• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.220-221
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• 2000

본 연구에서 목표로 하는 집속광학계는 레이저 다이오드의 emitting area가 50$mu extrm{m}$$\times$1.0$\mu\textrm{m}$ 이고 pumping 매질인 crystal의 TE $M_{00}$ mode 발생을 위한 최소 입사빔의 단면도가 단축과 장축의 직경이 각각 206$\mu\textrm{m}$, 204$\mu\textrm{m}$인 타원이어야 하기 때문에 수직 방향으로는 200배 수평 방향으로는 4배의 확대를 할 수 있는 광학계 이어야 한다. 일반적으로 레이저 다이오드용 집속광학계는 레이저다이오드의 수직 수평 emitting area가 다르기 때문에 실린더형, 원통형 또는 toroidal형의 렌즈를 조합하여 구성한다. 그러나 우리의 경우는 emitting area의 수직 수평비 즉 집속광학계의 수직 수평의 굴절능( power )의 비가 50:1 이어야 하기 때문에 그림1과 같은 일반적인 실린더형, 원통형 또는 toroidal형의 렌즈의 조합으로 집속광학계를 구성하기에는, 렌즈 power비를 50:1로 하기 위해 필요로 하는 공간이( 첫번 렌즈와 마지막 렌즈까지의 거리 ) 커지는 점, 필요로 하는 렌즈의 매수가 많아지는 점, 집속 beam의 형상 즉 단면의 이심률이 커져서 pumping에 비효율적이라는 점 등에서, 부적절하다. (중략)략)

• Journal of Drive and Control
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• v.9 no.1
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• pp.18-24
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• 2012

The paper deals with the design of a new low-friction seal for a pneumatic cylinder with high speed actuation. The seal performance with variation of the cross sections in piston seals with elastomeric material was investigated to minimize the friction forces using ABAQUS. The contact stress and strain distributions and frictional forces of the piston seals were investigated with variation of interference fits, supply pressures and friction coefficients. To develop adequate and productive procedures, the finite element models of the piston seals were created and nonlinear analysis of a seal design was conducted in order to build further knowledge and understanding of the seal's performance characteristics.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.2
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• pp.173-178
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• 2015

Laser-assisted machining (LAM) is an effective machining method for processing difficult-to-cut materials. Prediction and estimation of preheating effect of the LAM is difficult because of moving heat source. So it is necessary to study the preheating effect of the laser heat source irradiated on the curved surfaces of workpieces of various shape. In this paper, thermal analysis of the LAM for 3-dimentional workpiece with cylindrical shape was performed. The results of this analysis can be applied to obtain the optimal preheating method and path for LAM of 3-dimensional workpiece.

• Journal of the Korean Society of Visualization
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• v.18 no.2
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• pp.39-45
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• 2020

Problems related with flows around structures are typical in various engineering fields. The characteristics of these flow structures depend strongly on the shape of the body. The flow regime around square cylinders which are also employed in various applications has also been investigated. In addition to a single body, flows past closely spaced structures arranged in tandem are observed in numerous practical applications. In this study, the flow characteristics around the circular and the square cylinder were investigated according to S/D. The velocity fields and Reynolds stress of the single cylinders were acquired to explain the flow behaviors between tandem cylinders. The differences observed in the flow behaviors of square and circular cylinders were studied. The flow patterns around two tandem cylinders can be classified into three types of wake interference behaviors according to S/D. This is related with the flows between cylinders.

• 기계와재료
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• v.25 no.3
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• pp.6-15
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• 2013

유압프레스의 단점을 극복하기 위해서 서보모트를 장착하여 성형속도를 높인 서보 유압프레스를 개발하게 되었으며, 특히나 서보모터를 국내산으로 적용하여 듀얼형으로 유압시스템의 효율성을 높여 최종적으로 개발함으로써 서보 유압프레스를 완전 국산화하였다. 또한 하사점 위치 제어의 용이성을 확보하기 위해 프레스 램용 메인 실린더에 톱니나사부를 만들어 임의의 위치에 정지할 수 있는 정지정도 및 하사점 위치 제어정밀도를 향상시켰으며, 유량의 미세 제어를 통해 프레스 램의 동작성을 개선코자 하였다. 다이쿠션은 메인 실린더와의 연계 제어를 통해 제품의 손상 방지 및 제품 추출의 용이성을 확보하였으며, 소재의 종류나 제품의 형상 특성에 따라 프리모션 제어가 가능한 지식기반형 자율제어 시스템을 적용하였다. 듀얼 서보시스템과 유압펌프가 연계구동함에 따라 기존 유압프레스 보다 약 40%이상의 에너지절감을 달성할 수 있을 것으로 예측되며, 현재 에코머신 인증제도에 대한 논의가 활발한 시점에서 매우 적합하고 필요한 하이브리드형 서보 유압프레스의 국산화 개발 사례라고 하겠다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.11
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• pp.1077-1084
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• 2017

