Amirkabir University of Technology

About: Amirkabir University of Technology is a education organization based out in Tehran, Iran. It is known for research contribution in the topics: Nonlinear system & Finite element method. The organization has 15254 authors who have published 31165 publications receiving 487551 citations. The organization is also known as: Tehran Polytechnic & Tehran Polytechnic University.

Three-dimensional chaotic autonomous system with only one stable equilibrium: Analysis, circuit design, parameter estimation, control, synchronization and its fractional-order form

Abstract: This paper proposes a three-dimensional chaotic autonomous system with only one stable equilibrium. This system belongs to a newly introduced category of chaotic systems with hidden attractors. The nonlinear dynamics of the proposed chaotic system is described through numerical simulations which include phase portraits, bifurcation diagrams and new cost function for parameter estimation of chaotic flows. The coexistence of a stable equilibrium point with a strange attractor is found in the proposed system for specific parameters values. The physical existence of the chaotic behavior found in the proposed system is verified by using the Orcard-PSpice software. A good qualitative agreement is shown between the simulations and the experimental results. Based on the Routh-Hurwitz conditions and for a specific choice of linear controllers, it is shown that the proposed chaotic system is controlled to its equilibrium point. Chaos synchronization of an identical proposed system is achieved by using the unidirectional linear and nonlinear error feedback coupling. Finally, the fractional-order form of the proposed system is studied by using the stability theory of fractional-order systems and numerical simulations. A necessary condition for the commensurate fractional order of this system to remain chaotic is obtained. It is found that chaos exists in this system with order less than three.

New adaptive steganographic method using least-significant-bit substitution and pixel-value differencing

Abstract: This study presents a new adaptive data-hiding method based on least-significant-bit (LSB) substitution and pixel-value differencing (PVD) for grey-scale images. The proposed method partition the cover image into some non-overlapping blocks having three consecutive pixels and select the second pixel of each block as the central pixel (called base-pixel). Then, k -bits of secret data are embedded in the base pixel by using LSB substitution and optimal pixel adjustment process (OPAP). The difference between the base-pixel value and other pixel values in the block are utilised to determine how many secret bits can be embedded in the two pixels. Also, the method divides all possible differences into lower level and higher level with a number of ranges. Then, it obtains the number of the secret bits that will be embedded into each block depending on the range which the difference values belong to. The experimental results show that the proposed method can embed a large amount of secret data while maintaining a high visual quality of the stego-images. The peak signal-to-noise ratio (PSNR) values and the embedding capacity of our method are higher than those of three other data-hiding methods which are investigated in this study.