Rail weld irregularities are one of the primary excitation sources for vehicle-track interaction dynamics in modern high-speed railways.They can cause significant wheel-rail dynamic interactions,leading to wheel-rail ...Rail weld irregularities are one of the primary excitation sources for vehicle-track interaction dynamics in modern high-speed railways.They can cause significant wheel-rail dynamic interactions,leading to wheel-rail noise,component damage,and deterioration.Few researchers have employed the vehicle-track interaction dynamic model to study the dynamic interactions between wheel and rail induced by rail weld geometry irregularities.However,the cosine wave model used to simulate rail weld irregularities mainly focuses on the maximum value and neglects the geometric shape.In this study,novel theoretical models were developed for three categories of rail weld irregularities,based on measurements of the high-speed railway from Beijing to Shanghai.The vertical dynamic forces in the time and frequency domains were compared under different running speeds.These forces generated by the rail weld irregularities that were measured and modeled,respectively,were compared to validate the accuracy of the proposed model.Finally,based on the numerical study,the impact force due to rail weld irrregularity is modeled using an Artificial Neural Network(ANN),and the optimum combination of parameters for this model is found.The results showed that the proposed model provided a more accurate wheel/rail dynamic evaluation caused by rail weld irregularities than that established in the literature.The ANN model used in this paper can effectively predict the impact force due to rail weld irrregularity while reducing the computation time.展开更多
A new type of vibration structure (i.e. supporting system, called swing frame cus- tomarily) of vertical dynamic balancing machine has been designed, which is based on an analysis for the swing frame of a traditiona...A new type of vibration structure (i.e. supporting system, called swing frame cus- tomarily) of vertical dynamic balancing machine has been designed, which is based on an analysis for the swing frame of a traditional double-plane vertical dynamic balancing machine. The static unbalance and couple unbalance can be e?ectively separated by using the new dynamic balancing machine with the new swing frame. By building the dynamics model, the advantages of the new structure are discussed in detail. The modal and harmonic response are analyzed by using the ANSYS7.0. By comparing the ?nite element modal analysis with the experimental modal analy- sis, the natural frequencies and vibration modes are found. There are many spring boards in the new swing frame. Their sti?nesses are di?erent and assorted with each other. Furthermore, there are three sensors on the measuring points. Therefore, the new dynamic balancing machine can measure static unbalance and coupling unbalance directly, and the interaction between them is faint. The result shows that the new vertical dynamic balancing machine is suitable for inertial measurement of ?ying objects, and can overcome the shortcomings of traditional double-plane vertical dynamic balancing machines, which the e?ect of plane-separation is inferior. The vertical dynamic balancing machine with the new vibration structure can ?nd wide application in the future. The modelling and analysis of the new vibration structure will provide theoretical basis and practical experience for designing new-type vertical dynamic balancing machines.展开更多
An analytical method is developed to investigate the dynamic response of a pile subjected to harmonic vertical loading.The pile is modeled as a one-dimensional（1D）elastic rod.The elastic soil is divided into a homog...An analytical method is developed to investigate the dynamic response of a pile subjected to harmonic vertical loading.The pile is modeled as a one-dimensional（1D）elastic rod.The elastic soil is divided into a homogeneous half space underlying the base of pile and a series of infinitesimally thin layers along the vertical shaft of pile.The analytical solution for the soil-pile dynamic interaction problem is obtained by the method of Hankel transformation.The proposed solution is compared with the classical plane strain solution.Arithmetical examples are presented to demonstrate the sensitivity of the vertical impedance of the pile to relevant parameters.展开更多
