This research aimed to overcome challenges such as high costs,lengthy optimization time,and low efficiency in resolving issues related to wheel-rail contact,rail wear,and vehicle dynamics.Based on the wheel-rail conta...This research aimed to overcome challenges such as high costs,lengthy optimization time,and low efficiency in resolving issues related to wheel-rail contact,rail wear,and vehicle dynamics.Based on the wheel-rail contact parameters,an optimal design method for rail grinding target profile is proposed from wear profile measurement to grinding profile design according to the actual railway track and vehicle operating conditions.We utilized Isight to create a simulation test and developed an RBF proxy model that incorporated both mechanical and geometric aspects of wheel-rail contact.By integrating rail modeling,wheel-rail contact analysis,and multi-objective optimization,we established a rail grinding optimization model that was solved using the NSGA-II algorithm.After optimization,the study achieved a 31.863%reduction in average contact stress,a 70.5%reduction in matching wear work,and a 100.391%increase in the difference in rolling radius between the wheel and rail.展开更多
Purpose–This paper investigates how high-speed rail(HSR)influences socioeconomic inequality by providing the first systematic bibliometric review of research trends,methodological approaches and thematic structures.I...Purpose–This paper investigates how high-speed rail(HSR)influences socioeconomic inequality by providing the first systematic bibliometric review of research trends,methodological approaches and thematic structures.It examines whether HSR fosters balanced regional development or reinforces spatial disparities.Design/methodology/approach–Using the Bibliometrix R package,237 records were retrieved from the Web of Science(1985–2024).Citation indicators,keyword co-occurrence and collaboration networks were combined with natural language processing(NLP)to classify studies by territorial scale,methodology,economic variables and inequality outcomes.Findings–The paper offers the first structured overview of how the literature conceptualizes the link between HSR and inequality.It highlights persistent gaps–scarcity of city-level analyses,limited socioeconomic indicators and reliance on Chinese case studies–providing a foundation for more comparative and interdisciplinary research.Originality/value–This paper contributes by offering a structured overview of how the literature has conceptualized and measured the relationship between HSR and inequality.By identifying persistent research gaps–such as the scarcity of city-level analyses,limited use of socioeconomic indicators,and overreliance on Chinese case studies–it provides a foundation for more comparative and interdisciplinary approaches.The study informs policymakers and researchers on how to design future infrastructure projects that balance efficiency with equity.展开更多
This article focuses on the remote diagnosis and analysis of rail vehicle status based on the data of the Train Control Management System(TCMS).It first expounds on the importance of train diagnostic analysis and desi...This article focuses on the remote diagnosis and analysis of rail vehicle status based on the data of the Train Control Management System(TCMS).It first expounds on the importance of train diagnostic analysis and designs a unified TCMS data frame transmission format.Subsequently,a remote data transmission link using 4G signals and data processing methods is introduced.The advantages of remote diagnosis are analyzed,and common methods such as correlation analysis,fault diagnosis,and fault prediction are explained in detail.Then,challenges such as data security and the balance between diagnostic accuracy and real-time performance are discussed,along with development prospects in technological innovation,algorithm optimization,and application promotion.This research provides ideas for remote analysis and diagnosis based on TCMS data,contributing to the safe and efficient operation of rail vehicles.展开更多
Purpose–This study aims to implement condition monitoring for urban rail train permanent magnet synchronous motors and inverter systems.Through the construction of a digital twin model,it performs fault diagnosis of ...Purpose–This study aims to implement condition monitoring for urban rail train permanent magnet synchronous motors and inverter systems.Through the construction of a digital twin model,it performs fault diagnosis of potential system failures,enabling rapid fault localization and protection.Design/methodology/approach–This research begins with a brief introduction to the structure and classification of permanent magnet synchronous motors(PMSMs),followed by a detailed analysis of their mathematical model.Subsequently,it thoroughly investigates the working principle of three-phase two-level inverters and the distribution of space voltage vectors.Based on the analysis of the main circuit topology,a digital twin model matching the external characteristics of the physical circuit is established using the model predictive control method,achieving accurate system simulation.Furthermore,through theoretical analysis and simulation verification of phase current characteristics under inverter switch tube faults,general patterns of phase currents under fault conditions are summarized.The established digital twin model is then employed to validate these patterns,confirming the model’s effectiveness in fault diagnosis.Findings–This study proposes a fault diagnosis method based on digital twins.Experimental and simulation results demonstrate that the established digital twin model can accurately simulate the external characteristics of the actual physical circuit,validating its effectiveness in inverter fault diagnosis.This approach offers practical value for condition monitoring in actual urban rail train systems.Originality/value–The study innovatively starts from a mathematical model and simulates the actual physical model through a virtual model,requiring only external characteristics to achieve system fault diagnosis,thereby enhancing diagnostic efficiency.展开更多
Within the transition process of urban rail transit systems,the challenges of high energy consumption,increasing carbon emissions,limited economic viability,and intricate risks emerge as significant hurdles.This paper...Within the transition process of urban rail transit systems,the challenges of high energy consumption,increasing carbon emissions,limited economic viability,and intricate risks emerge as significant hurdles.This paper proposes a novel energy utilization framework for the urban rail transit system that incorporates underground energy storage systems characterized by high resilience and low carbon.First,existing methods employed in urban rail transit are comprehensively reviewed.Then,a novel framework and strategic significance of the urban rail transit system incorporating underground energy storage systems are introduced.This integration effectively utilizes and manages diverse renewable energy sources and the available space resources.The viability is demonstrated through a case study by combining Nanjing metro.Finally,suggestions for research in pivotal areas are summarized.展开更多
