Effect and mechanism of on-chip electrostatic discharge protection circuit under fast rising time electromagnetic pulse

The electrostatic discharge(ESD)protection circuit widely exists in the input and output ports of CMOS digital circuits,and fast rising time electromagnetic pulse(FREMP)coupled into the device not only interacts with the CMOS circuit,but also acts on the protection circuit.This paper establishes a model of on-chip CMOS electrostatic discharge protection circuit and selects square pulse as the FREMP signals.Based on multiple physical parameter models,it depicts the distribution of the lattice temperature,current density,and electric field intensity inside the device.At the same time,this paper explores the changes of the internal devices in the circuit under the injection of fast rising time electromagnetic pulse and describes the relationship between the damage amplitude threshold and the pulse width.The results show that the ESD protection circuit has potential damage risk,and the injection of FREMP leads to irreversible heat loss inside the circuit.In addition,pulse signals with different attributes will change the damage threshold of the circuit.These results provide an important reference for further evaluation of the influence of electromagnetic environment on the chip,which is helpful to carry out the reliability enhancement research of ESD protection circuit.

Performance of Lateral 4H-SiC Photoconductive Semiconductor Switches by Extrinsic Backside Trigger

Photoconductive semiconductor switch(PCSS)can be applied in pulsed high power systems and microwave techniques.However,reducing the damage and increasing the lifetime of silicon carbide(SiC)PCSS are still faced severe challenges.In this study,PCSSs with various structures were prepared on 4-inch diameter,500μm thick high-purity semi-insulating 4H-SiC substrates and their on-state resistance and damage mechanisms were investigated.It was found that the PCSS of an Au/TiW/Ni electrode system annealed at 950℃had a minimum on-state resistance of 6.0Ωat 1 kV bias voltage with a 532 nm and 170 mJ pulsed laser by backside illumination single trigger.The backside illumination single trigger could reduce on-state resistance and alleviate the damage of PCSS compared to the frontside trigger when the diameter of the laser spot was larger than the channel length of PCSS.For the 200 s trigger test by a 10 Hz laser,the black branch-like ablation on Au/TiW/Ni PCSS was mainly caused by thermal stress owing to hot carriers.Replacing metal Ni with boron gallium co-doped zinc oxide(BGZO)thin films annealed at 400℃,black branch-like ablation was alleviated while concentric arc damage was obvious at the anode.The major causes of concentric arc are both pulsed laser diffraction and thermal effect.

基于物联网技术的变电站避雷器仪表智能读数图像识别方法

在使用UNet架构计算变电站避雷器仪表指针的刻度范围位置时,易受轻量级自注意力参数变化影响,导致识别性能较差。因此,设计了基于物联网技术的变电站避雷器仪表智能读数图像识别方法。通过拉普拉斯卷积运算均值化处理避雷器仪表读数图像;进一步去噪后,通过无线通信技术将图像传输到云端,进行目标表盘定位识别校正;基于物联网技术和神经网络算法,实现避雷器仪表读数的智能分割识别。实验结果表明,设计方法的识别召回率、精确率、平均交并比、平均精度均值、F1值均较高,证明该方法的识别性能良好,可靠性高。

基于传感器阵列的SF_(6)仪表图像识别方法

SF_(6)仪表图像中存在多个亮暗区域、反光和阴影等问题,以单一传感器为基础的识别方法缺陷明显。为此,引入传感器阵列,提出SF_(6)仪表图像识别方法。将索尼的IMX219作为核心图像传感器,设计传感器阵列,全方位捕捉SF_(6)仪表图像信息,在TCP/IP协议下实时处理和传输传感器阵列采集的数据。通过特征向量和相似度参数对图像去噪与多尺度小波变换,得到不同尺度下的纹理特征。利用支持向量机(Support Vector Machine,SVM)实现对SF_(6)仪表图像信息的识别。测试结果表明,该设计图像识别方法不仅具有优越的去噪效果,对于具体示数的识别结果也有更低的误差。

基于激光雷达的大型吊车机械臂避障控制方法

常规的大型吊车机械臂避障控制方法,以广义直线距离控制为主,忽略了机械臂瞬时速度引起的抖振误差造成的空间感,以半周期轨迹生成器迭代,近似于全周期控制过程,影响吊车避障控制效果。设计了基于激光雷达的大型吊车机械臂避障控制方法。将吊车机械臂运行路径上的障碍物近似为包围球,避免单纯直线距离判断的弊端。基于激光雷达测算机械臂与障碍物包围球的距离,判定机械臂与障碍物之间的碰撞情况,构建机械臂避障控制模型,设计全周期机械臂轨迹生成器,控制机械臂在预设的轨迹上运行,优化大型吊车机械臂的避障轨迹控制。实验结果表明:应用该方法的避障控制,使机械臂关节的位置误差在9.2×10-7 rad内,角速度误差在6.2×10-7 rad/s内。

