bipartite graphs, the resonance theory of related molecular graphs and their related properties can be well studied.【Methods】Based on the theorem related to Clar covering polynomials of plane bipartite graphs, the method of generating functions is utilized to compute Clar covering polynomials of plane bipartite graphs.【Results】Recurrence relations for Clar covering polynomials of a special class of graphs are derived. In turn, explicit expressions for the Clar covering polynomials of two classes of catacondensed plane bipartite graphs are computed using the generating function method.【Conclusion】On the Clar covering polynomials of plane bipartite graphs, it is possible to understand the electronic structure of chemical molecules, predict their chemical properties and reaction behavior, and design new molecular structures.
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【Objective】Fully exploiting the spatial correlation of passenger flow between related stations in the subway network has a positive effect on the improvement of subway passenger flow prediction accuracy. Capturing and quantifying spatial patterns in passenger flow data is difficult due to the difficulty of learning and transferring spatial correlations between metro stations. 【Method】An improved graph-convolution gated recurrent neural network metro passenger flow prediction model is proposed to enhance the model"s ability to handle different data types by integrating multivariate spatio-temporal data. A spider wasp optimisation algorithm based on Tent chaotic mapping and Levi"s flight perturbation strategy is used to dynamically adjust the model structural parameters in order to optimise the hidden layer structure of the gated recurrent neural network.【Result】Prediction results on weekdays and weekends show that 20 iterations lead to optimal results, with higher prediction accuracy with larger training samples. 【Conclusion】Dynamic optimisation of the hidden structure of gated recurrent networks can lead to better convergence of the prediction model and higher prediction accuracy.
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【Objective】To grasp the deformation characteristics of Jiangxi red clay under the action of straight shear plus unloading and the law of energy dissipation. 【Methods】Direct shear tests under shear loading and unloading conditions were carried out on Jiangxi red clay, and its strength-deformation characteristics and energy dissipation laws were analyzed. 【Results】The results show that: 1) Overall, the shear elastic displacement increases with the increase of normal stress. The shear elastic displacement at different unloading positions under the same unloading condition increases with the increase of unloading times. In the case of low normal stress, the slope of the red clay hysteresis curve with the increase of the number of unloading shows a nonlinear decay change, and the decay rate under the low normal stress condition is from slow to fast; 2) the red clay in the unloading and loading of the straight shear test process as a whole shows a shear shrinkage deformation, the shear unloading stage of the normal displacement increases, and then loading stage of the normal displacement first increases and then reduces the deformation, resulting in shear expansion deformation, and shear expansion is over when shear displacement reaches the value of unloading before. When the shear displacement reaches the value before unloading, the shear expansion ends. Shear unloading will increase the normal displacement of red clay, increase the shear shrinkage, unloading effect on the normal displacement with the increase of normal stress gradually decreases; 3) the same loading and unloading conditions of red clay shear strength with the increase of normal stress increases. The effect of loading and unloading on the shear strength of red clay is larger, and the effect of shear unloading under high normal stress is more obvious than that under low normal stress. 4) The dissipation energy of different unloading times under the same unloading condition increases with the increase of normal stress and the number of unloading and loading times, and the normal stress is between 100kPa and 300kPa, the dissipation energy of the unloading two conditions is larger than that of the unloading one condition. The dissipation energy of unloading twice is larger than that of unloading once at 100kPa to 300kPa, while that of unloading three times and four times is smaller than that of unloading twice, and that of unloading more times is larger than that of unloading once at 400kPa normal stress. 【Conclusion】: The dissipation energy and deformation of red clay under different loading and unloading conditions have certain regularity.
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【Objective】Aiming at the characteristics of various target scales, complex background and dense small targets in aerial images of unmanned aerial vehicles,a small target detection algorithm LM-YOLO based on YOLOV5 is proposed.【Method】Firstly,increase the small target detection head and K-DBSCAN clustering algorithm is used to optimize the anchor frame ,so as to generate an anchor frame more suitable for small target detection and improve the detection accuracy of the algorithm.Then,a more efficient MobileNetV3-CBAM is designed as a feature extraction network to reduce the size of the network model.Finally,the large kernel selective attention mechanism LSK is introduced into the feature fusion network to increase the resolution of the model to similar targets.【Result】The experimental results on the public data set VisDrone2019 show that the average detection accuracy of LM-YOLO for all targets is improved by 7.6% and the model size is reduced by 45% compared with the benchmark model YOLOV5.【Conclusion】Experiments show that the proposed algorithm can reduce the model size while maintaining good detection accuracy, and is suitable for the target detection task of aerial images.
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To address the challenge of identifying traveling waves with different components, including fault point incident waves, reflected waves, and waves reflected by AT, which makes fault location on all parallel AT traction networks difficult, this paper proposes a wave similarity-based fault location method using Adaptive Projection Intrinsically Transformed Multivariate Empirical Mode Decomposition (APIT-MEMD). The APIT-MEMD algorithm is applied to adaptively decompose the fault signals of multi-conductor lines in both directions to extract transient high-frequency characteristics representing different components of fault traveling waves. By constructing the cross-correlation function matrix of different wave mode components to identify traveling waves along different paths and calculating the corresponding maximum time delay of the cross-correlation function, the fault location of the traction network"s traveling waves is achieved. Experimental results demonstrate that the proposed method, based on time-frequency mode feature extraction, achieves fault location accuracy within 102 m with an average absolute error of 49 m.Compared with the results of different projection parameters in the multi-dimensional empirical mode decomposition algorithm, the effectiveness of fault location accuracy is optimized. The optimized fault location algorithm meets the requirements for high-precision fault location.
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【AIMS】 In view of the lack of comprehensive evaluation system for high-speed train wheel and rail optimization scheme, this study aims to develop an evaluation method based on improved fuzzy hierarchy analysis method to determine the most appropriate equivalent conicity scheme and ensure the smooth operation of the train.【Methods】Firstly, in the light of the main kinetic factors affecting the selection of equivalent conicity, 14 evaluation indexes were selected to construct the index decomposition model, and the improved three-scale hierarchy analysis method was applied to determine the weight of each index. Subsequently, three different working conditions with equivalent conicity were established in the dynamics software Simpack, and the underlying index values were calculated and dimensionless to determine the fuzzy evaluation membership matrix, and the fuzzy theory system evaluation model was constructed to obtain the comprehensive evaluation results of the three schemes.【Results】The comprehensive evaluation results show that the scores of the three equivalent conicity schemes are: M1:26.2%, M2:17.9%, and M3:16.2%, from which M1 was determined as the optimal choice. By calculating the kinetic simulation of the two groups and observing the intuitive simulation results of the post-processing module, the results are consistent with the conclusion of the comprehensive evaluation system, and then the reliability of the evaluation method is verified.【Conclusion】The method of equivalent conicity evaluation of high-speed train wheel and rail based on improved fuzzy hierarchy analysis proposed in this study is effective, which can provide scientific basis for the optimization of equivalent conicity scheme of high-speed trains and ensure the stability and safety of trains.
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Density Peak Clustering (DPC) has been widely used as an efficient and non-iterative clustering algorithm. However, studies have found that DPC struggles to select correct cluster centers, especially in datasets with non-spherical clusters and non-uniform density. Moreover, the algorithm is heavily influenced by the truncation distance parameter. 【Objective】In order to address the issue of poor performance of DPC on datasets with uneven density distributions, 【Method】we propose a density peak clustering algorithm based on natural and weighted shared nearest neighbors. This algorithm first introduces natural nearest neighbor computations to calculate weights, then redefines the similarity between data objects based on the definitions of first-order and second-order shared nearest neighbors. Subsequently, by fusing the definitions of shared nearest neighbor similarity and natural nearest neighbor weights, relative density and relative distance are calculated. Finally, a novel strategy for distributing cluster centers is designed. 【Result】Experimental results on sixs different types of datasets demonstrate that the proposed algorithm outperforms four other comparative algorithms significantly in terms of clustering performance. 【Conclusion】The method achieves better cluster center identification on datasets with non-uniform density, effectively addressing the aforementioned issues.
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In order to explore whether time-dependent fare strategy can be introduced into the metro operation of Type I big cities to alleviate the severe passenger flow congestion brought by holidays, the survey data of Nanchang metro respondents is used to analyze the travel time choice behavior of subway passengers in Type I big cities. SP survey method was used to collect data on respondents’ travel time choice preferences under the influence of three scheme variables: travel time change, fare and congestion level. Conditional logit model and mixed logit model were used to estimate the variable coefficients of utility function. The results show that the change length of travel time has a significant and negative effect on travel time choice behavior, and the fare level has a significant and positive effect on travel time choice behavior. The survey sample could not reflect the significant impact of congestion level on travel time choice behavior. Compared with the change length of travel time and the congestion level, the fare has a greater impact on the travel time choice behavior, and the respondents are more willing to choose the pre-peak period. Compared with other age groups, the group <35 years old is more willing to delay departure, the group with a monthly income <5000 yuan is more willing to change the travel time than the group with a higher monthly income, and the respondents with a travel time of 16-30 minutes are more willing to change the travel time than other groups. Therefore, according to the conclusion, it is feasible to design the time fare scientifically and reasonably to alleviate the severe congestion of metro stations on holidays in Type I big cities.
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To solve the problem of low magnetic field utilization of conventional MR brakes, a drum MR brake with internal and external fluid flow channel was designed. By adding non-magnetic rings and non-magnetic disk to the magnetic material rotary sleeve and the stator magnetic cylinder, the magnetic flux was guided meander through six effective damping gaps in the internal and external axial flow channels. Therefore, the torque performance was improved under the premise that the outer dimension of the brake remains unchanged. The structure and working principle of the internal and external fluid flow MR brake were described, and the mathematical model of braking torque were deduced and established. Based on the analysis of electromagnetic field and torque, the accuracy of the model was predicted by theoretical calculation and DOE experiment orthogonal method, and the multi-objective optimization of the MR brake with internal and external fluid flow channel was carried out by using the NSGA-Ⅱ algorithm. The results show that, with an applied current of 2.0 A, the braking torque of the initial and optimal MR dampers are 36.38N.m and 47.35N.m, respectively, with dynamic adjustable ranges of 18.28 and 21.31, respectively. Compared with the initial damper, the braking torque increased by 21.31%, and the dynamic adjustable range increased by 16.58.
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【Objective】Hypergraph neural networks (HGNN) have the ability to learn inter-class uniqueness and intra-class commonality, which can significantly improve learning performance. However, traditional HGNN methods lack the strong relational induction that determines how low-dimensional data nodes interact with each other. To solve this problem, a fuzzy HGNN(FHGNN) classification algorithm based on fuzzy theory is proposed, and hypergraph structure is constructed according to the characteristic information of data nodes. 【Method】FHGNN first uses an edge-focused GNN to make edge prediction through iterative updates of edge labels. The fuzzy membership function is designed according to the output of edge prediction to achieve a more accurate representation of the connection relationship between nodes. Finally, the hypergraph is constructed by the relation representation, then the nodes are classified again and the result is obtained. The edge label loss function and node label loss function are used in FHGNN and their parameters are trained and learned respectively. 【Result】Experimental results prove the proposed FHGNN method is more suitable for small-scale data with low node information dimension, and performs well in node classification tasks.【Conclusion】For classification tasks of different data sets, FHGNN can learn the relevant feature information of nodes more effectively and improve the learning effect.
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Based on the theory of fracture mechanics, combined with rail bottom measurement, the model of rail bottom crack expansion has been established and indicators such as critical crack size, average crack extension rate as well as remaining life has been quantified. In terms of the rail material, residual stress, temperature stress and other factors, work conditions are respectively designed to explore the influences of rail bottom crack expansion. It is found that there exists positive correlation between the fracture toughness of rail material and the remaining life. The remaining life of U95Cr H is less than U78CrV H, which is less than U75V H. Take U78CrV H, used in the line under test, as an example, when the residual stress grows from 0 to 300 MPa, the critical crack size grows by about 2.5% and the remaining life decreases by about 6%; and when the residual stress is 200 MPa, increasing the temperature stress from 0 to 200MPa, the critical crack size does not change much and is within 1%.
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【Objective】As an important connecting part of new energy vehicles, special vehicles, locomotives and other means of transportation, rubber bushing plays a crucial role in the stability of the whole vehicle handling.【Method】In order to avoid the tedious work of repeated debugging in engineering practice, paper proposes an optimal design method of rubber bushing all-directional stiffness (radial, axial, yaw and torsional stiffness) taking into account the material hardness and diameter reduction. Firstly, the Ogden model is used as the constitutive model of rubber bushing. Second, by combining experimental design with finite element analysis, the isotropic stiffness of rubber bushing with different inner core outer diameter, rubber height, diameter reduction and material hardness is calculated. The second-order response surface model of isotropic stiffness is established, accuracy of the model is verified by Latin hypercube sampling and variance analysis. Finally, a multi-objective optimization method of isotropic stiffness of rubber bushing is proposed using genetic algorithm.【Result】The results show that the relative errors between the measured radial, axial, yaw and torsional stiffness and objective stiffness are 7.72%, 9.06%, -6.33% and 9.16% respectively, which are all within ±10% and meet the requirements of engineering application.【Conclusion】The validity of the established second-order response surface model of isotropic stiffness and the feasibility of the proposed optimization design method are verified to provide guidance for the product design of rubber bushing, which can greatly shorten the research and development cycle of rubber bushing.
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Study on mechanical properties of concrete composite beams strengthened with corrugated steel plates
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In order to study the local load transfer mechanism and mechanical properties of tunnel lining reinforced with corrugated steel plate lining, the tunnel lining unit was regarded as a beam unit, and a bending performance test of concrete beam reinforced with corrugated steel plate was carried out. Establish a corresponding three-dimensional refined finite element model, verify the model through test results, and analyze the load transfer mechanism. Research results show that compared with unreinforced beams, the ultimate load of beams reinforced with corrugated steel plates is increased by 30% to 41%, and the ultimate load increases with the increase in the number of anchor bolts. The relative slip between the corrugated steel plate and the concrete structure decreases as the number of anchor bolts increases. At the initial stage of loading, the corrugated steel plate is in the neutral layer position, and the strain is basically zero; after reaching the cracking load, the entire corrugated steel plate peak is in a compressive state, while the corrugated steel plate trough is always in a tensile state.
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To explore the accuracy and feasibility of the evaluation method for determining the bearing capacity of continuous beam bridges under the coupled vibration of vehicles and bridges, a vehicle-bridge coupled vibration model was established based on a two span continuous beam bridge in actual engineering. The dynamic time-history response of the bridge structure control section was extracted, and the dynamic components were removed using empirical mode decomposition (EMD) and variational mode decomposition (VMD). Subsequently, the quasi-static response curve was identified to analyze the impact of bridge deck roughness and vehicle speed alignment on the accuracy of static response identification. Futhermore, the loading efficiency at different loading positions was calculated based on the different responses generated by the control section during vehicle driving. The "Chang Ding model" was employed to calculate the standard calibration coefficient of the quasi-static response for the damaged bridge control section under light load efficiency. This procedure aimed to evaluate the bearing capacity of the damaged continuous beam bridge. The results indicate that the quasi-static response curve decomposed by VMD aligns more with the static response curve compared to EMD. Moreover, the error between the identified quasi-static response and the static response gradually increases with the augmentation of both the roughness of the bridge deck and moving speed of the loaded vehicle. The quasi-static response identified during the loading process of mobile vehicles demonstrates relatively accuracy and can be utilized as the measured static load value for subsequent calculation. The calculated standard calibration coefficients are all greater than 1, accurately evaluating the damage status of the bridge.Hence, the evaluation of bridge bearing capacity based on vehicle bridge coupling vibration exhibits significant applicability and feasibility.
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The objective of this paper is to investigate the vibration source intensity characteristics of a high-speed underground line with a maximum speed of 160 km/h. The paper adopts on-site measurements to investigate the vibration characteristics of multiple sections of a regional express line in a coastal city. Through data analysis, the paper explores the impact of factors such as train speed, tunnel depth, and curves on the vibration source intensity. The analysis results indicate that in straight (curved) sections, the vibration source intensity ranges from 71 dB to 80 dB when the train speed is between 90 km/h and 160 km/h. With increasing speed, the vibration source intensity also increases, and for every 20 km/h increase in speed, the vibration source intensity increases by 3.72 dB. The vibration source intensity decreases with an increase in tunnel depth, and for every 10 m increase in tunnel depth, the vibration source intensity decreases by 4.9 dB. Under the same conditions, the vibration source intensity in curved sections (with a curve radius of 1850 m) is greater than that in straight sections by approximately 7 dB. After one year of train operation, due to the deterioration of the wheel-rail condition, the vibration source intensity increases, and there is significant variation among different trains. Analysis of monitoring data from a specific section over seven months during the operational period indicates that the vibration source intensity stabilizes after a period of operation.
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【Objective】The overall elastic buckling performance of corroded cold-formed thin-walled steel columns was investigated in this paper. 【Method】The finite element eigenvalue buckling analysis method was used to study the effects of corrosion location, corrosion area length and width on the elastic overall buckling of cold-formed thin-walled steel columns. The calculation method for the elastic overall buckling stress of corroded cold-formed thin-walled steel columns was proposed, and the theoretical calculation results were compared with the finite element eigenvalue buckling analysis values. 【Result】The results show that as the degree of corrosion increased, the elastic bending buckling stress and the elastic bending torsional buckling stress gradually decreased. The effect of web corrosion on elastic bending buckling stress was greater than that of flange corrosion, while the effect of web corrosion and flange corrosion on elastic bending torsional buckling stress was similar. The elastic bending buckling stress gradually decreased with the increase of the corrosion area length, and the rate of decrease showed a decreasing trend. However, the elastic bending torsional buckling stress approximately linearly decreased with the increase of the corrosion area length. With the increase of the corrosion area width, the elastic bending torsional buckling stress decreased faster than the elastic bending buckling stress. The theoretical calculation values were in good agreement with the finite element simulation results. 【Conclusion】The calculation method proposed in this paper can be used to calculate the elastic overall buckling stress of corroded cold-formed thin-walled steel columns.
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In order to effectively enhance the coverage capability of heterogeneous? wireless sensor networks (HWSN), this paper proposes an Improved Honey Badger optimization Algorithm (IHBA). Firstly, Combined with the adaptive fruit fly optimization algorithm, the random search ability of the algorithm is enhanced, which is convenient for the algorithm to obtain the global optimal solution. Then, the strategy of replacing the worst individual is introduced to avoid adapting to the low individual to occupy the population position, while introducing new individuals to improve the population diversity and avoid the individual prematurity of the algorithm. The experimental results show that the proposed algorithm can improve the coverage of wireless heterogeneous sensor networks. Compared with the standard Honey Badger algorithm, the coverage of wireless heterogeneous sensor networks is improved by 18.2%, and the node distribution in the whole network is more uniform.
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Aiming at the safety hidden problem caused by overhead contact wire defects during railway operation, an improved YOLOv7x method for overhead contact wire defect identification was proposed. Firstly, Swin Transformer network is introduced at the end of the backbone feature extraction layer to replace the original extended and efficient layer aggregation network module, so as to improve the ability of the network to grasp global information. Then the SIoU(SCYLLA-IoU) loss function is used to replace the original network loss function, and the direction penalty mechanism is added to the convergence process of the prediction frame. Finally, Coordinate Attention is used to integrate the extended efficient layer in the neck layer to aggregate the network module, enhance the global receptive field of the neck network module. Experimental simulation results show that the accuracy of the model trained by the improved algorithm reaches 95.9%, which is 4.7% higher than that of the original YOLOv7x algorithm, and the detection speed reaches 52 frames per second. The improved algorithm solves the problem of low detection efficiency in the field of hanging strings defect identification, and can improve the efficiency of detection of hanging strings defect in practice.
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Based on the measured data of a deep foundation pit of Nanchang Metro Line 4, FLAC3 D software is used to simulate the whole process of deep foundation pit excavation. The displacement variation law of adjacent pipelines caused by foundation pit excavation is analyzed from different pipe materials, pipe diameters, buried depths, buried distances and with or without internal supports. The results show that the internal support plays a good role in limiting the displacement of the adjacent pipeline during the construction of the foundation pit. The influence of pipeline factors is mainly concentrated in the first 6m of the excavation depth of the foundation pit, and the deformation of the pipeline gradually tends to be stable after 6m; the stiffness of pipe material has obvious influence on the displacement of pipeline in the process of foundation pit excavation. The larger the stiffness is, the smaller the settlement displacement of pipeline is. The influence of changing pipe diameter on pipeline settlement displacement is more significant than that of horizontal displacement, and the influence of pipe diameter on pipeline settlement displacement is greater than that of pipe material on pipeline settlement displacement. When the buried depth of the pipeline is 10 m, the settlement displacement is zero and the horizontal displacement of the pipeline is the largest. It is speculated that the underground continuous wall at the buried depth of 10 m is at the highest point of deformation, and relevant monitoring and protection need to be strengthened. The pipeline still has a horizontal displacement of nearly 1mm at a distance of 20 m from the foundation pit. It is concluded that the influence range of foundation pit excavation on the horizontal displacement of adjacent pipelines is greater than that of its settlement displacement.
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To better evaluate the prestress loss of in-service prestressed concrete bridge structures, this article takes the 32m prestressed concrete box girder, which is widely used in domestic high-speed railways, as the research object. 26 test model beams using C50 concrete were produced by converting the box girder into a T-shaped section at a scale of 1:16. The strain and elongation of the prestressed steel strand in the experimental beam were continuously and continuously monitored to determine the actual value of prestress loss, which was then compared and analyzed with the values calculated by commonly used prestress loss calculation specifications at home and abroad. The findings demonstrate that prestress loss mainly occurs in the early stage, which is instantaneous loss, accounting for about 70% of the total loss. 84.6% of the anchoring losses of the experimental beam account for over 70% of the total instantaneous losses, with a maximum of 80.57%. The long-term loss of the experimental beam fluctuates dramatically in the first 10 days after anchoring and gradually stabilizes in the later stage. Comparing the calculation results of the five specifications with the measured values in the experiment, the data shows that the calculation results of (TB 10002-2017) are the most consistent with the measured data in this experiment for long-term losses. The research results can provide reference for the calculation of prestress loss of prestressed beams in practical engineering.
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In order to study the longitudinal force and deformation law of CWR of ballastless track on the continuous rigid bridge of the metro, based on the principle of beam-plate-rail interaction, a spatial fine coupling model of CWR of the integral track bed type ballastless track on the continuous rigid bridge of the metro with 100m roadbed + 4×40m continuous rigid bridge + 4×40m continuous rigid bridge + 100m subgrade was established, and under stretching, bending, braking and broken rail conditions,the displacementtrack and longitudinal force of track structure and bridge were calculated, and the static characteristics of the track structure were compared and analyzed. This paper provides a reference for the design of CWR track structure on continuous rigid bridge of metro. The results show that when the midpoint of the double-line train load coincides with the end of the middle beam, the vertical load of the train is the most unfavorable working condition, and the force of the rail and the displacement of the rail and bridge are the largest, and the values are 70.3kN, 0.6mm and 0.8mm, respectively. When the tail of the double-line brake load train is located at the end of the beams on both sides, the most unfavorable working condition of the train braking load, at this time, the longitudinal force of the rail and the longitudinal displacement of the rail and the bridge are the largest, and the values are 107.8kN, 1.6mm and 1.7mm, respectively. Under telescopic force, each end bridge joint is a weak part, and attention should be paid to the structure at the end bridge joint of the beam in the usual maintenance to prevent rail breakage due to excessive expansion force; When the rail is broken under cooling conditions, the longitudinal force and longitudinal displacement of the broken rail are abruptly changed at the fracture, which seriously affects the safety of the line.
