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Strain-based structural health monitoring technology has been widely used in the field of transportation. The existing strain damage identification methods have defects such as complex process, lag in state evaluation, and low intelligence. This paper adopts the deep learning method to establish a network model that uses the strain field information to map directly to the damage information, and takes a subway bolster as the engineering background to realise the end-to-end automatic damage identification. Firstly, the problem of damage identification in strain field is described, combined with the idea of fully convolutional network. The basic structure of damage identification network is modularised, and the overall design framework is proposed. Then, the damage simulation method is determined, and the feasibility of using this method to construct a strain field damage dataset is verified. The batch random damage model generation and the random noise signal addition program are coded, and the datasets of the bolster under static/dynamic force are obtained. Finally, the deep learning model is applied to the bolster damage dataset, and a residual module BolRes_Att that integrates spatial attention and channel attention mechanism is proposed. It has better damage identification performance without an increase in model parameters. The average number of faulty elements on the two bolster test sets of the improved damage identification network is 3.02 and 2.92, respectively, accounting for about 0.016% of all elements. The average processing time for a set of data is only 0.014 s. The results show that the deep learning model constructed in this paper can accurately and quickly identify the damage information of elements according to the strain field information. [ABSTRACT FROM AUTHOR]

With large volume of passengers boarding and alighting through subway platforms, the stations are getting crowded, resulting in drops in the level of service and safety concerns, especially for subway systems operating at capacity during peak hours. Thus, it is crucial for subway agencies to sense changes in travel demand and adjust their management schemes accordingly. In this paper we propose a statistical approach to estimate dynamic passenger flows with automated data. First, we develop a dynamic logistic model for calculating passenger tap-out times, which can be employed to infer passenger flow characteristics at the aggregate level. In addition, a new passenger-to-train assignment model for any subway route is derived based on the dynamic model. Subsequently, we apply an expectation-maximization algorithm to estimate the model parameters with automated fare collection and automated vehicle location data. Finally, a cross-validation method is employed to validate our approach with data obtained from several routes in Beijing subway system in China. Results of 95% prediction intervals indicate the effectiveness of the models and the proposed estimation methods. • Propose a dynamic logistic model for inferring and predicting subway passenger tap-out times. • Apply an expectation-maximization algorithm for model parameters estimation. • Develop a novel passenger-to-train assignment strategy. • No prior distributions of parameters or additional information required in the proposed methods. • Results show good effectiveness of the models and acceptable accuracy of the prediction methods. [ABSTRACT FROM AUTHOR]

This paper develops a nonlinear Discrete-Event (DE) model for Intersecting Lines (ILs) of a Subway Network (SN). A class of Monte Carlo (MC) methods based on repeated random values is employed to validate the model. Model validation is performed by generating random values for delay rates and external disturbances. After model validation, a Robust State Feedback (RSF) controller is designed to compensate the delays caused by disturbances. Simulations are performed based on the characteristics and actual data of lines 2 and 4 of the Tehran subway to demonstrate the effectiveness of the proposed approach. Simulation results show the accuracy and proper performance of the proposed model. In addition, the closed-loop responses demonstrate the effectiveness of the proposed RSF controller for centralized and decentralized control configurations. • A nonlinear discrete-event state-space model of two intersecting metro lines is introduced by considering the effect of the transfer stations. • The introduced model is validated using repeated random sampling based on the Monte Carlo method. • A robust state feedback controller using a linear matrix inequality is designed to compensate any delays. • Two centralized and decentralized control structures are considered to evaluate and compare the performance of the control structures in metro traffic regulation. [ABSTRACT FROM AUTHOR]

• A soil-tunnel periodic model with a track slab was proposed based on wave transform. • Train load and its component were mathematically decomposed in the generalised modal space. • Two measures to improve calculation efficiency without loss of accuracy were presented. • Accuracy and efficiency were verified by comparing the results with literature and measurements. The prediction of ground-borne vibrations induced by underground trains in tunnels is advantageous for guiding vibration-mitigation designs. The supporting forces of the fastener acting on the track bed that is induced by the train operation are spatially periodic in the tunnel axis direction. Utilising this feature, this paper proposes a novel periodic tunnel-soil model with a track slab to simulate the propagation of train-induced vibrations. The periodic tunnel-soil model based on wave transformations is briefly introduced, and then the slab beam is solved analytically and combined with the tunnel invert using equivalent springs based on the generalised modal function series. The train load and its single component are mathematically decomposed in a generalised modal space for application to the semi-analytical periodic model. Two measures for further improving the calculation efficiency of the semi-analytical model under the moving train load are presented and discussed in detail. The formulation correctness of this model is ensured by literature verification. Furthermore, an in-situ measurement of the vibration on the tunnel wall and ground surface by the train passage in the Hefei metro is conducted to validate this semi-analytical model. It is demonstrated that the proposed model is accurate and efficient for predicting ground-borne vibrations generated by train loads, thus it has the potential to predict vibration levels at a large number of receiver points around a newly constructed metro line. [ABSTRACT FROM AUTHOR]

Urban green spaces are increasingly recognized for their positive impact on well-being, quality of life, and public health. Researchers have explored how green space characteristics, such as size, theme, and convenience, influence urban movement. However, an important aspect that has received limited attention is the relative attractiveness of green spaces. When residents have access to similar green spaces nearby, their inclination to visit more distant ones decreases. This leads to the central research question: How does the relative attractiveness of urban green spaces affect urban movements? The existing literature lacks a comprehensive theory to address this question. To bridge this gap, this paper introduces the Potential to Kinetic Energy (PKE) framework, inspired by principles from physics. In this framework, potential energy represents the relative attractiveness of green spaces between the travel origin and destination, while kinetic energy signifies the urban movement resulting from the this attractiveness. To demonstrate the PKE framework's applicability, this paper analyzes green space data and smart card subway ridership records from Beijing. The results show that a unit increase in size, cultural, attraction, proximity, and location potential energy is associated with a 0.22%, 0.27%, 0.14%, 0.19%, and 0.02% increase in urban movement. The findings provide compelling evidence for the significant role of relative attractiveness in shaping urban movements and offer valuable insights for urban planning and policy development. The proposal of the PKE framework encourages interdisciplinary discussions among urban planners, environmental scientists, and transportation experts, fostering collaborative efforts to enhance the sustainability of cities. • A Potential to Kinetic Energy (PKE) framework is introduced to investigate the relationship between green space attractiveness and urban movements. • Potential energy contains five sub-concepts: size, culture, attraction, proximity and location. • Kinetic energy represents urban movement that characterizes the motion of objects resulting from potential energy conversion. • Empirical analysis of Beijing shows the significant role of relative green space attractiveness in shaping urban movement patterns. • The PKE framework supports urban planners to evaluate green space attractiveness, examine the impact of landscape change, and promote inclusive urban environments. [ABSTRACT FROM AUTHOR]

