Synthesis of ZnAl2O4/α-Al2O3 complex substrates and growth of GaN films

With the solid phase reaction between pulsed-laser-deposited (PLD) ZnOfilm and α-Al2O3 substrate, ZnAl2O4/α-Al2O3 complex substrates were synthesized. X-ray diffraction (XRD) spectra show that as the reaction proceeds, ZnAl2O4 changes from the initial (111)-oriented single crystal to poly-crystal, and then to inadequate (111) orientation. Corresponding scanning electron microscope (SEM)images indicate that the surface morphology of ZnAl2O4 transforms from uniform islands to stick structures, and then to bulgy-line structures. In addition, XRDspectra present that ZnAl2O4 prepared at low temperature is unstable at the environment of higher temperature. On the as-obtained ZnAl2O4/α-Al2O3 substrates, GaN films were grown without any nitride buffer using light-radiation heating low-pressure MOCVD (LRH-LP-MOCVD). XRD spectra indicate that GaN film on this kind of complex substrate changes from c-axis single crystal to poly-crystal as ZnAl2O4 layer is thickened. For the single crystal GaN, its full width at half maximum (FWHM) of X-ray rocking curve is 0.4°. Results indicate that islands on thin ZnAl2O4 layer can promote nucleation at initial stage of GaN growth, which leadsto the (0001)-oriented GaN film.     

Pb/Sn凸剪切性能研究

在实际使用条件下,Pb/Sn凸点会由于承受温度循环而产生剪切应力,剪切应力导致的主要失效方式是开裂.通过对倒装焊后Pb/Sn凸点剪切强度的测量及对剪切后断口的分析,发现破坏主要发生在凸点下金属(UBM)层内部或UBM与Al焊盘之间,平均剪切强度受凸点尺寸影响很小,范围在21～24MPa。     

最大似然方法和Bayes方法在结构方程模型分析中的讨论(英文)

本文通过模拟研究,讨论了最大似然方法和Bayes方法在分析结构方程模型中的相似点和不同之处。     

无线电能传输技术近在眼前

可能在不远的将来,用户就有可能摆脱使用充电器充电、更换电池以及接插家电设备电源线等麻烦.利用无线方式将电能传输到所用产品的技术即将进入实际应用阶段.     

Effects of Dual-Electrode Biasing on Er in a Toroidal Plasma

Two externally biased electrodes were inserted into the plasma on the KT-5C tokamak to test the effects on modifying the radial electric field Er, other than single biasing. Using various combinations of biasing voltage,the influences of double biasing are compared with the single biasing. It turns out that the effect of dual-biasing is also effective as a single one, but the outer electrode seems to be shielded by the inner one and show less influence. The results clearly show that the radial electric field Er changed by external biasing is intrinsically an effect localized at the edge of the plasma, which is caused by the electrode induced radial current; and dualelectrode biasing using the method similar to the single biasing seems not to be able to increase more distinctly the peaking effect on Er than the single biasing.     

劳动力供给带弹性的Solow模型

本文给出了在劳动力供给带弹性条件下的Ｓｏ１ｏｗ增长模型，给出了经济增长的黄金律和均衡处资本稳定性的证明，并且与不带弹性的Ｓｏｌｏｗ模型作了比较．     

基于DVB标准的数字卫星电视系统简介

简要分析DVB标准的数字卫星电视系统的基本原理,讨论了DVB-S系统的信源编码和信道编码,并介绍了DVB-S系统的基本结构.     

CDMA在卫星移动通信中的应用

在介绍卫星移动通信的发展历史和现状基础上，分析了ＣＤＭＡ技术的优势以及彩ＣＤＭＡ技术的卫星移动通信系统在当前的应用发展。