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The main research focus of this study is the collaborative optimization of mixed-operation bus departure intervals and vehicle utilization plans, involving both fuel-powered and electric buses. The optimization objectives are to achieve smooth departure intervals and minimize overall operational costs. Multiple constraints are considered, including departure interval range, number of vehicles, vehicle connectivity, and electric bus range. An optimization model is established to address these aspects. A genetic algorithm is designed to solve the two-stage model, enhancing efficiency and accuracy of the solution. The case demonstrate that compared to the existing operating scheme, this optimization model can allocate the number of buses used more reasonably with a relatively uniform departure interval. It achieves off-peak charging for electric buses, enhances vehicle utilization, and saves up to 13.04% of the total operational cost of vehicles.
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To enable conflict avoidance operation planning for support vehicles in complex environments, a dynamic priority classification method has been proposed. This method prioritizes conflict avoidance based on two levels of operation efficiency and risk. Additionally, a conflict avoidance operation planning model has been established, along with a two-stage algorithm for global path optimization. A low time complexity conflict detection method has also been proposed to ensure accuracy while solving large-scale complex problems quickly. Experimental results show that the proposed model can reasonably plan vehicle conflict avoidance paths, with the two-stage algorithm based on dynamic priority strategy proving to be more effective in both large and small scale scenarios. Compared to the fixed-priority-based two-stage algorithm, the proposed approach improves conflict point reduction by 7.6% and reduces the vehicle-aircraft conflict ratio by 7.5%.
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In order to solve the problems of insufficient feature extraction and weak ability of multi-target defect detection of YOLOX algorithm in steel surface defect detection, a multi-dimensional feature fusion strip material surface defect detection algorithm based on improved loss function is proposed. First of all, apply SPP_SF to the Backbone part to retain multi-scale feature information and improve classification accuracy. Secondly, the multi-dimensional feature fusion module MDFFM is added in the Neck part to integrate the channel, space and position information into the feature vector to strengthen the feature ex-traction ability of the algorithm. Finally, the introduction of Varifocal Loss and α-CIoU weighted positive and negative samples to improve the regression accuracy of the prediction box. The experimental results show that YOLOX-αSMV in NEU-DET data set mAP@0.5:0.95 reaches 47.54%, which is 3.43% higher than YOLOX algorithm. While keeping the detection speed basically unchanged, the ability to identify and locate fuzzy defects and small target defects is significantly improved.
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Lightweight foam concrete has been widely applied in the field of geotechnical engineering in the last decade or so, but relatively little research has been carried out on the selection and optimal proportioning of foam agent solutions. In this paper, the surface tension, foaming multiplicity, half-life and stability of the foam produced by several typical foam agents are studied systematically, and the performance indicators and concentration values of the preferred foam agents are proposed. In this paper, the surface tension, foaming rate, half-life and foam stability of several typical foam agents were systematically studied, and the optimum performance index and concentration value of foam agents were proposed. On this basis, with the C40 soil-cement mix ratio as reference, the prepared foam and C40 cement grout were mixed according to different injection volume ratios, and the dry and wet weights were measured to determine the ratio scheme of lightweight foamed concrete under different design weights. Furthermore, unconfined compressive strength tests were carried out to determine the compressive strength values of lightweight foamed concrete specimens under different stress conditions, and scanning electron microscopy tests were conducted to understand the microstructure of the specimens. The results show that the optimal concentration of foam agent is about 3%, foaming rate is 25, surface tension is 32mN/m, half-life is 15min. The density and strength of lightweight foamed concrete decreased significantly with the increase of foam injection rate, and the dispersion of bubble population and pore size increased significantly. The dry density of lightweight foamed concrete has a decaying exponential relationship with the injection rate, and the unconfined uniaxial compressive strength has a non-gentle and progressive exponential relationship with the dry density of lightweight foamed concrete. The empirical formulas can be fitted by nonlinear curves to be applied in geotechnical engineering. On this basis, the prepared foam is mixed with C40 cement slurry at different injection volume ratios, and its dry and wet weights are measured to determine the proportioning scheme for lightweight foam concrete under different design weight conditions. Further, unconfined compressive strength tests are carried out to determine the compressive strength of the lightweight foam concrete at different weights. Electronic microscope scanning tests are carried out to investigate the microstructure. The test results show that the optimum concentration of foam agent is approximately 3%, the foaming multiplicity is 25, the surface tension is 32 mN/m and the half-life is 15 min. The density and strength of lightweight foam concrete decrease significantly with increasing of foam injection rate, and the corresponding bubble group content and pore size dispersion increased significantly. The dry density of lightweight foamed concrete has a decaying exponential relationship with the injection rate, and the unconfined uniaxial compressive strength has a non-gentle and progressive exponential relationship with the dry density of lightweight foamed concrete.
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Aiming at the problem of poor real-time performance and low precision of traditional pavement crack detection, this paper uses the advantages of deep learning network in target detection, and proposes an improved yolov5 algorithm, which is called yolov5s-attention in this paper, to realize the automatic detection and recognition of pavement cracks. Firstly, the collected crack images are manually labeled with LabelImg annotation software, and then the network model parameters were obtained by improving the YOLOv5 network training. Finally, the model is used to verify and predict the cracks. In addition, F1 and mean Average Precision (mAP) are used to compare the performance of the original YOLOv5s and YOLOv5s-attention models in detecting and identifying pavement cracks. The comparison between YOLOv5s and YOLOv5s-attention showed that the accuracy of YOLOv5s attention increased by 1.0%, F1 increased by 0.9%, and mAP increased by 1.8%. It can be seen that the network has certain practical significance in realizing the automatic recognition of road cracks.
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In order to study the vibration characteristics of subway stations caused by subway entry and exit, a three-line parallel transfer subway station in a domestic city was taken as the research object, and the vibration characteristics and propagation rules of the station were analyzed based on the field measurement data. The analysis results show that, affected by the completion and operation of the line, the vibration response of each platform in the station is quite different. Under the inbound condition, the average Z-vibration level of platform 1, platform 2 and platform C is 81.9, 91.4 and 61.7 dB, and the main frequency band of platform 1 and platform 2 is 75~125 Hz. Under outbound conditions, the average Z vibration levels of the three platforms are: 82.7, 93.8 and 63.7 dB, the main frequency band of vibration of platforms 1 and 2 is 50~100 Hz, while the vibration response of platform C is concentrated within 50~60 Hz under both conditions. It can be found in most measuring points in the station that the vibration under outbound conditions is greater than that under inbound conditions, and the maximum difference is about 2.5dB. After the vehicle-induced vibration is transmitted to the ground floor, it will first produce a certain attenuation, and if it continues to be transmitted to the ground floor, it will produce an amplification effect, and the vibration is about 3.6~5dB. The attenuation of vehicle-induced vibration transmitted in the station building is small, and the vibration attenuation mainly depends on the soil layer, and the vibration attenuation is about 0.53 dB/m. The research results can provide a reference for vibration prediction, vibration comfort evaluation and vibration reduction design of subway stations and buildings with similar structures.
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In recent years, visible-infrared person re-identification has attracted the attention of many scholars, and its goal is to match person images with the same identity from images of different modalities. Due to the huge difference between visible images and infrared images, visible-infrared person re-identification is a very challenging image retrieval problem. Existing research focuses on mitigating modal differences by designing network structures to extract shared features or generate intermediate modalities, which are susceptible to areas other than person. In order to solve such problems, focus on person information, and further reduce the difference between the two modes, a network structure of dual attention mechanism is proposed for visible-infrared person re-identification, on the one hand, through the dual attention mechanism to mine person spatial information of different scales and enhance the channel interaction ability of local features. On the other hand, the use of global branches and local branches, learn multi-granular feature information, so that different granular information can complement each other to form a more discriminating feature. Experimental results on two public datasets show that the proposed method has a significant improvement compared with the baseline, and shows ideal performance on both the RegDB dataset and the SYSU-MM01 dataset.
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To explore the vibration and noise characteristics of high-speed railway track box girder structures using different track types, the paper establishes a coupled dynamic model of high-speed train-ballastless track elevated- box girder through finite element method and multi body dynamics, and studies the structural dynamic response of trains, tracks, and box girders when trains pass at high speeds. And establish a boundary element model to explore the noise characteristics of the structure when laying different types of ballastless tracks on elevated box girders. The results show that when the train passes through the laying of Type III plates and double block elevated box girders, the maximum wheel load reduction rates of the train are 0.0 536 and 0.1 657, respectively, and the bridge deflection is 1/9 673 and 1/8 457, respectively. The vibration displacement of the track plate and base of Type III plate is smaller, and the vertical vibration transmission rate of the track box beam structure is smaller, resulting in better vibration reduction performance. The noise characteristics of elevated box girders using two types of track structures have little difference at the far point below the bridge, with peak frequencies of 31.5Hz; However, there is a significant difference under the bridge, with a peak frequency of 63Hz for the Type III plate and 20Hz for the dual block type, but the peak difference is very small. And the total sound pressure level of the box beam noise
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Establishing the connection between deterministic safety design and reliability design of pile plate structure subgrade, this paper first derives the analytical solution for settlement calculation of pile plate structure subgrade and establishes the reliability analysis model for the subgrade. The influence of the variability coefficient of subgrade soil elastic modulus, upper load, and pile spacing on the failure probability of subgrade settlement is studied. Subsequently, a framework for settlement safety criteria of pile plate structure subgrade based on the generalized reliability ration of safety margin is proposed. The relationship between the relative safety margin of the generalized reliability index and the safety factor’s relative safety margin is analyzed, and the effect of overlying load on the critical pile spacing is discussed. The results show that the settlement calculation method in this paper can better reflect the settlement deformation characteristics of the pile plate structure subgrade. The settlement of the pile plate structure subgrade is jointly determined by the upper load and the combined stiffness of the plate, and its failure probability curve with the load level changes from a steep increase to linear growth as the variability coefficient of the subgrade soil elastic modulus increases. The relative safety margin of the generalized reliability index and the safety factor"s relative safety margin exhibit an approximately linear relationship, and by allowing the failure probability to calibrate the allowable safety factor, the basic consistency of deterministic design and reliability design of the pile plate structure subgrade is ensured. In addition, an increase in overlying load will lead to a logarithmic non-linear decrease in the critical pile spacing.
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The load of electric vehicles has characteristics such as mobility and randomness. The disorderly connection of a large number of electric vehicles will bring huge pressure to the operation of the power grid. Reasonable charging and discharging control strategies for electric vehicles are particularly important for the power grid. To analyze the influencing factors and laws of electric vehicle group charging and discharging decisions in the process of vehicle network interaction, established a decision evolution game model among different individuals within the electric vehicle group, introduced user preference influence factors to improve the replication dynamic equation, analyzed the process of the evolution of electric vehicle group strategies, and analyzed the impact of various factors on the interaction strategies of electric vehicle groups. The simulation results indicate that when considering the influence of user preferences, the proportion of electric vehicle users who choose charging strategies increases from 65% to 75%. When the sensitivity of user economic benefits increases from 0 to 2, the proportion of charging and discharging users decreases by 50% and 10% respectively, while the proportion of discharging users increases by 60%. The sensitivity of user preferences and economic benefits will increase the proportion of electric vehicle users participating in vehicle network interaction, while external environmental disturbances will not affect the final selection results of electric vehicle users. The established stochastic evolutionary game model can analyze the strategy evolution process within the electric vehicle group, providing a new method for analyzing the behavioral characteristics of the electric vehicle group during vehicle network interaction.
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【Objective】The purpose of this paper is to address the issue of excessive axial force in the first support of a narrow and long deep excavation of metro stations during construction.【Method】Through the method of finite element analysis using the hardening soil model with small strain stiffness (HSS), the excavation method of the station pit , poor quality of steel support installation, and the untimely stressing of the steel support are simulated in a refined way to analyze the influence on the axial force of the first support. 【Result】The results show that: the use of basin excavation has a significant effect on the axial force of the first support, which increases by 45% compared with the case of layered excavation, and the corresponding position of the steel support should be installed in time; when the prestress of the installed steel support does not reach the design value, it will lead to an increase in the axial force of the top support at the end of the excavation, with an increase of 10% or less, and a decrease in the axial force of the bottom support.【Conclusion】Basin over-excavation should be strictly limited during excavation of narrow and long deep excavation of metro stations; The effect of temperature changes on support axial forces cannot be ignored; when the prestressing force of the installed lower steel support fails to reach the design value, it will lead to a large axial force of the top support at the bottom of excavation.
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In order to explore the elastic wave propagation law in the ballastless track structure on the periodic bridge, the ballastless track-bridge coupling structure is considered as a four-layer Timoshenko beam coupling model including rail, track plate, base plate and bridge. The plane wave series expansion method-energy method is used to solve its dispersion characteristics. The accuracy of the proposed method is verified by comparing with the finite element simulation results. Then, based on this method, the influence of structural stiffness change on elastic wave propagation is explored, and the formation mechanism of band gap in dispersion characteristics is clarified. The results show that there are two forbidden bands in the structure within 0-50 Hz, and the initial frequency and cut-off frequency are mainly affected by the longitudinal stiffness of each connecting layer. The first and second cut-off frequencies increase with the increase of glide lamella stiffness and fastener layer stiffness respectively. The research provides a theoretical reference for the vibration reduction of ballastless track structure on bridge.
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To solve the problems of selecting grinding modes based on experience and unpredictable grinding results in the current grinding operation by rail grinding trains, this paper takes the GMC-96X rail grinding train as the research object, to research the effects of different grinding modes by means of numerical simulation through MATLAB. By combining the distribution of grinding wheels in the grinding train, the basic model library of rail grinding is established, and a design method of rail grinding mode based on the grinding amount curve is proposed, which realizes the automatic generation of grinding mode and the precise repair of the rail head profile. The field test results show that the grinding mode designed by this method includes all angles of each grinding wheel of the grinding train, that can be directly input to the control system, which is more suitable for practical applications; and by comparing the measured rail profile before grinding, after theoretical grinding, and after actual grinding, the reliability of the method is verified. And this method can be combined with eddy current testing equipment to remove cracks on the surface of the rail.
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【Objective】The shear tests of four rectangular reinforced concrete (RC) beams were conducted to investigate the effects of the end-anchorage method and preloading on the shear behavior of the carbon fiber reinforced polymer (CFRP)-strengthened RC beams. 【Method】The failure mode, load-deflection curve, characteristic load, strain developments of the stirrup and CFRP were analyzed. 【Result】The test results show that the using U-shaped CFRP strengthening can significantly enhance the shear behavior of RC beams under the reliable end-anchorage. The shear strengthening efficiency is significantly affected by the end-anchorage methods. The mechanical anchorage is obviously superior to the CFRP sheet anchorage. Compared with the unstrengthened beam, the shear capacity of the strengthened beam with the mechanical anchorage increases by about 60%, whereas that with the CFRP sheet anchorage only increases by 9.8%. The preloading significantly decreases the cracking load of the strengthened beams, but has almost no effect on the shear capacity. Finally, the shear capacity of the specimens was predicted using the existing calculation methods for the shear capacity of the CFRP-strengthened RC beam. 【Conclusion】The predicted results agree well with the test results.
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Vehicle suspension is one of the important components of the vehicle driving system, mainly to bear the weight of the body and reduce the excitation from the road surface, its performance directly affects the safety and handling stability of the vehicle, and also has a great impact on the riding comfort of the occupants. The traditional passive suspension structure parameters are fixed, the vibration damping effect is limited, and the semi-active suspension can change the damping and stiffness of the suspension through the control algorithm, which can achieve the same control effect as the active suspension, and the structure is simpler and lower cost than the active suspension. Air springs and magnetorheological dampers can change the stiffness and damping of semi-active suspension, respectively, and are important research objects for semi-active suspension damping. On the basis of introducing the working principle and single control strategy of magnetorheological semi-active air suspension, this paper focuses on the composite control strategy of magnetorheological semi-active air suspension, and finally discusses the development trend and problems of magnetorheological semi-active air suspension, so as to provide further reference for the technical development of magnetorheological semi-active air suspension.
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In order to investigate the lubricity of methanol and isopropanol under the same load and the different rotational speed, and the effect of rotational speed on the lubricity is mainly emphasize investigated. The tribological properties of methanol and isopropanol under 98 N and 400, 500 and 600 r/min are conducted using four-ball wear machine, combination of optical microscope, Raman spectra, transition electron microscope, the lubrication mechanism of methanol and isopropanol is well investigated. The experimental results show that in terms of lubrication system of methanol, the run-in stage is shortened with increasing rotational speed, and the smallest wear scar diameter is obtained at 500 r/min. The low friction and wear is attributed to the micro-bearing consisting of tungsten oxide (WO2 and WO3), methanol, friction-induced amorphous carbon and tribo-pairs. In terms of the lubrication system of isopropanol, friction coefficient is kept the constant with increasing the rotational speed, but the wear scar diameter initially decreases and then increases with increasing rotational speed, and the smallest one is obtained at 500 r/min. The excellent tribological performance of the tribosystem is assigned to the effect of amorphous carbon with lubricity that induced by tribochemistry. The research results can provide references for the application of alcohols in the field of precision equipment.
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With the rapid growth of various mobile applications and services, the contradiction between the battery capacity and the energy consumption at mobile terminals is becoming increasingly prominent. In addition, the ultra-dense deployment of small base stations (SBSs) in ultra-dense network (UDN) makes network interference more complicated, and servers deployed at the edge of the network are also vulnerable to malicious attacks. In view of this, by jointly optimizing the user equipment (UE) association, cryptographic service assignment, UE power control, and computational resource allocation of UEs and SBSs, the sum of weighted standardized total energy consumption and standardized total security cost is minimized for the multi-task UDN. Specifically, mobile edge computing (MEC) and local computing models are first built for multi-task UDN. Then, a mixed-integer and non-linear optimization problem with minimizing the sum of weighted normalized total energy consumption and normalized total safety cost is formulated, and a joint optimization strategy is designed for it. In such a strategy, an adaptive diversity-guided genetic algorithm (ADGGA) is first executed for a coarse-grained search, and then adaptive particle swarm optimization (APSO) algorithm is run for a fine-grained search. The two-step search procedure is regarded as a further improved hierarchical adaptive search (FIHAS) algorithm. The simulation results show that the proposed algorithm may achieve better system performance than other existing algorithms.
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Leng Hao, Liu Shiyang, Li Zongyi, Zhang Yi’an, Zhang Jiarui
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In order to explore the distribution law of crystal blockage in the drainage pipeline of the tunnel drainage system under the effect of groundwater seepage, the 1:5 tunnel drainage system indoor simulation test was established based on the Liaoshan Tunnel Project of the Ehan Expressway, and the same ionic composition test solution was prepared based on the analysis results of the on-site sampling groundwater to carry out the indoor test. The results show that: (1) The crystal stacking mode is mainly mass stacking, and the crystal structure type is irregular and square, belonging to isomerism crystal type, and the main component is calcite calcium carbonate; (2) With the increase of water flow, the crystallization amount increases and the crystallization rate becomes faster. The cumulative total crystallization reaches 106.4g under the condition of 266.8mL/s water flow at the lateral drainage outlet; (3) the gentle slope of the drainage pipe is conducive to the formation of crystals in the drainage pipe of the tunnel; (4) The total amount of crystallization at the joint of the drainage pipe (30%)>the total amount of crystallization at the horizontal drainage outlet (27%)>the total amount of crystallization at the horizontal drainage pipe (19%)>the total amount of crystallization at the longitudinal drainage pipe (15.2%)>the total amount of crystallization at the circumferential drainage pipe (8.3%). The key positions of crystal blockage in the tunnel drainage system are the interface of the drainage system and the outlet of the horizontal drainage pipe. The research results are helpful to the optimal design and construction quality control of the tunnel drainage system, and are of great significance to ensure the smooth and effective operation of the tunnel drainage system.
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Xiao Qian, Li Kai-wen, Zhou Sheng-tong, Wang Han-jun, Bin Hao-xiang, Chang Yun-qing
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The MR-DCA based rolling bearing fault diagnosis method is proposed for the problem that rolling bearing weak faults are difficult to identify. The input samples are pre-processed by using the maximun correlated kurtosis deconvolution and resonance-based sparse signal decomposition, which can effectively filter out the noise of original signal and feature the fault impact components. The obtained two-dimensional time-frequency diagrams of the fault components and the original signal are used as the training samples of the network, and after two feature learning modules, the input features are filtered using the attention mechanism, and the model computational efficiency and recognition accuracy can be effectively improved by weight reassignment. In order to verify the model performance, a rolling bearing weak fault dataset is used for fault diagnosis analysis, while ablation experiments are carried out to verify the effectiveness of each module of the diagnostic model. The results show that the proposed model can achieve good diagnostic performance in the diagnosis of rolling bearing weak faults.
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Zhang Bing, Liao Qinghua, Qu Yongqiang, Wang Mingjie, Tao Wenkang
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In order to study the satisfaction of the elderly in bus travel under the influence of the epidemic and to improve the bus travel conditions of the elderly, based on the traditional passenger satisfaction index model, the latent variable "safety perception under the influence of the epidemic" was added to reflect the psychological changes of the elderly in bus travel due to the epidemic, and the partial least squares structural equation model of the elderly"s bus travel satisfaction under the impact of the epidemic is constructed. Taking the elderly people in Nanchang City as an example, we evaluated their satisfaction with bus travel under the influence of epidemic, verified the rationality of the constructed model, and concluded that the satisfaction of elderly passengers with bus travel is mainly affected by the perceived quality and the perceived safety under the influence of epidemic, with path coefficients of 0.474 and 0.219, respectively. At the same time, using the importance and performance analysis, focusing on the improvement priority of the subordinate items of the perceived quality and the perceived safety under the influence of epidemic subordinate items improvement priorities, the results show that the overall quality of bus services for the elderly in Nanchang is low and needs to be improved. The aspects that need to be focused on improvement are: the degree of driver"s compliance with epidemic prevention measures, the density of passengers in the bus, the ventilation in the bus, the sensitive behavior of other passengers and other passengers" sensitive behavior, etc., which provide a basis for further improving the satisfaction of elderly people"s bus trips.
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Complex dispersion analysis of vertical bending vibration wave of periodic ballasted track structure
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The periodic characteristics of the track structure have filtering characteristics for the propagation of vibration waves within the structure, and dispersion analysis is important for understanding the vibration transmission characteristics of the track structure. Based on the virtual spring model and the energy functional variation principle, we propose a new method to calculate the complex dispersion of the periodic structure of the rail based on the virtual spring model and the energy functional variation principle, which can consider the damping factor and the material frequency variation effect. The accuracy of the method is verified by comparing with the existing literature, and the method is used to analyze the influence law of fastener stiffness frequency variation effect, fastener damping and ballast damping on the vibration wave complex dispersion characteristics of track structure. The results show that the stiffness frequency variation effect and the fastener and ballast damping have a large influence on the attenuation domain and the attenuation speed of the vibration, which must be considered in the vibration transmission analysis of the track structure.
