研究目的:本文以某山地米轨铁路为例,研究坡度250‰以上有砟轨道结构的稳定性和极限坡度。首先进行米轨混凝土枕的道床阻力测试试验,并建立轨排结构有限元模型,分析坡度和扣件阻力对轨排结构稳定性的影响;接着建立米轨有砟轨道三维有限...研究目的:本文以某山地米轨铁路为例,研究坡度250‰以上有砟轨道结构的稳定性和极限坡度。首先进行米轨混凝土枕的道床阻力测试试验,并建立轨排结构有限元模型,分析坡度和扣件阻力对轨排结构稳定性的影响;接着建立米轨有砟轨道三维有限元模型,研究坡度与竖曲线半径对有砟道床稳定性的影响;最后,根据扣件阻力、道床阻力与大坡道有砟轨道稳定性的关系提出米轨有砟轨道极限坡度和竖曲线半径的建议值。研究结论:(1)通过试验测试,得到了道床阻力-位移关系,结果表明轨排结构的稳定性随坡度增大而减弱,在扣件阻力不大于10 k N/组时其极限坡度为500‰;(2)有砟道床的稳定性随着坡度的增大而逐渐减弱,在列车荷载作用下,有砟道床保持稳定的最大坡度为500‰;(3)变坡点凸形竖曲线附近道床稳定性弱于直坡道地段,且其稳定性随着竖曲线半径的增大而逐渐增强,在坡度为250‰的情况下,为了保持有砟道床稳定竖曲线半径不能小于400 m;(4)本文研究成果可为米轨铁路大坡道有砟轨道结构稳定性分析提供理论与试验依据。展开更多
Rail wear has dramatic impact on track performance, ride quality and maintenance costs. The amount of rail wear is influenced by various elements among which geometric parameters play an important role. The amount of ...Rail wear has dramatic impact on track performance, ride quality and maintenance costs. The amount of rail wear is influenced by various elements among which geometric parameters play an important role. The amount of wear in Iran’s railway lines and its imposed maintenance costs oblige us to make modifications on the various geometrical parameters. In order to ensure the effectiveness of these changes, it is necessary to investigate these parameters and their effects on the wear. This research is aimed at studying the effects of different track geometrical parameters on the vertical and lateral wear by conducting a three phase field investigation. The first phase was carried out at the switches of a station, the second phase at a straight line, and the third at a curved line out of the station. The results obtained are analyzed and the role of each track geometrical parameter in the rail wear is discussed. Recommendations for prevention or reduction of rail wear are presented.展开更多
Existing studies contend that latent heating(LH)will replace sensible heating(SH)to become the dominant factor affecting the development of the Tibetan Plateau vortex(TPV)after it moves off the Tibetan Plateau(TP).How...Existing studies contend that latent heating(LH)will replace sensible heating(SH)to become the dominant factor affecting the development of the Tibetan Plateau vortex(TPV)after it moves off the Tibetan Plateau(TP).However,in the process of the TPV moving off the TP requires that the airmass traverse the eastern slope of the Tibetan Plateau(ESTP)where the topography and diabatic heating(DH)conditions rapidly change.How LH gradually replaces SH to become the dominant factor in the development of the TPV over the ESTP is still not very clear.In this paper,an analysis of a typical case of a TPV with a long life history over the ESTP is performed by using multi-sourced meteorological data and model simulations.The results show that SH from the TP surface can change the TPV-associated precipitation distribution by temperature advection after the TPV moves off the TP.The LH can then directly promote the development of the TPV and has a certain guiding effect on the track of the TPV.The SH can control the active area of LH by changing the falling area of the TPV-associated precipitation,so it still plays a key role in the development and tracking of the TPV even though it has moved out of the main body of the TP.展开更多
This paper investigates the noise inside a metro coach running through the most recent tunnel of Cairo.The study focuses on the effects of alignment profiles on the A-weighted noise level.Although the latest line has ...This paper investigates the noise inside a metro coach running through the most recent tunnel of Cairo.The study focuses on the effects of alignment profiles on the A-weighted noise level.Although the latest line has not been studied yet,noise levels inside the old lines attracted the attention of researchers due to their importance as the first mass transit system in Africa.Given that windows are usually kept open,measurements were conducted inside the empty cabin at the end of the train with open windows according to ISO 3381:2005.Results showed that noise emissions inside the running coaches are high and do not follow either international or general national legislation,which presents health hazards for drivers and commuters.Speech intelligibility is required for train radio units and driver consoles for voice communications,which provides a safe working environment for the train crew.The present study reveals that tight curves mainly contribute to high noise.The noise levels are further raised by the reflective surface of the tunnel with a circular cross-section and the unballasted track.Moreover,the noise level is affected by the location of the coach and window conditions(open/close)to some extent.展开更多
A joint-pixel clutter suppression method based on slope compensation is proposed in this paper, In order to eliminate the effect of the terrain interferometric phase caused by the cross-track baseline in hybrid baseli...A joint-pixel clutter suppression method based on slope compensation is proposed in this paper, In order to eliminate the effect of the terrain interferometric phase caused by the cross-track baseline in hybrid baseline InSAR, the local independent identical distribution of the clutter is satisfied by using the slope compensation technique, and thus the clutter can be suppressed successfully by using the orthogonality of the clutter subspace and the noise subspace. This approach utilizes the information contained in the current pixel as well as in its neighbors, showing robustness to the image coregistration errors. Both the simulated data and the real airborne data are used in proving the validity of the presented approach.展开更多
