On the Dynamics of

We investigate the existence of unbounded solutions and the period-two convergence of solutions of the equation in the title with the parameter γ positive, the remaining parameters nonnegative, and with nonnegative initial conditions.     

Understanding periodically twinned structure in nano-wires

Using first-principles calculations we have investigated the high stability of twinned nano-wires, which explains why the stacking faults always appear. Furthermore, we present a growth model to describe the formation mechanism of the stacking faults in the compound nano-wire with zinc-blende structure (e.g. SiC). And the model is confirmed by the numerical calculation based on the point charge approximation.     

A study of the properties of mixed nonionic surfactants microemulsions by NMR, SAXS, viscosity and conductivity

The pseudoternary phase behavior of the water/sucrose laurate/ethoxylated mono-di-glyceride/R (+)-limonene systems was investigated for different surfactants mixing ratios (w/w) at 25 °C. The microemulsion boundaries were determined and the surfactants content at the interface of water- R (+)-limonene was estimated. For surfactants mixing ratio (w/w) equals unity, the area of the one phase microemulsion region reaches its maximum. The system with the maximum microemulsion area was investigated using electrical conductivity, dynamic viscosity, small angle X-ray scattering, and nuclear magnetic resonance. Electrical conductivity increases as the water volume fraction increases and a percolation threshold was observed. Dynamic Viscosity varies as function of the water volume fraction in a non-monotonic way giving two-peaked plot. The characteristics of the domain size of the microemulsions called periodicity measured by small angle X-ray scattering increases with the increase in the water volume fraction. The correlation length of the domain size reaches a maximum when plotted against the water volume fraction in the microemulsions. Relative diffusion coefficients of water increase and those of oil decrease with increasing the water volume fractions in the microemulsions indicating structural transitions.     

相对论速调管放大器辐射频率可调性机理

 用场方法研究了相对论速调管放大器辐射频率的可调性。发现调制电流频率的可调性与一阶Bessel函数的周期相关，对应相同的一阶Bessel函数值，可以有多个不同数值的宗量，调制电流的频率与Bessel函数宗量数值包括中间腔与提取腔之间的距离和电子束的传输速度等因素相联系。理论估计的调制电流频率可调范围与实验测得的结果符合得很好。相对论速调管放大器辐射频率的可调性还取决于提取腔的设计。     

A multigrid method for predicting periodically fully developed flow

The use of multigrid methods in complex fluid flow problems is still under development. In this paper a full multigrid procedure has been incorporated in a finite volume solution for predicting fully developed fluid flow in a streamwise periodic geometry. Steady computations in two-dimensional body fitted co-ordinates have shown considerable savings in computation time by this multigrid method.     

On Periodic (Co)Homology of Groups

Here we show that a countable group G has periodic cohomology of period q after some steps with the periodicity isomorphisms induced by cup product with an element in H ^q (G, ?) if and only if G has periodic homology of period q after some steps with the periodicity isomorphisms induced by cap product with an element in H ^q (G, ?). In [2 Asadollahi , J. , Hajizamani , A. , Salarian , Sh. Periodic flat resolutions and periodicity in group (co)homology. To appear in Forum Mathematicum.  [Google Scholar]] Asadollahi, Hajizamani, and Salarian showed that, if a group G is such that every flat ?G-module has finite projective dimension, then G has periodic cohomology of period q after some steps with the periodicity isomorphisms induced by cup product with an element in H ^q (G, ?) if and only if G has periodic homology of period q after some steps with the periodicity isomorphisms induced by cap product with an element in H ^q (G, C), where C is the cotorsion envelope of the trivial ?G-module ?.     

On the periodic nature of the solutions of the reciprocal difference equation with maximum

We prove that every positive solution of the third order difference equation

     

Globally asymptotical stability and periodicity for a nonautonomous two-species system with diffusion and impulses

Existence and globally asymptotical stability of positive periodic solutions for a nonautonomous two-species competition system with diffusion and impulses are studied in this paper. By employing Mawhin continuation theorem, a set of easily verifiable sufficient conditions are obtained for the existence of at least one positive periodic solution, and by means of a suitable Lyapunov functional, the globally asymptotical stability of positive periodic solution is presented. Finally, an illustrative example and simulations are given to show the effectiveness of the main results.