Yang Z.-Y.,Baoji University of Arts And Sciences
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2010
The relations between the spin Hamiltonian (SH) parameters and crystal structure of Cr4+:α-Al2O3 crystals have been established. On the basis of this, the SH parameters including zero-field splitting parameter D and Zeeman g-factors (g|| and g⊥) for Cr4+ ions in Cr4+:α-Al2O3 crystals, taking into account the spin-spin (SS), spin-other-orbit (SOO) and orbit-orbit (OO) magnetic interactions in addition to the spin-orbit (SO) magnetic interaction, are theoretically investigated using complete diagonalization method (CDM). The theoretical results are in excellent agreement with the experimental ones when the upper three O2- ions rotate 0.94° toward [1 1 1] axis and the lower three O2- ions rotate 0.92° toward it. Hence, the local structure distortion effect plays an important role in explaining the spectroscopic properties of Cr4+ ions in Cr4+:α-Al2O3 crystals. This study shows that for Cr4+:α-Al2O3 the contributions arising from SS, SOO, and OO interactions to the zero-field splitting (ZFS) parameter D are appreciable, whereas those to g|| and g⊥ are quite small. © 2009 Elsevier B.V. All rights reserved.
Li H.,Baoji University of Arts And Sciences
Computers and Mathematics with Applications | Year: 2014
A diffusive predator-prey system with modified Leslie-Gower and Crowley-Martin functional response is considered. The extinction and permanence of the time-dependent system are determined by virtue of the comparison principle. Then, the sufficient and necessary conditions for the existence of coexistence states are obtained. Furthermore, the stability, uniqueness and exact multiplicity of coexistence states are investigated by means of the combination of the perturbation theory, bifurcation theory and degree theory. Our results indicate that c1 have an effect on the stability and exact multiplicity of coexistence states. Finally, some numerical simulations are presented to verify and complement the theoretical results. © 2014 Elsevier Ltd. All rights reserved.
Chen H.,Baoji University of Arts And Sciences
Materials Characterization | Year: 2010
The oxidation behaviors of AZ91D magnesium alloy in 1,1,1,2- tetrafluoroethane/air atmospheres at temperatures between 660 °C and 760 °C have been studied. The experimental results show that with the increase of melt temperature, the oxidation rate of molten AZ91D magnesium alloy in 1,1,1,2-tetrafluoroethane/air atmospheres increased and the oxidation kinetics changed from parabolic law to linear law. On the other hand, the amount of MgF2 in the oxide film formed on AZ91D decreased, and the amount of MgO increased. The effect of melt temperature on the oxidation behaviors is primarily related to the relative content of MgO and MgF2 in the film, as well as the diffusion rate and the evaporation rate of magnesium through the film. © 2010 Elsevier Inc. All rights reserved.
Tian D.,Baoji University of Arts And Sciences
Knowledge-Based Systems | Year: 2014
Automatic image annotation has been an active research topic in recent years due to its potential impact on both image understanding and semantic based image retrieval. In this paper, we present a novel two-stage refining image annotation scheme based on Gaussian mixture model (GMM) and random walk method. To begin with, GMM is applied to estimate the posterior probabilities of each annotation keyword for the image, during which a semi-supervised learning, i.e. transductive support vector machine (TSVM), is employed to enhance the quality of training data. Next, a label similarity graph is constructed by a weighted linear combination of label similarity and visual similarity of images associated with the corresponding labels. In this way, it can seamlessly integrate the information from image low-level visual features and high-level semantic concepts. Followed by a random walk process over the constructed label graph is implemented to further mine the correlation of the candidate annotations so as to capture the refining results, which plays a crucial role in semantic based image retrieval. Finally, extensive experiments carried out on two publicly available image datasets bear out that this approach can achieve marked improvement in annotation performance over several state-of-the-art methods. © 2014 Elsevier B.V. All rights reserved.
