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Wu C.-M.,Xian University of Posts and Telecommunications
Tien Tzu Hsueh Pao/Acta Electronica Sinica | Year: 2013

From the viewpoint of optimal image contrast measure, a kind of optimization mathematical models and its enhanced methods are proposed for image enhancement by histogram equalization. For the shortcoming of low operation efficiency of optimal contrast image enhancement method by linear programming, the gray level mapping optimization mathematical model for classical histogram equalization is established to improve its mathematical theory. The improved gray level mapping optimization models for histogram equalization are constructed by means of weighted geometry averaging in order to avoid the shortcoming of classical histogram equalization. The good properties of its optimal solution for gray level mapping optimization models are discussed, and the classical and adjustable histogram equalization methods are regarded as special cases of the proposed optimization mathematical models for image enhancement. Experimental results show that the optimization model of histogram equalization is reasonable and can obtain satisfactory image enhancement effect. To some extent, it is more universal than classical and adjustable histogram equalization methods.

Qi J.-X.,Xian University of Posts and Telecommunications
Guangdianzi Jiguang/Journal of Optoelectronics Laser | Year: 2014

2-dimensional metallic nanostructures were fabricated by self-assembling silver nanoparticles on 3-Aminopropyltrimethoxysilane (APS)-modified glass substrate. Surface enhanced Raman scattering (SERS) is investigated for Rhodamine 6G molecules deposited on the prepared 2-dimensional substrates. The experimental observation shows that the fabricated substrate presents strong Raman enhancement, and the enhanced factor is about 107 times with 532 nm excited laser beam. Higher intensity of local electric field and stronger coupling of surface plamon resonance in cluster silver nanostructure are obtained more effectively. The results suggest that a metallic substrate with 2-dimensional nanostructure can produce good Raman enhancement, which is important for studying the mechanism and expanding the potential applications of enhanced Raman effect.

Wu X.,Xian University of Posts and Telecommunications
International Journal of Digital Content Technology and its Applications | Year: 2011

Mobility, uncertainty and heterogeneity of mobile P2P systems make trust management much more complicated, so current existing trust models or trust management systems are inadequate in the mobile computing environments in which the clients are mobile, volatile and undetermined. In this paper we propose a novel Stable Group-based Trust Management Scheme (SGTMS). Within the same stable group, mobile peers are geographically and operationally close, i.e., sharing common mobility and tend to have a high probability of keeping stable distances from each other. Therefore, sufficient and reliable trust relationships are constructed in the group without relying on any fixed networking infrastructure or centralized entities. The simulation results show that our scheme is highly scalable, robust, and self-organizing in that it handles peer join and leave from the network.

Wu C.-M.,Xian University of Posts and Telecommunications
Wuli Xuebao/Acta Physica Sinica | Year: 2014

To improve the image scrambling and encryption effect in traditional two-dimensional discrete Arnold transform, a new nonlinear transform for image scrambling is proposed which improves the classical discrete Arnold transform with quasi-affine properties, and can be applied in image scrambling and encryption researching. This method first makes good use of the construction thought in classical discrete standard map, and embeds the nonlinear expressions of output results of one congruence equation for classical two-dimensional discrete Arnold transform into the input item of the other congruence equation for two-dimensional discrete Arnold transform. Then a new transform with good nonlinear characteristics is constructed on the basis of classical two-dimensional discrete Arnold transform in order to quickly improve the scrambling effect of the gray image. In the end, through mathematical proof it is shown that the proposed transform no longer has the quasi-affine invariance properties in the existing two-dimensional discrete Arnold transform, but it is still a reversible mapping with periodic properties; and when it is applied in image scrambling encryption, the original image can be restored from the scrambling and encryption in gray image for its periodic properties or inverse transform. Some experimental results show that the proposed nonlinear transform is effective, and can obtain better scrambling and encryption quality than the existing discrete two-dimensional Arnold transform, meanwhile it is more practical than the standard Arnold transform in view of security. © 2014 Chinese Physical Society.

Hu M.-L.,Xian University of Posts and Telecommunications
Annals of Physics | Year: 2012

Dynamics of disentanglement as measured by the tripartite negativity and Bell nonlocality as measured by the extent of violation of the multipartite Bell-type inequalities are investigated in this work. It is shown definitively that for the initial three-qubit Greenberger-Horne-Zeilinger (GHZ) or W class state preparation, the Bell nonlocality suffers sudden death under the influence of thermal reservoirs. Moreover, all the Bell-nonlocal states are useful for nonclassical teleportation, while there are entangled states that do not violate any Bell-type inequalities, but still yield nonclassical teleportation fidelity. © 2012 Elsevier Inc.

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