• Journal of Digital Contents Society
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• v.11 no.1
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• pp.91-97
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• 2010

Flash memory has been used by many digital devices for data storage, exploiting the advantages of non-volatility, low power, stability, and so on, with the help of high integrity, large capacity, and low price. As the fast growing popularity of flash memory, the density of it increases so significantly that its entire address mapping table becomes too big to be stored in SRAM. This paper proposes the associated page address cache with an efficient table management scheme for hybrid flash translation layer mapping. For this purpose, all tables are integrated into a map block containing entire physical page tables. Simulation results show that the proposed scheme can save the extra memory areas and decrease the searching time with less 2.5% of miss ratio on PC workload and can decrease the write overhead by performing write operation 33% out of total writes requested.

• Journal of Korea Multimedia Society
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• v.18 no.9
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• pp.1098-1104
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• 2015

With the widespread use of smartphones and IoT (Internet of Things), data are being generated on a large scale, and there is increased for the analysis of such data. Hence, distributed processing systems have gained much attention. Hadoop, which is a distributed processing system, saves the metadata of stored files in name nodes; in this case, the main problems are as follows: the memory becomes insufficient; load occurs because of massive small files; scheduling and file processing time increases because of the increased number of small files. In this paper, we propose a solution to address the increase in processing time because of massive small files, and thus improve the processing performance, using the Reuse JVM method provided by Hadoop. Through environment setting, the Reuse JVM method modifies the JVM produced conventionally for every task, so that multiple tasks are reused sequentially in one JVM. As a final outcome, the Reuse JVM method showed the best processing performance when used together with CombineFileInputFormat.

• Journal of KIISE
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• v.41 no.11
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• pp.878-884
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• 2014

File I/O buffer cache plays an important role in narrowing the wide speed gap between the main memory and the secondary storage. However, data loss or inconsistencies may occur if the system crashes before the data that has been updated in the buffer cache is flushed to storage. Thus, most operating systems adopt a daemon that periodically flushes dirty data to the secondary storage. In this study, we show that periodic flushes account for 30-70% of the total write traffic to storage and remove this inefficiency by implementing a small, non-volatile buffer cache. Specifically, we present space-efficient management techniques, such as delta-write and fragment-grouping, and show that the storage write traffic and throughput can be improved by a margin of 44.2% and 23.6%, respectively, with only a small NVRAM.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.574-577
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• 2007

While disk can be overwritten on updating data, because flash memory can not be overwritten on updating data, new data are updated in new area. If data are frequently updated, garbage collection, which is achieved by erasing blocks, should be performed to reclaim new area. Hence, because the number of erase operations is limited due to characteristics of flash memory, every block should be evenly written and erased. However, if data with access locality are processed by cost benefit algorithm with separation of hot block and cold block, though the performance of processing is high, wear-leveling is not even. In this paper, we propose CB-MB (Cost Benefit between Multi Bank) algorithm in which hot data are allocated in one bank and cold data in another bank, and in which role of hot bank and cold bank is exchanged every period. CB-MB showed that its performance was similar to that of others for uniform workload, however, the method provides much better performance than that of others for workload of access locality.

• Journal of Biomedical Engineering Research
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• v.19 no.3
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• pp.251-260
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• 1998

The Holter monitoring system is a widely used noninvasive diagnostic tool for ambulatory patient who may be at risk from latent life-threatening cardiac abnormalities. In this paper, we design a high performance intelligent holter monitoring system which is characterized by the small-sized and the low-power consumption. The system hardware consists of one-chip microcontroller(68HC11E9), ECG preprocessing circuit, and flash memory card. ECG preprocessing circuit is made of ECG preamplifier with gain of 250, 500 and 1000, the bandpass filter with bandwidth of 0.05-100Hz, the auto-balancing circuit and the saturation-calibrating circuit to eliminate baseline wandering, ECG signal sampled at 240 samples/sec is converted to the digital signal. We use a linear recursive filter and preprocessing algorithm to detect the ECG parameters which are QRS complex, and Q-R-T points, ST-level, HR, QT interval. The long-term acquired ECG signals and diagnostic parameters are compressed by the MFan(Modified Fan) and the delta modulation method. To easily interface with the PC based analyzer program which is operated in DOS and Windows, the compressed data, that are compatible to FFS(flash file system) format, are stored at the flash memory card with SBF(symmetric block format).

