• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권4호
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• pp.1123-1146
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• 2023

In South Korea, there have been many studies on efficient building-energy management using renewable energy facilities in single zero-energy houses or buildings. However, such management was limited due to spatial and economic problems. To realize a smart zero-energy city, studying efficient energy integration for the entire city, not just for a single house or building, is necessary. Therefore, this study was conducted in the eco-friendly energy town of Chungbuk Innovation City. Chungbuk successfully realized energy independence by converging new and renewable energy facilities for the first time in South Korea. This study analyzes energy data collected from public buildings in that town every minute for a year. We propose a smart city building-energy management model based on the results that combine various renewable energy sources with grid power. Supervised learning can determine when it is best to sell surplus electricity, or unsupervised learning can be used if there is a particular pattern or rule for energy use. However, it is more appropriate to use reinforcement learning to maximize rewards in an environment with numerous variables that change every moment. Therefore, we propose a power distribution algorithm based on reinforcement learning that considers the sales of Energy Storage System power from surplus renewable energy. Finally, we confirm through economic analysis that a 10% saving is possible from this efficiency.

• 한국언론정보학보
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• 제40권
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• pp.287-320
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• 2007

이 연구는 한국전쟁(6 25전쟁) 기간 북한이 남한에서 시행한 언론정책과 그에 따른 주요 언론활동을 고찰했다. 또한 언론활동의 구체적인 내용과 특성을 이해하기 위해 북한이 남한에서 발행한 대표적인 두 신문 $\ulcorner$조선인민보$\lrcorner$와 $\ulcorner$해방일보$\lrcorner$에 대해 분석했다. 북한은 서울을 점령한 그날부터 방송을 운영했고 바로 신문을 창간했다. 이어 북한과 소련의 신문과 정기간행물을 보급하기 시작했고 영화를 상영했으며, 주간지를 창간하는 등 적극적으로 언론활동을 전개했다. 이와 같이 여러 매체들이 출현했으나 그 목표는 모두 같았다. 성공적인 전쟁수행과 점령한 남한지역에 북한식 제도와 법을 도입하여 공산주의체제로 만들고자하는 김일성의 계획을 지원하는 것이었다. 두 신문은 권력의 대행자로서 비현실적 낙관주의를 바탕으로 선동적 거짓말을 과장해서 보도한 수단적 존재였다. 그리하여 당시 남한의 독자들을 사상적으로 동원하고, 그들의 시각과 행동을 주조하려 한 것이다. 그러나 두 신문을 비롯한 한국전쟁 기간 북한이 남한에서 운영한 언론매체들은 수용자인 남한 주민들로부터 신뢰와 호응을 받지 못했다. 대부분의 남한주민들은 북한 언론매체의 일방적이며 진실성이 결여된 끊임없는 선전과 선동, 이데올로기적 교화에 피곤해했다. 따라서 한국전쟁 개시 이후 북한이 남한에서 전개한 언론활동은 그들이 목표로 한 남한 주민들을 사상적으로 조직하고 동원하는 데 많은 한계가 있었다고 평가할 수 있을 것이다.

• Nuclear Engineering and Technology
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• 제53권3호
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• pp.699-714
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• 2021

Supercritical CO₂ (S-CO₂) Brayton cycle has been applied to various heat sources in recent decades, owing to the characteristics of compact structure and high efficiency. Understanding the research development in this emerging research field is crucial for future study. Thus, a bibliometric approach is employed to analyze the scientific publications of S-CO₂ cycle field from 2000 to 2019. In Scopus database, there were totally 724 publications from 1378 authors and 543 institutes, which were distributed over 55 countries. Based on the software-BibExcel, these publications were analyzed from various aspects, such as major research areas, affiliations and keyword occurrence frequency. Furthermore, parameters such as citations, hot articles were also employed to evaluate the research output of productive countries, institutes and authors. The analysis showed that each paper has been cited 13.39 times averagely. United States was identified as the leading country in S-CO₂ research followed by China and South Korea. Based on the contents of publications, existing researches on S-CO₂ are briefly reviewed from the five aspects, namely application, cycle configurations and modeling, CO₂-based mixtures, system components, and experiments. Future development is suggested to accelerate the commercialization of S-CO₂ power system.

• 한국정보시스템학회지:정보시스템연구
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• 제28권1호
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• pp.115-132
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• 2019

Purpose The purpose of this study is to explain the agrophotovolatic system built by the Korea South-East Power Company and to propose methods to activate the agrophotovolatic system for the development of the renewable energy industry. Design/methodology/approach We conducted a three-step simulation in order to design a photovoltaic module, and we built the agrophotovolatic system based on the results of the simulation. Then, we analyzed the monthly generation of power and the rice harvests produced on farmland using the photovoltaic module. Based on the results of the analysis, we proposed institutional improvements to increase the use of the agrophotovolatic system, and we proposed new business models to increase the participation of farmers and business persons. Findings When we compared the agrophotovolastic system with the general photovoltaic system, we found that the agrophotovoltaic system had higher utilization rates and power generation. An analysis of rice produced on farmland using the photovoltaic module showed that more than 80% of the rice produced on general farmland was harvested. We suggested activation plans that involved the revision of the farmland law and the introduction of renewable energy certificate (REC). We also proposed a land lease model and a farmer participation model as two new business models, and we conducted economic evaluations and sensitivity analyses for both models.

