Influence of static and dynamic internal actions on elastic nonlinear properties of a granulated unconsolidated medium

We have studied the influence of external static (pressure) and dynamic (caused by an elastic wave with a finite amplitude) actions on the linear and nonlinear elastic properties of a granulated unconsolidated medium, which was simulated by steel spheres with diameters of 2 and 4 mm. We have analyzed the equation of state for such a medium taking into account the presence of weakly and strongly deformed contacts between individual spheres. We have obtained expressions for the elasticity coefficient and second- and third-order nonlinear elastic parameters, and we have experimentally studied the influence of external static pressure on their values. We have measured the dependence of the velocity of elastic waves on external static pressure and the probing signal amplitude. In the studied medium, a number of structural phase transitions were observed, related to rearrangement of the packing of spheres, which were caused by both static and dynamic actions. The structural phase transition was accompanied by an anomalous change in the nonlinear elastic parameters of the medium and the velocity of elastic waves. We have analyzed the results based on the Hertz theory of contact interaction.     

Influence of structure on the dynamic mechanical properties of crystalline polymers

A dynamk mechanical theory is presented whose structural elements correspond to such physically measurable material parameters as the compliance of the phases, the percent crystallinity, and the orientation of the crystalline and noncrystalline regions. The theory is tested by using both structural and dynamk mechanical data from samples of isotactic polyproylene films of varying crystallinity and orientation. For the specific case of isotactic polypropylene the general theory is shown to reduce to a simple two-parameter model. It is further shown that the two-parameter model not only identifies the unique properties of each of the phases separately, but also predicts the dynamic mechanical properties of the polymer over a temperature range of—130°C to 120°C, for samples ranging from unoriented to highly oriented, and varying in crystallinity from 40 to 70%. The model can also predict the dynamic mechanical properties over the same temperature range for strips of these samples cut at varying angles to the machine direction.     

Influence of optical-damage-resistant dopants on the nonlinear optical properties of lithium niobate

Using the chemical-bond method, nonlinear optical properties of lithium niobate containing different dopants are calculated. In crystals with stoichiometric composition the second order nonlinear susceptibility decreases approximately linearly with increasing dopant concentration. Among the dopants studied – Mg, Zn and In – this behaviour is most highly expressed for In doping. In contrast to that, congruently grown crystals show a different behaviour; only a weak dependence on the dopant concentration is found for, for example, Mg-doped material. Received: 24 October 2000 / Published online: 21 March 2001     

Influence of dynamic scattering on the critical transport properties of ferromagnetic metals

Using the general properties of the dynamic spin-spin correlation function it is shown that the critical behavior of electrical transport coefficients will be the same as that of the magnetic energy. Hence, the temperature and magnetic field behavior of these coefficients, in the vicinity of the critical temperature, T_c, do not depend on whether the scattering processes are elastic or inelastic.     

Influence of different stabilizers on the optical and nonlinear optical properties of CdTe nanoparticles

CdTe semiconductor nanocrystals were synthesized with three different stabilizers: Mercaptoacetic Acid (MAA), Mercaptopropionic Acid (MPA) and 2-Mercaptoethanol (ME) at pH ≈ 11.2 by wet chemical route using potassium tellurite and cadmium chloride as starting materials. The effect of capping agent on the preparation of these samples was evaluated using UV-Visible absorption and photoluminescence analysis. With the same reaction time but with different stabilizers, nanocrystals of different diameters were obtained. The average full width at half maximum of the photoluminescence spectra was about 69 nm which indicates that the monodispersity was quite good. The particle size was calculated by Debye-Scherrer equation from XRD data. Further characterization studies such as FT-IR and optical nonlinearity studies on the samples were carried out and the results are discussed.     

Influence of nonlinear effects on the statistical properties of a high power density laser beam

The second-order intensity correlation function g⁽²⁾(0) of a laser beam passing through a nonlinear medium has been experimentally found to be a decreasing function of the power density in the medium.     

