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1.
R. Jiang M. B. Hu B. Jia R. L. Wang Q. S. Wu 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(2):267-273
This paper studies a new model, which considers the effects of
drivers reaction delay in the Nagel-Schreckenberg model. We studied
the traffic flow properties in the new model under both periodic and
open boundary conditions. The fundamental diagram, spatio-temporal
patterns, density-density correlation functions, relaxation time,
and distance headway distribution are investigated. Several
interesting results are reported, for example, (i) the jam becomes
less condensed when the delay effect is considered; (ii) the
distance headway of the new model exhibits a multi-peak distribution
when randomization p is small; (iii) for large p, the
distribution of distance headway follows a power law in the new
model; (iv) under open boundary conditions, the existence of a
stationary jam near the left boundary will lower the flow rate. 相似文献
2.
The synchronized flow traffic phase of Kerner’s three-phase traffic theory can be well reproduced by the model proposed by Jiang and Wu [R. Jiang, Q.S. Wu, J. Phys. A: Math. Gen. 36 (2003) 381]. But in the Jiang and Wu model, the rule for brake light-after switching on, the brake light will not set off until the vehicle accelerates-is obviously unrealistic. Thus we improved the model by considering the difference in accelerating and decelerating performance under different driving conditions. The fundamental diagram and spatial-temporal diagrams are analyzed. We confirmed that the new model could reproduce the synchronized flow by two methods, i.e. the traffic flow interruption effect and performing microscopic analysis of time series data. Simulation results show that the decelerating difference is an important factor to reproduce the synchronized flow. We expect that our work could make contributions to understanding the mechanism of the synchronized flow. 相似文献
3.
交通流演化复杂性的研究有助于深刻理解交通系统的内在演化规律,为交通流的预测和控制提供理论依据.多尺度熵方法在生理时间序列和计算机网络流量的分析中得到了广泛的应用.考虑到交通流中的车辆到达和计算机网络中的分组到达具有类似特性,本文以刹车灯模型的车头时距为分析对象,利用多尺度熵方法来分析交通流演化的复杂性.分析结果表明:1)车头时距的复杂性随着时间尺度的增加而降低,反映了交通流的短时间难预测性;2)当时间尺度较小时,车头时距复杂性在自由流时和同步流时差异不大,但是,随着时间尺度的增加,自由流时车头时距的熵值迅速下降,而同步流时车头时距的熵值下降较慢.这一特性对于识别自由流中是否产生了同步流有非常重要的参考价值.本文的研究可以为揭示交通流演化的复杂性提供新的思路和方法. 相似文献
4.
The effect of stochastic accelerating and delay probability with the velocity and the gap between vehicles on traffic flow
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This paper proposes a new combined cellular automaton (CA) model
considering the driver behavior of stochastic acceleration and delay
with the velocity of the preceding vehicle and the gap between the
successive vehicles based on the WWH model and the noise-first NaSch
model. It introduces the delay probability varying with the gap,
adds the anticipation headway and increases the acceleration with a
certain probability. Through these simulations, not only can the
metastable state and start--stop wave be obtained but also the synchronized flow
which the wide moving jam results in. Moreover, the
effect of stochastic acceleration and delay on traffic flow is
discussed by analyzing the correlation of traffic data. This indicates
that synchronized flow easily emerges in the critical area between
free flow and synchronized flow when acceleration and delay are
synchronized or their probability is close to 0.5. 相似文献
5.
Based on the Nagel-Schreckenberg model, we study the impact of deceleration in advance on the dynamics of traffic flow. In the process of deceleration in advance, the effect of reaction delay and the effect of expectation are considered respectively. The traffic flow properties are studied by analyzing the fundamental diagram, spatio-temporal patterns, distance headway distribution and car accidents. The simulation results show that reaction delay brings complex traffic flow patterns and expectation makes the serious car accidents rarely happen. 相似文献
6.
On the Intrinsic Concordance between the Wide Scattering Feature of Synchronized Flow and the Empirical Spacing Distributions
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We discuss the intrinsic concordance between the wide scattering feature of density-flow plot and the empirical spazing distributions for traffic flows. It is shown that by choosing a proper threshold parameter, the boundaries of truncated spacing distributions could well determine the envelope of the 2D region of synchronized flow. 相似文献
7.
8.
