Algebraic Independence of Certain Generalized Mahler Type Numbers

In this paper the generalized Mahler type number Mh（g;A,T） is defined, and in the case of multiplicatively dependent parameters gi, hi（1 ≤ i ≤ s） the algebraic independence of the numbers Mhi （gi; A, T）（1 ≤ i ≤ s） is proved, where A and T are certain infinite sequences of non-negative integers and of positive integers, respectively. Furthermore, the algebraic independence result on values of a certain function connected with the generalized Mahler type number and its derivatives at algebraic numbers is also given.     

pH调控合成溴氧铋纳米片的底物依赖光催化特性

近年来,半导体光催化技术已广泛用于去除水中有机污染物.在各类光催化剂中,具有合适禁带宽度的溴氧铋(BiOBr,2.7 eV)材料吸引了众多研究者兴趣.通常情况下,半导体光催化降解有机污染物性能主要与光催化材料的结构性质,如物相组成、颗粒粒径、材料表面结构等相关.研究已经证实了TiO2光催化降解有机污染物具有底物依赖的特性,但是BiOBr的有机物降解特性与底物性质的关系研究尚未见文献报道.为发展高效的BiOBr太阳光催化污染净化技术,研究有机底物与BiOBr光催化降解性能的关系具有重要意义.本文分别在pH =1和pH =3条件下采用水热法合成了BiOBr纳米片(BOB-1和BOB-3),并通过X射线粉末衍射(XRD),扫描电子显微镜(SEM),透射电子显微镜(TEM),紫外-可见漫反射(DRS)等技术表征了所制备半导体光催化材料.结果表明,在不同pH条件下均能合成具有高结晶度的四方相BiOBr, BOB-1和BOB-3均由不规则的纳米片组成, BOB-3纳米片宽度大约为0.6–1.5μm,厚度大约27–44 nm,而BOB-1纳米片宽度大约为0.7–2.0μm,厚度大约50 nm.选区电子衍射观察到了BOB-1和BOB-3清晰的晶格条纹,晶格间距为0.20和0.28 nm,分别对应着四方晶系的(020)面和(110)面.选取罗丹明B(RhB)和水杨酸(SA)为典型有机底物分子,研究了BOB-1和BOB-3纳米片的底物依赖光催化特性.结果表明, BOB-1吸附SA和RhB 1 h后,吸附率分别仅为0.2%和0.8%,而BOB-3对SA和RhB的效率分别可达9.1%和12.7%;光催化降解两种底物分子的结果表明, BOB-1和BOB-3降解RhB的速率分别为4.00以及16.10 g·min–1·m2,而降解SA的速率分别为和2.35 g·min–1·m2.可见, BOB-1显示了高效降解SA的能力,而, BOB-3则表现出更强的降解RhB活性.电化学Mott-Schottky和电动电位测试结果表明, BOB-1比BOB-3有更正的价带电位和更低的表面电荷.捕获实验(KI捕获空穴, K2Cr2O7捕获电子,氩气捕获超氧负离子,异丙醇捕获羟基自由基)表明光生空穴与超氧负离子是BOB-3降解RhB的主要活性物种,而BOB-1降解SA主要是光生空穴作用,电子顺磁共振(ESR)测试进一步证实了以上结果.光电流密度测试结果表明,可见光作用下RhB可被激发到RhB*,导致BOB-3的电子空穴对分离效率高;而当电解质中存在SA时,催化剂的表面羟基与SA形成氢键,致使光生电子与空穴分离效果变差,因而光电流减少.本文提出了pH调控合成溴氧铋纳米片的底物依赖光催化降解RhB和SA机理,与BiOBr导带电位、底物分子吸附量、底物分子物理化学性质相关. BOB-1和BOB-3纳米片催化剂在可见光激发下能产生光生导带电子和价带空穴,这些光生载流子可迁移到催化剂表面.染料分子RhB在可见光作用下能发生光敏化作用生成激发态RhB*, RhB*可以将电子注入BOB-3催化剂的导带,导带上的光生电子与RhB*注入电子与吸附在其表面的氧气共同作用生成更多的超氧负离子,从而高效降解RhB.由于BOB-1比BOB-3有更正导带电势,导带电子无法直接还原氧气生成超氧负离子,仅能依靠光生空穴直接氧化RhB,导致BOB-1表现出降解RhB性能弱;对于无色的底物SA,吸附较多SA的BOB-3催化剂上的表面羟基与SA之间形成氢键作用,抑制了光生电子与空穴对的分离,导致BOB-3在可见光光催化降解SA活性弱,而BOB-1表面吸附SA较少,同时BOB-1有更负的价带电位,利用光生空穴与吸附在催化剂表面的SA反应,从而表现出高效降解SA的性能.     

