State-of-Arts of Mechanics of Rolling Contact and Its Application to Analysis of the Interactions between Wheel and Rail

A few typical models of theory on rolling contact of bodies are reviewed, and the advantages and disadvantages in the applications to the dynamics of railway vehicles and the wheel/rail rolling contact are discussed in detail in the present paper.

Mechanical characteristic variation of ballastless track in highspeed railway:effect of train–track interaction and environment loads

Due to the fact that ballastless tracks in highspeed railways are not only subjected to repeated train–track dynamic interaction loads,but also suffer from complex environmental loads,the fundamental understanding of mechanical performance of ballastless tracks under sophisticated service conditions is an increasingly demanding and challenging issue in high-speed railway networks.This work aims to reveal the effect of train–track interaction and environment loads on the mechanical characteristic variation of ballastless tracks in high-speed railways,particularly focusing on the typical interface damage evolution between track layers.To this end,a finite element model of a double-block ballastless track involving the cohesive zone model for the track interface is first established to analyze the mechanical properties of the track interface under the loading–unloading processes of the negative temperature gradient load(TGL)followed by the same cycle of the positive TGL.Subsequently,the effect of wheel–rail longitudinal interactions on the nonlinear dynamic characteristics of the track interface is investigated by using a vehicle-slab track vertical-longitudinal coupled dynamics model.Finally,the influence of dynamic water pressure induced by vehicle dynamic load on the mechanical characteristics and damage evolution of the track interface is elucidated using a fluid–solid coupling method.Results show that the loading history of the positive and negative TGLs has a great impact on the nonlinear development and distribution of the track interface stress and damage;the interface damage could be induced by the wheel–rail longitudinal vibrations at a high vehicle running speed owing to the dynamic amplification effect caused by short wave irregularities;the vehicle dynamic load could produce considerable water pressure that presents nonlinear spatial–temporal characteristics at the track interface,which would lead to the interface failure under a certain condition due to the coupled dynamic effect of vehicle load and water pressure.

An efficient method for train-track-substructure dynamic interaction analysis by implicit-explicit integration and multi-time-step solution

In this work,a method is put forward to obtain the dynamic solution efficiently and accurately for a large-scale train-track-substructure(TTS)system.It is called implicit-explicit integration and multi-time-step solution method(abbreviated as mI-nE-MTS method).The TTS system is divided into train-track subsystem and substruc-ture subsystem.Considering that the root cause of low effi-ciency of obtaining TTS solution lies in solving the alge-braic equation of the substructures,the high-efficient Zhai method,an explicit integration scheme,can be introduced to avoid matrix inversion process.The train-track system is solved by implicitly Park method.Moreover,it is known that the requirement of time step size differs for different sub-systems,integration methods and structural frequency response characteristics.A multi-time-step solution is pro-posed,in which time step size for the train-track subsystem and the substructure subsystem can be arbitrarily chosen once satisfying stability and precision demand,namely the time spent for m implicit integral steps is equal to n explicit integral steps,i.e.,mI=nE as mentioned above.The numeri-cal examples show the accuracy,efficiency,and engineering practicality of the proposed method.

Beam-track interaction of high-speed railway bridge with ballast track

Based on the construction bridge of Xiamen-Shenzhen high-speed railway(9-32 m simply-supported beam + 6×32 m continuous beam),the pier-beam-track finite element model,where the continuous beam of the ballast track and simply-supported beam are combined with each other,was established.The laws of the track stress,the pier longitudinal stress and the beam-track relative displacement were analyzed.The results show that reducing the longitudinal resistance can effectively reduce the track stress and the pier stress of the continuous beam,and increase the beam-track relative displacement.Increasing the rigid pier stiffness of continuous beam can reduce the track braking stress,increase the pier longitudinal stress and reduce the beam-track relative displacement,Increasing the rigid pier stiffness of simply-supported beam can reduce the track braking stress,the rigid pier longitudinal stress and the beam-track relative displacement.

