Changsha University

Changsha, China

Changsha University

Changsha, China

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Pan Z.,Changsha University
Proceedings - 2016 International Conference on Smart City and Systems Engineering, ICSCSE 2016 | Year: 2016

In this paper, we focus on the problem of Urban vegetation type analysis, which is a key problem in Urban construction. Firstly, our proposed Urban vegetation type classification system is made up of three parts: 1) Image pre-procesing, 2) Feature space mapping, and 3) Classification. Secondly, in order to tackle the feature space mapping problem, we exploit the Kernel-based Principal Component Analysis (KPCA) technology, which means a nonlinear feature extraction approach. Moreover, KPCA can map the data from the original input space into a higher dimensional feature space with a nonlinear map function. Thirdly, we choose the Gaussian radial basis function as the kernel for KPCA, and then build up the feature vectors of high resolution satellite images. Fourthly, the Urban vegetation type is analyzed based on the support vector machine. Finally, experimental results show that the proposed method can significantly improve the Urban vegetation type classification accuracy. © 2016 IEEE.

Xu D.,Wuhan University of Technology | Xu D.,Changsha University | Cheng B.,Wuhan University of Technology | Cao S.,Wuhan University of Technology | Yu J.,Wuhan University of Technology
Applied Catalysis B: Environmental | Year: 2015

Silver chromate-graphene oxide (Ag2CrO4-GO) composites are prepared by a facile precipitation method. The resulting Ag2CrO4-GO composites exhibit excellent photocatalytic activity and stability towards the degradation of the dyes and phenol in aqueous solution under visible-light irradiation. The optimal composite with 1.0wt% GO content shows the highest photocatalytic activity for methylene blue (MB) degradation, which is 3.5 times that of pure Ag2CrO4 particles. The enhanced photocatalytic activity is mainly attributed to the formation of Ag2CrO4-GO Z-scheme heterojunction that can not only facilitate the separation and transfer of the photogenerated charge carriers, but also preserve a strong oxidation and reduction ability. The high photocatalytic stability is due to the successful inhibition of the photocorrosion of Ag2CrO4 by transferring the photogenerated electrons of Ag2CrO4 to GO. The present work provides a new understanding into design and fabrication of the GO/silver compound composite photocatalysts. © 2014 Elsevier B.V.

Yu W.,Wuhan University | Xu D.,Changsha University | Peng T.,Wuhan University
Journal of Materials Chemistry A | Year: 2015

Photocatalytic CO2 reduction into renewable hydrocarbon solar fuels is considered as a promising strategy to simultaneously address the global energy and environmental issues. In this study, a binary g-C3N4/ZnO photocatalytic system was constructed via a one-step facile calcination method and further used as a photocatalyst for CO2 reduction. It was shown that the as-prepared g-C3N4/ZnO photocatalytic system exhibited enhanced photocatalytic activity for CO2 reduction by a factor of 2.3 compared with pure g-C3N4, while maintaining the original selectivity of pure g-C3N4 to convert CO2 directly into CH3OH. For the first time, the coupling effect of ZnO responsible for the improved photoactivity of g-C3N4 was fully illustrated and a direct Z-scheme mechanism rather than the conventional heterojunction-type mechanism was proposed to explain the better performances of the g-C3N4/ZnO binary composite photocatalytic system. The enhancement of photocatalytic CO2 reduction activity is attributed to the highly efficient ZnO-to-g-C3N4 electron transfer occurring at the intimate contact interface between the g-C3N4 phase and ZnO phase. This work will provide new deep insights into the rational construction of a g-C3N4-based photocatalytic system and the design of a direct Z-scheme system without an electron mediator for photocatalytic CO2 reduction reactions. © The Royal Society of Chemistry 2015.

Yang R.,Changsha University | He Y.,National University of Defense Technology
Applied Physics Letters | Year: 2015

Anisotropy and inhomogeneity of carbon fiber reinforced polymers (CFRPs) result in that many traditional non-destructive inspection techniques are inapplicable on the delamination evaluation. This letter introduces eddy current pulsed phase thermography (ECPPT) for CFRPs evaluation considering volumetric induction heating due to small electrical conductivity, abnormal thermal wave propagation, and Fourier analysis. The proposed methods were verified through experimental studies under transmission and reflection modes. Using ECPPT, the influence of the non-uniform heating effect and carbon fiber structures can be suppressed, and then delamination detectability can be improved dramatically over eddy current pulsed thermography. © 2015 AIP Publishing LLC.

