A rising water table increases soil water content,reduces soil strength,and amplifies vibrations under identical train loads,thereby posing greater risks to train operations.To investigate this phenomenon,we used a 2....A rising water table increases soil water content,reduces soil strength,and amplifies vibrations under identical train loads,thereby posing greater risks to train operations.To investigate this phenomenon,we used a 2.5D finite element(FE)model of a coupled vehicle–embankment–ground system based on Biot’s theory.The ground properties were derived from a typical soil profile of the Yangtze River basin,using geological data from Shanghai,China.The findings indicate that a rise in the water table leads to increased dynamic displacements of both the track and the ground.This amplification effect extends beyond the depth of the water table,impacting the entire embankment–foundation cross-section,and intensifies with higher train speeds.However,the water table rise has a limited impact on the critical speed of trains and dominant frequency contents.The dynamic response of the embankment is more significantly affected by water table rises within the subgrade than by those within the ground.When the water table rises into the subgrade,significant excess pore pressure is generated inside the embankment,causing a substantial drop in effective stress.As a result,the stress path of the soil elements in the subgrade approaches the Mohr-Coulomb failure line,increasing the likelihood of soil failure.展开更多
Rolling noise is produced by vibration of the wheels and track,induced by their combined surface roughness.It is important to know the relative contributions of the different sources,as this affects noise control stra...Rolling noise is produced by vibration of the wheels and track,induced by their combined surface roughness.It is important to know the relative contributions of the different sources,as this affects noise control strategies as well as acceptance testing of new rolling stock.Three different techniques are described that aim to use pass-by measurements to separate the wheel and track components of rolling noise.One is based on the TWINS model,which is tuned to measured track vibration.The second is based on the advanced transfer path analysis method,which provides an entirely experimental assessment.The third is based on the pass-by analysis method in combination with static vibroacoustic transfer functions which are obtained using a reciprocity method.The development of these methods is described and comparisons between them are presented using the results from three experimental measurement campaigns.These covered a metro train,a regional train and a high-speed train at a range of speeds.The various methods agree reasonably well in terms of overall trends,with moderate agreement in the mid-frequency region,and less consistent results at low and high frequency.展开更多
Acoustic models of railway vehicles in standstill and pass-by conditions can be used as part of a virtual certification process for new trains.For each piece of auxiliary equipment,the sound power measured on a test b...Acoustic models of railway vehicles in standstill and pass-by conditions can be used as part of a virtual certification process for new trains.For each piece of auxiliary equipment,the sound power measured on a test bench is combined with meas-ured or predicted transfer functions.It is important,however,to allow for installation effects due to shielding by fairings or the train body.In the current work,fast-running analytical models are developed to determine these installation effects.The model for roof-mounted sources takes account of diffraction at the corner of the train body or fairing,using a barrier model.For equipment mounted under the train,the acoustic propagation from the sides of the source is based on free-field Green’s functions.The bottom surfaces are assumed to radiate initially into a cavity under the train,which is modelled with a simple diffuse field approach.The sound emitted from the gaps at the side of the cavity is then assumed to propagate to the receivers according to free-field Green’s functions.Results show good agreement with a 2.5D boundary element model and with measurements.Modelling uncertainty and parametric uncertainty are evaluated.The largest variability occurs due to the height and impedance of the ground,especially for a low receiver.This leads to standard deviations of up to 4 dB at low frequencies.For the roof-mounted sources,uncertainty over the location of the corner used in the equivalent barrier model can also lead to large standard deviations.展开更多
