显微激光拉曼光谱测定甲烷水合物的水合指数

甲烷水合物是由甲烷气体分子与水分子在低温高压下形成的一种笼型结构化合物,广泛存在于海底陆架区和陆地冻土区,被认为是一种潜在的能源资源。在水合物的晶格中,水分子在氢键的作用下形成大小不同的笼子,甲烷分子可分别进入大笼(51262)和小笼(512)中。在自行研制的实验装置上,分别合成了一系列不同体系下的甲烷水合物,包括十二烷基硫酸钠(SDS)水溶液-甲烷体系、冰粉-甲烷体系以及冰粉-不同粒度砂-甲烷体系。对这些甲烷水合物样品进行了激光拉曼光谱分析,测定了其水合指数,笼占有率等结构参数。结果表明,这些甲烷水合物都为Ⅰ型结构,其水合指数和笼占有率基本不受沉积物粒径大小的影响。在3种体系中生成的水合物,大笼中甲烷分子基本占满,占有率大于97%;小笼中甲烷分子占有率为80%～86%,测得的水合指数为6.05～6.15。     

硝基甲烷与硝基乙烷266 nm光解动力学

利用单光子激光诱导荧光技术，在硝基甲烷与硝基乙烷气相条件下266 nm光解过程中，对初生态的解离产物OH进行了测量．结果表明，两个解离过程中产生的初生态OH都没有振动激发．硝基甲烷光解过程中产生的OH的转动分布可以用玻尔兹曼温度简单的表示，相对于自旋轨道分裂的2|3=2与2|1=2两个态，其转动温度分别为2045§150与1923§150 K．硝基乙烷光解过程中产生的OH不是简单的玻尔兹曼分布，因此不能用玻尔兹曼温度来描述，这一结果 意味着硝基甲烷与硝基乙烷在生成OH的过程中经历了不同的解离过程．硝基甲烷     

分子构型对分子器件伏-安特性的影响

本文以4，4’-二巯基联苯分子为研究对象，利用从头计算方法和弹性散射格林函数理论，研究了苯环之间的不同位置取向对分子的电子结构以度该分子结的伏安特性的影响．计算结果表明苯环扭转角不同会改变分子的电子结构。扭转角的增大会导致分子轨道的扩展性变差，从而使体系的导电性能降低．     

白噪声扰动在波长调制离轴积分腔输出光谱技术中的应用研究

离轴积分腔输出光谱技术是痕量气体检测的重要方法,这种测量方法的检测限容易受到残余腔模式噪声和背景噪声的影响。通过注入射频白噪声到激光器的调制电流中,以减小离轴积分腔输出光谱中的残余腔模式噪声,同时利用波长调制技术抑制了背景信号的影响,进一步提高了基于离轴积分腔输出光谱技术的甲烷传感系统的信噪比。首先,详细研究了不同功率射频白噪声对空气中甲烷吸收光谱的影响,并对吸收谱的线宽进行了分析,计算出了不同功率噪声扰动下的吸收谱对应的最佳调制幅度。随后,研究了不同功率的射频白噪声对2f信号的影响。结果表明,随着扰动噪声功率的增加,基线噪声水平和2f信号幅值同时减小。对几组2f信号的信噪比进行分析,确定了射频白噪声提高系统信噪比的最佳功率为-25 dBm。最后,研究了0.05～2.2×10~(-6)浓度范围内,甲烷浓度与2f信号之间的对应关系,结果表明:在甲烷浓度小于1.0×10~(-6)时,甲烷浓度与2f信号之间的线性度为0.999 6;在甲烷浓度为0.1～2.2×10~(-6)时,甲烷浓度与2f信号之间呈曲线关系,二阶多项式拟合的相关度为0.999 89。此外,对浓度为2.2×10~(-6)的甲烷气体进行了长时间的测量,并利用Allan方差对系统的稳定性进行了分析,分析结果表明系统的最佳积分时间为1 250 s,系统的可探测极限约为1.2×10~(-9)。最后,使用建立的甲烷气体探测系统,对大气环境中的甲烷气体浓度进行了长达两个昼夜的检测,结果显示甲烷浓度的昼夜变化规律是昼降夜升,浓度昼夜波动范围在2.02～2.3×10~(-6)范围内,平均浓度为2.14×10~(-6)。本研究为离轴积分腔输出光谱技术在痕量气体测量方面的应用提供了一定的参考,对高精密的原位痕量气体测量仪器的研发具有重要的指导价值。     

含乙二醇水合物形成条件理论与实验研究

利用可视化高压流体测试装置在0.78～5.17 MPa压力范围内测定了乙二醇水溶液中合成天然气（甲烷、乙烷和丙烷的混合物）水合物的形成条件。根据vanderWaals-Platteeuw的理想溶液等温吸附理论和Moshfeghian-Maddocd的数学模型,给出了含抑制剂体系气体水合物相平衡计算数学模型。计算结果表明该模型可较好地预测含抑制剂（乙二醇）体系的水合物形成条件。     

