• 대한조선학회지
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• 제13권1호
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• pp.11-16
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• 1976

The effect of the bow shape on the ship motion response in longitudinal regular waves of water of finite depth is investigated by employing the strip theory. The two-dimensional hydrodynamic forces(added mass and damping) were calculated by close-fit method for water of finite depth. The models for investigation are U and V bow ship forms of block coefficient 0.8 with constant after body which were used by Yourkov [2] and recently by Kim [3] for their deep water investigations. The following results are obtained by the present numerical experiments. (1) It is confirmed that the damping coefficient of the V-bow ship is greater than that of U-bow ship and in consquence the amplitude of heave and pitch of V-bow ship is smaller than that of U-bow ship among longitudinal regular head waves in water of finite depth (2) The merit of the V-bow ship on the motion damping is more significant in heave than in pitch, and is decreasing with the shallowness of water depth. (3) The change of bow form gives little effect on the wave exciting force and moment compared with the motion responce.

• 대한조선학회지
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• 제24권4호
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• pp.9-18
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• 1987

The hydrodynamic radiation forces acting on a ship travelling in waves have been conventionally treated by strip theories or by direct three dimensional approaches, most of which have been formulated in frequency domain. If the forward speed of a ship varies with time, or if its path is not a straight line, conventional frequency domain analysis can no more be used, and for these cases time domain analysis may be used. In this paper, formulations are made in time domain with applications to some problems the results of which are known in frequency domain. And the results of both domains are compared to show the characteristics and validity of time domain solutions. The radiation forces acting on a three dimensional body within the framework of a linear theory. If the linearity of entire system is assumed, radiation forces due to arbitrary ship motions can be expressed by the convolution integral of the arbitrary motion velocity and the so called impulse response function. Numerical calculations are done for some bodies of simple shapes and Series-60[$C_B=0.7$] ship model. For all cases, integral equation techniques with transient Green's function are used, and velocity or acceleration potentials are obtained as the solution of the integral equations. In liner systems, time domain solutions are related with frequency domain solutions by Fourier transform. Therefore time domain solutions are Fourier transformed by suitable relations and the results are compared with various frequency domain solutions, which show good agreements.

• 한국해양공학회지
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• 제26권6호
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• pp.39-45
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• 2012

Underwater robots are generally used for the construction of seabed structures, deep-sea ecosystem research, ocean energy development, etc. A ducted marine propulsor is widely used for the thruster of an underwater robot because of its collision protection, efficiency increase, cavitation reduction, etc. However, the flow of a ducted propeller is very complex because it involves strong flow interactions between the blade impeller and duct. The present work aimed to design a ducted propeller using 2-D strip theory and CFD analysis. The hydrodynamic forces (i.e. and ) were computed to set the local angle of attack in a spanwise direction of the propeller blade. After the propeller design, performance coefficients such as the thrust, torque, and efficiency were computed to check whether the designed performance was achieved. To validate the present analysis, the thrust was compared with experimental data and good agreement was obtained.

• 대한조선학회지
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• 제12권1호
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• pp.47-58
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• 1975

The effect of the bow shape on the ship motion response among longitudinal regular waves, is investigated employing the strip theory. The two dimensional hydrodynamic forces such as added mass and damping are calculated by the integral equation method for arbitrary sections. Nine ship models are selected for investigation. They are U, UV and V bow ship forms of different block coefficient of 0.6, 0.7 and 0.8 with constant after body. The heave amplitude of the V bow ship is smaller than that of the U bow ship in the whole range of wave length except extremely short wave as were stated by the earlier investigators. This results holds also in the case of bow vertical motions such as vertical relative displacement, velocity and acceralation. As to the pitch amplitudes, the V bow ship gives smaller value in long waves but larger value in short waves. However, heave and pitch phase angles are practically not influenced by the form of the fore body sections. In the bow motions, a little difference in phase angle is appeared in the vicinity of the wave which has same ship length. With respect to the wave exiting force and moment unfovourable effects could be expected in V bow ships. And these tendency hold also in the wave bending moment.

