第一性原理的形变势理论研究声学声子散射对电荷传输的影响

本文应用密度泛函理论和玻尔兹曼方程,在形变势理论的框架和驰豫时间近似下,研究了分子晶体中电子与声学声子散射对电荷传输的影响.针对蒽、萘、丁省和并五苯的计算表明,非局域化电子的传输过程主要受到来自于声学声子的散射.对于蒽晶体,与以前的Holstein-Peierls模型计算结果相比,发现纵向声学声子对空穴的散射强度是光学声子的3倍,所得到的空穴迁移率更接近超纯单晶样品的实验测量结果.同时,我们发现电子的本征迁移率比空穴还要大,应用前线轨道交叠分析可以合理地解释这一结果.     

Electric-field-induced fabrication of covalently linked second-order nonlinear optical multilayer films on nonconductive substrates

A highly stable second-order nonlinear optical multilayer film was constructed on insulating substrates using the electric-field-induced layer-by-layer assembly technique. The substrates used in this method could be arbitrary. In another, the substrates could be modified with polyanion solution by spin coating as cladding layer. Then, the nonlinear optical multilayer films were assembled on the cladding layer directly by the electric-field-induced layer-by-layer assembly technique. The resulting cross-linked multilayer films fabricated by this method displayed high optical transparency, good thermal stability, and excellent nonlinear optical properties which can be made into waveguide devices directly.     

激光扫描显示对视觉感知的影响

研究了激光扫描显示(LSD)对视觉感知的一些重要影响.LSD可提供一种能对视觉系统产生特殊影响的高亮度单色图像.在受试者观看激光扫描显示或投影视频时,对其视觉调节进行了测量.单色显示器可能由于色适应对感知产生影响.在使用显示器之前和之后测试了受试者的色觉.当用激光扫描显示器时,发现视觉调节量不断增加,但影响的强度由显示器扫描速度来界定.调节方差的最大差异出现在处于低速扫描的视频显示器和激光扫描显示器之间.在一些受试者中,观看激光扫描显示还导致了可测的色觉变化.实验结果表明:观看激光扫描显示器会对视觉调节反应和色觉产生影响.     

封装材料对光纤器件的性能影响

为查明熔锥型光纤器件封装材料对器件光学性能的影响,基于弱波导耦合模理论,建立了封装材料折射率与光纤耦合器分光比的数学模型,找到了它们之间的关联规律.以六轴光纤耦合器熔融拉锥机制作耦合器样品,以H2O与NaCl的不同配比实现封装材料折射率的变化,进行了相应的光学实验.实验结果表明:光纤耦合器的分光比对封装材料的折射率很敏感,折射率在一定的范围内,随着封装材料折射率的增大,耦合器分光比增大,并且具有单调性.这为封装材料的选取提供了理论依据与实验指导.     

并联微环谐振器耦合诱导透明传输特性研究

通过对并联微环谐振器传输特性进行研究分析,针对结构参数影响耦合诱导透明效应的问题。文中采用微环传输矩阵理论得出传输函数表达式,利用Matlab软件仿真了各参数变化对透明效应的影响。研究结果表明,耦合系数k的增大,传播损耗系数a的减小或两环间距L的增大,均会使透明效应减弱;微环半径R的增大,透明效应无明显的变化,但谐振波长发生改变。     

单端口声表面波谐振器在片去嵌方法分析

为了准确地设计声表滤波器,需要从参考声表面波(SAW)谐振器的测量值中提取精确的材料参数。测量SAW谐振器时,单个谐振器无法直接进行测试,需要引出传输线并使用GSG或GS探针进行测量,消除传输线影响的去嵌入过程对于SAW谐振器材料参数的准确提取非常重要。该文介绍了几种声表面波谐振器的去嵌入技术,包括Open-Short算法、电磁仿真方法、分段等效电路模型方法、集总参数等效电路法。通过实例验证了几种常用的去嵌方法并对其进行了分析。     

变电站双视在线监测智能预警系统的研究与实现

研发了一种用于变电站的双视在线监测智能预警系统和方法,由视频监控前端系统和后端管理平台系统构成。系统利用了最先进的压缩技术与网络传输技术,解决了多路红外热像与CCD图像的数字化时实传输、图像融合问题。支持视频输出扩展,用户可参照CCD图像确定故障部位,实现了用鼠标点击红外图像的任意部位同时显示该部位的CCD图像并进行测温。通过RJ45网线实现对仪器的设置、自动报警、自动录像和对云台的控制,大大方便了安装施工,减少了故障发生率。     

模糊FP-growth在入侵检测中的应用

关联规则挖掘技术目前被广泛应用于入侵检测系统中。关联规则挖掘算法之一的FP-growth算法在处理数值量的输入时需要二值化,使得准确率不高;而Fuzzy Apriori算法需要重复扫描数据库,效率较低。针对此问题,改进现有的FP-growth算法,提出模糊化FP-growth算法,从而提取模糊关联规则,用于N类异常数据的分类入侵检测。在KDDCup＇99数据集上评估,结果表明对于数值量的输入,该方法应用于入侵检测准确率高于FP-growth算法,学习效率高于Fuzzy Apriori算法。     

High pressure synthesis and thermoelectric performances of Cu2Se compounds

The Cu₂Se samples were synthesized by high pressure directly at room temperature in several minutes. The composition evolution under high pressure demonstrates that the critical conditions to synthesize Cu₂Se are the pressure of 1 GPa and the reaction time of 5 min. The synthetic pressure can effectively tune the morphology, carrier concentration and the electrical transport properties. The low lattice thermal conductivity less than 0.5 Wm^?1 K^?1 is obtained because of the intrinsic superionic character and the microstructures by high pressure including abundant micropores and lattice defects. A maximum zT of 0.92 at 783 K is achieved for Cu₂Se synthesized at 1 GPa. This work indicates the potentiality of high pressure technique to further enhance the thermoelectric properties of Cu₂Se materials.     

Synthesis and characterization of phenyl polysiloxane modified polyurea/polyurethanes

A series of phenyl polysiloxane‐modified polyurea/polyurethanes ( SPUs ) with different silicone loadings (10, 20, 30, and 40 wt %) have been designed and synthesized. The structures of SPUs were confirmed by ¹H NMR, ¹³C NMR, and FT‐IR. The impact of phenyl polysiloxane content on the properties of SPUs was fully studied. The residual methoxy groups on silicon could help SPUs form interpenetrating networks accompanying with the residual isocyanate under moisture, which was different with the conventional moisture‐crosslinking polyurethane system. The properties of SPUs films have been fully researched by attenuated total reflection flourier transformed infrared spectroscopy, thermal analysis, tensile tests, water contact angle, X‐ray photoelectron spectroscopy, SEM, and AFM. Results indicated that the introduction of phenyl polysiloxane improved the thermal stability and remarkably increased the water contact angles accompanying with a comparable mechanical strength to the pure polyurethane. Meanwhile, it also brought out the decreased microphase separation and water absorption. The obvious surface migration has been observed in the SPUs , which changed their surface properties. Some voids were observed in all moisture curing SPUs system, but the phenyl silicone content impacted on the numbers and sizes of the voids. The phenyl groups introduced and carbon dioxide produced in the crosslinking procedure helped to form and stabilize the voids in the SPUs . © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1794–1805