Alloy states in dilute GaAs1-xNx alloys (x < 1%)

A set of GaAs1-xNx samples with small nitrogen composition (x<1%) were investigated by continuous-wave photoluminescence (PL), pulse-wave excitation PL, and time-resolved PL. In the PL spectra, an extra transition located at the higher-energy side of the commonly reported N-related emissions was observed. By measuring the PL dependence on temperature and excitation power, the PL peak was identified as a transition of alloy band edge-related recombination in GaAsN. The PL dynamics further confirms its intrinsic nature as being associated with the band edge rather than N-related bound states. (C) 2003 American Institute of Physics.

Polishing-related optical anisotropy of semi-insulating GaAs studied by reflectance difference spectroscopy

The strong in-plane optical anisotropy of (001) semi-insulating GaAs, which comes from the submicron region under the surface, has been observed by reflectance difference spectroscopy. The optical anisotropy can be explained by the anisotropic strain that is introduced by the asymmetric distribution of 60 degrees dislocations during surface polishing. The simulated spectra reproduce the line shape of the experimental ones. The simulations show that the anisotropic strain is typically about 2.3x10(-4). (C) 2000 American Institute of Physics. [S0021-8979(00)01315-3].

一种认证密钥协商协议的安全分析及改进

针对用于移动通信的可证安全的双向认证密钥协商协议MAKAP给出了一种有效攻击，指出谊协议存在安全缺陷，它不能抵抗未知密钥共享攻击．分析了这些安全缺陷产生的原因，并给出了一种改进的协议MAKAP-I．改进后的MAKAP-I协议不但是可证安全的，而且无论从计算开销、通信开销、存储开销以及实现成本等方面，都比原MAKAP协议更高效、更实用．

一种基于Messy GA的结构测试数据自动生成方法

结构性测试是标识测试用例的基本方法之一．由于程序语言的复杂性以及被测程序的多样性，自动生成结构测试数据的一种有效方法是根据程序运行结果指导生成过程，通过不断迭代，生成符合要求的测试数据集．提出一种基于Messy GA的结构测试数据自动生成方法，将测试覆盖率表示为测试输入集X的函数F（X），并利用Messy GA不需要染色体模式排列的先验知识即可进行优化求解的性质对F（X）的进行迭代寻优，进一步提高了搜索的并行性，并最终提高测试覆盖率．对一组标准测试程序和若干实际应用程序的实验结果表明，较之现有基于遗传算法的生成方法，该方法能够以更高的效率生成更高质量的测试数据，并适用于较大规模的程序．

非局部理论新框架和基于新框架的塑性应变梯度理论

<正>纳米材料和器件的蓬勃发展,微机电系统和微电子元件微型化趋势,先进材料微结构设计以及精细薄膜涂层,促使材料科学家和力学家关注微米尺度和纳米尺度范围内材料的力学行为。大量实验表明,当非均匀塑性变形的特征长度在微米量级时,金属材料材料呈现很强的尺度效应。典型的实验包括:细铜丝扭转;纯镍薄膜弯曲;不同金属材料的微纳米压痕;炭化硅粒子增强的铝-镁基

超临界压力下航空煤油水平管内对流换热特性数值研究

采用RNG(renormalization group)k-ε湍流模型和近壁区的Wolfstein一方程模型对超临界压力下大庆RP-3航空煤油在水平圆管内的流动和换热特性进行了数值研究.超临界压力下,由于航空煤油在拟临界点附近热物性的剧烈变化,浮升力将引起显著的二次流动.二次流动使得水平圆管的下表面湍流强度和对流换热增强,而上表面的湍流强度和对流换热减弱.最后分析了两种水平管内对流换热受浮升力影响判别标准在超临界流体中的适用性