X光背光观测烧蚀面扰动引起内界面扰动的增长

 侧向背光照相能直接反映靶表面扰动幅度的变化情况。在神光Ⅱ装置上，实验利用侧向背光照相技术，对烧蚀面扰动引起的内界面扰动增长进行了观测。实验结果表明，观察到的内界面扰动幅度大于期望值。分析认为，造成内界面较大扰动增长的原因主要是2维效应。X光辐照的主要是烧蚀面的中间部分，烧蚀面扰动引起的内界面的扰动就呈现出一幅从中间的扰动区域逐渐过渡到四周的图像。由此，提出了新的靶优化设计方案，应尽可能减小沿背光方向的样品尺寸。     

爆轰加载下高纯铜界面Rayleigh-Taylor不稳定性实验研究

金属界面不稳定性是内爆物理压缩过程中关注的重要问题,与传统流体界面不稳定性具有显著区别.由于相关理论和实验诊断技术的限制,目前该问题的研究还明显不足.为加深对金属界面不稳定性扰动增长行为的认识,本文建立了爆轰加载下高纯铜界面Rayleigh-Taylor不稳定性研究的实验诊断技术和数据处理方法,得到了扰动发展早期不同时刻界面扰动增长的X光图像.实验结果分析表明:在爆轰产物的无冲击加载条件下扰动波长基本保持不变,而初始扰动幅值越大,界面扰动增长的趋势就越明显;同时随着样品前界面扰动的不断发展,在样品的后自由面也出现了与前界面初始相位相反的扰动特征,即样品前界面扰动为波谷的位置所对应的后界面先运动而逐渐演变为波峰,而前界面扰动为波峰的位置所对应的后界面则演变为波谷;在5.26μs时刻,界面扰动幅值增长为初始值的700%左右,应变率达到了约105/s.结合数值模拟研究表明:在此情况下常用的Steinberg-Cochran-Guinan模型在一定程度上低估了高纯铜材料强度的强化特性,无法准确地描述强度对界面扰动增长的制稳作用,从而导致数值模拟结果要大于实验测量结果.     

Perturbation of chiral solitons

This paper studies the perturbation of soliton due to the chiral nonlinear Schrödinger's equation by the aid of soliton perturbation theory. The perturbation term that is studied is the quantum potential perturbation of the chiral soliton that is known as Bohm potential. The stable fixed point of the chiral soliton parameters is obtained.     

Source-filter Comparison of Measurements of Fundamental Frequency Perturbation and Amplitude Perturbation for Synthesized Voice Signals

SUMMARY: An investigation of the effect of glottal source aperiodicities (jitter, shimmer, and aspiration noise) on the estimation of fundamental frequency (f0) perturbation and amplitude perturbation, of synthesized, glottal source and voiced speech waveforms, is considered. Firstly, 4, cycle-event f0 estimators are examined: (1) waveform matching of the low-pass filtered waveform, (2) positive peaks (PPs) from the speech waveform, (3) PPs from the low-pass filtered waveform, and (4) positive zero crossings from the low-pass filtered waveform. The analysis shows that f0 perturbation measures taken from the low-pass filtered waveform are affected by both amplitude perturbation and random glottal noise, whereas, f0 perturbation measures taken from the PPs of the original waveform are affected by noise but not by amplitude perturbation. It is shown for the low-pass filter methods that the effects of amplitude perturbation and noise lead to increased errors in the measurement of f0 perturbation for the synthesized speech waveforms when compared with the synthesized glottal waveforms. Shimmer of the synthesized speech waveform is approximately equal to shimmer of the synthesized glottal source. However, noise and jitter affect measures of amplitude perturbation. The estimation of f0 perturbation from the synthesized speech waveform is shown to be nonlinearly related to f0 perturbation estimation from the synthesized glottal waveform as a consequence of the filtering action of the vocal tract. Low-pass filtering the voiced speech waveform is shown to provide a partial solution to this problem.     

Cumulants in perturbation expansions for non-equilibrium field theory

The formulation of perturbation expansions for a quantum field theory of strongly interacting systems in a general non-equilibrium state is discussed. Non-vanishing initial correlations are included in the formulation of the perturbation expansion in terms of cumulants. The cumulants are shown to be the suitable candidate for summing up the perturbation expansion. Also a linked-cluster theorem for the perturbation series with cumulants is presented. Finally, a generating functional of the perturbation series with initial correlations is studied. We apply the methods to a simple model of a fermion-boson system.     

