• Journal of Environmental Science International
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• v.30 no.12
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• pp.1067-1079
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• 2021

The coastal water is a space where salmon (Oncorhynchus keta), critical energy-conveying mediator, stay to adapt to different environments while traveling between ocean and river ecosystems for spawning and growth. The mid-eastern coast of Korea (MECW) is the southern limit of salmon distributed in the North Pacific Ocean. Understanding the distribution and migration characteristics of salmon in the MECW is important for the prediction of changes in the amount and distribution of salmon related to changes in the future marine environment. We analyzed the relationship between the salmon migratory timing ascending the Wangpi river and change in vertical seawater temperature and tidal elevation. Overall results highlight that (1) Salmon began to ascend the river when the sea surface water temperature (SST) decreased below 20℃; (2) The number of salmon ascending the river increased when the temperature difference between the upper and lower layers decreased, but decreased when the temperature difference was higher than 5℃; (3) The number of salmon ascending the river peaked, when the SST was 18℃-19℃ and sea levels rose at high tide. This study provide important insight into predicting changes in the ecosystem energy circulation through climate change at its southern distribution limit.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.2
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• pp.299-308
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• 2022

Recent, energy transition policies are driving to increase in the number of small photovoltaic(PV) generators. It is difficult for system operators to accurately anticipate the amount of power generated from such small scale PV generation, and this may disrupt dispatch schedules and result in an increase in cost. The need for a Virtual Power Plant(VPP) is emerging as a way of resolving these problems, as it would integrate small-scale PV plants and eliminate uncertainty about the amount of power generated, control voltage, and provide power reserves. In this paper, the cost evaluation methods are described for determination of VPP cloud charges both Net Present Value(NPV) method and Profitability Index(PI) method, the calculated outcomes of the two types of cost evaluation methods are presented in detail. It seems we secure profitability as we get 1.22 of profitability index from calculation results, it may be attractive for the aggregator as NPV is enough for satisfying profitability.

• Journal of Energy Engineering
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• v.23 no.2
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• pp.125-148
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• 2014

This paper performs a historical analysis on the various factors contributing to the current carbon lock-in of Korean electricity industry by using techo-institutional complex. The possibilities of the industry's carbon lock-out toward more sustainable development are also investigated. It turns out that market, firm, consumer, and government factors are all responsible for the development of the carbon lock-in of Korean power industry; the Korean government consistently favoring large power plants based on the economy of scale; below-cost electricity tariff; inflation policy to suppress increases in power price; rapid demand growth in summer and winter seasons; rigidities of electricity tariff; and expansion of gas-fired and imported coal-fired large power plants. On the other hand, except for nuclear power generation and smart grid, environment laws and new and renewable energy laws are the other remaining factors contributing to the carbon lock-out. Considering three key points that Korea is an export-oriented economy, the generation mix is the most critical factor to decide the amounts of carbon emission in the power industry, and the share of industry and commercial power consumption is over 85%, it is unlikely that Korea will achieve the carbon lock-out of power industry in the near future. Therefore, there are needs for more integrated approaches from market, firm, consumer, and government all together in order to achieve the carbon lock-out in the electricity industry. Firstly, from the market perspective, it is necessary to persue more active new and renewable energy penetration and to guarantee consumer choices by mitigating the incumbent's monopoly power as in the OECD countries. Secondly, from the firm perspective, the promotion of distributed energy system is urgent, which includes new and renewable resources and demand resources. Thirdly, from the consumer perspective, more green choices in the power tariff and customer awareness on the carbon lock-out are needed. Lastly, the government shall urgently improve power planning frameworks to include the various externalities that were not properly reflected in the past such as environmental and social conflict costs.

• Tunnel and Underground Space
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• v.25 no.2
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• pp.199-209
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• 2015

The rebound hardness test using the SilverSchmidt hammer was performed for diorite, granodiorite, and andesite exposed around the King Sejong Station, Barton peninsula. Then, the R-value and uniaxial compressive strength (UCS) of these rocks were estimated from the Q-values which were obtained from the SilverSchmidt hammer. The Q-value of diorite was distributed in the range from 67.0 to 89.5, granodiorite of the range from 57.5 to 89.0, and andesite of the range from 58.0 to 76.5. The average Q-values of diorite, granodiorite, and andesite were 76.0, 72.0, and 67.0, respectively. The converted UCS of diorite was distributed in the range from 118 to 195 MPa, granodiorite of the range from 91 to 193 MPa, and andesite of the range from 92 to 148 MPa. The average UCS of diorite, granodiorite, and andesite were 147, 136, and 117 MPa, respectively. The converted R-value of diorite was distributed in the range from 53.0 to 72.2, granodiorite of the range from 45.4 to 71.8, and andesite of the range from 45.8 to 60.9. The average Q-values of diorite, granodiorite, and andesite were 60.0, 58.0, and 53.0, respectively. The R-value was represented approximately 20% lower than the Q-value. In conclusion, it will be possibile that the R-value and UCS of rocks under the extreme area from the SilverSchmidt Q-value are evaluated.

