Planar Alignment of Columnar Discotic Liquid Crystals by Isotropic Phase Dewetting on Chemically Patterned Surfaces

A novel method of creating planar aligned columnar discotic liquid crystals (cDLCs) on surfaces, which also gives control over the azimuthal angle, is presented. Surfaces are chemically patterned with stripes via microcontact printing of organothiol self‐assembled monolayers (SAMs) on gold, or via deep UV patterning of organosilane SAMs on silicon. These are then used to isolate long droplets of cDLCs by dewetting in the isotropic phase. Upon cooling from the isotropic into the hexagonal columnar phase, polarizing microscopy reveals that the cDLC aligns in a planar orientation. Results for three triphenylene derivatives (HAT‐6, HHTT, H7T) and for a phthalocyanine derivative (8H₂Pc) are presented. H7T and HAT‐6 are found to align with the director perpendicular to the stripe direction, but HHTT and 8H₂Pc align parallel to the stripe direction. This relatively simple new method for creating planar aligned columnar phases of DLCs gives control over the azimuthal angle: a condition required for organic field‐effect transistor applications of cDLCs.     

Microcutting Materials on Polymer Substrates

The production of micrometer and sub‐micrometer features over large areas for use in electronic and optical structures remains challenging, particularly as requirements extend beyond traditional electronic materials to ceramics and polymers. We demonstrate that the technique of microcutting allows patterning of such structures on polymer substrates of these materials as exemplified by the ceramic indium tin oxide (ITO) and the conducting polymer poly(3,4‐ethylenedioxythiophene) (PEDOT). Given the brittleness of most ceramics such as ITO, this is very unexpected, but we find no evidence for microcracking and find high electrical conductivities in narrow tracks (∼2.5 μm) that are separated by less than 500 nm. The micrometer‐scale patterns also act as very efficient alignment layers for liquid crystals (LCs), and allow complex alignment patterns.     

LDA端泵浦固体激光器的新型耦合系统--圆锥形导管

报道了一种适用于面阵激光二极管阵列（LDA）的新型耦合系统——圆锥形导管,它利用折射原理压缩出射光束的发散角。在光线追迹的基础上给出了圆锥形导管的传输规律,并用计算机模拟得到了其具有良好的传输特性。结果表明,LDA出射的空间非连续分布的激光束通过圆锥形导管后,在近场可以得到近高斯形的场分布;圆锥形导管不仅具有结构简单和传输效率高的优点,而且较好地均衡了快慢轴2个方向上的光束质量,输出光束具有较小的发散角和光斑尺寸。     

Optical proximity correction for a versatile LCD based direct write maskless photoplotter

The digital simulation of a photoplotter’s direct write process, where the reconfigurable mask is a liquid crystal microdisplay, leads to the development of two proximity correction techniques. The first works by modifying dimensions and in adding serifs or assistant features to the original structure design. The second, more innovative and only exploitable with a grey level capable direct writing device, precompensates structures with a multilevel spatial modulation of the luminous energy. We also present the computer simulation used to develop these OPC techniques and confirm its performance by comparing modelled and experimental results.     

一种基于PL-LCD体系结构的新型图像拼接技术的研究

“像移法”是一种基于光致发光-液晶显示器(PL-LCD)体系结构的新型显示器图像拼接设计,它增强了用无缝拼接的办法制作大屏幕显示器的基本概念。这项专利技术利用了光学透明棱镜的折射现象[1]。如果把两个完全相同的直角棱镜的斜面相对,那么,来自第一棱镜的入射光线将偏移一定距离从另一面出射时,但仍与入射光线保持平行。通过对棱镜的精确取向和适当选择,可以通过组合这些棱镜结构使光线向中间移动,从而达到无缝拼接的目的(图1)[2]。     

一种新的紧凑型人工磁导体结构

本文提出了一种新型的紧凑型人工磁导体(AMC)结构,同样的单元尺寸可以获得较低频率的反射相位阻带带隙,可以比较有效地解决AMC结构的大尺寸问题。制作了相应的实际电路,测量结果与仿真结果基本一致。     

一种新型宽带电磁带隙结构

该文研究了实现宽带EBG(Electromagnetic Band-Gap)结构的方法。仿真结果表明利用周期渐变技术可以明显增加阻带带宽,进而采用单元尺寸加窗技术可以改善通带和阻带的平坦度。在该文的例子中,-20dB的阻带带宽增加了2096以上,3GHz以下的通带插损小于0.4dB。制作了相应的实际电路,实验结果与仿真结果基本相符。     

