• International Journal of Naval Architecture and Ocean Engineering
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• 제10권1호
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• pp.85-94
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• 2018

For the design of wind-power facilities, the highest and lowest astronomical tides (HAT and LAT, respectively) are needed for the tidal-water levels regarding international designs; however, the approximate highest high water and approximate lowest low water AHHW and ALLW, respectively, have been used in Korea. The HAT and LAT in the wind-farm test-bed sea should be estimated to satisfy the international standard. In this study, the HAT and LAT are therefore estimated using the hourly tidal-elevation data of the Eocheongdo, Anmado, Younggwang, Gunsan, Janghang, and Seocheon tidal-gauging stations that are located in the adjacent coastal sea. The nodal variation patterns of the major lunar components, such as $M_2$, $O_1$, and $K_1$ are analyzed to check the expected long-term lunar cycle, i.e., 18.61 year's nodal-variation patterns. The temporal amplitude variations of the $M_2$, $O_1$, and $K_1$ clearly show the 18.61-years periodic patterns in the case of the no-nodal correction condition. In addition, the suggested HAT and LAT elevations, estimated as the upper and lower confidence limits of the yearly HAT and LAT elevations, are 50 cm greater than the AHHW and 40 cm lower than the ALLW, respectively.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.181-184
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• 2006

Knowledge of the ionospheric peak parameter foF2 (the critical frequency of F2 layer) is one of key essential factors for predicting ionospheric characteristics and delay correction of satellite positioning. However, the foF2 was almost estimated using an empirical model of International Reference Ionosphere (IRI) or other expensive observing techniques, such as ionosondes and scatter radar. In this paper, the ionospheric peak parameter foF2 is the first observed by ground-based GPS with all weather, low-cost and near real time properties. Compared with the IRI-2001 and independent ionosondes at or near the GPS receiver stations, the foF2 obtained from ground-based GPS is in better agreement, but closer to the ionosonde. However, during nighttime, the IRI model overestimated the GPS observed values during winter and equinox months.Furthermore, seasonal variation trend of the foF2 in 2003 is studied using foF2 monthly median hourly data measured over South Korea. It has shown that the systematic diurnal changes of foF2 are apparent in each season and the higher values of foF2 are observed during the equinoxes (semiannual anomaly) as well as in mid-daytime of each season.

• 한국농림기상학회지
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• 제11권1호
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• pp.13-18
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• 2009

기상대에서 측정한 '일적산수평면일사량'을 토대로 임의 경사면 상의 '일적산경사면일사량'을 비교적 정확하고 간편하게 알아낼 수 있는 지형보정계수를 고안하였다. 주어진 시간대의 수평면 청천일사량에 대한 경사면 청천일사량의 비율을 '매시일사보정계수'라 정의하고, 청천일사량을 기준으로 수평면의 시간대별 상대 일사강도와 수평면에 대한 경사면의 일사수광비율의 곱으로 표현하였다. 매시일사보정계수를 하루 단위로 적산한 것이 해당 날짜의 지형보정계수이다. 제주도 내 기생화산 '높은오름'의 등고도면 8 방위에서 사면일사수광량을 1년간 관측하는 한편, 이들 지점의 일사량을 지형보정계수에 의해 추정하여 서로 비교하였다. 지형보정계수에 의한 일사추정값의 편차평방근오차는 연평균 $1.61MJ\;m^{-2}$ 이었으나, 4월부터 10월 사이 영농기간에는 절반 이하로 줄어들었다. 경사향에 무관하게 10월에 가장 오차가 작은 반면, 11월에는 경사향에 따른 오차의 변동폭이 가장 컸다. RMSE 값의 연중변동폭은 남향과 북향사면에서 가장 컸고, 남서-남동-북서사면 순으로 줄어들었다. 어떤 경사면이든 365일 동안의 지형보정계수를 한번만 계산해 두면 인근 기상대에서 관측한 임의 날짜의 전천일사량에 이 계수를 적용함으로써 그 날의 적산일사량을 실용적인 오차범위 내에서 추정할 수 있어 복잡지형의 일사수광량 분포를 용이하게 파악할 수 있다.

• 한국대기환경학회지
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• 제19권5호
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• pp.515-528
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• 2003

The characteristics of one year observation aerosol data in Seoul, 200 I was studied using an OPC (Optical Particle Counter). The size resolved aerosol number concentrations of 0.3 ∼ 25 11m were measured. The results were compared with PM$_{10}$ mass concentration data under various meteorological conditions including dust and precipitation events. For fine particles whose diameter is less than 2.23 ${\mu}{\textrm}{m}$, the number concentration increases in the early morning which is considered due to transportation. while the coarse mode particles increase during daytime. This increase can be explained as local sources and human activities near sampling site. Hourly averaged data show that there exists diurnal variation. Generally, PM$_{10}$ data showed a similar tendency with OPC data. The size resolved OPC data showed that the particles of 0.5 ∼ 3.67 ${\mu}{\textrm}{m}$ are positively correlated with PM$_{10}$ data. The accumulated volume fraction of size resolved aerosol concentration in 0.5 ∼ 10 ${\mu}{\textrm}{m}$ showed that 0.5 ∼ 2.23 ${\mu}{\textrm}{m}$ particles occupied 59.2% of total aerosol volume of 0.5 ∼ 10 ${\mu}{\textrm}{m}$./TEX>.

