分子结构振动固有频率与链烷烃热力学性质的定量关系

用分子结构固有频率和分子中的甲基数作为分子结构信息指数,建立链烷烃分子结构与热力学性质的双参数QSPR模型.该模型用于18种链烷烃分子的标准生成焓、标准熵和标准生成自由能实验值的回归分析,得到相关程度大于0.999的标准生成焓、标准熵回归方程和相关程度大于0.99的标准生成自由能回归方程.所得方程用于67种链烷烃的标准生成焓、标准熵和标准生成自由能预测,结果与实验值的相关程度均大于0.9950.     

直链烷烃结构型和凝聚型性质的递变规律研究

用图示法和非线性规划的方法对直链烷烃同系物最高成键分子轨道能级、最低成键分子轨道能级,电离电位,氧化半波电位,正常沸点,正常熔点、临界压力、临界温度、密度、折光率、表面张力和粘度和１２种结构型性质和凝聚型性质的变化规律进行研究,结果发现,直链烷烃结构型性质和凝聚型性质一般能遵守同系对数递变规律,各种结构型性能和凝聚型性能均与对数递变函数呈优良的相关性,相关系数均大于０．９９,用同系对数递变规律对直     

用相互作用势指数估算单取代烷烃生成焓

基于直链烷烃生成焓的实验值提出16种取代基X(OH、SH、NH₂、Br、Cl、I、NO₂、CN、CHO、COOH、CH₃、CH=CH₂、C≡CH、Ph、COCH₃、COOCH₃)的相互作用势指数IPI(X). 用IPI(X)和极化效应指数建立模型,对单取代烷烃RX(包括含支链的化合物)的生成焓进行估算,所得回归方程有良好的相关性,该模型既考虑了基团R和X的贡献,又考虑了R与X相互作用的贡献. 并采用留一法对其稳定性和预测能力进行验证.     

直链烷烃物理性质递变规律研究

以直链烷烃同系物结构重复单元数值连续变化为模型假定,获得了描述直链烷烃同系物物理性质递变规律的数学表达式：P=α+bn^(1/c),其中α、b、c均为常数,n为结构重复单元数值,P为直链烷径同系物的物理性质。通过非线性回归分析,得到回归方程,结果表明直链烷烃同系物的物理性质与重复单元数值之间满足上述关系式,均显示优良的相关性。     

由13C NMR化学位移测定值确定烷烃生成焓

本文通过分析烷烃核磁共振碳谱（¹³C NMR）化学位移与生成焓之间的关系,提出由¹³C NMR化学位移的测定值来确定烷烃生成焓的新方法．用53个烷烃分子的¹³C NMR化学位移总和（SCS）、三键数（P3）以及碳原子数目（n）与生成焓实验值进行相关,所得回归方程的相关性良好（相关系数R=0.998 2,标准偏差S=3.5 kJ/mol）．进而,通过随机抽样和留一法证实该方程具有良好的稳定性和预测能力．将烷烃¹³C NMR化学位移与其生成焓定量联系起来,不仅有利于深入理解分子结构与性能关系,还为预测那些难于测定且费时的物理化学性质提供了新思路．     

关于对称尖刃式簧片固有频率的理论和实验研究

本文研究簧片哨里簧片的固有频率.根据Leitner和Hiedemann的簧片基频计算方法,推出了簧片二次频的公式.提出簧片基频在液体介质中的近似公式.在水中获得的实验结果与近似公式相符合.     

计算饱和醇异构体标准生成焓的新方法

基于极性叠加原理,在成功设计烷烃异构体和多氯代烷烃生成焓计算新方法的基础上,设计了一种计算多元醇异构体生成焓的新方法,并合理地假定任一异构体的原子化焓等于三种键（C-C、C-H和C-O-H键）的键能、极性叠加能项以及氢键能项的加和。用这一模型拟合24种原子化粹数据,得到了标准生成焓的估算公式。为了检验预测的精确性,又设计了一种预测方法,使用在排除液预测的化合物条件下回归得到的参数,预测该化合物的生成焓。按这种方法,预测了24种异构体的生成焓。通过该5参数预测的相对于实验值的各种误差（平均绝对误差、均方根误差和最大绝对误差）不仅比7参数的基团法预测的对应误差小得多,而且比相应实验数据的误差还要小。与键加和法比较,该方法的模型包含了极性叠加能和氢键能量,该两项代表了主要的非键相互作用能,表征了不同异构体的结构差异,并大大减少了参数。     

