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排序方式: 共有479条查询结果,搜索用时 31 毫秒
31.
Solid-solution red phosphors for white LEDs 总被引:1,自引:0,他引:1
Gwan-Hyoung Lee 《Journal of luminescence》2011,131(12):2582-2588
Solid solutions of Eu3+-doped metal tungstate and molybdate phosphors were synthesized by solid-state reactions. The crystal structure of the solid-solution phosphors was determined to be tetragonal with a space group of I41/c. The red-emitting solid-solution phosphors exhibited a broad absorption band in the range 220-340 nm and sharp excitation peaks in the near UV to green region. The emission intensities of the solid-solution phosphors were enhanced due to the stiff lattices, as a result of the ordered distribution of cations and anions according to differences in ionic size. The increase in the energy transfer is discussed in terms of metal-ligand distances, ionization potential of Mo and the relatively large overlap between the excitation and emission spectra. Such solid-solution phosphors with a bright red emission intensity, relatively short decay time and appropriate color chromaticity have potential for use as red-emitting materials for white LEDs. 相似文献
32.
Alban A. Letailleur Sergey Yu Grachev Elin Søndergård Christophe Couteau Gilles Lérondel Emmanuelle Peter 《Journal of luminescence》2011,131(12):2646-2651
The application of alumina-doped ZnO (AZO) films as luminescent material for large area lighting sources has been evaluated. Thin films were grown on quartz using magnetron sputtering and subsequently annealed under argon atmosphere in a rapid thermal annealing experiment. Below 550 °C, red-shift of the optical band gap and increase of the visible emission are observed in agreement with Al diffusion and formation of interstitial oxygen atoms. At temperatures higher than 800 °C, diffusion is activated and Ostwald ripening leads to the formation of larger grains and an increase of the crystalline phase. The photoluminescence (PL) intensity is enhanced, specifically in the UV range. As a result the emission spectrum of AZO thin films can be adjusted by the annealing conditions, with equal contributions from the UV and orange parts of the PL spectrum resulting in an efficient white emission as quantified using the color space map of the Commission Internationale de l'Éclairage. 相似文献
33.
Wenyu Ji Letian Zhang Mo Liu Jing Wang Guoqiang Liu Wenfa Xie Hanzhuang Zhang 《Current Applied Physics》2011,11(6):1410-1413
White top-emitting organic light-emitting devices (TEOLEDs) were fabricated on a glass substrate with metal/organic multilayer of (Ag/Alq3)2 (Alq3 is tris-(8-hydroxyquinoline) aluminum) as cathode. White TEOLEDs with high efficiency were obtained due to the microcavity effects. And the (Ag/Alq3)2 cathode, which adjusted the optical characteristics of the devices, played an important role. In addition, Alq3–Ag–Alq3 multilayer could work as a buffer layer, which would simplify the process of encapsulation for devices. We also calculated the electroluminescence spectrum of devices encapsulated with Al2O3 (150 nm) and Al2O3(75 nm)/ZrO2(75 nm). And the results indicated that the CIE coordinates is almost the same between with and without encapsulating. 相似文献
34.
Brain tissue changes accompany multiple neurodegenerative and developmental conditions in adolescents. Complex processes that occur in the developing brain with disease can be evaluated accurately only against normal aging processes. Normal developmental changes in different brain areas alter tissue water content, which can be assessed by magnetic resonance (MR) T2 relaxometry. We acquired proton-density (PD) and T2-weighted images from 31 subjects (mean age±S.D., 17.4±4.9 years; 18 male), using a 3.0-T MR imaging scanner. Voxel-by-voxel T2-relaxation values were calculated, and whole-brain T2-relaxation maps constructed and normalized to a common space template. We created a set of regions of interest (ROIs) over cortical gray and white matter, basal ganglia, amygdala, thalamic, hypothalamic, pontine and cerebellar sites, with sizes of ROIs varying from 12 to 243 mm3; regional T2-relaxation values were determined from these ROIs and normalized T2-relaxation maps. Correlations between R2 (1/T2) values in these sites and age were assessed with Pearson's correlation procedures, and gender differences in regional T2-relaxation values were evaluated with independent-samples t tests. Several brain regions, but not all, showed principally positive correlations between R2 values and age; negative correlations emerged in the cerebellar peduncles. No significant differences in T2-relaxation values emerged between males and females for those areas, except for the mid pons and left occipital white matter; males showed higher T2-relaxation values over females. The findings indicate that T2-relaxation values vary with development between brain structures, and emphasize the need to correct for such age-related effects during any determination of potential changes from control values. 相似文献
35.
