Study on the properties of amino acid ionic liquid EMIGly

In terms of standard addition method, the density and surface tension of an amino acid ionic liquid EMIGly(1-ethyl-3-methylimidazolium aminoacetate) were measured under dry argon atmosphere in the temperature range of 288.15-343.15 K. The properties of volume and surface for pure EMIGly were discussed in terms of the interstice model and Glasser's theory. The thermal expansion coefficient alpha = 5.03 x 10(-4) K(-1) calculated using interstice model is in good agreement with alpha (experimental) = 5.20 x 10(-4) K(-1).     

Stereoselective generation of (E)- and (Z)-2-fluoroalkylidene-type carbenoids from (2-fluoro-1-alkenyl)iodonium salts and their application for stereoselective synthesis of fluoroalkenes

Alkylidene-type carbenoids, generated from (Z)- or (E)-(2-fluoro-1-alkenyl)iodonium salts by treatment with LDA, reacted with trialkylboranes to give (E)- or (Z)-(fluoroalkenyl)boranes stereoselectively. The resulting (fluoroalkenyl)borane can be used for the selective synthesis of (E)- or (Z)-fluoroalkenes, (E)- or (Z)-fluoroiodoalkenes, and alpha-fluoroketones. [reaction: see text]     

Efficient calculation of electron diffraction for the structural determination of nanomaterials

A critical advance in the technique of low-energy electron diffraction is presented and shown to enable determining detailed structures of nanomaterials, based on experimental methods that already exist or have been proposed. Our new cluster approach speeds up the computation to scale as n logn, rather than the current n3 or n2, with n the number of atoms, for example. Applications are illustrated for C60 molecules adsorbed on a Cu(111) surface, with and without coadsorbed metal atoms, exhibiting sensitivity to important structural features such as buckyball size and deformation.     

深证成指周收益率波动性的实证研究

利用GARCH模型,对深圳成分指数的周收益率波动性进行了实证研究。以深证成指周收盘数据建立了GARCH模型,利用估计出的GARCH模型得到深证成指周收益率序列的条件方差的估计值,预测出深证成指周收益率序列未来若干期的条件方差。结果表明,深证成指周收益率序列的波动性可以用GARCH模型进行很好的拟合。     

Superconvergence analysis of FEMs for the Stokes–Darcy system

We consider a superconvergence analysis for quadratic finite element approximations of the Stokes–Darcy system. The superclose property of an extra half order is proven for uniform triangular meshes. Based on the result of the superclose property, global superconvergence is derived by applying a postprocessing technique. In addition, some numerical examples are presented to demonstrate our theoretical results. Copyright © 2010 John Wiley & Sons, Ltd.     

Hazard regression with penalized spline: The smoothing parameter choice and asymptotics

In this article, we use penalized spline to estimate the hazard function from a set of censored failure time data. A new approach to estimate the amount of smoothing is provided. Under regularity conditions we establish the consistency and the asymptotic normality of the penalized likelihood estimators. Numerical studies and an example are conducted to evaluate the performances of the new procedure.     

Mn掺杂对ZnO∶Mn薄膜结构特性的影响

利用射频磁控溅射方法在玻璃衬底上室温沉积了一系列不同Mn掺杂的ZnO∶Mn薄膜。结合Raman光谱,XRD谱和SEM分析了ZnO∶Mn薄膜的结构特性。Raman拟合结果显示,在Mn摩尔分数从0增加到5.6%的过程中,ZnO∶Mn薄膜始终保持着六角纤锌矿结构;随着Mn掺杂浓度的增大,437 cm-1和527 cm-1位置上的Raman散射峰出现红移现象,说明Mn掺杂量的增加导致晶格更加无序,缺陷增多;当Mn摩尔分数达到15.8%时,647 cm-1处的Raman散射峰出现,暗示了MnO的产生,同时薄膜结晶质量变差。这一结论也得到了XRD和SEM结果的支持。     

一种基于BOTDA与FBG传感的共线温度测试技术

根据大型结构全尺度分布式高精度温度测量要求,组合应用布里渊时域分析(BOTDA)技术和光纤布拉格光栅(FBG)温度传感技术,设计了一种由BOTDA分析仪、FBG解调仪、共线传感探头和光开关组成的温度传感测试系统。实验测试证明,该系统具备大范围分布式温度测量与局部高精度温度测量功能,而且实现了BOTDA测温技术与FBG温度传感技术的有效互补,解决了测量范围和测量精度的矛盾问题,并且具有良好的温度重复性,达到了预期的设计要求。该共线测试技术方案在大规模结构温度监测中具有广阔的应用前景。     

基于STC89C51的新型液氮低温微创冷冻控制系统设计

设计了一种新型液氮低温微创冷冻控制系统,详述了系统的控制原理及各功能模块的实现.采用热流平衡原理、PID技术与STC89C51单片机及外围控制电路对冷冻冻结面范围、液氮瓶压力及冷刀刀头温度进行实时控制和显示.应用结果表明:该系统运行稳定,可靠性高,操作简单.     

一种新型高双折射光子晶体光纤特性研究

设计了一种高双折射高非线性光子晶体光纤, 采用全矢量有限元法研究了这种光纤的基模模场、双折射、非线性、有效模面积及色散特性. 数值研究发现, 减小孔间距Λ的大小, 在波长1550 nm 处, 该光纤可获得10^-2 数量级的双折射B, 比普通的椭圆保偏光纤高约两个数量级; 同时, 该光纤可获得42 W^-1·km^-1 的高非线性系数γ. 另外,分别在可见光和近红外波段出现了两个零色散波长, 在波长800–2000 nm 之间具有良好的色散平坦特性. 这种设计为获得高双折射高非线性超平坦色散光子晶体光纤提供了一种新的方法, 该光纤在偏振控制、非线性光学和色散控制方面具有广泛的应用前景. 关键词： 光子晶体光纤 高双折射 高非线性 有限元法