• The Bulletin of The Korean Astronomical Society
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• v.24 no.1
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• pp.27-27
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• 1999

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2018.05a
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• pp.415-416
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• 2018

• KIPS Transactions on Software and Data Engineering
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• v.5 no.4
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• pp.171-180
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• 2016

As social networking services such as twitter become increasingly popular, data streams are widely prevalent these days. In order to search data accumulated from data streams efficiently, the use of an index structure is essential. In this paper, we propose an update-efficient, disk-based inverted index structure for efficient keyword search on data streams. When new data arrive at the data stream, the index needs to be updated to incorporate the new data. The traditional inverted index is very inefficient to update in terms of disk I/O, because all index data stored in the disk need to be read and written to the disk each time the index is updated. To solve this problem, we divide the whole inverted index into a sequence of inverted indices with exponentially increasing size. When new data arrives, it is first inserted into the smallest index and, later, the small indices are merged with the larger indices, which leads to a small amortize update cost for each new data. Furthermore, when indices stored in the disk are merged with each other, we minimize the disk I/O cost incurred for the merge operation, resulting in an even smaller update cost. Through various experiments, we compare the update efficiency of the proposed index structure with the previous one, and show the performance advantage of the proposed structure in terms of the update cost.

• The KIPS Transactions:PartD
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• v.13D no.4 s.107
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• pp.463-476
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• 2006

R-trees have been traditionally optimized for the I/O performance with the disk page as the tree node. Recently, researchers have proposed cache-conscious variations of R-trees optimized for the CPU cache performance in main memory environments, where the node size is several cache lines wide and more entries are packed in a node by compressing MBR keys. However, because there is a big difference between the node sizes of two types of R-trees, disk-optimized R-trees show poor cache performance while cache-optimized R-trees exhibit poor disk performance. In this paper, we propose a cache and disk optimized R-tree, called the PR-tree (Prefetching R-tree). For the cache performance, the node size of the PR-tree is wider than a cache line, and the prefetch instruction is used to reduce the number of cache misses. For the I/O performance, the nodes of the PR-tree are fitted into one disk page. We represent the detailed analysis of cache misses for range queries, and enumerate all the reasonable in-page leaf and nonleaf node sizes, and heights of in-page trees to figure out tree parameters for best cache and I/O performance. The PR-tree that we propose achieves better cache performance than the disk-optimized R-tree: a factor of 3.5-15.1 improvement for one-by-one insertions, 6.5-15.1 improvement for deletions, 1.3-1.9 improvement for range queries, and 2.7-9.7 improvement for k-nearest neighbor queries. All experimental results do not show notable declines of the I/O performance.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.1
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• pp.1-10
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• 2010

Recently heterogeneous storage system such as hybrid hard disk drive (H-HDD) combining flash memory and magnetic disk is launched, according as the read performance of NAND flash memory is enhanced as similar to that of hard disk drive (HDD) and the power consumption of NAND flash memory is reduced less than that of HDD. However, the read and write operations of NAND flash memory are slower than those of rotational disk. Besides, serious overheads are incurred on CPU and main memory in the case that intensive write requests to flash memory are repeatedly occurred. In this paper, we propose the Least Frequently Used-Hot scheme that replaces the data blocks whose reference frequency of read operation is low and update frequency of write operation is high, and the data flushing scheme that rearranges the data blocks into the multi-zone of the rotation disk. Experimental results show that the execution time of the proposed method is 38% faster than those of conventional LRU and LFU block replacement schemes in I/O performance aspect and the proposed method increases the life span of Non-Volatile Cache 40% higher than those of conventional LRU, LFU, FIFO block replacement schemes.

