Triacetate cellulose gate dielectric organic thin-film transistors

Here, we report on the performance and the characterization of all solution-processable top-contact organic thin-film transistors (OTFTs) consisting of a natural-resourced triacetate cellulose gate dielectric and a representative hole-transport poly[2,5-bis(3-dodecylthiophen-2-yl)thieno[3,2-b]thiophene] (pBTTT) semiconductor layer on rigid or flexible substrates. The bio-based triacetate cellulose layer has an important role in the OTFT fabrication because it provides the pBTTT semiconducting polymer with highly suitable gate dielectric properties including a low surface roughness, hydrophobic surface, appropriate dielectric constant, and low leakage current. The triacetate cellulose gate dielectric-based pBTTT OTFTs exhibit an average filed-effect mobility of 0.031 cm²/Vs similar to that obtained from a SiO₂ gate dielectric-based OTFT device in ambient conditions. Even after a bending stimulation of 100 times and in an outward bending state, the flexible triacetate cellulose gate pBTTT OTFT device still showed excellent electrical device performance without any hysteresis.     

参考光为平面波和球面波时焦距检测对比研究

为了研究参考光波面形状对于测量透镜焦距值的影响,采用数字全息的方法进行了理论分析和实验验证。通过在两种色光下进行实验,分别测量出参考光为平面波和球面波时的焦距值,并与标称值和理论计算值进行了比较。结果表明,当参考光为平面波时,测量到的透镜焦距值与标称值和理论计算值相对误差在5%以上; 而当参考光为球面波时,与两者的相对误差均在2%以下,因此当参考光为球面波时所测量的焦距值精度更高; 通过计算得出这两种参考光所测量的焦距值都在理论焦深范围内,故利用测量焦距值对全息图进行重构时所获得的再现像与用标称值和理论计算值所得到的再现像质量相当。这一结果对测量透镜焦距值和数字全息图重建方面有一定的帮助。     

反应温度对亲核试剂引发点击化学制备聚合物分散液晶电光性能的影响

光聚合诱导相分离法是应用最广泛的制备聚合物分散液晶(PDLC)膜的方法。为了提高PDLC的对比度(CR),通常在PDLC膜中引入二色性染料。然而,目前商业化的染料掺杂PDLC膜还很少,因为光聚合诱导相分离法使用的紫外光会使染料分解;另外,染料会吸收紫外光导致预聚物的聚合速率变慢。亲核试剂引发点击化学反应是最近合成化学的研究热点,可在无紫外光的条件下发生。因此,用亲核试剂引发点击化学反应制备PDLC膜,有望克服传统光聚合诱导相分离法的缺点。本论文,采用亲核试剂引发巯基-烯烃点击化学反应制备PDLC膜,并研究了反应温度对PDLC电光性能的影响。结果表明,温度的改变导致液晶微滴的尺寸发生变化,进而对PDLC的电光性能产生影响。温度升高使得开态透过率(Ton)变小,阈值电压(V_(th))和饱和电压(V_(sat))升高。     

原子力显微镜在聚合物溶液结构研究中的应用

驱油用水溶性聚合物溶液的应用性能由其聚合物溶液的微观结构所决定,因此在驱油用聚合物合成及配方研究中迫切需要研究其溶液的微观结构。本文使用原子力显微镜（AFM）、环境扫描电镜（ESEM）和透射电镜（TEM）观察了水溶液中聚合物（HAWSP,AP-P4）的微观结构。研究发现常温常压下原子力显微镜观察到的聚合物网络结构图案清晰,边界分辨率高。透射电镜观察到的聚合物网络结构较模糊且网络结构有断裂现象。环境扫描电镜观测到的网络结构尺寸大小是AFM观测到的几倍甚至是十几倍。动态光散射（dynamic light scattering,DLS）结果证明AFM和TEM所观测到的聚合物结构最接近于真实结构。结果表明使用原子力显微镜在观察水溶性聚合物类样品时,能够较真实反映其微观结构。     

Consideration of chiral optical fibres

Circular birefringence is a property of chiral materials. In this work, we consider the use of chiral materials in optical fibres to produce circularly birefringent optical fibres and in fibres where a contrast in circular birefringence contributes to forming the waveguide. (-)-menthyl methacrylate is also investigated as a possible material for the fabrication of such fibres.     

