质子化丙酮分子团簇的结构和振动光谱

用密度泛函B3LYP/ 6 3 1G(d)方法 ,对质子化丙酮分子团簇 (CH3COCH3) nH+ (n =1～ 7)弱相互作用体系进行了全自由度能量梯度优化 ,得到了该系列团簇的稳定结构及其对应的体系能量 .通过对构型的分析得出了质子化丙酮分子团簇 (CH3COCH3) nH+ (n =1～ 7)的生长规律 .计算了中性丙酮分子团簇体系的质子亲合能并总结出其变化趋势 .分析讨论了质子化团簇的红外振动光谱 ,发现质子化团簇的振动光谱普遍较中性环型团簇的振动光谱复杂 ,最强的振动峰来源于质子在溶剂壳中两个氧原子之间的振动 ,而且随着团簇尺寸的增加羰基的伸缩振动峰的数目也随之增多     

Writing Waveguide in LN With fs Laser

We investigated the waveguide formation in Lithium Niobate with Femtosecond laser pulse writing directly. The output optical field through waveguide has been observed and refractive-index change was characterized by using grating method.     

C2（a 3Πu）+NO 的反应机理研究

在G2 (CC ,MP2 )理论水平上研究了C2 (a3 Πu)自由基与NO分子的反应 .计算了反应体系最低二重态势能面上各驻点的构型参数、振动频率和能量 ,揭示了此反应存在两种反应机理 :由NO中的O原子进攻C2 自由基形成CCON中间体的CCON机理和NO中的N进攻C2 自由基形成CCNO中间体的CCNO机理 ,分析了对应与这两种反应机理的五个可能的反应通道 ,得出了由NO中的N原子进攻3 C2 自由基 ,生成中间体CCNO自由基 ,最终得到产物CN +CO的通道是最有利的通道 .     

An Improved Synthesis of Retinoic Acid from β-Ionone

A convenient and large-scale preparation of retinoic acid 1 from β-ionone in five steps with 38% overall yield is described.The key steps are the epoxidization of 2 with a new methylated agent and the condensation 4 with tetraethyl methylenediphophonate in one-pot procedure to prepare 6.     

Silane photoabsorption spectra mear the Si 2p thresholds：the geometry of Si 2p excited SiH4

Based on the multiple-scattering self-consistent-field method, we have studied the photoabsorption spectra near the Si 2p thresholds of silane. According to our calculations, the clear assignments of the inner-shell photoabsorption spectra are provided. In comparison with the high-resolution experimental spectra, the geometric structure of the Si 2p-excited SiH_{4}^{**} is recommended to be of a C_{2v} symmetry. More specifically, the Si 2p-excited SiH_{4}^{**} have two bond lengths of 2.50 a.u. and another two bond lengths of 2.77 a.u., and the corresponding two bond angles are 104.0° and 112.5° respectively.     

Duffing-van der Pol振子随机分岔的全局分析

应用广义胞映射方法研究了参激和外激共同作用的Duffing-van der Pol振子的随机分岔.以 系统参数通过某一临界值时，如果系统的随机吸引子或随机鞍的形态发生突然变化，则认为 系统发生随机分岔为定义，分析了参激强度和外激强度的变化对于随机分岔的影响.揭示了 随机分岔的发生主要是由于系统的随机吸引子与系统的随机鞍碰撞产生的.分析表明，广义 胞映射方法是分析随机分岔的有力工具，这种全局分析方法可以清晰地给出随机分岔的发生 和发展. 关键词： 随机分岔 全局分析 广义胞映射方法 随机吸引子 随机鞍     

Bi12TiO20纳米粉体的制备及其光吸收特性研究

以钛酸四丁酯和硝酸铋为原料 ,利用化学溶液分解法制备了Bi12 TiO2 0 纳米多晶粉体 .采用XRD和TEM对其结构和形貌进行了表征 .结合热重 差热 (TG DTA)分析 ,探讨了Bi12 TiO2 0 晶相的形成机理 .通过UV Vis漫反射谱的测定 ,研究了Bi12 TiO2 0 纳米晶粉体的光吸收特性 .结果显示 ,从组成为化学计量比的前驱液中可以很容易制得纯Bi12 TiO2 0 纳米晶粉体 ,该Bi12 TiO2 0 纳米晶粉体呈现了在很宽的波长范围内 (5 6 0～ 385nm )对光的吸收的特性 .     

Moisture barrier of AlxOy coating on poly(ethylene terephthalate), poly(ethylene naphthalate) and poly(carbonate) substrates

The moisture barrier property of Al_xO_y coated poly(ethylene terephthalate) (PET), poly(ethylene naphthalate) (PEN) and poly(carbonate) (PC), have been investigated. The differences in the morphology of the Al_xO_y sputtered grown on these substrate were investigated using atomic force microscopy (AFM). The initial growth of the Al_xO_y followed closely the topology of the substrate and an amplified roughness was observed. In the fully grown Al_xO_y, the comparative roughness followed that of the substrates. It has been found that a single layer Al_xO_y improved the moisture barrier of PET by an order of magnitude, PC by two orders of magnitude while no improvement was observed for PEN. UV-ozone treatment on PC further improved the moisture barrier, while no improvement was observed for PET and PEN. The comparative effects of the substrate surface roughness and surface energy on the moisture barrier are discussed.     

Asymptotic properties of computationally efficient alternative estimators for a class of multivariate normal models

Parameters of Gaussian multivariate models are often estimated using the maximum likelihood approach. In spite of its merits, this methodology is not practical when the sample size is very large, as, for example, in the case of massive georeferenced data sets. In this paper, we study the asymptotic properties of the estimators that minimize three alternatives to the likelihood function, designed to increase the computational efficiency. This is achieved by applying the information sandwich technique to expansions of the pseudo-likelihood functions as quadratic forms of independent normal random variables. Theoretical calculations are given for a first-order autoregressive time series and then extended to a two-dimensional autoregressive process on a lattice. We compare the efficiency of the three estimators to that of the maximum likelihood estimator as well as among themselves, using numerical calculations of the theoretical results and simulations.     

Lyapunov-type inequalities for nonlinear systems

In this paper, by using elementary analysis, we establish some new Lyapunov-type inequalities for nonlinear systems of differential equations, special cases of which contain the well-known equations such as Emden-Fowler-type and half-linear equations. The inequalities obtained here can be used as handy tools in the study of qualitative behaviour of solutions of the associated equations.