Xie Z.-X.,Hunan University of Technology |
Chen K.-Q.,Hunan University of Technology |
Duan W.,Tsinghua University
Journal of Physics Condensed Matter | Year: 2011
The thermal transport properties by phonons in zigzag graphene nanoribbons with structural defects are investigated by using nonequilibrium phonon Green's function formalism. We find that the combined effect of the edge and local defect plays an important role in determining the thermal transport properties. In the limit T → 0, the thermal conductance approaches the universal quantum value 3K0(K0 = π2k2 B T/3h) even when structural defects are presented in graphene nanoribbons. The thermal transport shows a noticeable transformation from quantum to classical features with increasing temperature in the system. A suggestion to tune the thermal conductance by modulating structural defects and the ribbon width in graphene nanoribbons is presented. © 2011 IOP Publishing Ltd.
Dou C.-X.,Yanshan University |
Liu B.,Hunan University of Technology |
Liu B.,Australian National University
IEEE Transactions on Smart Grid | Year: 2013
This paper studies the smart control issue for an autonomous microgrid in order to maintain the secure voltages as well as maximize economic and environmental benefits. A control scheme called as multi-agent based hierarchical hybrid control is proposed versus the hierarchical control requirements and hybrid dynamic behaviors of the microgrid. The control scheme is composed of an upper level energy management agent, several middle level coordinated control agents and many lower level unit control agents. The goals of smart control are achieved by designed control strategies. The simulations are given to demonstrate the effectiveness of proposed smart control for an autonomous microgrid. © 2010-2012 IEEE.
Zhang A.,Hunan University of Technology
Neural Processing Letters | Year: 2015
This paper discusses the issue of a class of cellular neural networks with continuously distributed delays in the leakage terms. By applying Lyapunov functional method and differential inequality techniques, without assuming the boundedness conditions on the activation functions, a new delay dependent sufficient condition is derived to ensure that all solutions of the networks converge exponentially to the zero point, which corrects some recent results of Xiong and Meng (Electron J Qual Theory Differ Equ, (10):1–12, 2013. http://www.math.u-szeged.hu/ejqtde/). © 2014, Springer Science+Business Media New York.
Li Q.-H.,Hunan University of Technology |
Chen S.-S.,Hunan University of Technology |
Kou G.-X.,Hunan University of Technology
Journal of Computational Physics | Year: 2011
The meshless local Petrov-Galerkin (MLPG) method in conjunction with the modified precise time step integration method in the time domain is proposed for transient heat conduction analysis in this paper. The MLPG method is often referred to as a truly meshless method because it requires no elements or background cells for either field interpolation or background integration. Local weak forms are developed using weighted residual method locally from the partial differential equation of transient heat conduction. In order to simplify the treatment of essential boundary conditions, the natural neighbour interpolation (NNI) is employed for the construction of trial functions. Moreover, the three-node triangular FEM shape functions are taken as test functions to reduce the order of integrands involved in domain integrals. The semi-discrete heat conduction equation is solved numerically with modified precise time step integration method in the time domain. The availability and accuracy of the present method for transient heat conduction analysis are tested through numerical examples. © 2011 Elsevier Inc.
Liu S.,Hunan University of Technology |
Huang C.,Central South University
Buildings | Year: 2016
The unique architectural style of traditional "Yinzi" dwellings inWestern Hunan, China, needs to be protected and their natural ventilation of patio space should also be promoted. Therefore, this study aimed at finding out the natural ventilation values and limitations of "Yinzi" dwellings as well as designing an optimum ventilation strategy for such dwellings. In this work, the thermal environment of a typical "Yinzi" dwelling was tested. The two patios and living room space of "Yinzi" dwellings was selected for a quantitative analysis, and CFD software was adopted to simulate the stack effect of different patio proportions under the same static wind environment conditions. In addition, an orthogonal experiment is combined with CFD simulation to explore the best proportion and position of patio of "Yinzi" dwellings. A final optimum ventilation strategy is provided for the "Yinzi" dwellings, which can significantly promote the natural stack effect of "Yinzi" dwellings in summer. © 2016 by the authors.
Cai S.-P.,Hunan University of Technology
Journal of Hydrodynamics | Year: 2010
In order to develop technologies of friction drag reduction with a flexible tube to be used for water transport, experimental studies were carried out on the influence of Young's modulus on the turbulent drag reduction. The friction coefficients of flexible tubes with different Young's modulus were examined by using a sleeve-tube structure. The fluctuating vibration of the outer wall and the fluctuating pressure on the inner wall of the tubes were measured with a laser displacement sensor and a pressure sensor. The results are as follows. The smaller the Young's modulus of a flexible tube and the larger the Reynolds number, the larger the turbulent drag reduction rates become. The transition from laminar flow to turbulent flow can be delayed with an appropriate Young's modulus. Non-dimensional amplitude of fluctuating vibration on the outer wall is smaller than that of a viscous sub-layer thickness, and is positively correlated with the friction drag reduction. © 2010 Publishing House for Journal of Hydrodynamics.
Chen Z.,Hunan University of Technology |
Yang M.,Jiaxing University
Neural Computing and Applications | Year: 2013
This paper considers exponential convergence for a class of high-order recurrent neural networks (HRNNs) with continuously distributed delays in the leakage terms (i.e., "leakage delays"). Without assuming the boundedness on the activation functions, some sufficient conditions are derived to ensure that all solutions of this system converge exponentially to zero point by using Lyapunov functional method and differential inequality techniques, which are new and complement previously known results. In particular, we propose a new approach to prove the exponential convergence of HRNNs with continuously distributed delays in the leakage terms. Moreover, an example is given to show the effectiveness of the proposed method and results. © 2012 Springer-Verlag London Limited.
Chen Z.,Hunan University of Technology
Neural Computing and Applications | Year: 2013
In this paper, a shunting inhibitory cellular neural network with leakage delays and continuously distributed delays of neutral type is considered. Some sufficient conditions are established to ensure that all solutions of the networks converge exponentially to zero point, which are new and complement of previously known results. © 2012 Springer-Verlag London.
Xu C.,Guizhou University of Finance and Economics |
Zhang Q.,Hunan University of Technology
Neural Computation | Year: 2014
In this letter, a class of Cohen-Grossberg shunting inhibitory neural networks with time-varying delays and impulses is investigated. Sufficient conditions for the existence and exponential stability of antiperiodic solutions of such a class of neural networks are established. Our results are new and complementary to previously known results. An example is given to illustrate the feasibility and effectiveness of our main results. © 2014 Massachusetts Institute of Technology.
He S.W.,Hunan University of Technology
Advanced Materials Research | Year: 2011
Warm compacting behaviors of pure titanium powders were studied. The results show that warm compaction can be applied to titanium powders. The green densities obtained through warm compaction are generally higher than obtained through cold compaction at the same pressure. The optimal warm compacting temperature is about 140 . At the compacting pressure of 500 Mpa, the ejection force of titanium powders through warm compaction is 32.4% lower than through cold compaction. At the same pressure, the effective compression force through warm compaction is bigger than one through cold compaction. In addition, the densification mechanism of warm compaction was discussed. © (2011) Trans Tech Publications.