• 대한토목학회논문집
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• 제29권5B호
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• pp.429-439
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• 2009

댐 붕괴로 인한 극한홍수가 발생하였을 경우, 홍수경보에 대한 대응시간은 일반적인 홍수의 경우보다 훨씬 짧다. 수치모형은 홍수파의 전파양상을 예측하고, 범람지역, 홍수파 도달시간 그리고 침수심 등에 관한 정보를 제공하는데 있어 강력한 도구가 될 수 있다. 그러나 댐 붕괴로 인한 홍수파의 전파는 불연속 흐름이나 마른하도의 전파를 포함하고 있으므로, 수학적으로 표현하기 어려운 경우가 많다. 그럼에도 불구하고 최근에 유한체적기법을 이용하여 댐 붕괴로 인한 홍수범람을 모의하기 위한 수치모형의 개발이 많이 이루어졌다. 유한체적기법은 적분보존형 방정식을 기본으로 하고 있으므로, 불연속 흐름이나 충격파의 해석에 용이하다. 따라서, 본 연구에서는 2차원 보존형 천수방정식의 해석을 위해 유한체적기법과 Riemann 근사해법을 이용한 수치모형을 개발하였다. 그리고 예측단계와 수정단계에서 연속방정식과 운동량 방정식의 보존변수 재구성을 위해 수면경사법과 연계한 MUSCL 기법을 적용하여 시간과 공간에서 2차정확도를 얻었다. 개발한 유한체적모형을 2차원 부분적 댐 붕괴 해석 및 삼각형 융기를 가진 하도에 대한 댐 붕괴 해석에 적용하고, 적용결과를 실험자료 및 기존 연구자의 계산결과와 비교하여 개발모형을 검증하였다.

• 대한기계학회논문집A
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• 제24권11호
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• pp.2796-2803
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• 2000

For traditional Leak-Before-Break(LBB) analyses, symmetric conditions were assumed for a pipe-nozzle interface to simplify the analysis in calculating J-integral. However. this assumption could result in an overly conservative design criteria for a pipe-nozzle interface, Since the pipe-nozzle interface is asymmetric due to the difference of stiffness between pipe and nozzle, it is required to develop a new methodology considering the nozzle effect. The objective of this paper is to evaluate the effect of nozzle no the development of LBB design criteria for nuclear pipings. For this purpose, extensive finite element analysis were performed to evaluate the effect of nozzle on Crack Opening Area(COA), Detectable Leakage Crack(DLC) length and J-integral values. In conclusion, it was proven that the application of LBB concept could be extended for more nuclear piping system by considering the nozzle.

• 화약ㆍ발파
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• 제20권2호
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• pp.7-19
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• 2002

The cut is placed high up in the section, the 1st sloping holes below the cut, and divided all the holes located below the 1st sloping holes into a certain area with longitudinal section, to lower pollution made from tunnel blasting. With the sequential blasting machine, after I first blasted holes around the cut holes by a pre-splitting method, blasted the cut area and the 1st sloping holes. The 1st and 2nd sloping holes divided areas are initiated gradually to free face upwards made by the cut. Especially, I pre-splinted contour holes previous blast the before sloping holes from the contours. The ground vibration from the earth surface just over the advance face decreased about 42.0% compare with the down blasting method under the condition of equal charge weight per delay. I controlled the crack and over break of the mother rock by pre-splitting contour holes before blast the first sloping holes from the contours. The peak values of noise and air blast by blasting decreased about 10dB more than the down blasting method. the noise and air blast diminished gradually as a round. The throw distance of the fly rock was decreased about 55%.

• 화약ㆍ발파
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• 제39권3호
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• pp.44-64
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• 2021

4차 산업혁명 시대의 도래와 함께 빅데이터의 활용과 인공지능 기법을 활용한 공학적 응용이 증가하고 있다. 발파 분야에서도 인공지능 기법을 활용한 다양한 연구들이 보고되고 있다. 본 논문에서는 발파분야에서 많이 활용되고 있는 인공신경망, 퍼지 이론, 유전자 알고리즘, 떼 지능, 서포트 벡터머신과 같은 인공지능 기법을 소개하고 이들 기법을 이용한 발파진동, 비석, 암석 파쇄도, 폭풍압, 여굴 예측 기법에 대한 연구들을 조사, 정리하였다. 향후 인공지능 기법을 활용하여 보다 효율적이고 안전한 발파설계, 발파 효율 향상과 발파에 의한 주변 환경에 미치는 영향을 최소화하기 위하기 위한 발전적인 접근 방향에 대한 논의에 활용할 수 있는 기초 자료를 제공하고자 한다.

• Nuclear Engineering and Technology
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• 제41권5호
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• pp.691-708
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• 2009

In order to analyze thermal hydraulic phenomena during a DVI (Direct Vessel Injection) line break LOCA (Loss-of-Coolant Accident) in the APR1400 (Advanced Power Reactor 1400 MWe), we performed experimental studies with the SNUF (Seoul National University Facility), a reduced-height and reduce-pressure integral test loop with a scaled down APR1400. We performed experiments dealing with eight test cases under varied tests. As a result of the experiment, the primary system pressure, the coolant temperature, and the occurrence time of the downcomer seal clearing were affected significantly by the thermal power in the core and the SI flow rate. The break area played a dominant role in the vent of the steam. For our analytical investigation, we used the MARS code for simulation of the experiments to validate the calculation capability of the code. The results of the analysis showed good and sufficient agreement with the results of the experiment. However, the analysis revealed a weak capability in predicting the bypass flow of the SI water toward the broken DVI line, and it was insufficient to simulate the streamline contraction in the broken side. We, hence, need to improve the MARS code.