Control of noise and vibration induced by railway traffic is one of the most prominent environmental challenges. Ground-borne noise and vibration play a crucial role in heavily populated urban areas, where underground railway infrastructures are nowadays the preferred means of rail-based transport. The reduction of ground-borne noise and vibration can be achieved with the implementation of different mitigation measures. This paper evaluates the effectiveness of building base isolation as a vibration mitigation measure applied on a building located close to an underground railway line. To do so, several experimental measurements were carried out, allowing the characterisation of the building-soil system. The obtained experimental data has been later employed to validate a three-dimensional model of the building-soil system. Based on that model, a numerical study involving vibrations induced by railway traffic has been performed, where the performance of the elastomeric bearing system for the base isolation of the building is presented and discussed. This study concludes that adopting building structure models that account for modal characteristics and incorporating detailed models of the excitation source are crucial strategies for accurately simulating the performance of base-isolation systems. • Real case study of a building with vibration base isolation. • Full characterized experimental test site, comprising the main characteristics of the ground and structure. • Documented experimental measurements conducted at different stages of building construction. • Validation of a numerical model of the building with the on-site experimental measurements. • Evaluation of the efficiency of the base isolation systems to mitigate the transmission of ground vibration. [ABSTRACT FROM AUTHOR]

Abstract The present paper deals with optimizing optimal operation interaction for GCUM 1st and 2nd lines by proposing a methodology based on field survey of travel time, actual headway, passenger waiting time, alighting and boarding passengers to determine the actual passenger density on platform, passenger density in train and target headway, consequently the ideal operation and the corresponding operational costs savers. Using four alternatives (change headway, divide the line into definite links, uses of suitable metro units and overflow of some through stations) under 5 restrictions (Passenger intensity into train, Passenger intensity on platform, Passenger exchange time at metro door, Factor of safety for metro headway and headway at the end of links) and without needing to any additional capital costs, the results show a valuable cost saving for both operation costs and rolling stock capital costs. This paper recommends this methodology to be applied on any metro lines worldwide. [ABSTRACT FROM AUTHOR]

• Statistical analysis of the parameters of soft and hard strata in China, as well as subway cross-sections and construction methods. • Stability grading criteria for subway stations in soft and hard strata. • Propose instability prevention measures for each stability grade of subway stations in soft and hard strata. In congested urban underground space, a subway station may have to be constructed within an unfavorable complex geological formation comprising upper-soft and lower-hard strata, at a higher risk of structure damage and ground surface subsidence during the construction process. When the subway station is constructed using the undercutting method in a complex urban environment, there is currently lack of theory or guidance on the selection of appropriate construction method for subway stations in different upper-soft and lower-hard strata conditions. This paper conducted a series of numerical simulation, model test, and field test to specifically investigate the stability classification of large-span underground subway stations in upper-soft and lower-hard strata. Results indicate the following: (1) The thickness of the overlying soft rock serves as an indicator for the stability classification of large-span subway stations in upper-soft and lower-hard strata. (2) The stability of large-span subway stations in upper-soft and lower-hard strata can be generally divided into five levels (W-I, W-II, W-III, W-IV, and W-V) from very stable to unstable. (3) For each classification, appropriate construction method was proposed and validated through typical engineering case studies. The research conclusions of this paper can provide effective reference for the selection of construction safety and stability methods for subway station excavation. [ABSTRACT FROM AUTHOR]

With the expansion of the city, the number of subway lines has increased, and the subway stations have become more and more crowded. Whether it is possible to transfer quickly and conveniently has become a concern of subway passengers. Especially in big cities, for the convenience of residents' travel, there are many transfer stations between subway lines, and the transfer layout and connection method between subway stations affect the transfer efficiency of passengers. Jiedaokou Station of Wuhan Metro Line 2 is located in the center of Wuhan and is one of the busiest transfer stations in Wuhan. AnyLogic builds a simulation model of passenger entrances and exits and transfers, and observes whether the design of subway station halls is reasonable from the perspective of regional density, regional density, average passenger flow speed and time distribution of entrances and exits. Then, according to the location of congestion and the degree of congestion, it will be designed, modified, optimized and upgraded. After the analysis, a comparison of various schemes and a new round of simulation analysis are carried out. On the basis of summarizing the analysis results of each strategy, the design optimization strategy of the subway station hall is comprehensively proposed. Finally, the feasibility of the optimization strategy is proved again through simulation experiments. This optimization can enable passengers to walk faster in the station and reduce the occurrence of problems such as stagnation and congestion. This paper aims to provide a certain degree of guidance for the design of subway station halls in the future by using AnyLogic simulation method. [ABSTRACT FROM AUTHOR]

With the expansion of the city and the rapid development of public transport, the subway as a mass public transport means to bear a very large number of passengers, so that in the morning and evening rush hour, some subway stations are almost saturated. Once a disaster happens in a subway station, the saturated space environment makes it difficult for passengers to evacuate. In addition, the subway station is usually located underground, buried depth of about 10m-30m, the accident station passengers have to overcome their own gravity to the ground to escape, which increases the difficulty of passenger evacuation. Fire is one of the biggest security hidden dangers in subway operation. Once it happens, it will bring huge loss to the safety of social resources and people's life and property. On the basis of summarizing the present situation of fire evacuation in urban rail transit stations at home and abroad, this paper firstly analyzes and studies the factors that affect the fire evacuation ability of stations. Then through the station fire evaluation index to build the safety evacuation evaluation index system. Finally, through the VR technology, computer simulation, field investigation and other methods to quantify the index, the Fuzzy Network analysis of the station fire safety evacuation capacity comprehensive evaluation and put forward targeted countermeasures and suggestions. [ABSTRACT FROM AUTHOR]

To address the increasing issue of cracks in metro shield tunnels, this paper proposes the YOLOv8-GSD model, which integrates DySnakeConv, BiLevelRoutingAttention, and the Gather-and-Distribute Mechanism with the YOLOv8 algorithm. This model is designed for detecting and segmenting cracks in tunnel linings and employs a pixel grouping method to measure crack length and width. Using a real crack dataset from a subway section in Suzhou, China, comparative experiments with YOLOv8x, BlendMask, SOLOv2, and YOLACT demonstrate that YOLOv8-GSD excels in segmentation performance (AP of 82.4 %) and accuracy (IoU of 0.812). The measured crack dimensions show an error within 5 % compared to actual values, confirming the model's effectiveness. These results highlight the potential of YOLOv8-GSD for enhancing the maintenance and safety of metro tunnels. • A crack segmentation model for metro tunnel environment is proposed; • Achieves high precision in extracting the edges of lining cracks; • The crack length and overall width distribution are accurately calculated; • The model shows strong performance in complex metro tunnel environment; [ABSTRACT FROM AUTHOR]

Few studies have calculated the magnitude of the modal accessibility gap between public and private transportation (MAG) by taking into account both population characteristics and time-varying characteristics. To incorporate the aforementioned characteristics, this study computed MAG within each population grid using the anticipated travel time between two grids in real time. Moreover, a representative case study focuses on the MAG in the urban area of Xi'an during three time periods. Research results indicate that the average travel time for private transportation in the study area is significantly lower than that of public transportation. Further, the subway line has an obvious impact on improving MAG. In addition, the development of public transportation in the peripheral regions lags behind that of the city center, and the subway network is inadequately serviced. As a result of utilizing the MAG method presented in this paper, the problem related to urban transportation planning can be addressed by incorporating both the population and time-varying factors. At the end of the paper, the limitations and future works are discussed. [ABSTRACT FROM AUTHOR]