Temperature dependant flash memory erase transient simulation (Part I)

We present a detailed and accurate physics based transient simulation for modeling flash memory erasing at ambient and non-ambient temperatures. Typical cells are erased by moving electrons from the floating gate to the drain, source or substrate. Part I of this paper addresses substrate erase modeling using a simulation based on the solution to Poisson’s equation with temperature as an independent variable. The goal of this paper is to demonstrate the derivation of an accurate erase simulation and show the effects of temperature on the threshold voltage shift during the erase process. Several papers have been published on this topic but fail to present detailed derivations and none using this exact set of equations to model the temperature dependent erasing process.     

基于先验形状的CV模型肝脏CT图像分割

针对目标被部分遮挡或部分信息丢失情况下CV模型不能正确识别的问题,提出一种新的分割算法。首先,利用数学形态学对原肝脏图像进行滤波,并结合其他算法建立肝脏先验形状;然后,采用边缘查找和区域标定等算法,对肝脏先验性状的边缘以及边缘内外区域进行赋值,构建执行效率高的符号函数距离函数,将其通过形状比较函数嵌入到CV模型的能量泛函中,形成新的基于先验形状的CV模型,并将此模型用于分割存在干扰或者被部分遮挡的肝脏CT图像。与CV模型分割结果相比,本文算法能在目标周围存在干扰信息或者被部分遮挡的情形下,成功地正确识别出目标区域。     

Lateral Inhomogeneity in the Electronic Structure of a Conjugated Poly(3‐hexylthiophene) Thin Film

How annealing influences the morphology of a highly regioregular poly(3‐hexylthiophene) (RR‐P3HT) film at the substrate interface as well as the lateral inhomogeneity in the electronic structure of the film are elucidated. Whereas previous studies have reported that high‐molecular‐weight (MW) RR‐P3HT films tend to show low crystallinity even after annealing, it is found that high‐MW RR‐P3HT does show high crystallinity after annealing at high temperature for a long time. Photoemission electron microscopy (PEEM), X‐ray photoemission spectroscopy, and ultraviolet photoemission spectroscopy results clearly resolve a considerable lateral inhomogeneity in the morphology of RR‐P3HT film, which results in a variation of the electronic structure depending on the local crystallinity. The PEEM results show how annealing facilitates crystal growth in a high‐MW RR‐P3HT film.     

聚乙二醇阴极修饰层改善聚合物太阳能电池光电性能的研究

通过将聚乙二醇(PEG)掺入活性层制备聚合物太阳 能电池,利用PEG的迁移特性获得阴极修饰层,研 究PEG阴极修饰层对聚合物太阳能电池光电性能的影响。X射线光电子能谱(XPS)分 析表明,掺入活性层中的 PEG迁移到活性层与Al电极之间,形成了阴极缓冲层。吸收光谱、电流密度-电压 特性曲线和外量子 效率谱的分析表明,PEG阴极缓冲层的形成改善了活性层与阴极的界面接触特性, 降低了活性层与电 极之间的能级势垒,有利于载流子传输,因此显著地改善了聚合物太阳能电池的光电性能, 使得器件的开 路电压Voc、短路电流密度Jsc和填充因子(FF)都有明显提高。当P3HT:PCBM 活性层中掺入体积比为0.5%的PEG时,聚合物太阳能电池的能量转换 效率(P CE)最高,达到了3.07%,比未掺杂PEG的参考器件提 高了38.5%。     

A two-stage shape retrieval (TSR) method with global and local features

A robust two-stage shape retrieval (TSR) method is proposed to address the 2D shape retrieval problem. Most state-of-the-art shape retrieval methods are based on local features matching and ranking. Their retrieval performance is not robust since they may retrieve globally dissimilar shapes in high ranks. To overcome this challenge, we decompose the decision process into two stages. In the first irrelevant cluster filtering (ICF) stage, we consider both global and local features and use them to predict the relevance of gallery shapes with respect to the query. Irrelevant shapes are removed from the candidate shape set. After that, a local-features-based matching and ranking (LMR) method follows in the second stage. We apply the proposed TSR system to MPEG-7, Kimia99 and Tari1000 three datasets and show that it outperforms all other existing methods. The robust retrieval performance of the TSR system is demonstrated.