Growth of AlGaN Epitaxial Film with Chemical Vapour High A1 Content by Metalorganic Deposition

A high-Al-content AlGaN epilayer is grown on a low-temperature-deposited AlN buffer on （0001） sapphire by low pressure metalorganic chemical vapour deposition. The dependence of surface roughness, tilted mosaicity, and twisted mosaicity on the conditions of the AlGaN epilayer deposition is evaluated. An AlGaN epilayer with favourable surface morphology and crystal quality is deposited on a 2Onto low-temperature-deposited AlN buffer at a low V/Ⅲ flow ratio of 783 and at a low reactor pressure of 100 Torr, and the adduct reaction between trimethylaluminium and NH3 is considered.     

Thickness measurement of GaN epilayer using high resolution X-ray diffraction technique

In this paper we propose a new method for measuring the thickness of the GaN epilayer, by using the ratio of the integrated intensity of the GaN epilayer X-ray diffraction peaks to that of the sapphire substrate ones. This ratio shows a linear dependence on the GaN epilayer thickness up to 2 μm. The new method is more accurate and convenient than those of using the relationship between the integrated intensity of GaN epilayer diffraction peaks and the GaN thickness. Besides, it can eliminate the absorption effect of the GaN epilayer.     

关于3-连通图最长圈的注

设C是3-连通图G的一个最长圈,H是G-V(C)的一个分支满足|H|≥3.文献[4]在给H附加一些条件后,证明|C|≥2d(u) 2d(v)-5,并且不等式严格成立除非G属于某些例外图类,这里u,v是G中两个不相邻的顶点.本文给出了上述例外图类的精确刻划.     

气液并流向上三相流化床流体流动性质的研究

本文研究气液并流向上兰相流化床的一般流体流动性质。阐明了不同性质及粒度的固体颗粒、流化床静止床高、气体及液体的表观线速、气体分布板结构等参数对床层的均匀性、气体及液体滞留量、床层膨胀高度及气泡形态及大小等影响的一般规律。提出了在液固两相流化床中通入气体后,床层膨胀比随着气体速度的增大而变化的规律具有五种不同类型。用气泡上升的平均真实速度V_g/ε_g作为V_g及V_L的函数作图,可以表明气体及液体的表观线速对气体滞留量及气泡大小的影响,并用在流化床上部的照片直观地表明了这一点。最后用关联式将本文数据进行关联,误差在±10%以内。     

Si(001)衬底上APCVD生长3C-SiC薄膜的微孪晶及含量

利用X射线双晶多功能四圆衍射仪,对在Si(001)衬底上使用常压化学气相方法(APCVD)生长的3C-SiC进行了微孪晶的分析.Φ扫描证明了3C-SiC外延生长于Si衬底上,生长的取向关系为：(001)_3C-SiC//(001)_Si,［111］_3C-SiC//［111］_Si.3C-SiC的{111}极图在χ=15.8°出现了新的衍射,采用六角相{10^{1010}晶面的极图以及孪晶SiC(002)的倒易空间Mapping分析了χ=15.8°处产生的衍射为3C-SiC的孪晶所致,并利用ω扫描估算了孪晶的含量约为1%.     

新的迭代法及其在力学中的应用

新的迭代法及其在力学中的应用袁镒吾（中南工业大学，长沙４１００１２）１引言试求解方程先把上式化成下列形式式中，ａ、ｂ、ｃ均为任意常数；ｆ（ｘ）及ｇ（ｘ）则均为ｘ的任意函数。设已知式（１）的一个近似根ｘ＿０，则函数ｇ（ｘ）在点ｘ＿０附近可用泰勒多项式表...     

高超声速三维化学非平衡流动简化NS方程数值解

本文研究用时间稳定法求解高超声速三维化学非平衡流动简化ＮＳ方程，把整个非平衡流体动力学问题分裂为流体力学问题和化学问题。流体力学与化学问题之间的耦合通过迭代方式加以处理。考虑高温空气分解与电离，七个化学组元，并认为化学反应是以有限速率进行的．差分格式采用无自由参数的混合反扩散格式，激波及壁面处理应用特征线理论．对来流攻角为１０°，马赫数为２６，飞行高度为８５ｋｍ的钝锥体，给出了流场参数和物面加热率的数值计算结果．     

LAMINAR BOUNDARY LAYER BETWEEN TWO PLANES PERPENDICULAR TO EACH OTHER

In this paper, we obtain a third-order approximate solution for the laminar boundarylayer between two plans perpendicular to each other.In boundary layer equations, the viscous and the inertial terms have the same quantitystep.In this paper, at first, supposing that the inertial terms are bigger than the viscousterms, we solve the boundary layer equations, and then we suppose that the viscous termsare bigger than the inertial terms. At last. we take the mean value as the valid solution of theboundary layer equations.The first-and the second-order approximate solutions obtained in this paper coincdewith the results in ref[1],while the third-order solution obtained in this paper is better thanthat in ref [1].     

Fe改性对Ru/Al_2O_3催化剂的马来酸二甲酯加氢性能影响

以Al2O3为载体,采用吸附-沉淀法制备一系列Ru-Fe/Al2O3催化剂,并进行了H2-TPR、XRD及XPS表征。以马来酸二甲酯(DMM)催化加氢合成丁二酸二甲酯(DMS)为探针反应,考察了Fe的加入对Ru/Al2O3催化性能的影响。评价结果表明,当Fe/Ru原子比小于2时,催化剂活性变化不大;但Fe/Ru原子比大于或等于2时,催化剂活性明显增加;与Ru/Al2O3催化剂相比,Fe的加入改善了催化剂的高温氧化还原处理稳定性。以甲醇为溶剂,在70℃、1.0 MPa压力、600 r/min转速下,Ru-Fe/Al2O3催化DMM的转化率与生成DMS的选择性均接近100%。XPS和H2-TPR表征结果表明,Ru-Fe/Al2O3中Fe与Ru产生较强的相互作用,促进Ru的分散且调变了Ru的电子特性。