Joo Young Hwang

A fast path planning by path graph optimization

A fast path planning method by optimization of a path graph for both efficiency and accuracy is proposed. A conventional quadtree-based path planning approach is simple, robust, and efficient. However, it has two limitations. We propose a path graph optimization technique employing a compact mesh representation. A world space is triangulated into a base mesh and the base mesh is simplified to a compact mesh. The compact mesh representation is object-dependent; the positions of vertexes of the mesh are optimized according to the curvatures of the obstacles. The compact mesh represents the obstacles as accurately as the quadtree even though using much fewer vertexes than the quadtree. The compact mesh distributes vertexes in a free space in a balanced way by ensuring that the lengths of edges are below an edge length threshold. An optimized path graph is extracted from the compact mesh. An iterative vertex pushing method is proposed to include important obstacle boundary edges in the path graph. Dijkstras shortest path searching algorithm is used to search the shortest path in the path graph. Experimental results show that the path planning using the optimized path graph is an order of magnitude faster than the quadtree approach while the length of the path generated by the proposed method is almost the same as that of the path generated by the quadtree.

A real-time disk scheduler for multimedia integrated server considering the disk internal scheduler

The SCSI or the fibre channel (FC) disk drive, called SCSI-FC disk drive has its own internal queue and internal scheduler which maximize its own throughput. The request service order scheduled by the block device drive in Linux is changed by the disk internal scheduler (DIS) and we call this reordering. The conventional real-time disk schedulers are based on Linux block device driver, and the deadlines of the real-time requests are not guaranteed by the reordering of the DIS. This paper proposes a real-time disk scheduling architecture on Linux which solves the reordering problem. It consists of the global scheduler and the local scheduler. The global scheduler selects the real-time requests, predicts their disk I/O times and determines the order based on the spatial locality. The local scheduler is the DIS controlled by the SCSI-FC device driver. The device driver notifies the DIS that the real-time requests with the earlier deadlines must be served before those with the later deadlines. The local scheduler feeds back the measured disk service time to the global scheduler when a requested disk service completes. We have implemented the proposed multimedia disk scheduler on Linux, and the experimental results show that the deadline misses of periodic requests can be reduced up to 19 times (94.7%) by the proposed method.

Simultaneous Quantitation and Validation of Triterpenoids and Phytosteroids in Phaseolus angularis Seeds

A reproducible analytical method using reverse-phase high liquid performance chromatography combined with UV detecting was developed for the quantitative determination of four compounds isolated from the ethanol extract of Phaseolus angularis seeds (PASE): oleanolic acid (1), oleanolic acid acetate (2), stigmasterol (3) and β-sitosterol (4). This method was fully validated in terms of linearity (r2 > 0.999), accuracy (98.5%–100.8%), precision (<0.92%), LOD (<0.0035 mg/mL), and LOQ (<0.0115 mg/mL). The effects of the PASE and isolated compounds 1–4 on TLR4 activation were tested in THP1-Blue cells. Among the tested substances, compound 2 showed potent inhibitory activity with an IC50 value of 3.89 ± 0.17 µM.

Write back routine for JFFS2 efficient i/o

When flash memory is used as a storage in embedded systems, block level translation layer is required between conventional filesystem and flash memory chips due to its physical characteristics. A far more efficient use of it is the design of a filesystem itself without no extra layer of translation. However, since flash filesystem does not use block device layer, it cannot utilize deferred I/O although deferred I/O enhances write latency by delaying the flushing jobs. Linux operating system generally uses the write back routine for deferred I/O using kernel thread, which writes back dirty pages and buffers through the block device layer. In this paper, we design and implement efficient I/O for JFFS2 flash filesystem based on flash memory. For this, we first analyze the write procedure of JFFS2 filesystem in detail, and derive the drawback and overhead. Then, we design the flash write back routine for deferred I/O. We apply it to the Linux JFFS2 by implementing fflush and flash_writeback kernel thread. The designed flash write back routine can reduce average write latency when the kernel buffers are enough to get the users data

Effect of Sunlight Radiation on the Growth and Chemical Constituents of Salvia plebeia R.Br.

This study investigated the chemical composition changes of Salvia plebeia R.Br. cultivated under different light sources, including florescent light and sunlight. The plants were exposed to fluorescent light for four months and sunlight and then examined for the next 5–7 months. Plants were harvested monthly during the seven months, and we examined whether the difference in light source affected the phenolic and flavonoid contents and antioxidant activity. A simple and reliable HPLC method using a PAH C18 column was applied for the quantitative analysis of two triterpenoids from the S. plebeia groups. Oleanolic acid (OA) and ursolic acid (UA) showed good linearity (R2 > 0.9999) within the test ranges (0.005–0.05 mg/mL), and the average percentage recoveries of the OA and UA were 95.1–104.8% and 97.2–107.1%, respectively. The intra- and inter-day relative standard deviations (RSDs) were less than 2.0%. After exposure to sunlight, the phenolic contents, including rosmarinic acid, showed a reduced tendency, whereas the flavonoid contents, including homoplantaginin and luteolin 7-glucoside, were increased. The content of the triterpenoids also showed an increased tendency under sunlight irradiation, but the variance was not larger than those of the phenolic and flavonoid contents. Among experimental groups, the group harvested at six months, having been exposed to sunlight for two months, showed the most potent antioxidant activity. Therefore, these results showed that the chemical composition and antioxidant activities of S. plebeia R.Br. was affected from environmental culture conditions, such as light source. Our studies will be useful for the development of functional materials using S. plebeia R.Br.