γ-TiAl单晶纳米杆拉伸变形的分子动力学研究

室温(300 K)情况下,利用分子动力学方法对γ-TiAl单晶纳米杆的拉伸变形过程进行了模拟研究,得到了应力应变曲线,并对其变形机理进行了分析,结果表明,γ-TiAl单晶纳米杆在室温下的形变机制为1/2[-1-10]普通位错及孪生,且首先发生1/6[-1-12]的孪生形变,随后通过部分位错1/6[-2-1-1]和1/6[-1-21]的反应形成1/2[-1-10]普通位错.     

金纳米颗粒烧结的分子动力学模拟

采用分子动力学模拟方法研究了不同尺寸Au纳米颗粒在烧结过程中晶型转变及烧结颈长大机制.研究发现纳米颗粒的烧结颈生长主要分为两个阶段:初始烧结颈的快速形成阶段和烧结颈的稳定长大阶段.不同尺寸纳米颗粒烧结过程中烧结颈长大的主要机制不同:当颗粒尺寸为4 nm时,原子迁移主要受晶界(或位错)滑移、表面扩散和黏性流动控制;当尺寸在6nm左右时,原子迁移主要受晶界扩散、表面扩散和黏性流动控制;当颗粒尺寸为9 nm时,原子迁移主要受晶界扩散和表面扩散控制.烧结过程中Au颗粒的fcc结构会向无定形结构转变.此外,小尺寸的纳米颗粒在烧结过程中由于位错或晶界滑移、原子的黏性流动等因素会形成hcp结构.     

纳米TiO_2晶型转化机制探讨

根据统计物理学方法推导出锐钛矿型TiO_2向金红石型TiO_2转化率关系式为InX_A=-v_0texp(-2U_x/kT),其中X_A为TiO_2中锐钛矿型的含量,v_0和U_x分别锐钛矿型TiO_2原子的振动频率和势函数,t、k和T分别为煅烧时间、玻兹曼常数和煅烧温度.TiO_2为三原子分子,理论上v_0和U_x计算十分复杂,本文通过在不同温度及时间下煅烧氨水水解TiOSO_4产物的方式制备了锐钛矿型、混晶型及金红石型纳米TiO_2粉末,将XRD分析所测数据及相应温度、时间条件代入转化率关系式,拟合求得:v_0=5.3×10~(10)/s,U_x=2.71×10~(-12)J.实验所测_A-t及X_A-T曲线与计算拟合曲线吻合较好,说明用氨水水解TiOSO_4产物的方式制备的锐钛矿型纳米TiO_2向金红石型纳米TiO_2的转化为扩散型转变.     

纳米磨削单晶和多晶3J33的分子动力学仿真

采用Voronoi算法构造多晶体3J33模型,再采用分子动力学(molecular dynamics,MD)实现单晶和多晶3J33的纳米磨削仿真,利用嵌入式原子势能(embeded atomic momentum,EAM)和Morse势函数对工件内部以及工件和磨粒之间的原子作用力进行计算。研究了单晶和多晶在不稳定和稳定两个阶段下纳米磨削过程的特点,结果表明,多晶体由于晶界的存在会阻止磨屑像单晶体一样沿直线行进,并且晶界会保护内部晶粒使其不易变形。探究了磨削力和磨削温度随磨削参数的变化情况,结果表明,单晶的切向力和法向力都大于多晶,但是多晶的磨削力波动比单晶大,磨削温度也比单晶高。     

纳米单晶铜板单向拉伸/压缩的分子动力学模拟

采用分子动力学方法模拟纳米单晶铜板的拉伸／压缩变形过程,得到了纳米单晶铜板在单向拉伸／压缩状态下的应力应变关系曲线和垂直于拉伸／压缩方向的泊松比．结果表明,纳米单晶铜板在单向拉伸／压缩状态下的弹性极限应变分别约为0．08和-0．03。在此范围内应力应变关系基本上表现为线弹性;垂直于拉伸／压缩方向的两个泊松比取值于0．3～0．4之间,但是不同方向上的泊松比数值不同,表现出由尺寸效应引起的材料力学行为的各向异性．     

