粘弹性阻尼对弹性杆内纵向孤波运动的影响

本文用微扰论的计算方法,求出在粘弹性阻尼较小但不可忽略的情况下,弹性杆内纵向孤波的形状、速度及能量随时间的变化规律。结果表明,粘弹性阻尼使孤波逐渐变矮、增宽、速度减慢,能量逐渐耗散,最后导致孤波的消失。 关键词：     

一维铁磁链中量子孤波的能级和磁矩

使用Hartree近似和一种简化的准离散多标度方法,研究了具有交换作用和经典磁矩相互作用的一维铁磁链中的量子孤波解. 这种一维铁磁链中不仅存在着运动的量子孤波,也存在着静态的量子孤波(即量子内禀局域模).利用所获得的量子孤波解,进一步研究了量子孤波的能级和由量子孤波所携带的磁矩. 研究表明,量子孤波的能量和磁矩都是量子化的,这些结果为正确理解磁性材料中像磁滞回线的量子台阶等宏观量子特性提供了一条可能的途径.     

机械孤波的MATLAB数值模拟及实验研究

针对一种产生机械孤波的多摆耦合系统建立了动力学模型,利用MATLAB进行了数值模拟并搭建装置进行了实验.模拟显示系统存在多种形式的孤波解.在实验中也发现了机械孤波,而且实测孤波速度与驱动强度的依赖关系定性上与数值模拟结果一致.     

负折射介质中啁啾暗孤立波的传输特性研究

本文求解了描述负折射介质中超短脉冲传输的归一化薛定谔方程,发现负折射介质中可以存在一种非线性啁啾暗孤波.结合负折射介质的特性,详细研究了该啁啾暗孤波的形成条件和传输特性.结果发现,与普通介质中的暗孤波不同,该啁啾暗孤波只能存在于介质的反常色散区,且孤被的速度影响其啁啾和幅度.另外,我们数值研究了该啁啾暗孤波在诸如频率偏移、功率波动和噪声干扰下的稳定性,结果表明,这种啁啾暗孤波在有限的扰动下具有很好的稳定性.     

激光偏振状态对磁化等离子体中电磁孤波的影响

强激光与等离子体之间相互作用,能够产生各种参量不稳定性过程和非线性效应。利用Karpman方法推导出横场包络所满足的非线性控制性方程,在一维情况下,获得孤波解。对孤波解进行分析,发现波包孤子的半宽反比于振幅;分析磁化等离子体中各参量对孤波半宽的影响。结果表明,在右旋圆偏振激光情况下,随着电子数密度的增大,孤波的半宽逐渐减小,而当磁场强度增大时,孤波的半宽逐渐增大;在左旋圆偏振激光情况下,随着电子数密度的增大,孤波的半宽逐渐增大,而当磁场强度增大时,孤波的半宽逐渐减小。     

螺旋波等离子体中螺旋波与Trivelpiece-Gould波模式耦合及线性能量沉积特性参量分析

采用有限温度等离子体介电张量模型,在考虑粒子热效应情形下,通过求解传导边界条件下等离子体柱中本征模的色散关系,分析了螺旋波等离子体中典型参量条件下螺旋波与Trivelpiece-Gould (TG)波的耦合特性及线性能量沉积特性.在ω/(2π)=13.56 MHz和T_(eV,i)=0.1 T_(eV,e)参量条件下计算结果表明:对于螺旋波,存在截止静磁场B_(0,H,cutoff)与截止等离子体密度n_(0,H,cutoff),在B_0 B_(0,H,cutoff)或n_0n_(0,H,cutoff)条件下,螺旋波变为消逝波;在ω/ω_(ce)∈(0.01,0.10)范围内,对于m=0角向模,TG波Landau阻尼致使的能量沉积占主导地位,而对于m=1角向模,螺旋波Landau阻尼或TG波Landau阻尼致使的能量沉积哪个占据主导地位则取决于B_0的大小;在ω_(pe)/ω_(ce)∈(3,100)范围内,TG波Landau阻尼致使的能量沉积占主导地位;在整体能量沉积过程中,对于m=0模和m=1模,Landau阻尼致使的能量沉积均占据主导地位.     

无限长粘弹性圆柱管中轴对称波的传播模式和衰减

在Kelvin-Voigt线性粘弹性模型框架内研究了无限长粘弹性圆柱管中轴对称波的传播和衰减。通过一个复根搜索程序对频散方程的求解得到无量纲化相速度频散曲线和衰减曲线。比较了引入损耗因子后粘弹性圆柱管与弹性圆柱管中轴对称波传播的特性。给出了圆柱管的外内径之比、损耗因子和材料参数对相速度和衰减的影响。分析结果表明与弹性圆柱管相比粘弹性圆柱管中轴对称波的各阶传播模式均存在衰减,高阶传播模式并无严格意义的截止频率。损耗因子对第一阶传播模式的相速度影响很小,而对衰减的影响则比较大,穿孔率对波传播的相速度和衰减有相当大的影响。     

加肋板稳态简谐响应的粘弹性阻尼控制研究

应用模态叠加法研究了用粘弹性阻尼控制加筋板的稳态简谐响应。考察了在板上加自由阻尼层和加粘弹性梁的情况，分析了阻尼材料损耗因子、阻尼层厚度以及粘弹性梁剖面尺寸对结构响应的影响。对３种阻尼处理情况进行了比较。结构的幅频特性表明，粘弹性材料能够有效地控制结构的共振响应。     

磁场对螺旋波等离子体波和能量吸收影响的数值研究

本文考察在径向电子数密度呈抛物形分布的情况下,外加稳恒磁场,射频通过螺旋波天线在等离子体中激发电磁波的传播性质.采用线性扰动波假设,数值求解Maxwell方程组,得到80—800 G(1 G=10-4T)磁场条件下等离子体中径向电、磁场强度及能量沉积密度的分布情形.计算结果表明,磁场增大(80→800G)时,螺旋波受到的阻尼较小,可深入等离子体传播;Trivelpiece-Gould(TG)波受到的阻尼增大,在等离子体-真空边界处衰减增强;整体的能量吸收向边界集中.磁感应强度小于100 G时,TG波可深入主等离子体区传播,等离子体径向能量吸收相对均匀.     

