Bing Hong Wang

Hybrid control of period-doubling bifurcation and chaos in discrete nonlinear dynamical systems

Abstract It is a typical route to generate chaos via period-doubling bifurcations in some nonlinear systems. In this paper, we propose a new hybrid control strategy in which state feedback and parameter perturbation are used to control the period-doubling bifurcations and to stabilize unstable periodic orbits embedded in the chaotic attractor of a discrete chaotic dynamical system. Simulation shows that the higher stable 2n-periodic orbit of the system can be controlled to lower stable 2m-periodic orbits (m

The distribution and scaling of fluctuations for Hang Seng index in Hong Kong stock market

Abstract:The statistical properties of the Hang Seng index in the Hong Kong stock market are analyzed. The data include minute by minute records of the Hang Seng index from January 3, 1994 to May 28, 1997. The probability distribution functions of index returns for the time scales from 1 minute to 128 minutes are given. The results show that the nature of the stochastic process underlying the time series of the returns of Hang Seng index cannot be described by the normal distribution. It is more reasonable to model it by a truncated Lévy distribution with an exponential fall-off in its tails. The scaling of the maximium value of the probability distribution is studied. Results show that the data are consistent with scaling of a Lévy distribution. It is observed that in the tail of the distribution, the fall-off deviates from that of a Lévy stable process and is approximately exponential, especially after removing daily trading pattern from the data. The daily pattern thus affects strongly the analysis of the asymptotic behavior and scaling of fluctuation distributions.

Impact of link deletions on public cooperation in scale-free networks

Working together in groups may be beneficial if compared to isolated efforts. Yet this is true only if all group members contribute to the success. If not, group efforts may act detrimentally on the fitness of their members. Here we study the evolution of cooperation in public-goods games on scale-free networks that are subject to deletion of links connected to the highest-degree individuals, i.e., on network that are under attack. We focus on the case where all groups a player belongs to are considered for the determination of payoffs; the so-called multi-group public-goods games. We find that the effect of link deletions on the evolution of cooperation is predominantly detrimental, although there exist regions of the multiplication factor where the existence of an optimal number of removed links for the deterioration of cooperation can also be demonstrated. The findings are explained by means of wealth distributions and analytical approximations, confirming that socially diverse states are crucial for the successful evolution of cooperation.

Flux information feedback strategy in intelligent traffic systems

To effectively alleviate the traffic congestion in urban areas, scientists and engineers have put forward intelligent traffic systems. The information feedback strategy, serving as the critical part of intelligent traffic systems, has been treated with growing emphasis. In this paper, we present two new strategies using the flux as feedback information. One is the time flux feedback strategy (TFFS), the other is the space flux feedback strategy (SFFS). We report the simulation results adopting these two feedback strategies together with the other previously reported ones in a two-route scenario with two exits. The result suggests that SFFS, which outperforms the other categories of feedback strategy, not only in terms of the value of vehicle number and average flux but also in terms of convenience of its application to real traffic conditions, is the best.

Transportation dynamics on networks of mobile agents.

Most existing works on transportation dynamics focus on networks of a fixed structure, but networks whose nodes are mobile have become widespread, such as cell-phone networks. We introduce a model to explore the basic physics of transportation on mobile networks. Of particular interest is the dependence of the throughput on the speed of agent movement and the communication range. Our computations reveal a hierarchical dependence for the former, while an algebraic power law is found between the throughput and the communication range with the exponent determined by the speed. We develop a physical theory based on the Fokker-Planck equation to explain these phenomena. Our findings provide insights into complex transportation dynamics arising commonly in natural and engineering systems.

Traffic-driven epidemic spreading on networks of mobile agents

The question as to how traffic or transportation processes on complex networks can shape the dynamics of epidemic spreading is of great interest for a number of areas. We study traffic-driven epidemic spreading on networks of mobile agents by incorporating two routing strategies: random and greedy. We find that for the case of infinite agent delivery capacity, increasing the moving velocity has opposite effects on the outbreak of epidemic spreading for the two routing strategies. However, expanding the communication range among agents can increase the transportation efficiency but counterintuitively suppress epidemic spreading. For finite delivery capacity, the emergence of traffic congestion can effectively inhibit epidemic spreading for both routing strategies. We provide a mean-field theory to explain the numerical findings. Our results can provide insights into devising effective strategies to suppress the spreading of harmful epidemics on time-varying networks.

ON THE AGING CHARACTERIZATION OF POLY(ETHYLENE TEREPHTHALATE) BY POSITRON SPECTROSCOPY

Abstract Positron spectroscopy was used to study the free volume properties of glassy poly(ethylene terephthalate) as a function of temperature and aging time. The experimental results indicate that the glass transition temperature increases with increasing aging time. This is confirmed by differential scanning calorimetry measurements. From the aging time dependence of the intensity of the ortho-positronium (o-Ps) component I3 and the fractional free volume, we observe that the concentration of free volume holes and the fractional free volume show a continuous decrease at a fixed aging temperature, which suggests that structural relaxation and segmental rearrangement occur during physical aging.