• Proceedings of the KIEE Conference
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• 2005.10c
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• pp.305-307
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• 2005

In the cold and temperate regions of Korea the icing and ice coats on 25[kV] electric car line during winter is a very serious problem. This generates shocks at the mechanical interface of the collecting strips of the pantograph and the contact wire and extra electrical resistance, which may affect quality of current collection at the contact wire / collecting strips of pantograph interface. De-icing operations should be performed just before train operation to avoid the formation of another ice layer. This paper presents temperature analysis of the de-icing system which could be applied to the electric car line of railways.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.11
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• pp.1004-1008
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• 2007

The ice coats are built on 25 kV overhead contact wire when the temperature is lower than $0^{\circ}C$. It generates shockwaves at the mechanical interface of the collecting strips of the pantograph and the contact wire. The de-icing processes should be performed to avoid shockwaves which are generated by a pulsed high-voltage arc discharge. This paper presents temperature analysis of the de-icing effects which could be applied to the overhead contact wire of railways using Joule heat. The results show that 350 A is the proper current for $0^{\circ}C$ conductor according to environmental condition such as velocity of air stream, ambient temperature and moisture.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.6
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• pp.512-515
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• 2019

Overhead contact systems (OCS) consist of contact and messenger wires, in which the contact wire supplies electric energy to the railway vehicle by contacting a pantograph. However, this mechanical contact is interrupted during frosts or temperatures below $0^{\circ}C$ in the winter. In these conditions, railway vehicle accidents can occur during operation because of the low energy efficiency that results from the increase in the arcing between the contact wire and pantograph. Therefore, the detection of frost or freezing temperatures is necessary to maintain the stable operation of these trains. In this study, we proposed the development of a frost or freezing condition monitoring system on the OCSs that utilizes wireless communication.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.31.2-31.2
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• 2018

미국 유타주 유타사막에 설치된 MDRS(Mars Desert Research Station)는 미국의 비영리기구인 화성학회(The Mars Society)에서 운영하는 화성탐사연구기지다. 화성학회는 1998년 우주비행사, 천문학자, 과학자 4000여명이 모여 만든 비영리연구단체다. 2001년 미국 유타주에 문을 연 MDRS에서는 토양 미생물 검출실험, 태양에너지 조리실험, 영구동토층 연구, 해빙 연구, 드론 정찰 및 지도 작성 등 인류가 화성에 도착했을 때 실제 수행할 연구들을 진행하고 있다. tVN <갈릴레오 : 깨어난 우주> 촬영 차 MDRS에 머물며 과학실험을 수행한 사례를 공유하고 이를 통해 천문학 및 우주탐사에 대한 대중화 방안에 대해 논의해 보고자 한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2020.11a
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• pp.1115-1117
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• 2020

환경 문제는 사람들이 직접적으로 보지 못하면 쉽게 이해하기 어렵다. 그리고 오랜 시간 동안 아주 조금씩 환경 파괴가 발생하는 경우가 많기 때문에, 실질적으로 환경 문제를 체감하는 것이 쉽지 않다. 본 연구에서는 몰입형 가상현실 시스템을 이용해서 기후변화의 원인인 지구온난화로 인해 북극과 남극의 바다 빙하가 녹고 있는 문제를 체험할 수 있도록 Melting Sea Ice 를 개발하였다. 사용자들은 몰입형 가상현실 장치를 착용하고 시간의 흐름에 따라 남극 북극 빙하가 녹은 모습과 해빙에 따른 생태 환경의 변화를 직접 돌아다니면서 관찰할 수 있다. 본 연구에서는 Melting Sea Ice 가상현실 콘텐츠를 통하여 기후 변화로 인한 환경 파괴 문제를 직관적으로 인식시키고 환경 문제를 해결하고자 하는 동기부여를 목적으로 두고 있다.

