Nanoscale structural characteristics and electron field emission properties of transition metal–fullerene compound TiC60 films

Transition-metal compound TiC₆₀ thin films were grown by co-deposition from two separated sources of fullerene C₆₀ powder and titanium. Study of structural properties of the films, by Raman spectroscopy, atomic force microscopy, and scanning tunneling spectroscopy reveals that the films have a deformed C₆₀ structure with certain amount of sp³ bonds and a rough surface with a large number of nanoclusters. z–V tunnelling spectroscopic measurements suggest that several charge transport mechanisms are involved in as the tip penetrates into the thin film. Conventional field electron emission (FEE) measurements show a high emission current density of 10 mA/cm² and a low turn-on field less than 8 V/μm, with the field enhancement factors being 659 and 1947 for low-field region and high-field region, respectively. By exploiting STM tunneling spectroscopy, local FEE on nanometer scale has also been characterized in comparison with the conventional FEE. The respective field enhancement factors are estimated to be 99–355 for a gap varying from 36 to 6 nm. The enhanced FEE of TiC₆₀ thin films can be ascribed to structural variation of C₆₀ in the films and the electrical conducting paths formed by titanium nanocrystallites embedded in C₆₀ matrix.     

Photoluminescence linewidth broadening due to alloy/thickness fluctuation of CdxZn1 − xSe/ZnSe triple quantum wells

Photoluminescence (PL) linewidth broadening of Cd_xZn_{1 − x}Se/ZnSe triple quantum wells, grown on GaAs substrates by molecular beam epitaxy (MBE), has been investigated. Various quantum well (QW) samples have been prepared with different QW thickness and composition (Cd-composition). Measured and calculated PL linewidth are compared. Both composition and thickness fluctuations are considered for the calculation with the parameters such as the volume of exciton, nominal thickness and composition of QWs. Surface roughness measured by atomic force microscopy (AFM) is used to estimate the interface roughness. Results show that when Cd-composition increases additional linewidth broadening due to Zn/Cd interdiffusion is enhanced.     

正交各向异性矩形板受迫振动的三维分析

从正交各向异性三维弹性动力学的控制方程出发，在求得四边简支矩形板自由振动频率和位移振型的基础上，构造了受迫振动的位移函数；利用自由振动位移振型的正交性，将控制方程的空间变量和时间变量分离，得到了广义质量、广义力和频率表示的关于时间的2阶常微分方程，从而得到了正交各向异性弹性矩形板在受迫振动下的位移场和应力场．给出了本文方法与薄板理论的算例．     

Asymmetric Regulation System Fit for Chinese Telecom Market

After the new round of restructuring of Chinese telecom sector,it's pressing to formulate and implement asymmetric regulation policies so as to shape an effectively competitive market structure in a relatively short term.This paper reviewed the asymmetric regulation policies and practices carried out in foreign telecom market,and then according to the specific situations of Chinese telecom market,proposed the principles and corresponding policies for establishing an asymmetric regulation system fit for Chin...     

介孔网络电路

用二次阳极氧化法制备纳米多孔氧化铝板,然后用磁控溅射方式在纳米多孔氧化铝板表面镀金得到介孔网络电路,对该介孔网络电路进行输运测量,发现其具有非线性电阻.     

用GSP进行"波动"教学案例

学生的学习需求是指学生要达到的目标水平与他现在实际水平之间的差距．本课的教学目标是：了解波的形成条件及过程、波的种类、振动和波的关系；理解波的传播规律和波的图象．学生的实际是只学过振动和振动的图象，会使用《几何画板》软件．此差距很明显．这就要求教师根据建构主义学习理论，通过创设情景、搭脚手架来降低知识的梯度，真正把教学目标转化为学生自己的学习需求．     

3,7-二硝基亚氨基-2,4-二氮杂双环[3,3,0]辛烷的放热分解反应动力学

在程序升温条件下 ,用DSC研究了标题化合物的放热分解反应动力学 .用线性最小二乘法、迭代法以及二分法与最小二乘法相结合的方法 ,以积分方程、微分方程和放热速率方程拟合DSC数据 .在逻辑选择建立了微分和积分机理函数的最可几一般表达式后 ,用放热速率方程得到相应的表观活化能 (Ea)、指前因子 (A)和反应级数 (n)的值 .结果表明 :该反应的微分形式的经验动力学模式函数、Ea 和A值分别为 (1-α) 0 .44、2 30 .4kJ/mol和 10 18.16s-1.借助加热速率和所得动力学参数值 ,提出了标题化合物放热分解反应的动力学方程 .该化合物的热爆炸临界温度为 30 2 .6℃ .上述动力学参数对分析、评价标题化合物的稳定性和热变化规律十分有用 .     

A new stochastic method of reconstructing porous media

We present a new stochastic method of reconstructing porous medium from limited morphological information obtained from two-dimensional micro- images of real porous medium. The method is similar to simulated annealing method in the capability of reconstructing both isotropic and anisotropic structures of multi-phase but differs from the latter in that voxels for exchange are not selected completely randomly as their neighborhood will also be checked and this new method is much simpler to implement and program. We applied it to reconstruct real sandstone utilizing morphological information contained in porosity, two-point probability function and linear-path function. Good agreement of those references verifies our developed method’s powerful capability. The existing isolated regions of both pore phase and matrix phase do quite minor harm to their good connectivity. The lattice Boltzmann method (LBM) is used to compute the permeability of the reconstructed system and the results show its good isotropy and conductivity. However, due to the disadvantage of this method that the connectivity of the reconstructed system’s pore space will decrease when porosity becomes small, we suggest the porosity of the system to be reconstructed be no less than 0.2 to ensure its connectivity and conductivity.     

半线性波动方程的自相似解

研究了具有非线性项|u|~αu的半线性波动方程的Cauclly问题,利用仿积分解及交换子估计等技术,证明了当α为一般的实数且满足一定的限制时,Cauchy问题自相似解的存在性。本文的结果回答了Planchon在其工作中所遗留的问题。     

Synthesis and Crystal Structure of a Novel Organic Adduct Nonlinear Optical Material: 3,5-Dinitrobenzonic Acid·ethanolamine (3,5-DNBEA)

The title compound (C2H7NO·C7H4N2O6) has been obtained by the reaction of etha- nolamine with 3,5-dinitrobenzoic acid in deionized water at room temperature. The crystal crystal- lizes in orthorhombic, space group P212121 with a = 6.048(2), b = 9.146(3), c = 21.955(7)(A), C9H11N3O7, Mr = 273.21, Z = 4, V = 1214.3(7)(A)3, Dc = 1.494 g/cm3, F(000) = 568, μ(MoKα) = 0.131 mm-1, R1 = 0.0338 and wR2 = 0.0497. The new organic adduct is composed of one ethanolamine and one 3,5-dinitrobenzoic acid, which are linked up by O-H…O and N-H…O types of hydrogen bonds to form a nine-membered ring and an eleven-membered ring, extending into a one-dimensional network structure.