The visible and ultraviolet organic light-emitting diodes with germanium dioxide as facile solution-processed anode buffer layer

Germanium dioxide (GeO₂) aqueous solutions are facilely prepared and the corresponding anode buffer layers (ABLs) with solution process are demonstrated. Atomic force microscopy, X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy measurements show that solution-processed GeO₂ behaves superior film morphology and enhanced work function. Using GeO₂ as ABL of organic light-emitting diodes (OLEDs), the visible device with tris(8-hydroxy-quinolinato)aluminium as emitter gives maximum luminous efficiency of 6.5 cd/A and power efficiency of 3.5 lm/W, the ultraviolet device with 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole as emitter exhibits short-wavelength emission with peak of 376 nm, full-width at half-maximum of 42 nm, maximum radiance of 3.36 mW/cm² and external quantum efficiency of 1.5%. The performances are almost comparable to the counterparts with poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) as ABL. The current, impedance, phase and capacitance as a function of voltage characteristics elucidate that the GeO₂ ABL formed from appropriate concentration of GeO₂ aqueous solution favors hole injection enhancement and accordingly promoting device performance.     

ZnS作为空穴缓冲层的新型有机发光二极管

采用磁控溅射方法在ITO表面沉积了不同厚度的ZnS超薄膜作为有机发光二极管(OLEDs)的缓冲层,使典型结构(ITO/TPD/Alq3/Al)的OLEDs的发光性能得到改善。ZnS缓冲层厚度对器件性能影响的实验结果表明,当ZnS缓冲层厚度为5nm时,器件电流密度提高了近2倍,亮度提高了2倍;当ZnS缓冲层厚度为10nm时,器件发光的电流效率提高18%,器件的性能得到改善。宽禁带的ZnS缓冲层对空穴从阳极到有机功能层的注入有阻碍作用,促进器件载流子平衡,提高了器件发光效率,改善了器件性能。     

(111)择优取向的Pb(Zr0.52Ti0.48)O3铁电薄膜的制备及研究

选用不同浓度的Pb(Zr_0.52Ti_0.48)O₃溶胶，用Sol-gel法在Pt/Ti/SiO₂/Si基片上沉积一层厚度不同的Pb(Zr_0.52Ti_0.48)O₃ (PZT52)过渡层，经400℃烘烤、550℃退火等程序后，再用Sol-gel法在PZT52过渡层上沉积Pb(Zr_0.52Ti_0.48)O _{关键词： PZT铁电薄膜 择优取向 过渡层 剩余极化强度}     

光突发交换的交换控制策略和光缓存配置

光突发交换是面向下一代互联网的光交换模式.讨论了异步光突发交换系统的交换控制策略以及相应光缓存的优化配置策略.除了传统预约模式的交换策略,还研究了非预约和改进型预约模式,它们的性能评估由计算机仿真给出.结果表明:在条件相当情况下,改进型预约模式具有最低的丢包率.同时光缓存的配置对上述几类交换控制策略的性能都有很大影响,仿真结果指出:光缓存的粒度对系统性能具有重要影响,所讨论的几类交换模式都存在最佳时延粒度,研究结果对光交换矩阵的设计有指导意义.     

Environmental Effect of Macrocyclic Molecules on the Oxidation of Triethylamine by Ferricyanide Ion in Aqueous Solution

The effect of 18-crown-6 and kryptofix (2,2,1) on the oxidation of triethylamine byaqueous ferricyanide ion has been studied at pH 4, 7, and 9.The macrocycle retarded the normal oxidation process at all pH values,the effect depending on the macrocyclic ligand concentration Kryptofix (2,2,1) had a greater effect than 18-crown-6 at all pHvalues in this study. For 18-crown-6, retardation decreases in the order pH 9 > 4 > 7 while forkryptofix it follows the order pH 9 > 7 > 4.     