• The closed-form solutions of an elastic half-plane subjected to a moving load under plane strain condition are obtained. • Two design schemes for periodic wave barriers are proposed and validated for vibration isolation of underground structures. • Some inherent properties of soil under a moving load are discovered. Most investigations on the control of ambient vibration caused by moving loads are partial to the ground buildings rather than underground structures. With the rapid development of rail transit, the effects of ambient vibration caused by moving loads on underground structures such as important underground military facilities or underground railway stations have been got wide attention in recent years. This paper focuses on the vibration attenuation of underground structures by periodic barriers under a single frequency moving concentrated force. First, under the assumption of plane strain and taking the Doppler effect into account, the closed-form solutions of an elastic half-plane subjected to a moving load on the surface are obtained, and are validated by numerical simulations. The frequency characteristics of the present solutions are comprehensively discussed. The isolation mechanism of periodic wave barriers under a moving load is revealed. Second, based on the characteristics of soil's frequency response under a moving load, two different schemes for designing wave barriers are provided for load speed less than S-wave speed of soil mass. The effectiveness of the proposed design schemes is verified through numerical simulations for different types of traffic loads. This study shows that the periodic wave barriers can play a great role in vibration isolation of underground engineering, and the design schemes proposed in this paper work very well. The present study provides a new insight for vibration attenuation of underground structures caused by moving loads. [ABSTRACT FROM AUTHOR]

This paper summarizes the classification method of domestic subway station, and points out the existing defects. In order to design of a relatively reasonable grading system, this paper reference to the existing classification method and passenger flow data. First, obtain a dynamic correction of parameters according to the static factors. Then, combine with the data of dynamic flow to determine the level of the station. [ABSTRACT FROM AUTHOR]

Drawing on complex network theory, this paper combines bus network and subway network into a multi-subnet composited complex network (MSCCN) of urban public transport (UPT). Then, the cascading failure of the MSCCN nodes and edges was modelled, and the passenger flow transfer rules were established under node and edge failures. Considering the impact of extreme weather on the UPT, a synthetic operator was created to measure the robustness of UPT MSCCN, in the light of network topology and passenger flow, and used to quantify the robustness of UPT MSCCN under extreme weather. Finally, a UPT MSCCN was set up for Qingdao, China, and subject to cascading failure simulation. The simulation results reveal how MSCCN robustness changes with different variables. The research findings help to optimize the response of the MSCCN to extreme weather. [ABSTRACT FROM AUTHOR]

This paper proposes an analytical solution for the calculation of vibrations from a twin tunnel embedded in a half-space to assess the influence of a neighbouring tunnel on the ground-borne vibrations due to underground railway traffic. Using the wave function method, the total wave field in a half-space containing two cavities is expanded as the combination of down-going plane waves from the free surface and outgoing cylindrical waves from each cavity. The two tunnels are modelled as hollow cylinders, and the wave field inside them can be represented as the superposition of outgoing and regular cylindrical waves. To solve this multiple scattering problem, three sets of coordinate system defined at the scattering surfaces are used to describe the cylindrical waves in polar coordinates and the plane waves in rectangular coordinates. The application of transformation and translation properties between plane and cylindrical waves makes it possible to represent the waves emanating from one scattering surface in terms of the coordinates defined at the other two surfaces. The boundary conditions at the free surface and two tunnels can then be applied to solve for the expansion coefficients for the vector wave functions of plane and cylindrical waves. The present approach is also valid for a multi-layered ground, and in the layer with the tunnels, the field is composed of outgoing waves from the tunnels, down-going waves from the upper interface of the layer and up-going waves from the lower interface. Numerical results show that there is one critical velocity around shear wave speed of soils for a single/twin tunnel in a homogeneous half-space. For a multi-layered geometry, two global critical velocities may exist for the twin tunnel case, and they are determined by the properties of the soil layer where the twin tunnel is located in and the layer below the tunnels. [ABSTRACT FROM AUTHOR]

Demand for taxis varies over time. Finding the factors that affect demand and understanding the dynamics of taxi demand will benefit different groups. It helps planners to improve their transportation systems and also help drivers to reduce their empty vacant time. This paper focuses on modeling and analyzing the taxi demand, using the demand for other transportation modes and weather conditions. We started with the linear regression model, and then combined with a time series models. This combined model is called "linear regression with ARMA errors". (ARMA: Auto Regressive Moving Average). We considered the borough of Manhattan in New York City, and collected three months of data of yellow cabs, subway, Uber, bike, temperature, and precipitation. The observations for each variable, are aggregated hourly. We analysed these data sets and removed their seasonality, and then applied the models to those data sets. The power of time series model in explaining a variable is discussed and the results show that the developed model outperforms the linear regression, by improving the R-squared more than %30. [ABSTRACT FROM AUTHOR]

• In order to overcome the problems of low parameter estimation accuracy and poor versatility in existing reliability models of train system components, an improved beluga whale optimization algorithm (IBWO) is proposed to calculate the reliability of bogie key components. • A new total maintenance cost model of bogie components is established based on the failure risk cost and preventive maintenance (PM) cost. • A PM model for key components of subway train bogie with consideration of failure risk is established. With the acceleration of urbanization, the number of urban rail transit trains has increased dramatically, and the economy and safety of subway trains have become important standards. As an essential subsystem of the subway train, the bogie has a long maintenance process and serious failure consequences. So, it is essential to formulate a reasonable maintenance strategy to ensure its operation. To solve the above problems, a preventive maintenance (PM) strategy for key components of train bogie is established with consideration of failure risk in this paper. Firstly, the failure risk factors of the bogie components are scored and weighted, and the failure risk cost model and PM cost model are established. Next, a Weibull distribution parameter estimation method for bogie components based on the improved beluga whale optimization algorithm (IBWO) is proposed, providing a theoretical basis for PM decision-making optimization. Then, the Lévy flight is introduced into particle swarm optimization to enhance the optimization performance of the model and obtain the optimal solution. Finally, the bogie key components of Nanning Metro line 1 are selected as a case study. The results show that the IBWO algorithm has strong applicability and feasibility, and can accurately calculate the Weibull parameter values of the bogie key components. Compared with the PM plan without considering the failure risk, the proposed method is more economical and safer, which can provide necessary theoretical support for the maintenance decision optimization of urban rail transit train components. [ABSTRACT FROM AUTHOR]

Abstract: With the urban rail transit network in Beijing becoming gradually intensive, the passenger flow organization also develops towards the type of the network mode. This paper analyzes the development trend of the urban rail transit network in Beijing. On the basis of a reasonable classification of emergencies occurred in urban rail transit, this paper puts forward the passenger organization model of rail transit network under emergency conditions, and then set a certain train accident of Beijing Metro Line 1 as an example to illustrate the practical application of the passenger emergency organization mode. [Copyright &y& Elsevier]

This paper aims at better understanding passenger valuation of subway crowding in New York City. To this end, we conducted a stated preference survey with a discrete choice experiment where New Yorkers chose an alternative from a set of two hypothetical unlabeled subway routes based on occupancy levels and other attributes. We used the collected data to estimate crowding multipliers that quantify the trade-off between travel time and standee density. The previous studies have resorted to parametric heterogeneity distributions in analyzing preference variations in crowding multipliers, which can lead to misspecification issues. The contribution of this study is thus to estimate crowding multipliers using state-of-the-art semi-nonparametric models – logit-mixed logit (LML) and mixture of normals multinomial logit (MON-MNL), and compare them across different parameter spaces. The estimated distribution of crowding multiplier of LML and MON-MNL coincide below median, but the former underestimates and the latter overestimates above median. Even though these flexible logit models can be useful for a comprehensive economic analysis of transit service improvements, these differences in estimates make model selection an important avenue for future research. [ABSTRACT FROM AUTHOR]

