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Forced vibrations resulting from moving loads, along with efficient vibration control, are essential in transportation engineering, earthquake engineering, and aerospace engineering. In this study, the vibrational response of an axially functionally graded (AFG) beam subjected to a moving harmonic load within a thermal environment was investigated. The primary aim was to explore the potential of controlling this vibration by incorporating a nonlinear energy sink (NES). A model for the AFG beam, with clamped–clamped boundary conditions, was developed using Euler–Bernoulli beam theory and the Lagrange method, accounting for the effects of the thermal environment and the moving load. The numerical simulations were performed using the Newmark method to solve the governing equations. The results demonstrated the effectiveness of the NES in mitigating the vibrational response of the beam under thermal and dynamic loading conditions. The effective reduction of maximum deflection caused by moving loads was set as the optimization objective to identify the most optimal parameters of the NES. The results were presented through a series of parameter analyses, revealing that the nonlinear damper can quickly dissipate the beam's energy when the loads exit the structure. Furthermore, a properly designed NES can result in a 2.4-fold increase in suppression efficiency. [ABSTRACT FROM AUTHOR]

The construction of transportation infrastructure lines alters the natural terrain, leading to uneven redistribution of snow under the influence of snow-drifting, which can compromise road safety. With the ongoing expansion of transportation networks in cold regions, transportation engineers are increasingly focusing on snow-drifting phenomena and the associated disasters. This study, based on a GIS platform, conducts a case study of a transport infrastructure project in Xinjiang to analyze the geographical and environmental conditions along the route. Through on-site monitoring and investigation, factors related to the occurrence of snow-drifting disasters were implied. The WOE (Weight of Evidence) model was selected as the base evaluation model, and the BP-GA algorithm was applied to optimize the weights of evaluation indicators. This led to the establishment of a susceptibility evaluation index system for snow-drifting disasters, improving both the computational efficiency and the accuracy of the evaluation model. The results indicate that the evaluation accuracies of the WOE, WOE-BP, and WOE-BP-GA models were 72.32%, 75.32%, and 85.18%, respectively. The use of the GA-BP algorithm effectively captured the complex nonlinear relationships among various factors, producing evaluation results highly consistent with real-world conditions. This method may efficiently identify high-risk areas of snow-drifting along transportation infrastructure lines, providing valuable insights for disaster prevention using ArcGIS. [ABSTRACT FROM AUTHOR]

Transportation engineers face challenging safety investment decisions, particularly for highway-railway grade crossings (HRGCs), where rare collision occurrences and incomplete historical records complicate the assessment of countermeasure cost-effectiveness. This study introduces an empirical Bayes (EB) observational before–after approach to address these challenges, specifically examining the impact of a widely used safety countermeasure: flashing lights, bells, and gates (FLBG). The research covers a total 171 FLBG crossings with pre-implementation conditions varying between standard reflective crossing signs and flashing lights and bells, utilizing collision data from 2000 to 2012 for analysis. This study is the first to substantiate quantitatively the effectiveness of FLBG treatment in improvising the safety of HRGCs and show that the effect is dependent of crossing characteristics, such as track angle, pavement conditions, and train speed limits. These findings can provide valuable support to decision-makers, enabling them to make more effective decisions for grade crossing safety improvement projects. [ABSTRACT FROM AUTHOR]

The research aims to develop an algorithm for modelling the process of cutting an infinite volume of soil with a flat cutter in the Abaqus software package. The hypothesis of the existence of energy and volume of resistance to cutting is proposed. The analysis of shock wave distribution in the soil volume is performed. Boundary conditions for the soil volume model are determined, as well as for a flat cutter with linear motion. Stress gradients in the soil during its deformation are determined. Confirmation of the hypothesis about the existence of energy and volume of resistance to cutting was obtained. A logarithmic regression equation was derived based on the obtained volume values. [ABSTRACT FROM AUTHOR]

In a developing country like India where jaywalking is prevalent than using designated crosswalks, pedestrian safety is a major concern. Development of pedestrian level of service (PLOS) is essential for monitoring pedestrian safety for these manoeuvres. The present research incorporates a new methodology to evaluate pedestrian LOS for jaywalkers. The study is conducted in a smart city of Bhubaneswar in India. The pedestrian crossing speeds ranged from 0.6 to 1.4 m/s. Artificial Neural Networks (ANN) are used to determine the pedestrian crossing speeds from vehicular and pedestrian counts whose outputs are close to the field data. A 2-step K-means clustering technique is employed to determine the Pedestrian LOS ranges based on pedestrian crossing speeds. Urban planners, transportation engineers, and legislators can use the methodology to determine PLOS levels to create the pedestrian-friendly infrastructure. [ABSTRACT FROM AUTHOR]

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Air compressors play an important role in energy, mining, civil engineering, and transportation engineering. However, the abnormal vibration and noise of air compressors may pose a serious threat to the structural stability and smooth operation of these types of engineering equipment. To address the broadband noise and vibration problems of a new oil-free piston air compressor, we developed a hybrid optimization method that combines experimental testing, theoretical evaluation, and numerical simulation. Firstly, we conduct noise experiment testing, identify the frequency band of aerodynamic noise using a coherence analysis method, and design orthogonal experiments to further optimize pipeline noise. Then, the vibration characteristics were discussed from both theoretical and simulation perspectives. The dynamic balance has been redesigned on the spindle counterweight plate to reduce the force on the bearings, and a multi-body dynamics model has been constructed to demonstrate the effectiveness of the optimization. Subsequently, a finite element model of the compressor housing was established to analyze the radiation noise characteristics. Finally, three weak points in the structure were selected as key objects, and the structural stiffness was increased to improve vibration stability. The simulation results of radiated noise show that the proposed design scheme can effectively reduce vibration and noise, with a maximum noise reduction rate of 7.45%. [ABSTRACT FROM AUTHOR]

