• Journal of Korea Society of Industrial Information Systems
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• v.18 no.4
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• pp.9-18
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• 2013

Flash memory is mostly used on smart devices and embedded systems because of its nonvolatile memory, low power, quick I/O, resistant shock, and other benefits. Generally the typical file systems base on the NAND flash memory are YAFFS2, JFFS2, UBIFS, and etc. In this paper, we had variously made an experiment regarding I/O performance using our schemes and the UBIFS of the latest Linux Kernel. The proposed I/O performance analyses were classified as a sequential access and a random access. Our experiment consists of 6 cases using kmalloc(), vmalloc(), and kmem_cache(). As a result of our experiment analyses, the sequential reading and the sequential rewriting increased by 12%, 11% when the Case 2 has applied vmalloc() and kmalloc() to the UBI subsystem and the UBIFS. Also, the performance improved more by 7.82%, 6.90% than the Case 1 at the random read and the random write.

• Journal of KIISE:Databases
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• v.36 no.5
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• pp.374-385
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• 2009

Flash memory becomes increasingly popular as data storage for various devices because of its versatile features such as non-volatility, light weight, low power consumption, and shock resistance. Flash memory, however, has some distinct characteristics that make today's disk-based database technology unsuitable, such as no in-place update and the asymmetric speed of read and write operations. As a result, most traditional disk-based database systems may not provide the best attainable performance on flash memory. To maximize the database performance on flash memory, some approaches have been proposed where only the changes made to the database, i.e., logs, are written to another empty place that has born erased in advance. In this paper, we propose an efficient log management scheme for flash-based database systems. Unlike the previous approaches, the proposed approach stores logs in specially allocated blocks, called log blocks. By evenly distributing logs across log blocks, the proposed approach can significantly reduce the number of write and erase operations. Our performance evaluation shows that the proposed approaches can improve the overall system performance by reducing the number of write and erase operation compared to the previous ones.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.293-300
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• 2016

Traditional databases exploit a record-based model, where the attributes of a record are placed contiguously in a slow hard disk to achieve high performance. On the other hand, for read-intensive data analysis systems, the column-based compressed database has become a proper model because of its superior read performance. Currently, flash memory SSD is largely recognized as the preferred storage media for high-speed analysis systems. This paper introduces a compressed column-storage model and proposes a new index and its data management scheme for a high-capacity data warehouse system. The proposed index management scheme is based on the asymmetric index duplication and achieves superior search performance using the master index and compact index, particularly for large read-mostly databases. In addition, the data management scheme contributes to the read performance and high reliability by compressing the related columns and replicating them in two mirrored SSD. Based on the results of the performance evaluation under the high workload conditions, the data management scheme outperforms the traditional scheme in terms of the search throughput and response time.

• Journal of Korean Library and Information Science Society
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• v.46 no.4
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• pp.299-324
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• 2015

This paper is a qualitative single case study and it was conducted for the purpose to explore change in interactive bibliotherapy experience with a middle-aged widowed spouse. A Middle-aged Widowed Spouse was taken as a research partaker. Through this research, we explored partitively the partaker's experience changes by each session during the commencing of interactive bibliotherapy and the partaker's inner/external experience change after the end of session. The result, interactive bibliotherapy facilitated and expressed the reaction of a partaker by its writing skills and reading materials including partaker's own poems. Furthermore, facilitated emotion from material and self-awareness made a partaker understand and accept itself through therapeutical interaction. In addition, those kind of changes appeared inner/external experience in life, and lasted after the end of the session. In this regard, the inner/external change appeared from a partaker means the effect of bibliotherapy, and we can notice that it is a result that facilitated through truthful reaction of counselor and texts.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.380-380
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• 2012

유기물 나노 복합체는 고집적/저전력/플렉서블 특성을 가지는 초고효율 비휘발성 메모리 소자를 제작하는데 많은 이점을 가지고 있어, 차세대 비휘발성 메모리 소자에 사용되는 소재로 매우 각광받고 있다. 그 중, WORM 특성을 가지는 메모리 소자는 1회 쓰기 후 수많은 읽기가 가능하기 때문에, 그 효율성이 매우 뛰어나 이목을 끌고 있다. 유기물 나노 복합체 중에서, poly(3-hexylthiophene) (P3HT)는 화학적/전기적 안정성과 전하의 이동도 특성이 뛰어나기 때문에 전자 소자에 응용하려는 연구가 활발히 진행되고 있다. 본 연구에서는 $P_3HT$ 고분자를 polymethylmethacrylate(PMMA) 고분자에 분산시킴으로써, 상태를 기억하는 저장 매체로 사용하였다. 본 연구의 소자를 제작하기 위하여 약 9 : 1 비율을 가지는 PMMA 와 $P_3HT$를 용매인 클로로벤젠에 녹여 용액을 준비하였다. Indium Tin Oxide (ITO)가 코팅된 glass를 화학적 처리를 통해 청결하게 만든 후, PMMA와 $P_3HT$가 용해되어 있는 용액을 스핀 코팅 방법으로 박막을 형성하였다. PMMA 속에 $P_3HT$가 분산되어 있는 활성층 위에 상부 전극으로 Al을 열 증착 방식을 통하여 형성하였다. 제작된 WORM 특성을 갖는 유기물 나노 복합체 플렉서블 소자의 메모리 효과에 대한 분석을 위하여, -5V에서 5V까지 전압을 인가하여 전류-전압 특성을 측정하였다. 초기 낮은 전도도 (OFF 상태, 10-10A에서 10-4A)를 유지하다가, 쓰기 전압을 1회 가해준 후부터는 높은 전도도 (ON 상태, 10-5A 에서 10-2A)를 유지하는 특성을 관측하였다. 또한 WORM 특성을 갖는 메모리 소자로써의 능력을 보여주기 위하여, 1회 쓰기 전압 후 읽기 전압인 1V를 인가하여 높은 전도도 상태에 대한 상태 유지 능력을 측정하였고, 전하 수송 메커니즘을 규명하기 위하여 피팅 모델을 통해 설명하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.1
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• pp.393-401
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• 2013

