• 한국해양학회지
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• v.20 no.2
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• pp.1-9
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• 1985

A simple analytic model of the sea surface temperature(SST) is developed in order to understand the effects of the Asian monsoon and the Kuroshio on the annual variations of SST by the Asian monsoon is almost in phase with the incoming radiation whereas that by the Kuroshio is out of phase with the incoming radiation. In the Yellow Sea, due to the heat advection by the Asian monsoon, the yearly mean SST is low and the annual range of SST exceeds 20$^{\circ}C$. The annual range of SST in the northwestern Japan Sea is large because of the combined effects of the Asian monsoon and the cold water advection. In the Kuroshio and in the Tsushima Current regions, the annual range of SST is small and the mean SST is high due to the heat advection by warm currents.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.205-205
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• 2009

태양광 발전은 다른 발전방식과는 달리 연료비가 불필요하고 대기오염이나 폐기물 발생이 없으며 부위가 반도체 소자이고 제어부가 전자제품이므로 기계적인 진동과 소음 등의 공해가 전혀 없는 에너지원이다. 그러나 태양광 발전은 에너지 밀도가 낮아 일사량, 온도, 계절 등 기상조건의 작은 변화에도 발전량의 편차가 심하고 출력이 불안정하여 상용전원과의 연계나 별도의 축전설비 또는 발전설비 없이 독립적으로 사용하기에는 다소 무리가 있다는 단점이 있다. 따라서 본 논문에서는 이러한 문제점을 해결하기 위해서 1년 동안 실증운전을 통한 종합적인 운전특성 데이터, 태양전지 어레이 출력의 전압 전류, 교류 전력 및 전력량, 일사량 및 모듈의 온도, 외기온도 등 분석기간 동안 수집된 운전 데이터를 이용하여 태양이 태양전지 모듈에 입사되는 각과 발전량 즉 태양 전지 어레이 형태와 발전량과의 상관관계를 정량적으로 규명하여 태양광 발전시스템의 설계 및 시공의 최적화가 이루어질 수 있도록 하였다.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.2
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• pp.70-80
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• 2014

We carried out numerical experiments to understand sedimentary environments in Gamak Bay where is located in the center of the southern coast of Korea. Deposition rates in Gamak Bay appeared to increase in the autumn and spring whereas they appeared to decrease in the summer and winter. These seasonal variations qualitatively coincided with seasonal variations of Ignition Loss (IL) for surface sediments. Furthermore, deposition rates turned out to be prevalent compared to erosion rates in most areas of the bay. On the other hand, current measurement results at both the northeast and south mouths of the bay showed their residual components to flow into the bay. Therefore, we can conclude that contaminated materials flowing into Gamak Bay will precipitate to be deposited in the bay as long as there is no specific events such as dredging.

• Journal of the Korean Society for Marine Environment & Energy
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• v.7 no.2
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• pp.104-110
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• 2004

This study was carried out to survey the pollution of bisphenol A(BPA) and total organic carbon(TOC) in surface sediments around Gwangyang bay. BPA is suspected chemicals as endocrine disruption. Gwangyang bay Is located on the mid south coast of Korea. It is a semi-closed bay which Yeosu petrochemical industrial complex, POSCO(Pohang Steel Company) and Gwangyang container harbor are located. The surface sediments were collected at 15 stations with gravity corer at October, 1999, February, May and August, 2000. Also, the stream and intertidal sediment were collected at 5 sites at August, 2000. Concentrations of BPA in surface sediments were in the range of 0.46 to 24.59 ng/g dry wt.. Seasonal range(mean value) of BPA are 0.59 to 9.00(1.88) ng/g dry wt. at October, 0.99 to 2.97(1.57) ng/g dry wt. at February, 0.46 to 24.59(2.53)ng/g dry wt. at May and 0.54 to 2.46 (1.29)ng/g dry wt. at August. BPA was seasonally fluctuated, and the highest mean value and range were detected at May, 2000. BPA was highly distributed in the inner part of Kwangyang bay than Yosu sound. Concentrations of BPA in stream and intertidal sediments showed the highest value in downstream near Yochon petrochemical industrial complex and Yondung stream. It suggests that the source of BPA are industrial wastewater and municipal sewage. TOC in surface sediments were in the range of 0.09∼1.22%. There was no any correlation between the BPA and TOC.

• Annual Conference of KIPS
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• 2022.11a
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• pp.273-274
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• 2022

본 논문에서는 제주지역의 전기자동차 충전 로그를 분석하여 일일 충전회수, 충전시간, 최대 동시 충전수 등의 데이터를 추출한다. 이 요소들에 의해 전기자동차 충전 수요, 전력량, 전력 등의 흐름을 파악할 수 있으며 전반적인 수요는 계절적 요인, 즉 휴가철 혹은 태풍 등의 영향을 받는다. 전력 수요는 아직 제주도 전체적인 전력소비에 비해 1.3 % 정도인 것을 파악되고 있으며 추후 태양발전과 같은 신재생 에너지와의 결합이나 광고 등의 비즈니스 모델 개발에 근거자료로 활용할 수 있다.

