不同退火方式对Ni/SiC接触界面性质的影响

采用快速热退火(rapid thermal annealing, RTA)法和脉冲激光辐照退火(laser spark annealing, LSA)法, 在n型4H-SiC的Si面制备出Ni电极欧姆接触. 经传输线法测得RTA样品与LSA样品的比接触电阻分别为5.2×10^-4 Ω·cm², 1.8× 10^-4 Ω·cm². 使用扫描电子显微镜、原子力显微镜、透射电子显微镜、拉曼光谱等表征手段, 比较了两种退火方式对电极表面形貌、电极/衬底截面形貌和元素成分分布、SiC衬底近表层碳团簇微结构的影响. 结果表明, 相比于RTA, LSA法制备出的欧姆接触在电极表面形貌、界面形貌、电极层组分均匀性等方面都具有明显优势, 有望使LSA成为一种非常有潜力的制备欧姆接触的退火处理方法.     

Anti-plane analysis of semi-infinite crack in piezoelectric strip

Using the complex variable function method and the technique of the conformal mapping, the fracture problem of a semi-infinite crack in a piezoelectric strip is studied under the anti-plane shear stress and the in-plane electric load. The analytic solutions of the field intensity factors and the mechanical strain energy release rate are presented under the assumption that the surface of the crack is electrically impermeable. When the height of the strip tends to infinity, the analytic solutions of an infinitely large piezoelectric solid with a semi-infinite crack are obtained. Moreover, the present results can be reduced to the well-known solutions for a purely elastic material in the absence of the electric loading. In addition, numerical examples are given to show the influences of the loaded crack length, the height of the strip, and the applied mechanical/electric loads on the mechanical strain energy release rate.     

Cu/Ni多层纳米线力学性能尺寸效应的分子动力学模拟

Cu/Ni多层纳米线因其特殊的结构和优异的物理性能在微/纳电子机械系统(MEMS/NEMS)中有广泛的应用.本文利用分子动力学方法模拟了Cu/Ni多层纳米线的拉伸变形,研究了纳米线屈服应力的尺寸效应,探讨了界面结构的差异对多层纳米线缺陷演化机制的影响.结果表明,带共格界面多层纳米线的屈服应力随单金属层厚度h的减小先升高...     

Riemann积分的历史与发展

总结Riemann积分的发展历史、基本思想及其各种推广,介绍Riemann积分的局限性和缺陷,以及由此推动产生Lebesgue积分的过程.     

多重调和Bergman空间上多重调和符号的Topelitz算子

研究多重调和Bergman空间上的Topelitz算子.对多重调和符号的Topelitz算子,给出了乘积性质、交换性质的符号描述.     

向量参变量的约束集族最大元的通有稳定性

利用集值映射方法定义约束广义最大元,在约束条件和向量参变量意义下,讨论了约束最大元映射、向量参数扰动时,特别是约束条件受到扰动时,向量参变量的约束集族最大元的通有稳定性,在最广的扰动下,获得了通有稳定性定理.     

STUDY OF LUNG FLUKES FROM PHILIPPINES——A PRELIMINARY REPORT

In this paper taxonomic study on paragonimus including their metacercariae obtainedfrom the crabs collected from Sorsogon, Luzon, Phi1ippines and adult worms and ova obtain-ed through animal feeding, with light microscopy and scanning electron microscopy revealedthat there may exist two or more species of lung flukes in Philippines.The occurrence ofSemisulcospira libertina in addition to Antemelania dactylus (Lea) as an additional snailhost is mentioned for the first time. The chromosome Karyotyping of the adult worms revealed that they belong to thediploid pattern. Electronic scanning showed that the cuticular spines of the Paragonimus from Sorsogonlook like "pineapple ears" both in distribution and In appearance, a new finding that has not been recorded before. In the lungs of a white rat killed 290 days after infection, two adult worms wereobtained within the solitary eyst. These 2 adult worms measured 4.5×2.5mm and 4.5×3.0 mm respectively. Their unusually small size and somewhat round shape suggest that theymay be of a different species from those hitherto reported in the Philippines. Clearcut evidence is presented for the first time, demonstrating the occurrence of the phemomenon of cross fertilization (allogamy) of lung flukes.     

核半径的弥散效应和形变效应

本文采用Yukawa折迭型密度分布函数, 在计及椭球形变和四面对称体形变的情况下给出了核电荷半径的计算公式. 对55种元素148个核素所作的计算表明, 计算值与实验值之间的总体偏差为0.034fm, 与参数较多的小液滴模型结果相近; 且可克服Z^1/3律在解释某些跨过大壳的同位素系列核半径变化时所遇到的困难. 本文还通过分析不同核素之间核表面宽度的涨落与中子壳层结构的关系, 解释了同位素核半径的精细结构.     

美国部分高等学校研究生考题分析和介绍(二)

(三)有心力方面的题目也是试题中的重要方面。因为自然界中天体的运行,以及人造天体的运行;在物理学中电子绕原子核的运动;带电粒子在核场中的散射等等,都与有心力问题有关。这方面题目除少数较难的题之外,大部分都是要求考生有清晰的物理思想,运用简单的物理规律即动量矩守恒和机械能守恒两个规律来分析解决问题。有人可能认为,质点在有心力场中的轨道是圆锥曲线(有心力大小与距离平方成反比的情况),要确定这些轨道,数学上比较复杂。因此在这类题目面前产生畏难情绪。实际上仔细分析这些考题,并不需要很复杂的数学。 [题3]地球可看作半径为…     

反相液相色谱中溶质保留与溶剂化结构参数间的定量关系

本文研究了等度条件下反相液相色谱中溶质保留与溶剂化结构参数间的定量关系;考察了反相液相色谱保留值变化规律式lnk'=a+cC~b中参数a.c 与溶剂化结构参数间的定量关系,结果表明能较好地预测等度和不同冲洗剂组成下溶质的保留值,将乙腈-水和甲醇-水冲洗剂下的a.c值定量关联,表明在考虑溶质的氢键作用参数后,其相关性有所提高.