Yang R.,Changsha University | He Y.,National University of Defense Technology
Infrared Physics and Technology | Year: 2014

Longitudinal heat conduction from surface to inside of solid material could be used to evaluate the subsurface defects. Considering that the skin depth of high frequency eddy current in metal is quite small, this paper proposed logarithmic analysis of eddy current thermography (ECT) to quantify the depth of subsurface defects. The proposed method was verified through numerical and experimental studies. In numerical study, ferromagnetic material and non-ferromagnetic material were both considered. Results showed that the temperature-time curve in the logarithm domain could be used to detect subsurface defects. Separation time was defined as the characteristic feature to measure the defect's depth based on their linear relationships. The thermograms reconstructed by logarithm of temperature can improve defect detectability. © 2014 Elsevier B.V. All rights reserved.

Mo H.,Changsha University of Science and Technology | Mo H.,Changsha University
Zidonghua Xuebao/Acta Automatica Sinica | Year: 2012

In order to describe the fuzzy set whose intention varies with time interval, we present the theory of time-varying universe of discourse and dynamic fuzzy rules by synthesizing fuzzy set, linguistic dynamic systems (LDS), and dynamic programming. The time-varying universe discourse is divided into two types: discrete type and continuous type, and each type is sorted into incremental, decremental, and mixed classes. Then, how to build dynamic fuzzy rules and how to compute with words on time-varying universe of discourse are discussed. Finally, the linguistic dynamic orbits on the time-varying universe of discourse are given. Copyright © 2012 Acta Automatica Sinica. All rights reserved.

Guo H.,Changsha University | Yue W.,Hunan University of Science and Technology
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2012

A robust design method of planar linkage mechanism is proposed when the length errors of links and the kinematic pair clearances are taken into account. The offset between the socket center and the pin center caused by the clearance in a pin joint is calculated and its effect on the positional posture of a planar linkage mechanism is analyzed. The position vector equation is used to represent the positional posture of a planar linkage mechanism with kinematic pair clearances. According to the pair elements of pin joints at the both ends of links, the links of a mechanism are classified into three types: the link with two sockets, the link with two pins, the link with one socket and one pin. The value and the direction of the offset in a pin joint are viewed as two random variables. Three effective length models corresponding to three link types are proposed and three calculation formulas of effective lengths are derived by using thecomplex number vector method. The calculation accuracy of the proposed effective length models is validated by simulations and it is showed that the calculation accuracy of the derived formulas is satisfactory to engineering design. Based on the proposed models, an example is given to achieve the robust design optimization of a slider-crank mechanism generating a given function. The example shows that the proposed method is practical and effective. © 2012 Journal of Mechanical Engineering.

Sheng W.,Changsha University | Bao Y.,Changsha University
Nonlinear Dynamics | Year: 2013

By adding an electronic throttle and a torque sensor to an engine, it is potentially possible to improve emissions and fuel economy while preserving the torque response of a conventional engine. To do so effectively, however, requires the use of proper control strategy for electronic throttle. In this paper, a kind of fractional order fuzzy PID controller is proposed and it is applied to an electronic throttle. An efficient way to tune fractional order fuzzy PID controller parameters is proposed using a fruit fly optimization algorithm (FOA), which treats the controller parameters tuning as an optimization problem with a proper fitness function. The obtained simulation results show the effective performance of the proposed method. © 2013 Springer Science+Business Media Dordrecht.

Zhu Y.,Changsha University
Advances in Information Sciences and Service Sciences | Year: 2011

Peer-to-Peer (P2P) network has become an essential transmission model for information dissemination and file sharing over the Internet. In this paper, we propose an information security scheme based on JXTA protocol, called XMLP2P. The scheme achieves the aim of hiding secret information in JXTA by modifying the XML documents. In addition, we use secret information dispersal algorithm to complete sensitive data transmission. Security analysis shows our secret scheme is effective in P2P environment.

Li Z.,Changsha University | Li J.,Changsha University
Current Organic Chemistry | Year: 2013

Dendrimers are highly branched macromolecules with well-defined molecular structures and nanometer-scale dimensions. Dendrimer-supported catalysts behave homogeneously during the reaction, but most of them can be separated from the reaction medium via solvent precipitation. Their catalytic properties can be fine-tuned by adjusting the structure, size and shape of the dendrimers. In many cases, interesting dendrimer effects were observed, including increased or decreased the catalytic activity, stability and enantioselectivity. This review focuses on the recent decade of progress concerning the dendrimer-supported catalysts in the following reactions: (a) asymmetric hydrogenation and hydrosilylation; (b) asymmetric transfer hydrogenation; (c) carbon-carbon bond-forming reactions; (d) miscellaneous reactions. © 2013 Bentham Science Publishers.

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