Purpose–Adding an appropriate pre-sag to the geometry of simple catenary systems for electric railways can improve their performance in dynamic interaction with the pantographs of trains operating under them.The valu...Purpose–Adding an appropriate pre-sag to the geometry of simple catenary systems for electric railways can improve their performance in dynamic interaction with the pantographs of trains operating under them.The value of pre-sag can be obtained by empirical approximation or computationally expensive optimisation.This study aims to define a simple but accurate method to determine a suitable pre-sag without dynamic simulations and to find its limitations.Design/methodology/approach–A quasi-static method to determine the ideal value of pre-sag is described based on elasticity variations.It considers variations of the static contact force.The limits of this method are investigated by comparing it to a parametric dynamic simulation study.In the dynamic simulation,an optimal level of pre-sag is identified for each contact force level.The influence of the speed in the dynamic simulation results is expressed in two parameters:the quasi-static influence in the mean contact force and the dynamic influence in the ratio between the vehicle speed and the wave propagation speed in the contact wire.Findings–The comparison between the suggested method and the dynamic simulations shows a high consistency up to a speed limit of around 40%of the wave propagation speed.The best agreement with the dynamic results is achieved by calculating the optimal pre-sag based on the absolute elasticity variation.Practical implications–The simplified approach for determining the pre-sag is valid for low-speed applications,such as suburban railway lines.For these cases,a highly suitable geometry can be obtained with the suggested method,meaning a significantly reduced computational effort.As a case study for this work,the results are applied to a Swedish suburban rail line upgrade case.Originality/value–The static uplift force is added as a varied parameter in dynamic simulations.The shift in system behaviour from low to high dynamics is described,and how the benefits from pre-sag are visible and then disappear.The limit value of the low-dynamics regime is identified to be 40%.展开更多
To address issues such as poor initial population diversity, low stability and local convergence accuracy, and easy local optima in the traditional Multi-Objective Artificial Hummingbird Algorithm (MOAHA), an Improved...To address issues such as poor initial population diversity, low stability and local convergence accuracy, and easy local optima in the traditional Multi-Objective Artificial Hummingbird Algorithm (MOAHA), an Improved MOAHA (IMOAHA) was proposed. The improvements involve Tent mapping based on random variables to initialize the population, a logarithmic decrease strategy for inertia weight to balance search capability, and the improved search operators in the territory foraging phase to enhance the ability to escape from local optima and increase convergence accuracy. The effectiveness of IMOAHA was verified through Matlab/Simulink. The results demonstrate that IMOAHA exhibits superior convergence, diversity, uniformity, and coverage of solutions across 6 test functions, outperforming 4 comparative algorithms. A Wilcoxon rank-sum test further confirmed its exceptional performance. To assess IMOAHA’s ability to solve engineering problems, an optimization model for a multi-track, multi-train urban rail traction power supply system with Supercapacitor Energy Storage Systems (SCESSs) was established, and IMOAHA was successfully applied to solving the capacity allocation problem of SCESSs, demonstrating that it is an effective tool for solving complex Multi-Objective Optimization Problems (MOOPs) in engineering domains.展开更多
Channel estimation is a well-known challenge for wireless orthogonal frequency division multiplexing(OFDM)communication systems with massive antennas on high speed rails(HSRs).This paper investigates this problem and ...Channel estimation is a well-known challenge for wireless orthogonal frequency division multiplexing(OFDM)communication systems with massive antennas on high speed rails(HSRs).This paper investigates this problem and design two practicable uplink and downlink channel estimators for orthogonal frequency division multiplexing(OFDM)communication systems with massive antenna arrays at base station on HSRs.Specifically,we first use pilots to estimate the initial angle of arrival(AoA)and channel gain information of each uplink path through discrete Fourier transform(DFT),and then refine the estimates via the angle rotation technique and suggested pilot design.Based on the uplink angel estimation,we design a new downlink channel estimator for frequency division duplexing(FDD)systems.Additionally,we derive the Cramér-Rao lower bounds(CRLBs)of the AoA and channel gain estimates.Finally,numerical results are provided to corroborate our proposed studies.展开更多
Accurate origin–destination(OD)demand prediction is crucial for the efficient operation and management of urban rail transit(URT)systems,particularly during a pandemic.However,this task faces several limitations,incl...Accurate origin–destination(OD)demand prediction is crucial for the efficient operation and management of urban rail transit(URT)systems,particularly during a pandemic.However,this task faces several limitations,including real-time availability,sparsity,and high-dimensionality issues,and the impact of the pandemic.Consequently,this study proposes a unified framework called the physics-guided adaptive graph spatial–temporal attention network(PAG-STAN)for metro OD demand prediction under pandemic conditions.Specifically,PAG-STAN introduces a real-time OD estimation module to estimate real-time complete OD demand matrices.Subsequently,a novel dynamic OD demand matrix compression module is proposed to generate dense real-time OD demand matrices.Thereafter,PAG-STAN leverages various heterogeneous data to learn the evolutionary trend of future OD ridership during the pandemic.Finally,a masked physics-guided loss function(MPG-loss function)incorporates the physical quantity information between the OD demand and inbound flow into the loss function to enhance model interpretability.PAG-STAN demonstrated favorable performance on two real-world metro OD demand datasets under the pandemic and conventional scenarios,highlighting its robustness and sensitivity for metro OD demand prediction.A series of ablation studies were conducted to verify the indispensability of each module in PAG-STAN.展开更多
