• 지구물리와물리탐사
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• 제7권1호
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• pp.56-61
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• 2004

In order to image the distribution of permeability in granitic rocks, we carried out two-dimensional (2D) resistivity profiling, together with in-situ permeability tests, electrical logging of boreholes, and resistivity measurements of rock core samples in a laboratory. Based on the electrical logging and in-situ permeability data from boreholes, we obtained empirical equations which relate resistivity and permeability of the granitic rocks in the area studied. We then applied the empirical equation to a 2D resistivity section, to produce a 2D permeability section of the granitic rocks. In this paper, we present details of the field data and of the procedure for conversion from the resistivity section to a permeability section. The observed relationship between resistivity and permeability of the rocks is also discussed.

• 한국결정성장학회지
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• 제18권1호
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• pp.1-4
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• 2008

The growth of composite-structured Nd:$GdVO_4$ single crystal rods by the double die EFG method is reported. Two crucibles are combined with an outer and inner die for ascending of different melt. The composite-structured Nd:$GdVO_4$ single crystal rods with a length of 50 mm and an outer diameter of 5 mm including of inner Nd-doped core region with diameter 3 mm were grown successfully. Nd distribution in the, radial direction has graded profile from result of EPMA. Absorption coefficient in the core region at 808 nm was $42cm^{-1}$. Finally, we demonstrated the laser oscillation using our composite crystal and 2-W output was obtained.

• KEPCO Journal on Electric Power and Energy
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• 제6권1호
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• pp.35-40
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• 2020

The purpose of this paper is to improve the grounding point measurement method for the maintenance of the earth resistance of the distribution line. This study defines the correlation among humidity of the soil, the earth resistivity and the grounding resistance. Based on the results of the study, the grounding resistance value measurement should be limited to the location where the earth resistivity change is large, and the measurement time and cost can be greatly reduced.

• KEPCO Journal on Electric Power and Energy
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• 제6권1호
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• pp.59-64
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• 2020

Scheduling of electric vehicles and optimizing for charging waiting time have been critical. Meanwhile, it is challengeable to exploit the fluctuating data from electric vehicles in real-time. We introduce an optimal routing algorithm and a simulator with electric vehicles obeying the Poisson distribution of the observed information about time, space and energy-demand. Electric vehicle routing is updated in every cycle even it is already set. Also, we suggest an electric vehicle routing algorithm for minimizing total trip time, considering a threshold of the waiting time. Total trip time and charging waiting time are decreased 34.3% and 86.4% respectively, compared to the previous algorithm. It can be applied to the information service of charging stations and utilized as a reservation service.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1825-1826
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• 2007

세계적으로 현장업무는 현장에서 접수하여 즉시 처리하는 방식으로 패러다임이 변화하고 있다. 현재 전력업무의 대표적인 모바일 시스템으로 기동보수/순시점검 모바일시스템이 시범운영되고 있으나, 자동처리 기능개선, 네비게이션 기능개발 등 자동화 및 지능화 기술개발이 필요하며 작업차량의 위치와 상태와 무관하게 운영되고 있는 업무들을 통합적으로 처리할 수 있는 모바일시스템 개발이 필요하다. 따라서 본 논문에서는 효율적인 배전운영 현장업무 처리를 위한 통합형 모바일시스템을 설계한다. 모바일 서버, 무선통신망, 단말기용 모바일시스템에 대한 전반적인 시스템의 구성방안 설명하고, 핵심적인 요소기술 개발사항과 방법을 제시한다.

• KEPCO Journal on Electric Power and Energy
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• 제5권2호
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• pp.113-120
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• 2019

We have developed 1 kW-class PEMFC-battery hybrid system independently powering to the building, through the process of system design, current load characteristics analysis, power system configuration for demonstration site and performance evaluation. In order to use the fuel cell and battery as the hybrid type, a control technology for the charging/discharging decision and charging speed of the battery is required rather than using fuel cell. Also output power distribution between PEMFC and the battery is a core of energy management technology. It is confirmed that it is possible to supply independently 1kW powering the building to ensure optimal energy management through the power control experiment of the hybrid system.

• 센서학회지
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• 제28권5호
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• pp.277-283
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• 2019

In this paper, we propose a distributed fusion estimation for sensor networks using a receding horizon strategy. Communication channels were modelled as Markov jump systems, and a posterior probability distribution for communication channel characteristics was calculated and incorporated into the filter to allow distributed fusion estimation to handle path loss observation situations automatically. To implement distributed fusion estimation, a Kalman-Consensus filter was then used to obtain the average consensus, based on the estimates of sensors randomly distributed across sensor networks. The advantages of the proposed algorithms were then verified using a large-scale sensor network example.

