• Journal of Ship and Ocean Technology
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• 제12권3호
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• pp.36-54
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• 2008

A jet stream applied tangential to a curved surface in fluid increases lift force by strengthening circulation around the surface and this phenomenon is known as the Coanda effect. Many experimental and numerical studies have been performed on the Coanda effect and the results found to be useful in various fields of aerodynamics. Recently, preliminary studies on Coanda control surface are in progress to look for practical application in marine hydrodynamics since various control surfaces are used to control behaviors of ships and offshore structures. In the present study, the performance of a Coanda control surface with different geometries of the jet injection nozzle was surveyed to assess applicability to ship rudders. A numerical simulation was carried out to study flow characteristics around a section of a horn type rudder subjected to a tangential jet stream. The RANS equations, discretized by a cell-centered finite volume method were used for this computation after verification by comparing to the experimental data available. Special attentions have been given to the sensitivity of the lift performance of a Coanda rudder to the location of the slit (outlet) and intake of the gap between the horn and rudder surface at the various angles of attack. It is found that the location of the water intake is important in enhancing the lift because the gap functions as a conduit of nozzle generating a jet sheet on the rudder surface.

• Ocean Systems Engineering
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• 제6권3호
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• pp.245-264
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• 2016

The iterative boundary element method (IBEM) developed originally before for cavitating two-dimensional (2-D) and three-dimensional (3-D) hydrofoils moving under free surface is modified and applied to the case of 2-D (two-dimensional) airfoils and 3-D (three-dimensional) wings over water. The calculation of the steady-state flow characteristics of an inviscid, incompressible fluid past 2-D airfoils and 3-D wings above free water surface is of practical importance for air-assisted marine vehicles such as some racing boats including catamarans with hydrofoils and WIG (Wing-In-Ground) effect crafts. In the present paper, the effects of free surface both on 2-D airfoils and 3-D wings moving steadily over free water surface are investigated in detail. The iterative numerical method (IBEM) based on the Green's theorem allows separating the airfoil or wing problems and the free surface problem. Both the 2-D airfoil surface (or 3-D wing surface) and the free surface are modeled with constant strength dipole and constant strength source panels. While the kinematic boundary condition is applied on the airfoil surface or on the wing surface, the linearized kinematic-dynamic combined condition is applied on the free surface. The source strengths on the free surface are expressed in terms of perturbation potential by applying the linearized free surface conditions. No radiation condition is enforced for downstream boundary in 2-D airfoil and 3-D wing cases and transverse boundaries in only 3-D wing case. The method is first applied to 2-D NACA0004 airfoil with angle of attack of four degrees to validate the method. The effects of height of 2-D airfoil from free surface and Froude number on lift and drag coefficients are investigated. The method is also applied to NACA0015 airfoil for another validation with experiments in case of ground effect. The lift coefficient with different clearance values are compared with those of experiments. The numerical method is then applied to NACA0012 airfoil with the angle of attack of five degrees and the effects of Froude number and clearance on the lift and drag coefficients are discussed. The method is lastly applied to a rectangular 3-D wing and the effects of Froude number on wing performance have been investigated. The numerical results for wing moving under free surface have also been compared with those of the same wing moving above free surface. It has been found that the free surface can affect the wing performance significantly.

• 대한수의사회지
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• 제8권2호
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• pp.3-16
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• 1964

For the purpose of researching the Erysipelothrix rhusiopathiae(E.r) organisms isolated from fish body surface and pathogenicity of domestic animals, I made practical isolation tests of the E. r. organisms for market fishes(Sea-fishes) at the market, and

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.458-463
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• 1997

In this paper, we propose a variable structure control approach for the system with matched and unmatched uncertainty. By using time-varying sliding mode, the reaching mode is removed, and the design methodology represents a realistic design approach with quadratic criterion for systems incorporating both matched and unmatched uncertainties. The criterion contains states and linear part of input for all time. The practical application of the control strategy is presented in the design of a stability augmentation system for an aircraft is presented.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1993년도 봄 학술발표회 논문집
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• pp.113-118
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• 1993

A method for approximating the failure surfaces for columns in compression and biaxial bending was proposed by using the moments along the line of a diagonal of the section. This method showed the better approximations for the failure surfaces of columns than the method of ACI. To calculate the moments along the line of a diagonal of the section, an approximate method which is not influenced by the number of steel s and the location of inner steels was proposed This method gave satisfactory approximations for practical sections of columns.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1997년도 추계학술대회 논문집
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• pp.196-201
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• 1997

The biggest challenge facing today's manufacturing industry is better quality and high productivit. From an economic point of view, productivity is the most important parameter, as high productivity will reduce the cost. However, the customers of today are not only cost concerned, but also quality conscious. So high accuracy levels should also be achieved in the manufacturing process. The aim of this paper is to get a comprehensive understanding of its machinability properties and to investigate the relationship between cutting conditions and surface roughness for Ball End Mill cutting process so as to enhance its practical application.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2003년도 춘계종합학술대회논문집
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• pp.426-429
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• 2003

본 논문에서는 3차원 물체의 인식을 위한 표면 분류시 그 임계치를 선정하는 방법에 대해 제안하고자 한다. 특히 보다 세밀하고 복잡한 물체의 표현을 위해 사용하여 왔던 평균 곡률과 가우스곡률이 가지고 있던 문제점인 임계치 선정 문제를 통계적 방법에 의해 해결하는 방법을 제안하고자 한다. 끝으로 본 논문의 유용성을 실험에 의해 입증하였다.

• 대한전자공학회논문지
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• 제25권4호
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• pp.407-416
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• 1988

Thick film city gas sensors were fabricated using \ulcornerFe2O3 and \ulcorner-Fe2O3 as raw materials. Their electrical properties and sensitivity characteristics were investigated and the surface conditions for various firing temperatures were analyzed. The fabricated devices exhibited high sensitivity to butane gas(75~80% n 1, 000ppm butane ambient). Also they showed good selectivity and long-term stability. A city gas alarm system using fabricated sensors was made for the practical application.

• 한국철도학회논문집
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• 제4권3호
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• pp.87-93
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• 2001

Characteristics of the local vibration modes of an aluminium extruded panel are investigated by the finite element analysis and modal testing. Practical methods to increase the damping of the local resonances are proposed. Effects by filling urethan foam in the core cavity and by coating tar on the panel surface are compared by experiments. Modified panel structures to shift the local resonance frequency band are proposed. The results of the study are utilized to predict the severe local resonances in the aluminium extruded panels and prevent their undesirable effect on the sound insulation.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 1998년도 가을 학술발표회논문집
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• pp.53-56
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• 1998

Polypyrrole (PPy) is regarded as one of the most Promising intrinsically or naturally conductive polymer for practical applications due to its relatively high electrical conductivity, environmental stability and low toxicity. The typical PPy, which is insoluble and infusible, exhibits poor processability and lacks essential mechanical properties. A number of papers have concerned the efforts to overcome these drawbacks. (omitted)