• 한국구조물진단유지관리공학회 논문집
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• 제3권2호
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• pp.199-204
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• 1999

최근에 복합재료는 콘크리트, 집성보와 같은 기존의 구조재를 보강하여 성능을 향상시킬 목적으로 적용되고 있다. 특히, 대규모의 집성보 구조물은 춤이 큰 부재를 필요로 하는데 섬유보강판을 이용하여 보의 상하부를 보강하면 춤을 크게 하지 않고도 보의 강도와 강성을 증가시킬 수 있다. 본 연구에서는 집성보에 유리섬유보강 플라스틱판(GFRP)을 붙여 스팬 중앙에 집중하중을 가한 휨실험을 수행하였고 실험결과를 층간이론을 이용한 수치해석법과 비교하였다.

• 대한조선학회논문집
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• 제29권4호
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• pp.152-172
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• 1992

대파고 파랑중을 항해하는 선박은 큰 선체 운동으로 인하여 수면하 단면 형상이 시시각각 크게 변하므로 자유 표면 조건, 물체 표면 조건의 비선형성에 의한 비선형 유체력의 영향이 무시될 수 없게 된다. 경우에 따라서는 선저가 파면으로부터 충격력을 받는 슬래밍 현상과 선수가 파도를 뒤집어 쓰는 청파 현상등과 같은 충격적 유체력이 선체에 가해지는 등 복잡한 문제가 발생하게 된다. 본 연구에서는 선체를 가변 단면보의 탄성체로 이상화하여 파랑중 선체 거동을 박육 단면보 이론에 의해 정식화하고 파랑 하중으로는 수면하 단면 형상 변화에 따른 비선형 유체력과 momentum slamming이론을 이용한 유체 충격력을 고려하여 대파고 파랑 중 탄성체인 선체의 응답을 추정하는 해석 기법을 개발하여 이를 기존의 실험결과와 비교 그 타당성을 확인하고, 이의 응용으로 본 기법에 의하여 4만톤급 정유 운반선에 적용하여 정면파 및 사파중에서 파고, 파장, 선속을 파라미터로 한 수치 계산을 수행하고 여러가지 파라미터 변화에 대한 선체 구조의 동적 강도 응답 특성을 계통적으로 분석하여 보았다. 본 연구에서 개발된 동적강도 해석법은 대파고 중에서 유체력의 비선형성 및 유체 충격력까지 고려한 해석기법이므로 신구조 방식 선박에 대한 직접 설계법의 확립 뿐만 아니라 슬래밍 등에 의한 선체 절손 사고의 원인 규명에도 유용하게 적용할 수 있을 것으로 사료된다.

• 만화애니메이션 연구
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• 통권29호
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• pp.173-207
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• 2012

