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This paper analyzed the security of an image encryption algorithm based on compound chaotic sequence, the proposed algorithm adopted three-level encryption structure of permutation-forward diffusion-reverse diffusion. Due to the forward diffusion and the reverse diffusion used the same one-dimensional diffusion sequence, therefore, this paper simplified the two level encryption structure of the forward diffusion and reverse diffusion to one-level diffusion encryption structure, further, simplified the three-level encryption structure of permutation-forward diffusion-reverse diffusion to two-level encryption structure of permutation and diffusion. Moreover, the chaotic sequences generated by the encryption algorithm were independent of the plaintext images or ciphertext images, consequently, it could crack the corresponding equivalent diffusion keys and equivalent permutation keys by chosen-plaintext attack. Theoretical analysis and numerical simulation experiment results verify the effectiveness of the analytical method. Finally, this paper proposed some improved suggestions for the original encryption algorithm to promote the security. [ABSTRACT FROM AUTHOR]

This paper developed an opportunistic maintenance strategy model of multi-component equipment based on disassembly sequence for the problem that disassembly is not considered in the maintenance of multi-component equipment. Firstly, it represented the disassembly sequence by the disassembly mixture diagram, and then obtained the disassembly time and cost of each component. It described the failure characteristics of each component by combining the mixed failure rate of decreasing service age factor and increasing failure rate factor according to the decline process of each component. Secondly, on this basis, it solved the optimal preventive maintenance plan with the equipment opportunity window as the decision variable and the lowest maintenance cost as the goal under the condition that the equipment met certain availability. Finally, through numerical simulation analysis, it verified the effectiveness of the proposed multi-component opportunistic maintenance strategy. [ABSTRACT FROM AUTHOR]

In order to study the anti-blast performance of flexible fabrics, the dynamic response and failure behavior of aramid fabric under blast impact were analyzed with the numerical simulation method. Mechanical tests of aramid fabric H I 000D-AP220 were carried out, and the constitutive model for woven fabric and the explosive numerical analysis model were established. The dynamic responses and failure modes of the fabrics under different loads were obtained by the analysis of fabrics with different thicknesses and different stacking angles. The results show that, there are 2 typical failure modes of fabrics under the explosive impact: the failure of the central hole and the tensile tear at the boundary, with obvious folds in the width direction of the fabric. The front and back layers absorb more energy than the middle ones. Better anti-explosion ability can be achieved through adjustment of the fabric stacking angle. [ABSTRACT FROM AUTHOR]