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71.
Luminescence characteristics of Eu3+ activated borate phosphor for white light emitting diode 下载免费PDF全文
In this paper, the Sr3Y2 (BO3)4:Eu3+ phosphor was synthesized by high temperature solid-state reaction method and the luminescence characteristics were investigated. The emission spectrum exhibits one strong red emission at 613nm corresponding to the electric dipole 5D0--7F2 transition of Eu3+ under 365nm excitation, this is because Eu3+ substituted for Y3+ occupied the non-centrosymmetric position in the crystal structure of Sr3Y2 (BO3)4. The excitation spectrum indicates that the phosphor can be effectively excited by ultraviolet (254nm, 365nm and 400nm) and blue (470nm) light. The effect of Eu3+ concentration on the red emission of Sr3Y2 (BO3)4:Eu3+ was measured, the result shows that the emission intensities increase with increasing Eu3+ concentration, then decrease. The Commission Internationale del'Eclairage chromaticity (x, y) of Sr3Y2(BO3)4:Eu3+ phosphor is (0.640,0.355) at 15 mol% Eu3+. 相似文献
72.
噪音对光学图象浑沌相位列阵加密和解密的影响 总被引:1,自引:0,他引:1
本文提出了一种用浑沌相位列阵对光学图象加密和解密的方法,并重点分析了加法高斯白噪音对光学图象浑沌相位列阵加密和解密的影响.通过计算机模拟发现加密后的图象与原图象相比,抗振幅噪音的能力增强,而抗相位噪音的能力下降.在一定信噪比范围内,相位噪音是影响解密图象质量的主要因素. 相似文献
73.
In the last paper, the geometry of the Sz.-Nagy-Foia
model for contraction operators on Hilbert spaces was used to advantage in several problems of multivariate analysis. The lifting of intertwining operators, one of the basic results from the Sz.-Nagy-Foia
theory, is now recognized as the most adequate operatorial form of the deep classical results of the extrapolation theory. The labeling of the exact intertwining dilations given by [1]Acta Sci. Math. (Szeged) 40 9–32] and the recursive methods used there open a broad perspective for using the Sz.-Nagy-Foia
model in multivariate filtering theory. In this paper, using the notion of correlated action (see [5 and 6] Rev. Roumaine Math. Pures Appl. 23, No. 9 1393–1423]) as a time domain, a linear filtering problem is formulated and its solution in terms of the coefficients of the analytic function which factorizes the spectral distribution of the known data and the coefficients of an analytic function which describes the cross correlations is given. In some special cases it is shown that the filter coefficients can be determined using recursive methods from the intertwining dilation theory, of the autocorrelation function of the known data and an intertwining operator, interpreted as the initial estimator given by the prior statistics. 相似文献
74.
Non-doped type white organic electroluminescent (EL) devices using vacuum-deposited organic thin films of blue-emitting 4,4-bis(2,2 diphenylvinyl)-1,1-biphenyl (DPVBi) and yellow-emitting ultrathin 5,6,11,12-tetraphenylnaphthacene (rubrene) to generate white emission were fabricated. The two emitting layers are separated by an electron blocking layer of N,N-bis-(1-naphthyl)-N,N-diphenyl-1,1-biph-enyl-4,4-diamine (NPB). The thickness of the blocking layer determines the spectrum of the devices. In a device with 5 nm electron blocker of NPB, the CIE coordinates were well within the white region for voltage raging from 3 V to 14 V. The device has a maximum luminance of 7400 cd/m2(at current density of 830 mA/cm2) and maximum power efficiency of 1.67 lm/W at 5 V. 相似文献
75.
Gang?ChengEmail author Yi?Zhao Jingying?Hou Yu?Duan Yuguang?Ma Shiyong?Liu 《Optical and Quantum Electronics》2004,36(14):1193-1203
In view of their potential applications in flat panel displays, organic light-emitting devices have attracted much attention in the past decade. A challenging target in this field is to realize full color display applications. One of the approaches proposed for these is combining white emission with color filters, where efficient and pure white emission (especially at high brightness) is necessary. In this paper, three kinds of white organic light-emitting devices with different structures and materials are fabricated and their characteristics are discussed. 相似文献
76.
A 'chaos expansion' of the intersection local time functional of two independent Brownian motions in R
d
is given. The expansion is in terms of normal products of white noise (corresponding to multiple Wiener integrals). As a consequence of the local structure of the normal products, the kernel functions in the expansion are explicitly given and exhibit clearly the dimension dependent singularities of the local time functional. Their L
p
-properties are discussed. An important tool for deriving the chaos expansion is a computation of the 'S-transform' of the corresponding regularized intersection local times and a control about their singular limit. 相似文献
77.
78.
用高温固相法合成了Eu2+,Mn2+共激活的Ca2SiO3Cl2高亮度白色发光材料,并对其发光性质进行了研究. 该荧光粉在近紫外光激发下发出强的白色荧光,Eu2+中心形成峰值为419 nm和498 nm的特征宽带,通过Eu2+中心向Mn2+中心的能量传递导致了峰值为578 nm的发射,三个谱带叠加从而在单一基质中得到了白光. 激发光谱均分布在250—415 nm的波长范围,红绿蓝三个发射带的激发谱峰值分别位于385 nm,412 nm,370 nm和396 nm处,可以被InGaN管芯产生的紫外辐射有效激发. Ca2SiO3Cl2:Eu2+,Mn2+是一种很有前途的单一基质白光LED荧光粉. 相似文献
79.
80.
Yunhua Xu Rong Guan Jiaxing Jiang Wei Yang Hongyu Zhen Junbiao Peng Yong Cao 《Journal of polymer science. Part A, Polymer chemistry》2008,46(2):453-463
A new strategy to realize efficient white‐light emission from a binary fluorene‐based copolymer (PF‐Phq) with the fluorene segment as a blue emitter and the iridium complex, 9‐iridium(III)bis(2‐(2‐phenyl‐quinoline‐N,C3′)(11,13‐tetradecanedionate))‐3,6‐carbazole (Phq), as a red emitter has been proposed and demonstrated. The photo‐ and electroluminescence properties of the PF‐Phq copolymers were investigated. White‐light emission with two bands of blue and red was achieved from the binary copolymers. The efficiency increased with increasing concentration of iridium complex, which resulted from its efficient phosphorescence emission and the weak phosphorescent quenching due to its lower triplet energy level than that of polyfluorene. In comparison with the binary copolymer, the efficiency and color purity of the ternary copolymers (PF‐Phq‐BT) were improved by introducing fluorescent green benzothiadiazole (BT) unit into polyfluorene backbone. This was ascribed to the exciton confinement of the benzothiadiazole unit, which allowed efficient singlet energy transfer from fluorene segment to BT unit and avoided the triplet quenching resulted from the higher triplet energy levels of phosphorescent green emitters than that of polyfluorene. The phosphorescence quenching is a key factor in the design of white light‐emitting polyfluorene with triplet emitter. It is shown that using singlet green and triplet red emitters is an efficient approach to reduce and even avoid the phosphorescence quenching in the fluorene‐based copolymers. The strategy to incorporate singlet green emitter to polyfluorene backbone and to attach triplet red species to the side chain is promising for white polymer light‐emitting diodes. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 453–463, 2008 相似文献