• 한국해양학회지
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• v.27 no.3
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• pp.250-258
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• 1992

The oxygen isotope composition of surface waters in the Bransfield Strait was determined as one extra state variable in order to characterize water masses in the region, since salinity is significantly modified due to the freezing and ice-melting in the polar region. The salinity, temperature, and $\delta$/SUP 18/O values vary from 34.0 to 34.5$\textperthousand$, -.05 to 2.1$^{\circ}C$ and -0.50 t -0.26$\textperthousand$, respectively. The combined effects of evaporation, precipitation, freezing, ice-melting are reflected in the widely scattered data. Although it is small, the distribution of $\delta$/SUP 18/O of the Bransfield Strait is strongly affected by the freezing-ice melting rather than the evaporation-precipitation. The ice melted fresh water which has higher temperature, depleted salinity and nutrients may be injected to the Bransfield Strait from the north. The concentrations of nutrients are decreasing gradually from the north to the south. The waters were characterized by two groups of higher (about 19.4) and lower N/P ratio (about 16.7). The lower N/P ratio is found in the northern part where ice-melted fresh water is injected. and the higher N/P ratio is found in the southern part of the Bransfield Strait. Although more precise work is needed, the deference of N/P ratio can be an evidence of the ice melted water injection to the Bransfield Strait. Chlorophyll a concentrations, in general, increase from northwest (Waddell Sea) to the southeast (Smith and Hosseason Islands). Probably the injection of nutrient depleted fresh water from the ice melting reduce the chlorophyll a concentration.

• Korean Journal of Soil Science and Fertilizer
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• v.28 no.2
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• pp.135-144
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• 1995

Understanding on nutrient solute movement during the course of freezing and thawing was attempted through laboratory and field obsevations. Small sectioned tubes with 5cm inner diameter, 0.2cm thick and 1cm long were connected to 30cm long soil columns for laboratory study. The columns were filled with soil, and treated with 20mmol/kg $KNO_3$ for upper 5cm. The upper end was set in the freezing section, and the lower end was set in the refrigerating section of a refrigerator. Temperature was controlled at $-7({\pm}1)^{\circ}C$ and $1.5({\pm}1)^{\circ}C$, respectively. After top 5cm soil was frozen, the columns were sectioned, and analyzed for $NO_3^-$, $NH_4^+$ and $K^+$. For field study, the 20cm inner diameter and lm long soil columns were installed in Chuncheon and Daegwanryung, where the altitude was 74m and 840m, respectively. The soils used were silt loam and clay loam. The top 20cm soils were treated with 50mmol/kg as $KNO_3$. The soil columns were taken during winter freezing and after thawing. By laboratiry study, upward movement of $NO_3^-$ and $K^+$ during the course of freezing was confirmed. The upward movement of $K^+$ was, however, one fifth to one tenth of $NO_3^-$. The upward movement of inorganic nitrogen as well as laboratory during the course of freezing, but large amount of nitrogen was lost from the profile after thawing in early spring. Leached nitrogen from the upper 20cm to lower part was 17 to 24 percents. The maximum depth of leaching during the experiment was 50cm for all soils. The net loss of inorganic nitrogen from the whole profile ranged 8.7 to 39.5 percents. The net loss was greater in Daegwanryung where temperature was lower and snowfall was larger than Chuncheon, and the loss was greater from the silt loam soil than clay loam soil of which percolation rate was small. The results implied that reasons for nitrogen loss during the winter might include surface washing by snow melt as well as leaching and denitrification.

• Korean Journal of Remote Sensing
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• v.37 no.5_1
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• pp.1177-1186
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• 2021

