A study on the short—wavelength and high—numerical—aperture phase—change recording

In this paper, we discuss the phase-change recording at a short-wavelength (514nm) and a high numerical aperture (0.85). Effects of recording power and pulse width on the size of the recording marks are studied. The minimum recording mark with a length of approximately 220nm has been observed. The capacity of about 17GB for a single-layer disc of a 12cm diameter can be obtained. The maximum carrier-to-noise ratio reaches 45dB at a writing power of 13--14mW.     

Simulation of current spreading for GaN-based light-emitting diodes

Uniform current spreading is crucial for the performance of light-emitting diodes (LEDs). It has been reported that the reliability and light distribution are affected by non-uniform current spreading. In this paper, the impact of different electrode patterns on the performance of LED chips is investigated. A hybrid modeling method is employed to analyze the electrical and thermal characteristics of LEDs with two different electrode mesa structures. Corresponding experiments are also carried out to validate the calculation results. It is found that increasing amount of p-electrodes in interdigitated electrode patterns is effective in improving the performance of LEDs.     

有机薄膜光盘的微区结构

通过光学显微镜（ＯＭ）扫描电镜（ＳＥＭ）和扫描隧道显微镜（ＳＴＭ）观察了光记录有机薄膜的微区结构，从微区结构的形貌可以看出光记录后酞菁薄膜上产生了鼓泡，通过这些观察方法的比较发现扫描隧道显微镜可以提供更加详细，精确的三维参数，薄膜的微区结构研究对于分析光盘的性能，了解记录机理具有重要意义。     

周期性磁谐振材料本构参数的理论分析

将薄的磁谐振介质板等效为面磁流, 利用周期性边界条件, 给出了面磁流的指数形式. 通过计算无穷个面磁流在不同空间位置上产生的总电场和总磁场, 推导出了周期性磁谐振人工材料的色散关系和布洛赫阻抗, 进而获取了布洛赫本构参数的理论计算公式. 由于考虑了磁谐振人工材料中的电反谐振对布洛赫介电常数和磁导率的影响, 所以基于仿真实验的布洛赫本构参数的提取值和布洛赫本构参数理论预测值之间的误差很小, 这说明本文推导的布洛赫本构参数的理论计算公式在描述周期性磁谐振材料的电磁特性方面是十分有效的. 这些理论公式将在解释磁谐振现象、设计和优化周期性磁谐振材料等方面提供重要的理论依据. 关键词： 周期性结构 磁谐振 布洛赫本构参数 面磁流     

Stray light analysis of low-level-light optical system with LightTools software北大核心CSCD

为解决低照度微弱信号探测的微光光学系统杂散光问题,研究了杂散光的原理和特性。利用光学系统建模软件LightTools对微光光学系统进行仿真建模,并开展杂散光分析。为减少杂散光,在物镜筒的筒壁加工消光螺纹,并针对不同形式的消光螺纹,开展了能量仿真模拟。仿真结果表明,采用螺距0.35 mm的消光螺纹,能够将杂散光系数从7%降低到4%。仿真分析结果与实验结果一致,为其他微弱信号探测光学系统在设计阶段对杂散光进行消除提供了指导。     

广义极限鞅的一个收敛定理

本文引进了广义极限鞅的概念,证明了 L~1有界的广义极限鞅 a.s.收敛于—可积随机变量。这样推广了通常极限鞅的相应收敛定理,并回答了 Stout 提出的问题:L~1有界的弱鞅在一定的条件下是 a.s.收敛的。     

举办《应用数学学校》和参加数学应用数学建模竞赛的实践和思考

通过开展应用数学教学活动和开办《应用数学学校》的多年实践 ,我校学生结合实际学习和应用数学知识的意识和能力不断提高 ,在上海市数学知识应用竞赛和美国大学生数学建模竞赛中连续取得好成绩 ,为了争取把这项工作做得更好 ,我们作了进一步思考和打算     

B值鞅不等式与Banach空间几何性质的刻划

本文建立了Ｂ值鞅的极大函数ｆ，平削函数ｆｐ＾＃，ｆｐ＾＃的凸Φ－不等式，反过来用这些不等式刻划了Ｂａｎａｃｈ空间的凸性和光滑性，同时给出了超自反空间以及与Ｈｉｌｂｅｒｔ空间同构的Ｂａｎａｃｈ空间的特征。本文的结论推广了一些熟知的重要结果。     

The first pulsar discovered by FAST

<正>To assist with the commissioning [1] of the Five-hundredmeter Aperture Spherical radio Telescope (FAST), we performed a pulsar search, with the primary goal of developing and testing the pulsar data acquisition and processing pipelines. We tested and used three pipelines, two (P1 and P2 hereafter) searched for the periodic signature of pulsars     

Temperature Dependence of In-plane Resistivity and Inverse Hall Angle in NLED Holographic Model

In the strange metal phase of the high-Tc cuprates, it is challenging to explain the linear temperature dependence of the in-plane resistivity and the quadratic temperature dependence of the inverse Hall angle. In this paper, we investigate the temperature dependence of the in-plane resistivity and inverse Hall angle in the nonlinear electrodynamics holographic model developed in our recent work. Maxwell electrodynamics and Born-Infeld electrodynamics are considered. Both cases support a wide spectrum of temperature scalings in parameter space. For Maxwell electrodynamics, the T-linear in-plane resistivity generally dominates at low temperatures and survives into higher temperatures in a narrow strip-like manner. Meanwhile, the T-quadratic inverse Hall angle dominates at high temperatures and extends down to lower temperatures. The overlap between the T-linear in-plane resistivity and the T-quadratic inverse Hall angle, if occurs, would generally present in the intermediate temperate regime. The Born-Infeld case with a 0 is quite similar to the Maxwell case. For the Born-Infeld case with a 0, there can be a constraint on the charge density and magnetic field. Moreover, the overlap can occur for strong charge density.