小分子液体的高温布里渊散射研究

利用金刚石对顶砧技术,采用180°背向散射和60°前向对称散射两种几何配置,对水、氨、二水合氨和甲烷等含氢小分子液体进行了高温高压布里渊散射研究,计算了在室温(296K)和高温(410K)下的声速,比较了不同小分子液体中的声速及绝热体弹模量随压力的变化关系。在等温条件下,各体系中声速随着压力的增加逐渐增加;在相同温度下,甲烷液体的声速随着压力增加的速率明显高于水、氨及二水合氨液体;在相同的温度和压力条件下,水、氨及二水合氨液体的体弹模量明显高于甲烷液体的体弹模量,表明氢键的存在对于小分子液体弹性具有较大影响。二水合氨的体弹模量斜率在1.5GPa左右发生改变,表明液体结构可能发生了改变,并分析了氢键对该体系弹性性质的影响。研究有助于理解其他含氢小分子液体中压力和温度诱导的分子结构变化。     

利用LED探测甲烷气体浓度的实验研究

报导了一个利用LED作光源探测甲烷浓度的差分探测系统,分析了系统中各光学元件的作用,给出甲烷浓度的计算方法及实验结果.选用甲烷在1.65 μm附近2ν3谱带中的R支作为探测对象.利用法布里-珀罗标准具的透过率曲线与甲烷吸收线相互匹配的方法滤掉无用光,并通过压电陶瓷改变标准具的腔长,从而实现了差分吸收探测,进一步提高了测量灵敏度,取得了较好的结果.     

BOXCARS测量燃烧场的温度

 介绍了用BOXCARS技术测量CH₄/air火焰的温度。给出了甲烷气体不同流量下和火焰不同高度处的温度测量结果，分析了温度随甲烷气体流量变化和火焰高度变化的变化趋势，根据实际的实验参数计算了相应的空间分辨率。实验结果表明：利用BOXCARS技术可进行高精度、高空间分辨的温度测量。     

撞击诱导硝基甲烷分子第一步分解反应的动力学计算

本文基于分子温度与压强的关系,计算在不同压强下基态和最低三态硝基甲烷的分子温度,对应计算其沿着CN键裂解反应的热化学和动力学参数.发现基态的硝基甲烷沿着CN键的分解反应是吸热反应,不具自发性,反应转换温度为1550.2 K,平衡常数在80-1202 K温度范围内很低.最低三态的硝基甲烷沿着CN键的裂解是放热反应,反应的Gibbs自由能在80-2558.5 K范围内为负,有好的自发性,且反应较为彻底.298.15-2558.5 K温度范围内反应活化能随着温度的升高而改变,使反应速率随着温度的升高而急剧增大.对应硝基甲烷爆压15 GPa,其分子温度为4617.6 K,该温度下三态分子分解反应的反应速率为1.088×10~8cm~3·mol~(-1)·s~(-1).推算硝基甲烷沿着CN键分解反应混合物的终态温度,当混合物为硝基、甲基和基态的硝基甲烷分子时,反应的终温为1611.37 K,等效能为1676.47 cm~(-1).当混合物为硝基、甲基、基态和最低三态的硝基甲烷分子时,反应的终温为1184.79 K,等效能为1232.65 cm~(-1).两种情况下终态等效能都足以维持硝基甲烷分子沿C-N键裂解反应的发生.这个能量也足以导致混合物中的NO_2分解为NO和O,这与实验检测的结论相一致.     

甲烷-湿空气对冲扩散火焰中CO的生成特性

本文描述了HAT循环中CO排放的基础研究结果。为了澄清加湿和CO排放的关系,采用GRI-mech3．0详细化学反应机理,对甲烷-湿空气对冲扩散火焰进行了数值研究。对不同的空气含湿量通过改变进口预热温度调节最高火焰温度,解耦湿空气影响火焰的温度和自由基浓度效应,研究甲烷-湿空气火焰中CO生成的化学机理。计算结果表明在火焰最高温度相同的情况下,湿空气中的水蒸汽使OH基浓度增加、O基和H基浓度降低,从而抑制CO的生成。这些结果有益于准确预测HAT循环中CO的排放。     

金属熔体黏度与结构相关性的分子动力学模拟

运用EAM(embed atom method)作用势，采用非平衡分子动力学模拟获得Al熔体的偶分布函数与黏度数值随温度的变化曲线，偶分布函数的计算结果与实验值符合得较好.对模拟所得到的黏度数据编程实现黏度的Arrhenius公式拟合，得到激活能E.并利用模拟所得到的黏度值及激活能对Lennard-Jones(L-J)作用势进行修正，获得黏度与偶分布函数及原子间相互作用势之间的关系式，两条黏度拟合曲线与分子动力模拟结果符合得比较好，说明拟合程序的编写是比较成功的，实现了对L-J作用势的修正.该研究为金属及合金原子间相互作用势的建立提供了新的思路. 关键词： 非平衡分子动力学模拟 L-J作用势修正 Al熔体 结构与黏度相关性     

