Efficiency improvement of red organic light-emitting diodes using a blue phosphorescent exciton blocking layer

Quantum efficiency of red organic light-emitting diodes was improved using a blue phosphorescent emitting layer as an exciton blocking layer. Compared with 8.1% quantum efficiency of standard devices without an exciton blocking layer, high quantum efficiency of 14.1% was obtained using a blue phosphorescent emitting layer between the hole transport layer and the red emitting layer.     

Dynamic pricing for load‐balancing in user‐centric joint call admission control of next‐generation wireless networks

Next‐generation wireless networks (NGWN) will be heterogeneous, comprising of a number of radio access technologies (RATs) co‐existing in the same geographical area. In NGWN, joint call admission control (JCAC) algorithms are required to select the most appropriate RAT for each incoming call. It is envisaged that these JCAC algorithms will be user‐centric (i.e. will consider users' preferences in making RAT selection decisions) in order to enhance user satisfaction. However, user‐centric JCAC algorithms can lead to highly unbalanced traffic load among the available RATs in NGWN because users act independently, and most of them may prefer to be connected through a particular RAT. Highly unbalanced traffic load in NGWN will result in high overall call blocking/dropping probability and poor radio result utilization. To address this problem, we propose dynamic pricing for balancing traffic load among available RATs in heterogeneous wireless networks where users' preferences are considered in making RAT selection decisions. By dynamically adjusting the service price in each of the available RATs, the proposed user‐centric JCAC scheme evens out the unbalanced traffic load caused by independent users' preferences. The JCAC scheme uses fuzzy multiple attribute decision‐making (MADM) technique to select the most appropriate RAT for each incoming call. We develop a Markov model to evaluate the overall call blocking/dropping probability and percentage load in each RAT in heterogeneous wireless networks. Performance of the proposed JCAC scheme is compared with that of a scheme that does not use dynamic pricing. Simulation results are given to show the effectiveness of the proposed JCAC scheme. Copyright © 2009 John Wiley & Sons, Ltd.     

多路径并行传输中接收缓存阻塞问题的研究

本文研究了多路径并行传输情况下接收缓存阻塞问题产生的原因及对传输性能的影响。同时提出了一种适用于多路径并行传输吞吐量分析的建模方法。该模型能够通过链路丢包率、往返传输时间等参数对吞吐量进行估计,并综合考虑了快速重传、拥塞窗口与接收缓存容量的关系对结果的影响。通过与仿真结果进行比较可以看出,该模型能够在网络性能参数发生变化时很好的预测吞吐量的变化情况。     

一种动态分配输入队列的片上虫孔路由器结构

为了降低片上网络（NoC）由于虫孔缓冲结构排头（HoL）阻塞导致的性能损失,同时消除虚通道缓冲结构对可变长度报文表现出的缓冲区低利用率现象,本文采用虚拟通道技术提出一种动态分配输入队列（DAIQ）的片上虫孔路由器结构.该结构采用一种令牌表的方式支持虚拟队列深度与数量的动态分配,同时为了支持同一报文微片能够连续调度,本文还提出一种新颖的开关分配机制——SRRM,该机制在高负载下进一步改善了开关的延迟与吞吐率.仿真与综合的结果表明,相比传统虚通道流控的片上路由器结构,DAIQ路由器以50%的缓冲面积获得类似的性能,在0.13微米CMOS工艺下节约了30.18%的标准单元面积与384%的功耗.     

Improvement of reverse blocking performance in vertical power MOSFETs with Schottky–drain-connected semisuperjunctions

