Experimental study of mode field evolution of dual-core photonic crystal fiber

The accurate mode field profile of high negative dispersion dual-core photonic crystal fiber (DCPCF) is measured. The mode field evolution of DCPCF with wavelength is studied experimentally for the first time. The measurement result shows that no individual inner core mode or outer core mode exists, but two modes coexist simultaneously, and either one of them is dominant. The mode field evolution versus wavelength indicates that the wavelength range where the modes coupling takes place between inner core and outer core is broader than that of theoretical design.

面向有差异群体的联合决策方案

公平性、透明性是联合决策的基本安全需求.结合多机构商务合作背景,利用具有同态性质的Paillier公钥密码系统和门限密码技术,提出了面向有差异群体的联合决策策略与方案,并对其安全性进行了分析和证明.

纳米二氧化钒薄膜的制备及红外光学性能

采用双离子束溅射方法在Si_3N_4/SiO_2/Si基底表面沉积氧化钒薄膜,在氮气气氛下热处理获得二氧化钒薄膜.利用x射线衍射(XRD)、扫描电子显微镜(SEM)和X射线光电子能谱(XPS)研究了热处理温度对氧化钒薄膜晶体结构、表面形貌和组分的影响,利用傅里叶变换红外光谱(FT-IR)对二氧化钒薄膜的红外透射性能进行了测试分析.结果表明,所制备的氧化钒薄膜以非晶态V_2O_5;和四方金红石结构VO_2为主,经400℃、2 h热处理后获得了(011)择优取向的单斜金红石结构纳米VO_2薄膜,提高热处理温度至450℃,纳米结构VO_2薄膜的晶粒尺寸减小.FT-IR结果显示,纳米VO_2薄膜透射率对比因子超过0.99,高温关闭状态下透射率接近0.小晶粒尺寸纳米VO_2:薄膜更适合在热光开关器件领域应用.

Wet Oxidation of AlxGa1-xAs/GaAs Distributed Bragg Reflectors

The wet oxidation of AlGaAs with high Al content in a distributed Bragg reflectors （DBR） is studied by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. Some voids distribute along the oxide/GaAs interfaces due to the stress induced by the wet oxidation of the AlGaAs layers. These voids decrease the shrinkage of the Al2O3 layers to 8% instead of the theoretical 20% when compared to the unoxidized AlGaAs layers. With the extension of oxidation time, the reactants are more completely transported to the front interface and the products are more completely transported out along the porous interfaces. As a result,the oxide quality is better.

Decay dynamics of excited CS2 and NH3 investigated by femtosecond laser

By using the home-made femtosecond laser system and the time-of-flight mass spectrometer, the decay dynamics of excited carbon disulfide (CS2) and ammonia (NH3) are investigated in real time by pump-probe multiphoton ionization detection. The estimated lifetime constant of the NH3 (A) over tilde (1)A(2)' state (51+/-4 fs) agreed quite well with the literature report. For the first time, the decay lifetime constants of the NH3 (E) over tilde'(1)A(1)' state (937+/-93 fs), the CS2 (a) over tilde (3)A(2) state (153+/-10 fs), and the CS2 Rydberg state [(3)/(2)]6ssigma(g) ((3)Pi(g)) (948+/-23 fs) are obtained.

人工小叶锦鸡儿(Caraganamicrophylla)灌丛土壤水分动态研究

采用由植被空间序列推断时间系列的方法 ,分析了 1984、1987、1995和 1999年建立的人工小叶锦鸡儿固沙植被土壤水分的时空变化特征 .结果表明 ,受沙地土壤机械组成的影响 ,沙地土壤组成以物理性沙粒为主 ,>0 .0 1mm沙粒占 97%以上 ,凋萎湿度为 1.5 5 % ,田间持水量为 5 .5 % ,土壤最大有效水为3.95 % .随着固沙植被优势度的增加 ,小叶锦鸡儿灌丛下土壤含水量持续下降 ,1984年建立的植被区土壤含水量明显低于 1999年建立的植被区 ;在年内土壤水分季节变化中 ,4个阶段植被区土壤水分状况在 4～6月不断降低 ,到 6月达到最低值 ,7～ 10月逐渐回升 ;对于建立较早的植被区 (1984和 1987年 ) ,土壤水分垂直变化表现出随着土层深度的增加 ,土壤含水量逐层递减的趋势 ,特别是 70cm下土层中 ,土壤含水下降明显 ,含水量低于凋萎湿度 ;由于对根际区域土壤水分的利用 ,加剧了固沙植被区深层土壤 (70cm下 )水分的亏缺 ,进而影响植被物种的组成 ,随着小叶锦鸡儿灌丛年龄的增加 ,浅根性植物所占比重增加 .

Determination of ascorbic acid by flow injection chemiluminescence suppression method

chemiluminescence suppression method for the determination of ascorbic acid based on Luminol-KIO4-H2O2-ascorbic acid system was established. The linear range for ascorbic acid is 1.0 x 10(-7) similar to 1.0 x 10(-5) mol/L and the detection limit is 6.0 x 10(-8) mol/L. The relative standard deviation (n = 11) is 1.0% for 8.0 x 10(-7) mol/L ascorbic acid. The method has been used to determine the content of ascorbic acid in tablets and injections with satisfactory results.

流动注射化学发光抑制法测定抗坏血酸

基于抗坏血酸对Ｌｕｍｉｎｏｌ－ＫＩＯ４－Ｈ２Ｏ２体系化学发光反应的抑制作用，建立了化学发光抑制快速测定抗坏血酸的新方法。该方法线性范围为 １．０ × １０－７～ １．０ × １０－５ ｍｏｌ／Ｌ，检出限为６．０× １０－８ｍｏｌ／Ｌ，对８．０× １０－７ｍｏｌ／Ｌ抗坏血酸 １１次平行测定的相对标准偏差为 １．０％。用于维生素Ｃ片剂及注射液中抗坏血酸含量的测定，结果令人满意。

Effects of molecular weight and interaction parameter on the glass transition temperature of polystyrene mixtures and its blends with polystyrene/poly(2,6-dimethyl-p-phenylene oxide)

The glass transition temperature (T-g) of mixtures of polystyrene (PS) with different molecular weight and of blends of poly(2,6-dimethyl-p-phenylene oxide) (PPO) and polystyrene with different molecular weight (DMWPS) was studied by a DSC method. For the whole range of composition, the curves of T-g vs composition obtained by experiment were compared with predictions from the Fox, Gordon-Taylor, Couchman and Lu-Weiss, equations. It was found that the experimental results were not in agreement with those from the Fox, Gordon-TayIor and Couchman equations for the binary mixtures of DMWPS, where the interaction parameter chi was approximately zero. However, for the blends PPO/DMWPS (chi < 0), with an increase of molecular weight of PS, it was shown that the experimental results fitted well with those obtained from the Couchman, Gordon-Taylor and Fox equations, respectively. Furthermore, the Gordon-Taylor equation was nearly identical to the Lu-Weiss equation when \chi\ was not very large. Further, the dependence of the change of heat capacity associated with the glass transition (Delta C-p) on the molecular weight of PS was investigated and an empirical equation was presented. (C) 1997 Elsevier Science Ltd.

Studies on structure-property relationship between color reagents and contrast of their color reactions with cerium by topological indices

In this paper, three topological indices A(m1), A(m2) and A(m3) have been applied to multivariate analysis in structure property relationship studies. The topological indices oi fourty-three asymmetrical phosphono bisazo derivatives of chromotropic acid have been calculated, The structure-property relationship between color reagents and contrast of color reactions with cerium has been studied by A, indices and structure selective factors, Good results have been obtained.