In order to standardize the design and delivery of digital results of land transportation infrastructure engineering such as highway and railway engineering, ensure the integrity, correctness and universality of the design data transferred to the construction phase, and improve the utilization rate and digitalization degree of design data, this paper, with reference to the research on the current situation of digital delivery of land transportation infrastructure design data at home and abroad, studies and formulates the digital delivery standards and delivery contents (descriptions, attachments, drawings and molds) of land transportation infrastructure design stage ( feasibility study, preliminary design and construction drawing design) on the basis of two-dimensional design delivery of railway projects and three-dimensional design data. The deliverables are divided into structured data, 3D information model and unstructured data. The structured data is stipulated on UML class diagrams and metadata subsets to sort out the relationship between services, and XML SCHEMA is adopted for digital delivery. The three-dimensional information model requires the delivery of the model in IFC format, the delivery content, depth requirements and model expression requirements ( basic model + reference model), information submission requirements, etc. Unstructured data is generally approved online in PDF format or tabular form. The standard stipulates the definition of BIM model, structured and unstructured expressions with attribute association mapping and standardized digital delivery standard process. It realizes the non-destructive transmission standard of highway and railway land transportation design data, solving the problem that computer can only recognize design delivery data poorly with low data reuse rate, and lays a foundation for digitization and intelligence of highway and railway land transportation industry in the full life circle. [ABSTRACT FROM AUTHOR]

Plant natural products (PNPs) exhibit a wide range of biological activities and have essential applications in various fields such as medicine, agriculture, and flavors. Given their natural limitations, the production of highvalue PNPs using microbial cell factories has become an effective alternative in recent years. However, host metabolic burden caused by its massive accumulation has become one of the main challenges for efficient PNP production. Therefore, it is necessary to strengthen the transmembrane transport process of PNPs. This review introduces the discovery and mining of PNP transporters to directly mediate PNP transmembrane transportation both intracellularly and extracellularly. In addition to transporter engineering, this review also summarizes several auxiliary strategies (such as small molecules, environmental changes, and vesicles assisted transport) for strengthening PNP transportation. Finally, this review is concluded with the applications and future perspectives of transportation engineering in the construction and optimization of PNP microbial cell factories. [ABSTRACT FROM AUTHOR]

Numerous applications in civil and transportation engineering require concrete with high early strength and good durability properties. Limited studies have revised the performance of high early-strength concrete prepared with calcium sulfoaluminate (CSA) cement and internal curing technology. This study evaluates the strength and durability properties of four concrete mixtures designed with low and high cement contents, incorporated with and without internal curing. Compressive and split tensile strength, autogenous and drying shrinkage, and freezing and thawing resistance were evaluated. High early-strength concrete mixtures with internal curing achieved lower strength and improved durability (shrinkage and freezing and thawing resistance) in comparison with their analogous control mixtures. All concrete mixtures obtained compressive strength higher than 17 MPa (2,500 psi) within the first 4 h. Concrete mixtures with high cement content showed less contraction (<200 με) than their analogous control mixtures. The internally cured concrete mixture with low cement content exhibited slight expansion instead of shrinkage. Finally, the freezing and thawing resistance showed great improvement because no or little damage was observed in the internally cured concrete mixtures. The internally cured concrete specimens overcame 300 cycles, whereas the control mixtures reached maximum 164 cycles. The internally cured mixtures with low and high cement contents showed a final relative dynamic of elasticity of 79.7% and 99%, respectively. Based on these results, using CSA concrete for repair works could be feasible with internal curing technique. Practical Applications: Extensive damage is observed in concrete pavements due to several factors, primarily due to freeze–thaw action and shrinkage. Given that replacing the damaged pavement is expensive and time-consuming, several transportation agencies prefer to restore/repair the degraded portion of pavement using high early-strength concrete. Using high early-strength concrete ensures the pavement achieves its design strength at an early age, which ultimately allows opening the roadway to oncoming traffic in a shorter duration. The use of calcium sulfoaluminate cement instead of ordinary portland cement in high early-strength concrete helps to reduce the overall carbon footprint due to lower energy consumed during calcium sulfoaluminate's clinkering process, along with relatively faster strength development. Previously, researchers have demonstrated the effectiveness of internal curing to improve durability of high early-strength concrete by better freeze–thaw and shrinkage resistance. Overall, the given study focuses on understanding the benefits of internal curing in high early-strength concrete mixtures prepared with a low and high calcium sulfoaluminate cement content. Irrespective of the cement content, high early-strength concrete mixtures with internal curing had superior freeze–thaw and shrinkage resistance, proving that internal curing effectively improves the durability properties without compromising on its design strength. [ABSTRACT FROM AUTHOR]

An essential aspect of pavement construction sustainability is its low-energy consumption and emissions. The study of pavement materials workability tests holds significant importance in terms of achieving well-mixed conditions with low-energy consumption. The complex components of the material and the uncertain kinematic behaviours of aggregates during mixing make this process challenging. And, few studies of the signal response of pavement materials have been found in the field of civil engineering. For this purpose, an accurate evaluation and monitoring approach for mixing are needed. In this paper, a wireless real-time sensing method is used to monitor the dynamic behaviour of aggregates during mixing. A 3D digital twin model, combining data-sensing techniques and numerical simulation, has been proposed for rapid identification of the mixing material. This model has been validated via a data-fusion algorithm. The application of this model makes a contribution to the data-intensive analysing jobs and decision-making tasks in pavement construction engineering. [ABSTRACT FROM AUTHOR]

