二维正方格子磁性光子晶体的界面传导模

采用平面波展开加超元胞方法计算了二维正方格子磁性光子晶体的光子带隙结构，其中散射子的形状分别为长方形，正方形，六角形和圆形.结果表明绝对带隙宽度和其宽高比远大于同种结构的非磁性光子晶体.在此基础上，构成了混合型异质结，并计算了相应的传导模，发现了理想的界面传导模，而且当磁性散射子为长方形、圆形、六角形散射子时产生传导模都不需要晶格畸变，这也是磁性光子晶体异质结所具备的优点. 关键词： 光子晶体 光子带隙结构 传导模     

Anion binding and transport by steroid-based receptors

The steroid nucleus is well-established as a scaffold for anion receptors. The bile acids are especially useful, providing inexpensive starting points with helpful substitution patterns. This article describes developments since an earlier review in 2003. Included are podand and cyclic structures, uncharged and positive receptors, and various arrays of H-bond donor and other binding functionality. Applications have been found in anion sensing, selective extractions, transport across bilayer membranes, and the discovery of antibiotics.     

Synthesis of macrocyclic 1,1′-biarenol derivatives by the tandem Claisen rearrangement and their binding properties

Crown ether-type macrocycles consisting of an enantiopure biarenol derivative and an oligoethylene glycol were synthesized by the Lewis acid-mediated tandem Claisen rearrangement. This is the first example of the successful application of the tandem Claisen rearrangement to the synthesis of enantiopure macrocyclic biarenol derivatives. The enantiopure macrocyclic biarenols were found to form 1:1 complexes with amino acid salts and to discriminate their chirality.     

A New Method for the Measurement of Thickness in Single Crystals

A new method for thickness determination of single-crystal thin samples at exact zone axis orientation, based on pattern recognition in convergent beam electron diffraction (CBED), is presented. The method is especially well suited to materials with a large unit cell in zone axis directions where the reciprocal lattice is uniformly dense with diffraction points. The new method is based on comparison of a measured CBED zone axis pattern with a set of calculated ones. Its accuracy was estimated to be around 10% in the 5–100 nm thickness range as checked for garnets at the [111] zone orientation.     

Photoluminescence of Ge nanostructures grown by gas source molecular beam epitaxy on silicon (1 1 8) surface

In this paper, we present a photoluminescence (PL) study of Si/Ge/SiGe/Si structures grown by gas source molecular beam epitaxy on an (1 1 8) undulated surface with various Ge coverage. Nucleation and growth of Ge films is obtained by the Stranski–Krastanov mechanism. The influence of the substrate orientation on the changeover 2D–3D growth mode is investigated. Furthermore, we show the use of growing an SiGe wetting layer to control the uniformity of the Ge island size. The PL signal related to the Ge islands is found to be highly dependent of the power excitation and is observed up to room temperature.     

铸造锌铝合金稀土变质机理的电子理论研究

根据分子动力学理论建立了液态锌铝合金ZA27的模型，结合计算机编程构造出了ZA27合金α 相与液相共存时的原子结构模型，利用递归方法计算了稀土固溶于晶粒内和富集于结晶前沿 时的电子结构.由此得出：稀土处于相界区比在晶内更稳定，从而解释了稀土在α相内溶解 度很小，结晶时富集于结晶前沿液体中的事实；稀土处于液态和晶态的结构能差相对于铝较 大解释了稀土在相界前的富集使α晶枝产生熔断、游离、增殖的观点.原子间的键级积分计 算也表明，稀土处于结晶前沿液体中与铝相比不容易结晶到晶体表面，起到阻碍晶粒长大， 细化晶粒的作用，这就从电子层次解释了稀土的变质机理. 关键词： 电子结构 液固相界原子结构模型 稀土变质机理     

Diffraction of a Plane Discontinuos Wave in Layered Anisotropic Elastic Media

The problem of transformation of the front of a plane longitudinal shock wave by curvilinear interfaces of layered anisotropic elastic media with different mechanical properties is considered. To solve the nonlinear Snell equations, the approach based on a synthesis of the Newton method and the algorithm of parametric continuation of a solution is used. The cases of focusing and scattering of rays by convex and concave interfaces of layered composite media and by convex lenses are investigated. Numerical examples are given for various ratios between the parameters of the elastic media.     

方阱链流体在固液界面分布的密度泛函理论研究

应用Yethiraj的加权密度近似泛函理论研究平板狭缝中方阱链流体的密度分布，系统的Helm holtz自由能泛函分为理想气体的贡献利剩余贡献两部分，其中剩余贡献部分分别采用刘洪 来等人建立的基于空穴相关函数的方阱链流体状态方程和Gil-Villegas等人提出的统计缔合 流体理论状态方程(SAFT-VR)结合简单加权密度近似计算.考察了不同链长、温度、系统密度 和壁面吸引强度下平板狭缝中方阱链流体的密度分布，并与Monte Carlo(MC)模拟结果进行 了比较.结果表明采用不同的状态方程对密度分布的计算有明显的影响，对于受限于硬壁狭 缝中的方阱链流体，温度和密度比较高时，两种状态方程计算的结果均与MC模拟符合得比较 好，在低温和低密度下效果变差，SAFT-VR方程的计算结果更接近于MC模拟结果.对于受限于 方阱壁狭缝中的方阱链流体，由于系统密度分布的非均匀性加强，采用两种状态方程计算的 结果均与MC模拟结果有一定偏差，寻找更合适的权重函数是进一步改进的关键. 关键词： 密度泛函理论 非均匀流体 密度分布 固液界面 方阱链     

Radon变换在二维条码图像识别中的应用

分忻了DataMatrix（简称DM）二维条码的符号结构特点，根据Radon变换的基本思想方法，提出一种对识别无间断的连续线段很有效的算法和一种对识别“铁路线”很有效的算法，运用这两途中算法，在二维条码图像最小模块仅为2.7像素的情况下，在图像轻微弯曲的情况下，可以对二维条码图像中的黑边和铁路线快速准确地定位，该算法可以应用于QR Code、DataMatrix、Code93和龙贝码等二维条码的图像识别。     

磁盘润滑膜全氟聚醚的分子动力学模拟研究

纳米润滑膜全氟聚醚(perfluoropolyether，简称PFPE)在固体表面的结构和迁移特性对于计 算机磁盘磁头驱动系统的可靠性具有重要的作用. 采用基于粗粒珠簧模型的分子动力学模拟 方法，考察了不同壁面和端基极性对于PFPE膜静态特性（如分子构型、单体密度分布、端基 密度分布）以及动态特性（如自扩散系数）的影响. 静态特性的模拟结果表明，非极性PFPE 膜在壁面附近具有单层厚度为一个单体直径的层状结构，而极性PFPE膜则具有复杂的层状结 构. 动态特性的模拟结果表明，PFPE膜的扩散能力因壁面作用而增强并因端基极性作用而减 弱. 关键词： 全氟聚醚膜 分子动力学模拟 薄膜润滑 固液界面结构