• Economic and Environmental Geology
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• v.21 no.4
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• pp.367-380
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• 1988

Most of the gold (-silver) vein deposits at Yeongdong District are mainly distributed in the precambrian metamorphic rocks. Based on the Ag/Au total production and ore grade ratios, the chemical composition of electrum and the associated sulfides, the gold(-silver) deposits at Yeongdong District may be classified into 4 classes: pyrrhotite - type gold deposits( I), pyrite - type gold deposits (IT A; massive vein), pyrite - type gold deposits (II B; nonmassive vein) and argentite - type gold - silver deposits(III). The chemical study on electrum(including native gold) revealed that Au content (2.8 to 92.4 atomic%) of electrums varies very widely for different classes of deposits. The Au content of electrum associated with pyrrhotite (Class I), ranging from 47.1 to 92.4 atomic% Au, is clearly higher than that associated with pyrite (Classes IIA, IIB and III). In contrast, classes I, II, and III deposits do not show clear differences in Au content of electrum. In general, pyrrhotite - type gold deposits(I) are characterized by features such as simply massive vein morphology, low values in the Ag/Au total production and ore grade ratios, the absence or rarity of silver - bearing minerals except electrum, and distinctively simple mineralogy. Although the geological and mineralogical features and vein morphology of pyrite - type gold deposits(IIA)are very similar to those of pyrrhotite - type gold deposits (I), Class II A deposits reveal significant differences in the associated iron sulfide (i. e. pyrite) with electrum and Au content of electrum. The Ag/Au total production and ore grade ratios from Class II A deposits are relatively slightly higher than those from Class I deposits. Pyrite - type gold deposits(II B) and argentite - type gold - silver deposits (III) have many common features; complex vein morphology, medium to high values in the Ag/Au total production and ore grade ratios and the associated iron sulfide (i. e. pyrite). In contrast to Class II B deposits, Class III deposits have significantly high Ag/Au total production and ore grade ratios. It indicates distinct difference in the abundance of silver minerals (i. e. native silver and argentite). The fluid inclusion analyses and mineralogical data of electrum tarnish method indicate that the gold mineralization of Classes I and II A deposits was deposited at temperatures between $230^{\circ}$ and $370^{\circ}C$, whereas the gold (-silver) mineralization of Classes ITB and ill formed from the temperature range of $150^{\circ}-290^{\circ}C$. Therefore, Classes I and IT A deposits have been formed at higher temperature condition and/or deeper positions than Classes IIB and III.

• The Journal of Engineering Geology
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• v.26 no.2
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• pp.197-205
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• 2016

Rainfall-induced landslide disaster case histories are typically required to establish critical lines based on the decrease coefficient for judging the likelihood of slope collapse or failure; however, reliably setting critical lines is difficult because the number of nationwide disaster case histories is insufficient and not well distributed across the region. In this study, we propose a method for setting the critical area to judge the risk of slope collapse without disaster case history information. Past 10 years rainfall data based on decrease coefficient are plotted as points, and a reference line is established by connecting the outermost points. When realtime working rainfall cross the reference line, warning system is operating and this system can be utilized nationwide through setting of reference line for each AWS (Automatic Weather Station). Warnings were effectively predicted at 10 of the sites, and warnings could have been issued 30 min prior to the landslide movement at eight of the sites. These results indicate a reliability of about 67%. To more fully utilize this model, it is necessary to establish nationwide rainfall databases and conduct further studies to develop regional critical areas for landslide disaster prevention.

• Korean Journal of Remote Sensing
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• v.35 no.2
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• pp.265-278
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• 2019

Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band (DNB) data help to enable rapid emergency responses through detection of the artificial and natural disasters occurring at night. The DNB data without correction of lunar irradiance effect distributed by Korea Ocean Science Center (KOSC) has advantage for rapid change detection because of direct receiving. In this study, radiance differences according to the phase of the moon was analyzed for urban and mountain areas in Korean Peninsula using the DNB data directly receiving to KOSC. Lunar irradiance correction algorithm was proposed for the change detection. Relative correction was performed by regression analysis between the selected pixels considering the land cover classification in the reference DNB image during the new moon and the input DNB image. As a result of daily difference image analysis, the brightness value change in urban area and mountain area was ${\pm}30$ radiance and below ${\pm}1$ radiance respectively. The object based change detection was performed after the extraction of the main object of interest based on the average image of time series data in order to reduce the matching and geometric error between DNB images. The changes in brightness occurring in mountainous areas were effectively detected after the calibration of lunar irradiance effect, and it showed that the developed technology could be used for real time change detection.

