级联长周期光纤光栅对的干涉谱分析及其在多信道滤波器中的应用

分析了由光纤级联的两个相同的长周期光纤光栅形成的干涉谱。根据设计中的关键技术,利用粒子群优化算法设计了长周期光纤光栅传输损耗为50％的平坦传输损耗谱.将相同的两个优化设计的长周期光纤光栅级联,可以实现一种实用的可调谐多信道隔离滤波器.讨论了级联长周期光纤光栅对之间光纤的偏振特性对干涉谱的影响.     

沉积速率和生长停顿对InAs/GaAs量子点超晶格生长影响的综合分析

采用动力学蒙特卡罗模型模拟了沉积速率和生长停顿对GaAs衬底中垂直耦合InAs 量子点超晶格生长早期阶段的影响.通过对生长表面形态、岛平均尺寸、岛尺寸分布及其标准差等方面的研究,发现综合控制沉积速率和生长停顿时间能够得到大小均匀、排列有序的岛阵列.这对后续量子点超晶格生长过程中量子点的定位有重要影响. 关键词： 动力学蒙特卡罗模拟 量子点超晶格 外延生长     

Impact of GaNAs strain compensation layer on the electronic structure of InAs/GaAs quantum dots

The strain and electron energy levels of InAs/GaAs(001) quantum dots (QDs) with a GaNAs strain compensation layer (SCL) are investigated. The results show that both the hydrostatic and biaxial strain inside the QDs with a GaNAs SCL are reduced compared with those with GaAs capping layers. Moreover, most of the compressive strain in the growth surface is compensated by the tensile strain of the GaNAs SCL, which implies that the influence of the strain environment of underlying QDs upon the next-layer QDs’ growth surface is weak and suggests that the homogeneity and density of QDs can be improved. Our results are consistent with the published experimental literature. A GaNAs SCL is shown to influence the strain and band edge. As is known, the strain and the band offset affect the electronic structure, which shows that the SCL is proved to be useful to tailor the emission wavelength of QDs. Our research helps to better understand how the strain compensation technology can be applied to the growth of stacked QDs, which are useful in solar cells and laser devices.     

基于超高效液相色谱-四极杆飞行时间高分辨质谱的高通量血清代谢组学方法

采用超高效液相色谱-四极杆飞行时间高分辨质谱(UPLC-QTOFMS)联用技术, 对血清前处理进行了考察和优化, 并对液-质联用分析条件进行了优化, 旨在建立用于血清中广谱小分子代谢物分析的高通量强耐用代谢组学方法, 以期满足大批次生物样本数代谢组学研究的要求(样本数≥400个). 通过考察不同有机溶剂沉淀蛋白对血清中蛋白的去除程度及38个代表性标准品化合物的提取效果, 确定采用甲醇/乙腈(体积比1: 9)沉淀蛋白法. 血清和有机溶剂的体积比不小于1: 4时, 达到最佳的沉淀蛋白处理效果, 符合大批量样本测试的要求; 预先冷藏沉淀蛋白的有机溶剂, 涡旋2 min, 超声1 min, 加入有机溶剂后冷冻静置10 min, 可以进一步提高前处理沉淀蛋白和化合物提取的效果. 通过对不同流动相体系和梯度条件的考察, 对液-质联用分析条件进行了优化. 方法学考察结果表明, 本方法重现性、 精密度及稳定性均良好. 对重现性和48 h稳定性数据进行变异系数分析和主成分分析法的多维分析, 证明本方法在代谢组学研究中的可重复性及所得数据的可靠性. 本方法高通量强耐用, 每天可测定100多个血清样本(13 min测定1个样本), 适用于代谢组学研究, 特别是大批次生物样本的代谢组学研究.     

Electronic structures of stacked layers quantum dots: influence of the non-perfect alignment and the applied electric field

Electronic structures of the artificial molecule comprising two truncated pyramidal quantum dots vertically coupled and embedded in the matrix are theoretically analysed via the finite element method.When the quantum dots are completely aligned,the electron energy levels decrease with the horizontally applied electric field.However,energy levels may have the maxima at non-zero electric field if the dots are staggered by a distance of several nanometers in the same direction of the electric field.In addition to shifting the energy levels,the electric field can also manipulate the electron wavefunctions confined in the quantum dots,in company with the non-perfect alignment.     

The equilibrium composition in GexSi1-x/Si self-assembled alloy quantum dot

<正>The equilibrium composition in strained quantum dot is the result of both elastic relaxation and chemical mixing effects,which have a direct relationship to the optical and electronic properties of the quantum-dot-based device.Using the method of moving asymptotes and finite element tools,an efficient technique has been developed to compute the composition profile by minimising the Gibbs free energy in self-assembled alloy quantum dot.In this paper,the composition of dome-shaped Ge_xSi_(1-x)/Si quantum dot is optimized,and the contribution of the different energy to equilibrium composition is discussed.The effect of composition on the critical size for shape transition of pyramid-shaped GeSi quantum dot is also studied.     

水滑石衍生复合氧化物的CO催化还原NO的性能

研究了以含Co水滑石类化合物为前体、经焙烧制得的复合氧化物催化剂对CO催化还原NO的催化作用,结果表明,这样制得的催化剂的活性远远高于由传统方法制备的具有尖晶石结构的催化剂,反应分步进行,NO先与CO反应生成N2O和CO2,随着反应温度的升高,最终得到的是N2和CO2,在所考察的催化剂中,反应活性随催化剂中Co含量的增加而升高,随焙烧温度的升高而降低,催化剂中晶格缺陷对活性有重要影响。     

基于连续弹性理论分析量子线线宽对应变分布和带隙的影响

基于连续弹性理论分别采用数值方法和格林函数法讨论了量子线的应变分布.格林函数法可以得到应变分布的解析表示式,对规则形状的量子线的应变分布计算比较方便;连续弹性理论采取的是数值解法,结果精度不如格林函数法,但是能方便计算任意形状量子线的应变分布情况, 并可以考虑不同材料的弹性常数的影响.文章还具体讨论了量子线线宽对应变分布和带隙的影响,结果表明：沿线宽方向,应变的绝对值逐渐减小,并随线宽的增加而变大;带隙则随线宽的减小而增大. 关键词： 连续弹性理论 格林函数法 应变 带隙     

有限元法分析不同形状量子点的应变能及弛豫度变化

利用有限元方法研究了不同形状量子点的应变能量分布和弛豫度随着高宽比变化的规律.分析了量子点间距和量子点形状对量子点应变弛豫的影响,定量地讨论了量子点的弛豫度与量子点形状之间的关系.计算结果表明,在不考虑表面能的情况下,当量子点高宽比增加时,弛豫度上升,并且发现平顶金字塔形量子点最先达到稳定;岛间距增大时,量子点内应变能下降,其中立方体形量子点应变能下降最快.研究表明,量子点的弛豫度可以成为控制量子点成岛形状的重要依据. 关键词： 量子点 弛豫度     

Designing of the 14 MeV neutron moderator for BNCT

In boron neutron capture therapy (BNCT), the ratio of the fast neutron flux to the neutron flux in the tumor (RFNT) must be less than 3%. If a D-T neutron generator is used in BNCT, the 14 MeV neutron moderator must be optimized to reduce the RFNT. Based on the neutron moderation theory and the simulation results, tungsten, lead and diamond were used to moderate the 14 MeV neutrons. Satisfying RFNT of less than 3%, the maximum neutron flux in the tumor was achieved with a three-layer moderator comprised of a 3 cm thick tungsten layer, a 14 cm thick lead layer and a 21 cm thick diamond layer.