The resilience of public transit systems has become a critical issue due to their essential role in urban mobility. However, the challenges of repair selection and sequencing in integrated public transportation networks (IPTN) have not been fully explored. Therefore, we propose a bi-level resilience-based repair strategy optimisation (RRSO) model to investigate the optimisation of resilience in IPTN. To consider trip selection and account for cascade failure processes, a lower-level traffic assignment model was integrated into a single-layer RRSO model. In the traffic assignment model, perceived travel time reflects the traffic impedance of public transportation. Additionally, to assess the performance of the RRSO model under emergency repair conditions, random variables were introduced to represent uncertain factors in the traffic environment. Finally, the results demonstrate that the RRSO model outperforms standard empirical repair strategies. This study provides theoretical insights into the management of urban public transportation. [ABSTRACT FROM AUTHOR]

Effective estimation and prediction of freeway congestion propagation is the basis for formulating a traffic management strategy. A new estimation and prediction model for congestion propagation based on coordinated vehicle positioning data collected from fixed detectors is proposed. A shockwave-based method is established to model the propagation trajectory of congestion in time and space using data filtered by the Savitzy-Golay. Bayesian ridge regression is applied to determine the probability range of the propagation path of the congestion. The proposed method was tested with Wi-Fi positioning data from a section of the Beijing-Kunming Freeway in China. The results of our method were compared with filed traffic conditions estimated by loop data. The results show a difference of approximately 200s between the start time of the estimated congestion and the observed time on the selected road section. The predicted congestion start time differs from the observed results by around 100s. [ABSTRACT FROM AUTHOR]

Rail transport is used not only by the civil sector but also by military transportation. This duality makes it crucial to maintain the functionality and security of the system. This research aims to determine the combined impact on maintaining the sector's functionality by analyzing the elements of civil transport safety and military defense security. The result of the research is the definition of a new evaluation index (RDSI) as a synthesis of the security and security factors, which can consider transport safety and defense security requirements. The calculated value of the index provides an idea of the civil safety and military security improvements needed on a railway line, thus increasing the level of protection and resilience of a country. Further use of the index can help to identify weak points of the rail transport system, give an idea of the protective utility of a railway line, find bypasses, and improve the impact of climate change on rail transport. The effectiveness of the index is demonstrated through a case analysis. [ABSTRACT FROM AUTHOR]

This study investigates the feasibility of integrating Hyperloop technology with hydrogen fuel systems. The primary objective was to evaluate how Hyperloop infrastructure can incorporate hydrogen refueling stations to optimize transport efficiency and sustainability. The research utilized simulation models developed with ArchiCAD and FlexSim software to analyze the integration of Hyperloop cargo and passenger transport with hydrogen refueling processes. The study included detailed simulations of Hyperloop operations and refueling logistics, focusing on safety, efficiency, and the potential for reducing carbon emissions. Key parameters such as capsule speed, refueling times, and infrastructure requirements were analyzed. Results indicated that Hyperloop technology can significantly enhance transport efficiency, particularly for high-value and time-sensitive goods, while hydrogen refueling stations offer a sustainable energy solution with considerable potential for reducing environmental impact. The findings demonstrate that integrating hydrogen refueling stations into the Hyperloop system can improve operational efficiency and sustainability. However, challenges remain in optimizing refueling processes and infrastructure development. Future research should address these challenges and explore additional AI-based optimization techniques to enhance the overall system performance. This research is especially useful for urban planners, transportation engineers, and policymakers aiming to develop efficient, sustainable transportation systems that incorporate cutting-edge technology like Hyperloop and hydrogen refueling infrastructure. [ABSTRACT FROM AUTHOR]

This study focuses on optimizing traffic flow at uncontrolled intersections by comparing the effectiveness of different intersection types: roundabouts, signal-controlled intersections, and turbo-roundabouts. The purpose is to determine which type offers the best solution for enhancing traffic efficiency, reducing delays, and improving safety. The research employs simulation-based modeling to analyze traffic performance under varying traffic conditions. Critical parameters such as vehicle flow rate, average delay time, and capacity are used to assess the performance of each intersection type. The results indicate that turbo-roundabouts outperform conventional roundabouts and signal-controlled intersections in terms of both capacity and reduction in delays. The findings suggest that implementing turbo-roundabouts at high-traffic intersections can significantly improve traffic flow and reduce congestion. However, the effectiveness of each solution is context-dependent, with signal-controlled intersections still being advantageous under specific conditions, particularly in highly urbanized areas. This study provides valuable insights for transportation planners and engineers, highlighting the importance of intersection design in traffic optimization. [ABSTRACT FROM AUTHOR]

The developing uses of nanotechnology in the domain of transportation engineering and highway construction are investigated in this work. The goal is to characterize the present situation of nanotechnology in transportation engineering together with its advantages and drawbacks. Using a descriptive research design and depending on a thorough review of current material from scholarly publications, research reports, and conference proceedings, the study The data's themes and patterns are found by means of thematic analysis and grouped to create categories. Themes found in the literature review and the research goals direct the study. According to the findings of the research, nanotechnology could transform the transportation sector in several different respects. Infrastructure's lifetime and durability have been demonstrated to be improved by nanomaterials including graphene, nanoclay, and nano cellulose; fuel economy has been raised as well as safety and visibility enhancement. Furthermore, promising for development of new kinds of lighting and signaling systems for use in infrastructure and vehicles are quantum dots. Adoption of nanotechnology in transportation engineering does, however, also bring certain difficulties. Among the main issues that have to be resolved are possible environmental effects, safety issues, and manufacturing and implementation costs. To guarantee the responsible and safe use of nanotechnologies in transportation engineering, these difficulties will call for major research and development activities, stakeholder cooperation, and regulatory control. This work offers a thorough summary of the developing uses of nanotechnology in transportation engineering, so stressing both its possible advantages and difficulties. The results of this study can guide legislators, scholars, and professionals in the transportation sector on the possibilities of nanotechnology to raise the efficiency, sustainability, and safety of transportation systems. [ABSTRACT FROM AUTHOR]