Sensitive factors research for track-bridge interaction of Long-span X-style steel-box arch bridge on high-speed railway

X-style arch bridge on high-speed railways(HSR)is one kind of complicated long-span structure,and the track-bridge interaction is essential to ensure the safety and smoothness of HSR.Taking an X-style steel-box arch bridge with a main span of450 m on HSR under construction for example,a new integrative mechanic model of rail-stringer-cross beam-suspenderpier-foundation coupling system was established,adopting the nonlinear spring element simulating the longitudinal resistance between track and bridge.The transmission law of continuous welded rail(CWR)on the X-style arch bridge was researched,and comparative study was carried out to discuss the influence of several sensitive factors,such as the temperature load case,the longitudinal resistance model,the scheme of longitudinal restraint conditions,the introverted inclination of arch rib,the stiffness of pier and abutment and the location of the rail expansion device.Calculating results indicate that the longitudinal resistance has a significant impact upon the longitudinal forces of CWR on this kind of bridge,while the arch rib’s inclination has little effect.Besides,temperature variation of arch ribs and suspenders should be taken into account in the calculation.Selecting the restraint system without longitudinally-fixed bearing and setting the rail expansion devices on both ends are more reasonable.

Train–track coupled dynamics analysis:system spatial variation on geometry,physics and mechanics

This paper aims to clarify the influence of system spatial variability on train–track interaction from perspectives of stochastic analysis and statistics.Considering the spatial randomness of system properties in geometry,physics and mechanics,the primary work is therefore simulating the uncertainties realistically,representatively and efficiently.With regard to the track irregularity simulation,a model is newly developed to obtain random sample sets of track irregularities by transforming its power spectral density function into the equivalent track quality index for representation based on the discrete Parseval theorem,where the correlation between various types of track irregularities is accounted for.To statistically clarify the uncertainty of track properties in physics and mechanics in space,a model combining discrete element method and finite element method is developed to obtain the spatially varied track parametric characteristics,e.g.track stiffness and density,through which the highly expensive experiments in situ can be avoided.Finally a train–track stochastic analysis model is formulated by integrating the system uncertainties into the dynamics model.Numerical examples have validated the accuracy and efficiency of this model and illustrated the effects of system spatial variability on train–track vibrations comprehensively.

Integrating innovative library e-reserves service into teaching and learning at Shanghai Jiao Tong University

Purpose: Fully integrating its e-reserves service into the university's course management system has become the primary design goal of the innovative e-reserves service system at Shanghai Jiao Tong University(SJTU) Library.Design/methodology/approach: Through blending library and information service into the teaching and learning process, SJTU Library has effectively combined its reserves service into the user learning environment. The main metadata model and the design of various interfaces of the e-reserves service system are introduced.Findings: E-reserves has been integrated into the course management system. Users can directly access relevant resources when they browse the customized course page. It is more convenient for teachers to add reserves items, and the added items can be made available simultaneously on SJTU Library's resource discovery platform automatically.Research limitations: At present, e-reserves items are mainly books, and more other types of reserves materials are needed to be provided. Some relevant copyright issues should be addressed.Practical implications: Using a series of interface interactions, the e-reserves service has been integrated into the university's course management system. It is convenient for students to access customized e-reserves service during their learning process.Originality/value: We achieved interconnection between the e-reserves and the university's course management system. Information on the e-reserves Web page is automatically updated.SJTU Library provides customized e-reserves service in the course management system.

Polygonisation of railway wheels:a critical review

Polygonisation is a common nonuniform wear phenomenon occurring in railway vehicle wheels and has a severe impact on the vehicle–track system,ride comfort,and lineside residents.This paper first summarizes periodic defects of the wheels,including wheel polygonisation and wheel corrugation,occurring in railways worldwide.Thereafter,the effects of wheel polygonisation on the wheel–rail interaction,noise and vibration,and fatigue failure of the vehicle and track components are reviewed.Based on the different causes,the formation mechanisms of periodic wheel defects are classified into three categories:(1)initial defects of wheels,(2)natural vibration of the vehicle–track system,and(3)thermoelastic instability.In addition,the simulation methods of wheel polygonisation evolution and countermeasures to mitigate wheel polygonisation are presented.Emphasis is given to the characteristics,effects,causes,and solutions of wheel polygonisation in metro vehicles,locomotives,and highspeed trains in China.Finally,the guidance is provided on further understanding the formation mechanisms,monitoring technology,and maintenance criterion of wheel polygonisation.

