On the Hydrodynamic Forces Acting on a Partially Submerged Bag

Lee, Gyeong-Joong The Society of Naval Architects of Korea 1994 Selected papers of the society of naval architects Vol.2 No.1

The hydrodynamic problem is treated here when a pressurized bag is submerged partially in the water and the end points of it oscillate. SES(Surface Effect Ship) has a bag filled with pressurized air at the stern in order to prevent the air leakage, and the pitch motion of SES is largely affected by the hydrodynamic force of the bag. The shape of a bag can be determined with the pressure difference between inside and outside. Once the hydrodynamic pressure is given, the shape of a bag can be obtained, however in order to calculate the hydrodynamic pressure we should know the shape change of the bag, and vice versa. Therefore the type of boundary condition on the surface of a bag is a moving boundary like a free surface boundary. The present paper describes the formulation of this problem and treats a linearized problem. The computations of the radiation problem for an oscillating bag are shown in comparison with the case that the bag is treated as a rigid body. The hydrodynamic forces are calculated for various values of the pressure inside the bag and the submerged depth.

Self-similarity in the equation of motion of a ship

Lee, Gyeong Joong The Society of Naval Architects of Korea 2014 International Journal of Naval Architecture and Oc Vol.6 No.2

If we want to analyze the motion of a body in fluid, we should use rigid-body dynamics and fluid dynamics together. Even if the rigid-body and fluid dynamics are each self-consistent, there arises the problem of self-similar structure in the equation of motion when the two dynamics are coupled with each other. When the added mass is greater than the mass of a body, the calculated motion is divergent because of its self-similar structure. This study showed that the above problem is an inherent problem. This problem of self-similar structure may arise in the equation of motion in which the fluid dynamic forces are treated as external forces on the right hand side of the equation. A reconfiguration technique for the equation of motion using pseudo-added-mass was proposed to resolve the self-similar structure problem; specifically for the case when the fluid force is expressed by integration of the fluid pressure.

Effects of Air Compressibility on the Hydrodynamic Forces of a Bag

Lee, Gyeong-Joong The Society of Naval Architects of Korea 1995 Journal of hydrospace technology Vol.1 No.1

The hydrodynamic problem when the pressurized bag submerges partially into water and oscillates was formulated by Lee(1992), and the solution method was given, In his formulation, however, the compressilbility of air was neglected and the pressure inside the bag was assumed to be constant. In this paper, the formulation was done including the air compressibility and the wall to block fling around phenomenon. The compression process was assumed to be a isothermal process for a static problem, isentropic process for a dynamic problem. And the stability was analyzed for the static problem. Through the various numerical calculations, the forces and the shape of the bag were compared with those of a rigid body case, constant pressure case, and variable pressure case.

Moment of inertia of liquid in a tank

Lee, Gyeong Joong The Society of Naval Architects of Korea 2014 International Journal of Naval Architecture and Oc Vol.6 No.1

In this study, the inertial properties of fully filled liquid in a tank were studied based on the potential theory. The analytic solution was obtained for the rectangular tank, and the numerical solutions using Green's 2nd identity were obtained for other shapes. The inertia of liquid behaves like solid in recti-linear acceleration. But under rotational acceleration, the moment of inertia of liquid becomes small compared to that of solid. The shapes of tank investigated in this study were ellipse, rectangle, hexagon, and octagon with various aspect ratios. The numerical solutions were compared with analytic solution, and an ad hoc semi-analytical approximate formula is proposed herein and this formula gives very good predictions for the moment of inertia of the liquid in a tank of several different geometrical shapes. The results of this study will be useful in analyzing of the motion of LNG/LPG tanker, liquid cargo ship, and damaged ship.

A Deformation Model of a Bag-Finger Skirt and the Motion Response of an ACV in Waves

Lee, Gyeong-Joong,Rhee, Key-Pyo The Society of Naval Architects of Korea 1994 Selected papers of the society of naval architects Vol.2 No.1

In this paper, the effect of a skirt deformation on the responses of an Air Cushion Vehicle in waves is investigated. The air in the bag and plenum chamber is assumed to be compressible and to have a uniform pressure distribution in each volume. The free surface deformation is determined in the framework of a linear potential theory by replacing the cushion pressure with the pressure patch which is oscillating and translating uniformly. And the bag-finger skirt assumed to be deformed due to the pressure disturbance while its surface area remained constant. The restoring force and moment due to the deformation of bag-finger skirt from equilibrium shape is incorporated with the equations of heave and pitch motions. The numerical results of motion responses due to various ratios of the bag and cushion pressure or bag-to-finger depth ratios are shown.

산적화물선 운항성능 분석을 위한 선속, 파고 및 풍속 자료의 유효성 분석

이경중(Gyeong-Joong Lee),신명수(Myung-Soo Shin),박범진(Beom-Jin Park),기민석(Min-Suk Ki),전경환(Kyung-Hwan Jeon) 한국마린엔지니어링학회 2019 한국마린엔지니어링학회지 Vol.43 No.3

Flanders 언어상호작용 분석법을 적용한 수학 교과 수업 분석

이윤경(Yoon-Gyeong LEE),이중권(Joong-Kweon LEE) 한국수산해양교육학회 2014 水産海洋敎育硏究 Vol.26 No.4

전기비저항 및 시추 ‧ 검층자료의 상관해석을 통한 소규모 산사태 지역의 지질 연약대 파악

이선중 ( Sun-joong Lee ),강유경 ( Yu-gyeong Kang ),이철희 ( Cheol-hee Lee ),전수인 ( Su-in Jeon ),김지수 ( Ji-soo Kim ) 대한지질공학회 2020 지질공학 Vol.30 No.1