The pantograph and its recess on the train roof are major aerodynamic noise sources on high-speed trains.Reducing this noise is particularly important because conventional noise barriers usually do not shield the pant...The pantograph and its recess on the train roof are major aerodynamic noise sources on high-speed trains.Reducing this noise is particularly important because conventional noise barriers usually do not shield the pantograph.However,less attention has been paid to the pantograph recess compared with the pantograph.In this paper,the flow features and noise contribution of two types of noise reduction treatments rounded and chamfered edges are studied for a simplified high-speed train pantograph recess,which is represented as a rectangular cavity and numerically investigated at 1/10 scale.Improved delayed detached-eddy simulations are performed for the near-field turbulent flow simulation,and the Ffowcs Williams and Hawkings aeroacoustic analogy is used for far-field noise prediction.The highly unsteady flow over the cavity is significantly reduced by the cavity edge modifications,and consequently,the noise radiated from the cavity is reduced.Furthermore,effects of the rounded cavity edges on the flow and noise of the pantographs(one raised and one folded)are investigated by comparing the flow features and noise contributions from the cases with and without rounding of the cavity edges.Different train running directions are also considered.Flow analysis shows that the highly unsteady flow within the cavity is reduced by rounding the cavity edges and a slightly lower flow speed occurs around the upper parts of the raised pantograph,whereas the flow velocity in the cavity is slightly increased by the rounding.Higher pressure fluctuations occur on the folded pantograph and the lower parts of the raised pantograph,whereas weaker fluctuations are found on the panhead of the raised pantograph.This study shows that by rounding the cavity edges,a reduction in radiated noise at the side and the top receiver positions can be achieved.Noise reductions in the other directions can also be found.展开更多
AIM: To demonstrate the potential of using 2-aminothiazoline-4-carboxylic acid(ATCA) as a novel biomarker/forensic biomarker for cyanide poisoning. METHODS: A sensitive method was developed and employed for the identi...AIM: To demonstrate the potential of using 2-aminothiazoline-4-carboxylic acid(ATCA) as a novel biomarker/forensic biomarker for cyanide poisoning. METHODS: A sensitive method was developed and employed for the identification and quantification of ATCA in biological samples, where the sample extraction and clean up were achieved by solid phase extraction(SPE). After optimization of SPE procedures, ATCA was analyzed by high performance liquid chromatographytandem mass spectrometry. ATCA levels following the administration of different doses of potassium cyanide(KCN) to mice were measured and compared to endogenous ATCA levels in order to study the significance of using ATCA as a biomarker for cyanide poisoning.RESULTS: A custom made analytical method was established for a new(mice) model when animals were exposed to increasing KCN doses. The application of this method provided important new information on ATCA as a potential cyanide biomarker. ATCA concentration in mice plasma samples were increased from 189 ± 28 ng/mL(n = 3) to 413 ± 66 ng/mL(n = 3) following a 10 mg/kg body weight dose of KCN introduced subcutaneously. The sensitivity of this analytical method proved to be a tool for measuring endogenous level of ATCA in mice organs as follows: 1.2 ± 0.1 μg/g for kidney samples, 1.6 ± 0.1 μg/g for brain samples, 1.8 ± 0.2 μg/g for lung samples, 2.9 ± 0.1 μg/g for heart samples, and 3.6 ± 0.9 μg/g for liver samples. CONCLUSION: This finding suggests that ATCA has the potential to serve as a plasma biomarker / forensic biomarker for cyanide poisoning.展开更多
The bogie region is a significant source of aerodynamic noise on high-speed trains. Owing to its complex geometry and flow field, numerical simulations using computational fluid dynamics are especially challenging. Th...The bogie region is a significant source of aerodynamic noise on high-speed trains. Owing to its complex geometry and flow field, numerical simulations using computational fluid dynamics are especially challenging. The main challenge is to achieve a grid with adequate resolution,especially in the boundary layer, while ensuring computational affordability. This challenge is addressed here by employing a hybrid grid,integrating a structured hexahedral mesh near solid surfaces with an unstructured polyhedral mesh in the remaining volume. To limit the number of cells in the boundary layer region, the delayed detached eddy simulation method is adopted. Additionally, to achieve a further reduction in the cell count, the Reynolds number of the model is decreased by scaling down the model size and lowering the inflow speed. The hybrid grid generation and numerical settings are guided by validated simulations of flow over cylinders. A grid sensitivity study, conducted with a simplified half-width bogie model, reveals the meshing requirements for the full-width model. Aerodynamic results highlight the rear section of the cavity and bogie as primary noise sources, emphasizing the critical role of the detached shear layer from upstream components.Time-resolved surface pressure data are input into the Ffowcs Williams–Hawkings equation for far-field noise calculation. The results indicate that the sound energy is concentrated below 200 Hz in the full-scale model, with the cavity contributing more than the bogie. This study provides a practical numerical approach for simulating a structure with complex geometry, offering insights for realistic model simulations.展开更多
基金supported by the National Key Research and Development Program Young Scientist Project(No.2024YFC2911000)the National Natural Science Foundation of China(No.52108308).