Abstract With the continuous progress of urbanization, excavation works near tunnel engineering projects are increasing. The stress relief caused by the excavation inevitably affects the deformation of a tunnel. Therefore, it is of great theoretical and practical significance to correctly evaluate the tunnel's transverse and longitudinal deformation to ensure its safe and normal operation. Many studies have been conducted on the effect of quadrangle excavation on the deformation of adjacent subway tunnels. However, the influence of circular excavation on tunnel deformation is still not fully understood, and remains the main technical barrier toward optimal engineering design and construction. Based on Mindlin's displacement solutions, an analytical model of tunnel deformation resulting from a circular excavation was developed, and the reliability of the solution was verified by comparison with existing centrifuge model test results and an analytical solution for a square excavation. On this basis, the influence of the basement geometry, relative position of the tunnel and basement, and soil's Young's modulus on tunnel deformation resulting from a circular excavation were analyzed. The results revealed that the analytical solutions proposed in this paper can better predict the maximum tunnel heave resulting from a circular excavation. Moreover, the maximum tunnel heave increased linearly as the diameter and depth of the circular basement excavation increased. However, the non-linearity decreased with the tunnel cover depth. The results obtained by this study can provide a simple calculation method to predict the maximum tunnel heave caused by a circular excavation, and can also be used to confirm the rationality of a numerical simulation. [ABSTRACT FROM AUTHOR]

• Six influence factors of fresh air induced by piston effect are analyzed. • The energy saving of optimal condition combination is remarkable. • An optimal energy-saving blockage ratio is obtained. • Innovative energy-saving measures for utilizing fresh air are proposed. Energy saving contributes to sustainable development, and the fresh air induced by piston effect is closely related to the ventilation and energy saving of subway system. This paper is aimed at finding the optimal combination and energy conservation of metro ventilation system based on factor analysis and environment control system operation strategy. The numerical simulation and experiment are carried out in this paper. Firstly the variation trend of velocity field is reasonable by being compared with on-site experimental data. Secondly, orthogonal experimental design is adopted to study the major factors affecting the fresh air volume flowing into the station from the station entrance-exit, and then the optimal combination of energy saving is obtained. Next, the calculation results show that the annual electricity saving amount of the optimal combination is obviously greater than that of actual metro station and previous literature. To be specific, the maximal energy saving of the optimal combination is 236729 kW·h, while that of the actual metro station is merely 75888 kW·h. Namely the maximal energy saving of the optimal combination is about 3 times as large as that of the actual metro station. Finally, the energy saving of key factors is discussed in detail, and the results prove the energy saving increase is consistent with the rise of the blockage rate and the distance between the piston vent and the station. Besides, the optimal energy saving blockage ratio is 0.6 considering the actual blockage ratio and economic cost. According to the above consequences, innovative energy saving measures about the utilization of unorganized fresh air are proposed, which is applicable to typical subway station. [ABSTRACT FROM AUTHOR]

• A novel method for obtaining transfer characteristics of subway-induced ground vibrations is proposed. • A hybrid method is adopted to predict railway-induced environmental vibrations. • The dominant influence range of fastening forces is discussed and determined. • The proposed method is proved to be accurate and applicable by comparison with the traditional numerical simulation method. Aiming at the multiple-input multiple-output vibration problem in rail transit, this paper presents a novel method for obtaining transfer characteristics of vehicle-induced vibrations. To verify its accuracy and applicability, the obtained transfer coefficients are further combined with vehicle-track coupling simulations to predict environmental vibrations under different conditions. The results prove that the transfer characteristics from the vibration source to the environment target can be accurately obtained through the multiple regression algorithm and superposition algorithm. Compared with the traditional numerical simulation method composed of both the vehicle-track coupling model and the track-tunnel-soil model, the coefficient of determination R-squared of the two methods in the time domain can reach above 0.9, and errors of the environment evaluation index in the frequency domain are within 0.2 dB. However, the computational effort has been reduced significantly without establishing a complex numerical model of the tunnel-soil (structure) system. Moreover, it is found that environmental vibrations on the ground surface are mainly affected by fastening forces in the vicinity of 60 m centered by the observation point. In particular, the proposed method is expected to supply a certain reference for predicting vibrations under multi-source load in mechanical science and civil engineering. [Display omitted] [ABSTRACT FROM AUTHOR]

• The strong correlation between the initial wheel high-order polygonal wear of subway trains and the small-radius (i.e., a radius no greater than 400 m) curve track was explained. • The formation mechanism and progression pattern of the wheel high-order polygonal wear were studied via modal analysis and transient dynamic analysis. • The finite element modeling method of ideal wheel polygonal wear and rail corrugation was proposed and verified. • The influence of rail corrugation on the evolution of wheel high-order polygonal wear was analyzed via dynamic simulation. The present paper aims to study the generation cause of initial high-order polygonization of subway wheels as well as its progression pattern. In analyzing the wear characteristics of out-of-round (OOR) wheels of metro trains obtained via field measurements, the distribution of wheel high-order OOR wear was found to be closely related to the small-radius (i.e., a radius no greater than 400 m) curve track. The friction-induced self-excited oscillation caused by the saturated wheel-rail creep force was used as the frequency-fixing mechanism of the wheel OOR wear, and the wheel polygonization induced via this oscillation was evaluated by finite element simulation. Furthermore, the influence of rail corrugation on the development of wheel OOR wear was analyzed, and it is found that, when the vehicle negotiates a small-radius curve track, an unstable oscillation of 87 Hz induced by the saturated creep force can lead to wheel 12th ∼ 13th-order OOR wear—mainly distributed along the inner wheel tread far from the wheel back. During vehicle operation, the vibrations caused by the wheel 12th ∼ 13th-order polygonization can excite the eigenmodes of the wheelset, leading to an increased wear intensity. In addition, wheel 12th-order polygonal wear interacts with the rail corrugation of the same wear wavelength but different phases, which can cause wheel 10th ∼ 11th- and 13th ∼ 17th-order polygonization. [ABSTRACT FROM AUTHOR]

With the development of urban rail transposition, the long-term deformation of soft clay under the subway vibration loading has drawn wide attention by researchers and engineers recently. In addition to the situ tests and laboratory triaxial tests, the microscope tests also provide an effective way to clarify the dynamic characteristics of soft clay. Moreover, the variations of the pore size distribution (PSD) of the silty clay before and after freezing-thawing have less been investigated. In this paper, the mercury intrusion porosimetry (MIP) tests were conducted to study the microscope pore structures of the silty clay before and after freezing-thawing which had experienced the cyclic loading by the cyclic triaxial tests. A bottleneck phenomenon with the pore radii of 0.1–0.6 μm exists in the mercury intrusion process. The log-differential pore volume curves of the silty clay show a unimodal mode, where the mode with pore radii range from 0.05 to 0.6 μm represents intra-aggregate pores. After freezing-thawing, the final mercury intrusion volume and the most probable pore size of the samples without cyclic loadings increase about 6.0% and 30.64%, respectively. Under the same cyclic loadings, the mercury intrusion volume increases with the freezing temperature decreasing. The lower the frequency and the larger the cyclic stress ratio (CSR) of cyclic loadings are, the larger the deformations of the samples are and the smaller the most probable pore size becomes. The pore volume of samples after freezing-thawing (F) with frequency of 2.5 Hz is 8.74% larger than that with 0.5 Hz, while it is 5.03% of undisturbed samples (U). The most probably pore size of the samples after freezing-thawing with CSR of 0.125 is about 81.2% larger than that with CSR of 0.375. The process of mercury intrusion in MIP tests is similar to the air injection in a saturated soil as described along the drying water retention curve (WRC). The mercury intrusion pressure and the normalized volume are equivalent to the soil suction and the air volume within the soil, respectively. The MIP derived WRC is suitable for the prediction of the soil-water characteristic curves with the van Genuchten model. In addition, the microscope pore structures of the silty clay exhibit fractal characteristics with the thermal fractal dimension model in MIP tests. [ABSTRACT FROM AUTHOR]

