The safety and stability of high-speed maglev trains traveling on viaducts in crosswinds critically depend on their aerodynamic characteristics.Therefore,this paper uses an improved delayed detached eddy simulation(ID...The safety and stability of high-speed maglev trains traveling on viaducts in crosswinds critically depend on their aerodynamic characteristics.Therefore,this paper uses an improved delayed detached eddy simulation(IDDES)method to investigate the aerodynamic features of high-speed maglev trains with different marshaling lengths under crosswinds.The effects of marshaling lengths(varying from 3-car to 8-car groups)on the train’s aerodynamic performance,surface pressure,and the flow field surrounding the train were investigated using the three-dimensional unsteady compressible Navier-Stokes(N-S)equations.The results showed that the marshaling lengths had minimal influence on the aerodynamic performance of the head and middle cars.Conversely,the marshaling lengths are negatively correlated with the time-average side force coefficient(CS)and time-average lift force coefficient(Cl)of the tail car.Compared to the tail car of the 3-car groups,the CS and Cl fell by 27.77%and 18.29%,respectively,for the tail car of the 8-car groups.It is essential to pay more attention to the operational safety of the head car,as it exhibits the highest time average CS.Additionally,the mean pressure difference between the two sides of the tail car body increased with the marshaling lengths,and the side force direction on the tail car was opposite to that of the head and middle cars.Furthermore,the turbulent kinetic energy of the wake structure on the windward side quickly decreased as marshaling lengths increased.展开更多
To study the influence of the speed-up of a freight train with mixed marshaling of light and heavy vehicles on the dynamic behavior,a dynamic model of the freight train was established based on the modular method of c...To study the influence of the speed-up of a freight train with mixed marshaling of light and heavy vehicles on the dynamic behavior,a dynamic model of the freight train was established based on the modular method of cyclic variables,and the dynamic behavior of the freight train was simulated and analyzed under different marshaling patterns,speeds and line conditions.On-site speed-up test with different marshaling freight trains was carried out,and the stability and ride-index of the train before and after the speed-up were compared and analyzed.The feasibility of increasing the speed of freight trains with mixed marshaling of light and heavy cars was demonstrated theoretically and experimentally.The results show that the theory is in good agreement with the test,which can effectively reflect the dynamic behavior of the vehicle.The dynamic behavior of the freight train in the study meets the requirements of increasing speed to 90 km/h.This paper provides a theoretical basis and method for railway freight transportation and the speed-up of freight vehicles.展开更多
目的:评估无水乙醇注射Marshall静脉(vein of Marshall,VOM)在持续性心房扑动(简称房扑)、心房颤动(简称房颤)二尖瓣峡部线性消融中的有效性和安全性。方法:收集2019年9月—2020年5月上海市胸科医院采用射频消融+无水乙醇注射VOM治疗持...目的:评估无水乙醇注射Marshall静脉(vein of Marshall,VOM)在持续性心房扑动(简称房扑)、心房颤动(简称房颤)二尖瓣峡部线性消融中的有效性和安全性。方法:收集2019年9月—2020年5月上海市胸科医院采用射频消融+无水乙醇注射VOM治疗持续性房扑、房颤患者72例(VOM组)的临床资料,同时选择采用左房线性消融治疗持续性房扑、房颤患者72例作为对照(对照组)。入选患者均行二尖瓣峡部线性消融手术,术中验证二尖瓣峡部线阻断情况,术后随访房性心律失常和心包积液发生情况,均随访12个月以上。结果:VOM组术中验证二尖瓣峡部线阻断63例,其中需要联合心内和心外膜补点消融达到二尖瓣峡部线14例,未能阻断二尖瓣峡部线9例。对照组术中验证二尖瓣峡部线53例,未能阻断19例。随访12~20个月,VOM组房性心律失常复发20例,而对照组房性心律失常复发30例。结论:在持续性房扑、房颤消融治疗中,经VOM行无水乙醇注射能有效阻断二尖瓣峡部线性传导,有助于提高二尖瓣峡部线成功率,减少房颤消融术中二尖瓣峡部相关的房扑发生率,且不增加严重并发症的发生率。展开更多