2014년 충남 태안 신진도리의 해안지역에서 일어난 작은 산사태 지역의 지하구조를 파악하기 위하여 전기비저항 및 하향식 탄성파탐사와 시추 · 물리검층을 실시하였다. 시추 · 검층자료에서 산사태 발생지역의 상부에 위치한 시추공 BH-2의 5~7 m 깊이에서 N값이 현저히 낮아지는 것을 확인하여 하향식 탄성파탐사를 추가 실시하고 이 깊이에서 지질 연약대가 연장되는 것으로 가정하여 하부의 시추공 BH-1 지점까지 전기비저항 탐사를 실시하였다. 8 m 내외의 두께를 갖는 150 Ω · m 이하의 저비저항 이상대는 시추 · 검층자료에서 해석된 세립 실트질 점토로 이루어진 풍화토층과 잘 상관되었다. 시추공 BH-2에 걸쳐있는 지질 연약대는 시추공 BH-1에 비해 상대적으로 작은 밀도 1.6~1.8 g/cm³와 150 Ω · m 이하의 비교적 낮은 전기비저항로 나타나며 포아송 비는 깊이에 따라 그 편차가 크게 나타난다. 이 지역의 산사태는 초과 강수와 이로 인한 상승 지하수면의 영향으로 물을 함유한 실트질 점토를 많이 포함하고 있는 풍화토가 전단력이 감소되어 미끄럼 활동으로 나타난 것으로 해석하였다. Electrical resistivity and downhole seismic surveys were conducted together with bore investigations and well-logging to examine subsurface structures in small-scale landslides at Sinjindo-ri, Geunheung-myeon, Taean-gun, Chungcheongnam-do, Republic of Korea in 2014. On the basis of the low N-values at depths of 5~7 m in borehole BH-2, downhole seismic and electrical dipole-dipole resistivity surveys were performed to delineate geological weak zones. The low-resistivity zones (<150 Ω · m) measure ~8 m in thickness and show a close depth correspondence to weathered soils consisting mainly of silty clays as identified from the bore investigations and well-logging data. Compared with weak zones in borehole BH-1, weak zones in BH-2 are characterized by lower densities (1.6~1.8 g/cm³) and resistivities (<150 Ω · m) and greater variation in Poisson’s ratio. These observations can be explained by the presence of wet silty clays rich in weathered soil material that have resulted from heavy rainfall and rises in groundwater level. Downslope movements are probably caused by the sliding of wet clay that acts to reduce the strength of the weathered soil.

Flanders 언어상호작용 분석법을 활용한 수학영재 수업 분석

이윤경(Yoon-Gyeong Lee),이중권(Joong-Kweon Lee) 한국콘텐츠학회 2014 한국콘텐츠학회논문지 Vol.14 No.5

본 연구는 Flanders 언어상호작용 분석법을 활용하여 대학부설영재원 수학영재 수업에서 교수-학생 간의 언어적 상호작용을 분석한다. 연구문제는 수학영재 수업의 1)Flanders 코드 항목별 결과는 어떠한가? 2)언어형태는 어떠한가? 3)Flanders 지수결과는 어떠한가? 연구대상은 대학부설 영재교육원 중등 수학반 수업이며, 수업과정을 비디오 녹화한 동영상을 AF분석 프로그램 3.54를 활용하여 분석한 결과 1)Flanders코드 항목별 분석결과, 교사의 비지시적 발언보다 지시적 발언이, 학생의 반응적인 발언보다 자진적인 발언이 많은 것으로 나타났고, 분류 항목별 빈도수는 강의, 학생의 자진적인 말, 활동 등이 전체수업의 대부분을 차지하였다. 2)수업 흐름은 대체적으로 바람직한 수업 흐름 모델을 따르지 않는 것으로 나타나, 학생 발언에 대한 교사의 적절한 피드백이 요구된다. 3)지수 분석 결과, 수정 비지시, 교사 질문비, 학생 발언비, 학생 질문 및 넓은 답변비는 분석기준보다 높게 나타났고, 비지시는 분석 기준보다 낮게 나타났다. The purpose of this study is to provide useful information for improving interaction between teacher and student by analysing gifted class in mathematics with the Flanders Category System. Research questions are as follow. In gifted class in mathematics, How is the result of analysis regarding interactions between the teacher and students, according to 1) Flanders Coding system? 2) Flanders’ language pattern? 3) Flanders’ Index system? For this, 3 gifted classes in mathematics were recorded by video camera and analyzed by Advanced Flanders (AF) analysis program version 3.54. Results are as follow. 1) Code Category Analysis mostly consists of lecture, voluntary speaking and chaos, silence work. 2) Most class patterns are not in accordance with effective class pattern models. So teacher needs to accept students opinion actively and give appropriate feedback. 3) In Indices Results, revised I/d ratio, teachers question ratio, students speaking ratio, Student question and wide answer ratio are higher than analysis standard, indirect ratio is lower than analysis standard.

내시경적 조기 진단으로 내과적 치료에 성공한 급성 봉소염성 위염

이대환,이옥재,정운태,이경원,정기욱,강석진,김훈구,조중현 대한소화기내시경학회 2001 Clinical Endoscopy Vol.23 No.4

Phlegmonous gastritis is a rare disorder caused by suppurative bacterial infection of the gastric wall. The mortality rate remains extremely high and the gastrectomy has been thought to be an effective form of treatment. We report a case of acute phlegmonous gastritis developed in a patient with advanced alcoholic liver cirrhosis, and recovered with early endoscopic diagnosis and antibiotics alone.