The large number and dense layout of rail fastening can significantly affect the aerodynamic performance of trains.Utilizing the Improved Delayed Detached Eddy Simulation(IDDES)approach based on the SST(Shear Stress T...The large number and dense layout of rail fastening can significantly affect the aerodynamic performance of trains.Utilizing the Improved Delayed Detached Eddy Simulation(IDDES)approach based on the SST(Shear Stress Transport)k-ωturbulent model,this study evaluates the effects of the rail fastening system on the aerodynamic force,slipstream and train wake under crosswind conditions.The results indicate that in such conditions,compared to the model without rails,the rail and the fastening system reduce the drag force coefficient of the train by 1.69%,while the lateral force coefficients increase by 1.16%and 0.87%,respectively.The aerodynamic force can be considered virtually unchanged within the error allowance.However,the rail and the fastening system cause an inward shift of the negative pressure center on the leeward side of the train.The peak slipstream velocity near the ground in the rail and rail fastening system model is significantly lower than that in the situation without rails.Additionally,the rail and the fastening system not only induce two displacements in the vortex structure of the train but also accelerate the dissipation of shedding vortex and the rapid decrease of turbulent kinetic energy.展开更多
Purpose-The aim of this work is to research and design an expert diagnosis system for rail vehicle driven by data mechanism models.Design/methodology/approach-The expert diagnosis system utilizes statistical and deep ...Purpose-The aim of this work is to research and design an expert diagnosis system for rail vehicle driven by data mechanism models.Design/methodology/approach-The expert diagnosis system utilizes statistical and deep learning methods to model the real-time status and historical data features of rail vehicle.Based on data mechanism models,it predicts the lifespan of key components,evaluates the health status of the vehicle and achieves intelligent monitoring and diagnosis of rail vehicle.Findings-The actual operation effect of this system shows that it has improved the intelligent level of the rail vehicle monitoring system,which helps operators to monitor the operation of vehicle online,predict potential risks and faults of vehicle and ensure the smooth and safe operation of vehicle.Originality/value-This system improves the efficiency of rail vehicle operation,scheduling and maintenance through intelligent monitoring and diagnosis of rail vehicle.展开更多
Purpose–This study aims to investigate the acoustic roughness of rails on China’s high-speed railways,with a focus on short-wavelength irregularities(less than 80 cm),which are known to significantly contribute to n...Purpose–This study aims to investigate the acoustic roughness of rails on China’s high-speed railways,with a focus on short-wavelength irregularities(less than 80 cm),which are known to significantly contribute to noise.The goal is to develop a specific acoustic roughness spectrum tailored for China’s high-speed railway system,as no such spectrum currently exists.Design/methodology/approach–A long-term tracking study was conducted on major railway lines in China,monitoring rail roughness throughout the initial operational period and the rails’service life.Data preprocessing techniques such as peak removal and curvature correction were applied for acoustic adjustments.A spatial-wavelength domain transformation was performed,providing the distribution patterns and statistical characteristics of acoustic roughness on China’s high-speed rails.Based on these analyses,a model for constructing the acoustic roughness spectrum was developed.Findings–The study found that the acoustic roughness of China’s high-speed railway rails follows aχ2 distribution with six degrees of freedom.For wavelengths greater than 8 cm,the acoustic roughness spectrum remains below the ISO specified limits.In the wavelength range of 3.2 cm to 6.3 cm,the roughness is comparable to or within the limits specified by ISO 3095:2005 and ISO 3095:2013.However,for wavelengths shorter than 2.5 cm,the roughness exceeds ISO limits.Originality/value–This research fills the gap in the lack of a specific acoustic roughness spectrum for China’s high-speed railways.By establishing a tailored spectrum based on long-term data analysis,the findings provide valuable insights for noise control and rail maintenance in the context of China’s high-speed rail system.展开更多
Purpose-This paper aims to analyze the stress and strain distribution on the track wheel web surface and study the optimal strain gauge location for force measurement system of the track wheel.Design/methodology/appro...Purpose-This paper aims to analyze the stress and strain distribution on the track wheel web surface and study the optimal strain gauge location for force measurement system of the track wheel.Design/methodology/approach-Finite element method was employed to analyze the stress and strain distribution on the track wheel web surface under varying wheel-rail forces.Locations with minimal coupling interference between vertical and lateral forces were identified as suitable for strain gauge installation.Findings-The results show that due to the track wheel web’s unique curved shape and wheel-rail force loading mechanism,both tensile and compressive states exit on the surface of the web.When vertical force is applied,Mises stress and strain are relatively high near the inner radius of 710 mm and the outer radius of 1110mmof the web.Under lateral force,high Mises stress and strain are observed near the radius of 670mmon the inner and outer sides of the web.As the wheel-rail force application point shifts laterally toward the outer side,the Mises stress and strain near the inner radius of 710 mm of the web gradually decrease under vertical force while gradually increasing near the outer radius of 1110 mm of the web.Under lateral force,the Mises stress and strain on the surface of the web remain relatively unchanged regardless of the wheel-rail force application point.Based on the analysis of stress and strain on the surface of the web under different wheel-rail forces,the inner radius of 870 mm is recommended as the optimal mounting location of strain gauges for measuring vertical force,while the inner radius of 1143 mm is suitable for measuring lateral force.Originality/value-The research findings provide valuable insights for determining optimal strain gauge locations and designing an effective track wheel force measurement system.展开更多
