Effects Of Trains Research Articles

Investigation into the reduction of aerodynamic drag via external windshields on high-speed trains

As train speeds increase, aerodynamic drag becomes a significant factor in train resistance. The geometric profile of the train’s end connection changes abruptly, enhancing this aerodynamic resistance. Implementing an external windshield effectively mitigates this resistance, particularly for middle- and rear-train cars. This study utilizes three-dimensional, steady Navier–Stokes (N-S) equations for open line conditions and three-dimensional, unsteady N-S equations for tunnel environments to analyze the drag reduction effects of trains with and without external windshields in both scenarios. The findings indicate that external windshields have minimal impact on the flow and pressure fields surrounding the entire train, whether operating on open lines or in tunnels. However, the installation of an external windshield creates a positive pressure zone on its surface, with varying pressure levels depending on whether the train is in open air or a tunnel. Additionally, a high-velocity airflow occurs in the gap between the external and internal windshields, reaching speeds up to 90 m/s. In open-line conditions, the external windshield decreases the train’s overall aerodynamic resistance by approximately 14.46%, while in tunnels, it achieves a reduction of about 24.48%. Furthermore, the pressure surrounding the windshield is higher during tunnel operations compared to open-line conditions.

Behavioral and Electrophysiological Evidence of Time Dilation Induced by Click Train in a Temporal Reproduction Task

Background: The temporal reproduction paradigm is extensively used to study human time perception. Despite extensive behavioral and physiological research, the effect of click trains on different supra-second interval timings in the time reproduction task remains unclear. Event-related potentials (ERPs), such as contingent negative variation (CNV), might provide further insight into the underlying processes occurring at various timing stages. Methods: In this study, constant and click trains stimuli were presented to the 33 participants in a time reproduction task. During the encoding phase, participants in each condition were given different click train interval timings (1400, 1600, 1800, and 2000 ms). In this original research, we examined the influence of click trains on time reproduction performance using behavioral and electrophysiological methods. Results: Findings revealed time dilation during the presentation of click trains in behavioral patterns (P-value = 0.001). Furthermore, electroencephalography (EEG) data revealed a distinct CNV during the encoding and reproduction of interval timings. In the reproduction phase, CNV amplitudes were more negative in the click trains condition compared with the constant auditory stimulation condition (P-value = 0.027). Statistically significant differences were also observed in the CNV amplitudes at various interval timings during the encoding phase, but the amplitude did not increase linearly. Conclusions: Intriguingly, according to the proposed neural mechanism studies, the brain structures affected by the click train corresponded to the electrodes that CNV was observed in the time reproduction task. These findings contribute to our understanding of the striatal-beat frequency (SBF) timing model.

The effect of ship-induced wave trains on periphytic algal communities in the littoral zone of a large regulated river (River Danube, Austria)

Riverine ecosystems are profoundly influenced by hydrological dynamics and natural flow regimes, which dictate the temporal variability of water levels and the amplitude of fluctuations. Human activities, particularly navigation and hydropower generation, have significantly altered these natural patterns, leading to detrimental impacts on the physical, chemical, and biological integrity of river ecosystems. The littoral zone, in particular, is highly susceptible to anthropogenic disturbances, experiencing disruptions in biological activity and biogeochemical processes. This study evaluates the effects of ship-induced wave trains on the structural and functional properties of periphytic algal communities in a regulated river environment. Using data from the Austrian Danube River, periphytic algae's immediate and long-term responses to wave events generated by different types of ships were investigated. Immediate reactions of periphytic algae to wave trains were characterized by reductions in the effective quantum yield of PS II, indicating stress-induced down-regulation of photosystem II photochemistry. Abrasion and remobilization of periphytic algae due to wave action led to increased resuspension of chlorophyll-a into the water column. Furthermore, ship-induced wave trains influenced the pigment composition of periphyton, with photoprotective mechanisms being activated in response to fluctuating light conditions. Long-term effects of wave impact on periphytic algae biomass varied depending on water depth and exposure to aerial stress. While wave action mitigated desiccation stress in shallow areas, it resulted in biomass reduction and alterations in community composition in deeper zones. Notably, the occurrence of diatoms decreased in wave-impacted areas, potentially shifting the community towards Chlorophyceae dominance. Overall, this study underscores the complexity of ship-induced wave impacts on riverine ecosystems and highlights the importance of considering both immediate and long-term responses of periphytic algal communities. Understanding these dynamics is crucial for informing sustainable management strategies aimed at mitigating the adverse effects of navigation activities on riverine biodiversity and ecosystem functioning.