• 한국태양에너지학회 논문집
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• 제26권1호
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• pp.29-39
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• 2006

Since the solar radiation is the main input for sizing any solar photovoltaic system, it will be necessary to understand and evaluate the solar radiation data. The works presented here are the analysis of solar radiation data for East Asia areas. The data, which consist of the global radiation on horizontal surface, were measured at 16 different stations over the South Korea and were estimated by using satellite at 12 different stations over the North Korea from 1982 to 2004. Also the data over the Japan have been collected for 30 years for the period from 1941 to 1970. The Result of the analysis shows that the annual-average daily global radiation on the horizontal surface is $3.55\;kWh/m^2$. We conclude, based on the analysis, that East Asia areas have sufficient solar energy resources for the photovoltaic power generation system.

• 대기
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• 제31권1호
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• pp.1-15
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• 2021

High-resolution wind resources maps (maps, here after) with spatial and temporal resolutions of 100 m and 3-hours, respectively, over South Korea have been produced and evaluated for the period from July 2016 to June 2017 using Korea Meteorological Administration (KMA) Post Processing (KMAPP). Evaluation of the 10 m- and 80 m-level wind speed in the new maps (KMAPP-Wind) and the 1.5 km-resolution KMA NWP model, Local Data Assimilation and Prediction System (LDAPS), shows that the new high-resolution maps improves of the LDAPS winds in estimating the 10m wind speed as the new data reduces the mean bias (MBE) and root-mean-square error (RMSE) by 33.3% and 14.3%, respectively. In particular, the result of evaluation of the wind at 80 m which is directly related with power turbine shows that the new maps has significantly smaller error compared to the LDAPS wind. Analyses of the new maps for the seasonal average, maximum wind speed, and the prevailing wind direction shows that the wind resources over South Korea are most abundant during winter, and that the prevailing wind direction is strongly affected by synoptic weather systems except over mountainous regions. Wind speed generally increases with altitude and the proximity to the coast. In conclusion, the evaluation results show that the new maps provides significantly more accurate wind speeds than the lower resolution NWP model output, especially over complex terrains, coastal areas, and the Jeju island where wind-energy resources are most abundant.

• International Journal of Precision Engineering and Manufacturing
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• 제1권1호
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• pp.42-48
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• 2000

Friction in bearing exerts an important effect upon power dissipation and heat generation of spindle system. This paper presents frictional moments derived from rotational axis coordinate system of spindle and frictional characteristics to spindle speed A frictional moment of spindle bearings is derived by work-energy method. Differential sliding moments in outer raceway has a major effect upon frictional resistance; spin sliding moments in inner raceway has a secondary effect. As spindle speed increases, also the frictional moments increase. In high-speed region, ceramic ball bearing 몬 smaller frictional moment than steel ball bearing.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2012년도 추계학술대회
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• pp.923-924
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• 2012

원자력발전은 기본적으로 공급의 안정성과 경제성을 갖추고 있는 에너지원으로서 전력생산에 관한 자원 및 환경문제의 한계를 극복한 에너지원으로 평가받고 있다. 그러나 최근 일본 후쿠시마 원전사고로 독일과 이탈리아 등은 원전의 단계적인 철폐와 도입을 취소하는 등 원전의 안정성에 대한 논의가 활발히 이루어지고 있다. 우리나라도 최근 원전부품 납품에 관한 비리가 발생하는 등 원전에 관한 크고 작은 안전사고가 발생하고 있다. 따라서 본 논문에서는 원전부품을 효율적이고 안전하게 관리하기 위해 RFID를 활용한 원전부품의 공급사슬관리시스템의 구축 방안을 제안한다.

• Journal of Electrical Engineering and Technology
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• 제7권6호
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• pp.859-868
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• 2012

A new fault location algorithm based on stationary wavelet transform and its verification experiment results are described for HVDC submarine cables in this paper. For wavelet based fault location algorithm, firstly, 4th level approximation coefficients decomposed by wavelet transform function are superimposed by correlation, then the distance to the fault point is calculated by time delay between the first incident signal and the second reflected signal. For the verification of this algorithm, the real experiments based on various fault conditions and return types of fault current are performed at HVDC submarine cable test yard located in KEPCO(Korea Electric Power Corporation) Power Testing Center of South Korea. It proves that the fault location method proposed in this paper is very simple but very quick and accurate for HVDC submarine cable fault location.

• 한국산학기술학회논문지
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• 제21권7호
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• pp.212-217
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• 2020

태양광 발전 시스템은 태양광 패널을 통해 발전된 전력을 계통연계를 통해 전송하는 종합 시스템이다. 발전량을 증대시키는 기술로써 태양광 입사각을 변화시켜 발전량을 증대시키는 추적식 태양광 발전장치 기술이 있다. 본 논문은 입사각을 변화시켜 발전량을 증대시키는 단축 추적식 태양광 발전장치의 구조물과 제어에 관한 연구이다. 핵심 내용은 태양광 구조물이 남북축을 중심으로 동서 방향으로 축회전하도록 구성한 단축 제어장치 및 기술이다. 일출로부터 일몰까지 동서방향으로 태양을 추종하는 태양광 구조물은 구조적 안정성과 태양광 추종 제어 성능 확보가 필요하다. 단축 추적 발전장치는 최대 25% 이상의 발전량 증대를 기대할 수 있다.