• 한국환경과학회지
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• 제20권7호
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• pp.857-872
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• 2011

The variation of groundwater level in Jeju Island is analyzed with the data of precipitation observed from 48 monitoring post and groundwater level observed from 84 monitoring wells during 2001 to 2009. The groundwater level rises in summer and falls in winter. The rise of groundwater level by precipitation is fast and small in the eastern region and slow and large in the western region. However, the speed of fall during the period of no rain is slower in the eastern region than in the western region. It tells that permeability is greater in the eastern region than in the western region. In this paper, we set up the base level of groundwater and calculate recharge volume between the base level and groundwater surface. During the period, the average recharge volume was $9.83{\times}10^9m^3$ and the maximum recharge volume was $2.667{\times}10^{10}m^3$ after the typhoon Nari. With these volume and the recharge masses obtained by applying the recharge ratio of 46.1%, estimated by Jeju Province (2003), the porous ratio over the whole Jeju Island is 16.8% in average and 4.6% in the case of maximum recharge volume just after typhoon Nari. A large difference in the two ratios is because that it takes time for groundwater permeated through the ground just after rain fall to fill up the empty porous part. Although the porous ratios over the whole Jeju Island obtained in this way has a large error, they give us the advantage to roughly estimate the amount of recharged groundwater mass directly from observing the groundwater level.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.100-107
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• 2002

This study investigates the seasonal variation and spatial distribution characteristics of pollutant load, as executing the quantity valuation of pollutant load inflowing into Yeong-Il bay from on-land including the Hyeong-san river. Annual total pollutant generating rate from Yeong-Il bay region are 202ton to BOD, 620ton to SS, 42ton to T-N, 16ton to T-P respectively, if expressly point out, pollutant generating rate from the Hyeong-san river is the greatest, which BOD ratio is 78.2%, SS 88.5%, T-N 62.5%, T-P 73.1%. As calculating Tank model with input value of daily precipitation and evaporation of 2001 year in drainage basin of the Hyeong-san river, Estimated result of the annual total river discharge effluencing from this river is $830{\times}106m^3$. As result to estimating annual total effluence rate outflowing at the rivers from each drainage basins, annual total inflow pollutant rate are BOD 10,633ton, SS 19,302ton, T-N 15,369ton, T-P 305ton. The III basin which is population congestion region of the Pohang-city drain away a good many pollutant load than the V basin including the Neang-Chun with wide drainage area. Especially, a great many T-N than T-P inflow into Yeong-Il bay. The accumulation of pollutant load effluenced from on-land will happen on at the inner coast region of Yeong-Il bay, finally we would make a prediction that the water quality will take a bad turn.

• 한국표면공학회지
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• 제54권5호
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• pp.248-259
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• 2021

This study examined the influence of post weld heat treatment (PWHT) conditions on corrosion behaviors of laser-welded super duplex stainless steel tube. Due to the high cooling rate of laser welding, the phase fraction of ferrite and austenite in the weld metal became unbalanced significantly. In addition, the Cr₂N particles were precipitated adjacent to the fusion line, which can be susceptible to the localized corrosion. On the other hand, the phase fraction in the weld metal was restored at a ratio of 5:5 when exposed to temperatures above 1060 ℃ during the post weld heat treatment. Nevertheless, the high beltline speed during the PWHT, leading to the insufficient cooling rate, caused a precipitation of σ phase at the interface between ferrite/austenite in both weld metal and base metal. This resulted in the severe corrosion damages and significant decrease in critical pitting temperature (CPT), which was even lower than that measured in as-welded condition. Moreover, the fraction of σ phase in the center region of post weld heat treated steel tube was obtained to be higher than in the surface region. These results suggest that the PWHT conditions for the steel tube should be optimized to ensure the high corrosion resistance by excluding the precipitation of σ phase even in center region.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2001년도 학술발표회 발표논문집
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• pp.314-318
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• 2001