Ground motions are significantly influenced by dynamic characteristics of overburden soil layers near ground surface,as thick and soft soil layers would obviously amplify the ground motion strength. The conventional r...Ground motions are significantly influenced by dynamic characteristics of overburden soil layers near ground surface,as thick and soft soil layers would obviously amplify the ground motion strength. The conventional research method on soil nonlinear dynamic characteristics under strong motions is based on experiments in laboratories for the deficiency of observation data,but it is difficult to reliably simulate the complex factors of soils in actual earthquake durations,including loading paths,boundary conditions,and drainage conditions. The incremental data of the vertical downhole observation array,which is comprised of at least one observation point on ground surface and one observation point in a downhole rock base, makes it possible to study soil nonlinear dynamics according to in situ observation data,and provides new basic data and development opportunities to soil nonlinear dynamics studies.展开更多
To analyse the vertical dynamic characteristics of the aircraft towing system under different constraints on the nose landing gear wheels of the aircraft during the towing slip-out mode,a dynamic model of the towing s...To analyse the vertical dynamic characteristics of the aircraft towing system under different constraints on the nose landing gear wheels of the aircraft during the towing slip-out mode,a dynamic model of the towing system considering the constraints between the clamping mechanism and the aircraft nose landing gear wheels was established based on the general towing system dynamic model.On this basis,an analysis was conducted to determine whether considering the aircraft wheel constraints affects the vertical vibration acceleration of the towing vehicle and the nose landing gear in low-speed(10 km/h)and high-speed(40 km/h)operating conditions.With the consideration of constraints at both ends of the aircraft wheels,the vertical acceleration of the towing vehicle’s centre of mass increased by 153%and 172%at low speed and high speed,respectively,compared to not considering the aircraft wheel constraints.Additionally,with the consideration of constraints at both ends of the aircraft wheels,the vertical acceleration of the nose landing gear’s centre of mass decreased to 20%and 57%at low speed and high speed,respectively,compared to not considering the aircraft wheel constraints.An analysis of the vertical vibration acceleration of the towing vehicle under different wheel constraint conditions found that the Root Mean Square(RMS)value of the vertical vibration acceleration of the towing vehicle’s centre of mass was minimized when the clamping angles of the clamping mechanism to the nose landing gear wheels were 63◦and 64◦,respectively.Under this clamping angle,the influence of the clamping forces at both ends of the clamping mechanism on the vertical vibration acceleration of the towing vehicle was minimal.The research results provide valuable reference for the direct constraints between the clamping mechanism and the nose landing gear wheels in the aircraft towing slip-out system.展开更多
The influence of a vertical jet located at the distributor in a cylindrical fluidized bed on the flow behavior of gas and particles was predicted using a filtered two-fluid model proposed by Sundaresan and coworkers. ...The influence of a vertical jet located at the distributor in a cylindrical fluidized bed on the flow behavior of gas and particles was predicted using a filtered two-fluid model proposed by Sundaresan and coworkers. The distributions of volume fraction and the velocity of particles along the lateral direction were investigated for different jet velocities by analyzing the simulated results. The vertical jet penetration lengths at the different gas jet velocities have been obtained and compared with predictions derived from empirical correlations; the predicted air jet penetration length is discussed. Agreement between the numerical simulations and experimental results has been achieved.展开更多
The response of the South China Sea（SCS） to Typhoon Chanchu（2006） was examined using the MM5 and POM model. In the POM model, sea surface boundary conditions were forced by the simulation wind field from MM5, the ...The response of the South China Sea（SCS） to Typhoon Chanchu（2006） was examined using the MM5 and POM model. In the POM model, sea surface boundary conditions were forced by the simulation wind field from MM5, the velocity forcing was introduced in the eastern boundary and the computational schemes of heat fluxes at the surface were introduced. Comparison with the observation data shows that the simulated results are reliable. In the response process of the SCS to Typhoon Chanchu, the influence of the heat fluxes on thermal structure of the SCS was regionally different. Strong wind forcing would lead to upwelling phenomenon in the lateral boundary of deep water basin. Furthermore, the Ekman pumping theory was used to discuss subsurface upwelling and downwelling phenomenon in typhoon forced stage.展开更多