Influence of domain structure on the nonlinear polarization properties of A 2 BX 4-group crystals

Harmonic analysis of repolarization in A ₂ BX ₄-group crystals in the ferroelectric phase near phase-transition temperature T _c is used to separate the contributions to the harmonic-component amplitudes in the output signal of a Sawyer-Tower circuit from charging the reference capacitor with capacitive and conductive current through such a crystal. Harmonic analysis of dielectric hysteresis loops obtained by placing a specimen in an electric field with harmonically changing strength reveals general regularities in the evolution of the domain walls of A ₂ BX ₄-group crystals. It is established that the domain structure affects the nonlinear polarization properties of our specimens. The dependence of the potential relief of ferroelectric ion motion in a harmonically changing electric field is plotted on the basis of the experimental results.     

黄土高原地表能量不闭合度与垂直感热平流的关系

地表能量不平衡问题一直是陆面过程研究的一个重要科学难题.本文利用在陇中黄土高原观测的陆面过程资料,分析了气候地表能量不闭合度和短期地表能量不闭合度的分布特征,研究了地表能量不闭合度与垂直速度之间的关系,发现地表能量不闭合与垂直速度具有很好的相关性.并且,估算了近地层垂直感热平流通量,分析了考虑垂直感热平流后的地表能量平衡的特征,发现引入垂直感热平流输送对地表能量不闭合度有明显的改进. 关键词： 黄土高原 非均匀性 垂直感热平流 能量不闭合度     

外加电压对分子器件电子输运特性的影响：非线性输运性质

根据第一性原理计算了由外电场引起的分子的几何结构和电子结构的变化，并利用弹性格林函数的方法计算了分子器件的电输运特性，从而研究了外电场对1,4-苯二硫酚分子电子输运特性的影响。计算结果表明，对于前线分子轨道，能级的移动和分子末端格点的展开系数在低电压范围内随外电压基本成线性变化。外电场对分子器件的伏安特性有很明显的影响，特别是对电导曲线的形状。考虑电场后的理论结果与实验结果符合得较好。     

Influence of the central metal atom on the nonlinear optical properties of MPcs solutions and thin films

Third order nonlinear optical susceptibility (χ^〈3〉) of metallophthalocyanines (MPcs, where M = Co, Cu, Zn, Mg) thin films and solutions was investigated by standard backward degenerate four wave mixing (DFWM) method at 532 nm. Third harmonic generation (THG) measurement at 1064 nm performed on MPcs thin films is also discussed. MPcs thin films were grown by conventional thermal evaporation in high vacuum and solution were dissolved in tetrahydrofuran (THF), in which the studied materials are soluble. In the case of microscopic nonlinearity, we calculated the second order hyperpolarizability (γ) for MPcs solutions. We found that the χ^〈3〉 and the γ values are affected by the nature of the central metal atom. We also found that the value is larger than that measured via THG experiment. The variation in χ^〈3〉 values occurs due to the different resonance contributions.     

厚度对非极性聚合物薄膜驻极体电荷储存及电荷动态特性的影响

以Du Pont公司的商用Teflon FEP A型薄膜为例，通过热脉冲技术、等温表面电位衰减测量和开路热刺激放电电流谱分析等实验结果，讨论了经常温和高温电晕充电后样品厚度对薄膜驻极体的沉积电荷密度、薄膜驻极体的内电场、体电导率以及电荷储存稳定性的影响.通过热脉冲技术组合电导率温度曲线的测量，研究了在不同温度条件下样品厚度对沉积电荷层的平均电荷重心移动的影响.结果表明：在充电参数一定的条件下，随着膜厚的降低，储存电荷密度上升，但电荷稳定性有所下降.因此，合理地调控薄膜厚度，可以有效地优化驻极体的电荷储存能 关键词： 厚度 驻极体 电荷储存能力 电荷稳定性     

Influence of nonlinear quantum dissipation on the dynamical properties of the f-deformed Jaynes-Cummings model in the dispersive limit

We investigate the effect of a static electric field on photoionization of the He atom in the ground 1S and low-lying 2S and 2P excited states. The field-affected ionization potential and photoionization cross-section are determined from the complex eigenvalues of the time-dependent Schr?dinger equation solved by the complex rotation method in the Floquet ansatz. Accuracy of the method is enhanced by the use of the Hylleraas basis set. For the ground state of helium, we find that the total photoionization cross-section remains constant or decreases as a function of the DC field strength until this field reaches a certain critical value. For the low-lying excited states, effect of the static field is similar to the ordinary DC Stark effect.     