基于滤波因子修正和超声红外技术的架空输电线路绝缘子状态检测

架空输电线的绝缘子检测与识别会受到复杂环境干扰,导致绝缘子检测的难度增加,为此,提出一种架空输电线路绝缘子状态检测新方法。通过超声传感器获取架空输电线路振动信号,采用卡尔曼滤波算法引入滤波因子,对架空输电线路绝缘子状态信号滤波与修正;利用红外传感器的入射和反射原理计算其倾斜角度;压缩融合处理传感器采集到的信号,得到聚类的最佳质心,实现架空输电线路绝缘子状态检测。实验证明,所提方法检测的最大相对误差控制在4%以下,并且状态检测的能量效率在90%以上,可以为架空输电线路运维提供可靠数据依据。

一种带压力传感器的变电站接地线装设装置研制

针对变电站内装设接地线存在的问题,研制一种带压力传感器的变电站接地线装设装置。该装置的线夹装有直流电机和压力感应器,可以无线遥控线夹的握紧、松放和监测接地线夹的挂接状态。通过接地线装设装置的升降平台和操作台机械臂,利用激光雷达扫描信息识别导线位置及距离,根据无线网络摄像机画面局部调整接地线夹位置,将接地线夹准确可靠地挂接到导线上。通过接地线夹的性能测试和现场挂接测试验证了该装置在挂接可靠性、作业效率、安全性方面的优越性。

基于直方图的红外图像细节增强算法研究

红外热成像技术广泛应用于故障检测中,但由于红外探测器各单元响应的非均匀性,使得红外图像对比度低、细节和边缘模糊,不利于人工观测和机器识别,因此对红外图像细节增强算法的研究具有深刻的意义。分析了传统直方图增强算法中的缺陷,提出了一种抑制背景的局部直方图均衡算法,并使用遗传算法加快了阈值求取的速度。实验结果表明,该方法可以在抑制背景的同时增强红外图像的细节,同时速度较快,可用于实时红外图像的预处理。

配网带电远程智能检测系统的设计与实现

配网在电力系统中具有重要作用,通常通过带电检测对其运行情况进行监测,以便于日常维护。传统检测系统需要大量的布线,不仅实现过程复杂,而且存在一定的安全隐患,为此,设计并实现了一种配网带电远程智能检测系统。给出系统总体设计,选用具有良好一次电光效应特性的铌酸锂晶体设计了无源集成的光电电压传感单元以及使用该单元的非接触式过电压监测传感器,通过相位合成完成分相检测,实现准确判断、显示全带电或缺相带电状态。利用单片机自动实现电磁闭锁,采用点阵图形式的LCD对检测结果进行显示,通过89C51单片机内集成的串行端口实现远程通信,将配网供电状态反馈至上位机,完成配电网带电的远程检测。软件设计中,给出了系统软件开发平台,详细介绍了信号采集的源代码。实验结果表明,所设计系统检测结果的一致性较好,达到了较高的检测准确度。

XLPE电缆检测现场试验等效性研究概况

当前用于XLPE电缆检测现场试验方法主要包括直流电压法、超低频(0.1 Hz)电压法、阻尼振荡波电压法,对各种方法的特点进行了论述,并介绍了不同试验方法等效性研究的发展概况。最后,在上述研究方法的基础上,结合实际经验,提出后续研究的内容及方法。

基于振荡波检测系统的电力电缆局部放电波形研究

介绍了局部放电电流法检测局部放电的基本原理,给出了振荡波局部放电测试电路,对基于这一检测原理的振荡波局部放电测试系统检测的波形信号进行分析。研究表明振荡波检测系统检测的局部放电信号会受电缆传播特性的影响产生衰减,且检测的信号波形基本上呈现脉冲型和脉冲振荡衰减型两种形态。

基于卷积神经网络的开关柜局部放电监测

提出了一种通过人工智能和机器学习理论来实现配网设备运行状况监测的方法,并展示了一套基于卷积神经网络使用超声波和地电波数据的开关柜自动局部放电现象的监测系统。设计了具体的卷积神经网络模型,使其在经过离线训练之后,可以对开关柜实际运行时所产生的信号进行实时的分析与辨别,进而判断设备的运行状况。实验结果表明,在错误信号进行降噪处理的前提下,该系统依然可以准确地给出设备运行的确切状况,这充分证明了提出方法的有效性。

基于BP神经网络补偿卡尔曼滤波的UWB精定位算法

本文研究典型应用场景下电力现场作业的超宽带精确定位,提出一种基于BP神经网络补偿卡尔曼滤波的UWB精定位算法。首先在某段时间内利用定位系统测得全部采样时刻的初始观测解,得到初始观测解集;其次根据卡尔曼滤波器的状态方程,初始观测解集输入卡尔曼滤波器;最后用BP神经网络补偿卡尔曼滤波,在最小均方误差下求得定位系统的二维状态向量的估计值。通过仿真表明:该补偿算法在原卡尔曼滤波算法上提升了定位精度。