In order to reflect the vertical random vibration characteristics of railway vehicles more truly and effectively,this paper regards the human body as a single-degree-of-freedom system attached to the bottom of the car...In order to reflect the vertical random vibration characteristics of railway vehicles more truly and effectively,this paper regards the human body as a single-degree-of-freedom system attached to the bottom of the carriage,and establishes a vertical dynamic model of railway vehicles by considering the influence of the coupling vibration effect between the passenger and the car body.The correctness of the model is verified by the real vehicle test.Then,the influence of the passengers on the vertical vibration characteristics of railway vehicles is analyzed,and the influence of the railway vehicle vibration on the vertical vibration characteristics of passengers is discussed in this paper.The research made in this paper can provide an effective model reference for the analysis of the vertical random vibration characteristics of railway vehicles and passengers,and for the optimization design of the suspension system parameters.展开更多
The seat-cabin system of fork lift trucks has a great influence on ride comfort.On the basis of the structure and characteristics of the seat-cabin system for a high-grade fork lift truck,a seat-cabin system vertical ...The seat-cabin system of fork lift trucks has a great influence on ride comfort.On the basis of the structure and characteristics of the seat-cabin system for a high-grade fork lift truck,a seat-cabin system vertical dynamic model was created.The vertical dynamic responses of the model under the random irregularities excitation were calculated.The calculated responses including the seat dynamic response and the cabin dynamic responses at the four corners are very close to the field measurement data and the relative deviations of the(root mean square)RMS acceleration responses are all less than 6.0%.The results show that the vertical dynamic model is acceptable and can truly describe the basic mechanical behavior of the seat-cabin system.The model provides a good basis for investigating the relations between the dynamic parameters and the vibration attenuation characteristics of the seat-cabin system to further improve ride comfort.展开更多
This study first investigates the effect of the Madden-Julian Oscillation(MJO)on the Northern Hemisphere(NH)mesosphere.Both observations and simulations suggest significant cooling in the NH polar mesosphere approxima...This study first investigates the effect of the Madden-Julian Oscillation(MJO)on the Northern Hemisphere(NH)mesosphere.Both observations and simulations suggest significant cooling in the NH polar mesosphere approximately 35 days after MJO phase 4(P4),which lags the MJO-induced perturbation in the upper stratosphere by 10 days.The enhanced planetary waves(PWs)propagate upward and result in wavenumber-1 pattern temperature anomalies in the mesosphere lagging MJO P4 by 25 days.The anomalous PWs also lead to the weaker eastward zonal wind in the upper stratosphere and lower mesosphere lagging MJO P4 by 30 days.Simultaneously,the weaker westerlies result in weaker climatological westward gravity waves(GWs)in the mesosphere due to critical-level filtering.The mesosphere meridional circulation is suppressed due to both anomalous PWs and GWs,and this suppression causes polar mesospheric cooling lagging MJO P4 by 35 days.展开更多
基金supported by Natural Science Foundation of China(52178441)the Scientific Research Projects of the China Academy of Railway Sciences Co.,Ltd.(Grant No.2022YJ043).
文摘Rail weld irregularities are one of the primary excitation sources for vehicle-track interaction dynamics in modern high-speed railways.They can cause significant wheel-rail dynamic interactions,leading to wheel-rail noise,component damage,and deterioration.Few researchers have employed the vehicle-track interaction dynamic model to study the dynamic interactions between wheel and rail induced by rail weld geometry irregularities.However,the cosine wave model used to simulate rail weld irregularities mainly focuses on the maximum value and neglects the geometric shape.In this study,novel theoretical models were developed for three categories of rail weld irregularities,based on measurements of the high-speed railway from Beijing to Shanghai.The vertical dynamic forces in the time and frequency domains were compared under different running speeds.These forces generated by the rail weld irregularities that were measured and modeled,respectively,were compared to validate the accuracy of the proposed model.Finally,based on the numerical study,the impact force due to rail weld irrregularity is modeled using an Artificial Neural Network(ANN),and the optimum combination of parameters for this model is found.The results showed that the proposed model provided a more accurate wheel/rail dynamic evaluation caused by rail weld irregularities than that established in the literature.The ANN model used in this paper can effectively predict the impact force due to rail weld irrregularity while reducing the computation time.
基金Project supported by the National Natural Science Foundation of China (No.10176011).
