位错引起晶体熔化的统计理论

建立三维晶体中缺陷引起晶体熔化的统计理论，讨论了三维品体中的缺陷—位错对的形成与长大过程，通过对无相互作用位错对“成核－长大”过程的统计计算，得到了理论相变温度Ｔｃ，文中还从理论上证明了此相变为一级相交，并得到了相交潜热的计算公式，最后还对理论预言进行了实验验证。     

一种计算高压下晶体熔点的方法

根据Lindemann定律和乘积(αBT)为常数的近似条件,提出了一种计算高压下晶体熔点的方法,并对LiF,NaCl和Al三种晶体在不同压强下的熔化温度进行了计算.结果表明,计算得到的熔化曲线与实验数据吻合较好.     

位错的统计力学以及位错引起晶体的熔化理论

在位错对详细讨论的基础上建立一个晶体熔化的理论模型。该理论预测一级相变并得出晶体熔化温度的上限。引起面心立方结构和体心立方结构熔化的位错类型是不同的,前者是偏位错引起,后者是全位错引起。计算出22种立方晶体的熔化温度接近实验得出的熔化温度。提出了偏位错熔化温度低,这应当是面心立方比体心立方熔化温度低的原因之一。     

薄膜材料刃位错的求解

以弹性力学的平面应力模型求解了材料的刃位错,论证了此解可描述薄膜材料的位错。与体相的位错结果比较表明,薄膜材料的位错具有较低的应力和较低的弹性能。将本文的结果应用于位错引起薄膜熔化理论,得到了薄膜的熔点低于体相的熔点。将薄膜中存在位错情况与材料表面情况进行类比,得出材料表面的熔点也将低于体相的熔点。     

分子动力学研究难熔金属(V、Nb和Ta)熔点

根据分析型嵌入原子模型(MAEAM)和分子动力学(MD)方法,在NPT系综条件下从原子尺度上研究难熔金属V、Nb、Ta的内能、结构、密度等物理量随温度变化,并根据各物理量随温度突变得出3种金属晶体熔点分别为(2 180±20) K、(2 820±20) K、(3 280±20) K,所得到的结果与已有实验值吻合.本文根据径向分布函数随温度变化,从微观方面探讨金属熔化过程及其引起它们熔化原因,为进一步研究金属在高温条件下特异性能打下了基础.     

固态相变材料的运动对熔化传热的影响

在熔化过程中,由于相变材料的固、液密度不同,引起未熔化的固态相变材料下沉或上浮.固态相变材料的运动对熔化传热过程有着重要影响.利用润滑近似理论,推导出了未熔化的相变材料的运动速度的计算式,分析了相变材料的运动对熔化传热的影响,并与自然对流对熔化传热的影响作了比较.     

固态相变材料的运动对熔化传热的影响

在熔化过程中,由于相变材料的固、液密度不同,引起未熔化的固态相变材料下沉或上浮．固态相变材料的运动对熔化传热过程有着重要影响．利用润滑近似理论,推导出了未熔化的相变材料的运动速度的计算式,分析了相变材料的运动对熔化传热的影响,并与自然对流对熔化传热的影响作了比较．     

小尺寸Au-Ag合金团簇负热容的模拟研究

利用分子动力学方法,研究了AuN-XAgX(N=144;X=0,24,48,72,96,120和144)纳米团簇熔化过程中的热力学性质.计算模型采用原子嵌入模型(EAM)和Johnson提出的贵金属原子间相互作用势函数.模拟结果表明:金银合金团簇在熔点附近具有负热容特性,负热容主要由相变前后团簇内部结构突变引起.     

熔融氯化钠晶体介电常数的模拟计算方法

由于分子模拟过程中存在周期性边界的影响,离子偶极矩定义模糊,导致传统的偶极矩涨落方法在计算熔融盐晶体或含有自由电荷体系的介电常数时存在一定阻碍。根据经典介电理论,通过电流关联函数计算熔融氯化钠(NaCl)晶体体系的介电常数,研究了不同温度下氯化钠的频率相关介电谱,并分析了晶体相变对介电特性的影响。结果表明：当NaCl为晶体状态时,介电谱显示出明显的共振吸收峰;在NaCl熔化以后,介电谱的共振吸收峰的带宽变宽,波形发生了明显变化。分别利用电流法和外加电场法计算了不同温度下NaCl的静态介电常数,结果显示：两种方法的计算结果的一致性良好,从而验证了本文方法的准确性;NaCl晶体在发生固液相变时,静态介电常数会在相变点发生跳变。     

(Fe Cr)_(83)B_(17)非晶合金结构及其晶化相变的研究

本文用DTA和X射线衍射技术,研究了(FeCr)_(83)B_(17)非晶合金晶化相变全过程。说明该非晶体系的晶化相变过程中,原子键力是晶化相变的驱动力。从“t-x”关系表明,在我们实验条件下(x=5％,15％,25％),高熔点的Cr含量(x)增大所引起晶化峰位向高温方向增大值具有良好的线性关系。实验指出,(Fe_(1-x)Cr_x)_(83)B_(17)非晶合金淬火态的结构单元是Fe_3B局域9原子多面体结构的原子团。     

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.     

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     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

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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