Structural and spectroscopic properties of small Pun （n= 2-5） molecules

The equilibrium structures and the electronic, spectroscopic and thermodynamic properties of small Pu_n (n=2-5) molecules are systematically investigated using the methods of general gradient approximation (GGA) of density functional theory (DFT). The results show that the bond length of the lowest-energy structure of Pu₂ is 2.578 AA. The ground state structure of Pu₃ is a triangle with D_3h symmetry, whereas for Pu₄, the ground state structure is a square (D_4h) and the spin polarization of 16 for molecule Pu₅ with square geometry (D_4h) is the most stable structure. For the ground state structures, the vibrational spectra as well as thermodynamic parameters are worked out. In addition, the values for the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) along with the energy gap of all the Pu_2-5 structures are presented. The relevant structural and chemical stabilities are predicted.     

Growth and properties of wide spectral white light emitting diodes

Wide spectral white light emitting diodes have been designed and grown on a sapphire substrate by using a metal-organic chemical vapor deposition system. Three quantum wells with blue-light-emitting, green-light-emitting and red-light-emitting structures were grown according to the design. The surface morphology of the film was observed by using atomic force microscopy. The films were characterized by their photoluminescence measurements. X-ray diffraction θ/2θ scan spectroscopy was carried out on the multi-quantum wells. The secondary fringes of the symmetric ω/2θ X-ray diffraction scan peaks indicate that the thicknesses and the alloy compositions of the individual quantum wells are repeatable throughout the active region. The room temperature photoluminescence spectra of the structures indicate that the white light emission of the multi-quantum wells is obtained. The light spectrum covers 400-700 nm, which is almost the whole visible light spectrum.     

在大学物理中讲授纵波的一点尝试

采用小球弹簧链模型和相对形变,以便于理解纵波的基本性质.     

The effects of sapphire nitridation on GaN growth by metalorganic chemical vapour deposition

In situ optical reflectivity measurements are employed to monitor the GaN epilayer growth process above a low-temperature GaN buffer layer on a c-plane sapphire substrate by metalorganic chemical vapour deposition. It is found that the lateral growth of the GaN islands and their coalescence are promoted in the initial growth stage if optimized nitridation time and temperature are selected when the substrate is pre-exposed to ammonia. As confirmed by atomic force microscopy observations, the quality of the GaN epilayers is closely dependent on the surface morphology of the nitridated buffer layer, especially grain size and nucleation density.     

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采用二维轴对称双温度化学非平衡(2T-NCE)模型,模拟了带有水冷约束管的大气压直流电弧氩等离子体发生器.得出了不同工作参数下等离子体中电子温度、重粒子温度的变化关系,表明直流电弧等离子体有很强的非平衡特性,且变化规律十分明显.     

浙江小黄山与河南贾湖遗址出土新石器时代前期陶器化学组成的WDXRF分析研究

利用能量色散X射线荧光光谱法(energy disperse X-ray fluorescence,EDXRF)对浙江嵊州小黄山与河南舞阳贾湖两处新石器时代前期遗址出土陶器的主量元素化学组成进行了分析测定.结果显示,这两处遗址出土陶器的化学组成地域特征明显,与贾湖遗址相比,小黄山遗址陶器具有我国南方陶瓷器普遍存在的“高...     

微小圆管中分裂火焰的实验与理论研究

对丙烷/空气在内径2 mm的圆管内的预混燃烧进行了实验研究,借助于高速数码摄像机发现了分裂火焰现象,其中一个为向上游传播的较亮的常规火焰,另一个为向下游传播的较暗的微弱火焰。这些火焰先后熄灭,经过一段时间后又重复发生自着火、分裂、反向传播、灭火过程。这种现象在富燃、化学恰当比以及贫燃火焰中都有存在。一维非稳态计算表明化...     

Characteristics of the crystalline and luminescence properties of a-plane GaN films grown on γ-LiAlO2 （302） substrates

A method of clarifying bioaerosol particles is proposed based on T-matrix. Size and shape characterizations are simultaneously acquired for individual bioaerosol particles by analyzing the spatial distribution of scattered light. The particle size can be determined according to the scattering intensity,while shape information can be obtained through asymmetry factor(AF) . The azimuthal distribution of the scattered light for spherical particles is symmetrical,whereas it is asymmetrical for non-spherical ones,and the asymmetry becomes intense with increasing asphericity. The calculated results denote that the 5 –10 scattering angle is an effective range to classify the bioaerosol particles that we are concerned of. The method is very useful in real-time environmental monitoring of particle sizes and shapes.     

基于压电探测判定激光支持燃烧波和爆轰波的点燃阈值

为了获得激光支持燃烧波和爆轰波的点燃阈值,采用压电探测器检测波长为1 064 nm的Nd:YAG激光作用在铝靶表面所产生的应变和冲压。从实验结果观察到压电信号的变化分为3个阶段,分别为光热弹性应变阶段、等离子体增强耦合阶段和激光支持爆轰波对靶表面的压力阶段,并从理论上研究了这3个阶段的激光与靶材料相互作用的机理,从而可以从压电信号是否发生跃变判断出激光支持燃烧波和激光支持爆轰波的点燃阈值,与其它方法所得到结果基本吻合。     

班主作工作效果的马尔可夫链评估法

本文研究了班主任工作效果的评估标准及马尔可夫链评估法，并通过实例分析指出了该方法的理论依据及其特点。