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151.
Chul Gyu Park 《Journal of multivariate analysis》2002,81(2):229
In this article, likelihood ratio tests (LRTs) are developed for detecting that stochastic trends of binary responses are ordered between 2×k contingency tables. We provide a simple iterative algorithm for the maximum likelihood estimators under the order restriction and construct the LRTs using those estimators. All the distributional results of these tests are based on the large sampling theory. The finite-sample behaviors of these tests are investigated through a simulation study. As an illustration of these tests, we analyze a set of data on wheeziness of smoking coalminers. 相似文献
152.
153.
Jonghee Lee Jeong‐Ik Lee Moo‐Jin Park Young Kwan Jung Nam Sung Cho Hoon Je Cho Do‐Hoon Hwang Sang‐Kyu Lee Jong‐Hwa Park Jiwon Hong Hye Yong Chu Hong‐Ku Shim 《Journal of polymer science. Part A, Polymer chemistry》2007,45(7):1236-1246
A novel series of poly(10‐hexyl‐phenothiazine‐S,S‐dioxide‐3,7‐diyl) and poly(9,9′‐dioctyl‐fluorene‐2,7‐diyl‐alt‐10‐hexyl‐3,7‐phenothiazine‐S,S‐dioxide) (PFPTZ‐SS) compounds were synthesized through Ni(0)‐mediated Yamamoto polymerization and Pd(II)‐catalyzed Suzuki polymerization. The synthesized polymers were characterized by 1H NMR spectroscopy and elemental analysis and showed higher glass transition temperatures than that of pristine polyfluorene. In terms of photoluminescence (PL), the PFPTZ‐SS compounds were highly fluorescent with bright blue emissions in the solid state. Light‐emitting devices were fabricated with these polymers in an indium tin oxide/poly(3,4‐ethylene dioxythiophene):poly(styrene sulfonate)/polymer/Ca/Al configuration. The electroluminescence (EL) of the copolymers differed from the PL characteristics: the EL device exhibited a redshifted greenish‐blue emission in contrast to the blue emission observed in the PL. Additionally, this unique phenothiazine‐S,S‐dioxide property, triggered by the introduction of an electron‐deficient SO2 unit into the electron‐rich phenothiazine, gave rise to improvements in the brightness, maximum luminescence intensity, and quantum efficiency of the EL devices fabricated with PFPTZ‐SS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1236–1246, 2007 相似文献
154.
Sang Kyu Lee Byung‐Jun Jung Taek Ahn Young Kwan Jung Jeong‐Ik Lee In‐Nam Kang Jonghee Lee Jong‐Hwa Park Hong Ku Shim 《Journal of polymer science. Part A, Polymer chemistry》2007,45(15):3380-3390
A series of fluorene‐based copolymers composed of blue‐ and orange‐light‐emitting comonomers were synthesized through palladium‐catalyzed Suzuki coupling reactions. 9,9‐Dihexylfluorene and 2‐(2,6‐bis‐{2‐[1‐(9,9‐dihexyl‐9H‐fluoren‐2‐yl)‐1,2,3,4‐tetrahydroquinolin‐6‐yl]‐vinyl}‐pyran‐4‐ylidene)‐malononitrile (DCMF) were used as the blue‐ and orange‐light‐emitting chromophores, respectively. The resulting single polymers exhibited simultaneous blue (423/450 nm) and orange (580–600 nm) emissions from these two chromophores. By adjusting the fluorene and DCMF contents, white light emission could be obtained from a single polymer; a device with an ITO/PEDOT:PSS/polymer/Ca/Al configuration was found to exhibit pure white electroluminescence with Commission Internationale de L'Eclairage (CIE) coordinates of (0.33, 0.31), a maximum brightness of 1180 cd/m2, and a current efficiency of 0.60 cd/A. Furthermore, the white light emission of this device was found to be very stable with respect to variation of the driving voltage. The CIE coordinates of the device were (0.32, 0.29), (0.32, 0.29), and (0.33, 0.31) for driving voltages of 7, 8, and 10 V, respectively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3380–3390, 2007 相似文献
155.
Jong Seong Bae Kyoo Sung Shim Soung-soo Yi Young Soo Kim 《Applied Surface Science》2006,252(13):4564-4568
The influence of lithium doping on the crystallization, the surface morphology, and the luminescent properties of pulsed laser deposited Y2−xGdxO3:Eu3+ thin film phosphors was investigated. The crystallinity, the surface morphology, and the photoluminescence (PL) of films depended highly on the Li-doping and the Gd content. The relationship between the crystalline and morphological structures and the luminescent properties was studied, and Li+ doping was found to effectively enhance not only the crystallinity but also the luminescent brightness of Y2−xGdxO3:Eu3+ thin films. In particular, the incorporation of Li and Gd into the Y2O3 lattice could induce remarkable increase in the PL. The highest emission intensity was observed Li-doped Y1.35Gd0.6O3:Eu3+ thin films whose brightness was increased by a factor of 4.6 in comparison with that of Li-doped Y2O3:Eu3+ thin films. 相似文献
156.
We have synthesized cone-like GeO2 structures via thermal heating of Ge powders. We have investigated the effects of substrate temperature on the sample morphology, revealing that cone-shaped structures are preferentially obtained at higher temperature. The cone-shaped structures, which gradually become thinner to form a sharp tip, appear to be a single-crystalline, hexagonal structure of GeO2. Room-temperature photoluminescence measurement revealed two emission peaks, at about 2.78 and 3.04 eV. 相似文献
157.
158.
J.S. Bae S.S. Yi J.H. Kim K.S. Shim B.K. Moon J.H. Jeong Y.S. Kim 《Applied Physics A: Materials Science & Processing》2006,82(2):369-372
Gd2O3:Eu3+ luminescent thin films have been grown on Al2O3(0001) substrates using pulsed-laser deposition. The films grown at different deposition conditions showed different crystalline
phases, surface morphologies and luminescent characteristics. Both cubic and monoclinic crystalline phases were observed for
the Gd2O3:Eu3+ films, and the crystalline structure and the surface morphology of the films were highly dependent on the oxygen pressure
and substrate temperature. The cubic system showed a higher luminescence than the monoclinic system. The luminescence characteristics
were strongly influenced by not only the crystalline structure but also the surface morphology of the films. The photoluminescencebrightness
data obtained from Gd2O3:Eu3+ films indicate that Al2O3(0001) is a promising substrate for growth of high-quality Gd2O3:Eu3+ thin-film red phosphor. In particular, the Gd2O3:Eu3+ films showed a much better photoluminescence behavior than a Y2O3:Eu3+ films with the same thickness.
PACS 78.20.-e; 78.55.-m; 78.66.-w 相似文献
159.
We have demonstrated the synthesis of one-dimensional (1D) structures of bismuth oxide (Bi2O3) by a reaction of a trimethylbismuth (TMBi) and oxygen (O2) mixture at 450 °C. Scanning electron microscopy showed that the product consisted of 1D materials with width or diameters less than 1 μm and lengths up to several tens of micrometers. The X-ray energy dispersive spectroscopy revealed that the materials contained elements of Bi and O. The results of X-ray diffraction and selected area electron diffraction pattern indicated that the obtained Bi2O3 were crystalline with monoclinic structure. 相似文献
160.