• Asian Journal of Atmospheric Environment
• /
• 제5권1호
• /
• pp.47-55
• /
• 2011

Variations in ambient atmospheric carbon monoxide(CO) observed at an inland mining site in the Indo-Gangetic plains, Jaduguda ($22^{\circ}38'N$, $86^{\circ}21'E$, 122m MSL, ~75 km away from the coast of the Bay of Bengal) during the Tsunami of 26 December 2004 were monitored. CO mixing ratio over this site was measured using a non-dispersive infrared analyzer (Monitor Europe Model 9830 B). Back trajectory analysis data obtained using NOAA Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) Model was also used for this study. Variations in CO mixing ratio at a coastal site, Thiruvananthapuram ($8^{\circ}29'N$, $76^{\circ}57'E$, located ~2 km from the Arabian Sea coast) have also been investigated using CO data retrieved from the Measurement Of Pollution In The Troposphere (MOPITT) instrument. Ground-based measurements indicated abnormal variations in CO mixing ratio at Jaduguda from 25 December 2004 evening (previous day of the Tsunami). MOPITT CO data showed an enhancement in CO mixing ratio over Thiruvananthapuram on the Tsunami day. Back trajectory analyses over Thiruvananthapuram and Jaduguda for a period of 10 days from $21^{st}$ to $30^{th}$ December 2004 depicted that there were unusual vertical movements of air from high altitudes from 25 December 2004 evening. CO as well as the back trajectory analyses data showed that the variations in the wind regimes and consequently wind driven transport are the most probable reasons for the enhancement in CO observed at Jaduguda and Thiruvananthapuram during the Tsunami.

• 한국물환경학회지
• /
• 제25권6호
• /
• pp.922-934
• /
• 2009

The transport of contaminants and spatial variation in a deep reservoir are certainly governed by the thermal structure of the reservoir. There has been continuous efforts to utilize three-dimensional (3D) hydrodynamic and water quality models for supporting reservoir management, but the efforts to validate the models performance using extensive field data were rare. The study was aimed to evaluate a 3D hydrodynamic model, ELCOM, in Daecheong Reservoir for simulating heat fluxes and stratification processes under hydrological years of 2001, 2006, 2008, and to assess the impact of internal wave on the reservoir mixing. The model showed satisfactory performance in simulating the water temperature profiles: the absolute mean errors at R3 (Hoenam) and R4 (Dam) sites were in the range of $1.38{\sim}1.682^{\circ}C$. The evaporative and sensible heat losses through the reservoir surface were maximum during August and January, respectively. The net heat flux ($H_n$) was positive from February to September, while the stratification formed from May and continued until September. Instant vertical mixing was observed in the reservoir during strong wind events at R4, and the model reasonably reproduced the mixing events. A digital low-pass filter and zero crossing method was used to evaluate the potential impact of wind-driven internal wave on the reservoir mixing. The results indicated that most of the wind events occurred in 2001, 2006, 2008 were not enough to develop persistent internal wave and effective mixing in the reservoir. ELCOM is a suitable 3D model for supporting water quality management of the deep and stratified reservoirs.

• 대한토목학회논문집
• /
• 제30권2C호
• /
• pp.77-84
• /
• 2010

연약지반에 지하차도의 기초로서 심층혼합처리공법을 적용하였다. 개량체는 실내배합실험으로 구한 배합비와 강도기준을 만족하는 치환율을 적용하였다. 개량체와 지반의 강성비 및 타설중심거리를 변화시키며 개량체와 지반에 발생한 응력 및 변위를 분석하였으며 지하차도의 부등침하에 미치는 영향을 분석하였다. 구조물의 침하기준과 부등침하를 만족하는 치환율은 10~35%이다. 강성비를 변화시킨 결과 강성비차가 30이상인 경우에는 응력집중 때문에 개량체에 769.2kPa까지 발생하여 기준을 초과한다. C.T.C가 5m인 경우에 지반으로 응력이 전이되어 응력이 커지기 때문에 설치간격을 고려하여야 한다. 복합지반강도 정수를 산정하여 수치해석 한 결과 연직침하는 0.6~1.56cm, 각변위 1/909~1/510이다.