The mechanism of rail corrugation remains unclear,and the research methods require improvement.The vibration characteristics represent the system's external manifestations,but a comprehensive analysis is still lac...The mechanism of rail corrugation remains unclear,and the research methods require improvement.The vibration characteristics represent the system's external manifestations,but a comprehensive analysis is still lacking.Taking the vibration characteristics of the wheel-rail system as a starting point,this study investigates the formation mechanisms of rail corrugation on measured metro lines.The line sections included both steel spring floating slab tracks and long sleeper embedded tracks.First,the wavelength and frequency attributes of rail corrugation were obtained through field measurements.Then,referencing line conditions,three-dimensional finite element numerical models were established,frequency response calculations were performed,and the relationship between the vibration responses of the wheel-rail system and rail corrugation was analyzed.Finally,a parameter sensitivity analysis of the wheel-rail system was conducted to control the further development of rail corrugation.The results show distinct corrugation phenomena on both inner and outer rails in the measured sections.The characteristic wavelengths of inner and outer rail corrugation on the steel spring floating slab track are 34 mm and 59 mm,respectively,and the characteristic wavelengths of inner and outer rail corrugation on the long sleeper embedded track are 46 mm and 47 mm,respectively.The frequency response analysis indicates that the numerical results exhibit eigenfrequencies close to the passing frequencies of the measured corrugations.The formation mechanism of inner rail corrugation on the steel spring floating slab track is attributed to the third-order bending vibration of the wheelset,which leads to the generation of inner rail corrugation.In contrast,the formation mechanism of outer rail corrugation is attributed to the lateral bending vibration of the outer rail.For the long sleeper embedded track,inner rail corrugation is generated by the lateral bending vibration of the inner rail,while outer rail corrugation results from the lateral bending vibration of the outer rail.Appropriate adjustments to the fastener's vertical and lateral stiffness,as well as the steel spring's vertical and lateral stiffness,can shift the rail corrugation eigenfrequencies,thereby inhibiting the development of corrugation with the original wavelength.Changes in other parameters have no effect on the rail corrugation eigenfrequencies and only influence the development speed of corrugation with the original wavelength.This research effectively elucidates the cause of rail corrugation from the system vibration perspective and provides a valuable complement to the corrugation analysis method.展开更多
Amphibian aircraft have seen a rise in popularity in the recreational and utility sectors due to their ability to take off and land on both land and water, thus serving a myriad of purposes, such as aerobatics, survei...Amphibian aircraft have seen a rise in popularity in the recreational and utility sectors due to their ability to take off and land on both land and water, thus serving a myriad of purposes, such as aerobatics, surveillance, and firefighting. Such seaplanes must be aerodynamically and hydrodynamically efficient, particularly during the takeoff phase. Naval architects have long employed innovative techniques to optimize the performance of marine vessels, including incorporating spray rails on hulls. This research paper is dedicated to a comprehensive investigation into the potential utilization of spray rails to enhance the takeoff performance of amphibian aircraft. Several spray rail configurations obtained from naval research were simulated on a bare Seamax M22 amphibian hull to observe an approximate 10% - 25% decrease in water resistance at high speeds alongside a 3% reduction in the takeoff time. This study serves as a motivation to improve the design of the reference airplane hull and a platform for detailed investigations in the future to improve modern amphibian design.展开更多
Monitoring the status of linear guide rails is essential because they are important components in linear motion mechanical production.Thus,this paper proposes a new method of conducting the fault diagnosis of linear g...Monitoring the status of linear guide rails is essential because they are important components in linear motion mechanical production.Thus,this paper proposes a new method of conducting the fault diagnosis of linear guide rails.First,synchrosqueezing transform(SST)combined with Gaussian high-pass filter,termed as SSTG,is proposed to process vibration signals of linear guide rails and obtain time-frequency images,thus helping realize fault feature visual enhancement.Next,the coordinate attention(CA)mechanism is introduced to promote the DenseNet model and obtain the CA-DenseNet deep learning framework,thus realizing accurate fault classifica-tion.Comparison experiments with other methods reveal that the proposed method has a high classification accuracy of up to 95.0%.The experimental results further demonstrate the effectiveness and robustness of the proposed method for the fault diagnosis of linear guide rails.展开更多
Ruby on Rails(简称ROR)是一个Web应用程序框架,以其能快速开发而备受敏捷开发实践者的推崇,它包含的重要概念有MVC模式、DSL、习惯约定优于配置、生成器、低重复等.以一个实际课题"中医药数据库共享平台"为例,研究如何应用RO...Ruby on Rails(简称ROR)是一个Web应用程序框架,以其能快速开发而备受敏捷开发实践者的推崇,它包含的重要概念有MVC模式、DSL、习惯约定优于配置、生成器、低重复等.以一个实际课题"中医药数据库共享平台"为例,研究如何应用ROR技术来满足一个实际需求的项目,涉及的技术有MVC模式、RESTful SOA、AJAX、Lighttpd&FCGI等.展开更多
随着Web服务的快速发展,基于REST(Representational State Transfer)风格的Web Service越来越受到业界的关注。在实现RESTful Web Service的众多框架中,Rails完整实现了MVC并对RESTful Web Service的开发作了极大的封装和简化,使得开发...随着Web服务的快速发展,基于REST(Representational State Transfer)风格的Web Service越来越受到业界的关注。在实现RESTful Web Service的众多框架中,Rails完整实现了MVC并对RESTful Web Service的开发作了极大的封装和简化,使得开发人员用Rails实现RESTful Web Service变得容易。对RESTful Web Service特征和Rails框架结构进行了概述,分析了Rails实现RESTfulWeb Service的原理,在此基础上结合实例给出了基于Rails的RESTful Web Service以及RESTful Web Service客户端的开发步骤和方法,并且利用Ruby进行了实现。展开更多
运用目前两种炙手可热的Web开发技术:AJAX和Ruby on Rails为WebGIS提供一个新的解决方案,AJAX技术作为一种新兴的网络技术比传统页面刷新模式具有更好的性能和友好的用户体验,不过在建立大量的Javascript的代码基础上的,本文通过对AJAX ...运用目前两种炙手可热的Web开发技术:AJAX和Ruby on Rails为WebGIS提供一个新的解决方案,AJAX技术作为一种新兴的网络技术比传统页面刷新模式具有更好的性能和友好的用户体验,不过在建立大量的Javascript的代码基础上的,本文通过对AJAX on Rails原理进行分析,运用Ruby on Rails的动态性和敏捷性使AJAX模式带来的程序量大、首页加载时间长的缺陷得到改善,进一步提高程序性能。在实现环节上,在该平台上结合使用Google Maps API,以GXmlHttp在Rails上实现了AJAX的WebGIS关键应用。展开更多
基金Supported by Fundamental Research Funds for the Central Universities(Grant No.2019JBM050).