긴 이야기구조의 기승전결인 네 국면의 플롯은 패턴화 되어 도식화된 경향이 있다. 인물의 행동에는 인류의 시작과 궤를 같이 하게 되는데 장편연재만화 플롯은 기본적으로 4국면이지만, 단순 배열이 아닌 인류의 추진력이나 행동과 느낌의 패턴을 정리하여 개발한 복잡 배열이다. 이 연구는 만화전문대학생 설문과 답변으로 결과지를 얻은 후, 통합적으로 추출된 장편연재만화작품의 설문 자료를 통하여 장편연재만화 아리스토텔레스 이론인 플롯의 국면, 네 단계와 캐롤 피어슨의 인물원형이론을 통한 4개의 인물의 유형화, 조셉 캠벨의 영웅의 여정이론을 네 단계로 유형화한다. 복잡한 장편연재만화의 이야기 구조가 가진 요소 중 하나인, 인물이 겪는 삶의 과정을 제시하여 간략성과 체계적 기술을 통해 유형화하는 이 연구는 결국 만화작가가 장편연재만화의 복잡하고 긴 이야기의 구조에서 은유하는 것은 무엇인가를 밝히고자함이다. 아리스토텔레스의 플롯이론을 근거로 하는 도입, 발전, 전개 결말구조의 의미가 인류의 삶과 운명의 메타포이며, 융 이론에 영향 받은 융 연구가 캐롤 피어슨의 인물 원형론의 성장단계가 인류의 삶과 운명의 메타포임을, 역시 융 이론에 영향 받은 인류학자 조셉 캠벨 이론들은 희노애락의 복합감정을 영웅원형에 투사하여 영웅의 여정이란 은유를 통해 인류의 삶과 운명의 메타포임을 밝히고 있다. 최종적으로, 제기된 이론들은 크리스토퍼 보글러의 저서에 작가의 '시나리오작성법'으로 접근하여 소개되고 있다. 한편으로 이 메타포는 이 연구목표이자 목적이기도 하다. 연구에서 추출된 장편연재만화는 긴 이야기가 복잡하고 얽힌 듯이 보여도 인물이 집을 떠나 모험과 난관을 겪고 세계와의 또 다른 만남을 통해 거부와 갈등, 그리고 경쟁과 전쟁, 시련을 겪으며 보상을 얻어 귀환하는 여정의 과정 중 정신적, 심리적, 상징적 성장으로 결국, 영웅으로 획득되며 만화라는 이미지를 통하여 우리의 내면 성찰에 대한 의미 부여를 플롯에 의해 서사적으로 표현하고 있다. 복잡해보이지만 장편연재만화이야기의 기본구조가 플롯 4단계이며 장편연재만화작품에서 범상치 않은 인물이 여행과 모험을 떠나는 과정에서 성장하는 삶의 방식을 크게 나누어 볼 때, 네 단계의 영유아동기, 청년기, 중년기, 말년기의 상징성을 지닌 심리적 성장과정이며, 인물이 유형화된 특성도 크게 네 단계의 부류로 나누어 성장과정을 설명할 수 있게 한다. 성장할 인물의 표상화인 영웅의 여정, 역시 크게 네 단계의 여정으로 압축되어 설명된다. 즉 이론을 통하여 만화의 4국면의 플롯의 복잡 배열은 삶의 순서를 통한 성장구조의 진행과의 흐름이 일치한다는 것을 발견하였다. 동시에 인물이 영웅으로 거듭나는 성찰의 메타포이며 장편연재만화작가들의 작품을 통하여 인생국면 4단계인 인물의 성장과 삶을 통찰하는 은유를 발견하였다. 만화작가가 의도하는 장편연재만화작품의 긴 이야기란, 플롯의 논리적구성법에 의해 인물이 여정을 떠나 역경과 어려움을 겪으며 삶이 변화되고 그의 성장과정은 유형화된 이미지로 제시하여 성찰에 도달함을 영웅적으로 표현하는 것이며, 독자는 삶과 인생에서 만화이야기의 이미지의 시공간을 공유하는 동시에 감동을 통하여 정서상 인물과 같은 체험을 하게 되었음을 인식하게 한다.

• International Journal of Aeronautical and Space Sciences
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• 제14권1호
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• pp.30-45
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• 2013

