Initiation of tantalum oxide pores grown on tantalum by potentiodynamic anodic oxidation

The initiation and growth of porous oxide on Ta was investigated in mixed H₂SO₄/HF electrolytes. Under selected potentiodynamic anodic oxidation conditions the formation of nearly uniform porous Ta₂O₅ layer was observed. The porous Ta₂O₅ layers consist of self-organized pore arrays with single pore diameters ranging from 2 to 10 nm. The morphology and the thickness of the layer depend strongly on the applied potential, the scan rate and on HF presence. The composition of the porous oxide layer is Ta₂O₅.     

Dielectric relaxation and breakdown detection of doped tantalum oxide high-k thin films

While TaO/sub x/, HfO/sub x/, ZrO/sub x/, Hf-doped TaO/sub x/, and Zr-doped TaO/sub x/ thin films are promising high-k gate dielectric candidates, their intrinsic reliability has not yet been investigated. In this paper, the authors examine some fundamental reliability aspects of these high-k films through ramp voltage stress testing. By studying dielectric relaxation and analyzing the transient conductivity, the breakdown mode of the tested high-k film is identified; a sensitive method of breakdown detection in ramped voltage tests is proposed and investigated.     

在绝缘诊断试验技术的发展中了解水树机理

近来 ,有几种测量介电常数和介质损失的诊断方法已被发展为用来对水树枝劣化 XL PE电缆进行非破坏性试验。当所施加的试验电压超过一定值时 ,发现临界劣化不仅仅与介电性能成比例。本文采用一种力学模型来描述水树枝现象的这种非线性。绝缘中的水树枝被认为是由被微裂纹区隔离的一系列充水微孔构成 ,在相对较低的含水量和较低试验电压下 ,有的裂纹区即可能产生自愈合作用并且恢复绝缘状态。当试验电压上升时 ,Maxwell电机械应力将导致水分侵入裂纹区 ,并导致拉长的水滴间出现电接触。对电场和损耗的有限元法数值计算结果表明 ,这种影响将使导电通道端部的电场增强 ,同时导致含水树枝绝缘的介质损耗增加。     

Residual stress analysis of all perovskite oxide cantilevers

We have used a method to experimentally determine the curvature of thin film multilayers in all oxide cantilevers. This method is applicable for large deflections and enables the radius of curvature of the beam, at a certain distance from the anchor, to be determined accurately. The deflections of the suspended beams are measured at different distances from the anchor point using SEM images and the expression of the deflection curve is calculated for each cantilever. With this expression it is possible to calculate the value of the radius of curvature at the free end of the cantilever. Together with measured values for the Youngs Modulus, this enabled us to determine the residual stress in each cantilever. This analysis has been applied to SrRuO ₃/BaTiO ₃/SrRuO ₃, BaTiO ₃/MgO/SrTiO ₃ and BaTiO₃/SrTiO₃ piezoelectric cantilevers and the results compared to two models in which the stresses are determined by lattice parameter mismatch or differences in thermal expansion coefficient. Our analysis shows that the bending of the beams is mainly due the thermal stress generated during the cooling down stage subsequent to the film deposition.     

含非线性应力管的电缆终端的电-热场分析

基于变分原理推导了非线性的时域有限元电场计算方程和稳态热场有限元方程,并分别利用商用软件IntegratedEngineering Software和有温度分布解析解的轴对称电缆结构验证了编制程序的正确性。然后,利用该方法分析了含线性、非线性以及复合结构的应力管时的电缆终端电场和热场分布。分析结果表明,线性、非线性以及复合结构的应力管在均匀电缆终端的场强分布时,适当的选择其结构和材料的参数都能很好的均匀终端的场强分布,但含非线性应力管的电缆终端的损耗和温升远小于含线性以及复合结构应力管的电缆终端。这为冷缩式电缆终端设计提供了一个指导方向。     

