Xu J.,Shaoyang University
Yadian Yu Shengguang/Piezoelectrics and Acoustooptics | Year: 2012
The effects of B 2O 3 with w=0.5% to 3.0% on the structure and microwave properties of Ba(Mg 1/3Ta 2/3)O 3(BMT) ceramic has been investigated. It has been found that B 2O 3 doping can improve the BMT microwave ceramic sintering. When w(B 2O 3) is equal to 1%, the densification sintering temperature of BMT ceramic has been reduced to 1200°C, the apparent density ρ is equal to 7306 g/cm 3, the relative density is 95.7%. The BMT microwave ceramic system has good microwave dielectric properties as follows: ε r=22.08, the quality factor Q·f =88 000 GHz(10 GHz), the coefficient of frequency to temperature τ f =3.3×10 -6/°C.
Liang G.,Central South University |
Liang G.,Shaoyang University |
Zhou J.,Central South University |
Huang X.,Central South University
Applied Energy | Year: 2011
The paper studied the performances of parallel thermoelectric generator (TEG) by theoretical analysis and experimental test. An analytical model of parallel TEG was developed by theoretical analysis and calculation, based on thermodynamics theory, semiconductor thermoelectric theory and law of conservation of energy. Approximate expressions of output power and current of parallel TEG were deduced by the analytical model. An experimental system was built to verify the model. The results indicate that only when all of the thermoelectric modules (TE modules) in the parallel TEG have the same inherent parameters and working conditions, the parallel properties of the TEG are the same as that of common DC power. The existence of contact resistance is just like the increase of the TE module's internal resistance, which leads to the deceases of output power. The thermal contact resistance reduces the output power by reducing the temperature difference between the two sides of the thermocouples. The results derived from the model are basically consistent with the experimental results, the model is suitable for the performance researching and designing of parallel TEG. © 2011 Elsevier Ltd.
Liu Y.,University for Business Studies |
Liu X.,Shaoyang University
Mathematical Methods in the Applied Sciences | Year: 2013
Sufficient conditions for the existence of at least one periodic solution of two classes of nonlinear higher order periodic difference equations are established, respectively. The results show us that sufficient conditions for the existence of T - periodic solutions of difference equation are different from those ones for the existence of T - periodic solutions of differential equation. Copyright © 2012 John Wiley & Sons, Ltd. Copyright © 2012 John Wiley & Sons, Ltd.
Du C.,Shaoyang University |
Huang W.,Guilin University of Electronic Technology
Nonlinear Dynamics | Year: 2013
The problem of limit cycles for the Kolmogorov model is interesting and significant both in theory and applications. In this paper, we investigate the center-focus problems and limit cycles bifurcations for a class of cubic Kolmogorov model with three positive equilibrium points. The sufficient and necessary condition that each positive equilibrium point becomes a center is given. At the same time, we show that each one of point (1,2) and point (2,1) can bifurcate 1 small limit cycles under a certain condition, and 3 limit cycle can occur near (1,1) at the same step. Among the above limit cycles, 4 limit cycles can be stable. The limit cycles bifurcations problem for Kolmogorov model with several positive equilibrium points are hardly seen in published references. Our result is new and interesting. © 2012 Springer Science+Business Media Dordrecht.
Tong S.,Shaoyang University
Advance Journal of Food Science and Technology | Year: 2015
Since food safety as a hot issue is directly related to China's international trade. This study takes the current situation of China's food trade as the breakthrough point, by means of analyzing the influence of food safety on export trade it explores the countermeasures of China's food safety for dealing with export trade based on TOPSIS method. © Maxwell Scientific Organization, 2015.