基于信噪歪度比的二次相位耦合信号增强新算法

提出了信噪歪度比分析法,在这个分析法中用三阶累积量切片首次定义了信噪歪度比的概念,导出了其理论计算公式。从理论分析可知：当背景噪声为对称分布噪声时,信噪歪度比为无限值;当背景噪声为非对称分布噪声时,在一定条件下,其大于等于输入信噪比。理论分析和仿真结果表明：用三阶累积量切片从非高斯非对称分布的噪声中提取二次相位(动态)耦合信号是有效的,且无需对背景噪声的分布作任何假定。这在工程实践中是非常有意义的。     

组合离子注入导致非对称耦合双量子阱界面混合效应光调制反射光谱

用分子束外延系统 (MBE)生长了 Ga As/ Al Ga As非对称耦合双量子阱 (ACDQW) ,用组合离子注入的方法 ,在同一块衬底上获得了不同注入离子 As+ 、 H+ 和不同注入剂量的 Ga As/ Al Ga As非对称耦合双量子阱单元 ,在未经快速热退火的条件下 ,于常温下测量了光调制反射光谱 ,发现各单元的子带间跃迁能量最大变化范围可达80 me V .     

Structure and conductivity of liquid crystal channel-like linic complexes of taper-shaped compounds

Molecular packing and electrical conductivity were studied in complexes of alkali trifluoromethanesulphonates with low-molar or polymeric compounds containing both taper-shaped mesogens were esters of either 3,4,5-tris [p-(n-dodecan-l-yloxy) benzyloxy] benzoic acid (I) or 3, 4, 5-tris (n-dodecan-l-yloxy) benzoic acid (II). In the hexagonal columnar liquid crystal phase the tapered mesogens fan out from the centre of the column, with the ionic receptors forming the central channel and the aliphatic tails constituting the continuum matrix. In the case of side-chain polymethacrylates the column core also contains the backbone chain. The DC conductivity σ of unoriented samples increases greatly at the crystal-columnar transition, with only a minor further change upon columnar-isotropic transition. σ was in the range 10^?9 ? 10^?6 in the columnar phase 40–90 °C, whilst the activation energies for conduction were between 28 kcal mol^?1 for the crown ether and only 2 kcal mo^?1 for the complex of LiCf₃SO₃ with the non-polymeric ester of tri(ethylene oxide) with I.     

一种应用于军事图像通信的UWB接收机

提出了一种改进型的基于前向自适应方式的TR接收机结构,并对其性能进行了理论论证和仿真分析．证明该接收机在特定的信道模型下有着可以与完全Rake相差不大的BER性能,硬件实现复杂度低,而且其特殊的信号结构设计特别适合用于脉冲同步的导频信号的接收。     

AWG中阵列波导耦合系数的计算

针对阵列波导光栅（AWG）中阵列波导耦合系数的计算问题，提出了基于光束传播方法（BPM）的叠加积分方法的修正方法。将修正前、后的结果与简单叠加积分方法的结果作了分析比较，从而验证了修正方法的正确性。分析了阵列波导之间的耦合对耦合系数的影响，阵列波导间距越小，影响越大。     

一种新的移动机器人全局定位算法

粒子滤波器能够给出移动机器人全局定位非线性非高斯模型的近似解.然而,当新感知出现在先验概率的尾部或者与先验相比感知概率太尖时,传统的粒子滤波器会退化导致定位失败.本文提出了一种重要性采样跟中心差分滤波器(central difference filter,CDF)相结合的新算法,并对测量更新步的加权粒子集应用基于KD-树的加权期望最大(weighted expectation maximization,WEM)自适应聚类算法获得表示机器人位姿状态后验密度的高斯混合模型(Gaussian mixture model,GMM).实验结果表明,新方法提高了定位准确率,降低了计算复杂度.     

Electromigration characteristics in dual-damascene copper interconnects by difference of via structures

In order to improve the interconnect performance, copper has been used as the interconnect material instead of aluminum. One of the advantages of using copper interconnects instead of aluminum is better electromigration (EM) performance and lower resistance for ultralarge-scale integrated (ULSI) circuits. Dual-damascene processes use different approaches at the via bottom for lowering the via resistance. In this study, the effect of a Ta/TaN diffusion barrier on the reliability and on the electrical performance of copper dual-damascene interconnects was investigated. A higher EM performance in copper dual-damascene structures was obtained in barrier contact via (BCV) interconnect structures with a Ta/TaN barrier layer, while a lower EM performance was observed in direct contact via (DCV) interconnect structures with a bottomless process, although DCV structures had lower via resistance compared to BCV structures. The EM failures in BCV interconnect structures were formed at the via, while those in DCV interconnect structures were formed in the copper line. The existence of a barrier layer at the via bottom was related to the difference of EM failure modes. It was confirmed that the difference in EM characteristics was explained to be due to the fact that the barrier layer at the via bottom enhanced the back stress in the copper line.     

