机器人柔性手臂动力分析的模态综合法

在机器人柔性手臂动力学的有限元分析中,往往导致很高的自由度,加之动力学方程的时变性,其动力响应的计算不仅十分复杂,而且可能因计算机内外存容量的限制及昂贵的机时费用而难以实现.本文将模态综合法引入机器人柔性手臂的动力学分析,把柔性手臂的各部件隔离成自由界面子结构,把其动力学有限元方程投影到各自的模态空间中,关节连接件(关节集中质量、关节阻尼、关节弹性)处理成耦合件,最终在诸子结构的模态坐标集上建立了整体系统的运动微分方程,使之大幅度降阶.     

非对称粘滞阻尼系统的约束部件模态综合

本文对具非对称粘滞阻尼的振动系统提出一种约束部件模态综合法。首先消除状态空间部件运动方程内不独立的界面位移与界面速度，然后以截断的约束部件复模态、位移约束模态及速度约束模态作为里兹基，减缩总体方程。文末以算例说明了方法的有效性。     

用部件模态综合法计算冷却塔整体结构的动力响应

冷却塔整体结构由旋转壳塔简和循环对称的支柱梁系组成。本文将它们作为两个子结构,用双协调模态综合法计算塔整体的固有振动、动力响应,并着重进行了地震应力分析,既相当精确地反应了壳体底局部应力和支柱梁系中的应力,又保持了单独分析两个子结构时精度高、计算量小的特点。理论分析和计算程序已被应用于冷却塔的设计。     

用于结构振动模态分析的改进的有限元法

提出了两种分别适用于板的面内振动和圆环板弯曲振动模态分析的Fourier级数形式的插值形函数。数值计算结果表明 :对于结构振动模态分析 ,Fourierp_单元法能够有效地提高计算精度及收敛速度 ,特别是对于较高阶的模态效果更为明显。     

自由拘束模态综合技术

本文提出一种新的模态综合技术-自由拘束法,它通过拘束的自由选择,将约束子结构法和双协调法扬长避短地融为一体,从而使模综率得到充分的提高.该技术还容许人为地制造子结构模式以便利用对称性与等同性.     

改进的特征值修正方法及其在阻尼结构复模态综合中的应用

本文在特征值修正方法的基础上提出了一种阻尼结构的复模态综合方法。该方法特别适合于部件对接界面自由度较少情况下的阻尼结构模态综合。文章对复模态综合中子结构具有刚体位移情况提出了具体的处理方法,推导了一种考虑刚体位移的特征值修正方法方式。同时,为了在模态截尾情况下提高综合精度,在特征值修正方法中计入了剩余柔度的影响,推导了综合过程中剩余柔度的递推计算公式。给出了一个算例说明方法的有效性。     

多转子系统振动的子系统分析方法——阻抗耦合法与分振型综合法

高速旋转机械,尤其是多转子系统,各转子之间相互耦合,其动力学特性是比较复杂的.子系统分析方法是处理这种多转子系统的有效手段.本文分析的阻抗耦合与分振型综合的子系统分析方法,可用于具有各向同性或正交特性的无阻尼与阻尼系统,尤其对于具有中介支点的多转子系统,可满意地进行分析.     

用复模态综合和优化方法求解结构局部动力修改逆问题

本文提出一种结构局部动力修改逆问题的求解方法。该方法利用复模态综合建立结构在广义坐标下的动力学模型,然后在广义坐标下导出以局部结构参数为未知量的逆特征方程,最后用优化方法求出结构修改参数。数值算例表明,本文方法精度能满足工程设计要求。     

部件试验模态综合的简便方法

本文将一种基于完备模态基的模态综合技术应用于子结构的试验模态综合,获得成功。这种半试验半理论的模态综合方法是一种较为简便的、要求试验工作量较小的试验模态综合法,因为它只要求测量子结构的振动模态和频率即可。数值仿真结果表明,这种简便的试验模态综合法是行之有效的。     

蛋白质结构的多分辨率分析及其应用

基于蛋白质骨架结构的BSSC生物信息学分析模型，利用多分辨率曲线小波分解方法，实现了对蛋白质骨架结构的多分辨层次描述，从而提供了一种在不同分辨率层次上对蛋白质结构进行分析和研究的新思路，为生物信息学中有关蛋白质的结构比较与分类、蛋白质折叠模式及其分子进化等问题的研究开辟了一条新途径。     

Eigenvalue Analysis for a Frictional Punch Problem of Concave Notch

A numerical solution for the eigenvalue in a frictional punch problem is presented, One edge of a concave notch is assumed to be traction free, and the other edge is in contact with the frictional punch ( Fig, 1), In addition to the normal pressure the friction force is also applied along the contact edge of punch. The friction coefficient δ is assumed within the range – 0.3 ⩾ 6 ⩾ 0,3. The notch angle β between two edges is varying within the range π ⩾ β ⩾ 2π. The target function method is used to evaluate the eigenvalue λ₁ in the stress expression σ_ij ≈ O(1/r^λ1). Finally, the obtained eigenvalues are expressed in the form of λ₁ = s(δ, β). The pressure under punch and the stresses at the corner points are singular in general.     

