• 한국군사과학기술학회지
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• 제18권3호
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• pp.220-225
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• 2015

In this study, the effect of stationary fin and buoyancy devices on dynamic pithing of the tracked vehicle was investigated. For this work, the stationary fin and buoyancy devices were installed in front of body and then pitching variation was measured when rapidly reducing the vehicle speed in water operation. According to the results of measuring the freeboard at each case, when only fin was installed, the effect on freeboard of tracked vehicle in water was negligible. However, when buoyancy devices were installed, front freeboard was approximately increased by about 20~25 mm and rear freeboard was decreased by about 10~15 mm per each addition of 100 kg buoyancy device. Based on the calculation result of pitching decrease rates, it was found that the pitching variation was decreased approximately 12.3 % by fin installation and approximately 2 % by installation of each 100 kg of buoyancy device. The case in which only fin installation was made showed the best efficiency in decreasing pitching variation of the tracked vehicle in water compared to the other cases.

• 한국습지학회지
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• 제5권1호
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• pp.41-52
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• 2003

The flood damage reduction studies have been performed by the channel improvement plan and the levee has mainly constructed with the freeboard concept. However, the freeboard concept might be an inappropriate choice as a safety factor of the levee because many uncertainties are involved in the procedure of the channel improvement plan studies. So, we considered the uncertainties In the discharge-probability, stage-discharge, and stage-damage functions and estimate the expected annual damage. The Monte Carlo technique for uncertainty analysis is used. As our results, the expected annual damage with uncertainty shows the larger value than without uncertainty. Since the expected annual damage with uncertainty already considers the safety factor it is the proper result. However, the expected annual damage without uncertainty does not consider the safety factor yet. Thus, if the expected annual damage without uncertainty considers the freeboard concept, it could be compared with the expected annual damage with uncertainty for the evaluation of the overestimation or underestimation of the levee construction.

• 한국해안·해양공학회논문집
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• 제36권3호
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• pp.105-115
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• 2024

호안을 포함한 해안구조물의 설계 시 월파량 평가는 주로 수리모형실험에 의존하며, 이를 기반으로 월파량 예측을 위한 많은 경험식이 제안되었다. 일반적으로 월파방지를 위한 호안구조물의 경우 설계조위에 설계파의 최대 수면진폭을 고려하여 마루높이가 결정되므로 입사파고에 비해 상대적으로 높은 여유마루고를 갖는다. 그러나, 월파를 원천적으로 차단하기 위해서는 비경제적인 구조물의 마루높이가 요구되기 때문에 호안구조물의 설계 시 월파량을 허용 가능한 수준으로 제한하는 허용월파량의 개념을 도입하고 있다. 따라서, 실해역에서는 입사파고에 비해 상대적으로 낮은 여유마루고를 갖는 호안구조물들이 존재한다. 본 연구에서는 수리모형실험을 통해 상대적으로 낮은 여유마루고를 갖는 사석경사제의 월파량에 관해 검토하였다. 또한, 월파량의 실험결과를 이용하여 기존 월파량 산정을 위한 경험식의 예측성능을 상호 비교·분석하였다.

• 한국연소학회지
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• 제16권4호
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• pp.8-15
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• 2011

The present study investigates the combustion phenomena in a sludge incinerator using experimental and numerical method. The temperature and gas concentration were measured at 33 points during operation of the incinerator in order to assess the mixing and combustion characteristics. Numerical simulation was also carried out using a commercial CFD code. Simplified inlet conditions were introduced in oder to predict the bulk solid combustion and the diffusion of the volatile matter released by pyrolysis of sludge. The experimental results showed that the combustion process is extremely inhomogeneous. Large variations were observed in the temperature and gas concentrations in the freeboard of the incinerator due to poor mixing performance between the air and the combustibles, which is caused by massive and bulk generation of volatile matter by fast pyrolysis of sludge particles. The boundary condition of the CFD simulation was found effective in predicting the poor mixing and combustion performance of the reactor.

• 한국농공학회:학술대회논문집
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• 한국농공학회 1999년도 Proceedings of the 1999 Annual Conference The Korean Society of Agricutural Engineers
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• pp.75-80
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• 1999

The water requirement of crops in paddy fields is composed of evapotranspiration and infiltration. The determination of effective rainfall has the great significance for the irrigation managements and system design. There are numerous methods to estimate effective rainfall. The FreeBoard Model(FBM), ond of them , is popular because it can describe the algorithm of effective rainfal with simplified and general formation. The purpose of this study is to evaluate effective rainfall by field measurement , to compare this closely with the results from freeboard model and modified freeboard model , and to find out which of two models is more consistent with the results obtained by measurements.