文摘A rising water table increases soil water content,reduces soil strength,and amplifies vibrations under identical train loads,thereby posing greater risks to train operations.To investigate this phenomenon,we used a 2.5D finite element(FE)model of a coupled vehicle–embankment–ground system based on Biot’s theory.The ground properties were derived from a typical soil profile of the Yangtze River basin,using geological data from Shanghai,China.The findings indicate that a rise in the water table leads to increased dynamic displacements of both the track and the ground.This amplification effect extends beyond the depth of the water table,impacting the entire embankment–foundation cross-section,and intensifies with higher train speeds.However,the water table rise has a limited impact on the critical speed of trains and dominant frequency contents.The dynamic response of the embankment is more significantly affected by water table rises within the subgrade than by those within the ground.When the water table rises into the subgrade,significant excess pore pressure is generated inside the embankment,causing a substantial drop in effective stress.As a result,the stress path of the soil elements in the subgrade approaches the Mohr-Coulomb failure line,increasing the likelihood of soil failure.
基金supported by the TRANSIT project(funded by EU Horizon 2020 and the Europe’s Rail Joint Undertaking under grant agreement 881771).
文摘Rolling noise is produced by vibration of the wheels and track,induced by their combined surface roughness.It is important to know the relative contributions of the different sources,as this affects noise control strategies as well as acceptance testing of new rolling stock.Three different techniques are described that aim to use pass-by measurements to separate the wheel and track components of rolling noise.One is based on the TWINS model,which is tuned to measured track vibration.The second is based on the advanced transfer path analysis method,which provides an entirely experimental assessment.The third is based on the pass-by analysis method in combination with static vibroacoustic transfer functions which are obtained using a reciprocity method.The development of these methods is described and comparisons between them are presented using the results from three experimental measurement campaigns.These covered a metro train,a regional train and a high-speed train at a range of speeds.The various methods agree reasonably well in terms of overall trends,with moderate agreement in the mid-frequency region,and less consistent results at low and high frequency.
基金The work described here has been supported by the TRANSIT project(funded by EU Horizon 2020 and the Europe’s Rail Joint Undertaking under grant agreement 881771).
文摘Acoustic models of railway vehicles in standstill and pass-by conditions can be used as part of a virtual certification process for new trains.For each piece of auxiliary equipment,the sound power measured on a test bench is combined with meas-ured or predicted transfer functions.It is important,however,to allow for installation effects due to shielding by fairings or the train body.In the current work,fast-running analytical models are developed to determine these installation effects.The model for roof-mounted sources takes account of diffraction at the corner of the train body or fairing,using a barrier model.For equipment mounted under the train,the acoustic propagation from the sides of the source is based on free-field Green’s functions.The bottom surfaces are assumed to radiate initially into a cavity under the train,which is modelled with a simple diffuse field approach.The sound emitted from the gaps at the side of the cavity is then assumed to propagate to the receivers according to free-field Green’s functions.Results show good agreement with a 2.5D boundary element model and with measurements.Modelling uncertainty and parametric uncertainty are evaluated.The largest variability occurs due to the height and impedance of the ground,especially for a low receiver.This leads to standard deviations of up to 4 dB at low frequencies.For the roof-mounted sources,uncertainty over the location of the corner used in the equivalent barrier model can also lead to large standard deviations.
基金This research project has been supported by the Iridis 4 and Lyceum High Performance Computing Facility at the University of Southampton.