故障机理深度关联的大型发电机保护新原理探讨

基于“碳达峰、碳中和”发展目标,新能源发电渗透率逐年提高,但其故障穿越能力差、不确定性强等问题愈发凸显。传统发电机组容量巨大,作为系统的主力支撑电源,其功率调节和安全支撑作用更为重要,增强其继电保护的性能和作用显得尤为紧迫。在配置和改进发电机保护原理时,应该与故障机理深度关联并提炼故障特征。对发电机零序横差保护不平衡电流的产生机理进行分析,得出零序横差不平衡电流与气隙电动势成正比的结论,并提出基于气隙电动势制动的零序横差保护判据,能够提高内部小匝差短路故障时保护的灵敏度。基于对定子单相接地故障风险的深度分析,利用接地故障电流反映故障风险,据此构建的定子接地保护方法能够通过发电机安全风险自适应选择出口方式。研究结果拟为基于故障机理的大型发电机组保护改进提供思路。     

Synthesis of homogeneous magnetic field in internal region of cylindrical solenoid

Contents The paper describes a method of synthesis of a magnetic field in the three-dimensional region lying inside a cylindrical solenoid. The application of the method is demonstrated by the example of a synthesis of a homogeneous field. A regularization method of ill-posed problems has been employed for the solution of the problem.

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Die Synthese eines homogenen Magnetfeldes im Inneren einer zylindrischen Spule

Übersicht Es wird eine Methode zur Synthese des Magnetfeldes im dreidimensionalen Bereich innerhalb einer zylindrischen Spule beschrieben. Die Anwendung der Methode wird am Beispiel der Synthese eines homogenen Feldes demonstriert. Zur Lösung des Problems wird eine Regularisations-Methode benützt.

     

内阻不平衡对铅酸蓄电池组温度场影响研究

针对阀控式铅酸蓄电池组因内阻不平衡出现温升的现象,搭建了三维蓄电池组仿真模型.分别研究了热老化和生产工艺问题所引起的内阻不平衡,仿真分析了对应情况的温度分布.建立了蓄电池放电试验平台,利用红外成像仪得到了实际温度分布,并与仿真结果进行了对比.研究结果表明电池内阻不平衡会导致其温度明显上升.其中,因热老化导致的内阻增大会...     

锂离子电池多点内短路及物理场变化

建立电-热耦合的内短路模型,分析单点或多点触发内短路后且发生热失控前,锂离子电池电流场及温度场的变化.两点内短路与单点内短路相比,单层内短路电池和多层内短路电池的最大局部电流分别下降到65％和56％左右,最高局部产热率分别下降到43％和30％左右.电池在发生热失控前,对于单层两点触发内短路工况,内短路点越靠近极耳,通过...     

内控机制在电网调度管理考核中的应用

根据国家电网调度中心提出的加强内控机制建设的工作要求,以信息技术为依托,以业务流程处理为基础,采用J2EE技术路线及面向服务体系结构(SOA),开发了内控机制管理平台,并应用于调度管理考核中.应用结果表明:内控机制的建设,实现了调度工作全面、全员、全过程、全方位的管理,为宁夏电力调度工作的考核提供了先进的技术平台.     

微管固体氧化物燃料电池的热应力分析

微管固体氧化物燃料电池(MT-SOFC)的寿命一直是制约其商业化进程的关键问题.希望利用多物理场耦合方式分析工作状态微管固体氧化物燃料电池在流体、热、力等作用下的应力分布,分析工作温度、温度梯度等因素对电池应力状态的影响.结果表明制造残余应力是电池失效的主要应力源,温度梯度造成这一残余应力进一步分化;工作温度升高有助于残余应力的降低,但电池的效率也会降低.该结果将为MT-SOFC寿命分析提供依据.     

内阻不一致对动力电池组温度场的影响

研究电池组的温度场对于电池系统设计和热管理设计具有十分重要的意义.实验研究了18650磷酸铁锂电池单体的基本性能,测量了不同温度和放电倍率下电池表面温升情况.根据实验结果及已有的生热模型和传热模型,利用Fluent仿真软件研究电池单体在不同温度和放电倍率下的温度场.构建了电池组热分析模型,模拟分析了电池组存在单体差异(...     