有阻尼结构线性振动系统的模态综合

研究了线性阻尼结构振动系统的模态综合技术．在线性阻尼结构振动系统实变换进行方程解耦的还原变换的基础上，构造了线性阻尼结构振动系统的固定界面模态综合方法。这一方法克服了以往的模态综合法中无法同时给出子结构刚度、阻尼和质量矩阵，以及只能给出复系数时域方程等不足，可直接给出子结构经模态降阶后的刚度、阻尼和质量矩阵。综合得到的整体方程仍是时域中的实系数二阶振动方程。数值算例表明了本文方法的正确和可行。     

非亏损对称系统的子结构灵敏度综合方法

本提出了一种利用子结构灵敏度综合对非亏损对称系统进行特征对灵敏度分析的方法。本利用固定界面模态综合和子结构约束模态以及约束主模态的二阶灵敏度，实现了非亏损对称系统的重特征值灵敏度分析。算例表明了本的方法是行之有效的。     

Generalized receptance‐based method for accurate and efficient modal synthesis

Modal synthesis plays an important role in efficient dynamic analyses of large structural assemblies. However, the numerical accuracy and the computational efficiency which existing modal synthesis methods have achieved to date are not quite satisfactory. This paper presents a new generalized receptance‐based modal synthesis method which is numerically very accurate and computationally very efficient. The method employs receptance data computed at just few frequency values to formulate a derived equivalent eigensys tem from which required eigenvalues and eigenvectors of interest can be solved. It provides mathematical generalization for existing mode‐based modal synthesis methods since modal data are essentially those receptance data at resonant frequencies. A normalization procedure is also presented which can be used to mass normalize computed mode shapes which are often required in practice. Compensation for the contribution of higher uncomputed modes to receptance data at lower frequency of interest is made to improve analysis accuracy by using lower calculated modes and known system matrices. Numerical results are presented to demonstrate the effectiveness of the proposed method. Copyright © 1999 John Wiley & Sons, Ltd.     

General Solutions for a Class of Inverse Quadratic Eigenvalue Problems

Based on various matrix decompositions, we compare different techniques for solving the inverse quadratic eigenvalue problem, where $n×n$ real symmetric matrices $M$, $C$ and $K$ are constructed so that the quadratic pencil $Q(λ) = λ^{2}M+λC+K$ yields good approximations for the given $k$ eigenpairs. We discuss the case where $M$ is positive definite for $1≤ k≤n$, and a general solution to this problem for $n+1≤k≤2n$. The efficiency of our methods is illustrated by some numerical experiments.     

应振型损伤特征量在混凝土结构损伤诊断中的应用

为检测混凝土构件损伤的出现、损伤位置及损伤程度，本利用位移振型特征量推导了相应的应变振型特征量，并利用Matlab软件编制了混凝土悬臂梁的有限元振动计算程序，对混凝土悬臂梁在发生损伤前后的位移和应变振型特征量进行了仿真计算。结果表明，位移和应变振型特征量均可确定混凝土悬臂梁上存在的损伤，并可确定损伤位置。应变振型特征量较位移振型特征量对损伤更敏感，可用于混凝土构件的损伤检测。     

极点加权模态分解及其在故障诊断中的应用

经验模态分解(EMD)是一种自适应信号分解方法,由于其能够同时提供振动信号时域和频域的局部信息,在机械故障诊断领域得到广泛应用.受EMD思想的启发,基于相邻极值加权构造均值曲线,提出一种新的自适应信号分解方法—极点加权模态分解(EPWMD).通过仿真信号分析,将提出的EPWMD方法与EMD和局部特征尺度分解(LCD)等...     

One‐Pot Synthesis of Multiple Protein‐Encapsulated DNA Flowers and Their Application in Intracellular Protein Delivery

Inspired by biological systems, many biomimetic methods suggest fabrication of functional materials with unique physicochemical properties. Such methods frequently generate organic–inorganic composites that feature highly ordered hierarchical structures with intriguing properties, distinct from their individual components. A striking example is that of DNA–inorganic hybrid micro/nanostructures, fabricated by the rolling circle technique. Here, a novel concept for the encapsulation of bioactive proteins in DNA flowers (DNF) while maintaining the activity of protein payloads is reported. A wide range of proteins, including enzymes, can be simultaneously associated with the growing DNA strands and Mg₂PPi crystals during the rolling circle process, ultimately leading to the direct immobilization of proteins into DNF. The unique porous structure of this construct, along with the abundance of Mg ions and DNA molecules present, provides many interaction sites for proteins, enabling high loading efficiency and enhanced stability. Further, as a proof of concept, it is demonstrated that the DNF can deliver payloads of cytotoxic protein (i.e., RNase A) to the cells without a loss in its biological function and structural integrity, resulting in highly increased cell death compared to the free protein.     

Calculation of eigenpair derivatives for asymmetric damped systems with distinct and repeated eigenvalues

An algorithm is derived for the computation of eigenpair derivatives of asymmetric quadratic eigenvalue problem with distinct and repeated eigenvalues. In the proposed method, the eigenvector derivatives of the damped systems are divided into a particular solution and a homogeneous solution. By introducing an additional normalization condition, we construct two extended systems of linear equations with nonsingular coefficient matrices to calculate the particular solution. The method is numerically stable, and the homogeneous solutions are computed by the second‐order derivatives of the eigenequations. Two numerical examples are used to illustrate the validity of the proposed method. Copyright © 2015 John Wiley & Sons, Ltd.     

基于经验模态分解和主成分分析的滚动轴承故障诊断研究

针对传统的振动信号特征提取效率低、诊断时间较长等问题,提出了基于经验模态分解与主成分分析的滚动轴承故障诊断方法。首先利用经验模态分解将振动信号分解为有限个本征模函数和一个残差函数,提取主要的本征模函数能量及其局部平均频率特征,最后将复合特征向量作为主成分分析分类器的输入,完成对故障的识别。实验结果表明:复合特征向量能够有效地反映轴承的运行状态;相比于BP神经网络、支持向量机、K-近邻算法,主成分分析分类法不仅能够准确地识别故障,而且训练时间短、使用方便。