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With the rapid development of rail transit, the operation and maintenance environment of high-speed EMUs becomes more complex, leading to frequent new and old faults. Therefore, an efficient, intelligent and accurate maintenance method is very important. Aiming at the problems of complex faults, outdated maintenance methods and lagging maintenance manual in the maintenance work of EMU coupler, an auxiliary maintenance method of EMU coupler based on mixed reality technology was proposed. With the help of mixed reality and data interaction technology, the overall model and technical framework of MR Auxiliary maintenance for the fault of EMU coupler were constructed. The key technologies such as virtual-real registration fusion, intelligent fault diagnosis, data information interaction and maintenance assistance guidance were studied, and various human-computer interaction assistance maintenance methods such as gesture recognition and eye tracking based on Unity3D-HoloLens were realized. Finally, an example of MR Assisted inspection for faults of close-connected coupler air path and control system of EMU verifies the effectiveness of the proposed method.
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Xu Yuping, Wu Zhigang, Wang Zongyu
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The 20th National Congress clearly proposed to promote new industrialization and accelerate the construction of a manufacturing, quality and transportation power. The State Council pointed out that promoting the linkage and coordination between manufacturing industry and logistics supply chain related service industries is conducive to building a service-oriented manufacturing industry. During the 14th Five-Year Plan period, Fujian Province actively promoted the integration and development of advanced manufacturing industry and related key industries, and made efforts to promote the optimization and upgrading of industrial supply chain. In recent years, Quanzhou"s manufacturing industry has continued to develop with high quality, integrating various manufacturing industries and logistics parks, and actively building an efficient modern logistics supply chain system. Based on the grey relational model and VAR model, this paper analyzes the correlation degree and linkage development between manufacturing industry and logistics supply chain development indicators in Quanzhou, Fujian Province from 2002 to 2021. The research shows that Quanzhou"s manufacturing industry has a strong correlation with the development of logistics supply chain, the collaborative development of multimodal transport among various logistics transportation modes needs to be improved, and the construction of comprehensive freight hub needs to be improved. Accordingly, policy suggestions are put forward for relevant departments.
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huangdawei, caiguoqing, xuchangjie, luowenjun, huguangjing, zhantao
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Based on the problem of earth pressure concentration in soil pressure cells, a water bladder earth pressure gauge was invented. The thickness of pressure sensing water bladder can be controlled within 5-10mm.The pressure sensing water bladder is connected with the electronic pressure gauge through the transparent PU air pressure hose. The height position of the electronic pressure gauge needs to be fixed when the water bladder earth pressure gauge is used.In order to verify the testing performance of the water bladder earth pressure gauge, a comparison test was conducted between the water bladder earth pressure gauge and the vibrating string earth pressure cell buried in soils with different compression modulus.The analysis of the results shows that, because the pressure sensing water bladder is thinner than the earth pressure cell, although the problem of high measured earth pressure is unavoidable, the stress concentration problem is significantly improved when the earth pressure in the stratum is tested with the water bladder earth pressure gauge compared with the earth pressure cell.The water bladder earth pressure gauge is used in the model test of shield tunnel response. The test results show that the water bladder earth pressure gauge is obviously different from the earth pressure cell.From the analysis of the changing trend of the test results, the test results of the water bladder earth pressure gauge are reliable.The test principle of the water bladder earth pressure gauge is simple, and the cost is low, and the precision is high.Because of its flexible construction, the pressure sensing water bladder can be used to test the earth pressure of non-plane structure surface according to the test demand.
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Tian Liang, Xing shouhang, Fan Lilong, Zhao Jian, Cheng bin, zhao xuemin
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Abstract: The U-rib-to-deck (RD) joint in steel bridge decks is prone to fatigue cracking under vehicle loads. It is of great practical value to predict the fatigue life of this type of joints by using appropriate theory. In order to further study the fatigue performance of RD joint, the RD joint was subjected to central loading by simulating wheel loads, and the fatigue life of RD joint under corresponding hot spot stress range was obtained by conducting fatigue tests. The 3D solid finite element model of RD joint in steel bridge decks was established by using ABAQUS, and the stress distribution of the RD joint under simulated wheel load was further analyzed. It is found that the test value is basically consistent with the simulation value. Based on the effective numerical model, the fatigue life of RD joint was compared and analyzed by using the hot spot stress method and the critical distance theory respectively. The results show that (1) the hot spot stress near the weld toe on the deck’s lower surface in RD joint is the largest when the central loading is applied, and fatigue crackings are easy to occur here; (2) Under the same finite element mesh, the hot spot stress results obtained by two-point extrapolation and three-point extrapolation are relatively close, while the characteristic stress obtained by point method using the critical distance theory is smaller than that obtained by line method. The three hot spot stress S-N curves recommended by IIW are used to evaluate the fatigue life of RD joints. The result shows that the evaluation results obtained by FAT 90 S-N curve are too conservative, while the prediction results of FAT 125 S-N curve are relatively close to the measured value. Compared with the hot spot stress method, the critical distance theory can get more accurate prediction results, in which the prediction errors obtained by the point method and the line method are 17% and 32%, respectively. In general, both the hot spot stress method and the critical distance theory can get relatively conservative fatigue life prediction results. Therefore, the two methods are feasible and safe for fatigue behavior evaluation of typical welded joints in steel bridge decks. However, the point method has higher prediction accuracy and is also more convenient in practical application.
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The subway station in a coastal city is located in soft soil, the diaphragm wall is used as the enclosure structure. The trench wall is instability in the construction process. In this paper, the causes of trench wall instability are analyzed and a series of measures are taken. The results show that: 1) The ratio of wall protective mud and the time of trench formation are the main factors affecting the stability. 2) The Extra-deep diaphragm wall, need to comprehensive analysis from the slotting time, the weight of the steel cage and other aspects to decide the framing design ; 3) For L-shape and Z-shape and other special amplitude diaphragm wall, use the three-axis mixing pile to reinforcement the trench wall, can greatly improve the stability of trench wall and to ensure the safety of engineering construction.
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In order to study the influence of this phenomenon on the force of the suspension cables, this paper designs a static tensile test scheme of axial deflection for the basic unit of the suspension cables. Firstly, the corroded steel wire specimens were prepared by accelerated copper salt corrosion method, and the static tensile tests were carried out on the specimens at four different coaxial deflection angles (0, 10, 20 and 30mrad). And Ansys is used to simulate the test and the pitting. The results show that the weight loss rate and the average corrosion depth of steel wire increase linearly with the corrosion time, but the corrosion rate decreases quadratically with the corrosion time. The ultimate tensile properties of steel wire decrease with the increase of deflection Angle. The coupling of deflection Angle and corrosion will accelerate the weakening of the tensile strength of steel wire. The numerical simulation is in good agreement with the experiment, which effectively verifies the law obtained by the experiment. The phenomenon of concentrated stress occurs when there are pits in steel wire, and the maximum stress increases with the increase of deflection Angle.
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GONG Kai, WANG Cheng, YANG Qiangqiang, LIU Linya, BIAN Wenjun
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The finite element approach is used to create an embedded track finite element model in order to investigate the applicability of embedded track in heavy-haul railway. The angle of rail stress, rail displacement, and track slab displacement are used to study the influence of truck axle load on the stress and deformation of embedded track structure, and the existing embedded track structure is adjusted. According to the findings, the truck axle load has a substantial impact on the stress at the head of the rail, the stress at the bottom of the rail, and the lateral and vertical displacement of the rail. Among them, rail head stress and rail lateral displacement all exceed the regulatory requirements, but have no effect on track slab displacement. Following the replacement of 60kg/m rail with 75kg/m rail, the stress in the rail head was significantly reduced, but the transverse displacement of the rail still exceeded the limit value.On this basis, as the elastic modulus of filling materials increases, the stress and displacement of rails are greatly decreased, and they are all within the code limitations. It is advised that the elastic modulus of filler materials be 400MPa. The preceding research findings can be used to develop an embedded track structure suited for heavy-haul railway transportation.
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SongXu, Lihong Tong, Changjie Xu, Haibin Ding, Zhilong Wu
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The foundation pit excavation has a significant impact on the deformation of retaining structure. PLAXIS 3D is utilized for numerical simulation in this paper based on the hardening model considering the small strain characteristics of the soil, combined on the foundation pit project of a subway station in Hangzhou. The influences of different excavation conditions on the deformation, axial force and surface settlement during construction are analyzed in detail. Results show that there is a significant deformation difference between the left and right sides of the retaining structure of the same foundation pit. The soil layer cannot be simply regarded as horizontally distributed soil layer during the process of analysis. The pile load of the soil on the side with large deformation should be reduced, as well as the load should be distributed on the side with small deformation of the retaining structure as far as possible. Meanwhile, the horizontal displacement, surface settlement, and deformation increase gradually with the foundation pit excavation and station construction. In addition, the deformation of the diaphragm wall is significantly affected by the excavation sequence of the foundation pit. The excavation from the middle to both sides has the smallest influence on the deformation of the retaining structure, only 18.35mm, which is about 25% less than the original condition, and has the most favorable influence on the project. The research results can provide a theoretical reference for the design and construction of subway foundation pit, and also have a good guiding significance for practical engineering.
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Parts lightweight is an important research direction in the field of mechanical manufacturing. In this study, the suspension column of the Formula Student Combustion China (FSCC) Formula Student BTR-X was taken as an example. Based on the analysis of its actual force, the Altair Inspire Form software was employed to perform weight reduction design and topology optimization with the goal of maximizing stiffness. The stress-strain values and safety factors of two different design schemes were obtained under the condition of entering the bend with brakes, and then their advantages and disadvantages were compared. In the best optimization scheme obtained, the maximum effective stress of the BTR-X suspension column was 557 MPa, and the weight was reduced by 18. 5%, thus improving the stability of the vehicle. Accordingly, the lightweight goal has been achieved, which has certain reference value for further improving the performance of FSCC racing cars. Finally, the molding process of the optimized suspension column structure has been successfully realized by selective laser sintering (Selective Laser Sintering, SLS), providing a new route for the lightweight design and processing of FSCC racing cars.
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Xu Zigang, Li Chunyu, Xia Zongyao
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Whether the diaphragm wall should be considered in the seismic design of the column-free large-span subway station has not been uniformly determined. Based on the finite element numerical analysis software ABAQUS, the soil-structure static and dynamic coupling finite element models are established to analyze the influence of diaphragm wall on the seismic response of column-free large-span subway station under horizontal and vertical earthquake load. The results show that the diaphragm wall can improve the lateral stiffness of the column-free large-span subway station system, and the horizontal relative deformation of the side wall is reduced when the diaphragm wall is considered; However, the existence of diaphragm wall will magnify the vertical inertia effect of the overlying soil of the subway station, and also make the internal force of the subway station redistribute. When the diaphragm wall is considered, the end of the bottom slab is a weak seismic link, which should be properly strengthened in the seismic design.
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Liu Yinfang, huchunhua, Qin Jinlong, Tong Lihong, Zhu Bitang, Guo Yimeng, Li Zhiping
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To improve the strength of powdered clay-cement mixed soil, it is made to work together with steel bars or sections to form a cement-cement mixed wall. In this paper, taking the powdered clay soil in Nanchang area as an example, based on the existing research on the performance of cement soil improver, indoor unconfined compressive strength test and permeability test were conducted on the mixed soil formed by 16 groups of powdered clay soil improvement schemes by selecting suitable curing agents and using orthogonal test to study the effects of different ratios of cement, water glass, gypsum and quicklime on the strength performance of the improved powdered clay soil. The results were analyzed by extreme difference and ANOVA. The results showed that the compressive strength of the mixed soil was influenced by the amount of cement, water glass, gypsum and quicklime in descending order, and the optimal ratio of cement, water glass, gypsum, quicklime and naphthalene water reducing agent was determined to be 24%, 6%, 2%, 0% and 1.5%, and was recommended to be used when the water-cement ratio was 1.5 and the moisture content of the powdered clay was 12%. After screening the curing agent and optimizing the proportion, the strength of the powdered clay could reach 8.6 MPa at the standard age of 28 d. Finally, the microstructure of the high-strength powdered clay-cement mix soil was analyzed by scanning electron microscope test, and the mechanism of the generation of high-strength cement mix soil was elaborated.
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Lei Xiaoyan, weng ling xiao, Yu Liangliang, Wang Pengsheng, Luo Kun
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In order to investigate the noise radiation of the symmetrical box girder structure and its influencing factors, the box girder of an elevated railway in Nanchang was examined. The structural noise in this box girder bridge was examined by using a hybrid finite element-statistical energy analysis model (FE-SEA) followed by simulation analysis and the findings were subsequently validated by using field tests. Accordingly, the influence of plate thickness on structural noise and the contribution of each box girder subsystem to the overall noise were analyzed. The results showed that the FE-SEA method is suitable for the studying structural noise in box girders. The peak noise frequency of the box girder structure ranges from 31.5 to 60 Hz. and the frequency of structural noise ranges from 50 to 160 Hz. The top plate and wing plate of the box girder contributed considerably to the far-field sound pressure level. The results indicated that increasing the thickness of each plate can reduce the structural noise, and this reduction is greater when the thickness of the top plate is increased. Therefore, in order to reduce vibration and noise in box girders, attention should be paid to the top and wing plates. In addition, we can increase the thickness of the top plate to reduce vibration and noise in box girders.
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Wan Qiwei, Ding Haibin, Wan Qiang, Xu Changjie, Tong Lihong
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With the development of urbanization, the environment of foundation pit is becoming more and more complex, and the deformation control of foundation pit engineering is becoming more and more stringent. At present, the design of foundation pit retaining structure is still controlled by strength, and the design strength is not reached due to the large deformation of conservative design. Based on the improvement of Ritz method based on matrix theory and the principle of minimum potential energy, the deformation coordination condition of retaining pile and horizontal support is considered, the total potential energy equation of retaining pile deformation is obtained, and the deformation of retaining pile is solved. a design method of foundation pit retaining pile based on deformation control is proposed. Finally, the theory is verified by the field measured data of three typical projects, and the results show that the absolute error of prediction increases with the increase of the maximum deformation of the retaining pile, and the average relative error is less than 10% of the maximum deformation.
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Yang Luojun, Zhang Cheng, Guo Junhua
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In the development of modern logistics, the timeliness and cost of multimodal transport are factors that cannot be ignored. Aiming at the transportation goal of highway-railway-waterway multimodal transport, this paper mainly studies the path optimization problem of green multimodal transport when the dual uncertainties of transportation time and transit time obey random distribution. The multi-objective optimization model of green multimodal transport path under the dual uncertainties of transportation time and transit time is established with transportation time, transportation route distance and transportation cost as objective functions and carbon emissions as constraints. Accordingly, Fuzzy adaptive genetic algorithm and Fast non-dominated sorting genetic algorithm (NSGA-II) are used to design the multimodal transport path optimization strategy. Finally, the path data from Nanchang to Berlin is used to verify the effectiveness of the proposed method and the results are compared and analyzed. This paper finds that the multi-objective optimization results based on NSGA-II algorithm are better, which can guide the multimodal operators to adjust the transportation plans and reduce the emission of carbon dioxide, providing a reference for logistics enterprises to carry out multimodal transportation.
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Wang Zihang, Liu Jianhua, Xue Xingsi, Zhu Jian, Chen Yuxiang
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Particle swarm optimization(PSO) is widely used to solve complex optimization problems in practical problems in the fields of engineering, science and management. Designing new strategies to deal with the performance and efficiency bottlenecks of the algorithm is a research hotspot in this field. In order to solve the problem that the original velocity limit strategy of PSO is relatively simple, which may easily lead to slow convergence speed and low performance of the algorithm, this paper proposes a new velocity limit strategy combining iteration and problem dimension. By analyzing the relationship of the evolutionary state evaluation to iterations and the dimension of problem for particle swarm optimization, a formula is designed to calculate the evolutionary state evaluation(ESE) which is influenced by the iterations and problem dimension, and calculates the velocity limit on the basis of the ESE, so a Particle swarm optimization with velocity limit combining iteration and problem dimension is obtained. Finally, the algorithm is affected by iteration and problem dimensions, adaptive and scalable for solving problems in different dimensions. The results show that the strategy improves the convergence speed and accuracy. Experimental results show the effectiveness of the algorithm.
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ZHONG Qiaocheng, WANG Li, WANG Jun
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In this paper, we consider the existence of nontrivial solutions for a fractional Schr?dinger-Poisson equations in a bounded domain. Under different assumptions of nonlinearities, we obtain existence and multiplicity by variational methods such as symmetric mountain pass theorem.
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fengyulin, houyu, hebinbin, zhouwangbao, mahongqiang
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Based on the pre-development general characterization model of track structure deformation and the evolution of interlayer interface state induced by the deformation of high-speed railway foundation, the description function of cosine subgrade settlement was implanted, and the Heaviside function was introduced to describe the contact nonlinearity between track and subgrade, the deformation equation of each layer of longitudinally connected ballastless track under cosine subgrade settlement was derived, the progressive approximation method was used to solve hyperstatic equation with contact nonlinearity, and the influence law of cosine subgrade settlement on the track structure deformation of each layer and the evolution of interlayer interface state was analyzed. Results indicate that: in the cosine subgrade settlement area, the track deforms accordingly with the subgrade settlement, when the subgrade settlement wavelength is constant, the track settlement and heaving increase with the increase of the subgrade settlement amplitude, when the settlement amplitude is constant, the track settlement increases with the increase of the subgrade settlement wavelength, but the track heaving decreases. The void area between track-subgrade and the track force curve are symmetrical, and the track overall stiffness affects the void length and height. When the subgrade settlement wavelength is 10m, with the increase of the subgrade settlement amplitude, the void height and length increase, it will also shift away from the settlement area as a whole. When the subgrade settlement amplitude is 10mm, it is necessary to focus on the uneven settlement with settlement wavelength less than 20m.
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WANG Cui, WANG Pengsheng, LEI Xiaoyan
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In order to study the environmental vibration caused by high-speed trains passing through elevated tracks, an experimental test site has been selected, corresponding to a stretch of the railway connection between Shanghai and Kunming,field measurement and finite element method were used to obtain the ground vibration characteristics. Comparing the calculated value with the measured value, the results show that the ground lateral vibration acceleration caused by the high-speed train crossing the bridge was slightly larger than the vertical vibration acceleration, and the main peak frequency point of the frequency spectrum curve could be regarded as the resonance frequency induced by the periodic load; The excellent frequency distribution range of lateral and vertical acceleration was 10-80 Hz, and the acceleration amplitude of each single frequency in the frequency band tended to fluctuate and decay with increasing distance; When the vibration peaks of different frequencies meet, the vibration superposition at the meeting point appeared amplification; The frequency band corresponding to the maximum vibration level of lateral and vertical acceleration appeared at 3.15 Hz of the range of 25-63 Hz; The numerical results of ground vibrations showed an acceptable agreement with the real measurements in amplitude and changing trend, and the maximum error of acceleration Z vibration level was 1.4dB. So the finite element model meets the accuracy requirement, which proves that this method can be used to predict the environmental vibration response.
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GONG Hong-hua, ZHOU Xu-ming, ZHAN Gang-yi, ShI Yu-feng, HU Jun-hao, JIANG Ya-long
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Abstract:
Construction of asymmetric load foundation pit adjacent to railway has a great impact on railway operation, and its deformation should be strictly controlled to reduce the impact on railway. Therefore, the design of foundation pit retaining structure is usually "conservative", and there is a possibility of optimization. In order to explore the possibility of retaining structure optimization in asymmetric load foundation pit, the deformation and internal force of the equal-length pile retaining structure and the long-length pile retaining structure on both sides of the railway are tested, and the measured results of the two sides of the pile retaining structure are compared and analyzed. The results show that: in this project, the deformation of the left and right sides of the foundation pit is small, both within the controllable range, and both the equal-length pile enclosure structure and the long-length pile enclosure structure can ensure the safety of the foundation pit and railway. Compared with the equal-length pile envelope, the maximum horizontal displacement and bending moment of the long and short pile envelope increase, the maximum horizontal displacement increases by 0.25mm, the maximum bending moment increases by 10.1410.14kN·m , both of which are small, the long and short pile envelope has a good supporting effect. The horizontal displacement and bending moment of the short and long pile envelope adjacent to the asymmetric load side are larger than those far from the asymmetric load side, but the difference between them is small, and the influence of the asymmetric load on the short and long pile envelope is small. The long and short pile envelope structure is applied effectively in this project, which can provide reference for related projects.
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zhangpengfei, huanganqi, hudagui, chenhuapeng
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To study the stress and deformation of ballastless track CWR on rigid frame bridge, predicated on the principle of beam-slab-rail interaction, the models of CRTSⅢ slab track and CRTSⅠ bi-block track jointless track on rigid frame bridge are established respectively. The longitudinal forces and displacements of each structure under the conditions of expansion, deflection, braking and rail breaking are calculated, and the static characteristics of two kinds of ballastless track structures are compared and analyzed, it provides consultation for the track structural design of CWR on rigid frame bridge. The results show that under temperature load and train load conditions the rail longitudinal force of CRTSI bi-block track CWR on rigid frame bridge is smaller, but the relative displacement of rail and track slab increases significantly, which may lead to potential safety hazards; Under the train braking load condition, the longitudinal stress of the rail and the relative displacement of the rail slab of CRTSⅢ slab track CWR on the rigid frame bridge are smaller; Under the broken track condition, the broken joint value of CRTSI bi-block track CWR on rigid frame bridge exceeds the allowable limit of the specification. CRTSIII slab track is recommended for rigid frame bridge.
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fanliyan, zhaoheyu, changjincai, liyinfeng
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Abstract:
Severe convective weather is one of the important factors affecting aircraft flight. In order to reduce the economic waste of diverting aircraft and the probability of encountering hazards, it is necessary to accurately delineate and predict the restricted areas. The first step is to extract the data on the thunderstorm points that affect aircraft flight. The initial polygon of the static flight restricted area is delineated using Graham"s algorithm. The change in geometry of the flight restricted area is predicted using the distance-mean method. Markov theory is introduced to predict the change of the center point position of the flight restricted area through the class state transfer matrix. The angular increment method is proposed to predict the angular change of the center point of the flight restricted area. The results show that the prediction accuracy is high and the deviation is low for radar weather data with low temporal resolution, and the prediction area can be updated in real time. The dynamic prediction is achieved on the basis of the static flight restriction zone, which makes the prediction results closer to the actual change.
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DOI:
Abstract:
The waterproofing of shield tail sealing system is an important factor affecting the safety of shield construction. A laboratory test of the shield tail sealing system was designed, and a corresponding simulation model was established based on the computational fluid dynamics to analyze the characteristics of waterproofing failure. The changes of volume distribution, pressure field and velocity field of two-phase fluid in the process of external hydraulic intrusion were analyzed, and the influence of shield tail structure parameters, tail brush parameters and grease parameters on seal performance was studied. The results show that: 1) increasing the number of shield tail brushes and the filling rate of shield tail brush steel wire can effectively improve the waterproofing ability; 2) In the process of waterproof failure, the peak point of flow velocity appears at the tail brush of shield, and the expansion distribution of flow velocity is consistent with the volume distribution of water. 3) The permeability of shield tail brush, the viscosity of grease and the exposed length of wire bundle are the sensitive factors affecting the initial leakage time. By reducing the permeability of shield tail brush, increasing the viscosity of grease and reducing the exposed length of wire bundle, the initial leakage time can be delayed, and the waterproof ability can be effectively improved.
