• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.300-300
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• 2008

우리나라의 전기에너지 수요가 지속적으로 증가함에 따라 새로운 송배전 선로의 구축이 필요하다. 하지만 현재 도심지의 전력구에는 더 이상의 지중선의 증설은 불가능하며 가공선 설치의 경우 환경 민원의 부담을 떠안게 된다. 그래서 기존 동도체의 회선당 송전 한계를 극복하고 대용량 송전 및 손실을 크게 줄일 수 있는 초전도 케이블의 연구가 세계적으로 활발히 진행되고 있다. 한국전력 전력연구원은 신 전력시스템으로서의 22.9 kV급 초전도케이블 시스템을 고창전력시험센터에 설치하고 운영 및 유지 보수 과정을 통하여 실제 계통 적용을 위한 최적 운전조건을 연구하고 있다. 이 논문에서는 실제 부하 상황을 모의하기 위하여 초전도케이블의 장기 부하변동 시험에 따른 케이블 송전 능력 확인 및 냉각시스템의 반응성을 살펴보고 부하변동 시험 후 초전도케이블 도체 열화 여부를 확인하기 위하여 직류 임계전류를 측정하였다. 그 결과 부하변동 시험 전의 임계전류 값과의 변화율이 삼상 모두 ${\pm}1$% 내외로서 오차범위를 벗어나지 않으므로 건전한 것으로 판단되었다.

• Journal of the Korean Solar Energy Society
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• v.33 no.5
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• pp.1-8
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• 2013

Wind resource data of short-term period has to be corrected a long-term period by using MCP method that Is a statistical method to predict the long-term wind resource at target site data with a reference site data. Because the field measurement for wind assessment is limited to a short period by various constraints. In this study, 2 different MCP methods such as Linear regression and Matrix method were chosen to compare the predictive accuracy between the methods. Finally long-term wind speed, wind power density and capacity factor at the target site for 20 years were estimated for the variability of wind and wind energy. As a result, for 20 years annual average wind speed, Yellow sea off shore wind farm was estimated to have 4.29% for coefficient of variation, CV, and -9.57%~9.53% for range of variation, RV. It was predicted that the annual wind speed at Yellow sea offshore wind farm varied within ${\pm}10%$.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.429-429
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• 2017

4대강 살리기 사업의 일환으로 농업용 저수지를 대상으로 둑 높이기 사업이 수행되었으며, 추가 저수량 확보를 통해 하천에 하천유지유량을 공급하고 있다. 하천유지유량은 저수지별로 평균갈수량과 기준갈수량의 범위 내에서 방류되고 있으며, 이로 인해 하천 유황의 변동이 있을 것으로 예측되나, 이로 인한 연구는 미흡하게 진행되어 왔다. 본 연구에서는 둑 높이기 저수지에서 하천유지유량 방류에 따른 하류하천의 유황변동을 분석하고자 한다. 유역의 유출량은 HSPF(Hydrological Simulation Program-Fortran)를 이용하여 모의하였으며, 저수지에서 발생하는 유량은 인위적 유량으로 고려하여 모의하였다. 저수지에서 여수로로 자연월류되는 수량과 하천유지유량의 방류조건을 고려한 저수지 방류량을 산정하기 위해 저수지 물수지 모형을 사용하였으며, 산정된 방류량을 HSPF 모형의 입력자료로 활용하였다. 본 연구의 결과는 둑 높이기 저수지의 하천유지유량이 하천 유황변동에 미치는 영향을 확인할 수 있을 것으로 예측되며, 추후 수계별, 저수지 규모별 등에 따른 추가 분석이 필요할 것으로 사료된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.274-274
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• 2022

확률론적 지진해일 재해도 평가(PTHA)는 최근 지진해일에 대한 연구에서는 관심을 많이 받고 있는 주제로 여러 국가에서 연구가 진행되고 있다. 단층매개변수의 민감도 분석은 일본(Goda et al., 2014), 미국(Sepúlveda and Liu, 2016), 뉴질랜드(D. Burbridge et al., 2015) 등에서 연구가 활발하게 이루어졌으며 현재도 활발한 연구가 진행되고 있다. 민감도 분석은 PTHA를 진행하기 위한 선행 과정으로 파향선 추적을 통한 대상지 설정 및 연구 대상 단층을 선정한 후 로직트리를 만들기 위해 각 단층 매개변수의 범위와 단위 폭을 제시한다. 해당 연구는 세 가지 단층 매개변수에 대한 지진해일 초기파와 파고에 대한 민감도 분석을 실행했다. 주향각은 초기파와 지진해일고에 대해서 임의의 변동을 보이지만 변동 폭은 다른 두 매개변수들과 비교하여 가장 크다. 경사각과 슬립각은 단층의 수직 움직임을 변화시키며 이를 통해 초기파의 변동을 예측할 수 있다. 초기파의 변동과 모양을 분석함으로써 수치 계산이 가설과 유사한 결과를 보임을 확인하였다. 경사각과 슬립각에 의한 지진해일고의 변화는 최저 지진해일고가 초기파의 총 에너지와 연관된다는 결론에 이른다. 지진해일 재해도는 해안지역에 도달하는 최종 파고와 관련이 있으므로 각 매개변수의 단위 폭은 지진해일고의 결과를 통해 선정되었다. 민감도 분석은 제시한 주향각, 경사각, 슬립각의 단위 폭을 이용하여 로직트리의 분기 수를 감소시켜 수치 계산 시간을 줄임으로써 PTHA의 효율성을 증대시킨다.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.251-258
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• 2012