文摘The pantograph and its recess on the train roof are major aerodynamic noise sources on high-speed trains.Reducing this noise is particularly important because conventional noise barriers usually do not shield the pantograph.However,less attention has been paid to the pantograph recess compared with the pantograph.In this paper,the flow features and noise contribution of two types of noise reduction treatments rounded and chamfered edges are studied for a simplified high-speed train pantograph recess,which is represented as a rectangular cavity and numerically investigated at 1/10 scale.Improved delayed detached-eddy simulations are performed for the near-field turbulent flow simulation,and the Ffowcs Williams and Hawkings aeroacoustic analogy is used for far-field noise prediction.The highly unsteady flow over the cavity is significantly reduced by the cavity edge modifications,and consequently,the noise radiated from the cavity is reduced.Furthermore,effects of the rounded cavity edges on the flow and noise of the pantographs(one raised and one folded)are investigated by comparing the flow features and noise contributions from the cases with and without rounding of the cavity edges.Different train running directions are also considered.Flow analysis shows that the highly unsteady flow within the cavity is reduced by rounding the cavity edges and a slightly lower flow speed occurs around the upper parts of the raised pantograph,whereas the flow velocity in the cavity is slightly increased by the rounding.Higher pressure fluctuations occur on the folded pantograph and the lower parts of the raised pantograph,whereas weaker fluctuations are found on the panhead of the raised pantograph.This study shows that by rounding the cavity edges,a reduction in radiated noise at the side and the top receiver positions can be achieved.Noise reductions in the other directions can also be found.
基金Supported by NIH:NIAID/USAMRICD Interagency Agreements(W911NF-07-D-0001)the USAMRICD under the auspices of the US Army Research Office Scientific Services Program administered by Battelle(Delivery order 0557,Contract No TCN 08284)the Robert A.Welch Foundation at Sam Houston State University,Huntsville,TX,United States
文摘AIM: To demonstrate the potential of using 2-aminothiazoline-4-carboxylic acid(ATCA) as a novel biomarker/forensic biomarker for cyanide poisoning. METHODS: A sensitive method was developed and employed for the identification and quantification of ATCA in biological samples, where the sample extraction and clean up were achieved by solid phase extraction(SPE). After optimization of SPE procedures, ATCA was analyzed by high performance liquid chromatographytandem mass spectrometry. ATCA levels following the administration of different doses of potassium cyanide(KCN) to mice were measured and compared to endogenous ATCA levels in order to study the significance of using ATCA as a biomarker for cyanide poisoning.RESULTS: A custom made analytical method was established for a new(mice) model when animals were exposed to increasing KCN doses. The application of this method provided important new information on ATCA as a potential cyanide biomarker. ATCA concentration in mice plasma samples were increased from 189 ± 28 ng/mL(n = 3) to 413 ± 66 ng/mL(n = 3) following a 10 mg/kg body weight dose of KCN introduced subcutaneously. The sensitivity of this analytical method proved to be a tool for measuring endogenous level of ATCA in mice organs as follows: 1.2 ± 0.1 μg/g for kidney samples, 1.6 ± 0.1 μg/g for brain samples, 1.8 ± 0.2 μg/g for lung samples, 2.9 ± 0.1 μg/g for heart samples, and 3.6 ± 0.9 μg/g for liver samples. CONCLUSION: This finding suggests that ATCA has the potential to serve as a plasma biomarker / forensic biomarker for cyanide poisoning.
基金The Ministry of Science and Technology of China has supported the work presented in this paper through the National Key Research and Development Program Grant No. 2016YFE0205200, “Joint Research into Key Technologies for Controlling Noise and Vibration of High-Speed Railways Under Extremely Complicated Conditions”
文摘The bogie region is a significant source of aerodynamic noise on high-speed trains. Owing to its complex geometry and flow field, numerical simulations using computational fluid dynamics are especially challenging. The main challenge is to achieve a grid with adequate resolution,especially in the boundary layer, while ensuring computational affordability. This challenge is addressed here by employing a hybrid grid,integrating a structured hexahedral mesh near solid surfaces with an unstructured polyhedral mesh in the remaining volume. To limit the number of cells in the boundary layer region, the delayed detached eddy simulation method is adopted. Additionally, to achieve a further reduction in the cell count, the Reynolds number of the model is decreased by scaling down the model size and lowering the inflow speed. The hybrid grid generation and numerical settings are guided by validated simulations of flow over cylinders. A grid sensitivity study, conducted with a simplified half-width bogie model, reveals the meshing requirements for the full-width model. Aerodynamic results highlight the rear section of the cavity and bogie as primary noise sources, emphasizing the critical role of the detached shear layer from upstream components.Time-resolved surface pressure data are input into the Ffowcs Williams–Hawkings equation for far-field noise calculation. The results indicate that the sound energy is concentrated below 200 Hz in the full-scale model, with the cavity contributing more than the bogie. This study provides a practical numerical approach for simulating a structure with complex geometry, offering insights for realistic model simulations.
