A Universal Matrix Perturbation Technique for Complex Modes

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Exploration of substitution of repeated mode subspaces for closely spaced mode subspaces

A new quantitative concept is introduced in this paper, which may be used to facilitate the measurement of the controllability of a subspace≈subspace controllability degree. Then the concrete form of the subspace controllability degree of a flexible structure is derived, and the errors of subspace controllability degree and dynamical response caused by the substitution of a repeated mode subspace for a closely spaced mode subspace are discussed. All the results show that this substitution is rational under some conditions. The project supported by the National Natural Science Foundation of China and the Doctoral Research Foundation of Chinese Ministry of Education.     

非对称矩阵特征值问题密集模态重分析方法

本文提出了一种非对称矩阵特征值问题的密集模态重分析方法。它将原密集特征值问题表达为与其临近的某一重特征值问题的小摄动,从而密集模态的重分析问题就转化为重频模态的重分析问题。     

密频系统的反馈控制

研究了如何将结构重频系统设计中的反馈控制律用到含有密频子结构的系统上去，主要解决了如何估计将重频系统控制律用到相应的密频系统对闭环系统的（指数）衰减律的影响，原系统的结构参数有少量变化后的新系统以及原系统是不可控的密频系统的情形．理论和数值算例表明，只要对重频系统设计的反馈律作正确的坐标变换，应用到上述三种情形时，其闭环系统的衰减律的误差只有相应频率分散度的一阶小量     

密集模态摄动的新方法

本文提出了一种密集模态结构系统(M_0,K_0)振动分析的矩阵摄动新方法.它将密集模态结构系统特征解的摄动问题转化为重特征值的摄动问题.文中给出了一个数值例子.     

Lattice dynamics investigations of SiGe core-shell nanowires

We present results from lattice dynamics calculations on the phonon modes and specific heat of SiGe core-shell nanowires. The results show that phonon dispersion relation of SiGe nanowires consists of four acoustic branches. The frequency of the first optical mode at Γ point shifts to low frequency as the Ge concentration is increasing. There are three strong peaks in the spectra of density of states. The peaks at 9.0 THz and 15.0 THz can be attributed to the high frequency Ge-Ge and Si-Si bond vibration. The broad peak around 3.0 THz of pure silicon nanowire corresponds to the transverse acoustic branch of bulk silicon. Moreover, specific heat of SiGe nanowires increases (decreases) with the increase of the concentration x at low (high) temperature. The specific heat at 300 K can be fitted by C _V = x ² C _Ge + (1 − x)C _Si, where C _Ge and C _Si are specific heat of pure germanium and silicon nanowires respectively.