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MOU Minghui, ZHAO Longzhi, CHEN Daoyun
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Abstract:
In order to find out the wheel rail rolling contact behavior of the train under traction and braking conditions, so as to provide a theoretical basis for the research on wheel rail damage mechanism in the future, taking CRH2-300 EMU wheel-rail as the research object, the wheel-rail contact mechanical behavior based on traction and braking performance adhesion coefficient model is studied by finiteelement simulation. The results show that the friction coefficient based on empirical model is significantly greater than that based on traction and braking model and Shinkansen model. The friction coefficient of Shinkansen model is close to that based on traction braking performance model. Under the traction condition, the tangential force image shows the form of two-point contact, and the point contact tangential force at the front end along the running direction is significantly greater than that at the rear end of the running direction. Under the braking condition, the tangential force is a single point contact at the beginning and then be a two-point contact. At the wheel rail contact point, the shear stress of the wheel S23 is in a circular arc shape, and the circular arc trend is consistent with the direction of the wheel angular velocity. The circular arc trend of the shear stress of the rail and the wheel S23 is symmetrical.
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DOI:
Abstract:
The opening rate is an important structural parameter of the shield machine cutter, and its size is directly related to the interaction between the cutter and the excavation surface.By designing a 1:10 model test, it realizes adjustable opening rate of cutter and real time weighing of residue,thus indirectly realizing the control of soil chamber fullness.The study analysis showed that under the condition that the actual rate of excavation is equal to the theoretical rate of excavation, increasing the rate of cutter opening can reduce the contact surface between the cutter surface and the excavation surface, thus reducing the cutter torque.The results show a 10% increase in cutter opening rate and an approximate 5.8% reduction in cutter torque.At the same emergence rate, the opening rate of the cutter has no significant effect on the maximum settlement of the ground surface.The support effect that the slag soil on the cutter gap can play on the excavation surface when the soil compartment is nearly full.
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LIU Tong, MA Wei, XIONG Leyan, GUO Zanru, ZHANG Jiali
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Abstract:
A series of PDAAM-co-PNIPAM-co-Mu copolymers were synthesized by RAFT polymerization from diacetone acrylamide (DAAM), N-isopropylacrylamide (NIPAM) and ureidopyrimidinone-containing monomer (Mu). Their structure and composition were characterized by Nuclear Magnetic Resonance (1H-NMR) and Gel Permeation Chromatography (GPC). Smart hydrogels crosslinked with acylhydrazone reversible covalent bonds were obtained by the reaction between PDAAM-co-PNIPAM-co-Mu and adipic dihydrazide (ADH). Due to the introduction of ureidopyrimidinone (UPy) hydrogen-bonding units into the network, the mechanical properties of the hydrogels were reinforced, and the compression strength of the hydrogel was increased by ca. 4 times. Meanwhile, the hydrogels exhibited pH and temperature dual-responsive and self-healing properties, and the compression strength was increased by ca. 30 times after heating.
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Yang Ke, Xiao Meihua, Zhong Xiaomei
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Abstract:
. Temporal logic studies the logic characteristics of the system whose state changes with time. It is widely used in software and hardware verification and is the basis of model checking. Based on the different descriptions of time models and in order to deal with more complex computational characteristics, many variants of temporal logic are derived, which have different expressive power. It is particularly important for the formal specification of system models to correctly understand their expressive power. Firstly, this paper introduces the discrete-time model LTL(Linear Temporal Logic), CTL(Computation Tree Logic) and CTL*,the continuous time model ITL(Interval Temporal Logic) and PTL(Projection Temporal Logic), the expressive power and the differences between them are elaborated in detail; Then, we summarize various temporal logic proposed to describe complex behaviors in random, real-time, hybrid and open systems, points out their characteristics and application scope; Finally, the future research direction of temporal logic is discussed.
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Wang Xin, Yang Songlin, Li Ang, Zhang Jiansong
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In a typical optomechanical system, the decay rate of an optical cavity must be smaller than the frequency of a mechanical oscillator (resolved sideband regime) in order to generate strong mechanical squeezing generally. This is difficult to implement in experiments. A scheme is proposed to generate strong mechanical squeezing and steady state entanglement in a hybrid atom-optomechanical system in the highly unresolved sideband regime (the decay rate of the optical cavity is much larger than the frequency of the mechanical oscillator). Two two-level atomic ensembles and two lasers with different amplitudes can be used to control the optomechanical system and the resolved sideband limit can be relaxed. Our results are as follows: if two atomic ensembles are put into the optomechanical system, the strong mechanical squeezing beyond 3dB is achieved even in the highly unresolved sideband regime; the steady state entanglement between the cavity and mechanical resonator can also be obtained.
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zhanpeng, hufengping, Long Lanlan
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Abstract:
n recent years, MOFs derived carbon-based materials have been widely used as green sorbents and efficient persulfate catalysts. This paper introduces the preparation process of MOFs derived carbon-based materials and analyzes their advantages and disadvantages. The mechanism of activated persulfate degradation of organic wastewater by MOFs derived carbon materials was reviewed in detail, including MOFs derived metal compounds, MOFs derived metal-free carbon materials and MOF derived transition metal/carbon composites. Finally, the application of moFS-derived carbon material adsorption removal and adsorption/oxidation coupling treatment of polluted organic wastewater were summarized.
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DOI:
Abstract:
Based on the engineering case of the pit in the pit of Nanchang aixihu tunnel，the deformation characteristics of the pit (including the influence range of surface settlement, the maximum surface settlement and the maximum horizontal displacement of the retaining structure) under different spatial forms of the pit (including the size, relative position and the insertion ratio of the retaining structure) are studied and analyzed by using the numerical calculation software. And the influence rate of foundation pit deformation is proposed, which can be used to comprehensively judge the sensitivity of pit spatial shape parameters to foundation pit deformation.The results show that the influence factors of the spatial form characteristics of the deformation characteristics of the pit in pit are mainly the relative size, relative position of the inner and outer pits and the insertion ratio of the enclosure structure. The specific sensitivity relationship is: relative depth > relative position > insertion ratio of the outer pit enclosure structure > insertion ratio of the inner pit enclosure structure > relative width.
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Ding Wenhao, Hu Minghua, Jiang Bin
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Abstract:
In order to accurately and effectively evaluate the operational efficiency of arrival flights in the terminal area, starting from the flight arrival efficiency and the capacity improvement capability of the airport terminal area, an efficiency evaluation index body for different runway operation modes and different types of flight procedures was established. An improved TOPSIS comprehensive evaluation model based on the entropy weight method is established to evaluate the efficiency of arriving flights in the terminal area. For the first time, the arrival efficiency index based on terminal area control load was introduced to evaluate the arrival efficiency of the flight, and the correlation analysis was carried out with the traditional efficiency index, which verifies the rationality of the index. Finally, taking Nanjing Lukou Airport as an example, the AirTop software is used to simulate the isolated operation and independent operation of typical daily flights (traditional ILS mode, based on RNP AR technology, and based on PMS technology), and compare and analyze various modes. The experimental results show that the approach efficiency under the PMS technology mode is optimal, with good approach efficiency and the ability to increase capacity. This study provides decision support for the perception of the airport"s operational efficiency and planning management.
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GAN Weihua, LIU Zheng, LIU Yanan, LI Chunzhi
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The rapid development of the online freight platform in recent years has brought great convenience to the freight market, meanwhile some regulatory problems occurred to the governments. Based on evolutionary game theory, with the introduction of reward and punishment mechanisms, an evolutionary game model between online freight platforms and government regulators is constructed in this paper, and the stability of their equilibrium points is analyzed. The results show that: (i) under static punishment, there is no equilibrium stability point in the system, no matter whether the reward mechanism is static or dynamic; (ii) under the static reward dynamic punishment and dynamic reward and punishment mechanism, both sides tend to a stable equilibrium point, and the effect is better under the dynamic reward and punishment mechanism; (iii) the online freight platforms" behavior is affected by the government"s reward and punishment mechanism, and the binding effect of the punishment mechanism is more significant.
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Mechanism and countermeasures of distresses occurring in transition pavement at tram grade crossings
Gao Boshun, Xiao Xin, Jiang Ligao, Yao Qing
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Abstract:
The road surface at tram grade crossings has borne combined loads of passing vehicles and tram. The load conditions and distresses of this area are complicated and varied, which becomes a relatively weak spot on municipal roads. In order to clarify the distress mechanism of this transition pavement at grade crossings, on the basis of field investigation, the statistics and classification of the distresses were carried out, and a 3D finite element model was established to analyze the mechanical response of the road-rail pavement structure, in which combined vehicle and tram loads had been conducted. The field investigation results show that the distresses in this transition area are mainly distributed within 30cm of the track side, and the settlement of pavement near the track is mostly distributed within 0-10mm. The numerical results show that the poor bearing capacity and strength and the disharmony deformation of pavement structure are the main reasons for the failure of the road-rail transition pavement. Focusing on the mechanism of the distress, the countermeasures of laying high modulus concrete under the pavement structure and adding transitional pavement materials between the road and the track are put forward.
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Pei Yingling, Luo Hui, Zhang Shihui, Li Jiamin, Xu Jie
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Abstract:
Aiming at the problem that the fasteners in the ballast-less track of high-speed railway become loose, resulting in the deflection or loss of high-speed railway fasteners, this paper proposes a high-speed railway fastener detection algorithm based on deformable convolution improved Faster R-CNN. Deformable Convolution is introduced in the feature extraction network to build Deformable Residual Convolution Block (DRCB), which makes the feature extraction process more focused on the fastener region to achieve accurate extraction of fastener state; and Alpha-IoU is used as the target regression loss function to improve the regression accuracy of high-speed railway fasteners. The experimental results show that in the detection of the fastener state of high-speed railway, the improved Faster R-CNN algorithm has 99.34% detection accuracy for the offset state of high-speed railway fasteners and 76.80% detection accuracy for the lost state, with an average accuracy mean value of 88.07%, compared with other algorithms, the improved Faster R-CNN algorithm has the highest detection accuracy.
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DOI:
Abstract:
Research on the problem of frequent failures of the potential transformer in the operation of the rolling stock, and concludes that the aging of the insulation in the natural environment and the influence of overvoltage and overcurrent on the insulation are the main reasons for the failure of the potential transformer, and proves the correctness of the theoretical analysis by simulation based on the finite element method. Finally, the insulation is optimized by adding an electrostatic screen and increasing the insulation distance of the first end of C section winding, the overload capacity is optimized by increasing the wire diameter of high-voltage winding, the cross-sectional area of the core, and the number of turns of winding, and the heat dissipation is optimized by increasing the heat transfer coefficient of the side surface so that the function of increasing the insulation strength, improving the overload capacity and reducing the temperature rise can be realized, and the finite element simulation analysis is carried out. The simulation results show that the maximum field strength of the optimized grid potential transformer is reduced from 2.79kV/mm to 2.24kV/mm, which increases the end in-sulation margin; the saturation degree can be controlled within 110% under 90kV frequency withstand voltage, and the excitation current can be within the limit capacity, which effectively improves the overload capacity; the hot spot temperature is reduced from 115.7℃ to 108.8℃, and the heat dissipation capacity is improved. The simulation results confirm the rationality of the optimized design and provide a reference for engineering ap-plications.
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DOI:
Abstract:
In this paper, motion stability of the high-speed maglev vehicle under steady aerodynamic load was studied. The dynamic model of the high-speed maglev vehicle on the curved guideway considering influence of aerodynamic loads was established. The critical speed concept of the maglev vehicle considering aerodynamic loads’ effect based on eigenvalues was presented. Vehicle speed, control parameters, and aerodynamic coefficients to make the critical speed of the high-speed maglev vehicle change in the critical state were also analyzed .?The results show that when the system reaches the critical state, it has two critical speed.?Under the conditions in the critical state, the position control parameters varys from 20000KN/m to 2000KN/m, and aerodynamic coefficients varys from 0.006 to 0.001, the critical speed gets larger.?The first critical speed occurs when the aerodynamic force is upward, and the second critical speed occurs when the aerodynamic force is downward.?Instability is caused by the change from the equilibrium position for the curved guideway and wind loads.?Aerodynamic down force and centrifugal wind loads is not good for stability, but aerodynamic lift force and centripetal wind loads improve stability. The horizontal angle can be matched with the centripetal force, but the vertical angle is allowed to be set in a small range.
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Fu Yichen, Zhou Jie, Shi Dapeng, Dong Chenxi, Sun Penghui, Li Yanjun, Cao Xinpeng, Zheng Haizhong
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Abstract:
In order to improve the wear resistance of CrN coating, magnetron sputtering technology was used to study the influence of external Cr layer on the wear width of CrN coating. The friction and wear of the surface were studied under different loads, rotational speeds and radii. The results show that the effect of centrifugal force is more obvious with the increase of rotation radius. When the rotation radius is 300r/min, the average wear width of the CrN coating without sputtering Cr layer reaches 945.7μm and the outer wear is more serious. Under the same conditions, the wear width of the outer Cr layer is 571.2μm. It shows that the outer Cr layer can effectively inhibit the increase of surface wear area during wear. After sputtering the outer Cr layer, the friction coefficient and the wear area width of the surface increase with the increase of the rotation radius at 200r/min. The wear marks on the surface are furrowed and the wear mechanism is abrasive wear.
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Li Mingcui, Chen Aixi, Zeng Wei
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Abstract:
Inspired by the recent experiments of cavity-magnon system and the theories of nonlinear reservoir, a scheme of coupling a cavity-magnon system to a squeezed reservoir is proposed to analyze the magnon blockade effect, and thus to realize the manipulation of magnetism in quantum level. An yttrium iron garnet sphere is located in a driven microwave cavity. The Kittel mode in the yttrium iron garnet sphere interacts with the microwave cavity mode, and the cavity field is coupled to a squeezed vacuum reservoir. By numerically solving the quantum master equation of the system, the influence of various factors such as coupling strength, detuning and dissipation rate on the correlation function is analyzed in detail. It is proved theoretically that the cavity-magnon system coupled to a squeezed reservoir can induce single-magnon blockade and two-magnon blockade, and the switching among single-magnon blockade, two-magnon blockade and two-magnon tunneling can be flexibly controlled by tuning the driving intensity or the detuning. The magnon blockade effect in the proposed scheme is mainly induced by the nonlinearity of the squeezed reservoir, which provides a possible new method to realize single or double magnon blockade in cavity-magnon system.
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XU Zhen-zhen, LIU Dong-feng, JIANG Ya-long
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Abstract:
This paper takes an iron ore project as the engineering background, simulate the mechanical characteristics of the solidified tailings with PFC, determine the meso-mechanical parameters of the solidified tailings, establish the uniaxial compression numerical model of solidified tailings. On this basis, studied the influence of particle size distribution and particle number simplification on mechanical characteristics of simulated solidified tailings. According to research findings, The average error between the numerical model and experimental results under uniaxial compression is 5.5. proved that the numerical model constructed by this method can effectively predict the uniaxial compressive strength of solidified tailings, and he effect of capturing the flexible and brittle failure mode of the solidified tailings is good, Further evidence that the PFC numerical model is effective and feasible to simulate the solidified tailings; because of different engineering conditions, the size distribution of tailings is quite different, If the size distribution of tailings is wide, The particle size distribution and particle number of tailings can be simplified when establish the numerical model of tailings. Analysis shows, In the case that the selection ratio of model tailings particle group range reaches more than 50%, The simulation of stress - strain curve and failure mode of solidified tailings is good.
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CHEN Shui-sheng, Ge Shi-qi, Gui Shui-rong, Zhao Hui
DOI:
Abstract:
In view of the characteristics of the beam bridge differential driving comfort, to explore the passing vehicle ride comfort, in the process of driving on the highway bridge was deduced in detail considering people - seat vibration equation of vehicle, with a beam bridge as the analysis object, based on the theory of vehicle bridge coupling vibration, further establish the interaction between vehicle and bridge coupled vibration differential equation. The seat acceleration of the vehicle was calculated by the self-programmed bridge coupling MATLAB program, and the ride comfort of the driver and passenger was evaluated according to the root mean square acceleration evaluation method in the international standard ISO2631-1. The influences of vehicle type, seat position, vehicle weight, bridge roughness, speed and many other factors on the ride comfort of the vehicle were analyzed. The results show that the driving comfort of car is better than that of truck and bus for different vehicle types. For a two-axle bus with multiple rows of seats, the ride comfort of the front seat is better than that of the back seat, and the farther the seat is from the vehicle centroid, the worse the ride comfort is. Vehicle ride comfort is very sensitive to bridge deck road condition, and it decreases rapidly with the deterioration of bridge deck road condition. Different vehicle weight, vehicle ride comfort increases with the increase of vehicle weight; Vehicle speed has a certain influence on ride comfort, but the influence is small. In order to improve ride comfort, it is suggested that speed limit measures should be adopted for driving vehicles of beam bridge.
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Xiong Liyan, Shu Yaosong, Zeng Hui, Huang Xiaohui
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Abstract:
When the mobile robot passes through the dynamic dense crowd, due to the insufficient understanding of environmental information, the robot navigation efficiency is low and the generalization ability is weak. To solve this problem, a double attention deep reinforcement learning algorithm is proposed. Firstly, the sparse reward function is optimized, and the distance penalty term and comfort distance are introduced to ensure that the robot approaches the target while taking into account the safety of navigation; Secondly, a state value network based on double attention is designed to process environmental information to ensure that the robot navigation system has both environmental understanding ability and real-time decision-making ability; Finally, the algorithm is verified in the simulation environment. Experimental results show that the proposed algorithm not only improves the navigation efficiency, but also improves the robustness of the robot navigation system. The main performance is that in 500 random test scenarios, the collision times and timeout times are 0, the navigation success rate is better than the comparison algorithm, and the average navigation time is 2% shorter than the best algorithm; When the number of pedestrians and navigation distance in the environment change, the algorithm is still effective, and the navigation time is shorter than the comparison algorithm.
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DOI:
Abstract:
To solve the optimal path problem of the traffic network, an improved travel time estimation model is proposed, and an optimal path algorithm based on this model is designed. The travel time estimation model is improved on the basis of the segment truncated quadratic velocity trajectory model by replacing the velocity measured at the same departure moment with the arrival velocity of the road segment nodes, and the travel time is estimated by constructing a velocity trajectory that is continuous in time and space. The optimal path algorithm based on travel time estimation firstly solves K shortest paths based on Yen"s KSP algorithm with road section distance as impedance, secondly estimates the travel time of K shortest paths by the improved travel time estimation model respectively, and finally selects the optimal path with travel time as cost. The validity and superiority of the model and algorithm are verified by numerical experiments of Sioux falls network. The experimental results show that: the improved segmented truncated quadratic speed trajectory model improves the accuracy by an average of 65% compared with the original model; the optimal path results based on the algorithm of this paper can reduce the number of intersections the path passes through and shorten the total length of the optimal path, Moreover, the estimated results of the optimal path"s travel time stay within 3% of the real value of MAPE. The results of this study provide a theoretical basis for the optimal path method for traffic networks.
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hong xian, guo wen jie, dai cheng xin
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In order to explore the effect of hysteresis damping on the band gap of periodic track structure, the ballast track of our country was taken as an example, and the band gap characteristics were analyzed based on the energy functional variational principle. By introducing hysteretic damping effect into rails, fasteners and track bed, the variation of dispersion characteristics with damping of periodic ballasted track is studied. Furthermore, the vibration transmission characteristics of the track structure under the effect of damping are studied. The results show that the band gap range of the undamped track structure is consistent with the attenuation range of the vibration response; the rail damping is very small and has little effect on the band gap of the track structure, which can be ignored when calculating and predicting vibration; the damping of the fasteners will slightly increase the track structural band gap and has little effect on the overall band gap, but for the vibration response, the dissipation effect of the fastener damping will increase the vibration attenuation range within 150Hz~500Hz; the increase of the ballast bed damping will increase the first-order band gap range, but it will decrease the second-order bandgap range, in the vibration response, increasing the damping of the track bed can dampen the vibration of the rail within 260 Hz.
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Density peak clustering (DPC) is a novel clustering algorithm based on density and distance. It is widely used in the field of data mining because of its simple principle, no iteration and the ability to process shape datasets. However, DPC algorithm also has some defects, such as the cutoff distance parameter is sensitive, the selection of initial clustering center is not automatic, and there is a chain problem in subsequent allocation, with high time complexity. This paper summarizes and arranges the research status of DPC algorithm. Firstly, it introduces the principle and process of DPC algorithm; Secondly, in view of the deficiencies of DPC algorithm, the optimization of DPC algorithm is summarized and analyzed, and points out the core technology, advantages and disadvantages of the optimization algorithm; Finally, the possible challenges and development trend of DPC algorithm in the future are prospected.
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huangyuchun, yutingying, wangning, linzhihang, gengdaxin
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The effect of geocell on the performance of ordinary subgrade is significant, but the degree of improvement of the bearing capacity of subgrade by adding geocell to the high fill subgrade with two side retaining walls is not clear. To explore the application effect of the geocell in this structure and Mechanical characteristics of geocells between different floors and retaining walls, three different reinforcement spacings and one unreinforced operating conditions are set to model test .The results show that: (1)in addition to the significant influence of reinforcement on bearing capacity, it also greatly improves the initial modulus of subgrade. When the allowable load is reached, it can still maintain the integrity of the structure itself. (2)The tensile stress of reinforcement is inversely proportional to the depth. The tensile stress and the lifting rate of the first layer are much greater than those of the other layers. (3) The stress distribution of retaining wall is triangular and increases suddenly at 0.22h. Based on the above conclusions, the reinforcement mode to maximize the benefit under the structure is summarized, which provides theoretical support and design reference for similar structures in the project.
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Study on the Influence of Groundwater Level and opening range on the anti-floating of subway station
DAI Wenchao, SHI Yufeng, CHEN Zhaoyang, HU Shaoling, FANG Tao, CHEN Xiaoyang, Zhan Yufei
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In order to speed up the construction progress of the whole line, it is proposed to add a track-laying base at a long station to be built. Meanwhile, to analyze the safety of the main structure of the station, it is necessary to calculate the anti-floating of the station when the underground water level rises. Based on the field monitoring data, using three-dimensional finite element software, the influence of the main structure floating caused by different underground water level and different opening scope of the roof of subway station is studied. The results show that, without considering the friction resistance between the main structure of the station and the enclosure structure, theamount of buoyancy near the railway track Wells is largeafter the closure of part of the precipitation Wells, and the influence degree of buoyancy is different in different parts of the station, so the anti-buoyancy measures should be considered separately. Under the condition of the same water level rise, the roof opening range and the maximum buoyancy of the main structure of the station show a nonlinear growth relationship. Therefore, different measures should be taken to suppress the buoyancy of the main structure of the station for the track wells, shield Wells and other special equipment wells with different opening ranges.
