真空开关电弧图像面积变化研究

真空电弧在燃烧过程中的形态变化对真空开关的开断性能有着重要的影响。为了实现对真空开关电弧形态燃烧过程的定量分析,提出了真空开关电弧图像面积概念,并对影响电弧面积变化的真空间隙、电压、磁场三因素进行了实验研究分析。结果表明:①真空间隙越大,电弧面积分布区域越广,减轻了电弧对触头表面的烧蚀;②开断容量越大,电弧的面积分布区域越大,同时对电弧表面的烧蚀越严重;③纵磁场的存在使电弧在真空间隙中分布更加均匀,有利于提高真空开关的开断能力。     

基于图像序列短间隙真空开关电弧形态研究

研究短间隙真空开关电弧扩散运动特性对促进真空开关向高电压等级、大容量及智能化发展具有重要的意义。本文利用高速摄像机CMOS对真空开关电弧图像进行了采集并获得了序列电弧图像;分析了真空电弧燃烧过程扩散运动的机理及特征。综合数字图像处理技术,提出了基于二值背景差分法电弧图像燃烧扩散运动识别算法。实验结果表明:运用图像系列背景差分法可实现对真空开关电弧图像面积扩散区域进行检测,且通过计算可得到真空开关电弧在燃烧过程中不同时刻的扩散速度。     

基于PIV技术真空开关电弧流场实验研究

为了对真空开关电弧燃烧过程及热形态变化规律研究,本文采用粒子成像测速(PIV)技术对短间隙真空开关电弧进行了实验研究,观察分析了电弧流场的信息,有明显的漩涡区。实验结果表明,运用PIV技术能较好地获取真空开关电弧燃烧二维速度场分布;随着电弧电流不断增大,真空间隙中金属蒸气压力不断增大,电弧加速向四周扩散运动,当电弧电流增大到一定值时,在电弧四周产生明显的涡流区域;电弧电流峰值过后,涡流区域不断减小,当电弧电流减小到一定值时,电弧不再向外扩散,而是向弧柱中心做集聚运动。     

真空开关电弧形态的实验研究

真空电弧形态的研究对真空开关能否有效控制和保护电路有着重要的影响.本文设计了真空开关电弧实验系统,建立了基于高速摄像设备CMOS的真空开关电弧采集系统.通过该采集系统可以每秒200,000帧采集速度得到了真空开关电弧图像.实验结果表明,真空开关电弧起始处于扩散形态,随着电流的增大,电弧月逐渐集聚,并产生阳极斑点,峰值电流过后再次转变成扩散形态,最终在阴极表面形成很多阴极斑点,做高速运动并数量不断减少至电弧完全熄灭.     

短间隙真空开关电弧图像边缘提取研究

为了研究短间隙真空开关电弧燃烧及其热形态变化过程,通过图像视觉系统对电弧起弧、燃烧及熄灭过程中的电弧图像进行采集,阐述了该实验系统的组成,利用图像处理技术对电弧图像进行了预处理,并通过Prewitt、LOG和Canny五种微分算子的边缘提取和结果对比。结果表明:比较3种微分算子对电弧图像边缘提取的结果,Canny算子可得到连续性、完整性和准确性均符合控制要求的电弧边缘结果,为实现真空电弧的调控提供了技术基础。     

真空开关电弧电子温度诊断的实验研究

金属蒸气等离子体是真空开关电弧的基本状态,为了实现对其等离子体电子温度诊断,提高真空开关的工作性能,本文提出了基于光学方法真空开关电弧电子温度诊断技术,阐述了二比色测温的基本原理,建立了真空开关电弧实验装置及相应的CCD光学图像采集系统。利用该实验系统得到了不同波长下的电弧图像,运用MATLAB经过图像处理得到真空电弧的灰度等值曲线,形象地表达了温度场的分布;通过计算得到了电子温度在不同电流下沿着径向的分布。试验结果表明:(1)在电弧电流为8.91kA时,电子温度最高可达3.42eV;(2)电子温度沿着径向不断的降低。     

基于MHD的小间隙真空电弧仿真研究

真空开关电弧电流过零前的电弧等离子体状态对真空开关能否顺利开断具有十分重要的影响。本文在建立小间隙真空电弧磁流体动力学(MHD)模型的基础上,采用通用计算流体力学仿真软件对电弧电流过零前0.5 ms时的电弧等离子体的特性进行数值仿真研究。计算得到了真空电弧等离子体压力、等离子体密度、离子纵向速度、阳极表面纵向电流密度和电弧电压等的空间分布。仿真结果表明:从阴极到阳极,真空电弧等离子体压力和密度逐渐增大,而等离子体速度逐渐减小;阳极表面电流密度存在较大径向梯度,最大值低于形成阳极斑点的极限收缩电流,阳极仍不活跃。仿真得到的等离子体密度分布与高速摄像机拍摄得到的CMOS图像光强基本吻合,计算得到的电弧电压与测得的电弧电压是一致的,从而验证了本模型的可行性。     

基于Zernike矩的真空开关分闸速度检测

真空开关分闸速度对真空电弧形态和弧后介质强度的恢复速度有重要影响,实现其分闸速度高精度检测并研究分闸速度对电弧特性影响是真空开关领域重要课题之一。为实现触头分闸速度高精度检测,本文提出用Zernike矩算法从真空开关分闸序列图像中精确跟踪动触头位置,进而计算出触头分闸速度的检测方法。首先利用Canny算子对所有可能的电弧边缘进行像素级定位,缩小精确定位的检测范围,然后用Zernike矩算子对所有可能的电弧边缘重新检测,最后实现触头分闸速度的亚像素级精确测量。实验结果表明:本算法能够高效的实现真空开关分闸速度的高精度检测,动触头边缘定位能精确到小数点后两位,算法运行速度较像素级精度提高了35%。     

真空开关电弧的产生及其触发电路的设计

本文对真空开关电弧的产生过程、实验室产生电弧方法及影响真空电弧触发因素进行了简要分析，在此基础上对真空电弧的触发电路进行了设计。通过实验表明，该触发电路能够成功可靠的起弧。     

真空开关电弧等离子体几何形态研究

真空断路器逐渐向高压等级发展,工作时电弧等离子体几何形态直接影响其开断能力。本文利用高速摄像机对电弧几何形态进行数字采集,运用图像去噪声、选取合适阈值方法,对采集数据进行形态学操作,得到内部高能等离子体及电弧外部轮廓的时间-面积变化曲线。从引弧、稳定燃弧、熄弧及弧后介质恢复四个角度,对不同阶段的电弧面积变化做出定量分析,并探究电弧熄弧阶段电弧内外面积差变化。实验表明,通过分析不同阶段的等离子体形态变化,能够找到电弧平稳燃弧及弧后介质恢复的关键点,为高压等级真空断路器研发设计及后期电弧形态诊断提供进一步参考。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...