具有分形特征的宽带人工磁导体结构

介绍了一种新型的具有分形特征的宽带 AMC 结构。这种结构是将普通 AMC 结构贴片的边缘用 Minkowski 环代替形成,结果发现使用这种结构可以得到更宽频带的电磁带隙。在3GHz 左右的频率,电磁带隙宽度可提高28%左右。这种结构可用于实际的宽带电路和天线中。     

基于对角加载的STAP性能改善

空时自适应处理(STAP)作为动目标检测的关键技术,但是非均匀环境将会造成协方差矩阵的估计误差,进而严重影响STAP性能。对角加载主要用于改善空间滤波器对于有用信号空域特征失配和空域协方差矩阵失配的稳健性。该文考虑将对角加载应用于STAP协方差矩阵失配(统计失配)时的性能改善,即在实际的协方差矩阵和其估计值之间存在误差时,通过对角加载改善STAP的稳健性。文中给出了加载电平的选择方法,并进行了详细的性能分析,即合理的对角加载可以提高检测概率和输出信噪比。仿真分析验证了理论分析的正确性。     

Novel multimedia traffic modeling based CAC scheme for CDMA communication systems

As the radio spectrum is a very scarce resource, the Call Admission Control （CAC） is one of the most important parts in radio resource management. The Code Division Multiple Access （CDMA） based next generation wireless communications systems will support the transmission of multimedia traffic, such as voice, video and data, thus the CAC, which can support the multimedia traffic and guarantee the Quality of Service （QoS） of different traffic, has gained broad attention. In this paper, a novel multimedia traffic modeling method and a corresponding dynamic QoS based CAC are proposed. The analysis and simulation results show that the proposed CAC scheme can guarantee the QoS to different traffic demand, and improve the system performance significantly.     

一种新的双模微基站非授权信道接入方法

利用非授权频段频谱资源提升网络容量需要有效地解决LTE(Long Term Evaluation)与WiFi的共存问题。最近,学术界和工业界相继提出了授权频段辅助接入机制和双模微基站技术提升蜂窝通信系统容量。考虑双模微基站与WiFi接入点覆盖范围存在部分重叠场景,该文提出一种新的双模微基站非授权信道接入机制及联合授权非授权的优化频谱资源分配方案。仿真结果表明,双模微基站和WiFi接入点互不可见时,新方案相比于现有方案由于考虑了空间复用具有更好的系统性能;双模微基站和WiFi接入点互相可见时,新方案与现有方案性能一致,即两者分时独立占用非授权频段频谱资源。     

混合粒子对优化算法在说话人识别中的应用

在粒子群优化(Particle Swarm Optimization, PSO)和混合蛙跳算法(Shuffled Frog-Leaping Algorithm, SFLA)的基础上,该文提出了一种新的混合粒子对优化(Shuffled Particle-Pair Optimizer, SPPO)算法,应用于矢量量化的说话人识别。该算法将全局信息交换和局部深度搜索相结合寻求最佳的说话人码本。群体按适应值分为3个粒子对,每个粒子对由两个粒子构成,按先后顺序执行PSO算法中的速度位置更新和LBG算法以实现局部细致搜索,间隔一定的迭代次数通过SFLA混合策略实现粒子对间的信息交换,从而使群体向全局最优解靠近。实验结果表明,本算法始终稳定地取得显著优于LBG,FCM,FRLVQ-FVQ和PSO算法的说话人识别性能,较好地解决了初始码本影响的识别性能的问题,且在计算时间和收敛速度方面有相当的优势。     

MIMO BC中新的TH预编码方法

针对多用户MIMO广播信道下预编码技术提出了发射端配置两根天线的改进T H预编码方案。该方法突破了传统TH预编码方案发射天线与接收天线数量的限制,并且得到 了很好的分集和复用增益。仿真结果表明,所提算法在容量上接近理论容量界,且当误码率 为10-2时,所提方案相比单天线THP有9 dB的增益。