Abstract Introduction The economic development, well-being of the population, and environmental protection are all strongly linked to a sustainable transportation network. In this sense, in order to ensure a high level of sustainability, it is crucial to have a comprehensive understanding of this sector. As an integrated element of these transportation systems, the efficiency assessment of taxis’ operations is essential in setting managerial strategies for leveraging the sustainability of taxi system. Methodology This study employs a two-stage bootstrap Data Envelopment Analysis approach to assess the efficiency of taxis’ operations, with a focus on minimizing service time and distance traveled. Additionally, this study innovates on investigating the impact of distinct contextual factors on efficiency scores attained to uncover the determinants of taxi operations’ efficiency. The methodology is validated using real data collected from onboard devices of a fleet operating in a Portuguese city over a one-year period. Results The results obtained show that taxis of the fleet can significantly reduce service time and distance traveled, without affecting output levels. Moreover, the decisive role of the stands where taxis queue on the efficiency of their operation is also verified. Conclusions The findings can support practitioners in reaching a more suitable and efficient allocation of resources, leading to a more sustainable transportation combined with improved business results. Furthermore, this study contributes to the current literature by suggesting recommendations to assist managers and public administrators in defining improvement actions for the taxi sector.

Abstract This paper conducts quantitative analysis and qualitative discussion on 7710 SMT-related publications over the past three decades, presenting the academic landscape of the field, identifying significant research topics and their evolution, and revealing the field’s knowledge diffusion paths. It opens avenues for research like modeling post-pandemic travel behavior and constructing “X-minute” cities, and provides insights into policy formulation, theoretical innovation, and technological reform for policymakers, researchers, and practitioners, respectively.

［Objective］ The lift wing structure of high-speed railway EMU (electric multiple units) can reduce the wheel-rail frictional resistance, thereby decreasing wheel wear. However, due to the complex and variable operating conditions of high-speed railway EMU, the dynamic loads on the lift wing constantly fluctuate. To ensure the safe and efficient operation of EMU while maximizing the energy-saving and drag-reduction performance of the lift wing structure, a suitable control scheme for the lift wing is required. ［Method］ The overall structural composition of the lift wing is introduced, and an active control scheme for its motion is proposed. A decoupling control algorithm for a multi-variable coupled system based on position tracking is designed for the bottom rotation mechanism. For the angle-of-attack transformation mechanism, a cross-coupled collaborative control algorithm based on LADRC (linear active disturbance rejection control) is developed. A control process and in-place parking circuit scheme is designed for the wing-tail extension mechanism. Simulation models are constructed to validate the control performance of the proposed bottom rotation and angle-of-attack transformation control schemes. ［Result & Conclusion］ The active control scheme for lift wing structure motion can meet the functional requirements of the lift wing, including the positioning accuracy of the bottom rotation mechanism, the synchronization control requirements of the angle-of-attack transformation mechanism, and the uniform motion and in-place parking requirements of the wing-tail extension mechanism. This scheme addresses deficiencies in existing control methods, enhancing the safety, stability, and reliability of the lift wing.

［Objective］ Currently, air-conditioning units in urban rail transit vehicles predominantly use an AC (alternating current) 380 V power supply mode, which requires two power conversions before reaching the end-use equipment, inevitably leading to some energy loss. Therefore, it is necessary to study the feasibility of applying DC (direct current)-powered air-conditioning units in urban rail transit vehicles. ［Method］ The operation mode of conventional AC 380V power supply is introduced, and a comparison is made between the circuit topologies of air-conditioning units under AC 380 V and DC 600 V power supply modes. The internal configurations of air-conditioning units in these two power supply modes are also compared. An energy-saving test is conducted using air-conditioning units of a rail transit vehicle in a Chinese city as example. Energy consumption indicators of the air-conditioning unit compressors under different frequencies for both power supply modes are tested, and a comparative analysis is performed on the energy consumption of conventional asynchronous motor fans and EC (electronically commutated) fans. ［Result & Conclusion］ Compared to AC 380 V-powered air-conditioning units, DC 600 V-powered units eliminate the two power conversion processes on the vehicle, achieving more significant energy saving effects. Additionally, DC 600 V-powered air-conditioning unit compressors demonstrate more pronounced energy-saving effects during low-frequency operation. Compared to conventional asynchronous motor fans, EC fans are more energy-efficient.

［Objective］ With the advancement of digitalization, MBD (model-based definition) technology is attracting increasing attention. With the significant advantage of this technology in improving the collaborative efficiency of design and manufacturing, it is aimed to explore integrated development technology for the design, process, and manufacturing of rail transit vehicle equipment based on MBD. ［Method］ The definition of MBD technology and its application in the aviation manufacturing and rail transit industries are discussed. The brake pipeline of rail transit vehicles is selected as the subject for the integrated development (including the entire process of design, process, and manufacturing). Using the Winchill system as the data management platform and Creo as the 3D design and annotation tool, a brake pipeline simulation software is developed, and an MBD-based integrated development platform is established, encompassing the design, process, manufacturing, and service of brake pipelines, enabling the release and inter-system transmission of design and process data based on 3D models. On this basis, an automated and unmanned MBD-based brake pipeline production line is built, along with a set of product specifications, standards, and workflows. ［Result & Conclusion］ The integrated development technology for the design, process, and manufacturing of brake pipelines based on MBD achieves the expected goal of collaborative operation over design, process, and manufacturing on a unified system platform under single-source product data management conditions.

