• 한국소음진동공학회논문집
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• 제14권3호
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• pp.244-252
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• 2004

The theoretical method is developed to investigate the vibration characteristics for the partially fluid-filled continuous cylindrical shells with the intermediate supports. The intermediate supports are simulated by two types of artificial springs : the translational spring for the translation for each direction and the rotational spring for a rotation. The springs are continuously distributed along the circumferential direction. By allowing the spring stiffness to become very high compared to the stiffness of the structure, the rigid intermediate supports are approximated. In the theoretical procedure, the Love's thin shell theory is adopted to formulate the theoretical model. The frequency equation of the continuous cylindrical shell is derived by the Rayleigh-Ritz approach based on the energy method. Comparison and convergence studies are carried out to verify and establish the appropriate number of series term and the artificial spring stiffness to produce results with an acceptable order of accuracy. The effect of intermediate supports, their positions and fluid level on the natural frequencies and mode shapes are studied.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.743-746
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• 1996

A hybrid control scheme to regulate the force and position by dual arms is proposed, where two arms are treated as one arm in a kinematic viewpoint. Our approach is different from other hybrid control approaches which consider robot dynamics, in the sense that we employ a purely kinematic based approach for hybrid control, with regard to the nature of position-controlled industrial robots. The proposed scheme is applied to sawing task. In the sawing task, the trajectory of the saw grasped by dual arms is planned in an offline fashion. When the trajectory of the saw is planned to follow a line in a horizontal plane, 3 position parameters are to be controlled(i.e, two translational positions and one rotational position). And a certain level of contact force has to be controlled along the vertical direction(i.e., minus z-direction) not to loose the contact with the object to be sawn. Typical feature of sawing task is that the contact position where the force control is to be performed is continuously changing. Therefore, the kinematic mapping between the force controlled position and the joint actuators has to be updated continuously. The effectiveness of the proposed control scheme is experimentally demonstrated. The proposed hybrid control scheme can be applied to arbitrary dual arm systems, regardless of their kinematic structure and the number of actuated joints.

• 전기학회논문지
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• 제64권9호
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• pp.1385-1390
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• 2015

This paper is analysis of multiple factor that should be considered in the design of an eddy current brake used as auxiliary brake system. The eddy current brake is a brake that generates a braking torque in a rotational direction opposite to the direction of the rotor by using a time-varying magnetic flux. The eddy current brake has the advantage of being able to take high current densities because this is used for a short period of time. Also, the eddy current brake is influenced by multiple factor such as number of slots, teeth width, coating thickness, air-gap length and so on. Therefore the eddy current brake was designed for use in railway application in consideration of the operation region and critical parameters.

• 한국항행학회논문지
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• 제16권2호
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• pp.204-210
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• 2012

본 논문에서 우리는 등간격 선형 어레이 (ULA : Uniform Linear Array) MIMO 레이더 시스템에 ESPRIT 알고리즘을 적용하여 전송각과 도래각을 추정하는 방법을 고려한다. 각 추정 성능을 높이기 위한 방안으로 물리적인 안테나 개수를 증가시키는 방법과 정합필터링 후의 스냅샷 수를 증가시키는 방법이 있지만 이러한 방법에는 복잡도 등의 다양한 제약이 따른다. 이에 본 논문에서는 단순히 전송, 수신 안테나 수를 적절히 분배함으로서 성능을 향상시키는 방법을 제안하고자 한다. 특히, 우리는 수신 안테나의 수가 송신 안테나 수의 약 두배가 되었을 때 최적의 성능이 얻어짐을 보인다.

• 한국전자파학회논문지
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• 제10권3호
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• pp.378-391
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• 1999

시간조화 평면파가 손실 매질내에 있는 high-contrast 구형 공동에 입사되었을 때 순방향에서 입사파 진행방향에 대해 수직인 측정면에서 계산된 입사파 분극방향(co-polarized) 총전계 전력을 주파수 평균하여 incoherent shadow 전계 전력패턴을 얻었다. 공동의 incoherent 영상은 구좌표 회전측정구조에서 얻은 incoherent shadow 전계 전력패턴을 역투시하여 얻었다. 비유전율이 2이고 도전율이 0.001, 0.003S/m인 손실매질내에 있는 공기로 채워진 구형 공동의 영상재현으로 이 영상재현법의 타당성을 보였으며, 보다 좋은 영상을 얻기 위한 조건들을 조사했다.