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Inconsistent monomer identification and warning method for power batteries based on isolated forests
Cheng Xianfu, Ma Xiaodong, Zeng Jianbang, Li Xiaojing
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The inconsistencies between the monomers of the power battery pack will occur due to the factors such as production process and service environment, which will affect the service life and driving safety of the battery. To meet the requirement of abnormal monomer diagnosis under inconsistent fault of power battery pack, based on data of vehicle network platform, a method of power battery monomer identification and early warning is proposed based on isolated forest method. The fault threshold T=0.75 is determined by counting the scores of normal and abnormal samples. At the same time, the data flowing into the diagnosis model is updated in real time by combining the sliding window to realize the recognition and warning of inconsistent monomers. The results show that the method can effectively identify inconsistent monomers, with the recall and accuracy of 0.91 and 0.95 respectively. When the size of sliding window is 15, the warning effect of real-time fault is the best. The research obtained in this paper is beneficial to reduce or avoid electric vehicle fire and explosion accidents caused by inconsistent power batteries, and is of great significance to promote the further popularization of electric vehicles.
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HU Yong, HUANG Zhi-qing, XIAO Qian
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Aiming at the safety problem of rash entry in the process of high frequency and long time dynamic test in rail vehicle production base, a new infrared anti-rash entry system is developed. According to the principle of infrared alarm, infrared transmitting and receiving devices are symmetrically installed on both sides of the vehicle dynamic test line. The infrared signal reception will be interrupted when the vehicle intrudes unlawfully, thus triggering the alarm device installed in the vehicle cab, triggering the electrical signal and transmitting it to the vehicle undergoing dynamic test, and issuing the command to start the vehicle emergency braking system, so as to ensure the safety of operation. The system solves the safety problems caused by human uncontrollable, equipment signal error, external interference and other factors. Meanwhile, the system is simple and reliable, low cost and convenient for long-term maintenance in the later period.
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LiPeng, ZhangChangyou, DuYibo, ChengWentao, ZhangJingqing, TangGan
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Self-healing material is usually used as a mechanical component, which not only needs to consider the topological optimization of the macro-configuration of the structure, but also needs to consider the influence of the size and distribution of self-healing agent carrier microcapsules on the mechanical properties and healing effect of self-healing material. Therefore, the collaborative optimization of structural macroscopic configuration and internal microcapsules is of great significance. The research is based on Movable Morphable Component, for isotropic material object, using structural compliance as the objective function, the material area as constraint conditions, the establishment of a built-in microcapsules component two-dimensional mathematical model, based on the method of moving asymptote (MMA), collaborative optimization design method of self-healing materials is given, and compared with the classic self-healing materials, the superiority of collaborative optimization is verified. The results show that: (1) The configuration of two self-healing materials is similar; (2) The structural compliance of the two kinds of self-healing materials increased with the increase of microcapsule volume fraction, and the mechanical properties deteriorated to different degrees; (3) Compared with the classical self-healing materials, the collaborative optimized self-healing materials showed more excellent mechanical properties with the increase of volume fraction. When the volume fraction was close to 14%, the compliance of the collaborative optimized self-healing materials was only 66.1% of that of the classical self-healing materials.
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He Ligong, Liu Wenwu, Luo Xinwei, Chen Yanming, Zhong Zhenlang, Xu Haoneng
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In this paper, the vibration acceleration of the ballast bed, pillar and cover plate of a typical double-deck metro depot is measured on site, and the characteristics of the vibration source and its transmission attenuation law are analyzed. The results show that the vibration of each ballast bed and pillar is not much different when the train passes through the first and second layers respectively, but the vibration attenuation of the first track bed-column is relatively large. The predominant frequency of the vibration of the cover plate is mainly concentrated in 30 ~ 80 Hz, and the vibration response of the measuring point near the center of the cover plate is greater than that at the end of the cover plate. The vibration response of the upper cover plate caused by the train running on the second floor of the operation zone is larger than that caused by the train running on the first floor. If the upper cover is developed, the vibration reduction design of the second floor should be considered. Whether it is a first-floor or a second-floor driving, the vibration is attenuated in the whole frequency range from the track bed to the column, and the low-frequency part of the vibration energy is easy to cause the resonance of the cover plate.
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Tan Chang, Zhang Lei Lei, Yang Hui, Zhang Jun Hui
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Aiming at the system errors caused by uncertain running resistances, model errors and other factors during the high-speed train operation, a new adaptive error compensation control scheme based on characteristic model is proposed to realize the asymptotic tracking of a given target speed curve. Firstly, the characteristic model of high-speed train with system errors is derived based on the characteristic modeling method and the parameter identification by the dynamic analysis of high-speed train. Secondly, an adaptive error compensation controller for high-speed train based on the characteristic model is designed by employing the ability of the extended state observer for the system error estimations, and the controller parameters are optimized based on the generalized minimum variance method, to achieve asymptotic tracking of a given speed profile even in the presence of the system errors. Such a control strategy can effectively deal with the uncertainties caused by system errors, improve the control accuracy, and guarantee the safe and reliable operation of high-speed train. To verify the effectiveness of the method proposed in this paper, simulation experiments are conducted by using the CRH380A type high-speed train as the controlled object. Simulation results show that the compensation control method designed in this paper has desired control performance despite the existence of unknown system errors.
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LIU Wenhai, LI zaiwei, HE Yuelei
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In order to study how to accurately predict the development trend of track irregularity in the absence of historical data. A track irregularity prediction method that can consider the prior information of experts is proposed. The questionnaire survey method is used to obtain expert experience information and build a Bayesian linear regression model with prior information. Then the Markov chain Monte Carlo method is used to solve the model parameters. Finally, the amplitude of track irregularity is predicted and error analysis is conducted, and the prediction effects of different models in the absence of historical data are compared. The results show that the method can accurately predict the development trend of the track irregularity in the short term, and the correlation coefficients are all above 0.9. In the absence of historical data, the Bayesian linear regression model can also maintain a high prediction accuracy and the R2 is 0.88, which is 17% higher than the traditional linear regression model. It is concluded that this method can effectively improve the accuracy of the operation and maintenance plan formulation at the initial stage of line operation, and is helpful to the realization of preventive maintenance of high-speed railway lines.
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FAN Xiujiang, FENG Guohui, XUE Fenfen, CHEN Guoping, DOU Bingjun, DING Shilong, Xu Changjie
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In order to explore the horizontal deformation law of adjacent pile foundation under tunnel excavation, an analytical method of horizontal deformation response of adjacent pile foundation is proposed. Firstly, the free-soils displacements induced by tunneling can be calculated by Loganathan formula. The Euler-Bernoulli beam is applied to simulate pile and the Kerr foundation model is used to simulate soil-pile interaction, then the horizontal force equilibrium of the existing pile can be established, later the analytical solution of horizontal deformation of pile can be obtained. Compared with existing finite element GEPAN data, the calculating result of the proposed method can be verified. Compared with existing theory solution, this method is closer to finite element GEPAN data. The parameters results show that the depth of horizontal maximum deformation position of pile will increases with increment with buried depth of tunnel and the maximum displacement of pile is increasing. The horizontal deformation of adjacent pile has increases with the increment of ground lose rate. Horizontal displacement of pile foundation decreases with the increase of horizontal distance between pile foundation and tunnel, but the depth of horizontal maximum deformation position of pile will decrease with the increment of tunnel-pile horizontal distance.
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Zhou Chao, Ding Chunlin, Li Guiyin, Zhu Haixing
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Based on the problem of adjacent construction of overpass bridge foundation and deep foundation pit of the underground station, this paper carried out a finite element numerical simulation of the whole construction process with Midas GTS NX where modified Mohr-Coulomb constitutive model was adapted on the soil, including foundation pit excavation, bridge foundation construction and braces demolition, to study the pattern of interaction between the bridge foundation and the underground station foundation pit. Having compared the numerical simulation results with on-site measured data, the results proved the accuracy of the simulation and showed that, during the excavation stage of the foundation pit, the deformation of the foundation pit continued to increase due to the horizontal unloading of the soil. The maximum settlement occurred at about 0.4 times the width of the foundation pit from the edge of it, and the maximum displacement of diaphragm wall occurred near the bottom of foundation pit. After the construction of the overpass bridge foundation, the surface settlement of the foundation pit and the lateral displacement of the diaphragm wall further increased, and the overpass bridge itself also had a modicum settlement. Thanks to the protection of the enclosure structure, the impact of the braces demolition was neither obvious on the pit nor the overpass bridge foundation.
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The shield tail synchronous grouting area is located behind the tunnel segment wall. Due to its closed space, it is difficult to visually observe the diffusion of slurry, resulting in the unclear distribution characteristics of synchronous grouting materials. Therefore, a shield tail synchronous grouting simulation device is developed to study the pressure change and upper soil settlement in the process of synchronous grouting. The results show that the soil pressure on the upper part of the moving axis of the slurry outlet increases gradually under the influence of grouting pressure, and decreases gradually with the distance from the slurry outlet, and the pressure on both sides increases gradually, resulting in obvious soil arching effect; The top pressure of the stabilized soil box, i.e. the internal pressure of the slurry, is determined by the upper load and has no direct connection with the grouting pressure; The surface settlement caused by grouting process is mainly determined by grouting pressure, followed by the influence of slurry properties; The thickness of the solidified grouting body is small in the transverse direction near the slurry outlet, relatively large on both sides, and the thickness distribution is relatively uniform in the longitudinal direction.
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Liu Xuxing, Deng Mingjun, Peng Liqun
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Aiming at the traffic saturation situation, a estimation method based on the maximum queuing length and initial queue of the period based on the maximum queuing length and initial queue of the period is proposed by using the vehicle arrival and parking position information provided by the real-time observation of the connected vehicle trajectory data during the period. Based on the trajectory of connected vehicles, the four critical points of vehicle arrival time, queuing time, start time and departure time are determined according to the arrival rate of each cycle according to the information provided by the critical point, and the initial queue length and maximum queuing length of each cycle are estimated by using shock wave theory, and the model is simulated and verified by the micro traffic simulation software SUMO. The experimental results show that under the permeability of 20%, the average absolute error between the estimated value of the queuing length model and the simulated value is 4.12 meters at the smallest, 7.83 meters at most, and the average relative error is at least 8.51% and 15.34% at most, indicating that even under the low permeability rate, the intersection queuing length estimation model based on vehicle trajectory can still estimate the maximum queuing length and initial queue length of supersaturated intersections more effectively.
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Unblocked road network is essential for the passage of people and the transportation of rescue resources when facing frequent natural disasters. The research objective is to analyze the seismic resilience change characteristic of urban road network. First, considering the spatial characteristic of earthquake and the comprehensive earthquake damage of road infrastructures, a link connectivity probability model based on intensity attenuation distribution is constructed, thus vulnerable sections are identified. Then, the seismic resilience of specific network under different scenarios is analyzed using a network structural resilience assessment model which considered 3 dimensions. Evaluation results of the effects of these vulnerable links elimination in the network show that network resilience is still strong when a few roads canceled, while this ability is significantly getting poor after the cumulative attack on the other vulnerable sections. Therefore, network transportation efficiency is reduced, and the connection between nodes are weakened. The network topology and simulation results lead to strategies of improving resilience.
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Bao yuanqiu, Jin Hui, Yang xiaoguang, Wu telan, Xuhui, Li jin
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In the critical period of epidemic prevention when a few infection cases occur or the epidemics spreads slightly in the city, public transit system offers the basic guarantee for urban trips. To ensure public transit operation performance and service quality during the critical period of epidemic prevention, aiming at the conflict states composed by the six strategies of the public transit provider and user in the critical period of epidemic prevention, a conflict graph model was constructed with the consideration of the balance and dynamic game between public transit providers and users. With sequence diagram, the relative preference of the decision-makers was ranked to the feasible states. For different types of conflict stabilities, the steady states were analyzed of the public transit provider and user. Case analysis was conducted on public transit of Suzhou to collect the preference of transit provider and user to different strategies via questionnaire. Then it is found that Nash steady state of public transit supply and demand is identified when the provider cuts transit shifts by 50% and stops transit service in isolation area, while the user stops unnecessary transit trips. The research provides scientific insights on public transit strategy in the critical period of epidemic prevention, conciliating the conflicts between transit supply and demand under special events for new balance.
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Zhou Jianmin, Liu Lulu, Yang Xiaotong, Wang Yunqin
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As a typical unsupervised learning model in neural networks, self-encoders have attracted widespread attention in various application areas, and their application in rolling bearing fault diagnosis is increasing. It has obvious advantages in data noise reduction and data visualization dimension reduction. In order to timely understand and master the application of auto-encoder and its improved algorithm in rolling bearing, this paper classifies and summarizes the representative auto-encoder related algorithms in recent years. Firstly, the principle of self-encoder and the theoretical sketch of several self-encoder methods based on its improvement are described, and the improvement purpose and improvement of these algorithms are analyzed. Then, the applications of these algorithms in the field of rolling bearing fault diagnosis are listed. Finally, the problems of present-day self-encoders and their improved algorithms are summarized, and the ideas for solving them are analyzed.
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As an emerging transportation infrastructure, the rapid development of high-speed railways has had a profound impact on social economy and people"s production and life in recent years. Based on urban data and railway data of ten prefecture-level cities in Zhejiang Province, except Zhoushan City, from 2006 to 2019, this paper uses a multi-period double difference method to explore the impact of high-speed rail on the income gap between urban and rural residents. It is found that: (1) The opening of high-speed rail and the increase in the frequency of trains have shortened inter-city travel time and significantly improved urban accessibility. (2) The opening of HSR widens the income gap between urban and rural residents, and affects the income gap between urban and rural residents through the mediating variable of changes in urban accessibility caused by changes in the frequency of trains. (3) There is an advance effect on the impact of HSR on the income of urban and rural residents, from the time when the construction of HSR starts, HSR will facilitate the reduction of the income gap between urban and rural residents in the region.
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Aiming at the problem of serious interference and low detection accuracy of insulator pictures collected in UAV patrol inspection, the optimization is carried out based on YOLOv5s algorithm, and the simulation research of insulator fault detection is carried out based on the improved YOLOv5s algorithm. The original algorithm is improved by adding CBAM attention module to the neck network, using k-means clustering to recalculate the size of a priori frame, and using MetaAconC as the activation function. The experimental results are analyzed based on python. The experimental results show that the advantage of this scheme is that the average accuracy of the algorithm mAP reaches 96.7%, which is 3.3% higher than the original YOLOv5s model; In addition, the weight file size of the algorithm training in this scheme is only 15.1M, which is only 0.1M larger than the original YOLOv5s, and still maintains the lightweight feature, which has a good prospect in the deployment of intelligent patrol work.
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Jiang Sicen, Chai Tianjian, Yan Jianwei
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In order to investigate the effects of new twin tunneling on the longitudinal displacement of existing shield tunnel, Pasternak double parameters of the elastic foundation and Euler Bernoulli beam model is employed to consider the new tunnel, existing tunnel skew angle and the tunnel excavation causing factors such as ground loss. The new double line tunnel excavation caused by free field vertical displacement of surrounding soils is determined by Loganathan-Poulos solution and superposition principle, and null space method is used to calculate the settlement deformation of the existing tunnel. Taking Shenzhen Metro Line 9 passing under Metro Line 4 as an example, the predicted results by the null space method is compared with the field-measured data. The effect of horizontal distance, ground loss, skew angle and depth of the new tunnel on existing tunnel settlement is further analyzed. The results show that the distance between the two lines of the new tunnel significantly affects the settlement of the existing tunnel in a range of 7 times its outer diameter. The settlement decreases with the increase of the distance, the settlement domain increases as the distance increases. The settlement pattern changes from "V" to "W". When the distance is larger than 7 times the outer diameter of the new tunnel, the settlement and pattern tend to be stable. In addition, ground loss, skew angle and the depth of the new tunnel significantly influences the settlement. It increases with the increase of ground loss, and decreases with the skew angle and the depth of the new tunnel. Reasonable regulation of the above influence factors in the actual construction process can effectively control both the tunnel subsidence.
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Chen Qinghua, Ge Xin, Hu Xiaoyu, Wang Kaiyun
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In order to investigate the influence of gauge rods on the dynamic performance in tight curves of heavy haul railway, the wheel-rail dynamic interaction and wheel-rail wear when the locomotive negotiates the R300 m curve at a running speed of 70 km/h were analyzed on the basis of vehicle track coupled dynamic theory. The influence of running speed and curve radius on gauge dynamic expansion, wear number, and gauge rods were analyzed. Furthermore, the influence of the spacing of gauge rods on the lateral stability of the track was studied. The simulation results indicate that the gauge rods can stabilize the gauge and reduce the turning angle of the rail at the outside curve. Compared with the curve without gauge rods, the contact point of the inner rail of the curve with gauge rods is closer to the inner side of the curve. The wear number and the dynamic gauge expansion when the locomotive negotiates a tight curve will increase with the decrease of curve radius and the increase of running speed. Increasing the arrangement density of gauge rods can effectively enhance the ability to stabilize the gauge. The dynamic gauge expansion will reduce by 36.3% when the spacing of gauge rods is reduced from 4 to 3 rail spans.
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DOI:
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The operation environment of high-speed trains is complex and changeable. The existing target curve of given operation speed mainly considers the safety and punctuality of train operation, which is difficult to improve other operation performance of trains. In order to meet the increasing traffic demand of high-speed trains and improve the running performance of trains, this paper proposes an improved multi-objective speed optimization method for safety, energy saving, punctuality and comfort, considering the optimal adhesion between wheels and rails. First of all, on the premise of meeting the restriction of interval speed limit and train dynamics model, four evaluation indexes of safety, energy saving, punctuality and comfort are established to form a multi-objective optimization model of high-speed train operation process; Secondly, the influence of adhesion between wheel and rail is considered in the energy-saving model, and the traction/braking force is optimized to keep it within the optimal adhesion range, so as to save operating energy consumption; Finally, the non-dominated
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luoruping, humingluqiu, zhubitang, wanganhui, yanwenkai
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In response to the problems that the sandy soil in the water-rich sand layer is prone to collapse, resulting in the weakening of bentonite slurry friction reducing effect and the increasing jacking force caused by construction halt during restart, a series of pipe-jacking model tests are conducted to investigate the influence of different mud sand content and different resting time on the effect of mud drag reduction and the changing characteristics of pipe jacking force. The results show that as the sand content of the mud increases, the friction between the pipe jacking and the mud interface increases exponentially. The pure slurry can reduce the friction force by 90%. When the sand content of the slurry is less than 20%, the sand content has little effect on the friction reduction effect, and the friction reduction effect is only reduced by 5%. With the increase of sand content in slurry, the effect of resting time on friction force between jacking pipe and slurry interface increased. When the sand content of the slurry is less than 60 %, the residual jacking force of the pipe-soil interface is not relevant to the resting time. When sand content reaches 80%, the residual friction strength increase of approx. 6% to 8% after 24h resting.
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Liu Shibing, Zhou Shihan, Dan Yeguang
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Aiming at the problem that the detection efficiency of high-speed railway catenary insulators is not high in complex background, the sample dataset is first expanded on a large scale. On the basis of the original YOLOv5s algorithm, in order to effectively improve the representation power of the model and increase the ECA attention mechanism, a cross-channel method without dimensionality reduction is carried out to focus on the position information of insulators. The BiFPN feature pyramid network is used to enrich the semantic information by multi-scale feature fusion. Select the Meta-ACON adaptive control activation function, and strictly control the upper and lower limits of the function within the maximum range allowed by the function to prevent the model from running out of control. The original GIOU loss function is replaced with the EIOU loss function, and the anchor box is further divided from the perspective of gradient, so as to improve the convergence speed of the network. Finally, according to the experimental results, the improved detection algorithm of YOLOv5s can be used to locate and identify the insulator more accurately, and the accuracy rate reaches 99.4%. The proposed detection algorithm provides a more accurate and faster method for insulator positioning detection.
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Zhu Huailong, Wang Qibiao, Zhu Bitang, Qiu Song, Liu Junjie
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As a new type of strain measuring instrument, fiber bragg gratings (FBG) strain sensors are gradually used in the field of civil engineering, and the key to their use lies in the deployment of sensors and the calibration of sensitivity coefficients according to different usage requirements and environments. The current conventional FBG installation methods are surface direct bonding and slotting implantation. In order to determine the measurement accuracy of the two installation methods, a calibration method of the unpacked FBG sensitivity coefficient used for the pile sinking test was proposed, the calibration test of the two deployment methods was carried out by using the circular seamless steel tube as the matrix, and the calibration results were compared with the theoretical values. The results show that in the stage of progressive loading, the calibration coefficient obtained by the method of slotted implantation method is smaller than that by surface adhesion method, while the calibration coefficient obtained by the surface adhesion method is closer to the theoretical value. The calibration coefficients obtained by the slotted implantation and surface adhesion methods were 2.84% and 0.33% respectively compared with the theoretical values; In the step-by-step unloading phase, there is a certain lag in the central wavelength of the two deployment methods, but the calibration coefficient is not much different from the loading stage. Therefore, it is necessary to choose a reasonable fiber grating layout scheme and calibration method according to the test environment and within the test tolerance range in the process of using FBG.
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Based on the Box-Behnken response surface method, a three-factor, three-level test was designed using Design-Expert 8.0.6 software with 5%-15% ceramic powder, 10%-20% ordinary silicate cement and 5%-15% quicklime as the factors considered to investigate the effects of each factor on the compressive strength and softening of gypsum-based composite cementitious materials at 7d and 28d ages coefficients at 7 and 28 d. The significance of each factor on compressive strength and softening coefficient was analyzed by quadratic regression fitted model ANOVA to determine the magnitude of the influence of each factor on admixture and the optimal mix ratio. The results showed that the effects of ceramic powder and cement admixture on 7d and 28d compressive strength were highly significant, followed by quicklime; the admixture of ceramic powder on softening coefficient was significant, followed by quicklime, and cement was the most inferior. The optimal ratio is 10.88% of ceramic powder, 15.51% of cement and 10.65% of quicklime, with a prediction error of no more than 10% verified by the test. The research results provide a test basis for further optimization of the constructability, self-warming and durability of gypsum-based composite cementitious materials.
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huyangyang, liuyinfang, sudeyin, guoyimeng, ZHU BITANG, huchunhua
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In this paper, the effects of cement content, water glass content and curing age on the impermeability performance of silty clay were discussed by indoor penetration test, scanning electron microscopy (SEM) and X-ray diffraction (XRD) test on the typical silty clay in Nanchang. The results showed that the permeability coefficient of improved silty clay decreased at a rate of 3 orders of magnitude higher than that of 14-28 d at a curing age of 7-14 d. With the continuous increase of cement content, the permeability coefficient of improved silty clay decreased and the decline rate gradually decreased. The increase of water glass content can significantly reduce the permeability coefficient of improved silty clay. Cement-water glass can synergistically improve the impermeability of silty clay, and the optimal ratio of 24% cement + 6% water glass has an optimal dosage. Compared with the improved silty clay with single cement, the incorporation of water glass did not change the main phase composition of the hydration product, but promoted the hydration reaction, increased the yield of hydration products such as C-S-H gel and C-A-S-H calcium vanadite, and greatly reduced the number of pores and fractures between soil particles.
