共查询到20条相似文献,搜索用时 171 毫秒
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初始啁啾对脉冲频谱演变的影响 总被引:11,自引:1,他引:10
本文从理论上分析了色散和非线性对脉冲频谱的影响 ,采用数值方法求解了非线性薛定谔方程的频域解。模拟了初始啁啾对不同形状脉冲频谱的作用。研究结果表明 :初始啁啾对频谱的影响随脉冲形状而变化。对高斯型脉冲 ,正的初始啁啾导致频谱严重展宽 ,负初始啁啾对频谱影响较小。超高斯型脉冲的频谱出现了旁瓣 ,这会引起能量的损失 ;而初始啁啾对其频谱的影响并不大。孤子型脉冲的频谱受初始啁啾的影响较大 ,尤其是高阶孤子。因此 ,为了保证脉冲稳定传输 ,必须消除初始啁啾。 相似文献
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用Laplace变换方法求出了Bloch方程在各种不同物理条件下的解析解,这些解析解物理图象清楚,便于分析,克服了数值解中的困难.解析解和相应的结论已用于水峰抑制和特形脉冲的设计.对于水峰抑制,本文指出抑制效果是有极限的,并给出了抑制效果的极限以及最佳抑制时间的近似计算公式.在特形脉冲的模拟过程中,我们发现只有同时考虑全部四类解析解,才能得到正确的模拟结果,另外,模拟还表明,要在保持激励频谱形状不变的条件下,得到不同倾倒角的脉冲必须改变激励脉冲的形状,相应实验的结果与我们给出的上述结论完全吻合。 相似文献
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本文详细地研究了哈肯激光方程的自脉冲不稳定性,得出了自脉冲解的解析表达式,并对其进行了稳定性分析。结果表明,无论是对于第三类激光系统还是对于第四类激光系统,哈肯激光方程的自脉冲解都是不稳定的。 相似文献
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利用由时域有限差分法和预估校正法求得全波Maxwell-Bloch方程的数值解,研究少周期超短激光脉冲在Ladder型三能级原子介质中传播时脉冲及介质粒子布居的空间分布.结果表明,脉冲及介质粒子布居的空间分布规律随脉冲面积的改变而发生明显的变化.当脉冲面积较小时,脉冲形状不规则,振荡次数较多;当脉冲面积较大时,脉冲形状变得较为规则,振荡次数明显减少.随着脉冲面积的增大,脉冲振幅和传播速度逐渐增大,各能级粒子布居振荡次数增多,不同时刻的脉冲和粒子布居空间分布的变化明显减小.粒子布居的空间分布与脉冲的空间分布密切相关. 相似文献
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在考虑了太赫兹光非对称解复用器 (TOAD)中半导体光放大器 (SOA)的增益饱和与恢复效应的基础上 ,深入研究了超高斯控制脉冲对半导体光放大器的动态增益响应及太赫兹光非对称解复用器开关特性的影响 ,并与高斯控制脉冲的情形进行了比较。结果表明 :相对于高斯控制脉冲而言 ,超高斯控制脉冲使半导体光放大器的增益转折区减小 ,显著影响太赫兹光非对称解复用器的开关窗口形状 ,当信号光相对于控制光时延一定 ,或环时间非对称性及信号光相对于控制光的全部时延一定时 ,超高斯控制脉冲都将使太赫兹光非对称解复用器的最大开关比降低 相似文献
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控制脉冲形状对太赫我非对称解复用器开关特性的影响 总被引:2,自引:1,他引:1
在考虑了太赫兹光非对称解复用器(TOAD)中半导体光放大器(SOA)的增益饱和与恢复效应的基础上,深入研究了超高斯控制脉冲对半导体光放大器的动态增益响应及太赫兹光非对称解复用器开关特性的影响,并与高斯控制脉冲的情形进行了比较。结果表明:相对于高斯控制脉冲而言,超高斯控制脉冲使半导体光放大器的增益转折区减小,显著影响太赫兹光非对称解复用器的开关窗口形状,当信号光相对于控制光时延一定,或环时间非对称性及信号光相对于控制光的全部时延一定时,超高斯控制脉冲都将使太赫兹光非对称解复用器的最大开关比降低。 相似文献
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K. Stefański 《Zeitschrift für Physik B Condensed Matter》1982,45(4):351-361
The renormalized Fokker-Planck equation for a dye laser is derived from the Liouvillevon Neuman equation and its stationary solution, as well as the numerically calculated line shapes and the noise spectra for the quantum threshold region are given. The calculations were performed for values of the laser parameters which enable to compare the semiclassical bistable solutions with the threshold and those without the threshold. A difference in the behavior of the line shapes in the threshold region for both cases are discussed. 相似文献
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Pierre Collet François Dunlop Damien P. Foster Thierry Gobron 《Journal of statistical physics》1997,89(3-4):509-536
A two-species asymmetric exclusion process is considered with general transition rates subject only to the constraint of charge
conservation. Conditions for the existence of a stationary product measure are found in both the cases of odd-even parallel
dynamics and continuous-time dynamics. The results are then applied to a one-dimensional restricted solid-on-solid model,
considered as a model of driven interfacial growth, showing a nontrivial dependence of the stationary measure on the external
driving field. The dependence of the growth velocity on the slope of the interface is given and interface shapes in finite
volume with opposite boundary conditions are investigated numerically 相似文献
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D.J. Gorman 《Journal of sound and vibration》1978,57(3):437-447
While the subject of free vibration analysis of the completely free rectangular plate has a history which goes back nearly two centuries it remains a fact that most theoretical solutions to this classical problem are considered to be at best approximate in nature. This is because of the difficulties which have been encountered in trying to obtain solutions which satisfy the free edge conditions as well as the governing differential equation. In a new approach to this problem, by using the method of superposition, it is shown that solutions which satisfy identically the differential equation and which satisfy the boundary conditions with any desired degree of accuracy are obtained. Eigenvalues of four digit accuracy are provided for a wide range of plate aspect ratios and modal shapes. Exact delineation is made between the three families of modes which are characteristic of this plate vibration problem. Accurate modal shapes are provided for the response of completely free square plates. 相似文献
