Simulation study on the quantitative phase retrieval method under two-step phase-shifting technique

Based on two-step phase-shifting technique, we present a new derivative method for phase information extraction in quantitative phase imaging (QPI). By acquiring two phase-shifted interferograms and numerically calculating their 1st order derivatives, one can directly obtain the quantitative phase information. We demonstrate the proposed method by comparing our simulated results with the experimental results of the red blood cell and the HeLa cell, respectively. It shows that our method can be generally applied to any QPI, such as on-axis and off-axis interferometry, especially for slightly off-axis interferometry, and it has the feature of efficient utility of camera spatial bandwidth and the ability of fast data processing.     

抗混叠轮廓波域采用压缩感知的云图融合方法

提出一种采用压缩感知的云图融合方法.该方法针对传统轮廓波存在频谱混叠的缺点,结合抗混叠塔式滤波器组和方向滤波器组,构造出一种抗混叠的轮廓波变换,并将其引入压缩感知中的稀疏表示环节,将云图分解成稠密和稀疏两部分|对稠密成份采用传统方法进行融合,而对稀疏成份,则在压缩感知框架下,通过少数线性测量的融合,并采用二步迭代收缩的图像重构算法,在迭代时利用前面两个估计值更新当前值,得到融合结果.实验表明,该方法的融合结果无论在视觉质量及定量指标上都明显优于传统方法,有利于揭示全面的天气信息.     

Zn-Mg合金的结构分析和Zn-Mg扩散体系的物相分布

分子动力学(MD)模拟常采用径向分布函数(RDF)、Honeycutt-Anderson (HA)键型指数法、原子团类型指数法(CTIM)表征物相的微观结构. 本文依据CTIM 理论, 对CTIM 进一步发展, 使CTIM 不仅能够表征bcc\fcc\hcp\非晶体, 也能表征其它晶系的晶体结构. 本文采用CTIM 完成Zn-Mg 合金标准晶体的结构表征和Zn-Mg扩散体系物相分布的分析. 结果表明: 合金组元的CTIM指数不仅反映了Mg₂₁Zn₂₅、MgZn₂、Mg₂Zn₁₁晶体结构的差异, 也说明了Mg₄Zn₇、MgZn₂晶体结构十分相近. Zn-Mg扩散体系两步法模拟后, 体系两端交替分布着hcp 与fcc 结构; 体系中部形成大量的非晶体; Zn原子端交替分布着hcp 与fcc 结构的界面区域主要是Zn12-C类原子.     

Copula models for insurance claim numbers with excess zeros and time-dependence

This paper develops two copula models for fitting the insurance claim numbers with excess zeros and time-dependence. The joint distribution of the claims in two successive periods is modeled by a copula with discrete or continuous marginal distributions. The first model fits two successive claims by a bivariate copula with discrete marginal distributions. In the second model, a copula is used to model the random effects of the conjoint numbers of successive claims with continuous marginal distributions. Zero-inflated phenomenon is taken into account in the above copula models. The maximum likelihood is applied to estimate the parameters of the discrete copula model. A two-step procedure is proposed to estimate the parameters in the second model, with the first step to estimate the marginals, followed by the second step to estimate the unobserved random effect variables and the copula parameter. Simulations are performed to assess the proposed models and methodologies.     

基于主元分析的随机相移算法

将统计理论中的主元分析应用到干涉条纹分析中,提出一种基于主元分析的随机相移算法。该算法先将多帧条纹数据分解成不相关的主元成分,然后从主元成分中提取2维相位信息。数值模拟结果表明:该算法不需要迭代运算就能从4帧完全随机相移干涉图中有效提取相位信息,运算时间少,精度高。实验结果表明主元分析相移算法比现有迭代相移算法更适合于随机相移干涉图分析。     

投影栅相移法中的相位波动误差及修正算法研究

分析了因测量系统非线性响应及局部饱和投影栅图像所导致的相位误差及其波动特性。经过实验验证,四步相移算法在抑制系统非线性响应所引起的相位误差方面优于三步相移算法。通过模拟分析得出,在采用传统相移算法对局部饱和条纹图像分析时,相位误差较大,且相位分布具有周期波动特性。为减小因图像局部饱和而产生的相位误差,文中采用了新的算法提取相位。实验分析结果验证了算法的正确性。     

光学干涉计量中的位相测量方法

对光学干涉计量中常用的位相测量方法进行了综述,包括时间相移法、空间相移法、空间载波相移法和Fourier变换法以及位相展开问题。     

铊玻璃自聚焦透镜边缘折射率分布的改进

本文用雅明干涉仪测定第一次离子交换后的径向折射率分布,边缘部分与理想分布有极大的偏差。在此基础上并进行了第二步高于交换,测定其边缘分布有进一步改进,同时,第二次成象比第一次有明显的改善。     

Preparation,Characterization of Ternary Europium Complex-Doped Thin Sol-Gel Hybrid Film by Fluorescence Spectroscopy

ernary europium complex with dibenzoylmethane(DBM), 1,10-phenanthroline(phen) was in-situ syn thesized in thin SiO₂/polyvinyl butyral(PVB) hybrid films by a two-step sol-gel process, characterized by means of fluorescence spectroscopy. The luminescence spectra, fluorescence lifetimes, photostability were all investigated. The results showed that the hybrid films exhibited the characteristic emission bands of the central rare earth Eu³⁺. In addition, Eu³⁺ presented longer fluorescence lifetime than in an ethanol solution, the complex had a higher photostability in the hybrid film than in the PVB film containing the corresponding pure complex.