• Economic and Environmental Geology
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• v.56 no.3
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• pp.229-238
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• 2023

Bentonite is a type of rock that has been used as a traditional mineral medicine. It has a variety of pharmacological activities, and is used in traditional Korean medicine to treat jaundice, diarrhea, and hemostasis. In modern medicine, it is used as a raw material and additive for medicines such as antacids, gastrointestinal protective agents, and laxatives. Bentonite produced in Korea was produced through diagenesis or hydrothermal alteration of tertiary volcanic debris distributed in the Pohang and Gyeongju areas. It is mainly used for industrial purposes such as papermaking, paint, civil engineering, casting, and animal feed. Recently, technology is being developed to use it in cosmetics and pharmaceuticals. In this study, the geochemical characteristics of bentonite were identified by analyzing the main components and trace elements of 40 and 21 types of bentonite produced in the Gampo Gyeongju and Yeonil Pohang area. Also it were classifed by formation envrionment of bentonite deposits in the Gampo and Yeonil. As a result of the study, bentonite from the reserch area may be cased by argillic alteraton that alkali elements are removed form basaltic rocks by hydrothermal fluids and AI-CCPI alteration indices wrere also indentified argillic alteraton. It was found that there is a correlation between the behavior characteristics of heavy metal elements (P b, Cr, As) and the hydrothermal alteration of bentonite in the reserch area.

• Journal of the Korean Solar Energy Society
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• v.28 no.2
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• pp.64-69
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• 2008

As the grid-connected photovoltaic power conditioning systems (PVPCS) are installed in many residential areas, these have raised potential problems of network protection on electrical power system. One of the numerous problems is an Islanding phenomenon. There has been an argument that it may be a non-issue in practice because the probability of islanding is extremely low. However, there are three counter-arguments: First, the low probability of islanding is based on the assumption of 100% power matching between the PVPCS and the islanded local loads. In fact, an islanding can be easily formed even without 100% power matching (the power mismatch could be up to 30% if only traditional protections are used, e.g. under/over voltage/frequency). The 30% power-mismatch condition will drastically increase the islanding probability. Second, even with a larger power mismatch, the time for voltage or frequency to deviate sufficiently to cause a trip, plus the time required to execute a trip (particularly if conventional switchgear is required to operate), can easily be greater than the typical re-close time on the distribution circuit. Third, the low-probability argument is based on the study of PVPCS. Especially, if the output power of PVPCS equals to power consumption of local loads, it is very difficult for the PVPCS to sustain the voltage and frequency in an islanding. Unintentional islanding of PVPCS may result in power-quality issues, interference to grid-protection devices, equipment damage, and even personnel safety hazards. Therefore the verification of anti-islanding performance is strongly needed. In this paper, improved RPV method is proposed through considering power quality and anti-islanding capacity of grid-connected single-phase PVPCS in IEEE Std 1547 ("Standard for Interconnecting Distributed Resources to Electric Power Systems"). And the simulation results are verified.

• Journal of the Korean Magnetics Society
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• v.22 no.2
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• pp.58-65
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• 2012

Since Nd-Fe-B magnet was first synthesized in 1983, many new applications have emerged in the past two decades. With regard to motor market, it will expand because of strong energy saving requirements from the automobile and electric application markets. Especially, permanent magnet motors for hybrid and electric vehicles are drawing great attention and the usage of Nd-Fe-B magnets will increase all the more hereafter. There is, however, a serious problem as motors in such eco-friendly cars are said to operate in high temperatures of about $200^{\circ}C$. Nd-Fe-B magnet has a drawback of dramatically decreasing coercive force with the rise of temperature. In order to improve this aspect. the best way is to add dysprosium (Dy) into the magnet. So, Dy has become an essential element for Nd-Fe-B high-performance magnet as it helps to maintain coercive force even at high temperatures. On the other hand, the rare earth resources in the earth crust are eccentrically-located and its majority is produced in China. There is a need to reduce its usage as, especially compared to light rare earth elements as neodymium (Nd) and samarium (Sm), heavy rare earth elements including Dy are unevenly distributed to a dramatic degree, their output low, and their prices are about 10 times that of Nd. The present article includes a summary of the trend in research and development of motors and permanent magnets to solve rare-earth resources problem.