• Journal of KIISE:Databases
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• v.28 no.4
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• pp.577-586
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• 2001

Recently data mining, which is analyzing the stored data and discovering potential knowledge and information in large database is a key research topic in database research data In this paper, we study methods of discovering association rules which are one of data mining techniques. And we propose a technique of discovering association rules using the relative support to consider significant rare data which have the high relative support among some data. And we compare and evaluate existing methods and the proposed method of discovering association rules for discovering significant rare data.

• Journal of KIISE:Databases
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• v.33 no.4
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• pp.353-362
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• 2006

A data warehouse is a data repository that enables users to store large volume of data and to analyze it effectively. In this research, we investigate an algorithm to establish a multidimensional data cube which is a powerful analysis tool for the contents of data warehouses and databases. There exists an inevitable retrieval overhead in a multidimensional data cube due to the sparsity of the cube. In this paper, we propose a dense sub-cube extraction algorithm that identifies dense regions from a large sparse data cube and constructs the sub-cubes based on the dense regions found. It reduces the retrieval overhead remarkably by retrieving those small dense sub-cubes instead of scanning a large sparse cube. The algorithm utilizes the bitmap and histogram based techniques to extract dense sub-cubes from the data cube, and its effectiveness is demonstrated via an experiment.

• The KIPS Transactions:PartD
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• v.11D no.3
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• pp.545-552
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• 2004

Association rules mining, which is one of data mining technologies, searches data among which are frequent and related to each other in database. But, although the data are not of frequent and rare in database, they have the enough worth of business information if the data ares important and strongly related to each other, In this paper, we propose the algorithm discovering association rules that consist of data, which are rare but, important and strongly related to each other in database. The proposed algorithm was evaluated through simulation. We found that the proposed algorithm discovered efficiently association rules among data, which are not frequent but, important.

• KIISE Transactions on Computing Practices
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• v.20 no.11
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• pp.610-614
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• 2014

Like many types of scientific data, results from simulations of volcanic ash diffusion are of a clustered sparse matrix in the netCDF format. Since these data sets are large in size, they generate high storage and transmission costs. In this paper, we suggest a new method that reduces the size of the data of volcanic ash diffusion simulations by converting the multi-dimensional index to a single dimension and keeping only the starting point and length of the consecutive zeros. This method presents performance that is almost as good as that of ZIP format compression, but does not destroy the netCDF structure. The suggested method is expected to allow for storage space to be efficiently used by reducing both the data size and the network transmission time.