• 열처리공학회지
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• 제22권2호
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• pp.101-107
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• 2009

Effect of isochronic aging on transformation behavior of Ti-50.85at%Ni alloy were investigated by differential scanning calorimeter (DSC). The martensitic transformation temperature increases with increasing annealing temperature until reaching a maximum, and then decreases with further increasing annealing temperature. This can be rationalized by interaction between the distribution of $Ti_3Ni_4$ precipitates and Ni content in the matrix. The R-phase transformation temperature increases with increasing annealing temperature until reaching a maximum, and then decreases with a further increase of annealing temperature. This is attributed to the change of Ni content in the matrix caused by precipitation of $Ti_3Ni_4$. The occurrence of the multiple-stage martensitic and R-phase transformation is attributed to precipitation-induced inhomogeneity of the matrix, both in terms of composition and of internal stress fields.

• 한국산업융합학회 논문집
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• 제9권2호
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• pp.111-116
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• 2006

This study provides the optimal conditions treating with the coagulation process and the other chemical treatment processes for dyeing wastewater, especially various dyeing complex wastewater. The results are shown as follows: 1. Optimum reaction condition of pH for ferrous sulfate was the range of 9 to 12. And when 3,000ppm(mg/l) of ferrous sulfate was dosed, the maximum $COD_{Mn}$ removal rate was approximately 40%. 2. In case of ferrous chloride and Bittern as coagulants, optimum pH range was 10 to 11. And maximum $COD_{Mn}$ removal rate was approximately 46% to 50% for dose of 2,000ppm(mg/l) to 6,000 ppm. 3. It is confirmed that the activated sludge process following coagulation precipitation method provides better treatment efficiency than the coagulation precipitation method following the activated sludge process. 4. The purpose of this study was to produce CGF (Cyanoguanidineformaldehyde resin) by organic compounds. 5. The complex coagulation agent by this study is the most economical coagulant with Alum(aluminum sulfate) and the removal efficiency is approximately 54% with 1,000ppm(mg/l) of pH range 6 to 7.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2021년도 학술발표회
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• pp.169-169
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• 2021

통계학적 가능최대강수량방법은 가능최대강수량(Probable Maximum Precipitation, PMP) 측정 방법 중 하나로 WMO에서 통계학적인 PMP 추정 방법으로 Hershfield가 제안한 공식을 제시했다. Hershfield는 95,000개의 자료를 분석하였으며, 기본적으로 통계학적 PMP 추정방법의 빈도계수는 k_m = 15로 제안하였다. 그러나 강우 지속기간 및 연최대 시계열의 평균에 따라 값이 변하게 되며, Hershfield(1965)는 지속시간과 연최대 시계열의 평균에 따른 빈도계수가 5 ~ 20 사이의 값을 갖는다고 제안한 바 있다. Hershfield의 빈도계수는 미국 지역의 2,645개의 관측소의 95,000개의 강우 자료 이용했기 때문에 우리나라의 적용하였을 때 신뢰성에 문제가 있을수 있으며, 우리나라에서는 통계학적 방법보다는 수문기상학적 PMP 추정 방법을 주로 사용하고 있다. 따라서 본 연구에서는 우리나라의 기상 자료중에서 가장 많은 양을 가지는 지점 10개를 선정하여 빈도계수를 산정하였다. 빈도계수를 산정하기 위해서는 시계열로 구성된 강우 자료를 사용해야하며, 본 연구에서는 기상 자료의 이상치 검정을 진행하였으며, 경향성의 경우 정상성을 가지는 것으로 가정하였다. 확률 분포형은 극치분포인 GEV분포, Gumbel분포, Log-Gumbel분포, Weibull분포를 비교하여 가장 적절한 분포형을 선정하여 진행하였다. 최종적으로 얻은 빈도계수를 이용하여 구한 PMP값과 기존 Hershfield가 제시한 빈도계수 값 k_m = 15를 이용한 PMP값을 비교하여 차이를 분석하였으며, 그 적용성을 평가하였다.

