New approach for the stability analysis of linear time-varying state-space models

A new approach is proposed to establish stability bounds on the parameters of linear time-varying systems. In particular, stability of the Mathieu equation is investigated and stability boundaries are established. The proposed method is computationally simple to apply and can be calculated easily by computer. Examples are given to illustrate the improvement of the proposed method over that reported by Yedavalli and Kolla (1988).     

Application of piecewise-linear polynomial functions in analysis of eigenvalue problems

By using the expansions of piecewise-linear polynomial functions, the Sturm-Liouville eigenvalue problem can be dealt with as a set of linear algebraic equations. Owing to the available recursive algorithm, these linear algebraic equations can be solved by straightforward substitution. An iterative improvement is used for finding eigenvalues in order to speed up the convergence. The usefulness of this method is demonstrated by an example and the results are satisfactory.     

不确定长时延网络控制系统的H∞鲁棒控制

在状态不完全可测的网络控制系统中,针对不确定网络长时延、网络噪声等问题系统性能造成的影响,研究了一类具有不确定长时延网络控制系统的H∞鲁棒控制问题.在不确定网络时延大于一个采样周期时,将采用动态输出反馈的网络控制系统建模为一类具有参数不确定性的线性离散系统.基于Lyapunov稳定性理论和线性矩阵不等式(LMI)方法,...     

COMPLEX VARIABLE BOUNDARY ELEMENT METHOD FOR TORSION OF COMPOSITE SHAFTS

The problem of torsion of composite shafts consisting of a cylindrical matrix surrounding a finite number of inclusions is solved by using the complex variable boundary element method. The method consists in reducing the problem to the solution of a singular integral equation in terms of an analytic function of a complex variable using the Cauchy integral. The resulting integral equation is then solved numerically by discretizing the boundaries into segments called complex boundary elements and replacing the analytic function on the boundaries by interpolating function. Numerical examples are given for a square shaft with a circular inclusion, and for an elliptic shaft with two elliptic inclusions. © 1997 by John Wiley & Sons, Ltd.     

流媒体代理缓存技术研究

随着流媒体技术在互联网上的广泛应用,原有用于加速Web内容分发的代理缓存技术也被应用于流媒体内容分发领域。然而,由于流媒体对象的一些独特特点,需要在传统Web缓存技术的基础上提出适用于流媒体对象的缓存技术。本文分析了基于代理缓存的流媒体分发中的关键问题和技术挑战,对现有的各种流媒体缓存方案进行了综述、分类和比较,最后对流媒体代理缓存的未来发展方向进行了展望。     

25％啶菌唑水乳剂高效液相色谱法分析

[目的]建立一种25%啶菌唑水乳剂的分析方法。[方法]采用高效液相色谱法,使用C18柱和PDA检测器,以乙腈和三乙胺溶液为流动相,梯度洗脱方式分离25%啶菌唑水乳剂中的杂质、助剂、异构体E及异构体Z,并测定啶菌唑的含量。[结果]采用该分析方法,啶菌唑异构体E及异构体Z的线性相关系数分别为1.0000、0.9999,啶菌唑精密度的RSD为1.53%,平均回收率为100.5%。[结论]该方法专属性强,精密度及准确度好,可以满足25%啶菌唑水乳剂的定量分析。     

短路还原法提取铁的研究

采用氧离子导体氧化锆管与还原剂碳、含有电活性物质FeO的熔渣组成电化学体系,利用原电池短路方法从氧化物熔渣中电化学还原得到了无碳金属．实验电池组成为：石墨,[O]Fe—C（aaturated）｜ZrO2（MgO）｜Cu（1）＋（FeO）（alag）,钼丝．利用电化学分析仪,通过测定外电路电流研究了渣中FeO含量、温度以及外电路电阻对熔渣中FeO电化学还原的影响．结果表明：在实验条件下,温度越高,渣中FeO含量越高,外电路电阻越小,熔渣电化学还原就越快．实际终还原率达95％以上．提出了可控氧流冶金中的一种还原方法,发展了可控氧流冶金理论．     

THE DEVELOPMENT OF CHROMIUM-DEPLETED ZONE IN 18-8 STAINLESS STEEL WITH TIME OF SENSITIZATION

利用以前报道过的恆电位量电法以及化学分析法,进一步研究了18鉻-8镍型不锈钢中的贫鉻区随着敏化处理时间的发展情况.得到了敏化时间不同时鉻在贫鉻区中的分布曲线,估计出鉻在650℃的溫度下在贫鉻区中离碳化物层100埃处的扩散系数为5×10~(-16)厘米~2/秒.结果表明,析出在晶界的碳化物的量大体上按对数规律随敏化时间增长.此外,18鉻-8镍型不锈钢中所含碳的总量中只要有1—2％析出在晶界,就足以引起严重的晶间腐蚀.     

基于可视化技术的核电站水下机器人地面站设计

针对当前水下机器人地面控制系统可视化程度低、操控不便的问题,基于可视化技术设计了一套水下机器人的岸上地面站系统。该系统可以控制水下机器人的半自主定航向和定深度航行,接受、储存、回放水下机器人拍摄的录像。采用编程技术实现三维动画空间,结合传感器回传数据控制三维动画显示,真实地反映真实世界中水下机器人的运动姿态、位置、运行状态。结合声纳成像信息、摄像机回传图像信息的综合显示,实现了微小型水下机器人的遥操作控制。     

COMPARISON OF THE CONFORMATION OF TOMATO PECTINS WITH APPLE AND CITRUS PECTINS

The conformation of hot break tomato pectins in water/glycerol solutions as a function of degree esterification was studied and compared with the conformation of apple and citrus pectin using reduced storage [G']_R and loss [G"]_R moduli and the theories of Marvin and McKinney for rod-like behavior and those of Rouse as well as Zimm for random coil conformation. In all three cases the theory of Zimm implying dominant hydrodynamic interactions fit the experimenal data best. This is consistent with current knowledge on chemical structure of pectin where the charged uronides clearly readily interact with each other.