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liang deng, cai xiaoyu, peng bo, xing ruru
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In order to identify the the traffic operation law of urban arterial road and support basis for traffic management department to formulating relevant traffic demand management policies, a vehicle travel group identification model of urban arterial road based on combined model was proposed. In this study, a travel characteristic indicator system was constructed from dimensions of travel intensity, travel time, travel habits for comprehensively describing the travel behavior rely on the the traffic bayonet data of Qingdao Jiaozhou Bay Tunnel. The redundant indicator was eliminated based on the correlation analysis to avoid the impact on identification research. For the mixed attribute travel characteristic indicator data, the improved K-prototypes algorithm was used to effectively classify the vehicle travel groups, and combined with GBDT, the identification model based on improved K-prototypes and GBDT was established. Randomly select 10000 samples to conduct identification research, and the result shows that there are 5 vehicle travel groups for the road in this research: high-frequency commuter groups, low-frequency commuter groups, operating groups, frequency stable groups, ordinary groups. For the 5 vehicle travel groups, the average identification accuracy rate exceed 97.75%, and the highest identification accuracy rate can reach 99.47%.
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Wu Songying, Liu Linya, Wan Qianghua, Jiang Jiaming, Song Rui
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Abstract:
In order to accurately detect the looseness position and degree of railway fasteners during service, a looseness detection algorithm of railway fasteners based on wavelet packet energy spectrum and improved BP neural network is proposed. First of all, referring to the current specifications, seven different loosening conditions of railway fasteners are designed on the spot, and the corresponding vertical vibration acceleration signals of rail under each condition are collected in turn; Then, the collected vertical vibration acceleration signal of the rail is decomposed by 7 layers of dB40 wavelet packet to obtain the corresponding wavelet packet node energy ratio data information under each working condition. On this basis, a vector dissimilarity coefficient index (VDC) is designed from the perspective of distance and dimension to realize the positioning of loose fasteners; In addition, according to the characteristics of the data, the particle swarm optimization algorithm is used to improve the BP neural network, build the PSO-BP railway fastener looseness detection model, and conduct parameter sensitivity analysis. The research results show that the minimum value of VDC of railway fastenings in healthy state is 0.17, and the maximum value is 0.41, which is significantly less than the VDC value of railway fastenings in each loose state. Based on this, accurate positioning of single and multiple loose fastenings can be achieved; The constructed PSO-BP railway fastener looseness detection model can achieve accurate detection of fastener looseness. When the number of neurons in the hidden layer is set to 20, the model detection effect is the best, and the corresponding recognition accuracy is 98.66%.
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WU Tongxi, ZHANG Huanlin, OU Yangjunshen, ZHANG Jun, HE Houzhu, DU Zhiyuan, PENG Xiaoming
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In recent years, a new bioelectrochemical system, constructed wetland microbial fuel cell (CW-MFC), has been formed by coupling constructed wetland (CW) with microbial fuel cell (MFC), and its reaction principle, composition structure and factors affecting the operation of the system have been extensively studied. Constructed wetland-microbial fuel cell (CW-MFC) has the advantages of both constructed wetland and microbial fuel cell, especially its ability to degrade pollutants and the biological power generation performance of MFC. This paper summarizes the functional characteristics and application of electrodes, introduces the influence of different electrode materials on pollutant degradation and power generation efficiency in wastewater treatment, analyzes the problems existing in the application of electrodes, and finally puts forward prospects for their future research directions.
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FU Jundong, CHEN Haojie, SUN Xiang, HUA Tianlian, LIU Shenshen, LIU Jun
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. Aiming at the problem of charging state balance management of lithium battery, a multi-agent based battery pack consistent charging state balance scheme was proposed. Firstly, the multi-agent control strategy is introduced into the sagging control of battery management, and the autonomous balancing under the active balancing circuit topology is realized. Secondly, the lead follower model is established, and the virtual agents with known parameters are used to make the state of each battery with inconsistent charge state close to it, so as to achieve the charge state balance in charge-discharge mode. Finally, simulation verification of the two-order multi-agent state load balancing control strategy is carried out. The experimental results show that, compared with the first-order balancing control strategy, the autonomous balancing time is reduced by 43%, the balancing time in charging mode is reduced by 68.95%, and the balancing time in discharge mode is reduced by 32.9%. The multi-agent system can achieve the balance of SOC in battery balancing management, effectively reducing the convergence time of SOC reaching the consistency of lithium battery.
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XIE Xianliang, ZHA Weixiong, WANG Yuqing, YAN Lixin
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To optimize emergency response and address the inefficiencies observed in traditional dispatch models, a study was conducted to develop a scheduling method that considers a range of emergency dispatch modes. The objective was to evacuate stranded passengers at disrupted stations using emergency buses while improving transportation efficiency. The dispatch model incorporated key factors such as the dispatching capacity of the emergency parking lot, vehicle capacity, and vehicle rescue time. The study developed a multi-objective combination scheduling optimization model utilizing a fast non-dominated sorting genetic algorithm (NSGA-II) to reduce transportation costs and the average passenger delay. The algorithm was improved to enhance the diversity and performance of the population, and a Pareto distribution optimization solution was ultimately obtained. The Nanchang Rail Transit Line 1 was used as an example to solve both the emergency bus combination dispatch plan and the single dispatch plan separately. Results revealed that the proposed combination dispatch plan reduced passenger delay time by 20.48% and transportation costs by 16.96% compared to traditional single dispatch plans. Additionally, the improved NSGA-II algorithm further reduced passenger delay time and transportation costs by 4.50% and 3.59%, respectively. Sensitivity analysis showed that fleet size negatively correlated with the average delay time of stranded passengers and positively correlated with emergency bus transportation costs, depending on the demand for transporting stranded passengers.
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DOI:
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At present, most studies rely on a large number of annotated samples to describe the feature distribution of known categories when solving the open set recognition problem of image classification models, which may lead to two problems: when the annotated samples are insufficient, the model training is easy to fall into the local extreme value; The decision boundary constructed according to the feature difference of known classes only reflects the feature distribution among known classes and lacks the generalization of open sets. In this paper, we propose a separate independent classification network structure, in which each category contains an independent linear feature layer. The neural nodes designed in the feature layer can capture the category features more accurately under limited data samples. At the same time, a class of negative samples without labeling is introduced in the model training, so that the model not only relies on the feature difference of the known categories when constructing the decision boundary, but also increases the open set generalization of the model decision boundary without adding additional labeled samples. The experimental results show that the open set recognition algorithm based on independent classification network and adaptive open set training on FDS and Imagenet-Crop data sets has better open set recognition performance than the existing open set recognition algorithm.
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PAN Yuan, ZHOU Shuang-xi, yangdan
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A crack detection method based on improved Unet model (A-Unet) is proposed to solve the problems of complex concrete cracks and many interference factors in bridges, tunnels and other environments. Firstly, Unet-based network, how the deep of the encoder affects the training time and detection accuracy of the model is studied. Secondly, in the decoder process, a fusion space and channel attention module is designed to give different weights to the high-resolution shallow features and the deep feature information obtained from the up-sampling to further enhance the crack features. At the same time, the dice loss function is added to evaluate the model to reduce the problem of inaccurate evaluation caused by the large difference between the number of detected objects and the background. The proposed method was evaluated in the test data set, the Precision, MIou and Recall rate reached 94.70%, 86.16% and 91.34% respectively. Also, the detection effect of A-Unet model is significantly better than the other five models. The results show that the accuracy of concrete crack detection by this method is greatly improved, and the model training time is saved, and the detection efficiency is improved.
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Wang Yi, Huang Hong, Shuai Zikun, Hu Wenbin
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In order to study the effect of recycled ceramic aggregate different types and replacement rates on the compressive strength and elastic modulus of concrete, recycled ceramic fine aggregate was used to replace natural river sand with the quality of 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100% replacement rate to produce recycled ceramic fine aggregate concrete (CRFC). On the basis of completely replacing (100%) natural fine aggregate with recycled ceramic fine aggregate, recycled ceramic coarse aggregate is used to replace natural gravel with quality of 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100% replacement rate to produce recycled ceramic coarse and fine aggregate concrete (CRC). The physical and mechanical properties of CRFC and CRC were studied, and the feasibility of waste tile ceramics as recycled concrete aggregate was analyzed. The results show that: 1) Recycled ceramic coarse and fine aggregate adopted in this paper are in line with the designed standards; 2) Recycled ceramic concrete is lighter than ordinary concrete, and its workability reaches ordinary concrete after adding additional water; 3) Recycled ceramic coarse aggregate has a significant effect on the reduction of compressive strength and elastic modulus of concrete compared with recycled ceramic fine aggregate; 4) The fracture failure of CRFC occurred in transition zone between natural coarse aggregate and cement mortar, while CRC mainly occurred in the interior of recycled ceramic coarse aggregate. 5) When replacement rate of CRC is greater than 50%, the crushing index of recycled ceramic coarse aggregate is the decisive factor for compressive strength.
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DOI:
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The low-carbon development of cities is an important lever in China"s ecological civilization construction, and the "strong provincial capital" strategy has had a significant impact on the coordinated development between regions, which puts forward new requirements for the low-carbon economic development and industrial selection of cities in the Yangtze River Economic Belt under the "strong provincial capital" strategy. In this regard, the study uses the random forest model to describe the low-carbon economic effects of the industries in the prefecture level cities of the Yangtze River Economic Belt, and discusses the problem of industry selection. The results indicate that: (1) The carbon emission reduction potential of urban industries in the Yangtze River Economic Belt is significant, with the construction industry being the largest. (2) Under the strategy of "strengthening provincial capitals", Shanghai, Wuhan, Chongqing, and Chengdu have relatively full development of low-carbon industries, while small core provincial capitals such as Nanchang, Guiyang, Kunming, and Changsha have great potential for emission reduction in manufacturing and some social service industries. (3) Provincial capital cities should focus on developing social service industries, while non provincial capital cities should select industries with their own characteristics for key development based on their own resource endowments.
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Lv Lu, Ding Tian, Guo Zhongyin
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To ensure the vehicles through the work zone crossovers for expressway construction smooth and fast, a graded speed limit plan for the traffic control zone was studied. Firstly, collect and analyze the traffic flow velocity and time headway in different traffic control zones. Secondly, according to the vehicle trajectory to calculate the value of the last speed limit sign, and a graded speed limit plan for the traffic control zone was formulated based on vehicle deceleration and driver gaze. Finally, the graded speed limit plan was evaluated by safety and efficiency indictors through driving simulator. The results show that the average speed and the time headway in work zone crossovers are the smallest. When the median width is 70 meters, the final speed limit value should be 40 km/h, forming a graded speed limit system in expressway construction with a deceleration amplitude of 20 km/h and a final speed limit sign positioned in 50 meters before the upstream of the transition area. The driving simulation test show that compared with the two-level speed limit scheme in the "Safety Work Rules for Highway Maintenance," the comprehensive efficiency index of the traffic control zone under established scheme has increased by 9.15%, and the extensive safety index has decreased by 27.62%.
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Baiwenchang, Yuanzhouzhiyuan, Jibohai, Fuhui
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In order to investigate the initiation characteristics and propagation laws of fatigue cracks in the U rib-to-deck weld joints of a steel bridge deck under wheel loads, a segment model of steel bridge deck was established using the finite element method. Deformation characteristics of the structure were analyzed under different wheel load positions, and the correspondence between the wheel load position and typical deformation characteristics was clarified. Local simplified models were then established based on this analysis. Using the local models, the crack initiation characteristics were determined based on stress distribution. Three-dimensional numerical simulation of crack propagation was carried out based on fracture mechanics to obtain the crack propagation law of the U rib-to-deck weld joint under different wheel load positions. The research shows that when the wheel load deviates from the weld, the fatigue crack tends to initiate at the weld root and weld toe of the deck and propagates along the thickness direction of the deck, with the crack extension type being mode I. When the wheel load is located directly above the weld, the fatigue crack prefers to initiate at the weld root of the deck and the weld toe of the U-rib, propagating obliquely perpendicular to the U-rib web. These cracks belong to the I-II-III composite type dominated by Mode I cracks, and their propagation rate is faster.
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Li Jie, Meng Fanxi, Zhang Zichen, Zhu Wei
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The change trend of exhaust gas temperature margin (EGTM) of civil aviation engine reflects its performance degradation. In order to employ the change trend of EGTM to map the performance degradation of the engine, an deep integrated neural network prediction method based on empirical mode decomposition (EMD) algorithm and convolution short-term memory network (CNN-LSTM) is proposed in this study. EMD is used to decompose the original EGTM sequence into multiple natural mode components and residual components, and all the resulting components are used as model input. The convolution long-term and short-term memory network is used to capture the nonlinear correlation of each component and extract the long-term dependence to construct the framework of deep learning model. In order to verify the effectiveness of the proposed method, the actual test data of EGTM of an airline for 10 years are used for experimental analysis, and five kinds of neural networks are designed as competitive models for comparative study. The experimental results show that the proposed EMD-CNN-LSTM fusion neural network model can reduce the mean absolute error and the root mean square error by 37.82% and 33.01%, and increase the goodness for fit by 1.02%, compared with competitive models. Furthermore, when EGTM is in the sensitive area, EGTM single-point prediction accuracy of the proposed model is significantly higher than that of other competitive models. Therefore, the proposed fusion neural network model has good accuracy and stability in EGTM prediction of civil aviation engine.
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DOI:
Abstract:
The planning of railway logistics park is mostly upgraded from the existing railway freight facilities. Following the analysis of the main functions and the requirements of the railway logistics parks layout planning, an optimization functional areas layout model is proposed to minimize transshipment costs and maximize relevance, considering the constraints of existing railway freight facilities, functional area length, shape, direction requirements, and entrance and exit settings. Route-based distance is used in the model. Based on the NSGA-II algorithm, the continuous penalty factor is designed according to the satisfaction of the layout result to the constraint condition, and the constraint condition is converted into the objective function penalty value. On this basis, the slice tree coding sequence and multiple mutation methods are introduced, and the algorithm can effectively avoid falling into the local optimum. Case analysis demonstrates that the algorithm is effective and has high solution accuracy, and the layout scheme is reasonable.
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RONG Xiaonan, TAN Jing, CAI Xiaoyu, PENG Bo, WANG Yuting
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Abstract:
Mountain city trunk line undertakes the main traffic volume of the city, which has the characteristics of large differences in traffic flow characteristics and uneven traffic distribution, which puts forward new requirements for traffic control. In order to improve the traffic efficiency of urban trunk line, this paper takes the mountain city trunk line system as the research object and establishes the optimization method of coordinated control of mountain city trunk line based on swarm algorithm. At the level of coordinated control, a coordinated control method for tracing the source of congestion based on the minimum delay in the sub area is established; At the single point control level, the optimal control based on hierarchical feedback is established, and finally the coordinated control scheme is generated by combining the regulation rate at the coordination level and the single point level. The example verification shows that for the trunk multi Lane merging system, the average delay and average parking times of swarm optimization algorithm scene are reduced by 22.06% and 28.42% respectively compared with the uncontrolled scene; Compared with the current control scheme scenario, the average delay, average parking times and average travel time of trunk multi Lane merging system have been reduced by 23.04%, 24.08% and 19.38% respectively. It can be proved that the swarm optimization algorithm has a good control effect on the multi Lane merging system of trunk lines in mountainous cities.
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ZHAN Jinqing, Wang Tingwei, Duan Dingqiang, LIU Min
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For the input coupling and output coupling issues of compliant mechanisms with multiple degrees of freedom, a method for topological design of fully decoupled compliant mechanisms with multiple materials is presented. The multiple materials interpolation model based on the element stacking method is adopted. The maximization of the weighted sum of multiple output displacements is applied as the objective function. Both input coupling and output coupling constraints are proposed to suppress the coupling issues. The coupling constraints and the structural volume for each material are used as the constraints. The model for topological design of fully decoupled compliant mechanisms with multiple degrees of freedom using multiple materials is established. The method of moving asymptotes is adopted to solve the topology optimization problem. The obtained compliant mechanisms considering the coupling issue is different from those without considering the coupling issue. Both input coupling and output coupling of compliant mechanisms with multiple degrees of freedom can be suppressed effectively. The input and output motions of the compliant mechanisms can be completely decoupled. The influence of different coupling coefficients on the results is analyzed
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Zhou Hang, zhangjing, Li Jun, Wei Tingsan
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Given the uncertainty of the severity of stray current on the corrosion area of buried pipelines along the subway line, a three-dimensional finite element analysis model of stray current is established to study the distribution of stray current under the operation mode of subway up and down trains. The dynamic change process of the cathode and anode area on the buried pipeline. Dynamic change process of cathode and anode area on the buried pipeline. Considering only the influence of anode stray current, the interference area and degree of the buried pipeline during train operation are judged by comparing different models. When the two trains are running in the opposite direction at the same time, the interference area of the buried pipeline is mainly distributed on both sides, and the interference area is symmetrical concerning the central position of the pipeline. When the up train starts 18s, 37s, and 55s earlier than the down train, the areas with strong interference degrees on the buried pipeline are mainly distributed on the right side of the pipeline. Among them, when the up train starts 55s earlier than the down train, there is a large interference current density on the buried pipeline, up to 18A/m2. In the later protection of subway stray current, corresponding measures can be taken for the serious interference area of pipeline in combination with finite element model.
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DOI:
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To study the eccentric mechanical properties of concrete filled steel tube reinforced concrete column (CFSTRC) under fire, a finite element model is developed. The failure mode, deformation, internal force, strain and stress, interaction between steel and concrete under fire are analyzed, and the results with different parameters are discussed. The results show that under fire, the CFSTRC column shows good plasticity with overall instability failure mode, and the eccentric mechanical response of the column can be roughly divided into three stages. There is a phenomenon of internal force redistribution in each part of the column; the tensile area of the column section gradually expands, and the interaction force between steel tube and concrete also increases gradually under fire. The section size and slenderness ratio of column have great influence on the bearing capacity of square steel tube-reinforced concrete column under fire. Based on the parametric results, the design method to evaluate the bearing capacity of CFSTRC members under fire are proposed.
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DOI:
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Prefabrication and assembly construction technology is more and more widely used in bridge construction because of its advantages of green environmental protection, convenient construction and controllable quality. Based on the project of national highway 329 smart expressway, this paper puts forward a new construction method of front supporting and rear anchoring based on the original prefabricated and assembled bent cap construction method, and studies the internal force of the whole construction process of the two methods through numerical analysis and comparison. The research shows that: (1) In the construction of front support and rear anchor, the internal force distribution of the capping beam is similar to that of a simply supported beam under the conditions of lifting the capping beam and front support, while the internal force distribution is similar to that of a cantilever beam under the conditions of removing the crane; (2) The structural internal force of the capping beam during the whole construction process of the front supported and rear anchored construction method is significantly less than that of the rear anchored construction method due to the synergistic effect of the front supported and the rear anchored. Especially when the crane is removed, the maximum bending moment of the capping beam is reduced by 73%, indicating that the front supported and rear anchored construction method have greater safety; (3) The maximum tensile stress of the bent cap in the whole construction process is only 1.2MPa, which is less than the design value of the axial tensile strength of the concrete of 1.83 MPa, indicating that the bent cap is always safe and reliable in the installation process. The proposal of front supported and rear anchored construction has important guiding significance for the innovation and development of construction technology of spliced bridge substructure.
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Xu Baogen, Zheng Mengmeng, Lan Ting
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With the rapid development of domination theory, the problem of edge domatic set partition of graphs has attracted much attention. Let be a nonempty graph, is said to be an edge domination set of if there exists an edge such that is adjacent to . is the set of all the edges of . And the maximum number of nonintersecting edge domination sets that it can be partitioned into is the edge domatic number of graph . The partition of edge domination set of Wheel graph with strong symmetry is the main research content, and the set edge domination number of wheel Graph is obtained by deductive reduction method, accordingly, the application of deductive reduction method in edge domatic set partition of special graph is realized.
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Zhao Yu, Yang Zhen, Yong Jiangping, Zhan Aiyun, Zhang Yuejin
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Since the traditional text encryption algorithm is not applicable to image encryption, the classical Logistic mapping has the problems of limited range of system parameters and unequal distribution of chaotic sequences. In this paper, an image encryption algorithm based on cyclic shift combined with improved Logistic and Tent mapping is proposed. The initial values and control parameters of improved Logistic and Tent mapping were set, and the bitt retake technology was applied to improve the chaos effect in the transition state, so as to improve the effect of image encryption algorithm. When the plaintext image is processed, Arnold transform and xOR pre-encryption are carried out first, and the image is partitioned, and then the sequence generated by Tent map is used for sorting index and circular shift. In the process of encryption, the plaintext image has undergone pixel replacement and pixel diffusion, so that the value and position of the plaintext pixel have changed. Experimental results show that this algorithm has good encryption performance and security.
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Ke Chan, Cheng Hongbo, Liu Jianpeng, Xiong Kuangwei, Shi Haiquan, Huang Kelin, Cheng Ziqiang
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Abstract:
Large-scale three-dimensional (3D) hierarchical Ag nanosheet-assembled films on an indium tin oxide (ITO) glass substrates were fabricated via two-step electrochemical deposition method, and its surface-enhanced Raman scattering effect (SERS) was studied. As a large number of hot spots are located at the edges of Ag nanosheets and the cross-linking gaps between the neighboring nanosheets across the whole substrate, using 3,3′-diethylthiatricarbocyanine iodide (DTTCI) as probing molecules, the Ag nanosheet-assembled film exhibits strong surface-enhanced Raman scattering (SERS) effect. The SERS experiments showed that the Ag film assembled by nanosheets with high pack density exhibited excellent detecting performance, which could be used as effective low-cost SERS substrate for ultrasensitive detecting of substances.
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Hu Weicheng, Yuan Ziting, Chen Hua-Peng, Liu Wei, Wang Yongxiang, Jin Junyan, Sun Shilong
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The fence height and incoming wind velocity are the main factors affecting the spatial dispersion of construction dust. Taking a construction site in Beijing as an example, the construction dust data of a certain period is selected for CFD simulation, and the results are compared with the actual measured dust concentration data of the site for verification. By analyzing the meteorological wind velocity data during the construction period of the site, 6 kinds of incoming wind velocities of 2 m·s-1, 3 m·s-1, 4 m·s-1, 5 m·s-1, 7 m·s-1 and 9 m·s-1 with exponential law are selected, and 6 kinds of fence heights of 1.8 m, 2.0 m, 2.2 m, 2.5 m, 2.8 m and 3.0 m are chosen. The CFD simulations are conducted to compare and analyze the spatial distribution and dispersion characteristics of construction dust under different fence heights and incoming wind velocities. In order to comprehensively evaluate the impact of construction dust on the human body and external environment, the averaged dust emission rate in the range of breathing height 0.5 m~1.5 m and the dust fugitive ratio are proposed as evaluation indexes. The results show that the averaged dust emission rate of 3.0 m fence height has the lowest overall index at the six incoming wind velocities, indicating that dust pollution has the least harm to the human body. The dust fugitive ratios of the six fence heights under the same incoming wind velocity are almost the same, which indicates that the impacts on the external environment are almost the same. The impacts of the construction dust on the human body and the external environment are the most serious when the incoming wind velocity is 3 m·s-1 and 5 m·s-1, respectively. The results of this research can provide a scientific basis for the development of control measures on construction dust pollution.