文摘研究目的:本文以某山地米轨铁路为例,研究坡度250‰以上有砟轨道结构的稳定性和极限坡度。首先进行米轨混凝土枕的道床阻力测试试验,并建立轨排结构有限元模型,分析坡度和扣件阻力对轨排结构稳定性的影响;接着建立米轨有砟轨道三维有限元模型,研究坡度与竖曲线半径对有砟道床稳定性的影响;最后,根据扣件阻力、道床阻力与大坡道有砟轨道稳定性的关系提出米轨有砟轨道极限坡度和竖曲线半径的建议值。研究结论:(1)通过试验测试,得到了道床阻力-位移关系,结果表明轨排结构的稳定性随坡度增大而减弱,在扣件阻力不大于10 k N/组时其极限坡度为500‰;(2)有砟道床的稳定性随着坡度的增大而逐渐减弱,在列车荷载作用下,有砟道床保持稳定的最大坡度为500‰;(3)变坡点凸形竖曲线附近道床稳定性弱于直坡道地段,且其稳定性随着竖曲线半径的增大而逐渐增强,在坡度为250‰的情况下,为了保持有砟道床稳定竖曲线半径不能小于400 m;(4)本文研究成果可为米轨铁路大坡道有砟轨道结构稳定性分析提供理论与试验依据。
文摘Rail wear has dramatic impact on track performance, ride quality and maintenance costs. The amount of rail wear is influenced by various elements among which geometric parameters play an important role. The amount of wear in Iran’s railway lines and its imposed maintenance costs oblige us to make modifications on the various geometrical parameters. In order to ensure the effectiveness of these changes, it is necessary to investigate these parameters and their effects on the wear. This research is aimed at studying the effects of different track geometrical parameters on the vertical and lateral wear by conducting a three phase field investigation. The first phase was carried out at the switches of a station, the second phase at a straight line, and the third at a curved line out of the station. The results obtained are analyzed and the role of each track geometrical parameter in the rail wear is discussed. Recommendations for prevention or reduction of rail wear are presented.
基金supported by the National Natural Science Foundation of China(Grant Nos.42175002,42030611,42075013)the Natural Science Foundation of Sichuan,China(Grant No.2023NSFSC0242)the Innovation Team Fund of Southwest Regional Meteorological Center,China Meteorological Administration(Grant No.XNQYCXTD-202202)。
文摘Existing studies contend that latent heating(LH)will replace sensible heating(SH)to become the dominant factor affecting the development of the Tibetan Plateau vortex(TPV)after it moves off the Tibetan Plateau(TP).However,in the process of the TPV moving off the TP requires that the airmass traverse the eastern slope of the Tibetan Plateau(ESTP)where the topography and diabatic heating(DH)conditions rapidly change.How LH gradually replaces SH to become the dominant factor in the development of the TPV over the ESTP is still not very clear.In this paper,an analysis of a typical case of a TPV with a long life history over the ESTP is performed by using multi-sourced meteorological data and model simulations.The results show that SH from the TP surface can change the TPV-associated precipitation distribution by temperature advection after the TPV moves off the TP.The LH can then directly promote the development of the TPV and has a certain guiding effect on the track of the TPV.The SH can control the active area of LH by changing the falling area of the TPV-associated precipitation,so it still plays a key role in the development and tracking of the TPV even though it has moved out of the main body of the TP.
基金The authors wish to express their gratitude to Prof.Dr.Tamer Elnady,Eng.Ahmed Abu Sariaa,Eng.Mina Wagih,Dr.Ashraf Abu Kresha,Mr.Michael Weekes,Mr.Malcolm Peart,Eng.Sherok El Gebaly,and the staff of the Egyptian Company for Metro Management.
文摘This paper investigates the noise inside a metro coach running through the most recent tunnel of Cairo.The study focuses on the effects of alignment profiles on the A-weighted noise level.Although the latest line has not been studied yet,noise levels inside the old lines attracted the attention of researchers due to their importance as the first mass transit system in Africa.Given that windows are usually kept open,measurements were conducted inside the empty cabin at the end of the train with open windows according to ISO 3381:2005.Results showed that noise emissions inside the running coaches are high and do not follow either international or general national legislation,which presents health hazards for drivers and commuters.Speech intelligibility is required for train radio units and driver consoles for voice communications,which provides a safe working environment for the train crew.The present study reveals that tight curves mainly contribute to high noise.The noise levels are further raised by the reflective surface of the tunnel with a circular cross-section and the unballasted track.Moreover,the noise level is affected by the location of the coach and window conditions(open/close)to some extent.
基金Supported in part by the National Nature Science Foundation of China (Grant No. 60802074)the Program for New Century Excellent Talents in University
文摘A joint-pixel clutter suppression method based on slope compensation is proposed in this paper, In order to eliminate the effect of the terrain interferometric phase caused by the cross-track baseline in hybrid baseline InSAR, the local independent identical distribution of the clutter is satisfied by using the slope compensation technique, and thus the clutter can be suppressed successfully by using the orthogonality of the clutter subspace and the noise subspace. This approach utilizes the information contained in the current pixel as well as in its neighbors, showing robustness to the image coregistration errors. Both the simulated data and the real airborne data are used in proving the validity of the presented approach.