结构参数K与过渡元素卤化物标准生成焓的关系研究

把键参数和量子数引入原子点价,重新定义原子点价为δki,并用δki构建分子结构参数K.K与33种AnXm型过渡元素卤化物的标准生成焓-ΔfHθm呈现高度的相关性,并给出了相关方程,其相关系数为0.991 0.与其它结构参数相比,本参数的计算更为准确.用此模型预测了5个过渡元素卤化物的-ΔfHθm,得到了满意的结果,表明该模型较好地提示了过渡元素卤化物-ΔfHθm的共同规律.     

非金属二元氢化物分子振动固有频率与pKa常数的定量关系

提出了非金属二元氢化物分子振动固有频率的计算原理与方法.将基频和总频作为结构信息指数用于非金属二元氢化物的分子结构与pK_a常数的定量关系研究,结果表明,其相关系数大于0.995,得到的回归方程用于pK_a的计算,计算值与实验值比较,平均绝对误差小于1.82.     

气体在液体中溶解的分子热力学模型

本文提出气体在液体中溶解的分子热力学模型并应用分子聚集型状态方程对CO_2在直链烷烃中的溶解度进行计算,取得较好结果. 一、前言 化学、环保、生化、能源工业的过程设计和开发需要大量的气体在水或有机溶剂或混     

研究温度波的传播特性

根据振动与波的原理,把样品上某点温度随时间的周期性变化看作一种振动,把这种温度变化向外传播的过程看作波动,引进温度波,说明样品上各点温度随时间、距离的变化;采用一维模型,写出温度波的传播方程.考虑到样品(铜棒)散热,引进衰减系数,描述温度幅度随频率及传播距离的变化关系.利用傅里叶变换分析实验数据,得到温度波幅度与角频率、位置的对应关系.根据温度幅度衰减公式拟合数据,算出基频及倍频对应的衰减系数.结果说明:衰减系数与温度波的频率相关,温度波的频率越高,衰减系数越大,温度幅度衰减得越快.     

Frequency spectra of beam-plates revisited

Based on Mindlin’s plate theory, the frequency spectra for flexural and thickness-shear vibrations of a finite beam-plate with different combinations of boundary conditions are presented and studied. Comparing them with the dispersion curves of the infinite beam-plate reveals an intrinsic relation between resonant vibration and guided wave propagation. The fundamental frequency spectra, which are for beam-plates with hinged and/or guided edges, are found to play an important role in understanding the spectra of beam-plates with other boundary conditions.     

一维共聚物链的色散关系研究

研究了一维共聚物链的晶格振动，得到了不同均聚物构型的色散关系，并分析了其振动模的结构特点.调整界面耦合，得到了界面模，其频率位于声频与光频或光频之间的带隙中.从晶格振动的角度分析了共聚物的量子阱或超晶格特征. 关键词： 共聚物 界面耦合 晶格振动     

Measurement of the dispersion relation of guided non-axisymmetric waves in filament-wound cylindrical structures

To determine the dispersion relation, guided waves are excited in specimens over a broad frequency range. The surface displacements are measured over time and space. The recorded data are analysed using a quasi-three-dimensional spectrum estimation algorithm. In the time domain a fast Fourier transform is used to extract the frequencies. To obtain the wave numbers, in space a two-dimensional matrix-pencil approach is applied to the data set. Using a suitable constitutive model (transversely isotropic or orthotropic) dispersion curves are calculated. Good agreement was found between the experimental and the numerically calculated dispersion relations after adjusting the material parameters. Since the dispersion relation of a structure depends on the mechanical material properties frequency-dependent material parameters can be extracted from the above-mentioned relation between frequency and wave number.     