Fatigue damage assessment of a large rail-cum-road steel truss-arch bridge using structural health monitoring dynamic data

Structural health monitoring (SHM) system provides valuable information for the fatigue assessment of existing rail-cum-road bridges. This paper aims to develop an effective fatigue assessment approach for the rail-cum-road bridge, Jiujiang Yangtze River Bridge, by utilising the SHM data, focusing on dynamic modal analysis, finite element model updating and fatigue assessment. First, the traffic load spectrum and modal characteristics of the bridge are investigated from the SHM data. A three-dimensional finite element model is constructed and then updated by using the measured modal data through the proposed regularised model updating method. Then, the updated numerical model is verified with the measured dynamic response data, which can be utilised for calculating stress response at critical structural components of the rail-cum-road bridge. Finally, an improved Corten-Dolan’s model is proposed to analyse the fatigue damage and structural reliability of the critical structural components of the bridge, taking into account the combined effects of train and highway vehicle loads. The results demonstrate that the proposed fatigue assessment method provides more reliable results for the rail-cum-road bridge by considering the combined effect of multi-level traffic loads and the non-linear fatigue damage accumulation. It is concluded that the short H-shaped suspender is identified as the most vulnerable structural member of the rail-cum-road bridge, and the remaining fatigue service life of the typical components of the bridge should meet the design requirement.

Analysis of train-induced aerodynamic characteristics and pressure-relief measures relating to fully enclosed noise barriers installed on railway bridges

Fully enclosed noise barriers (FENBs) are increasingly being installed on high-speed railway bridges for noise pollution control. However, the aerodynamic effects of high-speed trains passing FENBs have an adverse impact on barrier durability and generate micro-pressure waves. In this paper, a numerical model of a train passing an FENB on a bridge is established. The aerodynamic pressure distribution along the FENB is analyzed for both a single train and two trains passing one another. The propagation characteristics and evolution mechanisms of pressure waves are then investigated. The results show that the pressure is lower at the ends of the FENB and higher in the middle along the direction of train travel. The peak positive and negative pressures at the mid-span are 1.95 and 4.47 times higher than those at the ends, respectively. This distribution is caused by the propagation, superposition, reflection, and attenuation of pressure waves. Compression waves account for 78.9% of the peak positive pressure. An amplification factor must be considered when estimating the impact of two trains passing one another. Analysis of five pressure-relief schemes shows that arranging a single pressure-relief hole at a high-pressure location effectively alleviates the over-pressure in the FENB. The overall pressure-relief effect is an exponential function of the single opening area. Considering a constant opening area, arranging several relief holes at equal spacing optimizes the adverse pressure distribution compared with the single-hole relief scheme. The equivalent forces of the multi-hole scheme are 3.35% and 7.58% lower than in the single-hole scheme.

Результаты оценки силового воздействия тяжеловесных и длинносоставных грузовых поездов на железнодорожный путь различными методами измерений

Objective: to assess the force effect of heavy and long-component freight trains on the railway track by various measurement methods: Schlumpf, influence matrices and the two-section method (PGUPS). Methods: measurements of the assessment of the force effect of heavy and long-component freight trains on the railway track were carried out using the Schlumpf methods, influence matrices and the two-section method (PGUPS). Results: it was found that measurements of vertical dynamic forces by three methods are well correlated with each other, and the Schlumpf method gives overestimated results when measuring horizontal transverse force. Practical importance: the two-section method can be recommended for measuring the force effect of both new and upgraded rolling stock on the railway track, as well as for operated rolling stock in order to identify defects and deviations on the rolling surface of the wheels