中年男性,因心房颤动消融术后7月余反复心悸入院,心电图提示房性心动过速(简称房速),电生理检查提示起源左侧房速,电激动标测提示二尖瓣峡部局灶性房速,给予45W AI 450 15 mL/min冷盐水射频消融,消融后心电传导顺序改变,心动周期不变;...中年男性,因心房颤动消融术后7月余反复心悸入院,心电图提示房性心动过速(简称房速),电生理检查提示起源左侧房速,电激动标测提示二尖瓣峡部局灶性房速,给予45W AI 450 15 mL/min冷盐水射频消融,消融后心电传导顺序改变,心动周期不变;重新标测,提示环右肺静脉折返,消融无效;再次标测,提示左上肺电激动最早,于左肺静脉嵴部进行线性隔离,消融过程中心动过速终止,电生理检查未再诱发心动过速,消融有效部位的二尖瓣峡部及左肺静脉脊部均为Marshall静脉分布区域,可能存在心外膜传导,Marshall静脉参与的折返性心动过速。展开更多
Based on the systematic analysis of the operation process at two-way marshaling station, the operation ways of through car flows, sorting car flows and loading car flows are comprehensively studied. An optimal model o...Based on the systematic analysis of the operation process at two-way marshaling station, the operation ways of through car flows, sorting car flows and loading car flows are comprehensively studied. An optimal model of system operation division of labor based on resource constraint is constructed. The model is solved by using genetic algorithm, and the improving strategy for solving the model is proposed. The application example indicates that the model and algorithm can effectively solve the problem of operation division of labor at two-way marshaling station.展开更多
The railway mobile communication system is undergoing a smooth transition from the Global System for Mobile Communications-Railway(GSM-R)to the Railway 5G.In this paper,an empirical path loss model based on a large am...The railway mobile communication system is undergoing a smooth transition from the Global System for Mobile Communications-Railway(GSM-R)to the Railway 5G.In this paper,an empirical path loss model based on a large amount of measured data is established to predict the path loss in the Railway 5G marshalling yard scenario.According to the different characteristics of base station directional antennas,the antenna gain is verified.Then we propose the position of the breakpoint in the antenna propagation area,and based on the breakpoint segmentation,a large-scale statistical model for marshalling yards is established.展开更多
基金supported by Wuyi University Hong Kong and Macao Joint Research and Development Fund(GrantsNos.2021WGALH15,2019WGALH17,2019WGALH15)the National Natural Science Foundation of China-Guangdong Joint Fund(GrantsNo.2019A1515111052)+2 种基金the National Natural Science Foundation of China(Grant No.52202426)a grant from the Research Grants Council(RGC)of the Hong Kong Special Administrative Region(SAR),China(Grants No.15205723)a grant from the Hong Kong Polytechnic University(Grant No.P0045325).
文摘The safety and stability of high-speed maglev trains traveling on viaducts in crosswinds critically depend on their aerodynamic characteristics.Therefore,this paper uses an improved delayed detached eddy simulation(IDDES)method to investigate the aerodynamic features of high-speed maglev trains with different marshaling lengths under crosswinds.The effects of marshaling lengths(varying from 3-car to 8-car groups)on the train’s aerodynamic performance,surface pressure,and the flow field surrounding the train were investigated using the three-dimensional unsteady compressible Navier-Stokes(N-S)equations.The results showed that the marshaling lengths had minimal influence on the aerodynamic performance of the head and middle cars.Conversely,the marshaling lengths are negatively correlated with the time-average side force coefficient(CS)and time-average lift force coefficient(Cl)of the tail car.Compared to the tail car of the 3-car groups,the CS and Cl fell by 27.77%and 18.29%,respectively,for the tail car of the 8-car groups.It is essential to pay more attention to the operational safety of the head car,as it exhibits the highest time average CS.Additionally,the mean pressure difference between the two sides of the tail car body increased with the marshaling lengths,and the side force direction on the tail car was opposite to that of the head and middle cars.Furthermore,the turbulent kinetic energy of the wake structure on the windward side quickly decreased as marshaling lengths increased.
