Theoretical studies on the optical absorption coefficients and refractive index changes in parabolic quantum dots in the presence of electric and magnetic fields

The optical absorption coefficients and the changes in the refractive index in GaAs/AlGaAs parabolic quantum dots(QDs) with applied electric and magnetic fields are studied in detail. Analytical expressions for the linear and nonlinear intersubband absorption coefficients and refractive index changes are obtained by using a compact density matrix approach and an iterative procedure. Finally, the calculated results show the incident optical intensity, the frequencies of the confined potential of the QDs and the applied electric and magnetic fields have a great influence on the optical absorption coefficients and refractive index changes in this system.     

一个新的三维混沌系统

构造了一个新的三维连续自治混沌系统.该系统含有两个参数、一个反正切函数形式的非线性项.基于线性矩阵不等式方法研究了系统的稳定性.通过理论分析、数值仿真、Lyapunov指数谱、分岔图以及Poincaré截面图分别研究了系统的复杂动力学特性. 关键词： 混沌系统 稳定性 线性矩阵不等式 Lyapunov指数谱     

减压氩气下基体对激光微等离子体电子温度的影响

以激光微区发射光谱分析仪结合CCD光栅光谱仪为装置，采用二谱线法，以FeⅠ356.54nm和FeⅠ358.12 nm为分析线，在减压氩气下，测量了镁基体、铝基体、硅基体和低碳钢标样6-0中的激光微等离子体的电子温度及其空间分布，给出了相同基体中微等子体电子温度的空间变化趋势和不同基体中相同空间位置处的电子温度的差异并进行了分析.利用测量的结果，以CuⅠ324.75 nm和ZnⅠ334.50 nm为分析线，从电子温度角度探索了两分析谱线相对强度的基体效应，给出了合理的解释. 关键词： 激光微等离子体 电子温度 减压氩气 基体     

一维光子晶体缺陷模的偏振特性研究

利用周期结构的布洛赫定理推导了一维无限光子晶体缺陷模方程,研究了缺陷模的偏振特性,以及在不同入射角和缺陷层厚度下缺陷模位置的变化.利用传输矩阵方法对有限周期数光子晶体也进行了研究,分别对应一维无限光子晶体和有限周期数光子晶体给出了数值计算结果.通过比较这两者的数值结果得出了缺陷模随入射角和缺陷层厚度变化的一般规律.     

The multicomponent （2＋1）-dimensional Glachette-Johnson （GJ） equation hierarchy and its super-integrable coupling system

This paper presents a set of multicomponent matrix Lie algebra, which is used to construct a new loop algebra A^-M. By using the Tu scheme, a Liouville integrable multicomponent equation hierarchy is generated, which possesses the Hamiltonian structure. As its reduction cases, the multicomponent （2＋1）-dimensional Glachette-Johnson （G J） hierarchy is given. Finally, the super-integrable coupling system of multicomponent （2＋1）-dimensional GJ hierarchy is established through enlarging the spectral problem.     

含Eu3+离子的Na2O-K2 O-SiO2-Al2O3系统玻璃的制备及其变温发射光谱与结构特性

通过高温熔融法制备了含Eu^3 离子的Na2O-K2O-SiO2-Al2O3系统玻璃。在488nm波长光的激发下，系统地研究了上述玻璃从77K到700K温度范围的变温发光特征。发现总的荧光强度首先随温度的升高而大幅度升高，然后随温度的升高而减少，用声子辅助吸收与热激活过程及温度淬灭效应定性地解释了上述强度的变化，同时测量与分析了Eu^3 离子的晶格场参量。结果表明，Eu^3 离子与氧离子的距离随着温度升高而变短，而Eu^3 离子的配位数不随温度而变化。     

Confirming the lattice contraction in CdSe nanocrystals grown in a glass matrix by Raman scattering

This work gives the evidence of the lattice contraction in CdSe nanocrystals (NCs) grown in a glass matrix. The CdSe NCs were investigated by atomic force microscopy (AFM), optical absorption (OA), and Raman spectroscopy. The average size of CdSe NCs can be estimated by AFM images. Using the OA spectra and the effective‐mass approximation, it was also possible to estimate the average sizes of CdSe NCs, which agree very well with the AFM data. These results showed that the CdSe NCs grow with increasing time of heat treatment. The blue shift of the longitudinal optical (LO) modes and surface optical (SO) phonon modes with an increase in the average radius of the NCs, shown in the Raman spectra, was explained by the lattice contraction in CdSe NCs caused by thermodynamic interactions at the interface with the host glass matrix. Copyright © 2010 John Wiley & Sons, Ltd.     

景观湖水质的三维荧光指纹

荧光光谱法灵敏度高、选择性强、测量快速便捷,而三维荧光光谱更有信息丰富的优点。荧光光谱与水样具有一一对应的关系,就像水样指纹一样,被称为“水质荧光指纹”。 该文采用三维荧光光谱法研究了北京两个相邻景观湖四季的水质变化。两湖湖水均具有明显的类蛋白质和类腐殖酸的荧光,且类蛋白质的荧光强度较强。荧光强度与自然和人为活动的相关性表明,两湖湖水水质随季节变化明显,春夏季节水质相对较好,秋冬季节水质相对较差;以游船为主的娱乐湖的水质主要受藻类和植物生长等自然因素的影响,而种植等人为因素对植物观赏湖的水质的影响十分重要。由此可见,湖水水质的变化是由湖的功能决定的。在春秋人工清理藻类和植物的残余有利于保护湖体水质。