• Journal of Korea Multimedia Society
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• v.5 no.4
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• pp.372-385
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• 2002

In this paper, we propose an efficient buffer replacement method for the real-time multimedia data. The proposed method has multi level priority to consider the real-time characteristics. Each priority level is divided into a cold data set that is likely to be referenced for the first time and a hot data set that is likely to be re-referenced. An operation to select the victim data is sequentially executed from the cold set with the minimum priority level to the hot set with the maximum Priority level. It is chosen only at the lower level than or equal to the priority of the transaction that requests a buffer allocation. In the cold set, our method selects a media that has the maximum size in the level for a target of victim first of all. And in the hot set, our method selects a medium that has the maximum interval of the reference first of all. Since it maintains many popular media in the limited buffer space, the buffer hit ratio is increased. It also manages many service requests. As a result, our method improves the overall performance of the system. We compare the proposed method with the Priority-Hints method in terms of the buffer hit ratio and the deadline missing ratio of transactions. It is shown through the performance evaluation that our method outperforms the existing methods.

• Journal of Korea Society of Industrial Information Systems
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• v.11 no.5
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• pp.18-27
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• 2006

Rapid increase of the amount of music data demands for a new method that allows efficient similarity retrieval of music genre using audio features in music databases. To build this similarity retrieval, an indexing techniques that support audio features as a time-series pattern and data mining technologies are needed. In this paper, we address the development of a system that retrieves similar genre music based on the indexing techniques. We first propose the structure of content-based music genre retrieval system based on the time-series pattern index file and data mining technologies. In addition, we implement the time-series pattern index file using audio features and present performance analysis of the time-series pattern index file for similar genre retrieval. The experiments are performed on real data to verify the performance of the proposed method.

• KIPS Transactions on Computer and Communication Systems
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• v.6 no.2
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• pp.95-104
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• 2017

As the technology in smart device is growing and Social Network Services(SNS) are becoming more common, the data which is difficult to be processed by existing RDBMS are increasing. As a result of this, NoSQL databases are getting popular as an alternative for processing massive and unstructured data generated in real time. The demand for the technique of digital investigation of NoSQL databases is increasing as the businesses introducing NoSQL database in their system are increasing, although the technique of digital investigation of databases has been researched centered on RDMBS. New techniques of digital forensic investigation are needed as NoSQL Database has no schema to normalize and the storage method differs depending on the type of database and operation environment. Research on document-based database of NoSQL has been done but it is not applicable as itself to other types of NoSQL Database. Therefore, the way of operation and data model, grasp of operation environment, collection and analysis of artifacts and recovery technique of deleted data in HBase which is a NoSQL column-based database are presented in this paper. Also the proposed technique of digital forensic investigation to HBase is verified by an experimental scenario.

• Journal of Information Management
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• v.31 no.1
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• pp.12-42
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• 2000

Digital library research has attracted much attention. While many research projects are funded by government agencies and national and international bodies, some are run by specific academic and research institutions and libraries. While some digital library projects, such as the ELINOR project in the UK, the first two phases of the eLib(Electronic Libraries) programme in the UK, and the first phase of the DLI(Digital Library Initiative) in the USA, are now over, a number of other projects are currently under-way in different parts of the world. Beginning with the definitions and characteristics of digital libraries proposed by various researchers, this paper provides brief accounts of some major digital library projects that are currently in progress, or are just completed, in different parts of the world. There follows a review of digital library research under 16 major headings. Literature for this review has been identified through a search on the LISA CD-ROM database and a Dialog search on library and information science databases, and the resulting output has been supplemented by a scan of the various issues of D-Lib Magazine and Ariadne, and the Web sites of various organizations and institutions engaged in digital library research. The review indicates that we have learned a lot through digital library research within a short span of time. However, a number of issues are yet to be resolved. The paper ends with an indication of the research issues that need to be addressed and resolved in the near future in order to bring the digital library from the researcher's laboratory to the real life environment.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.2
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• pp.1-9
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• 2013

In recent years, numerous mega-size and complex civil infrastructures have been constructed worldwide. For the more precise construction and maintenance process management of these civil infrastructures, the application of a variety of smart sensor-based structural health monitoring (SHM) systems is required. The efficient management of both sensors and collected databases is also very important. Recently, several kinds of database access technologies using Quick Response (QR) code and Augmented Reality (AR) applications have been developed. These technologies provide software tools incorporated with mobile devices, such as smart phone, tablet PC and smart pad systems, so that databases can be accessed very quickly and easily. In this paper, an AR-based structural health monitoring technique is suggested for sensor management and the efficient access of databases collected from sensor networks that are distributed at target structures. The global positioning system (GPS) in mobile devices simultaneously recognizes the user location and sensor location, and calculates the distance between the two locations. In addition, the processed health monitoring results are sent from a main server to the user's mobile device, via the RSS (really simple syndication) feed format. It can be confirmed that the AR-based structural health monitoring technique is very useful for the real-time construction process management of numerous mega-size and complex civil infrastructures.

