The randomly fluctuating impurity strength initiated excitation in doped quantum dots

We investigate the excitation behavior of a repulsive impurity doped quantum dot under the influence of randomly fluctuating dopant potential. We have considered Gaussian impurity centers doped at different locations. The investigation reveals the interplay between dopant location and dopant’s spatial stretch in modulating the excitation pattern. Maximization in the excitation rate has been observed as a function of fluctuating dopant strength owing to the conflict between opposing influences that promote and hinder excitation.     

半绝缘GaAs光电导开关非线性电脉冲超快上升特性研究

利用流体模型对光生载流子的输运进行了模拟研究,结果表明载流子在输运过程中形成的光激发电荷畴是产生电脉冲超快上升特性的主要原因.对光激发电荷畴的形成和吸收过程的进一步研究表明：1)形成过程中的光激发电荷畴增强了电子的浓度梯度;2)光激发电荷畴在被阳极吸收的过程中,光电导开关偏置电压的快速下降能促进电流上升速度.光激发电荷畴的形成和吸收两大过程共同作用下,形成了电脉冲的超快上升特性. 关键词： 光电导开关 非线性模式 光激发电荷畴 上升时间     

计算机模拟光波的干涉

采用时域有限差分方法模拟了光的干涉这一物理现象.在物理实验的教学过程中光学实验以其高精度、高复杂度使得在实验教学过程中产生了一些负面影响.学生往往花费了较大精力去调节仪器,最终却得不到满意的实验数据,甚至得不到正确的实验结果.针对这一问题,可以采用数值模拟的方法得到很好的解决.文中不但模拟了实验现象,还验证了实验的理论公式,使得学生在观察现象的同时,对理论公式也能产生深刻的认识,最终起到了良好的课堂效果.     

铁电体中新畴成核经典模型的改进

新畴成核是外加低场下铁电体中铁电畴反转的一个重要的过程.首先介绍了新畴成核的经典模型,采用该模型研究了铁电畴反转的新畴成核过程,发现理论计算的成核速率与外场关系和实验观测结果不一致.在Tagantsev模型的基础上,选取不同的成核形状对新畴成核的经典模型进行了改进,并获得了和实验观测相符的理论计算结果. 关键词： 铁电体 铁电畴 成核速率     

三维时域有限差分法计算金纳米粒子尺寸与SERS活性的关联

通过合成一系列不同粒径(16～160 nm)的金纳米粒子.观察到120～135 nm的金纳米粒子在632.8nm波长激发下具有最高的SERS活性,这与前人报道的电磁场理论及实验的结果不同.利用三维时域有限差分法对金纳米粒子的SERS活性与其尺寸以及入射光波长的关系进行模拟计算.在632.8 nm激发线下,金纳米粒子二聚体体系在粒径为110 nm左右具有最佳增强效应,其光电场耦合最强的热点处的增强因子高达109考虑到体系的平均SERS增强因子通常会比最大值低约2个数量级,计算得到的107的增强因子与实验测量值相符.同时对目前实验上尚难以合成的大尺寸的金纳米粒子进行模拟,结果表明受多极矩和大尺寸效应的影响在粒径220 nm时又出现SERS增强另一峰值.在325 nm的紫外激发线下,计算得到的增强因子仅为102.     

Correlation of Cooperatively Localized Rearrangement on the “Fluidized Domain” of Polymers to Their Nonexponentially Viscoelastic Behaviors at Double Aging Processes (I): A Set of Reduced Universal Equations on the Stress Relaxation Modulus and Creep Comp

基于α-和β-微区、微晶、交联和缠结链组网络结构和非线性粘弹性复相涨落模型,提出了双重(物理和力学)老化下不同尺寸和末端向量高分子链组的流动化微区内关联性局部化重排动力学新理论,它能把初级α-微区的降解作用和次级β-微区的再生效应对剪切速率、尺寸大小和温度依赖性有机结合起来．然后用统计力学和动力学结合法计算了三种不同类型高聚物在等温等压双重老化过程中多元链组的总构象改变自由能,证实了它起源于多元链组的尺寸大小、形状和体积的变化．推导出了它们单向拉伸下的本构方程、应力松弛模量和蠕变柔量表征式以及它们相对应的两组对比态普适方程．结果表明该两组对比态下应力松弛模量和蠕变柔量普适方程均具有同K-W-W伸展指数函数完全一致的形式．最终又建立了该两组对比态普适方程中三个分子参数同老化条件、温度和高聚物起始结构之间的相关性．     

High Tc superconductors with different Cu2+/Cu3+ ratios in the Y–Ba–Cu–O system

Studies on different phases in the Y-Ba-Cu-O system have revealed that T_C around 90 K is obtainable with different Cu /Cu ratios provided the correct oxygen proportion is maintained.     

Plasmonic planar lens based on stack of metal–insulator–metal waveguides with height tuning

We introduce a technique capable of focusing electromagnetic (EM) waves through plasmonic nanoslits symmetrically arranged along the indented semi-circular surface in silver background. The EM transports through the tuning slits in the form of surface plasmon polaritons (SPPs), and gets the required phase retardations to focus at the focal plane. Due to the subwavelength nature of planar metallic lens, we present the rigorous electromagnetic analysis by using two dimensional (2D) finite difference time domain (FDTD) method. These height-modulated slits with uniform width are demonstrated to have unique advantages in beam manipulation. In combination with previous studies, it is expected that our structure with small number of slits could lead to realization of optimum designs of plasmonic nano-lens.     

Krull property of generalized power series rings

Let D be an integral domain and let $(S,\le )$ be a torsion-free, ≤-cancellative, subtotally ordered monoid. We show that the generalized power series ring $?D^{S,\le }?$ is a Krull domain if and only if D is a Krull domain and S is a Krull monoid.