• Proceedings of the Korea Information Processing Society Conference
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• 2012.04a
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• pp.699-701
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• 2012

USB flash drive와 같은 이동형 저장매체는 한 손에 쏙 들어오는 작은 크기와 가벼운 무게로 뛰어난 휴대성을 제공하고 있다. 많은 사용자들은 자신의 데이터를 저장하기 위해 고용량을 제공하는 이동형 저장매체에 관심을 보이고 있다. 하지만 이동형 저장매체는 휴대성으로 인한 도난 및 분실당할수 있다. 개인 정보가 유출되는 등의 많은 문제들이 발생하고 있다. 인터넷의 발달과 클라우드 컴퓨팅 붐을 통하여 이동형 저장매체의 문제점을 해결할 수 있는 클라우드 스토리지 서비스가 급증하고 있다. 하지만 이러한 클라우드 스토리지 서비스는 인터넷이 가지고 있는 취약성 및 서버와 서버의 관리자의 비신뢰성 등의 문제를 가지고 있으며, 이로 인한 몇몇 사고가 발생하였다. 이러한 문제를 해결하기 위해서 클라우드 스토리지 환경에서는 데이터를 암호화 저장하고 이를 복호화 과정 없이 검색할 수 있는 검색 가능한 암호 기술의 필요성이 대두되고 있다. 하지만 기존의 검색가능 암호 기술은 사용자가 저장하고자 하는 데이터를 직접 업로드하고, 해당 자료를 필요에 따라 공유 하고, 공유대상이 변화되는 클라우드 스토리지 환경에서 비효율성을 가지고 있어 실제 서비스에 적용하기 힘든 단점을 가지고 있다. 따라서 본 논문에서는 클라우드 컴퓨팅 환경을 고려하여 검색가능한 암호화 색인 생성 및 이를 재암호화를 통해 다른 사용자와 안전하게 공유할 수 있는 검색가능한 재 암호화 시스템을 제안한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.4 s.346
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• pp.31-38
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• 2006

In this paper, we propose an efficient preceding scheme for STBC-Spatial Muiltiplexing OFDM systems. In MIMO systems, the precoder is designed on the assumption that feedback channel information is perfectly known to transmitter and receiver. However, feedback delay and link errors in real environment make the transmitter use the incorrect channel information and consequently cause the performance degradation. The proposed precoder is designed to compensate for the performance degradation by the diversity gain provided by STBC. At the transmitter, the precoder for each subcarrier is constructed by using the index of codebook, subcarrier correlation, and auto correlation of channel. From the simulation results, STBC-spatial multiplexing OFDM outperforms the preceded-spatial multiplexing OFDM at $SER=10^{-3}$ when the Doppler frequency is greater than 60Hz.

• The KIPS Transactions:PartB
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• v.9B no.3
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• pp.343-350
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• 2002

A scene change detection which involves finding a cut between two consecutive shots is an important step for video indexing and retrieval. This paper proposes an algorithm for fast and accurate detection of abrupt scene changes in an MPEG compressed domain with minimal decoding requirements arid computational effort. The proposed method compares two successive DC images of I-frames for finding the GOP (group of picture) which contain a scene change and uses macroblock-coded type information contained in B-frames to detect the exact frame where the scene change occurred. The experiment results demonstrate that the proposed algorithm has better detection performance, such as precision and recall rate, than the existing method using all DC images. The algorithm has the advantage of speed, simplicity and accuracy. In addition, it requires less amount of storage.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.16 no.2
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• pp.139-156
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• 2005

In this paper, we design and implement electronic book system providing web-based interface for the ebook. The aim of this study is to optimize the effective reading and management of electronic text for its users(readers and librarians). Advanced functions of the electronic book system are the following: 1) Electronic book system is not dependent to specific software and tool. 2) Electronic book system is able to. minimize images(table, image, icon etc) to improve the meaning and readability of information. 3) Electronic book system is able to reduce the effort for indexing extraction and constructing the table of content. 4) The system is able to collect the user log files that are created during the process of reading ebook from various points of view. 5) When reading, the system uses the DRM through decoding and encoding the ebook.

• 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.

