• Nuclear Engineering and Technology
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• 제53권1호
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• pp.111-120
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• 2021

During the core disruptive accident (CDA) of sodium-cooled fast reactor (SFR), the molten fuel and steel are solidified into debris particles, which form debris bed in the lower plenum. When the boiling occurs inside debris bed, the flow of coolant and vapor makes the debris particles relocated and the bed flattened, which called debris bed relocation. Because the thickness of debris bed has great influence on the cooling ability of fuel debris in low plenum, it's very necessary to evaluate the transient changes of the shape and thickness in relocation behavior for CDA simulation analysis. To simulate relocation behavior, a large number of debris bed relocation experiments were carried out by improved bottom gas-injection experimental method in this paper. The effects of different experimental factors on the relocation process were studied from the experiments. The experimental data were also used to further evaluate a semi-empirical onset model for predicting relocation.

• 한국산학기술학회논문지
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• 제17권5호
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• pp.325-331
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• 2016

본 연구에서는 홍수 시 부유물의 충돌하중을 고려하여 교량의 홍수 취약도 곡선을 도출하였다. 자연재해에 의해 불가피하게 발생하는 사회기반시설물의 손상 또는 기능 손실은 심각한 인명피해 뿐만 아니라 국가적으로 사회적, 경제적 손실을 불러올 수 있다. 따라서 국가주요시설물을 재난으로부터 효과적으로 유지관리하기 위해 취약도 곡선은 중요한 도구로 사용되고 있다. 특히 한국은 산지 지형이 많이 형성되어 있고 하절기에 강수량의 2/3이상이 집중되어, 홍수 피해 가능성이 매우 높다. 홍수 시 교량 파괴의 주원인으로는 부유물의 충돌과 하상세굴이 있는데, 부유물의 충돌은 여러 가지 불확실성으로 인하여 상대적으로 연구가 부족한 실정이다. 본 연구에서는 FERUM-ABAQUS 기반의 취약도 해석 시스템을 도입하여, 홍수시 부유물의 충돌에 대한 교량의 취약성을 평가하였다. 교량의 취약도 해석을 효과적으로 수행하기 위하여 한계상태함수, 손상도 지수, 확률변수, 유한요소모델, 취약도 해석 소프트웨어 시스템을 주로 고려하였으며, 가속도 및 변위 응답해석을 통하여 모델 상태를 확인하였다. 다음으로는 홍수 시 부유물 충돌에 발생 가능한 다양한 파라미터를 기반으로 교량의 취약도 곡선을 성공적으로 도출하였다.

• 지질공학
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• 제28권3호
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• pp.341-348
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• 2018

Landslides can be caused by localized intense rainfall. The loss of human lives and damage to property from landslides is increasing. However, little information exists on the movement and flow of sediment material at the time of rapid landslides. In this study, a field survey was conducted of landslides that occurred in 2013 in the Hadari area of Yeoju city in Korea. This was followed by numerical analysis. The purpose is to analyze the characteristics of a consequent debris flow and its movement at the time of failure. The results of the field survey and numerical analysis are consistent with each other. The maximum velocity of the debris flow was ~9.335 m/s and the maximum sediment thickness ~4.674 m. The latter is similar to the traces of debris flow observed in the field.

• 한국지반신소재학회논문집
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• 제16권2호
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• pp.79-87
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• 2017

본 연구에서는 2006년부터 2013년 까지 강원도 영서 인근 지역의 토석류 피해지역 43개소에 대한 현장조사 결과를 바탕으로 토석류 규모를 산정하고 영향인자가 토석류 규모에 미치는 상관성 분석을 실시하였다. 토석류의 규모는 발생지역별로 큰 차이를 보이나 계곡형이 사면형보다 약 6.5배 큰 것으로 조사되었으며 계곡형 발생부의 토석류 규모는 전체의 약 5% 정도의 규모인 것을 확인하였다. 침식률은 계곡형에서 전체 토석류 발생량이 $10,000m^3$ 보다 큰 대규모인 경우 $19m^3/m$, $10,000m^3$ 보다 작은 경우 $8m^3/m$의 값을 갖고, 사면형은 $5m^3/m$로 산정되었다. 토석류 규모의 영향인자에 대한 상관성 분석결과, 토석류 유하부의 길이와 폭은 상관성이 높은 것으로 나타났으며, 평균경사와 침식 깊이는 상관성이 낮은 것으로 나타났다. 특히, 침식깊이는 규모와 상관성 없이 0.5~2.6m의 범위로 Ikeya(1981)가 제안한 값과 유사하였다. 연속강우량, 최대시간강우량 등 토석류 유발강우와 토석류 규모는 상관성이 낮은 것으로 분석되었다.

