电磁轴承系统的刚度阻尼特性分析

分析了电磁轴承系统的刚度阻尼特性与系统结构参数及其控制器频响特性之间的关系。给出了系统控制电流的相位对系统稳定性和刚度阻尼特性的影响。提出了电磁轴承系统的复阻尼概念，以及部分刚度阻尼特性指标的实际意义和计算方法。     

Stress-strain analysis of a composite truncated conical shell

The stress-strain state of a nonshallow truncated conical shell made of a composite material and subjected to axial forces at the ends is studied. A variational difference method is used. Calculations are carried out for an orthotropic shell with low shear stiffness __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 7, pp. 66–72, July 2007.     

高精度转台控制系统研究

—本文针对精密转台控制系统在大偏差下的不稳定问题，对其控制系统进行了分析和设计，同时对其高分辨率的指令系统进行了设计，为提高转台的精度及其动态性能提供了新的途径。     

求解阶梯连续梁的通用方程

考虑阶形变化截面及不等跨度的情况,建立了求解多跨连续梁变形的通用方程．根据挠曲微分方程并采用奇异函数求解,给出了分析此类连续梁位移的边界参数方程．该参数方程中含有若干待定的初参数和支反力．进一步导出计算变刚度不等跨连续梁位移的递推格式．最后考虑了位移协调条件及平衡条件而得到求解支反力的代数方程组．其计算的实例表明该方法适于编程运算．     

山地输电线动刚度计算及模态分析

为了揭示地形变化对连续档输电线动态特性的影响，本文提出了基于任意高差角的动刚度理论．首先将单档导线视为连续档导线的子结构，构建了两悬挂点不等高的单档导线振动方程，并在该理论方程中引入了二次项，能够考虑重力沿弦向分量的影响，推导出绝缘子串绕其悬挂点转动的动刚度计算方法，通过动刚度理论研究连续档导线横向振动模态和频率，并应用有限元软件ABAQUS 验证理论模态和频率公式的准确性．所得结果表明，动刚度的计算方法具有较高的精度，理论模态与有限元输出结果吻合较好，同时获得的频率和模态可为山地高压输电线路防舞技术的研究提供依据．     

Flutter instability and other singularity phenomena in symmetric systems via combination of mass distribution and weak damping

The local dynamic instability of autonomous conservative, lumped-mass (discrete) systems, is thoroughly discussed when negligibly small dissipative forces are included. It is shown that such small forces may change drastically the response of these systems. Hence, existing, widely accepted, findings based on the omission of damping could not be valid if damping, being always present in actual systems, is included. More specifically the conditions under which the above systems may experience dynamic bifurcations associated either with a degenerate or a generic Hopf bifurcation are examined in detail by studying the effect of the structure of the damping matrix on the Jacobian eigenvalues. The case whereby this phenomenon may occur before divergence is discussed in connection with the individual or coupling effect of non-uniform mass and stiffness distribution. Jump phenomena in the critical dynamic loading at a certain mass distribution are also assessed. Numerical results verified by a non-linear dynamic analysis using 2-DOF and 3-DOF models confirm the validity of the theoretical findings as well as the efficiency of the technique proposed herein.     

半刚性钢框架的内力分析

采用二阶非线性分析方法分析和设计半刚性钢框架，包括连接的柔性以及构件的几何非线性的影响，提出了半刚性钢框架中梁柱单元刚度矩阵和半刚性梁的单元刚度矩阵；推导了半刚性梁在集中荷载，均布荷载，线性荷载作用下的固端弯矩的求解公式；连接的柔性对无支撑框架的侧移有很大的影响，设计时通过变化连接的刚度以平衡梁的跨中和端弯矩。     

Ultrastiff Hydrogels Prepared by Schiff's Base Reaction of Bis(p‐Formylphenyl) Sebacate and Pillar[5]arene Appended with Multiple Hydrazides

Herein a facile method is reported to prepare polymer gels based on the formation of acylhydrazone bond under mild conditions. A pillar[5]arene derivative appended with ten hydrazide groups provides multiple sites for the reaction with the aldehyde groups of bis(p‐formylphenyl) sebacate in the presence of a small amount of HCl as the catalyst in dimethyl sulfoxide (DMSO), producing transparent polymer organogels. The mechanical properties of gels can be easily tuned by the molar ratio of the reactant compounds. After solvent exchange from DMSO to water, translucent polymer hydrogels with dramatically enhanced strength and stiffness are obtained. The tensile breaking stress and Young's modulus of hydrogels are 20−60 and 1.2–2.7 MPa, respectively, 100 and 20 times those of the corresponding organogels. These robust hydrogels with ultrahigh stiffness should find applications such as in load‐bearing artificial organs. This work should merit designing functional materials using other macrocycles.

     

Parsing disease‐relevant protein modifications from epiphenomena: perspective on the structural basis of SOD1‐mediated ALS

Conformational change and modification of proteins are involved in many cellular functions. However, they can also have adverse effects that are implicated in numerous diseases. How structural change promotes disease is generally not well‐understood. This perspective illustrates how mass spectrometry (MS), followed by toxicological and epidemiological validation, can discover disease‐relevant structural changes and therapeutic strategies. We (with our collaborators) set out to characterize the structural and toxic consequences of disease‐associated mutations and post‐translational modifications (PTMs) of the cytosolic antioxidant protein Cu/Zn‐superoxide dismutase (SOD1). Previous genetic studies discovered >180 different mutations in the SOD1 gene that caused familial (inherited) amyotrophic lateral sclerosis (fALS). Using hydrogen–deuterium exchange with mass spectrometry, we determined that diverse disease‐associated SOD1 mutations cause a common structural defect – perturbation of the SOD1 electrostatic loop. X‐ray crystallographic studies had demonstrated that this leads to protein aggregation through a specific interaction between the electrostatic loop and an exposed beta‐barrel edge strand. Using epidemiology methods, we then determined that decreased SOD1 stability and increased protein aggregation are powerful risk factors for fALS progression, with a combined hazard ratio > 300 (for comparison, a lifetime of smoking is associated with a hazard ratio of ~15 for lung cancer). The resulting structural model of fALS etiology supported the hypothesis that some sporadic ALS (sALS, ~80% of ALS is not associated with a gene defect) could be caused by post‐translational protein modification of wild‐type SOD1. We developed immunocapture antibodies and high sensitivity top‐down MS methods and characterized PTMs of wild‐type SOD1 using human tissue samples. Using global hydrogen–deuterium exchange, X‐ray crystallography and neurotoxicology, we then characterized toxic and protective subsets of SOD1 PTMs. To cap this perspective, we present proof‐of‐concept that post‐translational modification can cause disease. We show that numerous mutations (N➔D; Q➔E), which result in the same chemical structure as the PTM deamidation, cause multiple diseases. Copyright © 2017 John Wiley & Sons, Ltd.     

Fixed Final Time Optimal Control via Simple Cell Mapping

A cell mapping strategy based on Bellman'sPrinciple of optimality (BP) is proposed to solve the fixed final time optimalcontrol of strongly nonlinear systems with state and control bounds. Thefixed final time problem is transformed into a fixed final time-fixed finalstate optimal control problem by reversing the time. This transformationallows to solve the problem in the framework of the BP. Backward searchingalgorithms within the cell mapping context are used to obtain the solution ofthe new problem. This approach reduces considerably the computational effortrequired for the original problem when it is solved by a forward searchingapproach. The vibration control problem of damped and undamped variablestiffness oscillators with bounded stiffness tuning range is studied todemonstrate the effectiveness of the approach. A numerical study on theconvergence of the method is also presented.