• Journal of KIISE:Computing Practices and Letters
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• v.8 no.3
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• pp.277-288
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• 2002

In this paper, we describe a design and implementation method of a smart card operating system for multi applications. A smart card is the independent computing system and is able to be used in multi applications such as the electronic commerce and the electronic cash. Smart card operation system(SCOS) provides a basis of smart card booting, and controls and manages application programs. SCOS can produce and control a file system to support multi applications in EEPROM, communicate commands and messages with outside devices, process a command, produce a reply message, and provide security functions of file security in EEPROM, and communication security. Therefor, in this paper, we design and implement SCOS system that provides the authentication between a card and a terminal, the session authentication for multi applications, the processing of commands, and the maintenance of the security.

• The Journal of the Korea Contents Association
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• v.16 no.10
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• pp.477-482
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• 2016

This paper presents a new method of parity storing for ECC(error correcting code) in SSD (solid-state drive) and suitable structure of the controller. In general usage of NAND flash memory, we partition a page into data and spare area. ECC parity is stored in the spare area. The method has overhead on area and timing due to access of the page memory discontinuously. This paper proposes a new parity policy storing method that reduces overhead and R(read)/W(write) timing by using whole page area continuously without partitioning. We analyzed overhead and R/W timing. As a result, the proposed parity storing has 13.6% less read access time than the conventional parity policy with 16KB page size. For 4GB video file transfer, it has about a minute less than the conventional parity policy. It will enhance the system performance because the read operation is key function in SSD.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.61-64
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• 2004

최근 PDA(Personal Digital Assistants)와 같은 휴대형 단말기들은 다양한 멀티미디어 기술과 무선 인터넷 기술의 영향으로 정보단말기로서 각광을 받고 있다. 그러나 현재의 단말기는 프로세서와 메모리의 한계로 인하여 원활한 음성인식 시스템을 구축하기에는 한계가 있다. 이를 보완하는 방법으로 본 논문에서는 Client/server로 분리된 음성 인식 시스템을 구축하였다. 구축한 시스템은 무선 네트워크 환경을 이용하여 PDA(Personal Digital Assistants)에서 음성 파일 또는 특징 파라미터를 Serve 측으로 전송하여 Server측에서 음성 인식을 수행한 후 그 결과를 모바일 단말기로 되돌려 주는 시스템이다. 구성된 시스템을 평가하기 위해서는 국어 공학센터의 음성 DB(KLE 452DB)를 이용하여 음향 모델을 생성한 후 다양한 환경(연구실, 복도, 주차장 도서관 로비)에서 발성한 후 이를 교내 무선 인터넷망(Nespot)을 통하여 송신하여 실시간 인식하였다. 실험 결과, 각각 $84.04\%\;72.28\%\;69.47\%\;67.61\%$의 평균 인식률을 얻을 수 있었다.

• Journal of IKEEE
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• v.24 no.1
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• pp.200-207
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• 2020

In this paper, an area-efficient feature extractor was proposed for security surveillance radar systems and FPGA-based implementation results were presented. In order to reduce the memory requirements, features extracted from Doppler profile for FFT window-size are used, while those extracted from total spectrogram for frame-size are excluded. The proposed feature extractor was design using Verilog-HDL and implemented with Xilinx Zynq-7000 FPGA device. Implementation results show that the proposed design can reduce the logic slice and memory requirements by 58.3% and 98.3%, respectively, compared with the existing research. In addition, security surveillance radar system with the proposed feature extractor was implemented and experiments to classify car, bicycle, human and kickboard were performed. It is confirmed from these experiments that the accuracy of classification is 93.4%.

• Journal of KIISE
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• v.42 no.4
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• pp.427-433
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• 2015

The rapid advancement of computing technology has triggered the need for fast data I/O processing and high-performance storage technology. Next generation memory technology, which we refer to as new memory, is anticipated to be used for high-performance storage as they have excellent characteristics as a storage device with non-volatility and latency close to DRAM. This research proposes NTL (New memory Translation layer) as a technology to make use of new memory as storage. With the addition of NTL, conventional I/O is served with existing mature disk-based file systems providing compatibility, while new memory I/O is serviced through the NTL to take advantage of the byte-addressability feature of new memory. In this paper, we describe the design of NTL and provide experiment measurement results that show that our design will bring performance benefits.

• KIISE Transactions on Computing Practices
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• v.23 no.7
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• pp.428-433
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• 2017

Recently, the demand for high performance non-volatile memory storage devices that can replace existing hard disks has been increasing in environments requiring high performance computing such as data-centers and social network services. The performance of such non-volatile memory can greatly depend on the interface between the host and the storage device. With the evolution of storage interfaces, the non-volatile memory express (NVMe) interface has emerged, which can replace serial attached SCSI and serial ATA (SAS/SATA) interfaces based on existing hard disks. The NVMe interface has a higher level of scalability and provides lower latency than traditional interfaces. In this paper, an evaluation and analysis are conducted of the performance of NVMe storage devices through various workloads. We also compare and evaluate the cost efficiency of NVMe SSD and SATA SSD.

• 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 the Korea Institute of Information and Communication Engineering
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• v.12 no.1
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• pp.108-114
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• 2008

Since flash memory cannot be overwritten, 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 count 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 ad cold block though the performance of processing is hight 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 shows that its performance is 30% better than cost benefit algorithm with separation of cold block and hot block its wear-leveling is about a third of that in standard deviation.

• The Journal of Korean Institute of Next Generation Computing
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• v.15 no.5
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• pp.7-19
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• 2019

Ransomware is a malicious program that requires the cost of decryption after encrypting files on the user's desktop. Since the frequency and the financial damage of ransomware attacks are increasing each year, ransomware prevention, detection and recovery system are needed. Baek et al. proposed SSD-Insider, an algorithm for detecting ransomware within SSD. In this paper, we propose an AdvanSSD-Insider algorithm that substitutes a hash table used for the overwriting check with a bloom filter in the SSD-Insider. Experimental results show that the AdvanSSD-Insider algorithm reduces memory usage by up to 90% and execution time by up to 77% compared to the SSD-Insider algorithm and achieves the same detection accuracy. In addition, the AdvanSSD-Insider algorithm can monitor 10 times longer than the SSD-Insider algorithm in same memory condition. As a result, detection accuracy is increased for some ransomware which was difficult to detect using previous algorithm.

• IEMEK Journal of Embedded Systems and Applications
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• v.2 no.3
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• pp.184-193
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• 2007

Flash memory adoption in the mobile devices is increasing or vanous multimedia services such as audio, videos, and games. Although the traditional research issues such as out-place update, garbage collection, and wear-leveling are important, the performance, memory usage, and fast mount issues of flash memory file system are becoming much more important than ever because flash memory capacity is rapidly increasing. In this paper, we address the problems of the existing log-based flash memory file systems analytically and propose an efficient log-based file system, which produces higher performance, less memory usage and mount time than the existing log-based file systems. Our ideas are applied to a well-known log-based flash memory file system (YAFFS2) and the performance tests are conducted by comparing our prototype with YAFFS2. The experimental results show that our prototype achieves higher performance, less system memory usage, and faster mounting than YAFFS2, which is better than JFFS2.