无机骨架和哌嗪客体构成的有机-无机杂化物的合成和结构研究

利用常温水溶液合成方法,采用过渡金属钴离子为桥连原子制得1种具有三维无机骨架结构的化合物(Hpip)2[{Co(H2O)4}4(H2W12O42)].10H2O(pip=piperazine).采用元素分析、红外光谱、热重分析和X射线单晶衍射技术对化合物进行了表征.晶体结构分析表明:[H2W12O42]10-为8齿配体,它的8个端氧原子与8个Co2+进行了配位,钴离子桥连2个[H2W12O42]10-阴离子,形成3D无机骨架;哌嗪分子和结晶水作为客体填充在孔道中,客体与骨架之间存在着大量的氢键.     

自组织纳米复合薄膜BiFeO3-CoFe2O4的微结构与相成分

采用先进电子显微术在原子尺度研究了(001)单晶SrTiO3衬底上生长的纳米复合薄膜0.65BiFeO3-0.35CoFe2O4的组织形态以及界面结构.BiFeO3 (BFO)和CoFe2O4(CFO)两相在外延生长过程中自发相分离,形成自组织的复合纳米结构.磁性尖晶石CFO呈方块状均匀分布于铁电钙钛矿BFO基体中,并沿[001]方向外延生长,形成垂直的柱状纳米结构.两相具有简单的立方-立方取向关系,即[001]BFO//[001]CFO和(100)BFo//(100)cFo,且界面为{110}晶面.薄膜表面起伏不平,形成CFO{111}小刻面而BFO则为平整的(001)表面.能谱分析结果表明各相成分均匀分布并无明显的元素互扩散发生.     

基于2-(1H-四唑-5-基)吡啶配体的双核铬配合物的合成,晶体结构与红外光谱分析

以金属盐Cr Cl3·6H2O与2-(1H-四唑-5-基)吡啶(tzp)配体通过H管溶剂扩散法合成了双核铬配合物[Cr2(Cl)2(tzp)4],并用X-射线衍射法测定了其单晶结构.X-射线单晶衍射表明,配合物中每个铬离子分别和四个tzp配体的四个氮原子,两个氯离子配位,形成畸变的八面体配位环境.另外对配体和配合物分别用红外光谱进行了表征.     

锆自辐射损伤的分子动力学模拟与缺陷判定研究

采用分子动力学方法,模拟了300 K温度时由能量10 keV到50 keV的初级反冲原子(primary knock-on atom, PKA)在密排六方(hexagonal close packed, HCP)结构锆晶体内自辐射造成的级联碰撞.采用离位原子判定法、自间隙原子(self-interstitial atom, SIA)判定法以及Wigner-Seitz(WS)原胞分割法等三种方法对级联碰撞过程中产生的点缺陷进行了判定.通过对比不同方法获得的点缺陷变化趋势、统计涨落、鲁棒性等特征,发现采用WS分割方法获得的点缺陷数更适合用于描述锆晶体中级联碰撞的辐射损伤.此外还研究了自间隙原子的基本扩散特征,结果发现其更倾向于一种二维(2D)扩散.     

单晶铜纳米压痕的取向效应和尺寸效应研究

采用离散位错动力学法(DDD)以及晶体塑性有限元法(CPFEM)对单晶(001)、(011)和(111)晶面进行纳米压痕模拟研究。分别分析了载荷-位移曲线、弹性模量、纳米硬度以及弹性回复率与晶粒取向和压入深度的关系。DDD和CPFEM的模拟结果均表明:压痕硬度均随压入深度的减小而增大,呈现明显的尺寸效应。不同的是DDD的模拟结果显示:不同压入晶面的硬度关系为(111)晶面(001)晶面(011)晶面,呈现明显的取向效应。而CPFEM的模拟结果显示:不同压入晶面的硬度大致相同。此外,DDD模拟相对于CPFEM模拟结果,得到3个压痕面的压痕响应差异较大。两种方法模拟结果的差异主要是因为模拟尺度的不同,DDD模拟的尺度较小,其硬度响应与位错结构紧密相关。而CPFEM相对唯象,其模拟的尺度较大,微结构敏感特性不明显。     

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。     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

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