［Objective］ To comprehensively grasp market demands and develop a competitive LRV (light rail vehicle) product, investigation research on articulated bogie LRV is conducted. ［Method］ The basic characteristics of light rail vehicles are described, including the overall structure of the vehicle, its bogies, carbody, and cabin. The development history, main technical features, and application scenarios of six typical articulated bogie LRV are analyzed. ［Result & Conclusion］ Through in-depth insights into the development trajectory, application scenarios, and the collection of key technical parameters of the six vehicle types, a solid foundation for market demand and feasibility guidance for development projects are provided for product design, facilitating rapid decision-making on vehicle technical parameters. Based on these research findings, design directions for developing more market-competitive LRV are proposed, including enhancing passenger convenience and vehicle performance.

［Objective］ Due to the influence of thermal conductivity and linear expansion characteristics of aluminum alloy materials, welding deformation is prone to occur during the welding process of aluminum alloy carbodies in high-speed railway EMU (electric multiple units). It is necessary to study the currently mature arc welding process and the next-generation friction stir welding process, so as to compare and analyze the welding deformations caused by these two methods. ［Method］ The experimental materials and methods are introduced, and three parameters of curvature, height, and deflection for carbody sidewalls are selected as indicators for comparing welding deformation. Based on results from reverse-assembly welding and forward-assembly welding experiments, the curvature, height, and deflection deformation values of carbody sidewalls are compared in terms of the arc welding and friction stir welding processes. The welding deformation changing trends under the two processes are analyzed. ［Result & Conclusion］ The aluminum alloy carbody sidewalls manufactured using friction stir welding process can effectively reduce welding deformation. The post-weld curvature deformation of friction stir welding is 20% of that of arc welding. Friction stir welding will not cause shrinkage deformation of sidewall profiles in the height direction. However, compared with arc welding, the deflection rebound of the sidewalls after welding is greater with friction stir welding.

［Objective］ Currently, the design speed of articulated LRV (light rail vehicle) is 100 km/h, which somewhat restricts the expansion of light rail lines to the suburbs, satellite cities, and other areas. Therefore, it is necessary to conduct in-depth research on key technologies for 120 km/h articulated LRV transit, including designs for the overall train, bogie and articulation devices. ［Method］ Based on the conditions and characteristics of LRV lines and the vehicle technical parameters, the boundary conditions for the overall design of 120 km/h LRV are determined. An overall design scheme for the 120 km/h articulated LRV is proposed, and the main train technical parameters are established. Through theoretical analysis, simulation modeling, and bench tests, precise dynamic parameters are obtained. Comprehensive analysis and evaluation are performed on the structural strength of the articulation devices, the bogie frame strength, and the dynamic responses of the vehicle system. ［Result & Conclusion］ The overall design scheme, bogie design scheme, and vehicle-end connection design scheme for this type of articulated train can effectively optimize the relationship between the bogie suspension system and the wheel-rail interaction, improve the train capability to negotiate curved sections, and enhance operational stability and safety.

［Objective］ To ensure the safety of traction transformers in dual current power supply lines and prevent issues such as transformer vibration and winding temperature increase caused by excessive DC bias current, which can lead to severe distortion of excitation current, it is essential to study the degree of DC bias in transformers of dual current power supply lines. ［Method］ The DC bias problem in transformers of dual current power supply lines is introduced. By dividing the line into smaller sections, with trains in the DC segment modeled as power sources, and trains in the AC segment and traction transformers modeled as resistances, a chain-circuit model for the dual current power supply system is established. Using continuous linear load flow calculation method, the DC bias current of transformers in the AC segment of a dual current power supply line is computed. The calculated results are compared with field-measured data to verify the validity and accuracy of the proposed method. ［Result & Conclusion］ The DC bias current in transformers significantly exceeds the standard at certain times. The proposed calculation method, characterized by minimal admittance matrix order and fast computation speed, is suitable for dynamic calculations of DC bias currents in transformers of dual current power supply lines.

［Objective］ It is aimed to investigate the relationship between the welding deformation degree of aluminum alloy materials and the welding methods, with the purpose of exploring the effects of different welding processes on aluminum alloy welding deformation. ［Method］ By comparing the weldability of CMT (cold metal transfer) welding technology with that of MIG (metal inert gas) welding, the characteristics and applications of the CMT welding process are discussed in detail. During the experiment, aluminum plates with thicknesses of 3 mm and 8 mm are welded using CMT and MIG welding processes respectively, and each resulting welding deformation is observed and recorded. ［Result & Conclusion］ For 3 mm thick aluminum plates, only minimal deformation is observed after CMT welding, whereas MIG welding led to significant welding deformation of 4 mm. For 8 mm thick aluminum plates, although both welding methods result in some deformation, the deformation with CMT welding is notably less than that with MIG welding. Additionally, both CMT and MIG welding processes produce uniform and aesthetically pleasing welds, with a weld penetration depth of 0.5 mm and showing no significant difference between the two. Consequently, the CMT welding process has a significant advantage in controlling welding deformation of aluminum alloys, making it suitable for welding aluminum alloy components that require strict control over deformation.

［Objective］ During the laser welding process of stainless steel carbody of rail transit vehicles, energy transfer from the laser beam to the material is dynamically variable. To ensure the quality of laser welding, non-destructive testing methods are required to evaluate the fusion state of the laser welds in stainless steel carbodies. Thus, the laser weld fusion state detection method based on quantitative ultrasonic testing technology is investigated. ［Method］ Materials and preparatory work for the experiments are introduced, and ultrasonic testing experiments are conducted. In the time domain, A-scan signals are extracted and analyzed. In the frequency domain, the FFT (fast Fourier transform) method is used to convert A-scan signals into the time-frequency domain, producing spectral characteristic curves. Using the A-scan signals in the time domain and the spectral characteristic curves in the frequency domain, a calculation model for the fusion width of the laser weld (hereinafter referred to as ′fusion width′) is established. The semi-attenuation method and frequency domain analysis method are used to obtain the simulated values of the fusion width, which are then compared with actual values, followed by the error statistical analysis. ［Result & Conclusion］ The variations in ultrasonic A-scan signals and main frequency amplitude correlate well with the probe position. The fusion widths obtained using the semi-attenuation method and frequency domain analysis method are both valid for assessing weld quality effectively. Compared to the semi-attenuation method, the frequency domain analysis method demonstrates higher accuracy and stability, with the detected error between the simulated fusion width and the actual value within 0.1 mm. This precision meets the requirements for practical engineering applications.

