Advanced Materials Research Vols. 143-144

Abstract: In a designated verifier proxy signature scheme, one can delegate his or her signing capability to another user in such a way that the latter can sign messages on behalf of the former, but the validity of the resulting signatures can only be verified by the designated verifier. Recently, Lee J-s et al. proposed a new ID-Based designated verifier proxy signature scheme. They didn't analysis the security of their scheme. We found out that anyone can generate a valid signature on any message m and mw he choose. To overcome this flaw in Lee J-s et al.'s scheme, we formalized the notion of designated verifier proxy signature scheme, provide a new ID-Based designated verifier proxy signature scheme. We also analyzed the proposed scheme.

Abstract: To improve the corrosion property of magnesium alloys, Mg-based amorphous composite coatings have been fabricated on AZ91D magnesium alloy by laser cladding using mixed powders Mg65Cu25Y10/SiC. The microstructure of the coating was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The corrosion resistance of the coatings was tested in 3.5wt.% NaCl solution. The results show that the coatings mainly consist of amorphous and different crystalline phases. The coatings compared to AZ91D magnesium alloy exhibit good corrosion resistance because of the presence of the amorphous phase in the coatings.

Abstract: The dynamics of a two degree-of-freedom (DOF) system consisting of a linear system coupled with a quadratic damping vibration absorber is studied. The nonlinear energy pumping phenomenon is verified by simulation and analyzed by Hilbert Transform. Performance of the quadratic damping absorber that is able to absorb vibration over a broad range of frequency (nonlinear energy sink, NES) is studied, and the results are compared with that of the classical linear vibration absorber. The relationship between parameters and performance of the absorber is analyzed, that is significant for engineering application.

Abstract: A surface reconstruction method for material shape analysis is presented. The three-dimensional shape reconstruction system detects object surface based on optical principle. A series of gratings are projected to the object, and the projected gratings are deformed by the object surface. From images of the deformed gratings, three-dimensional profile of the material surface can be obtained. The basic aspects of the method are discussed, including the vision geometry, the light projection and code principle. The proposed method can deal with objects with various discontinuities on the material surface, thus increasing the flexibility and robustness of shape reconstruction process. The experimental results show the efficiency of the method, the material surface can be reconstructed with high precision in various applications.

Abstract: This paper studied the influence of asymmetric information and demand disruption on the decision of the supply chain. We analyzed the supply chain decision models based on a Stackelberg game under normal circumstances and demand disruption situation. The conclusion indicates when the market demand is disrupted, the optimal wholesale price, the retail price, the supplier’s expected profit and the supply chain system’s expected profit change in the same direction as the demand disruption, while the optimal production quantity and the retailer’s profit both have certain robustness under disruption. Finally we gave a numerical example to illustrate our analysis.

Abstract: This paper presents an efficient method for motion objects detection in dynamic background.Three main aspects compose the proposed method.Firstly,abundant SIFT matching pairs were obtained from two successive frames.Secondly, a robust global motion estimation method based on SIFT matching pairs was presented.Finally, the moving objects could be detected after we compensate the global motion.Evaluations based on extensive experiments have shown that the proposed method can achieve the motion detection in dynamic backgrounds.

Abstract: Air-deck ratio plays a decisive role in blasting engineering. Researchers have conducted extensive work to study the optimal air-deck ratio. But consensus has not been achieved. Especially slotted charge blasting, the study on it just starts. For its complicated physical process in blasting, it is difficult to perform theoretical analysis to obtain the law between blasting result and air-deck ratio. The numerical simulation method is adopted to study the effect of different air-deck ratio on stress distribution at first. And then laboratory tests are carried out to validate the simulation results. The conclusion may be drawn that good directional fracture could be obtained with air-deck ratio 33.3% ~ 50%. The achievement could provide reference for blasting engineering.

Abstract: Nanowire-mesoporous network structured fluorocarbon polymer films were prepared by radio-frequency (RF) magnetron sputtering of a polytetrafluoroethylene (PTFE) target on a poly(ethylene terephthalate) (PET) substrate. The fluorocarbon films were used as precursor materials to prepare fluorocarbon/ZnO double-layered hybrid films by reaction sputtering of a Zn target on the fluorocarbon films. The hybrid films had strong UV absorption that was far larger than the sum of the individual absorptions of fluorocarbon film and ZnO film because of a synergistic effect. The hybrid films exhibited multi-enhanced ultraviolet absorption due to the π-conjugated molecular structure, the nanoparticle-mesoporous reflection of fluorocarbon polymer films, and the absorption effect of nanosized ZnO particles.

Abstract: By numerical simulation, the researches of effecting initial crack forming with slotted charge blasting are performed. The effecting factories conclude radial uncoupled parameter α and seam width W. Herein α adopts 1.43, 1.67 and 2, and 4, 6, 8 and 10 are adopted by W separately. The pressure peak is 15.5 GPa under α=1.67, and formed long cracks. With 6 and 8 mm seam widths, energy focus phenomenon is remarkable. The results show that initial damage of rock are decided by peak pressure of gas and function time. The seam width has significant effect to initial damage. With W adopting 6 and 8 mm, effective energy propagation is ensured and excessive damage area is avoided. The experiments validate the simulation results.

Abstract: To understand the creep damage mechanism of a standard 3D Carbon fiber reinforced silicon carbide composite (C/SiC) in high temperature combustion gas at 1300 °C, the creep tests were carried out in a combustion wind tunnel and the mechanisms were investigated by the extension of specimens and the microstructure of fracture section. It was found that the external tensile load was bore by the carbon fibers in the active region during the stressed oxidation process. The oxidation mechanisms of the active region were determined by a normalized threshold stress. Below the normalized threshold stress, the oxidation was controlled by internal diffusion of oxidizing gases through microcracks in SiC matrix. Above the normalized threshold stress, the oxidation was controlled by the reaction of carbon fiber with oxygen and water vapor.