用时间分辨光谱研究红细胞悬液的荧光发射

实验获得了激光照射红细胞悬液的荧光光谱,并分别监测不同荧光峰值波长处强度随时间的衰变过程,测试了其相应的荧光寿命。结果表明,在波长为407nm的激光照射下,红细胞悬液向外发射中心波长分别位于596,628,692nm的荧光光谱,各荧光峰对应衰变过程的平均荧光寿命分别为1.97,13.31,14.58ns。利用荧光强度和吸收率的加和性表示了混合物的总吸收率和总荧光发射强度,通过理论计算获得了红细胞悬液中锌卟啉、原卟啉和其他游离物参与荧光发射的相对含量和相对强度在不同荧光峰位的变化关系,进一步解释了不同峰位处荧光发射强度和平均荧光寿命的变化原因。     

Fabrication and luminescence behavior of phosphate glass ceramics co-doped with Er3+ and Yb3+

Transparent phosphate glass ceramics co-doped with Er³⁺ and Yb³⁺ in the system P₂O₅Li₂OCaF₂TiO₂ were successfully synthesized by melt-quenching and subsequent heating. Formation of the nanocrystals was confirmed by X-ray powder diffraction. Judd–Ofelt analyses of Er³⁺ ions in the precursor glasses and glass ceramics were performed to evaluate the intensity parameters Ω_2,4,6. Under 975 nm excitation, intense upconversion (UC) and infrared emission (1545 nm) were observed in the glass ceramics by efficient energy transfer from Yb³⁺ to Er³⁺. The luminescence processes were explained and the emission cross section was calculated by Fuchtbauer–Ladenburg (F–L) formula. The results confirm the potential applications of Er³⁺/Yb³⁺ co-doped glass ceramics as laser and fiber amplifier media.     

First-principles study of structural stability and elastic property of pre-perovskite PbTiO3

The structural stability and the elastic properties of a novel structure of lead titanate,which is named preperovskite PbTiO₃ （PP-PTO） and is constructed with TiO₆ octahedral columns arranged in a one-dimensional manner,are investigated by using first-principles calculations.PP-PTO is energetically unstable compared with conventional perovskite phases,however it is mechanically stable.The equilibrium transition pressures for changing from preperovskite to cubic and tetragonal phases are 0.5 GPa and 1.4 GPa,respectively,with first-order characteristics.Further,the differences in elastic properties between pre-perovskite and conventional perovskite phases are discussed for the covalent bonding network,which shows a highly anisotropic character in PP-PTO.This study provides a crucial insight into the structural stabilities of PP-PTO and conventional perovskite.     

Doctor-bladed Cu2ZnSnS4 light absorption layer for low-cost solar cell application

The doctor-blade method is investigated for the preparation of Cu2ZnSnS4 films for low-cost solar cell application.Cu2ZnSnS4 precursor powder,the main raw material for the doctor-blade paste,is synthesized by a simple ball-milling process.The doctor-bladed Cu2ZnSnS4 films are annealed in N2 ambient under various conditions and characterized by X-ray diffraction,ultraviolent/vis spectrophotometry,scanning electron microscopy,and current-voltage(J-V) meansurement.Our experimental results indicate that(i) the X-ray diffraction peaks of the Cu2ZnSnS4 precursor powder each show a red shift of about 0.4°;(ii) the high-temperature annealing process can effectively improve the crystallinity of the doctor-bladed Cu 2 ZnSnS 4,whereas an overlong annealing introduces defects;(iii) the band gap value of the doctor-bladed Cu 2 ZnSnS 4 is around 1.41 eV;(iv) the short-circuit current density,the open-circuit voltage,the fill factor,and the efficiency of the best Cu2ZnSnS4 solar cell obtained with the superstrate structure of fluorine-doped tin oxide glass/TiO2/In2S3/Cu2ZnSnS4/Mo are 7.82 mA/cm2,240 mV,0.29,and 0.55%,respectively.     

Geometric convergence of rational approximations toe −z in infinite sectors

Summary In this paper, we study the geometric convergence of rational approximations toe ^–z in infinite sectors symmetric about the positive real axis.Research supported in part by the Air Force Office of Scientific Research under Grant AFOSR-74-2688, and by the University of South Florida Research CouncilResearch supported in part by the Air Force Office of Scientific Research under Grant AFOSR-74-2729, and by the Atomic Energy Commission under Grant AT (11-1)-2075     

熊猫光纤的结构与双折射特性关系研究

本文用微元算法研究了熊猫光纤的结构参量对熊猫光纤双折射特性(拍长)的影响.由实验数据拟合出了计算拍长的熊猫光纤掺杂区的有效热膨胀系数.计算结果表明,熊猫光纤的猫眼半径、猫眼与纤芯的距离、猫眼的不一致等都是影响拍长的因素.所得结果对熊猫光纤的制作提供了理论指导.     

FERRIMAGNETIC PHASES OF THE BLUME-EMERY-GRIFFITHS MODEL AND THE POTTS MODEL ON THE DIAMOND LATTICE

The phase transitions in the Blume-Emery-Griffiths (BEG) model and antiferromagnetic Potts model on the diamond lattice are investigated using the cluster-variation method in the pair approximation. The ferrimagnetic phases are found to be different from those on the simple-cubic lattice. The phase diagrams of the BEG model are also calculated. In the vicinity of the parameter line where the BEG model reduces to the three-state antiferromagnetic Potts model, new types of phase diagram are obtained. The results are different from those of the mean-field theory, which is a good approximation only for large coordination number of the lattice.     

一种采用JPEG标准的实时视频图像压缩处理系统

本文重点探讨了在设计ＪＰＥＧ视频压缩应用系统时，应着重考虑的几个重要技术问题，并介绍了一种采用以ＰＣ为平台，以ＣＬ５５０视频压缩处理器和８２Ｃ９００１视频窗口控制器为基础的实时视频图像压缩处理系统。描述了该系统总体构成，深入讨论了图像数据缓冲存储和压缩速率控制等关键技术问题。     

紫外线的应用、探测及其新发展

紫外辐射在电磁辐射波谱中的波长范围为４００～１０ｎｍ。随着波长的变化，紫外线具有各种不同的物理特性和效应。本文概述了各种紫外线效应及其应用，尤其指出了它在军事应用方面的新发展及其广阔前景，例如：紫外线制导，紫外线告警，紫外线通讯和干扰等。上述应用得到了广泛的重视和迅猛的发展。紫外技术的应用与探测技术有关。本文指出了紫外探测的三种方法：紫外荧光转换法，分光光度法和卫星遥感法。并着重指出了上述应用中需解决的有关探测技术方面的关键问题：紫外大气传输理论和散射模型及其仿真系统，新型高灵敏度低噪声紫外探测器，低噪声信息处理系统，高性能紫外光源和紫外光学系统。