• Journal of KIISE
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• v.43 no.6
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• pp.627-635
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• 2016

When many processes issue write operations alternately on Log-structured File System (LFS), the created files can be fragmented on the file system layer although LFS sequentially allocates new blocks of each process. Unfortunately, this file fragmentation degrades read performance because it increases the number of block I/Os. Additionally, read-ahead operations which increase the number of data to request at a time exacerbates the performance degradation. In this paper, we suggest a new cleaning method on LFS that minimizes file fragmentation. During a cleaning process of LFS, our method sorts valid data blocks by inode numbers before copying the valid blocks to a new segment. This sorting re-locates fragmented blocks contiguously. Our cleaning method experimentally eliminates 60% of file fragmentation as compared to file fragmentation before cleaning. Consequently, our cleaning method improves sequential read throughput by 21% when read-ahead is applied.

• Journal of Environmental Impact Assessment
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• v.27 no.6
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• pp.618-634
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• 2018

This study examined ecological network change affected by the 2020 invalidation of decisions on urban parks with a focus on Busan. The analyses were conducted to five scenarios using FRAGSTATS. The green space in scenario 1 assuming all development for unexecuted urban park would decrease by 7,339.75 ha compared to scenario 5, which assumes the entire conservation of unexecuted urban parks, and the fragmentation of the ecological space in scenario 1 increased. In scenario 1, 8.06% of the total area of core habitats and 28.23% of connectivity would decrease. However, scenario 3, which assumes the conservation of environmentally sensitive areas of unexecuted urban parks, can achieve 94% of green space and 95.6% of the connectivity of the scenario 5. Scenario 3 has effects similar to scenario 5 in terms of defragmentation. Thus, conservation of environmentally sensitive areas in parks is critical and effective in maintaining ecological networks.