• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.270.2-270.2
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• 2013

직선운동하는 하전입자의 진행방향에 수직한 평면상에 서로 직교하는 전기장과 자기장을 걸어주면, 하전입자에는 전기장에 의한 힘 FE와 자기장과 속도 v에 의한 로렌츠력 $F_B=q(v{\times}B)$가 동시에 작용하게 된다. 이때 Wien 조건 FB=-FE를 만족하는 질량 mA과, 에너지 EA를 가지는 하전입자 A는 휘지 않고 직선운동을 계속하나, 하전입자 A와 다른 에너지 $E_B\;(=E_A+{\delta}E)$나 질량 $m_B\;(=m_A+{\delta}m)$을 가지는 하전입자는 휘게 되며, 그 휘는 정도는 ${\delta}E$나 ${\delta}m$에 비례하게 된다. 이 현상을 이용하여 다양한 종류의 에너지 또는 질량 분석기가 독일, 미국, 일본 등의 분석기기 선진국에서 개발되어 왔고, 전자현미경의 이미지 필터로도 활용되고 있으며, 통상 EXB 필터 또는 발명자의 이름을 딴 Wien 필터로 불리어지고 있다. $E{\times}B$ 필터는 일반적인 하전입자빔 렌즈와 다른 광학특성을 가지며, 지난 발표에서는 $E{\times}B$ 필터의 기본 궤도 방정식 및 다양한 2차 기하 수차 방정식의 유도과정 및 결과를 보여주었다. 본 발표에서는 EXB 필터의 전후에 배치시켜, 초점거리 등의 조정을 수행할 4극자와, $E{\times}B$ 필터에서 발생하는 2차 수차의 보정을 수행할 6극자의 광학특성의 계산 결과를 보여준다. 4극자-6극자-EXB필터-6극자-4극자 조합의 기본 광학궤도 계산 결과는 빔 다이어그램으로 보여준다. 6극자에 의해 수차를 줄여서 향상되는 에너지 분해능 값은 수치적으로 추정한다. 실제 제작이 된 각 부품의 외형 및 사진을 보여주어 에너지 필터의 제작 진행 상황을 보고한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.6
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• pp.653-663
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• 2012

The study considers the high maneuverability flight and path optimization is conducted to investigate the appropriate generation of the lift and thrust considering the angle of the stroke plane. The path optimization problem is defined according to the various purposes of the high maneuverability flight. The flying purposes are to maximize thrust force, lift force and both lift and thrust forces. The flapping motion of the airfoil is made by a combined sinusoidal plunging and pitching motion in each problem. The optimization process is carried out by using well-defined surrogate models. The surrogate model is determined by the results of two-dimensional computational fluid dynamics analysis. The Kriging method is used to make the surrogate model and a genetic algorithm is utilized to optimize the surrogate model. The optimization results show the flapping motions for the high maneuverable flight. The effects on the generation of lift and thrust forces are confirmed by analyzing the vortex.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.10
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• pp.805-815
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• 2015

The present study numerically investigated two-dimensional dielectrophoretic motions of a pair of particles suspended freely in a viscous fluid, interacting with a nearby nonconducting planar wall, under an external uniform electric field. The results show that the motions depend strongly on the set of two electric conductivity signs and the particles-wall separation gap. When both particles have the same sign, they revolve and finally align parallel to the electric field. In contrast, with different signs, they revolve in the opposite direction and finally align perpendicular to the field. Simultaneously, they are repelled to move farther away from the wall regardless of their conductivity set. With further separation from the wall, the particles-wall interaction effect diminishes and tthe particle-particle effect dominates.

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.1
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• pp.16-22
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• 2016

The research on two-wheeled inverted pendulum (TWIP) mobile robots has been ongoing in a number of robotic laboratories around the world. In this paper, we consider a robust controller design for the TWIP mobile robot driving on uniform slopes. We use a 2 degree-of-freedom (DOF) model which is obtained by restricting the spinning motion in a 3 DOF motion dynamic equation. In order to design the robust controller guaranteeing stability of the TWIP mobile robot driving on inclined surface, we propose a sliding mode control based on the theory of variable structure systems and design a sliding surface using the theory of the linear quadratic regulation (LQR). For simulation, the dynamic model of the TWIP mobile robot is constructed using Mathworks' Simulink and the sliding mode control is also implemented using Simulink. From simulation results, we show that the proposed controller effectively controls the TWIP mobile robot driving on slopes.