• 한국수자원학회논문집
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• 제53권7호
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• pp.469-480
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• 2020

본 연구는 레이더와 TM간 유역평균강수량 측정의 차이를 2018년 발생한 상당 규모의 호우시 한강과 낙동강의 51개 표준유역을 대상으로 분석하였다. 그 결과 레이더와 TM간의 유역평균강수량 값이 누적강수량은 -65.05~26.09%, 10분최대 강수량은 -82.00~3.80%의 차이가 발생하였다. 이러한 차이를 유역의 특성인 유역면적, 유역평균고도, 유역형상계수 등과 비교하였으나 뚜렷한 상관성을 찾기가 어려웠으며, 지점강수량도 유역평균강수량과 비슷한 경향을 보이는 것을 확인하였다. 따라서 강우형태와 같은 기상학적 조건과의 상관성을 확인하기 위해 고도별 레이더 반사도 값을 분석하였으며 이를 통해 레이더와 TM간 유역평균강수량 측정값의 차이는 유역특성과 같은 지형적 조건 보다는 기상학적 조건과 더 상관성이 있는 것을 확인할 수 있었다.

• 한국수자원학회논문집
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• 제53권11호
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• pp.999-1013
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• 2020

전세계적으로 기상조절 연구가 활발히 수행되어져 왔으나 연구 효과를 보다 정량적으로 검증할 수 있는 기술이 필요하다. 본 연구에서는 기상조절 실험에 대한 강수 증가 효율인 시딩효과(seeding effect)를 레이더 자료를 이용하여 검증하였다. 또한, 시딩물질이 대기수상체 변화에 미치는 영향을 분석하였다. 이를 위해 레이더 자료, 기상조건, 확산 수치모의 자료가 사용되었다. 먼저, 시딩전, 시딩중, 시딩후의 세 단계로 시딩효과를 분석할 수 있는 방법을 제안하였다. 제안한 방법을 강원도와 서해 지역을 대상으로 수행된 세 개의 기상조절 실험 사례에 적용하였다. 그 결과, 자연강수가 없을 때는 강수 변화가 예측된 구역에서 감지된 레이더 반사도가 시딩효과로 판단되었다. 자연강수가 발생하면 관측된 최대 반사도에서 자연강수의 영향을 제외하여 시딩효과를 결정하였다. 적용사례에 대해 시딩효과로 강수강도가 0.1 mm/h 증가한 것으로 나타났다. 아울러 시딩 구름에 빙정이나 과냉각 수적, 혼합상의 수상체가 분포한 것으로 나타났다. 이러한 기상조절 연구 결과는 수자원 확보와 구름 물리 연구에 활용할 수 있을 것으로 판단된다.

• Journal of Ecology and Environment
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• 제35권4호
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• pp.323-329
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• 2012

The Standardized Precipitation Index (SPI) is a widely used drought index to provide good estimations of the intensity, magnitude and spatial extent of droughts. The objective of this study was to analyze the spatial pattern of drought by SPI index. In this paper, the patterns of drought hazard in Iran are evaluated according to the data of 40 weather stations during 1967-2009. The influenced zone of each station was specified by the Thiessen method. It was attempted to make a new model of drought hazard using GIS. Three criteria for drought were studied and considered to define areas of vulnerability. Drought hazard criteria used in the present model included: maximum severity of drought in the period, trend of drought, and the maximum number of sequential arid years. Each of the vulnerability indicators were mapped and these as well as a final hazard map were classified into 5 hazard classes of drought: one, slight, moderate, severe and very severe. The final drought vulnerability map was prepared by overlaying three criteria maps in a GIS, and the final hazard classes were defined on the basis of hazard scores, which were determined according to the means of the main indicators. The final vulnerability map shows that severe hazard areas (43% of the country) which are observed in the west and eastern parts of country are much more widespread than areas under other hazard classes. Overall, approximately half of the country was determined to be under severe and very severe hazard classes for drought.

• 한국방재학회 논문집
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• 제3권3호
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• pp.125-132
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• 2003

본 연구에서는 국지성 이상호우에 대한 하천의 치수 안전도를 분석하기 위하며 서울의 도시하천중 지방2급 하천인 홍제천을 연구 대상하천으로 선정하였고, 최근 발생한 이상호우 중에서 서울에 많은 피해를 입힌 2001년 7월 14일${\sim}$15일 강우 310.1mm와 서울지역 가능최대강수량(PMP)740.0mm를 적용 강우로 선정하였다. 홍제천의 치수 안전도를 분석한 결과, 계획빈도인 50년인 경우, 안전단면이 85%, 관리단면이 15%, 위험단면은 발생치 않았으나, 100년 빈도에서 안전단면이 5% 감소하고 관리단면이 4% 위험단면은 2% 증가하였다. 빈도가 증가함에 따라 증감율은 작게 나타났고 200년 빈도 이후에는 관리단면은 거의 변화가 없었으며 위험단면이 다소 증가하여 300년 빈도에서는 50년 빈도에 비해 8%, 500년 빈도에서는 12% 증가하였고 1000년 빈도에서는 위험단면이 19%, 관리단면이 13% 크게 증가하였다.

