• Atmosphere
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• v.20 no.3
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• pp.221-228
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• 2010

Aerosol particles with different size-cuts ($PM_{10}$, $PM_{2.5}$, and $PM_{1.0}$) were collected at Gosan Superstation on Jeju Island from August 2007 to June 2008. Mean concentrations of $PM_{10}$, $PM_{2.5}$ and $PM_{1.0}$ were $29.28{\mu}gm^{-3}$, $17.83{\mu}gm^{-3}$, and $14.30{\mu}gm^{-3}$, respectively. Soluble ions comprised 45.7%, 53.9%, and 60.3% of the total mass of $PM_{10}$, $PM_{2.5}$, and $PM_{1.0}$, respectively. While sulfate was the most dominant species of fine mode ($PM_{1.0}$), nitrate was enriched in coarse mode ($PM_{1.0-10}$). When the concentrations of coarse mode particles were greatly increased, nitrate tended to be enhanced in coarse mode with high calcium but low sulfate concentrations. During the high $PM_{1.0}$ events, however, nitrate was increased with sulfate at fine mode. Particularly, nitrate concentrations were substantially enhanced during high particle episodes, leading high ratios of nitrate to sulfate in air under northwest wind during wintertime. On the other hand, the levels of nitrate were lower than those of sulfate at average particle concentrations. The backward air mass trajectories indicated that nitrate concentrations were elevated in air arriving Gosan passing through Santung peninsula or near South Korea.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.45 no.6
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• pp.95-107
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• 2008

In this paper, we propose a fast mode decision method for temporal and spatial scalability to reduce computational complexity of mode decision that used to be computationally one of the most intensive processes of the MPEG-4 AVC|H.264 SE(Scalable Extension) encoding. For temporal scalability, we propose an early skip method and MHM(mode history map) method. The early skip method confines macroblock modes of backward and forward frames within selected a few candidates. The MHM method utilizes stored information of frames inside a GOP of lower levels for the decision of MHM at higher level. For the spatial scalability, we propose the method that uses a candidate mode according to the MHM method and adds the BL_mode as candidates. The proposed scheme reduces the number of candidate modes to reduce computational complexity in mode decision. The proposed scheme reduces total encoding time by about 52% for temporal scalability and 47% for spatial scalability without significant loss of RD performance.

• Journal of the Korean Operations Research and Management Science Society
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• v.19 no.2
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• pp.85-105
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• 1994

As an exploratory attempt, this study examined the correlates of different strategic groups in the Korean health food industry. Many prior studies believe that different entry mode such as entry timing and patterns, and different cognitive structure of top managers lead to the formation of different strategic groups in the same industry. Different strategic groups with different sources or mobility barriers are also expected to produce different level of economic performance. Multivariate statistical analyses of data from 32 firms in the Korean health food industry revealed the following results. i) There are four different strategic groups with different levels of mobility barriers in terms of firm size, scope of product/market domain, degree of forward and backward integration. ii) Differences in both entry timing and environmental perception of top managers are associated with different stratetic groups. However, the patterns of entry are not significantly different among four strategic groups. iii) Four strategic groups exhibit different level of economic performance in terms of sales growth rate and return on investment. Finally, this study tried to identify commonalities and differences among various strategic groups found in several industries in Korea. The results offered some implications to search for developing a useful theory of strategic groups in Korea.

• 한국전산유체공학회:학술대회논문집
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• 2001.10a
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• pp.84-90
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• 2001

Secondary instability of flow past a circular cylinder is examined using direct numerical simulation at Reynolds number 220 and 250. The higher-order finite difference scheme is employed for the spatial distributions along with the second order Adams-Bashforth and the first order backward-Euler time integration. In x-y plane, the convection term is applied by the 5th order upwind scheme, and the pressure and viscosity terms are applied by the 4th order central difference. In spanwise, Navier-Stokes equation is distributed using Spectral Method. The critical Reynolds number for this instability is found to be about Re=190. The secondary instability leads re three-dimensionality with a spanwise wavelength about 4 cylinder diameters at onset (A-mode). Results of three-dimensional effect in wake of a circular cylinder are represented with spanwise and streamwise vorticity contours as Reynolds numbers.

• Journal of Broadcast Engineering
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• v.15 no.6
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• pp.868-875
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• 2010

AT-DMB was developed to raise the transmission rate of existing T-DMB with backward compatability. The transmission and hierarchical video service technique were legislated as Korean TTA standards, and other application service techniques including data services are being developed for the commercial service. In this paper, we consider the power of transmission power level of signals in Advanced Terrestrial Digital Multimedia System according to the constellation ratio. And we propose a new scheme for normalization of transmission signal power level in AT-DMB system. Adopting this scheme, the signal power level of hierarchical modulated signal can be uniform in AT-DMB system both for B Mode and Q Mode.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.6
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• pp.844-849
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• 2012

In this paper, a bidirectional Zeta-Flyback converter is proposed. The topology of the proposed converter is analyzed, which is superposition of bidirectional Flyback converter mode and bidirectional Zeta converter mode in a cycle. The proposed converter allows power flow in either a forward direction or a backward direction. Bidirectional power flow is obtained by a transformer and components. The proposed converter's output is controlled by duty of constant frequency PWM of switch. Compared to conventional bidirectional isolated DC-DC converters, the proposed isolated bidirectional DC-DC converter has high power density and high transformer utilization. To confirm the proposed converter, the simulation and experimental results are presented.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2006.11a
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• pp.187-190
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• 2006

In this paper, we describe a new 1/4 rate robust modulation techniques for Enhanced-x VSB system which is fully backward compatible with ATSC 8-VSB standard. 1/4 rate mode Enhanced-xVSB system provides broadcasters with a wide choice of trade-offs of data rate vs amount of robustness of enhanced data for pedestrian/mobile services. Lab test results of proposed Enhanced-xVSB 1/4 rate mode robust stream are a significantly improved multipath as well as AWGN reception performance for Enhanced-xVSB receiver. We suggest an Enhanced-xVSB terrestrial broadcasting system for ATSC HDTV and pedestrian/portable TV simultaneous broadcasting service providing.

• Journal of Broadcast Engineering
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• v.17 no.1
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• pp.108-121
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• 2012

As Scalable Video Coding (SVC) is a video compression standard extended from H.264/AVC, it is a way to provide scalability in terms of temporal, spatial and quality. Although the compression efficiency of SVC is increased due to the scalability in many aspect, it is essential to reduce the complexity in order to efficiently use because the complexity is relatively increased. To reduce the complexity of SVC in the paper, we propose fast mode decision algorithm to reduce the complexity of encoding process using direction information of B-picture by efficiently performing inter-layer prediction. The proposed algorithm is a fast mode decision algorithm that makes different from detection mode number of forward and backward, bi-direction in the way using best mode of base-layer up-sampled after simply SKIP mode detection using the direction information of best mode of base-layer up-sampled. The experimental results show that the proposed algorithm approach can achieve the maximum computational time saving about 53% with almost no loss of rate distortion (RD) performance in the enhancement layer.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.195-199
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• 1993

In the analysis of metal forming processes by the finite element method, there are many numerical instabilities such as element locking, hourglass mode, shear locking. These instabilities may have a bad effect upon accuracy and convergence. The present work is concerned with improvement of stability and efficiency in two dimensional rigid-plastic finite element method using various type of elements and numerical integration schemes. AS metal forming examples, upsetting and backward extrusion are taken for comparison among the methods : various element types and numerical integration schemes. comparison is made in terms of stability and efficiency. As a result, it has been shown that the finite element computation is stabilized from the viewpoint of computational time, convergency, and numerical instability.