• Polymer(Korea)
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• v.30 no.4
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• pp.362-366
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• 2006

It was found by polarized FTIR spectroscopic studies that pentacene molecules are arranged with their molecular axes perpendicular to the substrate surface when pentacene films are deposited on a polyimide alignment layer. The ring plane in a pentacene molecule is arranged parallel to the rubbing direction of the polyimide alignment film while no specific arrangement of vertically deposited pentacene molecules was found for the film without rubbing. The pentacene band at $1296cm^{-1}$ which has a transition dipole moment parallel to the ring plane is much stronger in a polarized IR spectrum of parallel to the rubbing direction, whereas the band at $908cm^{-1}$ whose transition dipole align normal to the ring plane shows much stronger intensity in a spectrum of perpendicular to the rubbing direction. These findings indicate that orientation of polyimide chains affects the arrangement of pentacene molecules when they are deposited on a polyimide alignment film.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.4
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• pp.92-98
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• 2006

In this paper, a planar car model with 3 degrees of freedom was analyzed using the concept of the roll center. To avoid ambiguity, force components which require experimental data were excluded. Only kinematic approach was used to find the position and orientation of the vehicle body and the position of the roll center. The roll center was found by the pole with infinitesimal movement and Kennedy-Aronhold theorem. Centrodes, which are the loci of instantaneous centers of planar motion, were constructed with analyzed results to show characteristics of vehicle body motion. To verify the presented analysis method in this paper, the locus of the roll center and the motion of a 3 D.O.F. planar car model were compared with those of the 1 D.O.F. model.

• Journal of Ocean Engineering and Technology
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• v.16 no.6
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• pp.25-31
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• 2002

A system identification method is introduced to increase the prediction accuracy of a ship's maneuverability in PMM test, analysis. To improve the accuracy of linear hydrodynamic coefficients, the analysis techniques of pure sway and yaw tests are developed, and confirmed. In the analysis of sway tests, accuracy to linear hydrodynamic coefficients depends on the frequency of sway motion. To obtain nonlinear hydrodynamic coefficients for large drift angles, a combined yaw test is introduced. Using this system identification method, runs of PMM test can be reduced while retaining sufficient accuracy, compared to the Fourier integration method. Through the comparisons with sea trial results and the Fourier integration method, the accuracy and efficiency of the newly proposed system identification method, based on least square method, has been validated.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.5
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• pp.1649-1656
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• 1991

본 연구에서는 가변구조제어에 의한 조준경 고각 안정화를 모색하였다. 이 를 위해 조준경 고각 안정화 시스템의 운동 방정식을 이용하여 가변구조제어기를 설계 하였으며 방정식을 이용하여 가변구조제어기를 설계하였으며 실제 주행시험결과 측정 된 차량의 각속도를 외란으로 사용하여 컴퓨터 시뮬레이션하여 가변구조제어에 의한 조준경 고각 안정화가 동적안정도를 충족시킴을 보였다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.4 s.97
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• pp.445-451
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• 2005

This paper is the result of a experimental study about non-linear one to one modal coupling of a flexible circular cantilever beam which was transversely excited with harmonic excitation. It was proved that 2 order jumping in out of plane was caused by jump phenomenon in in-plane of flexible circular cantilever beam, because of non-linear coupling. In addition, cantilever beam showed hardening spring characteristics in in-plane and softening spring characteristics in out-of-plane.

• Journal of the Korean Geotechnical Society
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• v.17 no.5
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• pp.17-27
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• 2001

지하 굴착공동의 천장면에 형성되는 잠재적 키블록의 존재성과 운동학적 거동 양상 및 안정성을 해석적으로 분석할 수 있는 시스템을 개발하였다. 천장에서 측정된 절리들의 상대적인 위치와 방향성 자료를 이용하여 데이타베이스를 구축하였으며, 굴착설계도와 연계된 전산절리도를 작성하였다. 잠재적 키블록의 존재성과 거동양상은 사면체로 가정된 블록 옆면의 3차원 공간에서의 평면식을 절리의 방향성에 의거하여 구성하며 대수학적으로 분석되었다. 블록의 안정성 분석은 자중에 의해 미끄러짐이 발생되는 블록면의 공간 기하학적 특성을 고려하여 수행하였다. 개발된 분석시스템의 현장활용성을 검증하기 위하여 언양 자수정동굴에서 키블록 형성 및 거동양상을 조사하여 분석결과와 비교하였다.