Effect of Carrier Gas Flux on ZnO Nanorod Arrays Grown by MOCVD

ZnO nanorod arrays with different morphologies were grown by metalorganic chemical vapor deposition （MOCVD）. The diameters of nanorods range from 150 nm to 20 nm through changing the carrier gas flux during the growth process. Measurements such as scanning electron microscope （SEM）, X-ray diffraction （XRD）, Raman scattering and photoluminescence （pL） spectrum were employed to analyze the differences of these nanorods. It was found that when both carrier gas flux of Zn and O reactant are 1 SLM, we can obtain the best vertically aligned and uniform nanorods. Furthermore, the PL spectrum reveals a blueshift of UV emission peak, which may be assigned to the increase of surface effect.

格点形状和取向对二维光子晶体禁带的影响

以椭圆形和正方形介质柱组成的二维正方晶格为例,讨论了格点形状和取向变化时对光子晶体能带的影响,对比分析了波矢在周期性平面和不在周期性平面2种情况下的能带图.计算表明:格点形状和取向的适当变化可以使没有完全带隙的光子晶体出现完全带隙,低阶的完全带隙转变成高阶完全带隙.此外,经对比发现:波矢偏离周期性平面对椭圆形介质柱的正方晶格形成的完全带隙的影响,要比正方形介质柱正方晶格的完全带隙的影响要大得多.

黄土与地球系统――李希霍芬对黄土研究的贡献及对地球系统科学研究的现实意义

IEECAS SKLLQG

基于FPGA的数字电源调节器研究与设计

详细描述了基于FPGA方案的数字电源调节器。首先介绍了数字调节器的硬件功能模块设计,重点对用于采样电源输出电流的高速高精度AD7634的工作原理做了描述,并给出了AD7634采集一个电压信号的工作波形;其次介绍了数字调节器的软件设计,包括调节器算法、功能以及在FPGA内的实现方法;最后,以一台15 A/15 V校正磁铁电源为样机,进行了闭环调节实验,给出了测试结果。

Oddball Y(4140) as the molecular cousin of Y(3930)

In my talk, we present the dynamical study of Y(4140) and Y(3930) under the D-s*(D) over bar (s)* and D*(D) over bar* molecular assignments respectively The importance to theoretically and experimentally study their open-charm decay, hidden-charm decay, radiative decay and double-photon decay is proposed combing with the theoretical calculation of the decay behavior of Y(4140) and Y(3930) According to the recent new experimental progress made by Belle, we further indicate the reasonability of molecular explanation to Y(4140) Another event cluster around 4270 MeV in the J/psi Phi invariant mass spectrum of B -> KJ/psi Phi can provide us more hints to reveal the creation mechanism of molecular structure in B meson decay, which will be helpful to clarify the underlying structure of Y(4140) and Y(3930)

Spatial and temporal flows of China's forest resources: Development of a framework for evaluating resource efficiency

Science & Technology Basic Work Program of China: Scientific Survey of the Middle-lower Reaches of Lantsang River and the Great Shangri-La Region [2008FY110300]; National Basic Research Program of China (973 Program): Ecosystem Services and Ecological Safety of the Major Terrestrial Ecosystems of China [2009CB421106]; National Natural Science Foundation of China [30670374]; EU ; European Commission, DG Research [003874]

Studies on the room temperature conductivity of PEO-LiClO4-Al2O3 composite polymer electrolyte

A composite polymer electrolyte of Polyethylene oxide (PEO)-LiClO4 containing fine Al2O3 particles was studied by using differential scanning calorimetry, infrared spectroscopy and electrochemical impedance spectroscopy. Compared with the polymer electrolyte without Al2O3 particles, the glass transition temperature and the degree of crystallinity were decreased, and the room temperature conductivity of PEO-LiClO4-Al2O3 composite polymer electrolyte was considerably enhanced. Moreover, the equivalent circuits and the effect of dc potential on impedance spectroscopy were discussed.

Isothermal melt and cold crystallization kinetics of poly(aryl ether ether ketone ketone) (PEEKK)

Isothermal melt and cold crystallization kinetics of PEEKK have been investigated by differential scanning calorimetry in two temperature regions. During the primary crystallization process, the relative crystallinity develops with a time dependence described by the Avrami equation, with exponent n = 2 for both melt and cold crystallization. The activation energies are -544.5 and 466.7 kJ/mol for crystallization from the melt and amorphous glassy state, respectively. The equilibrium melting point T-m(o) is estimated to be 371 degrees C by using the Hoffman-Weeks approach. The lateral and end surface free energies derived from the Lauritzen-Hoffman spherulitic growth rate equation are sigma=10 erg/cm(2) and sigma(e) = 60 erg/cm(2), respectively. The work of chain folding q is determined as 3.98 kcal/mol. These observed crystallization kinetic characteristics of PEEKK are compared with those of PEEK. (C) 1997 Elsevier Science Ltd.