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Université de Fribourg

Local preferential attachment model for hierarchical networks

Wang, Li-Na ; Guo, Jin-Li ; Yang, Han-Xin ; Zhou, Tao

In: Physica A: Statistical Mechanics and its Applications, 2009, vol. 388, no. 8, p. 1713-1720

A railway transportation system can be represented by a bipartite network consisting of trains and stations, where a train is connected to all stations where it stops. In this paper, motivated by the resource-allocation process taking place on networks, we design a method to project a Chinese train-station bipartite network into a weighted station network. A new metric is proposed to quantify the...

Université de Fribourg

Empirical analysis of dependence between stations in Chinese railway network

Wang, Yong-Li ; Zhou, Tao ; Shi, Jian-Jun ; Wang, Jian ; He, Da-Ren

In: Physica A: Statistical Mechanics and its Applications, 2009, vol. 388, no. 14, p. 2949-2955

A railway transportation system can be represented by a bipartite network consisting of trains and stations, where a train is connected to all stations where it stops. In this paper, motivated by the resource-allocation process taking place on networks, we design a method to project a Chinese train-station bipartite network into a weighted station network. A new metric is proposed to quantify the...

Université de Fribourg

Accelerating consensus of self-driven swarm via adaptive speed

Zhang, Jue ; Zhao, Yang ; Tian, Baomei ; Peng, Liqian ; Zhang, Hai-Tao ; Wang, Bing-Hong ; Zhou, Tao

In: Physica A: Statistical Mechanics and its Applications, 2009, vol. 3888, no. 7, p. 1237-1242

In recent years, the well-developed Vicsek model has attracted more and more attention. Unfortunately, in-depth research on its convergence speed is not yet completed. In this paper, we investigate some key factors governing the convergence speed of the Vicsek model with the assistance of extensive numerical simulations. A significant phenomenon surfaces that the convergence time scales obeys a...

Université de Fribourg

Scale invariance of human electroencephalogram signals in sleep

Cai, Shi-Min ; Jiang, Zhao-Hui ; Zhou, Tao ; Zhou, Pei-Ling ; Yang, Hui-Jie ; Wang, Bing-Hong

In: Physical Review E, 2007, vol. 76, p. 061903

In this paper, we investigate the dynamical properties of electroencephalogram (EEG) signals of humans in sleep. By using a modified random walk method, we demonstrate that scale-invariance is embedded in EEG signals after a detrending procedure is applied. Furthermore, we study the dynamical evolution of the probability density function (PDF) of the detrended EEG signals by nonextensive...

Université de Fribourg

Role of activity in human dynamics

Zhou, Tao ; Kiet, H. A. T. ; Kim, B. J. ; Wang, B.-H. ; Holme, P.

In: Europhysics Letters, 2008, vol. 82, no. 2, p. 28002

The human society is a very complex system; still, there are several non-trivial, general features. One type of them is the presence of power-law–distributed quantities in temporal statistics. In this letter, we focus on the origin of power laws in rating of movies. We present a systematic empirical exploration of the time between two consecutive ratings of movies (the interevent time). At an...

Université de Fribourg

Modeling human dynamics with adaptive interest

Han, Xiao-Pu ; Zhou, Tao ; Wang, Bing-Hong

In: New Journal of Physics, 2008, vol. 10, p. 073010

Increasing recent empirical evidence indicates the extensive existence of heavy tails in the inter-event time distributions of various human behaviors. Based on the queuing theory, the Barabási model and its variations suggest the highest-priority-first protocol to be a potential origin of those heavy tails. However, some human activity patterns, also displaying heavy-tailed temporal statistics,...

Université de Fribourg

Enhanced synchronizability via age-based coupling

Lu, Yu-Feng ; Zhao, Ming ; Zhou, Tao ; Wang, Bing-Hong

In: Physical Review E, 2007, vol. 76, p. 057103

In this Brief Report, we study the synchronization of growing scale-free networks. An asymmetrical age-based coupling method is proposed with only one free parameter α. Although the coupling matrix is asymmetric, our coupling method could guarantee that all the eigenvalues are non-negative reals. The eigenratio R will approach 1 in the large limit of α

Université de Fribourg

Recommendation model based on opinion diffusion

Zhang, Yi-Cheng ; Medo, Matúš ; Ren, Jie ; Zhou, Tao ; Li, T. ; Yang, F.

In: Europhysics Letters, 2007, vol. 80, no. 6, p. 68003

Information overload in the modern society calls for highly efficient recommendation algorithms. In this letter we present a novel diffusion-based recommendation model, with users' ratings built into a transition matrix. To speed up computation we introduce a Green function method. The numerical tests on a benchmark database show that our prediction is superior to the standard recommendation...

Université de Fribourg

Information filtering via self-consistent refinement

Ren, Jie ; Zhou, Tao ; Zhang, Yi-Cheng

In: Europhysics Letters, 2008, vol. 82, no. 5, p. 58007

Recommender systems are significant to help people deal with the world of information explosion and overload. In this letter, we develop a general framework named self-consistent refinement and implement it by embedding two representative recommendation algorithms: similarity-based and spectrum-based methods. Numerical simulations on a benchmark data set demonstrate that the present method...

Université de Fribourg

Note on two-phase phenomena in financial markets

Jiang, Shi-Mei ; Cai, Shi-Min ; Zhou, Tao ; Zhou, Pei-Ling

In: Chinese Physics Letters, 2008, vol. 25, no. 6, p. 2319-2322

The two-phase behaviour in financial markets actually means the bifurcation phenomenon, which represents the change of the conditional probability from an unimodal to a bimodal distribution. We investigate the bifurcation phenomenon in Hang–Seng index. It is observed that the bifurcation phenomenon in financial index is not universal, but specific under certain conditions. For Hang–Seng index...