A new car-following model termed as multiple headway, velocity, and acceleration difference (MHVAD) is proposed to describe the traffic phenomenon, which is a further extension of the existing model of full velocity difference (FVD) and full velocity and acceleration difference (FVAD). Based on the stability analysis, it is shown that the critical value of the sensitivity in the MHVAD model decreases and the stable region is apparently enlarged, compared with the FVD model and other previous models. At the end, the simulation results demonstrate that the dynamic performance of the proposed MHVAD model is better than that of the FVD and FVAD models.

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The ability to obtain accurate predictions of bus arrival time on a real-time basis is a vital element to both bus operations control and passenger information systems. Several studies had been devoted to this arrival time prediction problem; however, few resulted in completely satisfactory algorithms. This paper presents a new system that can be used to predict the expected bus arrival times at individual bus stops along a service route. The proposed prediction algorithm combines real-time location data from Global Positioning System receivers with average travel speeds of individual route segments, taking into account historical travel speed as well as temporal and spatial variations of traffic conditions. A geographic information system–based map-matching algorithm is used to project each received location onto the underlying transit network. The system is implemented as a finite state machine to ensure its regularity, stability, and robustness under a wide range of operating conditions. A case study on a real bus route is conducted to evaluate the performance of the proposed system in terms of prediction accuracy. The results indicate that the proposed system is capable of achieving satisfactory accuracy in predicting bus arrival times and perfect performance in predicting travel direction.

We view web forums as virtual living organisms feeding on user's clicks and investigate how they grow at the expense of clickstreams. We find that (the number of page views in a given time period) and (the number of unique visitors in the time period) of the studied forums satisfy the law of the allometric growth, i.e., . We construct clickstream networks and explain the observed temporal dynamics of networks by the interactions between nodes. We describe the transportation of clickstreams using the function , in which is the total amount of clickstreams passing through node and is the amount of the clickstreams dissipated from to the environment. It turns out that , an indicator for the efficiency of network dissipation, not only negatively correlates with , but also sets the bounds for . In particular, when and when . Our findings have practical consequences. For example, can be used as a measure of the “stickiness” of forums, which quantifies the stable ability of forums to remain users “lock-in” on the forum. Meanwhile, the correlation between and provides a method to predict the long-term “stickiness” of forums from the clickstream data in a short time period. Finally, we discuss a random walk model that replicates both of the allometric growth and the dissipation function .

An adaptive control approach is proposed for trajectory tracking and obstacle avoidance for mobile robots with consideration given to unknown sliding. A kinematic model of mobile robots is established in this paper, in which both longitudinal and lateral sliding are considered and processed as three time-varying parameters. A sliding model observer is introduced to estimate the sliding parameters online. A stable tracking control law for this nonholonomic system is proposed to compensate the unknown sliding effect. From Lyapunovstability analysis, it is proved, regardless of unknown sliding, that tracking errors of the controlled closed-loop system are asymptotically stable, the tracking errors converge to zero outside the obstacle detection region and obstacle avoidance is guaranteed inside the obstacle detection region. The efficiency and robustness of the proposed control system are verified by simulation results.