The structural assessment of segmental grey cast iron (GCI) tunnel linings to nearby construction is challenging due to the presence of the joints affecting the stiffness of the tunnel lining. This paper presents an extensive investigation, using 3D finite element (FE) analyses, into the bending moment-rotation (M-θ) behaviour of two GCI tunnel joint geometries. These two geometries correspond to standard running and station tunnels of the London Underground network. The contribution of this study is two-fold. i) The novel characterisation of the M-θ response enables the development of new models for simulating the mechanical response of GCI tunnel joints with structural elements which can be used in simplified, 2D geotechnical analysis for tunnel safety assessments. ii) The analyses provide insight into the behaviour of GCI tunnel linings that would be difficult to achieve through experimental and field observations alone. More specifically, the analyses show that when the bolts are removed from the joints the possibility of tensile failure can be disregarded; that the initial bolt preload influences the rotational stiffness only after some rotation has taken place and does not alter the bending moment of opening; and that the out-of-plane displacement restraint has little influence on the joint response. [ABSTRACT FROM AUTHOR]

• The crown spring connector failure was caused by insufficient cable capacity and the degraded contacts. • The cable capacity is 11.6% insufficient. The wear and the oxidation of the contacts increases the contact resistance 23%. • The heat power causes decomposition of the insulation material and further increases the temperature. • A solution to increase the cable size from 50 mm2 to 70 mm2 is proposed to reduce the maximum temperature rise by 18.4%. With the fast development of the rail transit system and the continuous speed increase of rail vehicles in China, the rated current of the power supply system in the trains rises accordingly, so the thermal reliability of the electrical connection system used in the power supply system has become one of the crucial factors whether the train can run normally for a long time. In this paper, aiming at an ablative failure of a special-shaped crown spring connector during the operation of a subway, both the failure mechanism and the solution method are studied. Firstly, the main influencing factors of the failure, both the cable size and the contact resistance degradation of the connector, were screened by fault tree establishment. Then the capacity of the selected cable was evaluated to be insufficient by current carrying test, with 11.6% lower than the safe margin. Further, the contact resistance degradation of the connector caused by vibration and corrosion was about 23%, studied by the experiments and thermal theory. By combining the theoretical model of temperature rise in the contact interface and the finite element simulation, the heat production of the connection system under actual working conditions was estimated to make the insulating materials near the contacts attain to the decomposition temperature, which was verified by the analysis of the failed samples with various service stages. The thermal analysis results was demonstrated to be consistent (less than 5% error) among the finite element simulation, the experiments and an existed thermal design method. Finally, a solution to increase the cable specification from 50 mm2 to 70 mm2 under complicated service conditions is proposed to reduce bulk resistance of the cables and increase the heat dissipation by cable heat conduction, the maximum temperature rise can reduce 18.4% so that the ablation failure of the connectors can be avoided. [ABSTRACT FROM AUTHOR]

• A transfer learning-based method was proposed for crashworthiness prediction. • Datasets of deformation images were efficiently constructed in TFRecord. • The number of full connection layers has an important effect on prediction. • Efficient prediction of structural crashworthiness was achieved and validated. Due to the lack of load/displacement sensors in a complex and uncertain crash test/accident of rail vehicles (e.g., vehicle-to-vehicle or train-to-train collision), only structural deformation images can be obtained while the crashworthiness indicators (e.g., force, displacement, energy absorption) cannot be measured directly. This paper aims to propose a transfer learning-based inverse method for extracting the structural parameters and crashworthiness characteristics by the deformed pictures of energy-absorbing structures. A finite element model of an energy-absorbing structure was firstly established and calibrated by experiments. Then, a number of deformation images were captured from the numerical design of experiment (DOE) through coding languages, which were saved as TFRecord format to reduce the computational time during the training of transfer learning models (i.e., VGG16, LetNet, AlexNet and ResNet50). The result showed that the transfer learning model, ResNet50, exhibited the best performance with R 2 of 0.736 and 0.981, respectively, for predicting the structural parameters and crashworthiness characteristics. In addition, the number of full connection layers should be reasonably selected on the premise of maintaining accuracy and efficiency. A group of deformation pictures were randomly used as samples to validate the prediction of structural parameters and crashworthiness through the trained transfer learning model, where good consistence was observed. The proposed method is expected to bring the image recognition and big data prediction into the design and test of composite energy-absorbing structures, thus, auxiliary improve the crashworthiness of rail vehicles. [Display omitted] [ABSTRACT FROM AUTHOR]

The characteristics of the fire environment in a subway station under fire situations was investigated in this paper. Visibility, temperature and carbon monoxide at the evacuation stairs in the subway station were computed by Fire Dynamics Simulator (FDS). The effects of different heat release rates on evacuation were discussed respectively. With the increase of heat release rate, evacuation will become even more difficult, and the overall efficiency of evacuation will be lower. Therefore, relevant departments should take preventive measures to prevent fires with large heat release rates from broking out. [ABSTRACT FROM AUTHOR]

This paper analyzes the theories of ventilation and heat transfer of subway environmental control system, and a relevant network model of subway lines has been built. Based on this model which can calculate air volume and thermal load of subway lines, the air flow distribution in each area of station under closed ventilation condition, opened ventilation condition, minimum fresh air condition, night ventilation condition and obstruction ventilation condition has been simulated, and the influence of open or close piston duct and bypass duct, mode of air supply and exhaust, air temperature in station hall and platform, minimum fresh air of air conditioning and VRV system of equipment room on the thermal environment has been studied. Finally concludes the specific affection of these factors to energy consumption of subway environmental control system and temperature of tunnel, and optimizes the operation scheme for subway environmental control system in different period and seasons. [ABSTRACT FROM AUTHOR]

This paper addresses the topic of transportation network vulnerability within the context of the New York City subway system. We propose a network model for it and an approach based on shortest-path passenger flow simulations in order to quantify delays experienced by passengers arising from disruptive events, particularly from those that occur simultaneously. We determine if and to what extent the effect under such simultaneous scenarios is greater than it would be had the same disruptions occurred as separate events. Our findings can be useful in supporting the planning decisions necessary to prepare for the harmful consequences arising from disruptions to complex urban networks. [ABSTRACT FROM AUTHOR]