Vehicle–track–tunnel dynamic interaction:a finite/infinite element modelling method

The aim of this study is to develop coupled matrix formulations to characterize the dynamic interaction between the vehicle,track,and tunnel.The vehicle–track coupled system is established in light of vehicle–track coupled dynamics theory.The physical characteristics and mechanical behavior of tunnel segments and rings are modeled by the finite element method,while the soil layers of the vehicle–track–tunnel(VTT)system are modeled as an assemblage of 3-D mapping infinite elements by satisfying the boundary conditions at the infinite area.With novelty,the tunnel components,such as rings and segments,have been coupled to the vehicle–track systems using a matrix coupling method for finite elements.The responses of sub-systems included in the VTT interaction are obtained simultaneously to guarantee the solution accuracy.To relieve the computer storage and save the CPU time for the large-scale VTT dynamics system with high degrees of freedoms,a cyclic calculation method is introduced.Apart from model validations,the necessity of considering the tunnel substructures such as rings and segments is demonstrated.In addition,the maximum number of elements in the tunnel segment is confirmed by numerical simulations.

On dynamic analysis method for large-scale train-track-substructure interaction

Train–track–substructure dynamic interaction is an extension of the vehicle–track coupled dynamics.It contributes to evaluate dynamic interaction and performance between train–track system and its substructures.For the first time,this work devotes to presenting engineering practical methods for modeling and solving such large-scale train–track–substructure interaction systems from a unified viewpoint.In this study,a train consists of several multi-rigid-body vehicles,and the track is modeled by various finite elements.The track length needs only satisfy the length of a train plus boundary length at two sides,despite how long the train moves on the track.The substructures and their interaction matrices to the upper track are established as independent modules,with no need for additionally building the track structures above substructures,and accordingly saving computational cost.Track–substructure local coordinates are defined to assist the confirming of the overlapped portions between the train–track system and the substructural system to effectively combine the cyclic calculation and iterative solution procedures.The advancement of this model lies in its convenience,efficiency and accuracy in continuously considering the vibration participation of multi-types of substructures against the moving of a train on the track.Numerical examples have shown the effectiveness of this method;besides,influence of substructures on train–track dynamic behaviors is illustrated accompanied by clarifying excitation difference of different track irregularity spectrums.

FPGA Implementation of Extended Kalman Filter for Parameters Estimation of Railway Wheelset

It is necessary to know the status of adhesion conditions between wheel and rail for efficient accelerating and decelerating of railroad vehicle.The proper estimation of adhesion conditions and their real-time implementation is considered a challenge for scholars.In this paper,the development of simulation model of extended Kalman filter(EKF)in MATLAB/Simulink is presented to estimate various railway wheelset parameters in different contact conditions of track.Due to concurrent in nature,the Xilinx®System-on-Chip Zynq Field Programmable Gate Array(FPGA)device is chosen to check the onboard estimation ofwheel-rail interaction parameters by using the National Instruments(NI)myRIO®development board.The NImyRIO®development board is flexible to deal with nonlinearities,uncertain changes,and fastchanging dynamics in real-time occurring in wheel-rail contact conditions during vehicle operation.The simulated dataset of the railway nonlinear wheelsetmodel is tested on FPGA-based EKF with different track conditions and with accelerating and decelerating operations of the vehicle.The proposed model-based estimation of railway wheelset parameters is synthesized on FPGA and its simulation is carried out for functional verification on FPGA.The obtained simulation results are aligned with the simulation results obtained through MATLAB.To the best of our knowledge,this is the first time study that presents the implementation of a model-based estimation of railway wheelset parameters on FPGA and its functional verification.The functional behavior of the FPGA-based estimator shows that these results are the addition of current knowledge in the field of the railway.

Simplified analytical solution for stress concentration ratio of piled embankments incorporating pile–soil interaction

Piled embankments have been extensively used for high-speed rail over soft soils because of their effectiveness in minimizing differential settlement and shortening the construction period.Stress concentration ratio,defined as the ratio of vertical stress carried by pile heads(or pile caps if applicable)to that by adjacent soils,is a fundamental parameter in the design of piled embankments.In view of the complicated load transfer mechanism in the framework of embankment system,this paper presents a simplified analytical solution for the stress concentration ratio of rigid pile-supported embankments.In the derivation,the effects of cushion stiffness,pile–soil interaction,and pile penetration behavior are considered and examined.A modified linearly elastic-perfectly plastic model was used to analyze the mechanical response of a rigid pile–soil system.The analytical model was verified against field data and the results of numerical simulations from the literature.According to the proposed method,the skin friction distribution,pile–soil relative displacement,location of neural point,and differential settlement between the pile head(or cap)and adjacent soils can be determined.This work serves as a fast algorithm for initial and reasonable approximation of stress concentration ratio on the design aspects of piled embankments.

