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Li Q.,Xian Technological University
International Review on Computers and Software | Year: 2012

Considering the weak points of FCM (Fuzzy C Means) algorithm and improved intra-class minimum, this paper proposes gray-level image threshold segmentation, based on double set FCM and improved intra-class minimum, which enhances the conventional methods in the following two aspects: first, double set methods can reduce time complexity of FCM algorithm and improved intra-class minimum; second, proper shifts of segmentation thresholds will advance the segmentation effect of improved intra-class minimum. From the mathematical analyses of experiment results in this paper, it can be found that the proposed algorithm has obvious advantages over FCM and improved intra-class minimum, especially in time spending and segmentation effect. © 2012 Praise Worthy Prize S.r.l. - All rights reserved. Source

Liansheng S.,Xian University of Science and Technology | Meiting X.,Xian University of Science and Technology | Ailing T.,Xian Technological University
Optics Letters | Year: 2013

A multiple-image encryption scheme is proposed based on the phase retrieval process and phase mask multiplexing in the fractional Fourier transform domain. First, each original gray-scale image is encoded into a phase only function by using the proposed phase retrieval process. Second, all the obtained phase functions are modulated into an interim, which is encrypted into the final ciphertext by using the fractional Fourier transform. From a plaintext image, a group of phase masks is generated in the encryption process. The corresponding decrypted image can be recovered from the ciphertext only with the correct phase mask group in the decryption process. Simulation results show that the proposed phase retrieval process has high convergence speed, and the encryption algorithm can avoid cross-talk; in addition, its encrypted capacity is considerably enhanced. © 2013 Optical Society of America. Source

Yu F.,Xian Technological University
Journal of Physical Chemistry A | Year: 2014

We have optimized two double-hybrid density functionals (DHDFs) within the frameworks of B2PLYP and mPW2-PLYP against the S22B database. These two functionals are denoted as B2NC-PLYP and mPW2NC-PLYP, where "NC" represents noncovalent interaction. The DHDFs of B2NC-PLYP and mPW2NC-PLYP are optimized free of dispersion and counterpoise corrections with triple-δ quality basis sets. Combined with the aug-cc-pVTZ basis set, these two functionals are further assessed with the S66 database. According to our computations, both the B2NC-PLYP and mPW2NC-PLYP functionals seem to be competent for investigating noncovalent interactions. Note that the triple-δ quality basis sets with adequate polarization and diffuse functions should be employed for practical applications. However, different exchange and correlation functionals may be selected and/or modified to reduce the amount of the Fock-exchange in the future. © 2014 American Chemical Society. Source

Guo H.-L.,Northwest University, China | Su P.,Northwest University, China | Kang X.,Northwest University, China | Ning S.-K.,Xian Technological University
Journal of Materials Chemistry A | Year: 2013

Nitrogen-doped graphene hydrogels (NGHs) were synthesized through a one-pot hydrothermal route with graphene oxide (GO) as raw material and urea as reducing-doping agents. The morphology, structure, and components of the NGHs were characterized by scanning electron microscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, methylene blue adsorption, thermogravimetric analysis and electrical conductivity measurements. The results demonstrated that nitrogen was doped into the graphene plane at the same time as the GO sheets were reduced, and the nitrogen content incorporated into the graphene lattice was in the range of 3.95 to 6.61 at.% with pyrrolic N as the main component. The NGHs contained about 97.6 wt% water and have a large specific surface area (SSA) of >1300 m2 g-1 in the wet state. In addition, the electrochemical performance of the NGHs was investigated. The sample NGHs-4 with a nitrogen content of 5.86 at.% and SSA of 1521 ± 60 m2 g-1 in the wet state showed excellent capacitive behavior (308 F g-1 at 3 A g-1) and superior cycling stability (92% retention after 1200 cycles) in 6 mol L-1 KOH. The experimental results indicated that not only the N-content but also the N-type have very significant impact on the capacitive behavior. Furthermore, NGHs strongly influenced the electrochemical properties because of their high SSAs and mesoporous structure. This journal is © The Royal Society of Chemistry 2013. Source

The intermolecular interactions of formic acid (HCOOH) with benzene (C 6H6) have been investigated using localized molecular orbital energy decomposition analyses (LMO-EDA) with ab initio MP2 and several double-hybrid density functionals. The molecular geometries of five HCOOH.C 6H6 complexes and corresponding benchmark total interaction energies at the CCSD(T)/CBS level are taken from literature (Zhao et al., J. Chem. Theory Comput. 2009, 5, 2726). According to the results of LMO-EDA with the MP2 method, the dispersion energies are found to be as important as the electrostatic energies for the total interaction energies of the five HCOOH.C6H6 complexes. Based on LMO-EDA with the double-hybrid density functionals of B2PLYP, B2K-PLYP, B2T-PLYP, and B2GP-PLYP computations, two new parameters for the framework of B2PLYP are extrapolated. These two new parameters are tested with other 10 complexes involving C 6H6 (Crittenden, J. Phys. Chem. A 2009, 113, 1663), and they perform well on predicting the corresponding total interaction energies. Interestingly, these two new parameters for the framework of B2PLYP also perform well on the noncovalent complexation energies database (NCCE31/05) developed by Truhlar's group (Zhao and Truhlar, J. Phys. Chem. A 2005, 109, 5656). Therefore, these two new parameters appear to be suitable for investigating the noncovalent interactions, and they are denoted as B2N-PLYP, where N stands for the noncovalent interaction. This study is expected to provide new insight into the derivation of double-hybrid density functionals for studying the noncovalent interactions. © 2013 Wiley Periodicals, Inc. Source

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