• Journal of computational fluids engineering
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• v.4 no.2
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• pp.39-46
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• 1999

The FVM(Finite Volume Method) have been used mainly for the flow analyses in the piston-cylinder. The objective of the present study is to analyze numerically the piston-driven intake flows using the FEM(Finite Element Method). The FEM algorithm used in this study is 4-step time-splitting method which requires much less execution time and computer storage than the velocity-pressure integrated method and the penalty method. And the explicit Lax-Wendroff scheme is applied to nonlinear convective term in the momentum equations to prevent checkerboard pressure oscillations. Also, the ALE(arbitrary Lagrangian Eulerian) method is adopted for the moving grids. The calculated results show good agreement in comparison with those by the FVM and the experimental results by the LDA.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.434-438
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• 2003

XeCl 엑시머 레이저로 펌핑되는 쌍공진기형 색소레이저와 2단 증폭시스템을 개발하여 원격계측 시스템에 적합한 두 개의 파장을 동시 또는 순차적으로 출력하였다. 개발된 쌍공진기는 1200 g/mm의 회절격자를 갖는 grazing-incidence 방법에서 제 1차 및 제 2차 회절차수를 이용하여 구성되었다. 출력특성은 스펙트럼 선폭이 10 pm이하이고, 펌프 에너지에 대하 전체효율은 6% 이상이다. 또한, 파장가변 영역은 제 1차 및 제 2차의 회절차수에 대해 각각 434-470 nm, 436-468 nm 이며, 2단의 증폭기의 증폭이득은 37dB, 추출효율은 9%이다. 개발된 레이저 증폭시스템에서 Coumarine-450의 색소로 발진하고, 이의 출력 6 mJ을 원격계측시스템에 적용하여 수원상공의 NO$_2$의 가스농도분포를 측정하였다. 이 결과 개발된 색소레이저 시스템은 원격계측 시스템의 광원으로 매우 적합함을 확인하였다.

• 한국전산유체공학회:학술대회논문집
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• 2007.04a
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• pp.8-13
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• 2007

Unsteady flow simulation for the tiltrotor Smart UAV configuration was performed to investigate the powered rotor wake effect on aerodynamic characteristics. Calculations were performed to simulate various flow conditions based on different flight modes including hover, conversion and cruise. Three-dimensional compressible Navier-Stokes equation code were used for flow calculation and Chimera grid technique overlapping individually generated grids was employed. A dynamic grid method was adopted in simulation of the rotating blades. Flow calculations were also conducted for the un-powered case. Aerodynamic interaction between the rotor and airframe was investigated comparing three data sets from the un-powered, powered, and isolated rotor cases.

• Transactions of Materials Processing
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• v.12 no.4
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• pp.401-407
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• 2003

This paper newly proposes a mesh regularization method for the enhancement of the efficiency in sheet metal forming analysis. The regularization method searches for distorted elements with appropriate searching criteria and constructs patches including the elements to be modified. Each patch is then extended to a three-dimensional surface in order to obtain the information of the continuous coordinates. In constructing the surface enclosing each patch, NURBS(Non-Uniform Rational B-Spline) surface is employed to describe a three-dimensional free surface. On the basis of the constructed surface, each node is properly arranged to form unit elements as close as to a square. The state variables calculated from its original mesh geometry are mapped into the new mesh geometry for the next stage or incremental step of a forming analysis. The analysis results with the proposed method are compared to the results from the direct forming analysis without mesh regularization in order to confirm the validity of the method.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.4
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• pp.412-412
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• 1996

To maintain high spacial accuracy and rapid CPU time in interpolating data from grid to random position or inversely in PIV, proposed many technuques are compared and discussed mainly in terms of interpolating error and computing time. And artificial PIV atmosphere data is furnished by CFD result. First, for interpolation from grid to random position, multiquadric method gives the highest accuracy with the longest CPU time and Taylor series expansion methods give reasonable accuracy with less calculating load. Secondly, the sub-pixel resolution analysis in estimating the coordinates of the maximum correlation coefficients essential in the grey level correlation PIV reveal that 8-neighbours 2nd-order least square interpolation gives utmost accuracy in terms of the real flow conditions.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.3
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• pp.62-70
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• 1989

For the conduct of optimum design for such complicated and large structures as ship structure by direct structural analysis such as finite element method, it is very important problem that the process needs much computational efforts due to the repeated structural analysis. In this study, the reanalysis technique based on the modified reduced basis method is applied in the process to reduce the computing time required in repeated structural analysis. Numerical examples to simple grillage and actual ship structure are performed and applicability of reanalysis technique to structural optimization process is discussed.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.8
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• pp.773-780
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• 2015

Navigation in outdoor environments is a fundamental and challenging problem for unmanned ground vehicles. Detecting lane markings or boundaries on the road may be one of the solutions to make navigation easy. However, because of various environments and road conditions, a robust lane detection is difficult. In this paper, we propose a new approach for estimating virtual lanes on a traversable region. Estimating the virtual lanes consist of two steps: (i) we detect virtual road region through road model selection based on traversability at current frame and similarity between the interframe and (ii) we estimate virtual lane using the number of lane on the road and results of previous frame. To improve the detection performance and reduce the searching region of interests, we use a probability map representing the traversability of the outdoor terrain. In addition, by considering both current and previous frame simultaneously, the proposed method estimate more stable virtual lanes. We evaluate the performance of the proposed approach using real data in outdoor environments.

• 한국전산유체공학회:학술대회논문집
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• 2003.08a
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• pp.43-48
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• 2003

When the Eulerian-Lagrangian method is used to analyze the particle laden two-phase flow, a large number of particles should be used to obtain statistically meaningful solutions. Then it takes too much time to track the particles and to average the particle properties in the numerical analysis of two-phase flow. The purpose of this paper is to reduce the computation time by means of a set of particle gird separate to the flow grid. Particle motion equation here is the simplified B-B-O equation, which is integrated to get the particle trajectories. Particle turbulent dispersion, wall collision, and wall roughness effects are considered but the two-way coupling effects between gas and particles are neglected. Particle laden 2-D channel flow is solved and it is shown that the computational efficiency is indeed improved by using the current method

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2006.11a
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• pp.362-365
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• 2006

본 논문에서는 인간 로봇 상호 작용을 위해 정확한 스켈레톤 특징점을 추출하는 강인한 추출기를 설계한다. 제안된 특징점 추출기는 인간의 움직임 정보로부터 얻어진 색상, 윤곽선, 시간차 정보 및 가상 신체 모델을 이용하여 정확한 특징점 위치를 찾아낸다. 또한 특징점 추출에 소요되는 탐색 시간을 줄이기 위해 격자박스를 이용한 원형 탐색 기법을 도입하였다. 최종적으로 기법의 우수성을 확인하기 위해 다양한 동작의 특징점 추출 실험을 수행하였다.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.854-857
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• 1995

We have studied the temperature dependence of the $^{1}H$ NMR spin-lattice relaxation for the impure $CuF_{2}.2H_{2}O$ over a temperature range from 77 K to room temperature. We find that the remperature dependence of the $^{1}H$ spin-lattice relaxation is dominated by the eletron spin-flip and the Raman process of eletron spin-lattice relaxation. The electron spin-flip exchange energy was calculated to be $1.8(\pm0.04)$ K.