具有迟滞非线性的金属橡胶隔振器参数识别研究

金属橡胶隔振器具有非线性的动力学特性,对这种迟滞阻尼隔振器进行建模研究,建立了参数有物理意义的动力学模型.根据单自由度性能试验,进行了有关参数的试验识别方法研究,应用能量法及最小二乘法将非线性方程组转化为关于参数的线性方程组,从而对金属橡胶隔振器参数进行识别.识别结果与实验结果有较好的一致性,识别结果也说明了结构参数对隔振器性能的影响. 关键词： 金属橡胶隔振器 动力学模型 迟滞非线性 参数识别     

受重力梯度扰动的空间机器人姿态动力学非线性特征分析

研究考虑重力梯度扰动的自由漂浮空间机器人姿态动力学建模方法.以二连杆空间机器人模型为基础,对机械臂构型固定时系统俯仰姿态受扰运动的非线性特征进行了深入分析.利用相平面轨迹和Poincaré截面对受扰运动特征进行了描述,反映出受扰运动对轨道偏心率的变化比较敏感,在圆轨道时仅有周期摆动和翻滚两种形式,而在椭圆轨道时出现了准周期运动.进一步利用系统分岔图、功率谱图对这种非线性运动特征进行了定量分析.     

Enhanced Kerr nonlinearity in a negative refractive atomic medium

The Kerr nonlinearity of a left-handed material is analyzed in a four-level atomic system.It is shown that,due to the effect of quantum interference,a large enhanced Kerr nonlinearity accompanied by vanishing absorption can be realized via choosing appropriate parameters in this negative refraction atomic medium.It not only shows the large nonlinearity but also acts as the phase and amplitude compensating effects.     

Flow of a non‐linear (density‐gradient‐dependent) viscous fluid with heat generation,viscous dissipation and radiation

In this paper, we study the flow of a compressible (density‐gradient‐dependent) non‐linear fluid down an inclined plane, subject to radiation boundary condition. The convective heat transfer is also considered where a source term, similar to the Arrhenius type reaction, is included. The non‐dimensional forms of the equations are solved numerically and the competing effects of conduction, dissipation, heat generation and radiation are discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Conservative finite-difference scheme for the problem of a femtosecond laser pulse with an axially symmetric profile propagating in a medium with cubic nonlinearity

Conservative finite-difference schemes are constructed for the problem of a femtosecond laser pulse propagating in a cubically nonlinear medium in the axially symmetric case with allowance for temporal dispersion of the nonlinear response of the medium. The process is governed by the nonlinear Schrödinger equation involving the time derivative of the nonlinear term. The invariants of the differential problem are presented. It is shown that the difference analogues of these invariants hold for the solution to the finite-difference schemes proposed for the problem. As an example, the numerical results obtained for the self-focusing of a femtosecond light beam are presented.     

On elliptic and parabolic systems with x‐dependent multivalued graphs

We consider elliptic and parabolic systems with multivalued x‐dependent graphs. The existence of solutions for elliptic equation was established in (Ann. Inst. H. Poincare Anal. Non Linéaire 1990; 7 (3):123–160; Boll. Unione Mat. Ital. Sez. B Artic. Ric. Mat. (8) 2004; 7 (1):23–59). We extend this result to the elliptic and parabolic systems, in particular to the systems describing a flow of non‐Newtonian incompressible fluids. Contrary to these two papers we follow the spirit of the compactness method of J. L. Lions for variational‐type operators, however, expanded on the framework of measure‐valued solutions. The main concept consists in applying the relation between x‐dependent maximal monotone graphs and 1‐Lipschitz Carathéodory functions to introduce the generalized Young measures. The method was announced in the short note (C. R. Math. Acad. Sci. Paris 2005; 340 (7):489–492). Copyright © 2006 John Wiley & Sons, Ltd.     

Deformation of flexible noncircular cylindrical shells under concurrent loads of two types

The paper presents an exact analytic solution to a nonlinear boundary-value problem for a long noncircular cylindrical shell with variable cross-sectional curvature under two concurrent loads: a surface force and bending moments. The behavior of the shell under these loads is analyzed __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 7, pp. 58–65, July 2007.     

A Wiener-type condition for Hölder continuity for Green's functions

Summary We investigate local properties of the Green function of the complement of a compact set Ein R^d, d>2. We give a Wiener type characterization for the H?lder continuity of the Green function, thus extending a result of L. Carleson and V. Totik. The obtained density condition is necessary, and it is sufficient as well, provided Esatisfies the cone condition. It is also shown that the H?lder condition for the Green function at a boundary point can be equivalently stated in terms of the equilibrium measure and the solution to the corresponding Dirichlet problem. The results solve a long standing open problem -- raised by Maz'ja in the 1960's -- under the simple cone condition.     

Ge-Ga-Cd硫化物玻璃的超快三阶非线性光学性质与结构关系研究

本文采用飞秒时间分辨光学克尔门技术测量了GeS2-Ga2S3-CdS硫化物玻璃体系的超快三阶非线性光学响应，所用激光波长分别为820nm和640nm。?实验结果证明了GeS2-Ga2S3-CdS组分玻璃具有很大的飞秒超快三阶非线性光学响应，另外，其Kerr信号随摩尔组分的不同呈显著变化。通过拉曼光谱结构分析，探讨了此系列硫化物玻璃的三阶非线性光学性质与结构的关系，结果表明构成玻璃网络的四面体结构单元[GeS4]([GaS4])对其超快三阶光学非线性起重要作用。实验还表明了此硫化物玻璃体系的超快三阶非线性不符合半经验的Miller定律。     

Nonlinear photoacoustic response of opaque media in gas microphone signal detection

We have theoretically studied the effect of thermal nonlinearity, due to the temperature dependence of the thermophysical and optical parameters for thermally thick opaque media, on the characteristics of the fundamental photoacoustic signal when the signal is detected by a gas microphone. We have shown that the dependence of the amplitude of the nonlinear component of the signal on the intensity of the incident radiation I₀ is expressed by means of the dependence of the temperature rise for the irradiated sample surface Θ₀ on I₀, and the thermal nonlinearity does not affect the phase of the photoacoustic signal. We propose a theory for generation of the second harmonic of the photoacoustic signal. We have established that the phase shift of the photoacoustic signal is equal to 3π/4, while its amplitude depends on the frequency (∼ω^−3/2) and the intensity (∼ I ₀ ² ). __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 170–176, March–April, 2006.