文摘This research aimed to overcome challenges such as high costs,lengthy optimization time,and low efficiency in resolving issues related to wheel-rail contact,rail wear,and vehicle dynamics.Based on the wheel-rail contact parameters,an optimal design method for rail grinding target profile is proposed from wear profile measurement to grinding profile design according to the actual railway track and vehicle operating conditions.We utilized Isight to create a simulation test and developed an RBF proxy model that incorporated both mechanical and geometric aspects of wheel-rail contact.By integrating rail modeling,wheel-rail contact analysis,and multi-objective optimization,we established a rail grinding optimization model that was solved using the NSGA-II algorithm.After optimization,the study achieved a 31.863%reduction in average contact stress,a 70.5%reduction in matching wear work,and a 100.391%increase in the difference in rolling radius between the wheel and rail.
文摘Purpose–This paper investigates how high-speed rail(HSR)influences socioeconomic inequality by providing the first systematic bibliometric review of research trends,methodological approaches and thematic structures.It examines whether HSR fosters balanced regional development or reinforces spatial disparities.Design/methodology/approach–Using the Bibliometrix R package,237 records were retrieved from the Web of Science(1985–2024).Citation indicators,keyword co-occurrence and collaboration networks were combined with natural language processing(NLP)to classify studies by territorial scale,methodology,economic variables and inequality outcomes.Findings–The paper offers the first structured overview of how the literature conceptualizes the link between HSR and inequality.It highlights persistent gaps–scarcity of city-level analyses,limited socioeconomic indicators and reliance on Chinese case studies–providing a foundation for more comparative and interdisciplinary research.Originality/value–This paper contributes by offering a structured overview of how the literature has conceptualized and measured the relationship between HSR and inequality.By identifying persistent research gaps–such as the scarcity of city-level analyses,limited use of socioeconomic indicators,and overreliance on Chinese case studies–it provides a foundation for more comparative and interdisciplinary approaches.The study informs policymakers and researchers on how to design future infrastructure projects that balance efficiency with equity.
文摘This article focuses on the remote diagnosis and analysis of rail vehicle status based on the data of the Train Control Management System(TCMS).It first expounds on the importance of train diagnostic analysis and designs a unified TCMS data frame transmission format.Subsequently,a remote data transmission link using 4G signals and data processing methods is introduced.The advantages of remote diagnosis are analyzed,and common methods such as correlation analysis,fault diagnosis,and fault prediction are explained in detail.Then,challenges such as data security and the balance between diagnostic accuracy and real-time performance are discussed,along with development prospects in technological innovation,algorithm optimization,and application promotion.This research provides ideas for remote analysis and diagnosis based on TCMS data,contributing to the safe and efficient operation of rail vehicles.
基金supported by the Fund of China State Railway Group Corporation Limited(L2023J001)the Fund of China Academy of Railway Sciences Corporation Limited(2023YJ247).
文摘Purpose–This study aims to implement condition monitoring for urban rail train permanent magnet synchronous motors and inverter systems.Through the construction of a digital twin model,it performs fault diagnosis of potential system failures,enabling rapid fault localization and protection.Design/methodology/approach–This research begins with a brief introduction to the structure and classification of permanent magnet synchronous motors(PMSMs),followed by a detailed analysis of their mathematical model.Subsequently,it thoroughly investigates the working principle of three-phase two-level inverters and the distribution of space voltage vectors.Based on the analysis of the main circuit topology,a digital twin model matching the external characteristics of the physical circuit is established using the model predictive control method,achieving accurate system simulation.Furthermore,through theoretical analysis and simulation verification of phase current characteristics under inverter switch tube faults,general patterns of phase currents under fault conditions are summarized.The established digital twin model is then employed to validate these patterns,confirming the model’s effectiveness in fault diagnosis.Findings–This study proposes a fault diagnosis method based on digital twins.Experimental and simulation results demonstrate that the established digital twin model can accurately simulate the external characteristics of the actual physical circuit,validating its effectiveness in inverter fault diagnosis.This approach offers practical value for condition monitoring in actual urban rail train systems.Originality/value–The study innovatively starts from a mathematical model and simulates the actual physical model through a virtual model,requiring only external characteristics to achieve system fault diagnosis,thereby enhancing diagnostic efficiency.
基金supported by the National Natural Science Foundation of China(Grant numbers 52177112 and 52278419)the Chinese Academy of Engineering(Grant number 2022--XY-75).
文摘Within the transition process of urban rail transit systems,the challenges of high energy consumption,increasing carbon emissions,limited economic viability,and intricate risks emerge as significant hurdles.This paper proposes a novel energy utilization framework for the urban rail transit system that incorporates underground energy storage systems characterized by high resilience and low carbon.First,existing methods employed in urban rail transit are comprehensively reviewed.Then,a novel framework and strategic significance of the urban rail transit system incorporating underground energy storage systems are introduced.This integration effectively utilizes and manages diverse renewable energy sources and the available space resources.The viability is demonstrated through a case study by combining Nanjing metro.Finally,suggestions for research in pivotal areas are summarized.
