International Journal of Modern Physics C

For the complex networks, including scale-free, small-world, local-world and random networks, the global quantitative evaluation of attack-induced cascade is investigated in this paper by introducing the risk assessment, which integrates the probability of occurrence with the damage size of attacks on nodes. It is discovered by simulations, among the several kinds of networks, that the small-world network has the largest risk assessment of attack-induced cascade; the risk assessment of three other networks are all very low and the most protection against attack should be given to the small-world network accordingly. Furthermore, the percentage of the most fragile nodes in the scale-free network is very low, compared with that in the small-world network.

In this paper, an extended FF model (floor field model) to simulate pedestrian dynamics in complex scenarios is proposed. Considering that pedestrians are unaware of the global view of traffic path, we introduce pedestrians' local views and propose a framework to change a pedestrian's static floor field each time they enter a new convex area. A pedestrian's view is limited to a convex polygon. When they travel from one convex area to another, they make decisions about the next goal according to the distances between them and the candidate goals, as well as densities of capacity and herding behaviors. Meanwhile, after making an initial decision about the next goal, a pedestrian can estimate the travel time to reach each visible goal and change their path adaptively within the convex area. Simulations in two scenarios are conducted and the results show that pedestrians under local views behave more practically than those under global views in complex scenarios. Parameter settings are also discussed along with suggestions that can be given to designers for improving traffic management.

It is well known that electromagnetic field excites acoustic wave in a porous elastic medium saturated with fluid electrolyte due to electrokinetic conversion effect. Pride's equations describing this process are written in isothermal approximation. Update of these equations, which allows to take influence of Joule heating on acoustic waves propagation into account, is proposed here. This update includes terms describing the initiation of additional acoustic waves excited by thermoelastic stresses and the heat conduction equation with right side defined by Joule heating. Results of numerical modeling of several problems of propagation of acoustic waves excited by an electric field source with and without consideration of Joule heating effect in their statements are presented. From these results, it follows that influence of Joule heating should be taken into account at the numerical simulation of electroacoustic logging and at the interpretation of its log data.

The image reconstruction using the EIT (Electrical Impedance Tomography) technique is a nonlinear and ill-posed inverse problem which demands a powerful direct or iterative method. A typical approach for solving the problem is to minimize an error functional using an iterative method. In this case, an initial solution close enough to the global minimum is mandatory to ensure the convergence to the correct minimum in an appropriate time interval. The aim of this paper is to present a new, simple and low cost technique (quadrant-searching) to reduce the search space and consequently to obtain an initial solution of the inverse problem of EIT. This technique calculates the error functional for four different contrast distributions placing a large prospective inclusion in the four quadrants of the domain. Comparing the four values of the error functional it is possible to get conclusions about the internal electric contrast. For this purpose, initially we performed tests to assess the accuracy of the BEM (Boundary Element Method) when applied to the direct problem of the EIT and to verify the behavior of error functional surface in the search space. Finally, numerical tests have been performed to verify the new technique.

Asset allocation is one of the most important and also challenging issues in finance. In this paper using level crossing analysis we introduce a new approach for portfolio selection. We introduce a portfolio index that is obtained based on minimizing the waiting time to receive known return and risk values. By the waiting time, we mean time that a special level is observed in average. The advantage of this approach is that the investors are able to set their goals based on gaining return and knowing the average waiting time and risk value at the same time. As an example we use our model for forming portfolio of stocks in Tehran Stock Exchange (TSE).

The road capacity can be greatly improved if an appropriate and effective information feedback strategy is adopted in the traffic system. In this paper, a strategy called piecewise function feedback strategy (PFFS) is introduced and applied into an asymmetrical two-route scenario with a speed limit bottleneck in which the dynamic information can be generated and displayed on the information board to guide road users to make a choice. Meanwhile, the velocity-dependent randomization (VDR) mechanism is adopted which can better reflect the dynamic behavior of vehicles in the system than NS mechanism. Simulation results adopting PFFS have demonstrated high efficiency in controlling spatial distribution of traffic patterns compared with the previous strategies.

This paper investigates the exponential synchronization of complex network with non-delayed and delayed coupling. A periodically intermittent controller is designed to synchronize the network onto a given orbit. Based on Lyapunov function and differential inequality method, the criteria for exponential synchronization are derived. Numerical simulation is presented to verify the effectiveness of the derived results.

By introducing a partition line into the walking strategies of the bi-directional pedestrian model recently proposed by Baek et al. [S. K. Baek, P. Minnhagen, S. Bernhardsson, K. Choi, B. J. Kim, Phys. Rev. E80, 016111 (2009)], we propose three walking strategies when pedestrians are moving outside the partition line, and carry out numerical simulations. The results show the proposed walking strategies have a significant impact on pedestrians' average walking velocity, pedestrians' distribution and road utilization.