• 한국지리정보학회지
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• 제10권1호
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• pp.158-168
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• 2007

본 연구에서는 소양호유역의 탁수 및 토사유실 저감을 위해 수립중인 다양한 대책중 산림청과 지자체를 중심으로 계획중인 사방댐에 대한 저감효과를 분석하였다. 2005년 강우와 GIS 자료를 이용하여 분석한 결과 소양호유역의 토사유실은 4,819,494 ton으로 평가되었으며, 단위토사유실분석에서는 추곡천, 자운천 그리고 오항천이 다른 유역들에 비해 높은 값을 보였다. 94개의 사방댐 지점을 중심으로 GIS 공간분석을 이용하여 사방댐유역을 추출하였으며, 사방댐유역의 토사유실량과 유사운송비를 이용하여 저감효과를 분석한 결과, 2005년 사방댐의 토사유실저감효과는 6.8%(330,203 ton)으로 분석되었다. 또한 사방댐의 위치를 5,000 ton 이상인 지역으로 이동한 시나리오에서의 사방댐의 토사유실저감효과는 10.5%(506,783 ton)으로 증가되었다.

• International Journal of Precision Engineering and Manufacturing
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• 제4권6호
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• pp.44-49
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• 2003

The morphological analysis of wear debris can provide early a failure diagnosis in lubricated moving system. It can be effective to analyze operating conditions of oil-lubricated tribological system with shape characteristics of wear debris in a lubricant. But, in order to predict and recognize an operating condition of lubricated machine, it is needed to analyze and to identify shape characteristics of wear debris. Therefore, If the morphological characteristics of wear debris are recognized by computer image analysis using the neural network algorithm, it is possible to recognize operating condition of hydraulic driving members. In this study, wear debris in the lubricating oil are extracted by membrane filter (0.45$\mu\textrm{m}$), and the quantitative values of shape parameters of wear debris are calculated by the digital image processing. This shape parameters are studied and identified by the artificial neural network algorithm. The result of study could be applied to prediction and to recognition of the operating condition of hydraulic driving members in lubricated machine systems.

• 대한공간정보학회지
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• 제24권2호
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• pp.15-24
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• 2016

This study conducted an evaluation of the extent of debris flow damage using SINMAP, which is slope stability analysis software based on the infinite slope stability method, and FLO-2D, a hydraulic debris flow analysis program. Mt. Majeok located in Chuncheon city in the Gangwon province was selected as the study area to compare the study results with an actual 2011 case. The stability of the slope was evaluated using a DEM of $1{\times}1m$ resolution based on the LiDAR survey method, and the initiation points of the debris flow were estimated by analyzing the overlaps with the drainage network, based on watershed analysis. In addition, the study used measured data from the actual case in the simulation instead of existing empirical equations to obtain simulation results with high reliability. The simulation results for the impact of the debris flow showed a 2.2-29.6% difference from the measured data. The results suggest that the extent of damage can be effectively estimated if the parameter setting for the models and the debris flow initiation point estimation are based on measured data. It is expected that the evaluation method of this study can be used in the future as a useful hazard mapping technique among GIS-based risk mapping techniques.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.698-707
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• 2010

Because of localized extreme rainfall followed by Typhoon Ewiniar in 2006, a lot of landslides and debris flows were occurred in Jinbu area of Gangwon Province. Field investigation performed in this area found that it can be divided into three categories i.e. large debris flow, small debris flow, and debris flow around forest road. We performed field investigation especially for the sites where debris flow occurred around forest road. And the characteristics of the debris flow around forest road were analyzed and compared with the other site of debris flow.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1998년도 제27회 춘계학술대회
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• pp.314-320
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• 1998

Wear debris morphology is closely related to the wear mode and mechanism occured. Image recognition of wear debris is, therefore, a powerful tool in wear monitoring. But it has usually required expert's experience and the results could be too subjective. Development of automatic tools for wear debris recognition is needed to solve this problem. In this work, an algorithm for automatic wear debris recognition was suggested and implemented by PC base software. The presented method defined a characteristic 3-dimensional feature space where typical types of wear debris were separately located by the knowledge-based system and compared the similarity of object wear debris concerned. The 3-dimensional feature space was obtained from multiple feature vectors by using a multi-dimensional scaling technique. The results showed that the presented automatic wear debris recognition was satisfactory in many cases application.

• Tribology and Lubricants
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• 제15권2호
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• pp.206-211
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• 1999

Wear debris morphology is closely related to the wear mode and mechanism occured. Image recognition of wear debris is, therefore, a powerful tool in wear monitoring. But it has usually required expert's experience and the results could be too subjective. Development of automatic tools for wear debris recognition is needed to solve this problem. In this work, an algorithm for automatic wear debris recognition was suggested and implemented by PC base software. The presented method defined a characteristic 3-dimensional feature space where typical types of wear debris were separately located by the knowledge-based system and compared the similarity of object wear debris concerned. The 3-dimensional feature space was obtained from multiple feature vectors by using a multi-dimensional scaling technique. The results showed that the presented automatic wear debris recognition was satisfactory in many cases application.