Electric characteristic and cavitation bubble dynamics using underwater pulsed discharge

Underwater pulsed discharge is widely applied in medicine, machining, and material modification. The induced cavitation bubble and subsequent cavitation collapse are considered the major motivations behind these applications. This paper presents an underwater pulsed discharge system. The experimental setup is established to induce and investigate the cavitation bubble assisted with a high-speed camera. Three aspects, including the characteristic of the discharge with different applied voltages and conductivities, the evolution of the cavitation bubble profile, and the energy efficiency of cavitation bubble inducing, are investigated, respectively. Especially, the mechanism of pre-discharge time delay in the low field intensity case is explained using the Joule heat effect. The results show the validity of the underwater pulsed discharger and experimental setup. The present underwater pulsed discharger is proved to be a simple, portable, and easy-to-implement device for the investigation of cavitation bubble dynamics.     

Diagnostic of capacitively coupled radio frequency plasma from electrical discharge characteristics: comparison with optical emission spectroscopy and fluid model simulation

The capacitively coupled radio frequency(CCRF)plasma has been widely used in various fields.In some cases,it requires us to estimate the range of key plasma parameters simpler and quicker in order to understand the behavior in plasma.In this paper,a glass vacuum chamber and a pair of plate electrodes were designed and fabricated,using 13.56 MHz radio frequency(RF)discharge technology to ionize the working gas of Ar.This discharge was mathematically described with equivalent circuit model.The discharge voltage and current of the plasma were measured atdifferent pressures and different powers.Based on the capacitively coupled homogeneous discharge model,the equivalent circuit and the analytical formula were established.The plasma density and temperature were calculated by using the equivalent impedance principle and energy balance equation.The experimental results show that when RF discharge power is 50–300 W and pressure is 25–250 Pa,the average electron temperature is about 1.7–2.1 e V and the average electron density is about 0.5?×?10~(17)–3.6?×?10~(17)m~(-3).Agreement was found when the results were compared to those given by optical emission spectroscopy and COMSOL simulation.     

超声降解有机磷农药的研究进展与比较分析

有机磷农药的毒性强,研究降解有机磷农药的有效方法已受到学术界的极大重视。对超声降解有机磷农药的机理进行了简介,综述了超声降解甲胺磷等五类农药的研究进展,比较分析了降解效果与关键物理参数之间的关系。依据对比分析结果提出了超声技术应用于农药降解时需重视的关键技术问题以及发展趋势。     

ADSL话音分离器幅频特性检测仪的研制

根据ADSL话音分离器快速检测的特殊要求,设计了一种综合应用MCU、DDS、LPF、自动控制、高频小信号放大等技术实现ADSL分离器多项幅频特性参数快速检测的仪器。经过与传统检测方法进行对比表明,所设计的检测仪具有检测速度快、准确性高、检测数据后期使用方便和检测成本低等特点。     

ADSL话音分离器测试仪的设计

针对目前国内市场普遍缺乏高效ADSL话音分离器测试仪的现状．在分析ADSL话音分离器的基本构造和测试原理的基础上，综合运用多种高速、高精度电子器件和嵌入式技术，研制一种符合国家相关标准，能快速、批量、准确测试ADSL话音分离器多种性能参数的测试仪．测试检验结果表明．研制的测试仪的各项指标均满足设计要求．     

高压大电流步进电机驱动器异常保护措施研究

高压步进电机及驱动器的保护电路是保证其长期稳定运行的关键,文章对其保护电路进行了设计.通过对错相和各种因素引起的过流等异常工作情形的反复试验表明,所设计的电路在错相和过流时均能有效地保护高压大电流步进电机驱动器.     

高压大功率步进电动机驱动器异常保护

高压步进电动机及驱动器的保护电路是保证其稳定长期运行的关键,对其保护电路进行了设计,通过错相和各种因素引起的过流等异常工作情形反复试验,表明设计电路在错相和过流时能有效保护高压大电流步进电动机驱动器。     

基于人工神经网络的聚类算法

研究连续型Hopfield神经网络的电路机理,推导出网络的权值计算公式,并运用连续型的神经网络模型构造出聚类算法;对20个随机生成数据计算模拟神经网络的运行,逐步调整类内精度多次训练,当参数a=b=500,c=200且类内精度控制不超过0.6时,有一个优化的聚类方案输出。     

Atmospheric Pressure Plasma Jet in Organic Solution: Spectra,Degradation Effects of Solution Flow Rate and Initial pH Value

The organic compounds of p-nitrophenol （PNP） solution was treated by the active species generated in a stirred reactor by an atmospheric pressure plasma jet （APPJ）. The emission intensities of hydroxyl （OH）, oxygen （O）, nitric oxide （NO）, hydrogen （H） and molecular （N2） were measured by optical emission spectroscopy （OES）. The relations between the flow rates of the PNP solution and degradation, the degradation effects and initial pH value of the solution were also investigated. Experimental results show that there exist intense emissions of O （777.1 nm）, N（337.1 nm）, OH （306-310 nm） and NO band （200-290 nm） in the region of plasma. Given the treatment time and gas flow rate, the degradation increased as a function of discharge energy and solution flow rate, respectively. The solution flow rate for the most efficient degradation ranged from 1.414 m/s to 1.702 m/s, and contributed very little when it exceeded 2.199 m/s. This indicates the existence of diffusion-controlled reactions at a low solution flow rate and activation- controlled reactions at a high solution flow rate. Moreover, increasing or decreasing the initial pH value of neutral PNP solution （pH=5.95） could improve the degradation efficiency. Treated by APPJ, the PNP solutions with different initial pH values of 5.95, 7.47 and 2.78 turned more acidic in the end, while the neutral solution had the lowest degradation efficiency. This work clearly demonstrates the close coupling of active species, photolysis of ultraviolet, the organic solution flow rate and the initial pH value, and thus is helpful in the study of the mechanism and application of plasma in wastewater treatment.     

铁路LED信号灯Buck转换器的设计

为了满足铁路信号灯系统要求发光二极管(LED)照明电源在恶劣环境下具有转换效率高,使用寿命长,稳定性好等特殊性能,对大功率LED在铁路信号灯应用中的部分特殊性进行了分析;设计了一种可与原有铁路变换器兼容的高效功率铁路LED信号灯恒压Buck转换器及恒流驱动电路.实验结果表明,电路可以达到预定的设计指标.