To enhance the reverse blocking capability with low specific on-resistance,a novel vertical metal-oxidesemiconductor field-effect transistor(MOSFET) with a Schottky-drian(SD) and SD-connected semisuperjunctions(SDD-semi-SJ),named as SD-D-semi-SJ MOSFET is proposed and demonstrated by two-dimensional(2D) numerical simulations.The SD contacted with the n-pillar exhibits the Schottky-contact property,and that with the p-pillar the Ohmic-contact property.Based on these features,the SD-D-semi-SJ MOSFET could obviously overcome the great obstacle of the ineffectivity of the conventional superjunctions(SJ) or semisuperjunctions(semi-SJ) for the reverse applications and achieve a satisfactory trade-off between the reverse breakdown voltage(BV) and the specific on-resistance(R_(on)A).For a given pillar width and n-drift thickness,there exists a proper range of n-drift concentration(N),in which the SD-D-semi-SJ MOSFET could exhibit a better trade-off of R_(on)A-BV compared to the predication of SJ MOSFET in the forward applications.And what is much valuable,in this proper range of N,the desired BV and good trade-off could be achieved only by determining the pillar thickness,with the top assist layer thickness unchanged.Detailed analyses have been carried out to get physical insights into the intrinsic mechanism of R_(on)A-BV improvement in SD-D-semi-SJ MOSFET.These results demonstrate a great potential of SD-D-semi-SJ MOSFET in reverse applications.     

管道内全阻塞障碍物对气相爆轰波传播特性的影响

建立了长2 800 mm、内径为50 mm的圆管内爆轰波传播实验装置,采用光电二极管探测火焰锋面以获得爆轰波的传播速度,采用烟迹法记录爆轰波的胞格结构。通过在管道不同位置设置阻塞率为1的聚丙烯薄膜,研究不同初始压力下不同氩气稀释浓度的C₂H₂+2.5O₂+nAr预混气体爆轰波在通过全阻塞障碍物前后传播速度及胞格结构的变化。结果表明,气相爆轰波在达到稳态爆轰后,在通过全阻塞薄膜障碍物的过程中会产生2种不同的传播形式:速度亏损和爆轰失效。气相爆轰波穿过不同区域的传播过程可以分为3个阶段:稳态传播阶段、速度亏损阶段或爆轰失效阶段、过驱爆轰阶段。     

一种改进的基于后处理去除块效应算法

在基于DCT压缩编码系统中,DCT都是基于模块的。即首先将图像分成8×8的像素块,然后对每块进行DCT得到64个DCT系数。但由于是分别对每块进行DCT,块与块之间的相关性被忽略,导致所谓的“块效应”。文中提出了一种改进的基于后处理的去块效应方法。在图像重建时,首先在块与块之间提出了4种模式,包括了3个与频率相关的模式和4个块拐角处的拐角模式。然后对不同模式下采用低复杂度的去块效应滤波器,最后重建图像。不论是视觉效果还是图像质量都有所提升。     

ZnO薄层对体异质结有机太阳能电池性能的影响

本文主要研究了ZnO薄层的插入对P3HT:PCBM为活性层的有机太阳能电池性能的影响,由于ZnO的功函数接近PCBM有利于电子的传输和ZnO低的HOMO起到阻挡空穴的作用,从而平衡电子和空穴的传输;在活性层和Al电极之间插入3 nm的ZnO薄层作为空穴阻挡层和电子选择层,使得电池转化效率由2.65;提高到3.45;.研究表明,由于ZnO薄层有利于改善活性层内部光场强度分布,从而使活性层的吸收进一步增强,进而达到了提高效率的目的.     

酶联放大安培检测基因传感器的封闭方式

在酶联放大安培检测过程中,酶和碱基链在金电极表面的非特异吸附是导致假阳性结果的主要来源.为减少非特异吸附,分别从封闭时间和封闭方式等考查巯基己醇(MCH)和牛血清白蛋白(BSA)对上述非特异性吸附因素的封闭效果.结果表明,BSA不论是对酶还是碱基链的封闭效果均优于MCH.经优化,确定BSA单一封闭剂(15min)为最佳封闭条件,并可用于急性早幼粒细胞白血病(PML-RARα)融合基因的检测.本方法可有效减少非特异吸附,缩短检测预处理时间,并使检测信号在一定程度上得到放大.     

视频编码中的去块滤波器

去块滤波器是视频编码的重要部分,它能显著提高恢复视频的主观和客观质量.文中分析了解码图像中块效应产生的原因;归纳了去块滤波器的种类,创造性地将环路滤波器分为"加残差前滤波器"和"加残差后滤波器"两类,并分析了各类去块滤波器的工作原理;研究了现存的各种视频编码标准中去块滤波器的特点,并通过仿真实验分析了各去块滤波器的性能,为设计更加智能化、简单化的去块滤波器奠定基础.