光纤中扰动的小信号增益

从非线性薛定谔方程出发,在小信号近似下,推导并求解了光纤中扰动相位和幅度的演化方程,利用得到的扰动相位及功率增益的表达式,研究了初相位和频率对传输过程中扰动增益的影响。研究表明：扰动的初相位对扰动增益的初值和初始阶段的演化规律有重要影响;取决于扰动初相位,任何一个频率的扰动增益都有可能达到一个共同的最大值;在被认为无调制不稳定的正色散区和扰动频率大于截止频率的负色散区,扰动增益随距离是振荡的;在被认为有调制不稳定的扰动频率小于截止频率的负色散区,频率相同而初相位不同的扰动增益将经历不同形式的演化后趋于同一正值。     

Perturbation to Mei symmetry and adiabatic invariants for Hamilton systems

Based on the concept of adiabatic invariant, this paper studies the perturbation to Mei symmetry and adiabatic invariants for Hamilton systems. The exact invariants of Mei symmetry for the system without perturbation are given. The perturbation to Mei symmetry is discussed and the adiabatic invariants induced from the perturbation to Mei symmetry of the system are obtained.     

Non-radiative ionization of perturbation centres by means of excitons in semi-conducting and dielectric crystals

Non-radiative ionization of a perturbation centre formed by an electron trapped in the Coulomb field of the perturbation by means of excitons of large radius in semi-conducting and dielectric crystals is theoretically investigated. It is shown that such non-radiative ionization may occur by two processes: the direct non-radiative transfer of the excitation energy from the exciton to the electron of the perturbation and by exchange non-radiative ionization whereby the electron on the perturbation recombines non-radiatively with the hole in the exciton and the electron of the exciton with the energy released during this recombination passes to the ionized state of the perturbation.The corresponding probabilities per sec and recombination coefficients are calculated as a function of the concentration of perturbation centres and the type of exciton according to its optical origin. The result is used for a theoretical estimate of the influence of perturbation centres of the given type on the optical life-time of the exciton.     

Perturbation to Mei symmetry and Mei adiabatic invariants for discrete generalized Birkhoffian system

Based on the concept of discrete adiabatic invariant,this paper studies the perturbation to Mei symmetry and Mei adiabatic invariants of the discrete generalized Birkhoffian system.The discrete Mei exact invariant induced from the Mei symmetry of the system without perturbation is given.The criterion of the perturbation to Mei symmetry is established and the discrete Mei adiabatic invariant induced from the perturbation to Mei symmetry is obtained.Meanwhile,an example is discussed to illustrate the application of the results.     

基于洛伦兹函数微扰的磁光光纤布喇格光栅线性透射谱和非线性双稳特性研究

基于非线性耦合模理论,利用逆向递推龙格-库塔法,数值研究了在磁光耦合系数中引入洛伦兹函数微扰后对磁光光纤布喇格光栅线性透射谱和非线性双稳特性的影响.研究结果表明:给磁光耦合系数引入洛伦兹微扰能在线性透射谱阻带中打开线宽极窄的一个透射窗口,微扰宽度和微扰中心位置可以影响透射窗口的位置、宽度以及峰值大小;当微扰宽度和微扰中心位置发生变化时,光栅的双稳特性表现出明显的差异,合理地选择微扰参量可以实现对其双稳特性的优化.     

Instability of Epitaxially Strained Thin Films Based on Nonlocal Elasticity

We perform a linear analysis of the elastic fields and stability of epitaxially strained thin films based on nonlocal elasticity. We derive expressions of perturbed stresses to the first order of perturbation amplitude, which show that the stresses are directly proportional to the lattice mismatch and the perturbation amplitude, and decrease with an increase in the perturbation wavelength. The critical perturbation wavelength distinguishes whether the flat film for the perturbation is stable, which is inversely proportional to the square of the mismatch and decreases with the thickness of the film.     

