• Journal of the Korea Society of Computer and Information
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• v.15 no.9
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• pp.35-46
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• 2010

Sequential pattern mining is one of the essential data mining tasks, and it is widely used to analyze data generated in various application fields such as web-based applications, E-commerce, bioinformatics, and USN environments. Recently data generated in the application fields has been taking the form of continuous data streams rather than finite stored data sets. Considering the changes in the form of data, many researches have been actively performed to efficiently find sequential patterns over data streams. However, conventional researches focus on reducing processing time and memory usage in mining sequential patterns over a target data stream, so that a research on mining more interesting and useful sequential patterns that efficiently reflect the characteristics of the data stream has been attracting no attention. This paper proposes a mining method of sequential patterns over data streams with a gap constraint, which can help to find more interesting sequential patterns over the data streams. First, meanings of the gap for a sequential pattern and gap-constrained sequential patterns are defined, and subsequently a mining method for finding gap-constrained sequential patterns over a data stream is proposed.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.25 no.2
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• pp.55-67
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• 2022

Land use is a critical factor that affects the hydrological characteristics of watersheds, thereby determining the biological condition of streams. This study analyzes the effects of land uses in the watersheds on biological indicators of streams across the Han River basin using a linear model (LM) and generalized additive model (GAM). LULC and biological monitoring data of streams were obtained from the Korean Ministry of Environment. The proportions of urban, agricultural, and forest areas in the watersheds were regressed to the three biological indicators, including diatom, benthic macroinvertebrate, and fish of streams. The estimated LM and GAM models for the biological indicators were then compared, using regression determination R² and AIC values. The results revealed that GAM models performed better than the LM models in explaining the variances of biological indicators of streams, indicating the non-linear relationships between biological indicators and land uses in watersheds. Also, the results suggested that the indicator of macroinvertebrates was the most sensitive indicator to land uses in watersheds. Although non-linear relationships between watershed land uses and biological indicators of streams could vary among biological indicators, it was consistent that streams' biological integrity significantly deteriorated by a relatively low percentage of urban areas. Meanwhile, biological indicators of streams were negatively affected by the relatively high percentage of agricultural areas. The results of this study can be integrated into effective quantitative criteria for the watershed management and land use plans to enhance the biological integrity of streams. In specific, land uses management plans in watersheds may need more close attention to urban land use changes than agricultural land uses to sustain the biological integrity of streams.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.11a
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• pp.1252-1255
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• 2013

오늘날 급변하는 IT 환경에 신속하게 대응하기 위한 기업의 데이터 관리시스템의 중요성이 강조되고 있다. 특히, 최근에는 기업의 시스템이 복잡해지고 데이터의 규모가 점점 대형화 되면서 기업들은 데이터 관리를 위해 메타데이터 관리시스템의 활용이 증가하고 있다. 하지만 현재 도입되는 메타데이터 관리시스템은 테이블 이관 시 모델과 실제 데이터베이스 사이의 정합성을 유지하기 위해 불필요한 반복적인 프로세스를 수행해야 하는 문제점을 가진다. 따라서 본 논문에서는 이러한 문제점을 해결하기 위하여 이관관리 프로세스 개선을 위한 메타데이터 관리시스템을 구현하고 테스트 하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.11a
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• pp.1222-1225
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• 2013

오늘날 기업의 시스템은 훨씬 복잡해지고 다루는 데이터의 규모는 점점 대형화됨에 따라 환경 변화에 기업이 대응하기가 어려워지고 있다. IT 환경의 변화에 기업이 대응하기 위해서는 메타데이터 관리시스템의 기능을 개선할 필요가 있다. 본 논문에서는 데이터 모델링에 대한 새로운 요구사항을 신속히 반영하기 위해서 모델의 변경 이력을 참조하지 않고 이관해야 할 목표 데이터베이스의 테이블의 형상을 비교하여 이관 관리 프로세스를 향상시킨 알고리즘을 설계하였다. 본 논문서 설계한 알고리즘을 통해 모델의 변경 이력을 참조할 경우 발생하는 데이터베이스 변경의 처리 횟수를 줄임으로써 프로세스 개선의 효과를 기대할 수 있는 알고리즘을 제시하였다.