The travel time (TT) prediction of underground mine transport trucks provides essential information for the precise scheduling of mine intelligent dispatching systems. Given the operational requirements and transportation environment of underground mines, in this study, a TT prediction method for underground mine transportation trucks is proposed based on stacking integrated learning. First, depending on the position and status of the transport truck, the truck operation cycle process is broken down into three sections and six stages. The influencing factors of the trucks' TT in each stage are determined from the perspectives of personnel, equipment, and environment. During the collection process of the influencing factors the road surface roughness data are collected through image processing as part of the influence factor data. The influencing factors' data are used as input parameters for the stacking integrated learning prediction model. The prediction performance of the fusion model is compared with that of the single models and their pairwise combinations. The final prediction results show that the fusion model performs the best in the drifts, ramps, and ground road sections. The average absolute percentage errors of the predicted values in the three road sections are 2.3091%, 4.3906%, and 4.5583%, respectively, and the corresponding decision coefficients are 0.9890, 0.9801, and 0.9050. These results show that the prediction model based on the stacking integrated framework proposed in this paper has a high prediction accuracy and stability. This accurate model can meet the requirements of intelligent dispatching systems for underground mines. • Studies the prediction of truck transportation travel time in underground mines. • Refines the underground mine truck transportation flow and predicts truck travel time by road section. • Analyzes the influencing factors of truck travel time from the perspectives of personnel, equipment and environment. • A multi-model ensemble learning prediction model is constructed based on Stacking ensemble learning framework. [ABSTRACT FROM AUTHOR]

To reduce air pollution, China gradually upgrades the fuel for vehicles while building the subway system in some major cities. Using panel data covering 16 major cities in China during the period between 2014 and 2017, this paper investigates the impacts of China Fuel Standard V for petrol and diesel and subway operation on Air Quality Index (AQI) and four pollutants, namely PM2.5, SO 2, NO 2 and CO. Empirical results find the positive impacts of Fuel Standard V on the reduction in SO 2 , PM2.5 and CO. The impact is strongest in the context of SO 2 , with Fuel Standard V Diesel having a larger impact compared to Fuel Standard V Petrol. In addition, the operation of subway systems leads to a decrease in CO. Furthermore, this paper explores not only separate but also the joint effects of fuel standards and subway. Interestingly, the results indicate that while the operation of the subway system itself cannot affect PM2.5 concentrations, it contributes to the reduction in PM2.5 when Fuel Standard V is implemented. These results emphasise the importance of policy coordination to reduce air pollution in China. Image 1 • China Fuel Standard V has positive impacts on the reduction in SO 2 , PM2.5 and CO. • China Fuel Standard V has the strongest impact in the context of SO 2. • Fuel Standard V Diesel has a larger impact compared to Fuel Standard V Petrol. • The subway system leads to a decrease in CO, but not on other pollutants. • Introducing the Fuel Standard V and subway jointly can reduce PM2.5 pollution. [ABSTRACT FROM AUTHOR]

The definition of how ground-borne noise is radiated into rooms in surrounding buildings due to underground subway lines is diverse in different countries, especially in the dominant frequency range. In the present paper, a set of field tests were carried out in Suzhou city, China to obtain ground vibration induced by subway vehicles and radiated noise in buildings. Preliminary analysis of frequency range is 1-300 Hz based on the strength of frequency domain analysis of the ground-borne vibration and noise and attenuation of vibration along propagation path. Furthermore, the ground-borne noise is recognized from the measured data by partial coherence function. Based on this theory, the contributions of different vibration sources to the noise are distinguished. The analyzed result shows that the recognized dominant frequency range of the ground-borne noise is between 20∼310 Hz. This research also indicates a difference of A-weighted sound levels between the tested result and contrasting criterions. [ABSTRACT FROM AUTHOR]

Considering an incident on a track of a double-track subway line, this paper formulates an optimization model to find near-optimal rescheduled timetables with the least total delay time compared to the original one, in which crossover tracks connecting two parallel subway lines are particularly taken into consideration for balancing the service quality under emergent situations. On the basis of a discrete event model where the train position state transitions are characterized as a series of discrete events, an efficient train rescheduling strategy (ETRS) is developed for solving the proposed model, in which a well-developed capacity check algorithm is particularly integrated to prevent the potential deadlocks. By using the infrastructure data of Beijing Yizhuang subway line of China, numerical case studies are implemented to demonstrate the effectiveness and efficiency of the proposed model and algorithm. [ABSTRACT FROM AUTHOR]

Trackless rubber-tyred vehicles are among the most widely used underground auxiliary transportation equipment in major coal mines at present. The migration of exhaust gas that threaten human health varies with the working conditions of trackless rubber-tyred vehicles. In order to better evaluate the health risks faced by underground personnel in the process of exhaust emission from underground diesel vehicles, in this paper, the migration of carbon monoxide (CO) and particulate matter (PM) emitted by trackless rubber-tyred vehicle under three working conditions was analyzed by using the method of CFD (Computational Fluid Dynamics) numerical simulation and field measurement. It can be concluded that the concentrations of CO and PM changed with the change of airflow field under different working conditions, and their distribution tended to be consistent on the whole. Although the migration of CO and PM were different under different working conditions, CO with high concentration (C ≥ 44.74 ppm) and PM with high concentration (C ≥ 89.47 mg/m³) were mainly distributed in the area near the exhaust pipe of trackless rubber-tyred vehicle. Therefore, the drivers of trackless rubber-tyred vehicle and underground personnel need to comprehensively consider the risk factors under different working conditions when carrying out personal protection. [Display omitted] • The migration of CO and PM was greatly affected by working conditions. • The concentration distribution of CO and PM changed with the airflow field. • CO and PM with high concentration were mainly distributed near the exhaust pipe. • Underground personnel needed to consider ventilation rate and layout of roadway. [ABSTRACT FROM AUTHOR]

This paper develops a Bayesian network-based approach for risk modeling of collapses and derivative accidents to systematically avoid subway construction collapse events and mitigating the loss from derivatives. Given it was not feasible for risk quantification based upon current safety standards, a risk-based method was proposed for numerical computation of severity values from the perspective of workers' safety. In order for dimensionality reduction, each node's importance in the network was estimated through the variation of Gini index in random forest algorithm. The Bayesian network of subway construction collapse risk (SCCR-BN) contained two sub-graphs. Sensitivity analyses were performed to determine critical causal factor events for each collapse or non-collapse event. Countermeasures can be tailored for better response to these causal factors for risk controlling. Three representative scenarios were selected for case studies with the objective of demonstrating the applicability of SCCR-BN for dynamic investigation and prediction of subway construction collapse risks. • A BN-based approach was proposed for modeling subway construction collapse risk. • Severity values of accidents were computed from the perspective of worker safety. • An accident data-driven method was employed for the establishment of SCCR-BN. • Typical scenarios were selected for investigating subway construction collapses. • Strategies were tailored for response to various causations for risk controlling. [ABSTRACT FROM AUTHOR]

In this paper, two-dimensional (2D) and new types of three-dimensional (3D) prediction models of environmental vibrations induced by underground railways with a direct fixation track and steel spring floating slab track are developed and verified. The ground surface responses calculated by the 2D prediction models with various equivalent forces are compared with those calculated by the 3D prediction models. The numerical results show that (a) the ratio of the computational time by the 2D prediction models to that by the 3D prediction models is less than 1/600; thus, the 2D prediction models can quickly provide useful results; (b) the equivalent forces in the 2D prediction models are key and are recommended for use as the equivalent wheel–rail force and equivalent steel spring force averaged over a vehicle length for an underground direct fixation track and steel spring floating slab track, respectively; and (c) the accuracy of the 3D prediction models is greater than that of the 2D prediction models; therefore, the 3D prediction models are required for absolute prediction due to their higher accuracy and applicability in a wider range of complex practical problems. [ABSTRACT FROM AUTHOR]

