Search

Most of the conventional cellular automaton (CA) traffic flow models have two shortcomings: unlimited deceleration capabilities and incapability of reproducing the synchronized flow in the three-phase traffic flow theory. Based on an original deceleration CA model that emphasizes limited mechanical capabilities and human overreaction as the origin of congested traffic states, this paper proposes a new deceleration CA model where the slow-to-start rules are incorporated. For periodic boundary conditions, one also finds that the present model can reproduce well the three different phases of traffic flow (free flow, synchronized traffic flow, wide moving jam) as well as two first-order phase transitions (the transitions from free flow to synchronized flow and from synchronized flow to wide moving jam) among them. Compared to the original deceleration CA model, one notes that the phase transition from the synchronized flow to wide moving jam becomes distinguishable. Furthermore, the present model can reliably reproduce most empirical findings including synchronized flow with different slopes, the so-called pinch effect, and the time-headway distribution of free flow and so on. Importantly, the synchronized flow with different slopes is supported by spatiotemporal diagrams and the statistical distribution of velocity and so on. For open boundary conditions, the present model can reproduce the spatiotemporal diagrams of well-known five patterns including moving synchronized flow pattern, localized synchronized flow pattern, widening synchronized flow pattern, dissolving general pattern and general pattern. [ABSTRACT FROM AUTHOR]

In this paper, a cellular automata model with dual cruise-control limit is refined where the length of each cell is set to 1.5 m and each vehicle can still occupy five cells. The prominent feature of this new model is that these vehicles with low-speed and high-speed are not affected by noise and the slow start rule of the Takayasu and Takayasu model is introduced if there is an empty cell in front of the stationary vehicle. Based on the computer simulation results, one obtains that the new refined model can successfully reproduce the empirical characteristics of three-phase traffic flow theory. In the fundamental diagram, there are three-phase traffic states: Free flow, synchronized flow and wide moving jam. In particular, 2 Z -characteristic for phase transitions can be presented. Furthermore, the propagation speed of the downstream front of the moving synchronized pattern (MSP) and wide moving jam is within the range of empirical observation data or close to the range of empirical observation data. [ABSTRACT FROM AUTHOR]

This study examines the cellular automata traffic flow model, which considers the asynchronous update of vehicles' velocities. Computer simulations are used to identify three typical phases: linear free flow phase, nonlinear moving phase and traffic jam phase. Compared to the original NaSch model, the system of the present model can reach the maximum flow when the vehicle density is higher. The influence of the delay probability and the maximum time step in which drivers intend to keep their current velocity on fundamental diagram is discussed. [ABSTRACT FROM AUTHOR]

The routing strategy plays a very important role in complex networks such as Internet system and Peer-to-Peer networks. However, most of the previous work concentrates only on the path selection, e.g. Flooding and Random Walk, or finding the shortest path (SP) and rarely considering the local load information such as SP and Distance Vector Routing. Flow-based Routing mainly considers load balance and still cannot achieve best optimization. Thus, in this paper, we propose a novel dynamic routing strategy on complex network by incorporating the local load information into SP algorithm to enhance the traffic flow routing optimization. It was found that the flow in a network is greatly affected by the waiting time of the network, so we should not consider only choosing optimized path for package transformation but also consider node congestion. As a result, the packages should be transmitted with a global optimized path with smaller congestion and relatively short distance. Analysis work and simulation experiments show that the proposed algorithm can largely enhance the network flow with the maximum throughput within an acceptable calculating time. The detailed analysis of the algorithm will also be provided for explaining the efficiency. [ABSTRACT FROM AUTHOR]

We study the traffic-driven epidemic spreading on scale-free networks with tunable degree distribution. The heterogeneity of networks is controlled by the exponent of power-law degree distribution. It is found that the epidemic threshold is minimized at about . Moreover, we find that nodes with larger algorithmic betweenness are more likely to be infected. We expect our work to provide new insights in to the effect of network structures on traffic-driven epidemic spreading. [ABSTRACT FROM AUTHOR]