• Journal of Environmental Science International
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• v.16 no.2
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• pp.203-210
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• 2007

The delivery load data obtained from Nakdong river basin are used for developing the model estimating the daily delivery load on the main side streams of Nakdong River. The developed model assesses the daily contamination loads of the main thirteen side streams that contribute to the main stream of Nakdong river. It is developed that the model using the simplified equation that can estimate the daily delivery loads on the side main streams of Nakdong river for a period of having no data of the water quality and flow. The developed model for estimating the daily delivery loads from the main side streams in Nakdong river basin on each item such as BOD, TN, and TP is expressed as Daily delivery load ($\frac{kg}{day}$) = Production load $(\frac{kg}{day}){\times}(1-{\alpha}){\times}(\frac{daily\;runoff}{average\;runoff\;per\;year}){\gamma}$. The estimated values obtained by using the model are almost fit to the calculated values (real data) that have been acquired from the thirteen main side streams in Nakdong river basin. The correlation coefficient values, R, that indicate the correlation between the estimated and the calculated show over 0.7 that mean the estimated values from the used model are adapted to the real data except TN values of Nam-river, Hwang-river, Gam-river, We-river. Especially, the correlation of TP values between the estimated and the calculated implies quite a creditable data to use.

• The KIPS Transactions:PartD
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• v.13D no.6 s.109
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• pp.755-764
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• 2006

In recent, data streams are generated in various application fields such as a ubiquitous computing and a sensor network, and various algorithms are actively proposed for processing data streams efficiently. They mainly focus on the restriction of their memory usage and minimization of their processing time per data element. However, in the algorithms, if data elements of a data stream are generated in a rapid rate for a time unit, some of the data elements cannot be processed in real time. Therefore, an efficient load shedding technique is required to process data streams effcientlv. For this purpose, a load shedding technique over a data stream is proposed in this paper, which is based on the predicting technique of the frequency of data element considering its current frequency. In the proposed technique, considering the change of the data stream, its threshold for tuple alive is controlled adaptively. It can help to prevent unnecessary load shedding.

• Journal of Korean Society on Water Environment
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• v.28 no.2
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• pp.213-218
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• 2012

Abnormal dissolved oxygen concentration in aquatic habitat, both depletion and supersaturation, can be stress factor to aquatic animals. In this study the nationwide distribution of oxygen supersaturation was analyzed for three categories of streams (43 urban streams, 15 rural streams, and 14 forest streams) by using monitoring network data of the Korean Ministry of Environment. From the distribution analysis 30% of urban streams showed hyperoxic condition of eutrophic level, while no forest stream showed hyperoxic condition. The physiological effect of hyperoxia on fish was examined using two species of fish Zacco koreanus, which resulted in higher concentration of a stress hormone (cortisol) in fish exposed to hyperoxic concentration (196%) of oxygen. This study shows that hyperoxic condition is ubiquitous in urban and rural Korean streams, and it can be a stress factor to aquatic animals.

• Ecology and Resilient Infrastructure
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• v.10 no.4
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• pp.116-124
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• 2023

As the flood damage on small streams increase due to the increase in frequency of extreme climate events, the need to measure hydraulic data of them has increased for disaster risk management. National Disaster Management Institute, Ministry of Interior and Safety develops CADMT, a CCTV-based automatic discharge measurement technology, and operates pilot small streams to verify its performance and develop disaster risk management technology. The research selects two small streams such as the Neungmac and the Jungsunpil streams to develop the Nomograph by using the 4-Parameter Logistic method using only the observed rainfall data from the Automatic Weather System operated by the Korea Meteorological Agency closest to the small streams and discharge data collected by using the CADMT. To evaluate developed Nomograph, the research forecasts floods discharges in each small stream and compares the result with the observed discharges. As a result of the evaluations, the forecasted value is found to represent the observed value well, so if more accurate observed data are collected and the Nomograph based on it is developed in the future, the high-accuracy flood prediction and warning will be possible.

• Journal of Korea Multimedia Society
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• v.8 no.12
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• pp.1597-1604
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• 2005

Recursive Patching is an efficient multicast technique for large-scale video on demand systems and recursively shares existing video streams with asynchronous clients. When Recursive Patching initiates a transition stream, it always makes a transition stream have additional data for the worst future request. In order to share a VOD server's limited network bandwidth efficiently, this paper proposes Practical Patching that removes the unnecessary data included in the transition stream. The proposed Practical Patching dynamically expands ongoing transition streams when a new request actually arrives at the server. As a result, the transition streams never have unnecessary data. Simulation result confirmed that the proposed technique is better than Recursive Patching in terms of service latency and defection rate.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.4
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• pp.1841-1865
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• 2017

This paper proposes a new interference mitigation scheme for device-to-device (D2D) communications underlaying a cellular network. The object of the proposed scheme is to determine the number of data streams, a precoding matrix, and a decoding matrix of D2D networks so as to maximize the system capacity given the number of data streams of a cellular network while satisfying the constraint of the inter-system interference from D2D networks to the cellular network. Unlike existing interference mitigation schemes based on the interference alignment technique, the proposed scheme operates properly regardless of the number of data streams of a cellular network and moreover it does not require changing the precoding and decoding matrices of a cellular network. The simulation results demonstrate that the proposed scheme significantly increases the system capacity by mitigating the intra- and inter-system interference.