平面对称标量场产生的引力孤波

求出了平面对称零质量标量场产生的一组引力孤波解，并讨论了这组引力孤波的奇异性和能量问题 关键词：     

APPROXIMATING THE HYSTERETIC DAMPING MATRIX BY A VISCOUS MATRIX FOR MODELLING IN THE TIME DOMAIN

The paper is concerned with modelling the dynamic behaviour of a structure with damping. Hysteretic damping is commonly accepted to be reasonably accurate in some circumstances, but can only be applied directly in the frequency domain. Dynamic (time) behaviour, however, is most conveniently predicted by a viscous model. A damping matrix is constructed for use in the viscous equation which gives a dissipation of energy approximating to the hysteretic model. The approximation is justified by comparing results in the frequency and time domains and against measured data from a loudspeaker diaphragm. The ability of the matrix to reflect different damping in various components of the structure is considered, together with predicted natural frequencies and modes.     

简谐振动实验中阻尼力作用的估算

根据振动振幅随时间的衰减来得到阻尼系数,并估算了阻尼力对振动周期和总机械能的影响。     

Decaying solitary waves propagating in one-dimensional damped granular chain

We numerically investigate the nonlinear waves propagating in a one-dimensional particle chain when the damping effect is taken into account. It is found that decaying solitary waves exist, in which the amplitude of the wave decreases exponentially as time increases. Meanwhile, the velocity of the solitary wave also slows down as time goes. This result implies that the damping coefficient is an important parameter in such a nonlinear system. Theoretical analysis has also been done by the reductive perturbation method. The result indicates that the nonlinear waves propagating in such a system can be described by the damped KdV equation.     

激励Brillouin散射非线性致稳过程的阻尼效应

本文研究了由非线性引起的Brillouin散射致稳效应。我们主要兴趣是Landau阻尼对非线性致稳的影响。我们求解了时间、空间和时-空有关的方程,得到了场能密度、场幅、饱和时间和空间大小等随物理参量变化的近似解析表达式。 关键词：     

FRICTION-INDUCED VIBRATION IN PERIODIC LINEAR ELASTIC MEDIA

For a one-dimensional finite elastic continuum with distributed contacts and periodic boundary conditions, the presence of unstable waves is investigated. The stability of the waves is evaluated and explanations for instabilities under a constant coefficient of friction are provided. A negative slope in the coefficient of friction as a function of sliding speed is not a necessary condition for the occurrence of dynamic instability. Dynamic instability occurs in the form of self-excited, unstable, travelling waves. The stabilizing effects of external and internal damping were studied. Low- and high-frequency terms of the travelling waves are stabilized by adding external and internal damping respectively. Responses corresponding to unstable eigenvalues can dominate the system response. It is presumed that this can lead to squeaking or squealing noise in applications.     

引力辐射阻尼对双星轨道要素变化的影响——对过近星点时刻的影响

在文献［１］研究的基础上对双星引力辐射阻尼的效应又做了进一步研究．首先给出文献［１］的主要结果及其更正，然后利用文献［１］的结果又给出引力辐射阻尼对双星过近星点时刻的影响。结果表明，引力辐射阻尼对双星过近星点时刻不仅产生周期变化的效应，而且还产生长期变化的效应，这后者的效应使得双星过近星点时刻提前。最后利用所推出的结果对三颗双星（Ｙ Ｃｙｇ，ＰＳＲ２３０２＋２４．ＰＳＲＩ９１３＋１６）做了数值的长期效应的计算。 关键词：     

Constraints on Non-Radial Oscillation Modes by Symmetry Energy Slope

The effect of the nuclear symmetry energy slope on the non-radial oscillation f-modes in neutron stars is calculated and discussed. Based on a conservative range of the symmetry energy slope constrained by the experiment and theoretical analysis, a constraint on the frequency and damping time of the gravitational radiation from the f-mode in neutron star is obtained. It is also shown that a higher symmetry energy slope corresponds with a smaller frequency and a longer damping time. Meanwhile, a new set of parameters is given to present the universal properties of the scaled frequency and damping time.     

Cu-Zn-Al合金中类液振荡的非线性机理

讨论了在Cu-Zn-Al合金表面观察到的非线性振荡现象.观测和计算表明,这些微米量级的原子胞体的类液振荡具有孤波运动特征,当外部激振较强时,其振荡可维持相当长的时间;如果内耗较强,原子波胞的振幅按照函数e^-kt规律随时间衰减.理论计算与实验符合较好. 关键词： Cu-Zn-Al合金 类液振荡 孤波     

Observation of depression solitary surface waves on a thin fluid layer

We report the observation of depression solitary surface waves on a layer of mercury when its depth is thin enough compared to the capillary length. These waves, as well as the well known elevation solitary waves, are studied with a new measurement technique using inductive sensors. The shape of the solitary waves, their amplitude-dependent velocity, and their damping rates by viscosity are found in good agreement with theoretical predictions.