Electrical discharge dressing of honing stones

Honing processes require a systematic preparation and a regeneration of the honing tool to guarantee a sufficient cutting behaviour and prevent unintended wear of the tool. These dressing processes are particularly important for the regeneration of the macro- and microscopic topography of the honing stones. The established method of manual shaping subsequent to a cylindrical grinding process demands a high skill level, a great amount of non-productive time and is not reproducible.In this paper the preparation of honing stones by use of electrical discharge machining (EDM) is presented. The aim is to ensure an automatic, systematic and reproducible process of resetting the bond of honing stones. Different tool electrode materials were analysed systematically for two different bond specifications of the honing stones. EDM process parameters were studied within a design of experiments (DoE) strategy and a subsequent effect analysis to assure the identification of most appropriate EDM process parameters. After this procedure various cycles of long-stroke honing processes were carried out. As a result, the new approach makes it possible to prepare honing stones with reproducible sharpness and macroscopic topography within an automated process. The dressing time t_d was reduced by 88 % compared to the established method.     

基于双管正激的电容器充电电源控制策略研究

分析了一种变压器二次侧采用二极管全桥不控整流的双管正激型电容器充电电源,其磁复位由直流电源和充电电容共同完成,增加了开关周期内传输的能量。详细分析了电路的工作原理和输出特性,比较了电容器充电过程中传统脉宽调制和开关频率调节两种控制方法。指出在恒流充电要求下,基于开关频率调节的控制策略有助于提高充电速率,并通过Matlab/Simulink仿真和实验验证了理论分析的正确性。     

浅述保障房外墙渗漏防治工程实例

本文以我公司建设安置小区外墙渗漏通病防治取得较为满意且成功的工程实例,对小区交付使用作者走访所在物业后进行了工作总结,详述了本小区在建设过程中倍受同行关注的一些做法。安置保障房涉及民生、民心,是全社会各界“聚焦”之所在。因此,作者将此成功的实例经验和举措奉献诸位同行共飨。     

空心板梁桥纠偏复位的关键设计及施工技术

以6×20m一联预应力空心板梁桥纠偏复位工程为背景,结合现场空心板梁自身结构特点及梁下空间,设计了顶升、滑移千斤顶同步系统,利用三向千斤顶提供主动纠偏力,驱动顶升顶及梁体滑移,实现梁体横向纠偏复位。其中重点介绍了纠偏复位方案的关键设计要点及施工技术。工程实践表明设计合理,施工经济便捷,达到了预期的工程效果,对同类工程具有可借鉴及推广性。     

DS7400Xi可编程输出口应用

DS7400Xi大型报警主机系统具有很强的实用性,被广泛应用在小区住户及周界报警系统、大楼安保系统、以及工厂、学校、仓储等各类大型安保系统,其可编程输出口功能较多,使用者难于掌握。文中就可编程输出口的防区报警、系统复位、出入口控制三种常用功能进行详细介绍,从使用范围、系统结构接线图设计、编程设置及效果等方面进行了总结归纳。     

隧道工程中专用发光水准尺改装方法探析

通过对国产3 m普通水准尺进行改装,在隧道内光线不足的情况下,使其能满足隧道内水准测量。实践证明,改装后的隧道洞内专用发光水准尺具有使用方便、节约人力、提高工作效率等优点。     

An impulsive dynamical systems framework for reset control systems

Impulsive dynamical systems is a well-established area of dynamical systems theory, and it is used in this work to analyse several basic properties of reset control systems: existence and uniqueness of solutions, and continuous dependence on the initial condition (well-posedness). The work scope is about reset control systems with a linear and time-invariant base system, and a zero-crossing resetting law. A necessary and sufficient condition for existence and uniqueness of solutions, based on the well-posedness of reset instants, is developed. As a result, it is shown that reset control systems (with strictly proper plants) do not have Zeno solutions. It is also shown that full reset and partial reset (with a special structure) always produce well-posed reset instants. Moreover, a definition of continuous dependence on the initial condition is developed, and also a sufficient condition for reset control systems to satisfy that property. Finally, this property is used to analyse sensitivity of reset control systems to sensor noise. This work also includes a number of illustrative examples motivating the key concepts and main results.     

地板辐射供冷系统的热性能研究

实验比较了双位开关控制、变流量控制和室外温度补偿+室温反馈控制方式下地板辐射供冷系统室内温度稳定性、地板表面温度稳定性以及结露发生频率.研究结果表明,室外温度补偿控制方式的最低供水温度为15℃,室外温度补偿率为0.25;在运行初期,双位开关控制室温稳定性优于其他控制方式,随着系统运行时间延长,室外温度补偿+室温反馈控制...     

一种煤矿提升机盘型闸间隙测量报警仪

以C08051F310单片机为核心,采用电池供电,设计了一套低功耗煤矿提升机盘型闸间隙测量装置。该装置自动检测盘型闸开关状态,提升机停用或盘型闸关闭期间,进入掉电模式;盘型闸开启时,开闸信号使装置自动上电复位并进行测量,若盘型闸间隙超过规定值能发出声光报警。     

非理想条件下有源箝位正激电路小信号模型分析

有源箝位正激变换器相对于其它复位方式，有很多优点，然而当输入源和负载发生变化时，却造成系统的不稳定性。文中分析了有源箝位正激变换器中复位电容对其小信号特性的影响，在考虑原边主管导通电阻的基础上，应用状态空间平均法，首次推导其小信号模型，并运用Mathcad仿真了该模型的频率特性，结合控制理论根之和的概念，分析了非理想条件下的有源箝位正激电路的小信号模型。