Influence of composition of carbonyl iron particles on dynamic mechanical properties of magnetorheological elastomers

Magnetorheological elastomers (MRE) are known as smart materials. However, the magnetorheological (MR) effect of MRE is not high enough at present, which limits its engineering applications. Prior studies have shown that magneto-induced shear storage modulus and MR effect were mainly determined by the performance of the ferromagnetic particles. In this paper, MRE samples were prepared by carbonyl iron particles (CIP) of different compositions based on silicon rubber under external magnetic field. Their microstructures were observed using an optical digital microscope and a scanning electron microscope. The dynamic mechanical properties of MRE samples were measured using a modified dynamic mechanical analyzer under varying magnetic field strength and frequency. The results show that the carbon content of CIP have a greater impact on the dynamic mechanical properties of MRE. The magneto-induced shear storage modulus and MR effect can be increased by selecting CIP of low carbon content. In addition, the damping property is also significantly influenced by the carbon content of the CIP. This study is expected to provide guidance for fabrication of high performance MRE.     

输入面纵向偏移诱导的强非局域非线性光传输特性变化

基于模式分解方法, 分析了输入面纵向偏移诱导的强非局域非线性光传输特性变化的普适性规律. 结果表明光束输入面移动后导致的影响包括: 光斑在每个周期内出现的位置和顺序的变化、 相同形状的光斑在输入面移动前后大小的差异以及波面曲率因子的演化. 这些性质可用一个简单的数学公式进行归纳; 利用这一公式可方便地由输入面移动前的任意光束解得到输入面纵向移动后的光束解. 关键词： 强非局域非线性 光束 输入面     

条状障碍物对超声非线性声场的影响研究

基于Khokhlov-Zabolotkaya-Kuznetsov(KZK)方程，在频域建立了求解三维非轴对称声场的方法，理论及实验研究了声波通过肋骨条状障碍物后的非线性声场分布，数值计算与实验结果相符.本文还讨论了条状障碍物对空间平均-时间平均声强(I_SATA)的影响. 关键词： 非轴对称 频域法 肋骨 衍射场     

Influence of operating conditions and interface properties on dynamic characteristics of liquid-crystal spatial light modulators

The effects of both varying the alignment films and the operating conditions on the dynamic characteristics of liquid-crystal spatial light modulators (LC-SLMs) have been investigated. The optimum operating conditions of LC-SLMs have been determined, and a proper choice of alignment films has been made. To interpret the high speed obtained for polyimide systems retaining their high resolution, a simulation of speed enhancement has been proposed.     

Influence of the initial conditions on the dynamics of nonlinear systems

The nonlinear dynamics of nondissipative systems of hydrodynamic type that are subjected to small, albeit finite, perturbations in the initial conditions is considered. The behavior of these systems is determined by equations of low-energy hydrodynamics with the potential obeying the Poisson equation. The relation of the hydrodynamic system under study to systems whose dynamics is determined by the Schrödinger equation and the wave equation is discussed.     

垂直磁场对光抽运信号的影响

保持扫场和垂直磁场合成的叠加磁场大小一定,定量研究了地磁场的垂直分量抵消不同时叠加磁场方向变化角度Δθ对光抽运信号幅度的影响.结果表明:光抽运信号幅度随叠加磁场方向变化角度Δθ的增大而增大,当Δθ=180°时,即地磁场的垂直分量完全抵消时,光抽运信号幅度最大,并用量子理论的观点解释了这一规律.