Study on the Superluminal Group Velocity in a Coaxial Photonic Crystal

In this paper, the superluminal group velocity in a coaxial photonic crystal is studied. The simulation of the effective refraction index in coaxial photonic crystal is performed. The group velocity is calculated based on the transmission line equations and compared with experimental results.     

界面剂对新旧混凝土界面粘结性能影响的试验研究

为研究界面剂对新旧混凝土界面粘结强度的影响及其粘结机理,进行未涂刷界面剂与涂刷水泥净浆、掺10%粉煤灰水泥浆、掺10%U型膨胀剂水泥浆、掺10%丁苯乳液水泥浆等5组Z形试件的直剪试验,测定各试件新旧混凝土界面的剪切强度;同时,采用显微硬度仪与扫描电子显微镜,分析界面过渡区的显微硬度值分布规律、微观结构形貌以及水化产物种类与分布特征.试验结果表明,新旧混凝土界面为薄弱区域,涂刷合适的界面剂可优化孔结构,改善界面密实度,增大新旧混凝土在微观层面上的机械咬合作用.此外,常用的4种界面剂中,水泥净浆和掺U型膨胀剂水泥浆的性价比相对较高.     

无人机遥感图像融合方法研究

针对待拼接的无人机遥感图像重叠区域不规则、焦距不固定、含噪声较多等问题, 在加权平均融合算法的基础上引入基于折线化思想的不规则重叠区域生成法, 减小算法误差, 并运用基于距离比的自适应算法实现权值自动匹配, 使算法在不受重叠区域形状限制的同时得到更精确的计算结果, 解决了图像拼接后融合区域分辨率低、拼接线明显的问题。仿真表明, 改进的加权平均融合算法在保持原算法快速性的同时, 达到了去除拼接缝隙、使图像融合区域过渡平滑的目的, 并获得了融合质量较好的大视野无缝拼接图像。     

基于本体的教育资源语义检索系统研究

为提高信息检索的准确率和全面性, 在对语义检索技术和领域本体的构建进行充分研究的基础上, 在网络教育资源的检索工作中应用了本体语义的概念, 提出对用户输入的查询条件进行基于本体的查询扩展算法,设计实现了使用Lucene 对扩展后的查询条件进行检索的语义检索模型。实验结果表明, 该检索模型的综合查全率为81郾5%, 综合查准率为83郾1%, 这两项指标均优于传统的关键字检索方法。     

基于复合主题演化模型的作者研究兴趣动态发现

以金融领域的科技文献作为实验数据,提出了一种新的用于动态挖掘领域相关的作者研究兴趣的复合主题演化模型。该模型能够获取作者在不同时间片下的主题概率分布以及主题下词汇概率分布,并充分考虑作者在合作作者文献中的排名对于其研究主题和主题变化的影响。通过金融领域的实证研究表明,该复合主题演化模型能够有效地揭示金融领域作者研究兴趣的动态变化。     

Generation of Linear and Parabolic Concentration Gradients by Using a Christmas Tree-Shaped Microfluidic Network

This paper describes a simple method of generating concentration gradients with linear and parabolic profiles by using a Christmas tree-shaped microfluidic network.The microfluidic gradient generator consists of two parts:a Christmas tree-shaped network for gradient generation and a broad microchannel for detection.A two-dimensional model was built to analyze the flow field and the mass transfer in the microfluidic network.The simulating results show that a series of linear and parabolic gradient profiles were generated via adjusting relative flow rate ratios of the two source solutions(R_L~2≥0.995 and _PR~2≥0.999),which could match well with the experimental results(R_L~2≥0.987 and _PR~2≥0.996).The proposed method is promising for the generation of linear and parabolic concentration gradient profiles,with the potential in chemical and biological applications such as combinatorial chemistry synthesis,stem cell differentiation or cytotoxicity assays.     

三七多糖的微波辅助提取工艺

采用正交试验法优化了三七多糖的微波提取工艺,采用激光粒度分析法探讨了提取机理,分析了多糖的单糖组成,并测定了多糖的溶解性。三七多糖的较佳微波辅助提取工艺条件为微波处理时间8min、浸泡时间60min、液固比30mL/g、粒度200目。微波辅助提取的多糖提取率(21.0mg/g)显著高于传统提取(12.7mg/g)。三七多糖的Molish反应呈阳性,多糖酸水解产物的薄层色谱呈现出3个斑点,分别与葡萄糖、半乳糖和阿拉伯糖相对应。微波辅助提取对三七多糖的提取效果明显优于传统提取,其机理可能是微波处理促进了三七样品的水化和溶胀过程,使样品结构变得松散、膨胀,从而促进了多糖从样品中扩散和溶出。三七多糖主要由葡萄糖、半乳糖和阿拉伯糖3种单糖构成,pH值对其溶解性影响较大。     

Synthesis and luminescence properties of Mn4+-dopant Ca14Zn6Ga10−xAlxO35 solid solution

Mn~(4+)-activated oxide phosphors,owing to their desirable spectral features,eco-friendly and low cost,are emerging as a new class of non-rare-earth red phosphors for warm white LEDs.However,these phosphors possess low photoluminescence quantum efficiency excited by blue chip currently.Herein we report an isostructural solid solution of Ca_(14)Zn_6Ga_(10-x)Al_xO_(35):0.15Mn~(4+)(0≤x≤10)synthesized by a traditional solidstate reaction route.The microstructure and luminescent performance of this red-emitting phosphor are investigated in detail with the aids of X-ray diffraction,diffuse reflection spectra,photoluminescence spectra/decay/QE,and temperature-dependent PL/QE measurements.Blue shift of energy peaks of~4A_2→~4T_1and~4A_2→~4T_2transition is illustrated by the Tanabe–Sugano diagram and the configurational coordinate diagram.The crystal field strength(Dq)and the Racah parameters(B and C)are carefully calculated to estimate the nephelauxetic effectβrespectively.Particularly we achieve external and internal quantum efficiencies as high as26.1%and 40.3%for Ca_(14)Zn_6Ga_6Al_4O_(35):0.15Mn~(4+)excited by 466 nm,the highest one ever reported in Mn~(4+)activated oxide phosphors under the similar condition.     

Nanoengineering of amino - functionalized mesoporous silica nanospheres as nanoreactors

Selective functionalization of mesoporous silica nanospheres (MSNs) is crucial for nanoengineering of MSNs. Herein, we have combined “surface-protected etching strategy” and “cationic surfactant assisted etching strategy” to prepare functionalized MSNs with externally attached amino groups. The externally attached NH2 groups endow the catalysts with excellent catalytic performance for nitroaldol reaction between nitromethane and benzaldehyde. In addition, those NH2-MSNs can also be used to support gold nanoparticles, which display very good catalytic performance for reduction of 4-nitrophenol. It can be envisioned that the synthesis protocol developed in this work could also be extended to nanoengineered MSNs, which provides opportunities for nanoreactors design.