正电子检测直拉硅的中子辐照缺陷

在90～300K温区范围内测试了中子辐照直拉硅单晶的正电子寿命谱及红外光谱,发现直拉硅单晶的中子辐照缺陷主要是双空位和氧-空位复合体.此外,还分析了这些缺陷的一些基本性质.     

W-K合金中空位型缺陷的浓度和尺寸研究

W-K合金具有熔点高,抗热冲击性能强,抗氢氦等离子辐照能力强等众多优点,特别是钾泡的形成能稳定晶界、充当钉扎点和细化晶粒的作用,从而改善了W-K合金材料的性能.由于正电子寿命谱分析技术对纳米尺度的空位型缺陷极为敏感,因此本文采用该方法测量了正电子在不同钾含量下W-K合金的寿命值大小和相应的强度,并依据正电子湮没的两态捕获模型,对拟合的正电子寿命成分进行数据处理,同时对钾泡浓度和尺寸的变化情况进行了分析和讨论.     

6H-SiC γ辐照的正电子研究

用正电子湮没寿命谱(PALS)方法对经过不同剂量γ辐照的n型6H-SiC内的缺陷进行研究.实验表明,辐照可以使样品内部产生单空位缺陷Vc.对实验中得到的寿命谱的变化进行分析发现,低剂量的γ辐照对n型6H-SiC有类似退火效应的作用.这些研究结果可以为n型6H-SiC的生产及其可能的应用提供有效的参考价值.     

未掺杂SI—InP中缺陷的正电子寿命研究

在１０－３００Ｋ的温度范围内,测量了用液封直拉法（ＬＥＣ）生长的ｎ－ＩｎＰ经高温退火后形成的未掺杂ＳＩ－ＩｎＰ晶体的正电子寿命谱,用ＰＡＴＦＩＴ和ＭＥＬＴ两种技术分析了正电子寿命谱。常温下的结果表明,ＳＩ－ＩｎＰ中存在甸空位ＶＩｎ或与杂质的复合体缺陷。观察到在１０－２２０Ｋ之间正电子的平均寿命τｍ随温度的升高而减小,表明上述缺陷是带负电荷的铟空位ＶＩｎ的氢复合体;但是在低温下还存在正电子浅捕获态。     

金属中电子结构的密度泛函方法与正电子湮没技术

以密度泛函理论为基础,利用简化的胶体模型,在局域密度近似下研究金属中的空位型缺陷的电子结构和以正电子寿命为表征的缺陷谱.结果表明,随着空位尺度的增加,正电子寿命亦增加并直到饱和值.     

用正电子研究Ⅲ—Ⅴ族化合物半导体的缺陷谱

简要介绍了本科研组近年来用正电子湮没谱学研究Ⅲ－Ⅴ族化合物半导体缺陷的最新进展,包括原生样品中缺陷的种类、大小、电荷态、负离子缺陷、缺陷与杂质的相互作用、辐照以及形变引入的缺陷等,研究表明,在原生半导体材料中存在各种缺陷,经过辐照和璩 变化有单空位、双空位及孔洞形成;在重掺杂材料中,空位还补偿载流子,使载流子发生饱和。     

塑性形变p型GaAs中的缺陷特性研究

用正电子湮没命谱研究了塑性变形ｐ型砷化镓中的缺陷性质,样品原始载流子浓度为２．６３×１０＾１８ｃｍ＾－３,形变量分别为２．５％,５％,７．５％,１０％和１５％,室温正电子寿命测量结构显示,形变样品中有新的空间型缺陷产生,鉴定为空位团,根据塑性多变样品中空位团的正电捕获率的大小和寿命谱温度关系初步判断,在ｐ型ＧａＡｓ中,塑性形变产生的空位团的荷电性为正,正电子寿命温度实验显示,在低温下形变样品中还存     

不同煅烧条件下合成β-C_2S的正电子湮没和水化研究

采用正电子湮没技术研究了不同煅烧条件下合成的β-C_S正电子寿命谱,按照正电子捕获理论,对实验所得寿命谱参数与β-C_S微观结构缺陷的关系进行了分析和讨论。此外,还就β-C_S的烧成条件、缺陷浓度和水化活性的关系进行了研究和讨论。     

6H-SiC表面热氧化SiO2的正电子谱研究

本文将慢正电子湮灭多普勒展宽谱技术,应用于对SiC表面热氧化生长的SiO2特性的研究。S参数和W参数在退火前后的变化,直观的反映出SiO2/SiC表面氧化层中空位型缺陷浓度的改变。通过与SiO2/Si样品的对比,证实C元素及其诱生空位型缺陷的存在,很可能是影响SiO2/SiC氧化层质量和SiC MOS击穿特性的重要因素,后退火工艺可以提高SiO2/SiC中氧化层的致密性。实验表明,慢正电子湮灭多普勒展宽谱是研究热氧化SiO2特性的有效手段。     

6H-SiC表面热氧化SiO2的正电子谱研究

本文将慢正电子湮灭多普勒展宽谱技术,应用于对SiC表面热氧化生长的SiO2特性的研究．S参数和W参数在退火前后的变化,直观的反映出SiO2/SiC表面氧化层中空位型缺陷浓度的改变．通过与SiO2/Si样品的对比,证实C元素及其诱生空位型缺陷的存在,很可能是影响SiO2/SiC氧化层质量和SiC MOS击穿特性的重要因素,后退火工艺可以提高SiO2/SiC中氧化层的致密性．实验表明,慢正电子湮灭多普勒展宽谱是研究热氧化SiO2特性的有效手段     

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     

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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Brief Introduction to “Journal of Jilin University( Science Edition) ”

<正>"Journal of Jilin University(Science Edition)"is a comprehensive academic journal in the fields of science sponsored by Jilin University and administrated by the Ministry of Education of the Peoples Republic of China.The journal started publication in 1955.The original name at starting publication was"Journal of Natural Science of Northeast People University",which was changed into"Acta Scientiarum Naturalium Universitatis Jilinensis"in 1958 owing to the name change of the university.The present journal name has