Multiscale methods for engineering double negative metamaterials

The approach taken here solves the Maxwell equations inside metamaterial crystals directly and explicitly with no approximations made. The Bloch wave solution and dispersion relation is given by a power series in the ratio between wave number and period. Each term is iteratively defined by the solution of an auxiliary problem depending on the configuration and shapes of the scatterers. The leading order term in the power series for the dispersion relation is given by the complex effective index of refraction. The effective properties and their resonance frequencies depend explicitly on the shape of the scatterers. Double negative behavior is explicitly controlled by the location of resonance frequencies related to spectra intrinsic to the geometric configuration of the multi-phase inclusions. This provides for the rational shape design of inclusions for control of double negative behavior across prescribed frequency ranges.     

Bi系高温氧化物超导体CuO2面内Cu-O键伸缩振动的分析

测试了一系列Ｂｉ系高温氧化物超导体的红外吸收谱，分析了Ｂｉ系超导样品ＣｕＯ２面内Ｃｕ－Ｏ键的伸缩振动与样品超电性的联系。结果表明，ＣｕＯ２面内Ｃｕ－Ｏ伸缩振动吸收峰强度的变化与样品零电阻的变化一致，其原因与微观结构内部声子与载流子的相互作用密切相关。其次，根据分子振动理论，采用简化模型计算了Ｂｉ系超导体ＣｕＯ２面内Ｃｕ－Ｏ振支频率     

Natural frequency split estimation for inextensional vibration of imperfect hemispherical shell

In this study, mathematical model of hemispherical shell is introduced using inextensional vibration mode shapes. Adopting energy equations, the natural frequency of the shell is determined by applying Rayleigh's energy method. Further, the vibration for imperfect shell is investigated with point mass elements representing imperfections on the structures. Also, the effects are considered via energy relations, and the split amount of the natural frequencies can be determined. Finally, the influences of point mass are presented by explicit functions for the split of the natural frequency and shifting angle of mode orientation. Based on the proposed model of imperfect shell with multiple point masses, the structure can be expressed as an equivalent single mass model.     

三氨基三硝基苯基高聚物粘结炸药热力学性质的理论计算研究

高聚物粘结炸药(PBX)的热力学性质是用于炸药结构响应、安全性评估、数值模拟分析等的重要参数.由于PBX结构的多尺度特性,完全采取实验方法精细表征这些参数存在巨大的挑战.本文运用第一性原理和分子动力学计算的方法,系统研究了三氨基三硝基苯(TATB)基高聚物粘结炸药的热力学参数和界面热传导性质.利用散射失配模型研究了TATB与聚偏二氟乙烯(PVDF)界面的热传导过程,发现热导率随温度升高而上升,并且在高温情况下接近于定值.基于分子动力学获得的TATB热导率并结合界面热导率,分析了PBX炸药的热导与颗粒尺寸的关系,当颗粒尺寸大于100 nm时,界面热阻对于PBX热导率的影响有限.     

Studying the buckling and vibration characteristics of single-walled zinc oxide nanotubes using a nanoscale finite element model

The free vibration and axial buckling of achiral zinc oxide nanotubes (ZnONTs) are studied in this paper based on a three-dimensional finite-element model in which bonds are modeled using beam elements and mass elements are placed at the joints of beams instead of atoms. To determine the mechanical properties of the nanotubes, a linkage is established between molecular mechanics and density functional theory. The fundamental frequency and critical buckling load of ZnONTs with different geometries, chiralities and boundary conditions are calculated. It is shown that zigzag nanotubes are more stable than armchair ones. Investigating the effect of aspect ratio on the critical force shows that longer nanotubes are less stable. Also, it is indicated that increasing the length of the nanotubes will result in decreasing the frequency. Moreover, as the aspect ratio increases, the effect of end conditions diminishes.     

Vibration frequency of a curved beam with tip mass

In flexible blade auto cooling fans, the first vibration frequency is of fundamental importance. These fan blades are usually curved and have a tip mass in the form of a strip along one edge. For the first frequence, the blade can be modelled as a curved beam with a tip mass. This paper reports on an investigation of the vibration frequency of a curved beam with a tip mass, in which both theoretical finite element and experimental methods were used. In the finite element methods, both the normal and tangential displacements are approximated by cubic polynomials to ensure that rigid body displacements are closely represented. The effect of the tip mass is incorporated into the mass matrix. The results show that the curvature has a slight effect on the first mode natural frequencies but has great influence on the higher frequencies, and that the coupling effect between the tip mass and the curvature is insignificant.