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991.
Xufeng Wu Gaoquan Shi Feng'En Chen Shaohu Han Junbiao Peng 《Journal of polymer science. Part A, Polymer chemistry》2004,42(12):3049-3054
Poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐p‐phenylenevinylene] (MEH‐PPV) with a molar mass of 26–47 × 104 g mol?1 and a polydispersity of 2.5–3.2 was synthesized by a liquid–solid two‐phase reaction. The liquid phase was tetrahydrofuran (THF) containing 1,4‐bis(chloromethyl)‐2‐methoxy‐5‐(2′‐ethylhexyloxy)benzene as the monomer and a certain amount of tetrabutylammonium bromide as a phase‐transfer catalyst. The solid phase consisted of potassium hydroxide particles with diameters smaller than 0.5 mm. The reaction was carried out at a low temperature of 0 °C and under nitrogen protection. No gelation was observed during the polymerization process, and the polymer was soluble in the usual organic solvents, such as chloroform, toluene, THF, and xylene. A polymer light‐emitting diode was fabricated with MEH‐PPV as an active luminescent layer. The device had an indium tin oxide/poly(3,4‐ethylenedioxylthiophene) (PEDOT)/MEH‐PPV/Ba/Al configuration. It showed a turn‐on voltage of 3.3 V, a luminescence intensity at 6.1 V of 550 cd/m2, a luminescence efficiency of 0.43 cd/A, and a quantum efficiency of 0.57%. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3049–3054, 2004 相似文献
992.
993.
核磁COLOC技术在一类多取代苯结构鉴定中的应用一类多取代苯结构的COLOC鉴定 总被引:2,自引:2,他引:0
通过非环前体的分子内成环反应,可合成一类多取代苯,对这类产物进行结构鉴定,有助于了解整个反应历程和机理。但取代基增多,势必导致各结构因素变得复杂,难以从各芳碳的经验计算式去推测各取代基所处的相对位置,而以一般的光、波谱方法也较难获得这类结构信息。实验表明,核磁COLOC技术是确定这类产物各取代基相对位置较为合适的方法,本文以NMR技术对这类产物进行了结构鉴定,并讨论了COLOC技术在确定其各取代基相对位置中的作用;同时通过对产物的结构确认,讨论了产物取代基间的相互作用所导致其芳碳化学位移实测值与经验计算值之间的差异,以及含氟基团对邻位芳碳的碳氟间三键偶合作用。 相似文献
994.
用修正的RELIEF方法测量高速空气流瞬时速度的理论研究 总被引:3,自引:1,他引:2
修正了拉曼激发激光感应电子荧光(RamanExciationpulseLaser-inducedElectronicFluorescence简称RELIEF)方法,以实现对亚音速和超音速空气流多点时速度的测量,测量精度优于2%。 相似文献
995.
从锕系区40多个核的正负宇称态的实验数据,如激发能、Jπ、电偶极跃迁等,得到一系列与核结构有关的物理量,如宇称劈裂能级差δEI,正负宇称带的第一和第二类转动惯量J(1)和J(2)及第一负宇称态的电偶极跃迁强度比等,以及它们与角动量I或转动角频率ω的动力学和核子数A的系统行为,从而为研究锕系核负宇称态的产生机制及动力学特点提供了信息. 相似文献
996.
997.
The characteristic junction parameter of a semiconductor laser and its relation with reliability 总被引:4,自引:0,他引:4
Shi Jiawei Jin Enshun Li Hongyan Ma Jing Qi Liyun Gao Dingsan 《Optical and Quantum Electronics》1996,28(6):647-651
We discuss the factors which affect the characteristic junction parameter m, which is obtained from the intercept of the / (dV/dl) vs / characteristic. The relation between m and the reliability of InGaAsP/InP BH laser devices is also discussed. 相似文献
998.
RANDOM WEIGHTING APPROXIMATION IN LINEAR REGRESSION MODELS 总被引:1,自引:0,他引:1
石坚 《应用数学学报(英文版)》1996,12(2):137-143
RANDOMWEIGHTINGAPPROXIMATIONINLINEARREGRESSIONMODELSSHIJIAN(DepartmentofProbabilityandStatistics,PekingUniversity,Beijing1008... 相似文献
999.
Xu Shi Yu Qiang Tu Hong Siang Tan Beng Kang Tay Milne W.I. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1996,24(6):1309-1318
An improved drift approximation model with an added radial electrostatic field has been successfully developed. Our model provides a computationally efficient way of quantitatively describing the plasma motion and predicting the plasma behavior in the toroidal solenoid in a filtered cathodic vacuum arc (FCVA) system. Storer's (1989) experimental results have been successfully simulated by this model. A good quantitative fit is obtained for our simulation results to the measured ion currents versus distance along the torus for various B field strengths, the attenuation length, and the wall current. The model describes the change of plasma density along the torus and provides the value of the electron-ion collision frequency at various conditions. The effect of the magnetic field and radial electric field on the plasma transportation can be assessed by the simulation and various plasma parameters can be determined. It is found that the radial electric field confines the 3-directional drift of the ions and is one of the most important parameters in determining the ion throughput. For any given B field strength and plasma parameters, there is a peak ion output corresponding to an optimal potential difference which can be obtained by the simulation. Over three times more ion output can be achieved when the torus wall is appropriately biased 相似文献
1000.
To analyze the isotonic regression problem for normal means, it is usual to assume that all variances are known or unknown but equal. This paper then studies this problem in the case that there are no conditions imposed on the variances. Suppose that we have data drawn fromkindependent normal populations with unknown meansμi's and unknown variancesσ2i's, in which the means are restricted by a given partial ordering. This paper discusses some properties of the maximum likelihood estimates ofμi's andσ2i's under the restriction and proposes an algorithm for obtaining the estimates. 相似文献