The roles of extrinsic periodic information on the stability of stock price

The perturbation expansion for the nonlinear Schrödinger equation with a random potential that was developed in earlier works by some of us is extended to higher orders. As the order is increased a solution that is valid for longer time can be found. In particular it is found that Anderson localization persists in the fifth and sixth orders for times when perturbation theory is valid. The perturbation expansion is asymptotic and for the value of the nonlinearity parameter used, the fifth order is the optimal order of the perturbation theory. There are indications that for the sixth order perturbation theory may not be valid.     

Covariant perturbation expansion in chiral theories with pions and nucleons

A covariant perturbation scheme is developed to give a coordinate independent perturbation expansion of the chiral invariant pion model with nucleons. On the mass shell the covariant approach is shown to be equivalent to the standard perturbation theory.     

Perturbative and nonperturbative parts of eigenstates and local spectral density of states: the wigner-band random-matrix model

The Wigner-band random-matrix model is studied by making use of a generalization of Brillouin-Wigner perturbation theory. Energy eigenfunctions are shown to be divided into perturbative and nonperturbative parts. Several perturbation strengths predicted by the perturbation theory are found to play important roles in the variation of the shape of the local spectral density of states with perturbation strength.     

JMCT反应性微扰计算功能的实现

蒙特卡罗中子输运程序用于反应堆设计与安全分析计算及校验时,微小的反应性扰动容易被统计涨落所掩盖,因此一般通过微扰计算处理此类问题。基于微分算子方法在JMCT程序中实现了反应性微扰计算功能。为保证计算的精度,JMCT考虑了非源扰动的高阶效应以及一阶裂变源扰动效应。选取了具有全局扰动、局部扰动的快中子与热中子裂变系统对JMCT反应性微扰计算功能进行了测试。测试系统覆盖了正负反应性变化。     

Modified Perturbation Theory of an Anharmonic Oscillator

A modification of the perturbation theory of a symmetrical anharmonic oscillator is suggested. A more complex zero-order approximation of perturbation theory that considers to a certain degree anharmonicities is chosen rather than a harmonic oscillator model. This approximation is an analog of the self-consistent field model well known in the theory of many-particle systems. A comparison of modified and conventional perturbation theories demonstrates that the modified perturbation theory has much wider applicability range. It can be used for larger values of the parameters at which the conventional perturbation theory becomes inapplicable, namely, for strong anharmonicity and upper energy levels.     

Perturbation theory for projected states in the pairing force model: (II). The problem of convergence

In a previous paper second-order calculations were carried out on the two-level pairing force model using perturbation theory for projected states and the results were compared with those of BCS or ordinary perturbation theory. In the present paper criteria for convergence are applied to two different forms of the perturbation series for both the projected and ordinary perturbation theories. It is found that the superior results obtained for the convergence rates in the projected theory tally neatly with the results of the second-order calculations, and give further support to the use of the projected perturbation theory.     

Hojman Exact Invariants and Adiabatic Invariants of Hamilton System

The perturbation to Lie symmetry and adiabatic invariants are studied. Based on the concept of higher-order adiabatic invariants of mechanical systems with action of a small perturbation, the perturbation to Lie symmetry is studied, and Hojman adiabatic invariants of Hamilton system are obtained. An example is given to illustrate the application of the results.     

无限方势阱本征态的稳定性

我们用存活率(SP)的概念研究了无限方势阱本征态的稳定性,做了理论上的推导,并进行了数值计算,发现基态在外界的扰动下非常稳定,而激发态则非常不稳定,能级越高,越不稳定.     

啁啾脉冲频域干涉测量技术的扰动重构理论模拟研究

利用啁啾脉冲的频域干涉测量技术,可实现对超快光学瞬态过程的单发诊断,此方法的时间分辨率和单发时间测量范围分别与啁啾脉冲的谱宽和脉冲宽度及光谱仪的工作性能有关。当两束线性啁啾脉冲进入光谱仪后,相同的频谱成分会发生干涉形成频谱干涉条纹,如果其中一束脉冲受到外界扰动的影响,可根据干涉条纹的形状重构出扰动的具体形式。理论研究和数值模拟了由频谱干涉图重构外界附加扰动的过程,模拟结果显示重构出的扰动同附加的真实扰动符合得较好;在频谱记录面有限的情况下,重构出的扰动信号带有强烈的振荡,通过平滑处理有效地抑制了振荡。