Viscosity,glass transition and activation energy of solid cis-polyisoprene and trans-polyisoprene blends

Blends of cis-polyisoprene (CPI) and trans-polyisoprene (TPI) have been prepared by solution casting to study viscosity, glass transition temperature and activation energy for the glass transition. The viscosity of blends having different weight ratios has been obtained through a single experiment measuring storage and loss modulus using the dynamic mechanical analyser technique. The glass transition temperature is determined through the temperature at which the minimum of temperature derivative curve of viscosity falls. The activation energy of glass transition and fragility index have been obtained by employing the Vogel–Fulchar–Tammann (VFT) equation by assuming non-Arrhenius behaviour of viscosity of polymer blends. Results indicate that both glass transition and activation energy for the glass transition are influenced by composition and crosslink density of the blend.     

Effects of Hall Currents and Gyroviscosity on the Instability of a Self-Gravitating Stratified Plasma

The instability in a horizontal layer of a partially ionized self gravitating plasma has been studied to include simultaneously the effects of Hall currents, viscosity and finiteness of Larmor radius (FLR). The ambient magnetic field is assumed to be uniform and vertical. Proper solutions have been obtained through the variational methods for a semi-infinite plasma in which the density has an exponential gradient along the vertical. The dispersion relation obtained has been solved numerically and it is found that the growth rate of unstable perturbations decreases with the effects of viscosity, neutral gas friction and FLR. The influence of effects of viscosity, neutral gas friction and FLR are consequently stabilizing. It is found that the Hall currents have a destabilizing influence as the growth rate is found to increase with this effect.     

Anisotropic Cosmological Models with Quintessence

In this paper anisotropic cosmological models with bulk viscosity and quintessence have been studied. Some exact solutions of Einstein field equations with bulk viscosity and quintessence on the background of anisotropic Bianchi Type I space-time are obtained. The new cosmological models approach to isotropy with evolution of the universe. Physical properties of these cosmological models have also been discussed.     

粘性流体对涡轮流量计仪表系数影响的实验研究

流体的粘性对涡轮流量计的仪表系数有很大影响．本文使用活塞式液体标准体积管在不同粘度下对涡轮流量计进行了实验研究，得出了仪表系数与流量、流体的粘度之间关系曲线．     

Viscous potential flow analysis of Kelvin-Helmholtz instability with mass transfer and vaporization

Viscous potential flow analysis of Kelvin-Helmholtz instability with heat and mass transfer has been studied. A dispersion relation has been obtained. Stability criterion is given by a critical value of relative velocity. It has been found that heat and mass transfer has destabilizing effect on relative velocity when lower fluid viscosity is low while it has stabilizing effect when lower fluid viscosity is high. Various graphs have been plotted for relative velocity and growth rate. In statically unstable situation viscosity has stabilizing effect while in statically stable situation it has destabilizing effect.     

Rheological properties of a vesicle suspension

The rheological properties of a vesicle suspension have been investigated in the limit of strong flows destroying the stationary form of vesicles. The dependence of the effective viscosity of the suspension on the velocity gradient and the properties of vesicles has been obtained for the case of the plane flow. In particular, it has been shown that the effective viscosity of the suspension can strongly depend on its initial state. The effect of thermal fluctuations on the rheological properties of the suspension has been analyzed.     

Density expansion of viscosity coefficient

The formalism developed earlier has been extended to obtain the density expansion of viscosity coefficient. The important role played by the Hartree average energy in obtaining an explicit temperature dependence for the density coefficients of the viscosity is demonstrated. The results obtained are compared with the available experimental data for the first density coefficient. A satisfactory agreement between theory and experiment is found.     

Temperature dependences of kinematic viscosity of bismuth,lead, and their mutual solutions

Measurement results for temperature dependences of kinematic viscosity in Bi-Pb melts are presented. Measurements were carried out in the temperature range between liquidus and 1400 K. The distinctive feature of experiments was their performance at heating after sample melting and further cooling. On the experimental temperature dependences of kinematic viscosity the values of viscosity at fixed temperature and activation energy of viscous flow have been calculated. Special attention was paid to non-coincidence of the curves obtained at heating and cooling. The specified anomaly is explained by the concept of metastable microcoherence of the studied melts.     

Transport and Turbulence Experiments in Three Regimes of a Magnetized Plasma

The occurrence of turbulence and its influence on plasma viscosity have been investigated. A simple model of turbulence has been obtained by the balance of the growth of the combined Rayleigh-Taylor and Kelvin-Helmholtz instability with the damping by friction against the neutrals, by kinetic viscosity and by turbulent viscosity itself. In the experiment, a hollow cathode arc, three regimes can be distinguished: a kinetic, a frictional and a turbulent regime. By variations of the discharge parameters around a suitably chosen operating point, transitions between the three regimes are caused. It appears that the longitudinal drift velocity is also influenced by the turbulence. A dispersion relation for the large scale oscillation of the whole arc has been derived and checked experimentally.