Additional to the basic Nagel-Schreckenberg model for single-lane traffic flow, we consider the effect of the velocity-difference between two successive vehicles on the randomization of the latter one. This modification improves the transit capacity of the model, which results in a much higher simulated flux. Moreover, in a circular road, this model simulates an abnormal hysteresis effect. The characteristic shape of hysteresis curves may shed some light on the distinguish of synchronized flow and jams. 相似文献
9.
R. Jiang M.-B. Hu B. Jia R. Wang Q.-S. Wu 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(2):197-206
In this paper, we have investigated the effects of adaptive cruise
control (ACC) vehicles in a mixture with manually-controlled
(manual) vehicles. The manual vehicles are simulated by using the
modified comfortable driving model, which can describe
synchronized traffic flow. The phase transition probabilities from free
flow to synchronized flow and from synchronized flow to jams are
studied. The impact of ACC vehicles on the flow rates in free flow
and synchronized flow and on the propagation velocity of the
downstream front of jams are investigated. The dependence of
microscopic properties of traffic flow, including the
spatiotemporal patterns and the velocity distribution, is
explored. Our results are expected to be useful for developing ACC
systems. 相似文献
10.
11.
Synchronized Anti-Phase and In-Phase Oscillations of Intracellular Calcium Ions in Two Coupled Hepatocytes System
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We study the dynamic behaviour of two intracellufar calcium oscillators that are coupled through gap junctions both to Ca^2+ and inositol(1,4,5)-trisphosphate (IP3). It is found that synchronized anti-phase and in-phase oscillations of cytoplasmic cadcium coexist in parameters space. Especially, synchronized anti-phase oscillations only occur near the onset of a Hopf bifurcation point when the velocity of IP3 synthesis is increased. In addition, two kinds of coupling effects, i.e., the diffusions of Ca^2+ and IP3 among cells on synchronous behaviour, are considered. We fnd that small coupling of Ca^2+ and large coupling of IP3 facilitate the emergence of synchronized anti-phase oscillations. However, the result is contrary for the synchronized in-phase case. Our findings may provide a qualitative understanding about the mechanism of synchronous behaviour of intercellular calcium signalling. 相似文献
12.
H. B. Zhu H. X. Ge L. Y. Dong S. Q. Dai 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(1):103-108
Based on the Nagel-Schreckenberg (NaSch)
model of traffic flow, a modified cellular automaton (CA) traffic
model with the density-dependent randomization (abbreviated as the
DDR model) is proposed to simulate traffic flow. The fundamental
diagram obtained by simulation shows the ability of this modified
NaSch model to capture the essential features of traffic flow,
e.g., synchronized flow, metastable state, hysteresis and phase
separation at higher densities. Comparisons are made between this
DDR model and the NaSch model, also between this DDR model and the
VDR model. And the underlying mechanism is analyzed. All these
results indicate that the presented model is reasonable and more
realistic. 相似文献
13.
Takashi Nagatani 《Physica A》2009,388(8):1673-1681
We present a cellular automaton (CA) model for vehicular traffic controlled by traffic lights. The CA model is not described by a set of rules, but is given by a simple difference equation. The vehicular motion varies highly with both signals’ characteristics and vehicular density. The dependence of tour time on both cycle time and vehicular density is clarified. In the dilute limit of vehicles, the vehicular motion is compared with that by the nonlinear-map model. The fundamental diagrams are derived numerically. It is shown that the fundamental diagram depends highly on the signals’ characteristics. The traffic states are shown for various values of cycle time in the fundamental diagram. We also study the effect of a slow vehicle on the traffic flow. 相似文献
14.
We investigate the traffic flow volume data on the time dependent activity of Beijing's urban road network. The couplings between the average flux and the fluctuations on individual links are shown to follow certain scaling laws and yield a wide variety of scaling exponents between 1/2 and 1. To quantitatively explain this interesting phenomenon, a non-stationary Poisson arriving model is proposed. The scaling property is interpreted as the result of the time- variation of the arriving rate of flux over the network, which nicely explicates the effect of aggregation windows, and provides a concise model for the dependence of scaling exponent on the external/internal force ratio. 相似文献
15.
In this paper, a recently introduced cellular automata (CA) model is used for a statistical analysis of the inner micro-scopic structure of synchronized traffic flow. The analysis focuses on the formation and dissolution of clusters or platoons of vehicles, as the mechanism that causes the presence of this synchronized traffic state with a high flow. This platoon formation is one of the most interesting phenomena observed in traffic flows and plays an important role both in manual and automated highway systems (AHS). Simulation results, obtained from a single-lane system under periodic boundary conditions indicate that in the density region where the synchronized state is observed, most vehicles travel together in pla- toons with approximately the same speed and small spatial distances. The examination of velocity variations and individual vehicle gaps shows that the flow corresponding to the synchronized state is stable, safe and highly correlated. Moreover, results indicate that the observed platoon formation in real traffic is reproduced in simulations by the relation between vehicle headway and velocity that is embedded in the dynamics definition of the CA model. 相似文献
16.