基于差分的等级依赖效用模型行为决策权重扩展(英文)

基于等级依赖期望效用模型(RDEU),提供了一个简单但有效的行为决策权重扩展.因结果序列具有直线增长趋势,介绍一种基于一阶差分的新权重,并证明其对拆分效应的有效性.差分权重和RDEU权重的凸组合构成最终决策权重命名为D'-RDEU权重,它不仅可继承RDEU的优点,也可克服RDEU的两个不足.特别是,它通过拆分获得随机优势,可从理论上解释拆分效应.也提供了连续形式的D'-RDEU模型,连续模型的存在证明D'-RDEU比D-RDEU更实用.     

微脉冲偏振激光雷达探测城市底层气溶胶

以单脉冲能量2μJ,重复频率1kHz的Nd:YAG固体激光器为光源研发了一台便携式人眼安全可三维扫描的微脉冲偏振激光雷达系统,可实现对城市底层气溶胶球形特性和分布情况的探测.为保证在西北地区等高密度气溶胶聚集的地域,实现近地表80~1000m范围内的精确探测,系统的光电检测采用模拟探测技术.利用该激光雷达系统首次对冬季西安局部地区1000m范围内大气气溶胶退偏比进行了俯仰扫描探测,并分析了天气过程和地面状况对退偏比的影响.实验结果表明,探测期间无明显沙尘事件发生,探测区域内气溶胶的退偏比在0.1左右,在无绿化带的交通干道交叉口等局部区域,受地面状况影响退偏比偏高,并获得了退偏比值与天气过程的初步关系,同时也验证了系统的可行性.研究成果可对城市底层气溶胶的产生、传输及扩散特性研究提供科学数据.     

三通道偏振成像系统及系统误差校正方法

为了解决现有偏振成像系统难以满足目标检测和跟踪等实时图像处理领域的要求,提出一种实时三通道偏振成像系统,并对该系统存在的视场差异和非一致性误差提出了校正方法.该系统采用三个独立通道采集0°、60°和120°方向上的偏振图像,针对三个独立通道之间存在的视场差异提出了采用尺度不变特征转换配准法进行校正的方法;同时针对三个独立通道之间的灰度响应非一致性现象,根据积分球的退偏特性和探测器的线性响应模型,利用积分球产生完全非偏振光对灰度响应非一致性误差进行了校正.对比实验证明:1)本文提出的三通道偏振成像系统进行校正后的成像效果能够接近单通道偏振成像系统的水平;2)该系统能够在实时采集图像的同时,克服了多通道带来的偏振图像质量下降问题,提高了实用性.     

A wideband tunable phase shifter based on orthogonal optical single-sideband

We present a novel technique to generate an orthogonally polarized optical single sideband （OSSB） generated by a tunable bandpass filter （TBF）. When the OSSB passes through the other polarization modulation （PolM） which is polarization dependent, the phase shift of the optical carrier and first-order sideband is different under different bias. As a result, a wideband tunable phase shifter is realized by adjusting the bias applied to the polarization modulator.     

Numerical study of negative index material with low loss and polarization-independence in mid-infrared spectrum

We engineer numerically a negative index material （NIM） based on a square ring pairs （SRP） array and a thin wire net pairs （WNP）. This metamaterial exhibits polarization-independence and low loss that is characterized by a figure of merit （FOM） up to 8.2 in mid-infrared spectrum.     

Double-wavelength polarization insensistive beam splitter used in optical storage technology

Device to read/write data from optical storage units have polarization insensitive character at two separated wavelength. Based on a key four-layer structure and some matching layers, an initial thin film stack system is constructed. After optimized alternately by simplex and conjugate graduate algorithm, a double- wavelength polarization insensitive beam splitter with splitting ratio of R ： T=50：50 at 650-nm wavelength and T ≥ 93% at 780-nm wavelength is gained. The design result shows that the difference between reflectivity of P and S light around wavelength range of 630-670 and 760-800 nm with incident angle of 40~-50~ is all very little. That indicates our design controls the polarization deviation well at two separate wavelengths with a reasonable range for both wavelength and incident nn~l~     

Polarimetric interferometer for measuring nonlinearity error of heterodyne interferometric displacement system

This letter presents a polarimetric interferometer(PI) that can measure the ellipsometric parameter θ with an accuracy of 0.01 leading to a potential accuracy of 17 pm.The PI is constructed and compared with a commercial heterodyne interferometer(HI).Given its low nonlinearity,the PI is used to measure the residual nonlinearity of a heterodyne interferometric displacement system.A rotating half-wave plate is used to compensate for a part of the nonlinearity error caused by the misalignment of the axis between input polarizing states and beamsplitter.     

Brief review of recent research on blue phase liquid crystal materials and devices

Both polymer stabilization and bent-shaped molecule doping strategies are utilized to widen the blue phase range of liquid crystals. The molecular structures of compositions are optimized for high thermo-optical and electro-optical performances. A low temperature applicable blue phase liquid crystal with suppressed hysteresis is achieved. The bistability of one blue phase liquid crystal is investigated. Based on these materials, fast tunable devices such as gratings with polarization insensitivity are designed and fabricated. The materials and device designs demonstrated here are suitable in wide applications requiring fast response time.