Rathore RK Gupta RK Agarwal S Trivedi R Tripathi RP Awasthi R 《Magnetic resonance imaging》2011,29(8):1088-1100
The study was aimed to test the feasibility of utilizing an algorithmically determinable stable fiber mass (SFM) map obtained by an unsupervised principal eigenvector field segmentation (PEVFS) for automatic delineation of 18 white matter (WM) tracts: (1) corpus callosum (CC), (2) tapetum (TP), (3) inferior longitudinal fasciculus (ILF), (4) uncinate fasciculus (UNC), (5) inferior fronto-occipital fasciculus (IFO), (6) optic pathways (OP), (7) superior longitudinal fasciculus (SLF), (8) arcuate fasciculus (AF), (9) fornix (FX), (10) cingulum (CG), (11) anterior thalamic radiation (ATR), (12) superior thalamic radiation (STR), (13) posterior thalamic radiation (PTR), (14) corticospinal/corticopontine tract (CST/CPT), (15) medial lemniscus (ML), (16) superior cerebellar peduncle (SCP), (17) middle cerebellar peduncle (MCP) and (18) inferior cerebellar peduncle (ICP). Diffusion tensor imaging (DTI)-derived fractional anisotropy (FA) and the principal eigenvector field have been used to create the SFM consisting of a collection of linear voxel structures which are grouped together by color-coding them into seven natural classes to provide PEVFS signature segments which greatly facilitate the selection of regions of interest (ROIs) for fiber tractography using just a single mouse click, as compared with a manual drawing of ROIs in the classical approach. All the 18 fiber bundles have been successfully reconstructed, in all the subjects, using the single ROIs provided by the SFM approach, with their reproducibility characterized by the fact that the ROI selection is user independent. The essentially automatic PEVFS method is robust, efficient and compares favorably with the classical ROI methods for diffusion tensor tractography (DTT). 相似文献
36.
37.
The relation between generalized operators and operator-valued distributions is discussed so that these two viewpoints can be used alternatively to explain quantum fields. 相似文献
38.
Summary This study describes the optimization of microextraction as a method for extracting volatile compounds from wine. The study
has been applied to twelve compounds present in wine: 3-methylbutyl acetate, 3-methyl-1-butanol, ethyl hexanoate, hexanol,
ethyl octanoate, butanoic acid, ethyl decanoate, diethyl succinate, hexanoic acid, phenylethanol, octanoic acid, and decanoic
acid. These compounds were selected from those identified by GC-MS analysis of a real wine sample.
By means of a synthetic wine, the study investigated the influence on extraction yield of the solvents and salts used, the
proportion of salts, and the agitation time. The determination was performed by GC with flame ionization detection and an
internal standard was used for quantification. The method was applied to samples of white wine from La Rioja. 相似文献
39.
40.
Xiaoming Wu Yulin Hua Zhaoqi Wang Jiajin Zheng Shougen Yin Jiachun Deng Kongwu Wu Songliu Feijian Zhu Xia Niu 《Optik》2006,117(8):373-376
A bright white organic light-emitting diode (OLED) has been successfully fabricated in which a greenish-white emitting host Bis-(2-(2-hydroxyphenyl) benzothiazole)zinc (Zn(BTZ)2) is doped with an orange-red fluorescent dye 5,6,11,12-tetraphenylnaphthacene (rubrene). The pure white light emission with CIE coordinates of (0.341, 0.334) is achieved at the driving voltage of 20 V, and the corresponding luminance and external quantum efficiency are 4000 Cd/m2 and 0.63%. On the other hand, the pure red, green, and blue (RGB) emissions are obtained from the white OLED combined well with RGB custom-built optical color filters (CFs) with peaks at 616, 556, and 456 nm, respectively. Moreover, based upon the color mixture principles, we build a model of multi-color display mixed by the pure RGB emissions under the controllable bias. 相似文献