E.G. Campari G. Levi 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(1):159-166
We present results relative to a simple cellular automata model without periodic boundary conditions for an highway with on-ramps.
Simulations performed with this model reproduce experimental phenomena observed in traffic such as free flow, synchronized
flow, congested flow, lane inversion, forward and backward propagating waves. On-ramps play the important role of nucleation
points for the dynamic features of traffic.
Received 4 February 2000 and Received in final form 5 May 2000 相似文献
17.
We investigate the structure of a perturbed stock market in terms of correlation matrices. For the purpose of perturbing a stock market, two distinct methods are used, namely local and global perturbation. The former involves replacing a correlation coefficient of the cross-correlation matrix with one calculated from two Gaussian-distributed time series while the latter reconstructs the cross-correlation matrix just after replacing the original return series with Gaussian-distributed time series. Concerning the local case, it is a technical study only and there is no attempt to model reality. The term ‘global’ means the overall effect of the replacement on other untouched returns. Through statistical analyses such as random matrix theory (RMT), network theory, and the correlation coefficient distributions, we show that the global structure of a stock market is vulnerable to perturbation. However, apart from in the analysis of inverse participation ratios (IPRs), the vulnerability becomes dull under a small-scale perturbation. This means that these analysis tools are inappropriate for monitoring the whole stock market due to the low sensitivity of a stock market to a small-scale perturbation. In contrast, when going down to the structure of business sectors, we confirm that correlation-based business sectors are regrouped in terms of IPRs. This result gives a clue about monitoring the effect of hidden intentions, which are revealed via portfolios taken mostly by large investors. 相似文献
18.
In this paper, we incorporate a limitation on the interaction range between neighboring vehicles into the cellular automaton model proposed by Gao and Jiang et al. [K. Gao, R. Jiang, S. X. Hu, B. H. Wang and Q. S. Wu, Phys. Rev. E 76 (2007) 026105], which was established within the framework of Kerner’s three-phase traffic theory and has been shown to be able to reproduce the three-phase traffic flow. This modification eliminates an unrealistic phenomenon found in the previous model, where the velocity-adaptation effect between neighboring vehicles can exist even if those vehicles are infinitely far away from each other. Therefore, in the improved model, we regulate that such interactions can only occur within a finite distance. For simplicity, we suppose a constant value to describe this distance in this paper. As a result, when compared to the previous model, the improved model mainly simulates the following results which are believed to be an improvement. (1) The improved model successfully reproduces the expected discontinuous transition from free flow to synchronized flow and the related “moving synchronized flow pattern”, which are both absent in the original model but have been observed in real traffic. (2) The improved model simulates the correlation functions, time headway distributions and optimal velocity functions which are all more consistent with the empirical data than the previous model and most of the other models published before. (3) Together with the previous two models considering the velocity-difference effect, this model finally accomplishes a significative process of developing traffic flow models from the traditional “fundamental diagram approach” to the three-phase traffic theory. This process should be helpful for us to understand the traffic dynamics and mechanics further and deeper. 相似文献
19.
Additive Temporal Coloured Noise Induced Eckhaus Instability in Complex Ginzburg-Landau Equation System
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The effect of additive coloured noises, which are correlated in time, on one-dimensional travelling waves in the complex Ginzburg-Landau equation is studied by numerical simulations. We found that a small coloured noise with temporal correlation could considerably influence the stability of one-dimensional wave trains. There exists an optimal temporal correlation of noise where travelling waves are the most vulnerable. To elucidate the phenomena, we statistically calculated the convective velocities Vg of the wave packets, and found that the coloured noise with an appropriate temporal correlation can decrease Vg, making the system convectively more unstable. 相似文献
20.
A new car-following model is proposed by taking into account two different time delays in sensing headway and velocity. The effect of time delays on the stability analysis is studied. The theoretical and numerical results show that traffic jams are suppressed efficiently when the difference between two time delays decreases and those can be described by the solution of the modified Korteweg–de Vries (mKdV) equation. Traffic flow is more stable with two delays in headway and velocity than in the case with only one delay in headway. The impact of local small disturbance to the system is also studied. 相似文献