基金Trafikföorvaltningen Region Stockholm and Trafikverket for funding and supporting this study.
文摘Purpose–Adding an appropriate pre-sag to the geometry of simple catenary systems for electric railways can improve their performance in dynamic interaction with the pantographs of trains operating under them.The value of pre-sag can be obtained by empirical approximation or computationally expensive optimisation.This study aims to define a simple but accurate method to determine a suitable pre-sag without dynamic simulations and to find its limitations.Design/methodology/approach–A quasi-static method to determine the ideal value of pre-sag is described based on elasticity variations.It considers variations of the static contact force.The limits of this method are investigated by comparing it to a parametric dynamic simulation study.In the dynamic simulation,an optimal level of pre-sag is identified for each contact force level.The influence of the speed in the dynamic simulation results is expressed in two parameters:the quasi-static influence in the mean contact force and the dynamic influence in the ratio between the vehicle speed and the wave propagation speed in the contact wire.Findings–The comparison between the suggested method and the dynamic simulations shows a high consistency up to a speed limit of around 40%of the wave propagation speed.The best agreement with the dynamic results is achieved by calculating the optimal pre-sag based on the absolute elasticity variation.Practical implications–The simplified approach for determining the pre-sag is valid for low-speed applications,such as suburban railway lines.For these cases,a highly suitable geometry can be obtained with the suggested method,meaning a significantly reduced computational effort.As a case study for this work,the results are applied to a Swedish suburban rail line upgrade case.Originality/value–The static uplift force is added as a varied parameter in dynamic simulations.The shift in system behaviour from low to high dynamics is described,and how the benefits from pre-sag are visible and then disappear.The limit value of the low-dynamics regime is identified to be 40%.
基金by National Natural Science Foundation of China(62373142,62033014)Natural Science Foundation of Hunan Province(2025JJ70017,2022JJ50074).
文摘To address issues such as poor initial population diversity, low stability and local convergence accuracy, and easy local optima in the traditional Multi-Objective Artificial Hummingbird Algorithm (MOAHA), an Improved MOAHA (IMOAHA) was proposed. The improvements involve Tent mapping based on random variables to initialize the population, a logarithmic decrease strategy for inertia weight to balance search capability, and the improved search operators in the territory foraging phase to enhance the ability to escape from local optima and increase convergence accuracy. The effectiveness of IMOAHA was verified through Matlab/Simulink. The results demonstrate that IMOAHA exhibits superior convergence, diversity, uniformity, and coverage of solutions across 6 test functions, outperforming 4 comparative algorithms. A Wilcoxon rank-sum test further confirmed its exceptional performance. To assess IMOAHA’s ability to solve engineering problems, an optimization model for a multi-track, multi-train urban rail traction power supply system with Supercapacitor Energy Storage Systems (SCESSs) was established, and IMOAHA was successfully applied to solving the capacity allocation problem of SCESSs, demonstrating that it is an effective tool for solving complex Multi-Objective Optimization Problems (MOOPs) in engineering domains.
基金National S&T Project 2018YJS036.This study is supported in part by Key Laboratory of Universal Wireless Communications(BUPT),Ministry of Education,P.R.China(No.KFKT-2018104)by the Natural Science Foundation of China(NSFC,No.61571037,61871026,61961130391,and U1834210)+2 种基金NSFC Outstanding Youth(No.61725101)National Key R&D Program of China under Grant 2016YFE0200900the Royal Society Newton Advanced Fellowship under Grant NA191006.
文摘Channel estimation is a well-known challenge for wireless orthogonal frequency division multiplexing(OFDM)communication systems with massive antennas on high speed rails(HSRs).This paper investigates this problem and design two practicable uplink and downlink channel estimators for orthogonal frequency division multiplexing(OFDM)communication systems with massive antenna arrays at base station on HSRs.Specifically,we first use pilots to estimate the initial angle of arrival(AoA)and channel gain information of each uplink path through discrete Fourier transform(DFT),and then refine the estimates via the angle rotation technique and suggested pilot design.Based on the uplink angel estimation,we design a new downlink channel estimator for frequency division duplexing(FDD)systems.Additionally,we derive the Cramér-Rao lower bounds(CRLBs)of the AoA and channel gain estimates.Finally,numerical results are provided to corroborate our proposed studies.
基金supported by the National Natural Science Foundation of China(72288101,72201029,and 72322022).
文摘Accurate origin–destination(OD)demand prediction is crucial for the efficient operation and management of urban rail transit(URT)systems,particularly during a pandemic.However,this task faces several limitations,including real-time availability,sparsity,and high-dimensionality issues,and the impact of the pandemic.Consequently,this study proposes a unified framework called the physics-guided adaptive graph spatial–temporal attention network(PAG-STAN)for metro OD demand prediction under pandemic conditions.Specifically,PAG-STAN introduces a real-time OD estimation module to estimate real-time complete OD demand matrices.Subsequently,a novel dynamic OD demand matrix compression module is proposed to generate dense real-time OD demand matrices.Thereafter,PAG-STAN leverages various heterogeneous data to learn the evolutionary trend of future OD ridership during the pandemic.Finally,a masked physics-guided loss function(MPG-loss function)incorporates the physical quantity information between the OD demand and inbound flow into the loss function to enhance model interpretability.PAG-STAN demonstrated favorable performance on two real-world metro OD demand datasets under the pandemic and conventional scenarios,highlighting its robustness and sensitivity for metro OD demand prediction.A series of ablation studies were conducted to verify the indispensability of each module in PAG-STAN.