Ecological risks associated with mineral resource extraction are of particular concern in the Belt and Road regions, yet ecological restoration has received little attention. This paper reviewed the mining situation and related ecological impacts in the Belt and Road areas, analyzed the factors impeding ecological restoration capability, assessed the capability, and then presented the key challenges and promotion strategy. The main results showed that: (1) Abundant mineral resources exist in the Belt and Road, covering up to 24,234 km2, accounting for 42.31% of the global mining areas; (2) Mining activities, open-pit or underground, can cause ecological disturbances such as excavation damage, land occupation, collapse, and pollution; (3) Economic development, environmental management, scientific and technological innovation, the political environment, investment by mining enterprises, and ecological conditions affect the ecological restoration capacity in each country; (4) The ecological restoration capability index was 67.14, 66.80, 65.12, 64.73, 60.20, and 58.89 in West Asia & North Africa, Northeast Asia & Russia, Southeast Asia, Central & Eastern Europe, Central Asia, and South Asia, with large regional and internal differences; (5) Key challenges include imperfect multi-stakeholder administration system, lack of effective remediation technologies, and shortage of financial support. Therefore, the countries in the Belt and Road regions should be united to establish extensive policy standards and mine governance systems applicable to the mining lifecycle, improve joint research and development of restoration technologies, and build multi-funding support systems. • Mining-induced damage and rehabilitation are critical issues facing the Belt and Road Initiative. • Weak economy, management, technological innovation, politics, mining enterprise, and natural conditions may hinder ecological restoration. • The challenges to be addressed include governance systems, technologies, and funding. • Suggest promoting governance system, scientific research, sustainable practice for the Belt and Road initiative. [ABSTRACT FROM AUTHOR]

Abstract: Can we construct transnational or international public service advertising to counterbalance the proliferation of transnational commercial advertising? As an important first step in exploring the possibility of such an application of shared media public diplomacy among nations, this paper describes a complete survey of commercial and public service advertisements collected from the public spaces of subway systems in American and Chinese cities in 2010 – New York, Washington, DC, Shanghai and Beijing – to reveal the range of themes of commercial and public service ads in these spaces. The study reveals first that analogous commercial and public service ads are ubiquitous in the public spaces of both Chinese and American cities. Second, many of the themes that might appear in international or transnational public service ads are already being portrayed in ads created by local or national governments or NGOs, although these themes are portrayed in ads created by different sets of actors in China and in the US: government actors and a few international NGOs in Chinese cities, and governments, corporations and non-profit organizations in the case of American cities. Finally, the survey reveals that in all four cities there are many commercial advertisements that appeal to the identity of a transnational consumer, but that there are almost no public service ads that appeal to the identity of a transnational citizen: merely local or national ones who can solve such public problems as global warming, education, and health issues. [Copyright &y& Elsevier]

Abstract: This paper addresses the problem of time-dependent tour planning in complex and large urban areas that may be of importance for different groups of people. The problem is determination of chronological sequences of attractive points during a specific period via several modes of transportation system. The proposed approach adopted a nested architecture in which tour planning routine calls multimodal shortest path subroutine to generate an itinerary based on user preferences and restrictions of interesting points. Two adapted genetic algorithms were employed in the engine of both blocks. In these algorithms, chromosomes with variable lengths and particularly defined evolutionary stages are used. The proposed process has been tested over the dataset of city of Tehran. The evaluation consists of preparation of 400 tours with different initial points, start time, and tour durations. It was assumed that just three modes of walking, bus, and subway are used to travel between points of interest. Moreover, some tests are applied to dataset to illustrate the adaptability and time-dependency nature of method. The experimental results and related indices such as optimality ratios show that the proposed algorithm can find optimum tour according to introduced constraints. [Copyright &y& Elsevier]

• Multivariate disturbances are considered to forecast the passenger flow, and a hybrid deep learning framework is proposed. • Constructing an inbound matrix from other stations of the target station can promote the performance of the model. • The tendency of audience can be extracted from social media which promotes the performance of the model. Subway passenger flow prediction is of great significance in transportation planning and operation. Special events, as for vocal concerts and sports games, lead large-scaled passenger flow with few periodic trends. Therefore, predicting subway outbound flow during events is a challenging task. In recent years, social media has been used for socio-economic forecasting. Correlation analysis shows that the trend of social media volume can be used for passenger flow prediction under events occurrences. In this paper, besides traditional smart card data, we incorporate social media data into passenger flow prediction. The multivariate disturbance-based hybrid deep neural network (MDB-HDNN), which models the disturbances of the inbound flow from the nearby stations and the social media post trends, is proposed for subway passenger flow prediction during events. Experimental results on three real-world datasets demonstrate that the MDB-HDNN performs well under various settings and has better robustness. Our findings and results can provide decision support for schedule formulation and passenger flow guidance. [ABSTRACT FROM AUTHOR]

With the boom of big data, the Internet contains more and more personal behavior information, but it is difficult to extract effectively. A model involving multivariate processing capability must be constructed to deal with these time series with complex characteristics. In this paper, a novel hybrid model embedding Baidu Search Index is therefore proposed to implement multi-step ahead subway passenger flow forecasting. Firstly, we collect data from informative Baidu Search Index, reduce dimensionality, and screen out the powerful predictors by statistical analysis. Secondly, we extract matching common modes at similar time scales between the subway passenger flow and screened Baidu Search Index via multivariate mode decomposition being optimized by multi-objective algorithm. Furthermore, to eliminate pseudo statistical causality, we select the optimal combination of modal components between subway passenger flow and its corresponding Baidu Search Index at each time scale by an innovative multi–modal analysis strategy. Thirdly, we reconstruct the forecasting values of each selected optimal combination as the final results. The empirical results of Beijing, Shanghai and Guangzhou show that the proposed model can significantly outperform six benchmark models in both the level and directional accuracy. So introducing Baidu Search Index creates a sound opportunity to enhance the subway passenger flow forecasting ability. [ABSTRACT FROM AUTHOR]

• A framework for optimizing the design of underground spaces is established. • The relationship between underground space and travel CO2 emissions is clarified. • Factors affecting underground space travel are quantified through multi-source data. The utilization of underground space plays a vital role in saving land, alleviating traffic pressure, and improving the utilization of resources. The combination of walking and metro instead of cars is an effective way to reduce energy consumption and CO2 emissions. However, transfer inconvenience, poor accessibility, lack of vitality, and other phenomena in the underground hinder this low-carbon transportation utilization. This paper aims to improve travel quality and efficiency by optimizing underground space design to reduce CO2 emissions and raise energy efficiency. Taking a typical underground space in Nanjing as an example, multi-source methods such as field measurement, POI, and space syntax are used to quantify the factors affecting underground space travel. Correlations between each factor and the density of passenger flow distribution are discussed. The results show that catering and shopping are the most correlated factors of the pedestrian flow distribution on weekdays and weekends, respectively. Through simulation, the optimized design can increase the passenger flow and reduce CO2 by 277.9 g/Km and 119.1 g/Km per minute on weekdays and weekends, respectively. The design is consistent with the result of 219 questionnaires. This research method has positive significance for developing underground space in other Chinese cities under low carbon background. [ABSTRACT FROM AUTHOR]