Dou S.,Baoji University of Arts And Sciences
Journal of Solid State Electrochemistry | Year: 2013
Layered structural lithium metal oxides with rhombohedral α-NaFeO2 crystal structure have been proven to be particularly suitable for application as cathode materials in lithium-ion batteries. Compared with LiCoO2, lithium nickel manganese oxides are promising, inexpensive, nontoxic, and have high thermal stability; thus, they are extensively studied as alternative cathode electrode materials to the commercial LiCoO2 electrode. However, a lot of work needs to be done to reduce cost and extend the effective lifetime. In this paper, the development of the layered lithium nickel manganese oxide cathode materials is reviewed from synthesis method, coating, doping to modification, lithium-rich materials, nanostructured materials, and so on, which can make electrochemical performance better. The prospects of lithium nickel manganese oxides as cathode materials for lithium-ion batteries are also looked forward to. © 2012 Springer-Verlag Berlin Heidelberg.
Tian D.P.,Baoji University of Arts And Sciences
International Journal of Multimedia and Ubiquitous Engineering | Year: 2013
Feature extraction and representation is a crucial step for multimedia processing. How to extract ideal features that can reflect the intrinsic content of the images as complete as possible is still a challenging problem in computer vision. However, very little research has paid attention to this problem in the last decades. So in this paper, we focus our review on the latest development in image feature extraction and provide a comprehensive survey on image feature representation techniques. In particular, we analyze the effectiveness of the fusion of global and local features in automatic image annotation and content based image retrieval community, including some classic models and their illustrations in the literature. Finally, we summarize this paper with some important conclusions and point out the future potential research directions.
Qian Y.,Baoji University of Arts And Sciences
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2014
We investigate the emergence of self-sustained oscillations in excitable Erdös-Rényi random networks (EERRNs). Interestingly, periodical self-sustained oscillations have been found at a moderate connection probability P. For smaller or larger P, the system evolves into a homogeneous rest state with distinct mechanisms. One-dimensional Winfree loops are discovered as the sources to maintain the oscillations. Moreover, by analyzing these oscillation sources, we propose two criteria to explain the spatiotemporal dynamics obtained in EERRNs. Finally, the two critical connection probabilities for which self-sustained oscillations can emerge are approximately predicted based on these two criteria. © 2014 American Physical Society.
Jiao J.-M.,Baoji University of Arts And Sciences
International Journal of Automation and Computing | Year: 2012
The robust stability and robust stabilization problems for discrete singular systems with interval time-varying delay and linear fractional uncertainty are discussed. A new delay-dependent criterion is established for the nominal discrete singular delay systems to be regular, causal and stable by employing the linear matrix inequality (LMI) approach. It is shown that the newly proposed criterion can provide less conservative results than some existing ones. Then, with this criterion, the problems of robust stability and robust stabilization for uncertain discrete singular delay systems are solved, and the delay-dependent LMI conditions are obtained. Finally, numerical examples are given to illustrate the effectiveness of the proposed approach. © 2012 Institute of Automation, Chinese Academy of Sciences and Springer-Verlag Berlin Heidelberg.
Wang H.,Baoji University of Arts And Sciences
Monatshefte fur Chemie | Year: 2013
Magnesium bis(trifluoromethane)sulfonimide [Mg(NTf2) 2] is an efficient catalyst for the synthesis of coumarins via the Pechmann condensation reaction of phenols and β-ketoesters under solvent-free conditions. © 2012 Springer-Verlag.
Qian Yu.,Baoji University of Arts And Sciences
Chinese Physics B | Year: 2012
The influence of long-range links on spiral waves in an excitable medium has been investigated. Spatiotemporal dynamics in an excitable small-world network transform remarkably when we increase the long-range connection probability P. Spiral waves with few perturbations, broken spiral waves, pseudo spiral turbulence, synchronous oscillations, and homogeneous rest state are discovered under different network structures. Tip number is selected to detect non-equilibrium phase transition between different spatiotemporal patterns. The Kuramoto order parameter is used to identify these patterns and explain the emergence of the rest state. Finally, we use long-range links to successfully control spiral waves and spiral turbulence. © 2012 Chinese Physical Society and IOP Publishing Ltd.