电网高压电缆外防护绝缘层局部放电识别研究

采用目前方法识别电缆绝缘层的局部放电事件时,无法准确定位局部放电源,导致对局部放电的定位精度不足。提出一种电网高压电缆外防护绝缘层局部放电识别方法。通过时窗能量比检测电网高压电缆外防护绝缘层中存在的局部放电事件,计算时变峰度变化率,以获取脉冲初至时刻,结合时间分析法完成局部放电源的定位;利用局部线性嵌入方法对局部放电信号进行降维处理,获得局部放电信号的特征,根据特征完成局部放电识别。实验结果表明,所提方法的定位精度高、识别准确率高、识别率高。

Electrochemical oxidation of rhodamine B by PbO_2/Sb-SnO_2/TiO_2 nanotube arrays electrode

A PbO2/Sb-SnO2/TiO2 nanotube array composite electrode was successfully synthesized and its electrochemical oxidation properties were investigated.Field-emission scanning electron microscopy(FE-SEM)and X-ray diffraction(XRD)results showed that the PbO2 coating was composed of anα-PbO2 inner layer and aβ-PbO2 outer layer.Accelerated life measurement indicated that the composite electrode had a lifetime of 815 h.Rhodamine B(RhB)was employed as a model pollutant to analyze the electrocatalytic activity of the electrode.The effects of initial RhB concentration,current density,initial pH,temperature,and chloride ion concentration on the electrochemical oxidation were investigated in detail.Inductively coupled plasma atomic emission spectroscopy(ICP-AES)results suggested that the concentration of leached Pb^2+in the electrolyte during the electrocatalytic oxidation process can be neglected.Finally,the degradation mechanism during the electrocatalytic oxidation process was proposed based on the results of solid-phase micro-extraction-gas chromatography-mass spectrometry(SPME-GC-MS).The high electrocatalytic performance of the composite electrode makes it a promising anode for the treatment of organic pollutants in aqueous solution.

A hybrid algorithm based on ILP and genetic algorithm for time-aware test case prioritization

To solve the problem of time-awarc test case prioritization,a hybrid algorithm composed of integer linear programming and the genetic algorithm(ILP-GA)is proposed.First,the test case suite which cm maximize the number of covered program entities a d satisfy time constraints is selected by integer linea progamming.Secondly,the individual is encoded according to the cover matrices of entities,and the coverage rate of program entities is used as the fitness function and the genetic algorithm is used to prioritize the selected test cases.Five typical open source projects are selected as benchmark programs.Branch and method are selected as program entities,and time constraint percentages a e 25%and 75%.The experimental results show that the ILP-GA convergence has faster speed and better stability than ILP-additional and IP-total in most cases,which contributes to the detection of software defects as early as possible and reduces the software testing costs.

基于多步相移和双平面的光轴坐标标定方法

针对传统标定方法过程复杂、测量精度不高的问题,在基于双平面相机模型标定的基础上结合多步相移法提出了一种新的摄像机光轴坐标标定的方法。该方法通过多步相移法计算出两个平行标定平面的相位分布,通过调整两个成像面相位差分布中心区域,根据主点处相位保持不变原理分别求出光轴的x,y方向坐标,采用电脑编程绘制光栅图案推送至液晶显示屏作为标定模板。实验结果表明,该方法相对于现有的标定方法操作更加灵活简便,标定成本低,有效降低了标定的复杂度,该方法所求得的光轴位置坐标在标定和三维测量时可达到较高的精度能满足测量的要求。

Multi-Omics and Its Clinical Application in Hepatocellular Carcinoma:Current Progress and Future Opportunities

Hepatocellular carcinoma(HCC)is the sixth most common malignancy and the fourth leading cause of cancer related death worldwide.China covers over half of cases,leading HCC to be a vital threaten to public health.Despite advances in diagnosis and treatments,high recurrence rate remains a major obstacle in HCC management.Multi-omics currently facilitates surveillance,precise diagnosis,and personalized treatment decision making in clinical setting.Non-invasive radiomics utilizes preoperative radiological imaging to reflect subtle pixel-level pattern changes that correlate to specific clinical outcomes.Radiomics has been widely used in histopathological diagnosis prediction,treatment response evaluation,and prognosis prediction.High-throughput sequencing and gene expression profiling enabled genomics and proteomics to identify distinct transcriptomic subclasses and recurrent genetic alterations in HCC,which would reveal the complex multistep process of the pathophysiology.The accumulation of big medical data and the development of artificial intelligence techniques are providing new insights for our better understanding of the mechanism of HCC via multi-omics,and show potential to convert surgical/intervention treatment into an antitumorigenic one,which would greatly advance precision medicine in HCC management.

电大开放教育小组合作学习之我见

小组合作学习于七十年代率先兴起于美国。小组合作学习不仅提高了学生学习的主动性和对学习的自我控制,提高了教学效率,也促进了学生间良好的人际合作关系,促进了学生心理品质发展和社会技能的进步。目前小组合作学习是一种全世界都提倡的学习方式之一,是远程开放教育人才培养模式改革的基本要求,是建立个别化自主学习模式的重要教学组织形式。小组学习的活动及其效果不仅直接影响教学质量,也在一定程度上关系到“开放教育试点”改革的成败。本文从电大开放教育小组合作学习的作用和现状出发,寻求搞好小组合作学习的有效方法。