• Journal of Information Management
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• v.30 no.4
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• pp.39-60
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• 1999

Digital library research has attracted much attention. While many research projects are funded by government agencies and national and international bodies, some are run by specific academic and research institutions and libraries. While some digital library projects, such as the ELINOR project in the UK, the first two phases of the eLib(Electronic Libraries) programme in the UK, and the first phase of the DLI(Digital Library Initiative) in the USA, are now over, a number of other projects are currently under-way in different parts of the world. Beginning with the definitions and characteristics of digital libraries proposed by various researchers, this paper provides brief accounts of some major digital library projects that are currently in progress, or are just completed, in different parts of the world. There follows a review of digital library research under 16 major headings. Literature for this review has been identified through a search on the LISA CD-ROM database and a Dialog search on library and information science databases, and the resulting output has been supplemented by a scan of the various Issues of D-Lib Magazine and Ariadne, and the Web sites of various organizations and institutions engaged in digital library research. The review indicates that we have learned a lot through digital library research within a short span of time. However, a number of issues are yet to be resolved. The paper ends with an indication of the research issues that need to be addressed and resolved in the near future in order to bring the digital library from the researcher's laboratory to the real life environment.

• The KIPS Transactions:PartD
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• v.9D no.4
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• pp.555-560
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• 2002

Subsequence matching, which consists of index searching and post-processing steps, is an operation that finds those subsequences whose changing patterns are similar to that of a given query sequence from a time-series database. This paper discusses optimization of post-processing for subsequence matching. The common problem occurred in post-processing of previous methods is to compare the candidate subsequence with the query sequence for discarding false alarms whenever each candidate subsequence appears during index searching. This makes a sequence containing candidate subsequences to be accessed multiple times from disk, and also have a candidate subsequence to be compared with the query sequence multiple times. These redundancies cause the performance of subsequence matching to degrade seriously. In this paper, we propose a new optimal method for resolving the problem. The proposed method stores ail the candidate subsequences returned by index searching into a binary search tree, and performs post-processing in a batch fashion after finishing the index searching. By this method, we are able to completely eliminate the redundancies mentioned above. For verifying the performance improvement effect of the proposed method, we perform extensive experiments using a real-life stock data set. The results reveal that the proposed method achieves 55 times to 156 times speedup over the previous methods.

• Journal of KIISE:Databases
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• v.29 no.4
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• pp.297-310
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• 2002

The 2PL-HP(Two Phase Locking with High Priority) method has been used to guarantee preceding process of a high priority transaction(HPT) in real-time database systems. The method resolves a conflict through aborting or blocking of a low priority transaction(LPT). However, if HPT is eliminated in a system because of its deadline missing, an unnecessary aborting or blocking of LPT is occurred. Recently, to resolve the problem, a concurrency control algorithm using alternative version was proposed. However, the algorithm must always create the alternative version and needs an addtional technique to manage complex alternative versions. In this paper, we propose an efficient concurrency control algorithm that prevents needless wastes of resources and eliminates unnecessary aborting or blocking of LTP. And it is shown through the performance evaluation that the proposed concurrency control algorithm outperforms the existing concurrency control algorithm using alternative version.

• KIPS Transactions on Software and Data Engineering
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• v.5 no.12
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• pp.623-634
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• 2016

Most of existing frequent pattern mining methods address time efficiency and greatly rely on the primary memory. However, in the era of big data, the size of real-world databases to mined is exponentially increasing, and hence the primary memory is not sufficient enough to mine for frequent patterns from large real-world data sets. To solve this problem, there are some researches for frequent pattern mining method based on disk, but the processing time compared to the memory based methods took very time consuming. There are some researches to improve scalability of frequent pattern mining, but their processes are very time consuming compare to the memory based methods. In this paper, we present PPFP as a novel disk-based approach for mining frequent itemset from big data; and hence we reduced the main memory size bottleneck. PPFP algorithm is based on FP-growth method which is one of the most popular and efficient frequent pattern mining approaches. The mining with PPFP consists of two setps. (1) Constructing an IFP-tree: After construct FP-tree, we assign index number for each node in FP-tree with novel index numbering method, and then insert the indexed FP-tree (IFP-tree) into disk as IFP-table. (2) Mining frequent patterns with PPFP: Mine frequent patterns by expending patterns using stack based PUSH-POP method (PPFP method). Through this new approach, by using a very small amount of memory for recursive and time consuming operation in mining process, we improved the scalability and time efficiency of the frequent pattern mining. And the reported test results demonstrate them.

• Journal of KIISE:Databases
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• v.30 no.6
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• pp.593-605
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• 2003

Since spatial join processing consumes much time, several algorithms have been proposed to improve spatial join performance. The M-way R-tree join (MRJ) is a join algorithm which synchronously traverses M R-trees in the M-way spatial join. In this paper, we introduce indirect predicates which do not directly come from the multi-way join conditions but are indirectly derived from them. By applying the concept of indirect predicates to MRJ, we improve the performance of MRJ. We call such a multi-way R-tree join algorithm using indirect predicates indirect predicate filtering (IPF). Through experiments using synthetic data and real data, we show that IPF significantly