GROWTH INTERRUPTION INDUCED INTERFACE MICROROUGHNESS IN SINGLE QUANTUM-WELLS

Growth interruption-induced microroughness is studied by photoluminescence (PL) of single quantum wells with different well widths and interruption times. Analysis of the peak splitting in the PL spectra shows that the adjacent peak splittings correspond to well width differences smaller than one monolayer. The number of split peaks increases with increasing well width, saturating when the well width exceeds 11 monolayers. This trend correlates well with the decrease in the lateral dimension of the exciton, which corresponds roughly to the minimum optically sampled area of the interface. For a given quantum well, a plot of the normalized integrated intensities of the split PL peaks versus the well width fluctuation is well described by a Gaussian distribution with an average fluctuation smaller than one monolayer. These results are consistent with the microroughness model.

电子束辐照下单壁碳纳米管的结构不稳定性

利用透射电镜（TEM）原位观察了一端固定一端自由和两端固定的单壁碳纳米管（SWNT（s））在电子束辐照下的结构不稳定性。研究发现,一端固定一端自由的SWNT优先轴向和径向收缩后颈缩,最后形成一个个碳笼紧密相连的收缩结构（“碳笼-碳笼”结构）;两端固定的SWNT仅径向收缩后颈缩,最后形成许多碳笼相连的类似结构。此外,后者在电子束辐照下断开后又会重新粘合起来,表现出很强的表面塑性流变或湿润效应。这些电子束辐照诱导SWNTs非热激活结构不稳定性现象可以用我们最近提出的表面纳米曲率效应和能量束超快诱导软模和点阵失稳进行全新、全面、正确的解释。

微波网络分析仪校准过程中校准方程的选

将线性方程组的误差理论应用于微波网络分析仪的夹具校准过程,提出了一种线性校准方程的通用选取原则,即选择系数矩阵的条件数最小的组合.用这个原则对TSD校准方法进行方程选择,并将不同方程组合的解与直测数据进行比较,结果证明根据误差理论选择的方程组合确实得到最精确稳定的解.

具有事件恢复功能的文件系统的研究与实现

把一个进程在其执行过程中对文件的一系列修改称为一个事件.为了解决如何方便有效地恢复某个事件对文件的修改,研究并实现了一个具有事件恢复功能的文件系统GobackFS.GobackFS是一个用户空间文件系统,基于FUSE框架实现.测试结果表明,GobackFS文件系统在读写性能方面略低于Ext3文件系统,寻道速度方面略高于后者.

Performance of an improved logarithmic phase mask with optimized parameters in a wavefront-coding system

In two papers [Proc. SPIE 4471, 272-280 (2001) and Appl. Opt. 43, 2709-2721 (2004)], a logarithmic phase mask was proposed and proved to be effective in extending the depth of field; however, according to our research, this mask is not that perfect because the corresponding defocused modulation transfer function has large oscillations in the low-frequency region, even when the mask is optimized. So, in a previously published paper [Opt. Lett. 33, 1171-1173 (2008)], we proposed an improved logarithmic phase mask by making a small modification. The new mask can not only eliminate the drawbacks to a certain extent but can also be even less sensitive to focus errors according to Fisher information criteria. However, the performance comparison was carried out with the modified mask not being optimized, which was not reasonable. In this manuscript, we optimize the modified logarithmic phase mask first before analyzing its performance and more convincing results have been obtained based on the analysis of several frequently used metrics. (C) 2010 Optical Society of America