• Geomechanics and Engineering
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• 제31권6호
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• pp.637-651
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• 2022

The seismic design of embankment dams requires more comprehensive studies to understand the behaviour of dams. Deformations primarily control this behaviour occur during or after earthquake loading. Dam failures and incidents show that the impacts of deformations should be reviewed for existing and new embankment dams. Overtopping erosion failure can occur if crest deformations exceed the freeboard at the time of the deformations. Therefore, crest settlement is one of the most critical deformations. This study developed empirical formulas using Gene Expression Programming (GEP) based on 88 cases. In the analyses, dam height (H_d), alluvium thickness (H_a), the magnitude-acceleration-factor (MAF) values developed based on earthquake magnitude (Mw) and peak ground acceleration (PGA) within this study have been chosen as variables. Results show that GEP models developed in the paper are remarkably robust and accessible tools to predict earthquake-induced crest settlement of embankment dams and perform superior to the existing formulation. Also, dam engineering professionals can use them practically because the variables of prediction equations are easily accessible after the earthquake.

• 시스템엔지니어링학술지
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• 제19권1호
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• pp.39-43
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• 2023

In ground weapon systems, the design and analysis technology for water operation stability is a relatively unknown area compared to maritime weapon systems. Through this study, it was confirmed that our weapon system satisfies the criteria for stability on the water when considering the operational concept and operational performance. However, there is a limitation of the study that it did not perform verification tests on the actual system. Therefore, in the future research and weapon system acquisition process, a procedure to prove the stability through freeboard analysis using the actual system is required.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.743-746
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• 2008

Recently, due to the effect of global warming and extreme rainfall, the magnitude of flood disaster and the frequency of flood is rapidly increasing. In order to mitigate the damage of human and property from this kind of meteorological phenomenon and manage water resources scientifically, effective operation of dam and reservoir is very important. In case of Andong dam which was not performed a flood control function needs to develop new types of dam safety management measure because of recent extraordinary flood by typhoons. In case of Andong dam and Imha dam, I am using HEC-5 model in order to apply reservoir simulation. In this case, complex conditions among 100-year floods , 200-year floods and PMF was used. Also, I modified the maximum outflow 3,800m3/s into 3,490m3/s and applied this modified discharge in order to secure freeboard in the downstream. In an analysis that I applied modified outflow by 100-year floods and 200-year floods to, the result showed that river didn't overflow in Andong area but some other places have relatively low freeboard. In the cases that I modified maximum outflow, results showed that freeboard of levee is larger than existed simulation. In the simulation that I applied 200-year floods and PMF to and under a condition connected with PMF, results showed overflowing the levees. Because of the difference between the frequency of dam outflow and the design flood in river, it is required to improve the existed flood plan in the downstream of Andong dam. As a result of this study, the optimal operation of reservoir systems can be proposed to mitigate the flood damage in the downstream of Andong dam and also can be used to establish the flood plans.

• 한국수자원학회논문집
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• 제45권12호
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• pp.1275-1292
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• 2012

본 연구에서는 월파조건에서 직립구조물을 따른 연파특성을 평면수조에서 수리실험을 통해 검토하였으며, 실험에 사용된 파랑은 Bretschneider-Mitsuyasu 주파수 스펙트럼을 가지는 일방향 불규칙파이다. 주된 내용은 상대여유고(R)의 변화에 따른 파고저감을 검토하는 것이며, 월파조건과 비월파조건에서의 파고계측 실험결과를 비교하였다. 상대여유고가 작아질수록 월파의 증대로 인해 상대유의파고는 감소하였으나, 연파 폭의 변화는 거의 나타나지 않았다. 그리고 본 실험조건내에서 상대여유고가 1보다 큰 경우는 월파에 의한 파고저감효과가 거의 없는 것으로 나타났으며, R =0.5인 경우는 R =1.5인 경우에 비해 구조물 전면의 파고가 약 10% 저감되는 것으로 나타났다.

• 한국지반환경공학회 논문집
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• 제18권3호
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• pp.31-38
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• 2017

본 연구의 목적은 지반공학적 물성정보가 거의 없는 국내 중소규모 댐의 지진 시 파괴확률을 간편하게 산정할 수 있는 도표를 제시하는 것이다. 기존의 댐의 지진 시 파괴확률을 산정하는 방법 및 절차를 검토하여, 댐의 지반공학적 물성정보와는 상관없이 지진 시 파괴확률이 '0'이 되는 지진파괴확률 영곡선을 댐높이-여유고율 평면에서 쌍곡선의 형태로 결정하였다. 국내 중소규모 댐들의 댐높이-여유고율 분포형태가 지진파괴확률 영곡선과 같이 쌍곡선의 형태를 이루는 것을 확인하여, 다수의 등파괴확률 곡선(seismic failure probability contour)이 댐높이-여유고율 평면에서 일정한 간격의 다수의 쌍곡선들로 표시되는 지진파괴확률 산정 도표를 작성하였다. 작성된 도표는 비교적 관리가 잘 되고, 지반공학적인 정보를 충분히 가진 2개의 중소규모 댐들의 지진 시 파괴 확률 산정에 적용하여, 기존 절차와 방법으로 산정된 결과와 비교하여 적용 타당성을 확인하였다. 향후, 제안된 도표는 중소규모댐의 지진대비 보수보강의 투자 우선순위 등을 고려할 때 유용하게 활용될 수 있을 것으로 기대된다.