基金The authors gratefully acknowledge the support of the School-enterprise cooperation projects(No.20200203)。
文摘To study the influence of the speed-up of a freight train with mixed marshaling of light and heavy vehicles on the dynamic behavior,a dynamic model of the freight train was established based on the modular method of cyclic variables,and the dynamic behavior of the freight train was simulated and analyzed under different marshaling patterns,speeds and line conditions.On-site speed-up test with different marshaling freight trains was carried out,and the stability and ride-index of the train before and after the speed-up were compared and analyzed.The feasibility of increasing the speed of freight trains with mixed marshaling of light and heavy cars was demonstrated theoretically and experimentally.The results show that the theory is in good agreement with the test,which can effectively reflect the dynamic behavior of the vehicle.The dynamic behavior of the freight train in the study meets the requirements of increasing speed to 90 km/h.This paper provides a theoretical basis and method for railway freight transportation and the speed-up of freight vehicles.
文摘目的:评估无水乙醇注射Marshall静脉(vein of Marshall,VOM)在持续性心房扑动(简称房扑)、心房颤动(简称房颤)二尖瓣峡部线性消融中的有效性和安全性。方法:收集2019年9月—2020年5月上海市胸科医院采用射频消融+无水乙醇注射VOM治疗持续性房扑、房颤患者72例(VOM组)的临床资料,同时选择采用左房线性消融治疗持续性房扑、房颤患者72例作为对照(对照组)。入选患者均行二尖瓣峡部线性消融手术,术中验证二尖瓣峡部线阻断情况,术后随访房性心律失常和心包积液发生情况,均随访12个月以上。结果:VOM组术中验证二尖瓣峡部线阻断63例,其中需要联合心内和心外膜补点消融达到二尖瓣峡部线14例,未能阻断二尖瓣峡部线9例。对照组术中验证二尖瓣峡部线53例,未能阻断19例。随访12~20个月,VOM组房性心律失常复发20例,而对照组房性心律失常复发30例。结论:在持续性房扑、房颤消融治疗中,经VOM行无水乙醇注射能有效阻断二尖瓣峡部线性传导,有助于提高二尖瓣峡部线成功率,减少房颤消融术中二尖瓣峡部相关的房扑发生率,且不增加严重并发症的发生率。
文摘中年男性,因心房颤动消融术后7月余反复心悸入院,心电图提示房性心动过速(简称房速),电生理检查提示起源左侧房速,电激动标测提示二尖瓣峡部局灶性房速,给予45W AI 450 15 mL/min冷盐水射频消融,消融后心电传导顺序改变,心动周期不变;重新标测,提示环右肺静脉折返,消融无效;再次标测,提示左上肺电激动最早,于左肺静脉嵴部进行线性隔离,消融过程中心动过速终止,电生理检查未再诱发心动过速,消融有效部位的二尖瓣峡部及左肺静脉脊部均为Marshall静脉分布区域,可能存在心外膜传导,Marshall静脉参与的折返性心动过速。
文摘Based on the systematic analysis of the operation process at two-way marshaling station, the operation ways of through car flows, sorting car flows and loading car flows are comprehensively studied. An optimal model of system operation division of labor based on resource constraint is constructed. The model is solved by using genetic algorithm, and the improving strategy for solving the model is proposed. The application example indicates that the model and algorithm can effectively solve the problem of operation division of labor at two-way marshaling station.
基金supported in part by the Fundamental Research Funds for the Central Universities under Grant No.2022JBXT001in part by NS⁃FC under Grant No.62171021+1 种基金in part by the Project of China State Rail⁃way Group under Grant No.P2021G012in part by ZTE Industry⁃University⁃Institute Cooperation Funds under Grant No.I21L00220.
文摘The railway mobile communication system is undergoing a smooth transition from the Global System for Mobile Communications-Railway(GSM-R)to the Railway 5G.In this paper,an empirical path loss model based on a large amount of measured data is established to predict the path loss in the Railway 5G marshalling yard scenario.According to the different characteristics of base station directional antennas,the antenna gain is verified.Then we propose the position of the breakpoint in the antenna propagation area,and based on the breakpoint segmentation,a large-scale statistical model for marshalling yards is established.
