• Bulletin of the Society of Naval Architects of Korea
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• v.23 no.2
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• pp.21-26
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• 1986

An analysis is made of hydrodynamic forces acting horizontally on a two-dimensional cylinder, when it is exposed to incident waves and consequently undergoes a swaying motion in shallow water. Applying the method of matched asymptotic expansions the added mass, wave damping and the wave exciting force are obtained in terms of the difference in potential across the cylinder in a simple manner. The potential jump is related to the so-called blockage coefficient which is determined purely from geometry. It is found that the wave damping coefficient can not exceed the blockage coefficient.

• Journal of Ocean Engineering and Technology
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• v.14 no.1
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• pp.1-5
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• 2000

A numerical analysis for wave motion in the shallow water is presented. The method is based on potential theory. The fully nonlinear free surface boundary condition is assumed in an inner domain and this solution is matched along an assumed common boundary to a linear solution in outer domain. In two-dimensional problem Cauchy's integral theorem is applied to calculate the complex potential and its time derivative along boundary.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.945-949
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• 2009

This paper proposes an enhanced motion estimation that is one of core parts affecting the coding performance and visual quality in video coding. Although the full search technique, which is the most basic method of the motion estimation, presents the best visual quality, its computational complexity is great, since the search procedures to find the best matched block with each block in the current frame are carried out for all points inside the search area. Thus, various fast algorithms to reduce the computational complexity and maintain good visual quality have been proposed. The PMVFAST adopted the MPEG-4 visual standard produces the visual quality near that by the full search technique with the reduced computational complexity. In this paper, we propose a new motion vector prediction method using median processing. The proposed method reduces the computational complexity for the motion estimation significantly. Experimental results show that the proposed algorithm is faster than the PMVFAST and better than the full search in terms of search speed and average PSNR, respectively.

• The Korean Journal of Nuclear Medicine Technology
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• v.17 no.1
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• pp.7-10
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• 2013

Purpose : This study evaluated the effects of breathing protocols on matching results of PET and CT images using two breathing protocols such as free breathing and acquisition in holding the breathing after the normal expiration in acquiring CT images. Materials and Methods: Whole body FDG PET and CT images of 200 patients (mean age: 58 (range 20~84), 103 males and 97 females) using Discovery VCT (GE Healthcare, Milwaukee, USA). When taking CT images, subjects were asked to breathe freely (free breathing, n=100) or hold the breathing after the normal expiration (Hold, n=100). In the whole body image coronal section where PET and CT were matched, the matched error of the boundary between diaphragm and liver was measured in length. The matched errors were compared according to breathing protocol by age, sex and disease. The verification of statistical significance was made by SPSS 15.0 (SPSS Inc., Chicago, IL, USA) via one way ANOVA. Results: The matched error in all was 0.87 mm. According to breathing protocol, there was no significant difference in matched error as1.01 mm in free breathing and as 0.73 mm in hold breathing (p=.688). The matched error according to sex did not show significant difference as 1.08 mm of males, and 0.93 mm of females in free breathing (p=.517). In hold breathing, there was no significant difference as 0.79 mm of males and 0.66 mm of females (p=.738). There was no significant difference in matched error by age between free breathing and hold breathing (free breathing (p=.728), hold (p=.465). There was no significant difference in matched error by disease between free breathing and hold breathing (free breathing (p=.197), hold (p=.518) Conclusion: The difference in matched error between free breathing and hold breathing was less than 5 mm at 99%. There was no statistically significant difference in matched error by breathing protocol, age and disease. It was proved that there was no difference in matched error between PET and CT images according to breathing protocol during PET/CT scan.

