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