聚合物的空间电荷效应与电击穿机理

本文采用电声脉冲法,实测了聚乙烯试样中空间电荷分布,在特制的试样上,显示了均匀电场中空间电荷在直流击穿和短路击穿中的极性效应.空间电荷效应、交直流叠加和升压速度的实验结果表明,均匀电场中聚乙烯的击穿规律与极不均匀电场中树枝化的特性是一致的,进一步证明了 Budenstein 的实验发现,即均匀电场中聚合物的击穿起始于界面的树枝化.最后,作者用高氏树枝化新理论,对击穿现象作出了满意的解释.     

极性反转时间对聚乙烯中空间电荷及瞬态电场的影响

基于电声脉冲空间电荷测量方法,测量了聚乙烯片状试样在常温(ΔT=0℃)及温度梯度(ΔT=40℃)下、-50kV/mm场强直流预压2h后,分别以不同反转时间(20s,30s,60s)反转到50kV/mm场强,再加压2h过程中的空间电荷变化,以及极性反转过程中最大瞬态电场的变化.结果表明:常温下电压极性反转越快,最大瞬态电场越大;温度梯度下,电压极性反转越快,最大瞬态电场越小;达到最大瞬态电场的时间均随着极性反转时间的增加而逐渐减少.     

臭氧发生器用（Sr,Ca）TiO3陶瓷电极材料的研制

研究了掺杂成分ＢａＴｉＯ３,ＣａＳｉＴｉＯ５,ＴｉＯ２,ＺｎＯ,Ｂｉ２Ｏ３对臭氧发生器用（Ｓｒ,Ｃａ）ＴｉＯ３陶瓷电极材料的介电常数、正切损耗、击穿电压、电阻率等电性能的影响．结果表明,Ｂｉ２Ｏ３的影响最大．最适合的掺杂配方是：Ｂｉ２Ｏ３１．４０％,ＴｉＯ２０．３０％,ＣａＳｉＴｉＯ５０．３１％,ＢａＴｉＯ３０．５０％和ＺｎＯ０．５２％．     

电压反转极性对温度梯度场下聚乙烯内空间电荷的影响

基于电声脉冲空间电荷测量方法,测量了聚乙烯片状试样在常温(△T=0℃)及温度梯度(△T=40℃)下、不同电压极性(±50 MV/m)作用2h过程中聚乙烯内的电荷积聚和场强分布特性,同时测量了加压2h后不同反转极性对温度梯度场下聚乙烯内电荷积聚和瞬态电场的影响.结果表明:无论反转极性如何,最大瞬态电场畸变率近似相同;电压...     

高氏聚合物击穿理论的验证及其在电缆上的应用

高氏聚合物击穿理论虽已发表4年,但是,它的核心部份——电子非辐射能量的转移,尚未被实验验征.本文以一种聚合物作为添加剂,掺杂到聚乙烯中,降低了聚乙烯的深陷阱浓度,增加了浅陷阱浓度。试验结果表明,这种掺杂能明显提高聚乙烯的树枝起始电压和击穿电压,从而间接证明了这种能量转移的存在.与传统的消除静电方法不同,以一种聚合物掺杂到聚乙烯中,几乎不影响聚乙烯作为优良的电介质,但能降低或消除注入的空间电荷效应,因而为今后研制超高压直流塑料电缆的绝缘开辟了新的方向;也为我国目前辐射交联聚乙烯电缆在生产过程中的带电问题找到了解决的办法.     

聚乙烯绝缘中空间电荷的抑制方法及原理

随着我国经济的高速发展,研制高压直流XLPE电力电缆已提到日程,目前迫切的任务是研发直流XLPE电缆料,研发的关键在于消除或抑制XLPE中的空间电荷。本文在介绍国内外抑制聚乙烯绝缘中空间电荷方法的基础上,讨论抑制空间电荷的原理。     

以BaTiO3作为填料改善聚乙烯的空间电荷效应

针对高压、超高压直流塑料电力电缆中存在的空间电荷效应,以强极性材料BaTiO     

场控变阻材料在高压陶瓷电容器边缘电场改善中的应用

利用场控变阻材料电阻率随电场变化的特点，改善留边型平板高压陶瓷电容器电极边缘的电场，可以大幅度提高陶瓷电容器的性能，探讨了ＰｂＯ－Ｂ２Ｏ３－ＳｉＯ２系玻璃加入掺杂ＺｎＯ制成的半导体玻璃釉对陶瓷电容器电击穿强度，充放电寿命的影响，通过配方，工艺、电极结构的优化可以使留边型高压陶瓷电容器的击穿强度提高８０％以上，充放电寿命提高了１０倍以上，并与具有类似场控变阻性能的半导体漆作了对比。     

原子吸收法连续测定氧化铝中微量钾与钙

以Ｈ３ＢＯ３－Ｎａ２ＣＯ３为熔剂，在铂坩锅中于１０００℃高温炉中熔融氧化铝试样，用ＨＣｌ浸取，加入ＳｒＣｌ２为释放剂，用空气－乙炔火焰原子吸收法连续测定Ａｌ２Ｏ３中Ｋ２Ｏ和ＣａＯ的含量。该法分析标样符合允差要求，与标准方法测定样品数据相吻合。Ｋ２Ｏ和ＣａＯ测定的相对标准偏差分别为２．８％和１．６％，回收率分别为１０６％和９５％。     

碱卤晶体在直流及交变电压下电击穿场强与温度关系的试验研究

本文介绍了碱卤晶体电击穿场强与温度关系的研究。提及弗列里赫低温及高温晶体电击穿理论的概念。对许多国外作者的试验结果进行了综述。本文对NaCl及KBr晶体的电击穿场强与温度关系进行了试验研究,采用一面有球穴的试样,试样两面均以真空喷镀铝金属膜作电极,然后放入充有约30大气压氮气的金属压力罐中,进行击穿试验。直流下Nacl约在50℃时出现最大击穿场强,其数值约1.5×10~6 伏/厘米,而KBr则在120℃左右出现最大值,其数值约0.95×10~6伏/厘米。实验结果应用弗列里赫低温及高温晶体电击穿理论来解释。而对实验中晶体电强度在直流及交变电压下出现不一致的现象,则提出了晶体中存在两种空间电荷影响击穿的看法。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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