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In the framework of a class of metrics allowing for a timelike and a spacelike symmetries, usually referred to as stationary
and axisymmetric gravitational fields, coupled to differentially rotating perfect fluids, the existing exact solutions to
the corresponding Einstein equations are analyzed from the point of view of the fulfillment of the energy conditions and the
existence of an axis of rotation. The main conclusion is that none of the reported exact solutions fulfills all these physical
requirements, and at most, they can be thought of as stationary cyclic symmetric cosmological spacetimes. 相似文献
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The nonlinear Schrödinger equation describing the evolution of the plane wave solutions of the Hirota equation and of the Boussinesq equation are obtained. The conditions for modulational instability and the localised stationary solutions are derived. 相似文献
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We consider the pattern-formation dynamics of a two-dimensional (2D) nonlinear evolution equation that includes the effects of instability, dissipation, and dispersion. We construct 2D stationary solitary pulse solutions of this equation, and we develop a coherent structures theory that describes the weak interaction of these pulses. We show that in the strongly dispersive case, 2D pulses organize themselves into V shapes. Our theoretical findings are in good agreement with time-dependent computations of the fully nonlinear system. 相似文献
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An analysis is presented for the free vibration of a circular plate restrained against deflection along radial segments. With the reaction forces acting on the segments regarded as unknown harmonic loads, the stationary response of the plate to these loads is expressed by the use of the Green function. The force distributions along the segments are expanded into Fourier series with unknown coefficients, and the homogeneous equations for the coefficients are derived by restraint conditions on the supports. The natural frequencies and the mode shapes of the plate are determined by calculating the eigenvalues and eigenvectors of the equations. The method is applied to circular plates supported along several radial segments located at equal angular intervals, the natural frequencies and the mode shapes of the plates are calculated numerically and the effect of the supports is discussed. 相似文献
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With the help of the invariant embedding method, we obtain an equation for the kernel of the backscattering operator and find numerically its solutions corresponding to the response of the medium to an incident delta-impulse. The statistical characteristics of reflections of such impulses are determined in the case of intense fluctuations of irregularities given the logarithmic derivative of the medium impedance is a continuous stationary centered Gaussian process with the unit variance and a finite correlation radius. We study the temporal evolution of the statistical distribution of reflected signals. Examples of reflections for various shapes of incident impulses are discussed. 相似文献
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Anatoly Tur 《Physica D: Nonlinear Phenomena》2011,240(13):1069-1079
In this work we present a new class of exact stationary solutions for two-dimensional (2D) Euler equations. Unlike already known solutions, the new ones contain complex singularities. We consider point singularities which have a vector field index greater than 1 as complex. For example, the dipole singularity is complex because its index is equal to 2. We present in explicit form a large class of exact localized stationary solutions for 2D Euler equations with a singularity whose index is equal to 3. The solutions obtained are expressed in terms of elementary functions. These solutions represent a complex singularity point surrounded by a vortex satellite structure. We also discuss the motion equation of singularities and conditions for singularity point stationarity which provide the stationarity of the complex vortex configuration. 相似文献
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Igor Schreiber Martin Holodniok Milan Kubíček Miloš Marek 《Journal of statistical physics》1986,43(3-4):489-519