• 대한조선학회논문집
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• 제37권2호
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• pp.77-87
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• 2000

항공기나 헬기에서 투하되어 수면으로 입수하는 경어뢰에 작용하는 충격력은 경어뢰 구성부의 손상을 유발시킬 수 있으므로 투하 속도 및 투하 고도를 제한하는 조건이 된다. 따라서, 투하 조건에 따라 입수 충격을 신뢰성 있게 추정할 필요가 있다. 본 연구에서는 선수부 형상에 대한 함수로 입수 충격을 근사적으로 추정할 수 있는 방법을 제시하고, 그 결과를 수치 해석 결과와 비교하여 타당성을 검증하였다. 본 연구에서 제시된 근사화 방법으로 추정한 입수 충격의 크기나 작용시간은 포텐셜 유동이나 점성 유동 해석에 의한 결과들과 비교적 잘 일치하므로 본 연구 결과는 초기 설계 단계에서 안전 발사 영역을 선정하기 위한 기법으로 유용하게 사용될 수 있다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권3호
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• pp.638-651
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• 2014

Main aim of this paper is to find the best combination of numerical schemes for 2-D SPH simulation of wedge water entry. Diffusion term is considered as laminar, turbulent, and artificial viscosity. Density filter that seriously affects the pressure distribution is investigated by adopting no filter, first order filter, and second order filter. Validation of the results indicates that turbulent model and first order density filter can lead to more reasonable solutions. This simulation was then conducted for wedge water entry with wide range of deadrise angles including 10 degrees, 20 degrees, 30 degrees, 45 degrees, 60 degrees and 81 degrees, with extreme deadrise angles of 10 degrees, 60 degrees and 81 degrees being considered. Comparison of SPH results with BEM solutions has displayed favorable agreement. In two particular cases where experimental data are available, the SPH results are shown to be closer to the experiments than BEM solution. While, accuracy of the obtained results for moderate deadrise angles is desirable, numerical findings for very small or very large deadrise angles are also very reasonable.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.518-530
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• 2020

The present study concerns the stern slamming load of container carriers, with stern bulb arrangement variation. First, a series of wedge drop tests were conducted using simple wedge models with fixed deadrise angles, and tests with the cross-section models of practical container carrier sterns were followed. The deadrise angle of the simple wedge ranged from 0° to 10°. The pressure measurement results of the simple wedge drop tests were distributed between empirical formula and analytic solution, so the experimental setup was validated. In the cases of practical hull cross-sections, the water entry of the bulb prior to that of the transom resulted in characteristic water film generation and delayed pressure peak appearance. The trapped air between the bulbs damped the pressure in the twin skeg hull case, reducing the pressure peak and causing the pressure oscillation during water entry.

• 한국측량학회지
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• 제26권2호
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• pp.175-182
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• 2008

지방정부는 자체 관할지역에 위치한 모든 자산들을 공적 업무수행을 통해 보호하고 관리하기 위해 공적문서를 작성할 필요가 있으며, 2007년 1월부터 중앙정부는 복식부기 회계제도를 도입하여 자산 및 채무에 관련된 각종 자산관리보고서를 작성하여 운영할 것을 지자체에 강력히 요구하고 있다. 하지만 지하에 설치된 시설물과 같이 몇몇 시설물들은 정확한 조사가 어려운 실정이다. 이에 본 연구에서는 GIS사업에서 구축한 데이터베이스를 사용하여 복식부기에 근거한 지자체의 사회간접자본시설물의 자산평가를 실시하기 위한 방안을 제시하였다. 경남 거제시의 경우를 분석한 결과, 도로 및 상수도시설물과 같은 시설물에 대해서는 GIS 데이터베이스에 있는 항목의 $70{\sim}80%$는 복식부기에 의한 자산평가에 활용될 수 있음을 알 수 있었다. 그러나 복식부기제도와 GIS사업간의 연계성이 미약한 관계로 향후 지자체에서 복식부기를 실질적으로 사용하기 위한 연구가 더 필요하다고 판단된다.

• Ocean Systems Engineering
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• 제8권2호
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• pp.183-199
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• 2018

The open source software OpenFOAM is utilised to simulate the water entry and hydrodynamic impact process of 2D wedges and ship hull sections. Incompressible multiphase flow solver interDyMFoam is employed to calculate the free fall of structure from air into water using dynamically deforming mesh technique. Both vertical and oblique entry of wedges of various dead-rise angles have been examined. A convergence study of dynamics as well as kinematics of the flow problem is carried out on successively refined meshes. Obtained results are presented and compared to the experimental measurements showing good agreement and reasonable mesh convergence of the solution.

