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In this paper, a three-dimensional chaotic system with a hidden attractor is introduced. The complex dynamic behaviors of the system are analyzed with a Poincaré cross section, and the equilibria and initial value sensitivity are analyzed by the method of numerical simulation. Further, we designed a new algorithm based on complementary ensemble empirical mode decomposition (CEEMD) and permutation entropy (PE) that can effectively enhance digital chaotic sequence complexity. In addition, an image encryption experiment was performed with post-processing of the chaotic binary sequences by the new algorithm. The experimental results show good performance of the chaotic binary sequence. [ABSTRACT FROM AUTHOR]

The tests of bullet impact on the base material (BM) of a simple specimen with a single resistance-spot-welded (RSW) nugget of TRIP800 steel are performed to investigate the response of the RSW specimen to the ballistic debris impact on the RSW specimen. A one-stage gas gun is used to fire the bullets while a laser velocity interferometer system for any reflector (VISAR) is used to measure the velocity histories of the free surfaces of the RSW specimen. The recovered RSW specimens are examined with the three-dimensional super depth digital microscope (SDDM) and the scanning electro microscope (SEM). For the tests of small multiple-bullet impact, it is revealed that the wave train of the VISAR measured results and the detachment of the base material interfaces in the recovered RSW specimens are directly related to the reflection and refraction of the curved stress waves incoming to the interfaces and the free surfaces in the RSW specimens. The detachment of BM interfaces can lead to the impact failure of the RSW joints for the larger multiple-bullet impact at higher velocity, the mechanism of which is different from the case for normal incidence (spalling). For the tests of single large bullet impact, it is brought to light experimentally that the plastic strain concentration at the “notch tip” spurs either the crack near the RSW joint or the split of the nugget. The numerical simulation shows up the process of splitting the nugget: a crack initiates at the “notch tip”, propagates across the nugget interface and splits the nugget into two parts. It is indicated that the interaction between the stress waves and many interfaces/free surfaces in the RSW specimen under ballistic impact causes variable local stress triaxialities and stress Lode angles, which affects the deformation and fracture mechanism of the RSW specimen including stretching and shearing failure. It is shown that the impact failure of the RSW joints is a mixture of brittle fracture and ductile fracture while the fracture or perforation of the BM is ductile. [ABSTRACT FROM AUTHOR]

Abstract: A kinetic–frictional model, which treats the kinetic and frictional stresses in an additive manner, was incorporated into the two fluid model based on the kinetic theory of granular flow to simulate three dimensional flow behaviors of dense phase pneumatic conveying of pulverized coal in horizontal pipe. The kinetic stress was modeled by the kinetic theory of granular flow, while the friction stress is from the combination of the normal frictional stress model proposed by Johnson and Jackson [1987. Frictional–collisional constitutive relations for granular materials, with application to plane shearing. Journal of Fluid Mechanics 176, 67–93] and the modeled frictional shear viscosity model proposed by Syamlal et al. [1993. MFIX documentation and theory guide, DOE/METC94/1004, NTIS/DE94000087. Electronically available from http://www.mfix.org], which was modified to fit experimental data. For the solid concentration and gas phase Reynolds number was high, the gas phase and particle phase were all treated as turbulent flow. The experiment was carried out to validate the prediction results by three kinds of measurement methods. The predicted pressure gradients were in good agreement with experimental data. The predicted solid concentration distribution at cross section agreed well with electrical capacitance tomography (ECT) image, and the effects of superficial velocity on solid concentration distribution were discussed. The formation and motion process of slug flow was demonstrated, which is similar to the visualization photographs by high speed video camera. [Copyright &y& Elsevier]