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41.
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。 相似文献
42.
Transparent phosphate glass ceramics co-doped with Er3+ and Yb3+ in the system P2O5Li2OCaF2TiO2 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 Ω2,4,6. 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. 相似文献
43.
First-principles study of structural stability and elastic property of pre-perovskite PbTiO3 下载免费PDF全文
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. 相似文献
44.
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. 相似文献
45.
46.
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 相似文献
47.
48.
FERRIMAGNETIC PHASES OF THE BLUME-EMERY-GRIFFITHS MODEL AND THE POTTS MODEL ON THE DIAMOND LATTICE 下载免费PDF全文
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. 相似文献
49.
50.
紫外线的应用、探测及其新发展 总被引:9,自引:0,他引:9
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。 相似文献