［Objective］ Superconducting magnet is the core of superconducting electric maglev trains, and countries such as Japan, Germany, and South Korea have conducted years of research and development in this area. To promote further research and development of superconducting electric maglev trains in China, it is necessary to study the global distribution of patents related to superconducting magnets, including the geographical distribution and patent holders. ［Method］ Based on patent data retrieved from the Derwent Innovation Index (2001-2022) and incoPat patent database, relevant data on superconducting magnet technology are statistically analyzed, including the annual number of patent applications from 2001 to 2022, the geographical distribution of these patents, and the number of patents held by various patent holders. Superconducting magnet technology is further divided into 13 technical subcategories, and an analysis of the main countries and leading patent holders for each subcategory is conducted. Finally, recommendations are provided for Chinese institutions and enterprises on patent layout strategies for superconducting magnets. ［Result & Conclusion］ The development of superconducting magnet technology demonstrates a trend of multi-country progression. China has already become a focal point for patent layout in superconducting magnet technology, although foreign enterprises still hold certain advantages in patent numbers and core technological subcategories (e.g., cooling systems, current leads, overall magnet structure). Chinese enterprises should develop their own strategies targeting the patent layout strategies of foreign enterprises.

［Objective］ Due to the relatively confined space and high passenger capacity of metro trains, fire safety and life protection are attracting significant attentions in the public transportation industry. To evaluate the emergency evacuation model of metro train in a certain American city rail system, the design requirements for floor structure fire resistance time, as specified in the NFPA 130:2023 Standard for Fixed Guideway Transit and Passenger Rail Systems issued by the National Fire Protection Association (NFPA), are adopted. The required evacuation time (RET) of passengers is compared with the available safe evacuation time (ASET) to verify the feasibility of the train fire protection design. ［Method］ Using the passenger evacuation capacity simulation software Pathfinder, an evacuation model is established to analyze the time required for passengers to escape from the train to a designated safe location, and the evacuation time from trains of different formations under various emergency stop conditions. ［Result & Conclusion］ The evacuation time to platform from two coupled trains under full-load conditions is less than 1 minute. In tunnels, the evacuation time for passengers from 4-car and 6-car train formations to the safe passage are 12 to 17 minutes respectively. Based on the aforementioned evacuation time, the total evacuation time including braking remains under the 30-minute threshold for floor structure fire resistance, proving the feasibility of the floor structure fire resistance design.

［Objective］ With the widespread application of rail transit vehicles such as high-speed and intercity trains, the increasing functional demands for these products have led to greater complexity in cable design. To enable rapid calculation, analysis, and warning of cable routing duty cycles, and to improve the safety and reliability for heat dissipation and electromagnetic compatibility after cable design and assembly, a duty cycle algorithm for 3D cable routing in rail transit vehicles is investigated, aiming to enhance the product performance. ［Method］ Through merging-simplifying cable branches and calculating the equivalent diameter of the merged cables, the results are compared and analyzed against the routing space capacity such as cable ducts, the compatibility between the electrical characteristics of 3D cable routing and the available space is ensured. Meanwhile, a standardized or parametrized model library of cable ducts and channels is established along with routing specifications, in order to facilitate quick reuse and improve design efficiency. ［Result & Conclusion］ The research and validation of the 3D cable routing duty cycle algorithm realize automated duty cycle calculation and early-warning functions, effectively reducing design errors, shortening the design cycle, and enhancing the rationality and safety of cable layouts. During duty cycle monitoring and validation process, the duty cycle of critical path nodes is calculated and monitored in real time, effectively mitigating cable overload risks and extending cable service life.

［Objective］ Conventional assembly welding fixtures for vehicle bogie frames in urban rail transit do not meet the requirements for reducing production costs, simplifying operational difficulty, improving the utilization rate of process equipment, and saving space. It is necessary to adopt more reasonable mechanical design concepts to optimize fixture structures and develop a generalized structural design scheme. ［Method］ Four main structural types of existing bogie frames for urban rail transit vehicles are listed, and the general design principles for fixtures associated with these structures are summarized. Based on determining the selection of reference positioning planes and thrust positioning reference planes, and clarifying the clamping method of the fixtures, the generalized structural design scheme (including positioning structure and clamping structure) is optimized. The allowable stress of the screw pair in the sliding screw drive, the self-locking performance of the thread, the strength of the nut and screw, and the thread strength are verified, resulting in an optimized generalized fixture design scheme. ［Result & Conclusion］ The optimized scheme adopts a self-positioning design structure that allows for single-person operation, ensuring even distribution of deformation dimensions in welded components and reducing unequal welding tolerances caused by welding deformation.

［Objective］ With the increasing number of large-scale sporting events hosted in China, themed trains have gradually become an important medium for showcasing the image of the host city and the country. Research on the coating design of themed trains aims to enhance the promotional impact of sports through unique designs, reflecting China′s technological and innovative capabilities. ［Method］ Taking the themed train for the 24th Beijing Winter Olympics as an example, design elements are extracted and reconstructed to visualize cultural symbols. This is paired with appropriate coating techniques to ensure that the design meets the requirements for the train′s elongated, unidirectional form and visual stability at high running speeds. The design conveys the Olympic theme, Chinese elements, and cultural characteristics of the Beijing-Zhangjiakou region. The coating design methods from cultural symbols to detailed designs, are summarized and successfully applied to the theme train for the 19th Asian Games in Hangzhou, highlighting Chinese elegance, Zhejiang characteristics, and the charm of Hangzhou. ［Result & Conclusion］ The themed trains designed with this coating method play a significant symbolic role in the context of sporting events, not only enhancing the promotional impact of the events，but also showcasing the innovative achievements of China′s high-speed railway.