• 한국농림기상학회지
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• 제6권1호
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• pp.49-60
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• 2004

Northern Gyeonggi Province(NGP), consisting of 3 counties, is the northernmost region in South Korea adjacent to the de-militarized zone with North Korea. To supplement insufficient spatial coverage of official climate data and climate atlases based on those data, high-resolution digital climate models(DCM) were prepared to support weather- related activities of residents in NGP Monthly climate data from 51 synoptic stations across both North and South Korea were collected for 1981-2000. A digital elevation model(DEM) for this region with 30m cell spacing was used with the climate data for spatially interpolating daily maximum and minimum temperatures, solar irradiance, and precipitation based on relevant topoclimatological models. For daily minimum temperature, a spatial interpolation scheme accommodating the potential influences of cold air accumulation and the temperature inversion was used. For daily maximum temperature estimation, a spatial interpolation model loaded with the overheating index was used. Daily solar irradiances over sloping surfaces were estimated from nearby synoptic station data weighted by potential relative radiation, which is the hourly sum of relative solar intensity. Precipitation was assumed to increase with the difference between virtual terrain elevation and the DEM multiplied by an observed rate. Validations were carried out by installing an observation network specifically for making comparisons with the spatially estimated temperature pattern. Freezing risk in January was estimated for major fruit tree species based on the DCMs under the recurrence intervals of 10, 30, and 100 years, respectively. Frost risks at bud-burst and blossom of tree flowers were also estimated for the same resolution as the DCMs.

• 환경영향평가
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• 제20권2호
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• pp.227-234
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• 2011

In the study, CE-QUAL-W2 was used and its examination and correction were conducted targeting 2001 and 2003 when the condition of rainfall was contradicted. Using the proved model in 2003, a scenario was implemented with management of locations for dewatering outlets and actual data for dam management in 1987 when inflow and outflow level were almost same. In case of the scenario which the location of dewatering outlets was 5m higher than usual location, exclusion efficiency for turbid water inflow at the beginning of precipitation was good. In case of the scenario which the location of dewatering outlets was 10m lower than usual location, exclusion efficiency for excluding turbid water remained in a reservoir after the end of precipitation. However, the scenario applying dam management data in 1987, exclusion efficiency was relatively low. In the scenario, power-generating water release spot at EL.57m for first four days after the beginning of precipitation, EL.52m for 5th to 8th and EL.42m from 9th days. An analysis of the scenario reveals that both excessive days exceeded 30 NTU and average turbidity levels were decreased comparing before and after the alteration on outlets. The average turbidity levels were decreased by minimum of 55% to maximum of 70% and 30NTU exceeding days were decreased by 45 days at maximum. Also, since it could exclude most of turbid water in a reservoir before the destatifcation, the risk for turbid water evenly distributed in a reservoir along with turn-over could be decreased as well.

• 대기
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• 제33권4호
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• pp.399-411
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• 2023

This study compares the three detection algorithms of East Asian summer atmospheric rivers (ARs). The algorithms developed by Guan and Waliser (GW15), Park et al. (P21), and Tian et al. (T23) are particularly compared in terms of the AR frequency, the number of AR events, and the AR duration for the period of 2016-2020. All three algorithms show similar spatio-temporal distributions of AR frequency, centered along the edge of the North Pacific high. The maximum AR frequency gradually shifts northward in early summer as the edge of the North Pacific High expands, and retreats in late summer. However, the detailed pattern and the maximum value differ among the algorithms. When the AR frequency is decomposed into the number of AR events and the AR duration, the AR frequencies detected by GW15 and P21 are equally explained by both factors. However, the number of AR events primarily determine the AR frequency in T23. This difference occurs as T23 utilizes the machine learning algorithm applied to moisture field while GW15 and P21 apply the threshold value to moisture transport field. When evaluating AR-related precipitation, the ARs detected by P21 show the closest relationship with total precipitation in East Asia by up to 60%. These results indicate that AR detection in the East Asian summer is sensitive to the choice of the detection algorithm and can be optimized for the target region.