Recently, NAND Flash memory structure is evolving from SDR (Single Data Rate) to high speed DDR(Double Data Rate) to fulfill the high performance requirement of SSD and SSS. Accordingly, the proper ways of transferring data that latches valid data stably and minimizing data skew between pins by using PHY(Physical layer) circuit techniques have became new issues. Also, rapid growth of speed in NAND flash increases the operating frequency and power consumption of NAND flash controller. Internal voltage variation margin of NAND flash controller will be narrowed through the smaller geometry and lower internal operating voltage below 1.5V. Therefore, the increase of power budge deviation limits the normal operation range of internal circuit. Affection of OCV(On Chip Variation) deteriorates the voltage variation problem and thus causes internal logic errors. In this case, it is too hard to debug, because it is not functional faults. In this paper, we propose new architecture that maintains the valid timing window in cost effective way under sudden power fluctuation cases. Simulation results show that the proposed technique minimizes the data skew by 379% with reduced area by 20% compared to using PHY circuits.

• Economic and Environmental Geology
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• v.38 no.1
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• pp.79-89
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• 2005

Groundwater level changes in coastal aquifers occur due to oceanic tides, where the properties of oceanic tides can be applied to estimate hyadraulic parameters. Hydraulic parameters of coastal aquifers located in eastern part of Jeju island were estimated using the tidal response technique. Groundwater level data from a saltwater intrusion monitoring well system was used which showed tidal effects from 3 to 5 km. The hydraulic gradient was assessed by utilizing the filtering method from 71 consecutive hourly water-level observations. Calculated hydraulic diffusivity ranged from 2.94${\times}10^7m^2d^{-1}$ to 4.36${\times}10^7m^2d^{-1}$ . The hydraulic gradient of the coastal aquifer area was found to be ~$10^{-4}$, whereas the gradient of the area between wells Handong-1 and 2 was found to be ~$10^{-6}$, which is very low comparatively. Analysis of groundwater monitoring data showed that groundwater levels are periodically higher near coastal areas compared to that of inner land areas due to oceanic tide influences. When assessing groundwater flow direction in coastal aquifers it is important to consider tidal fluctuation.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.37 no.1
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• pp.1-9
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• 2000

In this paper, we design a robust output feedback controller for robot manipulators with bounded parametric uncertainties using high-gain observer. The proposed control scheme with integral action improves tracking error due to limit of the robust feedback gains. High-gain observer is used to solve the noise problem with the joint velocity measurement. This controller avoids the limitation on the variation of unknown parameters and guarantees the uniformly ultimate boundedness of the closed-loop system. The performance of the proposed method is demonstrated by simulation on a 2-link manipulator.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.7053-7060
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• 2015

The use of FRP(Fiber-reinforced polymer) bars results in larger crack widths under service load due to the generally low elastic modulus and poor bond characteristics of FRP as compared with steel reinforcing bars. The work presented herein includes the results from 12 beams composed of nine rectangular beams and three T-beams reinforced with FRP bars tested under four-point bending. It was investigated that the bond coefficient, $k_b$ in ACI 440.1R-06 equation had high variability which the coefficient of variation was 40% in the range of 0.6 to 1.88 with average 1.05.

• Journal of Korea Water Resources Association
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• v.43 no.11
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• pp.933-944
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• 2010

This study compares the CEM and SGS methods which are geostatistical stochastic simulation methods for assessing the uncertainty by spatial variability in the estimation of the spatial distribution of probability rainfall. In the stochastic simulations using CEM and SGS, two methods show almost similar results for the reproduction of spatial correlation structure, the statistics (standard deviation, coefficient of variation, interquartile range, and range) of realizations as uncertainty measures, and the uncertainty distribution of basin mean rainfall. However, the CEM is superior to SGS in aspect of simulation efficiency.

• Journal of Korean Society of Archives and Records Management
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• v.23 no.1
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• pp.27-45
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• 2023

A source of records is critical and highly valuable for records management. The compositions and functions of an administrative organization, which is the source of public records, are changing according to its frequent reorganizations. In particular, changes in local governments are frequent, and the possibility of change increases over time. The processing department is responsible for various records management tasks as the source and producer of records; however, its scope of qualifications is unclear. As such, this study aims to clarify these sources of records and suggest ways to improve their management. For the objective, this study selected D regional local government and analyzed the forms and frequency of its administrative organizational changes. In particular, the processing department's modified organizational functions and compositions due to reorganizations were also examined. Through the analysis, problems concerning records sources that could arise from changes in the administrative organization and processing department were identified, and improvement plans for records management were suggested.