• 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.

• Membrane and Water Treatment
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• 제6권3호
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• pp.237-249
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• 2015

In this study we investigate a laboratory scale vacuum membrane distillation system to produce pure water from model oil in water emulsion. Experimental determination of liquid entry pressure (LEP) of a commercial Durapore$^{TM}$ GVPH flat sheet membrane using model emulsions in various oil concentrations has been carried out. Two different methods of liquid entry pressure determination - a frequently used, so-called static and a novel dynamic method - have been investigated. In case of static method, LEP value was found to be 2.3 bar. No significant effect of oil content on LEP was detected up to 3200 ppm. In contrast, LEP values determined with dynamic method showed strong dependence on the oil concentration of the feed and decreased from 2.0 bar to a spontaneous wetting at 0.2 bar in the range 0-250 ppm, respectively. Vacuum membrane distillation tests were also performed. The separation performance is evaluated in terms of flux behavior, total organic carbon removal and droplet size distribution of the feed and final retentate. No significant effect of oil content on the flux was found ($5.05{\pm}0.31kgm^{-2}h^{-1}$) up to 250 ppm, where a spontaneous wetting occurred. High separation performance was achieved along with the increasing oil concentration between 93.4-97.0%.

• Biomolecules & Therapeutics
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• 제9권2호
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• pp.125-130
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• 2001

Shin-Ki-Hwan (Shen-Qi-Wan, SKH), Bo-Jung-Ik-Ki-Tang (Bu-Zhong-Yi-Qi-Tang, BJIKT), and Sa-Mul-Tang (Si-Wu-Tang, SMT) have been used for various kinds of deficiency syndromes, such as 'yang', 'qi', and 'blood', respectively. The objects of this study were to determine the effects of water extracts of three different kinds of traditional Chinese medicine (TCM), SKH, BJIKT, and SMT, on the anxiolytic activities in the elevated plus-maze test and to clarify the differences among 'yang', 'qi', and 'blood'. The water extracts of SKH, BJIKT, and SMT were orally administered to male SD rats, at 1.0 g/kg for 10 days. All rats were subjected to behavioral tests for the anxiolytic activity at 10 days. SKH, for the benefiting 'yang'agents, significantly increased the ratio of open arms entry to the total arms entry and time spent in the open arms (p<0.05), suggesting anxiolytic effect. However, both BJIKT and SMT decreased the ratio of open arms entry to the total arms entry and increased times spent in the closed arms (p<0.05). From these findings, it can be speculated that SKH only exhibits anxiolytic effect and that the different anxiolytic effects in the elevated plus-maze test may be come from the meanings of 'yang', 'qi', and 'blood'in oriental diagnostics though the cases are restricted.

• 한국군사과학기술학회지
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• 제20권2호
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• pp.217-224
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• 2017

This study proposes an evaluation method for time delay function(TDF) of Point Detonation(PD) fuse using underwater explosion and water entry phenomena. Until now, nothing but the naked eyes of an observer or video images have been used to determine whether the TDF of PD fuze is operated or not. The observer has verified the performance of TDF by analysing the shape of the plume formed by underwater explosion. However, it is very difficult to evaluate the TDF of PD fuse by these conventional methods. In order to overcome this issue, we propose a method using underwater sound signal emitted from the underwater explosion of high explosive charge. The result shows that the measured sound signal is in accord with the physical phenomena of water entry of warhead as well as underwater explosion. Also, from the hypothesis test of bubble period, difference on underwater sound analysis between dud event and delay one is proved.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1998년도 춘계 학술대회논문집
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• pp.190-201
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• 1998

The numerical methodology for computing the impact forces of the water entry bodies has been developed. The present method assumed the impact occurs within a very short time interval and the viscous effects do not have time enough to play a significant role in the impact forces, that is, the flow around a water-entry object was assumed as an inviscid potential flow and is solved by the source panel method. The elements fully submerged into the water are routinely treated, but the elements intersected with the effective planar free surface are redefined and reorganized to be amendable to the source panel method. To validate the present code, it has been applied to disk and ogive model and compared with experimental data. Good agreement has been obtained.