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Zhu H.-P.,Lishui University | Dai C.-Q.,Zhejiang Agriculture And forestry University
Annals of Physics | Year: 2014

Two kinds of Gaussian-type light bullet (LB) solutions of the (3+1)-dimensional Schrödinger equation with cubic and power-law nonlinearities in PT-symmetric potentials are analytically obtained. The phase switches, powers and transverse power-flow densities of these solutions in homogeneous media are studied. The linear stability analysis of these LB solutions and the direct numerical simulation indicate that LB solutions are stable below some thresholds for the imaginary part of PT-symmetric potentials in the defocusing cubic and focusing power-law nonlinear medium, while they are always unstable for all parameters in other media. Moreover, the broadened and compressed behaviors of LBs in the exponential periodic amplification system and diffraction decreasing system are discussed. Results indicate that LB is more stable for the sign-changing nonlinearity in the exponential periodic amplification system than for the non-sign-changing nonlinearity in the diffraction decreasing system at the same propagation distances. © 2014 Elsevier Inc. Source


Dai C.-Q.,Zhejiang Agriculture And forestry University | Zhu H.-P.,Lishui University
Annals of Physics | Year: 2014

The one-to-one correspondence between a (3 + 1) -dimensional variable-coefficient nonlinear Schrödinger equation with linear and parabolic potentials and a standard nonlinear Schrödinger equation is given, and an exact superposed Akhmediev breather solution in certain parameter conditions is obtained. These precise expressions for the peak, width, center and phase indicate that diffraction and chirp factors influence the evolutional characteristics such as phase, center and width, while the gain/loss parameter only affects the evolution of the peak. Moreover, by modulating the relation between the terminal accumulated time T e or the maximum accumulated time T m and the accumulated time T0 based on the maximum amplitude of Akhmediev breather, the controllability for the type of excitation such as postpone, maintenance and restraint of the superposed Akhmediev breather is discussed. © 2013 Elsevier Inc. Source


Zhu H.-P.,Lishui University | Zhu H.-P.,Ningbo University
Nonlinear Dynamics | Year: 2014

The (3+1)-dimensional nonlinear Schrödinger equation with different distributed transverse diffraction and dispersion is studied based on the similarity transformation, and exact bright soliton solution on cnoidal wave backgrounds is derived. Moreover, three kinds of dynamical behaviors of these soliton solutions in three different dispersion/diffraction decreasing media with the Gaussian, hyperbolic, and Logarithmic profiles are discussed. Solitons interact with cnws and/or the change of characteristics of solitons by an addition of cnws are studied. Result of comparison with three media indicates that for the same parameters, the bright soliton in the Gaussian profile is compressed to the utmost degree. These results are potentially useful for future experiments in the optical communications, long-haul telecommunication networks, and Bose-Einstein condensations. © 2014 Springer Science+Business Media Dordrecht. Source


The utilization of activated carbon derived from 'waste' bamboo culms (BAC) for the removal of Disperse Red 167 (DR167), an azo disperse dye, was investigated. Studies of the properties of the adsorbent, the effect of contact time, the initial pH of the solution, the initial concentration of the dye solution and temperature indicated that a low initial pH or concentration of dye solution favors the adsorption process; temperature exerts a greater effect on the removal of azo disperse red 167 dye from aqueous solution. Kinetic and isotherm data were fitted to five non-linear kinetic and nine non-linear isotherm equations. In addition, the fits were evaluated in terms of the non-linear coefficient, Chi-square test, Marquardt's percent standard deviation error function and small-sample-corrected Akaike Information Criterion (AICc) methodology. The results showed that the AICc analysis was the best statistical tool for analyzing the data, the intra-particle diffusion and the pseudo-first-order models played important roles in the controlling rate step, and the Temkin equation best described the BAC isotherm data. Furthermore, the thermodynamic analysis indicated that the adsorption was a spontaneous, endothermic, entropy-increasing and physical process. Two types of commercial activated carbon, Filtrasorb 400 and Filtrasorb (F400 and F300), were used as contrast adsorbents. The contrast experiments revealed that BAC exhibits similar properties to F400 and F300. The utilization of bamboo wastes as carbon precursors is feasible. © 2012 Elsevier Ltd. Source


Dai C.-Q.,Zhejiang Agriculture And forestry University | Dai C.-Q.,Australian National University | Zhu H.-P.,Lishui University
Journal of the Optical Society of America B: Optical Physics | Year: 2013

The 2 1-dimensional coupled nonlinear Schrödinger equation with distributed coefficients in a graded-index grating waveguide is investigated, and an exact two-breather solution for certain functional relations is obtained. From this solution, the superposed Kuznetsov-Ma (KM) solitons can be constructed. The explicit functions that describe the evolution of the peak, width, center, and phase are found exactly, from which one knows that diffraction and chirp factors play important roles in the evolutional characteristics, such as phase, center and widths, while the gain/loss parameter only affects the evolution of their peaks. Moreover, we can change the propagation type of the superposed KM solitons by adjusting the relation between the maximumeffective propagation distance Zm and the periodic locations Zij based on the maximum amplitude of the superposed KM solitons. The controllability for the type of excitation, such as partial excitation, maintenance, and postponement of the superposed KM solitons, is exhibited. © 2013 Optical Society of America. Source

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