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Charging pricing strategy for electric vehicles considering balanced time distribution of power load
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As environmental pollution and energy crisis become more and more serious, electric vehicles have attracted widespread attention due to their advantages of low emission and low noise. But a flood of electric vehicles plugged into the grid will have a huge impact on the power system. Especially in the living area, EV users are generally used to enter the community to charge their cars immediately after work, and this period is the peak period of household electricity consumption. Large-scale uncontrolled charging behavior will cause security risks to the power grid and affect the normal operation of the power grid. On account of this phenomenon, a two-level programming model aiming at ‘peak cut’ for time-of-use price of electric vehicles in residential areas was established. The lower was minimization model of charging cost for lower users, getting the charging load. The upper was load time distribution equilibrium model of upper power grid, obtaining time-of-use price of fast and slow charging power. It could change the charging behavior of residents by time-of-use price. Finally, the calculation example showed that the power supply stability of the grid was improved by 57.66%.
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DOI:
Abstract:
The design, manufacture and prototype experiment of a new fire-monitor to substitute the traditional bend flow channel with a straight one are presented in this paper in order to cut down the pressure drop when hydraulic fluid goes through it, and the structure with a multi-bar linkage plus a revolute pair is used so as to realize two rotations. The dimensional optimization of four-bar linkage as well as the design of the oscillating mechanism is delivered in sequence; the prototype has also been developed and its performance test has been carried out, finally. The expected results of the work has achieved based on the experimental ends, which has guidance to the redevelopment of novel fire-monitor with longer distance, higher efficiency and lower energy consumption than traditional one.
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Wang Sen, Liu Chen, Xing Shuaijie
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Cluster analysis is an important technique for data mining. In the 5G era, massive data have high dimensions and large data sets. The K-means algorithm is susceptible to outliers, and the k value and the selection of initial clustering centers affect the stability and accuracy of the clustering result. It even causes the clustering to fall into the local optimum, so the improvement of the K-means algorithm has attracted the attention of many researchers. This article mainly summarizes the current research status of K-means clustering. Firstly, it introduces the principle of K-means algorithm; Secondly, according to the selection of the initial clustering center point, the determination of the K value, and the outliers, the existing improved algorithms are classified and summarized based on density and distance, and the advantages and disadvantages of each improved algorithm are analyzed; finally, the K-means algorithm is analyzed. Prospects for possible future research directions and trends.
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DOI:
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Traditional grinding robots are fixed on the base or installed on the guide rail, which has low mobility and limited working area. Aiming at the high mobility of indoor wall grinding robot, a four-wheel grinding robot mobile platform based on mcnamu wheel is proposed. Firstly, the structure of a single mcnamu wheel is analyzed to understand its motion mode, then the forward and inverse kinematics of the mcnamu four-wheel mobile platform are analyzed, and the inverse kinematics formula of the four-wheel mobile platform is obtained. Then the inverse kinematics model is established in Simulink, and finally the forward kinematics is verified in vrep (virtual robot experiment platform). The results show that the analysis of the mcnamu wheel mobile platform is correct, and the mcnamu wheel mobile platform can fully improve the mobility of the grinding robot and lay a good foundation for the automatic grinding of the robot.
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yuan yisheng, Liu Wei, Liu Wenqin, Zhang Zhiqin
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Aiming at the problems of electromagnetic interference and shortening the service life of input source caused by inherent intermittent ripple current on the input side of switching converter, a passive ripple compensation circuit for Flyback converter is proposed. The circuit is composed of transformer, diode and electrolytic capacitor.Under the designed ripple suppression condition, it works in a similar Flyback state and generates compensation current, which effectively suppresses the inherent intermittent ripple current on the input side. On the basis of explaining its working principle, the parameter calculation methods of system gain, suppression conditions of ripple current and related variables are deduced by using the formula. An experimental prototype with 6080V input, 30V rated output voltage and 65W rated power is built. The experimental results verify the feasibility of the proposed passive ripple compensation circuit and the correctness of theoretical analysis.
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Rao Li, Jin Yihao, Liu Fei, Zhao Longzhi
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The semi-solid billet of AlMgLi0.5Zn0.5Cu0.2 light-high entropy alloy was prepared by isothermal heat treatment and the effects of holding temperature and holding time on the microstructure evolution of AlMgLi0.5Zn0.5Cu0.2 light-high entropy alloy were investigated. The results show that, with the increase of holding temperature, the average grain size of semi-solid AlMgLi0.5Zn0.5Cu0.2 light-weight high entropy alloy decreases first and then increases, while the roundness of the grains increases first and then decreases. With the prolongation of holding time, the average grain size and roundness of AlMgLi0.5Zn0.5Cu0.2 light-weight high entropy alloy increase. The best semi-solid microstructure of AlMgLi0.5Zn0.5Cu0.2 light-weight high entropy alloy was obatined at 460℃ for 60min, whose average grain size is about 41μm, roundness is 0.82, and coarsest coefficient K=20.95μm3/s.
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Zhang Bing, Yu Fengjun, Liu Jianrong, Zhou Xun, Wang Mingjie
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The elderly due to physical fitness and travel time different from commuters, they usually travel by bus or walking. Using the confirmatory factor analysis and binary logit model, studying the influences of the elderly"s personal statistical attributes and psychological factors on the travel behavior, such as their attitude towards daily travel, their feelings about taking buses at peak times, and their travel intention to avoid rush hours before and after the preferential policy of suspending public transport at morning peak hours. The latent classification model was used to classify and analyze the elderly groups. The results show that all kinds of psychological factors have significant influence on elderly’s short-distance trips. The bus preferential policy and the group"s support for off-peak travel have a significant impact on the elderly’s choice. The latent classification model shows that the survey objects have necessary travel purpose, and the proportion of elderly groups who are sensitive to bus travel and off-peak travel is low.
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DOI:
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In the current research of traffic flow prediction, the time step mainly depends on the artificial selection which is easy to be disturbed, and there is a lack of method to select the time step from the theoretical aspect. In order to adaptively select the time step, three typical algorithms of least squares support vector machine (LSSVM), random forest (RF) and long short-term memory (LSTM) in machine learning are used to predict traffic flow with multiple time step based on the autocorrelation analysis of traffic flow historical time series and explore the feasibility of selecting the best time step by the value of autocorrelation coefficient. The experimental results show that when the autocorrelation coefficient of the time step is 0.83-0.91, LSSVM can obtain better prediction accuracy while the autocorrelation coefficient is 0.47-0.51, LSTM can have better prediction accuracy. However, due to the low autocorrelation degree of the time step corresponding to the lowest error of traffic flow prediction, the autocorrelation analysis method may not be applicable to RF.
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Ye Yuling, Liu Kai, Liu Jialin
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Transportation industry is one of the main sources of pollution emission at present. To reduce environmental pollution in freight industry, it has become an important measure to guide freight flow from road transportation to rail transportation in view of the advantages of railway transportation in environmental protection. Therefore, this paper studies the choice of freight transport mode considering environmental cost under the competition between road transportation and rail transportation, where the environmental influence on share rate is quantified. The unit environmental cost is calculated by various pollutants emissions and cost factors and the unit time value of goods is calibrated via the Logit model. Aiming at the minimization of the total social cost composed of transportation cost, time cost and environmental cost, a choice model for freight transportation is then formulated. Taking the freight data of road network and railway network in Shandong as an example, the transportation mode and route selection schemes are discussed under different values of environmental cost coefficient. It is found that considering the environmental cost, the freight market share of railway transportation will increase, transportation cost and pollutant emission will decrease correspondingly.
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WAN Ming, LIANG Ying, ZHOU Tuqiang, YAN Lixin, GUO Junhua, LI Fangyuan
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In order to quantitatively analyze the influence of highway dynamic congestion traffic information caused by traffic accidents and traveler heterogeneity on travel choice behavior, a large-scale SP/RP survey data that covering 2500 highway users in west Japan is used for this study. Latent Class Analysis (LCA) is adopted for extracting different preference features on traffic information, followed by a multilevel model which sets the results of LCA as explanatory variable. The research results show that: according to investigation information,travelers can be divided into three groups：high-dependence group, low-dependence group and non-dependence group accounting for 38.8%, 36.1% and 25.1% respectively; the model considering data hierarchical structure is more accurate than the general discrete choice model; and travelers with different heterogeneity of traffic information have obvious differences in travel behavior under dynamic traffic information.
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DOI:
Abstract:
During the epidemic prevention and control period, the safety and limitations of the online vehicle operation model lead to difficulties in meeting the safe travel needs of residents in areas with recurring epidemics. To realize the requirement of synergistic development of the quality of net-hailing services and environmental benefits, the current problem of electric vehicle ridesharing is studied about the characteristics of the COVID-19 prevention and control. Considering the heterogeneity of passengers" own infection risk, the characteristics of virus transmission, and vehicle charging, different riding strategies are adopted to identify the types of passengers" infection risk. From the perspective of epidemic prevention and control, vehicle route constraints, vehicle disinfection constraints, and vehicle charging constraints are established, and the total profit of the driver, consisting of driver compensation, government subsidies, and vehicle operating costs, is taken as the optimization objective to build a ridesharing optimization model with epidemic prevention and control characteristics. A small-scale example is designed and solved using a Lingo18.0 solver. The analysis of the example proves the validity of the optimization model, and at the same time, it can provide an effective value reference for the network car operation model in the real environment.
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Huang Zhengkai, Zhao Zehui, Wen Zhiqiang, Nie Qixiang, Wang Haicheng
DOI:
Abstract:
There are both import pratical value and scientific research significance of monitoring the global terrestrial water storage change (TWSC) by satellite gravity technology. Based on the GRACE time-varying gravitational field model, this paper obtains the TWSC of global typical river basins from 2002 to 2020, and discusses the influence of climate and human factors on the regional TWSC. The research results show that the TWSC in similar geographic regions have similar cycles and amplitudes, while the TWSC of adjacent watersheds located in the northern and southern hemispheres present opposite periodic signals. The TWSC in the Murray-Darling Basin is affected by precipitation and evaporation, while the Indus-Ganga River Basin has been declining due to excessive groundwater extraction. The correlation between GARCE and GLDAS acquired water storage changes in the Amazon basin reached 0.86. At the same time, it was found that GRACE has a unique advantage in detecting regional drought events.
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DOI:
Abstract:
The performance of passive flexible protective structure includes mechanical performance, energy dissipation performance and deformation performance, but most of the current research is focused on the former two, and only a few scholars have studied its deformation performance. Taking "residual interception height" and "falling rock buffer distance" as the key technical indexes to evaluate the deformation performance of passive flexible protective structures, a new passive flexible rockfall barrier for intercepting and buffering the impact energy of falling rocks is proposed. Based on ANSYS/LS-DYNA, three types of ring net models are established, and the energy consumption and deformation performance of ring net are analyzed from three aspects: maximum energy consumption, residual interception height and falling rock buffer distance. The results show that the ring net with vertical support can effectively reduce the buffer distance of falling rocks and increase the residual interception height of the ring net, but the maximum energy consumption of the ring net has decreased to some extent. Compared with unsupported and double-supported ring nets, single-supported ring nets have the following advantages: the maximum energy consumption ratio is relatively high, it has the function of rapidly attenuating the impact energy of falling rocks under the action of instantaneous impact load, the buffer distance of falling rocks is small, and the stability with the change of impact position is good. Therefore, it is suggested that the single-supported ring net should be preferentially used in rockfall protection projects such as the slope with the rockfall barrier laying position close to the road, the horizontal laying of rockfall barrier in the steep slope and the secondary protection.
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SUN Yang, LUO Wei, RONG Yao, LI Jiabao
DOI:
Abstract:
In order to analyze the influence of rainfall seepage on the stability of cofferdam, relying on an navigation-power junction project in Jiangxi Province, based on the unsaturated seepage theory, we simulate and analyze the condition of the seepage and the stability of cofferdam under different rainfall conditions by using the Geo-studio numerical simulation software, and the influence of different rain patterns on the stability of cofferdam is obtained. The results show that the influence of rainfall on the cofferdam has a hysteretic quality. The influence of different rainfall types on the strength hysteresis of weir body is as follows: rear peak type, uniform type, middle peak type and front peak type, and the hysteresis is affected by rainfall intensity. The rainfall infiltration is affected by the time of the peak rainfall, and the safety factor of the cofferdam decreases sharply with the peak rainfall intensity. Compared with the initial stability conditions, the front peak type rainfall has the least impact on the stability of the cofferdam, and the rear peak rainfall has the greatest impact on the stability of the cofferdam. Under the influence of early rainfall, the permeability coefficient of soil in the slope will be at a high level. At this time, the ability of Cofferdam to resist sudden heavy rainfall will weaken with the increase of permeability coefficient.
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DOI:
Abstract:
In order to avoid the shortcomings, e.g., difficulty in obtaining values of soil parameters and inaccuracy of theoretical assumptions, in the traditional elastic settlement calculation method of pile raft foundation, a practical calculation method for pile raft foundation based on static load test curves is proposed. In view of that the characteristics of the settlement of pile raft foundation is in the linear elastic stage under design load, based on the vertical stiffness of single pile obtained from the static load test curve, the calculation method of the overall vertical stiffness of pile raft foundation is established based on relevant theories and empirical formulas, and on this basis, the practical calculation method of the average settlement of pile raft foundation under working load is proposed. Via the comprehensive analysis of the field measurement and calculation results of 8 engineering cases in 4 categories of high-rise building foundation in soft soil area and loess area, rock-socketed pile foundation and large traffic engineering, the validity of the proposed method is examined. The calculated settlement value is basically 0.8~1.5 times of the measured settlement, which verifies the reliability of the proposed settlement calculation method in practical engineering. In addition, the calculation method can provide a reference for the preliminary design of settlement calculation of actual pile raft foundations.
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Dong Jing Liang, Chen Lei Wei, Zhang Haina, Wang Lijiu
DOI:
Abstract:
The Pisha Sandstone has caused serious soil erosion in the Inner Mongolia area. It is the main source of coarse silt in the middle and lower reaches of the Yellow River. In order to reveal the formation mechanism of soil erosion in the Pisha Sandstone area and the research and developing methods to control soil erosion in the Pisha Sandstone area, it is necessary to clear the root cause of the collapse of Pisha Sandstone. This paper analyzes the structural composition and mineral composition of the Pisha Sandstone by means of quantitative XRD and optical microscope analysis. The results show: (1) This paper found the soft rock is a kind of mudstone with severe weathering and loose structure. The structure of Pisha Sandstone is composed of granular skeleton material and clay cementation material, and its cementation is contact cementation. (2) The granular skeleton material is mainly composed of quartz, calcium carbonate and the structure of granular skeleton. Montmorillonite, chlorite, kaolinite and iron oxide are cementation materials. (3) Pisa Sandstone is a solid mixture. Granular skeleton crystals (quartz and feldspar) are linked together by the cementing force of the hydrophilic and weak cemented clay, and the friction between crystals, mechanical bite force and particle support. Due to incomplete filling of cementing materials, there are many pores between particles and particulates. Its structure is composed of granular support and osmotic structure.
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duan hongwei, gao jianping, zou hengzhi, cao zhong min, liu hong
DOI:
Abstract:
In view of severe corrosion problems of reinforced concrete bridge pier columns in strong saline soil / salt lakes of Western China,a new type of composite structure "steel reinforced polyethylene plastic pipe(SRPE) confined reinforced concrete column" is proposed, In order to study the mechanical properties of specimens under eccentric load, the 8 SRPE confined reinforced concrete columns and 4 unconfined control columns were tested subjected to eccentric load, and the influence of design parameters such as pressure level of SRPE pipe, eccentric distance and slenderness ratio on the mechanical properties of specimens was analyzed subjected to eccentric load., The bearing capacity calculation equation about SRPE confined reinforced concrete columns subjected to eccentric load is given for reference of engineering application. The results show that the SRPE pipe can significantly improve the extreme bearing capacity and ductility of the reinforced concrete column under eccentric load; the higher the pressure level of the SRPE pipe is, the better the improvement effect of bearing capacity is, but the improvement effect of ductility is not obvious;the ultimate bearing capacity of specimens decreases with the increase of eccentricity and slenderness ratio. The ductility of specimens decreases with the increase of slenderness ratio; The peak deflection in the column of the specimen is much larger than that of the control specimens, and it increases with the increase of eccentricity and slenderness ratio; The lateral deflection curve of specimen under ultimate load is close to sinusoidal half-wave curve.
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Zhang LIiping, Xiong Kaiqi, Zhao Xuanli, Wang Haohao, Xiao Xueyi
DOI:
Abstract:
In recent years, the integrity of railway scientific research has aroused concern from all walks of life. In order to analyze the integrity of railway scientific research in China, based on the Triple Helix Model and centered on the credibility of railway scientific research personnel,the cooperative relationship among universities, government and enterprises is expounded. And the current situation of the research integrity of our country and railway industry, analyzing the present situation and problems of research integrity from the system construction, moral construction and information management three aspects, this paper discusses the problem of railway research integrity in our country, and puts forward corresponding countermeasures, scientific misconduct, governance should be from the three aspects of system, education, information technology, Build railway scientific research integrity of "government, industry and learning" governance model.
岩土工程（路基、基坑、边坡）
载运装备运维 （材料、机械、(智能)制造、运维）
桥梁与隧道（设计建造、抗震减振、智能监测）
交叉学科前沿（基础研究、交叉学科前沿）
交通管理控制2（运输规划管理、智慧出行、物流、交通运输经济）
岩土工程（路基、基坑、边坡）
载运装备运维 （材料、机械、(智能)制造、运维）
交通管理控制1（电气化、信号信息、智能交通、交通系统工程）
载运装备运维 （材料、机械、(智能)制造、运维）
交叉学科前沿（基础研究、交叉学科前沿）
交通管理控制2（运输规划管理、智慧出行、物流、交通运输经济）
载运装备运维 （材料、机械、(智能)制造、运维）
交叉学科前沿（基础研究、交叉学科前沿）
载运装备运维 （材料、机械、(智能)制造、运维）
桥梁与隧道（设计建造、抗震减振、智能监测）
交叉学科前沿（基础研究、交叉学科前沿）
交通管理控制1（电气化、信号信息、智能交通、交通系统工程）
桥梁与隧道（设计建造、抗震减振、智能监测）
交通管理控制2（运输规划管理、智慧出行、物流、交通运输经济）
载运装备运维 （材料、机械、(智能)制造、运维）
桥梁与隧道（设计建造、抗震减振、智能监测）
道路与铁道（路面工程、轨道工程）
交通管理控制1（电气化、信号信息、智能交通、交通系统工程）
桥梁与隧道（设计建造、抗震减振、智能监测）
交通管理控制1（电气化、信号信息、智能交通、交通系统工程）
桥梁与隧道（设计建造、抗震减振、智能监测）
岩土工程（路基、基坑、边坡）
桥梁与隧道（设计建造、抗震减振、智能监测）
载运装备运维 （材料、机械、(智能)制造、运维）
交通管理控制1（电气化、信号信息、智能交通、交通系统工程）
桥梁与隧道（设计建造、抗震减振、智能监测）
载运装备运维 （材料、机械、(智能)制造、运维）
交通管理控制1（电气化、信号信息、智能交通、交通系统工程）
桥梁与隧道（设计建造、抗震减振、智能监测）
载运装备运维 （材料、机械、(智能)制造、运维）
交通管理控制2（运输规划管理、智慧出行、物流、交通运输经济）
桥梁与隧道（设计建造、抗震减振、智能监测）
交叉学科前沿（基础研究、交叉学科前沿）
载运装备运维 （材料、机械、(智能)制造、运维）
桥梁与隧道（设计建造、抗震减振、智能监测）
交通管理控制2（运输规划管理、智慧出行、物流、交通运输经济）
交叉学科前沿（基础研究、交叉学科前沿）
综合（经济、文学、艺术，及其他未列学科）
桥梁与隧道（设计建造、抗震减振、智能监测）
交叉学科前沿（基础研究、交叉学科前沿）
桥梁与隧道（设计建造、抗震减振、智能监测）
载运装备运维 （材料、机械、(智能)制造、运维）
桥梁与隧道（设计建造、抗震减振、智能监测）
交叉学科前沿（基础研究、交叉学科前沿）
桥梁与隧道（设计建造、抗震减振、智能监测）
交通管理控制2（运输规划管理、智慧出行、物流、交通运输经济）
桥梁与隧道（设计建造、抗震减振、智能监测）
载运装备运维 （材料、机械、(智能)制造、运维）
交通管理控制1（电气化、信号信息、智能交通、交通系统工程）
桥梁与隧道（设计建造、抗震减振、智能监测）
载运装备运维 （材料、机械、(智能)制造、运维）
交叉学科前沿（基础研究、交叉学科前沿）
桥梁与隧道（设计建造、抗震减振、智能监测）
交叉学科前沿（基础研究、交叉学科前沿）
交通管理控制1（电气化、信号信息、智能交通、交通系统工程）
载运装备运维 （材料、机械、(智能)制造、运维）
交叉学科前沿（基础研究、交叉学科前沿）
桥梁与隧道（设计建造、抗震减振、智能监测）
载运装备运维 （材料、机械、(智能)制造、运维）
道路与铁道（路面工程、轨道工程）
交通管理控制1（电气化、信号信息、智能交通、交通系统工程）
桥梁与隧道（设计建造、抗震减振、智能监测）
道路与铁道（路面工程、轨道工程）
桥梁与隧道（设计建造、抗震减振、智能监测）
交通管理控制1（电气化、信号信息、智能交通、交通系统工程）
交通管理控制2（运输规划管理、智慧出行、物流、交通运输经济）
载运装备运维 （材料、机械、(智能)制造、运维）
交叉学科前沿（基础研究、交叉学科前沿）
数字交通专栏
桥梁与隧道（设计建造、抗震减振、智能监测）
数字交通专栏
桥梁与隧道（设计建造、抗震减振、智能监测）
载运装备运维 （材料、机械、(智能)制造、运维）
桥梁与隧道（设计建造、抗震减振、智能监测）
数字交通专栏
岩土工程（路基、基坑、边坡）
交叉学科前沿（基础研究、交叉学科前沿）
载运装备运维 （材料、机械、(智能)制造、运维）
交通管理控制2（运输规划管理、智慧出行、物流、交通运输经济）
交通管理控制1（电气化、信号信息、智能交通、交通系统工程）
桥梁与隧道（设计建造、抗震减振、智能监测）
交叉学科前沿（基础研究、交叉学科前沿）
道路与铁道（路面工程、轨道工程）
桥梁与隧道（设计建造、抗震减振、智能监测）
载运装备运维 （材料、机械、(智能)制造、运维）
交通管理控制2（运输规划管理、智慧出行、物流、交通运输经济）
交通管理控制1（电气化、信号信息、智能交通、交通系统工程）
载运装备运维 （材料、机械、(智能)制造、运维）
桥梁与隧道（设计建造、抗震减振、智能监测）
交叉学科前沿（基础研究、交叉学科前沿）
岩土工程（路基、基坑、边坡）
交叉学科前沿（基础研究、交叉学科前沿）
交通管理控制1（电气化、信号信息、智能交通、交通系统工程）
载运装备运维 （材料、机械、(智能)制造、运维）
交叉学科前沿（基础研究、交叉学科前沿）
载运装备运维 （材料、机械、(智能)制造、运维）
交通管理控制1（电气化、信号信息、智能交通、交通系统工程）
交通管理控制2（运输规划管理、智慧出行、物流、交通运输经济）
交通管理控制1（电气化、信号信息、智能交通、交通系统工程）
交叉学科前沿（基础研究、交叉学科前沿）
道路与铁道（路面工程、轨道工程）
桥梁与隧道（设计建造、抗震减振、智能监测）
交叉学科前沿（基础研究、交叉学科前沿）
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Xiao Qian, Fu Yuanhang, Chen Daoyun
2024,41(5):1-9, DOI:
Abstract:
【Objective】In order to better analyze the fatigue life of the high-speed train bogie frame.【Method】dy namic stress measurements are conducted on the fatigue concern measuring points of a certain type of bogie frame,and the data is post-processed. A one-dimensional stress spectrum is compiled using the rain-flow count ing method and the fluctuation center method. By analyzing and calculating the Miner linear cumulative damage model, a nonlinear cumulative damage model considering load interaction and inherent attribute damage, and the Cotern-Dolan nonlinear cumulative damage model, their fatigue life is inferred and compared in three aspects. 【Result】The results show that the difference between the analysis results of the nonlinear model considering in herent damage and the calculation results of the linear model is small, indicating that its nonlinear attribute is not obvious.【Conclusion】The life analysis results of the Cotern-Dolan nonlinear cumulative damage model are overall smaller than other kinds, but the trend is the same, indicating that it is more conservative for fatigue life assessment.
