混沌实验教学之路

混沌电路实验包括非线性元件如电阻或电感的选择、电路构建与波形的分析、混沌吸引子显示与模拟等内容,采用分立元件与学生自组的实验方案,坚持实验过程与理论分析相结合,是一个颇有趣味的非线性物理实验.     

传感技术在大学物理实验中的应用

随着传感技术的迅速发展,越来越多的大学物理实验开始使用各种传感器进行测量.如利用温度、位移、压力等传感器改进传统实验装置,促进大学物理实验与高新技术的融合,以提高大学物理实验的教学质量.     

3kA冷绝缘高温超导电缆的设计和短路冲击试验

为验证接入系统的高温超导电缆的暂态特性,研制了220kV/3kA 1.5米冷绝缘高温超导模型电缆,并成功进行了短路电流为40.4kArms、持续时间为2s的短路冲击试验。文中详细阐述了起到支撑、液氮流通通道和保护作用的铜骨架的设计,超导电缆本体均流设计,并对该模型电缆进行了接入系统的短路冲击试验,试验表明,该超导电缆可满足220kV电网暂态冲击要求,验证了超导电缆本体和铜骨架设计的正确和合理性。     

Local Unitary Invariants for Multipartite States

We study the invariants of arbitrary dimensional multipartite quantum states under local unitary transformations. For multipartite pure states, we give a set of invariants in terms of singular values of coefficient matrices. For multipartite mixed states, we propose a set of invariants in terms of the trace of coefficient matrices. For full rank mixed states with non-degenerate eigenvalues, this set of invariants is also the set of the necessary and sufficient conditions for the local unitary equivalence of such two states.     

A Feasible Add-On Upgrade on a Commercial Two-Photon FLIM Microscope for Optimal FLIM-FRET Imaging of CFP-YFP Pairs

Fluorescence lifetime imaging microscopy (FLIM) based on time-correlated single photon counting (TCSPC) is a widely used method for fluorescence resonance energy transfer (FRET). Here we report a feasible add-on approach to upgrade a commercial two-photon FLIM microscope into a single-photon FLIM microscope which provides optimal FLIM-FRET imaging of FRET pairs consisting of cyan fluorescent proteins (CFPs) as the donor and yellow fluorescent proteins (YFPs) as the acceptor. The capability of the upgraded system is evaluated and discussed, and the imaging performance of the system is demonstrated using FLIM-FRET experiments with a representative CFP-YFP FRET pair (mCerulean-mCitrine).     

电子磁矩对同步辐射频谱的修正

本文从偶极子辐射场的Heaviside-Feynman表达式出发, 用经典的电动力学方法推导了考虑内禀磁矩影响后的相对论电子辐射频谱分布的表达式, 并对做匀速圆周运动的极端相对论性电子的同步辐射, 计算了两个偏振方向上的考虑磁矩修正后的辐射谱. 计算结果表明对于特征频率为ω_c的同步辐射, 如果ħω_c≥10 keV, 内禀磁矩对辐射的修正是可观的. 通过同步辐射的内禀磁矩修正, 本文讨论了电子束极化度与辐射场偏振度的依赖关系, 并基于此关系提出一种测量电子束极化度的新方法. 关键词： 同步辐射 电子内禀磁矩 同步辐射偏振度 束流极化度     

链间耦合对极化子非弹性散射性质的影响

基于一维紧束缚的Su-Schreiffer-Heeger模型, 采用非绝热动力学方法, 研究了链间耦合对聚合物中极化子对非弹性散射性质的影响: 激子的产生依赖于链间耦合, 随着耦合强度的增加, 正负极化子对的电子波函数交叠增强, 利于提高激子的产率; 当耦合区域是极化子的宽度时, 正负极化子对波函数的耦合最充分、耦合最强, 电荷跃迁更容易, 激子产率最大. 关键词： 聚合物 极化子 激子     

送粉角度对激光熔覆铁基复合涂层形状特征的影响

通过分析激光熔覆过程中光束、粉末和熔池间的作用机理,建立了送粉式激光熔覆材料有效利用率的数学模型,在此基础上推导了送粉角度与工艺参数之间的定量关系式,并计算了不同送粉角度下的熔覆材料有效利用率、熔高和横截面积。结果表明,在熔覆工艺参数不变的条件下,理论计算的熔覆材料有效利用率、熔覆层高度和横截面积均随送粉角度的增加而增大,且均高于实验检测值。激光熔覆过程中,由于粉末烧损和机械损失,使熔覆材料有效利用率、熔高和横截面积随送粉角度变化出现最大值,理想送粉角度为60。     

Direct observation of surface‐enhanced Raman scattering in ZnO nanocrystals

We have been able to observe the surface‐enhanced Raman scattering (SERS) from 4‐mercaptopyridine (4‐Mpy) molecules adsorbed on ZnO nanocrystals, which display 10³ enhancement factors (EFs). An excitation wavelength‐dependent behavior is clearly observed. Another molecule BVPP is also observed to have surface‐enhanced Raman signals. The chemical enhancement is most likely responsible for the observed enhancement, since plasmon resonances are ruled out. The research is important not only for a better understanding of the SERS mechanism, but also for extension of the application of Raman spectroscopy to a variety of adsorption problems on a semiconductor surface. Copyright © 2009 John Wiley & Sons, Ltd.     

一类参数不确定统一混沌系统的脉冲滞后同步

针对一类具有传输信道时间延迟且参数不确定的统一混沌系统，提出了一种脉冲控制同步方法.该方法将两个非自治混沌系统之间脉冲同步的实用稳定性问题转化为同步误差系统在原点的实用稳定性问题，基于脉冲微分方程的相关理论，给出了同步误差系统在原点的实用稳定判据，仿真结果验证了方法的有效性. 关键词： 统一混沌系统 混沌同步 脉冲控制 实用稳定性