开敞式蜗壳轴流式水轮机湍流计算及性能预估

本文在进行模型水轮机试验的基础上,完成了开敞式蜗壳轴流式模型水轮机的全流道三维定常湍流计算。计算程序以雷诺时均连续方程和N-S方程作为控制方程,选用标准κ-ε双方程湍流模型使方程组封闭。数值求解通过CIMPLEC算法实现速度、压力的分离求解,离散差分格式具有二阶精度。通过计算获得了各过流部件的流动细节,预估了水轮机的能量性能,并与试验结果进行了比较。     

Ne同位素替代下Ne-HF碰撞截面的理论计算

采用Huxley势函数拟合QCISD(T)/ aug-cc-pVTZ计算的相互作用势能面,通过精确度较高的密耦近似方法计算了E=100 meV时,氖原子的三种同位素 ¹⁶Ne, ²⁰Ne, ³⁴Ne与HF分子碰撞系统的微分截面和分波截面.探讨了Ne的同位素替代引起的Ne-HF碰撞激发 截面的变化规律.     

First-principles investigation on the elastic stability and thermodynamic properties of Ti2SC

Using Vanderbilt-type plane-wave ultrasoft pseudopotentials within the generalized gradient approximation（GGA） in the frame of density functional theory（DFT）,we have investigated the crystal structures,elastic,and thermodynamic properties for Ti2SC under high temperature and high pressure.The calculated pressure dependence of the lattice volume is in excellent agreement with the experimental results.The calculated structural parameter of the Ti atom experienced a subtle increase with applied pressures and the increase suspended under higher pressures.The elastic constants calculations demonstrated that the crystal lattice is still stable up to 200 GPa.Investigations on the elastic properties show that the c axis is stiffer than the a axis,which is consistent with the larger longitudinal elastic constants（C 33,C 11） relative to transverse ones（C 44,C 12,C 13）.Study on Poisson＇s ratio confirmed that the higher ionic or weaker covalent contribution in intra-atomic bonding for Ti2SC should be assumed and the nature of ionic increased with pressure.The ratio（B/G） of bulk（B） and shear（G） moduli as well as B/C 44 demonstrated the brittleness of Ti2SC at ambient conditions and the brittleness decreased with pressure.Moreover,the isothermal and adiabatic bulk moduli displayed opposite temperature dependence under different pressures.Again,we observed that the Debye temperature and Gru篓neisen parameter show weak temperature dependence relative to the thermal expansion coefficient,entropy,and heat capacity,from which the pressure effects are clearly seen.     

He-NO碰撞体系微分截面的理论计算

首先用Huxley势函数形式拟合了在RCCSD(T)/aug-cc-pVTZ+bf理论水平下计算的He-NO相互作用能数据，获得了He原子与NO分子相互作用的各向异性势，然后采用密耦近似方法计算了He-NO碰撞体系的总微分截面、弹性微分截面和非弹性微分截面，并总结了微分散射截面的变化规律. 结果表明，拟合势不但表达形式简洁，而且较好地描述了He-NO系统相互作用的各向异性特征；利用碰撞体系分子间势的量子化学从头计算结果,可解决势能参数难以确定的问题，对进一步研究原子与分子碰撞机理有一定参考价值. 关键词： 各向异性势 势能参数 密耦近似 微分截面     

Mechanism of Striation in Dielectric Barrier Discharge

The mechanism of striations in dielectric barrier discharge in pure neon is studied by a two-dimensional particle- in-cell/Monte Carlo collision （PIC-MCC） model. It is shown that the striations appear in the plasma background, and non-uniform electrical field resulting from ionization and the negative wall charge appear on the dielectric layer above the anode. The sustainment of striations is a non-local kinetic effect of electrons in a stratified field controlled by non-elastic impact with neutral gases. The striations in the transient dielectric barrier discharge are similar to those in dc positive column discharge.     

Theoretical calculation of the partial cross section for first vibrational excitation in He-H2（D2,T2） collisions

In this paper, close-coupling method was applied to the He-H2 （D2,T2） system, and the first vibrational excitation cross sections of ＇00-10, 00-12, 00-14, 00-16＇ at different incident energy have been calculated. By analyzing the ditferences of these partial wave cross sections, this paper have obtained the change rules of the partial wave cross sections with increases of quantum number, and with change of reduced mass of system. Based on the calculation, influence on the partial wave cross sections brought by the variations in the reduced mass of systems and in the relative kinetic energy of incident atoms is discussed.[第一段]     

Ne原子与H2分子碰撞的同位素替代效应研究

使用密耦近似（Close-Coupling）方法、采用Tang-Toennies势模型计算了惰性气体原子Ne与H₂分子及同位素D₂分子在碰撞能量为83.8 meV时的微分散射截面及分波截面, 并与实验值和文献值进行比较.计算得到的微分散射截面值与实验值符合得较好,分波截面值与文献值也相符合.使用同样的方法和模型,文中对Ne-H₂(D₂,T₂)三个体系的微分截面和分波截面进行了系统计算和比较分析,得出对称同位素替代碰撞体系的散射截面规律.     

氦原子与一氧化碳分子各向异性势的计算研究

本文用高精度的量子力学ab initio方法计算了氦原子与一氧化碳分子相互作用各向异性势能面,通过三重激发校正耦合簇、二次组态相互作用等方法和不同基组的计算结果比较,并采用BSSE方法消除了基组重叠误差,得到了氦原子与一氧化碳分子体系相互作用各向异性势,然后采用精确度较高的密耦（Close-Coupling）近似方法,研究了氦原子与一氧化碳分子碰撞的散射截面,通过计算得出了该体系碰撞激发微分截面和分波截面,计算得到的微分截面数据与实验值符合较好,说明本文得到的势能面是准确的.     

Fe和Ni共掺杂ZnO的电子结构和光学性质

基于密度泛函理论的第一性原理研究Fe,Ni单掺杂和(Fe,Ni)共掺杂纤锌矿型ZnO的能带结构、电子态密度分布、介电函数、光学吸收系数,分析了掺杂后电子结构与光学性质的变化.计算结果表明：掺杂体系的费米能级附近电子态密度主要来源于Fe 3d,Ni 3d态电子的贡献;与纯净ZnO相比,Fe,Ni单掺杂和(Fe,Ni)共掺杂ZnO的介电函数虚部均在0.46eV左右出现了一个新峰;Fe,Ni单掺杂和共掺杂ZnO的吸收光谱均发生明显的红移,并都在1.3eV处出现较强吸收峰.结合他人的计算和实验结果,给出了定性的讨 关键词： 氧化锌 掺杂 第一性原理 光学性质     

Characterisation of the high-pressure structural transition and elastic properties in boron arsenic

This paper carries out the First principles calculation of the crystal structures (zinc blende (B3) and rocksalt (B1)) and phase transition of boron arsenic (BAs) based on the density-functional theory. Using the relation between enthalpy and pressure, it finds that the transition phase from the B3 structural to the B1 structural occurs at the pressure of 113.42GPa. Then the elastic constants C₁₁, C₁₂, C₄₄, bulk modulus, shear modulus, Young modulus, anisotropy factor, Kleinman parameter and Poisson ratio are discussed in detail for two polymorphs of BAs. The results of the structural parameters and elastic properties in B3 structure are in good agreement with the available theoretical and experimental values.