This paper studies the effect of vehicles' changing lanes in the original Biham-Middleton-Levine traffic flow model. According to local vehicular information, the dynamics allows for vehicles changing their rows or columns. Simulation results show that the intermediate stable phase identified in the original model can be observed and maintained in a wide range of the vehicle density in our model. Some new kinds of space configurations have been first presented and discussed. One also notes that the geometric structure of such intermediate stable phases is highly regular for square and rectangular aspect rations. [ABSTRACT FROM AUTHOR]

The static topology properties of financial networks have been widely investigated since the work done by Mantegna, yet their dynamic evolution with time is little considered. In this paper, we comprehensively study the dynamic evolution of financial network by a sliding window technique. The vertices and edges of financial network are represented by the stocks from S&P500 components and correlations between pairs of daily returns of price fluctuation, respectively. Furthermore, the duration of stock price fluctuation, spanning from January 4, 1985 to September 14, 2009, makes us to carefully observe the relation between the dynamic topological properties and big financial crashes. The empirical results suggest that the financial network has the robust small-world property when the time evolves, and the topological structure drastically changes when the big financial crashes occur. This correspondence between the dynamic evolution of financial network and big financial crashes may provide a novel view to understand the origin of economic crisis. [ABSTRACT FROM AUTHOR]

Traffic flow at a single crossroad consisting of two perpendicular one-lane roads, treated earlier by Ishibashi and Fukui [ J. Phys. Soc. Jpn. 70, 2793 (2001); 70, 3747 (2001)], has been studied on the basis of the local occupation probability method. However, in this work, based on the novel theoretical analysis and computer simulations, we have studied this crossroad traffic model again and presented the same phase diagrams of traffic flow in the case of various maximum vehicle velocities. We have also derived the flow formulas in all regions in the phase diagrams, which are in good agreement with computer simulation results. Compared with the previous local occupation probability method, our analytical way is simpler and may be widely used for other traffic bottlenecks research. [ABSTRACT FROM AUTHOR]

Congestion in communication networks is a topic of theoretical interest and practical importance. In this work, we propose a mixed routing strategy by considering the global static information (topology of the network) and local dynamic information (queue length of neighbor nodes). Under this routing strategy, the traffic capacity can be remarkably promoted compared with that by former efficient routing strategy [G. Yan et al., Phys. Rev. E73, 046108 (2006)]. Besides, the traffic capacity, the average packet number as well as the travel time are almost independent of a time delay in updating the local dynamic information. [ABSTRACT FROM AUTHOR]

In this paper, we investigate two two-route traffic models, i.e. asymmetric and symmetric two-route traffic models, with mean velocity information feedback strategy. The simulation results show that, for asymmetric two-route model, average flux can be significantly improved if only partial road information is provided for road users. However, for symmetric two-route model, average flux of the two routes adopting information feedback cannot outweigh the flux of two routes chosen completely at random. We explain the results by studying the vehicle number on two routes. We hope the study may provide a good suggestion to the design of Advanced Traveler Information Systems. [ABSTRACT FROM AUTHOR]

In this brief report, we investigate the synchronizability of the complex network. In order to optimize the synchronizability, we propose a method by introducing a weight matrix, which makes the synchronized states stable for the widest range of the overall coupling strength. We give a proof in mathematics and gain the exact form of the weight matrix, which is equal to Lβ. Matrix L is the one that describes the optimal network and matrix β is constructed by the eigenvalues and eigenvectors of the usual Laplacian matrix. This result may provide us insight into the synchronization of complex network more deeply. [ABSTRACT FROM AUTHOR]

We propose an opinion dynamics model to study the effects of heterogeneous influence of individuals on the global consensus. Each individual is assigned a weight that is proportional to the power of its degree, where the power exponent α is an adjustable parameter. Interestingly, it is found that there exists an optimal value of α leading to the shortest consensus time for scale-free networks, random networks and small-world networks. Other quantities, such as the probability that an individual's initial opinion becomes the final opinion as a function of degree, the evolution of the number of opinion clusters, as well as the relationship between average consensus time and the network size, are also studied. Our results are helpful for understanding the role of heterogeneous influence in the opinion dynamics. [ABSTRACT FROM AUTHOR]

