Unsteady Zone Research Articles

Dynamics of traffic flow affected by the future motion of multiple preceding vehicles under vehicle-connected environment: Modeling and stabilization

Connected vehicles that communicate via vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication technologies have become a hot topic in the transportation control field. Benefit from these new technologies, this work constructs a modified intelligent microscopic model considering driver reaction to future motion of preceding vehicles. First, we mimic the impact of anticipative motion of multiple preceding vehicles on the traffic stream, developing a new model, which is further investigated by applying the linear and nonlinear analytical methods. Also, the corresponding neutral and coexisting stability conditions are determined. Analytical results indicate that the information about the future motion of multiple preceding vehicles can improve traffic stability significantly. Besides, the phase diagram is presented by plotting the neutral stability lines and coexisting curves; three zones are created by partitioning the phase diagram with the neutral line and coexisting line, namely, the unsteady zone under the coexisting line, the stable zone above the neutral line, and the metastable zone between the two lines. Finally, the emulation experiments are conducted to validate the analytical conclusions. The results show that the information on a changing trend of multiple headways obviously smooths the traffic flow and restrains the formation of traffic jams.

Water percolation in a thick unsaturated loess layer considering the ground‐atmosphere interaction

AbstractThe key objective of this paper is to advance our present understanding of how surface water infiltrates in thick unsaturated loess, which is found in arid and semiarid regions of the world, considering the ground‐atmosphere interaction. In situ data for a period of 1 year in thick loess layer at a site in the Loess Plateau of China that has groundwater table at 97.5 m depth were collected for achieving this objective. Climate factors, mainly rainfall and actual evaporation, were measured. In addition, variations of soil temperature and water content at different depths in the unsaturated zone were also measured. The data were used to interpret the water percolation characteristics by dividing the thick unsaturated zone into three zones; namely, (i) surface zone, which constitutes the top 1.0 m, (ii) unsteady zone, which is from 1.0 to 7.0 m, and (iii) steady zone, which is below 7.0 m. In the surface zone, soil temperature and water content are sensitive to climate factors. There is a variation of water content associated with the cumulative influence of infiltration and evaporation in the precipitation and nonprecipitation periods, respectively. In the unsteady zone, the water content is relatively constant; however, temperature varies in different seasons. Water percolation in this zone is both in liquid and vapour phases. In the steady zone, both soil temperature and water content are constant during the entire investigation period. The percolation velocity in this zone is approximately 1.23 × 10−8 m/s or 0.39 m/year, which suggests that it will take approximately 230.8 years for surface water to pass through the thick unsaturated zone and recharge the groundwater.

Distribution of Cotton in Rectangular Pipeline for Horizontal Foreign Fiber Removed Device

A numerical simulation method using the model of the gas-cotton two-phase is used to analyze the distribution of the cotton in the rectangular pipeline for a horizontal foreign fiber removed device. According to the motion characteristics of the cotton, the optimum length of the rectangular pipeline is found and the distribution of the cotton in the pipeline is obtained. The simulation results show that the optimum length is for the cross-section pipeline. At the same time, in the range of the cotton mainly flows in the middle of the pipeline bottom and the maximum volume fraction of the cotton is 4.5%, at the both sides of the pipeline bottom the cotton is less and the average volume fraction of the cotton is 1%, and there is no the cotton in the middle and upper part of the pipeline; in the range of , the cotton increases rapidly in the middle and upper part of the pipeline and the volume fraction is about 2.7% at ; in the range of , the cotton flows steadily and the volume fractions of the cotton are the same in the middle and upper part of the pipeline, about 2.7% but 1.5% in the lower part of the one. In addition, for the level centers of the cross-sections perpendicular to the cotton flow direction, in the unsteady zone the volume fraction curves of the cotton are symmetrical like a saddle, and in the steady zone the cotton is evenly distributed and its volume fraction curves are horizontal lines.