［Objective］ During the operation of superconducting maglev trains, factors such as inconsistencies in ground coil alignment and large electromagnetic air gaps often generate significant high-order higher harmonics in the magnetic field. These harmonics considerably affect the suspension performance of the train. It is essential to study the electromagnetic characteristics and the distribution of superconducting and suspension magnetic fields under high-speed operation conditions. ［Method］ Using the MLX01 train on Yamanashi Maglev Test Line as a case study, the suspension mechanism of superconducting maglev trains is introduced, and the theoretical foundations for calculating superconducting and suspension magnetic fields are explained. The magnetomotive force distribution models of coil along the train operating and suspension directions are established. The space harmonic method is used to decouple the energy conversion process of ′superconducting magnetic field—8-shaped coil induced current—suspension magnetic field′, and to analyze the proportion of high-order harmonics in the superconducting magnetic field. Based on the 8-shaped coil structure and parameters, the induced current in 8-shaped coils is calculated, and a harmonic analysis of the suspension magnetic field is performed. ［Result & Conclusion］ On the surface of 8-shaped coils, the fundamental wave and the third harmonic dominate the superconducting magnetic field magnetic flux density, with a fundamental wave amplitude of 1.113 T, and a third harmonic proportion of 19.40% of fundamental wave. In the suspension magnetic field magnetic flux density, the fundamental wave and the fifth harmonic dominate, with a fundamental wave amplitude of 0.065 T, and a fifth harmonic proportion of 46.70% of fundamental wave.

［Objective］ The grid-side converter is a core electrical component in high-speed railway EMU traction drive system, and its reliability is directly related to the safe operation of the train. Therefore, it is essential to simulate and analyze the temperature rise characteristics of the grid-side converter in high-speed EMU to explore the relationship between temperature rise, operating conditions, and environmental factors, providing theoretical support for temperature evaluation during actual train operation. ［Method］ The temperature rise characteristics of power devices are examined, and an electrothermal simulation model is established incorporating the power loss model and thermal network model. The former is used to quantify the losses of power devices under different operating conditions, while the latter simulates internal heat conduction and dissipation processes of power devices considering the train′s operating environment. The simulation accounts for multiple influencing factors such as operating conditions and ambient temperature, dynamically analyzing the temperature variation trends of power devices and their impact on converter performance. ［Result & Conclusion］ Simulation results demonstrate that the established electrothermal simulation model accurately reflects the temperature rise characteristics of power devices. This research provides critical data support for evaluating temperature changes in grid-side converters during actual train operation.

［Objective］ The fracture of seat back bolts in high-speed railway EMU (electric multiple units) trains results in the back support performance failure and the angle adjustment feature malfunction. A high frequency of bolt fractures with consistent fracture pattern in seatbacks is found in maintenance inspections. Thus, it is necessary to identify the causes of the bolt fractures and propose corresponding countermeasures. ［Method］ Chemical composition checks, tensile tests and mechanical performance tests such as shear and hardness tests are conducted on the bolts, to evaluate the mechanical properties and verify the bolt quality. Metallographic analysis and electron microscopy scanning are employed to examine the macro and micro characteristics of the bolt fracture surfaces, identifying the types of bolt fracture. Theoretical analysis of the service conditions of the bolts is finally conducted to determine the primary cause of bolt fractures. Structural modifications are made, including the addition of auxiliary support brackets, to improve the loading conditions of bolts. ［Result & Conclusion］ The bolt fractures are not due to inherent quality issues but are identified as ductile fatigue fractures. The bolts are subjected to asymmetric loads under cantilever structures, and the resulted bending will lead to reduced fatigue performance and subsequent fractures. After implementing the countermeasures, no similar bolt fracture issues occurred during one year of high-speed railway EMU operation.

［Objective］ The large-scale application of silicon-containing anode materials in soft-pack battery for urban rail transit vehicles faces many challenges, primarily the failure of electrical performance due to the volume expansion of silicon. To address this issue, a more in-depth studies on the perfor-mance of new silicon-carbon anode materials in soft-pack battery is necessary. ［Method］ A comparative analysis is conducted between Ah-level soft-pack batteries containing standard silicon-carbon materials (′N1 batteries′) and those using silicon-carbon materials with an embedded structure (′N2 batteries′) regarding their cycle decay characteristics. Cycle performance tests are carried out on these two types of batteries, and post-cycle analysis is conducted on the disassembled batteries. The anode materials are tested and the results are analyzed to verify the optimization effects of the silicon anode structure at the full battery level. ［Result & Conclusion］ The main cause of failure in N1 batteries is excessive volume expansion of silicon in the anode, leading to the detachment of active materials and electrode breakage, ultimately resulting in the loss of electrical contact. In N2 batteries, the nanoscale silicon is uniformly dispersed within the carbon-based materials and encapsulated by carbon, effectively limiting the volume expansion of silicon during the battery cycle and maintaining structural integrity of the anode throughout the entire cycle process. The cycle performance of N2 batteries is superior to that of N1 batteries. Embedded structure silicon-carbon materials in lithium-rich silicon-carbon system batteries show promising application prospects.

