有机蒸气-空气扩散系数的分子动力学模拟

气体扩散系数是一个重要的传质基础数据,基于分子模拟理论,利用分子模拟软件Materials Studio 7.0对部分有机蒸气-空气扩散系数,包括正戊烷、正己烷、正庚烷、正辛烷,进行分子动力学模拟,建立气体分子结构模型,构建晶胞,经弛豫、分子动力学运行后,对平衡体系进行分子动力学运行和分析,得到气体分子的均方位移曲线。输出相关数据并计算扩散系数,然后分析分子量及体系温度对模拟结果的影响情况,同时将扩散系数模拟值与实测值进行对比分析,从而验证了该方法的可行性。     

Sn-Cu钎料液态结构与黏度分子动力学研究

应用基于MEAM势的分子动力学模拟,研究了Sn-0.7%Cu和Sn-1.8%Cu两种钎料在503~773K液态结构和黏度的变化规律.首先,通过模拟数据分别计算得出不同温度下两种钎料熔体的双体分布函数g(r)以及Cu元素和Sn元素在两种钎料合金中的均方位移,由均方位移得出自扩散系数,然后依据Stokes-Einstein方程计算出两种钎料的液态黏度,模拟计算液态黏度结果与实验数据基本一致.随着温度降低,黏度呈上升趋势,并且在黏度曲线上均出现跳跃点,以跳跃点为分界点,黏度曲线可以明显分为低温区和高温区.模拟得到的双体分布函数曲线符合热力学普遍规律,随着温度降低,第一峰和第二峰都变得更尖锐一些.     

基于介观分析的HT-PEM燃料电池阴极扩散层传质研究

目的研究高温质子交换膜燃料电池阴极扩散层中传质过程,解决扩散环境因素降低传质扩散效率的问题.方法基于Martini力场原理建立介观力学数学模型,采用Materals Studio软件中Mesocite模块构建气体与扩散层的粗粒化几何模型,通过介观动力学方法分析温度、扩散层孔隙曲折度、孔隙率和气体组分等因素对阴极扩散层中传质过程的影响,并根据均方位移研究不同因素对扩散系数的影响.结果随着温度升高,气体各组分在扩散层中的扩散系数增大;碳纳米管长度变大,氧气分子扩散系数下降,而水分子扩散系数上升;水分子质量分数增大,氧气分子的扩散系数下降,而水分子的扩散系数上升.结论在一定范围内增大扩散层的孔隙率以及降低反应时水分子的质量浓度会有利于反应气体的扩散,提高反应效率.     

载铜活性炭络合吸附乙烯的研究

通过分子轨道计算对CuCl2络合吸附C2H4的行为进行了分子模拟研究,并在计算过程中考虑了载体活性炭的影响因素,确定了活性炭上CuCl2与C2H4作用的微观吸附结构,一个CuCl2分子至多只能吸附一个C2H4分子。     

线形四原子分子C2H2的高温光谱研究

在直接计算分子配分函数的基础上，将无转动跃迁偶极矩平方近似为一常数，计算了线形四原子分子C2H2 010011 u-000101 g跃迁在常温、中等温度和高温下的线强度.计算结果在300 K及中等温度500和800 K时与HITRAN数据库的结果吻合相当好.在温度高达3000 K时与HITRAN数据库的结果仍符合较好，表明分子配分函数和线强度的高温计算是可靠的.在此基础上，进一步计算了线形四原子分子C2H2 010011 u-000101 g跃迁带在极端高温4000和5000 K的线强度并报道其模拟光谱.     

柴油机冷启动HC在LTA沸石中吸附的分子模拟

为了对柴油机冷启动过程产生的碳氢化合物(HC)进行吸附处理,需要对冷启动过程中的HC吸附过程进行研究.以乙烯(C2H4)和丙烯(C3H6)为探针分子,利用巨正则蒙特卡罗法(GCMC)对LTA型分子筛的HC吸附性能进行分子模拟研究,获得特定温度下的纯组分和混合组分吸附等温线以及吸附粒子云分布.研究结果表明:在柴油机冷启动条件下,C3H6和C2H4在LTA型分子筛上的吸附量显示出类似的趋势,均随着压力的升高而增加,随着温度的升高而减少；当二者同时存在时会发生了竞争行为,C2H4受到的影响比C3H6要大,LTA型分子筛对C3H6的吸附效果要好于对C2H4的吸附效果；C3H6在LTA型分子筛的α笼和β笼中均有分布,而C2H4在LTA型分子筛中的分布主要集中在分子筛的α笼中,只有少量分布在分子筛的β笼中.     

金红石型TiO2结构随温度变化的分子动力学模拟

常压下,采用经典离子晶体相互作用势模型,并进行量子化修正,对金红石型TiO2结构随温度变化进行分子动力学模拟,计算了键长、键角、均方位移、特征(110)面分布函数及TiO6八面体结构随温度变化特性.模拟结果表明,当温度由300 K升至1 800 K时,TiO2中阴、阳离子振动偏离原来的平衡位置,均方位移逐渐增加,形成晶体的热膨胀;尤其在温度高于1 000 K时,TiO2体系中Ti-O键、键角、均方位移等特征参数出现较明显的变化,特征晶面(110)及八面体构型出现扭曲,精细结构在一定程度上受到破坏,晶体的无序度逐渐增大,呈现出短程有序、长程无序的高温非晶结构特征,这些模拟结果与相关实验结果基本一致.     

气体分子扩散的蒙特卡罗模拟

使用蒙特卡罗方法,对气体分子在背景气体中扩散的过程进行了计算机模拟,背景气体均匀分布于三维无界空间中。模拟结果显示,气体分子的扩散是各向同性的,扩散经历的时间越长,分子分布的范围越大,分子扩散的方均位移与时间成正比关系。使用本文的模拟方法还可估算气体扩散系数的数量级,对1标准大气压下、15°C时氧气的自扩散系数,以及氧气在氮气中的互扩散系数进行了估算,得到的扩散系数数量级与实验测量结果符合得很好。     

木质素磺酸钠在水溶液中的分子构型拟合

通过过滤及凝胶渗透色谱分离提纯木质素磺酸钠(NaLS);利用静态光散射测定其绝对分子质量,并通过加盐的方法消除慢运动峰对测量的影响;采用动态光散射测定不同温度下NaLS分子的扩散系数.根据测定的扩散系数及绝对分子质量,使用Perrin公式拟合计算不同温度下NaLS分子的椭球结构.结果表明:光散射法测得的NaLS分子的绝对分子质量大于凝胶渗透色谱(GPC)测定的相对分子质量,更接近于真实分子质量;温度升高,NaLS分子扩散系数增大,布朗运动加快;Pellin公式拟合显示不同温度下NaLS分子均为长短轴比7.5以上的接近碟状的扁平椭球结构,该结构随着温度升高变扁.此外,结合已有木质素磺酸盐的结构研究结果,建立了不同温度下NaLS分子的椭球模型.     

分子动力学模拟烷烃链条数对其在氧修饰石墨烯纳米孔中迁移的影响

为了分析高分子在纳米孔中迁移问题,更好地为纳米器件的设计提供理论支持,采用分子动力学方法模拟了一系列链条数不同的烷烃分子在氧修饰石墨烯纳米孔中的钻孔,研究了链条数N对钻孔条数的影响,给出了均方位移MSD和扩散系数D随N变化的规律.研究结果表明:穿孔条数随着链条数的增加上升明显,但当链条数多到一定程度后,穿孔烷烃数较为缓慢地下降.     

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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