• 한국안전학회지
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• 제20권2호
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• pp.32-37
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• 2005

The purpose of this study is for the sensitivity study f9r a Steam Generator Tube Rupture (SGTR) of the System-integrated Modular Advanced ReacTor for a Pilot (SMART-P) plant. The thermal hydraulic analysis of a SGIR for the Limiting Conditions for Operation (LCO) is performed using TASS/SMR code. The TASS/SMR code can calculate the core power, pressure, flow, temperature and other values of the primary and secondary system for the various initiating conditions. The major concern of this sensitivity study is not the minimum Critical Heat Flux Ratio(CHFR) but the maximum leakage amount from the primary to secondary sides at the steam generator. Therefore the break area causing the maximum accumulated break flow is researched for this reason. In the case of a SGIR for the SMART-p, the total integrated break flow is 11,740kg in the worst case scenario, the minimum CHFR is maintained at Over 1.3 and the hottest fuel rod temperature is below 606"I during the transient. It means that the integrity of the fuel rod is guaranteed. The reactor coolant system and the secondary system pressures are maintained below 18.7MPa, which is system design pressure.

• 한국수자원학회논문집
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• 제49권2호
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• pp.121-132
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• 2016

본 연구에서는 DAMBRK 모형을 2002년 태풍 루사로 인해 붕괴된 남대천 유역의 장현저수지와 동막저수지에 적용하여 붕괴상황을 재현하였다. 두 저수지는 병렬로 위치하고 있으며, 이 두 저수지의 붕괴 모의를 위해 Relaxation 기법을 DAMBRK 모형에 추가하였다. 그리고 ASDSO (2005)에서 제안한 흙댐 붕괴지속시간과 첨두붕괴유량 산정을 위한 Froehlich 등의 경험공식을 활용한 저수지의 붕괴지속시간 추정 방법을 제안하였다. 제안 방법으로 선정된 붕괴지속시간으로 장현저수지 단일붕괴와 장현 및 동막저수지 연속붕괴에 대해 적용하여 붕괴유출 수문곡선을 계산하였다. 계산된 붕괴유량이 하류로 전파하면서 예상되는 홍수량 및 홍수위를 주요 하도지점에서 계산하고, 유량이 감쇠되는 특성을 해석하였다. 그리고 계산 홍수위와 현장 조사된 홍수위와의 비교를 통해 적용 모형의 매개변수 및 정확성을 검증하였다.

• 한국환경농학회지
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• 제41권3호
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• pp.199-205
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• 2022

BACKGROUND: The freezing injury by pruning can be reduced by suspending pruning work when severe cold weather (-23 to -49℃) is forecast. Minimum air temperature of the study area, Gunwi region at February 3, 2012 was -21.9℃, and the subzero temperature continued until April 8, 2012. This study was conducted in two years to investigate the effect of delaying winter pruning until full bloom on shoot growth and fruit quality of 'Fuji'/M.9 apple trees. METHODS AND RESULTS: The time of pruning were March 26 for dormant, April 3 for bud break, and May 2 for full bloom. The winter pruning at full bloom significantly reduced fruit weight for two years compared with the control (winter pruning at dormant), and shoot growth was reduced only in the following year. There was no significant effect of delaying winter pruning at bud break on soluble solid content, fruit red color, return bloom, and pruning weight for two years compared with the control. CONCLUSION(S): These results indicated the delaying winter pruning at bud break of 'Fuji'/M.9 apple tree did not offer any disadvantage over comparable dormant pruning, since the fruit quality was not affected. The delayed pruning at full bloom resulted in decreased fruit weight, though shoot growth, fruit quality, and return bloom were not affected by the delayed pruning. So, the delayed pruning should be considered carefully only for the fruit tree orchards in diseases.

• 한국산업융합학회 논문집
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• 제9권1호
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• pp.73-78
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• 2006

Constructing a long, linear structure such as a high-way may cause the break-up of the natural ecology by cutting off the trails of animals. We could observe 12 kinds of mammals, 49 kinds of birds and 10 kinds of amphibia and reptilia at the research area. With this research, we were so sure of the necessity of building ecological corridors to prevent the ecological break-up of wild animals that we studied the building and maintaining of 3 types of ecological corridors; tunnel types, over-bridge type and line type.

• 한국수산과학회지
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• 제36권4호
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• pp.346-351
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• 2003

Single-cell gel electrophoresis (comet assay) was used to detect DNA single strand break in blood cells from several marine fish species. Three fish species were collected from Georgia coastal area. Mummichog, Fundulus heteroclitus showed higher DNA damage than sea bass, Lateolabrax japonicus and trout, Oncorhynchus masou masou under the same experimental conditions. Mummichogs had more alkaline-labile sites on their DNA than other fish species. The comet assay with mummichog blood cells at pH 12.5 showed a dose-response curve with the increasing concentrations of hydrogen peroxide. While the isolated leucocytes showed no increase of DNA damage after in vitro exposure to 2-methyl-1,4-naphthoquinone (MNQ), erythrocytes showed dose-dependent DNA damage. These results indicate that the comet assay can be applied successfully as a bioassay using erythrocyte for environmental monitoring.