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Huang Zhichao, Wang Jiaxuan, HuYihua
2024,41(5):10-17, DOI:
Abstract:
【Objective】In order to investigate the static characteristics and lightweight optimization of the rear axle housing of a new pickup truck vehicle,【Method】a research method combining finite element platform sim ulation and bench testing was adopted. Firstly, a finite element model with high computational accuracy was es tablished in Hypermesh software. Secondly, the stress and displacement of the axle shell under full load condi tion were analyzed using ABAQUS simulation platform, and the location of the dangerous cross-section was de termined. Subsequently, the dimensional optimization of the axle shell and the steel plate spring seat and other components was carried out through Optistruct optimization module, and then the reliability of the lightweight optimization was verified through vertical bending static stiffness bench test. Finally, the reliability of light weight optimization was verified by vertical bending static stiffness bench test.【Result】Finite element analysis results show that the dangerous cross-section of the axle housing is located in the housing steel plate spring seat and housing connection with the maximum stress and deformation of 307.20 MPa and 1.440 mm. Size optimiza tion of the axle housing weight decreases from 59.07 kg to 52.55 kg and the weight reduction rate is 11.04%. The stress rises to 310.10 MPa, but it is still less than the yield strength of 45 steel of the axle housing material, which is 355.00 MPa, and the deformation is less than the standard 1.400 mm. The results of the bench test show that the axle housing passes the vertical bending static stiffness test, and conforms to the standard of the automo bile drive axle bench test.【Conclusion】The established finite element model has high accuracy, and the simula tion results are highly close to the results of the bench test. The axle housing optimized by Optistruct has good mechanical behavior performance, and the module has high reliability in axle housing lightweighting.
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Ding Ruqi, Sun Guohua, Zhu Hongdong, Li Gang, Xie Zhicong, Liu Ying, Xu Congcong
2024,41(5):18-28, DOI:
Abstract:
【Objective】The hydraulic manipulator has the characteristics of strong load capacity, fast response speed, wide range of stepless speed regulation, small radiation electromagnetic interference and so on. It is wide ly used in the construction of transportation infrastructure, such as tunnel boring and bridge construction equip ments. This paper aims to summarize the contact operation control methods of hydraulic manipulator, and intro duce the precise coordination control methods of force and position, and finally provide an outlook on future re search directions. 【Method】In practical engineering applications, the hydraulic manipulator often has contact with the external environment, and its contact operation control involves the precise coordinated control of force and position. However, the precise control of force and position requires an accurate dynamic model and accu rate estimation of terminal force. 【Result】Both domestic and international scholars have conducted in-depth re search on the precise coordination control of force and position, achieving significant results in ensuring stable, accurate, and safe contact operations of hydraulic robotic arms. 【Conclusion】Based on these achievements, this paper describes the hydraulic manipulator dynamics modeling, dynamics parameter identification, end contact force estimation methods, and compliance control. Furthermore, it put forward suggestions and prospects for re search.
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Zhou Yunlai, Yao Feng, Bai Chunyu, Li Kaixiang, Zhu Shengyang
2024,41(5):29-38, DOI:
Abstract:
【Objective】To address the issues of imprecise modeling and high computational cost in structural damage detection using the finite element method (FEM), this study proposes a structural health monitoring (SHM) technique that combines the spectral element method (SEM) with the Northern Goshawk Optimization (NGO) algorithm.【Method】Firstly, the spectral element method was used to establish the frequency response function of the structure, which was then applied to construct the objective function for damage localization and detection. This approach divided the damage detection problem into two stages, reducing the optimization dimension and complexity. Secondly, NGO algorithm was introduced to optimize and solve the objective function. Finally, planar truss structure and ASCE Benchmark Structure were used as case studies to compare the damage detection performance of NGO, Particle Swarm Optimization (PSO), and Ant Lion Optimization (ALO) algorithms under various damage cases.【Result】The results show that for low-dimensional and simple structures, NGO, PSO, and ALO algorithms all exhibit good solving capabilities. However, for high-dimensional and large complex structures, NGO demonstrates superior damage detection capability and robustness compared to PSO and ALO.【Conclusion】The improved method enhances the accuracy of numerical modeling in damage detection.
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Liu Chengqing, Wu Zebin, Xiao Guangcai, Yang Delei
2024,41(5):39-47, DOI:
Abstract:
【Objective】 To generate a representative time history set of entirely non-stationary seismic motion processes that adhere to the design response spectrum stipulated in the codes for seismic design of highway and urban bridges.【Method】 An evolutionary power spectrum model for entirely non-stationary seismic motion pro cesses was initially formulated by integrating the intensity-frequency modulation function,pertinent to non-sta tionary seismic motion processes,with the Clough-Penzien power spectrum model,applicable to stationary seis mic motion processes. The parameters for this evolutionary power spectrum model were subsequently calibrated in accordance with relevant specifications. According to the spectral representation approach for the simulation of entirely non-stationary seismic motion processes,a MATLAB program was written to generate a representative time history set of the entirely non-stationary seismic motion processes. The fitting error between their mean re sponse spectrum and the code response spectrum was calculated and iteratively corrected. 【Result】 The parame ters of the evolutionary power spectral model for different site classifications and design earthquake groups were derived based on the codes for seismic design of highway and urban bridges. The generated representative seis mic time history set exhibits the typical characteristics of entirely non-stationary seismic motion processes,dem onstrating a satisfactory overall fit between its mean response spectrum and the code response spectrum,with an average relative error within 5%. 【Conclusion】 By employing the evolutionary power spectrum model,a MAT LAB program can be devised to simulate the spectral representation method of entirely non-stationary seismic motion processes. It successfully generated a representative time history set that complied with the requirements of the codes for seismic design of highway and urban bridges. The mean response spectrum of the generated time histories is consistent with the code response spectrum,verifying the effectiveness of the given method and MAT LAB program. This provides reliable seismic inputs essential for the seismic performance evaluation of bridge structures.
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Bai Xubo, Zhang Xianying, Li Yue
2024,41(5):48-55, DOI:
Abstract:
【Objective】Train wheel is a significant noise source in the rolling noise, and predicting its vibroacou stic behavior involves calculating the large scale acoustic problems. To improve the computational efficiency of wheel sound radiation, this paper introduces the Boundary Element Method with Adaptive Order (BEMAO). 【Method】The sound radiation of the wheel in free space was studied by using the combination of the finite ele ment method and the boundary element method. The BEMAO was used to calculate the sound power radiated by the wheel, the sound pressure at standard measurement point, and the directivity of the wheel acoustic radiation. Comparison was then made with the corresponding results obtained by the conventional boundary element meth od (CBEM) and the fast multipole boundary element method (FMBEM) as well as the computational time.【Result】The sound radiation obtained by three different boundary element methods are basically consistent, but the BEMAOis about 36 times faster than the CBEM, and 11 times than the FMBEM.【Conclusion】The calculation efficiency of the BEMAO is obviously higher than that of other boundary element methods, and remarkable ad vantages and good applicability are shown in studying the sound radiation from the wheel at high frequency. The outcomes of this paper can provide reference for calculations of large scale acoustic problems.
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Hu Zhaolei, Song Xin, Xu Yunhang, Zhang Pengfei, Zhang Hong, Yu Lu
2024,41(5):56-64, DOI:
Abstract:
【Objective】To promote the informatisation and intelligence of railway engineering operation and maintenance, and to improve the efficiency of maintenance, 【Method】 Based on the secondary development of Revit and Unity3D platform, a railway track engineering operation and maintenance intelligent information plat form is developed. The platform adopts a three-layer structure of data layer, application layer and interface layer, integrates three modules of human-computer interaction, operation and maintenance information management and technical information access, and can realize functions such as AR scanning, BIM model roaming display, animation simulation of complex facilities disassembling and assembling operation, drawing of track geometric waveform, calculation of TQI, access to maintenance records, querying of technical regulations and CAD draw ings, et al., which is of high utility, high portability, and strong operability. It has the features of high practicality, good portability and strong operability. 【Result】 The platform performs well in the field application test of pub lic works, and all functions can run stably, which achieves the expected purpose of research and development. 【Conclusion】 The construction and development of the platform provides a new way of thinking to promote the informatisation and intelligentisation of railway engineering operation and maintenance.
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YanLixin, HuXinhui, Liu Qingmei, JinWujie
2024,41(5):65-73, DOI:
Abstract:
【Objective】To improve the accuracy of predicting the severity of traffic accidents and clarify the key in fluencing factors of traffic accident severity.【Method】Fourteen factors related to people, vehicles, roads, and envi ronment that affect traffic accident severity were selected from 885 road traffic accident case data, and a traffic acci dent classification prediction model was constructed using a convolutional neural network with channel attention (CA-CNN). On this basis, the significant influencing factors of traffic accident severity were analyzed using the method of marginal utility.【Result】The results show that compared with the 6 prediction models such as convolu tional neural network (CNN), random forest (RF), NaiveBayes, logistics regression (Logistics), decision table (De cision_table), and bagging algorithm (Bagging), the convolutional neural network model with channel attention fu sion has better overall prediction performance in terms of accuracy, precision, and recall, etc. Among the influenc ing factors of traffic accident severity, the season, whether it is a workday, road type, accident type, illegal lane change, failure to yield, and improper braking have significant effects (p≤0.05).【Conclusion】CA-CNN is an effec tive traffic accident severity prediction model, and the analysis results are helpful in reducing the incidence and se verity of traffic accidents.
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Zou Dandan, Song Zixun, Pan Jianbing
2024,41(5):74-83, DOI:
Abstract:
【Objective】Aiming at the significant degradation of air gap insulation performance of electrical equipment under high-altitude, low-pressure and low-oxygen environments, a study was carried out to character ize the flow propagation under different air pressures and oxygen contents. 【Method】By combining the fluid model with the plasma chemical reaction, a rod-plate electrode structure and a high-altitude low-pressure low oxygen air injection discharge simulation model were constructed to simulate the air injection propagation pro cess under different air pressures and oxygen contents, and to analyze the effects of air pressure and oxygen con tent on the injection propagation speed, electron density, injection channel radius and electric field intensity dis tribution. It analyzed the effects of air pressure and oxygen content on the propagation speed, electron density, channel radius and electric field distribution. 【Result】The results show that,with the reduction of air pressure, the flow injection propagation speed is accelerating, the flow injection head and channel electron density and electric field strength is decreasing trend, the flow injection channel radius on the whole increased; with the reduction of the oxygen content, the flow injection propagation speed is decreasing significantly, the electron densi ty is increasing, while the electric field strength on the whole increases, and the radius of the flow injection chan nel is decreasing. 【Conclusion】The factors of gas pressure and oxygen content have an important influence on the flow injection discharge characteristics and plasma reaction mechanism, which should be considered compre hensively in the actual engineering design.
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Zhang Jianie, Sun Wenjing, Wang Jiahao, Zhou Jinsong
2024,41(5):84-93, DOI:
Abstract:
【Objective】To address the significant difference of interior noise between the motor car (M car) and the trailer (T car) during the operation of an urban rail vehicle, this research examines the impact of the motor car's traction drive system on interior noise through a combination of numerical simulation and real-world vehi cle testing. 【Method】Initially, spectral responses and transmission characteristics of the vibration and noise with in and outside the car body of both the motor car and the trailer were analyzed based on test results. Subsequent ly, a full-frequency vehicle interior noise simulation model was developed by integrating the statistical energy method (SEA) and the finite element method (FEA) for numerical simulation purposes. The simulation revealed the distribution patterns of high-frequency airborne sound and low-frequency structural sound within the vehicle. Through computational superposition of structural and airborne sound, comprehensive noise distribution charac teristics across the full frequency band were obtained and compared with corresponding measured data from the rail line. 【Result】The results show that a prominent peak exists in the interior noise of the motor car within the frequency range of 150 to 400 Hz, which corresponds with the vibration peak of the floor structure within the vehi cle. 【Conclusion】The simulation outcomes of the low-frequency structural acoustic model of the vehicle exhibit a high degree of consistency with the actual measured data. The high-frequency noise within the vehicle is pri marily attributed to wheel-rail rolling noise and the airborne acoustic propagation path of the traction system's sound source. The peak noise levels in the motor car are a result of structural vibrations from the traction drive system, which includes the motor and gearbox, being transmitted through the frame and secondary suspension components to the vehicle body structure, leading to increased levels of low-frequency structural noise. These findings may provide some reference for mitigating the impact of the traction drive system on the interior noise of urban rail vehicles.
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Li Zhongqi, Zeng Xiangquan, Yu Jianfeng
2024,41(5):94-104, DOI:
Abstract:
【Objective】To address the challenge of achieving high-precision trajectory tracking control for heavy haul trains under complex track conditions, this paper proposes a multi-mass model for heavy haul trains and a radial basis function neural network sliding mode control (RBFNNSMC) method. 【Method】First, considering the constraints of air brakes and coupler devices, a multi-mass model of the heavy haul trains was established, and the model uncertainty problems caused by human measurement errors and vehicle parameter differences were estimated by using RBFNN. Second, a nonlinear disturbance observer (NDO) was designed to be utilized for re al-time estimation of strong wind, rain, snow, and other external fast time-varying disturbances during the opera tion of trains. Then, a Lyapunov function was designed to prove the stability of the entire system. 【Result】Based on actual track data from the Daqin Railway, speed tracking comparison experiments were conducted using the RBFNNSMC method, PID method, and SMC method. Simulation results show that the speed error of the RBF NNSMC method is within ±0.15 km/h, which is superior to the other two methods. Furthermore, the inclusion of the NDO significantly enhances the RBFNNSMC method's disturbance rejection capability. 【Conclusion】The tracking accuracy of the RBFNNSMC method based on NDO is improved by 27.3% and 28.9% respectively compared to the SMC method in the absence and presence of disturbances, with enhanced robustness as well.
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Jing Wenqian, Zeng Xianglong, Ye Ling
2024,41(5):105-114, DOI:
Abstract:
【Objective】In order to improve the reconstruction accuracy of the particle velocity and ensure the ac curacy of source identification, 【Method】this paper proposes a compressed equivalent source based-NAH mod el with the sparse acoustic vector sensor array CESM-v by substituting the particle velocity measurement for the traditional pressure measurement and combining the acoustic vector sensor with the sparse sampling and sparse regularization. Several numerical simulations and experiments were carried out to exam the efficiency of the pro posed model. Through multiple analysis of the particle velocity reconstruction, the equivalent source strength re construction and the error calculation, the proposed CESM-v model was compared with the traditional equivalent source based-NAH with particle velocity measurement (ESM-v) and the existed CESM-p model. 【Results】The proposed CESM-v model always performs better than the other two models. Even though using sparse sam pling, the CESM-v model can generate comparable effect of the particle velocity reconstruction to that of tradi tional ESM with adequate sampling, and can give higher and more stable accuracy in particle velocity recon struction than that of the CESM-p model. In short, both simulation and experimental results show that the CESM-v model has better stability and reliability, can obtain good particle velocity reconstruction results with a small number of sampling points, and then the accuracy of sound source identification can be ensured. 【Conclusion】With the robustness of sound field reconstruction, the CESM-v model can be extended to practical projects such as rail transportation for noise source identification and fault diagnosis.
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Tang Baizan, Yu Guangshan, Gong Kai, Zhuang Haiyang, Liu Xuchen, Zhang Ji, Guo Wenjie
2024,41(5):115-126, DOI:
Abstract:
To solve the problems of high energy consumption and high pollution of buildings, China has been ac tively promoting the development of green, energy-saving and environmentally friendly wall structures. Among them, as a new type of wall structure, the lattice concrete shear wall structure has multiple functions such as heat preservation, energy saving, sound insulation, fire resistance, light weight bearing, convenient construction and environmental protection, becoming a hot spot of application and research in recent years. This study briefly in troduces the form of lattice concrete wall structure, summarizes the axial compression, corrosion resistance, ther mal, sound insulation, weather resistance, seismic and other properties of lattice concrete wall, and puts forward the problems and deficiencies in the research of lattice concrete wall at present. It shows that the development of lattice concrete wall structure is a major demand for the recycling of building materials and construction waste, which can be used for seismic design of building structures. In the future, its physical properties can be improved from the aspects of new materials, overall structural fire prevention, freeze-thaw in complex environment, etc., and the research on recoverable functionality and high-rise application can be carried out in combination with shock absorption technology to further improve its seismic performance. It provides important scientific basis and technical support for the wide application of lattice concrete walls and their structures.
Volume 41,2024 Issue 5
专家约稿
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Li Mingcui, Chen Aixi, Zeng Wei
2023,40(1):99-105, DOI: 10.16749/j.cnki.jecjtu.20230209.002
Abstract:
Inspired by the recent experiments of cavity-magnon system and the theories of nonlinear reservoir, a scheme of coupling a cavity-magnon system to a squeezed reservoir is proposed to analyze the magnon blockade effect, thus realizing the manipulation of magnetism at quantum level. An yttrium iron garnet sphere was located in a driven microwave cavity. The Kittel mode in the yttrium iron garnet sphere interacted with the microwave cavity mode, and the cavity field was coupled to a squeezed vacuum reservoir. By numerically solving the quantum master equation of the system, the influence of various factors such as coupling strength, detuning and dissipation rate on the correlation function was analyzed in details. It is proved theoretically that the cavity-magnon system coupled to a squeezed reservoir can induce single-magnon blockade and two-magnon blockade, and the switching among single-magnon blockade, two-magnon blockade and two-magnon tunneling can be flexibly controlled by tuning the driving intensity or the detuning. The magnon blockade effect in the proposed scheme is mainly induced by the nonlinearity of the squeezed reservoir, which provides a possible new method to realize single or double magnon blockade in cavity-magnon system.
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Fu Yichen, Zhou Jie, Shi Dapeng, Dong Chenxi, Sun Penghui, Li Yanjun, Cao Xinpeng, Zheng Haizhong
2023,40(1):92-98, DOI: 10.16749/j.cnki.jecjtu.20230209.009
Abstract:
In order to improve the wear resistance of CrN coating, magnetron sputtering technology was used to study the influence of external Cr layer on the wear width of CrN coating. The friction and wear of the surface were studied under different loads, rotational speeds and radius. The results show that the effect of centrifugal force is more obvious with the increase of rotation radius. When the rotation speed is 300 r/min, the average wear width of the CrN coating without sputtering Cr layer reaches 945.7 μm and the outer wear is more serious. Under the same conditions, the wear width of the outer Cr layer is 571.2 μm. It shows that the outer Cr layer can effectively inhibit the increase of surface wear area. When the outer Cr layer is being sputtered, the friction coefficient and the wear area width of the surface increase with the increase of the rotation radius at 200 r/min. The wear marks on the surface are furrowed and the wear mechanism is abrasive.
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Chen Shiyi, Pan Yiyong, Wei Shuangqiu
2023,40(1):60-66, DOI: 10.16749/j.cnki.jecjtu.20230209.008
Abstract:
To solve the optimal path problem of the traffic network, an improved travel time estimation model was proposed, and an optimal path algorithm based on this model was designed. The travel time estimation model was improved on the basis of the segment truncated quadratic velocity trajectory model by replacing the velocity measured at the same departure moment with the arrival velocity of the road segment nodes, and the travel time was estimated by constructing a velocity trajectory that is continuous in time and space. The optimal path algo-rithm based on travel time estimation firstly solved K shortest paths based on Yen′s KSP algorithm with road section distance as impedance, then estimated the travel time of K shortest paths by the improved travel time es-timation model respectively, and finally selected the optimal path with travel time as cost. The validity and superiority of the model and algorithm were verified by numerical experiments of Sioux falls network. The experimental results show that the improved segmented truncated quadratic speed trajectory model improves the accuracy by an average of 65% compared with the original model and the optimal path results based on the proposed al-gorithm can reduce the number of intersections the path passes through and shorten the total length of the opti-mal path. Moreover, the estimated results of the optimal path's travel time stay within 3% of the real value of MAPE. The results of this study may provide a theoretical basis for the optimal path method for traffic networks.
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Gan Weihua, Liu Zheng, Liu Yanan, Li Chunzhi
2023,40(1):34-43, DOI: 10.16749/j.cnki.jecjtu.20230209.012
Abstract:
Based on evolutionary game theory, with the introduction of reward and punishment mechanisms, an evolutionary game model between online freight platforms and government regulators is constructed, and the stability of their equilibrium points is analyzed. The results show that under static punishment, there is no equilibrium stability point in the system, no matter whether the reward mechanism is static or dynamic; under the static reward dynamic punishment and dynamic reward and punishment mechanism, both sides tend to reach a stable equilibrium point, and the effect is better under the dynamic reward and punishment mechanism; the online freight platforms' behavior is affected by the government′s reward and punishment mechanism, and the binding effect of the punishment mechanism is more significant.
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Yu Zhiwu, Li Yanxia, Xu Lei, Ma Jian, Zhao Miao
2023,40(1):25-33, DOI: 10.16749/j.cnki.jecjtu.20230209.003
Abstract:
Motion stability of the high-speed maglev vehicle under steady aerodynamic load was studied. The dynamic model of the high -speed maglev vehicle on the curved guideway considering influence of aerodynamic loads was established. The critical speed concept of the maglev vehicle considering aerodynamic loads′ effect based on eigenvalues was presented. Vehicle speed, control parameters, and aerodynamic coefficients to make the critical speed of the high-speed maglev vehicle change in the critical state were also analyzed. The results show that when the system reaches the critical state, it has two critical speeds. Under the conditions in the critical state, the position control parameters vary from 20 000 kN/m to 2 000 kN/m, and aerodynamic coefficients vary from 0.05 to 0.01, the critical speed gets larger. When the real part of the eigenvalue is zero, but the imaginary part is not zero, the first kind of critical velocity occurs. When both the real part and the imaginary part of the eigenvalue is zero, the second kind of critical velocity appears. Instability is caused by the change from the equilibrium position for the curved guideway and wind loads. Aerodynamic downward force and centrifugal wind loads are not good for stability, but aerodynamic upward force and centripetal wind loads improve stability. The horizontal angle can be matched with the centripetal force, but the vertical angle is allowed to be set in a small range.