The analysis of the spatial extent of flood inundation is important for flood mitigation. Geographic Information System (GIS) has advantage of analyzing spatial distributed data. Hydrologic Engineering Center's River Analsysis System(HEC-RAS) with HEC-GeoRAS was used to analyze flood inundation. HEC-GeoRAS, which is an ArcView GIS extension designed to process geospatial data for HEC-RAS, is a useful tool for storing, managing, analyzing, and displaying spatially distributed data. Rational formula and 24-hr duration probability precipitation data of Suwon meteorological station were used to estimate the flood runoff. And water profiles were calculated using the HEC-RAS model with HEC-GeoRAS. The flooded region is 8.24ha when 50-yr probability precipitation was applied and 8.8ha when 100-yr was applied to Bahlan study watershed which is located in Whasung county, Kyunggi province, having an area of $29.79km^{2}$.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.552-555
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• 2007

In this study, the MODIS NDVI for the period of $2000{\sim}2007$ was collected and processed to obtain VCI and SVI which are the quantitative indexes of drought. The VCI and SVI based on NDVI can be used for understanding seasonal pattern of vegetation, drought identification and quantitative analysis of drought. VCI and SVI compared with monthly precipitation ratio to average, Standardized Precipitation Index(SPI), and etc., which are used to identify spring drought, to analyze drought region, similarity and difference in drought severity. In addition, frequency of Spring droughts were calculated for the period of $2000{\sim}2007$, and the usability of the MODIS images as a tool for establishing countermeasures against drought was presented by analyzing drought frequently areas.

• 산업기술연구
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• 제31권A호
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• pp.87-94
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• 2011

This paper is results of analyzing characteristics of landslides occurred in Wonju, Gangwondo, around July, 16 in 2006, caused by heavy rainfall and antecedent precipitation by two typhoons of Ewiniar and Bilis. The main causes of landslides were antecedent precipitation during July 8 to 15, resulting in weakening grounds by increasing the degree of saturation previously, and the heavy rainfall during July 15 to 16. Most of landslides in natural slopes were transitional failures occurred along the boundary between the residual weathered soil in shallow depth and the hard mother rock. From results of conclusive analyses regarding 28 sites in Wonju region where landslides occurred, the slope length of landslide, the slope width, and the slope area were less than 50m with 71% of frequency, 20m with 79% of frequency and $300m^2$ of 64% of frequency respectively. The average value of slope angle was $35^{\circ}$. The most probable direction of slope was found to be north because of topography and advancing direction of seasonal rain front.

• Journal of Welding and Joining
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• 제11권4호
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• pp.70-78
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• 1993

An attempt was made to investigate the effect of brazing time on microstructure, microhardness, and corrosion of Zircaloy -4as well as the beryllium diffusion into its sheet. The sheets were coated with beryllium and brazed at $1020^{\circ}C$ for 20-40 minutes in $2{\times}10^{-5}$ torr vacuum atmosphere. 1. Microstructurally the brazed zone was largely divided into three regions: a region of continuous or partially formed of eutectic liquid films along grain boundaries; a region of precipitation in both grains and grain boundaries; a region of elongated wide structure of .alpha.-laths, which was not affected by beryllium. 2. Due to the precipitates, the beryllium-migrated region was hardened and the width of the hardened region increased with increasing brazing time. 3. Beryllium brazed Zircaloy -4 sheets showed a higher corrosion rate than those of as-received and heat-treated at a brazing temperature. 4. Diffusion coefficient of beryllium into Zircaloy -4 at $1020^{\circ}C$ for 30 minutes was $7.67{\times}10^{-7}cm^2/sec.$ It seemed that Be penetrated Zircaloy -4 by forming eutectic liquid films along grain boundaries in the proximity of Be/Zr interface and it, thereafter, diffused into Zircaloy mainly by interstitial solid solution.

