• Journal of Environmental Impact Assessment
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• v.20 no.4
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• pp.489-496
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• 2011

The water pollution such as oil spill from stream and river because of car accidents have been frequent cases in the watershed of Dam. However we don't have any simulation methods about flow modeling on the watershed and stream tree. In this study aims to analyze water pollution accidents area on impact range for ANDONG-Dam. The focused watershed and the risk range of path analysis model was designed by GIS database. The frequency of transportation accidents which may occur from road accidents in the level of quantitative and qualitative analysis to map flow analysis using ArcHydro Model and Open Geospatial Consortium(OGC) API. and the path way from the accident point to the reservoir stayed on the path was simulated. The area of risk accessment index was displayed with cell and grid of dam area.

• Journal of Internet Computing and Services
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• v.9 no.1
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• pp.79-90
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• 2008

In the ubiquitous environment sensor network technologies have advanced for collecting information of the environment. With the rapid growth of sensor network technology, it is necessary and important to share the collected sensor data with a large base of diverse users. In order to provide dissemination of sensor data, we design an information dissemination system using an independent disseminator between provider and consumer. This paper describes how we designed the information dissemination system using one of the possible dissemination patterns for sensor networks, and an efficient matching algorithm called CGIM (Classed Grouping Index Matching) which employs a dynamic re-grouping scheme.

• Journal of Environmental Science International
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• v.27 no.2
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• pp.135-141
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• 2018

The specification of surface vegetation is essential for simulating actual evapotranspiration of water resources. The availability of land cover maps based on remotely collected data makes the specification of surface vegetation easier. The spatial resolution of hydrologic models rarely matches the spatial scales of the vegetation data needed, and remotely collected vegetation data often are upscaled up to conform to the hydrologic model scale. In this study, the effects of the grid scale of of surface vegetation on the results of actual evapotranspiration were examined. The results show that the coarser resolution causes larger error in relative terms and that a more realistic description of area-averaged vegetation nature and characteristics needs to be considered when calculating actual evapotranspiration.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05c
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• pp.1531-1534
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• 2003

최근 들어 이동 통신 서비스에서 이동하는 고객의 위치 정보와 관련된 서비스가 중요한 서비스로 부각되고 있다. 이동객체의 경우 갱신 연산이 많고, 부하가 특정 지역에 집중되는 특징이 있다. 이러한 위치 기반 서비스에서 범위질의는 중요한 질의 중 하나이다. 범위 질의는 윈도우나 원 형태로 수행되는데 윈도우의 경우에는 질의 범위 밖에 해당하는 객체를 쉽게 필터링 할 수 있는 반면 원 형태일 경우에는 대부분의 경우 거리 계산을 해야 하는 불편함이 있다. 본 논문에서는 객체의 위치 갱신 연산에 따른 인덱스 구조의 변화를 최소화하기 위해 고정 그리드 방식을 사용하고 VP 필터링 기법을 적용하여 원 범위 질의에서 범위 밖의 객체를 필터링하기 위한 방법을 제시한다.

• IE interfaces
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• v.14 no.2
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• pp.190-197
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• 2001

Growth curves including Logistic and Gompertz functions are widely used in forecasting the market demand. To estimated the parameters of those functions, we use the non-linear least square method. However, it is difficult to set up the starting points for each parameter. If a wrong starting point is selected, the result reveals the local optimum or does not converge to a certain value. The purpose of this paper is to resolve the problem of selecting a starting point. Especially, rescaling the market data using the national economic index make it possible to figure out the range of parameters and to utilize the grid search method. Applications to some real data are also included.

• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1171-1181
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• 2014

Different power quality (PQ) disturbance sources can have major impacts on the power supply grid. This study proposes, for the first time, an early warning approach to identifying PQ problems and providing early warning prompts based on the monitored data of PQ disturbance sources. To establish a steady-state power quality early warning index system, the characteristics of PQ disturbance sources are analyzed and summed up. The higher order statistics anomaly detection (HOSAD) algorithm, based on skewness and kurtosis, and hierarchical power quality early warning flow, were then used to mine limit-exceeding and abnormal data and analyze their severity. Cases studies show that the proposed approach is effective and feasible, and that it is possible to provide timely power quality early warnings for limit-exceeding and abnormal data.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.5
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• pp.248-252
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• 2004

Since DC ground resistance, which is a good index of the performance of a grounding system in low frequency. does not show the performance in transient state. We measured ground impedances in frequency domain ranging from 0.1 Hz to 900 KHz maximum to quantify the transient grounding performance of 4 types of grounding system. Transfer function was derived from the measured frequency-dependant ground impedance of a grounding grid. A simulation has been performed to verify the transfer function using EMTP (Electro-Magnetic Transient Program).

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.4
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• pp.263-270
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• 2021

Active AC/DC converters with PWM operation are utilized to regulate rectified DC bus voltage of a permanent magnet synchronous generator in the maritime DC power system. A DC bus voltage regulation strategy that exploits the six-step operation is proposed in this study. Compared with that of the PWM operation, switching loss of the converter can be significantly reduced under the six-step operation. Moreover, conduction loss can also be reduced due to the high modulation index and reduced flux-weakening current of the six-step operation. A controller is used for the proposed DC bus voltage regulation strategy to verify its validity with the simulation and experimental setup. The simulation and the experimental test results showed that the converter loss reduces to a maximum of 70% and 19%, respectively.

• International Journal of Contents
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• v.17 no.1
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• pp.61-70
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• 2021

As the resolution of climate change scenario data applied with regional models increased, Earth System Grid Federation (ESGF) was established around major climate-related organizations to jointly operated and manage large-scale climate data. ESGF developed standard software to provide model output, observation data management, dissemination, and analysis using Peer to Peer (P2P) computing technology. Roles of each institution were divided into index and data nodes. Therefore, ESGF data node was established at APEC Climate Center in Korea on behalf of Asia to share data on climate change scenarios of CORDEX-East Asia (CORDEX-EA) to study climate changes in Eastern Asia. Climate researchers are expected to play a large role in researching causes of global warming and responding to climate change by providing CORDEX-EA regional model data to the world through ESGF data node.

• International Journal of Internet, Broadcasting and Communication
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• v.15 no.2
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• pp.22-30
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• 2023

The portable mobile devices with high performance and high speed 5G network activate and explode the demands for ubiquitous information services that remove the limitations of time for the communication and places to request for the information. NN (Nearest Neighbor) search is one of the most important types of queries to be processed efficiently in the information services. Various indexes have been proposed to support efficient NN search in the wireless broadcast system. The indexes adopting Hilbert curve, grid partition or Voronoi diagram enable the clients to search for NN quickly in the wireless broadcast channel. It is necessary that an efficient means to evaluate the performances of various indexes. In this paper, we propose an open framework that can adopt a variety of indexing schemes and evaluate and compare the performances of them. The proposed framework is organized with open and flexible structure that can adopt hybrid indexing schemes extensible to Voronoi diagram as well as simple indexing schemes. With the implemented framework, we demonstrate the efficiency and scalability and flexibility of the proposed framework by evaluating various indexing schemes for NN query.