• Journal of Advanced Research in Ocean Engineering
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• 제4권4호
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• pp.146-162
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• 2018

The unsteady problem of a rigid body impact onto a floating plate is studied. Both the plate and the water are at rest before impact. The plate motion is caused by the impact force transmitted to the plate through an elastic layer with viscous damping on the top of the plate. The hydrodynamic force is calculated by using the second-order model of plate impact by Iafrati and Korobkin (2011). The present study is concerned with the deceleration experienced by a rigid body during its collision with a floating object. The problem is studied also by a fully-nonlinear computational-fluid-dynamics method. The elastic layer is treated with a moving body-fitted grid, the impacting body with an immersed boundary method, and a discrete-element method is used for the contact-force model. The presence of the elastic layer between the impacting bod- ies may lead to multiple bouncing of them, if the bodies are relatively light, before their interaction is settled and they continue to penetrate together into the water. The present study is motivated by ship slamming in icy waters, and by the effect of ice conditions on conventional free-fall lifeboats.

• 한국수자원학회논문집
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• 제41권10호
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• pp.1009-1021
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• 2008

본 연구에서는 댐이 하류하천에 미치는 영향권을 산정하기 위하여 수리 수문적, 지형적, 환경 생태적, 사회적 영향의 4개 지표와 38개 항목을 선정하고, 계층분석법을 적용하여 댐의 영향권 산정 지표와 항목의 중요도를 평가하였다. 댐 영향권 산정 지표의 평가결과는 수리 수문적 영향권이 1순위, 환경 생태적 영향권이 2순위, 지형적 영향권 및 사회적 영향권이 각각 3순위와 4순위 이었으며, 항목의 평가결과는 댐설계방류량이 1순위, 하천의 기본 및 계획홍수량이 2순위, 계획홍수량비가 3순위, 유역면적비가 4순위, 하류댐 배수위가 5순위로 평가되었다. 대청댐의 영향권을 산정한 결과, 댐설계방류량 지표는 47.21 km, 하천계획홍수량 지표는 45.71 km, 유역면적비 지표는 13.94 km로 산정되었다.

• 환경영향평가
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• 제23권3호
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• pp.177-186
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• 2014

Depending on the change of lifestyle and the improvement of people's living standards and rapid industrialization, urbanization of recent, demand for water is increasing rapidly. So emissions of domestic wastewater and various industrial waste water has increased, and water quality is worsening day by day. Therefore, in order to provide a measure against the occurrence of water pollution accident, this study was tried to simulate water pollution accident. This study simulated 2008 Gimcheon phenol accident using 1,2-D model, and analyze scenario for prevent of water pollution accident. Consequently the developed 1-D model presents high reappearance when compared with 2-D model, and has been able to obtain results in a short simulation run time. This study will contribute to the water pollution incident response prediction system and water quality analysis in the future.

• 신재생에너지
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• 제4권2호
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• pp.31-38
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• 2008

Using a surplus head in presented water supply pipes, we have studied to improve the operating efficiency of small hydro generator, which was chosen for a test model with 00 hydro power plant. With regard to power control and countermeasure of water hammer impact, Finally we have represented the optimal control method through the synthetical analysis of existing system symptoms, operation efficiency, the effect of water hammer impact and system configuration.

• 한국군사과학기술학회지
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• 제20권4호
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• pp.467-473
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• 2017

In this paper, impact characteristics of a water entry gliding vehicle were analyzed using a finite element method. To guarantee the validity of analysis results, a convergence test was performed for several ratios of Euler and Largrange mesh sizes. The impact coefficient was calculated with respect to entry angles and angle of attacks. It can be observed that the impact coefficient was large at a high cross-section gradient and was also affected by cavitation. This study could be useful in the preliminary design stage of a water entry bomb development.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.877-888
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• 2021

The water entry behaviors of projectiles with different cone-headed angles were studied numerically, experimentally and theoretically, mainly focusing on the hydrodynamic impact in the initial stage. Based on MMALE algorithm, it was proposed a formula of impact deceleration, which relied on the initial entry velocity and cone-headed angle. Meanwhile, in order to verify the validity of the simulation model, experiments using accelerometer and high-speed camera were carried out, and their results were in a good agreement with simulation results. Also, theoretical calculation results of cavity diameter were compared with experiments and simulation results. It was observed that the simulation method had a good reliability, which would make forecast on impact deceleration in an engineering project.

• 한국철도학회논문집
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• 제9권5호
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• pp.524-531
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• 2006

Environmental problem is one of important global issues. Transportations are main pollutant emission sources. Although railroad is stilt an environmental-friendly transportation, its environmental impact has been increased continuously. Especially, because a large amount of environmental impact is released from vehicles and facilities, it is necessary to assess and to reduce their environmental impact. Life cycle assessment (LCA) is a representative method which can evaluate environment impact through the whole life cycle of a product or a process. In this study, the environmental impact of seat in the electric motor unit (EMU) was analyzed quantitatively with its material using lift cycle assessment (LCA). As a result, the characteristics of environmental impact were investigated differently with the material of seat. Among ten impact categories, the seat with aluminum and FRP showed the highest ozone depletion (OD). On the other hand, in the seat with stainless steel and plastic, fresh water aquatic ecotoxicity (FAET) and marine water aquatic ecotoxicity (MAET) were high relatively. Therefore, the parts of EMU must be selected considering the characteristics of environmental impact in future.

• 환경영향평가
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• 제12권2호
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• pp.109-120
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• 2003

This paper examined the impacts of dam construction on fog characteristics over surrounding areas. Juamdam which only supplies the water for use and Chungjudam which generates electricity were selected. The number of foggy days, fog occurrence and dissipation time and the differences of each lake water temperature and air temperature at Sunchun and Chungju were analyzed. After the construction of dam, the relative humidity and water vapor pressure were decreased at Sunchun and Chungju. The number of foggy days did not increase at Sunchun while largely increased at Chungju. Just because Juamdam were contained water, the water vapor pressure at surrounding areas of the weather station were largely decreased. It delayed the time of fog occurrence by bringing out the decrease of steam fog. The foggy days increased over the Chungju area due to the difference between air and cold outlet water temperature. The increase of foggy days mainly resulted from evaporation during colder seasons and from the temperature inversion over the water surface during warmer seasons.

• 환경영향평가
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• 제4권1호
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• pp.9-15
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• 1995

For the purpose of saving the waste disposal cost a self-governing community on the whole reclamates the wetland and uses it as a landfill site. During the operation period of site, the environmental impact by the leachate is usually neglected. Therefore, to predict the environmental impact and dispersion of leachate, the wetland adjacent to the South Han River in Chungju is selected as a site of case study. The main content of this article is to apply the simulation model CONMIG to leachate transfer in the ground water and to derive the impact by the leachate. A kind of non-reacting conservative material, chloride ion is used as a tracer to quantify impacts by the leachate.

• 상하수도학회지
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• 제20권6호
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• pp.919-926
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• 2006

In this study, environmental impact assessments of wastewater treatment plant (WWTP), sewerage system, and tailrace were performed using LCA methodology. The life cycle stages were divided into 3 categories; construction stage, maintenance stage and demolition & disposal stage. As a tool of impact assessment, Ecoindicator99 containing fate analysis, exposure & effect analysis and damage analysis, was used. As tile results of WWTP LCA, more than 80% of environmental impact was produced from maintenance stage. On the other hand, most of environmental impact was produced from construction stage in the case of tailrace and sewerage system construction.