Influence of disorder and deformation on the optical properties of two-dimensional photonic crystal waveguide

We investigate the effect of disorder and mechanical deformation on two- dimensional photonic crystal waveguide. The dispersion characteristics and transmittance of the waveguide are studied by using the finite element method. Results show that the geometric change of the dielectric material perpendicular to the light propagation direction has a larger influence on the waveguide characteristics than that parallel to the light propagation direction. Mechanical deformation has an obvious influence on the performance of the waveguide. In particular, longitudinal deformed structure exhibits distinct optical characteristics from the ideal one. Studies on this work will provide useful guideline to the fabrications and practical applications based on photonic crystal waveguides.     

Donor-bound electron states in a two-dimensional quantum ring under uniform magnetic field

The electron states in a two-dimensional GaAs/AlGaAs quantum ring are theoretically studied in effective mass approximation. On-centre donor impurity and uniform magnetic field perpendicular to the ring plane are taken into account. The energy spectrum with different angular momentum changes dramatically with the geometry of the ring. The donor impurity reduces the energies with an almost fixed value; however, the magnetic field alters energies in a more complex way. For example, energy levels under magnetic field will cross each other when increasing the inner radius and outer radius of the ring, leading to the fact that the arrangement of energy levels is distinct in certain geometry of the ring. Moreover, energy levels with negative angular momentum exhibit the non-monotonous dependence on the increasing magnetic field.     

空位结构缺陷对C纳米管弹性性质的影响

用分子动力学方法对不同空位缺陷的扶手椅型与锯齿型单壁C纳米管杨氏弹性模量进行了计算和分析. 结果表明：扶手椅型（5, 5）, （10,10）和锯齿型（9, 0）, （18, 0） 纳米管在无缺陷时其杨氏模量分别为948,901和804,860 GPa. 随管径的增大,扶手椅型和锯齿型单壁C纳米管弹性模量分别减小和增大,表现出完全不同的变化规律. 随着C纳米管中单点空位缺陷的均匀增加,杨氏模量下降,当缺陷比率增加到一定程度时,杨氏模量下降骤然趋缓,形成一下降平台;双空位缺陷对C纳米管杨氏模量的影响与其分布方向有关;随单点空位缺陷间原子数的增加,在轴向上,杨氏模量下降到某一值小幅波动,而在周向上杨氏模量先下降,然后上升到某一稳定值. 随两单点空位缺陷的空间距离进一步增大,杨氏模量又呈微降趋势. 通过分子间σ键与π键特征及缺陷间近程电子云耦合作用规律与空位缺陷内部5-1DB缺陷的形成特点等理论对上述规律进行了分析. 关键词： 空位缺陷 C纳米管 分子动力学 杨氏模量     

Skeletal Rearrangement of Substituted Benzaldoxime 3- (2,2-Dichlorovinyl)-2,2-dimethyl Cycle-propane Carboxylates under EI-MS

Introduction Substituted benzaldoxime 3-( 2, 2-dichlorovinyl )-2,2-dimethyl cyclopropanecarboxylates,considered as pyrethroid analogs, show a good bioactivity such as fungicidal, herbicidal and plantgrowth regulating activities[1,2]. EI-MS spectra of those compounds show the rearrangement of their structures, which has prompted us to elucidate their behavior under EI conditions. All the compounds studied have M-165 and M-99 fragment ions in the EI-MS spectra, but there is no segment with the mass of 165 and 99 lost directly from the molecular ions. So we postulated the process of rearrangement, it involved the cleavage of the C2C3 bond in the substituted cyclopropyl accompanied by the migration of disubstitued methylene-amino moiety to C2 or C3 position and elimination of a conjugated group with the mass of 165 or 99 to afford the even electron ion, of which the important step is the cleavage of the N-O bond. Although the cleavage of the alkoxy bond in the pyrethroids[3-5] has been reported, there has been no rearrangement reported. In order to test our postulations, MIKES and EI-HR-MS were carried out to elucidate the fragmentation pathways. The substituents in the phenyl ring played important roles in the stabilization of the product ions. The focal point of our work was to investigate two pathways of the skeletal rearrangement and the effect of the substituents.     

