• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.2
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• pp.315-320
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• 2009

Since flash memory can not be overwritten on updating data, new data are updated in new area and old data should be invalidated and erased for garbage collection. With develop of flash memory technology, capacity of flash memory is rapidly increasing. It increases rapidly execution time of CPU to search an entire flash memory of large capacity when choosing the block to erase in garbage collection. To solve the problem that is increasing execution time of CPU, flash memory is partitioned into several groups, the block to erase in garbage collection is searched within the corresponding group. In workload of access locality, we enhanced wear-leveling within group by allocating hot data to hot group and cold data to cold group respectively and enhanced wear-leveling among groups by exchanging periodically hot group and cold group.

• The Journal of Society for e-Business Studies
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• v.15 no.4
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• pp.101-121
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• 2010

This paper presents an intelligent prefetching technique that significantly improves performance of hybrid fash-disk storage, a combination of flash memory and hard disk. Since flash memory embedded in a hybrid device is much faster than hard disk in terms of I/O operations, it can be utilized as a 'cache' space to improve system performance. The basic strategy for prefetching is to utilize sequential pattern mining, with which we can extract the access patterns of objects from historical access sequences. We use two techniques for enhancing the performance of hybrid storage with prefetching. One of them is to modify a FAST algorithm for mapping the flash memory. The other is to extend the unit of prefetching to a block level as well as a file level for effectively utilizing flash memory space. For evaluating the proposed technique, we perform the experiments using the synthetic data and real UCC data, and prove the usability of our technique.

• The Journal of Society for e-Business Studies
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• v.15 no.4
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• pp.21-31
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• 2010

Recently e-business such as online financial trade and online shopping using mobile computes are widely spread. Most of mobile computers use NAND flash memory-based storage devices for storing data. Flash memory storage devices use a software called flash translation layer to translate logical address from a file system to physical address of flash memory by using mapping tables. The legacy FTLs have a problem that they must maintain very large mapping tables in the RAM. In order to address this issues, in this paper, we proposed a new caching scheme of mapping tables. We showed through the trace-driven simulations that the proposed caching scheme reduces the space overhead dramatically but does not increase the time overhead. In the case of online transaction workload in e-business environment, in particular, the proposed scheme manifests better performance in reducing the space overhead.

• Journal of KIISE
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• v.43 no.4
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• pp.411-418
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• 2016

In recent times, NAND flash memory has become widely used as secondary storage for computing devices. Accordingly, to take advantage of NAND flash memory, new file systems have been actively studied and proposed. The performance of these file systems is generally measured with benchmark tools. However, since benchmark tools are executed by software simulation methods, many researchers get non-uniform benchmark results depending on the system environments. In this paper, we use Filebench, one of the most popular and representative benchmark tools, to analyze benchmark results and study the reasons why the benchmark result variations occur. Our experimental results show the differences in benchmark results depending on the system environments. In addition, this study substantiates the fact that system performance is affected mainly by background I/O requests and fsync operations.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.190-192
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• 2007

모바일 장치에서 사용하는 카메라 모듈을 가지고 MBA2440 보드에서 WINDOWS CE 운영체제의 디바이스 드라이버를 통하여 카메라 장치로부터 동영상 데이터를 얻어 화면에 표시하고, 여기서 획득된 화면정보를 Nand Flash 메모리에 저장하는 내용을 다룬다. 테스트에 사용된 카메라 모듈은 PIXELPLUS사의 모바일용 초소형 VGA급 30만 화소 카메라로 카메라모듈과 MBA2440보드 사이에 하드웨어적인 부분이 정상 작동하는지 확인을 위하여 펌웨어 상에서 카메라의 동영상 화면을 캡쳐하는 프로그램을 만들고, 이를 FAT File System을 이용하여 Nand Flash에 Image 파일 형태로 저장할 수 있도록 한다.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.4
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• pp.607-614
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• 2011

This paper describes the development of pulse code modulation(PCM) data recorder with design, implementation and environmental test. PCM serial data that diverged from telemetry encoder output is used as the input and is reformed to parallel signal through FPGA processing. Controllers construct the packet by the sector and record it into non-volatile memory. Compact flash(CF) memory for data storage media, USB interface for data downloading, and a software for operating status diagnosis and file format conversion are used.

• Proceedings of the Korean Information Science Society Conference
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• 2007.06b
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• pp.377-380
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• 2007

플래시 메모리는 무게, 내구성, 전력 소비량 측면에서 기존 디스크보다 우수하기 때문에 주로 휴대용 기기의 저장장치로 사용되었다. 최근에는 집적도가 향상되면서 SSD(Solid State Disk)형태로 노트북에서도 활용되고 있다. 이러한 플래시 메모리는 제자리 갱신이 불가능한 특징 때문에 저장장치로 사용하기 위해서는 FTL(Flash Memory Translation Layer)이라는 주소사상 소프트웨어가 필요하다. 그리고 FTL은 블록을 재활용하기 위해 병합 연산을 수행하게 되는데 이 병합 연산의 비용이 시스템 성능에 큰 영향을 미친다. 아울러 FTL 상에서 동작하는 파일 시스템의 경우도 디스크 기반 파일 시스템과 같이 단편화 문제로 인한 성능 저하가 발생하게 된다. 본 논문에서는 플래시 메모리 기반 파일 시스템에서 단편화 현상을 줄이기 위해 FTL의 병합동작의 특성을 활용한 조각 모음 기법을 제안한다. 실험결과는 제안한 기법이 결국 FTL에서 병합 연산의 비용을 줄임으로써 성능을 향상시킬 수 있음을 보여준다.

• Proceedings of the KIEE Conference
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• 2004.05a
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• pp.147-149
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• 2004

Although most of the people have studied English for a long time, their English conversation capability is low. When we provide them portable conversational-type English learners by the application of computer and information process technology, such portable learners can be used to enhance their English conversation capability by their conventional conversation exercises. The core technology to develop such learner is the development of a voice recognition and synthesis module under an embedded environment. This paper deals with voice recognition and synthesis, prototype of the learner module using a DSP(Digital Signal Processing) chip for voice processing, voice playback function, flash memory file system, PC download function using USB ports, English conversation text function by the use of SMC(Smart Media Card) flash memory, LCD display function, MP3 music listening function, etc. Application areas of the prototype equipped with such various functions are vast, i.e. portable language learners, amusement devices, kids toy, control by voice, security by the use of voice, etc.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.647-650
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• 2009

IPTV(Internet Protocol Television)는 차별화된 초고속 광대역 네트워크를 기반으로 기존 TV의 단점을 보완하여 차세대 DTV 시장을 주도할 것으로 예상된다. IPTV의 저장용량이 증가하는 추세에 따라 SSD(Solid State Disk)가 NAND 플래시 메모리를 대체 할 것으로 예상된다. 본 논문에서는 IPTV의 저장장치인 SSD의 수명을 증가시키고 플래시메모리의 특성인 마모도 제한을 고려하지 않은 지움 정책(Garbage-Collection)을 사용하는 YAFFS(Yet Another Flash FileSystem)의 문제점을 해결하기 위해 블록을 내용기반 리스트로 관리하고 블록스왑을 사용하는 내용기반 지움 정책을 제안한다. 기존 파일시스템 보다 수명을 향상 시키는 내용기반 파일시스템을 설계 및 구현하여 성능을 분석하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06a
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• pp.331-332
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• 2008