Previous wind tunnel experiments on snow drift usually used artificial snow as a substitute of natural snow, which can not fully reflect the motion characteristics of snow drift in natural environments. In this paper ...Previous wind tunnel experiments on snow drift usually used artificial snow as a substitute of natural snow, which can not fully reflect the motion characteristics of snow drift in natural environments. In this paper we conducted a series of experiments in wind tunnel to investigate the motion of natural snow (fresh snow and old snow), which was collected out-door without destroying the surface structure. The results indicated that the threshold velocity of fresh snow is less than that of old snow, and that the mass flux rates of the two kinds of snow exponentially decrease with height whereas the snow transport rate increases exponentially with wind velocity. Based on the PIV measuring of the velocities of snow particles over two kinds of terrains (flat ground and roadbed), we found that the particle velocity obeys a Gaussian distribution for flat ground, top surface and leeward slope of the roadbed. However, for the windward slope of roadbed the particle velocity distribution displays poor correlation with a Gaussian function due to the acceleration of snow particles when saltating across the slop. Statistical analysis showed that impacting and liftoff velocities of snow particles also obey Gaussian distributions.展开更多
This paper investigates the networked evolutionary model based on snow-drift game with the strategy of rewards and penalty. Firstly, by using the semi-tensor product of matrices approach, the mathematical model of the...This paper investigates the networked evolutionary model based on snow-drift game with the strategy of rewards and penalty. Firstly, by using the semi-tensor product of matrices approach, the mathematical model of the networked evolutionary game is built. Secondly, combined with the matrix expression of logic, the mathematical model is expressed as a dynamic logical system and next converted into its evolutionary dynamic algebraic form. Thirdly, the dynamic evolution process is analyzed and the final level of cooperation is discussed. Finally, the effects of the changes in the rewarding and penalty factors on the level of cooperation in the model are studied separately, and the conclusions are verified by examples.展开更多
To investigate the deposition distribution of snow particles in the bogie surfaces of a high-speed train,a snow particle deposition model,based on the critical capture velocity and the critical shear velocity,was elab...To investigate the deposition distribution of snow particles in the bogie surfaces of a high-speed train,a snow particle deposition model,based on the critical capture velocity and the critical shear velocity,was elaborated.Simulations based on the unsteady Reynolds-Averaged Navier-Stokes(RANS)approach coupled with Discrete Phase Model(DPM)were used to analyze the motion of snow particles.The results show that the cross beam of the bogie frame,the anti-snake damper,the intermediate brake clamps in the rear wheels,the traction rod and the anti-rolling torsion bar are prone to accumulate snow.The accumulation mass relating to the vertical surface in the rear region,horizontal surface in the front region and the corner area of the bogie is high.The average snow accumulation mass for each component ordered from high to low is as follow:traction rod,frame,bolster,brake clamp 2,anti-rolling torsion bar,brake clamp 1,transverse damper,axle box 2,axle box 1,air spring,anti-snake damper,tread cleaning device.The snow accumulation mass on the front components of the bogie is more significant than that relating to the rear components.Particularly,the average snow accumulation mass of rear brake clamp 2 and axle box 2 is about twice as high as that of the front brake clamp 1 and axle box 1.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 40971009 and 10811130470)the National Basic Research Program of China ("973" Project) (Grant No. 2009CB421304)
文摘Previous wind tunnel experiments on snow drift usually used artificial snow as a substitute of natural snow, which can not fully reflect the motion characteristics of snow drift in natural environments. In this paper we conducted a series of experiments in wind tunnel to investigate the motion of natural snow (fresh snow and old snow), which was collected out-door without destroying the surface structure. The results indicated that the threshold velocity of fresh snow is less than that of old snow, and that the mass flux rates of the two kinds of snow exponentially decrease with height whereas the snow transport rate increases exponentially with wind velocity. Based on the PIV measuring of the velocities of snow particles over two kinds of terrains (flat ground and roadbed), we found that the particle velocity obeys a Gaussian distribution for flat ground, top surface and leeward slope of the roadbed. However, for the windward slope of roadbed the particle velocity distribution displays poor correlation with a Gaussian function due to the acceleration of snow particles when saltating across the slop. Statistical analysis showed that impacting and liftoff velocities of snow particles also obey Gaussian distributions.
文摘This paper investigates the networked evolutionary model based on snow-drift game with the strategy of rewards and penalty. Firstly, by using the semi-tensor product of matrices approach, the mathematical model of the networked evolutionary game is built. Secondly, combined with the matrix expression of logic, the mathematical model is expressed as a dynamic logical system and next converted into its evolutionary dynamic algebraic form. Thirdly, the dynamic evolution process is analyzed and the final level of cooperation is discussed. Finally, the effects of the changes in the rewarding and penalty factors on the level of cooperation in the model are studied separately, and the conclusions are verified by examples.
基金supported by the National Key Research and Development Program of China[Grant No.2016YFB1200402].
文摘To investigate the deposition distribution of snow particles in the bogie surfaces of a high-speed train,a snow particle deposition model,based on the critical capture velocity and the critical shear velocity,was elaborated.Simulations based on the unsteady Reynolds-Averaged Navier-Stokes(RANS)approach coupled with Discrete Phase Model(DPM)were used to analyze the motion of snow particles.The results show that the cross beam of the bogie frame,the anti-snake damper,the intermediate brake clamps in the rear wheels,the traction rod and the anti-rolling torsion bar are prone to accumulate snow.The accumulation mass relating to the vertical surface in the rear region,horizontal surface in the front region and the corner area of the bogie is high.The average snow accumulation mass for each component ordered from high to low is as follow:traction rod,frame,bolster,brake clamp 2,anti-rolling torsion bar,brake clamp 1,transverse damper,axle box 2,axle box 1,air spring,anti-snake damper,tread cleaning device.The snow accumulation mass on the front components of the bogie is more significant than that relating to the rear components.Particularly,the average snow accumulation mass of rear brake clamp 2 and axle box 2 is about twice as high as that of the front brake clamp 1 and axle box 1.