The Effects of B2C Interaction on Customer Loyalty

Purpose： This research attempts to examine the relationship between B2C interaction and customer loyalty in Business-to-Customer（B2C） context from a new perspective of the interactive tool.Design/methodology/approach： The scale for B2C interactive tools is of seven dimensions： efficiency, security, fulfillment, mobility, community, cultivation, and customization. A model reflecting the influences of these attributes on customer loyalty is developed and empirically examined based on data collected from 265 B2C customers. Findings： Results reveal that the fulfillment, mobility, community, and customization of B2C interactive tools can enhance customer loyalty directly and significantly. Efficiency and security, serving as the premise for possible purchase behavior, facilitate fulfillment. In addition, cultivation promotes the formation of customization, which directly strengthens customer loyalty.Research limitations： Models considering individual-level indicators and combined with classic loyalty mechanisms in B2C context may lead to a deeper understanding of the tested effects of interaction on customer loyalty.Practical implications： To strengthen B2C interaction and further cultivate loyal customers, making interactive tools more fundamental, flexible, and personalized is critical for B2C enterprises. Originality/value： This study proposes a new perspective from interactive tools when measuring the relationship between B2C interaction and customer loyalty, and offers a useful theoretical lens and reasonable explanations for investigating customer loyalty in B2C e-commerce context.

ExperimentalVerificationofaDetailedVehicle┐TrackVerticalInteractionModel

A theoretical model has been developed to investigate vertical dynamic interactions between railway vehicles and tracks. Wheel rail forces and dynamic responses of vehicle and track components can be simulated with the model. The model has been applied to the study of high speed and heavy haul railway dynamic problems. In order to verify the model completely, a full scale field experiment was performed on the Chinese Datong Qinhuangdao railway. Accelerations of rail, sleeper and ballast were measured and compared with the simulated results both in time domain and in frequency domain.

Development of rail technology for high speed railway in China

Purpose–The purpose of this paper is to summarize the status and characteristics of rail technology of high-speed railway in China,and point out the development direction of rail technology of high-speed railway.Design/methodology/approach–This study reviews the evolution of high-speed rail standards in China,comparing their chemical composition,mechanical attributes and geometric specifications with EN standards.It delves into the status of rail production technology,shifts in key performance indicators and the quality characteristics of rails.The analysis further examines the interplay between wheels and rails,the implementation of grinding technology and the techniques for inspecting rail service conditions.It encapsulates the salient features of rail operation and maintenance within the high-speed railway ecosystem.The paper concludes with an insightful prognosis of high-speed railway technology development in China.Findings–The rail standards of high-speed railway in China are scientific and advanced,highly operational and in line with international standards.The quality and performance of rail in China have reached the world’s advanced level.The 60N profile guarantees the operation quality of wheel–rail interaction effectively.The rail grinding technology system scientifically guarantees the long-term good service performance of the rail.The rail service state detection technology is scientific and efficient.The rail technology will take“more intelligent”and“higher speed”as the development direction to meet the future needs of high-speed railway in China.Originality/value–The development direction of rail technology for high-speed railway in China is defined,which will promote the continuous innovation and breakthrough of rail technology.

电商客服对话提示信息的双任务操作注意分配研究

目的 为研究双任务操作下,不同类型对话提示信息对电商客服注意分配的影响.方法 选取视觉呈现位置和三种常见提示音为自变量,设计了三种实验情景:只呈现两种位置差异的视觉信息、只呈现三种不同的听觉信息、同时呈现视听觉组合信息,对被试人员操作过程中的反应时及正确率进行了分析.结果 电商客服人员在同时接收视听觉对话提示信息时,存在注意分配,视觉上更偏向左侧,听觉上更偏向于机械提示音,当位于左侧的视觉对话提示信息与钢琴音同时出现时,电商客服的操作表现优于其他组合的视听觉对话提示信息.结论 研究对话提示信息双任务操作的注意分配,为电商企业提升客服注意力培训、设计对话提示信息具有一定指导意义.