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.3
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• pp.41-50
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• 2009

The flash memory has many advantages such as low power consumption, strong shock resistance, fast I/O and non-volatility. And it is increasingly used in the mobile storage device. Many researchers are studying the YAFFS, NAND flash file system, which is widely used in the embedded device. However, the existing YAFFS has two problems. First, it takes long time to mount the YAFFS file system because it scans whole spare areas in all pages. Second, the cleaning policy of the YAFFS does not consider the wear-leveling so that it cannot guarantee the duration of data completely. In order to solve these problems, this paper proposes a new content-based YAFFS that consists of a mounting time reduction technique and a content-cleaning policy by using content-based block management. The proposed method only scans partial spare areas of some special pages and provides the block swapping which enables the wear-leveling of data blocks. We performed experiments to compare the performance of the proposed method with those of the JFFS2 system and YAFFS system. Experimental results show that the proposed method reduces the average mounting time by 82.2% comparing with JFFS2 and 42.9% comparing with YAFFS. Besides, it increases the life time of the flash memory by 35% comparing with the existing YAFFS whereas no overheat is added.

• Journal of the Korea Society of Computer and Information
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• v.14 no.4
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• pp.9-17
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• 2009

In this paper, we propose a dynamic load distribution technique at the operating system level in mobile storage systems with a heterogeneous storage pair of a small form-factor and disk and a flash memory, which aims at saving energy consumption as well as enhancing I/O performance. Our proposed technique takes a combinatory approach of file placement and buffer cache management techniques to find how the load can be distributed in an energy and performance-aware way for a heterogeneous mobile storage air of a hard disk and a flash memory. We demonstrate that the proposed technique provides better experimental results with heterogeneous mobile storage devices compared with the existing techniques through extensive simulations.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06b
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• pp.321-322
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• 2011

차세대 저장매체로 각광받고 있는 BPRAM을 이용해, NAND Flash memory의 결점을 보완하고자 하는 많은 연구들이 진행되고 있다. 본 논문에서는 BPRAM과 NAND Flash를 이용하여, 계층적 스토리지에 사용하는 하이브리드 파일 시스템인 Compressing Metadata File System(CMFS)을 개발하였다. CMFS는 Mount time에 필요한 메타데이터를 BPRAM에 저장하여 마운트 시간을 줄이고, 메타데이터를 Update하기 위한 Overhead를 줄이기 위해 부분 갱신 기법을 개발하였다. 또한 메타데이터의 저장을 위해 필요한 BPRAM의 용량를 줄이기 위해 메타데이터를 경량화 및 압축하고, 압축률을 높이기 위해 Hybrid Coding 압축기법을 개발하여 적용한다. Marvel PXA320(806MHz) 보드를 이용하여 CMFS의 성능을 측정하였으며, 타 압축 기법보다 높은 메타데이터의 압축률을 보였다.

• Journal of Korea Society of Digital Industry and Information Management
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• v.12 no.1
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• pp.97-106
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• 2016

3D virual reality technique develop rapidly such as parts of education, health, national defense, etc. This paper implements an education contents utilizing 3D virtual reality based on HMD. In this paper, contents make up Changdeokgung Palace using to 3Dmax and Unity program, it shows on implemented Helmet Mounted Display. HMD obtain dynamic image from the target source of smart phone. Also, contents consist of service senerio through divided palace position and King's a day's journey especially. Above all, this paper indicate improving performance according to reduced cybersickness and immersion enlargement. And memory capacity reduced by various technique such that file type, compressed file, minimized resource. Proposed technique can obtain dynamic 3D image by HMD implementation at real time basis so that it is possible to use simultaneously multi-source. From the various and practical experiment, it is confirm that proposed 3D VR education system is useful for experience of virtual reality practically.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04a
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• pp.61-63
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• 2002

컴퓨터 및 네트워크 기술의 눈부신 성장은 PDA, MP3 플레이어, 디지털 카메라와 같은 임베디드 시스템의 급성장을 가져왔다. 이러한 임베디드 시스템에는 그 시스템의 목적에 맞도록 특화된 실시간 운영체제가 탑재되게 되고, 그에 맞게 각 저장 장치들을 제어할 수 있는 파일 시스템도 필요하다. 본 논문에서는 삼성전자에서 개발한 CalmRISC16 마이크로 프로세서 코어를 사용하는 임베디드 시스템에 탑재될 실시간 운영체제를 위한 임베디드 파일 시스템을 구현하였다. 부 논문에서 구현된 임베디드 파일 시스템은 가상 과인 시스템으로 동작하며 In-memory 파일 시스템과 FAT를 사용하는 SmartMedia를 지원한다.