• The Transactions of the Korea Information Processing Society
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• v.2 no.4
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• pp.543-553
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• 1995

While RAID 5 disk arrays offer advantages of performance and reliability on wide variety of applications, they suffer from the performance degradation with write jobs. To reduce the effect of this problem, parity logging scheme was suggested. This scheme reduces disk busy time by transforming many small random accesses into large sequential accesses. This paper presents a new parity logging technique which prevents parity update image from redundant storing in the disk buffer and reduces parity maintenance overhead. A analytical model and several simulation results of our proposed scheme are presented.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.16-16
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• 2017

국내 농업인구 감소 대비 식품소비량이 증가함에 따라 농가의 인력을 대체하고 다양한 작업이 가능하며 가격이 저렴한 국내 기계화 기술이 필요하다. 무동력 디스크해로우 작업기는 경운과 배토가 가능한 복합작업기로서 작업기를 구성하는 주요 구성품들은 필드작업에 의해 발생되는 하중에 구조적 강도와 신뢰성이 충분히 확보되어야 한다. 또한, 실제로 필드 작업 시 작업기에 걸리는 하중은 복합하중 형태로 전달되기 때문에 단순한 형태 하중에 비해 하중계측에 어려운 점이 있으므로 하중계측점의 선정이 매우 중요하다. 본 논문에서는 하중계측점을 선정하기 위하여 복합기의 주요 구성품인 치즐(chisel) 및 디스크해로우암(disk harrow arm)에 대하여 구조해석을 수행하였으며, 3축 방향의 단위하중 응력 계산결과로부터 load reconstruction을 위한 스트레인 게이지 위치를 선정하였다. 또한, 스트레인 게이지의 신호가 하중해석에 적절한 값이 되도록 기존의 형상을 수정하였다.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.1
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• pp.44-52
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• 1999

The purpose of this study was to investigate the distribution of CGRP immunoreactive nerve fibers in rat squamosomandibular joint with postnatal development. Squamosomandibular joint with adjacent tissue of 8 groups of rats(1, 5, 10, 15, 20, 25, 35-postnatal day and adult groups) were removed on bloc and processed for immunohistochemistry and were subjected to light microscopic examination. The results obtained were as follows; 1. The anterior portion of the articular disk was most densely innervated, followed by the posterior, lateral, and medial portions in each group. 2. Increase of CGRP immunoreactive nerve fibers was evident in 10, 15, 20 postnatal day groups. 3. Almost no CGRP immunoreactive nerve fibers were observed in articular surface of disk proper, mandibular fossa and condyle head of each group. These result suggest that CGRP immunoreactive nerve fibers increased in synovial membrane and peripheral portion of articular disk during 10-20 postnatal day may play a important role in squamosomandibular joint function after weaning period.

• Proceedings of the KIEE Conference
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• 2008.10a
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• pp.175-176
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• 2008

An ultrasonic motor of high torque with a new configuration for application in automobiles is proposed. The newly designed stator is two sided vibrator consisting of a toothed metal disk with a piezoelectric ceramic ring bonded on both faces of the disk which generates a flexural traveling wave along the circumference of disk. In this configuration, the displacement on the surface of stator may not be confined. It also produces a large vibrating force and amplitude because the vibrator is sandwiched by two piezoelectric plates. It is possible to increase the torque by improving the vibration characteristics. To compute the vibration mode of the motor of diameter 48 mm, the finite element method was used. A 6th mode was chosen as the operation mode with a resonance frequency of about 64.4 kHz. According to this design and measured its performance, a prototype was fabricated. The performance measurement of the prototype motor showed that its stall torque was about 1.8 Nm and efficiency was 37 % at 60 % of the maximum torque.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.187-188
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• 2008

An ultrasonic motor of high torque with a new configuration for application in automobiles is proposed. The newly designed stator is a two sided vibrator consisting of a toothed metal disk with a piezoelectric ceramic ring bonded on both faces of the disk which generates a flexural traveling wave along the circumference of disk. In this configuration, the displacement on the surface of stator may not be confined. It also produces a large vibrating force and amplitude because the vibrator is sandwiched by two piezoelectric plates. It is possible to increase the torque by improving the vibration characteristics. To compute the vibration mode of the motor of diameter 48 mm, the finite element method was used. A 6th mode was chosen as the operation mode with a resonance frequency of about 64.4 kHz. According to this design and measured its performance, a prototype was fabricated. The performance measurement of the prototype motor showed that its stall torque was about 1.8 Nm and efficiency was 37% at 60% of the maximum torque.