• Journal of Ocean Engineering and Technology
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• v.25 no.1
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• pp.1-7
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• 2011

The radiation of water waves by a heaving truncated circular cylinder with damping plate is solved in the frame of the three-dimensional linear potential theory. The damping plate has a distinct advantage in reducing the motion response of a floating circular cylinder by increasing the added mass and the damping coefficient. Using the matched eigenfunction expansion method, the characteristics of hydrodynamic added mass and the damping coefficient are investigated with various system parameters, such as the radius and submergence depth of the damping plate. It is found that both added mass and the damping coefficient are significantly increased due to the arranged features of the larger damping plate with shallow submergence, which are positive factors as a motion reduction device of the floating offshore platform. Also the numerical results for an oscillating submerged disk show that the added mass is negative and that the damping coefficient has a peak value at resonant frequency when submergence depth is sufficiently small.

• International Journal of Naval Architecture and Ocean Engineering
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• v.8 no.1
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• pp.53-65
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• 2016

The interaction between incident waves and a floating rectangular breakwater with the vertical porous side plates has been investigated in the context of the two-dimensional linear potential theory. The matched eigenfunction expansion method(MEEM) for multiple domains is applied to obtain the analytic solutions. The dependence of the transmitted coefficients and motion responses on the design parameters, such as porosity and protruding depth of side plates, is systematically analyzed. It is found that the non-dimensional wavelength where the sudden drop of transmission coefficients occurs, corresponds to the heave resonant frequency obtained from Ruol et al. (2013) for $\pi$-type floating breakwater. It is concluded that both properly selected porosity and deeper protruding depth of side plates are helpful in reducing the transmission coefficients and also extending the wider applicable extent of incident wavelength for performance enhancement.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.922-927
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• 2003

In this paper, slurry fluid motion, abrasive particle motion, and roles of groove patterns on the pads are numerically investigated in the 2D and 3D geometries. The simulation results are analyzed in terms of experimental removal rate and WIWNU (within wafer non-uniformity) for ILD (inter level dielectric) CMP process. Numerical investigations reveal that the grooves in the pad behave as uniform distributor of abrasive particles and enhance the removal rate by increasing shear stress. Higher removal rate and desirable uniformity are numerically and experimentally observed at the pad with grooves. Numerical analysis is very well matched with experimental results and helpful for understanding polishing mechanism and local physics.

• Journal of Welding and Joining
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• v.31 no.4
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• pp.28-33
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• 2013

The effects of laser welding beam quality is very large. However, not an analysing case was found for the difference on the plasma emission signal during laser welding according to the beam quality. Therefore, in this study, we compared and evaluated penetration and signal change according to the beam quality at the a similar wavelength band by using a fiber laser and Nd:YAG laser. In addition, we took high speed videography in order to make sure that FFT analysis reflects the actual motion period of keyhole and found the period of video analysis and FFT mostly matched. As a result, it is expected to secure higher reliability than evaluating signal intensity when appling FFT to monitoring.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.1
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• pp.1-8
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• 2016

Permanent deformation plays a key role in performance based earthquake resistant design. In order to estimate permanent deformation after earthquake, it is essential to secure reliable response history analysis(RHA) as well as earthquake scenario. This study focuses on permanent deformation of an inverted T-type wall under earthquake. The study is composed of two separate parts. The first one is on the verification of RHA and the second one is on an effect of input earthquake motion. The former is discussed in this paper and the latter in the companion paper. The verification is conducted via geotechnical dynamic centrifuge test in prototype scale. Response of wall stem, ground motions behind the wall obtained from RHA matched pretty well with physical test performed under centrifugal acceleration of 50g. The rigorously verified RHA is used for parametric study to investigate an effect of input earthquake motion selection in the companion paper.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.4 s.235
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• pp.435-440
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• 2005

In this paper, slurry fluid motion, abrasive particle motion, and roles of groove patterns on the pads are numerically investigated in the 2D and 3D geometries. The simulation results are analyzed in terms of experimental removal rate and WIWNU (Within Wafer Non-Uniformity) for ILD (Inter Level Dielectric) CMP process. Numerical investigations reveal that the grooves in the pad behave as uniform distributor of abrasive particles and enhance the removal rate by increasing shear stress. Higher removal rate and desirable uniformity are numerically and experimentally observed at the pad with grooves. Numerical analysis is very well matched with experimental results and helpful fur understanding polishing mechanism and local physics.