电极加工时间对电火花加工效率影响规律研究

研究电极加工时间对电火花加工效率的影响规律可以为控制电极加工时间来提高电火花加工效率提供重要理论依据.首先通过实验检测不同电极加工时间对应的有效放电频率,发现在带抬刀的电火花加工中,加工效率随电极加工时间的增加而先增加后降低.随后通过观察放电过程中加工间隙内气泡和加工屑的运动,发现底面间隙内加工屑浓度随电极加工时间的增长而增加.在此基础上,证明了加工效率随电极加工时间的变化规律具有确定性.     

三维电阻抗成像的测量模式

电阻抗成像技术（EIT）是一种非侵入的成像技术,通过测量介质的边界参数,从而获得介质的分布状态．为研究EIT的测量模式对其数据测量和图像重建的影响,借助仿真软件COMSOL建立了具有双层电极结构的EIT系统．设计和采用了4种典型的激励模式和2种测量模式,并通过评价指标进行比较．结果显示,在理想条件下,几种模式的组合表现均可．考虑到既易于测量且成像质量高,推荐双层24电极EIT系统使用同层准对向驱动模式．     

超声液位传感器有限元模型及其声学特性分析

运用ANSYS有限元软件建立超声液位传感器有限元模型,利用其谐波响应、瞬态响应分析技术分析了超声液位传感器声学特性．阐明了超声液位传感器声学特性分析的有限元理论,给出了建模过程若干关键问题的解决方法．研究了保护膜厚度、材料及压电元件的电学品质因数对传感器声学特性的影响,并通过实验验证了谐振频率和最大发射电压响应的仿真计算结果的合理性．由此可见,所建立的分析模型可较准确地对超声液位传感器的声学特性进行仿真模拟,为该传感器的优化设计提供了一种有效的方法．     

Compound machining of silicon carbide ceramics by high speed end electrical discharge milling and mechanical grinding

A compound process that integrates end electrical discharge (ED) milling and mechanical grinding to machine silicon carbide (SiC) ceramics is developed in this paper. The process employs a turntable with several uniformly-distributed cylindrical copper electrodes and abrasive sticks as the tool, and uses a water-based emulsion as the machining fluid. End electrical discharge milling and mechanical grinding happen alternately and are mutually beneficial, so the process is able to effectively machine a large surface area on SiC ceramic with a good surface quality. The machining principle and characteristics of the technique are introduced. The effects of polarity, pulse duration, pulse interval, open-circuit voltage, discharge current, diamond grit size, emulsion concentration, emulsion flux, milling depth and tool stick number on performance parameters such as the material removal rate, tool wear ratio, and surface roughness have been investigated. In addition, the microstructure of the machined surface under different machining conditions is examined with a scanning electron microscope and an energy dispersive spectrometer. The SiC ceramic was mainly removed by end ED milling during the initial rough machining mode, whereas it is mainly removed by mechanical grinding during the later finer machining mode; moreover, the tool material can transfer to the workpiece surface during the compound process.     

Changes in the power spectrum of electrical signals in maize leaf induced by osmotic stress

To quantify the characteristics of the power spectrum of plant electrical signals, we defined the following concepts:spectral edge frequency (SEF), spectral center frequency (SCF), power index (PI) and power spectral entropy (PSE). These parameters were used to examine and quantify changes in the power spectrum of electrical signals in maize leaves under osmotic stress. In the absence of osmotic stress, the SEF of the electrical signal in maize leaves was approx. 0.2 Hz and the SCF was approx. 0.1 Hz. The electrical signal in maize leaves was mainly a slow wave signal with a frequency of 0-0.1 Hz. After 2 h osmotic stress, the SEF and SCF of the electrical signal increased to higher frequencies. The proportion of the fast wave frequency also increased to 0.1-0.2 Hz, resulting in a dramatic increase in PSE. We also found that the changes in PSE and SCF were significantly correlated during osmotic stress. We propose that the changes in the PSE and SCF in maize leaves can be used as a sensitive signal indicating water deficit in leaf cells under osmotic stress. Thus, measurement of SCF or PSE of electrical signals in maize leaves could be used to develop early warning and rapid diagnosis techniques for the water demands of plants.     

基于Web服务器的机电运控系统代理软件设计

通过对Web服务器的研究,结合高速公路现有机电设备及管理现状,提出了一种在Linux环境下基于Web服务器的机电系统运控代理软件设计思想。介绍了该运控软件的模块构成、工作原理及流程,详述了该软件中Web服务器、HTTP(超文本传输协议)动态页面、socket通信、交叉编译、定时轮询等相关技术。通过仿真,验证了代理软件设计的可行性。     

高职高频电子技术实验实训课程改革探索

高频电子技术是电子与通信类专业中一门重要基础课。本文按“项目引领、任务驱动”法对实验实训内容进行调整,合理安排实验实训内容,借此探索高频电子技术课程的实验实训教学改革,加强学生实践能力和创新精神的培养。     

瑞光工程低压系统电气调试问题解析

列举了瑞光工程低压厂用系统电气调试过程中出现的典型问题,并对问题产生的原因进行了分析。     

基于RFID和GPS技术的电力设备巡检系统研究

在电力系统中,采用纸面记录的传统的设备巡检方法无法满足信息管理的需要,针对这一问题,研究了一套基于RFID和GPS技术的电力设备巡检系统。该系统由现场巡检设备、RFID标识牌、手持终端和管理后台组成,采用多层架构,是基于分布式、计算机、电子信息、数据库等技术的系统,实现了手持终端和后台的数据同步与传输。现场运行表明,该系统很好地实现了电力设备巡检的无纸化作业,避免了人员不到位等主观因素,大大提高了巡检系统的工作效率。     

扩容器选择数学模型建立及仿真实现

为了解决手工设计时,工作效率低、无法保证发电机组的安全和经济运行等问题,建立了扩容器选择数学模型,并采用Visual Basic 6.0开发扩容器选择计算机系统. 在系统中使用ActiveX数据对象通过OLE DB Provider访问数据库服务器中的数据,具有对基础数据的管理功能. 利用扩容器选择计算机系统可以做到操作简单,减少人为造成的误差,提高设计效率.