Most traditional databases exploit record-oriented storage model where the attributes of a record are placed contiguously in hard disk to achieve high performance writes. However, for search-mostly datawarehouse systems, column-oriented storage has become a proper model because of its superior read performance. Today, flash memory is largely recognized as the preferred storage media for high-speed database systems. In this paper, we introduce fast column-oriented database model and then propose a new column-aware index management scheme for the high-speed column-oriented datawarehouse system. Our index management scheme which is based on enhanced $B^+$-Tree achieves high search performance by embedded flash index and unused space compression in internal and leaf nodes. Based on the results of the performance evaluation, we conclude that our index management scheme outperforms the traditional scheme in the respect of the search throughput and response time.

• Journal of KIISE:Databases
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• v.36 no.1
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• pp.1-7
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• 2009

Flash memory has its unique characteristics: i.e., (1) the write operation is much more costly than the read operation. (2) In-place updating is not allowed. In this paper, we first analyze how these characteristics affect the performance of record management in flash memory, and discuss the problems with previous methods for record management when they are applied to flash memory environment. Next, we propose a new record management method to be suitable for flash memory environment. The proposed method employs a new concept of a container that makes it possible to overwrite data on flash memory several times when performing insertions, deletions, and modifications of records. As a result, this method reduces the number of overwrite operations, and consequently does the number of erase operations. The results of experiments show that our method improves the performance by up to 34%, compared with the previous one.

• The KIPS Transactions:PartD
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• v.17D no.6
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• pp.383-394
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• 2010

Flash memory based SSDs are currently being considered as a promising candidate for replacing hard disks due to several superior features such as shorter access time, lower power consumption and better shock resistance. However, SSDs have different characteristics from hard disk such as difference of unit and time for read, write and erase operation and impossibility for over-writing. Because of these reasons, SSDs have disadvantages on hard disk based systems, so FTL(Flash Translation Layer) is designed to increase SSDs' efficiency. In this paper, we propose an advanced logical address mapping method for increasing SSDs' performance, which is named HAMM(Hybrid Address Mapping Method). HAMM addresses drawbacks of previous block-mapping method and super-block-mapping method and takes advantages of them. We experimented our method on our own SSDs simulator. In the experiments, we confirmed that HAMM uses storage area more efficiently than super-block-mapping method, given the same buffer size. In addition, HAMM used smaller memory than block-mapping method to construct mapping table, demonstrating almost same performance.

• Trans-
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• v.6
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• pp.43-78
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• 2019

Dance is an art that includes not only art historical facts, but also a series of processes for dancers' body, choreography, and the creation of entire process of dances and their lives. In other words, dance is the art of embodying the experience and consciousness of the dancer as the subject, and embodying it through the physical body, and therefore, the existing empirical study which relies solely on the literature in the history of dance study is difficult to deliver a complete history. Oral history is a new methodology historical writing that overcomes the limitations of research methods based on literature centered documents. Oral history in the field of dance is that the dancer becomes the subject of the history of dance's narrative. The memory and testimony of a dancer can become a history, complement the missing parts of the documentary record, and amount to analysis and interpretation to attempt the history of dance from various perspectives. The history of dance through oral history analysis thus generates another view from the literature. The oral history is acted as a prism that can explore the sociocultural discourse of the time and the history of dance. As a new academic challenge for the history of dance field, I expect to be able to review the artistic, social, and cultural functions and roles of dance beyond the limit of existing literature-oriented history study and to be able to progress to various the history of dance.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.7
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• pp.48-56
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• 2011

Recently, new storage device SSD(Solid State Disk) based on NAND flash memory is gradually replacing HDD(Hard Disk Drive) in mobile device and thus a variety of research efforts are going on to find the cost-effective ways of performance improvement. By increasing the NAND flash channels in order to enhance the bandwidth through parallel processing, DRAM buffer which acts as a buffer cache between host(PC) and NAND flash has become the bottleneck point. To resolve this problem, this paper proposes an efficient low-cost scheme to increase SSD performance by improving DRAM buffer bandwidth through scheduling techniques which utilize DRAM multi-banks. When both host and NAND flash multi-channels request access to DRAM buffer concurrently, the proposed technique checks their destination and then schedules appropriately considering properties of DRAMs. It can reduce overheads of bank active time and row latency significantly and thus optimizes DRAM buffer bandwidth utilization. The result reveals that the proposed technique improves the SSD performance by 47.4% in read and 47.7% in write operation respectively compared to conventional methods with negligible changes and increases in the hardware.