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Wen W.,Hohai University | Zhao C.,Hohai University | Ma X.,Xinjiang Normal University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

We present an investigation of generation, dynamics, and stability of dark solitons in anisotropic Fermi gases for a range of particle numbers and trap aspect ratios within the framework of the order-parameter equation. We calculate the periods of dark solitons oscillating in a trap and find good agreement with the results based on the Bogoliubov-de Gennes equations. By studying the stability of initially off-center dark solitons under various tight transverse confinements in the unitarity limit, we not only give the criterion of dynamical stability, but also find that the soliton and a hybrid of solitons and vortex rings can be characterized by different oscillation periods. The stability criterion is not fulfilled by the parameters of the recent experiment of Yefsah. Therefore, instead of a very slow oscillation as observed experimentally, we find that the created dark soliton undergoes a transverse snake instability with a collapse into vortex rings, which propagate in solitonlike manner with a nearly 2 times larger period. © 2013 American Physical Society.

Wang P.,Xinjiang Normal University | Wang P.,Shanghai University
Nonlinear Dynamics | Year: 2012

Perturbation to Noether symmetries and adiabatic invariants of discrete nonholonomic nonconservative mechanical systems on an uniform lattice are investigated. Firstly, we review Noether symmetry and conservation laws of a nonholonomic nonconservative system. Secondly, we study continuous Noether symmetry of a discrete nonholonomic system, give the Noether symmetry criterion and theorem of discrete corresponding holonomic system and nonholonomic system. Thirdly, we study perturbation to Noether symmetry of the discrete nonholonomic nonconservative system, give the criterion of perturbation to Noether symmetry for this system, and based on the definition of adiabatic invariants, we construct the theorem under which can lead to Noether adiabatic invariants for this system, and the forms of discrete Noether adiabatic invariants are given. Finally, we give an example to illustrate our results. © 2011 Springer Science+Business Media B.V.

In this paper, a class of stochastic impulsive high-order BAM neural networks with time-varying delays is considered. By using Lyapunov functional method, LMI method and mathematics induction, some sufficient conditions are derived for the globally exponential stability of the equilibrium point of the neural networks in mean square. It is believed that these results are significant and useful for the design and applications of impulsive stochastic high-order BAM neural networks. © 2010 Elsevier B.V.

Li J.,South China Normal University | Shen L.,Xinjiang Normal University | Pan Y.,South China Normal University | Li R.,South China Normal University
Optics Express | Year: 2014

A method for optical image hiding and for optical image encryption and hiding in the Fresnel domain via completely optical means is proposed, which encodes original object image into the encrypted image and then embeds it into host image in our modified Mach-Zehnder interferometer architecture. The modified Mach-Zehnder interferometer not only provides phase shifts to record complex amplitude of final encrypted object image on CCD plane but also introduces host image into reference path of the interferometer to hide it. The final encrypted object image is registered as interference patterns, which resemble a Fresnel diffraction pattern of the host image, and thus the secure information is imperceptible to unauthorized receivers. The method can simultaneously realize image encryption and image hiding at a high speed in pure optical system. The validity of the method and its robustness against some common attacks are investigated by numerical simulations and experiments. © 2014 Optical Society of America.

Lei X.-L.,Xinjiang Normal University
Journal of Cluster Science | Year: 2011

Successively substituted Al13 cluster by B atom both neutral and anionic AlnBm(n + m = 13) clusters have been investigated by the density functional theory (DFT) at B3LYP/6-31G (d) level, the aim is to understand the evolution of the structural and electronic properties as a function of composition. The results clearly show Al13 cluster as well as Al rich AlnBm clusters prefer the icosahedral geometries while increasing boron contents promote quasi-planar configurations. The geometrical structures of the optimized anionic AlnBm- clusters are very close to those of the neutral clusters with smaller structural modifications. Overall, the vertical ionization potential (VIP), the adiabatic electron affinity (AEA), and the energy gaps (Eg) of AlnBm clusters decrease with increasing of substitution. The largest values of second-order energy differences (Δ2E), VIP, and Eg of Al12B cluster indicate it possesses the most stability among all the investigated clusters, which accords to the experimental results. The simulated photoelectron spectroscopies (PES) of AlnBm- clusters have also been discussed in this article. © 2011 Springer Science+Business Media, LLC.

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