As the Arctic melt ponds play an important role in determining the interannual variation of the sea ice extent and changes in the Arctic environment, it is crucial to monitor the Arctic melt ponds with high accuracy. Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2), which is the NASA's latest altimeter satellite based on the green laser (532 nm), observes the global surface elevation. When compared to the CryoSat-2 altimetry satellite whose along-track resolution is 250 m, ICESat-2 is highly expected to provide much more detailed information about Arctic melt ponds thanks to its high along-track resolution of 70 cm. The basic products of ICESat-2 are the surface height and the number of reflected photons. To aggregate the neighboring information of a specific ICESat-2 photon, the segments of photons with 10 m length were used. The standard deviation of the height and the total number of photons were calculated for each segment. As the melt ponds have the smoother surface than the sea ice, the lower variation of the height over melt ponds can make the melt ponds distinguished from the sea ice. When the melt ponds were extracted, the number of photons per segment was used to classify the melt ponds covered with open-water and specular ice. As photons are much more absorbed in the water-covered melt pondsthan the melt ponds with the specular ice, the number of photons persegment can distinguish the water- and ice-covered ponds. As a result, the suggested melt pond detection method was able to classify the sea ice, water-covered melt ponds, and ice-covered melt ponds. A qualitative analysis was conducted using the Sentinel-2 optical imagery. The suggested method successfully classified the water- and ice-covered ponds which were difficult to distinguish with Sentinel-2 optical images. Lastly, the pros and cons of the melt pond detection using satellite altimetry and optical images were discussed.

• The Korean Journal of Quaternary Research
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• v.33 no.1_2
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• pp.1-23
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• 2021

In response to the increase in atmospheric carbon dioxide and greenhouse gases, the global mean temperature is rising rapidly. In particular, the warming of the Arctic is two to three times faster than the rest. Associated with the rapid Arctic warming, the sea ice shows decreasing trends in all seasons. The faster Arctic warming is due to ice-albedo feedback by the presence of snow and ice in polar regions, which have higher reflectivity than the ocean, the bare land, or vegetation, higher long-wave heat loss to space than lower latitudes by lower surface temperature in the Arctic than lower latitudes, different stability of atmosphere between the Arctic and lower latitudes, where low stability leads to larger heat losses to atmosphere from surface by larger latent heat fluxes than the Arctic, where high stability, especially in winter, prohibits losing heat to atmosphere, increase in clouds and water vapor in the Arctic atmosphere that subsequently act as green house gases, and finally due to the increase in sensible heat fluxes from low latitudes to the Arctic via lower troposphere. In contrast to the rapid Arctic warming, in midlatitudes, especially in eastern Asia and eastern North America, cold air outbreaks occur more frequently and last longer in recent decades. Two pathways have been suggested to link the Arctic warming to cold air outbreaks over midlatitudes. The first is through troposphere in synoptic-scales by enhancing the Siberian high via a development of Rossby wave trains initiated from the Arctic, especially the Barents-Kara Seas. The second is via stratosphere by activating planetary waves to stratosphere and beyond, that leads to warming in the Arctic stratosphere and increase in geopotential height that subsequently weakens the polar vortex and results in cold air outbreaks in midlatitudes for several months. There exists lags between the Arctic warming and cold events in midlatitudes. Thus, understanding chain reactions from the Arctic warming to midlatitude cooling could help improve a predictability of seasonal winter weather in midlatitudes. This study reviews the results on the Arctic warming and its connection to midlatitudes and examines the trends in surface temperature and the Arctic sea ice.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.10a
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• pp.69-70
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• 2013

IPCC (International Panel on Climate Change) reported that the arctic sea-ice extent has been decreased by 2.7% per decades since satellite observations in 1978. The decreased sea-ice extent has gained an international attention due to its economical benefits from the NSR (Northen Sea Route). The NRS - not a clearly defined single route, but a number of alternative routes across the top of Russiahas a 37 % reduction in sailing distance, comparing to the SSR (Southen Sea Route) passing thourgh the Suez Canal. Sailing days are consequently reduced from 30 days to 20 days. Also, it is estimated that the Northen Sea has 20 to 25% of world's oil resources and occupies 40% of the world's fishery production. As Republic of Korea was admitted as an observer to the Arctic Council on May 15, 2013, there has been increasing needs to explore new route in the Northen Sea. In this situation, Korea Institute of Ocean Science & Technology (KIOST) is preparing a plan for the development of Arctic-circle Ocean Environmental Information System to support the ice navigation and resource exploration in the Arctic. We will introduce a conceptual design of a satellite-based ice navigation supporting system for the northern sea route.