• 한국대기환경학회지
• /
• 제14권4호
• /
• pp.321-332
• /
• 1998

Various meleorologlcal dada obtained by SODAR system in shoreline area surrounding Boryung power plant have been analysed to investigate atmospheric diffusibility. Important conclusion may be summarized as follows; (i) Stability classification scheme based on co (standard deviation of wind direction in degree for averaging time of 1 hour) appears to evaluate certain atmospheric velocity and : indicate horizontal mean wind speed. Thus different scheme for stability classification seems to be preferable in order to appropriately estimate lateral and vertical dispersion coefficients cy and cz, respectively. (ii) As a result of comparisons between 3 available schemes for estimating of mixing height, best one turned out to be the double height scheme where height corresponds to maximum cw.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 하계학술대회 논문집 C
• /
• pp.1509-1511
• /
• 2001

In this study, etching characteristics of polyimide(Pl) film with $O_2/CF_4$ gas mixing ratio was studied using inductively coupled plasma (ICP). The etch rate and selectivity were evaluated to chamber pressure and gas mixing ratio. High etch rate (over 8000$\AA$/min) and vertical profile were acquired in $CF_4$/($CF_4+O_2$) of 0.2. The selectivities of polyimide to PR and polyimide to $SiO_2$ were 1.15, 5.85, respectively. The profiles of polyimide film etched in $CF_4/O_2$ were measured by a scanning electron microscope (SEM) with using an aluminum hard mask pattern. The chemical states on the polyimide film surface were measured by x-ray photoelectron spectroscopy (XPS).

• 한국해양공학회지
• /
• 제7권1호
• /
• pp.81-91
• /
• 1993

Studies on the flow pattern due to reclamation in the Myunggi-Nocksan region are carried out based on field observations and numerical experiments. Serial time series measurement of current, temperature and salinity were conducted for 1 tidal period at intervals of 1 hour from surface to bottom on station located at 128.deg. 54' 44" E, 35.deg. 01' 04" N in April and June 1992. Surface current opposite to the subsurface current causes turbulent mixing to make homogeneous salinity pattern in vertical section. Reclamation has little effect on the wave pattern and flow patterns are also nearly similar except on the nearby region of reclamation where flow speed somewhat weakened.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2001년도 추계학술대회 논문집
• /
• pp.209-212
• /
• 2001

Polyimide(PI) films have been considered as the interlayer dielectric materials due to low dielectric constant, low water absorption, high gap-fill and planarization capability. The PI film was etched with using inductively coupled plasma (ICP). The etching characteristics such as etch rate and selectivity were evaluated to gas mixing ratio. High etch rate was 8300$\AA$/min and vertical profile was approximately acquired 90$^{\circ}$ at CF$_4$/(CF$_4$+O$_2$) of 0.2. The selectivies of polyimide to PR and SiO$_2$ were 1.2, 5.9, respectively. The etching profiles of PI films with an aluminum pattern were measured by a scanning electron microscope (SEM). The chemical states on the PI film surface were investigated by x-ray photoelectron spectroscopy (XPS). Radical densities of oxygen and fluorine in different gas mixing ratio of 07CF4 were investigated by optical emission spectrometer (OES).

