This paper attempts to introduce an improved difference model that modifies a car-following model, which takes the next-nearest-neighbor interaction into account. The hnprovement of this model over the previous one li...This paper attempts to introduce an improved difference model that modifies a car-following model, which takes the next-nearest-neighbor interaction into account. The hnprovement of this model over the previous one lies in that it performs more realistically in the dynamical motion for small delay time. The traffic behavior of the improved model is investigated with analytic and numerical methods with the finding that the new consideration could further stabilize traffic flow. And some simulation tests verify that the proposed model can demonstrate some complex physical features observed recently in real traffic such as the existence of three phases： free flow, coexisting flow, and jam flow; spontaneous formation of density waves; sudden flow drop in flow-density plane; traffic hysteresis in transition between the free and the coexisting flow. Furthermore, th.e improved model also predicts that the stable state to relative density in the coexisting flow is insusceptible to noise.展开更多
Traffic flow model is improved by introducing variable brake distances with varying slopes.Stability of the traffic flow on a gradient is analyzed and the neutral stability condition is obtained.The KdV(Korteweg-de Vr...Traffic flow model is improved by introducing variable brake distances with varying slopes.Stability of the traffic flow on a gradient is analyzed and the neutral stability condition is obtained.The KdV(Korteweg-de Vries)equation is derived the use of nonlinear analysis and soliton solution is obtained in the meta-stable region.Solitary density waves are reproduced in the numerical simulations.It is found that as uniform headway is less than the safety distance solitary wave exhibits upward form,otherwise it exhibits downward form.In general the numerical results are in good agreement with the analytical results.展开更多
We introduce the path length probability density function(PPDF) method, which is based on an equivalence theorem and parameterizes the aerosol scattering effect by adding four factors to the atmospheric transmittance ...We introduce the path length probability density function(PPDF) method, which is based on an equivalence theorem and parameterizes the aerosol scattering effect by adding four factors to the atmospheric transmittance model. Using simulated observations in the O2-A band, we examined the utility of the PPDF-based method to account for the aerosol scattering effect. First, observations were simulated using a forward model under different aerosol conditions; PPDF factors were then retrieved using an optimal estimation method; PPDF factors were used to reconstruct the observations; and finally, simulated true observations and reconstructions were compared. Analysis of the difference between the true observations and reconstructions confirmed the utility of the PPDF-based method. Additionally, the O2 band was demonstrated to be an efficient observing band for assisting the remote sensing of atmospheric trace gases in the near-infrared band.展开更多
基金The project supported by the Key Foundation Project of Shanghai under Grant No. 032912066
文摘This paper attempts to introduce an improved difference model that modifies a car-following model, which takes the next-nearest-neighbor interaction into account. The hnprovement of this model over the previous one lies in that it performs more realistically in the dynamical motion for small delay time. The traffic behavior of the improved model is investigated with analytic and numerical methods with the finding that the new consideration could further stabilize traffic flow. And some simulation tests verify that the proposed model can demonstrate some complex physical features observed recently in real traffic such as the existence of three phases： free flow, coexisting flow, and jam flow; spontaneous formation of density waves; sudden flow drop in flow-density plane; traffic hysteresis in transition between the free and the coexisting flow. Furthermore, th.e improved model also predicts that the stable state to relative density in the coexisting flow is insusceptible to noise.
基金Supported by the National Natural Science Foundation of China under Grant No. 61174175Postdoctoral Science Foundation of China under Grant No. 20100481265+1 种基金Special Foundation for Postdoctoral Innovation Program of Shandong Province under Grant No. 201102025the Scientific Project of Jinan City under Grant No. 201118006
文摘Traffic flow model is improved by introducing variable brake distances with varying slopes.Stability of the traffic flow on a gradient is analyzed and the neutral stability condition is obtained.The KdV(Korteweg-de Vries)equation is derived the use of nonlinear analysis and soliton solution is obtained in the meta-stable region.Solitary density waves are reproduced in the numerical simulations.It is found that as uniform headway is less than the safety distance solitary wave exhibits upward form,otherwise it exhibits downward form.In general the numerical results are in good agreement with the analytical results.
基金supported by the Key Program of the National Natural Science Foundation of China(Grant No.41130528)
文摘We introduce the path length probability density function(PPDF) method, which is based on an equivalence theorem and parameterizes the aerosol scattering effect by adding four factors to the atmospheric transmittance model. Using simulated observations in the O2-A band, we examined the utility of the PPDF-based method to account for the aerosol scattering effect. First, observations were simulated using a forward model under different aerosol conditions; PPDF factors were then retrieved using an optimal estimation method; PPDF factors were used to reconstruct the observations; and finally, simulated true observations and reconstructions were compared. Analysis of the difference between the true observations and reconstructions confirmed the utility of the PPDF-based method. Additionally, the O2 band was demonstrated to be an efficient observing band for assisting the remote sensing of atmospheric trace gases in the near-infrared band.