• International Journal of Fluid Machinery and Systems
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• 제3권1호
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• pp.1-10
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• 2010

The present study is a fundamental approach to develop the measuring technology for minute fluctuating pressures on the three-dimensional blade surfaces of the fan which rotates with an arbitrary rotation-axis direction. In this situation, we are required to correct the centrifugal-force effect, the gravitational-force effect and the other leading-error effects for accurate measurements of the minute pressures. The working fluid is air. A pressure transducer rotating with an arbitrary attitude is closely sealed by a twofold shroud system. The rotational motion with an arbitrary attitude is produced by fixing the pressure transducer to the cantilever which is connected to a motor-driven disc of 500mm in diameter and 5mm in thickness. As a result, we have quantitatively determined main governing effects upon the non-effective component of the pressure-transducer signal.

• 천문학회보
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• 제44권1호
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• pp.34.3-34.3
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• 2019

We report our discovery of observational evidence for the coherence between galaxy rotation and the average motion of neighbors. Using the Calar Alto Legacy Integral Field Area (CALIFA) survey data analyzed with the Python CALIFA STARLIGHT Synthesis Organizer (PyCASSO) platform, and the NASA-Sloan Atlas (NSA) catalog, we estimate the angular momentum vectors of 445 CALIFA galaxies and build composite maps of their neighbor galaxies on the parameter space of velocity versus distance. The composite radial profiles of the luminosity-weighted mean velocity of neighbors show striking evidence for dynamical coherence between the rotational direction of the CALIFA galaxies and the average moving direction of their neighbor galaxies. The signal of such dynamical coherence is significant for the neighbors within 800 kpc distance from the CALIFA galaxies with a confidence level of $3.5{\sigma}$, when the angular momentum is measured at the outskirt ($Re<R{\leq}2Re$) of each CALIFA galaxy. We also find that faint or kinematically misaligned galaxies show stronger coherence with neighbor motions than bright or kinematically well-aligned galaxies do. Our results show that the rotation of a galaxy, particularly at its outskirt, may be significantly influenced by recent interactions with its neighbors.

• Journal of Ship and Ocean Technology
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• 제6권3호
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• pp.37-45
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• 2002

A series of detailed study was performed to identify the sources of the propeller blade failure and resolve the problem systematically, by use of the theoretical tools and by the direct measurement and observation in the full-scale sea trials. The selection of inexperienced propulsion control system with a reversible gear system is shown to cause the serious damage to the propeller blades in crash astern maneuver, when the rotational direction of the propeller is changed rapidly. Quasi-steady analysis for propeller blade strength using FEM code in bollard backing condition indicates that the safety factor should be order of 18∼20 to avoid the structural failure for the selected propeller geometry and reduction gear system.

• 한국정밀공학회지
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• 제24권9호
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• pp.76-85
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• 2007

An optical rotary encoder is easy to implement for automatic control applications. In particular, the output of the encoder has a digital form pulse, which is also easy to be connected to a popular digital controller. By using the encoder, there are various angular velocity detecting methods, M-, T-, and M/T-method. Each of them has a property of its own. They have common limitation that the angular velocity detection period is strongly subject to the destination velocity magnitude in case of ultimate low range. They have ultimate long detection period or cannot even detect angular velocity at near zero velocity. This paper proposes a dual encoder system with two encoders of normal resolution. The dual encoder system is able to keep detection period moderately at near zero velocity and even detects zero velocity within nominal period. It is useful for detecting velocity in case of changing rotational direction at which there occurs zero velocity. In this paper, various experimental results are shown for the dual encoder system validity.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.2529-2534
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• 2003

A quadruped walking robot has a superior adaptablility as well as highly adaptable mobility in various environments. These special advantages are outstanding in the mobile robot group. In this work, we introduce the method for omni-directional gait and rotational gait which is the generalized control algorithm to perform any direction commands. In addition, to improve the stability of quadruped walking robot, we performed the optimization between walking angle and sequence of feet. The proposed ideas are applied to the actual design of MRWALLSPECT III(Multifunctional Robot for Wall inSpection version 3) that is designed to inspect of the large surface of industrial utilities. By implementing the proposed idea on the robot, it’s effectiveness is experimentally confirmed.