In this paper, traffic bottleneck is introduced on one of the routes (say route A) in a two-route scenario with mean velocity information feedback. The simulations show that four different system states, i.e. zero state (no dynamic vehicle chooses route A), periodic oscillation state (mean velocity on route A is in periodic oscillations), alternation state (alternation of zero state and oscillation state), and equal velocity state (mean velocities on the two routes are equal), are identified. Complex nonlinear changing behavior of critical vehicle arrival probability λc depending on bottleneck length and location as well as dynamic vehicle ratio is revealed. Our work is expected to be useful for designing Advanced Traveller Information Systems. [ABSTRACT FROM AUTHOR]

In this paper, traffic flow at a signal controlled T-shaped intersection with three input roads is investigated by using the cellular automata model. When each road is a double lane, the model only exists in three conflict points among three directions of flows. We introduce three-phase traffic signal and two types of signal controlling strategies, i.e. fixed signal phase order as well as adaptive signal phase order strategy, to control the traffic flow at the intersection. The phase diagram, the capacity and the average travel time of the system are investigated and compared under both strategies. The simulation results show that the traffic adaptive signal strategy is better than the fixed signal phase order strategy. [ABSTRACT FROM AUTHOR]

In this paper, the statistical property, namely degree correlation between users and objects, is taken into account and be embedded into the similarity index of collaborative filtering (CF) algorithm to improve the algorithmic performance. The numerical simulation on a benchmark data set shows that the algorithmic accuracy of the presented algorithm, measured by the average ranking score, is improved by 18.19% in the optimal case. The statistical analysis on the product distribution of the user and object degrees indicate that, in the optimal case, the distribution obeys the power-law and the exponential is equal to -2.33. Numerical results show that the presented algorithm can provide more diverse and less popular recommendations, for example, when the recommendation list contains 10 objects, the diversity, measured by the hamming distance, is improved by 21.90%. Since all of the real recommendation data evolving with time, this work may shed some light on the adaptive recommendation algorithm which could change its parameter automatically according to the statistical properties of the user-object bipartite network. [ABSTRACT FROM AUTHOR]

In this paper, based on a weighted projection of the user-object bipartite network, we study the effects of user tastes on the mass-diffusion-based personalized recommendation algorithm, where a user's tastes or interests are defined by the average degree of the objects he has collected. We argue that the initial recommendation power located on the objects should be determined by both of their degree and the user's tastes. By introducing a tunable parameter, the user taste effects on the configuration of initial recommendation power distribution are investigated. The numerical results indicate that the presented algorithm could improve the accuracy, measured by the average ranking score. More importantly, we find that when the data is sparse, the algorithm should give more recommendation power to the objects whose degrees are close to the user's tastes, while when the data becomes dense, it should assign more power on the objects whose degrees are significantly different from user's tastes. [ABSTRACT FROM AUTHOR]

In this paper, we propose a spreading activation approach for collaborative filtering (SA-CF). By using the opinion spreading process, the similarity between any users can be obtained. The algorithm has remarkably higher accuracy than the standard collaborative filtering using the Pearson correlation. Furthermore, we introduce a free parameter β to regulate the contributions of objects to user–user correlations. The numerical results indicate that decreasing the influence of popular objects can further improve the algorithmic accuracy and personality. We argue that a better algorithm should simultaneously require less computation and generate higher accuracy. Accordingly, we further propose an algorithm involving only the top-N similar neighbors for each target user, which has both less computational complexity and higher algorithmic accuracy. [ABSTRACT FROM AUTHOR]

In this paper, we numerically investigate the structural characteristics that affect the synchronizability of coupled identical oscillators on scale-free networks. By using the edge-exchange method, we can change the network structure with degree sequence fixed. An optimal algorithm, namely Tabu Search, is applied, respectively, to enhance and weaken the synchronizability. The numerical results indicate that the synchronizability is most sensitive to the maximal betweenness. By tracking the optimization process, most previous works suggest that the synchonizability can be enhanced by reducing assortative coefficient and clustering coefficient; however, interestingly, our numerical simulations show that the depression of synchronizability also corresponds to the reduction process of those two coefficients. [ABSTRACT FROM AUTHOR]

