Enhancement of upconversion luminescence of YAlO3:Er3+ by Gd3+ doping

The upconversion luminescences of YAlO3:Er3+ phosphor co-doping with different Gd3+ concentrations are investigated under the excitation of 980- and 532-nm diode lasers. A near ultraviolet upconversion emission at 410 nm is observed in YAlO3 under 532-nm excitation. Moreover, the inactive Gd3+ ions can improve the upconversion intensity efficiently in a certain range of concentration. Under 980-nm excitation, the visible upconversion emissions at 546 and 646 nm are enhanced by about 10 and 8 times at the Gd3+ concentration of 40%, respectively. The upconversion emission at 410 nm under 532-nm excitation is also enhanced by 7 times. The substitution of Gd3+ ions for Y3+ sites changes the local symmetry of Er3+, leading to the improvement of upconversion efficiency.     

Exploration of the sum of flexoelectric coef ficients of nematic liquid crystals

We present a theoretical calculation of the dependence of reflectivity Rpp of the improved fully leaky waveguide geometry,which comprises pyramid,matching fluid,and strongly anchored hybrid aligned nematic liquid crystal(NLC) cell on the internal angle.The calculation is based on the multi layer optical theory and the elastic theory of liquid crystals.For different sums of flexoelectric coefficients e11 and e33,the curve of Rpp moves a distance to the left or the right relative to the case of ignoring the flexoelectric effect and the distance of the movement varies with different flexoelectric coefficients.Consequently,the sum of flexoelectric coefficients can be explored by measuring the distance of the movement.     

浅谈光缆敷设技术

介绍了两种光缆敷设方法—牵引法和气吹法,给出了牵引法中牵引张力的计算公式;分析了气吹法的构成及施工工序,这为施工人员灵活选用敷设方法提供了参考价值.     

PCB设计课程项目驱动教学改革的探索

PCB设计是一门实践性非常强的课程,需要结合企业需求,培养学生的实际应用能力,而当前的PCB设计课程还是采用传统的教学模式,阻碍了学校教育与企业需求的对接,因此,提出了以工程项目实例驱动形式展开PCB设计课程的教学工作,并取得了卓有成效的进展。     

生物科技的新引擎——生物芯片（上）

一 前言 当初次听到“生物芯片”时,很多人会把它当作一种新的电脑芯片。实际上,生物芯片和微处理器芯片有着本质区别。微处理器芯片是由硅、锗等半导体材料经微电子加工技术制作的集成电路设备;而生物芯片只是一种执行生物检测和分析的微型设备。不过从起源     

今日科技塑造未来 北电引领4G和下一代移动通信

与传统的宽带系统相比,WiMAX网络具有众多优势,如WiMAX网络极为灵活,可实现有线和无线业务的混合连接.由于WiMAX网络不需要固定线路,部署一个WiMAX网络所需投资仅相当于部署一个有线网络总投资的三分之一,而且可以减少网络部署时间以及运营和维护的成本,因此有助于提高运营商的效益.此外,WiMAX可提供极高的数据吞吐量和移动性,让用户能够随时在线,即使处于移动状态也能获得真正的宽带体验.为此WiMAX正以飞快的速度在全球发展.     

毛细管电泳-电化学检测法检测水解植物蛋白调味液中的3-氯-1,2-丙二醇及其应用

运用毛细管电泳-电化学检测法研究了水解植物蛋白液中3-氯-1,2-丙二醇(3-MCPD)含量的测定。探索了3-MCPD检测的最佳电泳条件。以328 μm的铜圆盘电极为工作电极,在电极电位为+0.65 V(参比电极为饱和甘汞电极),检测池缓冲液为0.05 mol/L氢氧化钠,运行缓冲液为30 mmol/L硼砂(pH 9.24)时,3-MCPD能被很好地分离。3-MCPD的线性范围为6.6~200 mg/L,检测限为0.22 mg/L。研究了水解缓冲液的pH值、水解温度、水解时间等因素对3-MCPD水解反应的影响,用毛细管电泳-电化学检测法检测水解反应过程中3-MCPD的含量。结果表明,在pH 8.0的水解缓冲液中,将水解植物蛋白调味液前体于90 ℃条件下恒温加热1 h,能有效地控制3-MCPD的含量在1.0 mg/kg以下,从而达到我国食品安全允许的限量标准。     

Anchoring properties of substrate with a grating surface

The anchoring properties of substrate with a grating surface are investigated analytically. The alignment of nematic liquid crystal (NLC) in a grating surface originates from two mechanisms, thus the anchoring energy consists of two parts. One originates from the interaction potential between NLC molecules and the molecules on the substrate surface, and the other stems from the increased elastic strain energy. Based on the two mechanisms, the expression of anchoring energy per unit area of a projected plane of this grating surface is deduced and called the equivalent anchoring energy formula. Both the strength and the easy direction of equivalent anchoring energy are a function of the geometrical parameters (amplitude and pitch) of a grating surface. By using this formula, the grating surface can be replaced by its projected plane and its anchoring properties can be described by the equivalent anchoring energy formula.     

紫外光接枝季铵盐抗菌聚乙烯膜的制备和表征

近年来出现的高分子杀菌剂,又称表面接触消毒剂,是将杀菌基团结合在不溶性载体上．此类杀菌剂不仅可以有效的避免二次污染,而且可以重复利用．由于杀菌基团集中在载体表面且浓度高,也使得消毒时间缩短．这些优点使高分子杀菌剂成为目前研究的热点。     

生长温度和结构参数对InGaAs／GaAs量子阱光学特性的影响

研究了不同生长温度下制备的In0.15Ga0.85As/GaAs应变量子阱的PL谱,结果表明,生长温度越高,In偏析和In-Ga互混越严重,同时,导致更多的In脱附,PL谱发光峰蓝移。对不同In含量的和不同InGaAs厚度的InGaAs/GaAs量子阱进行PL谱测试,分析表明In含量<0.2,生长温度低于560℃时,In含量和InGaAs层量子阱的厚度对In偏析、脱附和In-Ga互混基本没有影响。