Some resonance effects of non-typical trains and railway bridges investigated by a frequency-domain method

Some resonance effects of non-typical trains and railway bridges investigated by a frequency-domain method

Exploring the Performance of Continuous-Time Dynamic Link Prediction Algorithms

Dynamic Link Prediction (DLP) addresses the prediction of future links in evolving networks. However, accurately portraying the performance of DLP algorithms poses challenges that might impede progress in the field. Importantly, common evaluation pipelines usually calculate ranking or binary classification metrics, where the scores of observed interactions (positives) are compared with those of randomly generated ones (negatives). However, a single metric is not sufficient to fully capture the differences between DLP algorithms, and is prone to overly optimistic performance evaluation. Instead, an in-depth evaluation should reflect performance variations across different nodes, edges, and time segments. In this work, we contribute tools to perform such a comprehensive evaluation. (1) We propose Birth–Death diagrams, a simple but powerful visualization technique that illustrates the effect of time-based train–test splitting on the difficulty of DLP on a given dataset. (2) We describe an exhaustive taxonomy of negative sampling methods that can be used at evaluation time. (3) We carry out an empirical study of the effect of the different negative sampling strategies. Our comparison between heuristics and state-of-the-art memory-based methods on various real-world datasets confirms a strong effect of using different negative sampling strategies on the test area under the curve (AUC). Moreover, we conduct a visual exploration of the prediction, with additional insights on which different types of errors are prominent over time.

Intraseasonal northward evolution of the extreme autumn rainfall event in West China in 2021

An excessive “autumn rain of West China” (ARWC) event, concentrated between August 23 and October 7, 2021, produced the greatest amount of precipitation recorded during 1961–2021. This event exhibited notable intraseasonal northward movement of rainfall from the first phase (P1; August 23–September 7) to the second phase (P2; September 17–October 7). Analysis links this event to two key atmospheric factors: the western North Pacific anticyclone (WNPAC) and the East Asian subtropical westerly jet (EAJ). Persistent and robust contrast in convection between the Maritime Continent (MC) and the central tropical Pacific strengthened the WNPAC, transporting moisture to West China. Simultaneously, the EAJ, positioned northward of West China, enhanced upward motion contributing to the excessive ARWC. During P1, anomalous cyclone prevails over the regions from northern China to Japan, due to the combined effects of tropical northward wave trains and quasi-barotropic wave trains from the North Pacific. This cyclonic circulation not only induces a southward shift in the EAJ but also restricts the northward expansion of the WNPAC, favoring its zonal development. In P2, the weakening of convective activity in the MC, coupled with changes in basic flow, leads to the attenuation of WNPAC. Additionally, influenced by the North Atlantic transient wave activity and wave trains originating from North Pacific, there is a transition in the mid-high latitudes wave trains, resulting in the presence of an anomalous anticyclone over Northeast Asia. Which drives the EAJ northward and facilitates the northeastward development of WNPAC. These factors contribute to a significant intraseasonal northward shift of ARWC in 2021. Such underlying mechanisms were also verified by using the dry Linear Baroclinic Model.

Research on Computer-aided Adjustment and Optimization of Train Service Plan based on Passenger Flow Assignment

Abstract According to the complex characteristics of the mutual influence of passenger flows between different train adjustment schemes, a computer-aided train service plan adjustment optimization model based on passenger flow assignment is proposed with the goal of minimizing the remaining passenger turnover. The actual operating effects of trains and the impact between different adjustment measures and between trains are also considered. A computer iterative optimization algorithm with 2 stages based on the greedy principle is designed. The computer processing is divided into two stages: train adjustment plan selection and passenger flow information analysis. The selection of adjustment schemes is feedback-corrected based on the results of passenger flow assignment. Finally, taking the train operation plan of the Beijing-Shanghai high-speed railway as the research object, an example is demonstrated, and the results show that the model and algorithm can effectively obtain the optimal train adjustment scheme under the current conditions.