The present work focuses on the unsteady aerodynamics and aeroelastic properties of a small-medium sized wind-turbine blade operating under ideal conditions. A tapered/twisted blade representative of commercial blades used in an experiment setup at the National Renewable Energy Laboratory is considered. The aerodynamic loads are computed using Computational Fluid Dynamics (CFD) techniques. For this purpose, FLUENT$^{(R)}$, a commercial finite-volume code that solves the Navier-Stokes and the Reynolds-Averaged Navier-Stokes (RANS) equations, is used. Turbulence effects in the 2D simulations are modeled using the Wilcox k-w model for validation of the CFD approach. For the 3D aerodynamic simulations, in a first approximation, and considering that the intent is to present a methodology and workflow philosophy more than highly accurate turbulent simulations, the unsteady laminar Navier-Stokes equations were used to determine the unsteady loads acting on the blades. Five different blade pitch angles were considered and their aerodynamic performance compared. The structural dynamics of the flexible wind-turbine blade undergoing significant elastic displacements has been described by a nonlinear flap-lag-torsion slender-beam differential model. The aerodynamic quasi-steady forcing terms needed for the aeroelastic governing equations have been predicted through a strip-theory based on a simple 2D model, and the pertinent aerodynamic coefficients and the distribution over the blade span of the induced velocity derived using CFD. The resulting unsteady hub loads are achieved by a first space integration of the aeroelastic equations by applying the Galerkin's approach and by a time integration using a harmonic balance scheme. Comparison among two- and three- dimensional computations for the unsteady aerodynamic load, the flap, lag and torsional deflections, forces and moments are presented in the paper. Results, discussions and pertinent conclusions are outlined.

• KSBB Journal
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• 제13권5호
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• pp.502-510
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• 1998

Stabilization of antibody, which is specific to Salmonella typhimurium antigens, present in dry states on membranes was accomplished, and its shelf-life, i.e., duration for maintaining minimum 90% of the initial activity, under optimal conditions was determined. To prepare two major components of an immuno-strip, the antibody was not only immobilized on nitrocellulose membrane surfaces but also placed within the pores of glass fiber membrane after conjugating it with old colloids as signal generator. Among potential stabilizers of the immuno-components, a disaccharide, trehalose, showed a significant protection effect of immunoglobulin structure from thermal energy. Optimal concentrations of trehalose for the respective component were significantly different (8-fold higher for the antibody-gold conjugate than for the immobilized antibody), which probably resulted from distinct densities and configurations of antibody present on the membranes. An additional requirement for the gold conjugate was freeze-drying of this substance such that the conjugate can be readily resolubilized upon contact with aqueous medium. By using the components prepared under optimal conditions, immuno-strips were constructed and exposed to thermal energy. Signals with less than 10% decrease in the intensity were maintained for approximately 21 days at 60$^{\circ}C$. Compared to previous reports, this result represented a 2-year shelf-life at room temperature. it was, however, two times longer if determined from thermal acceleration tests based on the theory of inactivation rate of protein. Such discrepancy between the two estimates could be mainly attributed to errors in accurately controlling temperatures and also to changes in the physical properties of membranes due to a high thermal energy.

• 한국환경복원기술학회지
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• 제6권3호
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• pp.17-28
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• 2003

The objective of this study is to review and verify whether the functions and effect of roadside trees generally known in theory are actually realized in urban roads and how well they are performed if the function and effect are really realized. The study was conducted with a focus on air purification effect of roadside trees. The m헤r study result is as follows. First, calculation of air purification effect of roadside trees showed that it is minimal. However, 7.4 units of broad-leaved trees is necessary in order to purify $SO_2$ discharged by one passenger car and 1,803.3 trees to purify $NO_2$. Second, regarding pollutant absorption capacity, air pollutant absorption capacity increased as the number of rows planted gets higher (i.e., 2-row plantation absorbs pollutant better than I-row plantation). In particular, "2-row plantation + lower-level shrub + buffer green belt" was as eight times high as "I-row plantation" in absorption capacity. Third, out of 30 roads with over 8 lanes in 15 cities, only 33.3% or a total of ten roads in seven cities had a median strip. Out of these ten roads, nine roads were planted in a double-layer consisting forest trees, shrubs, ground plants (grass). Analysis showed that out of six tree species planted along these roads, about a half of them were weak to air pollution. Also, based on the outcome of this study, charging a "plantation due" when people purchase a new car, improving layout of roadside trees, and reinforcing plantation of air purification tree species when selecting tree species for roadside trees were proposed.