顾企互动视角下顾客体验的前因组态研究———NCA与fsQCA混合方法

当前体验经济下顾客体验成为企业吸引顾客和塑造竞争优势的关键所在,学者们越来越关注顾企互动对价值共创的作用,然而过往研究大多关注单一要素对顾客体验的净效应,忽视了多因素间的联动效应。因此,本文基于顾企互动视角,使用NCA与fsQCA混合方法,对315份有效问卷数据进行分析,探索影响顾客体验的商业模式创新类型、资源整合、价值感知、关系倾向和顾客参与的不同组态效应。研究结果表明:引致积极顾客体验的路径有三种类型;提升顾客体验既不能简单追求商业模式创新,也不能简单追求高水平顾客参与;高水平资源整合和价值感知有助于构建积极顾客体验;低水平关系倾向会带来消极顾客体验,但高水平的关系倾向不一定产生积极顾客体验。基于组态理论从顾企互动视角计算积极与消极顾客体验的路径,为企业实践中营造好的顾客体验提供决策依据、增进对策建议的有效性。

国内外顾客互动研究进展与热点分析——基于科学知识图谱视角

[目的/意义]随着信息技术的不断发展,顾客互动成为企业实践关注的焦点,然而既有的综述文献不仅时间偏早且多为主观定性分析,随着研究的深入,国内外相关文献不断涌现,对现有研究进行梳理十分必要。[方法/过程]以SSCI和CSSCI文献数据为样本,通过Citespace软件进行文献计量分析,从前沿文献特征、科研合作、基础知识结构和研究热点等方面,对中外顾客互动领域的研究进展和前沿进行对比研究与全景展示,最后提出了未来的研究趋势。另外,针对目前中文期刊Citespace研究范式存在的问题,利用DEAN数据清洗流程与系统化的检索策略优化数据质量,增强了文献计量分析结论的准确性。[结果/结论]国内外顾客互动领域的研究合作均较为紧密,且国外研究在近年更为活跃;国内外基础文献的演进脉络主线都是从顾客参与、互动到顾客契合的转变,但二者的支线脉络与显示出的研究前沿有所不同;国内外前沿文献的研究内容本同末异,但国外前沿文献的研究情境与方法要更加丰富。

价值共创感知体验、数字平台交互场景与颠覆性创新

数字化转型背景下如何通过数字平台交互场景来协同顾客,对平台型企业突破瓶颈期并实现颠覆性创新具有重要意义。以参与数字平台交互的顾客为研究对象,构建了“价值共创感知—平台交互场景—颠覆性创新”研究框架,通过问卷调查的研究方法来探究顾客参与价值共创的感知体验,及其对颠覆性创新的影响路径。实证研究表明:价值共创感知体验(利益性感知体验、社交性感知体验、自我效能性感知体验、独特性感知体验)和数字平台交互场景均对颠覆性创新具有显著正向影响;数字平台交互场景在价值共创感知体验的四个层面与颠覆性创新之间均具有部分中介效应;平台干预度在社交性、自我效能性、独特性感知体验与颠覆性创新之间起到负向调节作用。研究结果能够为企业优化顾客参与价值共创体验、构建数字平台交互场景提供新的理论视角与发展战略。

搜索引擎用户体验“定制化”交互及优化策略

[研究目的]定制化的“自主性”交互是提高用户服务精准度的关键要素,也是搜索引擎提升用户搜索体验的重要策略。当前,随着搜索引擎的运营能力得到极大提升,如何为细分的用户群体提供更匹配的个性化服务已上升为提高市场核心竞争力的重要课题,而提供基于定制化服务理念的个性化、多样化、智能化的交互式服务正是实现这一目标的关键。[研究方法]选取国内5大具有代表性的搜索引擎为研究对象,从用户界面、搜索功能、个性化自定义设置三个维度,对这5大搜索引擎的用户服务设计进行梳理,得到界面功能交互、搜索功能交互、搜索展示交互、界面展示交互四个类别的用户体验定制化交互内容。在此基础上,按照定量评分的思想对5大搜索引擎的定制化交互性进行初步评估和分析。[研究结论]结果显示,5大搜索引擎都存在不同程度的薄弱环节,还有待于从多方面交互因素入手,全面提升交互性,进而实现个性化定制策略与用户需求和偏好的高匹配。最后,从提高个性化服务水平、推行定制化策略、深化人工智能融合应用、实时跟进维护、注重安全治理五个方面,对优化搜索引擎定制化交互性的策略进行了探讨。