• Journal of the Korean Institute of Gas
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• v.23 no.2
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• pp.74-81
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• 2019

Expansion turbine system to recover the electricity energy from natural gas transmission stations is a well-known technique. The turbo-expander efficiency depends on the ratio of the natural gas flow rates to the design flow rate of the turbo-expander. However, if there is a big difference of the natural gas flow rate through the pressure letdown station because of seasonal supply pattern, that is, high flow rate in winter while low flow rate in summer, single turbo-expander system is not so efficient as to recover the pressurized energy from the low flow-rate natural gas. Therefore, we have proposed a new concept of double turbo-expander system: one is a big capacity and the other a small capacity. Here we have theoretically computed the electric powers at the pressure reduction from 18.5 bar to 7.5 bar depending on the inlet conditions of temperature and flow rate. The calculated electricity generation has been increased by 30% from 12.4 MW in a single turbo expander to 16.1 MW in the proposed double turbo-expander system when a minimal design efficiency of 0.72 is applied.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.2
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• pp.76-88
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• 2012

In order to investigate the distribution of water masses and spatio-temporal variation of nutrients in the coastal areas of Gangwon province of the Korean East Sea, a survey of the physico-chemical parameters (temperature and salinity) and nutrients ($NO_2$-N, $NO_3$-N, $NH_4$-N, $PO_4$-P, and $SiO_2$-Si) was carried out at 5 locations (Goseong, Sokcho, Yangyang, Gangneung, and Donghae) in February, May, August, and November 2009. The water masses included in the study area were divided into 4 groups; 1) Tsushima Surface Water (TSW), 2) Tsushima Middle Water (TMW), 3) North Korean Cold Water (NKCW), and 4) East Sea Proper Water (ESPW). The distribution of water masses was affected by the change of season. In February, surface water was derived from the TMW. The TSW was not observed in May, but only observed in August. In November, as the influence of the TSW weakened, that of the NKCW strengthened. Considering the vertical profiles of nutrients, the concentrations in all the seasons were very low within the surface water, but increased rapidly near the thermocline. Most of nutrient concentrations, except for dissolved silicate, remained constant below the depth of 200 m. However, the dissolved silicate concentration increased with depth, suggesting that silicate has a delayed regenerative pattern. The ESPW had the highest nutrient concentration, followed by the NKCW, TMW, and TSW. In February, May, and November, the N/P ratio in most of the water masses was similar to or larger than the Redfield ratio, indicating that nitrogenous nutrients did not act as a limiting factor for phytoplankton growth. However, in August, the N/P ratio in the TSW was less than the Redfield ratio, and the concentration of $NO_2$-N+$NO_3$-N was 0.86 ${\mu}m$, indicating that nitrogenous nutrients did act as a limiting factor for phytoplankton growth in the study area.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.632-637
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• 2016

A streetlight control system was developed using information technology and LED lights for efficient management and energy savings. The proposed system can control the power usage of an LED streetlight luminaire using GPS satellite communication and an Arduino with a built-in microprocessor. A control circuit was designed to control the current using GPS, a control unit, transistor, resistor, and constant-current supply circuit. The circuit was validated through experiments with normal operation. Using GPS, the control system extracts accurate time and location information according to the season, and it controls the current supplied to the LED streetlight according to the extracted time. Power consumption was reduced by more than 11%. The control system could reduce accidents caused by conventional lighting systems used to save energy, and it could improve the inefficient management of energy by preserving constant brightness of a streetlight at times and in areas that have less traffic.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.2
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• pp.101-110
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• 2012

In order to understand temperature and salinity variations, and the characteristics of the seawater exchange through two channels of Gamak Bay, we conducted measurements of water temperature, salinity and current for fifteen days in the summer and winter. Based on the observational data, the current seemed to have a close relation with wind. In addition, a correlation analysis result proved that water temperature is likely to be more influenced by air temperature rather than tide. Moreover, water temperatures at the south channel varied more sensitively with the season rather than at the east channel because of its shallow depth. Seawater exchange rates were estimated to be 0.5~29.9% (mean: 11.6%) at the east channel but 1.3~62.6% (mean: 18.6%) at the south channel in summer. On the contrary, they were estimated to be 0.3~28.5% (mean: 8.9%) at the east channel but 0.1~97.9% (mean: 31.2%) at the south channel in winter. Thus, the rates of seawater exchange in Gamak Bay turned out that the south mouth is approximately three times higher than the east mouth, and it also suggested that seasonal winds affect the rates of seawater exchange in Gamak Bay.

• Journal of the Korean Society for Marine Environment & Energy
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• v.3 no.4
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• pp.76-90
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• 2000

The estimation of material cycle of pollutants is necessary for the environment management in coastal zone. Model for material budgets are useful tools to understand the phenomena of natural system and to provide an insight into the complex processes including physical, chemical and biological processes occuring in natural system. Budgets of fresh water, salt and nutrients were estimated in order to clarify the characteristics of seasonal material cycle in Keum river estuary. Inflow volumes of freshwater into system was approximately 1.014×10/sup 8/～12.565×10/sup 8/m³/month and discharge in Keum river has occupied 99.7% of total freshwater. Seasonal variations of freshwater volume in the system were found to be very high in the range of about 4 ～ 14 times due to rainfall in summer season. Existing water mass of freshwater in system calculated by salt budget was approximately 0.339×10/sup 8/～0.652×10/sup 8/m³. Mean residence time of freshwater was calculated to be about 1.6～10.0day, and exchange time was calculated to be about 2.2～11.9day. Mean residence time was short as 1.6day in summer due to precipitation, and long as 10.1day in winter due to a drought. Inflow masses of DIP and DIN were approximately 5.57～32.68ton/month and 234.93～2,373.39ton/month, respectively. Seasonal inflow mass of DIP was larger than the outflow mass except for summer season. Thus, we postulate that accumulation of DIP in the system will happen. Residence times of DIP and DIN were calculated to be 1.1～6.4day and 1.8～10.9day, respectively. The ratio of water residence time versus DIP, DIN residence time was calculated to be 0.39～2.31 times and 0.83～1.13 times, respectively.