This work used the computational fluid dynamics method combined with full-scale train tests to analyze the train aerodynamic performance on special slope topography. Results show that with the increment in the slope g...This work used the computational fluid dynamics method combined with full-scale train tests to analyze the train aerodynamic performance on special slope topography. Results show that with the increment in the slope gradient, the aerodynamic forces and moment increase sharply. Compared with the flat ground condition, the lateral force, lift force, and overturning moment of the train on the first line increase by 153.2%, 53.4% and 124.7%, respectively, under the slope gradient of 20°. However, with the increment of the windward side's depth, the windbreak effect is improved obviously. When the depth is equal to 10 m, compared with the 0 m, the lateral force, lift force and overturning moment of the train on the first line decrease by 70.9%, 77.0% and 70.6%,respectively. Through analyzing the influence of slope parameters on the aerodynamic performance of the train, the relationships among them are established. All these will provide a basic reference for enhancing train aerodynamic performances under different slope conditions and achieve reasonable train speeds for the operation safety in different wind environments.展开更多
Inorder to carry out trunk extension by lateral buds ,the laws of trunk extension and branching sprouted from lateral buds were investigated in 1-year-old seedlings of P.tomentosaxP,fortunei 33 under natural condition...Inorder to carry out trunk extension by lateral buds ,the laws of trunk extension and branching sprouted from lateral buds were investigated in 1-year-old seedlings of P.tomentosaxP,fortunei 33 under natural conditions.The results indicated：（1）Under conditions of high density and extensive management,42%of individuals in P.tomentosaxP.fortunei 33 showed pseudo dichotomous branching characteristics and could not extend their trunks in the second year.But other individuals showed the characteristics of sympodial branching and pseudo monopodial branching （not from terminal buds ）and could realize natural trunk extension.All the 3types of branching could be called branching of pseudo asis;（2）The stem form quotieties of extended trunk in all individuals wrer larger in the second year ,but only 14%of them could straight extend their trunks and 86%of them needed2-3years to reach straight trunk estension;（3）Among individuals which could extend their trunks ,from upper lateral buds to lower lateral buds on trunks ,the lengths and diameters of branches sprouted from lateral buds became smaller and smaller ,but the angles of branching up to trunk became larger and larger ,and the fourth pair of lateral branches reached to the largest,Under the fourth pair ,the angles of branches became smaller again and those branches all died.展开更多
基金Projects(U1334205,U1134203)supported by the National Natural Science Foundation of ChinaProject(132014)supported by the Fok Ying Tong Education Foundation,ChinaProjects(2014T001-A,2015T002-A,2015J007-N)supported by China Railways Corporation
文摘This work used the computational fluid dynamics method combined with full-scale train tests to analyze the train aerodynamic performance on special slope topography. Results show that with the increment in the slope gradient, the aerodynamic forces and moment increase sharply. Compared with the flat ground condition, the lateral force, lift force, and overturning moment of the train on the first line increase by 153.2%, 53.4% and 124.7%, respectively, under the slope gradient of 20°. However, with the increment of the windward side's depth, the windbreak effect is improved obviously. When the depth is equal to 10 m, compared with the 0 m, the lateral force, lift force and overturning moment of the train on the first line decrease by 70.9%, 77.0% and 70.6%,respectively. Through analyzing the influence of slope parameters on the aerodynamic performance of the train, the relationships among them are established. All these will provide a basic reference for enhancing train aerodynamic performances under different slope conditions and achieve reasonable train speeds for the operation safety in different wind environments.
基金Foundation of Research Startup for Returned Student From Abroad Science Foundation of Henan Province forDistinguished Young Scholars(No.002).
文摘Inorder to carry out trunk extension by lateral buds ,the laws of trunk extension and branching sprouted from lateral buds were investigated in 1-year-old seedlings of P.tomentosaxP,fortunei 33 under natural conditions.The results indicated：（1）Under conditions of high density and extensive management,42%of individuals in P.tomentosaxP.fortunei 33 showed pseudo dichotomous branching characteristics and could not extend their trunks in the second year.But other individuals showed the characteristics of sympodial branching and pseudo monopodial branching （not from terminal buds ）and could realize natural trunk extension.All the 3types of branching could be called branching of pseudo asis;（2）The stem form quotieties of extended trunk in all individuals wrer larger in the second year ,but only 14%of them could straight extend their trunks and 86%of them needed2-3years to reach straight trunk estension;（3）Among individuals which could extend their trunks ,from upper lateral buds to lower lateral buds on trunks ,the lengths and diameters of branches sprouted from lateral buds became smaller and smaller ,but the angles of branching up to trunk became larger and larger ,and the fourth pair of lateral branches reached to the largest,Under the fourth pair ,the angles of branches became smaller again and those branches all died.
