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The present work examines in detail the existence, stability and dynamics of travelling solitary waves in a Schrödinger lattice with saturable nonlinearity. After analysing the linear spectrum of the problem in the travelling wave frame, a pseudo-spectral numerical method is used to identify weakly nonlocal solitary waves. By finding zeros of an appropriately crafted tail condition, we can obtain the genuinely localized pulse-like solutions. Subsequent use of continuation methods allows us to obtain the relevant branches of solutions as a function of the system parameters, such as the frequency and intersite coupling strength. We examine the stability of the solutions in two ways: both by imposing numerical perturbations and observing the solution dynamics, as well as by considering the solutions as fixed points of an appropriate map and computing the corresponding Floquet matrix and its eigenvalues. Both methods indicate that our solutions are robustly localized. Finally, the interactions of these solutions are examined in collision type phenomena, observing that relevant collisions are near-elastic, although they may, under appropriate conditions, lead to the generation of an additional pulse. 相似文献
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本文利用变分方法给出了具不对称非线性项的二阶常微分方程周期解的存在性的充分条件,通过例子说明本文的主要结果可看作是Landesman-Lazer条件的补充。 相似文献
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Yuming Chen 《Applied Mathematics Letters》2002,15(8):1348-979
We propose the difference equation xn+1 = xn − f(xn−k) as a model for a single neuron with no internal decay, where f satisfies the McCulloch-Pitts nonlinearity. It is shown that every solution is truncated periodic with the minimal period 2(2l + 1) for some l ≥ 0 such that (k - l)/(2l + 1) is a nonnegative even integer. The potential application of our results to neural networks is obvious. 相似文献
958.
Characterizing the Structures of Cryptographic Functions Satisfying the Propagation Criterion for Almost All Vectors 总被引:1,自引:0,他引:1
Many practical information authentication techniques are based on such cryptographic means as data encryption algorithms and one-way hash functions. A core component of such algorithms and functions are nonlinear functions. In this paper, we reveal a relationship between nonlinearity and propagation characteristic, two critical indicators of the cryptographic strength of a Boolean function. We also investigate the structures of functions that satisfy the propagation criterion with respect to all but six or less vectors. We show that these functions have close relationships with bent functions, and can be easily constructed from the latter. 相似文献
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Youichi Bitou 《Optical Review》2002,9(5):227-229
A simple method to reduce the polarization mixing in a two-beam interferometer is proposed. A small separation angle Wollaston prism and an optical wedge were added to the conventional heterodyne setup. It was experimentally demonstrated that the polarization mixing error was reduced below 52.4 mrad by this method. 相似文献
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Xueming Liu Hanyi Zhang 《International Journal of Infrared and Millimeter Waves》2001,22(7):1055-1064
In this paper, A novel wavelength divison multiplexing (WDM) nets is proposed by use of cascaded second-order nonlinearities ((2):(2)) in the D-fiber grating after periodically thermal/electric-field poling, and is theoretically analyzed for the first time. The coupled mode equations of the (2):(2) nonlinearities are derived, and the analytic expressions for the electric-field amplitude of converted light wave and the conversion efficiency are obtained under the small signal approximation, which are well consistent with numerical calculations. Both analytic expressions and numerical results show that, under the phase matching, is proportional to the logarithm of the square of pump light power, and the 4th power of the grating length L and the second-order nonlinearity d. The calculated results also show that and of this fiber grating can be reached over -17dB and 120nm, respectively. With the increase of L, increases rapidly while decreases quickly. The results of simulated calculations and theoretical analysis show that the cascaded (2):(2) process is different from quasi-phases-matched difference-frequency generation. 相似文献