Camshaft engines designed for constant engine loads have been applied to existing marine diesel engines. However, due to environmental regulations, electro-hydraulic servo mechanisms, which have a loaddependent cylinder liner jacket water cooling system (LDCL-JWCS), have been recently developed to individually control the temperature of the cylinders depending on the engine load. In this system, the 3-way valve, which prevents low temperature corrosion by reducing the temperature difference between the upper and lower parts of the cylinder, has been employed, but the outlet mass flow of the existing valve is low. In this study, the design of the internal shape of the 3-way valve was performed by analyzing the effects of the design parameters of the valve shape on the performance (i.e., the outlet mass flow rate and temperature). The proposed model was verified by comparing its performance to that of existing marine diesel engine valves.

• The Journal of the Acoustical Society of Korea
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• v.33 no.5
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• pp.282-290
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• 2014

Though there have been advances in the numerical analysis of the acoustic scattering by smooth objects, numerical analysis of the acoustic scattering by the objects that are partially exposed on the interface are still rare. In determining the backscattering amplitude by a partially buried cylinder on a seabed, reverberation by the interface changes the feature of the scattering form function. Current study adopted the Method of moments (MoM) to provide the numerical analysis on the backscattering amplitude for a partially buried cylinder on a flat interface. Suggested numerical analysis showed the good agreements with the measurements and the analytic solution obtained by the Kirchhoff approximation. Numerical analysis described in the current study can be applied to the backscattering problem of any shape of the objects partially imbedded on a seabed by combining the reverberation from the seabed with the scattered wave from the objects.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.1
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• pp.82-90
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• 2000

An experimental study has been carried out at circulating water channel to investigate the non-breaking and breaking waves generated by a submerged circular cylinder steadily moving under the free surface. Free surface profiles and pressure distributions on cylinder surface were measured at various submerged depths of cylinder. They were complemented by the measurements of velocities, head losses and turbulence intensities in the wakes of body and "breaker". Part 1 of this three-part paper describes the experimental arrangement and the patterns of wave profile and pressure distribution at various depths of submergence. These databank contributions are of special interest in traditional ship hydrodynamics. In Part 2, special focuses are made to elucidate the viscous and turbulent aspects of flow field. Finally Part 3 will deal with the visualization of instantaneous vortical flow to study the mutual interaction between vorticies shedded from the free-surface and the cylinder using a Particle Image Velocimetry.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2424-2429
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• 2015

In an oil hydraulic piston pump, the cylinder block and valve plate in high speed relative sliding motion have the characteristics which should be extremely controlled for the optimization of leakage and friction losses, and pressure-resistance design of them is very important for high pressure performance. But the studies on the stress analysis of those parts have not been performed briskly. Therefore, in this paper, the stress and displacement distributions of the cylinder block and valve plate in the oil hydraulic piston pump with a swash plate type are discussed through the static stress analysis using CATIA V5. The stress and displacement of the cylinder block are more influenced by the axial pressure than by the radial pressure, and are larger by approximately 66% and 30%, respectively. The results show that a review of the material and shape of the valve plate is required.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.31 no.4
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• pp.423-434
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• 1995

It was used boundary element method(BEM) and analysed axisymmetric problem to solve hydraulic cylinder for large vessel acting uniform internal pressure(25N/m super(2)) within elastic limit. This paper was utilized the carbon steel tubes for machine structural purposed model, inner radius was 150mm and outer radius was 250mm, axial length was semi-infinite and the isoparametric element was used. The important results obtained in this study were summarized as follows. Radial, tangential and shearing stress occured the maximum stresses(48, -20 and 34MPa) at the inner radius and the minimum stresses(32, -4 and 18MPa) at the outer radius of the hydraulic cylinder for large vessel. But negative signs have meaning compressive stress and stress diminution ratio was about 0.15MPa/mm. The use of isoparametric element raised accuracy and the increment of input data lessened the error in internal point but computer run-time was increased. The double node was improved the internal solutions to settle discontinuity at corner and the double exponential formula lessened error of stress value at boundary neighborhood. And then coincidence between the analytical and exact results is found to be fairly good, showing that the proposed analytical by BEM is reliable.