管输系统天然气泄漏量计算模式及泄漏检测最佳条件的确定

采用静态和动态试验对天然气泄漏量计算模式进行了筛选和验证,同时采用静态试验对不同风速、风向条件下天然气泄漏检测最佳条件进行筛选。试验结果表明：采用折线积分法和相关曲线法计算泄漏最,较能反映输、配气站场泄漏的真实情况;在风速小于0．8m/s（包括静风）时,距设备泄漏点下风向1．5－2．0cm处,由测试浓度计算泄漏速率的准确性较高;当风速为0．8－1．3m/s时,距设备泄漏点下风向1．0cm左右,由测试浓度计算泄漏速率的准确性较高;当风速大于1．3m／s时,应停止进行天然气泄漏检测工作。     

CLOSED FORMULAE FOR THE GENERALIZED ℋ︁∞ SENSITIVITY MINIMIZATION PROBLEM

The paper presents a complete solution for the multivariable, continuous-time Generalized ℋ︁_∞ (𝒢ℋ︁_∞) sensitivity minimization problem. In contrast with existing solutions, derived via polynomial methods, the state-space solution given here is essentially non-iterative. Closed formulae for the minimum and a particular optimal controller are derived in terms of a real Schur decomposition, the solution of two Lyapunov equations and a single, well-conditioned eigenvalue problem. © 1997 by John Wiley & Sons, Ltd.     

WiMAX技术标准的发展进程

IEEE 802.16 is very attractive since its publication,.The growth of WiMAX organization accxelerates the development of 802.16 standard,The mobile WiMAX——802.16e standard is especially attractive,This article presents the status quo and the development of WiMAX technical standard along with the work plan of the standard organization in the next stage.The article also introduces the conditions that the development of mobile WiMAX technical standard is attracting people＇s attention.     

Feedback representations of critical controls for well-posed linear systems

This is the first part in a three part study of the suboptimal full information H^∞ problem for a well-posed linear system with input space U, state space H, and output space Y. We define a cost function Q(x₀,u)=∫〈y(s),Jy(s)〉_Yds, where y∈L²_loc( R ⁺; Y) is the output of the system with initial state x₀∈H and control u∈L²_loc( R ⁺; U), and J is a self-adjoint operator on Y. The cost function Qis quadratic in x₀ and u, and we suppose (in the stable case) that the second derivative of Q(x₀, u) with respect to u is non-singular. This implies that, for each x₀∈H, there is a unique critical control u^crit such that the derivative of Q(x₀, u) with respect to u vanishes at u=u^crit. We show that u^crit can be written in feedback form whenever the input/output map of the system has a coprime factorization with a (J, S)-inner numerator; here S is a particular self-adjoint operator on U. A number of properties of this feedback representation are established, such as the equivalence of the (J, S)-losslessness of the factorization and the positivity of the Riccati operator on the reachable subspace. © 1998 John Wiley & Sons, Ltd.     

一种新的Ad Hoc信道接入协议

Ad Hoc网络是共享无线传输媒体的多点网络,首先研究了Ad Hoc网络存在的特有的隐藏终端和暴露终端问题,围绕结点信息栈,提出了一种新的Ad Hoc网络信道接入协议——ISCAP（node information stack channel access protocol）。其中,包括隐藏终端和暴露终端的解决方案,以友基于结点信息栈的一种新的随机退避算法,以达到在保证多个结点公平接入共享信道的基础上提高信道利用率的效果。最后,从理论上和具体应用两方面,分析了这种新的接入协议的正确性和有效性。     

基于OPNET的移动WiMAX网络仿真

结合OPNET和IEEE 802.16e协议,采用OPNET的三层建模机制、基于包的通信机制和离散事件驱动机制首次完成对移动WiMAX网络系统级建模.建模内容划分为无线通信网络建模,IEEE 802.16e协议建模,统计信息建模三部分.通过仿真获得了移动WiMAX网络在轻负载情况下的时延性能.     

利用冷却塔排放烟气技术介绍

在火力发电厂中烟囱成为火电厂必不可少的重要设施,利用冷却塔排放烟气不但可以节约工程投资和运行费用,而且有利于提高冷却塔的冷却效率,是一种技术先进,经济适用的方法。本文将主要介绍利用冷却塔排放烟气的工艺流程、烟气排放对冷却塔热力性能的影响、排烟冷却塔的结构稳定性及存在的问题。     

钢管树状结构设计

钢管树状结构受力合理,承载力高,不仅体现了钢结构的优势,而且使建筑与结构完美统一。结合工程实例介绍了钢管树状结构的设计、制作安装要点,为大型空间建筑或钢结构艺术建筑采用钢管树状结构积累经验,为完善树状结构工程设计抛砖引玉。     

An H∞ approach to linear iterative learning control design

A new design methodology for iterative learning control systems is developed. It is based on the convergence condition for systems operating on an infinite time interval which is of the H_∞ type. The principal idea of the design technique is to design a learning controller such that the speed of convergence is maximized, with a compromise to robustness. The issue of finite versus infinite trial lengths is addressed, as well as limitations on the best achievable rate of convergence due to structural properties of the plant.     

醋酸乙烯下游产品在胶粘剂行业中的应用现状

介绍了国内外醋酸乙烯下游产品聚乙烯醇、聚醋酸乙烯乳液、 Ｖ Ａ Ｅ 乳液和 Ｅ Ｖ Ａ 树脂在胶粘剂行业中的生产与应用现状,并对有关技术进展作了简单的概述