• 수산해양기술연구
• /
• 제14권2호
• /
• pp.113-116
• /
• 1978

우리나라 근해의 열 에너지 이용 가능성을 알기 위하여 황해 동부해역의 연직온도차 분포상황 및 그 계절적 변동을 조사하였고, 이들과 해수유동과의 관련성에 관하여 고찰하였다. 하계에는 거안 약 40mile 해역인 125${\circ}$30'E 이서의 34${\circ}$N이북에 연직온도차가 16$^{\circ}C$ 이상 되는 곳이 존재하는 바, 이것은 따뜻한 황해 난류계수의 표면가열과 저층의 황해냉수에 기인하는 것으로 생각된다. 연안으로 갈수록 연직 온도차는 줄어지고, 거안 약 30mile 해역에서는 약 1$0^{\circ}C$이다. 이를 이용하여 온도차발전이 가능하다고 보아진다. 제주도 남부 및 서부해역은 연직 온도차가 약 14$^{\circ}C$ 이상을 보인다. 겨울에는 왕성한 대류혼합으로 연직 온도차는 거의 없어진다. 그러나 겨울에는 강한 계절풍이 계속 발전체계를 여름에는 온도차발전, 겨울에는 파력 및 풍력발전을 하는 방식으로 체계화하면 주년 계속 발전이 가능할 것이라 생각된다.

• Ocean and Polar Research
• /
• 제27권3호
• /
• pp.251-263
• /
• 2005

In order to study changes in the marine ecosystem of the East China Sea derived by the global warming and construction of the Three Gorges Dam in the middle of the Changjiang, temperature, salinity, nutrients, and chlorophyll-a were studied intensively in the northern part of the East China Sea during the summer of 2003 and spring of 2004. According to the previous studies, the upwelling of the Kuroshio Current and the Changjiang resulted in a major inputs of nutrients in the East China Sea, but these two inputs may not contribute gently to a build up of nutrients in the northern East China Sea. In spring, relatively high concentrations of nitrates and phosphates were observed in the western part of the study area, which resulted from the supply of high concentrations of nutrients showing up in the surface waters as a result of vertical mixing from the ocean bottom. The concentrations of nitrates and phosphates observed in summer were lower than those in spring, since the surface waters were well stratified by the larger discharge of fresh water from the Changjiang in summer. The surface nitrate/phosphate ratios ranged from 1.3 to 16 in spring and from 1.1 to 15 in summer and were lower than the Redfield ratio of 16, indicating that the growth of phytoplankton is limited by nitrogen. This results are contrary to the previous results, in which the growth of phytoplankton was limited by phosphate in the East China Sea. The reason for this contrary result is that most nutrients in the surface waters are supplied by vertical mixing from the bottom waters with low nitrate/phosphate ratios, not directly influenced by the Changjiang with high nitrate/phosphate ratios. The depth-integrated chlorophyll observed in summer was similar to the previous results, but those measured in spring were almost twice as high as those found in previous results. The depth-integrated chlorophyll in spring was higher than that of summer, which results from high concentrations of nitrates and phosphates in the surface waters in spring due to active vertical mixing.

• 한국환경과학회지
• /
• 제17권9호
• /
• pp.1053-1068
• /
• 2008

This study aims to produce fundamental database for Environment Impact Assessment by monitoring vertical structure of the atmosphere due to the mountain valley wind in spring season. For this, we observed surface and upper meteorological elements in Sangin-dong, Daegu using the rawinsonde and automatic weather system(AWS). In Sangin-dong, the weather condition was largely affected by mountains when compared to city center. The air temperature was low during the night time and day break, and similar to that of city center during the day time. Relative humidity also showed similar trend; high during the night time and day break and similar to that of city center during the day time. Solar radiation was higher than the city, and the daily maximum temperature was observed later than the city. The synoptic wind during the measurement period was west wind. But during the day time, the west wind was joined by the prevailing wind to become stronger than the night time. During the night time and daybreak, the impact of mountain wind lowered the overall temperature, showing strong geographical influence. The vertical structure of the atmosphere in Dalbi valley, Sangin-dong had a sharp change in air temperature, relative humidity, potential temperature and equivalent potential temperature when measured at the upper part of the mixing layer height. The mixing depth was formed at maximum 1896m above the ground, and in the night time, the inversion layer was formed by radiational cooling and cold mountain wind.