基金funded by the National Natural Science Foundation of China(Grant No.12172308).
文摘The large number and dense layout of rail fastening can significantly affect the aerodynamic performance of trains.Utilizing the Improved Delayed Detached Eddy Simulation(IDDES)approach based on the SST(Shear Stress Transport)k-ωturbulent model,this study evaluates the effects of the rail fastening system on the aerodynamic force,slipstream and train wake under crosswind conditions.The results indicate that in such conditions,compared to the model without rails,the rail and the fastening system reduce the drag force coefficient of the train by 1.69%,while the lateral force coefficients increase by 1.16%and 0.87%,respectively.The aerodynamic force can be considered virtually unchanged within the error allowance.However,the rail and the fastening system cause an inward shift of the negative pressure center on the leeward side of the train.The peak slipstream velocity near the ground in the rail and rail fastening system model is significantly lower than that in the situation without rails.Additionally,the rail and the fastening system not only induce two displacements in the vortex structure of the train but also accelerate the dissipation of shedding vortex and the rapid decrease of turbulent kinetic energy.
基金supported by Hunan Province Enterprise Technology Innovation and Entrepreneurship Team Support Program Project,Hunan Province Science and Technology Innovation Leading Talent Project[2023RC1088]Hunan Province Science and Technology Talent Support Project[2023TJ-Z10].
文摘Purpose-The aim of this work is to research and design an expert diagnosis system for rail vehicle driven by data mechanism models.Design/methodology/approach-The expert diagnosis system utilizes statistical and deep learning methods to model the real-time status and historical data features of rail vehicle.Based on data mechanism models,it predicts the lifespan of key components,evaluates the health status of the vehicle and achieves intelligent monitoring and diagnosis of rail vehicle.Findings-The actual operation effect of this system shows that it has improved the intelligent level of the rail vehicle monitoring system,which helps operators to monitor the operation of vehicle online,predict potential risks and faults of vehicle and ensure the smooth and safe operation of vehicle.Originality/value-This system improves the efficiency of rail vehicle operation,scheduling and maintenance through intelligent monitoring and diagnosis of rail vehicle.
基金supported by multiple funding sources,including the China State Railway Group Co.,Ltd.’s Science and Technology Development Plan(Project Code:P2022Z003).
文摘Purpose–This study aims to investigate the acoustic roughness of rails on China’s high-speed railways,with a focus on short-wavelength irregularities(less than 80 cm),which are known to significantly contribute to noise.The goal is to develop a specific acoustic roughness spectrum tailored for China’s high-speed railway system,as no such spectrum currently exists.Design/methodology/approach–A long-term tracking study was conducted on major railway lines in China,monitoring rail roughness throughout the initial operational period and the rails’service life.Data preprocessing techniques such as peak removal and curvature correction were applied for acoustic adjustments.A spatial-wavelength domain transformation was performed,providing the distribution patterns and statistical characteristics of acoustic roughness on China’s high-speed rails.Based on these analyses,a model for constructing the acoustic roughness spectrum was developed.Findings–The study found that the acoustic roughness of China’s high-speed railway rails follows aχ2 distribution with six degrees of freedom.For wavelengths greater than 8 cm,the acoustic roughness spectrum remains below the ISO specified limits.In the wavelength range of 3.2 cm to 6.3 cm,the roughness is comparable to or within the limits specified by ISO 3095:2005 and ISO 3095:2013.However,for wavelengths shorter than 2.5 cm,the roughness exceeds ISO limits.Originality/value–This research fills the gap in the lack of a specific acoustic roughness spectrum for China’s high-speed railways.By establishing a tailored spectrum based on long-term data analysis,the findings provide valuable insights for noise control and rail maintenance in the context of China’s high-speed rail system.
基金funded by the Fund Project of China Academy of Railway Sciences Corporation Limited[Grant No.2022YJ194,2023YJ254].
文摘Purpose-This paper aims to analyze the stress and strain distribution on the track wheel web surface and study the optimal strain gauge location for force measurement system of the track wheel.Design/methodology/approach-Finite element method was employed to analyze the stress and strain distribution on the track wheel web surface under varying wheel-rail forces.Locations with minimal coupling interference between vertical and lateral forces were identified as suitable for strain gauge installation.Findings-The results show that due to the track wheel web’s unique curved shape and wheel-rail force loading mechanism,both tensile and compressive states exit on the surface of the web.When vertical force is applied,Mises stress and strain are relatively high near the inner radius of 710 mm and the outer radius of 1110mmof the web.Under lateral force,high Mises stress and strain are observed near the radius of 670mmon the inner and outer sides of the web.As the wheel-rail force application point shifts laterally toward the outer side,the Mises stress and strain near the inner radius of 710 mm of the web gradually decrease under vertical force while gradually increasing near the outer radius of 1110 mm of the web.Under lateral force,the Mises stress and strain on the surface of the web remain relatively unchanged regardless of the wheel-rail force application point.Based on the analysis of stress and strain on the surface of the web under different wheel-rail forces,the inner radius of 870 mm is recommended as the optimal mounting location of strain gauges for measuring vertical force,while the inner radius of 1143 mm is suitable for measuring lateral force.Originality/value-The research findings provide valuable insights for determining optimal strain gauge locations and designing an effective track wheel force measurement system.