• 한국지구과학회지
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• 제38권3호
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• pp.182-193
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• 2017

A typical snowfall pattern occurs over the east coastal region of the Korean Peninsula, known as the Yeongdong region. The precipitation over the Yeongdong region is influenced by the cold and dry northeasterly wind which advects over warm and moist sea surface of the East Sea of Korea. This study reveals the influence of large-scale factors, affecting local to remote areas, on the mesoscale snowfall system over the Yeongdong region. The National Centers for Environmental Prediction-Department of Energy reanalysis dataset, Extended Reconstructed sea surface temperature, and observed snowfall data are analyzed to reveal the relationship between February snowfall and large-scale factors from 1981 to 2014. The Yeongdong snowfall is associated with the sea level pressure patterns over the Gaema Plateau and North Pacific near the Bering Sea, which is remotely associated to the sea surface temperature (SST) variability over the North Pacific. It is presented that the relationship between the Yeongdong snowfall and large-scale factors is strengthened after 1999 when the central north Pacific has warm anomalous SST. These enhanced relationships explain the atmospheric patterns of recent strong snowfall years (2010, 2011, and 2014). It is suggested that the newly defined index in this study based on related SST variability can be used for a seasonal predictor of the Yeongdong snowfall with 2-month leading.

• 한국토양비료학회지
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• 제42권5호
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• pp.348-354
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• 2009

제주도 지역을 대상으로 기후요인과 토양분포의 관계를 알아보기 위하여 기온, 강우량, 증발산량 등 기후요인을 이용하여 분석하였다. 온도를 기준으로 하여 중심지역의 Mesic상 지역과 주변부의 Thermic상 지역으로 구분하고, 월별 수분수지빈도를 기준으로 4개로 구분하여, 온도, 수분수지로 전체를 온대수분과 다지역(집단1), 난대수분과다지역(집단2), 난대수분균형지역(집단3), 난대수분부족지역(집단4), 난대수분매우부족지역(집단5)의 5개의 집단으로 구분할 수 있었다. 집단1에서 집단5로 갈수록 토양분류측면에서는 andisols, inceptisols, alfisols, ultisols의 분포 비중이, 토색측면에서는 흑색토양, 농암갈색토양, 암갈색토양의 분포비중이 높아지는 경향이었다.

• 한국농림기상학회지
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• 제26권3호
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• pp.161-173
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• 2024

우리나라는 여름 장마철에 연 강우량의 50~65%가 집중되는 특징이 있다. 2023년 장마기간에는 전국적으로 660.2mm의 강우가 발생하였으며, 남부지방에서는 712.3mm가 기록되어 관측 이래로 가장 많은 비가 내렸다. 산림지역에서의 집중호우는 산사태를 유발하는 주요 원인이다. 따라서 장마철 산사태 재난 예방을 위해서는 산림지역에서 발생하는 강우를 정확하게 모니터링하고, 그 특성을 파악하는 것이 중요하다. 따라서 본 연구에서는 2023년 장마철 산악지역의 강우 특성을 살펴보기 위해 산림청 산악기상관측소(AMOS, Automatic Mountain Meteorology Observation Stations)의 자료를 활용하였으며, 비산악지역과의 강우량 비교를 위해 기상청의 강우량 관측 자료를 함께 활용하였다. 또한, 산사태 피해가 발생했던 경상북도 지역의 강우 분포를 확인하기 위해 MK-PRISM (Modified Korean-Parameter elevation Regressions an Independent Slopes Model)을 사용하여 강우량 분포도를 생산하였다. 강우량 관측 자료를 분석한 결과, 장마기간 중 강우량은 대체로 고도가 높은 산악지역에서 더 많은 것으로 나타났으며, 산사태가 발생했던 경북의 문경시, 봉화군, 영주시에서는 산악지역과 비산악지역 간의 강우량 차이가 최대 270mm였다. 특히, 이 지역에서는 산사태가 발생하기까지 50시간 이상의 연속 강우와 시간 당 30mm/hr 이상의 집중호우, 300mm 이상의 누적 강우가 발생했다. 강우분포도를 이용하여 산사태 발생 지역의 강우량을 비교한 결과, 장마기간 동안의 누적강우량은 평균 기후값 대비 2배 이상 많은 것으로 나타났다. 향후 효과적인 산사태 재난 대비를 위해서는 산림지역에서의 정확한 강우 관측과 함께 최근의 강우 특성을 고려한 기준 마련이 필요할 것으로 사료된다.