用PID控制弧焊逆变电源的试验研究

本文介绍了对逆变电源进行数字PID控制的原理和方法,分析了采样周期、PID参数及不同的焊接工况对控制特性的影响。试验表明,只要恰当地选择PID(或PI)参数,不仅能实现高精度的恒流控制,而且能使系统的动态性能显著提高。     

浅谈基坑支护的有关技术问题

随着我国社会建设的持续推进,基坑工程数量急剧增加,基坑工程所处的地质条件、周边建筑物、通行道路及地下设施等外部环境越来越趋于复杂,明挖缓坡基坑趋于减少,基坑开挖后要保证周围建筑物、道路正常通行等要求的基坑工程数量趋于增多。基坑支护的安全性直接威胁到周边建筑物、道路、地下室及施工人员的安全,基坑一旦失稳,很可能会造成巨大的人员和财产损失,对社会安定造成重大影响。因此,基坑支护工程是基坑工程中的重中之重,需要设计、施工、监理及有关管理部门高度重视。     

市政工程给水管道施工质量控制

在各个城市市政工程给水管道的施工中,相关部门在质量监测和管理等方面的工作中仍然存在不足之处。因此,如何解决市政工程给水管道施工中出现的各种故障,是相关施工人员值得思考的问题。     

An innovative technique for web text watermarking (AITW)

ABSTRACT

Embedding a hidden stream of bits in a cover file to prevent illegal use is called digital watermarking. The cover file could be a text, image, video, or audio. In this study, we propose invisible watermarking based on the text included in a webpage. Watermarks are based on predefined structural and syntactic rules, which are encrypted and then converted into zero-width control characters using binary model classification before embedding into a webpage. This concept means that HTML (Hyper Text Markup Language) is used as a cover file to embed the hashed and transparent zero-width watermarks. We have implemented the proposed invisible watermarking against various attacks to reach optimum robustness.     

赞比亚Lunzua水电站施工控制网的建立

文章结合工程实例,介绍南半球国家施工控制网的建立、平差与投影变形的解决方法.     

统计过程控制(SPC)在龙滩水电站混凝土生产质量控制中的应用

混凝土生产工艺流程复杂,控制工序多,生产过程除易受系统因素影响外,还受随机因素的干扰较大,生产质量不易控制,本文应用统计过程控制(SPC)在龙滩水电站混凝土生产中的质量控制实践来谈点初浅的认识.     

Bounded Consensus Algorithms for Multi‐Agent Systems in Directed Networks

In this paper, the consensus problem is investigated via bounded controls for the multi‐agent systems with or without communication. Based on the nested saturation method, the saturated control laws are designed to solve the consensus problem. Under the designed saturated control laws, the transient performance of the closed‐loop system can be improved by tuning the saturation level. First of all, asymptotical consensus algorithms with bounded control inputs are proposed for the multi‐agent systems with or without communication delays. Under these consensus algorithms, the states’ consensus can be achieved asymptotically. Then, based on a kind of novel nonlinear saturation functions, bounded finite‐time consensus algorithms are further developed. It is shown that the states’ consensus can be achieved in finite time. Finally, two examples are given to verify the efficiency of the proposed methods.     

Stability and control of nonlinear systems described by retarded functional equations: a review of recent results

This paper reports on recent results in a series of the work of the authors on the stability and nonlinear control for general dynamical systems described by retarded functional differential and difference equations. Both internal and external stability properties are studied. The corresponding Lyapunov and Razuminkhin characterizations for input-to-state and input-to-output stabilities are proposed. Necessary and sufficient Lyapunov-like conditions are derived for robust nonlinear stabilization. In particular, an explicit controller design procedure is developed for a new class of nonlinear time-delay systems. Lastly, sufficient assumptions, including a small-gain condition, are presented for guaranteeing the input-to-output stability of coupled systems comprised of retarded functional differential and difference equations.     

在ASP.NET 2.0中自动化构建数据访问层

使用ASP.NET2.0所提供的BuildProvider类,将自动化构建的数据访问层源代码编译到程序集中,使得开发者利用Ob-jectDataSource控件,可以简单、快速地实现三层架构的Web应用。     

DCS系统在新型干法水泥生产线中的应用

介绍了在新型干法水泥生产线中全厂全线采用DCS系统进行设计应用,对企业降低费用、提高效率和生产率具有十分重大意义。