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51.
The barium titano-silicate phosphors doped with Eu3+ were synthesized by high temperature solid state reaction. The structures of as-synthesized samples were characterized by powder XRD. The maximum peaks of emission spectra of Ba2TiSi2O8 and Ba2TiSi2O8∶Eu3+ were respectively located at 450 and 618 nm, coming from the transitions of charge-transfer bands of Ti4+-O2- and forced electric-dipole transition 5D0-7F2 of Eu3+. The luminous mechanisms of Ba2TiSi2O8 and Ba2TiSi2O8∶Eu3+ were suggested. The effects of concentration of Eu3+ on the luminous performance of Ba2TiSi2O8∶Eu3+ were also studied and the results showed that the optimum concentration of Eu3+ was 0.12 mol per mole of matrix. 相似文献
52.
Equilibrium geometries of 16 possible isomers for C74(BN)2 were studied by INDO series of methods, to indicate that the most stable three geometries are those where boron and nitrogen atoms substitute carbon atoms located at the same hexagon near the longest axis of C78 (C2v) to form B-N-B-N unit. Electronic spectra of C74(BN)2 were investigated with INDO/CIS method. The reason for the red shift of UV absorptions for C74(BN)2 compared with those of C78 (C2v) was discussed. IR spectra for 9,8,28,29-C74(BN)2 and 28,29,30,31-C74(BN)2 were calculated on the basis of AM1 geometries. 相似文献
53.
稀土红色荧光粉SrZnO2∶Eu3+的发光性能 总被引:4,自引:0,他引:4
A series of novel luminescent materials, SrZnO2∶M (M=Eu3+, or Eu3+ + Li+) have been synthesized by high-temperature solid-state reaction. The structure and luminescence properties of SrZnO2∶Eu3+ phosphor were studied through XRD, photoluminescence and Raman spectroscopy. The excitation spectra show a broad intense band and a number of small peaks corresponding to the inner 4f-shell excitations of Eu3+ (the strongest one is at 395 nm for 7F0-5L6). After SrZnO2∶Eu3+ phosphor was co-doped with Li+ ions, its charge transfer band extended to longer wavelengths. This resulted in increase of luminescent quantum efficiency of the sample. SrZnO2∶Eu3+,Li+ phosphor can be efficiently excited by longer UV. From the fluorescence spectrum of SrZnO2∶Eu3+ phosphor, apart from transition emissions of 5D0→ 7FJ (J=0~4), the transition emissions from 5D1 → 7FJ (J=0~2) have been observed. For the SrZnO2∶Eu3+ phosphor, under excitation of UV, the dominant emission is at about 612 nm, due to the 5D0→ 7F2 hypersensitive transition. The incorporation of Li+ ions greatly enhanced the luminescence intensity and made emission peak from 5D0 → 7F2 transition red-shifted. 相似文献
54.
ShiGuoSUN XiaoJunPENG MingWenFAN YongQianXU LeiSHI LiChengSU 《中国化学快报》2004,15(8):965-968
Two novel rhenium(I) 2, 2′-bipyridyl complexes, [(4,4′-di-COOEt-bipy) Re(CO)3 (NCCH3)PF6] and [(4,4′-di-COOEt-bipy) Re (CO)3 (NCS)], a model complex [(4,4′-di-COOEt-bipy) Re (CO)3 (pyridine)PF6], were synthesized. Their ground state electronic spectra and emission spectra were measured in acetonitrile. The MLCT absorption maximum of the complex exhibited a considerable red shift as the ligand changed from pyridine to CNCH3, or SCN. 相似文献
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局部方差在图像质量评价中的应用 总被引:4,自引:0,他引:4
将灰度图像的局部方差分布(QLS)作为表征图像结构信息的一个重要特征,对局部方差分布矩阵进行奇异值分解,计算得到相应的奇异值特征向量;通过计算降质图像与原参考图像局部方差矩阵奇异值特征向量的夹角大小度量两图像的结构相似度,实现了对降质图像的质量评价。实验结果表明:局部方差分布更能突出图像的结构特征,评价结果优于传统的均方误差(MSE)、峰值信噪比(PSNR)、结构相似度(SSIM)以及直接评价图像像素分布的奇异值分析(SVD)等方法,与人眼视觉感知效果的一致性较好。 相似文献
59.
提出了一种双层相变蓄能地板辐射末端系统,该系统上下叠放蓄热层和蓄冷层,每层都内嵌毛细管网,通过蓄能和放能,实现夏季辐射供冷、冬季辐射供暖。该系统采用电驱动热泵系统为冷热源,可以实现"移峰填谷"缓解电网压力,同时提高空调的舒适性。作者搭建了两个模拟测试房间:A房间蓄冷层在上,B房间蓄热层在上。进行了供暖和供冷实验,分别测量了在蓄能和放能过程中,末端系统各结构层温度、房间内各高度室温随时间变化的情况。结果表明:当冷热源给水温度分别为40℃和15℃时,供暖时室内温度可保持在16.5℃以上;供冷时室内温度能保持27℃以下;室内垂直温差控制在3℃以内,能满足室内环境温度和热舒适性温差要求,同时还保证热泵机组工作在良好的工况范围。实验数据对比发现蓄热层在上、蓄冷层在下的结构方案(B房间)相对更加合理,该方案辐射供暖效果好,而且能降低辐射供冷时地表温度过低引起凝露的风险。 相似文献
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