• 한국해양학회지:바다
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• 제23권4호
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• pp.179-191
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• 2018

황해 동부해역 표층퇴적물의 중금속 분포 특성을 파악하기 위하여 입도, 유기탄소(TOC)와 함께 중금속 원소들(Cu, Pb, Zn, Cd, Cr, Mn, As, Ni, Co, Li, Fe, Al)의 농도를 분석하였다. 연구결과에 따르면, 일부 정점에서 Pb, Mn, As를 제외하면 모든 중금속 농도의 분포는 입도 및 TOC의 분포와 유사하게 황해 중앙해역에서 상대적으로 높고, 한국 연안으로 갈수록 감소하는 경향을 보였다. 입도와 중금속 농도간의 관계를 통하여 대부분의 금속은 입도가 세립할수록 농도가 높게 나타나는 일반적인 경향을 보였다. 그러나 일부 정점에서 Pb은 조립질 퇴적물에서의 암석기원(feldspar) 영향, Mn은 생물기원($CaCO_3$) 영향, As는 중광물(pyrite) 특성에 따라 분포 양상이 다르게 나타났다. 과거에 조사한 자료(2000년)와 비교했을 때, 황해 동부해역에서 지난 15년 동안의 추가적인 중금속 농축은 없었고, 투기해역에 대한 저질환경은 과거에 비해 크게 개선되지 못한 것으로 나타났다. 연구해역 내 모든 중금속의 농도는 한국과 중국에서 규정하고 있는 최소기준(TEL, MSQ-1)보다 낮았지만, 농축지수(enrichment factor; EF), 농집지수(geo-accumulation index; $I_{geo}$), 생태위해성지수(ecological risk index; ERI)는 Cu, Pb, Zn, Cr이 황해 중앙해역에서 상대적으로 높게 나타났다.

• KEPCO Journal on Electric Power and Energy
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• 제1권1호
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• pp.141-144
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• 2015

The superconducting fault current limiter (SFCL) is an electric power device that limits the fault current immediately in a power grid. Korea Electric Power Corporation (KEPCO) has been developing a 154 kV, 2 kA SFCL since 2011 to protect power grids from increasing fault current and improve the stability and quality of electric power. This SFCL adopts 2G YBCO wires and operates at 71 K and 5 bars. In this paper, a cooling system for the 154 kV SFCL and its cooling test results are reported. This cooling system uses a Stirling-type cooler to make sub-cooled liquid nitrogen ($LN_2$), which cools the superconductor modules of the SFCL. The $LN_2$ is circulated between the cooler and the cryostat that contains superconductor modules. The $LN_2$ also plays the role of a high voltage insulator between the modules and the cryostat, so the pressure was maintained at 5 bars for high insulation performance. After installation in a test site, the cooling characteristics of the system were tested. In this operation test, some important data were measured such as temperature distribution in $LN_2$, pressure change, performance of the heat exchanger, and cooling capacity of the total system. Consequently, the results indicate that the cooling system operates well as designed.

• Journal of Ginseng Research
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• 제46권2호
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• pp.296-303
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• 2022

Background: Skin microbiota is important for maintenance of skin homeostasis; however, its disturbance may cause an increase in pathogenic microorganisms. Therefore, we aimed to develop a red ginseng formulation that can selectively promote beneficial bacteria. Methods: The effects of red ginseng formulation on microorganism growth were analyzed by comparing the growth rates of Staphylococcus aureus, S. epidermidis, and Cutibacterium acnes. Various preservatives mixed with red ginseng formulation were evaluated to determine the ideal composition for selective growth promotion of S. epidermidis. Red ginseng formulation with selected preservative was loaded into a biocompatible polymer mixture and applied to the faces of 20 female subjects in the clinical trial to observe changes in the skin microbiome. Results: Red ginseng formulation promoted the growth of S. aureus and S. epidermidis compared to fructooligosaccharide. When 1,2-hexanediol was applied with red ginseng formulation, only S. epidermidis showed selective growth. The analysis of the release rates of ginsenoside-Rg1 and -Re revealed that the exact content of Pluronic F-127 was around 11%. The application of hydrogel resulted in a decrease in C. acnes in all subjects. In subjects with low levels of S. epidermidis, the distribution of S. epidermidis was significantly increased with the application of hydrogel formulation and total microbial species of subjects decreased by 50% during the clinical trial. Conclusion: We confirmed that red ginseng formulation with 1,2-hexanediol can help maintain skin homeostasis through improvement of skin microbiome.