［Objective］ With the increase of train operating speed, noise levels have gradually become a critical factor restricting the development of high-speed railways. It is essential to explore the potential for positive aerodynamic acoustic optimization in the pantograph area and propose an optimized design scheme for reducing the aerodynamic noise in this region. ［Method］ Using the Fuxing Standard EMU (model CR400BF) as the research object, the research content, technical approach, and methodology are expounded. The LES (large eddy simulation) algorithm and FW-H (Ffowcs Williams-Hawkings) equation are employed to investigate the aerodynamic noise in the pantograph area of high-speed railway EMU. Additionally, the aerodynamic acoustic performance of the pantograph area in existing high-speed railway CRH380BL EMU is studied. Six combined optimization schemes are designed, focusing on the upper body structure and the bottom diversion structure of the pantograph. The aerodynamic noise reduction effectiveness of each scheme is evaluated, and the optimal scheme is applied to the CR400BF EMU to further test its noise reduction performance. ［Result & Conclusion］ Scheme 4 is identified as the optimal solution. When applied to the CR400BF EMU operating at a speed of 350 km/h, the overall train radiated noise sound pressure level at the nearest standard measuring point to the pantograph is reduced by 0.99 dB(A), while the radiated noise sound pressure level in the pantograph area is reduced by 1.70 dB(A). As a novel noise reduction method for pantographs, Scheme 4 has low technical requirements and larger potential for market application.

［Objective］ Bogies of urban rail transit vehicles often adopt a swing-arm positioning structure, within which the primary steel springs are prone to fracture, and typical fractures occur at the first working coil in contact with the support ring. Various factors contribute to the fatigue fracture of steel springs, necessitating an in-depth analysis. ［Method］ Considering actual vehicle operating conditions, the stress calculation method for steel springs is optimized. Using specific project design parameters as inputs, the stress levels of the steel springs under lateral load conditions are evaluated, and the proportion of stress contributions is calculated. A bench test is conducted on the primary steel spring set of a selected project bogie, and the setup and tooling of the bench test, including the arrangement of the inner and outer strain gauges on primary helical steel springs, test loading procedures, and data analysis methods, are expounded. Stress test results for the inner coil of Spring Group B are analyzed. Using a measurement point on the swing-arm side as an example, the operating conditions of steel springs when vehicle adopts a swing-arm positioning structure is analyzed, with emphasis on the impact of swing-arm rotation on stress at different steel spring positions. Finally, countermeasures against spring fatigue fractures are proposed by improving spring fatigue stress and controlling catenary wire continuity. ［Result & Conclusion］ The fatigue fractures of such springs are not caused by insufficient design margins, but rather by manufacturing defects, such as sand inclusions, powder aggregation, and improper manual grinding, that result in discontinuities in catenary wires, leading to stress concentration in the steel springs.

［Objective］ Excessive traction and braking loads are significant factors contributing to inducing fatigue cracks in the welded joints of the ′TBB (traction beam-bolster beam-buffer beam) structure′ in urban rail transit vehicles. To effectively mitigate the risk of structural cracking, it is essential to thoroughly investigate the methods for analyzing the structural strength of vehicles under traction and braking conditions during design phase. ［Method］ Taking a specific urban rail transit line in China as the research object, the line test data are analyzed to study the phase relationships of loads at stress points. The phase test results for traction and braking loads are examined. Based on the theoretical load distribution under traction and braking conditions, four finite element model constraint schemes are designed to analyze the strength of the TBB structure in different schemes. Simulated and experimental load values are compared. Three primary welds at the junctions of the TBB structure and the underframe are selected, and the fatigue assessment results of the 3 welds in 4 modeling schemes are analyzed. ［Result & Conclusion］ Under Scheme 1-3, the loads are applied as inertial loads, resulting in dissonance between load distribution proportion and direction at stress points under traction/breaking conditions, and those under train operating conditions. Scheme 4 (concentrated force loading form) can effectively reflect the phase relationship and magnitudes of the loads at the stress points.

［Objective］ The bolster hanger, as a critical component of the bolster spring suspension system, is highly susceptible to fatigue cracks due to excessive dynamic loads and prolonged service life, significantly impacting railway operational safety. To meet the intelligent magnetic particle flaw detection requirements for bolster hangers and assist inspection personnel in the flaw detection work, special research on crack identification and flaw detection evaluation of bolster hangers is conducted based on machine vision. ［Method］ To address the limitations of the YOLOv5 algorithm backbone network in capturing crack information, it is proposed to integrate the SimAM (similarity-aware attention module) mechanism into the backbone network to enhance the model′s sensitivity to crack information and its resistance to background noise interference synchronously. In addition, to overcome the potential information loss during the feature fusion stage of the Neck network, an enhanced BiFPN (bidirectional feature pyramid network) structure is introduced for efficient fusion of multi-scale feature maps. By implementing a weighted fusion strategy and bidirectional connection mechanism, the loss of critical bottom-level information is effectively reduced. ［Result & Conclusion］ The performance of the YOLOv5-SA-BF model is tested using an image acquisition system for bolster hangers. Experimental results demonstrate that the improved algorithm achieved a MAP (mean average precision) of 98.08%, representing a 2.91% increase over the original model, and a Recall increase of 4.13%. The model effectively addresses background false positives and low detection accuracy issues, meeting the requirements in actual inspection.

［Objective］ Friction stir welding is a key welding technology for next-generation. To address welding quality defects associated with friction stir welding, it is necessary to conduct an in-depth study of its welding process and explore its equipment optimization strategies. ［Method］ The working mechanism of friction stir welding is analyzed, identifying four common types of its quality defects. Based on TRIZ theory, potential quality defects in the welding process are examined, leading to the identification of three pairs of technical contradictions. By querying the contradiction matrix in TRIZ theory, inventive principles are derived to optimize existing welding processes and equipment. Based on this, improvement of the stir pin shoulder structure, optimization of the stir pin design, and enhancement of the metal insulation ring cover three optimization strategies are proposed. These optimization strategies are evaluated using the Analytic Hierarchy Process (AHP) to determine the best solution. ［Result & Conclusion］ Improvement of the stir pin shoulder structure is the optimal solution， it effectively addresses the welding quality defects of friction stir welding, improves welding quality, and enhances processing efficiency.