Актуализация методики учета аэродинамического воздействия от поездов на высокоскоростных железнодорожных магистралях

In the calculation of structures located near railway tracks (noise protection screens along the tracks, overpasses over high-speed railway lines (HSM) of deck elements with downhill driving, etc.), the aerodynamic effects of high-speed trains shall be considered. Objective: study of the aerodynamic impact of a moving high-speed train on structures and structures, Located in the immediate vicinity of the highspeed railway line with subsequent adjustment of the current regulatory framework for the design of TSM infrastructure facilities. Methods: mathematical modeling in a specialized software complex of computational hydrogas dynamics with experimental verification of the developed calculation models and subsequent analysis and generalization of the obtained results. Results: distribution patterns and aerodynamic intensities from a moving high-speed train for the two most characteristic design cases: impact on a vertical surface parallel to the track axis and on a horizontal surface, located above the axis of train movement. For the calculation cases under consideration, the intensity of the impact was related to parameters such as the distance to the structure from the path axis (for the vertical surface) and the height above the rail head (for the horizontal surface). Practical importance: the need Development of proposals for adjustment and addition of the current regulatory framework for the design of structures and structures included in the infrastructure of high-speed railway lines.

Time-dependent fatigue reliability analysis of heavy-haul railway steel bridges

Fatigue of heavy-haul railway bridges has been an ongoing concern due to the excessive stresses and frequent cyclic effects of freight trains. Current fracture-based fatigue research, which promotes fatigue reliability analysis caused by crack propagation, is challenged by the dilemma between the detailed modeling of cyclic stress and the reflection of temporal characteristics of loading conditions. In addition, due to the strong non-Gaussian nature of the fatigue limit state function and the computational inefficiency of integrating finite element analysis, current time-dependent reliability methods need to be further developed. To evaluate the fatigue reliability of heavy-haul railway steel bridges considering the temporal dependence of cyclic train loading, a time-dependent fatigue reliability methodology is developed in this study with two innovations. Firstly, a cyclic stress range model is proposed based on the load analysis at the bridge level, which can capture the time-dependent characteristics of the incurred stress range throughout service life. Then, an improved outcrossing rate method for strong non-Gaussian fatigue limit state functions is developed to reduce the computational costs associated with reliability analysis integrated with the finite element model. The developed time-dependent fatigue reliability methodology is then applied to a heavy-haul railway steel truss bridge located in Shandong, China, which proves its efficiency and accuracy in evaluating the time-dependent fatigue reliability of heavy-haul railway steel bridges. Furthermore, the developed methodology is able to provide insight into the balance between bridge fatigue damage and freight volume, and it is found that the combination of small train axle weight and high operation frequency is the optimal solution to achieve the fatigue reliability of the steel bridge while fulfilling the freight demand.

Aerodynamic effects of trains circulating through a bifurcated tunnel

Aerodynamic effects of trains circulating through a bifurcated tunnel

Alternate deposition and remelting microdroplets via single laser for printing low-defect and high-performance metal micropillars

Laser-induced forward transfer (LIFT) has emerged as a versatile technique for printing high-resolution metal microstructures. However, a common drawback of this method is the inadequate coalescence of the deposited metal microdroplets, which results in inferior electrical and mechanical properties. This paper proposes a novel approach for fabricating high-performance metal micropillars using a single-pulsed laser to alternately deposit and remelt metal microdroplets. Specifically, an ultraviolet nanosecond laser was used to induce the deposition of copper microdroplets, forming a patterned powder bed with high resolution. Subsequently, a laser pulse train was applied to fuse the patterned powder bed. The results showed that voids and microdroplet delamination were eliminated in the printed copper micropillars, whose yield strength and elastic modulus increased threefold, approaching 63% of those of the bulk metal. The remelting behavior of the deposited microdroplets was elucidated by modelling and analysing the thermal accumulation effects of a laser pulse train. A remelting map was proposed, including the non-melting, remelting, and vaporizing regimes. According to the depth of melt pool, the evolutions of morphology and microstructure in the depositing and remelting process were elucidated. Hence, this study advances the LIFT process for fabricating high-performance metal microstructures.