• The effect of strain rate on dynamic splitting loading of combined circular tubes are studied analytically and their results are validated by FE simulations. • Impact experiment results show that the combined circular tubes energy absorber experience steady dynamic splitting deformation. • Multi-objective optimization for combined splitting circular tubes energy absorber is performed under the eccentric collision distance of H = 40 mm. This paper proposes a new type of combined splitting circular tube energy absorber for subway vehicles. An impact experiment is conducted to investigate the dynamic crushing performance of this combined splitting circular tube energy absorber. The results show that the combined tubes experience steady dynamic splitting deformation. The crush force efficiency (CFE) and effective stroke ratio (ESR) of the combined splitting circular tube energy absorber are 85.7% and 85.9%, respectively. A theoretical solution for the dynamic splitting crushing load is derived. Finite element (FE) models of the energy absorber are then established, and the dynamic crushing forces agree well with those of the impact experiment. The cumulative error and validation metrics of the crushing force obtained from the numerical simulation and impact experiment are 0.0938 and 0.9122, respectively. The effect of the strain rate of AISI 1020 steel on dynamic steady-state forces is analytically studied, and the results are compared with those of FE simulations and impact experiments. The numerical results show that the dynamic steady-state force of the combined splitting circular tubes under dynamic loading increases by 31.69% compared to that of the tubes under quasistatic loading. The effects of various structural parameters are discussed using the validated FE models. The results show that the combined splitting tube energy absorber has excellent crashworthiness under eccentric loading. The eccentric impact of the two absorbers has a significant influence on the crashworthiness performance of the structure. The specific energy absorption (SEA) increases by 15.2% as the eccentric distance increases from 20 to 80 mm. Compared with the influence of the wall thickness t of the combined splitting circular tubes, the tube radius and die angle have a more significant influence on the SEA. To improve the crashworthiness of combined splitting circular tubes under eccentric loading, a Pareto front of the SEA and average axial crushing force (AACF) under an eccentric distance of H = 40 mm was obtained after optimization by multiobjective particle swarm optimization (MOPSO). The results show that the SEA and AACF are positively correlated and that a balance between the SEA and AACF was obtained at optimal point B (SEA = 14.6 kJ/kg and AACF = 938 kN). [ABSTRACT FROM AUTHOR]

• A one-dimensional brake disc model is proposed to obtain the temperature field. • The velocity-dependent friction coefficient and slop track are considered. • The method of lines (MOL) is applied to solve the mathematical model. • The model is verified by the experimental data. Friction heating during braking may causes premature wear, thermal cracks and other damages which could weak the braking performance of subway vehicles. It is therefore important to determine the temperature field of the brake disc. The purpose of this paper is to propose a one-dimensional brake disc model and apply a new solution algorithm to obtain the temperature field of the brake disc, which is validated by the Renk Dynamometer test bench. The advantage of this numerical model is that the variable friction coefficient and slope are taken into account. The experimental dependency of the coefficient of friction on the velocity is approximated by interpolation and applied to the numerical model. The calculation is based on two cases of constant and velocity-dependent friction coefficient (COF) by using the method of lines (MOL), which has the advantage of shorter computation time and improved accuracy. The numerical results agree well with the experimental data. It was proved that disregarding the velocity dependence of the coefficient of friction, the maximum temperature during the entire braking process was underestimated by 15%. In addition, the subway vehicle braking on slope should decrease the speed limit appropriately to reduce the maximum temperature of the brake disc. This study can provide a theoretical basis for further fatigue study of brake discs. [ABSTRACT FROM AUTHOR]

• First time to measure microclimatic parameters before an intact tomb excavated. • Short variable phase in burial time is as short as 0.3 h. • Rapid variation of microclimate will trigger deteriorations of historical artifacts. • Local average annual temperature is the optimal preservation temperature. The development and utilization of urban underground space have contributed to more excavation of ancient tombs in recent years. The microclimate in the burial environment is crucial for the sustainability of historical artifacts. In this paper, the variation in thermal and humid conditions during the burial time from the closure of a tomb to excavation was investigated by field testing and computational fluid dynamics (CFD) modeling. The selected object is the famous M1 tomb chamber of the mausoleum Zhang An-shi, which has a 2000-year history. It was found that the average air temperature (T) and relative humidity (RH) of the M1 tomb chamber before excavation were 12.7 °C and 93.0%, respectively. The results of the CFD simulation suggest that the burial time of an ancient tomb consists of a very short variable phase and a long stable phase. The very beginning phase may be as short as 0.3 h. The dramatic changes in temperature and RH were more than 10 °C and 20%, respectively. Consequently, dramatic changes in the thermal and humid environment will trigger the deterioration of historical artifacts. Current findings further suggest that the local annual average temperature is optimal for the conservation of underground artifacts excavated from the soil thermostatic layer. This study paves the way for characterizing the environment of an ancient tomb chamber, as well as museum design, energy savings that support cultural heritage protection and preventive conservation. [ABSTRACT FROM AUTHOR]

The excessive environmental impacts from the construction of subway infrastructure have become a concern for operators who are keen on continuing to lower the environmental footprint, but the factors affecting the impacts are yet to be fully identified. Excavation scheme is the governing factor in subway construction, not only because it prescribes the ensuing construction procedures, but it also epitomizes the design philosophy towards the interaction between the subway structure and city environment. In this paper, a comparative assessment is made among the fifteen mid-point environmental impacts from the two major excavation schemes in subway construction, i.e. the open-excavation (OE) and underground-excavation (UE) scheme. The case station provides a perfect example for such a comparison as it consists of both OE and UE section at the same buried depth. GHG emissions are identified as the largest contributor after normalization. However, GHG emissions are not representative for the overall impacts. The UE section is responsible for more impacts per area than that of OE section in all the investigated categories. The gap between the two sections is attributable to the extra reinforcement procedures that protect the surrounding infrastructure from adverse settlement. Though the underground environment limits the use of construction machines, the UE construction involves more on-site impacts because it requires 11.79 times the labor used in the OE section. Based on the results, the adaptability of the two methods was discussed, considering the life-cycle performance and their interaction with the city environment. • GHG emissions are the most prominent impact for URT construction, but not a representative indicator for the whole process. • Environmental impacts from the UE section are larger than the OE section, which results from the reinforcement measures. • Underground excavation creates more on-site impacts due to excessive labor demands. [ABSTRACT FROM AUTHOR]

The quest for efficient aircraft boarding strategies continues to generate lots of business and scientific discussions. Boarding strategies define rules and procedures aimed to reduce boarding time and operational cost. Most of the proposed strategies do not account for passengers' non-compliance with boarding rules. Non-compliance is one of the major non-deterministic problems that can degrade any performance improvement to be expected from adopting a boarding strategy. To that, it is of paramount interest to shed light on this problem and introduce approaches for mitigating any related performance degradation in the boarding process. Although some recent research investigations considered the effect of non-compliance on the overall boarding time under different strategies, there was a lack of remedial actions. This paper dissects the operational characteristics of the non-compliance activity, proposes two different intervention approaches to deal with non-complying passengers, and analyzes the resulting impact under different categories of boarding strategies using a cellular-automaton-based simulation. • Intervention approaches to mitigate the impact of non-complying passengers with boarding strategies • Performance analysis under various conditions such as different Companion Percentages, Carry-on Luggage Percentages, Boarding Strategies, Intervention Approaches, and Non-Compliance Rates. • Novel grid to classify boarding strategies based on the level of randomness and companion-friendliness. [ABSTRACT FROM AUTHOR]