• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.11
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• pp.1052-1057
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• 2010

Dynamic stability of rotating blade considering gravity effect is investigated in this paper. Equations of motion for the beam is derived by employing hybrid deformation variable method and transformed into dimensionless form. The present modeling method is verified by RecurDyn. Stability diagrams are presented to show the influence of the configuration of the beam and angular velocity on the dynamic stability by applying Floquet's theory. Since the natural frequencies are varied when the blade has rotating motion, it is found that relatively large unstable regions exist approximately 1.1 times as high as the first bending natural frequency and half of the sum of first and second bending natural frequency.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.7
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• pp.662-668
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• 2013

In this paper, possibility of controlling motion of a floating structure using a tuned liquid damper (TLD) is numerically investigated. A TLD is a tank partially filled with liquid. Sloshing motion of liquid inside a tank is known to suppress movement of the tank subject to external excitations at specific frequency. The effects of sloshing phenomena inside a rectangular floating body on its surge motion are investigated by varying external excitation frequency. First, a grid-refinement study is carried out to ensure validity of grid independent numerical solutions using present numerical techniques. Then, surge motion of the floating body subjected to external wave is simulated for five different excitation frequencies of which the center frequency equals to the natural frequency of internal liquid sloshing. The normalized amplitudes of surge motion of the target floating body are compared according to the excitation frequency, for the cases with and without water inside the floating body. It is shown that the motion of the floating body can be minimized by matching the sloshing natural frequency to the excitation frequency.

• East Asian mathematical journal
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• v.24 no.3
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• pp.275-287
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• 2008

In this paper, using large deviation results for Gaussian processes, we establish some functional limit theorems for increments of a fractional Brownian motion in the usual sup-norm via estimating large deviation probabilities for increments of a fractional Brownian motion.

• Reproductive and Developmental Biology
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• v.37 no.1
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• pp.9-16
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• 2013

Artificial insemination (AI) has been performed widely in swine industry using fresh liquid sperm instead of frozen type of sperm. However fresh sperm are not able to preserve more than three days with optimal motility and other sperm parameters for the successful fertilization, since in vitro stored sperm has an oxidative stress that resulted increase of abnormality and acrosome reation. To overcome these major problems, novel preservative formulation is needed to neutralize the oxidative stress and to provide suitable physiological environment for sperm in in vitro. In this study, naturally derived substances such as Poncirus trifoliate (Trifoliate orange), Garcinia mangostana (Mangosteen), pig placenta and testis extracts were tested as sperm preservative agents. Placenta extracts (PE), trifoliate orange extracts (TOE), testes extracts (TE) and mangosteen extracts (ME) were applied to analyze specific parameters for sperm motion characteristics individually and combinatorial. Each individual extract treatment can accelerate the sperm motility but noticeably TOE, TE and ME treatments exhibited the considerable and significant preservation of sperm motility. PE, TE and ME showed a significant (p<0.05) increase in ALH after one week. Further we evaluated the five different combinations of these extracts on sperm motility and its motion characteristics. Surprisingly even after one week ME, TOE and TE combination significantly preserved the sperm motility about 75%. It is noteworthy that unlike individual extract treatment, combination of ME, TOE and TE simultaneously protect the sperm motility and its motion characteristics. Taken together these data conclude that addition of ME, TOE and TE can be effective for preservation of pig sperm.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.3
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• pp.296-303
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• 2014

This paper describes the simplified simulation method of the wire-guided underwater test body with natural supercavitation. In this paper, the simulation based model of the wire-guided underwater body with natural supercavitation is proposed by using preceding research and commercial flow-analysis software. By using the model, the 1-dimensional wire-guided body motion in natural supercavitation can be solved very fast with reliability. The suggested model is validated by the comparison of simulation results with experimental data.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.349-354
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• 2001

A structure which is accelerated in the chordwise direction induces variation of the bending stiffness due to inertia force. Thus, the characteristic of natural vibration is also changed. This paper presents a modeling method for the vibration analysis of translationally accelerated cantilever plates. The dependence of natural frequencies and modes on the acceleration changes of the plate is investigated. Particularly, a natural frequency loci veering is observed and discussed in the present study.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.7 s.94
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• pp.1719-1730
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• 1993

This paper presents the theoretical natural frequencies of out-of-plane deformable ring based on the variables such as out-of-plane deflection, torsional rotation and shear rotation. Based on the same variables, a finite element eigen analysis is carried out by using the $C^0$-continuous, isoparametric element which has three nodes per element and three degrees-of-freedom at each node. Numerical experiments are peformed to find the integration scheme which produces accurate natural frequencies, natural modes and correct rigid body motion. The uniformly reduced integration and the selective reduced integration give more accurate numerical frequencies than the uniformly full integration, but the uniformly reduced integration produces incorrect rigid body motion while selective reduced integration does correct one. Therefore, the ring element based on the three variables which employes selective reduced integration is recommended to avoid spurious modes, to alleviate the error due to shear locking and to produce correct rigid body motion, simultaneously.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.11
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• pp.727-734
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• 2010

The present study numerically investigates the motion of a solid body suspended in the square enclosure with natural convection. A two-dimensional circular cylinder levitated thermally has been simulated by using thermal lattice Boltzmann method(TLBM) with the direct-forcing immersed boundary method. To deal with the ascending, falling or levitation of a circular cylinder in natural convection, the immersed boundary method is expanded and coupled with the TLBM. The circular cylinder is located at the bottom of a square enclosure with no restriction on the motion and freely migrates due to the Boussinesq approximation which is employed for the coupling between the flow and temperature fields. For different density ratio between the cylinder and the fluid, the motion characteristics of the circular cylinder for various Grashof numbers have been carried out. The Prandtl number is fixed as 0.7.

• Journal of Korea Entertainment Industry Association
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• v.14 no.3
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• pp.133-138
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• 2020

Interaction is an important component in the sense of immersion in augmented reality. However, the function of interaction in augmented reality contents is very weak. Bringing a lot of real environmental information is one of the ways to develop augmented reality, and interaction will naturally develop. In this paper, Leap Motion was used for natural interaction in augmented reality environment through the hand widely used as an interface tool, and extended more from the limited interaction of conventional display touch methods to create a natural interaction. This development of interaction will contribute to the development of various contents as well as augmented reality later.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.1
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• pp.10-16
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• 2004

There are a lot of roots of errors in a motion of the optical pick-up actuator being one of the most significantcomponents in a CD-ROM drive. Most of the studios recently performed have a tendency to seek for the causes from an actuator itself. This paper presents dynamic characteristics of an actuator affected by the motion of a feeding deck. The feeding system is modeled as a rigid body with eight degree-of-freedom. Using Largrange's equation, we derive linear equations of motion with respect to the rectangular coordinate. We found that the ranges of the natural frequencies of a feeding deck and the actuator are close to each other. The time responses are also computed by the Newmark method and Runge-Kutta method. The result show that it is important effect to consider feeding deck in modeling and designing an optical pick-up.