• The KIPS Transactions:PartD
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• v.14D no.5
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• pp.459-470
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• 2007

A data stream is a massive unbounded sequence of data elements continuously generated at a rapid rate. Query processing for such a data stream should also be continuous and rapid, which requires strict time and space constraints. In most DSMS(Data Stream Management System), the selection predicates of continuous queries are grouped or indexed to guarantee these constraints. This paper proposes a new scheme tailed an ASC(Attribute Selection Construct) that collectively evaluates selection predicates containing the same attribute in multiple continuous queries. An ASC contains valuable information, such as attribute usage status, partially pre calculated matching results and selectivity statistics for its multiple selection predicates. The processing order of those ASC's that are corresponding to the attributes of a base data stream can significantly influence the overall performance of multiple query evaluation. Consequently, a method of establishing an efficient evaluation order of multiple ASC's is also proposed. Finally, the performance of the proposed method is analyzed by a series of experiments to identify its various characteristics.

• Journal of Information Management
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• v.35 no.4
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• pp.81-105
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• 2004

In this study, the way of the automatic text categorization on web-based query was implemented. X2 methods based on the Supported Vector Machine were used to test the efficiency of text categorization on queries. This test is carried out by the model using the Synonymy List. 713 synonyms were extracted manually from the tested documents. As the result of this test, the precision ratio and the recall ratio were decreased by -0.01% and by 8.53%, respectively whether the synonyms were assigned or not. It also shows that the Value of F1 Measure was increased by 4.58%. The standard deviation between the recall and precision ratio was improve by 18.39%.

• The Journal of the Korea Contents Association
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• v.22 no.8
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• pp.681-691
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• 2022

The purpose of this study is to construct a digital archive system by analyzing the collections of the Korean Christian Museum at S University, which has a large number of materials related to Korean Christianity published in the modern period from the time of Korea's enlightenment until liberation. In order to construct a digital archive system, indexes and metadata for the collection are complied according to the pre-defined format. After digitizing the selected collection, a database is built using metadata information, and the actual system is divided into a web standard-based management system and a user service system. Also a content-based search system is constructed, which provides the matching value of retrieval results in units of one character and an automatic search term completion function to enhance user convenience. Therefore, collections in the museum, which are difficult to access the original text, are digitized and provided so that they can be easily used, laying the foundation for the long-term development of humanities contents for improving the accessibility and availability of collections for both researchers and the public.

• Journal of Korean Library and Information Science Society
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• v.50 no.4
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• pp.539-559
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• 2019

One of the fundamental roles of libraries is to provide users with efficient and easy retrieval of materials. Various discussions have been made at domestic and abroad to improve the accessibility of materials by category, user, and collection, and at the center of this is the issue of improving classification and cataloging systems. However, there are few studies in this area dealing with the data accessibility of the DLS catalog, which is a central tool for accessing domestic school library materials. This study started from the appeal of school library users to the difficulty of searching and accessing books, especially literature. This study is an exploratory study that attempts to derive problems by finding the causes of there difficulties from various aspects. To this study, we surveyed and analyzed the current status of school library collections, the data registration of the school library support system DLS, the subject accessibility of catalog records produced through this, and the recognition and opinions of school library professionals. As a result, school library collections were highly concentrated in the literature field, and it was found that there was not enough catalog bibliographic records to provide efficient access to these collections. In addition, it was found to be somewhat lacking through the DLS search function to compensate for this. Surveys of school librarians and librarians have also identified this problem, and a rich topic index and search keyword assignments have been drawn to the majority of opinions as a way to improve access to materials in school library catalogs. As a continuous discussion on this subject, the plan for improving access to school library materials will be more concrete through future user studies and new challenges for bookshelf classification.

• Journal of KIISE:Databases
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• v.30 no.5
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• pp.451-463
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• 2003

Recently, there have been various research efforts to develop strategies for accelerating OLAP operations on huge amounts of spatio-temporal data. Most of the work is based on multi-tree structures which consist of a single R-tree variant for spatial dimension and numerous B-trees for temporal dimension. The multi~tree based frameworks, however, are hardly applicable to spatio-temporal OLAP in practice, due mainly to high management cost and low query efficiency. To overcome the limitations of such multi-tree based frameworks, we propose a new approach called Hilbert Cube(H-Cube), which employs fractals in order to impose a total-order on cells. In addition, the H-Cube takes advantage of the traditional Prefix-sum approach to improve Query efficiency significantly. The H-Cube partitions an embedding space into a set of cells which are clustered on disk by Hilbert ordering, and then composes a cube by arranging the grid cells in a chronological order. The H-Cube refines cells adaptively to handle regional data skew, which may change its locations over time. The H-Cube is an adaptive, total-ordered and prefix-summed cube for spatio-temporal data warehouses. Our approach focuses on indexing dynamic point objects in static spatial dimensions. Through the extensive performance studies, we observed that The H-Cube consumed at most 20% of the space required by multi-tree based frameworks, and achieved higher query performance compared with multi-tree structures.