The effect of high-speed railway train on the seismic response of bridge under earthquakes

This study aims to discuss the effect of high-speed railway train on the seismic response of bridge girder under earthquakes especially pay attention to the possible response reduction to the bridge caused by vehicle, utilizing experimental and simulation methods. A 1:10 scale model for the train-track-bridge system was built and a high-speed train running test platform based on shaking table array was constructed for the seismic loading test at varying running speed. To account the effects of different earthquake characteristics, earthquakes under the four types of site soil in the far-field and near-field were selected. The vehicle was modeled in two kinds of ways to distinguish the effects of spring-mass vehicle and additional mass which means a vehicle was set with spring suspension and mass, while another with additional mass only. Through a large amount of numerical simulation dates to determine the distribution interval of specific reduction value caused by the vehicle under the earthquake. Results in running tests and numerical simulation indicate that the lateral acceleration of the bridge girder can be effectively reduced when the train is stationary. The reduced ratios were about 4%− 8% compared without train on bridges. As the speed increases, the response of bridge is generally intense and the reduction is also weakened. Similar reduction was not observed in the response of vertical earthquake excitations, and high-frequency earthquakes have adversely affected this kind of reduction. The main reason for the reduction of lateral seismic response of bridge girder in the presence of static vehicle can be attributed to the phase difference between vehicle and bridge caused by a mass damper-like action, and the additional mass cannot cause similar changes alone.

Neural effects of TMS trains on the human prefrontal cortex

How does a train of TMS pulses modify neural activity in humans? Despite adoption of repetitive TMS (rTMS) for the treatment of neuropsychiatric disorders, we still do not understand how rTMS changes the human brain. This limited understanding stems in part from a lack of methods for noninvasively measuring the neural effects of a single TMS train—a fundamental building block of treatment—as well as the cumulative effects of consecutive TMS trains. Gaining this understanding would provide foundational knowledge to guide the next generation of treatments. Here, to overcome this limitation, we developed methods to noninvasively measure causal and acute changes in cortical excitability and evaluated this neural response to single and sequential TMS trains. In 16 healthy adults, standard 10 Hz trains were applied to the dorsolateral prefrontal cortex in a randomized, sham-controlled, event-related design and changes were assessed based on the TMS-evoked potential (TEP), a measure of cortical excitability. We hypothesized that single TMS trains would induce changes in the local TEP amplitude and that those changes would accumulate across sequential trains, but primary analyses did not indicate evidence in support of either of these hypotheses. Exploratory analyses demonstrated non-local neural changes in sensor and source space and local neural changes in phase and source space. Together these results suggest that single and sequential TMS trains may not be sufficient to modulate local cortical excitability indexed by typical TEP amplitude metrics but may cause neural changes that can be detected outside the stimulation area or using phase or source space metrics. This work should be contextualized as methods development for the monitoring of transient noninvasive neural changes during rTMS and contributes to a growing understanding of the neural effects of rTMS.

Influence of the door opening on the pressure transient caused by the high-speed subway train passing through the double-track tunnel with the mid-partition wall

Double track tunnel with mid-partition wall is a widely used subway tunnel. In such tunnels, in order to avoid the fire door on the middle partition wall from invading the gauge, the fire door is often removed to form door openings. The existence of door opening connects two parallel tunnels, which affects the aerodynamic effect caused by high-speed subway train passing through the tunnel. In this study, a double track tunnel with mid-partition wall was taken as an example to analyze the aerodynamic effect of high-speed subway train under the door opening conditions, moreover, the surface pressure of two adjacent tunnels and train surface pressure was also analyzed. In addition, the propagation mechanism of pressure wave in open door tunnel was analyzed in detail, and the superposition law of branch pressure wave caused by open door was pointed out. The results indicated that the presence of door openings is beneficial for controlling the peak pressure on the tunnel surface and train surface. For a door opening with a cross-sectional area of 5 m2 (cross-sectional area ratio of 0.116), when the door opening is located 300 m and 700 m away from the tunnel entrance, the peak positive pressure can be reduced by up to 21.9 % and the peak negative pressure can be reduced by 21.1 %. The cross-sectional area and number of door openings have a limited effect on reducing the peak pressure of the tunnel. Compared to the number of door openings, the position of the door opening has a more significant impact on the peak pressure inside the tunnel and on the surface of the train.

