Stability Analysis for Time-delay Systems via a Novel Negative Condition of the Quadratic Polynomial function

This paper studies the stability analysis problem for time-varying delay systems. An appropriate Lyapunov-Krasovskii functional (LKF) is constructed where its derivative is a quadratic polynomial function of the delay. A novel negative condition of the mentioned quadratic function with two variable parameters is developed to ensure that the LKF derivative is negative, reducing conservatism on some similar results. Besides, an extended version of Bessel-Legendre inequality is introduced to be employed in the stability analysis of time-varying delay systems. Then, some stability criteria with less conservatism are derived for two kinds of the time-varying delay. Finally, the effectiveness of the proposed stability criteria is demonstrated through three examples.

     

Robust Control of Networked System and Its Application

International Journal of Control, Automation and Systems - In this paper, the stability issue of networked system with dynamical topology in intelligent vehicle is studied. The systems are...     

Theoretical Investigation of the Viscous Damping Coefficient of Hydraulic Actuators

The viscous damping coefficient(VDC) of hydraulic actuators is crucial for system modeling,control and dynamic characteristic analysis.Currently,the researches on hydraulic actuators focus on behavior assessment,promotion of control performance and efficiency.However,the estimation of the VDC is difficult due to a lack of study.Firstly,using two types of hydraulic cylinders,behaviors of the VDC are experimentally examined with velocities and pressure variations.For the tested plunger type hydraulic cylinder,the exponential model B=αυ~(-β),(α0,β0)or B=α_1e~(-β_1υ)+α_2e~(-β_2υ)(α_1,α_20,β_1,β_20),fits the relation between the VDC and velocities for a given pressure of chamber with high precision.The magnitude of the VDC decreases almost linearly under certain velocities when increasing the chamber pressure from 0.6 MPa to 6.0 MPa.Furthermore,the effects of the chamber pressures on the VDC of piston and plunge type hydraulic cylinders are different due to different sealing types.In order to investigate the VDC of a plunger type hydraulic actuator drastically,a steady-state numerical model has been developed to describe the mechanism incorporating tandem seal lubrication,back-up ring related friction behaviors and shear stress of fluid.It is shown that the simulated results of VDC agree with the measured results with a good accuracy.The proposed method provides an instruction to predict the VDC in system modeling and analysis.     

水电黑启动的实现方法

以水电黑启动在重庆彭水电站的实现方法为例,对彭水电站黑启动初始状态、总体思路及其步骤进行详细论述,总结出彭水电站黑启动的重要性,同时提出实施过程中的注意事项。     

Dynamic buffering performance of the honeycomb paperboard filled with polyurethane

A new kind of composite buffering material was made by filling the voids of honeycomb paperboard with polyurethane. Drop tests were performed to evaluate the dynamic energy absorption capacity of the material. Based on the tests results, we analyzed the mechanical behaviors of the material under different conditions and obtained the inherent influencing laws of some factors on the material＇s dynamic buffering performance. It was shown that the dynamic buffering performance varied directly with impact velocity, and inversely with the void diameter, thickness and buffeting area of the composite material.     

2013年全球天文学天体物理学SCI论文的计量分析

本文对2013年全球发表的天文学天体物理学SCI论文进行了计量分析。结果表明,美国和法国国家科研中心分别是发文最多的国家和机构,而加拿大和史密森尼学会的论文相对引文影响指标最高,中国和俄罗斯以及中国科学院和俄罗斯科学院的论文引文影响力低于世界平均水平。此外,天文学天体物理学领域的基金资助机构以各类科学基金会、国家政府部门和国立科研机构为主。美国是提供基金资助最多的国家,其中又以美国国家科学基金会和国家航空航天局为主。     

符号几何规划问题的求解新方法

对符号几何规划问题,给出一种求其全局最优解的分支定界算法。利用不同的凸化方法将算法中关键的定下界操作转化为易于求解的凸规划问题。最后给出算法的收敛性证明和数值实验结果。     

提高高等学校课堂教学有效性的应对策略

探讨高等学校课堂教学现状,分析存在的问题,找寻其中原因,提出应对策略：学生提高自我管理能力、转变学习方法、明确学习目的和增加专业认同感;教师端正教学态度、改变教学方法、提高教学能力;学校实行样本课程、完善教学基础设施、健全和改革学生和教师评价制度等.     

Differences in electrochemical corrosion behaviours between selective laser melted and wrought Ti6Al4V alloys in acid fluoride-containing artificial saliva

Journal of Applied Electrochemistry - In this work, the electrochemical corrosion behaviours of selective laser melted (SLMed) and wrought Ti6Al4V alloys in acid fluoride-containing artificial...     

视觉检测系统中亮度不均匀背景的一种去除方法

刀具形状视觉检测系统中，照明不均匀对测量结果影响很大。针对这种情况，提出了基于二维二阶多项式拟合并去除不均匀背景的方法。遵循最小均方程差原理，给出了二维二阶拟合的矩阵表达式。在编制的程序中，拟合点以人机交互形式由鼠标点击选出，程序自动记录所选点的图象人材与亮度值信息，然后拟合出背景曲面，并以二值图象形式给出去除背景后的目标图象。对一幅光照模型未知的网络图象进行了背景去除，实验结果良好。