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Zhao X.,Chongqing University | Yang Y.,Chongqing University | Wu G.,Yingxiuwan Hydropower Plant | Yang J.,Chongqing Communication College | Xue X.,Chongqing University
Journal of Convergence Information Technology

The project portfolio selection has great strategic value for R&D projects. However, the decision makers have to rely on qualitative, dynamic and uncertain information in the decision process which could cause adverse effects on the portfolio outcome. To counteract these soft factors, technical capability, satisfactory degree of project benefit and the crossing similarity were selected as indicators to comprehensively and systematically evaluate candidate projects, and three different fuzzy approaches were proposed to quantify these indicators respectively. A multi-objective trade-off model was then constructed, and a simulated annealing genetic algorithm was introduced to solve it. An illustrative example was presented to verify the effectiveness of the approach. Source

Yang J.,Chongqing Communication College | Chen L.,Chongqing Communication College | Yuan Y.,Chongqing Communication College
Journal of Convergence Information Technology

Wireless Sensor Networks(WSNs) can real-time monitor, collect and process all kinds of information. They have wide applications. The demands of spectrum in WSNs rose sharply, thereby how to deal with the spectrum allocation of WSNs is a difficult problem. A dynamical and real-time spectrum allocation system is proposed, which was based on the network architecture of Internet of things by the means of Cognitive Radio and cloud computing, it include Cloud resource scheduling configuration, Real-time data memory, Distributional policy-making support and so on. Dynamic spectrum allocation system of WSNs assigned the spectrum dynamically and real-timely that it can improve the spectrum utilization rate. This system is an efficient path to face the spectrum needs of WSNs. Source

Chen L.,Chongqing University | Chai Y.,Chongqing University | Wu R.,Anhui University | Yang J.,Chongqing Communication College
IEEE Transactions on Circuits and Systems II: Express Briefs

This brief discusses the stability and stabilization of a class of fractional-order nonlinear systems with Caputo derivative. On the basis of the stability theory of fractional-order linear differential equation, Mittag-Leffler function, Laplace transform, and the Gronwall inequality, two sufficient conditions are derived for the asymptotical stability of a class of fractional-order nonlinear systems with fractional-order α 0 < \alpha \leq 1 and 1 < \alpha < 2, respectively. Then, two sufficient conditions for asymptotical stabilization of such fractional-order systems are obtained, in which feedback gains could be ensured by the pole placement technique. Finally, some numerical examples are provided to show the validity and feasibility of the proposed method. © 2004-2012 IEEE. Source

Shengchun W.,Chongqing University | Shengchun W.,Chongqing Communication College | Zhaoxiang D.,Chongqing University | Weidong S.,Chongqing Communication College
Composite Structures

A theoretical study on the sound transmission loss (STL) characteristics of unbounded orthotropic sandwich panels considering the transverse shear deformation is presented. With the transverse shear deformation taken into account, the governing equation of bending vibration for unbounded orthotropic sandwich panels is derived and implemented to the sound transmission problem. The expressions for impedance and transmission coefficient are also derived. The accuracy of the theoretical predictions is checked against available experimental data. The influence of several key parameters on the sound insulation properties of the orthotropic sandwich panel is then systematically studied, including shear rigidity of the core, face sheet thickness, and core thickness. Numerical analysis shows that shear rigidity has evident effect on coincidence critical frequency and STL property, and should not be neglected when predicting STL. Increasing face sheet thickness can move coincidence critical frequency to lower frequency region and improve STL, which is much more effective than increasing the core thickness. © 2010 Elsevier Ltd. Source

Song S.-H.,Chongqing University | Song S.-H.,Chongqing Communication College | Liao Q.,Chongqing University | Shen W.-D.,Chongqing Communication College
Applied Thermal Engineering

It is novel and better method that microencapsulated phase change material (MPCM) slurry and the tube with twisted tape inserts are adopted together to enhance convective heat transfer. In this paper, numerical analyses were carried out to study laminar heat transfer and friction characteristics of MPCM slurry in a circular tube with twisted tape inserts. It is found that the MPCM slurry in the tube with twisted tape insert leads to the best performance of convective heat transfer for the bigger apparent specific heat and the intensive swirl flow. Furthermore, the modified average Nusselt number increases with decreasing bulk Stefan number, twisted ratio and increasing Re, while the friction factor increases with increasing Re and decreasing twisted ratio. It is also found that the heat transfer enhanced efficiency increases with increasing Re and decreasing Steb, and the heat transfer enhancement effects of twisted tape for low Steb slurry are better than that for high Ste b slurry. Moreover, the thermal-hydraulic performance ratios increase to a peak, then decrease gradually with increasing Re for different twist ratio. The performance ratio increases with decreasing the twist ratio only in a definite Re range, and the Re range decreases with decreasing twist ratio. © 2012 Elsevier Ltd. All rights reserved. Source

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