High resolution X-ray diffraction of GaN grown on Si (1 1 1) by MOVPE

High temperature GaN layers have been grown on Si (1 1 1) substrate by metalorganic vapor phase epitaxy (MOVPE). AlN was used as a buffer layer and studied as a function of thickness and growth temperature. The growth was monitored by in situ laser reflectometry. High resolution X-ray diffraction (HRXRD) revealed that optimized monocrystalline GaN was obtained for a 40 nm AlN grown at 1080 °C. This is in good agreement with the results of morphological study by scanning electron microscopy (SEM) and also confirmed by atomic force microscopy (AFM) observations. The best morphology of AlN with columnar structure and lower rms surface roughness is greatly advantageous to the coalescence of the GaN epilayer. Symmetric and asymmetric GaN reflections were combined for twist and stress measurements in monocrystalline GaN. It was found that mosaicity and biaxial tensile stress are still high in 1.7 μm GaN. Curvature radius measurement was also done and correlated to the cracks observations over the GaN surface.     

Transesterification of an RNA model in buffer solutions in H2O and D2O

Transesterification of a phosphodiester bond of RNA models has been studied in various buffer solutions, under neutral and slightly alkaline conditions in H₂O and D₂O. The results show that imidazole is the only buffer system where a clear buffer catalysis on the cleavage of a phosphodiester bond is observed. The rate enhancement in sulphonic acid buffers is smaller, and a sulphonate base, particularly, is inactive as a catalyst. The rate‐enhancing effect of imidazole is, however, catalytic, and the catalytic inactivity of sulphonate buffers can be attributed to their structure and/or charge. The catalysis by imidazole is a complex system which, in addition to first‐order reactions, involves a process that shows a second‐order dependence in imidazole concentration. The latter reaction becomes significant in acidic imidazole buffers (pH < pK_a), as the buffer concentration increases. The kinetic solvent deuterium isotope effect k_H/k_D, referring to first‐order catalysis by imidazole base, is 2.3 ± 0.3. That referring to second‐order catalysis is most probably much larger, but an accurate value could not be obtained. Copyright © 2007 John Wiley & Sons, Ltd.     

Time dependent analysis of finite buffer fluid flows and risk models with a dividend barrier

Based on the matrix-analytic approach to fluid flows initiated by Ramaswami, we develop an efficient time dependent analysis for a general Markov modulated fluid flow model with a finite buffer and an arbitrary initial fluid level at time 0. We also apply this to an insurance risk model with a dividend barrier and a general Markovian arrival process of claims with possible dependencies in successive inter-claim intervals and in claim sizes. We demonstrate the implementability and accuracy of our algorithms through a set of numerical examples that could also serve as test cases for comparing other solution approaches.      

基于队列式缓存结构的视频图像存储算法

针对视频图像数据实时存储过程中普遍存在的丢帧问题，通过深入分析典型的存储算法，找出实时存储过程中视频图像数据丢失的原因：计算机在连续存储相同大小的文件时，存储速度在一定的范围内波动.本文采用队列式缓存结构有效地消除了存储速度波动所带来的影响，保证了在数据流速小于磁盘平均存储速度的前提下,高速视频图像数据的实时存储，解决了丢帧问题.实践验证了该算法的可行性与可靠性.     

Cyclic networks with general blocking and starvation

We introducegeneral starvation and consider cyclic networks withgeneral blocking and starvation (GBS). The mechanism of general blocking allows the server to process a limited number of jobs when the buffer downstream is full, and that of general starvation allows the server to perform a limited number of services in anticipation of jobs that are yet to arrive. The two main goals of this paper are to investigate how the throughput of cyclic GBS networks is affected by varying (1) the total number of jobsJ, and (2) the buffer allocationk=(k₁..., k_m) subject to a fixed total buffer capacityK=k ₁ +... + k_m. In particular, we obtain sufficient conditions for the throughput to be symmetric inJ and to be maximized whenJ=K/2. We also show that the equal buffer allocation is optimal under the two regimes of light or heavy usage. In order to establish these results, we obtain several intermediate structural properties of the throughput, using duality, reversibility, and concavity, which are of independent interest.Research supported in part by NSF Grant No. ECS-8919818.