Volume 15, Issue 1

This paper proposes a chaos-based color image encryption scheme using one-time keys and Choquet fuzzy integral (CFI). The major core of the encryption algorithm is a pseudo-random number generator based on the CFI, and the key is plain-image dependent. Before encrypting the color image, the hash function is applied to generate the 256-bit key, and the hyper chaotic Qi system is iterated for limited times to generate the initial parameters sequences for the CFI. The outputs of the CFI are employed to confuse and diffuse the red, green and blue components for the image respectively. Experiment results and security analysis show that the scheme not only can achieve good encryption result and large key space, but also can resist against common attacks, so the scheme is reliable to be adopted for image encryption in secure communications.

This paper shows the application of the heuristic Differential Evolution (DE) algorithm to maximize the positive Lyapunov exponent in a third-order multi-scroll chaotic oscillator. The case of study is the saturated nonlinear function series-based chaotic oscillator. The positive Lyapunov exponent is computed for a 4-scrolls chaotic oscillator by varying the coefficients of the dynamical system ( a , b , c , d 1 ), in the range [0.001..1.000]. The experiments are performed and compared executing DE and a simple Genetic algorithm. The results show that DE algorithm is quite suitable to maximize the positive Lyapunov exponent of truncated coefficients over the continuous parameter spaces, because statistical studies show a small standard deviation. The comparison of the phase space diagrams of non-optimized and optimized chaotic oscillators show that for a low value of the positive Lyapunov exponent the attractor is well defined, while for its maximum value the attractor is not well appreciated, but the higher value of the exponent increases the unpredictability grade of the chaotic system.

This paper suggests a novel modified homotopy perturbation transform method (MHPTM) for a nonlinear boundary layer problem by suitable choice of an initial solution. The steady Navier–Stokes equations are reduced to nonlinear ordinary differential equations by using similarity variables. The governing nonlinear differential equations are solved by means of MHPTM. The equations are Laplace transformed and the nonlinear terms represented by He's polynomials. The series solution of the nonlinear boundary layer problem is obtained. For such a boundary layer problem, the second derivative at zero is an important point of function, so we have computed f ″(0) and compared it with other results. An excellent agreement between the MHPTM and HPM is achieved. Such flow analysis is even not available yet for the hydrodynamic fluid. The series solution for MHD boundary layer problem with slip condition by means of MHPTM is yet not available in the literature

This work focuses on the mixed convection stagnation point flow subject to the convective boundary conditions. Mathematical formulation involves the constitutive equations of thermodynamic second grade fluid. Analysis has been performed when thermal radiation effect is present. Nonlinear flow analysis is computed for the homotopic solutions in the series forms. Behaviors of different arising physical parameters are examined. Numerical values of local Nusselt number are given and analyzed.

The (3+1)-dimensional quantum Zakharov-Kuznetsov equations with variable coefficients have the applications to nonlinear ion-acoustic waves in dense magnetoplasmas. Via a simplified bilinear method and symbolic computation, we construct the multiple solitary wave solutions, analyze the elastic collisions with the constant and variable coefficients, and observe that solitons no longer keep rectilinear propagation and display different shapes because of the inhomogeneities of media. Then, a dense magnetoplasma consisting of electrons and singly charged ions is considered. The basic set of quantum hydrodynamic is reduced to the quantum Zakharov-Kuznetsov equation by using the reductive perturbation technique. Parametric analysis is carried out in order to illustrate that the soliton amplitude, width and velocity are affected by the quantum diffraction and obliqueness effect. Furthermore, propagation characteristics and interaction behaviors of the solitons are also discussed through the graphical analysis and the characteristic-line method.

Based on the Wen's 1966 empirical momentum transfer coefficient relation of gas-particle two-phase turbulent flows, a new model to make up for the discontinuous characteristics is developed using a three-stage continuous function with switch weight function. Incorporated into the kinetic theory of granular flows to consider particle collisions and the unified second-order moment two phase turbulent model, it is utilized to predict the hydrodynamics of swirl gas-particle turbulent flows and the validation from the experimental measurements by Sommerfeld and Qiu 1991 is also carried out as well. Numerical simulated results showed that the prediction results by this model are well in agreements with experimental results. The particle dispersion distributions have the distinctively anisotropic behaviors due to complicated effects of centrifugal force, turbulent diffusion and particle inertia, which are quietly different from gas flows. Meanwhile, distributions of axial-axial particle-gas correlated velocity fluctuation is always greater than axial-tangential particle-gas and the tangential-tangential particle-gas velocity fluctuation is also greater than tangential-axial particle-gas phase. At the stronger shear and the vortex flow regions, its results agreed with experiments are much better than Wen's model.

Water infiltration and its effects on road structures is a topic of great interest in civil engineering. Water is one of the primary factors which affects the mechanical function of roads. Road structures are more often found in unsaturated conditions as opposed to saturated ones. Under unsaturated conditions water flow is primarily by capillarity, while under saturation gravity is the primary force causing water movement. Moreover, under unsaturated conditions the equations describing water flow into soils are highly nonlinear, showing a higher difficulty in its numerical solution. At present there is a limited volume of literature on the hydraulic properties and numerical simulation of water flow in road structures under unsaturated conditions. This paper presents experimental data and nonlinear numerical simulations using the finite element method (FEM) to analyze the water infiltration through a road should structure in unsaturated conditions. Results show that the shoulder section evaluated in this study does not represent a zone of high water infiltration due to the low infiltration capacity of the materials evaluated, and that hydraulic properties measured in the laboratory can be successfully used in numerical codes for assessing water flow through road structures in future analysis. This work indicates that continuous rainfall events, even of low intensity, can cause more infiltration than a single rainfall event of high intensity.

Micro-machined multilayered structure plays a significant role as sensing or actuating components in MEMS. Since different thermal expansion parameters and uneven cooling processes in anodic bonding films, it is important to analyze and measure residual stress of the multi-layer glass/aluminum anodic bonding in the cooling process. In this paper, experiments of three-layer, five-layer glass and aluminum anodic bonding samples were made by the public anode method at 400 °C, 600 V and 0.05∼1 MPa for 15 min. Chemical element analysis of the transition layer formed between glass and aluminum during anodic bonding process was analyzed by Energy Dispersive Spectrometry (EDS). Subsequently, residual stresses and strains in cooled three-layer, five-layer and seven-layer anodic bonding samples was analyzed using nonlinear finite element simulation software MARC. Finite element analysis showed that the residual stress and strain distribution in different multi-layer glass and aluminum samples was similar. Simultaneously, finite element analysis indicated that three-layer glass and aluminum anodic bonding samples had smallest residual stress and equivalent strain values in all samples, an important advantage in MEMS fabrication.

This paper is devoted to examine the thermally stratified mixed convection flow of an Oldroyd-B fluid. The stagnation point flow towards a stretching surface is discussed. The boundary layer flow and energy equations are employed. Resulting partial differential systems are converted into the ordinary differential systems. Convergent series solutions for velocity and temperature are developed and analyzed. Numerical values of Nusselt number is computed and examined. Comparison of present study is shown with the previous results. It is found that velocity decreases through the stratified effects.