自动控制系统稳定性的判断

控制系统性能的优劣 ,有许多具体的性能指标来体现。这些性能指标的确定必须以系统稳定为前提。判断一个系统是否稳定 ,常用的有古尔维茨判据即代数稳定判据和奈奎斯特稳定判据     

波德图相频特性的研究

为了更完整地画出对数相频特性曲线 ,用公式扒导和举例印证两面三刀种方法在理论和实践上得出含有不稳定环节时开环系统对数相频特性曲线的画法 :第一步 ,画出除ω=0 + 以外的对数相频特性曲线 φ(ω) ;第二步 ,当 p 为偶数时 ,从lgω轴上往负相位方向补画辅助曲线 ,当 p为奇数时 ,从 φ(ω) =- 180 ° 线上开始补画辅助曲线 ;与 φ(ω) 连接起来 ,加上对数幅频特性曲线 ,即可应用对数频率判据全面地判断闭环系统的稳定性     

蠕变条件下完整岩石的起裂和扩展准则

The mechanism and criterion of crack initiation and propagation of rocks were investigated by many researchers,And the creep behaviour of rocks was also theoretically and experimentally studied by some scientists and engineers.The characteristics of crack initation and propagation of rocks under creep condition.however,are very improtant for rock engineering and still not paid enough attention by researchers,In this paper,the criterion and mechanism of crack initiation and propagation under creep condition were investigated using specimens collected from sandstone rock formations outcropping in the Emei Mountain,the Sichuan Province of China.Cuboid specimens under three point bending were used in this investigation.All specimens were classified into four sorts and used for Mode-I fracutre of creep frcture tests.The experimental result shows that due to creep deformation.rock crack will inevitably initialt and propagate under a load of KI,which is less than fracture toughness KIC but not less than a constant(marked as KIC2),KIC2 indicates the ability of rock to resist crack initiation and propagation under creep conditions and is less than fracture tough ness KIC.defined as creep fracture toughness in this paper,KIC2 should be considered as an importnat parameter on design and computation of rock engineering.The microstructureal mechanism for crack initiation and propagation of rock materials under creep condition was introduced based on competitive model between softening effect and hardening effect,and the validity of test result was explained.The test result was also verified in rheological theory.When KI is more than KIC2 but less than KIC,rock crack will initiate and propagate after a time interval of sustained loading under creep condition.In order to find the relation between duration of sustained lading.which can lead to crack initiation and propagation,and the initial stress intensity factor KI,an unequal0interval time sequence forecasting and predicting model was introduced,and the relation was obtained for homogeneous and isotropic fine-grained red sandstone.Finally a modified fracture toughness formula was given,in which the influence of fracture process zone(FPZ) was fully considered.     

自动控制系统稳定性的判断

控制系统性能的优劣，有许多具体的性能指标来体现，这些性能指标的确定必须以系统稳定为前提，判断一个系统是否稳定，常用的有古尔维茨判据即代数稳定判据和奈奎斯特稳定判据。     

一类偶数阶偏微分方程的振动判据

用微分不等式方法讨论了一类偶数阶中立型偏微分方程的振动性 ,得到了该类偏微分方程振动的判据     

一种稳定性研究的模拟实验电路的

本文介绍了一种控制系统稳定性研究的模拟电路的参数改进设计,并且进行了理论计算和实验证明。     

基于压力的静电感度仪爆炸判据的确定

针对测定炸药静电感度值的标准实验仪器--JY-50Ⅱ型静电感度仪存在的爆炸判据难以准确判定的问题,以炸药在炸药小室发生爆炸后压力会发生变化这一现象为依据,并结合计算机与传感技术,设计出了其爆炸判据的实验确定方法.     

负系数混合型奇数阶差分方程的振动性质

研究了一类负系数混合型奇数阶差分方程的振动性质,得到了这类差分方程振动的判据.     

芳香性理论研究方法及其在结构化学教学中的应用

本文概括性地介绍了芳香性的一些常用概念,判据以及理论研究方法,并讨论了各种研究方法的发展现状及其在结构化学教学中的应用,指出了将芳香性理论研究方法引入结构化学教学中,能更好地促进学生理解结构化学教学内容。     

一小型化工企业的一次供电方案改造

本文结合一个工程实例,介绍了一台抽背压式汽轮发电机组的孤岛运行改造,并提出了一个小型化工企业经常会遇到的电气接线(中压系统)的备自投配置方案。