文摘A new type of vibration structure (i.e. supporting system, called swing frame cus- tomarily) of vertical dynamic balancing machine has been designed, which is based on an analysis for the swing frame of a traditional double-plane vertical dynamic balancing machine. The static unbalance and couple unbalance can be e?ectively separated by using the new dynamic balancing machine with the new swing frame. By building the dynamics model, the advantages of the new structure are discussed in detail. The modal and harmonic response are analyzed by using the ANSYS7.0. By comparing the ?nite element modal analysis with the experimental modal analy- sis, the natural frequencies and vibration modes are found. There are many spring boards in the new swing frame. Their sti?nesses are di?erent and assorted with each other. Furthermore, there are three sensors on the measuring points. Therefore, the new dynamic balancing machine can measure static unbalance and coupling unbalance directly, and the interaction between them is faint. The result shows that the new vertical dynamic balancing machine is suitable for inertial measurement of ?ying objects, and can overcome the shortcomings of traditional double-plane vertical dynamic balancing machines, which the e?ect of plane-separation is inferior. The vertical dynamic balancing machine with the new vibration structure can ?nd wide application in the future. The modelling and analysis of the new vibration structure will provide theoretical basis and practical experience for designing new-type vertical dynamic balancing machines.
基金supported by the National Natural Science Foundation of China (no.51622803 and 51420105013)
文摘An analytical method is developed to investigate the dynamic response of a pile subjected to harmonic vertical loading.The pile is modeled as a one-dimensional（1D）elastic rod.The elastic soil is divided into a homogeneous half space underlying the base of pile and a series of infinitesimally thin layers along the vertical shaft of pile.The analytical solution for the soil-pile dynamic interaction problem is obtained by the method of Hankel transformation.The proposed solution is compared with the classical plane strain solution.Arithmetical examples are presented to demonstrate the sensitivity of the vertical impedance of the pile to relevant parameters.
基金funded by the Special Research Fund for Seismology(201408020)the Natural Science Foundation of China (51578514,U1434210)
文摘Ground motions are significantly influenced by dynamic characteristics of overburden soil layers near ground surface,as thick and soft soil layers would obviously amplify the ground motion strength. The conventional research method on soil nonlinear dynamic characteristics under strong motions is based on experiments in laboratories for the deficiency of observation data,but it is difficult to reliably simulate the complex factors of soils in actual earthquake durations,including loading paths,boundary conditions,and drainage conditions. The incremental data of the vertical downhole observation array,which is comprised of at least one observation point on ground surface and one observation point in a downhole rock base, makes it possible to study soil nonlinear dynamics according to in situ observation data,and provides new basic data and development opportunities to soil nonlinear dynamics studies.
基金supported by the the Fundamental Research Funds for the Central Universities,China(Grant No.3122022066)Postgraduate Research and Innovation Fund,China(Grant No.2022YJS056)National Natural Science Foundation of China(Grant No.U2033208).
文摘To analyse the vertical dynamic characteristics of the aircraft towing system under different constraints on the nose landing gear wheels of the aircraft during the towing slip-out mode,a dynamic model of the towing system considering the constraints between the clamping mechanism and the aircraft nose landing gear wheels was established based on the general towing system dynamic model.On this basis,an analysis was conducted to determine whether considering the aircraft wheel constraints affects the vertical vibration acceleration of the towing vehicle and the nose landing gear in low-speed(10 km/h)and high-speed(40 km/h)operating conditions.With the consideration of constraints at both ends of the aircraft wheels,the vertical acceleration of the towing vehicle’s centre of mass increased by 153%and 172%at low speed and high speed,respectively,compared to not considering the aircraft wheel constraints.Additionally,with the consideration of constraints at both ends of the aircraft wheels,the vertical acceleration of the nose landing gear’s centre of mass decreased to 20%and 57%at low speed and high speed,respectively,compared to not considering the aircraft wheel constraints.An analysis of the vertical vibration acceleration of the towing vehicle under different wheel constraint conditions found that the Root Mean Square(RMS)value of the vertical vibration acceleration of the towing vehicle’s centre of mass was minimized when the clamping angles of the clamping mechanism to the nose landing gear wheels were 63◦and 64◦,respectively.Under this clamping angle,the influence of the clamping forces at both ends of the clamping mechanism on the vertical vibration acceleration of the towing vehicle was minimal.The research results provide valuable reference for the direct constraints between the clamping mechanism and the nose landing gear wheels in the aircraft towing slip-out system.
