• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.105-106
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• 2011

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.366-371
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• 2001

Dynamic stability of an oscillating cantilever plate is investigated in this paper. The equations of motion include harmonically oscillating parameters which originate from the motion-induced stiffness variation. Using the multiple scale perturbation method is employed to obtain a stability diagram. The tability diagram shows that relatively large unstable regions exist when the frequency of oscillation is near twice the frequencies of the 1st torsion natural mode and the 1st chordwide bending mode.

• Fashion & Textile Research Journal
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• v.18 no.5
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• pp.685-694
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• 2016

This study investigates the problems of fitness and motion suitability for Korean male military winter jackets (inner and outer) and provides data for new pattern development. We analyzed fitness and motion suitability by a questionnaire survey with 140 Korean male soldiers and a wearing evaluation with 7 subjects of central army male size. A survey of male soldiers indicated that the fitness and motion suitability satisfaction was over 3.0 (Likert scale) for both inner and outer jackets. There were opinions that the sleeve length was short for the inner jacket and the waist girth and hem girth was slightly large for the outer jacket. In the wearing evaluation results with subjects of central army male size, fitness of total length, sleeve length and collar height showed a score lower than 3.0 for the inner jacket and collar height on the outer jacket. The motion suitability result showed a low score (1.0-2.0) in an arm raising motion for the inner jacket and 2.0-3.0 at neck motion in the outer jacket. In conclusion, there is more dissatisfaction in inner jackets than outer jackets. For the inner jacket, sleeve is short, sleeve hem is narrow, collar height is a little high and the sleeve creeps up during arm motion. The waist girth and hem girth was slightly large and collar height was a little high for the outer jacket.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.6
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• pp.348-357
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• 2021

In this paper, the generalized hydrodynamic force and response of a flexible body are calculated at different reference coordinate systems. We generalize the equation of motion for a flexible body by using the conservation of momentum (Mei et al., 2005). To obtain the equations in the generalized mode, two different reference coordinates are adopted. The first is the body-fixed coordinate system by a rigid body motion. The other is the inertial coordinate system which has been adopted for the analysis. Using the perturbation scheme in the weakly-nonlinear assumption, the equations of motion are expanded up to second-order quantities and several second-order forces are obtained. Numerical tests are conducted for the flexible barge model in head waves and the vertical bending is only considered in the hydroelastic responses. The results show that the linear response does not have the difference between the two formulations. On the other hand, second-order quantities have different values for which the rigid body motion is relatively large. However, the total summation of second-order quantities has not shown a large difference at each reference coordinate system.

• Structural Engineering and Mechanics
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• v.11 no.2
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• pp.185-197
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• 2001

This paper presents the effect of axial stretching on large amplitude free vibration of an extensible suspended cable supported at the same level. The model formulation developed in this study is based on the virtual work-energy functional of cables which involves strain energy due to axial stretching and work done by external forces. The difference in the Euler equations between equilibrium and motion states is considered. The resulting equations govern the horizontal and vertical motion of the cables, and are coupled and highly nonlinear. The solution for the nonlinear static equilibrium configuration is determined by the shooting method while the solution for the large amplitude free vibration is obtained by using the second-order central finite difference scheme with time integration. Numerical examples are given to demonstrate the vibration behaviour of extensible suspended cables.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.1
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• pp.105-112
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• 2013

This paper presents the structural design and finite element analysis of precision stage based on a double triangular parallel mechanism for precision positioning and large force generation. Recently, with the acceleration of miniaturization in mobile appliances, the demand for precision aligning and bonding has been increasing. Such processes require both high precision and large force generation, which are difficult to obtain simultaneously. This study aimed at constructing a precision stage that has high precision, long stroke, and large force generation. Actuators were tactically placed and flexure hinges were carefully designed by optimization process to constitute a parallel mechanism with a double triangular configuration. The three actuators in the inner triangle function as an in-plane positioner, whereas the three actuators in the outer triangle as an out-of-plane positioner. Finite element analysis is performed to validate load carrying performances of the developed precision stage.

• Journal of Computing Science and Engineering
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• v.7 no.2
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• pp.122-131
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• 2013

The MPI CyberMotion Simulator provides a unique motion platform, as it features an anthropomorphic robot with a large workspace, combined with an actuated cabin and a linear track for lateral movement. This paper introduces the simulator as a tool for studying human perception, and compares its characteristics to conventional Stewart platforms. Furthermore, an experimental evaluation is presented in which multimodal human control behavior is studied by identifying the visual and vestibular responses of participants in a roll-lateral helicopter hover task. The results show that the simulator motion allows participants to increase tracking performance by changing their control strategy, shifting from reliance on visual error perception to reliance on simulator motion cues. The MPI CyberMotion Simulator has proven to be a state-of-the-art motion simulator for psychophysical research to study humans with various experimental paradigms, ranging from passive perception experiments to active control tasks, such as driving a car or flying a helicopter.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.3
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• pp.137-146
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• 1997

External linkage type spine motion analysis was developed for relative trunk motion respect to the pelvis. A special programs for calculation of the relative angular motion and for graphical display were also developed. The developed device assured its accuracy and conveniency after application to 15 normal vol- unteers. Compare to the normal subjects, 18 patients treated with fixations and decompression surgery showed relatively large coupling motion. Optimal trajectory of the trunk motion derived from mathematical model in flexion and extension matched well with measurement for normal subjects.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.1 s.145
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• pp.15-21
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• 2006

Recently, the attention to large container ships whose size is greater than 10,000 TEU container ship has been increased due to their increasing demand. The large container ship has twin skegs because of the engine capacity and large beam-draft ratio. In this paper, the maneuvering characteristics of a container ship with twin skegs were investigated through 4DOF(four degree of freedom) HPMM(Horizontal Planar Motion Mechanism) test and computer simulation. A mathematical model for maneuvering motion with 4DOF of twin skegs system was established to include effects of roll motion on the maneuvering motion. And to obtain roll-coupling hydrodynamic coefficients of a container ship, 4DOF HPMM system of MOERI which has a roll moment measurement system was used. HPMM tests were carried out for a 12,000 TEU class container ship with twin skegs at scantling load condition. Using the hydrodynamic coefficients obtained, simulations were made to predict the maneuvering motion. Rudder forces of twin-rudders were measured at the angles of drift and rudder. The neutral rudder angles with drift angles of ship was quite different with those of single skeg ship. So other treatment of flow straightening coefficient $\gamma_R$ was used and the simulation results was compared with general simulation result. The treatment of experimental result at static drift and rudder test was very important to predict the maneuverability of a container ship with twin skegs.

• ETRI Journal
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• v.23 no.4
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• pp.190-198
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• 2001

The performance of Motion Compensated Discrete Cosine Transform (MC-DCT) video coding is improved by using the region adaptive subband image coding [18]. On the assumption that the video is acquired from the camera on a moving platform and the distance between the camera and the scene is large enough, both the motion of camera and the motion of moving objects in a frame are compensated. For the compensation of camera motion, a feature matching algorithm is employed. Several feature points extracted using a Sobel operator are used to compensate the camera motion of translation, rotation, and zoom. The illumination change between frames is also compensated. Motion compensated frame differences are divided into three regions called stationary background, moving objects, and newly emerging areas each of which is arbitrarily shaped. Different quantizers are used for different regions. Compared to the conventional MC-DCT video coding using block matching algorithm, our video coding scheme shows about 1.0-dB improvements on average for the experimental video samples.