应变补偿层对量子点生长影响的理论研究

量子点的光学特性与量子点的大小均匀性、密度、内部应变以及隔离层的厚度等有密切关系.文中从理论角度定量研究了GaNXAs1-X应变补偿层对InAs/GaAs量子点生长质量的改善作用,分析了应变补偿层对隔离层厚度减小的作用.讨论了应变补偿层的补偿位置和补偿层N组分X对量子点生长时局部应变和体系应变的补偿作用.分析了应变补偿层对体系应变的减少作用,并计算了相邻层量子点的垂直对准概率.研究结果对实验中应变补偿的优化和高质量量子点阵列的生长实现提供了理论依据.     

柚子皮挥发油化学成分分析

使用水蒸气蒸馏法提取柚子皮中的挥发油,利用气相色谱-质谱联用技术对柚子皮化学成分进行分离鉴定,采用色谱峰面积归一化法确定各成分的相对含量。分析结果表明,共检测出62种组分,鉴定了其中的31种组分,占挥发油组分总量的50.0%。主要成分是β-蒎烯、4,4A,5,6,7,8-六氢-4,4A-二甲基-6-(1-甲基亚乙基)-(4R-顺)-2(3H)-萘酮、氧化芳樟醇、(E,E)-3,7,11,15-四甲基-1,6,10,14-十六碳四烯-3-醇。     

大质量样品厚度对中子活化定量分析的影响和修正

滑石粉的主要化学成分是Mg3[Si_4010](OH)_2,通过检测面粉中~(24)Mg和~(28)Si原子核的含量,可以计算出面粉中滑石粉的含量.利用中子活化分析方法测量面粉中~(24)Mg和~(28)Si原子核的含量问题时,被测样品内部中子通量和能量随厚度的变化以及γ射线自吸收效应会对测量结果有较大的影响.利用MCNP5 (Monte Carlo N-particle transport code system 5)模拟了中子通量和能量与样品厚度变化的关系,并利用氦3正比计数管测量样品不同厚度处中子通量,结果显示MCNP5模拟结果与实验测量结果基本相符.通过MCNP5模拟和碘化钠探测器测量,研究了γ射线自吸收效应与样品厚度的关系,确定了6.6 cm的样品厚度为最佳实验条件,根据模拟结果给出了特征γ射线计数与样品厚度的关系式,并与实验进行对比,结果符合得较好.     

Piezoelectric effects and electronic structures of InAs/GaAs quantum dots grown along (111) and (011) directions

Piezoelectric effects and electronic structures of InAs/GaAs quantum dots grown along (111) and (011) directions are investigated in this paper. The finite element method is used. Electronic energy levels are calculated by solving the three-dimensional effective mass Schr?dinger equation including a strain modified confinement potential and piezoelectric effects. The difference in electronic structure between quantum dots grown along the (111) direction and the (011) direction are compared. The cubic and truncated pyramidal shaped quantum dots are adopted.     

丙酮-水混合溶剂中3-甲基吡啶的电氧化

在以质子交换膜为隔膜的电解槽内, 通过3-甲基吡啶在PbO2电极上的电氧化研究, 发现在丙酮-水混合溶剂中, 与纯水作溶剂相比, 不仅在相同阳极电位下电流密度大幅度上升, 3-甲基吡啶电氧化生成烟酸的选择性和电流效率也明显提高. 通过循环伏安、极化曲线和恒电位电解实验, 研究了在丙酮-水混合溶剂中3-甲基吡啶的电氧化条件, 并比较了不同条件下的选择性和电流效率.     

含酯基聚合物液相色谱填料的制备与性能

采用新的聚合工艺制备了用于高效液相色谱的双甲基丙烯酸乙二醇酯-苯乙烯-二乙烯苯共聚物柱填料.该球形聚合物的料径为5±2μm,测定了渗透性、理论塔板高度和选择性等柱参数,并与文献中类似填料的数据作比较.此种含酯基聚合物柱效较高、刚性好、渗透性强,适于分离芳胺、酚类和环己酮过氧化物等中等极性混合物.