基金Supported by National Natural Science Foundation of China(Grant No.11772230)。
文摘The mechanism of rail corrugation remains unclear,and the research methods require improvement.The vibration characteristics represent the system's external manifestations,but a comprehensive analysis is still lacking.Taking the vibration characteristics of the wheel-rail system as a starting point,this study investigates the formation mechanisms of rail corrugation on measured metro lines.The line sections included both steel spring floating slab tracks and long sleeper embedded tracks.First,the wavelength and frequency attributes of rail corrugation were obtained through field measurements.Then,referencing line conditions,three-dimensional finite element numerical models were established,frequency response calculations were performed,and the relationship between the vibration responses of the wheel-rail system and rail corrugation was analyzed.Finally,a parameter sensitivity analysis of the wheel-rail system was conducted to control the further development of rail corrugation.The results show distinct corrugation phenomena on both inner and outer rails in the measured sections.The characteristic wavelengths of inner and outer rail corrugation on the steel spring floating slab track are 34 mm and 59 mm,respectively,and the characteristic wavelengths of inner and outer rail corrugation on the long sleeper embedded track are 46 mm and 47 mm,respectively.The frequency response analysis indicates that the numerical results exhibit eigenfrequencies close to the passing frequencies of the measured corrugations.The formation mechanism of inner rail corrugation on the steel spring floating slab track is attributed to the third-order bending vibration of the wheelset,which leads to the generation of inner rail corrugation.In contrast,the formation mechanism of outer rail corrugation is attributed to the lateral bending vibration of the outer rail.For the long sleeper embedded track,inner rail corrugation is generated by the lateral bending vibration of the inner rail,while outer rail corrugation results from the lateral bending vibration of the outer rail.Appropriate adjustments to the fastener's vertical and lateral stiffness,as well as the steel spring's vertical and lateral stiffness,can shift the rail corrugation eigenfrequencies,thereby inhibiting the development of corrugation with the original wavelength.Changes in other parameters have no effect on the rail corrugation eigenfrequencies and only influence the development speed of corrugation with the original wavelength.This research effectively elucidates the cause of rail corrugation from the system vibration perspective and provides a valuable complement to the corrugation analysis method.
文摘Amphibian aircraft have seen a rise in popularity in the recreational and utility sectors due to their ability to take off and land on both land and water, thus serving a myriad of purposes, such as aerobatics, surveillance, and firefighting. Such seaplanes must be aerodynamically and hydrodynamically efficient, particularly during the takeoff phase. Naval architects have long employed innovative techniques to optimize the performance of marine vessels, including incorporating spray rails on hulls. This research paper is dedicated to a comprehensive investigation into the potential utilization of spray rails to enhance the takeoff performance of amphibian aircraft. Several spray rail configurations obtained from naval research were simulated on a bare Seamax M22 amphibian hull to observe an approximate 10% - 25% decrease in water resistance at high speeds alongside a 3% reduction in the takeoff time. This study serves as a motivation to improve the design of the reference airplane hull and a platform for detailed investigations in the future to improve modern amphibian design.
基金supported by the following organizations:National Natural Science Foundation of China(Grant Nos.52375522,52207036,and 62203010)the Anhui Provincial Nat-ural Science Foundation(Grant Nos.2308085Y03 and 2208085QE167)+2 种基金the Project of the Outstanding Young Talents in Colleges and Universities of Anhui Province(Grant No.gxyqZD2022006)the College Natural Science Research Key project of Anhui Education Department(Grant No.KJ2021A0018)the University Outstanding Youth Research Project of Anhui Province(Grant No.2022AH030016)。
文摘Monitoring the status of linear guide rails is essential because they are important components in linear motion mechanical production.Thus,this paper proposes a new method of conducting the fault diagnosis of linear guide rails.First,synchrosqueezing transform(SST)combined with Gaussian high-pass filter,termed as SSTG,is proposed to process vibration signals of linear guide rails and obtain time-frequency images,thus helping realize fault feature visual enhancement.Next,the coordinate attention(CA)mechanism is introduced to promote the DenseNet model and obtain the CA-DenseNet deep learning framework,thus realizing accurate fault classifica-tion.Comparison experiments with other methods reveal that the proposed method has a high classification accuracy of up to 95.0%.The experimental results further demonstrate the effectiveness and robustness of the proposed method for the fault diagnosis of linear guide rails.
文摘Ruby on Rails(简称ROR)是一个Web应用程序框架,以其能快速开发而备受敏捷开发实践者的推崇,它包含的重要概念有MVC模式、DSL、习惯约定优于配置、生成器、低重复等.以一个实际课题"中医药数据库共享平台"为例,研究如何应用ROR技术来满足一个实际需求的项目,涉及的技术有MVC模式、RESTful SOA、AJAX、Lighttpd&FCGI等.
文摘随着Web服务的快速发展,基于REST(Representational State Transfer)风格的Web Service越来越受到业界的关注。在实现RESTful Web Service的众多框架中,Rails完整实现了MVC并对RESTful Web Service的开发作了极大的封装和简化,使得开发人员用Rails实现RESTful Web Service变得容易。对RESTful Web Service特征和Rails框架结构进行了概述,分析了Rails实现RESTfulWeb Service的原理,在此基础上结合实例给出了基于Rails的RESTful Web Service以及RESTful Web Service客户端的开发步骤和方法,并且利用Ruby进行了实现。
文摘运用目前两种炙手可热的Web开发技术:AJAX和Ruby on Rails为WebGIS提供一个新的解决方案,AJAX技术作为一种新兴的网络技术比传统页面刷新模式具有更好的性能和友好的用户体验,不过在建立大量的Javascript的代码基础上的,本文通过对AJAX on Rails原理进行分析,运用Ruby on Rails的动态性和敏捷性使AJAX模式带来的程序量大、首页加载时间长的缺陷得到改善,进一步提高程序性能。在实现环节上,在该平台上结合使用Google Maps API,以GXmlHttp在Rails上实现了AJAX的WebGIS关键应用。