• Asian Journal of Atmospheric Environment
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• 제6권1호
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• pp.23-32
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• 2012

The ionic composition of $PM_{2.5}$ samples was investigated by their datasets of cationic ($Na^+$, $NH_4^+$, $K^+$, $Mg^{2+}$, and $Ca^{2+}$) and anionic components ($Cl^-$, $NO_3^-$, and $SO_4^{2-}$) along with relevant environmental parameters collected from an urban monitoring site in Korea at hourly intervals in 2010. The mean (and SD) annual concentration of $PM_{2.5}$ was computed as 25.3 ${\mu}g\;m^{-3}$ with the wintertime maximum. In addition, sum concentrations (neq $m^{-3}$) of five cationic species (291) were slightly lower than 3 anionic species (308). Most cations exhibited the highest seasonal values in spring, while anions showed more diversified seasonal patterns. According to PCA, five major source categories were apparent with the relative dominance of secondary inorganic aerosols (SIA). The results of our study suggest consistently that the distribution of ionic constituents in an urban area is affected by the combined effects of both natural and anthropogenic processes.

• 노동경제논집
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• 제35권3호
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• pp.83-100
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• 2012

본 연구는 2004년부터 점진적으로 실시된 주40시간 근무제, 이른바 '주5일 근무제'의 도입이 근로시간, 임금 및 고용에 미친 효과를 "고용형태별근로실태조사" 원자료를 이용하여 추정하였다. 법정 근로시간 단축이 연도별 산업별 및 사업체 규모별로 단계적으로 적용되었던 점에 착안하여 삼중차감 모형을 사용하였다. 희귀분석 결과, 주 40시간 근무제의 도입으로 실제 근로 시간은 약 43분 단축되었고, 시간당 임금은 약 6.6% 상승한 것으로 나타났으나 신규 고용은 약 2.3%포인트 하락시킨 것으로 나타났다.

• Asian Journal of Atmospheric Environment
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• 제12권2호
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• pp.178-191
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• 2018

The concentrations and chemical compositions of volatile organic compounds (VOCs), including volatile fatty acids, phenols, indoles, aldehydes, and ketones, which are the main organic compounds generated by swine, were investigated in July and October 2016 and January 2017. In addition, the emission rates and annual emissions of these components from the swine shed were estimated. The concentrations of VOCs in the swine shed averaged $511.3{\mu}g\;m^{-3}$ in summer, $315.5{\mu}g\;m^{-3}$ in fall and $218.6{\mu}g\;m^{-3}$ in winter. Acetone, acetic acid, propionic acid, and butyric acid were the predominant components of the VOCs, accounting for 80-88% of the total VOCs. The hourly variations of VOC concentrations in the swine shed in fall and winter suggest that the VOC concentrations were related to the ventilation rate of the swine shed, the activity of the swine, and the temperature in the swine shed. Accordingly, the emission rates of VOCs from the swine shed were $1-2{\times}10^3{\mu}g(h\;kg-swine)^{-1}$.

• 한국대기환경학회지
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• 제10권4호
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• pp.252-259
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• 1994

A ground station has been established at Kosan, Cheju Island, since January of 1992 for the monitoring of background air Pollutant levels in Korea. Anthropogenic pollutant sources and meteorological conditions of Kosan were surveyed. Concentrations of SO$_2$, NO, NO$_{y}$ and $O_3$, were measured and analyzed for the period of February through December, 1992. The annual means of NO and SO$_2$, levels were very low in comparison to other urban's levels and similiar to other country's background levels. The annual mean of $O_3$, level was higher than urban's but comparable to other coastal region's. The NO concentration showed a distinct seasonal and diurnal variations. Summer peak was detected in the monthly means of NO and smooth peak around noon was found in the annual means of hourly data. Diurnal variation of the SO$_2$ concentration was barely detected but a slice increase in winter was detected. The $O_3$, concentration data, however, showed seasonal and diurnal variations similar to the urban's.an's.

• 대기
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• 제20권2호
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• pp.195-210
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• 2010

This study uses mesoscale model WRF to investigate characteristics of wind fields in South Korea, a region with a complex terrain. Hourly wind fields were simulated for one year representing mean characteristics of an 11-year period from year 1998 to year 2008. The simulations were performed on a nested grid from 27 km down to 1 km horizontal resolution. Seasonal variation of wind speed indicates that wind is strongest during the spring and winter seasons. Spatial distribution of mean wind speed shows wind energy potential at its peak in mountainous region of Gangwon-do, the east coast, and Jeju Island. Wind speed peaks at night in mountainous and eastern coastal regions, and in the afternoon inland and in the southwestern coastal region. The simulated wind map was verified with four upper-air sounding observations. Wind speed was shown to have a more pronounced overestimation tendency relative to observation in the winter rather than summer. The results of this wind mapping study help identify locations with the highest wind energy potential in South Korea.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2000년도 학술발표회 발표논문집
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• pp.536-542
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• 2000

The purpose of this study is to evaluate the effect of stream quality by the farmer＇s livestock wastes management in a typical small agricultural watershed. AGNPS model has the capability to adjust the level of pollutant load from farmstead and the fertilization level of upland field. A small agricultural watershed(4.12 $\textrm{km}^2$) which has as livestock farmhouses located in Gosan-myun, Ansung-gun was selected. AGNPS data were prepared by using Arc/info and Idrisi. 4 storm events in 1999 was used for runoff calibration, and 2 storm event which is measured in hourly-base at 4 locations along the stream were used for water quality(TN, TP) calibration. Model＇s behavior to stream quality for 3 cases was investigated. First, the variation of pollution produced from the cattle shed affected little to the stream quality because the cattle sheds were roofed. Second, the good management of ground in farmstead affected to stream quality with 11% and 17% decrease in TN and TP, respectively. Third, the reduction of fertilization level to upland field affected to stream quality with 27.2% and 38.5% decrease in TN and TP, respectively.