异步电机转子三维温度场及热应力场研究

针对异步电机转子温度场及热应力场难以测量,转子导条经常发生断裂故障等问题,以一台Y100L-2型电机为研究对象,采用有限元法建立电机转子三维导热模型.在理论分析的基础上,结合实验测量,对模型边界条件进行确定,并以此为基础对转子温度场和热应力场进行仿真研究.研究结果显示电机转子温升的高低直接影响热应力大小,温升越高,热应力越大;转子导条热应力的分布在各个方向上并不均匀;在负载电机转子温度较高时,不均匀的热应力将直接影响电机寿命,是转子导条断裂的主要原因之一;负载时,整个转子热应力最大值出现在导条与端环连接处,说明该处最容易发生断裂故障,这一结论也与电机实际情况相符;导条法线方向正热应力要大于剪切热应力,与国内外相关研究结果比较,仿真结果在分布规律上基本一致.     

含有非线性应力管的电缆终端电场的有限元分析

利用时域有限元方法分析了含不同应力控制管时的电缆终端电场分布。分析结果表明,采用由电容性和非线性电阻性材料复合绝缘结构的应力控制管时,电缆终端的电场分布最为均匀。进一步分析电缆终端中电容性和非线性电阻性材料知其分界面处含有气晾时的电场分布。     

Resistance variation in donor-doped PZT stacks with Cu inner electrodes under high field stress

Changes of the resistance of donor-doped lead zirconate titanate (PZT) under high voltages were investigated at temperatures from 350 to 500°C in different gas atmospheres. Measurements on individual ceramic layers (about 75 μm thickness) of PZT multilayer stacks with Cu inner electrodes allowed numerous experiments on nominally identical PZT material. Under high fields, the conductivity decreased significantly on time scales much longer than needed for capacitor charging. At 350°C, for example, decay times of several 1000 s were found. The time constant of this conductivity decay depends exponentially on temperature with activation energies of about 1.3 eV in air. After interrupting the field stress, thermally activated (ca. 1.1 eV) relaxation of the conductivity was found on an even longer time scale. The results are interpreted in terms of oxygen vacancy motion under high fields (stoichiometry polarization) and diffusive relaxation. The importance of oxygen migration despite donor doping is attributed to the high PbO volatility of PZT which readily leads to significant oxygen deficiency. Oxygen diffusion coefficients are estimated.     

铟对铅在硫酸溶液中生长的阳极Pb(Ⅱ)氧化物膜的影响

采用电化学阻抗频谱法和线性电位扫描法研究了铟对铅在 0 9V (vs.Hg/Hg2 SO4 )电位下 ,4 5mol·dm- 3H2 SO4 溶液中生长的阳极Pb (Ⅱ )氧化物膜的影响。结果表明 :铟的添加可有效地抑制阳极Pb (Ⅱ )膜的生长并显著降低Pb (Ⅱ )膜的阻抗     

Time evolution of current through insulating paper under DC voltage stress

The use of paper in electrical insulation, especially in power transformers, remains a topical subject. The interest for the insulating paper, despite the emergence of many synthetic materials is ascribed to its low cost price and its ability to an oil impregnation. However its strong hydrophilic character remains the main difficulty for its implementation in electrical insulation. This affinity to water absorption and/or adsorption shows that a good understanding of the moisture effect becomes imperative. Several studies were carried out on the subject but a systematic study of the moisture effect on overall behavior of paper has not been achieved. This work is meant to be a contribution for this systematic investigation. The first step of this study, which is the object of the present article, concerns an examination of time variation of the electrical currents, under DC stress, for different moisture levels. A particular attention is given to the polarization and depolarization currents. These currents are examined during alternate charges and discharges sequences. An increase of the current, during the application of continuous voltage was noticed. This unexpected phenomenon would be related to an electro-dissociation and/or polarization processes.     

大口径球阀内部流场的数值模拟与研究

在FLUENT环境下完成了大口径球阀内部流场的三维可视化数值模拟与研究,通过变工况获取相关计算结果,对大口径球阀两种典型形式（即全舱口球阀和特性化球阀）内部流场的涡流和压力分布情况、阀门前后压力降、阀门压头损失系数、阀门流量系数、阀门气穴指数等几个较为重要的阀门特性参数进行了比较与分析。最终以图表的形式对这些参数与阀门开度以及与雷诺数之间的变化规律做了说明并给出了相关结论,供工程实际应用作参考。     

蓄电池塑料槽内应力分析及工艺控制

分析、探讨了塑料槽内应力的形成机理及消除应力的方法。