In this article, we propose a network spreading model for HIV epidemics, wherein each individual is represented by a node of the transmission network and the edges are the connections between individuals along which the infection may spread. The sexual activity of each individual, measured by its degree, is not homogeneous but obeys a power-law distribution. Due to the heterogeneity of activity, the infection can persistently exist at a very low prevalence, which has been observed in the real data but cannot be illuminated by previous models with homogeneous mixing hypothesis. The model displays a clear picture of hierarchical spread: In the early stage the infection is adhered to these high-risk persons, and then, diffuses toward low-risk population. Furthermore, we find that to reduce the risky behaviors is much more effective in the fight against HIV/AIDS rather than the antiretroviral drug therapies. The prediction results show that the development of epidemics can be roughly categorized into three patterns for different countries, and the pattern of a given country is mainly determined by the average sex-activity and transmission probability per sexual partner. In most cases, the effect of HIV epidemics on demographic structure is very small. However, for some extremely countries, like Botswana, the number of sex-active people can be depressed to nearly a half by AIDS. [ABSTRACT FROM AUTHOR]

In this paper, we propose an alternative model for collaboration networks based on nonlinear preferential attachment. Depending on a single free parameter "preferential exponent", this model interpolates between networks with a scale-free and an exponential degree distribution. The degree distribution in the present networks can be roughly classified into four patterns, all of which are observed in empirical data. And this model exhibits small-world effect, which means the corresponding networks are of very short average distance and highly large clustering coefficient. More interesting, we find a peak distribution of act-size from empirical data which has not been emphasized before. Our model can produce the peak act-size distribution naturally that agrees with the empirical data well. [ABSTRACT FROM AUTHOR]

In this paper, some new lane-changing rules for one-way two-lane traffic with one work zone are proposed. Considering their velocities difference between the vehicle in the current lane and some vehicle behind/ahead in the target lane, and its own velocity, driver will choose to change lanes if necessary. Unlike some previous studies, one-way two-lane with one work zone is divided into three sections: symmetrical zone, conversion zone and work zone. In the conversion zone, the maximum velocity of vehicles in merge lane depends on the number of unsuccessful lane-changing. Based on the refined Nagel–Schreckenberg model, all vehicles update their corresponding velocities and positions in own respective lanes, employing open boundary conditions. The computer results show that the system has two states: unsaturated state and saturated state. In the saturated state, these vehicles on these two lanes have the same occupancy, which change steadily without inflection point when approaching the conversion zone, especially for upstream of the work zone. As one of the results of vehicle self-organization, the system can reach the saturated state in a short period of time as the injection probability increases. This saturated state can also spread across the conversion zone to the symmetrical zone. In the unsaturated state, one also finds that the velocity distribution can be consistent with the actual traffic conditions for upstream of the work zone. We selected three road sections with work zone to carry out field test, and the flow of these three road sections is basically consistent with the flow of the saturated state for the present model. [ABSTRACT FROM AUTHOR]

In the upstream of the highway work zone, vehicles will change lanes automatically or forcibly, which has complexity and randomness. Most studies fail to consider the impact of actual mixed traffic characteristics on traffic flow. For example, the dependence of the lane-changing behaviors of Connected and Automated Vehicles (CAVs) on the length of the zone is ignored in upstream of work zone. In addition, it is assumed that vehicles in the merge lane of the work zone would “yield” or not consider an impact on vehicles in the through lane. This simplifies the complex dynamics of the interaction between the two streams of traffic, which leads to the results of the study and the actual situation inconsistency. Based on the Gipps model, the adaptive cruise control (ACC) and the collaborative adaptive cruise control (CACC) vehicle-following models, this paper proposes a continuous cellular automata model under Vehicle-Road Collaboration and studies the mixed traffic flow characteristics in the work zone. By setting a metering zone before the lane reduction sign, ACC/CACC can adjust headway by obtaining road information in advance. The simulation results indicate that ACC/CACC vehicles have better following response compared to human-driven vehicles. In other words, the platoon composed of ACC/CACC vehicles has stability and can improve the traffic capacity of the work zone. The results of the study also found that the insertion of vehicles from adjacent lane into the ACC/CACC vehicles platoon is detrimental, especially when the penetration rate (Pinter) is high. Furthermore, when the length of the metering zone (Lmeter) is set at 120–150m, it can significantly improve the road congestion in the work zone. [ABSTRACT FROM AUTHOR]