The reversal of surface air temperature anomalies in China between early and late winter 2021/2022: Observations and predictions

During winter of 2021/2022, the temperature in China is characterized by a warm-to-cold transition, and the average temperature anomaly in February 2022 is −1.6 °C, the coldest February in 2013–2022. We revealed the circulation regimes and physical mechanisms associated with this reversal event and demonstrated the advantage of a regional model downscaling over the use of the global model alone in predicting. In early winter, the warm anomalies are mainly related to an anomalous anticyclonic system downstream of a PNA-like (Pacific–North America) Rossby-wave train induced by La Niña. In late winter, due to the circulation response to the central Pacific warming and negative tropical Indian Ocean Dipole (TIOD), two ‘−＋−’ Rossby-wave trains from high latitudes and the tropical Indian Ocean jointly lead to an anomalous cyclonic system in China. Meanwhile, an anticyclonic blocking system on the northern side of Baikal brings strong and cold air to China. These two systems together cause a significant drop in surface air temperature anomaly in China during the late winter. The Beijing Climate Center climate system model (BCC_CSM1.1 m) can essentially predict this temperature reversal in China about five months in advance. However, the reversal amplitude is weaker due to warm deviations over the tropical Pacific Ocean and equatorial Indian Ocean. Using dynamic downscaling, a regional Climate–Weather Research and Forecasting (CWRF) model correctly predicts the cold SAT anomalies in late winter 2021/2022. The regional model depicts more realistic circulation patterns in East Asia; the anomalous cyclonic system in Inner Mongolia accompanied by the northerly anomalies contribute to a lower-than-normal SAT over China. This study reveals the cooperative effect of wave trains from high latitudes and the tropics on the subseasonal temperature reversal and demonstrates a possible solution to improve the forecast skill by dynamic downscaling according to precise characterization of local surface information.

Changes to the lambda model for fatigue loads on steel railway bridges in Europe

AbstractFor the fatigue design of steel railway bridges in Europe, the European standards EN 1991‐2 and EN 1993‐2 provide a factored Load Model '71, called the lambda model. The stress range in the fatigue detail of study should be determined with this model. Engineers can easily verify their structural design for fatigue by comparing this stress range to the fatigue reference strength of the detail.This paper compares the load effect caused by the lambda model with the load effect of actual trains measured with ‘Weigh In Motion’ systems during 7 years at 81 locations in the rail network of The Netherlands. Locations with heavy loads are selected and their load effects in terms of stress ranges and fatigue damage are determined for various influence lines, including one, two and three span beams with spans ranging between 1 and 150 m. The design (i.e. elastic section modulus) is optimized such that the calculated fatigue damage using the damage accumulation rule of Palmgren Miner equals 1 for a 100 years design life for these locations. This elastic section modulus is compared to the elastic section modulus obtained by designing according to the lambda model.Improvements are proposed to the lambda model based on this comparison, such that the resulting design gives a reasonable agreement with the design based on measured loads, while maintaining the current ease of use of the lambda model. Uncertainties such as possible changes in axle loads and train speeds in future are taken into account.

Noise in the LIGO livingston gravitational wave observatory due to trains

Environmental seismic disturbances limit the sensitivity of LIGO gravitational wave detectors. Trains near the LIGO Livingston detector produce low frequency (0.5–) ground noise that couples into the gravitational wave sensitive frequency band (10–) through light reflected in mirrors and other surfaces. We investigate the effect of trains during the Advanced LIGO third observing run, and propose a method to search for narrow band seismic frequencies responsible for contributing to increases in scattered light. Through the use of the linear regression tool Lasso (least absolute shrinkage and selection operator) and glitch correlations, we identify the most common seismic frequencies that correlate with increases in detector noise as 0.6–, 1.7–, 1.8–, and 2.3– in the LIGO Livingston corner station.