基金This work was supported by the Natural Science Foundation of China through Grant No. 21676051, New Century Excellent Talents in University （NCET-12-0703）. One of the authors （Shuyan Wang） thanks the China Scholarship Council （CSC） for providing financial support to the Sundaresan＇s group of Princeton University.
文摘The influence of a vertical jet located at the distributor in a cylindrical fluidized bed on the flow behavior of gas and particles was predicted using a filtered two-fluid model proposed by Sundaresan and coworkers. The distributions of volume fraction and the velocity of particles along the lateral direction were investigated for different jet velocities by analyzing the simulated results. The vertical jet penetration lengths at the different gas jet velocities have been obtained and compared with predictions derived from empirical correlations; the predicted air jet penetration length is discussed. Agreement between the numerical simulations and experimental results has been achieved.
基金supported by the National Nature Science Foundation of China(Grant No.40906006)the Fundamental Research Funds for the Central Universities
文摘The response of the South China Sea（SCS） to Typhoon Chanchu（2006） was examined using the MM5 and POM model. In the POM model, sea surface boundary conditions were forced by the simulation wind field from MM5, the velocity forcing was introduced in the eastern boundary and the computational schemes of heat fluxes at the surface were introduced. Comparison with the observation data shows that the simulated results are reliable. In the response process of the SCS to Typhoon Chanchu, the influence of the heat fluxes on thermal structure of the SCS was regionally different. Strong wind forcing would lead to upwelling phenomenon in the lateral boundary of deep water basin. Furthermore, the Ekman pumping theory was used to discuss subsurface upwelling and downwelling phenomenon in typhoon forced stage.
基金This work is supported by the National Natural Science Foundation of China(51575325).
文摘In order to reflect the vertical random vibration characteristics of railway vehicles more truly and effectively,this paper regards the human body as a single-degree-of-freedom system attached to the bottom of the carriage,and establishes a vertical dynamic model of railway vehicles by considering the influence of the coupling vibration effect between the passenger and the car body.The correctness of the model is verified by the real vehicle test.Then,the influence of the passengers on the vertical vibration characteristics of railway vehicles is analyzed,and the influence of the railway vehicle vibration on the vertical vibration characteristics of passengers is discussed in this paper.The research made in this paper can provide an effective model reference for the analysis of the vertical random vibration characteristics of railway vehicles and passengers,and for the optimization design of the suspension system parameters.
文摘The seat-cabin system of fork lift trucks has a great influence on ride comfort.On the basis of the structure and characteristics of the seat-cabin system for a high-grade fork lift truck,a seat-cabin system vertical dynamic model was created.The vertical dynamic responses of the model under the random irregularities excitation were calculated.The calculated responses including the seat dynamic response and the cabin dynamic responses at the four corners are very close to the field measurement data and the relative deviations of the(root mean square)RMS acceleration responses are all less than 6.0%.The results show that the vertical dynamic model is acceptable and can truly describe the basic mechanical behavior of the seat-cabin system.The model provides a good basis for investigating the relations between the dynamic parameters and the vibration attenuation characteristics of the seat-cabin system to further improve ride comfort.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB 41000000)the National Natural Science Foundation of China(Grant Nos.41874180,41974175,41831071,and 41874181)the Open Research Project of Large Research Infrastructures of CAS—“Study on the interaction between low/mid-latitude atmosphere and ionosphere based on the Chinese Meridian Project”.
文摘This study first investigates the effect of the Madden-Julian Oscillation(MJO)on the Northern Hemisphere(NH)mesosphere.Both observations and simulations suggest significant cooling in the NH polar mesosphere approximately 35 days after MJO phase 4(P4),which lags the MJO-induced perturbation in the upper stratosphere by 10 days.The enhanced planetary waves(PWs)propagate upward and result in wavenumber-1 pattern temperature anomalies in the mesosphere lagging MJO P4 by 25 days.The anomalous PWs also lead to the weaker eastward zonal wind in the upper stratosphere and lower mesosphere lagging MJO P4 by 30 days.Simultaneously,the weaker westerlies result in weaker climatological westward gravity waves(GWs)in the mesosphere due to critical-level filtering.The mesosphere meridional circulation is suppressed due to both anomalous PWs and GWs,and this suppression causes polar mesospheric cooling lagging MJO P4 by 35 days.
